JP2749859B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member excellent in sensitivity and potential stability.

[Conventional technology]

Conventionally, as an electrophotographic photoreceptor, those having a photosensitive layer mainly composed of an inorganic compound such as selenium, zinc oxide, and cadmium sulfide have been widely used. However, these inorganic photoreceptors have thermal stability, moisture resistance, and the like. It is not always satisfactory in terms of harmfulness.

On the other hand, electrophotographic photoreceptors having a photosensitive layer containing an organic compound as a main component have many advantages, such as film-forming properties, pollution-free properties, and easy production, as compared with inorganic ones. .
In particular, a layer containing a substance that generates charges by irradiating light (charge generation layer) and a layer containing a substance that transports charges (charge transfer layer)
Some of the laminated photoreceptors, which have higher sensitivity and more stable charging ability than conventional photoreceptors, have been put to practical use.

For example, JP-A-59-33445 and JP-A-60-111249 are known as photoreceptors using an azo pigment as a charge generating substance. However, photoreceptors using these azo pigments as charge generating substances are not always satisfactory in sensitivity, residual potential or stability upon repeated use, and the selection range of charge transporting substances is limited. It does not fully satisfy the broad requirements of the photographic process.

[Problems to be solved by the invention]

An object of the present invention is to provide an electrophotographic photosensitive member having high sensitivity and high durability.

[Means for solving the problem]

That is, the present invention provides an electrophotographic photoreceptor having a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer has a structure represented by the following general formula (1) or (2). An electrophotographic photoreceptor characterized by being dispersed and contained as a charge generating substance.

In the formula, A ₁ and A ₃ represent a group having an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, and A ₂
Represents a hydrogen atom.

Examples of the group having an aromatic hydrocarbon ring include an aromatic monocyclic group such as benzene, naphthalene, anthracene, phenanthrene, pyrene, azulene, indene and fluorene, an aromatic condensed polycyclic group, and a monocyclic or condensed polycyclic group thereof. A ring assembly in which two or more of the ring systems are directly bonded by a double bond or the like,
Aromatic ketone groups such as benzophene, fluorenone, benzuanthrone, indanone, and suberenone, and their sulfur derivatives (eg, thiobenzophenone), dicyanomethylene derivative, benzoquinone, naphthoquinone, anthraquinone, phenanthrenequinone, and pyrenequinone. Group quinone groups and their sulfur derivative groups, dicyanomethylene derivative groups, and the like. Examples of the group having an aromatic heterocyclic group include furan, thiophene, pyrrole, oxazole, thiazole, imidazole, pyrazole, pyridine, pyrazine, piperazine, benzofuran, benzothiophene, indole, benzoxazole, benzothiazole, dibenzofuran, dibenzothiophene, and carbazole. , Phenazine, phenoxazine, phenothiazine, thianthrene, acridone, and other heterocyclic groups condensed with a benzene ring or an aromatic condensed polycyclic ring, and two or more of these monocyclic and condensed polycyclic rings A ring assembly group in which the ring system is directly bonded by a double bond or the like can be mentioned.

Examples of the substituents having an aromatic hydrocarbon ring group and an aromatic heterocyclic group that may be possessed include halogen groups such as fluorine, chlorine, bromine and iodine, and alkyl groups such as methyl, ethyl, propyl and butyl. And methoxy, ethoxy, phenoxy and other alkoxy groups, nitro groups, cyano groups, substituted amino groups such as dimethylamino, diethylamino, diphenylamino, dibenzylamino, morpholino, piperidino and pyrrolidino.

N represents an integer of 1, 2 or 3. Further, in the present invention, in the general formulas (1) and (2), when A ₁ is an electron donating part, A ₃ is an electron accepting part, and when A ₁ is an electron accepting part, A ₃ is A _3. Is an electron donating part. Especially,
Good characteristics are provided when an electron donating part is present on the N side of the> C = N-bond and an electron accepting part is present on the C side.

Examples of the electron-donating moiety include electron-donating aromatic monocyclic groups such as benzene, naphthalene, anthracene, phenanthrene, indene, and fluorene having an electron-donating substituent and pyrene which may have an electron-donating substituent. Or an electron-donating aromatic condensed polycyclic group, an electron-donating aromatic amine group such as triphenylamine, diphenylamine, or diphenylmethylamine which may have an electron-donating substituent, or an electron-donating substituent. Furan, thiophene, pyrrole, oxazole, thiazole, imidazole, pyridine, pyrazine, acridine, phenazine, benzofuran, benzothiophene, dibenzofuran, dibenzothiophene, benzoxazole, benzothiazole, thianthrene, phenoxazine, phenothiazine and electron donating substituents Has Electron-donating heterocyclic monocyclic groups such as indole, carbazole, iminodibenzyl, tetrathiafulvalene and dibenzotetrathiafulvalene, or electron-donating condensed heterocyclic groups condensed with a benzene ring or an aromatic condensed polycyclic ring 2 of monocyclic and condensed rings
And an electron-donating ring assembly in which two or more ring systems are directly bonded by a double bond or the like.

