JPH0157896B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and more particularly to a novel electrophotographic photoreceptor having a photosensitive layer containing an amorphous bisazo compound.

Conventionally, inorganic photoreceptors having a photosensitive layer containing an inorganic photoconductive compound such as selenium, zinc oxide, or cadmium sulfide as a main component have been widely used as electrophotographic photoreceptors. However, these methods are not necessarily satisfactory in terms of sensitivity, thermal stability, moisture resistance, durability, etc., and in recent years, organic photoreceptors having photosensitive layers mainly composed of various organic photoconductive compounds have been developed. Research is being actively conducted.

In particular, attempts have been made to develop organic photoreceptors with higher performance by assigning carrier generation and carrier transport functions to different substances. Many studies have been conducted on such so-called functionally separated electrophotographic photoreceptors because each material can be selected from a wide range and a photoreceptor with arbitrary performance can be produced relatively easily. Ta.

A large number of compounds have been proposed as carrier generating substances in functionally separated electrophotographic photoreceptors. As, JP-A-47-37543
Publication No., JP-A-54-21728, JP-A-54-
Publication No. 22834, JP-A-56-116038, JP-A-56-
Publication No. 116040 and the like are already known. However, these bisazo compounds have poor characteristics such as sensitivity, residual potential, and stability during repeated use.
This method is not necessarily satisfactory, and the selection range of carrier transport materials is also limited, so that it does not fully satisfy the wide range of demands of electrophotographic processes.

A problem with using such organic dyes and pigments as photosensitive layers of electrophotographic photoreceptors is that various crystal forms, including amorphous forms, greatly affect the electrophotographic performance of the organic dyes and pigments. For example, JP-A-56
Publication No. 116038 discloses that a crystalline bisazo compound has about five times the sensitivity of an amorphous compound. It is also known that when chlorodiane blue is used as a carrier generating substance, sensitivity is higher in an amorphous form than in a crystalline state.

Further, JP-A-51-108847 discloses that a copper phthalocyanine pigment having a specific crystal form among the many crystal forms of the copper phthalocyanine pigment can be used as an active ingredient of an electrophotographic photoreceptor.

As described above, it is difficult to predict the influence of the crystal form of individual organic dyes and pigments on electrophotographic performance, and it is also difficult to control the crystal form.

Control of the crystal form of organic dyes and pigments is described, for example, in U.S. Patent No.
Examples include a method of transforming the crystal form of a copper phthalocyanine pigment using shearing force, as described in JP-A No. 3510721, and a method of treating the pigment with a solvent while grinding it in a ball mill, as described in JP-A-57-35210.

However, no matter which method is used, it is difficult to predict how the crystal form of other organic dyes and pigments will change, and furthermore, it is difficult to predict how the changed crystal form will affect electrophotographic performance. It is even more difficult to predict and can be said to be a property unique to each individual organic dye and pigment.

An object of the present invention is to provide a highly sensitive electrophotographic photoreceptor.

As a result of intensive research to achieve the above object, the present inventors found that a bisazo compound represented by the following general formula [] has a diffraction intensity at 2θ=35° in a powder X-ray diffraction diagram using copper Kα rays. When used as a standard
The maximum value of the diffraction intensity from 2θ = 26° to 2θ = 28° is three times the average value of the diffraction intensity from 2θ = 18° to 2θ = 22°, based on the diffraction intensity at 2θ = 35°. The present invention was completed based on the discovery that when it is in a small amorphous form, it can act as an effective ingredient in photoreceptors.

General formula [] [In the formula, Ar ₁ , Ar ₂ and Ar ₃ represent a substituted/unsubstituted phenylene group, a substituted/unsubstituted naphthylene group,
Examples of substituents include halogen atoms, substituted/unsubstituted alkyl groups, and substituted/unsubstituted alkoxy groups. R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom or a cyano group. However, at least one of R ₁ , R ₂ , R ₃ and R ₄ represents a cyano group.

A is , and Ar ₄ represents a substituted or unsubstituted aromatic carbocyclic group or a substituted or unsubstituted aromatic aromatic heterocyclic group.

