JPH07261419A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To obtain a well-balanced electrophotographic photoreceptor having high sensitivity and low residual potential and free from the rising delay of charging potential by adding a specific naphthoquinone or naphthoquinone derivative into one of layers. CONSTITUTION:In the laminated electrophotographic photoreceptor having at least a charge generating layer and a charge transfer layer on a conductive supporting body, the naphthoquinone or naphthoquinone derivative expressed by formulas I-III is incorporated in one of the layers. In the formulas I-III, each of R<1>-R<6> represents hydrogen atom, an alkyl group, cycloalkyl group, aryl group, arylalkyl group, nitrogroup, hydroxyl group or a halogen atom. As the alkyl group, 1-10C, preferably 1-5C linear or branched alkyl group such as methyl group, ethyl group, propyl group or the like is exemplified and cyclohexyl group as the cycloalkyl group, phenyl group or the like as the aryl group, benzyl group as the arylalkyl group and chlorine or bromine as the halogen atom are exemplified.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in electrophotographic photoreceptors.

[0002]

2. Description of the Related Art Heretofore, inorganic photoconductive substances such as selenium and selenium alloys, zinc oxide, and cadmium sulfide have been mainly used as photosensitive materials for electrophotographic photoreceptors. On the other hand, recently, a material using an organic photosensitive material, which has advantages of low cost, productivity, and no pollution, has begun to be used. Polyvinyl carbazole (P
VK) represented by photoconductive resin, PVK-TNF
(2,4,7-trinitrofluorenone), a charge-transfer complex type, a phthalocyanine-binder, a pigment-dispersed type, and a function-separated type photoconductor in which a charge generation substance and a charge transfer substance are used in combination. Is known, and in particular, a function-separated type photoconductor is drawing attention. However, when such a function-separated type photoreceptor is applied to the Carlson process, the chargeability is low, the charge retention is poor (dark reduction is large), and the deterioration of these characteristics is large due to repeated use. , Density unevenness, density decrease on the image,
Further, in the case of reversal development, there is a drawback that background stain occurs.

In order to improve the electrical characteristics of such a photoreceptor, it is considered effective to provide an intermediate layer between the substrate and the photoreceptor. Generally, the purpose of providing such an intermediate layer is to improve the adhesiveness, improve the coating property of the photosensitive layer, protect the substrate, cover defects on the substrate, protect the photosensitive layer from electrical damage, and protect the substrate from the photosensitive layer. And the improvement of the charge injection property.

For example, JP-A-47-6341, 48-3
In 544 and 48-12034, a cellulose nitrate resin intermediate layer is disclosed in JP-A-48-47344, 52-2563.
8,58-30757,58-63945,58-95
351, 58-98739 and 60-66258, a nylon resin intermediate layer; JP-A-49-69332 and 52-10138, a maleic acid resin intermediate layer; and JP-A-58-105155. Each polyvinyl alcohol resin-based intermediate layer is disclosed. Also,
An intermediate layer has been proposed in which various conductive additives are contained in a resin in order to control the electric resistance of the intermediate layer. For example, JP-A-51-65942 discloses an intermediate layer in which a carbon or chalcogen-based substance is dispersed in a curable resin.
No. 82238, a thermal polymer intermediate layer containing a quaternary ammonium salt and an isocyanate-based curing agent is disclosed in Japanese Patent Laid-Open No.
A resin intermediate layer containing a resistance adjusting agent is disclosed in JP-A-5-1130451, and a resin intermediate layer containing an oxide of aluminum or tin dispersed therein is disclosed in JP-A-58-58556.
No. 93062, a resin intermediate layer containing an organometallic compound is disclosed in JP-A-58-93063, 60-97363 and 6;
No. 0-11125 discloses a resin intermediate layer in which conductive particles are dispersed, and JP-A No. 59-17557 discloses a layer in which magnetite is dispersed in a resin.
Ti in 7,59-93453 and 60-32054
A resin intermediate layer in which O ₂ and SnO ₂ powder are dispersed is also disclosed in JP-A-64-68762, 64-68763, 64-73.
352, 64-73353, Japanese Patent Application Laid-Open No. 1-118848,
No. 1-118849 discloses an intermediate layer of a resin in which powders of borides such as calcium, magnesium and aluminum, nitrides, fluorides and oxides are dispersed. Also,
In order to improve the charging property, for example, JP-A-64-57.
1 and JP-A-3-23464 disclose a resin intermediate layer containing polyalkylene glycol or polyethylene glycol.

