JP3337152B2 - Manufacturing method of electrophotographic photoreceptor - Google Patents

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, and more particularly, to a method for producing an electrophotographic photosensitive member having excellent environmental characteristics, comprising titanium oxide particles as a main component. The present invention relates to a method for dispersing titanium oxide particles for forming an undercoat layer.

[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. For these reasons, a stacked photoreceptor has been proposed in recent years in which a carrier generating function and a carrier transporting function are shared by different substances. By adopting this structure, charging characteristics and sensitivity are greatly improved, especially using an azo pigment having a high carrier generation ability for the charge generation layer, and combining this with a charge transfer substance having a high carrier transport ability such as a hydrazone compound. As a result, those having a sensitivity close to that of an inorganic photoreceptor such as selenium have appeared. As a result, at present, electrophotographic photoreceptors containing these types of organic photoconductive compounds as main components have begun to enter into fields such as copying machines and optical printers.

In an electrophotographic photosensitive member, processes such as charging, exposure, and static elimination are repeated in a copying machine, a printer, and the like, and fluctuations in an initial potential after charging and a residual potential after static elimination affect an output image. It must be suppressed as much as possible. However, in general, these photoconductors have reduced chargeability and increased residual potential due to fatigue due to repeated charging and exposure.

In order to compensate for the above-mentioned disadvantages, a method has been proposed in which an undercoat layer is provided between a conductive substrate and a photosensitive layer. For example, JP-A-48-47344 and JP-A-52-25638.
JP-A-58-30757, JP-A-58-63945, JP-A-58-98739, and JP-A-60-66258 disclose a nylon resin-based subbing layer and JP-A-49-693.
JP-A Nos. 32 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 Japanese Patent Application Laid-Open No. 55-1180451.
In Japanese Patent Application Laid-Open No. Sho 5 (1993), an undercoat layer to which a resistance controlling agent is added is disclosed.
Japanese Unexamined Patent Publication No. 8-58556 discloses an undercoat layer in which a tin or aluminum oxide is dispersed.
No. 60-97363 and No. 60-11255
In Japanese Patent Application Laid-Open No. Sho 5 (1993), an undercoat layer in which conductive particles are dispersed is disclosed.
9-93453 and JP-A-63-298251.
In each of Japanese Patent Laid-Open Publications Nos. 2000-205, and 2006-157, an undercoat layer in which titanium oxide particles are dispersed is disclosed.

However, the conventional electrophotographic photoreceptor is
Deterioration of chargeability and increase in residual potential due to repeated fatigue of charging and exposure is still insufficient, and there is a problem that the rise in residual potential is particularly large under low temperature and low humidity. Was rare.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an electrophotographic photosensitive member whose characteristics are stabilized by repeated use even at a low temperature and a low humidity when repeatedly used in an electrophotographic process. Is to do.

[0010]

Means for Solving the Problems The inventors of the present invention have made various studies to achieve the above object, and as a result, have found that a titanium oxide particle is dispersed on a conductive support in a binder. In the method for producing an electrophotographic photoreceptor formed by sequentially laminating layers and photosensitive layers, the material of the dispersion medium for dispersing the titanium oxide particles is titania or zirconia, so that the material is extremely low temperature and low humidity. It has been found that an electrophotographic photoreceptor exhibiting excellent charging and exposure repetition characteristics can be obtained.

Hereinafter, the components of the present invention will be described in detail. Titanium oxide particles used in the present invention, compared with other white pigments, a large refractive index, physically and chemically stable, hiding power, printing ink as a pigment excellent in whiteness,
It is used in the field of paints and other various fields, and there are two types of crystal types, rutile type and anatase type, and any of them can be used. In the present invention, it is preferable to use rutile type. 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 the binder by a dispersing machine using a dispersing medium such as a ball mill, a vertical sand mill, a horizontal sand mill, a paint conditioner and the like. Is not used.

The material of the dispersion medium used in the present invention must be zirconia or titania. The dispersing medium is introduced into the above-mentioned dispersing machine together with the titanium oxide particles and gives a strong force to the titanium oxide to pulverize and disperse the titanium oxide in the binder. Various shapes such as a bead having a diameter of several mm, a ball having a diameter of several mm to several cm, and a column can be used. When a dispersion medium other than zirconia or titania is used, for example, zircon, which is said to have the same wear resistance as zirconia or titania, a dispersion medium such as alumina, or a glass dispersion medium that is inexpensive and very often used An electrophotographic photoreceptor having an undercoat layer formed by coating a titanium oxide dispersion prepared using the method described above has poor properties at low temperature and low humidity, and the effects of the present invention cannot be obtained.

