阅读说明：本技术 电子照相感光体、处理盒和图像形成装置 (Electrophotographic photoreceptor, process cartridge, and image forming apparatus ) 是由 川畑幸美 兼子奈都实 胜原秀弥 于 2021-06-24 设计创作，主要内容包括：本发明涉及电子照相感光体、处理盒和图像形成装置。该电子照相感光体具有高感光度并抑制黑点产生。该电子照相感光体具有：导电性基体；以及单层型感光层,其设置在所述导电性基体上,且含有粘合剂树脂、电荷产生材料、空穴输送材料和电子输送材料,在磨损后的所述感光层的厚度与磨损前的所述感光层的厚度之比(磨损后的所述感光层的厚度/磨损前的所述感光层的厚度)为0.8时,磨损后的所述感光层的体积电阻率为5.0×10～(10)Ω·cm以上且2.0×10～(11)Ω·cm以下。(The invention relates to an electrophotographic photoreceptor, a process cartridge and an image forming apparatus. The electrophotographic photoreceptor has high sensitivity and suppresses black dot generation. The electrophotographic photoreceptor comprises: a conductive substrate; and a monolayer type photosensitive layer provided on the aboveA conductive substrate, and containing a binder resin, a charge generation material, a hole transport material and an electron transport material, wherein when the ratio of the thickness of the photosensitive layer after abrasion to the thickness of the photosensitive layer before abrasion (the thickness of the photosensitive layer after abrasion/the thickness of the photosensitive layer before abrasion) is 0.8, the volume resistivity of the photosensitive layer after abrasion is 5.0 × 10 10 Omega cm or more and 2.0X 10 11 Omega cm or less.)

1. An electrophotographic photoreceptor, comprising:

a conductive substrate; and

a single-layer photosensitive layer provided on the conductive substrate and containing a binder resin, a charge generating material, a hole transporting material, and an electron transporting material,

when the ratio of the thickness of the photosensitive layer after abrasion to the thickness of the photosensitive layer before abrasion (thickness of the photosensitive layer after abrasion/thickness of the photosensitive layer before abrasion) was 0.8, the volume resistivity of the photosensitive layer after abrasion was 5.0 × 10¹⁰Omega cm or more and2.0×10¹¹omega cm or less.

2. The electrophotographic photoreceptor according to claim 1,

a ratio of a volume resistivity of the photosensitive layer after abrasion to a volume resistivity of the photosensitive layer before abrasion (volume resistivity of the photosensitive layer after abrasion/volume resistivity of the photosensitive layer before abrasion) is 1/100 or more and 7/100 or less.

3. The electrophotographic photoreceptor according to claim 1 or 2, wherein a mass ratio of the hole transporting material to the electron transporting material (mass of the hole transporting material/mass of the electron transporting material) is 19/5 or more and 28/5 or less.

4. The electrophotographic photoreceptor according to claim 3,

the content of the hole-transporting material is 38 mass% or more and 44 mass% or less with respect to the total solid content of the photosensitive layer.

5. The electrophotographic photoreceptor according to any one of claims 1 to 4,

the hole transport material is a hole transport material having a benzidine skeleton.

6. The electrophotographic photoreceptor according to claim 5,

the hole transporting material having a benzidine skeleton is a hole transporting material represented by the following general formula (HT1 a):

in the general formula (HT1a), R^C21、R^C22And R^C23Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a carbon atomAn aryl group having 6 to 10 atoms.

7. The electrophotographic photoreceptor according to any one of claims 1 to 6,

the electron transport material is an electron transport material with a diphenoquinone skeleton.

8. The electrophotographic photoreceptor according to claim 7,

the electron transporting material having a diphenoquinone skeleton is an electron transporting material represented by the following general Formula (FK):

in the general Formula (FK), R^k1～R^k4Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group.

9. An electrophotographic photoreceptor, comprising:

a conductive substrate; and

a single-layer photosensitive layer provided on the conductive substrate and containing a binder resin, a charge generating material, a hole transporting material, and an electron transporting material,

the ratio of the amount of the hole transporting material present on the front side of the photosensitive layer to the amount of the hole transporting material present on the back side of the photosensitive layer (the amount of the hole transporting material present on the front side of the photosensitive layer/the amount of the hole transporting material present on the back side of the photosensitive layer) is 1/6 or more and 1/3 or less.

10. A process cartridge comprising the electrophotographic photoreceptor according to any one of claims 1 to 9, and being attachable to and detachable from an image forming apparatus.

11. An image forming apparatus includes:

an electrophotographic photoreceptor according to any one of claims 1 to 9;

a charging unit that charges a surface of the electrophotographic photoreceptor;

an electrostatic latent image forming unit that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

a developing unit that develops an electrostatic latent image formed on a surface of the electrophotographic photoconductor with a developer containing a toner to form a toner image; and

a transfer unit that transfers the toner image to a surface of a recording medium.

12. An image forming apparatus includes:

an electrophotographic photoreceptor according to any one of claims 1 to 9;

a charging unit that charges a surface of the electrophotographic photoreceptor;

an electrostatic latent image forming unit that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

a developing unit that develops an electrostatic latent image formed on a surface of the electrophotographic photoconductor with a developer containing a toner to form a toner image; and

a direct transfer type transfer unit having a transfer member that directly transfers the toner image from the electrophotographic photoconductor to a surface of a recording medium,

the relationship among the rotation speed P (mm/s) of the electrophotographic photoreceptor, the transfer current value I (μ A) for directly transferring the toner image from the electrophotographic photoreceptor to the surface of the recording medium, and the length L (mm) of the transfer member satisfies the following formula (PIL):

formula (PIL): -1.07X 10^-3≤I/(P×L)≤-4.30×10^-4。

Technical Field

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

Background

In a conventional electrophotographic image forming apparatus, a toner image formed on the surface of an electrophotographic photoreceptor is transferred to a recording medium by processes of charging, electrostatic latent image formation, development, and transfer.

For example, patent document 1 discloses "an electrophotographic photoreceptor including: a conductive substrate; and a monolayer type photosensitive layer provided on the conductive substrate, the monolayer type photosensitive layer including a binder resin, a charge generation material, an electron transport material, and a hole transport material, the product of the volume resistivity (G.OMEGA.. m) and the elastic modulus (GPa) of the monolayer type photosensitive layer being 90 or more ".

Patent document 2 discloses "an image forming apparatus including a photoconductive layer containing a charge generating substance, a hole transporting substance, an electron transporting substance, and an organic binder resin on a conductive support, and having a resistivity ρ of the photoconductive layer of ρ <10¹¹A single-layer positively chargeable organic photoreceptor of Ω · m (where ρ is a resistivity at an electric field intensity of 20V/μm), and a charging member for charging a surface of the photoreceptor, wherein the charging member is a non-contact charging member ".

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-049149

Patent document 2: japanese laid-open patent publication No. 2002-

Disclosure of Invention

The invention provides an electrophotographic photoreceptor having a single-layer photosensitive layer containing a binder resin, a charge generating material, a hole transporting material and an electron transporting material, and a method for producing the sameThe volume resistivity of the photosensitive layer after abrasion is less than 5.0 x 10 when the ratio of the thickness of the photosensitive layer after abrasion to the thickness of the photosensitive layer before abrasion is 0.8¹⁰Omega cm or more than 2.0X 10¹¹Omega cm, or a ratio of the amount of the hole transporting material present on the front side of the photosensitive layer to the amount of the hole transporting material present on the back side of the photosensitive layer is less than 1/6 or greater than 1/3.

<1> according to one aspect of the present disclosure, there is provided an electrophotographic photoreceptor having:

a conductive substrate; and

a single-layer photosensitive layer provided on the conductive substrate and containing a binder resin, a charge generating material, a hole transporting material, and an electron transporting material,

when the ratio of the thickness of the photosensitive layer after abrasion to the thickness of the photosensitive layer before abrasion (thickness of the photosensitive layer after abrasion/thickness of the photosensitive layer before abrasion) was 0.8, the volume resistivity of the photosensitive layer after abrasion was 5.0 × 10¹⁰Omega cm or more and 2.0X 10¹¹Omega cm or less.

<2> in the electrophotographic photoreceptor of <1>, it is preferable that a ratio of a volume resistivity of the photosensitive layer after abrasion to a volume resistivity of the photosensitive layer before abrasion (volume resistivity of the photosensitive layer after abrasion/volume resistivity of the photosensitive layer before abrasion) is 1/100 or more and 7/100 or less.

<3> in the electrophotographic photoreceptor of <1> or <2>, it is preferable that the mass ratio of the hole transporting material to the electron transporting material (mass of the hole transporting material/mass of the electron transporting material) is 19/5 or more and 28/5 or less.

<4> in the electrophotographic photoreceptor of <3>, it is preferable that the content of the hole transporting material is 38 mass% or more and 44 mass% or less with respect to the total solid content of the photosensitive layer.

<5> in the electrophotographic photoreceptor according to any one of <1> to <4>, it is preferable that the hole transporting material is a hole transporting material having a benzidine skeleton.