Further, such a function-separated type photoconductor has high sensitivity, but in recent years, there has been a demand for higher sensitivity of the photoconductor in order to cope with high speed machines. In order to further increase the sensitivity of the function-separated type photoreceptor, there is a method of using a charge generating substance having a high charge generating efficiency.

Generally, as the charge generating substance, for example, CI Pigment Blue 25 [color index (C
I) 21180], Sea Pigment Red 41 [C
I21200], CI Acid Red 52 [CI
45100], CI Basic Red 3 [CI 4
5210], a phthalocyanine-based pigment having a porphyrin skeleton, an azurenium salt pigment, a squalic salt pigment, and an azo pigment having a carbazole skeleton (Japanese Patent Laid-Open No.
95033), azo pigments having a stilstilbene skeleton (described in JP-A-53-138229), azo pigments having a triphenylamine skeleton (described in JP-A-53-132547), and dibenzothiophene. Azo pigments having a skeleton (described in JP-A-54-21728), azo pigments having an oxadiazole skeleton (described in JP-A-54-12742), azo pigments having a fluorenone skeleton (JP-A-54). No. 22834), an azo pigment having a bisstilbene skeleton (described in JP-A-54-17733), and an azo pigment having a distyryloxadiazole skeleton (JP-A-54-21).
29), azo pigments having a distyrylcarbazole skeleton (described in JP-A-54-17734), and triazo pigments having a carbazole skeleton (JP-A-57-195767 and 57-195768). , Etc., and further, CI Pigment Blue 16
Phthalocyanine pigments such as (CI 74100), indigo pigments such as CIVAT BROWN 5 (CI 73410) and CIVAT Die (CI 73030),
There are organic pigments such as perylene-based pigments such as Argos scarlet B (manufactured by Violet) and Industrance scarlet R (manufactured by Bayer).

Among these charge-generating substances, a photoreceptor using an azo pigment having a fluorene skeleton has high sensitivity. Further, a photoreceptor using an azo pigment having a fluorenone skeleton is characterized in that the sensitivity is further improved as the thickness of the charge transport layer is increased. However, when the thickness of the charge transport layer is increased, the residual potential is increased by repeated use, and further improvement has been desired.

[0008]

As a conventional problem, when charging a photosensitive member, the surface potential does not rise in proportion to the supplied charge amount, and the surface potential rises after a certain fixed charge amount is given. There is a delay in the rise of the so-called charging potential. This is because when the photoreceptor is repeatedly used,
Especially appears. An object of the present invention is to prevent the delay of rising of the charging potential. Furthermore, in the system using the intermediate layer using the white inorganic pigment and the asymmetric bisazo pigment,
It is an object of the present invention to provide a well-balanced electrophotographic photosensitive member having a high sensitivity, a low residual potential, and a delay in rising of a charging potential, which has never been achieved.

[0009]

The present invention relates to a laminated electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, and any one of the following general formulas (Formula 1) It is characterized by containing naphthoquinone or a naphthoquinone derivative represented by (Chemical Formula 2) or (Chemical Formula 3).

Further, the present invention is an electrophotographic photosensitive member having an intermediate layer, a charge generating layer and a charge transport layer in this order on a conductive substrate, wherein the intermediate layer contains a white metal compound and the charge generating layer is Containing a charge generating substance represented by the general formula (Formula 4), and in any of the layers, the following general formula (Formula 1),
It is characterized by containing naphthoquinone or a naphthoquinone derivative represented by (Chemical Formula 2) or (Chemical Formula 3).

[0011]

[Chemical 1]

[Chemical 2]

[Chemical 3]

[Chemical 4]

In the general formulas (Formula 1), (Formula 2) and (Formula 3), R ^{1 to} R ⁶ are hydrogen atoms, alkyl groups, cycloalkyl groups, aryl groups, aralkyl groups, nitro groups and hydroxy groups. Represents a group or a halogen atom. As the alkyl group, a linear or branched alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group. Group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, tert-
Examples thereof include a pentyl group. A cyclohexyl group is mentioned as a cycloalkyl group. Examples of the aryl group include a phenyl group and a tolyl group. Examples of the aralkyl group include a benzyl group and a phenylethyl group. The halogen atom includes chlorine, bromine, iodine,
Examples thereof include fluorine. In the general formula (Formula 4),
A and B represent diazo coupler residues having different structures.
The diazo coupler residue is derived from various conventionally known diazonium salts (ArN ₂ · X, Ar: aromatic group, X: anion). Further, the diazo-type coupler residues A and B have different structures. In this case, the difference in the structure includes the case where the entire structure is different, and also the structure such as a substituent or a double bond. Including cases where the parts are different.

