JPS6034103B2 - Method for manufacturing photoconductive materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a photoconductive material, in particular a capsule wall film made of a lipophilic polymer in which a sensitizer for zinc oxide is encapsulated on the surface of particles of photoconductive zinc oxide powder. The present invention relates to a method for producing a photoconductive material comprising:

Generally, in forming a copy image by electrophotography, an electrophotographic photoreceptor is mounted on a photoreceptor conveyance device of a copying machine, and a charging process is performed in which the photosensitive layer is charged by corona charging, and a static latent image is formed by image exposure. a development process in which the formed electrostatic latent image is visualized with a developer called toner, a transfer process in which this toner image is transferred onto transfer paper, and a cleaning process for the photosensitive layer after transfer. The wafer is conveyed on a moving path passing through a series of cleaning steps in this order, and is again prepared for the next electrophotographic process consisting of a series of these steps.

Then, a copy image is formed by fixing the toner image on the transfer paper. The photosensitive layer of the electrophotographic photoreceptor used in such electrophotography is composed of various photoconductive materials. Zinc oxide, cadmium sulfide, selenium, and other materials are known as photoconductive materials, but photoreceptors are easy to manufacture and cost is low, and they are light element oxides that are suitable for living organisms including humans. Photoconductive materials consisting of zinc oxide are preferred because they are non-toxic. However, since the photosensitivity of photoconductive zinc oxide alone is in the ultraviolet region, in practice it is necessary to bring rose bengal or other sensitizer into contact with the surface of the zinc oxide powder particles to perform so-called spectral sensitization. It is. For this reason, the photosensitive layer of an electrophotographic photoreceptor is usually constructed by dispersing zinc oxide powder and a sensitizer in a binder resin. However, the photoconductivity of zinc oxide is said to be caused by the action of active species from oxygen atoms such as 03, 03, 02, etc., and these active species are adsorbed to the zinc oxide powder in the cooking process, which increases the conductivity of zinc oxide. The zinc oxide has high resistance because a large number of carrier electrons in the band are trapped, and when irradiated with light, active species are desorbed and electrons are released, resulting in high electrical conductivity. In an actual electrophotographic process, it is said that the active species are mainly generated by corona discharge by a charger in a charging step.

Therefore, in a zinc oxide photosensitive layer constructed by dispersing zinc oxide powder and a sensitizer in a binder resin, the active species involved in the photoconductivity of the zinc oxide powder cause the zinc oxide powder to exhibit its photoconductivity. It not only acts on the sensitizer and binder resin directly, but also acts directly on the sensitizer and binder resin, and since this active species has extremely high oxidizing power, the sensitizer and binder resin are rapidly oxidized and deteriorated. As a result, when an electrophotographic photoreceptor having such a photosensitive layer is used to form a copy image in an electronic copying machine, its service life is short, and the maximum number of copies that can be made is about 1000 at most.

Furthermore, a photosensitive layer made of a photoconductive material made of zinc oxide has the disadvantage that the solar resistance recovers slowly when the light irradiation is stopped and the photoreceptor is returned to the room. As mentioned above, although it is used in a copying machine in an atmosphere rich in active species, it has a large memory effect, and once exposed to light, the photosensitive layer returns to a state exhibiting sufficient dark resistance. It takes a long time to do so.

Therefore, a photoreceptor that has undergone one electrophotographic process must be left for a certain period of time before being subjected to the next process, and continuous copying cannot be performed at high speed unless special means are used. It is not possible to increase the image density of the image. Furthermore, since zinc oxide powder itself is hydrophilic,
The dispersibility in the binder resin, which is usually made of lipophilic resin, is generally poor, and as a result, the formed photosensitive layer has a high porosity and lacks toughness, and therefore has low durability.
Furthermore, the production of photoreceptors is also subject to various restrictions.

In view of the above-mentioned circumstances, the present inventors have completed the present invention as a result of extensive research into photoconductive materials having coatings on the surfaces of photoconductive zinc oxide powder particles.

The general purpose of the present invention is to provide spectrally sensitized zinc oxide particles that have the original features of photoconductive zinc oxide and have excellent properties, particularly as an element constituting the photosensitive layer of an electrophotographic photoreceptor. An object of the present invention is to provide a method that can advantageously produce a photoconductive material.

An object of the present invention is to provide excellent image forming properties such as a long service life and almost no memory effect when used as an element in the photosensitive layer of an electrophotographic photoreceptor, and to provide the photosensitive layer with a long service life. It is an object of the present invention to provide a method for advantageously producing a light guide material in which spectrally sensitized zinc oxide particles are coated with a lipophilic polymer, in which a sufficient dispersion state can be obtained.

A specific object of the present invention is to provide a photoconductive material having a capsule wall made of a lipophilic polymer on the surface of zinc oxide particles, and in which a sensitizer for zinc oxide is encapsulated by the capsule wall. The object of the present invention is to provide a method that allows direct production with fewer steps.

