JPH04172362A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent a delay in the rise of electrifying potential even after the repetition of electrification and exposure by containing metallic oxide particles having the surfaces treated with a titanate coupling agent, and binding resin in an undercoat layer. CONSTITUTION:An undercoat layer containing metallic oxide particles treated with titanate coupling agent and diffused in binding resin, is provided between a conductive base material and a sensitive layer. Titanium oxide, tin oxide, indium oxide, zinc oxide or the like, whether surface treated or not, is preferably used as the metallic oxide particles treated with the titanate coupling agent and contained in the aforesaid undercoat layer. Also, a complex metallic oxide composed of one or more of the aforesaid metallic oxides can be mentioned. According to the aforesaid constitution, the electrification characteristics of the sensitive body become free from deterioration, even after the body is repeatedly subjected to electrification and exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor comprising a photosensitive layer consisting of a substrate, an undercoat layer, a charge generation layer, and a charge transport layer.
In particular, it relates to an electrophotographic photoreceptor with an improved undercoat layer.

[Conventional technology]

In recent years, organic photosensitive materials, which have advantages such as low cost, productivity, and non-pollution, have become popular as photoconductors used in electrophotographic copying machines.

Organic electrophotographic photoreceptors include photoconductive resins such as polyvinylcarbazole (PVK) and PVK-TN.
A charge transfer complex type photoreceptor represented by F (2,4,7-trinitrofluorenone), a pigment dispersion type represented by a phthalocyanine binder, and a functionally separated type photoreceptor using a combination of a charge generation substance and a charge transport substance. etc. are known,
In particular, functionally separated photoreceptors are attracting attention.

When such a functionally separated high-sensitivity photoreceptor is applied to the Carlson process, it has low chargeability, poor charge retention (high dark decay), and deterioration of these characteristics such as increased residual potential due to repeated use. The major disadvantages are that density unevenness and fogging occur on images, and in the case of reversal development, scumming occurs.

In order to improve the electrical properties of the photoreceptor, improve the adhesion between the photosensitive layer and the support, improve the coatability of the photosensitive layer, or protect the support from defects, for example, 6341
．． No. 411-3544 and No. 411-120.34 have cellulose nitrate resin intermediate layers, as disclosed in JP-A-48L4734.
4.52-25638.58-30757.58-63
945.58-95351.58-98739 and 6
No. 0-66258 has a nylon resin intermediate layer, JP-A-49-69332 and JP-A-52-10138 have a maleic acid-based resin intermediate layer, and JP-A-58-105155 has a maleic acid resin intermediate layer.
In the issue, the polyvinyl alcohol resin middle layer is disclosed. In addition, intermediate layers have been proposed in which various conductive additives are contained in a resin in order to control the electrical resistance of the intermediate layer. For example, JP-A-51-65942 discloses an intermediate layer in which carbon or chalcogen-based substances are dispersed in a curable resin, and JP-A-52-82238 discloses an isocyanate-based curing agent with the addition of a quaternary ammonium salt. The thermopolymer intermediate layer used is a resin intermediate layer containing a resistance modifier in JP-A-55-1130451, and a resin intermediate layer in which aluminum or tin oxide is dispersed in JP-A-58-58556. However, in JP-A-58-93062, a resin intermediate layer to which an organometallic compound is added is disclosed in JP-A-58-93063.6.
Nos. 0-97363 and 60-111255 have a resin intermediate layer in which conductive particles are dispersed, as disclosed in JP-A-59-17557.
No. 59-84257.59-93453 and 60-60-84257 have a layer in which magnetite is dispersed in resin.
No. 32054 also discloses a resin intermediate layer in which TiO□ and SnO□ powder are dispersed, as disclosed in JP-A-64-68762.64-61.
1763.64-73352.64-73353, JP-A-1-118849, and JP-A-1-118848 disclose a resin intermediate in which powders of borides, nitrides, fluorides, and oxides such as calcium, magnesium, and aluminum are dispersed. The layers are disclosed.

