Patent Description:
In a conventional electrophotographic image forming apparatus, after a toner image is transferred onto a transfer paper sheet or an intermediate transfer member, unnecessary transfer residual toner adhering to the surface of an image bearer as the cleaning target member, such as a photoconductor, is removed with a cleaning blade serving as a cleaning unit. A strip-shaped blade member is used as this cleaning blade, because such a blade member generally has a simple structure and shows excellent cleaning performance.

In a cleaning blade of a blade cleaning system, the blade member is supported by a supporting member that is made of a material having high rigidity such as a metal and is fixed to the main frame of a cleaning device, and the edge line portion of the blade member is pressed against the peripheral surface of an image bearer, to remove adhering matter adhering to the image bearer. Such a cleaning blade of a blade cleaning system has a simple structure, is inexpensive, and excels in adhering matter removal performance. Accordingly, such cleaning blades are widely used.

<CIT> discloses a cleaning blade that includes a blade member having a double-layer stack structure formed with elastic members having different characteristics from each other. The edge line portion of the edge layer to be brought into contact with an image bearer as the cleaning target member is impregnated with a resin, and the surface of the impregnated edge line portion is further coated with a surface layer having a relatively high degree of hardness, so that the hardness of the edge line portion is increased.

In the cleaning blade disclosed in <CIT>, the hardness of the edge line portion is increased with the impregnated portion and the surface layer. Accordingly, deformation at the edge line portion becomes smaller, and an increase in the contact area can be prevented. Thus, the contact pressure can be set at a high value, and cleaning performance can be improved.

The inventors observed the contact pressure that was applied to an image bearer by a blade member over a long period of time. As a result, the inventors discovered that the blade member was permanently deformed into a curved shape, or permanent deformation occurred. The contact state varied from the initial contact state, the contact pressure became lower, and there was a possibility of defective cleaning. Even in a case where a blade member having a double-layer stack structure formed with an edge layer having a high degree of hardness and a backup layer having a low degree of hardness was used, the edge line portion was subjected to an impregnation treatment, and the impregnated portion was further coated with a surface layer, the initial excellent cleaning performance was not fully maintained depending on a combination of permanent elongation rates of the edge layer, the backup layer, and the edge line portion. <CIT> relates to a blade for electrophotographic device and method for manufacturing the blade. There is provided a blade for an electro-photographic device formed by two layers, which undergoes minimal permanent deformation and offers excellent mechanical strength, wear resistance and compliance to the use environment. A blade for an electro-photographic device whose edge and base are constituted by different materials, wherein such blade for an electro-photographic device is characterized in that at least the edge is made of ester polyurethane and the base other than the edge is made of ether polyurethane. <CIT> relates to an image forming apparatus and process cartridge. There is provided an image forming apparatus including electrophotographic photoreceptor, a charging unit, an electrostatic latent image forming unit, a developing unit, and a residual toner removing unit, the surface protective layer of the electrophotographic photoreceptor having a surface free energy of <NUM> mN/m to <NUM> mN/m, the toner in the developing unit includes silica, and the residual toner removing unit including a blade member including a base layer and an edge layer having a type A durometer hardness of from HsA <NUM> to HsA <NUM> at <NUM>, the hardness of the edge layer being higher than the hardness of the base layer. <CIT> relates to an image forming apparatus, process cartridge, and image forming method. An image forming apparatus, including: an image bearing member; a charging unit; an exposure unit; a developing unit; a transfer unit; a fixing unit; and a cleaning unit including a cleaning blade, wherein the charging unit includes a charging roller that is brought into contact with the image bearing member for charging, the charging roller abutting the image bearing member at a pressing force of <NUM> mN/cm to <NUM>,<NUM> mN/cm, wherein the cleaning blade includes an elastic member that abuts the surface of the image bearing member to remove a residue attached to the surface of the image bearing member, and wherein an abutment part of the elastic member, which abuts the surface of the image bearing member, includes a cured product of an ultraviolet curable composition containing a (meth)acrylate compound having an alicyclic structure having <NUM> or more carbon atoms in a molecule. <CIT> relates to a cleaning blade and image forming apparatus. The cleaning blade has a two-layer structure of a cleaning layer directing the side of the photoreceptor and a rear face layer directing the rear side for the photoreceptor. In the cleaning blade for bringing an edge of the cleaning layer into contact with the photoreceptor and removing the residue of a development material of the surface of the photoreceptor, the rear face layer and the cleaning layer are integrally molded, and surface roughness Ra of the cleaning layer is <NUM> or less. <CIT> relates to a cleaning blade, image forming apparatus, and process cartridge. In the cleaning blade in which the leading end ridge part of an elastic blade abuts on a photoreceptor, the elastic blade is urethane rubber that is <NUM> or higher in tanδ peak temperature and <NUM>° or higher in an amount of change in JIS-A hardness from <NUM> to <NUM>. A portion of the elastic blade which portion includes the leading end ridge part is impregnated with UV curable resin with a Martens hardness of <NUM> to <NUM> N/mm and an elastic power of <NUM>% or less. In addition, the surface of the elastic blade including the leading end ridge part is provided with a surface layer with a thickness of <NUM> or less, the surface layer being harder than the elastic blade. <CIT> relates to an elastic rubber member made of polyurethane for cleaning blade for electrophotography, and cleaning blade. An elastic rubber member made of polyurethane for the cleaning blade for electrophotography comprises an edge layer and a backup layer. The edge layer is made of polyurethane using <NUM>,<NUM>-naphthalene diisocyanate (NDI) as an isocyanate component and having a hardness of ≥<NUM>° (JIS-A), and the backup layer is made of polyurethane using an isocyanate component other than NDI and having a hardness of <<NUM>°. <CIT> relates to an image forming apparatus. In an image forming apparatus provided with a cleaning means that abuts on the endless belt body which rotates in a stretched manner by a stretch section, and that removes an attachment on the endless belt body, the endless belt body is formed so that an indentation Young's modulus is <NUM> GPa or higher and <NUM> GPa or lower, and a degree of mirror plane of a face abutting on the cleaning section is <NUM> or higher and <NUM> or lower. <CIT> relates to a cleaning device and image forming apparatus using the same. The cleaning device includes the cleaning blade that comes into contact with the surface of a member to be cleaned to remove a residue remaining on the surface of the member to be cleaned, and that includes multiple layers, wherein the leading end of the cleaning blade shifts in a separating direction from the surface of the member to be cleaned due to a difference in thermal expansion property among the multiple layers when temperature rises. ;
<CIT> relates to a blade for electrophotographic device. The cleaning device includes the cleaning blade that comes into contact with the surface of a member to be cleaned to remove a residue remaining on the surface of the member to be cleaned, and that includes multiple layers, wherein the leading end of the cleaning blade shifts in a separating direction from the surface of the member to be cleaned due to a difference in thermal expansion property among the multiple layers when temperature rises. <CIT> relates to a blade member. In the blade member provided with a rubber elastic body <NUM> which is used by bringing its tip part into contact with a member to be contacted, the rubber elastic body consists of polyurethane rubber and at least the surface of the tip part of the rubber elastic body is coated with surface treatment layers formed by a surface treatment solution containing at least one polymer selected from fluorine group polymers and silicon group polymers and isocyanate component, a surface treatment solution containing carbon black, the above polymer and an isocyanate component. <CIT> relates to a blade for electronic camera and its manufacturing method. The blade for the electronic camera is supported by a plate type holder and used while the blade is in contact with a contacted member. The blade is formed of an elastic body using a urethane rubber composition and a contact part of the blade has (A) a silicon layer which contains silicon being reduced from the surface layer of the contact part toward an inner side and (B) a hardened layer as a surface layer of the silicon layer.

In view of the above, there is a need to provide a cleaning blade, an image forming apparatus and a process cartridge that have a structure including a blade member having a stack structure formed with layers, and can improve its cleaning performance while preventing permanent deformation of the blade member over time. In order to achieve the above-mentioned object, there is provided a cleaning blade according to claim <NUM>. In addition, there is provided an image forming apparatus according to claim <NUM>. Furthermore, there is provided a process cartridge according to claim <NUM>. Advantageous embodiments are defined by the dependent claims.

According to the present invention, an excellent effect to improve cleaning performance while reducing permanent deformation of a blade member over time can be achieved.

The following is a description of an embodiment of an electrophotographic printer (hereinafter referred to simply as a printer) as an image forming apparatus to which the present invention is applied. First, the fundamental structure of the printer according to this embodiment is described.

<FIG> is a schematic diagram illustrating the structure of a printer <NUM> according to this embodiment. The printer <NUM> is designed to form full-color images, and includes an image forming unit <NUM>, an intermediate transfer device <NUM>, and a sheet feeding unit <NUM>. In the description below, the subscripts Y, C, M, and Bk indicate that the components are made for yellow, cyan, magenta, and black, respectively.

In the image forming unit <NUM>, a process cartridge 121Y for yellow toner, a process cartridge 121C for cyan toner, a process cartridge <NUM> for magenta toner, and a process cartridge 121Bk for black toner are provided. These process cartridges <NUM> (Y, C, M, and Bk) are substantially arranged in a straight horizontal line. The process cartridges <NUM> (Y, C, M, and Bk) are integrally and detachably mounted in the printer <NUM>.

The intermediate transfer device <NUM> includes an endless intermediate transfer belt <NUM> supported by supporting rollers, primary transfer rollers <NUM> (Y, C, M, and Bk), and a secondary transfer roller <NUM>. The intermediate transfer belt <NUM> extends in the moving direction of the surfaces of the respective drum-shaped photoconductors <NUM> (Y, C, M, and Bk) serving as latent image bearers that are provided on the respective process cartridges <NUM> (Y, C, M, and Bk) and performs surface movement. The intermediate transfer belt <NUM> performs surface movement in synchronization with movement of the surfaces of the photoconductors <NUM> (Y, C, M, and Bk). The respective primary transfer rollers <NUM> (Y, C, M, and Bk) are placed along the inner peripheral surface of the intermediate transfer belt <NUM>, and the surface of the intermediate transfer belt <NUM> is weakly pressed against the surfaces of the respective photoconductors <NUM> (Y, C, M, and Bk) by virtue of these primary transfer rollers <NUM> (Y, C, M, and Bk).

The structure and operations to form toner images on the respective photoconductors <NUM> (Y, C, M, and Bk) and transfer the toner images onto the intermediate transfer belt <NUM> are substantially the same between the respective process cartridges <NUM> (Y, C, M, and Bk). However, the primary transfer rollers <NUM> (Y, C, and M) corresponding to the three color process cartridges <NUM> (Y, C, and M) is equipped with a swinging mechanism (not shown) that causes these three color process cartridges <NUM> (Y, C, and M) to swing vertically. The swinging mechanism operates such that the intermediate transfer belt <NUM> is not brought into contact with the photoconductors <NUM> (Y, C, and M) when no color images are formed. An intermediate transfer belt cleaning device <NUM> for removing adhering matter adhering to the intermediate transfer belt <NUM>, such as residual toner after the secondary transfer, is placed on a portion of the intermediate transfer belt <NUM> located downstream of the secondary transfer roller <NUM> and upstream of the process cartridge 121Y in the surface moving direction.

