JP2024101280A - Electrophotographic photoreceptor and method for manufacturing the same, image forming apparatus, and image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor that has a functional layer including a nature-originated component and preventing changes over time of a surface shape and electrical characteristics.

SOLUTION: An electrophotographic photoreceptor has a conductive support, and a functional layer including a charge generating layer and a charge transport layer arranged on the conductive support. At least one layer of the functional layer contains resin including a partial structure derived from a cinnamic acid or a derivative thereof.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an electrophotographic photoreceptor and a method for manufacturing the same, as well as an image forming apparatus and an image forming method using the same.

Conventionally, electrophotographic image formation has been widely used in the field of copying machines and the like because of its advantages of high speed and high print quality. Electrophotographic photoreceptors used in image forming devices usually have a conductive support and a functional layer disposed on the conductive support. The functional layer often includes an undercoat layer for suppressing charge injection from the substrate, a charge generation layer for generating charge at a location irradiated with light, a charge transport layer for transporting the charge generated in the charge generation layer to the photoreceptor surface, and a surface protection layer for protecting the surface. Here, each layer in the functional layer is required to have a surface shape that is unlikely to change over time, and furthermore, to have electrical properties that are unlikely to change over time.

In recent years, polycarbonate resins containing bisphenol Z-type structural units represented by the following chemical formula have often been used as binder resins for charge generating layers, charge transport layers, and the like (see, for example, Patent Document 1).

JP 2014-2356 A

However, according to the inventors' intensive research, when bisphenol Z type polycarbonate is used in the functional layer, the electrical properties of the photoreceptor may change over time. Therefore, it is desirable to provide an electrophotographic photoreceptor whose electrical properties are less likely to change over time.

In recent years, interest in resource depletion and global warming has been growing year by year, and efforts are being made worldwide to reduce carbon dioxide emissions by converting fossil fuel-derived raw materials to non-fossil fuel-derived raw materials. In particular, there is a desire to reduce the environmental burden by converting fossil fuel-derived raw materials to biomass raw materials, which are plant-derived materials. However, the current situation is that a material with excellent electrical properties that can be used for electrophotographic photoreceptors has not yet been found.

The present invention has been made in consideration of these problems. The purpose of the present invention is to provide an electrophotographic photoreceptor having a functional layer that contains naturally occurring components and whose surface shape and electrical properties are unlikely to change over time, a method for producing the same, an image forming apparatus that includes the electrophotographic photoreceptor, and an image forming method that uses the same.

One embodiment of the present invention provides an electrophotographic photoreceptor having a conductive support and functional layers including a charge generating layer and a charge transport layer disposed on the conductive support, at least one layer of the functional layer containing a resin including a partial structure derived from cinnamic acid or a derivative thereof.

Another embodiment of the present invention provides a method for producing an electrophotographic photoreceptor having a conductive support and a functional layer including a charge generating layer and a charge transport layer disposed on the conductive support, the method including a step of applying a functional layer coating liquid containing a resin including a partial structure derived from cinnamic acid or a derivative thereof onto the conductive support.

An embodiment of the present invention provides an image forming apparatus including the electrophotographic photoreceptor.

Furthermore, one embodiment of the present invention provides an image forming method using the above image forming device.

According to the present invention, an electrophotographic photoreceptor is provided that contains cinnamic acid or a cinnamic acid derivative, which is a naturally occurring component, and has a functional layer whose surface shape and electrical properties are unlikely to change over time.

1A and 1B are schematic cross-sectional views showing the layer structure of an electrophotographic photoreceptor according to one embodiment.

One embodiment of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the embodiment described below.

1. Electrophotographic Photoreceptor The electrophotographic photoreceptor of the present embodiment has at least a conductive support and a functional layer disposed on the conductive support. The functional layer has at least a charge generating layer and a charge transport layer, and may further have, for example, an undercoat layer or a protective layer. Examples of the layer structure of the functional layer include the following four.
(1) A layer structure including an undercoat layer/a charge generating layer/a charge transport layer in this order. (2) A layer structure including an undercoat layer/a layer in which a charge generating layer and a charge transport layer are integrated/a protective layer in this order. (3) A layer structure including an undercoat layer/a charge generating layer/a charge transport layer/a protective layer in this order. (4) A layer structure including an undercoat layer/a layer in which a charge generating layer and a charge transport layer are integrated/a protective layer in this order.

As in (2) or (4) above, the charge generation layer and the charge transport layer can be made into a single layer by including the charge generation material and the charge transport material in the same layer. However, from the viewpoint of suppressing the increase in residual potential that occurs with repeated use and making it easier to control the characteristics of the electrophotographic photoreceptor according to the purpose, it is preferable to make them into separate layers. In other words, the layer structure of (1) or (3) is preferable, and the layer structure of (3) is more preferable.

A partial schematic cross-sectional view of an electrophotographic photoreceptor 100 having a functional layer 120 with a layer structure of (1) is shown in FIG. 1A. In the electrophotographic photoreceptor 100 shown in FIG. 1A, a conductive support 110, an undercoat layer 121, a charge generation layer 122, and a charge transport layer 123 are laminated in this order. (A partial schematic cross-sectional view of an electrophotographic photoreceptor 100 having a functional layer 120 with a layer structure of 39 is shown in FIG. 1B. In the electrophotographic photoreceptor 100 shown in FIG. 1B, a conductive support 110, an undercoat layer 121, a charge generation layer 122, a charge transport layer 123, and a protective layer 124 are laminated in this order.

Here, in the electrophotographic photoreceptor 100 of this embodiment, at least one layer of the functional layer 120 contains a resin that includes a partial structure derived from cinnamic acid or a derivative thereof.

As mentioned above, the electrical properties of the functional layer containing the polycarbonate resin having the conventional bisphenol Z structure tended to deteriorate over time. The reason for this is unclear, but it is believed to be as follows. The cyclohexyl group of the bisphenol Z structure is bulky and perpendicular to the phenyl group, so when the polymer chains overlap during the formation of the functional layer, sparse portions are generated in the functional layer. Since the state in which such portions exist is unstable, such overlapping of the polymer chains changes to a more stable higher-order structure over time or when exposed to a high-temperature environment. In other words, the three-dimensional structure of the polymer chains changes in the direction in which the above-mentioned sparse portions are eliminated. As a result, it is thought that the problem of the electrical properties of the functional layer (electrophotographic photoreceptor) immediately after production being different from the electrical properties of the functional layer (electrophotographic photoreceptor) after a certain time has passed since the film formation is likely to occur.

In contrast, the structure derived from cinnamic acid or its derivatives, the structure of which will be shown in detail later, has a relatively small spatial molecular spread. Therefore, the three-dimensional structure of a resin containing this structure is unlikely to change over time or in a high-temperature environment. Therefore, the electrical properties of a telegraph photoreceptor having a functional layer containing this resin are unlikely to change over time. Furthermore, such a resin with a relatively small spatial molecular spread makes it easy to obtain a functional layer whose surface shape is unlikely to change over time. Furthermore, cinnamic acid or its derivatives are mainly obtained from biomass, and have the advantage of being environmentally friendly.

Below, we will explain the resin containing a partial structure derived from cinnamic acid or its derivatives, and then we will explain each component of the electrophotographic photoreceptor.

[Resin containing a partial structure derived from cinnamic acid or its derivatives]
In this embodiment, the resin containing a partial structure derived from cinnamic acid or a derivative thereof refers to a resin containing any of the following structures (hereinafter, these structures are also referred to as "cinnamic acid skeleton") in a part of the molecular chain. In this specification, for convenience, the wavy line in the chemical formula represents a bond to another atom or a molecular structure, and the bond partner is not limited. In addition, the three-dimensional structure of the resin containing the partial structure may be a cis type, a trans type, or a mixture of these.

In this specification, the term "resin" includes not only polymers but also oligomers (including dimers and trimers of cinnamic acid or its derivatives) and cinnamic acid or its derivatives themselves, i.e., monomers. However, since it is preferable that a resin containing a cinnamic acid skeleton functions as a binder resin in any of the functional layers, the resin is usually a polymer and may contain an oligomer or monomer as a part of it. Below, an example will be described in which a resin containing a cinnamic acid skeleton is a binder resin in any of the functional layers, but the resin may perform functions other than that of a binder resin in the functional layer.

It is preferable that the resin containing a cinnamic acid skeleton contains a partial structure represented by any one of general formulas (1) to (3).

一般式（１）において、波線は、結合手を表す。 First, the partial structure represented by general formula (1) is shown below.

In formula (1), the wavy line represents a bond.

^R1 and ^{R2 each} independently represent a monovalent atom such as a halogen atom, or ^a monovalent atomic group having a molecular weight of 200 or less, preferably 100 or less.

Specific examples of monovalent atomic groups include:
A linear or branched alkyl group having 1 to 32 carbon atoms;
A linear or branched alkenyl group having 2 to 32 carbon atoms;
A linear or branched alkynyl group having 2 to 32 carbon atoms;
Aryl groups such as a phenyl group;
a cycloalkyl group having 3 to 12, preferably 5 to 7, carbon atoms;
A cycloalkenyl group having 3 to 12, preferably 5 to 7, carbon atoms;
Alkoxy groups such as a methoxy group and an ethoxy group;
Aryloxy groups such as a phenoxy group;
5- to 7-membered heterocyclic groups such as a 2-furyl group, a 2-thienyl group, a 2-pyrimidinyl group, and a 2-benzothiazolyl group;
5- to 7-membered heterocyclic oxy groups such as a 3,4,5,6-tetrahydropyranyl-2-oxy group and a 1-phenyltetrazole-5-oxy group;
5- to 7-membered heterocyclic thio groups, such as a 2-pyridylthio group, a 2-benzothiazolylthio group, and a 2,4-diphenoxy-1,3,5-triazole-6-thio group;
acylamino groups such as an alkylcarbonylamino group or an arylcarbonylamino group;
Sulfonamide groups such as alkylsulfonylamino groups and arylsulfonylamino groups;
ureido groups such as alkylureido groups and arylureido groups;
Sulfamoylamino groups such as alkylsulfamoylamino groups and arylsulfamoylamino groups;
Imido groups such as a succinimide group, a 3-heptadecylsuccinimide group, a phthalimide group, and a glutarimide group;
spiro compound residues such as spiro[3.3]heptan-1-yl;
Residues of bridged hydrocarbon compounds such as bicyclo[2.2.1]heptan-1-yl, tricyclo[3.3.1.3.7]decan-1-yl, and 7,7-dimethyl-bicyclo[2.2.1]heptan-1-yl;
Sulfonyl groups such as alkylsulfonyl, arylsulfonyl, halogen-substituted alkylsulfonyl, and halogen-substituted arylsulfonyl;
Sulfinyl groups such as alkylsulfinyl and arylsulfinyl;
Sulfonyloxy groups such as alkylsulfonyloxy and arylsulfonyloxy;
Sulfamoyl groups such as N,N-dialkylsulfamoyl, N-N-diarylsulfamoyl, and N-alkyl-N-arylsulfamoyl;
Phosphoryl groups such as alkoxyphosphoryl, aryloxyphosphoryl, alkylphosphoryl, and arylphosphoryl;
Carbamoyl groups such as N,N-dialkylcarbamoyl, N,N-diarylcarbamoyl, and N-alkyl-N-arylcarbamoyl;
Acyl groups such as alkylcarbonyl and arylcarbonyl;
acyloxy groups such as alkylcarbonyloxy;
Oxycarbonyl groups such as alkoxycarbonyl and aryloxycarbonyl;
Pyrrolyl groups such as 1-pyrrolyl;
Tetrazolyl groups such as 1-tetrazolyl;
Halogen-substituted alkoxy groups such as α-halogen-substituted alkoxy;
Halogen-substituted aryloxy groups such as tetrafluoroaryloxy and pentafluoroaryloxy;
Halogenated alkyl groups such as a trifluoromethyl group, a heptafluoroisopropyl group, and a nonylfluoro-t-butyl group;
Halogenated aryl groups such as tetrafluoroaryl groups and pentafluoroaryl groups;
Siloxy groups such as a trimethylsiloxy group, a triethylsiloxy group, and a dimethylbutylsiloxy group;
Amino group-containing groups such as an amino group, an alkylamino group, an alkoxycarbonylamino group, or an aryloxycarbonylamino group;
Sulfur-containing groups such as mercapto groups, alkylthio groups, and arylthio groups;
Anilino groups; cyano groups; nitro groups; thioureido groups; hydroxy groups; and the like.

