JPH1115174A - Composition for charge transfer layer and electrophotographic photoreceptor using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure high printed image quality and high printing resistance and long life and high photoresponsiveness by incorporating a polysulfone resin having specified repeating structural units and an amino resin. SOLUTION: This composition contains the polysulfone resin (A) having the repeating structural units represented by the formula and the amino resin (B), and the resin (A) has a weight average molecular weight Mw of 20,000-900,000, preferably, 30,000-250,000. The resin (B) can be embodied by a known resin, for example, obtained by etherifying an addition reaction product of melamine or benzoguanamine or the like amine material with formaldehyde, with a 1-4C alkyl alcohol. The resin (B) is used in combination, preferably, in an amount of 1-100 weight % of the resin (A), furthermore preferably, 2-30 weight %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a charge-transporting layer of a function-separated type organic electrophotographic photoreceptor, which is used by being mounted on an electrophotographic apparatus (printer, copier, etc.) by the Carlson method. The present invention relates to an electrophotographic photosensitive member using the composition.

[0002]

2. Description of the Related Art Electrophotographic photoreceptors using an organic photoconductive compound have been extensively studied recently because they are advantageous in terms of flexibility, lightness, surface smoothness, and price. Among them, a function-separated electrophotographic photoreceptor provided with a charge generation layer that generates charge carriers by light absorption and a charge transport layer that transports the generated charge carriers by an electric field has been conventionally used.
Recently, rapid progress has been made because photoresponsiveness and sensitivity, which were major drawbacks of electrophotographic photoreceptors using an organic photoconductive compound, can be greatly improved.

A function-separated type organic electrophotographic photoreceptor comprises a charge generation layer mainly composed of a photoconductive substance on a conductive substrate, and a charge transport layer composed of a charge transportable substance and a binder resin. I have. Since the charge transport layer is the outermost layer as a photoreceptor, it must be chemically stable and must withstand mechanical abrasion due to the development and cleaning processes.

Hitherto, as a binder resin for a charge transport layer of an electrophotographic photosensitive member, a bisphenol A type polycarbonate resin represented by the following structural formula 2 has been most commonly used in terms of transparency and mechanical strength. .

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[0005] The composition for the charge transport layer comprises a charge transport material,
It is prepared by uniformly dissolving or dispersing in a solvent a bisphenol A-type polycarbonate resin as a binder resin and additives used as required, such as a plasticizer, a fluidity-imparting agent, and a pinhole controlling agent.

In order to obtain high-speed photoresponsiveness, it is general to increase the amount of the charge transporting substance in the composition for the charge transporting layer.

However, recently, the electrophotographic photoreceptor has been required to obtain a high quality printed image obtained by an electrophotographic apparatus such as a copying machine and a laser beam printer and to increase the printing speed by downsizing the electrophotographic apparatus. There is an increasing demand for higher image quality, longer printing life, and faster light response of printed images.

In the composition for a charge transporting layer in which the amount of the charge transporting substance is increased, the charge transporting substance and the bisphenol A type polycarbonate resin are uniformly dissolved in a solution state, but this is dried and the solvent is removed. In the formed solid-state charge transport layer, the charge transport material and the bisphenol A-type polycarbonate resin undergo phase separation, and the coating film tends to be non-uniform in both morphology and composition. When an electrophotographic photoreceptor is formed using the layer composition, fog, black spots, image defects such as white spots occur from the beginning of use,
It is not possible to obtain an electrophotographic photoreceptor that satisfies high-speed light responsiveness and high image quality.Because of poor abrasion resistance, repeated use reduces the thickness of the photoreceptor and causes image defects such as fog and black spots. During repeated use, the developer (toner) adheres, causing a so-called filming phenomenon, which may cause a problem such as a streak-like defect in an image, and the printing life is not sufficient. . On the other hand, the movement to protect the global environment has been intensified, and the elimination of CFCs that destroy the ozone layer and the regulation of halogenated solvents that contaminate groundwater have been increasing.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and provides an electrophotographic photoreceptor which is excellent in print image quality, printing life, and light response. It is.

