JPH02293757A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity and to lessen the degradation in chargeability due to electrostatic fatigue by incorporating zirconium oxide particles subjected to a surface treatment with an org. titanium compd. and binder resin into an under coating layer to be provided on a conductive base body. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating the under coating layer, a charge generating layer and a charge transfer layer on the photosensitive base body. The zirconium oxide particles subjected to the surface treatment with the org. titanium compd. and the binder resin are incorporated into the under coating layer and the reaction cured matter of a polyacetal resin and a cyclic aliphat. isocyanate compd. is used for the binder resin. The high sensitivity is obtd. in such a manner; in addition, the rise of the electrostatic potential is expedited and the residual potential is lessened even after the repetition of the electrostatic charge exposing. The change in the electrical characteristics with temp. and humidity is lessened as well.

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.
In particular, it relates to an electrophotographic photoreceptor with an improved undercoat layer.

[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 sulfate. Dispersed in a binder, organic photoconductive materials such as boly-N-vinyl rubazole and trinitrofluorenone or azo pigments, and non-quality silicon-based materials are generally known. .

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 to create an electrostatic latent material. An image was obtained, and this latent image area was developed and visualized with electroscopic fine particles (L-ner) composed of a coloring material such as a dye or pigment and a binder such as a polymer substance to form an image. It is one of the image forming methods.

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) The electric charge can be quickly dissipated by light irradiation.

Examples include.

In addition to these basic characteristics, each of the above photoreceptors has excellent features and drawbacks in practical use, but in recent years, they have become particularly popular, with low manufacturing costs, low environmental pollution, and relatively free use. The development of organic photoreceptors is remarkable due to the ability to design photoreceptors.

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
Charge transport l that has the function of transporting charges injected from L
(CTL), and a functionally separated type that has a laminated layer that has functions such as blocking charge injection from the support or preventing light reflection from the support as necessary. Are known.

Although these organic photoreceptors have excellent features as described above, they have the following drawbacks because they are organic materials.

(1) Low chargeability and charge retention.

(2) Residual charge causes image fogging and density unevenness.

(3) Defects such as white spots and black spots occur on images because the chemical, physical, and mechanical properties of the substrate are nonuniform.

In particular, when a high-sensitivity photoreceptor is subjected to repeated charging and exposure, 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. In other words, due to repeated charging exposure, the remaining charges move to the surface at the start of the next charging operation and neutralize the charged charges.
The required rapid rise in surface potential at the initial stage of charging cannot be achieved.

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.

For the above-mentioned drawbacks, for example, Japanese Patent Application Laid-Open No. 47-6341,
48-3544 and 48-12034, cellulose nitrate resin intermediate layers are disclosed in Japanese Patent Application Laid-open Nos. 48-47344 and 52.
-25638, 58-30757, 58-63945,
58-95351, 58-98739 and 60662
No. 58 has a nylon resin intermediate layer, which was published in JP-A-49-69.
Nos. 332 and 52-10138 disclose a maleic acid resin intermediate layer, and JP-A-58-105155 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, and JP-A No. 52-82238 uses an isocyanate-based curing agent with the addition of a quaternary ammonium salt. The thermopolymer intermediate layer
JP-A No. 55-1180451 discloses a resin intermediate layer containing a resistance adjusting agent, JP-A No. 58-58556 discloses a resin intermediate layer containing aluminum or tin oxide dispersed therein, and JP-A No. 58-93062 discloses a resin intermediate layer containing an oxide of aluminum or tin dispersed therein. JP-A-5893063, 60-9736 discloses a resin intermediate layer to which an organometallic compound is added.
3 and 60-1]. Is No. 1255 conductive? JP-A-59-17557 discloses a resin intermediate layer in which magnetite is dispersed in a resin, and JP-A-59-17557 discloses a layer in which magnetite is dispersed in a resin.
84257, 59-93453 and 60-32054
No. 3 discloses a resin intermediate layer in which TiO■, SnO, and powder are dispersed.

However, conventionally known electrophotographic photoreceptors are still insufficient in terms of deterioration in chargeability due to repeated use, particularly in terms of delay in the rise of the charge level, and furthermore, residual potential changes are large, which is still a major problem. Furthermore, many of the resins, inorganic particles, dyes, and other organic substances used in the intermediate layer are easily affected by temperature and humidity, to varying degrees, and as a result, the resistance value of the intermediate layer changes widely. . Even if an intermediate layer of a certain suitable material and film thickness is provided at normal temperature and humidity, the electrostatic characteristics of the photoreceptor change significantly at low temperature and low humidity or high temperature and high humidity.

