JP2023047285A - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

To provide an electrophotographic photoreceptor that is excellent in electrical characteristics and less likely to cause the occurrence of peeling of a photosensitive layer.SOLUTION: An electrophotographic photoreceptor comprises a conductive substrate, and a lamination type photosensitive layer having a charge generating layer and a charge transport layer. The charge transport layer contains a polyester resin (1) having a dicarboxylic acid unit (A) represented by a specific formula (A) and a diol unit (B) represented by a specific formula (B), and a charge transport material. When the weight average molecular weight Mw of the polyester resin (1) included in the charge transport layer is defined as A (ten thousand), the value of the ratio M1/M2 of mass M1 of the charge transport material included in the charge transport layer to mass M2 of the charge transport layer as Cs, and the average thickness of the charge transport layer as Ds(μm), 5≤A≤40, 0.28≤Cs≤0.55, 27≤Ds≤50, and 2.5≤(A×Ds)/(Cs×100)≤70.0 are satisfied.SELECTED DRAWING: None

Description

The present invention relates to an electrophotographic photoreceptor, a process cartridge and an image forming apparatus.

Patent Document 1 discloses an electrophotographic photoreceptor having a photosensitive layer containing a polyester resin having a biphenyl structure as a repeating unit.

Patent Document 2 discloses an electrophotographic photoreceptor having a photosensitive layer containing a polyester resin having a biphenyl structure and a bisphenol structure as repeating units.

Patent Document 3 discloses, for example, a diphenyl ether-4,4'-dicarboxylic acid unit, a 4,4'-diphenyldicarboxylic acid unit, and a 2,2-bis(4-hydroxy-3-methylphenyl)propane unit. is disclosed as an electrophotographic photoreceptor having a photosensitive layer containing a polyester resin having as a repeating structure.

Patent Document 4 discloses an electrophotographic photoreceptor having a photosensitive layer containing a polyarylate resin having a repeating structure of 4,4′-diphenyldicarboxylic acid units and 2,2-bis(4-hydroxyphenyl)butane units. is disclosed.

Patent Document 5 discloses an electrophotographic photoreceptor having a surface layer containing a polyester resin having 2,6-naphthalene dicarboxylic acid units, diphenyl ether-4,4′-dicarboxylic acid units and bisphenol units as structural units. disclosed.

Japanese Patent Application Laid-Open No. 2001-265021 Japanese Patent Application Laid-Open No. 2001-265022 JP 2016-133795 A WO2017/073176 JP 2017-146548 A

An object of the present disclosure is to provide an electrophotographic photoreceptor that is excellent in electrical properties and in which peeling of the photosensitive layer is less likely to occur.

Specific means for solving the above problems include the following aspects.

<1> comprising a conductive substrate and a laminated photosensitive layer having a charge generation layer and a charge transport layer disposed on the conductive substrate;
The charge transport layer contains a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), and a charge transport material. ,
The weight average molecular weight Mw of the polyester resin (1) contained in the charge transport layer is A (10,000), and the ratio M1 between the mass M1 of the charge transport material contained in the charge transport layer and the mass M2 of the charge transport layer When the value of /M2 is Cs and the average thickness of the charge transport layer is Ds (μm),
An electrophotographic photoreceptor satisfying 5≦A≦40, 0.28≦Cs≦0.55, 27≦Ds≦50, and 2.5≦(A×Ds)/(Cs×100)≦70.0.
<2> comprising a conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate;
The single-layer type photosensitive layer comprises a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), and a charge transport material. contains,
The weight average molecular weight Mw of the polyester resin (1) contained in the single-layer type photosensitive layer is defined as A (10,000), and the mass M1 of the charge transport material contained in the single-layer type photosensitive layer and the weight of the single-layer type photosensitive layer When the value of the ratio M1/M2 to the mass M2 is Ct and the average thickness of the single-layer type photosensitive layer is Dt (μm),
An electrophotographic photoreceptor satisfying 5≦A≦40, 0.40≦Ct≦0.60, 27≦Dt≦50 and 2.5≦(A×Dt)/(Ct×100)≦48.0.
<3> The electrophotographic photoreceptor according to <1>, which satisfies 3.6≦(A×Ds)/(Cs×100)≦46.0.
<4> The electrophotographic photoreceptor according to <2>, which satisfies 3.5≦(A×Dt)/(Ct×100)≦40.0.
<5> The electrophotographic photoreceptor according to <1> or <3>, which satisfies 30≦Ds≦48.
<6> The electrophotographic photoreceptor according to <2> or <4>, which satisfies 30≦Dt≦48.
<7> The electrophotographic photoreceptor according to any one of <1> to <6>, which satisfies 6≦A≦30.
<8> The electrophotography of any one of <1> to <7>, wherein the dicarboxylic acid unit (A) accounts for 15% by mass or more and 60% by mass or less in the polyester resin (1). photoreceptor.
<9> The electrophotographic photoreceptor according to any one of <1> to <8>, wherein ⁿ¹ is 2 in formula (A).
<10> In formula (B), at least one of Rb ¹ and Rb ² is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms. or an aralkyl group having 7 to 10 carbon atoms, or Rb ¹ and Rb ² combine to form a cyclic alkyl group having 5 to 12 carbon atoms, The electrophotographic photoreceptor according to any one of items 1 to 3.
<11> In formula (B), at least one of Rb ¹ and Rb ² is a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms, <1> to <10 > the electrophotographic photoreceptor according to any one of the above.
<12> A process cartridge that includes the electrophotographic photoreceptor according to any one of <1> to <11> and is detachable from an image forming apparatus.
<13> The electrophotographic photoreceptor according to any one of <1> to <11>, a charging means for charging the surface of the electrophotographic photoreceptor, and an electrostatic charge on the surface of the charged electrophotographic photoreceptor. electrostatic latent image forming means for forming a latent image; developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; and a transfer means for transferring an image onto the surface of a recording medium.

According to the inventions <1>, <3>, <5>, <7>, <8>, <9>, <10>, or <11>, the electrophotographic photoreceptor includes a laminated photosensitive layer. Therefore, the wear resistance of the photosensitive layer is excellent compared to the electrophotographic photoreceptor in which the value of (A × Ds) / (Cs × 100) is less than 2.5, and the value of (A × Ds) / (Cs × 100) is excellent. Provided is an electrophotographic photoreceptor that is superior in electrical properties to an electrophotographic photoreceptor having a value of more than 70.0 and in which peeling of the photosensitive layer is less likely to occur.
According to the inventions <2>, <4>, <6>, <7>, <8>, <9>, <10> or <11>, the electrophotographic photoreceptor comprising a single-layer type photosensitive layer The value of (A × Dt) / (Ct × 100) is excellent in abrasion resistance of the photosensitive layer as compared with an electrophotographic photoreceptor having a value of less than 2.5, and (A × Dt) / (Ct × 100) is more than 48.0.
According to the invention according to <12>, when the value of (A×Ds)/(Cs×100) or (A×Dt)/(Ct×100) of the electrophotographic photoreceptor is less than 2.5, The abrasion resistance of the photosensitive layer is excellent compared to the above, and the value of (A × Ds) / (Cs × 100) is more than 70.0 or the value of (A × Dt) / (Ct × 100) is more than 48.0 A process cartridge is provided which has excellent electrical characteristics and is less susceptible to peeling of the photosensitive layer than in the case of the conventional process cartridge.
According to the invention according to <13>, when the value of (A × Ds) / (Cs × 100) or (A × Dt) / (Ct × 100) related to the electrophotographic photosensitive member is less than 2.5 The abrasion resistance of the photosensitive layer is excellent compared to the above, and the value of (A × Ds) / (Cs × 100) is more than 70.0 or the value of (A × Dt) / (Ct × 100) is more than 48.0 Provided is an image forming apparatus which is excellent in electrical properties and in which peeling of the photosensitive layer is less likely to occur than in the case.

1 is a partial cross-sectional view showing an example of a layer structure of an electrophotographic photoreceptor according to a first embodiment; FIG. FIG. 5 is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to a second embodiment; 1 is a schematic configuration diagram showing an example of an image forming apparatus according to an embodiment; FIG. FIG. 2 is a schematic configuration diagram showing another example of the image forming apparatus according to the embodiment;

Embodiments of the present disclosure will be described below. These descriptions and examples are illustrative of embodiments and do not limit the scope of embodiments.

In the present disclosure, a numerical range indicated using "to" indicates a range including the numerical values before and after "to" as the minimum and maximum values, respectively.

In the numerical ranges described step by step in the present disclosure, the upper limit or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described step by step. . Moreover, in the numerical ranges described in the present disclosure, the upper or lower limits of the numerical ranges may be replaced with the values shown in the examples.

In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved.

In the present disclosure, when embodiments are described with reference to drawings, the configurations of the embodiments are not limited to the configurations shown in the drawings. In addition, the sizes of the members in each drawing are conceptual, and the relative relationship between the sizes of the members is not limited to this.

In the present disclosure, each component may contain multiple types of applicable substances. When referring to the amount of each component in the composition in the present disclosure, when there are multiple types of substances corresponding to each component in the composition, unless otherwise specified, the multiple types of substances present in the composition It means the total amount of substance.

Particles corresponding to each component in the present disclosure may include a plurality of types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means a value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

In the present disclosure, the notation “(meth)acryl” means either “acryl” or “methacryl”.

In the present disclosure, alkyl groups include both linear, branched and cyclic, unless otherwise specified.

<Electrophotographic photoreceptor>
The present disclosure provides a first embodiment and a second embodiment as electrophotographic photoreceptors (hereinafter also referred to as "photoreceptors").

A photoreceptor according to a first embodiment includes a conductive substrate, and a laminated photosensitive layer having a charge generation layer and a charge transport layer disposed on the conductive substrate. The photoreceptor according to the first embodiment may further include other layers (eg, undercoat layer, intermediate layer).

A photoreceptor according to a second embodiment includes a conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate. The photoreceptor according to the second embodiment may further include other layers (eg, undercoat layer, intermediate layer).

FIG. 1 is a partial cross-sectional view schematically showing an example of the layer structure of a photoreceptor according to the first embodiment. The photoreceptor 10A shown in FIG. 1 has a laminated photoreceptor layer. The photoreceptor 10A has a structure in which an undercoat layer 2, a charge generation layer 3 and a charge transport layer 4 are laminated in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 are formed on a photosensitive layer 5 ( It constitutes a so-called function-separated photosensitive layer). Photoreceptor 10A may have an intermediate layer (not shown) between undercoat layer 2 and charge generation layer 3 .

FIG. 2 is a partial cross-sectional view schematically showing an example of the layer structure of a photoreceptor according to the second embodiment. The photoreceptor 10B shown in FIG. 2 has a single layer type photoreceptor layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are laminated in this order on a conductive substrate 1 . Photoreceptor 10B may have an intermediate layer (not shown) between undercoat layer 2 and photosensitive layer 5 .

In the photoreceptor according to the first embodiment, the charge transport layer comprises a polyester resin (1 ) and a charge transport material,
The weight average molecular weight Mw of the polyester resin (1) contained in the charge transport layer is defined as A (10,000), and the value of the ratio M1/M2 of the mass M1 of the charge transport material contained in the charge transport layer and the mass M2 of the charge transport layer is Cs and the average thickness of the charge transport layer is Ds (μm), 5≦A≦40, 0.28≦Cs≦0.55, 27≦Ds≦50 and 2.5≦(A×Ds) /(Cs×100)≦70.0 is satisfied.

In the photoreceptor according to the second embodiment, the single-layer type photoreceptor layer is a polyester resin having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B). (1) and a charge transport material,
The weight average molecular weight Mw of the polyester resin (1) contained in the single-layer type photosensitive layer is defined as A (10,000), and the mass M1 of the charge transport material contained in the single-layer type photosensitive layer and the mass M2 of the single-layer type photosensitive layer are calculated. When the value of the ratio M1/M2 is Ct and the average thickness of the single-layer type photosensitive layer is Dt (μm), 5≦A≦40, 0.40≦Ct≦0.60, 27≦Dt≦50 and 2 .5≦(A×Dt)/(Ct×100)≦48.0.

In formula (A), n ¹ is 1, 2 or 3, n ¹ m ¹ is each independently 0, 1, 2, 3 or 4, m ¹ Ra ¹ is each independently , an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

In formula (B), Rb ¹ and Rb ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. , Rb ³ , Rb ⁴ , Rb ⁵ , Rb ⁶ , Rb ⁷ , Rb ⁸ , Rb ⁹ and Rb ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms , an aralkyl group having 7 to 20 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and Rb ¹ and Rb ² may combine to form a cyclic alkyl group.

Hereinafter, both forms will be collectively referred to as the present embodiment when describing matters common to the first embodiment and the second embodiment.

