JP2659561B2 - Electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photosensitive member containing a novel styryl compound.

(B) Prior Art and Problems 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. Have been. 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 thermal stability in selenium photoreceptors, deterioration of characteristics due to crystallization, difficulty in production, etc., and in the case of cadmium sulfide, moisture resistance,
In contrast to the situation where it is not always possible to be satisfied due to durability, industrial waste treatment problems, etc.
Organic materials have good film-forming properties and excellent flexibility,
It has advantages such as light weight, good transparency, and easy design of a photoreceptor for a wide range of wavelengths by a suitable sensitization method.

By the way, the photoreceptor used in electrophotographic technology is
In general, the following are required as basic properties. That is, (1) high chargeability with respect to corona discharge in a dark place, (2) little leakage (dark decay) of the obtained charged charge in a dark place, and (3) charge by light irradiation. Dissipation of charge (light decay) is rapid, and (4) residual charge after light irradiation is small.

However, to date, much research has been conducted on photoconductive polymers such as polyvinyl carbazole as organic photoconductive materials, but these have not always had sufficient film properties, flexibility, and adhesiveness. It is difficult to say that the photoconductor has sufficient basic properties as a photoconductor.

On the other hand, as for the organic low-molecular-weight photoconductive compound, a photoconductor having excellent mechanical strength such as film properties, adhesion, and flexibility can be obtained by selecting a binder and the like used for forming the photoconductor. Although possible, 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 generation function and a carrier transport 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. Has been advanced.

(C) Object of the Invention As described above, various improvements have been made in the preparation of an electrophotographic photoreceptor. However, the basic properties required for the photoreceptor and the high durability and the like are required. The one that satisfies the demand has not yet been sufficiently obtained.

An object of the present invention is to provide an electrophotographic photosensitive member having high sensitivity and high durability. In particular, the photoreceptor of the present invention
An object of the present invention is to provide a photoreceptor which has a high charging characteristic, hardly causes a decrease in photosensitivity even when used repeatedly, and has a stable charging potential.

(D) Constitution of the Invention As a result of research on a photoconductive substance having high sensitivity and high durability, the present inventors have found that a novel styryl compound represented by the following general formula (I) is effective. The present invention has been found.

(Wherein R ₁ and R ₂ may be the same or different and represent a hydrogen, an alkyl group, an aryl group or a styryl group which may have a substituent, and at least one is an aryl group or a styryl group. R ₃ represents an alkyl group, an aralkyl group or an aryl group which may have a substituent, and R ₄ and R ₅ may be the same or different and have a hydrogen atom, an alkyl group or a substituent. Represents a benzyl group or a phenyl group, and R ₆ represents hydrogen, an alkyl group, an alkoxy group, or a halogen.) Here, specific examples of the R ₁ and R ₂ substituents include a hydrogen atom, a methyl group, and an ethyl group. Groups, n-propyl group, isopropyl group, butyl group, and other alkyl groups, phenyl group, naphthyl group, anthryl group, tolyl group, xylyl group, chlorophenyl group, methoxyphenyl group, bromophenyl group, ethoxyphenyl group An aryl group and a substituted aryl group such as a methylnaphthyl group, a methoxynaphthyl group, and a chloronaphthyl group are substituted with a styryl group, a p-chlorostyryl group, a p-methoxystyryl group, and a substituted styryl group such as a p-methylstyryl group; _{3 As a} substituent, methyl group, ethyl group, n-
Alkyl groups such as benzyl, phenylethyl, naphthylmethyl, methylbenzyl, ethylbenzyl, chlorobenzyl, methoxybenzyl, methoxyphenylethyl, etc. And a substituted aralkyl group, a phenyl group, a naphthyl group, a tolyl group, a xylyl group, a chlorophenyl group, a methoxyphenyl group, a substituted aryl group such as a methylnaphthyl group, R ₄ and R ₅ Atom, alkyl group such as methyl group, ethyl group, propyl group, benzyl group, chlorobenzyl group, substituted benzyl group such as methylbenzyl group, phenyl group, methoxyphenyl group, tolyl group, substituted phenyl group such as chlorophenyl group; Group represented by R ₆ substituent such as hydrogen atom, methyl group, ethyl group, etc. Examples include an alkoxy group such as an alkyl group, a methoxy group and an ethoxy group, and a halogen atom such as chlorine and bromine.

