JP2595530B2 - Photoconductor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member having a photosensitive layer containing a styryl compound as a main component.

Conventional Technology and Problems Electrophotographic photoreceptors include a function-separated type in which a charge generation layer and a charge transport layer are laminated on a conductive support, and a photoconductive layer in which photoconductive particles are dispersed in a resin. A dispersion type formed on a support is widely known.

In the function-separated type, the surface function is high, the charge holding power is high, the photosensitivity is high, and the repetition characteristics are stable by dividing the basic functions of the photoreceptor, that is, the generation and transport of charge carriers, into separate substances. A photosensitive layer can be obtained. It is known that a large number of compounds are both effective as charge-generating materials for charge generation and charge-transporting materials for charge transport of a function-separated type. For example, many charge transport layers using a low-molecular organic photoconductor have been proposed. However, the use of 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole described in U.S. Pat. No. 3,189,447 has low compatibility with the fixing agent, Easily precipitates. Also,
The one using the diarylalkane derivative described in U.S. Pat.No. 3,820,989 has good compatibility with the binder, but has a sensitivity change when used repeatedly, and still has initial sensitivity and residual potential. There are points to be greatly improved in characteristics, sensitivity change and durability when repeatedly used.

Means for Solving the Problems An object of the present invention is to provide an electrophotographic photoreceptor which solves the above-mentioned conventional disadvantages, has high photosensitivity, and has stable electrophotographic characteristics even after repeated use. .

That is, the gist of the present invention is to provide a photosensitive member having a photosensitive layer containing a charge generating material and a charge transporting material, wherein the charge transporting material has the following general formula [I] (In the formula, Ar _{1 to} Ar ₄ are independently an alkyl group, an aromatic heterocyclic group which may have a substituent, or a dialkylamino group, a diaralkylamino group, an alkyl group as a substituent,
Represents an aromatic hydrocarbon group which may have an alkoxy group.
Provided that at least one of Ar _{1 to} Ar ₄ is an aromatic heterocyclic group or an aromatic hydrocarbon group, (Wherein, Ar ₅ and Ar ₆ are an aryl group or a heterocyclic group,
These groups may have a substituent).

A represents an alkylene group, an arylene group or a divalent heterocyclic group which may have a substituent. And a styryl compound represented by the formula:

In the present invention, by utilizing the excellent charge transporting ability of the styryl compound of the present invention represented by the above general formula [I] and using it as a charge transporting material for an electrophotographic photoreceptor, the film properties are excellent and the charge retention is excellent. An electrophotographic photoreceptor having excellent electrophotographic characteristics such as performance, sensitivity, and residual potential, exhibiting little fatigue deterioration even when repeatedly used, and exhibiting stable characteristics can be produced.

Preferred specific examples of the styryl compound represented by the general formula [I] of the present invention include, for example, those having the following structural formulas, but are not limited thereto.

The styryl compound represented by the general formula [I] is, for example, represented by the following general formula [II]: [Wherein, Ar ₁ and Ar ₂ have the same meanings as [I], and R ₂ and R _{3 each} represent an alkyl group, a cycloalkyl group, an aralkyl group, or an aryl group that forms a phosphonium salt. A phosphorus compound represented by the following general formula [III]: [Wherein, Ar ₃ and Ar ₂ have the same meanings as [I]]. The styryl compound represented by the general formula [I] is represented by the following general formula [IV]; [Wherein, R ₂ and R ₃ have the same meaning as [II]. ] Represented by the following general formulas [V] and [VI]; [Wherein Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ have the same meaning as [I]. ]
Can also be obtained by a condensation reaction with a ketone compound represented by Of the phosphorus compound represented by the general formula [II]
R ₂ and R ₃ are particularly preferably a cyclohexyl group, a benzyl group, a phenyl group or a lower alkyl group.

As the reaction solvent in the above method, for example, hydrocarbons, alcohols, ethers are good, methanol,
Ethanol, isopropanol, butanol, 2-methoxyethanol, 1,2-dimethoxyethane, bis (2-
Methoxyethyl) ether, dioxane, tetrahydrofuran, toluene, xylene dimethyl sulfoxide, N,
N-dimethylformamide, N-methylpyrrolidone, 1,3
-Dimethyl-2-imidazolidinone and the like.
Among them, polar solvents such as N, N-dimethylformamide and dimethylsulfoxide are preferred.

