Electrophotographic photoreceptor, electrophotographic photoreceptor cartridge, and image forming apparatus

Abstract

Disclosed is an electrophotographic photoreceptor which comprises at least a photosensitive layer on a conductive support. The outermost surface layer of the electrophotographic photoreceptor contains a polymer which comprises a constituent unit (A) that has a silicone structure and a constituent unit (B) that has a charge transporting structure, wherein the constituent unit (A) that has a silicone structure includes a structure represented by formula (1). (In formula (1), X1 to X4 each independently represent an alkylene group having 1 to 3 carbon atoms, which may be ethylene oxide-modified or propylene oxide-modified. Each of R1 to R4 independently represents a hydrogen atom or a bond group that is bonded with another constituent unit. Each of n1 and n2 is an integer of 1 or more. When n2 is an integer of 2 or more, the two or more R1, two or more R2, two or more X1, and two or more X2 may be the same as or different from each other, respectively. At least one of R1 and R2 is a bond group that is bonded with another constituent unit. The chain of the structure to which n1 and n2 are attached may be a random chain or a block chain.)

Description

Electrophotographic photoreceptor, electrophotographic photoreceptor cartridge and image forming apparatus

[0001] The present invention relates to an electrophotographic photoreceptor used in a copying machine, a printer, etc., and a cartridge and an image forming apparatus using the same.

[0002] In printers and copiers, when a charged organic photoconductor (OPC) drum is irradiated with light, the part is discharged, an electrostatic latent image is formed, and an image is obtained by attaching toner to the electrostatic latent image. In such devices that use electrophotography, the photoconductor is a key component.

[0003] Because this type of organic photoreceptor offers a wide range of material options and allows for easy control of photoreceptor properties, "function-separated photoreceptors," in which the functions of negative charge generation and transport are shared by separate compounds, have become mainstream. For example, known electrophotographic photoreceptors include a single-layer electrophotographic photoreceptor (hereinafter referred to as a single-layer photoreceptor) that contains a charge generation material (CGM) and a charge transport material (CTM) in the same layer, and a multi-layer electrophotographic photoreceptor (hereinafter referred to as a multi-layer photoreceptor) that comprises a charge generation layer containing a charge generation material (CGM) and a charge transport layer containing a charge transport material (CTM). Furthermore, photoreceptor charging methods include a negative charging method in which the photoreceptor surface is negatively charged, and a positive charging method in which the photoreceptor surface is positively charged. Currently available photoreceptor layer configuration and charging method combinations include a "negatively charged multi-layer photoreceptor" and a "positively charged single-layer photoreceptor."

[0004] A "negatively charged laminated photoreceptor" generally has a configuration in which an undercoat layer (UCL) made of a resin or the like is provided on a conductive support such as an aluminum tube, on which a charge generation layer (CGL) made of a charge generation material (CGM) and a resin or the like is provided, and on which a charge transport layer (CTL) made of a hole transport material (HTM) and a resin or the like is provided.

[0005] On the other hand, a "positively charged single-layer photoreceptor" generally has a configuration in which an undercoat layer (UCL) made of a resin or the like is provided on a conductive support such as an aluminum tube, and a single-layer photosensitive layer made of a charge generating material (CGM), a hole transport material (HTM), an electron transport material (ETM), and a resin or the like is provided thereon (see, for example, Patent Document 1).

[0006] In either case, the surface of the photoreceptor is first charged using corona discharge or contact, and then the photoreceptor is exposed to light to neutralize the surface charge, forming an electrostatic latent image due to the potential difference with the surrounding surface. Toner is then brought into contact with the photoreceptor surface to form a toner image corresponding to the electrostatic latent image, which is then transferred to paper or other media and heated to fuse and fix to create a print.

[0007] As described above, the basic structure of an electrophotographic photoreceptor is a photosensitive layer formed on a conductive support, but in order to improve wear resistance, etc., a protective layer is provided on the photosensitive layer.

[0008] As a technique for improving the mechanical strength or abrasion resistance of the surface of a photoreceptor, a photoreceptor has been disclosed in which a layer containing a compound having a chain-polymerizable functional group, i.e., a curable resin compound, is formed as a binder resin in the outermost layer of the photoreceptor, and this is polymerized by applying energy such as heat, light, or radiation to form a cured resin layer (protective layer) (see, for example, Patent Documents 1 and 2).

[0009] In recent years, there has been an increasing demand for improved lifespan, i.e., improved wear resistance, especially for photoreceptors used in multifunction printers, in order to reduce maintenance costs. To improve wear resistance, it is known to form a layer called a protective layer (also referred to as an "OCL") on the photosensitive layer. To improve slipperiness, a surface modifier such as a silicone polymer may be added to these protective layers. By providing slipperiness, it is possible to suppress squealing caused by the blade as a cleaning means and to prevent chipping of the blade due to load on the blade, resulting in poor image quality.

[0010] For example, Patent Documents 3 and 4 disclose the use of a linear silicone polymer having a polymerizable functional group as a surface modifier added to a protective layer. The greater the amount of surface modifier added to the protective layer, the more effective the function and the longer the durability. On the other hand, adding a large amount of surface modifier can lead to problems such as poor application properties, resulting in repellency and uneven application. To prevent these problems, particularly when a polymerizable compound is used as a protective layer forming material and the protective layer is formed by curing, it is necessary to also add metal oxide particles surface-treated with a compound having a polymerizable functional group. Furthermore, the use of a side-chain silicone polymer as a surface modifier has also been disclosed, but in this case, the aforementioned metal oxide particles also needed to be added (Patent Document 5).

[0011] US Patent No. 9417538 International Publication No. WO 2010 / 035683 JP 2011-170129 A JP 2010-107696 A JP 2014-145891 A

[0012] In general, metal oxide particles are difficult to dissolve in a coating solution for forming a protective layer and may precipitate, so the inclusion of metal oxide particles is undesirable from the viewpoint of the storage stability of the coating solution. Therefore, there is a demand for a method for continuously improving the lubricity of the surface of a photoreceptor by using a polymerizable compound and a surface modifier as materials for forming the outermost layer of the photoreceptor without using metal oxide particles.

[0013] An object of the present invention is to provide an electrophotographic photoreceptor that can solve the above problems.

[0014] The present inventors have found that the above-mentioned problems can be solved by an electrophotographic photoreceptor that includes at least a photosensitive layer on a conductive support, in which the outermost surface layer contains a polymer that includes a structural unit having a specific silicone structure and a structural unit having a charge transport structure.

[0015] The gist of the present invention resides in the following [1] to

[11] .

[0016] [1] An electrophotographic photoreceptor including at least a photosensitive layer on a conductive support, wherein the outermost layer contains a polymer including a structural unit (A) having a silicone structure and a structural unit (B) having a charge transport structure, and the structural unit (A) having a silicone structure includes a structure represented by the following formula (1):

[0017]

[0018] (In formula (1), X １ ~X ４ R each independently represents an alkylene group having 1 to 3 carbon atoms which may be modified with ethylene oxide or propylene oxide. １ ~R ４ Each independently represents a hydrogen atom or a bonding group to another structural unit. １ , n ２ are each an integer of 1 or greater. ２ is an integer of 2 or more, there are two or more R １ , R ２ , X １ , X ２ may be the same or different. １ , R ２ At least one of n is a bonding group to another structural unit. １ , n ２ The linkage of the structures marked with may be random or block.)

[0019] [2] The electrophotographic photoreceptor according to [1], wherein the charge transporting structure includes at least one structure selected from the group consisting of a heterocyclic structure selected from the group consisting of carbazole, indole, imidazole, oxazole, pyrazole, thiadiazole, and benzofuran, and a hydrazone structure, an arylamine structure, a stilbene structure, a butadiene structure, and an enamine structure.

[0020] [3] The electrophotographic photoreceptor according to [1] or [2], wherein the structural unit (B) having a charge transport structure has a structure represented by the following formula (2):

[0021]

[0022] (In formula (2), Ar ４１ ~Ar ４３ are each independently a divalent aromatic group. ４１ ~R ４３ are each independently a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a halogenated alkyl group, a halogen atom, a benzyl group, or a bonding group to another structural unit. ４１ Comrade, R ４２ Comrade, R ４３ are bonded to each other to form Ar ４１ , Ar ４２ , Ar ４３ may form a ring fused to the aromatic ring of ４１ ~n ４３ are each independently an integer of 1 or more, and n ４１ ~n ４３ Two selected from among n are 1. ４１ ~n ４３ If is 1, R ４１ ~R ４３ is a bonding group to other structural units. ４１ is an integer of 2 or more, there are two or more R ４１ may be the same or different, but at least one of them is a bonding group to another structural unit. ４２ is an integer of 2 or more, there are two or more R ４２ may be the same or different. ４３ is an integer of 2 or more, there are two or more R ４３ may be the same or different.)

[0023] [4] The electrophotographic photoreceptor according to [3], wherein the bonding group to another structural unit in the formula (2) has a structure represented by the following formula (3):

[0024]

[0025] (In formula (3), R ５１ represents a hydrogen atom or a methyl group. ５２ , R ５３ R each independently represents a hydrogen atom, a hydrocarbon group, or an alkoxy group. ５４represents a single bond or an oxygen atom. ５１ represents an integer of 0 to 10. ２ is Ar in the formula (2). ４１ ~Ar ４３ indicates the bond with

[0026] [5] The electrophotographic photoreceptor according to any one of [1] to [4], wherein the bonding group to the other structural unit in the formula (1) includes the following formula (1a) or the following formula (1b):

[0027]

[0028] (In formula (1a) and formula (1b), * represents X in formula (1) １ ~X ４ indicates the bond with

[0029] [6] The electrophotographic photoreceptor according to any one of [1] to [5], wherein the functional group equivalent of the bonding group to the other structural unit in the formula (1) is 4000 g / eq or less.

[0030] [7] The electrophotographic photoreceptor according to any one of [1] to [6], wherein the structural unit having the structure represented by the formula (1) has a structure represented by the following formula (1A):

[0031]

[0032] (In formula (1A), X １ , X ２ , R １ , R ２ , n １ , n ２ are X in the formula (1), respectively. １ , X ２ , R １ , R ２ , n １ , n ２ is synonymous with

[0033] [8] The electrophotographic photoreceptor according to any one of [1] to [7], wherein the polymer further contains a structural unit (C) other than the structural unit (A) having the silicone structure and the structural unit (B) having the charge transport structure, and the structural unit (C) has a structure derived from at least one selected from the group consisting of an acryloyl group, a methacryloyl group, a vinyl group, and an epoxy group.

[0034] [9] The electrophotographic photoreceptor according to any one of [1] to [8], wherein a protective layer is provided on the photosensitive layer, and the outermost surface layer is the protective layer.

[0035]

[10] An electrophotographic photoreceptor cartridge having the electrophotographic photoreceptor according to any one of [1] to [9].

[0036]

[11] An image forming apparatus having the electrophotographic photoreceptor according to any one of [1] to [9].

[0037] The electrophotographic photoreceptor of the present invention can continuously improve the lubricity of the surface of the photoreceptor without using metal oxide particles.

[0038] Fig. 1 is a diagram showing an example of the configuration of an image forming apparatus that can be constructed using an electrophotographic photoreceptor according to an example of the present invention. Fig. 2 is a schematic diagram showing a method for measuring frictional force in Examples.

[0039] The following describes in detail the mode for carrying out the present invention (hereinafter, "embodiments of the invention"). The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

[0040] <<Present Electrophotographic Photoreceptor>> An electrophotographic photoreceptor according to one example of the embodiment of the present invention (also referred to as “present electrophotographic photoreceptor”) is an electrophotographic photoreceptor including at least a photosensitive layer on a conductive support, in which the outermost layer contains a polymer (also referred to as “present polymer”) including a structural unit (A) having a silicone structure and a structural unit (B) having a charge transport structure, and the structural unit (A) having a silicone structure has a structure represented by the following formula (1):

[0041]

[0042] (In formula (1), X １ ~X ４ R each independently represents an alkylene group having 1 to 3 carbon atoms which may be modified with ethylene oxide or propylene oxide. １ ~R ４ Each independently represents a hydrogen atom or a bonding group to another structural unit. １ , n ２ are each an integer of 1 or greater. ２ is an integer of 2 or more, there are two or more R １ , R ２ , X １ , X ２ may be the same or different. １ , R ２ At least one of n is a bonding group to another structural unit. １ , n ２ The linkage of the structures marked with may be random or block.)