Z represents an atomic group necessary to constitute a substituted/unsubstituted aromatic carbocycle or a substituted/unsubstituted aromatic heterocycle.

Preferred substituents for Ar ₁ , Ar ₂ , Ar ₃ , and Ar ₄ include halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms, alkyl groups having 1 to 4 carbon atoms, and 1 to 4 carbon atoms. It represents an alkoxy group or a trifluoromethyl group, and more preferred alkyl groups include a methyl group and an ethyl group, and even more preferred alkoxy groups include a methoxy group and an ethoxy group.

That is, in the present invention, when the bisazo compound represented by the general formula [] is in an amorphous form, an electrophotographic photoreceptor having a photosensitive layer containing the bisazo compound is prepared to achieve high sensitivity, which is the object of the present invention. An electrophotographic photoreceptor can be obtained.

Specific examples of the bisazo compound useful in the present invention represented by the general formula [] include those having the following structural formula, but the bisazo compound of the present invention is not limited thereby.

The above bisazo compounds were obtained by patent application in 1983.
It can be easily synthesized by the method described in No. 169554.

The bisazo compound according to the present invention can be obtained by amorphizing the bisazo compound synthesized in this way.

On the other hand, confirmation of the crystal form of organic dyes and pigments is usually performed using powder
This is done using the line diffraction method. If copper is used as the anticathode of the X-ray tube and nickel is used as the filter, Cu-Kα rays (1.5418 Å) can be extracted, and for example, at 2θ = 26.0°, a diffraction pattern with the interplanar spacing α = 3.4268 Å can be obtained. Become. It is also known that amorphous compounds exhibit a wide range of diffraction patterns between 2θ=10° and 2θ=30°.

The amorphization treatment is carried out by dissolving the bisazo compound in a good solvent and then reprecipitating it with a large amount of a poor solvent. Examples of good solvents include organic primary amines such as propylamine, isopropylamine, butylamine, isobutylamine, sec-butylamine, tert-butylamine, ethylenediamine, isopropanolamine, cyclohexylamine, and ethanolamine, as well as methylamine. , a mixed solvent in which ethylamine is dissolved in an organic solvent, or a solution in which an inorganic base such as sodium acetate, potassium acetate, sodium hydroxide, potassium hydroxide, etc. is dissolved in an organic solvent are preferably used.

As the poor solvent, water, alcohol such as methanol, ethanol, etc. are preferably used.

The degree of crystallinity of the bisazo compound obtained by such amorphization treatment was examined by powder X-ray diffraction method.

The powder X-ray diffraction pattern was obtained using Geigerflex D-6C manufactured by Rigaku Denki Co., Ltd., using copper as the anticathode of the X-ray tube and nickel as the filter.
Measurements were made using −Kα radiation at a tube current of 27 KV, a scanning speed of 1° per minute (2θ), and a time constant of 1 second. Based on the obtained powder X-ray diffraction pattern, the crystallinity (P) of the bisazo compound was defined as follows. Diffraction intensity at 2θ=35° (D ₃₅ )
The average value of diffraction intensity (D 20 ) at 2θ = 20° (18° to 22°) is used as a measure of amorphization, and the average value of diffraction intensity (D ₂₀ ) at 2θ = 27 ± 1° (from 26° to 28°) is used as a measure of crystallization. The maximum value (D ₂₇ ) of the diffraction intensity at ) is taken and the formula P=(D ₂₇
-D ₃₅ )/(D ₂₀ -D ₃₅ ) to evaluate the crystallinity and examine its correlation with electrophotographic performance.

As a result, it has been found that a highly sensitive electrophotographic photoreceptor can be produced using the bisazo compound represented by the general formula [] according to the present invention when it is in an amorphous form.

By utilizing the degree of crystallinity as defined above, it becomes possible to control the crystal form, thus completing the present invention.

