JPS5845018B2 - electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor having a binder type photosensitive layer.

Generally, this type of electrophotographic photoreceptor has a photosensitive layer formed by dispersing photoconductive material powder in a binder resin, either directly on a conductive support or laminated with a suitable intermediate layer interposed therebetween. It is usually used as an electronic copying machine (in which it is used as a master).

That is, this electrophotographic photoreceptor is mounted on a photoreceptor conveyance device of a copying machine, and undergoes a charging process in which the photosensitive layer is charged, an exposure process in which an electrostatic latent image is formed by imagewise exposure, and a formed electrostatic latent image. The image is conveyed on a moving path through a development process in which the image is developed with toner to form a toner image, a transfer process in which this toner image is transferred to transfer paper, and a cleaning process in which the photosensitive layer after the transfer is cleaned. This series of steps again prepares for the electrophotographic process.

The toner image transferred to the transfer paper is then fixed to form a photographic image.

Various types of binder-type photosensitive layers for such electrophotographic photoreceptors have been proposed and used in the past, but one of the most suitable binder resins is a resin consisting of an acrylic resin component and an amino resin component. Some of these have epoxy resin added to them.

In other words, when this resin is used, the formed photosensitive layer has high mechanical strength, and the surface is less likely to be damaged during actual use, resulting in slow deterioration, long service life, and excellent printing durability. The number of times that the image can be effectively subjected to the electrophotographic process, that is, the maximum number of times of copying, is large, and at the same time, for the same reason, it is possible to form a clean copied image with less background smudge.

- Zinc oxide, titanium oxide, selenium, and other materials are known as force-leading conductive materials, but they are easy to manufacture, low cost, and are light element compounds that are not harmful to living organisms including humans. Therefore, zinc oxide is preferred.

However, since the sensitivity of zinc oxide alone is in the ultraviolet region, it is necessary to carry out so-called spectral sensitization using rose bengal or other sensitizers to extend the sensitivity to the visible region.

From the above point of view, if a photoconductive material made of zinc oxide powder is dispersed in a binder resin containing an acrylic resin component and an amino resin component, a photosensitive layer can be formed by containing a co-O sensitizer. , a reasonably suitable electrophotographic photoreceptor can be obtained, and in fact, such a photoreceptor has been put into practical use.

However, in this electrophotographic photoreceptor, the memory effect of the photosensitive layer is large, and when the photosensitive layer that has been irradiated with light and has high electrical conductivity is placed in a dark place again, the dark resistance of the photosensitive layer increases again. It takes a long time to return to the state indicated by , and as a result, continuous high-speed copying cannot be performed.
Alternatively, if continuous copying is performed (this has the drawback that the density of the images produced by the second and subsequent copies is significantly lower than that of the images produced by the first copying).

For this reason, in conventional electronic copying machines, so-called pre-exposure is performed before the start of the first copy.
This does not essentially eliminate the drawbacks of the photosensitive layer, but it focuses on the fact that if no pre-exposure is performed, the density of the copied image after the second exposure becomes gradually stable, although it is low. The photosensitive layer is in a state that has undergone one copying process, and the appearance is nothing other than the above solution.

The large memory effect of this photosensitive layer is caused by the binder resin, and it is not uncommon for Wagyu beef to have a memory effect that does not pose a practical problem when using other types of resin.In short, the acrylic resin component and the amino acid In photosensitive layers made of binder resins containing these components, a large memory effect is a fatal drawback.

On the other hand, when forming a binder type photosensitive layer using zinc oxide powder as a photoconductive material, there are the following drawbacks.

The photoconductivity of zinc oxide is 03.0. . It is caused by the action of active species released from oxygen atoms such as 07,
In the dark, these active species are adsorbed on the surface of zinc oxide particles, which traps electrons, which are majority carriers, in the conduction band of zinc oxide, making the zinc oxide high in resistance, and when irradiated with light. Then, these active species are desorbed and electrons are released, increasing the electrical conductivity. In the electrophotographic process, these active species are restored to a sufficiently adsorbed state before entering the charging process. Although it is desirable that the resistance be high, the fact that this re-adsorption is not quickly resolved causes the memory effect described above.