[0043] The present electrophotographic photoreceptor preferably has a protective layer on the photosensitive layer from the viewpoint of increasing the mechanical strength or abrasion resistance of the photoreceptor surface. The present electrophotographic photoreceptor may optionally have layers other than the photosensitive layer and the protective layer. The charging method of the present electrophotographic photoreceptor may be either a negative charging method in which the photoreceptor surface is negatively charged, or a positive charging method in which the photoreceptor surface is positively charged. The layer forming the outermost surface layer of the present electrophotographic photoreceptor is preferably a charge transport layer in a multilayer photoreceptor, a photosensitive layer in a single-layer photoreceptor, or a protective layer in both photoreceptors.

[0044] In the present electrophotographic photoreceptor, the side opposite to the conductive support is the upper side or front side, and the conductive support side is the lower side or back side.

[0045] <Outermost Surface Layer> The outermost surface layer (also simply referred to as the "outermost surface layer") of the present electrophotographic photoreceptor contains the present polymer, which includes a structural unit (A) having a silicone structure represented by the formula (1) above and a structural unit (B) having a charge transport structure. The present polymer contains, for example, a charge transport compound having two or more polymerizable functional groups that serves as a binder resin, and a specific silicone compound, and can be formed from a composition containing a polymerizable compound other than the charge transport compound and the silicone compound, a polymerization initiator, inorganic particles, and other materials, as necessary. However, the present polymer is not limited to being formed from such a composition.

[0046] When the electrophotographic photoreceptor has a protective layer, the protective layer (also referred to as "the present protective layer") is preferably the outermost layer, i.e., the outermost layer located on the opposite side from the conductive support, from the viewpoint of better obtaining the effects of the present invention. However, the effects of the present invention can be obtained even if the present protective layer is not necessarily the outermost layer.

[0047] (Structural Unit (A) Having a Silicone Structure) The electrophotographic photoreceptor contains a polymer in the outermost layer, and the polymer has a structural unit (A) having a silicone structure represented by the following formula (1).

[0048]

[0049] (In formula (1), X １ ~X ４ R each independently represents an alkylene group having 1 to 3 carbon atoms which may be modified with ethylene oxide or propylene oxide. １ ~R ４ Each independently represents a hydrogen atom or a bonding group to another structural unit. １ , n ２ are each an integer of 1 or greater. ２ is an integer of 2 or more, there are two or more R １ , R ２ , X １ , X ２ may be the same or different. １ , R ２At least one of n is a bonding group to another structural unit. １ , n ２ The linkage of the structures marked with may be random or block.)

[0050] The reason why the inclusion of the structural unit (A) in the outermost layer provides a sustained effect of slippage is thought to be as follows: Generally, when a linear polydimethylsiloxane is used in the layer forming the outermost surface of an electrophotographic photoreceptor, the polydimethylsiloxane segregates on the surface of the photoreceptor due to low surface free energy. Conventionally, terminal reactive group types used have a small number of functional groups, so film strength is not achieved, and the polydimethylsiloxane segregated on the surface is worn away by printing durability (repeated printing), making it impossible to sustain slippage. However, when a bonding group R derived from a polymerizable functional group is attached to a side chain of the polydimethylsiloxane main chain, as in the structural unit (A), １ and / or R ２ By introducing the above, compatibility with other components is improved and segregation is alleviated compared to conventional terminal reactive group types having polymerizable functional groups only at the ends of the polydimethylsiloxane main chain, and the polydimethylsiloxane main chain is more likely to exist in the depths of the layer that forms the outermost surface, making it easier for the lubricity to be maintained even after wear. １ and / or R ２ By introducing this, it is possible to increase the number of polymerizable functional groups compared to conventional terminal reactive group types, which results in improved film strength, reduced loss of silicone structure due to wear, and maintained slipperiness.

[0051] The number of bonding groups to other structural units in the formula (1) may be 1 or more, preferably 3 or more, more preferably 5 or more, and even more preferably 10 or more. On the other hand, there is no particular upper limit on the number of bonding groups to other structural units, but it is usually 1,000 or less.

[0052] In addition, in the formula (1), the functional group equivalent of the bonding group to other structural units is preferably 4000 g / eq or less, more preferably 3000 g / eq or less, even more preferably 2000 g / eq or less, and particularly preferably 1000 g / eq or less, from the viewpoint of improving coating strength. On the other hand, the lower limit of this functional group equivalent is preferably 200 g / eq or more, more preferably 400 g / eq or more, even more preferably 600 g / eq or more, and particularly preferably 800 g / eq or more, from the viewpoint of proper segregation of the structural unit (A) having a silicone structure to the surface of the photoreceptor. The above-mentioned preferred upper and lower limits can be arbitrarily combined. The functional group equivalent is as described below.

[0053] The bonding group to other structural units in the formula (1) is not particularly limited, but is preferably a structure containing an acryloyl group or a methacryloyl group, and is preferably a structure represented by the following formula (1a) or (1b), and from the viewpoints of curing speed and compatibility with other structural components, a structure containing the following formula (1b) is more preferred.

[0054]

[0055] (In formula (1a) and formula (1b), * represents X in formula (1) １ ~X ４ indicates the bond with

[0056] A specific example of the structure represented by the formula (1) is a structure represented by the following formula (1A).

[0057]

[0058] (In formula (1A), X １ , X ２ , R １ , R ２ , n １ , n ２ are X in the formula (1), respectively. １ , X ２ , R １ , R ２ , n １ , n ２ It is agreed that

[0059] X in the formulas (1) and (1A) １, X ２ each independently represents an alkylene group having 1 to 3 carbon atoms, which may be modified with ethylene oxide or propylene oxide. Of these, from the viewpoint of improving sliding performance, ethylene oxide-modified or unmodified groups are preferred, and unmodified groups are more preferred. Examples of the alkylene group include a methylene group, an ethylene group, and an n-propylene group. Of these, a methylene group and an n-propylene group are preferred, and a methylene group is more preferred.

[0060] The R １ , R ２ each independently represents a hydrogen atom or a bonding group to another structural unit. Among them, from the viewpoint of curing rate and compatibility, a group derived from an acryloyloxy group represented by formula (1a) or a group derived from a methacryloyloxy group represented by formula (1b) is preferred, and a group derived from a methacryloyloxy group is more preferred.

[0061] The n １ , n ２ are integers of 1 or more. １ is preferably 1 or more and 1000 or less, and more preferably 10 or more and 500 or less. ２ is preferably 1 or more and 1000 or less, and more preferably 10 or more and 500 or less. １ , n ２ The chain of the structure marked with may be random or block, but is preferably random from the viewpoint of obtaining a uniform crosslinked structure.

[0062] The structure represented by the formula (1) having a bonding group to another structural unit on a side chain of a polydimethylsiloxane main chain can be obtained, for example, by polymerizing a composition containing, as a surface modifier, a silicone compound having a main chain with a repeating unit of a dimethylsiloxane structure and a side chain with a polymerizable functional group (also referred to as the present silicone compound).

[0063] The polymerizable functional group of the silicone compound is not particularly limited, but is preferably an acryloyloxy group or a methacryloyloxy group, and from the viewpoint of curing speed and compatibility, a methacryloyloxy group is more preferred.In addition, when the polymerizable functional group is a methacryloyloxy group, it is preferably trifunctional or more in order to improve crosslink density, and the polymerizable functional group is attached to the side chain of the main chain rather than both ends of the main chain, and exhibits good properties.The dimethylsiloxane structure can be a straight chain type, a branched chain type, a cage type, etc., but from the viewpoint of maintaining slipperiness, a straight chain type is preferred.

[0064] The number of polymerizable functional groups possessed by the present silicone compound may be 1 or more, preferably 3 or more, more preferably 5 or more, and even more preferably 10 or more. On the other hand, there is no particular upper limit to the number of polymerizable functional groups, but it is usually 1,000 or less.

[0065] Furthermore, the functional group equivalent of the polymerizable functional group of the present silicone compound is preferably 4000 g / eq or less, more preferably 3000 g / eq or less, even more preferably 2000 g / eq or less, and particularly preferably 1000 g / eq or less, from the viewpoint of improving the coating strength. On the other hand, the lower limit of this functional group equivalent is preferably 200 g / eq or more, more preferably 400 g / eq or more, even more preferably 600 g / eq or more, and particularly preferably 800 g / eq or more, from the viewpoint of appropriate segregation of the structural unit (A) derived from the present silicone compound to the surface of the photoreceptor. The above-mentioned preferred upper and lower limits can be arbitrarily combined.

[0066] In this specification, the functional group equivalent of a polymerizable functional group refers to the molecular weight of a silicone compound per polymerizable functional group, and the functional group equivalent of a polymerizable functional group corresponds to the functional group equivalent of the bonding group to other structural units in formula (1). The functional group equivalent of a polymerizable functional group can be determined using various analytical instruments such as infrared spectroscopy and nuclear magnetic resonance spectroscopy. In addition, when the present silicone compound is synthesized by introducing a polymerizable functional group into a commercially available polydimethylsiloxane, the functional group equivalent of the present silicone compound can also be calculated based on the functional group equivalent of the organic group bonded to the polymerizable functional group possessed by the polydimethylsiloxane raw material. When all of the organic groups are used to bond to the polymerizable functional group, the functional group equivalent of the organic group of the polydimethylsiloxane raw material can be considered as the functional group equivalent of the present silicone compound.

[0067] Specific examples of the present silicone compound include compounds having a structure represented by the following formula (1B).

[0068]

[0069] (In formula (1B), X １ , X ２ , n １ , n ２ R has the same meaning as in the formula (1) and formula (1A). １１ , R １２ each independently represents a hydrogen atom, an acryloyloxy group, or a methacryloyloxy group. ２ is an integer of 2 or more, there are two or more R １１ , R １２ may be the same or different, but R １１ , R １２ At least one of the groups is an acryloyloxy group or a methacryloyloxy group.

[0070] X in the formula (1B) １ , X ２ , n １ , n ２ Regarding X in the formulas (1) and (1A), １ , X ２ , n １ , n ２The same applies to the preferred examples of the R １１ , R １２ each independently represents a hydrogen atom, an acryloyloxy group, or a methacryloyloxy group. Among these, from the viewpoints of curing speed and compatibility, an acryloyloxy group or a methacryloyloxy group is preferred, and a methacryloyloxy group is more preferred.

[0071] The silicone compound used in the present invention, which has a main chain with a repeating unit of a dimethylsiloxane structure and a side chain with a polymerizable functional group, is not commercially available, and has been newly synthesized in the present invention by the method described below. An example of a method for synthesizing the silicone polymer is given below, but the method for synthesizing the silicone compound is not limited to the method described below.

[0072] A 50 mL two-neck flask equipped with a stirrer and condenser is charged with 10.0 g of a polydimethylsiloxane having hydroxyl groups on the side chains, such as "X-22-4039" manufactured by Shin-Etsu Chemical Co., Ltd., and 10.0 g of methylene chloride, and stirred until uniformly dissolved. The reaction solution is cooled to 0°C on an ice bath while stirring, and 1.3 g of methacrylic acid chloride is added dropwise using a syringe. The mixture is then stirred at room temperature for 3 hours. The reaction slurry solution in which triethylamine hydrochloride has precipitated is filtered using a Kiriyama funnel, and the salt is washed off with 20 g of methylene chloride. The resulting mixture is purified directly by silica gel column chromatography (hexane / ethyl acetate = 50 / 50) to obtain 10 g of this silicone compound having polymerizable functional groups on the side chains.

[0073] In the present invention, the present silicone compound having a repeating unit of a dimethylsiloxane structure in the main chain and a polymerizable functional group in the side chain may be used alone or in combination of two or more types.

