JPH0547103B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor having a photosensitive layer with improved characteristics by containing a specific disazo pigment and a polycarbonate Z resin. [Prior Art] Conventional electrophotographic photoreceptors include those using inorganic photoconductive materials such as selenium, cadmium sulfide, zinc oxide, and amorphous silicon, and those using photoconductive materials such as poly-N-vinylcarbazole and polyvinylanthracene. polymer, or diethylaminobenzaldehyde
Those using various low-molecular organic photoconductive substances such as N,N-diphenylhydrazone and those in which organic pigments are dispersed are known. Among these, organic pigments used in electrophotographic photoreceptors include azo pigments such as Sudan Red and Diane Blue, disazo pigments, quinone pigments such as Algol Yellow and pyrene quinone, quinocyanine pigments, perylene pigments, and indigo pigments such as indigo and thioindigo. , bisbenziimidazole pigments such as India first ore toner, phthalocyan pigments such as copper phthalocyanine, and quinacridone pigments. Although some photoreceptors having these pigments dispersed therein have been put to practical use, they are not fully satisfactory in terms of sensitivity. This is because pigments require a binder to form a film, and this binder inhibits the movement of charges. Therefore, when using pigments, it is essential to use a binder that is optimal for the pigments. On the other hand, in the case of a functionally separated photosensitive layer in which the photosensitive layer is divided into a charge generation layer that generates charges by light and a charge transport layer that transports the charges, a pigment is used in the charge generation layer. In this case, not only the binder of the charge generation layer but also the binder of the charge transport layer becomes a factor in determining the sensitivity. In other words, the key to high sensitivity is to efficiently inject the charges generated in the charge generation layer into the charge transport layer, but if the combination of the pigment in the charge generation layer and the binder in the charge transport layer is poor, the interface between the two layers This creates an injection barrier and reduces injection efficiency. Therefore, even in the functionally separated photosensitive layer, it is essential to select a binder for the charge transport layer that is optimal for the pigment. [Problems to be Solved by the Invention] In view of the above-mentioned conventional techniques, the present invention aims to create an electrophotographic photoreceptor with higher sensitivity by combining a pigment contained in a photosensitive layer and a binder resin. The purpose is to provide. Still another object is to provide an electrophotographic photoreceptor with excellent production stability. [Means and effects for solving the problems] The present invention uses at least one disazo pigment represented by the general formula (1) below as a pigment, and polycarbonate Z represented by the general formula (2) below as a binder. The above object is achieved by combining the resin with the resin. That is, the present invention relates to an electrophotographic photoreceptor having a photosensitive layer containing at least one disazo pigment represented by the following general formula (1) and a polycarbonate Z resin represented by the following general formula (2). configured. general formula In the formula, A represents a coupler residue having a phenolic OH group. general formula In the formula, n represents the average degree of polymerization and is in the range of 50 to 5000. According to the present invention, the disazo pigment represented by the general formula (1) has higher sensitivity and less deterioration due to light irradiation than other organic pigments, and is highly durable. Furthermore, polycarbonate Z represented by general formula (2)
By combining it with a resin, a highly durable photosensitive layer with high sensitivity and little mechanical surface deterioration is formed. The coupler residue having a phenolic OH group represented by A in the above general formula (1) can be obtained from groups represented by the following general formulas (3) to (9). general formula In the formula, Residues necessary for formation are shown, and among them, naphthalene ring, anthracene ring, benzcarbazole ring, and carbazole ring are more preferable. R ₁ and R ₂ are a hydrogen atom, a group selected from an alkyl group that may have a substituent, an aralkyl group, an aryl group, and a heterocyclic group, or
Indicates a cyclic amino group formed with the nitrogen atom to which R ₁ and R ₂ are bonded. Specific examples of alkyl groups include methyl, ethyl, propyl, and butyl, and specific examples of aralkyl groups include benzyl, phenethyl, and naphthylmethyl. Examples of the aryl group include phenyl, diphenyl, naphthyl, and anthryl, and examples of the heterocyclic group include carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. Examples of the substituents that the alkyl group, aralkyl group, aryl group, and heterocyclic group may have include alkyl groups such as methyl, ethyl, and propyl;
Examples include alkoxy groups such as methoxy, ethoxy, and propoxy; halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; and substituted amino groups such as nitro group, cyano group, dimethylamino, dibenzylamino, and diphenylamino. . general formula general formula R ₃ and R ₄ in the general formulas (4) and (5) represent a group selected from an alkyl group, an aralkyl group, and an aryl group that may have a substituent. As a specific example of R ₃ and R ₄ above, the general formula
The same examples as R ₁ and R ₂ in (3) and (4) are given. general formula general formula Y in the general formulas (6) and (7) represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group containing a nitrogen atom in the ring. The divalent group of the aromatic hydrocarbon mentioned above is 0-
Divalent groups of monocyclic aromatic hydrocarbons such as phenylene, 0-naphthylene, perinaphthylene, 1,2-
Examples of divalent groups of polycyclic aromatic hydrocarbons such as anthrylene and 9,10-phenanthrylene include heterocyclic divalent groups containing a nitrogen atom in the ring.
