JP2012008384A - Method for manufacturing electrifying member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrifying member which has a low compression set even in a high-temperature and high-humidity environment and has a uniform electric resistance by suppressing bleed-out of an ionic conducting agent.SOLUTION: The method for manufacturing an electrifying member having a conductive support body and a conductive elastic layer includes a step of coating a surface of the conductive support body with a rubber composition containing epichlorohydrin rubber, a carbon black having a pH of 9 or higher and a DBP oil absorption of 50 to 69 ml/100 g, an ionic conducting agent, a zinc oxide, and sulfur and next cross-linking the rubber composition to form the conductive elastic layer.

Description

  The present invention relates to a method for manufacturing a charging member.

  A charging member for charging a photosensitive member by contacting the photosensitive member generally has a conductive elastic layer and a surface layer on a conductive support. Since such a charging member is constantly pressed against the photoconductor, compression permanent deformation (hereinafter referred to as “C set”) may occur at a contact portion with the photoconductor. The C set may generate an electrophotographic image (hereinafter, referred to as “C set image”) having a horizontal stripe resulting from the C set. Therefore, it is necessary to reduce the compression set of the charging member. Particularly at high temperature and high humidity, compression set tends to increase. In order to suppress the compression set of the charging member, a method such as adding a reinforcing agent to the conductive elastic layer or increasing the crosslinking density of the conductive elastic layer is used.

  In addition, the conductive elastic layer is required to have appropriate flexibility in order to properly contact the photoreceptor, and therefore, a plasticizer is generally mixed. Further, a conductive agent is mixed in order to obtain conductivity necessary for the charging member. If the plasticizer or conductive agent added to the conductive elastic layer is an ionic conductive agent, it may bleed out from the conductive elastic layer and contaminate the photoreceptor. Further, when the ionic conductive agent bleeds out, the electric resistance of the conductive elastic layer may become non-uniform.

  Patent Document 1 proposes a charging roller having a conductive elastic layer containing carbon black having a pH of 6.0 or less in a blend rubber of epichlorohydrin rubber and acrylonitrile butadiene rubber. The elastic elastic layer is reinforced. However, with carbon black having a pH of 6.0 or less, the vulcanization rate of the blend rubber is lowered and the crosslinking efficiency is not improved. Therefore, the C set property may not be improved. In addition, carbon black having a pH of 6.0 or less has no effect of adsorbing the ionic conductive agent, and the ionic conductive agent may bleed out and contaminate the photoreceptor. Moreover, when the ionic conductive agent bleeds out, the electric resistance of the conductive elastic layer may become non-uniform.

  Patent Document 2 proposes a charging member having a conductive elastic layer containing carbon black of 70 ml / 100 g or more of dibutyl phthalate oil absorption (hereinafter referred to as “DBP oil absorption”). Carbon black prevents bleed-out by adsorbing the ion conductive agent, but the DBP oil absorption is too large, so that the ion conductive agent involved in conductivity is adsorbed more than necessary, and the desired electrical resistance can be obtained. There are cases where it is not possible.

JP 2002-108063 A JP 2002-108062 A

  An object of the present invention is to provide a method for producing a charging member that has a small compression set even in a high-temperature and high-humidity environment and that has a uniform electric resistance by suppressing bleed-out of an ionic conductive agent.

  The said subject is solved by the following this invention.

  The present invention relates to a method for producing a charging member having a conductive support and a conductive elastic layer, wherein epichlorohydrin rubber has a pH of 9 or more and a DBP oil absorption of 50 ml / 100 g to 69 ml / 100 g. Production of a charging member comprising a step of coating a surface of a conductive support with a rubber composition containing carbon black, an ionic conductive agent, zinc oxide, and sulfur, and then forming a conductive elastic layer by crosslinking the rubber composition Is the method.

  The charging member obtained by the production method of the present invention has a small compression set even when pressed against a photoconductor for a long time in a high temperature and high humidity environment, and can suppress the occurrence of image defects. In addition, since the bleed-out of the ionic conductive agent can be suppressed, the electrical resistance of the charging member is uniform, a good image can be obtained in the long term, and contamination of the photoreceptor can be prevented.

