JP2018132658A - Charging member, charging device, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging member that reduces the occurrence of uneven charging.SOLUTION: A charging member comprises: a conductive substrate; an elastic layer that is provided on the conductive substrate; and a surface layer that is provided on the elastic layer and contains a binder resin, metal oxide, and carbon black having a DBP oil absorption of 130 or more and a ph of 6 or more and 10 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a charging member, a charging device, a process cartridge, and an image forming apparatus.

In an image forming apparatus using an electrophotographic method, an image holding member (electrophotographic photosensitive member) is charged by a charging device or the like to form a charge, and after forming an electrostatic latent image by a laser or the like that modulates an image signal, The electrostatic latent image is developed with charged toner to form a toner image. Then, the required image is obtained by transferring the toner image to a recording medium via an intermediate transfer member.
In this image forming apparatus, a non-contact charging device such as a corotron or a scorotron that is charged by a corona discharge generated by applying a high voltage to a conventional metal wire is known as a charging device. However, in recent years, instead of this, a charging device using a charging roll has been widely used because, for example, the applied voltage is small and the amount of ozone generated is small.

  Here, Patent Document 1 is a charging member having a conductive substrate and a conductive surface layer, and the surface layer includes a binder resin and composite particles dispersed in the binder resin. The surface of the charging member has convex portions derived from the composite particles, the composite particles have an average particle diameter of 1 μm or more and 30 μm or less, and the core portion is coated with a conductive material, The core portion includes a polymer including units derived from ethylene oxide, and the content of the units derived from ethylene oxide is 20% by mass to 100% by mass with respect to the polymer, and the conductive material Discloses a charging member including at least one selected from the group consisting of carbon black, a conductive polymer, a metal oxide, and a metal.

  Patent Document 2 discloses a charging member having a surface layer on a conductive support, and the surface layer is made of a binder resin, graphite particles, and calcium titanate, barium titanate, and strontium titanate. Containing ferroelectric particles selected from the group, the surface of the charging member is formed with convex portions derived from graphite particles (graphite convex portions) and convex portions derived from ferroelectric particles (ferroelectric convex portions). When a plane including three vertices of the graphite convex part adjacent to the ferroelectric convex part is formed, the ferroelectric convex part lower than the plane is 80% or more of the total ferroelectric convex part. A member is disclosed.

Patent Document 3 includes a shaft body, a resistance adjustment layer formed directly or via another layer on the outer periphery of the shaft body, and a protective layer formed on the outer periphery of the resistance adjustment layer. A charging roll comprising the following (A) binder polymer, (B) porous particles having a specific surface area of 9 m ² / g or more, and (C) a conductive agent. Is disclosed.

JP 2010-197936 A JP 2010-102016 A JP 2009-175427 A

  An object of the present invention is to provide a surface layer containing a binder resin, a metal oxide, and carbon black, wherein the carbon black is a carbon black having a DBP oil absorption of less than 130 ml / 100 g or a pH of less than 6. The object is to provide a charging member that suppresses uneven charging as compared with the member.

  The above problem is solved by the following means.

The invention according to claim 1
A conductive support;
A surface layer provided on the conductive support and containing a binder resin, a metal oxide, and carbon black having a DBP oil absorption of 130 ml / 100 g or more and a pH of 6 or more and 10 or less;
A charging member.

The invention according to claim 2
The charging member according to claim 1, wherein the carbon black has a DBP oil absorption of 150 ml / 100 g or more.

The invention according to claim 3
The charging member according to claim 1, wherein the metal oxide is tin oxide.

The invention according to claim 4
The charging member according to claim 1, wherein the binder resin is a polyamide resin.

The invention according to claim 5
The charging member according to claim 1, wherein the surface layer further includes polyamide resin particles.

The invention according to claim 6
6. A charging device comprising a charging member according to claim 1, wherein the charging device is a charging member that contacts the surface of the member to be charged and charges the surface of the member to be charged.

The invention according to claim 7 provides:
The charging device according to claim 6, wherein the surface of the member to be charged is charged by a direct current charging method.

The invention according to claim 8 provides:
An image carrier,
The charging device according to claim 6 or 7, wherein the image carrier is charged;
With
A process cartridge attached to and detached from the image forming apparatus.

The invention according to claim 9 is:
9. The process cartridge according to claim 8, wherein the image carrier is an electrophotographic photosensitive member having at least a surface layer having a charge transporting property of 25 μm or more on a substrate.

The invention according to claim 10 is:
An image carrier,
The charging device according to claim 6 or 7, wherein the image carrier is charged;
A latent image forming apparatus for forming a latent image on the surface of the charged image carrier;
A developing device for developing a latent image formed on the surface of the image carrier with toner to form a toner image;
A transfer device for transferring the toner image formed on the surface of the image carrier to a recording medium;
An image forming apparatus comprising:

The invention according to claim 11 is:
The image forming apparatus according to claim 10, wherein the image carrier is an electrophotographic photosensitive member having at least a surface layer having a charge transporting property of 25 μm or more on a substrate.

According to the invention of claim 1, a surface layer comprising a binder resin, a metal oxide, and carbon black, wherein the carbon black is a carbon black having a DBP oil absorption of less than 130 ml / 100 g or a pH of less than 6. A charging member that suppresses uneven charging compared to a charging member having a layer is provided.
According to the second aspect of the present invention, there is provided a charging member that suppresses uneven charging as compared with a case where the carbon black has a DBP oil absorption of less than 150 ml / 100 g. According to the invention which concerns on Claim 3, compared with the case where a metal oxide is a zinc oxide, the charging member which suppresses charging nonuniformity is provided.
According to the invention which concerns on Claim 4, compared with the case where binder resin is a polyester resin, the charging member which suppresses charging nonuniformity is provided.
According to the invention which concerns on Claim 5, compared with the case where a surface layer contains only a polymethyl methacrylate resin particle as a resin particle, the charging member which suppresses charging nonuniformity is provided.

According to the invention of claim 6, a surface layer comprising a binder resin, a metal oxide, and carbon black, wherein the carbon black is a carbon black having a DBP oil absorption of less than 130 ml / 100 g or a pH of less than 6. As compared with a case where a charging member having a layer is provided, a charging device that suppresses uneven charging is provided.
According to the invention of claim 7, a surface layer comprising a binder resin, a metal oxide, and carbon black, wherein the carbon black is a carbon black having a DBP oil absorption of less than 130 ml / 100 g or a pH of less than 6. As compared with a case where a charging member having a layer is provided, there is provided a charging device that suppresses uneven charging even when the surface of an object to be charged is charged by a DC charging method.

According to the invention of claim 8, a surface layer containing a binder resin, a metal oxide, and carbon black, wherein the carbon black is carbon black having a DBP oil absorption of less than 130 ml / 100 g or a pH of less than 6. As compared with a case where a charging member having a layer is provided, a process cartridge that suppresses image defects caused by charging unevenness is provided.
According to the invention of claim 9, a surface layer comprising a binder resin, a metal oxide, and carbon black, wherein the carbon black is a carbon black having a DBP oil absorption of less than 130 ml / 100 g or a pH of less than 6. Compared with the case where a charging member having a layer is provided, even if the electrophotographic photosensitive member has at least a surface layer having a charge transporting property of 25 μm or more on the substrate, the image retention resistance is caused by uneven charging. A process cartridge that suppresses defects is provided.