In the actual process, these active species are generated by the discharge of the charger during the charging process, but since these active species have strong oxidizing power, their adsorption and desorption causes the sensitizer and binder to be removed. The resin rapidly oxidizes and deteriorates, and as a result, the usable life of an electrophotographic photoreceptor having such a photosensitive layer is short, and the maximum number of copies that can be made is 1 at most.
000 times.

However, it is impossible to purge the atmosphere containing the active species by exhausting the area around the charger, for example, based on the above-mentioned principle of operation.

In addition, since zinc oxide powder itself is hydrophilic, its dispersibility in binder resins, which are usually lipophilic resins, is generally poor, and the characteristics of the photosensitive layer tend to be non-uniform. subject to restrictions.

In view of the above circumstances, the present invention provides a photosensitive layer in which a photoconductive material made of zinc oxide powder is dispersed in a binder resin containing an acrylic resin component and an amino resin component, and whose memory effect is extremely small. An object of the present invention is to provide an electrophotographic photoreceptor having the following characteristics.

Another object of the present invention is that a photoconductive material made of zinc oxide powder is dispersed in a binder resin containing an acrylic resin component and an amino resin component, and has extremely high printing durability with little deterioration. An object of the present invention is to provide an electrophotographic photoreceptor that is provided with a photosensitive layer and that can obtain a very high maximum number of copies when subjected to electrophotography.

Still another object of the present invention is to have a photosensitive layer in which a photoconductive material made of zinc oxide powder is extremely uniformly dispersed in a binder resin containing an acrylic resin component and an amino resin component, and thus to provide an excellent photosensitive layer. An object of the present invention is to provide an electrophotographic photoreceptor capable of forming a copied image.

In order to achieve the above object, in the present invention, a capsule wall film made of resin is formed on the surface of particles of photoconductive zinc oxide powder, and a sensitizer for zinc oxide is contained in the capsule wall film. The encapsulated material is used as a photoconductive material, and a photosensitive layer in which this photoconductive material is dispersed in a binder resin containing a thermosetting acrylic resin component and an amino resin component is placed on a conductive support. The electrophotographic photoreceptor is formed by providing the electrophotographic photoreceptor directly or by laminating them via a necessary intermediate layer.

According to the electrophotographic photoreceptor of the present invention having such a configuration, as will be clear from what will be described later, even though the binder resin of the photosensitive layer contains an acrylic resin component and an amino resin component, the photosensitive layer The memory effect is extremely small, so that a copied image with stable image density can be obtained from the first copying, and continuous high-speed copying is possible.

In addition, deterioration due to oxidation of the binder resin, which itself has great printing durability, can be effectively prevented along with deterioration of the sensitizer, and the service life of the photosensitive layer can be extended. The number of copies that can be made can be greatly increased.

Furthermore, since the photoconductive material is extremely uniformly dispersed in the photosensitive layer, uniform image forming characteristics can be obtained.

In the present invention, the sensitizer may be encapsulated between the inner surface of the capsule wall and the surface of the zinc oxide particles, contained and encapsulated in the membrane of the capsule wall, or partially encapsulated. is encapsulated between the capsule wall membrane and the zinc oxide particles, and the remainder is contained in the membrane body of the capsule wall membrane.

It is preferable that the capsule wall film covers substantially the entire surface of the unit body of zinc oxide particles, but when it covers the exposed surface of the aggregate of zinc oxide particles, It is also effective when covering only a portion.

The electrophotographic photoreceptor of the present invention can be manufactured as follows.

That is, a photoconductive zinc oxide powder is added to a solution of a sensitizer, stirred, and then dried in an oven, or the solvent is removed by evaporation to produce a sensitized zinc oxide in which the sensitizer is adsorbed. A capsule wall film made of resin is formed on the surface of the particles.

Although any known method may be used to form the capsule wall, it is preferable to use a coacervation method or an in-situ polymerization method.

When using the coacervation method, the sensitized zinc oxide powder is added to a solution of the material resin for the capsule wall membrane, and a non-sensitized zinc oxide powder that is freely miscible with the solvent of the solution but does not dissolve the material resin is added. By adding a solvent or further evaporating only the solvent, the solubility of the solution in the material resin is reduced, and the material resin is deposited on the surface of the sensitized zinc oxide particles.

