JPH08202056A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE: To provide an electrophotographic photoreceptor high in sensitivity and durability. CONSTITUTION: The electrophotographic photoreceptor contains on a conductive substrate as a photoconductor the stilbene compound represented by the formula in which each of R1 -R4 is, independently, an H atom or each an optionally substituted alkyl or aralkyl or aryl or heterocyclic group, except the cases when each of R1 and R2 is an H atom at the same time, and when each of R3 and R4 is an II atom at the same time; each of R5 and R6 is, independently, an H atom or an alkyl or aryl or heterocyclic group; each of R7 and R8 is, independently, an H or halogen atom or each an optionally substituted alkyl or alkoxy group; each of Ar1 and Ar2 is each an optionally substituted aromatic or hetero-cyclic group; and n is 0 or 1 or 2.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrophotographic photoreceptor containing a novel stilbene compound.

[0002]

2. Description of the Related Art In the past, inorganic photoconductive substances 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, research has been actively conducted on organic photoconductive materials for these inorganic materials, and some of them have been put to practical use as electrophotographic photoreceptors.

Generally speaking, inorganic materials such as selenium photoconductors have thermal stability, deterioration of characteristics due to crystallization, difficulty in production, and cadmium sulfide has moisture resistance and durability. However, compared with the situation that it is not always satisfactory due to the problem of the property and the disposal of industrial waste, the organic material has good film-forming property, excellent flexibility, and light weight. However, it has advantages such as good transparency and easy design of a photoconductor for a wide range of wavelengths by an appropriate sensitizing method, and therefore its practical application is gradually receiving attention.

By the way, the photoconductor used in the electrophotographic technique is generally required to have the following basic properties. That is, (1) high chargeability against corona discharge in the dark, (2) little leakage (dark decay) of the obtained charged charge in the dark, and (3) charge charging by light irradiation. Dissipation of light (light attenuation) is rapid, (4)
For example, the residual charge after light irradiation is small.

[0005]

However, much research has been conducted on photoconductive polymers such as polyvinyl carbazole as an organic photoconductive substance up to now, but these are not necessarily film-forming, flexible, It is difficult to say that the adhesiveness is not sufficient and the basic properties of the above-mentioned photoreceptor are sufficiently provided.

On the other hand, regarding the organic low-molecular-weight photoconductive compound, by selecting a binder or the like used for forming the photosensitive member, a photosensitive member excellent in mechanical strength such as film-forming property, adhesion and flexibility can be obtained. Although obtainable, it is difficult to find a suitable compound that can retain the highly sensitive property.

In order to improve such points, the development of an organic photoconductor having higher sensitivity characteristics by sharing the function of generating carriers and the function of transporting carriers by different substances has been carried out. A characteristic of such a photoconductor, which is called a function-separated type, is that materials suitable for each function can be selected from a wide range, and many studies have been carried out because a photoconductor having arbitrary performance can be easily produced. Has been promoted.

As described above, various improvements have been made in the production of electrophotographic photoconductors, but the basic properties required for the photoconductors listed above and the requirements for high durability are satisfied. I haven't got enough to do yet.

An object of the present invention is to provide an electrophotographic photoreceptor having high sensitivity and high durability. In particular, the photoreceptor of the present invention is to provide a photoreceptor having a high charging characteristic, a decrease in sensitivity hardly occurring even after repeated use, and a stable charging potential.

[0010]

Means for Solving the Problems As a result of research on a photoconductive substance having high sensitivity and high durability, the present inventors have found that the stilbene compound represented by the above general formula 1 is effective. The present invention has been found out.

In the chemical formula ₁ , R ₁ , R ₂ , R ₃ and R ₄ may be the same or different and each is a hydrogen atom, an optionally substituted alkyl group, an aralkyl group, an aryl group or a heterocycle. Indicates a group. However, the case where both R ₁ and R ₂ are hydrogen atoms and the case where both R ₃ and R ₄ are hydrogen atoms are excluded. R ₅ and R ₆ may be the same or different and each is a hydrogen atom, an alkyl group,
It represents an aryl group or a heterocyclic group, and R ₇ and R ₈ may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or an alkoxy group. Ar
₁ and Ar ₂ represent an aryl group or a heterocyclic group which may have a substituent. n represents an integer of 0 to 2.