According to the invention of claim 10, a surface layer comprising a binder resin, a metal oxide, and carbon black, wherein the carbon black is a carbon black having a DBP oil absorption of less than 130 ml / 100 g or a pH of less than 6. As compared with a case where a charging member having a layer is provided, an image forming apparatus that suppresses image defects caused by uneven charging is provided.
According to the invention of claim 11, a surface layer containing a binder resin, a metal oxide, and carbon black, wherein the carbon black is carbon black having a DBP oil absorption of less than 130 ml / 100 g or a pH of less than 6. Compared with the case where a charging member having a layer is provided, even if the electrophotographic photosensitive member has at least a surface layer having a charge transporting property of 25 μm or more on the substrate, the image retention resistance is caused by uneven charging. An image forming apparatus that suppresses defects is provided.

It is a schematic sectional drawing of an orthogonal | vertical direction to the axis | shaft of a roll which shows an example of the charging member which concerns on this embodiment. It is a schematic sectional drawing of the orthogonal | vertical direction to the axis | shaft of a roll which shows the other example of the charging member which concerns on this embodiment. 1 is a schematic diagram illustrating a basic configuration of an image forming apparatus according to a first embodiment. FIG. 4 is a schematic diagram illustrating a basic configuration of an image forming apparatus according to a second embodiment. It is the schematic which shows the basic composition of the image forming apparatus which concerns on 3rd Embodiment. It is the schematic which shows an example of the process cartridge which concerns on this embodiment.

Hereinafter, an embodiment which is an example of the present invention will be described in detail.
In this specification, the term “conductive” means that the volume resistivity at 20 ° C. is less than 1 × 10 ¹³ Ωcm.

[Charging member]
The charging member according to this embodiment is provided with a conductive support, a conductive support, a binder resin, a metal oxide, and carbon black having a DBP oil absorption of 130 ml / 100 g or more and a pH of 6 or more and 10 or less. Including a surface layer.

Here, as a means for charging the member to be charged, a charging member that contacts the surface of the member to be charged and charges the surface of the member to be charged (hereinafter also referred to as “contact charging member”) is known. Yes. The contact charging type charging member includes, for example, at least a surface layer containing a conductive agent for imparting conductivity on a conductive support.
However, the contact charging type charging member cannot easily suppress electrical unevenness, and uneven charging (that is, a phenomenon in which the amount of charge with respect to an object to be charged varies depending on the location) may occur. For this reason, for example, when used as a charging member for charging an image carrier (electrophotographic photosensitive member, etc.) in an image forming apparatus, uneven charging occurs on the image carrier, and image defects (density) due to uneven charging. Unevenness, color spots, white spots, and stripe-like image defects extending in the axial direction (direction intersecting the recording medium conveyance direction) may occur. The cause of the uneven charging is thought to be due to the non-uniform surface layer conductivity.

In contrast, the charging member according to the present embodiment has a surface layer containing a binder resin, a metal oxide, and a carbon black having a DBP oil absorption of 130 ml / 100 g or more and a pH of 6 or more and 10 or less. It is suppressed. The reason is not clear, but is presumed as follows.
The metal oxide functions as a conductive agent, and the conductive path is likely to be fine and nearly uniform as compared with the case of carbon black alone.
On the other hand, carbon black having a DBP oil absorption and pH in the above range has high conductivity and high dispersibility stability.
Therefore, when carbon black having a DBP oil absorption and pH in the above range is used in combination with the metal oxide, the “fine and nearly uniform conductive path” due to the metal oxide is not easily broken, and the target conductivity is the surface layer. To be granted. That is, the conductivity of the surface layer becomes uniform while having the resistance (conductivity) of the target surface layer. Therefore, it is considered that charging unevenness is suppressed.

  In the process cartridge and the image forming apparatus including the charging member according to the present embodiment, image defects (density unevenness, color point, white point, and axial direction (recording medium conveyance) Stripe-like image defects extending in the direction intersecting the direction) are suppressed.

  In addition, the charging member according to the present embodiment has uniform surface layer conductivity, and the desired resistance (conductivity) of the surface layer is easily obtained. In the process cartridge and the image forming apparatus provided with the charging member according to the present embodiment, the image defects (density unevenness, color point, white point, and axial direction (direction intersecting with the conveyance direction of the recording medium)) over time. The occurrence of elongated stripe-like image defects and the like) is suppressed.

  Here, in a charging device including a contact charging type charging member, there is a direct current charging method in which only a direct current is applied as a method for applying a voltage, or an alternating current superposition method in which alternating current is superimposed on direct current (alternating current charging method). In the direct current charging method, wear of the member to be charged is more easily suppressed, and generation of discharge sound due to vibration of the member to be charged is also suppressed as compared with the alternating current charging method. Also, the power supply cost is reduced. On the other hand, uneven charging tends to occur more than in the AC charging method. However, the charging member according to the present embodiment is likely to suppress uneven charging even when the object to be charged is charged by the DC charging method.

  In addition, when the image carrier (electrophotographic photosensitive member) as an object to be charged has a surface layer having charge transportability, the uneven charging is caused by the thickness of the surface layer having charge transportability (charge transportability on the surface). In the case where a plurality of layers are stacked, the total thickness (of the plurality of layers) tends to occur more thickly. In particular, when the thickness of the surface layer is 25 μm or more, the tendency of uneven charging increases. However, the charging member according to the present embodiment is likely to suppress uneven charging even when an electrophotographic photosensitive member having a charge transporting surface layer thickness of 25 μm or more is charged.

  Hereinafter, the configuration of the charging member according to the present embodiment will be described in detail.

The form of the charging member includes, but is not particularly limited to, a roll shape, a sheet shape, a blade shape, etc. Among them, at least the surface layer on the outer peripheral surface of a cylindrical or columnar conductive support. A roll-shaped charging roll provided with is preferable.
Hereinafter, the configuration of the charging member, which is one form of the charging member, will be described as an example.

FIG. 1 is a schematic cross-sectional view perpendicular to the axis of the roll, showing an example of a charging member (charging roll) according to the present embodiment. The charging roll shown in FIG. 1 includes an adhesive layer 32, an elastic layer 33, and a surface layer 35 on a conductive support 31.
FIG. 2 is a schematic sectional view in a direction perpendicular to the axis of the roll, showing another example of the charging member (charging roll) according to the present embodiment. The charging roll shown in FIG. 2 includes an adhesive layer 32, an elastic layer 33, an intermediate layer 34, and a surface layer 35 on a conductive support 31.
Note that the configuration of the charging roll according to the present embodiment is not limited to this, and any other configuration may be used as long as it includes the conductive support and the surface layer having the above-described configuration. For example, the adhesive layer 32 shown in FIGS. 1 and 2 may not be provided.

  Hereinafter, the structure of the charging roll shown in FIG. 1 will be mainly described. In the following description, reference numerals may be omitted.

