JPH0833678B2 - Organic photoconductor for electrophotography - Google Patents

Description

The present invention relates to an electrophotographic organic photoconductor having excellent aging characteristics.

(Prior Art) In an organic photoreceptor for electrophotography, a single layer type photoreceptor in which a charge generating material is dispersed in a charge transporting medium to form a photosensitive layer or a function of the photosensitive layer is a charge generating layer and a charge transporting layer. There is a layered type photoconductor divided into and.

The charge generating material includes, for example, a perylene pigment.
The red perylene pigment has a sensitivity region near 500 to 600 nm, and since this region is close to human visual sensitivity, it is suitable as a charge generation material in terms of spectral characteristics. However, the organic photoreceptor using this perylene pigment as a charge generating material has a large half-exposure amount defined in the field of electrophotography. That is, the sensitivity is low because the initial charge amount decay rate is small due to exposure.

As a perylene pigment having excellent sensitivity, for example, a compound represented by the following formula has been proposed.

However, in the case of an organic photoconductor manufactured using these charge generating materials, when the usual electrophotographic copying process (Carlson process) is repeated, the charging potential decreases and the residual potential after exposure also increases. Therefore, the image density of the copied image becomes low if the organic photoconductor is repeatedly copied. Fogging may occur in the image due to the residual potential.

(Problems to be Solved by the Invention) The present invention is to solve the above-mentioned conventional problems, and it is an object of the present invention to prevent the charging potential from decreasing or the residual potential to increase even after repeated use. Another object is to provide an organic photoconductor for electrophotography, which has excellent aging characteristics.

(Means for Solving Problems) The organic photoconductor for electrophotography of the present invention is represented by the following formula as an electric charge generating material having an average particle size of 0.05 to 0.1 μm and a crystalline state of metastable phase. Contains a perylene pigment,
Thereby, the above object is achieved.

Conventionally known perylene pigments usually have an average particle size of 0.05.
It is smaller than μm. Perylene pigments of such particle size are
Poor dispersibility in a binder resin (eg, polyvinylcarbazole) for organic photoconductor. According to this perylene-based pigment, since secondary aggregation in the resin is strong, a uniform photosensitive layer cannot be formed. Therefore, if copying is performed using the obtained organic photoconductor, image unevenness or the like occurs. Even if the particles are uniformly dispersed by the dispersing operation, the particle size of the perylene-based pigment is too small, so that sufficient image characteristics such as charging potential cannot be obtained. When the average particle size exceeds 0.1 μm, the aging characteristics of the obtained organic photoconductor deteriorate.

The crystalline state of the perylene pigment is a metastable phase. The metastable phase refers to an intermediate state between the α-type perylene pigment and the β-type perylene pigment. An X-ray diffraction chart of the metastable phase perylene pigment is shown in FIG. 1, for example. As a control, α
An X-ray diffraction chart of the perylene type pigment is shown in FIG.
When the crystalline state of the perylene-based pigment is set to the metastable phase in this way, an organic photoreceptor having excellent aging characteristics can be obtained as compared with the α-type or β-type perylene-based pigment.

The perylene-based pigment used in the organic photoreceptor of the present invention is
For example, it is prepared as follows.

A perylene pigment represented by the following formula (N, N'-di (3,5-dimethoxyphenyl) perylene-3,4,9,10-tetracarboxylic acid diimide) is dissolved in sulfuric acid.

By adding this sulfuric acid solution dropwise to ice water, an α-perylene pigment is prepared. The dispersion is filtered, washed with water,
Create a clude. When nitrobenzene or dichloromethane is added to the crude as a solvent, the α-type perylene pigment is converted to β-type. By mixing the solution of the β-type perylene-based pigment in a ball mill, the perylene-based pigment in an intermediate state (metastable phase) between the α-type and the β-type can be obtained (grinding adjustment) by milling in the ball mill. Add methanol to the mixture and filter. The filtered product is dried, then pulverized and classified to obtain a metastable phase perylene-based pigment having an average particle size of 0.05 to 0.1 μm.

The organophotoreceptor of the present invention is a single-layer type photoreceptor, in which the perylene pigment having a mean particle size of 0.05 to 0.1 μm and a metastable phase is dispersed in a charge transport medium together with an appropriate solvent to obtain a conductive material. It is obtained by coating on a substrate. In the case of a laminated type photoreceptor, it is obtained by applying a resin dispersion of the above perylene pigment on a conductive substrate and then further laminating a charge transport medium. As the charge transport medium, all known materials are used, for example, hydrazone derivatives, pyrazoline derivatives, triphenylamine derivatives, polyvinylcarbazole, and binder resins,
There are polyester, polycarbonate, polyurethane, epoxy resin, xylene resin, acrylic resin, and styrene-butadiene copolymer.

(Examples) The present invention will be described below with reference to Examples.

Example 1 N, N'-di (3,5-dimethoxyphenyl) perylene-3,4,9,10-tetracarboxylic acid diimide 1 represented by the following formula
Parts by weight were dissolved in 100 parts by weight of sulfuric acid. 10 parts by weight of this solution was added dropwise to 200 parts by weight of ice water. This was filtered and washed with water to obtain crude. 250 parts by weight of crude was mixed with 1500 parts by weight of nitrobenzene in a ball mill for 48 hours. 1500 parts by weight of methanol was added to the mixed solution and filtered.
The filtrate was vacuum dried at 50 ° C. for 48 hours, then pulverized by a vibration mill and classified to obtain a metastable phase perylene pigment having an average particle diameter of 0.08 μm.

