JP2000258940A - Coating fluid for production of electrophotographic photoreceptor and electrophotographic photoreceptor using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating fluid for the production of an electrophotographic photoreceptor excellent in stability and causing few coating defects and to obtain an electrophotographic photoreceptor having a layer formed using the coating fluid and less liable to a change in electrification characteristics and residual potential in repetitive use in an electrophotographic process. SOLUTION: Titanium dioxide particles are dispersed in 1,3-dioxolane containing a dissolved alcohol-soluble nylon resin as a solvent to obtain the objective coating fluid for forming an undercoat layer disposed between an electrically conductive substrate and a photosensitive layer in an electrophotographic photoreceptor. In the electrophotographic photoreceptor having at least the undercoat layer and the photosensitive layer on the electrically conductive substrate, a layer formed using the coating fluid is used as the undercoat layer.

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, and more particularly, to a coating liquid for forming an undercoat layer provided between a conductive support and a photosensitive layer in the electrophotographic photosensitive member. A coating solution with excellent stability and few coating defects,
The present invention relates to an electrophotographic photoreceptor having a layer formed using the coating liquid and having small changes in charging characteristics and residual potential due to repetition.

[0002]

2. Description of the Related Art Heretofore, as an electrophotographic photoreceptor, a photoreceptor having a photosensitive layer mainly composed of an inorganic photoconductor such as selenium, zinc oxide and cadmium sulfide has been widely known. However, they are not always satisfactory in sensitivity, heat stability, moisture resistance, durability, and the like. In particular, selenium and cadmium sulfide are restricted in production and handling due to toxicity.

On the other hand, an electrophotographic photosensitive member having a photosensitive layer containing an organic photoconductive compound as a main component is relatively easy to manufacture, inexpensive, easy to handle,
In addition, it generally has many advantages such as superior thermal stability as compared with selenium photoreceptors, and has attracted much attention in recent years. Such organic photoconductive compounds include poly-N
-Vinyl carbazole is well known,
An electrophotographic photoreceptor having a photosensitive layer mainly composed of a charge transfer complex formed with a Lewis acid such as 4,7-trinitro-9-fluorenone is described in JP-B-50-10469. However, this photoreceptor is not always satisfactory in sensitivity, film formability, and durability.

On the other hand, low-molecular-weight organic photoconductors represented by hydrazones and pyrazolines have been proposed. By combining these with an appropriate binder, the film-forming properties have been greatly improved, but the sensitivity and durability have not been sufficiently improved. Under such circumstances, a function-separated type photoconductor has been proposed in recent years, in which a charge generation function and a charge transfer function are shared by different substances. In this configuration, an organic pigment having a particularly high charge generation ability is used as a charge generation substance, and a charge transfer substance having a high charge transfer ability such as a hydrazone compound is combined with the charge transfer substance to significantly improve the charging characteristics and sensitivity. And others having a sensitivity close to that of an inorganic photoreceptor. As a result, electrophotographic photoreceptors containing these types of organic photoconductive compounds as main components have largely entered into fields such as copying machines and optical printers.

On the other hand, such an organic photoconductor undergoes complicated processes such as charging, exposure, and static elimination in a copying machine.
The compound is not only responsible for the generation and transfer of electric charge, but is also stimulated by ozone, light and the like in a high electric field. Therefore, as the process is repeated, there are still many problems in use, such as a decrease in the initial potential after charging and an increase in the residual potential after static elimination.

In order to compensate for the above-mentioned drawbacks, there has been proposed a method of providing an undercoat layer between a conductive support and a photosensitive layer.
For example, JP-A-48-47344 and JP-A-52-2563.
No. 8, No. 58-30757, No. 58-63945,
JP-A-58-98739 and JP-A-60-66258 disclose a nylon resin-based subbing layer and JP-A-49-69.
Nos. 332 and 52-10138 disclose a maleic acid resin-based subbing layer, and JP-A-58-105155 discloses a polyvinyl alcohol resin subbing layer.

