Source: http://patents.com/us-9817328.html
Timestamp: 2018-11-21 17:54:17
Document Index: 227286842

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US Patent # 9,817,328. Charging member, process cartridge, and image forming apparatus - Patents.com
United States Patent 9,817,328
Miura , et al. November 14, 2017
A charging member includes a support member, a conductive elastic layer disposed on the support member, and a front surface layer disposed on the conductive elastic layer. Irregularities with a cycle of shorter than 0.1 mm and irregularities with a cycle of 0.1 mm or longer are distributed on an entirety of an outer circumferential surface of the charging member, and satisfy the following conditions of (1) and (2): (1) the irregularities with the cycle of shorter than 0.1 mm have an average height of greater than 0 .mu.m and 4 .mu.m or less; and (2) the irregularities with the cycle of 0.1 mm or longer have an average height of from 5 .mu.m to 30 .mu.m. A half-value width of a maximum frequency value of height distribution on the outer circumferential surface is from 1 .mu.m to 3 .mu.m.
Miura; Hiroyuki (Kanagawa, JP), Narita; Kosuke (Kanagawa, JP), Hayashi; Yoshiyuki (Kanagawa, JP)
Family ID: 1000002947349
15/218,264
US 20170277059 A1 Sep 28, 2017
Current CPC Class: G03G 15/0233 (20130101); G03G 21/1814 (20130101); G03G 21/18 (20130101)
Current International Class: G03G 15/02 (20060101); G03G 21/18 (20060101)
6684043 January 2004 Zona
2007/0189790 August 2007 Miura
2010/0135695 June 2010 Mayuzumi
2014/0219680 August 2014 Hagiwara
2016/0154336 June 2016 Masu
Translation of reference Tatsumi et al. (JP 2015-045,788 A) Pub date Mar. 12, 2015 Listed in IDS and translation provided by Applicant. cited by examiner.
1. A charging member comprising: a support member; a conductive elastic layer disposed on the support member; and a front surface layer disposed on the conductive elastic layer, wherein irregularities with a cycle of shorter than 0.1 mm and irregularities with a cycle of 0.1 mm or longer are distributed on an entirety of an outer circumferential surface of the charging member, and satisfy the following conditions of (1) and (2): (1) the irregularities with the cycle of shorter than 0.1 mm have an average height of greater than 0 .mu.m and 4 .mu.m or less; and (2) the irregularities with the cycle of 0.1 mm or longer have an average height of from 5 .mu.m to 30 .mu.m, and wherein a half-value width of a maximum frequency value of height distribution on the outer circumferential surface is from 1 .mu.m to 3 .mu.m.
2. The charging member according to claim 1, wherein the irregularities with the cycle of shorter than 0.1 mm have an average height of from 0.5 .mu.m to 3.5 .mu.m.
3. The charging member according to claim 1, wherein the irregularities with the cycle of shorter than 0.1 mm have an average height of from 1.0 .mu.m to 3.0 .mu.m.
4. The charging member according to claim 1, wherein the irregularities with the cycle of 0.1 mm or longer have an average height of from 5 .mu.m to 20 .mu.m.
5. The charging member according to claim 1, wherein the irregularities with the cycle of 0.1 mm or longer have an average height of from 6 .mu.m to 10 .mu.m.
6. The charging member according to claim 1, wherein a mean cycle of the irregularities with the cycle of shorter than 0.1 mm is 5 .mu.m or longer.
7. The charging member according to claim 1, wherein a mean cycle of the irregularities with the cycle of shorter than 0.1 mm is 50 .mu.m or shorter.
8. The charging member according to claim 1, wherein a mean cycle of the irregularities with the cycle of 0.1 mm or longer is 0.15 mm or longer.
9. The charging member according to claim 1, wherein a mean cycle of the irregularities with the cycle of 0.1 mm or longer is 0.45 mm or shorter.
10. The charging member according to claim 1, wherein the front surface layer contains an electronically conductive agent.
