JP3233757B2 - 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 an electrophotographic photosensitive member containing a novel stilbene compound.

[0002]

2. Description of the Related Art Conventionally, inorganic photoconductive materials such as selenium, cadmium sulfide, zinc oxide, and silicon have been known for electrophotographic photoreceptors, and have been extensively studied and put to practical use. . In recent years, organic photoconductive materials have been actively studied for these inorganic materials, and some of them have been put to practical use as photoconductors for electrophotography.

Generally speaking, inorganic materials such as selenium photoreceptors have thermal stability, deterioration of characteristics due to crystallization, difficulty in production, and cadmium sulfide have moisture resistance and durability. Organic materials have better film-forming properties, better flexibility, and lighter Because of its advantages such as good transparency and easy design of a photoreceptor for a wide range of wavelengths by an appropriate sensitization method, its practical use is gradually receiving attention.

Incidentally, the photoreceptor used in the electrophotographic technology is generally required to have the following basic properties. That is, (1) high chargeability against corona discharge in a dark place, (2) little leakage (dark decay) of the obtained charge in a dark place, and (3) charge charge by light irradiation. Rapid dissipation (light decay) of (4)
For example, the residual charge after light irradiation is small.

[0005]

However, many studies have been made on photoconductive polymers such as polyvinyl carbazole as organic photoconductive substances to date. It is difficult to say that the adhesiveness is not sufficient and that the above-mentioned basic properties of the photoreceptor are sufficiently provided.

On the other hand, as for the organic low-molecular-weight photoconductive compound, a photoreceptor having excellent mechanical strength such as film property, adhesion and flexibility can be obtained by selecting a binder or the like used for photoreceptor formation. Although it can be obtained, it is difficult to find a compound that is suitable for retaining high-sensitivity properties.

In order to improve such a point, an organic photoreceptor having higher sensitivity characteristics has been developed in which a carrier generating function and a carrier transporting function are shared by different substances. The feature of such a photoreceptor, which is called a function-separated type, is that a material suitable for each function can be selected from a wide range, and a photoreceptor having an arbitrary performance can be easily manufactured. Has been advanced.

As described above, various improvements have been made in the production of electrophotographic photoreceptors, but the basic properties required for the above-described photoreceptors and the requirements for high durability are satisfied. What to do has not yet been obtained.

An object of the present invention is to provide an electrophotographic photosensitive member having high sensitivity and high durability. In particular, it is an object of the present invention to provide a photoreceptor which has a high charging characteristic, has almost no decrease in sensitivity even when used repeatedly, and has a stable charging potential.

[0010]

The present inventors have studied a photoconductive substance having high sensitivity and high durability and found that the novel stilbene compound represented by the above formula (1) is effective. The present invention has been reached.

In Chemical Formula 1, R ₁ and R ₂ represent a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group, an aryl group, or a heterocyclic group. However, this excludes the case where both R ₁ and R ₂ are hydrogen atoms. R ₃ represents a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and R ₄ and R ₅ represent a hydrogen atom, an alkyl group which may have a substituent, an aryl group, a styryl group, or a heterocyclic group. However, this excludes the case where R ₄ and R ₅ are both hydrogen atoms. Ar represents an aryl group which may have a substituent. X represents an oxygen atom, a sulfur atom, or NR ₆ . R ₆ represents an optionally substituted alkyl group, aralkyl group, aryl group, or heterocyclic group.

