Patent Publication Number: US-7711308-B2

Title: Cleaning device, process cartridge, and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application claims priority to and incorporates by reference the entire contents of Japanese priority document, 2006-245040 filed in Japan on Sep. 11, 2006, Japanese priority document, 2006-245041 filed in Japan on Sep. 11, 2006 and Japanese priority document, 2007-184258 filed in Japan on Jul. 13, 2007. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a cleaning device for use in an image forming apparatus. 
   2. Description of the Related Art 
   Various types of image forming apparatuses, such as electrophotographic types and ink-jet types, are conventionally known. Such image forming apparatuses generally include surface moving members. For example, some electrophotographic image forming apparatuses include surface moving members, such as a latent-image bearing member (an image bearing member), e.g. a photoconductor drum, an intermediate transfer medium (an image bearing member), e.g. an intermediate transfer belt, and a recording material conveyor member, e.g. a paper conveyor belt. Furthermore, some ink-jet image forming apparatuses include surface moving members, such as a recording material conveyor member, e.g. a paper conveyor belt. Generally, unwanted deposit, e.g. toner, may be attached onto a surface of such surface moving member during a use of such image forming apparatuses, thereby causing various problems. Therefore, a cleaning unit that removes the unwanted deposit from the surface of a surface moving member is required. As such cleaning unit, a blade is widely used because preferable performance of removing deposit can be achieved with a simple configuration of the blade. Specifically, such blade removes a deposit by squeezing a cleaning blade made of an elastic material, e.g., polyurethane rubber, onto the surface of a surface moving member. 
   For a cleaning device having such a blade, two types are known, i.e., a trailing type and a counter type. Respective cleaning devices of the two types are explained below with examples of a cleaning device for a photoconductor in an electrographic image forming apparatus. 
     FIG. 17A  is a schematic diagram for explaining a conventional cleaning device of a trailing type. The conventional cleaning device shown in  FIG. 17A  includes a photoconductor (surface moving member)  10  and a cleaning blade  231 . The photoconductor  10  has a drum shape. The cleaning blade  231  is made of a long elastic material extending along the direction of a photoconductor rotation axis orthogonal to a surface moving direction A of the photoconductor  10 . The conventional cleaning device is configured in such a manner that a longitudinally extending edge of the cleaning blade  231  (hereinafter, “contact edge”) is to be pressed on the surface of the photoconductor  10 . In the trailing type, the cleaning blade  231  is held with a blade holder (holding member)  232  supported upstream of a normal line N in the photoconductor-surface moving direction by the main body of the cleaning device, where the normal line N is normal to a contact point P on the photoconductor surface in contact with the contact edge of the cleaning blade  231 . The trailing type means a configuration in which the holding member holds the elastic member; the supporting unit supports the holding member against the main body of the cleaning device; and the supporting unit is arranged upstream of a normal line in the surface moving direction of the surface moving member, where the normal line is normal to a contact point on the surface of the surface moving member in contact with the contact edge of the elastic member. 
     FIG. 17B  is a schematic diagram for explaining a conventional cleaning device of a counter type. The conventional cleaning device shown in  FIG. 17B  is configured in such a manner, similar to that shown in  FIG. 17A , that the cleaning blade  231  made of a long elastic material extends along the direction of the photoconductor rotation axis orthogonal to the surface moving direction A of the photoconductor  10 , and a longitudinally extending contact edge of the cleaning blade  231  is to be pressed on the surface of the photoconductor  10 . In the counter type, the cleaning blade  231  is held with the blade holder  232  supported downstream of the normal line N in the photoconductor-surface moving direction by the main body of the cleaning device, the normal line N being normal to the contact point P in contact with the contact edge of the cleaning blade  231 . The counter type means a configuration in which the holding member holds the elastic member; the supporting unit supports the holding member against the main body of the cleaning device; and the supporting unit is arranged downstream of the normal line in the surface moving direction of the surface moving member, where the normal line is normal to the contact point on the surface of the surface moving member in contact with the contact edge of the elastic member. 
   In both, the trailing type and the counter type, if a friction force between the cleaning blade  231  and the photoconductor surface changes due to some reasons while the photoconductor  10  is rotating in operation, flapping (loose movement) of the cleaning blade  231  occurs, consequently causing a problem, such as damage to the photoconductor  10 , or abnormal noise. In the trailing type, flapping occurs less often than in the counter type, and even if flapping occurs, it causes few problems. The reason for this is because when the friction force between the cleaning blade  231  and the photoconductor surface increases while the photoconductor  10  is rotating in operation, the cleaning blade  231  of the trailing type can warp towards a direction to release a vertical resistance of the cleaning blade  231 ; in contrast, the cleaning blade  231  of the counter type cannot warp towards the direction to release the vertical resistance. Moreover, in the counter type, the cleaning blade  231  cannot warp towards the direction to release the vertical resistance, and when the friction force between the cleaning blade  231  and the photoconductor surface increases, a serious problem, i.e., a blade turnup, may occur. 
   On the other hand, in the counter type, a contact pressure can be increased to be higher than that in the trailing type, so that a removal performance by the counter type is higher than that by the trailing type. 
   More specifically, in the case of the trailing type, if the cleaning blade  231  is pressed with a large force to increase the contact pressure, the cleaning blade  231  warps, thus causing a redundant touch, in which an upstream side surface  231   a  of the cleaning blade  231  touches on the photoconductor surface. In this case, the upstream side surface  231   a  is a surface of the cleaning blade  231  positioned upstream of the contact edge in the photoconductor-surface moving direction. If the redundant touch occurs, a contact area between the cleaning blade  231  and the photoconductor surface suddenly increases. As a result, the contact pressure is inversely decreased despite pressing the cleaning blade  231  with a large force, thus degrading the removal performance. By contrast, in the case of the counter type, even if pressing the cleaning blade  231  with a large force to increase the contact pressure, a friction force works against a warp in the cleaning blade, so that the cleaning blade  231  warps little. Accordingly, a redundant touch less easily occurs even if pressing the cleaning blade  231  with a large force, and a large pressing force can be applied onto a small contact area. Thus, a high contact pressure can be achieved, and a preferable removal performance can be achieved. 
   Japanese Patent Application Laid-Open No. S60-198574 discloses (see  FIG. 8 ) a cleaning device of the trailing type that cleans a photoconductor. The cleaning device includes a backup member that supports, from the back surface, a force received by the tip of the cleaning blade due to rotation of the photoconductor. 
   It is appropriately determined whether to use the trailing type or the counter type based on consideration of respective advantages and respective disadvantages. If a high removal performance is required, it is preferable to employ the counter type because of high performance efficiency described above. Specifically, a recent electrophotographic image forming apparatuses often uses a toner of which particles are spherical and have a small diameter, particularly, a polymerized toner, so that an excellent removal performance is required to remove such toner. Thus, a cleaning device of the counter type tends to be employed in many cases, because its removal performance is preferable while the removal performance by a cleaning device of the trailing type is insufficient. 
   However, the conventional counter type cleaning device has a problem that life durations of the photoconductor and the cleaning blade are shortened, because the cleaning blade is excessively pressed with a large force to increase the contact pressure for obtaining a preferable removal performance. As a result, the photoconductor (surface moving member) to be cleaned and the cleaning blade are excessively worn. 
   On the other hand, the cleaning device disclosed in the above document No. S60-198574 can achieve a higher contact pressure than that by a general trailing type as shown in  FIG. 17A . However, to achieve a contact pressure in the cleaning device as high as that in the counter type, a backup member and a mechanism to support the backup member needs to be reinforced to press down a warp in the cleaning blade. To achieve a similar contact pressure, a simpler configuration and a lower cost can be realized in a cleaning device of the counter type than those in the cleaning device disclosed in the above document No. S60-198574. 
   Because the counter type can provide a higher contact pressure than the trailing type, the counter type has an advantage of a higher removal performance than the trailing type, and is widely used, as disclosed in Japanese Patent Application Laid-Open No. 2001-312191. 
   To explain in detail, in the case of the trailing type, if pressing the cleaning blade  231  with a large force to provide a high contact pressure, the cleaning blade  231  warps, and a redundant touch occurs so that the upstream side surface  231   a  touches on the photoconductor surface. If the redundant touch occurs, a contact area between the cleaning blade  231  and the photoconductor surface suddenly increases. As a result, the contact pressure is inversely decreased despite pressing the cleaning blade  231  with a large force, thus degrading the removal performance. By contrast, in the case of the counter type, even if pressing the cleaning blade  231  with a large force to provide a high contact pressure, a friction force works against a warp in the cleaning blade, so that the cleaning blade  231  warps little. Accordingly, a redundant touch less easily occurs even if pressing the cleaning blade  231  with a large force, and a large pressing force can be applied onto a small contact area. Thus, a high contact pressure can be achieved, and an excellent removal performance can be obtained. 
   However, when the friction force between the cleaning blade  231  and the photoconductor surface increases while the photoconductor  10  is rotating in operation, the cleaning blade  231  of the trailing type can warp towards a direction to release a vertical resistance of the cleaning blade  231 ; in contrast, the cleaning blade  231  of the counter type cannot warp towards the direction to release the vertical resistance. Consequently, when the friction force between the cleaning blade  231  and the photoconductor surface increases, a serious problem may occur, e.g., a blade turnup, or an excess load applied on operation of the photoconductor. 
   Specifically, a recent electrophotographic image forming apparatuses often uses a toner of which particles are spherical and have a small diameter, particularly, a polymerized toner, so that an excellent removal performance is required to remove such toner. Therefore, a sufficient removal performance needs to be ensured, by employing a cleaning device of the counter type, and setting the contact pressure of the cleaning blade as high as possible. Under such situation, a problem easily occurs, such as a blade turnup or an excess load on operation of the photoconductor, because the maximum value of a friction force arising from fluctuation in the friction force between the cleaning blade and the photoconductor surface changes while the photoconductor is rotating in operation. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to at least partially solve the problems in the conventional technology. 
   According to an aspect of the present invention, there is provided a cleaning device that removes deposit on a surface of a surface moving member and includes an elastic member configured to be pressed onto the surface of the surface moving member with a longitudinal edge of the elastic member to apply a first force in a normal line direction at a contact point on the surface of the surface moving member, thereby removing deposit from the surface of the surface moving member, wherein the longitudinal edge is extended along a longitudinal direction of the elastic member, the longitudinal direction orthogonal to a surface moving direction of the surface moving member, is in contact with the surface moving member at a contact point on the surface of the surface moving member, and receives a second force towards downstream in the surface moving direction from the surface of the surface moving member when the surface of the surface moving member moves, and surfaces of the elastic member includes a first surface, a second surface, and a third surface, wherein the first surface and the second surface adjoin each other with respect to the longitudinal edge, the first surface being positioned upstream of the longitudinal edge in the surface moving direction, and the second surface being positioned downstream of the longitudinal edge in the surface moving direction, and the third surface is positioned on an opposite side of the first surface on the elastic member; a warp restrictive member that restricts a warp in the elastic member, the warp being formed in a manner that the first surface expands and the third surface shrinks; and a holding member that supports the elastic member, and is supported by a main body of the cleaning device in a downstream side in the surface moving direction with respect to a normal line to the contact point, wherein the elastic member is formed to have a first thickness thicker than a second thickness, the first thickness being a dimension in a direction orthogonal to both the longitudinal direction and a direction of the second force, and the second thickness being a dimension in a direction substantially parallel to the direction of the second force, the warp restrictive member is arranged on the third surface, and the holding member holds the elastic member via the warp restrictive member. 
   The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram for explaining relevant parts of a cleaning device for a printer, viewed from a photoconductor rotation axis direction, according to a first embodiment of the present invention; 
       FIG. 2  is a schematic diagram for explaining an outline configuration of the printer according to the first embodiment; 
       FIG. 3  is a schematic diagram for explaining an outline configuration of a process cartridge to be provided in the printer shown in  FIG. 2 ; 
       FIG. 4  is a perspective view of relevant parts of the cleaning device shown in  FIG. 1 ; 
       FIG. 5  is a schematic diagram for explaining a measuring device for a pressing force of a blade to be provided in the cleaning device shown in  FIG. 4 ; 
       FIG. 6  is a schematic diagram for explaining relevant parts of a cleaning device, viewed from a photoconductor rotation-axis direction, according to a modification of the present invention; 
       FIG. 7  is a perspective view of relevant parts of the cleaning device shown in  FIG. 6 ; 
       FIGS. 8A and 8B  are schematic diagrams of shapes of toners; 
       FIG. 9  is a schematic diagram for explaining of relevant parts of a cleaning device for a printer, viewed from the photoconductor rotation axis direction, according to a second embodiment of the present invention; 
       FIG. 10  is a schematic diagram for explaining an outline configuration of a process cartridge to be provided in the printer according to the second embodiment; 
       FIG. 11  is a perspective view of relevant parts of the cleaning device shown in  FIG. 9 ; 
       FIG. 12  is a schematic diagram for explaining a measuring device for a pressing force of a blade to be provided in the cleaning device shown in  FIG. 11 ; 
       FIG. 13  is a schematic diagram for explaining another example of a blade to be provided in the cleaning device shown in  FIG. 11 ; 
       FIG. 14  is a schematic diagram for explaining a modification of the cleaning device shown in  FIG. 11 ; 
       FIG. 15  is a side view of an example of a photoconductor to be used in the printer according to the second embodiment; 
       FIG. 16  is a schematic diagram for explaining a charging device, viewed from the direction orthogonal to the photoconductor rotation-axis direction, to be used in the printer according to the second embodiment; 
       FIG. 17A  is a schematic diagram for explaining a conventional cleaning device of a trailing type; and 
       FIG. 17B  is a schematic diagram for explaining a conventional cleaning device of a counter type. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Exemplary embodiments of the present invention will be explained below in detail with reference to the accompanying drawings. 
     FIG. 2  is a schematic diagram of an outline configuration of a printer according to a first embodiment of the present invention. 
   A printer  100  is to form a full color image, and includes an image forming unit  120  and a paper feeding unit  130 . Hereinafter, characters Y, C, M, and Bk are attached to respective members to indicate that each of the members is for yellow, cyan, magenta or black. 
   In the image forming unit  120 , from the left of  FIG. 2 , a process cartridge  121 Y for a yellow toner, a process cartridge  121 C for a cyan toner, a process cartridge  121 M for a magenta toner, and a process cartridge  121 Bk for a black toner are provided in order. The process cartridges  121 Y,  121 C,  121 M, and  121 Bk are aligned and arranged along a substantially horizontal direction. 
   A secondary transfer device  160  includes an intermediate transfer belt  162 , primary transfer rollers  161 Y,  161 C,  161 M, and  161 Bk, and a secondary transfer roller  165 . The intermediate transfer belt  162  is an endless intermediate transfer medium, which covers across a plurality of supporting rollers. The intermediate transfer belt  162  is arranged along a surface moving direction of photoconductors  10 Y,  10 C,  10 M, and  10 Bk. The photoconductors  10 Y,  10 C,  10 M, and  10 Bk are latent-image bearing members in a drum shape, which are image bearing members as surface moving members, provided for the process cartridges  121 Y,  121 C,  121 M, and  121 Bk, respectively, above the respective process cartridges. The surface movement of the intermediate transfer belt  162  is synchronized with the surface movement of the photoconductors  10 Y,  10 C,  10 M, and  10 Bk. The primary transfer rollers  161 Y,  161 C,  161 M, and  161 Bk are arranged on the inner surface of the intermediate transfer belt  162 . The outer surface positioned underneath the intermediate transfer belt  162  is in contact with the outer surfaces of the photoconductors  10 Y,  10 C,  10 M, and  10 Bk under low pressure applied by the primary transfer roller. 
   Configurations and operations to form respective toner images on the photoconductors  10 Y,  10 C,  10 M, and  10 Bk and to transfer the toner images onto the intermediate transfer belt  162  are substantially identical with one another in relation to the process cartridges  121 Y,  121 C,  121 M, and  121 Bk. However, each of the primary transfer rollers  161 Y,  161 M, and  161 M corresponding to each of the three of the process cartridges  121 Y,  121 C, and  121 M for color is equipped with a swing mechanism (not shown) to swing the process cartridge. The swing mechanism works not to allow the intermediate transfer belt  162  to contact the photoconductors  10 Y,  10 C, and  10 M when forming a monochrome image by the photoconductor  10 Bk. 
