JP2595528B2 - 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 basic functions of the photoreceptor, that is, the generation and transport of charge carriers, are shared by separate substances, resulting in high surface potential, high charge retention, high photosensitivity, and stable repetition characteristics. 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-diethylaluminophenyl) -1,3,4-oxadiazole described in U.S. Pat. No. 3,189,447 has no compatibility with the binder. Low and easy to precipitate crystals. 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 photoconductor having a photosensitive layer containing an electron generating material and a charge transport material, wherein the charge transport material is represented by the following general formula [I]: Wherein Ar ₁ is an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, Ar ₂ is a divalent aromatic hydrocarbon group which may have a substituent, Ar ₃ represents an aromatic hydrocarbon group which may have a substituent, and R ₁ represents an alkyl group, an aralkyl group or an aromatic hydrocarbon group which may have a substituent. However, when R ₁ is an aromatic hydrocarbon group, Ar ₁
Is a substituent Wherein Ar ₄ and Ar ₅ represent an aromatic hydrocarbon group or a heterocyclic group having an aryl group or a heterocyclic group which may have a substituent. And an electrophotographic photosensitive member.

In the present invention, the styryl compound represented by the general formula [I] is used as a charge transporting material for an electrophotographic photoreceptor by utilizing the excellent charge transporting ability of the styryl compound. Further, an electrophotographic photoreceptor which is excellent in electrophotographic characteristics such as residual potential and the like, has little fatigue deterioration even when repeatedly used, and can exhibit stable characteristics can be produced.

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

[8] [9] [Ten] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [twenty one] [twenty two] [twenty three] [twenty four] [twenty five] [26] The styryl compound represented by the general formula [I] is, for example,
The following general formula [II]: [Wherein, Ar ₃ and R ₁ 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. Is condensed with an acrolein compound represented by the following general formula [III] Ar ₂ —CH ＝ CH—Ar ₁₂ CHO [III] wherein Ar ₁ and Ar ₂ have the same meaning as [I]. To be obtained. 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, and 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-imidazolidine and the like. Among them, polar solvents such as N, N-dimethylformamide and methylsulfoxide are preferred.

As the condensing agent, caustic soda, caustic potash, sodium amide, sodium hydrogen and sodium methylate, and alcoholates such as potassium tert-bromide are used.

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 can be 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 photoconductor 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 present 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 comprises a styryl compound represented by the general formula [I] dissolved or dispersed in a suitable solvent together with a binder, and if necessary, a photoconductive material, 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, a function-separated type photoconductor having a charge transport layer and a charge generation layer laminated on a conductive support and having the same configuration as the photoconductor of FIG. 2 described above is provided 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 material 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 to 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.
Is good. If the amount of the photoconductive material to be used is too small, the sensitivity is poor, and if it is too large, the chargeability is deteriorated, or the strength of the photoconductive layer is weakened, and the amount of the photoconductive material in the photoconductive layer is 0.01 to 2 parts by weight, preferably 1 part by weight of resin, preferably
The amount is preferably 0.05 to 1 part by weight, and the ratio of the styryl compound is 1
0.01 to 2 parts by weight, preferably 0.02 to 1.2 parts by weight,
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-separated type and the photoconductive material in the separated type of the electrophotographic photoreceptor of the present invention include bisazo pigments, triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, and cyanine. Pigments, styryl pigments, pyrylium dyes, azo pigments, quinacridone dyes, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indathrone pigments, squarylium pigments, phthalocyanine pigments Organic substances such as pigments and inorganic substances such as selenium, selenium / tellurium, selenium / arsenic, cadmium sulfide, amorphous silicon and the like can be mentioned. 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.

 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]) 3.18 g of a phosphonate represented by the following formula; Dissolve 2.79 g of the aldehyde compound represented by in 30 ml of dimethylformamide and, while heating to 30 to 40 ° C., in 70 ml of dimethylformamide, 5 g of potassium-ter-butoxide
Was added dropwise. 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 acetonitrile to obtain 3.5 g of yellow needle crystals.
(Yield: 82%) 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. The amount of exposure E _1/2 ( ₁ ux · sec) required to perform the measurement was measured, and the decay rate DDR ₁ (%) of the initial potential when left in the dark for 1 second was measured.