[Problem to be solved by the invention]

The present invention provides electrophotography that is highly sensitive, has a significantly small drop in chargeability due to electrostatic fatigue, and has a fast rise in charging potential and small change in residual potential even after repeated charging and exposure. Another object of the present invention is to provide an electrophotographic photoreceptor that has good charging properties and does not change its residual potential even under high temperature and high humidity conditions and at varying temperatures and low humidity.

〔composition〕

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 has an oxidized An electrophotographic photoreceptor characterized by containing zirconium particles and a binder resin is provided.

The present inventor focused on the subbing 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 conducted extensive studies to eliminate the above-mentioned drawbacks. result,
By setting the components of the undercoat layer to the above-mentioned specific composition, an electrophotographic photoreceptor is provided that has little delay in the rise of charge potential after repeated use, has little change in residual potential, and has little change in characteristics with respect to temperature and humidity. The present inventors have discovered that the following can be obtained, and have completed the present invention.

The present invention will be explained in detail below.

The zirconium oxide contained in the undercoat layer usually has a purity of 90% or more, preferably 99.5% or more. Also, 1 of zirconium oxide
The average particle size of the secondary particles is 0.5μ or less, preferably 0.3μ
It is preferable that the dispersion is below 0.5 μm. If the dispersion is above 0.5 μm, roughness of letters, stains, etc. will be noticeable on the image, and the electrostatic properties will have large variations in sensitivity and poor quality stability.

In the present invention, an organic titanium compound is used as a surface treatment agent for this zirconium oxide.

As the organic titanium compound, at least one of the compounds represented by the general formula (1), the general formula (I1), and the general formula (III) is usually used.

(General formula (1), (■), OR,. 0112
, OR3 and OR4 represent an alkoxy group, a carbalkoxy group, a phenoxy group, a sulfoxy group, or a phosphooxy group, and n represents O or an integer of 1 or more) Ti(L)nX4-n
(III) (In the general formula (III), L is a chelate group, X is an ester group, and n is an integer of 1 to 4) Examples of the compound represented by the general formula (1) include tetramethyl orthotitanate, tetraethyl Ortho titanate, tetra n-probyl ortho titanate, tetraisobutyl ortho titanate, tetrabutyl ortho titanate, tetraisobutyl ortho titanate, tetracresyl titanate, tetrastearyl titanate, tetra 2-ethylhexyl titanate, isoprobyl triisostearyl titanate, Isoprobil tridodecylbenzenesulfonyl titanate, isoprobil tris(
Examples include dioctyl diphosphate) titanate.

Examples of the compound represented by general formula (II) include:
Examples include tetrabutyl polytitanate, tetracresyl polytitanate, and tetraacetylacetonate-1 to polytitanate.

Examples of the compound represented by the general formula (m) include diisopropoxytitanium-bis-octanediol,
Examples include diisoproboxytitanium-bis-hexanediol, diisoproboxytitanium-bis(acetylacetonate), titanium tetraherlactate ethyl ester, and tetratriethanolamine titanium chelate.

Other titanium compounds include titanium tetraammonium lactate, titanium tetraacetylacetonate ammonium lactate, tetraisopropyl bis(dioctyl phosphate) titanate, tetraoctyl bis(ditridecyl phosphate) titanate 1~, tetra (2,2-Diaryloxymethyl-1-butyl)bis(tetridecyl phosphate) titanate, bis(dioctylpicophosphate)
In addition to oxyacetate 1-titanate, tris(dioctyl piophosphate) ethylene titanate, and the like, the following titanium compounds may also be mentioned.

Isoprobil tris isostearyl titanate, isoprobil tris (dioctyl piophosphate), isopropyl tri(N-aminoethylaminoethyl) titanate, tetraoctyl bis(di-1-lidecylphosphite-1) titanate, tetra(2) .2'-diallyloxymethyl-1-butyl) bis(ditridecyl) phosphite titanate, bis(dioctylpyrophosphate) oxyacetate titanate, bis(dioctylpyrophosphate) ethylene titanate, isoprobyl trioctanoyl titanate, isoprobyl di Methacryl isostearyl titanate, isoprobyl tridodecyl benzenesulfonyl titanate, isoprobyl isostearoyl diacryl titanate, isopropyl tri(
dioctyl phosphate) titanate, isoprobyl tricumyl phenyl titanate, tetraisopropyl pyrubis (dioctyl phosphite) titanate, etc.