For example, 3,4-pyrazolediyl, 2,3-pyridinediyl, 4,5-pyrimidinediyl, 6,7
-imidazolediyl, 5,6-benzimidazolediyl, 6,7-quinolinediyl, and other 5- or 6-membered heterocyclic groups that are divalent. general formula In the formula, R ₅ and R ₆ are a hydrogen atom, a group selected from an aryl group which may have a substituent, and a heterocyclic group, or 5 together with the carbon atom to which R ₅ and R ₆ are bonded.
Residues forming a member or a 6-membered ring, and this 5-membered
The membered or six-membered ring may have a fused aromatic ring, and Z is a naphthalene ring fused with a benzene ring, an anthracene ring, a carbazole ring, a benzcarbazole ring, a dibenzofuran ring, a benzonaphthofuran ring, and a diphenylene ring. Indicates the residues necessary to form a polycyclic aromatic ring selected from the phaide ring or a heterocycle. Specific examples of the alkyl group mentioned above include methyl, ethyl, propyl, butyl, etc. Specific examples of the aralkyl group include benzyl, phenethyl, naphthylmethyl, etc. Specific examples of the aryl group include phenyl, naphthyl, anthryl, and pyrenyl. Specific examples of groups such as heterocyclic groups include pyridyl, thienyl,
Examples include groups such as furyl and carbazoyl, and further substituents that the above groups may have include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom, methyl, ethyl, propyl, butyl, etc. Alkyl group, methoxy, ethoxy, proboxy,
Examples include alkoxy groups such as butoxy, nitro groups, cyano groups, and substituted amino groups such as dimethylamino, diethylamino, dipropylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino. Specific examples of residues that form a 5- or 6-membered ring together with the carbon atoms to which R ₅ and R ₆ are bonded, and where this 5- or 6-membered ring may have a fused aromatic ring are: Examples include groups such as cyclopentylidene, cyclohexylidene, and 9-xanthenylidene. general formula In the formula, R ₇ and R ₈ are a hydrogen atom, a group selected from an alkyl group, an aralkyl group, an aryl group, and a heterocyclic group which may have a substituent, or 5 together with the carbon atom to which R ₇ and R ₈ are bonded. This 5- or 6-membered ring may have a fused aromatic ring, and Z is a naphthalene ring, an anthracene ring, a carbazole ring fused with a benzene ring, Indicates a residue necessary to form a polycyclic aromatic ring or a heterocycle selected from a benzcarbazole ring, a dibenzofuran ring, a benzonaphthofuran ring, and a diphenylene sulfide ring. Specific examples of the alkyl group in the above group include methyl,
Examples of groups such as ethyl, propyl, and butyl; specific examples of aralkyl groups include groups such as benzyl, phenethyl, and naphthylmethyl; specific examples of aryl groups include groups such as phenyl, diphenyl, naphthyl, anthryl, and pyrenyl; and heterocyclic groups. Specific examples include groups such as pyridyl, thienyl, furyl, and carbazoyl, and further substituents that the above groups may have include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom, methyl , alkyl groups such as ethyl, propyl, butyl, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, nitro group, cyano group, dimethylamino, diethylamino, dipropylamino, dibenzylamino, diphenylamino, morpholino, piperidino, pyrrolidino, etc. Examples include substituted amino groups. Specific examples of residues that form a 5- or 6-membered ring together with the bonded carbon atoms of R ₇ and R ₈ above, and this 5- or 6-membered ring may have a fused aromatic ring include: Examples include groups such as cyclopentylidene, cyclohexylidene, and 9-xanthenylidene. Specific examples of the disazo pigment represented by the general formula (1) are shown below. In addition to these exemplary pigments, there are many disazo pigments included in general formula (1). The polycarbonate Z resin represented by the general formula (2) has (a) good transparency, (b) high electrical insulation and withstand voltage, and (c) a hard surface with appropriate lubricity. It has characteristics such as being resistant to mechanical wear and (d) excellent stability when dissolved in a solvent. Ordinary polycarbonate resin, i.e. Bisphenol A type