Above the intermediate transfer device <NUM>, toner cartridges <NUM> (Y, C, M, and Bk) corresponding to the respective process cartridges <NUM> (Y, C, M, and Bk) are aligned substantially in the horizontal direction. An exposure device <NUM> that forms an electrostatic latent image by irradiating the surfaces of charged photoconductors <NUM> (Y, C, M, and Bk) with laser light is placed below the process cartridges <NUM> (Y, C, M, and Bk).

The sheet feeding unit <NUM> is placed below the exposure device <NUM>. The sheet feeding unit <NUM> includes sheet feeding cassettes <NUM> that house transfer paper sheets as recording media, and sheet feeding rollers <NUM>. A transfer paper sheet is fed to the secondary transfer nip portion between the intermediate transfer belt <NUM> and the secondary transfer roller <NUM> via a pair of registration rollers <NUM> at a predetermined time.

A fixing device <NUM> is placed downstream of the secondary transfer nip portion in the transfer paper conveyance direction, and paper ejection rollers and an ejected paper housing unit <NUM> that houses ejected transfer paper sheets are placed downstream of the fixing device <NUM> in the transfer paper conveyance direction.

<FIG> is a diagram schematically illustrating an example structure of a process cartridge <NUM> in the printer <NUM>. Since the structures of the respective process cartridges <NUM> (Y, C, M, and Bk) are substantially the same, the structure of operation of a process cartridge <NUM> will be described below while omitting the color-indicating alphabets Y, C, M, and Bk.

As shown in <FIG>, the process cartridge <NUM> includes a drum-shaped photoconductor <NUM>, a cleaning device <NUM> placed in the vicinity of the photoconductor <NUM>, a charging unit <NUM>, and a developing unit <NUM>.

The cleaning device <NUM> presses the edge line portion <NUM> of a cleaning blade <NUM> against the surface of the photoconductor <NUM>. The cleaning blade <NUM> is a strip-shaped elastic member that is long in the direction of the rotational axis of the photoconductor <NUM>. The edge line portion <NUM> is an edge line that extends in a direction perpendicular to the direction of rotation of the photoconductor. With this structure, adhering matter such as transfer residual toner adhering to the surface of the photoconductor <NUM> is separated and removed from the surface of the photoconductor <NUM>. The removed adhering matter such as toner is then ejected from the cleaning device <NUM> by an ejecting screw <NUM>.

The charging unit <NUM> is formed mainly with a charging roller <NUM> facing the photoconductor <NUM>, and a charging roller cleaner <NUM> that rotates in contact with the charging roller <NUM>.

The developing unit (developing device) <NUM> supplies toner to the surface of the photoconductor <NUM> and turns an electrostatic latent image into a visible image, and includes a developing roller <NUM> as a developer bearer that bears a developer (carrier, toner) on its surface. The developing unit <NUM> is formed mainly with this developing roller <NUM>, a stirring screw <NUM> that conveys the developer housed in a developer container unit while stirring the developer, and a supplying screw <NUM> that conveys the stirred developer while supplying the stirred developer to the developing roller <NUM>.

Each of the four process cartridges <NUM> having the above described structure can be individually detached and exchanged for a new one by a maintenance engineer or a user. As for a process cartridge <NUM> detached from the printer <NUM>, each of the photoconductor <NUM>, the charging unit <NUM>, the developing unit <NUM>, and the cleaning device <NUM> can be individually exchanged for a new one. Each process cartridge <NUM> may include a toner waste tank that houses transfer residual toner collected by the cleaning device <NUM>. In this case, if the toner waste tank can be individually detached and exchanged for a new one in each process cartridge <NUM>, a higher level of user-friendliness is achieved.

Referring to <FIG>, operation of the printer <NUM> is described.

The printer <NUM> receives a printing instruction from an operation panel (not shown) or an external device such as a personal computer. First, each photoconductor <NUM> is rotated in the moving direction (the rotational direction) indicated by an arrow A in <FIG>, and the surface of each photoconductor <NUM> is uniformly charged with a predetermined polarity by the charging roller <NUM> of the charging unit <NUM>. The exposure device <NUM> irradiates the charged photoconductors <NUM> with laser beams for the respective colors that are optically modulated in accordance with input color image data, and thus forms electrostatic latent images for the respective colors on the surfaces of the respective photoconductors <NUM>. Developers of the respective colors are supplied to the respective electrostatic latent images from the developing rollers <NUM> of the developing units <NUM> for the respective colors, and the electrostatic latent images in the respective colors are developed with the developers for the respective colors and are turned into visible images that are toner images corresponding to the respective colors.

A transfer voltage of the polarity that is the opposite of the polarity of the toner is then applied to the primary transfer rollers <NUM>, so that a primary transfer field is formed between each photoconductor <NUM> and each corresponding primary transfer roller <NUM>, with the intermediate transfer belt <NUM> being interposed. At the same time, the primary transfer rollers <NUM> weakly presses against the intermediate transfer belt <NUM>, so that primary transfer nips are formed. Through these actions, primary transfer of the toner images on the respective photoconductors <NUM> onto the intermediate transfer belt <NUM> is efficiently performed. The toner images in the respective colors formed by the respective photoconductors <NUM> are transferred onto the intermediate transfer belt <NUM> in an overlapping manner, and a stacked toner image is formed.

At a predetermined time, a transfer paper sheet stored in a sheet feeding cassette <NUM> is fed to the stacked toner image transferred onto the intermediate transfer belt <NUM> by the primary transfer via the corresponding sheet feeding roller <NUM>, the pair of registration rollers <NUM>, and the like. A transfer voltage of the polarity that is opposite to the polarity of the toner is then applied to the secondary transfer roller <NUM>, so that a secondary transfer field is formed between the intermediate transfer belt <NUM> and the secondary transfer roller <NUM>, with the transfer paper sheet being interposed, and the stacked toner image is transferred onto the transfer paper sheet. The transfer paper sheet onto which the stacked toner image has been transferred is sent to the fixing device <NUM>, and fixing is performed with heat and pressure. The transfer paper sheet onto which the toner image has been fixed is ejected to the ejected paper housing unit <NUM> by the paper ejection rollers. Meanwhile, the transfer residual toner remaining on each respective photoconductor <NUM> after the primary transfer is scraped off and removed with the cleaning blade <NUM> of each corresponding cleaning device <NUM>.

Next, the cleaning blade <NUM> of each cleaning device <NUM>, which is the characteristic component of this printer <NUM>, is described.

First, the problems with conventional cleaning blades are described. <FIG> are schematic diagrams for explaining a conventional cleaning blade. A conventional cleaning blade <NUM> includes a single-layer blade member <NUM> in which the entire strip-shaped member is formed with a uniform elastic member, and a supporting member <NUM> that fixes the blade member <NUM> to the main frame of the cleaning device and is made of a material having high rigidity, such as a metal. Specifically, the blade member <NUM> is fixed to one end of the supporting member <NUM> with an adhesive agent or the like, and the other end of the supporting member <NUM> is cantilevered by the main frame of the cleaning device. As an edge line portion <NUM> that is an edge line extending in a direction perpendicular to the rotational direction of a photoconductor (not shown) serving as the member to be cleaned, the blade member <NUM> removes adhering matter such as transfer residual toner or a toner additive adhering to the surface of the photoconductor.

The blade member <NUM> of a cleaning blade is expected to be in contact with the surface of a photoconductor with a high contact pressure so as to achieve excellent removal performance, and the initial contact state is required to be maintained to achieve stable removal performance over a long period of time. However, with the single-layer blade member <NUM> in which the entire blade member is made of a uniform elastic material, it is difficult to increase the contact pressure and maintain the initial contact state at the same time. The reasons for this are as follows.

As shown in <FIG>, when a single-layer blade member <NUM> made of an elastic material having a relatively high degree of hardness such as urethane rubber is used, deformation of the edge line portion <NUM> in contact with an image bearer is small, and increases in the contact area can be restrained. Accordingly, the contact pressure can be made higher, and the cleaning performance can be improved. However, an elastic material having a high degree of hardness generally has a high permanent elongation rate. The blade member <NUM> is brought into contact with a photoconductor and is bent, with the edge line portion <NUM> being pressed against the circumferential surface of the photoconductor. If the blade member <NUM> made of the elastic material having a high permanent elongation rate is in contact with the photoconductor over a long period of time, the blade member <NUM> is permanently deformed in a bent shape, or permanent deformation occurs. As a result, the contact state becomes different from the initial contact state, causing defective cleaning.

As shown in <FIG>, in a case where the entire blade member <NUM> is made of an elastic material having a relatively low degree of hardness, permanent deformation hardly occurs even if the blade member <NUM> is in contact with a photoconductor over a long period of time, because an elastic material having a low degree of hardness generally has a low permanent elongation rate. Accordingly, the initial contact state can be maintained. However, the deformation of the edge line portion <NUM> in contact with the photoconductor is large, and the contact area becomes larger accordingly. As a result, the contact pressure becomes lower, and the cleaning performance becomes insufficient.

As described above, with a single-layer blade member, it is difficult to increase the contact pressure and maintain the initial contact state at the same time. Therefore, it is difficult to stably achieve high cleaning performance over a long period of time.

As shown in <FIG>, another conventional cleaning blade <NUM> includes: a blade member <NUM> having a double-layer stack structure formed with an edge layer 301a that is the layer to be in contact with a photoconductor (not shown), and a backup layer 301b stacked on the back surface of the edge layer 301a; and a supporting member <NUM>. The edge layer 301a is made of a urethane rubber having a high degree of hardness and a high permanent elongation rate, and the backup layer 301b is made of a urethane rubber having a low degree of hardness and a low permanent elongation rate. A single-layer blade member is too rigid to be sufficiently bent when being brought into contact with a photoconductor. As a result, the cleaning blade cannot adequately cope with unevenness or the like of the surface of the photoconductor, and the cleaning properties are degraded. In the blade member having a double-layer stack structure, on the other hand, the backup layer 301b has reasonable elasticity, and the edge layer 301a including the edge line portion has an increased degree of hardness. Accordingly, the cleaning blade can appropriately cope with unevenness or the like of the surface of the photoconductor, and excellent cleaning properties can be guaranteed. In the blade member <NUM> having such a double-layer structure, deformation of the edge line portion <NUM> in contact with the photoconductor as the member to be cleaned is small, and increase in the contact area can be restrained. Accordingly, the contact pressure can be made higher. Furthermore, the degree of hardness of the backup layer 301b not in contact with the photoconductor is low, and the rate of permanent elongation of the backup layer 301b is low. Accordingly, permanent deformation does not occur as easily as that in the above described single-layer blade member <NUM> having a high degree of hardness, and the initial contact state can be maintained.