To treat the surface of zirconium oxide using these organic titanium compounds, the organic titanium compound is usually diluted with an appropriate solvent such as n-hexane or alcohol, and then mixed with the dried zirconium oxide. , filtration, washing, drying, and dispersion operation.

Various binder resins can be used, but polyacetal resins reaction-cured with isocyanate-1 compounds are preferably used.

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 R.

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 follows.

(n, m, n: integer) Usually Q is 50-80 moR%, m is 10 mofl% or less. Preferably, it has a value of 30 to 50 moro.

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. 011 content is usually 1~
10tat%. Preferably, it is 3 to 8 tyt%. O
The l+ content rate is roughly considered from the following two points.

(1) The undercoat layer should contain a curable amount of OH groups to the extent that the undercoat layer does not dissolve in the solvent of the coating liquid for the charge generation layer laminated on the undercoat layer.

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

Examples of isocyanate compounds include cycloaliphatic diisocyanates such as 4,4'-methylenebis(cyclohexyl isocyanate), isophorone diisocyanate, and 1,3-(isocyanate)cyclohexane, as well as adducts obtained by adding isocyanate compound monomers to polyols, such as An isocyanate compound having the following structure in which three molecules of isophorone diisocyanate are added to trimethylolpropane is also used.

Furthermore, isocyanurates in which three molecules of cycloaliphatic diisocyanate are polymerized can also be used.

These isocyanate compounds undergo a thermal crosslinking reaction with a polymeric compound containing an OH group to form a cured coating film. In this case, it is necessary to add an amount (equivalent) of the isocyanate compound commensurate with the amount of OH groups.

However, in some cases, zirconium oxide particles
A large amount of adsorbed water is contained, and sufficient drying cannot be achieved by heat drying.Also, the solvent used in the coating solution contains a small amount of water, and the isocyanate compound is not equivalent to the resin. Even if it is added, it will actually be insufficient.

Therefore, the undercoat layer is cured with a large amount of uncrosslinked hydroxyl groups remaining, 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 isocyanate compound added is determined by the ratio of the number of NGO groups in the isocyanate compound to the number of OH groups in the polyacetal resin (NGO/OH) of 1.
By setting the ratio within the range of /1 to 571, preferably 1/1 to 3/1, stable charging performance is ensured even under fluctuations in temperature and humidity.

When the NGO/OH ratio is less than 1/1, the above problems are likely to occur, and when it is 5/1 or more, the good properties inherent to the polyacetal resin are lost.

The ratio of the zirconium oxide particles to the binder resin is 1:1 to 19/1, preferably 3:1 to 10/1, by weight.6 If the ratio is less than 171, the effect will be small;
If it exceeds /1-15-, air bubbles will remain in the underlayer, causing defects in the charge generation layer and charge transfer layer coatings, which is not preferred.

The thickness of the undercoat layer is 0.3 to 10 μm, preferably 0.3 μm to 10 μm.
．． It is 5 to 5.0μ. If the thickness of the undercoat layer is less than 0.3 .mu.m, the effect will be poor, and if it is 10 .mu.m or more, residual potential will accumulate, which is not desirable.

In the present invention, in order to form the undercoat layer, a solution in which the above components are dissolved or dispersed is applied onto the conductive substrate and dried. Drying conditions are usually 80-150℃, 20
minutes to 10 hours.

The conductive substrate may be one having a volume resistance of 101 Ωcm 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. , aluminum alloy, nickel, stainless steel, etc. plates and their D. I. ,I. I. 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, etc.

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-vinyl Rubazole, polyacrylamide, etc. are used.

Examples of the charge generating substance include C.I. Picment Blue-25 [Color Index (CI) 21180],
CI pigment red 41 (CI 21200),
C.I. Acid Red 52 (CI 45100), C.I. Basic Red 3 (CI 45210), and a lid cyanine pigment having a porphyrin skeleton,
Azulenium salt pigments, squalic salt pigments, azo pigments with a carbazole skeleton (described in JP-A-53-95033), azo pigments with a stilstilbene skeleton (
(described in JP-A No. 53-138229), azo pigments having a triphenylamine skeleton (described in JP-A-53-1325)
47), azo pigments having a dibenzothiophene skeleton (described in JP-A No. 54-21728), azo pigments having an oxadiazole skeleton (described in JP-A-54-1988),
274 No. 2), azo pigments having a fluorenone skeleton (described in JP-A-54-22834), azo pigments having a bisstilbene skeleton (described in JP-A-54-17)
733), an azo pigment having a distyryl oxadiazole skeleton (described in JP-A-54-2129), an azo pigment having a distyryl oxadiazole 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)
In addition, CI Pigmen 1 Blue 16 (CI 7410
0), C.I. Butt Brown 5 (CI 73410), C.I. Butt Dye (CI
73030), Argo Scarlet B (manufactured by Violet Co., Ltd.), Indus Thread Scarlet 1
Organic pigments such as perylene pigments such as -R (manufactured by Bayer AG) can be used.