It is still clear why an electrophotographic photosensitive member having an undercoat layer formed by coating a titanium oxide dispersion liquid using a medium made of zirconia or titania material has extremely excellent environmental characteristics. But not
Possibly, as the dispersion process proceeds, some interaction between the surface of the titanium oxide particles and these media acts to improve the electrical properties of the resulting subbing layer.

In the present invention, as the binder for dispersing the titanium oxide particles, styrene, vinyl acetate,
Acrylic esters, polymers and copolymers of vinyl compounds such as methacrylic esters, silicone resins, phenoxy resins, polysulfone resins, polyvinyl butyral resins, polyvinyl formal resins, polyester resins,
Cellulose ester resin, cellulose ether resin, urethane resin, phenol resin, epoxy resin, polycarbonate resin, polyarylate resin, polyamide resin,
Any of various polymers such as a polyimide resin can be used, but a polyamide resin is particularly preferable, and an alcohol-soluble nylon resin is particularly preferable.

Alcohol-soluble nylon resins are soluble only in lower aliphatic alcohols such as methanol and ethanol. Therefore, when a photosensitive layer is provided on an undercoat layer made of these resins, solvents other than lower alcohols are used as coating solvents. 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, inconveniences such as mixing with the undercoat layer and deteriorating the properties, and depending on the coating method, making the coated surface non-uniform occur. Alcohol-soluble nylon resins can be generally classified into two types, one of which is nylon 6, nylon 66, nylon 61.
A type of so-called copolymer nylon obtained by copolymerizing 0, nylon 11, nylon 12, and the like.
It is a type called modified nylon obtained by chemically modifying nylon, such as -alkoxymethyl-modified nylon and N-alkoxyethyl-modified nylon. The alcohol-soluble nylon resin used in the present invention is more preferably a copolymer nylon.

In the present invention, as a coating solvent for dispersing titanium oxide in a binder to form an undercoat layer, any solvent can be used as long as it dissolves the binder. In particular, when the above-mentioned alcohol-soluble nylon resin is selected as the binder, the lower aliphatic alcohol is mainly used, but water, benzyl alcohol, n
A mixed solvent to which -propyl alcohol, iso-propyl alcohol, or the like is added may be used.

The ratio of titanium oxide to binder in the present invention is 1 to 1000 parts by weight, preferably 1 to 4 parts by weight, per 100 parts by weight of titanium oxide.
It is used in the range of 00 parts by weight. The thickness of the undercoat layer is suitably 0.05 to 50 μm.

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 photosensitive layer in the present invention is composed of a single layer type in which a charge generation material and a charge transfer material are dispersed and mixed and confined in a binder, and a laminated type in which the charge generation material and the charge transfer material are separated and sealed in a binder. You. Although the present invention can be applied to any system, it is preferably used in a system of a function-separated type laminated photoreceptor in which the performance of the charge generation material and the charge transfer material is easily maximized.

The charge generation layer can be provided by dispersing a pigment or a dye, preferably together with a binder, in a solvent and coating. Pigments used include azo pigments represented by monoazo pigments, polyazo pigments, metal complex salt azo pigments, pyrazolone azo pigments, stilbene pigments and thiazole azo pigments; perylene represented by perylene anhydride and perylene imide; Anthraquinone or polycyclic quinone pigments represented by anthraquinone derivatives, anthanitronone derivatives, dibenzopyrene quinone derivatives, pyranthrone derivatives, biolanthrone derivatives and isoviolanthrone derivatives; metal phthalocyanines, metal naphthalocyanines, Phthalocyanine pigments represented by metal phthalocyanine, metal-free naphthalocyanine, and the like are listed. The dyes used include triphenylmethane dyes typified by methyl violet, quinone dyes such as quinizarin and pyrium salts,
Thiapyrylium salts, benzopyrylium salts and the like.

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 No. 1-202775 and the like.

