JPS63113459A - Electrophotographic sensitive body having fine particle which can prevent interference - Google Patents

Abstract

PURPOSE:To prevent formation of uneven interference fringe shapes by incorporating at least a binder and fine transparent particles into an electric charge transfer layer and specifying the difference between the refractive index of said fine particles and the refractive index of the charge transfer layer so as to be maintained in a 0.03-0.3 range. CONSTITUTION:This photosensitive body has an electric charge generating layer 2 and the charge transfer layer 3 on a conductive substrate 1. The layer 3 contains at least the binder and the fine transparent particles 5 and the difference between the refractive index of said fine particles 5 nd the refractive index of the layer 3 is in the 0.03-0.3 range. The fine transparent particles are incorporated near the boundary between the charge generating layer and the charge transfer layer. The formation of the uneven interference fringes is thereby prevented without affecting the electrophotographic characteristics in maintaining the good image characteristics while the production at a low cost is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor for laser exposure that can prevent moiré patterns while having good image characteristics.

[Background of the Invention] In recent years, development of laser beam printers that utilize electrophotographic processes and form images using laser light as a light source has become active. He as a laser beam
- Gas lasers such as He and Ar and semiconductor lasers are used.

However, since laser light is coherent, new problems have arisen. That is, for example, when an organic photoreceptor in which a charge transport layer is laminated on a charge generation layer is irradiated with laser light, the irradiation light damages both the charge transport layer and the charge generation layer (or the conductive support). The reflected light beams interfere with each other, causing a pattern called moiré on the printed image and greatly reducing the image quality. This is a particularly significant drawback in the case of

Conventional techniques for solving this problem include a method of providing a subbing layer having a light-diffusing and reflecting surface between the conductive support and the photosensitive layer (see JP-A-80-188850); Method of using titanium black as an undercoat layer between
80-184258), a method in which the charge generation layer absorbs most of the light from the light source (see 58-8224).
(see No. 1), a method of causing the binder resin constituting the charge transport layer to have a microphase separation structure (see No. 81-18983), when exposing a photosensitive layer with a refractive index of n to light of wavelength λ,
A method of providing unevenness with a roughness of 4n or more in the lower part of the photosensitive layer (see No. 80-247847), a method of incorporating a substance that absorbs or scatters coherent light into the photoconductor layer (No. 80-247847).
88550).

[Problems to be Solved by the Invention] However, these conventional techniques have the following drawbacks. That is, in the method of providing an undercoat layer having a light diffusing and reflecting surface between the conductive substrate and the photosensitive layer, it is difficult to control the unevenness of the rough surface of the undercoat layer, and it is difficult to reproduce the same rough surface with good accuracy. be. In addition, in order for the undercoat surface to be roughened to the extent that it is effective against interference fringes, the film needs to be quite thick, which affects the electrophotographic properties such as the sensitivity of the photoreceptor and the adhesion. It is something. Further, the use of such a complicated undercoat layer also increases costs.

The method of using titanium black as an undercoat layer between the conductive substrate and the photosensitive layer is difficult because the energy levels of the titanium black-containing layer, the charge generating material, and the charge transporting material are not well matched. It has the disadvantage of adversely affecting photographic properties.

The method for absorbing most of the light from the light source in the charge generation layer is as follows: 1. Make the charge generation layer thicker.

■ Bringing the peak of the spectral absorption of the charge generation layer closer to the wavelength of the light source used; ■ Adding a dye that absorbs the light from the light source used. Among these, ■ causes an increase in thermally excited carriers, which adversely affects dark decay and acceptance potential. (2) Such materials are difficult to obtain, and even if they are available, there are few that have sufficient performance, making it difficult to make full use of them. Further, even if the absorption peak overlaps with the light source used, there is still a limit to the absorption intensity. Regarding (2), it is thought that this mixing may have an effect on the electrophotographic properties, and it is difficult to find a dye that has little effect.

In the method of making the binder resin constituting the charge transport layer have a microphase separation structure, the binder resin used must be a block copolymer or a graft copolymer, etc., and must satisfy the electrophotographic properties. Moreover, it is difficult to obtain a desirable microphase-separated structure.

Many methods have been proposed for providing unevenness at the bottom of the photosensitive layer, but the unevenness sufficient to prevent unevenness in the form of interference fringes hinders uniform film formation of the photosensitive layer. Since the charge generation layer is generally a thin layer, the thickness of the charge generation layer becomes nonuniform, which often adversely affects image characteristics.