   The secondary transfer device  160  is configured to be demountable from the main body of the printer  100 . Specifically, a front cover (not shown) in front of paper in  FIG. 2  that covers the image forming unit  120  can be opened, the secondary transfer device  160  can be sided from back of the paper in  FIG. 2  to the front side, so that the secondary transfer device  160  can be demounted from the printer  100 . When mounting the secondary transfer device  160  into the printer  100 , a reverse process of the demounting process. 
   A cleaning device for removing deposit, such as residual toner after a secondary transfer, can be provided downstream of the secondary transfer roller  165  and upstream of the process cartridge  121 Y in the surface moving direction on the intermediate transfer belt  162 . In this case, the cleaning device can employ the same configuration as the cleaning device for a photoconductor, which will be described later. The cleaning device is preferably provided at the secondary transfer device  160  in such a position that the cleaning device is supported together with the intermediate transfer belt  162 . 
   Toner cartridges  159 Y,  159 C,  159 M, and  159 Bk respectively corresponding to the process cartridges  121 Y,  121 C,  121 M, and  121 Bk are aligned and arranged in a substantially horizontal direction above the secondary transfer device  160 . 
   An exposure device  140  that forms an electrostatic latent image by irradiating a laser beam onto the surfaces of the photoconductors  10 Y,  10 C,  10 M, and  10 Bk that is electrostatically charged below the process cartridges  121 Y,  121 C,  121 M, and  121 Bk. 
   Furthermore, the paper feeding unit  130  is arranged below the exposure device  140 . The paper feeding unit  130  includes paper feeding cassettes  131  and paper feeding rollers  132 , which accommodate transfer paper as a recording material, and feed the transfer paper via a pair of register rollers  133  towards a secondary transfer nip between the intermediate transfer belt  162  and the secondary transfer roller  165  with certain timing. 
   A fixing device  90  is arranged on the delivery side of the secondary transfer nip. An ejected-paper container unit  135  that accommodates paper ejecting rollers and ejected transfer paper is arranged downstream of the fixing device  90  in the transfer-paper carrying direction. 
     FIG. 3  is a schematic diagram of an outline configuration of a process cartridge to be provided in the printer  100 . 
   Configurations of the process cartridges are substantially similar to each other, so that a configuration and an operation of one of the process cartridges is explained in the following explanation without attached characters Y, C, M, and Bk for distinguishing between the process cartridges in terms of color. 
   The process cartridge  121  includes the photoconductor  10 , and a cleaning device  30 , an electric charger  40 , and a developing device  50 , three of which are arranged around the photoconductor  10 . 
   The cleaning device  30  includes a cleaning blade (hereinafter, “blade”)  31  that is an elastic member used longitudinally extending along the rotational axis direction of the photoconductor  10 . The cleaning device  30  removes unwanted deposit, such as transfer residual toner on a photoconductor surface, by pressing a longitudinally extending edge (contact edge) of the blade  31  onto the surface of the photoconductor  10 . According to the first embodiment, polyurethane rubber is used as a material of the blade  31 , because polyurethane rubber has more excellent characteristics for wear properties of the photoconductor  10  and in wear resistance of the blade  31  itself than other elastic materials. The cleaning device  30  will be explained in detail later. 
   A lubricant applicator can be provided in the cleaning device  30 . As the lubricant applicator, a device that includes a solid lubricant, a lubricant supporting member for supporting the solid lubricant, and a brush roller for applying the lubricant by rotating in contact with both the solid lubricant and the photoconductor  10 , can be used. Such lubricant applicator applies powdery lubricant with the brush roller scraped by the brush roller from the solid lubricant onto the surface of the photoconductor  10 . Alternatively, an applying blade can be arranged downstream of the brush roller in the photoconductor-surface moving direction to be in contact with the surface of the photoconductor  10 . The applying blade is supported by an applying blade holder by keeping the tip of the applying holder in contact with the surface of the photoconductor  10 , for making uniform the thickness of lubricant applied on the photoconductor  10 . 
   The electric charger  40  includes a charging roller  41  that is arranged to come in contact with the photoconductor  10 , and a charging roller cleaner  42  that rotates in contact with the charging roller  41 . 
   The developing device  50  is configured to produce a visible image from an electrostatic latent image by feeding toner onto the surface of the photoconductor  10 , and includes a developing roller  51 , a stirring screw  52 , and a feeding screw  53 . The developing roller  51  is a developer bearing member that bears a developer on its surface. The stirring screw  52  stirs a developer contained in a developer container unit. The feeding screw  53  feeds the stirred developer onto the developing roller  51 . 
   Each of the four of the process cartridges  121  configured as described above can be individually demounted and replaced by a service person or a user. In the process cartridge  121  demounted from the printer  100 , any of the photoconductor  10 , the electric charger  40 , the developing device  50 , and the cleaning device  30  can be individually replaced with a new one. The process cartridge  121  can include a used toner tank that collects transfer residual toner collected by the cleaning device  30 . In such case, if the process cartridge  121  includes the used toner tank in a configuration in which the used toner tank can be individually demounted and replaced, the convenience is enhanced. 
   Operations of the printer  100  are explained below. 
   Upon receiving a command to print, the photoconductor  10  is rotated in the direction of an arrow A shown in  FIG. 3 , and the surface of the photoconductor  10  is uniformly charged with a certain polarity by the charging roller  41  of the electric charger  40 . The exposure device  140  irradiates a modulated light that is modulated correspondingly to receive color image data, e.g., a laser beam for each color, onto the photoconductor  10  after charged. Accordingly, an electrostatic latent image of each color is formed on the surface of the photoconductor  10 . The developing roller  51  of the developing device  50  feeds each color developer for the electrostatic latent image, develops the electrostatic latent image in each color with the color developer, forms a toner image corresponding to each color, and produce a visible image. A transfer electric field is then formed by applying a transfer voltage of the reversed polarity to the toner image onto a primary transfer roller  161 , and the primary transfer roller  161  presses the intermediate transfer belt  162  at low pressure and comes in contact, so that a primary transfer nip is formed. According to the operations, the toner image formed on each of the photoconductors  10  is efficiently transferred primarily onto the intermediate transfer belt  162 . On the intermediate transfer belt  162 , the toner images of the respective colors formed by the respective photoconductors  10  are transferred in a superposed manner, so that a multilayered toner image is formed. 
   Transfer paper stocked in the paper feeding cassette  131  is fed via the paper feeding roller  132  and the pair of register rollers  133  with a certain timing, and a transfer electric field is generated on the secondary transfer roller  165  by applying a transfer voltage of the reversed polarity to the multilayered toner image, so that the multilayered toner image is transferred onto the transfer paper. The multilayered toner image secondarily transferred onto the transfer paper is sent to the fixing device  90 , and fixed by the fixing device  90  with heat and pressure. The fixed transfer paper is ejected by the paper ejecting rollers to the ejected-paper container unit  135 , and placed therein. On the other hand, transfer residual toners, which has been left on the photoconductors  10  after the first transfer, are scraped off and removed by the blade  31  of the cleaning device  30 . 
     FIG. 1  is a schematic diagram for explaining relevant parts of the cleaning device  30 , viewed from the rotation axis direction of the photoconductor  10  (y axis direction). 
     FIG. 4  is a perspective view of relevant parts of the cleaning device  30 . 
   In the first embodiment, the cleaning device  30  includes a blade holder  32  that holds the blade  31 , and is made of a rigid material. The blade holder  32  has a substantially L-shaped cross section that is cut orthogonally to the rotation axis of the photoconductor  10 . The blade  31  is bonded on the upper surface of a horizontal portion  32 A of the blade holder  32 , where the horizontal portion  32 A is a portion extending along a substantially horizontal direction in  FIG. 3 , and the upper surface is a surface facing upstream in the photoconductor-surface moving direction. A method of bonding can be adhesive bonding, hot melt, or the like. According to the first embodiment, the horizontal portion  32 A functions as a warp restrictive member to restrict a warp in the blade  3 . 
   The blade holder  32  includes a vertical portion  32 B, which vertically extends in  FIG. 3 . A bottom end (extremity downstream in the photoconductor-surface moving direction) of the vertical portion  32 B is pivotably supported by a shaft  34 , which is provided on a frame  33  of the cleaning device  30 . According to the first embodiment, the horizontal portion  32 A, on which the blade  31  is bonded, is held with the vertical portion  32 B of the blade holder  32 , which is supported downstream of a normal line N in the photoconductor-surface moving direction by the shaft  34  on the frame  33  of the cleaning device  30 , i.e., supported by the main body of the cleaning device  30 , where the normal line N is normal to a contact point P on the surface of the photoconductor  10  in contact with the contact edge of the blade  31 . In other words, the cleaning device  30  is a counter type, and the vertical portion  32 B of the blade holder  32  functions as a holding member. 
   In addition, the cleaning device  30  includes springs  36  as a force assistance unit, which enhances a pressing force applied by the blade  31  in the direction of the normal line N to the contact point P on the surface of the photoconductor  10 . According to the first embodiment, two of the springs  36  are provided, each of which is arranged at a distance of 110 millimeters from the center in the longitudinal direction of the blade  31  (the photoconductor rotation-axis direction) towards a longitudinal end. An end of the spring  36  is connected to an end of the horizontal portion  32 A, and the other end of the spring  36  is connected to an adjustive screw  37 , which is an assistance-force adjustment unit. The adjustive screw  37  is engaged in a screw hole arranged in the frame  33  of the cleaning device  30 . When adjusting the pressing force by using the adjustive screw  37 , an adjusting stick is inserted through a notched hole from the outside of the frame  33  of the cleaning device  30 , and the length of the spring  36  is adjusted by turning the adjustive screw  37  with the adjusting stick. 
   Adjustment of the pressing force of the blade  31  to the surface of the photoconductor  10  is explained below. 
     FIG. 5  is a schematic diagram for explaining a measuring device  200  for a pressing force of the blade  31 . In practice, the measuring device  200  can be a commercially available conditioner for sensor, WGA-710B (manufactured by KYOWA DENGYO Co., Ltd.), and a load cell, LMA-A-20N (manufactured by KYOWA DENGYO Co., Ltd.), which can be used in combination with the conditioner. The measuring device  200  includes three of load cells  201 . The load cells  201  are fastened on a cell mount  202 , which is in a semicylindrical shape, at three points in total: one is at the center in the longitudinal direction of the blade  31 ; and the other two in a distance of 140 millimeters from the center towards respective longitudinal ends. Jigs  203  are placed on the load cells  201 . The jigs  203  have a curved surface having the same curvature radius as the photoconductor  10 . The jigs  203  are arranged three in line along the longitudinal direction of the blade  31 , each of the load cells  201  is set at the center of the bottom surface of each of the jigs  203 . 
   The blade  31  is set on the measuring device  200  such that a positional relation with the jigs  203  is to be the same as that with the photoconductor  10 . 
   When adjusting the pressing force of the blade  31  by using the measuring device  200 , the measuring device  200 , instead of the photoconductor  10 , is mounted onto the process cartridge  121  in a state where the cleaning device  30  is assembled in the printer  100 . Specifically, by using a supporting unit to support a driving shaft of the photoconductor  10 , the cell mount  202  on which three of the load cells  201  are fastened, and three of the jigs  203  are mounted on the process cartridge  121 . When mounting, the cell mount  202  and the jigs  203  are set in such a manner that a virtual line between the contact edge of the blade  31  and each of the load cells  201  is to become perpendicular to the bottom surface of each of the jigs  203 . A load applied via each of the jigs  203  is then detected by each of the load cells  201 , and the pressing force of the blade  31  is adjusted by regulating the adjustive screw  37 , while watching a value displayed on a sensor conditioner  204  connected to the measuring device  200 . 
   When measuring, a predetermined weight needs to be placed on each of the jigs  203  in advance, and the adjustive screws  37  has to be set such that each value displayed on the sensor conditioner  204  is to be the same, and the value displayed on the sensor conditioner  204  is to be such a value that a load applied by the jig  203  is cancelled. 
   When adjusting a load balance to make the pressing force of the blade  31  uniform in the longitudinal direction of the blade  31 , the load balance is adjusted by turning the adjustive screws  37  in such a manner that differentials of values of the load cells  201  displayed on the sensor conditioner  204  are to fall within a margin of plus or minus 10 grams. 
   When adjusting the pressing force of the blade  31 , it is fundamentally necessary to adjust the contact pressure between the blade  31  and the surface of the photoconductor  10  to be a target value. However, a contact width (nip width) between the blade  31  and the surface of the photoconductor  10  is difficult to measure. Therefore, the pressing force is generally adjusted in such a manner that a linear pressure is to be a target value. The linear pressure means a pressure applied on a contact point between the blade  31  and the surface of the photoconductor  10  per unit length in the photoconductor rotation-axis direction. Specifically, a linear pressure (N/cm) is a value obtained by dividing the total load of summing values of the load cells  201  displayed on the sensor conditioner  204  by a length T 3  of the blade  31  in the longitudinal direction. 
   According to the first embodiment, the pressure force is adjusted to lead the sum total (total load) of values displayed on the sensor conditioner  204  to 26.0 plus or minus 0.29 newton, so that the linear pressure is to be as high as a linear pressure set by the conventional counter type, i.e., approximately 0.790 N/cm. As a warp in the blade  31  is the larger, the contact width between the blade  31  and the surface of the photoconductor  10  is the longer as described above, and moreover, as a deformation in the blade  31  is the larger, the contact width is the longer. In the cleaning device  30  according to the first embodiment, a warp in the blade  31  is restricted with the horizontal portion  32 A as described above, so that the warp in the blade  31  hardly occurs. Consequently, the warp can be ignored when comparing with a warp in a blade of the cleaning device of the conventional counter type shown in  FIG. 17B . Therefore, in the cleaning device  30  according to the first embodiment, the contact width mainly depends on elastic deformation (compressive deformation) of the blade in the photoconductor-surface moving direction. Thus, the cleaning device  30  according to the first embodiment can make the contact width shorter than that in the cleaning device of the conventional counter type shown in  FIG. 17B . As a result, according to the first embodiment, wear on the photoconductor  10  and the blade  31  can be reduced relatively to the cleaning device of the conventional counter type. 
   Moreover, because the cleaning device  30  according to the first embodiment can make a shorter contact width, even if pressing the blade  31  with a linear pressure as high as that applied by the cleaning device of the conventional counter type, a contact pressure generated by the linear pressure is higher than that in the cleaning device of the conventional counter type. Conversely, to obtain a contact pressure as high as that in the cleaning device of the conventional counter type, the cleaning device  30  requires a smaller pressing force of the blade  31  than the cleaning device of the conventional counter type. The contact width in the first embodiment is expected to be substantially shorter than that in the cleaning device of the conventional counter type. Based on the expectation, it is conceivable that a substantially lower linear pressure than that generated in the cleaning device of the conventional counter type can achieve a contact pressure as high as that in the cleaning device of the conventional counter, and the similar removal performance. This is also effective to reduce wear on the photoconductor  10  and the blade  31 . 
   Moreover, the cleaning device  30  according to the first embodiment can more easily increase the contact pressure than the cleaning device of the conventional counter type. Accordingly, the cleaning device  30  can deliver a sufficient removal performance on toners of spherical particles in small diameters, which are difficult to be removed by the cleaning device of the conventional counter type. 
   The force assistance unit, such as the springs  36 , is not necessarily to be provided, so that the end of the horizontal portion  32 A can be connected to the frame  33  without such force assistance unit. However, in such case, the blade holder  32  cannot be displaced in relation to the frame  33 . Consequently, in a case where a positional relation between the frame  33  and the photoconductor  10  is fixed, if a distance relation between the frame  33  and the surface of the photoconductor  10  is changed, e.g., due to eccentricity of the photoconductor  10 , the blade holder  32  cannot be displaced in response to the change. Therefore, a high manufacturing precision is required such that the distance relation between the frame  33  and the surface of the photoconductor  10  is not to be changed. Moreover, a high assembling precision is also required for assembling the blade  31  to the photoconductor  10 . By contrast, in a case where the force assistance unit as used in the first embodiment is provided, even if a distance relation between the frame  33  and the surface of the photoconductor  10  is changed, e.g., due to eccentricity of the photoconductor  10 , the blade holder  32  can be displaced in accordance with the change. Accordingly, a high precision is required neither for the distance relation between the frame  33  and the surface of the photoconductor  10 , nor for assembling the blade  31  to the photoconductor  10 . 
