JPH01173042A - Dispersing method for organic photoconductive particle - Google Patents

Abstract

PURPOSE:To obtain a satisfactory dispersion liquid by executing a wet dispersion in a state that organic photoconductor particles is ground to a prescribed grain diameter in a short time and is converted to a small diameter by dispersing said organic photoconductor particles to be disposed after having brought it to dry grinding in advance in the same dispersing machine. CONSTITUTION:In a pot 1, plural inner plate disks 2 are provided on a shaft 3 in the height direction, only ground mediums 4 and organic photoconductive body grains 5 are thrown into the pot 1, and they are brought to dry grinding by rotating the shaft 3. Subsequently, after a prescribed time has elapsed, a solvent and a binder resin or a solution liquid 6 obtained by melting the binder resin in the solvent in advance are thrown in, and a wet dispersion is executed for a prescribed time by continuing a rotation of the shaft 3. In such a case, at the time when the dry grinding is ended, desirably at the time point when an average grain diameter becomes <=50mum and the electrification quantity becomes >=0.01muC/g, it is shifted to the wet dispersion. In such a way, in a state that the grain diameter has become smaller, the wet dispersion is executed, by which a satisfactory dispersion liquid is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for dispersing organic photoconductor particles used in the production of electrophotographic photoreceptors.

[Conventional technology]

An electrophotographic photoreceptor has a basic structure in which a photosensitive layer is formed on a conductive substrate. As a photoconductive material for forming this photosensitive layer, selenium has conventionally been commonly used, and other inorganic photoconductive materials such as cadmium sulfide and zinc oxide are also known.

However, in recent years, attempts have been made to improve film formability by using organic photoconductive substances and to increase productivity by producing by coating.

When forming a photoreceptor, organic photoconductor particles (ffin material) are used as a dispersant in a solvent, and if necessary, a binder resin is further added, and after dispersing the face material 4 in the dispersion, conductive It is coated on a substrate having a

Regarding the above dispersion, JP-A-58-194036.60
-29753.60-61756.60-136747
As shown in the above publication, it is known to use a sand grinder, attritor, kneader, ball mill, etc.

[Problems to be Solved by the Invention] However, in the conventional dispersion method, particles are introduced into a dispersion liquid from the beginning and wet dispersion is performed, and therefore the dispersion efficiency (degree of dispersion) is low.

When a photoreceptor was manufactured using such a dispersion, its electrophotographic properties were insufficient.

Therefore, the main object of the present invention is to provide a dispersion method that provides a high degree of dispersion and a good dispersion state.

[Means for solving problems]

The above object is achieved by dry-pulverizing the organic photoconductor particles to be dispersed in the same disperser and then wet-dispersing them.

[For production]

In the present invention, wet dispersion is not carried out from the beginning, but wet dispersion is carried out after the organic photoconductor particles are dry-pulverized in advance.

If wet dispersion is performed from the beginning, the pigment concentration of the dispersion liquid for forming a photosensitive layer for producing a photoreceptor is quite low, so there is little chance that the particles will be crushed or ground by the stirring blade. On the other hand, in the present invention, since dry pulverization is performed in advance, the particles are pulverized to a certain particle size in a short time. Thereafter, wet dispersion is performed in a state where the diameter is reduced, so a short dispersion time is sufficient.

On the other hand, with dry grinding, particles are trapped in the grinding media, making it appear as if the grinding media were coated with particles. At this time, the particles are charged by friction with the grinding media, and when wet-dispersed in this state, a repulsive force between the particles acts in the dispersion liquid, causing the particles to separate from each other, thereby improving dispersibility.

By the way, prior to wet dispersion, dry pulverization may be performed using a pulverizer separate from the dispersion machine, but this not only increases the equipment cost due to the need for a separate pulverizer for dry pulverization, but also requires the use of the dispersion machine. During the transfer process, the amount of charge decreases due to separation from the grinding media, and dispersibility becomes insufficient.

[Specific structure of the invention]

The present invention will be explained in more detail below.

For dry grinding and dispersion in the present invention, all known dispersing machines such as sand grinders, attritors, kneaders, and ball mills can be used.

FIG. 1 shows an example of dispersion in a sand grinder. In this sand grinder, a circular disk 2 is installed in a pot l and is attached to a plurality of shafts 3 in the height direction.

In such a dispersing machine, first, only the grinding media (sand) 4 and organic photoconductor particles 5 are placed in a pot 1, and the shaft 3 is rotated to perform dry grinding. Next, after a predetermined period of time, a solvent and a binder resin, or a solution 6 in which the binder resin is dissolved in a solvent in advance, are introduced, and the shaft 3 is
continue to rotate for a predetermined period of time to achieve wet dispersion.

FIG. 2 shows an example of an attritor, in which a stirring rod 2A is integrated into the shaft 1 instead of a disk, and similar dry grinding and dispersion is possible.

Incidentally, the degree or time of dry pulverization can be determined as appropriate, but at the end of dry pulverization, the average particle size is 5.
It is desirable to shift to wet dispersion when the particle size becomes 0 μm or less and the amount of charge becomes 0.01 μC/g or more.

The thus obtained dispersion liquid is coated onto a conductive substrate to form a photoreceptor.

The photoreceptor to be finally obtained by employing the present invention is a single-layer photoreceptor in which organic photoconductor particles (pigments) are dispersed in a charge transport material as a charge generation material on a conductive substrate. and a functionally separated photoreceptor in which a charge transporting material layer is formed on a conductive substrate and a charge generating material layer is formed thereon.