Examples of the condensing agent include sodium hydroxide, potassium hydroxide, sodium amide, sodium hydrogen and sodium methylate, and alcoholates such as potassium tert-butoxide.

The reaction temperature can be selected over a wide range from about 0 ° C to about 100 ° C. Preferably it is 10 to 80 degreeC.

The compound [II] used according to the present invention uses a corresponding quaternary phosphonium salt, for example, a triphenylphosphonium salt, instead of a phosphorus compound, and is used in Wittig.
It is obtained by condensing with an aldehyde compound [III] via the phosphorylene step by the method of ig). These styryl compounds may be used alone or as a mixture.

Examples of the constitution of an electrophotographic photosensitive member using the styryl compound of the present invention are schematically shown in FIGS.

FIG. 1 shows a photoreceptor in which a photosensitive layer (4) in which a photoconductive material (3) and a charge transport material (2) are mixed with a binder is formed on a substrate (1). The styryl compounds of the invention have been used.

FIG. 2 shows a function-separated type photoreceptor having a charge generation layer (6) and a charge transport layer (5) as a photosensitive layer. The charge transport layer (5) is formed on the surface of the charge generation layer (6). I have. The charge transport layer (5) contains the styryl compound of the present invention.

FIG. 3 shows a function-separated type photoreceptor having a charge generation layer (6) and a charge transport layer (5) as in FIG. 2, but the surface of the charge transport layer (5) is opposite to FIG. A charge generation layer is formed.

FIG. 4 shows that the surface protective layer (7) is further provided on the surface of the photoreceptor of FIG. 1, and the photosensitive layer (4) is separated into a charge generation layer (6) and a charge transport layer (5). It may be a function separated type.

FIG. 5 shows that an intermediate layer (8) is provided between the substrate (1) and the photosensitive layer (4). The intermediate layer (8) improves the adhesiveness, the coating property, and protects the substrate. Can be provided for improving the charge injection property from the substrate to the photoconductive layer. As the intermediate layer, a polyimide resin, a polyester resin, a polyvinyl butyral resin, casein, or the like may be used. In the photoconductor of this embodiment, the photosensitive layer may be of a function-separated type.

The electrophotographic photoreceptor of the present invention is prepared by dissolving or dispersing a styryl compound represented by the general formula [I] in a suitable solvent together with a binder, and if necessary, a photoconductive material and an electron withdrawing compound, or a sensitizing dye. And a coating solution obtained by adding other pigments onto a conductive substrate, followed by drying to form a photosensitive layer having a thickness of usually 5 to 30 μm, preferably 6 to 20 μm.

Specifically, the charge separation layer and the charge transport layer are laminated on the conductive support, and the function-separated type photosensitive member having the same configuration as the photosensitive member in FIG. 2 described above is formed on the conductive support. Vacuum deposition of the charge generation material, or, if necessary, an appropriate solvent or, if necessary, a coating solution prepared by dispersing in a solution in which a binder resin is dissolved, and drying to form a charge generation layer,
A solution obtained by dissolving a styryl compound and a binder resin as a charge transport material in a suitable solvent is applied thereon and dried to form a charge transport layer. In the case of performing vacuum deposition, phthalocyanines such as metal-free phthalocyanine, titanyl phthalocyanine, and aluminum chlorophthalocyanine are used. When dispersing, for example, a disazo pigment is used. At this time, the thickness of the charge generation layer is 4 μm or less, preferably 2 μm or less, and the thickness of the charge transport layer is 3 to 30 μm, preferably 5 to 20 μm. The ratio of the styryl compound in the charge transport layer is from 0.02 to 2 parts by weight, preferably from 0.03 to 2 parts by weight, per part by weight of the binder resin.
Preferably it is 1.3 parts by weight. Further, another charge transporting agent may be combined. In the case of a polymer charge transporting material that can be used as a binder itself, other binders may not be used. The configuration of the photoreceptor is the third
Similarly to the photoreceptor shown in the figure, a configuration in which a charge transport layer is formed on a conductive support and a charge generation layer is laminated thereon may be employed.