   In the first embodiment, the blade  31  is in the shape of a rectangular parallelepiped longitudinally extending in the photoconductor rotation-axis direction (y axis direction). Lengths T 1  and T 2  (see  FIG. 4 ) of two surfaces, i.e., an upstream side surface  31   a  and a downstream side surface  31   b , respectively, are lengths orthogonal to the contact edge on the two surfaces  31   a  and  31   b , which adjoin each other with respect to the contact edge as shown in FIG.  1 . The length T 2  is formed longer than the length T 1 . Instead of such rectangular parallelepiped, the blade  31  can take any three-dimensional shape that has the two surfaces  31   a  and  31   b  adjoining each other with respect to the contact edge, and allows the blade  31  to satisfactorily remove deposit on the photoconductor surface along the photoconductor rotation-axis direction. Each of the outer surfaces of the blade  31  is not necessarily flat, but can be curved. 
   The shorter length of the blade  31  along a direction of compressive deformation caused by moving the surface of the photoconductor  10  results in the smaller extent of elastic deformation due to the compressive deformation. A length of the blade  31  in the compression direction is approximately equivalent to the length T 2  of the downstream side surface  31   b  in the photoconductor-surface moving direction. In  FIG. 17B , when measuring a length of each surface of the cleaning blade  231  in a direction orthogonal to the contact edge on the corresponding surface, a length T 1  is a length of the upstream side surface  231   a , and a length T 2  is a length of a downstream side surface  231   b . Comparing the length T 2  according to the first embodiment with the length T 2  in the cleaning device of the conventional counter type shown in  FIG. 17B , the former is much shorter than the latter. Consequently, at least comparing the extents of elastic deformations, the cleaning device  30  would have less deformation than the cleaning device of the conventional counter type. Thus, it is obvious that the contact width in the cleaning device  30  according to the first embodiment is shorter than that in the cleaning device of the conventional counter type. 
   When the blade  31  in the shape of a rectangular parallelepiped is used similarly to the first embodiment, the lengths T 1 , T 2 , and T 3  of the edges of the rectangular parallelepiped are preferably configured to satisfy T 3 &gt;T 1 ≧T 2 . More preferably, T 2  is not less than one millimeter, and not more than T 1 . If T 2  is less than one millimeter, an unusual noise occurs more easily. If a pressure-relieving elastic material is used for the blade  31 , or a material with a high degree in JIS A-hardness is selected, a wider preferable range of the lengths can be achieved. The lengths of the blade  31  according to the first embodiment are as follows: T 1  is 12 millimeters, T 2  is 4 millimeters, and T 3  is 325 millimeters; however, the lengths are not thus limited. 
   The blade  31  according to the first embodiment uses polyurethane rubber that has JIS A-hardness 75 degree, as a material. The material and hardness of the blade  31  are not thus limited, and can be appropriately selected. 
   The blade holder  32  according to the first embodiment is made from a metal material mainly containing iron, which has a sufficient rigidity to suppress a warp satisfactorily, even if the blade  31  receives a force from the photoconductor  10  while the photoconductor  10  is rotating in operation. 
   According to the first embodiment, the cleaning device is configured to press the blade  31  on the surface of the photoconductor  10  in such a manner that an upstream side part in the photoconductor-surface moving direction of the downstream side surface  31   b  of the blade  31  and a downstream side part in the surface moving direction of the tangent line M to the contact point P on the surface of the photoconductor  10  form an angle θ (hereinafter “contact angle”) of approximately 15 degrees when the blade  31  is not pressed on the surface of the photoconductor  10  (see  FIG. 1 ). The contact angle θ is appropriately set within a range between 5 degrees and 50 degrees. It is difficult to set the contact angle θ to less than 5 degree due to the layout around the photoconductor  10 . If the contact angle θ is set to more than 50 degrees, it is much difficult to achieve a sufficient removal performance. More preferably, the contact angle θ is set within a range between 7 degrees and 40 degrees. 
   In the first embodiment, the whole of the opposed surface of the upstream side surface  31   a  of the blade  31  is bonded to the horizontal portion  32 A of the blade holder  32 , as shown in  FIG. 1 . A bonding method other than the adhesive bonding employed in the first embodiment, such as bonding with double-faced adhesive tape, or hot melt, can be employed. Thus, according to the first embodiment, even if the photoconductor  10  is rotated while the blade  31  is pressed onto the surface of the photoconductor  10 , a substantial warp in the blade  31  hardly occurs. 
   Accordingly, robustness against environmental variation is improved. More specifically, in a configuration that a warp in a blade may occur, such as a case where a free length of the blade is long, a force caused by the warp in the blade is changed depending on humidity. For example, if a warped blade is left as it is in a hot and humid environment, the blade is plastically deformed, and a permanent set occurs. In such case, the attitude of the blade to the surface of the photoconductor  10  changes, and a cleaning performance is degraded, so that there is a possibility that a cleaning failure may occur. By contrast, in the first embodiment where a substantial warp in the blade  31  hardly occurs, robustness against environmental variation can be improved. 
   Occurrence of a warp in a blade means that the blade has a flexibility that allows the blade to warp. If the flexibility of the blade is large, in a case of the counter type, a blade turnup, which is a serious problem, easily occurs, when a friction force between the blade and the photoconductor surface increases. In the first embodiment where a substantial warp in the blade  31  does not occur, a blade turnup is prevented. 
   According to the first embodiment, an end of the horizontal portion  32 A facing the surface of the photoconductor  10 , i.e., the end of the horizontal portion  32 A coupled to the vertical portion  32 B, is arranged at the same position as a border edge between the opposed surface (bonding surface) of the upstream side surface  31   a  and the downstream side surface  31   b , as shown in  FIG. 1 . However, even if the end of the horizontal portion  32 A is arranged to extend closer to the surface of the photoconductor  10  than the border edge of the blade  31 , a substantial warp in the blade  31  hardly occurs, similarly to the first embodiment. 
   Alternatively, the end of the horizontal portion  32 A does not need to be extended until the border edge of the blade  31 . As long as a warp in the blade  31  can be virtually restricted, the end of the horizontal portion  32 A does not need to reach the border edge. In other words, if a warp in the blade  31  is virtually restricted, the end of the horizontal portion  32 A can be more distant from the photoconductor surface than the border edge. In such case, to what extent the end of the horizontal portion  32 A can keep an additional distance from the photoconductor surface relative to the border edge is determined depending on hardness of the blade  31 , a friction coefficient between the blade  31  and the surface of the photoconductor  10 , and the like. An allowable range of the distance can be, for example as a guidepost for determination, a distance according to which a resultant length (contact width) of a contact point in the photoconductor-surface moving direction is to be not more than 50 micrometers, when pressing the blade  31  onto the surface of the photoconductor  10  to apply a linear pressure of 0.790 N/cm. It is estimated that up to a quarter of the length T 2  of the downstream side surface  31   b  can be allowable as a distance between the end of the horizontal portion  32 A and the border edge. Furthermore, there is a possibility that a range from a half of T 2  up to the almost same level as T 2  can be allowable. 
   Moreover, the blade  31  can be bonded to the horizontal portion  32 A of the blade holder  32  by applying adhesive to only part of the bonding surface of the blade  31 . However, it is desirable that bonding is performed at least on a marginal area close to the surface of the photoconductor  10  from across an overlapping area where the horizontal portion  32 A and the opposed surface (bonding surface) of the upstream side surface  31   a  overlap one another. As the horizontal portion  32 A of the blade holder  32  and the blade  31  are securely bonded in the end area, flapping of the blade  31  can be stably prevented, even if a friction force between the blade  31  and the photoconductor surface is changed for some reasons while the photoconductor is rotating in operation. This is the same to other bonding methods. 
     FIG. 6  is a schematic diagram for explaining relevant parts of a cleaning device according to a modification of the cleaning device  30  viewed from the photoconductor rotation-axis direction. 
   In the cleaning device according to the modification, an upstream side surface of the blade  31  includes a first upstream side-surface  31   c  and a second upstream side-surface  31   d . The first upstream side-surface  31   c  is adjacent to the downstream side surface  31   b . The second upstream side-surface  31   d  extends in substantially parallel with a direction (substantially the same as a direction along which the horizontal portion  32 A of the blade holder  32  extends) orthogonal to both of two directions, i.e., the direction of a force received by a contact edge from the photoconductor surface when moving the surface of the photoconductor  10  (substantially the same as a direction along which the vertical portion  32 B of the blade holder  32  extends), and the longitudinal direction of the blade  31 . The blade  31  is configured to have an obtuse angle between the back surface of the first upstream side-surface  31   c  and the back surface of the downstream side surface  31   b  (hereinafter, “blade tip angle δ”). Other configurations than the blade tip angle of the cleaning device  30  according to the modification are similar to those according to the first embodiment. 
   According to the cleaning device  30  of the modification, the following effects can be obtained. 
   Generally, the blade tip angle is 90 degrees as described in the first embodiment. However, the present inventors revealed that a blade having the blade tip angle larger than 90 degrees, i.e., an obtuse angle, can largely reduce wear amount on the blade  31 . The reason why the wear amount on the blade  31  can be largely reduced is explained below. The blade  31  is deformed by receiving an effect of a friction force between the blade  31  and the surface of the photoconductor  10 , and the amount of the deformation in a case of an obtuse blade tip angle is smaller than that in a case when the blade tip angle is 90 degrees. The contact width between the blade  31  and the surface of the photoconductor  10  in the case of an obtuse blade tip angle is smaller than that in the case when the blade tip angle is 90 degrees, thereby reducing the wear amount on the blade  31 . When the contact width becomes smaller, the contact pressure generated by the same pressing force with the blade  31  onto the surface of the photoconductor  10  is increased. Conversely, to obtain the contact pressure, the pressing force can be reduced. Thus, toner can be removed with a smaller pressing force. 
   According to the modification, the blade tip angle is 120 degrees. As shown in  FIG. 7 , the blade tip angle is preferably between 95 degrees and 140 degrees. Particularly, a blade having an obtuse angle smaller than 95 degrees cannot achieve a sufficient effect. 
   Toners to be used in the printer according to the first embodiment are explained below. 
   Because the cleaning device  30  according to the first embodiment can achieve an excellent removal performance, the cleaning device  30  can be used for removing a toner having the average circularity of 0.940 or more, and further that between 0.960 and 0.998. Furthermore, effects of the present invention can be sufficiently delivered for removing a toner having the average circularity between 0.960 and 0.998. 
   Such toner can be obtained by thermally or mechanically conglobating a toner manufactured by dry grinding. As a thermal conglobation process, it can be considered that toner particles are sprayed together with hot air by atomizer. As mechanical conglobation process, it can be considered that toner particles are charged and stirred in a mixer, such as a ball mill, together with a mixing medium, such as glass of light specific gravity. However, a further classification process is required, because toner particles having a large diameter are produced by agglomerating in the thermal conglobation process, and microparticles are produced in the mechanical conglobation process. If a toner is manufactured in an aqueous solvent, the spherical shape can be controlled by giving a strong stir during a process of removing the solvent. 
   The circularity of a toner is a value obtained by optically detecting toner particles, and the circumferential length of a circle which has an area equivalent to the projection area of the toner is divided by a circumferential length of an actual toner particle. Specifically, the average circularity of the toner is measured using a flow particle image analyzer (FPIA-2000; manufactured by SYSMEX Corp.). In to a given vessel, 100 milliliters to 150 milliliters of water from which solid impurities are preliminarily removed is charged, 0.1 milliliter to 0.5 milliliter of a surfactant is added as a dispersant, and approximately 0.1 gram to 9.5 grams of a sample of a toner is further added. The suspension of the dispersed sample is dispersed for approximately one minute to three minutes using an ultrasonic dispersing apparatus, to make a concentration of the dispersant 3,000 pcs/μL to 10,000 pcs/μL, and then the shape and distribution of the toner is measured. The circularity is defined as follows: Circularity SR=(circumferential length of circle having area equivalent to projection area of toner/circumferential length of actual toner particle). When the toner is the closer to a complete spherical, the circularity is the closer to 1. 
   A toner having a high circularity tends to be influenced by electric flux line on the carrier or on the surface of the developing roller  51 , and an image is precisely developed along the electric flux line of an electrostatic latent image. Accordingly, when reproducing fine latent image dots, a minute and uniform toner arrangement is made, so that reproducibility of a thin line is high. The toner having a high circularity has a smooth surface and adequate flow ability, so that the toner tends to be influenced by electric flux line, an image can be precisely and easily transferred along the electric flux line, a transfer rate is high, and a high quality of the image can be obtained. The primary transfer roller  161  presses the intermediate transfer belt  162  with pressure and comes in contact, so that the primary transfer nip is formed. A transfer electric field is then formed by applying a transfer voltage of the reversed polarity to the toner image onto the primary transfer roller  161 . When the toner image formed on each of the photoconductors  10  is transferred primarily onto the intermediate transfer belt  162 , the toner having a high circularity touches the intermediate transfer belt  162 , and contact area of the toner becomes uniform, thereby improving the transfer rate. 
   However, if the average circularity of the toner is less than 0.93, precise development and transfer at high transfer rate cannot be achieved. The reason for this is because if the toner has amorphous shapes, electrostatic charge on the toner surfaces is not uniform, and the center of gravity and the center of electrostatic charge are deviated, so that it is difficult to achieve precise movement in accordance with the electric field. 
   In terms of volume average diameter of the toner, the smaller value can improve the reproducibility of a thin line, a toner having the diameter at most seven micrometers or smaller is preferably used. However, because the smaller particle diameter degrades development properties, the particle diameter is preferably at least three micrometers or larger. If the diameter is less than three micrometers, microparticles of a toner that are difficult to be developed on the carrier or the surface of the developing roller  51  are increased. As a result, contact and friction of other toners with the carrier or the developing roller  51  becomes insufficient, so that reversely charge toners are increased. Accordingly, an erroneous image, such as fog, is formed, which is unfavorable. If a toner has the volume average diameter of two micrometers or more, the cleaning device  30  can deliver a sufficient removal performance. Particularly, if the volume average diameter is three micrometers or more, more favorable removal performance can be delivered. The ratio between a volume average diameter Dv and a number average diameter Dn is preferably between 1.0 and 1.4 approximately. 
   The volume average diameter of a toner is measured as follows. 
   A surfactant (preferably, alkylbenzene sulfonate) as dispersant between 0.1 milliliter and 5 milliliters is added into 100 milliliters to 150 milliliters of an electrolyte aqueous solution. The electrolyte solution is a 1% NaCl aqueous solution prepared by using a first grade sodium chloride, that is, ISOTON R-II (manufactured by Coulter Scientific Japan, Ltd.) is used. In to the mixed solution, 2 milligrams to 20 milligrams of a sample of a toner is added, suspended in the electrolyte solution, and dispersed for approximately one minute to three minutes using an ultrasonic dispersing apparatus. With the measuring device, using a 100 micrometer aperture, the volume and the number of pieces in the sample of the toner are measured channel by channel, and then the distribution of volumes and the distribution of the number of pieces of the toner are calculated. 
   The following 13 channels are used: from 2.00 micrometers to 2.52 micrometers; from 2.52 micrometers to 3.17 micrometers; from 3.17 micrometers to 4.00 micrometers; from 4.00 micrometers to 5.04 micrometers; from 5.04 micrometers to 6.35 micrometers; from 6.35 micrometers to 8.00 micrometers; from 8.00 micrometers to 10.08 micrometers; from 10.08 micrometers to 12.70 micrometers; from 12.70 micrometers to 16.00 micrometers; from 16.00 micrometers to 20.20 micrometers; from 20.20 micrometers to 25.40 micrometers; from 25.40 micrometers to 32.00 micrometers; and from 32.00 micrometers to 40.30 micrometers. 
   From among toners that satisfies the average circularity described above, a toner of which a shape factor SF- 1  falls within a range between 100 and 160, and of which a shape factor SF- 2  falls within a range between 100 and 160 is preferable. 
     FIGS. 8A and 8B  are schematic diagrams of shapes of toners.  FIG. 8A  is a schematic diagram for explaining the shape factor SF- 1 , and  FIG. 8B  is a schematic diagram for explaining the shape factor SF- 2 . 
   The shape factor SF- 1  indicates a degree of roundness of a toner shape, and presented in the following Equation (1). The square of the maximum length MXLNG of a projection shape created by projecting a toner particle onto a two-dimensional flat plane is divided by the graphic area AREA, and multiplied by 100π/4. When the SF- 1  is 100, the toner particle has a complete spherical shape. As the SF- 1  increases, the toner shape becomes more amorphous.
 