These styryl compounds represented by the general formula (I) can be produced by the method of the following synthesis examples.

Synthesis Example (1) (Exemplified Compound No. 1) 6 g of diethylbenzhydrylphosphonate and N-β-methallyl-diphenylamine-4-carboxaldehyde
5 g was dissolved in DMF (45 ml), and potassium-tert.
-Add 3.4 g of butoxide. Stir at room temperature for 5 hours. The reaction solution was poured into water, and the precipitated oily substance was extracted with benzene, and the extracted oily substance was subjected to column chromatography to obtain a target compound. Solid with yellow fluorescence. 85 ° -87 ° C., yield 2.0 g.

The structure of this compound was confirmed by NMR. FIG. 1 shows the infrared absorption spectrum of this compound.

Synthesis Example (2) (Exemplified Compound No. 8) 3 g of α-naphthylmethyl-diethylphosphonate and N-
2.5 g of β-methallyl-diphenylamine-4-carboxaldehyde was dissolved in 20 ml of DMF, and 2.4 g of potassium-tret-butoxide was added under stirring at room temperature. The reaction is carried out at room temperature for 3 hours, and the reaction solution is poured into water. The deposited yellow solid was collected and recrystallized twice from acetonitrile. 96 ゜ -98 ° C, yield 3.0g.

The structure was confirmed by NMR.

 FIG. 2 shows the infrared absorption spectrum of this compound.

As can be seen from the above synthesis example, the method for synthesizing the present styryl compound involves performing a Wittig reaction in the presence of an alkali using a certain solvent, in which case the double bond of the β-alkenylamino group is It was found that isomerization resulted in the formation of a styryl compound having an enamine structure. This structure is effective as a photoconductor.

Now, the styryl compounds according to the present invention will be exemplified, but the present invention is not limited thereto.

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

Various methods are known for using these styryl compounds as electrophotographic photoreceptors. For example, a photoconductor in which a styryl 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. Alternatively, in the form of a laminated structure composed of a carrier generation layer and a carrier transport layer, the present invention is applied to a carrier generation layer provided mainly with a carrier generation substance having a high carrier generation efficiency, such as a dye or a pigment, on a conductive support. A photoreceptor formed by laminating a styryl compound as a carrier transport layer by dissolving or dispersing in a binder resin by adding a chemical sensitizer or an electron-withdrawing compound as necessary, There is a photoreceptor obtained by laminating a carrier transport layer on a conductive support in reverse, and the present invention can be applied to any case.

As a support for preparing a photoreceptor 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 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 And phenoxy resins. Among them, polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, polyarylate resin, phenoxy resin and the like are excellent in potential characteristics as a photoreceptor.

These resins can be used alone or as a mixture of one or more of them as a copolymer.

On the other hand, when used as a printing plate,
An alkali-soluble binder is required. That is, acidic groups soluble in water or alcoholic alkaline solvents, such as acid anhydrides, carboxyl groups, phenolic hydroxyl groups, sulfonic acid groups, sulfonamide groups, a resin having a sulfonamide group, etc., usually has an acid value of 100 or more. Are preferred. Resins having a high acid value suitable for these uses include, for example, styrene / maleic anhydride, vinyl acetate / maleic anhydride, vinyl acetate / crotonic acid, methacrylic acid / methacrylic acid ester, phenolic resin, methacrylic acid / styrene / Copolymer resins such as methacrylic acid esters.