(Conductive support)
The conductive support will be described.
The conductive support functions as an electrode and a support member for the charging roll, and is a metal or alloy such as aluminum, copper alloy, or stainless steel; iron plated with chromium, nickel, etc., for example, as shown in JIS G4804 The free-cutting steel made of a material plated with chromium, nickel or the like is used. The plating may be formed by an electrolytic plating method or an electroless plating method, and is not limited.

(Adhesive layer)
The material for forming the adhesive layer is not particularly limited. For example, polyolefin, chlorine rubber, acrylic, epoxy, polyurethane, nitrile rubber, vinyl chloride, vinyl acetate, polyester, phenol, silicone From the viewpoint of adhesion to rubber and elastomer forming the elastic layer, polyolefin-based and phenol-based materials are particularly preferable.

The adhesive layer may have a single layer configuration or a combination of a plurality of layers.
Carbon black such as conductivity imparted ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, stainless steel; tin oxide, indium oxide, titanium oxide Various conductive metal oxides such as tin oxide-antimony oxide solid solution, tin oxide-indium oxide solid solution; the surface of an insulating material made conductive; Good.

  The thickness of the adhesive layer is not particularly limited, but is preferably 1 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less.

(Elastic layer)
The elastic layer is a member having a function of imparting elasticity to the charging member according to the present embodiment, and the nip with the member to be charged is favorably formed by providing the elastic layer. The charging member including the elastic layer tends to cause the above-described charging unevenness with the formation of the nip with the member to be charged. The occurrence of uneven charging is suppressed satisfactorily.

-Rubber component-
The elastic layer can be formed of rubber components such as various rubbers and various elastomers.
As the rubber component, epichlorohydrin rubber is preferable from the viewpoint of suppressing resistance unevenness, and epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber and the like are particularly preferable.
The elastic layer preferably contains the epichlorohydrin rubber as a main component. “Epichlorohydrin rubber as the main component” means that the rubber component contained in the rubber composition forming the elastic layer contains the most epichlorohydrin rubber, and the epichlorohydrin rubber is included in the rubber component. The amount is preferably 50% by mass or more, more preferably 90% by mass or more, and all the rubber components are particularly preferably (100% by mass) epichlorohydrin rubber.

Other rubber components used in combination with epichlorohydrin rubber, or other rubber components used in place of the above epichlorohydrin rubber include, for example, isoprene rubber, chloroprene rubber, butyl rubber, polyurethane, silicone rubber, fluorine rubber, styrene-butadiene rubber, Examples thereof include butadiene rubber, nitrile rubber, ethylene propylene rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), and natural rubber.
A rubber component may be used independently and may be used in combination of 2 or more type.

-Conductive agent-
A conductive agent may be added to the elastic layer from the viewpoint of imparting conductivity. As the conductive agent, an electronic conductive agent or an ionic conductive agent is used.
Examples of the electronic conductive agent include carbon black such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, stainless steel; tin oxide, indium oxide, titanium oxide And various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution;

  Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; alkaline earth metal perchlorates and chlorates; Can be mentioned.

A conductive agent may be used independently and may be used in combination of 2 or more type.
The addition amount of the conductive agent is not particularly limited, but in the case of the electronic conductive agent, it is preferably in the range of 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component. A range of 25 parts by mass or less is more preferable.
On the other hand, in the case of the ionic conductive agent, it is preferably in the range of 0.1 parts by mass or more and 5.0 parts by mass or less, and 0.5 parts by mass or more and 3.0 parts by mass with respect to 100 parts by mass of the rubber component. The following range is more preferable.

-Crosslinking agent-
In the case of crosslinking the rubber component, materials such as a crosslinking agent and a crosslinking accelerator are further used. Generally, the types of cross-linking with a cross-linking agent include sulfur cross-linking, peroxide cross-linking, quinoid cross-linking, phenolic resin cross-linking, amine cross-linking, metal oxide cross-linking, etc., but cross-linking with materials having double bonds. From the viewpoint of easy handling and the flexibility of the crosslinked rubber, crosslinking with sulfur is preferred. Even in the sulfur cross-linking, cross-linking using a cross-linking agent that releases activated sulfur from a compound is preferable because it can shorten the distance between bonds, and 4,4′-dithiodimorpholine is preferable.

  Examples of the crosslinking accelerator include thiazole, thiuram, sulfenamide, thiourea, dithiocarbamate, guanidine, aldehyde-ammonia, and mixtures thereof.

-Other additives-
The rubber composition forming the elastic layer may contain other additives as necessary. Examples of other additives include fillers and crosslinking accelerators.
Other fillers include silica, calcium carbonate, clay and the like.
Examples of the vulcanization acceleration aid include blending of zinc oxide and the like.

  The amount of other additives added is in the range of 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the rubber component, including particles such as carbon black and zinc oxide as a vulcanization acceleration aid. Is preferable, and the range of 20 parts by mass or more and 80 parts by mass or less is more preferable.

  The constituent material (rubber composition) of the elastic layer may be used as a constituent material of the resistance layer when the resistance layer is formed.

The thickness of the elastic layer is preferably 1 mm or more and 10 mm or less, and more preferably 2 mm or more and 5 mm or less.
The volume resistivity of the elastic layer is preferably 10 ³ Ωcm or more and 10 ¹⁴ Ωcm or less.

The volume resistivity is a value measured by the following method.
A sheet-shaped measurement sample is collected from the measurement object, and a measurement jig (R12702A / B resiliency chamber: manufactured by Advantest) and a high resistance measuring instrument (R8340A) are obtained according to JIS K 6911 (1995). After applying a voltage adjusted so that the electric field (applied voltage / composition sheet thickness) is 1000 V / cm for 30 seconds using a digital high resistance / microammeter (manufactured by Advantest), from the value of the flowing current, Calculate using the formula.
Volume resistivity (Ωcm) = (19.63 × applied voltage (V)) / (current value (A) × measured sample thickness (cm))

-Formation of elastic layer-
The elastic layer is prepared, for example, by kneading a mixture of the components listed above to prepare a composition for forming an elastic layer, and using an extrusion molding machine, an injection molding machine, a press molding machine or the like equipped with a crosshead. Then, the composition is formed by extruding and vulcanizing the composition on the conductive support.

(Middle layer)
The intermediate layer is provided as necessary for resistance adjustment when the electric resistance of the elastic layer is low. The material constituting the intermediate layer is not particularly limited, but epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene copolymer rubber (NBR), natural Examples thereof include rubbers and blended rubbers thereof.

(Surface layer)
The surface layer includes a binder resin, a metal oxide, and carbon black. Further, particles for adjusting the surface roughness of the surface layer (hereinafter also referred to as “filler”), other additives, and the like may be included.