<6> in the electrophotographic photoreceptor of <5>, it is preferable that the hole transporting material having a benzidine skeleton is a hole transporting material represented by the following general formula (HT1 a):

in the general formula (HT1a), R^C21、R^C22And R^C23Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms.

<7> in the electrophotographic photoreceptor according to any one of <1> to <6>, it is preferable that the electron transport material is an electron transport material having a diphenoquinone skeleton.

<8> in the electrophotographic photoreceptor of <7>, it is preferable that the electron transporting material having a diphenoquinone skeleton is an electron transporting material represented by the following general Formula (FK):

in the general Formula (FK), R^k1～R^k4Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group.

<9> according to another aspect of the present disclosure, there is provided an electrophotographic photoreceptor having:

a conductive substrate; and

a single-layer photosensitive layer provided on the conductive substrate and containing a binder resin, a charge generating material, a hole transporting material, and an electron transporting material,

the ratio of the amount of the hole transporting material present on the front side of the photosensitive layer to the amount of the hole transporting material present on the back side of the photosensitive layer (the amount of the hole transporting material present on the front side of the photosensitive layer/the amount of the hole transporting material present on the back side of the photosensitive layer) is 1/6 or more and 1/3 or less.

<10> according to another aspect of the present disclosure, there is provided a process cartridge which includes the electrophotographic photoreceptor according to any one of <1> to <9> and is attachable to and detachable from an image forming apparatus.

<11> according to another aspect of the present disclosure, there is provided an image forming apparatus including:

the electrophotographic photoreceptor according to any one of <1> to <9 >;

a charging unit that charges a surface of the electrophotographic photoreceptor;

an electrostatic latent image forming unit that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

a developing unit that develops an electrostatic latent image formed on a surface of the electrophotographic photoconductor with a developer containing a toner to form a toner image; and

a transfer unit that transfers the toner image to a surface of a recording medium.

<12> according to another aspect of the present disclosure, there is provided an image forming apparatus including:

the electrophotographic photoreceptor according to any one of <1> to <9 >;

a charging unit that charges a surface of the electrophotographic photoreceptor;

an electrostatic latent image forming unit that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

a developing unit that develops an electrostatic latent image formed on a surface of the electrophotographic photoconductor with a developer containing a toner to form a toner image; and

a direct transfer type transfer unit having a transfer member that directly transfers the toner image from the electrophotographic photoconductor to a surface of a recording medium,

the relationship among the rotation speed P (mm/s) of the electrophotographic photoreceptor, the transfer current value I (μ A) for directly transferring the toner image from the electrophotographic photoreceptor to the surface of the recording medium, and the length L (mm) of the transfer member satisfies the following formula (PIL):

formula (PIL): -1.07X 10^-3≤I/(P×L)≤-4.30×10^-4

Effects of the invention

According to<1>The electrophotographic photoreceptor has a monolayer type photosensitive layer containing a binder resin, a charge generating material, a hole transporting material and an electron transporting material, and the volume resistivity of the abraded photosensitive layer is less than 5.0 x 10 when the ratio of the thickness of the abraded photosensitive layer to the thickness of the photosensitive layer before abrasion is 0.8¹⁰Omega cm or more than 2.0X 10¹¹Compared with the case of Ω · cm, the photosensitive resin composition has high sensitivity and suppresses the generation of black spots.

According to the aspect of <2>, there is provided an electrophotographic photoreceptor having high sensitivity and suppressing generation of black spots as compared with the case where the ratio of the volume resistivity of the photosensitive layer after abrasion to the volume resistivity of the photosensitive layer before abrasion (volume resistivity of the photosensitive layer after abrasion/volume resistivity of the photosensitive layer before abrasion) is less than 1/100 or more than 7/100.

According to the aspect of <3>, there is provided an electrophotographic photoreceptor having high sensitivity and suppressing generation of black spots as compared with the case where the mass ratio of the hole transporting material to the electron transporting material (the hole transporting material/the electron transporting material) is less than 19/5 or more than 28/5.

According to the aspect of <4>, there is provided an electrophotographic photoreceptor having high sensitivity and suppressing generation of black spots as compared with the case where the content of the hole transporting material with respect to the photosensitive layer is less than 38% by mass or more than 44% by mass.

According to the aspect of <5> or <6>, there is provided an electrophotographic photoreceptor having high sensitivity and suppressing generation of black spots as compared with the case where the hole transporting material is an HTM-B hole transporting material used in a comparative example described later.

According to the aspect of <7> or <8>, there is provided an electrophotographic photoreceptor having high sensitivity and suppressing generation of black spots as compared with the case where the electron transporting material is an ETM-C electron transporting material used in a comparative example described later.

According to the aspect of <9>, there is provided an electrophotographic photoreceptor having a monolayer type photosensitive layer containing a binder resin, a charge generating material, a hole transporting material and an electron transporting material, which has high sensitivity and suppresses generation of black spots as compared with the case where the ratio of the amount of the hole transporting material present on the front side of the photosensitive layer to the amount of the hole transporting material present on the back side of the photosensitive layer (the amount of the hole transporting material present on the front side of the photosensitive layer/the amount of the hole transporting material present on the back side of the photosensitive layer) is less than 1/6 or more than 1/3.

According to<10>Or<11>The present invention provides a process cartridge or an image forming apparatus, comprising an electrophotographic photoreceptor having a monolayer type photosensitive layer containing a binder resin, a charge generating material, a hole transporting material and an electron transporting material, and having a volume resistivity of the photosensitive layer after abrasion of less than 5.0 × 10 when a ratio of a thickness of the photosensitive layer after abrasion to a thickness of the photosensitive layer before abrasion is 0.8¹⁰Omega cm or more than 2.0X 10¹¹The electrophotographic photoreceptor of Ω · cm has high sensitivity and suppresses generation of black dots, compared with the case of the electrophotographic photoreceptor.

According to the aspect of <12>, there is provided an image forming apparatus capable of suppressing an afterimage phenomenon (hereinafter, also referred to as "ghost") caused by a hysteresis residue of a previous image during a period from an initial stage to an end of a life of an electrophotographic photoreceptor, as compared with a case where the formula (PIL) is not satisfied.

Drawings

Exemplary embodiments of the invention are described in detail based on the following drawings, in which:

FIG. 1 is a schematic partial cross-sectional view showing one example of a layer structure of an electrophotographic photoreceptor of an exemplary embodiment;

FIG. 2 is a schematic configuration diagram showing an example of an image forming apparatus of an exemplary embodiment;

fig. 3 is a schematic configuration diagram showing another example of the image forming apparatus of the exemplary embodiment.

Detailed Description

Exemplary embodiments of the present invention will be described in detail below.

In the numerical ranges recited in the present specification, the upper limit or the lower limit recited in one numerical range may be replaced with the upper limit or the lower limit recited in another numerical range recited in a stepwise manner. In the numerical ranges described in the present specification, the upper limit or the lower limit of the numerical range may be replaced with the values shown in the examples.

In the present specification, the term "step" includes not only an independent step but also a step that can achieve the intended purpose of the step even when the step is not clearly distinguished from other steps.

Each component may comprise a plurality of corresponding substances.

In the case where the amount of each component is referred to, in the case where there are a plurality of substances corresponding to each component, the total amount of the plurality of substances is referred to unless otherwise specified.

The electrophotographic photoreceptor having a single-layer type photosensitive layer is also referred to as a "single-layer type photoreceptor". The single-layer photosensitive layer is a photosensitive layer having a hole transporting property and an electron transporting property in addition to a charge generating ability.

Electrophotographic photoreceptor

First exemplary embodiment

The electrophotographic photoreceptor of the first exemplary embodiment has: a conductive substrate; and a single-layer photosensitive layer which is provided on the conductive substrate and contains a binder resin, a charge generation material, a hole transport material, and an electron transport material.

Further, the ratio of the thickness of the photosensitive layer after abrasion to the thickness of the photosensitive layer before abrasion (thickness of the photosensitive layer after abrasion/photosensitive layer before abrasion)Thickness of layer) of 0.8, the volume resistivity of the photosensitive layer after abrasion was 5.0 × 10¹⁰Omega cm or more and 2.0X 10¹¹Omega cm or less.

The electrophotographic photoreceptor of the first exemplary embodiment has high sensitivity and suppresses generation of black dots by the above-described configuration. The reason is presumed as follows.

First, when an image is repeatedly formed using a single-layer type photoreceptor, black spots may be generated due to cracks in the photosensitive layer. In the single layer type photoreceptor, the initial single layer type photosensitive layer before abrasion has a target volume resistivity and film strength, whereby occurrence of black spots after abrasion of the single layer type photosensitive layer can be suppressed.

However, black spots caused by current leakage (hereinafter, also referred to as "leakage") due to an increase in the total amount of charges flowing through the monolayer photosensitive layer after repeated image formation may occur as black spots caused by factors other than cracks in the monolayer photosensitive layer.

On the other hand, when the ratio of the thickness of the photosensitive layer after the progress of the abrasion (thickness of the photosensitive layer after the abrasion/thickness of the photosensitive layer before the abrasion) to the thickness of the photosensitive layer before the abrasion is 0.8 (thickness of the photosensitive layer after the abrasion/thickness of the photosensitive layer before the abrasion), the volume resistivity of the photosensitive layer after the abrasion is increased to 5.0 × 10¹⁰Omega cm or more, can inhibit the black spot that is caused by the electric leakage that the total charge quantity that flows in the single-layer type photosensitive layer increases after forming the picture repeatedly.

