JPS62201460A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance electrophotographic characteristics and durability by incorporating a specified resin and a specified compound in a protective layer. CONSTITUTION:The protective layer is composed of a specified butylated melamine.formaldehyde resin, a polyvinyl acetal resin, and a film obtained by heat hardening a coating film containing a fluororesin having hydroxyl groups and an electron donative carboxylic acid and/or such polycarboxylic anhydride. The butylated melamine.formaldehyde resin has a number average molecular weight of <=1,500, and if above 1,500, reactivity lowers, and this resin has 2-4 combined formaldehyde units and 1 or 2 methylol groups per one melamine ring, thus permitting electrophotographic characteristics and durability to be enhanced.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electrophotographic photoreceptor having a protective layer.

(Prior Art) In an electrophotographic photoreceptor that uses a photoconductive substance as a photosensitive material, conventional photoconductive substances are used as photoconductive substances.

Inorganic photoconductive materials such as selenium, zinc oxide, titanium oxide, and cadmium sulfide have been mainly used.

However, many of these are generally highly toxic and there are problems in how to dispose of them.

On the other hand, the use of organic photoconductive compounds is generally less toxic than the use of inorganic photoconductive substances, and is also advantageous in terms of transparency, flexibility, light weight, and price. It has been widely studied recently.

Among them, composite photoreceptors that separate the functions of charge generation and transport can significantly improve sensitivity, which was a major drawback of conventional photoreceptors that used organic photoconductive compounds. , has been making rapid progress in recent years.

(Problems to be Solved by the Invention) When these composite photoreceptors are applied to an electrophotographic device using the Carlson method, an electrostatic latent image is first formed on the surface of the photoreceptor, and the image is 9th charged with an opposite sign. A toner image is transferred to another substrate 1, such as paper, by a developer generally called a toner.
It is fixed and you can get a copy. At this time, it is necessary to remove (clean) the slight amount of toner remaining on the surface of the photoreceptor using a brush, blade, or the like.

By repeating the steps of development, transfer, and cleaning in this way, the surface of the photoreceptor is worn and damaged, and as a result, the transferred image becomes unclear.

In some cases, the charge transport layer or charge generation layer may peel off, resulting in a significantly shortened life of the photoreceptor. Due to these problems, photoreceptors are required to have strong durability.

Therefore, in order to improve the durability, JP-A-52-7692
It has been proposed to provide a protective layer on the surface as disclosed in Japanese Patent Application Laid-open No. 8 and Japanese Patent Application Laid-open No. 17732/1984. However, when thermoplastic resin is used as in the conventional protective layer, the abrasion resistance effect is not sufficient, and when thermosetting resin is used, high temperature and long time are required to form the protective layer. The electrophotographic properties deteriorate due to thermal deterioration of the materials in the underlying charge generation layer and charge transport layer, and furthermore, in order to improve wear resistance, it is necessary to increase the thickness of the protective layer. It has the disadvantage that it tends to cause an increase in residual potential and a decrease in sensitivity in the electrophotographic characteristics, and therefore there is a desire for a groove in the protective layer that has high abrasion resistance and does not impair the electrophotographic characteristics.

Therefore, an object of the present invention is to provide an electrophotographic photoreceptor that satisfies the above requirements and has excellent electrophotographic characteristics and durability.

(Means for Solving the Problems) The present invention solves the above problems by providing a specific protective layer.

That is, the present invention provides an electrophotographic photoreceptor in which a charge generation layer containing an organic pigment that generates a charge, a charge transport layer containing a charge transporting substance, and a protective layer are sequentially laminated on a conductive layer. In the protective layer.

! al A butyl etherified melamine/formaldehyde resin having a number average molecular weight of 1,500 or less, the number of bound formaldehydes per melamine nucleus being 2 to 4 and the number of methylol groups being 1 to 2.

(bl Polyvinyl acetal resin.

fc) A hydroxyl group-containing fluoropolymer; and (d) an electrophotographic photoreceptor comprising a cured film of an electron-donating carboxylic acid compound and/or an electron-donating polycarboxylic acid anhydride.

The materials used in the electrophotographic photoreceptor of the present invention will be described in detail below.

First, in the present invention, the conductive layer is a conductor such as paper or plastic film subjected to conductivity treatment, a plastic film laminated with metal foil such as aluminum, a metal plate, a metal drum, or the like.

The charge-generating organic pigments contained in the charge generation layer include azoxybenzene-based, disazo-based, trisazo-based, benzimidazole-based, polycyclic quinoline-based, indigoid-based, quinacridone-based, phthalocyanine-based, perylene-based,
Pigments known to generate charges upon irradiation with light, such as methine-based pigments, can be used. These pigments are 1 e.g.
% JP-A-47-37453, JP-A-47-37544, JP-A-47-18543, JP-A-47-18544
issue.