However, conventionally known electrophotographic photoreceptors are still insufficient in terms of deterioration in charging performance due to repeated use, especially in terms of delay in the rise of the electrification position 5, and furthermore, the residual potential increases significantly, and even more Improvements are desperately needed.

[Problem to be solved by the invention]

The present invention provides an electrophotographic photosensitive material that is highly sensitive, has a significantly small drop in chargeability due to pre-exposure fatigue, has no delay in the rise of charging potential even after repeated charging and exposure, and has small changes in residual potential. The purpose is to provide the body.

[Means to solve the problem]

According to the present invention, in an electrophotographic photoreceptor in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive substrate, the undercoat layer is treated with a titanate camping agent. Provided is an electrophotographic photoreceptor characterized by containing metal oxide particles and a binder resin.

The present inventors focused on the subbing layer of an electrophotographic photoreceptor, which is formed by sequentially laminating a subbing layer, a charge generation layer, and a charge transport layer on a conductive substrate, and conducted extensive studies to eliminate the above-mentioned drawbacks. result,
By containing at least one of the metal oxides surface-treated with a titanate coupling agent in the undercoat layer, there is no delay in the rise of the electrification position 5 after repeated use,
The present inventors have discovered that an electrophotographic photoreceptor with a small increase in residual potential can be obtained, and have completed the present invention.

The present invention will be explained in detail below.

In the present invention, as described above, an undercoat layer containing metal oxide particles treated with a titanate coupling agent dispersed in a binder resin is provided between the conductive substrate and the photosensitive layer. will be established. Examples of metal oxide particles that can be treated with the titanate coupling agent contained in the undercoat layer include titanium oxide, tin oxide, indium oxide, zinc oxide, aluminum oxide, magnesium oxide, and surface-treated titanium oxide. Examples include calcium, beryllium oxide, silicon oxide, antimony oxide, ferric oxide, and zirconium oxide, with titanium oxide and tin oxide being preferably used. Also included are composite metal oxides of one or more of these metal oxides.

Examples of such composite metal oxides include Ti02
-ZnO1T 102-3 iOz, TiO2-5n0
2, Ti027MKO1T102-ZtO2, ZtO-
ZtO2, ZnO-3b203.5n02-V2O3,
5nO2-CuO1Sn02-3b20. Examples include. To obtain these compounds, such as Ti02-ZnO, a solution of TiCQ4 dissolved in water and a solution of ZnCjlz dissolved in water are mixed, urea is added and stirred, and the solution is then heated to 95-98°C to obtain the obtained product. The resulting coprecipitate was filtered, thoroughly washed with distilled water, and the precipitate was dried.
A method such as firing at 00° C. for several hours may be employed.

These metal oxide powders preferably have an average particle size of l.

The oxide is a granular material with a particle diameter of 0 μm or less, and the crystal system of the oxide is not particularly limited.

Further, in order to obtain the desired electrical conductivity of the undercoat layer, two or more powders having different specific resistances can be appropriately selected and used.

Another feature of the electrophotographic photoreceptor of the present invention is that by treating the metal oxide with a titanate coupling agent, it imparts water repellency to the metal oxide, and at the same time improves its dispersibility in the binder resin. By increasing the compatibility, the dispersion stability of the coating solution for the undercoat layer and the uniformity of the coating film are improved, and at the same time, the conductive performance is improved to the expected effect.

The titanate coupling agent used in the present invention can be selected as appropriate in consideration of compatibility with the resin used, and examples thereof include the compounds shown below.