Examples of the electron donating substituent include an alkyl group such as methyl, ethyl, propyl, and butyl, an aryl group such as phenyl and naphthyl, an aralkyl group such as benzyl and phenethyl, an alkoxy group such as methoxy and ethoxy, dimethylamino and diphenylamino. , Morpholino and the like.

On the other hand, examples of the electron-accepting part include an electron-accepting aromatic monocyclic group or an electron-accepting condensed aromatic polycyclic group such as benzene, naphthalene, anthracene, phenanthrene, indene, and fluorene having an electron-accepting substituent; Electron-accepting aromatic ketone groups such as benzophenone, fluorenone, and benzuanthrone which may have an electron-accepting substituent, and their didiamethylene derivative groups, electron-accepting aromatic thioketone groups, benzoquinone, naphthoquinone,
An electron-accepting aromatic quinone group such as anthraquinone and pyrenequinone and their dicyanomethylene derivative groups, furan, thiophene, pyrrole, oxazole, thiazole, imidazole, pyridine, pyrazine, acridine, phenazine, benzofuran, benzothiophene having an electron-accepting substituent , Dibenzofuran, dibenzothiophene, benzoxazole, benzothiazole, thianthrene, phenoxazine, phenothiazine, etc .; an electron-accepting condensed heterocyclic group condensed with a benzene ring or an aromatic condensed polycyclic ring; An electron-accepting ring assembly in which two or more of these single rings or fused rings are directly bonded by a double bond or the like.

Examples of the electron-accepting substituent include a halogen group such as fluorine, chlorine, bromine and iodine, a nitro group and a cyano group.

A ₂ is a hydrogen atom.

In order to increase the spectral sensitivity of the electrophotographic photoreceptor, it is necessary to increase the absorption spectrum of the charge generating material, such as by extending the π-electron conjugate system and increasing the intermolecular interaction. It has been known. As for the substituent effect of substituted azobenzene compounds, it has been reported that the absorption spectrum becomes longer as the electron donating property of the substituent increases and as the electron accepting property increases. It is believed to be due to intramolecular charge transfer interactions via the azo group (-N = N-) which is a chain [Color and Construction of Organisms, Academic by J. Griffiths]. Press London, 1976], and a combination of a large electron donating substance and a large electron accepting substance is expected to significantly increase the wavelength.

On the other hand, in the electrophotographic photoreceptor, it is necessary to increase the charge carrier generation efficiency in order to improve the sensitivity, and one of the factors controlling the charge carrier generation efficiency is the carrier dissociation efficiency. Phthalocyanine compounds have been reported to have a large effect on the carrier dissociation efficiency due to the local electric field created by ion-adsorbed gas and the like [for example, Journal of the Electrophotographic Society, 1987, 20, 216
It is thought that the local electric field based on the charge transfer interaction between the electron donating substance and the electron accepting substance also promotes the generation of the charge carrier.

In view of the above, the photoconductive compound of the present invention particularly shows that the electron-donating part and the electron-accepting part interact through> C = N-bond, and furthermore, in a crystalline state, the electron-donating part and the electron-accepting part intermolecularly. Good properties when the active part has a charge transfer interaction.

Representative examples of the compounds represented by formulas (1) and (2) are shown below.

The compounds represented by the general formulas (1) and (2) are easily synthesized by a dehydration condensation reaction of the corresponding aromatic amine and aromatic aldehyde in the presence of an acid or base catalyst as shown in the following reaction formula. I can do it.

The electrophotographic photoreceptor of the present invention has a photosensitive layer containing a compound represented by the general formula (1) or (2) on a conductive support.

The photosensitive layer may take any form, but the photosensitive layer containing the compound represented by the general formula (1) or (2) is used as a charge generation layer, and the charge transport layer contains a charge transport material. A function-separated type photosensitive layer in which layers are laminated is particularly preferred.

The charge generation layer can be formed by applying a coating solution obtained by dispersing the above compound together with a binder resin in an appropriate solvent onto a conductive support by a known method, and has a thickness of, for example, 5 μm. Or less, preferably 0.01
It is desirable to form a thin film layer of μm to 1 μm.