In other words, the bisazo compound represented by the above general formula [] has low sensitivity when the degree of crystallinity is high (P≧3), especially when the sensitivity is low in a low electric field, and when used as an electrophotographic photoreceptor, fogging may occur. Cause.
On the other hand, when the bisazo compound with a low degree of crystallinity (P<3) obtained by amorphization treatment is used to produce an electrophotographic photoreceptor, a photoreceptor with high sensitivity can be obtained. High sensitivity in electric field.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the embodiments of the present invention are not limited thereby.

Example 1 Exemplified compound (K-7) was dissolved in an N,N-dimethylformamide solution containing a small amount of butylamine, poured into a large amount of water, and the resulting precipitate was filtered and amorphized. K-7) was obtained.

A layer of vinyl chloride-vinyl acetate-maleic anhydride copolymer "Eslec MF-10" (manufactured by Sekisui Chemical Co., Ltd.) is placed on a conductive support made of aluminum foil laminated on a polyester film.
An intermediate layer of 0.05 μm was provided, and 2 parts by weight of the amorphized exemplified compound (K-7) (crystallinity P = 1.5, whose powder X-ray diffraction pattern is shown in Fig. 1) was added.
A carrier-generating layer was formed by dispersing and mixing a liquid in 140 parts by weight of 2-dichloroethane and applying the solution to a dry film thickness of 0.5 μm.

In addition, P-(N,N-diethylamino)benzaldehyde-1,1-diphenylhydrazone 16 shown in the following structural formula is added as a carrier generating substance.
Weight part and 10 parts by weight of polycarbonate "Panlite L-1250" (manufactured by Teijin Kasei) was dissolved in 90 parts by weight of 1,2-dichloroethane, and this solution was applied to a carrier so that the film thickness after drying was 10 μm. A transport layer was formed to produce an electrophotographic photoreceptor of the present invention.

The electrophotographic properties of this electrophotographic photoreceptor were measured by a dynamic method using an electrostatic copying paper testing device "SP-428 model (manufactured by Kawaguchi Electric Seisakusho)".

The photoreceptor surface of the photoreceptor was charged with a voltage of -6.0KV.
Surface potential V _A when charged for 2.5 seconds, then 5
The surface potential V _I after being left in the dark for a second, then the illuminance of the tungsten lamp light on the photoreceptor surface is
Exposure amount E1/2 (lux・sec) required to irradiate to 35lux and attenuate the surface potential V _I by half,
Exposure amount required to attenuate the surface potential from -500V to -50V E ⁵⁰⁰ ₅₀ (lux・sec) and 30lux・sec
The surface potential V _R after exposure with the exposure amount was determined.

The results were: V _A = -822V V _I = -694V E1/2 = 1.7 lux sec E ⁵⁰⁰ ₅₀ = 3.8 lux sec V _R = OV.

Comparative Example 1 In place of the amorphized exemplified compound (K-7) as a carrier generating substance, an exemplified compound (K-7) whose crystallinity was improved by recrystallization (P=4.0) A comparative photoreceptor was prepared in the same manner as in Example 1, except that a ray diffraction pattern was used.

When this comparative photoreceptor was measured in the same manner as in Example 1, the following results were obtained.

V _A = -742V V _I = -662V E1/2 = 4.1lux・sec E ⁵⁰⁰ ₅₀ = 12.2lux・sec V _R =OV As is clear from the above results, the electrophotographic photoreceptor of the present invention Compared to photographic photoreceptors, it has high sensitivity and is extremely superior.

Example 2 In place of the amorphized exemplified compound (K-7) as a carrier generating substance, the amorphized exemplified compound (K-24) (crystallinity P=1.0 is shown in the powder X in Fig. 3). Example 1 except that a line diffraction diagram was used.
An electrophotographic photoreceptor of the present invention was prepared in the same manner as described above.

When this photoreceptor was measured in the same manner as in Example 1, the following crystals were obtained.

V _A = -750V V _I = -543V E1/2 = 1.7 lux・sec E ⁵⁰⁰ ₅₀ = 3.9 lux・sec V _R = OV Comparative Example 2 Example compound (K-7) that has been amorphized as a carrier generating substance Alternatively, an untreated exemplary compound,
A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that (K-24) (crystallinity P=3.0. Its powder X-ray diffraction pattern is shown in FIG. 4).