However, if the strength of the elastic material of the edge layer 301a is further increased so as to improve cleaning performance by reducing adhesion of the toner additive to the surface of the photoconductor and to the charging roller, there is a limit to the increase in the strength in the case of the double-layer blade member <NUM>. In a case where a urethane rubber having a low rate of permanent elongation is used as the backup layer 301b, the permanent elongation of the edge layer 301a using an elastic material having a higher degree of strength becomes dominant. As a result, a decrease in the contact pressure and defective cleaning due to permanent deformation become problems. A decrease in permanent elongation can be corrected by reducing the thickness of the edge layer 301a by a possible amount. However, the strength of the elastic material used as the edge layer 301a cannot be made infinitely higher, and there is a limit to the increase in the strength of the elastic material due to the relationship with permanent deformation. Therefore, with a double-layer blade member, there is a limit to the increase in the strength of the edge line portion for improving cleaning performance by reducing adhesion of the toner additive to the surface of a photoconductor and to the charging roller.

<FIG> are schematic diagrams for explaining yet another conventional cleaning blade. <FIG> is a schematic diagram for explaining an impregnation treatment. <FIG> is a schematic diagram for explaining deformation of the blade member when a cleaning blade is brought into contact with a photoconductor. The conventional cleaning blade <NUM> shown in <FIG> includes a strip-shaped single-layer blade member <NUM>, and a supporting member <NUM> that fixes the blade member <NUM> to the main frame of the cleaning device and is made of a material having high rigidity, such as a metal. In the cleaning blade <NUM>, so as to increase the strength of the edge line portion <NUM>, the single-layer urethane rubber blade member <NUM> is impregnated with acrylic resin or isocyanate resin, and an impregnated portion <NUM> is formed, as shown in <FIG>. Alternatively, coating is performed on part of or all of the impregnated portion <NUM>, and a surface layer <NUM> is formed, as shown in <FIG>. As shown in <FIG>, the impregnation treatment is performed by immersing the blade member <NUM> of the cleaning blade <NUM> in an impregnating coating solution perpendicularly to the liquid level of the impregnating coating solution. Other than the method involving immersion in an impregnating coating solution, the impregnation treatment may be performed by brush coating, spray coating, dip coating, or the like. The impregnated portion <NUM> having the elastic material strength increased through the impregnation treatment is formed in a portion including the edge line portion <NUM>, and in the photoconductor-facing surface <NUM> and the non-photoconductor-facing surface <NUM> that are adjacent to each other across the edge line portion <NUM>. When being brought into contact with a photoconductor <NUM> as shown in <FIG>, the cleaning blade <NUM> is deformed such that the portion of the photoconductor-facing surface <NUM> expands and the portion of the non-photoconductor-facing surface <NUM> contracts. In this manner, the cleaning blade <NUM> evenly comes into contact with the photoconductor <NUM>.

However, in a case where the blade member <NUM> having the impregnated portion <NUM> is brought into contact with a photoconductor (not shown), the non-photoconductor-facing surface <NUM> other than the edge line portion <NUM> has its strength increased by the impregnation treatment. Therefore, as shown in <FIG>, the portion of the photoconductor-facing surface <NUM> does not easily expand, the portion of the non-photoconductor-facing surface <NUM> does not easily contract, and the edge line portion <NUM> does not easily bend. As a result, the contact with the photoconductor <NUM> becomes uneven, and the uneven contact causes degradation in cleaning performance. Also, as shown in <FIG>, stress from the non-photoconductor-facing surface <NUM> (indicated by a solid-line arrow in <FIG>) concentrates on the edge line portion <NUM>. Therefore, unnecessarily high stress is applied to the edge line portion <NUM>, and the edge line portion <NUM> easily becomes worn, resulting in a problem in terms of durability.

In view of the above, when the single-layer blade member <NUM> of a cleaning blade <NUM> is immersed in an impregnating coating solution obliquely with respect to the liquid level, as shown in <FIG>, which is a schematic diagram for explaining another impregnation treatment, an impregnated portion <NUM> is formed on an edge line portion <NUM> and part of a cut surface <NUM> formed to be interposed between a photoconductor-facing surface <NUM> and a non-photoconductor-facing surface <NUM> and continue to the both surfaces, and the non-photoconductor-facing surface <NUM> is not immersed in the impregnating coating solution, as shown in <FIG>. With this arrangement, the portion of the non-photoconductor-facing surface <NUM> is deformed so as to sufficiently contract, and the portion of the photoconductor-facing surface <NUM> is deformed so as to sufficiently expand. Accordingly, the flexibility of the edge line portion <NUM> is maintained. In this manner, the contact with a photoconductor (not shown) as the member to be cleaned becomes uniform, and a sufficient effect to increase the strength of the edge line portion <NUM> is achieved. Thus, cleaning performance can be improved by reducing adhesion of the toner additive to the surface of the photoconductor and to the charging roller.

However, even in a case where the impregnated portion <NUM> is formed on the portions of the edge line portion <NUM> and the cut surface <NUM> but is not formed on the portion of the non-photoconductor-facing surface <NUM> as in the cleaning blade <NUM> shown in <FIG>, there is the problem described below if a single-layer blade member is used. Specifically, in view of permanent elongation, the single-layer blade member <NUM> needs to be made of an elastic material that has a low rate of permanent elongation and a relatively low degree of hardness, as described above. However, in a case where an elastic material having a low degree of hardness is used as the base material so as to increase the hardness of the edge line portion <NUM> through an impregnation treatment, the amount of impregnation needs to be made larger than that in a case where an elastic material having a high degree of hardness is used as the base material. Therefore, the impregnation time needs to be made longer, or the concentration of the impregnating coating solution needs to be made higher. This results in an increase in cost due to the elongated production time, or an increase in the cost of the impregnating coating solution due to the increased concentration of the impregnating coating solution.

Next, the principal characteristics of the above described conventional cleaning blades and example cleaning blades according to this embodiment are described in conjunction with the results of verification experiments. In the verification experiments described below, the principal characteristics such as the Young's moduli and the rates of permanent elongation of the respective components of each blade member were measured.

<FIG> is a schematic diagram for explaining a cleaning blade having a double-layer blade member. It should be noted that any impregnation treatment has not been performed on the blade member shown in <FIG>. The principal characteristics of Experiment <NUM> are shown in Table <NUM>.

In a cleaning blade <NUM> that includes the double-layer blade member <NUM> shown in <FIG>, the edge layer 601a of the blade member <NUM> is made of a urethane rubber having a high Young's modulus (<NUM> MPa) (high strength), so as to improve cleaning performance, reduce adhesion of the toner additive to the surface of a photoconductor, and reduce staining of the charging roller. As described above, there is a correlation between permanent elongation of a cleaning blade and the decrease in contact pressure due to permanent deformation over time. As the rate of permanent elongation becomes higher, the contact pressure tends to become lower. Normally, permanent deformation becomes a problem, when the rate of permanent elongation exceeds <NUM>%. The urethane rubber used as the edge layer 601a, which is a single layer, has a permanent elongation rate of <NUM>%, as shown in Table <NUM>. Since the rate of permanent elongation is higher than <NUM>%, permanent deformation becomes a problem in a cleaning blade having a single-layer blade member. In view of this, a urethane rubber that has a low Young's modulus (<NUM> MPa) (low strength) and a permanent elongation rate of <NUM>% is used as the backup layer 601b to realize a double-layer structure. As a result, the permanent elongation rate of the entire blade member <NUM> becomes <NUM>%, which is not higher than <NUM>% and does not cause the problem of permanent deformation.

<FIG> is a schematic diagram for explaining a cleaning blade having a double-layer blade member. It should be noted that any impregnation treatment has not been performed on the blade member shown in <FIG>. The film thicknesses and the sizes of the respective layers are the same as those of the cleaning blade used in Experiment <NUM>. The principal characteristics of Experiment <NUM> are shown in Table <NUM>.

In a cleaning blade <NUM> that includes the double-layer blade member <NUM> shown in <FIG>, the edge layer 701a of the blade member <NUM> is made of a high-hardness urethane rubber having an even higher Young's modulus (<NUM> MPa) than that in Experiment <NUM>, so as to improve cleaning performance, reduce adhesion of the additive to the surface of a photoconductor, and reduce staining of the charging roller more effectively than in Experiment <NUM>. The urethane rubber used as the edge layer 701a, which is a single layer, has a permanent elongation rate of <NUM>%, which is much higher than <NUM>%, as shown in Table <NUM>. Therefore, even if a urethane rubber that has a permanent elongation rate of <NUM>% is used as the backup layer 701b to realize a double-layer structure, the permanent elongation rate of the entire blade member <NUM> is <NUM>%, which is higher than <NUM>% and causes the problem of permanent deformation. This is supposedly because the permanent elongation rate of the edge layer 701a is higher than that of the backup layer 701b, and the permanent elongation of the edge layer 701a becomes dominant in the permanent elongation of the entire blade member, as described above.

In a cleaning blade <NUM> that includes the double-layer blade member <NUM> shown in <FIG>, the portion of a photoconductor-facing surface <NUM> is formed with a first edge layer <NUM> as the cleaning layer and a second edge layer <NUM> as the edge layer. The first edge layer <NUM> is formed in a portion including an edge line portion <NUM>, and becomes gradually thicker in the direction toward the edge line portion <NUM>. The first edge layer <NUM> is made of an elastic material that has a Young's modulus of <NUM> Mpa and a permanent elongation rate of <NUM>%, which is not desirable in terms of permanent elongation. The proportion of the portion of the first edge layer <NUM> to the photoconductor-facing surface <NUM> is lower than that of the portion of the second edge layer <NUM>. Therefore, the permanent elongation of the second edge layer <NUM> is dominant in the permanent elongation of the entire blade member, and the permanent elongation rate of the entire blade member is <NUM>%, which is not higher than <NUM>%. Thus, permanent deformation over time can be reduced, and high cleaning performance can be maintained over a long period of time by virtue of the effect to reduce adhesion of the toner additive to the surface of a photoconductor and the effect to reduce staining of the charging roller.

Next, the elastic power of the cleaning layer is described.

In the cleaning blade shown above in Table <NUM>, the first edge layer (the cleaning layer) is made of an elastic material having a high Young's modulus. The elastic power of this material is <NUM>%. Normally, when the Young's modulus of an elastic material is made larger, the value of the elastic power thereof tends to become smaller. The elastic power is a value indicating a relation between elastic workload and plastic workload, and indicates plastic deformability of the material. In a cleaning blade, the plastic deformability of the edge line portion to be in contact with a photoconductor greatly affects toner removal performance. That is, if the edge line portion of a cleaning blade has a high degree of plastic deformability, part of the edge line of the cleaning blade is once deformed downstream in the photoconductor moving direction by the frictional force between the cleaning blade and the photoconductor. In that case, the original edge shape is not easily restored, and toner easily escapes through the site. As a result, a streaky abnormal image is obtained due to defective cleaning that is caused by the streaky toner escape. Since toner easily continues to escape through the same site, part of the edge line portion becomes locally worn. Such degradation of cleaning properties due to a low elastic power occurs notably in low-temperature environments.