JP-A-48-43942, JP-A-48-70538 % JP-A-49-1231, JP-A-49-105536
No., JP-A-50-75214, JP-A-50-9273
This is disclosed in Publication No. 8, etc. Unexamined Japanese Patent Publication No. 58-182 in %
Publication No. 640 and European Patent Application Publication No. 92255
τ and τ′ described in the publication.

η and η' type gold metal phthalocyanine has high sensitivity up to long wavelengths, and is also effective as an electrophotographic photoreceptor for printers equipped with diode lasers.

In addition to these, any organic pigment that generates charge carriers upon irradiation with light can be used.

Further, additives such as a binder, a plasticizer, a fluidity imparting agent, a pinhole inhibitor, and the like, which are commonly used in electrophotographic photoreceptors, can be used in the charge generation layer, if necessary. Examples of the binder include silicone resin, polyamide resin, polyurethane resin, polyester resin, epoxy resin, polyketone resin, polycarbonate resin, polystyrene resin, polymethyl methacrylate resin, and polyacrylamide resin. Heat and/or photocurable resins can also be used. In any case, there is no particular restriction as long as the resin is electrically insulating and can form a film under normal conditions.

In the charge generating layer, the binder has a content of 300% relative to the organic pigment.
Use in amounts below % by weight. 9 if it exceeds 300% by weight
．． Electrophotographic properties deteriorate.

Examples of the plasticizer include halogenated paraffin, dimethylnaphthalene, and dibutyl phthalate. As the fluidity imparting agent, Modaflow (manufactured by Monsando Chemical Company),
Acronal 4F (manufactured by Pasuf Co., Ltd.) is exemplified as a pinhole suppressor.

Examples include benzoin and dimethyl phthalate.

Each of these is preferably used in an amount of not more than 5% by weight relative to the organic pigment.

The electron-donating charge-transporting substance used in the charge-transporting layer has the function of transporting positive charge carriers (holes),
Specifically, carbazole, 3-phenylcarbazole, 2-phenylindole.

2-phenylnaphthalene, oxadiazole, oxatriazole, 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline, 2-phenyl-4-(4-diethylaminophenyl)-5- Low molecular weight compounds such as phenyloxazole, triphenylamine, imidazole, poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole.

Vinyl birene, polyvinyl indoquinoxaline,
Polyvinylbenzothiophene, polyvinylanthracene, polyvinylacridine. Examples include polymer compounds such as polyvinylpyrazoline and derivatives thereof.

The same binder, plasticizer, fluidity imparting agent, pinhole inhibitor, etc. as in the charge generation layer can be used in the charge transport layer as necessary. Among these, the binder is preferably 400% by weight or less based on the charge transporting substance so as not to deteriorate the electrophotographic properties, and when using a low molecular weight compound, on the other hand, the binder should be 500% by weight or more based on the film properties. preferable. The amount of other additives is preferably 5% by weight or less based on the charge transporting substance.

Next, the protective layer will be explained.

The protective layer of the present invention comprises a specific butyl etherified melamine.
It is mainly formed by a cured film of formaldehyde resin, polyvinyl acetal resin, hydroxyl group-containing fluoropolymer, and electron-donating carboxylic acid compound and/or electron-donating polycarboxylic acid anhydride, but this cured film is a coating film containing these. It can be obtained by curing by heating.

Butyl etherified melamine used in the present invention
The formaldehyde resin has a number average molecular weight of 1,500 or less, and when the number average molecular weight exceeds 1.500, the reactivity decreases. The resin also has 2 to 4 bound formaldehydes per melamine core. If the number exceeds 4, the reactivity decreases, and if the number is less than 2, the storage stability of the resin deteriorates.
The cured coating becomes brittle. Furthermore, the resin has 1 to 2 methylol groups f per melamine nucleus. If the number of methylol groups exceeds 2, the storage stability of the resin will be poor and the cured coating will become brittle. Moreover, if it is less than one, the reactivity is poor.

Such butyl etherified melamine/formaldehyde resin can be produced by dissolving melamine in butanol and dropping formaldehyde thereto to perform an addition reaction and butyl etherification reaction, or by dissolving melamine and formaldehyde in butanol and heating the solution. It can be produced by a method of carrying out an addition reaction and a butyl etherification reaction. In these methods, the reaction is preferably carried out at pH 3 to 6 by adding an acidic catalyst such as nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, or p-)luenesulfonic acid. refluxed Et, temperature,
Preferably, the temperature is about 90-100°C. In the present invention, 4 butanol is used per mole of melamine.
Using ~5 mol and 3-7 mol of formaldehyde,
Preferably, a prevapi reaction is carried out.

The butyl etherified melamine/formaldehyde resin used in the protective layer of the present invention can be cured at a lower temperature than conventional melamine resins, so it does not cause thermal deterioration of the electrophotographic photoreceptor during the formation of the protective layer, and has excellent abrasion resistance. A protective layer with straight edges can be formed.

Polyvinyl acetal resin c in the present invention.

Those having a number average molecular weight of 5.000 to 250,000 are preferable, and are represented by the following formulas ■ to ■ or! -11 repeating units.