Among these charge-generating substances, azo pigments are particularly preferred, and among azo pigments, disazo pigments and 1.lisazo pigments shown below are most preferred.

Specific examples of azo pigments are shown below.

32 - 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 O to 100 parts by weight, preferably O.
~50 parts by weight.

The charge generation layer is prepared by dispersing a charge generation substance together with a binder resin if necessary using a ball mill, attritor, sand mill, etc. using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, etc., and diluting the dispersion liquid appropriately. It can be formed by applying it.

Coating can be carried out 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 μm, preferably 0.1 to 2 pm.

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.

Examples of hole transport substances include poly-N-vinyl rubazole and its derivatives, poly-γ-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, and oxadiazole. derivative, imidazole derivative, triphenylamine derivative, 9(p-diethylaminostyryl)anthracene, 1,1-bis=(4-dibenzylaminophenyl)
Examples include electron-donating substances such as propane, styryl anthracene, styryl pyrazoline, phenylhydrazones, and α-phenylstilbene derivatives.

Examples of the electron transport substance include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinone dimethane-2.4.7-trinitro-9-fluorenone, 2,4,5.7-tetranito-9-fluorenone, 2,4,5.7-te1heranitroxanthone, 2,4
, 8-trinitrothioxanthone, 2,6.8-trinitro 4H-indeno (1.2-bl thiophen-4-one, l., 3.7 trinitrodibenzothiophenone-5
, 5-dioxide and other electron-accepting substances.

These charge transport materials may be used alone or in combination of two or more.

Further, as the binder resin used as necessary in the present invention, polystyrene, styrene-acrylonyl 1-lyl copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, Vinyl chloride vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyaryle 1 resin,
Phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, polyN-
Vinyl Rubazol, acrylic resin, silicone resin,
Examples include thermoplastic or thermosetting resins such as 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 μm.

Further, in the present invention, a plasticizer or a leveling agent may be added to the charge transport layer. As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the appropriate amount to be used is about θ to 30% by weight based on the binder resin. 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% by weight 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.

Example I The following undercoat layer coating solution was dip-coated on an AQ board, and
Dry at ℃ for 30 minutes to a film thickness of 2. An undercoat layer containing OR zirconium oxide was formed.

[Undercoat layer coating liquid]

525 g of a 5.7% by weight cyclohexanone solution of butyral resin (S-LEC BL-1: Sekisui Chemical Co., Ltd.) and 465 g of zirconium oxide (manufactured by Daiichi Kigenso Kogyo Co., Ltd.) surface-treated with an organic titanium compound according to the following recipe were added to a Pall Mill pot ( 15φG hard glass), filled with PSZ balls (made of partially stable zirconia) to about half of the content, and dispersed in a ball mill for 100 hours.

(Surface treatment of zirconium oxide) Zirconium oxide particles (Zr02-EP type) dried at 120° C. for 24 hours were mixed into a 5.0 weight methanol solution of tetra n-probyl titanate and stirred.

The filtrate was then filtered, and the filtered product was washed with a large amount of methanol, and then dried at 120° C. for 1 hour to obtain zirconium oxide whose surface was treated with an organic titanium compound.

224g of this mill base and 127g of methyl ethyl ketone
After dilution by adding 9 g of 1.3-(isocyanate methyl)cyclohexane and
0 wt% cyclohexanone solution) was added to adjust the molar ratio of isocyanate groups to hydroxyl groups to 3.0:1 (NCO/
OH=3.0/1) and the weight ratio of zirconium oxide particles to binder resin to 6:1 to prepare an undercoat layer coating solution.

Next, on this undercoat layer, the following charge generation layer coating solution was applied by dipping coating, and after drying at 120° C. for 10 minutes, a charge generation layer having a thickness of 0.7 μm was formed.