11. The charging member according to claim 10, wherein the electronically conductive agent is a metal oxide.
12. A process cartridge that is attached to or is detached from an image forming apparatus, comprising: an electrophotographic photoreceptor; and a charging device that includes the charging member according to claim 1, that applies, to the charging member, only a DC voltage or a voltage obtained by superimposing an AC voltage to a DC voltage, and that charges a front surface of the electrophotographic photoreceptor by a contact charging method.
13. An image forming apparatus comprising: an electrophotographic photoreceptor; a charging device that includes the charging member according to claim 1, that applies, to the charging member, only a DC voltage or a voltage obtained by superimposing an AC voltage to a DC voltage, and that charges a front surface of the electrophotographic photoreceptor by a contact charging method; a latent image forming device that forms a latent image on the front surface of the charged electrophotographic photoreceptor; a developing device that develops the latent image formed on the front surface of the electrophotographic photoreceptor, using developer containing toner, and forms a toner image on the front surface of the electrophotographic photoreceptor; and a transfer device that transfers the toner image formed on the front surface of the electrophotographic photoreceptor to a recording medium.
According to an aspect of the invention, a charging member includes:
a conductive elastic layer disposed on the support member; and
a front surface layer disposed on the conductive elastic layer. Irregularities with a cycle of shorter than 0.1 mm and irregularities with a cycle of 0.1 mm or longer are distributed on an entirety of an outer circumferential surface of the charging member, and satisfy the following conditions of (1) and (2):
(1) The irregularities with the cycle of shorter than 0.1 mm have an average height of greater than 0 .mu.m and 4 .mu.m or less; and
(2) The irregularities with the cycle of 0.1 mm or longer have an average height of from 5 .mu.m to 30 .mu.m.
A half-value width of a maximum frequency value of height distribution on the outer circumferential surface is from 1 .mu.m to 3 .mu.m.
FIG. 2B shows an example of an approximate curve for obtaining a "half-value width of the maximum frequency value of height distribution on the outer circumferential surface";
A charging member according to the exemplary embodiment includes a support member, a conductive elastic layer disposed on the support member, and a front surface layer disposed on the conductive elastic layer. In other words, the charging member according to the exemplary embodiment includes at least the conductive elastic layer and the front surface layer which are laminated on the support member.
Then, irregularities with a cycle of shorter than 0.1 mm and irregularities with a cycle of 0.1 mm or longer, are distributed on the entirety of the outer circumferential surface of the charging member according to the exemplary embodiment. Also, the charging member according to the exemplary embodiment satisfies the following conditions of (1) and (2). A half-value width of the mode of the height distribution on the outer circumferential surface is in a range of from 1 .mu.m to 3 .mu.m.
(1) The irregularities with the cycle of shorter than 0.1 mm have an average height of greater than 0 .mu.m and 4 .mu.m or less.
FIG. 1 is a view showing an example of the charging member according to the exemplary embodiment. A charging member 208 shown in FIG. 1 includes a support member 30 which is a bar-shaped member (shaft) having a cylindrical shape or a column shape, a conductive elastic layer 31 disposed on an outer circumferential surface of the support member 30, and a front surface layer 32 disposed on an outer circumferential surface of the conductive elastic layer 31.
FIG. 2A is a view schematically showing an example of irregularities which are distributed on the outer circumferential surface of the charging member according to the exemplary embodiment. FIG. 2A shows a shape viewed when the front surface layer 32 and the conductive elastic layer 31 of the charging member 208 are cut in a thickness direction and in an axial direction of the support member 30. The outer circumferential surface of the charging member 208 is shaped by the front surface layer 32 disposed on undulation formed on the conductive elastic layer 31.
The image forming apparatus employs a charging method in which only a DC voltage is applied to the charging member, or a charging method in which a voltage obtained by superimposing an AC voltage to a DC voltage is applied to the charging member. In a case where only the DC voltage is applied to the charging member and the photoreceptor is charged in a contact charging method, an unintended micro-chromatic line is produced on an image in some cases. Meanwhile, in a case where the voltage obtained by superimposing the AC voltage to the DC voltage is applied to the charging member and the photoreceptor is charged by a contact charging method, an unintended white spot is produced on an image in some cases. The charging member of the exemplary embodiment reduces production of both the micro-chromatic line and the white spot. As a mechanism for less production thereof, the following description is assumed.