Isopropyl triisostearoyl titanate, isopropyl tris(dioctyl birophosphate) titanate, isopropyl tri(N-aminoethyl-aminethyl) titanate, tetraoctylhis(ditridecylphosphate) titanate, tetra(2,2-diallyloxymethyl-1- Butyl)bis(ditridecyl)phosphite titanate, bis(dioctylpyrophosphate)oxyacetate titanate, bis(dioctylpyrophosphate)ethylene titanate, isopropyltrioctanoyltitanate, isopropyldimethacrylylisostearoyltitanate, isopropyltridodecylbenzenesulfonyltitanate, isopropyl Isostearoyl diacryl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctyl phosphate) titanate, isopropyl tricumylphenyl titanate, tetraisopropyl bis(dioctyl phosphate) titanate, etc.

As a method for treating the surface of a metal oxide using such a titanate coupling agent, a dry treatment method or a wet treatment method is employed.

The dry processing method is a method in which metal oxide particles are placed in a machine capable of high-speed stirring such as a Henschel mixer, and the coupling agent as it is or a diluted solution thereof is slowly dropped or sprayed while stirring at high speed.

- The wet treatment method is a method in which metal oxide particles are treated in a solution and then dried, and the coupling agent solution may be an aqueous solution or an alcoholic solution.

The amount of titanate coupling agent used is 1 part metal oxide
0.01-20 parts by weight, preferably 0.1-3 parts by weight.

The resin used for the undercoat layer includes thermoplastic resins such as polyamide, polyester, vinyl chloride-vinyl acetate copolymer, thermosetting resins, etc.
It is also possible to use thermosetting resins obtained by thermally polymerizing a compound containing a plurality of hydrogen groups (such as hydrogen groups, -NH groups, etc.) and a compound containing a plurality of isocyanate groups and/or a compound containing a plurality of epoxy groups. In this case, the compound containing multiple active hydrogens includes, for example, polyvinyl butyral, phenoxy resin, phenol resin, polyamide, polyester, polyethylene glycol, polypropylene glycol, polybutylene glycol, hydroxyethyl methacrylate group, etc. Examples include acrylic resin. Examples of compounds containing a plurality of isocyanate groups include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and prepolymers thereof, and examples of compounds containing a plurality of epoxy groups include bisphenol A type epoxy resins. can give.

Also oil-free alkyd resins and amino resins, e.g.
Thermosetting resin made by thermally polymerizing butylated melamine resin, etc.
Furthermore, photocurable resins such as polyurethane with unsaturated bonds, resins with unsaturated bonds with unsaturated polyesters, thioxanthone compounds, and combinations with photopolymerization openers such as methylbenzylformate are also used as binders. Can be used as resin.

The ratio of the metal oxide and binder resin used is 1/1 by weight.
1-9515, preferably 3/2-10/1.

If the ratio of metal oxide to binder resin is less than 1/1, the effect will be small, and if it exceeds 9515, air bubbles will remain in the undercoat layer, causing defects in the charge generation layer and charge transfer layer coatings. So I don't like it.

Further, the thickness of the subbing layer is 0.3 to 30 μm, preferably 0.3 to 30 μm.
A suitable thickness is 5-20 μm. If the thickness of the subbing layer is less than 0.3 pm, the effect will be small, and 30/l+
If it exceeds 11, residual potential will accumulate, which is undesirable.

In the present invention, in addition to the coupling agent-treated metal oxide, it is also effective to mix white powder in order to adjust the electrical resistance of the undercoat layer, improve whiteness, reduce costs, etc. Examples of the white powder include untreated titanium oxide, calcium carbonate, barium sulfate, barium carbonate, calcium sulfate, and the like.

The undercoat layer is made by dispersing a metal oxide treated with a titanate coupling agent and a binder resin using a ball mill, sand mill, attritor, etc., and then hardening (crosslinking) as necessary. After adding necessary chemicals, solvents, additives, curing accelerators, etc., it is formed on the substrate by conventional methods such as blade coating or dip coating.
It is dried or hardened by oxidation treatment such as drying, heating, and light.

In some cases, a resin layer or a resin layer in which white pigment powder is dispersed may be further provided on the undercoat layer thus formed in order to prevent injection of free carriers from the substrate side.