(However, R is hydrogen or an alkyl group such as a methyl group.) The repeating units of formulas 1 to 2 of the vinyl acetate group include 70 or more vinyl acetal groups and 4 vinyl alcohol groups.
Preferably, a resin having ~25 weight groups and a vinyl acetate group of 26 weight or less is used. Among these, the ratio of vinyl alcohol groups is particularly important; if it is less than 4 times #L, the curing reaction when forming a protective layer by heat curing in combination with the above-mentioned butyl etherified melamine formaldehyde resin will be slow, and the Abrasion resistance is also likely to deteriorate. If it exceeds 25% by weight, the protective layer tends to become brittle. To describe an example of a method for producing polyvinyl acetal resin, first, vinyl acetate monomer is polymerized to synthesize polyvinyl acetate. Polyvinyl alcohol is produced by saponifying polyvinyl acetate.

At this time, some vinyl acetate groups remain.

Next, an aldehyde such as butyraldehyde or formaldehyde is added to perform acetalization, thereby producing a 1-ribolyvinyl acetal resin.

The hydroxyl group-containing fluoropolymer used as a material for the protective layer is a polymer that has a hydroxyl group and fluorine in each molecule, and the hydroxyl groups are present in the molecule so that the hydroxyl value of one polymer is 5 to 100. It is preferable that the hydroxyl value is 8.
It is preferable to set it to 70. If the hydroxyl value is too small, the crosslinking density of the butyl etherified melamine/formaldehyde resin will not increase and the abrasion resistance of the protective layer will not improve. If the hydroxyl value is too large, the compatibility with the butyl etherified melamine/formaldehyde resin will be poor.

The above-mentioned hydroxyl group-containing fluoropolymer is composed of fluoroethylene such as chlorotrifluoroethylene, trifluoroethylene, and tetrafluoroethylene, and noalkyl vinyl ether such as ethyl vinyl ether, flobyl vinyl ether, butyl vinyl ether, and hexyl vinyl ether (even if it is fluorine-substituted). or cycloalkyl vinyl ethers such as cyclohexyl vinyl ether (which may be fluorine-substituted) and hydroxyethyl vinyl ether, hydroxypropyl vinyl ether,
It can be obtained by copolymerizing hydroxyalkyl vinyl ethers such as hydroxybutyl vinyl ether, and carboxyalkyl vinyl ethers such as carboxyethyl vinyl ether, ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, and vinyl acetate.

It may contain n-vinyl butyrate, methyl methacrylate, methacrylic acid, acrylic acid, etc. as a copolymerization component.

In the total amount of the above components, fluoroolefin is a.

Preferably it contains 70 molti.

Further, the alkyl vinyl ether and cycloalkyl vinyl ether are in at of the component.

It is preferable to use it so that the total amount is 5 to 60 molti. If these amounts are too small, it will be difficult to dissolve in an organic solvent, making it difficult to form a single layer.

Other copolymerization components are 30 mol 5.00 in the total amount of the above components.
It is preferably 0 to 150,000 (in terms of standard polystyrene in liquid chromatography). If the molecular weight is too small, the film will be weak, and if it is too large, the viscosity will be high when dissolved in a solvent.

A layer is formed and K<'.

The hydroxyl group-containing fluoropolymer of the present invention also includes primary ones.

That is, a graft copolymer having zero-reactive carbon-carbon double bonds and having a hydroxyl group is also included in the hydroxyl group-containing fluoropolymer of the present invention.

The fluorine-containing resin has 0.001 to 0.025 mol, preferably 0.003 to 0.015 mol, of one emetic carbon-carbon double bond per 100 g of the resin.

If it is less than 1 mole of OO, graft polymerization becomes difficult when polymerizing with component 131, and if it exceeds 0.025 mole, gelation tends to occur during polymerization.
The fluorine-containing resin has an alkoxy group or a cycloalkyloxy group. Thereby, it can be made soluble in organic solvents such as xylene, toluene, butyl acetate, and methyl isobutyl ketone.

Furthermore, by containing fluorine, the durability of the protective layer using the graft copolymer obtained by the present invention is improved.

The above-mentioned fluorine-containing resin has a molecular weight of about t, ooo~
200,000 is preferred.

Particularly preferred is about 10,000 to 100,000. If the molecular weight is too low, durability tends to decrease, and if it is too high, gelation tends to occur when an ethylenically unsaturated monomer is polymerized in the presence of fluorine and a resin containing it.

It can be obtained by reacting an α,β-unsaturated carboxylic acid such as methacrylic acid, acrylic anhydride, methacrylic anhydride, or their acid chloride, or a reactive derivative thereof with a hydroxyl group.

In this case, 0.001 to 0.025 mol of the α,β-unsaturated carboxylic acid or its hydroxyl-reactive derivative is reacted with respect to 100 g of the co(d,)polymer having hydroxyl groups.