Hereinafter, a micro-chromatic line produced when the photoreceptor is subjected to contact charging by the charging member, to which only the DC voltage is applied, is simply referred to as the micro-chromatic line. A white spot produced when the photoreceptor is subjected to contact charging by the charging member, to which the voltage obtained by superimposing the AC voltage to the DC voltage is applied, is simply referred to as the white spot.
It is considered that the micro-chromatic line is produced due to a low discharge frequency of discharge phenomena (post-discharge) that occurs immediately after a contact between the photoreceptor and the charging member. In the case where only the DC voltage is applied, it is considered that the discharge frequency of the post-discharge is low, and regions which are not sufficiently charged are irregularly formed on the outer circumferential surface of the charging member. As a result, the micro-chromatic line is likely to be produced, compared to the case where the AC voltage is superimposed to the DC voltage. When the charging member is continuously used, toner or the like is accumulated on the outer circumferential surface of the charging member. Thus, it is considered that when the charging member is used continuously, the toner or the like is accumulated on the outer circumferential surface of the charging member, and therefore, the discharge frequency of the post-discharge is further lowered and the micro-chromatic line is more clearly viewed.
Meanwhile, it is considered that the white spot is produced due to locally strong discharge which is likely to occur when the AC voltage is superimposed to the DC voltage.
The micro-chromatic line and the white spot are both likely to be produced and more clearly viewed in a case where an image is formed at a higher speed and in a case where an image is formed using toner having a smaller particle diameter.
In order to reduce the production of the micro-chromatic line, it is effective that the irregularities are distributed on the outer circumferential surface of the charging member, thereby increasing a discharge space between the photoreceptor and the charging member and promoting the post-discharge. However, only the distribution of the irregularities on the outer circumferential surface of the charging member does not result in effective reduction in the production of the micro-chromatic line, and does not result in reduction in the occurrence of the locally strong discharge and reduction in the production of the white spot, either.
According to the charging member of the exemplary embodiment, while the mechanism is not entirely clear, it is considered that the "irregularities with the cycle of shorter than 0.1 mm" (roughness components) and the "irregularities with the cycle of 0.1 mm or longer" (waviness components) are distributed on the outer circumferential surface of the charging member so as to have the average heights of greater than 0 .mu.m and 4 .mu.m or less and of from 5 .mu.m to 30 .mu.m, respectively, and both types of irregularities are arranged, thereby promoting the post-discharge when only the DC voltage is applied, reducing the occurrence of the locally strong discharge when the AC voltage is superimposed to the DC voltage, and then causing the toner or the like to be unlikely to be attached to the outer circumferential surface, and, as a result, reducing the production of the micro-chromatic line and the production of the white spot.
The average height of the roughness components is preferably greater than 0 .mu.m and 4 .mu.m or less, more preferably from 0.5 .mu.m to 3.5 .mu.m, and still more preferably from 1.0 .mu.m to 3.0 .mu.m.
The average height of the waviness components is preferably from 5 .mu.m to 30 .mu.m, more preferably from 5 .mu.m to 20 .mu.m, and still more preferably from 6 .mu.m to 10 .mu.m.
In the exemplary embodiment, the "half-value width of the maximum frequency value of the height distribution on the outer circumferential surface" is from 1 .mu.m to 3 .mu.m. The half-value width of wider than 3 .mu.m means variations in the height of the irregularities on the outer circumferential surface. In this case, it is difficult to reduce both the micro-chromatic line and the white spot. It is considered that it is more desirable as the half-value width is narrower in terms of low variations in the height of the irregularities on the outer circumferential surface. However, when the half-value width is decreased to be narrower than 1 .mu.m, the heights of the irregularities, which are distributed on the outer circumferential surface, are lowered, the outer circumferential surface becomes close to an even surface, and it is difficult to reduce the micro-chromatic line and the white spot. In addition, it is difficult to have the half-value width of narrower than 1 .mu.m, while the conductive elastic layer is manufactured by extrusion molding which is suitable for mass production.