Here, specific examples of R ₁ and R ₂ include alkyl groups such as methyl group, butyl group and 3-methyloctyl group, and aralkyl groups such as benzyl group, 4-methylbenzyl group and 2-chlorophenethyl group. Group, phenyl group, tolyl group,
An aryl group such as a chlorophenyl group and a naphthyl group, or a heterocyclic group such as a heterocyclic group such as a pyridyl group and an indolyl group; specific examples of R ³ include a hydrogen atom, a methyl group, and a propyl group. Alkyl groups, methoxy groups, alkoxy groups such as ethoxy groups, halogen atoms such as fluorine, chlorine, bromine, and the like, specific examples of R ₄ and R ₅ include a hydrogen atom, or an alkyl group such as a methyl group or an ethyl group; Phenyl group, tolyl group, chlorophenyl group, naphthyl group, aryl group such as biphenyl group, styryl group, styryl group such as 4-methylstyryl group, pyridyl group, heterocyclic group such as indolyl group, as a specific example of R ₆ Represents an aralkyl group such as an alkyl group such as a methyl group or an ethyl group, a benzyl group, a 4-methylbenzyl group, or a 2-chlorophenethyl group; a phenyl group; a tolyl group; Aryl groups such as xyphenyl group and chlorophenyl group; heterocyclic groups such as pyridyl group and indolyl group; specific examples of Ar include phenyl group such as phenyl group, 4-methylphenyl group, 4-chlorophenyl group and naphthyl group. And heterocyclic groups such as pyridyl group and thienyl group.

The compounds represented by Chemical Formula 1 can be produced by the methods of the following synthesis examples. Synthesis Example 1 (Synthesis of Exemplified Compound 6)

2-bromo-1,1,2-triphenylethylene (4.01 g), 4-hydroxystilbene (3.19 g), 1,3-dimethyl-2-imidazolidinone (1.12 g), carbonic acid Potassium (1.29 g) and copper acetylacetone (0.2 g) are heated and stirred at 140 ° C. for 1.5 hours. The reaction is stopped by adding water to the reaction solution, and extracted with chloroform. The separated organic layer is dried over anhydrous sodium sulfate and concentrated under reduced pressure using an evaporator. The residue was purified by silica gel chromatography to obtain 4.18 g of Exemplified Compound 6.

Melting point 164.2-164.8 ° C., yield 7
7.6%

Synthesis Example 2 (Synthesis of Exemplified Compound 39)

[0017]

Embedded image

Cinnamyl bromide (3.35 g) and triethyl phosphite (2.83 g) are heated and stirred at 150 ° C. for 3 hours. When the generation of ethyl bromide is completed, the mixture is cooled to room temperature, an aldehyde compound of the formula (3.31 g) and a DMF solution (70 ml) are added, and the mixture is stirred for 10 minutes. potassium
t-Butoxide (3.08 g) was slowly added, and the mixture was further stirred at room temperature for 30 minutes. Then, 300 ml of water was added to stop the reaction. The solution is extracted with chloroform, and the organic layer is dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel chromatography to obtain 2.93 g of Exemplified Compound 39.

Melting point: 81.1 to 84.4 ° C., yield: 72.
4%.

The following Tables 1 to 4 show stilbene compounds according to the present invention, but are not limited thereto.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

The electrophotographic photosensitive member according to the present invention is obtained by containing one or more stilbene compounds as described above, and has excellent performance.

There are various embodiments of the electrophotographic photoreceptor containing these stilbene compounds. For example, a photoconductor in which a stilbene compound and a sensitizing dye are dissolved or dispersed in a binder resin by adding a chemical sensitizer or an electron-withdrawing compound as necessary, and provided on a conductive support. Or, in the form of a laminated structure containing a carrier generation layer and a carrier transport layer, on the conductive support,
A carrier-generating layer provided mainly with a carrier-generating substance having a high carrier-generating efficiency, for example, a dye or a pigment, is provided, and the stilbene compound is bound thereon by adding a chemical sensitizer or an electron-withdrawing compound as necessary. Such as a photoconductor obtained by laminating or dissolving or dispersing in an agent resin as a carrier transport layer, or a photoconductor obtained by reversely laminating a carrier generation layer and a carrier transport layer on a conductive support. However, it is possible to apply in any case.

As a support for producing a photoreceptor by using the compound of the present invention, a metal drum, a metal plate, a paper subjected to conductive processing, a plastic film or a belt-like support is used. As the film-forming binder resin used for forming a photosensitive layer on such a support, various resins can be mentioned depending on the application field. For example, for photoreceptors for copying, polystyrene resin, polyvinyl acetate
Resin, polysulfone resin, polycarbonate resin, vinyl acetate / crotonic acid copolymer resin, polyphenylene oxide resin, polyester resin, alkyd resin, polyarylate resin, acrylic resin, methacrylic resin, phenoxy resin and the like. Among them, polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, polyarylate resin, phenol resin and the like are excellent in the potential characteristics as a photoconductor.

