JPH03209261A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity and speed in rising of electric charging potential even after repeated cycles of charging and exposure and to reduce residual potential by forming an undercoat layer composed of zirconium particles and a specified binder resin. CONSTITUTION:The undercoat layer is composed of the zirconium oxide and the binder resin prepared by adding a polyvinyl acetal resin to a methylethylketoxim block type hexamethylenediisocyanate trimer to react and harden them. It is preferred to treat the surface of the zirconium oxide with a silane coupling agent in order to enhance dispersibility, thus permitting the obtained electrophotographic sensitive body to be small in delay in rising of electric charging potential after repeated uses and small in change of residual potential.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor comprising a photosensitive layer consisting of a substrate, an undercoat layer, a charge generation layer, and a charge transport layer, and particularly relates to This invention relates to an improved electrophotographic photoreceptor.

[Conventional technology]

Conventionally, photoreceptors used in electrophotography include those with a photoconductive layer mainly made of selenium or selenium alloys on a conductive support, and inorganic photoconductive materials such as zinc oxide and cadmium sulfide. Generally known are those that use organic photoconductive materials such as poly-N-vinylcarbazole and trinitrofluorenone or azo pigments, and those that use amorphous silicon-based materials. There is.

By the way, in general, the "electrophotographic method" means that a photoconductive photoreceptor is first charged in a dark place by, for example, corona discharge, and then imagewise exposed to selectively dissipate the charge only in the exposed area, thereby increasing the electrostatic potential. Image formation in which an image is obtained by obtaining an image, and developing and visualizing this latent image area with electrostatic fine particles (toner) made of coloring materials such as dyes and pigments and binders such as polymeric substances to form an image. It is one of the laws.

The basic characteristics required of the photoreceptor in such electrophotography are (1) the ability to be charged to an appropriate potential in a dark place;

(2) Less charge dissipation in the dark.

(3) Charge can be quickly dissipated by light irradiation.

Examples include.

In addition to these basic characteristics, each of the above-mentioned photoconductors has excellent features and disadvantages in practical use, but in recent years, photoconductors that have low manufacturing costs, little environmental pollution, and are relatively free have been developed. Organic photoreceptors are rapidly developing due to their ease of design.

In general, an organic photoreceptor is a material in which a charge-generating material and a charge-transporting material are dispersed or dissolved in a binder resin and coated on a conductive support. Single layer type with transport function, charge generation layer (CGL) with charge generation function, charge retention and CG
A charge transport layer having a function of transporting charges injected from L (
CTL) and, if necessary, block charge injection from the support.

Alternatively, a functionally separated type is known, which has a structure in which layers having functions such as preventing light reflection on a support are laminated.

Although these organic photoreceptors have excellent characteristics as described above, they have the following drawbacks.

(1) Low chargeability and charge retention.

(2) Residual charge causes fog and density unevenness on the image.

(3) Because the chemical, physical, and mechanical properties of the substrate are nonuniform, defects such as white spots and black spots occur on the image.

In particular, when a high-sensitivity photoreceptor is repeatedly charged and exposed to light, the characteristic (1) above appears as a significant deterioration due to so-called electrostatic fatigue. Such fatigue is said to occur mainly because positive and/or negative charges remain in a movable state in the photoreceptor. That is, due to repeated charging exposure, residual charges move to the surface and neutralize the 1F charges at the start of the next charging operation, making it impossible to obtain the rapid rise in surface potential required at the initial stage of charging.

For this reason, a desired surface potential cannot be obtained within the time set in the charging process, which poses a serious problem particularly in high-speed copying processes.

Furthermore, in optical printers using LD light, it is common practice to use an undercoat layer in which inorganic particles are dispersed in order to prevent light interference. However, due to insufficient dispersion stability of the undercoat layer coating liquid and insufficient life span of the dispersion liquid, deterioration of image quality related to the above (3) becomes a problem.

For the above-mentioned drawbacks, for example, Japanese Patent Application Laid-Open No. 47-6341.
4g-3544 and 4g-12034 have a cellulose nitrate resin intermediate layer, which is disclosed in Japanese Patent Application Laid-Open No. 48-47344, 52.
-25638.58-30757.58-63945.
58-95351.58-98739 and 60-66
No. 258 has a nylon resin intermediate layer, which is disclosed in Japanese Patent Application Laid-Open No. 49-6
Nos. 9332 and 52-10138 disclose a maleic acid resin intermediate layer, and JP-A-5G-105155 discloses a polyvinyl alcohol resin intermediate layer. In addition, intermediate layers have been proposed in which various conductive additives are contained in a resin in order to control the electrical resistance of the intermediate layer.

