Electrophotographic photoreceptor

Abstract

To provide an electrophotographic photoreceptor comprising at least a photosensitive layer and a protective layer sequentially on a conductive support, wherein the electrophotographic photoreceptor achieves improved electrical properties, particularly residual potential and potential holding ratio.SOLUTION: The present invention provides an electrophotographic photoreceptor comprising at least a photosensitive layer and a protective layer sequentially on a conductive support, wherein an electron-transporting compound contained in the photosensitive layer and an electron-transporting compound contained in the protective layer satisfy formula (I): EAETM<EAOCL (I) (where EAETM represents the electron affinity (eV) of the electron-transporting backbone of the electron-transporting compound contained in the photosensitive layer and EAOCL represents the electron affinity (eV) of the electron-transporting backbone of the electron-transporting compound contained in the protective layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrophotographic photoreceptor for use in copiers, printers, etc., which has at least a photosensitive layer and a protective layer sequentially provided on a conductive support, and which has improved electrical properties such as residual potential characteristics, and improved mechanical properties such as hardness and elastic deformation rate. [Background technology]

[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 generated, and an image is obtained by attaching toner to the electrostatic latent image. In such devices that use electrophotography, the photoconductor is the core material.

[0003] This type of organic photoreceptor has a wide range of material options and is easy to control the characteristics of the photoreceptor, so that "functionally separated photoreceptors" in which the functions of charge generation and transport are shared by different compounds are becoming mainstream. For example, a single-layer electrophotographic photoreceptor (hereinafter referred to as a "single-layer photoreceptor") having a charge generation material (CGM) and a charge transport material (CTM) in the same layer, and a laminated electrophotographic photoreceptor (hereinafter referred to as a "laminated photoreceptor") formed by laminating a charge generation layer containing a charge generation material (CGM) and a charge transport layer containing a charge transport material (CTM) are known. In addition, the charging method of the photoreceptor can be 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. Combinations of layer structures and charging methods of photoreceptors currently in practical use include "negatively charged multi-layer photoreceptors" and "positively charged single-layer photoreceptors."

[0004] A "negatively charged laminated photoreceptor" generally has a structure in which an undercoat layer (UCL) made of a resin or the like is provided on a conductive substrate 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, 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 substrate such as an aluminum tube, and a single-layer photosensitive layer made of a charge generating material (CGM), a hole transporting material (HTM), an electron transporting material (ETM), and a resin or the like is provided on top of the undercoat layer (UCL) (see, for example, Patent Document 1).

[0006] In either photoconductor, the surface of the photoconductor is first charged using corona discharge or contact, then the photoconductor 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 photoconductor surface to form a toner image that corresponds to the electrostatic latent image, which is then transferred to paper or the like and heated to melt and fix it, completing the print.

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

[0008] As a technique for improving the mechanical strength or abrasion resistance of the photoreceptor surface, a photoreceptor has been disclosed in which a layer containing a compound having a chain-polymerizable functional group as a binder resin is formed in the outermost layer of the photoreceptor, and this is polymerized by applying energy such as heat, light, or radiation to form a hardened resin layer (see, for example, Patent Documents 1 and 2). Such a protective layer is generally formed by dissolving a curable composition containing a compound having a chain polymerizable functional group in an organic solvent to prepare a coating liquid for forming a protective layer, and then coating the coating liquid for forming a protective layer on the surface of the photoreceptor. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Pat. No. 9,417,538 [Patent Document 2] International Publication No. 2010 / 035683 Summary of the Invention [Problem to be solved by the invention]

[0010] It is known that a protective layer is provided to improve the abrasion resistance of a photoreceptor. Among them, a protective layer using a curable compound (a compound having a chain-polymerizable functional group) is particularly excellent in mechanical strength. Moreover, from the viewpoint of improving the electrical properties of the photoreceptor, the protective layer is also required to have good electron transport properties. In order to improve the electrical properties of the photoreceptor, it is considered effective to incorporate a compound having an electron transport structure into the protective layer. However, it has been found that, depending on the combination of the composition of the photosensitive layer and the protective layer, the electrical properties (residual potential and potential retention rate) of the photoreceptor on which the protective layer is formed may be insufficient.

[0011] An object of the present invention is to provide an electrophotographic photoreceptor having at least a photosensitive layer and a protective layer in this order on a conductive support, which can improve electrical characteristics, particularly residual potential and potential retention rate. [Means for solving the problem]

[0012] The present inventors have found that when the electron affinity of the electron transport compound contained in the photosensitive layer and the electron affinity of the electron transport compound contained in the protective layer satisfy a specific relationship, the electron injection property from the photosensitive layer to the protective layer is improved, and the electrical characteristics of the photoreceptor are improved. The present invention has been achieved based on these findings, and has the following gist.

[0013] [1] An electrophotographic photoreceptor having at least a photosensitive layer and a protective layer in this order on a conductive support, The electron transporting compound contained in the photosensitive layer and the electron transporting compound contained in the protective layer satisfy the following formula (I): EA ETM <EA OCL (I) (In formula (I), EA ETMrepresents the electron affinity (eV) of the electron transport skeleton of the electron transport compound contained in the photosensitive layer, and EA OCL represents the electron affinity (eV) of the electron transporting skeleton of the electron transporting compound contained in the protective layer.

[0014] [2] The electrophotographic photoreceptor according to [1] above, wherein the photosensitive layer contains an electron transporting compound that satisfies the following formula (II): EA ETM ≧3.8eV (II) (In formula (II), EA ETM represents the electron affinity (eV) of the electron transporting skeleton of the electron transporting compound contained in the photosensitive layer.

[0015] [3] The electrophotographic photoreceptor according to [1] or [2] above, wherein the electron transporting compound contained in the protective layer includes a compound represented by formula (1) described below.

[0016] [4] The electrophotographic photoreceptor according to [3] above, wherein in formula (1), X is represented by any of formulas (A-1) to (A-27) described below. [5] The electrophotographic photoreceptor according to the above [3] or [4], wherein at least one of A in the formula (1) is represented by the above formula (2). [6] In the formula (2), L 1 and L 2 At least one of the following is a group represented by formula (1A) or a group represented by formula (3A):

[0017] [7] The electrophotographic photoreceptor according to any one of [3] to [6] above, wherein the compound represented by formula (1) has at least one polymerizable functional group in one molecule. [8] The electrophotographic photoreceptor according to [7] above, wherein the polymerizable functional group is selected from the groups represented by formulae (M1) to (M7) described below.

[0018] [9] In the formula (2), R 1 The electrophotographic photoreceptor according to any one of the above [3] to [8], wherein is an alkyl group which may have a substituent.

[0019]

[10] The electrophotographic photoreceptor according to any one of [1] to [9] above, wherein the protective layer further contains a polymer of a polymerizable compound having no electron transport skeleton.

[11] The electrophotographic photoreceptor according to any one of [1] to

[10] above, wherein the protective layer further contains an electron-donating compound.

[0020]

[12] The electrophotographic photoreceptor according to any one of [1] to

[11] above, wherein the electron transporting compound contained in the photosensitive layer includes at least one of compounds represented by formulas (100) to (104) described below.

[0021]

[13] An electrophotographic photoreceptor cartridge comprising the electrophotographic photoreceptor according to any one of [1] to

[12] .

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

[12] . Effect of the Invention

[0022] According to the present invention, it is possible to provide an electrophotographic photoreceptor having at least a photosensitive layer and a protective layer in this order on a conductive support, and having excellent electrical properties such as residual potential characteristics and potential retention rate. [Brief description of the drawings]

[0023] [Figure 1] 1 is a diagram illustrating an example of the configuration of an image forming apparatus that can be configured using an electrophotographic photoreceptor according to an example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The following describes in detail the mode for carrying out the present invention (hereinafter, the embodiment of the invention). Note that the present invention is not limited to the following embodiment, and can be carried out in various modifications within the scope of the gist of the present invention.

[0025] <<Photoreceptor of the present invention>> An electrophotographic photoreceptor according to one embodiment of the present invention (hereinafter also referred to as "photoreceptor of the present invention") is an electrophotographic photoreceptor having at least a photosensitive layer and a protective layer, successively provided on a conductive support.

[0026] The photoreceptor of the present invention may optionally have layers other than the photosensitive layer and the protective layer. The charging method of the photoconductor of the present invention may be either a negative charging method in which the surface of the photoconductor is negatively charged or a positive charging method in which the surface of the photoconductor is positively charged. Among them, from the viewpoint of requiring the protective layer to have electron transport properties, the positive charging method is preferred because it is considered that the effect of the present invention can be further obtained with the positive charging method.

[0027] In the photoreceptor of the present invention, the side opposite the conductive support is the upper side or front side, and the conductive support side is the lower side or back side.

[0028] <Electron affinity> In the photoreceptor of the present invention, it is preferable that the electron transporting compound contained in the photosensitive layer (referred to as the "photosensitive layer electron transporting compound") and the electron transporting compound contained in the protective layer (referred to as the "protective layer electron transporting compound") satisfy the following formula (I). EA ETM <EA OCL (I) (In formula (I), EA ETM represents the electron affinity (eV) of the electron transport skeleton of the electron transport compound contained in the photosensitive layer, and EA OCL represents the electron affinity (eV) of the electron transporting skeleton of the electron transporting compound contained in the protective layer.

[0029] One of the reasons why the electrical properties of the photosensitive layer are insufficient is presumably due to poor electron injection from the photosensitive layer to the protective layer. It is believed that when the electron transport compound of the photosensitive layer and the electron transport compound of the protective layer satisfy the above formula (I), the barrier for electron injection from the photosensitive layer to the protective layer becomes small, and the electron injection property becomes good. On the other hand, when formula (I) is not satisfied, the electron injection from the photosensitive layer to the protective layer requires energy equivalent to the difference, and therefore the electron injection property is thought to be poor.

[0030] Among them, EA ETM and E.A. OCL The difference is preferably 0.01 eV or more, more preferably 0.05 eV or more, and even more preferably 0.10 eV or more. On the other hand, from the viewpoint of the electron injection barrier from the photosensitive layer to the protective layer, the difference is preferably 1.0 eV or less, more preferably 0.50 eV or less, and even more preferably 0.30 eV or less. In addition, when the photosensitive layer contains two or more kinds of electron transport compounds, EA ETM The value of the electron transport compound having the largest electron affinity of the electron transport skeleton is used as the EA. Similarly, when the protective layer contains two or more kinds of electron transport compounds, the EA OCL As the electron affinity, the value of the electron transporting compound having the largest electron affinity of the electron transporting skeleton is used.

[0031] In the present invention, the term "electron transporting compound" refers to a compound having an electron transporting property, in other words, a compound having an electron transporting skeleton.

[0032] Furthermore, in the photoreceptor of the present invention, it is particularly preferable that the electron transporting compound in the photosensitive layer satisfies the following formula (II). EA ETM ≧3.8eV (II) (In formula (II), EA ETM represents the electron affinity (eV) of the electron transporting skeleton of the electron transporting compound in the photosensitive layer.

[0033] When the photoreceptor of the present invention satisfies the above formulae (I) and (II), the electron transporting properties of the electron transporting compounds in the photosensitive layer and protective layer become more excellent, resulting in more excellent electrical properties. From this perspective, EA ETM is more preferably 3.82 eV or more, more preferably 3.88 eV or more, and even more preferably 3.93 eV or more. On the other hand, from the viewpoint of stability, it is preferably 5.0 eV or less, even more preferably 4.8 eV or less, and even more preferably 4.5 eV or less.

[0034] On the other hand, the protective layer electron transporting compound preferably satisfies the above formulas (I) and (II), and from this viewpoint, it is particularly preferable that the protective layer electron transporting compound satisfies the formula (III). 5.0eV ≥ EA OCL ≧3.8eV (III) (In formula (III), EA OCL represents the electron affinity (eV) of the electron transporting skeleton of the electron transporting compound in the protective layer.

[0035] From this perspective, EA OCL is more preferably 3.9 eV or more, more preferably 4.0 eV or more, and even more preferably 4.1 eV or more. On the other hand, from the viewpoint of stability, it is preferably 4.8 eV or less, even more preferably 4.5 eV or less, and even more preferably 4.3 eV or less. The electron affinity can be determined by the method described in the Examples below.

[0036] <Main protective layer> The protective layer of the photoreceptor of the present invention (sometimes referred to as the "present protective layer") preferably contains the above-mentioned protective layer electron transport compound, and the protective layer electron transport compound preferably contains a compound represented by the following formula (1) (sometimes referred to as the "present ETM compound"). In addition, when the ETM compound of the present invention has a polymerizable functional group in one molecule, it may be present in the form of a polymer in the protective layer after curing. For example, the ETM compound of the present invention may be polymerized with itself, or when the protective layer contains a curable compound, it may be polymerized with the curable compound.

[0037] TIFF2025002420000002.tif25170

[0038] The mechanism by which the photoreceptor of the present invention containing the ETM compound of the present invention exhibits the effect of excellent electrical properties is believed to be as follows. Since the ETM compound of the present invention has an electron transport structure, by using the ETM compound of the present invention in forming the protective layer, charge injection from the photosensitive layer to the protective layer and charge mobility to the outermost surface are improved through the electron transport skeleton, making it possible to obtain an electrophotographic photoreceptor with excellent electrical properties such as residual potential characteristics. In addition, when the ETM compound of the present invention has a polymerizable functional group, the ETM compound of the present invention is polymerized in the protective layer forming step described below to form a polymer, which can form a protective layer with excellent mechanical strength. In this case, the polymer may be a polymer formed by polymerizing the ETM compound of the present invention with itself, or, when the protective layer contains a polymerizable compound that does not have an electron transport skeleton, it may be a copolymer formed by polymerizing the polymerized compound with the ETM compound of the present invention.