The basic structure of the photoconductor of the present invention comprises a charge generating layer 3 and a charge transport layer 4 on a conductive support 1 as shown in FIG. 1, or a conductive material as shown in FIG. Support 1
It is a laminated type photosensitive layer comprising an intermediate layer 2, a charge generation layer 3 and a charge transfer layer 4 on the top.

Next, each constituent material used in the present invention will be described.

The addition amount of naphthoquinone and naphthoquinone derivative used in the present invention is 0.
It is from 01 to 20% by weight, preferably from 0.05 to 5% by weight.

The conductive substrate has a volume resistance of 10 ¹⁰ Ωc.
Those exhibiting conductivity of m or less, for example, a metal such as aluminum, nickel, chromium, nichrome, copper, silver, gold, platinum, a metal oxide such as tin oxide, indium oxide, or the like in a film shape or a cylindrical shape by vapor deposition or sputtering. Of plastic, paper, etc., the above metal or conductive carbon dispersedly contained in a film-shaped or cylindrical plastic, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc., and D. I. (Drawing idling), I.
I. (Impact idling), extrusion, drawing, etc., after forming a raw tube, a tube that has been surface-treated by cutting, superfinishing, polishing, etc. can be used.

The intermediate layer is made of a white metal compound. As the metal compound, any white compound may be used, and examples thereof include titanium oxide, tin oxide, zinc oxide, indium oxide, which are conventionally used as white pigments.
Examples thereof include metal oxides and metal sulfides such as magnesium oxide, barium oxide, zinc sulfide, and lithopone, and metal fluorides such as titanium fluoride. The average particle size of the metal compound is 0.1 to 1 μm, preferably 0.3 to 0.6 μm. These white metal compounds are coated on a conductive support together with a binder resin and used as an intermediate layer. As the binder resin, polyamide, vinyl chloride-vinyl acetate copolymer, casein, polyvinyl alcohol, polyvinyl acetal, polyvinyl benzene, polyacrylic anilide, polyacrylate, polyhydroxymethacrylate, epoxy resin, alkyd resin, melamine resin, silicone Resin, phenol resin, urethane resin and the like can be mentioned. These may be used alone or in combination. The thickness of the intermediate layer is preferably 0.05 to 10 μm, more preferably 0.2 to 5 μm.

Specific examples of the charge generating substance (asymmetric bisazo pigment) represented by the above general formula (Formula 4) used as the charge generating substance of the present invention include the following.

[0019]

[Table 1] [In the above formula, R ₁ and R ₂ of (1) -a to c are H, Cl, and B.
r, OCH ₃ , CH ₃ , CF ₃ or NO ₂ is shown. ; However, R ₁ and R ₂ may have different kinds of substituents or only different positions of substitution]

[0020]

[Table 2] [In the above formula, R ₃ of (1) -d to i is H, Cl, CH ₃
Or indicates NO ₂ ]

These charge generating substances may be used alone or in combination of two or more. The binder resin used for applying the charge generating substance is appropriately used in an amount of 0 to 100 parts by weight based on 100 parts by weight of the charge generating substance,
It is preferably 0 to 50 parts by weight.

The charge generating layer is a layer containing a charge generating substance as a main material, and the charge generating substance is used together with a binder resin if necessary, using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane or the like, a ball mill, an attritor, a sand mill or the like. It can be formed by dispersing the dispersion liquid by, and diluting the dispersion liquid appropriately and applying. The application is
It can be performed using a dip coating method, a spray coating method, a bead coating method, or the like. The thickness of the charge generation layer is 0.01
About 5 μm is suitable, and preferably 0.1 to 2 μm
Is.

The charge transport layer comprises a charge transport material and a binder resin used as necessary. The charge transport layer can be formed by dissolving or dispersing the above substances in a suitable solvent and applying and drying the substances.

