JPH04273247A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor comprising a photosensitive layer including a charge generation layer and a charge transfer layer on a conductive substrate.

0002

2. Description of the Related Art Electrophotographic photoreceptors (hereinafter simply referred to as photoreceptors) generally include a photosensitive layer containing a photoconductive substance on a conductive substrate. In electrophotographic image formation related to Carlson's invention, the surface of the photoreceptor is charged, imagewise exposed to form an electrostatic latent image, and the electrostatic latent image is developed with toner to form a visible image. Then, the visible image is transferred and fixed onto a support such as paper. On the other hand, the surface of the photoreceptor is cleaned by removing residual toner and eliminating static electricity, and is used repeatedly over a long period of time. Therefore, as a photoreceptor, it is important not only to have good electrophotographic properties such as charging properties, charge retention properties, and photosensitivity, but also to have good electrophotographic properties such as stability, abrasion resistance, and ozone resistance even after repeated use over a long period of time. , durability, such as resistance to ultraviolet rays, etc., and the environment during use (low temperature/
It is required that there be little variation in characteristics due to low humidity, high temperature/high humidity).

Conventionally, inorganic photoreceptors containing inorganic photoconductive substances such as selenium, zinc oxide, and cadmium sulfide as a main component have been widely used as photoreceptors. but,
These inorganic photoreceptors also have various drawbacks such as photosensitivity, thermal stability, durability, environmental resistance, and toxicity, and are not always fully satisfactory.

In contrast to these inorganic photoreceptors, photoreceptors using organic photoconductive materials have been actively researched and developed in recent years, and some of them have been put into practical use.

[0005] Organic photoreceptors are attracting attention because they are less toxic than inorganic photoreceptors and have excellent light weight, flexibility, and productivity. For example, Japanese Patent Publication No. 50-10496 proposes a photoreceptor containing poly-N-vinylcarbazole and 2,4,7-trinitro-9-fluorenone, and Japanese Patent Publication No. 48-25658 proposes a photoreceptor containing poly-N- - A photoreceptor in which vinyl carbazole is sensitized with pyrylium dye has been proposed. However, these photoreceptors were not necessarily fully satisfactory in terms of photosensitivity and durability. after that,
When the photosensitive layer is exposed to light in the presence of an electric field, it is functionally separated into a layer that generates charges and a layer that moves the generated charges.
So-called functionally separated photoreceptors have been proposed, and the performance of organic photoreceptors has improved dramatically. For example, Tokuko Sho 55-4238
No. 0 proposes a functionally separated photoreceptor using chlorodiane blue and a hydrazone compound.

In this way, by separating the photosensitive layer into a charge generation layer and a charge transfer layer and assigning their functions, it is possible to easily produce photoreceptors with various characteristics, such as high photosensitivity and durability. It is expected that a photoreceptor with excellent properties will be obtained. The charge generation layer of such a photoreceptor is generally composed of an organic pigment as a charge generation substance and a binder resin as a binder. This is because if the charge generation layer is made of only organic pigments, it itself has no film-forming ability, resulting in poor adhesion to the substrate and charge transfer layer, resulting in insufficient mechanical strength of the photoreceptor. This is because such problems tend to occur, and the dispersibility and dispersion stability of the coating liquid are insufficient, resulting in the problem that continuous coating cannot be performed industrially. Examples of binder resins used as such binders include polyvinyl butyral resin (disclosed in JP-A No. 58-105154), acrylic resin with an acid value of 10 to 40, and a glass transition temperature of 70°C or less (especially (Disclosed in JP-A-58-192040), polyvinylpyrrolidone resin (Disclosed in JP-A-56-12646),
Polyvinylpyridine resin (disclosed in JP-A-56-60443), phenol resin (JP-A-58-17448)
Various methods have been proposed, such as those disclosed in Japanese Patent Publication No.