 SF− 1={( MXLNG ) 2 /(AREA)}×(100π/4)  (1)
 
   The shape factor SF- 2  indicates the degree of the concavity and convexity of a toner shape, and presented in the flowing Equation (2). The square of the periphery PERI of the projection shape is divided by the graphic area AREA, and multiplied by 100π/4. When the SF- 2  is 100, the surface of the toner particle does not have concavity and convexity. As the SF- 2  increases, the toner surface is much rougher.
 
 SF− 2={( PERI ) 2 /(AREA)}×(100/4π)  (2)
 
   To determine the shape factors, specifically, a photograph of particles of a toner is taken using a scanning electron microscope (S-800, manufactured by Hitachi Ltd.); and the taken particle images are analyzed using an image analyzer (LUSEX 3 manufactured by Nireco Corp.). 
   When the toner has a particle shape near the complete spherical shape, the contact area of a particle of the toner with another particle decreases and turns to point contact. As a result, the adhesion between the toner particles decreases, and flow ability of the toner increases. Moreover, absorbability between the toner particles and the photoconductor  10  decreases, the transfer rate increases, so that residual toner particles remaining on the surface of the photoconductor  10  can be cleaned more easily. As the shape factors SF- 1  and SF- 2  increase, the shape turns to be amorphous, the distribution of the charge amount of the toner is widened, the development image is less precise to the latent image, and transfer is not performed precisely in accordance with the transfer electric field, resulting in degradation of the image qualities. Therefore, it is preferred that the shape factors SF- 1  and SF- 2  do not exceed 180. 
   A substantially spherical toner as described above can be preferably obtained by crosslinking and/or elongating toner constituents including a polyester prepolymer having a functional group having a nitrogen atom, a polyester, a colorant, and a release agent, in an aqueous medium under presence of resin particles. According to a manufacturing method of conventional grinded toners, comparing to any parameter of the circularity, the average diameter, and the shape factors SF- 1  and SF- 2 , satisfactory toner cannot be produced, or the toner produced by polymerization has advantages in terms of manufacturing costs and yield. However, among toners produced by the polymerization, it is difficult for a toner produced by the suspension polymerization or emulsion polymerization to obtain a complete spherical shape. Particularly, a toner produced by a dissolving suspension has a kind of spherical shape, but amorphous toner, so that satisfactory image quality is hardly obtained. 
   Constituent materials and preferable producing methods of the toner obtained by crosslinking and/or elongating toner constituents including a polyester prepolymer having a functional group having a nitrogen atom, a polyester, a colorant, and a release agent, in an aqueous medium under presence of resin particles, are explained below. Polyester is obtained by polycondensation reaction between polyhydric alcohol compounds and polyvalent carboxylic acid compounds. 
   Examples of polyhydric alcohol compounds (PO) include dihydric alcohol (DIO) and trihydric or more alcohols (TO); and dihydric alcohol (DIO) alone or a mixture of dihydric alcohol (DIO) with a small amount of trihydric alcohol (TO) are preferable. 
   Examples of dihydric alcohol (DIO) include alkylene glycol having a carbon number from 2 to 12 and the adducts of alkylene oxides of the bisphenols. Particularly preferable are the adducts of alkylene oxides of the bisphenols, and a combination of the adducts of alkylene oxides of the bisphenols and alkylene glycol having a carbon number from 2 to 12. 
   Trihydric or more alcohols (TO) include trihydric to octahydric alcohols and more aliphatic alcohols (e.g., glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, and sorbitol); trivalent or more phenols (e.g., trisphenol PA, phenol novolak, and cresol novolak); and adducts of alkylene oxides of the trivalent or more polyphenols. 
   Examples of a polyvalent carboxylic acid (PC) include a divalent carboxylic acid (DIC) and a trivalent or more carboxylic acid (TC). The divalent carboxylic acid (DIC) alone and a mixture of the divalent carboxylic acid (DIC) and a small amount of the trivalent or more carboxylic acid (TC) are preferable. Examples of divalent carboxylic acids (DIC) include the alkenylene dicarboxylic acids having a carbon number from 4 to 20 and the aromatic dicarboxylic acids having a carbon number from 8 to 20. Examples of trivalent or more carboxylic acids (TC) include aromatic polyvalent carboxylic acids having a carbon number from 9 to 20 (e.g., trimellitic acid and pyromellitic acid). 
   A ratio between the polyhydric alcohol (PO) and the polyvalent carboxylic acid (PC) is usually from 2/1 to 1/1, preferably from 1.5/1 to 1/1, more preferably from 1.3/1 to 1.02/1, as an equivalent ratio of [OH]/[COOH] between a hydroxyl group [OH] and a carboxyl group [COOH]. 
   For polycondensation reaction, under presence of an esterification catalyst, such as tetrabutoxy titanate or dibutyltin oxide, a polyvalent alcohol (PO) and a polyvalent carboxylic acid (PC) are heated to between 150° C. and 280° C., the pressure is reduced as required, and produced water is removed, so that a polyester having a hydroxyl group is obtained. 
   The polyesters include an unmodified polyester obtained from the polycondensation, and moreover, preferably a urea modified polyester. An urea modified polyester is obtained as follows: a carboxyl group or a hydroxyl group at an end of a polyester obtained by the polycondensation, and a polyvalent isocyanate compound (PIC) are exposed to reaction; a polyester prepolymer (A) having an isocyanate group is obtained; the obtained polyester prepolymer (A) and amines are exposed to reaction so that molecular chains are crosslinked and/or elongated. 
   Examples of polyvalent isocyanate compounds (PIC) are aliphatic polyvalent isocyanates, alicyclic polyisocyanates, aromatic diisocyanates, aromatic aliphatic diisocyanates, isocyanates, compounds formed by blocking these polyisocyanates by a phenol derivative, an oxime, a caprolactam and a combination of at least two of these. 
   A ratio of the polyvalent isocyanate compounds (PIC) is usually from 5/1 to 1/1, preferably from 4/1 to 1.2/1, and more preferably from 2.5/1 to 1.5/1, as an equivalent ratio of [NCO]/[OH] between an isocyanate group [NCO] and a hydroxyl group [OH] of a hydroxyl group-containing polyester. 
   The content of the polyvalent isocyanate compound (PIC) in the isocyanate group-containing polyester prepolymer (A) ranges usually from 0.5 wt % to 40 wt %, preferably from 1 wt % to 30 wt %, and more preferably from 2 wt % to 20 wt %. 
   The number of isocyanate groups contained in one molecule of the isocyanate group-containing polyester prepolymer (A) is usually at least 1, preferably, an average of 1.5 to 3, and more preferably, an average of 1.8 to 2.5. 
   Further, amines (B) that are reacted with the polyester prepolymer (A) include divalent amine compounds (B 1 ), trivalent or more amine compounds (B 2 ), amino alcohols (B 3 ), amino mercaptans (B 4 ), amino acids (B 5 ), and the compounds (B 6 ) of B 1  to B 5  in which their amino groups are blocked. 
   Examples of the divalent amine compounds (B 1 ) include aromatic diamines, alicyclic diamines, and aliphatic diamines. 
   Examples of the trivalent or more amine compounds (B 2 ) include diethylene triamine and triethylene tetramine. 
   Examples of the amino alcohols (B 3 ) include ethanolamine and hydroxyethylaniline. 
   Examples of the amino mercaptans (B 4 ) include aminoethyl mercaptan and aminopropyl mercaptan. 
   The preferable amines among the amines (B) are B 1  and a mixture of B 1  with a small amount of B 2 . 
   A ratio of amines (B) is usually 1/2 to 2/1, preferably 1.5/1 to 1/1.5, and more preferably 1.2/1 to 1/1.2 as an equivalent ratio of [NCO]/[NHx] between an isocyanate group [NCO] in the isocyanate group-containing polyester prepolymer (A) and an amine group [NHx] in the amines (B). 
   The urea-modified polyester is manufactured by a one shot method. Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) is heated to 150° C. to 280° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate and dibutyltin oxide, and by distilling water generated while pressure is reduced if required, and polyester having the hydroxyl group is obtained. Polyvalent isocyanate compound (PIC) is reacted with the polyester at a temperature of 40° C. to 140° C. to obtain isocyanate group-containing polyester prepolymer (A). The amine group (B) is further reacted with (A) at the temperature of 0° C. to 140° C. to obtain the urea-modified polyester. 
   When (PIC) is reacted or (A) and (B) are reacted, a solvent can be used if necessary. Examples of available solvent include those inactive to isocyanate, such as an aromatic solvent, ketone group, and ester group. 
   A reaction inhibitor is used as required for crosslinking reaction and/or elongation reaction between polyester prepolymer (A) and amines (B), thereby adjusting the molecular weight of the urea-modified polyester obtained. Examples of the reaction inhibitor include monoamines (e.g., diethylamine, dibutylamine, butylamine, and laurylamine), and ketimine compounds in which the monoamines are blocked. 
   The weight-average molecular weight of the urea-modified polyester is usually not less than 10,000, preferably 20,000 to 10,000,000, and more preferably 30,000 to 1,000,000. A number-average molecular weight of the urea-modified polyester is not particularly limited when the native polyester is used, and the number-average molecular weight should be one that is easily obtained to get a weight-average molecular weight. When the urea-modified polyester is used alone, the number-average molecular weight is usually 2,000 to 15,000, preferably 2,000 to 10,000, and more preferably 2,000 to 8,000. 
   A weight ratio between the native polyester and the urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, and particularly preferably 80/20 to 93/7. A glass transition point (Tg) of binder resin including the native polyester and the urea-modified polyester is usually set to be 45° C. to 65° C., and preferably 45° C. to 60° C. 
   As for a colorant, all known dyes and pigments are available for a colorant, and the followings and mixtures thereof can be used, e.g., carbon black, nigrosine dye, naphthol yellow S, cadmium yellow, yellow iron oxide, chrome yellow, minium, red lead, cadmium red, lithol fast scarlet G, benzidine orange, oil orange, cobalt blue, cerulean blue, alkali blue lake, fast sky blue, indigo, ultramarine blue, Prussian blue, manganese violet, dioxane violet, chrome green, pyridian, emerald green, pigment green B, phthalocyanine green, and anthraquinone green. The content of the colorant is usually 1 wt % to 15 wt %, and preferably 3 wt % to 10 wt % in toner particles. 
   The colorant can also be used as a master batch mixed with resin. Examples of binder resin used to manufacture such a master batch or to be kneaded with the master batch include styrenes such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, and substituted polymer thereof, or copolymer of these compounds and vinyl compounds, polymethyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, chlorinated paraffin, and paraffin wax. These materials can be used alone or as a mixture thereof. 
   Known charge control agents can be used as a charge control agent, and include, e.g., nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, phosphorus alone or compounds thereof, tungsten alone or compounds thereof, fluorine-based active agents, salicylic acid metal salts, and metal salts of salicylic acid derivatives. More specific examples of the charge control agents are Bontron 03 as nigrosine dyes, E-84 as salicylic acid metal complex, E-89 as phenol type condensate (these are manufactured by Orient Chemical Industries, Ltd.), TP-302 and TP-415 as quaternary ammonium salt molybdenum complexes (manufactured by Hodogaya Chemical Industries, Ltd.), Copy Charge PSY VP2038 as quaternary ammonium salt, Copy Blue PR as triphenylmethane derivative, LRA-901 and LR-147 as boron complex (manufactured by Japan Carlit Co., Ltd.), copper phthalocyanine, perylene, quinacridone, azo type pigments, and polymer compounds having a functional group such as a sulfonic acid group, a carboxyl group, and a quaternary ammonium salt group. Among these, a material that controls the toner to have negative polarity is preferably used. 
   The use amount of the charge control agent is determined depending on the type of binder resins, presence or absence of additives to be used as required, and a method of manufacturing toner including a dispersion method, and hence, it is not uniquely limited. However, the charge control agent is used preferably in a range from 0.1 parts by weight (wt. parts) to 10 wt. parts, and more preferably from 0.2 wt. parts to 5 wt. parts, per 100 wt. parts of the binder resin. If it exceeds 10 wt. parts, the toner is charged too highly, which causes effects of the charge control agent to be decreased, electrostatic attracting force with a developing roller to be increased, fluidity of the developer to be lowered, and image density to be reduced. 
   A wax having a low melting point in a range from 50° C. to 120° C. effectively functions as a release agent in dispersion with binder resin. Such wax components include the followings. Examples of waxes include waxes from plants such as carnauba wax and cotton wax; waxes from animals such as beeswax and lanolin; waxes from mineral substances such as ozokerite and cercine; and petroleum waxes such as paraffin, microcrystalline, and petrolatum. 
   Examples of waxes apart from these natural waxes include synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax; and synthetic waxes such as ester, ketone, and ether. 
   Inorganic fine particles are preferably used as an external additive to facilitate fluidity, developing performance, and chargeability of toner particles. Such an inorganic fine particle has preferably a primary particle diameter of 5×10 −3  to 2 micrometers. In particular, the primary particle diameter is preferably 5×10 −3  to 0.5 micrometers. 
   A specific surface area by the BET method is preferably 20 m 2 /g to 500 m 2 /g. The use ratio of the inorganic fine particles is preferably 0.01 wt % to 5 wt % in toner particles, and more preferably 0.01 wt % to 2.0 wt %. 
   Specific examples of the inorganic particles include silica, alumina, titanium oxide, barium titanate, zinc oxide, calcium carbonate, silicon carbide, and silicon nitride. Among these materials, hydrophobic silica particles and hydrophobic titanium oxide particles are preferably used in combination as a fluidizing agent. 
   A method of producing toner is explained below in detail. In the following description, although a preferred method is shown, the present invention is not limited to this. 
   A colorant, an unmodified polyester, a polyester prepolymer having an isocyanate group, and a release agent are dispersed into an organic solvent, and then a toner material solution is prepared. The organic solvent is preferably volatile with a boiling point lower than 100° C., because the organic solvent can be easily removed after toner base-particles are formed. Specifically, an aromatic solvent, such as toluene or xylene; a halogenated hydrocarbon, such as methylene chloride, 1, 2-dichloroethane, chloroform, or carbon tetrachloride; and the like can be used alone or in combination of two or more of those. The amount of the organic solvent to be used for 100 wt. parts of the polyester prepolymer is generally between 0 wt. part and 300 wt. parts, preferably between 0 wt. part and 100 wt. parts, and more preferably between 25 wt. part and 70 wt. parts. 
   The toner material solution is emulsified in an aqueous medium including a surfactant and resin microparticles. The aqueous medium can be water alone, or can include an organic solvent: an alcohol, such as methanol; dimethylformamide; tetrahydrofuran; one of Cellosolves; one of lower ketones; or the like. The amount of the aqueous medium to be used for 100 wt. parts of the toner material solution is generally between 50 wt. parts and 2,000 wt. parts, and preferably between 100 wt. parts and 1,000 wt. parts. If the amount of aqueous medium is less than 50 wt. parts, toner materials are not dispersed sufficiently in the toner material solution, so that a predetermined particle diameter of toner particles is not satisfied. If the amount of the aqueous medium is more than 20,000 wt. parts, it is not favorable in terms of costs. 
   To achieve satisfactory dispersion in the aqueous medium, a dispersant, such as a surfactant and resin microparticles, can be added as required. The surfactant can be an anionic surfactant, such as alkylbenzene sulfonate; a cationic surfactant of a quaternary ammonium salt, such as alkylamine salt, aminoalcohol fatty acid derivative, polyamine fatty acid derivative, and alkyltrimethyl ammonium salt; or the like. By using a surfactant having a fluoroalkyl group, effects of the surfactant can be obtained in a small amount. 
   The substances described above can be used as the resin microparticles. Additionally, an inorganic compound dispersant, such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite, can be used. Material-dispersed fluid can be stabilized with a high-polymer protective colloid, which can be used as a dispersant together with the resin microparticles and an inorganic compound dispersant. For example, an acid can be used, such as acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, or maleic anhydride. Alternatively, an acrylic monomer or a methacrylic monomer containing hydroxyl group can used, such as β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, or γ-hydroxypropyl acrylate. 
   A dispersing method is not particularly limited, and a known facility, e.g., by low-speed shearing, high-speed shearing, friction dispersion, high-pressure jetting, or ultrasonic dispersion, can be applied. To make dispersed particles with particle diameter between 2 micrometers and 20 micrometers, the high-speed shearing method is preferred. When a high-speed shearing dispersing machine is used, the number of rotation is not particularly limited, but is generally between 1,000 rpm and 30,000 rpm, and preferably between 5,000 rpm and 20,000 rpm. A dispersion time is not particularly limited, but is generally between 0.1 minute and 5 minutes in a batch system. The temperature for dispersing is generally between 0° C. and 150° C. under pressure, and preferably between 40° C. and 98° C. 
   When an emulsified liquid is prepared, an amine (B) is simultaneously added to the emulsified liquid, and is cause to react with a polyester prepolymer (A) having an isocyanate group. The reaction involves cross-linking and/or extending molecular chains. The reaction time for cross-linking and/or extending is appropriately selected in accordance with the reactivity of an isocyanate group structure of the polyester prepolymer (A) to the amine (B), and is generally between 10 minutes and 40 hours, and preferably between 2 hours and 24 hours. The reaction temperature is generally between 0° C. and 150° C., and preferably between 40° C. and 98° C. A known catalyst can be used as required. Specifically, for example, dibutyltin laurate, or dioctyltin laurate can be used. 
   After the reaction is completed, the organic solvent is removed from the emulsified dispersion (reaction mixture), the residue is washed and dried, and then toner base-particles are obtained. To remove the organic solvent, the entire system is gradually heated while stirring in a laminar flow. In a predetermined range of temperature, the system is strongly stirred, and then the organic solvent is removed, consequently toner base-particles, which are substantially spherical in shape, can be prepared. In the process, another shape, for example, a spindle shape, can be formed from an absolute sphere. Furthermore, morphology of the surface can be controlled, for example, from a smooth surface into a wrinkly one. When an acid such as calcium phosphate or a substance soluble in alkaline is used as a dispersion stabilizer, the calcium phosphate is removed from the toner base-particle by dissolving the calcium phosphate with an acid such as hydrochloric acid, and then washing with water. Alternatively, the calcium phosphate can also be removed by enzymolysis. 
   A process of maturing the prepared toner particles can be provided, in which the emulsified dispersion liquid is left standing at a certain temperature for a certain time period before or after the process of washing and removing the solvent. The process allows a toner particle to have a desired diameter. The temperature of the maturing process is preferably between 25° C. and 50° C., and the time period is preferably between 10 minutes and 23 hours. 
   A charge-controlling agent is implanted into the toner base-particles obtained in the above process, and then inorganic microparticles, such as silica microparticles and titanium oxide microparticles, are externally added to the toner base-particles, consequently a toner is produced. 
   Implanting of the charge-controlling agent and external adding of inorganic microparticles are performed by a known method, for example, by using a mixer. 
   The method allows toner particles easily to have a sharp distribution of particle diameters, each of which is small. 
   The toner according to the embodiment of the present invention is mixed with a magnetic carrier to be used as a two-component developer. However, the toner can be used as a magnetic toner or a non-magnetic toner of a one-component developer without using a carrier. 
   The two-component developer can be made from a magnetic carrier of which particles have diameters between 20 micrometers and 200 micrometers selected from conventionally known magnetic carriers, for example, iron powder, ferrite powder, magnetite powder, and a magnetic resin carrier. As a covering material for the toner, an amino resin, for example, a urea-formaldehyde resin, a melamine resin, a benzoguanamine resin, a urea resin, a polyamide resin, or an epoxy resin, can be used. Moreover, one of polyvinyl resins or polyvinylidene resins, for example, an acrylic resin, a polymethyl methacrylate resin, a polyacrylonitrile resin, a polyvinyl acetate resin, a polyvinyl alcohol resin, and a polyvinyl butyral resin; a polycarbonate resin, a polyethylene resin, a silicon resin, or the like, can be used. In addition, conductive powder can be included in the covering resin material as required. As the conductive powder, metal powder, carbon black, titanium oxide, tin oxide, zinc oxide, or the like, can be used. 
   The average particle diameter of the conductive powder is preferably one micrometer or smaller. If the average particle diameter is larger than one micrometer, it becomes difficult to control electric resistance. 
   According to the first embodiment, spherical ferrite particles having an average particle diameter of approximately 50 micrometers are used as a core material. A coating material includes an aminosilane coupling agent and a silicone resin, both of which are dispersed in toluene. The dispersion liquid and the core material are charged into a coating device, in which a rotary base-plate disk and stirring blades are arranged in a fluidized bed to perform coating while making a rotational flow, so that the dispersion liquid is applied over particles of the core material. The resultant coated core material is then calcined in an electric furnace at 250° C. for two hours, as a result, carrier particles coated with a silicon resin layer of 0.5 micrometer in average thickness are prepared. An initial developer is made by uniformly mixing and electrically charging 100 wt. parts of the carrier with 7 wt. parts of a toner described in the following examples by using a tumbler mixer, in which contents are stirred by rotating a container. 
   Examples of the toner are explained below. 
   Although toners of respective examples were produced as described below, the present invention is not limited to this. 
   A toner 1 was produced according to the following procedures. 
   A resin microparticle emulsion was synthesized as follows: 683 wt. parts of water, 11 wt. parts of sodium salt of methacrylic acid ethylene oxide adduct sulfate (ELEMINOL RS-30, manufactured by Sanyo Chemical Industries, Ltd.), 83 wt. parts of styrene, 83 wt. parts of methacrylic acid, 110 wt. parts of butyl acrylate, and one part of ammonium persulfate were charged into a reaction vessel equipped with a stirrer and a thermometer; and the contents of the reaction vessel were stirred at 3,800 rpm for 30 minutes; as a result, a white emulsion was obtained. The temperature in the system was heated to 75° C., and the obtained white emulsion was exposed to reaction for four hours. Furthermore, the reaction mixture was added with 30 wt. parts of 1% ammonium persulfate aqueous-solution, and then matured at 75° C. for six hours. As a result, a microparticle emulsion  1  was obtained, which was an aqueous dispersion liquid of a vinyl resin (a copolymer of styrene, methacrylic acid, butyl acrylate, and sodium salt of methacrylic acid ethylene oxide adduct sulfate). Diameters of particles in the microparticle emulsion  1  were measured by a laser scattering particle-size distribution analyzer (LA-920, manufactured by HORIBA, Ltd.). It was 110 nanometers in volume average. Part of the microparticle emulsion  1  was dried, and the resin was isolated. The shape of a resin microparticle was spherical. The glass transition temperature (Tg) of the resin was 58° C., and the weight average molecular weight was 130,000. 
   An aqueous phase was prepared as follows: 990 wt. parts of water, 83 wt. parts of the microparticle emulsion  1 , 37 wt. parts of a 48.3% aqueous solution of sodium dodecyl diphenylether disulfonic acid (ELEMINOL MON-7, manufactured by Sanyo Chemical Industries, Ltd.) and 90 wt. parts of ethyl acetate were mixed and stirred; and then a milky-white liquid was obtained. This is an aqueous phase  1 . 
   A low-molecular-weight polyester was synthesized as follows: 724 wt. parts of bisphenol A ethylene oxide dimolar adduct, and 276 wt. parts of terephthalic acid were charged into a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen inlet tube; the contents of the reaction vessel were exposed to polycondensation under normal pressure at 230° C. for seven hours, and further exposed to reaction under a reduced pressure between 10 mmHg and 15 mmHg for five hours; and then a low-molecular-weight polyester  1  was obtained. Of the low molecular weight polyester  1 , the number average molecular weight was 2,300, the weight average molecular weight was 6,700, the peak molecular weight was 3,800, the Tg was 43° C., and the acid value was four. 
   An intermediate polyester was synthesized as follows: 682 wt. parts of bisphenol A ethylene oxide dimolar adduct, 81 wt. parts of bisphenol A propylene oxide dimolar adduct, 283 wt. parts of terephthalic acid, 22 wt. parts of anhydrous trimellitic acid, and 2 wt. parts of dibutyl tin oxide were charged into a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen inlet tube; the contents of the reaction vessel were exposed to reaction under normal pressure at 230° C. for seven hours, and further exposed to reaction under a reduced pressure between 10 mmHg and 15 mmHg for five hours; and then an intermediate polyester  1  was obtained. Of the intermediate polyester  1 , the number average molecular weight was 2,200, the weight average molecular weight was 9,700, the peak molecular weight was 3,000, the Tg was 54° C., the acid value was 0.5, and the hydroxyl value was 52. In the next step, 410 wt. parts of the intermediate polyester  1 , 89 wt. parts of isohorone diisocyanate, and 500 wt. parts of ethyl acetate, were charged into a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen inlet tube, and exposed to reaction at 100° C. for five hours, and then a prepolymer  1  was obtained. The percent by weight of free isocyanate included in the prepolymer  1  was 1.53%. 
   A ketimine was synthesized as follows: 170 wt. parts of isohorone diamine and 75 wt. parts of methyl ethyl ketone were charged into a reaction vessel equipped with a stirrer and a thermometer; the contents of the reaction vessel were exposed to reaction at 50° C. for four and a half hours; and then a ketimine compound  1  was obtained. The amine value of the ketimine compound  1  was 417. 
   A masterbatch was synthesized as follows: 1,200 wt. parts of water, 540 wt. parts of carbon black (Printex 35, manufactured by Degussa AG) (dibutyl phthalate (DBP) oil absorption=42 ml/100 mg, pH=9.5), and 1,200 wt. parts of polyester resin were added and mixed in a Henschel mixer (manufactured by MITSUI MINING Co., Ltd.); the mixture was then kneaded at 130° C. for an hour by using two rollers, cooled by flatting, ground with a pulverizer; so that a masterbatch  1  was obtained. 
   An oil phase was prepared as follows: 378 wt. parts of the low-molecular-weight polyester  1 , 100 wt. parts of carnauba wax, and 947 wt. parts of ethyl acetate were charged into a vessel equipped with a stirrer and a thermometer; and the contents of the vessel were heated to 80° C. while stirring, maintained at 80° C. for five hours, and then cooled to 30° C. in an hour. 
   In the next step, 500 wt. parts of the masterbatch  1  and 500 wt. parts of ethyl acetate were charged into a vessel, and mixed for an hour, as a result, a material solution  1  was obtained. In to another vessel, 1,324 wt. parts of the material solution  1  was poured, and carbon black and wax were dispersed by using a bead mill (Ultra Visco Mill, manufactured by AIMEX Co., Ltd.) under the following conditions: at liquid feed rate of 1 kg/hr, at disk circumferential velocity of 6 m/sec, with 0.5 millimeter zirconia beads filled to 80% by volume, and trough three passes. In the next step, 1,324 wt. parts of 65% ethyl acetate solution of the low-molecular-weight polyester  1  was added, and then dispersed through two passes by the bead mill under the conditions, as a result, a pigment-and-wax dispersion liquid  1  was obtained. The solids concentration of the pigment-and-wax dispersion liquid  1  was 50%. 
   The liquid was emulsified and a solvent was removed as follows: 749 wt. parts of the pigment-and-wax dispersion liquid  1 , 115 wt. parts of the prepolymer  1 , and 2.9 wt. parts of the ketimine compound  1  were charged into a vessel; the contents of the vessel were mixed at 5,000 rpm for two minutes by a TK homomixer (manufactured by TOKUSHU KIKA KOGYO Co., Ltd.); 1,200 wt. parts of the aqueous phase  1  was added into the vessel; and then the contents of the vessel were mixed by the TK homomixer at 13,000 rpm for 25 minutes; as a result, an emulsion slurry  1  was obtained. 
   The emulsion slurry  1  was charged into a vessel equipped with a stirrer and a thermometer, then the solvent was removed at 30° C. for seven hours, and the residue was matured at 45° C. for seven hours, as a result, a dispersion slurry  1  was obtained. 
   Rinsing and drying were carried out as follows. After 100 wt. parts of the dispersion slurry  1  was filtered under reduced pressure;
     (1) the filter cake was added with 100 wt. parts of ion-exchanged water, mixed in the TK homomixer (at 12,000 rpm for 10 minutes), and then filtered;   (2) the filter cake obtained at the step (1) was added with 1% hydrochloric acid by controlling the pH between 3.5 and 4.5, and mixed in the TK homomixer (at 12,000 rpm for 15 minutes), and then filtered;   (3) a series of operations of adding 300 wt. parts of ion-exchanged water to the filter cake obtained at the step (2), mixing them in the TK homomixer (at 12,000 rpm for 10 minutes), and filtering the mixture, was repeated twice, as a result, a filter cake  1  was obtained; and   (4) the filter cake  1  was dried in an air-circulating dryer at 40° C. for 40 hours, and then sifted through a sieve with 75 micrometer mesh, as a result, toner base-particles  1  were obtained. After that, 1,100 wt. parts of the toner base-particles  1  was added with 1.5 wt. parts of hydrophobic silica and 0.5 wt. part of hydrophobized titanium oxide, and all of them were mixed in the Henschel mixer, and then sifted through a sieve with 35 micrometer mesh, as a result the toner 1 was obtained. Physical properties of the toner 1 are shown in the table 1.   