In the function-separated type photoreceptor, a charge generation layer is formed by mixing at least these charge generation substances and a binder resin. Polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylates, methacrylates, silicone resins, phenoxy resins, butyral resins, butyral resins, formal resins, phenol resins, polycarbonates, polyarylates, and polyamides as binder resins , A thermosetting resin such as a polyimide resin, an epoxy resin, a urethane resin, and the like, and a photocurable resin. 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 from 0.1 to 20
μm is preferred.

The charge transfer material used for the charge transfer layer 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 transporting substance 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, hydrazone compounds, stilbene compounds, and the like are preferable because they have high charge (hole) mobility and provide excellent photoreceptors. For example, in the case of a hydrazone compound, the above-mentioned Japanese Patent Publication Sho 55
And Japanese Patent Laid-Open No. 1-100
555, 2-10367, 2-511
No. 63, JP-A-2-96767, JP-A-2-1832
No. 60, No. 2-184856, No. 2-184
858, 2-184859, 2-22
The hydrazone compounds described in JP-A-6160 and the like can be used.

Examples of the binder resin used for the charge transfer layer include an acrylic resin represented by polystyrene and 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 400 parts by weight based on 100 parts by weight of the charge transfer material. The thickness of the charge transfer layer is 5 to 1
00 μm is preferred.

The electrophotographic photoreceptor of the present invention may contain an antioxidant such as 2,6-dibutyl butyl paracresol and DL-α-tocopherol in order to prevent deterioration of the constituent organic compounds due to oxidation. . Further, a well-known plasticizer may be used in order to improve film forming property, flexibility, and mechanical strength.

Further, in the electrophotographic photoreceptor of the present invention, in the case of a pigment, the pigment is dispersed in a solvent, and the dye, binder and charge transfer material are dissolved and used. Solvents used are halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, trichloroethane, and trichloroethylene; aromatic hydrocarbons such as benzene, toluene, and xylene; ethers such as dioxane, tetrahydrofuran, and dimethoxyethane; methyl cellosolve, and dimethyl cellosolve. ,
A single solvent such as a cellosolve-based solvent such as methyl cellosolve acetate or a mixed solvent of two or more thereof or, if necessary, a solvent such as alcohols, acetonitrile, N, N'-dimethylformamide, methyl ethyl ketone can be further used. When coating the drum, a dip coating method or the like is used.

[0029]

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 resin (CM-4000, nylon 6/66/610/12 copolymer, manufactured by Toray Industries, Inc.)
1 part by weight is dissolved in 100 parts by weight of methanol, 9 parts by weight of titanium oxide (rutile type, R-310 manufactured by Sakai Chemical Co., Ltd.) are mixed, and the mixture is placed in a container made of polypropylene together with zirconia beads having a diameter of 1 mm as a dispersion medium. The dispersion was carried out for 5 hours using a conditioner. The titanium oxide dispersion thus obtained was applied to a thin metal aluminum plate (JIS standard # 1050) using an applicator and dried at 80 ° C. for 30 minutes to form an undercoat layer having a thickness of about 0.5 μm.

[0031]

Embedded image

Next, 1 part by weight of the bisazo pigment of Chemical Formula 1 and 1 part by weight of a phenoxy resin (PKHJ manufactured by Union Carbide) were mixed with 100 parts by weight of dimethoxyethane, and the mixture was soaked in a paint conditioner together with soda glass beads having a diameter of 1 mm for 2 hours. Dispersed. The pigment dispersion thus obtained was applied on the undercoat layer with an applicator,
After drying for 5 minutes, a charge generation layer having a thickness of about 0.2 μ was formed.

Next, the hydrazone compound 10 represented by the following chemical formula 2
10 parts by weight of a polyarylate resin (U-Polymer manufactured by Unitika) are dissolved in 200 parts by weight of dichloroethane, and this solution is applied on a film of the carrier-generating substance by an applicator to obtain a dry film having a thickness of 20 μm. A charge transfer layer was formed.

[0034]

Embedded image

The laminated electrophotographic photoreceptor thus prepared is stored in the dark at room temperature for 24 hours, and then the photoreceptor is removed using an electrostatic recording tester “SP-428” (manufactured by Kawaguchi Electric Works Co., Ltd.). After charging with a charged voltage of -4.8 kV, 2 l
ux was irradiated with tungsten light, and the half-life exposure amount E1 / 2 of the photoreceptor was measured. Separately, using a drum photoreceptor evaluation apparatus (Cynthia 30 manufactured by Gentech), at a room temperature of 23 ° C. and a relative humidity of 55%, the charge and discharge of 1000 were performed.
Before and after the repetition, the potential and the residual potential of the photoconductor after charging were measured. The same repetitive test was performed under the conditions of room temperature 5 ° C. and relative humidity 30%. Table 1 shows the results
And given in Table 2.