(cL) The copolymer is similar to the hydroxyl group-containing fluoropolymer described above, and is a polymer having 9 hydroxyl groups and fluorine in its molecules, with 0 hydroxyl groups and 0.57 hydroxyl groups in the polymer. ~
It is preferable that the hydroxyl value be present in the molecule so that the hydroxyl value is 100, and it is particularly preferable that the hydroxyl value be 3 to 70.

If the hydroxyl value is too small, sufficient double bonds cannot be introduced. Moreover, if the hydroxyl value is too large, the solubility in organic solvents tends to be limited.

Specifically, the ω0 copolymer is a fluoroolefin like the hydroxyl group-containing fluoropolymer described above.

It can be obtained by copolymerizing an alkyl vinyl ether or a cycloalkyl vinyl ether and a hydroxyalkyl vinyl ether, and may contain other copolymerization components. These components and amounts used are the same as those described in *ml, but the hydroxyalkyl vinyl ether is preferably used so that the hydroxyl value of the copolymer is 0.57 to 100, particularly 3 to 100. Preferably, the number is 100.

Examples of the ethylenically unsaturated monomer include alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, and 2-ethylhexyl acrylate, similar alkyl methacrylates, styrene, L<H vinyltoluene, α-methyl Substituted styrenes such as styrene and chlorostyrene, acrylonitrile, methacrylonitrile, vinyl chloride, vinyl acetate, maleic acid dialkyl esters can be used, and furthermore, 2-hydroxyethyl acrylate, 2-
Hydroxypropyl acrylate.

Hydroxyalkyl acrylates such as 2-hydroxybutyl acrylate, similar hydroxyalkyl methacrylates, monoacrylates or monomethacrylates of polyhydric alcohols such as glycerin and trimethylolpropane, ethylene having hydroxyl groups such as N-methylol acrylamide and N-methylol methacrylamide. Polymer unsaturated monomers can be used. In addition, if necessary, unsaturated amides such as acrylamide and methacrylamide, unsaturated monomers having an oxirane group such as glycidyl methacrylate and glycidyl acrylate, α- and β-monomers such as acrylic acid, methacrylic acid, and maleic acid monoalkyl esters
Unsaturated luponic acids can be used. If the amount of unsaturated monomers containing unsaturated amide and oxirane groups is too large, the water resistance of the coating film tends to decrease or the number of solvents for one reaction is limited. It is preferable to use it once at 30% by weight or less based on the total amount of polymers, α,! - If the amount of unsaturated carboxylic acid is too large, the water resistance of the coating film tends to decrease, so it is preferable to use it in amounts of 10 or more.

Further, the ethylenically unsaturated monomer having a hydroxyl group is appropriately used so that the hydroxyl value of the resulting graft copolymer is from 5 to 100, particularly from 8 to 70.

The fluorine-containing resin and the ethylenically unsaturated monomer are preferably used in a weight ratio of 50,150 to 99,510.5. When this ratio is 50150 or more, durability, especially durability during long-term use, is excellent. Further, from the viewpoint of solubility of the organic solvent, the above weight ratio is preferably 99.5/0.5 or less. The above weight ratio is particularly preferably 60/40 to 9515.

The polymerization of the ethylenically unsaturated monomer in the presence of the fluorine-containing resin can be carried out using toluene, xylene, methyl isobutyl ketone, phtyl acetate, if necessary.

Ethyl acetate, cellosolve acetate, butyl cellonorb.

1-butanol, 2-butanol, 1-propanol,
Using an organic solvent such as 2-propatol as a reaction solvent and a peroxide such as benzoyl peroxide, ditertiary-butyl peroxide, or cumene hydroperoxide, or an azobis-based compound such as azobisisobutyronitrile as a polymerization catalyst. This can be carried out by heating the reaction at 50 to 200°C for 1 to 10 hours. The reaction is preferably carried out in an atmosphere of an inert gas such as nitrogen gas or under a stream of air.
As the polymerization catalyst, peroxide is preferable from the viewpoint of improving the grafting rate, and it is preferable to use peroxide and an azobis-based compound in combination in order to reduce the amount of residual polymer. Polymerization thus includes bulk polymerization and solution polymerization, as well as suspension polymerization if necessary.

This can be carried out by emulsion polymerization or the like.

Although it is possible to form a protective layer with excellent abrasion resistance even with the cured film made of the butyl etherified melamine formaldehyde resin and polyvinyl acetal resin, by using the hydroxyl group-containing fluoropolymer as one material of the protective layer. , the abrasion resistance can be further improved, and the abrasion resistance can be improved with a thinner layer.

The butyl etherified melamine/formaldehyde resin, polyvinyl acetal resin, and hydroxyl group-containing fluoropolymer each contain 30 to 95% by weight.

3 to 60% by weight and 2 to 40% by weight, totaling 100% by weight
It is preferable to use it by blending it so that it becomes
It is preferable to mix and use them so that the total length is 100 layers with 0 layers.

Outside this range, the wear resistance of the protective layer will not be sufficiently improved.

The present invention further adds the following features to the use of an electron-donating carboxylic acid compound and/or an electron-donating polycarboxylic anhydride-kfe as a material for protection J-.