These resins can be used alone or as a mixture of two or more as homopolymers or copolymers. The amount of the binder resin to be added to the photoconductive compound is 0.2 to 10 times by weight, preferably 0.5 to 5 times, and more preferably 0.5 to 5 times. The compound precipitates in the photosensitive layer or on the surface, which deteriorates the adhesion to the support, and when the amount increases, the sensitivity is lowered.

Some of these film-forming binder resins to be used are rigid and have low mechanical strength such as tension, bending, compression, etc. In order to improve these properties, it is necessary to add a substance imparting plasticity. Becomes These materials include phthalic acid esters (eg, DOP, DBP,
DIDP, etc.), phosphate esters (eg, TCP, TO
P, etc.), sebacic esters, adipic esters,
Examples include nitrile rubber and chlorinated hydrocarbons. In the case of adding such a substance that imparts plasticity, the addition of more than necessary deteriorates the potential characteristics. Therefore, the ratio is preferably 20% or less by weight with respect to the binder resin.

Next, sensitizing dyes added to the photosensitive layer include triphenylmethane dyes, acridine dyes, cyanine dyes, pyrylium dyes, thiapyrylium dyes, and squarium dyes.

In the photosensitive layer, photoconductive pigments which generate carriers with extremely high efficiency by light absorption include perylene-based pigments such as peryleneimide and perylene anhydride, other quinacridone pigments, anthraquinone-based pigments, and azo-based pigments. There are pigments and the like.

Among these pigments, those using bisazo pigments, trisazo pigments, and phthalocyanine pigments having high carrier generation efficiency give high sensitivity and provide excellent electrophotosensitive materials. In addition, the dye added to the above-mentioned photosensitive layer can be used alone as a carrier-generating substance. However, by coexisting with a pigment, a carrier may be generated with higher efficiency. Further, examples of the inorganic photoconductive substance include selenium, a selenium-tellurium alloy, cadmium sulfide, zinc sulfide, and amorphous silicon. In addition to the above-mentioned sensitizers (so-called spectral sensitizers), sensitizers (so-called chemical sensitizers) for the purpose of further improving the sensitivity can be added.

Examples of the chemical sensitizer include p-chlorophenol, m-chlorophenol, p-nitrophenol, 4-chloro-m-cresol, p-chlorobenzoylacetanilide, N, N'-diethylbarbituric acid , 3- (β-oxyethyl) -2-phenyliminothiazolidone, malonic acid dianilide, 3,5,3 ′,
5'-tetrachloromalonic acid dianilide, α-naphtho-
And p-nitrobenzoic acid.

Further, a certain kind of electron-withdrawing compound can be added as a sensitizer for forming a charge transfer complex with the stilbene compound of the present invention and further increasing the sensitizing effect. Examples of the electron-withdrawing substance include 1-chloroanthraquinone, 1-nitroanthraquinone, 2,3-dichloronaphthoquinone, 3,3-dinitrobenzophenone, 4-
Nitrobenzalmalone nitrile, phthalic anhydride, 3-
(Α-cyano-p-nitrobenzal) phthalide, 2,
Examples thereof include 4,7-trinitrofluorenone, 1-methyl-4-nitrofluorenone, and 2,7-dinitro-3,6-dimethylfluorenone. In addition, an antioxidant, an anti-curl agent and the like can be added as necessary to the photoreceptor.

The stilbene compound of the present invention is dissolved or dispersed in an appropriate solvent together with the various additives described above depending on the form of the photoreceptor, and the coating solution is coated on the above-mentioned conductive support. And dried to produce a photoreceptor.

As the coating solvent, solvents such as halogenated hydrocarbons such as chloroform, dichloroethane, trichloroethane, and trichloroethylene; aromatic hydrocarbons such as benzene, toluene, and xylene; dioxane, tetrahydrofuran, methyl cellosolve, dimethyl cellosolve, and methyl cellosolve acetate; Or a mixed solvent of two or more thereof or, if necessary, a solvent such as alcohols, acetonitrile, N, N-dimethylformamide, methyl ethyl ketone and the like.