-Binder resin-
Examples of the binder resin (polymer material) include acrylic resin, fluorine-modified acrylic resin, silicone-modified acrylic resin, cellulose resin, polyamide resin, copolymer nylon, polyurethane resin, polycarbonate resin, polyester resin, polyimide resin, and epoxy resin. , Silicone resin, polyvinyl alcohol resin, polyvinyl butyral resin, cellulose resin, polyvinyl acetal resin, ethylene tetrafluoroethylene resin, melamine resin, polyethylene resin, polyvinyl resin, polyarylate resin, polythiophene resin. Polyethylene terephthalate resin (PET), fluororesin (polyvinylidene fluoride resin, tetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc. ). In addition, examples of the binder resin include those obtained by curing or crosslinking a curable resin with a curing agent or a catalyst. Further, the binder resin may be an elastic material.
The binder resin may be used alone or in combination of two or more. In the case of a crosslinkable resin, it may be used after being crosslinked.
Here, the copolymer nylon is a copolymer containing any one or more of 610 nylon, 11 nylon, and 12 nylon as polymerized units. The copolymer nylon may contain other polymer units such as 6 nylon and 66 nylon.

  Among these, as the resin, a polyvinylidene fluoride resin, a tetrafluoroethylene resin, and a polyamide resin are preferable, and a polyamide resin is more preferable, from the viewpoint of suppressing contamination of the surface layer and facilitating generation of uneven charging. The polyamide resin hardly causes frictional charging due to contact with an object to be charged (for example, an image holding member), and adhesion of toner and external additives is easily suppressed.

  Examples of the polyamide resin include polyamide resins described in the polyamide resin handbook, Osamu Fukumoto (Nikkan Kogyo Shimbun). Among these, in particular, the polyamide resin is preferably an alcohol-soluble polyamide, more preferably an alkoxymethylated polyamide (alkoxymethylated nylon) from the viewpoint of suppressing contamination of the surface layer and suppressing charging unevenness, and more preferably a methoxymethylated polyamide ( More preferred is methoxymethylated nylon.

  The number average molecular weight of the binder resin (polymer material) is preferably in the range of 1,000 to 100,000, and more preferably in the range of 10,000 to 50,000.

-Metal oxide-
Examples of the metal oxide include tin oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, and tin oxide-indium oxide solid solution.
Among these, tin oxide is preferable as the metal oxide from the viewpoint of suppressing charging unevenness.

The average particle diameter of the metal oxide is preferably 10 nm or more and 100 nm or less, and more preferably 20 nm or more and 80 nm or less from the viewpoint of suppressing charging unevenness.
In addition, the average particle diameter of the metal oxide was measured with an electron microscope using a sample obtained by cutting out a layer containing the metal oxide, and 100 diameters (average diameter) of the metal oxide were measured. To calculate. Further, the average particle diameter may be measured using, for example, Zetasizer Nano ZS manufactured by Sysmex Corporation.

The content of the metal oxide is preferably 30 parts by mass or more and 100 parts by mass or less, and more preferably 40 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the binder resin.
If a large amount of metal oxide is contained in order to obtain the desired conductivity of the surface layer, the elongation characteristics or hardness of the surface layer is lost, which causes cracking or wear of the surface layer. However, by using carbon black having a specific DBP oil absorption and pH together with the metal oxide, even in the range of the metal oxide content (content in the above range) in which cracking or abrasion of the surface layer is difficult to occur, The target resistance (conductivity) is imparted to the surface layer.

-Carbon black-
Carbon black is a carbon black having a DBP oil absorption of 130 ml / 100 g or more and a pH of 6 or more and 10 or less.

The DBP oil absorption amount of carbon black is preferably 150 ml / 100 g or more, more preferably 200 ml / 100 g or more, and further preferably 300 ml / 100 g or more, from the viewpoint of suppressing charging unevenness. However, the upper limit of the DBP oil absorption of carbon black is exemplified by 400 ml / 100 g or less.
The DBP oil absorption amount indicates the amount of dibutyl phthalate (DBP) absorbed by 100 g of carbon black, and is a value defined by ASTM (American Standard Test Method) D2414-6TT.
When two or more types of carbon black are used in combination, the DBP oil absorption amount of the carbon black is a weighted average value for the content.

The pH of carbon black is preferably 8 or more and 9.5 or less from the viewpoint of suppressing charging unevenness.
The pH is a pH of an aqueous solution obtained by adding 50 g of carbon black to 1000 ml of water at 20 ° C., and is a value measured by a pH measurement method defined in JIS Z8802 (2011).
In addition, when using 2 or more types of carbon black together, the pH of carbon black is taken as the weighted average value about content.

The average particle size of carbon black is preferably 10 nm or more and 100 nm or less, and more preferably 20 nm or more and 50 nm or less, from the viewpoint of suppressing charging unevenness.

  The content of carbon black is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 2 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the binder resin.

-Filler-
Examples of the filler include resin particles and inorganic particles. The filler may be porous particles or non-porous particles. Moreover, the uneven | corrugated particle | grains may serve as the electrically conductive agent.
Examples of the resin particles include polyamide resin particles, polyimide resin particles, polyacrylic acid resin particles, polymethacrylic resin particles, polystyrene resin particles, fluororesin particles, and silicone resin particles.
Examples of the inorganic particles include carbon particles, metal particles, metal oxide particles obtained by sintering carbon black, graphite, and phenol resin.

Among these, as the filler, polyamide resin particles are preferable from the viewpoint of suppressing charging unevenness.
Examples of the polyamide resin particles include polyamide resin particles described in the polyamide resin handbook, Osamu Fukumoto (Nikkan Kogyo Shimbun). Among these, in particular, as the polyamide resin, alcohol-soluble polyamide particles are preferable, alkoxymethylated polyamide particles (alkoxymethylated nylon particles) are more preferable, and methoxymethylated polyamide particles ( More preferred are methoxymethylated nylon particles.

The average particle diameter of the filler is preferably 2 μm or more and 20 μm or less, more preferably 3 μm or more and 15 μm or less, and further preferably 3 μm or more and 12 μm or less from the viewpoint of suppressing charging unevenness.
In addition, the average particle diameter of a filler is measured by the same method as the average particle diameter of a metal oxide.

  The content of the filler is preferably 1 part by mass or more and 50 parts by mass or less, and more preferably 3 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

Here, the surface roughness Rz of the surface layer formed by the filler is preferably 2 μm or more and 15 μm or less, and more preferably 3 μm or more and 10 μm or less, from the viewpoint of suppressing unevenness in charging.
The surface roughness Rz is the ten-point average roughness Rz of JIS B0601 (1994). For the surface roughness Rz, a surface roughness measuring machine (Surfcom 1400 manufactured by Tokyo Seimitsu Co., Ltd.) was used, and the measurement target 3 was measured under the conditions of a cutoff of 0.8 mm, a measurement length of 4.0 mm, and a traverse speed of 0.3 mm / sec. A place (for example, in the case of a roll, 20 mm positions at both ends in the axial direction and three places at the center) is measured, and the average value is calculated.

-Other additives-
Examples of other additives include known additives such as a curing agent, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a dispersant, a surfactant, and a coupling agent.

-Formation of surface layer-
The surface layer is formed by dispersing or dissolving the above components in a solvent to prepare a coating solution, and applying and drying the coating solution on the elastic layer prepared in advance. Examples of the application method of the coating liquid include a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method.
The solvent used in the coating solution is not particularly limited, and general solvents are used. For example, alcohols such as methanol, ethanol, propanol and butanol; ketones such as acetone and methyl ethyl ketone; tetrahydrofuran; diethyl ether and dioxane Solvents such as ethers may be used.