[0007]

[Problems to be Solved by the Invention] The required performances for the binder resin used as a binder in the charge generation layer are as follows: (1) good dispersibility of the organic pigment as the charge generation substance;
Good dispersion stability. (2) Good adhesion to the conductive substrate or subbing layer and charge transfer layer. (3) It should not be attacked by the charge transfer layer coating liquid or the intermediate layer coating liquid. (4) It should be stable against changes in temperature and humidity and have good light resistance. The binder resin has become a major factor influencing the performance of the charge generation layer and, ultimately, the performance of the photoreceptor.

However, there is no governing rule regarding the selection of binder resins, and the actual situation is that they are selected empirically depending on the type of organic pigment as a charge-generating substance and its film quality. I haven't gotten what I could have.

The present invention has been made in view of the above points, and by using a specific binder resin as a binder for the charge generation layer, it has high sensitivity, excellent durability,
The object of the present invention is to provide a photoreceptor whose characteristics are stable for long-term repeated use and whose characteristics are less likely to fluctuate due to changes in temperature and humidity.

0010

[Means for Solving the Problems] According to the present invention, in an electrophotographic photoreceptor comprising a photosensitive layer including a charge generation layer and a charge transfer layer on a conductive substrate, the charge generation layer is The problem is solved by providing a photoreceptor that contains an organic pigment as a charge generating substance and a binder resin as a binding agent, and the binder resin contains poly(p-vinylphenol) resin.

Poly(p-vinylphenol) resin is a p-vinylphenol resin.
- Obtained by copolymerizing vinylphenol alone or with other monomers or vinyl monomers, specific products include Marukalinka M (average molecular weight 2,000 to 3
0,000), Marukalinka MB (average molecular weight 6,00
0 to 7,000) (manufactured by Idemitsu Petrochemical), etc. are known.

The poly(p-vinylphenol) resin content of the binder resin is preferably 50% by weight or more, more preferably 70% by weight or more.

Examples of binder resins that can be used together with poly(p-vinylphenol) resin include vinyl acetate resin, methacrylic resin, polyester resin, polystyrene resin, and butyral resin. In particular, when a resin having a functional group capable of crosslinking by reacting with the phenolic hydroxyl group contained in the poly(p-vinylphenol) resin, such as an epoxy resin, is used, the resulting photoreceptor has repeated use characteristics and environmental resistance characteristics. This is preferable because it further improves.

The organic pigments for the charge generation layer include azo pigments, anthraquinone pigments, polycyclic quinone pigments, indigo pigments, diphenylmethane pigments, azine pigments, cyanine pigments, quinoline pigments, benzophenone, and naphthoquinone pigments. Pigments, perylene pigments, fluorenone pigments, squarylium pigments, azulenium pigments, perinone pigments, quinacridone pigments, phthalocyanine pigments, naphthalocyanine pigments, polyphylline pigments, etc. are used. In this invention, among these, polycyclic quinone pigments such as 3,9-dibromoanthanthrone, metal-free phthalocyanine, copper phthalocyanine, chloraluminum phthalocyanine, vanadyl phthalocyanine, titanyl phthalocyanine, and those represented by the following general formula are used in particular. Azo pigments are effective.

[0015]

[Chemical formula 1]

[In the formula, R1 represents a halogen atom, an alkyl group, or an alkoxy group, R2 represents an alkyl group that may have a substituent, and R3 represents a hydrogen atom, a cyano group, or a carbamoyl group. , a carboxyl group, an ester group, or an acyl group, and R4 represents any one of a hydrogen atom, a halogen atom, a nitro group, an alkyl group, and an alkoxy group. ]

Specific examples of these azo pigments are as follows.

[0018]

[Case 2]

[0019]

[Chemical formula 3]

[0020]

[C4]

[0021]

[C5]

[0022]

[C6]

[0023]

[C7]

These pigments can be used alone or in any combination of pigments of any type in any proportion.

Further, as the organic solvent, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, acetone, dimethyl formamide, etc. are used.