[0039] From the viewpoint of more effectively obtaining the effect of the ETM compound of the present invention, the present protective layer is preferably the outermost layer, that is, the outermost layer located on the opposite side to the conductive support. However, the present protective layer does not necessarily have to be the outermost layer, and the effect of the present invention can be obtained. For example, when some kind of segregation layer exists on the outermost layer of the photoreceptor, the present protective layer can be used to obtain the effect even if it is not the outermost layer.

[0040] In the following, we will first explain the ETM compound of the present invention used in forming the protective layer of the present invention, and then we will explain the composition containing the ETM compound of the present invention (hereinafter also referred to as the "composition of the present invention" or "this composition") and the electrophotographic photoreceptor of the present invention.

[0041] The content of the ETM compound of the present invention in the protective layer is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, based on 100% by mass of the entire protective layer, from the viewpoint of electron transportability. Also, from the viewpoint of solubility, the content is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. From the viewpoint of electron transportability, the content of the ETM compound of the present invention is preferably 100 parts by mass or more, more preferably 150 parts by mass or more, even more preferably 200 parts by mass or more, and particularly preferably 250 parts by mass or more, relative to 100 parts by mass of the electron transport compound in the photosensitive layer, while from the viewpoint of solubility, the content is preferably 350 parts by mass or less, more preferably 300 parts by mass or less, and even more preferably 295 parts by mass or less. The total content of the protective layer electron transport compound including the ETM compound of the present invention in the protective layer is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on 100% by mass of the entire protective layer, from the viewpoints of film hardness and elastic deformation rate, and is preferably 100% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, from the viewpoint of solubility.

[0042] <ETM compound of the present invention> The ETM compound of the present invention is a compound represented by the following formula (1).

[0043] TIFF2025002420000003.tif25170

[0044] <x> In the above formula (1), X represents an electron transporting skeleton having a valence of n. X is preferably a skeleton represented by any of the following formulas (A-1) to (A-27). When the electron transporting skeleton is a skeleton represented by the following formula (A-10), (A-11), or (A-26), the electron transporting property is excellent and the electrical characteristics (VL) are further improved, which is more preferable.

[0045] TIFF2025002420000004.tif44170

[0046] TIFF2025002420000005.tif50170

[0047] TIFF2025002420000006.tif48170

[0048] TIFF2025002420000007.tif47170

[0049] TIFF2025002420000008.tif44170

[0050] TIFF2025002420000009.tif48170

[0051] TIFF2025002420000010.tif49170

[0052] TIFF2025002420000011.tif47170

[0053] TIFF2025002420000012.tif49170

[0054] TIFF2025002420000013.tif50170

[0055] TIFF2025002420000014.tif51170

[0056] TIFF2025002420000015.tif63170

[0057] TIFF2025002420000016.tif47170

[0058] TIFF2025002420000017.tif48170

[0059] TIFF2025002420000018.tif45170

[0060] TIFF2025002420000019.tif39170

[0061] TIFF2025002420000020.tif48170

[0062] TIFF2025002420000021.tif58170

[0063] TIFF2025002420000022.tif56170

[0064] TIFF2025002420000023.tif62170

[0065] TIFF2025002420000024.tif56170

[0066] TIFF2025002420000025.tif53170

[0067] TIFF2025002420000026.tif68170

[0068] TIFF2025002420000027.tif44170

[0069] TIFF2025002420000028.tif48170

[0070] TIFF2025002420000029.tif52170

[0071] TIFF2025002420000030.tif36170

[0072] In the formulae (A-1) to (A-27), * represents a bond to A. R A11 , R A21 , R A31 , R A41 , R A51 , R A61 , R A62 , R A71 , R A72 , R A81 , R A82 , R A91 , R A92 , R A101 , R A111 , R A121 , R A131 , R A141 , R A151 , R A161 , R A171 , R A181 , R A182 , R A191 , R A192 , R A201 , R A202 , R A211 , R A212 , R A221 , R A222 , R A231 , R A232 , R A241 , R A242 , R A251 , R A252 , R A261 , R A262 each independently represents a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aromatic group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, an acyl group which may have a substituent, an ester group which may have a substituent, a cyano group, a nitro group, a sulfone group which may have a substituent, a hydroxy group, an aldehyde group which may have a substituent, or a halogen atom.

[0073] In formulas (A-1) to (A-27), m11, m21, m31, m41, m51, m61, m62, m71, m72, m81, m82, m91, m92, m101, m111, m121, m131, m141, m151, m161, m171, m181, m182, m191, m192, m201, m202, m211, m212, m221, m222, m231, m232, m241, m242, m251, m252, m261, and m262 each independently represent an integer of 0 or more. When m11, m21, m31, m41, m51, m61, m62, m71, m72, m81, m82, m91, m92, m101, m111, m121, m131, m141, m151, m161, m171, m181, m182, m191, m192, m201, m202, m211, m212, m221, m222, m231, m232, m241, m242, m251, m252, m261, and m262 are each 2 or more, R A11 ~R A262 may be different from each other.

[0074] <n> In the above formula (1), n ​​represents an integer of 1 or more, and when n is 2 or more, a plurality of As may be the same or different.

[0075] A in the above formula (1) is a hydrogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, a heteroaryloxy group which may have a substituent, an alkoxycarbonyl group which may have a substituent, a dialkylamino group which may have a substituent, a diarylamino group which may have a substituent, an arylalkylamino group which may have a substituent, an acyl group which may have a haloalkyl group, an alkylthio group which may have a substituent, an arylthio group which may have a substituent, a silyl group which may have a substituent, a siloxy group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, an aromatic heterocyclic group which may have a substituent, a group represented by the following formula (2), or a group represented by the following formula (1B).

[0076] In the present invention, the phrase "optionally has a substituent" means that the group can have a substituent, and includes both the case where the group has a substituent and the case where the group does not have a substituent.

[0077] When n is 1, A in formula (1) is a group represented by the following formula (2) or a group represented by the following formula (1B). When n is 2 or more, a plurality of As may be the same or different, and at least one As is a group represented by the following formula (2) or a group represented by the following formula (1B).

[0078] Among these, from the viewpoint of further improving the solubility in organic solvents, at least one of A is preferably a group represented by the following formula (2).

[0079] (Group represented by formula (2)) The group represented by formula (2) is an example of A in the above formula (1).

[0080] TIFF2025002420000031.tif30170

[0081] In formula (2), * represents a bond to X. R 1 and R 2 each independently represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryloxy group, an optionally substituted heteroaryloxy group, an optionally substituted alkoxycarbonyl group, an optionally substituted dialkylamino group, an optionally substituted diarylamino group, an optionally substituted arylalkylamino group, an optionally substituted acyl group, an optionally substituted haloalkyl group, an optionally substituted alkylthio group, an optionally substituted arylthio group, an optionally substituted silyl group, an optionally substituted siloxy group, an optionally substituted aromatic hydrocarbon group, an optionally substituted aromatic heterocyclic group, or a group represented by the following formula (1B):

[0082] From the viewpoint of further improving the solubility in an organic solvent, the group represented by formula (2) preferably has two branches and a polymerizable functional group in the side chain. 1 is an alkyl group which may have a substituent, the formula (2) is branched at the alkyl group, and the solubility in organic solvents is further improved, which is preferable.

[0083] In formula (2), L 1 and L 2 each independently represents a direct bond, a divalent group, a group represented by the following formula (1A) or a group represented by the following formula (3A). In particular, if the side chains having urethane bonds are branched, the solubility in organic solvents is further improved, so L 1 and L 2 At least one of the above is preferably a group represented by the following formula (1A) or a group represented by the following formula (3A).

[0084] In formula (2), Z represents a hydrogen atom, an alkyl group, an alkoxy group, an amide group, or a polymerizable functional group. x1 is an integer from 0 to 2, y1 is an integer from 1 to 3, and x1+y1=3. x2 is an integer from 0 to 2, y2 is an integer from 1 to 3, and x2+y2=3. When x1 is an integer of 2 or more, R 1 may be the same or different. When y1 is an integer of 2 or more, R 2、 x2, y2, L 1、 L 2 and Z may be the same or different from each other. When x2 is an integer of 2 or more, R2 may be the same or different from each other. When y2 is an integer of 2 or more, L 2 and Z may be the same or different from each other.

[0085] (Group represented by formula (1B)) The group represented by formula (1B) is also an example of A in the above formula (1), and L in the above formula (2) 1 and L 2 This is also an example of.

[0086] TIFF2025002420000032.tif36170

[0087] In formula (1B), * represents a bond to any atom in formula (1) or (2). B 1 and B. 2 each independently represents a direct bond or a divalent group. R 3 represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryloxy group, an optionally substituted heteroaryloxy group, an optionally substituted alkoxycarbonyl group, an optionally substituted dialkylamino group, an optionally substituted diarylamino group, an optionally substituted arylalkylamino group, an optionally substituted acyl group, an optionally substituted haloalkyl group, an optionally substituted alkylthio group, an optionally substituted arylthio group, an optionally substituted silyl group, an optionally substituted siloxy group, an optionally substituted aromatic hydrocarbon group, an optionally substituted aromatic heterocyclic group, or a polymerizable functional group.

[0088] (Group represented by formula (1A)) The group represented by formula (1A) is L in the above formula (2). 1 and L 2 This is an example.

[0089] TIFF2025002420000033.tif44170

[0090] In formula (1A), * represents a bond to any atom in formula (1) and formula (2). B 1 and B. 2 each independently represents a direct bond or a divalent group. Examples of the divalent group include an alkylene group, a divalent group having a ketone group, a divalent group having an ether bond, a divalent group having an ester bond, or a group formed by linking these groups.

[0091] (Group represented by formula (3A)) The group represented by formula (3A) is L in the above formula (2). 1 and L 2 This is an example.

[0092] TIFF2025002420000034.tif41156

[0093] In formula (3A), * represents a bond to any atom in formula (1) and formula (2). n is an integer of 1 or greater.

[0094] <Polymerizable Functional Group> The ETM compound of the present invention preferably has at least one polymerizable functional group in one molecule. By having one or more polymerizable functional groups, crosslinking property is enhanced, hardness of the present protective layer is increased, and mechanical strength can be increased. The ETM compound of the present invention may have one or more polymerizable functional groups, but from the viewpoints of solubility in an organic solvent and curability, the number of polymerizable functional groups is preferably two or more, and more preferably four or more. On the other hand, from the viewpoint of compound stability, the number of polymerizable functional groups possessed by the ETM compound of the present invention is preferably 12 or less, more preferably 10 or less, and more preferably 8 or less.

[0095] The polymerizable functional group is not particularly limited as long as it is a functional group having polymerizability, and examples thereof include polymerizable functional groups represented by the following formulae (M1) to (M7).

[0096] TIFF2025002420000035.tif56170

[0097] In the above formulas (M1) to (M7), R 110 represents a hydrogen atom or an alkyl group which may have a substituent, and * represents the bonding position.

[0098] R in the above formulas (M1) to (M7) 110 As the group, a hydrogen atom or an alkyl group having no substituent is preferable, a hydrogen atom or an alkyl group having 1 to 10 carbon atoms is preferable, and a hydrogen atom or a methyl group is particularly preferable. When the ETM compound of the present invention has two or more polymerizable functional groups, they do not all need to be the same and may be different, but from the viewpoint of curability, it is preferable that they are the same.

[0099] <Example> Specific examples of the ETM compound of the present invention include the following: However, the ETM compound of the present invention is not limited to the following compounds.

[0100] TIFF2025002420000036.tif32170

[0101] TIFF2025002420000037.tif50170

[0102] TIFF2025002420000038.tif67170

[0103] TIFF2025002420000039.tif51170

[0104] TIFF2025002420000040.tif65170

[0105] TIFF2025002420000041.tif66170

[0106] TIFF2025002420000042.tif47170

[0107] TIFF2025002420000043.tif64170

[0108] TIFF2025002420000044.tif57170

[0109] TIFF2025002420000045.tif63170

[0110] TIFF2025002420000046.tif74170

[0111] TIFF2025002420000047.tif73170

[0112] TIFF2025002420000048.tif73170

[0113] TIFF2025002420000049.tif65170

[0114] <Solubility of the ETM compound of the present invention> The ETM compound of the present invention has excellent solubility in organic solvents, particularly alcoholic solvents and mixed solvents containing alcoholic solvents, and is preferably soluble in a mixed solvent of toluene and 2-propanol (toluene 30% by mass, 2-propanol 70% by mass) at 3% by mass or more, particularly 6% by mass or more.

[0115] <<The composition>> The composition of the present invention (hereinafter also referred to as "the composition") contains the above-mentioned protective layer electron transport compound, and is used as a curable composition for preparing a coating liquid for forming a protective layer of the electrophotographic photoreceptor of the present invention, as described below.

[0116] The composition contains an electron transporting compound including at least a protective layer electron transporting compound, and optionally contains a polymerizable compound not having an electron transporting skeleton, an electron donor compound, a polymerization initiator, inorganic particles, and other materials. In the present invention, the term "composition" refers to a composition that is made up of only solid components that do not contain a solvent. Therefore, the content of each component, such as the protective layer electron transport compound, in 100 parts by mass of the present composition described below corresponds to the content of each component in 100 parts by mass of the total mass of the protective layer formed using the present composition. The total mass of the protective layer means the total mass of the protective layer after curing, that is, the total mass of the solid content in the coating liquid for forming the protective layer, which will be described later.