polycarbonate resin, which has the structural formula different. By combining the specific disazo pigment of the present invention with polycarbonate Z resin, the extent to which a barrier layer is formed at the interface between the pigment particles and the resin to prevent charge movement during light irradiation is much greater than when combining with other than polycarbonate Z resin. The benzene ring and cyclohexyl group of the polycarbonate Z resin structure facilitate charge transfer and seem to improve sensitivity. The form of the electrophotographic photoreceptor according to the present invention includes (a) a photosensitive layer in which a disazo pigment represented by general formula (1) (hereinafter referred to as "disazo pigment") is dispersed in polycarbonate Z resin; (b) disazo pigment (c) Disazo pigment dispersed in a binder resin (polycarbonate Z resin or other resin may be used) ) is used as a charge generation layer, and a functionally separated photosensitive layer is formed by laminating a charge transport layer containing a polycarbonate Z resin and a charge transport substance thereon; (d) a disazo pigment and a polycarbonate Z resin are placed on the charge transport layer; Examples include a functionally separated photosensitive layer in which a charge generation layer containing the following is laminated. Examples of electron-donating compounds include polycyclic aromatic rings such as anthracene, pyrene, phenanthrene, and coronene in the main chain or side chain, or indole, carbazole,
Oxazole, isoxazole, thiazole,
imidazole, pyrazole, oxadiazole,
Examples include compounds having nitrogen-containing heterocycles such as pyrazoline, thiadiazole, and triazole, hydrazone compounds, and aromatic amino compounds. Examples of electron-accepting compounds include aliphatic cyclic compounds, aromatic compounds, and heterocyclic compounds having electron-accepting substituents such as nitro, nitroso, and cyano groups, such as tetracyanoethylene, trinitrobenzene, Dinitroacetophenone, trinitroanisole, tetranitronaphthalene, terephthalonitrile, isophthalonitrile, benzoyl cyanide, quinoline cyanide, cyanopyridine, nitroanthracene, dinitrofluorenone, trinitrofluorenone, tetranitrofluorenone, tetracyanopyrene etc. Electron-accepting compounds are generally not preferred due to their carcinogenicity and other harmful properties. When an electron donating compound is used, the above-mentioned form (c) is used for negative charging, and the form (d) is used for positive charging. The charge transport layer contains a charge transport material and a resin in a ratio of 5:1 to 5:1.
It is formed by mixing at a ratio of about 1:2 (weight ratio), and the film thickness is about 5 to 20 μm. In addition to polycarbonate Z, polyester,
Polyvinyl benzafure, polyvinyl butyral, polyvinylpyrrolidone, methylcellulose,
Polyacrylic esters, cellulose esters, etc. are used as appropriate. Dispersion can be carried out by a conventional method such as a ball mill, roll mill, sand mill, or colloid mill after the pigment is mixed into the resin solution. The thickness of the charge generation layer is 0.01~1μ, preferably 0.05
~0.5μ. When formed on top of the charge transport layer, it is thicker, on the order of 0.5 to 5 microns, and the pigment to resin ratio is on the order of 5:1 to 1:2. [Effects of the Invention] In the electrophotographic photoreceptor of the present invention, the photosensitive layer containing a specific disazo pigment and polycarbonate Z resin has high sensitivity and low residual potential, and also has low charging and
The bright area potential is stable without increasing after repeated exposure, and the surface is coated with polycarbonate Z.
Due to the presence of resin, the surface has a high surface roughness and has excellent lubricity, making it difficult to get scratches and improving mechanical durability. Furthermore, since the polycarbonate Z resin solution has good storage stability, it can improve productivity and contribute to quality stabilization. [Examples] Examples 1 to 6 An aluminum cylinder with a wall thickness of 0.5 mm and a size of 60φ×260 mm was prepared as a base. Next, copolymerized nylon (product name CM8000, Toray Industries, Inc.)