The photoreceptor according to the present embodiment has a value of (A×Ds)/(Cs×100) of less than 2.5 or a value of (A×Dt)/(Ct×100) of less than 2.5 A photoreceptor in which the wear resistance of the photosensitive layer is superior to that of the photoreceptor and the value of (A × Ds) / (Cs × 100) is greater than 70.0 or (A × Dt) / (Ct × 100) is more than 48.0. The reason for this is presumed to be as follows.

As a technique for improving the abrasion resistance of a photosensitive layer, it is known to use a polyester resin having a rigid skeleton in which aromatic rings repeat as a binder resin for the photosensitive layer. However, when a polyester resin having a rigid skeleton with repeating aromatic rings is used as the binder resin for the photosensitive layer, the dispersibility of the charge transport material tends to decrease, and as a result, the electrical properties of the photoreceptor do not meet the expected values. Sometimes I don't. In addition, if a polyester resin having a rigid skeleton with repeating aromatic rings is used as the binder resin for the photosensitive layer, the photosensitive layer may become hard or the adhesiveness to other layers may decrease, resulting in peeling of the photosensitive layer. may occur.

On the other hand, the inventors of the present invention used the polyester resin (1) as the binder resin for the photosensitive layer to improve the wear resistance of the photosensitive layer while increasing the range of (A×Ds)/(Cs×100). 2.5 or more and 70.0 or less, or the range of (A×Dt)/(Ct×100) is 2.5 or more and 48.0 or less, so that the electrical characteristics of the photoreceptor are excellent, and It was found that peeling of the photosensitive layer can be suppressed.

When the value of (A×Ds)/(Cs×100) or (A×Dt)/(Ct×100) is less than 2.5, the weight average molecular weight Mw of the polyester resin (1) or the average The value of the thickness Ds or the average thickness Dt of the single-layer type photosensitive layer is too small, or the content ratio Cs or Ct of the charge transport material is too large (that is, the content ratio of the polyester resin (1) is too small). , the abrasion resistance of the photosensitive layer becomes insufficient. From this point of view, the values of (A × Ds) / (Cs × 100) and (A × Dt) / (Ct × 100) are 2.5 or more, preferably 3.6 or more, and 7.2 or more More preferably, 7.7 or more is even more preferable.

When the value of (A × Ds) / (Cs × 100) is more than 70.0 or the value of (A × Dt) / (Ct × 100) is more than 48.0, the weight average molecular weight of the polyester resin (1) Mw or the average thickness Ds of the charge transport layer or the average thickness Dt of the single-layer type photosensitive layer is too large, or the content ratio Cs or Ct of the charge transport material is too small (that is, the polyester resin (1) If the content ratio is too large), peeling of the photosensitive layer may occur. From this viewpoint, the value of (A×Ds)/(Cs×100) is 70.0 or less, preferably 46.0 or less, more preferably 33.0 or less, and even more preferably 25.0 or less. From this viewpoint, the value of (A×Dt)/(Ct×100) is 48.0 or less, preferably 40.0 or less, more preferably 27.0 or less, and even more preferably 20.0 or less.

The polyester resin (1) contained in the charge transport layer in the first embodiment and the polyester resin (1) contained in the single-layer photosensitive layer in the second embodiment have a weight average molecular weight Mw of A (10,000). , the value of A is 5 or more and 40 or less. That is, the polyester resin (1) has a weight average molecular weight Mw of 50,000 or more and 400,000 or less.
If the value of A is less than 5, the strength of the charge transport layer or single-layer type photosensitive layer is lowered. From this viewpoint, the value of A is 5 or more, preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more.
When the value of A is more than 40, the viscosity of the coating liquid for forming the charge transport layer or single-layer type photosensitive layer increases, making stable coating difficult. Also, the adhesion of the charge transport layer or the single-layer type photosensitive layer to other layers is lowered, and the charge-transport layer or the single-layer type photosensitive layer is easily peeled off. From this viewpoint, the value of A is 40 or less, preferably 30 or less, more preferably 25 or less, and even more preferably 20 or less.

Regarding the charge transport layer in the first embodiment, the value Cs of the ratio M1/M2 between the mass M1 of the charge transport material contained in the layer and the mass M2 of the layer is 0.28≦Cs≦0.55. .
Regarding the single-layer type photosensitive layer in the second embodiment, the value Ct of the ratio M1/M2 between the mass M1 of the charge transport material contained in the layer and the mass M2 of the layer is 0.40≦Ct≦0.60. is.
If the Cs value is less than 0.28 or the Ct value is less than 0.40, the content ratio of the charge transport material in the charge transport layer or single-layer type photosensitive layer is small, resulting in poor electrical properties. From this viewpoint, the value of Cs is 0.28 or more, preferably 0.31 or more, more preferably 0.33 or more, and still more preferably 0.34 or more. From this viewpoint, the Ct value is 0.40 or more, preferably 0.43 or more, more preferably 0.44 or more, and still more preferably 0.45 or more.
When the Cs value exceeds 0.55 or the Ct value exceeds 0.60, the content ratio of the charge transport material contained in the charge transport layer or single-layer type photosensitive layer is too large (that is, the polyester resin (1) is too small), the strength of the charge-transporting layer or single-layer type photosensitive layer is lowered, resulting in poor abrasion resistance. From this viewpoint, the value of Cs is 0.55 or less, preferably 0.50 or less, more preferably 0.48 or less, and even more preferably 0.46 or less. From this point of view, the Ct value is 0.60 or less, preferably 0.58 or less, more preferably 0.56 or less, and even more preferably 0.55 or less.

In a preferred embodiment of the photoreceptor according to the first embodiment, the ratio Mw/Mn between the weight average molecular weight Mw and the number average molecular weight Mn of the polyester resin (1) contained in the charge transport layer is set to B, and the charge transport layer where Cs is the ratio M1/M2 between the mass M1 of the charge transport material contained in the charge transport material and the mass M2 of the charge transport layer, 2.1≦B≦4.0 and 0.60≦(B×Cs)≦ 2.10.
In a preferred embodiment of the photoreceptor according to the second embodiment, the value of the ratio Mw/Mn between the weight average molecular weight Mw and the number average molecular weight Mn of the polyester resin (1) contained in the single-layer type photosensitive layer is B, When the ratio M1/M2 of the mass M1 of the charge transport material contained in the layered photosensitive layer to the mass M2 of the single layered photosensitive layer is Ct, 2.1≤B≤4.0 and 0.90≤Ct. (B×Ct)≦2.30 is satisfied.
When the value of (B×Cs) is less than 0.60 or the value of (B×Ct) is less than 0.90, the molecular weight distribution Mw/Mn of the polyester resin (1) is too narrow (low If the ratio of the molecular weight component is small), the dispersion uniformity of the charge transport material contained in the charge transport layer or single-layer type photosensitive layer is lowered, or the value of the content ratio Cs or Ct of the charge transport material is too small. Therefore, it is presumed that the electrical characteristics are inferior. From this viewpoint, the value of (B×Cs) is preferably 0.60 or more, more preferably 0.70 or more, still more preferably 0.80 or more, and still more preferably 0.90 or more. From this viewpoint, the value of (B×Ct) is preferably 0.90 or more, more preferably 1.00 or more, still more preferably 1.10 or more, and even more preferably 1.20 or more.
When the value of (B×Cs) exceeds 2.10 or the value of (B×Ct) exceeds 2.30, the molecular weight distribution Mw/Mn of the polyester resin (1) is too broad (low The ratio of the molecular weight component is large), or the content ratio Cs or Ct of the charge transport material is too large (the content ratio of the polyester resin (1) is too small). It is presumed that the strength of the layer is lowered and the wear resistance is inferior. From this viewpoint, the value of (B×Cs) is preferably 2.10 or less, more preferably 1.90 or less, still more preferably 1.70 or less, and even more preferably 1.50 or less. From this viewpoint, the value of (B×Ct) is preferably 2.30 or less, more preferably 2.20 or less, still more preferably 2.10 or less, and even more preferably 2.00 or less.

The polyester resin (1) contained in the charge transport layer in the first embodiment and the polyester resin (1) contained in the single-layer type photosensitive layer in the second embodiment each have a weight average molecular weight Mw and a number average molecular weight Mn. It is preferable that the value B of the ratio Mw/Mn satisfies 2.1≤B≤4.0.
When the value of B is 2.1 or more, Mw/Mn is not too narrow (the ratio of the low-molecular-weight component in the polyester resin (1) is not too small), and the charges contained in the charge transport layer or single-layer type photosensitive layer The distribution uniformity of the transport material is good. From this viewpoint, the value of B is preferably 2.1 or more, more preferably 2.3 or more, still more preferably 2.4 or more, and even more preferably 2.5 or more.
When the value of B is 4.0 or less, the Mw/Mn ratio is not too wide (the proportion of the low-molecular-weight component in the polyester resin (1) is not too large), and the strength of the charge-transporting layer or single-layer type photosensitive layer is moderate. and the abrasion resistance of the photosensitive layer is good. From this viewpoint, the value of B is preferably 4.0 or less, more preferably 3.8 or less, still more preferably 3.7 or less, and even more preferably 3.6 or less.

The value B of the ratio Mw/Mn related to the polyester resin (1) depends, for example, on polymerization conditions (solvent composition, concentration, temperature, stirring speed, amount of polymerization catalyst) or purification conditions (solvent composition and concentration during reprecipitation). can be controlled. For example, by adjusting the solvent composition or concentration during polymerization so that the solubility of the monomer and polymer is increased, or by reducing the stirring speed, the reaction rate can be made uneven and the value B of Mw/Mn can be increased. can. In addition, the value B of Mw/Mn can be reduced by homogenizing the reaction rate by the opposite measure, or by sufficiently removing components that deactivate the reaction activity such as water before polymerization. . Moreover, the value B of Mw/Mn can also be reduced by reprecipitating with a solvent composition having a large difference in solubility between high-molecular-weight components and low-molecular-weight components at the time of purification.

In the first embodiment, the methods for measuring the weight average molecular weight Mw and number average molecular weight Mn of the polyester resin (1) contained in the charge transport layer are as follows.
The photoreceptor is immersed in various solvents (a mixed solvent may be used) to determine the solvent in which the charge transport layer dissolves. The charge transport layer is extracted by immersing the photoreceptor in a solvent in which the charge transport layer is dissolved. The solution obtained by extracting the charge transport layer is added to a poor solvent for the polyester resin (1) (for example, a nonpolar solvent such as hexane or toluene, or a lower alcohol such as methanol or isopropanol. The poor solvent may be a mixed solvent.). Add dropwise to reprecipitate the resin. If necessary, the reprecipitation treatment is repeated twice, and the reprecipitated resin is vacuum-dried to obtain a polyester resin (1). The polyester resin (1) is subjected to molecular weight measurement by GPC (gel permeation chromatography), which will be described later, to specify Mw and Mn.
In the second embodiment, the above "charge transport layer" is replaced with "single-layer type photosensitive layer" and measured in the same manner.

In the first embodiment, the method for measuring the mass M1 of the charge transport material contained in the charge transport layer and the mass M2 of the charge transport layer are as follows.
The solution from which the charge-transporting layer was extracted was concentrated, vacuum-dried, and then weighed to obtain the mass M2 of the charge-transporting layer.
The remaining solution after the above reprecipitation treatment is concentrated, each material is isolated by preparative thin-layer chromatography, and the yield is quantified. The charge transport material is identified from each material isolated by NMR (nuclear magnetic resonance) measurements, and the charge transport material yields are summed to give M1.
In the second embodiment, the above "charge transport layer" is replaced with "single-layer type photosensitive layer" and measured in the same manner.

The average thickness Ds of the charge transport layer in the first embodiment and the average thickness Dt of the single-layer type photosensitive layer in the second embodiment are 27 μm or more and 50 μm or less.
When the average thickness Ds and the average thickness Dt are 27 μm or more, the abrasion margin of the photoreceptor can be secured, and the life of the photoreceptor can be extended. From this viewpoint, the average thickness Ds and the average thickness Dt are 27 μm or more, preferably 31 μm or more, more preferably 35 μm or more, and even more preferably 37 μm or more.
When the average thickness Ds and the average thickness Dt are 50 μm or less, the electrical properties can be maintained both at the initial stage and after abrasion, and peeling of the photosensitive layer can be suppressed. From this viewpoint, the average thickness Ds and the average thickness Dt are 50 μm or less, preferably 48 μm or less, more preferably 46 μm or less, and even more preferably 45 μm or less.

In the first embodiment, the average thickness Ds of the charge-transporting layer was measured at 40 points, that is, 10 points evenly in the axial direction of the photoreceptor and 4 points in the circumferential direction (in increments of 90°). It is the value obtained by measuring the layer thickness and arithmetically averaging it.
In the second embodiment, the average thickness Dt of the single-layer type photosensitive layer is obtained in the same manner by replacing the above-mentioned "charge transport layer" with "single-layer type photosensitive layer".