The coating liquid for the charge generation layer is prepared by dispersing a binder resin containing the above-mentioned poly(p-vinylphenol) resin, an organic pigment, and an organic solvent using a dispersion device such as a ball mill, sand mill, or attritor. A spreading agent, a surfactant, etc. may be added to the coating liquid as necessary. Further, the mixing ratio of the binder resin and the organic pigment in the coating liquid is preferably 5 parts by weight to 200 parts by weight, more preferably 10 parts by weight to 100 parts by weight, based on 100 parts by weight of the organic pigment. If it is less than 5 parts by weight, the effect of the binder resin of the present invention is small, and if it is more than 200 parts by weight, the photosensitivity tends to decrease.

The charge generation layer is formed by applying such a coating liquid onto a conductive substrate, drying it, and further curing it by heating if necessary. The thickness of the charge generation layer is preferably 0.05 μm to 5 μm. If the thickness is less than 0.05 μm, film forming properties are poor and defects are likely to occur in the image, and if it is more than 5 μm, the photoreceptor characteristics such as charging characteristics deteriorate.

On this charge generation layer, a coating liquid in which a high molecular compound as a charge transfer substance is dispersed and dissolved in an organic solvent, or a low molecular compound as a charge transfer substance and a binder resin as a binder is applied to an organic solvent. A coating liquid dispersed and dissolved in a solvent is applied and dried to form a charge transfer layer to form a photoreceptor.

Polymer compounds suitable as charge transfer substances include poly(N-vinylcarbazole), poly(vinylanthracene), poly(9,10-anthracenylendodecanedicarboxylate), polysilane, polygermane, poly (p-phenylene sulfide), etc. Low molecular weight compounds suitable as charge transfer substances include hydrazone compounds, pyrazoline compounds, enamine compounds, styryl compounds, arylmethane compounds, arylamine compounds, Examples include butadiene compounds and azine compounds, which may be used alone or in combination.

Binder resins used in combination with low-molecular compounds as charge transfer substances include polycarbonate, polyester, polyurethane, epoxy resins, silicone resins, styrene resins, acrylic resins, and methacrylic resins. Or used in combination. The mixing ratio of the low molecular compound and the binder resin is preferably 50 parts by weight to 200 parts by weight of the binder resin per 100 parts by weight of the low molecular compound.

[0031] If necessary, stabilizers such as antioxidants, ultraviolet absorbers, and proton absorbers can be added to the coating liquid for the charge transfer layer. A spreading agent, anti-sagging agent, etc. can also be added to prevent sagging.

The thickness of the charge transfer layer is arbitrarily determined depending on the charging characteristics, photosensitivity, printing durability, etc. required for the photoreceptor, but is usually 5 μm to 50 μm, preferably 10 μm to 3 μm.
It is assumed to be 0 μm.

[0033]

[Action] By including poly(p-vinylphenol) resin in the binder resin of the charge generation layer of the functionally separated photoreceptor, it has high sensitivity, excellent durability, and is suitable for long-term repeated use. Therefore, it is possible to obtain a photoreceptor whose characteristics are stable and whose characteristics are less likely to fluctuate due to changes in temperature and humidity. Furthermore, by incorporating a resin having a functional group capable of crosslinking by reacting with the phenolic hydroxyl group contained in the poly(p-vinylphenol) resin into this binder resin, repeated use characteristics and environmental resistance characteristics are further improved. can be improved.

[0034]

EXAMPLES Examples of the present invention will be described in detail below, but the present invention is not limited thereto.

Example 1 8 parts by weight of chlorinated aluminum phthalocyanine chloride purified by sublimation and 563 parts by weight of methyl ethyl ketone were ground and dispersed in a glass ball mill at room temperature for 10 hours. In the resulting dispersion, 5.6 parts by weight of poly(p-vinylphenol) resin (manufactured by Idemitsu Petrochemical Co., Ltd.: Maruka Linker MB) and 2.4 parts by weight of polyester resin (manufactured by Toyobo Co., Ltd.: Vylon 200) were dissolved to form a charge generation layer. A coating liquid was prepared. On the other hand, 1 of polyamide (manufactured by Toray: Copolymerized nylon CM-4001)
The wt% solution was applied to a 100 μm thick aluminum sheet so that the dry thickness was 0.1 μm to prepare a conductive substrate. The charge generation layer coating liquid prepared above was applied onto this conductive substrate and dried at 100° C. for 1 hour to form a charge generation layer with a thickness of 0.1 μm.