On the other hand, if the volume resistivity of the photosensitive layer after abrasion is made too high, the sensitivity is lowered, and therefore the volume resistivity of the photosensitive layer after abrasion is controlled to 2.0 × 10¹¹Omega cm or less.

From the above, it can be presumed that: the electrophotographic photoreceptor of the first exemplary embodiment has high sensitivity and suppresses generation of black dots by the above-described configuration.

Second exemplary embodiment

The electrophotographic photoreceptor of the second exemplary embodiment has: a conductive substrate; and a single-layer photosensitive layer which is provided on the conductive substrate and contains a binder resin, a charge generation material, a hole transport material, and an electron transport material.

Further, the ratio of the amount of the hole transporting material present on the front side of the photosensitive layer to the amount of the hole transporting material present on the back side of the photosensitive layer (the amount of the hole transporting material present on the front side of the photosensitive layer/the amount of the hole transporting material present on the back side of the photosensitive layer) is 1/6 or more and 1/3 or less.

The electrophotographic photoreceptor of the second exemplary embodiment has high sensitivity and suppresses generation of black dots by the above-described configuration. The reason for this is presumed as follows.

As described above, when the single layer type photoreceptor is used, black spots caused by current leakage (hereinafter, also referred to as leakage) due to an increase in the total charge amount flowing in the single layer type photosensitive layer after repeated image formation may occur as black spots caused by factors other than cracks in the single layer type photosensitive layer.

In contrast, the ratio of the amount of the hole transport material present on the front side of the photosensitive layer to the amount of the hole transport material present on the back side of the photosensitive layer is 1/3 or less, and the hole transport material is biased toward the conductive substrate side of the photosensitive layer. This can increase the volume resistivity of the photosensitive layer after abrasion, and can suppress the occurrence of black spots due to leakage caused by an increase in the total charge amount flowing through the monolayer type photosensitive layer after repeated image formation.

On the other hand, the ratio of the amount of the hole transport material present on the front side of the photosensitive layer to the amount of the hole transport material present on the back side of the photosensitive layer is 1/6 or more, and excessive concentration of the hole transport material on the conductive substrate side of the photosensitive layer is suppressed. This prevents the volume resistivity of the photosensitive layer after abrasion from becoming too high, and thus can suppress a decrease in sensitivity.

From the above, it can be presumed that: the electrophotographic photoreceptor of the second exemplary embodiment has high sensitivity and suppresses generation of black dots by the above-described configuration.

Exemplary embodiments

Hereinafter, an electrophotographic photoreceptor corresponding to any one of the electrophotographic photoreceptors of the first and second exemplary embodiments (hereinafter also referred to as "the electrophotographic photoreceptor of the exemplary embodiments") will be described in detail. However, one example of the electrophotographic photoreceptor of the present invention is any electrophotographic photoreceptor corresponding to any one of the electrophotographic photoreceptors of the first and second exemplary embodiments.

Hereinafter, the electrophotographic photoreceptor of the exemplary embodiment will be described in detail.

In the electrophotographic photoreceptor of the exemplary embodiment, the volume resistivity of the photosensitive layer after abrasion when the ratio of the thickness of the photosensitive layer after abrasion to the thickness of the photosensitive layer before abrasion (thickness of the photosensitive layer after abrasion/thickness of the photosensitive layer before abrasion) is 0.8 is 5.0 × 10¹⁰Omega cm or more and 2.0X 10¹¹Not more than Ω · cm, but preferably 6.5 × 10 from the viewpoint of high sensitivity and suppression of black dot generation¹⁰Omega cm or more and 1.5X 10¹¹Omega cm or less, more preferably 8.0X 10¹⁰Omega cm or more and 1.0X 10¹¹Omega cm or less.

From the viewpoint of high sensitivity and suppression of black dot generation, the ratio of the volume resistivity of the photosensitive layer after abrasion to the volume resistivity of the photosensitive layer before abrasion (volume resistivity of the photosensitive layer after abrasion/volume resistivity of the photosensitive layer before abrasion) is preferably 1/100 or more and 7/100 or less, more preferably 1/50 or more and 3/50 or less, and further preferably 3/100 or more and 2/50 or less.

The volume resistivity of the photosensitive layer before and after abrasion is determined by, for example:

1) temperature of coating liquid for forming photosensitive layer (preferably, temperature is lowered)

2) Temperature of the conductive substrate in application of the coating liquid (preferably, temperature is lowered)

3) Drying temperature (preferably lowering temperature)

4) Kinds of hole transporting materials (preferably, hole transporting materials having a benzidine skeleton are used)

5) Kinds of Electron transporting materials (Electron transporting materials having a Bibenzoquinone skeleton are preferably used)

And so on.

The volume resistivity of the photosensitive layer before and after abrasion was measured as follows.

A sample of the photosensitive layer was collected from the photoreceptor to be measured as follows. The photoreceptor was cut into a cylindrical shape having a length of 6cm, and further cut into half-circles. The end of the photoreceptor slice is sandwiched by a vice, and a force is applied to increase the curvature of the semicircle, thereby peeling the photosensitive layer from the substrate and collecting the photosensitive layer.

Next, the collected sliced sample of the photosensitive layer was sputtered to form an electrode having an area of 1cm on the front side surface of the photosensitive layer²The Au electrode of (2) is formed with an Al electrode on the entire film surface on the back side of the photosensitive layer. Then, in an environment of 30 ℃ and 80% relative humidity, a voltage adjusted so that the electric field (applied voltage/thickness of the measurement sample) becomes 20V/. mu.m was applied for 30 seconds under a dark condition using a frequency response analyzer (model 1260, Solartron Co., Ltd.), and then the value of the flowing current (A) was measured.

Then, the following formula is used to calculate the current value. The volume resistivity obtained was taken as the volume resistivity of the photosensitive layer before abrasion.

Equation: volume resistivity (Ω · m) ═ 10^-4(m²) X applied voltage (V))/(Current value (A) × measurement specimen thickness (m))

On the other hand, the collected sliced sample of the photosensitive layer was fixed with a tape on a rotary table of a friction wear tester (FPR2100, Rhesca) so that the front side of the photosensitive layer was positioned on the top. A polishing sheet (alumina abrasive grain, particle size 9 μm) was attached to the presser head.

The abrasion was started from the front side of the photosensitive layer at a rotational speed of 100 rpm. The amount of abrasion was adjusted while confirming the thickness of the abraded film using a level-difference meter (SURFCOM S1500, manufactured by Tokyo Seisakusho K.K.).

The volume resistivity of the measurement sample after abrasion was calculated in the same manner as described above. The volume resistivity obtained was used as the volume resistivity of the photosensitive layer after abrasion.

In the electrophotographic photoreceptor of the exemplary embodiment, the ratio of the amount of the hole transporting material present on the front side of the photosensitive layer to the amount of the hole transporting material present on the back side of the photosensitive layer (the amount of the hole transporting material present on the front side of the photosensitive layer/the amount of the hole transporting material present on the back side of the photosensitive layer) is 1/6 or more and 1/3 or less, but from the viewpoint of high sensitivity and suppression of black dot generation, it is preferably 1.1/6 or more and 3/10 or less, and more preferably 1/5 or more and 1/4 or less.

The ratio of the amount of the hole transporting material present is controlled by the same method as the volume resistivity of the photosensitive layer before and after abrasion described above.

The "photosensitive layer front side" refers to a surface opposite to the conductive substrate, out of two surfaces facing each other in the thickness direction of the photosensitive layer. The "photosensitive layer back side" refers to a surface on the conductive substrate side out of two surfaces facing each other in the thickness direction of the photosensitive layer.

The amount of the hole transporting material present is measured as follows.

First, a sample of the photosensitive layer is collected from the photoreceptor to be measured as follows. A square of 0.5cm × 0.5cm was cut by cutting into the film with a single-edged knife so as to reach the substrate, and the film was naturally peeled off from the substrate in the square portion of 0.5cm × 0.5 cm. The peeled photosensitive layer sheet was used as a sample.

Next, fourier transform infrared analysis was performed on the front side surface of the photosensitive layer in the obtained sample by total reflection measurement (i.e., ATR method). Specifically, an infrared spectrometer (NiCOLET 6700FT-IR, manufactured by Thermo Fisher Co., Ltd.) was used as a measuring device, and in the measuring region: 650cm^-1～4000cm^-1Resolution ratio: 4cm^-1And the accumulated times: 32-order, refractive medium: ZnSe, depth of assay: the measurement was carried out under the condition of 2 μm.