For example, JP-A No. 51-65942 uses an intermediate layer in which carbon or chalcogen-based substances are dispersed in a curable resin, while J-Kokai @ 52-82238 uses an isocyanate-based curing agent with the addition of a quaternary ammonium salt. JP-A-55-1180451 discloses a resin intermediate layer containing a resistance modifier, and JP-A-58-58556 discloses a resin intermediate layer in which aluminum or tin oxide is dispersed. ,
JP-A No. 58-93062 discloses a resin intermediate layer containing an organic gold-sulfur compound;
Nos. 363 and 60-111255 have a resin intermediate layer in which conductive particles are dispersed, and JP-A-59-17557 has a layer in which magnetite is dispersed in a resin.
-84257.59-93453 and 60-3205
No. 4 discloses a resin intermediate layer in which Tie, SnO, and powder are dispersed.

However, conventionally known electrophotographic photoreceptors still have major problems, such as a decrease in chargeability or a large change in residual potential due to repeated use.

[Problem to be solved by the invention]

The present invention provides high sensitivity, extremely small decrease in chargeability due to electrostatic fatigue, rapid rise in charging potential even after repeated charging and exposure, and furthermore, a small change in residual potential for electrons. The purpose is to provide a photographic photoreceptor.

[Means to solve the problem]

According to the present invention, in an electrophotographic photoreceptor in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive substrate, the undercoat layer is made of zirconium oxide particles and a binder resin,
Further, an electrophotographic photoreceptor is provided, wherein the binder resin is a binder resin obtained by blending a methyl ethyl ketoxime block type hexamethylene diisocyanate trimer and a polyvinyl acetal resin and curing the mixture by reaction.

In addition, in an electrophotographic photoreceptor in which a subbing layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive substrate, the subbing layer is made of zirconium oxide particles and a binder resin, and the binder resin is made of methyl ethyl ketone. There is provided an electrophotographic photoreceptor characterized in that it is a binder resin in which an oxime block type xamethylene diisocyanate trimer and a styrene-methyl methacrylate-2-hydroxyethyl methacrylate copolymer are blended and cured by reaction.

The present inventor focused on the undercoat layer of an electrophotographic photoreceptor, which is formed by sequentially laminating a subbing layer, a charge generation layer, and a charge transport layer on a conductive substrate, and as a result of studies aimed at solving the above-mentioned drawbacks. It was discovered that by setting the components of the undercoat layer to the above-mentioned specific composition, an electrophotographic photoreceptor with less delay in the rise of the 4th charge and less change in residual potential after repeated use can be obtained. He has completed his invention.

The present invention will be explained in detail below.

The zirconium oxide contained in the undercoat layer is usually 9
A purity of 0% or more, preferably a purity of 99.5% or more is used.

In addition, it is preferable that the average particle size of the primary particles of zirconium oxide is 0.5 pm or less, and the average particle size of the secondary particles is dispersed to be 0.1 pm or less. Textures and stains are noticeable on the top, and the electrostatic characteristics have large variations in sensitivity and poor quality stability.

In the present invention, the surface of this zirconium oxide is preferably treated with a silane coupling agent in order to improve dispersibility.

Such silane coupling agents include trimethylmonoethoxysilane, dimethyljethoxysilane, methyltrimethoxysilane, tetraethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and δ-(methacryloxypropyl). ) trimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-β(aminoethyl)-γ
-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane.

To treat the surface of zirconium oxide using these silane coupling agents, the silane coupling agent is usually used in an appropriate solvent such as an aliphatic hydrocarbon such as n-hexane or an alcohol such as methanol or ethanol. diluted, then mixed with dried zirconium oxide, filtered,
It may be washed, dried, and subjected to a dispersion operation.

The binder resin used in the present invention is a mixture of methyl ethyl ketone oxime block type hexamethylene diisocyanate trimer and polyvinyl acetal resin or styrene-methyl methacrylate-2-hydroxyethyl methacrylate copolymer and cured in one reaction. .

