JPH01200261A - electrophotographic photoreceptor - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a laminated electrophotographic photoreceptor, particularly an organic electrophotographic photoreceptor.

[Prior Art] Conventionally, electrophotographic photoreceptors include those in which a layer of a composition in which a photoconductive pigment is dispersed in an electrically insulating binder resin is provided on a conductive support; A charge generating layer, a resin layer containing a charge transporting substance provided on the charge generating layer, a resin layer containing a charge transporting substance on a conductive support, and a charge generating layer provided thereon, and a charge generating layer having the above charge. It is known that a composition in which a charge generating substance is dispersed in a transport layer is provided on a conductive support.

These electrophotographic photoreceptors are susceptible to photofatigue, and are particularly sensitive to light including ultraviolet rays. For example, when a photoreceptor exposed to fluorescent light is subjected to a process consisting of charging, exposure, development, transfer, cleaning, etc. to form an image, an image with low image density and fog is obtained.

These phenomena are caused by deterioration of charging characteristics due to pre-exposure fatigue, and in particular, residual potential tends to increase.

This phenomenon occurs particularly markedly when the process is carried out under high temperature and high humidity conditions. In order to prevent this phenomenon, attempts have been made to add ultraviolet absorbers such as benzotriazole and benzophenone, but satisfactory results have not yet been obtained.

[Purpose] The present invention relates to an electrophotographic photoreceptor that prevents the above-mentioned exposure fatigue and exhibits stable performance even under high temperature and high humidity environments. It is an object of the present invention to provide an electrophotographic photoreceptor that exhibits a small increase in residual potential even if it is repeatedly used after being exposed to the electrophotographic photoreceptor.

[Structure] The structure of the present invention for achieving the above object is that in an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support, the charge transport layer contains a phenolic antioxidant. This is an electrophotographic photoreceptor containing an organic sulfur-based antioxidant and an organic sulfur-based antioxidant.

That is, in the present invention, compared to the case where a phenolic antioxidant and an organic sulfur antioxidant are mixed together in a predetermined total amount, it is better to use the antioxidants together at a fixed gold ratio.
This is based on the discovery that the effect of suppressing the increase in residual potential due to pre-exposure fatigue is synergistically improved.

The above phenolic antioxidant used in the present invention is 2,6
-tert-butylphenol, 2.6 gter
t-Butyl-4-methoxyphenol, 2,6-sheet
ert-butyl-4-methylphenol, 2-tert
t-Butyl-4-methoxyphenol, 2,4-dimethyl-6-tert-butylphenol, butylhydroxyanisole, 2,2-methylenebis(6-tert
-butyl-4-methylphenol), 2-tert-
Butyl-6 (3-tert-butyl-5-methyl-
2'-Hydroxybenzyl)-4-methylphenylacrylate, 4゜4'-butylidene-bis-(3-methyl-6-tert-butylphenol), n-octadecyl-5-(3--5''-di-tert- Butyl 4'-
hydroxyphenyl)buhyroonate, 4,4-thiobis(6-tert-butyl-3methylphenol),
α-Tocopherol, β-Tocopherol, 2,2.4
-trimethyl-6-hydroxy-7-tert-butylchroman, tetrakis[methylene-3(3,5-di-tert)
-Butyl-4-hydroxyphenyl)propionate comethane, 1,1,3-tris(2-methyl-4-hydroxy-3-Lertbutylphenyl)butane, 2,5-
Hindered substituted phenols, including various phenolic compounds such as di-LerL-butylhydroquinone, are particularly effective.

Further, the organic sulfur-based antioxidants used in the present invention include dilaurylthiodipropionate, distearylthiodipropionate, lauryl stearylthiodipropionate, simiristylthiodipropionate, distearyl β, β' - Thiodibutyrate, etc. can be used.

The blending ratio of the phenolic antioxidant and the organic sulfur antioxidant is 20:1 to 1:5 molar ratio, preferably 5:1 to 5:1.
The ratio is 1:1.

Also, the composition of both these components is 0.0% relative to the charge transport material.
Old to 5% by weight is appropriate, preferably 0.04 to 24%
Weight%.