(11'It Child Since the child-resistant carboxylic acid compound/or electron-donating polycarboxylic acid anhydride accelerates the curing reaction, the curing reaction can be completed at a lower temperature and in a shorter time. As a result, during the curing reaction The deterioration of electrophotographic characteristics due to thermal deterioration of the photoreceptor can be significantly reduced.

(2) Since the curing reaction is accelerated as described above, the wear resistance of the protective layer is further improved, and the life of the photoreceptor can be extended.

(3) Since the carboxylic acid and acid anhydride are electron-donating, this property is introduced into the protective layer. As a result, holes are efficiently injected into the protective layer, and a decrease in sensitivity and an increase in residual potential after light irradiation can be extremely minimized. Therefore, the protective layer can be made thicker, and the life of the photoreceptor can be further extended.

Examples of the electron-donating carboxylic acid compound include electron-donating groups such as amine groups, hydroxyl groups, and nitrogen groups.

There are compounds that have one or more aromatic rings substituted with one or more alkoxyl groups, alkyl groups, etc. and a carboxyl group, and compounds that have an electron-donating core and a carboxyl group.The former includes 4-aminobenzoic acid. , 4-dimethylaminobenzoic acid.

3.4-bis(dimethylamine)benzoic acid, 3,4.5
-tris(dimethylamino)phthalic acid, salicylic acid, 4
-Chlor-salicylic acid, 3,4-dibromobenzoic acid, 3
．． 4-dimethoxybenzoic acid, 3,4.5-4rimethoxybenzoic acid, 2,4,5. -trimethoxybenzoic acid, 3,
4.5-trimethoxyphenylacetic acid, diphenylamine-2-carboxylic acid, 2.5-pyridinedicarboxylic acid, 3
, 4.5-trimethoxyphthalic acid.

3-ethyl-4,5-dimethoxybenzoic acid, 3.4
-dimethoxy-5-chlorophenylpropionic acid.

4-tert-butyl-5-methoxybenzene, IJ acid, 1-carboxy-Z3-dimethylaminonaphthalene, 1°8-dicarboxy-2,3,4-trimethoxynaphthalene, 2-
Carboxy-3,6,7-1rimethoxyanthracene,
These include 2-carboxy-3,6-bis(dimethylamine)anthracene, and the latter include oxazole, oxydiazole, pyrazoline, stilbenehydrazone,
There are substituents of electron-donating compounds such as virol, imidazole, carbazole, indole, etc. and their derivatives with one or more carboxyl groups, specifically 2-(
2-carboxy-4-diethylamine)phenyl-1,
3-oxazole, 1-(4-carboxy)phenyl-
3-(4-diethylaminostyryl)-5-(4-diethylamino)phenylpyrazoline, α-phenyl-4'
-N, N'-dicarboxyphenylaminostilbene, N-methyl-N-carboxyphenylhydrazono-3
-Methylidene-9-nityllupazole, pyrrole-2
-Carboxylic acids, etc.

The electron-donating polycarboxylic acid anhydride is an acid anhydride of one of the electron-donating carboxylic acid compounds having two or more carboxyl groups.

Specifically, 3,4.5-t'Js(dimethylamino)
Phthalic anhydride, 3,4,5-methoxyphthalic anhydride, 1,8-dicarboxy-2,3,4-)I
Examples include acid anhydrides of J methoxynaphthalene.

One or more of the electron-donating carboxylic acid compounds and electron-donating polycarboxylic anhydrides have been used for some time, and the amount used is based on the total amount of the butyl etherified melamine/formaldehyde resin and the polyvinyl acetal resin. It is preferably 0.1 to 40% by weight, particularly preferably 1 to 20% by weight.

If the amount used is too small, it will be difficult to exhibit the above-mentioned characteristics, and if it is too large, the moisture resistance of the protective layer will tend to decrease.

The protective layer in the present invention may further contain additives such as a fluidity imparting agent and a pinhole inhibitor that may be used in the charge generation layer and charge transport layer.

The electrophotographic photoreceptor according to the present invention has a structure in which a charge generation layer, a charge transport layer, and a protective layer are sequentially laminated on a conductive layer.

In this electrophotographic photoreceptor, the thickness of the charge generation layer is 0.
The thickness is preferably 0.001 to 10 μm, particularly preferably 0.2 to 5 μm. If the charge generation layer is less than 0.001 μm, the electrophotographic properties (especially sensitivity) tend to be poor, and if it exceeds 10 μm, the residual potential tends to increase.

The thickness of the charge transport layer is preferably 5 to 50 μm.

Particularly preferred is 8 to 20 μm. If it is less than 5 μm, the initial potential tends to be low, and if it exceeds 50 μm, the sensitivity tends to decrease.

The thickness of the protective layer is preferably 0.01 to 10 μm.

Particularly preferred is 0.1 to 5 μm. If the thickness is less than 0.01 μm, the effect as a protective layer will be low and the durability will be poor, and if it exceeds 10 μm, the sensitivity will be poor and the residual potential will tend to increase.

