JPS61107354A - Pretreatment of pigment for organic photosensitive body and dispersing method of photosensitive liquid using said pigment - Google Patents

Abstract

PURPOSE:To prevent the flocculation of an electric charge generating pigment and to improve the dispersion efficiency thereof by immersing preliminarily said pigment into a solvent. CONSTITUTION:The immersion stage is executed by putting, for example, the charge generating pigment and solvent into a suitable glass bottle, placing the glass bottle on the sand of a ball mill dispersing machine and dispersing the same at a suitable rotating speed, for example, 80rpm. The immersion time is set in a 6-24 hours range. The immersion liquid dispersed uniformly with the pigment by the immersion process is then incorporated into a binder soln. dissolved in the same solvent as the above- mentioned solvent and is thus subjected to the dispersion treatment. The dispersion stage is used for dispersion of an ordinary photosensitive liquid. Said dispersion is executed by setting adequately the rotating speed and dispersion time in, for example, a homo mixer or ultrasonic dispersion machine. The resultant photosensitive liquid is coated on an aluminum cylindrical drum by various coating methods such as immersion method and blade coating methods. The coating is thereafter dried for one hour at about 100 deg.C, by which the photosensitive drum having the uniform layer thickness of 10-15mum after drying is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for pretreating a pigment for an organic photoreceptor (0, P, C,) and a method for dispersing a photosensitive liquid using the pigment.

(Prior Art) In order to obtain clear electrophotography, an electrophotographic photoreceptor must be uniformly charged. For this purpose, it is essential that the photosensitive layer be formed on the surface of the conductive substrate to be smooth and to have a uniform thickness. Various inorganic and organic photosensitive materials are known for forming the photosensitive layer 1. Among them, the photosensitive layer made of charge-generating pigments and binders can be prepared using an ultrasonic dispersion method or a ball mill method. Alternatively, a dispersion method such as a homomixer method is used. In the ultrasonic dispersion method, a charge-generating pigment is first pre-dispersed in an organic solvent such as toluene in a dispersing machine, and then a binder solution is added thereto for dispersion treatment. However, in this method, the pre-dispersion treatment is performed for a short time of 30 seconds to 1 minute, so the pigment is not sufficiently dispersed in the solvent. Therefore, even if the subsequent binder solution is added and mixed, the pigment cannot be sufficiently dispersed in the binder. In the ball mill method, a charge-generating pigment, a binder, and an organic solvent are simultaneously introduced into a dispersion machine and a dispersion process is performed. However, this method involves mechanical dispersion using stainless steel poles.

If the treatment lasts for a long time, fragments of the stainless steel poles will mix into the dispersion treatment solution, which is undesirable. In the homomixer method, after the charge-generating pigment is dispersed together with a solvent in a dispersion machine, a binder or its solution is added and the dispersion process is continued. However, this method is also a mechanical dispersion process.

Sufficient dispersion cannot be achieved.

In particular, when the above-mentioned dispersion treatment is carried out using a charge transport medium mainly composed of polyvinylcarbazole resin as a binder, the dispersion efficiency of the charge generating pigment into the polyvinylcarbazole resin is extremely poor. This is because polyvinylcarbazole resin has a complex polymer structure with a large π-electron system in the side chain.

This is due to the fact that a large amount of oxygen in the air is originally adsorbed on the surface of the charge-generating pigment.

These adsorbed oxygens do not easily replace charge transport media such as polyvinylcarbazole resins or organic solvents. Therefore, charge-generating pigments cause aggregation.

Polyvinylcarbazole resins having a complex structure are difficult to adsorb onto these surfaces. Such photosensitive liquids have not yet been completely dispersed.

This causes a decrease in the surface potential of the photoconductor and an increase in the residual potential, resulting in a photoconductor with low sensitivity. Furthermore, if the aggregated particles of the charge-generating pigment are mixed with a photosensitive liquid and applied to a conductive substrate to form a photosensitive layer, it causes white spots due to pinholes and background stains due to toner adhesion. In the electrophotographic process, when toner remaining on the photosensitive layer is scraped off by a cleaning blade, etc.
These aggregated particles are also scraped off at the same time, creating depressions in the photosensitive layer. This depression becomes the white spot caused by the pinball in electrophotography. Furthermore, when a portion of the aggregated particles protrudes from the surface of the photosensitive layer, toner adheres around this protrusion, causing background stains.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems of the prior art,
The purpose is to provide a method for pre-treating pigments for organic photoreceptors, which prevents agglomeration of charge-generating pigments and has high dispersion efficiency. Another object of the invention is.

The object of the present invention is to provide a method for dispersing a photosensitive liquid that can form an organic photoreceptor with high sensitivity using the above pigment.