There has also been proposed a method of controlling the electric resistance of the undercoat layer by incorporating various conductive additives into the undercoat layer. For example, JP-A-51-65942 discloses an undercoat layer in which a carbon or chalcogen-based substance is dispersed in a curable resin, and JP-A-52-82238 discloses an isocyanate-based layer in which a quaternary ammonium salt is added. A thermopolymer undercoat layer using a curing agent is disclosed in JP-A-55-118045, and an undercoat layer to which a resistance modifier is added is disclosed in JP-A-58-18045.
Japanese Patent Application Laid-Open No. 58-93063 discloses a subbing layer in which a tin or aluminum oxide is dispersed.
JP-A-60-97363 and JP-A-60-111255 disclose an undercoat layer in which conductive particles are dispersed.
JP-A-93453 and JP-A-63-298251 each disclose an undercoat layer in which titanium oxide particles are dispersed.

Among these, an electrophotographic photoreceptor using an undercoat layer in which titanium oxide particles are dispersed in an alcohol-soluble nylon resin has been known to reduce the initial potential after charging and the residual potential after static elimination during the process. The rise has been significantly improved,
Some have been put to practical use.

However, in a coating solution for forming an undercoat layer in which titanium oxide particles are dispersed in a solvent in which an alcohol-soluble nylon resin is dissolved, the titanium oxide particles are liable to agglomerate or settle in the coating solution, resulting in a short circuit life of the coating solution. Productivity tends to decrease due to coating defects. In addition, since methanol or ethanol is mainly used as a solvent for dissolving the alcohol-soluble nylon resin, clouding (brushing) is likely to occur on the surface of the coating film due to the magnitude of the latent heat of evaporation and the hygroscopicity of the solvent. Difficult to get.

In order to solve the above problems, the addition of a dispersing aid or a leveling agent to a coating solution has been studied, but these adversely affect the image characteristics and electrical characteristics of the completed electrophotographic photosensitive member. Often. As a result, it is very difficult to obtain an electrophotographic photoreceptor having an undercoat layer in which titanium oxide particles are dispersed in an alcohol-soluble nylon resin and having good characteristics.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an undercoat layer provided between a conductive support and a photosensitive layer in an electrophotographic photosensitive member. An object of the present invention is to provide an electrophotographic photoreceptor having a small amount of a coating liquid and having a layer formed using the coating liquid and having little change in charging characteristics and residual potential due to repetition.

[0012]

Means for Solving the Problems The present inventors have conducted various studies to achieve the above object, and as a result, have found that an undercoat layer provided between a conductive support and a photosensitive layer in an electrophotographic photosensitive member. For forming an electrophotographic photoreceptor obtained by dispersing titanium oxide particles in a solvent in which an alcohol-soluble nylon resin is dissolved, to form 1,3,3
-It has been found that by containing dioxolane, a coating liquid having excellent coating liquid stability and few coating defects can be obtained. Further, it has been found that by using a layer formed using the coating solution as the undercoat layer, an electrophotographic photoreceptor exhibiting excellent charging and exposure repetition characteristics can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The components of the present invention will be described below in detail.

The titanium oxide particles used in the coating solution for producing an electrophotographic photoreceptor of the present invention have a higher refractive index, are physically and chemically stable, have a higher hiding power and whiteness, as compared with other white pigments. It is used as an excellent pigment in printing inks, paints and other various fields.
There are anatase type, brookite type and amorphous, and any of them can be used, and any of acicular crystals and granular crystals can be used.
Further, those whose surface is treated with a hydrated oxide such as aluminum or silicon, or stearic acid or the like can be used.

The titanium oxide particles are dispersed in a solvent in which a binder has been dissolved by a disperser such as a ball mill, a vertical sand mill, a horizontal sand mill, or a paint conditioner.

The coating solution for producing an electrophotographic photoreceptor of the present invention,
The alcohol-soluble nylon resin used as the binder resin is soluble only in lower aliphatic alcohols. Therefore, as a coating solvent for coating the photosensitive layer on the undercoat layer composed of these resins, a solvent other than lower alcohol is used. May be used, and the range of choice of the solvent is increased. When the photosensitive layer is coated with a solvent that dissolves the undercoat layer, the photosensitive layer is mixed with the undercoat layer to deteriorate the characteristics, and depending on the coating method, disadvantages such as a non-uniform coated surface occur. Alcohol-soluble nylon resins can be generally classified into two types.
One is a so-called copolymer nylon obtained by copolymerizing nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, and the like, and the other is N-alkoxymethyl-modified nylon or N-alkoxyethyl-modified nylon. This is a type called modified nylon obtained by chemically modifying nylon, and any type can be used.

