阅读说明：本技术 导电性辊 (Conductive roller ) 是由 大浦孝祐 铃木章吾 福冈智 佐佐木宪司 于 2019-08-29 设计创作，主要内容包括：导电性辊包括芯材、配置于芯材的周围的橡胶基材、以及配置于橡胶基材的周围的表层。表层的表面的顶点的算术平均曲率S_(pc)是1,880(1/mm)以上、且14,024(1/mm)以下。(The conductive roller comprises a core material and a conductive layer disposed on the core materialA surrounding rubber base material, and a surface layer disposed around the rubber base material. Arithmetic mean curvature S of the apex of the surface of the skin pc Is 1,880(1/mm) or more and 14,024(1/mm) or less.)

1. An electrically conductive roller, comprising:

a core material;

a rubber base material disposed around the core material; and

a surface layer disposed around the rubber base material,

arithmetic mean curvature S of the apex of the surface of the skin_pcIs not less than 1,880(1/mm)And 14,024(1/mm) or less.

2. The conductive roller as claimed in claim 1,

the skin layer has:

a conductive base body including a base material formed of an insulator and a conductive material dispersed in the base material; and

particles of a surface roughness imparting material are dispersed in the conductive matrix.

3. The conductive roller as claimed in claim 2,

the particles of the surface roughness-imparting material are formed of an insulator.

Technical Field

The present invention relates to a conductive roller used for a charging roller or the like of an image forming apparatus.

Background

The image quality of an image forming apparatus such as an electrophotographic copier depends on the uniformity of the charged state of a photoreceptor, and the surface roughness of a charging roller affects the uniformity of the charged state. Conventionally, patent documents 1 to 3 are known as techniques relating to the surface roughness of a charging roller.

Patent document 1 describes a technique relating to a charging member (charging roller) including a conductive support, a conductive elastic layer laminated on the conductive support, and a conductive resin layer laminated as an outermost layer on the conductive elastic layer. The conductive resin layer contains at least one type of particles selected from the group consisting of a matrix, resin particles and inorganic particles, the particles contain first particles, and when the layer thickness of a portion of the conductive resin layer formed solely of the matrix is defined as A [ mu ] m]The average particle diameter of the particles was B1[ mu.m ]]And the distance between the particles is S_m[μm]When A is 10 to 7.0 μm, B1/A is 5.0 to 30.0, S_mIs 50 to 400 μm.

Patent document 2 describes a technique relating to an image forming apparatus including: a positively charged single-layer type electrophotographic photoreceptor; a charging device having a contact charging member for charging a surface of the photoreceptor; an exposure device for exposing the surface of the charged image carrier and forming an electrostatic latent image on the surface of the image carrier; a developing device for developing the electrostatic latent image as a toner image; and a transfer device for transferring the toner image from the image carrier to the image bearing memberAnd (4) transferring the printing body. The contact charging member is a charging roller formed of a conductive rubber having a rubber hardness of 62 DEG to 81 DEG at an Asker-C hardness, and the roller surface roughness of the charging roller of the contact charging member is an average interval S of unevenness_m55-130 μm and a ten-point average roughness R_ZIs 9 to 19 μm.

Patent document 3 describes a technique relating to a charging roller including a conductive support, a semiconductive elastic layer formed in a roller shape on the conductive support, and a protective layer formed on the surface of the semiconductive elastic layer. The protective layer is formed by applying a protective layer forming coating liquid containing fine particles having a function of preventing foreign substances from adhering to the protective layer, the volume average particle diameter of the fine particles being made fine so that the surface roughness of the protective layer is 1[ mu ] m or less.

According to patent documents 1 to 3, it is desired to improve image quality by adjusting the surface roughness of the outermost surface of the charging roller with fine particles contained in the surface layer so as to make the discharge between the charging roller and the photoreceptor as uniform as possible.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2015-121769;

patent document 2: japanese patent laid-open publication No. 2012-14141;

patent document 3: japanese patent laid-open No. 2005-91414.

Disclosure of Invention

Problems to be solved by the invention

For image forming apparatuses, the demand for high image quality is increasing.

