JP5600817B1 - Electrophotographic process cartridge and electrophotographic apparatus - Google Patents

Abstract

An object of the present invention is to improve charging unevenness and to suppress generation of a banding image due to slippage between a charging member and an electrophotographic photosensitive member.
A charging member and an electrophotographic photosensitive member contact-charged by the charging member, the charging member having a conductive substrate and a surface layer formed on the conductive substrate, The surface layer contains at least a binder resin, an electronic conductive agent, and resin particles having a plurality of pores therein, and the surface layer has convex portions derived from the resin particles on the surface, and The electrophotographic photosensitive member has a support and a photosensitive layer formed on the support, and the surface layer of the electrophotographic photosensitive member contains a specific component.
[Selection] Figure 6

Description

  The present invention relates to an electrophotographic process cartridge and an electrophotographic image forming apparatus (hereinafter referred to as “electrophotographic apparatus”).

  As a charging method for the surface of the electrophotographic photosensitive member, there is a contact charging method that uses a charging member in contact with the surface of the electrophotographic photosensitive member. In the contact charging method, it is said that uneven charging easily occurs on the surface of the electrophotographic photosensitive member because the discharge region between the charging member and the electrophotographic photosensitive member is narrow. For such a problem, a charging member has been proposed in which roughness-forming particles are included in the surface layer and the surface is roughened (Patent Document 1).

  On the other hand, toner that has not been transferred to a transfer material such as paper in the transfer process may adhere to the surface of the electrophotographic photoreceptor mounted in the electrophotographic apparatus. Hereinafter, such toner is also referred to as residual toner. In order to remove the residual toner from the surface of the electrophotographic photosensitive member and to use the electrophotographic photosensitive member for the next electrophotographic image forming process, a cleaning member or the like is brought into contact with the surface of the electrophotographic photosensitive member. Therefore, appropriate lubricity and slipperiness are required for the surface of the electrophotographic photosensitive member. In order to deal with this problem, it has been proposed to include a silicone oil such as polydimethylsiloxane in the surface layer of the electrophotographic photoreceptor (Patent Document 2).

JP 2009-175427 A Japanese Patent No. 3278016

  According to the study by the present inventors, when contact charging is performed using a charging member having a roughened surface for an electrophotographic photoreceptor having improved surface lubricity, the electrophotographic photoreceptor and Since the contact area at the nip with the charging member is reduced, a minute slip may occur when the electrophotographic photosensitive member and the charging member are in contact with each other and rotate. Such slip causes uneven charging on the electrophotographic photosensitive member and causes horizontal stripes on the electrophotographic image. Hereinafter, an electrophotographic image having a horizontal stripe may be referred to as a “banding image”.

  Accordingly, an object of the present invention is to provide an electronic device capable of improving the uneven charging, which is a problem of the contact charging method, and suppressing the generation of banding images due to the slip between the charging member and the electrophotographic photosensitive member. The provision of a photographic process cartridge.

  Another object of the present invention is to provide an electrophotographic apparatus capable of forming a high-quality electrophotographic image.

  According to the present invention, in an electrophotographic process cartridge having a charging member and an electrophotographic photosensitive member that is contact-charged by the charging member, the charging member includes a conductive substrate and a surface formed on the conductive substrate. The surface layer contains at least a binder resin, an electronic conductive agent, and resin particles having a plurality of pores therein, and the surface layer has convex portions derived from the resin particles on the surface. The electrophotographic photoreceptor has a support and a photosensitive layer formed on the support, and the surface layer of the electrophotographic photoreceptor has the following resin (1) and resin (2). And an electrophotographic process cartridge containing compound (3).

Resin (1): at least one resin selected from the group consisting of a polycarbonate resin having no siloxane structure at the terminal and a polyester resin having no siloxane structure at the terminal;
Resin (2): at least one resin selected from the group consisting of a polycarbonate resin having a siloxane structure at a terminal, a polyester resin having a siloxane structure at a terminal, and an acrylic resin having a siloxane structure at a terminal;
Compound (3): At least one compound selected from the group consisting of methyl benzoate, ethyl benzoate, benzyl acetate, ethyl 3-ethoxypropionate, and diethylene glycol ethyl methyl ether.

  In addition, according to the present invention, there is provided an electrophotographic apparatus on which the electrophotographic process cartridge is mounted.

  According to the present invention, by using a charging member having a rough surface, it is possible to suppress uneven charging due to the narrowness of the discharge region, which is a problem of the contact charging method. In addition, according to the present invention, even when a charging member having a rough surface is brought into contact with an electrophotographic photosensitive member having improved surface lubricity and charged, the slip between the charging member and the electrophotographic photosensitive member is caused. Is suppressed, and generation of banding images due to the slip can be effectively suppressed.

FIG. 2 is a cross-sectional view of a charging roller according to the present invention, which is a charging roller having a surface layer on a conductive substrate. FIG. 2 is a cross-sectional view of a charging roller according to the present invention, and is a charging roller having a conductive elastic layer between a conductive substrate and a surface layer. FIG. 2 is a cross-sectional view of the charging roller according to the present invention, which is a charging roller having a conductive adhesive layer and a conductive elastic layer between a conductive substrate and a surface layer. It is sectional drawing of the porous particle disperse | distributed in the surface layer of the charging roller which concerns on this invention, and shows the state in which a void | hole exists in the upper part of a convex part. It is sectional drawing of the porous particle disperse | distributed in the surface layer of the charging roller which concerns on this invention, and shows the state in which a void | hole exists in a convex part. It is sectional drawing of the hollow particle disperse | distributed in the surface layer of the charging roller which concerns on this invention. FIG. 6 is a schematic diagram of a method for measuring an electric resistance value of a charging roller. 1 is a schematic cross-sectional view of an example of an electrophotographic apparatus according to the present invention. 1 is a schematic cross-sectional view of an example of an electrophotographic process cartridge according to the present invention. It is sectional drawing of the resin particle which forms the convex part of the surface layer of a charging member. It is a three-dimensional schematic diagram of resin particles that form convex portions of the surface layer of the charging member. It is the schematic of the apparatus used for the discharge observation in the nip of a charging roller. It is explanatory drawing of the flow of binder resin and a solvent in the drying process of the coating film of the coating liquid for surface layer formation which concerns on this invention. It is explanatory drawing of the flow of binder resin and a solvent in the drying process of the coating film of the coating liquid for surface layer formation which concerns on this invention. It is explanatory drawing of the flow of binder resin and a solvent in the drying process of the coating film of the coating liquid for surface layer formation which concerns on this invention. It is explanatory drawing of the flow of binder resin and a solvent in the drying process of the coating film of the coating liquid for surface layer formation which concerns on this invention. It is explanatory drawing of the flow of binder resin and a solvent in the drying process of the coating film of the coating liquid for surface layer formation which concerns on this invention. It is explanatory drawing of the calculation method of the porosity of a resin particle.

<Suppression mechanism of banding image>
The electrophotographic process cartridge according to the present invention includes a charging member and an electrophotographic photosensitive member that is contact-charged by the charging member.

  The charging member has a conductive substrate and a surface layer formed on the conductive substrate, and the surface layer contains at least a binder resin, an electronic conductive agent, and resin particles having a plurality of pores therein. In addition, the surface layer has a convex portion derived from the resin particles on the surface.

  On the other hand, the electrophotographic photoreceptor has a support and a photosensitive layer formed on the support, and the surface layer of the electrophotographic photoreceptor has the following resin (1), resin (2) and compound (3). Contains.

Resin (1): at least one resin selected from the group consisting of a polycarbonate resin having no siloxane structure at the terminal and a polyester resin having no siloxane structure at the terminal;
Resin (2): at least one resin selected from the group consisting of a polycarbonate resin having a siloxane structure at a terminal, a polyester resin having a siloxane structure at a terminal, and an acrylic resin having a siloxane structure at a terminal;
Compound (3): At least one compound selected from the group consisting of methyl benzoate, ethyl benzoate, benzyl acetate, ethyl 3-ethoxypropionate, and diethylene glycol ethyl methyl ether.

  The present inventors have presumed as follows the mechanism by which an electrophotographic process cartridge comprising a combination of the charging member and the electrophotographic photosensitive member can suppress the generation of banding images.

  The compound (3) present in the surface layer of the electrophotographic photoreceptor according to the present invention has polarity. Therefore, when a DC voltage is applied to the charging member during the formation of the electrophotographic image, the compound (3) is polarized in the surface layer, and the convex portions of the charging member that is in contact with the electrophotographic photosensitive member and the electrophotographic photosensitive member. An electric attractive force acts between them, and the electrophotographic photosensitive member is pressed against the convex portion on the surface of the charging member. At this time, since the resin particles generating the convex portions on the surface layer of the charging member have a plurality of holes therein, the convex portions pressed by the electrophotographic photosensitive member are distorted, and the electrophotographic photosensitive member is deformed. The contact area between the charging member and the charging member increases. As a result, it is presumed that the occurrence of minute slips in the nip between the electrophotographic photosensitive member and the charging member is suppressed, and as a result, the banding image is suppressed.

<Electrophotographic photoreceptor>
The electrophotographic photosensitive member according to the present invention has a support and a photosensitive layer formed on the support. The photosensitive layer is separated into a single-layer type photosensitive layer containing a charge transport material and a charge generation material in the same layer, or a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. And a laminated type (function separation type) photosensitive layer. In the present invention, a laminated photosensitive layer is preferred. In addition, the charge generation layer may have a stacked structure, and the charge transport layer may have a stacked structure. Further, for the purpose of improving the durability of the electrophotographic photosensitive member, a protective layer may be formed on the photosensitive layer.

[Surface layer]
The surface layer of the electrophotographic photoreceptor according to the present invention contains the resin (1), the resin (2), and the compound (3). Here, when the charge transport layer is the surface layer of the electrophotographic photosensitive member, the charge transport layer is the surface layer. When a protective layer is provided on the charge transport layer, the protective layer is a surface layer.

  The resin (1) is at least one resin selected from the group consisting of a polycarbonate resin having no terminal siloxane structure and a polyester resin having no terminal siloxane structure. The resin (2) is at least one resin selected from the group consisting of a polycarbonate resin having a siloxane structure at a terminal, a polyester resin having a siloxane structure at a terminal, and an acrylic resin having a siloxane structure at a terminal. Compound (3) is at least one compound selected from the group consisting of methyl benzoate, ethyl benzoate, benzyl acetate, ethyl 3-ethoxypropionate, and diethylene glycol ethyl methyl ether.

[Resin (1)]
In the resin (1), the polycarbonate resin having no siloxane structure at the terminal is preferably a polycarbonate resin A having a structural unit represented by the following formula (A). Moreover, it is preferable that the polyester resin which does not have a siloxane structure at the terminal is the polyester resin B which has a structural unit shown by following formula (B).

In formula (A), R ^{21 to} R ²⁴ each independently represent a hydrogen atom or a methyl group. X ¹ represents a single bond, a cyclohexylidene group, or a divalent group having a structural unit represented by the following formula (C).

In formula (B), R ^{31 to} R ³⁴ each independently represents a hydrogen atom or a methyl group. X ² represents a single bond, a cyclohexylidene group, or a divalent group having a structural unit represented by the following formula (C). Y ¹ represents an m-phenylene group, a p-phenylene group, or a divalent group in which two p-phenylene groups are bonded via an oxygen atom.

In formula (C), R ⁴¹ and R ⁴² each independently represent a hydrogen atom, a methyl group, or a phenyl group.

  Below, the specific example of the structural unit of polycarbonate resin A shown by Formula (A) is shown.

  The polycarbonate resin A is a polymer containing only one type of structural unit selected from the structural units represented by the above formulas (A-1) to (A-8), or a co-polymer containing two or more of these structural units. It is preferably a coalescence. Among these structural units, structural units represented by formulas (A-1), (A-2), and (A-4) are preferable.

  Below, the specific example of the structural unit of the polyester resin B shown by Formula (B) is shown.

  The polyester resin B is a polymer containing only one type of structural unit selected from the structural units represented by the above formulas (B-1) to (B-9), or a co-polymer containing two or more of these structural units. It is preferably a coalescence. Among these structural units, structural units represented by formulas (B-1), (B-2), (B-3), (B-6), (B-7), and (B-8) are included. preferable.

  The polycarbonate resin A and the polyester resin B can be synthesized by, for example, a known phosgene method. It can also be synthesized by transesterification.

  When the polycarbonate resin A or the polyester resin B is a copolymer, the form of copolymerization may be any form of block copolymerization, random copolymerization, and alternating copolymerization. These polycarbonate resin A and polyester resin B can be synthesized by a known method. For example, it is compoundable by the method as described in Unexamined-Japanese-Patent No. 2007-047655 and 2007-072277.

  The mass average molecular weight of the polycarbonate resin A and the polyester resin B is preferably 20,000 or more and 300,000 or less, and more preferably 50,000 or more and 200,000 or less. The mass average molecular weight of the resin is a polystyrene equivalent mass average molecular weight measured by the method described in JP-A-2007-79555 in accordance with a conventional method.

  Further, the polycarbonate resin A or the polyester resin B as the resin (1) has a structural unit containing a siloxane structure in the main chain in addition to the structural unit represented by the above formula (A) or the formula (B). A copolymer may also be used. Specific examples of such a structural unit include structural units represented by the following formula (H-1) or formula (H-2). Furthermore, you may have a structural unit shown by the following formula (H-3).

  The specific resin used as resin (1) is shown below.

  In Table 1, in the structural units represented by the above formulas (B-1) and (B-6) in the resin B (1) and the resin B (2), the molar ratio of the terephthalic acid structure to the isophthalic acid structure (terephthalic acid) (Acid skeleton / isophthalic acid skeleton) is 5/5.

[Resin (2)]
The resin (2) is at least one resin selected from the group consisting of a polycarbonate resin having a siloxane structure at a terminal, a polyester resin having a siloxane structure at a terminal, and an acrylic resin having a siloxane structure at a terminal. These resins (2) have good compatibility with the resin of the resin (1), and the mechanical durability of the surface layer of the electrophotographic photosensitive member is maintained high. Further, by having a siloxane moiety at the terminal, the surface layer has high lubricity, and the initial friction coefficient of the surface layer can be reduced. By having a dimethylpolysiloxane (siloxane) moiety at the end, the degree of freedom of the siloxane portion is increased, and there is a high probability that the resin (2) will migrate to the surface layer in the surface layer, and it exists on the surface of the electrophotographic photoreceptor. It seems that it is easy.

  In the present invention, the polycarbonate resin having a siloxane structure at the terminal is preferably a polycarbonate resin A ′ having a structural unit represented by the following formula (A ′) and a terminal structure represented by the following formula (D). Further, the polyester resin having a siloxane structure at the terminal is preferably a polyester resin B ′ having a structural unit represented by the following formula (B ′) and a terminal structure represented by the following formula (D).

In formula (A ′), R ^{25 to} R ²⁸ each independently represent a hydrogen atom or a methyl group. X ³ represents a single bond, a cyclohexylidene group, or a divalent group having a structural unit represented by the following formula (C ′).