Examples of the support member include a metal member formed of iron (free-machining steel or the like), copper, brass, stainless steel, aluminum, nickel, or the like; a iron member subjected to coating processing using chrome, nickel, or the like; a member subjected to plating processing on an outer circumferential surface of a resin or ceramic member; a resin or ceramic member which contains a conductive agent; or the like.
It is desirable that volume resistivity of the conductive elastic layer is from 10.sup.3 .OMEGA.cm to 10.sup.14 .OMEGA.cm. An electronically conductive agent content in the conductive elastic layer is preferably from 1 part by weight to 30 parts by weight, and more preferably from 15 parts by weight to 25 parts by weight, with respect to 100 parts by weight of the elastic material. An ion conductive agent content in the conductive elastic layer is preferably from 0.1 parts by weight to 5 parts by weight, and more preferably from 0.5 parts by weight to 3 parts by weight, with respect to 100 parts by weight of the elastic material.
A vulcanization accelerator content in the conductive elastic layer is preferably from 1 part by weight to 10 parts by weight, and more preferably from 2 parts by weight to 6 parts by weight, with respect to 100 parts by weight of the elastic material.
A vulcanization accelerator aid content in the conductive elastic layer is preferably from 1 part by weight to 15 parts by weight, and more preferably from 3 parts by weight to 10 parts by weight, with respect to 100 parts by weight of the elastic material.
A filler content in the conductive elastic layer is preferably from 5 parts by weight to 100 parts by weight, and more preferably from 10 parts by weight to 60 parts by weight, with respect to 100 parts by weight of the elastic material.
The layer thickness of the conductive elastic layer is preferably from 1 mm to 10 mm, more preferably from 2 mm to 8 mm, and still more preferably from 3 mm to 6 mm. The layer thickness of the conductive elastic layer is a value obtained by observing a cross section of the charging member cut in a direction orthogonal to the rotating direction using an optical microscope and by measuring random ten points and obtaining an average value.
An average height of the "irregularities with the cycle of 0.1 mm or longer" (waviness components) which are distributed on the outer circumferential surface of the conductive elastic layer is preferably from 5 .mu.m to 30 .mu.m. In addition, a mean cycle of the waviness components on the outer circumferential surface of the conductive elastic layer, that is, a mean cycle of the "irregularities with the cycle of 0.1 mm or longer" (waviness components) distributed on the outer circumferential surface of the conductive elastic layer, is preferably 0.15 mm or longer, more preferably, 0.20 mm or longer, and still more preferably 0.25 mm or longer, and is preferably 0.45 mm or shorter, more preferably, 0.35 mm or shorter, and still more preferably 0.30 mm or shorter.
(ii) A die temperature obtained when the conductive elastic layer forming composition is extruded from the extruder: as the die temperature is higher, the waviness components tend to become decreased. It is preferable that the die temperature is in a range of from 40.degree. C. to 90.degree. C.
(iii) As the heating temperature and a period of heating time obtained when the conductive elastic layer forming composition is heated to be subjected to the cross-linking reaction: as the heating temperature is increased, the waviness components tend to be decreased. As the period of heating time is increased, the waviness components tend to be decreased. When a furnace is used for heating, the heating temperature is preferably in a range of from 120.degree. C. to 180.degree. C., and the period of heating time is preferably in a range of from 20 minutes to 90 minutes.
For example, the front surface layer is provided so as to reduce contamination of the charging member by the toner or the like.
An exemplary embodiment of the front surface layer includes a binder resin, particles, and another additive. It is desirable that the particles contained in the front surface layer are disposed in the binder resin.