[0010]

The present invention has achieved the above object by using a phenoxy resin having a specific repeating structural unit and an amino resin in a composition for a charge transport layer.

That is, the present invention provides a compound represented by the general formula (I)

Embedded image A charge transport layer composition comprising a polysulfone resin having a repeating structural unit represented by the formula: and an amino resin. The present invention also relates to a composition for a charge transport layer containing a non-halogen solvent capable of dissolving the phenoxy resin.
The present invention also relates to an electrophotographic photoreceptor having a charge transport layer using the composition for a charge transport layer.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polysulfone resin having a repeating structural unit represented by the general formula (I) used in the present invention has a molecular weight of 20,000 to 90 as a weight average molecular weight Mw in terms of standard polystyrene measured by gel permeation chromatography.
000, preferably 30,000 to 250,000. When the molecular weight is less than 20,000,
The abrasion resistance of the charge transport layer tends to decrease, and 900,
If it exceeds 000, it tends to be difficult to form a uniform film thickness.

The amino resin used in the present invention is a known resin and is commercially available. For example, an addition reaction product of an amino raw material such as melamine and benzoguanamine with formaldehyde is alkyl etherified with an alcohol having 1 to 4 carbon atoms. Amino resin is
By crosslinking with polysulfone resin and crosslinking between amino resins, the hardness of the coating film is increased and the abrasion resistance is improved.

In the present invention, the blending ratio of the polysulfone resin represented by the general formula 3 (I) and the amino resin is as follows:
Amino resin 1 per 100 parts by weight of polysulfone resin
The amount is preferably from 100 to 100 parts by weight, more preferably from 2 to 30 parts by weight based on 100 parts by weight of the polysulfone resin. When the amount of the amino resin is less than 1 part by weight, the abrasion resistance is inferior.

The composition for a charge transporting layer of the present invention further contains a charge transporting substance. As the charge transporting substance, various known substances can be used. Examples of the charge transporting substance include fluorene, fluorenone, 2,7-dinitro-9-fluorenone, and 4H-indeno (1,2,6).
Thiophene-4-one, 3,7-dinitro-dibenzothiophene-5-oxide, 1-bromopyrene, 2-phenylpyrene, carbazole, 3-phenylcarbazole, 2-phenylindole, 2-phenylnaphthalene, oxazole, oxadiazole , Oxatriazole, triphenylamine, imidazole, chrysene,
Tetraphen, acridene, various hydrazones, styryl compounds, poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, 1-phenyl-3-
(4-diethylaminostyryl) -5- (4-diethylaminophenyl) pyrazoline, polyvinylpyrene, 2-
Phenyl-4- (4-diethylaminophenyl) -5
Phenyloxazole, polyvinyl indoloquinoxaline, 1,1-bis (p-diethylaminophenyl)-
Examples include 4,4-diphenyl-1,3-butadiene, polyvinyl benzothiophene, polyvinyl anthracene, polyvinyl acridine, benzidine, polyvinyl pyrazoline, and derivatives thereof.

In the composition for a charge transport layer of the present invention,
If the boiling point of the solvent used is too low or too high, the thickness of the coating film becomes uneven when immersion coating is performed, and the characteristics vary depending on the obtained photoreceptor position. It is a problem. Therefore, a solvent having a boiling point of 35C to 170C is preferable, and a solvent having a boiling point of 40C to 155C is more preferable.

In order to make the coating film morphologically and compositionally uniform, the solvent is a polysulfone resin having a repeating structural unit represented by the above-mentioned general formula 3 (I), an amino resin and the above-mentioned resin. It is necessary that the charge transporting substance can be dissolved. Examples of such a solvent include solvents such as methylene chloride, teratohydrofuran, methyl ethyl ketone, cyclohexanone, benzene, toluene, and xylene. These may be used alone or in combination of two or more. The amount of the solvent used is in the range of 300 to 900 parts by weight based on 100 parts by weight of the total amount of the charge transporting substance and the polysulfone resin having the repeating structural unit represented by the general formula (I) and the amino resin. Is preferred. If the amount is less than 300 parts by weight, the viscosity of the composition tends to be too high to form a uniform coating film. On the other hand, if it exceeds 900 parts by weight, the viscosity of the composition tends to be too low, and the thickness of the coating film tends to be too thin.

