JPS61107355A - Pretreatment of pigment for organic photosensitive body and dispersing method using said pigment - Google Patents

Abstract

PURPOSE:To prevent the flocculation of an electric charge generating pigment and to improve dispersion efficiency by stirring preliminarily said pigment together with a solvent under the reduced pressure. CONSTITUTION:For example, a perylene pigment as the charge generating pigment 2 to be stirred and, for example, tetrahydrofuran as the solvent 3 are charged through a feed port 111 into a vessel 11 and a cap 114 is closed. Stirring is then executed. The inside of the vessel 11 is evacuated at the same instant. The pressure thereof is set in a 20-50mmHg range. The stirring time is adequately set according to the kind and quantity of the pigment 2 and the solvent 3 to be stirred and the degree of the pressure reduction. The dispersion is recovered after the end of the stirring. The dispersion is then incorporated into a binder soln. dissolved in the same solvent as the above-mentioned solvent and is subjected to the dispersion treatment. The resultant photosensitive liquid is coated on, for example, an aluminum cylindrical drum, by which the photosen sitive drum having the uniform layer thickness of 10-15mum after drying is manufactured.

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 a photosensitive layer. Among these, the photosensitive layer consisting of a charge-generating pigment and a binder is prepared using an ultrasonic dispersion method, a ball mill method, or Dispersion methods such as the homomixer method are used. In the ultrasonic dispersion method,
First, the charge-generating pigment is pre-dispersed in an organic solvent such as toluene in a fractionator, and then a binder solution is added thereto for dispersion. However, in this method, the predispersion process is performed in 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 distributed 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 its side chain, and the surface of the charge-generating pigment inherently adsorbs a large amount of oxygen from the air. to cause.

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. These depressions become white spots due to pinholes 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.

Still another object of the present invention is to provide a method for pre-treating a pigment for an organic photoreceptor, which can be carried out in 9 minutes in an extremely short time, and a method for dispersing a photosensitive liquid using the pigment.

(Means for Solving the Problems) The method for pre-treating pigments for organic photoreceptors of the present invention includes stirring the charge-generating pigment with a solvent capable of dissolving the binder under reduced pressure; The above objective is achieved.

Furthermore, a method for dispersing a photosensitive liquid using the above pigment of the present invention is as follows:
A step of stirring the charge-generating pigment with a solvent capable of dissolving the binder under reduced pressure to obtain a dispersion; and a step of dispersing the dispersion together with a binder solution previously dissolved in the solvent. However, the above objective is thereby achieved. One feature of the present invention is that the charge-generating pigment is stirred together with the solvent in advance under reduced pressure. 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, a dispersion liquid in which the pigment is uniformly dispersed in the solvent is obtained.

The above-mentioned stirring step is carried out in a stirring device 1 as shown in FIG. 3, for example. The stirring device 1 is a closed container 11 made of glass or the like.
and an impeller 12 housed within the container 11. This impeller 12 is driven by a driving means 121. The container 11 has a solution inlet 111, for example. A solution outlet 112 and an exhaust port 113 are provided. For example, the inlet 111 has a lid 114 and an outlet 112.
For example, a valve 115 or the like is arranged. The exhaust port 113 is connected to, for example, a pump for reducing pressure.

In this container 11, as the charge generating pigment 2 to be stirred, 1
For example, a perylene pigment and 1 as the solvent 3, for example, tetrahydrofuran, are introduced from the inlet 111, and the lid 1
Close 14. Next, the impeller 12 is operated by the driving means 121 to perform stirring.

At the same time, the inside of the container 11 is depressurized by a decompression pump (not shown in Figure 1). The pressure is set within the range of 20-50 mHg. The stirring time is appropriately set depending on the type and amount of the pigment 2 and solvent 3 to be stirred, the degree of pressure reduction, etc. 9 Usually, about 3
Set to 0 minutes. After the stirring is completed, the dispersion liquid is recovered by opening the valve 115.

In this way, the pigment from which the adsorbed oxygen has been desorbed is transferred to the solvent IC#.
-CGIkLE□Yoka3, Ah, Eka. , 13:□1 is received. The pigment in the solvent has a concentration of 0.1 to 10%, preferably 0.
．． It is dispersed in a concentration range of 5-5%.

The dispersion liquid in which the pigment is uniformly dispersed by the above stirring process is 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 commonly used for dispersing 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 formed by providing a layer of .