As a charge generating substance, C.I. Pigment Blue 25
[Color Index (CI) 211801, CI Pigment Red 41 (CI 2+200), CI Acid Red 52 (CI 45100),
CI Basic Red 52 (CI 45100
), CI Basic Red 3 (CI 452
10), azo pigments having a carbazole skeleton (described in JP-A No. 53-95033), azo pigments having a styrylstilbene skeleton (described in JP-A-53-133229), azo pigments having a triphenylamine skeleton, etc. Pigments (described in JP-A-53-132547), azo pigments having a dibenzothiophene skeleton (JP-A-54-217)
No. 287), azo pigments having an oxadiazole skeleton (described in Japanese Patent Publication No. 54-127427), azo pigments having a fluorenone skeleton (Japanese Patent Application Laid-open No. 54-228)
No. 37, an azo pigment with H bisstilbene skeleton (described in JP-A-54-17733), an azo pigment with a distyryloxadiazole skeleton (JP-A-54-17733),
-2129), azo pigments with a distyryl-rbazole skeleton (described in JP-A-54-17734), azo pigments with a carbazole skeleton (described in JP-A-57-1983),
-195767), phthalocyanine pigments such as CI Pigment Blue 18 (CI 741.00), CI Bat Brown 5 (
CI 73410), sea eye bat die (CI
Indigo pigments such as 73030) and perylene pigments such as Argo Scarlet B (manufactured by Bayer) are used alone or in combination.

Among these charge-generating substances, there are disazo pigments having a fluorenone skeleton represented by the following - drinking material (A) and the following -
Tris-A having a triphenylamine skeleton represented by (B) (wherein A1 is, where X' SA r ', A r '
, R', and R2 are as follows.

XI, an aromatic ring such as a benzene ring or a naphthalene ring, or a hetero ring such as an indole ring, a carbazole ring, or a benzofuran ring, or a substituted product thereof, Ar': an aromatic ring such as a benzene ring or a naphthalene ring, or dibenzofuran Heterocycles such as rings or substituted products thereof, Ar2: aromatic rings such as benzene ring, naphthalene ring, or substituted products thereof, R1 hydrogen, lower alkyl group or phenyl group, or substituted products thereof, R2, alkyl group, carbamoyl group, carboxyl group or its ester) (wherein A2 is, where X', Ar3, Ar4, Ar5, R3,
R4 and R5 are as follows.

X2. Aromatic rings such as benzene rings and naphthalene rings, or hetero rings such as indole rings, carbazole rings, and benzofuran rings, or substituted products thereof; Ar3, Ar': aromatic rings such as benzene rings and naphthalene rings; , or a hetero ring such as a dibenzofuran ring or a substituent thereof, A"5: aromatic ring such as a benzene ring or naphthalene ring or a substituent thereof, R3, R5, hydrogen, a lower alkyl group or a phenyl group, or a substituent thereof , R4, an alkyl group, a carbamoyl group, a carboxyl group or an ester thereof) As a substituent for Xl in the general formula (A) and X2 in the general formula (B), a chlorine atom, a bromine atom, etc.
Examples include a rogene atom, an alkoxy group, and an alkyl group.

- Substituents for Ar' in the drinking price (A) and Ar" and Ar' in the general formula (B) include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, methoxy group, ethoxy group, propoxy groups, alkoxy groups such as butoxy groups, chlorine atoms such as chlorine atoms, bromine atoms,
dialkylamino groups such as dimethylamino group and diethylamino group, dialkylamino groups such as dibenzylamino group, halomethyl group such as trifluoromethyl group, nitro group, cyano group, carboxyl group or ester thereof;
Examples include hydroxyl groups, sulfonic acid groups such as -5O3Na, and the like.

In addition, Ar' in general formula (A) and general formula (B)
Examples of substituents for Ar5 include alkyl groups such as methyl, ethyl, propyl, and butyl; alkoxy groups such as methoxy, ethquin, propoxy, and butoxy; nitro, chlorine, and bromine; Examples include halogen atoms, dialkylamino groups such as dimethylamino groups and diethylamino groups.

Further, examples of the substituent for the phenyl group of R1 in the general formula (A) and R3 and R5 in the general formula (B) include halogen atoms such as a chlorine atom and a bromine atom.

For specific compounds of general formula (A), please refer to JP-A-53
It is described in detail in JP-A-132547.

For specific compounds of general formula (B), please refer to JP-A-54
It is described in detail in JP-A-22834.

As the binder used in the charge generation layer, polyvinyl butyral resin, polyvinyl formal resin, polyester resin, polycarbonate resin, polystyrene, polyvinyl acetate, polyamide, polyurethane, various celluloses, etc. are used.

The charge generating layer can be provided on a support by dispersing a charge generating substance in a solvent together with a binder if necessary, and by coating, dipping or the like. The binder is a charge generating substance 100
It is appropriate to use about 5 to 150 parts by weight per part by weight.

Thickness of charge generation layer: 0.05 to 20μ, preferably 0.1μ
~2μ is appropriate.

The charge transport layer contains a charge transport substance and a binder.