The invention aims to provide a conductive roller capable of reducing image unevenness.

Means for solving the problems

The conductive roller according to the present invention includes: a core material; a rubber base material disposed around the core material; and a surface layer disposed around the rubber base material, wherein an arithmetic mean of vertexes of a surface of the surface layerCurvature (arithmetric mean peak curvature) S_pcIs 1,880(1/mm) or more and 14,024(1/mm) or less. According to this aspect, image unevenness can be reduced.

Preferably, the skin layer has: a conductive base body including a base material formed of an insulator and a conductive material dispersed in the base material; and particles of a surface roughness imparting material dispersed in the conductive base.

Preferably, the particles of the surface roughness-imparting material are formed of an insulator.

Drawings

Fig. 1 is a schematic view showing an example of an image forming apparatus using a charging roller according to an embodiment of the present invention;

fig. 2 is a cross-sectional view showing an example of a charging roller according to an embodiment of the present invention;

fig. 3 is a cross-sectional view of the rubber base material and the surface layer cut along the axial direction of the charging roller.

Detailed Description

The following describes in detail embodiments for carrying out the present invention. Hereinafter, a charging roller will be described as an example of the conductive roller. The scale in the drawings does not necessarily accurately represent products or samples of the embodiments, and may sometimes exaggerate a portion of the dimensions.

As shown in fig. 1, the image forming apparatus according to the embodiment of the present invention includes a photoreceptor 1. Around the photoreceptor 1, a developing section 2, an exposing section 3, a charging section 4, a transfer section 6, and a cleaning section 5 are arranged. The developing unit 2 is provided with a developing roller 20, a regulating blade 21, and a supply roller 22, and is filled with toner 23. The charging section 4 is provided with a charging roller 40. The transfer portion 6 transfers the toner image onto a sheet 60 of paper as a recording medium. The toner image transferred by the transfer unit 6 is fixed by a fixing unit, not shown.

The cylindrically rotating photoreceptor 1 contacts the cylindrically rotating charging roller 40 at the nip 50. In a region 51 in front of the nip 50 in the rotation direction of the photoreceptor 1 and the charging roller 40 (including a region 52 after the nip 50 in addition to the region 51 in front, depending on the case), electric discharge occurs between the photoreceptor 1 and the charging roller 40, and the surface of the photoreceptor 1 is charged. The charged state of the surface of the photoreceptor 1 is preferably uniform in the circumferential direction and the axial direction of the photoreceptor 1.

Fig. 2 is a cross-sectional view showing an example of the charging roller according to the embodiment of the present invention. As shown in fig. 2, charging roller 40 includes a core 401, a rubber base 402 formed on the outer peripheral surface of core 401, and a surface layer 403 coated on the outer peripheral surface of rubber base 402. By forming the surface layer 403 with the coating composition on the outer peripheral surface of the rubber base 402 and making the surface state of the surface layer 403 appropriate, the discharge unevenness between the photoreceptor 1 and the charging roller 40 can be eliminated, and the discharge to the photoreceptor 1 can be made uniform, and the developing section 2 can attach the toner of an amount exactly corresponding to the latent image formed by the exposure section 3 to the surface of the photoreceptor 1.

< core Material >

Core material 401 may be formed of, but not limited to, a metal or resin material having excellent thermal conductivity and mechanical strength, for example, a metal material such as stainless steel, nickel (Ni), a nickel alloy, iron (Fe), magnetic stainless steel, or a cobalt-nickel (Co-Ni) alloy, or a resin material such as PI (polyimide resin). The structure of core material 401 is not particularly limited, and may be hollow or non-hollow.

< rubber substrate >

Rubber base 402 is disposed on the outer peripheral surface of core 401, and is formed of conductive rubber having conductivity. The rubber base 402 may have 1 layer or 2 or more layers. Further, an adhesion layer, an adjustment layer, or the like may be provided between core material 401 and rubber base material 402 as necessary.