It is sectional drawing of the charging member of this invention. It is the schematic of the manufacturing process of the charging member of this invention. 1 is a schematic view of an electrophotographic apparatus provided with a charging member of the present invention. It is the schematic of the resistance measuring apparatus of the charging member of this invention.

  Hereinafter, preferred embodiments of the present invention will be described.

  The charging member of the present invention is a charging member having a conductive elastic layer on a conductive support. Examples of the charging member include a roller shape (charging roller), a brush type, and a blade type. A roller charging method using a charging roller is preferable in terms of discharge stability and is widely used.

  The conductive elastic layer is a cross-linked rubber composition containing at least epichlorohydrin rubber, carbon black having a pH of 9 or more and a DBP oil absorption of 50 ml / 100 g to 69 ml / 100 g, an ionic conductive agent, zinc oxide, and sulfur. It is made.

  FIG. 1 is a schematic view of a charging roller as a charging member. The charging roller 10 includes a conductive support 11 and a conductive elastic layer 12, and a surface layer 13 can be provided as necessary.

  The carbon black of the present invention has a pH of 9 or more and a DBP oil absorption of 50 ml / 100 g or more and 69 ml / 100 g or less. When the pH is less than 9, the vulcanization rate is lowered and the crosslinking density is lowered. Further, when the DBP oil absorption is less than 50 ml / 100 g, the adsorptive power of the ionic conductive agent is low, and the ionic conductive agent bleeds out from the conductive elastic layer. When it exceeds 69 ml / 100 g, the ionic conductive agent is adsorbed more than necessary, and it is difficult to obtain a conductive elastic layer having a desired electric resistance value. As a guideline for the amount of carbon black having a pH of 9 or more and a DBP oil absorption of 50 ml / 100 g or more and 69 ml / 100 g or less to 100 parts by mass of rubber, it is 0.5 parts or more and 15 parts by mass or less.

  The epichlorohydrin rubber of the present invention is a ternary copolymer composed of a unit derived from epichlorohydrin, a unit derived from ethylene oxide, and a unit derived from allyl glycidyl ether. In particular, the ratio is from 20 mol% to 25 mol% of units derived from epichlorohydrin, from 70 mol% to 75 mol% of units derived from ethylene oxide, and from 1 mol% to 5 mol% of units derived from allyl glycidyl ether. It is preferable.

  When the composition ratio of the unit derived from ethylene oxide is 70 mol% or more, the conduction path of the ionic substance related to the electric resistance increases, and a good electric resistance is obtained. On the other hand, if it is 75 mol% or less, crystallinity due to units derived from ethylene oxide can be suppressed, and workability can be maintained. The unit derived from alkylene oxide is not particularly limited, but preferably exhibits appropriate molecular mobility. The unit derived from allyl glycidyl ether is in the range of 1 mol% to 5 mol%. By setting the composition ratio of the unit derived from allyl glycidyl ether to 1 mol% or more and 5 mol% or less, the crosslinking density at the time of vulcanization is increased and the conductivity is improved.

  In the present invention, the following are used as the ion conductive agent. Quaternary ammonium salts such as methyl-dihydroxyethyl-dodecylammonium perchlorate, tetrabutylammonium perchlorate, tetraethylammonium chloride, stearyltrimethylammonium chloride and its modified polyethylene oxide, metal salts such as lithium perchlorate, sodium bromate, Or ester plasticizers and surfactants. In particular, quaternary ammonium perchlorate is preferable as an ionic conductive agent that lowers the resistance more uniformly. Further, it is more preferable to use a quaternary ammonium salt having the structure represented by the following chemical formula (1) from the viewpoint of compatibility with epichlorohydrin rubber.

In the above formula (1), R ^{1 to} R ⁴ are each independently selected from alkyl groups having 1 to 16 carbon atoms and functional groups represented by the following chemical formula (2).

In the above formula (2), R ⁵ is any one selected from (—CH ₂ CH ₂ —O—) and an alkylene group having 1 to 6 carbon atoms, and n is 0 or 1.