In formula (B ′), R ^{35 to} R ³⁸ each independently represent a hydrogen atom or a methyl group. X ⁴ represents a single bond, a cyclohexylidene group, or a divalent group having a structural unit represented by the following formula (C ′). Y ² represents an m-phenylene group, a p-phenylene group, or a divalent group in which two p-phenylene groups are bonded through an oxygen atom.

In formula (C ′), R ⁴³ and R ⁴⁴ each independently represent a hydrogen atom, a methyl group, or a phenyl group.

  In the formula (D), a and b represent the number of repeating structural units in parentheses, the average value of a is 20 or more and 100 or less, and the average value of b is 1 or more and 10 or less. More preferably, the average value of a is 30 or more and 60 or less, and the average value of b is 3 or more and 10 or less.

  In the present invention, the polycarbonate resin A ′ and the polyester resin B ′ have a terminal structure represented by the above formula (D) at one or both ends of the resin. In the case where the terminal structure represented by the above formula (D) is present at one end of the resin, a molecular weight regulator (terminal stopper) is used. Examples of the molecular weight regulator include phenol, p-cumylphenol, p-tert-butylphenol, or benzoic acid. In the present invention, phenol or p-tert-butylphenol is preferable.

  In the case where the terminal structure represented by the above formula (D) is present at one end of the resin, the structure at the other end (other terminal structure) is the structure shown below.

  Below, the specific example of the terminal siloxane structure shown by Formula (D) is shown.

  Specific examples of the structural unit represented by the formula (A ′) in the polycarbonate resin A ′ include structural units represented by the formulas (A-1) to (A-8). Polycarbonate resin A ′ is a polymer containing only one type of structural unit selected from the structural units represented by formulas (A-1) to (A-8), or a copolymer containing two or more of these structural units. It is preferable that Among these structural units, the formulas (A-1), (A-2) and (A-4), particularly the structural unit represented by the formula (A-4) is preferable.

  In the polyester resin B ′, specific examples of the structural unit represented by the formula (B ′) include structural units represented by the formulas (B-1) to (B-9). Polyester resin B ′ is a polymer containing only one type of structural unit selected from the structural units represented by formulas (B-1) to (B-9), or a copolymer containing two or more of these structural units. It is preferable that Among these structural units, structural units represented by formulas (B-1), (B-2), (B-3), (B-6), (B-7), and (B-8), Furthermore, the structural units represented by the formulas (B-1) and (B-3) are particularly preferable.

  When the polycarbonate resin A ′ or the polyester resin B ′ is a copolymer, the copolymer form may be any of block copolymerization, random copolymerization, and alternating copolymerization. The polycarbonate resin A ′ or the polyester resin B ′ may have a structural unit having a siloxane structure in the main chain. Examples of such a resin include a copolymer having a structural unit represented by the following formula (H).

  In formula (H), f and g represent the number of repeating structural units in parentheses, the average value of f is 20 or more and 100 or less, and the average value of g is 1 or more and 10 or less. Specific examples of the structural unit represented by the formula (H) include the structural unit represented by the formula (H-1) or (H-2).

  In the present invention, the “siloxane moiety” of the polycarbonate resin A ′ and the polyester resin B ′ refers to the area within the dotted line frame of the terminal structure represented by the following formula (DS). Further, when the polycarbonate resin A ′ and the polyester resin B ′ have the structural unit represented by the formula (H), the structure within the dotted frame of the structural unit represented by the following formula (HS) as the siloxane moiety Is also included.

In the present invention, the polycarbonate resin A ′ and the polyester resin B ′ can be synthesized by a known method, for example, a method described in JP-A-2007-199688. In the present invention, the same synthesis method can be used to synthesize the polycarbonate resin A ′ and the polyester resin B ′ shown in the synthesis examples in Table 2 using raw materials corresponding to the polycarbonate resin A ′ and the polyester resin B ′. The purification of the polycarbonate resin A ′ and the polyester resin B ′ is carried out by fractionation and separation using size exclusion chromatography, and each fraction component is subjected to ¹ H-NMR measurement to determine the relative ratio of the siloxane moiety in the resin. Can determine the resin composition. Table 2 shows the weight average molecular weight and the content of the siloxane moiety of the synthesized polycarbonate resin A ′ and polyester resin B ′.

  Specific examples of the polycarbonate resin A ′ and the polyester resin B ′ are shown below.

  In Table 2, in resin A ′ (3), the mass ratio of each structural unit in the main chain is (A-4) :( H−2) = 9: 1.

  In the present invention, the acrylic resin having a siloxane structure at the terminal is at least one selected from the group consisting of structural units represented by the following formula (F-1), formula (F-2) and formula (F-3). An acrylic resin F having one structural unit is preferable.

In formula (F-1), R ⁵¹ represents hydrogen or a methyl group. c represents the number of repetitions in parentheses, and the average value of c is 0 or more and 5 or less. R ^{52 to} R ⁵⁴ each independently represent a structure represented by the following formula (F-1-2), a methyl group, a methoxy group, or a phenyl group. At least one of R ^{52 to} R ⁵⁴ has a structure represented by the following formula (F-1-2).

In formula (F-1-2), d represents the number of repetitions in parentheses, and the average value of d is 10 or more and 50 or less. R ⁵⁵ represents a hydroxyl group or a methyl group.

In the formula (F-3), R ⁵⁶ represents hydrogen, a methyl group, or a phenyl group. e represents 0 or 1;

  In the present invention, the “siloxane moiety” of the acrylic resin F refers to the inside of a dotted line frame having a structure represented by the following formula (FS) or formula (FT).

  Specific examples of structural units of the acrylic resin F are shown in Tables 3-1 to 3-4 below. In Tables 3-1 to 3-4, the “mass ratio of structural units” is “(F-1) / (F-2) or (F-3)”. In Tables 3-3 and 3-4, “Ar” represents an aryl group.

  Of the specific examples of the acrylic resin F shown in Tables 3-1 to 3-4, resins represented by the compound examples (FB) and (FE) are preferable.

  These acrylic resins can be synthesized by known methods, for example, the methods described in JP-A Nos. 58-167606 and 62-75462.

  The content of the resin (2) contained in the surface layer of the electrophotographic photosensitive member from the viewpoint of reducing the initial friction coefficient of the surface layer and suppressing the bright portion potential fluctuation during repeated use is the resin (1). It is preferable that it is 0.1 to 50 mass% with respect to the total mass of. The content is more preferably 1% by mass or more and 50% by mass or less. By setting the content of the resin (2) within the above range, the degree of freedom of the compound (3) in the surface layer is improved and it becomes easy to polarize, so that the grip property with the charging member is improved. Is expressed.

[Compound (3)]
The surface layer of the electrophotographic photoreceptor according to the present invention is at least selected from the group consisting of methyl benzoate, ethyl benzoate, benzyl acetate, ethyl 3-ethoxypropionate, and diethylene glycol ethyl methyl ether as the compound (3). Contains one compound.

  When the surface layer contains these compounds, the electrophotographic photosensitive member can obtain the effect of the stability of potential during repeated use and the suppression of slippage with the charging member, and the compound ( 3) is polarized, and the effect of improving the grip with the charging member is obtained. Therefore, it is preferable that the addition amount of a compound (3) is 0.001 mass% or more and 0.5 mass% or less with respect to the total mass of a surface layer. Since the compound (3) is easily volatilized in the heating and drying step when forming the surface layer, the content (% by mass) of the compound (3) in the surface layer coating solution is the compound (3) in the surface layer. ) Content (mass%) is preferable. Therefore, the content of the compound (3) in the surface layer coating solution is preferably 5% by mass or more and 80% by mass or less with respect to the total mass of the surface layer coating solution.

Content of the compound (3) in a surface layer can be calculated | required with the measuring method shown below, for example.
It is measured using HP7694 Headspace sampler (manufactured by Agilent Technologies) and HP6890 series GS System (manufactured by Agilent Technologies). A sample piece having a surface layer and a size of 5 mm × 40 mm is cut out from the manufactured electrophotographic photosensitive member. The sample piece is placed in a vial, the headspace sampler (HP7694 Headspace sampler) is set to 150 ° C., 150 ° C., and 150 ° C. transfer line, and the gas generated from the sample piece is gas chromatographed (HP 6890 series GS). System).
Further, the mass of the surface layer of the sample piece is measured as follows. First, the mass of the sample piece subjected to the above measurement is measured. Here, the mass of the compound (3) volatilized from the surface layer by the measurement by the gas chromatography is considered to be negligible. Next, the sample piece is immersed in methyl ethyl ketone for 5 minutes to peel off the surface layer and dried at 100 ° C. for 5 minutes. The mass of the obtained sample piece after surface layer peeling is measured. From the difference between these masses, the mass of the surface layer of the sample piece is determined.

[Support]
The support for the electrophotographic photosensitive member is one having conductivity (conductive support). For example, metals or alloys such as aluminum, stainless steel, copper, nickel, and zinc can be used. In the case of an aluminum or aluminum alloy support, ED tube, EI tube, and these are cut, electrolytic composite polishing (electrolysis with an electrode having an electrolytic action and polishing with a grindstone having a polishing action), wet or dry type A honing treatment can also be used. Moreover, what formed the thin film of electrically conductive materials like aluminum, an aluminum alloy, or an indium oxide tin oxide alloy on the metal support body or the resin support body is also mentioned.

  In addition, a support in which conductive particles such as carbon black, tin oxide particles, titanium oxide particles, and silver particles are impregnated in a resin, or a plastic having a conductive binder resin can also be used. The surface of the conductive support may be subjected to cutting treatment, surface roughening treatment, or alumite treatment for the purpose of preventing interference fringes due to scattering of laser light.

[Conductive layer]
In the electrophotographic photosensitive member according to the present invention, a conductive layer having conductive particles and a resin may be provided on the support. The conductive layer is a layer formed using a conductive layer coating liquid in which conductive particles are dispersed in a binder resin.

  Examples of the conductive particles include carbon black, acetylene black; powders of metals such as aluminum, nickel, iron, nichrome, copper, zinc, and silver; powders of metal oxides such as conductive tin oxide and ITO.

  Examples of the binder resin used for the conductive layer include polyester resin, polycarbonate resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, and alkyd resin.

  Examples of the solvent for the conductive layer coating liquid include ether solvents, alcohol solvents, ketone solvents, and aromatic hydrocarbon solvents. The thickness of the conductive layer is preferably 0.2 μm or more and 40 μm or less, particularly 1 μm or more and 35 μm or less, more preferably 5 μm or more and 30 μm or less.

[Middle layer]
An intermediate layer may be provided between the conductive support or conductive layer and the photosensitive layer. The intermediate layer is formed to improve the adhesion of the photosensitive layer, improve the coating property, improve the charge injection property from the conductive support, and protect the photosensitive layer from electrical breakdown.

  The intermediate layer can be formed by applying an intermediate layer coating solution containing a binder resin on the conductive support or the conductive layer, and drying or curing it.

  Examples of the binder resin for the intermediate layer include polyacrylic acids, methylcellulose, ethylcellulose, polyamide resin, polyimide resin, polyamideimide resin, polyamic acid resin, melamine resin, epoxy resin, and polyurethane resin. The binder resin used for the intermediate layer is preferably a thermoplastic resin, and specifically, a thermoplastic polyamide resin is preferable. The polyamide resin is preferably a low crystalline or non-crystalline copolymer nylon that can be applied in a solution state. Examples of the solvent for the intermediate layer coating solution include ether solvents, alcohol solvents, ketone solvents, and aromatic hydrocarbon solvents. The thickness of the intermediate layer is preferably 0.05 μm or more and 40 μm or less, and more preferably 0.1 μm or more and 30 μm or less. Further, the intermediate layer may contain semiconductive particles, an electron transporting material, or an electron accepting material.

(Photosensitive layer)
A photosensitive layer (charge generation layer, charge transport layer) is formed on the conductive support, the conductive layer, or the intermediate layer. The charge generation layer can be formed by applying a charge generation layer coating solution obtained by dispersing a charge generation material together with a binder resin and a solvent and drying the coating solution. The charge generation layer may be a vapor generation film of a charge generation material.

  Examples of the charge generating material include azo pigments, phthalocyanine pigments, indigo pigments, and perylene pigments. These charge generation materials may be used alone or in combination of two or more. Among these, oxytitanium phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine are particularly preferable because of high sensitivity.

  As the binder resin used for the charge generation layer, polycarbonate resin, polyester resin, polybutyral resin, polyvinyl acetal resin, acrylic resin, vinyl acetate resin, urea resin, and a monomer that is a raw material of the resin are copolymerized. And copolymer resins. Among these, a butyral resin is particularly preferable. These resins can be used alone or in combination of two or more.

  Examples of the dispersion method include a method using a homogenizer, an ultrasonic wave, a ball mill, a sand mill, an attritor, and a roll mill. The ratio between the charge generating material and the binder resin is preferably in the range of 0.1 to 10 parts by weight with respect to 1 part by weight of the binder resin, preferably 1 to 3 parts by weight. The following is more preferable. Examples of the solvent used in the charge generation layer coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. The thickness of the charge generation layer is preferably from 0.01 μm to 5 μm, and more preferably from 0.1 μm to 2 μm.

  In addition, various sensitizers, antioxidants, ultraviolet absorbers, and plasticizers can be added to the charge generation layer as necessary. Further, in order to prevent the flow of electric charges (carriers) in the charge generation layer, the charge generation layer may contain an electron transport material and an electron accepting material. In an electrophotographic photosensitive member having a multilayer photosensitive layer, a charge transport layer is provided on the charge generation layer. The charge transport layer can be formed by applying a charge transport layer coating solution obtained by dissolving a charge transport material and a binder resin in a solvent, and drying it. Examples of the charge transport material include triarylamine compounds, hydrazone compounds, styryl compounds, and stilbene compounds. A compound represented by the following structural formulas (CTM-1) to (CTM-7) is preferable.

  In the present invention, when the charge transport layer is a surface layer, the binder resin contains the resin (1) and the resin (2), but other resins may be further mixed and used. . Other resins that may be used in combination are as described above. The thickness of the charge transport layer is preferably 5 to 50 μm, more preferably 10 to 30 μm. The mass ratio of the charge transport material and the binder resin is preferably 5: 1 to 1: 5, more preferably 3: 1 to 1: 3. Examples of the solvent used in the charge transport layer coating solution include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Xylene, toluene, and tetrahydrofuran are preferable.