From the infrared absorption spectrum on the front side of the photosensitive layer in the infrared absorption spectrum obtained by the above measurement, the areas of absorption peaks derived from the hole transporting material (for example, 680cm in the case where the hole transporting material is a hole transporting material having a benzidine skeleton^-1Above 720cm^-1The area of an absorption peak of the hole transport material appearing below) and the area of an absorption peak derived from the binder resin (for example, in the case where the binder resin is a polycarbonIn the case of the acid ester resin, at 1675cm^-11860cm above^-1C ═ the area of the absorption peak of the O bond derived from the binder resin appearing below), and the amount of the hole transporting material present on the positive side of the photosensitive layer was determined with (the above-mentioned peak area of the hole transporting material/the above-mentioned peak area of the resin) ═ the amount of the hole transporting material present.

On the other hand, the fourier transform infrared analysis was performed on the backside of the photosensitive layer in the obtained sample by the total reflection measurement method as described above, and the amount of the hole transporting material present on the backside of the photosensitive layer was determined.

Next, an electrophotographic photoreceptor of an exemplary embodiment will be described in detail with reference to the drawings.

Fig. 1 schematically shows a partial cross section of an electrophotographic photoreceptor 7 of an exemplary embodiment.

The electrophotographic photoreceptor 7 shown in fig. 1 is configured, for example, such that: the photosensitive layer comprises a conductive substrate 3, and a monolayer photosensitive layer 2 as an outermost layer is provided on the conductive substrate 3.

In addition, other layers may be provided as necessary. Examples of the other layer include an undercoat layer provided between the conductive substrate 3 and the monolayer type photosensitive layer 2, and a protective layer provided on the monolayer type photosensitive layer 2.

Hereinafter, each layer of the electrophotographic photoreceptor of the exemplary embodiment will be described in detail. In addition, the reference numerals are omitted for explanation.

(conductive substrate)

Examples of the conductive substrate include a metal plate, a metal drum, and a metal belt containing a metal (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, or the like) or an alloy (stainless steel or the like). Examples of the conductive substrate include paper, resin film, and tape coated, vapor-deposited, or laminated with a conductive compound (e.g., a conductive polymer, indium oxide, or the like), a metal (e.g., aluminum, palladium, gold, or the like), or an alloy. Wherein "electrically conductive" means having a volume resistivity of less than 10¹³Ω·cm。

In the case where the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened so that the center line average roughness Ra is 0.04 μm or more and 0.5 μm or less in order to suppress interference fringes generated when laser light is irradiated. In addition, in the case of using non-interference light in the light source, roughening for preventing interference fringes is not particularly necessary, but since roughening suppresses generation of defects due to surface irregularities of the conductive substrate, it is suitable to extend the life of the conductive substrate.

Examples of roughening methods include wet honing performed by suspending an abrasive in water and blowing the abrasive onto a support, centerless grinding in which a conductive base is pressed against a rotating grinding wheel and continuously subjected to grinding, anodizing treatment, and the like.

As a method of roughening, the following methods can be cited: instead of roughening the surface of the conductive substrate itself, a layer of a conductive or semiconductive powder is dispersed in a resin, the resin is formed on the surface of the conductive substrate, and the surface of the conductive substrate is roughened by particles dispersed in the layer.

The roughening treatment by anodic oxidation is to anodize a conductive substrate made of metal (for example, aluminum) in an electrolytic solution using the conductive substrate as an anode, thereby forming a porous anodic oxide film on the surface of the conductive substrate. Examples of the electrolyte solution include a sulfuric acid solution and an oxalic acid solution. However, the porous anodic oxide film formed by anodic oxidation is chemically active in such a state, and is easily contaminated, and the resistance fluctuation due to the environment is also large. Therefore, the following sealing treatment is preferably performed: the porous anodic oxide film is hydrated in pressurized steam or boiling water (a metal salt such as nickel may be added), and the micropores of the porous anodic oxide film are blocked by volume expansion due to the hydration reaction, thereby becoming a more stable hydrated oxide.

The thickness of the anodic oxide film is preferably 0.3 μm or more and 15 μm or less, for example. When the film thickness is within the above range, barrier properties against implantation tend to be exhibited, and an increase in residual potential due to repeated use tends to be suppressed.

The conductive substrate may be subjected to treatment with an acidic treatment solution or boehmite treatment.

The treatment with the acidic treatment solution 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 is in the range of 10 mass% to 11 mass%, chromic acid is in the range of 3 mass% to 5 mass%, hydrofluoric acid is in the range of 0.5 mass% to 2 mass%, and the concentration of the whole of these acids may be in the range of 13.5 mass% to 18 mass%. The treatment temperature is, for example, preferably 42 ℃ to 48 ℃. The film thickness of the coating film formed by the treatment with the acidic treatment liquid is preferably 0.3 μm or more and 15 μm or less.

The boehmite treatment is performed, for example, by immersing in pure water at 90 ℃ or higher and 100 ℃ or lower for 5 minutes to 60 minutes, or by contacting in heated steam at 90 ℃ or higher and 120 ℃ or lower for 5 minutes to 60 minutes. The film thickness of the coating film formed by boehmite treatment is preferably 0.1 μm or more and 5 μm or less. The boehmite-treated conductive substrate may be further subjected to anodic oxidation treatment using an electrolyte solution having low coating film solubility, such as a solution of adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, citrate, or the like.

(Single layer type photosensitive layer)

The monolayer type photosensitive layer contains a binder resin, a charge generating material, a hole transporting material and an electron transporting material. The monolayer type photosensitive layer may also contain other additives as needed. Hereinafter, each component contained in the monolayer type photosensitive layer will be described in detail.

Adhesive resin

The binder resin is not particularly limited, and examples thereof include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol resin, styrene-alkyd resin, poly-N-vinylcarbazole, polysilane, and the like.

These binder resins may be used alone or in combination of two or more.

Among the binder resins, polycarbonate resins and polyarylate resins are preferable.

In addition, from the viewpoint of film forming properties of the photosensitive layer, at least one of a polycarbonate resin having a viscosity average molecular weight of 30000 or more and 80000 or less and a polyarylate resin having a viscosity average molecular weight of 30000 or more and 80000 or less may be used.

The viscosity average molecular weights of the polycarbonate resin and the polyarylate resin are measured, for example, by the following methods. 1g of the resin was dissolved in 100cm³In dichloromethane of (2), the specific viscosity eta sp is measured by a Ubbelohde viscometer under the measuring environment of 25 ℃, and the relation eta sp/c is [ eta ] +0.45 [ eta ])²c (wherein c represents concentration (g/cm)³) Obtaining the intrinsic viscosity [ eta ] (cm)³G) according to the relation [ η ] given by h.schnell as 1.23 × 10^-4Mv^0.83The viscosity average molecular weight Mv was determined.

As the binder resin, a polycarbonate resin containing at least one of a structural unit represented by the following general formula (PCA) and a structural unit represented by the following general formula (PCB) is particularly preferable.

In the formulae (PCA) and (PCB), R^P1、R^P2、R^P3And R^P4Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms or an aryl group having 6 to 12 carbon atoms. X^P1Represents phenylene, biphenylene, naphthylene, alkylene or cycloalkylene.

In the general formulae (PCA) and (PCB),as R^P1、R^P2、R^P3And R^P4Examples of the alkyl group include linear or branched alkyl groups having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms).

Specific examples of the linear alkyl group include a methyl group, an ethyl group, a n-propyl group, a n-butyl group, a n-pentyl group, and a n-hexyl group.

Specific examples of the branched alkyl group include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, and a tert-hexyl group.

Among them, lower alkyl groups such as methyl and ethyl are preferable as the alkyl group.

In the formulae (PCA) and (PCB), as R^P1、R^P2、R^P3And R^P4As the cycloalkyl group, for example, cyclopentyl, cyclohexyl and cycloheptyl can be exemplified.

In the formulae (PCA) and (PCB), as R^P1、R^P2、R^P3And R^P4Examples of the aryl group include phenyl, naphthyl and biphenyl.

In the formulae (PCA) and (PCB), as X^P1Examples of the alkylene group include linear or branched alkylene groups having 1 to 12 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms).

Specific examples of the linear alkylene group include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, an n-nonylene group, an n-decylene group, an n-undecylene group, and an n-dodecylene group.

Specific examples of the branched alkylene group include isopropylene, isobutylene, sec-butylene, tert-butylene, isopentylene, neopentylene, tert-pentylene, isohexylene, sec-hexylene, tert-hexylene, isoheptylene, sec-heptylene, tert-heptylene, isooctylene, sec-octylene, tert-octylene, isononyl, sec-nonylene, tert-nonylene, isodecylene, sec-decylene, tert-decylene, isoundecylene, sec-undecylene, tert-undecylene, neoundecylene, isododecylene, sec-dodecylene, tert-dodecylene and neododecylene.

Among them, lower alkyl groups such as methylene, ethylene and butylene are preferable as the alkylene group.

In the formulae (PCA) and (PCB), as X^P1The cycloalkylene group represented by (a) includes cycloalkylene groups having 3 to 12 carbon atoms (preferably 3 to 10 carbon atoms, and more preferably 5 to 8 carbon atoms).

Specific examples of the cycloalkylene group include cyclopropylene group, cyclopentylene group, cyclohexylene group, cyclooctylene group, cyclododecylene group and the like.

Among them, as the cycloalkylene group, a cyclohexylene group is preferable.