  In the present invention, zinc oxide is used for the purpose of activating crosslinking. In the present invention, sulfur is used for the purpose of vulcanizing (crosslinking) rubber. As sulfur, powder sulfur, insoluble sulfur, and various sulfur-containing organic compounds can be used. Powdered sulfur, insoluble sulfur, and various sulfur-containing organic compounds are preferably used because adjustment of vulcanization characteristics is easy.

  As other additives, various inorganic fillers such as calcium carbonate, talc, clay and silica can be added. In addition, for the purpose of improving the polishing properties, it is preferable to add calcium carbonate having low reinforcing properties, and 30 parts by mass or more and 150 parts by mass or less can be added with respect to 100 parts by mass of the rubber. The average particle size of calcium carbonate is preferably 0.8 μm or more and 2.0 μm or less. By setting the particle diameter to 0.8 μm or more, the dispersibility is improved due to the difficulty of forming an agglomerate during the mixing process of the rubber composition. Further, when the particle diameter is 2.0 μm or less, the surface roughness of the charging member can be controlled, the resistance unevenness can be reduced, and the charging uniformity is improved.

  Moreover, you may add acid acceptors, such as a hydrotalcite and magnesium oxide, and can add 1 to 10 mass parts with respect to 100 mass parts of rubber | gum.

  As the plasticizer, known oil or the like can be appropriately added. Since the electroconductive elastic layer of the present invention is mainly composed of epichlorohydrin rubber, it is preferable to use various ester plasticizers. Specific examples include adipic acid esters, sebacic acid esters, phthalic acid esters, and the like. It is done. In addition, the conductive member used in contact with the photoconductor may contaminate the photoconductor due to migration of the plasticizer to the photoconductor, so that the ester compound reacts with propylene glycol or the like as the plasticizer. An ester compound having a high molecular weight is preferred. In addition, an aging inhibitor, a vulcanization retarder, a processing aid, and the like may be added as appropriate.

  These various materials can be mixed and dispersed in rubber using a closed mixer such as a Banbury mixer or a pressure kneader or an open mixer such as an open roll.

  In the present invention, the surface of the conductive support is coated with the rubber composition containing the above components, and then the rubber composition is crosslinked to form a conductive elastic layer. The conductive support can be coated with the rubber composition by, for example, an extrusion method.

  The extrusion temperature of the conductive elastic layer is preferably in the range of 70 ° C. or higher and 100 ° C. or lower. By setting the extrusion temperature to 70 ° C. or higher, the rubber fluidity is improved, and the shape stability during extrusion is improved. By setting the temperature to 100 ° C. or less, it is possible to suppress the heat generation of rubber during extrusion and to prevent early rubber vulcanization (hereinafter referred to as “scorch”).

  Next, the extrusion molding will be described in detail. First, epichlorohydrin rubber, carbon black, calcium carbonate, zinc oxide and the like are blended and kneaded to prepare an unvulcanized rubber composition. Subsequently, the obtained unvulcanized rubber composition is extruded together with the conductive support to coat the conductive support with the unvulcanized rubber composition. FIG. 2 is an explanatory view schematically showing this process. The extruder 20 includes a cross head 21. The conductive support 11 is sent to the crosshead 21 by the conductive support feed roller 22 and the unvulcanized rubber composition is sent to the crosshead 21 by the extruder 20. In the cross head 21, a roller in which the periphery of the conductive support 11 is coated with an unvulcanized rubber composition is obtained. An end portion of the unvulcanized rubber composition layer is cut off by a cut-off jig 23 to obtain a non-vulcanized roller 24.

  Vulcanization may be any method such as a hot stove, vulcanizer, hot platen, far / near infrared, induction heating, etc. The heating conditions are 130 ° C. or more and 250 ° C. or less and 5 minutes or more and 120 minutes or less, preferably 140 ° C. or more It is carried out at 200 ° C. or less for 10 minutes or more and 40 minutes or less. Further, secondary vulcanization can be performed as necessary. The roller after vulcanization may be adjusted to have a desired shape or the surface roughness of the roller by polishing or the like.