Each layer of the polyester resin (1) and the photoreceptor will be described in detail below.

[Polyester resin (1)]
The polyester resin (1) has at least a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B). The polyester resin (1) may contain dicarboxylic acid units other than the dicarboxylic acid unit (A). The polyester resin (1) may contain diol units other than the diol unit (B).

The dicarboxylic acid unit (A) is a structural unit represented by formula (A) below.

In formula (A), n ¹ is 1, 2 or 3, n ¹ m ¹ is each independently 0, 1, 2, 3 or 4, m ¹ Ra ¹ is each independently , an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

In formula (A), ⁿ¹ is 1, 2 or 3, with 2 being preferred.
When n ¹ is 2, the two benzene rings in formula (A) may be the same benzene ring or different benzene rings for m ¹ and Ra ¹ .
When n ¹ is 3, the three benzene rings in formula (A) may be the same benzene ring or different benzene rings for m ¹ and Ra ¹ .

When ⁿ¹ is 2 or 3 in formula (A), the linking position between benzene rings may be ortho, meta or para, preferably meta or para.

In formula (A), m ¹ is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1, even more preferably 0.
When m ¹ is 2, two Ra ^1s bonded to the same benzene ring may be the same type of group or different types of groups.
When m ¹ is 3, the three Ra ^1s bonded to the same benzene ring may be groups of the same type or groups of different types.
When m ¹ is 4, the four Ra ^1s bonded to the same benzene ring may be groups of the same type or groups of different types.

In formula (A), the alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or 2.
In formula (A), the aryl group having 6 to 12 carbon atoms may be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less.
In formula (A), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 or more and 6 or less carbon atoms is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

In formula (A), the linear alkyl group having 1 to 10 carbon atoms includes a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group and an n-heptyl group. , n-octyl group, n-nonyl group and n-decyl group.
Examples of branched alkyl groups having 3 to 10 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group and tert- hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, A tert-decyl group and the like can be mentioned.
As the cyclic alkyl group having 3 to 10 carbon atoms, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and these monocyclic alkyl groups linked together Polycyclic (eg, bicyclic, tricyclic, spirocyclic) alkyl groups are included.

In formula (A), examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group and a 2-naphthyl group.

In formula (A), linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. .
In formula (A), the branched alkoxy group having 3 to 6 carbon atoms includes an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, and a tert-pentyloxy group. group, isohexyloxy group, sec-hexyloxy group, tert-hexyloxy group and the like.
In formula (A), examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, and the like.

When m ¹ in formula (A) is 1, 2, 3 or 4, Ra ¹ is preferably a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 3 to 6 carbon atoms, A linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 or 4 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.

Dicarboxylic acid units (A-1) to (A-13) are shown below as specific examples of the dicarboxylic acid unit (A). The dicarboxylic acid unit (A) is not limited to this.

As the dicarboxylic acid unit (A), the above specific examples (A-1), (A-7) and (A-12) are preferred, and (A-12) is most preferred.

The dicarboxylic acid unit (A) contained in the polyester resin (1) may be of one type or two or more types.

A diol unit (B) is a structural unit represented by the following formula (B).

In formula (B), Rb ¹ and Rb ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. , Rb ³ , Rb ⁴ , Rb ⁵ , Rb ⁶ , Rb ⁷ , Rb ⁸ , Rb ⁹ and Rb ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms , an aralkyl group having 7 to 20 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and Rb ¹ and Rb ² may combine to form a cyclic alkyl group.

In formula (B), the alkyl group having 1 to 20 carbon atoms for Rb ¹ and Rb ² may be linear, branched or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 15 or less, more preferably 1 or more and 12 or less, and even more preferably 1 or more and 10 or less.
In formula (B), the aryl group having 6 to 12 carbon atoms for Rb ¹ and Rb ² may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less.
In formula (B), the aryl group in the aralkyl group having 7 to 20 carbon atoms for Rb ¹ and Rb ² may be either monocyclic or polycyclic, and the alkyl group in the aralkyl group having 7 to 20 carbon atoms The groups may be linear, branched or cyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 5 or less, and even more preferably 1 or more and 4 or less.
In formula (B), the number of carbon atoms in the cyclic alkyl group that may be formed by combining Rb ¹ and Rb ² is preferably 5 or more and 15 or less, more preferably 6 or more and 12 or less.

In formula (B), the alkyl group having 1 to 10 carbon atoms for Rb ³ , Rb ⁴ , Rb ⁵ , Rb ⁶ , Rb ⁷ , Rb ⁸ , Rb ⁹ and Rb ¹⁰ may be linear, branched or cyclic. Either The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or 2.
In formula (B), the aryl group having 6 to 12 carbon atoms for Rb ³ , Rb ⁴ , Rb ⁵ , Rb ⁶ , Rb ⁷ , Rb ⁸ , Rb ⁹ and Rb ¹⁰ may be monocyclic or polycyclic. good. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less.
In formula (B), the aryl group in the aralkyl group having 7 or more and 20 or less carbon atoms for Rb ³ , Rb ⁴ , Rb ⁵ , Rb ⁶ , Rb ⁷ , Rb ⁸ , Rb ⁹ and Rb ¹⁰ may be monocyclic or polycyclic. The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 5 or less, and even more preferably 1 or more and 4 or less.
In formula (B), the alkyl group in the alkoxy group having 1 to 6 carbon atoms for Rb ³ , Rb ⁴ , Rb ⁵ , Rb ⁶ , Rb ⁷ , Rb ⁸ , Rb ⁹ and Rb ¹⁰ is linear, It may be branched or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 or more and 6 or less carbon atoms is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

In the formula (B), the linear alkyl group having 1 to 20 carbon atoms includes a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group and an n-heptyl group. , n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, tridecyl group, n-tetradecyl group, n-pentadecyl group, n-heptadecyl group, n-octadecyl group, n -nonadecyl group, n-icosyl group and the like.
Examples of branched alkyl groups having 3 to 20 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group and tert- hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, isododecyl group, sec-dodecyl group, tert-dodecyl group, tert-tetradecyl group, tert-pentadecyl group and the like.
As the cyclic alkyl group having 3 to 20 carbon atoms, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, etc., and these monocyclic alkyl groups are linked. and polycyclic (eg, bicyclic, tricyclic, spirocyclic) alkyl groups.

In formula (B), examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group and a 2-naphthyl group.

In formula (B), the aralkyl group having 7 to 20 carbon atoms includes benzyl, phenylethyl, phenylpropyl, 4-phenylbutyl, phenylpentyl, phenylhexyl, phenylheptyl, and phenyloctyl groups. , phenylnonyl group, naphthylmethyl group, naphthylethyl group, anthratylmethyl group, phenyl-cyclopentylmethyl group and the like.

In the formula (B), examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. .
In formula (B), the branched alkoxy group having 3 to 6 carbon atoms includes an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, and a tert-pentyloxy group. group, isohexyloxy group, sec-hexyloxy group, tert-hexyloxy group and the like.
In formula (B), examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, and the like.

In formula (B), Rb ¹ and Rb ² are each independently a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms. or an aralkyl group having 7 or more and 10 or less carbon atoms, or Rb ¹ and Rb ² being bonded to form a cyclic alkyl group having 5 or more and 12 or less carbon atoms.
In formula (B), Rb ¹ and Rb ² are each independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 1 to 10 carbon atoms, or Rb ¹ and Rb ² are more preferably combined to form a cyclic alkyl group having 5 or more and 12 or less carbon atoms.
In formula (B), Rb ¹ and Rb ² are each independently more preferably a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, or a branched alkyl group having 1 to 10 carbon atoms.

In formula (B), at least one of Rb ¹ and Rb ² is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or carbon It is preferably an aralkyl group having a number of 7 or more and 10 or less, or Rb ¹ and Rb ² are bonded to form a cyclic alkyl group having 5 or more and 12 or less carbon atoms.
In formula (B), at least one of Rb ¹ and Rb ² is more preferably a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms.
When at least one of Rb ¹ and Rb ² is as described above, the other of Rb ¹ and Rb ² is preferably a hydrogen atom or a linear alkyl group having 1 to 3 carbon atoms.

The diol unit (B) is preferably a structural unit represented by formula (B') below.

Rb ¹ , Rb ² , Rb ⁴ and Rb ⁹ in formula (B′) have the same meanings as Rb ¹ , Rb ² , Rb ⁴ and Rb ⁹ in formula (B), and preferred forms are also the same.

As the diol unit (B), in the formula (B'),
Rb ¹ is a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms or a branched alkyl group having 3 carbon atoms, and Rb ² is a linear alkyl group having 4 to 10 carbon atoms, or a linear alkyl group having 4 to 10 carbon atoms. It is preferably a branched alkyl group, an aryl group having 6 to 10 carbon atoms or an aralkyl group having 7 to 10 carbon atoms, and Rb ⁴ and Rb ⁹ are each independently a hydrogen atom or a methyl group;
Rb ¹ is a hydrogen atom or a methyl group, Rb ² is a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms, and Rb ⁴ and Rb ⁹ are each independently hydrogen Atoms or methyl groups are more preferred.

Diol units (B-1) to (B-38) are shown below as specific examples of the diol unit (B). The diol unit (B) is not limited to this.

The diol unit (B) contained in the polyester resin (1) may be of one type or two or more types.

The mass ratio of the dicarboxylic acid unit (A) in the polyester resin (1) is preferably 15% by mass or more and 60% by mass or less.
When the mass ratio of the dicarboxylic acid unit (A) is 15% by mass or more, the abrasion resistance of the photosensitive layer is good. From this point of view, the mass ratio of the dicarboxylic acid unit (A) is more preferably 20% by mass or more, and even more preferably 25% by mass or more.
When the mass ratio of the dicarboxylic acid unit (A) is 60% by mass or less, peeling of the photosensitive layer can be further suppressed. From this point of view, the mass ratio of the dicarboxylic acid unit (A) is more preferably 55% by mass or less, and even more preferably 50% by mass or less.

The mass ratio of the diol unit (B) in the polyester resin (1) is preferably 25% by mass or more and 60% by mass or less.
When the mass ratio of the diol unit (B) is 25% by mass or more, peeling of the photosensitive layer can be further suppressed. From this point of view, the mass ratio of the diol unit (B) is more preferably 30% by mass or more, and even more preferably 35% by mass or more.
When the mass ratio of the diol unit (B) is 60% by mass or less, the abrasion resistance can be improved while maintaining the solubility in the coating liquid for forming the photosensitive layer. From this point of view, the mass ratio of the diol unit (B) is more preferably 55% by mass or less, and even more preferably 50% by mass or less.

The polyester resin (1) may contain dicarboxylic acid units other than the dicarboxylic acid unit (A).

Other dicarboxylic acid units include, for example, dicarboxylic acid units (C) represented by the following formula (C).

In formula (C), Rc ¹ , Rc ² , Rc ³ , Rc ⁴ , Rc ⁵ and Rc ⁶ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms. or an alkoxy group having 1 to 6 carbon atoms.

In formula (C), the alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or 2.
In formula (C), the aryl group having 6 to 12 carbon atoms may be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less.
In formula (C), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 or more and 6 or less carbon atoms is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

Examples of the respective forms of the alkyl group, aryl group and alkoxy group in formula (C) include the same groups as those listed for formula (A).

In formula (C), Rc ¹ , Rc ² , Rc ³ , Rc ⁴ , Rc ⁵ and Rc ⁶ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, or a linear alkyl group having 1 to 6 carbon atoms. It is preferably a branched alkyl group, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 1 to 4 carbon atoms, a hydrogen atom, or 1 to 3 carbon atoms. or a branched alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.

As the dicarboxylic acid unit (C), a 2,6-naphthalenedicarboxylic acid unit (formula below) is most preferred.

The dicarboxylic acid unit (C) contained in the polyester resin (1) may be of one type or two or more types.

When the polyester resin (1) has dicarboxylic acid units (C), the mass ratio of the dicarboxylic acid units (C) in the polyester resin (1) is preferably 1% by mass or more and 20% by mass or less.

Other dicarboxylic acid units include, for example, dicarboxylic acid units (D) represented by the following formula (D).

In formula (D), Rd ¹ , Rd ² , Rd ³ , Rd ⁴ , Rd ⁵ , Rd ⁶ , Rd ⁷ and Rd ⁸ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, 6 carbon atoms It is an aryl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 6 carbon atoms.

In formula (D), the alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or 2.
In formula (D), the aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less.
In formula (D), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 or more and 6 or less carbon atoms is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

Examples of the form of each of the alkyl group, aryl group and alkoxy group in formula (D) include the same groups as those listed for formula (A).