In the general formulae (PCA) and (PCB), R^P1、R^P2、R^P3And R^P4The above-mentioned substituents also include groups having substituents. Examples of the substituent include a halogen atom (e.g., fluorine atom and chlorine atom), an alkyl group (e.g., an alkyl group having 1 to 6 carbon atoms), a cycloalkyl group (e.g., a cycloalkyl group having 5 to 7 carbon atoms), an alkoxy group (e.g., an alkoxy group having 1 to 4 carbon atoms), and an aryl group (e.g., phenyl, naphthyl, biphenyl).

In the general formula (PCA), R is preferred^P1And R^P2Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R is more preferably^P1And R^P2Represents a hydrogen atom.

In the general formula (PCB), R is preferred^P3And R^P4Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and X^P1Represents an alkylene group or a cycloalkylene group.

Specific examples of the structural unit represented by the general formula (PCA) and the structural unit represented by the general formula (PCB) include, but are not limited to, the following structural units.

As the binder resin, a polycarbonate resin containing both a structural unit represented by the general formula (PCA) and a structural unit represented by the general formula (PCB) is more preferable.

Specific examples of the polycarbonate resin containing both a structural unit represented by the general formula (PCA) and a structural unit represented by the general formula (PCB) include, but are not limited to, the following exemplified compounds. In the exemplified compounds, pm and pn represent copolymerization ratios.

(PC-1)

(PC-2)

(PC-3)

Among these, in the polycarbonate resin containing both the structural unit represented by the general formula (PCA) and the structural unit represented by the general formula (PCB), the content (copolymerization ratio) of the structural unit represented by the general formula (PCA) may be in the range of 5 mol% or more and 95 mol% or less with respect to the entire structural units constituting the polycarbonate resin, and from the viewpoint of improving the abrasion resistance of the photosensitive layer (charge transport layer), a range of 5 mol% or more and 50 mol% or less is preferable, and a range of 15 mol% or more and 30 mol% or less is more preferable.

Specifically, in the above-mentioned exemplary compounds of the polycarbonate resin, pm and pn represent copolymerization ratios (molar ratios), and pm: pn 95: 5-5: range of 95, 50: 50-5: 95, more preferably 15: 85-30: 70, or less.

In the case where a polycarbonate resin containing at least one of a structural unit represented by the general formula (PCA) and a structural unit represented by the general formula (PCB) is used in combination with another binder resin, the content of the other binder resin may be 10% by mass or less (preferably 5% by mass or less) with respect to the entire binder resin.

The content of the binder resin may be 35% by mass or more and 60% by mass or less, preferably 40% by mass or more and 55% by mass or less, with respect to the total solid content of the photosensitive layer.

Charge generation material

As the charge generating material, there can be mentioned: azo pigments such as disazo and trisazo pigments; fused ring aromatic pigments such as dibromoanthanthrone; perylene pigments; a pyrrolopyrrole pigment; phthalocyanine pigments; zinc oxide; trigonal selenium, and the like.

Among them, in order to cope with laser exposure in the near infrared region, a metal phthalocyanine pigment or a metal-free phthalocyanine pigment is preferably used as the charge generating material. Specifically, for example, more preferred are: hydroxygallium phthalocyanines disclosed in Japanese patent laid-open Nos. 5-263007 and 5-279591; chlorogallium phthalocyanine disclosed in Japanese patent laid-open No. 5-98181 and the like; dichlorotin phthalocyanines disclosed in Japanese patent laid-open Nos. 5-140472 and 5-140473; oxytitanium phthalocyanine disclosed in Japanese patent laid-open publication No. 4-189873 and the like.

On the other hand, in order to cope with laser exposure in the near ultraviolet region, as the charge generating material, preferred are: fused ring aromatic pigments such as dibromoanthanthrone; thioindigo pigments; a porphyrazine compound; zinc oxide; trigonal selenium; and disazo pigments disclosed in Japanese patent laid-open Nos. 2004-78147 and 2005-181992.

That is, as the charge generating material, for example, an inorganic pigment is preferable in the case of using a light source having an exposure wavelength of 380nm to 500nm, and a metal or metal-free phthalocyanine pigment is preferable in the case of using a light source having an exposure wavelength of 700nm to 800 nm.

Among these, as the charge generating material, at least one selected from the group consisting of hydroxygallium phthalocyanine pigments and chlorogallium phthalocyanine pigments is preferable, and hydroxygallium phthalocyanine pigments are more preferable, from the viewpoint of increasing the sensitivity of the single-layer type photoreceptor.

The hydroxygallium phthalocyanine pigment is not particularly limited, and a V-type hydroxygallium phthalocyanine pigment can be used.

In particular, the hydroxygallium phthalocyanine pigment is preferably a hydroxygallium phthalocyanine pigment having a maximum peak wavelength in a wavelength range of 810nm or more and 839nm or less in an absorption spectrum in a wavelength range of 600nm or more and 900nm or less, for example, from the viewpoint of obtaining more excellent dispersibility. When used as a material for an electrophotographic photoreceptor, excellent dispersibility, sufficient sensitivity, chargeability, and dark decay characteristics are easily obtained.

The above hydroxygallium phthalocyanine pigment having a maximum peak wavelength in the range of 810nm to 839nm is preferably one having an average particle diameter in a specific range and a BET specific surface area in a specific range. Specifically, the average particle diameter is preferably 0.20 μm or less, more preferably 0.01 μm or more and 0.15 μm or less, and the BET specific surface area is preferably 45m²A value of at least 50 m/g, more preferably²A specific ratio of the total amount of the components is 55m or more²More than 120 m/g²The ratio of the carbon atoms to the carbon atoms is less than g. The average particle diameter is a volume average particle diameter (d50 average particle diameter) and is measured by a laser diffraction scattering particle size distribution measuring apparatus (LA-700, manufactured by horiba Seisakusho Co., Ltd.). The BET specific surface area is a value measured by a nitrogen substitution method using a BET specific surface area measuring instrument (FlowSorb II2300, manufactured by Shimadzu corporation).

Wherein the average particle diameter is more than 0.20 μm or the specific surface area is less than 45m²In the case of the solid-state image sensor,/g, the pigment particles tend to be coarsened or aggregates of the pigment particles are formed, and defects tend to be easily generated in the characteristics such as dispersibility, sensitivity, chargeability, and dark decay characteristics, whereby image quality defects are easily generated in some cases.

The maximum particle diameter (maximum value of primary particle diameter) of the hydroxygallium phthalocyanine pigment is preferably 1.2 μm or less, more preferably 1.0 μm or less, and still more preferably 0.3 μm or less. When the maximum particle diameter exceeds the above range, black spots are easily generated.

From the viewpoint of suppressing concentration unevenness caused by exposure of the photoreceptor to a fluorescent lamp or the like, it is preferable that the hydroxygallium phthalocyanine pigment has an average particle diameter of 0.2 μm or less, a maximum particle diameter of 1.2 μm or less, and a specific surface area value of 45m²/gThe above.

The hydroxygallium phthalocyanine pigment is preferably of the form V, which has diffraction peaks at bragg angles (2 θ ± 0.2 °) of at least 7.3 °, 16.0 °, 24.9 ° and 28.0 ° in an X-ray diffraction spectrum using CuK α characteristic X-rays.

On the other hand, as the chlorogallium phthalocyanine pigment, preferred is a chlorogallium phthalocyanine pigment which can obtain excellent sensitivity as an electrophotographic photoreceptor material and has diffraction peaks at bragg angles (2 θ ± 0.2 °) of 7.4 °, 16.6 °, 25.5 ° and 28.3 °.

In addition, the maximum peak wavelength, average particle diameter, maximum particle diameter and specific surface area value of the chlorogallium phthalocyanine pigment in an appropriate absorption spectrum are the same as those of the hydroxygallium phthalocyanine pigment.

The content of the charge generating material may be 1 mass% or more and 5 mass% or less, preferably 1.2 mass% or more and 4.5 mass% or less, with respect to the total solid content of the photosensitive layer.

Hole transport material

The hole-transporting material is not particularly limited, and examples thereof include the following: oxadiazole derivatives such as 2, 5-bis (p-diethylaminophenyl) -1,3, 4-oxadiazole; pyrazoline derivatives such as 1,3, 5-triphenyl-pyrazoline and 1- [ pyridyl- (2) ] -3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline; aromatic tertiary amino compounds such as triphenylamine, N' -bis (3, 4-dimethylphenyl) biphenyl-4-amine, tris (p-methylphenyl) amino-4-amine, and dibenzylaniline; aromatic tertiary diamino compounds such as N, N '-bis (3-methylphenyl) -N, N' -diphenylbenzidine; 1,2, 4-triazine derivatives such as 3- (4 '-dimethylaminophenyl) -5, 6-bis- (4' -methoxyphenyl) -1,2, 4-triazine; hydrazone derivatives such as 4-diethylaminobenzaldehyde-1, 1-diphenylhydrazone; quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline; benzofuran derivatives such as 6-hydroxy-2, 3-bis (p-methoxyphenyl) benzofuran; α -stilbene derivatives such as p- (2, 2-diphenylvinyl) -N, N-diphenylaniline; an enamine derivative; carbazole derivatives such as N-ethylcarbazole; poly-N-vinylcarbazole and its derivatives, and the like; and a polymer having a group composed of the above compound in a main chain or a side chain. One kind of these hole transport materials may be used, or two or more kinds may be used in combination.