The "alkyl" and "aryl" in the above specific examples are not particularly limited as long as they satisfy the above molecular weight. Furthermore, the above-mentioned atomic groups may be bonded as substituents to the alkyl chains or aromatic rings in the above atomic groups.

Among the above, the monovalent atomic group represented by ^R1 or ^R2 is preferably an alkyl group having 1 to 12 carbon atoms, an alkoxy group containing an alkyl group having 1 to 12 carbon atoms, an aryloxy group, or a combination thereof. Among these, an alkoxy group containing an alkyl group having 1 to 12 carbon atoms is preferred, and a methoxy group is particularly preferred.

In the above general formula (1), L and M each represent an integer of 0 to 4, and more preferably 0 to 2. When L or M is 1 or more, the interaction between other components contained in the functional layer, such as a charge transport agent, a compound that is prone to π-π interaction, and a resin containing a cinnamic acid skeleton can be appropriately suppressed. As a result, when the functional layer is formed, aggregation is unlikely to occur between the compound that is prone to π-π interaction and the resin containing a cinnamic acid skeleton, and the solubility of these in the solvent is improved. Therefore, the desired functional layer is more easily obtained. In addition, when L and M are 2 or more, multiple R ^1s or multiple R ^2s may be the same group or different groups.

In the structure represented by the above general formula (1), the carbonyl group is arranged diagonally across the four-membered ring, but the resin in this embodiment may have a structure in which two carbonyl groups are arranged at adjacent positions on the four-membered ring of the structure represented by general formula (1). However, in this structure, the two oxygen atoms (-O-) that form the main chain are also adjacent, so the polymerization reaction points are three-dimensionally crowded. Therefore, since the polymerization rate decreases, it is preferable that the carbonyl groups are arranged diagonally across the four-membered ring as in the above general formula (1).

一般式（１１）における、Ｒ^１、Ｒ^２、Ｌ、およびＭは、上記一般式（１）におけるＲ^１、Ｒ^２、Ｌ、およびＭとそれぞれ同様である。
一方、Ｒ^８およびＲ^９はそれぞれ独立に一価の原子、または分子量が２００以下、好ましくは１００以下の一価の原子団を表し、上記一般式（１）におけるＲ^１およびＲ^２で表される原子または原子団と同様である。ただし、Ｒ^８およびＲ^９はアルキル基またはアリール基、若しくはこれらの組み合わせが好ましい。 The partial structure represented by the above general formula (1) is more preferably a structural unit represented by the following general formula (11).

In the general formula (11), R ¹ , R ² , L, and M are the same as R ¹ , R ² , L, and M in the above general formula (1), respectively.
Meanwhile, ^R8 and ^R9 each independently represent a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less, preferably 100 or less, and are the same as the atoms or atomic groups represented by ^R1 and ^R2 in the above general formula (1). However, ^R8 and ^R9 are preferably an alkyl group or an aryl group, or a combination thereof.

Specific examples of the structure represented by the above general formula (11) include structures represented by the following (A-1) to (A-9).

一般式（１－１）における、Ｒ^１、Ｒ^２、Ｒ^８、Ｒ^９、Ｌ、およびＭは、上記一般式（１１）におけるＲ^１、Ｒ^２、Ｒ^８、Ｒ^９、Ｌ、およびＭとそれぞれ同様である。当該樹脂には、上記一般式（１―１）で表される構造単位が一種のみ含まれていてもよく、二種以上含まれていてもよい。 Further, specific examples of the resin containing a cinnamic acid skeleton, including the structure represented by the above general formula (11), include a resin containing a structural unit represented by the following general formula (1-1).

In general formula (1-1), R ¹ , R ² , R ⁸ , R ⁹ , L, and M are the same as R ¹ , R ² , R ⁸ , R ⁹ , L, and M in general formula (11), respectively. The resin may contain only one type of structural unit represented by general formula (1-1), or may contain two or more types.

一般式（１－１－ＰＣ）における、Ｒ^１、Ｒ^２、Ｒ^８、Ｒ^９、Ｌ、およびＭは、上記一般式（１１）におけるＲ^１、Ｒ^２、Ｒ^８、Ｒ^９、Ｌ、およびＭとそれぞれ同様である。 Specific examples of the resin represented by the above general formula (1-1) include polycarbonate resins containing a structure represented by the following general formula (1-1-PC).

In general formula (1-1-PC), R ¹ , R ² , R ⁸ , R ⁹ , L, and M are the same as R ¹ , R ² , R ⁸ , R ⁹ , L, and M in general formula (11), respectively.

The polycarbonate resin may contain structural units other than the structural units represented by the general formula (1-1-PC) above, for example, structural units containing a bisphenol Z-type structure in part. However, the proportion of the number of moles of the structural units represented by the general formula (1-1-PC) in the polycarbonate resin relative to the total number of moles of the structural units constituting the polycarbonate resin is preferably 20 mol % or more, more preferably 50 mol % or more, and even more preferably 80 mol % or more. When the proportion of the structural units represented by the general formula (1-1-PC) is within the above range, a functional layer whose electrical properties are less likely to change over time is obtained.

On the other hand, specific examples of the resin represented by the above general formula (1-1) include polyester resins obtained by polymerizing a diol containing the structure represented by the above general formula (1-1) with a dicarboxylic acid. The type of dicarboxylic acid polymerized with the above diol is not particularly limited, and may have any structure, such as an aliphatic dicarboxylic acid, a dicarboxylic acid containing an alicyclic structure, or an aromatic dicarboxylic acid. The dicarboxylic acid is not particularly limited as long as it satisfies the desired performance, and may be an aliphatic, aromatic, or derivative thereof, but is preferably derived from biomass. Examples of dicarboxylic acids derived from biomass include aliphatic carboxylic acids such as succinic acid, fumaric acid, aspartic acid, adipic acid, and sebacic acid; aromatic dicarboxylic acids such as terephthalic acid and furandicarboxylic acid. Among them, fumaric acid and terephthalic acid are preferred from the viewpoint of film strength and electrical properties.

Furthermore, the number average molecular weight of the resin containing the structural unit represented by general formula (1-1) is preferably 1000 to 100,000, more preferably 3000 to 80,000, and more preferably 5000 to 50,000. The number average molecular weight is a value measured by gel permeation chromatography (GPC) and is a styrene-equivalent value. The molecular weight distribution (weight average molecular weight/number average molecular weight) is preferably 1.01 to 10.0, more preferably 1.03 to 8.0, and even more preferably 1.05 to 5.0. When the number average molecular weight and molecular weight distribution are within the above ranges, it is easy to form a layer containing the resin, and it is easy to obtain a desired functional layer.

一般式（２）において、波線は結合手を表す。
また、Ｒ^３およびＲ^４は、それぞれ独立に水素原子、ハロゲン原子、炭素数が１以上３以下のアルキル基、アミノ基、ヒドロキシ基、チオール基を表し、好ましくは水素原子である。 Next, the partial structure represented by general formula (2) is shown below.

In formula (2), the wavy line represents a bond.
^R3 and ^R4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, an amino group, a hydroxyl group, or a thiol group, and are preferably a hydrogen atom.

Furthermore, ^R5 represents a substituent, i.e., a group other than a hydrogen atom, and represents a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less, preferably 100 or less. Specific examples of the monovalent atom or monovalent atomic group include those exemplified as the atoms or atomic groups represented by ^R1 and ^R2 in the above general formula (1). Among the above, ^R5 is preferably a halogen atom, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, a halogen-substituted or unsubstituted alkoxy group containing an alkyl group having 1 to 12 carbon atoms, and an aryloxy group, and among these, an alkoxy group containing an alkyl group having 1 to 8 carbon atoms is more preferable, and an alkoxy group containing an alkyl group having 1 to 4 carbon atoms is even more preferable.

X represents an integer of 0 to 5, and X is preferably 0 to 3, more preferably 1. When X is 1 or more, the interaction between other components contained in the functional layer, such as a charge transport agent, which is prone to π-π interaction, and a resin containing a cinnamic acid skeleton can be appropriately suppressed. As a result, when the functional layer is formed, aggregation is unlikely to occur between the compound which is prone to π-π interaction and the resin containing a cinnamic acid skeleton, and the solubility in the solvent of these is improved. Therefore, the desired functional layer is more easily obtained. In addition, when X is 2 or more, multiple R ^5s may be the same group or different groups.

一般式（３）において、波線は結合手を表す。
Ｒ^６およびＲ^７は置換基、すなわち水素原子以外の基を表し、一価の原子、または分子量が２００以下、好ましくは１００以下の一価の原子団を表す。当該一価の原子、または一価の原子団の具体例には、上述の一般式（１）のＲ^１およびＲ^２で表される原子または原子団で挙げたものが含まれる。Ｒ^６およびＲ^７はそれぞれ、上述の一般式（２）のＲ^５と同様の基が好ましい。また、ＹおよびＺはそれぞれ独立に０以上５以下の整数を表し、０以上３以下が好ましく、１がより好ましい。なお、ＹまたはＺが２以上である場合、複数のＲ^６またはＲ^７は、互いに同一の基であってもよく、異なる基であってもよい。 Next, the partial structure represented by general formula (3) is shown below: The partial structure represented by general formula (3) represents a dimerized structure of the partial structure represented by general formula (2) above.

In formula (3), the wavy line represents a bond.
R ⁶ and R ⁷ each represent a substituent, that is, a group other than a hydrogen atom, and represent a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less, preferably 100 or less. Specific examples of the monovalent atom or monovalent atomic group include those listed as the atoms or atomic groups represented by R ¹ and R ² in the above general formula (1). R ⁶ and R ⁷ are preferably the same groups as R ⁵ in the above general formula (2). Y and Z each independently represent an integer of 0 to 5, preferably 0 to 3, more preferably 1. When Y or Z is 2 or more, multiple R ^6s or R ^7s may be the same group or different groups.

On the other hand, specific examples of the structural unit represented by the above general formula (2) include structures represented by the following (B-1) to (B-50), and specific examples of the structural unit represented by the above formula (3) include dimers thereof.

上記一般式（２－１）および（３－１）におけるＲ^３、Ｒ^４、Ｒ^５、Ｒ^６、およびＲ^７、ならびにＸ、Ｙ、およびＺは、上述の一般式（２）および（３）におけるＲ^３、Ｒ^４、Ｒ^５、Ｒ^６、およびＲ^７、ならびにＸ、Ｙ、およびＺと同様である。当該樹脂には、上記一般式（２―１）または（３－１）で表される構造単位が一種のみ含まれていてもよく、二種以上含まれていてもよい。 Specific examples of the resin containing the structure represented by the general formula (2) or the structure represented by the general formula (3) include polyvinyl resins containing a structural unit represented by the following general formula (2-1) or the following general formula (3-1).

R ³ , R ⁴ , R ⁵ , R ⁶ , and R ⁷ , as well as X, Y, and Z in the above general formulae (2-1) and (3-1) are the same as R ³ , R ⁴ , R ⁵ , R ⁶ , and R ⁷ , as well as X, Y, and Z in the above general formulae (2) and (3). The resin may contain only one type of structural unit represented by the above general formula (2-1) or (3-1), or may contain two or more types.