In formula (D), Rd ¹ , Rd ² , Rd ³ , Rd ⁴ , Rd ⁵ , Rd ⁶ , Rd ⁷ and Rd ⁸ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, or a carbon It is preferably a branched alkyl group having a number of 1 to 6, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 1 to 4 carbon atoms, a hydrogen atom, A linear alkyl group having 1 to 3 carbon atoms or a branched alkyl group having 1 to 3 carbon atoms is more preferable, and a hydrogen atom is particularly preferable.

The dicarboxylic acid unit (D) is preferably a structural unit represented by formula (D') below.

Rd ¹ , Rd ² , Rd ³ and Rd ⁴ in formula (D′) have the same meanings as Rd ¹ , Rd ² , Rd ³ and Rd ⁴ in formula (D), and preferred forms are also the same.

As the dicarboxylic acid unit (D), a diphenyl ether-4,4'-dicarboxylic acid unit (formula below) is most preferred.

The dicarboxylic acid unit (D) contained in the polyester resin (1) may be of one type or two or more types.

When the polyester resin (1) has dicarboxylic acid units (D), the mass ratio of the dicarboxylic acid units (D) in the polyester resin (1) is preferably 1% by mass or more and 20% by mass or less.

Other dicarboxylic acid units include, for example, aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid, ) units, alicyclic dicarboxylic acid (eg, cyclohexanedicarboxylic acid) units, and lower (eg, having 1 to 5 carbon atoms) alkyl ester units thereof. These dicarboxylic acid units contained in the polyester resin (1) may be of one type or two or more types.

The polyester resin (1) may contain diol units other than the diol unit (B).

Other diol units include, for example, diol units (E) represented by the following formula (E).

In formula (E), Re ¹ , Re ² , Re ³ , Re ⁴ , Re ⁵ , Re ⁶ , Re ⁷ and Re ⁸ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, 6 carbon atoms an aryl group having 12 or more carbon atoms, an aralkyl group having 7 or more and 20 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

In formula (E), the alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or 2.
In formula (E), the aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less.
In formula (E), the aryl group in the aralkyl group having 7 to 20 carbon atoms may be either monocyclic or polycyclic, and the alkyl group in the aralkyl group having 7 to 20 carbon atoms is linear, It may be branched or cyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 5 or less, and even more preferably 1 or more and 4 or less.
In formula (E), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 or more and 6 or less carbon atoms is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

Examples of the form of each of the alkyl group, aryl group, aralkyl group and alkoxy group in formula (E) include the same groups as those listed for formula (B).

In formula (E), Re ¹ , Re ² , Re ³ , Re ⁴ , Re ⁵ , Re ⁶ , Re ⁷ and Re ⁸ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, or a carbon It is preferably a branched alkyl group having a number of 1 to 6, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 1 to 4 carbon atoms, a hydrogen atom, A linear alkyl group having 1 to 3 carbon atoms or a branched alkyl group having 1 to 3 carbon atoms is more preferable, and a hydrogen atom or a methyl group is particularly preferable.

The diol unit (E) is preferably a structural unit represented by formula (E') below.

Re ¹ , Re ² , Re ³ and Re ⁴ in formula (E′) have the same meanings as Re ¹ , Re ² , Re ³ and Re ⁴ in formula (E), and preferred forms are also the same.

As the diol unit (E), any one of the following is most preferable.

The diol unit (E) contained in the polyester resin (1) may be of one type or two or more types.

When the polyester resin (1) has diol units (E), the mass ratio of the diol units (E) in the polyester resin (1) is preferably 1% by mass or more and 20% by mass or less.

Other diol units include, for example, diol units (F) represented by the following formula (F).

In formula (F), Rf ¹ , Rf ² , Rf ³ , Rf ⁴ , Rf ⁵ , Rf ⁶ , Rf ⁷ and Rf ⁸ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, 6 carbon atoms an aryl group having 12 or more carbon atoms, an aralkyl group having 7 or more and 20 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

In formula (F), the alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or 2.
In formula (F), the aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less.
In formula (F), the aryl group in the aralkyl group having 7 to 20 carbon atoms may be either monocyclic or polycyclic, and the alkyl group in the aralkyl group having 7 to 20 carbon atoms is linear, It may be branched or cyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 9 or less. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 5 or less, and even more preferably 1 or more and 4 or less.
In formula (F), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 or more and 6 or less carbon atoms is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

Examples of the form of each of the alkyl group, aryl group, aralkyl group and alkoxy group in formula (F) include the same groups as those listed for formula (B).

In formula (F), Rf ¹ , Rf ² , Rf ³ , Rf ⁴ , Rf ⁵ , Rf ⁶ , Rf ⁷ and Rf ⁸ are each independently a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, or a carbon It is preferably a branched alkyl group having a number of 1 to 6, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 1 to 4 carbon atoms, a hydrogen atom, A linear alkyl group having 1 to 3 carbon atoms or a branched alkyl group having 1 to 3 carbon atoms is more preferable, and a hydrogen atom or a methyl group is particularly preferable.

The diol unit (F) is preferably a structural unit represented by the following formula (F').

Rf ¹ , Rf ² , Rf ³ and Rf ⁴ in formula (F′) are synonymous with Rf ¹ , Rf ² , Rf ³ and Rf ⁴ in formula (F), respectively, and preferred forms are also the same.

A bis(4-hydroxyphenyl)ether unit (formula below) is most preferred as the diol unit (F).

The diol unit (F) contained in the polyester resin (1) may be of one type or two or more types.

When the polyester resin (1) has diol units (F), the mass ratio of the diol units (F) in the polyester resin (1) is preferably 1% by mass or more and 20% by mass or less.

Other diol units include, for example, aliphatic diol (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) units, alicyclic diols (e.g., cyclohexanediol, cyclohexane dimethanol, hydrogenated bisphenol A) units. These diol units contained in the polyester resin (1) may be of one type or two or more types.

The polyester resin (1) can be obtained by polycondensing a monomer that provides a dicarboxylic acid unit (A) and a monomer that provides a diol unit (B), and optionally other monomers, in a conventional manner. . Methods of polycondensation of monomers include an interfacial polymerization method, a solution polymerization method, a melt polymerization method and the like. The interfacial polymerization method is a polymerization method for obtaining a polyester by mixing a dihydric carboxylic acid halide dissolved in an organic solvent immiscible with water and a dihydric alcohol dissolved in an alkaline aqueous solution. References relating to the interfacial polymerization method include W. et al. M. Eareckson, J.; Poly. Sci. , XL399, 1959, and JP-B-40-1959. Since the interfacial polymerization method has a faster reaction than the solution polymerization method, hydrolysis of the divalent carboxylic acid halide can be suppressed, and as a result, a high-molecular-weight polyester resin can be obtained.

The ends of the polyester resin (1) may be blocked or modified with a terminal blocker or molecular weight modifier used during production. Terminal blocking agents or molecular weight modifiers include, for example, monohydric phenols, monohydric acid chlorides, monohydric alcohols, and monohydric carboxylic acids.
Examples of monohydric phenol include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propyl Phenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m -phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol , 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, 2-phenyl -2-(3-hydroxyphenyl)propane.
Examples of monoacid chlorides include benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetic acid chloride, butyric acid chloride, octylic acid chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzene monofunctional acid halides such as phosphonyl chlorides and substituted products thereof;
Examples of monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenethyl alcohol.
Examples of monovalent carboxylic acids include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid and p-methoxyphenylacetic acid.

[Conductive substrate]
Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). is mentioned. Examples of conductive substrates include paper, resin films, belts, etc., coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. is also mentioned. Here, "conductivity" means that the volume resistivity is less than 1×10 ¹³ Ωcm.

When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate has a center line average roughness Ra of 0.04 μm or more and 0.5 μm for the purpose of suppressing interference fringes generated when laser light is irradiated. It is preferable that the surface is roughened to the following. When non-interfering light is used as the light source, surface roughening is not particularly necessary to prevent interference fringes, but it is suitable for longer life because it suppresses the occurrence of defects due to irregularities on the surface of the conductive substrate.

Surface roughening methods include, for example, wet honing in which an abrasive is suspended in water and sprayed against the conductive substrate, and centerless grinding in which the conductive substrate is pressed against a rotating grindstone and continuously ground. , anodizing, and the like.

As a roughening method, conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate without roughening the surface of the conductive substrate. A method of roughening with particles dispersed in a layer is also included.

In the surface roughening treatment by anodization, an oxide film is formed on the surface of a conductive substrate by anodizing a metal (eg, aluminum) conductive substrate as an anode in an electrolytic solution. Examples of electrolyte solutions include sulfuric acid solutions and oxalic acid solutions. However, the porous anodic oxide film formed by anodic oxidation is chemically active as it is, is easily contaminated, and has large resistance fluctuations depending on the environment. Therefore, the micropores of the porous anodized film are filled with pressurized steam or boiling water (a metal salt such as nickel may be added) by volume expansion due to the hydration reaction, thereby achieving more stable hydration and oxidation. It is preferable to perform a pore-sealing treatment that transforms into a product.

The film thickness of the anodized film is preferably 0.3 μm or more and 15 μm or less, for example. When this film thickness is within the above range, there is a tendency for the film to exhibit barrier properties against injection, and the increase in residual potential due to repeated use tends to be suppressed.

The conductive substrate may be treated with an acidic treatment liquid or treated with boehmite.
The treatment with an acidic treatment liquid is performed, for example, as follows. First, an acidic treatment liquid containing phosphoric acid, chromic acid and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment liquid is, for example, phosphoric acid in the range of 10% by mass to 11% by mass, chromic acid in the range of 3% by mass to 5% by mass, and hydrofluoric acid in the range of 3% by mass to 5% by mass. It is preferable that the total concentration of these acids is in the range of 0.5 mass % or more and 2 mass % or less, and the range of 13.5 mass % or more and 18 mass % or less. The treatment temperature is preferably 42° C. or higher and 48° C. or lower, for example. The film thickness of the coating is preferably 0.3 μm or more and 15 μm or less.

The boehmite treatment is performed, for example, by immersing the substrate in pure water at a temperature of 90° C. or higher and 100° C. or lower for 5 to 60 minutes, or by contacting the substrate with heated steam at a temperature of 90° C. or higher and 120° C. or lower for 5 to 60 minutes. The film thickness of the coating is preferably 0.1 μm or more and 5 μm or less. This may be further anodized using an electrolytic solution with low film solubility such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, citrate, etc. good.

[Undercoat layer]
The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

Examples of inorganic particles include inorganic particles having a powder resistance (volume resistivity) of 1×10 ² Ωcm or more and 1×10 ¹¹ Ωcm or less.
Among these, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles are preferable as the inorganic particles having the above resistance value, and zinc oxide particles are particularly preferable.

The specific surface area of the inorganic particles by the BET method is preferably 10 m ² /g or more, for example.
The volume average particle diameter of the inorganic particles is, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

The content of the inorganic particles is, for example, preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, relative to the binder resin.

The inorganic particles may be surface-treated. Two or more kinds of inorganic particles having different surface treatments or different particle diameters may be mixed and used.

Examples of surface treatment agents include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, and surfactants. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

Silane coupling agents having an amino group include, for example, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-amino Examples include, but are not limited to, propylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and the like.

You may use a silane coupling agent in mixture of 2 or more types. For example, a silane coupling agent having an amino group and another silane coupling agent may be used in combination. Other silane coupling agents include, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycol sidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-( aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, etc., but are not limited thereto. not a thing

The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

The treatment amount of the surface treatment agent is preferably 0.5% by mass or more and 10% by mass or less with respect to the inorganic particles, for example.

Here, the undercoat layer preferably contains an electron-accepting compound (acceptor compound) together with the inorganic particles from the viewpoint of enhancing the long-term stability of electrical properties and the carrier-blocking property.

Examples of electron-accepting compounds include quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, and the like. fluorenone compounds; 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4- Oxadiazole compounds such as oxadiazole and 2,5-bis(4-diethylaminophenyl)-1,3,4 oxadiazole; xanthone compounds; thiophene compounds; 3,3′,5,5′ tetra- diphenoquinone compounds such as t-butyldiphenoquinone; benzophenone compounds; and other electron-transporting substances.
A compound having an anthraquinone structure is particularly preferable as the electron-accepting compound. As the compound having an anthraquinone structure, for example, hydroxyanthraquinone compounds, aminoanthraquinone compounds, aminohydroxyanthraquinone compounds, etc. are preferable, and specifically, for example, anthraquinone, alizarin, quinizarin, anthrafin, purpurin, etc. are preferable.

The electron-accepting compound may be dispersed in the undercoat layer together with the inorganic particles, or may be attached to the surfaces of the inorganic particles.

Examples of the method of adhering the electron-accepting compound to the surface of the inorganic particles include a dry method and a wet method.