Example 2 A titanium oxide dispersion was prepared in the same manner as in Example 1 except that the dispersion medium was changed to titania beads having a diameter of 1 mm, and an electrophotographic photosensitive member was prepared and tested in the same manner as in Example 1. . The results are shown in Tables 1 and 2.

Comparative Examples 1 to 3 A titanium oxide dispersion was prepared in the same manner as in Example 1 except that the dispersion medium was changed as shown in Table 3, and an electrophotographic photosensitive member was prepared and the test was conducted in the same manner as in Example 1. went. The results are shown in Tables 1 and 2. As can be seen from these results, the electrophotographic photoreceptors prepared by the methods of the examples have extremely excellent repetition characteristics, especially repetition characteristics under low temperature and low humidity.

Example 3 Alcohol-soluble nylon resin was converted to diamide 1874
(Copolymer nylon mainly composed of nylon 12, manufactured by Daicel Corp.) A titanium oxide dispersion was prepared in the same manner as in Example 1, and an electrophotographic photoreceptor was formed in the same manner as in Example 1. The test was performed. The results are shown in Tables 1 and 2.

Example 4 A titanium oxide dispersion was prepared in the same manner as in Example 1, except that TTO-55N (rutile type, manufactured by Ishihara Sangyo) was used instead of titanium oxide. The body was prepared and tested. The results are shown in Tables 1 and 2.

Example 5 Alcohol-soluble nylon resin (CM-8000, nylon 6/66/610/12 copolymer, manufactured by Toray Industries, Inc.)
5 parts by weight, dissolved in a mixed solution of 300 parts by weight of methanol and 700 parts by weight of methyl ethyl ketone, 95 parts by weight of titanium oxide (rutile type, SR-1 manufactured by Sakai Chemical Co., Ltd.) were mixed and dispersed using a horizontal sand mill for 2 hours. Zirconia beads having a diameter of 0.5 mm were used as a dispersion medium. The titanium oxide dispersion thus obtained is coated on a metal aluminum plate (JIS standard # 1050) with an applicator, and
After drying at a temperature of 30 minutes, an undercoat layer having a thickness of about 0.8 μm was formed.

1 part by weight of the bisazo pigment of Chemical Formula 3 and 1 part by weight of butyral resin (# 3000-K, manufactured by Denki Kagaku) were mixed with 100 parts by weight of tetrahydrofuran, and the mixture was mixed with soda glass beads by a paint conditioner.
The pigment dispersion obtained by dispersion over time was applied with an applicator and dried at 80 ° C. for 15 minutes to form a charge generation layer having a thickness of about 0.2 μm.

[0042]

Embedded image

Next, the hydrazone compound 10 represented by the chemical formula 4
Parts by weight, polycarbonate resin (Z-2 manufactured by Mitsubishi Gas Chemical)
00) 10 parts by weight were dissolved in 160 parts by weight of 1,2-dichloroethane, and this solution was applied on the above-mentioned carrier-generating substance film with an applicator.
A 0 μm charge transfer layer was formed. The photoreceptor thus prepared was subjected to the same repetitive test as in Example 1. The results are shown in Tables 1 and 2.

[0044]

Embedded image

Comparative Example 4 A titanium oxide dispersion was prepared in the same manner as in Example 5, except that the dispersion medium was changed to alumina beads having a diameter of 0.5 mm. went.
The results are shown in Tables 1 and 2.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

As is apparent from the above, according to the present invention, it is possible to provide a method for producing an electrophotographic photoreceptor having high sensitivity and excellent charge and exposure repetition characteristics even under low temperature and low humidity conditions.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-61756 (JP, A) JP-A-4-362654 (JP, A) JP-A-2-132162 (JP, A) JP-A-60-61756 19054 (JP, A)

Claims (1)

(57) [Claims] 1. A method for producing an electrophotographic photoreceptor, wherein an undercoat layer in which titanium oxide particles are dispersed in a binder and a photosensitive layer are sequentially laminated on a conductive support. A method for producing an electrophotographic photosensitive member, wherein the material of the dispersion medium for dispersion is titania or zirconia.