[Charging device]
The charging device according to the present embodiment is a charging member that contacts the surface of the member to be charged and charges the surface of the member to be charged, and includes the charging member according to the present embodiment.
The charging device according to the present embodiment may be configured by only the charging member according to the present embodiment, for example, or the charging member and the cleaning member according to the present embodiment are arranged in contact with each other with a specific biting amount. It may be a configuration.

  As a method for applying a voltage to the charging member, there are a DC charging method in which only a DC voltage is applied, and an AC superposition method in which an AC voltage is superimposed on the DC voltage and applied. In the present embodiment, a DC charging method by applying a DC voltage is preferable from the viewpoint of wear of the photoconductor, generation of ozone, and discharge noise due to vibration of the photoconductor. Note that the above-described charging unevenness tends to occur more in the DC charging method than in the AC charging method. However, according to this embodiment, the occurrence of the charging unevenness is suppressed even when the DC charging method is adopted. Is done.

-Use-
The charging device including the charging member according to the present embodiment is used for the purpose of charging the object to be charged while being in contact with the object to be charged. For example, it is preferably used as a charging member in an image forming apparatus, and specifically, a charging member for charging an image carrier (electrophotographic photosensitive member), and toner is transferred from the image carrier (electrophotographic photosensitive member) to a recording medium. Used as a transfer member or the like.

[Image forming apparatus]
An image forming apparatus according to the present embodiment includes an image carrier, and a charging device that includes the charging member according to the present embodiment and charges the image carrier by bringing the charging member into contact with the surface of the image carrier. A latent image forming device that forms a latent image on the surface of the charged image carrier, a developing device that forms a toner image by developing the latent image formed on the surface of the image carrier with the toner, and the image carrier A transfer device that transfers the toner image formed on the surface of the body to a recording medium.
Hereinafter, an image forming apparatus according to the present embodiment will be described with reference to the drawings.

-First embodiment-
FIG. 3 is a schematic diagram illustrating a basic configuration of the image forming apparatus according to the first embodiment. An image forming apparatus 200 shown in FIG. 3 includes an electrophotographic photosensitive member (an example of an image holding member) 207, a charging device 208 that charges the electrophotographic photosensitive member 207, a power source 209 connected to the charging device 208, and a charging device. An exposure apparatus (an example of a latent image forming apparatus) 206 that exposes an electrophotographic photosensitive member 207 charged by 208 to form a latent image, and a latent image formed by the exposure apparatus 206 is developed with toner to form a toner image. A developing device 211 to be formed, a transfer device 212 that transfers a toner image formed by the developing device 211 to the recording medium 500, a cleaning device 213, a static eliminator 214, and a fixing device 215 are provided. Note that the static eliminator 214 illustrated in FIG. 3 may not be provided.

  The electrophotographic photosensitive member 207 is not particularly limited, and a known electrophotographic photosensitive member is used. For example, an undercoat layer, a charge generation layer, and a charge transport layer are laminated in this order on a conductive substrate, and a function-separated type photosensitive layer in which the charge generation layer and the charge transport layer are separately provided is provided. Examples include a photoreceptor. Further, it may be a photoreceptor having a function-integrated type photosensitive layer having both charge generation ability and charge transport ability. Further, the electrophotographic photoreceptor 207 may not include an undercoat layer, or an intermediate layer may be provided between the undercoat layer and the photosensitive layer, or a protective material including a charge transport material on the photosensitive layer. A layer may be provided.

In the electrophotographic photosensitive member 207 according to this embodiment, the total thickness of the surface layers having charge transporting properties is preferably 25 μm or more from the viewpoint of suppressing the occurrence of image defects and extending the lifetime, and is 25 μm or more. More preferably, it is 32 μm or less.
However, as the thickness of the surface layer having the charge transport property in the electrophotographic photosensitive member 207 increases, the above-described charging unevenness tends to occur more, particularly when the thickness is 25 μm or more. . On the other hand, in the present embodiment, by providing the charging member according to the present embodiment, the occurrence of charging unevenness is suppressed even when the thickness of the surface layer having charge transportability is 25 μm or more.

  Here, in the present embodiment, the “surface layer having charge transport properties” of the photoreceptor means a charge transport layer when the charge transport layer containing the charge transport material is the outermost surface layer in the function-separated type photosensitive layer. And a protective layer containing a charge transport material on the charge transport layer is the total thickness of the charge transport layer and the protective layer, and the function-integrated type photosensitive layer containing the charge transport material is the outermost surface. In the case of a layer, this is the photosensitive layer, and in the case where a protective layer containing a charge transport material is provided on the function-integrated type photosensitive layer, the total thickness of the photosensitive layer and the protective layer.

  The charging device 208 is of a type (contact charging method) in which a charging member (charging roll) is brought into contact with the surface of the electrophotographic photosensitive member 207 to charge the surface of the photosensitive member 207, and according to the above-described embodiment. A charging device including a charging member is used.

  As the exposure device 206, an optical system device that can expose a light source such as a semiconductor laser, an LED (light emitting diode), and a liquid crystal shutter on the surface of the electrophotographic photosensitive member in a desired image-like manner can be used.

  The developing device 211 stores toner. The toner used in the present embodiment includes, for example, a binder resin and a colorant. Examples of the binder resin include homopolymers and copolymers of styrenes, monoolefins, vinyl esters, α-methylene aliphatic monocarboxylic acid esters, vinyl ethers, vinyl ketones, etc. Typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include coalescence, polyethylene, and polypropylene. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax, and the like can also be mentioned.

  Coloring agents include magnetic powders such as magnetite and ferrite, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, and lamp black. Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 is a typical example.

The toner may be internally added or externally added with known additives such as a charge control agent, a release agent, and other inorganic particles.
Typical examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, Fischer-Tropsch wax, montan wax, carnauba wax, rice wax, and candelilla wax.
Known charge control agents can be used, but charge control agents such as azo-based metal complex compounds, metal complex compounds of salicylic acid, and resin types containing polar groups can be used.

As other inorganic particles, small-diameter inorganic particles having an average primary particle size of 40 nm or less are used for the purpose of powder fluidity, charge control, and the like. Inorganic or organic particles may be used in combination. As these other inorganic particles, known ones can be used.
In addition, the surface treatment of the small-diameter inorganic particles is effective because the dispersibility becomes high and the effect of increasing the powder fluidity increases.

  As a method for producing the toner used in the exemplary embodiment, a polymerization method such as an emulsion polymerization aggregation method or a dissolution suspension method is preferably used because high shape controllability can be obtained. In addition, a manufacturing method may be performed in which the toner obtained by the above method is used as a core, and agglomerated particles are further adhered and heat-fused to give a core-shell structure. When an external additive is added, it can be produced by mixing the toner and the external additive with a Henschel mixer or a V blender. In addition, when the toner is manufactured by a wet method, it may be externally added by a wet method.

  The transfer device 212 is capable of supplying a current having a predetermined current density toward the electrophotographic photosensitive member when the toner image formed on the electrophotographic photosensitive member 207 is transferred to the recording medium 500. Is preferred.