In the dry method, for example, an electron-accepting compound dissolved in an organic solvent is added dropwise while stirring inorganic particles with a mixer having a large shearing force, and the electron-accepting compound is sprayed with dry air or nitrogen gas. It is a method of adhering to the surface of inorganic particles. Dropping or spraying of the electron-accepting compound is preferably carried out at a temperature not higher than the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be further performed at 100° C. or higher. Baking is not particularly limited as long as the temperature and time are such that electrophotographic properties can be obtained.

In the wet method, for example, by stirring, ultrasonic waves, sand mill, attritor, ball mill, etc., while inorganic particles are dispersed in a solvent, an electron-accepting compound is added, stirred or dispersed, and then the solvent is removed to obtain electrons. This is a method of adhering a receptive compound to the surface of inorganic particles. Solvent removal methods include distilling off by filtration or distillation. After removing the solvent, baking may be further performed at 100° C. or higher. Baking is not particularly limited as long as the temperature and time are such that electrophotographic properties can be obtained. In the wet method, the water contained in the inorganic particles may be removed before adding the electron-accepting compound, examples of which include a method of removing while stirring and heating in a solvent, and a method of removing by azeotroping with a solvent. mentioned.

Attachment of the electron-accepting compound may be performed before or after the surface treatment with the surface-treating agent on the inorganic particles, or may be performed simultaneously with attachment of the electron-accepting compound and surface treatment with the surface-treating agent.

The content of the electron-accepting compound is, for example, 0.01% by mass or more and 20% by mass or less, preferably 0.01% by mass or more and 10% by mass or less, relative to the inorganic particles.

Examples of binder resins used in the undercoat layer include acetal resins (for example, polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, and unsaturated polyesters. Resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenolic resins, phenol-formaldehyde resins, melamine resins, Urethane resins, alkyd resins, known polymer compounds such as epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds;
Examples of the binder resin used in the undercoat layer include charge-transporting resins having a charge-transporting group, conductive resins (eg, polyaniline, etc.), and the like.

Among these, resins that are insoluble in the coating solvent of the upper layer are suitable as the binder resin used in the undercoat layer. Thermosetting resins such as resins, alkyd resins and epoxy resins; at least one resin selected from the group consisting of polyamide resins, polyester resins, polyether resins, methacrylic resins, acrylic resins, polyvinyl alcohol resins and polyvinyl acetal resins; Resins obtained by reaction with a curing agent are preferred.
When two or more of these binder resins are used in combination, the mixing ratio is set according to need.

The undercoat layer may contain various additives for improving electrical properties, environmental stability, and image quality.
Examples of the additive include known materials such as electron-transporting pigments such as polycyclic condensed and azo-based pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. be done. The silane coupling agent is used for the surface treatment of the inorganic particles as described above, and may be added to the undercoat layer as an additive.

Silane coupling agents as additives include, for example, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3- glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2- (Aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane and the like.

Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetoacetate, zirconium triethanolamine, zirconium acetylacetonate butoxide, ethyl zirconium butoxide acetoacetate, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium methacrylate butoxide, zirconium stearate butoxide, zirconium isostearate butoxide and the like.

Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-normal butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt. , titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, polyhydroxytitanium stearate, and the like.

Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, ethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

These additives may be used alone or as mixtures or polycondensates of multiple compounds.

The undercoat layer preferably has a Vickers hardness of 35 or higher.
The surface roughness (ten-point average roughness) of the undercoat layer is 1/(4n) (n is the refractive index of the upper layer) to 1/2 of the exposure laser wavelength λ used to suppress moiré images. should be adjusted to
Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. Further, the surface of the undercoat layer may be polished to adjust the surface roughness. Polishing methods include buffing, sandblasting, wet honing, and grinding.

The formation of the undercoat layer is not particularly limited, and a known formation method is used. and, if necessary, by heating.

Solvents for preparing the undercoat layer-forming coating liquid include known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents, Solvents, ester solvents and the like can be mentioned.
Specific examples of these solvents include methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, Ordinary organic solvents such as n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene and toluene can be used.

Examples of the method for dispersing the inorganic particles when preparing the undercoat layer-forming coating solution include known methods such as a roll mill, ball mill, vibrating ball mill, attritor, sand mill, colloid mill, and paint shaker.

Examples of methods for applying the undercoat layer-forming coating liquid onto the conductive substrate include blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating. Ordinary methods such as

The thickness of the undercoat layer is set, for example, preferably in the range of 15 μm or more, more preferably 20 μm or more and 50 μm or less.

[Middle layer]
An intermediate layer may be further provided between the undercoat layer and the photosensitive layer.
The intermediate layer is, for example, a layer containing resin. Examples of resins used for the intermediate layer include acetal resins (for example, polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, Polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, melamine resins and other high-molecular compounds can be mentioned.
The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used for the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese and silicon.
These compounds used for the intermediate layer may be used singly or as a mixture or polycondensate of a plurality of compounds.

Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

Formation of the intermediate layer is not particularly limited, and a known forming method is used. It is done by heating according to.
As the coating method for forming the intermediate layer, usual methods such as dip coating, thrust coating, wire bar coating, spray coating, blade coating, knife coating and curtain coating can be used.

The thickness of the intermediate layer, for example, is preferably set in the range of 0.1 μm or more and 3 μm or less. An intermediate layer may be used as an undercoat layer.

[Charge generating layer]
The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Also, the charge generation layer may be a deposited layer of a charge generation material. The deposited layer of the charge generating material is suitable for use with non-coherent light sources such as LEDs (Light Emitting Diodes) and organic EL (Electro-Luminescence) image arrays.

Examples of charge-generating materials include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments;

Among these, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material in order to cope with laser exposure in the near-infrared region. Specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine are more preferable.

On the other hand, in order to correspond to laser exposure in the near-ultraviolet region, charge generation materials include condensed ring aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments. etc. are preferred.

In the case of using an incoherent light source such as an LED or an organic EL image array having a central emission wavelength of 450 nm or more and 780 nm or less, the above charge generation material may be used. When a thin film is used, the electric field strength in the photosensitive layer becomes high, and charge deterioration due to charge injection from the substrate tends to cause image defects called black spots. This becomes remarkable when a charge-generating material such as trigonal selenium, phthalocyanine pigment, or the like, which is a p-type semiconductor and tends to generate dark current, is used.

On the other hand, when n-type semiconductors such as condensed aromatic pigments, perylene pigments, and azo pigments are used as the charge generation material, dark current is less likely to occur, and image defects called black spots can be suppressed even if the film is formed into a thin film. . The n-type is determined by the time-of-flight method, which is commonly used, by the polarity of the flowing photocurrent, and the n-type is defined as a material in which electrons are more likely to flow as carriers than holes.

The binder resin used in the charge generation layer is selected from a wide range of insulating resins, and the binder resin is selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene and polysilane. You may choose.
Examples of binder resins include polyvinyl butyral resins, polyarylate resins (polycondensates of bisphenols and aromatic divalent carboxylic acids, etc.), polycarbonate resins, polyester resins, phenoxy resins, vinyl chloride-vinyl acetate copolymers, Polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin and the like can be mentioned. Here, "insulating" means having a volume resistivity of 1×10 ¹³ Ωcm or more.
These binder resins may be used singly or in combination of two or more.

The mixing ratio of the charge-generating material and the binder resin is preferably in the range of 10:1 to 1:10 in mass ratio.

The charge generation layer may contain other known additives.

The formation of the charge-generating layer is not particularly limited, and a known forming method is used. and, if necessary, by heating. The charge generation layer may be formed by vapor deposition of a charge generation material. Formation of the charge-generating layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or perylene pigment is used as the charge-generating material.

Solvents for preparing the charge-generating layer-forming coating solution include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, and n-acetic acid. -butyl, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene and the like. These solvents are used singly or in combination of two or more.

Examples of the method for dispersing particles (for example, charge-generating material) in the coating liquid for forming the charge-generating layer include media dispersing machines such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, stirring, and ultrasonic dispersing machines. , roll mills, high-pressure homogenizers, and other medialess dispersers are used. Examples of high-pressure homogenizers include a collision system in which a dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high-pressure state, and a penetration system in which a fine flow path is penetrated and dispersed in a high-pressure state.
During this dispersion, it is effective to set the average particle size of the charge generating material in the coating liquid for forming the charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, more preferably 0.15 μm or less.

Examples of the method for applying the charge generation layer forming coating liquid onto the undercoat layer (or onto the intermediate layer) include blade coating, wire bar coating, spray coating, dip coating, bead coating, and air knife coating. conventional methods such as coating method, curtain coating method, and the like.

The thickness of the charge generation layer is set, for example, preferably within the range of 0.1 μm or more and 5.0 μm or less, more preferably 0.2 μm or more and 2.0 μm or less.

[Charge transport layer]
The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may be a layer comprising a polymeric charge transport material.

Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanyl and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; ; cyanovinyl-based compounds; and electron-transporting compounds such as ethylene-based compounds. Charge transport materials also include hole-transporting compounds such as triarylamine-based compounds, benzidine-based compounds, arylalkane-based compounds, aryl-substituted ethylene-based compounds, stilbene-based compounds, anthracene-based compounds, and hydrazone-based compounds. These charge transport materials may be used singly or in combination of two or more, but are not limited to these.

Polymeric charge-transporting materials include known compounds having charge-transporting properties such as poly-N-vinylcarbazole and polysilane. For example, a polyester-based polymer charge transport material is preferable. A polymer charge transport material may be used alone or in combination with a binder resin.

Charge transport materials or polymeric charge transport materials include polycyclic aromatic compounds, aromatic nitro compounds, aromatic amine compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds (especially are triphenylamine compounds), diamine compounds, oxadiazole compounds, carbazole compounds, organic polysilane compounds, pyrazoline compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, Also included are cyano compounds, benzofuran compounds, aniline compounds, butadiene compounds and resins having groups derived from these substances. Specifically, paragraphs 0078 to 0080 of JP 2021-117377, paragraphs 0046 to 0048 of JP 2019-035900, paragraphs 0052 to 0053 of JP 2019-012141, JP 2021-071565 Paragraphs 0122 to 0134 of the publication, paragraphs 0101 to 0110 of JP 2021-015223, paragraph 0116 of JP 2013-097300, paragraphs 0309 to 0316 of WO 2019/070003, JP 2018-159087 Examples include compounds described in paragraphs 0103 to 0107 of the publication and paragraphs 0102 to 0113 of JP-A-2021-148818, respectively.

From the viewpoint of charge mobility, the charge transport material includes a compound (G1) represented by the following formula (G1), a compound (G2) represented by the formula (G2), and a compound represented by the formula (G3) ( G3) and at least one selected from the group consisting of compounds (G4) represented by formula (G4).

In formula (G1), Ar ^T1 , Ar ^T2 and Ar ^T3 are each independently an aryl group, —C ₆ H ₄ —C(R ^T4 )=C(R ^T5 )(R ^T6 ) or —C ₆ H ₄ —CH =CH-CH=C(R ^T7 )(R ^T8 ). R ^T4 , R ^T5 , R ^T6 , R ^T7 and R ^T8 are each independently a hydrogen atom, an alkyl group or an aryl group. When R ^T5 and R ^T6 are aryl groups, the aryl groups are linked by -C(R ⁵¹ )(R ⁵² )- and/or -C(R ⁶¹ )=C(R ⁶² )- divalent groups. may R ⁵¹ , R ⁵² , R ⁶¹ and R ⁶² are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

The group in formula (G1) is substituted by a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted by an alkyl group having 1 to 3 carbon atoms. may have been

From the viewpoint of charge mobility, the compound (G1) is preferably a compound having at least one aryl group or —C ₆ H ₄ —CH═CH—CH═C(R ^T7 )(R ^T8 ), and has the following formula: Compound (G'1) represented by (G'1) is more preferred.

In formula (G'1), R ^T111 , R ^T112 , R ^T121 , R ^T122 , R ^T131 and R ^T132 are each independently a hydrogen atom, a halogen atom, an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) , an alkoxy group (preferably an alkoxy group having 1 to 3 carbon atoms), a phenyl group or a phenoxy group. Tj1, Tj2, Tj3, Tk1, Tk2 and Tk3 are each independently 0, 1 or 2;

In formula (G2), R ^T201 , R ^T202 , R ^T211 and R ^T212 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or 1 or 2 carbon atoms. an amino group substituted with an alkyl group, an aryl group, -C(R ^T21 )=C(R ^T22 )(R ^T23 ) or -CH=CH-CH=C(R ^T24 )(R ^T25 ); R ^T21 , R ^T22 , R ^T23 , R ^T24 and R ^T25 are each independently a hydrogen atom, an alkyl group or an aryl group. R ^T221 and R ^T222 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. Tm1, Tm2, Tn1 and Tn2 are each independently 0, 1 or 2;

The group in formula (G2) is substituted by a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted by an alkyl group having 1 to 3 carbon atoms. may have been

From the viewpoint of charge mobility, the compound (G2) is preferably a compound having at least one alkyl group, aryl group, or -CH=CH-CH=C(R ^T24 )(R ^T25 ). More preferred are compounds having two groups, or -CH=CH-CH=C(R ^T24 )(R ^T25 ).