In the present invention, a solvent is prepared that dissolves both a sensitizer for photoconductive zinc oxide, which will be described later, and a material for the capsule wall film, which will be described later, and this solvent is used throughout for sensitization. The agent adsorption process and the capsule wall thickness formation process are carried out without pulling up the introduced photoconductive zinc oxide powder from the liquid phase.
They are carried out simultaneously and/or sequentially while remaining dispersed in the liquid phase.

For example, in one embodiment of the present invention, a sensitizer is first dissolved in the solvent, and photoconductive zinc oxide powder is introduced into the resulting solution and dispersed, so that the surface of the zinc oxide particles is coated with the sensitizer. A sensitizer process is carried out by adsorbing a sensitizer to produce spectrally sensitized zinc oxide powder.

In this sensitizer adsorption step, by heating the system, adsorption of the sensitizer to the surface of the zinc oxide particles can be promoted and the adsorption can be strengthened. The spectrally sensitized zinc oxide powder is dispersed in the capsule wall film material (hereinafter referred to as "capsule material material") in the solvent constituting the liquid phase of the system.

), dissolve and mix thoroughly. Thereafter, a non-solvent that is freely miscible with the solvent but does not dissolve the encapsulant material is substantially added, thereby increasing the concentration of the non-solvent in the liquid phase of the system and increasing the solubility of the liquid phase in the encapsulant material. The encapsulant material is precipitated on the surface of the zinc oxide particles to which the sensitizer has been adsorbed as a nucleus, thereby forming a capsule wall film made of a lipophilic polymer. Perform a film forming step. Thereafter, the solid material is collected in an oven, washed if necessary, and dried to produce a photoconductive material consisting of spectrally sensitized zinc oxide particles having a capsule wall film.

The above-mentioned capsule wall film forming process is based on the so-called coacervation method, in which a polymer is used as the capsule material, and this polymer is deposited as it is to form the capsule wall film.

The non-solvent used in this method may be one that is miscible with the solvent used in the sensitizing agent adsorption step described later but does not dissolve the capsule material, such as water, hydrocarbons, halogenated hydrocarbons, methanol, etc. ,ethanol,
It can be selected from alcohols such as propanol, ketones, esters, ethers such as diethyl ether, etc., but especially when high boiling point isoparaffins are used, the hardening of the capsule wall film described below can be achieved by heating under normal pressure or low pressure. This is preferable because it allows the system to be heated to the required temperature when achieving this goal. A specific example of such high boiling point Ibarafin is Esso Orderless Solvent No. 1, Iso/Guichi E, Iso Hi, Iso/Guichi K, Isopar L, Isopar M (manufactured by Esso Standard Oil Co., Ltd.), Isopar E, Isopar G, Iso/r Ichi, Iso/Guichi L, Iso/
Guichi M (manufactured by Esso Chemical Co., Ltd.), and others. However, it is of course possible to use a pressure cooker or the like to use Isopar C (manufactured by Essoigakusha), which has a lower boiling point, or other non-solvents. It is independent of the boiling point of the solvent. In the capsule wall film forming process using the coacervation method, "substantially adding a non-solvent" does not mean actually adding a non-solvent, but also adding a non-solvent in advance or actually adding a non-solvent. In this case, the concept includes evaporating and excluding only the solvent from the system by utilizing, for example, the boiling point difference. In addition to the above-mentioned coacervation method, the capsule wall film forming step in the present invention includes depositing the capsule material substance from a solution on the surface of the zinc oxide particles either as is or by causing a chemical change. Any method that can be used can be used. For example, an in-situ polymerization method may be used in which a polymerizable monomer or prepolymer is used as the encapsulant material and the monomer or prepolymer is polymerized and deposited on the surface of the zinc oxide particles. Can be done. In this case as well, a non-solvent that is miscible with the solvent of the solution of the encapsulant material but does not dissolve the material is substantially added, thereby promoting the formation of polymers on the surface of the zinc oxide particles. In order to further promote the formation of the polymer, heating, drying, etc. can be carried out. Also, when a polymerization catalyst is required, it is also possible to have such a catalyst present in the solution. The capsule wall film formed by the deposit from the solution uniformly covers substantially the entire surface of the zinc oxide particles. In the present invention, by performing the capsule wall film forming step after the sensitizer adsorption step is completed as in the above-mentioned example, the capsule wall made of lipophilic polymer is formed on the surface of zinc oxide particles which are originally hydrophilic. Formation of the film can be achieved smoothly.

However, in the present invention, the operation of the sensitizer adsorption step and the operation of the capsule wall film formation step may be performed in whole or in part at the same time. For example, it is also possible to dissolve both the sensitizer and the capsule material in a solvent, add zinc oxide powder to this solution, and then pour it into the solution to proceed with the formation of the capsule wall membrane. In this case, the sensitizer in the solution can be adsorbed in advance by the affinity with the surface of the zinc oxide particles using various means described below, and in this way, most of the sensitizer As in the case where the adsorption step is performed first, a photoconductive material is obtained in which the sensitizer is adsorbed onto the surface of zinc oxide particles and is covered with a capsule wall film. As will be described later, the ideal form of the photoconductive material to be used in the production method of the present invention is one in which the upper layer of zinc oxide particles coated with a sensitizer is covered with a capsule wall film. As long as the deviation from such an ideal form is not large, the basic performance of the photoconductive material of the present invention is satisfied.