In the composition for a charge transport layer of the present invention, the total amount of the polysulfone resin having the repeating structural unit represented by the above general formula 3 (I) and the amino resin does not degrade the electrophotographic properties and the film properties. In view of this, it is preferable to use 50 to 450 parts by weight based on 100 parts by weight of the charge transporting substance.

Furthermore, the composition for a charge transport layer of the present invention may contain additives such as known plasticizers, fluidity-imparting agents and pinhole controlling agents, if necessary. Each of these additives is preferably used in an amount of 5 parts by weight or less based on 100 parts by weight of the charge transporting substance.

The present invention further relates to an electrophotographic photoreceptor having a charge transport layer formed using the charge transport layer composition prepared as described above. Hereinafter, a method for manufacturing the photoconductor will be described in detail.

The electrophotographic photoreceptor is obtained by forming a charge generation layer and a charge transport layer after providing an undercoat layer on a conductive substrate as needed. As the conductive substrate, a metal such as aluminum, iron, copper, nickel or the like, or paper or plastic which has been subjected to conductive treatment is used in the form of a film, a sheet or a seamless belt. Also,
Plastic films, sheets and seamless belts in which metal foils such as aluminum are laminated can also be used. Metal can also be used as a drum.

On the conductive substrate as described above, a known undercoat layer which is usually used can be provided. As the undercoat layer, for example, titanium oxide, aluminum oxide, zirconia, titanic acid, zirconic acid, lanthanum lead,
Fine particles such as titanium black, silica, lead titanate, and barium titanate, and components such as polyamide resin, phenol resin, casein, melamine resin, benzoguanamine resin, polyurethane resin, epoxy resin, cellulose, and polyvinyl butyral resin can be used. . These fine particles and resins can be used alone or in combination of two or more. In particular, when the fine particles and the resin are used together, the resin is adsorbed on the fine particles and a smooth film can be obtained. Therefore, it is desirable to use the fine particles and the resin together.

As a method for forming the undercoat layer, a solution obtained by dispersing and dissolving the fine particles and / or the resin in a solvent is coated on a conductive substrate by a dip coating method, a spray coating method, a roll coating method, or the like.
It can be formed by coating using a coating method such as an applicator coating method or a wire bar coating method and drying.

Examples of the solvent used at this time include solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, toluene, ethyl acetate, toluene, xylene, cellosolve, methanol, isopropyl alcohol, isobutyl alcohol, and n-butyl alcohol. Can be The thickness of the undercoat layer is usually 0.01 to 20.0 μm, preferably 0.1 to 3 μm.
0 μm. When this thickness is less than 0.01 μm,
It becomes difficult to form an undercoat layer uniformly, and 20.0 μm
If it exceeds m, the electrophotographic properties tend to decrease.

After forming the undercoat layer as described above,
A charge generation layer and a charge transport layer are sequentially laminated and formed on this layer.

In the present invention, the photoconductive substance used in the charge generation layer includes azoxybenzene, disazo, trisazo, benzimidazole, polycyclic quinoline, indigoid, quinacridone, phthalocyanine, and the like. Known organic pigments, such as naphthalocyanine-based, pyrrolo-pyrrole-based, perylene-based, and methine-based organic pigments, which generate electric charge by light irradiation.

When the charge generation layer is formed using only the photoconductive substance, a vacuum deposition method or the like is used.
When the charge generation layer is formed using the photoconductive substance and other components, the photoconductive substance, a binder and a plasticizer, a curing catalyst, a fluidity imparting agent, a pinhole controlling agent, and the like are required. The additives used in accordance with the above, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, ethyl acetate, cellosolve, methanol, isopropyl alcohol, isobutyl alcohol, n- butyl alcohol and the like, and uniformly dissolved in these solvents or A dispersion of the charge generation layer forming coating liquid is prepared, and the coating liquid is coated on the undercoat layer by a dip coating method, a spray coating method, a roll coating method, an applicator coating method, a coating method such as a wire bar coating method, or the like. It can be applied and dried to form.