Among them, as the hole transporting material, a triarylamine-based hole transporting material represented by the following general formula (HT1) and a hole transporting material having a benzidine skeleton described later can be suitably exemplified.

(triarylamine-based hole transport material)

In the general formula (HT1), Ar^T1、Ar^T2And Ar^T3Each independently represents aryl or-C₆H₄-C(R^T4)＝C(R^T5)(R^T6)。R^T4、R^T5And R^T6Each independently represents a hydrogen atom, an alkyl group or an aryl group. R^T5And R^T6Or may be bonded to form a hydrocarbon ring structure.

In the general formula (HT1), as Ar^T1、Ar^T2And Ar^T3Examples of the aryl group include aryl groups having 6 to 15 (preferably 6 to 9, more preferably 6 to 8) carbon atoms.

Specific examples of the aryl group include a phenyl group, a naphthyl group, and a fluorenyl group.

Among them, as the aryl group, a phenyl group is preferable.

In the general formula (HT1), as R^T4、R^T5And R^T6Alkyl group represented by the formula (HT1a) with R in the general formula (HT1a) described later^C21、R^C22And R^C23The alkyl groups are represented by the same examples, and the preferred ranges are also the same.

In the general formula (HT1), as R^T4、R^T5And R^T6Aryl of formula (I), with Ar^T1、Ar^T2And Ar^T3The aryl groups are represented by the same examples, and the preferred ranges are also the same.

In addition, in the general formula (HT1), Ar^T1、Ar^T2And Ar^T3And R^T4、R^T5And R^T6The above-mentioned substituents also include groups having substituents. As a replacement forExamples of the group include a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and an aryl group having 6 to 10 carbon atoms. Further, as the substituent of each of the above substituents, there may be mentioned a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

The triarylamine-based hole transport material (HT1) may be used alone or in combination of two or more.

Among them, triarylamine-based hole transport materials represented by the general formula (HT1), particularly those having — "C", are preferable from the viewpoint of charge mobility₆H₄-C(R^T4)＝C(R^T5)(R^T6) The triarylamine-based hole transport material of (1). Among these, triarylamine-based hole-transporting materials represented by specific examples (HT1-4) of triarylamine-based hole-transporting materials (HT1) described later are preferable.

(Biphenylamine-based hole transport Material)

In particular, from the viewpoint of controlling the volume resistivity of the photosensitive layer before and after the abrasion and the presence amount ratio of the electron transporting material, having high sensitivity, and suppressing the generation of black spots, a hole transporting material having a benzidine skeleton is preferable as the hole transporting material. As the hole transporting material having a benzidine skeleton, a benzidine-based hole transporting material represented by the following general formula (HT1a) is more preferable.

In the general formula (HT1a), R^C21、R^C22And R^C23Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms.

In the general formula (HT1a), as R^C21、R^C22And R^C23Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like. Among these, as the halogen atom, a fluorine atom and a chlorine atom are preferable, and a chlorine atom is more preferable.

In the general formula (HT1a), as R^C21、R^C22And R^C23Examples of the alkyl group include linear or branched alkyl groups having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms).

Specific examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group.

Specific examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, 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, and tert-decyl group.

Among them, lower alkyl groups such as methyl, ethyl and isopropyl are preferable as the alkyl group.

In the general formula (HT1a), as R^C21、R^C22And R^C23Examples of the alkoxy group include linear or branched alkoxy groups having 1 to 10 (preferably 1 to 6, more preferably 1 to 4) carbon atoms.

Specific examples of the linear alkoxy group include a methoxy group, an ethoxy group, a n-propoxy group, a n-butoxy group, a n-pentoxy group, a n-hexoxy group, a n-heptoxy group, a n-octoxy group, a n-nonoxy group, and a n-decoxy group.

Specific examples of the branched alkoxy group include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, a tert-hexyloxy group, an isoheptylyl group, a sec-heptyloxy group, a tert-heptyloxy group, an isooctyloxy group, a sec-octyloxy group, a tert-octyloxy group, an isononyloxy group, a sec-nonyloxy group, a tert-nonyloxy group, an isodecyloxy group, a sec-decyloxy group and a tert-decyloxy group.

Among them, the alkoxy group is preferably a methoxy group.

In the general formula (HT1a), as R^C21、R^C22And R^C23Examples of the aryl group include aryl groups having 6 to 10 (preferably 6 to 9, more preferably 6 to 8) carbon atoms.

Specific examples of the aryl group include a phenyl group and a naphthyl group.

Among them, as the aryl group, a phenyl group is preferable.

In the general formula (HT1a), R^C21、R^C22And R^C23The above-mentioned substituents also include groups having substituents. Examples of the substituent include the above-exemplified atoms and groups (e.g., halogen atom, alkyl group, alkoxy group, aryl group, etc.).

The biphenylamine-based hole transporting material represented by the general formula (HT1a) may be used alone or in combination of two or more.

Specific examples (HT1-1) to (HT1-10) of the triarylamine-based hole transporting material (HT1) and the biphenylamine-based hole transporting material (HT1a) are shown below, but the triarylamine-based hole transporting material (HT1) and the biphenylamine-based hole transporting material (HT1a) are not limited thereto.

From the viewpoint of high sensitivity and black dot generation suppression, the content of the hole transporting material may be 20 mass% or more and 45 mass% or less, preferably 34 mass% or more and 44 mass% or less, more preferably 38 mass% or more and 44 mass% or less, and further preferably 38 mass% or more and 42 mass% or less, with respect to the total solid content of the photosensitive layer.

Further, from the viewpoint of high sensitivity and suppression of black dot generation, the mass ratio of the hole transporting material to the electron transporting material (hole transporting material/electron transporting material) is preferably 19/5 or more and 28/5 or less, more preferably 20/5 or more and 26/5 or less, and further preferably 21/5 or more and 24/5 or less.

Electron transport material

The electron transport material is not particularly limited, and examples thereof include the following: quinone compounds such as chloranil and bromoquinone; tetracyanoquinodimethanes; fluorenone compounds such as 2,4, 7-trinitro-9-fluorenone, 2,4, 5, 7-tetranitro-9-fluorenone, and octyl 9-dicyanomethylene-9-fluorenone-4-carboxylate; oxadiazole compounds such as 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3, 4-oxadiazole, 2, 5-bis (4-naphthyl) -1,3, 4-oxadiazole, and 2, 5-bis (4-diethylaminophenyl) 1,3, 4-oxadiazole; xanthone compounds; a thiophene compound; dinaphthoquinones such as 3, 3' -di-tert-amyl-dinaphthoquinone; diphenoquinone compounds such as 3, 3 ' -di-tert-butyl-5, 5 ' -dimethyldiphenoquinone and 3, 3 ', 5, 5 ' -tetra-tert-butyl-4, 4' -diphenoquinone; and a polymer having a group composed of the above compound in a main chain or a side chain. These electron transport materials may be used alone or in combination of two or more.

Among them, from the viewpoint of controlling the volume resistivity of the photosensitive layer before and after the abrasion and the existing amount ratio of the electron transporting material, having high sensitivity and suppressing the generation of black spots, as the electron transporting material, an electron transporting material having a diphenoquinone skeleton is preferable, and an electron transporting material represented by the following general Formula (FK) is more preferable.

In the general Formula (FK), R^k1～R^k4Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group.

In addition, R^k1Preferably with R^k2～R^k4At least any one of the different groups.

From the viewpoint of suppressing cracking of the photosensitive layer due to crystallization of the electron transporting material, R^k1And R^k3Each independently preferably an alkyl group having 3 to 12 carbon atoms, an alkoxy group having 3 to 12 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group, more preferably a branched alkyl group having 3 to 12 carbon atoms or a branched alkyl group having 3 to 12 carbon atomsA branched alkoxy group, a cycloalkyl group, an aryl group or an aralkyl group, more preferably a branched alkyl group having 3 to 8 carbon atoms or a branched alkoxy group having 3 to 8 carbon atoms, and particularly preferably a tert-butyl group.

Furthermore, R^k1And R^k3Preferably the same groups.

R^k2And R^k4Each independently of the other, is preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a linear alkoxy group having 1 to 4 carbon atoms, still more preferably a linear alkyl group having 1 to 3 carbon atoms, or a linear alkoxy group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

R^k2And R^k4Preferably the same groups.

Further, R^k1And R^k2Preferably different radicals, and additionally, R^k3And R^k4Preferably different groups.

Hereinafter, R illustrating an electron transporting material represented by the general Formula (FK) is shown^k1～R^k4The electron transporting material represented by the general Formula (FK) is not limited to the exemplary compounds 1 to 7. In addition, the exemplified compound represented by the following number is also expressed as "exemplified compound (1-number)". Specifically, for example, "exemplary compound 5" is also expressed as "exemplary compound (1-5)".