In the method of mixing a substance that absorbs or scatters coherent light into the photoconductor layer, if an absorbing substance is added, the sensitivity will decrease, and if a scattering substance is mixed, one image blur etc. 1. This results in deterioration of image characteristics.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned drawbacks, to maintain good image characteristics, and to eliminate interference fringes without affecting electrophotographic characteristics, even though it can be manufactured at low cost. An object of the present invention is to provide an electrophotographic photoreceptor for laser exposure that prevents the occurrence of unevenness.

[Means for Solving the Problems] The present inventor has conducted extensive research in order to solve the above problems, and as a result has arrived at the present invention.

That is, the electrophotographic photoreceptor according to the present invention has a charge generation layer and a charge transport layer on a conductive substrate, the charge transport layer containing at least a binder and transparent fine particles, and the refraction of the fine particles. It is characterized in that the difference between the refractive index and the refractive index of the charge transport layer is in the range of 0.03 to 0.3.

According to the present invention, the thickness of the charge transport layer is d, M, and the refractive index is n.
, the particle size of the fine particles is rp, and the refractive index is n. When the irradiated light with wavelength is transmitted through the fine particles, (d-r
p)n
If this difference rp(n-np) is equal to or greater than /4n, the phase of light that passes through the fine particles and light that does not pass will be shifted by at least π/2, and interference of light within the charge transport layer can be prevented.

Further, according to the present invention, there is no need to use light scattering, so there is no need to worry about image blurring, etc. Also, since there is no absorption of light that does not contribute to charge generation, there is no decrease in sensitivity, and the undercoat layer is This is advantageous in terms of manufacturing, since it is not necessary to provide any part of the photosensitive layer with unevenness.

Furthermore, according to the present invention, there is no need to use a special binder resin in the charge transport layer, and 1! It also does not cause deterioration of child photographic characteristics.

The present invention will be explained in detail below.

Preferred embodiments of the layer structure of the electrophotographic photoreceptor of the present invention include the following layer structures (1) to (6).

(1) As shown in Figure 1, from the upper layer, charge transport P32
A.? lf charge generation layer 2B and conductive substrate l, which are configured in this order.

(2) As shown in FIG. 2, in the layer structure shown in (1) above, an undercoat layer 4 is provided between the charge generation layer 2B and the conductive substrate l.
(a layer with functions such as an intermediate layer and an adhesive layer).

(3) As shown in FIG. 3, from the upper layer, the charge generation layer 2B
, a charge transport layer 2A, and a conductive substrate 1, in this order.

(4) As shown in FIG. 4, in the layer structure shown in (3) above, an undercoat layer 4 is provided between the charge transport layer 2A and the conductive substrate l.
(a layer that functions as an intermediate layer, adhesive layer, etc.)

(5) As shown in FIG. 5, from the upper layer, a charge generation layer 2C1 containing a charge generation substance and a charge transporting substance, a charge transport layer 2A,
A conductive substrate 1 is constructed in this order.

(6) As shown in FIG. 6, in the layer structure shown in (5) above, an undercoat layer 4 is provided between the charge transport layer 2A and the conductive substrate l.
(a layer with functions such as an intermediate layer and an adhesive layer).

Further, in the above layer structure, an intermediate layer may be provided between each layer, and a surface protective layer may be formed as the uppermost layer.

As the conductive substrate used in the present invention, metals such as aluminum, nickel, brass, and stainless steel are molded into a drum shape, or are used as sheet-like films or foils, and polyethylene terephthalate, nylon, polyarylate, etc. It is used by molding a polymeric material such as polyimide or polycarbonate or an insulating material such as hard paper into a drum shape or by applying a conductive treatment to a sheet-like film. Methods for conductive treatment include impregnation with conductive substances, lamination of metal chains (e.g. aluminum foil), vapor deposition of metals (e.g. aluminum, indium, tin oxide, yttrium, etc.),
There are methods such as conductive processing.