   
     
       
         
             
             
             
           
             
                 
               TABLE 1 
             
           
          
             
                 
                 
             
             
                 
               Toner particle 
                 
             
             
                 
               diameter 
             
          
         
         
             
             
             
             
             
             
          
             
                 
               Volume 
                 
                 
                 
                 
             
             
                 
               particle 
                 
               Average 
               Shape factor 
             
          
         
         
             
             
             
             
             
             
          
             
                 
               diameter 
               Dv/Dn 
               circularity 
               SF-1 
               SF-2 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
             
          
             
               Toner 1 
               3.5 
               1.34 
               0.998 
               105 
               102 
             
             
               Toner 2 
               4.8 
               1.14 
               0.961 
               120 
               115 
             
             
               Toner 3 
               2.4 
               1.14 
               0.985 
               141 
               135 
             
             
               Toner 4 
               5.9 
               1.13 
               0.933 
               159 
               150 
             
             
               Toner 5 
               5.5 
               1.22 
               0.921 
               170 
               180 
             
             
               Toner 6 
               5.7 
               1.46 
               0.937 
               148 
               138 
             
             
               Toner 7 
               7.2 
               1.22 
               0.975 
               176 
               160 
             
             
               Toner 8 
               8.0 
               1.24 
               0.948 
               185 
               190 
             
             
                 
             
          
         
       
     
   
   A toner 2 was produced similarly to the toner 1 except the following conditions changed as described below. 
   Physical properties of the toner 2 are shown in the table 1. 
   A resin microparticle emulsion was synthesized as follows: 683 wt. parts of water, 11 wt. parts of sodium salt of methacrylic acid ethylene oxide adduct sulfate (ELEMINOL RS-30, manufactured by Sanyo Chemical Industries, Ltd.), 83 wt. parts of styrene, 83 wt. parts of methacrylic acid, 110 wt. parts of butyl acrylate, and one part of ammonium persulfate were charged into a reaction vessel equipped with a stirrer and a thermometer; the contents of the vessel were stirred at 3,800 rpm for 30 minutes; as a result, a white emulsion was obtained. The temperature in the system was raised to 75° C. by heating up, and the obtained white emulsion was exposed to reaction for an hours. Furthermore, the reaction mixture was added with 30 wt. parts of 1% ammonium persulfate aqueous-solution, and then matured at 75° C. for six hours. As a result, a microparticle emulsion  2  was obtained, which was an aqueous dispersion liquid of a vinyl resin (a copolymer of styrene, methacrylic acid, butyl acrylate, and sodium salt of methacrylic acid ethylene oxide adduct sulfate). Diameters of particles in the microparticle emulsion  2  were measured by a laser scattering particle-size distribution analyzer (LA-920, manufactured by SYSMEX Corp.). It was 40 nanometers in volume average. Part of the microparticle emulsion  2  was dried, and the resin was isolated. The shape of a resin microparticle was spherical. The Tg of the resin was 56° C., and the weight average molecular weight was 120,000. 
   A toner 3 was produced similarly to the toner 1 except the following conditions changed as described below. 
   Physical properties of the toner 3 are shown in the table 1. 
   The liquid was emulsified and the solvent was removed as follows: 749 wt. parts of the pigment-and-wax dispersion liquid  1 , 115 wt. parts of the prepolymer  1 , and 2.9 wt. parts of the ketimine compound  1  were charged into a vessel; the contents of the vessel were mixed at 5,000 rpm for two minutes by the TK homomixer; 1,200 wt. parts of the aqueous phase  1  was added into the vessel; and then the contents of the vessel were mixed by the TK homomixer at 13,000 rpm for 10 minutes; as a result, an emulsion slurry  2  was obtained. 
   The emulsion slurry  2  was charged into a vessel equipped with a stirrer and a thermometer, then the solvent was removed at 30° C. for six hours, and the residue was matured at 45° C. for five hours, as a result, a dispersion slurry  2  was obtained. 
   The toner 4 was produced similarly to the toner 1 except the following conditions changed as described below. 
   Physical properties of the toner 4 are shown in the table 1. 
   The liquid was emulsified and the solvent was removed as follows: 749 wt. parts of the pigment-and-wax dispersion liquid  1 , 115 wt. parts of the prepolymer  1 , and 2.9 wt. parts of the ketimine compound  1  were charged into a vessel; the contents of the vessel were mixed at 5,000 rpm for two minutes by the TK homomixer; 1,200 wt. parts of the aqueous phase  1  was added into the vessel; and then the contents of the vessel were mixed by the TK homomixer at 13,000 rpm for 40 minutes; as a result, an emulsion slurry  3  was obtained. 
   The emulsion slurry  3  was charged into a vessel equipped with a stirrer and a thermometer, then the solvent was removed at 30° C. for eight hours, and the residue was matured at 45° C. for five hours, as a result, a dispersion slurry  3  was obtained. 
   A toner 5 was produced similarly to the toner 1 except the following conditions changed as described below. 
   Physical properties of the toner 5 are shown in the table 1. 
   An oil phase was prepared as follows: 378 wt. parts of the low-molecular-weight polyester  1 , 130 wt. parts of carnauba-rice wax (weight ratio of five to five), and 947 wt. parts of ethyl acetate were charged into a vessel equipped with a stirrer and a thermometer, heated to 80° C. while stirring, maintained at 80° C. for four hours, and then cooled to 30° C. in an hour. In the next step, 500 wt. parts of the masterbatch  1  and 500 wt. parts of ethyl acetate were charged into a vessel, and mixed for two hours, as a result, a material solution  2  was obtained. 
   In to another vessel, 1,324 wt. parts of the material solution  2  was poured, and carbon black and wax were dispersed by using the bead mill under the following conditions: at liquid feed rate of 1 kg/hr, at disk circumferential velocity of 6 m/sec, with 0.5 millimeter zirconia beads filled to 80% by volume, and trough ten passes. In the next step, 1,324 wt. parts of 65% ethyl acetate solution of the low-molecular-weight polyester  1  was added, and then dispersed through five passes by the bead mill under the conditions, as a result, a pigment-and-wax dispersion liquid  2  was obtained. 
   The solids concentration of the pigment-and-wax dispersion liquid  2  was 50%. 
   The toner 6 was produced similarly to the toner 1 except the following conditions changed as described below. 
   Physical properties of the toner 6 are shown in the table 1. 
   An oil phase was prepared as follows: 378 wt. parts of the low-molecular-weight polyester  1 , 100 wt. parts of carnauba-rice wax (weight ratio of three to seven), and 947 wt. parts of ethyl acetate were charged into a vessel equipped with a stirrer and a thermometer, heated to 80° C. while stirring, maintained at 80° C. for four hours, and then cooled to 30° C. in an hour. In the next step, 500 wt. parts of the masterbatch  1  and 500 wt. parts of ethyl acetate were charged into a vessel, and mixed for 0.8 hour, as a result, a material solution  3  was obtained. 
   In to another vessel, 1,324 wt. parts of the material solution  3  was poured, and carbon black and wax were dispersed by using a bead mill (Ultra Visco Mill, manufactured by AIMEX Co., Ltd.) under the following conditions: at liquid feed rate of 1 kg/hr, at disk circumferential velocity of 6 m/sec, with 0.5 millimeter zirconia beads filled to 80% by volume, and trough five passes. In the next step, 1,324 wt. parts of 65% ethyl acetate solution of the low-molecular-weight polyester  1  was added, and then dispersed through three passes by the bead mill under the conditions, as a result, a pigment-and-wax dispersion liquid  3  was obtained. The solids concentration of the pigment-and-wax dispersion liquid  3  was 50%. 
   The toner 7 was produced similarly to the toner 1 except the following conditions changed as described below. 
   Physical properties of the toner 7 are shown in the table 1. 
   A low-molecular-weight polyester was synthesized as follows: 229 wt. parts of bisphenol A ethylene oxide dimolar adduct, 529 wt. parts of bisphenol A propylene oxide trimolar adduct, 208 wt. parts of terephthalic acid, 46 wt. parts of adipic acid, and 2 wt. parts of dibutyl tin oxide were charged into a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen inlet tube; the mixture were exposed to reaction under normal pressure at 230° C. for seven hours, and further exposed to reaction under a reduced pressure between 10 mmHg and 15 mmHg for five hours; subsequently 44 wt. parts of trimellitic anhydride was added into the reaction vessel, and the mixture was exposed to reaction at 180° C. under normal pressure for three hours; and then a low-molecular-weight polyester  2  was obtained. Of the low molecular weight polyester  2 , the number average molecular weight was 2,300, the weight average molecular weight was 6,700, the peak molecular weight was 3,100, the Tg was 43° C., and the acid value was 25. 
   In a vessel equipped with a stirrer and a thermometer, 378 wt. parts of the low-molecular-weight polyester  2 , 100 wt. parts of carnauba wax, and 947 wt. parts of ethyl acetate were charged, heated to 80° C. while stirring, maintained at 80° C. for five hours, and then cooled to 30° C. in an hour. In the next step, 500 wt. parts of the masterbatch  1  and 500 wt. parts of ethyl acetate were charged into a vessel, and mixed for an hour, as a result, a material solution  4  was obtained. 
   In to another vessel, 1,324 wt. parts of the material solution  4  was poured, and carbon black and wax were dispersed by using a bead mill (Ultra Visco Mill, manufactured by AIMEX Co., Ltd.) under the following conditions: at liquid feed rate of 1 kg/hr, at disk circumferential velocity of 6 m/sec, with 0.5 millimeter zirconia beads filled to 80% by volume, and trough three passes. In the next step, 1,324 wt. parts of 65% ethyl acetate solution of the low-molecular-weight polyester  2  was added, and then dispersed through three passes by the bead mill under the conditions, as a result, a pigment-and-wax dispersion liquid  4  was obtained. The solids concentration of the pigment-and-wax dispersion liquid  4  was 50%. 
   In a vessel, 749 wt. parts of the pigment-and-wax dispersion liquid  4 , 115 wt. parts of the prepolymer  1 , and 2.9 wt. parts of the ketimine compound  1  were charged, and mixed at 5,000 rpm for two minutes by a TK homomixer (manufactured by TOKUSHU KIKA KOGYO Co., Ltd.), then added with 1,200 wt. parts of the aqueous phase  1  into the vessel, and mixed by the TK homomixer at 13,000 rpm for 40 minutes, as a result, an emulsion slurry  4  was obtained. 
   The emulsion slurry  4  was charged into a vessel equipped with a stirrer and a thermometer, then the solvent was removed at 30° C. for eight hours, and the residue was matured at 45° C. for five hours, as a result, a dispersion slurry  4  was obtained. 
   A toner 8 was produced similarly to the toner 1 except the following conditions changed as described below. 
   Physical properties of the toner 8 are shown in the table 1. 
   Into a vessel equipped with a stirrer and a thermometer, 378 wt. parts of the low-molecular-weight polyester  1 , 380 wt. parts of carnauba wax, and 947 wt. parts of ethyl acetate were charged, heated to 80° C. while stirring, maintained at 80° C. for five hours, and then cooled to 30° C. in four hours. In the next step, 500 wt. parts of the masterbatch  1  and 500 wt. parts of ethyl acetate were charged into a vessel, and mixed for two hours, as a result, a material solution  5  was obtained. 
   Into another vessel, 1,324 wt. parts of the material solution  5  was poured, and carbon black and wax were dispersed by using a bead mill (Ultra Visco Mill, manufactured by AIMEX Co., Ltd.) under the following conditions: at liquid feed rate of 1 kg/hr, at disk circumferential velocity of 6 m/sec, with 0.5 millimeter zirconia beads filled to 80% by volume, and trough seven passes. In the next step, 1,324 wt. parts of 65% ethyl acetate solution of the low-molecular-weight polyester  1  was added, and then dispersed through four passes by the bead mill under the conditions, as a result, a pigment-and-wax dispersion liquid  5  was obtained. The solids concentration of the pigment-and-wax dispersion liquid  5  was 50%. 
   After each of the toners in the examples was prepared as a developer, the toner was charged into the printer  100  according to the first embodiment, and then comparative experiments between the cleaning device  30  according to the first embodiment and the conventional apparatus were carried out by performing the following initial running tests. 
   In this case, the conventional apparatus was the cleaning device of the counter type shown in  FIG. 17B . The blade material was made from polyurethane rubber at 70 degrees JIS A-hardness. The blade had dimensions of T 1  is 2.0 millimeters, and T 3  is 326 millimeters, and a rectangular parallelepiped shape. The blade was bonded to the blade holder with a double-sided tape. The blade length extending to the photoconductor surface from the blade holder (free length L) was 7.6 millimeters. The contact angle θ was set to 21.6 degrees, and the amount of bite was 1.0 millimeter. The linear pressure was 0.788 N/cm. An organic photoconductor was used as the photoconductor  10 . 
   The running tests were carried out by the printer  100 , by replacing only the cleaning device  30  with the conventional apparatus. In the running tests, a pattern on A4 size at an image area rate of 5% was continuously printed, and a removal performance (cleaning performance) was evaluated at the starting time, the 5,000th sheet, and the 10,000th sheet. However, when a toner was visually evaluated as poor in the total evaluation, the initial running test for the toner is terminated. 
   When evaluating cleaning performance; after a pattern at an image area rate of 75% was continuously printed for 100 sheets, toner remaining on the photoconductor after going through the cleaning device was transferred with Printac C Tape (manufactured by NITTO DENKO Co., Ltd.); and the tape was stuck on white paper, and measured by Macbeth reflection densitometer RD514. The results were evaluated as follows: a difference from the blank density less than 0.005 was “excellent”, a difference between 0.005 and 0.010 was “good”, a difference between 0.011 and 0.02 was “passable”, and a difference more than 0.02 was “poor”. 
   The visual total evaluation was performed as follows: 
   Excellent: Capable in practical use. No abnormal noise, such as flapping. No toner particle passing through. Even if there were some, those were not able to be observed by a method of transferring dirt onto a tape and determining a degree of dirt on the tape stuck on white paper with naked eyes. 
   Good: Adequate for practical use. No abnormal noise. No stripe, or only thin stripes. Passing through toner particles were observed. 
   Passable: There was a possibility of rejection in practical use. Some indication of abnormal noise. There were one to ten stripes less than one millimeter in width on an image of A4 landscape size. 
   Poor: Incapable in practical use. Abnormal noise and signs of damage on the photoconductor were observed. There were strips across the whole surface. 
   The results of the running tests are as shown in the following table 2. 
   
     
       
         
             
             
             
           
             
                 
               TABLE 2 
             
           
          
             
                 
                 
             
             
                 
               Cleaning 
                 
             
             
                 
               performance evaluation 
               Total Evaluation (Visual) 
             
          
         
         
             
             
             
             
             
             
             
          
             
                 
                 
               5,000th 
               10,000th 
                 
               5,000th 
               10,000th 
             
             
                 
               Start 
               sheet 
               sheet 
               Start 
               sheet 
               sheet 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
             
             
             
          
             
               Toner 1 
               Conventional 
               Poor 
               — 
               — 
               Poor 
               — 
               — 
             
             
                 
               apparatus 
             
             
                 
               Embodiment 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
               Toner 2 
               Conventional 
               Good 
               Passable 
               Poor 
               Passable 
               Passable 
               Poor 
             
             
                 
               apparatus 
             
             
                 
               Embodiment 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
               Toner 3 
               Conventional 
               Poor 
               — 
               — 
               Poor 
               — 
               — 
             
             
                 
               apparatus 
             
             
                 
               Embodiment 
               Excellent 
               Excellent 
               Good 
               Excellent 
               Good 
               Good 
             
             
                 
               apparatus 
             
             
               Toner 4 
               Conventional 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
                 
               Embodiment 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
               Toner 5 
               Conventional 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
                 
               Embodiment 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
               Toner 6 
               Conventional 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
                 
               Embodiment 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
               Toner 7 
               Conventional 
               Passable 
               Poor 
               — 
               Passable 
               Poor 
               — 
             
             
                 
               apparatus 
             
             
                 
               Embodiment 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
               Toner 8 
               Conventional 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
                 
               Embodiment 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
               Excellent 
             
             
                 
               apparatus 
             
             
                 
             
          
         
       
     
   