Examples of the binder resin of the front surface layer include polyamide, polyimide, polyester, polyethylene, polyurethane, a phenolic resin, a silicone resin, an acrylic resin, a melamine resin, an epoxy resin, polyvinylidene fluoride, a tetrafluoroethylene copolymer, a polyvinyl butyral, ethylene-tetrafluoroethylene copolymer, fluororubber, polycarbonate, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, an ethylene-vinyl acetate copolymer, cellulose, and the like. As the binder resin, one type thereof may be individually used, or a combination of two or more types thereof may be used.
An example of particles contained in the front surface layer is a conductive agent. It is desirable that conductive particles having an average particle diameter of 3 .mu.m or smaller and volume resistivity of 10.sup.9 .OMEGA.cm or less as the conductive agent contained in the front surface layer. Examples of the conductive particles include a metal oxide such as a tin oxide, a titanium oxide, or a zinc oxide; carbon black; and the like. As the conductive particles, it is preferable to use the tin oxide in terms of reduction in the production of the micro-chromatic line, and it is preferable to use the tin oxide individually, or to use both the tin oxide and the carbon black.
A conductive agent content in the front surface layer is preferably from 10 parts by weight to 90 parts by weight, and more preferably from 40 parts by weight to 70 parts by weight, with respect to 100 parts by weight of the binder resin.
The front surface layer may contain particles other than the conductive agent particles in order to control the shape of the front surface of the charging member. Examples of the particles include polyamide particles, fluororesin particles, silicone resin particles, and the like, and it is preferable to use polyamide particles in terms of reduction in the production of the micro-chromatic line. As the particles, one type thereof may be individually used, or a combination of two or more types thereof may be used.
A particle content in the front surface layer is preferably from 1 part by weight to 20 parts by weight, and more preferably from 2 parts by weight to 10 parts by weight, with respect to 100 parts by weight of the binder resin.
A particle diameter of a granulated substance (conductive agent, polyamide particles, or the like) contained in the front surface layer is preferably at most 10 .mu.m or smaller and more preferably 7 .mu.m or smaller, and preferably at least 1 .mu.m or larger and more preferably 3 .mu.m or larger. The particle diameter of the granulated substance contained in the front surface layer is obtained by observing a cross section of the front surface layer using an optical microscope.
An example of a method of forming the front surface layer on the conductive elastic layer is, for example, a method in which a front surface layer forming composition obtained by mixing a binder resin, particles, and another additive is applied on the conductive elastic layer, a layer of the front surface layer forming composition is formed, and then the layer of the front surface layer forming composition is dried. Examples of a method of applying the front surface layer forming composition on the conductive elastic layer include, for example, dip coating, roll coating, blade coating, wire bar coating, spraying, bead coating, air knife coating, and curtain coating.
The layer thickness of the front surface layer is preferably from 3 .mu.m to 20 .mu.m, and more preferably from 5 .mu.m to 15 .mu.m. The layer thickness of the front surface layer is a value obtained by observing a cross section of the charging member cut in a direction orthogonal to the rotating direction using an optical microscope and by measuring random hundred points and obtaining an average value.
It is desirable that the "irregularities with the cycle of shorter than 0.1 mm" (roughness components) which are distributed on the outer circumferential surface of the charging member are the irregularities originating from the front surface layer. The highly uniform roughness components can be distributed in a method in which the "irregularities with the cycle of shorter than 0.1 mm" are formed on the front surface layer and, then, the roughness components are distributed on the outer circumferential surface of the charging member, rather than in a method in which the "irregularities with the cycle of shorter than 0.1 mm" are formed on the conductive elastic layer and, then, the roughness components are distributed on the outer circumferential surface of the charging member.
An average height of the "irregularities with the cycle of shorter than 0.1 mm" (roughness components) which are distributed on the outer circumferential surface of the front surface layer is preferably greater than 0 .mu.m and 4 .mu.m or less. In addition, a mean cycle of the roughness components on the outer circumferential surface of the front surface layer is preferably 2 .mu.m or longer, more preferably, 3 .mu.m or longer, and still more preferably 5 .mu.m or longer, and is preferably 50 .mu.m or shorter, more preferably, 20 .mu.m or shorter, and still more preferably 15 .mu.m or shorter.