In the present invention, an undercoat layer can be provided on the conductive substrate in order to improve adhesiveness or electrical properties, and materials used for the undercoat layer include aluminum oxide, indium oxide, titanium oxide, etc. Metal oxides, acrylic resins, methacrylic resins, vinyl chloride resins, vinyl acetate resins, epoxy resins, urethane resins, polyester resins, phenolic resins, alkyd resins, polycarbonate resins,
Silicone resin, melamine resin, polyvinyl formal resin, polyvinyl butyral resin, polyvinyl alcohol resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-
14. Polymer materials such as vinyl acetate-maleic anhydride copolymer, vinylidene chloride-acrylonitrile copolymer, styrene-butadiene copolymer, etc. Examples include celluloses such as ethyl cellulose and carboxymethyl cellulose, and each can be used alone or in combination of two or more. Note that the undercoat layer is formed to a predetermined thickness by dissolving the above-mentioned materials in a suitable solvent and coating the solution on the conductive substrate. As for the application method.

When the conductive substrate is in the form of a drum, a dipping method, a spray method, an extrusion method, a slide hopper method, etc. are preferable, and when the conductive substrate is in the form of a sheet, a roll method, extrusion, slide hopper method, etc. are preferable. Preferably adopted. The thickness of the undercoat layer formed in this way is 0.01~1O
The range of ILm is preferable, and the range of 0.05 to 5 hiro is more preferable.

The charge-generating layer of the present invention is a layer containing at least a charge-generating substance, and is preferably formed by coating the substance alone or by dispersing it in a binder on the conductive substrate or the undercoat.

Charge-generating substances suitable for the present invention include organic pigments that absorb visible light and generate charges, as shown in the following representative examples.

(1) Azo pigments such as 7-7zo pigments, polyazo pigments, metal rust salt azo pigments, pyrazolone azo pigments, stilbene azo pigments and thiazole azo pigments (2) Perylene pigments such as perylenic anhydride and perylenic acid imide (3) anthraquinone derivatives, anthanthrone derivatives, dibenzpyrenequinone derivatives, pyrantrone derivatives,
Anthraquinone or polycyclic quinone pigments such as violanthrone derivatives and inviolanthrone derivatives (4) Indigoid pigments such as incoconductors and thioindigo derivatives (5) Phthalocyanine pigments such as metal phthalocyanines and metal-free phthalocyanines (6) Diphenylmethane pigments pigments, carbonium pigments such as triphenylmethane pigments, xanthine pigments and acridine pigments (7) xanthine pigments such as azine pigments, oxazine pigments and thiazine pigments (8) methine pigments such as cyanine pigments and azomethine pigments (9) quinoline pigments Pigments (10) Nitro pigments (11) Nitroso pigments (12) Benzoquinone and naphthoquinone pigments (13)
Naphthalimide pigments (14) Perinone pigments such as bisbenzimidazole derivatives, but preferably azo, phthalocyanine or polycyclic quinone pigments having an electron-withdrawing group.

It is preferable to disperse and contain the particles in the photosensitive layer as particles having an average particle diameter of 2 mm or less, particularly IIL- or less.

In this case, the electrophotographic properties of the photoreceptor, such as photosensitivity, memory phenomenon, residual potential, etc., become better. In addition, the azo pigment has a higher electron transfer rate in the photosensitive layer when the surface of the photosensitive layer is negatively charged than when it is positively charged (that is, the photosensitivity when negatively charged is high). The generated electrons cancel out the positive charge on the surface of the photosensitive layer, making it possible to exhibit high photosensitivity.

In particular, when used in the surface layer of a positively charged photoreceptor, it is extremely advantageous in terms of photosensitivity.

Examples of azo pigments suitable for the present invention include those shown in the following exemplary compound groups [I] to [17].

CI) CP-N=N-A-N=N-CI) where c
p represents a coupler component, and all commonly known coupler components can be used.

Moreover, A represents a divalent bonding group.

Specific examples of CP and A include the following.

OCH3 and so on.

(II) Cp-N = N-A I-N lI
N-A! −N = N −Cp where A r , A
! represents an aromatic or heterocyclic group. Specifically, there are the following.

U R, -It represents hydrogen, chlorine or bromine atom. Also, Xl is an iodine atom, N Ot, CN or CC
Indicates Hs etc. n is an integer of 0.2.3 or 4.

X is a chlorine, bromine or iodine atom or a nitro group,
Indicates cyano group, acetyl group, etc. n is an integer of 0°2.3 or 4.

More specifically, the following compounds may be mentioned.

(G-1) (G-2) (G-3) (G-4) (G-5) (G-10) (G-11) Q-gate
υ＝
υ (G-23) (G-24) (G-25) (G-26) (G-27) (G-29) (G-30) (G-31) υ (G-32) (G- 33) (G-34).