The ratio of titanium oxide to alcohol-soluble nylon resin in the present invention is 1 to 10 parts by weight of titanium oxide and 1 to 10 parts by weight of alcohol-soluble nylon resin.
00 parts by weight, preferably in the range of 1 to 400 parts by weight.

As the coating solvent used in the coating solution for producing an electrophotographic photosensitive member of the present invention, a mixed solvent is used. The mixed solvent is a mixture of a lower aliphatic alcohol that dissolves the alcohol-soluble nylon resin as a main solvent (true solvent) and 1,3-dioxolan as an auxiliary solvent. As the lower aliphatic alcohol which is a main solvent, methanol and ethanol are mainly used in terms of binder dissolving ability and coating film drying speed.

The use ratio of 1,3-dioxolan in the total solvent of the coating solution is used within a range that does not inhibit the solubility of the alcohol-soluble nylon resin. Decrease, the shortage of the life of the coating liquid due to the increase in viscosity or gelation of the coating liquid, or the deterioration of the coating property due to the deposition of the binder resin after the evaporation of the true solvent during the coating may occur.If the amount is too small, the coating property is improved. 20% by weight or more of the total solvent,
It is preferably 0% by weight or less. In addition, other alcohols and aromatic hydrocarbons, as long as the effects of the present invention are not impaired,
A halogen-containing hydrocarbon may be added for use.

As the conductive support on which the photoreceptor is formed in the present invention, any of those used for known electrophotographic photoreceptors can be used. Specifically, for example, a metal drum or sheet of aluminum, copper, or the like, a laminate of these metal foils, a deposit, or the like can be given. Further, plastic films, plastic drums, paper, and the like, which are subjected to a conductive treatment by applying a conductive substance such as metal powder, carbon black, copper iodide, and a polymer electrolyte together with a suitable binder, may be mentioned. Further, a plastic sheet or drum containing a conductive substance such as a metal powder, carbon black, or carbon fiber to become conductive may be used.

The photoreceptor of the present invention comprises a photosensitive layer formed on an undercoat layer formed by applying the undercoat layer-forming coating solution. The form of the photosensitive layer to be formed is a function separation single layer type in which a charge generation material and a charge transfer material are dispersed and mixed, and a function separation layered type in which a charge generation material and a charge transfer material are separated. Although the present invention can be applied to any system, it is preferably used in a system of a function-separated laminated type photoreceptor in which the performance of the charge generating material and the charge transfer material is easily maximized. Further, a surface layer may be provided on the surface of the photosensitive layer in order to improve abrasion resistance and gas barrier properties of the photosensitive member.

The organic charge generating substance used in the present invention includes azo pigments represented by monoazo pigments, polyazo pigments, metal complex salt azo pigments, pyrazolone azo pigments, stilbene azo pigments and thiazole azo pigments, and perylene anhydrides. And anthraquinone or polycyclic quinone pigments represented by anthraquinone derivatives, anthranthrone derivatives, dibenzpyrene quinone derivatives, pyranthrone derivatives, biolanthrone derivatives and isoviolanthrone derivatives. Phthalocyanine pigments such as metal phthalocyanine, metal naphthalocyanine, metal-free phthalocyanine, and metal-free naphthalocyanine; pigments such as porphyrin derivatives; triphenylmethane dyes such as methyl violet; quinizarin Quinone dyes and pyrylium salts, thiapyrylium salts, dyes such as Benzopiriumu salt.

Of these, those using bisazo pigments, trisazo pigments, and phthalocyanine pigments, which have particularly high carrier generation efficiency, are preferable because they provide high sensitivity and provide excellent photoreceptors. For example, in the case of a bisazo pigment, JP-A-62-286058, JP-A-63-32557, JP-A-63-243948, JP-A-64-21453, JP-A-64-21455, and JP-A-Hei. -94350, 1-20026
No. 7, JP-A 1-202775 and the like, compounds can be used. Examples of phthalocyanine pigments include metals such as metal-free phthalocyanine, copper, indium, titanium, gallium, germanium, and vanadium, or Phthalocyanines coordinated with their oxides, chlorides, hydroxides and the like, mixed crystals thereof, naphthalocyanines and the like can be mentioned.