The polyvinyl resin containing the structure represented by the above general formula (2-1) is preferably one in which the structure represented by the above general formula (2) is introduced into the side chain of polyvinyl alcohol. In this case, the ratio of the number of moles of the structural units into which the structure represented by the above general formula (2) is introduced to the number of moles of all structural units of the resin is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 40 mol% or more.

Furthermore, the number average molecular weight of the polyvinyl resin containing the structure represented by the above general formula (2-1) is not particularly limited as long as the desired physical properties are obtained, but is preferably 1000 to 80000, more preferably 2000 to 65000, and even more preferably 3000 to 50000. The number average molecular weight is a value measured by gel permeation chromatography (GPC) and is a styrene-equivalent value. The molecular weight distribution (weight average molecular weight/number average molecular weight) is preferably 1.01 to 10.0, more preferably 1.03 to 8.0, and even more preferably 1.05 to 5.0. When the number average molecular weight and molecular weight distribution are within the above ranges, it is easy to form a layer containing the polyvinyl resin, and it is easy to obtain a desired functional layer.

Specific examples of resins containing the structure represented by general formula (2) include compounds obtained by reacting an acid chloride containing the structure represented by general formula (2) with a monohydric or polyhydric alcohol (hereinafter also referred to as "cinnamic acid compounds"). Examples of monohydric or polyhydric alcohols include, but are not limited to, alcohols containing a triphenylamine structure, adonitol, arabitol, 1,2,4-butanetriol, 1,2,3-hexanetriol, 1,2,6-hexanetriol, glycerin, diglycerin, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, galactitol, glucose, cellobiose, inositol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. Among the above, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol are preferred, and trimethylolpropane is particularly preferred. Examples of resins containing the structure represented by the above general formula (3) include resins obtained by dimerizing the cinnamic acid skeleton of the cinnamic acid compound.

(Synthesis Method)
The method for synthesizing the above-mentioned resin containing a cinnamic acid skeleton is not particularly limited, but it can be synthesized, for example, by the following method.

First, cinnamic acid or a derivative thereof is prepared. The cinnamic acid or a derivative thereof may be a synthetic product, but from the viewpoint of environmental consideration, it is preferable to use one isolated from biomass. Examples of cinnamic acid derivatives obtained from biomass include coumaric acid, ferulic acid, sinapic acid, ethyl cinnamate, ethyl methoxycinnamate, caffeic acid, etc. Substituents may be introduced into the cinnamic acid or a derivative thereof obtained from biomass, if necessary.

For example, when synthesizing a polycarbonate resin containing a structural unit represented by the general formula (1-1-PC), a compound having an OH group on the benzene ring of the above-mentioned cinnamic acid skeleton is prepared and first dimerized. The dimerization method is not limited, and light irradiation is one example. Then, other monomers are added to the dimer as necessary, and polycarbonation is performed by a known method (such as the phosgene method), thereby obtaining a polycarbonate resin containing a structural unit represented by the general formula (1-1-PC).

When synthesizing a polyester resin containing a structural unit represented by the above general formula (1-1), a compound having an OH group on the benzene ring of the above-mentioned cinnamic acid skeleton is prepared and first dimerized. The method of dimerization is not limited, and one example is light irradiation. The desired polyester resin is then obtained by polymerizing the dimer with an appropriate dicarboxylic acid.

On the other hand, when synthesizing a resin containing a structural unit represented by the above general formula (2-1), an acid halide (preferably an acid chloride) of cinnamic acid or a derivative thereof is prepared. Then, the acid halide is reacted with the OH group of polyvinyl alcohol by a known method. As a result, the structure represented by the above general formula (2) is introduced into the side chain of polyvinyl alcohol, and the desired resin is obtained.

Furthermore, a resin containing a structural unit represented by the above general formula (3-1) can be obtained by irradiating a resin containing a structural unit represented by the general formula (2-1) with light to dimerize the cinnamic acid skeleton.

The above-mentioned cinnamic acid-based compound can be obtained by preparing an acid chloride containing a structure represented by general formula (2) and reacting it with a monohydric or polyhydric alcohol by a known method. In addition, a compound in which the cinnamic acid skeleton is dimerized (a compound containing a structure represented by general formula (3)) can be obtained by irradiating the cinnamic acid-based compound with light.

[Each component of the electrophotographic photoreceptor]
Hereinafter, each component of the electrophotographic photoreceptor 100 having the configuration shown in FIG. 1B will be described.

(Conductive Support)
The conductive support 110 is not particularly limited as long as it is conductive, and examples thereof include metals such as aluminum, copper, chromium, nickel, zinc, stainless steel, etc., formed into a drum or sheet shape, metal foils such as aluminum or copper laminated onto plastic films, plastic films onto which aluminum, indium oxide, tin oxide, etc. have been vapor-deposited, metals, plastic films, and papers onto which a conductive layer has been provided by applying a conductive substance alone or together with a binder resin, and the like.

(Functional layer)
The functional layer 120 is disposed on the conductive support 110, and is a layer for forming an electrostatic latent image corresponding to a desired image on the photoreceptor surface by exposure. In this embodiment, the undercoat layer 121, the charge generation layer 122, the charge transport layer 123, and the protective layer 124 are collectively referred to as the functional layer 120. At least one layer of the functional layer 120 may contain the above-mentioned resin containing a cinnamic acid skeleton, and two or more layers may contain a resin containing a cinnamic acid skeleton, or all layers may contain the resin. In addition, when two or more layers contain a resin containing a cinnamic acid skeleton, the resin contained in each layer may be the same or different.

Undercoat Layer The undercoat layer 121 is a layer for suppressing charge injection from the conductive support 110 to the charge generation layer 122, improving the adhesion of the charge generation layer 122, and preventing moire caused by light scattering. The undercoat layer 121 can be a layer containing a binder resin and conductive particles or metal oxide particles.

The binder resin is not particularly limited, and may be, for example, a resin containing the above-mentioned cinnamic acid skeleton. When the above-mentioned resin containing the cinnamic acid skeleton is used, a polyvinyl resin containing a structural unit represented by the above-mentioned general formula (2-1) or a structural unit represented by the general formula (3-1) is preferred, and a polyvinyl resin containing a structural unit represented by the general formula (3-1) is more preferred. Examples of binder resins that can be used other than the resin containing the cinnamic acid skeleton include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide resin, polyurethane resin, gelatin, etc. The binder resin may contain only one type of the above-mentioned resin, or may contain two or more types. When the binder resin contains a resin containing a cinnamic acid skeleton, it is preferable that the binder resin contains 25% by mass or more of the resin containing the cinnamic acid skeleton, and more preferably 75% by mass or more of the resin containing the cinnamic acid skeleton with respect to the total amount of the binder resin. When the binder resin contains a resin containing a cinnamic acid skeleton, the electrical properties of the electrophotographic photoreceptor 100 are less likely to change over time.

On the other hand, examples of conductive particles include tin-doped indium oxide, antimony-doped tin oxide, zirconium oxide, etc. Examples of metal oxide particles include aluminum oxide, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, etc. The undercoat layer 121 may contain only one of these, or may contain two or more types. Furthermore, when two or more types are combined, they may take the form of a solid solution or fusion. From the viewpoint of the surface smoothness of the undercoat layer 121, the number average primary particle size of the conductive particles or metal oxide particles is preferably 0.3 μm or less, and more preferably 0.1 μm or less.

In this specification, the number-average primary particle size of particles is measured by the following method unless otherwise specified. A 10,000 times magnified photograph of a sample taken by a scanning electron microscope (manufactured by JEOL Ltd.) is imported into a scanner. Next, from the obtained photographic image, 300 particle images excluding aggregated particles are randomly binarized using an automatic image processing and analysis system Luzex AP Software Ver. 1.32 (manufactured by Nireco Corporation) to calculate the horizontal Feret diameter of each of the particle images. Then, the average value of the horizontal Feret diameters of each of the particle images is calculated to be the number-average primary particle size. Here, the "horizontal Feret diameter" refers to the length of the side parallel to the x-axis of the circumscribing rectangle when the particle image is binarized.

The amount of conductive particles or metal oxide particles in the undercoat layer 121 is preferably 20 to 400% by mass, more preferably 50 to 350% by mass, based on the total mass of the binder resin.

The thickness of the undercoat layer 121 is preferably 0.1 to 15 μm, more preferably 0.3 to 10 μm, from the viewpoint of adjusting the electrical resistance.

Charge Generation Layer The charge generation layer 122 is a layer that generates charges upon exposure to light, and is a layer that mainly contains a binder resin and a charge generation material.

The binder resin is not particularly limited, and for example, the above-mentioned resin containing a cinnamic acid skeleton can be used. When the above-mentioned resin is used, a polyvinyl resin containing the structural unit represented by the above-mentioned general formula (2-1) or the structural unit represented by the general formula (3-1) is preferred, and a polyvinyl resin containing the structural unit represented by the general formula (3-1) is more preferred. In addition to the above-mentioned resin containing a cinnamic acid skeleton, examples of resins that can be used as binder resins include polystyrene resins, polyethylene resins, polypropylene resins, acrylic resins, methacrylic resins, vinyl chloride resins, vinyl acetate resins, polyvinyl butyral resins, epoxy resins, polyurethane resins, phenolic resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymers containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers), polyvinyl carbazole resins, etc. These may be used alone or in combination of two or more. The binder resin may contain only one of these, or may contain two or more. When the binder resin contains a resin containing a cinnamic acid skeleton, the binder resin preferably contains 25% by mass or more, and more preferably 75% by mass or more, of the resin containing a cinnamic acid skeleton relative to the total amount of the binder resin. When the binder resin contains a resin containing a cinnamic acid skeleton, the electrical characteristics of the charge generating layer 122, and therefore the electrophotographic photoreceptor 100, are less likely to change over time.

The charge generating material is not particularly limited, and examples include azo materials such as Sudan Red and Diane Blue; quinone pigments such as pyrenequinone and anthanthrone; quinocyanine pigments; perylene pigments; indigo pigments such as indigo and thioindigo; polycyclic quinone pigments such as pyranthrone and diphthaloylpyrene; phthalocyanine pigments; and the like. Among these, polycyclic quinone pigments and titanyl phthalocyanine pigments are preferred. The charge generating material may contain only one of these, or two or more of them.

The amount of the charge generating material in the charge generating layer 122 is preferably 1 to 600% by weight, and more preferably 50 to 500% by weight, relative to the total weight of the binder resin. When the amount of the charge generating material is within this range, an electrophotographic photoreceptor 100 with relatively low electrical resistance is obtained. As a result, the increase in residual potential that occurs with repeated use can be suppressed.

The thickness of the charge generating layer 122 is preferably 0.01 to 5 μm, and more preferably 0.05 to 3 μm.

Charge Transport Layer The charge transport layer 123 is a layer for transporting holes, among the charges generated in the charge generation layer 122, to the surface of the electrophotographic photoreceptor 100 (here, the surface of the protective layer 124). The charge transport layer 123 mainly contains a binder resin and a charge transport material.

The binder resin is not particularly limited, and for example, the above-mentioned resin containing a cinnamic acid skeleton can be used. When using the above-mentioned resin containing a cinnamic acid skeleton, a resin containing a structural unit represented by the above-mentioned general formula (1-1) is preferable. In addition to the above-mentioned resin containing a cinnamic acid skeleton, examples of resins that can be used for the binder resin include polycarbonate resins other than those mentioned above, polyacrylate resins, polyester resins, polystyrene resins, styrene-acrylonitrile copolymers, polymethacrylic acid ester resins, styrene-methacrylic acid ester copolymers, etc. Examples of polycarbonate resins other than those mentioned above include bisphenol A type, bisphenol Z type, dimethyl bisphenol A type, and bisphenol A type-dimethyl bisphenol A type copolymer type polycarbonate resins. The binder resin may contain only one of these, or may contain two or more types. When the binder resin contains a resin containing a cinnamic acid skeleton, it is preferable that the binder resin contains 25% by mass or more of the resin containing a cinnamic acid skeleton, and more preferably 75% by mass or more of the resin containing a cinnamic acid skeleton relative to the total amount of the binder resin. When the binder resin contains a resin that has a cinnamic acid skeleton, the electrical characteristics of the charge transport layer 123, and therefore the electrophotographic photoreceptor 100, are less likely to change over time.