In this case, the so-called methyl ethyl ketoxime blocked hexamethylene diisocyanate trimer, which is a hexamethylene diisocyanate trimer blocked with methyl ethyl ketoxime, is used as the methyl ethyl ketoxime blocked hexamethylene diisocyanate trimer.

Blocked isocyanates are generally stable at room temperature, but easily dissociate into the original isocyanate when heated, or undergo exchange reactions with active hydrogenated compounds.

Irishi 001 Dishima; R-NGO + R'H2 = Go R-NH-Co-R' Dissociation reaction The dissociation reaction of the block isocyanate compound does not occur unless the temperature is 180 to 200'C or higher in the case of no catalyst, so 160 ``To dissociate at low temperatures below C, a catalyst is required.

When the undercoat layer is heated and dried at an appropriate temperature in this manner, the isocyanate is activated and undergoes a thermal crosslinking reaction with the polymeric compound containing OH groups, resulting in a cured coating film.

The polyacetal resin used in the present invention generally includes polyvinyl acetal resins containing the following repeating units, and forms resins with different characteristics depending on the type of H.

Specific examples of this polyvinyl acetal resin include resins containing repeating units as shown below.

Furthermore, in the present invention, a polyvinyl butyral resin containing vinyl acetate and vinyl alcohol monomers at the same time in the monomer composition (4) is preferably used as described below.

(ff, m, n: ll number) Normally a is 50-50-8O%, beauty is 10moff%
Hereinafter, those in which n is 30-50+go parts are preferred.

In this way, in addition to at least one type of repeating unit selected from (1) to (5) above, the resin may contain two or more other types of repeating units in order to improve properties.

In this case as well, the resin must have OH groups present for the curing reaction. What is the OH content?

It is usually 1 to 10 wt%, preferably 3 to 8 wt%. The OH content rate is roughly considered from the following two points.

(1) An amount of O that can be cured to the extent that the undercoat layer does not dissolve in the solvent of the coating solution for the charge generation layer laminated on the undercoat layer.
) Contains an I group.

(2) Contains an amount of OR groups that facilitates dispersion of zirconium oxide in the resin.

Styrene-methyl methacrylate used in the present invention
The 2-hydroxyethyl methacrylate copolymer resin can be obtained by radical polymerization by mixing styrene, methyl methacrylate and 2-hydroxyethyl methacrylate in desired proportions. A molecular weight of 20,000 to 50,000 that has the following repeating unit is suitable. Further, by changing the mixing ratio of these monomers, a desired copolymer can be obtained.

02=30-75, FI()-60, n=3-4 In this case also OH groups must be present in the resin for the curing reaction, the OH content is usually 1-10
wt%, preferably 3-8wtZ. The OH content rate is roughly considered from the following two points.

(1) An amount of O that can be cured to the extent that the undercoat layer does not dissolve in the solvent of the coating solution for the charge generation layer laminated on the undercoat layer.
Contains an H group.

(2) Contains an amount of OH groups that facilitates dispersion of zirconium oxide in the resin.

In this case, it is necessary to add the incyanate compound in an amount (equivalent) commensurate with the OH group content.

However, in some cases, zirconium oxide particles
A large amount of adsorbed water is contained, and sufficient drying cannot be obtained by heat drying.Also, the solvent used in the coating liquid contains a small amount of water, and the isocyanate compound is not applied to the resin. Even if an equivalent amount is added, it will actually be insufficient. For this reason, a large amount of uncrosslinked hydroxyl groups remain,
The undercoat layer is cured, and as a result, the influence of temperature and humidity on the photoreceptor appears to be greater.

In this case, in the present invention, the amount of the methyl ethyl ketoxime block type hexamethylene diisocyanate compound added is adjusted to the ratio of the number of NCO groups to the number of OH groups in the polyacetal resin or styrene-methyl methacrylate-2-hydroxyethyl methacrylate copolymer (NGOloH
) is in the range of 171 to 5/1, preferably 1/1 to 3/1, thereby ensuring stable charging performance even under fluctuations in temperature and humidity.

When the NGO10H ratio is less than 1/1, the above-mentioned problems are likely to occur, and when it is 571 or more, the inherent good properties of the polyacetal resin or styrene-methyl methacrylate-2-hydroxyethyl copolymer are lost.