In the function-separated type photoreceptor, a charge generating layer is formed by mixing these charge generating substances and, if necessary, a binder resin. Examples of the binder resin include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylate, and methacrylate, silicone resin, phenoxy resin, butyral resin, formal resin, phenol resin, polycarbonate, polyarylate, and the like. Thermosetting resin such as epoxy resin and urethane resin,
Photocurable resins and the like can be mentioned. 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 charge generating substance. The thickness of the charge generation layer is preferably from 0.1 to 20 μm.

The organic charge transfer material used in the present invention includes a hole transfer material and an electron transfer material. Examples of the former include oxadiazoles disclosed in JP-B-34-5466, triphenylmethanes disclosed in JP-B-45-555, and JP-B-52-4188.
Pyrazolines disclosed in Japanese Patent Publication No. 55-42
Hydrazones disclosed in JP-A-380 / 380
Oxadiazoles described in JP-A-123544, triarylamines described in JP-B-58-32372, stilbenes described in JP-A-58-198043, and the like. Can be. On the other hand, examples of the electron transfer material include chloranil, tetracyanoethylene, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitroxanthone,
Examples include 1,3,7-trinitrodibenzothiophene. These charge transfer materials can be used alone or in combination of two or more.

Among these charge transfer materials, hydrazones and stilbenes have high charge (hole) mobility,
It is preferable to provide an excellent photoreceptor. Among hydrazones, JP-A-1-100555 and 2-103
Nos. 67, 2-51163, 2--9676
No. 7, JP-A-2-183260, JP-A-2-2-1848
Nos. 56, 2-184858 and 2-184
Nos. 859 and 2-226160 and 5-18
Compounds described in JP-A-8609 and JP-A-7-140686 are particularly preferred. Among stilbenes, JP-A-2-51162 and JP-A-2-184857,
JP-A-3-75660, JP-A-4-177358,
The compounds described in JP-A-6-194851, JP-A-7-120945, JP-A-7-140683, JP-A-10-78671, and JP-A-10-90923 are particularly preferable.

In the function-separated type photoreceptor, a charge transfer layer is formed by mixing at least the charge transfer material and the binder resin. As the binder resin used in the charge transfer layer, polystyrene, an acrylic resin represented by polymethyl methacrylate, a polycarbonate resin having a bisphenol A or Z skeleton, a polyarylate resin, a polyphenylene ether resin, a polyether sulfone resin, a polyamide resin, A polyimide resin, a polyester resin, or the like can be used. In the charge transfer layer, the binder is used in an amount of 10 to 4 with respect to 100 parts by weight of the organic charge transfer material.
It is used in the range of 00 parts by weight. The thickness of the charge transfer layer is
5 to 100 μm is preferred.

The electrophotographic photoreceptor of the present invention has a structure of 2,6-di-te, in order to prevent deterioration of constituent organic compounds due to oxidation.
An antioxidant such as rt-butyl-p-cresol and DL-α-tocopherol may be added. Further, a well-known plasticizer may be used in order to improve film formability, flexibility, and mechanical strength.

Further, at the time of producing the photosensitive layer of the electrophotographic photosensitive member of the present invention, in the case of a pigment, a coating solution which is dispersed in a solvent and in which a dye, a binder and a charge transfer material are dissolved is used. Solvents used are halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, benzene, toluene,
Solvents such as aromatic hydrocarbons such as xylene, ethers such as dioxane, tetrahydrofuran and dimethoxyethane, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone alone or as a mixture of two or more solvents or, if necessary, cyclohexanone etc. A solvent can be further added and used. The coating methods include spin coating, blade coating, knife coating, reverse roll coating,
Known methods such as rod bar coating and spray coating can be used. In particular, when coating on a drum-shaped support, a dip (dip) coating method or the like is used.

[0030]

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 Alcohol-soluble nylon (Toray; CM-8000)
5 parts by weight were dissolved in a mixed solvent of 60 parts by weight of methanol as a main solvent and 40 parts by weight of 1,3-dioxolane as an auxiliary solvent, and titanium oxide (manufactured by Ishihara Sangyo; TTO-
S-1) 5 parts by weight were mixed and dispersed together with zirconia beads having a diameter of 1 mm using a sand grind mill for 5 hours to prepare a coating liquid for forming an undercoat layer.