On this charge generation layer, 10 parts by weight of p-diethylaminobenzaldehyde (diphenylhydrazone) and polycarbonate resin (manufactured by Mitsubishi Gas Chemical: PCZ) were applied.
A charge transfer layer was formed by coating a solution consisting of 10 parts by weight of 100) and 72 parts by weight of 1,2 dichloroethane so that the film thickness after drying was 15 μm, and a photoreceptor was prepared.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the amount of polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) used as a binder resin in the coating liquid for the charge generation layer was changed to 8 parts by weight. A photoreceptor was prepared.

Comparative Example 2 In Example 1, the amount of polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) used as a binder resin in the coating liquid for the charge generation layer was changed to 4 parts by weight, and poly(p-vinylphenol) resin ( Idemitsu Petrochemical: Maruka Linker-MB)
A photoreceptor was produced in the same manner as in Example 1 except that the amount of was changed to 4 parts by weight.

Comparative Example 3 In Example 1, the amount of polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) used as a binder resin in the coating liquid for the charge generation layer was changed to 5.6 parts by weight, and poly(p-vinylphenol) Resin (manufactured by Idemitsu Petrochemical: Maruka Linker-M)
A photoreceptor was produced in the same manner as in Example 1 except that the amount of B) was changed to 2.4 parts by weight.

Example 2 8 parts by weight of X-type metal-free phthalocyanine and 563 parts by weight of methyl ethyl ketone were mixed in a glass ball mill at room temperature.
It was crushed and dispersed for 0 hours. Poly(p-
A coating liquid for the charge generation layer was prepared by dissolving 5.6 parts by weight of vinylphenol resin (Maruka Linker-M, manufactured by Idemitsu Petrochemical) and 2.4 parts by weight of polyvinyl butyral resin (BM-2, manufactured by Sekisui Chemical). did. This coating liquid was applied onto the same conductive substrate as in Example 1 and dried at 100° C. for 1 hour to form a charge generation layer with a thickness of 0.4 μm.

On this charge generation layer, 10 parts by weight of 4-(diethylamino)styryl-2-anthracene and 10 parts by weight of polycarbonate resin (PCZ-300 manufactured by Mitsubishi Gas Chemical Co., Ltd.) were applied.
A charge transfer layer was formed by applying a solution containing 72 parts by weight of 1,2 dichloroethane to a thickness of 15 μm after drying, thereby preparing a photoreceptor.

Comparative Example 4 Example 2 except that the amount of polyvinyl butyral resin (BM-2, manufactured by Sekisui Chemical Co., Ltd.) used as a binder resin in the coating liquid for the charge generation layer was changed to 8 parts by weight. A photoreceptor was produced in the same manner as described above.

Comparative Example 5 In Example 2, the amount of polyvinyl butyral resin (BM-2, manufactured by Sekisui Chemical Co., Ltd.) used as a binder resin in the coating liquid for the charge generation layer was changed to 4.8 parts by weight, and
A photoreceptor was produced in the same manner as in Example 2, except that the amount of p-vinylphenol resin (Maruka Linker-M, manufactured by Idemitsu Petrochemical) was changed to 3.2 parts by weight.

Example 3 A coating solution for a charge generation layer was prepared in the same manner as in Example 1 except that the chlorinated aluminum phthalocyanine chloride was replaced with the following azo pigment. This coating liquid was applied onto the same conductive substrate as in Example 1 to form a charge generation layer having a thickness of 0.5 μm.

[0045]

[Chemical formula 8]

A charge transfer layer was formed on this charge generation layer in the same manner as in Example 1 to obtain a photoreceptor.

Comparative Example 6 The same procedure as in Example 3 was carried out except that the amount of polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) used as a binder resin in the coating liquid for the charge generation layer was changed to 8 parts by weight. A photoreceptor was prepared.