Known electron-donating compounds can be used as the charge-transporting substance, and among them, an α-substituted stilbene compound represented by the following general formula (C), which is an electron-donating compound, and a compound represented by the following general formula (D
) are preferred.

(C) (wherein R6 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, R7, Re and R9 are hydrogen atoms, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group) , Ar6 represents a substituted or unsubstituted aryl group, and Ar7 represents a substituted or unsubstituted arylene group. Ar6 and R6 may jointly form a ring. n is an integer of 0 or 1. ) Examples of the alkyl groups in R6, R7, R8 and R9 of the above general formula (C) include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, etc., and substituents in the substituted alkyl group include is a methoxy group,
Alkoxy groups such as ethoxy, propoxy, butoxy, and pentyloxy groups; aryloxy groups such as phenoxy, tolyloxy, and naphthyloxy groups; aryl groups such as phenyl and naphthyl groups; dimethylamino, diethylamino, and dimethylamino groups; Examples include alkylamino groups such as propylamino group and N-methyl-N-ethylamino group, arylamino groups such as N-phenylamino group and N,N-diphenylamino group, hydroxy group, and amino group. There may be one or more substituents on the alkyl group, and when there are two or more substituents, they may be the same group or different groups.

Specific examples of substituted alkyl groups include alkoxyalkyl groups, aryloxyalkyl groups, aminoalkyl groups, hydroxyalkyl groups, aralkyl groups, alkylaminoalkyl groups, and arylaminoalkyl groups.

Further, the aryl group in Arc, R', R7, R' and R9 is a carbocyclic or polycyclic mononuclear or polynuclear aromatic ring residue, more specifically a phenyl group,
naphthyl group, anthryl group, thienyl group, pyridyl group,
Furyl group, carbazolyl group, styryl group, etc. are mentioned, and substituents in the substituted aryl group include alkylamino groups such as dimethylamino group, diethylamino group, dipropylamino group, methoxy group, ethoxy group, propokine group, butoxy group, etc. Alkoxy groups, phenoxy groups, tolyloxy groups, aryloxy groups such as naphthyloxy groups, alkyl groups such as diphenylamino groups, methyl groups, ethyl groups, propyl groups, butyl groups, amino groups such as ditolylamino groups, hydroxy groups, phenyl Examples include halogen atoms such as chlorine atom and bromine atom, alkylthio groups such as cyano group, nitro group and ethylthio group, and arylthio groups such as phenylthio group and naphthylthio group.

There may be one or more substituents on the aryl group,
When there are two or more groups, they may be the same group or different groups. Specific examples of the substituted aryl group include dialkylaminoaryl group, alkoxyaryl group, aryloquinaryl group, alkylaryl group, diarylaminoaryl group, aminoaryl group, hydroxyaryl group,
Examples include a phenylaryl group, a haloaryl group, a cyanoaryl group, a nidroaryl group, a thioalkoxyaryl group, and a thioaryloxyaryl group.

Examples of the arylene group of Ar7 include the above-mentioned carbocyclic or heterocyclic mononuclear or polynuclear aromatic residues,
Further, examples of the substituent in the substituted arylene group include the substituents in the above-mentioned substituted aryl group. The arylene group may have one or more substituents, and 2
If there are more than two groups, they may be the same group or different groups.

Examples of those in which Ar6 and R6 jointly form a ring include furorenyl, cyclopentagenyl, cyclohexagenyl, cyclohexenyl, and cyclopentenyl. These rings may have the above-mentioned substituents.

Specific examples of α-substituted styryl compounds are as follows, and other specific examples are described in detail in JP-A-60-98437.

The hydrazone compound shown in (D) below is also preferable as a charge transport substance, and can exhibit remarkable effects when used in combination with the photodegradation inhibitor of the present invention.