(Charge generation layer coating liquid) PSZ balls were put into a 15φ hardened glass pot to about half of the content, and then the azo pigment Nα39 2
5 g and 415 g of cyclohexanone were charged. After 50 hours of ball milling, additional 560 g of cyclohexanone
was added and ball milled for 24 hours. Add cyclohexanone to this mill base for about 2. A charge generation layer coating solution was prepared by diluting it to Owt%.

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

(Charge transport layer coating liquid) 20 g of charge transport material having the following structural formula Tetrahydrofuran 160 g Example 2 In Example 1, the amount of millbase for the undercoat layer coating liquid was 208 g, the amount of methyl ethyl ketone was 136 g, 1
．． An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that the amount of 3-(isocyanatomethyl)cyclohexane was changed to 6.5 g and the amount of butyral resin was changed to 35 g.

Example 3 In Example 1, the amount of mill base in the undercoat layer coating solution was 243 g, the amount of methyl ethyl ketone was 124 g, 1.3
-(isocyane-1-methyl)cyclohexane 3.8g
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that 3 g of the butyral resin solution was used.

Example 4 In Example 1, except that the surface treatment liquid for the zirconium oxide particles was replaced with a 3wt% n-hexane solution of diisopoxytitanium-bis-hexanediol, and the azo pigment, which was the charge-generating material, was changed from Nα39 to Nα1. An electrophotographic photoreceptor was produced in the same manner as in Example 1.

Example 5 An electrophotographic photoreceptor was produced in the same manner as in Example 4, except that the undercoat layer coating solution having the composition shown in Example 2 was used.

Example 6 An electrophotographic photoreceptor was prepared in the same manner as in Example 4, except that the undercoat layer coating solution having the composition shown in Example 3 was used.

Comparative Example 1 An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that ordinary zirconium oxide particles whose surface had not been surface-treated with an organic titanium compound were used.

Comparative Example 2 In Comparative Example 1, the amount of mill base in the undercoat layer coating solution was 177 g, the amount of methyl ethyl chloride was 130 g, 1.
Comparative Example 1 was carried out in the same manner as in Comparative Example 1, except that the 3-(incyane-1-methyl)cyclohexane group was changed to 1.4 g, the amount of butyral resin liquid was changed to 71 g, and the azo pigment, which was a charge generating material, was changed from Nn39 to N01. An electrophotographic photoreceptor was prepared.

Each of the electrophotographic photoreceptors produced as described above was charged by performing -6KV corona discharge for 20 seconds using a commercially available electrostatic copying paper tester (Kawaguchi Electric Seisakusho SP-428). The surface potential (v2) after seconds was measured. After charging for 20 seconds, a 2856°K tungsten lamp was heated to 20ρux. The surface potential VR (residual potential) after see irradiation was measured. Then again -800
After being charged to a surface potential of V, it was exposed to light using the tungsten lamp, and the exposure amount S required for the surface potential to attenuate to -400V was measured.

Furthermore, in order to understand the repeated fatigue characteristics, -
Charging at 7 KV and exposure at 30 Qux were alternately repeated for 1 hour to measure V2'lVR' and S' after fatigue. The results are shown in Table-1.

Further, the electrophotographic photoreceptors of Examples 1 to 3 in the form of a drum were attached to a laser beam printer, and 3
The image quality was evaluated by repeatedly subjecting the electrophotographic photoreceptor to fatigue by repeatedly printing 5,000 sheets in environments of 0° C., 90% RH and 15° C., 20% RH.

After continuous printing, a clear image with no deterioration similar to the initial image was obtained.

〔Effect of the invention〕

The electrophotographic photoreceptor of the present invention is cured by reaction on a substrate with zirconium oxide particles surface-treated with an organic titanium compound and preferably a cycloaliphatic isocyanate compound at an NGO/OH ratio of 171 to 5/1. By using an undercoat layer made of polyacetal resin as a binding material, it has high sensitivity and even after repeated charging exposure.
It has the remarkable characteristics that the charging potential rises quickly and the residual potential is small.

Further, the electrophotographic photoreceptor of the present invention exhibits extremely small changes in electrical characteristics with respect to temperature and humidity.

Therefore, according to the electrophotographic photoreceptor of the present invention, it is possible to prevent abnormal images from occurring due to optical interference even in exposure using coherent light from a laser printer or the like.

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, zirconium oxide particles surface-treated with an organic titanium compound are included in the undercoat layer. An electrophotographic photoreceptor characterized by containing a binder resin. (2) The electrophotographic photoreceptor according to claim 1, wherein the binder resin is a reaction cured product of a polyacetal resin and a cycloaliphatic isocyanate compound.