As a means for dispersing the charge generating substance, it is possible to add the charge generating substance to a suitable solvent or binder solution, and use a dispersing means such as a sand mill, a ball mill, or an ultrasonic dispersion.

Suitable solvents include 1,2-dichloroethane, chloroform, 1,1.1-)lichloroethane, dichloromethane, acetone, dioxane, methyl ethyl ketone,
Tetrahydrofuran, benzene, toluene, xylene,
Examples include diethyl ether.

The mixing ratio of the charge generating substance and the binder is 10 to 500 parts, preferably 30 to 200 parts, of the binder to 100 parts of the charge generating substance.

The thickness of the charge generation layer is 0. O1-10. Bm is preferred;
More preferably it is 0.05-2.

As the charge transport substance used in the charge transport layer of the present invention, triazole derivatives (for example, Japanese Patent Publication No. 34-5487), oxazole derivatives (for example, Japanese Patent Publication No. 35-1125)
, oxadiazole derivatives (e.g. No. 34-5466), pyrazoline derivatives (e.g. No. 34-10368)
, imidazole derivatives (e.g. No. 35-11215,
37-16096), fluorenone derivatives (Japanese Patent Application Laid-open Nos. 52-128373 and 54-110837), carbazole derivatives (e.g. 54-59142), as well as 58-134642, 58-65440, etc. The following substances can be mentioned.

Preferred charge transport materials in the present invention include compounds represented by the following general formulas (1) to (7).

General formula (1) General formula (3) General formula (5) General formula (6) In the above formula, R, -R,, R6-R14, R+a to Rt4,
R1, ~R31SRss"-Rss is a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a hydroxy group,
Cyano group, dialkylamino group, diarylamino group,
Represents a dialkylamino group, nitro group, or methoxy group, R6 represents an alkyl group, a phenyl group that may have a substituent, or a naphthyl group that may have a substituent, R6 represents a hydrogen atom, an alkyl group, or a phenyl group that may have a substituent. R+s represents a hydrogen atom, a phenyl group that may have a substituent, a cyano group, or an alkyl group, Ar+ represents f14+ In the formula, R31, R4°, and R41 are alkyl groups,
Represents a benzyl group, phenyl group or naphthyl group (each of which may have a substituent), and Rat represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a hydroxy group, a dialkylamino group or a nitro group .

), R□, and Rst represent a hydrogen atom or a phenyl group. n represents 0 or a positive integer.

Margin below Specific examples include the following compounds.

In the present invention, the Tt charge transport layer contains at least a binder and transparent fine particles in addition to the above charge transport substance.

As a binder, it has high compatibility with charge transport substances,
Furthermore, materials with high transparency and insulation properties are preferred, and all materials commonly used in electrophotographic photoreceptors can be used, such as polyester resins, polyethylene resins, polyamide resins, polycarbonate resins, epoxy resins,
Examples include polyvinyl butyral resin and polymethyl methacrylate resin.

The charge transport layer of the present invention contains transparent fine particles 5 as shown in FIG. 7. The transparent fine particles used in the present invention are preferably those that are incompatible with the binder resin.1 For example, Teflon resin, polyvinylidene fluoride resin. , tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene resin, polyvinyl chloride resin.

Polypropylene resins, polyphenylene resins, polyphenylene sulfide resins, polystyrene resins, polycarbonate resins, polyester resins, acrylic resins, epoxy resins, urethane resins, etc. are used.The transparent fine particles used in the present invention are used in a solvent when obtaining a coating liquid for a charge transport layer. It is preferable that the resin is not dissolved in the resin, and therefore it is also preferable to use a crosslinkable resin.

Preferred combinations of binder resin, coating solvent, and fine particles in the present invention include, for example, the following combinations.

Bawagoo / Solvent / Fine Particles 1) Polycarbonate / DioxaO Edane / Polyvinylidene Fluoride 2) Polyh-bonate / Tetrahydrofurady / Polycarbonate 3) Polycarbonate / DixaO Edane / Crosslinked Bottle Methyl methacrylate 4) Polymethyl methacrylate/tetrachloromethacrylate Teflon 5)
Polymethyl methacrylate l toluene/crosslink 1 polystyrene 8) Methyl methacrylate-styrene u combination/
Tetrahuman afuran l poly! Styrene 7) Methyl methacrylate-styrene copolymer l toluene/bolyphenylecis sulfide 8) Polystyrene/tetrahydrofuran/1mj trimethyl methacrylate The manufacturing methods of the fine particles used in the present invention include emulsion polymerization, gas phase polymerization, and suspension. The resin may be formed into fine particles from the beginning by a polymerization method or the like, or the resin may be made into fine particles through a process such as crushing or classification, or both may be used in combination.