IO [wherein R10 is a methyl group, an ethyl group, a propyl group, 2
- represents a substituted or unsubstituted alkyl group such as a hydroxyethyl group, a 2-chloroethyl group, or a benzyl group, or a substituted or unsubstituted phenyl group, and R11 is a methyl group, an ethyl group, a benzyl group, or a substituted or unsubstituted phenyl group; Represents a substituted phenyl group, R12 is hydrogen, chlorine, bromine, or has 1 carbon number
-4 alkyl group, C1-C4 alkoxyl group, dialkylamino group or nitro group. ] Specific examples of hydrazone compounds include the following, and other specific examples can be found in JP-A-55-
46711iO for details, other electron-donating compounds include alkyl groups such as methyl groups, alkoxy groups,
A compound containing at least one of an amino group, an imino group, and an imide group, or a polycyclic aromatic residue such as anthracene, pyrene, phenanthrene, coronene, or indole, carbazole, oxazole, isoxazole, or thiozole in the main chain or side chain. There are compounds having nitrogen-containing ring residues such as , imidazole, pyrazole, oxadiazole, thiodiazole, and triazole. Specifically, as low molecular weight compounds, hexamethylene diamine, N-(4-
(aminobutyl) cadaverine, as-didodecylhydrazine, p-toluidine, 4-amino-0-xylene, N,
N--diphenyl-1,2-diaminoethane, o-,
m, or p-ditolylamine, triphenylamine, diphenylmethane, triphenylmethane, durene, 2-bromo-3,7-dimethylnaphthalene, 2°3.
5-) Trimethylnaphthalene, N--(3-bromphenyl)-N-(β-naphthyl)urea, N-methyl-N-
(α-naphthyl)urea, N,N--diethyl-N-(α
-naphthyl) urea, 2.6-dimethylanthracene, anthracene, 2-phenylanthracene, 9.10-diphenylanthracene, 9°9'-bianthranil, 2
-dimethylaminoanthracene, phenanthrene, 9-
aminophenanthrene, 3,6-dimethylphenanthrene, 5,7-dipromo-2-phenylindole, 2,
3-dimethylindoline, 3-indolylmethylamine, carbazole, 2-methylcarbazole, N-ethylcarbazole, 9-phenylcarbazole, 1,1-dicarbazole, 3-(p-methoxyphenyl)oxazolidine, 3,4. 5-trimethylisoxazole,
2-anilino-4゜5-diphenylthiazole, 2,4
．． 5-trinitrophenylimidazole, 4-amino-
3,5-dimethyl-1-phenylpyrazole, 2,5-
diphenyl-1,3,4-oxadiazole, 1,3.
Poly-N- Vinylcarbazole and its derivatives (for example, those having a halogen such as chlorine or bromine, or a substituent such as a methyl group or an amino group in the carbazole skeleton), polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde condensation polymer and its derivatives (for example, those having a pyrene skeleton) Examples include those containing halogens such as bromine, and substituents such as nitro groups.

Binders used in the charge transport layer include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. combination, polyvinyl acetate, polyvinylidene chloride,
Polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate, ethyl cellulose, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenolic resin , thermoplastic resins such as alkyd resins, thermosetting resins, and the like. The amount used is 10:1 to 1:10, preferably 1:2 to 1:10 by weight with the charge transport material.
The range is 2:1.

In addition, known plasticizers, leveling agents, etc. can be added to the charge transport layer. The thickness of the charge transport layer is 2 to 20
0μ, preferably 5 to 30μ.

The conductive support may be a plastic film or cylinder on which aluminum, nickel, chromium, tin oxide, indium oxide, or the like is deposited (plastics include polyester, polypropylene, cellulose acetate, etc.).

) Paper or plastic film laminated with a conductive thin film such as aluminum foil: Examples include plates or cylinders made of metals such as aluminum, nickel, stainless steel, and iron.

The undercoat layer is provided for the purpose of improving chargeability, improving adhesive properties, and preventing moire, and is made of polyamide, polyvinyl acetate, polyurethane, alcohol-soluble nylon, polyvinyl butyral, water-soluble polyvinyl butyral, etc. The main component is resin, aluminum oxide,
Tin oxide, conductive carbon, zinc oxide, etc. can also be dispersed.

The thickness of the undercoat layer is suitably about 0.01 to 10 .mu.m, preferably 0.01 to 5 .mu.m.

The present invention will be explained below with reference to Examples. Note that both parts and percentages are based on weight.

Example 1 1.7 parts of a disazo pigment represented by the following structural formula, 13.6 parts of a 5% tetrahydrofuran solution of polyvinyl butyral (XYHL manufactured by Union Carbide Plastics) and 44.2 parts of tetrahydrofuran were dispersed in a ball mill for 48 hours. Then, 22.3 g of tetrahydrofuran and 37.2 g of ethyl cellosolve were added and dispersed for 1 hour. The obtained mill base was diluted with tetrahydrofuran at a weight ratio of 4:6 and the solid content concentration was 1%, and this was applied with a doctor blade onto a polyester film on which aluminum was vapor-deposited. It was dried at 80° C. for 5 minutes to form a charge generation layer with a thickness of about 0.8 μl.

Polycarbonate (Panlite K 1300 manufactured by Ondai Kasei Co., Ltd.) 20 parts Silicone oil (K F 50 manufactured by Shin-Etsu Chemical Co., Ltd.) 0.004 parts Methylene chloride 152 parts 2.6-sheet tert-butyl-4-methylphenol 0.0311 parts A charge transport layer forming solution consisting of 0.118 parts of distearyl-3,3' monothiodipropionate was applied using a doctor blade, and dried at 80°C for 2 minutes and then at 130°C for 5 minutes to form a charge transport layer with a thickness of about 19 μm. A transport layer was formed.

Comparative Example 1 A photoreceptor was prepared in exactly the same manner as in Example 1 except that distearyl-3゜3゛-thiodipropionate was removed.

Comparative Example 2 2,6-LerL-butyl-4 from the formulation of Example 1
- A photoreceptor was prepared in exactly the same manner except that methylphenol was removed.

Comparative Example 3 Distearyl-3,3'-thiodipropionate was removed from the formulation of Example 1, and 2,6-sheet tcrt-
A photoreceptor was prepared in the same manner as in Example 1 except that butyl-4-methylphenol was changed to 0.076 parts.

Comparative Example 4 2.6-sheet tcrt-butyl-4 from the formulation of Example 1
- excluding methylphenol, and distearyl-3,
A photoreceptor was prepared in the same manner as in Example 1 except that 3°-thiodipropionate was changed to 0.238 parts.

The electrophotographic photoreceptor prepared as described above was tested using an electrostatic copying paper tester (manufactured by Kawaguchi Electric Seisakusho Co., Ltd., model 5P428).
Electrophotographic characteristics were evaluated under the following conditions (measured in dynamic mode). First, -6 kV corona discharge was performed for 20 seconds to charge the battery, and after leaving it in a dark place for 20 seconds, 4.5
Irradiated with 1ux white tungsten light.

The surface potential V 30 (VolL) after 30 seconds of irradiation was measured and used as the initial characteristics.

Then, using a daylight fluorescent lamp, 1000I was applied to the photoreceptor surface.
It was set to ux and irradiated with light for 30 minutes. moreover,
Transfer the irradiated photoreceptor to a dedicated fatigue testing machine and test it at 451u.
The current flowing through the photosensitive layer when irradiated with x light is 9.6 μ.
The discharge current of the charger was adjusted so that A was obtained, and light irradiation and discharge were applied continuously for 30 minutes. Immediately after fatigue, the photoreceptor was transferred to the electrostatic copying paper tester described above, and V2O was determined at 411j under the same conditions as when the initial characteristics were measured, and the fatigue characteristics were determined. The measurement results are shown in Table 1.

Table 1 It can be seen that the increase in residual potential due to repeated use of the pre-fatigued photoreceptor is suppressed under normal temperature and normal humidity and high temperature and high humidity conditions.

Example 2 2,6-LerL-butyl-4 from the formulation of Example 1
- Photoreceptors were prepared in the same manner as in Example 1 except that methylphenol was replaced with the phenolic antioxidant shown below.

Phenolic antioxidant Addition amount (^) 2.6-tart-butyl-phenol 0.038 part (B) 2.2'-
Methylenebis(4-methyl-6-LerL-butyl-phenol) 0.
059 parts (C) Butylhydroxyanisole 0.0
31 parts (D) Tetra hand [methylene-5-(3°,
5°-di-tert-butyl-4-hydroxy-phenyl)propionate 1-methane
0.200 parts and as a comparative example, photoreceptors A', B-1C', and D' were prepared from the formulations of ASB, C, and D above, except that the organic sulfur antioxidant was removed.

A fatigue test was conducted on the above eight photoreceptors in the same manner as in Example 1. The results are shown in Table 2.

Table 2 Example 3 From the formulation of Example 1, distearyl-3,3°-thiodipropionate was changed to the organic sulfur antioxidant shown below, and photoreceptors were prepared in the same manner as in Example 1.

Organic sulfur-based antioxidant Addition amount (E) 0.099 part (r')
dilauryl-3,3-thiopropione)'
0.089 parts (G) dimethyl-3,
3-thiopropione) 0.03
6 parts or 1 as a comparative example, E', F', and G obtained by removing the phenolic antioxidant 11-agent from the formulations of E, F, and G above, respectively.
- A photoreceptor was created.

A fatigue test was conducted on the above six photoreceptors in the same manner as in Example 1. The results are shown in Table 3.

Table 3 [Effects] As explained above, by suppressing the deterioration of the photoreceptor due to pre-exposure fatigue, the operability of the photoreceptor is improved.

Claims (1)

[Claims] An electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer laminated on a conductive support, characterized in that the charge transport layer contains a phenolic antioxidant and an organic sulfur antioxidant. Electrophotographic photoreceptor.