Room temperature 20 ° C., relative humidity 45%, air pressure 760
Under a condition of mmHg, an aluminum drum tube was dip-coated with the undercoat layer-forming coating solution and air-dried to form an undercoat layer having a dry film thickness of 0.5 μm. The state of the dried coating surface and the state after the coating liquid for forming an undercoat layer was allowed to stand for 10 days were visually observed. Table 1 shows the results.

Next, an X-ray diffraction spectrum using CuKα ray is shown in FIG. 1. One part by weight of a titanyl phthalocyanine pigment having a crystal form, and a styrene-butadiene copolymer resin (GO
Odyear; Pliolite S-5D) 1 part by weight was mixed with 100 parts by weight of tetrahydrofuran, and dispersed together with low alkali glass beads having a diameter of 1 mm using a sand grind mill for 2 hours. The thus-obtained coating liquid for forming a charge generation layer was applied onto the undercoat layer by dip coating, followed by natural drying to form a charge generation layer having a dry film thickness of about 0.2 μm.

Further, 10 parts by weight of a stilbene compound represented by the following chemical formula (1), 10 parts by weight of a polycarbonate resin (C-1400, manufactured by Teijin Chemicals Limited), 2,6-di-ter
0.1 parts by weight of t-butyl-p-cresol was dissolved in 130 parts by weight of methylene chloride. The coating liquid for forming a charge transfer layer was applied onto the charge generation layer by dip coating, and dried by heating at 80 ° C. for 2 hours to form a charge transfer layer having a dry film thickness of 25 μm.

[0035]

Embedded image

The electrophotographic photoreceptor thus prepared was stored in a dark place at room temperature for 24 hours, and then stored at room temperature of 23 ° C. and a relative humidity of 55%.
Under the conditions described above, using a drum photoreceptor evaluation device (Gentec; Cynthia 90), a process speed of 190
mm / sec, charging voltage: -7.0 kV, exposure light wavelength: 78
Under the conditions of 0 nm, exposure light intensity: ² μW / cm ² , and light elimination: tungsten lamp array, the charging, exposure, and elimination processes were performed, and the half-exposure amount was measured. This process was repeated 10,000 times, and before and after that, the charged potential and the residual potential of the photoconductor were measured. Table 2 shows the results.

Examples 2 to 5 and Comparative Examples 1 to 5 The solvent in the coating liquid for forming the undercoat layer was prepared by mixing methanol as a main solvent and a solvent shown in Table 1 as a secondary solvent in a mixing ratio (weight ratio) shown in Table 1. An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the mixed solvent used was used, and the same measurements and evaluations as in Example 1 were performed. The results are shown in Tables 1 and 2.

[0038]

[Table 1]

[0039]

[Table 2]

Embodiments 1, 2, and 3 correspond to claims 1, 2, and 3 of the present invention, and embodiments 4 and 5 correspond to claims 1 and 3 of the present invention. Applicable, Comparative Example 1
It shows characteristics superior to 5. Examples 1, 2, and 3 and Examples 4 and 5 show excellent characteristics in both groups, but Examples 1, 2, and 3 are more excellent when both groups are compared.

[0041]

As is evident from the above, according to the present invention, it is possible to provide a coating liquid having excellent coating liquid stability and few coating defects, and to have a layer formed using the coating liquid. In addition, it is possible to provide an electrophotographic photoreceptor having small changes in charging characteristics and residual potential due to repetition.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction spectrum of a titanyl phthalocyanine pigment used in Example 1.

Claims (3)

[Claims] 1. A coating liquid for producing an electrophotographic photosensitive member, comprising titanium oxide particles dispersed in a solvent in which an alcohol-soluble nylon resin is dissolved, wherein 1,3-dioxolan is contained as the solvent. Coating solution for manufacturing photoreceptors. 2. The method according to claim 1, wherein the content of 1,3-dioxolane is 20% by weight or more and 60% by weight or less of the total amount of the solvent contained in the coating solution for producing an electrophotographic photosensitive member. Coating solution for the production of electrophotographic photoreceptors. 3. An electrophotographic photosensitive member comprising a layer formed using the coating solution for producing an electrophotographic photosensitive member according to claim 1.