  Various additives can be added to each layer of the electrophotographic photoreceptor according to the present invention. Examples of the additive include deterioration inhibitors such as antioxidants, ultraviolet absorbers, and light stabilizers, organic fine particles, and inorganic fine particles. Examples of the deterioration inhibitor include hindered phenol antioxidants, hindered amine light resistance stabilizers, sulfur atom-containing antioxidants, and phosphorus atom-containing antioxidants. Examples of the organic fine particles include polymer resin particles such as fluorine atom-containing resin particles, polystyrene fine particles, and polyethylene resin particles. Examples of the inorganic fine particles include metal oxides such as silica and alumina. When applying the coating liquid for each of the above layers, a dip coating method (dip coating method), a spray coating method, a spinner coating method, a roller coating method, a Meyer bar coating method, or a blade coating method can be used. . Of these, the dip coating method is preferable. The drying temperature at which the coating liquid for each layer is dried to form a coating film is preferably 60 ° C. or higher and 150 ° C. or lower. Among these, the drying temperature of the charge transport layer coating liquid (surface layer coating liquid) is particularly preferably 110 ° C. or higher and 140 ° C. or lower. Moreover, as drying time, 10 to 60 minutes are preferable and 20 to 60 minutes are more preferable.

<Charging member>
The charging member according to the present invention can take a shape such as a roller shape, a flat plate shape, or a belt shape. Hereinafter, the charging member according to the present invention will be described by taking the roller-shaped charging member (hereinafter also referred to as “charging roller”) shown in FIGS. 1A, 1B, and 1C as an example. The charging roller shown in FIG. 1A has a conductive substrate 1 and a surface layer 2 formed on the substrate. The charging roller shown in FIG. 1B has a conductive elastic layer 3 between the conductive substrate 1 and the surface layer 2. The conductive elastic layer 3 may have a plurality of layer configurations. The charging roller shown in FIG. 1C is an example in which a conductive adhesive layer 4 is provided between the conductive substrate 1 and the conductive elastic layer 3.

[Surface layer]
The surface layer contains a binder resin, an electronic conductive agent, and resin particles having a plurality of pores therein, and the surface layer has a convex portion derived from the resin particles on the surface. In addition to the inclusions, the surface layer can optionally contain insulating metal particles, a leveling agent, a plasticizer, and a softening agent. The film thickness of the surface layer is preferably about 0.1 μm to 100 μm in order to form convex portions derived from the resin particles.

The volume resistivity of the surface layer is preferably 1 × 10 ² Ω · cm or more and 1 × 10 ¹⁶ Ω · cm or less in an environment of a temperature of 25 ° C. and a relative humidity of 50%. In order to appropriately charge by discharging with the electrophotographic photosensitive member, a range of 1 × 10 ⁵ Ω · cm to 1 × 10 ⁸ Ω · cm is more preferable.

  The volume resistivity of the surface layer is determined as follows. First, a surface layer is cut out from the charging member into sections having a length of 5 mm, a width of 5 mm, and a thickness of about 1 mm. Next, a sample for measurement is obtained by vapor-depositing metal on both sides of the section. If the surface layer cannot be cut out as a thin film, apply a conductive resin composition for forming the surface layer on the aluminum sheet to form a coating film, deposit a metal on the coating surface, and prepare a measurement sample. obtain. A voltage of 200 V is applied to the obtained measurement sample using a microammeter (trade name: ADVANTEST R8340A ULTRA HIGH RESISTANCE METER, manufactured by Advantest Corporation). Then, the current after 30 seconds is measured, and the volume resistivity is obtained by calculating from the film thickness and the electrode area. The volume resistivity of the surface layer can be adjusted by an electronic conductive agent such as conductive fine particles and an ionic conductive agent.

[Resin particles having a plurality of pores]
The resin particles that have raised portions on the surface of the charging member have a plurality of holes therein. A void | hole is an area | region which contains air inside. A charging member having a convex portion caused by resin particles having a plurality of pores can be formed using “hollow particles” and “porous particles” described later.

Here, “porous particles” are defined as particles having pores penetrating the surface (hereinafter also referred to as “through holes” or “pores”). Particles that contain air in the interior and have pores that do not penetrate the surface (hereinafter also referred to as “non-through holes”) are also defined as “porous particles”.
On the other hand, “hollow particles” are defined as particles having only non-through holes.

The discrimination between the porous particles and the hollow particles can be performed, for example, by the following method.
That is, the resin particles to be discriminated are made into a photocurable resin, for example, a visible light curable embedding resin (trade name: D-800, manufactured by Nissin EM Co., Ltd., trade name: Epok812 set, Oken Shoji ( Etc.). At this time, when the resin particles to be discriminated are porous particles, the embedded resin enters the through holes in the resin particles. On the other hand, when the resin particles to be discriminated are hollow particles, the embedded resin particles cannot enter the non-through holes in the resin particles.
Next, an ultramicrotome (trade name: LEICA EM UCT, manufactured by Leica) equipped with a diamond knife (trade name: DiATOMECRYRO DRY, manufactured by DIATOME), and a cryo system (trade name: LEICA EM FCS, manufactured by Leica) After chamfering, the center of the resin particles (so that the vicinity of the center of gravity 17 shown in FIG. 8 is included) is cut out, and a section having a thickness of 100 nm is created. Thereafter, the embedding resin is dyed using a dye of either osmium tetroxide, ruthenium tetroxide, or phosphotungstic acid. Next, a cross-sectional image of the resin particles is taken from the section with a transmission electron microscope (trade name: H-7100FA, manufactured by Hitachi, Ltd.).
Thereby, the through-hole which embedded resin penetrate | invaded is observed as a black part. On the other hand, the non-through hole into which the embedding resin cannot enter is observed as a brighter white portion than the resin portion.
Therefore, when the void into which the embedding resin has entered is observed as a black portion, it can be seen that the resin particles to be discriminated are porous particles. Moreover, when the said black part is not observed and the bright white part which is the hole which is not embedded with embedding resin is observed, it turns out that the resin particle of discrimination | determination object is a hollow particle. Hereinafter, the above method may be referred to as “embedding method”.

  FIG. 2A and FIG. 2B show a cross section of the surface layer formed using the porous particles in the vicinity of the convex portion due to the porous particles.

FIG. 2A is a cross-sectional view of the surface layer according to the first embodiment of the present invention formed using porous particles, in which the pores 7 inside the resin particles 6 are “projection apex side regions of the resin particles 6. ”Is shown. Reference numeral 5 denotes a resin composition (conductive resin composition) in the surface layer.
FIG. 2B is a cross-sectional view of the surface layer according to the second embodiment of the present invention formed using porous particles, and the pores 7 inside the resin particles 6 are concentrated on the inner layer portion of the resin particles 6. Indicates the state.
The resin particles in the surface layer preferably have a porosity in the “convex portion apex side region” of 5% by volume or more. Moreover, it is preferable that this porosity is 20 volume% or less. Note that the “convex portion apex side region” means that when the resin particles forming the convex portions of the surface layer of the charging member are assumed to be solid particles having no pores, It means a region that occupies 11% by volume in the actual particles and has the longest distance from the conductive substrate. Specifically, the “convex portion apex side region” is a region indicated by reference numeral 18 in FIG. The method for measuring the porosity in the “convex portion apex side region” will be described later (see Examples).

  In the present invention, for example, a surface layer having convex portions derived from resin particles having a plurality of pores therein can be formed by forming a surface layer using porous particles described later. The porous particles have a plurality of pores (through holes) each having a region containing air. In the formation process of the surface layer, binder resin or the like may enter the pores, but the pores can be prevented from being completely buried by adjusting the manufacturing conditions of the surface layer. . For this reason, pores can exist in the resin particles formed by forming convex portions on the surface layer.

  Specifically, the number and size of the remaining pores are determined depending on the type of coating liquid for forming the surface layer containing the porous particles, the electronic conductive agent, and the binder resin, the coating conditions, and the application of the coating liquid. By controlling the drying conditions of the membrane, the pore diameter and the porosity can be controlled.

  The surface layer forming method according to the present invention may be any method as long as the surface layer can be provided with convex portions on the surface of the charging member and can have resin particles having a plurality of pores therein. But it can also be used. Specifically, for example, a dip coating method using a coating solution for forming a surface layer and a ring coating method using a ring-shaped coating head can be mentioned.

  In the present invention, it is more preferable that the vacancies in the resin particles that cause the convex portions on the surface of the charging member are concentrated in the “convex apex side region” of the resin particles. When the charging member in such a state comes into contact with the electrophotographic photosensitive member, only the vicinity of the apex of the convex portion derived from the resin particles is distorted, so that the slip between the electrophotographic photosensitive member and the charging member does not weaken the discharge in the nip. The effect which suppresses can be exhibited more reliably.

  FIG. 3 shows a cross section in the vicinity of the convex portion due to the hollow particles of the surface layer formed using the hollow particles.

  Hereinafter, “porous particles” and “hollow particles” as raw materials for the resin particles in the surface layer according to the present invention will be described in detail.

[Porous particles]
As the porous particles, it is preferable that the porosity and the pore diameter of the outer layer portion of the particle are larger than the porosity and the pore diameter of the inner layer portion of the particle, respectively. By using porous particles having such a core-shell structure, a state as shown in FIG. 2A can be formed. Moreover, when the porous particle which does not have the said core-shell structure is used, a state as shown to FIG. 2B can be formed.

  Examples of the material of the porous particles include acrylic resin, styrene resin, acrylonitrile resin, vinylidene chloride resin, and vinyl chloride resin. These resins can be used alone or in combination of two or more. Furthermore, monomers used as raw materials for these resins may be copolymerized and used as a copolymer. You may contain other well-known resin as needed for these resins as a main component.

  The porous particles in the present invention are known in the art such as suspension polymerization method, interfacial polymerization method, interfacial precipitation method, in-liquid drying method, or a method in which a solute or solvent that lowers the solubility of the resin is added to the resin solution and precipitated. It can produce by the manufacturing method of. For example, in the suspension polymerization method, a porous agent is dissolved in a polymerizable monomer in the presence of a crosslinkable monomer to prepare an oily mixed solution. Using this oily mixture, aqueous suspension polymerization is carried out in an aqueous medium containing a surfactant and a dispersion stabilizer, and after completion of the polymerization, washing and drying steps are performed to remove water and the porosifying agent, and resin particles Can be obtained. A compound having a reactive group that reacts with the functional group of the polymerizable monomer, or an organic filler can also be added. In order to form pores inside the porous particles, it is preferable to perform polymerization in the presence of a crosslinkable monomer.

  Examples of the polymerizable monomer include the following. Styrene monomers such as styrene, p-methylstyrene, and p-tert-butylstyrene; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, Ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, benzyl methacrylate, phenyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, glycidyl methacrylate, hydrofurfuryl methacrylate, and methacryl (Meth) acrylic acid ester monomers such as lauryl acid. These polymerizable monomers may be used alone or in combination of two or more. In the present invention, the term “(meth) acryl” is a concept including both acrylic and methacrylic.

  The crosslinkable monomer is not particularly limited as long as it has a plurality of vinyl groups, and the following can be exemplified. Ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, decaethylene glycol di (meth) acrylate, pentadecaethylene glycol di (meth) acrylate, pentacontactor ethylene glycol di ( (Meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, allyl methacrylate , Trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, diethylene glycol di (meth) acrylate phthalate, caprolactone-modified dipentaeri Ritoruhekisa (meth) acrylate, caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate, polyester acrylates, such as urethane acrylate (meth) acrylic acid ester monomer, divinylbenzene, divinyl naphthalene, and derivatives thereof. These can be used alone or in combination of two or more.

  The crosslinkable monomer is preferably used in an amount of 5% by mass to 90% by mass in the monomer mixture. By setting it within this range, it is possible to reliably form pores inside the porous particles.

As the porosifying agent, a non-polymerizable solvent, a mixture of a linear polymer and a non-polymerizable solvent dissolved in a mixture of polymerizable monomers, or a cellulose resin can be used.
The following can be illustrated as a non-polymerizable solvent. Toluene, benzene, ethyl acetate, butyl acetate, normal hexane, normal octane, normal dodecane.
Although it does not specifically limit as a cellulose resin, Ethyl cellulose can be mentioned. These porous agents can be used alone or in combination of two or more.
The amount of the porosifying agent can be appropriately selected according to the purpose of use, but from 20 parts by mass to 90 parts by mass in 100 parts by mass of the oil phase comprising the polymerizable monomer, the crosslinkable monomer and the porosifying agent. It is preferable to use within the range of parts. By setting it within this range, the porous particles are not easily fragile, and a void is easily formed in the nip between the charging member and the electrophotographic photosensitive member.

  Although it does not specifically limit as a polymerization initiator, A thing soluble in a polymerizable monomer is preferable. Known peroxide initiators and azo initiators can be used, and the following can be exemplified. 2,2′-azobisisobutyronitrile, 1,1′-azobiscyclohexane 1-carbonitrile, 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, and 2,2′- Azobis-2,4-dimethylvaleronitrile.

  The following can be illustrated as surfactant. Anionic surfactants such as sodium lauryl sulfate, polyoxyethylene (degree of polymerization 1-100) sodium lauryl sulfate, and polyoxyethylene (degree of polymerization 1-100) lauryl sulfate triethanolamine; stearyltrimethylammonium chloride, diethylamino stearate Cationic surfactants such as ethylamide lactate, dilaurylamine hydrochloride, and oleylamine lactate; adipic acid diethanolamine condensate, lauryldimethylamine oxide, glyceryl monostearate, sorbitan monolaurate, and diethylaminoethylamide lactate stearate Nonionic surfactants such as salt; palm oil fatty acid amidopropyldimethylaminoacetic acid betaine, lauryl hydroxysulfobetaine, and β-laurylaminopropion Ampholytic agents such as sodium; polyvinyl alcohol, starch, and, such as polymer dispersant carboxymethylcellulose.

  The following can be illustrated as a dispersion stabilizer. Organic fine particles such as polystyrene fine particles, polymethyl methacrylate fine particles, polyacrylic acid fine particles and polyepoxide fine particles; silica such as colloidal silica; calcium carbonate, calcium phosphate, aluminum hydroxide, barium carbonate, and magnesium hydroxide.

  Among the above polymerization methods, a specific example of the suspension polymerization method is shown below. Suspension polymerization is preferably carried out in a sealed manner using a pressure vessel. The raw material components may be suspended in a disperser before polymerization and then transferred to the pressure vessel for suspension polymerization. It may be clouded. The polymerization temperature is more preferably 50 ° C to 120 ° C. The polymerization may be performed under atmospheric pressure, but it is preferably performed under pressure (under a pressure obtained by adding 0.1 to 1 MPa to atmospheric pressure) in order to prevent the porous agent from being gaseous. After completion of the polymerization, solid-liquid separation and washing may be performed by centrifugation or filtration. After solid-liquid separation and washing, drying or pulverization may be performed at a temperature lower than the softening temperature of the resin constituting the resin particles. Drying and pulverization can be performed by a known method, and an air flow dryer, a normal air dryer or a Nauta mixer can be used. Further, drying and pulverization can be simultaneously performed by a pulverization dryer. Surfactants and dispersion stabilizers can be removed by repeating washing filtration after production.

