JP2006215388A - Method for manufacturing conductive member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably manufacturing a conductive member capable of outputting an excellent image free from an image defect over a long term even when an electrophotographic device to be applied is an electrophotographic device using only DC voltage as voltage to be applied to an electrifying member. <P>SOLUTION: A conductive covering layer provided on a conductive supporting body is a layer in which conductive particles are dispersed. Processing for stirring a mixture for forming the layer at the time of forming the layer is performed in a plurality of stages. In each stage, dispersion share in the succeeding stage is switched to be low. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a conductive member (for example, a charging member, a developer carrying member, a transfer member, and a cleaning member) that electrically controls an object to be contacted in an image forming apparatus employing an electrophotographic system such as a printer, a facsimile machine, and a copying machine. , A static elimination member, etc.).

  An image forming apparatus employing an electrophotographic system, that is, an electrophotographic apparatus, generally includes an electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a transfer unit.

  Further, as this charging means, a voltage (a voltage of only DC voltage or a voltage obtained by superimposing an AC voltage on a DC voltage) is applied to a charging member that is in contact with or close to the surface of the electrophotographic photosensitive member. Many systems that charge the surface of the photoreceptor are used. As a voltage to be applied to the charging member, when a voltage obtained by superimposing an AC voltage on a DC voltage is used, an AC power source is required, leading to an increase in size and cost of the electrophotographic apparatus, an increase in power consumption, From the above viewpoint, the voltage applied to the charging member may be only a DC voltage because the durability of the charging member and the electrophotographic photosensitive member may decrease due to the large amount of ozone generated by the use of alternating current. preferable.

  Furthermore, a contact-type charging method is preferably used from the viewpoint of stably charging, reducing the generation of ozone, or reducing the cost.

  When the voltage applied to the charging member is a DC voltage only, the charged potential on the surface of the charged object is likely to be uneven, and minute streak-like image defects are likely to occur, and the charging uniformity. May be difficult to obtain. In addition, when the charging member is deteriorated by energization due to continuous use, there is a problem that the resistance of the charging member is likely to increase (charge up), and the charging potential on the surface of the charged object is reduced accordingly. Further, in the image forming apparatus using the contact-type charging method, when the charging member is contaminated (development of the developer surface, etc.), there is a problem that image density unevenness is caused by the charging failure due to the contamination. . In particular, in the charging method in which only a DC voltage is applied to the charging member, the influence of contamination on the charging member tends to appear as an image defect compared to a charging method in which a voltage in which an AC voltage is superimposed on the DC voltage is applied.

  To solve this problem, Patent Document 1 discloses a technique for obtaining uniformity of resistance by using conductive particles for the purpose of obtaining uniformity of charging.

  However, particles having a small particle size have a large surface energy, so that the particles have a strong cohesive force and often form secondary aggregates such as a structure structure. For this reason, it is not easy to uniformly disperse the conductive particles having a small particle diameter in the conductive member, and micro resistance unevenness is likely to occur, and it may be difficult to obtain resistance uniformity.

On the other hand, Patent Documents 2 and 3 disclose techniques for increasing the dispersion share and efficiency by increasing the number of dispersers and processes in the dispersion process and obtaining high dispersibility.
Japanese Patent Laid-Open No. 06-250494 JP 2003-207966 A JP 09-146342 A

  However, if dispersion processing is performed with a strong share in order to obtain high dispersibility, when the dispersion process is completed, it is suddenly released from the share, so reaggregation may occur repulsively. However, there is a problem that the dispersion state of the conductive particles becomes unstable and the stability is poor.

  The object of the present invention is to provide a conductive member that can electrically control a contacted object, in particular, a conductive member for charging a contacted object by applying a DC voltage, and has a good dispersibility of conductive particles. It is another object of the present invention to provide a method capable of manufacturing a conductive member in which uniformity of resistance is ensured. Another object of the present invention is to have a conductive coating layer that has good dispersibility of conductive particles, does not cause microscopic resistance unevenness, and has uniform resistance, An object of the present invention is to provide a method for producing a conductive member suitable as a charging member for direct current application which has improved the problem of occurrence of image defects and has improved resistance uniformity over a long period of time.