The charge transport material is not particularly limited, and examples thereof include triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds, etc. In particular, when the protective layer 124 described below is included, a material with high charge transport performance is preferred. Examples of such charge transport materials include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, etc. The charge transport layer 123 may contain only one of these, or may contain two or more of them.

The content of the charge transport material in the charge transport layer 123 is preferably in the range of 10 to 500% by weight, more preferably in the range of 20 to 250% by weight, based on the total weight of the binder resin.

The thickness of the charge transport layer 123 is preferably 10 to 50 μm, and more preferably 15 to 40 μm.

The charge transport layer 123 may further contain an antioxidant, an electronic conductive agent, a stabilizer, silicone oil, etc. The antioxidant is preferably one disclosed in JP-A-2000-305291, and the electronic conductive agent is preferably one disclosed in JP-A-50-137543 and JP-A-58-76483.

Protective Layer The protective layer 124 is a layer for protecting the surface of the electrophotographic photoreceptor 100, improving abrasion resistance and scratch resistance, and reducing the occurrence of toner slip-through. The protective layer 124 can extend the life of the electrophotographic photoreceptor, and ultimately the image forming apparatus. The protective layer 124 can contain, for example, a binder resin, inorganic fine particles, and a charge transport material.

The binder resin is not particularly limited, and for example, the above-mentioned resin containing a cinnamic acid skeleton can be used. When using the above-mentioned resin containing a cinnamic acid skeleton, a cinnamic acid-based compound containing a structure represented by general formula (2) or general formula (3) is more preferable. Even more preferably, a photocurable resin containing a cinnamic acid-based compound containing a structure represented by general formula (2) is used.

Here, the protective layer 124 is preferably obtained by curing a curable composition. As the monomer in the curable composition, it is preferable to use a combination of monofunctional and polyfunctional monomers in order to obtain film strength and desired electrical properties. In addition, a compound having triarylamine, a structure of general formula (2), is introduced into the monomer in order to obtain the desired performance. These structures may be bonded to a monofunctional or polyfunctional bond.

Examples of monofunctional monomers include compounds having triarylamines with electron transport properties. As polyfunctional monomers, compounds having general formula (2) bonded to polyhydric alcohols are preferably used. The polyfunctional monomer is preferably bifunctional or more and octafunctional or less, more preferably trifunctional or more and hexafunctional or less, and even more preferably trifunctional.

Examples of polyhydric alcohols include, but are not limited to, adonitol, arabitol, 1,2,4-butanetriol, 1,2,3-hexanetriol, 1,2,6-hexanetriol, glycerin, diglycerin, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, galactitol, glucose, cellobiose, inositol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, etc. Among the above, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol are preferred, and trimethylolpropane is particularly preferred.

The binder resin may contain only one of these, or may contain two or more of them. If the binder resin contains a resin that contains a cinnamic acid skeleton, the surface shape of the protective layer 124 and the electrical properties of the electrophotographic photoreceptor 100 may be less likely to change over time.

Other examples of resins that can be used as binder resins besides the above-mentioned resins include polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer, polymethacrylate resin, styrene-methacrylate copolymer, etc. Curable resins may also be used. Curable types include heat curing and photocuring, with photocuring being preferred.

There are no particular limitations on the inorganic fine particles as long as they are compounds that are stable in the air, but insulating oxide particles are preferred in order not to impede the function of the charge transport material. Examples of inorganic fine particles include silica, alumina, magnesium oxide, zirconium oxide, calcium titanate, and the like. The protective layer 124 may contain only one of these, or may contain two or more types.

The numerical average particle diameter of the inorganic fine particles is preferably in the range of 5 to 100 nm, and more preferably in the range of 20 to 50 nm. If the numerical average particle diameter is 5 nm or more, it becomes easier to form the protective layer 124 without causing the inorganic fine particles to aggregate. If the numerical average particle diameter is 100 nm or less, the inorganic fine particles are less likely to aggregate and form coarse particles. The numerical average particle diameter of the inorganic fine particles is measured by the method described above.

The content of inorganic fine particles is preferably 5 to 50% by mass, and more preferably 10 to 30% by mass, based on the total mass of the binder resin. If it is 5% by mass or more, the abrasion resistance of the electrophotographic photoreceptor is easily sufficient. Also, if it is 50% by mass or less, the strength of the protective layer 124 is easily sufficient, and cracks and the like are less likely to occur.

The charge transport material is the same as the charge transport material contained in the charge transport layer described above. The content of the charge transport material is preferably 30 to 200% by mass, more preferably 50 to 150% by mass, based on the total mass of the binder resin.

The thickness of the protective layer 124 is preferably in the range of 1 to 30 μm, and more preferably in the range of 5 to 20 μm.

The protective layer 124 may further contain an antioxidant, an electronic conductive agent, a stabilizer, silicone oil, etc. It is preferable to use the antioxidant disclosed in JP-A-2000-305291, and the electronic conductive agent disclosed in JP-A-50-137543 and JP-A-58-76483, etc.

Others In the above description, the charge generation layer 122 and the charge transport layer 123 are separated. However, as described above, the charge generation layer 122 and the charge transport layer 123 can be a single layer by including a charge generation material and a charge transport material in the same layer. One example of such a single layer is a layer in which a charge generation material and a charge transport material are dispersed in a binder resin. The binder resin in this case is not particularly limited, and the same binder resin as that described for the charge generation layer 122 can be used.

When the charge generating layer 122 and the charge transport layer 123 are formed as a single layer, the thickness of the layer is preferably 10 to 50 μm, and more preferably 20 to 40 μm.

2. Method for Producing Electrophotographic Photoreceptor The method for producing the electrophotographic photoreceptor of the present embodiment is not particularly limited, and the electrophotographic photoreceptor can be produced, for example, by a production method including the following steps (1) to (4).

Step (1): A step of applying an undercoat layer coating liquid onto the outer peripheral surface of a conductive support to form an undercoat layer. Step (2): A step of applying a charge generation layer coating liquid onto the undercoat layer to form a charge generation layer. Step (3): A step of applying a charge transport layer coating liquid onto the charge generation layer to form a charge transport layer. Step (4): A step of applying a protective layer coating liquid onto the charge transport layer to form a protective layer.

The process for forming each layer is explained in detail below.

(Step (1): Formation of Undercoat Layer)
The method for forming the undercoat layer is not particularly limited. For example, a coating liquid for the undercoat layer may be prepared, coated on the conductive support, and then solidified or cured.

The composition of the undercoat layer coating liquid is appropriately selected depending on the type of binder resin desired. When the binder resin is a resin other than a resin containing a cinnamic acid skeleton, an undercoat layer coating liquid is prepared that contains a resin that will become the binder resin or a precursor thereof, and conductive particles or metal oxide particles.

There are no particular limitations on the solvent used in the undercoat layer coating solution, so long as it is capable of dispersing the conductive particles or metal oxide particles well and dissolving the resin or its precursor that will become the binder resin. Examples include alcohols having 2 to 4 carbon atoms, such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, and sec-butanol. These may be used alone or in combination of two or more.

In addition, from the viewpoint of improving the storage stability of the undercoat layer coating solution and the dispersibility of the particles, a co-solvent can be used in combination. Examples of the co-solvent include, for example, methanol, benzyl alcohol, toluene, cyclohexanone, tetrahydrofuran, etc.

The means for dispersing the conductive particles or metal oxide particles when preparing the undercoat layer is not particularly limited, and examples include an ultrasonic disperser, a ball mill, a sand grinder, and a homomixer.

The method for applying the undercoat layer coating solution is not particularly limited, and includes, for example, known methods such as dip coating, spray coating, spinner coating, bead coating, blade coating, beam coating, slide hopper method, and circular slide hopper method.

The method for solidifying the coating can be selected appropriately depending on the type of solvent, the thickness of the layer, and the type of binder resin, and can be done, for example, by natural drying or heating.

When the binder resin is a polyvinyl resin containing a structural unit represented by the above general formula (2-1) or the above general formula (3-1), a composition containing a polyvinyl resin containing a structural unit represented by the above general formula (2-1), conductive particles or metal oxide particles, and other components as necessary is prepared as the undercoat layer coating liquid. Then, a step of coating the undercoat layer coating liquid on the conductive support is performed. The solvent used in the undercoat layer coating liquid and the coating method of the undercoat layer coating liquid are the same as those described above.

Then, a process of solidifying or curing the undercoat layer coating liquid is carried out. In this process, when the desired binder resin is a polyvinyl resin containing a structural unit represented by the above general formula (2-1), the coating film of the undercoat layer coating liquid is solidified by natural drying or heating. The heating temperature when heating is preferably 90°C or higher and 130°C or lower, and more preferably 100°C or higher and 120°C or lower. The heating time is preferably 5 minutes or higher and 90 minutes or lower, and more preferably 10 minutes or higher and 60 minutes or lower.

On the other hand, when the desired binder resin is a polyvinyl resin containing a structural unit represented by the above general formula (3-1), the coating film is irradiated with light after the undercoat layer coating liquid is applied. The type of light to be irradiated may be any light capable of dimerizing the above cinnamic acid skeleton, and light having a wavelength of 250 nm or more and 450 nm or less is preferred, and a wavelength of 300 nm or more and 400 nm or less is more preferred. With these lights, dimerization can be efficiently performed. The type of light source at this time is appropriately selected according to the wavelength of the desired light. In addition, the light irradiation time is appropriately selected according to the irradiation intensity, and is preferably 5 minutes or more and 60 minutes or less, and more preferably 10 minutes or more and 30 minutes or less. Furthermore, the illuminance is more preferably 50 mW/cm ² or more and 1000 mW/cm ² or less.

After the light irradiation, further heating and drying may be performed as necessary. The heating temperature is preferably 90°C or more and 130°C or less, and more preferably 100°C or more and 120°C or less. The heating time is preferably 5 minutes or more and 90 minutes or less, and more preferably 10 minutes or more and 60 minutes or less.

(Step (2): Formation of Charge Generation Layer)
The method for forming the charge generating layer is not particularly limited. For example, a coating liquid for the charge generating layer may be prepared, coated on the undercoat layer, and then solidified or cured.

The composition of the charge generating layer coating liquid is appropriately selected depending on the type of binder resin desired. When the binder resin is a resin other than a resin containing a cinnamic acid skeleton, a charge generating layer coating liquid is prepared containing a resin that will become the binder resin or a precursor thereof and a charge generating material. Before applying the charge generating layer coating liquid, it is preferable to filter out foreign matter and aggregates from the coating liquid.

The solvent for dissolving the binder resin is not particularly limited, and examples include toluene, xylene, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine.

The means for dispersing the charge generating material is not particularly limited, and examples include an ultrasonic disperser, a ball mill, a sand grinder, and a homomixer.

Methods for applying the charge generating layer coating solution include known methods such as dip coating, spray coating, spinner coating, bead coating, blade coating, beam coating, slide hopper, and circular slide hopper, with the dip coating method being particularly preferred.

The method for solidifying the coating can be selected appropriately depending on the type of solvent, the thickness of the layer, and the type of binder resin, and can be done, for example, by natural drying or heating.