As a method for forming the charge generation layer, when only an organic pigment is used, vacuum deposition can be performed, but the organic pigment and optionally a binder and additives are all acetone. Methyl ethyl ketone, tetrahydrofuran, toluene, xylene, methylene chloride.

It can also be formed by uniformly dissolving or dispersing in a solvent such as trichloroethane, then coating and drying.

A charge-transporting substance when forming a charge-transporting layer.

It can be formed by uniformly dissolving the binder and optionally additives in the same solvent as in the case of the charge generation layer, and then coating and drying.

When forming the protective layer of the present invention, the above-mentioned butyl etherified melamine φ formaldehyde resin, polyvinyl acetal resin, electron-donating carboxylic acid compound and/or electron-donating polycarboxylic acid anhydride, and other materials as necessary. It can be formed by uniformly dissolving additives and the like in a solvent, then coating and curing by heating. The heating temperature at this time is preferably 90 to 140°C.

The electrophotographic photoreceptor of the present invention further includes a charge transport layer containing an electron-accepting charge transport substance immediately above the conductive layer;
It may also have a thin adhesive or barrier layer.

When copying or printing using the electrophotographic photoreceptor of the present invention, the surface is negatively charged as in the conventional case.

After exposure, development is performed, and the image is transferred onto a transfer material such as plain paper and fixed.

(Example) Next, the present invention will be explained in detail based on examples.

The present invention is not limited to this.

Each material used in the examples below is listed below. Abbreviations are shown in parentheses.

(1) Charge-generating organic pigment τ-type metal-free phthalocyanine (τ-H2PC) (2) Charge-transporting substance 2-(p-dimethylamino)phenyl-4-(p-dimethylamino)phenyl-5-(0 -chlorophenyl')
-1,3-Oxazole (OXZ) (3) Binder (A) Binder silicone varnish for charge generation layer: KR-255 [Shin-Etsu Chemical ■Product name] fBl Binder polyester resin for charge transport layer: Vylon 200 [ Toyobo ■Product name] (4) Material for protective layer Butyl etherified melamine formaldehyde resin (BMF) (Synthesis of BMF-1) Melamine 1269.1-butanol in a flask equipped with a stirrer, reflux condenser, and thermometer 4449 and 0.29% of a 61% nitric acid aqueous solution were added, the temperature was raised to 100°C, and 169 g of paraformaldehyde was added at equal intervals in 6 portions over 130 minutes, and then reacted at reflux temperature for 30 minutes.
Moisture was removed and the solvent was removed so that the heating residue was 50%. The viscosity of the obtained resin solution was determined by Gardner (25
℃) was B.

(Synthesis of BMF-2) Using the same apparatus as for the synthesis of BMF-1, melamine izs
g, n-butanol 444g, 61 nitric acid water bath solution 0.2
g and 169q of paraformaldehyde were mixed and charged, the temperature was raised to io0°C, and the mixture was reacted for 30 minutes. Then, reflux dehydration was performed for 30 minutes.

In addition to removing water, the solvent was removed so that the heating residue was 50%. The resulting resin solution had a Gardner viscosity of C at 25°C.

(Synthesis of BMF-3) Paraformaldehyde 217.59. 4449 g of n-butanol and 126 g of melamine were weighed out and an addition reaction was carried out at 90 to 100° C. for 30 minutes. Thereafter, the mixture was cooled to 40 to 45°C, 0.19'i of phthalic acid was added, and reflux dehydration and dissolution were performed under acidic conditions. After this, the heating residue was adjusted to 50%.

The viscosity at this time was (Gardner/25°C) B.

Melamine core 1 of BMF-1, BMF-2 and BMF-3
The number of formaldehyde bonds, the number of butyl ether groups, the number of methylol groups, and the number average molecular weight per each are shown in Table 1 below.

However, the number of bound formaldehyde is determined by measuring the amount of unreacted formaldehyde using the charged amount and the sodium sulfite method, and the number of butyl ether groups is determined by measuring the amount of butanol charged and unreacted butanol by gas chromatography using 5ec-butyl alcohol as an internal standard solution. The methylol group was determined from the above number of butyl ether groups and the NMR spectrum. Further, the number average molecular weight was determined by gel permeation chromatography using a standard polystyrene calibration curve.

Table 1 Properties of butyl etherified melamine resin (Bl
Polyvinyl acetal resin 0 Polyvinyl butyral resin (Al): Denka Butyral Su3000-1 [Denka Kagaku Kogyo ■] 0 Polyvinyl formal II resin (A2): Denka Formal Φ20 [Denki Kagaku Kogyo ■] (Characteristics of each resin are shown in Table 2) Table 2 Characteristics of polyvinyl acetal resin (C) Fluorine-containing resin copolymer with a hydroxyl value of 5 to 100 and a fluorine atom directly bonded to the polymer main chain +11... Lumiflon LF-200D [Asahi Glass ■] However, , Lumiflon LF-200D is prepared by dissolving the above resin in a mixed solvent of xylene and methyl isobutyl ketone to form a solution with a solid content of 50% by weight.