(Means for Solving the Problems) The method for pre-treating pigments for organophotoreceptors of the present invention includes immersing a charge-generating pigment in a solvent capable of dissolving a binder, whereby the above-mentioned The purpose is achieved.

Furthermore, a method for dispersing a photosensitive liquid using the above pigment of the present invention is as follows:
A step of immersing a charge-generating pigment in a solvent capable of dissolving a binder; and a step of dispersing the immersion liquid together with a binder solution previously dissolved in the solvent, thereby achieving the above-mentioned purpose. is achieved.

The present invention is thus characterized in that the charge-generating pigment is immersed in a solvent in advance. As a result, oxygen adsorbed on the surface of the pigment replaces the particles of the solvent, and aggregation of the pigment is prevented. As a result, an immersion liquid is obtained in which the pigment is uniformly dispersed in the solvent.

In the above dipping step, for example, the charge-generating pigment and the solvent are placed in a glass bottle, the glass bottle is placed on the stand of a ball mill dispersion machine, and the rotation speed is adjusted to an appropriate rotational speed.

This is done at 80 rpm. The immersion time is set within the range of 6 to 24 hours. If the soaking time is less than 6 hours.

Dispersion is incomplete and becomes saturated after 24 hours.

The immersion liquid in which the pigment was uniformly dispersed by the above immersion process was 1
Next, it is mixed into a binder solution dissolved in the same solvent as the above solvent and subjected to a dispersion treatment. This dispersion process is used for dispersing ordinary photosensitive liquids.

For example, it is carried out in a homomixer or an ultrasonic dispersion machine by appropriately setting the rotation speed and dispersion time.

The photosensitive liquid thus obtained is applied to a cylindrical drum made of aluminum by various coating methods such as dipping and blade coating. After that, 1 at about 100℃
After drying for several hours, the layer thickness after drying is 10μm to 15μm.
A uniform photoreceptor drum is produced.

As the organic photosensitive liquid prepared by the method for pre-treating pigments for organic photoreceptors and the method for dispersing photosensitive liquids using the pigments of the present invention, all kinds of dispersions for photosensitive layers of organic photoconductors can be used. . The photosensitive layer may be a functionally separated organic photosensitive layer with a layer of charge-generating pigment on the surface of a conductive substrate and a layer of charge-transporting medium thereon, or a dispersion of a charge-generating pigment in a charge-transporting medium on the surface of the substrate. There is an organic photosensitive layer that has a layer of .
(As the charge-generating pigment, all photoconductive organic pigments conventionally used in electrophotographic photoreceptors can be used. For example, perylene pigments, quinacridone pigments, pyranthrone pigments, phthalocyanine pigments, Examples include disazo pigments, trisazo pigments, etc.As the binder, one that itself has charge transport properties is preferably used.
Charge transporting resins such as polyvinylcarbazole may be used alone or in combination with other resins that do not themselves have photoconductivity, such as polyester resins, epoxy resins, polycarbonate resins, acrylic resins, etc.

A resin in which a low-molecular binder such as a hydrazone derivative or a pyrazoline derivative is dispersed is used. others,
A sensitizer such as a Lewis acid or dye, or a leveling agent such as silicone oil is appropriately used in the photosensitive liquid.

As the solvent used in the present invention, an organic solvent capable of dissolving the binder is appropriately used. For example, benzene, toluene,
Aromatic hydrocarbon organic solvents such as xylene; cyclic ether organic solvents such as tetrahydrofuran and dioxane;
Cyclohexanone.

Ketone organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone; aliphatic hydrocarbon organic solvents such as dichloroethane; or fatty acid ester organic solvents such as ethyl acetate. Used alone or in combination of two or more. be done.

In the present invention, in particular, perylene pigments 1. When a polyvinylcarbazole resin is used as the binder, an organic solvent such as tositeketone, particularly cyclohexanone, is used. Thereby, the perylene pigment is more efficiently dispersed in the solvent. The pigment is present in the solvent at a concentration of 0.1-10%, preferably 0.
．． It is dispersed in a concentration range of 5-5%.

(Example) The present invention will be explained in detail below based on examples.

Example I N-N“-di(3,5-dimethylphenyl)perylene-
10 parts by weight of 3,4,9,1o-tetracarboxylic acid diimide and 150 parts by weight of tetrahydrofuran were placed in a glass bottle, and the bottle was immersed for 24 hours at a rotation speed of 80 rpm using a ball mill stand to pre-treat the pigment.

Next, poly-N-vinylcarbazole (Rubican M-1
The above immersion liquid was added to a solution consisting of 100 parts by weight of polyester resin (Byron 200; manufactured by Toyobo Co., Ltd.), 100 parts by weight of polyester resin (Byron 200; manufactured by Toyobo Co., Ltd.), and 1000 parts by weight of tetrahydrofuran, and this was poured into a homomixer. 80
Dispersion was carried out for 20 minutes at a rotation speed of rpm.