  The cleaning device 213 is for removing residual toner adhering to the surface of the electrophotographic photosensitive member after the transfer process. The cleaned electrophotographic photosensitive member is repeatedly used for the image forming process described above. . As the cleaning device, brush cleaning, roll cleaning, and the like can be used in addition to the cleaning blade. Among these, it is preferable to use the cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

  In addition, as shown in FIG. 3, the image forming apparatus according to the present embodiment may further include an erase light irradiation device 214 as a charge eliminator for removing the residual potential of the electrophotographic photosensitive member. As a result, when the electrophotographic photosensitive member is repeatedly used, the phenomenon that the residual potential of the electrophotographic photosensitive member is brought into the next cycle is prevented, so that the image quality can be further improved.

-Second Embodiment-
FIG. 4 is a schematic diagram illustrating a basic configuration of an image forming apparatus according to the second embodiment. The image forming apparatus 210 shown in FIG. 4 transfers the toner image formed on the electrophotographic photosensitive member 207 to the primary transfer member 212a and then supplies it between the primary transfer member 212a and the secondary transfer member 212b. In this transfer, a current having a predetermined current density can be supplied from the primary transfer member 212a to the electrophotographic photosensitive member. ing. Although not shown in FIG. 4, the image forming apparatus 210 may further include a static eliminator as in the image forming apparatus 200 shown in FIG. Other configurations of the image forming apparatus 210 are the same as those of the image forming apparatus 200.
As described above, the image forming apparatus 210 is different in that the intermediate transfer method is applied. However, as in the case of the image forming apparatus 200 according to the first embodiment, the electrophotographic photosensitive member 207 and the present embodiment. By combining with the charging device including the charging member according to the embodiment, the occurrence of image defects is suppressed.

  Further, when the toner image formed on the electrophotographic photosensitive member 207 is transferred to the primary transfer member 212a, a current having a predetermined current density is supplied from the primary transfer member 212a to the electrophotographic photosensitive member 207. As a result, fluctuations in the transfer current due to the type and material of the recording medium 500 can be suppressed, so that the amount of charge flowing into the electrophotographic photosensitive member 207 can be accurately controlled. As a result, it is possible to achieve higher image quality and reduced environmental burden at a higher level.

-Third embodiment-
FIG. 5 is a schematic diagram showing a basic configuration of an image forming apparatus according to the third embodiment. An image forming apparatus 220 shown in FIG. 5 is an intermediate transfer type image forming apparatus. In the housing 400, four electrophotographic photoreceptors 401a to 401d (for example, the electrophotographic photoreceptor 401a is yellow and the electrophotographic photoreceptor 401b is magenta). The electrophotographic photosensitive member 401c can form an image of cyan and the electrophotographic photosensitive member 401d can form a black color) are arranged in parallel along the intermediate transfer belt 409.

  Each of the electrophotographic photoreceptors 401a to 401d can be rotated in a specific direction (counterclockwise on the paper surface), and charging members (charging rolls) 402a to 402d, developing devices 404a to 404d, and 1 are provided along the rotation direction. Next transfer rolls 410a to 410d and cleaning blades 415a to 415d are arranged. Each of the developing devices 404a to 404d can supply toner of four colors, black, yellow, magenta, and cyan accommodated in the toner cartridges 405a to 405d. Further, the primary transfer rolls 410a to 410d are in contact with the electrophotographic photosensitive members 401a to 401d via the intermediate transfer belt 409, respectively.

  Further, a laser light source (exposure device) 403 is disposed in the housing 400, and it is possible to irradiate the surfaces of the electrophotographic photoreceptors 401a to 401d after charging with laser light emitted from the laser light source 403. ing. Accordingly, charging, exposure, development, primary transfer, and cleaning are sequentially performed in the rotation process of the electrophotographic photosensitive members 401a to 401d, and the toner images of the respective colors are transferred onto the intermediate transfer belt 409 in an overlapping manner.

  The intermediate transfer belt 409 is supported with tension by a drive roll 406, a back roll 408, and a tension roll 407, and can rotate without causing deflection due to the rotation of these rolls. The secondary transfer roll 413 is disposed so as to contact the back roll 408 via the intermediate transfer belt 409. The intermediate transfer belt 409 that has passed between the back roll 408 and the secondary transfer roll 413 is cleaned by, for example, a cleaning blade 416 disposed in the vicinity of the drive roll 406 and then repeatedly used for the next image forming process. Is done.

  In addition, a recording medium storage container 411 is provided in the housing 400, and the recording medium 500 such as paper in the recording medium storage container 411 is moved between the intermediate transfer belt 409 and the secondary transfer roll 413 by the transfer roll 412. Further, the paper is sequentially transferred between the two fixing rolls 414 that are in contact with each other, and then discharged to the outside of the housing 400.

  In the above description, the case where the intermediate transfer belt 409 is used as the intermediate transfer member has been described. However, the intermediate transfer member may have a belt shape like the intermediate transfer belt 409 or a drum shape. There may be.

[Process cartridge]
The process cartridge according to the present embodiment is a charging member that contacts the surface of the image carrier and the surface of the charged body to charge the surface of the charged body, and includes the charging member according to the present embodiment. And is attached to and detached from the image forming apparatus.

FIG. 6 is a schematic view showing an example of a process cartridge according to the present embodiment. A process cartridge 300 shown in FIG. 6 includes an electrophotographic photosensitive member (an example of an image carrier) 207, a charging device 208, a developing device 211, a cleaning device 213, an opening 217 for exposure, and an opening for static elimination exposure. 218 is combined and integrated using mounting rails 216. The developing device 211 supplies toner to the electrophotographic photosensitive member 207.
The process cartridge 300 is detachably attached to an image forming apparatus main body including a transfer device 212, a fixing device 215, and other components (not shown), and the image forming apparatus together with the image forming apparatus main body. Configure.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited by the following Example. Unless otherwise specified, “part” means “part by mass”.

(Preparation of electrophotographic photoreceptor 1)
Zinc oxide: (average particle size 70 nm: manufactured by Teika: specific surface area value 15 m ² / g) 100 parts of tetrahydrofuran were stirred and mixed, and 1.25 parts of silane coupling agent (KBM603: manufactured by Shin-Etsu Chemical Co., Ltd.) was added. Added and stirred for 2 hours. Thereafter, toluene was distilled off under reduced pressure and baked at 120 ° C. for 3 hours to obtain a silane coupling agent surface-treated zinc oxide pigment.

60 parts of the surface-treated zinc oxide pigment, 0.6 parts of alizarin, curing agent: 13.5 parts of blocked isocyanate (Sumidule 3175: manufactured by Sumitomo Bayern Urethane Co., Ltd.), butyral resin (ESREC BM-1) : Sekisui Chemical Co., Ltd.) and 15 parts of methyl ethyl ketone were obtained. 38 parts of this mixed liquid and 25 parts of methyl ethyl ketone were mixed, and dispersion was performed for 2 hours with a sand mill using glass beads of 1 mmφ to obtain a dispersion. To the obtained dispersion, 0.005 part of dioctyltin dilaurate as a catalyst and 4.0 parts of silicone resin particles (Tospearl 145: manufactured by Momentive Performance Materials) are added to form an undercoat layer. A coating solution was obtained.
This coating solution was applied onto an aluminum substrate by a dip coating method, followed by drying and curing at 170 ° C. for 40 minutes to obtain an undercoat layer having a thickness of 25 μm.

