JPH1184691A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure stability of electrical characteristics in repetitive use and to suppress variation particularly in dark potential and light potential by incorporating a ketone resin having a specified structure into a photosensitive layer. SOLUTION: When a photosensitive layer contg. an org. material as a principal component is formed on an electrically conductive substrate to obtain an electrophotographic photoreceptor, a ketone resin having a structure represented by formula I and/or a ketone resin having a structure represented by formula II is incorporated into the photosensitive layer. In the formulae I, II, R<1> and R<3> are individually H or alkyl, R<2> is H, alkyl, aralkyl, aryl or allyl and (m) and (n) are integers of 500-10,000. When the photoreceptor is a function separated photoreceptor with a photosensitive layer formed by laminating an electric charge generating layer and an electric charge transferring layer, one or both of the ketone resins are used in one or both of the laminated layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used in an electrophotographic printer, a copying machine, and the like, and more particularly, to a constituent material of a photosensitive layer containing an organic material as a main component.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member has a basic structure in which a photosensitive layer having a photoconductive function is laminated on a conductive substrate. In recent years, photoreceptors for organic electrophotography using organic compounds as functional components responsible for charge generation and transport have been actively researched and developed due to the variety of materials, high productivity, and safety. Applications to printers and printers are being promoted.

A photoreceptor is required to have a function of retaining surface charges in a dark place, a function of receiving light to generate charge carriers, and a function of receiving light and transporting charge carriers. A so-called single-layer type photoreceptor with a single-layer photosensitive layer that combines the functions of: a charge-generating layer mainly responsible for generating charge carriers when receiving light; and a function of retaining surface charges in dark places. There is a so-called function-separated layered photoconductor having a photosensitive layer in which a function-separated layer is stacked on a charge transport layer which has a function of transporting charge carriers when receiving light.

Recently, a function-separated laminated photoreceptor, in particular, a layer formed by applying an organic pigment as a charge generating material and dissolving and dispersing it in an organic solvent together with a resin binder in an organic solvent to form a film is referred to as a charge generating layer. A charge transporting layer composed of a low-molecular organic compound as a charge transporting material and a coating solution prepared by dissolving and dispersing it in an organic solvent together with a resin binder into a film. Laminated electrophotographic photoconductors have become mainstream.

[0005]

However, at present,
The organic photoreceptor does not always sufficiently satisfy the required performance required for the photoreceptor. In particular, the stability of electrical characteristics during repeated use is one of the required characteristics for which its improvement is strongly desired. Specifically, when the photoreceptor is used continuously and repeatedly in an actual machine, potential fluctuations such as a decrease in dark area potential and an increase in light area potential occur, resulting in deterioration of print quality and copy image quality. Factors of such potential fluctuation include fatigue, deterioration of organic materials due to light, heat, ozone, etc. due to continuous use in the actual machine, and accumulation of photocarriers generated in processes such as exposure and static elimination in the organic film. And the like. In particular, the accumulation of photocarriers is considered to be caused by charge traps in the charge generation layer and the charge transport layer. Improvements have been made mainly on charge generation materials and charge transport materials. There are no means or materials that can be fully solved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is an excellent organic photoreceptor having stable electrical characteristics during repeated use, and in particular, has a small variation in dark area potential and light area potential. The purpose is to provide.

[0007]

According to the present invention, there is provided an electrophotographic photoreceptor having a photosensitive layer containing an organic material as a main component on a conductive substrate. The problem can be solved by providing a photoconductor containing a ketone resin having a structure represented by the general formula (I) and / or a ketone resin having a structure represented by the following general formula (II).

[0008]

Embedded image [In the formulas (I) and (II), R ¹ and R ³ each represent a hydrogen atom or an alkyl group, and R ² represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or an allyl group. M and n each represent an integer of 500 or more and 10,000 or less. By using a ketone resin having a specific structure as described above alone or in an appropriate combination as a mixture for the photosensitive layer, the stability of the electrical characteristics upon repeated use, in particular, the dark area potential and the light area potential And an excellent organic photoreceptor having a small fluctuation of the organic photoreceptor can be obtained.

In the case where the photosensitive layer is a function-separated type photoreceptor in which a charge generation layer and a charge transport layer are laminated, if the charge generation layer and the charge transport layer are used alone or simultaneously for both layers. Good. Furthermore, when the outermost layer of the photoreceptor is a charge transport layer, the charge transport layer contains the above-described ketone resin, whereby the advantage of improving the printing durability of the charge transport layer and improving the durability of the photoreceptor can be obtained. .

The compound represented by the general formula (I) includes, for example, compounds represented by the following structural formulas (I-1) to (I-3).

[0011]

Embedded image Further, as the compound represented by the general formula (II),
For example, compounds of the following structural formulas (II-1) to (II-6) can be mentioned.

[0012]

Embedded image

[0013]

Embedded image

[0014]

FIG. 1 is a schematic cross-sectional view showing an example of the structure of a photoreceptor according to the present invention, in which a charge generating layer 4 and an undercoat layer 2 are provided on a conductive substrate 1. Charge transport layer 5
Is a negatively-charged, function-separated, laminated photoreceptor having a photosensitive layer 3 that is sequentially laminated. The conductive substrate 1 is
At the same time as the role of one electrode of the photoreceptor, it serves as a support for each layer constituting the photoreceptor, and may be in any shape such as a cylindrical shape, a plate shape, and a film shape. Or a material obtained by conducting a conductive treatment on a surface of glass, resin, or the like.

The undercoat layer 2 is made of a layer mainly composed of a resin or a metal oxide film such as alumite. The undercoat layer 2 controls the injection of electric charge from the conductive substrate to the photosensitive layer. It is provided as needed for the purpose of coating, improving the adhesiveness of the photosensitive layer, and the like. Examples of the resin material used for the undercoat layer include insulating polymers such as casein, polyvinyl alcohol, polyamide, melamine, and cellulose, and conductive polymers such as polythiophene, polypyrrole, and polyaniline. These resins may be used alone. Alternatively, they can be used in combination as appropriate. These resins may contain metal oxides such as titanium dioxide and zinc oxide.

The charge generation layer 4 is composed of an organic charge generation material and a resin binder. As a charge generation material,
Various phthalocyanine compounds, azo compounds, polycyclic quinone compounds, squarium compounds and derivatives thereof are used. Examples of the resin binder include polycarbonate resin, polyester resin, polyamide resin, polyurethane resin, epoxy resin, polyvinyl butyral resin, polyvinyl acetal resin, phenoxy resin, silicone resin, acrylic resin, vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, and formal. Resins, cellulose resins, or copolymers of these resins, halides,
A cyanoethyl compound or the like can be used.

The charge transport layer 5 is composed of a charge transport material and a resin binder. As the charge transporting material, a hydrazone compound, a butadiene compound, a diamine compound, an indole compound, an indoline compound, a stilbene compound, a distilbene compound, or the like is used alone or in combination as appropriate. As the resin binder, a polycarbonate resin such as a bisphenol A type, a bisphenol Z type, a bisphenol A-biphenyl copolymer, a polystyrene resin, a polyphenylene resin, or the like is used.

Further, the undercoat layer, the charge generation layer, and the charge transport layer may be provided as necessary for the purpose of improving sensitivity, reducing residual potential, or improving environmental resistance and stability against harmful light. Thus, an electron accepting substance, an antioxidant, a light stabilizer and the like can be added. Further, on the surface of the photosensitive layer, a surface protective layer may be further provided as necessary for the purpose of further improving environmental resistance and mechanical strength. It is desired that the surface protective layer is made of a material having excellent durability against mechanical stress and excellent environmental resistance, and has a performance of transmitting light to which the charge generating layer is sensitive as much as possible.

Although the function-separated laminated type photoreceptor has been described above, the present invention is of course also effective in the case of a single-layer type photoreceptor, and the ketone resin according to the present invention is contained in the single-layered photosensitive layer. Thus, a similar effect can be obtained.

[0020]

Embodiments of the present invention will be described below. Example 1 An alumite layer having a thickness of about 7 μm was formed on the outer peripheral surface of an aluminum cylinder as a conductive substrate to form an undercoat layer.

On the undercoat layer, 1 part by weight of X-type phthalocyanine as a charge generating material and a modified vinyl chloride resin as a resin binder (manufactured by Nippon Zeon Co., Ltd .; trade name "M")
R-110 ") 0.8 part by weight and the structural formula (I-
A coating solution prepared by dispersing 0.2 parts by weight of the ketone resin shown in 1) in 50 parts by weight of dichloromethane is dip-coated,
After drying at a temperature of 80 ° C. for 30 minutes, a charge generation layer having a thickness of about 0.3 μm was formed. On this charge generation layer, 10 parts by weight of a hydrazone compound represented by the following structural formula (III), bisphenol A type polycarbonate resin (Teijin Chemical Co., Ltd.)
Co., Ltd .; trade name "L-1225") A coating solution prepared by dissolving 10 parts by weight in 90 parts by weight of dichloromethane is dip-coated and dried at a temperature of 90 ° C. for 60 minutes to form a charge transport layer having a film thickness of about 20 μm. Was formed to produce a photoreceptor.

[0022]

Embedded image Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1 except that the composition of the resin binder in the coating solution for the charge generation layer was changed to 1 part by weight of a modified vinyl chloride resin, and no ketone resin was used. .

Comparative Example 2 The procedure of Example 1 was repeated except that the composition of the resin binder in the coating solution for the charge generation layer was changed to 0.8 parts by weight of a ketone resin and 0.2 parts by weight of a modified vinyl chloride resin. Thus, a photoreceptor was prepared. Thus the respective photosensitive body obtained, mounted on Hewlett Packard Co. printer "Laser Jet III", measure the initial and dark potential V _D of letter size paper 20,000 sheets after printing and the light portion potential V _I Then, the characteristic fluctuation was evaluated. Table 1 shows the results.

[0024]

[Table 1] As can be seen from Table 1, the initial characteristics are almost the same for each photoreceptor, but after printing 20,000 sheets, the photoreceptor of Comparative Example 1 has a larger light-area potential than the photoreceptor of Example 1. Has risen to
It can be seen that the fluctuation is suppressed by adding the ketone resin according to the present invention. In addition, from the characteristics of the photoconductor of Comparative Example 2, it is found that a large amount of the ketone resin causes a decrease in dark area potential. The addition amount of the ketone resin is preferably 1% by weight to 30% by weight based on the total solid content of the layer to which the ketone resin is added.

Example 2 An alumite layer having a thickness of about 7 μm was formed on the outer peripheral surface of an aluminum cylinder as a conductive substrate to form an undercoat layer.
On this undercoat layer, 1 part by weight of an X-type phthalocyanine as a charge generating material and a modified vinyl chloride resin as a resin binder (manufactured by Zeon Corporation; trade name "MR-11")
0 ") A coating liquid prepared by dispersing 1 part by weight in 50 parts by weight of dichloromethane was applied by dip coating, and dried at a temperature of 80 ° C. for 30 minutes to form a charge generating layer having a thickness of about 0.3 μm.
On this charge generation layer, 10 parts by weight of a hydrazone compound represented by the structural formula (III) as a charge transport material, 4 parts by weight of a ketone resin represented by the structural formula (I-1) as a resin binder, and bisphenol A type Polycarbonate resin (manufactured by Teijin Chemicals Limited; trade name "L-1225")
A coating solution prepared by dissolving 6 parts by weight in 90 parts by weight of dichloromethane was applied by dip coating and dried at a temperature of 90 ° C. for 60 minutes to form a charge transport layer having a thickness of about 20 μm to prepare a photoreceptor. .

Comparative Example 3 In Example 2, the composition of the resin binder of the coating solution for the charge transport layer was changed to the bisphenol A type polycarbonate resin 10
A photoconductor was prepared in the same manner as in Example 2, except that the ketone resin was not used and the amount thereof was changed to parts by weight. Comparative Example 4 Example 2 was repeated except that the composition of the resin binder in the coating solution for the charge transport layer was changed to 5 parts by weight of a ketone resin and 5 parts by weight of a bisphenol A-type polycarbonate resin.
A photoreceptor was produced in the same manner as described above.

Each photoreceptor obtained in this manner was used for He
Wlett Packard's printer “Lase
mounted on r Jet III ", it was evaluated initially and letter size paper 20,000 sheets after printing light portion durability of variability and a charge transport layer of the potential V _I a (film scraping amount). Table 2 shows the results.
Shown in

[0028]

[Table 2] As can be seen from Table 2, there is almost no difference in characteristics between the respective photoconductors at the initial stage, but after printing 20,000 sheets, the photoconductor of Comparative Example 3 has a brighter potential than the photoconductor of Example 2. Significantly increased, and it was found that the fluctuation was suppressed by adding the ketone resin according to the present invention. Also, from the thickness of the charge transport layer of the photoreceptor of Comparative Example 4 after printing 20,000 sheets, it can be seen that if the added amount of the ketone resin is large, the durability of the charge transport layer is reduced. The amount of the ketone resin to be added is preferably 1% by weight to 40% by weight of the total solid content of the layer to which the ketone resin is added.

Example 3 An alumite layer having a thickness of about 7 μm was formed on the outer peripheral surface of an aluminum cylinder as a conductive substrate to form an undercoat layer.
On this undercoat layer, 1 part by weight of an X-type phthalocyanine as a charge generating material and a modified vinyl chloride resin as a resin binder (manufactured by Zeon Corporation; trade name "MR-11")
0 ") A coating solution prepared by dispersing 0.8 part by weight of the ketone resin represented by the structural formula (I-1) and 0.2 part by weight of the ketone resin represented by the structural formula (I-1) in 50 parts by weight of dichloromethane was dip-coated, and the temperature was 80 ° C
For 30 minutes to form a charge generation layer having a thickness of about 0.3 μm. On this charge generation layer, 10 parts by weight of a hydrazone compound represented by the above structural formula (III) as a charge transport material, and a bisphenol A type polycarbonate resin as a resin binder (manufactured by Teijin Chemicals Limited; trade name “L-12”)
25 ") A coating solution prepared by dissolving 10 parts by weight in 90 parts by weight of dichloromethane is applied by dip coating,
After drying for about 20 minutes, a charge transport layer having a thickness of about 20 μm was formed to prepare a photoreceptor.

Comparative Example 5 A photoconductor was prepared in the same manner as in Example 3 except that the composition of the resin binder in the coating solution for the charge generation layer was changed to 1 part by weight of a modified vinyl chloride resin, and no ketone resin was used. Was prepared. Comparative Example 6 Photosensitization was performed in the same manner as in Example 3 except that the composition of the resin binder in the coating solution for the charge generation layer was changed to 0.8 parts by weight of a ketone resin and 0.2 parts by weight of a modified vinyl chloride resin. The body was made.

Each photoreceptor obtained in this manner was used for He
Wlett Packard's printer “Lase
It mounted on r Jet III ", to measure the initial and dark potential V _D and light portion potential V _I of letter size paper 20,000 sheets after printing was investigated the variation. Table 3 shows the results.

[0032]

[Table 3] As can be seen from Table 3, the initial characteristics are almost the same for each photoreceptor, but after printing 20,000 sheets, the photoreceptor of Comparative Example 5 has a much brighter potential than the photoreceptor of Example 3. Has risen to
It can be seen that the fluctuation is suppressed by adding the ketone resin according to the present invention. Also, from the characteristics of the photoconductor of Comparative Example 6, it is found that a large amount of the ketone resin causes a decrease in dark area potential. The addition amount of the ketone resin is preferably 1% by weight to 30% by weight based on the total solid content of the layer to which the ketone resin is added.

Example 4 An alumite layer having a thickness of about 7 μm was formed on the outer peripheral surface of an aluminum cylinder as a conductive substrate to form an undercoat layer.
On this undercoat layer, 1 part by weight of an X-type phthalocyanine as a charge generating material and a modified vinyl chloride resin as a resin binder (manufactured by Zeon Corporation; trade name "MR-11")
0 ") A coating liquid prepared by dispersing 1 part by weight in 50 parts by weight of dichloromethane was applied by dip coating, and dried at a temperature of 80 ° C. for 30 minutes to form a charge generating layer having a thickness of about 0.3 μm.
On this charge generation layer, 10 parts by weight of a hydrazone compound represented by the structural formula (III) as a charge transporting material, 4 parts by weight of a ketone resin represented by the structural formula (II-1) as a resin binder, and bisphenol A type Polycarbonate resin (manufactured by Teijin Chemicals Limited; trade name “L-122”
5)) A coating solution prepared by dissolving 6 parts by weight in 90 parts by weight of dichloromethane is applied by dip coating, and dried at a temperature of 90 ° C. for 60 minutes to form a charge transport layer having a thickness of about 20 μm. Was prepared.

Comparative Example 7 In Example 4, the composition of the resin binder in the charge transport layer coating solution was changed to the bisphenol A type polycarbonate resin 10
A photoconductor was prepared in the same manner as in Example 4, except that the ketone resin was not used. Comparative Example 8 Example 4 was repeated except that the composition of the resin binder in the coating solution for the charge transport layer was changed to 5 parts by weight of a ketone resin and 5 parts by weight of a bisphenol A-type polycarbonate resin.
A photoreceptor was produced in the same manner as described above.

[0035] The thus the photosensitive body obtained, the initial and dark potential V _D of letter size paper 20,000 sheets after printing, the light portion potential V _I measured in accordance with Example 1, evaluate the variation did. Table 4 shows the results.

[0036]

[Table 4] As can be seen from Table 4, there is almost no difference in characteristics between the respective photoconductors at the initial stage, but after printing 20,000 sheets, the photoconductor of Comparative Example 8 has a brighter potential than the photoconductor of Example 4. Significantly increased, and it was found that the fluctuation was suppressed by adding the ketone resin according to the present invention. Also, from the thickness of the charge transport layer of the photoreceptor of Comparative Example 8 after printing 20,000 sheets, it can be seen that if the amount of the ketone resin added is large, the durability of the charge transport layer is reduced. The amount of the ketone resin to be added is preferably 1% by weight to 40% by weight of the total solid content of the layer to which the ketone resin is added.

Example 5 An undercoat layer and a charge generation layer were formed on a conductive substrate in the same manner as in Example 2. On this charge generation layer, the hydrazone compound 1 represented by the above structural formula (III) was used as a charge transport material.
0 parts, 2 parts by weight of a ketone resin represented by the structural formula (I-1) as a resin binder, 2 parts by weight of a ketone resin represented by the structural formula (II-1), and a bisphenol A type polycarbonate resin (Teijin Chemical ( Co., Ltd .; trade name "L-
1225 ") A coating solution prepared by dissolving 6 parts by weight in 90 parts of dichloromethane is applied by dip coating and dried at a temperature of 90 ° C. for 60 minutes to form a charge transport layer having a thickness of about 20 μm, thereby producing a photoreceptor. did.

Comparative Example 9 In Example 5, the composition of the resin binder in the charge transport layer coating liquid was changed to the bisphenol A type polycarbonate resin 10
A photoconductor was prepared in the same manner as in Example 5 except that the ketone resin was not used. Comparative Example 10 In Example 5, the ketone resin having the composition of the resin binder of the coating solution for the charge transport layer represented by the structural formula (I-1) .2.
A photoconductor was prepared by the same way as that of Example 5 except that 5 parts by weight, 2.5 parts by weight of ketone resin represented by the above structural formula (II-1) and 6 parts by weight of bisphenol A type polycarbonate resin were used.

Comparative Example 11 In Example 5, the composition of the resin binder in the coating solution for the charge transport layer was 1 part by weight of the ketone resin represented by the structural formula (I-1), and represented by the structural formula (II-1). A photoconductor was prepared by the same way as that of Example 5 except that 3 parts by weight of ketone resin and 6 parts by weight of bisphenol A-type polycarbonate resin were used.

Comparative Example 12 In Example 5, the composition of the resin binder in the coating solution for the charge transport layer was 3 parts by weight of the ketone resin represented by the structural formula (I-1), and represented by the structural formula (II-1). A photoconductor was prepared by the same way as that of Example 5 except that 1 part by weight of ketone resin and 6 parts by weight of bisphenol A-type polycarbonate resin were used.

Each photoreceptor produced in this manner was replaced with Hew.
Let Packard printer "Laser
It mounted on Jet III ", was evaluated initially and letter size paper 20,000 sheets after printing light portion durability of variability and a charge transport layer of the potential V _I a (film scraping amount). Table 5 shows the results.

[0042]

[Table 5] As can be seen from Table 5, the photoreceptor of Comparative Example 9 was replaced by the photoreceptor of Example 5 after printing 20,000 sheets. As compared with the above, the bright part potential is significantly increased, and it can be seen that the fluctuation is suppressed by adding the ketone resin according to the present invention. Also,
From the thickness of the charge transport layer of the photoreceptor of Comparative Example 10 after printing 20,000 sheets, it can be seen that a large amount of the ketone resin causes a decrease in the durability of the charge transport layer. Further, from the results of Comparative Example 11 and Comparative Example 12, the light portion potential was found to be lower than the compounding ratio of the ketone resin represented by the structural formula (I-1) to the ketone resin represented by the structural formula (II-1). Regardless, it can be seen that the characteristics change depending on the total amount of the ketone resin. The amount of the ketone resin to be added is preferably 1% by weight to 40% by weight of the total solid content of the layer to which the ketone resin is added.

[0043]

According to the present invention, in an electrophotographic photoreceptor having a photosensitive layer containing an organic material as a main component on a conductive substrate, the above-mentioned formula (I) and / or By using a photoreceptor containing a ketone resin having the structure represented by the general formula (II), the stability of the electrical characteristics during repeated use, in particular, the variation in the dark portion potential and the bright portion potential is small, and an excellent property is obtained. A photoreceptor can be obtained. Further, in the function separation laminated type photoreceptor, in the photoreceptor in which the charge transport layer is the outermost surface, by including the ketone resin in the charge transport layer, the printing durability is improved,
A photosensitive member having excellent durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one configuration example of a photoreceptor according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 undercoat layer 3 photosensitive layer 4 charge generation layer 5 charge transport layer

Claims (2)

[Claims] 1. An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer containing an organic material as a main component, wherein the photosensitive layer comprises a ketone resin having a structure represented by the following general formula (I): Or an electrophotographic photoreceptor comprising a ketone resin having a structure represented by the following general formula (II). Embedded image [In the formulas (I) and (II), R ¹ and R ³ each represent a hydrogen atom or an alkyl group, and R ² represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or an allyl group. M and n each represent an integer of 500 or more and 10,000 or less. ] 2. A ketone resin having a structure represented by the general formula (I) and / or a ketone having a structure represented by the general formula (II), wherein the photosensitive layer is formed by laminating a charge generation layer and a charge transport layer. 2. The electrophotographic photoconductor according to claim 1, wherein the resin is contained in the charge generation layer and / or the charge transport layer.