JP2002244311A - Electrophotographic sensitive body, and image forming device and process cartridge using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic sensitive body where uneven gradation and interference fringe are not caused on a halftone image even when it is an electrophotographic sensitive body produced by a spray coating method by using a conductive supporting body whose surface roughness is small, and an image forming device using the same. SOLUTION: In this electrophotographic sensitive body constituted by laminating at least an under coating layer, a charge generating layer and a charge transporting layer on the conductive supporting body, at least the charge transporting layer is formed by the spray coating method. Then, the electrophotographic sensitive body satisfies a following expression. ΔUL<=2 and (7.ΔTG)-2+(5.ΔCTL)-2<=10-2 where ΔUL means the maximum film thickness difference (μm) of the under coating layer in an effective image area, ΔTG means the maximum transmittance difference (%) of the charge generating layer in the effective image area (the measured wavelength of the transmittance is wavelength where the light absorption of a charge generating agent becomes maximum), ΔCTL means the maximum film thickness difference (μm) of the charge transporting layer in the effective image area. Then, the image forming device and the process cartridge equipped with the electrophotographic sensitive body are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic photosensitive member, an image forming apparatus using the electrophotographic photosensitive member, and a process cartridge.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, a Carlson process and various deformation processes thereof are known, and are widely used in copiers and printers. Electrophotographic photosensitive members used in such an electrophotographic method include those using an organic photosensitive material and those using an inorganic photosensitive material.

On the other hand, electrophotographic photoreceptors include a drum-shaped photoreceptor and a belt-shaped photoreceptor having a photosensitive layer formed on a metallic hollow drum, and have various advantages in terms of cost, design form, and the like. Currently, the shape of the electrophotographic photosensitive member is properly used according to the characteristics of the electrophotographic apparatus to be developed.

In recent years, colorization of electrophotographic apparatuses has been advanced, and high image quality, low cost, high speed, and the like have been demanded. As a means of improving image quality, a method of forming an electrostatic latent image with high resolution using laser light exposure of a shorter wavelength and a smaller beam spot has been put to practical use. Although the belt-shaped photoreceptor has a large outer diameter of the belt, it has advantages such as its flexibility, which allows it to be used in a desired form, and that it can be designed in a form convenient for opposing four-color developing machines.
In color electrophotographic apparatuses, the advantages of the belt-shaped photoconductor have been reconsidered. The belt-shaped photoreceptor is, for example,
Using a seamless belt mainly composed of nickel as disclosed in US Pat. No. -8774 as a support, a photosensitive layer is provided on the support by dip coating, spray coating, or the like, and cut into a desired length. It is a photoreceptor. As the photosensitive layer forming method, dip coating method, spray coating method,
Although there is a nozzle coating method and the like, in the case of an electrophotographic photosensitive member, a dip coating method is generally used industrially in many cases. On the other hand, in the spray coating method, the coating liquid is used up, it is suitable for small-quantity production of other varieties, the equipment is not large, and it can correspond to a large diameter photoreceptor, so the advantages of the coating method have recently been reviewed. I have.

[0005]

SUMMARY OF THE INVENTION In an electrophotographic apparatus having a laser writing optical system of 600 dpi or more,
When a halftone image is output using a function-separated type organic electrophotographic photosensitive member, density unevenness and interference fringes may occur. Shading unevenness in the halftone image is caused by a small sensitivity unevenness due to a slight difference in film thickness between the thick and thin portions of the charge generation layer and the charge transport layer. This is considered to occur because the dot becomes thicker, and conversely, the dot becomes thinner in the portion where the film thickness is thin and the sensitivity is slow. The thickness difference of the undercoat layer also affects the dot thickness. Considering the method of forming the photosensitive layer, the photosensitive layer produced by the spray coating method tends to have a undulation-like film thickness difference of about 5 to 30 mm in the photosensitive member 1 (see Japanese Utility Model Laid-Open No. 5-7364). An example of the film thickness distribution is disclosed.) It is very difficult to make such a film thickness difference zero by the spray coating method.
Extremely long coating time leads to an increase in cost. An electrophotographic photosensitive member having a photosensitive layer formed by a spray coating method provided on a conductive support causes uneven shading in a halftone image due to the nonuniform film thickness as described above.

Next, regarding the interference fringes of the halftone image, the light transmitted through the charge generation layer is reflected by the lower layer or the surface of the conductive support, and the reflected light and the light reflected by the surface of the charge transport layer interfere with each other. Is considered to occur. As means for preventing such interference fringes, methods have been proposed such as roughening the surface of the conductive support or providing a subbing layer containing an inorganic pigment between the conductive support and the charge generation layer. I have. However, in an electroformed nickel seamless belt or an aluminum-evaporated PET which is practically used as a conductive support having flexibility, these surfaces usually have a surface roughness close to a mirror surface, and the surface is roughened. For this purpose, such steps must be performed extra, leading to an increase in cost and a decrease in the yield rate. In addition, the roughening tends to cause uneven points on the surface of the support, which may cause background contamination. Also in the method of providing the undercoat layer, when the smoothness of the conductive support is high, it is necessary to increase the film thickness in order to increase the degree of concealment by the undercoat layer. Bring. As a result, the light reflected on the surface of the undercoat layer may cause a moire phenomenon.

[0007] Therefore, as disclosed in JP-A-6-138865 and JP-A-8-248663, a method of scattering light reflected on the surface of a photoreceptor by providing a protective layer having a roughened surface on the photosensitive layer. Etc. have also been proposed.
However, all of these require a step of providing a protective layer, leading to an increase in cost and a decrease in the yield rate.
Further, when the protective layer is roughened by containing organic or inorganic fine particles, there is a concern that deterioration in image quality, such as reproducibility of fine dots, may be caused in improving image quality and resolution.