Examples 2 to 4 In the same manner as in Example 1 and having the same constitution, except that styryl compounds [5], [6] and [7] are 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 Disazo compound represented by the following general formula (B) 0.45 part and 0.45 part of a polystyrene resin (molecular weight: 40,000) were dispersed together with 50 parts of cyclohexanone by a sand grinder. Thickness of the obtained disazo compound dispersion 10
Using a film applicator on a 0-μm aluminized mylar using a film applicator, the film was applied so as to have a dry film thickness of 0.3 g / m ² and then dried. On the charge generation layer thus obtained, 70 parts of styryl compound [8] and polyarylate resin (U
A solution in which 70 parts of -100 (manufactured by Unitika Ltd.) was dissolved in 400 parts of 1,4-dioxane was applied to a dry film thickness of 16 μm to form a charge transport layer. Thus, an electrophotographic photoreceptor having a two-layer photosensitive layer was produced.

Examples 6 and 7 Photoreceptors having the same constitution as in Example 5 but using styryl compounds [9] and [14] instead of styryl compound [8] used in Example 5 were prepared. did.

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

Example 8 50 parts of copper phthalocyanine and 0.2 part of tetranitro copper phthalocyanine were dissolved in 500 parts of 98% concentrated sulfuric acid while being charged and stirred, and this was poured into 5,000 parts of water 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, melamine resin (Super Beckamine J820; manufactured by Dainippon Ink Co., Ltd.) 7.5 parts, the styryl compound [1
4] 15 parts were put in a ball mill pot together with 100 parts of a mixed solvent in which methyl ethyl ketone and xylene were mixed in the same amount, and dispersed for 48 hours to prepare a photosensitive coating solution. This coating solution was applied on an aluminum substrate and dried. Then, a photosensitive layer having a thickness of about 15 μm was formed to produce 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 9 and 10 Production of photoreceptors having the same constitution as in Example 8 except that styryl compounds [17] and [26] are used instead of styryl compound [14] used in Example 8 did.

The thus obtained photosensitive member was measured _{V 0, E 1/2,} DDR 1 in the same manner as in Example 8.

Comparative Examples 1 to 4 In the same manner as in Example 8, having the same constitution, except that the styryl compound [14] used in Example 8 was replaced by the following compounds (C), (D), (E), and (F) A photosensitive member was produced in exactly the same manner as in Example 8 except that each of the above was used.

Thus the obtained photoreceptors, a V _0, E _1/2 in the same manner as in Example 8, was DDR ₁ were measured.

Comparative Examples 5 to 7 The same configuration as in Example 8, except that the following styryl compounds (G), (H) and (I) were used instead of the styryl compound [14] used in Example 8 A photoreceptor was produced in exactly the same manner as in Example 8 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 8.

V _{0 of} the photoreceptors obtained in Examples 1 to 10 and Comparative Examples 1 to 7,
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, whether it is a laminated type or a single layer type, has a dark decay rate that is small enough to be used as a photoreceptor, and also has a sensitivity. The superiority is clear from the data.

Further, a repetitive real-photographing test was performed on a photoconductor of Example 8 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 effectively suppresses light fatigue, reduces the surface potential and increases the residual potential, reduces the change in sensitivity in repeated use, and stabilizes 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 styryl compound represented by the following general formula [I]: Wherein Ar ₁ is an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent; Ar ₂ is a divalent aromatic hydrocarbon group which may have a substituent; ₃ represents an aromatic hydrocarbon group which may have a substituent; R ₁ represents an alkyl group, an aralkyl group or an aromatic hydrocarbon group which may have a substituent. However, when R ₁ is an aromatic hydrocarbon group, Ar ₁ is a substituent (Ar ₄ and Ar ₅ each represent an aryl group or a heterocyclic group which may have a substituent.)