The method for producing a conductive member according to the present invention is a method for producing a conductive member having at least a conductive coating layer containing conductive particles on a conductive support.
Preparing a mixture containing at least a layer forming material and conductive particles;
Stirring the mixture to disperse conductive particles in the mixture;
Forming a conductive layer from a mixture containing the conductive particles in a dispersed state;
Having the conductive layer as a coating layer on a conductive support,
Conductive particles are dispersed in the mixture by n-stage (n ≧ 2) stirring processes with different dispersion shares, and the dispersion share of the (n + 1) th stage is smaller than the dispersion share of the n-stage. It is a manufacturing method of an electroconductive member.

  According to the present invention, even a conductive member having a conductive coating layer in which conductive particles are dispersed as a surface layer can easily disperse particles uniformly, resulting in microscopic resistance unevenness. And uniform resistance, and suitable as a conductive member (for example, a charging member, a developer carrying member, a transfer member, a cleaning member, or a charge removing member of an electrophotographic apparatus) for electrically controlling an object to be contacted. A conductive member can be obtained. In particular, by using this conductive member as a contact charging member of an electrophotographic apparatus, it is possible to produce a good image output that is less likely to cause charging defects and has no image defects, and has a uniform resistance over a long period of time. It is possible to provide a contact charging member capable of maintaining the above.

  The conductive member to which the production method of the present invention can be applied has a structure having at least a conductive coating layer on a conductive support, and can have a layer structure corresponding to its use. The conductive member obtained by the production method of the present invention can be used as a charging member, a developer carrying member, a transfer member, a cleaning member, a charge eliminating member, etc. of an electrophotographic apparatus, particularly a member used by applying a DC voltage, It can be particularly suitably used as a charging member. Furthermore, it is possible to effectively improve the characteristics of the conductive member by applying a plurality of stirring processes having different dispersion shares according to the present invention to the formation of the surface layer of the conductive member.

  An example of the structure of the conductive member when used as a charging member is shown in FIGS. The charging member shown in FIG. 2 has a roller shape as shown in FIG. 2, and is composed of a conductive support 2a and an elastic layer 2b integrally formed on the outer periphery thereof as a coating layer. Another configuration of the charging member is shown in FIG. As shown in FIG. 3, the charging member may be a two-layer coating layer composed of an elastic layer 2b and a surface layer 2c, a three-layer layer composed of an elastic layer 2b, a resistance layer 2d and a surface layer 2c, and a resistance layer. It is good also as a structure which provided the 2nd resistance layer 2e between 2d and the surface layer 2c, and formed four or more layers on the electroconductive support body 2a.

  As the conductive support 2a, a round bar made of a metal material such as iron, copper, stainless steel, aluminum and nickel can be used. Furthermore, these metal surfaces may be plated for the purpose of providing rust prevention and scratch resistance, but it is necessary not to impair the conductivity.

  In the charging roller having the above-described configuration, the elastic layer 2b has appropriate conductivity and elasticity in order to supply power to the electrophotographic photosensitive member as the member to be charged and to ensure good uniform adhesion to the electrophotographic photosensitive member 1. It is. In order to ensure uniform adhesion between the charging roller and the electrophotographic photosensitive member, it is preferable to form the elastic layer 2b in a so-called crown shape by polishing so that the central portion is thickest and narrows toward both ends. In the structure of a general electrophotographic apparatus, the charging roller 2 applies a predetermined pressing force to both ends of the support 2a and is in contact with the electrophotographic photosensitive member 1, so that the pressing force at the center is small, Since both ends are large, there is no problem if the straightness of the charging roller 1 is sufficient, but if it is not sufficient, density unevenness may occur in the images corresponding to the center and both ends. The crown shape is formed to prevent this.