Illustrative Compounds	Rk1	Rk2	Rk3	Rk4
					1	t-C4H9	CH3	t-C4H9	CH3
2	t-C4H9	H	t-C4H9	H
					3	t-C4H9	CH3O	t-C4H9	CH3O
4	t-C4H9O	CH3	t-C4H9O	CH3
					5	c-C6H11	CH3	c-C6H11	CH3
6	C6H5	CH3	C6H5	CH3
					7	C6H5CH2	CH3	C6H5CH2	CH3

In addition, abbreviations and the like in the above exemplified compounds represent the following meanings.

·t-C₄H₉: tert-butyl radical

·CH₃O: methoxy radical

·t-C₄H₉O: tert-butoxy radical

·c-C₆H₁₁: cyclohexyl radical

·C₆H₅: phenyl radical

·C₆H₅CH₂: benzyl radical

The content of the electron transporting material is preferably 4 mass% or more and 20 mass% or less, more preferably 6 mass% or more and 18 mass% or less, and further preferably 8 mass% or more and 16 mass% or less, with respect to the total solid content of the photosensitive layer.

Other additives

The monolayer type photosensitive layer may contain other known additives such as an antioxidant, a light stabilizer and a heat stabilizer. Further, when the monolayer type photosensitive layer is a surface layer, fluorine resin particles, silicone oil, and the like may be contained.

Formation of monolayer type photosensitive layer

The monolayer photosensitive layer is formed using a photosensitive layer-forming coating liquid prepared by adding the above components to a solvent.

Examples of the solvent include common organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and dichloroethane, and cyclic or linear ethers such as tetrahydrofuran and diethyl ether. These solvents are used alone or in combination of two or more.

As a method of dispersing particles (for example, a charge generating material) in the coating liquid for photosensitive layer formation, a media disperser such as a ball mill, a vibration ball mill, an attritor, a sand mill, and a horizontal sand mill, an inorganic media disperser such as a stirrer, an ultrasonic disperser, a roll mill, and a high-pressure homogenizer, and the like can be used. Examples of the high-pressure homogenizer include a collision type in which a dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high-pressure state, and a penetration type in which a dispersion liquid is dispersed through a fine flow path in a high-pressure state.

Examples of the method of applying the coating liquid for forming a photosensitive layer to the undercoat layer include a dip coating method, an extrusion coating method, a wire bar coating method, a spray coating method, a blade coating method, a curtain coating method, and the like.

The film thickness of the single-layer photosensitive layer is set as follows: preferably 5 to 60 μm, more preferably 5 to 50 μm, and still more preferably 10 to 40 μm.

[ IMAGE FORMING APPARATUS (AND PROCESS CARTRIDGE) ]

An image forming apparatus according to an exemplary embodiment includes: an electrophotographic photoreceptor; a charging unit that charges a surface of the electrophotographic photoreceptor; an electrostatic latent image forming unit that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing unit that develops an electrostatic latent image formed on a surface of the electrophotographic photoconductor with a developer containing a toner to form a toner image; and a transfer unit that transfers the toner image to a surface of the recording medium. Further, as the electrophotographic photoreceptor, the electrophotographic photoreceptor of the above-described exemplary embodiment may be applied.

The image forming apparatus of the exemplary embodiment can be applied to known image forming apparatuses such as: a device including a fixing unit that fixes the toner image transferred to the surface of the recording medium; a direct transfer type device that directly transfers a toner image formed on a surface of an electrophotographic photoreceptor to a recording medium; an intermediate transfer type device that primarily transfers a toner image formed on a surface of an electrophotographic photoreceptor to a surface of an intermediate transfer body, and secondarily transfers the toner image transferred to the surface of the intermediate transfer body to a surface of a recording medium; a device provided with a cleaning unit that cleans the surface of the electrophotographic photoreceptor after the transfer of the toner image and before charging; a device provided with a charge erasing unit that irradiates the surface of the electrophotographic photoconductor with a charge erasing beam to erase charges after transferring the toner image and before charging; and an apparatus provided with an electrophotographic photoreceptor heating member for raising the temperature of the electrophotographic photoreceptor and reducing the relative humidity.

For the intermediate transfer type apparatus, the transfer unit can be applied, for example, a structure having: an intermediate transfer body that transfers the toner image on a surface; a primary transfer unit that primarily transfers a toner image formed on a surface of the electrophotographic photoreceptor to a surface of the intermediate transfer body; and a secondary transfer unit that secondarily transfers the toner image transferred to the surface of the intermediate transfer body to a surface of a recording medium.

The image forming apparatus of the exemplary embodiment may be any one of a dry development type image forming apparatus and a wet development type (development type using a liquid developer) image forming apparatus.

In the image forming apparatus of the exemplary embodiment, for example, the portion provided with the electrophotographic photoreceptor may be a cartridge structure (process cartridge) that is attachable to and detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge provided with the electrophotographic photoreceptor of the exemplary embodiment can be suitably used. In addition, the process cartridge may further include at least one selected from a charging unit, an electrostatic latent image forming unit, a developing unit, and a transferring unit, in addition to the electrophotographic photoreceptor.

An example of the image forming apparatus of the exemplary embodiment will be described below, but is not limited thereto. In addition, main portions shown in the drawings will be described, and descriptions of other portions will be omitted.

Fig. 2 is a schematic configuration diagram showing an example of an image forming apparatus of the exemplary embodiment.

As shown in fig. 2, the image forming apparatus 100 according to the exemplary embodiment includes: a process cartridge 300 provided with an electrophotographic photoreceptor 7; an exposure device 9 (an example of an electrostatic latent image forming unit); and a transfer device 40 (an example of a transfer unit). In the image forming apparatus 100, the exposure device 9 is disposed at a position where the electrophotographic photoreceptor 7 can be exposed from the opening of the process cartridge 300, and the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 through the recording medium transport belt 50.

The process cartridge 300 in fig. 2 integrally supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging unit), a developing device 11 (an example of a developing unit), and a cleaning device 13 (an example of a cleaning unit) in a casing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is provided so as to contact the surface of the electrophotographic photoreceptor 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. 2, an example in which a fibrous member 132 (roller-shaped) for supplying the lubricant 14 to the surface of the electrophotographic photoreceptor 7 and a fibrous member 133 (flat brush-shaped) for assisting cleaning are provided as the image forming apparatus is shown, but these components may be arranged as needed.

The respective components of the image forming apparatus of the exemplary embodiment will be explained below.

Charging device

As the charging device 8, a contact type charger using, for example, a conductive or semiconductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, or the like can be used. Further, a non-contact type roller charger, a grid corotron charger using corona discharge, a corotron charger, and the like known per se may be used.

Exposure device

The exposure device 9 may be, for example, an optical system device that exposes the surface of the electrophotographic photoreceptor 7 to a specific image by light such as semiconductor laser light, LED light, and liquid crystal shutter light. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. As the wavelength of the semiconductor laser, near infrared rays having an oscillation wavelength of around 780nm are mainly used. However, the wavelength is not limited to this, and a laser having an oscillation wavelength of the order of 600nm or a blue laser having an oscillation wavelength of 400nm to 450nm may be used. In addition, a surface-emission type laser light source of a type capable of outputting a plurality of light beams to form a color image is also useful.

Developing device

As the developing device 11, for example, a general developing device that performs development with or without contact with a developer is cited. The developing device 11 is not particularly limited as long as it has the above-described functions, and may be selected according to the purpose. Examples thereof include a known developing device having a function of attaching a single component type developer or a two component type developer to the electrophotographic photosensitive member 7 with a brush, a roller, or the like. Among them, the following developing devices are preferable: the developing device uses a developing roller that carries a developer on a surface.

The developer used in the developing device 11 may be a one-component developer composed only of toner, or may be a two-component developer including toner and carrier. Further, the developer may be magnetic or non-magnetic. Known developers can be used for these developers.

Cleaning device

The cleaning device 13 may be a cleaning blade type device provided with a cleaning blade 131.

In addition, a brush cleaning type and a simultaneous development cleaning type may be employed in addition to the cleaning blade type.

Transfer printing device

Examples of the transfer device 40 include a contact type transfer charger using a belt, a roller, a film, a rubber blade, and the like, and a transfer charger known per se such as a scorotron transfer charger and a corotron transfer charger using corona discharge.

Recording medium transport belt

As the recording medium transport belt 50, a belt-shaped recording medium transport belt (intermediate transfer belt) containing polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, or the like, to which semiconductivity is applied, can be cited.

Fig. 3 is a schematic configuration diagram showing another example of the image forming apparatus of the exemplary embodiment.

The image forming apparatus 120 shown in fig. 3 is a tandem multicolor image forming apparatus having four process cartridges 300 mounted thereon. In the image forming apparatus 120, four process cartridges 300 are arranged side by side on the intermediate transfer body 50, and a structure in which one electrophotographic photoreceptor is used for one color is made. Image forming apparatus 120 has the same configuration as image forming apparatus 100, except for the tandem system.

Among them, in the image forming apparatus of the exemplary embodiment, in the case where the image forming apparatus is provided with a direct transfer type transfer unit including a transfer member that directly transfers the toner image from the electrophotographic photoreceptor to the surface of the recording medium, it is preferable that a relationship among the rotation speed P (mm/s) of the electrophotographic photoreceptor, the transfer current value I (μ a) for directly transferring the toner image from the electrophotographic photoreceptor to the surface of the recording medium, and the length l (mm) of the transfer member satisfies the following expression (PIL).