[0074] The content of the present silicone compound in the outermost surface layer is preferably 0.03 mass% or more and 3.00 mass% or less, more preferably 0.30 mass% or more and 1.00 mass% or less, from the viewpoint of the balance between slipperiness and other properties.The content of the present silicone compound corresponds to the content of the structural unit (A) derived from the present silicone compound, which is introduced into the polymer contained in the outermost surface layer by polymerization reaction, and this content usually corresponds to the content of the present silicone compound relative to the total mass of the solid content in the coating liquid for forming the outermost surface layer.The same applies to the content of the charge transport compound having a polymerizable functional group and the content of the polymerizable compound not having a charge transport structure, which will be described later.

[0075] (Structural Unit (B) Having Charge-Transporting Structure) The present polymer contained in the outermost layer of the present electrophotographic photoreceptor contains a structural unit (B) having a charge-transporting structure. The structural unit (B) having a charge-transporting structure in the present polymer can be obtained, for example, by polymerizing a composition containing a charge-transporting compound having a polymerizable functional group.

[0076] Examples of the polymerizable functional group of the charge transport compound having a polymerizable functional group that forms the structural unit (B) having a charge transport structure contained in the protective layer include an acryloyl group (including an acryloyloxy group), a methacryloyl group (including a methacryloyloxy group), a vinyl group, and an epoxy group. Among these, an acryloyl group or a methacryloyl group is preferred from the viewpoint of curability.

[0077] Here, in the present invention, from the viewpoint of slipperiness and film formation, the number of polymerizable functional groups in the charge transport compound having a polymerizable functional group is preferably 2 or more. From the viewpoint of reaction with the silicone compound having the above-mentioned polymerizable functional group, the number of polymerizable functional groups in the charge transport compound may be 1. However, in a curable compound having 1 polymerizable functional group, the film shrinkage that occurs during curing tends to be anisotropic, making it difficult to successfully form a film as the outermost surface layer. In particular, when a charge transport compound having a polymerizable functional group is mainly used as in the present invention, from the viewpoint of film formation, the number of polymerizable functional groups in the charge transport compound having a polymerizable functional group is preferably 2 or more. Note that the number of polymerizable functional groups may be 2 or more, but from the viewpoint of solubility, it is usually 2 or more and 10 or less.

[0078] The structure of the portion having charge transport capability of the charge transport compound having a polymerizable functional group, i.e., the charge transport structure of the structural unit (B) having a charge transport structure, preferably includes at least one selected from the group consisting of heterocyclic structures such as carbazole, indole, imidazole, oxazole, pyrazole, thiadiazole, and benzofuran, hydrazone structures, arylamine structures, stilbene structures, butadiene structures, and enamine structures. Also included are structures in which multiple types of these structures are bonded together, and structures derived from electron-donating substances such as polymers having groups containing these structures in the main chain or side chain. Among these, from the viewpoint of electrical properties, carbazole structures, arylamine structures, stilbene structures, butadiene structures, and enamine structures, as well as structures derived from multiple types of these structures are preferred, with arylamine structures being more preferred. Among the arylamine structures, triarylamine structures are preferred.

[0079] The charge transporting compound having two or more polymerizable functional groups is preferably a compound represented by the following formula (4).

[0080]

[0081] (In formula (4), Ar ４１ ~Ar ４３ are each independently a divalent aromatic group. ６１ ~R６３ are each independently a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a halogenated alkyl group, a halogen atom, a benzyl group, or a group represented by the following formula (5): ６１ Comrade, R ６２ Comrade, R ６３ are bonded to each other to form Ar ４１ , Ar ４２ , Ar ４３ may form a ring fused to the aromatic ring of ４１ ~n ４３ are each independently an integer of 1 or more, and n ４１ ~n ４３ Two selected from among n are 1. ４１ ~n ４３ If is 1, R ６１ ~R ６３ is a group represented by formula (5). ４１ is an integer of 2 or more, there are two or more R ６１ may be the same or different, but at least one of them is a group represented by the following formula (5): ４２ is an integer of 2 or more, there are two or more R ６２ may be the same or different. ４３ is an integer of 2 or more, there are two or more R ６３ may be the same or different.)

[0082]

[0083] (In formula (5), R ５１ represents a hydrogen atom or a methyl group. ５２ , R ５３ R each independently represents a hydrogen atom, a hydrocarbon group, or an alkoxy group. ５４ represents a single bond or an oxygen atom. ５１ represents an integer of 0 to 10. ２ is Ar in the formula (4). ４１ ~Ar ４３ indicates the bond with

[0084] Ar in formula (4) ４１ ~Ar ４３Examples of the divalent aromatic group include arylene groups such as a phenylene group and a naphthylene group, and heteroarylene groups, and are preferably a phenylene group, a naphthylene group, etc., and more preferably a phenylene group. ６１ ~R ６３ The groups each independently include an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group such as a phenyl group or a naphthyl group, a halogenated alkyl group, a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom, and a benzyl group, and are preferably an alkyl group having 1 to 20 carbon atoms.

[0085] R in formula (5) ５２ , R ５３ The hydrocarbon groups are each independently an alkyl group having 1 to 10 carbon atoms.

[0086] Examples of compounds represented by formula (4) are shown below, but the charge transporting compound having two or more polymerizable functional groups used in the present invention is not limited to the following example compounds.

[0087]

[0088] Among the above compounds, from the viewpoint of electrical properties, compounds represented by formula (4-1), formula (4-2), formula (4-3), formula (4-4), formula (4-6), formula (4-7), and formula (4-10) are preferred, compounds represented by formula (4-1), formula (4-2), formula (4-3), and formula (4-10) are more preferred, and compounds represented by formula (4-2) or formula (4-10) are even more preferred.

[0089] The charge transporting compound having a polymerizable functional group may be used alone or in combination of two or more.

[0090] When the outermost layer is a photosensitive layer, the content of the charge transport compound having a polymerizable functional group in the outermost layer is preferably 60 parts by mass or more, particularly 70 parts by mass or more, and especially 80 parts by mass or more, relative to 100 parts by mass of the total mass of the outermost layer of the electrophotographic photosensitive member. When the content of the charge transport compound having a polymerizable functional group is equal to or greater than the above-mentioned lower limit, the mechanical strength and charge transport properties of the photosensitive member surface are improved. On the other hand, from the viewpoint of film-formability, the content of the charge transport compound having a polymerizable functional group is preferably equal to or less than 95 parts by mass, particularly 90 parts by mass or less, relative to 100 parts by mass of the total mass of the outermost layer of the electrophotographic photosensitive member. When the outermost layer is a photosensitive layer, the content of the charge transport compound having a polymerizable functional group in the outermost layer is preferably equal to or greater than 5 parts by mass, particularly 10 parts by mass or more, and especially 20 parts by mass or more, relative to 100 parts by mass of the total mass of the outermost layer of the electrophotographic photosensitive member. When the content of the charge transport compound having a polymerizable functional group is equal to or greater than the above-mentioned lower limit, the mechanical strength and charge transport properties of the photosensitive member surface are improved. On the other hand, from the viewpoint of film-forming properties, the content of the charge transport compound having a polymerizable functional group is preferably 50 parts by mass or less, particularly 40 parts by mass or less, relative to 100 parts by mass of the total mass of the outermost layer of the electrophotographic photosensitive member. The content of the charge transport compound having a polymerizable functional group corresponds to the content of the structural unit (B) having a charge transport structure in the polymer, and this content usually corresponds to the content of the charge transport compound having a polymerizable functional group relative to the total mass of the solids of the outermost layer-forming composition for forming the outermost layer.

[0091] A preferred charge transport structure in the structural unit (B) having a charge transport structure is the same as the structure of the portion having charge transport ability in the charge transport compound having the polymerizable functional group described above. Also, a preferred example of the structural unit (B) having a charge transport structure is a structure having a bonding group to another structural unit in place of the group represented by formula (5) in formula (4).

[0092] That is, the structural unit (B) having the charge-transporting structure preferably has a structure represented by the following formula (2), and the bonding group to other structural units in the following formula (2) preferably has a structure represented by the following formula (3):

[0093]

[0094] (In formula (2), Ar ４１ ~Ar ４３ are each independently a divalent aromatic group. ４１ ~R ４３ are each independently a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a halogenated alkyl group, a halogen atom, a benzyl group, or a bonding group to another structural unit. ４１ Comrade, R ４２ Comrade, R ４３ are bonded to each other to form Ar ４１ , Ar ４２ , Ar ４３ may form a ring fused to the aromatic ring of ４１ ~n ４３ are each independently an integer of 1 or more, and n ４１ ~n ４３ Two selected from among n are 1. ４１ ~n ４３ If is 1, R ４１ ~R ４３ is a bonding group to other structural units. ４１ is an integer of 2 or more, there are two or more R ４１ may be the same or different, but at least one of them is a bonding group to another structural unit. ４２ is an integer of 2 or more, there are two or more R ４２ may be the same or different. ４３ is an integer of 2 or more, there are two or more R ４３ may be the same or different.)

[0095]

[0096] (In formula (3), R ５１ represents a hydrogen atom or a methyl group. ５２ , R ５３ R each independently represents a hydrogen atom, a hydrocarbon group, or an alkoxy group. ５４ represents a single bond or an oxygen atom. ５１ represents an integer of 0 to 10. ２is Ar in the formula (2). ４１ ~Ar ４３ indicates the bond with

[0097] Ar in formula (2) ４１ ~Ar ４３ , n ４１ ~n ４３ are Ar in formula (4), respectively. ４１ ~Ar ４３ , n ４１ ~n ４３ The same applies to the preferred examples. ４１ ~R ４３ is R in formula (4) ６１ ~R ６３ R in formula (3) is preferred. ５１ ~R ５４ , n ５１ are R in formula (5), respectively. ５１ ~R ５４ , n ５１ The same applies to the preferred ones.

[0098] (Structural Unit (C)) The present polymer contained in the outermost layer of the present electrophotographic photoreceptor can contain a structural unit (C) other than the structural unit (A) having the silicone structure and the structural unit (B) having the charge transport structure. The present polymer preferably further contains the structural unit (C), thereby improving the mechanical strength and film-forming properties of the outermost layer. The structural unit (C) preferably has a structure derived from at least one selected from the group consisting of an acryloyl group, a methacryloyl group, a vinyl group, and an epoxy group. The structural unit (C) in the present polymer can be obtained, for example, by polymerizing an outermost layer-forming composition containing the above-mentioned silicone compound and a charge transport compound having a polymerizable functional group, as well as a polymerizable compound not having a charge transport structure, as described below.

[0099] Examples of the polymerizable compound having no charge transport structure that is used to form the structural unit (C) include curable compounds such as photocurable compounds, heat-curable compounds, and radiation-curable compounds. Of these, photocurable compounds are preferred from the viewpoint of improving abrasion resistance.

[0100] The curable compound is preferably, for example, a compound having a polymerizable functional group. From the viewpoint of reactivity, the compound having a polymerizable functional group usually has two or more, preferably three or more, more preferably four or more polymerizable functional groups, and on the other hand, usually has 20 or less, preferably 10 or less, more preferably 6 or less polymerizable functional groups.

[0101] Examples of the polymerizable functional group of the compound having the polymerizable functional group include an acryloyl group, a methacryloyl group, a vinyl group, and an epoxy group. Among them, examples of the polymerizable functional group capable of radical polymerization include an acryloyl group, a methacryloyl group, and a vinyl group, and from the viewpoint of curing speed, an acryloyl group and a methacryloyl group are preferred. The polymerizable compound not having a charge transport structure is not particularly limited as long as it is a known material, but from the viewpoint of curing property, a monomer, oligomer, or polymer having an acryloyl group or a methacryloyl group is preferred.