[0117] <Electron transport compound> The electron transporting compound contained in the present composition includes at least the ETM compound of the present invention, and may contain an electron transporting compound other than the ETM compound of the present invention as necessary. The composition may contain only one type of the ETM compound of the present invention, or may contain two or more types.

[0118] Examples of electron transporting compounds other than the ETM compound of the present invention include the compounds shown below.

[0119] TIFF2025002420000050.tif198170

[0120] TIFF2025002420000051.tif88170

[0121] As for the electron transporting compounds other than the ETM compound of the present invention, only one type may be contained in the composition, or two or more types may be contained.

[0122] From the viewpoint of electron transportability, the content of the electron transport compound in the composition is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more, relative to 100 parts by mass of the total mass of the composition, while from the viewpoint of the hardness and elastic deformation rate of the protective layer, the content is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less. In addition, when the composition contains an electron transporting compound other than the ETM compound of the present invention, from the viewpoint of effectively obtaining the excellent solvent solubility, electrical properties, and mechanical properties provided by the ETM compound of the present invention, the content of the ETM compound of the present invention is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more, relative to 100 parts by mass of the total mass of the electron transporting compounds in the composition, and may be 100 parts by mass.

[0123] <Polymerizable Compound Not Having Electron Transporting Skeleton> The present composition may contain a polymerizable compound that does not have an electron transport skeleton. When the present composition contains a polymerizable compound that does not have an electron transport skeleton, the present protective layer described below contains a polymer of a polymerizable compound that does not have an electron transport skeleton. Since the ETM compound of the present invention has one or more polymerizable functional groups, it can also function as a curable compound. Therefore, even if the composition does not contain a polymerizable compound that does not have an electron transport skeleton, a protective layer can be formed with good curability by the method described below. However, by using a polymerizable compound that does not have an electron transport skeleton in addition to the ETM compound of the present invention, the mechanical strength of the protective layer formed can be further improved.

[0124] The polymerizable compound without an electron transport backbone may be a compound having a chain polymerizable functional group. Among them, a monomer, oligomer or polymer having a radical polymerizable functional group is preferable. Among them, a curable compound having crosslinking properties, particularly a photocurable compound, is preferable. For example, a curable compound having two or more radical polymerizable functional groups can be mentioned. A compound having one radical polymerizable functional group can also be used in combination.

[0125] The radically polymerizable functional group may be either an acryloyl group (including an acryloyloxy group) or a methacryloyl group (including a methacryloyloxy group), or both of these groups.

[0126] Preferred examples of the curable compound having a radically polymerizable functional group are given below. Examples of monomers having an acryloyl group or a methacryloyl group include trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, glycerol triacrylate, tris(acryloxyethyl)isocyanurate, dipentaerythritol hexaacrylate, dimethylolpropane tetraacrylate, pentaerythritol ethoxy tetraacrylate, EO-modified phosphate triacrylate, 2,2,5,5-tetrahydroxymethylcyclopentanone tetraacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, polyethylene glycol diacrylate, and the like. acrylate, polypropylene glycol diacrylate, polytetramethylene glycol diacrylate, EO-modified bisphenol A diacrylate, PO-modified bisphenol A diacrylate, 9,9-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, hexanediol dimethacrylate, and the like.

[0127] Examples of oligomers and polymers having an acryloyl group or a methacryloyl group include urethane acrylate, ester acrylate, acrylic acrylate, epoxy acrylate, etc. Among these, urethane acrylate and ester acrylate are preferred, and among these, ester acrylate is more preferred.

[0128] The above compounds can be used alone or in combination of two or more kinds.

[0129] A preferred example of a polymerizable compound that does not have an electron transport skeleton is a polyfunctional acrylate compound that does not have an aromatic ring such as a benzene ring, as shown in the following structure. By including such a polyfunctional acrylate compound, the crosslinking property is increased, the hardness of the protective layer is increased, and the mechanical strength is increased. In addition, the ETM compound of the present invention can be dispersed and crystallization can be suppressed. Crystallization causes leakage current, which is not preferable for a photoreceptor.

[0130] TIFF2025002420000052.tif75170

[0131] When the present composition contains such a polymerizable compound having no electron transport skeleton, the content ratio (mass ratio) of the polymerizable compound to the electron transport compound in the present composition is preferably 1.5 or less, more preferably 1.0 or less, and even more preferably 0.75 or less from the viewpoint of electron transportability, while the content ratio (mass ratio) is preferably 0.2 or more, more preferably 0.3 or more, and even more preferably 0.4 or more from the viewpoint of hardness and elastic deformation rate of the protective layer. The content of the polymerizable compound not having an electron transport skeleton in the present composition corresponds to the content of the polymer in the present protective layer described below.

[0132] <Electron donor compound> The present composition may further contain an electron donating compound. When the present composition contains an electron donating compound, the present protective layer described below contains the electron donating compound.

[0133] In the present invention, the term "electron donating compound" refers to a compound that can donate electrons to the protective layer. In other words, the term "electron donating compound" refers to a compound that can reduce the energy barrier during electron transfer in the target compound (electron transporting compound) in the protective layer by any mechanism, and can inject electrons into the target compound. The mechanism may be, for example, a mechanism in which the electron donating compound directly transfers electrons to the target compound, a mechanism in which the electron donating compound and the target compound form a hydrogen bond to transfer electrons, or a mechanism in which the electron donating compound and the target compound form a hydrogen bond to reduce the energy barrier during electron transfer, and an electron transferred from the photosensitive layer is injected into the target compound present in the protective layer.

[0134] Examples of currently known electron donating compounds include compounds having structures such as triphenylmethane, acridine, amine, amidine, aniline, pyridine, xanthene, benzimidazole, guanidine, and phosphazene. Compounds that will be recognized to have such effects in the future are also included.

[0135] As described above, examples of the electron donating compound include compounds having structures such as triphenylmethane, acridine, amine, amidine, aniline, pyridine, xanthene, benzimidazole, guanidine, and phosphazene. Among them, compounds having a benzimidazole structure or a guanidine structure are preferred from the viewpoint of stability. As the guanidine structure, both a chain guanidine structure and a cyclic guanidine structure can be used, but from the viewpoint of stability, a cyclic guanidine structure is preferred.

[0136] The electron donor compound is preferably a compound having one or more heteroatoms in the molecule, and more preferably a compound having one or more nitrogen atoms (N atoms) in the molecule. From the viewpoint of stability, the number of heteroatoms in one molecule of the electron donor compound is preferably one or more, more preferably two or more, and even more preferably three or more. In addition, from the viewpoint of electron donating ability, the number of nitrogen atoms (N atoms) in one molecule of the electron donor compound is preferably one or more, more preferably two or more, and even more preferably three or more. From the viewpoint of stability, the electron donating compound is preferably a compound having one or more cyclic structures.

[0137] The electron donor compound is preferably an electron donor compound represented by the following formula (4) or (5). These electron donor compounds are activated, for example, when heated to room temperature or higher, and can donate electrons to the protective layer. Specifically, the electron donor compound represented by the following formula (4) is activated when heated to about 80° C. or higher, and can donate electrons to the protective layer. The electron donor compound represented by the following formula (5) is activated when heated to room temperature or higher, and can donate electrons to the protective layer. Thus, for example, when forming a protective layer, these compounds are activated by the temperature rise caused by ultraviolet irradiation, and can donate electrons to the protective layer.

[0138] TIFF2025002420000053.tif65170

[0139] In formula (4), E 1 ~E 4 are each independently preferably a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted thioalkyl group, an optionally substituted thioaryl group, an optionally substituted arylsulfonyl group, an optionally substituted amino group, an optionally substituted alkylamino group, an optionally substituted arylamino group, an optionally substituted hydroxy group, an optionally substituted alkoxy group, an optionally substituted acylamino group, an optionally substituted acyloxy group, an optionally substituted aromatic hydrocarbon group, an optionally substituted carboxy group, an optionally substituted carboxamido group, an optionally substituted carboalkoxy group, an optionally substituted acyl group, an optionally substituted sulfonyl group, an optionally substituted cyano group, an optionally substituted nitro group, or a derivative of any of these groups. Also, E 1 ~E 4 may be bonded to each other to form a ring.

[0140] In the above formula (4), h is an integer of 0 or more, and from the viewpoint of stability, it is preferably 2 or less, more preferably 1 or less, and even more preferably 0.

[0141] In the above formula (5), g1 is an integer of 1 or more, and from the viewpoint of electrical properties, it is preferably 4 or less, more preferably 3 or less, and even more preferably 2 or less.

[0142] In the above formula (5), Ar is preferably represented by the following formula (6).

[0143] TIFF2025002420000054.tif43170

[0144] In formula (6), * represents G in formula (5). 21 Represents a bond with. G 22 is preferably an alkyl group which may have a substituent, an alkoxy group which may have a substituent, or a halogen atom.

[0145] In formula (6), g2 is an integer of 0 or more, and from the viewpoint of stability, preferably 2 or less, more preferably 1 or less, and most preferably 0.

[0146] G in Equation (5) 21 is preferably a hydrocarbon group which may have a substituent. The number of carbon atoms in the hydrocarbon group is preferably 1 or more, more preferably 3 or more, and is preferably 12 or less, more preferably 10 or less. When g1 is 1, the hydrocarbon group is preferably an alkyl group, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, an octyl group, or a decyl group. When g1 is 2, the hydrocarbon group is preferably an alkylene group, such as a methylene group or an ethylene group.

[0147] From the viewpoint of electrical properties, the content of the electron donor compound in the composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the total composition. On the other hand, from the viewpoint of electrical properties, the content is preferably 25 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 5.0 parts by mass or less, relative to 100 parts by mass of the total composition.

[0148] Specific examples of the electron donating compound are shown below, but the compounds are not limited thereto.

[0149] TIFF2025002420000055.tif124170

[0150] The composition may contain one or more of these electron donor compounds.

[0151] <Polymerization initiator> Examples of the polymerization initiator include a thermal polymerization initiator and a photopolymerization initiator. Examples of the thermal polymerization initiator include peroxide compounds such as 2,5-dimethylhexane-2,5-dihydroperoxide, and azo compounds such as 2,2'-azobis(isobutyronitrile).

[0152] Photopolymerization initiators can be classified into direct cleavage type and hydrogen abstraction type depending on the radical generation mechanism. Direct cleavage photopolymerization initiators generate radicals by cleaving some of the covalent bonds in the molecule when they absorb light energy, whereas hydrogen abstraction photopolymerization initiators generate radicals when the molecule becomes excited by absorbing light energy and abstracts hydrogen from the hydrogen donor.

[0153] 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.

[0154] Examples of the hydrogen abstraction type photopolymerization initiator 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 the photopolymerization initiator include camphorquinone, 1-phenyl-1,2-propanedione-2-(o-ethoxycarbonyl)oxime, acridine compounds, triazine compounds, and imidazole compounds.

[0155] In order to efficiently absorb light energy and generate radicals, the photopolymerization initiator preferably has an absorption wavelength in the wavelength region of the light source used for light irradiation. Among them, it is preferable to contain an acylphosphine oxide compound having an absorption wavelength on the relatively long wavelength side. In addition, from the viewpoint of supplementing the curability, it is more preferable to use an acylphosphine oxide compound and a hydrogen abstraction initiator in combination. In this case, the content ratio of the hydrogen abstraction initiator relative to the acylphosphine oxide compound is not particularly limited. From the viewpoint of supplementing the surface curability, it is preferably 0.1 parts by mass or more relative to 1 part by mass of the acylphosphine oxide compound, and from the viewpoint of maintaining the internal curability, it is preferably 5 parts by mass or less.

[0156] In addition, a photopolymerization promoter may be used alone or in combination with the photopolymerization initiator. Examples of photopolymerization promoters include triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino)ethyl benzoate, and 4,4'-dimethylaminobenzophenone.

[0157] The polymerization initiator may be used alone or in combination of two or more. The content of the polymerization initiator is 0.5 to 40 parts by mass, preferably 1 to 20 parts by mass, based on 100 parts by mass of the total content having radical polymerizability. The total content having radical polymerizability includes the ETM compound of the present invention and the polymerizable compound not having an electron transport skeleton.

[0158] <Inorganic particles> The composition may contain inorganic particles from the viewpoint of improving the strong exposure characteristics and mechanical strength of the protective layer to be formed, or from the viewpoint of imparting charge transporting ability, although the inorganic particles are not an essential component of the composition of the present invention. In the present invention, by using the ETM compound of the present invention, it is possible to form a protective layer having excellent mechanical strength without the need to contain inorganic particles.

[0159] Examples of the inorganic particles include metal powders, metal oxides, metal fluorides, potassium titanate, and boron nitride. Generally, any inorganic particles that can be used for electrophotographic photoreceptors can be used. The inorganic particles may be of one type only, or a mixture of a plurality of types of particles.

[0160] <Other ingredients> The composition may contain other materials other than those described above, if 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 ratio and combination of two or more.

[0161] <Method of forming the protective layer> The protective layer is preferably formed from the composition described above. The method for forming the protective layer using the composition will be described below.

[0162] (Coating solution for forming protective layer) The protective layer can be formed by applying the above-mentioned composition, i.e., a curable composition containing an electron transporting compound including the ETM compound of the present invention, and optionally a polymerizable compound not having an electron transporting skeleton, an electron donating compound, a polymerization initiator, inorganic particles, and other materials, to the photosensitive layer and curing the coating liquid (hereinafter also referred to as "coating liquid for forming the protective layer") in which the composition is dissolved in a solvent or dispersed in a dispersion medium.