The binder resin used at this time is selected from a wide range of insulating resins or organic photoconductive polymers, but polyvinyl butyral, polyvinyl benzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulose resin, acrylic resin, urethane resin And the like, and the amount used is 80 in terms of the content in the charge generation layer.
% By weight, preferably 40% by weight or less.

The solvent used is preferably selected from those that dissolve the resin and do not dissolve the charge transport layer and the undercoat layer described below. Specifically, tetrahydrofuran, 1,4-
Ethers such as dioxane; ketones such as cyclohexanone and methyl ethyl ketone; amides such as N, N-dimethylformamide; esters such as methyl acetate and ethyl acetate; aromatics such as toluene, xylene and monochlorobenzene; methanol and ethanol And alcohols such as 2-propanol; and aliphatic halogenated hydrocarbons such as chloroform and methylene chloride.

The charge transport layer is stacked on or below the charge generation layer, and has a function of receiving a charge carrier from the charge generation layer in the presence of an electric field and transporting the charge carrier to the surface. The charge transporting layer is formed by dissolving a charge transporting material in a solvent together with a suitable binder resin as required and applying the solution. The film thickness is generally 5 μm to 40 μm, particularly 15 μm to 30 μm
Is preferred.

The charge transport material includes an electron transport material and a hole transport material,
Examples of the electron transporting material include electron-withdrawing substances such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil, and tetracyanoquinodimethane, and these electron-withdrawing substances. Molecularized ones are exemplified.

Examples of the hole transporting substance include polycyclic aromatic compounds such as pyrene and anthracene; heterocyclic compounds such as carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, pyrazoline, thiadiazole, and triazole; p-diethylaminobenzaldehyde- Hydrazone-based compounds such as N, N-diphenylhydrazone, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole; α-phenyl-4′-N,
N-diphenylaminostilbene, 5- [4- (di-p
-Tolylamino) benzylidene] -5H-dibenzo [a,
d] styryl-based compounds such as cycloheptene; benzidine-based compounds; triarylmethane-based compounds; triphenylamine or polymers having a tombstone composed of these compounds in the main chain or side chain (for example, poly-N-vinylcarbazole, polyvinylanthracene) Etc.).

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, and amorphous silicon can also be used.

These charge transport materials can be used alone or in combination of two or more.

When the charge transport material does not have a film-forming property, an appropriate binder resin can be used, and specifically, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-sterene copolymer, polysulfone, polyacrylamide And insulating resins such as polyamide and chlorinated rubber, and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene.

As the conductive support, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, titanium, or the like can be used. In addition, plastics formed by coating these metals by a vacuum deposition method, and conductive particles (for example,
Carbon black, silver particles, etc.) with a suitable binder on a plastic or metal support,
Alternatively, plastic particles or paper impregnated with conductive particles can be used.

An undercoat layer having a barrier function and an adhesive function can be provided between the conductive support and the photosensitive layer. The thickness of the undercoat layer is suitably 5 μm or less, preferably 0.1 μm to 3 μm. The undercoat layer is casein, polyvinyl alcohol,
Nitrocellulose, polyamide (nylon 6, nylon
66, nylon 610, copolymerized nylon, N-alkoxymethylated nylon, etc.), polyurethane, aluminum oxide and the like.

The crystal form of the compound represented by the general formula (1) or (2) used in any of the electrophotographic photoreceptors may be crystalline or amorphous. It is also possible to use a combination of two or more of the compounds represented by (1) or (2) at the same time, or to use them in combination with a known charge generating substance.

The electrophotographic photoreceptor of the present invention can be widely used not only for electrophotographic copying machines but also for electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

Examples 1 to 38 A solution prepared by dissolving 5 g of methoxymethylated nylon resin (number average molecular weight 32,000) and 10 g of alcohol-soluble copolymerized nylon resin (number average molecular weight 29000) in 95 g of methanol was applied to an aluminum substrate with a Meyer bar, and dried. Later film thickness is 1 μm
Was provided.

Next, the compound No.
A solution prepared by dissolving 2 g of butyral resin (butyralization degree: 63 mol%) in 95 g was dispersed in a sand mill for 20 hours. The thickness of this dispersion after drying on the undercoat layer formed earlier is 0.
The resultant was coated with a Meyer bar to a thickness of 2 μm to form a charge generation layer.

Then, the following structural formula 5 g of a hydrazone compound and 5 g of a polymethyl methacrylate resin (number-average molecular weight 100,000) are dissolved in 40 g of monochlorobenzene, and this is coated on a charge generation layer with a Meyer bar and dried to form a 20 μm charge transport layer. A photoconductor of Example 1 was prepared.