The conductivity of the elastic layer 2b is a conductive agent having an electron conduction mechanism selected from carbon black, graphite and a conductive metal oxide in an elastic material such as rubber, and ions such as alkali metal salts and quaternary ammonium salts. It is preferable to adjust to less than 10 ¹⁰ Ωcm by appropriately adding a conductive agent having a conduction mechanism.

  Specific elastic materials as a layer forming material for forming the elastic layer 2b include, for example, natural rubber, ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), silicone rubber, urethane rubber, epichlorohydrin rubber, isoprene. Synthetic rubbers such as rubber (IR), butadiene rubber (BR), nitrile butadiene rubber (NBR), and chloroprene rubber (CR), as well as polyamide resins, polyurethane resins, and silicone resins are also included.

In a charging member that applies a direct current voltage to charge the object to be charged, in order to achieve charging uniformity, particularly a moderate resistance polar rubber (eg, epichlorohydrin rubber, NBR, CR, urethane rubber, etc.) It is preferable to use polyurethane resin as an elastic material. These polar rubbers and polyurethane resins are considered to have a slight conductivity due to moisture and impurities in the rubber and resin as carriers, and these conduction mechanisms are considered to be ionic conduction. However, an elastic layer is prepared without adding a conductive agent to these polar rubbers and polyurethane resins, and the obtained charging member has a high resistance value of 10 ¹⁰ Ωcm or more in a low temperature and low humidity environment (L / L). Therefore, a high voltage must be applied to the charging member.

Therefore, it is preferable to adjust the conductive member having the above-described electronic conductive mechanism and the conductive agent having the ionic conductive mechanism by appropriately adding so that the resistance value of the charging member is less than 10 ¹⁰ Ωcm in the L / L environment. However, the conductive agent having an ionic conduction mechanism has a small effect of lowering the resistance value, and particularly in the L / L environment. Therefore, the resistance adjustment may be performed by supplementarily adding a conductive agent having an electronic conductive mechanism in addition to the addition of a conductive agent having an ionic conductive mechanism.

  The elastic layer 2b may be a foam obtained by foaming these elastic materials.

  The thickness of the elastic layer is preferably 0.5 to 20 mm, particularly 1 to 10 mm.

  The surface layer 2c constitutes the surface of the charging member, and is not preferable in a material configuration that contaminates the photoconductor because it contacts the photoconductor that is the object to be charged. Moreover, it can be said that the thing with surface releasability is preferable. Therefore, it can be said that it is preferable to use a resin as the layer forming material (binding material) for forming the surface layer.

  As the binder resin material for the surface layer 2c, fluororesin, polyamide resin, acrylic resin, polyurethane resin, silicone resin, butyral resin, styrene-ethylene-butylene-olefin copolymer (SEBC), and olefin-ethylene-butylene-olefin It is preferable to use a copolymer (CEBC) or the like. When the surface layer 2c is formed by the coating layer forming step according to the production method of the present invention, a fluororesin, an acrylic resin, a silicone resin, and the like are particularly preferable.

  For the purpose of reducing the static friction coefficient to these binder resins, solid lubricants such as graphite, mica, molybdenum disulfide and fluororesin powder, or fluorosurfactants, wax, silicone oil, etc. may be added. Good.

  Various conductive particles are appropriately used for the surface layer 2c. Examples of the conductive particles include metal oxide-based conductive particles, metal-based conductive particles, carbon black, and carbon-based conductive particles. In the present invention, in order to obtain a desired electric resistance, Two or more kinds of the various conductive particles may be used in combination.