In formula (G3), R ^T301 , R ^T302 , R ^T311 and R ^T312 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or 1 or 2 carbon atoms. an amino group substituted with an alkyl group, an aryl group, -C(R ^T31 )=C(R ^T32 )(R ^T33 ) or -CH=CH-CH=C(R ^T34 )(R ^T35 ); R ^T31 , R ^T32 , R ^T33 , R ^T34 and R ^T35 are each independently a hydrogen atom, an alkyl group or an aryl group. R ^T321 , R ^T322 and R ^T331 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms. To1, To2, Tp1, Tp2, Tq1, Tq2 and Tr1 are each independently 0, 1 or 2;

The group in formula (G3) is substituted by a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted by an alkyl group having 1 to 3 carbon atoms. may have been

In formula (G4), R ^T401 , R ^T402 , R ^T411 and R ^T412 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or 1 or 2 carbon atoms. an amino group substituted with an alkyl group, an aryl group, -C(R ^T41 )=C(R ^T42 )(R ^T43 ) or -CH=CH-CH=C(R ^T44 )(R ^T45 ); R ^T41 , R ^T42 , R ^T43 , R ^T44 and R ^T45 are each independently a hydrogen atom, an alkyl group or an aryl group. R ^T421 , R ^T422 and R ^T431 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2 and Tv1 are each independently 0, 1 or 2;

The group in formula (G4) is substituted by a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted by an alkyl group having 1 to 3 carbon atoms. may have been

The content of the charge transport material contained in the charge transport layer is preferably 28% by mass or more and 55% by mass or less with respect to the total solid content.

The charge transport layer contains at least polyester resin (1) as a binder resin. The ratio of the polyester resin (1) to the total amount of the binder resin contained in the charge transport layer is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and 95% by mass or more. Particularly preferred, 100% by mass is most preferred.

The charge transport layer may contain a binder resin other than the polyester resin (1). Other binder resins include polyester resins other than polyester resin (1), polycarbonate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, and styrene-butadiene copolymers. , vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly- Examples include N-vinylcarbazole and polysilane. These binder resins are used singly or in combination of two or more.

The charge transport layer may contain other known additives. Examples of additives include antioxidants, leveling agents, antifoaming agents, fillers, viscosity modifiers and the like.

Formation of the charge transport layer is not particularly limited, and a known formation method is used. , by heating if necessary.

Solvents for preparing the coating liquid for forming the charge transport layer include aromatic hydrocarbons such as benzene, toluene, xylene and chlorobenzene; ketones such as acetone and 2-butanone; methylene chloride, chloroform and ethylene chloride. Halogenated aliphatic hydrocarbons; ordinary organic solvents such as cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents are used alone or in combination of two or more.

Coating methods for coating the charge transport layer forming coating liquid on the charge generation layer include blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain. Ordinary methods such as a coating method can be used.

The average thickness of the charge transport layer is preferably 27 μm or more and 50 μm or less, more preferably 31 μm or more and 48 μm or less, and even more preferably 35 μm or more and 46 μm or less.

[Single layer type photosensitive layer]
The single-layer type photosensitive layer (charge-generating/charge-transporting layer) is a layer containing a charge-generating material, a charge-transporting material, a binder resin, and optionally other additives. These materials are the same as those described for the charge generation layer and charge transport layer.

The single-layer type photosensitive layer contains at least polyester resin (1) as a binder resin. The ratio of the polyester resin (1) to the total amount of the binder resin contained in the single-layer type photosensitive layer is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and 95% by mass. Above is particularly preferable, and 100% by mass is most preferable.

The content of the charge-generating material in the single-layer type photosensitive layer is preferably 0.1% by mass or more and 10% by mass or less, preferably 0.8% by mass or more and 5% by mass or less, based on the total solid content.

The content of the charge-transporting material contained in the single-layer type photosensitive layer is preferably 40% by mass or more and 60% by mass or less with respect to the total solid content.

The method for forming the single-layer type photosensitive layer is the same as the method for forming the charge generation layer and the charge transport layer.

The average thickness of the single-layer type photosensitive layer is preferably 27 μm or more and 50 μm or less, more preferably 31 μm or more and 48 μm or less, and even more preferably 35 μm or more and 46 μm or less.

[Protective layer]
A protective layer is optionally provided on the photosensitive layer. The protective layer is provided, for example, for the purpose of preventing chemical changes in the photosensitive layer during charging and further improving the mechanical strength of the photosensitive layer.
Therefore, it is preferable to apply a layer composed of a cured film (crosslinked film) as the protective layer. Examples of these layers include layers shown in 1) or 2) below.

1) A layer composed of a cured film of a composition containing a reactive group-containing charge-transporting material having a reactive group and a charge-transporting skeleton in the same molecule (that is, a polymer or cross-linked of the reactive group-containing charge-transporting material layer containing the body)
2) A layer composed of a cured film of a composition containing a non-reactive charge-transporting material and a reactive group-containing non-charge-transporting material that does not have a charge-transporting skeleton and has a reactive group (that is, A layer containing a non-reactive charge-transporting material and a polymer or crosslinked product of the reactive group-containing non-charge-transporting material)

Reactive groups of the reactive group-containing charge transport material include chain polymerizable groups, epoxy groups, —OH, —OR [wherein R represents an alkyl group], —NH ₂ , —SH, —COOH, and —SiR. ^Q1 _3-Qn (OR ^Q2 ) _Qn [where R ^Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, and R ^Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group. Qn represents an integer of 1 to 3].

The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, and is, for example, a functional group having at least a group containing a carbon double bond. Specific examples include groups containing at least one selected from a vinyl group, a vinyl ether group, a vinylthioether group, a phenyl vinyl group, a vinyl phenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof. Among them, a group containing at least one selected from a vinyl group, a phenylvinyl group, a vinylphenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof, as the chain polymerizable group, because of its excellent reactivity. is preferably

The charge-transporting skeleton of the reactive group-containing charge-transporting material is not particularly limited as long as it has a known structure in electrophotographic photoreceptors. Examples include triarylamine-based compounds, benzidine-based compounds, hydrazone-based compounds and the like. which is a skeleton derived from a nitrogen-containing hole-transporting compound and is conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferred.

The reactive group-containing charge-transporting material, the non-reactive charge-transporting material, and the reactive group-containing non-charge-transporting material having a reactive group and a charge-transporting skeleton may be selected from known materials.

The protective layer may contain other known additives.

Formation of the protective layer is not particularly limited, and a known forming method is used. Curing treatment such as heating is performed as necessary.

Solvents for preparing the coating solution for forming a protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; , dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; alcohol solvents such as isopropyl alcohol and butanol. These solvents are used alone or in combination of two or more.
The protective layer-forming coating liquid may be a solventless coating liquid.

Methods for applying the protective layer-forming coating solution onto the photosensitive layer (for example, the charge transport layer) include dip coating, thrust coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating. Ordinary methods such as the method can be used.

The thickness of the protective layer is set, for example, preferably within the range of 1 μm or more and 20 μm or less, more preferably 2 μm or more and 10 μm or less.

<Image forming apparatus, process cartridge>
An image forming apparatus according to the present embodiment includes an electrophotographic photosensitive member, a charging unit that charges the surface of the electrophotographic photosensitive member, and an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member. means, developing means for developing an electrostatic latent image formed on the surface of an electrophotographic photosensitive member with a developer containing toner to form a toner image, and transfer means for transferring the toner image onto the surface of a recording medium; Prepare. As an electrophotographic photoreceptor, the electrophotographic photoreceptor according to the exemplary embodiment is applied.

The image forming apparatus according to the present embodiment includes fixing means for fixing a toner image transferred to the surface of a recording medium; direct transfer for directly transferring a toner image formed on the surface of an electrophotographic photosensitive member to a recording medium. Apparatus of this type: Intermediate transfer that primarily transfers the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the intermediate transfer member, and then secondarily transfers the toner image transferred on the surface of the intermediate transfer member to the surface of the recording medium. A device equipped with a cleaning means for cleaning the surface of the electrophotographic photosensitive member before charging after transferring the toner image; A known image forming apparatus such as an apparatus equipped with a static eliminating means for eliminating static electricity by means of an electrophotographic photosensitive member; and an apparatus equipped with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

In the case of an intermediate transfer type apparatus, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred, and a primary transfer means for primarily transferring a toner image formed on the surface of an electrophotographic photosensitive member to the surface of the intermediate transfer body. A configuration having transfer means and secondary transfer means for secondarily transferring the toner image transferred on the surface of the intermediate transfer member to the surface of the recording medium is applied.

The image forming apparatus according to the present embodiment may be either a dry developing type image forming apparatus or a wet developing type image forming apparatus (a developing type using a liquid developer).

In the image forming apparatus according to the present embodiment, for example, the portion including the electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to this embodiment is preferably used. In addition to the electrophotographic photosensitive member, the process cartridge may include, for example, at least one selected from the group consisting of charging means, electrostatic latent image forming means, developing means, and transfer means.

An example of the image forming apparatus according to the present embodiment will be shown below, but the present invention is not limited to this. The main part shown in the figure will be explained, and the explanation of the others will be omitted.

FIG. 3 is a schematic configuration diagram showing an example of an image forming apparatus according to this embodiment.
The image forming apparatus 100 according to the present embodiment includes, as shown in FIG. a transfer device) and an intermediate transfer member 50 . In the image forming apparatus 100 , the exposure device 9 is arranged at a position where the electrophotographic photosensitive member 7 can be exposed from the opening of the process cartridge 300 , and the transfer device 40 transfers the image onto the electrophotographic photosensitive member 7 via the intermediate transfer member 50 . A part of the intermediate transfer member 50 is arranged in contact with the electrophotographic photosensitive member 7 . Although not shown, it also has a secondary transfer device for transferring the toner image transferred to the intermediate transfer member 50 onto a recording medium (for example, paper). The intermediate transfer member 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) correspond to an example of transfer means.

The process cartridge 300 in FIG. 3 integrates an electrophotographic photosensitive member 7, a charging device 8 (an example of charging means), a developing device 11 (an example of developing means), and a cleaning device 13 (an example of cleaning means) in a housing. supported by The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131 , and the cleaning blade 131 is arranged so as to contact the surface of the electrophotographic photosensitive member 7 . The cleaning member may be a conductive or insulating fibrous member instead of the cleaning blade 131 , and may be used alone or in combination with the cleaning blade 131 .

In FIG. 3, as an image forming apparatus, a fibrous member 132 (roll-shaped) for supplying the lubricant 14 to the surface of the electrophotographic photosensitive member 7 and a fibrous member 133 (flat brush-shaped) for assisting cleaning are provided. are shown, but they can be placed as needed.

Each configuration of the image forming apparatus according to the present embodiment will be described below.

- Charging device -
As the charging device 8, for example, a contact type charger using a conductive or semi-conductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, or the like is used. In addition, a known charger such as a non-contact roller charger, a scorotron charger using corona discharge, a corotron charger, or the like may also be used.

-Exposure equipment-
Examples of the exposure device 9 include an optical device that exposes the surface of the electrophotographic photosensitive member 7 to light such as semiconductor laser light, LED light, and liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity region of the electrophotographic photosensitive member. As for the wavelength of semiconductor lasers, near-infrared light having an oscillation wavelength near 780 nm is predominant. However, the wavelength is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a blue laser having an oscillation wavelength of 400 nm or more and 450 nm or less may also be used. A surface emitting laser light source capable of outputting multiple beams is also effective for color image formation.

- Developing device -
As the developing device 11, for example, a general developing device that develops by contacting or non-contacting a developer can be used. The developing device 11 is not particularly limited as long as it has the functions described above, and is selected according to the purpose. For example, a known developing device having a function of adhering a one-component developer or a two-component developer to the electrophotographic photosensitive member 7 using a brush, a roller, or the like can be used. Among them, it is preferable to use a developing roller holding a developer on its surface.

The developer used in the developing device 11 may be a one-component developer containing only toner, or may be a two-component developer containing toner and carrier. Also, the developer may be magnetic or non-magnetic. Known developers are applied.

－Cleaning device－
As the cleaning device 13, a cleaning blade type device having a cleaning blade 131 is used. In addition to the cleaning blade method, a fur brush cleaning method and a simultaneous development cleaning method may be employed.

-Transfer device-
As the transfer device 40, for example, a known transfer charger such as a contact type transfer charger using a belt, a roller, a film, a rubber blade, etc., a scorotron transfer charger using corona discharge, a corotron transfer charger, or the like can be used. mentioned.

-Intermediate transfer body-
As the intermediate transfer member 50, a belt-like member (intermediate transfer belt) containing semiconductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, or the like is used. Further, as the form of the intermediate transfer body, a drum-shaped one may be used instead of the belt-shaped one.