In any case, the organic photoconductor particles according to the present invention used as a charge generating material include azo pigments, anthanthrone pigments, perylene pigments, phthalocyanine pigments,
Quinacridone pigments, cyanine pigments, biryllium pigments, thiobyriliu J pigments, indigo pigments, scaric acid pigments, polycyclic bovine non-based pigments, and the like can be used.

As pigment dispersants, alcohol solvents such as methanol, ethanol, and isopropyl alcohol, acetone,
Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, aromatic solvents such as benzene, toluene, xylene, and chlorobenzene, DMF, D
Various solvents such as MAC can be used. .

Binder resins include polyvinyl butyral, formal resin, polyamide resin, polyurethane resin, cellulose resin, polyester resin, polysulfone resin,
Polycarbonate resin, acrylic resin, styrene resin, etc. are used.

When constructing a functionally separated photoreceptor, the charge generation layer can be formed by coating the above dispersion directly on a conductive substrate or on an intervening adhesive layer, and a charge transport layer is formed on the charge generation layer. Formed by coating. It is also possible that the charge generation layer is coated on the charge transport layer. The thickness of the charge generation layer is 5μ or less, preferably 0.5μ or less. O1~1μ
It is desirable to form a thin film layer with a thickness of . Most of the incident light is absorbed by the charge generation layer to generate a large amount of charge, and the generated charge carriers need to be injected into the charge transport layer without being deactivated by recombination or trapping. Thickness is preferred.

Coating is done by dip coating method, spray coating method,
spinner coating method, bead coating method, Meyer bar coating method, blade coating method,
This can be carried out using a coating method such as a roller coating method or a curtain coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying can be carried out at a temperature of 30 to 200° C. for a period of 5 minutes to 2 hours, either stationary or with ventilation.

The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving and taking charge carriers injected from the charge generation layer in the presence of an electric field, and transporting these charge carriers to the surface. have. At this time, as described above, this charge transport layer may be laminated on or under the charge generation layer. However, it is desirable that the charge transport layer is laminated on the charge generation layer.

The material for transporting charge carriers in the charge transport layer (hereinafter simply referred to as charge transport material) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The term "electromagnetic waves J" as used herein includes a broad definition of "light rays" including T-rays, X-rays, ultraviolet rays, visible light, near-infrared rays, infrared rays, far-infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both trap each other, resulting in a decrease in sensitivity.

As the charge transport material, any known material can be used, and examples thereof include hydrazone derivatives, pyrazoline derivatives, triphenylamine derivatives, polyvinylcarbazole, and the like.

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can also be used.

Further, these charge transport materials can be used alone or in combination of two or more.

When the charge transport material does not have film-forming properties, a film can be formed by selecting an appropriate binder. Examples of resins that can be used as binders include acrylic resin,
polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer,
Insulating resins such as acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formal, polysulfone polyacrylamides, polyamides, chlorinated rubber, or organic photoconductive polymers such as poly-N-vinyl rubadur, polyvinylanthracene, polyvinylpyrene, etc. Can be done.

As the conductive substrate, materials that are themselves conductive can be used, such as aluminum, aluminum platinum, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum. , as well as aluminum, aluminum alloy,
Plastics (e.g., polyethylene, polypropylene,
Polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluorinated ethylene, etc.), conductive particles (e.g. carbon black, silver particles, etc.) coated on plastic snacks with a suitable binder, conductive particles coated with plastic or paper It can be used for substrates impregnated with conductive polymers, plastics containing conductive polymers, etc.

A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer.

〔Example〕

Next, the effects of the present invention will be clarified by examples.

(Example 1) After dry pulverization, wet dispersion was performed according to the following recipe.

<Formulation> - Organic photoconductor particles of formula (1) double layer part/polycarbonate 1 part by weight/MEK
The dispersion machine using 250 parts by weight was a ball mill, the shaft rotation speed was 7 Orpm, dry grinding was carried out for 24 hours, and wet dispersion was carried out for 48 hours.

(Comparative Example 1) The procedure was the same as in Example 1 except that wet dispersion was performed for 72 hours from the beginning without dry pulverization.

(Example 2) With the same formulation as Example 1, 30
While rotating at 0 rpm, dry pulverization was performed for 10 minutes and wet dispersion was performed for 34 hours.

(Comparative Example 2) Wet dispersion was carried out for 3 hours from the beginning without dry grinding.
The procedure was the same as in Example 2 except that O minutes was carried out.

<Results> For each of the above sides, the viscosity as an indicator of the degree of dispersion was measured using an "E-type viscometer" according to the dispersion time, and the results are shown in Figures 1 and 2. Ta. Further, the average particle size after completion of dispersion was measured using rCAPA-500J manufactured by Horiba, Ltd., and the charged stitch was further measured using a blow-off type Faraday gauge, and the results shown in Table 1 were obtained.

Table 1 [Effects of the Invention] As described above, according to the present invention, it is possible to obtain a dispersion liquid with an increased degree of dispersion and a good dispersion state.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams of dispersion device examples, and FIGS. 3 and 4 are graphs showing viscosity changes in Examples and Comparative Example 1 over time of pulverization. 2... Disk, 2 people... Stirring rod, 4...
- Grinding media, 5... Organic photoconductor particles, 6...
Lysis solution.

Claims (3)

[Claims] (1) A method for dispersing organic photoconductor particles, which comprises dry-pulverizing the organic photoconductor particles to be dispersed in advance in the same dispersion machine, and then performing wet dispersion. (2) The dispersion method according to item 1, in which particles with an average particle size of 50 μm or less are produced by dry grinding. (3) Dry grinding reduces the charge amount of particles by 0.01μC/
A dispersion method for the first term that is equal to or greater than g.