The transparent fine particles used in the present invention may have any size as long as it fits within the thickness of the photosensitive layer, but preferably 0.5 to 10 g, more preferably 1 to 5 JLll.
It is.

Further, the fine particles do not need to be spherical, and may be acicular or plate-shaped, and if the particles are acicular, the length of the minor axis is preferably 0.5 to 10 gm, and if the particle is plate-shaped, the thickness is preferably 0.5 to 10 gm. Preferably, the particle size is 1 to 5 liters, and the width and length of needle-shaped long sleeves and plate-shaped particles are preferably 2 to 50 JL11.If the fine particles are too large, they may adversely affect charge transport or damage the photosensitive layer. If the thickness is too small, it will be less effective in preventing interference ring-like density unevenness.

In the present invention, it is sufficient that the transparent fine particles and the charge transport layer have different refractive indexes, and the refractive index is in the range of 0.03 to 0.3, preferably in the range of 0.05 to 0.2. . If it is smaller than 0.03, there will be little effect in preventing density unevenness like interference fringes, and if it is larger than 0.3, light scattering will increase.
Image blur, etc. will occur.

In this specification, the refractive index refers to the value under the wavelength of light used for imagewise exposure. Examples of light used for imagewise exposure include He-Ne laser light, semiconductor laser light (wavelength 7
80mm) etc.

The transparent fine particles of the present invention may be contained anywhere in the charge transport layer, but preferably near the boundary with the charge generation layer. interval! (See FIG. 7). If such a gap exists, a phase shift will occur, and the effect of preventing interference will be increased. The fine particles contained in the charge transport layer may protrude from the charge transport layer and partially straddle the charge generation layer.

In the present invention, the charge transport layer can be coated by the same coating method as the subbing layer. In the present invention, the fine particles may contain a charge transport substance, and in that case, the charge transport substance may be incorporated into the fine particles during production of the fine particles, or by swelling in the charge transport layer coating solvent during coating. A charge transport substance may also be included.

In the present invention, the following method can be used to concentrate the fine particles near the interface with the charge generation layer.

(2) In the case of a sheet-like photoreceptor in which the charge generation layer is on the substrate side, by selecting a solvent with a low specific gravity for the fine particles, the fine particles will naturally settle during coating and be localized on the charge generation layer side.

(2) In the case of a sheet-like photoreceptor in which the charge generation layer is above the charge transport layer, by selecting a solvent with a high specific gravity for the fine particles, the fine particles are floated and localized in the same manner as in (2).

(2) Divide the charge transport layer coating solution containing fine particles into two coats, and apply the charge transport layer containing fine particles on the side closer to the charge generation layer.

■Create a charge transport layer containing fine particles and a charge transport layer not containing fine particles at the same time using a coating method that allows multi-layer coating such as a slide hopper, or a method such as coating from two coaters in one coating process.

When the charge transport layer is formed in two regions, the binder used for each sound may be of the same kind or different kinds, and the interface of the charge transport layer formed in the two regions may be uneven. Good too.

The composition in the charge transport layer of the present invention is binder 100ffi
- Preferably 25%
~200 parts by weight (more preferably 50 to 100 parts by weight)
.

The fine particles of the present invention are preferably 0.1 to 20 parts by weight (more preferably 0.3 to 10 parts by weight). If the fine particles are too large, residual potential tends to remain, and if it is too small, moiré patterns are reduced. It has no effect.

In the present invention, the thickness of the charge transport layer is preferably 5 to 50 #Lm, more preferably 10 to 30 #Lm, whether it is one layer or two or more layers.

[Effects of the Invention] According to the present invention, although it can be manufactured at low cost, interference fringes can be reduced while maintaining good image characteristics and without affecting electrophotographic characteristics. It is possible to provide an electrophotographic photoreceptor for laser exposure in which this phenomenon is prevented.