Rubber base 402 is formed by molding around core 401 a rubber composition obtained by adding a conductivity-imparting material, a crosslinking agent, and the like to a conductive rubber. Examples of the conductive rubber include urethane rubber (PUR), epichlorohydrin rubber (ECO), nitrile rubber (NBR), styrene rubber (SBR), Chloroprene Rubber (CR), and the like.

As the conductivity imparting material, an electron conductivity imparting material such as carbon black or metal powder, an ion conductivity imparting material, or a mixture thereof can be used.

Examples of the ion conductivity imparting material include organic salts, inorganic salts, metal complexes, ionic liquids, and the like. Examples of the organic salt include sodium trifluoroacetate, and examples of the inorganic salt include lithium perchlorate and a quaternary ammonium salt. Further, examples of the metal complex include iron halide-ethylene glycol, and specifically, a metal complex described in japanese patent No. 3655364. The ionic liquid is a molten salt which is liquid at room temperature, also referred to as an ambient temperature molten salt, and particularly a salt having a melting point of 70 ℃ or less, preferably 30 ℃ or less. Specifically, there can be mentioned salts described in Japanese patent laid-open No. 2003-202722.

The crosslinking agent is not particularly limited, and examples thereof include sulfur and a peroxide curing agent.

If necessary, a crosslinking aid or the like for accelerating the action of the crosslinking agent may be added to the rubber composition. Examples of the crosslinking assistant include inorganic zinc oxide and magnesium oxide, and organic stearic acid and amines. For the purpose of shortening the crosslinking time, thiazole compounds and other crosslinking accelerators may be used. Other additives may be added to the rubber composition as required.

In the present embodiment, the surface of the rubber base 402 formed on the outer peripheral surface of the core 401 is ground to a predetermined thickness by a grinder, and then dry-ground using a grinding wheel, and then the surface layer 403 is formed on the outer peripheral surface of the rubber base 402. Such polishing is performed in order to appropriately adjust the surface roughness of the rubber base 402 and to adjust the surface state of the outer surface layer 403.

In the case where the surface roughness of the rubber base material 402 is made as small as possible, the surface roughness R of the rubber base material 402 (ten point height of irregular roughness according to JIS B0601: 1994) is_ZPreferably 8.5 μm or less. In this case, the surface roughness R_ZIs a value measured by a contact surface roughness meter.

For example, in a state where the rubber base 402 is rotated, dry grinding (plunge grinding) is performed by moving the rotary grinding wheel in the axial direction while contacting the rubber base 402. In the case where the surface roughness of the rubber base 402 is made as small as possible, the number of revolutions of the grinding wheel of the grinder may be increased in the order of 1000rpm, 2000rpm, and 3000rpm during rotation, for example. Alternatively, the kind of the grinding wheel may be changed, and for example, GC (green silicon carbide) wheels may be sequentially raised to perform grinding as GC60, GC120, and GC 220.

Further, the surface of the rubber base 402 may be subjected to dry polishing, and then wet polishing may be further performed by a wet polishing machine using water-resistant polishing paper or the like. Here, the wet polishing is performed by using water-resistant polishing paper such as water-resistant sandpaper, and bringing the rubber base material 402 into contact with the water-resistant polishing paper while supplying a polishing liquid.

< rubber hardness of rubber substrate >

The rubber base material 402 preferably has a hardness in the range of 50 ° to 64 ° as measured by a durometer ("type a" in accordance with "JIS K6253" and "ISO 7619").

Since the outer surface layer 403 of the rubber base 402 is thin, the hardness of the surface of the charging roller 40 affects the rubber base 402. When the hardness of the rubber base 402 is less than 50 °, the convex portion on the surface of the charging roller 40 is crushed, and the photoreceptor 1 is easily contaminated, thereby causing image failure. On the other hand, when the hardness of the rubber base material 402 is greater than 64 °, the convex portion of the surface of the charging roller 40 may be reflected to the image.

< surface layer >

In the present embodiment, the surface layer 403 can be formed by applying a coating liquid to the outer peripheral surface of the rubber base material 402, drying, and curing. As a method of applying the coating liquid, a dip coating method, a roll coating method, a spray coating method, or the like can be used.