In the case of a cleaning blade in which the elastic power of the cleaning layer is high, and the portion in the vicinity of the edge line portion has a low plastic deformation rate, even if part of the edge line is deformed downstream in the photoconductor moving direction, the original shape is promptly restored. Therefore, defective cleaning due to streaky escape of toner, and an abnormal image are hardly caused. Further, part of the edge line portion does not become locally worn.

As for the above described defective cleaning and the local wear, the relation between the elastic material used as the cleaning layer and its elastic power was examined through Experiment <NUM>, which is described below.

In Experiment <NUM>, as opposed to the cleaning blade shown in Table <NUM> (hereinafter referred to as the "cleaning blade <NUM>-<NUM>"), two kinds of cleaning blades <NUM>-<NUM> and <NUM>-<NUM> that differed from each other in the elastic power of the first edge layer were prepared, and the respective edge line portions were compared with one another in terms of plastic deformation. In Experiment <NUM>, the cleaning blades <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> were brought into contact with a photoconductor at a linear pressure of <NUM>/cm in a <NUM>-°C environment, and the photoconductor was rotated by ten revolutions in a no-toner input state that generated a higher frictional force than a toner input state. The diameter of the photoconductor was <NUM>. As shown in <FIG>, after the photoconductor was rotated, the edge line of each blade was observed with a microscope, and the deformation amount generated by plastic deformation was calculated. The plastic deformation amounts of the edge lines are shown below in Table <NUM>. The cleaning blade <NUM>-<NUM> having an elastic power of <NUM>% was hardly deformed. On the other hand, the maximum plastic deformation amounts of the cleaning blades <NUM>-<NUM> and <NUM>-<NUM> were <NUM> and <NUM>, respectively.

In view of the above, by adjusting the elastic power of the portion of the cleaning layer in the vicinity of the edge line portion to be approximately <NUM>% or higher, neither defective cleaning due to plastic deformation nor local wear is caused in a low-temperature environment, even if an elastic material with a high Young's modulus is used.

In a cleaning blade <NUM> that includes the double-layer blade member <NUM> shown in <FIG>, the portion of a photoconductor-facing surface <NUM> is formed with a first edge layer <NUM> and a second edge layer <NUM>. The first edge layer <NUM> is formed near an edge line portion <NUM>, and becomes gradually thicker in the direction toward the edge line portion <NUM>. The Young's modulus of the first edge layer <NUM> is <NUM> MPa, which is lower than that of the first edge layer <NUM> shown in <FIG>, and the strength of the portion including the edge line portion <NUM> is not sufficient. Therefore, the cleaning performance is poorer than that of the cleaning blade <NUM> shown in <FIG>, and the reduction of adhesion of the toner additive to the photoconductor surface and the reduction of staining of the charging roller are smaller than those by the cleaning blade <NUM>. The proportion of the portion of the second edge layer <NUM> to the photoconductor-facing surface <NUM> is higher than that of the portion of the first edge layer <NUM>. Therefore, the permanent elongation due to the Young's modulus of the second edge layer <NUM> is dominant, and cleaning performance is degraded due to permanent deformation over time.

As can be seen from the results of the verification experiments in Experiments <NUM> through <NUM> and Experiment <NUM>, the degree of hardness (strength or Young's modulus) of the edge line portion needs to be made higher, so as to realize excellent cleaning performance through a reduction of adhesion of the additive to the photoconductor surface and a reduction of staining of the charging roller. For example, as shown in each of <FIG>, and <FIG>, the first edge layer is provided most upstream in the photoconductor moving direction, and the second edge layer is provided downstream of the first edge portion. Also, the first edge layer has the highest Young's modulus. So as to reduce permanent deformation that occurs over time, the second edge layer has a lower Young's modulus than that of the first edge layer, and the backup layer has a lower Young's modulus than that of the second edge layer. The backup layer is in contact with the side of the first edge layer and/or the second edge layer opposite to the side of the second edge layer and the edge line portion facing the photoconductor.

In the blade member <NUM> of a cleaning blade <NUM> shown in <FIG>, a first edge layer <NUM> is formed in a portion including an edge line portion <NUM>, and the film thickness thereof may become gradually thicker in the direction toward the edge line portion <NUM>. In the blade member <NUM> of a cleaning blade <NUM> shown in <FIG>, a first edge layer <NUM> is formed in a portion including an edge line portion <NUM>, and may be formed over an edge 1101a and a backup layer 1101b. In the blade member <NUM> of a cleaning blade <NUM> shown in <FIG>, a first edge layer <NUM> and a second edge layer <NUM> may be formed so that the film thickness of each of the edge layers <NUM> and <NUM> becomes gradually thicker in the direction toward an edge line portion <NUM>. In the blade member <NUM> of a cleaning blade <NUM> shown in <FIG>, the portion of the photoconductor-facing surface <NUM> of an edge layer 1301a may be formed with a first edge layer <NUM> that is made of a high-hardness elastic material and is located in a portion including an edge line portion <NUM>, and a second edge layer <NUM> made of a low-hardness elastic material.

Next, an example of a cleaning blade according to the above described embodiment is described.

<FIG> is a schematic diagram for explaining the example of a cleaning blade. The cleaning blade <NUM> of the example shown in <FIG> includes a double-layer blade member <NUM> formed with an edge layer 1401a and a backup layer 1401b that are made of elastic materials having different degrees of hardness from each other, and a supporting member <NUM> that fixes the blade member <NUM> to the main frame of the cleaning device and is made of a material having high rigidity, such as a metal. Specifically, the blade member <NUM> is fixed to one end of the supporting member <NUM> with an adhesive agent or the like, and the other end of the supporting member <NUM> is cantilevered by the main frame of the cleaning device. In the blade member <NUM>, an impregnation treatment is performed, so that a region extending from the edge layer 1401a to the backup layer 1401b in a portion including an edge line portion <NUM> is impregnated with resin. In this manner, an impregnated portion <NUM> as the cleaning layer is formed. Specifically, a portion including the edge line portion <NUM> is impregnated with acrylic resin or the like, so that the impregnated portion <NUM> has a degree of hardness increased through ultraviolet curing. The principal characteristics of the cleaning blade of this example are shown below in Table <NUM>. The degrees of Martens hardness [N/mm<NUM>] in Table <NUM> are characteristic values for comparing the impregnated portion subjected to the impregnation treatment with the edge layer and the backup layer. The impregnated portion <NUM> shown in <FIG> is an impregnated portion extending approximately <NUM> along the photoconductor-facing surface <NUM> from the edge line portion <NUM>. Since this is an extremely narrow region, it is difficult to detect changes in macroscopic characteristics such as a Young's modulus before and after the impregnation treatment. Therefore, there are no numerical values that represent minute changes in hardness and indicate the effect of the impregnation treatment.

Next, a comparative example of a cleaning blade is described.

<FIG> is a schematic diagram for explaining a comparative example of a cleaning blade. The cleaning blade <NUM> of the comparative example shown in <FIG> includes a strip-shaped single-layer blade member <NUM>, and a supporting member <NUM> that fixes the blade member <NUM> to the main frame of the cleaning device and is made of a material having high rigidity, such as a metal. In the single-layer blade member <NUM> shown in <FIG>, an impregnation treatment is performed on a portion including an edge line portion <NUM>, to form an impregnated portion <NUM>. The portion including the edge line portion <NUM> is impregnated with an impregnating coating solution such as acrylic resin, so that the impregnated portion <NUM> has a degree of hardness increased through ultraviolet curing. The principal characteristics of the cleaning blade of this example are shown below in Table <NUM>.

The cleaning blade <NUM> shown in <FIG> and the cleaning blade <NUM> shown in <FIG> are immersed in and impregnated with the same impregnating coating solution, but require different impregnation treatment periods to obtain the target Martens hardness (at a site <NUM> away from the edge line portion, for example). If the Young's modulus of the rubber member prior to the impregnation treatment is low or the Martens hardness is low, a long impregnation treatment period is required to achieve the target Martens hardness, and the impregnated region becomes wider. Also, the high-hardness region expands outside the region surrounding the edge line portion. Therefore, as the high-strength region becomes larger, the contact portion of the blade member is not evenly brought into contact with the surface of a photoconductor as the member to be cleaned, and cleaning performance is degraded.

As described above, rather than performing the impregnation treatment on a single-layer blade member with low strength as shown in <FIG>, by performing the impregnation treatment on a double-layer blade member that is formed with a high-hardness edge layer and a low-hardness backup layer as shown in <FIG>, a structure with even higher strength is obtained. As only the edge line portion is made to have the target high degree of hardness as described above, the impregnation treatment period is shortened. Accordingly, productivity is increased, costs can be lowered, and permanent deformation over time can be reduced. At the same time, excellent cleaning performance can be maintained through a reduction of adhesion of the toner additive to the surface of a photoconductor and a reduction of staining of the charging roller.

Also, as in a cleaning blade <NUM> that is a first modification shown in <FIG>, an impregnated portion <NUM> may be formed by performing the impregnation treatment only on the portion of the edge line portion <NUM> of an edge layer 1601a while not performing the impregnation treatment on the portion of a backup layer 1601b. As in a cleaning blade <NUM> that is a second modification shown in <FIG>, an impregnated portion <NUM> may be formed by performing the impregnation treatment on a portion that extends from an edge layer 1701a to a backup layer 1701b and includes an edge line portion <NUM>. As shown in <FIG>, in a cleaning blade <NUM> that is a third modification, an edge layer 1801a may be designed so that the film thickness thereof becomes gradually greater in the direction toward an edge line portion <NUM>, and an impregnated portion <NUM> may be formed by performing the impregnation treatment only on a portion of the edge layer 1801a including the edge line portion <NUM>. As shown in <FIG>, in a cleaning blade <NUM> that is a fourth modification, an edge layer 1901a may be designed such that the film thickness thereof becomes gradually greater in the direction toward an edge line portion <NUM>, and an impregnated portion <NUM> may be formed by performing the impregnation treatment only on a portion that extends from the edge layer 1901a to a backup layer 1901b and includes the edge line portion <NUM>. As in the cleaning blades <NUM>, <NUM>, <NUM>, and <NUM> of the first through fourth modifications shown in <FIG>, the impregnation treatment is performed on a portion including the edge line portion of a double-layer blade member, so that the double-layer blade member includes at least an edge layer, a backup layer, and an impregnated portion (the cleaning layer). Accordingly, permanent deformation over time can be reduced more effectively than in a single-layer blade member having the impregnation treatment performed on a portion including the edge line portion, and excellent cleaning performance can be maintained through a reduction of adhesion of the toner additive to the surface of a photoconductor and a reduction of staining of the charging roller more effectively than in the single-layer blade member.