The height and the cycle of the roughness components on the outer circumferential surface of the front surface layer, and the height and the cycle of the roughness components on the outer circumferential surface of the charging member are controlled, for example, with the particle diameter and the amount of the granulated substance contained in the front surface layer forming composition. It is desirable that the irregularities are formed, on the front surface of the front surface layer, of the granulated substance or an aggregation substance of the granulated substance contained in the front surface layer forming composition.
A charging device is a charging device that includes the charging member according to the exemplary embodiment, and that charges the front surface of the photoreceptor by a contact charging method. The charging device is a charging device which applies only the DC voltage to the charging member or a charging device which applies the voltage obtained by superimposing the AC voltage to the DC voltage.
An image forming apparatus according to the exemplary embodiment includes the photoreceptor, the charging device, a latent image forming device that forms a latent image on the front surface of the charged photoreceptor, a developing device that develops the latent image formed on the front surface of the photoreceptor by using developer containing toner, and that forms a toner image on the front surface of the photoreceptor, and a transfer device that transfers the toner image formed on the front surface of the photoreceptor to a recording medium. The image forming apparatus according to exemplary embodiment may further include at least one device selected from a fixing device that fixes the toner image to the recording medium; a cleaning device that cleans the front surface of the photoreceptor after the transfer of the toner image and before the charging; or a neutralization device that irradiates the front surface of the photoreceptor with light and neutralizes the charge on the front surface of the photoreceptor after the transfer of the toner image and before the charging.
The charging device 208A is a contact charging type charging device that is formed by a roll-shaped charging member, that contacts with the front surface of the photoreceptor 207, and that charges the front surface of the photoreceptor 207. Only the DC voltage is applied or the voltage obtained by superimposing the AC voltage to the DC voltage is applied to the charging device 208A from the power supply 209.
Examples of the transfer device 212 include, for example, a corona discharge generator, and a conductive roll that is pressed to the photoreceptor 207 with the recording medium. 500 interposed therebetween.
The charging roll 402a is the contact charging type charging device that contacts with the front surface of the photoreceptor 401a and charges the front surface of the photoreceptor 401a. Only the DC voltage is applied or the voltage obtained by superimposing the AC voltage to the DC voltage is applied to the charging roll 402a from a power supply.
The charging device 208A that is included in the process cartridge 300 is the contact charging type charging device that is formed by a roll-shaped charging member, that contacts with the front surface of the photoreceptor 207, and that charges the front surface of the photoreceptor 207. When the process cartridge 300 is mounted on the image forming apparatus and an image is formed, only the DC voltage is applied or the voltage obtained by superimposing the AC voltage to the DC voltage is applied to the charging device 208A from the power supply.
The volume average particle size (D50v) of the toner particles is preferably from 2 .mu.m to 10 .mu.m and more preferably from 4 .mu.m to 8 .mu.m.
An adhesive (epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber) is applied on an outer circumferential surface of a shaft which is formed of SUM23L having a diameter of 8 mm and is subjected to hexavalent chromium acid treatment after electroless nickel plating, and then an adhesive layer having a thickness of 5 .mu.m is formed. A composition obtained by kneading the following materials by a 2.5 L kneader and the shaft having the adhesive layer are extruded from an extruder (set at a die temperature of 90.degree. C.) including a cross head die, a layer of the composition is formed on the outer circumferential surface of the shaft, and then the layer is heated at 160.degree. C. for 70 minutes by using air heating furnace, thereby obtaining a conductive elastic layer roll (having an average diameter of 12 mm).
Epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber (HYDRIN T3106 by Zeon Chemicals L.P) 100 parts
Carbon black (#3030B by Mitsubishi Chemical Corporation) 5 parts
Ion conductive agent (benzyltrimethylammonium chloride, BTEAC by Lion Specialty Chemicals Co., Ltd.) 1 part
Vulcanizing agent: 4,4'-dithiodimorpholine (VALNOC R by Ouchi Shinko Chemical Industrial Co., Ltd.) 1.5 parts
Vulcanization accelerator: di-2-benzothiazolyl disulfide (NOCCELER DM-P by Ouchi Shinko Chemical Industrial Co., Ltd.) 1.5 parts
Vulcanization accelerator: tetraethylthiuram disulfide (NOCCELER TET-G by Ouchi Shinko Chemical Industrial Co., Ltd.) 1.8 parts
Vulcanization accelerator aid: zinc oxide (Seido Chemical Industry Co., Ltd.) 3 parts
Vulcanization accelerator aid: stearic acid 1 part
Heavy calcium carbonate 40 parts
--Forming of Front Surface Layer--
A dispersion liquid obtained by mixing the following materials, being diluted with methanol, and being subjected to dispersion processing in a bead mill is applied on the outer circumferential surface of the conductive elastic layer roll by dip applying, and then is heated at 160.degree. C. for 30 minutes, and thereby a charging roll having a front surface layer with an average layer thickness of 10 .mu.m is obtained.
N-methoxymethylnylon (F30K by Nagase ChemteX Corporation) 100 parts
Polyvinyl butyral resin (S-LEC BL-1 by Sekisui Chemical Co., Ltd.) 10 parts
Tin oxide (S-2000 with an average particle diameter of 15 nm by Mitsubishi Materials Corporation) 70 parts
Polyamide particles (Orgasol 2001 DNat1 with an average particle diameter of 5 .mu.m by Arkema Group) 3 parts
Catalyst (NACURE 4167 by Kusumoto Chemical Industry Co., Ltd.) 1 part
Methanol 700 parts
Butanol 200 parts
The charging roll is obtained in the same way as in Example 1 except that conditions of forming the conductive elastic layer and composition of the front surface layer forming compositions are changed as shown in Table 1.
The charging roll is obtained in the same way as in Example 1 except that, after the conductive elastic layer roll with a mean diameter of 15 mm is formed, the mean diameter is reduced to 12 mm by polishing, and composition of the front surface layer forming compositions is changed as shown in Table 1.
The charging roll is obtained in the same way as in Example 1 except that the conductive elastic layer is formed by using the same compositions but the conductive elastic layer is prepared by injection molding using a mold.
The charging roll is obtained in the same way as in Example 1 except that conditions of forming the conductive elastic layer and composition of the front surface layer forming compositions are changed as shown in Table 1. In Comparative Example 2, polyamide particles are changed to the following material.
Polyamide particles (Orgasol 2002 EXDNat1 with an average particle diameter of 10 .mu.m by Arkema Group)
In a modified apparatus of DocuCentre-IV C2260 which includes the contact charging type charging device that applies only the DC voltage to the charging roll, the charging roll of each of Examples and Comparative Examples is incorporated, and a halftone image having image density of 30% on an entire surface is printed on 5,000 sheets of A4 paper under an high-temperature and high-humidity environment (28.degree. C. and 85% RH). The last printed image on the paper is visually observed and classification is performed as follows. G0 and G1 are within a range of permission.
In a modified apparatus of DocuCentre-IV C2260 which includes the contact charging type charging device that applies, to the charging roll, the voltage obtained by superimposing the AC voltage to the DC voltage, the charging roll of each of Examples and Comparative Examples is incorporated, and a halftone image having image density of 60% on an entire surface is printed on a sheet of A3 paper under a low-temperature and low-humidity environment (10.degree. C. and 15% RH). The printed image is visually observed and classification is performed as follows. G0 and G1 are within a range of permission.
G0: No white spot is recognized.
G1: One to ten white spots are produced.
G2: 11 to 25 white spots are produced.
G3: 26 to 50 white spots are produced.
G4: 51 white spots or more are produced.
