JPH09297417A - Production of electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an electrophotographic photoreceptor having a good coating surface without causing any image defect such as pinhole and irregular density. SOLUTION: By this method, an electrophotographic photoreceptor is produced by dispersing an azo pigment expressed by formula with a butylal resin having >70mol% butylation degree in at least one kind of solvent selected from fatty acid esters having carbon atoms between >=4 and <=6 and then applying the prepared coating liquid on a conductive base body. In formula, R1 is a hydrogen atom, alkyl group having <=8 carbon atoms, alkoxy group, alkylthio group or five-member ring which may contain atoms except for carbon, R2 is a methyl group, ethyl group, halogen atom, nitro group or cyano group, m1 and m2 may be same or different and are 0, 1, 2, and n is 0 or 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrophotographic photosensitive member having a good coated surface and free from image defects such as pinholes and uneven density.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic photosensitive member,
Those having a photosensitive layer containing an inorganic photoconductive substance such as selenium, cadmium sulfide, zinc oxide, and silicon as a main component are widely known. However, they are not always satisfactory in sensitivity, thermal stability, moisture resistance, durability and the like, and in particular, selenium and cadmium sulfide have restrictions in production and handling due to their toxicity.

Generally speaking, a photosensitive layer containing an inorganic material as a main component is formed on a conductive support by a vacuum deposition method or a sputtering method. However, the manufacturing in a vacuum requires a large-scale manufacturing facility and is not always satisfactory in terms of cost, such as the problem of the growth speed of the photosensitive layer. On the other hand, an electrophotographic photoreceptor having a photosensitive layer containing an organic material as a main component is relatively easy to manufacture, is inexpensive, and is superior in thermal stability to an inorganic photoreceptor. It has many advantages, and its practical application is gradually attracting attention.

By the way, when an organic material is coated on a conductive support, a constituent substance soluble in a solvent such as a resin can be dissolved in the solvent and applied, but a pigment or the like is generally insoluble in the solvent. Since such constituent substances cannot be applied as they are, a method of dispersion is necessary. Dispersion described here is to make the pigment, etc., into fine particles in a solvent to make it a suspended state without sediment, and the stability of dispersion means that the particle size is uniform and stable in the solvent for a long time. Means saved.

When the dispersibility of the pigment or the like is deteriorated, the coated surface becomes rough, which causes image defects such as pinholes and uneven density in the electrophotographic photosensitive member. Further, since the dispersed particles settle out over time and the concentration of the dispersion becomes non-uniform, uneven image density may occur between the obtained photoconductors or parts of the same photoconductor even when the same coating liquid is applied, This also leads to a decrease in productivity such that the dispersion liquid thickens and the amount of coating varies.

In order to obtain a good pigment dispersion, a method of controlling the agglomeration state by changing a part of the molecular structure of the pigment or mixing pigments having different structures, or using a solvent on the surface of the pigment There is a method of adsorbing a soluble resin. However, with these techniques, the electrophotographic properties of the original pigment,
In other words, a situation has emerged in which the sensitivity, repeatability, etc. have changed, and the initial objectives of the photoreceptor as a basic performance of the pigment cannot be achieved.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an electrophotographic photosensitive member which has a good coated surface and is free from image defects such as pinholes and uneven density.

[0008]

DISCLOSURE OF THE INVENTION As a result of various studies to achieve the above object, the present inventors have found that an azo pigment represented by the following formula 1 is used together with a butyral resin having a butyralization degree of 70 mol% or more and a carbon atom. It has been found that it is effective to apply a coating solution dispersed in at least one solvent selected from fatty acid esters of 4 to 6 to a conductive support, and the present invention has been completed. It is a thing.