A uniformly dispersed photosensitive liquid was obtained.

The photosensitive liquid thus obtained was coated onto an 80 μm thick aluminum plate using a blade coater.
A heat treatment was performed at .degree. C. for 1 hour to produce a photosensitive plate having a photosensitive layer thickness of 12 .mu.m.

Next, the sensitivity and charge amount of the photosensitive plate prepared in this way were measured using an electrostatic paper analyzer (
(manufactured by Kawaguchi Electric). The measurement was carried out in measurement mode 5tat2; applied voltage +6.0 kvolt;
The test was carried out under a white tungsten lamp with an irradiation light of 301 ux. Regarding sensitivity, half-decreased exposure amount (lux −
5ec) was used. The measurement results are shown in the table below.

A photosensitive plate was prepared in the same manner as in Example 1 except that 150 parts by weight of cyclohexanone was used as a solvent in the pigment pretreatment step of Example 1. The sensitivity and charge amount were measured. The results are shown in the table below.

Calibration stop No pre-treatment of the pigment as in the above examples.

N-N'-di(3,5-dimethylphenyl)perylene-
1 part by weight of 3,4,9,10-tetracarboxylic acid diimide)'10, 100 parts by weight of poly N-vinylcarbazole, 10 parts by weight of polyester resin, and 1 part by weight of tetrahydrofuran.
Put 50 parts by weight into a stainless steel ball mill at the same time.
A photosensitive solution was prepared by performing dispersion for 24 hours at a rotational speed of rpm. A photosensitive plate was prepared using the obtained photosensitive liquid in the same manner as in Example 1, and the sensitivity and charge amount of this photosensitive plate were measured. The results are shown in the table below.

(Effects of the Invention) According to the present invention, as described above, by treating the pigment with an organic solvent in advance, the photosensitive liquid obtained by the subsequent dispersion treatment exhibits extremely good dispersion efficiency. A photoreceptor obtained by applying this photoreceptor to a conductive substrate can exhibit a significantly high degree of irradiation. In particular, when a perylene pigment is used as the pigment, a photosensitive liquid with extremely high dispersion efficiency can be obtained by selecting cyclohexanone as the organic solvent. Further, since there are no aggregated particles of pigment in this photosensitive liquid, the resulting photoreceptor does not have white spots due to pinholes or background stains due to toner adhesion.

that's all

Claims (1)

[Scope of Claims] 1. A method for pre-treating a pigment for an organic photoreceptor, which includes immersing a charge-generating pigment in a solvent that can dissolve a binder. 2. The pretreatment method according to claim 1, wherein the charge-generating pigment is a perylene pigment. 3. The pretreatment method according to claim 1, wherein the binder is a charge transport medium mainly composed of polyvinylcarbazole resin. 4. Claim 1, wherein the solvent is at least one of an aromatic hydrocarbon organic solvent, a cyclic ether organic solvent, a ketone organic solvent, a fatty acid ester organic solvent, and an aliphatic hydrocarbon organic solvent. Pretreatment method described in Section. 5. The pretreatment method according to claim 4, wherein the pigment is dispersed in the solvent at a concentration of 0.1 to 10%. 6. The pretreatment method according to claim 4, wherein the solvent is a ketone organic solvent. 7. The pretreatment method according to claim 1, wherein the pigment is immersed in the solvent for 6 to 24 hours. 8. Dispersion of a photosensitive liquid, which includes a step of immersing a charge-generating pigment in a solvent capable of dissolving a binder; and a step of dispersing the immersion liquid together with a binder solution previously dissolved in the solvent. Method. 9. The method for dispersing a photosensitive liquid according to claim 8, wherein the charge-generating pigment is a perylene pigment. 10. The method for dispersing a photosensitive liquid according to claim 8, wherein the binder is a charge transport medium mainly composed of polyvinylcarbazole resin. 11. Claim 8, wherein the solvent is at least one of an aromatic hydrocarbon organic solvent, a cyclic ether organic solvent, a ketone organic solvent, a fatty acid ester organic solvent, and an aliphatic hydrocarbon organic solvent. Dispersion method of photosensitive liquid as described in section. 12. The dispersion method according to claim 11, wherein the pigment is dispersed in the solvent at a concentration of 0.1 to 10%. 13. The method for dispersing a photosensitive liquid according to claim 11, wherein the solvent is a ketone organic solvent. 14. The method for dispersing a photosensitive liquid according to claim 8, wherein the pigment is immersed in the solvent for 6 to 24 hours.