JPH0549101B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a photosensitive layer with improved characteristics by containing a specific trisazo 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. , bisbenzimidazole pigments such as India First Orange Toner, phthalocyanine 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 trisazo pigment represented by the general formula (1) described below as a pigment, and polycarbonate Z represented by the general formula (2) described later as a binder.
The above object is achieved by combining the resin with the resin. That is, the present invention provides an electrophotographic photoreceptor having a photosensitive layer containing at least one trisazo pigment represented by the following general formula (1) and a polycarbonate Z resin represented by the following general formula (2). It consists of 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 trisazo 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) is 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. Specific 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 general formulas (4) and (5) represent groups selected from alkyl groups, aralkyl groups, and aryl groups that may have substituents. 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 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. 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, diphenyl, naphthyl, anthryl, etc. Specific examples of groups such as , pyrenyl, and heterocyclic groups include groups such as pyridyl, thienyl, furyl, carbazoyl, etc. Furthermore, as substituents that the above groups may have, fluorine atoms, chlorine atoms, Halogen atoms such as bromine and iodine atoms; alkyl groups such as methyl, ethyl, propyl, and butyl; alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy; nitro groups, cyano groups, dimethylamino, diethylamino, dipropylamino, and Examples include substituted amino groups such as benzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino. A residue that forms a 5- or 6-membered ring together with the carbon atom to which R ₅ and R ₆ are bonded, and this 5
Specific examples of groups in which the membered or six-membered ring may have a condensed aromatic ring 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 groups mentioned above include methyl, ethyl, propyl, butyl, etc. Specific examples of the aralkyl groups include benzyl, phenethyl, naphthylmethyl, etc. Specific examples of the aryl groups include phenyl, naphthyl, anthryl, diphenyl, etc. The basis of
Specific examples of heterocyclic groups include groups such as pyridyl, thienyl, furyl, and carbazoyl, and examples of substituents that the above groups may have include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc. Halogen atoms, alkyl groups such as methyl, ethyl, propyl, butyl, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, nitro groups, cyano groups, dimethylamino, diethylamino, dipropylamino, dibenzylamino, diphenylamino, morpholino, Examples include substituted amino groups such as piperidino and pyrrolidino. A specific example of a group that forms a 5- or 6-membered ring together with the carbon atom to which R ₇ and R ₈ are bonded, and this 5- or 6-membered ring may have a fused aromatic ring. Examples include groups such as cyclopentylidene, cyclohexylidene, and 9-xanthenylidene. Specific examples of the trisazo pigment represented by the general formula (1) are shown below. No. Exemplary compound In addition to these exemplary pigments, there are many other trisazo 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. (d) It has 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 trisazo pigment of the present invention and 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. small, and
It appears that the benzene ring and cyclohexyl group in the polycarbonate Z resin structure facilitate charge transfer and improve sensitivity. The form of the electrophotographic photoreceptor according to the present invention includes (a) a photosensitive layer in which a trisazo pigment represented by general formula (1) (hereinafter referred to as "trisazo pigment") is dispersed in polycarbonate Z resin; (b) trisazo pigment (c) Trisazo pigment dispersed in a binder resin (polycarbonate Z resin or other resin may be used); ) is used as a charge generation layer, and a charge transport layer containing a polycarbonate Z resin and a charge transport substance is laminated thereon.(d) A functionally separated photosensitive layer in which a charge transport layer containing a trisazo pigment and a polycarbonate Z resin is laminated 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,
Examples include tetracyanopyrene. Electron-accepting compounds are generally not preferred due to their carcinogenicity and other harmful properties. When using an electron donating compound, 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, polyvinyl pyrrolidone, methylcellulose, polyacrylic acid esters, cellulose esters, etc. are appropriately used as the binder resin for the trisazo pigment in the form (c) above. Ru. 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
It is 0.05-0.5μ. When formed on the charge transport layer, it is thicker, on the order of 0.5 to 5 μm. The ratio of pigment to resin is about 5:1 to 1:2. [Effects of the Invention] In the electrophotographic photoreceptor of the present invention, the photosensitive layer containing a specific trisazo pigment and polycarbonate Z resin has high sensitivity and low residual potential, and furthermore, the bright area potential increases when charging and exposure are repeated. Furthermore, since the polycarbonate Z resin is present on the surface, the surface is high 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. [Example] 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.)
) 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 applied onto the above substrate by dip coating to form a 0.6μ thick layer. A polyamide undercoat layer was formed. Next, 10 parts of a trisazo pigment selected from the exemplary pigments of trisazo pigments represented by general formula (1) and polyvinyl butyral (trade name Eslec BM-
2. Sekisui Chemical Co., Ltd.) 10 parts to 120 parts of cyclohexanone
The mixture was dispersed for 10 hours in a sand mill apparatus. 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 16μ. Exemplary trisazo pigments (1), (9), (14) of the above selections,
Electrophotographic photoreceptors of Examples 1 to 6 were prepared corresponding to (18), (22), and (32). 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 characteristics 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 The following A to D were used instead of the trisazo pigment of Example 1.
Electrophotographic photoreceptors were prepared in the same manner as in Example 1, except that the organic pigment was used (Comparative Examples 1 to 4 correspond to A to D). 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) C D

[Table] As described above, the electrophotographic photoreceptor of the example had higher sensitivity than the comparative example, and moreover, clear images without fog were obtained. Example 7 An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the above-mentioned Exemplary Pigment (4) was used in place of the trisazo pigment of Example 1. 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 (trade name BR-80, manufactured by Mitsubishi Rayon Co., Ltd.) Comparative example 6: Polystyrene (trade 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, V and V, V after 10,000 sheets durability.
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 Panlite 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 trisazo pigment of the above-mentioned 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. Example 9 An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the trisazo pigment of Exemplified Compound (3) was used in place of the trisazo pigment of Example 1. A corona discharge of -5 KV was applied to the electrophotographic photoreceptor. The surface potential at this time was measured (initial potential _VO ). Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 5 seconds (dark decay V _K ). Sensitivity was evaluated by measuring the exposure amount (E1/2 μJ/cm ² ) required to attenuate the potential V _K by 1/2 after dark decay. At this time, a gallium/aluminum/arsenic ternary semiconductor laser (output: 5 W, oscillation wavelength 778 nm) was used as a light source. The results were as follows. V _O : -680V, V _K : 98%, E1/2: 0.9 μJ/cm ^Second , a laser beam printer (manufactured by Canon Inc., An actual image forming test was carried out by replacing the above photoreceptor with an LBP-CX photoreceptor. The conditions are as follows. Surface potential after primary charging: -170V, surface potential after exposure: -150V (exposure amount 2μJ/cm ² ), transfer potential: +700V, development polarity: negative polarity, process speed: 50mm/sec, development conditions (development bias ): -450V, Image exposure scan method: Image scan, Exposure before primary charging: 50 lux sec red full exposure Image formation was performed by line scanning a laser beam in accordance with character and image signals. After copying 10,000 copies, clear images with no fog were obtained. On the other hand, images on photoreceptors prepared using different resins in the same manner as in Comparative Examples 5 to 8 had low image densities and fog, and good images could not be obtained.

Claims (1)

[Scope of Claims] 1. An electrophotographic photosensitive layer comprising a photosensitive layer containing at least one trisazo 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 aracyl 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 trisazo pigment of the general formula (1) as a charge generating material, dispersed in a charge transporting material and a polycarbonate Z resin of the 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 trisazo 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 trisazo 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.