JP3086284B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an electrophotographic photosensitive member used for an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art In recent years, organic photoconductors which are excellent in processability and economy and have a high degree of freedom in functional design have been widely used as electrophotographic photoconductors in various image forming apparatuses. When a copy image is formed using an electrophotographic photosensitive member, the Carlson process is widely used. The Carlson process includes a charging process for uniformly charging a photoconductor by corona discharge, an exposure process for exposing an original image on the charged photoconductor to form an electrostatic latent image corresponding to the original image, and a toner image forming process. A developing step of developing with a developer containing a toner image to form a toner image, a transferring step of transferring the toner image to a base material such as paper, a fixing step of fixing the toner image transferred to the base material, and after the transferring step And a cleaning step of removing the toner remaining on the photoreceptor. In the Carlson process, in order to form a high-quality image, it is required that the electrophotographic photosensitive member has excellent charging characteristics and photosensitive characteristics, and that the residual potential after exposure is low.

Conventionally, inorganic photoconductors such as selenium and cadmium sulfide have been known as electrophotographic photoreceptor materials.
They are toxic and have the disadvantage of high production costs. Therefore, so-called organic electrophotographic photoreceptors using various organic substances instead of these inorganic substances have been proposed. Such an organic electrophotographic photoreceptor has a photosensitive layer including a charge generating material that generates a charge by exposure and a charge transporting material having a function of transporting the generated charge.

In order to satisfy various conditions desired for such an organic electrophotographic photosensitive member, it is necessary to appropriately select a charge generating material and a charge transporting material. Various substances have been studied as charge transport materials, and many substances such as polyvinyl carbazole, oxadiazole compounds, pyrazoline compounds, and hydrazone compounds have been proposed. Since these charge transporting materials are hole transporting materials, a function-separated type photoreceptor, which is currently the mainstream of organic electrophotographic photoreceptors, necessarily requires a negative charging process. However, the negative polarity corona discharge is inherently unstable and has problems such as deterioration of the photoreceptor due to ozone generation and contamination of the use environment. In order to solve these problems, an organic electrophotographic photosensitive member which operates by positive charge using an electron transporting material as a charge transporting material may be employed. The electron transporting material is described in JP-A-1-206349. A compound having a diphenoquinone structure has been proposed. This is an electron acceptor having a delocalized π-electron system, which can transport electrons by an electron transfer reaction involving an anion radical state.

[0005]

However, for example, as shown by the following formula (A), the same substituent C (CH ₃ ) ₃
Are symmetrically arranged, the diphenoquinone-based compound has low compatibility with the binder resin constituting the photoreceptor, and also has poor solubility in a solvent, and therefore contains a large amount of the diphenoquinone-based compound in the photosensitive layer. Because it cannot be
There is a drawback that sufficient sensitivity cannot be obtained.

[0006]

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An object of the present invention is to solve such a technical problem and to provide a high-sensitivity electrophotographic photosensitive member.

[0008]

The electrophotographic photoreceptor of the present invention for achieving the above object contains a quinone compound represented by the following general formula (I) on a conductive substrate. A photosensitive layer is provided.

[0009]

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(Wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are the same or different and are each a hydrogen atom, an alkyl group,
A cycloalkyl group, an aryl group, an alkoxy group, a cyano group, a halogen atom or an amino group,
Each of the cycloalkyl group, the aryl group, and the alkoxy group may have a substituent. ) The quinone compound (I) is used as an electron transport material. Such a quinone compound (I) is rotatable around a single bond connecting two quinones, and therefore, the compatibility with the binder resin and the solubility in the solvent are represented by the above formula (A). It is significantly improved over diphenoquinone compounds. Thereby, the electrophotographic photoreceptor of the present invention exhibits excellent effects such as excellent sensitivity and charging ability.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group and a hexyl group. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group.

As the aryl group, for example, a phenyl group,
Examples include a naphthyl group, a biphenylyl group, an anthryl group and a phenanthryl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, a butoxy group, a t-butoxy group, and a hexyloxy group. Halogen atoms include chlorine, iodine, bromine,
Fluorine.

The above substituents include, for example, an amino group, a hydroxyl group, a carboxyl group which may be esterified, a cyano group, a C ₁ -C ₆ alkyl group which may have a substituent such as a halogen atom and an alkyl group. , C ₁ -C ₆ alkoxy group, C ₂ -C ₆ alkenyl group which may have an aryl group. The substituent may be two or more, and two substituents may form a ring.

The quinone compound represented by the general formula (I) can be produced, for example, by an oxidative coupling reaction represented by the following reaction formula. Reaction formula:

[0015]

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(Wherein, R ^{1 to} R ⁶ are the same as described above.) The reaction is carried out in an organic solvent such as ethyl alcohol as a catalyst using bis (1,3-propanediaminato) copper (II) chloride complex as a catalyst. (E.g., SMPa
raskevas et al., Synthesis, 1988, 897). The photosensitive layer in the invention contains one or more of the quinone compounds represented by the general formula (I).