FIG. 4 is a schematic configuration diagram showing another example of the image forming apparatus according to this embodiment.
The image forming apparatus 120 shown in FIG. 4 is a tandem type multicolor image forming apparatus in which four process cartridges 300 are mounted. In the image forming apparatus 120, four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and one electrophotographic photosensitive member is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100 except that it is a tandem system.

The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following description, "parts" and "%" are based on mass unless otherwise specified.

In the following description, synthesis, processing, manufacture, etc. were performed at room temperature (25°C ± 3°C) unless otherwise noted.

<Production of polyester resin (1)>
[Polyester resin (1-1)]
12.6373 g of 4,4′-(2-ethylhexylidene)diphenol, 0.1233 g of 4-tbutylphenol, 0.0632 g of sodium hydrosulfite, and 240 mL of water are placed in a reaction vessel equipped with a stirrer, A suspension was prepared. To this suspension, 4.8392 g of sodium hydroxide, 0.1981 g of benzyltributylammonium chloride and 160 mL of water were added under stirring at a temperature of 20° C. and stirred for 30 minutes under nitrogen atmosphere. 220 mL of o-dichlorobenzene was added to this aqueous solution, and after stirring for 30 minutes in a nitrogen atmosphere, 12.0000 g of 4,4'-biphenyldicarbonyl chloride was added as powder. After the addition was completed, the reaction was allowed to proceed by stirring for 4 hours under a nitrogen atmosphere at a temperature of 20°C. The solution after polymerization was diluted with 300 mL of o-dichlorobenzene, and the aqueous layer was removed. After washing with a dilute acetic acid solution and ion-exchanged water, the polymer was precipitated by pouring it into methanol. The precipitated polymer was filtered off and dried at 50°C. This polymer was re-dissolved in 900 mL of tetrahydrofuran and poured into methanol to precipitate the polymer. The precipitated polymer was separated by filtration, washed with methanol, and dried at 50° C. to obtain 17.5 g of a white polymer.
Molecular weight measurements by GPC (gel permeation chromatography) were performed using tetrahydrofuran as an eluent, and the molecular weights of the polymers were determined as polystyrene-equivalent molecular weights. Table 1 and the like show the weight average molecular weight Mw and the molecular weight distribution Mw/Mn of the polymer.

[Polyester resins (1-2) to (1-20) and (C1) to (C6)]
Synthesize polyester resins (1-2) to (1-20) and (C1) to (C6) in the same manner as in the production process of polyester resin (1-1) except for changing the type of monomer used and the amount added. bottom. Table 1 and the like show the types and amounts of monomers of polyester resins.

[Polyester resin (1-21)]
12.6373 g of 4,4'-(2-ethylhexylidene)diphenol, 8.7845 g of triethylamine, and 70 mL of methylene chloride were put into a reactor equipped with a stirrer to form a solution. To this solution was added 11.9555 g of 4,4'-biphenyldicarbonyl chloride as powder at a temperature of 5°C under stirring. After the addition, the temperature was raised to 30° C. and the reaction was allowed to proceed with stirring for 4 hours under a nitrogen atmosphere. The solution after polymerization was diluted with 850 mL of tetrahydrofuran and poured into methanol to precipitate a polymer. The precipitated polymer was separated by filtration, washed with methanol, and dried at 50°C. This polymer was redissolved in 850 mL of tetrahydrofuran and added to methanol to precipitate the polymer. The precipitated polymer was separated by filtration, washed with methanol, and dried at 50° C. to obtain 19.2 g of a white polymer.
10.0000 g of the above polymer, 1.2941 g of triethylamine, and 110 mL of methylene chloride were placed in a reactor equipped with a stirrer to form a solution. To this solution was added 1.7121 g of benzoyl chloride at a temperature of 5° C. under stirring. After the addition, the temperature was raised to 30° C. and the reaction was allowed to proceed with stirring for 4 hours under a nitrogen atmosphere. The solution after the reaction was diluted with 400 mL of tetrahydrofuran and poured into methanol to precipitate a polymer. The precipitated polymer was separated by filtration, washed with methanol, and dried at 50°C. This polymer was re-dissolved in 400 mL of tetrahydrofuran and poured into methanol to precipitate the polymer. The precipitated polymer was separated by filtration, washed with methanol, and dried at 50° C. to obtain 8.8 g of a white polymer.
Molecular weight measurements by GPC (gel permeation chromatography) were performed using tetrahydrofuran as an eluent, and the molecular weights of the polymers were determined as polystyrene-equivalent molecular weights. Table 2 shows the weight average molecular weight Mw and the molecular weight distribution Mw/Mn of the polymer.

Tables 1 to 4 show "constitutional unit:composition ratio" (eg, A-12:41.3). The composition ratio is the mass % of each dicarboxylic acid unit (a unit obtained by removing two OH atoms from the raw material dicarboxylic acid) and a diol unit (a unit obtained by removing two H atoms from the raw material diol).
A-12 etc. described in Table 1 etc. are specific examples of the dicarboxylic acid unit (A) described above.
B-24 etc. described in Table 1 etc. are specific examples of the diol unit (B) described above.
C-1 etc. described in Table 1 etc. are the following dicarboxylic acid units or diol units.
C-1: naphthalene dicarboxylic acid unit D-1: diphenyl ether dicarboxylic acid unit E-1: o,o'-dimethylbiphenol unit F-1: diphenyl ether diol unit

<Production of Photoreceptor with Laminated Photoreceptor Layer>
[Example S1]
-Formation of undercoat layer-
As a conductive substrate, an aluminum cylindrical tube having an outer diameter of 30 mm, a length of 250 mm and a wall thickness of 1 mm was prepared.

100 parts of zinc oxide (average particle size: 70 nm, specific surface area: 15 m ² /g, manufactured by Tayca) was stirred and mixed with 500 parts of toluene, and a silane coupling agent (trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd., N-2- (Aminoethyl)-3-aminopropyltrimethoxysilane) (1.3 parts) was added and stirred for 2 hours. After that, toluene was distilled off under reduced pressure, and baking was performed at 120° C. for 3 hours to obtain zinc oxide surface-treated with a silane coupling agent.

110 parts of the surface-treated zinc oxide was stirred and mixed with 500 parts of tetrahydrofuran, a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added, and the mixture was stirred at 50° C. for 5 hours. Thereafter, the solid content was separated by filtration under reduced pressure and dried under reduced pressure at 60° C. to obtain alizarin-imparted zinc oxide.

60 parts of alizarin-imparted zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, product name: Sumidur 3175, manufactured by Sumitomo Bayern Urethane) and 15 parts of butyral resin (product name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) 100 parts of a solution obtained by dissolving 1 part in 68 parts of methyl ethyl ketone and 5 parts of methyl ethyl ketone, and dispersed for 2 hours in a sand mill using glass beads of 1 mmφ to obtain a dispersion liquid. 0.005 part of dioctyltin dilaurate as a catalyst and 4 parts of silicone resin particles (trade name: Tospearl 145, manufactured by Momentive Performance Materials) were added to the dispersion to obtain a coating liquid for forming an undercoat layer. rice field. The undercoat layer-forming coating solution was applied to the outer peripheral surface of the conductive substrate by dip coating, and dried and cured at 170° C. for 40 minutes to form an undercoat layer. The average thickness of the undercoat layer was 25 μm.

- Formation of charge generation layer -
Hydroxygallium phthalocyanine as a charge-generating substance (Cukα characteristic X-ray, Bragg angle (2θ ± 0.2°) of X-ray diffraction spectrum is at least 7.5°, 9.9°, 12.5°, 16.3°) °, 18.6°, 25.1° and 28.3°. ) and 200 parts of n-butyl acetate were dispersed in a sand mill for 4 hours using glass beads with a diameter of 1 mm. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion liquid and stirred to obtain a coating liquid for forming a charge generation layer. The charge-generating layer-forming coating solution was dip-coated on the undercoat layer and dried at room temperature (25° C.±3° C.) to form a charge-generating layer having an average thickness of 0.18 μm.

-Formation of charge transport layer-
60 parts of polyester resin (1-1) as a binder resin and 140 parts of HTM-1 as a charge transport material were dissolved in 270 parts of tetrahydrofuran and 30 parts of toluene to obtain a coating liquid for forming a charge transport layer. The charge-transporting layer-forming coating liquid was applied onto the charge-generating layer by dip coating and dried at 145° C. for 30 minutes to form a charge-transporting layer. Table 1 shows the average thickness Ds (μm) of the charge transport layer.

[Examples S2 to S26, Comparative Examples SC1 to SC9]
In the same manner as in Example S1, except that in the formation of the charge transport layer, the type of polyester resin (1), the type and amount of the charge transport material, and the average thickness Ds of the charge transport layer were set as shown in Tables 1 and 2. Each photoreceptor was produced by changing the specifications. Charge transport materials HTM-2 to HTM-5 are the following compounds.

[Example S27]
In the same manner as in Example S1, except that alizarin was changed to 2,3,4-trihydroxybenzophenone in the formation of the undercoat layer, and in the formation of the charge transport layer, the type of polyester resin (1) and charge transport layer The average thickness Ds of was changed to the specifications shown in Table 2, and photoreceptors were produced.

<Production of Photoreceptor Equipped with Single-Layer Type Photosensitive Layer>
[Example T1]
- Formation of single-layer type photosensitive layer -
52.75 parts of polyester resin (1-1) as a binder resin and V-type hydroxygallium phthalocyanine as a charge generating material (Cukα characteristic X-ray X-ray diffraction spectrum Bragg angle (2θ±0.2°) (having diffraction peaks at least at 7.3°, 16.0°, 24.9°, and 28.0°), 1.25 parts, and 7.8 parts of ETM-1, which is an electron-transporting material; 38.2 parts of HTM-1 which is a hole transport material (mass ratio of ETM-1 and HTM-1 is 17:83) and 175 parts of tetrahydrofuran and 75 parts of toluene as solvents are mixed, and glass beads having a diameter of 1 mm are prepared. was dispersed in a sand mill for 4 hours to obtain a coating solution for forming a single layer type photosensitive layer.
The obtained coating solution for forming a photosensitive layer is applied onto an aluminum substrate having an outer diameter of 30 mm, a length of 244.5 mm and a thickness of 1 mm by a dip coating method, and dried and cured at a temperature of 110° C. for 40 minutes. A single layer type photosensitive layer was formed. Table 3 shows the average thickness Dt (μm) of the single-layer type photosensitive layer.

[Examples T2 to T19, Comparative Examples TC1 to TC9]
In the same manner as in Example T1, except that in the formation of the single-layer type photosensitive layer, the type of polyester resin (1) and the amount of charge transport material (however, the mass ratio of ETM-1 and HTM-1 was the same as in Example T1. 17:83) and the average thickness Dt of the single-layer type photosensitive layer was changed to the specifications shown in Tables 3 and 4, and respective photoreceptors were produced.

<Performance Evaluation of Photoreceptor>
[Abrasion resistance]
The photoreceptor was mounted on an electrophotographic image forming apparatus (DocuCentre f1100 manufactured by Fuji Xerox Co., Ltd.), and a 100% solid image and an image density ( area coverage) 100,000 sheets of 100% solid images were formed. The average thickness of the charge transport layer (or single-layer type photosensitive layer) was obtained before and after the image formation, and the difference between the average thicknesses before and after the image formation was taken as the wear amount (nm). A Permascope manufactured by Fischerscope was used as a film thickness measuring device. The amount of wear was classified as follows. Tables 1 to 4 show the results.
A: The amount of wear is less than 500 nm B: The amount of wear is 500 nm or more and less than 1000 nm C: The amount of wear is 1000 nm or more and less than 1500 nm D: The amount of wear is 1500 nm or more and less than 2000 nm E: The amount of wear is 2000 nm or more

[Electrical characteristics]
In the above image formation, the residual potential on the surface of the photoreceptor was measured after printing the first sheet and after printing 100,000 sheets. The absolute value of the residual potential after output) was obtained and taken as an increase in the absolute value of the residual potential. These were classified as follows. Tables 1 to 4 show the results.
A: Increase in absolute value of residual potential is less than 20 V B: Increase in absolute value of residual potential is 20 V or more and less than 30 V C: Increase in absolute value of residual potential is 30 V or more and less than 40 V D: Increase in absolute value of residual potential is less than 40 V Increase in absolute value is 40 V or more and less than 50 V E: Increase in absolute value of residual potential is 50 V or more

[Peeling of photosensitive layer]
After printing 100,000 sheets in the above image formation, the photoreceptor was observed, and the state of peeling of the film over the entire surface of the photoreceptor was classified as follows. Tables 1 to 4 show the results.
A: Peeling is not observed.
B: Peeling within a width of 2 mm is observed at the edge.
C: Peeling within a width of 2 mm is observed both at the center and at the edges.
D: Peeling within a width of 5 mm is observed both at the center and at the edges.
E: Peeling with a width of 5 mm or more is observed on the entire surface.