The ratio of the zirconium oxide particles to the binder resin is 1'1/1-19/1, preferably 3/1-10/I by weight.
There is t'.

If the usage ratio is less than 1/1, the effect will be small;
Exceeding this is not preferable because air bubbles remain in the undercoat layer, causing defects in the charge generation layer and charge transfer layer coatings.

The thickness of the undercoat layer is 0.3 to 10/a+, preferably 0.5 to 5.0/a+. Undercoat layer thickness is 0.3pa+
If it is less than 10, the effect will be poor, and if it is more than 10, residual potential will accumulate, which is not desirable.

In the present invention, in order to form the undercoat layer, a liquid in which the above components are dissolved or dispersed is applied onto the conductive substrate,
dry. Drying conditions are usually 80-200℃, 20℃
Minutes to IO hours.

Further, if necessary, a catalyst such as dibutyltin laurate may be added to promote the reaction. In this case, the blending amount of dibutyltin laurate is preferably about 0.5 to 3 Ovt% based on the block type isocyanate.

Examples of conductive substrates include those exhibiting conductivity with a volume resistance of 101 oΩc11 or less, such as aluminum, nickel,
Metals such as chromium, nichrome, copper, silver, gold, and platinum, and metal oxides such as tin oxide and indium oxide are coated on film or cylindrical plastics, paper, etc. by vapor deposition or sputtering, or aluminum. , plates of aluminum alloy, nickel, stainless steel, etc., and their adhesives; 1. ．． 1. ．． 1. It is possible to use pipes that have been made into blank pipes by methods such as , extrusion, and drawing, and then surface-treated by cutting, superfinishing, polishing, and the like.

Next, the charge generation layer will be explained.

The charge generation layer is a layer mainly composed of a charge generation substance, and a binder resin may be used as necessary.

Binder resins include polyamide, polyurethane,
Polyester, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone,
Polystyrene, poly-N-vinylcarbazole, polyacrylamide, etc. are used.

As the charge generating substance, for example, CI Pigment Blue 25 [Color Index (CI) 21180]
, CI Pigment Red 41 (CI 21200)
, Sea Eye Acid Red 52 (CI 45100),
CI Basic Red 3 (CI 45210), further contains a phthalocyanine pigment having a porphyrin skeleton, an azulenium salt pigment, a squalic salt pigment, an azo pigment having a carbazole skeleton (described in JP-A-53-95033), and a stilstilbene skeleton. (described in JP-A No. 53-138229), azo pigments having a triphenylamine skeleton (described in JP-A-53-132
547), an azo pigment having a dibenzothiophene skeleton (described in JP-A-54-21728),
Azo pigments having an oxadiazole skeleton
12742), an azo pigment having a fluorenone skeleton (described in JP-A No. 54-22834), an azo pigment having a bisstilbene skeleton (described in JP-A-54-17)
733), azo pigments having a distyryloxadiazole skeleton (described in JP-A-54-2129), azo pigments having a distyrylcarbazole skeleton (described in JP-A-54-2129),
(described in JP-A No. 54-17734), triazo pigments having a carbazole skeleton (described in JP-A-57-195767)
Publication No. 57-195768), and CI Pigment Blue 16 (CI 74100).
), C.I. Butt Brown 5 (CI 73410), C.I. Butt Dye (CI
73030), Argo Scarlet B (manufactured by Violet Co., Ltd.), Indus Thread Scarlet R
Organic pigments such as perylene pigments such as (Bayer Il) can be used.

Among these charge-generating substances, azo pigments are particularly preferred, and among azo pigments, disazo pigments and trisazo pigments shown below are most preferred.

Specific examples of azo pigments are shown below.

These charge generating substances may be used alone or in combination of two or more.

The binder resin is suitably used in an amount of 0 to 100 parts by weight, preferably 0 to 100 parts by weight, based on 100 parts by weight of the charge generating substance.
~50 parts by weight.

The charge generation layer contains a charge generation substance, along with a binder resin if necessary, tetrahydrofuran, cyclohexanone,
It can be formed by dispersing in a ball mill, attritor, sand mill, etc. using a solvent such as dioxane or diglolethane, and diluting the dispersion liquid appropriately and applying it. Application can be performed using a dip coating method, a spray coating method, a bead coating method, or the like.

The thickness of the charge generation layer is suitably about 0.01 to 5 pa, preferably 0.1 to 2 pa.