The dispersion type photoreceptor having a photoconductive layer formed on a conductive support and having the same configuration as the photoreceptor of FIG. 1 described above is obtained by dissolving fine particles of a photoconductive material in a styryl compound and a binder resin. It is obtained by dispersing in a solution, applying this on a conductive support, and drying to form a photoconductive layer. At this time, the thickness of the photoconductive layer is 3 to 30 μm, preferably 5 to 20 μm.
m is good. If the amount of the photoconductive material to be used is too small, the sensitivity is poor, and if the amount is too large, the chargeability is deteriorated, or the photoconductive strength is weakened, and the amount of the photoconductive material in the photoconductive layer is 0.01 to 2 parts by weight, preferably 0.05 to 1 part by weight per 1 part by weight of the resin, and the ratio of the styryl compound is 0.01 to 2 parts by weight, preferably 0.02 to 1.
2 parts by weight are preferred. Further, it may be used in combination with a polymer photoconductor such as polyvinyl carbazole which can be used as a binder by itself. Further, it may be combined with another charge transporting material, for example, a hydrazone compound.

The charge generating material in the function separation type of the electrophotographic photoreceptor of the present invention and the photoconductive material in the dispersion type are bisazo pigments, triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, cyanine Pigments, styryl formulas, pyrylium dyes, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indathrone pigments, squarylium pigments, phthalocyanines Organic substances such as pigments and inorganic substances such as selenium, selenium / tellurium, selenium / arsenic, cadmium sulfide, and amorphous silicon. Other than this,
Any material that absorbs light and generates charge carriers with extremely high efficiency can be used.

Those usable as binders are electrically insulating, and any of thermoplastic resins, thermosetting resins, photocurable resins, and photoconductive resins known per se can be used. Examples of suitable binder resins include, but are not limited to, saturated polyester resins, polyamide resins, acrylic resins, ethylene-vinyl acetate copolymers, ionically crosslinked olefin copolymers (ionomers),
Thermoplastic binders such as styrene-butadiene block copolymer, polyarylate, polycarbonate, vinyl chloride-vinyl acetate copolymer, cellulose ester, polyimide, styrene resin; epoxy resin, urethane resin, silicone resin, phenol resin, melamine Thermosetting binders such as resins, xylene resins, alkyd resins, and thermosetting acrylic resins; photocurable resins; photoconductive resins such as poly-N-vinylcarbazole, polyvinylpyrene, and polyvinylanthracene. These can be used alone or in combination. It is desirable that these electrically insulating resins have a volume resistance of 1 × 10 ¹² Ω · cm or more when measured alone. More preferred are polyester resin, polycarbonate and acrylic resin.

The electrophotographic photoreceptor of the present invention, together with a binder, halogenated paraffin, polychlorinated biphenyl, dimethylnaphthalene, dibutyl phthalate, a plasticizer such as o-terphenyl, chloranil, tetracyanoethylene, 2,4,7
Electron-withdrawing sensitizers such as trinitro-9-fluorenone, 5,6-dicyanobenzoquinone, tetracyanoquinodimethane, tetrachlorophthalic anhydride, 3,5-dinitrobenzoic acid, methyl violet, rhodamine B, cyanine dye, A sensitizer such as a pyrylium salt or a thiapyrylium salt may be used.

The electrophotographic photoreceptor thus formed may have an adhesive layer, an intermediate layer, and a surface protective layer as necessary as shown in FIGS. 4 and 5 described above.

As a material used for the intermediate layer, polyimide, polyamide, nitrocellulose, polyvinyl butyral, a polymer such as polyvinyl alcohol as it is, or a dispersion of a low-resistance compound such as tin oxide or indium oxide, aluminum oxide, zinc oxide, A deposited film of silicon oxide or the like is suitable.

 The thickness of the intermediate layer is desirably 1 μm or less.

As a material used for the surface protective layer, a polymer such as an acrylic resin, a polyaryl resin, a polycarbonate resin, or a urethane resin as it is, or a material in which a low-resistance compound such as tin oxide or indium oxide is dispersed is appropriate. . Also, an organic plasma polymerized film can be used. The organic plasma polymerized film is appropriately oxygen if necessary,
It may contain nitrogen, halogen, atoms of groups III and V of the periodic table.

 Alternatively, the thickness of the surface protective layer is desirably 5 μm or less.