The conductive support is conductive so long as it has a function of closely supporting the conductive elastic layer laminated thereon so that the surface of the photoreceptor can be charged to a desired potential. Either is acceptable. A surface layer can be provided on the surface of the conductive elastic layer as necessary. A schematic diagram is shown in FIG. By providing the surface layer, even when a defect such as a pinhole occurs on the photoconductor, the concentration of the charging current to the pinhole is alleviated and the image defect is suppressed. The volume resistivity of the surface layer is preferably 1 × 10 ⁸ Ω · cm or more and 1 × 10 ¹² Ω · cm or less.

  The surface layer is made of a binder resin, conductive particles, conductive composite particles, and the like. As the binder resin, a resin such as a thermosetting resin or a thermoplastic resin is used. Specifically, urethane resin, fluorine resin, silicone resin, acrylic resin, polyamide resin, and the like can be given. A urethane resin obtained by crosslinking a lactone-modified acrylic polyol with an isocyanate is particularly preferably used. For the surface layer, conductive particles such as conductive metal oxide selected from carbon black, graphite, conductive titanium oxide, conductive tin oxide, etc., or a conductive composite in which the conductive particles are combined with other particles An appropriate amount of particles and the like can be dispersed. Further, by forming minute irregularities on the surface of the conductive elastic layer, it is possible to improve the charging uniformity. Examples of the method for forming the irregularities include a method of adjusting the surface roughness of the conductive elastic layer after vulcanization with a grindstone, a method of incorporating a surface roughening material into the surface layer, and the like. As the surface roughening material, fine particles such as urethane fine particles, silicone fine particles, acrylic fine particles, fine particle-containing oxides, and conductive fine particles can be used.

  In addition to the surface roughening material, insulating inorganic particles may be added for the purpose of adjusting the physical property value of the surface layer. As the inorganic particles, it is preferable to use inorganic fine powders such as silica, titanium oxide, zinc oxide, and magnesium oxide. As a method for forming the surface layer, first, a binder resin as described above is dissolved or dispersed in a solvent, and conductive particles, a surface roughening material, and inorganic fine powder are dispersed therein. Furthermore, the method of coating the obtained liquid on the surface of the conductive elastic layer by a coating method such as dipping, beam coating, roll coater or the like can be mentioned. Second, there is a method of coating the outer periphery of the conductive elastic layer using kneaded conductive particles, surface roughening material, and inorganic fine powder in a binder resin, which are molded into a cylindrical shape by an extruder or the like. Can be mentioned.

  The charging member in the present invention can be provided with functional layers such as an adhesive layer, a diffusion prevention layer, a base layer, and a primer layer in addition to the conductive elastic layer and the surface layer as necessary. The compression set of a charging member such as a charging roller can be evaluated by an acceleration test using a 40 ° C./95% RH environment in which both temperature and humidity are higher than those in a normal electrophotographic use environment.

  FIG. 3 is a schematic configuration diagram of an image forming apparatus provided with a charging roller as a charging member of the present invention. The image forming apparatus includes a photosensitive member 30, a charging device that charges the photosensitive member with a charging roller 10, a latent image forming device 40 that performs exposure, a developing device 50 that develops a toner image, a transfer device 60 that transfers to a transfer material, and a photosensitive member. The image forming apparatus includes a cleaning device 70 that collects the transfer toner above, a fixing device (not shown) that fixes a toner image, and a light irradiation device 80 that serves as a pre-exposure unit for discharging charges.