The charge transport material includes a hole transport material and an electron transport material. Examples of the hole transport material include poly-N-vinylcarbazole and its derivative, poly-γ-carbazolylethylglutamate and its derivative, pyrene-
Formaldehyde condensate and its derivative, polyvinylpyrene, polyvinylphenanthrene, oxazole derivative, oxadiazole derivative, imidazole derivative, triphenylamine derivative, 9- (p-diethylaminostyryl) anthracene, 1,1-bis- (4-dibenzyl) Aminophenyl) propane, styrylanthracene,
Examples thereof include electron-donating substances such as styrylpyrazoline, phenylhydrazones, and α-phenylstilbene derivatives. Examples of the electron transport material include chloranil, bromanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2, 4,5,7-Tetranitroxanthone, 2,
4,8-Trinitrothioxanthone, 2,6,8-trinitro-4H-indeno {1,2-b} thiophene-4
Electron-accepting substances such as -one and 1,3,7-trinitrodibenzothiophenone-5,5-dioxide. These charge transport materials may be used alone or in combination of two or more.

Further, in the present invention, as the binder resin used for coating the charge generating substance and the like as required, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer are used. Polymer, 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 Examples thereof include thermoplastic or thermosetting resins such as poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, and alkyd resin.

As the solvent, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride or the like is used.

A suitable thickness of the charge transport layer is about 5 to 100 μm. Further, in the present invention, a plasticizer or a leveling agent may be added to the charge transport layer. As a plasticizer,
What is used as a plasticizer for general resins such as dibutyl phthalate and dioctyl phthalate can be used as it is, and the amount thereof is 0 to 30 relative to the binder resin.
About wt% is appropriate. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil are used, and the amount thereof is suitable to be about 0 to 1% by weight based on the binder resin.

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples. All parts and% shown below are based on weight.

Example 1 The following intermediate layer coating liquid was applied onto an aluminum drum (80φ) by a dipping method, and dried by heating at 120 ° C. for 10 minutes to give a film thickness of 0.
An undercoat layer of 5 μm was provided. [Coating liquid for undercoat layer] Alcohol-soluble polyamide resin (Amilan CM-8000, manufactured by Toray Industries, Inc.) 8 parts Methanol 60 parts Butanol 32 parts Next, the following charge generation layer coating liquid was applied on the undercoat layer. Coating by immersing method, heat-drying at 130 ℃ for 20 minutes and film thickness 0.2
A charge generation layer of μm was provided. [Coating Liquid for Charge Generation Layer] 20 parts of charge generation substance (bisazo pigment) represented by the following (Chemical Formula 5) 2,000 parts of cyclohexanone (20 parts of the bisazo pigment and 400 parts of cyclohexanone are kneaded and dispersed in a ball mill for 48 hours, Further, 600 parts of cyclohexanone was added, and the mixture was kneaded and dispersed for 2 hours, and 1000 parts of cyclohexanone was added dropwise to this dispersion)

[Chemical 5] Further, the following charge transport layer coating solution was applied onto the charge generation layer by a dipping method and dried by heating at 130 ° C. for 15 minutes to give a film thickness of 25.
A μm charge transfer layer was formed to obtain an electrophotographic photoreceptor. [Coating Liquid for Charge Transport Layer] Charge transport material represented by the following (Chemical Formula 6) 9 parts Polycarbonate Z resin (manufactured by Teijin Chemicals Ltd .: viscosity average molecular weight 50,000) 10 parts 1,2-naphthoquinone 0.01 Part Silicon oil (KF-50, manufactured by Shin-Etsu Silicone Co., Ltd.) 0.002 part MDC (methylene chloride) 110 parts

[Chemical 6]

Example 2 The 1,2-naphthoquinone of Example 1 was converted into 2-methyl-1,4
— An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that naphthoquinone was used instead.

Example 3 An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge generating material of Example 1 was replaced with the charge generating material represented by the following (Chemical formula 7).

[Chemical 7]

Example 4 An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge transporting material of Example 1 was replaced with the charge transporting material represented by the following (Chemical formula 8).

[Chemical 8]

Comparative Example 1 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that 1,2-naphthoquinone was not added.

Example 5 TiO ₂ (TM-1, manufactured by Fuji Titanium Industry) 1500 g Acrylic resin (Acryde Ink A-460-60, manufactured by Dainippon Ink and Chemicals, Inc., solid content concentration 60% by weight) 300 g Melamine resin (super) Beckamine L-121-60, manufactured by Dainippon Ink and Chemicals, Inc., solid content concentration 60% by weight) 167 g MEK (methyl ethyl ketone) 750 g The above materials were placed in a hard glass pot of 15 cmφ with 1 c.
It was charged together with mφ alumina sintered balls and milled for 24 hours. A liquid consisting of 1,2-naphthoquinone 20 g MEK 563 g IPA (isopropyl alcohol) 438 g was added to this liquid, and the mixture was milled for another 3 hours. The liquid taken out had a solid content concentration of 50% by weight and a solvent ratio (weight ratio) ME.
It diluted so that it might become K / IPA = 75/25, and produced the intermediate layer coating liquid.