Therefore, if there is no means to construct such an ideal form or if it cannot be adopted, the photoconductive material that is the subject of the manufacturing method of the present invention may be used in at least a necessary and sufficient amount. Most of the sensitizer is retained in the capsule wall membrane or between the capsule wall membrane and the surface of the zinc oxide particles. That is, if the sensitizer applied in the solvent used does not retain sufficient adsorption capacity to the surface of the zinc oxide particles, it may be effective to add an appropriate non-solvent (for the sensitizer) to the system. In this case, a non-solvent that is also a non-solvent for the capsule material used should be selected and the capsule wall forming step should be carried out by using or assisting the coacervation method. is advantageous. In many cases, the photoconductive material obtained by such a method has a sensitizer retained in the capsule wall membrane and between the photoconductive material and the surface of the zinc oxide particles. Equivalent effects can be obtained by using photoconductive materials of different shapes. As the solvent used in the above method, any solvent can be used as long as it dissolves both the sensitizer and the capsule material, such as alcohols such as methanol, ethanol, and propanol, acetone, and metal ethyl ketone. , ketones such as methyl lysoptyl ketone, esters such as ethyl formate, ethyl formate, ethyl acetate, butyl acetate, aliphatic hydrocarbons such as n-hexane and octane, aromatic carbonization such as benzene and toluene. The solvent may be selected from among hydrogens, halogenated hydrocarbons such as chloroform, dichloroethazo, and chlorobenzene, and other solvents, taking into account the type of sensitizer and capsule material used.

On the other hand, any sensitizer may be used in the present invention, and specific examples include xanthene dyes such as fluorescein, erythrosin, phloxine, rose bengal, and rhodamine flu; promocresol green, crystal violet, and malachite green; Examples include triphenylmethane dyes, acridine dyes such as acridine orange, cyanine dyes such as merocyanine, indoaniline dyes, anthraquinone dyes such as anthraquinone violet, indigo dyes, azo dyes, and others.

The sensitizer, which is normally present in free form in the capsule wall or on the outer surface of the membrane, and therefore in the binder resin of the photoreceptor manufactured from the photoconductive material, reduces the electrical performance of the photoreceptor. There are many cases.

Therefore, as described above, the photoconductive material produced by the production method of the present invention ideally has a form in which the upper layer of zinc oxide particles, which are first coated with a sensitizer, is covered with a capsule wall film. Therefore, in the present invention, in order to achieve sufficient and reliable spectral sensitization of zinc oxide in the sensitizer adsorption step, the sensitizer is added to the surface of the zinc oxide particles dispersed in the sensitizer solution. It is preferable to use a combination of a solvent and a sensitizer that can provide a large equilibrium adsorption amount of.

The term "equilibrium adsorption amount" herein refers to the amount defined as the maximum amount of sensitizer adsorbed by a unit amount of zinc oxide particles from a sensitizer solution of a constant concentration in a sensitizer solution zinc monoxide particle system. . Therefore, although a preferred solvent dissolves the sensitizer well, the sensitizer adsorbed on the surface of the zinc oxide particles is difficult to dissolve. Once adsorbed to the surface, it will not dissolve in the solvent. By setting the amount of sensitizer initially dissolved in the solvent to be less than a sufficient amount to cover the adsorption surface area of the zinc oxide used, the sensitizer can be dissolved in the solution after the sensitizer adsorption step is substantially completed. It is also possible to take measures to ensure that no residue remains.

By using the above-mentioned means alone or in combination, in many cases, substantially the above-mentioned ideal form,
That is, it is possible to realize a state in which the upper layer of zinc oxide particles coated with a necessary and sufficient amount of sensitizer is covered with the capsule wall membrane.

Furthermore, the non-solvents used to add to the system in the capsule wall film forming step include those that do not dissolve again the sensitizer adsorbed on the surface of the zinc oxide particles in the sensitizer adsorption step;
Alternatively, those with a small amount of dissolution are preferable.

From this point of view, among the specific examples of the sensitizers mentioned above, xanthene dyes or triphenylmethane dyes having an acid or lactone structure in their molecular structure,
It is a preferable sensitizer because it is generally highly soluble, has a large affinity for the surface of zinc oxide particles, and has a large equilibrium adsorption amount.Also, when aromatic hydrocarbons, ketones, or esters are used as a solvent, these sensitizers are preferred. Advantageous properties are fully obtained and therefore their use in combination is highly preferred.

If there are other sensitizers that can be appropriately modified to have properties similar to those described above, it is desirable to carry out such modification. In the present invention, various kinds of lipophilic polymers can be used to form the capsule wall, and preferred examples thereof include silicone resin, urethane resin,
Silicon-modified urethane resin, epoxy resin, silicon-modified epoxy resin, etc. Therefore, as the capsule material, these resins themselves, monomers that give these resins, prepolymers, or a combination of them can be used. good.