[0163] The content of the electron transport compound including the ETM compound of the present invention in the coating solution for forming the protective layer is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the solvent, from the viewpoints of film uniformity and solubility of the protective layer. The total content of the curable compounds in the coating liquid for forming a protective layer, i.e., the ETM compound of the present invention and the polymerizable compound having no electron transport skeleton, is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass, relative to 100 parts by mass of the solvent, from the viewpoint of the residual potential, while it is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of the hardness and elastic deformation rate of the protective layer.

[0164] The contents of other components in the present protective layer-forming coating liquid, i.e., components other than the electron transporting compound and the curable compound contained in the present composition, are similar to the contents of each component in the present composition described above.

[0165] As the solvent used in the present protective layer-forming coating liquid, for example, an organic solvent can be used. Examples of the organic solvent include alcohols such as methanol, ethanol, propanol, and 2-methoxyethanol; ethers such as tetrahydrofuran, 1,4-dioxane, and dimethoxyethane; esters such as methyl formate and ethyl acetate; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene, and anisole; chlorinated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, tetrachloroethane, 1,2-dichloropropane, and trichloroethylene; nitrogen-containing compounds such as n-butylamine, isopropanolamine, diethylamine, triethanolamine, ethylenediamine, and triethylenediamine; and aprotic polar solvents such as acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide, and dimethylsulfoxide. Mixed solvents of any combination and ratio among these can also be used. Among these, from the viewpoints of solubility and coatability, alcohols, ethers, aromatic hydrocarbons, and aprotic polar solvents are preferred, alcohols, ethers, and aromatic hydrocarbons are more preferred, alcohols and ethers are even more preferred, and alcohols are most preferred.

[0166] In addition, even if the organic solvent does not dissolve the electron transporting compound used in the protective layer of the photoreceptor of the present invention by itself, it can be used if it can dissolve the compound by mixing it with the above-mentioned organic solvent. In general, 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 viewpoint, it is particularly preferable to include an alcohol.

[0167] The ratio of the solvent to the solid content used in the coating solution for forming a protective layer varies depending on the coating method of the coating solution for forming a protective layer, and may be appropriately changed so as to form a uniform coating film in the coating method to be used.

[0168] (Method of applying the coating solution for forming the protective layer) The method for applying the coating solution for forming the protective layer is not particularly limited, and examples thereof include spray coating, spiral coating, ring coating, and dip coating.

[0169] After forming the coating film by the above coating method, the coating film is dried. In this case, the temperature and time of drying are not important as long as necessary and sufficient drying is obtained. However, if the protective layer is coated only by air drying after the photosensitive layer coating, it is preferable to perform sufficient drying by the method described later in the photosensitive layer forming method.

[0170] (Method of curing the protective layer) The protective layer can be formed by applying the coating solution for forming the protective layer and then curing the coating solution by applying external energy thereto. The external energy used in this case can include heat, light, and radiation.

[0171] Examples of methods for applying heat energy include heating methods using air, gases such as nitrogen, steam, various heat media, infrared rays, and electromagnetic waves. The heating can be performed from the coated surface side or the support side. The heating temperature is preferably 100°C or higher and 170°C or lower.

[0172] As for light energy, UV irradiation light sources that mainly emit light in the ultraviolet (UV) range, such as high-pressure mercury lamps, metal halide lamps, electrodeless lamp bulbs, light-emitting diodes, etc. It is also possible to select a visible light source according to the absorption wavelength of the polymerizable compound or photopolymerization initiator.

[0173] The light irradiation dose was set to 10 J / cm from the viewpoint of curing. 2 More than 15 J / cm is preferable. 2 More preferably, 20 J / cm or more. 2 More preferably, the electric field strength is 400 J / cm or more. 2 Less than 200 J / cm is preferable. 2 Less than 150 J / cm is more preferable. 2 The following is even more preferred: On the other hand, examples of radiation energy include those using electron beams (EB).

[0174] Among these energies, light energy is preferred from the viewpoints of ease of reaction rate control, simplicity of the device, and long pod life.

[0175] After the protective 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.

[0176] (layer thickness) From the viewpoint of abrasion resistance, the thickness of the protective layer is preferably 0.5 μm or more, more preferably 1 μm or more, and from the viewpoint of electrical properties, the thickness is preferably 5 μm or less, more preferably 4 μm or less. From the same viewpoint, the thickness of the protective layer is preferably 1 / 50 or more of the thickness of the photosensitive layer, more preferably 1 / 40 or more, and even more preferably 1 / 30 or more, while it is preferably 1 / 5 or less, more preferably 1 / 10 or less, and even more preferably 1 / 20 or less.

[0177] <Main photosensitive layer> The photosensitive layer in the photoreceptor of the present invention (hereinafter also referred to as "the present photosensitive layer") may be a layer containing at least the above-mentioned electron transporting compound, that is, a photosensitive layer electron transporting compound.

[0178] The photosensitive layer may be a single-layer type photosensitive layer containing both a charge generating material and a charge transporting material in the same layer, or may be a laminated type photosensitive layer separated into a charge generating layer and a charge transporting layer. In the case of a laminated type photosensitive layer, the arylamine compound described later is preferably contained in the charge transporting layer. The photosensitive layer of the present invention is preferably a single-layer type photosensitive layer, since the effects of the present invention can be more effectively enjoyed.

[0179] <Single-layer type photosensitive layer> When the photosensitive layer is a single-layer type photosensitive layer, it is preferable that the layer contains at least a charge generating material (CGM), a hole transporting material (HTM), an electron transporting material (ETM), and a binder resin.

[0180] (Charge generating material) As the charge generating material (CGM) used in the present photosensitive layer, for example, various photoconductive materials such as inorganic photoconductive materials and organic pigments can be used. Among them, organic pigments are particularly preferred, and phthalocyanine pigments and azo pigments are more preferred.

[0181] In particular, when a phthalocyanine pigment is used as the charge generating material, specifically, metal-free phthalocyanine, phthalocyanines coordinated with metals such as copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, germanium, etc., or oxides, halides, etc. thereof are used. Among them, particularly highly sensitive X-type and τ-type metal-free phthalocyanine, A-type, B-type, D-type titanyl phthalocyanine, vanadyl phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, etc. are preferred.

[0182] When an azo pigment is used, various known bisazo pigments and trisazo pigments are preferably used.

[0183] The charge generating substance may be used alone or in any combination and ratio of two or more. When two or more charge generating substances are used in combination, the charge generating substances may be mixed after the charge generating substances are mixed, or may be mixed during the production or processing steps of the charge generating substances, such as synthesis, pigmentation, or crystallization.

[0184] From the viewpoint of electrical properties, it is desirable that the particle diameter of the charge generating material is small. Specifically, the particle diameter of the charge generating material is preferably 1 μm or less, more preferably 0.5 μm or less, and the lower limit is 0.01 μm or more. Here, the particle diameter of the charge generating material means the particle diameter in the state in which it is contained in the photosensitive layer.

[0185] The amount 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.

[0186] (charge transport material) Charge transport materials are classified into hole transport materials having mainly hole transporting ability and electron transport materials having mainly electron transporting ability. However, when the present photosensitive layer is a single-layer type photosensitive layer, it is preferable that at least a hole transport material and an electron transport material are contained in the same layer.

[0187] (electron transport material) The photosensitive layer preferably contains at least an electron transporting material, that is, an electron transporting compound.

[0188] Preferred specific examples of the electron transport compound in the photosensitive layer include compounds represented by any one of the following formulas (100) to (104) (also referred to as "ketone compounds"). It is preferable to include at least one or more of these compounds.

[0189] TIFF2025002420000056.tif49170

[0190] In formula (100), Ar ETM is selected from the following formulae (100-1) to (100-3): Each R independently represents a hydrogen atom, an alkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, or a halogen atom.

[0191] TIFF2025002420000057.tif38170

[0192] In formulas (100-1) to (100-3), each R independently represents a hydrogen atom, an alkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, or a halogen atom.

[0193] TIFF2025002420000058.tif65170

[0194] TIFF2025002420000059.tif51170

[0195] TIFF2025002420000060.tif52170

[0196] TIFF2025002420000061.tif49170

[0197] In the formulas (101) to (104), each R independently represents a hydrogen atom, an alkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, or a halogen atom.

[0198] Among the compounds having a ketone group represented by any one of the formulae (100) to (104), from the viewpoint of electron transporting properties, the compounds having a ketone group represented by the formulae (100), (101) or (103) are preferred. Among them, the compounds having any one of the following structures are more preferred.

[0199] TIFF2025002420000062.tif85170

[0200] Among these, from the viewpoint of electrical properties, ET-1, ET-2 or ET-4 is preferred, ET-1 or ET-4 is more preferred, and ET-1 is particularly preferred.

[0201] The content of the ketone compound in the photosensitive layer of the present invention is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, based on 100% by mass of the entire photosensitive layer of the present invention, from the viewpoint of electron transportability. Also, from the viewpoint of solubility, it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. In addition, when the photosensitive layer of the present invention contains an arylamine compound described later, the content of the ketone compound in the photosensitive layer of the present invention is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and particularly preferably 70 parts by mass or more, relative to 100 parts by mass of the arylamine compound in the photosensitive layer of the present invention, from the viewpoint of electron transportability. On the other hand, from the viewpoint of solubility, it is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less.

[0202] The photosensitive layer of the present invention may contain "another electron transport material (ETM)" in addition to the above ketone compound. In this case, the "other electron transport material (ETM)" can be selected from known materials. For example, electron-withdrawing substances such as aromatic nitro compounds such as 2,4,7-trinitrofluorenone, cyano compounds such as tetracyanoquinodimethane, quinone compounds such as diphenoquinone, known cyclic ketone compounds, and perylene pigments (perylene derivatives) can be mentioned. Among these, from the viewpoint of electrical properties, quinone compounds and perylene pigments (perylene derivatives) are preferred, and quinone compounds are more preferred.

[0203] Among the quinone compounds, diphenoquinone or dinaphthylquinone is preferable from the viewpoint of electrical properties, and among them, dinaphthylquinone is more preferable.

[0204] The above-mentioned "other electron transport material (ETM)" may be used alone or in any combination of two or more kinds in any ratio.

[0205] The total content of the electron transport material including the ketone compound in the photosensitive layer of the present invention is preferably 15% by mass or more, more preferably 25% by mass or more, based on 100% by mass of the entire photosensitive layer of the present invention, from the viewpoint of electron transportability, and is preferably 40% by mass or less, more preferably 30% by mass or less, from the viewpoint of solubility.

[0206] (Hole transport material) The hole transport material (HTM) can be selected from known materials and can be used, for example, electron donating materials such as heterocyclic compounds such as carbazole derivatives, indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, thiadiazole derivatives, and benzofuran derivatives, aniline derivatives, hydrazone derivatives, arylamine derivatives, stilbene derivatives, butadiene derivatives, and enamine derivatives, as well as compounds in which a plurality of these compounds are bonded, and polymers having groups made of these compounds in the main chain or side chain. The hole transport material may be used alone or in any combination of two or more kinds in any ratio.

[0207] Among these, it is preferable to include an arylamine compound as a hole transport material (HTM). Since the arylamine structure has a small ionization potential and is highly stable in a cationic state, the arylamine compound has excellent hole transport properties. Therefore, by incorporating an arylamine compound in the photosensitive layer and incorporating the imide compound of the present invention in the protective layer, the hole transport properties of the photosensitive layer of the present invention and the electron transport properties of the protective layer of the present invention can be improved, resulting in good electrical properties. In addition, since both the arylamine compound and the cyclic imide compound have a nitrogen-containing structure, they have a high affinity for each other, and the photosensitive layer of the present invention and the protective layer of the present invention containing each have excellent contact at the interface, which makes it easier to transfer charges between the photosensitive layer of the present invention and the protective layer of the present invention, thereby making it possible to further improve the electrical properties.

[0208] Among them, the arylamine compound preferably contains a compound represented by the following formula (200) or (201) from the viewpoint of hole transporting properties. In addition, the arylamine compound is meant to include derivatives of arylamine compounds, and "including a compound represented by the following formula (200) or (201)" is meant to include derivatives of the compound represented by the following formula (200) or (201).

[0209] TIFF2025002420000063.tif50163

[0210] TIFF2025002420000064.tif50163

[0211] In the formula (200) or (201), Ar HTM is selected from the following formulae (200-1) to (200-3). Among these, formula (200-1) is preferred. In formula (200) or (201), each R independently represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aromatic hydrocarbon group, an optionally substituted aromatic heterocyclic group, or a halogen atom. h1 represents an integer of 0 to 5.

[0212] TIFF2025002420000065.tif45170

[0213] In (200-1) to (200-3), each R independently represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aromatic hydrocarbon group, an optionally substituted aromatic heterocyclic group, or a halogen atom. Among these, a hydrogen atom or an optionally substituted alkyl group is preferred. h4 represents an integer from 0 to 2.

[0214] Among the arylamine compounds represented by the formula (200) or (201), the arylamine compound represented by the formula (201) is preferred from the viewpoint of hole transporting properties. Among them, the compound having the following structure is more preferred.