As shown in fig. 3, the cured surface layer 403 has a conductive substrate 404 and particles 405 of, for example, an insulating surface roughness-imparting material (also referred to as a roughness-imparting material) dispersed in the conductive substrate 404. The particles 405 of the roughness-imparting material impart an appropriate surface roughness to the surface layer 403. The conductive base 404 functions to hold the particles 405 of the roughness imparting material at a fixed position and to discharge electricity to the photoreceptor 1. The conductive base 404 includes a base material and a conductive agent dispersed in the base material. As described above, in the region 51 (and in some cases, the region 52), electric discharge occurs between the charging roller 40 and the photoreceptor 1.

In the example shown in fig. 3, the particles 405 of the roughness-imparting material are not completely buried in the conductive matrix 404, but may be completely buried in the conductive matrix 404. When the thickness of the conductive substrate 404 is small, the ability to hold the particles 405 of the roughness imparting material is low, and therefore the conductive substrate 404 preferably has an appropriate thickness with respect to the diameter of the particles 405 of the roughness imparting material. When the particles 405 of the roughness imparting material are insulators, the thickness of the conductive substrate 404 is large, and the electrical resistance of the conductive substrate 404 is large, discharge is often difficult to occur, but by increasing the proportion of the conductive agent contained in the conductive substrate 404, the electrical resistance of the conductive substrate 404 can be reduced, and discharge can be made easy to occur.

In the present embodiment, the surface state of the surface layer 403 is adjusted by dispersing particles 405 of the roughness imparting material in the surface layer 403 formed on the rubber base material 402 whose surface roughness is adjusted.

In the present embodiment, it is considered that the film thickness of the conductive substrate 404 of the surface layer 403 is preferably within an appropriate numerical range. If the thickness is too large, the surface roughness of the surface layer 403 is considered to be too small, which causes image unevenness.

In the present embodiment, it is considered that the content of the particles 405 of the roughness-imparting material of the surface layer 403 is preferably within an appropriate numerical range. It is considered that when the content of the particles is large, the particles overlap with each other, and thus the surface of the surface layer 403 becomes rough, which causes image unevenness.

In the present embodiment, the coating liquid as the material of the surface layer 403 contains at least a base material, a conductive agent, and particles 405 of a surface roughness imparting material. After curing the coating liquid, the base material and the conductive agent become components of the conductive base 404.

The coating liquid is obtained by, for example, dissolving components having the following composition in a diluting solvent.

Substrate: 10 to 80 parts by weight.

Conductive agent: 1 to 50 parts by weight.

Surface roughness imparting material: 70 wt% or less of the total amount of the coating liquid.

When the surface condition of the surface layer 403 is appropriate, it is considered that the discharge between the charging roller 40 and the photoreceptor 1 is almost uniform in the gap immediately before the nip where the charging roller 40 and the photoreceptor 1 contact each other, and the discharge unevenness does not occur at the time of forming an image, whereby an image of a desired density is formed, and the image quality is improved.

It is considered that the surface state of the surface layer 403 can be appropriately adjusted by appropriately adjusting the particle diameter and the addition amount of the particles 405 of the surface roughness-imparting material.

< substrate >

The base material contained in the coating liquid is an insulator. Examples of the base material include urethane resin, acrylic urethane resin, amino resin, silicone resin, fluororesin, polyamide resin, epoxy resin, polyester resin, polyether resin, phenol resin, urea resin, polyvinyl butyral resin, melamine resin, nylon resin, and the like. These substrates may be used alone or in any combination.

< conductive agent >

Examples of the conductive agent contained in the coating liquid include carbon black such as acetylene black, ketjen black, and japan carbon black (TOKABLACK), carbon nanotubes, ions such as lithium perchlorate, a plasma liquid such as 1-butyl-3-methylimidazolium hexafluorophosphate, metal oxides such as tin oxide, and conductive polymers. These conductive agents may be used alone or in any combination.