The final capsule wall membrane needs to be a polymer having a three-dimensional silk-like structure, and for this purpose, it may be cross-linked and cured during or after the capsule wall formation step. To accomplish this, means such as heating with or without a crosslinking agent can be used. In the case of crosslinking and curing by heating, it is preferable that the entire system can be heated to the required temperature as mentioned above. Therefore, when using the coacervation method, the non-solvent used is one with a high boiling point. It is preferable that The thickness of the capsule wall film is 5 angstroms to 1 micron, preferably 10 to 1000 angstroms, more preferably 20 angstroms.
~100 angstroms. The method of the present invention is as described above, but when producing a photoconductive material in which zinc oxide particles with a sensitizer adsorbed on the surface are covered with a capsule wall film, the following method is usually used. Bye.

That is, a sensitizer is dissolved in a suitable solvent, photoconductive zinc oxide powder is added and dispersed in the sensitizer solution, and the solid material is separated in an oven, collected in a bottle, and then dried or heated. Alternatively, the solvent is completely evaporated to dry the solid material, the sensitized zinc oxide powder exposed to the sensitizer is taken out, and a capsule wall film is formed using the sensitized zinc oxide powder. It is. According to such a method, a sensitized zinc oxide powder in which the sensitizer is completely adhered to the zinc oxide particles may be obtained at first glance, and may be considered a preferable method. If an excessive amount of sensitizing agent is deposited on the capsule, the sensitization efficiency may be lowered, and the smooth formation of the capsule wall may be inhibited. As a result, unnecessary sensitizer is distributed in the binder resin for forming the photosensitive layer, resulting in deterioration of the electrical properties of the photoreceptor. Also, when the solvent for taking out the sensitized zinc oxide powder is evaporated, the distance between individual zinc oxide particles gradually shortens, and eventually they are completely eroded and become in an aggregated state, resulting in the sensitized zinc oxide powder. Generally, fine powders and binders become aggregates formed when they lose their impregnated liquid content. Since the cohesive energy of this agglomerate is extremely large, it is extremely difficult to disintegrate this agglomerate into individual unit particles, and furthermore, it requires a lot of labor because the agglomerates must be mechanically pulverized. In addition, due to the mechanical force applied to the particles during crushing, a part of the sensitizer may be peeled off from the surface of the zinc oxide particles, or the zinc oxide particles themselves may be crushed and the sensitizer may be removed. In many cases, a new surface is formed that has not been previously treated, and it is not always possible to maintain a sufficient tingling effect.
In addition, since complete scales cannot be formed, a capsule wall film is formed on the outer peripheral surface of the capsule wall using the zinc oxide particle aggregate as a core in the subsequent formation of the capsule wall, and the resulting photoconductive material is The particles have irregular particle sizes and tend to contain giant particles, making it impossible to obtain uniform and excellent characteristics in the photosensitive layer of an electrophotographic photoreceptor produced using the particles. However, according to the present invention, there are no such drawbacks. That is, since the sensitizer adsorption step and the capsule wall film formation step are carried out without taking out the zinc oxide powder from the system, the zinc oxide particles do not aggregate and a sufficiently high dispersion state is obtained. Since shark particle manipulation is not required, there are no harmful effects caused by these, and a capsule wall film can be reliably formed and sensitized on the surface of each sensitized zinc oxide particle, making it possible to produce photoconductive materials with uniform particle sizes. Using this, an electrophotographic photoreceptor with excellent characteristics can be obtained. Moreover, in the sensitizer adsorption step, when a method is adopted to adsorb the sensitizer under equilibrium conditions, the molecules of the sensitizer are physically or chemically absorbed at the adsorption points on the surface of the zinc oxide particles. It is thought that it is adsorbed and forms a monomolecular layer.

If a capsule wall film is formed on the outer peripheral surface of the zinc oxide particles in this state, the amount of adsorption of the sensitizer to the surface of the zinc oxide particles will be sufficient for the spectral sensitization of the zinc oxide. Furthermore, sufficient sensitizing effect can be obtained because the sensitizer is distributed close to the surface of the zinc oxide particles, the sensitizing efficiency of the sensitizer is high, and there is no excess sensitizer. The photoreceptor obtained using this method always has stable and excellent electrical properties, and the capsule wall film can be formed smoothly. In addition to the above, according to the present invention, since the same solvent is consistently used in both the sensitizer adsorption process and the capsule wall film formation process, the desired photoconductivity can be achieved with less solvent consumption and fewer operational steps. Since the material can be manufactured, it is suitable for mass production, and costs can be significantly reduced.

As described above, according to the present invention, a photoconductive material having extremely excellent properties can be advantageously produced.