[0009]

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In the formula 1, R ₁ represents a hydrogen atom, an alkyl group having up to 8 carbon atoms, an alkoxy group, an alkylthio group, or a 5-membered ring which may contain atoms other than carbon atoms. R ₂ represents a methyl group, an ethyl group, a halogen atom, a nitro group, or a cyano group. Further, m ₁ and m ₂ may be the same or different and represent 0, 1, or 2. n represents 0 or 1.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Each constituent element of the present invention will be described in detail below.

The electrophotographic photoreceptor is a single layer type in which a charge generating substance and a charge transfer substance are dispersed and mixed and sealed in a binder, and a charge generating layer in which a charge generating substance is sealed in a binder and a charge transfer substance are sealed in a binder. It is configured by a function separation laminated type in which charge transfer layers are laminated. Although the present invention can be applied to the production of any system, it is used in the production of the charge generation layer of the system of the function-separated layered photoreceptor in which the performances of the charge generation substance and the charge transfer substance are easily maximized. Preferably.

Table 1 shows the charge generating material according to the present invention.
The azo pigment represented by formula 1 given in the above can be used.

[0014]

[Table 1]

In the present invention, a butyral resin having a butyralization degree of 70 mol% or more is used as the binder in which the azo pigment particles represented by the above formula 1 are dispersed. Butyral resins are made by reacting polyvinyl alcohol with butyraldehyde. However, polyvinyl alcohol cannot be completely converted to butyral, and the butyral resin is composed of a vinyl butyral portion, a vinyl alcohol portion, and a vinyl acetate portion. The butyralization degree represents the molar fraction of the vinyl butyral portion in the butyral resin, and the theoretical maximum butyralization degree is 81.
It is said to be 6 mol%. The chemical properties differ depending on the butyralization degree, and the butyral resin having a butyralization degree of 70 mol% or more has excellent solubility in a solvent. However, a butyral resin having a low degree of butyralization has poor solubility in a solvent and is not preferable as a binder for dispersing azo pigment particles.

The binder is used in an amount of 1 to 1000 parts by weight, preferably 1 to 400 parts by weight, based on 100 parts by weight of the azo pigment. The thickness of the charge generation layer is preferably from 0.1 to 20 μm.

The solvent used for dispersing the azo pigment in the present invention is a fatty acid ester having 4 to 6 carbon atoms (hereinafter, the fatty acid ester having 4 to 6 carbon atoms is referred to as the fatty acid ester according to the present invention. ), And specific examples thereof include propyl formate, isopropyl formate, butyl formate, isobutyl formate, t-butyl formate, amyl formate, isoamyl formate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate. , Acetic acid t-
Butyl, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, methyl isobutyrate, and ethyl isobutyrate, as well as methyl lactate, ethyl lactate, methyl pyruvate, ethyl cellosolve, and Examples thereof include fatty acid esters having various substituents such as ethyl chloroacetate.

Among these fatty acid esters according to the present invention, not only the dispersibility of the pigment is excellent, but also the solvent is less likely to volatilize at room temperature (at the time of preparation of the coating solution), and the solvent evaporation property which is easily evaporated at the time of coating drying is excellent. ASTM. D. 35
Particularly preferred are isopropyl acetate and propyl acetate having a relative evaporation rate of 2 to 4 defined in 39.76.

On the other hand, even if a fatty acid ester is used, the solvent other than the fatty acid ester according to the present invention has a poor solvent evaporation balance, and as is seen in the fatty acid ester having 3 or less carbon atoms, it is at room temperature (at the time of preparing the coating liquid). ) Easily volatilizes and the fluctuation of the coating liquid concentration is large, and conversely, as is often seen in fatty acid esters having 7 or more carbon atoms, it is difficult to evaporate even when the coating is dried, and an electrophotographic photoreceptor is efficiently produced. It is not preferable because it cannot be done.