[0102] Preferred examples of the polymerizable compound not having a charge transport structure are given below. Examples of monomers having an acryloyl group or a methacryloyl group include trimethylolpropane triacrylate (A-TMPT), trimethylolpropane trimethacrylate, HPA-modified trimethylolpropane triacrylate, EO-modified trimethylolpropane triacrylate, PO-modified trimethylolpropane triacrylate, caprolactone-modified trimethylolpropane triacrylate, HPA-modified trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, glycerol triacrylate, ECH-modified glycerol triacrylate, EO-modified glycerol triacrylate, PO-modified glycerol triacrylate, tris(acryloxyethyl)isocyanurate, caprolactone-modified tris(acryloxyethyl)isocyanurate, EO-modified tris(acryloxyethyl)isocyanurate, PO-modified tris(acryloxyethyl)isocyanurate, and PO-modified tris(acryloxyethyl)isocyanurate. aryloxyethyl) isocyanurate, dipentaerythritol hexaacrylate (A-DPH), caprolactone-modified dipentaerythritol hexaacrylate, dipentaerythritol hydroxypentaacrylate, alkyl-modified dipentaerythritol pentaacrylate, alkyl-modified dipentaerythritol tetraacrylate, alkyl-modified dipentaerythritol triacrylate, dimethylolpropane tetraacrylate, pentaerythritol ethoxy tetraacrylate, EO-modified phosphate triacrylate, 2,2,5,5-tetrahydroxymethylcyclopentanone tetraacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, polytetramethylene glycol diacrylate, EO-modified bisphenol A diacrylate, PO-modified bisphenol A diacrylate, 9,Examples of such esters include 9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, tricyclodecane dimethanol diacrylate, decanediol diacrylate, hexanediol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, EO-modified bisphenol A dimethacrylate, PO-modified bisphenol A dimethacrylate, tricyclodecane dimethanol dimethacrylate, decanediol dimethacrylate, and hexanediol dimethacrylate.

[0103] Examples of oligomers and polymers having an acryloyl group or a methacryloyl group include known urethane acrylates, ester acrylates, acrylic acrylates, and epoxy acrylates. Examples of the urethane acrylates include "EBECRYL8301," "EBECRYL1290," "EBECRYL1830," and "KRM8200" (Daicel-Allnex Corporation), "UV1700B," "UV7640B," "UV7605B," "UV6300B," and "UV7550B" (Mitsubishi Chemical Corporation). Examples of the ester acrylates include "M-7100," "M-7300K," "M-8030," "M-8060," "M-8100," "M-8530," "M-8560," and "M-9050" (Toagosei Co., Ltd.). Examples of the acrylic acrylate include "8BR-600", "8BR-930MB", "8KX-078", "8KX-089", and "8KX-168" (Taisei Fine Chemical Co., Ltd.).

[0104] These may be used alone or in combination of two or more. Among these, it is preferable to contain urethane acrylate from the viewpoint of electrical properties.

[0105] The content of the polymerizable compound not having a charge transport structure is preferably 1 part by mass or more, 5 parts by mass or more, particularly 10 parts by mass or more, and especially 15 parts by mass or more, relative to 100 parts by mass of the total mass of the outermost layer of the electrophotographic photoreceptor. When the content of the polymerizable compound not having a charge transport structure is equal to or more than the above-mentioned lower limit, the outermost layer has good mechanical strength and film-formability. On the other hand, from the viewpoint of gradation under high temperature and high humidity, the content of the polymerizable compound not having a charge transport structure is preferably 40 parts by mass or less, particularly 30 parts by mass or less, relative to 100 parts by mass of the total mass of the outermost layer of the electrophotographic photoreceptor. The content of the polymerizable compound corresponds to the content of the structural unit (C) in the polymer, and this content usually corresponds to the content of the polymerizable compound not having a charge transport structure relative to the total mass of the solids of the outermost layer-forming composition for forming the outermost layer.

[0106] In addition, from the viewpoints of film-formability and gradation under high temperature and high humidity, the mass ratio of the charge transport compound having a polymerizable functional group to the polymerizable compound not having a charge transport structure in the outermost layer of the electrophotographic photoreceptor is preferably charge transport compound having a polymerizable functional group:polymerizable compound not having a charge transport structure=95 to 85:5 to 15, particularly 90 to 85:10 to 15. Note that this mass ratio corresponds to the content mass ratio of the structural unit (B) having a charge transport structure to the structural unit (C) in the polymer, and this content mass ratio usually corresponds to the content mass ratio of the charge transport compound having a polymerizable functional group to the polymerizable compound not having a charge transport structure in the outermost layer-forming composition for forming the outermost layer.

[0107] (Other Components) The outermost layer of the electrophotographic photoreceptor may further contain a charge transport compound other than the charge transport compound having a polymerizable functional group, i.e., a charge transport compound having no polymerizable functional group, for the purpose of imparting charge transport capability. Furthermore, a polymerization initiator may be contained to promote the polymerization reaction of the outermost layer-forming composition.

[0108] The polymerization initiator and the charge transporting compound having no polymerizable functional group will be described in detail below.

[0109] (Polymerization Initiator) The polymerization initiator includes a thermal polymerization initiator, a photopolymerization initiator, and the like.

[0110] Examples of the thermal polymerization initiator include peroxide compounds such as 2,5-dimethylhexane-2,5-dihydroperoxide, dicumyl peroxide, benzoyl peroxide, t-butyl peroxide, t-butylcumyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, and lauroyl peroxide, and azo compounds such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(methyl isobutyrate), 2,2'-azobis(isobutylamidine hydrochloride), and 4,4'-azobis-4-cyanovaleric acid.

[0111] Photopolymerization initiators can be classified into direct cleavage type and hydrogen abstraction type based on the radical generation mechanism. Direct cleavage type photopolymerization initiators generate radicals by cleaving some of the covalent bonds within the molecule when they absorb light energy. On the other hand, hydrogen abstraction type photopolymerization initiators generate radicals when the molecule becomes excited by absorbing light energy and abstracts hydrogen from the hydrogen donor.

[0112] Examples of the direct cleavage type photopolymerization initiator include acetophenone or ketal compounds such as acetophenone, 2-benzoyl-2-propanol, 1-benzoylcyclohexanol, 2,2-diethoxyacetophenone, benzyl dimethyl ketal, and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone; benzoin ether compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, benzoin isopropyl ether, and O-tosylbenzoin; and acylphosphine oxide compounds such as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and lithium phenyl(2,4,6-trimethylbenzoyl)phosphonate.

[0113] Examples of hydrogen abstraction photopolymerization initiators include benzophenone-based compounds such as benzophenone, 4-benzoylbenzoic acid, 2-benzoylbenzoic acid, methyl 2-benzoylbenzoate, methyl benzoylformate, benzyl, p-anisil, 2-benzoylnaphthalene, 4,4'-bis(dimethylamino)benzophenone, 4,4'-dichlorobenzophenone, and 1,4-dibenzoylbenzene, and anthraquinone- or thioxanthone-based compounds such as 2-ethylanthraquinone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone. Other examples of photopolymerization initiators include camphorquinone, 1-phenyl-1,2-propanedione-2-(o-ethoxycarbonyl)oxime, acridine-based compounds, triazine-based compounds, and imidazole-based compounds.

[0114] In order to efficiently absorb light energy and generate radicals, the photopolymerization initiator preferably has an absorption wavelength in the wavelength range of the light source used for light irradiation. On the other hand, if any component other than the photopolymerization initiator among the compounds contained in the protective layer has absorption in this wavelength range, the photopolymerization initiator may not be able to absorb sufficient light energy, resulting in reduced radical generation efficiency. Because common binder resins and charge transport materials have absorption wavelengths in the ultraviolet (UV) range, this effect is particularly pronounced when the light source used for light irradiation is ultraviolet (UV). To prevent such problems, it is preferable to use an acylphosphine oxide-based compound, which has an absorption wavelength relatively toward the long wavelength side among photopolymerization initiators. Furthermore, acylphosphine oxide-based compounds have a photobleaching effect, in which the absorption wavelength range shifts to the low wavelength side upon self-cleavage, allowing light to penetrate deep into the protective layer and providing good internal curing properties. In this case, it is even more preferable to use a hydrogen abstraction initiator in combination with the protective layer to enhance the curing properties of the surface of the protective layer. The content ratio of the hydrogen abstraction initiator relative to the acylphosphine oxide-based compound is not particularly limited, but from the viewpoint of supplementing surface curability, it is preferably 0.1 parts by mass or more relative to 1 part by mass of the acylphosphine oxide-based compound, and from the viewpoint of maintaining internal curability, it is preferably 5 parts by mass or less.

[0115] Furthermore, a compound having a photopolymerization promoting effect can be used alone or in combination with the above photopolymerization initiator, such as triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino)ethyl benzoate, and 4,4'-dimethylaminobenzophenone.

[0116] These polymerization initiators may be used alone or in combination of two or more.

[0117] The content of the polymerization initiator in the outermost surface layer is 0.5 to 40 parts by mass, and preferably 1 to 20 parts by mass, relative to 100 parts by mass of the total content of the radically polymerizable compounds, i.e., the charge transport compound having a polymerizable functional group, the polymerizable compound not having a charge transport structure, and the silicone compound, as the content in the outermost surface layer-forming composition for forming the outermost surface layer.

[0118] (Charge Transport Compound Having No Polymerizable Functional Group) When the outermost layer is a photosensitive layer, the outermost layer may further contain a charge transport compound having no polymerizable functional group. In this case, examples of the charge transport compound having no polymerizable functional group contained in the outermost layer include the charge generation material, hole transport material, and electron transport material contained in the present photoreceptor described below. In this case, the content of the charge transport compound having no polymerizable functional group in the outermost layer is preferably 5 parts by mass or more, particularly 10 parts by mass or more, and especially 20 parts by mass or more, relative to 100 parts by mass of the total weight of the outermost layer of the present electrophotographic photoreceptor. Meanwhile, the upper limit is preferably 50 parts by mass or less, particularly 40 parts by mass or less, and especially 30 parts by mass or less, relative to 100 parts by mass of the total weight of the outermost layer.

[0119] (Other Materials) The outermost layer of the electrophotographic photoreceptor may contain other materials in addition to the above-mentioned components, as necessary. Examples of other materials include stabilizers (heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, etc.), dispersants, antistatic agents, colorants, lubricants, etc. These may be used alone or in any combination and ratio.

[0120] <Method for Forming Outermost Surface Layer> Next, a method for forming the outermost surface layer of the present electrophotographic photoreceptor will be described. The method for forming the outermost surface layer is not particularly limited. For example, the outermost surface layer can be formed by applying a coating liquid (coating liquid for forming outermost surface layer) in which a charge transporting compound having a polymerizable functional group, a polymerizable compound not having a charge transporting structure, the present silicone compound, and other substances are dissolved in a solvent or dispersed in a dispersion medium. When the present electrophotographic photoreceptor has a protective layer on the photosensitive layer and the outermost surface layer is the protective layer, the coating liquid for forming outermost surface layer is used as the coating liquid for forming the protective layer.

[0121] The solvent or dispersion medium used in forming the outermost layer and the coating method will be described below.

[0122] ketones such as acetone, methyl ethyl ketone, cyclohexanone, etc.; aromatic hydrocarbons such as benzene, toluene, xylene, anisole, etc.; chlorinated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, tetrachloroethane, 1,2-dichloropropane, trichloroethylene, etc.; nitrogen-containing compounds such as n-butylamine, isopropanolamine, diethylamine, triethanolamine, ethylenediamine, triethylenediamine, etc.; and aprotic polar solvents such as acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, etc. Any combination and mixed solvent of these may be used in any ratio. Furthermore, even if an organic solvent does not dissolve the material for the outermost layer of the electrophotographic photoreceptor by itself, it can be used if it can dissolve the material by mixing it with the above-mentioned organic solvent. Generally, the use of a mixed solvent can reduce coating unevenness. When using a dip coating method as the coating method described below, it is preferable to select a solvent that does not dissolve the lower layer. From this perspective, it is preferable to add an alcohol that has low solubility in polycarbonate and polyarylate, which are suitable for use in the photosensitive layer.

[0123] The ratio of the amount of the organic solvent to the amount of the solid content used in the coating liquid for forming the outermost surface layer varies depending on the coating method for forming the coating liquid for forming the outermost surface layer, and may be appropriately changed so as to form a uniform coating film in the coating method to be applied.

[0124] (Coating Method) The method for applying the coating liquid to form the outermost surface layer is not particularly limited, and examples thereof include spray coating, spiral coating, ring coating, and dip coating.

[0125] After forming a coating film by the above coating method, the coating film is dried. In this case, the drying temperature and time are not important as long as necessary and sufficient drying is obtained. However, when the electrophotographic photoreceptor has a protective layer on the photosensitive layer and the outermost layer is the protective layer, if the coating solution for forming the outermost layer (protective layer) is applied by only air drying after applying the photosensitive layer, it is preferable to dry the coating film sufficiently by the method described below as a method for drying the coating film in the method for forming the photosensitive layer.