  Examples of the metal oxide conductive particles include zinc oxide, tin oxide, indium oxide, titanium oxide (titanium dioxide, titanium monoxide, etc.), iron oxide, aluminum oxide, and the like. Some of the metal oxide-based conductive particles show sufficient conductivity by themselves, but some of them do not. In order to make the conductivity of the particles sufficient, a dopant may be added to these particles. In general, it is considered that surplus electrons are generated due to the presence of metal oxide lattice defects and show conductivity, and formation of lattice defects is promoted by addition of a dopant, and sufficient conductivity can be obtained. For example, aluminum is used as a dopant for zinc oxide, antimony is used as a dopant for tin oxide, and tin is used as a dopant for indium oxide. Moreover, when obtaining the electroconductivity of titanium oxide, what coated electroconductive tin oxide on titanium oxide etc. can be mentioned. Furthermore, the thing which coat | covered the layer containing carbon black on the surface of the base | substrate which consists of metal oxides, such as a silica, etc. are mentioned.

  Examples of the metal conductive particles include silver, copper, nickel, and zinc.

  Examples of carbon black include acetylene black, furnace black, and channel black.

  Examples of the carbon conductive particles include graphite, carbon fiber, activated carbon, charcoal and the like.

  The average particle size of the conductive particles is preferably less than 1.0 μm. If the average particle size exceeds 1.0 μm, pinhole leakage may occur if pinholes exist on the photosensitive drum. When the specific gravity of the conductive particles is heavy, if the average particle size exceeds 1.0 μm, the conductive particles are likely to settle in the coating solution, and the dispersion stability of the coating solution may be deteriorated.

  The specific gravity of the conductive particles is preferably 0.8 to 8.0, particularly 1.0 to 7.0.

  These particles may be subjected to surface treatment, modification, introduction of functional groups, coating, and the like.

The resistance value of the surface layer is preferably 10 ⁴ to 10 ¹⁵ Ωcm. Moreover, it is preferable that thickness is 1-500 micrometers. In particular, it is preferably 1 to 50 μm. The thickness of the resistance layer is also preferably the same as that of the surface layer.

  The surface coating layer, the elastic coating layer, and the resistance layer may be formed by, for example, adhering or coating a sheet-shaped or tube-shaped layer formed in advance to a predetermined film thickness, or electrostatic spraying. The coating may be performed by a coating method such as coating or dipping. Moreover, after forming a layer roughly by extrusion molding, the method of adjusting the shape of a layer by grinding | polishing etc. may be used, and the method of hardening and shaping | molding material to a predetermined shape within a type | mold may be used. That is, when a sheet-like or tube-like layer is formed in advance and this layer is coated on a conductive support to form a coating layer, the conductive layer is formed from a mixture containing conductive particles in a dispersed state. And when the conductive layer is provided directly on the conductive support as in the coating method, these steps are performed as separate steps. A process is performed as one process.

  When a layer is formed by a coating method, the solvent used in the coating solution is a solvent that can dissolve or disperse a layer forming material, for example, a binding material or other materials necessary for forming a coating layer. Well, for example, alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and sulfoxides such as dimethyl sulfoxide , Ethers such as tetrahydrofuran, dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, and aliphatic halogenated carbonization such as chloroform, ethylene chloride, dichloroethylene, carbon tetrachloride and trichloroethylene Motoya, benzene, toluene, xylene, ligroin, chlorobenzene, and aromatic compounds such as dichlorobenzene.

  In order to disperse the conductive particles in a desired degree of dispersion in the mixture containing the conductive particles and the layer forming material, the mixture is supplied to a ribbon blender, a Nauter mixer, a Henschel mixer, a super mixer, etc. Existing methods such as stirring and mixing, or stirring and mixing with a Banbury mixer, a pressure kneader, or the like can be used. For the layer formation by the coating method, a solvent, a layer forming material and conductive particles are mixed, and the conductive liquid is made conductive in the coating solution by using a conventionally known solution dispersing means such as a ball mill, a sand mill, a paint shaker, a dyno mill and a pearl mill. Disperse the particles, apply a coating solution in which the conductive particles thus obtained are in a dispersed state to a predetermined position of the conductive support, and perform a drying treatment as necessary to improve the dispersibility of the conductive particles. A covering layer can be formed. In the present invention, among these dispersers, it is preferable to use a bead mill that can continuously perform the step of dispersing conductive particles, has an appropriate dispersion share, and can easily change the share.