[0215] TIFF2025002420000066.tif60163

[0216] The content of the arylamine compound in the photosensitive layer of the present invention is preferably 20% by mass or more, more preferably 30% by mass or more, based on 100% by mass of the entire photosensitive layer of the present invention, from the viewpoint of hole transportability, and is preferably 60% by mass or less, more preferably 50% by mass or less, from the viewpoint of solubility. The content of the arylamine compound in the photosensitive layer of the present invention is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, based on 100 parts by mass of the ETM compound of the present invention in the protective layer of the present invention, from the viewpoint of hole transportability, and is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, from the viewpoint of solubility. When the photosensitive layer of the present invention contains the above-mentioned ketone compound, the content of the arylamine compound in the photosensitive layer of the present invention is preferably 110 parts by mass or more, more preferably 120 parts by mass or more, relative to 100 parts by mass of the ketone compound in the photosensitive layer of the present invention, from the viewpoint of hole transportability, and is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, from the viewpoint of solubility.

[0217] The total content of the hole transport material in the photosensitive layer of the present invention is preferably 20% by mass or more, more preferably 30% by mass or more, based on 100% by mass of the entire photosensitive layer of the present invention, from the viewpoint of hole transportability, and is preferably 55% by mass or less, more preferably 45% by mass or less, from the viewpoint of solubility.

[0218] (binder resin) Examples of the binder resin used in the photosensitive layer include vinyl polymers or copolymers thereof such as polymethyl methacrylate, polystyrene, and polyvinyl chloride; vinyl alcohol resins; polyvinyl butyral resins; polyvinyl formal resins; partially modified polyvinyl acetal resins; polyarylate resins; polyamide resins; polyurethane resins; polycarbonate resins; polyester resins; polyester carbonate resins; polyimide resins; phenoxy resins; epoxy resins; silicone resins; and partially crosslinked cured products thereof. The above resins may be modified with silicon reagents or the like. These may be used alone or in any ratio and combination of two or more.

[0219] The binder resin used in the present photosensitive layer preferably contains one or more types of polymers obtained by interfacial polymerization.

[0220] The binder resin obtained by the above interfacial polymerization is preferably a polycarbonate resin or a polyester resin, more preferably a polycarbonate resin or a polyarylate resin, and more preferably a polymer made from an aromatic diol.

[0221] (Other substances) In addition to the above materials, the photosensitive layer may contain additives such as well-known antioxidants, plasticizers, ultraviolet absorbers, electron-withdrawing compounds, leveling agents, and visible light shielding agents in order to improve film-forming properties, flexibility, coating properties, contamination resistance, gas resistance, and light resistance. The photosensitive layer may also contain various additives such as sensitizers, dyes, pigments (excluding the charge generating materials, hole transport materials, and electron transport materials described above), and surfactants, as necessary. Examples of surfactants include silicone oils and fluorine-based compounds. In the present invention, these may be used alone or in any ratio and combination of two or more of them.

[0222] For the purpose of reducing frictional resistance on the surface of the photosensitive layer, the photosensitive layer may contain a fluorine-based resin, a silicone resin, or the like, and may contain particles made of these resins or particles of an inorganic compound such as aluminum oxide.

[0223] (layer thickness) When the photosensitive layer is a single-layer type photosensitive layer, the thickness of the photosensitive layer is preferably 20 μm or more, more preferably 25 μm or more, from the viewpoint of dielectric breakdown resistance, and is preferably 50 μm or less, more preferably 40 μm or less, from the viewpoint of electrical properties.

[0224] <Laminated photosensitive layer> When the photoreceptor of the present invention is a laminated type photosensitive layer, for example, a structure in which a charge transport layer (CTL) containing a charge transport material is laminated on a charge generation layer (CGL) containing a charge generation material (CGM) can be mentioned. In this case, it is possible to provide layers other than the charge generation layer (CGL) and the charge transport layer (CTL).

[0225] Even when the photoreceptor of the present invention has a multi-layer photosensitive layer, the types and contents of the arylamine compound, hole transport material, ketone compound and electron transport material in the charge transport layer are the same as those in the single-layer photoreceptor.

[0226] (Charge Generation Layer (CGL)) The charge generating layer (CGL) usually contains a charge generating material (CGM) and a binder resin. The charge generating material (CGM) and the binder resin are the same as those described in the single-layer type photosensitive layer above.

[0227] In addition to the charge generating material and the binder resin, the charge generating layer may contain other components as necessary. 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, stain resistance, gas resistance, light resistance, etc.

[0228] In the charge generation layer, if the 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, while if the ratio of the charge generation material is too low, the sensitivity of the photoreceptor may decrease, so the compounding ratio (mass) of the charge generation material is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, relative to 100 parts by mass of the binder resin. On the other hand, the compounding ratio (mass) of the charge generation material is preferably 1000 parts by mass or less, more preferably 500 parts by mass or less, relative to 100 parts by mass of the binder resin, and from the viewpoint of film strength, the ratio is more preferably 300 parts by mass or less, and particularly preferably 200 parts by mass or less.

[0229] 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.

[0230] (Charge transport layer (CTL)) The charge transport layer (CTL) usually contains a charge transport material and a binder resin. The types and contents of the charge transport material and binder resin are the same as those explained in the single-layer type photosensitive layer.

[0231] In the charge transport layer (CTL), the mixing ratio of the hole transport material (HTM) to the binder resin is preferably 20 parts by mass or more per 100 parts by mass of the binder resin, more preferably 30 parts by mass or more from the viewpoint of reducing the residual potential, and even more preferably 40 parts by mass or more from the viewpoint of stability and charge mobility during repeated use. On the other hand, from the viewpoint of the thermal stability of the photosensitive layer, it is preferable to mix 200 parts by mass or less of the hole transport material (HTM) to 100 parts by mass of the binder resin, more preferably 150 parts by mass or less from the viewpoint of compatibility between the hole transport material (HTM) and the binder resin, and particularly preferably 120 parts by mass or less from the viewpoint of the glass transition temperature.

[0232] In the charge transport layer (CTL), the blending ratio of the electron transport material (ETM) to the binder resin is preferably 20 parts by mass or more per 100 parts by mass of the binder resin, more preferably 30 parts by mass or more from the viewpoint of reducing the residual potential, and even more preferably 40 parts by mass or more from the viewpoint of stability and charge mobility during repeated use. On the other hand, from the viewpoint of the thermal stability of the photosensitive layer, the blending ratio of the electron transport material (ETM) to 100 parts by mass of the binder resin is preferably 200 parts by mass or less, and from the viewpoint of compatibility between the electron transport material (ETM) and the binder resin, more preferably 150 parts by mass or less, and particularly preferably 120 parts by mass or less from the viewpoint of the glass transition temperature.

[0233] The charge transport layer may contain other components as necessary in addition to the electron transport material (ETM), hole transport material (HTM) 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, coatability, stain resistance, gas resistance, light resistance, etc.

[0234] The thickness of the charge transport layer is not particularly limited, but from the viewpoints of electrical characteristics, image stability, and high resolution, it is preferably from 5 μm to 50 μm, more preferably from 10 μm to 40 μm, and even more preferably from 15 μm to 35 μm.

[0235] <Method of forming the present photosensitive layer> In either the laminated type or the single layer type, the above layers can be formed as follows. The substance to be contained is dissolved or dispersed in a solvent to obtain a coating solution, which is then 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 are then coated and dried in sequence to form a layer. However, the method is not limited to this.

[0236] The solvent or dispersion medium used in preparing the coating liquid is not particularly limited. Specific examples include alcohols, ethers, aromatic hydrocarbons, chlorinated hydrocarbons, etc. In addition, these may be used alone or in any combination of two or more kinds.

[0237] The amount of the solvent or dispersion medium used is not particularly limited. Taking into consideration the purpose of each layer and the properties of the selected solvent or dispersion medium, it is preferable to appropriately adjust the solid content concentration, viscosity, and other physical properties of the coating liquid so that they fall within the desired range. The coating film is preferably dried to the touch at room temperature, and then heated and dried for 1 minute to 2 hours at a temperature in the range of 30° C. to 200° C., either stationary or with a fan. The heating temperature may be constant, or the temperature may be changed during drying.

[0238] <Conductive support> The conductive support of the photoreceptor of the present invention (hereinafter also referred to as "the conductive support") is not particularly limited as long as it supports a layer formed thereon and exhibits electrical conductivity. Examples of the conductive support that can be used include metal materials such as aluminum, aluminum alloys, stainless steel, copper, and nickel; resin materials that have been made conductive by the coexistence of conductive powders such as metal, carbon, and tin oxide; and resins, glass, and paper with conductive materials such as aluminum, nickel, and ITO (indium oxide tin oxide) vapor-deposited or applied to their surfaces. The conductive support may be in the form of a drum, cylinder, sheet, belt, or the like. The conductive support may be a conductive support made of a metal material on which a conductive material having an appropriate resistance value is applied in order to control the conductivity and surface properties or to cover defects.

[0239] When a metal material such as an aluminum alloy is used as the conductive support, the metal material may be provided with an anodized coating before use. The average thickness of the anodic oxide coating is preferably 20 μm or less, and more preferably 7 μm or less. When forming an anodized coating on a metal material, it is preferable to carry out a sealing treatment. The sealing treatment can be carried out by a known method.

[0240] The surface of the conductive support may be smooth, or may be roughened by using a special cutting method, by polishing, or by mixing particles of an appropriate particle size into the material constituting the support.

[0241] <Main undercoat layer> The photoreceptor of the present invention may have an undercoat layer (also referred to as "subsequent undercoat layer") between the present conductive substrate and the present photosensitive layer in order to improve adhesion, blocking properties, and the like.

[0242] The undercoat layer may be made of, for example, a resin, a resin in which organic pigments or particles of metal oxides are dispersed, etc. The undercoat layer may also contain a known antioxidant, etc.

[0243] Examples of organic pigments used in the undercoat layer include phthalocyanine pigments, azo pigments, perylene pigments, etc. Among them, phthalocyanine pigments and azo pigments, specifically, the phthalocyanine pigments and azo pigments used as the charge generating material described above can be mentioned.

[0244] Examples of metal oxide particles used in the present undercoat layer include metal oxide particles containing one type of metal element, such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, iron oxide, etc., and metal oxide particles containing multiple metal elements, such as calcium titanate, strontium titanate, barium titanate, etc. In the undercoat layer, only one type of particle as above may be used, or multiple types of particles may be mixed in any ratio and combination.

[0245] Among the above metal oxide particles, titanium oxide and aluminum oxide are preferred, with titanium oxide being particularly preferred.

[0246] The particle size of the metal oxide particles used in the present undercoat layer is not particularly limited. From the viewpoint of the characteristics of the undercoat layer and the stability of the dispersion liquid for forming the undercoat layer, the average primary particle size is preferably 10 nm or more, and is preferably 100 nm or less, more preferably 50 nm or less.

[0247] The binder resin used in the present undercoat layer may be selected from, for example, polyvinyl acetal resins such as polyvinyl butyral resins; 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, and styrene-alkyd resins. However, the binder resin is not limited to these polymers. These binder resins may be used alone or in a mixture of two or more kinds, or may be used in a cured form together with a curing agent. Among these, polyvinyl acetal resins, alcohol-soluble copolymerized polyamides, modified polyamides, etc. are preferred because they exhibit good dispersibility and coatability, and among these, alcohol-soluble copolymerized polyamides are particularly preferred.

[0248] The mixing ratio of the particles to the binder resin can be selected arbitrarily, but it is preferable to use it in the range of 10% by mass to 500% by mass from the viewpoint of the stability and coatability of the dispersion.

[0249] The thickness of the undercoat layer can be freely selected, but is preferably 0.1 μm or more and more preferably 20 μm or less in view of the characteristics of the electrophotographic photoreceptor and the coatability of the dispersion.

[0250] <Other layers> The photoreceptor of the present invention may have other layers, if necessary, in addition to the conductive substrate, photosensitive layer, protective layer and undercoat layer described above.

[0251] <Physical Properties of the Photoreceptor of the Present Invention> The photoreceptor of the present invention may have the following physical properties.

[0252] (Martens hardness) In the photoreceptor of the present invention, in order to provide sufficient wear resistance for practical use, the Martens hardness is set to 175 N / mm 2 More preferably, it is 200N / mm 2 Above all, 220N / mm 2 More preferably, it is equal to or greater than this. In the present invention, the Martens hardness of the photoreceptor means the Martens hardness measured from the surface side of the photoreceptor. The Martens hardness can be measured by the method described in the Examples below.

[0253] (Elastic deformation rate) In order to provide the photoreceptor of the present invention with sufficient wear resistance for practical use, its elastic deformation rate, although varying depending on the component composition of the protective layer, is preferably 25% or more, more preferably 30% or more, and even more preferably 40% or more. In the present invention, the elastic deformation rate of the photoreceptor means the elastic deformation rate measured from the surface side of the photoreceptor. The elastic deformation rate can be measured by the method described in the Examples below.

[0254] (residual potential) In the photoreceptor of the present invention, from the viewpoint of providing a residual potential sufficient for practical use, the residual potential, although varying depending on the component composition of the protective layer, is preferably 150 V or less, more preferably 100 V or less, even more preferably 60 V or less, and even more preferably 50 V or less. In the present invention, the residual potential of the photoconductor means the potential of the photoconductor after it has been charged and irradiated with exposure light. The residual potential can be measured by the method described in the Examples below.

[0255] (Potential holding rate) In the photoreceptor of the present invention, from the viewpoint of having a potential retention rate sufficient for practical use, the potential retention rate varies depending on the component composition of the protective layer, but is preferably 75% or more, more preferably 80% or more, and even more preferably 83% or more. In the present invention, the potential retention rate of the photoreceptor means the surface potential retention rate when the photoreceptor with a charged surface is left for a certain period of time, and can be measured by the method described in the examples below.