  The particle size of the porous particles depends on the mixing conditions of the oil-based liquid mixture composed of a polymerizable monomer and a porosizing agent and an aqueous medium containing a surfactant and a dispersion stabilizer, the amount of dispersion stabilizer added, and stirring and dispersing. It can be adjusted according to conditions. By increasing the addition amount of the dispersion stabilizer, the average particle diameter can be lowered. Moreover, it is possible to reduce the average particle diameter of the porous particles by increasing the stirring speed under stirring dispersion conditions. The volume average particle size of the porous particles in the present invention is preferably in the range of 5 to 60 μm. Furthermore, it is more preferable that it is the range of 10-50 micrometers. By setting it within this range, the discharge in the nip can be generated more stably. In addition, a volume average particle diameter can be measured by the method described in the Example mentioned later.

  Moreover, the pore diameter of the porous particles, the pore diameter inside, and the ratio of the region containing air can be adjusted by the addition amount of the crosslinkable monomer and the kind and addition amount of the porous agent.

  The pore diameter can be reduced by increasing the addition amount of the crosslinkable monomer. Moreover, a pore diameter can be further enlarged by using a cellulose resin as a porosifying agent.

  The pore diameter of the porous particles is preferably 10 to 500 nm and within a range of 20% or less with respect to the average particle diameter of the resin particles. Furthermore, it is more preferable that it is in the range of 20 to 200 nm and 10% or less with respect to the average particle diameter of the resin particles. By being within this range, when added to the surface layer, a state as shown in FIG. 2B having a plurality of pores in the inner layer portion of the resin particles can be formed. It is preferable that the hole diameter inside the resin particle which forms a convex part is 60-300 nm. More preferably, it is 80-150 nm. By satisfying this more preferable range, the hardness of the convex portion derived from the resin particles is reduced, and the distortion of the convex portion in contact with the electrophotographic photosensitive member can be increased. As a result, the contact state between the electrophotographic photosensitive member and the charging member is stabilized.

  In addition, as described above, in order to form a state in which the pores included in the resin particle as shown in FIG. 2A are concentrated in the “convex portion apex region” of the resin particle, It is preferable to make the porosity and the pore diameter of the resin particles larger than the porosity and the pore diameter of the inner layer portion of the resin particles, respectively.

  Two types of porosifying agents are used for porous particles in which the porosity of the outer layer portion is larger than the porosity of the inner layer portion used in the present invention and the outer layer portion has a larger pore size than the inner layer portion. In particular, it can be produced by using two kinds of porosifying agents having different solubility parameters (hereinafter referred to as “SP values”).

  As a specific example, a case where normal hexane and ethyl acetate are used as the porosifying agent will be described below as an example. When the above two kinds of porosifying agents are used, when an oily mixture obtained by mixing a polymerizable monomer and a porosifying agent is added to an aqueous medium, ethyl acetate having an SP value close to that of water is obtained on the aqueous medium side, that is, Many of them are present in the outer layer portion of the suspension droplet. On the other hand, more normal hexane exists in the inner layer portion of the droplet. Since ethyl acetate present in the outer layer portion of the droplet has a SP value close to that of water, a certain amount of water is dissolved in ethyl acetate. In this case, in the outer layer portion of the droplet compared to the inner layer portion of the droplet, the solubility of the porous agent in the polymerizable monomer is reduced, and the polymerizable monomer and the porous agent are separated from each other in the inner layer portion. It is in the state which is easy to separate compared with. That is, in the outer layer portion of the droplet, the porosifying agent tends to exist in a larger mass than the inner layer portion. In this way, by performing the above-described polymerization reaction and further post-treatment in a state in which the presence of the porosifying agent is controlled to be different between the inner layer portion and the outer layer portion of the droplet, Can be produced.

  Therefore, by making one of the two types of porosifying agents have a small difference in SP value from water as the medium, the pore diameter of the outer layer portion of the porous particles is increased and the porosity is increased. Can be increased. Preferred examples of the porosifying agent used in the above means include ethyl acetate, methyl acetate, propyl acetate, isopropyl acetate, butyl acetate, acetone, and methyl ethyl ketone. On the other hand, by using a porous agent having a high solubility of the polymerizable monomer and a large SP value difference with water, it is possible to produce the core-shell structure porous particles described above. it can. Preferable porosifying agents used in the above means include normal hexane, normal octane, and normal dodecane.

[Hollow particles]
Examples of the material of the hollow particles include the same resin as that of the porous particles. These resins can be used alone or in combination of two or more. Furthermore, monomers used as raw materials for these resins may be copolymerized and used as a copolymer. You may contain other well-known resin as needed for these resins as a main component.

  The hollow particles in the present invention can be produced by a known production method such as a suspension polymerization method, an interfacial polymerization method, an interfacial precipitation method, or a submerged drying method. Among these production methods, the following production method (a) is mentioned as a preferred suspension polymerization method.

(A) Method using aqueous medium In the presence of a crosslinkable monomer, a hydrophobic polymerizable monomer (hydrophobic monomer), a hydrophilic polymerizable monomer (hydrophilic monomer), An oily mixed solution composed of a polymerization initiator is prepared. This oily mixture is subjected to aqueous suspension polymerization in an aqueous medium containing a dispersion stabilizer, and after completion of the polymerization, hollow particles can be obtained through washing and drying processes.
According to this method, in the polymerization process, when the oily mixed liquid and the aqueous medium liquid are mixed, water enters the droplets of the oily mixed liquid. Thereafter, the polymerizable monomer in the droplets is polymerized while the water is taken in, thereby forming resin particles in which the water is taken up. By drying the resin particles at a temperature of 100 ° C. or higher to vaporize water in the resin particles, non-through holes can be formed in the resin particles. In addition, it is thought that water remains in the resin particle also by the said drying process, and a through-hole is not formed. Alternatively, the hollow particles can be obtained by previously adding water to an oily mixed solution and dispersing the emulsified mixed solution in an aqueous medium solution and further performing suspension polymerization.

  In the above case, with respect to the total of the hydrophobic monomer and the hydrophilic monomer, the hydrophobic monomer is from 70% by mass to 99.5% by mass, and the hydrophilic monomer is from 0.5% by mass. It is preferable to adjust to 30 mass%. Thereby, it becomes easy to form hollow particles.

  Examples of hydrophobic monomers include (meth) acrylic acid ester monomers, polyfunctional (meth) acrylic acid ester monomers, styrene monomers such as styrene, p-methylstyrene, α-methylstyrene, and vinyl acetate. It is done. Among these, from the viewpoint of thermal decomposability, (meth) acrylic acid ester monomers are preferred, and methacrylic acid ester monomers are more preferred. Examples of the (meth) acrylic acid ester monomer include the following. Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate , 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate. You may use the said hydrophobic monomer in combination of multiple types.

  Examples of the hydrophilic monomer include a hydroxyl group-terminated polyalkylene glycol mono (meth) acrylate, and examples thereof include the following. Polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, poly (ethylene glycol-propylene glycol) mono (meth) acrylate, polyethylene glycol-polypropylene glycol mono (meth) acrylate, poly (meth) acrylate, poly (propylene Glycol-tetramethylene glycol) mono (meth) acrylate, propylene glycol polybutylene glycol mono (meth) acrylate. You may use these in combination of multiple types.

  As the crosslinkable monomer, the same monomer as in the production of the porous particles can be used. It is preferable to adjust from 0.5% by mass to 60% by mass with respect to the total of the hydrophobic monomer and the hydrophilic monomer. By setting it within this range, it becomes possible to reliably form pores inside the porous particles.

  In addition, for the polymerization initiator, the surfactant, and the dispersion stabilizer, the same compounds as in the production of the porous particles can be used. The polymerization initiators, dispersion stabilizers and surfactants may be used alone or in combination of two or more. The use ratio of the polymerization initiator is preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the monomer. The proportion of the dispersion stabilizer used is preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the monomer. The proportion of the surfactant used is preferably 0.001 to 0.3 parts by mass with respect to 100 parts by mass of water.

  The polymerization reaction is performed by mixing the oily mixture and the aqueous medium and then raising the temperature while stirring. The polymerization temperature is preferably 40 to 90 ° C., and the polymerization time is preferably about 1 to 10 hours. By setting it within this range, it becomes possible to reliably form holes (non-through holes) inside the hollow particles. At this time, the average particle diameter of the hollow particles can be appropriately determined by controlling the mixing conditions and stirring conditions of the monomer and water.

  The average diameter of the pores (non-through holes) contained in the hollow particles is preferably 0.05 μm or more and 15 μm or less. More preferably, it is 0.1 μm or more and 10 μm or less. By setting it within this range, the hardness of the convex portion derived from the resin particles is reduced, the distortion of the convex portion is increased, the electric attractive force is increased, and the contact state between the electrophotographic photosensitive member and the charging member is further improved. Can be stabilized.

[Binder resin]
Examples of the binder resin include known rubbers or resins. Examples of rubber include natural rubber, a vulcanized product thereof, and synthetic rubber.

  The following are mentioned as a synthetic rubber. Ethylene propylene rubber, styrene butadiene rubber (SBR), silicone rubber, urethane rubber, isoprene rubber (IR), butyl rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), acrylic rubber, epichlorohydrin rubber and fluorine rubber.

  As the resin, for example, a resin such as a thermosetting resin or a thermoplastic resin can be used. Among these, fluorine resin, polyamide resin, acrylic resin, polyurethane resin, acrylic urethane resin, silicone resin, and butyral resin are more preferable, and acrylic resin and polyurethane resin are particularly preferable. By using this resin, the contact state between the charging member and the electrophotographic photosensitive member is stabilized, and slip is easily suppressed.

  These may be used alone or in combination of two or more. Moreover, it is good also as a copolymer by copolymerizing the monomer which is the raw material of these binder resins. Among these, it is preferable to use the above-mentioned resin as the binder resin. This is because it is possible to more easily control adhesion and friction with the electrophotographic photosensitive member.

[Electronic conductive agent]
Examples of the electronic conductive agent include the following. Metal-based fine particles and fibers such as aluminum, palladium, iron, copper, and silver; metal oxides such as titanium oxide, tin oxide, and zinc oxide; electrolytic treatment on the surface of the metal-based fine particles, fibers, and metal oxides Composite particles surface-treated by spray coating and mixed shaking; furnace black, thermal black, acetylene black, ketjen black; carbon powder such as PAN (polyacrylonitrile) carbon and pitch carbon. Examples of furnace black include the following. SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, I-ISAF-HS, HAF-HS, HAF, HAF-LS, T-HS, T-NS, MAF, FEF, GPF, SRF-HS- HM, SRF-LM, ECF, and FEF-HS. Examples of the thermal black include FT and MT.

  Moreover, these electronic conductive agents can be used individually or in combination of 2 or more types. Further, the electronic conductive agent has an average primary particle size of more preferably 0.01 μm to 0.9 μm, still more preferably 0.01 μm to 0.5 μm. Within this range, the volume resistivity of the surface layer of the charging member can be easily controlled. The average primary particle size of the electronic conductive agent in the surface layer is measured as follows, for example. That is, a test piece having a thickness of about 100 nanometers is cut out using a microtome, and an enlarged photograph at a magnification of 80000 to 100000 times is taken using the test piece using an electron microscope. From the obtained photograph, 100 electronic conductive agents that are not aggregated are selected. For each selected electronic conductive agent, the maximum length on the photograph is regarded as the diameter of each electronic conductive agent, and the value of the diameter of each electronic conductive agent is calculated based on the magnification of the photograph. Let the arithmetic average value of the diameter of each calculated electronic conductive agent be an average primary particle diameter of the electronic conductive agent contained in the said test piece.

  The content of these electronic conductive agents in the surface layer is suitably 2 to 80 parts by mass, preferably 20 to 60 parts by mass with respect to 100 parts by mass of the binder resin.

  Further, the surface of the electronic conductive agent may be surface-treated. As the surface treatment agent, organosilicon compounds such as alkoxysilanes, fluoroalkylsilanes, and polysiloxanes; various coupling agents such as silane, titanate, aluminate, and zirconate; oligomers or polymer compounds can be used. These may be used alone or in combination of two or more. Preferred are organosilicon compounds such as alkoxysilanes and polysiloxanes; various silane, titanate, aluminate or zirconate coupling agents, and more preferred are organosilicon compounds. By using the surface treatment agent, the dispersibility of the electronic conductive agent is improved, and desired electrical characteristics are easily obtained.

  When carbon black is used as the electronic conductive agent, it is more preferably used as composite conductive fine particles obtained by coating metal oxide fine particles with carbon black. Since carbon black forms a structure, it tends to be difficult for the carbon black to exist uniformly with respect to the binder resin. When carbon black is used as composite conductive fine particles coated with a metal oxide, the electronic conductive agent can be uniformly present in the binder resin, and the volume resistivity of the surface layer of the charging member can be more easily controlled.

[Other materials]
The surface layer of the charging member according to the present invention may contain insulating particles in addition to the electronic conductive agent. Examples of the material of the insulating particles include the following. Zinc oxide, tin oxide, indium oxide, titanium oxide (titanium dioxide, titanium monoxide, etc.), iron oxide, silica, alumina, magnesium oxide, zirconium oxide, strontium titanate, calcium titanate, magnesium titanate, barium titanate, Calcium zirconate, barium sulfate, molybdenum disulfide, calcium carbonate, magnesium carbonate, dolomite, talc, kaolin clay, mica, aluminum hydroxide, magnesium hydroxide, zeolite, wollastonite, diatomaceous earth, glass beads, bentonite, montmorillonite , Hollow glass spheres, organometallic compounds and organometallic salts. Further, iron oxides such as ferrite, magnetite and hematite and activated carbon can also be used.

  The surface layer of the charging member may further contain a release agent in order to improve the releasability. By including a release agent in the surface layer, it is possible to prevent dirt from adhering to the surface of the charging member and improve the durability of the charging member. When the release agent is a liquid, it also acts as a leveling agent when forming the surface layer. The surface layer may be subjected to surface treatment. Examples of the surface treatment include a surface processing treatment using UV or electron beam and a surface modification treatment for attaching and / or impregnating a compound to the surface.

[Conductive substrate]
The conductive substrate of the charging member is conductive and has a function of supporting the surface layer provided thereon. Examples of the material include metals such as iron, copper, stainless steel, aluminum, and nickel, and alloys thereof. In addition, for the purpose of imparting scratch resistance to these surfaces, plating treatment may be performed within a range not impairing conductivity. Further, as the conductive substrate (conductive shaft), the surface of a resin base material coated with a metal to be surface conductive, or one manufactured from a conductive resin composition can be used.

[Conductive elastic layer]
In the charging member according to the present invention, a conductive elastic layer can be disposed between the conductive substrate and the surface layer as necessary. As the conductive elastic layer, a material obtained by mixing a resin (rubber) and a conductive substance is generally used. As the resin (rubber), acrylonitrile butadiene rubber, acrylic rubber, epichlorohydrin rubber, urethane rubber, ethylene propylene rubber, styrene butadiene rubber, silicone rubber, and acrylic rubber can be used. These may be used alone or in combination of two or more. More preferable resins (rubbers) are acrylonitrile butadiene rubber, acrylic rubber, and epichlorohydrin rubber.