Graft polymer (11) The above copolymer (1), namely Lumiflon LP-20
0D, 1 part by weight of maleic anhydride, and 1 part by weight of xylene were charged into a flask equipped with a stirrer and a reflux condenser, and reacted at 50°C for 1 hour and then at 120°C for 2 hours to form polymerizable carbon-carbon. A fluorine-containing resin having 0.02 mol of double bonds per 100 g of resin was synthesized, and the solid content was adjusted with xylene to obtain a resin m liquid with a solid content of 50% by weight.

Next, 60 parts by weight of this resin solution (solid content 30 parts by weight) and 6 parts of bath agent (Tsurupez 100.Esso Petrochemicals trade name)
0 parts by weight, 10 parts by weight of n-butanol were charged into a flask, and while keeping the temperature at 120°C, 12 parts by weight of 2-hydroxyethyl methacrylate, butyl methacrylate) 257
Part II, 12-5 parts by weight of ethyl acrylate, 18 parts by weight of methyleneno.

2.5 parts by weight of methacrylic acid, 2.5 parts by weight of azobisisobutyronitrile, and 0.0 parts by weight of di-t-butyl peroxide.
After 5 parts by weight of the mixed solution was added dropwise over 2 hours, the mixture was further kept at the same temperature for 1 hour, and then heated to 140°C and reacted for 4 hours to obtain a graft polymer (11). N-butanol was added so that the obtained graft polymer (:1) had a solid content of about 50 wtfk%.

The obtained graft polymer (11) had a hydroxyl value of 32.

(dl Compound having an aromatic ring substituted with one or more electron-donating groups and one or more carboxyl groups and/or acid anhydride...λ4.5-trimethoxyphenylacetic acid (e)
Electron-donating compound having one or more carboxyl group and/or acid anhydride in the molecule...Virrole-2-carboxylic acid Comparative Example 1 τ-H2PC2,09-Silicone Face (K3-25
5) 4.09 and 94 g of tetrahydrofuran were kneaded for 8 hours using a Q ball mill (3-inch bot mill manufactured by Nihon Kagaku Togyo Co., Ltd.). The obtained pigment dispersion was applied onto an aluminum plate (thickness: 0.1 mm) using an applicator.
The charge generating layer was dried at 00° C. for 15 minutes to form a charge generating layer with a thickness of about 1.0 μm.

Next, oxzsg and polyester resin (Byron 200)
159 was mixed with tetrahydrofuran 1409 and allowed to dissolve completely. The obtained liquid-resistant material was applied onto the charge generation layer using an applicator.

It was dried at 90° C. for 20 minutes to form a charge transport layer of 15 μm.

Comparative Examples 2 to 3 A charge generation layer and a charge transport layer were formed in the same manner as in Comparative Example 1, and then a solution consisting of BMF-3,409 (20 g in solid content) and 60 g of isopropanol was applied using an applicator. . Table 3 shows the curing conditions and film thickness of the protective layer.

Comparative Examples 4 to 5 A charge generation layer and a charge transport layer were formed in the same manner as in Comparative Example 1, and then a solution consisting of BMF-1,409 (20 g in solid content) and 60 g of isopropanol was applied using an applicator. , heated at 110℃ for 1 hour to a thickness of 1-3μ
A protective layer of m was formed.

Comparative Examples 6 to 7 A charge generation layer and a charge transport layer were formed in the same manner as in Comparative Example 1, and then BMF-1,329 (solid content: 169),
Polyvinyl butyral resin 49 and isopropanol 6
A solution consisting of 49 was applied using an applicator. Table 3 shows the curing conditions and film thickness of the protective layer.

Comparative Example 8 A charge generation layer and a charge transport layer were formed in the same manner as in Comparative Example 1, and then BMF-1,329 (solid content: 169), polyvinyl butyral tlIIiW4g, 3°4,5-
A solution consisting of 1 g of trimethoxyphenylacetic acid and 639 g of a mixed solvent of isopropanol and tetrahydrofuran was applied using an applicator.

Table 3 shows the curing conditions and film thickness of the protective layer.

Examples 1 to 6 A charge generation layer and a charge transport layer were formed in the same manner as in Comparative Example 1, and then a protective layer solution having the composition ratio shown in Table 3 (1/1 mixed solvent of tetrahydrofuran/isopropanol = 1/1) was added.
Apply fc using an applicator. Table 3 shows the curing conditions and film thickness of the protective layer.

The electrophotographic properties of the obtained electrophotographic photoreceptor were measured using an electrostatic recording paper tester (5P-428 manufactured by Kawaguchi Denki), and the results are shown in Table 3.

The initial potential Vo (V) in the table indicates the charging potential when a negative 5KV corona is discharged for 10 seconds in dynamic measurement, and the dark decay VKi%l indicates the potential retention rate when left in the dark for 30 seconds. +E56°E75 indicates the amount of light (lx·S) required for the potential to drop by 50 lux and 75%, respectively, when irradiated with 10 lux white light.