(manufactured by Dainippon Ink Chemical Co., Ltd.) and 4 parts of Type 8 nylon (trade name Lacucamide 5003, manufactured by Dainippon Ink Chemical Co., Ltd.) were dissolved in 50 parts of methanol and 50 parts of n-butanol, and the solution was dip coated onto the above substrate to a thickness of 0.6μ. A polyamide undercoat layer was formed. Next, 10 parts of a disazo pigment selected from the exemplary disazo pigments of the general formula (1) and 10 parts of polyvinyl butyral (trade name Eslec BM-2, manufactured by Sekisui Chemical Co., Ltd.) were mixed with 120 parts of cyclohexanone in a sand mill. It was dispersed for 10 hours. 30 parts of methyl ethyl ketone was added to the dispersion and coated on the undercoat layer to form a charge generation layer with a thickness of 0.15 μm. Next, polycarbonate Z resin (Mitsubishi Gas Chemical Co., Ltd.)
Prepare 10 parts of a product (manufactured by) with a weight average molecular weight of 120,000,
Along with 10 parts of a hydrazone compound with the following structural formula It was dissolved in 80 parts of monochlorobenzene. This was applied onto the charge generation layer to form a charge transport layer with a thickness of 116μ. Exemplary disazo pigments of the above selection (1), (10), (15),
Electrophotographic photoreceptors of Examples 1 to 6 were prepared corresponding to (27), (30), and (38). The electrophotographic photoreceptor thus produced was -
5.6KV corona charging, image exposure, dry toner development,
Toner transfer to plain paper, urethane rubber blade (altitude 70°, pressure 5Kgw/cm ² , angle to photoconductor)
The electrophotographic properties were evaluated by attaching it to an electrophotographic copying machine that has a cleaning process at 20°). When the potential was measured, the dark potential (V _D ) was -700V.
Potential when exposed to light of 10 lux/second (V _L )
The results are shown in Table 1. Comparative Examples 1 to 4 Electrophotographic photoreceptors were prepared in the same manner as in Example 1, except that the following organic pigments A to D were used in place of the disazo pigment of Example 1 (Comparative examples corresponding to A to D Examples 1 to 4). The measurement results of electrophotographic properties are shown in Table 1. Organic pigment A β-type copper phthalocyanine (Dainippon Ink Chemical Co., Ltd.)
(However, it is a pigment produced by sequential hot filtration with water, ethanol, and methyl ethyl ketone)

[Table] As described above, the electrophotographic photoreceptor of the example had higher sensitivity than the comparative example, and moreover, clear images without fogging were obtained. Example 7 The above exemplary pigment was used instead of the disazo pigment of Example 1.
An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that (4) was used. Comparative Examples 5 to 8 Electrophotographic photoreceptors were prepared in the same manner as in Example 7 except that the following resins were used in place of the polycarbonate Z resin used in forming the charge transport layer in Example 7. Comparative example 5: Acrylic resin (product name BR-80, Mitsubishi Rayon
Comparative Example 6: Polystyrene (product name Styron-470, manufactured by Asahi Kasei Co., Ltd.) Comparative Example 7: Phenoxy resin (product name YP40, manufactured by Toto Kasei Co., Ltd.) Comparative Example 8: Polyester (product name Vylon) -300, manufactured by Toyobo Co., Ltd.) An electrophotographic copying machine having the same process as in Example 1 using these electrophotographic photoreceptors (however,
The evaluation was performed using the exposure amount (7.2 lux·sec).
The evaluation is initial V _D , V _L and V _D after 10,000 sheets durability,
V _L A further comparison was made by looking at the 10,000th image. The results are shown in Table 2.

[Table] From Kaburi
As described above, in terms of durability after 10,000 cycles, the examples of the present invention using polycarbonate Z resin in particular proved to be excellent in terms of sensitivity, potential stability, and image quality. Comparative Example 9 Polycarbonate A resin (trade name Vanlite L-1250, Teijin Kasei Co., Ltd.) was used instead of polycarbonate Z resin used in forming the charge transport layer in Example 7.
When an electrophotographic photoreceptor was produced using the same method as in Example 7, the characteristics as an _{electrophotographic} photoreceptor were as follows. , there was no significant difference. However, the resin solution of polycarbonate A resin and hydrazone compound had a viscosity of 3 after 24 hours.
In contrast, polycarbonate Z resin showed no change at all even after 48 hours, and the fluidity was lost after 48 hours.