  There are two types of conductive materials that can be applied to the conductive elastic layer: an electronic conductive agent and an ionic conductive agent. Examples of electronic conductive agents include metal-based fine particles and fibers such as aluminum, palladium, iron, copper, and silver; metal oxides such as titanium oxide, tin oxide, and zinc oxide; metal-based fine particles, carbon black, and carbon-based fine particles. Is mentioned. Moreover, these can be used individually or in combination of 2 or more types. Among electronic conductive agents, carbon black is preferably used because it can maintain electric resistance over a long period of time. This is because carbon black does not increase in resistance due to oxidative degradation. The amount of the electronic conductive agent contained in the conductive elastic layer is suitably 2 to 200 parts by mass, preferably 5 to 100 parts by mass with respect to 100 parts by mass of the resin (rubber).

  Examples of ionic conductive agents include inorganic ionic substances such as lithium perchlorate, cationic surfactants such as modified aliphatic dimethylethylammonium ethosulphate, zwitterionic surfactants such as dimethylalkyllauryl betaine, and trimethyloctadecyl perchlorate. Examples thereof include quaternary ammonium salts such as ammonium and organic acid lithium salts such as lithium trifluoromethanesulfonate. These can be used alone or in combination of two or more. Among ionic conductive agents, quaternary ammonium perchlorate is particularly preferably used because of its resistance to environmental changes. The amount of the ionic conductive agent contained in the conductive elastic layer is suitably 0.01 to 5 parts by mass, preferably 0.1 to 2 parts by mass with respect to 100 parts by mass of the resin (rubber). is there.

  The conductive substrate may be bonded to the conductive elastic layer directly thereon via a conductive adhesive layer. In this case, it is preferable to use a conductive adhesive to form the conductive adhesive layer. In order to make the adhesive conductive, a known conductive agent can be used. Examples of the binder of the adhesive include a thermosetting resin and a thermoplastic resin, and known urethane, acrylic, polyester, polyether, and epoxy resins can be used. As a conductive agent for imparting conductivity to the adhesive, it can be appropriately selected from the electronic conductive agent and the ionic conductive agent, and can be used alone or in combination of two or more.

[Method of manufacturing charging member]
The charging member according to the present invention can be manufactured by forming a surface layer on a conductive substrate, and a conductive elastic layer is formed on the conductive substrate, and a surface layer is further formed thereon. Can be manufactured by.

[Method of forming conductive elastic layer]
First, as a material for forming the conductive elastic layer, resin (rubber), conductive agent, plasticizer, filler, other various additives (vulcanizing agent, vulcanization accelerator, anti-aging agent, foaming agent, etc. ) In a kneader to produce a raw rubber composition. Examples of the kneader include a ribbon blender, a Nauta mixer, a Henschel mixer, a super mixer, a Banbury mixer, and a pressure kneader. Further, in the step of kneading the vulcanizing agent and the vulcanization accelerator, kneading using an open roll is desirable in order to prevent the vulcanization of the resin (rubber) due to the temperature rise.

  As a method for forming a conductive elastic layer from a raw rubber composition, for example, using an extrusion molding apparatus equipped with a crosshead, a conductive base coated with an adhesive is used as a central axis and is coaxially cylindrical. Examples thereof include a method in which the raw rubber composition is coated and the conductive substrate and the raw rubber composition are integrally extruded. The crosshead is a device generally used for covering electric wires and wires, and is used by being attached to a rubber discharge portion of a cylinder of an extruder.

  Another example is a method in which a rubber tube is formed from the raw rubber composition, a conductive substrate coated with an adhesive is inserted into the tube, and bonded. Another example is a method in which a conductive substrate coated with an adhesive is coated with an unvulcanized rubber sheet and vulcanized in a mold.

  The surface of the obtained charging member may be polished. As a cylindrical polishing machine that forms a predetermined outer diameter, a traverse NC cylindrical polishing machine, a plunge cut NC cylindrical polishing machine, or the like can be used. The plunge cut type NC cylindrical polishing machine is preferable because it uses a grinding wheel that is wider than the traverse method, so that the processing time can be shortened and the diameter change of the grinding wheel is small.

[Method for forming surface layer]
Examples of the method for forming the surface layer include the following methods. First, a conductive elastic layer is formed on a conductive substrate by the method described above. Then, the surface of the elastic layer is covered with a layer of a surface layer coating liquid described later, followed by drying, curing, or crosslinking. Coating methods include electrostatic spray coating method, dipping coating method, roll coating method, method of adhering or coating a sheet-shaped or tube-shaped layer formed to a predetermined film thickness, and the outer periphery of the elastic layer in the mold. And a method of curing by disposing a coating solution for the surface layer in the part.

  Further, when these coating methods are used, a “surface layer coating solution” is prepared in which resin particles, an electronic conductive agent such as an ionic conductive agent or conductive fine particles are dispersed in a binder resin. In order to make the control of the porosity of the resin particles easier, it is preferable to use a solvent for the coating liquid. In particular, it is preferable to use a polar solvent capable of dissolving the binder resin and having high affinity with the resin particles. Specific examples of the solvent include the following. Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; alcohols such as methanol, ethanol and isopropanol; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; sulfoxides such as dimethyl sulfoxide; tetrahydrofuran Ethers such as dioxane and ethylene glycol monomethyl ether; esters such as methyl acetate and ethyl acetate.

  In addition, as a method of dispersing the binder resin, resin particles, an electronic conductive agent such as an ionic conductive agent or conductive fine particles in the coating liquid, solution dispersing means such as a ball mill, a sand mill, a paint shaker, a dyno mill, and a pearl mill are used. be able to.

  A specific example of the method for forming the surface layer is shown below. First, a dispersion component other than resin particles, such as conductive fine particles, is mixed with a binder resin together with glass beads having a diameter of 0.8 mm and dispersed using a paint shaker disperser for 5 to 36 hours. Next, resin particles are added and dispersed. The dispersion time is preferably 2 minutes or longer and within 30 minutes. Here, it is necessary for the resin particles to be in a condition that prevents the resin particles from being pulverized. Then, it adjusts so that it may become a viscosity of 3-30 mPa * s, More preferably, 3-20 mPa * s, The coating liquid for surface layers is obtained. Next, it is preferable to form a surface layer on the conductive elastic layer by dipping so that the film thickness after drying is 0.5 to 50 μm, more preferably 1 to 20 μm, and particularly preferably 1 to 10 μm. .

  The film thickness of the surface layer can be measured by cutting the cross section of the charging member with a sharp blade and observing with an optical microscope or an electron microscope. Measurements are made at a total of 9 points, 3 points in the longitudinal direction of the charging member and 3 points in the circumferential direction, and the average value is taken as the film thickness.

  When the film thickness is large, that is, when the amount of solvent of the coating solution is small, bubbles may be easily generated in the surface layer. Therefore, it is preferable that the solid content concentration of the coating liquid is relatively small. The proportion of the solvent with respect to the coating liquid is preferably 40% by mass or more, more preferably 50% by mass or more, and particularly preferably 60% by mass or more.

  As specific gravity of a coating liquid, it is preferable to adjust to 0.8000 or more and 1.200 or less, and 0.9000 or more and 1.000 or less are more preferable. By setting it within this range, it becomes easy to generate the flow of the coating liquid and bubbles are easily removed. In addition, controlling the difference between the specific gravity of the resin particles and the specific gravity of the coating liquid to be smaller can facilitate the movement of the resin particles due to the flow of the coating liquid and suppress the sedimentation of the resin particles. More preferred.

  Moreover, after application | coating of the said coating liquid, it is preferable to make it dry once at the temperature of about 20-50 degreeC. When the treatment such as curing or crosslinking is performed, it is preferably performed after the drying. If a high temperature (for example, higher than the boiling point of the solvent) is applied immediately after application of the coating liquid, bumping of the solvent occurs and it is difficult to form a coating film uniformly, which is not preferable. When a high temperature is required for curing or crosslinking treatment, pre-drying is preferably performed in an environment of about 20 to 30 ° C. before the curing treatment in order to suppress the bumping. This makes it possible to reliably form a uniform coating film.

  In the present invention, as shown in FIG. 2A, in order to make the resin particles in which the pores are concentrated in the convex portion apex side region exist in the surface layer, as a raw material for the resin particles, the porosity of the inner layer portion is used. It is also preferable to use porous particles having a large porosity in the outer layer portion and a larger pore diameter in the outer layer portion than in the inner layer portion.

  When the surface layer is formed using such porous particles, the reason why the porosity is more easily controlled in the convex portion on the surface of the charging member will be described below with reference to FIGS. 10A to 10E. .

  FIG. 10A is a schematic view showing a state immediately after the coating film 26 of the coating liquid for the surface layer is applied to the surface of the conductive substrate or the surface of the conductive elastic layer by the coating method described above. The coating film 26 contains a solvent, a binder resin, an electronic conductive agent, and porous particles 23, and the porous particles 23 are formed by an inner layer region 24 and an outer layer region 25. In the porous particles, the porosity of the outer layer region is larger than the porosity of the inner layer region, and the pore size of the outer layer region is larger than the pore diameter of the inner layer region. In the above state, it is presumed that at least the solvent and the binder resin are uniformly permeated into the pores of the porous particles. And immediately after apply | coating the said coating liquid on the surface of an electroconductive base | substrate, volatilization of a solvent generate | occur | produces also from the surface side. At this time, since the volatilization of the solvent proceeds in the direction indicated by 27 in FIG. 10B, the concentration of the binder resin increases on the surface side of the coating film 26. Inside the coating film, a force is applied to keep the concentration of the solvent and the binder resin constant, and the binder resin in the coating film flows in the direction indicated by 28.

  On the other hand, the inner layer part region 24 of the porous particles has a pore diameter smaller than that of the outer layer part region 25 and a lower porosity, so that the moving speed of the solvent and the binder resin in the inner layer part region 24 is set to be lower. It is slower than the moving speed of the solvent and binder resin. Therefore, although the binder resin moves in the direction of 28, the binder resin in the outer layer region is more than the concentration of the binder resin in the inner layer region due to the difference in the moving speed in the inner layer region and the outer layer region of the porous particles. A state occurs in which the concentration of is increased. FIG. 10C shows a state in which the concentration of the binder resin is higher in the outer layer region 25 than in the inner layer region 24.

  Then, a binder resin flow 29 is generated in a direction that reduces the difference in concentration of the binder resin between the inner layer region and the outer layer region of the porous particles. Since the volatilization of the solvent always proceeds in the direction of 27, the state in which the concentration of the binder resin in the outer layer region is lower than that in the inner layer region of the porous particles, that is, the state shown in FIG. 10D. Become.

  In the state shown in FIG. 10D, the solvent remaining in the outer layer region of the porous particles at a time by drying, curing, or crosslinking the coating film at a temperature equal to or higher than the boiling point of the solvent used. It volatilizes and, finally, pores 30 can be formed in the outer layer region of the porous particles.

  The present inventors consider that the use of the above method makes it possible to reliably control the porosity of the convex portion of the charging member described above.

  In order to perform the above control more easily, it is more preferable to control the ratio of the porosity and the pore diameter of the inner layer region and the outer layer region of the porous particles. That is, the porosity of the outer layer part is preferably 1.5 times or more and 3 times or less of the porosity of the inner layer part, and the pore diameter of the outer layer part is smaller than the hole diameter of the inner layer part. It is preferable to be 2 times or more and 10 times or less. Moreover, in order to control the flow of the solvent, it is preferable to use the polar solvent described above having high affinity with the porous particles. Among the above solvents, it is more preferable to use ketones and esters.

  In the step of drying, curing, or crosslinking after applying the surface layer coating solution, it is preferable to control the temperature and time. By controlling the temperature and time, the moving speed of the solvent and the binder resin can be controlled. And specifically, it is preferable to make the process after coating film formation into three steps or more. Hereafter, the state at the time of making the process after coating-film formation into three steps is demonstrated in detail.

  In the first stage, it is preferable that the film is allowed to stand for 15 minutes or more and 1 hour or less in a room temperature atmosphere after forming the coating film. Thereby, it becomes easy to form the state of FIG. 10B described above gently.

  In the second stage, it is preferable to stand at a temperature not lower than room temperature and not higher than the boiling point of the solvent used for 15 minutes or longer and 1 hour or shorter. Although there are some differences depending on the type of solvent used, specifically, it is more preferable that the temperature is controlled to 40 ° C. or higher and 100 ° C. or lower and left for 30 minutes or longer and 50 minutes or shorter. And by this 2nd step, the volatilization rate of the solvent of FIG. 10C becomes large, and the control which raises the density | concentration of the binder resin of the inner layer part area | region 24 of a porous particle can be performed more easily.

  The third stage is a drying, curing, or crosslinking process at a temperature equal to or higher than the boiling point of the solvent. At that time, it is preferable to control the temperature of the second stage and the third stage by rapidly raising the temperature. Thereby, it becomes easy to form a hole near the convex portion apex. Specifically, instead of temperature control in the same drying furnace, the second and third stage drying furnaces are preferably different devices or different areas, and the movement of the devices or areas is It is preferable to set the time as short as possible.

That is, examples of the method for forming the surface layer of the charging member of the present invention include a method having the following steps (1) and (2).
(1) On the surface of the conductive substrate or the surface of the conductive resin layer (conductive elastic layer) formed on the conductive substrate, a binder resin, a solvent, an electronic conductive agent, and resin particles as a raw material ( Forming a coating film of a coating liquid for the surface layer containing porous particles),
(2) A step of volatilizing the solvent in the coating film to form a surface layer.

Step (2) is a process of volatilizing the solvent in the coating film, and preferably includes the following step (3) and step (4).
(3) a step of replacing the binder resin with the solvent that has penetrated into the pores of the porous particles;
(4) A step of drying the coating film at a temperature not lower than the boiling point of the solvent.
The porous particles are porous resin particles in which the porosity of the outer layer region is larger than the porosity of the inner layer region, and the pore diameter of the outer layer portion is larger than the pore diameter of the inner layer region. It is preferable.

[Measurement method of physical properties]
FIG. 4 shows a method for measuring the electric resistance value of the charging roller 8. A load is applied to both ends of the conductive substrate of the charging roller, and the charging roller is brought into contact with the cylindrical metal 9 having the same curvature as that of the electrophotographic photosensitive member so as to be parallel. In this state, a cylindrical metal is rotated by a motor (not shown), and a DC voltage of −200 V is applied from the stabilized power source while the charging roller in contact is driven to rotate. The current flowing at this time is measured with an ammeter, and the electric resistance value of the charging roller is calculated. In the present invention, the load is 500 g, the diameter of the columnar metal is 30 mm, and the rotation of the columnar metal is a peripheral speed of 45 mm / sec.

  The charging roller according to the present invention has a crown that is thickest at the center in the longitudinal direction and narrows toward both ends in the longitudinal direction from the viewpoint of making the nip width in the longitudinal direction uniform with respect to the electrophotographic photosensitive member. Shape is preferred. The crown amount (average value of the difference between the outer diameter d1 of the central portion and the outer diameter d2 at positions 90 mm away from the central portion in the direction of both ends) is preferably 30 μm or more and 200 μm or less.