The charge transport layer consists of a charge transport substance and a binder resin used as necessary.

A charge transport layer can be formed by dissolving or dispersing the above-mentioned substances in a suitable solvent and applying and drying the solution.

Charge transport materials include hole transport materials and electron transport materials.

As hole transport substances, poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole Derivatives, imidazole derivatives, triphenylamine derivatives, 9-(P-diethylaminostyryl)anthracene, ■, 1-bis(4-dibenzylaminophenyl)propane, styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene Examples include electron-donating substances such as derivatives.

Examples of the electron transport substance include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4,7-dolinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone,
2,4,5.7-titranitroxanthone, 2,4°8
-trinidrothioxanthone, 2,6.8-trinitro-4H-indeno(1,2-b)thiophen-4-one, 1,3,7-trinitrodibenzothiophenone-5,
Examples include electron-accepting substances such as 5-dioxide.

These charge transport substances may be used alone or in a mixture of two or more.

Binder resins used as necessary in the present invention include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride- Vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone Examples include thermoplastic or thermosetting resins such as resins, epoxy resins, melamine resins, urethane resins, phenolic resins, and alkyd resins.

As the solvent, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride, etc. are used.

The appropriate thickness of the charge transport layer is about 5 to 100 μl.

Furthermore, in the present invention, a plasticizer or a leveling agent may be added to the charge transport layer.

Those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is 0 to 30% based on the binder resin.
A weight of about 2 is appropriate. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil are used, and the appropriate amount thereof is about 0 to 1 weight x based on the binder resin.

In the present invention, it is also possible to further provide an insulating layer or a protective layer on the photosensitive layer.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

To Example I〇 The following subbing layer coating solution (A) was applied with a blade onto a vapor-deposited polyester film, and dried at 120°C for 30 minutes to form a subbing layer containing zirconium oxide with a film thickness of i and ops. Formed.

[Subbing layer coating liquid (A)]

530 g of a 7.7% by weight cyclohexanone solution of butyral resin (S-LEC BL-1: Sekisui Chemical Co., Ltd.) and 450 g of zirconium oxide (TZ-0: Tosoh Corporation) were put into a ball mill pot (15φ hard glass), and P
The container was filled with Sz balls (made of partially stable zirconia) to about half the content, and ball milled for 100 hours.

64.3 parts by weight of this mill base, 3.4 parts by weight of a 75% by weight solution of methyl ethyl ketoxime block type hexamethylene diisocyanate trimer in turbenzi naphtha, and 32 parts by weight of a 2% by weight cyclohexanone solution of the butyral resin.
2 parts by weight were mixed to prepare an undercoat layer coating solution.

Next, the charge generation layer coating solution shown below was coated with a blade on this undercoat layer, and after drying at 120° C. for 10 minutes, a charge generation layer having a thickness of 0.7 mm was formed.

(Charge generation layer coating liquid) PSZ balls were put into a 15φcm hardened glass pot to about half of the content, and then the azo pigment h3925 was added to the pot.
g and 415 g of cyclohexanone were added. After ball milling for 50 hours, 560 g of cyclohexanone was further added and ball milling was carried out for 24 hours. Cyclohexanone was added to this mill base to dilute it to about 2.0 wt % to prepare a charge generation layer coating solution.

Next, the charge transport layer coating solution shown below was coated with a blade on the charge generation layer, and dried at 120°C for 20 minutes to a film thickness of 20 μm.
A charge transport layer was provided to obtain an electrophotographic photoreceptor of the present invention.

(Charge transport layer coating liquid) Charge transport material having the following structural formula 20g Tetrahydrofuran 160g Example 2 In Example 1, the subbing layer coating liquid (A) was replaced with the following subbing layer coating liquid (8). An electrophotographic photoreceptor of the present invention was produced in the same manner as in Example 1 except for this.

[Subbing layer coating liquid]

Styrene-methyl methacrylate-2-hydroxyethyl methacrylate copolymer resin (copolymerization ratio styrene:
Methyl methacrylate: 2-hydroxyethyl methacrylate = 49:34:11.5 (molar ratio) of 7.7
530 parts by weight of a 7:3 weight percent solution (mixture of cellosolve acetate and methyl isobutyl ketone) and 450 parts by weight of zirconium oxide (TZ-0: Tosoh Corporation) were put into a ball mill pot (made of 15φ hard glass). death,
PSz balls (partially stabilized zirconia) were filled to about half of the content and ball milled for 100 hours.