Examples of the binder include silicone resin, polyamide resin, polyurethane resin, polyester resin, epoxy resin, polyketone resin, polycarbonate resin, polystyrene resin, polymethacrylate resin,
Polyacrylamide resin, polybutadiene resin, polyisoprene resin, melamine resin, benzoguanamine resin,
Polychloroprene resin, polyacrylonitrile resin, ethyl cellulose resin, nitrocellulose resin, urea resin, phenol resin, phenoxy resin, polyvinyl butyral resin, formal resin, vinyl acetate resin, vinyl acetate / vinyl chloride copolymer, polyester carbonate resin, etc. Can be Also, heat and / or photo-curable resins can be used. In any case, there is no particular limitation as long as the resin is electrically insulating and can form a film in a normal state.

As described above, when the charge generation layer is formed using the photoconductive substance and other components, the binder resin in the charge generation layer is based on 100 parts by weight of the photoconductive substance. Preferably 5 to 200 parts by weight.
More preferably, it is 0 parts by weight. If the amount is less than 5 parts by weight, the film of the charge generation layer tends to be nonuniform, and the image quality tends to be poor. If it exceeds 200 parts by weight, the sensitivity tends to decrease and the residual potential tends to increase.

As the plasticizer, halogenated paraffin,
Dimethylnaphthalene, dibutylphthalate and the like can be mentioned. Examples of the curing catalyst include sulfonic acids such as methanesulfonic acid, dodecylbenzenesulfonic acid, and dinonylnaphthalenedisulfonic acid. Examples of the fluidity-imparting agent include Modaflow (trade name of Monsanto Chemical Co., Ltd.) and Acronal 4F (trade name of Basff Co., Ltd.). Further, examples of the pinhole controlling agent include benzoin, dimethylphthalate and the like. Each of these is preferably used in an amount of 5 parts by weight or less based on the photoconductive substance.

The thickness of the charge generation layer is usually from 0.01 to
It is 0.2 μm, preferably 0.1 to 0.8 μm. If the thickness is less than 0.01 μm, it becomes difficult to form the charge generating layer uniformly, and if it exceeds 2.0 μm, the electrophotographic properties tend to be reduced. After the charge generation layer is formed as described above, the composition for the charge transport layer produced as described above is further coated on this layer by dip coating, spray coating, roll coating, applicator coating. , And is formed by coating using a coating method such as a wire bar coating method and drying. The thickness of the charge transport layer is usually 5 to 50 μm.
m, preferably 8 to 35 μm. This thickness is 5 μm
If less than 50 μm
If the ratio exceeds the above range, the electrophotographic properties tend to decrease.

In the electrophotographic photosensitive member according to the present invention, a protective layer may be further formed on the charge transport layer from the viewpoint of abrasion resistance. The thickness of the protective layer is 0.01 to 10 μm, preferably 0.1 to 3 μm. This thickness is 0.01μ
If it is less than 10 m, the effect of the protective layer is not obtained, and the durability is poor.
If it exceeds μm, the sensitivity tends to decrease and the residual potential tends to increase.

When printing is performed using the electrophotographic photoreceptor according to the present invention, after performing the charging and exposure in the same manner as in the related art, development is performed, and the image is transferred onto plain paper and fixed.

[0034]

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

Each material used in the following examples is listed below. The abbreviation is shown in parentheses. (A) Photoconductive substance generating charge τ-type metal-free phthalocyanine (τ-H2Pc) (manufactured by Toyo Ink Manufacturing Co., Ltd.)

(B) Charge transporting substance

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(A) MX1970 (MX1970) for undercoat layer Solid content 100% by weight (manufactured by Nippon Rilsan Co., Ltd.) Melan 2000 (ML2000) (butylated melamine resin having a bound formaldehyde number of 4.0 and a methylol group of 1.0) , Solid content 50% by weight (manufactured by Hitachi Chemical Co., Ltd.)