Next, a photosensitive layer (photosensitive layer having a laminated structure of a charge generation layer and a charge transport layer) was formed on the formed undercoat layer as follows.
First, the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using the Cukα ray as the charge generation material is at least 7.3 °, 16.0 °, 24.9 °, 28.0 °. A mixture comprising 15 parts of hydroxygallium phthalocyanine having a diffraction peak at a position, 10 parts of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nihon Unicar) as a binder resin, and 200 parts of n-butyl acetate Was dispersed in a sand mill for 4 hours using 1 mmφ glass beads. To the obtained dispersion, 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added and stirred to obtain a coating solution for a charge generation layer.
This charge generation layer coating solution was dip coated on the undercoat layer and dried at room temperature (22 ° C.) to form a charge generation layer having a thickness of 0.2 μm.

Next, 1 part of tetrafluoroethylene resin particles, 0.02 part of fluorine-based graft polymer, 5 parts of tetrahydrofuran, and 2 parts of toluene are sufficiently mixed by stirring to obtain a tetrafluoroethylene resin particle suspension. It was.
Next, 4 parts of N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1 ′] biphenyl-4,4′-diamine as a charge transport material and bisphenol Z-type polycarbonate 6 parts of resin (viscosity average molecular weight 40,000) and 23 parts of tetrahydrofuran are mixed and dissolved in 10 parts of toluene, and then the tetrafluoroethylene resin particle suspension is added and stirred and mixed. Using a high-pressure homogenizer (trade name LA-33S, manufactured by Nanomizer Co., Ltd.) equipped with a penetrating chamber with a pressure of 400 kgf / cm ² (3.92 × 10 ⁻¹ Pa), the dispersion treatment was performed 6 times. Repeatedly, a tetrafluoroethylene resin particle dispersion was obtained. Further, 0.2 part of 2,6-di-t-butyl-4-methylphenol was mixed to obtain a coating solution for forming a charge transport layer. This coating solution was applied onto the charge generation layer and dried at 115 ° C. for 40 minutes to form a charge transport layer having a thickness of 22 μm.
Thus, an electrophotographic photoreceptor 1 having a charge generation layer and a charge transport layer in this order on the undercoat layer was obtained.

(Preparation of electrophotographic photoreceptor 2)
An electrophotographic photoreceptor 2 was produced in the same manner as the electrophotographic photoreceptor 1 except that the thickness of the charge transport layer was 34 μm.

<Example 1>
-Production of rubber composition-
A rubber composition 1 was obtained by kneading a mixture having the following composition with a 2.5 L kneader.
・ 100 parts by mass of rubber material (epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber Hydrin T3106: manufactured by Nippon Zeon Co., Ltd.)
-Conductive agent (carbon black # 3030B: manufactured by Mitsubishi Chemical Corporation) 5 parts by mass-Ion conductive agent 1 part by mass (benzyltrimethylammonium chloride, trade name "BTEAC" Lion Specialty Chemicals)
・ Vulcanizing agent 1.5 parts by mass (Organic sulfur 4,4'-dithiodimorpholine Balnock R: Ouchi Shinsei Chemical Co., Ltd.)
-Vulcanization accelerator A 1.5 parts by mass (thiazole di-2-benzothiazolyl disulfide Noxeller DM-P: manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ 1.8 parts by mass of vulcanization accelerator B (thiuram-based tetraethylthiuram disulfide noxeller TET-G: manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization acceleration aid (Zinc oxide, 1 type of zinc oxide: manufactured by Shodo Chemical Industry Co., Ltd.) 3 parts by mass ・ Stearic acid 1.0 part by mass ・ Heavy calcium carbonate 40 parts by mass

-Production of elastic rolls-
After electroless nickel plating having a thickness of 5 μm, a conductive support made of SUM23L having a diameter of 8 mm and subjected to hexavalent chromic acid was prepared.
The rubber composition A1 is extruded at a screw rotation of 25 rpm using a uniaxial rubber extruder with a cylinder inner diameter of 60 mm and L / D20, and the conductive support is continuously passed through a crosshead, thereby providing a conductive support. The rubber composition A1 was coated on the body. The temperature conditions of the extruder were set to 80 ° C. for all of the cylinder part, screw part, head part, and die part. The unvulcanized rubber roll formed of the conductive support and the coated rubber composition was vulcanized at 165 ° C. for 70 minutes in an air heating furnace to obtain an elastic roll A1 having a diameter of 12 mm.

-Formation of surface layer-
Dispersion 1 obtained by dispersing the following mixture in a bead mill was obtained. The dispersion 1 was diluted with methanol and dip-coated on the surface of the elastic roll A1, and then heated and dried at 160 ° C. for 30 minutes to form a surface layer having a thickness of 6 μm, whereby the charging roll 1 was obtained.
・ Binder resin (polymer material) 100 parts by mass (N-methoxymethylated nylon F30K: manufactured by Nagase ChemteX Corporation)
・ Binder resin (polymer material) 10 parts by mass (polyvinyl butyral resin ESREC BL-1: manufactured by Sekisui Chemical Co., Ltd.)
・ 60 parts by mass of metal oxide (tin oxide 6010: manufactured by Mitsui Kinzoku Mining Co., Ltd.)
Carbon black 3 parts by mass (Ketjen Black EC300J: manufactured by Lion Specialty Chemicals, DBP oil absorption = 360 ml / 100 g, pH = 9)
-Filler 10 parts by mass (polyamide resin particles Orgasol 2001 DNat1: manufactured by Arkema)
・ Catalyst (Nacure 4167: manufactured by Enomoto Kasei Co., Ltd.) 1 part by mass. Solvent (methanol) 700 parts by mass. Solvent (butanol) 200 parts by mass

<Example 2>
Except for changing the carbon black of the surface layer of Example 1 to “carbon black (Denka Black powder: manufactured by Denka Co., Ltd., DBP oil absorption = 175 ml / 100 g, pH = 9) 3 parts by mass”, as in Example 1, A charging roller 2 was produced.

<Example 3>
The carbon black of the surface layer of Example 1 was changed to “carbon black (# 3030B: manufactured by Mitsubishi Chemical Corporation, DBP oil absorption = 130 ml / 100 g, pH = 6.5) 3 parts by mass” in the same manner as in Example 1. A charging roll 3 was produced.
3 parts by mass of carbon black (# 3030B: manufactured by Mitsubishi Chemical Corporation)

<Example 4>
A charging roll 4 was produced in the same manner as in Example 1 except that the amount of the metal oxide in the surface layer of Example 1 was changed to “90 parts by mass”.