Specific examples of R ₁ , R ₂ , R ₃ and R ₄ include hydrogen atom, alkyl groups such as methyl group, butyl group and 3-methyloctyl group, benzyl group and 4-methylbenzyl group. , An aralkyl group such as a 2-chlorophenethyl group, an aryl group such as a phenyl group, a tolyl group, a chlorophenyl group and a naphthyl group, or a heterocyclic group such as a thienyl group, a pyridyl group and an indolyl group, and R ₅ and R Specific examples of ₆ include a hydrogen atom, a methyl group, a butyl group, an alkyl group such as a 3-methyloctyl group, a phenyl group, a 4-methoxyphenyl group, an aryl group such as a naphthyl group, a thienyl group, a pyridyl group, and an indolyl group. A heterocyclic group such as R ₇ , R ₈
As specific examples of, a hydrogen atom, or a halogen atom such as fluorine, chlorine, or bromine, an alkyl group such as a methyl group or a propyl group, an alkoxy group such as a methoxy group or an ethoxy group,
Specific examples of Ar ₁ and Ar ₂ include aryl groups such as phenyl group, tolyl group, 4-chlorophenyl group and naphthyl group, and heterocyclic groups such as pyridyl group and thienyl group.

These compounds represented by Chemical formula 1 are produced by the methods of the following synthetic examples. Synthesis Example (Synthesis of Exemplified Compound 9)

[0014]

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A tetrahydrofuran solution (200 ml) in which the aldehyde compound of formula 2 (5.01 g) and titanium tetrachloride (11.89 g) were dissolved was cooled to -30 ° C and stirred,
A suspension of zinc powder (6.42 g) in tetrahydrofuran (60 ml) is added slowly. After 2 hours, the temperature is returned to room temperature and stirring is continued for 2 hours again. The reaction is stopped by adding water and the mixture is extracted with ethyl acetate. The solution is dried over anhydrous sodium sulfate and concentrated under reduced pressure. 1,4-dioxane (100 ml) was added to the obtained pale yellow residue, and the mixture was stirred under
Heat to reflux for 4 hours. After cooling, the solution was concentrated under reduced pressure, and the obtained pale yellow residue was purified by silica gel chromatography to obtain 0.98 g of Exemplified Compound 11. Melting point 74.6-76.7 ° C, yield 20.4%.

Next, the stilbene compound according to the present invention will be exemplified, but the invention is not limited thereto.

[0017]

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[0018]

[Chemical 4]

[0019]

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[0020]

[Chemical 6]

[0021]

[Chemical 7]

[0022]

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[0023]

[Chemical 9]

[0024]

[Chemical 10]

[0025]

[Chemical 11]

[0026]

[Chemical 12]

[0027]

[Chemical 13]

[0028]

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[0029]

[Chemical 15]

[0030]

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[0031]

[Chemical 17]

[0032]

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[0033]

[Chemical 19]

[0034]

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[0035]

[Chemical 21]

[0036]

[Chemical formula 22]

[0037]

[Chemical formula 23]

[0038]

[Chemical formula 24]

[0039]

[Chemical 25]

[0040]

[Chemical formula 26]

[0041]

[Chemical 27]

[0042]

[Chemical 28]

[0043]

[Chemical 29]

[0044]

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[0045]

[Chemical 31]

[0046]

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[0047]

[Chemical 33]

[0048]

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[0049]

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[0050]

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[0051]

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[0052]

[Chemical 38]

[0053]

[Chemical Formula 39]

[0054]

[Chemical 40]

[0055]

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[0056]

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[0057]

[Chemical 43]

[0058]

[Chemical 44]

[0059]

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[0060]

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[0061]

[Chemical 47]

[0062]

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[0063]

[Chemical 49]

[0064]

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[0065]

[Chemical 51]

[0066]

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[0067]

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[0068]

[Chemical 54]

[0069]

[Chemical 55]

[0070]

[Chemical 56]

[0071]

[Chemical 57]

[0072]

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[0073]

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[0074]

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[0075]

[Chemical formula 61]

[0076]

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[0077]

[Chemical formula 63]

[0078]

[Chemical 64]

[0079]

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[0080]

[Chemical formula 66]

[0081]

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[0082]