(B) Binder resin for charge generation layer Brominated phenoxy resin YPB-43 (YPB-43), solid content 40% by weight (manufactured by Toto Kasei Co., Ltd.)

(C) Binder resin for charge transport layer Polycarbonate resin having the following repeating structure

Embedded image Lexane 141-111 (L141), solid content 100% by weight (manufactured by GE), GP having the following repeating structure
C, polysulfone resin having a molecular weight of 53,000 in terms of polystyrene, Udel, solid content 100% by weight (manufactured by Amoco Chemical Japan Limited)

Embedded image Polycarbonate resin having the following repeating structure, T
S-2050 (TS-2050), solid content 100% by weight
(Manufactured by Teijin Chemicals Limited)

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The amino resin Melan 2000 (ML200
0, solid content 50% by weight) (same as for the undercoat layer) Amino resin Melan 365W (ML365, solid content 60)
Wt%) (manufactured by Hitachi Chemical Co., Ltd.)

Example 1 70 g of MX 1970, 140 g of ML2000 and 4.2 g of trimellitic acid were added to methyl ethyl ketone 360
0 g was completely dissolved. This solution was applied on an aluminum drum (outer diameter 120 mm, length 486 mm, thickness 4 mm) by dip coating, dried at 120 ° C. for 30 minutes, and dried to a film thickness of 0.1 mm.
An undercoat layer of 3 μm was formed.

Next, 100 g of τ-H ₂ Pc, 200 g
Of YPB-43 and 3,700 g of tetrahydrofuran were dispersed using an ultrasonic disperser for 80 hours. The obtained coating liquid for a charge generation layer was applied on the undercoat layer by a dip coating method, and dried at 140 ° C. for 30 minutes to form a 0.3 μm-thick charge generation layer.

Next, 140 g of PBD, 234 g of Udel and 43 g of ML2000 were added to methylene chloride 2400
g. This solution was applied on the charge generation layer having the undercoat layer by a dip coating method, and dried at 100 ° C. for 30 minutes to form a charge transport layer having a thickness of 18 μm, thereby forming an electrophotographic photosensitive member.

Example 2 An undercoat layer and a charge generation layer were formed on an aluminum drum using the materials and operations described in Example 1. Next, 140
g PBD, 234 g Udel and 43 g ML36
5 W was dissolved in 2400 g of methylene chloride. This solution was applied on the charge generation layer having the undercoat layer by a dip coating method, and dried at 100 ° C. for 30 minutes to form a charge transport layer having a thickness of 18 μm, thereby forming an electrophotographic photosensitive member.

Example 3 An undercoat layer and a charge generation layer were formed on an aluminum drum using the materials and operations described in Example 1. Next, 140
g PBD, 182 g Udel and 130 g ML3
65 W was dissolved in 2400 g of methylene chloride. This solution was applied on the charge generation layer having the undercoat layer by a dip coating method, and dried at 100 ° C. for 30 minutes to form a charge transport layer having a thickness of 18 μm, thereby forming an electrophotographic photosensitive member.

Comparative Example 1 An undercoat layer and a charge generation layer were formed on an aluminum drum using the materials and operations described in Example 1. Next, 140
g of PBD and 260 g of L141 in methylene chloride 24
00g. This solution was applied on the charge generation layer having the undercoat layer by a dip coating method.
After drying for 0 minutes, a charge transport layer having a film thickness of 17 μm was formed, and an electrophotographic photoreceptor was formed.

Comparative Example 2 A subbing layer having a thickness of 0.3 μm was formed on an aluminum drum (120 mm in outer diameter, 486 mm in length, and 4 mm in thickness) using the materials and operations shown in Example 1. Next, a charge generation layer having a thickness of 0.3 μm was formed on the undercoat layer using the substances and operations described in Example 1.

Next, 140 g of PBD and 260 g of T
S-2050 was dissolved in 2400 g of methylene chloride. This solution is applied on the charge generation layer having the undercoat layer by a dip coating method, and dried at 100 ° C. for 30 minutes to form a film having a thickness of 16 μm.
A μm charge transport layer was formed to form an electrophotographic photoreceptor.