  The surface hardness of the charging member is preferably 90 ° or less, more preferably 40 ° or more and 80 ° or less in terms of micro hardness (MD-1 type). By setting it within this range, it is easy to stabilize the contact between the charging member and the electrophotographic photosensitive member, and more stable in-nip discharge can be performed.

  The 10-point average surface roughness (Rzjis) of the surface of the charging member is preferably 8 μm or more and 100 μm or less. More preferably, they are 12 micrometers or more and 60 micrometers or less. Further, the average unevenness (Rsm) on the surface is 20 μm or more and 300 μm or less, more preferably 50 μm or more and 200 μm or less. By setting it within this range, it becomes easy to form a gap in the nip between the charging member and the electrophotographic photosensitive member, and stable in-nip discharge can be performed.

  The ten-point average surface roughness and the uneven average interval were measured according to the standard of JIS B 0601-1994, and the surface roughness measuring instrument “SE-3500” (trade name, Kosaka Laboratory Ltd.) Made). The ten-point average surface roughness is an average value obtained by measuring six arbitrary points on the charging member. Further, the average unevenness interval is calculated as an average value of “each average value of 6 locations” by measuring 10 unevenness intervals at each of the 6 arbitrary locations and obtaining an average value thereof. In the measurement, the cutoff value is set to 0.8 mm, and the evaluation length is set to 8 mm.

  According to the present invention, the surface roughness (Rzjis, Rsm) of the charging member having convex portions derived from the resin particles on the surface is mainly the particle size of the resin particles as the raw material, the coating liquid for forming the surface layer It is adjusted by the viscosity, the content of the resin particles in the coating liquid for forming the surface layer, and the thickness of the surface layer. For example, increasing the particle size of the resin particles as the raw material acts to increase Rzjis. Increasing the specific gravity and viscosity of the coating liquid for forming the surface layer acts to reduce Rzjis. Further, increasing the thickness of the surface layer acts in the direction of reducing Rzjis. Furthermore, increasing the content of the resin particles as a raw material in the coating liquid acts in the direction of reducing Rsm. Based on these, it is possible to obtain a charging member having a desired surface roughness by appropriately adjusting the above-described elements.

[Evaluation of discharge in nip]
The surface layer of the charging member according to the present invention has a convex portion formed on the surface of the surface layer by resin particles having a plurality of pores therein, so that the discharge in the nip is stabilized. This is because the resin particles have a plurality of pores therein, so that the convex portions formed of the resin particles are appropriately distorted, and it is easy to maintain a gap necessary for discharge. This distortion has the effect of reducing the slip between the charging member and the electrophotographic photosensitive member, and contributes to the stabilization of the discharge gap. That is, by using resin particles having a plurality of holes therein, it is possible to achieve both suppression of banding images and stabilization of discharge in the nip.

  The method of observing the discharge in the nip is to discharge the electric charge generated on the conductive substrate by bringing the charging member into contact with the conductive substrate formed of a transparent material in the dark room and applying a desired voltage to the charging member. A method of observing light with a high-speed and high-sensitivity camera can be mentioned. Details of the evaluation will be described later. When a charging roller is used as the charging member, it is desirable to observe the discharge light while rotating the charging roller. This is because the rotated configuration is more similar to the actual machine. Further, the discharge light can be estimated from the intensity of the light by using the imaging tube and using the light as an electric signal. In the present invention, the stability of the discharge in the nip is evaluated by estimating the discharge amount from the discharge light using an image intensifier capable of amplifying weak light.

<Electrophotographic process cartridge>
The electrophotographic process cartridge according to the present invention is an electrophotographic process cartridge having the charging member and the electrophotographic photosensitive member. FIG. 6 shows an electrophotographic process cartridge in which the electrophotographic photosensitive member, the charging device, the developing device, the cleaning device, and the like are integrated and designed to be detachable from the electrophotographic device.

<Electrophotographic device>
The electrophotographic apparatus according to the present invention is an electrophotographic apparatus equipped with the electrophotographic process cartridge according to the present invention. The electrophotographic apparatus shown in FIG. 5 includes an electrophotographic process cartridge in which an electrophotographic photosensitive member, a charging device, a developing device, a cleaning device, and the like are integrated, a latent image forming device, a developing device, a transfer device, and a fixing device. It is configured.

  The electrophotographic photoreceptor 10 is a rotating drum type having a photosensitive layer on a conductive support. The electrophotographic photosensitive member is driven to rotate at a predetermined peripheral speed (process speed) in the direction of the arrow. The charging device includes a contact-type charging roller 8 that is placed in contact with the electrophotographic photosensitive member by being brought into contact with the electrophotographic photosensitive member with a predetermined pressing force. The charging roller is driven rotation that rotates in accordance with the rotation of the electrophotographic photosensitive member, and charges the electrophotographic photosensitive member to a predetermined potential by applying a predetermined DC voltage from a charging power source.

  For example, an exposure apparatus such as a laser beam scanner is used as the latent image forming apparatus 11 that forms an electrostatic latent image on the electrophotographic photosensitive member. An electrostatic latent image is formed by performing exposure corresponding to image information on the uniformly charged electrophotographic photosensitive member. The developing device has a developing roller 12 disposed close to or in contact with the electrophotographic photosensitive member. The toner electrostatically processed to the same polarity as the charged polarity of the electrophotographic photosensitive member is reversely developed to visualize and develop the electrostatic latent image into a toner image.

  The transfer device has a contact-type transfer roller 13. The toner image is transferred from the electrophotographic photosensitive member to a transfer material 14 such as plain paper. The transfer material is conveyed by a paper feeding system having a conveying member. The cleaning device includes a blade-type cleaning member 15 and a collection container, and after transferring, mechanically scrapes and collects transfer residual toner remaining on the electrophotographic photosensitive member. Here, it is possible to omit the cleaning device by adopting a development simultaneous cleaning system in which the transfer device collects the transfer residual toner. The fixing device 16 is composed of a heated roll or the like, and fixes the transferred toner image on a transfer material and discharges it outside the apparatus.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. First, prior to Examples, electrophotographic photoreceptor production examples A1 to A12, resin particle evaluation methods, resin particle production examples B1 to B20, fine particle production examples C1 and C2, and charging member production examples D1 to D1 D20 will be described. In the following description, “part” means “part by mass”.

<A. Production example of electrophotographic photoreceptor>
[Production Example A1]
An aluminum cylinder having a diameter of 24 mm and a length of 261.6 mm was used as a support. Next, SnO ₂ coated barium sulfate (conductive particles) 10 parts, titanium oxide (resistance pigment) 2 parts, phenol resin (binder resin) 6 parts, silicone oil (leveling agent) 0.001 part, methanol A conductive layer coating solution was prepared using a mixed solvent of 4 parts and 16 parts of methoxypropanol. This conductive layer coating solution was dip-coated on a support and cured (thermosetting) at 140 ° C. for 30 minutes to form a conductive layer having a thickness of 15 μm on the support.

  Next, an intermediate layer coating solution was prepared by dissolving 3 parts of N-methoxymethylated nylon and 3 parts of copolymer nylon in a mixed solvent of 65 parts of methanol and 30 parts of n-butanol. This intermediate layer coating solution was dip-coated on the conductive layer and dried at 80 ° C. for 10 minutes to form an intermediate layer having a thickness of 0.7 μm on the conductive layer.

  Next, 7.5 °, 9.9 °, 16.3 °, 18.6 °, 25.1 ° and 28.3 with Bragg angles 2θ ± 0.2 ° in CuKα characteristic X-ray diffraction as charge generation materials. 10 parts of a crystalline hydroxygallium phthalocyanine crystal (charge generation material) having a strong peak at 0 ° was used. This was added to a solution obtained by dissolving 5 parts of polyvinyl butyral resin (trade name: ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd.) in 250 parts of cyclohexanone. This was dispersed in a sand mill apparatus using glass beads with a diameter of 1 mm in an atmosphere of 23 ± 3 ° C. for 1 hour, and 250 parts of ethyl acetate was added to prepare a charge generation layer coating solution. This charge generation layer coating solution was dip coated on the intermediate layer and dried at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.26 μm on the intermediate layer.

  Next, 5.6 parts of the compound represented by the above formula (CTM-1) (charge transporting substance), 2.4 parts of the compound represented by the above formula (CTM-2) (charge transporting substance), polycarbonate resin A ( 1) 10 parts of (resin A (1) shown in Table 1) and 0.36 part of polycarbonate resin A ′ (1) (resin A ′ (1) shown in Table 2) 2.5 methyl benzoate A part was dissolved in 20 parts of dimethoxymethane and 30 parts of o-xylene to prepare a charge transport layer coating solution. The charge transport layer coating solution was dip-coated on the charge generation layer and dried at 125 ° C. for 30 minutes to form a charge transport layer having a thickness of 15 μm on the charge generation layer. It was confirmed by gas chromatography that the formed charge transport layer contained 0.028% by mass of methyl benzoate.

  Thus, an electrophotographic photoreceptor A1 having a charge transport layer as a surface layer was produced.

[Production Examples A2 to A6]
Electrophotographic photoreceptors A2 to A6 were produced in the same manner as in Production Example A1, except that in Production Example A1, the type and content of compound (3) were changed as shown in Table 4.

[Production Example A7]
In Production Example A1, the drying temperature and time for forming the charge transport layer were changed to 145 ° C. for 60 minutes, and the solvent mixing ratio was changed as shown in Table 4. Otherwise, the electrophotographic photoreceptor A7 was produced in the same manner as in Production Example A1.

[Production Examples A8 and A9]
Electrophotographic photoreceptors A8 and A9 were produced in the same manner as in Production Example A1, except that the thickness of the charge transport layer in Production Example A1 was changed to 30 μm in Production Example A8 and 10 μm in Production Example A9.

[Production Examples A10 and A11]
The drying temperature, time, and thickness of the charge transport layer when forming the charge transport layer in Production Example A1 were changed to 130 ° C., 60 minutes, 10 μm in Production Example A10, and 120 ° C., 20 minutes, 10 μm in Production Example A11. Except that, electrophotographic photoreceptors A10 and A11 were produced in the same manner as in Production Example A1.

[Production Example A12]
In Production Example A1, an electrophotographic photosensitive member A12 was produced in the same manner as in Production Example A1, except that compound (3) was not used.

  Table 4 shows the production conditions and the like of the surface layers of Production Examples A1 to A12.

[Method for evaluating resin particles]
(1-1) Measurement of three-dimensional particle shape of resin particles (hollow particles and porous particles) as raw materials Resin particles as raw materials for resin particles according to the present invention (hereinafter simply referred to as “resin particles as raw materials”) As for hollow particles and porous particles used for the above, only the primary particles excluding the secondary agglomerated particles are focused on a focused ion beam by 20 nm (trade name: FB-2000C, manufactured by Hitachi, Ltd.) And cut an image of the cross section. For the same particle, the photographed cross-sectional images are combined at intervals of 20 nm to calculate the “three-dimensional particle shape” of the particle to be measured. This operation is performed for 100 arbitrary particles. In the cross-sectional image, since the resin portion appears gray and the air region appears white, the resin portion and the air region can be distinguished.

(1-2) Measurement of Volume Average Particle Size of Resin Particles as Raw Material For the “stereoscopic particle shape” particles obtained by the method described in (1-1), the total including the region containing air The volume is calculated, and the diameter of a sphere having a volume equal to this volume is obtained. The average diameter of a total of 100 obtained spheres is defined as the “volume average particle diameter dv” of the resin particles.

(1-3) Measurement of ratio of region containing air inside resin particles as raw material From the “three-dimensional particle shape” obtained by the method described in (1-1), a region containing air is calculated. And the ratio which the total volume of the said area | region occupies for the total volume including the area | region containing the air of the said resin particle is calculated. The arithmetic average value of the above-mentioned ratios of 100 resin particles as raw materials (the ratio of the total volume of the region including air to the total volume including the region including the air of the resin particles) The ratio of the area including air ”.

(1-4) Measurement of average diameter of non-through holes of resin particles (porous particles, hollow particles) as a raw material From the “three-dimensional particle shape” obtained by the method described in (1-1) above, Each volume is calculated about arbitrary 10 places of the part (non-through-hole) which does not penetrate the surface of the resin particle among the regions containing air, and the diameter of a sphere having a volume equal to this volume is obtained. This operation is performed for 10 arbitrary resin particles, and the average diameter of a total of 100 obtained spheres is calculated. This is defined as the “average diameter d _H of non-through holes” of the resin particles.

(1-5) Measurement of average diameter of through-hole of resin particle (porous particle) as raw material Region containing air from “stereoscopic particle shape” obtained by the method according to (1-1) Among these, a cross-sectional view is taken for any 10 portions of the portion (through hole) penetrating the surface of the resin particle. From this cross-sectional view, the cross-sectional area of the through hole is calculated, and the diameter of a circle having an area equal to this area is obtained. This operation is performed for 10 arbitrary resin particles, and the average diameter of a total of 100 obtained circles is calculated. This is defined as “the average diameter d _{P of the} through holes” of the resin particles.

(2-1) Observation of a cross section of porous particles as a raw material having a core-shell structure For resin particles as a raw material having a core-shell structure, first, the resin particles are converted into a photocurable resin, for example, a visible light curable package. Embed by embedding resin (trade name: D-800, manufactured by Nissin EM Co., Ltd., or trade name: Epok 812 set, manufactured by Oken Shoji Co., Ltd.). Next, an ultramicrotome (trade name: LEICA EM UCT, manufactured by Leica) equipped with a diamond knife (trade name: DiATOMECRYRO DRY, manufactured by DIATOME), and a cryo system (trade name: LEICA EM FCS, manufactured by Leica) After chamfering, the center of the resin particles (so that the vicinity of the center of gravity 17 shown in FIG. 8 is included) is cut out, and a section having a thickness of 100 nm is created. Thereafter, staining is performed using any of osmium tetroxide, ruthenium tetroxide, and phosphotungstic acid, and a transmission electron microscope (trade name: H-7100FA, manufactured by Hitachi, Ltd.) Then, a cross-sectional image of the resin particles is taken. This is done for any 100 particles. At this time, the resin portion is observed to be white and the pore portion is observed to be black. The embedding resin and the staining agent are appropriately selected depending on the material of the resin particles. At this time, a combination in which the pores of the resin particles can be clearly confirmed is selected. For example, the resin particles produced in the following Production Example B1 are observed using a visible light curable embedding resin D-800 and ruthenium tetroxide, so that the pores into which the visible light curable embedding resin has entered are clearly observed. Can be confirmed.

(2-2) Porosity of porous particles as a raw material having a core-shell structure A method for calculating the porosity of porous particles as a raw material having a core-shell structure will be described in detail below with reference to FIG. To do.