As the charge-generating pigment, all photoconductive organic pigments conventionally used in electrophotographic photoreceptors can be used. Examples include perylene pigments, quinacridone pigments, lanthrone pigments, phthalocyanine pigments, disazo pigments, and trisazo pigments. As the binder, it is preferable to use a binder which itself has charge-transporting properties, such as a charge-transporting resin such as polyvinylcarbazole or other resins which do not themselves have photoconductivity.

A combination of a polyester resin, an epoxy resin, a polycarbonate resin, an acrylic resin, etc., or a resin in which a low-molecular charge transport medium such as a hydrazone derivative or a pyrazoline derivative is dispersed is used. In addition, aggravating agents such as Lewis acids and dyes, or leveling agents such as silicone oil are 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, penzene, 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, particularly when a perylene pigment is used as the charge generating pigment and a polyvinylcarbazole resin is used as the charge transport medium, a ketone organic solvent, particularly cyclohexanone, is used as the organic solvent. Thereby, the perylene pigment is more efficiently dispersed in the solvent.

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

For large-scale operations, 10 parts by weight of N-N-di(3,5-dimethylphenyl)perylene-3,4,9,10-tetracarboxylic acid diimide and 200 parts by weight of tetrahydrofuran were added to the container 11 of the stirring device 1. 3.
The pigment was pretreated by stirring for 30 minutes under a reduced pressure of 80 flHg.

Next, poly-N-vinylcarbazole (Rubican M-1
70; manufactured by BASF) 100 parts by weight, polyester resin (Byron 200; manufactured by Toyobo Co., Ltd.) 10 parts by weight,
The above dispersion was added to a solution consisting of 600 parts by weight of tetrahydrofuran, and this was placed in a homomixer at 80 rpm.
Dispersion was carried out for 20 minutes at a rotation speed of .

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 solution 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.

Example 2 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.

Comparative example No pre-treatment of the pigment as in the above examples.

N-N"-di(3,5-dimethylphenyl)perylene-
3,4,9,10-tetracarboxylic acid diimide 10ui
t part, 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.
Dispersion was performed for 24 hours at a rotational speed of rpm to prepare a photosensitive solution. A photosensitive plate was prepared in the same manner as in Example 1 using the obtained photosensitive liquid, and the sensitivity and charge amount of this photosensitive plate were determined as follows:
It was measured. The results are shown in the table below.

(Hereinafter in the margin) (Effects of the Invention) According to the present invention, by treating the pigment with an organic solvent in advance in this way, the photosensitive liquid obtained by the subsequent dispersion treatment exhibits extremely good dispersion efficiency. Moreover, since one dispersion is carried out within an extremely short period of time, work efficiency is significantly improved. and.

A photoreceptor obtained by coating this photosensitive liquid on a conductive substrate can exhibit extremely high sensitivity. In particular, when a perylene pigment is used as the R material, 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.

4. Simple amount of surface (2) The figure is a sectional view of a main part showing an example of a stirring device embodying the pretreatment method of the present invention.

DESCRIPTION OF SYMBOLS 1... Stirring device, 2... Charge generating pigment, 3... Solvent.

Claims (1)

[Claims] 1. A method for pre-treating pigments for organic photoreceptors, which comprises stirring a charge-generating pigment with a solvent capable of dissolving a binder under reduced pressure. 2. The pretreatment method according to claim 1, wherein the pressure is within a range of 20 to 50 mmHg. 3. The pretreatment method according to claim 1, wherein the charge-generating pigment is a perylene pigment. 4. The pretreatment method according to claim 1, wherein the binder is a charge transport medium mainly composed of polyvinylcarbazole resin. 5. 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. 6. The pretreatment method according to claim 5, wherein the pigment is dispersed in the solvent at a concentration of 0.1 to 10%. 7. The pretreatment method according to claim 5, wherein the solvent is a ketone organic solvent. 8. Stirring the charge-generating pigment with a solvent capable of dissolving the binder under reduced pressure to obtain a dispersion; and dispersing the dispersion together with a binder solution previously dissolved in the solvent. A method for dispersing a photosensitive liquid, including: 9. The method for dispersing a photosensitive liquid according to claim 8, wherein the pressure is within the range of 20 to 50 mmHg. 10. The method for dispersing a photosensitive liquid according to claim 8, wherein the charge-generating pigment is a perylene pigment. 11. The method for dispersing a photosensitive liquid according to claim 8, wherein the binder is a charge transport medium mainly composed of polyvinylcarbazole resin. 12. 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. 13. The dispersion method according to claim 12, wherein the pigment is dispersed in the solvent at a concentration of 0.1 to 10%. 14. The method for dispersing a photosensitive liquid according to claim 12, wherein the solvent is a ketone organic solvent.