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 10 times.
If the amount is less than 5 times, the photoconductive compound precipitates in the photosensitive layer or on the surface, and the adhesion to the support is deteriorated. If the amount is more than 5 times, the sensitivity is lowered.

Next, some of the film-forming binder resins used are rigid and have low mechanical strength such as tension, bending, and compression.In order to improve these properties, it is necessary to add a substance that gives plasticity. Become.

These materials include phthalic acid esters (eg, DO
P, DBP, DIDP, etc.), phosphates (eg TCP, TOP
And the like, sebacic esters, adipic esters, nitrile rubbers, chlorinated hydrocarbons and the like. In the case of adding such a substance that imparts plasticity, if added in excess, the potential characteristics will be deteriorated. Therefore, the ratio is preferably 20% or more by weight with respect to the binder resin.

Next, sensitizing dyes added to the photosensitive layer include triphenylmethane dyes represented by methyl violet, crystal violet, ethyl violet, night blue, Victoria blue, etc., erythrosine, rhodamine B, rhodamine 3B, acridine red. B, etc., acridine dyes represented by acridine orange 2G, acridine orange R, flaveosin, etc., thiazine dyes represented by methylene blue, methylene green, oxazine dyes represented by capri blue, Meldora blue, etc. And cyanine dyes, styryl dyes, pyrylium salts, thiapyrylium salts, and squarium salt dyes.

In the photosensitive layer, photoconductive pigments that generate carriers with extremely high efficiency by light absorption include metal-free phthalocyanines, phthalocyanine-based pigments such as phthalocyanines containing various metals or metal oxides, perylene imide, perylene acid Perylene pigments such as anhydrides,
Other examples include quinacridone pigments, anthraquinone pigments, and azo pigments.

Among these pigments, those using bisazo pigments, trisazo pigments, and phthalocyanine pigments with particularly high carrier generation efficiency provide high sensitivity and excellent electrophotographic photoreceptors.

Further, 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 Lewis acid compound include p-chlorophenol, m-chlorophenol, p-nitrophenol,
-Chloro-m-cresol, p-chlorobenzoylacetanilide, N, N'-diethylbarbituric acid, N, N'-
Diethylthiobarbituric acid, 3- (β-oxyethyl) -2-phenylimino-thiazolidone, malonic acid dianilide, 3,5,3 ′, 5′-tetrachloromalonic acid dianilide, α-naphthol, p-nitrobenzoic acid, etc. There is. Further, a certain kind of electron-withdrawing compound can be added as a sensitizer for forming a charge transfer complex by binding to the styryl compound of the present invention and further increasing the sensitizing effect.

Examples of the electron-withdrawing substance include 1-chloroanthraquinone, 1-nitroanthraquinone, 2,3-dichloro-naphthoquinone, 3,3'-dinitrobenzophenone,
4-nitrobenzalmalone nitrile, phthalic anhydride, 3
-(Α-cyano-p-nitrobenzal) phthalide, 2,4,
Examples thereof include 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 styryl 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 conductive support described above,
Dry to produce a photoreceptor. Examples of the coating solvent include halogenated hydrocarbons such as chloroform, dichloroethane, trichloroethane, and trichloroethylene; aromatic hydrocarbons such as benzene, toluene, xylene, and monochlorobenzene; and solvents such as dioxane, tetrahydrofuran, and methylcellosolve acetate alone or A mixed solvent of at least one kind or, if necessary, a solvent such as alcohols, acetonitrile, N, N-dimethylformamide, methyl ethyl ketone and the like can be further used.

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 A polyester film laminated with aluminum foil (Alpet 85 made by Mitsubishi Plastics, film thickness 85μ, aluminum foil thickness 10μ) was used as a support, and the following structural formula 1% by weight of a bisazo pigment represented by
Was applied and dried to form a 0.5 μm-thick film of a carrier-generating substance. Next, Exemplified Compound No. 1
Is 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. Was applied using an applicator to form a carrier transport layer having a dry film thickness of 20 μm.