  As described above, as the layer forming material to be included in the mixture, materials selected from various rubbers and resins are used in the formation of the conductive elastic layer (2b). Various additives for controlling properties and the like can be further added. In the formation of the surface layer (2c), a binder material, preferably a binder resin, is a layer forming material. In this case as well, various additives for controlling conductivity and the like are added as necessary. Can be added. Moreover, although a solvent can be added to a mixture as needed, a solvent is essential for formation by a coating method. What is necessary is just to select a composition required in order to obtain the electroconductive coating layer which has a desired function and characteristic as a composition of a mixture. At that time, the ratio of the binder material to the conductive particles is preferably binder resin: conductive particles = 1: 0.2 to 1: 2.5 (weight ratio), and the inclusion of the conductive particles in the coating liquid The amount is preferably 1 to 20% by weight, and the content of the binder resin in the coating solution is preferably 5 to 40% by weight.

  Regarding the content of the solvent, it is added so that the viscosity of the coating solution is 1 to 500 mPa · s, more preferably 5 to 100 mPa · s, and the content is preferably 10 to 90 wt%, particularly 30 to 80 wt%. % Is preferred.

  Although the mechanism by which the dispersibility in the coating layer of the conductive particles is improved by providing a stirring process having a different dispersion share in the production method of the present invention has not been clarified, The following were clarified.

  The uniformity of charging of the member is largely due to the dispersibility of the conductive agent and functional particles used as the material constituting the charging member. When the dispersibility of the conductive agent is inferior, the uniformity of resistance is not sufficient, so that it is difficult to obtain the uniformity of charging. In addition, the conductive agent is likely to be deteriorated by energization. When conductive particles are used as the conductive agent in order to obtain uniformity of resistance, the cohesive force between the particles is strong, and in order to disperse the particles up to the vicinity of the primary particle size, It has been found necessary to break up the aggregates of strong particles. Moreover, it is thought that the dispersion | distribution state of electroconductive particle and the contact state of electroconductive particles are also affecting the deterioration by electricity supply. If the dispersibility of the conductive particles is improved, it is considered that the resistance does not increase even when the charging member is continuously used (continuous energization). However, if dispersion processing is performed with a strong share, when the dispersion process is completed, it is suddenly released from the share, so re-aggregation tends to occur repulsively, the dispersion state of the conductive particles becomes unstable, and stability is improved. It gets worse. As the dispersion process progresses, by gradually weakening the share, there is no sudden change in energy applied to the conductive particles, so the dispersion process can be completed in a state close to the stable state, so in the long term A stable dispersion state can be obtained.

  The maximum peripheral speed of the stirring unit when dispersed by the stirring type dispersing device is preferably 2 to 12 m / s, and particularly preferably 4 to 10 m / s. The degree of reduction when switching shares is preferably 1 to 2 m / s. The number of times of switching shares is preferably 1 to 4 times. That is, the number (n) of stages with different distribution shares is preferably in the range of 2-5.

  Through various studies as described above, in the method for producing a conductive member containing conductive particles in the coating layer, in the step of dispersing the conductive particles in the coating layer, the dispersion share of two or more stages is achieved. By switching and gradually decreasing the dispersion share, it is possible to produce a conductive member that can maintain the uniformity of resistance and the uniform dispersion state of conductive particles for a long period of time. .