[Chemical 68]

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

The electrophotographic photoreceptor containing these stilbene compounds can be embodied in various forms. For example, a stilbene compound and a carrier-generating substance are added to a chemical sensitizer or an electron-withdrawing compound, if necessary, and then dissolved or dispersed in a binder resin to be provided on a conductive support. In the form of a photoconductor or a laminated structure containing a carrier generating layer and a carrier transporting layer, a carrier generating layer mainly composed of a carrier generating substance is provided on a conductive support, and the present stilbene compound is required on this. Depending on, a photosensitizer formed by laminating a carrier sensitizer or an electron-withdrawing compound dissolved or dispersed in a binder resin as a carrier transport layer, and its carrier generation layer and carrier transport layer There is a photoconductor in which the above is laminated on a conductive support in an inverted manner, but it is applicable to any case. Further, the present stilbene compound can be used together with a known carrier transport substance.

As a support for producing a photoreceptor using the compound of the present invention, a metal drum, a metal plate, conductive processed paper, a plastic film or a belt-shaped support is used. As the film-forming binder resin used for forming the photosensitive layer on those supports, various resins can be mentioned depending on the field of use. For example, in the use of photoconductors for copying, polystyrene resin, polyvinyl acetal 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 these, polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, polyarylate resin, phenol resin and the like have excellent potential characteristics as a photoreceptor.

These resins may be used alone or as a mixture of two or more as a homopolymer or a copolymer. The amount of these binder resins added to the photoconductive compound is 0.2 to 10 times by weight, preferably 0.5 to 5 times, and if it is less than this, the photoconductive property is reduced. The compound is deposited in the photosensitive layer or on the surface, which deteriorates the adhesion to the support, and when the amount is large, the sensitivity is lowered.

Some of these film-forming binder resins used are rigid and weak in mechanical strength such as tension, bending and compression, and it is necessary to add a substance that imparts plasticity in order to improve these properties. Becomes Examples of these substances include phthalic acid dioctyl ester, phthalic acid dibutyl ester, phthalic acid diisodecyl ester and other phthalic acid esters, phosphoric acid tricresyl ester, phosphoric acid tris (2-ethylhexyl) ester and other phosphoric acid esters, sebacic acid ester. , Adipic acid ester, nitrile rubber, chlorinated hydrocarbon and the like. In the case of adding these plasticizing substances, if added more than necessary, the potential characteristics will be deteriorated, so the proportion thereof is preferably 20% or less by weight ratio with respect to the binder resin.

As the carrier-generating substance, triphenylmethane dye, acridine dye, cyanine dye, pyrylium dye, thiapyrylium dye, squarium dye,
Examples include perylene pigments, quinacridone pigments, anthraquinone pigments, phthalocyanine pigments, and azo pigments.

Among these pigments, those using a bisazo pigment, a trisazo pigment or a phthalocyanine pigment as those having a particularly high carrier generation efficiency give high sensitivity and an excellent electrophotosensitive material. Further, examples of the inorganic photoconductive substance include selenium, selenium tellurium alloy, cadmium sulfide, zinc sulfide, and amorphous silicon. In addition to the above carrier-generating substances, it is possible to add a sensitizer (so-called chemical sensitizer) for the purpose of further improving the sensitivity.

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 ′,
There are 5'-tetrachloromalonic acid dianilide, α-naphthol, p-nitrobenzoic acid and the like.

It is also possible to add a certain electron-withdrawing compound as a sensitizer which forms a charge transfer complex with the stilbene compound of the present invention and further enhances the sensitizing effect. Examples of the electron-withdrawing substance include 1-chloroanthraquinone, 1-nitroanthraquinone, 2,3-dichloronaphthoquinone, 3,3-dinitrobenzophenone, 4-
Nitrobenzalmalon nitrile, phthalic anhydride, 3-
(Α-cyano-p-nitrobenzal) phthalide, 2,
4,7-trinitrofluorenone, 1-methyl-4-nitrofluorenone, 2,7-dinitro-3,6-dimethylfluorenone and the like can be mentioned. Other additives such as an antioxidant and an anti-curl agent may be added to the photoreceptor as needed.