   The conventional apparatus had a poorer cleaning performance for a toner having the particle diameter of three micrometers or less, or a toner having the average circularity of 0.96 or higher. Particularly, where the average circularity was up to 0.96, and the toner diameter was approximately six micrometers, there was a large difference in the cleaning performances. Although there was no abnormal noise from the blade, and no sign of damage on the photoconductor, strips were observed. Therefore, it was predicted that if the running test was further extended, wear on the blade and the photoconductor would occur. 
   By contrast, in a case where the cleaning device  30  is used, there was no sign of deterioration of the cleaning performance, abnormal noise from the blade, and damage on the photoconductor, using any toner. However, when using the toner 3, a phenomenon of passing through of toner particles was observed, although the cleaning performance is still better than that by the conventional apparatus. Not obvious strip, but a sign of strips was observed, so that it was predicted that if a toner particle diameter was approximately three micrometers or less, substantial effect would not be expected even to the cleaning device  30 . Combinations with further toner characteristics, such as distribution of particle diameters, and variations of physical properties, would be required. 
   The running tests were carried out in a process of the initial running test, to compare differences in physical properties of toners. There is a further possibility that further differences will be revealed by carrying out a long-term deterioration mode or a running mode added with environmental variations. 
   The cleaning device  30  according to the first embodiment can make the contact width short, while maintaining the contact pressure as high as that in the cleaning device of the conventional counter type, thereby reducing wear on the photoconductor  10  and the blade  31 . Flapping of the blade  31  hardly occur easily. 
   The cleaning device  30  according to the modification can reduce wear on the blade  31  further effectively. According to the first embodiment, the blade  31  has no free length part, so that warp in the blade  31  can be effectively restricted. 
   According to the first embodiment, because the horizontal portion  32 A of the blade holder  32  is bonded to the whole of the opposed surface of the upstream side surface  31   a  of the blade  31 , adhesion between the horizontal portion  32 A of the blade holder  32  and the blade  31  is firm, thereby preventing the blade from flapping effectively. 
   As bonding is performed at least on a marginal area close to the surface of the photoconductor  10  from across an overlapping area where the horizontal portion  32 A and the opposed surface of the upstream side surface  31   a  overlap one another, flapping of the blade  31  can be prevented effectively. 
   Because of the springs  36  provided as a force assistance, even if a distance relation between the frame  33  and the surface of the photoconductor  10  is changed, for example, due to eccentricity of the photoconductor  10 , the blade holder  32  can be displaced in accordance with the change, so that a high precision is required neither for the distance relation between the frame  33  and the surface of the photoconductor  10 , nor for assembling the blade  31  to the photoconductor  10 . 
   According to the first embodiment, the blade  31  is configured to have the contact angle θ between 5 degrees and 50 degrees, thereby achieving a sufficient removal performance (cleaning performance) easily. 
   Although the cleaning device  30  for a photoconductor is explained above in the first embodiment, the first embodiment can be applied to a cleaning device for a surface moving member in any image forming apparatus, as well as the printer  100 . For example, the first embodiment can be applied to a monochrome image forming apparatus, and an image forming apparatus that includes a photoconductor and a plurality of developing devices (for example, for four colors), toner images of the respective colors are produced by rotating the developing devices, and then an image is formed finally by transferring the toner images onto transfer paper. Not only for a printer, the first embodiment can be used as a cleaning device for a photocopier, a facsimile, or a multifunctional peripheral having a plurality of functions. Regardless of an electrophotography type, an ink jet type, or another type, as long as an image forming apparatus includes a surface moving member and requires to remove deposit remaining on the surface of the surface moving member, the first embodiment can be applied to the image forming apparatus. Deposit to be removed can be toner, paper powder, metal powder, and any other powdery substance, and even a liquid, such as a developer, so that the first embodiment can be similarly applied. 
   In addition to the cleaning device for the photoconductor, the first embodiment can be applied to a cleaning device for removing deposit, such as residual toner, reaming on the surface on a surface moving member other than the photoconductor, e.g., the intermediate transfer belt  162 . Moreover, the first embodiment can be applied to a cleaning device for removing deposit, such as toner or paper powder, attached on a recording material conveyor member that supports and conveys a recording material on its surface. The first embodiment can be applied to a cleaning device for any surface moving member that requires to remove deposit attached on its surface. The surface moving member can be drum, a belt, or in any other shape, of which member surface moves. When the cleaning device is used for the surface moving member of a belt, generally the cleaning device is arranged to catch the belt between the blade and a supporting roller that supports the belt. However, a backup member, such as a flat plate member, can be arranged on the internal side of the belt, and the cleaning device can be arranged to catch the belt between the blade and the backup member. When a target to be cleaned is the photoconductor  10 , the cleaning device according to the first embodiment can be applied for any photoconductor, which can be an organic photoconductor, an amorphous silicon photoconductor, or a photoconductor of which a protective layer made from a binder resin having a crosslinked structure is provided on an organic photoconductor surface. When a target to be cleaned is the intermediate transfer belt  162 , the cleaning device according to the first embodiment can be applied for any intermediate transfer belt, which can be an intermediate transfer belt made form polyimides considering heat resistance and strechability, an intermediate transfer belt using polyethylene materials, or an intermediate transfer belt made of fluoric materials and rubber materials. 
   In the various applications explained above, the configuration of the cleaning device  30  for a photoconductor explained in the first embodiment can be used without substantial change, or a configuration that is appropriately modified in accordance with each of the application can be used. 
   Another cleaning device according to a second embodiment of the present invention, which is different from the cleaning device described above, is explained below. 
     FIG. 9  is a schematic diagram for explaining relevant parts of the cleaning device  30  viewed from the rotation axis direction (y axis direction) of the photoconductor  10  according to the second embodiment. 
     FIG. 10  is a schematic diagram for explaining an outline configuration of a process cartridge according to the second embodiment to be provided in the printer shown in  FIG. 2 . 
   Configurations of a plurality of the process cartridges to be arranged for forming an image are substantially similar to one another, so that a configuration and an operation of one of the process cartridges is explained in the following explanation without attached characters Y, C, M, and Bk for distinguishing between the process cartridges in terms of color. 
   The process cartridge  121  includes the photoconductor  10 , and the cleaning device  30 , the electric charger  40 , and the developing device  50 , three of which are arranged around the photoconductor  10 . 
   The cleaning device  30  includes the blade  31  that is an elastic member used longitudinally extending along the rotation axis direction of the photoconductor  10 . The cleaning device  30  removes unwanted deposit, such as transfer residual toner on a photoconductor surface, by pressing a longitudinally extending edge (contact edge) of the blade  31  onto the surface of the photoconductor  10 . According to the second embodiment, polyurethane rubber is used as a material of the blade  31 , because polyurethane rubber has more excellent characteristics for wear properties of the photoconductor  10  and in wear resistance of the blade  31  itself than other elastic materials. The cleaning device  30  will be explained in detail later. 
   A lubricant applicator can be provided in the cleaning device  30 . Particularly in the second embodiment, using a so-called spherical toner, the blade  31  needs to clean the spherical toner, so that the blade  31  is pressed to contact with the photoconductor  10  by applying a high load. For this reason, blade wear and coat scrape on the photoconductor  10  are increased. By applying lubricant over the surface of the photoconductor  10 , wear on the blade  31  and coat scrape on the photoconductor  10  can be reduced. When the photoconductor  10  is electrostatically charged by the electric charger  40 , which uses an electrostatic discharge as described later, the photoconductor surface is gradually reformed due to the electrostatic discharge, and a surface energy is increased. In such case, a cleaning failure occurs more often. However, by applying lubricant, reforming of the photoconductor surface is suppressed, so that the quality of cleaning spherical toner can be maintained over the elapse of time. 
   As the lubricant applicator, a device that includes a solid lubricant, a lubricant supporting member for supporting the solid lubricant, and a brush roller for applying the lubricant by rotating in contact with both the solid lubricant and the photoconductor  10 , can be used. Such lubricant applicator applies powdery lubricant with the brush roller scraped by the brush roller from the solid lubricant onto the surface of the photoconductor  10 . Alternatively, a spreading member can be arranged downstream of the brush roller in the photoconductor-surface moving direction to be in contact with the surface of the photoconductor  10 . The spreading member is supported by keeping the tip of the spreading member in contact with the surface of the photoconductor  10 , for making uniform the thickness of lubricant applied on the photoconductor  10 . As the spreading member, an elastic solid, such as a urethane rubber blade, or an elastic roller is made in contact with the photoconductor  10  at an appropriate pressure. In another example of the lubricant applicator, a pocket for powdery lubricant is arranged on the opposite side of the surface of the photoconductor  10 , and the powdery lubricant is fed onto the surface of the photoconductor  10 . 
   Although an application position of the lubricant can be arranged upstream of the contact point of the blade  31  in the surface moving direction of the photoconductor  10 , the lubricant may be removed together with toner that is removed by the blade  31 , so that there is a possibility that a coat of the lubricant may not be uniformly formed over the photoconductor surface. For this reason, the application position of the lubricant is preferably arranged downstream of the contact point of the blade  31  and upstream of the electric charger  40 . In such case, the lubricant can be applied uniformly, because the lubricant is to be applied on the photoconductor surface from which toner has been removed. 
   As the lubricant, a lamella crystal powder, such as zinc stearate can be preferably used. Lamella crystals have a layer structure of self-organization of amphipathic molecules, so that the lamella crystals are easily broken along interlamellar boundaries when a shearing force is applied, and easily turn to lubricate a surface. It is considered that the action is effective on lowering a friction coefficient. Other materials, such as fatty acid salts, waxes, silicone oils, can also be used as the lubricant. Specific examples of the fatty acids include undecylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachic acid, montanic acid, oleic acid, arachidonic acid, caprylic acid, capric acid, and caproic acid. Specific examples of metals of metallic salts for the fatty acids include zinc, iron, copper, magnesium, aluminum, and calcium. 
   The electric charger  40  includes the charging roller  41  arranged to come in contact with the photoconductor  10 , and the charging roller cleaner  42  rotates in contact with the charging roller  41 . 
   The developing device  50  is configured to produce a visible image from an electrostatic latent image by feeding toner onto the surface of the photoconductor  10 , and includes the developing roller  51 , the stirring screw  52 , and the feeding screw  53 . The developing roller  51  is a developer bearing member that bears a developer on its surface. The stirring screw  52  stirs a developer contained in a developer container unit. The feeding screw  53  feeds the stirred developer onto the developing roller  51 . 
   Each of the four of the process cartridges  121  configured as described above can be individually demounted and replaced by a service person or a user. In the process cartridge  121  demounted from the printer  100 , any of the photoconductor  10 , the electric charger  40 , the developing device  50 , and the cleaning device  30  can be individually replaced with a new one. The process cartridge  121  can include a used toner tank that collects transfer residual toner collected by the cleaning device  30 . In such case, if the process cartridge  121  includes the used toner tank in a configuration such that the used toner tank can be individually demounted and replaced, the convenience is enhanced. 
     FIG. 11  is a perspective view of relevant parts of the cleaning device  30  according to the second embodiment. 
   In the second embodiment, the cleaning device  30  includes the blade holder  32  that holds the blade  31 , and is made of a rigid material. The blade holder  32  has a substantially L-shaped cross section that is cut orthogonally to the rotation axis of the photoconductor  10 . The blade  31  is bonded on the upper surface of the horizontal portion  32 A of the blade holder  32 , where the horizontal portion  32 A is a portion extending along a substantially horizontal direction in  FIG. 3 , and the upper surface is a surface facing upstream in the photoconductor-surface moving direction). A method of bonding can be adhesive bonding, hot melt, or the like. According to the second embodiment, the horizontal portion  32 A functions as a warp restrictive member to restrict a warp in the blade  3 . 
   The blade holder  32  includes the vertical portion  32 B, which vertically extends in  FIG. 10 . A bottom side (portion downstream in the photoconductor-surface moving direction) of the vertical portion  32 B is supported by a blade bracket  38  to be slidable in the substantially vertical direction. A bottom end of the blade bracket  38  (extremity downstream in the photoconductor-surface moving direction) is pivotally supported by the shaft  34  provided on the frame  33  of the cleaning device  30 . According to the second embodiment, the blade  31  is held via the horizontal portion  32 A with the vertical portion  32 B of the blade holder  32  and the blade bracket  38 , which is supported downstream of a normal line N in the photoconductor-surface moving direction by the shaft  34  on the frame  33  of the cleaning device  30 , that is, supported by the main body of the cleaning device  30 , where the normal line N is normal to the contact pint P on the surface of the photoconductor  10  in contact with the contact edge of the blade  31 . In other words, the cleaning device  30  is a counter type, and the vertical portion  32 B of the blade holder  32  and the blade bracket  38  function as a holding mechanism. 
   Compression springs  39  are arranged as an elastic-force applying unit between the upper end of the blade bracket  38  (end portion upstream in the photoconductor-surface moving direction) and the horizontal portion  32 A. Between the upper end of the blade bracket  38  and the horizontal portion  32 A, a force works in directions to separate each other by the elastic force of the compression springs  39 . As the bottom end of the blade bracket  38  is supported by the shaft  34  on the frame  33 , the blade bracket  38  is configured not to be vertically displaced. Thus, the horizontal portion  32 A of the blade holder  32  is vertically assisted with the elastic force of the compression springs  39 . With the elastic force, the blade  31  can come in contact with the surface of the photoconductor  10  from an angle θ (hereinafter “contact angle”) of approximately 15 degrees formed between an upstream side part in the photoconductor-surface moving direction of the downstream side surface  31   b  and a downstream side part in the surface moving direction of the tangent line M to the contact point P on the surface of the photoconductor  10  when the blade  31  is not pressed on the surface of the photoconductor  10 , as shown in  FIG. 9 . The contact angle θ is appropriately set within a range between 5 degrees and 50 degrees. It is difficult to set the contact angle θ to less than 5 degree due to the layout around the photoconductor  10 . If the contact angle θ is set to more than 50 degrees, a possibility that a sufficient removal performance may not be obtained is increased. More preferably, the contact angle θ is set within a range between 7 degrees and 40 degrees. 
   As shown in  FIG. 11 , to apply the elastic force onto a plurality of points, three points positioned differently from each other along the longitudinal direction of the blade  31  according to the second embodiment, three of the compression springs  39  are provided. Accordingly, even if the elastic force of each of the compression springs  39  is relatively small, a sufficient elastic force can be obtained. 
   In addition, the cleaning device  30  includes the springs  36  as a force assistance unit, which enhances a pressing force applied by the blade  31  in the direction of the normal line N to the contact point P on the surface of the photoconductor  10 . According to the second embodiment, two of the springs  36  are provided, each of which is arranged at a distance of 110 millimeters from the center in the longitudinal direction of the blade  31  (the photoconductor rotation-axis direction) towards a longitudinal end. An end of the spring  36  is connected to an end of the horizontal portion  32 A, the other end of the spring  36  is connected to the adjustive screw  37 , which is an elastic-force adjustment unit. The adjustive screw  37  is engaged in a screw hole arranged in the frame  33  of the cleaning device  30 . When adjusting the pressing force by using the adjustive screw  37 , an adjusting stick is inserted through a notched hole from the outside of the frame  33  of the cleaning device  30 , and the length of the spring  36  is adjusted by turning the adjustive screw  37  with the adjusting stick. 
   Adjustment of the pressing force of the blade  31  to the surface of the photoconductor  10  is explained below. 
     FIG. 12  is a schematic diagram for explaining the measuring device  200  for a pressing force of the blade  31 . In practice, the measuring device  200  can be a commercially available conditioner for sensor, WGA-710B (manufactured by KYOWA DENGYO Co., Ltd.), and a load cell, LMA-A-2-N (manufactured by KYOWA DENGYO Co., Ltd.), which can be used in combination with the conditioner. The measuring device  200  includes three of the load cells  201 . The load cells  201  are fastened on the cell mount  202 , which is in a semicylindrical shape, at three points in total: one is at the center in the longitudinal direction of the blade  31 ; and the other two in a distance of 140 millimeters from the center towards respective longitudinal ends. The jigs  203  are placed on the load cells  201 . The jigs  203  have a curved surface having the same curvature radius as the photoconductor  10 . The jigs  203  are arranged three in line along the longitudinal direction of the blade  31 , each of the load cells  201  is set at the center of the bottom surface of each of the jigs  203 . 
   The blade  31  is set on the measuring device  200  such that a positional relation with the jigs  203  is to be the same as that with the photoconductor  10 . 
   When adjusting the pressing force of the blade  31  by using the measuring device  200 , the measuring device  200 , instead of the photoconductor  10 , is mounted onto the process cartridge  121  in a state where the cleaning device  30  is assembled in the printer  100 . Specifically, by using a supporting unit to support a driving shaft of the photoconductor  10 , the cell mount  202  on which three of the load cells  201  are fastened, and three of the jigs  203  are mounted on the process cartridge  121 . When mounting, the cell mount  202  and the jigs  203  are set such that a virtual line between the contact edge of the blade  31  and each of the load cells  201  is to become perpendicular to the bottom surface of each of the jigs  203 . A load applied via each of the jigs  203  is then detected by each of the load cells  201 , and the pressing force of the blade  31  is adjusted by regulating the adjustive screw  37 , while watching a value displayed on the sensor conditioner  204  connected to the measuring device  200 . 
   When measuring, a predetermined weight needs to be placed on each of the jigs  203  in advance, and the adjustive screws  37  has to be set in such a manner that each value displayed on the sensor conditioner  204  is to be the same, and the value displayed on the sensor conditioner  204  is to be such a value that a load applied by the jig  203  is cancelled. 
   When adjusting a load balance to make the pressing force of the blade  31  uniform in the longitudinal direction of the blade  31 , according to the second embodiment, the load balance is adjusted by turning the adjustive screws  37  such that differentials of values of the load cells  201  displayed on the sensor conditioner  204  are to fall within a margin of plus or minus 10 grams. 
   When adjusting the pressing force of the blade  31 , it is fundamentally necessary to adjust the contact pressure between the blade  31  and the surface of the photoconductor  10  to be a target value. However, a contact width (nip width) between the blade  31  and the surface of the photoconductor  10  is difficult to measure. Therefore, the pressing force is generally adjusted in such a manner that a linear pressure is to be a target value. The linear pressure means a pressure applied on a contact point between the blade  31  and the surface of the photoconductor  10  per unit length in the photoconductor rotation-axis direction. Specifically, a linear pressure (N/cm) is a value obtained by dividing the total load of summing values of the load cells  201  displayed on the sensor conditioner  204  by a length T 3  of the blade  31  in the longitudinal direction. 
   As a warp in the blade  31  is the larger, the contact width between the blade  31  and the surface of the photoconductor  10  is the longer, and moreover, as a deformation in the blade  31  is the larger, the contact width is the longer. In the cleaning device  30  according to the second embodiment, a warp in the blade  31  is restricted with the horizontal portion  32 A as described above, so that the warp in the blade  31  hardly occurs. Consequently, the warp can be ignored when comparing with a warp in a blade of the cleaning device of the conventional counter type shown in  FIG. 17B . Therefore, in the cleaning device  30  according to the second embodiment, the contact width mainly only depends on elastic deformation (compressive deformation) of the blade  31  in the photoconductor-surface moving direction. Thus, the cleaning device  30  according to the second embodiment can make the contact width shorter than that in the cleaning device of the conventional counter type shown in  FIG. 17B . Accordingly, even if pressing the blade  31  with a linear pressure as high as that applied by the cleaning device of the conventional counter type, a contact pressure generated by the linear pressure is higher than that in the cleaning device of the conventional counter type. Conversely, to obtain a contact pressure as high as that in the cleaning device of the conventional counter type, the cleaning device  30  requires a smaller pressing force of the blade  31  than the cleaning device of the conventional counter type. The contact width in the second embodiment is expected to be substantially shorter than that in the cleaning device of the conventional counter type. Based on the expectation, it is conceivable that a substantially lower linear pressure than that generated in the cleaning device of the conventional counter type can achieve a contact pressure as high as that in the cleaning device of the conventional counter, and the similar removal performance. 
   The force assistance unit, such as the springs  36 , is not necessarily to be provided, so that the end of the horizontal portion  32 A can be connected to the frame  33  without such force assistance unit. However, in such case, when the vertical portion  32 B of the blade holder  32  slides relatively to the blade bracket  38 , the end of the horizontal portion  32 A of the blade holder  32  needs to be displaced to the sliding direction in relation to the frame  33 . 