The impregnation treatment for impregnating the cleaning blade <NUM> shown in <FIG> with an ultraviolet curable resin can be performed by brush coating, spray coating, dip coating, or the like. The ultraviolet curable resin for impregnation is preferably a material that has a Martens hardness of <NUM> to <NUM> N/mm<NUM>, and an elastic power of <NUM>% or lower, or more preferably, an elastic power of <NUM> to <NUM>%. The Martens hardness and the elastic power of the ultraviolet curable resin for impregnation are the results of measurement carried out on a resin film that was formed on a glass substrate and had a thickness of <NUM> to <NUM>. With this arrangement, the edge line portion <NUM> of the cleaning blade <NUM> brought into contact with the photoconductor <NUM> as shown in <FIG> can be prevented from being deformed in the moving direction of the photoconductor surface. Furthermore, when the inside is exposed due to wear of the surface layer over time, deformation can also be prevented by virtue of an action of inward impregnation.

The Martens hardness as the hardness of the ultraviolet curable resin was measured with a microhardness measurement instrument, HM-<NUM>, manufactured by Fischer Instruments K. Specifically, the ultraviolet curable resin is applied onto a glass substrate so that the thickness becomes <NUM>. A Vickers indenter is pushed into the applied ultraviolet curable resin with a force of <NUM> mN in <NUM> seconds, and is kept therein for five seconds. The Vickers indenter is then pulled out with a force of <NUM> mN in <NUM> seconds. Measurement is carried out in this manner. The elastic power is a characteristic value that is calculated, as described below, from the total stress obtained at the time of the Martens hardness measurement. Where the total stress caused when the Vickers indenter is pushed into the ultraviolet curable resin is represented by Wplast, and the total stress caused when the test load is removed is represented by Welast, the elastic power is a characteristic value defined by the expression, Welast/Wplast × <NUM>% (see <FIG>). A higher elastic power means smaller hysteresis loss (plastic deformation) or greater rubbery characteristics. If the elastic power is too low, the ultraviolet curable resin is more like glass than rubber.

The Martens hardness of the portion in the vicinity of the edge line portion <NUM> shown in <FIG> is the Martens hardness measured when the cleaning blade <NUM> was impregnated with an ultraviolet curable resin, and differs from the Martens hardness of the above described ultraviolet curable resin.

The ultraviolet curable resin for the impregnation treatment is preferably a material having high hardness and high elasticity, such as an acrylate or methacrylate having a tricyclodecane or adamantane skeleton. The toner removal performance is greatly improved, and the wear of the cleaning blade is reduced. Accordingly, excellent cleaning performance can be maintained over a long period of time. Also, the coefficient of friction between the cleaning blade and the photoconductor is reduced, and the wear of the photoconductor is reduced. Accordingly, the life of the photoconductor and the life of the image forming apparatus can be prolonged. Further, as the cleaning blade does not rub the toner additive or the like against the surface of the photoconductor, any abnormal image with blanks is not generated. The acrylate or methacrylate having a tricyclodecane or adamantane skeleton is preferable, because the special structure of a tricyclodecane or adamantane skeleton can compensate for shortage of cross-linking points, even if the number of functional groups is small. Examples of acrylates or methacrylates having a tricyclodecane or adamantane skeleton include tricyclodecane dimethanol diacrylate, <NUM>,<NUM>-adamantane dimethanol diacrylate, <NUM>,<NUM>-adamantane dimethanol dimethacrylate, <NUM>,<NUM>,<NUM>-adamantane trimethanol triacrylate, and <NUM>,<NUM>,<NUM>-adamantane trimethanol trimethacrylate. A mixture of two or more of these materials may be used.

The number of functional groups of the acrylate or methacrylate having a tricyclodecane or adamantane skeleton is preferably one to six, and more preferably, two to four. If the number of functional groups is one, the cross-linked structure is weak. If the number of functional groups is five or greater, steric hindrance might occur. Therefore, it is preferable to mix acrylates or methacrylates having different numbers of functional groups. The molecular weight of the acrylate or methacrylate having a tricyclodecane or adamantane skeleton is preferably <NUM> or smaller. If the molecular weight is <NUM> or greater, the molecular size becomes larger. As a result, the cleaning blade is not easily impregnated with the ultraviolet curable resin, and it becomes difficult to achieve a higher degree of hardness.

An acrylate monomer of <NUM> to <NUM> in molecular weight may be mixed with the impregnating coating solution for impregnating the cleaning blade <NUM> with an ultraviolet curable resin by brush coating, spray coating, dip coating, or the like. Examples of acrylate monomers include dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, pentaerythritol ethoxy tetraacrylate, trimethylol propane triacrylate, trimethylol propane ethoxy triacrylate, <NUM>,<NUM>-hexanediol diacrylate, ethoxylated bisphenol A diacrylate, propoxylated ethoxylated bisphenol A diacrylate, <NUM>,<NUM>-butanediol diacrylate, <NUM>,<NUM>-pentanediol diacrylate, <NUM>,<NUM>-hexanediol diacrylate, <NUM>,<NUM>-heptanediol diacrylate, <NUM>,<NUM>-octanediol diacrylate, <NUM>,<NUM>-nonanediol diacrylate, <NUM>,<NUM>-decanediol diacrylate, <NUM>,<NUM>-undecanediol diacrylate, <NUM>,<NUM>-octadecanediol diacrylate, glycerin propoxy triacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, PO-modified neopentyl glycol diacrylate, PEG600 diacrylate, PEG400 diacrylate, PEG200 diacrylate, neopentyl glycol hydroxypivalic acid ester diacrylate, octyl/decyl acrylate, isobornyl acrylate, ethoxylated phenyl acrylate, and <NUM>,<NUM>-bis[<NUM>-(<NUM>-acryloyloxyethoxy)phenyl]fluorene. One of these materials or two or more of these materials may be mixed with the impregnating coating solution.

The diluent for the impregnating coating solution can solve an ultraviolet curable resin, and preferably has a low boiling point. Particularly, the boiling point is not higher than <NUM>, or more preferably, not higher than <NUM>. Examples of diluting solvents that can be used herein are organic solvents including: hydrocarbon-based solvents such as toluene and xylene; esters such as ethyl acetate, n-butyl acetate, methyl cellosolve acetate, and propylene glycol monomethyl ether acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, and cyclopentanone; ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and propylene glycol monomethyl ether; alcohols such as ethanol, propanol, <NUM>-butanol, isopropyl alcohol, and isobutyl alcohol.

The above diluent has the effect to facilitate impregnation at the time of coating. However, the above diluent might degrade physical properties and wear resistance, such as when a residual solvent exists in the rubber, and the rubber remains expanded and does not return to its original thickness. Also, if drying is conducted by heating so as to remove the residual solvent, the physical properties of the rubber are changed, and the cleaning properties might be degraded. In view of this, it is preferable to lower the temperature for the drying heat, or perform vacuum drying or the like, instead of drying by heating. In this manner, the density of the residual solvent can be lowered.

Next, specific examples of impregnating coating solutions are described.

Next, the toner to be used in the printer <NUM> of this embodiment is described.

In this printer <NUM>, a low-temperature fixing toner that has a glass transition temperature (Tg) of <NUM> to <NUM> is used so as to save energy in the fixing device <NUM> of the image forming apparatus.

So as to realize a toner that excels in low-temperature fixability, hot-offset resistance, and heat-resistant preservability, the toner of this embodiment is a polyester resin as a binder resin that satisfies the following conditions: <NUM>) the glass transition temperature (Tg) is <NUM> to <NUM>, and <NUM>) the value (Mw/Tg) obtained by dividing the weight-average molecular weight (Mw) of the THF soluble portion by the glass transition temperature (Tg/°C) is <NUM> to <NUM>.

In the conventionally-used polyester resin, Mw tends to drop rapidly as Tg becomes lower than <NUM>. Therefore, it is difficult for the conventionally-used polyester resin to excel in low-temperature fixability, hot-offset resistance, and heat-resistant preservability. If Tg of the polyester resin is lower than <NUM>, the heat-resistant preservability cannot be improved, no matter how well Mw is adjusted. Therefore, the range of Tg that can keep the physical properties of the toner in balance is <NUM> to <NUM>, and the range of the value of Mw/Tg is <NUM> to <NUM>. As long as the value of Mw/Tg stays within the above range, the polyester resin has such Tg as to maintain excellent heat-resistant preservability, and the molecular weight can also be reduced. Accordingly, the low-temperature fixability of the toner can be further improved, and excellent heat-resistant preservability can be maintained. It should be noted that Mw and Tg are measured by the technique described below, and the unit of Tg in the value of Mw/Tg is°C.

The glass transition temperature (Tg) is measured at a temperature rise rate of <NUM>/min with Rigaku THRMOFLEX TG8110, manufactured by Rigaku Corporation.

The molecular weight is measured by GPC (gel permeation chromatography) as follows. A column is steadied in a heat chamber at <NUM>, and THF is applied as the solvent at a flow rate of <NUM>/min to the column at the temperature. Measurement is then carried out by injecting <NUM> to <NUM>µl of a THF sample solution of a resin adjusted to a sample density of <NUM> to <NUM> wt. When the molecular weight of a sample is measured, the molecular weight distribution of the sample is calculated from the relation between the logarithmic value of the created calibration curve and the count number obtained from several kinds of monodisperse polystyrene standard samples. The appropriate standard polystyrene samples for creating a calibration curve are at least ten standard polystyrene samples, which are manufactured by Pressure-Chemical Co. or Tosoh Corporation, and have molecular weights of <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, and <NUM> × <NUM>, for example. Here, an RI (refractive index) detector is used as the detector.

The chemical structure of the polyester resin that satisfies the above conditions preferably has the following features. Specifically, the molar ratio (benzene ring skeleton/<NUM>,<NUM>-cyclohexylene skeleton) between the benzene ring skeleton and the <NUM>,<NUM>-cyclohexylene skeleton in the polyester resin is <NUM> to <NUM>, and the molar ratio (benzene skeleton/double-end ester-bond alkylene skeleton) between the benzene skeleton and the alkylene skeleton having ester bonds at both ends is <NUM> or higher.

The glass transition temperature (Tg) of the polyester resin is governed mainly by its chemical structure, and Tg tends to become higher as the benzene ring skeleton extends longer or the content of the benzene ring skeleton becomes larger. Also, Tg tends to become lower, as the alkylene skeleton becomes longer or the content of the alkylene skeleton becomes larger. Therefore, if the content of the benzene ring skeleton is large, the hot-offset resistance and the heat-resistant preservability are improved, but the low-temperature fixability are degraded. If the content of the alkylene skeleton is large, the low-temperature fixability is advantageously improved, but the hot-offset resistance and the heat-resistant preservability is adversely affected. Meanwhile, with an appropriate amount of the <NUM>,<NUM>-cyclohexylene skeleton, the weight-average molecular weight of the resin can be adjusted while Tg is maintained. Accordingly, the low-temperature fixability can be further improved.