Using this perylene-based pigment, a photosensitive layer coating solution for a single-layer type photoreceptor was prepared with the following formulation.

The above-mentioned perylene pigment 8 parts by weight Poly-N-vinylcarbazole 100 parts by weight 2,3-dichloro-1,4-naphthoquinone 20 parts by weight Phenanthrene 40 parts by weight Vinylidene chloride resin (Saran F310: manufactured by Dow Chemical Company) 10 parts by weight Tetrahydrofuran 1000 parts by weight The above materials were placed in a ball mill and dispersed for 24 hours. This coating solution was applied to an aluminum pipe having an outer diameter of 78 mm and a length of 230 mm and dried at 100 ° C. for 1 hour to obtain a photosensitive layer having a film thickness of 8 μm.

The initial and 1000 of the organophotoreceptor thus obtained
The electrical characteristics after making a copy were measured under the following conditions. An electrophotographic method was used to measure the electrical characteristics.

Process speed 140mm / sec Inflow current value + 60μA Irradiation light intensity 0.92mW / cm ² Light source Halogen lamp Color temperature 300 ° K As a result of measurement, the charge amount was 650V (initial) and 620V (1000V).
After copying one sheet), and residual potential is 30V (initial) and 30V
It was (after copying 1000 sheets).

Example 2 A metastable perylene pigment having an average particle size of 0.06 μm was obtained in the same manner as in Example 1 except that dichloromethane was used instead of nitrobenzene, and the mixing time by a ball mill was 24 hours. .

An organic photoreceptor was produced in the same manner as in Example 1 using this perylene pigment.

The electrical characteristics of the obtained organic photoreceptor were measured in the same manner as in Example 1 at the initial stage and after copying 1000 sheets.

As a result of the measurement, the charge amount is 650 V (initial) and 610 V (1000
After copying one sheet), and residual potential is 30V (initial) and 30V
It was (after copying 1000 sheets).

Comparative Example 1 An organic photoconductor was produced in the same manner as in Example 1 except that a perylene-based pigment having an average particle diameter of 0.08 μm and a metastable-phase perylene-based pigment was replaced with a perylene pigment having an average particle diameter of 0.2 μm. .

The electrical characteristics of the obtained organic photoreceptor were measured in the same manner as in Example 1 at the initial stage and after copying 1000 sheets.

As a result of the measurement, the charge amount is 650V (initial) and 440V (1000
After copying one sheet), and residual potential is 30V (initial) and 50V
It was (after copying 1000 sheets).

Comparative Example 2 An organophotoreceptor was produced in the same manner as in Example 1 except that a perylene-based pigment having an average particle diameter of 0.08 μm was used in place of the metastable-phase perylene-based pigment. .

When ordinary copying was performed using this organic photoreceptor, image unevenness was observed in the copied image.

Comparative Example 3 An organophotoreceptor was produced in the same manner as in Example 1 except that an α-type perylene pigment was used in place of the metastable phase perylene pigment.

The electrical characteristics of the obtained organic photoreceptor were measured in the same manner as in Example 1 at the initial stage and after copying 1000 sheets.

As a result of the measurement, the charge amount is 650V (initial) and 470V (1000
After copying one sheet), and residual potential is 30V (initial) and 55V
It was (after copying 1000 sheets).

Comparative Example 4 An organophotoreceptor was produced in the same manner as in Example 1 except that a β-type perylene pigment was used instead of the metastable phase perylene pigment.

The electrical characteristics of the obtained organic photoreceptor were measured in the same manner as in Example 1 at the initial stage and after copying 1000 sheets.

As a result of the measurement, the charge amount is 650V (initial) and 450V (1000
After copying one sheet), and residual potential is 30V (initial) and 50V
It was (after copying 1000 sheets).

As is clear from the examples and comparative examples, the average particle size is 0.
The electrophotographic organic photoreceptor of the present invention using the perylene-based pigment in the metastable phase state of 05 to 0.1 μm has a high charging potential even after 1000 copies. The value of the residual potential does not become higher than that at the initial stage. Organophotoreceptors using perylene pigments with an average particle size of 0.2μm or perylene pigments that are not metastable, such as α-type or β-type, have a lower charging potential after the 1000th copy than in the initial stage. The residual potential becomes high.
With a perylene pigment having an average particle size of 0.02 μm, image unevenness occurs in the copied image.

(Effect of the Invention) Since the organic photoreceptor for electrophotography of the present invention thus contains the metastable phase perylene pigment having an average particle diameter of 0.05 to 0.1 μm, it has excellent aging characteristics. Even if this organic photoreceptor is repeatedly used, the charging potential does not decrease and the residual potential does not increase. As a result, if a copy is made using this organic photoreceptor, a clear copy image without fog can be obtained. No image unevenness occurs.

[Brief description of drawings]

FIG. 1 is a graph showing X-ray diffraction of a perylene pigment of the present invention in a metastable crystalline state, and FIG. 2 is a graph showing X-ray diffraction of a similar perylene pigment in an α-type crystalline state. is there.

Claims (1)

[Claims] 1. A charge generation material having an average particle size of 0.05 to 0.
An organophotoreceptor for electrophotography, which contains a perylene-based pigment represented by the following formula and having a crystalline state of 1 μm and a metastable phase.