Further, in the present invention, the fatty acid ester according to the present invention and halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, trichloroethane and trichloroethylene, aromatic hydrocarbons such as benzene, toluene and xylene, dioxane, tetrahydrofuran and dimethoxyethane. It is also possible to use a mixed solvent with a solvent such as an ether-based solvent such as, and a cellosolve-based solvent such as methyl cellosolve, dimethyl cellosolve, and methyl cellosolve acetate. However, when the fatty acid ester according to the present invention is mixed with another solvent, the fatty acid ester according to the present invention is preferably 70 vol% or more of all the solvents.

The apparatus used for dispersion in the present invention is a dispersion machine using a dispersion medium such as a ball mill, a vertical bead mill, a horizontal bead mill, a paint conditioner manufactured by Red Devil Co., USA, and a dispersion medium such as a roll mill or an impact mill. A disperser without is not used.

As the material of the dispersion medium used in the present invention, soda glass (SiO ₂ 70 to 73%, Na ₂ O 1
3% to 15%), low-alkali glass (SiO ₂ 42 to 52
%, Al ₃ O ₃ 13-23%, CaO 10-25%, C
aO + MgO 18 to 32%) and yttria-containing zirconia (ZrO ₂ 93 to 95%, Y ₂ O ₃ 4 to 6%) are preferable. The shape of the dispersion medium is often a bead shape having a diameter of several mm.

Examples of the charge transfer substance used in the present invention include the triphenylamine derivatives represented by the exemplified compounds 3 to 7, the stilbene derivatives represented by the exemplified compounds 8 to 16, and the exemplified compound 17 Examples thereof include, but are not limited to, butadiene derivatives represented by 18 and hydrazone derivatives represented by Chemical Formulas 19 to 27.

[0024]

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[0025]

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[0026]

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[0027]

[Chemical 6]

[0028]

[Chemical 7]

[0029]

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[0030]

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[0031]

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[0032]

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[0033]

[Chemical 12]

[0034]

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[0035]

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[0036]

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[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

[Chemical 21]

[0043]

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[0044]

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[0045]

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[0046]

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[0047]

[Chemical formula 26]

[0048]

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In the laminated type photoreceptor, a charge transfer layer is formed by at least these charge transfer substances and a binder.

As the binder used in the charge transfer layer, polystyrene, acrylic resin typified by polymethylmethacrylate, polycarbonate resin having bisphenol A or Z skeleton, polyarylate resin, polyphenylene ether resin, polyether sulfone resin, polyamide A resin, a polyimide resin, a polyester resin, or the like can be used. Charge transfer material 1 in the charge transfer layer
The binder is used in the range of 10 to 400 parts by weight based on 00 parts by weight. The thickness of the charge transfer layer is 5 to 10
0 μm is preferred.

When the coating liquid for producing an electrophotographic photosensitive member is applied, in addition to the dip coating method, it may be applied by an applicator. When coating on a drum, a dip coating method is used.

As the conductive support on which the electrophotographic photoreceptor according to the present invention is formed, any one which is used for a well-known electrophotographic photoreceptor can be used. Specific examples include drums, sheets, belts of gold, silver, platinum, titanium, aluminum, copper, zinc, iron, metal oxides having a conductive treatment, laminates of these thin films, vapor depositions and the like. To be

Further, a conductive material such as a metal powder, a metal oxide, carbon black, carbon fiber, copper iodide, a charge transfer complex, an inorganic salt, and an ionic conductive polymer electrolyte is applied with a suitable binder to form a polymer matrix. Drums, sheets, belts, etc. composed of plastic, ceramic, paper, etc. embedded in and subjected to conductive processing, and drums of plastic, ceramic, paper, etc., which contain such conductive substances and become conductive, Seats, belts and the like.

The electrophotographic photosensitive member according to the present invention may be added with various antioxidants in combination in order to prevent deterioration of the organic compounds of the constituent materials due to oxidation, and film-forming property, flexibility, mechanical property A well-known plasticizer may be added together to improve the mechanical strength.

A blocking layer (undercoat layer) may be provided between the photosensitive layer and the conductive support to control charge injection from the photosensitive layer to the conductive support. A surface layer may be provided to improve the durability of the photoconductor.