Next, as a preferred application of the conductive member of the present invention, an example in which it is used as a contact charging member (charging roller) of an electrophotographic apparatus will be described based on a schematic configuration of an image forming apparatus.
(1) Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus provided with a process cartridge of the present invention. The image forming apparatus of this example is a reversal developing method using transfer type electrophotography, and a developing and cleaning method (cleanerless). A rotary drum type electrophotographic photosensitive member 1 as an image carrier is disposed in the process cartridge 6 and is driven to rotate at a predetermined peripheral speed (process speed) in the direction of the arrow. Around the electrophotographic photosensitive member 1, first, a charging roller 2 as a charging unit is disposed in a state of being in contact with the electrophotographic photosensitive member 1 with a predetermined pressing force. In this example, the charging roller 2 is driven to rotate at the same speed as the electrophotographic photosensitive member 1. A predetermined DC voltage (in this case, -1180 V) is applied to the charging roller 2 from the charging bias application power source S1, so that the surface of the electrophotographic photosensitive member 1 has a predetermined polarity potential (dark part potential -400 V). ) Is uniformly charged by a contact charging method or a DC charging method.

  The exposure unit 3 is, for example, a laser beam scanner. The exposure unit 3 performs exposure L corresponding to target image information on the charging surface of the electrophotographic photosensitive member 1, so that the surface potential of the electrophotographic photosensitive member 1 is changed to the potential of the exposure bright portion (bright portion potential of −120 V The electrostatic latent image is formed by selectively decreasing (attenuating). The toner (negative toner) charged with the same polarity as the charging polarity of the electrophotographic photosensitive member 1 (developing bias −350 V) is selectively applied to the exposed bright portion of the electrostatic latent image of the electrophotographic photosensitive member by the reversal developing unit 4. And the electrostatic latent image is visualized as a toner image. In the figure, 4a is a developing roller, 4b is a toner supply roller, and 4c is a toner layer thickness regulating member.

  The transfer roller 5 serving as a transfer unit is disposed in contact with the electrophotographic photosensitive member 1 with a predetermined pressing force to form a transfer portion, and the electrophotographic photosensitive member rotates in the forward direction with the rotation of the electrophotographic photosensitive member 1. It rotates at the same peripheral speed as the rotational peripheral speed of 1. Further, a transfer voltage having a polarity opposite to the charging polarity of the toner is applied from the transfer bias applying power source S2. The transfer material P is fed to the transfer portion from a paper feed mechanism portion (not shown) at a predetermined control timing, and the back surface of the fed transfer material P is charged with toner by the transfer roller 5 to which a transfer voltage is applied. The toner image on the electrophotographic photosensitive member 1 is electrostatically transferred to the transfer material P at the transfer portion.

  The transfer material that has received the transfer of the toner image at the transfer portion is separated from the electrophotographic photosensitive member, introduced into a toner image fixing means (not shown), subjected to a toner image fixing process, and output as an image formed product. In the case of the double-sided image formation mode or the multiple image formation mode, this image formed product is introduced into a recirculation conveyance mechanism (not shown) and reintroduced into the transfer unit.

  Residues on the electrophotographic photosensitive member such as transfer residual toner are charged to the same polarity as the charging polarity of the electrophotographic photosensitive member by the charging roller 2. Then, the transfer residual toner reaches the developing means 4 through the exposure portion, and is electrically collected in the developing device by the back contrast, thereby achieving development and cleaning (cleanerless).

  In this example, the electrophotographic photosensitive member 1, the charging roller 2, and the developing means 4 are integrally supported, and the process cartridge 6 is detachable from the main body of the image forming apparatus. At this time, the developing means 4 may be a separate body.

  Further, the electrophotographic apparatus to which the conductive member obtained by the manufacturing method according to the present invention is applied is not limited to the configuration shown in FIG. 1, and the illustrated configuration having at least a charging member and an electrophotographic photosensitive member is as follows. Different process cartridges can be used (developing means using the main body side or cleaning means having a cleaning means between the toner image transfer region and the charging member). Furthermore, it is possible to employ a configuration in which each member necessary for the apparatus main body is arranged without using the process cartridge.