The photoconductive material produced by the method of the present invention is dispersed in a binder resin together with its solvent by a known method, and the resulting coating solution for forming a photosensitive layer is applied onto a support and dried to form a photosensitive layer. An electrophotographic photoreceptor is constructed.

Here, any binder resin can be used, such as acrylic resin, silicone resin,
Preferred examples include modified silicone resins, polyester resins, alkyd resins, phenolic resins, polycarbonate resins, and others. As described above, when the photoconductive material produced by the method of the present invention is used as an element constituting the photosensitive layer of an electrophotographic photoreceptor, the following benefits can be obtained.

Since the sensitizer is encapsulated by the tl' capsule wall film, it is possible to protect the sensitizer, which is susceptible to oxidation and the effects of moisture, light, and heat, and prevent its deterioration. The use life of the electrophotographic photoreceptor becomes longer, and the maximum number of copies that can be made by the electrophotographic photoreceptor can be dramatically increased.

{2} In photoconductive materials, an optimal amount of sensitizer can be adsorbed on the surface of zinc oxide particles in a very suitable and stable state, and in this case, stable and excellent photoconductive properties can be maintained for a long time. It is demonstrated throughout.

[3] Because a capsule wall film is formed on the surface of the zinc oxide particles, the time required for the floor resistance to recover when the photosensitive layer is once irradiated with light and then returned to a dark place is extremely short, resulting in a memory effect. Therefore, a constant high charging potential can be obtained at all times during charging, so that copied images with sufficiently high image density and excellent gradation reproducibility can always be formed.

The reason for this is not clear, but it may be that the sensitizing agent encapsulated in the capsule wall plays the same function as the oxidizing active species involved in the photoconductivity of the zinc oxide particles, or that the photoconductivity of the zinc oxide particles A sufficient amount of active species to cause haze is confined within the capsule wall film, and those active species that are desorbed from the surface of the zinc oxide particle by light irradiation are still trapped near the surface of the zinc oxide particle by the capsule wall film. Part of the reason for this is thought to be that the active species are retained at high concentrations in the zinc oxide particles, so that they can be readsorbed remotely onto the surface of the zinc oxide particles.

In fact, the fact that the active species generated by the corona discharge from the charged electrode installed in the copying machine does not contribute to the recovery of the 8-tone resistance of the photosensitive layer means that the active species were actively removed by exhausting air around the charged electrode. This is also supported by the fact that the memory effect is hardly large even in the case of

Therefore, by actively eliminating oxidizing active species in this way, it is possible to prevent deterioration of the binder resin and sensitizer of the photosensitive layer due to oxidation, and from this point of view, the service life of the electrophotographic photoreceptor can be reduced. can be extended. Furthermore, since there is virtually no memory effect, high-speed continuous copying is of course possible. Since the zinc oxide particles are almost completely covered by the '4' capsule wall film, the following effects can be fully obtained due to the properties of the capsule wall film.

[a} By making the capsule wall film composed of a lipophilic polymer, it is usually advantageously used to constitute the photosensitive layer, and the dispersibility in the solution of the lipophilic binder resin is improved, making it easier than conventional dispersion. The range of selection of binder resins has been expanded, such as making it possible to use resins that could not be put to practical use due to their low properties as binder resins, and it has also become possible to obtain coating liquids for forming photosensitive layers in a stable dispersion state. Application of the forming coating solution can be achieved in a suitable manner, and a photosensitive layer with fine and uniform properties can be obtained, and therefore the photosensitive layer can be made strong and a good reproduced image can be formed. can.

Moreover, by making the lipophilic resin that forms the capsule wall film have a three-dimensional network structure, the capsule wall film is stable without melting in the coating solution for forming the photosensitive layer, and there is no problem such as uneven sensitivity. A photosensitive layer with uniform characteristics can be obtained.

'b' The surface reactivity of zinc oxide particles, which are highly associative and tend to form aggregates, is blocked by the capsule wall film. It can be improved. {c- By forming the capsule wall film from a lipophilic polymer, the moisture resistance of the photoconductive material and the photosensitive layer formed therefrom can be improved.

td} By making the capsule wall film made of an electrically insulating polymer, even if the particles of the photoconductive material in the photosensitive layer are in contact with each other, no current conduction path is formed, and current conduction occurs when the photosensitive layer is charged. Deterioration of the photosensitive layer due to the phenomenon is prevented.

(51) Since each photoconductive material particle is made up of almost a single zinc oxide particle that has been sensitized and a capsule wall film formed, it is necessary to manipulate the scales in the photosensitive layer forming process. It is possible to form a photosensitive layer that is homogeneous, has excellent properties, and is dense, and as a result, it is possible to form a clear copy image with high resolution.

Examples of the present invention will be described below, but it goes without saying that the present invention is not limited thereto.

Example 1 Free acid rose bengal obtained by acid decomposition of normal rose bengal disodium salt. 100g of photoconductive zinc oxide powder was added to this solution and dispersed for 1 hour using a ball mill to adsorb the free acid Rose Bengal on the surface of the zinc oxide powder particles. Then, prepare a sensitized zinc oxide dispersion.