< materials for imparting surface roughness >

Examples of the particles 405 of the surface roughness-imparting material contained in the coating liquid include acrylic particles, urethane particles, polyamide resin particles, silicone resin particles, fluororesin particles, styrene resin particles, phenol resin particles, polyester resin particles, olefin resin particles, epoxy resin particles, nylon resin particles, carbon, graphite, carbide spheres (carbide balls), silica, alumina, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, calcium sulfate, calcium carbonate, magnesium carbonate, calcium silicate, aluminum nitride, boron nitride, talc, kaolin, diatomaceous earth, glass beads, hollow glass spheres, and the like. These particles may be used alone or in any combination.

It is considered that there is a preferable range in the relationship between the particle diameter and the particle content of the particles 405 of the surface roughness-imparting material in the coating liquid for the purpose of improving the image quality.

< dilution solvent >

The diluting solvent contained in the coating liquid is not particularly limited, but examples thereof include water, and solvents such as methyl acetate, ethyl acetate, butyl acetate, Methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK), methanol, ethanol, butanol, 2-propanol (IPA), acetone, toluene, xylene, hexane, heptane, chloroform, and the like.

Examples

Hereinafter, examples of the present embodiment will be described in more detail.

Experiment 1

< preparation of rubber substrate >

A rubber composition obtained by adding 0.5 parts by weight of sodium trifluoroacetate, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid and 1.5 parts by weight of a crosslinking agent as an electrical conductivity-imparting material to 100 parts by weight of epichlorohydrin rubber (Epichlomer CG-102; manufactured by Osaka Cao, Japan) was kneaded by means of a roll kneader.

The kneaded rubber composition was wound as a sheet-like material on the surface of a core material 401 (core metal) having a diameter of 6mm, and press-molded to obtain a rubber base material 402 formed of the crosslinked epichlorohydrin rubber.

The hardness of the rubber base material 402 thus obtained was measured using a durometer ("type a" in accordance with "JIS K6253" and "ISO 7619"), and the measured value was 50 ° to 64 °.

< polishing of rubber substrate surface >

The surface of the rubber base material 402 is ground by a grinder. Specifically, the surface of the resulting rubber base material 402 was ground to a predetermined thickness (1.25mm) by a grinder, and then the grinding wheel rotation speed of the grinder was increased in the order of 1000rpm, 2000rpm, and 3000rpm, and the grinding was performed by dry grinding. That is, in experiment 1, the surface roughness of the rubber base material 402 was made as small as possible.

< preparation of coating solution >

A coating liquid for forming a surface layer 403 on the outer peripheral surface of the rubber base material 402 was prepared.

The composition of the coating liquid is shown in table 1.

[ Table 1]

As the urethane particles, urethane beads manufactured by kayaku co.

The relationship between the average particle diameter of urethane beads and the product name is as follows. However, in practice, one product contains particles having a particle size different from the average particle size.

6 μm: carbamate beads "C-800"

10 μm: carbamate beads "C-600"

15 μm: carbamate beads "C-400"

22 μm: carbamate beads "C-300"

In experiment 1, samples having different surface states of the surface layer 403 were produced by coating the coating solution containing particles 405 of the surface roughness imparting material having different particle diameters and different amounts. The particle size and amount of particles 405 in these samples are shown in table 2. In table 2, samples 1 to 11 are samples of experiment 1. However, in sample 5, the particles 405 of the roughness-imparting material were not contained in the surface layer 403.

The coating liquid having the above composition was subjected to dispersion mixing for 3 hours by a ball mill.

[ Table 2]

< production of charging roller >

The surface layer 403 is formed by applying the coating liquid to the outer peripheral surface of the rubber base material 402 to be polished, and the charging roller 40 is manufactured. Specifically, the coating liquid was stirred, sprayed on the surface of the rubber substrate 402, and dried in an electric furnace at 120 ℃ for 60 minutes to form the surface layer 403 on the outer peripheral surface of the rubber substrate 402, thereby producing a charging roller.

<Arithmetic mean curvature S of the apex_pcMeasurement of (2)>

Arithmetic mean peak curvature S for the vertices of the surface of skin 403_pcThe measurements were carried out (according to ISO 25178).