[0126] (Method for curing outermost layer) The outermost layer is formed by applying the coating liquid for forming the outermost layer and then curing it with external energy. Examples of external energy used in this process include heat, light, and radiation. Heat energy can be applied by heating from the coated surface side or the support side using gases such as air and nitrogen, steam, various heat media, infrared rays, or electromagnetic waves. The heating temperature is preferably 100°C or higher and 170°C or lower. At or above the lower limit temperature, the reaction proceeds at a sufficient rate and completely. At or below the upper limit temperature, the reaction proceeds uniformly, preventing significant distortion in the outermost layer. To ensure uniform curing, it is also effective to heat the coating at a relatively low temperature below 100°C, and then further heat to 100°C or higher to complete the reaction.

[0127] As for light energy, UV irradiation light sources such as high-pressure mercury lamps, metal halide lamps, electrodeless lamp bulbs, and light-emitting diodes, which have emission wavelengths mainly in the ultraviolet (UV) range, can be used, but it is also possible to select a visible light source in accordance with the absorption wavelength of the polymerizable compound and photopolymerization initiator. The light irradiation dose is set to 0.1 mJ / cm from the viewpoint of curing properties. ２ More than 0.5 mJ / cm is preferable. ２ More preferably, 1 mJ / cm or more ２ In addition, from the viewpoint of electrical properties, 150 mJ / cm ２ Preferably, 100 mJ / cm or less ２ More preferably, 50 mJ / cm or less ２ The following are particularly preferred: As the radiation energy, an electron beam (EB) can be used.

[0128] Among these energies, light energy is preferred from the viewpoints of ease of reaction rate control, simplicity of the apparatus, and long pot life.

[0129] After the outermost layer is cured, a heating step may be added from the viewpoints of relieving residual stress, relieving residual radicals, and improving electrical properties. The heating temperature is preferably 60° C. or higher, more preferably 100° C. or higher, and is preferably 200° C. or lower, more preferably 150° C. or lower.

[0130] (Thickness of outermost surface layer) The thickness of the outermost surface layer is appropriately selected depending on the material used, the type of the outermost surface layer (function of the outermost surface layer), etc. When the electrophotographic photoreceptor has a protective layer on the photosensitive layer and the outermost surface layer is a protective layer, from the viewpoint of the service life of the photoreceptor, the thickness of the protective layer as the outermost surface layer (thickness after curing) is preferably 0.1 μm or more, more preferably 0.2 μm or more, and particularly preferably 0.5 μm or more. On the other hand, from the viewpoint of electrical properties, the thickness of the protective layer as the outermost surface layer is preferably 10 μm or less, more preferably 5 μm or less, and particularly preferably 3 μm or less. In particular, from the viewpoint of suppressing the occurrence of ghosts, the thickness of the protective layer as the outermost surface layer is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 0.5 μm or more, and particularly preferably 0.8 μm or more. On the other hand, it is preferably 5 μm or less, and more preferably 3 μm or less.

[0131] When the outermost layer is a charge transport layer in a multi-layer photoreceptor, the thickness of the charge transport layer as the outermost layer is the same as the layer thickness of the charge transport layer in a multi-layer photoreceptor described later.When the outermost layer is a single-layer photosensitive layer in a single-layer photoreceptor, the thickness of the single-layer photosensitive layer as the outermost layer is the same as the thickness of the present photosensitive layer described later.

[0132] Furthermore, when the electrophotographic photoreceptor has a protective layer on the photosensitive layer and the outermost layer is the protective layer, from the viewpoint of film-forming property, the ratio A / B of the thickness A of the protective layer as the outermost layer to the thickness B of the photosensitive layer described later is preferably 0.002 or more, more preferably 0.005 or more, even more preferably 0.008 or more, and particularly preferably 0.01 or more. On the other hand, from the viewpoint of durability, the ratio A / B of the thickness A of the protective layer as the outermost layer to the thickness B of the photosensitive layer is preferably 0.5 or less, more preferably 0.4 or less, even more preferably 0.3 or less, and particularly preferably 0.2 or less.

[0133] <Photosensitive Layer of the Present> The photosensitive layer in the present electrophotographic photoreceptor (also referred to as "photosensitive layer of the present") may be a single-layer photosensitive layer in which a charge generating material (CGM), a hole transporting material (HTM), and an electron transporting material (ETM) are present in the same layer, or may be a multi-layer photosensitive layer separated into a charge generating layer and a charge transporting layer.

[0134] <Laminated Photosensitive Layer> The laminated photosensitive layer in the electrophotographic photoreceptor may be configured by laminating a charge transport layer (CTL) containing a hole transport material (HTM) on a charge generation layer (CGL) containing a charge generation material (CGM), or by laminating the charge generation layer (CGL) on the charge transport layer (CTL). Among these, a configuration in which the charge transport layer (CTL) is laminated on the charge generation layer (CGL) is preferred. In this case, it is also possible to provide layers other than the charge generation layer (CGL) and the charge transport layer (CTL). The charge transport layer (CTL) may further contain an electron transport material (ETM).

[0135] <Charge Generation Layer (CGL)> The charge generation layer usually contains a charge generation material (CGM) and a binder resin.

[0136] (Charge-Generating Material (CGM)) Examples of the charge-generating material include inorganic photoconductive materials such as selenium and its alloys, and cadmium sulfide, and organic photoconductive materials such as organic pigments. Among these, organic photoconductive materials are preferred, and organic pigments are particularly preferred. Among these, phthalocyanine pigments and azo pigments are more preferred, and phthalocyanine pigments are even more preferred. All of these terms indicate the skeletal structures of compounds, and include compounds having these skeletal structures, i.e., derivatives.

[0137] When an organic pigment is used as the charge generating material, fine particles of the organic pigment are usually used in the form of a dispersed layer bound with various binder resins.

[0138] Specific examples of the phthalocyanine pigment include metal-free phthalocyanine, phthalocyanine dimers using oxygen atoms as bridging atoms, and the like, which have various crystal types and are coordinated with metals such as copper, gallium, tin, and titanium, or their oxides or halides. Particularly preferred are highly sensitive crystal types such as X-type, τ-type metal-free phthalocyanine, A-type (also known as β-type), B-type (also known as α-type), titanyl phthalocyanine (also known as oxytitanium phthalocyanine) such as D-type (also known as Y-type), which exhibits a clear peak at a diffraction angle 2θ (±0.2°) of 27.1° or 27.3° in powder X-ray diffraction, chlorogallium phthalocyanine such as II-type, and hydroxygallium phthalocyanine such as V-type.

[0139] The charge-generating material may be used alone or in any combination and ratio of two or more. When two or more charge-generating materials are used in combination, the charge-generating materials may be mixed after each other or may be mixed during the production or processing steps of the charge-generating material, such as synthesis, pigmentization, or crystallization. Known examples of such treatments include acid paste treatment, grinding treatment, and solvent treatment.

[0140] The particle diameter of the charge generating material is usually 1 μm or less, preferably 0.5 μm or less. Furthermore, from the viewpoint of sensitivity, the content of the charge generating material in the photosensitive layer is usually preferably 0.1% by mass or more, more preferably 0.5% by mass or more. Furthermore, from the viewpoint of sensitivity and chargeability, it is usually preferably 50% by mass or less, more preferably 20% by mass or less.

[0141] (Binder Resin) The binder resin used in the charge generating layer can be used without any particular limitation. Examples include polyvinyl acetal resins such as polyvinyl butyral resins, polyvinyl formal resins, and partially acetalized polyvinyl butyral resins in which a portion of butyral is modified with formal or acetal; polyarylate resins, polycarbonate resins, polyester resins, phenoxy resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyvinyl acetate resins, polystyrene resins, acrylic resins, methacrylic resins, polyacrylamide resins, polyamide resins, polyurethane resins, epoxy resins, silicone resins, and polyvinyl alcohol resins; and vinyl chloride-vinyl acetate copolymers. Among these resins, polyvinyl acetal resins or polyvinyl acetate resins are preferred in terms of pigment dispersibility, adhesion to the conductive support or undercoat layer, and adhesion to the charge transport layer. These binder resins may be used alone or in any combination of two or more.

[0142] (Other Components) In addition to the charge generating material and the binder resin, the charge generating layer may contain other components as needed. For example, known additives such as antioxidants, plasticizers, ultraviolet absorbers, electron-withdrawing compounds, leveling agents, visible light shielding agents, and fillers may be contained in order to improve film-forming properties, flexibility, coating properties, contamination resistance, gas resistance, light resistance, etc.

[0143] (Composition ratio) In the charge generation layer, if the composition ratio of the charge generation material is too high, the stability of the coating liquid may decrease due to aggregation of the charge generation material, etc., whereas if the composition ratio of the charge generation material is too low, the sensitivity of the photoreceptor may decrease. Therefore, the composition ratio (by mass) of the binder resin to the charge generation material is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, of the charge generation material per 100 parts by mass of the binder resin, and is preferably 1000 parts by mass or less, more preferably 500 parts by mass or less. From the viewpoint of film strength, it is more preferably 300 parts by mass or less, and even more preferably 200 parts by mass or less.

[0144] (Layer Thickness) The thickness of the charge generating layer is preferably 0.1 μm or more, more preferably 0.15 μm or more, and is preferably 10 μm or less, more preferably 0.6 μm or less.

[0145] <Charge Transport Layer (CTL)> The charge transport layer (CTL) usually contains a hole transport material (HTM) and a binder resin. It may further contain an electron transport material (ETM). When the outermost layer of the electrophotographic photoreceptor is a charge transport layer in a laminated photoreceptor, the charge transport layer (CTL) contains the above-described present polymer. From the viewpoint of improving the mechanical strength and charge transport properties of the photoreceptor surface, the content of the present polymer is preferably 5 parts by mass or more, particularly 10 parts by mass or more, relative to 100 parts by mass of the binder resin. From the viewpoint of compatibility with the binder resin, the content of the present polymer is preferably 120 parts by mass or less, particularly 100 parts by mass or less, particularly 80 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0146] (Hole Transport Material (HTM)) The hole transport material (HTM) is not particularly limited. For example, it is preferable to use a material containing at least one selected from the group consisting of a heterocyclic structure such as a carbazole structure, an indole structure, an imidazole structure, an oxazole structure, a pyrazole structure, a thiadiazole structure, or a benzofuran structure, an aniline structure, a hydrazone structure, an arylamine structure, a stilbene structure, a butadiene structure, and an enamine structure. Other examples include electron donating substances such as those in which a plurality of these structures are bonded, and polymers having a group containing these structures in the main chain or side chain.

[0147] Among these, a carbazole structure, an arylamine structure, a stilbene structure, a butadiene structure, an enamine structure, and a structure in which two or more of these structures are combined are preferred, and a compound containing an arylamine structure or an enamine structure is more preferred, with a compound containing an enamine structure being even more preferred because it is difficult to inject electrons.

[0148] Suitable examples of the hole transport material (HTM) include compounds having any of the structures represented by the following structural formulas. However, the HTM is not limited to these. Any one of these may be used alone, or two or more may be used in any combination. When the outermost layer of the electrophotographic photoreceptor is a charge transport layer, the HTM may contain the charge transport compound having the polymerizable functional group described above.

[0149]

[0150] Among the above-mentioned exemplary compounds, it is preferable to include a compound represented by the following formula (i) as the hole transport material (HTM) because the effects of the present invention can be more effectively obtained.

[0151]

[0152] Among the hole transport materials (HTM), compounds having two or more nitrogen atoms in one molecule are preferred, and compounds having a bilaterally symmetric structure are also preferred.

[0153] The content of the hole transport material (HTM) in the charge transport layer is preferably 10 parts by weight or more, more preferably 20 parts by weight or more, and even more preferably 30 parts by weight or more, per 100 parts by weight of the binder resin, and is preferably 150 parts by weight or less, more preferably 120 parts by weight or less, and even more preferably 100 parts by weight or less.