The amount of rose bengal remaining in the solution at this point was quantified by colorimetry, and the total amount was 0.0067 g.
The amount was almost negligible. Silicon modified epoxy resin "ESIOOI" was added to this dispersion as an encapsulant material.
N” (manufactured by Shin-Etsu Chemical Co., Ltd.) 2. Add the key and 1.3 g of a 1% by weight solution of titanium tetraisopropoxide, its hardening agent, in methyl isobutyl ketone, and mix well to dissolve.

While dispersing this liquid using ultrasonic waves, 100M of a non-solvent "Aisopa Hichichi" (manufactured by Esso Chemical Co., Ltd.) which does not dissolve the silicone-modified epoxy resin was added dropwise over a period of 2 hours, and the sensitized zinc oxide The silicone-modified epoxy resin is deposited on the surface of the particles to form a capsule wall film, and this dispersion is further heat-treated at a temperature of 12,000 for 3 hours to harden the resin constituting the capsule wall film. It was separated in an oven and dried to produce a photoconductive material. Photoconductive material thus obtained 10wt% solution of female acrylic resin "Dianal HR-112" (manufactured by Mitsubishi Rayon Co., Ltd.)
30 Z-butylated melamine resin “Super Beckamine J
-820'' (manufactured by Dainippon Ink & Chemicals) 5% by weight solution 6. Epoxy resin ``Epicote 1004'' (manufactured by Shell Chemical Company)
Shigeru Toluene 100
m{(However, the solvent for the acrylic resin solution is xylene, and the solvent for the butylated melamine resin solution is a mixed solvent of n-butanol and xylene.

) The above substances were mixed and dispersed in a Pall mill for 1 hour to prepare a coating solution for forming a photosensitive layer.

The photosensitive layer forming coating solution was applied to a support consisting of a polyester film laminated with an aluminum film and a casein intermediate layer with a thickness of 2 microns formed thereon, so that the amount of adhesion after drying was 3 mm/㎜. A photosensitive layer was formed by coating and drying to produce an electrophotographic photoreceptor.
This is designated as sample 1. When this sample 1 was installed in the electronic copying machine "Kubics 2000R" (manufactured by Konishi Roku Photo Industry Co., Ltd.) and a copying test was carried out, the resolution was 8.0 lines/line or more, the image density was high, and the gradation reproducibility was good. Copied images of excellent high quality were obtained, and even when a high-speed continuous copying test was performed and the number of copies exceeded 10,000, the same excellent quality as described above was obtained.

Also, the aperture value that provides proper exposure is 10,000 from the beginning of copying.
It was necessary to open by 0.75 between copies. Comparative example
1 Free acid rose bengal obtained by decomposing ordinary rose bengal disodium salt 0. In this solution, 10 μm of photoconductive zinc oxide powder was added and dispersed in a ball mill for 1 hour, after which the methyl ethyl ketone was evaporated and the free acid Rose Bengal was coated. Zinc oxide sensitive particles were prepared and further dried under reduced pressure at a temperature of 12,000.

Since what was obtained here was an aggregated mass, this was disintegrated using a Henschel mixer to obtain a sensitized zinc oxide powder. Add this sensitized zinc oxide powder to methyl isobutyl ketone 2
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 type0 type resin type resin type resin type resin type resin type resin type resin type resin type resin type resin type resin type resin type resin type resin type resin type 2 type type.
．． 5 g of titanium tetraisopropoxide as a hardening agent in a 1% by weight solution of methyl isobutyl ketone. A photoconductive material was produced by adding the following steps, and then processing in exactly the same manner as in Example 1. An electrophotographic photoreceptor was prepared using the same recipe and method for the coating solution for forming a photosensitive layer as in Examples except that the photoconductive material thus obtained was used.

This will be referred to as comparative sample 1. When the same test as in Example 1 was conducted using Comparative Sample 1, it was found that the copied image obtained in the initial copying was almost the same as that in Example 1 in terms of image density and tone reproduction. No difference was observed, but there were "white spots (vitiligo)" in some places on the copied image.
, there are defects called black spots, and the resolution is 8.
．． The number of treetops was poor with 0 trees per side.

Moreover, since the sensitivity was low, the appropriate aperture for exposure had to be opened by 0.5 aperture compared to Example 1. Furthermore, in a high-speed continuous copying test, sensitivity decreased after the number of copies exceeded 5,000, and if the initial exposure aperture value was used, natural blurring occurred in the copied image, so after 10,000 copies, proper exposure was performed. In order to achieve this, it was necessary to open the aperture by 1.0 more than the initial value. Example 2 A sensitized zinc oxide dispersion was obtained in the same manner as in Example 1, except that 0.35 g of free acid rose bengal was used.