[0256] <<Image forming apparatus of the present invention>> An image forming apparatus (hereinafter, also referred to as "image forming apparatus of the present invention") can be constructed using the photoreceptor of the present invention. However, the image forming apparatus of the present invention described below is one example of an image forming apparatus that can be constructed using the present electrophotographic photoreceptor.

[0257] As shown in FIG. 1, the image forming apparatus of the present invention is configured to include a photoreceptor 1 of the present invention, 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 necessary.

[0258] The photoreceptor 1 of the present invention is not particularly limited as long as it is the photoreceptor of the present invention described above. As an example, Fig. 1 shows a drum-shaped photoreceptor in which the above-mentioned photosensitive layer is formed on the surface of a cylindrical conductive support. A charging device 2, an exposure device 3, a developing device 4, a transfer device 5, and a cleaning device 6 are arranged along the outer circumferential surface of the photoreceptor 1 of the present invention.

[0259] Examples of the charging device 2 include a non-contact corona charging device such as a corotron or scorotron, or a contact-type charging device (direct-type charging device) that charges the photoconductor surface by contacting a charging member to which a voltage is applied. 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.

[0260] The type of exposure device 3 is not particularly limited as long as it can expose the photoreceptor 1 of the present invention to light and form an electrostatic latent image on the photosensitive surface of the photoreceptor 1 of the present invention. Moreover, the exposure may be performed by an internal exposure method of the photoconductor.

[0261] The type of toner T is arbitrary, and in addition to powder toner, polymerized toner produced by a suspension polymerization method, an emulsion polymerization method, or the like can be used.

[0262] The developing device 4 may have any configuration. The developing device 4 shown in Fig. 1 has a configuration in which the toner T is made into a thin layer by a regulating member (developing blade) 45, is triboelectrically charged to a predetermined polarity, and is carried by a developing roller 44 while being transported to contact the surface of the photoconductor 1. However, the configuration is not limited to this. The type of the 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.

[0263] There is no particular limitation on the cleaning device 6. For example, any cleaning device can be used, such as a brush cleaner, a magnetic roller cleaner, a blade cleaner, etc. If there is little or almost no toner remaining on the photoreceptor surface, the cleaning device 6 may not be necessary. The fixing device 7 may also have any configuration. In addition to the above-mentioned configuration, the image forming apparatus may be configured to perform, for example, a charge removal process.

[0264] Furthermore, the image forming apparatus may be further modified, for example, to be configured to perform processes such as a pre-exposure process and an auxiliary charging process, to be configured to perform offset printing, or even to be configured as a full-color tandem system using multiple types of toner.

[0265] <<Cartridge of the present invention>> The photoreceptor 1 of the present invention can be combined with one or more of a charging device 2, an exposure device 3, a developing device 4, a transfer device 5, a cleaning device 6, and a fixing device 7 to form an integrated cartridge (referred to as the "cartridge of the present invention"). However, the cartridge of the present invention described below is one example of an electrophotographic cartridge that can be constructed using the present electrophotographic photoreceptor.

[0266] The cartridge of the present invention can be configured to be detachable from the main body of an electrophotographic device such as a copying machine, a laser beam printer, etc. In that case, for example, when the photoreceptor 1 of the present invention or other members deteriorate, the electrophotographic photoreceptor cartridge can be removed from the main body of the image forming device and a new electrophotographic photoreceptor cartridge can be mounted in the main body of the image forming device, thereby facilitating the maintenance and management of the image forming device.

[0267] <<Explanation of terms>> In the present invention, when expressed as "X to Y" (X and Y are any numbers), 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". In addition, when it is stated that the term is "X or more" or "X≦" (X is any number), it also means that the term is "preferably greater than X" unless otherwise specified, and when it is stated that the term is "Y or less" or "≦Y" (Y is any number), it also means that the term is "preferably smaller than Y" unless otherwise specified. EXAMPLES

[0268] Hereinafter, the embodiment of the present invention will be described in more detail with reference to examples. However, the following examples are provided to explain the present invention in detail, and the present invention is not limited to the examples shown below, and can be modified as desired without departing from the gist of the present invention. In the following examples and comparative examples, the term "parts" refers to "parts by mass" unless otherwise specified.

[0269] As used herein, DMF means N,N-dimethylformamide, NMP means N-methyl-2-pyrrolidone, Et means ethyl group, Ac means acetyl group, and MEHQ means 4-methoxyphenol.

[0270] [Synthesis of Compounds] The synthesis methods of the following compounds 1 to 9 will be described below.

[0271] <Synthesis of Compound 1> The synthesis scheme of compound 1 is shown below.

[0272] TIFF2025002420000067.tif121170

[0273] The synthesis procedure for compound 1 is shown below. (Synthesis of intermediate 1-1) Under a nitrogen atmosphere, 100 mL of 1,4-dioxane was added to a mixture of succinic anhydride (11.0 g, 109.5 mmol) and 4-DMAP (4-dimethylaminopyridine, 0.26 g, 2.19 mmol) to prepare a solution. A solution of glycerol dimethacrylate (25 g, 109.5 mmol) and MEHQ (27 mg, 0.22 mmol) dissolved in 50 mL of 1,4-dioxane was added dropwise to this solution and stirred at 80 ° C for 9 hours. After cooling to room temperature, it was poured into 200 mL of water and extracted with dichloromethane, and the organic layer was washed with water and then dried with magnesium sulfate. The solid was filtered, the solvent of the filtrate was distilled off under reduced pressure, and the residue was dried to obtain intermediate 1-1 (yield 30 g, yield 83% by mass).

[0274] (Synthesis of intermediate 1-2) Under a nitrogen atmosphere, 100 mL of dehydrated dichloromethane and 1 mL of dehydrated dimethylformamide were added to intermediate 1-1 (21.6 g, 65.8 mmol) and cooled on ice. Oxalyl chloride (11.2 mL, 131.6 mmol) was added dropwise, and the mixture was stirred for 2 hours under ice cooling and then stirred at room temperature for 12 hours. After distilling off the solvent under reduced pressure, the residue was dried to obtain intermediate 1-2 (yield 21.5 g, 94% by mass).

[0275] (Synthesis of intermediate 1-3) Under a nitrogen atmosphere, 5,6,12,13-Tetrachloroperylo[3,4-cd:9,10-c'd']dipyran-1,3,8,10-tetrone (13.0 g, 24.5 mmol) and L-(+)-leucinol (7.2 g, 61.3 mmol) were added to 200 mL of toluene and stirred at 110 ° C for 9 hours. After cooling to room temperature, this solution was poured into 200 mL of ice water, and 1N hydrochloric acid was added to make the reaction solution acidic. Extraction was performed with toluene and tetrahydrofuran, and the organic layer was washed with water and then dried over magnesium sulfate. The obtained solid was filtered, the solvent of the filtrate was distilled off under reduced pressure, and the residue was dried to obtain intermediate 1-3 (yield 11.8 g, yield 66% by mass).

[0276] (Synthesis of Compound 1) Under a nitrogen atmosphere, 100 mL of dehydrated dichloromethane and triethylamine (6.6 mL, 47.8 mmol) were added to intermediate 1-3 (5.8 g, 7.96 mmol) and 4-methoxyphenol (0.05 g), and the mixture was cooled on ice. Intermediate 1-2 (8.3 g, 23.9 mmol) dissolved in 70 mL of dehydrated dichloromethane was added dropwise, and the mixture was stirred for 1 hour under ice cooling and then stirred at room temperature for 12 hours. The reaction solution was poured into 200 mL of ice water, extracted with dichloromethane, and the organic layer was washed with water and then dried over magnesium sulfate. The obtained solid was filtered, the solvent of the filtrate was distilled off under reduced pressure, and the residue was subjected to silica gel column chromatography to obtain compound 1 (yield 5.7 g, yield 53% by mass).

[0277] <Synthesis of compound 2> The synthesis scheme of compound 2 is shown below.

[0278] TIFF2025002420000068.tif44170

[0279] The synthesis procedure for compound 2 is shown below.

[0280] (Synthesis of compound 2) Under a nitrogen atmosphere, 70 mL of dehydrated dichloromethane was added to intermediate 1-3 (5.1 g, 6.93 mmol), and 2-(acryloyloxy)ethyl isocyanate (2.5 g, 17.3 mmol) was added dropwise. 0.1 mL of dibutyltin dilaurate was added and stirred at room temperature for 12 hours. The reaction solution was poured into 200 mL of water, extracted with dichloromethane, and the organic layer was washed with water and then dried over magnesium sulfate. The obtained solid was filtered, the solvent of the filtrate was distilled off under reduced pressure, and the residue was subjected to silica gel column chromatography to obtain compound 2 (yield 2.3 g, yield 33% by mass).

[0281] <Synthesis of compound 3> The synthesis scheme of compound 3 is shown below.

[0282] TIFF2025002420000069.tif74170

[0283] The synthesis procedure for compound 3 is shown below.

[0284] (Synthesis of intermediate 3-1) Under a nitrogen atmosphere, 250 mL of acetic acid was added to a mixture of benzene-1,2,4,5-tetracarboxylic anhydride (19.3 g, 88.4 mmol) and L-leucine (23.2 g, 176.9 mmol), and the mixture was stirred at room temperature for 12 hours and at 130° C. for 12 hours. After cooling to room temperature, the mixture was poured into 400 mL of ice water, and the solid was filtered and washed with water. After drying, intermediate 3-1 (yield 38.7 g, 98%) was obtained.

[0285] (Synthesis of intermediate 3-2) Under a nitrogen atmosphere, 200 mL of dehydrated dichloromethane and 1 mL of dehydrated dimethylformamide were added to intermediate 3-1 (23.0 g, 51.8 mmol) and cooled on ice. Oxalyl chloride (26.6 mL, 310.5 mmol) was added dropwise, and the mixture was stirred for 2 hours under ice cooling and then at room temperature for 12 hours. After distilling off the solvent under reduced pressure, the solid was filtered and washed with hexane. After drying, intermediate 3-2 (yield 23.5 g, 94% by mass) was obtained.

[0286] (Synthesis of compound 3) Under a nitrogen atmosphere, 4-methoxyphenol (0.01 g) was added to N-(2-hydroxyethyl)acrylamide (17.9 g, 51.7 mmol), and then 200 mL of dehydrated dichloromethane and triethylamine (43 mL, 310.2 mmol) were added and cooled with ice. Intermediate 3-2 (23.5 g, 48.8 mmol) dissolved in 100 mL of dehydrated dichloromethane was added dropwise, and the mixture was stirred for 2 hours under ice cooling and then stirred at room temperature for 2 hours. After distilling off the solvent under reduced pressure, the residue was subjected to silica gel column chromatography to obtain compound 3 (yield 14.2 g, 46 mass %).

[0287] <Synthesis of compound 4> The synthesis scheme of compound 4 is shown below.

[0288] TIFF2025002420000070.tif144170

[0289] The synthesis procedure for compound 4 is shown below.

[0290] (Synthesis of intermediate 4-1)

[0291] Under a nitrogen atmosphere, 100 mL of dichloromethane was added to mono(2-acryloyloxyethyl)succinate (11.7 g, 54.1 mmol) to prepare a solution, which was then cooled on ice. Oxalyl chloride (6.0 mL, 70.3 mmol) was added dropwise to this solution, which was then stirred for 1 hour under ice cooling and then stirred at room temperature for 12 hours. After the solvent was distilled off under reduced pressure, intermediate 4-1 (yield 12 g, 94% by mass) was obtained.

[0292] (Synthesis of intermediate 4-2) Under a nitrogen atmosphere, 300 mL of ethanol was added to 3-methoxyacetophenone (16 g, 106.5 mmol) and cooled on ice. Sodium borohydride (6.0 g, 159.8 mmol) was added in several portions, and the mixture was stirred for 1 hour under ice cooling and then stirred at room temperature for 2 hours. The reaction solution was poured into 300 mL of water, and the organic layer was extracted with ethyl acetate and washed with salt water. After drying with magnesium sulfate, the solvent was distilled off under reduced pressure to obtain intermediate 4-2 (yield 15.1 g, 94% by mass).

[0293] (Synthesis of intermediate 4-3) Under a nitrogen atmosphere, 300 mL of acetic acid was added to a mixture of 1-naphthol (32.5 g, 225.4 mmol) and intermediate 4-2 (22.9 g, 150.2 mmol), and 8.0 mL of sulfuric acid was added dropwise. After stirring at room temperature for 40 minutes, the mixture was poured into 300 mL of water, and the organic layer was extracted with dichloromethane and washed with water. After drying with magnesium sulfate, the solvent was distilled off under reduced pressure, and the residue was subjected to silica gel column chromatography to obtain intermediate 4-3 (yield 17 g, 41% by mass).

[0294] (Synthesis of intermediate 4-4) Under a nitrogen atmosphere, 500 mL of chloroform was added to intermediate 4-3 (17 g, 61.1 mmol), and chloranil (15 g, 61.1 mmol) was added. After stirring at room temperature for 24 hours, the mixture was filtered with dichloromethane. The solvent in the filtrate was distilled off under reduced pressure, and the residue was subjected to silica gel chromatography to obtain intermediate 4-4 (yield 15 g, 89% by mass).