  The center 108 of the circle 201 having the same area as the cross-sectional image of the particle obtained in (2-1) is calculated. The circle is superimposed on the cross-sectional image so that the center 108 and the center of gravity 17 of the resin particle coincide with each other, and a point (for example, 113) obtained by equally dividing the circumference of the circle 201 into 100 is calculated. And draw a straight line connecting the center of gravity of the resin particles. A position (for example, 109) moved by √3 / 4 times the particle diameter 110 from the center 108 of the circle toward the outside of the particle, for example, from 108 to 113 is calculated. This calculation is performed for all the points (113-1, 113-2, 113-3,...) On the circumference divided into 100, and 100 points (109-1, 109−) corresponding to 109 are obtained. 2, 109-3,...). The region 112 on the center 108 side of the region connecting these 100 points with a straight line is defined as an inner layer region of the resin particles, and the region 111 on the outer side 111 is defined as an outer layer region of the resin particles.

  Then, in each of the inner layer portion region and the outer layer portion region of the resin particle, the ratio of the total area of the hole portion in the cross-sectional image is calculated with respect to the total area including the region including the hole portion. This average is defined as the porosity.

(2-3) Pore diameter of porous particles as a raw material having a core-shell structure For each of the inner layer portion region and outer layer portion region of the resin particles, ten randomly selected hole portions observed in black are selected, and The area of the part is measured, and the arithmetic average value of the diameters of the circles having the same area as the area is defined as the pore diameter of the porous particle having the core-shell structure.

(3) Measurement of “three-dimensional particle shape” of resin particles contained in surface layer An area of 200 μm in length and 200 μm in width that is parallel to the surface of the charging member at an arbitrary convex portion on the surface of the charging member Then, it is cut out by a focused ion beam (trade name: FB-2000C, manufactured by Hitachi, Ltd.) by 20 nm from the apex side of the convex portion of the charging member, and a cross-sectional image thereof is taken. And the image which image | photographed the same particle | grains is combined by 20 nm space | interval, and a "three-dimensional particle shape" is calculated. This operation is performed at any 100 locations on the surface of the charging member.

(4) Measurement of volume average particle diameter of resin particles contained in surface layer In “stereoscopic particle shape” obtained by the method described in (3) above, the total volume including the region containing pores is calculate. This is the volume of the resin particles when the resin particles are assumed to be solid particles. Then, the diameter of a sphere having a volume equal to this volume is obtained. The average diameter of a total of 100 obtained spheres is calculated, and this is defined as the “volume average particle diameter dv” of the resin particles.

(5) Measurement of porosity of resin particles contained in surface layer From the “three-dimensional particle shape” obtained by the method described in (3) above, it was assumed that the resin particles were solid particles. The “convex vertex side region” of the solid particle at the time is calculated. 7 and 8 are a cross-sectional view and a three-dimensional schematic diagram of the resin particles forming the convex portions on the surface of the charging member. The method for calculating the porosity will be described below using this drawing. First, the gravity center 17 of the resin particle is calculated from the “three-dimensional particle shape”. Then, a virtual plane 19 that is parallel to the surface of the charging member and passes through the center of gravity of the resin particles is produced, and this plane is projected from the center of gravity of the resin particles by a distance of √3 / 2 times the radius r of the sphere. The position 20 on the vertex side, that is, the center of gravity 17 is translated to the position of the virtual plane 21. The region on the convex vertex side surrounded by the virtual plane 21 and the surface of the resin particle is defined as the “convex vertex side region” of the solid particle when the resin particle is assumed to be a solid particle. . In this region, the total volume of holes is calculated from the “three-dimensional particle shape”, and the ratio of the region to the total volume including the holes is calculated. This is the porosity of the “convex portion apex side region” (hereinafter also referred to as “porosity B”).

  Further, the total volume of pores of the entire resin particle is calculated from the “three-dimensional particle shape”, and the ratio to the total volume including the region including the pore of the resin particle is calculated. This is the porosity of the entire resin particle (hereinafter also referred to as “porosity A”).

(6) Measurement of pore diameter of resin particles contained in surface layer In the “convex portion apex region” of the solid particles when the resin particles are assumed to be solid particles, the “three-dimensional” From the “typical particle shape”, the maximum length and the minimum length of the pores are measured for 10 locations of the pores, and the average value of these two lengths is calculated. And this operation | work is performed about arbitrary resin particles. An average value of 100 measured values obtained in total is calculated, and this is defined as a pore diameter in the “convex portion apex side region” of the resin particles.

<B. Example of production of resin particles as raw material>
(Production Example B1)
An aqueous medium was prepared by adding 8 parts by mass of tricalcium phosphate to 400 parts by mass of deionized water. Next, 20 parts by mass of methyl methacrylate, 10 parts by mass of 1,6-hexanediol dimethacrylate, 75 parts by mass of n-hexane, and 0.3 parts by mass of benzoyl peroxide were mixed to prepare an oily mixture. This oily mixture was dispersed in the aqueous medium with a homomixer at a rotational speed of 3000 rpm. Thereafter, the mixture was charged into a nitrogen-substituted polymerization reaction vessel, and suspension polymerization was carried out at 60 ° C. for 6 hours while stirring at 250 rpm to obtain an aqueous suspension containing porous particles and n-hexane. To this aqueous suspension, 0.4 parts by mass of sodium dodecylbenzenesulfonate was added, and the concentration of sodium dodecylbenzenesulfonate was adjusted to 0.1% by mass with respect to water.

  The obtained aqueous suspension was distilled to remove n-hexane, and the remaining aqueous suspension was repeatedly filtered and washed with water, followed by drying at 80 ° C. for 5 hours. Crushing and classification were performed with a sonic classifier to obtain resin particles B1 having a volume average particle diameter dv of 30.5 μm. When observed by the above-described embedding method, the resin particle B1 was a porous particle having a large number of pores penetrating the surface.

(Production Examples B2 to B4)
Resin particles B2 to B4 were obtained in the same manner as in Production Example B1, except that the number of rotations of the homomixer was changed to 4500 rpm, 5000 rpm, and 2500 rpm, respectively. All the resin particles were porous particles like the resin particles B1.

(Production Example B5)
An aqueous medium was prepared by adding 10.5 parts by weight of tricalcium phosphate and 0.015 parts by weight of sodium dodecylbenzenesulfonate to 300 parts by weight of deionized water. Subsequently, 65 parts by mass of lauryl methacrylate, 30 parts by mass of ethylene glycol dimethacrylate, 5 parts by mass of poly (ethylene glycol-tetramethylene glycol) monomethacrylate, and 0.5 parts by mass of azobisisobutyronitrile are mixed to form an oily mixture. Was prepared. This oily mixture was dispersed in the aqueous medium at a rotational speed of 4000 rpm with a homomixer. Thereafter, the polymer was charged into a polymerization reaction vessel purged with nitrogen, and suspension polymerization was performed at 70 ° C. for 8 hours while stirring at 250 rpm. After cooling, hydrochloric acid was added to the resulting suspension to decompose calcium phosphate, and filtration and washing were repeated. After drying at 80 ° C. for 5 hours, pulverization and classification were performed with a sonic classifier to obtain resin particles B5 having a volume average particle diameter dv of 35.2 μm. When observed by the above-described embedding method, the resin particle B5 was a hollow particle having only a plurality of hollow portions (non-through holes) inside the particle. The average diameter _{d H} of blind holes was 3.5 [mu] m.

(Production Examples B6, B10, B12 and B13)
Resin particles B6, B10, B12, and B13 were obtained in the same manner as in Production Example B5, except that the number of rotations of the homomixer was changed to 3500 rpm, 2700 rpm, 3000 rpm, and 2500 rpm, respectively. All the resin particles were hollow particles like the resin particle B5.

(Production Example B7)
8 parts by mass of polyvinyl alcohol (saponification degree 85%) was added to 400 parts by mass of deionized water to prepare an aqueous medium. Next, 6.5 parts by mass of methyl methacrylate, 6.5 parts by mass of styrene, 9 parts by mass of divinylbenzene, 85 parts by mass of n-hexane, and 0.3 parts by mass of lauroyl peroxide were mixed to prepare an oily mixture. . This oily mixture was dispersed in the aqueous medium with a homomixer at a rotational speed of 2000 rpm. Thereafter, the mixture was charged into a nitrogen-substituted polymerization reaction vessel, and suspension polymerization was carried out at 60 ° C. for 6 hours while stirring at 250 rpm to obtain an aqueous suspension containing porous particles and n-hexane. Thereafter, resin particles B7 were obtained in the same manner as in Production Example B1. This resin particle was a porous particle similarly to the resin particle B1.

(Production Example B8)
Resin particles B8 were obtained in the same manner as in Production Example B7, except that the number of revolutions of the homomixer was changed to 1800 rpm. This resin particle was a porous particle similarly to the resin particle B1.

(Production Example B9)
An aqueous medium was prepared by adding 8 parts by mass of tricalcium phosphate to 400 parts by mass of deionized water. Next, 33 parts by mass of methyl methacrylate, 17 parts by mass of 1,6-hexanediol dimethacrylate, 50 parts by mass of n-hexane, and 0.3 parts by mass of benzoyl peroxide were mixed to prepare an oily mixture. This oily mixture was dispersed in the aqueous medium with a homomixer at a rotational speed of 4800 rpm. Thereafter, the mixture was charged into a nitrogen-substituted polymerization reaction vessel, and suspension polymerization was carried out at 60 ° C. for 6 hours while stirring at 250 rpm to obtain an aqueous suspension containing porous particles and n-hexane. To this aqueous suspension, 0.2 parts by mass of sodium lauryl sulfate was added, and the concentration of sodium lauryl sulfate was adjusted to 0.05% by mass with respect to water. Thereafter, resin particles B9 were obtained in the same manner as in Production Example B1. This resin particle was a porous particle similarly to the resin particle B1.

(Production Examples B15 to B17)
Cross-linked polymethyl methacrylate resin particles (trade name: MBX-30, manufactured by Sekisui Plastics Co., Ltd.) are classified, and resin particles B15 and B16 having volume average particle diameters of 18.2 μm and 12.5 μm, respectively, are obtained. Obtained. Further, a non-classified product of MBX-30 was designated as resin particle B17. The resin particles of this production example did not have pores inside.

(Production Example B11)
Resin particles B11 were obtained in the same manner as in Production Example B8, except that the rotation speed of the homomixer was changed to 1500 rpm. This resin particle was a porous particle similarly to the resin particle B1.

(Production Example B14)
Resin particles B14 were obtained in the same manner as in Production Example B9, except that the number of revolutions of the homomixer was changed to 5000 rpm. This resin particle was a porous particle similarly to the resin particle B1.

(Production Example B18)
To 400 parts by mass of deionized water, 8.0 parts by mass of tricalcium phosphate was added to prepare an aqueous medium. Next, 38.0 parts by weight of methyl methacrylate as a polymerizable monomer, 26.0 parts by weight of ethylene glycol dimethacrylate as a crosslinkable monomer, and 34.1 parts by weight of normal hexane as a first porogen An oily mixture was prepared by mixing 8.5 parts by weight of ethyl acetate as a second porosifying agent and 0.3 parts by weight of 2,2′-azobisisobutyronitrile. This oily mixture was dispersed in the aqueous medium with a homomixer at a rotational speed of 2000 rpm. Then, it is charged into a polymerization reaction vessel purged with nitrogen and subjected to suspension polymerization at 60 ° C. for 6 hours while stirring at 250 rpm. An aqueous suspension containing porous resin particles, normal hexane and ethyl acetate is obtained. Obtained. To this aqueous suspension, 0.4 parts by mass of sodium dodecylbenzenesulfonate was added, and the concentration of sodium dodecylbenzenesulfonate was adjusted to 0.1% by mass with respect to water.

  The obtained aqueous suspension was distilled to remove normal hexane and ethyl acetate, and the remaining aqueous suspension was repeatedly filtered and washed with water, and then dried at 80 ° C. for 5 hours. Crushing and classification were performed with a sonic classifier to obtain resin particles B18 having a volume average particle diameter dv of 30.5 μm. When the cross section of the particle is observed by the above-described method, the resin particle B18 is porous having pores having a diameter of about 21 nm in the inner layer region of the resin particles and pores having a diameter of about 87 nm in the outer layer region. It was a particle.

(Production Examples B19 and B20)
As the oily mixture, the polymerizable monomer, the crosslinkable monomer, the first porogen, and the second porogen are changed as shown in Table 5, and the rotation speed of the homomixer is expressed. Resin particles B19 and B20 were obtained in the same manner as in Production Example B18, except that changes were made as shown in FIG. The obtained resin particles were porous particles.

(Characteristic evaluation of resin particles)
For each of the resin particles B1 to B17 obtained in each of the above production examples, the volume average particle diameter dv, the shape of the particles, the average diameter d _{H of} the non-through holes, the number of non-through holes (whether there are a plurality of through holes), and the penetration The average diameter d _{P of the} pores and the ratio of the region containing air in the particles were measured. The results are shown in Table 6.

  Further, for each of the resin particles B18 to B20 obtained in each of the above production examples, the volume average particle diameter dv, the porosity of the inner layer region and the outer layer region, and the pore diameter of the inner layer region and the outer layer region Was measured. The results are shown in Table 7.

<C. Production example of conductive particles and insulating particles>
[Production Example C1]
To 7.0 kg of silica particles (average particle size 15 nm, volume resistivity 1.8 × 10 ¹² Ω · cm), 140 g of methyl hydrogen polysiloxane was added while operating the edge runner, and 588 N / cm (60 kg / cm The mixture was stirred for 30 minutes under a linear load. The stirring speed at this time was 22 rpm. In that, 7.0 kg of carbon black “# 52” (trade name, manufactured by Mitsubishi Chemical Co., Ltd.) was added over 10 minutes while the edge runner was running, and a wire of 588 N / cm (60 kg / cm) was further added. The mixture was stirred for 60 minutes under load. After carbon black was adhered to the surface of the silica particles coated with methyl hydrogen polysiloxane in this way, drying was performed at 80 ° C. for 60 minutes using a dryer, to produce composite conductive fine particles C1. The stirring speed at this time was 22 rpm. The obtained composite conductive fine particles had an average primary particle size of 15 nm and a volume resistivity of 1.1 × 10 ² Ω · cm.

[Production Example C2]
1000 g of acicular rutile type titanium oxide particles (average particle size 15 nm, length: width = 3: 1, volume resistivity 2.3 × 10 ¹⁰ Ω · cm), 110 g of isobutyltrimethoxysilane as a surface treatment agent, and toluene as a solvent A slurry was prepared by blending 3000 g. After mixing this slurry with a stirrer for 30 minutes, it is supplied to viscomill in which 80% of the effective internal volume is filled with glass beads having an average particle diameter of 0.8 mm, and wet crushing is performed at a temperature of 35 ± 5 ° C. It was. Toluene was removed from the slurry obtained by wet pulverization by vacuum distillation (bath temperature: 110 ° C., product temperature: 30-60 ° C., degree of vacuum: about 100 Torr) using a kneader, and the surface was kept at 120 ° C. for 2 hours. The treating agent was baked. The baked particles were cooled to room temperature and then pulverized using a pin mill to prepare surface-treated titanium oxide particles C2. The obtained surface-treated titanium oxide particles (insulating particles) had an average primary particle size of 15 nm and a volume resistivity of 5.2 × 10 ¹⁵ Ω · cm.