It was significantly superior in terms of solution stability. Example 8 10 parts of polyvinyl carbazole (weight average molecular weight 60,000) and 2 parts of m-terphenyl were dissolved in 80 parts of monochlorobenzene and 20 parts of methylene chloride. This was applied by dip coating onto the undercoat layer formed in the same manner as in Example 1 to provide a charge transport layer with a thickness of 18 μm. Next, 10 parts of the disazo pigment of the exemplary pigment (6) was added to an 8% cyclohexanone solution of polycarbonate Z resin (manufactured by Teijin Kasei Ltd., weight average molecular weight 150,000).
In addition to 250 parts, the mixture was dispersed in a sand mill for 10 hours.
This dispersion was spray coated onto the charge transport layer while rotating the drum. In this way 3μ
A thick charge generation layer was formed. This electrophotographic photoreceptor was attached to the same electrophotographic copying machine as in Example 1 and evaluated. However, the corona charge was set to +5.2KV. As a result, V _D was 700 V, and V _L was 140 V when exposed at 7.5 lux/second, and a good image could be obtained, and the same results as in Example 7 could be obtained. On the other hand, even when electrophotographic photoreceptors were produced using different resins in the same manner as in Comparative Examples 5 to 8, the results were still similar to those in Comparative Examples 5 to 8.

Claims (1)

[Scope of Claims] 1. An electrophotographic photosensitive layer comprising a photosensitive layer containing at least one disazo pigment represented by the following general formula (1) and a polycarbonate Z resin represented by the following general formula (2). body. general formula In the formula, A represents a coupler residue having a phenolic OH group. general formula In the formula, n represents the average degree of polymerization and is in the range of 50 to 5000. 2. The electrophotographic photoreceptor according to claim 1, wherein A in the general formula (1) is selected from coupler residues having a phenolic OH group represented by the following general formulas (3) to (9). general formula In the formula, Indicates the residue necessary to form a hydrogen atom, R ₁ and R ₂ are a group selected from a hydrogen atom, an alkyl group that may have a substituent, an aralkyl group, an aryl group, and a heterocyclic group, or R ₁ ,
Indicates a cyclic amino group formed together with the nitrogen atom to which R ₂ is bonded. general formula general formula R ₃ and R ₄ in the general formulas (4) and (5) represent a group selected from an alkyl group, an aralkyl group, and an aryl group that may have a substituent. general formula general formula Y in the general formulas (6) and (7) represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group containing a nitrogen atom in the ring. general formula In the formula, R ₅ and R ₆ are a hydrogen atom, a group selected from an alkyl group that may have a substituent, an aralkyl group, an aryl group, and a heterocyclic group, or 5 together with the carbon atom to which R ₅ and R ₆ are bonded. This 5- or 6-membered ring may have a fused aromatic ring, and Z is a naphthalene ring, an anthracene ring, a carbazole ring fused with a benzene ring, Indicates a residue necessary to form a polycyclic aromatic ring or a heterocycle selected from a benzcarbazole ring, a dibenzofuran ring, a benzonaphthofuran ring, and a diphenylene sulfide ring. general formula In the formula, R ₇ and R ₈ are a hydrogen atom, a group selected from an alkyl group, an aralkyl group, an aryl group, and a heterocyclic group which may have a substituent, or 5 together with the carbon atom to which R ₇ and R ₈ are bonded. This 5- or 6-membered ring may have a fused aromatic ring, and Z is a naphthalene ring, an anthracene ring, a carbazole ring fused with a benzene ring, Indicates a residue necessary to form a polycyclic aromatic ring or a heterocycle selected from a benzcarbazole ring, a dibenzofuran ring, a benzonaphthofuran ring, and a diphenylene sulfide ring. 3. Claims 1 or 2, wherein the photosensitive layer comprises a disazo pigment of general formula (1) as a charge generating material, dispersed in a charge transporting material and a polycarbonate Z resin of general formula (2). The electrophotographic photoreceptor described above. 4. Claim 1, wherein the photosensitive layer is a laminate of a charge generation layer containing a disazo pigment of general formula (1), a charge transport material, and a charge transport layer containing a polycarbonate Z resin of general formula (2), or The electrophotographic photoreceptor according to item 2. 5. Claims 1 or 2, wherein the photosensitive layer is a charge-generating layer containing a disazo pigment of general formula (1) and a polycarbonate Z resin of general formula (2) laminated on a charge transport layer. The electrophotographic photoreceptor described above.