As described above, the styryl compound of the present invention can be easily produced, and a photoreceptor containing the same can be used as a function-separated type or a dispersed type, and can be combined with various charge generating materials and binder resins. Optionally, other charge transport materials can be added. Therefore, the electrophotographic photoreceptor containing the styryl compound of the present invention is extremely easy to manufacture and has a wide range of use. In addition, the styryl compound effectively prevents photo-fatigue and has excellent repetition characteristics, thereby improving sensitivity and improving surface potential. There will be little change.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Synthesis Example (Compound [4]) 3.76 g of a phosphonate represented by the following formula; 2.96 g of a ketone compound represented by dimethylformamide 3
The mixture was dissolved in 0 ml, and a suspension containing 5 g of potassium ter-butoxide was dropped into 70 ml of dimethylformamide while cooling to 5 ° C. or lower. Then, after stirring at room temperature for 8 hours, the mixture was left overnight. The obtained mixture was added to 900 ml of ice water, neutralized with dilute hydrochloric acid, and after about 30 minutes, the precipitated crystals were filtered. The filtered product was washed with water and further purified by recrystallization with toluene to obtain 60 g of yellow needle crystals. (Yield 84
%) The elemental analysis is as follows.

Example 1 Disazo compound represented by the following general formula (A) 0.45 parts of a polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) and 0.45 parts of the resin were dispersed together with 50 parts of cyclohexanone by a sand grinder. The obtained dispersion of the disazo compound was applied on a 100-μm-thick aluminized mylar using a film applicator so that the dry film thickness became 0.3 g / m ^2, and then dried. A solution prepared by dissolving 70 parts of a styryl compound [4] and 70 parts of a polycarbonate resin (manufactured by K-1300 Teijin Chemicals Ltd.) in 400 parts of 1,4-dioxane was dried on the charge generation layer thus obtained. 16 film thickness
It applied so that it might be set to micrometer, and formed the charge transport layer. Thus, an electrophotographic photosensitive member having a two-layer photosensitive layer was obtained.

The photoreceptor thus obtained was corona-charged at −6 KV using a commercially available electrophotographic copying machine (EP-470Z manufactured by Minolta Camera Co., Ltd.), and the initial surface potential V ₀ (V) and the initial potential were halved. exposure _{E 1/2 (lux · sec} ) taken to, it was measured decay rate of the initial potential when left in a second dark DDR ₁ (%).

Examples 2 to 4 In the same manner as in Example 1, the same configuration was used, except that styryl compounds [6], [8], and [12] were used instead of styryl compound [4] used in Example 1. A photoreceptor was produced.

The thus obtained photosensitive member was measured _{V 0, E 1/2,} DDR 1 in the same manner as in Example 1.

Example 5 Diazo compound represented by the following general formula (B) 0.45 part and 0.45 part of a polystyrene resin (molecular weight: 40000) were dispersed together with 50 parts of cyclohexanone by a sand glider. The dispersion of the obtained disazo compound was added to a thickness of 100.
Using a film applicator, the composition was applied on a micronized aluminized mylar using a film applicator to a dry film thickness of 0.3 g / m ² and then dried. On the charge generation layer thus obtained, 70 parts of a styryl compound [14] and a polyarylate resin (U-
100; manufactured by Unitika Co., Ltd.) A solution prepared by dissolving 70 parts in 400 parts of 1,4-dioxane was applied so that the dry film thickness became 16 μm.
A charge transport layer was formed. Thus, an electrophotographic photoreceptor having a two-layer photosensitive layer was produced.

Examples 6 to 8 The same method as in Example 5 having the same constitution, except that styryl compounds [17], [18] and [21] are used instead of styryl compound [14] used in Example 5 A photoreceptor was produced.

The thus obtained photosensitive member was measured _{V 0, E 1/2,} DDR 1 in the same manner as in Example 1.

Example 9 Copper phthalocyanine (50 parts) and tetranitro copper phthalocyanine (0.2 parts) were dissolved in 98% concentrated sulfuric acid (500 parts) with sufficient stirring and dissolved in water (5,000 parts) to prepare a photoconductive material composition of copper phthalocyanine and tetranitro copper phthalocyanine. After the precipitation, the precipitate was filtered, washed with water, and dried at 120 ° C. under reduced pressure.

10 parts of the photoconductive composition thus obtained was mixed with a thermosetting acrylic resin (Acrydic A405; manufactured by Dainippon Ink Co., Ltd.) 2
2.5 parts, 7.5 parts of melamine resin (Super Beckamine J820; manufactured by Dainippon Ink Co., Ltd.), 15 parts of the above styryl compound [6], and 100 parts of a mixed solvent obtained by mixing methyl ethyl ketone and xylene in the same amount in a ball mill pot. The mixture was dispersed for 48 hours to prepare a photosensitive coating solution, and this coating solution was applied on an aluminum substrate and dried to form a photosensitive layer having a thickness of about 15 μm, thereby producing a photosensitive member.