The stilbene compound of the present invention is dissolved or dispersed in a suitable solvent together with the above-mentioned various additives according to the form of the photoreceptor, and the coating solution is coated on the above-mentioned conductive support. Then, the photoconductor is manufactured by drying.

As the coating solvent, halogenated hydrocarbons such as chloroform, dichloroethane, trichloroethane and trichloroethylene, aromatic hydrocarbons such as benzene, toluene and xylene, 1,4-dioxane, tetrahydrofuran, methyl cellosolve, dimethyl cellosolve,
Solvent such as methyl cellosolve acetate alone or 2
A mixed solvent of at least one kind or a solvent such as alcohols, acetonitrile, N, N-dimethylformamide, methyl ethyl ketone and the like can be further added and used.

[0094]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention thereto. Example 1

[0095]

[Chemical 69]

1 part by weight of the compound of Chemical formula 69 and 1 part by weight of a polyester resin (Vylon 200 manufactured by Toyobo) were mixed with 100 parts by weight of tetrahydrofuran, and the mixture was dispersed together with glass beads for 2 hours by a paint conditioner device. The pigment dispersion thus obtained was coated on a polyester film vapor-deposited on aluminum with an applicator and dried to form a film of a carrier-generating substance having a thickness of about 0.2 μm.

Next, the stilbene compound represented by Exemplified Compound 3 was mixed with a polyarylate resin (U-polymer manufactured by Unitika) at a weight ratio of 1: 1 to prepare a 10% solution using dichloromethane as a solvent to generate the above carrier. This solution was applied onto the material coating 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 by an electrostatic recording tester (SP-428 manufactured by Kawaguchi Denki Co., Ltd.). Measurement condition: Applied voltage -6
KV, static No. 3 (rotation speed mode of turntable with sample attached). As a result, the half-photoexposure amount for white light during charging was 1.0 lux · sec, which was a very high sensitivity value.

Further, repeated use was evaluated using the same apparatus. When the change of the charging potential due to the repetition of 10 ³ times was obtained, it was 10 with respect to the initial potential of −710 V for the first time.
The charging potential at the ^third time was -700 V, and it was found that the potential did not decrease with repetition and was stable, showing excellent characteristics.

Examples 2 to 7 Laminated photoreceptors were prepared in the same manner as in Example 1 except that the stilbene compounds shown in Table 1 were used instead of the stilbene compounds used in Example 1, and the same procedure as in Example 1 was carried out. Under the measurement conditions, the light half exposure amount E1 / 2 (lux / sec) and initial potential Vo
(Volts) were measured and the values are shown in Table 1. Furthermore, electrification and static elimination (static elimination light: irradiation with white light 400 lux x 1 second)
After repeating 10 ³ times as one cycle,
Table 1 shows the initial potential Vo (volt) and the light half exposure amount E1 / 2.
It was shown to.

[0101]

[Table 1]

Examples 8-14 1 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 by a paint conditioner device. The pigment dispersion thus obtained was coated on the same support as in Example 1 with an applicator to form a carrier generation layer. The thickness of this thin film was about 0.2μ.

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

[0104]

[Table 2]

[0105]

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Comparative Example 1 Instead of the stilbene compound of the present invention as a comparative example,
When a charge transfer layer was prepared using the compound represented by 0 in the same manner as in Example 1, the compound was insoluble in the solvent dichloromethane. Inevitably, this suspension was forcibly applied onto a coating of X-type metal-free phthalocyanine to measure the electrophotographic characteristics, but no light attenuation was observed and the half-exposure amount could not be obtained.

[0107]

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)

[Claims] 1. An electrophotographic photoreceptor containing a stilbene compound represented by the following chemical formula 1. Embedded image (In the chemical formula 1, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different and may be a hydrogen atom, an optionally substituted alkyl group, an aralkyl group, an aryl group or a heterocyclic group. Provided that R ₁ and R ₂ are both hydrogen atoms, and R ₃ and R ₄
Except when both are hydrogen atoms. R ₅ and R ₆ may be the same or different and each represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, and R ₇ and R ₈ may be the same or different, and may be a hydrogen atom, a halogen atom or a substituent. The alkyl group and the alkoxy group which may have a group are shown. Ar ₁ and Ar ₂
Represents an aryl group or a heterocyclic group which may have a substituent. n represents an integer of 0 to 2. )