Comparative Example 3 A subbing layer having a thickness of 0.3 μm was formed on an aluminum drum (outer diameter: 120 mm, length: 486 mm, thickness: 4 mm) using the materials and operations described in Example 1. Next, a charge generation layer having a thickness of 0.3 μm was formed on the undercoat layer using the substances and operations described in Example 1.

Next, 140 g of PBD and 260 g of Udel were dissolved in 2400 g of methylene chloride. This solution was applied on the charge generation layer having the undercoat layer by a dip coating method, and dried at 100 ° C. for 30 minutes to form a charge transport layer having a thickness of 18 μm, thereby forming an electrophotographic photosensitive member.

The photoresponsiveness and image quality (initial and after printing at 100 kP) of the electrophotographic photosensitive members obtained in the above Comparative Examples and Examples were evaluated by the following methods.

The light response was measured by a light attenuation measurement (manufactured by Midoriya Electric Co., Ltd.
Using Cynthia 30), corona charging is performed so that the surface potential becomes -700 V, and light having a wavelength of 780 nm
The evaluation was based on the time required for V ₀ to become −350 V when irradiated with ms.

The image quality was evaluated by using an image evaluator (negative charging, reversal developing method), fog, black spot,
Evaluation was made based on image density of white spots, filming, and black background. The surface potential was -700 V, and the bias potential was -600 V. The image density on a black background was measured using a Macbeth reflection densitometer (A Divisi
on of Kollmorgen Corporation). Table 1 summarizes the results of these evaluations.

[0054]

[Table 1]

When a bisphenol A type polycarbonate resin was used for the charge transport layer (Comparative Example 1), the photoresponsiveness was 1
8 ms. The initial image had many fog, black spots, and white spots, and the image density was 1.2. Therefore, this photoconductor was not subjected to the 100 kP printing test. When a bisphenol Z-type polycarbonate resin was used for the charge transport layer (Comparative Example 2), the photoresponsiveness was 17 ms. The initial image was good without fogging, black spots, white spots, and image streaks caused by toner filming on the surface of the charge transport layer, and the image density was 1.4. However, the image after the 100 kP printing test had black streak-like defects caused by filming. The amount of decrease in film thickness after the 100 kP printing test was as large as 4.0 μm. When only the polysulfone resin represented by the formula (I) was used for the charge transport layer (Comparative Example 3), the photoresponsiveness was 18 ms. Initial and 10
The image after the 0 kP printing test was good, but the decrease in film thickness after the 100 kP printing was as large as 4.2 μm.

On the other hand, each of the electrophotographic photosensitive members according to the present invention (Examples 1, 2 and 3) has a photoresponsiveness of 18%.
ms. The initial image was good without fogging, black spots, white spots, and image streaks caused by toner filming on the surface of the charge transport layer, and the image density was 1.4.
The image after the 100 kP printing test was also favorable without black streak-like defects due to fog, black spots, and white spots, and had an image density of 1.4. In addition, the decrease in film thickness after the 100 kP printing test was as small as 2 μm or less, which proved to be excellent in abrasion resistance.

[0057]

According to the charge transport layer composition of the present invention and the electrophotographic photoreceptor using the composition, the charge transport material in the charge transport layer, the binder polysulfone resin and the amino resin are mixed. Because it is considered to be uniform, when printing continuously using a high-speed printer, it produces excellent image quality without fogging, black spots, white spots, filming, and abrasion resistance is there. Therefore, the electrophotographic photoreceptor of the present invention can be very advantageously applied to a printer that requires high-speed response, high image quality, and a high number of printed sheets.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Susumu Sakio Inventor, Yamazaki Plant, Hitachi Chemical Co., Ltd. 4-3-1 Higashicho, Hitachi City, Ibaraki Prefecture

Claims (2)

[Claims] 1. The general formula 1 (I) A charge transport layer composition comprising a polysulfone resin having a repeating structural unit represented by formula (1) and an amino resin. 2. An electrophotographic photoreceptor having a charge transport layer using the composition for a charge transport layer according to claim 1.