  The photosensitive member 30 is a rotating drum type having a photosensitive layer on a conductive substrate, and is a photosensitive drum in which an organic photosensitive layer having a film thickness of 18 μm is coated on an aluminum cylinder. The photoreceptor is driven to rotate in the direction of the arrow at a predetermined peripheral speed (process speed). The charging roller 10 is a contact-type charging roller that is placed in contact with the photosensitive member by being brought into contact with the photosensitive member with a predetermined pressing force. The charging roller is driven rotation that rotates in accordance with the rotation of the photosensitive member, and charges the photosensitive member to a predetermined potential by applying a predetermined DC voltage from a charging power source. As the latent image forming apparatus 40 that forms an electrostatic latent image on the photosensitive member, for example, an exposure apparatus such as a laser beam scanner is used. An electrostatic latent image is formed by performing exposure corresponding to image information on a uniformly charged photoconductor. The developing device 50 has a contact-type developing roller disposed close to or in contact with the photoreceptor. The toner electrostatically processed to the same polarity as the charged polarity of the photosensitive member is reversely developed, and the electrostatic latent image is visualized and developed into a toner image. The toner is a polymerized toner obtained by polymerizing a random copolymer of styrene and butyl acrylate containing a charge control agent, a pigment and the like with a wax at the center, polymerizing a thin polyester layer, and externally adding silica fine particles. The transfer device 60 has a contact-type transfer roller. The toner image is transferred from the photoreceptor to a transfer material 61 such as plain paper (the transfer material is conveyed by a paper feed system having a conveying member). The cleaning device 70 includes a blade-type cleaning member and a collection container, and mechanically scrapes and collects the transfer residual toner remaining on the photosensitive member after the transfer. Here, it is also possible to remove the cleaning device by adopting a development simultaneous cleaning system in which the transfer device collects the transfer residual toner. The fixing device (not shown) includes a heated roll or the like, fixes the transferred toner image, and discharges the toner image outside the apparatus. The light irradiation device 80 is disposed so as to irradiate a region after the transfer process and before the charging process as a pre-exposure means for discharging the charge on the electrophotographic photosensitive member generated by the transfer bias.

Hereinafter, it demonstrates in detail by an Example and a comparative example.
Example 1
<1. Preparation of rubber composition>
The following were prepared as raw materials for the rubber composition. Epichlorohydrin rubber (epichlorohydrin: ethylene oxide: allyl glycidyl ether = 23 mol%: 73 mol%: 4 mol%, referred to as “epichlorohydrin rubber 1”) 100 parts by mass, perchloric acid as ionic conductive agent Quaternary ammonium salt (methyl-dihydroxyethyl-dodecylammonium perchlorate: referred to as “ionic conductive agent A”) 2 parts by weight, heavy calcium carbonate 60 parts by weight (average particle size 1.3 μm) as filler, reinforcing agent Carbon black (Printex300 Degussa pH 9.5, DBP oil absorption 66 ml / 100 g) 5 parts by mass, zinc oxide 5 parts by mass, zinc stearate 1 part by mass, anti-aging agent, 2-mercaptobenzimidazole (MB) 0. 5 parts by mass, 5 parts by mass of sebacic acid polyester as a plasticizer. These raw materials were kneaded for 10 minutes in a pressure kneader whose temperature was adjusted to 100 ° C. to prepare an unvulcanized rubber composition. 1 part by mass of tetramethylthiuram monosulfide (referred to as “vulcanization accelerator A”) as a vulcanization accelerator and dipentamethylene thiuram tetrasulfide (referred to as “vulcanization accelerator B”) in this unvulcanized rubber composition. ) 1 part by mass and 1.2 parts by mass of sulfur as a vulcanizing agent were added and kneaded for 10 minutes with an open roll whose temperature was adjusted to 25 ° C.

<2. Formation of conductive elastic layer>
The obtained unvulcanized rubber composition was supplied to the extruder (inner diameter 50 mm, L / D 20) shown in FIG. 2 and sent to the crosshead 21 at a screw rotation speed of 15 rpm, a cylinder temperature and a head temperature of 80 ° C. As the conductive support 11, a cylindrical steel rod (surface is nickel-plated) having a diameter of 6 mm and a length of 250 mm coated with a thermosetting adhesive (trade name: METALOC U-20) was used. In the cross head 21, the periphery of the conductive support 11 was coated with an unvulcanized rubber composition. Next, this coating was cut off with a cut-off jig 23 to obtain a non-vulcanized roller 24. Extrusion processability during molding was evaluated according to the following evaluation criteria. The results are shown in Table 3.
○: Good workability,
X: Scorch is generated.

  Vulcanization and curing of the adhesive were performed in an electric oven at 160 ° C. for 2 hours. Subsequently, both end portions of the rubber portion were removed, and the rubber portion was polished by a plunge polishing machine (grinding stone GC120, grinding wheel diameter φ300 mm, grinding wheel rotation speed 2500 rpm, workpiece rotation speed 333 rpm), end diameter 8.3 mm, central diameter A charging roller having an 8.5 mm crown-shaped elastic layer was obtained.

<3. Curing speed of conductive elastic layer>
The vulcanization rate of the conductive elastic layer was measured by the method described below. The results are shown in Table 3.

  As a measuring method, the unvulcanized rubber composition after kneading with an open roll is used at 160 ° C. for 30 minutes using a vulcanization tester rotorless rheometer RLR-3 (manufactured by Toyo Seiki) in accordance with JIS-K6300. Then, the elapsed time t90 (minutes) from the start of measurement was measured until it increased from the minimum torque ML by 90% of the difference between the maximum torque MH and the minimum torque ML. This time was taken as the vulcanization rate (min, T90).

<4. Mooney scorch of conductive elastic layer>
The Mooney scorch of the conductive elastic layer was measured by the method described below. The results are shown in Table 3. As a measurement method, the unvulcanized rubber composition after kneading with an open roll is subjected to viscosity at a measurement temperature of 125 ° C. using a Mooney viscometer SMV-300 (manufactured by Shimadzu Corporation) in accordance with JIS-K6300. The time t5 (minutes) from the lowest value until 5 Mooney rises was measured. This time was taken as Mooney scorch (min, 125 ° C.).

<5. Swelling degree of conductive elastic layer>
The degree of swelling of the conductive elastic layer was measured by the method described below. The results are shown in Table 3. As a measuring method, based on JIS K6258, it was left to stand for 24 hours in toluene at room temperature of 23 ° C., and the values of the volume V1 before being left and the volume V2 after being left were measured. . A sample was prepared by slicing a rubber portion from a conductive elastic layer and processing it into an arc shape having a length of 20 mm and a thickness of 2 mm.
(Formula 1) Swelling degree (%) = (V2 / V1-1) × 100

<6. Preparation of surface layer paint>
(6-1. Production of conductive particles X)
To 7.0 kg of silica particles (average particle diameter 13.5 nm, volume resistivity 1.5 × 10 ¹² Ω · cm), 140 g of methylhydrogenpolysiloxane was added while operating the edge runner, and 588 N / cm. The mixture was stirred for 30 minutes with a linear load of (60 Kg / cm). The stirring speed at this time was 22 rpm. Next, 7.0 kg of carbon black particles (particle diameter 17 nm, volume resistivity 1.9 × 10 ² Ω · cm) was added over 10 minutes while operating the edge runner, and further 588 N / cm (60 Kg / cm). ) For 60 minutes with a linear load, carbon black was adhered to the methylhydrogenpolysiloxane-coated silica particles, and then dried at 80 ° C. for 60 minutes using a dryer to obtain conductive particles X. . The stirring speed at this time was 22 rpm.

The obtained conductive particles X had a volume average particle size of 15 nm and a volume resistivity of 2.0 × 10 ² Ω · cm. The volume average particle diameter was obtained by randomly sampling 10 conductive particle images enlarged to 1 million magnification using a transmission electron microscope (TEM) and obtaining the projected area based on the image information. The equivalent circle diameter of the area was calculated and obtained. The volume resistivity was calculated from the resistance value measured using Loresta GP MCP-T600 (manufactured by Mitsubishi Chemical Corporation). The applied voltage was 100 V and the applied pressure was 10 MPa.

(6-2. Production of metal oxide particles Y)
A slurry was prepared by blending 1000 g of rutile-type titanium oxide particles (average particle size 15 nm, volume resistivity 5.2 × 10 ¹⁰ Ω · cm), 110 g of isobutyltrimethoxysilane as a surface treating agent, and 3000 g of toluene as a solvent.

  This slurry was mixed with a stirrer for 30 minutes, and then supplied to Viscomill in which 80% of the effective internal volume was filled with glass beads having an average particle diameter of 0.8 mm, and wet crushing was performed at a temperature of 35 ± 5 ° C. . Toluene was removed from the slurry obtained by the wet pulverization treatment by distillation under reduced pressure (bath temperature: 110 ° C., product temperature: 30-60 ° C., degree of vacuum: about 100 Torr) using a kneader, at 120 ° C. for 2 hours, The surface treatment agent was baked. The particles after the baking treatment were cooled to room temperature and then pulverized using a pin mill to obtain metal oxide particles Y.

(6-3. Preparation of coating solution for surface layer)
Methyl isobutyl ketone was added to a caprolactone-modified acrylic polyol solution (trade name: Plaxel DC2016, manufactured by Daicel Chemical Industries, Ltd.) to prepare a solid content of 20% by mass.

The following five components were further added to 500 parts by mass of this solution to prepare a mixed solution.
-Conductive particles X: 45 parts by mass,
-Metal oxide particles Y: 25 parts by mass,
Cross-linked acrylic particles (trade name: MBX-8, manufactured by Sekisui Chemical Co., Ltd.): 10 parts by mass Modified dimethyl silicone oil (trade name: SH28PA, manufactured by Toray Dow Corning Silicone Co., Ltd.): 0.08 parts by mass ,
Block isocyanate mixture: 80.14 parts by mass.

  At this time, the blocked isocyanate mixture had an amount of OH in the caprolactone-modified polyol solution and “NCO / OH = 1.0” as the isocyanate amount NCO. In a 450 mL glass bottle, 280 g of the above mixed solution and 200 g of glass beads having an average particle diameter of 0.8 mm as a medium were mixed and dispersed for 12 hours using a paint shaker disperser to obtain a dispersed solution.

<7. Production of charging roller with surface layer>
This surface layer coating solution is dipped on the conductive elastic layer once, air-dried at room temperature for 30 minutes, then dried in a hot air circulating dryer set at 80 ° C. for 1 hour, and further set at 160 ° C. The surface layer was formed by drying with a hot air circulating dryer for 1 hour. The dipping coating dipping time is 9 seconds, the dipping coating lifting speed is adjusted so that the initial speed is 20 mm / s and the final speed is 2 mm / s, and the time between 20 mm / s and 2 mm / s is relative to the time. The speed was changed linearly. Thus, a charging roller having a conductive elastic layer and a surface layer in this order on a conductive support was produced.

  The electric resistance value of the charging roller was measured by the method shown in FIG. In the figure, symbol 10 is a charging roller, 90 is a cylindrical electrode made of stainless steel, 91 is a resistor, and 92 is a recorder. The charging roller was brought into contact with the cylindrical electrode at both ends thereof with a pressing force of 4.9 N springs. The resistance value (average value) was measured when -200 V was applied from the external DC power supply 93 for 10 seconds while rotating the cylindrical electrode at 30 rpm. The results are shown in Table 3.

<8. C set image evaluation>
The charging roller was brought into contact with the electrophotographic photosensitive drum and left in a 40 ° C./95% RH environment for 1 month. The photosensitive drum had a diameter of 24 mm, and the charging roller was brought into contact with a pressing force of a spring of 4.9 N at one end and 9.8 N at both ends. After being left in a 40 ° C./95% RH environment for 1 month, the charging roller was taken out from the environment in contact with the photosensitive drum and left in a 23 ° C./50% RH environment for 6 hours. After that, the contacted charging roller is mounted on an electrophotographic apparatus having a configuration shown in FIG. 3 (a voltage of only DC voltage is applied to the charging roller), and a halftone image is obtained in a 23 ° C./50% RH environment. The output image was evaluated. The surface potential (dark portion potential) VD of the electrophotographic photosensitive member charged by the charging roller was adjusted to be −450V. The process speed was 94 mm / s. The output image was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3.
Rank 1: No image defect is confirmed on the halftone image.
Rank 2: Partially thin streak-like image defects are confirmed on the halftone image, but there is no practical problem.
Rank 3: There is a streak-like image defect in a part of the halftone image.
Rank 4: A streak-like image defect is conspicuous on the entire surface of the halftone image.

<9. Measurement of C set amount>
Using the conductive support of the charging roller as an axis, the radius of the roller was measured, and the difference in radius between the most deformed portion and the non-contact portion of the contact portion was used as the C set amount. Using a fully automatic roller measuring device manufactured by Tokyo Koden Kogyo Co., Ltd., 360 ° measurement was performed by rotating the charging member by 1 °. The measurement positions were a total of three locations, the central portion of the roller and 90 mm from the central portion toward both ends, and the largest deformation amount was the C set amount of the charging roller. The evaluation results are shown in Table 3. In Example 1, the vulcanization rate of the conductive elastic layer is fast and the degree of toluene swelling is reduced, that is, the crosslinking density is improved, so that the amount of C set due to contact with the photoconductor in a high temperature and high humidity environment can be reduced. Even in the case of severe contact and neglect, a good image was obtained.

(Examples 2-9)
As shown in Tables 1 to 3, a charging roller was produced and evaluated in the same manner as in Example 1 except that the types of carbon black, ionic conductive agent, and epichlorohydrin rubber were changed. The evaluation results are shown in Table 3. In any of the examples, the degree of toluene swelling was reduced and the crosslinking density was improved, so that the amount of C set due to contact with the photoconductor under high temperature and high humidity could be reduced, and severe contact leaving was performed. Even in the case, a good image was obtained.

(Comparative Examples 1-8)
A charging roller was produced and evaluated in the same manner as in Example 1 except that the composition shown in Table 4 was used. The evaluation results are shown in Table 4. In Comparative Example 1, the degree of toluene swelling was large, the amount of C set was also large, and a C set image was generated. In Comparative Example 2, the pH of carbon black was small, the vulcanization rate was lowered, and sufficient vulcanization was not obtained. Therefore, the degree of toluene swelling was large, the amount of C set was increased, and a C set image was generated. In Comparative Example 3 and Comparative Example 4, the degree of toluene swelling was large, the amount of C set was also large, and a C set image was generated. In Comparative Example 5, since the DBP oil absorption amount was large, the Mooney scorch time was short, and the vulcanization speed was high, rubber scorch occurred during extrusion. Along with the generation of the C set image, an image defect due to the appearance due to the scorch occurred. In Comparative Example 6, an image defect in which the resistance of the conductive elastic layer was considered to be high occurred, and a C set image was generated. In Comparative Example 7, vulcanization did not proceed sufficiently, the degree of toluene swelling was large, the amount of C set was also large, and a C set image was generated. In Comparative Example 8, vulcanization did not proceed and a conductive elastic layer could not be formed.

DESCRIPTION OF SYMBOLS 10 Charging roller 11 Conductive support body 12 Conductive elastic layer 13 Surface layer 14 Charging bias application power source 20 Extruder 21 Crosshead 22 Core metal feed roller 23 Cut-off jig 24 Unvulcanized roller 30 Photosensitive drum 40 Laser beam scanner 50 Development Device 60 Transfer roller 61 Transfer material 62 Transfer bias application power supply 70 Cleaning blade 80 Light irradiation device 90 Stainless steel cylindrical electrode 91 Resistance 92 Recorder 93 DC power supply

Claims (2)

  A method for producing a charging member having a conductive support and a conductive elastic layer, comprising epichlorohydrin rubber, carbon black having a pH of 9 or more and a DBP oil absorption of 50 ml / 100 g to 69 ml / 100 g, ion A method for producing a charging member, comprising: covering a surface of a conductive support with a rubber composition containing a conductive agent, zinc oxide, and sulfur, and then crosslinking the rubber composition to form a conductive elastic layer.   The epichlorohydrin rubber has a composition ratio of 20 mol% to 25 mol% of units derived from epichlorohydrin, 70 mol% to 75 mol% of units derived from ethylene oxide, and 1 mol% of units derived from allyl glycidyl ether. The method for producing a charging member according to claim 1, wherein the amount is 5 mol% or less.

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