[0154] (Electron Transport Material (ETM)) The electron transport material (ETM) is not particularly limited, and examples thereof include electron-withdrawing substances such as aromatic nitro compounds such as 2,4,7-trinitrofluorenone, cyano compounds such as tetracyanoquinodimethane, quinone compounds such as diphenoquinone and dinaphthylquinone, and the like, as well as compounds in which a plurality of these compounds are bonded, or polymers having a group consisting of these compounds in the main chain or side chain. However, the electron transport material is not limited to these, and known electron transport materials can be used. Among these, quinone compounds and perylene pigments (perylene derivatives) are preferred from the viewpoint of electrical properties, and quinone compounds are more preferred. Among the quinone compounds, diphenoquinone or dinaphthylquinone are preferred from the viewpoint of electrical properties. Of these, dinaphthylquinone is more preferred.

[0155] Further examples include compounds having any of the following structures:

[0156]

[0157] The above electron transport materials may be used alone or in any combination of two or more.

[0158] The content of the electron transport material (ETM) in the charge transport layer is preferably 10 parts by weight or more, more preferably 20 parts by weight or more, and even more preferably 30 parts by weight or more, per 100 parts by weight of the binder resin, and is preferably 150 parts by weight or less, more preferably 120 parts by weight or less, and even more preferably 100 parts by weight or less.

[0159] The content of the electron transport material (ETM) in the charge transport layer is preferably 0.1 parts by weight or more, more preferably 0.3 parts by weight or more, and even more preferably 0.5 parts by weight or more, per 100 parts by weight of the hole transport material (HTM) in the charge transport layer, and is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, and even more preferably 5 parts by weight or less.

[0160] (Binder Resin) Examples of the binder resin for the charge transport layer include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymers thereof, thermoplastic resins such as polycarbonate, polyarylate, polyester, polyester polycarbonate, polysulfone, phenoxy, epoxy, and silicone resins, and various thermosetting compounds. Among these resins, polycarbonate resins and polyarylate resins are preferred in terms of light attenuation characteristics and mechanical strength as a photoreceptor.

[0161] The viscosity average molecular weight (Mv) of the binder resin is usually in the range of 5,000 to 300,000, preferably 10,000 to 200,000, more preferably 15,000 to 150,000, and particularly preferably 20,000 to 80,000. If the viscosity average molecular weight (Mv) is excessively small, the mechanical strength of the photosensitive layer tends to decrease. On the other hand, if the viscosity average molecular weight (Mv) is excessively large, the viscosity of the coating solution increases, making it difficult to coat the layer to an appropriate thickness.

[0162] (Other Components) The charge transport layer may contain other components as needed in addition to the hole transport material (HTM), electron transport material (ETM), and binder resin. For example, known additives such as antioxidants, plasticizers, ultraviolet absorbers, electron-withdrawing compounds, leveling agents, visible light shielding agents, and fillers may be contained for the purpose of improving film-forming properties, flexibility, coating properties, contamination resistance, gas resistance, light resistance, etc.

[0163] (Layer Thickness) The layer thickness of the charge transport layer is not particularly limited. From the viewpoints of electrical characteristics, image stability, and high resolution, the layer thickness is preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more or 35 μm or less, and even more preferably 15 μm or more or 25 μm or less.

[0164] <Single-Layer Photosensitive Layer> When the photosensitive layer of the present electrophotographic photosensitive member is a single-layer photosensitive layer, it usually contains a binder resin, a charge generating material, a hole transport material, and an electron transport material in the same layer. When the outermost layer of the present electrophotographic photosensitive member is a single-layer photosensitive layer in a single-layer photosensitive member, this photosensitive layer contains the above-mentioned present polymer, and the content thereof is preferably 5 parts by mass or more, particularly 10 parts by mass or more, relative to 100 parts by mass of the binder resin, from the viewpoint of improving the mechanical strength and charge transport property of the photosensitive member surface, and is preferably 120 parts by mass or less, particularly 100 parts by mass or less, particularly 80 parts by mass or less, relative to 100 parts by mass of the binder resin, from the viewpoint of compatibility with the binder resin.

[0165] The charge generating material, the hole transporting material, and the electron transporting material are the same as those explained for the laminated photosensitive layer.

[0166] The content of the charge generating material in the single-layer photosensitive layer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, from the viewpoint of sensitivity, and is preferably 50% by mass or less, more preferably 20% by mass or less, from the viewpoint of sensitivity and chargeability.

[0167] In a single-layer photosensitive layer, the content ratio of the binder resin and the hole transport material constituting the photosensitive layer is preferably 20 parts by mass or more of the hole transport material per 100 parts by mass of the binder resin, more preferably 30 parts by mass or more from the viewpoint of reducing residual potential, and even more preferably 40 parts by mass or more from the viewpoints of stability and charge mobility during repeated use. On the other hand, from the viewpoint of the thermal stability of the photosensitive layer, the content ratio of the hole transport material per 100 parts by mass of the binder resin is preferably 200 parts by mass or less, more preferably 150 parts by mass or less from the viewpoint of compatibility between the hole transport material and the binder resin, and particularly preferably 120 parts by mass or less from the viewpoint of abrasion resistance.

[0168] The content ratio of the binder resin and the electron transport material in the single-layer photosensitive layer is preferably 5 parts by mass or more of the electron transport material per 100 parts by mass of the binder resin. From the viewpoint of reducing the residual potential, 10 parts by mass or more is more preferable, and from the viewpoints of stability during repeated use and charge mobility, 20 parts by mass or more is even more preferable. On the other hand, from the viewpoint of the thermal stability of the photosensitive layer, the content of the electron transport material per 100 parts by mass of the binder resin is preferably 100 parts by mass or less. From the viewpoint of compatibility between the electron transport material and the binder resin, 80 parts by mass or less is more preferable, 60 parts by mass or less is even more preferable, and 50 parts by mass or less is particularly preferable.

[0169] In the single-layer photosensitive layer, the content ratio (mass ratio) of the electron transport material (ETM) to the hole transport material (HTM) is preferably 0.3 or more, more preferably 0.4 or more, and even more preferably 0.5 or more, and is preferably 1 or less, more preferably 0.9 or less, and even more preferably 0.8 or less.

[0170] The content ratio of the binder resin and the charge transport material (electron transport material and hole transport material) constituting the single-layer photosensitive layer is arbitrary, but it is preferable that the charge transport material be 25 parts by mass or more per 100 parts by mass of the binder resin. From the viewpoint of reducing residual potential, it is preferably 35 parts by mass or more. Furthermore, from the viewpoints of stability and charge mobility during repeated use, it is more preferably 45 parts by mass or more. On the other hand, from the viewpoint of thermal stability of the photosensitive layer, it is preferable that the charge transport material be 200 parts by mass or less per 100 parts by mass of the binder resin. Furthermore, from the viewpoint of compatibility between the charge transport material and the binder resin, it is more preferably 150 parts by mass or less, even more preferably 125 parts by mass or less, and particularly preferably 100 parts by mass or less.

[0171] <Method of Forming Each Layer of the Present Photosensitive Layer> In both the multilayer type and the single-layer type, the above-mentioned layers can be formed as follows. A coating liquid obtained by dissolving or dispersing a substance to be contained in a solvent can be applied to a conductive support by a known method such as dip coating, spray coating, nozzle coating, bar coating, roll coating, or blade coating, and the layers can be formed by repeating the steps of coating and drying sequentially for each layer. However, the formation method is not limited to this.

[0172] The solvent or dispersion medium used in preparing the coating liquid is not particularly limited. Specific examples include alcohols such as methanol, ethanol, propanol, and 2-methoxyethanol; ethers such as tetrahydrofuran, 1,4-dioxane, and dimethoxyethane; aromatic hydrocarbons such as benzene, toluene, xylene, and anisole; and chlorinated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, tetrachloroethane, 1,2-dichloropropane, and trichloroethylene. These solvents may be used alone, or two or more may be used in any desired ratio and combination.

[0173] The amount of solvent or dispersion medium used is not particularly limited. It is preferable to appropriately adjust the solids concentration, viscosity, and other physical properties of the coating solution so that they fall within the desired range, taking into account the purpose of each layer and the properties of the selected solvent or dispersion medium. The coating film is preferably dried by heating, usually at a temperature of 30°C or higher and 200°C or lower, for 1 minute to 2 hours, either stationary or under airflow. The heating temperature may be constant, or the temperature may be varied during drying.

[0174] <Thickness of the Photosensitive Layer> From the viewpoint of residual potential, the thickness of the photosensitive layer is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 19 μm or more, even more preferably 20 μm or more, even more preferably 22 μm or more, and even more preferably 24 μm or more. On the other hand, from the viewpoint of chargeability, the thickness is preferably 40 μm or less, even more preferably 35 μm or less, and even more preferably 30 μm or less. Note that the thickness of the photosensitive layer here refers to the thickness of a single-layer photosensitive layer, and refers to the combined thickness of the charge generating layer and the charge transport layer in the case of a multi-layer photosensitive layer. The ratio A / B of the thickness A of the protective layer to the thickness B of the photosensitive layer is as described above.

[0175] <Conductive Support> The conductive support of the electrophotographic photoreceptor is not particularly limited as long as it supports the layer formed thereon and exhibits conductivity. Examples of conductive supports include metal materials such as aluminum, aluminum alloys, stainless steel, copper, and nickel, resin materials imparted with conductivity by the coexistence of conductive powders such as metals, carbon, and tin oxide, and resins, glass, and paper on whose surfaces conductive materials such as aluminum, nickel, and ITO (indium oxide tin oxide alloy) are vapor-deposited or coated. Examples of forms that can be used include drums, sheets, and belts. A conductive material with an appropriate resistance value may be coated on a metallic conductive support to control conductivity and surface properties or to cover defects.

[0176] When a metal material such as an aluminum alloy is used as the conductive support, the metal material may be anodized before use.

[0177] The average thickness of the anodic oxide coating is usually 20 μm or less, and preferably 7 μm or less.

[0178] When forming an anodized film on a metal material, it is preferable to perform a sealing treatment. The sealing treatment can be performed by a known method.

[0179] The surface of the conductive support may be smooth or may be roughened by using a special cutting method or by polishing. Alternatively, the surface may be roughened by mixing particles of an appropriate particle size into the material constituting the support. An undercoat layer, which will be described later, may be provided between the conductive support and the photosensitive layer to improve adhesion, blocking resistance, etc.

[0180] <Undercoat Layer> The present electrophotographic photoreceptor may have an undercoat layer between the present photosensitive layer and the conductive support.

[0181] The undercoat layer may be made of, for example, a resin or a resin in which organic pigments or particles of metal oxides or the like are dispersed. The organic pigments used in the undercoat layer are not particularly limited. Examples thereof include the phthalocyanine pigments and azo pigments used as the charge generating material described above.

[0182] Examples of metal oxide particles used in the undercoat layer include metal oxide particles containing one type of metal element such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, and iron oxide, and metal oxide particles containing multiple metal elements such as calcium titanate, strontium titanate, and barium titanate. The undercoat layer may contain only one type of particle, or multiple types of particles may be mixed in any ratio and combination.

[0183] Among the above metal oxide particles, titanium oxide and aluminum oxide are preferred, and titanium oxide is particularly preferred. The titanium oxide particles may have their surfaces treated with any inorganic or organic substance, for example. The crystalline form of the titanium oxide particles may be any of rutile, anatase, brookite, and amorphous. Titanium oxide particles may also be present in a variety of crystalline forms.

[0184] The particle size of the metal oxide particles used in the undercoat layer is not particularly limited. In terms of the properties of the undercoat layer and the stability of the solution for forming the undercoat layer, the average primary particle size is preferably 10 nm or more, and 100 nm or less, more preferably 50 nm or less.

[0185] Here, the undercoat layer is preferably formed in a form in which particles are dispersed in a binder resin. Examples of binder resins used in the undercoat layer include polyvinyl acetal-based resins such as polyvinyl butyral resins, polyvinyl formal resins, and partially acetalized polyvinyl butyral resins in which butyral is partially modified with formal or acetal, and insulating resins such as polyarylate resins, polycarbonate resins, polyester resins, phenoxy resins, acrylic resins, methacrylic resins, polyamide resins, polyurethane resins, epoxy resins, silicone resins, polyvinyl alcohol resins, styrene-alkyd resins, silicone-alkyd resins, and phenol-formaldehyde resins. However, the binder resin is not limited to these polymers. These binder resins may be used alone or in combination, or may be used in a cured form with a curing agent. Among these, polyvinyl acetal-based resins, alcohol-soluble copolymerized polyamides, modified polyamides, and the like are preferred due to their excellent dispersibility and coatability. Among these, alcohol-soluble copolyamides are particularly preferred.