[Initial image quality and image quality after driving]
The photoreceptor was mounted in a drum cartridge, mounted in an image forming apparatus ApeosPort C4300 (manufactured by Fuji Xerox Co., Ltd.) equipped with a potential sensor, and 50% half on A4 size paper in an environment of 28°C temperature and 85% relative humidity. 100,000 sheets of tone images were output. The image graininess of the 1st and 100,000th output images was observed visually and with a loupe, and classified as follows. Tables 1 to 4 show the results.
A: No image defect.
B: Slight image defects can be seen when viewed with a magnifying glass, but within the allowable range for practical use.
C: Image defects are visually observed.
D: An image defect is visually observed and extends in a streak-like manner.
E: An image defect is visually observed and extends in a streaky shape. Clear density unevenness is confirmed.

(((1)))
comprising a conductive substrate and a laminated photosensitive layer having a charge generation layer and a charge transport layer disposed on the conductive substrate;
The charge transport layer contains a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), and a charge transport material. ,
The weight average molecular weight Mw of the polyester resin (1) contained in the charge transport layer is A (10,000), and the ratio M1 between the mass M1 of the charge transport material contained in the charge transport layer and the mass M2 of the charge transport layer When the value of /M2 is Cs and the average thickness of the charge transport layer is Ds (μm),
5≤A≤40,
0.28≤Cs≤0.55,
27≦Ds≦50 and 2.5≦(A×Ds)/(Cs×100)≦70.0,
Electrophotographic photoreceptor.
(((2)))
The electrophotographic photoreceptor according to ((1)), which satisfies 3.6≦(A×Ds)/(Cs×100)≦46.0.
(((3)))
The electrophotographic photoreceptor according to (((1))) or (((2))), which satisfies 30≦Ds≦48.
(((4)))
The electrophotographic photoreceptor according to any one of (((1))) to (((3))), which satisfies 6≦A≦30.
(((5)))
Any one of (((1))) to (((4))), wherein the proportion by mass of the dicarboxylic acid unit (A) in the polyester resin (1) is 15% by mass or more and 60% by mass or less The electrophotographic photoreceptor described in .
(((6)))
The electrophotographic photoreceptor according to any one of ((1)) to (((5))), wherein ⁿ¹ is 2 in formula (A).
(((7)))
In formula (B), at least one of Rb ¹ and Rb ² is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a carbon an aralkyl group having a number of 7 or more and 10 or less, or Rb ¹ and Rb ² combined to form a cyclic alkyl group having 5 or more and 12 or less carbon atoms, (((1))) to ((( 6))) The electrophotographic photoreceptor according to any one of the above.
(((8)))
(((1)) ⁾ to ⁽ The electrophotographic photoreceptor according to any one of ((7))).
(((9)))
comprising a conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate;
The single-layer type photosensitive layer comprises a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), and a charge transport material. contains,
The weight average molecular weight Mw of the polyester resin (1) contained in the single-layer type photosensitive layer is defined as A (10,000), and the mass M1 of the charge transport material contained in the single-layer type photosensitive layer and the weight of the single-layer type photosensitive layer When the value of the ratio M1/M2 to the mass M2 is Ct and the average thickness of the single-layer type photosensitive layer is Dt (μm),
5≤A≤40,
0.40≦Ct≦0.60,
27≦Dt≦50 and 2.5≦(A×Dt)/(Ct×100)≦48.0,
Electrophotographic photoreceptor.
(((10)))
The electrophotographic photoreceptor according to ((9)), which satisfies 3.5≦(A×Dt)/(Ct×100)≦40.0.
(((11)))
The electrophotographic photoreceptor according to (((9))) or (((10))), which satisfies 30≦Dt≦48.
(((12)))
The electrophotographic photoreceptor according to any one of (((9))) to (((11))), which satisfies 6≦A≦30.
(((13)))
Any one of (((9))) to (((12))), wherein the proportion by mass of the dicarboxylic acid unit (A) in the polyester resin (1) is 15% by mass or more and 60% by mass or less The electrophotographic photoreceptor described in .
(((14)))
The electrophotographic photoreceptor according to any one of (((9))) to (((13))), wherein ⁿ¹ is 2 in formula (A).
(((15)))
In formula (B), at least one of Rb ¹ and Rb ² is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a carbon An aralkyl group having a number of 7 or more and 10 or less, or Rb ¹ and Rb ² combined to form a cyclic alkyl group having 5 or more and 12 or less carbon atoms, (((9))) to ((( 14)))).
(((16)))
((9) ⁾ to ⁽ ((15))) The electrophotographic photoreceptor according to any one of (15)).
(((17)))
The electrophotographic photoreceptor according to any one of (((1))) to (((16))),
A process cartridge that can be attached to and detached from an image forming apparatus.
(((18)))
The electrophotographic photoreceptor according to any one of (((1))) to (((16)));
charging means for charging the surface of the electrophotographic photosensitive member;
an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
a developing means for developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
a transfer means for transferring the toner image onto the surface of a recording medium;
An image forming apparatus comprising:

(((1))), (((2))), (((3))), (((4))), (((5))), (((6))), (( According to the invention of (7))) or (((8))), the electrophotographic photoreceptor has a laminated photosensitive layer, wherein the value of (A×Ds)/(Cs×100) is 2.0. The wear resistance of the photosensitive layer is superior to that of the electrophotographic photoreceptor having a value of less than 5, and the electrical properties are superior to those of the electrophotographic photoreceptor having a value of (A×Ds)/(Cs×100) exceeding 70.0. Provided is an electrophotographic photoreceptor which is excellent and whose photosensitive layer is less likely to peel off.
(((9))), (((10))), (((11))), (((12))), (((13))), (((14))), (( (15))) or (((16))), an electrophotographic photoreceptor having a single-layer type photosensitive layer, wherein the value of (A×Dt)/(Ct×100) is 2 Excellent wear resistance of the photosensitive layer compared to electrophotographic photoreceptors of less than .5, and electrical properties compared to electrophotographic photoreceptors with a value of (A × Dt) / (Ct × 100) exceeding 48.0 Provided is an electrophotographic photoreceptor which is excellent in photosensitivity and in which peeling of the photosensitive layer is less likely to occur.
According to the invention relating to ((17)), the value of (A x Ds) / (Cs x 100) or (A x Dt) / (Ct x 100) relating to the electrophotographic photoreceptor is less than 2.5 The abrasion resistance of the photosensitive layer is excellent compared to the case where the value of (A × Ds) / (Cs × 100) is more than 70.0 or the value of (A × Dt) / (Ct × 100) is 48.0. Provided is a process cartridge which is superior in electrical characteristics to those in the case where it is greater than 0 and in which peeling of the photosensitive layer is less likely to occur.
According to the invention relating to ((18)), the value of (A x Ds) / (Cs x 100) or (A x Dt) / (Ct x 100) relating to the electrophotographic photoreceptor is less than 2.5 The abrasion resistance of the photosensitive layer is excellent compared to the case where the value of (A × Ds) / (Cs × 100) is more than 70.0 or the value of (A × Dt) / (Ct × 100) is 48.0. An image forming apparatus is provided which has excellent electrical properties and is less susceptible to peeling of the photosensitive layer than when it is greater than 0.

REFERENCE SIGNS LIST 1 conductive substrate 2 undercoat layer 3 charge generating layer 4 charge transport layer 5 photosensitive layer 10A photoreceptor 10B photoreceptor

7 Electrophotographic photosensitive member 8 Charging device 9 Exposure device 11 Developing device 13 Cleaning device 14 Lubricant 40 Transfer device 50 Intermediate transfer member 100 Image forming device 120 Image forming device 131 Cleaning blade 132 fibrous member (roll shape), 133 fibrous member (flat brush shape), 300 process cartridge

Claims (18)

comprising a conductive substrate and a laminated photosensitive layer having a charge generation layer and a charge transport layer disposed on the conductive substrate;
The charge transport layer comprises a polyester resin (1) having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by the following formula (B), and a charge transport material and
The weight average molecular weight Mw of the polyester resin (1) contained in the charge transport layer is A (10,000), and the ratio M1 between the mass M1 of the charge transport material contained in the charge transport layer and the mass M2 of the charge transport layer When the value of /M2 is Cs and the average thickness of the charge transport layer is Ds (μm),
5≤A≤40,
0.28≤Cs≤0.55,
27≦Ds≦50 and 2.5≦(A×Ds)/(Cs×100)≦70.0,
Electrophotographic photoreceptor.

In formula (A), n ¹ is 1, 2 or 3, n ¹ m ¹ is each independently 0, 1, 2, 3 or 4, m ¹ Ra ¹ is each independently , an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.
In formula (B), Rb ¹ and Rb ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. , Rb ³ , Rb ⁴ , Rb ⁵ , Rb ⁶ , Rb ⁷ , Rb ⁸ , Rb ⁹ and Rb ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms , an aralkyl group having 7 to 20 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and Rb ¹ and Rb ² may combine to form a cyclic alkyl group. 2. The electrophotographic photoreceptor according to claim 1, which satisfies 3.6≦(A×Ds)/(Cs×100)≦46.0. 2. The electrophotographic photoreceptor according to claim 1, which satisfies 30≦Ds≦48. 2. The electrophotographic photoreceptor according to claim 1, which satisfies 6≤A≤30. 2. The electrophotographic photoreceptor according to claim 1, wherein the dicarboxylic acid unit (A) accounts for 15% by mass or more and 60% by mass or less in the polyester resin (1). 2. The electrophotographic photoreceptor according to claim ¹ , wherein n1 is 2 in formula (A). In formula (B), at least one of Rb ¹ and Rb ² is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a carbon 2. The electrophotographic photoreceptor according to claim 1, which is an aralkyl group having a number of 7 or more and 10 or less, or Rb ¹ and Rb ² combine to form a cyclic alkyl group having 5 or more and 12 or less carbon atoms. 2. The electrophotographic photosensitive material according to claim 1, wherein at least one of Rb ¹ and Rb ² in formula (B) is a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms. body. comprising a conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate;
The single-layer type photosensitive layer is a polyester resin (1) having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by the following formula (B), and an electric charge containing transport materials and
The weight average molecular weight Mw of the polyester resin (1) contained in the single-layer type photosensitive layer is defined as A (10,000), and the mass M1 of the charge transport material contained in the single-layer type photosensitive layer and the weight of the single-layer type photosensitive layer When the value of the ratio M1/M2 to the mass M2 is Ct and the average thickness of the single-layer type photosensitive layer is Dt (μm),
5≤A≤40,
0.40≦Ct≦0.60,
27≦Dt≦50 and 2.5≦(A×Dt)/(Ct×100)≦48.0,
Electrophotographic photoreceptor.

In formula (A), n ¹ is 1, 2 or 3, n ¹ m ¹ is each independently 0, 1, 2, 3 or 4, m ¹ Ra ¹ is each independently , an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.
In formula (B), Rb ¹ and Rb ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. , Rb ³ , Rb ⁴ , Rb ⁵ , Rb ⁶ , Rb ⁷ , Rb ⁸ , Rb ⁹ and Rb ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms , an aralkyl group having 7 to 20 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and Rb ¹ and Rb ² may combine to form a cyclic alkyl group. 10. The electrophotographic photoreceptor according to claim 9, which satisfies 3.5≦(A×Dt)/(Ct×100)≦40.0. 10. The electrophotographic photoreceptor according to claim 9, which satisfies 30≤Dt≤48. 10. The electrophotographic photoreceptor according to claim 9, which satisfies 6≤A≤30. 10. The electrophotographic photoreceptor according to claim 9, wherein the dicarboxylic acid unit (A) accounts for 15% by mass or more and 60% by mass or less in the polyester resin (1). 10. The electrophotographic photoreceptor according to claim 9, wherein ⁿ¹ is 2 in formula (A). In formula (B), at least one of Rb ¹ and Rb ² is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a carbon 10. The electrophotographic photoreceptor according to claim 9, which is an aralkyl group having 7 or more and 10 or less, or Rb ¹ and Rb ² combine to form a cyclic alkyl group having 5 or more and 12 or less carbon atoms. 10. The electrophotographic photosensitive material according to claim 9, wherein at least one of Rb ¹ and Rb ² in formula (B) is a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms. body. Equipped with the electrophotographic photoreceptor according to any one of claims 1 to 16,
A process cartridge that can be attached to and detached from an image forming apparatus. The electrophotographic photoreceptor according to any one of claims 1 to 16,
charging means for charging the surface of the electrophotographic photosensitive member;
an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
developing means for developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
a transfer means for transferring the toner image onto the surface of a recording medium;
An image forming apparatus comprising:

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