Therefore, the ranges of the molar ratio (benzene ring skeleton/<NUM>,<NUM>-cyclohexylene skeleton) and the molar ratio (benzene skeleton/double-end ester-bond alkylene skeleton) are specified as described above. If the molar ratio (benzene ring skeleton/ <NUM>,<NUM>-cyclohexylene skeleton) is lower than <NUM>, the polyester resin becomes brittle, and the toner loses its durability. If the molar ratio (benzene ring skeleton/ <NUM>,<NUM>-cyclohexylene skeleton) is higher than <NUM>, it becomes difficult to reduce the molecular weight while maintaining the glass transition temperature, and therefore, low-temperature fixability cannot be achieved. Further, if the molar ratio (benzene skeleton/double-end ester-bond alkylene skeleton) is lower than <NUM>, it is difficult to maintain heat-resistant preservability.

The molar ratio (benzene ring skeleton/<NUM>,<NUM>-cyclohexylene skeleton) and the molar ratio (benzene skeleton/double-end ester-bond alkylene skeleton) can be calculated from the raw-material composition ratio between polyprotic carboxylic acid and polyhydric alcohol, which are the raw materials of the resin. Alternatively, these molar ratios can be calculated by carrying out <NUM>-NMR (nuclear magnetic resonance) measurement on the generated resin.

So as to maintain heat-resistant preservability as well as low-temperature fixability and hot-offset resistance, it is critical to adjust the weight-average molecular weight (Mw) of the polyester resin, and Mw of the THF soluble portion of the polyester resin is preferably set at <NUM>,<NUM> to <NUM>,<NUM> in the present invention. If Mw is less than <NUM>,<NUM>, the oligomer component increases. Therefore, even if the chemical structure is controlled as described above, the heat-resistant preservability is degraded. If Mw exceeds <NUM>,<NUM>, the melting temperature becomes higher, and the low-temperature fixability is degraded.

The toner characteristics such as low-temperature fixability, hot-offset resistance, heat-resistant preservability, and charging stability can also be improved by adjusting the acid value of the polyester resin to <NUM> to <NUM> KOHmg/g.

The low-temperature fixing toner of this embodiment can be manufactured by using the above described polyester resin as the binder resin, and mixing therein a polymer (hereinafter referred to as the "prepolymer") having parts that are reactive with a compound containing active hydrogen groups as described later in detail. As this prepolymer is mixed with a compound containing active hydrogen groups, elongation or a cross-linking reaction can be caused during the toner manufacturing process, and the above toner characteristics can be improved.

If the acid value of the polyester resin exceeds <NUM> KOHmg/g, the elongation or the cross-linking reaction of the prepolymer becomes insufficient, and the hot-offset resistance is adversely affected. If the acid value is smaller than <NUM> KOHmg/g, the elongation or the cross-linking reaction of the prepolymer is easily facilitated, and a problem is caused in production stability.

The acid value of the polyester resin is measured by a method compliant with JIS K0070. However, if a sample is not dissolved, dioxane or THF is used as the solvent, for example. Further study indicates that not only the acid value of the polyester resin but also the acid value of the toner is critical in maintaining low-temperature fixability and hot-offset resistance. The acid value of the toner is preferably <NUM> to <NUM> KOHmg/ g. If the acid value of the toner exceeds <NUM> KOHmg/g, the elongation or the cross-linking reaction of the prepolymer becomes insufficient, and the hot-offset resistance is adversely affected. If the acid value is smaller than <NUM> KOHmg/g, the elongation or the cross-linking reaction of the prepolymer is easily facilitated, and a problem is caused in production stability. The acid value of the toner can be measured in the same manner as the measurement of the acid value of the polyester resin.

So as to achieve low-temperature fixability, heat-resistant preservability, and high durability, the glass transition temperature of the toner is preferably <NUM> to <NUM>. If the glass transition temperature is lower than <NUM>, toner blocking in the developing machine or filming on the photoconductor easily occurs. If the glass transition temperature exceeds <NUM>, the low-temperature fixability is easily degraded. The glass transition temperature of the toner can be measured in the same manner as the measurement of the glass transition temperature of the polyester resin.

In the low-temperature fixing toner of this embodiment, the volume-average particle diameter (Dv) of the toner is preferably <NUM> to <NUM>, and more preferably, the ratio (Dv/Dn) of the volume-average particle diameter (Dv) to the number-average particle diameter (Dn) is in a range of <NUM> to <NUM>. As Dv/Dn is specified in this manner, a toner having high resolution and high image quality can be obtained. So as to obtain an image with even higher quality, Dv is preferably set at <NUM> to <NUM>, Dv/Dn is preferably set at <NUM> to <NUM>, and the number of particles of <NUM> or smaller is preferably set at <NUM> to <NUM> in percentage. More preferably, Dv is set at <NUM> to <NUM>, and Dv/Dn is set at <NUM> to <NUM>. Such a toner excels in heat-resistant preservability, low-temperature fixability, and hot-offset resistance. Particularly, such a toner excels in image glossiness when used in a full-color copying machine or the like. Further, in a two-component developer, even if the toner is supplied and consumed over a long period of time, variations in the particle diameter of the toner in the developer become smaller. Even if the toner is stirred in the developing device over a long period of time, preferred stable developing properties can be achieved.

The average particle size and the granularity distribution of the toner were measured with a Coulter counter Type TA-II, to which an interface that outputs a number distribution and a volume distribution (manufactured by the Institute of Japanese Union of Scientists & Engineers) and a PC9801 personal computer (manufactured by NEC Corporation) were connected.

Example preparations of low-temperature fixing toners of this embodiment are now described.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of terephthalic acid, <NUM> parts of ethylene glycol, and <NUM> parts of hydrogenated bisphenol A are introduced. In a normal-pressure nitrogen gas stream, a condensation reaction was conducted at <NUM> for <NUM> hours, and the condensation reaction was continued at a reaction temperature of <NUM> for five hours. After the reaction was further continued for five hours while dehydration was conducted at a reduced pressure of <NUM> to <NUM> mmHg, cooling was conducted, to obtain a polyester resin (PE1). Of the obtained polyester resin (PE1), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, the acid value was <NUM> KOHmg/g, and the glass transition temperature (Tg) was <NUM>. The ratio (Mw/Tg) between the weight-average molecular weight and the glass transition temperature was <NUM>. The molar ratio between the benzene ring skeleton and the <NUM>,<NUM>-cyclohexylene skeleton was <NUM>, and the molar ratio between the benzene ring skeleton and double-end ester-bond alkylene skeleton was <NUM>.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of isophthalic acid, <NUM> parts of terephthalic acid, and two parts of dibutyltin oxide were introduced. A condensation reaction was then conducted in a normal-pressure nitrogen gas stream at <NUM> for eight hours. After the reaction was continued for five hours while dehydration was conducted at a reduced pressure of <NUM> to <NUM> mmHg, cooling to <NUM> was performed, and a reaction with <NUM> parts of isophorone diisocyanate was conducted in ethyl acetate for two hours, to obtain a prepolymer (a1). Of the obtained prepolymer (a1), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, and the average number of functional groups was <NUM>.

Into a reaction vessel equipped with a mixing stick and a thermometer, <NUM> parts of isophorodiamine and <NUM> parts of methyl ethyl ketone were introduced. A reaction was then conducted at <NUM> for five hours, to obtain a ketimine compound (b1).

Eighty-five parts of the polyester (PE1), <NUM> parts of the prepolymer (a1), two parts of the ketimine compound (b1), five parts of desolated-fatty-acid-type carnauba wax, <NUM> parts of carbon black (#<NUM>, manufactured by Mitsubishi Chemical Corporation), one part of metal-containing azo compound, and five parts of water were mixed and stirred with a Henschel mixer. The resultant material was then heated and dissolved with a roll mill at a temperature of <NUM> to <NUM> for approximately <NUM> minutes. After cooled to room temperature, the resultant kneaded material was pulverized and classified with a jet mill and a pneumatic classification apparatus, to obtain a toner matrix. With the obtained toner matrix, <NUM> parts of hydrophobic silica was additionally mixed, and a toner (I) was completed.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of terephthalic acid, <NUM> parts of ethylene glycol, and <NUM> parts of hydrogenated bisphenol A are introduced. A polyester resin (PE2) was then obtained in the same manner as in Example Preparation <NUM>. Of the obtained polyester resin (PE2), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, the acid value was <NUM> KOHmg/g, and the glass transition temperature (Tg) was <NUM>. The ratio (Mw/Tg) between the weight-average molecular weight and the glass transition temperature was <NUM>. The molar ratio between the benzene ring skeleton and the <NUM>,<NUM>-cyclohexylene skeleton was <NUM>, and the molar ratio between the benzene ring skeleton and double-end ester-bond alkylene skeleton was <NUM>.

Eighty-five parts of the polyester resin (PE2), <NUM> parts of the prepolymer (a1), two parts of the ketimine compound (b1), five parts of desolated-fatty-acid-type carnauba wax, <NUM> parts of carbon black (#<NUM>, manufactured by Mitsubishi Chemical Corporation), one part of metal-containing azo compound, and five parts of water were mixed and stirred with a Henschel mixer. The resultant material was then heated and dissolved with a roll mill at a temperature of <NUM> to <NUM> for approximately <NUM> minutes. After cooled to room temperature, the resultant kneaded material was pulverized and classified with a jet mill and a pneumatic classification apparatus, to obtain a toner matrix. With the obtained toner matrix, <NUM> parts of hydrophobic silica was additionally mixed, and a toner (II) was completed.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of terephthalic acid, <NUM> parts of ethylene glycol, and <NUM> parts of hydrogenated bisphenol A are introduced. A polyester resin (PE3) was then obtained in the same manner as in Example Preparation <NUM>. Of the obtained polyester resin (PE3), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, the acid value was <NUM> KOHmg/g, and the glass transition temperature (Tg) was <NUM>. The ratio (Mw/Tg) between the weight-average molecular weight and the glass transition temperature was <NUM>. The molar ratio between the benzene ring skeleton and the <NUM>,<NUM>-cyclohexylene skeleton was <NUM>, and the molar ratio between the benzene ring skeleton and double-end ester-bond alkylene skeleton was <NUM>.

Eighty-three parts of the polyester resin (PE3), <NUM> parts of the prepolymer (a1), two parts of the ketimine compound (b1), five parts of desolated-fatty-acid-type carnauba wax, <NUM> parts of carbon black (#<NUM>, manufactured by Mitsubishi Chemical Corporation), one part of metal-containing azo compound, and five parts of water were mixed and stirred with a Henschel mixer. The resultant material was then heated and dissolved with a roll mill at a temperature of <NUM> to <NUM> for approximately <NUM> minutes. After cooled to room temperature, the resultant kneaded material was pulverized and classified with a jet mill and a pneumatic classification apparatus, to obtain a toner matrix. With the obtained toner matrix, <NUM> parts of hydrophobic silica was additionally mixed, and a toner (III) was completed.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of terephthalic acid, eight parts of ethylene glycol, and <NUM> parts of hydrogenated bisphenol A are introduced. A polyester resin (PE4) was then obtained in the same manner as in Example Preparation <NUM>. Of the obtained polyester resin (PE4), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, the acid value was <NUM> KOHmg/g, and the glass transition temperature (Tg) was <NUM>. The ratio (Mw/Tg) between the weight-average molecular weight and the glass transition temperature was <NUM>. The molar ratio between the benzene ring skeleton and the <NUM>,<NUM>-cyclohexylene skeleton was <NUM>, and the molar ratio between the benzene ring skeleton and double-end ester-bond alkylene skeleton was <NUM>.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of isophthalic acid, <NUM> parts of terephthalic acid, and two parts of dibutyltin oxide were introduced. In a normal-pressure nitrogen gas stream, a condensation reaction was then conducted at <NUM> for eight hours. After the reaction was continued for five hours while dehydration was conducted at a reduced pressure of <NUM> to <NUM> mmHg, cooling to <NUM> was performed, and a reaction with <NUM> parts of isophorone diisocyanate was conducted in ethyl acetate for two hours, to obtain a prepolymer (a2). Of the obtained prepolymer (a2), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, and the average number of functional groups was <NUM>.