TABLE-US-00001 TABLE 1 Front Surface Layer Conductive Elastic Layer Amount Molding Die Vulcanization Condition Conductive Agent of Polyamide Method Temperature Temperature Time Type Amount Particles Example 1 Extrusion 90.degree. C. 160.degree. C. 70 minutes Tin Oxide 70 parts 3 parts Molding Example 2 Extrusion 85.degree. C. 160.degree. C. 70 minutes Tin Oxide 70 parts 3 parts Molding Example 3 Extrusion 90.degree. C. 160.degree. C. 70 minutes Tin Oxide 70 parts 6 parts Molding Example 4 Extrusion 80.degree. C. 155.degree. C. 60 minutes Tin Oxide 70 parts 3 parts Molding Example 5 Extrusion 85.degree. C. 160.degree. C. 70 minutes Tin Oxide 70 parts 6 parts Molding Example 6 Extrusion 85.degree. C. 155.degree. C. 60 minutes Tin Oxide 70 parts 10 parts Molding Example 7 Extrusion 85.degree. C. 160.degree. C. 70 minutes Tin Oxide 70 parts 10 parts Molding Example 8 Extrusion 90.degree. C. 160.degree. C. 70 minutes Carbon 15 parts 6 parts Molding Black Example 9 Extrusion 90.degree. C. 160.degree. C. 70 minutes Tin Oxide 70 parts 6 parts Molding + Polishing Comparative Extrusion 165.degree. C. 165.degree. C. 10 minutes Tin Oxide 70 parts 3 parts Example 1 Molding Mold Vulcanization Temperature in Mold Comparative Extrusion 85.degree. C. .degree.160.degree. C. 70 minutes Tin Oxide 70 parts 20 parts Example 2 Molding Comparative Extrusion 100.degree. C. 170.degree. C. 70 minutes Tin Oxide 70 parts 6 parts Example 3 Molding Comparative Extrusion 85.degree. C. 160.degree. C. 70 minutes Tin Oxide 70 parts 13 parts Example 4 Molding Surface Texture of Outer Circumferential Surface Average Height Mean Cycle Average Height Mean Cycle Image Quality Half-Value of Roughness of Roughness of Waviness of Waviness Micro-Chro- White Width Component Components Components Components matic Line Spot Example 1 1.5 .mu.m 0.8 .mu.m 16 .mu.m 5.1 .mu.m 0.29 mm G0 G1 Example 2 2.3 .mu.m 0.8 .mu.m 18 .mu.m 6.5 .mu.m 0.31 mm G0 G1 Example 3 2.2 .mu.m 2.5 .mu.m 12 .mu.m 5.1 .mu.m 0.29 mm G0 G0 Example 4 2.9 .mu.m 0.8 .mu.m 16 .mu.m 9.0 .mu.m 0.28 mm G1 G1 Example 5 2.8 .mu.m 2.5 .mu.m 18 .mu.m 6.5 .mu.m 0.31 mm G1 G0 Example 6 2.7 .mu.m 4.0 .mu.m 8 .mu.m 8.2 .mu.m 0.30 mm G1 G0 Example 7 2.7 .mu.m 4.0 .mu.m 8 .mu.m 6.5 .mu.m 0.31 mm G1 G0 Example 8 2.2 .mu.m 2.5 .mu.m 11 .mu.m 5.1 .mu.m 0.29 mm G1 G1 Example 9 2.2 .mu.m 2.5 .mu.m 12 .mu.m 5.1 .mu.m 0.12 mm G1 G0 Comparative 0.8 .mu.m 0.8 .mu.m 15 .mu.m 2.2 .mu.m 0.15 mm G0 G2 Example 1 Comparative 9.6 .mu.m 8.2 .mu.m 7 .mu.m 6.5 .mu.m 0.31 mm G3 G0 Example 2 Comparative 2.2 .mu.m 2.5 .mu.m 12 .mu.m 2.4 .mu.m 0.20 mm G2 G0 Example 3 Comparative 2.8 .mu.m 4.5 .mu.m 8 .mu.m 6.5 .mu.m 0.31 mm G2 G0 Example 4
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