Next, the structure of the electrophotographic photoreceptor of the present invention will be explained in more detail.

As the conductive substrate, materials exhibiting conductivity with a volume resistance of 1010 Ωem or less, such as metals such as aluminum, nickel, chromium, nichrome, copper, silver, gold, and platinum, and metal oxides such as tin oxide and indium oxide, Film-like or cylindrical plastic, paper, etc. coated by vapor deposition or sputtering, or plates of aluminum, aluminum alloy, nickel, stainless steel, etc., and their coatings; 1. ．． 1.1. It is possible to use pipes that have been made into blank pipes using methods such as extrusion or drawing, and then surface-treated by cutting, superfinishing, polishing, etc., and cylindrical or plate-shaped substrates made by dispersing and molding conductive powder into plastic. can.

Next, the charge generation layer will be explained.

The charge generation layer is a layer mainly composed of a charge generation substance, and a binder resin may be used as necessary.

Binder resins include polyamide, polyurethane,
Polyester, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone,
Polystyrene, poly-N-vinylcarbazole, polyacrylamide, etc. are used.

Examples of the charge generating substance include CI Pigment Blue 25 [Color Index (CI) 211801,
CI Pigment Red 41 (CI 21200),
C.I. Acid Red 52 (CI 45100), C.I. Basic Red 3 (C145210), phthalocyanine pigments having a porphyrin skeleton, azulenium salt pigments, squalic salt pigments, azo pigments having a carbazole skeleton (JP-A-53-95033) ), an azo pigment having a stilstilbene skeleton (described in JP-A-53-138229), an azo pigment having a triphenylamine skeleton (described in JP-A-53-13254)
7), an azo pigment having a dibenzothiophene skeleton (described in JP-A No. 54-21728), an azo pigment having an oxadiazole skeleton (described in JP-A-54-12)
742), an azo pigment having a fluorenone skeleton (described in JP-A No. 54-22834), an azo pigment having a bisstilbene skeleton (described in JP-A-54-1773)
3), an azo pigment having a distyryloxadiazole skeleton (described in JP-A-54-2129)
, azo pigments having a distyrylcarbazole skeleton (described in JP-A-54-17734), triazo pigments having a carbazole skeleton (described in JP-A-57-195767 and JP-A-57-195768), and the like. ,
Phthalocyanine pigments such as CI Pigment Blue 16 (CI 74100), CI Butt Brown 5 (
CI 73410), sea eye bat die (CI 73
Indigo pigments such as 030), Argo Scarlet B (
Organic pigments such as perylene pigments such as Violet Co., Ltd.) and Indus Thread Scarlet R (Bayer aJ) can be used.

Among these charge-generating substances, azo pigments are particularly preferred, and among azo pigments, disazo pigments and trisazo pigments shown below are most preferred.

Specific examples of azo pigments are shown below.

These charge generating substances may be used alone or in combination of two or more.

The binder resin is suitably used in an amount of 0 to 100 parts by weight, preferably 0 to 100 parts by weight, based on 100 parts by weight of the charge generating substance.
-50 parts by weight.

The charge generation layer contains a charge generation substance, along with a binder resin if necessary, tetrahydrofuran, cyclohexanone,
It can be formed by dispersing with a ball mill, attritor, sand mill, etc. using a solvent such as dioxane or dichloroethane, diluting the dispersion liquid appropriately, and applying the dispersion. Application can be carried out using a dip coating method, a spray neat method, a bead coating method, or the like.

The thickness of the charge generation layer is suitably about 0.01 to 5 IJa, preferably 0.1 to 2 μs.

The charge transport layer consists of a charge transport substance and a binder resin used as necessary.

A charge transport layer can be formed by dissolving or dispersing the above-mentioned substances in a suitable solvent and applying and drying the solution.

Charge transport materials include hole transport materials and electron transport materials.