When the binder resin is a polyvinyl resin containing a structural unit represented by the above general formula (2-1) or the above general formula (3-1), a composition containing a polyvinyl resin containing a structural unit represented by the above general formula (2-1), a charge generating material, and other components as necessary is prepared as the charge generating layer coating liquid. Then, a step of coating the charge generating layer coating liquid on the undercoat layer is performed. The solvent used in the charge generating layer coating liquid and the coating method of the charge generating layer coating liquid are the same as those described above.

Then, a process of solidifying or curing the charge generating layer coating liquid is carried out. Here, if the desired binder resin is a polyvinyl resin containing a structural unit represented by the above general formula (2-1), the coating film of the charge generating layer coating liquid is solidified by natural drying or heating.

On the other hand, when the desired binder resin is a polyvinyl resin containing a structural unit represented by the above general formula (3-1), after the charge generating layer coating liquid is applied, the coating film is irradiated with light to dimerize the above cinnamic acid skeleton. The type of light to be irradiated may be any light capable of dimerizing the above cinnamic acid skeleton, but the wavelength is preferably 250 nm or more and 450 nm or less, and more preferably 300 nm or more and 400 nm or less. With light of such a wavelength, the cinnamic acid skeleton can be efficiently dimerized. In addition, the irradiation time is appropriately selected according to the irradiation intensity, and is not particularly limited, but is preferably 5 minutes or more and 60 minutes or less, and more preferably 10 minutes or more and 30 minutes or less. Furthermore, the illuminance is more preferably 50 mW/cm ² or more and 1000 mW/cm ² or less.

After the light irradiation, further heating and drying may be performed as necessary. The heating temperature is preferably 90°C or more and 130°C or less, and more preferably 100°C or more and 120°C or less. The heating time is preferably 5 minutes or more and 90 minutes or less, and more preferably 10 minutes or more and 60 minutes or less.

The charge generating layer can also be formed by vacuum deposition of the charge generating material. In this case, the binder resin does not need to be used.

(Step (3): Formation of Charge Transport Layer)
The method for forming the charge generating layer is not particularly limited. For example, a coating liquid for the charge transport layer may be prepared, coated on the charge generating layer, and then solidified or cured.

The composition of the charge transport layer coating liquid is appropriately selected depending on the type of binder resin. If the binder resin is a resin other than the above-mentioned resin containing a cinnamic acid skeleton, a charge transport layer coating liquid is prepared that contains a resin that will become the binder resin or a precursor thereof and a charge transport material.

The solvent used in the charge transport layer coating liquid, the means for dispersing the charge transport material, the coating method for the charge transport layer coating liquid, and the solidification (drying) method are the same as those used in forming the charge generation layer. The charge transport layer coating liquid is preferably applied using a dip coating method.

When the binder resin contains a resin containing a structural unit represented by the above general formula (1-1), a charge transport layer coating liquid is prepared containing the resin containing the structural unit represented by the above general formula (1-1), a charge transport material, and other components as necessary. This is then applied onto the charge generation layer and solidified (cured). This allows the desired charge transport layer to be formed. The solvent used in the charge transport layer coating liquid and the method of applying the charge transport layer coating liquid are the same as those described above.

The charge transport layer can also be formed by vacuum deposition of the charge transport material. In this form, the binder resin does not need to be used.

(Step (4): Formation of protective layer)
The method for forming the protective layer is not particularly limited. For example, a protective layer coating liquid may be prepared, coated on the charge transport layer, and solidified or cured.

The composition of the protective layer coating liquid is appropriately selected depending on the type of binder resin. A charge transport layer coating liquid containing a resin to be the binder resin or a precursor thereof and a charge transport material is prepared.
The protective layer coating solution is preferably applied by a slide hopper method using a circular slide hopper coating device, and can be applied by the method disclosed in, for example, JP-A-2015-114454.

The method of applying the protective layer coating solution and the method of solidifying (drying) it can be appropriately selected depending on the type of solvent, the thickness of the layer, and the type of binder resin, and can be performed, for example, by natural drying or heating. When the above-mentioned cinnamic acid-based compound is used as the binder resin, light irradiation or the like may be performed as necessary.

The type of light to be irradiated may be any light capable of dimerizing the above-mentioned cinnamic acid skeleton, and the wavelength is not particularly limited, but is preferably 250 nm or more and 450 nm or less, and more preferably 300 nm or more and 400 nm or less. Light with such a wavelength can efficiently dimerize the cinnamic acid skeleton. The irradiation time is appropriately selected according to the irradiation intensity, and is not particularly limited, but is preferably 5 minutes or more and 60 minutes or less, and more preferably 10 minutes or more and 30 minutes or less. Furthermore, the illuminance is more preferably 50 mW/ ^cm2 or more and 1000 mW/ ^cm2 or less.

After the light irradiation, further heating and drying may be performed as necessary. The heating temperature is preferably 90°C or higher and 130°C or lower, and more preferably 100°C or higher and 120°C or lower. The heating time is preferably 5 minutes or higher and 90 minutes or lower, and more preferably 10 minutes or higher and 60 minutes or lower.

3. Image Forming Apparatus An image forming apparatus using the above-mentioned electrophotographic photoreceptor may include at least the above-mentioned electrophotographic photoreceptor, and has the same configuration as a general image forming apparatus of an electrophotographic photosensitive type.

For example, the device may include an electrophotographic photoreceptor, a charging means for charging the electrophotographic photoreceptor, a means for exposing the electrophotographic photoreceptor to light and forming an electrostatic latent image, a developing means for attaching toner to the electrostatic latent image to obtain a toner image, and a means for transferring the toner image onto a transfer medium such as paper or a transfer belt. The configuration other than the electrophotographic photoreceptor is the same as that of each of the known means.

The electrophotographic photoreceptor described above can be used in various known electrophotographic photosensitive image forming apparatuses. For example, it can be used in both monochrome image forming apparatuses and full-color image forming apparatuses. It can also be used in a four-cycle image forming apparatus that is composed of four types of color developing means for yellow, magenta, cyan, and black, and one electrophotographic photoreceptor, and it can also be used in a tandem image forming apparatus that has color developing means and an electrophotographic photoreceptor for each color.

4. Image Forming Method The image forming method using the above-mentioned image forming apparatus is also similar to the image forming method of a general image forming apparatus. For example, an image can be formed by carrying out a step of charging the surface of an electrophotographic photoreceptor, a step of forming an electrostatic latent image by exposing the surface of the electrophotographic photoreceptor, a developing step of visualizing the electrostatic latent image with toner to form a toner image, and a step of transferring the toner image to a transfer medium. Each of these steps is similar to a general image forming method.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these.

1. Synthesis of resin containing cinnamic acid skeleton As described below, cinnamic acid or its derivatives were prepared and further modified to obtain a resin containing cinnamic acid skeleton.

(1) Preparation of cinnamic acid or its derivatives (1-1) Isolation of p-coumaric acid and ferulic acid With reference to the method described in "Materials, 1967, Vol. 16, pp. 844", p-coumaric acid and ferulic acid were isolated by the following method. First, rice straw (Usui Agricultural and Livestock Co., Ltd.) was air-dried. 45 g of the obtained dried rice straw was pulverized for 5 minutes with a high-speed mill (LaboNext Co., Ltd.). Then, it was sieved with 80 mesh (opening 0.198 mm). This operation was repeated 25 times to obtain 1083 g of rice straw powder. The obtained rice straw powder was further dried in an oven at 80 ° C. for 18 hours and stored in a desiccator at room temperature. Next, 1080 g of the above-mentioned rice straw powder was extracted with an ethanol/benzene mixture (mass ratio 1/2) and 95 mass% ethanol in order for 48 hours each using multiple Soxhlet extractors, and 205 g of defatted rice straw powder was obtained.

200 g of the obtained defatted rice straw powder was stirred in 1 L of toluene for 24 hours at 50°C, and the solids were filtered off using a 0.1 μm PTFE filter. The obtained solids were extracted with a dioxane/water mixture (mass ratio 9/1), and the dioxane was distilled off under reduced pressure. The residue was then dissolved in acetic acid, and a dichloroethane/ethanol mixture (volume ratio 2/1) was added to the solution. The solution was vigorously stirred and then slowly dripped into 10 times the amount of petroleum ether. The petroleum solution after dripping was stirred for 1 hour, and the solids were filtered off using a 0.1 μm PTFE filter and washed with petroleum ether to obtain 112 g of dioxane lignin.

100 g of the dioxane lignin was dissolved in 5000 ml of 1N sodium hydroxide solution and heated at 70°C for 3 hours. After cooling, the mixture was acidified with dilute hydrochloric acid and filtered. The filtrate was extracted with ether and concentrated, and the oily mixture was isolated by column chromatography using a chloroform/acetic acid mixture (volume ratio 9/1) as a developing agent. As a result, 2.7 g (0.16 mmmol/g [relative to lignin]) and 2.1 g (0.11 mmmol/g [relative to lignin]) of p-coumaric acid and 2.1 g (0.11 mmmol/g [relative to lignin]) of ferulic acid were obtained, respectively. The structures were confirmed by ¹ H-NMR and IR.

(1-2) Isolation of Sinapic Acid Sinapic acid, a cinnamic acid derivative, was isolated from the cork saponification product in an amount of about 5% by mass based on the total amount, with reference to "Forest Products Journal, 1958, Vol. 8, pp. 335". The structure was confirmed by ¹ H-NMR and IR.

(1-3) Synthesis of p-coumaric acid methyl ester With reference to "Synthetic Communications, 2005, 35(1), pp.145", p-coumaric acid methyl ester was synthesized by the following method. First, two three-way stopcocks, a thermometer and a ball stopper were placed in a 100 mL four-neck flask, and the inside of the vessel was decompressed and then replaced with nitrogen. This operation was performed three times. While flowing nitrogen, 30 ml of dehydrated DMF (dimethylformamide), 3.29 g (20 mmol) of p-coumaric acid obtained in (1-1) above, and 2.40 g (24 mmol) of potassium hydrogen carbonate were added and stirred at room temperature for 2 hours. Then, 4.26 g (30 mmol) of methyl iodide was added and heated and stirred at 40°C. After confirming the disappearance of coumaric acid by TLC (thin layer chromatography), 50 ml of water was added and extraction was performed with 30 ml of ethyl acetate. After separating the aqueous layer, the obtained organic layer was washed with 5% sodium bicarbonate and water. The finally obtained organic layer was dried over magnesium sulfate, and then the solid matter was filtered off, and ethyl acetate was distilled off under reduced pressure using a rotary evaporator. The obtained solid matter was purified by column chromatography using an ethyl acetate/n-heptane mixture (volume ratio 1/9). As a result, 3.25 g (yield 91%) of coumaric acid methyl ester was obtained. The structure was confirmed by ¹ H-NMR and IR.

(1-4) Synthesis of ferulic acid methyl ester and sinapic acid methyl ester The ferulic acid and sinapic acid obtained above were esterified in the same manner as in the above "Synthesis of p-coumaric acid methyl ester", to obtain 3.67 g (yield 88%) and 4.01 g (yield 84%) of ferulic acid methyl ester and sinapic acid methyl ester, respectively. The structures were confirmed by ^1H -NMR and IR.

(1-5) Synthesis of coumaric acid n-octyl ester ChemSusChem, 2021, 14(6), pp. 1586 was referred to, and coumaric acid n-octyl ester was synthesized as follows. 2.46 g (15 mmol) of p-coumaric acid obtained above, 0.5 g of ion exchange resin (Amberlite IR-120, Merck) and 19.5 g (150 mmol) of n-hexyl alcohol were charged into a 50 ml eggplant flask and heated and stirred at 120 ° C. for 12 hours. After confirming the disappearance of p-coumaric acid by TLC, 50 ml of ethyl acetate was added, and the solution was passed through a φ60 mm Kiriyama funnel (No. 5C filter paper / Celite) to remove the ion exchange resin. The obtained solution was distilled under reduced pressure using a rotary evaporator. The solid obtained after removing ethyl acetate was purified by column chromatography using a mixed solvent of ethyl acetate/n-heptane (volume ratio 1/9). As a result, 3.28 g (yield 79%) of coumaric acid n-octyl ester was obtained. The structure was confirmed by ¹ H-NMR and IR.