Into a beaker, <NUM> parts of the prepolymer (a2), <NUM> parts of the polyester resin (PE4), and <NUM> parts of ethyl acetate were introduced, and these materials were stirred and dissolved. Into a bead mill, <NUM> parts of rice bran wax as a release agent, four parts of copper phthalocyanine blue pigment, and <NUM> parts of ethyl acetate were introduced. These materials were then dispersed for <NUM> minutes. The two solutions were mixed, and were stirred with a TK homomixer at <NUM>,<NUM> rpm for five minutes. After that, the mixture was subjected to a dispersion treatment with a bead mill for ten minutes. The resultant material is a toner material oil dispersion liquid (<NUM>).

Into a beaker, <NUM> parts of ion exchanged water, <NUM> parts of tricalcium phosphate <NUM>% suspension, and <NUM> parts of sodium dodecylbenzenesulfonate are introduced. While being stirred with a TK homomixer at <NUM>,<NUM> rpm, the toner material oil dispersion liquid (<NUM>) and <NUM> parts of the ketimine compound (b1) were added to the aqueous dispersion liquid. A reaction was then conducted while the stirring was continued for <NUM> minutes. The organic solvent was removed, within one hour, from the reacted dispersion liquid (viscosity: <NUM>,<NUM> mPa • s) at a reduced pressure and a temperature of <NUM> or lower. After that, filtration, washing, drying, and pneumatic classification were performed, to obtain a spherical toner matrix.

Into a Q mixer (manufactured by Mitsui Mining Co. ), <NUM> parts of the obtained matrix particles and <NUM> parts of charge control agent (BONTRON E-<NUM>, manufactured by Orient Chemical Industries Co. ) were introduced. The circumferential speed of a turbine blade was set at <NUM>/sec, and mixing was performed. In this case, the mixing operation was performed in five cycles of a two-minute operation and a one-minute interval, and the total processing time was <NUM> minutes. Further, <NUM> parts of hydrophobic silica (H2000, manufactured by Clariant (Japan) K. ) was added, and mixing was performed. In this case, the mixing operation was performed in five cycles of <NUM>-second mixing and a one-minute interval at a circumferential speed of <NUM>/sec. As a result, a toner (IV) was completed.

The physical properties related to the polyester resins (PE1) through (PE4) used in the toners (I) through (IV) are shown below in Table <NUM>.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of terephthalic acid, <NUM> parts of ethylene glycol, and <NUM> parts of hydrogenated bisphenol A are introduced. A polyester resin (PE5) was then obtained in the same manner as in Example Preparation <NUM>. Of the obtained polyester resin (PE5), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, the acid value was <NUM> KOHmg/g, and the glass transition temperature (Tg) was <NUM>. The ratio (Mw/Tg) between the weight-average molecular weight and the glass transition temperature was <NUM>. The molar ratio between the benzene ring skeleton and the <NUM>,<NUM>-cyclohexylene skeleton was <NUM>, and the molar ratio between the benzene ring skeleton and double-end ester-bond alkylene skeleton was <NUM>.

Eighty-five parts of the polyester resin (PE5), <NUM> parts of the prepolymer (a1), two parts of the ketimine compound (b1), five parts of desolated-fatty-acid-type carnauba wax, <NUM> parts of carbon black (#<NUM>, manufactured by Mitsubishi Chemical Corporation), one part of metal-containing azo compound, and five parts of water were mixed and stirred with a Henschel mixer. The resultant material was then heated and dissolved with a roll mill at a temperature of <NUM> to <NUM> for approximately <NUM> minutes. After cooled to room temperature, the resultant kneaded material was pulverized and classified with a jet mill and a pneumatic classification apparatus, to obtain a toner matrix. With the obtained toner matrix, <NUM> parts of hydrophobic silica was additionally mixed, and a toner (V) was completed.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of terephthalic acid, <NUM> parts of ethylene glycol, and <NUM> parts of hydrogenated bisphenol A are introduced. A polyester resin (PE6) was then obtained in the same manner as in Example Preparation <NUM>. Of the obtained polyester resin (PE6), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, the acid value was <NUM> KOHmg/g, and the glass transition temperature (Tg) was <NUM>. The ratio (Mw/Tg) between the weight-average molecular weight and the glass transition temperature was <NUM>. The molar ratio between the benzene ring skeleton and the <NUM>,<NUM>-cyclohexylene skeleton was <NUM>, and the molar ratio between the benzene ring skeleton and double-end ester-bond alkylene skeleton was <NUM>.

Into a beaker, <NUM> parts of the prepolymer (a1), <NUM> parts of the polyester resin (PE6), and <NUM> parts of ethyl acetate were introduced, and these materials were stirred and dissolved. Into a bead mill, <NUM> parts of rice bran wax as a release agent, four parts of copper phthalocyanine blue pigment, and <NUM> parts of ethyl acetate were introduced. These materials were then dispersed for <NUM> minutes. The two solutions were mixed, and were stirred with a TK homomixer at <NUM>,<NUM> rpm for five minutes. After that, the mixture was subjected to a dispersion treatment with a bead mill for ten minutes. The resultant material is a toner material oil dispersion liquid (<NUM>).

Into a Q mixer (manufactured by Mitsui Mining Co. ), <NUM> parts of the obtained matrix particles and <NUM> parts of charge control agent (BONTRON E-<NUM>, manufactured by Orient Chemical Industries Co. ) were introduced. The circumferential speed of a turbine blade was set at <NUM>/sec, and mixing was performed. In this case, the mixing operation was performed in five cycles of a two-minute operation and a one-minute interval, and the total processing time was <NUM> minutes. Further, <NUM> parts of hydrophobic silica (H2000, manufactured by Clariant (Japan) K. ) was added, and mixing was performed. In this case, the mixing operation was performed in five cycles of <NUM>-second mixing and a one-minute interval at a circumferential speed of <NUM>/sec. As a result, a toner (VI) was completed.

Into a reaction vessel equipped with a condenser tube, a mixer, and a nitrogen introduction tube, <NUM> parts of bisphenol-A ethylene oxide two-molar adduct, <NUM> parts of terephthalic acid, <NUM> parts of ethylene glycol, and <NUM> parts of hydrogenated bisphenol A are introduced. A polyester resin (PE7) was then obtained in the same manner as in Example Preparation <NUM>. Of the obtained polyester resin (PE7), the weight-average molecular weight (Mw) of the THF soluble portion was <NUM>,<NUM>, the acid value was <NUM> KOHmg/g, and the glass transition temperature (Tg) was <NUM>. The ratio (Mw/Tg) between the weight-average molecular weight and the glass transition temperature was <NUM>. The molar ratio between the benzene ring skeleton and the <NUM>,<NUM>-cyclohexylene skeleton was <NUM>, and the molar ratio between the benzene ring skeleton and double-end ester-bond alkylene skeleton was <NUM>.

Into a beaker, <NUM> parts of the prepolymer (a2), <NUM> parts of the polyester resin (PE7), and <NUM> parts of ethyl acetate were introduced, and these materials were stirred and dissolved. Into a bead mill, <NUM> parts of rice bran wax as a release agent, four parts of copper phthalocyanine blue pigment, and <NUM> parts of ethyl acetate were introduced. These materials were then dispersed for <NUM> minutes. The two solutions were mixed, and were stirred with a TK homomixer at <NUM>,<NUM> rpm for five minutes. After that, the mixture was subjected to a dispersion treatment with a bead mill for ten minutes. The resultant material is a toner material oil dispersion liquid (<NUM>).

Into a Q mixer (manufactured by Mitsui Mining Co. ), <NUM> parts of the obtained matrix particles and <NUM> parts of charge control agent (BONTRON E-<NUM>, manufactured by Orient Chemical Industries Co. ) were introduced. The circumferential speed of a turbine blade was set at <NUM>/sec, and mixing was performed. In this case, the mixing operation was performed in five cycles of a two-minute operation and a one-minute interval, and the total processing time was <NUM> minutes. Further, <NUM> parts of hydrophobic silica (H2000, manufactured by Clariant (Japan) K. ) was added, and mixing was performed. In this case, the mixing operation was performed in five cycles of <NUM>-second mixing and a one-minute interval at a circumferential speed of <NUM>/sec. As a result, a toner (VII) was completed.

The physical properties related to the polyester resins (PE5) through (PE7) used in the toners (V) through (VII) are shown below in Table <NUM>.

As for the above described toners (I) through (VII) as examples of low-temperature fixing toners of this embodiment, low-temperature fixability, high-temperature offset resistance, and heat-resistant preservability was evaluated. The evaluated items of the toners, and the evaluation method are as follows.

A paper sheet Type <NUM>, manufactured by Ricoh Company, Ltd. , was set on an apparatus produced by modifying the fixing unit of a copying machine MF2200, manufactured by Ricoh Company, Ltd. , which used a fixing roller made of Teflon (a registered trade name). Copying tests were then conducted. The fixing temperature was varied, to determine a cold offset temperature (the lower fixing temperature limit) and a hod offset temperature (a hot-offset-resistant temperature). The lower fixing temperature limit of a conventional low-temperature fixing toner is approximately <NUM> to <NUM>. The conditions under which low-temperature fixability was evaluated are as follows. The linear velocity of paper sheet feeding is <NUM> to <NUM>/sec, the surface pressure was <NUM> kgf/cm<NUM>, and the nip width was <NUM>. As for the conditions in which hot offset was evaluated, the linear velocity of paper sheet feeding was <NUM>/sec, the surface pressure was <NUM> kgf/cm<NUM>, and the nip width was <NUM>.

The criteria for evaluation on the respective properties are as follows.

Twenty grams of each toner sample was put into a <NUM>-ml glass bottle, and the glass bottle was tapped approximately <NUM> times, to tightly gather the sample. The sample was then put into a high-temperature vessel at <NUM>, and was left there for <NUM> hours. After that, a penetrometer was used to determine a degree of penetration as follows. <NUM>) Heat-resistant preservability (five levels).

The results of the toner evaluations are shown below in Table <NUM>.