<D. Manufacturing example of charging member>
[Production Example D1]
(1. Production of conductive substrate)
A thermosetting adhesive containing 10% by mass of carbon black was applied to a stainless steel substrate having a diameter of 6 mm and a length of 244 mm, and the dried product was used as a conductive substrate.

(2. Production of conductive rubber composition)
Epichlorohydrin rubber (EO-EP-AGE terpolymer, EO / EP / AGE = 73 mol% / 23 mol% / 4 mol%) 100 parts by mass, other seven kinds of materials shown in Table 8 below were added, and 50 A raw material compound was prepared by kneading for 10 minutes in a closed mixer adjusted to ° C.

  To this, 0.8 part by mass of sulfur as a vulcanizing agent, 1 part by mass of dibenzothiazyl sulfide (DM) and 0.5 part by mass of tetramethylthiuram monosulfide (TS) were added as a vulcanization accelerator. Subsequently, it knead | mixed for 10 minutes with the double roll machine cooled at 20 degreeC, and produced the conductive rubber composition. At that time, the gap between the two rolls was adjusted to 1.5 mm.

(3. Fabrication of elastic roller)
Using an extrusion molding apparatus equipped with a cross head, the outer peripheral portion of the conductive base was covered with the conductive rubber composition in the form of a coaxial cylinder with the conductive base as the central axis to obtain a rubber roller. The thickness of the coated rubber composition was adjusted to 1.75 mm.

  After heating this rubber roller in a hot air oven at 160 ° C. for 1 hour, the end of the conductive elastic layer is removed to a length of 226 mm, and further, secondary heating is performed at 160 ° C. for 1 hour. A roller having a pre-coating layer having a thickness of 1.75 mm was prepared.

  The outer peripheral surface of the obtained roller was polished using a plunge cut type cylindrical polishing machine. A vitrified wheel was used as the polishing wheel, the abrasive grains were green silicon carbide (GC), and the particle size was 100 mesh. The rotational speed of the roller was 350 rpm, and the rotational speed of the grinding wheel was 2050 rpm. The rotation direction of the roller and the rotation direction of the grinding wheel were the same direction (driven direction). The cutting speed is changed stepwise from 10 mm / min to 0.1 mm / min from when the grindstone contacts the unpolished roller until it is polished to Φ9 mm, and the spark-out time (time at 0 mm cutting) is 5 seconds. A conductive elastic roller was prepared. The thickness of the elastic layer was adjusted to 1.5 mm. The crown amount of this roller was 100 μm.

(4. Preparation of coating solution for surface layer formation)
Methyl isobutyl ketone was added to a caprolactone-modified acrylic polyol solution “Placcel DC2016” (trade name, manufactured by Daicel Corporation) to adjust the solid content to 12% by mass. Four other kinds of materials shown in the column of component (1) in Table 9 below were added to 834 parts by mass of this solution (100 parts by mass of caprolactone-modified acrylic polyol solid content) to prepare a mixed solution. At this time, the blocked isocyanate mixture was such that the amount of isocyanate was “NCO / OH = 1.0”.

  Next, 188.5 g of the above mixed solution was put in a glass bottle having an internal volume of 450 mL together with 200 g of glass beads having an average particle diameter of 0.8 mm as a medium, and dispersed for 20 hours using a paint shaker disperser. After dispersion, 7.2 g of resin particles B1 were added. In addition, this is 40 mass parts equivalent amount of resin particle B1 with respect to 100 mass parts of caprolactone modified acrylic polyol solid content. Then, it was dispersed for 5 minutes, and the glass beads were removed to prepare a coating solution for the surface layer. The specific gravity of the coating solution was 0.9260. The specific gravity was measured by putting a commercially available hydrometer into the coating solution.

(5. Formation of surface layer)
The elastic roller was coated in the dipping method by immersing it in the surface layer coating solution with its longitudinal direction set to the vertical direction. The dipping time was 9 seconds, the pulling speed was 20 mm / s for the initial speed, 2 mm / s for the final speed, and the speed was changed linearly with respect to the time. The obtained coated material is air-dried at 23 ° C. for 30 minutes, and then dried by a hot air circulating dryer at a temperature of 80 ° C. for 1 hour and further at a temperature of 160 ° C. for 1 hour to cure the coating film, and the outer circumference of the elastic layer A charging roller D1 having a surface layer formed on the part was obtained. The film thickness of the surface layer was 5.6 μm. In addition, the film thickness of the surface layer was measured in the location where the resin particle does not exist.

[Production Examples D2 to D20]
Charging rollers D2 to D20 were produced in the same manner as in Production Example D1, except that the materials shown in Table 10 and Table 11 were changed. Tables 10 and 11 show the physical property values of the completed charging roller and the physical property values of the resin particles contained in the surface layer of the charging roller. The surface roughness (Rzjis and Rsm) of each charging roller is measured by the method described above.

<Example 1>
[1. Evaluation of banding image occurrence (Evaluation A)]
The charging roller D18 and the electrophotographic photosensitive member A1 were incorporated into an electrophotographic apparatus, and a durability test was performed in a low temperature and low humidity environment (temperature 15 ° C., relative humidity 10%). As an electrophotographic apparatus, a color laser jet printer manufactured by Canon Inc. (trade name: SateraLBP5400) was modified to a recording medium output speed of 200 mm / sec (A4 vertical output). Further, the spring used for the bearing of the charging roller was changed, and the charging roller was remodeled so as to contact the electrophotographic photosensitive member with a pressing force of 2.9 N at one end and 5.9 N at both ends. By reducing the contact pressure in this way, a situation where banding images are more likely to occur can be achieved. The resolution of the image is 600 dpi, and the primary charging output is a DC voltage of −1100V. The electrophotographic process cartridge for the printer was used as the electrophotographic process cartridge. The output image was a halftone image in which a horizontal line having a width of 1 dot and an interval of 2 dots was drawn in the direction perpendicular to the rotation direction of the electrophotographic photosensitive member. The output halftone image is visually checked for the presence or absence of streaks extending in the rotation direction of the electrophotographic photosensitive member, that is, in the direction perpendicular to the paper discharge direction and appearing in synchronization with the rotation cycle of the charging roller. Observed. And it evaluated on the following references | standards. The evaluation results are shown in Table 12.

Rank 1: No streak is recognized.
Rank 2: A slight streak is recognized.
Rank 3: streaks are noticeable.

[2. Evaluation of discharge strength in nip (Evaluation B)]
An ITO film having a thickness of 5 μm was formed on the surface of a glass plate (length 300 mm, width 240 mm, thickness 4.5 mm), and only a charge transport layer was formed thereon to a thickness of 17 μm. As shown in FIG. 9, from the surface side of the glass plate 22 after the film formation, a tool that can contact the charging roller 8 with a pressing force of a spring of 4.9 N at one end and a total of 9.8 N at both ends. Further, the glass plate 22 can be scanned at 200 mm / s. Using the glass plate 22 as an electrophotographic photosensitive member, a high speed gate I.D. from the lower side of the contact portion (the side opposite to the surface of the glass plate 22). I. The image was taken with a high-speed camera FASTCAM-SA1.1 (product name, manufactured by Hamamatsu Photonics) through a unit C9527-2 (product name, manufactured by Hamamatsu Photonics). The voltage applied to the charging roller 8 was a superimposed voltage of alternating current and direct current, the alternating voltage was peak peak voltage (Vpp) 1400V, the frequency (f) 1350 Hz, and the direct current voltage (Vdc) was −560V. The measurement environment was a low temperature and low humidity environment (temperature 15 ° C., relative humidity 10%).

  The shooting conditions are a shooting speed of 3000 fps and a shooting time of about 0.3 seconds. In photographing, the sensitivity was adjusted as appropriate, and the brightness of the photographed image was adjusted. And the image which averaged the obtained moving image was created. This image is referred to as an in-nip discharge image. Such in-nip discharge images were prepared for each of the initial stage and after the endurance test, and were compared and evaluated based on the following criteria. The evaluation results are shown in Table 12.

Rank 1: Even after endurance, the discharge intensity in the nip has not changed from the initial level.
Rank 2: After the endurance, the discharge intensity in the nip slightly changed compared to the initial stage.
Rank 3: After the endurance, the discharge intensity in the nip was greatly reduced compared to the initial stage.
Rank 4: No discharge occurred in the nip after the endurance.

<Examples 2-110>
With respect to the electrophotographic process cartridge shown in Table 12 in which the charging roller and the electrophotographic photosensitive member are combined, the banding image and the in-nip discharge strength were evaluated. The evaluation results are shown in Table 12.

<Comparative Example 1>
Except for changing the electrophotographic photosensitive member A1 to the electrophotographic photosensitive member A12, the banding image and the in-nip discharge intensity were evaluated for the electrophotographic process cartridge in the same manner as in Example 1. The evaluation results are shown in Table 13.

<Comparative Examples 2 to 64>
With respect to the electrophotographic process cartridge shown in Table 13 in which the charging roller and the electrophotographic photosensitive member are combined, the banding image and the discharge strength in the nip were evaluated. The evaluation results are shown in Table 13.

1. 1. Conductive substrate 2. Surface layer 3. Conductive elastic layer 4. Conductive adhesive layer 5. Resin composition in the surface layer Resin particles7. Hole 8 Charging roller 9. Cylindrical metal10. 10. Electrophotographic photosensitive member Latent image forming apparatus 12. Developing roller 13. Transfer roller 14. Transfer material 15. Cleaning member 16. Fixing device 17. 18. Center of gravity of resin particles 18. Projection vertex side region of resin particle 15. Virtual plane passing through the center of gravity of resin particles 21. The point moved from the center of gravity of the resin particle to the apex side of the convex portion by a distance of √3 / 2 times the radius. A virtual plane 22 parallel to the virtual plane 19 and passing through the point 20. Glass plate 23. Porous particles 24. Inner layer region 25. Outer layer region 26. Coating film 27. Solvent volatilization direction 28. Direction in which binder resin in coating film flows 29. Direction in which the binder resin in the coating film flows 30. Vacancy

Claims (9)

In an electrophotographic process cartridge having a charging member and an electrophotographic photosensitive member that is contact-charged by the charging member,
The charging member is
A conductive substrate and a surface layer formed on the conductive substrate;
The surface layer contains at least a binder resin, an electronic conductive agent, and resin particles having a plurality of pores therein, and the surface layer has a convex portion derived from the resin particles on the surface, And,
The electrophotographic photoreceptor has a support and a photosensitive layer formed on the support, and the surface layer of the electrophotographic photoreceptor comprises the following resin (1), resin (2) and compound (3). An electrophotographic process cartridge characterized by containing:
Resin (1): at least one resin selected from the group consisting of a polycarbonate resin having no siloxane structure at the terminal and a polyester resin having no siloxane structure at the terminal;
Resin (2): at least one resin selected from the group consisting of a polycarbonate resin having a siloxane structure at a terminal, a polyester resin having a siloxane structure at a terminal, and an acrylic resin having a siloxane structure at a terminal;
Compound (3): At least one compound selected from the group consisting of methyl benzoate, ethyl benzoate, benzyl acetate, ethyl 3-ethoxypropionate, and diethylene glycol ethyl methyl ether.   When the resin particles are assumed to be solid particles, the porosity of the resin particles in a region occupying 11% by volume of the solid particles and farthest from the conductive substrate is 5 volumes. The electrophotographic process cartridge according to claim 1, which is at least%. The process cartridge according to claim 1 or 2, wherein the polycarbonate resin having no siloxane structure at the terminal is a polycarbonate resin A having a structural unit represented by the following formula (A).

[In formula (A), R ^{21 to} R ²⁴ each independently represents a hydrogen atom or a methyl group. X ¹ represents a single bond, a cyclohexylidene group, or a divalent group having a structure represented by the following formula (C).

[In Formula (C), R ⁴¹ and R ⁴² each independently represent a hydrogen atom, a methyl group, or a phenyl group. ]]. The polycarbonate resin A is a polymer having only one structural unit selected from structural units represented by the following formulas (A-1) to (A-8), or a combination of any two or more structural units. The process cartridge according to claim 3, wherein the process cartridge is:

The process cartridge according to any one of claims 1 to 4, wherein the polyester resin having no siloxane structure at the terminal is a polyester resin B having a structural unit represented by the following formula (B).

[In Formula (B), R ^{31 to} R ³⁴ each independently represent a hydrogen atom or a methyl group. X ² represents a single bond, a cyclohexylidene group, or a divalent group having a structure represented by the following formula (C). Y ¹ represents an m-phenylene group, a p-phenylene group, or a divalent group in which two p-phenylene groups are bonded via an oxygen atom.

[In Formula (C), R ⁴¹ and R ⁴² each independently represent a hydrogen atom, a methyl group, or a phenyl group. ]]. The polyester resin B is a polymer having only one structural unit selected from structural units represented by the following formulas (B-1) to (B-9), or a combination of any two or more structural units. The process cartridge according to claim 5, wherein the process cartridge is:

The polycarbonate resin having a siloxane structure at the terminal is a polycarbonate resin A 'having a structural unit represented by the following formula (A') and a terminal structure represented by the following formula (D). The process cartridge according to one item:

[In Formula (A ′), R ^{25 to} R ²⁸ each independently represent a hydrogen atom or a methyl group. X ³ represents a single bond, a cyclohexylidene group, or a divalent group having a structure represented by the following formula (C ′).

[In formula (C ′), R ⁴³ and R ⁴⁴ each independently represents a hydrogen atom, a methyl group, or a phenyl group. ]],

[In the formula (D), a and b represent the number of repeating structural units in parentheses, the average value of a is 20 or more and 100 or less, and the average value of b is 1 or more and 10 or less. ]. The polyester resin having a siloxane structure at the terminal is a polyester resin B 'having a structural unit represented by the following formula (B') and a terminal structure represented by the following formula (D). The process cartridge according to one item:

[In Formula (B ′), R ^{35 to} R ³⁸ each independently represent a hydrogen atom or a methyl group. X ⁴ represents a single bond, a cyclohexylidene group, or a divalent group having a structure represented by the following formula (C ′). Y ² represents an m-phenylene group, a p-phenylene group, or a divalent group in which two p-phenylene groups are bonded through an oxygen atom.

[In formula (C ′), R ⁴³ and R ⁴⁴ each independently represents a hydrogen atom, a methyl group, or a phenyl group. ]],

[In the formula (D), a and b represent the number of repeating structural units in parentheses, the average value of a is 20 or more and 100 or less, and the average value of b is 1 or more and 10 or less. ].   An electrophotographic apparatus in which the electrophotographic process cartridge according to claim 1 is mounted.

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