[0037]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example 1

[0038]

Embedded image

1 part by weight of the compound of formula 3 and 1 part by weight of a polyester resin (Vylon 200 manufactured by Toyobo) were mixed with 100 parts by weight of tetrahydrofuran, and dispersed together with glass beads for 2 hours using a paint conditioner. The pigment dispersion thus obtained was applied on an aluminum-evaporated polyester film using an applicator and dried to form a carrier-generating substance film having a thickness of about 0.2 μm.

Next, the stilbene compound represented by Exemplified Compound 5 was mixed with a polyarylate resin (U-Polymer manufactured by Unitika) at a weight ratio of 1: 1 to prepare a 10% solution using dichloroethane as a solvent, and the carrier generation was performed. This solution was applied on the material film by an applicator to form a carrier transport layer having a dry film thickness of 20 μm.

The laminated electrophotographic photoreceptor thus produced was evaluated for electrophotographic characteristics using an electrostatic recording tester (SP-428, manufactured by Kawaguchi Electric). Measurement conditions: applied voltage -6
KV, static No. 3 (rotation speed mode of the turntable with the sample attached). As a result, the light half-life exposure amount with respect to white light at the time of charging was 1.4 lux · sec, which was a very high sensitivity value.

Further, repeated use was evaluated using the same apparatus. Repeated by the place of obtaining the change in the charge potential at 10 ³ times with respect to the first initial potential -710V, 10
^{The third} charging potential was -700 V, and it was found that the reduction in potential due to repetition was small and stable, indicating excellent characteristics.

Examples 2 to 8 A laminated photoreceptor was prepared in the same manner as in Example 1 except that the stilbene compounds shown in Table 5 were used instead of the stilbene compounds used in Example 1, and the same procedures as in Example 1 were carried out. Under the measurement conditions, the light half-life exposure amount E1 / 2 (looks / second) and the initial potential Vo
(Volts) were measured, and the values are shown in Table 1. Further charge-discharge (discharge light: 400 lux x 1 second irradiation with white light)
After the 10 ³ times the same repeated as one cycle,
Table 1 shows the initial potential Vo (volt) and the light half-life exposure amount E1 / 2.
It was shown to.

[0044]

[Table 5]

Examples 9 to 16

One part by weight of X-type metal-free phthalocyanine and 1 part by weight of a polyester resin (Vylon 200 manufactured by Toyobo) were mixed with 100 parts by weight of tetrahydrofuran, and dispersed together with glass beads for 2 hours using a paint conditioner. The pigment dispersion thus obtained was applied on the same support as in Example 1 using an applicator to form a carrier generating layer. The thickness of this thin film was about 0.2 μ.

Next, a laminated photoreceptor was prepared in the same manner as in Example 1 except that the stilbene compounds shown in Table 6 were used instead of the compounds used in Example 1. With respect to this photoreceptor, the half-exposure amount with light having a wavelength of 800 nm (10 μW / cm ² ) was determined. Table 6 shows the results. The numerical values are represented by reciprocals (unit: cm ² / μJ) of the half-life exposure amount.

[0048]

[Table 6]

[0049]

As is apparent from the above, according to the present invention, an electrophotographic photosensitive member having high sensitivity and high durability can be provided.

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor comprising a stilbene compound represented by the following formula 1. Embedded image (In the formula ₁ , R ₁ and R ₂ represent a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group, an aryl group, or a heterocyclic group. However, both R ₁ and R ₂ are hydrogen atoms. R ₃ represents a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and R ₄ and R ₅ represent a hydrogen atom, an alkyl group which may have a substituent, an aryl group, a styryl group, A cyclic group, provided that R ₄ and R ₅ are both hydrogen atoms, and Ar is an aryl group which may have a substituent;
Shows a heterocyclic group. X represents an oxygen atom, a sulfur atom, or NR ₆ . R ₆ represents an optionally substituted alkyl group, aralkyl group, aryl group, or heterocyclic group. )