Silicone polyol {KR302A'' (manufactured by Shin-Etsu Chemical Co., Ltd.) was added to this dispersion as an encapsulant material2. Female and polysocyanate "KR30" (manufactured by Shin-Etsu Chemical Co., Ltd.)
1.0 g was added and stirred to dissolve. While ultrasonically dispersing the resulting system, 100% of the non-solvent "Isopar C" (manufactured by Esso Chemical Co., Ltd.), which does not dissolve any of the capsule material substances, was added dropwise over a period of 2 hours. Both of the encapsulant materials were deposited on the surface of sensitized zinc oxide particles. Thereafter, this dispersion was heated to a temperature of 80q.
o for 3 hours to cause the silicone polyol and polyisocyanate to react, thereby obtaining a dispersion of particles having a capsule wall made of silicone urethane resin. Thereafter, the solid material was ground and dried to produce a photoconductive material. Photoconductive material thus obtained: 50 g solution of thermosetting acrylic resin "Dyanal HR-116" (manufactured by Mitsubishi Rayon Co., Ltd.)
40 and butylated melamine resin "Super Beckamine J-820" (manufactured by Dainippon Ink & Chemicals) 50 g
Solution 10' silicone oil "K"
F96” (manufactured by Shin-Etsu Chemical Co., Ltd.)
1'Toluene
(However, the solvent for the acrylic resin solution is xylene, and the solvent for the butylated melamine resin solution is a mixed solvent of n-butanol and xylene.

) An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 1 using the above formulation of the coating solution for forming a photosensitive layer.

This is designated as sample 2. When this sample 2 was installed in the electronic copying machine "Kubics 2000R" (manufactured by Konishi Roku Photo Industry Co., Ltd.) and a copying test was carried out, the resolution was 8 lines per side or more, the image density was high, and the gradation reproducibility was excellent. A high-quality copy image was obtained, and even when a high-speed continuous copying test was performed and the number of copies exceeded 10,000, an image quality equivalent to that of the cut-off copy image was obtained.

Further, the shift in sensitivity value from the initial stage of copying to the 10,000th copying was 0.5 in terms of aperture value. Comparative Example 2 A sensitized zinc oxide powder was obtained in exactly the same manner as in Comparative Example 1, except that 0.3 doses of free acid rose bengal was used.

This sensitized zinc oxide powder was mixed with methyl lysoptyl ketone 200
Add it all over the desk and disperse it for 1 hour using a ball mill.
Then, the same encapsulant materials as in Example 2, namely 2.0 g of silicone polyol "KR302A" and 1.0 g of polyisocyanate "KR30 group" were added. After that, the same treatment as in Example 2 was carried out to produce a photoconductive material.

Furthermore, an electrophotographic photoreceptor was produced using the same recipe and method as in Example 2, except that the photoconductive material thus obtained was used.

This will be referred to as comparative sample 2. When the same test as in Example 1 was conducted using this Comparative Sample 2, the maximum density and gradation reproducibility of the initial copy image were almost at the same level as Example 2, but there were also white spots and It had a defect called black spot, and the resolution was very low at 8.0 lines/skin.

Compared to sample 2, the aperture of "U-Pix 2000R" was only 1.0 worse, and after 10,000 continuous copies, the aperture was even worse by 1.0. It decreased by the same amount.

Example 3 0.7 g of free acid rose bengal as a sensitizer and silicone-modified epoxy resin "ESIO" as a capsule material substance
OIN” (manufactured by Shin-Etsu Chemical Co., Ltd.) 2. A 1% by weight solution of titanium tetraisopropoxide, a hardening agent, in methyl isobutyl ketone. The sensitizer and capsule material are dissolved in a mixed solvent of 170% methyl isobutyl ketone, which is a solvent for these substances, and 30% "Isopar" (manufactured by Esso Chemical Co., Ltd.), which is a non-solvent. It was made into a substance solution.

Next, 10 pieces of photoconductive zinc oxide powder were added to this solution and subjected to ultrasonic dispersion for 1 hour.

At this time, an amount of sensitizer corresponding to the equilibrium adsorption amount is adsorbed on the particle surface of the zinc oxide powder, forming a sensitized zinc oxide powder. And methyl lysobutyl ketone from this dispersion.

- The sensitizer remaining in the solution and the silicone-modified epoxy resin were gradually evaporated using a tally evaporator, thereby depositing the sensitizer remaining in the solution and the silicone-modified epoxy resin on the surface of the sensitized zinc oxide particles. Furthermore, after adding the above-mentioned non-solvent "Isopar H" 170, methyl isobutyl ketone was completely evaporated, and the resulting dispersion was heated to a temperature of 120° C. for 3 hours to harden the resin constituting the capsule wall membrane. I let it happen. Thereafter, the solid material was separated in an oven and dried to produce a photoconductive material in which a sensitizer was present in the capsule wall film and between the capsule wall film and the surface of the zinc oxide particles. An electrophotographic photoreceptor was produced using the same recipe and method as in Example 1, except that the photoconductive material thus obtained was used.

This is designated as sample 3. When a copying test similar to that in Example 1 was conducted using this sample 3, the initial copied image was almost at the same level as in Example 1.