First, the surface of the center portion in the axial direction of the charging roller 40 is imaged using a non-contact laser microscope. The laser microscope used was "VK-X200" manufactured by Yonzhi, Kyowa, Japan. The magnification is 400 times, and the field of view is 528.7 μm in the circumferential direction of the charging roller 40 and 705.1 μm in the axial direction of the charging roller 40.

Next, the geometric data obtained by imaging was subjected to a quadric surface correction by a multi-file analysis application program "VK-H1 XM" version1.2.0.116 manufactured by kynz co. The quadric surface correction is a process of removing a data component corresponding to the cylindrical surface of the charging roller 40 from the geometric data obtained by the photographing. In other words, the processing is to convert the geometric data of the cylindrical surface obtained by the imaging into the geometric data for the plane.

Thereafter, by the application program, an arithmetic mean curvature S of the vertex is calculated_pc. Arithmetic mean curvature S of the apex_pcThe wolff pruning (Wolf pruning) value in the calculation of (1) is 5%. That is, the arithmetic mean curvature S of the vertex is calculated from a region having an amplitude greater than 5% of the maximum amplitude (difference between the maximum height and the minimum height) of the profile curve_pc. The arithmetic mean curvature Spc of the vertex thus obtained is shown in table 2.

< evaluation of image unevenness and discharge unevenness >

An image evaluation test of the charging roller was performed using a copying machine. The copier is a color multifunction peripheral (MFP) "bizhub C3850" (direct current voltage application type) manufactured by konica minolta corporation (tokyo, japan).

The electrified applied voltage was measured by a tester. In experiment 1, an external power source was used to apply a voltage (REF-100V) 100V lower than the normal voltage (REF).

The charging roller was applied to a copying machine, and image unevenness was evaluated for images (halftone images and pure white images) printed under the following printing conditions. The results are shown in Table 2.

For the evaluation of image unevenness, partial discharge determination is performed on a halftone image, and brightness determination is performed on a pure white image. The presence of partial discharge can be confirmed by visually observing the occurrence of white spots, black spots, white streaks, and black streaks in a halftone image.

[ printing conditions ]

Voltage application: REF-100V

Speed: 38 pieces/minute

Printing environment: the temperature is 23 ℃ and the humidity is 55%

(evaluation of partial discharge)

The halftone image was visually judged for image unevenness due to partial discharge based on the following criteria.

Good: no image unevenness due to partial discharge

Poor: with image non-uniformity caused by partial discharge

(Brightness judgment)

L values (L values, brightness) were measured at 7 positions in the image using a color difference meter ("CR-400" manufactured by konica minolta corporation). The brightness determination was evaluated according to the following evaluation criteria. The reason for measuring the brightness is to determine the presence or absence of a smear, that is, a fog (printing at a position where printing should not be performed).

[ evaluation standards ]

Good: dirty-free edition (L95.5 above)

Poor: dirty type (lower than L95.5)

The samples in which image unevenness or smear due to partial discharge occurred were judged to be defective by image integration judgment, and these are shown in table 2.

Experiment 2

< preparation of rubber substrate >

A rubber composition obtained by adding 0.5 parts by weight of sodium trifluoroacetate, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid and 1.5 parts by weight of a crosslinking agent as a conductivity-imparting material to 100 parts by weight of epichlorohydrin rubber (Epichlomer CG-102; manufactured by Osakabia, Co., Ltd.) was kneaded by a roll kneader.

The kneaded rubber composition was wound as a sheet-like material on the surface of a core material 401 (core metal) having a diameter of 8mm, and press-molded to obtain a rubber base material 402 formed of the crosslinked epichlorohydrin rubber.

The hardness of the rubber base material 402 thus obtained was measured using a durometer ("type a" in accordance with "JIS K6253" and "ISO 7619"), and the measured value was 50 ° to 64 °.

< polishing of rubber substrate surface >

The surface of the rubber base material 402 is ground by a grinder. Specifically, the surface of the resulting rubber base material 402 was ground to a predetermined thickness (2mm) by a grinder, and then ground by dry grinding. In experiment 2, the wheel speed was not changed.

< preparation of coating liquid >

A coating liquid for forming a surface layer 403 on the outer peripheral surface of the rubber base material 402 was prepared.