   In the second embodiment, the elastic force generated by three of the compression springs  39  that form the elastic-force applying unit is preferably set to an elastic force as high as the compression springs  39  can contract, when a friction force smaller than the maximum static friction force is generated between the blade  31  and the surface of the photoconductor  10 . Accordingly, when the blade  31  receives a large force towards the shaft  34  due to the maximum static friction force generated between the blade  31  and the surface of the photoconductor  10  during the period of starting operation of the photoconductor  10 , the compression springs  39  contract, the blade  31  slides together with the blade holder  32  relatively to the blade bracket  38 , and the blade  31  can be displaced towards the direction away from the surface of the photoconductor  10 . Consequently, in the period of starting operation of the photoconductor  10 , during which the contact pressure between the blade  31  and the surface of the photoconductor  10  tends to increase excessively, the contact pressure can be released, and excessive increase in the contact pressure can be suppressed. 
   The elastic force generated by three of the compression springs  39  is preferably set in such a manner that the maximum displacement of the blade  31  when receiving from the photoconductor  10  a force towards downstream in the photoconductor-surface moving direction is to be less than or equal to five millimeters. If the blade  31  is configured to be displaced substantially largely, there is a possibility that the contact angle θ of the blade  31  can be widened beyond a predetermined range. If the contact angle θ of the blade  31  is widened and becomes too large beyond a predetermined range, the regular contact pressure is increased. As a result, there is a possibility that the surface of the photoconductor  10  may be worn heavily, or the regular operational load onto the photoconductor  10  is increased. 
   However, even if the elastic force generated by three of the compression springs  39  is set in such a manner that the maximum displacement of the blade  31  is to be less than or equal to five millimeters, it is conceivable that the blade  31  is displaced by beyond five millimeters due to an unexpected sudden increase in the friction force. If the blade  31  is displaced to the direction that the compression springs  39  contract, the blade  31  turns around the shaft  34  with assistant force applied by the springs  36 , and the contact point P on the photoconductor surface shifts downstream in the photoconductor-surface moving direction. If the amount of displacement of the blade  31  is small, the contact point P can return to the initial point with the elastic force of the compression springs  39 . However, if the amount of displacement of the blade  31  is large, there is a possibility that the contact point P cannot return to the initial point only with the elastic force of the compression springs  39 . The reason for this is because as the amount of displacement of the blade  31  is the larger, the amount of shifting the contact point P on the photoconductor surface in the photoconductor-surface moving direction is the larger. Accordingly, the contact angle θ is increased, and a force component in the direction of the normal to the contact point P in the elastic force of the compression springs  39  is increased, thus increasing the friction force. 
   Therefore, a displacement restrictive unit is preferably provided, which restricts an upper limit of the displacement amount of the cleaning device  30  when receiving a force towards downstream in the photoconductor-surface moving direction from the photoconductor  10 , in order to ensure that the contact edge can return to the initial point, even if an unexpected sudden increase in the friction force occurs. For example, a stopper provided on the frame  33  to be in contact with the horizontal portion  32 A of the blade holder  32  can be the displacement restrictive unit. 
   In the second embodiment, the blade  31  is in the shape of a rectangular parallelepiped longitudinally extending in the photoconductor rotation-axis direction (y axis direction). Lengths T 1  and T 2  (see  FIG. 11 ) of two surfaces, i.e., the upstream side surface  31   a  and the downstream side surface  31   b , respectively, are lengths orthogonal to the contact edge on the two surfaces  31   a  and  31   b , which adjoin each other with respect to the contact edge as shown in  FIG. 9 . The length T 2  is formed longer than the length T 1 . Instead of such rectangular parallelepiped, the blade  31  can take any three-dimensional shape that has the two surfaces  31   a  and  31   b  adjoining each other with respect to the contact edge, and allows the blade  31  to satisfactorily remove deposit on the photoconductor surface along the photoconductor rotation-axis direction. Each of the outer surfaces of the blade  31  is not necessarily flat, but can also be curved. 
   The shorter length of the blade  31  along a direction of compressive deformation caused by moving the surface of the photoconductor  10  results in the smaller extent of elastic deformation due to the compressive deformation. A length of the blade  31  in the compression direction is approximately equivalent to the length T 2  of the downstream side surface  31   b  in the photoconductor-surface moving direction. In  FIG. 17B , when measuring a length of each surface of the cleaning blade  231  in a direction orthogonal to the contact edge on a corresponding surface, a length T 1  is a length of an upstream side surface  231   a , and a length T 2  is a length of the downstream side surface  231   b . Comparing the length T 2  according to the second embodiment with the length T 2  in the cleaning device of the conventional counter type shown in  FIG. 17B , the former is much shorter than the latter. Consequently, at least comparing the extents of elastic deformations, the cleaning device  30  would have less deformation than the cleaning device of the conventional counter type. For this reason, it is obvious that the contact width in the cleaning device  30  according to the second embodiment is shorter than that in the cleaning device of the conventional counter type. 
   When using the blade  31  in the shape of a rectangular parallelepiped similarly to the second embodiment, the lengths T 1 , T 2 , and T 3  of the edges of the rectangular parallelepiped are preferably configured to satisfy T 3 &gt;T 1 ≧T 2 . More preferably, T 2  is not less than one millimeter, and not more than T 1 . If it is less than one millimeter, an unusual noise occurs more easily. If a pressure-relieving elastic material is used for the blade  31 , or a material with a high degree in JIS A-hardness is selected, a wider preferable range of the lengths can be expected. The lengths of the blade  31  according to the second embodiment are as follows: T 1  is 12 millimeters, T 2  is 4 millimeters, and T 3  is 325 millimeters; however, the lengths are not limited to this. 
   The blade  31  according to the second embodiment uses polyurethane rubber that has JIS A-hardness 75 degree, as a material. The material and hardness of the blade  31  are not limited to this, and can be appropriately changed. If a pressure-relieving elastic material, specifically, an elastic member having an impact resilience of 30% or less at 23° C. is used for the blade  31 , stick-slip movement is reduced, so that the pressure-relieving elastic material is favorable. There are two reasons for the impact resilience to be 30% or less as described below. One is because less vibration of the blade  31  at the contact edge is better to clean spherical toner. Another is because low impact resilience is preferred for wear on the blade  31 . Conventionally, when cleaning grinded toner, some blades have an effect that toner particles are hit away by touching the contact edge of a blade. Accordingly, there is a problem that the hitting-away effect does not work sufficiently at a low rate of impact resilience. However, when cleaning spherical toner particles, the particles go through the blade before the blade hits them, so that the hitting-away effect does not work. In a case where a blade has high impact resilience, if the contact edge of the blade easily vibrates to the photoconductor  10 , the high impact resilience encourages spherical toner particles to go through the blade. On the other hand, the lower impact resilience is more advantageous for wear on the blade  31 . On repeated image forming processes, a blade gradually wears out due to rubbing with a photoconductor. A mechanism of wear is considered that the stick-slip movement of the blade causes tear and fatigue breakdown on polymer molecules (for example, polyurethane rubber) forming the blade  31 ; as a result, wear occurs. In such case, part of the contact edge of the blade is cut, and toner particles go through there. By contrast, if the blade has an low impact resilience, the stick-slip movement of the blade is reduced. Accordingly, even after repeated operation processes, an accumulated number of times of vibration at the top edge of the blade is fewer than a high impact resilience blade, thus reducing fatigue breakdown. As a result, even after the image forming process is repeated, wear on the blade  31  does not advance, so that the cleaning performance is to be maintained for long time. 
   The blade holder  32  according to the second embodiment is made from a metal material mainly containing iron, which has a sufficient rigidity to suppress a warp satisfactorily, even if the blade  31  receives a force from the photoconductor  10  while the photoconductor  10  is rotating in operation. 
   In the second embodiment, the whole of the opposed surface of the upstream side surface  31   a  of the blade  31  is bonded to the horizontal portion  32 A of the blade holder  32 , as shown in  FIG. 11 . A bonding method other than the adhesive bonding employed in the second embodiment, such as bonding with double-faced adhesive tape, or hot melt, can be employed. Thus, according to the second embodiment, even if the photoconductor  10  is rotated while the blade  31  is pressed onto the surface of the photoconductor  10 , a substantial warp in the blade  31  does not occurs. 
   Accordingly, robustness against environmental variation is improved. More specifically, in a configuration that a warp in a blade may occur, e.g., when a free length of the blade is long, a force caused by the warp in the blade changes depending on humidity. For example, if a warped blade is left as it is in a hot and humid environment, the blade is plastically deformed, and a permanent set occurs. In such case, the contact pressure of the blade onto the surface of the photoconductor  10  is decreased, and a cleaning performance is depreciated. Thus, there is a possibility that a cleaning failure may occur. By contrast, in the second embodiment where a substantial warp in the blade  31  hardly occurs, robustness against environmental variation is improved. 
   Occurrence of a warp in a blade means that the blade has a flexibility that allows the blade to warp. If the flexibility of the blade is large, in a case of the counter type, a blade turnup, which is a serious problem, easily occurs, when a friction force between the blade and the photoconductor surface increases. In the second embodiment where a substantial warp in the blade  31  hardly occurs, a blade turnup is prevented. 
   Furthermore, starting torque of the photoconductor  10  can be reduced. Specifically, as described above, if a blade warps, this means that the blade has a flexibility that allows the blade to warp. Due to a large friction force during the period of starting operation of the photoconductor, if the blade has a large flexibility, the blade is largely deformed in a moment, and torque is increased. By contrast, the blade  31  has substantially no warp according to the second embodiment, so that starting torque of the photoconductor  10  can be reduced. 
   According to the second embodiment, an end of the horizontal portion  32 A facing the surface of the photoconductor  10 , i.e., the end of the horizontal portion  32 A coupled to the vertical portion  32 B, is arranged at the same position as a border edge between the opposed surface (bonding surface) of the upstream side surface  31   a  and the downstream side surface  31   b , as shown in  FIG. 9 . However, even if the end of the horizontal portion  32 A is arranged to extend closer to the surface of the photoconductor  10  than the border edge of the blade  31 , a substantial warp in the blade  31  hardly occurs, similarly to the first embodiment. 
   Alternatively, the end of the horizontal portion  32 A does not need to be extended until the border edge of the blade  31 . As long as a warp in the blade  31  can be virtually restricted, the end of the horizontal portion  32 A does not need to reach the border edge. In other words, if a warp in the blade  31  is virtually restricted, the end of the horizontal portion  32 A can be more distant from the photoconductor surface than the border edge. In such case, to what extent the end of the horizontal portion  32 A can keep an additional distance from the photoconductor surface relative to the border edge is determined depending on hardness of the blade  31 , a friction coefficient between the blade  31  and the surface of the photoconductor  10 , and the like. An allowable range of the distance can be, e.g., as a guidepost for determination, a distance according to which a resultant length (contact width) of a contact point in the photoconductor-surface moving direction is to be not more than 50 micrometers, when pressing the blade  31  onto the surface of the photoconductor  10  to apply a linear pressure of 0.790 N/cm. It is estimated that up to a quarter of the length T 2  of the downstream side surface  31   b  can be allowable as a distance between the end of the horizontal portion  32 A and the border edge. Furthermore, there is a possibility that a range from a half of T 2  up to the almost same level as T 2  can be allowable. 
   Moreover, the blade  31  can be bonded to the horizontal portion  32 A of the blade holder  32  by applying adhesive to only part of the bonding surface of the blade  31 . However, it is desirable that bonding is performed at least on a marginal area close to the surface of the photoconductor  10  from across an overlapping area where the horizontal portion  32 A and the opposed surface (bonding surface) of the upstream side surface  31   a  overlap one another. As the horizontal portion  32 A of the blade holder  32  and the blade  31  are securely bonded in the end area, flapping of the blade  31  can be stably prevented, even if a friction force between the blade  31  and the photoconductor surface is changed for some reasons while the photoconductor is rotating in operation. This is the same to other bonding methods. 
   Thus, according to the second embodiment, when the blade  31  receives a force toward downstream in the photoconductor-surface moving direction, the whole of the blade  31  can be displaced away from the surface of the photoconductor  10 . Accordingly, when the contact pressure is set to a relatively high level to obtain an excellent removal performance, even if a friction force between the blade  31  and the surface of the photoconductor  10  is increased during operation of the photoconductor  10 , and the contact edge of the photoconductor  10  is displaced downstream in the photoconductor-surface moving direction, the blade  31  can escape away from the surface of the photoconductor  10 . Thus, the maximum friction force arising from a change in the friction force between the blade  31  and the surface of the photoconductor  10  during operation of the photoconductor  10  is smaller than that in the conventional counter type. As a result, a frequency of giving an excessive operational load onto the photoconductor  10  is reduced. 
   Particularly, according to the second embodiment, the length of the blade  31  in the compression direction is shorter than that in the conventional counter type. Suppose the whole of the blade  31  were not configured capable to be displaced away from the surface of the photoconductor  10 . When a large friction force occurs between the blade  31  and the surface of the photoconductor  10  during operation of the photoconductor  10  so that the blade receives a large force towards the shaft  34 , a margin in which the blade  31  can be compressed and deformed by the received force is narrower than that in the conventional counter type. A contact pressure generated between the blade  31  and the surface of the photoconductor  10  would be higher than that in the conventional counter type, thereby causing a high frequency of giving an excessive operational load onto the photoconductor  10 . For this reason, the configuration according to the second embodiment in which the whole of the blade can be displaced away from the surface of the photoconductor  10 , and a resultant reduction in the frequency of giving an excessive operational load onto the photoconductor  10 , are effective in the configuration that the length of the blade  31  in the compression direction is short. 
   The blade  31  can be arranged based on the configuration of the conventional counter type as shown in  FIG. 13  in which the whole of the blade  31  can be displaced away from the surface of the photoconductor  10  when receiving a force towards downstream in the photoconductor-surface moving direction. In such configuration, the frequency of giving an excessive operational load onto the photoconductor  10  can be reduced, and an occurrence frequency of a blade turnup can be reduced. The blade  31  shown in  FIG. 13  has the length T 1  of two millimeters on the upstream side surface  31   a , and the length T 2  of 14 millimeters on the downstream side surface  31   b , and 70 degrees of JIS A-hardness. 
   Alternatively, the blade  31  and the blade holder  32  can be configured in such a manner that the contact edge of the blade  31  can swing around a virtual axis tilted towards upstream of the normal line N in the photoconductor-surface moving direction, where the normal line N is normal to the contact point P on the surface of the photoconductor  10 . Specifically, for example, as shown in  FIG. 14 , a rotation shaft  32 C is provided on the vertical portion  32 B of the blade holder  32 , and a long hole  38 A is provided on the blade bracket  38  for the rotation shaft  32 C to be inserted, so that the contact edge of the blade  31  can swing around the rotation shaft  32 C. Thus, even if the contact edge of the blade  31  is tilted due to a poor adhesion of the blade  31  to the blade holder  32 , such tilt can be adjusted automatically. In such configuration, the compression spring  39  can be arranged at one position corresponding to the center of the blade  31  in the longitudinal direction, but also can be arranged at a plurality of points as shown in  FIG. 14 . Thus, the attitude of the blade  31  can be stably maintained. Moreover, such configuration can control displacement of the rotation shaft  32 C with inner walls of the long hole  38 A, thereby providing the same function as the displacement control unit described above. 
   The photoconductor  10  to be used in the printer according to the second embodiment is explained below. 
   To clean spherical toner, a larger load needs to be applied than that applied on the blade  31  when cleaning a conventional grinded toner. As a result, wear on the photoconductor  10  advances faster than in the conventional case, improvement in wear resistance of the photoconductor  10  is desired. An example of the photoconductor  10  used in the second embodiment is described below. 
     FIG. 15  is a side view of an example of the photoconductor  10  according to the second embodiment. 
   The photoconductor  10  used in the second embodiment is an organic photoconductor of negative charge, and includes an electroconductive base  500  that has the shape of drum of 30 millimeters in diameter, on which layers, such as a photosensitive layer, is provided. The electroconductive base  500  is a base layer, on which a base coating layer  510  that is an insulating layer is provided. On the base coating layer  510 , a charge generation layer  520 , and a charge transport layer  530  are provided. Furthermore, on the charge transport layer  530 , a protective layer  540  for the surface is layered. 
   As the electroconductive base  500 , a base made from a material showing electroconductivity of volume resistance 10 10  Ω·cm or less can be used. For example, the following materials can be used: a film sheet or a cylinder of plastic or paper coated with a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, or the like, or a metal oxide such as tin oxide, indium oxide, or the like, by evaporation or sputtering; a plate of aluminum, aluminum alloy, nickel, stainless, or the like; or a pipe obtained by forming a crude pipe from the plate by extruding or drawing followed by surface treatment such as cutting, super finishing, polishing or the like. An endless nickel belt and endless stainless belt disclosed in Japanese Patent Application Laid-Open No. S52-36016 can also be used for the electroconductive base  500 . 
   In addition to this, a base coated with an electroconductive powder dispersed in an appropriate binder resin can also be used as the electroconductive base  500 . Such electroconductive powders include carbon black, acetylene black, metal powder of aluminum, nickel, iron, nichrome, copper, zinc, silver, and the like, and metal oxide powder such as electroconductive tin oxide, indium tin oxide (ITO), and the like. The binder resins to be used with the electroconductive powder include thermoplastic, thermosetting resins, and photo-curing resins, such as polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, polyvinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyacrylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenolic resin, alkyd resin, and the like. Such electroconductive layer can be formed by applying a coating liquid in which an electroconductive powder and a binder resin are dispersed in an appropriate solvent, such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, toluene, or the like. Furthermore, an appropriate cylindrical base on which an electroconductive layer is formed using a thermally contractive tube made from a material, such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, TEFLON (registered trademark), or the like, added with the electroconductive powder, can also be favorably used as the electroconductive base  500 . 
   The photosensitive layer is explained below. 
   The photosensitive layer can be either a single layer, or a laminated layer. For convenience of explanation, a case of a laminated-layer configuration including a charge generation layer and a charge transport layer is explained below at first. 
   The charge generation layer  520  includes a charge generation material as a main component. Known charge generation materials can be used for the charge generation layer  520 . Typical materials include monoazo pigment, bisazo pigment, trisazo pigment, perylene pigment, perinone pigment, quinacridone pigment, quinone polycondensed compound, squaric acid dyes, other phthalocyanine pigments, naphthalocyanine pigment, and azulenenium dyes. The charge generation materials can be used alone or in combination. 
   The charge generation substance(s), together with a binder resin as required, are dispersed in an appropriate solvent by using a ball mill, an attritor, a sand mill, or ultrasonic wave, the obtained product is applied on the electroconductive base  500  or the base coating layer  510 , and then dried, so that the charge generation layer  520  is formed. 
   For the charge generation layer  520 , the charge generation materials can be dispersed in a binder resin as required. Suitable binder resins, which can be included in the charge generation layer  520 , include polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, poly-N-vinylcarbazole, polyacrylamide, polyvinyl benzene, polyester, phenoxy resin, polyvinyl-chloride/acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, and polyvinyl pyrrolidone. An appropriate amount of the binder resin is between 0 wt. part and 500 wt. parts per 100 wt. parts of the charge generation material, preferably between 10 wt. parts and 300 wt. parts. Addition of the binder resin can be either before or after dispersion. As a solvent to be used here, isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, or ligroin can be used. Particularly, a ketone solvent, an ester solvent, or an ether solvent is preferably used. The solvents can be used alone or in combination. 
   The charge generation layer  520  include a charge generation material, a solvent, and a binder resin, as main components, each of which can contain any additive, such as sensitizers, dispersants, surfactants and silicone oils. 
   As a coating method for an application liquid, dip coating, spray coating, bead coating, nozzle coating, spinner coating, ring coating, or the like, can be used. The appropriate thickness of the charge generation layer  520  is approximately between 0.01 micrometer and 5 micrometers, preferably between 0.1 micrometer and 2 micrometers. 
   The charge transport layer  530  can be formed by dissolving or dispersing a charge transport material and a binder resin in an appropriate solvent, applying the resultant solution on the charge generation layer  520 , and drying. In addition to this, one or more of a plasticizer, a leveling agent, an antioxidant, and the like, can be added. 
   The charge transport materials include positive hole transport materials and electron transport materials. The electron transport materials include electron accepting materials, such as chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno[1,2,-b]thiophene-4-on, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, benzoquinone derivative, and the like. 