Residual potential VR (Vl) indicates the surface potential after irradiation with 10 lux white light for 30 seconds.

In addition, using a friction tester (manufactured by Gas Test Instruments), the surface of the electrophotographic photoreceptor is rubbed with gauze, and the wear resistance is measured by the number of times of sliding until the wear scratches on one surface pass through the protective layer and reach the layer below. Rated 9. In the case of Comparative Example 1, the number of times of sliding until fiber traces of the gauze were visually confirmed was measured. The results are shown in Table 4. Further, the electrophotographic photosensitive plates of Comparative Examples 1 to 8 and Examples 1 to 6 were subjected to a continuous printing test using an image evaluation machine to evaluate the printing life until one image quality deteriorated. The results are also shown in Table 4.

Margin Table 4 Below: Abrasion resistance and printing life Comparative Example 1 has excellent electrophotographic properties, but because no protective layer is provided, the abrasion resistance is extremely poor at 200 cycles. Further, a case where a butyl etherified melamine formaldehyde resin (BMF-3) outside the scope of the present invention was used as the protective layer material (Comparative Example 2.3).

When the curing temperature is low (110°C), there is no effect of improving wear resistance due to insufficient curing (Comparative Example 2);
160°C), and the curing time was 3 hours, making the film thickness t-3μ! 1] is the result of thickening.

Abrasion resistance was slightly improved (Comparative Example 3). However, the electrophotographic properties deteriorated significantly, that is, the Eso*Eys* VR increased significantly, and as a result, background c'9 distortion occurred from the beginning, making it impossible to evaluate the image.

When a melamine resin within the scope of the present invention is used alone (Comparative Example 4.5), low temperature curing becomes possible and wear resistance is improved, but when the film thickness is 1 μm, the printing life is 15. 0
00 sheets, which is still low (Comparative Example 4).

However, when the film thickness is increased to 3 μm, the wear resistance improves.

EqJ* E7! Is VR increased and background staining occurred (Comparative Example 5).

On the other hand, when a butyl etherified melamine formaldehyde resin and a polyvinyl butyral resin within the scope of the present invention were used together (Comparative Example 6.7).

As expected, curing progresses at low temperatures and in a short time, and even if the film thickness is as thin as 0.5 μm, the wear resistance is greatly improved, and the printing life is 65%.
OO becomes 0 sheets (Comparative Example 6). However, if the thickness of the protective layer was increased to 3 μm in order to further increase the abrasion resistance and printing life, compared to Comparative Example 3, which was dried at high temperature and for a long time, e.g.
Egg E7SI Although the increase in Va was small, background staining occurred on the 0th image (Comparative Example 7).

On the other hand, when the carboxylic acid component (d) is added to the protective layer (Comparative Example 8), it cures at a lower temperature and in a shorter time than in Comparative Examples 6 and 7, and the thickness of the protective layer also improves the wear resistance. It can be seen that this is improved compared to Comparative Examples 3.5 and 7, which are the same as 3 μm. Also, the electrophotographic properties are good even though the protective layer is as thick as 3 μm.

It is also comparable to Comparative Example 1 without a protective layer, and it can be seen that by adding component (d), abrasion resistance and, ultimately, printing life can be improved without impairing electrophotographic properties.

However, the protective layer according to the second invention is a system in which a fluorine-containing resin having a hydroxyl value of 5 to 100, which is the component (C), and in which a fluorine atom is directly bonded to the polymer main chain is added, and Examples 1 to 6 are used.
As shown in Figure 2, the electrophotographic properties are the same as those of Comparative Example 1 without a protective layer, and the wear resistance is significantly improved (compared to Comparative Example 8, which does not contain the C1 component), and the printing life is 23% in both cases.
It can be seen that it has an extremely long life of more than 10,000 sheets.

As described above, the electrophotographic photoreceptors shown in Examples 1 to 6 of the present invention have significantly improved wear resistance while maintaining good electrophotographic properties, and as a result, have a printing life of more than 230,000 sheets. It was confirmed that it has.

(Effects of the Invention) The electrophotographic photoreceptor according to the present invention has excellent electrophotographic properties, has an extremely long printing life, and has long life durability.

Claims (1)

[Claims] 1. An electrophotographic photosensitive material in which a charge generation layer containing an organic pigment that generates a charge, a charge transport layer containing an electron donating charge transporting substance, and a protective layer are sequentially laminated on a conductive layer. In the body, the protective layer is (a) a butyl etherified melamine formaldehyde resin having a number average molecular weight of 1.500 or less, the number of bound formaldehydes per melamine nucleus is 2 to 4, and the number of methylol groups is 1 to 2; , (b) a polyvinyl acetal resin, (c) a hydroxyl group-containing fluoropolymer, and (d) an electrophotographic photoreceptor comprising a cured film of an electron-donating carboxylic acid compound and/or an electron-donating polycarboxylic acid anhydride.