The photosensitive layer according to the present invention includes a single layer type in which a charge generating material, a quinone compound represented by the above general formula (I), which is a charge transporting material, and a binder resin are mixed. Although there is a laminated type in which a transport layer is laminated, the photosensitive layer of the present invention can be applied to any of them. To obtain a laminated electrophotographic photoreceptor, a charge generation layer containing a charge generation material is formed on a conductive substrate, and on this charge generation layer,
What is necessary is just to form a charge transport layer containing the quinone compound (I) which is a charge transport material. Alternatively, the charge generation layer may be provided on the charge transport layer by reversing the stacking order.

Examples of the charge generating material include selenium, selenium-tellurium, selenium-arsenic, amorphous silicon, pyrylium salts, azo compounds, disazo compounds, phthalocyanine compounds, anthanthrone compounds, and perylene compounds which have been conventionally used. Compounds, indigo compounds, triphenylmethane compounds, sulene compounds, toluidine compounds, pyrazoline compounds, perylene compounds, quinacridone compounds, pyrrolopyrrole compounds and the like. These charge generation materials can be used alone or in combination of two or more.

The quinone compound (I), which is a charge transport material, can be used in combination with other conventionally known charge transport materials. Conventionally known charge transporting materials include, for example, 2,5-di (4-methylaminophenyl)
Oxadiazole compounds such as -1,3,4-oxadiazole, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, 1-phenyl-3- (p
Pyrazoline compounds such as-(dimethylaminophenyl) pyrazole, triphenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds,
Examples thereof include nitrogen-containing cyclic compounds such as imidazole compounds, pyrazole compounds, and triazole compounds, and condensed polycyclic compounds. In the case where a charge transporting material having a film forming property such as polyvinyl carbazole is used, a binder resin is not necessarily required.

As the binder resin, various resins can be used, for example, a styrene polymer, a styrene-butadiene copolymer, a styrene-acrylonitrile copolymer, a styrene-maleic acid copolymer, and an acrylic copolymer. Coalesce, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, polycarbonate, Thermoplastic resins such as polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, silicone resin, epoxy resin, other crosslinkable thermosetting resins, epoxy acrylate, urethane acrylate How such photocurable resins. These binder resins can be used alone or in combination of two or more.

Examples of the solvent for dispersing or dissolving the charge generation material, the charge transport material and the binder resin to form a coating solution include alcohols such as methanol, ethanol, isopropanol and butanol, n-hexane, octane and the like. , Aliphatic hydrocarbons such as cyclohexane,
Benzene, toluene, aromatic hydrocarbons such as xylene, dichloromethane, dichloroethane, carbon tetrachloride, halogenated hydrocarbons such as chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethers such as diethylene glycol dimethyl ether, acetone, methyl ethyl ketone, Examples include ketones such as cyclohexanone, esters such as ethyl acetate and methyl acetate, dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide. These solvents can be used alone or in combination of two or more.

Further, in order to improve the sensitivity of the charge generation layer, a known sensitizer such as terphenyl, halonaphthoquinones, acenaphthylene and the like may be used together with the charge generation material. Further, a surfactant, a leveling agent, and the like may be used to improve the dispersibility, dyeing property, and the like of the charge transporting material and the charge generating material.

As the conductive substrate, for example, aluminum, copper, tin, platinum, silver, vanadium, molybdenum,
Chrome, cadmium, titanium, nickel, palladium,
Simple metals such as indium, stainless steel, brass, etc., and plastic materials on which the above metals are deposited or laminated,
Examples include glass coated with aluminum iodide, tin oxide, indium oxide, and the like.

The conductive substrate may be in the form of a sheet, a drum or the like, as long as the substrate itself has conductivity or the surface of the substrate has conductivity. Also,
The substrate preferably has a sufficient mechanical strength when used. In the laminate type electrophotographic photoreceptor, the charge generation material and the binder resin constituting the charge generation layer can be used in various ratios, but the charge generation material is 5 to 500 parts by weight based on 100 parts by weight of the binder resin. Parts by weight, especially 10-25
It is preferable to use 0 parts by weight.

The charge generation layer may have an appropriate thickness, but is preferably formed to a thickness of about 0.01 to 5 μm, particularly about 0.1 to 3 μm. The quinone compound (I) (charge transport material) and the binder resin constituting the charge transport layer can be used in various ratios, but the charge generated in the charge generation layer by light irradiation can be easily transported. As much as possible, the quinone compound (I) is preferably used in a proportion of 10 to 500 parts by weight, particularly 25 to 200 parts by weight, based on 100 parts by weight of the binder resin.

The charge transport layer has a thickness of 2 to 100 μm.
m, particularly preferably about 5 to 30 μm. In a single-layer type electrophotographic photoreceptor, the binder resin 1
2 to 20 parts by weight, more preferably 3 to 15 parts by weight, of the quinone-based compound (I) (charge transporting material) is 40 to 200 parts by weight, particularly 50 to 150 parts by weight, per 100 parts by weight. Respectively. The thickness of the single-layer type photosensitive layer is 10 to 50 μm, especially 1 to 50 μm.
It is preferably about 5 to 30 μm.