(1-6) Synthesis of coumaric acid phenyl ester After reducing the pressure in a 100 mL 4-neck flask equipped with a nitrogen inlet tube, a dropping funnel, and a thermometer, nitrogen replacement was performed. This operation was performed three times. While flowing nitrogen, 50 mL of dehydrated THF (tetrahydrofuran), the p-coumaric acid (10.0 g, 60.9 mmol) obtained above, and several drops of DMF were added and stirred at room temperature to dissolve. This solution was cooled in an ice bath, and the liquid temperature was maintained at 10°C or less. Then, oxalyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) (8.51 g, 67.0 mmol) was dropped into this solution over 30 minutes, and then the ice bath was removed to return the liquid temperature to room temperature and stirred for 1 hour. 6.31 g (67.0 mmol) of phenol was added to this solution, and the solution was heated to reflux for 2 hours. After cooling to room temperature, the reaction solution was transferred to a separatory funnel, washed with water and THF, extracted, and dried. The obtained solid was purified by column chromatography using a mixture of ethyl acetate and n-heptane (volume ratio 1/9). As a result, 6.01 g (yield 41%) of coumaric acid phenyl ester was obtained. The structure was confirmed by ¹ H-NMR and IR.

(1-7) Synthesis of O-methyl coumaric acid The synthesis was performed with reference to New Journal of Chemistry, 2018, 42 (11), pp. 8831-8842. Two three-way stopcocks, a thermometer, a dropping funnel and a ball stopper were placed in a 500 mL four-head flask, and the inside of the vessel was decompressed and then replaced with nitrogen. This operation was performed three times. While flowing nitrogen, 300 ml of dehydrated DMF and the p-coumaric acid (5.9 g, 35.9 mmol) obtained above were added, and after complete dissolution, the solution was cooled to 10°C or less in an ice bath. After the temperature was stabilized, 55% sodium hydride dispersed in liquid paraffin (4.71 g, 107.9 mmol, manufactured by Kanto Chemical Co., Ltd.) was slowly added under nitrogen flow. When gas generation had settled, dimethyl sulfate (13.6 g, 107.7 mmol, manufactured by Tokyo Kasei Co., Ltd.) was added and stirred at room temperature for 24 h. 90 ml of 10% hydrochloric acid was added to this solution, and after stirring for 1 hour, the solid content was filtered using a Kiriyama funnel. The obtained solid content was placed in a 500 ml eggplant flask, 150 ml of ethanol (manufactured by Kanto Chemical Co., Ltd.) was added, and after complete dissolution, 180 ml (180 mmol) of 1.0 M aqueous sodium hydroxide solution was added, and the mixture was heated under reflux for 1 hour. After cooling to room temperature, 10% aqueous hydrochloric acid was added until the pH of the solution became acidic. The solution was transferred to a separatory funnel, and 100 ml of ethyl acetate was added to extract the reaction product. After removing the aqueous layer, the mixture was washed with water three times, and the obtained organic layer was dried with magnesium sulfate. After filtering off the magnesium sulfate, the obtained filtrate was concentrated in an evaporator to obtain a solid content. This solid content was recrystallized with methanol. As a result, 5.3 g (yield 83%) of O-methyl coumaric acid was obtained. The structure was confirmed by ¹ H-NMR and IR.

(1-8) Synthesis of O-methyl coumaric acid chloride 50 mL of CH ₂ Cl ₂ , the O-methyl coumaric acid (10.0 g, 56.1 mmol) obtained above, and a few drops of DMF were added to a 100 mL 4-neck flask equipped with a nitrogen inlet tube, a dropping funnel, and a thermometer, and stirred at room temperature to dissolve. This solution was cooled in an ice bath, and the liquid temperature was maintained at 10°C or less. Then, oxalyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) (7.8 g, 61.7 mmol) was dropped into this solution over 30 minutes, and then the ice bath was removed, the liquid temperature of the solution was brought to room temperature, and the solution was stirred for 5 hours. The solution was concentrated under reduced pressure using a rotary evaporator, and 50 mL of CH ₂ Cl ₂ was added again, followed by concentration under reduced pressure using a rotary evaporator. This operation was repeated three times. As a result, 10.6 g of O-methyl coumaric acid chloride was obtained (yield 96%).

(1-9) Synthesis of O-methylferulic acid and O-methylsinapic acid With reference to the synthesis of O-methylcoumaric acid (1-7) above, O-methylferulic acid and O-methylsinapic acid were synthesized by replacing p-coumaric acid with ferulic acid and sinapic acid, respectively.

(1-10) Synthesis of O-methylferulic acid chloride and O-methylsinapic acid chloride With reference to the synthesis of O-methylcoumaric acid chloride (1-8) above, O-methylferulic acid chloride and O-methylsinapic acid chloride were synthesized by replacing O-methylcoumaric acid with O-methylferulic acid and O-methylsinapic acid, respectively.

(1-11) Synthesis of O-octyl coumaric acid The following synthesis was carried out with reference to Materials Advances, 2020, 1 (4), pp. 584. In a 200 ml eggplant flask, 8.21 (50.0 mmol) of p-coumaric acid obtained above, 100 ml of a mixed solvent of a mixture of ethanol and water (volume ratio 3/1), 8.42 g (0.15 mmol) of potassium hydroxide and 1.66 g (10 mmol) of potassium iodide were added and heated and stirred for 1 hour. After cooling to room temperature, 7.16 g (55.0 mmol) of 1-bromooctane was added and heated and stirred for 24 hours. After cooling to room temperature, concentrated hydrochloric acid was added to precipitate. The solution was then passed through a φ60 mm Kiriyama funnel (No. 5C filter paper / Celite) and washed with water. The resulting solid was recrystallized from a mixed solvent of ethanol/water (volume ratio 3/1) to obtain 9.6 g (yield 69%) of O-octylcoumaric acid, the structure of which was confirmed by ¹ H-NMR and IR.

(1-12) Synthesis of O-octyl coumaric acid chloride With reference to the synthesis of O-methyl coumaric acid chloride (1-8), O-octyl coumaric acid chloride was synthesized by replacing O-methyl coumaric acid with O-octyl coumaric acid.

(1-13) Isolation of p-methoxy ethyl cinnamate and ethyl cinnamate 1 kg of roots of Indonesian Kaempferia galanga was finely chopped and placed in a 5 L eggplant flask. Then, 1.5 L of ethanol was added and heated to reflux for 1 hour. After cooling, the ethanol was removed by decantation, and 1.5 L of ethanol was added and heated to reflux for 1 hour. After ethanol extraction was performed three times, the ethanol in the obtained solution was distilled under reduced pressure using a rotary evaporator. 53 g of a light brown solid was obtained. This solid was set in a distillation apparatus and fractionated into fractions around 145 ° C and around 185-190 ° C under a reduced pressure of 15 mmHg. Only the main spot of each of the obtained fractions was isolated by column chromatography using a mixed solution of ethyl acetate/heptane (volume ratio 1/6). The structures were confirmed by ¹ H-NMR, mass spectrum and IR, and it was found that 24 g and 5.1 g of ethyl cinnamate and ethyl p-methoxycinnamate were obtained, respectively.

(1-14) Synthesis of cinnamic acid 15.0g (85.1mmol) of ethyl cinnamate and 300ml of ethanol (Kanto Chemical Co., Ltd.) were added to a 1000ml flask and stirred for 5 minutes. 450ml of 2N aqueous sodium hydroxide solution was added to this solution and stirred at room temperature for 2 hours. The reaction solution was transferred to a separatory funnel and neutralized with 2N hydrochloric acid, and then 200ml of ethyl acetate was added to extract the reaction product. After removing the aqueous layer, the solution was washed with water three times, and the resulting organic layer was dried with magnesium sulfate. After filtering off the magnesium sulfate, the obtained filtrate was concentrated with an evaporator to obtain a solid content. This solid content was purified by column chromatography using a heptane/acetone mixture (volume ratio 3/3). As a result, 11.1g (yield 88%) of cinnamic acid was obtained. The structure was confirmed by ^1H -NMR and IR.

(1-15) Synthesis of cinnamic acid chloride 50 mL of CH ₂ Cl ₂ , the above-obtained cinnamic acid (10.0 g, 67.5 mmol), and a few drops of DMF were added to a 100 mL 4-neck flask equipped with a nitrogen inlet tube, a dropping funnel, and a thermometer, and the mixture was stirred at room temperature to dissolve. The solution was cooled in an ice bath, and the liquid temperature was maintained at 10°C or less. Then, oxalyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) (9.4 g, 74.3 mmol) was dropped into the solution over 30 minutes, and then the ice bath was removed, the liquid temperature of the solution was brought to room temperature, and the solution was stirred for 5 hours. The solution was concentrated under reduced pressure using a rotary evaporator, and 50 mL of CH ₂ Cl ₂ was added again, followed by concentration under reduced pressure using a rotary evaporator. This operation was repeated three times. As a result, 10.9 g of cinnamic acid chloride was obtained (yield 97%).

(1-16) Synthesis of dimer (D-1) (dimer of coumaric acid methyl ester) European Journal of Medicinal Chemistry, 2018, 154, pp. 233-252 was used as a reference to synthesize a dimer (D-1) of coumaric acid methyl ester. Specifically, 3.0 g of the above-mentioned coumaric acid was placed in a crystallizing dish made of Pyrex (registered trademark) with a diameter of 10 cm and a height of 5 cm, and set on a tabletop vibrator (manufactured by JANTAI Co., Ltd.). A cloth was placed between the vibrator and the crystallizing dish to adjust the vibration so that crystals would not come out due to vibration. Two handy UV lamps were set on the crystallizing dish. The UV illuminance at the crystal position was measured separately and set to 1.5 μW/cm ^2. Then, light with a wavelength of 365 nm was irradiated to the vibrated crystal for 5 days. The reaction was monitored by ¹ H-NMR, and irradiation was terminated when coumaric acid had almost disappeared. The obtained crystals were dissolved in ethyl acetate and purified by column chromatography using a mixed solvent of ethyl acetate/heptane (volume ratio 1/9) to obtain 2.85 g of a coumaric acid methyl ester dimer (dimer (D-1)) having the following structure. The structure was confirmed by ¹ H-NMR, mass spectrum, and IR.

(1-17) Synthesis of Dimers (D-2) to (D-5) The above-mentioned n-octyl coumarate, phenyl coumarate, methyl ferulate, and methyl sinapic acid were also dimerized with reference to the synthesis method of the above-mentioned dimer (D-1). The structures were confirmed by ¹ H-NMR and IR.

(2) Synthesis of resin containing cinnamic acid skeleton (2-1) Synthesis of polycarbonate (PC-1) Two three-way cocks, a thermometer, a dropping funnel and a ball stopper were placed in a 300 mL four-head flask, and the inside of the vessel was decompressed and then replaced with nitrogen. This operation was performed three times. While flowing nitrogen, 124.9 g of pure water was added, followed by 16.1 g of a 25% by mass aqueous sodium hydroxide solution and 10 mg of sodium dithionite. After confirming complete dissolution, 11.3 g of the above-mentioned coumaric acid methyl ester dimer (D-1) was added and stirred for 1.0 hour. Then, while flowing nitrogen, 48 g of dichloromethane, 6.7 g of triphosgene and 1.0 g of activated carbon were added and stirred for 1.0 hour. In order to expel excess phosgene from the system, one three-way cock was opened, and nitrogen was bubbled into the solution while stirring it. After 1.0 hour, 1.2 g of a 16% by mass solution of p-t-butylphenol in dichloromethane was added. Filter paper and diatomaceous earth were placed in a 9 cm Nutsche tube, and the activated carbon in the solution was removed. The resulting solution was separated into an organic layer and an aqueous layer using a 500 ml separatory funnel. This organic layer was placed in a 200 ml four-head flask equipped with a mechanical stirrer, and then 24 g of dichloromethane, 4.7 g of a 25% by mass aqueous sodium hydroxide solution, 17.4 g of pure water, and 3 mg of triethylamine were added and stirred at 10° C. for 3 hours.