<Example 5>
A charging roll 5 was produced in the same manner as in Example 1 except that the metal oxide of the surface layer of Example 1 was changed to the following “zinc oxide”.
・ 60 parts by mass of zinc oxide (MZ-300: manufactured by Teika)

<Example 6>
A charging roll 6 was prepared in the same manner as in Example 1 except that the binder resin and the curing agent of the surface layer of Example 1 were changed as follows and the dilution solvent was changed to MEK.
・ Binder resin (polymer material) 100 parts by mass (saturated copolymer polyester resin solution Byron 30SS: manufactured by Toyobo Co., Ltd.)
Curing agent 25 parts by mass (amino resin solution Super Becamine G-821-60: manufactured by Dainippon Ink & Chemicals, Inc.)

<Example 7>
A charging roll 7 was produced in the same manner as in Example 1 except that the filler of the surface layer of Example 1 was changed to “polymethyl methacrylate” described below.
・ 10 parts by mass of polymethyl methacrylate (MBX-8: manufactured by Sekisui Plastics Co., Ltd.)

<Comparative Example 1>
A charging roll C1 was produced in the same manner as in Example 1 except that the carbon black of the surface layer of Example 1 was changed to unblended.

<Comparative example 2>
A charging roll C2 was produced in the same manner as in Example 1 except that the amount of the metal oxide in the surface layer of Comparative Example 1 was changed to “120 parts by mass”.

<Comparative Example 3>
A charging roll C3 was prepared in the same manner as in Example 1 except that the metal oxide of the surface layer of Example 1 was not blended and the amount of carbon black was changed to “12 parts by mass”.

<Comparative Example 4>
Charging was performed in the same manner as in Example 1 except that the carbon black of the surface layer of Comparative Example 3 was changed to “carbon black (MONARCH1000: manufactured by Cabot Corporation, DBP oil absorption = 105 ml / 100 g, pH = 2.5) 18 parts by mass”. Roll C4 was produced.

<Evaluation>
-Evaluation of uneven charging-
The charging roll obtained in each example was mounted on a drum cartridge manufactured by Fuji Xerox Co., Ltd. as a contact charging type charging device for charging an image carrier (electrophotographic photosensitive member). The image quality was evaluated by 50%, 30%, and 0% halftone printing after printing 20,000 sheets, and evaluated according to the following evaluation criteria. However, in order to eliminate the influence of abrasion of the photoreceptor, an unused photoreceptor was used after printing 20,000 sheets.

The image quality evaluation was performed both when the electrophotographic photosensitive member 1 (charge transport layer thickness 22 μm) was attached and when the electrophotographic photosensitive member 2 (charge transport layer thickness 34 μm) was attached.
However, the image quality evaluation with the electrophotographic photoreceptor 1 (charge transport layer film thickness 22 μm) was performed only when charging was performed by the DC charging method (charging condition: DC voltage = −1100 V) (this evaluation in the table). Is expressed as “Charging Unevenness Evaluation 1”).
On the other hand, the image quality evaluation with the electrophotographic photosensitive member 2 (charge transport layer film thickness 34 μm) is charged by a DC charging method (charging condition: DC voltage = -1210 V, AC current = 1.5 mA, frequency of AC voltage = 1000 Hz). , DC voltage = −550 V) (in the table, this evaluation is expressed as “charging unevenness evaluation 21”) and when charging is performed by the AC charging method (in the table, this evaluation is referred to as “charging unevenness evaluation 22”). ")") And both.

The results are shown in Tables 1 to 3 below.
A (◎): Image defects such as density unevenness, white spots, color spots, streaks have not occurred.
B (◯): Image defects such as slight density unevenness, white spots, color spots, and streaks partially occur.
C (Δ): Image defects such as slight density unevenness, white point, color point, streak occur.
D (x): Image defects such as density unevenness, white spots, color spots, streaks occur.

-Surface condition of the charging roll-
When the electrophotographic photosensitive member 2 (charge transport layer film thickness 34 μm) was mounted and charged by an AC charging method, the surface state of the charging roll was observed with an optical microscope. The results are shown in Tables 1-3.

  From the above results, it can be seen that the charging roller of this example has suppressed charging unevenness compared to the charging roller of the comparative example. It can also be seen that image defects due to uneven charging (density unevenness, color points, white dots, and streak-like image defects extending in the axial direction (direction intersecting the conveyance direction of the recording medium)) are suppressed. .

  It can also be seen that the charging roll of this example has a good surface condition over time.

DESCRIPTION OF SYMBOLS 31 ... Electroconductive support, 32 ... Adhesive layer, 33 ... Elastic layer, 34 ... Intermediate | middle layer, 35 ... Surface layer, 200, 210, 220 ... Image forming apparatus, 206 ... Exposure apparatus, 207 ... Electrophotographic photoreceptor, 208 DESCRIPTION OF SYMBOLS ... Charging device, 209 ... Power source, 211 ... Developing device, 212 ... Transfer device, 213 ... Cleaning device, 214 ... Static eliminator, 215 ... Fixing device, 216 ... Mounting rail, 217 ... Opening for exposure, 218 ... Static elimination Opening for exposure, 300 ... process cartridge, 400 ... housing, 401a to 401d ... electrophotographic photosensitive member, 402a to 402d ... charging member (charging roll), 403 ... laser light source (exposure device), 404a to 404d ... development Device, 405a to 405d ... Toner cartridge, 406 ... Drive roll, 407 ... Stretch roll, 408 ... Low back 409 ... intermediate transfer belt, 410a to 410d ... primary transfer roll, 411 ... recording medium storage container, 412 ... transfer roll, 413 ... secondary transfer roll, 414 ... fixing roll, 415a to 415d ... cleaning blade, 416 ... cleaning Blade, 500 ... recording medium

Claims (11)

A conductive support;
A surface layer provided on the conductive support and containing a binder resin, a metal oxide, and carbon black having a DBP oil absorption of 130 ml / 100 g or more and a pH of 6 or more and 10 or less;
A charging member.   The charging member according to claim 1, wherein the carbon black has a DBP oil absorption of 150 ml / 100 g or more.   The charging member according to claim 1, wherein the metal oxide is tin oxide.   The charging member according to claim 1, wherein the binder resin is a polyamide resin.   The charging member according to claim 1, wherein the surface layer further includes polyamide resin particles.   6. A charging device comprising a charging member according to claim 1, wherein the charging device is a charging member that contacts the surface of the member to be charged and charges the surface of the member to be charged.   The charging device according to claim 6, wherein the surface of the member to be charged is charged by a direct current charging method. An image carrier,
The charging device according to claim 6 or 7, wherein the image carrier is charged;
With
A process cartridge attached to and detached from the image forming apparatus.   9. The process cartridge according to claim 8, wherein the image carrier is an electrophotographic photosensitive member having at least a surface layer having a charge transporting property of 25 μm or more on a substrate. An image carrier,
The charging device according to claim 6 or 7, wherein the image carrier is charged;
A latent image forming apparatus for forming a latent image on the surface of the charged image carrier;
A developing device for developing a latent image formed on the surface of the image carrier with toner to form a toner image;
A transfer device for transferring the toner image formed on the surface of the image carrier to a recording medium;
An image forming apparatus comprising:   The image forming apparatus according to claim 10, wherein the image carrier is an electrophotographic photosensitive member having at least a surface layer having a charge transporting property of 25 μm or more on a substrate.