The thus obtained photosensitive member, the same method as that in Example 1, except V ₀ and subjected to corona charging at _{+ 6KV, E 1/2,} DDR
₁ was measured.

Examples 10 to 12 In the same manner as in Example 9, having the same constitution, except that styryl compounds [8], [14] and [22] are used instead of styryl compound [6] used in Example 9 A photoreceptor was produced.

The thus obtained photosensitive member was measured _{V 0, E 1/2,} DDR 1 in the same manner as in Example 9.

Comparative Examples 1 to 4 In the same manner as in Example 9 and having the same constitution, except that the styryl compound [6] used in Example 9 was replaced with the following compounds (C), (D), (E) and (F) A photosensitive member was produced in the same manner as in Example 9 except that each of the above was used.

The thus obtained photosensitive member was measured _{V 0, E 1/2,} DDR 1 in the same manner as in Example 9.

Comparative Examples 5 to 7 In the same manner as in Example 9 and having the same constitution, except that the following styryl compounds (G), (H) and (I) were used instead of the styryl compound [6] used in Example 9 A photoconductor was prepared in the same manner as in Example 9 except for using the same.

The thus obtained photosensitive member was measured _{V 0, E 1/2,} DDR 1 in the same manner as in Example 9.

V _{0 of} the photoreceptors obtained in Examples 1 to 12 and Comparative Examples 1 to 8,
The measurement results of the E _1/2, DDR ₁ are summarized in Table 1.

As can be seen from Table 1, the photoreceptor of the present invention has a sufficient charge retention ability in both a lamination type and a single layer type, has a small dark decay rate as a photoreceptor can be sufficiently used, and has excellent sensitivity. Is clear from the data.

Further, a repetitive real-photographing test was performed on a photoconductor of Example 9 with a commercially available electrophotographic copying machine (EP-350Z manufactured by Minolta Camera Co., Ltd.) at the time of positive charging. In the final image, a clear image was obtained with excellent gradation and no change in sensitivity, and it was found that the photoreceptor of the present invention had stable repetition characteristics.

Effect of the Invention The photoreceptor of the present invention, by containing the above styryl compound, is excellent in charge transportability, has a stable initial surface potential, has a sufficiently small dark decay rate, and has good chargeability. Have. In addition, there is little carrier trapping, high sensitivity, and little light fatigue.

The electrophotographic photoreceptor obtained by using the compound of the present invention can effectively suppress light fatigue, reduce the surface potential and increase the residual potential, reduce the change in sensitivity when used repeatedly, and stabilize the electrophotographic characteristics. And high sensitivity, a clear image can be obtained.

In addition, styryl compounds are particularly effective as charge transport materials for function-separated photoconductors.

[Brief description of the drawings]

FIGS. 1 to 5 are schematic views of a photoreceptor according to the present invention. FIGS. 1, 4, and 5 show a dispersion type photoreceptor obtained by laminating a photosensitive layer on a conductive support. 2 and 3 show the structure of a function-separated type photoconductor in which a charge generation layer and a charge transport layer are laminated on a conductive support. DESCRIPTION OF SYMBOLS 1 ... Conductive support, 2 ... Charge transport material 3 ... Photoconductive material (charge generation material), 4 ... Photosensitive layer 5 ... Charge transport layer, 6 ... Photoconductive layer 7 ... Surface protection Layer 8, middle layer

Claims (1)

(57) [Claims] 1. A photoreceptor having a photosensitive layer containing a charge generation material and a charge transport material, wherein the charge transport material is a distyryl compound represented by the following general formula [I]: (Wherein, Ar _{1 to} Ar ₂ are independently an alkyl group, an aromatic heterocyclic group which may have a substituent, or a dialkylamino group, a diaralkylamino group, an alkyl group,
Represents an aromatic hydrocarbon group which may have an alkoxy group.
Provided that at least one of Ar _{1 to} Ar ₄ is an aromatic heterocyclic group or an aromatic hydrocarbon group, (Wherein, Ar ₅ and Ar ₆ are an aryl group or a heterocyclic group,
These groups may have a substituent). A represents an alkylene group, an arylene group or a divalent heterocyclic group which may have a substituent. ]