Comparative Example 7 In Example 3, the amount of polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) used as a binder resin in the coating liquid for the charge generation layer was changed to 6.4 parts by weight, and poly(p-
A photoreceptor was produced in the same manner as in Example 3, except that the amount of (vinylphenol) resin (manufactured by Idemitsu Petrochemical Co., Ltd.: Maruka Linker-MB) was changed to 1.6 parts by weight.

Example 4 10 parts by weight of 3,9-dibromoanthanthrone and 600 parts by weight of cyclohexanone were ground and dispersed in a sand mill. To this dispersion, 5 parts by weight of poly(p-vinylphenol) resin (manufactured by Idemitsu Petrochemical Co., Ltd.: Marukalinka-MB), epoxy resin (manufactured by Ciba Geigy Co., Ltd.: Araldite XNR4)
254) and 1.42 parts by weight of its curing agent (manufactured by Ciba Geigy: Araldite curing agent XNH4254) were dissolved to prepare a coating liquid. This coating liquid was applied onto the same conductive substrate as in Example 1 and dried to form a film with a thickness of 0.5 μm, and heated and cured at a temperature of 120° C. for 2 hours to form a charge generation layer.

A solution consisting of 10 parts by weight of an enamine compound represented by the following formula, 10 parts by weight of polycarbonate resin (PCZ-300 manufactured by Mitsubishi Gas Chemical), and 72 parts by weight of 1,2-dichloroethane was applied onto this charge generation layer. , and was dried to form a charge transfer layer with a thickness of 15 μm to obtain a photoreceptor.

[0051]

[Chemical formula 9]

Comparative Example 8 In Example 4, the amount of the epoxy resin (Araldite Araldite hardener XNH
A photoreceptor was produced in the same manner as in Example 4 except that the amount of (4254) was changed to 3.79 parts by weight.

The electrophotographic properties of the photoreceptor thus obtained were measured using an electrostatic recording paper tester "SP-428" manufactured by Kawaguchi Electric.

The photoreceptor was charged with corona at -6.0 kV in a dark place, the surface potential V0 (volt) was measured, and then the surface potential decay rate was measured by leaving the photoreceptor in a dark place with corona discharge stopped for 5 seconds. DDR5 (%) was measured. Next, Example 1 using a phthalocyanine pigment as a charge generating substance,
2 and Comparative Examples 1 to 5, the wavelength was 780.
The half-reduction exposure energy E1/2 (μJ/cm2) was determined by irradiating light with a light intensity of 3.84 μw/cm2 and measuring the time for the surface potential to decay to 1/2, and then after 1.3 seconds of light irradiation. The residual potential Vr (volt) on the surface of the sample was measured. In addition, the photoreceptors of Example 3 and Comparative Examples 6 and 7 use an azo pigment as a charge-generating substance, and the photoreceptors of Example 4 and Comparative Example 8 use 3,9-dibromoanthanthrone.
For the photoreceptor, irradiate it with white tungsten light of 20 lux, measure the time for the surface potential to decay to 1/2, find the half-decreased exposure energy E1/2 (lux/sec), and further calculate the 1.3 lux of light irradiation. The residual potential Vr (volt) on the surface after seconds was measured.

[0055] The measurement results of these initial characteristics were summarized in Example 1,
The photoreceptors of Examples 3 and 4 and Comparative Examples 6 to 8 are shown in Table 1. The photoreceptors of Examples 3 and 4 and Comparative Examples 6 to 8 are shown in Table 2.

[0056]

[Table 1]

[0057]

[Table 2]

In Tables 1 and 2, when comparing the corresponding examples and comparative examples, it is found that the photoreceptor containing a larger amount of poly(p-vinylphenol) resin as the binder resin of the electrogenerating layer has better initial characteristics, especially photoreceptor. It can be seen that the sensitivity is good.

Next, changes in characteristics of these photoreceptors were investigated when the above-mentioned charging and photostatic discharge were repeated 2,500 times. The results are shown in Tables 3 and 4.