[Example] Preferred examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1 10 g of polyvinyl formal resin (trade name: Vinyrec L, manufactured by Qiang Co., Ltd.) was mixed with 1.00 g of 1.2-dichloroethane.
It was dissolved in 0+osL and applied to an aluminum cylinder by dip coating to form a subbing layer with a thickness of about 0.15 gm.

Next, 4 g of polyvinyl formal resin (trade name: DENKA FORMER/L/1100, manufactured by Denki Kagaku Co., Ltd.), polyvinyl butyral resin (trade name: S-LEC BLS, manufactured by Block Chemical Co., Ltd.), and 10 g of (G-7) as a charge generating substance.

1,000 tan of 1,2-dichloroethane was pulverized and dispersed in a ball mill to obtain a dispersion.

The resulting dispersion was applied onto the subbing layer by a dip method and dried at 100° C. for 10 minutes to form a charge generation layer with a thickness of 0.2 μm.

Next, 120 g of polycarbonate resin (Panlite 11300 manufactured by Teijin Kasei), 80 g of charge transport material (c)
, methyl methacrylate) per 100 parts by weight,
A cross-linked polymethyl methacrylate resin suspension-polymerized with the addition of 2 parts by weight of divinylbenzene was pulverized and classified, and 4 g of transparent fine particles with an average particle size of 5.2 mm were dissolved in 1,000 ml of 1,2-dichloroethane. Dispersed and coated on the charge generation layer by dip coating method, and heated at 110°C for 1
After drying for 0 minutes, a first charge transport layer having a film thickness of about 22 cm was formed.

The refractive indexes of the charge transport layer and the fine particles were measured separately using a 630 nm monochrome photon and 7-hubet refractometer, and were found to be 1.57 and 1.49, respectively.

Furthermore, polycarbonate resin (Panlite -1300
, manufactured by Kijin Kasei Co., Ltd.) 150g, charge transport substance (C) 75
g, 1.2-dichloroethane 1. It was dissolved in a liquid solution and coated on the first charge transport layer using a dip coating method, and dried at 110°C for 10 minutes to give a total film thickness of 21 pm.
A charge transport layer was formed. The photoreceptor thus obtained has an oscillation wavelength of 833! Small helium-neon laser
When the printer was attached to an experimental laser printer equipped with a laser printer and halftone images were produced using various dot patterns, no interference fringe-like unevenness was observed. Sharp images were also obtained for line images such as character patterns.

Comparative Example 1 A photoreceptor obtained by forming a photosensitive layer in the same manner as in Example 1 except that no fine particles were added to the first charge transport layer was installed in the same experimental machine as in Example 1. When images were produced, sharp images were obtained for line images such as single character patterns, but interference fringe-like unevenness was observed in halftone images formed by various dot patterns.

Example 2 A photosensitive layer was formed on a Fulmi XIJi PET base in the following manner.

First, polyvinyl formal resin (trade name: Vinylec K, manufactured by Chisso Corporation) log is 1.2-dichloroethane 1
,000 +jl and coated on the aluminum vapor-deposited PET base using a roll coater to form an undercoat layer with a film thickness of 0.18 cm.

Next, polycarbonate resin (product name: Panrai) L
-1250, manufactured by Kijin Kasei Co., Ltd.) 5 g, as a charge generating substance (Ni-12) 10 g, 1.2-dichloroethane 1.
000 ml was ground and dispersed in a sand grinder for 4 hours to obtain a dispersion. The resulting dispersion was applied onto the undercoat layer using a roll coater to give a film thickness of 0.18 #L! l
A charge generation layer was formed.

Next, polycarbonate resin (-1300 for Panlite)
100g, charge transport material (a) 75g, polyvinylidene fluoride resin (FORAFLON 100OVLII,
(manufactured by Showa Denko) was classified to have an average particle size of 4.2JL11, and 8g of fine particles were mixed with 1.000 g of 1,2-dichloroethane.
It is dissolved and dispersed in rtrl to make a charge transport layer lower layer liquid, and then polycarbonate resin (product name: Panlite-1
300) 100g charge transport material (a) 75g 1.2
~Dissolve in 1.000 ml of dichloroethane to make the charge transport layer upper layer liquid, and use a slide hopper for applying blood to the ffi layer.
The upper and lower layers were simultaneously coated and dried at 120° C. for 5 minutes to form a charge transport layer having a thickness of about 22 mm.

still,? When we measured the refractive index of the charge transport layer and fine particles using 90 nm monochromatic photons, we found that! , 57 and 1.
It was 42.