  When a DC voltage is applied to the charging member 2 of the apparatus shown in FIG. 1, a discharge occurs in a minute space between the charging member and the photosensitive member, and the surface of the photosensitive member 1 is charged. If the conductive member obtained by the production method of the present invention is used as the charging member 2, not only can the charging uniformity of the charging member be improved, but also the resistance change can be suppressed, so a very excellent image can be obtained. Obtainable. In particular, as shown in FIG. 1, a plurality of image forming apparatuses adopting a so-called developing and cleaning (cleanerless) system that does not have a developing and independent cleaning unit and collects toner remaining on the photosensitive member after transfer by the developing unit. It is extremely effective in enabling sheet printing.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
A charging roller as a charging member of the present invention was produced in the following manner.
Epichlorohydrin rubber: 100 parts by mass Quaternary ammonium salt: 2 parts by mass Calcium carbonate: 90 parts by mass Zinc oxide: 5 parts by mass Fatty acid: 5 parts by mass After kneading the above materials for 10 minutes in a closed mixer adjusted to 60 ° C. Then, 15 parts by mass of an ether ester plasticizer was added to 100 parts by mass of epichlorohydrin rubber, and the mixture was further kneaded for 20 minutes with a closed mixer cooled to 20 ° C. to prepare a raw material compound. To this compound, 100 parts by mass of epichlorohydrin rubber as a raw rubber, 1 part by mass of sulfur as a vulcanizing agent, 1 part by mass of noxeller DM (dibenzothiazyl sulfide) as a vulcanization accelerator, and noxeller TS (tetramethylthiuram monosulfide) 0.5 parts by mass was added and kneaded for 10 minutes in a two-roll mill cooled to 20 ° C. The obtained compound is molded in an extruder so as to form a roller around a φ6 mm stainless steel support, heated and steam vulcanized, and then polished to an outer diameter of φ12 mm to obtain an elastic layer. It was. The roller length was 230 mm.
Subsequently, the following materials:
Acrylic polyol solution (manufactured by Daicel Chemical Industries: PLACEL DC2016): 100 parts by mass;
Isocyanate A (IPDI) (manufactured by Degussa: VESTANAT B1370): 27 parts by mass;
Isocyanate B (HDI) (Asahi Kasei Chemicals Corporation: DURANATE TPA-B80E): 17 parts by mass;
Conductive particles (CS-Bk100Y manufactured by Toda Kogyo Co., Ltd .: silica particles coated with carbon black): 13 parts by mass;
Modified dimethyl silicone oil (SH28PA manufactured by Toray Dow Corning Silicone): 0.3 parts by mass; and methyl isobutyl ketone: 300 parts by mass were stirred using a mixer to prepare a mixed solution. Next, this mixed solution was mixed with a bead mill disperser (Ultra Visco Mill manufactured by IMEX Co., Ltd.) filled with glass beads having an average particle diameter of 0.8 mm as a medium at a filling rate of 80% with respect to the volume of the vessel. Circulation was carried out for 21 hours at a speed of 8 m / s and a processing speed of 600 ml / min to carry out dispersion treatment. Further, the disk peripheral speed was continuously changed to 6 m / s, and dispersion treatment was performed for 2 hours to obtain a dispersion solution. This dispersion solution was applied by a dipping method to coat and form a surface layer having a film thickness of 15 μm to obtain a roller-shaped charging member.

“Evaluation of stability of dipping coating solution over time”
The viscosity of the coating solution for dipping produced by the above method was measured on the first day of production and 7 days after production. The viscosity was measured at 60 rpm using a No. 1 rotor with a Bismetron viscometer (VDA-L type) manufactured by Shibaura System. The results are shown in Table 1. After the production, the viscosity of the paint that is considered to have decreased dispersibility is large.