The reaction solution was transferred to a separating funnel, and 1N aqueous sodium hydroxide solution was added until the pH became alkaline, and the aqueous layer was separated. Then, pure water and 1N aqueous hydrochloric acid were added until the pH became acidic, and the aqueous layer was separated. Finally, pure water was added to wash the organic layer. 800 ml of pure water was placed in a 2 L beaker and vigorously stirred. The dichloromethane solution of the polymer obtained above was slowly dropped into this over 30 minutes. After filtering with a 12.5 cm Nutsche, it was dried at 120° C. for 48 hours to obtain 10.2 g of polycarbonate (PC-1) having the following structural unit. In addition, gel permeation chromatography (GPC) was performed under the following conditions, and the number average molecular weight was 28,300 and the molecular weight distribution was 2.5. The structure was confirmed by ¹ H-NMR and IR.

(GPC measurement conditions)
・HLC-8220GPC (manufactured by TOSOH Corporation)
Column: TSK-GEL SUPER HM-M (6.0 x 150 mm)
Card column: TSK-GUARD COLUMN SUPER H-H (4.6 x 35 mm)
Solvent: THF
Temperature: 40°C
・Flow rate: 0.6ml/min

(2-2) Synthesis of polycarbonates (PC-2) to (PC-5) With reference to the synthesis method of the polycarbonate (PC-1), the above-mentioned dimer of n-octyl coumarate (D-2), dimer of phenyl coumarate (D-3), dimer of methyl ferulate (D-4), and dimer of methyl sinapate (D-5) were used to obtain polycarbonates (PC-2) to (PC-5) having the following structural units. The number average molecular weights (molecular weight distributions) of each were 21100 (2.8), 20200 (2.7), 26300 (2.2), and 23100 (2.3).

(2-3) Synthesis of polyester (PES-1) 8.0 g (22.4 mmol) of coumaric acid methyl ester dimer (D-1), 1.8 g (10.8 mmol), 1.1 g (9.5 mmol) of fumaric acid, and 34.3 mg (0.08 mmol) of tin octoate (esterification catalyst) were added to a 50 ml four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple, and a polycondensation reaction was carried out for 8 hours at a temperature of 230° C. The polycondensation reaction was further continued for 1 hour at 8 kPa, and then cooled to 160° C. to obtain PES-1.

(2-4) Synthesis of polycarbonate (PC-A) A polymer (PC-A) having the following structural units was synthesized in the same manner as in the synthesis of the above-mentioned polycarbonate (PC-1), except that all of the coumaric acid methyl ester dimers (D-1) used in the synthesis of the above-mentioned polycarbonate (PC-1) were replaced with bisphenol Z (Bis-Z, manufactured by Honshu Chemical Industry Co., Ltd.) The number average molecular weight (molecular weight distribution) was 23,200 (2.9).

(2-5) Synthesis of polycarbonate (PC-1/PC-A (molar ratio 50/50)) Polycarbonate (PC-1/PC-A (molar ratio 50/50)) was synthesized in the same manner as in the synthesis of the above-mentioned polycarbonate (PC-1), except that a part of the coumaric acid methyl ester dimer (D-1) used in the synthesis of the polycarbonate (PC-1) was replaced with bisphenol Z (Bis-Z, manufactured by Honshu Chemical Industry Co., Ltd.). The number average molecular weight (molecular weight distribution) was 24,900 (3.1).

(2-6) Synthesis of polycarbonate (PC-1/PC-A (molar ratio 10/90)) A copolymer (PC-1/PC-A (molar ratio 10/90)) was synthesized in the same manner as in the synthesis of the polycarbonate (PC-1) described above, except that a part of the coumaric acid methyl ester dimer (D-1) used in the synthesis of the polycarbonate (PC-1) was replaced with bisphenol Z (Bis-Z, manufactured by Honshu Chemical Industry Co., Ltd.). The number average molecular weight (molecular weight distribution) was 28,700 (2.5).

(2-7) Synthesis of polymer (PV-1) (introduction rate of O-methylcoumaric acid moiety: 51%)
40 mL of anhydrous dimethylacetamide was placed in a 100 mL eggplant flask, and 2.0 g (43.4 mmol) of Denka Poval K-17E (manufactured by Denka Co.) was added little by little while stirring, and the mixture was stirred at room temperature for a while. After confirming that the additives were completely dissolved, 2.1 g of pyridine and 0.32 g of dimethylaminopyridine were added, and the solution was cooled to 0°C in an ice bath. 5 mL of anhydrous dimethylacetamide and 5.1 g (25.9 mmol) of the above-mentioned O-methyl coumaric acid chloride were placed in a 10 mL dropping funnel, and the mixture was dropped into the cooled poval solution over 10 minutes. After the dropwise addition, the ice bath was removed, and the mixture was stirred at room temperature for 24 hours to obtain a reaction solution.
Next, 800 ml of ethyl alcohol was placed in a 1 L beaker, a mechanical stirrer and Teflon (registered trademark) blades were installed, and the resulting reaction solution was dropped into the stirred mixture over 1 hour. After stirring for 2 hours, the mixture was filtered under reduced pressure using a Nutsche filter with a diameter of 8 cm and filter paper. The resulting solid was dried under reduced pressure at 60°C to obtain 7.1 g (yield 71.8%) of polymer (PV-1) containing the following three structural units. As a result of measuring the polymer (PV-1) by ¹ H-NMR and IR, it was confirmed that O-methyl coumaric acid was introduced into the poval. In addition, the amount of structural units containing cinnamic acid derivative moieties calculated from ¹ H-NMR was 51 mol%.

(2-8) Synthesis of Polymers (PV-2) to (PV-4) Polymers (PV-2) to (PV-4) containing the structural units shown below were obtained by synthesizing polymers in the same manner as in the synthesis of polymer (PV-1), except that 5.1 g (25.9 mmol) of the O-methyl coumaric acid chloride was replaced with the same molar amount of O-octyl coumaric acid chloride, O-methyl ferulic acid chloride, or O-methyl sinapic acid chloride. The amounts of structural units containing cinnamic acid derivative moieties were 48 mol % (PV-2), 49 mol % (PV-3), and 46 mol % (PV-4), respectively.

(2-9) Synthesis of Polymer (PV-5) Polymer (PV-5) having the structural unit shown below was synthesized in the same manner as above-mentioned polymer (PV-1) except that the amount of O-methyl coumaric acid chloride was changed to 1.3 g (6.6 mmol). The amount of the structural unit containing the cinnamic acid derivative moiety (structure derived from O-methyl coumaric acid chloride) was 11 mol%.

(2-10) Synthesis of Polymer (PV-1S) to Polymer (PV-4S) Polymer (PV-1S) to Polymer (PV-4S) were synthesized in the same manner as for polymer (PV-1) to (PV-4), respectively, except that Denka Poval K-17E (manufactured by Denki Kagaku Kogyo Co., Ltd.) was replaced with Denka Poval B-05 (manufactured by Denki Kagaku Kogyo Co., Ltd.) The amounts of structural units containing cinnamic acid derivative moieties were 59 mol%, 62 mol%, 57 mol%, and 21 mol%, respectively.

(2-11) Preparation of Polymer (PV-AS) A commercially available polybutyral resin (#6000-C, manufactured by Denki Kagaku Kogyo Co., Ltd.) was prepared.

(2-12) Synthesis of Compound (S1) A 100 mL four-neck flask was equipped with two three-way stopcocks, a thermometer, a dropping funnel and a ball stopper, and the inside of the container was decompressed and replaced with nitrogen. This operation was performed three times. While flowing nitrogen, 40 ml of dehydrated THF, 5.9 g (22.4 mmol) of trimethylolpropane and 2.14 g (27.1 mmol) of pyridine were added, and after complete dissolution, the solution was cooled to 10°C or less in an ice bath. While flowing nitrogen into the dropping funnel, 4.1 g (24.6 mmol) of cinnamic acid chloride and 10 ml of dehydrated THF were added. While maintaining the internal temperature at 10°C or less, cinnamic acid chloride was added dropwise, and the mixture was stirred for 30 minutes, the ice bath was removed, and the mixture was further stirred for 1 hour. The reaction solution was transferred to a separatory funnel, washed with water and ethyl acetate, extracted and dried, and the resulting solid was purified by column chromatography using an ethyl acetate/n-heptane mixture (volume ratio 1/9). As a result, 5.51 g (yield 47%) of compound (S1) represented by the following structural formula was obtained. The structure was confirmed by ¹ H-NMR and IR.

(2-13) Synthesis of Compound (S2) With reference to the synthesis method described in JP2011-99960A, a compound represented by the following structural formula, which is a hydroxyl group-substituted triarylamine compound, was synthesized.

Using this compound and cinnamic acid chloride, a reaction between the hydroxyl group and the acid chloride was carried out with reference to the synthesis method of the above-mentioned polymer (PV-1). The reaction solvent was washed with water and ethyl acetate, extracted and dried, and the obtained solid was purified by column chromatography using an ethyl acetate/n-heptane mixture (volume ratio 1/9). As a result, 4.67 g (yield 89%) of compound (S2) represented by the following structural formula was obtained. The structure was confirmed by ¹ H-NMR and IR.

(2-14) Preparation of Compound (SA) Compound (SA) having the structure shown below, manufactured by Osaka Organic Chemical Industry Ltd., was prepared.

(2-15) Synthesis of Compound (SB) With reference to JP 2011-99960 A, compound (SB), which is a triarylamine group-substituted acrylate compound having the structure shown below, was synthesized.

2. Production of Electrophotographic Photoreceptor (1) Preparation of Electrophotographic Photoreceptor 1 Electrophotographic photoreceptor 1 was prepared by the following procedure.

<Conductive Support>
The surface of a cylindrical aluminum support having a diameter of 30 mm was machined to prepare a conductive support having a surface roughness Rz of 1.5 (μm).