The composition of the coating liquid is shown in table 1.

Urethane beads manufactured by Kokusan Kogyo Co., Ltd were used as the urethane particles.

The relationship between the average particle diameter of urethane beads and the product name is as follows. However, in practice, one product contains particles having a particle size different from the average particle size.

6 μm: carbamate beads "C-800"

10 μm: carbamate beads "C-600"

15 μm: carbamate beads "C-400"

22 μm: carbamate beads "C-300"

32 μm: carbamate beads "C-200"

In experiment 2, samples having different surface states of the surface layer 403 were produced by coating the coating solution containing particles 405 of the surface roughness imparting material having different particle diameters and different amounts. The particle size and amount of particles 405 in these samples are shown in table 2. In table 2, samples 21 to 35 are samples of experiment 2.

The coating liquid having the above composition was subjected to dispersion mixing for 3 hours using a ball mill.

< production of charging roller >

The surface layer 403 is formed by applying the coating liquid to the outer peripheral surface of the rubber base material 402 to be polished, and the charging roller 40 is manufactured. Specifically, the coating liquid was stirred, sprayed on the surface of the rubber substrate 402, and dried in an electric furnace at 120 ℃ for 60 minutes to form the surface layer 403 on the outer peripheral surface of the rubber substrate 402, thereby producing a charging roller.

<Arithmetic mean curvature S of the apex_pcMeasurement of (2)>

The arithmetic mean curvature S of the apex of the surface layer 403 was calculated in the same manner as in experiment 1_pcAnd (4) carrying out measurement. The resulting arithmetic mean curvature S of the apex_pcAs shown in table 2.

< evaluation of image non-uniformity and discharge non-uniformity >

An image evaluation test of the charging roller was performed using a copying machine. The copier is a color multifunction peripheral (MFP) "MP C5503" (ac/dc voltage superposition type) manufactured by japan kokusho, japan.

The direct-current voltage is a normal voltage (REF), and the alternating-current voltage Vpp depends on the control of the copying machine.

In experiment 2, an alternating current (1.45mA) lower than the normal alternating current (REF) of the copying machine was set.

The charging roller was applied to a copying machine, and image unevenness was evaluated for images (halftone images and pure white images) printed under the following printing conditions. The results are shown in Table 2.

For the evaluation of image unevenness, partial discharge was determined for a halftone image. The presence of partial discharge can be confirmed by visually observing the occurrence of white spots, black spots, white streaks, and black streaks in a halftone image. With respect to the pure white image, determination of the smear, that is, the fog was visually confirmed.

[ printing conditions ]

Speed: 30 sheets/minute

Printing environment: the temperature is 23 ℃ and the humidity is 55%

(evaluation of partial discharge)

The halftone image was visually judged for image unevenness due to partial discharge based on the following criteria.

Good: no image unevenness due to partial discharge

Poor: with image non-uniformity caused by partial discharge

(dirty type judgment)

With respect to the pure white image, the presence or absence of smear, that is, fogging (printing on a position where printing should not be performed) was visually determined.

[ evaluation standards ]

Good: contamination-free plate

Poor: dirty plate

The samples in which image unevenness or smear due to partial discharge occurred were judged to be defective by image integration judgment, and these are shown in table 2.

As is apparent from table 2, image unevenness occurred in sample 1 and sample 11, and good images were made in the other samples.

Thus, the arithmetic mean curvature S of the apex of the surface of skin 403_pcPreferably 1,880(1/mm) or more and 14,024(1/mm) or less.

The charging roller has been described as an embodiment, but the conductive roller according to the present invention can be applied to a developing roller, a transfer roller, a change roller, a toner supply roller, and the like, in addition to a charging roller of an image forming apparatus such as an electrophotographic copier or a printer.

Description of the symbols

1: a photoreceptor;

2: a developing section;

20: a developing roller;

21: a limiting scraper;

22: a supply roller;

23: a toner;

3: an exposure section;

4: a charging section;

40: a charging roller;

401: a core material;

402: a rubber substrate;

403: a surface layer;

5: a cleaning section;

6: a transfer section;

60: a sheet.