As hole transport substances, poly-N-vinylcarbazole and its derivatives, poly-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole Derivatives, imidazole derivatives, triphenylamine derivatives, 9-(P-diethylaminostyryl)anthracene, 1,1-bis-(4-dibenzylaminophenyl)furopane, styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenyl Examples include electron-donating substances such as stilbene derivatives.

Examples of the electron transport substance include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4,7-)dinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone,
2,4,5.7-titranitroxanthone, 2,4°8
-Trinidrothioxanthone, 2,6.8-trinitro-48-indeno(1,2-b)thiophen-4-one, 1,3.7-dolinitrodibenzothiophenone-5
, 5-dioxide and other electron-accepting substances.

These charge transport materials may be used alone or in a mixture of two or more.

Binder resins used as necessary in the present invention include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride- Vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole cone resin, epoxy resin , melamine resin, urethane resin, phenol resin, alkyd resin, and other thermoplastic or thermosetting resins.

As the solvent, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride, etc. are used.

The appropriate thickness of the charge transport layer is about 5 to 100 μs.

Further, in the present invention, a plasticizer or a leveling agent may be added to the charge transport layer. As the plasticizer, those used as plasticizers for general resins, such as dibutyl phthalate and dioctyl phthalate, can be used as they are, and the appropriate amount to be used is about 0 to 30% by weight based on the binder resin. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil are used, and the appropriate amount thereof is about 0 to 1% by weight based on the binder resin.

In the present invention, it is also possible to further provide an insulating layer or a protective layer on the photosensitive layer.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Production Example 1) Isopropyl tris (dioctyl pyrophophosphate) titanate, (Blenact KR38S manufactured by Ajinomoto Co., Inc.)
0.25 g of n-hexane and 495 g of n-hexane, 50 g of tin oxide fine powder (S-1: manufactured by Mitsubishi Metals, Ltd.) was added, and ultrasonic waves were applied for 20 minutes while stirring, and stirring was continued for 2 hours. . Thereafter, the solvent was filtered and dried at 120° C. for 2 hours to obtain tin oxide powder treated with a titanate coupling agent.

(Production Example 2) Tin oxide powder treated with a titanate coupling agent was obtained in the same manner as in Example 1 except that the amount of isopropyl tris(dioctyl birophosphate) titanate in Reference Example 1 was changed to 0.75 g. Ta.

(Production Example 3) Isopro and lutris (dioctyl pyrophosphate) titanate of Production Example 2 were converted to bis(dioctyl pyrophosphate) ethylene titanate (Plenac KR238S:
A tin oxide powder treated with a titanate-based coupling agent was obtained in the same manner as in Example 1, except that the titanate-based coupling agent was used instead.

(Production Example 4) The isopropyl tris(dioctylpyrophophosphate) titanate of Production Example 2 was substituted with (Plenact 3311X: (manufactured by Ajinomoto Co., Inc.)), and the tin oxide fine powder was substituted with titanium oxide (C
Titanium oxide powder treated with a titanate coupling agent was obtained in the same manner as in Example 2 except that REL (manufactured by Ishihara Sangyo Co., Ltd.) was used.

Example 1 9.5 cm, which is 1/2 the volume, in a 50 cc hard glass bottle
φP32 ball and tin oxide powder 5 obtained in Production Example 1
g and oil-free alkyd resin (Beracolite M64
01-50, solid content concentration 50% by weight, 2.4 g (M) of Nihon Ink Kagaku Co., Ltd. and butylated melamine resin (Super Beckamine G32l-60, solid content concentration 60% by weight: Dainippon Ink Chemical Co., Ltd.) 3 g of Nitrogen and 14.6 g of methyl ethyl ketone were added and milled for 30 hours to obtain a coating solution for the undercoat layer.

The above coating solution for undercoat layer was coated with a plate onto a nickel sheet prepared by electroplating, and dried and cured for 20 minutes to form an undercoat layer with a thickness of about 12 μm.