The laminated electrophotographic photosensitive member thus produced was evaluated for electrophotographic characteristics using an electrostatic recording paper test apparatus (SP-428 manufactured by Kawaguchi Electric).

Measurement conditions: applied voltage -6KV, static No.3. As a result, the light half-life exposure to white light during charging was 2.5 lux-sec, which was a very high sensitivity value. Furthermore was subjected to repeated characterization using the device, 10 ³ times repeated the results of the initial potential of 10 ^third to first initial potential 1050V is 1030V, found to be stable And excellent properties.

Examples 2 to 6 A laminated photoreceptor was prepared in the same manner as in Example 1 except that the styryl compounds shown in Table 1 were used instead of the styryl compounds used in Example 1, and the measurement conditions were the same as in Example 1. And the light half-life exposure amount E 1/2 (Look · sec) and 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)
Was repeated 10 ³ times, and the initial potential Vo (volt) and the light half-life exposure amount E 1/2 are shown in Table 1.

Example 7 A bisazo pigment having the following structural formula was used instead of the pigment used in Example 1. Was used. That is, 1 part by weight of this pigment 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. The pigment dispersion thus obtained was applied on the same support as in Example 1 using an applicator to form a carrier generation layer. The thickness of this thin film was about 0.2μ.

Next, a carrier transporting layer was formed using Exemplified Compound No. 8 in the same manner as in Example 1 to prepare a laminated photoreceptor.
This photoreceptor was evaluated under the same measurement conditions as in Example 1. Vo
Was 810 volts and E 1/2 was 1.8 lux-seconds.

Examples 8 to 12 Laminated photoconductors were prepared in the same manner as in Example 7, except that the styryl compounds shown in Table 2 were used instead of the styryl compounds used in Example 7, and evaluation was performed under the same measurement conditions. .
The results are shown in Table 2.

Example 13 Styrene was placed on an aluminum plate subjected to sandy surface oxidation.
/ n-butyl methacrylate / methacrylic acid copolymer (acid value 185) and Exemplified Compound No. 1 were mixed at a weight ratio of 1.5: 1.
Type copper phthalocyanine in a weight ratio to the styryl compound
10%, dispersed in a ball mill using a dioxane solvent, and applied and dried with a wire bar to prepare a photoreceptor for a printing plate having a thickness of about 4 μm.

The photoreceptor thus prepared was evaluated for electrophotographic characteristics using the above-described electrostatic recording paper test apparatus. Evaluation conditions: Applied voltage -5.5KV, measured with static No.3, the initial potential was 410 volts, the light half-life was 7.5 lux
Seconds.

Further, when the photoreceptor is subjected to an etching treatment with an alkali treatment solution (for example, a 3% triethanolamine, 10% ammonium carbonate, 20% aqueous polyethylene glycol solution having an average molecular weight of 190 to 210) after the toner development treatment, Elutes easily, leaving a toner image. Next, when the plate surface was treated with water containing sodium silicate, a solid printing plate could be obtained.

It was found that the printing plate had a printing durability of over 50,000 sheets by offset printing.

[Brief description of the drawings]

FIG. 1 shows the infrared absorption spectrum of Exemplified Compound No. 1, and FIG. 2 shows the infrared absorption spectrum of Exemplified Compound No. 8.

Claims (1)

(57) [Claims] An electrophotographic photoreceptor characterized in that a styryl compound represented by the following general formula (I) is contained in a photosensitive layer formed on a conductive support. (Wherein R ₁ and R ₂ may be the same or different and represent a hydrogen, an alkyl group, an aryl group or a styryl group which may have a substituent, and at least one is an aryl group or a styryl group. R ₃ represents an alkyl group, an aralkyl group or an aryl group which may have a substituent, and R ₄ and R ₅ may be the same or different and have a hydrogen atom, an alkyl group or a substituent. Represents a benzyl group or a phenyl group, and R ₆ represents a hydrogen, an alkyl group, an alkoxy group, or a halogen.)