When using an in-situ polymerization method, sensitized zinc oxide powder is added to a solution of a monomer or prepolymer that provides the resin for the capsule wall, and while the monomer or prepolymer is polymerized, the Deposit on the surface of sensitized zinc oxide particles.

In this in-situ polymerization method, means for promoting the formation and deposition of the monomer or prepolymer, such as the above-mentioned coacervation method, heating,
Stirring or the like can be used in combination, and if a polymerization catalyst is required, it is also possible to add such a catalyst to the solution.

According to these methods, it is possible to form a capsule wall film made of a polymer that covers substantially the entire surface of the zinc oxide particles.

In the photoconductive material thus obtained, the sensitizer is adsorbed on the surface of the zinc oxide powder particles, so that the sensitizer is absorbed between the inner surface of the capsule wall and the surface of the zinc oxide particles. It will be enclosed in.

However, if a part of the adsorbed sensitizer is dissolved in the solution for forming the capsule wall, the sensitizer will be contained in the membrane of the capsule wall formed.

Alternatively, the sensitizer is not adsorbed onto the surface of the zinc oxide particles but is dissolved in the solution for forming the capsule wall film, and the sensitizer is coated onto the surface of the zinc oxide particles at the same time as the capsule wall film is formed. In this case, the photoconductive material may contain a sensitizer in the membrane of the capsule wall.

However, the sensitizer may also be adsorbed onto the zinc oxide particles prior to the formation of the capsule wall.

Various types of resins can be used to form the capsule wall film, and preferred examples include silicone resins, urethane resins, silicone-modified urethane resins, epoxy resins, silicone-modified epoxy resins, and others.

The capsule wall film is preferably made of a resin having a three-dimensional network structure, and for this purpose, the capsule wall film shaped by the method described above can be cross-linked and cured at the same time as or after its formation. Often, means such as heating with or without a crosslinking agent can be used to accomplish this.

Further, the thickness of the cavecell wall film is between 5 angstroms and 1 angstrom.
Micron, preferably 10 to 1000 angstroms, more preferably 20 to 100 angstroms.

In the present invention, any sensitizer can be used, examples of which include xanthine dyes such as fluorescein, erythrosine, phloxine, rose bengal, and rhodamine blue, bromocresol green, crystal violet, and malachite. Examples include triphenylmethane dyes such as green, 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. .

Among these, xanthine dyes or triphenylmethane dyes having an acid or lactone structure are particularly preferred because they have high solubility and are strongly adsorbed on the surface of zinc oxide particles.

A photoconductive layer-forming coating solution was prepared by cross-dispersing a photoconductive material having a capsule wall film as described above in a binder resin described below together with its solvent, and this was applied directly onto or onto a conductive support. The photosensitive layer is coated on the intermediate layer, dried, and heat-treated to shape the photosensitive layer, thereby producing the electrophotographic photoreceptor of the present invention.

As the binder resin, a resin containing a thermosetting acrylic resin component and an amino resin component, or a resin further containing an epoxy resin component is used.

Here, the ratio of the thermosetting acrylic resin component to the amino resin component may be within the range of 1:0.05 to 15 by weight, and when the epoxy resin component is further included,
:0.05-15:0.02-7, but practically it is preferably in the range of 1:0.1-0.5:0.05-0.3.

Such a binder resin is added in an amount of 5 to 45 parts by weight, preferably 15 to 35 parts by weight, particularly (
It is preferably used in an amount of 20 to 30 parts by weight.

The thermosetting acrylic resin used in the present invention is a copolymer resin that has acrylic acid, methacrylic acid, or esters thereof as a basic component, and further contains a preemptive component having a functional group, and other crosslinkable resins. A polymer or prepolymer that crosslinks when heated with a component or by itself in the presence of a catalyst or without a catalyst, and has the following general formula C
I) is used.

[In the formula, n□2 R2j R3, R4 and R5 indicate the weight ratio (to), n□+n2 is 30 to 95, R3 is 5 to 7
0, R4 is 0-10, and n is O-15.

] In this general formula CI), +A+ can be copolymerized with acrylic acid, methacrylic acid, or their esters by some means, and the glass transition point of the homopolymer formed only from its repeating units is 25 ℃
The above structure is shown below.

Specific examples include those derived from nutylene, vinyltoluene, and acrylonitrile.

+B+ is a repeating unit having a carboxyl group, and is derived from acrylic acid, methacrylic acid, crotonic acid, a-carboxyacrylic acid, itaconic acid, maleic acid, fumaric acid, etc.

The second repeating unit in the general formula CI), like (-A+), has a structure such that the glass transition point of the homopolymer formed only from the repeating unit is 25°C or higher, It is a unit derived from a methacrylic acid ester, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, and cyclohexyl methacrylate.

On the other hand, the third repeating unit in the general formula CI),
That is, it has a structure in which the glass transition point of the homopolymer determined only by its repeating units is below 25°C, and includes those derived from various esters of acrylic acid and methacrylic acid.

That is, R□ is hydrogen or a methyl group, and when Ro is hydrogen, R3 is methyl ethyl, propyl, n-butyl,
It is a group such as isobutyl, 2-ethylhexyl, etc., and when R□ is a methyl group, R3 is butyl, 2-ethylhexyl,
It is a group such as lauryl tridecyl.

Furthermore, the last repeating unit in general formula (1), ie, R4, is a structure derived from an acrylic acid or methacrylic acid derivative having various functional groups.

That is, R□ is hydrogen or a methyl group, R4 is elementary,
and represents an alkyl group having 1 to 4 carbon atoms.

In this structural progression, ÷A+ and the second repeating unit are the structural units that impart hardness to the resin, and the third repeating unit is the structural unit that imparts flexibility to the resin, thus both of these repeating units An acrylic resin containing the unit has good paint properties.

In the structure described above, each repeating unit may be a single type of structural unit, or may be a structural unit consisting of two or more types.

Specific examples of acrylic resins suitably used in the present invention are listed below, but of course the present invention is not limited to these.

In addition, the names of commercially available thermosetting acrylic resins that can be used in the present invention include Dianal H manufactured by Mitsubishi Rayon Co., Ltd.
R-112 (15-18), HRl 16 (5-7),
HR-1, 24 (5-7), HR-405 (11-14
), HR-556 (11-14), HR-566 (7-
9), HR-575 (2-3), HR-606 (7-9
), HR-607 (7-9), HR-633 (6-8)
, HR-634 (7-9), HR-680 (7-9),
HR-687 (6-9), Acridic A-405 (4-8) A-406 (3-8) manufactured by Dainippon Ink and Chemicals Co., Ltd.
7), A-407 (3 to 7), and Thermolac 5T-10 (9 to 11) manufactured by Soken Kagaku Co., Ltd., and others.

Note that the numerical value within 0 indicates the acid value. Typical amino resins that can be used in the present invention include aniline resins, sulfamide resins, melamine resins, guanamine resins, urea resins, and polyamide resins.

Among these, examples of the aniline resin include polymers having a repeating unit of ←N-CH2÷ or.

Melamine resins and guanamine resins have the structural formula (A1 represents a hydrogen atom, an amine group, an alkyl group having 1 to 4 carbon atoms, or a phenyl group).

), or polymethylolmelamine formed by adding formaldehyde to the hydrogen atoms of at least two amino groups in It is obtained by condensation polymerization by heating or the like.

Representative examples of preferred melamine and guanamine are shown below.

Amino resins that can be used in the present invention include [r-820J, JG-821], 1L from Dainippon Ink Chemical Industries, Ltd.
-101J, "L-103J, [, -105J (butylated melamine resin)" Super Beckamine TD-x2
6j (butylated benzoguanamine resin), "Beccamin P-138", 1 Beckamine Q-1800j (butylated urea resin), Nippon Carbide Co., Ltd., "Nikarank MS-11J (methylated melamine resin)", "Nikarank BL- 60j (methylated benzoguanamine resin), Nippon Ka Co., Ltd. as Melan 20j (butylated melamine resin), and Fujika Co., Ltd. as 1 Delamine T-10.
Includes those commercially available as 0s and j.

Further, as the epoxy resin that can be contained in the present invention, any epoxy resin can be used, but a condensation product of bisphenol A and epichlorohydrin is preferable.

As a commercially available product, “Epicote 828J” manufactured by Shell Chemical Co., Ltd.
, "Epicoat 1001", "Epicoat 1004J" and "Epicron 850J" of Dainippon Ink and Chemicals Co., Ltd.
There are "Epicron 1050" and "Epicron 4050J.

The electrophotographic photoreceptor of the present invention is as described above, and since the binder resin in the photosensitive layer is preferably composed of an acrylic resin component and an amino resin component, it has excellent abrasion resistance, chemical resistance, and stain resistance. By further containing the epoxy resin component, the time required for drying the dispersion for forming a photosensitive layer can be significantly shortened. By using a material having a group, the above-mentioned excellent properties can be sufficiently and reliably obtained.

In the present invention, as will be clear from the examples described below, the photoconductive material powder dispersed in the binder resin to constitute the photosensitive layer has a capsule wall film formed on the surface of the zinc oxide particles. Since the sensitizer for the zinc oxide is encapsulated in this capsule wall film, the memory effect of the photosensitive layer occurs even though the binder resin contains an acrylic resin component and an amino resin component. Since the dark resistance can be significantly reduced and the recovery of dark resistance is fast and sufficient, it is possible to perform high-speed continuous copying, and it is possible to achieve stable and sufficient image density from the first copying. A duplicate image is obtained.

Further, according to the present invention, the usable life of the photosensitive layer is significantly longer than that of an electrophotographic photoreceptor having a conventional photosensitive layer made of a similar binder resin, and the maximum number of copies that can be made is dramatically increased. Can be done.

The reason why these effects are obtained is not clear, but the sensitizer encapsulated by the capsule wall film in close contact with the surface of the zinc oxide particles is absorbed into the zinc oxide like active species such as 03, 03, and 02. The photoconductivity of the zinc oxide is obtained by imparting a trapping level to electrons, which are the majority carriers of the zinc oxide, and when irradiated with light, these electrons are released by charge transfer from the trapping level to the conduction band of the zinc oxide. Therefore, the memory effect is reduced because the dark resistance is recovered more quickly than when the active species is re-adsorbed, or the active species trapped within the capsule wall film contributes to the development of photoconductivity of the zinc oxide. Therefore, it is thought that the memory effect is reduced because the re-adsorption is achieved quickly.

In any case, the external active species are no longer directly involved in the development of photoconductivity of zinc oxide. It is also approved because it performs a function equal to or greater than that of .

Since the sensitizer is encapsulated within the capsule wall,
Deterioration of the binder resin and sensitizer due to oxidation is suppressed, and as mentioned above, it is possible to actively purge oxidizing active species from around the photoreceptor, thereby further reducing the oxidation of the photosensitive layer. It is possible to prevent the deterioration due to this, and the service life can be significantly extended.

As a result, according to the present invention, the serious drawback of the binder resin containing an acrylic resin component and an amino resin component, that is, the drawback of large memory effect, can be almost completely eliminated, and in addition, the binder resin has great durability. It becomes possible to make full use of.

In addition, in the present invention, since a photoconductive material is used in which the surface of the zinc oxide particles is covered with a capsule wall film made of resin, it is possible to make the particles of the photoconductive material lipophilic. It can be uniformly and stably dispersed in the binder resin solution, and as a result, a photosensitive layer having uniform image forming properties can be obtained.

In addition, the capsule wall membrane alleviates differences in zinc oxide, such as differences in average particle size and degree of deviation from stoichiometries, so constant characteristics are always maintained regardless of the type or loft of zinc oxide. There is also the advantage that a photosensitive layer having the following characteristics can be obtained.

Furthermore, in the present invention, since almost all of the sensitizer is kept in contact with the surface of the zinc oxide particles, its effect can be obtained with high efficiency, and the same degree of sensitization can be obtained. It is possible to reduce the amount of sensitizer required for the binder resin, and to prevent a decrease in charging ability due to the inclusion of an excessive amount of sensitizer in the binder resin.

If, for example, various silicone oils or fluorocarbons are added to the coating liquid during the coating process, the spreadability of the coating liquid can be increased and the coating properties can be improved, and these substances can be contained in the photosensitive layer. Therefore, toner filming resistance may be improved.