76.6 parts by weight of this millbase and methyl ethyl ketoxime blocked hexamethylene diisocyanate trimer (
2.3 parts by weight of solvent naphtha (75% by weight solution) and 21.0 parts by weight of the above copolymer resin liquid (10% by weight of the above mixed solvent)
Parts by weight and appropriate amounts of methyl ethyl ketone were added to prepare an undercoat layer coating solution.

Comparative Example 1 In preparing the undercoat layer coating solution of Example 1, toluylene diisocyanate was used instead of methyl ethyl ketoxime block type hexamethylene diisocyanate, and 37.2 weight of the mill base and 0.0.
In the same manner as in Example 1, except that the undercoat layer coating solution was prepared by mixing 8 parts by weight of the butyral resin solution, 12.0 parts by weight of the butyral resin solution (10% by weight cyclohexanone solution), and 37.9 parts by weight of the diluting solvent. A photoreceptor was created.

Comparative Example 2 In preparing the undercoat layer coating solution of Example 2, toluylene diisocyanate was used instead of methyl ethyl ketoxime block type hexamethylene diisocyanate, and 37.2 parts by weight of mill base and 0 of the above isocyanate were used.
．． Example 2 except that the undercoat layer coating solution was prepared by mixing 8 parts by weight of the butyral resin solution, 12.0 parts by weight of the butyral resin solution (10% by weight cyclohexanone solution), and 37.9 parts by weight of the diluting solvent.
A photoreceptor was prepared in the same manner as above.

Using a commercially available electrostatic copying paper tester (Kawaguchi Denki Seisakusho 5P-428), each of the electrophotographic photoreceptors produced as described above was charged by performing corona discharge at -6 KV for 20 seconds, and then charging started 2. The surface potential (v2) after seconds was measured. In addition, after 20 seconds of dark decay, the surface potential VR (residual potential) after irradiation with a 2856 tungsten lamp at 135 Qux and sac was measured.
After being charged to a surface potential of 0V, it was exposed to light using the tungsten lamp, and the exposure amount 5 (Qux-sec) required for the surface potential to attenuate to 1400V was measured.

Furthermore, in order to determine the repeated fatigue characteristics, charging at 17 KV and exposure at 3 Hux were alternately repeated for 1 hour using the above apparatus, and v2', vR' and S' after fatigue were measured.

The results are shown in Table-1.

Table 1 Table 2 Furthermore, the undercoat layer coating liquids of Examples 1 and 2 and Comparative Examples 1 and 2 were stored at room temperature, and the viscosity increase and average particle size of the liquids were measured.

The results are shown in Table-2.

Viscometer: E-type viscometer (Tokyo Keiki) Average particle size: Particle size distribution measuring device ICAPA-500 (Horiba, Ltd.) From Table 2, the values of Examples 1 and 2 are lower than those of Comparative Examples 1 and 2. It can be seen that the increase in viscosity of the layer coating liquid is almost negligible and the dispersibility is also good. On the other hand, in Comparative Examples 1 and 2, the viscosity significantly increased after one week, making them unusable.

〔Effect of the invention〕

Since the electrophotographic photoreceptor of the present invention has the above-mentioned structure, it has remarkable characteristics such as high sensitivity, rapid rise of the charging position 4, and small residual potential even after repeated charging and exposure.

In addition, the life of the undercoat layer coating liquid is long, and there is almost no increase in viscosity or decrease in dispersibility, so it is possible to form an undercoat layer with stable properties, and its production is stable and inexpensive.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive substrate, the undercoat layer is made of zirconium oxide particles and a binder resin, and the binder resin is An electrophotographic photoreceptor characterized in that the binder resin is a mixture of a methyl ethyl ketoxime block type hexamethyl diisocyanate trimer and a polyvinyl acetal resin and is cured by reaction. (2) In an electrophotographic photoreceptor in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive substrate, the undercoat layer is made of zirconium oxide particles and a binder resin, and the binder resin is An electrophotographic photoreceptor comprising a binder resin containing a methyl ethyl ketoxime block type hexamethylene diisocyanate trimer and a styrene-methyl methacrylate-2-hydroxyethyl methacrylate copolymer and curing the mixture by reaction.