The sheet-like photoreceptor thus obtained was cut into a suitable size and then ultrasonically fused to form an endless belt.

When this photoreceptor belt was attached to an experimental laser printer equipped with a semiconductor laser with an oscillation wavelength of 7110 nm, halftone images were produced using various dot patterns.
No interference ring-like unevenness was observed at all. Sharp images were also obtained for line images such as character patterns.

Comparative Example 2 A photosensitive layer was formed in the same manner as in Example 2, except that fine particles were not added to the charge transport layer lower layer solution, and an endless belt-shaped photoreceptor was further prepared.

When this photoreceptor belt was attached to an experimental laser printer having a semiconductor laser with an oscillation wavelength of 790 nm and images were produced, sharp images were obtained for line images such as single character patterns. However, unevenness like interference fringes can be seen in halftone images created by various dot patterns.
Depending on the dot pattern, it appeared strongly in some cases.

Example 3 An endless belt-shaped photoreceptor was obtained in the same manner as in Example 2, except that the combination of the charge-generating substance and the charge-transporting substance was changed to the one shown on the next page.

When this photoreceptor belt was attached to an experimental laser printer equipped with a semiconductor laser with an oscillation wavelength of 790 nm and halftone images were produced using various dot patterns, no striped unevenness was observed in any of the combinations. I couldn't. Sharp images were also obtained for line images such as character patterns.

Comparative Example 3 After forming up to the charge generation layer in exactly the same manner as in Example 2,
150 g of methyl methacrylate-styrene block copolymer with a ratio of 80 parts of methyl methacrylate and 20 parts of styrene, 120 g of charge transport material (a), and 1,000 m of toluene were dissolved in a charge transport layer coating solution in a slide hopper. Apply by coating method.

110" was dried for 0.20 minutes to obtain a translucent charge transport layer having a thickness of 19JL11.

This photoreceptor was further processed to obtain an endless belt-like photoreceptor. When this photoreceptor belt was attached to an experimental laser printer equipped with a semiconductor laser with an oscillation wavelength of 790 ros and an image was produced, no interference fringe-like unevenness was observed in the intermediate m image, but the sensitivity was low and a fogged image was observed. A sharp image could not be obtained for a line image such as the upper one character pattern.

Comparative Example 4 The same as Example 1 except that the fine particles added to the charge transport layer were replaced with white opaque precipitated barium sulfate having a refractive index of 1.64 and an average particle size of 4.2 pm instead of the crosslinked polymethyl methacrylate resin. A photoreceptor was prepared in the same manner, and an intermediate yJ image output test was performed in the same manner as in Example 1. Although no dry #stripe unevenness was observed, the photoreceptor of Example 1 had an appropriate image density. While the laser power required to obtain this was 1.3 W, a laser power of 3.3 mW was required.

Comparative Example 5 A test was conducted in exactly the same manner as in Example except that the fine particles added to the charge transport layer were uncrosslinked polymethyl methacrylate resin instead of crosslinked polymethyl methacrylate resin. It did not show any effect on preventing unevenness in the form of interference fringes.

Comparative Example 6 Completely the same as Example 1, except that the fine particles added to the charge transport layer were fine powder of high refractive index glass with a refractive index of 83 (average particle size 5.1 μM) instead of the crosslinked polymethyl methacrylate resin. I tested it with .

Although no interference fringe-like unevenness was observed, there were slight pockets in the image, and the laser output required to obtain the appropriate image density was 2.1 mW, which was lower in sensitivity than the photoconductor of Example 1. A decrease was observed.

[Brief explanation of the drawing]

1 to 6 show the layers of the electrophotographic photoreceptor of the present invention, 1. l
FIG. 7 is a schematic sectional view showing an embodiment of r&, and is an explanatory view showing the state of existence of transparent fine particles used in the present invention.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor having a charge generation layer and a charge transport layer on a conductive substrate, the charge transport layer contains at least a binder and transparent fine particles, and the refractive index of the fine particles is different from the refractive index of the charge transport layer. An electrophotographic photoreceptor characterized in that the difference is in the range of 0.03 to 0.3. (2) The electrophotographic photoreceptor according to claim 1, wherein transparent fine particles are contained near the boundary between the charge generation layer and the charge transport layer.