The blocking layer used between the photoreceptor and the conductive support is a mixture of a resin soluble in alcohol or water and an inorganic pigment such as titanium oxide. Copolymerized nylon, N-methoxymethylated nylon are known as alcohol-soluble resins, and polyethylene glycol, polyvinyl alcohol, polyacrylic acid, etc. are known as water-soluble resins.

The thickness of the blocking layer is determined according to the surface degree of the conductive support and the electrophotographic characteristics at low temperature and low humidity.

[0058]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 1 part by weight of an azo pigment, which is a pigment for an electrophotographic photoreceptor represented by Exemplified Compound P12, and a butyral resin (manufactured by Sekisui Chemical; B
1 part by weight of L-S, butyralization degree of 70 mol% or more) and 100 parts by weight of isopropyl acetate are mixed, and a diameter of 1 m is obtained by a paint conditioner device manufactured by Red Devil.
m low alkali glass beads (manufactured by Ohara Kogaku; Hibe D
-Dispersed for 4 hours with 20). The pigment dispersion thus obtained is applied to a thin aluminum metal plate (JIS standard # 1050).
Apply it with an applicator on top, and the film thickness will be about 0.2 μm.
A film of the charge-generating material was formed. Table 2 shows the results of coating properties.
Give to.

Next, 10 parts by weight of the hydrazone compound represented by Exemplified Compound 23 and 10 parts by weight of a polycarbonate resin (manufactured by Teijin Chemicals; Panlite K-1300) are dissolved in 200 parts by weight of dichloromethane to prepare the above charge generating substance. This solution was applied onto the coating film by an applicator to form a charge transfer layer having a dry film thickness of 20 μm.

The laminated electrophotographic photosensitive member thus produced was attached to a drum-shaped aluminum base tube, mounted on a commercial copying machine for office use to form an image, and it was investigated whether or not the image had a failure. The results are given in Table 2.

Examples 2 to 4 The dispersion solvent was propyl acetate, ethyl acetate, or a mixed solvent of isopropyl acetate and toluene (toluene 20 vol).
%), A photoconductor was prepared in the same manner as in Example 1, and the coating properties and images were investigated. The results are given in Table 2.

Comparative Examples 1 to 3 Photoreceptors were prepared in the same manner as in Example 1 except that toluene, dichloroethane, and methyl formate were used as dispersion solvents, and coating properties and images were investigated. The results are given in Table 2.

[0064]

[Table 2]

From Table 2, when a fatty acid ester having 4 to 6 carbon atoms was used as the dispersion solvent, the coatability was good and no image failure occurred. In particular, when isopropyl acetate or propyl acetate was used as a solvent, the dispersibility of the azo pigment was very good as well as the coating property and image quality. On the other hand, when toluene or dichloroethane was used as the dispersion solvent, the dispersibility of the azo pigment was poor, resulting in poor coatability. Even in the case of the same ester solvent as the fatty acid ester, methyl formate having 2 carbon atoms has high volatility, so that the solvent evaporates from the time of preparation of the coating solution to a non-negligible level, and the concentration of the coating solution increases. And the coatability was poor.

Example 5 Alcohol-soluble nylon (Toray; CM-8000)
1 part by weight was dissolved in 100 parts by weight of methanol, 9 parts by weight of titanium oxide (rutile type, manufactured by Sakai Chemical Co .; R-310) was mixed, and zirconia beads having a diameter of 1 mm (manufactured by Nikkato) were applied by a paint conditioner device manufactured by Red Devil. YTZ) and dispersed for 5 hours. The titanium oxide dispersion liquid thus obtained was applied to a thin aluminum metal plate (JIS standard).
# 1050) was coated by a dip coating method to form an undercoat layer having a film thickness of 0.5 μm.