Furthermore, when a high-speed continuous copying test was conducted, high quality images were still obtained even after copying exceeded 10,000 times.
The initial copying sensitivity was the same as that of Example 1, but the shift in sensitivity value from the initial copying to the 10,000th copying was 1.0 at the aperture value. Example 4 2.5 g of silicone-modified epoxy resin "ESIOOIN" (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.3 g of a 1% by weight acetone solution of its hardening agent titanium tetraisopropoxide,
Acetone 200' and non-solvent 'Isopar day' (
(manufactured by Esso Chemical Co., Ltd.) 50M to prepare a capsule material solution.

100g of photoconductive zinc oxide powder was added to this solution,
After sufficient cooling, 0.5 g of free acid rose bengal, which is a sensitizer, was added and dissolved. The equilibrium adsorption amount from the acetone solution to the surface of the zinc oxide particles is a few degrees higher than that from the methyl isobutyl ketone solution in Example 1, so
A significant portion of the free acid Rose Bengal became molten with the encapsulant material. Next, the acetone was gradually evaporated using a rotary evaporator, and the silicon-modified resin was deposited on the surface of the zinc oxide particles. At this time, the free acid rose bengal dissolved in the solution was also deposited at the same time, so that the free acid rose bengal also existed in the capsule wall film. Next, the above-mentioned non-solvent "Isopar Hi" 150 was added, and after the acetone was completely evaporated, the resin was heated at a temperature of 120 oo for 3 hours to harden the resin constituting the capsule wall film, and then the solid material was separated in a furnace. By drying, a photoconductive material was produced in which the sensitizer was retained in the capsule wall and between the capsule wall and the surface of the zinc oxide particles.

An electrophotographic photoreceptor was produced using the same recipe and method as in Example 1, except that the photoconductive material thus obtained was used.

This is designated as sample 4. When a copying test similar to that in Example 1 was conducted using this sample 4, the initial copied image was almost at the same level as in Example 1, but the actual copying sensitivity was still slower than that in Example 1. "Kubix 200
It was defective by 0.5 with an aperture of "0R".

Further, high-speed continuous copying was performed, and even after the number of copies exceeded 10,000, high-quality images were still obtained. 100 from the beginning
The moving print value of the sensitivity value up to 00 copies was 0.75. The first and 5000th high-speed continuous copying tests were conducted on the above samples 1 to 4 and comparative samples 1 and 2.
The value of the maximum image density DMx and the degree of image distortion for the copied images obtained in the 1st and 10000th copying are shown in the table together with the appropriate aperture value and the scale image power value of the 1st copying image. .

The unit of "resolution" in the table is the skin of a book.

As judged from the results in this table, according to the present invention, an excellent photoconductive material can be produced by a simple method.

Claims (1)

[Scope of Claims] 1 A capsule wall film made of a new oil-based polymer having a three-dimensional network structure in which a sensitizer for zinc oxide is encapsulated is provided on the surface of particles of photoconductive zinc oxide powder. In the method for producing a photoconductive material, a solvent that dissolves both the sensitizer and the capsule wall material is prepared, and using this solvent, (A) the sensitizer is dissolved in the solvent; a sensitizer adsorption step in which the sensitizer is adsorbed onto the surface of the particles of the zinc oxide powder dispersed in the sensitizer solution; particles of the zinc oxide powder dispersed in the material solution by means of dissolving the material into a material solution and adding substantially a non-solvent that is miscible with the solvent but does not dissolve the material; A method for producing a photoconductive material, characterized in that the capsule wall film forming step of forming the capsule wall film on the surface of the photoconductive material is performed without taking out the zinc oxide powder from the solvent system. 2. The method for producing a photoconductive material according to claim 1, wherein the sensitizer adsorption step is performed prior to the capsule wall film forming step. 3. The method for producing a photoconductive material according to claim 1, wherein the sensitizer adsorption step and the capsule wall film forming step are performed simultaneously. 4. The method for producing a photoconductive material according to claim 1, 2, or 3, wherein the system is heated in the sensitizer adsorption step. 5. According to any one of claims 1 to 4, wherein in the capsule wall film forming step, the material is a polymer, and this is deposited as it is on the surface of the particles of zinc oxide powder. A method of manufacturing the photoconductive material described. 6. In the capsule wall forming step, the material is a polymerizable monomer or prepolymer, which is deposited on the surface of the zinc oxide powder particles while polymerizing or is polymerized after being deposited. Range 1st to 4th
A method for producing a photoconductive material according to any one of Items. 7 Claim 1, characterized in that the polymer forming the capsule wall film is cured by heating.
7. A method for producing a photoconductive material according to any one of items 6 to 6. 8. The method for producing a photoconductive material according to any one of claims 1 to 7, wherein the polymer forming the capsule wall film is cured with a curing agent. 9. Use a solvent selected from aromatic hydrocarbons, ketones, and esters, and use a sensitizer that belongs to xanthene or triphenylmethane dyes and has an acid or lactone structure in its molecular structure. A method for producing a photoconductive material according to any one of claims 1 to 8, characterized in that: