JPS598818B2 - electrophotographic photoreceptor - Google Patents

Description

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

Generally, this type of electrophotographic photoreceptor has a photosensitive layer formed by dispersing photoconductive material powder in a binder resin, which is laminated either directly on a conductive support or via a suitable intermediate layer. It is usually used as a master in electronic copying machines. 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 image exposure, and an electrostatic latent image that has been formed. The latent image is 5 due to toner.
A developing process in which a toner image is formed by development, a transfer process in which this toner image is transferred to a transfer paper, and a cleaning process in which the photosensitive layer after transfer is cleaned. , and is again prepared for the electrophotographic process consisting of these series of steps.

The toner image transferred to the transfer paper is then fixed to form a copy 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 a silicone resin component and an acrylic resin component. There is a type that has ethyl cellulose resin added to it.

That is, by using silicone resin, it is possible to sufficiently increase the charging potential of the photoreceptor, and moreover, it is possible to exhibit excellent sensitivity and memory characteristics. Further, since the acrylic resin is used, sufficient coating film strength is obtained, resulting in high mechanical strength and excellent stain resistance of the photoreceptor. If ethyl cellulose resin is used in combination with this, the adhesion of the photosensitive layer to the support will be improved, the coating properties of the coating solution for forming the photosensitive layer will be improved, and the memory properties can be further improved. In this way, a high performance and highly durable photoreceptor can be obtained. On the other hand, zinc oxide, titanium oxide, selenium, and other materials are known as photoconductive materials, but they are easy to manufacture, low cost, and are light element compounds that are not harmful to living organisms including humans. 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 viewpoint, a photosensitive layer is formed by dispersing a photoconductive material made of zinc oxide powder and containing a sensitizer in a binder resin containing a silicone resin component, an acrylic resin component, and an ethyl cellulose resin component. Thus, a reasonably suitable electrophotographic photoreceptor can be obtained, and in fact, such a photoreceptor is in practical use.

However, in this electrophotographic photoreceptor, the dispersibility of the zinc oxide particles in the coating solution for forming the photosensitive layer is generally poor, and it is difficult to obtain a uniform and smooth photosensitive layer when this is coated on a support and dried. This method has a serious drawback in that it is not possible to provide a copy image that is precise and has excellent resolution, and is subject to various restrictions in its manufacture.

Furthermore, by using silicone resin and ethyl cellulose resin, this electrophotographic photoreceptor is compared to an electrophotographic photoreceptor that uses other resin components as a binder resin and contains zinc oxide powder and a sensitizer. Although this has been considerably improved, there is still a significant memory effect.

In other words, in this electrophotographic photoreceptor, the photosensitive layer has a large memory effect, and when the photosensitive layer, which has been irradiated with light and has become highly conductive, is placed in a dark place again, the photosensitive layer becomes highly dark again. It takes a long time to return to the state showing resistance, and for this reason, continuous high-speed copying cannot be performed, or when continuous copying is performed, the image is There is a drawback that the density of the image after the second copy is greatly reduced. For this reason, in conventional electronic copying machines, so-called pre-exposure is performed before the start of the first copy, but this does not essentially eliminate the drawbacks of the photoreceptor; Focusing on the fact that if this process is not carried out, the density of the copied image after the second copy will gradually become stable, although it is low, the photosensitive layer will essentially be in a state that has undergone one copying process, and the apparent density will be lower. It's nothing more than a solution.

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 caused by the action of active species consisting of oxygen atoms such as 03, 03-02, etc.
In the dark, these active species are adsorbed onto the surface of zinc oxide particles, which traps the majority carrier electrons in the conduction band of zinc oxide, making the zinc oxide highly resistive. When irradiated, 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. It is desirable that the re-adsorption is not achieved quickly. This causes the memory effect mentioned above. In actual processes, these active species are generated by the discharge of the charger during the charging process, but since these active species have a large oxidizing power, the sensitizer and binder resin are absorbed as they are adsorbed and desorbed. is rapidly oxidized and deteriorated, and as a result, an electrophotographic photoreceptor having such a photosensitive layer has a short service life, and the maximum number of copies that can be made is about 1000 at most. However, it is impossible to purge the atmosphere containing the active species by, for example, exhausting air around the charger based on the above-mentioned principle of operation.
In view of the above circumstances, the present invention provides a photosensitive layer in which a photoconductive material made of zinc oxide powder is extremely uniformly dispersed in a binder resin containing five silicone resin components, an acrylic resin component, and an ethyl cellulose resin component. It is an object of the present invention to provide an electrophotographic photoreceptor that can form a good copy image that is dense and has excellent resolution.

Another object of the present invention is to provide a photosensitive layer in which a photoconductive material made of zinc oxide powder is dispersed in a binder resin containing a silicone resin component, an acrylic resin component, and an ethyl cellulose resin component, and which has a significantly small memory effect. An object of the present invention is to provide an electrophotographic photoreceptor having the following features.

Still another object of the present invention is that a photoconductive material made of zinc oxide powder is dispersed in a binder resin containing a silicone resin component, an acrylic resin component, and an ethyl cellulose resin component, and has a sufficiently high charging potential. It has excellent sensitivity, good adhesion to the support, and high mechanical strength.
Furthermore, it is an object of the present invention to provide an electrophotographic photoreceptor that is provided with a photosensitive layer that exhibits little deterioration and has extremely high printing durability, and that can provide an extremely high maximum number of copies when subjected to electrophotography.

In order to achieve the above objects, in the present invention, a capsule coating film made of resin is formed on the surface of particles of photoconductive zinc oxide powder, and a sensitizer for zinc oxide is enclosed within this capsule wall film. The photoconductive material is used as a photoconductive material, and a photosensitive layer in which this photoconductive material is dispersed in a binder resin containing a silicone resin component, an acrylic resin component, and an ethyl cellulose resin component is directly deposited on a conductive support. Alternatively, the electrophotographic photoreceptor may be constructed by laminating them with a required intermediate layer interposed therebetween.

According to the electrophotographic photoreceptor of the present invention having such a structure, the photoconductive material is dispersed extremely uniformly in the photosensitive layer, or is not too dispersed, and the surface of the photosensitive layer has a fine uniform roughness. As a result, the electrical characteristics are improved, and it is possible to obtain a good image with high precision and excellent resolution.As will be explained later, the memory effect of the photosensitive layer is extremely small, and therefore the first copy Copied images with stable density can be obtained from the first printing, and continuous high-speed copying is possible. Furthermore, since the charging potential is sufficiently high and excellent sensitivity is achieved, a copied image with high image density and good contrast can be provided. Furthermore, 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, making it suitable for use in electrophotography. The maximum number of copies that can be made can be greatly increased. In the present invention, the sensitizer may be encapsulated between the inner surface of the capsule wall membrane and the surface of the zinc oxide particles, contained in the membrane body of the capsule wall membrane, or partially encapsulated. The zinc oxide particles can be encapsulated between the capsule wall membrane and the zinc oxide particles, and the remainder can be 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 covering the exposed surface of an aggregate of zinc oxide particles, or covering part of the entire exposed surface of a single particle or an aggregate. It is also effective when covering only the area. 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, separated and dried, or the solvent is evaporated 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. Any method may be used to form this capsule wall film, but coacervation method or in-situ method may be used.
It is preferable to use a polymerization method (in situ). When using the coacelvation method, the sensitized zinc oxide powder is added to a solution of the material resin for the capsule wall membrane, and is mixed freely with the solvent of the solution, but does not contain the material resin. By adding an insoluble non-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 the in-situ monopolymerization 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 monopolymerization method, means for promoting the formation and deposition of the monomer or prepolymer, such as the above-mentioned coacervation method, heating, stirring, etc., can be used in combination; When 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 in advance on the surface of the zinc oxide powder particles, so the sensitizer is present between the inner surface of the capsule wall and the surface of the zinc oxide particles. It will be in an enclosed state.

However, if 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 that is 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 capsule wall membrane.

However, the sensitizer may also be adsorbed onto the zinc oxide particles prior to the formation of the capsule wall membrane. Various types of resin can be used to form the capsule wall membrane, but
Suitable examples include silicone resin, urethane resin,
Silico7 modified urethane resin, epoxy resin, silicone modified epoxy resin, 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 formed by the method described above may be cross-linked and cured at the same time as or after its formation. To accomplish this, means such as heating with or without a crosslinking agent can be used. The thickness of the capsule wall is 5 angstroms to 1 micron, preferably 10 to 1000 angstroms, and more preferably 20 to 100 angstroms. In the present invention, any sensitizer can be used, examples of which include xanthine dyes such as fluorescein, erythrosin, phloxine, rose bengal, and rhodamine blue, bromocresol green, crystal violet, Examples include triphenylmethane pigments such as malachite green, acridine pigments such as acridine orange, cyanine pigments such as merocyanine, indoaniline pigments, anthraquinone pigments such as anthraquinone violet, indigo pigments, azo pigments, and others. I can do it.

Among these, compounds having an acid or lactone structure, such as xanthine dyes or triphenylmethane dyes, are particularly preferable because they have high solubility and are strongly adsorbed on the surface of zinc oxide particles. A coating solution for forming a photosensitive layer is prepared by cross-dispersing a photoconductive material having a capsule wall film in a binder resin, which will be described later, together with its solvent.
This is applied directly onto a conductive support or onto an intermediate layer formed thereon, dried, and further heat-treated to form a photosensitive layer, thereby producing the electrophotographic photoreceptor of the present invention. If, for example, various silicone oils or fluorocarbons are added to the coating solution during coating production, the spreadability of the coating solution can be increased and coating properties can be improved. Due to its inclusion, toner filming resistance may be improved. As the binder resin, a resin consisting of a silicone resin component and an acrylic resin component, or a resin further containing an ethyl cellulose resin component is used.

Although the ratio of the silicone resin component and the acrylic resin component is arbitrary, it is preferable to use 20 to 70% by weight of the silicone resin and 10 to 70% by weight of the acrylic resin based on the total amount of the binder resin. . Furthermore, it is preferable to use ethyl cellulose resin in an amount of 50% by weight or less based on the total amount of binder resin. The binder resin is used in an amount of 5 to 45 parts by weight, preferably 15 to 35 parts by weight, particularly preferably 20 to 30 parts by weight, based on 100 parts by weight of the photoconductive material made of zinc oxide having the capsule wall film described above. used at a rate of There are various acrylic resins that can be used in the present invention, including polymers of acrylic acid or methacrylic acid or derivatives thereof, or polymers of these and other vinyl monomers, such as styrene, vinyltoluene, acrylonitrile, maleic acid, and It is a copolymer with one or more of its esters, itaconic acid, etc. Further, as so-called functional groups [in the formula, n1, N2, N3
, N4 and N5 represent the polymerization percentage, and n1+N2 is 2
0-95, N3 is 2-280, N4 is 0-101, and N5 is 0-15. [0A+] In this general formula [1], 0A+ can be copolymerized with acrylic acid, methacrylic acid, or their esters by some means, and the glass transition point of 3 is a homopolymer consisting only of repeating units thereof. It shows a structure that allows the temperature to exceed 25°C. Specific examples include those derived from styrene, vinyltoluene, and acrylonitrile.
Moreover, -1:1B+ is a repeating unit having a carboxyl group.
It is at the J position and is derived from acrylic acid, methacrylic acid, crotonic acid, α-carboxyacrylic acid, itaconic acid, maleic acid, fumaric acid, etc.

The second repeating unit in general formula [1], ie, R, represents a lower alkyl group.

) etc. A typical example of such acrylic resin is one represented by the following general formula [1].

General formula [1] I ←C-CH2+ is the same as ←A+, its repeated single VlZ
The structure is such that the glass transition point of the homopolymer consisting only of
It is a unit derived from tertiarybutyl methacrylate and cyclohexyl methacrylate.

On the other hand, the third repeating unit in general formula [1],
That is, ←C-CH2+ has a structure such that the glass transition point of the homopolymer consisting only of the repeating unit L is below 25°C, and includes those derived from various acrylic acid and methacrylic acid esters. .

That is, R is a hydrogen atom or a methyl group, and when R1 is hydrogen, R3 is methyl, ethyl, n-butyl, isobutyl, 2-ethylhexyl, etc., and when R1 is a methyl group, R3 is butyl, These include 2-ethylhexyl, lauryl, and tridecyl groups. Furthermore, the last repeating unit in general formula [1], ←C-CH2+, has a structure derived from an acrylic acid or methacrylic acid derivative having various functional groups as R4.

That is, R1 is a hydrogen atom or a methyl group, and R4
For example, -01?4, -NHCH2OR5 or -NH2
and -R'4 is -CH2CH2OH, -CH,CH
It represents CH3, or -CH2-CH\CH2, etc., and /R5 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, etc.

In this structural formula, +AB- and +C-CH2+ are structural units that impart hardness to the acrylic resin, and +C
-CH2+- is a structural unit that provides flexibility, and thus an acrylic resin containing both of these repeating units has good coating properties.

In addition, in the above structure, +A+, Seal +-C-CH2+, Self 1-C-CH2+, ? +-B+ and +-C-CH2+ may be a single type of structural unit, two or more types of structural units.

Specific examples of acrylic resins suitably used in the present invention are listed below, but of course the present invention is not limited thereto. Compound Examples Acrylic resins that can be used in the present invention include Dianal H manufactured by Mitsubishi Rayon Co., Ltd. as a thermosetting acrylic resin.
R-112 (15-18), HR-116 (5-7),
HR-124 (5-7), HR-405 (11-14)
, HR-556 (11J~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 to 9), Dainippon Ink and Chemicals Co., Ltd. Acridik A-405 (4 to 8), A-406 (
3 to 7), A-407 (3 to 7), and Thermorack ST-10 (9 to 11) manufactured by Soken Chemical Co., Ltd.

In addition, as thermoplastic acrylic resins, Dianal LR-216 (2 to 4) and LR-396 (manufactured by Mitsubishi Rayon Co., Ltd.) are also used.
3-5), LR-866 (1-4), LR-904 (3
-5), and Acridik A-125-50 (1-5), A-156 (3-5), manufactured by Dainippon Ink and Chemicals.
There are A-196 (ku4) etc.

Here, the numerical value in (d) indicates the acid value.

The silicone resin that can be used in the present invention is a polymer having a polysiloxane repeating structure in its molecular main chain, and the silicone resin itself or its precursor is soluble in the coating solvent used to coat and manufacture the photosensitive layer of the present invention. Although a wide range of materials can be used regardless of type or structure, a group of alkyl silicone varnishes, allyl silicone varnishes, and alkyl allyl silicone varnishes can be suitably used.

Among these, methyl silicone varnish and phenylmethyl silicone varnish are particularly suitable. Methyl silicone varnish is generally a copolymer made by combining J+O-Si-0+, (CH3-Si-0+ structural units).

Phenylmethyl silicone varnish is generally 1
It is a copolymer made by combining structural units such as 1 +O-Si-0+ and (0-Si-0+).

Representative examples of these include KR manufactured by Shin-Etsu Chemical Co., Ltd.
l52, KRl55, KR22OlKR25l, KR2
55, KR27l, KR28O, KR28l. Toray Silicone Co., Ltd. SH8O3, SH8O4, SH8O6A, .
There are SH8O8, SH84O, etc. In addition, among alkyl silicone varnishes and alkylaryl silicone varnishes, -CH2CH2CN, -C
Includes those having H2CH2CF3.

Further, silicone resins preferably used in the present invention include those having reactive functional groups.

Reaction & l?
” The functional group is -SiHl-Si-0H1-Si-0
C0CH3, -Si-0R (where R represents a lower alkyl group).

), -Si I CH=CH2 There is.

A typical example is KR2l manufactured by Shin-Etsu Chemical Co., Ltd.
l, KR2l2, KR2l3, KR2l4, KR2l5
, KR2l6, KR2l8 SH5O manufactured by Toray Silicone Co., Ltd.
5O, SH6Ol8SH6l88, etc. In the present invention, an ethyl erulose resin component is further used.

Ethylcellulose is represented by the general formula []. General formula [] [In the formula, Et represents an ethyl group C2H,-, J. kll
・m・n・o゛, P. Each q represents a polymerization percentage.

] That is, poly 1,4-β-D-glucopyranose is obtained by ethyl etherifying the hydroxyl group of cellulose, and the degree of etherification may be arbitrary, but it is preferably used in the present invention. The degree of etherification is 2.
．． 2-2.6 (ethoxy group content 44.0-49.5%)
belongs to.

Typical examples of these include Hercules
T. cules). ．． N,. K. G. D type,
Standard ethoxy content type, medium ethoxy content type, and low ethoxy content type (types 7, 10, 20, and 45, respectively) manufactured by DOw Chemical.
, 70, 100, 1501200, etc., with different degrees of polymerization. )and so on. The electrophotographic photoreceptor of the present invention is as described above, and since the binder resin in the photosensitive layer is preferably made of a silicone resin component,
Excellent charging characteristics and sensitivity can be obtained, and in addition, by using an acrylic resin, the photoreceptor has high mechanical strength and stain resistance. Furthermore, since ethyl cellulose resin is used in combination, the adhesion of the photosensitive layer to the support becomes extremely strong, and the coating production thereof becomes extremely easy.
In the present invention, as is clear from the examples described below, the photoconductive material powder that is dispersed in the binder resin and constitutes the photosensitive layer has a capsule wall film formed on the surface of the zinc oxide particles. Since the capsule wall film encapsulates the sensitizer for the zinc oxide, the photoconductive The dispersibility of the material powder in the coating solution for forming a photosensitive layer is extremely good, and there is no particular difficulty in manufacturing it, and the photosensitive layer obtained by coating it on a support has high uniformity and a fine, uniform roughness. In this way, an electrophotographic photoreceptor is obtained which provides a dense copy image with excellent resolution.

Originally, if silicone resin or acrylic resin and ethyl cellulose resin were used as the binder resin for this type of photoreceptor, the memory effect could be suppressed to a sufficiently low level, but in the present invention, the photoconductive powder is further used as a photoconductive powder. By using a zinc oxide powder having a capsule wall film containing a sensitizer on its surface, this memory effect is further reduced to a level that practically does not need to be considered as a memory phenomenon.

However, this memory effect is almost impossible even if the area around the photoreceptor is actively purged to eliminate oxidizing active species such as 03, 03-, 02, etc., which are composed of oxygen atoms. It never increases. In this way, an electrophotographic photoreceptor suitable for high-speed continuous copying and capable of stably producing copied images of sufficient density can be obtained. Further, according to the present invention, a photoreceptor has a significantly longer service life and a dramatically increased maximum number of copies than an electrophotographic photoreceptor having a conventional photosensitive layer made of a similar binder resin. Given.

In an electrophotographic copying machine equipped with the photoreceptor of the present invention, if the area around the photoreceptor is purged using a suitable exhaust fan or the like to remove the oxidizing active species consisting of oxygen atoms from the atmosphere, Furthermore, it is possible to effectively extend the life of the photoreceptor. In the present invention, by covering the zinc oxide particles with the capsule wall film, the following advantages can be obtained. In other words, for conventional photoreceptors using zinc oxide, it is important to carefully control the various properties of the zinc oxide powder used for it, down to the type, brand, and rod, in order to ensure that the photoreceptor has the desired characteristics and is free from variations. This is an essential requirement for producing a photoreceptor with characteristics that do not have the same characteristics. However, when zinc oxide particles are coated according to the present invention, various possible differences in the material zinc oxide powder, such as differences in its average particle size or deviation from the zinc-oxygen stoichiometry, can be avoided. It is possible to reduce and alleviate the effects on various properties of the photosensitive layer produced using the photosensitive layer, and a photosensitive layer having always constant properties 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, the sensitizing effect can be obtained with high efficiency, and the same level of sensitization can be obtained. It is possible to reduce the amount of sensitizer required for this purpose, and also to prevent a decrease in the charging ability of the photoreceptor due to the inclusion of an excessive amount of sensitizer in the binder resin. In the present invention, since a photoconductive material is used in which the surface of zinc oxide particles is covered with a capsule wall film made of resin, it is possible to make the particle surface of the photoconductive material lipophilic, and therefore most of the particles are lipophilic. It becomes possible to quickly and uniformly disperse the binder resin in the above-mentioned binder resin solution.

Moreover, since this uniform dispersion state is stably maintained, a photoreceptor in which the photoconductive material is uniformly dispersed in the photosensitive layer can be obtained, and an electrophotographic photoreceptor that provides a reproduced image that is dense and has excellent resolution can be obtained. A photoreceptor will be manufactured. Furthermore, the electrophotographic photoreceptor of the present invention has an extremely small memory effect, and even when the active species containing oxygen atoms are actively removed from the vicinity of the photoreceptor, this excellent memory property is almost completely lost. The fact that it is not damaged is not found in conventional photoreceptors and is extremely novel.

The reason why such an effect is obtained is not clear, but the sensitizer encapsulated by the capsule wall film in close contact with the surface of the zinc oxide particles has the same effect as the oxidizing active species consisting of oxygen atoms. It functions to provide a trapping level to the majority carrier electrons in zinc oxide, and when irradiated with light, these electrons are released from the trapping level to the conduction band of zinc oxide by charge transfer. A photoconductive mechanism is established around zinc oxide,
Therefore, the elimination of the active species described above, which involves the movement of atomic groups,
It can be inferred that the dark resistance recovers much more quickly than in the case of a photoconductive mechanism based on adsorption, resulting in better memory characteristics. Other reasons to consider are as follows. That is, in the photoreceptor of the present invention, as with conventional photoreceptors, although the presence of active species containing oxygen atoms is essential for the development of photosensitivity, in reality, the presence of active species containing oxygen atoms is essential for the development of the photosensitivity. All of the active species are encapsulated within the capsule wall membrane, and even after being desorbed from the surface of the zinc oxide particles upon irradiation with light, they remain in close proximity to the surface of the zinc oxide particles, resulting in the photosensitive After the irradiation of the body with light is interrupted, it is re-adsorbed very quickly and thus the memory effect becomes extremely small. In any event, the need for active species to diffuse through the capsule wall membrane or binder resin layer to the surface of the zinc oxide particles is eliminated, and the atmosphere outside the capsule wall membrane is now free of zinc oxide light. It has no effect on the mechanism of conductivity, does not deteriorate the memory characteristics of the photoreceptor, and eliminates various oxidizing active species from the surrounding area to protect each component of the photoreceptor from deterioration due to oxidation. It also became possible to do so. In this way, the sensitizer is originally encapsulated within the capsule wall, and its oxidative deterioration is suppressed, and an ultra-long life of the photoreceptor has been achieved. According to the present invention, as described above, Siri.

Not only can the defects of conventional photosensitive layers using acrylic resin components and acrylic resin components be eliminated, but also various advantages can be brought about as described above. Examples of the present invention will be described below, but the embodiments of the present invention are not limited thereby. Comparative Example 1 0.5r of the free acid rose bengal obtained by acid decomposition of ordinary rose bengal disodium salt was dissolved in 100 wt of methyl ethyl ketone, and in this solution was added at a temperature of 1.
Photoconductive zinc oxide powder 100 dried under reduced pressure at 20°C
After adding r and dispersing in a ball mill for 1 hour,
Sensitized zinc oxide powder adsorbed with rose bengal was obtained by evaporating methyl ethyl ketone.

This sensitized zinc oxide powder is used as a non-solvent for the silicone epoxy varnish described below.
(manufactured by Etsuso Petrochemical Co., Ltd.) and 170 d of methyl ethyl ketone in a mixed solvent, and further added silicone epoxy varnish "ESlOOlN" (manufactured by Shin-Etsu Chemical Co., Ltd.) 2.2V and its hardening agent "D-15" ( (manufactured by Shin-Etsu Chemical Co., Ltd.) at 0.3 V was added and subjected to ultrasonic dispersion for 1 hour.

Next, methyl ethyl ketone is 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 the mixture, it was heat-treated at 150° C. for 3 hours, and then the solid material was filtered through a glass filter and dried to produce a conductive material having a capsule wall film made of silicon-modified epoxy resin. Photoconductive material thus obtained 100? toluene
100d 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 the above mixture was applied onto a casein barrier layer with a thickness of 2 microns formed on a support made of a polyester film laminated with aluminum foil. The ratio after drying the coating liquid is 30t/
Apply it so that it becomes a
Further, heat treatment was performed for 1 hour in a dryer at a temperature of 100° C. to produce an electrophotographic photoreceptor of the present invention.

This will be referred to as [Sample 1]. Example 1 Comparative example except that ethyl cellulose resin [STD-45'' (7.5% by weight toluene solution) (manufactured by Tau Chemical Co., Ltd.) 60y was added to the formulation for the coating solution for forming a photosensitive layer in Comparative example 1. A photosensitive layer coating solution was prepared in exactly the same manner as in Example 1, and an electrophotographic photoreceptor of the present invention was produced.

This will be referred to as "Sample 2." In this way, when ethyl cellulose was used in combination, the coating properties were improved and a better coating film could be obtained. Example 2 100 t of dry photoconductive zinc oxide powder was added to a mixed solvent of 150 d of ethyl acetate and 50-proof [Isobah-H] in which 0.5 f of free acid rose bengal was dissolved, and the mixture was mixed and dispersed in a ball mill for 1 hour. After that, silicone polyol “KR3O2A” (manufactured by Shin-Etsu Chemical Co., Ltd.) 1.0
0.57 of polyisocyanate [KR3O2B" (manufactured by Shin-Etsu Chemical Co., Ltd.) were added, and the mixture was further dispersed in a ball mill for 1 hour.

Next, ethyl acetate was evaporated using a rotary evaporator, and 150 ml of [isobar-H] was added, followed by heat treatment at a temperature of 130°C for 1 hour. After that, the solid matter was separated and dried. A photoconductive material having a capsule wall film made of urethane resin was manufactured. Photoconductive material thus obtained
100t toluene 1
EXAMPLE 1 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 3 100 tons of sensitized zinc oxide powder similar to that in Comparative Example 1 was mixed with silicone varnish [KR2l4] (manufactured by Shin-Etsu Chemical Co., Ltd.).
Add 1.5t to 200ml of ethyl acetate, and add 400ml of non-solvent "Isopa-H" to this dispersion while stirring.
Add m1 dropwise over a period of 2 hours by liquid loading,
Thereafter, the mixture was heat-treated at 100° C. for 3 hours, and the solid matter was separated and vacuum-dried at 100° C. for 3 hours to produce a photoconductive material having a capsule wall made of silicone resin.

The thus obtained photoconductive material 1007 toluene 100ml The mixture according to the above formulation was treated in the same manner as in Comparative Example 1 to produce an electrophotographic photoreceptor of the present invention.

This will be referred to as "Sample 4." Comparative Example 2 An electrophotographic photoreceptor was produced in exactly the same manner as in Comparative Example 1, except that the sensitized zinc oxide powder was used as the photoconductive material.

This will be referred to as [Sample 5]. Comparative Example 3 In Comparative Example 1, acrylic resin "HR-
112'' (50% by weight solution) (manufactured by Mitsubishi Rayon Co., Ltd.) 50
An electrophotographic photoreceptor was produced in exactly the same manner except that y was used.

This will be referred to as "Sample 6". A charging test and a copying test were conducted on each of the samples produced as described above and comparative samples.

In the charging test, the sample or comparison sample was attached to the "Electrostatic Copying Paper Tester SP-428" (manufactured by Kawaguchi Denki Seisakusho), and the voltage applied to the charger discharge electrode was set to -6K, and the sample was discharged for 5/7 seconds. The photosensitive layer is charged, and then 5
The series of operations of dark decaying for seconds and light irradiation was repeated continuously for the 1st, 2000th, and 5000th time.
and the surface potential V of the photosensitive layer after dark decay at the 10,000th operation. (volts), and this surface potential V.
In the first operation, the irradiation exposure amount required to attenuate to 1/2, that is, the half-reduced exposure amount E1/2 (lux seconds) is measured. V in the second operation on the value of . The ratio of the values, that is, the potential restoration rate m (%) was measured.
Further, the smoothness (M77!Hg) of the photosensitive layer was measured using "Smoothta SM-6B" (manufactured by Toei Electronics Co., Ltd.).

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-Bixl5OO" (manufactured by Konishiroku Photo Industry Co., Ltd.).
measuring the maximum image density DMAX of the copied images in the 5000th and 10000th copying operations;
The image quality of each was also evaluated in terms of background fog and image irregularities. The results of the above tests are shown in the table below. As judged from this table, sample 2 according to the present invention
The electrophotographic photoreceptor of No. 4 to 4 can withstand a very large number of copies, and since the surface of the photoreceptor is moderately rough and extremely uniform, it has excellent electrical properties such as a high charging potential, and can produce good copies. It is capable of forming images, and in particular, the resolution of the copied images obtained from it is extremely high. Furthermore, as is clear from the value of the potential restoration rate m, the surface potential o of the photosensitive layer obtained by the second charging is only slightly lower than that in the first charging, and the memory effect is very small. It is something.

Claims (1)

[Claims] 1. A photoconductive material powder formed by forming a capsule wall film containing a sensitizer for zinc oxide on the surface of zinc oxide particles is mixed with a silicone resin component, an acrylic resin component, and an ethyl cellulose 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. Claim 1, wherein 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 remainder is contained in the membrane of the capsule wall.
The electrophotographic photoreceptor described in . 5. The electrophotographic photoreceptor according to claim 1, wherein the capsule wall film is made of a resin having a three-dimensional network structure. 6. The electrophotographic photoreceptor according to any one of claims 1 to 5, wherein the resin constituting the capsule wall film is insoluble in a solvent in which the binder resin is dissolved.