<Undercoat layer (UCL)>
The following materials were mixed and dispersed in a batch-type sand mill for 10 hours. After standing overnight, the mixture was filtered (filter: Nippon Pall Corporation Rigimesh 5 μm filter was used) to prepare an undercoat layer coating solution. This undercoat layer coating solution was applied to the conductive support by dip coating to form an undercoat layer with a dry thickness of 2 μm.
Polyamide resin CM8000 (manufactured by Toray Industries, Inc.) (binder) 1 part by weight Titanium oxide SMT500SAS (manufactured by Teica Corporation) 3 parts by weight Methanol 15 parts by weight Tetrahydrofuran 5 parts by weight

<Charge Generation Layer (CGL)>
The following materials were mixed and dispersed for 10 hours using a sand mill to prepare a charge generating layer coating solution. This coating solution was applied onto the above undercoat layer by dip coating to form a charge generating layer having a dry thickness of 0.3 μm. The titanyl phthalocyanine pigment below has a maximum diffraction peak at at least 27.3° in Cu-Kα characteristic X-ray diffraction spectrum measurement.
Charge generating material: 20 parts by weight of titanyl phthalocyanine pigment, polyvinyl butyral resin (#6000-C: manufactured by Denki Kagaku Kogyo Co., Ltd.)
(Binder) 10 parts by weight t-Butyl acetate 700 parts by weight 4-Methoxy-4-methyl-2-pentanone 300 parts by weight

<Charge transport layer (CTL)>
The following materials were mixed to prepare a charge transport layer coating solution: This coating solution was applied onto the charge generating layer by dip coating to form a charge transport layer having a dry thickness of 20 μm.
Polymer (PC-1) (binder): 100 parts by weight Charge transport material: CTM-1 having the following chemical structure: 50 parts by weight Antioxidant (Irganox 1010: manufactured by BASF Japan)
2 parts by weight Tetrahydrofuran 540 parts by weight Toluene 135 parts by weight Silicone oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by weight

<Protective layer (OCL)>
The following materials were mixed to prepare a solution. Next, as inorganic fine particles, 30% of AEROSIL (registered trademark) RX50 silica particles (manufactured by Nippon Aerosil Co., Ltd., number-first average particle size 40 nm) that had been surface-modified with hexamethyldisilazane were added. The protective layer coating liquid was prepared by mixing the dispersion obtained by ultrasonically dispersing 400 parts by weight of the cellulose acylate in 400 parts by weight of tetrahydrofuran with the above solution. The coating liquid was then applied onto the charge transport layer using a circular slide hopper type coater. The resulting mixture was dried at 120° C. for 70 minutes to form a protective layer having a dry thickness of 17 μm, thereby obtaining a photoreceptor 1. The following polycarbonate resin A is a polymer of bisphenol AP and has an average viscosity of The molecular weight is 20,000.
Polycarbonate resin A (Iupizeta (registered trademark) FPC-0220
(binder): manufactured by Mitsubishi Gas Chemical Company, Inc.) 100 parts by weight Charge transport material: CTM-1 having the above chemical structure 50 parts by weight Antioxidant (Irganox 1010: manufactured by BASF Japan Ltd.) 2 parts by weight Tetrahydrofuran 400 parts by weight Toluene 200 parts by weight Silicone Oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by mass

(2) Preparation of Electrophotographic Photoreceptors 2 to 11 Electrophotographic photoreceptors were obtained in the same manner as in the electrophotographic photoreceptor 1, except that the binder in the charge transport layer was changed to a resin shown in Table 1. However, as shown in Table 1, in the electrophotographic photoreceptors 8 and 11, a protective layer was not formed.

(3) Preparation of Electrophotographic Photoreceptors 12 to 19 Electrophotographic photoreceptors were obtained in a similar manner to that of electrophotographic photoreceptor 1, except that a polycarbonate resin having a bisphenol Z structure (=PC-A) was used as the binder resin of the electron transport layer, and the binder of the charge generation layer was changed to a resin shown in Table 1. However, except for electrophotographic photoreceptor 13, after the charge generation layer coating liquid was applied, light irradiation was performed under the following conditions.

<Light irradiation>
After coating the charge generating layer coating liquid, the coating was irradiated with ultraviolet light using a xenon lamp for 20 minutes under conditions where the illuminance of light measured using an ultraviolet illuminance meter UIT-201 (manufactured by Ushio Inc.) was 500 mW/ ^cm2 , and then dried at 110°C for 70 minutes.

(4) Preparation of Electrophotographic Photoreceptors 20 to 25 Electrophotographic photoreceptors were obtained in substantially the same manner as for the electrophotographic photoreceptor 1, except that a polycarbonate resin having a bisphenol Z structure (=PC-A) was used as the binder resin of the electron transport layer, and the binder of the undercoat layer was changed to a resin shown in Table 1. In addition, except for the electrophotographic photoreceptor 21, after the undercoat layer coating liquid was applied, light irradiation was performed under the same conditions as for the electrophotographic photoreceptor 12 and the like.

(5) Preparation of Electrophotographic Photoreceptor 26 A polycarbonate resin having a bisphenol Z structure (=PC-A) was used as the binder resin of the electron transport layer, and the binder of the protective layer was changed to the protective layer coating liquid shown below, and other than that, an electrophotographic photoreceptor was obtained in substantially the same procedure as for the electrophotographic photoreceptor 1. In addition, after the protective layer coating liquid was applied, light irradiation was performed under the same conditions as for the electrophotographic photoreceptor 12.

Compound (S1) 50 parts by weight Compound (S2) 50 parts by weight Photopolymerization initiator: Irgacure 819 (manufactured by BASF Japan) 2 parts by weight Solvent: 2-butanol 80 parts by weight Solvent: 2-methyltetrahydrofuran 40 parts by weight Silicone oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.1 parts by weight

(6) Preparation of Electrophotographic Photoreceptor 27 An electrophotographic photoreceptor was prepared in the same manner as electrophotographic photoreceptor 26, except that the compound (S1) and the compound (S2) in the protective layer coating liquid were replaced with the compounds (SA) and (SB), respectively, and light irradiation was performed under the following conditions.

<Light irradiation>
After applying the protective layer coating solution, the coating was irradiated with ultraviolet light using a xenon lamp for 1 minute under conditions where the illuminance of light measured using an ultraviolet illuminance meter UIT-201 (manufactured by Ushio Inc.) was 100 mW/ ^cm2 , and then dried at 110°C for 70 minutes.

(7) Preparation of Electrophotographic Photoreceptors 28 to 32 Electrophotographic photoreceptors 28 to 32 were prepared, except that each layer was made of a resin shown in Table 1 and, if necessary (described in Table 1), light irradiation was performed under the same conditions as for the above-mentioned electrophotographic photoreceptor 11.

3. Evaluation The prepared photoreceptors 1 to 36 were mounted on a full-color multifunction printer "bizhub C650i" (manufactured by Konica Minolta) employing a contact charging method, and the following evaluations were carried out. The surface roughness (Ra) and electrical properties (V0, E1/2) of the photoreceptors were measured as follows. In addition, in order to evaluate the stability of the photoreceptors, they were placed in an environment of 80°C and 90% RH for 10 days and forcibly deteriorated. Then, the surface roughness (Ra) of the electrophotographic photoreceptor and the electrical properties (V0, E1/2) of the electrophotographic photoreceptor surface before and after the forced deterioration test were evaluated according to the following criteria. The results are shown in Table 1.

<Surface roughness (Ra)>
The roughness of the surface of the electrophotographic photoreceptor was measured using SRUFCOM1400 (manufactured by Tokyo Seimitsu Co., Ltd.). Then, the change in surface roughness before and after the forced deterioration test, that is, (surface roughness before test-surface roughness after test)/(surface roughness before test)×100 was calculated. The evaluation criteria are as follows.
○: The above value is less than ±3% △: The above value is between ±3% and ±5% ×: 5% or more

<Electrical characteristics (initial surface potential V0, half-life exposure E1/2)>
The electrical characteristics of the photoconductor surface were measured using a DMS-30 (Vantec Systems Co., Ltd.). The change in electrical characteristics before and after the forced deterioration test, i.e., (electrical characteristics before test-electrical characteristics after test)/(electrical characteristics before test)×100, was calculated for each of the initial surface potential V0 and half-life exposure E1/2. The evaluation criteria were as follows:

[Evaluation Criteria for Initial Surface Potential V0]
○: The above value is less than ±3% △: The above value is between ±3% and ±5% ×: 5% or more

[Evaluation Criteria for Half Exposure E1/2]
○: The above value is less than ±3% △: The above value is between ±3% and ±5% ×: 5% or more

As shown in Table 1 above, when any of the functional layers contained a structure derived from cinnamic acid or its derivatives (photoreceptor numbers 1-9, 12-18, 20-24, 26, 28-32), the electrical properties were not easily changed even after a polarity degradation test, and the surface shape was also not easily changed.

In the electrophotographic processed body of the present invention, one of the functional layers contains a resin containing a naturally occurring cinnamic acid skeleton. Therefore, it is very excellent from the viewpoint of environmental consideration. Furthermore, the surface and electrical properties of the functional layer are unlikely to change over time. Therefore, it is very useful in image formation in various industrial fields.

REFERENCE SIGNS LIST 100 Electrophotographic photoreceptor 110 Conductive support 120 Functional layer 121 Undercoat layer 122 Charge generation layer 123 Charge transport layer 124 Protective layer

Claims (14)

A conductive support;
a functional layer including a charge generating layer and a charge transport layer disposed on the conductive support;
having
At least one layer of the functional layer contains a resin containing a partial structure derived from cinnamic acid or a derivative thereof.
Electrophotographic photoreceptor. The partial structure is a structure represented by any one of the following general formulas (1) to (3):
The electrophotographic photoreceptor according to claim 1 .

(In the general formula (1),
R ¹ and R ² each independently represent a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
L and M each represent an integer of 0 to 4,
The wavy lines represent bonds.)

(In the general formula (2),
^R3 and ^R4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, an amino group, a hydroxyl group, or a thiol group;
^R5 represents a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
X represents an integer of 0 to 5,
The wavy lines represent bonds.)

(In the general formula (3),
^R6 and ^R7 each independently represent a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
Y and Z each independently represent an integer of 0 to 5;
The wavy lines represent bonds.) The resin is a resin containing a structural unit represented by the following general formula (1-1):
The electrophotographic photoreceptor according to claim 1 .

(In the general formula (1-1),
R ¹ and R ² each independently represent a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
^R8 and ^R9 each independently represent a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
L and M each represent an integer of 0 to 4. the charge transport layer contains a resin containing a structural unit represented by the general formula (1-1),
The electrophotographic photoreceptor according to claim 3 . The resin is a polyvinyl resin containing a structural unit represented by the following general formula (2-1) or the following general formula (3-1):
The electrophotographic photoreceptor according to claim 1 .

(In the general formula (2-1),
^R3 and ^R4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, an amino group, a hydroxyl group, or a thiol group;
^R5 represents a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
X represents an integer of 0 to 5,

(In the general formula (3-1),
^R6 and ^R7 each independently represent a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
Y and Z each independently represent an integer of 0 to 5. the charge generating layer or the charge transporting layer contains the polyvinyl resin;
The electrophotographic photoreceptor according to claim 5 . The functional layer further includes an undercoat layer and/or a protective layer,
the undercoat layer and/or the protective layer contains the resin;
The electrophotographic photoreceptor according to claim 5 . A method for producing an electrophotographic photoreceptor having a conductive support and a functional layer including a charge generating layer and a charge transport layer disposed on the conductive support,
The method includes a step of applying a functional layer coating liquid containing a resin having a partial structure derived from cinnamic acid or a derivative thereof onto the conductive support,
A method for manufacturing an electrophotographic photoreceptor. The partial structure is a structure represented by any one of the following general formulas (1) or (2):
The method for producing an electrophotographic photoreceptor according to claim 8 .

(In the general formula (1),
R ¹ and R ² each independently represent a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
L and M each represent an integer of 0 to 4,
The wavy lines represent bonds.)

(In the general formula (2),
^R3 and ^R4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 200 carbon atoms, an amino group, a hydroxyl group, or a thiol group;
^R5 represents a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
X represents an integer of 0 to 5,
The wavy lines represent bonds.) The partial structure is a structure represented by general formula (2),
The method further includes a step of irradiating the functional layer coating liquid applied on the conductive support with light to cure the functional layer coating liquid.
The method for producing an electrophotographic photoreceptor according to claim 9 . The resin is a polyvinyl resin containing a structural unit represented by the following general formula (2-1):
The method for producing an electrophotographic photoreceptor according to claim 10 .

(In the general formula (2-1),
^R3 and ^R4 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, an amino group, a hydroxyl group, or a thiol group;
^R5 represents a monovalent atom or a monovalent atomic group having a molecular weight of 200 or less;
X represents an integer of 0 to 5. In the step of irradiating light, light having a wavelength of 280 nm or more and 480 nm or less is irradiated.
The method for producing an electrophotographic photoreceptor according to claim 10 . The electrophotographic photoreceptor according to any one of claims 1 to 7 is included.
Image forming device. Using the image forming apparatus according to claim 13,
Imaging method.

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