As can be seen from Table <NUM>, the toners (I) through (IV), (VI), and (VII) having glass transition temperatures (Tg) between <NUM> and <NUM> achieved excellent low-temperature fixability, high hot-offset resistances, and excellent heat-resistant preservability. However, the toner (V) having a lower glass transition temperature (Tg) than <NUM> was excellent in low-temperature fixability and hot-offset resistance, but was poor in heat-resistant preservability, as indicated by "E" in the column of heat-resistant preservability. This confirmed that a toner having a glass transition temperature (Tg) between <NUM> and <NUM> excels in low-temperature fixability, high hot-offset resistance, and heat-resistant preservability.

The above described embodiment is merely an example, and the present invention exhibits a unique effect in each of the following modes.

A cleaning blade <NUM> is formed with a blade member <NUM> having a stack structure of elastic materials having different degrees of hardness from each other, the edge line portion <NUM> of the blade member <NUM> being brought into contact with the surface of a cleaning target member such as a photoconductor <NUM> performing surface movement, the blade member <NUM> removing adhering matter from the surface of the photoconductor <NUM>. In this cleaning blade <NUM>, the cleaning layer including the edge line portion <NUM> is impregnated with a resin or is made of an elastic material having a high degree of hardness, and the permanent elongation rate of the entire blade member is set at <NUM>% or lower.

As mentioned above in the description of the embodiment, so as to increase the hardness of the edge line portion by impregnating the edge line portion with a resin in a single-layer blade member, it is necessary to use an elastic material that has a low permanent elongation rate and a relatively low degree of hardness. In a case where an elastic material having a low degree of hardness is used as the base material and the hardness of the edge line portion through an impregnation treatment is increased, the amount of impregnation needs to be made larger than that in a case where an elastic material having a high degree of hardness is used as the base material. Therefore, the impregnation time needs to be made longer, or the concentration of the impregnating coating solution needs to be made higher. This results in an increase in cost due to the elongated production time, or an increase in the cost of the impregnating coating solution due to the increased concentration of the impregnating coating solution. In view of this, elastic members made of elastic materials having different degrees of hardness from each other are bonded to each other, the edge layer 1401a in contact with the cleaning target member is made of an elastic material having a high degree of hardness, and the cleaning layer including the edge line portion <NUM> is subjected to the impregnation treatment in this embodiment. A blade member having a double-layer stack structure that can be formed in a shorter period of time than the impregnation treatment for an elastic material having a low degree of hardness is used. So as to achieve a higher degree of hardness, the cleaning layer including the edge line portion <NUM> is impregnated with a resin or is made of an elastic material having a high degree of hardness. Also, the permanent elongation rates of the edge layer 1401a, the backup layer 1401b, and the edge line portion <NUM> are combined, so that the permanent elongation rate of the entire blade member is set at <NUM>% or lower. As can be seen from the above described verification experiments, the deformation of the edge line portion <NUM> brought into contact with the photoconductor <NUM> is small, an increase in the contact area can be prevented, and the contact pressure can be increased. Further, permanent deformation over time can be effectively reduced.

This is supposedly because the backup layer 1401b bonded to the edge layer 1401a in contact with the photoconductor <NUM> has a lower degree of hardness and a lower permanent elongation rate than the edge layer 1401a and the edge line portion <NUM>, and accordingly, permanent deformation over time is reduced in the entire blade member. As the permanent elongation rate of the entire blade member is set at <NUM>% or lower, permanent deformation can be made smaller than that in the cleaning blade disclosed in Patent Document <NUM>, even if the blade member <NUM> stays in contact with the photoconductor <NUM> over a long period of time. Accordingly, the initial contact state can be maintained. This is also supposedly because the cleaning layer including the edge line portion <NUM> of the blade member <NUM> is subjected to the impregnation treatment to obtain a higher degree of hardness, or the cleaning layer is made of an elastic material having a high degree of hardness, so that the degree of hardness of the edge line portion <NUM> is made higher than those of the edge layer 1401a and the backup layer 1401b, and the contact pressure can be set at a high value. Accordingly, when the edge line portion <NUM> is brought into contact with the photoconductor <NUM>, the deformation of the edge line portion <NUM> is small, an increase of the contact area can be prevented, and cleaning performance can be improved.

In (Mode A), the blade member <NUM> includes: the cleaning layer such as an impregnated portion <NUM> including the edge line portion <NUM>; the edge layer 1401a having a surface facing the surface of the photoconductor <NUM>; and the backup layer 1401b having a non-photoconductor-facing surface opposite to the photoconductor-facing surface <NUM>, and the degrees of hardness of the elastic materials of the impregnated portion <NUM>, the edge layer 1401a, and the backup layer 1401b differ from one another.

According to this, a blade member is formed with a double-layer stack structure including at least an edge layer and a backup layer, and the edge line portion <NUM> is made to have a higher degree of hardness through an impregnation treatment as described above in an example of the embodiment. In this aspect, this blade member differs from a single-layer blade member in which the edge line portion is made to have a higher degree of hardness through an impregnation treatment. Accordingly, an increase in cost due to a prolonged production time or an increase in cost of the impregnating coating solution due to an increase in the concentration of the impregnating coating solution, and permanent deformation over time can be prevented. At the same time, excellent cleaning performance can be maintained over a long period of time.

In (Mode A) or (Mode B), the Young's modulus of the elastic material of the impregnated portion <NUM> is higher than those of the edge layer 1401a and the backup layer 1401b.

According to this, the Young's modulus of the impregnated portion <NUM> including the edge line portion <NUM> is made higher than those of the edge layer 1401a and the backup layer 1401b, and accordingly, the contact pressure with which the edge line portion <NUM> is to be brought into contact with the image bearer can be set at a high value, as described above in an example of the embodiment.

In (Mode A) through (Mode C), the Young's modulus of the elastic material of the impregnated portion <NUM> is higher than that of the edge layer 1401a, and the Young's modulus of the elastic material of the edge layer 1401a is higher than that of the backup layer 1401b.

According to this, the Young's modulus of the edge line portion <NUM> is made higher than those of the edge layer 1401a and the backup layer 1401b, and accordingly, the contact pressure can be set at a high value, as described above in an example of the embodiment. As the backup layer 1401b has a lower Young's modulus and a lower permanent elongation rate than those of the edge layer 1401a, permanent deformation over time can be reduced in the entire blade member. Accordingly, even if the blade member <NUM> is kept in contact with the photoconductor <NUM> over a long period of time, permanent deformation does not easily occur, and the initial contact state can be maintained.

In (Mode A) through (Mode D), the elastic power of the portion in the vicinity of the edge line portion of the cleaning layer is <NUM>% or higher.

According to this, defective cleaning and local wear due to plastic deformation can be prevented even in a low-temperature environment, as described above in an example of the embodiment.

In any of (Mode A) through (Mode E), at the edge line portion <NUM>, a cross-linked structure is formed with an ultraviolet curable resin containing at least an acrylate or methacrylate having a tricyclodecane or adamantane skeleton.

According to this, the toner removal performance is greatly improved, the wear of the cleaning blade is reduced, and excellent cleaning performance can be maintained over a long period of time, as mentioned above in the description of the embodiment. Also, the coefficient of friction between the cleaning blade and the photoconductor is reduced, and the wear of the photoconductor is reduced. Accordingly, the life of the photoconductor and the life of the image forming apparatus can be prolonged. Further, as the cleaning blade does not rub the toner additive or the like against the surface of the photoconductor, any abnormal image with blanks is not generated.

In (Mode F), the number of functional groups of the acrylate or methacrylate having a tricyclodecane or adamantane skeleton is one to six.

According to this, the hardness of the edge line portion of the blade member can be further increased. Accordingly, too large deformation of the edge line portion of the blade member can be prevented, the contact pressure can be made higher, and permanent deformation can be reduced. At the same time, excellent cleaning performance can be maintained over a long period of time, as mentioned above in the description of the embodiment.

In (Mode F) or (Mode G), the acrylate or methacrylate having the tricyclodecane or adamantane skeleton has a molecular weight of <NUM> or smaller.

According to this, the molecular weight of the acrylate or methacrylate having the tricyclodecane or adamantane skeleton is <NUM> or smaller. Accordingly, the molecular size becomes smaller, and impregnating the cleaning blade becomes easier, facilitating an increase in hardness, as mentioned above in the description of the embodiment.

In any of (Mode F) through (Mode H), an acrylate monomer having the molecular weight of <NUM> to <NUM> is mixed with the acrylate or methacrylate having a tricyclodecane or adamantane skeleton.

According to this, an acrylate monomer having a molecular weight of <NUM> to <NUM> is mixed with the acrylate or methacrylate having the tricyclodecane or adamantane skeleton, so that the blade member can be impregnated with a resin by brush coating, spray coating, dip coating, or the like, as mentioned above in the description of the embodiment.

An image forming apparatus includes: an image bearer such as a photoconductor <NUM>; and a cleaning member that is in contact with the surface of the image bearer to remove adhering matter adhering to the surface of the image bearer. In this image forming apparatus, an image formed on the image bearer is eventually transferred onto a recording medium, and the cleaning blade of any of (Mode A) through (Mode I) is used as the cleaning member.

According to this, the image bearer can be properly cleaned over a long period of time, and excellent image formation can be performed, as mentioned above in the description of the embodiment.

A process cartridge <NUM> that is detachably attached to an image forming apparatus includes: an image bearer such as a photoconductor <NUM>; and a cleaning member that is in contact with the surface of the image bearer to remove adhering matter adhering to the surface of the image bearer. In this process cartridge <NUM>, the cleaning blade of any of (Mode A) through (Mode I) is used as the cleaning member.

According to this, cleaning performance can be improved while permanent deformation of the blade member over time is reduced, as mentioned above in the description of the embodiment. Also, with the form of a process cartridge, higher operability can be achieved.

Claim 1:
A cleaning blade (<NUM>; <NUM>; <NUM>-<NUM>) comprising:
an edge layer (1201a; 1401a; 1601a-1901a) including an edge line portion (<NUM>; <NUM>-<NUM>) to contact a surface of a cleaning target performing surface movement to remove adhering matter from the surface of the cleaning target;
a backup layer (1201b; 1401b; 1601b-1901b) formed with elastic materials having different degrees of hardness from the edge layer (1201a; 1401a; 1601a-1901a),
wherein the edge layer (1201a; 1401a; 1601a-1901a) is impregnated with a resin or is made of an elastic material having a higher degree of hardness than the backup layer (1201b; 1401b; 1601b-1901b), and
a permanent elongation rate of the entire blade including the edge layer and the backup layer is set at <NUM>% or lower,
wherein
the edge layer (1201a) includes a first edge layer (<NUM>) including the edge line portion (<NUM>) and a second edge layer (<NUM>) including a surface (<NUM>) facing the surface of the cleaning target,
the backup layer (1201b) includes a non-facing surface opposite to the facing surface (<NUM>), and
degrees of hardness of elastic materials of the first edge layer (<NUM>), the second edge layer (<NUM>), and the backup layer (14201b) differ from one another,
characterized in that the film thickness of the first layer (<NUM>) and the second layer (<NUM>) becomes gradually thicker in the direction toward the edge line portion (<NUM>).