Next, in a 15 cm pot, 50 g of a charge generating substance (bisazo pigment) represented by the following (Chemical Formula 9) and 380 g of MEK were charged, milled with a YTZ ball for 7 days, and further 600 g of cyclohexanone.

[0036]

[Chemical 9]

The mixture was added and milled for 1 hour, and the liquid was taken out and diluted with a liquid consisting of polyvinyl butyral (XYHL, Union Carbide Plastics Co., Ltd.) MEK Anon to obtain a solid content of 1.7% by weight and a pigment / resin. Weight ratio = 10/1, MEK / Anone weight ratio = 3 /
7 was used as the charge generation layer coating liquid.

Charge transport material represented by the above (Chemical formula 6) 266 g Polycarbonate Z resin (manufactured by Teijin Chemicals Ltd .: viscosity average molecular weight 50,000) 380 g Silicon oil (KF-50, manufactured by Shin-Etsu Silicone Co., Ltd.) A liquid containing 08 g MDC 4000 g was prepared and used as a charge transport layer coating liquid.

An aluminum drum having a wall thickness of 1 mm and a length of 340 mm was dipped and coated with the prepared intermediate layer coating solution, and the temperature was set to 130 ° C. 2
It was heated and dried for 0 minutes to provide an intermediate layer having a film thickness of 3 μm.

Further, a charge generation layer coating solution was applied by dip coating on this and heated and dried at 110 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.2 μm.

Further, a charge transport layer coating solution was applied by dip coating on this, and dried by heating at 130 ° C. for 15 minutes to form a charge transport layer having a film thickness of 25 μm.

Examples 6 to 9 Photoreceptors were prepared in the same manner as in Example 5 except that the white pigment and the additives in the intermediate layer and the charge generating substance in the charge generating layer were changed as shown in Table 3 below.

[0043]

[Table 3]

Comparative Example 2 An electrophotographic photosensitive member was prepared in the same manner as in Example 5 except that 1,2-naphthoquinone was not added.

The photoconductor thus obtained was mounted on a copying machine FT4820 manufactured by Ricoh, and the surface potential V after charging was set.
_O (V), surface potential V _L (V) after exposure, surface potential V after static elimination
_R (V) was measured. The lamp voltage was adjusted so that V _L was 100 v. Further, after the image was printed on 10,000 sheets, the same measurement was performed. Table 4 below shows the evaluation results of the above photoreceptors.

[0046]

[Table 4]

[0047]

As described above, it is understood that the photoconductor of the present invention has excellent photosensitivity, and in particular, there is little deterioration in chargeability after many uses and the residual potential is also small.

[Brief description of drawings]

FIG. 1 is a schematic view of a cross section for explaining an example of a layer structure of a photoconductor of the present invention.

FIG. 2 is a schematic cross-sectional view for explaining another example of the layer structure of the photoconductor of the present invention.

[Explanation of symbols]

 1 Conductive Support 2 Intermediate Layer 3 Charge Generation Layer 4 Charge Transport Layer

Claims (2)

[Claims] 1. A laminated electrophotographic photosensitive member having at least a charge generation layer and a charge transport layer on a conductive support, wherein any one of the following general formulas (Formula 1), (Formula 2) or (Formula 3) ) A naphthoquinone or a naphthoquinone derivative represented by [Chemical 1] [Chemical 2] [Chemical 3] [In the general formulas shown in (Chemical Formula 1), (Chemical Formula 2) and (Chemical Formula 3), R ^{1 to} R ⁶ are a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a nitro group, Represents a hydroxy group or a halogen atom] 2. An intermediate layer, a charge generation layer, and
In an electrophotographic photosensitive member having a charge transport layer in sequence, the intermediate layer contains a white metal compound, the charge generation layer contains a charge generation substance represented by the following general formula (Formula 4), and any one of the layers An electrophotographic photoconductor comprising: a naphthoquinone or a naphthoquinone derivative represented by the following general formula (Chemical Formula 1), (Chemical Formula 2) or (Chemical Formula 3). [Chemical 1] [Chemical 2] [Chemical 3] [In the general formulas shown in (Chemical Formula 1), (Chemical Formula 2) and (Chemical Formula 3), R ^{1 to} R ⁶ represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a nitro group, Represents a hydroxy group or a halogen atom] (In the above formula, A and B represent coupler residues having different structures)