[0295] (Synthesis of intermediate 4-5) Under a nitrogen atmosphere, 200 mL of dichloromethane was added to intermediate 4-4 (14 g, 25.3 mmol) and cooled to -70°C. 130 mL of 1 mol / L boron tribromide in dichloromethane was added dropwise, the mixture was warmed to room temperature, and stirred for 12 hours. The mixture was cooled to 0°C and 150 mL of water was added dropwise. After warming to room temperature, the organic layer was extracted with dichloromethane and washed with water. After drying with magnesium sulfate, the mixture was dissolved in 200 mL of chloroform, chloranil (5.1 g, 20.7 mmol) was added, and the mixture was stirred at room temperature for 2.5 hours. The mixture was filtered with dichloromethane. The solvent of the filtrate was distilled off under reduced pressure, and the residue was subjected to silica gel chromatography to obtain intermediate 4-5 (yield 9.6 g, yield 72% by mass).

[0296] (Synthesis of compound 4) Under a nitrogen atmosphere, 100 mL of dichloromethane was added to a mixture of intermediate 4-5 (7.6 g, 14.5 mmol) and 0.05 g of 4-methoxyphenol to prepare a solution, which was then cooled on ice. Triethylamine (8.0 mL, 58.0 mmol) was added to this solution, and intermediate 4-1 (7.5 g, 31.9 mmol) was then added dropwise, and the mixture was stirred for 1 hour under ice cooling and then stirred at room temperature for 12 hours. The reaction solution was poured into 200 mL of water, extracted with dichloromethane, and the organic layer was washed with water. After drying with magnesium sulfate, the solvent was distilled off under reduced pressure, and the residue was subjected to silica gel chromatography to obtain compound 4 (yield 4.4 g, 33% by mass).

[0297] <Synthesis of compound 5> The synthesis scheme of compound 5 is shown below.

[0298] TIFF2025002420000071.tif51170

[0299] The synthesis procedure for compound 5 is shown below.

[0300] (Synthesis of Compound 5) Under a nitrogen atmosphere, 200 mL of dichloromethane was added to a mixture of intermediate 4-5 (5.5 g, 10.5 mmol) obtained in the above procedure and 0.05 g of MEHQ to prepare a solution, which was then cooled on ice. Triethylamine (7.3 mL, 52.4 mmol) was added to this solution, and intermediate 1-2 (10.9 g, 31.5 mmol) was then added dropwise, and the mixture was stirred for 1 hour under ice cooling and then stirred at room temperature for 2 hours. The reaction solution was poured into 100 mL of water, extracted with dichloromethane, and the organic layer was washed with water. After drying with magnesium sulfate, the solvent was distilled off under reduced pressure, and the residue was subjected to silica gel chromatography to obtain compound 5 (yield 4.8 g, 40% by mass).

[0301] <Synthesis of compound 6> The synthesis scheme of compound 6 is shown below.

[0302] TIFF2025002420000072.tif94170

[0303] The synthesis procedure for compound 6 is shown below.

[0304] (Synthesis of intermediate 6-1) Under a nitrogen atmosphere, 60 mL of N,N-dimethylformamide was added to naphthalene-1,4,5,8-tetracarboxylic dianhydride (7.18 g, 26.8 mmol) to prepare a solution. A solution of L-(+)-leucinol (4.71 g, 40.2 mmol) and 2-ethylhexylamine (5.19 g, 40.2 mmol) dissolved in 40 mL of N,N-dimethylformamide was added dropwise to this solution, and the mixture was stirred at 120°C for 8 hours. After cooling to room temperature, the solution was poured into 200 mL of ice water, and 1N hydrochloric acid was added to make the reaction solution acidic. Extraction was performed with dichloromethane, and the organic layer was washed with water, dried over magnesium sulfate, and the obtained solid was filtered. The solvent of the filtrate was distilled off under reduced pressure, and the residue was dried to obtain intermediate 6-1 (yield 10.7 g, yield 84% by mass).

[0305] (Synthesis of compound 6) Under a nitrogen atmosphere, 150 mL of dehydrated dichloromethane and triethylamine (11.7 mL, 84.4 mmol) were added to intermediate 6-1 (10.1 g, 21.1 mmol) and 4-methoxyphenol (0.01 g), and the mixture was cooled on ice. Intermediate 1-2 (14.6 g, 42.2 mmol) dissolved in 50 mL of dehydrated dichloromethane was added dropwise, and the mixture was stirred for 1 hour under ice cooling and then stirred at room temperature for 12 hours. The reaction solution was poured into 100 mL of water, extracted with dichloromethane, and the organic layer was washed with water and then dried over magnesium sulfate. The obtained solid was filtered, the solvent of the filtrate was distilled off under reduced pressure, and the residue was subjected to silica gel column chromatography to obtain compound 6 (yield 5.3 g, yield 32% by mass).

[0306] <Synthesis of compound 7> The synthesis scheme of compound 7 is shown below.

[0307] TIFF2025002420000073.tif84170

[0308] The synthesis procedure for compound 7 is shown below.

[0309] (Synthesis of intermediate 7-1) Under a nitrogen atmosphere, 3,4,9,10-perylenetetracarboxylic dianhydride (11.4 g, 29.0 mmol), zinc acetate (5.32 g, 29.0 mmol), 50 g of imidazole, and L-(+)-leucinol (8.5 g, 72.5 mmol) were mixed and stirred at 160 ° C for 7 hours. After cooling to room temperature, the mixture was dissolved in dichloromethane, and the solution was poured into 200 mL of ice water, and 1N hydrochloric acid was added to make the reaction solution acidic. Extraction was performed with dichloromethane, and the organic layer was washed with water and then dried over magnesium sulfate. The obtained solid was filtered, the solvent of the filtrate was distilled off under reduced pressure, and the residue was subjected to silica gel column chromatography to obtain intermediate 7-1 (yield 12.0 g, yield 70 mass%).

[0310] (Synthesis of compound 7) Under a nitrogen atmosphere, 150 mL of dehydrated dichloromethane and triethylamine (29.5 mL, 213 mmol) were added to intermediate 7-1 (21.0 g, 35.5 mmol) and 4-methoxyphenol (0.05 g), and the mixture was cooled on ice. Intermediate 1-2 (36.9 g, 107 mmol) dissolved in 50 mL of dehydrated dichloromethane was added dropwise, and the mixture was stirred for 1 hour under ice cooling and then stirred at room temperature for 2 hours. The reaction solution was poured into 100 mL of water, extracted with dichloromethane, and the organic layer was washed with water and then dried over magnesium sulfate. The obtained solid was filtered, the solvent of the filtrate was distilled off under reduced pressure, and the residue was subjected to silica gel column chromatography to obtain compound 7 (yield 32.5 g, yield 76% by mass).

[0311] <Synthesis of compound 8> The synthesis scheme of compound 8 is shown below.

[0312] TIFF2025002420000074.tif72170

[0313] (Synthesis of compound 8) Under a nitrogen atmosphere, 200 mL of dehydrated dichloromethane and triethylamine (29 mL, 208.2 mmol) were added to a mixture of N-(2-hydroxyethyl)acrylamide (5.99 g, 52.0 mmol), 2-acetamidoethanol (5.37 g, 52.0 mmol) and 4-methoxyphenol (0.03 g), and the mixture was cooled on ice. A solution of intermediate 3-2 (16.7 g, 34.7 mmol) obtained in the above procedure dissolved in 100 mL of dehydrated dichloromethane was added dropwise, and the mixture was stirred for 2 hours under ice cooling and at room temperature for 2 hours. After distilling off the solvent under reduced pressure, the residue was subjected to silica gel column chromatography to obtain compound 8 (yield 3.4 g, yield 16 mass%, molar ratio of compound 8-a, compound 8-b, and compound 8-c 8-a:8-b:8-c=2:1:1).

[0314] <Synthesis of compound 9> The synthesis scheme of compound 9 is shown below.

[0315] TIFF2025002420000075.tif103170

[0316] The synthesis procedure for compound 9 is shown below.

[0317] (Synthesis of intermediate 9-1) Under a nitrogen atmosphere, 100 mL of dehydrated dichloromethane was added to [2-(2-methoxyethoxy)ethoxy]acetic acid (6.3 g, 35.3 mmol) and cooled on ice. 0.5 mL of N,N-dimethylformamide was added to this solution, and then oxalyl chloride (6.1 mL, 70.7 mmol) was added dropwise, and the mixture was stirred for 1 hour under ice cooling and then stirred at room temperature for 12 hours. After the solvent was distilled off under reduced pressure, the residue was dried to obtain intermediate 9-1 (yield 6.9 g, 99% by mass).

[0318] (Synthesis of Compound 9) Under a nitrogen atmosphere, 200 mL of dehydrated dichloromethane and triethylamine (19.5 mL, 141 mmol) were added to intermediate 7-1 (13.9 g, 23.5 mmol) and 4-methoxyphenol (0.04 g), and the mixture was cooled on ice. Intermediate 9-1 (12.2 g, 35.3 mmol) and intermediate 1-2 (6.94 g, 35.3 mmol) dissolved in 80 mL of dehydrated dichloromethane were added dropwise, and the mixture was stirred for 1 hour under ice cooling and at room temperature for 12 hours. The solvent of the reaction solution was distilled off under reduced pressure, and the residue was subjected to silica gel column chromatography to obtain compound 9 (yield 22 g, yield 88 mass%, molar ratio of compound 9-a and compound 9-b 9-a:9-b=2:1).

[0319] [Table 1]

[0320] In Table 1, in the column for formula (1), "○" means that the formula (1) applies.

[0321] [Preparation of electrophotographic photoreceptor] <Preparation of Coating Solution P1 for Forming Undercoat Layer> 20 parts of D-type titanyl phthalocyanine, which shows a clear peak at a diffraction angle 2θ=27.3°±0.2° in powder X-ray diffraction using CuKα radiation, was mixed with 280 parts of 1,2-dimethoxyethane, and ground for 2 hours in a sand grinding mill to carry out a fine dispersion treatment. 400 parts of a 1,2-dimethoxyethane solution containing 2.5% by mass of polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., product name "Denka Butyral" #6000C) and 170 parts of 1,2-dimethoxyethane were further added and mixed to prepare a coating solution P1 for forming an undercoat layer with a solid content concentration of 3.4% by mass.

[0322] <Preparation of Coating Solution Q1 for Forming Single-Layer Photosensitive Layer> The compound was a mixture of 2.6 parts of D-type titanyl phthalocyanine, which exhibits a clear peak at a diffraction angle 2θ=27.3°±0.2° in powder X-ray diffraction using CuKα radiation, 0.5 parts of polyvinyl butyral resin, 90 parts of the following arylamine compound 1 (molecular weight 748.38) as a hole transporting compound, 70 parts of the following ketone compound 1 (molecular weight 424.24, electron affinity of electron transporting skeleton 3.83 eV) as an electron transporting compound, and a perylene pigment (electron A single-layer type photosensitive layer-forming coating solution Q1 having a solid content concentration of 25 mass % was prepared by mixing 11.3 parts of a transport skeleton (electron affinity 3.94 eV), 100 parts of a polycarbonate resin having a biphenyl structure, 0.05 parts of a silicone oil (manufactured by Shin-Etsu Silicones: product name KF-96) as a leveling agent, and 793.35 parts of a mixed solvent of tetrahydrofuran (hereinafter appropriately abbreviated as THF) and toluene (hereinafter appropriately abbreviated as TL) (THF 90 mass %, TL 10 mass %).

[0323] TIFF2025002420000077.tif66170

[0324] TIFF2025002420000078.tif73170

[0325] TIFF2025002420000079.tif45163

[0326] <Preparation of Coating Solutions S1 to S13 for Forming Protective Layer> The curable compounds (polymerizable compounds not having an electron transport skeleton) shown in Tables 2 and 3, the electron donor compounds shown in Tables 3, and the electron transport compounds shown in Tables 2 and 3 were used in the amounts shown in Tables 2 and 3 to obtain protective layer-forming coating solutions S1 to S13 (solid concentration: approximately 8.0% by mass), each of which had a solvent composition of toluene / 2-propanol = 3 / 7 (mass ratio).

[0327] The symbols of the curable compounds and electron donor compounds in Tables 2 and 3 represent the following. Curable compound: A-DPH (dipentaerythritol polyacrylate, product name "NK Ester A-DPH", manufactured by Shin-Nakamura Chemical Co., Ltd.) Curable compound: M9050 (Toagosei Co., Ltd. polyester acrylate product name "Aronix M-9050") Electron donor compound: N-DMBI (N,N-dimethylbenzylamine, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0328] [Examples 1 to 4, Comparative Examples 1 to 9] In Examples 1 to 4 and Comparative Examples 1 to 9, single-layer photoreceptors A1 to A13 as shown in Tables 2 and 3 were produced and evaluated.

[0329] <Preparation of Single-Layer Photoreceptors A1 to A13> A single-layer photoreceptor was prepared according to the following procedure. An aluminum cylinder with a diameter of 30 mm and a length of 244 mm, the surface of which had been machined, was dip-coated with coating solution P1 for forming an undercoat layer, so that an undercoat layer was formed with a film thickness of 0.3 μm after drying. On the undercoat layer, coating solution Q1 for forming a single-layer type photosensitive layer was dip-coated, and dried at 100° C. for 24 minutes, so that a single-layer type photosensitive layer was formed with a film thickness of 32 μm after drying. Each of coating solutions S1 to S13 for forming a protective layer was ring-coated on the single-layer type photosensitive layer, and immediately after coating, 0.9 W / cm 365 nm LED light was applied while rotating the photoreceptor at 60 rpm under a nitrogen atmosphere. 2 Photoreceptor 2 was irradiated for 30 seconds, photoreceptors 1, 4, and 7 for 60 seconds, and photoreceptors 3, 5, 6, 8 to 12 for 2 minutes at an intensity of 1.5 to 2.0 μm after curing to form protective layers, thereby producing photoreceptors A1 to A13, respectively.