Examples of the present invention will be described below, but it goes without saying that these do not limit the scope of the present invention.

Example 1 Free acid rose bengal obtained by acid decomposition of normal rose bengal disodium salt. i was dissolved in 100 ml of methyl ethyl ketone, and in this solution the temperature was 12
Photoconductive zinc oxide powder 100 dried under vacuum at 0°C
! After adding i' and dispersing it in a ball mill for 1 hour, methyl ethyl ketone was evaporated to obtain a sensitized zinc oxide powder adsorbed with rose bengal.

This sensitized zinc oxide powder is mixed in a mixed solvent of isoparaffin "Isopar H" (manufactured by Esso Chemical Co., Ltd.) 307711 (manufactured by Esso Chemical Co., Ltd.) and methyl ethyl ketone 1707711, which is a non-solvent for the silicone epoxy varnish described below, and then added to the silicone epoxy varnish. Varnish “ESloolN” (manufactured by Shin-Etsu Chemical Co., Ltd.) 2.2. ! 9 and its curing agent “D-15
0.3 g of J (manufactured by Shin-Etsu Chemical Co., Ltd.) was added and subjected to ultrasonic dispersion for 1 hour.

Methyl ethyl ketone is then gradually evaporated from this dispersion using a rotary evaporator, thereby depositing the silicone epoxy varnish on the surface of the particles of the sensitized zinc oxide powder.
After adding 170 ml of J, the mixture was heat-treated at 150° C. for 3 hours, and then the solid material was separated in a furnace through a glass filter and dried, thereby producing a photoconductive material having a capsule wall film made of a silicone-modified epoxy resin.

(However, the solvent for the thermosetting acrylic resin solution and the butylated melamine resin solution is a mixed solvent of n-butanol and xylene.

) The mixture of the above formulation was dispersed in a ball mill for 1 hour to prepare a coating solution for forming a photosensitive layer, and then applied onto a 2-micron-thick casein barrier layer formed on a support made by laminating aluminum foil onto a polyester film. The coating solution was coated to a dry ratio of 30 g/m'', dried with hot air at a temperature of 70°C, and further heat-treated in a dryer at a temperature of 100°C for 1 hour to produce an electrophotographic photoreceptor of the present invention. was created.

This will be referred to as "Sample 1". Example 2 A photosensitive layer coating solution was prepared in exactly the same manner as in Example 1 except that 4 g of epoxy resin "Epicoro 004J (manufactured by Shell Chemical Co., Ltd.) was added to the formulation for the coating solution for forming a photosensitive layer in Example 1. An electrophotographic photoreceptor of the present invention was produced in the same manner except that the heat treatment was carried out at a temperature of 100° C. for 30 minutes.

This will be referred to as "Sample 2."

When an epoxy resin is used in combination in this way, sufficient curing of the coating film can be achieved with a significantly short heat treatment.

Example 3 100 g of dry photoconductive zinc oxide powder was added to a mixed solvent of 150 ml of ethyl acetate and 50 ml of Isopar HJ in which 0.5 g of free acid Rose Bengal was dissolved, and the mixture was mixed and dispersed in a ball mill for 1 hour. Silicone polyol "KR302Aj (manufactured by Shin-Etsu Chemical Co., Ltd.)"
1.1 and polyisocyanate "KR302B" (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5. ! i' was added and further dispersed in a ball mill for 1 hour.

Next, ethyl acetate was evaporated using a rotary evaporator, and 150 ml of "Isopar" (j) was added, followed by heat treatment at a temperature of 130°C for 1 hour, after which the solid material was separated in an oven and dried, thereby obtaining a rose bengal-containing silicone. A photoconductive material with a capsule wall film that is more effective than a modified urethane resin was manufactured.

An electrophotographic photoreceptor of the present invention was produced using the mixture of the above formulation in exactly the same manner as in Example 1.

This will be referred to as "Sample 3."

Example 4 Sensitized zinc oxide powder 10 (['
was added to 200 mA of ethyl acetate together with 1.5 g of silicone resin KR214 (manufactured by Shin-Etsu Chemical Co., Ltd.), and the non-solvent Isopar HJ was added to the dispersion while stirring.
400 ml was added dropwise from a separatory funnel over a period of 2 hours, followed by heat treatment at a temperature of 100°C for 3 hours, and the solid material was separated in a furnace and dried under vacuum at a temperature of 100°C for 3 hours. A photoconductive material with a hollow capsule wall film was produced.