"Evaluation of image when only DC voltage is applied to charging roller"
The charging roller obtained above is attached to the electrophotographic image forming apparatus shown in FIG. 1, and a halftone image is output in an L / L environment (temperature 15 ° C./humidity 10%). Images were evaluated. The applied voltage (DC voltage only) was adjusted so that the surface potential (dark portion potential) VD of the electrophotographic photosensitive member charged by the charging member was around −400V. In Table 2, A indicates that the obtained image is very good, B indicates good, C indicates that the halftone image has a slight streak-like defect, and D indicates that the image defect of the streak is conspicuous.

  Further, before the image evaluation was started, the resistance of the charging roller was measured by the method shown in FIG. The results are shown in Table 2. In the figure, 2 is a conductive member, 11 is a cylindrical electrode made of stainless steel, 12 is a resistor, and 13 is a recorder. The pressing force between them is the same as that of the image forming apparatus used, and the resistance value when -200 V is applied from the external power source S3 is measured. In addition, as an evaluation of the uniformity of resistance, the ratio of the measured maximum resistance value to the minimum value was defined as resistance unevenness. The results are shown in Table 2.

  The above evaluation was performed on each of the charging rollers prepared using the dipping coating liquid on the first day of production and 7 days after the production. When the evaluation after 7 days from the production was A or B, the produced charging roller was good, and for C and D, the image result was not good.

(Example 2)
A charging member was produced in the same manner as in Example 1 except that the dispersion treatment of the conductive particles was performed in three stages, and the disk peripheral speed in the third stage was 4 m / s and additional treatment was performed for 2 hours. The charging roller was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

(Example 3)
A charging member was produced in the same manner as in Example 1 except that the disk peripheral speed at the first stage when the conductive particles were dispersed was 10 m / s. The charging roller was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

Example 4
A charging member was produced in the same manner as in Example 1 except that carbon black (MA77 manufactured by Mitsubishi Chemical Corporation) was used as the conductive particles.
The charging roller was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

(Comparative Example 1)
A charging member was produced in the same manner as in Example 1 except that the conductive particles were dispersed only in one stage at a disk peripheral speed of 8 m / s. The charging roller was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

(Comparative Example 2)
A charging member was produced in the same manner as in Example 1 except that the conductive particles were dispersed only in one stage at a disk peripheral speed of 6 m / s. The charging roller was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.
(Comparative Example 3)
A charging member was produced in the same manner as in Example 4 except that the dispersion treatment of the conductive particles was performed only at one stage at a disk peripheral speed of 8 m / s.

1 is a schematic configuration diagram of an image forming apparatus of the present invention. It is the schematic of a charging roller. It is the schematic of the charging roller which shows another Example. It is the schematic of the resistance measuring apparatus of a charging member.

Explanation of symbols

1; Image carrier (electrophotographic photosensitive member)
2; Charging member (charging roller)
3; Image exposure means 4; Development means 5; Transfer means (transfer roller)
6; cleaning means S1, S2, S3; bias application power source P; transfer material 11; cylindrical electrode (metal roller)
12; Fixed resistor 13; Recorder

Claims (4)

In the method for producing a conductive member having at least a conductive coating layer containing conductive particles on a conductive support,
Preparing a mixture containing at least a layer forming material and conductive particles;
Stirring the mixture to disperse conductive particles in the mixture;
Forming a conductive layer from a mixture containing the conductive particles in a dispersed state;
Having the conductive layer as a coating layer on a conductive support,
Conductive particles are dispersed in the mixture by n-stage (n ≧ 2) stirring processes with different dispersion shares, and the dispersion share of the (n + 1) th stage is smaller than the dispersion share of the n-stage. A method for producing a conductive member.   2. The method for producing a conductive member according to claim 1, wherein a disperser used in the step of dispersing the conductive particles in the mixture is a bead mill.   The method for producing a conductive member according to claim 1 or 2, wherein the conductive particles have a multilayer structure, and the conductive substance contained in the outermost layer of the conductive particles is carbon black.   The method for producing a conductive member according to claim 3, wherein the outermost layer is coated on a layer containing a metal oxide.

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