Photoreceptors corresponding to Examples 2 to 47 were prepared in the same manner by using other exemplified compounds in place of compound No. A-1.

The electrophotographic photoreceptor thus prepared was negatively charged with a corona discharge of -5 KV using an electrostatic copying paper tester (Model SP-428) manufactured by Kawaguchi Electric Co., Ltd., left in a dark place for 1 second, and then halogenated. It was exposed to light having an illuminance of 10 lux using a lamp, and the charging characteristics were evaluated. As the charging characteristics, the surface potential V ₀ and the exposure amount E1 / 2 required for the surface potential after being left in a dark place to attenuate to half were measured. The results are shown in Tables 1 and 2.

Examples 39 to 43 Using the apparatus shown in Example 1, the electrophotographic photoreceptors prepared in Examples 4, 9, 14, 32 and 37 were charged to -700 V, and the potential of the electrophotographic photoreceptors was reduced to half. Exposure required for (E1 /
2: μJ / cm ² ) was measured. As a light source, an aluminum / gallium / arsenic semiconductor laser (oscillation wavelength: 780 nm) was used. Table 3 shows the results.

These results show that the electrophotographic photoreceptor of the present invention has sufficient sensitivity even in the oscillation wavelength range of the semiconductor laser.

Examples 44 to 46 An electrophotographic copying machine equipped with a -6.5 KV corona charger, an exposure optical system, a developing device, a transfer charger, a charge-removal exposure optical system, and a cleaner of the electrophotographic photosensitive member prepared in Example 3 was used. Pasted on the cylinder.

Initial dark potential V _D and the light portion potential V _L respectively -700 V, -2
The potential at the dark portion and the potential at the bright portion were measured when the voltage was set at around 00 V and the device was used 5,000 times repeatedly.

The photoreceptors prepared in Examples 19 and 37 were similarly evaluated. The results are shown in Table 4.

Example 47 An undercoat layer of polyvinyl alcohol having a thickness of 0.5 μm was formed on an aluminum surface of an aluminum-deposited polyethylene terephthalate film. A dispersion of the compound used in Example 3 was applied thereon with a Meyer bar and dried to form a 0.2 μm-thick charge generation layer.

Then, the following structural formula 5 g of styryl compound and 5 g of polycarbonate resin (number average molecular weight 55000) dissolved in 40 g of tetrahydrofuran are coated on the charge generating layer and dried to form a film having a thickness of 20 μm.
m of the charge transport layer was formed. The charging characteristics and durability characteristics of the photoreceptors thus prepared were measured by the same methods as in Examples 1 and 44. The results are shown below.

It should be noted that a negative sign in the fluctuation amount (ΔV) of the potential indicates a decrease in the absolute value of the potential, and a positive sign indicates an increase.

V ₀ : 705 (−V) E1 / 2: 2.1 (lux · sec) ΔV _D : 10 (V) ΔV _L : 10 (V) Example 48 The charge generation layer and the charge transport of the photoreceptor prepared in Example 47 A photoreceptor having the layers applied in reverse order was prepared, and the charging characteristics were evaluated in the same manner as in Example 1. However, the charging was positive.

V ₀ : 690 (+ V) E1 / 2: 3.5 (lux · sec) Example 49 On the charge generation layer prepared in Example 47, 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-4,4 '-Dioxydiphenyl-2,2'-propane carbonate (molecular weight 30,000
0) A solution in which 5 g was dissolved in 50 g of tetrahydrofuran was applied by a Meyer bar and dried to form a charge transport layer having a thickness of 18 μm.

The electrophotographic photosensitive member thus produced was evaluated for charging characteristics in the same manner as in Example 1. However, the charging was positive.

V ₀ : 680 (+ V) E1 / 2: 3.9 (lux · sec) [Effect of the Invention] As described above, the electrophotographic photoreceptor of the present invention has an increased intramolecular and intermolecular interaction, and has sensitivity and repetition. Characteristics with excellent potential stability during use are obtained.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Moto Miyazaki, Inventor 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Hideyuki Takai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Masakazu Matsumoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-63-292139 (JP, A) JP-A-63-292140 (JP) , A) JP-A-61-279861 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor having a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer comprises a compound having a structure represented by the following general formula (1) or (2). An electrophotographic photoreceptor characterized by being dispersedly contained as a generating substance. (Wherein, A ₁ and A ₃ represents a group having an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, A ₁
Is an electron donating moiety, A ₃ is an electron accepting moiety,
When A ₁ is an electron accepting part, A ₃ is an electron donating part, A ₂ represents a hydrogen atom, and n represents an integer of 1, 2 or 3. )