The mixture according to the above formulation was treated in the same manner as in Example 1 to produce an electrophotographic photoreceptor of the present invention.

This will be referred to as "Sample 4."

Comparative Example 1 An electrophotographic photoreceptor was produced in exactly the same manner as in Example 1 except that the sensitized zinc oxide powder was used as the photoconductive material.

This will be referred to as "comparative sample 1."

Comparative Example 2 In Example 1, a 40% solution of thermoplastic acrylic resin "Dyanal LR-211" (manufactured by Mitsubishi Rayon Co., Ltd.) was used instead of the thermosetting acrylic resin in the formulation for the coating solution for forming the photosensitive layer. 5 (An electrophotographic photoreceptor was produced in exactly the same manner except that [' was used.

This will be referred to as "comparative sample 2." Each of the samples and comparative samples produced as described above was subjected to a charging test and a copying test.

In the charging test, the sample or comparison sample was attached to an electrostatic copying paper tester 5P-428J (newly manufactured by Kawaguchi Denki), and the voltage applied to the discharge electrode of the charger was set to -6 KV, and the voltage was discharged for 5/7 seconds to expose the sample to light. Charge the layer, then 5
The series of operations of dark decaying for seconds and light irradiation was repeated continuously for the 1st, 2000th, and 5000th time.
Surface potential (■) of the photosensitive layer after dark decay at the 10,000th and 10,000th operation.

(volts), and this surface potential■.

Measure the irradiation exposure amount required to attenuate the rays to a minimum, that is, the half-reduction exposure amount E% (lux seconds), and also measure (1) in the first operation.

V in the second operation on the value of .

The ratio of the values, that is, the potential recovery rate m (%) was measured.

In addition, in the copying test, a running test was carried out by attaching the sample or comparative sample to the electronic copying machine "U Bix 1500J (manufactured by Konishiroku Photo Industry Co., Ltd.).
The maximum image density DMAX was measured for the copied images obtained in the 000th, 5000th, and 10000th copying operations, and the quality of each image was evaluated in terms of natural blur and image unevenness.

The results of the above tests are shown in the table below.

As judged from this table, the electrophotographic photoreceptor according to the present invention can withstand a very large number of copies and can produce good copied images, especially as is clear from the value of the potential recovery rate m. , surface potential of the photosensitive layer obtained by the second charging.

is only slightly lower than that in the first round, and the memory effect is very small.

It should be noted that there was no blurring in any of the copied images obtained in the first copying, and the 10,000th charging operation and copying operation for Comparative Sample 1 were impossible.

Claims (1)

[Claims] 1. A photoconductive material powder that forms a capsule wall film containing a sensitizer for zinc oxide on the surface of zinc oxide particles, and a thermosetting acrylic resin component and an amino resin component. An electrophotographic photoreceptor comprising a photosensitive layer dispersed in a binder resin. 2. The electrophotographic photoreceptor according to claim 1, wherein the sensitizer is encapsulated between the inner surface of the capsule wall film and the surface of the zinc oxide particles. 3. The electrophotographic photoreceptor according to claim 1, wherein the sensitizer is contained in the film body of the capsule wall film. 4. A part of the sensitizer is encapsulated between the inner surface of the capsule wall and the surface of the zinc oxide particles, and the remaining part is contained in the film body of the capsule wall. 5. The electrophotographic photoreceptor according to claim 1. 5. The electrophotographic photoreceptor according to claim 1 to 3 or 4, wherein the capsule wall film is made of a resin having a three-dimensional network structure. 6. The electrophotographic photoreceptor according to Claims 1 to 4 or 5, wherein the binder resin further contains an epoxy resin component. 7. The binder resin further contains an epoxy resin component. The electrophotographic photoreceptor according to Claims 1 to 5 or 6, which is crosslinked with a resin component.8 The resin constituting the capsule wall film is dissolved in a solvent in which the binder resin is dissolved. The electrophotographic photoreceptor according to claims 1 to 6 or 7, which does not contain any of the following.