Next, 1 part by weight of an azo pigment, which is a pigment for an electrophotographic photoreceptor represented by Exemplified Compound P22, and butyral resin (manufactured by Electrochemical; # 3000K, butyralization degree 70 m).
1 part by weight) was mixed with 100 parts by weight of isopropyl acetate, and dispersed with a soda glass bead (manufactured by Toshiba Barodyni; GB) having a diameter of 0.5 mm for 4 hours by a paint conditioner device manufactured by Red Devil. The pigment dispersion thus obtained was applied onto the above-mentioned undercoat layer by a dip coating method to form a film of a charge generating substance having a film thickness of about 0.2 μm. The coatability results are given in Table 3.

Next, 10 parts by weight of the stilbene compound represented by Chemical Formula 12 and 10 parts by weight of a polyarylate resin (U-polymer manufactured by Unitika Ltd.) were added to dichloroethane 200.
It is dissolved in 1 part by weight, and this solution is applied onto the film of the above charge generating substance by a dip coating method to obtain a dry film thickness of 20 μm.
Was formed.

Using this photoreceptor, the same image test as in Example 1 was conducted. The results are given in Table 3.

Examples 6 to 8 Photosensitive members were prepared in the same manner as in Example 1 except that the dispersion solvent in Example 3 was propyl acetate, butyl acetate, or a mixed solvent of propyl acetate and dichloroethane (10% by volume of dichloroethane). The image was investigated. The results are given in Table 3.

Comparative Examples 4 to 6 Photoreceptors were prepared in the same manner as in Example 1 except that the dispersing solvent in Example 3 was propanol, dichloroethane and propyl butyrate, and the coating properties and images were investigated. The results are given in Table 3.

[0072]

[Table 3]

From Table 3, when a fatty acid ester having 4 to 6 carbon atoms was used as the dispersing solvent, the coatability was good and no image failure occurred. In particular, when isopropyl acetate or propyl acetate was used as a solvent, the dispersibility of the azo pigment was very good as well as the coating property and image quality. On the other hand, when propanol or dichloroethane was used as the dispersion solvent, the dispersibility of the azo pigment was poor and, as a result, the coatability was poor. Further, even with the same ester solvent as the fatty acid ester, in the case of propyl butyrate having 7 carbon atoms, the evaporation rate was slow and the coatability was poor.

Comparative Examples 7 to 8 A phenoxy resin having substantially no vinyl butyral group (PKHJ manufactured by Union Carbite) was used as the binder for the charge generation layer in Example 1, and a butyralization degree of 70 m.
Butyral resin of less than ol% (manufactured by Sekisui Chemical; BL-1,
With a butyralization degree of 63 ± 3 mol%), a photoconductor was prepared in the same manner as in Example 1, and the coating properties and images were investigated. The results are given in Table 4.

[0075]

[Table 4]

From the results shown in Table 4, the degree of butyralization is 70 mo.
It can be seen that when 1% or more of a binder other than butyral resin is used, the coatability is deteriorated even when the dispersion solvent is isopropyl acetate.

[0077]

As is apparent from the above, according to the present invention, it is possible to provide a method for producing an electrophotographic photosensitive member having a good coated surface and having no image failure.

Claims (1)

[Claims] 1. An azo pigment represented by the following formula 1 is dispersed together with a butyral resin having a butyralization degree of 70 mol% or more in at least one solvent selected from fatty acid esters having 4 to 6 carbon atoms. A method for producing an electrophotographic photosensitive member, characterized in that the coating solution is applied onto a conductive support. Embedded image (In Formula 1, R ₁ represents a hydrogen atom, an alkyl group having up to 8 carbon atoms, an alkoxy group, an alkylthio group, and a 5-membered ring which may contain atoms other than carbon atoms. R ₂ represents a methyl group,
It represents an ethyl group, a halogen atom, a nitro group, and a cyano group. In addition, m ₁ and m ₂ may be the same or different, and 0,
Indicates 1 or 2. n represents 0 or 1. )