When the photosensitive layer including the charge generating layer and the charge transporting layer is formed by a coating means, the charge generating material or the charge transporting material and the binder resin are mixed with a conventionally known method, for example, a roll mill, a ball mill, an attritor, A coating solution is prepared using a paint shaker, an ultrasonic disperser, or the like.

[0028]

The present invention will be described below in detail with reference to examples and comparative examples. Example 1 (Laminated photosensitive layer) 1 part by weight of metal-free phthalocyanine as a charge generating material,
1 part by weight of polyvinyl butyral resin, 1 part of dichloromethane
20 parts by weight were dispersed for 2 hours with a paint shaker using stainless beads (2 mm diameter). The obtained dispersion was applied on an aluminum sheet using a wire bar, and dried at 60 ° C. for 1 hour to obtain a 0.5 μm charge generation layer.

A solution obtained by dissolving 75 parts by weight of a quinone-based compound (charge transporting material) represented by the following formula (1) and 100 parts by weight of a polycarbonate resin in a predetermined amount of benzene is provided on the charge generation layer by a wire bar. Coated, 1 at 100 ° C
After drying for 22 hours, a charge transport layer having a thickness of 22 μm was formed to obtain a positively charged electrophotographic photosensitive member.

[0030]

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Examples 2 to 6 (Laminated photosensitive layer) Instead of the diphenoquinone-based compound represented by the above formula (1), quinone-based compounds represented by the following formulas (2) to (6) were used. Otherwise in the same manner as in Example 1, a positively charged electrophotographic photosensitive member was obtained.

[0032]

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[0033]

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Comparative Example 1 (Laminated Photosensitive Layer) The charge transporting material of Example 1 was the same as the charge transporting material except that the diphenoquinone-based compound represented by the formula (A) was used in an amount of 30 parts by weight based on 100 parts by weight of the resin. In the same manner as in the above, a negatively charged electrophotographic photosensitive member was obtained. The reason why the amount of the diphenoquinone-based compound was set to 30 parts by weight was that this compound was at the limit of dissolving in the binder resin and could not be dissolved any more. Example 7 (Single-layer type photosensitive layer) (Components) (parts by weight) Metal-free phthalocyanine 1 Binder resin 100 (the above-mentioned polycarbonate resin) Quinone-based compound represented by the above formula (1) 60 N, N, N ', N'-Tetrakis (3-methylphenyl) -1,3-diaminobenzene 40 Each of these components was added to a predetermined amount of tetrahydrofuran, and dispersed for 2 hours with a paint shaker using stainless beads (2 mm diameter). Was. The resulting dispersion was applied on an aluminum sheet using a wire bar,
After drying at 1 ° C. for 1 hour, a photosensitive layer having a thickness of 20 μm was formed to obtain a single-layer type electrophotographic photosensitive member. Examples 8 to 12 (Single-layer type photosensitive layer) Instead of the quinone compound represented by the above formula (1), the quinone represented by the same formula (2) to (6) as used in Examples 2 to 6 A single-layer type electrophotographic photoreceptor was obtained in the same manner as in Example 7 except that a system compound was used. Comparative Example 2 (Single-layer type photosensitive layer) The same as Example 7 except that the diphenoquinone-based compound represented by the above formula (A) was used as the charge transporting material.
An electrophotographic photosensitive member was obtained. However, the amount of the diphenoquinone-based compound (A) used was 30 parts by weight, which was the same as in Comparative Example 1.

(Evaluation Test) The surface potential, half-exposure (E _1/2 ), and residual potential of the photoreceptors obtained in each of the examples and comparative examples were evaluated using an evaluation tester (“EPA8100” manufactured by Kawaguchi Electric Co., Ltd.).
Was measured. The measurement conditions are as follows. Light intensity: 10 μW / cm ² Exposure time: 2 seconds Surface potential: (±) The flowing current value was adjusted to be around 700 V.

Light source: 780 nm light Static elimination: 200 lux Measurement of residual potential: The potential one second after the start of exposure was measured. Table 1 shows the test results of Examples 1 to 12 and Comparative Examples 1 and 2. The photosensitive members having the single-layer photosensitive layers of Examples 7 to 12 and Comparative Example 2 were tested for positive charge and negative charge, respectively. In the table, the numbers indicating the charge transporting materials indicate the formula numbers of the quinone compounds used.

[0037]

[Table 1]

From the test results, it can be seen that the photoreceptors of the examples are superior in half-exposure exposure and residual potential as compared with those of the comparative examples, and that the sensitivity is remarkably improved.

[0039]

As described above, since the electrophotographic photoreceptor of the present invention uses a specific quinone compound as a charge transporting material, it has an effect of being excellent in sensitivity characteristics.

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing a quinone compound represented by the following general formula (I) provided on a conductive substrate. Embedded image (Wherein, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are the same or different and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a cyano group, a halogen atom or an amino group And the alkyl group, cycloalkyl group, aryl group and alkoxy group may each have a substituent.)