When this photoreceptor was measured in the same manner as in Example 1, the following results were obtained.

V _A = -730V V _I = -610V E1/2 = 3.9lux・sec E ⁵⁰⁰ ₅₀ = 11.5lux V _R = OV Comparative Example 3 As a carrier generating substance, an exemplary compound (K -24) (Crystallinity P = 4.4
FIG. 5 shows its powder X-ray diffraction pattern. ) was used to prepare a comparative electrophotographic photoreceptor in the same manner as in Comparative Example 2, and it was evaluated as an electrophotographic photoreceptor.

The results were as follows.

V _A = -640V V _I = -522V E1/2 = 7.1lux・sec E ⁵⁰⁰ ₅₀ = 14.2lux・sec V _R =OV As is clear from the above results, the electrophotographic photoreceptor of the present invention Compared to photographic photoreceptors, it has high sensitivity and is extremely superior.

Example 3 Aluminum was vapor-deposited on a polyester film, the intermediate layer used in Example 1 was provided, and the layer was further amorphized (crystallinity P = 1.3. Figure 6 shows the powder X diffraction pattern. ) Exemplary compound (K-
A carrier generation layer was prepared by dispersing and mixing 1) in 140 parts by weight of tetrahydrofuran and applying the solution to a dry film thickness of 0.5 μm.

Next, 6 parts by weight of 1-phenyl-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline and 10 parts by weight of polyester "Vylon 200" (manufactured by Toyobo Co., Ltd.) were mixed with 90 parts by weight of tetrahydrofuran. The electrophotographic photoreceptor of the present invention was prepared by dissolving this solution in a carrier transport layer and applying the solution to a dry film thickness of 12 μm.

When this photoreceptor was measured in the same manner as in Example 1, the following results were obtained.

V _A = -790V V _I = -540V E1/2 = 1.7 lux・sec E ⁵⁰⁰ ₅₀ = 3.8 lux・sec V _R = OV Example 4 The electrophotographic photoreceptor obtained in Example 1 was used in an electrophotographic copying machine. U-Bix2000R" (manufactured by Konishi Roku Photo Industry Co., Ltd.) was used to copy images, and a copied image faithful to the original, with high contrast and excellent gradation was obtained. Even after repeating this process 20,000 times, the same copy image as the initial one was obtained without any change.

[Brief explanation of drawings]

Figures 1 to 6 show powder X-ray diffraction patterns (Cu-Kα line) of bisazo compounds. The horizontal axis shows 2θ (unit degree) and the vertical axis shows the diffraction intensity (unit is arbitrary).

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor having a photosensitive layer containing a bisazo compound represented by the following general formula [] on a conductive support, wherein the bisazo compound is a powder X-ray using copper Kα rays. In the diffraction diagram, the average value of the diffraction intensity from 2θ=18° to 2θ=22° based on the diffraction intensity at 2θ=35° is 2θ= An electrophotographic photoreceptor characterized in that it is an amorphous type in which the maximum value of diffraction intensity from 26° to 2θ=28° is less than 3 times. General formula [] [In the formula, Ar ₁ , Ar ₂ and Ar ₃ represent a substituted/unsubstituted phenylene group, a substituted/unsubstituted naphthylene group,
Examples of substituents include halogen atoms, substituted/unsubstituted alkyl groups, and substituted/unsubstituted alkoxy groups. R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom or a cyano group. However, at least one of R ₁ , R ₂ , R ₃ and R ₄ represents a cyano group. A is , and Ar ₄ represents a substituted or unsubstituted aromatic carbocyclic group or a substituted or unsubstituted aromatic heterocyclic group. Z represents an atomic group necessary to constitute a substituted/unsubstituted aromatic carbocycle or a substituted/unsubstituted aromatic heterocycle. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains a carrier transporting substance and a carrier generating substance, and the carrier generating substance is an amorphous bisazo compound represented by the general formula [ ]. .