Next, 3 parts of a disazo pigment with the following structural formula, 0.3 parts of borihinyl petyral (trade name: 90 parts and 15 parts of methyl ethyl ketone
0 parts was added to this dispersion to prepare a charge generation layer coating solution.

This coating solution was applied onto the undercoat layer using a doctor blade and dried by heating at 120° C. for 20 minutes to form a charge generation layer having a thickness of 0.3 part m.

Next, a charge transport layer forming liquid consisting of 0.004 parts of silicone oil and 173 parts of methylene chloride is coated on the charge generation layer with a blade, and dried at 1310°C for 20 minutes to form a charge transport layer with a thickness of about 20 μm. An electrophotographic photoreceptor of Example I was prepared.

Example 2 An electrophotographic photoreceptor of Example 2 was produced in the same manner as in Example 1 except that the tin oxide powder obtained in Production Example 2 was used in place of the tin oxide powder.

Example 3 An electrophotographic photoreceptor of Example 3 was produced in the same manner as in Example 1, except that the tin oxide powder obtained in Production Example 3 was used instead of the tin oxide powder.

Example 4 An electrophotographic photoreceptor of Example 4 was produced in the same manner as in Example 1 except that the tin oxide powder was replaced with the titanium oxide powder obtained in Production Example 4.

Comparative Example 1 An electrophotographic photoreceptor of Comparative Example 1 was prepared in the same manner as in Example 1 except that the undercoat layer was not provided.

Comparative Examples 2 and 3 In Example 1, tin oxide powder was changed to tin oxide fine powder not treated with a titanate coupling agent (Comparative Example 2), and titanium oxide powder not treated with a titanate coupling agent (
Electrophotographic photoreceptors of Comparative Examples 2 and 3 were prepared in the same manner as in Example 1, except that Comparative Example 3) was used.

The photoreceptor characteristics of these photoreceptors were measured using an electrostatic paper analyzer 5P-428 manufactured by Kawaguchi Electric Co., Ltd. under the following conditions.

Charging 20sec (applied voltage -6KV) Dark decay 20
sec exposure 30sec (exposure intensity 51ux) charging 1sec
The subsequent value was defined as 1, the voltage after 30 seconds of exposure was defined as V2O, and the amount of exposure required to lower the surface potential of -800 µ to 1/J was defined as E1/l.

The fatigue conditions were such that the photoreceptor was subjected to fatigue for 15 minutes while adjusting the applied voltage and light intensity so that the current was -9.6 μA and the surface potential of the photoreceptor was 1800 μA. Thereafter, the post-fatigue characteristics of the photoreceptor were measured under the same conditions as the initial characteristics. The results are shown in Table-1.

〔Effect of the invention〕

The electrophotographic photoreceptor of the present invention has the above structure and contains at least one metal oxide treated with a titanate coupling agent in the undercoat layer, so that it has high sensitivity and reduces pre-exposure fatigue. The deterioration in chargeability caused by the electrification is extremely small, and the chargeability does not deteriorate even after repeated charging and exposure, and the increase in residual potential is small, so it has remarkable effects.

Further, according to the electrophotographic photoreceptor of the present invention, it is possible to prevent abnormal images from occurring due to optical interference even in exposure using coherent light from a laser printer or the like.

Patent applicant Rico Co., Ltd. Representative patent attorney: Toshiaki Ikeura (and one other person)

Claims (3)

[Claims] (1) In an electrophotographic photoreceptor in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive substrate, the undercoat layer has a metal oxide surface treated with a titanate coupling agent. A photoreceptor for electrophotography, characterized in that it contains particles and a binder resin. (2) The electrophotographic photoreceptor according to claim 1, wherein the metal oxide particles are titanium oxide. (3) The electrophotographic photoreceptor according to claim 1, wherein the metal oxide particles are tin oxide.