   The positive hole transport materials include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensate and derivatives thereof, polyvinyl pyrene, polyvinyl phenanthrene, polysilane, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazoline derivatives, divinyl benzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, bisstilbene derivatives, enamine derivatives, and other known materials. These charge transport materials can be used alone or in combination of two or more. 
   The binder resins include thermoplastic and thermosetting resins, such as polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, polyvinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinlydene chloride, polyarate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenolic resin, alkyd resin, and the like. 
   The appropriate amount of the charge transport material is between 20 wt. parts and 300 wt. parts per 100 wt. parts of the binder resin, preferably between 40 wt. parts and 150 wt. parts. The thickness of the charge transport layer  530  is preferably less than or equal to 25 micrometers, in light of resolutions and responsiveness. The lower limit of the thickness is preferably more than or equal to five micrometers, although it depends on a system to be used (particularly, depending on charge potential). The solvents used herein include tetrahydrofurane, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexane, methyl ethyl ketone, acetone, and the like. The solvents can be used alone or in combination of two or more. 
   A case of the photosensitive layer has a single-layer configuration is explained below. 
   The photosensitive layer is formed by dissolving or dispersing the charge generation material, the charge transport material, and the binder resin into an appropriate solvent, and applying the resultant solution on the electroconductive base  500  or the base coating layer  510 , and then drying. The photosensitive layer can be formed only from the charge generation material and the binder resin, without containing the charge transport material. Furthermore, a plasticizer, a leveling agent, an antioxidant, and the like, can be added as required. 
   In addition to the binder resins listed in the description of the charge transport layer  530 , the binder resins listed in the description of the charge generation layer  520  can be used by mixing. The high-molecular charge transport materials described above can also be used. The amount of the charge generation material per 100 wt. parts of the binder resin is preferably between 5 wt. parts and 40 wt. parts, and the amount of the charge transport material is preferably between 0 part and 190 wt. parts, more preferably between 50 wt. parts and 150 wt. parts. 
   The photosensitive layer can be formed by applying a coating solution that the charge generation material, the binder resin, and the charge transport material are dispersed by a dispersing machine into a solvent, such as tetrahydrofuran, dioxane, dichloroethane, cyclohexane, or the like, by dipping coating, spray coating, bead coating, ring coating, or the like. The appropriate thickness of the photosensitive layer is between 5 micrometers and 25 micrometers. 
   On the photoconductor  10  according to the second embodiment, the base coating layer  510  can be provided between the electroconductive base  500  and the photosensitive layer. Generally, a base coating layer includes a resin as a main component. The resin desirably has high resistance to general organic solvents, in light of use of a solvent for applying the photoconductive layer onto the resin. Such resins include a water-soluble resin, such as polyvinyl alcohol, casein, and sodium polyacrylate; an alcohol-soluble resin, such as copolymerized nylon and methoxy methylated nylon; a thermosetting resin forming a three-dimensional network structure, such as polyurethane, melamine resin, phenolic resin, alkyd-melamine resin, and epoxy resin. In addition, a fine powdery pigment of a metal oxide, such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, or indium oxide, can be added to the base coating layer  510  for prevention of moire, reduction of residual potential, and the like. The base coating layer  510  can be formed using a suitable solvent and an appropriate coating method similarly to the photosensitive layer described above. As the base coating layer  510 , a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like, can be used. Moreover, for the base coating layer  510 , a substance having Al 2 O 3  provided by anodic oxidation, or a substance having organics, such as polypropylenes (parylene), or inorganics such as SiO 2 , SnO 2 , TiO 2 , ITO, CeO 2 , and the like, provided by a vacuum thin film forming method, can also be favorably used. Other known substances can also be used as well as the above. 
   The appropriate thickness of the base coating layer  510  is between 0 micrometer and 5 micrometers. 
   To prevent wear on mechanics, the protective layer  540  can be provided on the top layer of the photoconductor  10 . For example, a photoconductor surface-coated with amorphous silicon to enhance wear resistance, or an organic photoconductor on which a top surface layer containing dispersed alumina or tin is provided further over the charge transport layer  530 . 
   The configuration of the photoconductor  10  that can be used in the embodiments is not limited to a particular configuration. The embodiments according to the present invention can be applied to photoconductors having various layer-configurations: a single-layer configuration in which only a photosensitive layer mainly including a charge generation material and a charge transport material is provided on an electroconductive base; a configuration in which a charge generation layer mainly including a charge generation material and a charge transport layer mainly including a charge transport material are layered on the electroconductive base; a configuration in which a photosensitive layer mainly including a charge generation material and a charge transport material is provided on the electroconductive base, and a protective layer is further provided on the photosensitive layer; a configuration in which a charge generation layer mainly including a charge generation material and a charge transport layer mainly including a charge transport material are layered on the electroconductive base, and a protective layer is further provided on the charge transport layer; and a configuration in which a charge transport layer mainly including a charge transport material and a charge generation layer mainly including a charge generation material are layered on the electroconductive base, and a protective layer is further provided on the charge generation layer. 
   As a binder configuration of the protective layer, a protective layer having a crosslinked structure is effectively used. To form a crosslinked structure, using a reactive monomer that has a plurality of crosslinked functional groups within a molecule, a crosslinking reaction is generated with light and heat energy, and a three-dimensional network structure is to be formed. The network structure functions as the binder resin, and realizes excellent wear resistance. In light of electrical stability, printing endurance, and life duration, an entire or partial use of a monomer having a charge transport force as the reactive monomer is effective. By using such monomer, a charge transport area is formed in the network structure, so that functions as the protective layer can be expressed sufficiently. Reactive monomers having the charge transport force include a compound that contains at least one each of charge transportable components and atoms of silicon having a hydrolytic substituent within a molecule, a compound that contains a charge transportable component and a hydroxyl group within a molecule, a compound that contains a charge transportable component and a carboxyl group within a molecule, a compound that contains a charge transportable component and an epoxy group within a molecule, a compound that contains a charge transportable component and an isocyanate group within a molecule, and the like. Charge transportable materials having the reactive groups can be used alone or in combination of two or more. More preferably, a reactive monomer having a triarylamine structure is effectively used, because the triarylamine structure has a high electrical stability and a high chemical stability as a monomer having a charge transport force, and the carrier has a high mobility. In addition, for the purpose of giving functions, such as viscosity control during application process, stress relaxation of a crosslinkage charge transport layer, lowering surface energy, and friction coefficient reduction, monofunctional and difunctional polymerization monomer and polymerization can be used in conjunction with the other materials. Known polymerization monomers or oligomers can be used. According to the embodiments of the present invention, polymerization or crosslinkage of a positive hole transport compound is performed thermally or by photoirradiation. When thermally polymerizing, in a case, polymerization is advanced only with thermal energy, by contrast, a polymerization initiator is required for polymerization in the other case. To advance the reaction at a lower temperature more efficiently, the use of a polymerization initiator is preferred. When photopolymerizing, ultraviolet rays are preferably used. However, polymerization is hardly advanced only with light energy, so that a photopolymerization initiator is generally used in conjunction with the other materials. In such case, the polymerization initiator mainly absorbs ultraviolet rays less than or equal to 400 nanometers, generates activated species, such as free radical or ion, and starts polymerization. Heat and the photopolymerization initiator can be used together. The charge transport layer having the network structure in this way has an excellent wear resistance, on the other hand, has large volume shrinkage during crosslinking reaction, so that an excessively thick coating may cause a crack. In such case, the protective layer can a layered structure, a protective layer made from a low-molecular-weight dispersion polymer is used for a lower layer (photosensitive layer side), and a protective layer having a crosslinked structure can be formed on an upper layer (surface side). 
   For an example of the photoconductor  10 , 182 wt. parts of methyltrimethoxysilane, 40 wt. parts of dihydroxymethyl triphenylamine, 225 wt. parts of 2-propanol, 106 wt. parts of 2% acetic acid, and 1 part of aluminum trisacetylacetonate are mixed, and then a coating liquid for protection is prepared. The coating liquid is applied on a charge transport layer, and dried. The resultant layer is then thermoset at 110° C. for an hour, so that a protective layer having a thickness of 3 micrometers is formed. 
   Another example of the protective layer is as follows. A surface protective layer coating liquid is prepared by dissolving 30 wt. parts of positive hole transport material, and 0.6 wt. parts of an acrylic monomer and a photopolymerization (1-hydroxy-cyclohexyl-phenyl-ketone), into a mix solvent of 50 wt. parts of monochlorobenzene and 50 wt. parts of dichloromethane. The coating liquid was applied on the charge transport layer by a spray coating method. The coated layer is then cured by being exposed to light emitted by a metal halide lamp with the intensity of 500 mW/cm 2  for 30 seconds. As a result, a surface protective layer of five micrometers in thickness is prepared. 
   The electric charger  40  to be used in the printer according to the second embodiment is explained below. 
   Conventionally, there is an electric charger by the corona charging method of charging up with corona discharge. According to the corona charging method, a charging wire is arranged in the vicinity of a charge target; corona discharge is generated between the charging wire and the charge target by applying a high voltage to the charging wire; and then the charge target is charged. However, in a case of the corona charging method, some discharge by-products, such as ozone and nitrogen oxide are produced along with the corona discharge. Because the discharge by-products may form a coat of nitric acid or nitrate, its production should be avoided, if possible. Recently, instead of the corona charging method, developments of a contact electrification method and a proximity electrification method are actively proceeding, which cause less discharge by-products and can perform electrification with low force. By the methods, a charging member, such as a roller, a brush, or a blade, is placed to face a charge target in contact or in proximity, and applied with a voltage, so that the surface of a charge target is charged. According to the methods, less discharge by-products and electrification with low force than the corona charging method can be achieved, thus making the methods be effective. Moreover, the methods do not require large charging equipment, so that a device can be reduced in size, which satisfies a need for miniaturization of equipment. For this reason, in the second embodiment, an example of the electric charger  40  using a non-contact roller charging method is described below, as an example of an electric charger that achieves reduction in power consumption, reduction in hazardous substances, and the need for miniaturization. 
   When using spherical toner, a cleaning failure tends to occur often than when using conventional grinded toner. Even if the cleaning failure occurs by any chance due to the configuration capable of blade cleaning of spherical toner, the non-contact roller charging method does not allow the electric charger to reach residual toner caused by the cleaning failure, so that there is an advantage that no erroneous image caused by irregular charge is created. The electric charger  40  charges a photoconductor by alternating-current application discharge using the charging roller  41 , which is a charging member arranged not in contact with but in proximity to the photoconductor. 
   Alternatively, there is another method according to which a photoconductor is charged by the alternating-current application discharged with a charging member arranged in contact with the photoconductor. If using the method, it is preferable that contact between the photoconductor surface and the charging member is to be improved, and an elastic member that does not apply any mechanical stress onto the photoconductor is to be used. However, if using the elastic member, a charging nip width is widened, consequently a charging roller may turns to deposit a protective material more easily. Therefore, to apply a greater durability to a charge target, a non-contact charging method is more advantageous. 
     FIG. 16  is a schematic diagram for explaining the electric charger  40  according to the second embodiment, viewed from the direction orthogonal to the rotation-axis direction of the photoconductor  10 . 
   The electric charger  40  includes the charging roller  41 , spacers  43 , springs  44 , and a power source  45 . The charging roller  41  includes a shaft  41   a  and a roller  41   b . The roller  41   b  is opposed to the photoconductor  10 , and responsible for charging the photoconductor surface, and configured to rotate by rotation of the shaft  41   a . The spacers  43  are space keeping members. To arrange a charge area on the surface of the roller  41   b  on the opposite side of the photoconductor surface with very small gap, the spacers  43  are provided on the charging roller  41 . From across the surface of the photoconductor  10 , an area facing an image forming area in which an image is to be formed is arranged not in contact with the photoconductor  10  by the spacers  43 . The longitudinal dimension (in the photoconductor rotation-axis direction) of the roller  41   b  is set longer than that of the image forming area on the photoconductor  10 . The spacers  43  are set in contact with no-image forming areas on the photoconductor  10 , so that a very small gap G is formed. The charging roller  41  is configured to rotate in conjunction with the photoconductor surface via the spacer  43 . The very small gap G is configured in such a manner that a distance at the closest point between the roller  41   b  and the photoconductor  10  is to be between 1 micrometer and 100 micrometers. More preferably, the closest distance is between 30 micrometers and 65 micrometers. In the second embodiment, the very small gap G is set to 50 micrometers. 
   The springs  44  are mounted on the shaft  41   a  for pressing the charging roller  41  towards the surface of the photoconductor  10 . The springs  44  ensures the electric charger  40  to maintain the very small gap G precisely. The charging roller  41  is connected to the power source  45 , and uniformly charges the surface of the photoconductor  10  by the alternating-current application discharge in the very small gap G. According to the second embodiment, an alternating voltage that a volt alternating current of an alternating current component is superposed on a volt direct current of a direct current component is applied to the roller  41   b  of the charging roller  41 . By using the alternating voltage, influences, such as variations in charged potential due to instability of the very small gap G, are suppressed, so that the photoconductor surface can be uniformly charged. 
   The charging roller  41  includes a cored bar as an electroconductive base in a cylindrical shape, and a resistance control layer formed on a circumferential surface of the cored bar. In the second embodiment, the diameter of the charging roller  41  is 10 millimeters. The surface of the charging roller  41  can be made from a known material, such as a rubber member, more preferably, a resin material. The reason for this is because a rubber member may absorb water, and deflect or warp, so that it turns difficult to maintain the very small gap G. Depending on an image forming condition, there is a possibility that only the central part of the charging roller  41  suddenly contacts the photoconductor surface. It is difficult to cope with irregularity in the photoconductor surface layer caused by such local and sudden contact of the charging roller  41  with the photoconductor  10 . If charging the photoconductor by the non-contact charging method, more preferably a rigid material is used in such a manner that the very small gap G can be maintained uniform between the charging roller  41  and the photoconductor  10 . 
   For forming the surface layer of the charging roller  41  from a rigid material, e.g., the following materials can be used. The resistance control layer is formed from thermo plastic resin constitutions, such as polyethylene, polypropylene, methyl polymethacrylate, polystyrene, and copolymer thereof, and the surface of the resistance control layer is hardened with a hardening agent. Coating hardening can be performed by dipping the resistance control layer in a treatment solution containing an isocyanate compound. Alternatively, another hardening coat layer can be additionally formed on the surface of the resistance control layer. 
   Details of toner to be used in the printer according to the second embodiment are the same as described above, so that explanation for it is omitted. 
   As described above, the cleaning device  30  according to the second embodiment can reduce the frequency of occurrence of blade turnup and the frequency of giving an excessive load onto operation of the photoconductor  10 , even when a high contact pressure is set to obtain an excellent removal performance. 
   Particularly, to apply the blade  31  an elastic force towards the opposite direction to the direction away from the surface of the photoconductor  10 , units that apply such elastic force generated by spring is used, that is the compression springs  39 , thereby achieving a simple configuration. 
   As shown in  FIG. 14 , if the contact edge of the blade  31  is tilted with respect to the photoconductor rotation-axis direction, the tilt can be automatically adjusted, because the contact edge of the blade  31  can swing around the rotation shaft  32 C. 
   In this case, the elastic force applied by the compression springs  39  has a force component in the direction of pressing the blade  31  onto the surface of the photoconductor  10  towards upstream in the photoconductor-surface moving direction. As the compression springs  39  apply the elastic force individually to a plurality of points different each other along the longitudinal direction of the blade  31 , the attitude of the blade  31  can be stably maintained. 
   In the period of starting operation of the photoconductor  10 , during which the contact pressure between the blade  31  and the photoconductor  10  tends to increase excessively, the contact pressure can be released, and excessive increase in the contact pressure can be suppressed. 
   The contact angle θ of the blade  31  can be prevented from widening beyond a predetermined range. As a result, the regular contact pressure is prevented from being increased, thereby avoiding heavy wear on the surface of the photoconductor  10 , and increase in the regular operational load onto the photoconductor  10 . 
   The cleaning device  30  can achieve a sufficiently high contact pressure. 
   If the friction force is suddenly increased unexpectedly, the contact edge of the blade  31  can return to the contact point P. 
   In the cleaning device  30 , wear on the blade  31  is suppressed. 
   The cleaning device  30  can make the contact width short, while maintaining the contact pressure as high as that in the cleaning device of the conventional counter type, thereby achieving a high contact pressure. 
   The blade  31  in the cleaning device  30  has no free length part, so that warp in the blade  31  can be effectively restricted. 
   In the second embodiment, a lubricant applying unit that feeds a lubricant onto the surface of the photoconductor  10  can be provided. 
   Although the cleaning device  30  for a photoconductor is explained above in the second embodiment, the second embodiment can be applied to a cleaning device for a surface moving member in any image forming apparatus, as well as the printer  100  according to the second embodiment. For example, the second embodiment can be applied to a monochrome image forming apparatus, and an image forming apparatus that includes a photoconductor and a plurality of developing devices (e.g., for four colors), toner images of the respective colors are produced by rotating the developing devices, and then an image is formed finally by transferring the toner images onto transfer paper. Not only for a printer, the second embodiment can be used as a cleaning device for a photocopier, a facsimile, or a multifunctional peripheral having a plurality of functions. Regardless of an electrophotographic type, an ink jet type, or another type, as long as an image forming apparatus includes a surface moving member and requires to remove deposit remaining on the surface of the surface moving member, the second embodiment can be applied to the image forming apparatus. Deposit to be removed can be toner, paper powder, metal powder, and any other powdery substance, and even a liquid, such as a developer, so that the second embodiment can be similarly applied. 
   In addition to the cleaning device for the photoconductor, the second embodiment can be applied to a cleaning device for removing deposit, such as residual toner, remaining on the surface on a surface moving member other than the photoconductor, e.g., the intermediate transfer belt  162 . Moreover, the second embodiment can be applied to a cleaning device for removing deposit, such as toner or paper powder, attached on a recording material conveyor member that supports and conveys a recording material on its surface. The second embodiment can be applied to a cleaning device for any surface moving member that requires to remove deposit attached on its surface. The surface moving member can be a drum, a belt, or in any other shape, of which member surface moves. When the cleaning device is used for the surface moving member of a belt, the cleaning device is generally arranged to catch the belt between the blade and a supporting roller that supports the belt. However, a backup member, such as a flat plate member, can be arranged on the internal side of the belt, and the cleaning device can be arranged to catch the belt between the blade and the backup member. When a target to be cleaned is the photoconductor  10 , the cleaning device according to the second embodiment can be applied for any photoconductor, which can be an organic photoconductor, an amorphous silicon photoconductor, or a photoconductor of which a protective layer made from a binder resin having a crosslinked structure is provided on an organic photoconductor surface. When a target to be cleaned is the intermediate transfer belt  162 , the cleaning device according to the second embodiment can be applied for any intermediate transfer belt, which can be an intermediate transfer belt made form polyimides considering heat resistance and strechability, an intermediate transfer belt using polyethylene materials, or an intermediate transfer belt made of fluoric materials and rubber materials. 
   In the various applications explained above, the configuration of the cleaning device  30  for a photoconductor explained in the second embodiment can be used without substantial change, or a configuration that is appropriately modified in accordance with each of the application can be used. 
   According to the embodiments of the present invention, a contact pressure higher than or equivalent to that in the cleaning device of the conventional counter type can be obtained, thereby achieving an excellent removal performance. On the other hand, a contact width can be made shorter than that in the cleaning device of the conventional counter type, wear on the surface moving member and the elastic member can be reduced. 
   Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.