[0186] The mixing ratio of the particles to the binder resin can be selected arbitrarily, but it is preferable to use the particles in the range of 10% by mass to 500% by mass in terms of the stability and coatability of the dispersion.

[0187] The thickness of the undercoat layer can be selected arbitrarily. In consideration of the characteristics of the electrophotographic photoreceptor and the coating properties of the dispersion, the thickness is preferably 0.1 μm or more and 20 μm or less. The undercoat layer may also contain a known antioxidant.

[0188] <Other Layers> The electrophotographic photoreceptor may have other layers as needed in addition to the conductive support, the photosensitive layer, the protective layer and the undercoat layer described above.

[0189] <Thickness of Part Other Than Conductive Support> From the viewpoint of leak resistance, the thickness of the electrophotographic photosensitive member excluding the conductive support, i.e., the thickness obtained by subtracting the thickness of the conductive support from the thickness of the electrophotographic photosensitive member, is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. On the other hand, from the viewpoint of chargeability, it is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 35 μm or less.

[0190] <<Present Image Forming Apparatus>> An image forming apparatus ("present image forming apparatus") can be configured using the present electrophotographic photoreceptor.

[0191] As shown in Figure 1, the image forming apparatus is configured to include an electrophotographic photoreceptor 1, a charging device 2, an exposure device 3, and a developing device 4, and may further include a transfer device 5, a cleaning device 6, and a fixing device 7 as needed. There are no particular limitations on the electrophotographic photoreceptor 1 as long as it is the electrophotographic photoreceptor described above. Figure 1 shows, as an example, a drum-shaped photoreceptor in which the above-described photosensitive layer is formed on the surface of a cylindrical conductive support. The charging device 2, exposure device 3, developing device 4, transfer device 5, and cleaning device 6 are arranged along the outer circumferential surface of the electrophotographic photoreceptor 1, respectively.

[0192] The charging device 2 charges the electrophotographic photoreceptor 1, uniformly charging the surface of the electrophotographic photoreceptor 1 to a predetermined potential. Typical charging devices include non-contact corona charging devices such as corotrons and scorotrons, and contact charging image forming devices (also referred to as "contact charging devices" or "direct charging devices") that charge the photoreceptor surface by bringing a charging member to which a voltage is applied into contact with the surface (also referred to as a "contact charging device" or "direct charging device"). Examples of contact charging devices include a charging roller and a charging brush. Note that FIG. 1 shows a roller-type charging device (charging roller) as an example of the charging device 2. Charging may be performed using a DC voltage, or by superimposing an AC voltage on a DC voltage.

[0193] The type of exposure device 3 is not particularly limited as long as it can expose the electrophotographic photoreceptor 1 to light and form an electrostatic latent image on the photosensitive surface of the electrophotographic photoreceptor 1. Furthermore, exposure may be performed by an internal photoreceptor exposure method. Any light may be used for exposure.

[0194] The type of toner T is arbitrary, and in addition to powder toner, polymerized toner produced by a suspension polymerization method or an emulsion polymerization method can be used.

[0195] The type of transfer device 5 is not particularly limited, and any device using any method, such as electrostatic transfer methods such as corona transfer, roller transfer, and belt transfer, pressure transfer, and adhesive transfer, can be used. Here, the transfer device 5 is assumed to be composed of a transfer charger, a transfer roller, a transfer belt, and the like, arranged opposite to the electrophotographic photosensitive member 1. The transfer device 5 applies a predetermined voltage value (transfer voltage) with a polarity opposite to the charged potential of the toner T, and transfers the toner image formed on the electrophotographic photosensitive member 1 onto recording paper (paper, medium) P.

[0196] There are no particular limitations on the cleaning device 6, and any cleaning device can be used, such as a brush cleaner, a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, or a blade cleaner. The cleaning device 6 scrapes off residual toner adhering to the photoreceptor 1 with a cleaning member and collects the residual toner. However, if there is little or almost no toner remaining on the photoreceptor surface, the cleaning device 6 may be omitted.

[0197] In the image forming apparatus configured as described above, an image is recorded as follows. First, the surface (photosensitive surface) of the photoreceptor 1 is charged to a predetermined potential (e.g., 600 V) by the charging device 2. At this time, charging may be performed using a DC voltage, or by superimposing an AC voltage on the DC voltage. Next, the charged photosensitive surface of the photoreceptor 1 is exposed by the exposure device 3 in accordance with the image to be recorded, forming an electrostatic latent image on the photosensitive surface. The electrostatic latent image formed on the photosensitive surface of the photoreceptor 1 is then developed by the developing device 4.

[0198] In the developing device 4, the toner T supplied by the supply roller 43 is thinned by a regulating member (developing blade) 45, frictionally charged to a predetermined polarity (here, positive, the same polarity as the charging potential of the photoreceptor 1), and carried by the developing roller 44 until it comes into contact with the surface of the photoreceptor 1. When the charged toner T carried by the developing roller 44 comes into contact with the surface of the photoreceptor 1, a toner image corresponding to the electrostatic latent image is formed on the photosensitive surface of the photoreceptor 1. This toner image is then transferred to the recording paper P by the transfer device 5. Thereafter, toner remaining on the photoreceptor surface of the photoreceptor 1 without being transferred is removed by a cleaning device 6.

[0199] After the toner image is transferred onto the recording paper P, the recording paper P is passed through a fixing device 7 to thermally fix the toner image onto the recording paper P, thereby obtaining a final image. Note that the image forming apparatus may be configured to be capable of performing, for example, a static elimination process in addition to the above-described configuration.

[0200] Furthermore, the image forming apparatus may be further modified and configured, for example, to be capable of performing processes such as a pre-exposure process and an auxiliary charging process, or to be configured to perform offset printing, or even to be configured as a full-color tandem system using multiple types of toner.

[0201] <<Present Electrophotographic Cartridge>> The present electrophotographic photosensitive member 1 can be combined with one or more of the charging device 2, the exposure device 3, the developing device 4, the transfer device 5, the cleaning device 6, and the fixing device 7 to form an integrated cartridge (referred to as the present electrophotographic cartridge).

[0202] The electrophotographic cartridge can be configured to be detachable from the main body of an electrophotographic apparatus such as a copying machine, a laser beam printer, etc. In this case, for example, when the electrophotographic photosensitive member 1 or other members deteriorate, the electrophotographic photosensitive member cartridge can be removed from the main body of the image forming apparatus and a new electrophotographic photosensitive member cartridge can be mounted in the main body of the image forming apparatus, thereby facilitating maintenance and management of the image forming apparatus.

[0203] <<Explanation of Terms>> In the present invention, when "X to Y" (X and Y are any numbers) is expressed, unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably larger than X" or "preferably smaller than Y". Furthermore, when "X or more" (X is any number) or "Y or less" (Y is any number) is expressed, it also includes the meaning of "preferably larger than X" or "preferably smaller than Y".

[0204] The present invention will be further illustrated by the following examples, which are not intended to limit the invention in any way. In the following, "parts" refers to "parts by mass."

[0205] (Synthesis Example 1: Synthesis of Silicone Compound 1) In a 50 mL two-necked flask equipped with a stirrer and a condenser, 10.0 g of polydimethylsiloxane having hydroxyl groups on the side chains ("X-22-4015" manufactured by Shin-Etsu Chemical Co., Ltd., hydroxyl value 30 mgKOH / g), 0.65 g of triethylamine, and 10.0 g of methylene chloride were charged and stirred until uniformly dissolved. The reaction solution was cooled to 0°C on an ice bath while stirring, and 0.67 g of methacrylic acid chloride was added dropwise using a syringe. The mixture was then stirred at room temperature for 3 hours. １ From H-NMR, the peaks derived from hydroxyl groups disappeared, confirming that the compound had been methacrylated. The reaction slurry solution from which triethylamine hydrochloride had precipitated was filtered using a Kiriyama funnel, and the salt was washed off with 20 g of methylene chloride. The solution was purified directly by silica gel column chromatography (hexane / ethyl acetate=50 / 50) to obtain Silicone Compound 1 having a polymerizable functional group on the side chain represented by the following formula (where n １ , n ２ The functional group equivalent of this silicone compound 1 was 1900 g / eq.

[0206]

[0207] (Synthesis Example 2: Synthesis of Silicone Compound 2) 10.0 g of polydimethylsiloxane having hydroxyl groups on the side chains ("X-22-4039" manufactured by Shin-Etsu Chemical Co., Ltd., hydroxyl value 58 mgKOH / g), 1.25 g of triethylamine, and 10.0 g of methylene chloride were charged into a 50 mL two-neck flask equipped with a stirrer and a condenser, and stirred until uniformly dissolved. The reaction solution was cooled to 0°C on an ice bath while stirring, and 1.3 g of methacrylic acid chloride was added dropwise using a syringe. The mixture was then stirred at room temperature for 3 hours. １ From H-NMR, the peaks derived from hydroxyl groups disappeared, confirming that the compound had been methacrylated. The reaction slurry solution from which triethylamine hydrochloride had precipitated was filtered using a Kiriyama funnel, and the salt was washed off with 20 g of methylene chloride. The solution was purified directly by silica gel column chromatography (hexane / ethyl acetate=50 / 50) to obtain Silicone Compound 2 having a polymerizable functional group on the side chain represented by the following formula (where n １ , n ２ The functional group equivalent of this silicone compound 2 was 970 g / eq.

[0208]

[0209] <Preparation of Coating Solution for Forming Undercoat Layer> (Coating Solution A for Forming Undercoat Layer) Titanium oxide particles, the surfaces of which had been treated with methyldimethoxysilane ("TSL8117" manufactured by Toshiba Silicones Co., Ltd.) using rutile titanium oxide ("TTO55N" manufactured by Ishihara Sangyo Kaisha, Ltd., average primary particle diameter 40 nm), and a copolymeric polyamide having the following composition ratio were mixed with stirring in a mixed solvent (methanol / 1-propanol / toluene in a mass ratio of 7 / 1 / 2) while heating to dissolve the copolymeric polyamide. Subsequently, the mixture was subjected to ultrasonic dispersion treatment using an ultrasonic oscillator with an output of 1200 W for 1 hour, and then filtered to obtain Coating Solution A for forming an undercoat layer, in which the mass ratio of surface-treated titanium oxide / copolymeric polyamide was 3 / 1 and the solids concentration was 18.0 mass%. Composition ratio (molar ratio) of copolymerized polyamide: ε-caprolactam / bis(4-amino-3-methylcyclohexyl)methane / hexamethylenediamine / decamethylenedicarboxylic acid / octadecamethylenedicarboxylic acid=75 / 9.5 / 3 / 9.5 / 3

[0210] <Preparation of Coating Liquid for Forming Charge Generating Layer> (Coating Liquid B for Forming Charge Generating Layer) The coating liquid for forming charge generating layer was prepared as follows. 20 parts of D-type (Y-type) oxytitanium phthalocyanine A as a charge generating material and 280 parts of 1,2-dimethoxyethane were mixed and ground in a sand grinding mill for 1 hour to perform a fine particle dispersion treatment. Subsequently, this finely ground solution was mixed with a binder liquid obtained by dissolving 10 parts of polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., "Denka Butyral" #6000C) in a mixture of 255 parts of 1,2-dimethoxyethane and 85 parts of 4-methoxy-4-methyl-2-pentanone, and 230 parts of 1,2-dimethoxyethane to prepare Coating Liquid B1 for forming charge generating layer.

[0211] On the other hand, as a charge generating material, 20 parts of A-type (β-type) oxytitanium phthalocyanine B and 280 parts of 1,2-dimethoxyethane were mixed and ground for 4 hours in a sand grind mill to perform a fine particle dispersion treatment. Subsequently, this fine particle treatment solution was mixed with a binder solution obtained by dissolving 10 parts of polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., "Denka Butyral" #6000C) in a mixture of 255 parts of 1,2-dimethoxyethane and 85 parts of 4-methoxy-4-methyl-2-pentanone, and 230 parts of 1,2-dimethoxyethane to prepare a charge generating layer forming coating solution B2.