Formula (PIL): -1.07X 10^-3≤I/(P×L)≤-4.30×10^-4

The I/(P × L) value represents the amount of charge theoretically received by the electrophotographic photoreceptor from the transfer member at the time of direct transfer.

The rotation speed P of the electrophotographic photoreceptor is a moving amount (also referred to as "process speed") per unit time (1 second) that the surface of the electrophotographic photoreceptor moves in the circumferential direction.

The transfer current value is a current value applied to the transfer member when the toner image is directly transferred from the electrophotographic photoreceptor to the surface of the recording medium.

The length of the transfer member is a length in a direction along the axial direction of the electrophotographic photoreceptor in a region opposed to the photosensitive layer of the electrophotographic photoreceptor.

In addition, the transfer member may be a contact type transfer member such as a transfer roller.

When the electrophotographic photoreceptor of the above-described exemplary embodiment is applied and directly transferred under the condition that the I/(P × L) value is within the above-described range, excessive charge injection from the transfer member to the electrophotographic photoreceptor at the time of transfer can be suppressed, thereby suppressing the image portion in the previous image from floating a shallow negative ghost, and insufficient charge injection from the transfer member to the electrophotographic photoreceptor at the time of transfer can be suppressed, thereby suppressing the image portion in the previous image from floating a deep negative ghost. Thereby, ghost (afterimage phenomenon due to hysteresis remaining of a previous image) can be suppressed from the initial stage to the end of the life of the electrophotographic photoreceptor.

From the viewpoint of ghost suppression, the value of I/(P.times.L) is more preferably-8.60X 10^-4Above and-3.43X 10^-4Hereinafter, more preferably-6.40X 10^-4Above and-4.30X 10^-4The following.

[ examples ] A method for producing a compound

The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples. In addition, "part" means "part by mass" and "%" means "% by mass" unless otherwise specified.

< examples 1 to 17 and comparative examples 1 to 7>

Preparation of coating liquid for Forming photosensitive layer

A mixture of a bisphenol Z polycarbonate resin (polycarbonate resin represented by the above formula PC-1, pm: 25, pn: 75, viscosity average molecular weight 5 ten thousand), a charge generating material (CGM in Table 1), a Hole Transporting Material (HTM) in Table 1, an electron transporting material (ETM in Table 1), and tetrahydrofuran in amounts of the solid content concentrations shown in Table 1 was dispersed with a high-pressure homogenizer to obtain a coating liquid for forming a photosensitive layer.

Formation of photosensitive layer

An aluminum substrate having a diameter of 30mm, a length of 244.5mm and a thickness of 1mm was prepared as a conductive substrate.

Subsequently, under the photosensitive layer formation conditions shown in table 1, a coating liquid for photosensitive layer formation was applied by a dip coating method onto an aluminum substrate, followed by drying and curing, thereby forming a single-layer photosensitive layer having a thickness of 30 μm on the aluminum substrate.

Thus, photoreceptors of respective examples were obtained.

< characteristics >

The following characteristics of the photoreceptor in each example were measured in accordance with the methods described above.

When the ratio of the thickness of the photosensitive layer after abrasion to the thickness of the photosensitive layer before abrasion (thickness of the photosensitive layer after abrasion/thickness of the photosensitive layer before abrasion) was 0.8, the volume resistivity of the photosensitive layer after abrasion was determined to be

Volume resistivity of the sensitive layer before abrasion

The ratio of the amount of electron transporting material present on the front side of the photosensitive layer to the amount of electron transporting material present on the back side of the photosensitive layer (in the table, referred to as "ETM present ratio between the front side and the back side of the photosensitive layer")

< evaluation >

The following evaluations were carried out using the photoreceptors of the respective examples.

(evaluation of chargeability)

The surface potential after 0.5 second of positive charging by corona discharge of 6.0kV was measured using an electrostatic copying paper testing apparatus (electrostatic analyzer EPA8100, manufactured by kaikou motor).

The chargeability was evaluated to be good when the surface potential was 780V or more.

(evaluation of sensitivity)

Feeling of photoreceptorThe luminosity was evaluated at half-subtracted amount when charged to + 800V. Specifically, after charging to +800V at 20 ℃ and 40% RH using an electrostatic transfer paper testing apparatus (EPA 8100 manufactured by Chuankou Motor), light from a tungsten lamp was converted to 780nm monochromatic light using a monochromator, and the converted light was adjusted to 1 μ W/cm on the surface of a photoreceptor²The irradiation is performed.

Then, the surface potential V0(V) of the photoreceptor surface immediately after charging and the half exposure E at which the surface potential became 1/2V 0(V) by light irradiation of the photoreceptor surface were measured_1/2(μJ/cm²)。

Further, the sensitivity was 0.15. mu.J/cm²The following half exposure dose was evaluated as high sensitivity.

(evaluation of Black Point)

Evaluation of black dots was carried out by printing 30000 sheets of an image specified in ISO/IEC19752 on A4 paper at 30 ℃ and 80% RH under high temperature and high humidity conditions using HL5340D manufactured by Brother corporation, then printing a 50% halftone image, and evaluating the black dots of the image according to the following criteria.

In addition, in the case of evaluation 3, a problem occurs in practical use.

Evaluation criteria

1: no black spot

2: having black spots but in a range without problems

3: have black spots and are in a range that may become a problem

(evaluation of ghost)

The photoreceptor in each example was mounted on an image forming apparatus "HL-L5200 DW (direct transfer type apparatus having a transfer roller with a length L of 235 mm) manufactured by Brother company".

Then, the transfer conditions of the process speed and the transfer current value were set to the conditions of the transfer condition 1+3, the transfer condition 2+3, the transfer condition 1+4, and the transfer condition 2+4 shown in table 3, respectively, and image formation was performed as follows.

A20 mm × 20mm image having an image density of 100% was output under a high temperature and high humidity condition of 32.5 ℃ and 80% RH, and an A4 full-area halftone 30% image was continuously output, and the density fluctuation in the halftone after one week of the photoreceptor was visually evaluated.

Then, the occurrence of ghosting of the tenth printed matter (labeled "initial ghosting" in the table), and ghosting of the 500000 printed matter (labeled "50 kpv post ghosting" in the table) was evaluated according to the following criteria.

In the ghost column in table 3, the expression of numerical value/numerical value means the evaluation result of transfer condition 1+ 3/the evaluation result of transfer condition 2+ 3/the evaluation result of transfer condition 1+ 4/the evaluation result of transfer condition 2+ 4. The image output section with an image density of 100% shows 1 to 3 when the density becomes darker and-1 to-3 when the density becomes lighter in the A4 halftone section 30% image.

Evaluation criteria

3: has obvious density variation and cannot be tolerated in image quality

2: has concentration variation and no problem in practical use

1: slightly varied in concentration and practically used without problems

0: no concentration variation

-1: slightly varied in concentration and practically used without problems

-2: has concentration variation and no problem in practical use

-3: has obvious density variation and cannot be tolerated in image quality

[ TABLE 1 ]

*1: the content (mass%) of the hole transport material with respect to the total solid content of the photosensitive layer

[ TABLE 2 ]

[ TABLE 3 ]

From the above results, it is understood that the photoreceptor of the present example has high sensitivity and suppresses the generation of black dots, as compared with the photoreceptor of the comparative example.

Further, the photoreceptor of the present example was also found to have good chargeability.

Further, it is also found that when an image is formed by the direct transfer type image forming apparatus including the photoreceptor of the present embodiment under the condition that the formula (PIL) is satisfied, the occurrence of ghost can be suppressed from the initial stage to the end of the life of the photoreceptor.

In addition, the abbreviations in table 1 refer to the following compounds.

Charge generation material

CGM-A: hydroxygallium phthalocyanine form V. An X-ray diffraction spectrum obtained using CuK alpha characteristic X-rays has diffraction peaks at Bragg angles (2 theta + -0.2 DEG) of at least 7.3 DEG, 16.0 DEG, 24.9 DEG and 28.0 deg. The maximum peak wavelength in the absorption spectrum of 600nm to 900nm is 820nm, the average particle diameter is 0.12 μm, the maximum particle diameter is 0.2 μm, and the BET specific surface area is 60m 2/g.

Hole transport material

HTM-A: examples of the compound having the following structure and the hole transport material represented by the general formula (HT1a) (HT1-1), N '-diphenyl-N, N' -bis (3-methylphenyl) - [1, 1 '] biphenyl-4, 4' -diamine

HTM-B: a compound of the structure

Electron transport material

ETM-A: examples of the compound having the following structure and the electron transporting material represented by the general Formula (FK) include compound (1-1) and 3, 3 '-di-tert-butyl-5, 5' -dimethylbenzoquinone.

ETM-B: a compound of the structure

ETM-C: a compound of the structure

For purposes of illustration and description, exemplary embodiments of the invention have been described above. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. The scope of the invention is defined by the claims and their equivalents.