[0060]

[Table 3]

[0061]

[Table 4]

From Tables 1 and 3, Tables 2 and 4, there is a tendency for the photoreceptors of Examples to have less variation in characteristics than the photoreceptors of Comparative Examples, and there is a particularly notable difference in residual potential Vr. It can be seen that the higher the content of poly(p-vinylphenol) resin, the better.

Next, the photoreceptors of Example 1, Comparative Example 1, Example 2, and Comparative Example 5 were each 80 mm in diameter and 400 m in length.
A durability test was conducted by attaching it to a commercially available semiconductor laser printer (NEC: LL-NIP) and printing on 150,000 sheets of A4 paper equivalent to the dark potential Vd (volts). , fluctuations in the exposed part potential Vi (volts) were investigated and the images were evaluated. These tests were performed at normal temperature and humidity (temperature 23℃, relative humidity 60%), low temperature and low humidity (temperature 7℃, relative humidity 50%), and high temperature and high humidity (temperature 35℃).
The test was carried out under various environments (°C, relative humidity 80%). The results are shown in Tables 5 and 6.

[0064] The photoreceptors of Example 3, Comparative Example 7, Example 4, and Comparative Example 8 each had a diameter of 80 mm and a length of 340 m.
Durability: 150,000 sheets of A4 paper equivalent to A4 paper can be printed under the same three environments as above by attaching it to a M aluminum tube and attaching it to a commercially available copier (manufactured by Minolta Camera: EP-4902). The test was conducted and the dark potential Vd (volts),
The image was evaluated by examining fluctuations in the blank area potential Vl (volts). The results are shown in Tables 7 and 8.

[0065]

[Table 5]

[0066]

[Table 6]

[0067]

[Table 7]

[0068]

[Table 8]

From Tables 5 to 8, the photoreceptor containing a larger amount of poly(p-vinylphenol) resin as the binder resin in the charge generation layer has less characteristic fluctuation during repeated use and is more stable against environmental changes. It can be seen that high quality images can be maintained. The content of the poly(p-vinylphenol) resin is preferably 50 parts by weight or more, more preferably 70 parts by weight or more.

[0070]

According to the present invention, by incorporating poly(p-vinylphenol) resin into the binder resin used as a binding agent in the charge generation layer of a functionally separated organic photoreceptor, high sensitivity and durability can be achieved. It is possible to obtain an electrophotographic photoreceptor that has excellent properties, stable properties for long-term repeated use, and less variation in properties due to changes in temperature and humidity.

The content of poly(p-vinylphenol) resin in the binder resin is preferably 50% by weight or more, more preferably 70% by weight or more. In addition, the binder resin includes a poly(p-vinylphenol) resin and a resin having a functional group capable of crosslinking by reacting with the phenolic hydroxyl group contained in the poly(p-vinylphenol) resin, such as an epoxy resin. When used, repeated use characteristics and environmental resistance are further improved.

Claims (5)

[Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer including a charge generation layer and a charge transfer layer on a conductive substrate, wherein the charge generation layer comprises an organic pigment as a charge generation substance and a binder as a binder. 1. A photoreceptor for electrophotography, characterized in that the binder resin contains a poly(p-vinylphenol) resin. 2. The electrophotographic photoreceptor according to claim 1, wherein the binder resin contains 50% by weight or more of poly(p-vinylphenol) resin. 3. The electrophotographic photoreceptor according to claim 1, wherein the binder resin contains 70% by weight or more of poly(p-vinylphenol) resin. 4. The binder resin includes a poly(p-vinylphenol) resin and a resin having a functional group capable of reacting with the phenolic hydroxyl group contained in the poly(p-vinylphenol) resin. Claims 1, 2,
3. The electrophotographic photoreceptor according to any one of 3. 5. The electrophotographic photoreceptor according to claim 4, wherein the resin having a functional group capable of reacting with the phenolic hydroxyl group contained in the poly(p-vinylphenol) resin is an epoxy resin.