[0212] Charge generating layer forming coating liquid B1 and charge generating layer forming coating liquid B2 were mixed in a mass ratio of 7:3 to prepare charge generating layer forming coating liquid B used in this example.

[0213] <Preparation of Coating Liquid for Forming Charge Transport Layer> (Coating Liquid C for Forming Charge Transport Layer) 66.64 parts of a polycarbonate resin represented by the following repeating structure (Resin X1, viscosity average molecular weight 0,000), 33.33 parts of HTM1 as a charge transport material, and 0.03 parts of silicone oil (KF96-10CS, manufactured by Shin-Etsu Chemical Co., Ltd.) as a leveling agent were dissolved in a mixed solvent of tetrahydrofuran and toluene at a ratio of 8:2 with heating and stirring to obtain Coating Liquid C for Forming Charge Transport Layer with a solids concentration of 18% by mass.

[0214] Resin X1 is a resin having the repeating structure shown below.

[0215]

[0216] HTM1 is a compound having the structure shown below.

[0217]

[0218] <Production of Coating Liquid for Forming Outermost Surface Layer (Protective Layer)> (Coating Liquid S1 for Forming Outermost Surface Layer (Protective Layer)) A mixture of 10 parts of polyester acrylate (manufactured by Toagosei Co., Ltd., product name "Aronix M-9050") as a polymerizable compound not having a charge transport structure, 90 parts of charge transport compound 1 having two polymerizable functional groups of the structure shown below, 2 parts of Omnirad TPO H (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide) and 1 part of benzophenone (BP) as a polymerization initiator, and 1 part of benzophenone (BP) as a leveling agent was prepared. Coating Solution S1 for forming an outermost surface layer (protective layer) was prepared by mixing 0.01 parts of a product named "KF-6001," 0.5 parts of a silicone compound 1 having a repeating unit of a dimethylsiloxane structure in its main chain and a polymerizable functional group in its side chain, which was synthesized in Synthesis Example 1, as a surface modifier, and 309 parts of a mixed solvent of toluene / 2-propanol = 3 / 7 (mass ratio).

[0219]

[0220] (Preparation of Coating Solution S2 for Forming Outermost Surface Layer (Protective Layer)) Coating Solution S2 for forming an outermost surface layer (protective layer) was obtained in the same manner as for Coating Solution S1 for forming an outermost surface layer (protective layer), except that Silicone Compound 2, which had a main chain having a repeating unit of a dimethylsiloxane structure and a side chain synthesized in Synthesis Example 2, was used instead of Silicone Compound 1 as the surface modifier.

[0221] (Preparation of Coating Solution S3 for Forming Outermost Surface Layer (Protective Layer)) Coating Solution S3 for forming an outermost surface layer (protective layer) was obtained in the same manner as for Coating Solution S1 for forming an outermost surface layer (protective layer), except that silicone compound 1 as the surface modifier was replaced with silicone compound 1 manufactured by Shin-Etsu Chemical Co., Ltd., product name "X-22-164" (a silicone compound having methacrylolyl groups at both ends, functional group equivalent weight 190 g / eq).

[0222] (Preparation of Coating Solution S4 for Forming Outermost Layer (Protective Layer)) Coating Solution S4 for forming outermost layer (protective layer) was obtained in the same manner as Coating Solution S1 for Forming Outermost Layer (Protective Layer), except that the surface modifier silicone compound 1 was not used.

[0223] <Production of Photoreceptor Drum> [Example 1] The undercoat layer forming coating liquid A prepared in the above coating liquid production example was applied by dip coating to an aluminum alloy cylinder (conductive support) with a rough-cut surface, having an outer diameter of 30 mm, a length of 357.4 mm, and a thickness of 0.75 mm, and air-dried to form an undercoat layer with a thickness of 1.5 μm. Next, the charge generation layer forming coating liquid B was applied by dip coating to the undercoat layer, and air-dried to form a charge generation layer with a thickness of 0.4 μm. Finally, the charge transport layer forming coating liquid C was applied by dip coating to the charge generation layer, and dried at 125° C. for 24 minutes to form a charge transport layer with a thickness of 24 μm, thereby obtaining a photoreceptor before the protective layer was applied.

[0224] Next, the outermost layer (protective layer) forming coating solution S1 was ring-coated onto the photoreceptor before the protective layer was applied, and the coating was dried at room temperature for 20 minutes. After that, the photoreceptor was rotated at 60 rpm in a nitrogen atmosphere (oxygen concentration 1% or less), and 365 nm LED light was applied at 0.7 mW / cm. ２ for 2 minutes (accumulated light amount: 27 mJ / cm ２ ), a polymer was formed, and a protective layer having a thickness of 3.0 μm after curing was formed as the outermost surface layer, thereby obtaining a photoreceptor of Example 1.

[0225] [Example 2] A photoreceptor of Example 2 was obtained in the same manner as in Example 1, except that the coating solution S2 for forming the outermost surface layer (protective layer) was used instead of the coating solution S1 for forming the outermost surface layer (protective layer).

[0226] [Comparative Example 1] A photoreceptor of Comparative Example 1 was obtained in the same manner as in Example 1, except that the coating solution S3 for forming the outermost surface layer (protective layer) was used instead of the coating solution S1 for forming the outermost surface layer (protective layer).

[0227] [Comparative Example 2] A photoreceptor of Comparative Example 2 was obtained in the same manner as in Example 1, except that the coating solution S4 for forming the outermost surface layer (protective layer) was used instead of the coating solution S1 for forming the outermost surface layer (protective layer).

[0228] <Evaluation of Slipperiness> The initial frictional force and the frictional force after printing of the photoreceptors obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were measured. The frictional force was measured using the Euler method shown in Figure 2. First, a Teflon sheet with a 75 g weight was draped over the surface of the photoreceptor and balanced. The force at this point was set to zero. Next, the force required to pull the Teflon sheet was measured. A large force indicates poor slipperiness, while a small force indicates good slipperiness. For the printing durability test, the photoreceptor was mounted in a photoreceptor cartridge of a commercially available contact-charging color copier, and 20,000 sheets were continuously printed at a temperature of 25°C and a relative humidity of 50%. Maintaining a low value even after continuous printing indicates that slipperiness is maintained. The results are shown in Table 1.

[0229]

[0230] <Discussion> From the results of the above examples, it was found that in a photoreceptor containing the present polymer in which the outermost surface layer contains a structural unit (A) having a silicone structure and a structural unit (B) having a charge transport structure, the structural unit (A) has a silicone structure in which the main chain has a repeating unit of a dimethylsiloxane structure and the side chain has a bonding group to other structural units, thereby providing good initial slipperiness and maintaining slipperiness even after continuous printing. As described above, Comparative Example 1, which contains a silicone structure having a bonding group to other structural units only at the end, had good initial slipperiness, but after printing, it was at the same level as Comparative Example 2, which did not contain a surface modifier. In contrast, it was found that Examples 1 and 2 maintained higher slipperiness than Comparative Example 2 even after printing. In Example 2, the functional group equivalent of the silicone compound was small, resulting in a polymer with a high crosslinking density, which improved film strength and reduced silicone loss due to wear, resulting in particularly excellent printing durability.

[0231] The effects of the present invention reside in the fact that, by introducing a polymerizable functional group into the side chain of the silicone compound, surface segregation of the silicone structure is moderately alleviated, the number of polymerizable functional groups is increased, film strength is improved, and loss of the silicone structure due to wear is reduced. Therefore, it is believed that the type of polymerizable functional group is not limited to a specific structure.

[0232] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications are possible within the scope of the effects of the invention. This application is based on Japanese Patent Application No. 2024-055840 filed on March 29, 2024, the entire contents of which are incorporated by reference.

[0233] REFERENCE SIGNS LIST 1 Electrophotographic photosensitive member 2 Charging device 3 Exposure device 4 Developing device 5 Transfer device 6 Cleaning device 7 Fixing device

Claims

1. An electrophotographic photoreceptor comprising at least a photosensitive layer on a conductive support, wherein the outermost layer contains a polymer comprising a structural unit (A) having a silicone structure and a structural unit (B) having a charge transport structure, and the structural unit (A) having a silicone structure comprises a structure represented by the following formula (1): (In formula (1), X １ ~X ４ R each independently represents an alkylene group having 1 to 3 carbon atoms which may be modified with ethylene oxide or propylene oxide. １ ~R ４ Each independently represents a hydrogen atom or a bonding group to another structural unit. １ , n ２ are each an integer of 1 or greater. ２ is an integer of 2 or more, there are two or more R １ , R ２ , X １ , X ２ may be the same or different. １ , R ２ At least one of n is a bonding group to another structural unit. １ , n ２ The linkage of the structures marked with may be random or block.) 2. The electrophotographic photoreceptor according to claim 1, wherein the charge transporting structure comprises a heterocyclic structure selected from the group consisting of carbazole, indole, imidazole, oxazole, pyrazole, thiadiazole, and benzofuran, and at least one structure selected from the group consisting of a hydrazone structure, an arylamine structure, a stilbene structure, a butadiene structure, and an enamine structure.

3. The electrophotographic photoreceptor according to claim 1 or 2, wherein the structural unit (B) having a charge transport structure has a structure represented by the following formula (2): (In formula (2), Ar ４１ ~Ar ４３ are each independently a divalent aromatic group. ４１ ~R ４３ are each independently a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a halogenated alkyl group, a halogen atom, a benzyl group, or a bonding group to another structural unit. ４１ Comrade, R ４２ Comrade, R ４３ are bonded to each other to form Ar ４１ , Ar ４２ , Ar ４３ may form a ring fused to the aromatic ring of ４１ ~n ４３ are each independently an integer of 1 or more, and n ４１ ~n ４３ Two selected from among n are 1. ４１ ~n ４３ If is 1, R ４１ ~R ４３ is a bonding group to other structural units. ４１ is an integer of 2 or more, there are two or more R ４１ may be the same or different, but at least one of them is a bonding group to another structural unit. ４２ is an integer of 2 or more, there are two or more R ４２ may be the same or different. ４３ is an integer of 2 or more, there are two or more R ４３ may be the same or different.) 4. The electrophotographic photoreceptor according to claim 3, wherein the bonding group to the other structural unit in the formula (2) has a structure represented by the following formula (3): (In formula (3), R ５１ represents a hydrogen atom or a methyl group. ５２ , R ５３ R each independently represents a hydrogen atom, a hydrocarbon group, or an alkoxy group. ５４ represents a single bond or an oxygen atom. ５１ represents an integer of 0 to 10. ２ is Ar in the formula (2). ４１ ~Ar ４３ indicates the bond with 5. The electrophotographic photoreceptor according to claim 1 or 2, wherein the bonding group to the other structural unit in the formula (1) includes the following formula (1a) or (1b): (In formula (1a) and formula (1b), * represents X in formula (1) １ ~X ４ indicates the bond with 6. The electrophotographic photoreceptor according to claim 1 or 2, wherein the functional group equivalent of the bonding group to the other structural unit in formula (1) is 4000 g / eq or less.

7. The electrophotographic photoreceptor according to claim 1 or 2, wherein the structural unit having the structure represented by formula (1) has a structure represented by formula (1A): (In formula (1A), X １ , X ２ , R １ , R ２ , n １ , n ２ are X in the formula (1), respectively. １ , X ２ , R １ , R ２ , n １ , n ２ is synonymous with 8. The electrophotographic photoreceptor according to claim 1 or 2, wherein the polymer further contains a structural unit (C) other than the structural unit (A) having the silicone structure and the structural unit (B) having the charge transport structure, and the structural unit (C) has a structure derived from at least one selected from the group consisting of an acryloyl group, a methacryloyl group, a vinyl group, and an epoxy group.

9. The electrophotographic photoreceptor according to claim 1 or 2, which has a protective layer on the photosensitive layer, and the outermost surface layer is the protective layer.

10. An electrophotographic photosensitive member cartridge comprising the electrophotographic photosensitive member according to claim 1 or 2.

11. An image forming apparatus having the electrophotographic photosensitive member according to claim 1 or 2.

Images