[0330] [Residual potential measurement] The obtained photoreceptors A1 to A13 were attached to an electrophotographic characteristic evaluation device manufactured in accordance with the measurement standard of the Society of Electrophotography (described in "Continued Fundamentals and Applications of Electrophotographic Technology," edited by the Society of Electrophotography, Corona Publishing, pp. 404-405), and the electrical characteristics were measured by a cycle of charging, exposure, potential measurement, and static elimination as follows. First, the grid voltage was adjusted to charge the photoconductor so that the initial surface potential (V0) was +700 V. Next, the exposure light was set to 1.3 μJ / cm 2 The residual potential (VL) was measured 60 milliseconds after irradiation. The exposure light was a halogen lamp light converted to monochromatic light of 780 nm using an interference filter. The measurement was performed in an environment of 25°C temperature and 50% relative humidity (N / N environment). The smaller the absolute value of the residual potential (V), the better the result, since it means that the charge has been transported sufficiently to lower the potential. In the present invention, a residual potential of 150 V or less was considered to be "passed."

[0331] [Potential holding rate] The obtained photoreceptors A1 to A13 were attached to an electrophotographic property evaluation device manufactured in accordance with the measurement standards of the Society of Electrophotography (described in "Continued Fundamentals and Applications of Electrophotographic Technology," edited by the Society of Electrophotography, Corona Publishing, pp. 404-405), and the potential retention rate after a cycle of charging, exposure, potential measurement, and static elimination was measured as follows. To evaluate the electrical characteristics, the potential retention rate (%) was measured after charging to +700V and leaving it for 5 seconds. The measurement was performed in an environment of 25°C temperature and 50% relative humidity (N / N environment). The results are shown in Tables 2 and 3. The potential retention rate represents the surface potential retention rate (%) when a photoconductor with a charged surface is left for a certain period of time. A higher surface potential retention rate (%) indicates better results, since the potential is maintained even over time and the charging properties are good. In the present invention, a potential retention rate of 75% or more is considered to be "passed."

[0332] [Table 2]

[0333] [Table 3]

[0334] In Tables 2 and 3, EA ETM represents the electron affinity (eV) of the electron transport skeleton of the electron transport compound contained in the photosensitive layer, and EA OCL represents the electron affinity (eV) of the electron transporting skeleton of the electron transporting compound contained in the protective layer. The electron affinity of the electron transport skeleton of each compound is a value calculated using the software "Spartan'18 Parallel Suite" (Wavefunction, Inc.) The method for calculating the electron affinity of the electron transport skeleton of a compound is described below. First, the density functional (DFT) method (functional "B3LYP", basis set "6-31G * ") was used for geometry optimization. Then, based on the optimized geometry, the "Energy at Ground state in Gas with Density Functional B3LYP 6-31G * " method to determine the lowest unoccupied molecular orbital (LUMO) level (E LUMO / eV) was calculated. The total charge was set to "Neutral (0)" and the unpaired electrons were set to "0". The obtained E LUMO From electron affinity "EA X " was calculated. EA X (eV)=-0.8059×E LUMO +1.1451

[0335] From the results of the above Examples and Comparative Examples, as well as the results of tests conducted by the present inventors, it has been found that when the electron affinity of the electron transport compound contained in the photosensitive layer and the electron affinity of the electron transport compound contained in the protective layer satisfy the following formula (I), the electron injection property from the photosensitive layer to the protective layer becomes good, and the electrical properties of the photoreceptor are improved. EA ETM <EA OCL (I) One of the reasons why the electrical properties of the photosensitive layer are insufficient is presumably due to poor electron injection from the photosensitive layer to the protective layer. It is believed that when the electron transport compound of the photosensitive layer and the electron transport compound of the protective layer satisfy the above formula (I), the barrier for electron injection from the photosensitive layer to the protective layer becomes small, and the electron injection property becomes good. On the other hand, when formula (I) is not satisfied, the electron injection from the photosensitive layer to the protective layer requires energy equivalent to the difference, and therefore the electron injection property is thought to be poor.

[0336] Furthermore, if the compound forming the protective layer has an electron transporting structure, it is considered that charge injection from the photosensitive layer to the protective layer and charge mobility to the outermost surface are enhanced through the electron transporting skeleton, making it possible to obtain an electrophotographic photoreceptor having excellent electrical properties such as residual potential characteristics. Furthermore, if the compound has a polymerizable functional group, the compound is polymerized in the step of forming the protective layer to form a polymer, which can form a protective layer having excellent mechanical strength. Therefore, it is presumed that if the electron transporting compound contained in the protective layer contains the compound represented by the above formula (1), the electrical properties of the photoreceptor can be further improved. [Explanation of symbols]

[0337] 1. Photoconductor (electrophotographic photoconductor) 2 Charging device (charging roller; charging section) 3 Exposure equipment (exposure section) 4. Developing device (developing section) 5. Transcription device 6 Cleaning device 7 Fixing device 41 Developer tank 42 Agitator 43 Supply roller 44 Developing roller 45 Regulatory Materials 71 Upper fixing member (pressure roller) 72 Lower fixing member (fixing roller) 73 Heating device T Toner P Recording paper (paper, medium) < / n> < / x>

Claims

1. An electrophotographic photoreceptor having at least a photosensitive layer and a protective layer in this order on a conductive support, The electron transporting compound contained in the photosensitive layer and the electron transporting compound contained in the protective layer satisfy the following formula (I): EA ＥＴＭ <EA ＯＣＬ (I) (In formula (I), EA ＥＴＭ represents the electron affinity (eV) of the electron transport skeleton of the electron transport compound contained in the photosensitive layer, and EA ＯＣＬ represents the electron affinity (eV) of the electron transporting skeleton of the electron transporting compound contained in the protective layer.

2. The electrophotographic photoreceptor according to claim 1 , wherein the electron transporting compound contained in the photosensitive layer satisfies the following formula (II): E A ＥＴＭ ≧3.8eV (II) (In formula (II), EA ＥＴＭ represents the electron affinity (eV) of the electron transport skeleton of the electron transport compound contained in the photosensitive layer.

3. The electrophotographic photoreceptor according to claim 1 , wherein the protective layer contains an electron transporting compound represented by the following formula (1): In formula (1), X represents an n-valent electron transport skeleton. A is a hydrogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, a heteroaryloxy group which may have a substituent, an alkoxycarbonyl group which may have a substituent, a dialkylamino group which may have a substituent, a diarylamino group which may have a substituent, an arylalkylamino group which may have a substituent, an acyl group which may have a haloalkyl group, an alkylthio group which may have a substituent, an arylthio group which may have a substituent, a silyl group which may have a substituent, a siloxy group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, an aromatic heterocyclic group which may have a substituent, a group represented by the following formula (2), or a group represented by the following formula (1B). n represents an integer of 1 or more. When n is 1, A is a group represented by the following formula (2) or a group represented by the following formula (1B). When n is 2 or more, a plurality of A's may be the same or different, and at least one A's is a group represented by the following formula (2) or a group represented by the following formula (1B). In formula (2), * represents a bond to X. R １ and R ２ each independently represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryloxy group, an optionally substituted heteroaryloxy group, an optionally substituted alkoxycarbonyl group, an optionally substituted dialkylamino group, an optionally substituted diarylamino group, an optionally substituted arylalkylamino group, an optionally substituted acyl group, an optionally substituted haloalkyl group, an optionally substituted alkylthio group, an optionally substituted arylthio group, an optionally substituted silyl group, an optionally substituted siloxy group, an optionally substituted aromatic hydrocarbon group, an optionally substituted aromatic heterocyclic group, or a group represented by the following formula (1B). L １ and L ２ each independently represents a direct bond, a divalent group, a group represented by the following formula (1A) or a group represented by the following formula (3A). Z represents a hydrogen atom, an alkyl group, an alkoxy group, an amide group, or a polymerizable functional group. x1 is an integer from 0 to 2, y1 is an integer from 1 to 3, and x1+y1=3. x2 is an integer from 0 to 2, y2 is an integer from 1 to 3, and x2+y2=3. When x1 is an integer of 2 or more, R １ may be the same or different from each other. When y1 is an integer of 2 or more, R ２、 x2, y2, L １、 L ２ and Z may be the same or different from each other. When x2 is an integer of 2 or more, R2 may be the same or different from each other. When y2 is an integer of 2 or more, L ２ and Z may be the same or different from each other. (In formula (1B), * represents a bond to any atom in formula (1) or (2), and B １ and B ２ R each independently represents a direct bond or a divalent group. ３ represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryloxy group, an optionally substituted heteroaryloxy group, an optionally substituted alkoxycarbonyl group, an optionally substituted dialkylamino group, an optionally substituted diarylamino group, an optionally substituted arylalkylamino group, an optionally substituted acyl group, an optionally substituted haloalkyl group, an optionally substituted alkylthio group, an optionally substituted arylthio group, an optionally substituted silyl group, an optionally substituted siloxy group, an optionally substituted aromatic hydrocarbon group, an optionally substituted aromatic heterocyclic group, or a polymerizable functional group. In formula (1A) and formula (3A), * represents a bond to any atom in formula (1) and formula (2). In formula (1A), B １ and B ２ Each independently represents a direct bond or a divalent group. In formula (3A), n is an integer of 1 or more.

4. The electrophotographic photoreceptor according to claim 3, wherein in formula (1), X is represented by any one of the following formulas (A-1) to (A-27): (In formulas (A-1) to (A-27), * represents a bond to A, and R Ａ１１ , R Ａ２１ , R Ａ３１ , R Ａ４１ , R Ａ５１ , R Ａ６１ , R Ａ６２ , R Ａ７１ , R Ａ７２ , R Ａ８１ , R Ａ８２ , R Ａ９１ , R Ａ９２ , R Ａ１０１ , R Ａ１１１ , R Ａ１２１ , R Ａ１３１ , R Ａ１４１ , R Ａ１５１ , R Ａ１６１ , R Ａ１７１ , R Ａ１８１ , R Ａ１８２ , R Ａ１９１ , R Ａ１９２ , R Ａ２０１ , R Ａ２０２ , R Ａ２１１ , R Ａ２１２ , R Ａ２２１ , R Ａ２２２ , R Ａ２３１ , R Ａ２３２ , R Ａ２４１ , R Ａ２４２ , R Ａ２５１ , R Ａ２５２ , R Ａ２６１ , R Ａ２６２ each independently represents a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aromatic group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, an acyl group which may have a substituent, an ester group which may have a substituent, a cyano group, a nitro group, a sulfone group which may have a substituent, a hydroxy group, an aldehyde group which may have a substituent, or a halogen atom. m11, m21, m31, m41, m51, m61, m62, m71, m72, m81, m82, m91, m92, m101, m111, m121, m131, m141, m151, m161, m171, m181, m182, m191, m192, m201, m202, m211, m212, m221, m222, m231, m232, m241, m242, m251, m252, m261, and m262 each independently represent an integer of 0 or more. When m11, m21, m31, m41, m51, m61, m62, m71, m72, m81, m82, m91, m92, m101, m111, m121, m131, m141, m151, m161, m171, m181, m182, m191, m192, m201, m202, m211, m212, m221, m222, m231, m232, m241, m242, m251, m252, m261, and m262 are each 2 or more, R Ａ１１ ~R Ａ２６２ may be different from each other.)

5. The electrophotographic photoreceptor according to claim 3 , wherein at least one A in the formula (1) is represented by the formula (2).

6. In the formula (2), L １ and L ２ The electrophotographic photoreceptor according to claim 3 , wherein at least one of the following is a group represented by formula (1A) or a group represented by formula (3A).

7. The electrophotographic photoreceptor according to claim 3 , wherein the compound represented by formula (1) has at least one polymerizable functional group in one molecule.

8. The electrophotographic photoreceptor according to claim 7, wherein the polymerizable functional group is selected from the following formulae (M1) to (M7): (In formulas (M1) to (M7), R 110 represents a hydrogen atom or an alkyl group which may have a substituent, and * represents the bonding position.

9. In the formula (2), R １ The electrophotographic photoreceptor according to claim 3 , wherein is an alkyl group which may have a substituent.

10. The electrophotographic photoreceptor according to claim 1 , wherein the protective layer further contains a polymer of a polymerizable compound having no electron transporting skeleton.

11. The electrophotographic photoreceptor according to claim 1 or 2, wherein the protective layer further comprises an electron donating compound.

12. 3. The electrophotographic photoreceptor according to claim 1, wherein the electron transporting compound contained in the photosensitive layer comprises at least one of compounds represented by the following formulas (100) to (104): (In formula (100), Ar ＥＴＭ is selected from the following formulas (100-1) to (100-3). Each R independently represents a hydrogen atom, an alkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, or a halogen atom. (In formulas (101) to (104), each R independently represents a hydrogen atom, an alkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, or a halogen atom.) (In formulas (100-1) to (100-3), each R independently represents a hydrogen atom, an alkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, or a halogen atom.)

13. 3. An electrophotographic photoreceptor cartridge comprising the electrophotographic photoreceptor according to claim 1.

14. 3. An image forming apparatus comprising the electrophotographic photoreceptor according to claim 1.

Images