The density unevenness and interference fringes in the above-mentioned halftone image are more remarkable as the latent image formation of the exposure optical system is advanced, the laser beam is shortened, and the beam diameter and dot diameter are reduced. Appears in the image.

The present invention has been made in view of the above-mentioned circumstances. Even in an electrophotographic photoreceptor produced by a spray coating method using a conductive support having a small surface roughness, unevenness in density and interference fringes in a halftone image can be obtained. It is an object of the present invention to provide an electrophotographic photoreceptor which does not cause the occurrence of an image, an image forming apparatus and a process cartridge using the electrophotographic photoreceptor.

[0010]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the maximum thickness difference between the undercoat layer, the charge generation layer and the charge transport layer, and the surface roughness of the photoreceptor. By setting the range to a specific range, it was found that even in an electrophotographic photoreceptor produced by a spray coating method using a conductive support having a small surface roughness, shading unevenness and interference fringes in a halftone image were eliminated. The invention has been completed.

According to the present invention, (1) in an electrophotographic photosensitive member having at least an undercoat layer, a charge generation layer and a charge transport layer laminated on a conductive support, at least the charge transport layer is spray-coated. formed by method, an electrophotographic photosensitive member ΔUL ≦ 2 and characterized by satisfying the following expression ^{(7 · ΔTG) -2 + (} 5 · ΔCTL) -2 ≦
^10-2 Here, ΔUL: maximum film thickness difference of the undercoat layer in the effective image area ([mu] m)? Tg: Maximum transmittance difference of the charge generating layer in the effective image area (%) (measurement wavelength of the transmittance of the charge generating agent ΔCTL: Maximum thickness difference of the charge transport layer in the effective image area (μm)

(2) The electrophotographic photosensitive member according to (1), wherein the maximum surface roughness of the electrophotographic photosensitive member is 0.2 μm or more and 0.6 μm or less; The electrophotographic photoreceptor according to the above (1) or (2), wherein the maximum surface roughness is 0.02 μm or more and 0.20 μm or less, and (4) the conductive support is a nickel seamless belt. (1) to (3) above,
(5) The electrophotographic photoreceptor according to any one of (1) to (5), wherein the electrophotographic photoreceptor is repeatedly subjected to at least charge, exposure with coherent light, development, and transfer.
(4) An image forming apparatus comprising the electrophotographic photosensitive member according to any one of (1) to (6), wherein (6) the exposure resolution by coherent light is 600 dpi or more. 4) The image forming apparatus according to any one of the above,
(7) A process cartridge for an image forming apparatus, comprising the electrophotographic photosensitive member according to any one of (1) to (4).

In the electrophotographic photoreceptor of the present invention, the maximum transmittance difference of the charge generation layer and the maximum thickness difference of the charge transport layer in the effective image area mutually affect each other, but within a range satisfying the above-mentioned formula (1). The maximum thickness difference of the undercoat layer is 2 μm independently.
If it is below, the halftone image density unevenness that can be visually confirmed is almost suppressed. In other words, it is not necessary to make the maximum thickness difference of each photosensitive layer completely uniform, and the maximum thickness difference may be present within a certain specific range. Time can be reduced. The range of the maximum film thickness difference of each photosensitive layer in the present invention is a result obtained by intensive studies, its action is not clear,
It is assumed that the sensitivity of the photoconductor depends on the thickness of each layer.

Since the surface of the conductive support used in the present invention does not require any particular step of roughening, the light is not sufficiently scattered. Therefore, the surface of the photoconductor is made rougher than the surface of the conductive support, and the range of the maximum surface roughness is set to 0.2.
By setting the thickness to be not less than μm and not more than 0.6 μm, light reflected on the outermost surface of the photoreceptor is scattered, and generation of interference fringes can be suppressed. Further, by providing the photosensitive member surface roughness as described above, a conductive support having a relatively small surface roughness of not more than 0.2 μm, such as a seamless electroformed nickel belt or an endless belt formed by bonding. An aluminum-deposited PET film or the like can be used without surface treatment. When the photoconductor surface roughness is smaller than 0.2 μm, scattering of reflected light becomes insufficient, moire occurs due to interference with the reflected light on the conductive support surface, and when larger than 0.6 μm, At the time of development, the reproducibility of one dot is reduced due to the minute unevenness, which causes a reduction in image quality.

Hereinafter, the present invention will be described in detail. First, a method for forming a photosensitive layer will be described. A spray coating method is used as the manufacturing method. The spray gun used in the present invention may be any of air spray, airless spray and electrostatic spray.

In FIG. 3, the conductive support 17 is the support 1
6 attached. The support 17 is horizontally mounted and rotates at a constant speed in a fixed direction by rotating a belt 20 wound around a pulley 19 of a center shaft 18. 21 are installed in close proximity. Spray gun 21 supports table 22
Scanning device 2 for screws etc. installed parallel to the longitudinal direction of 7
3 and a pipe 25 for leading a carrier gas to a jet nozzle 24 at the tip is provided.
A coating solution pipe 27 is provided from the
It is configured such that the application liquid is sucked and ejected together with the injection of the carrier gas. Further, a gas pressure adjusting valve 28 is attached to the pipe 25. A pump for sending the coating liquid may be provided between the coating liquid tank and the spray gun.

The coating of the photosensitive layer is performed by rotating the photosensitive layer with the support 17 attached thereto,
This is performed by ejecting the coating liquid in the coating liquid tank 26 together with the carrier gas adjusted by the gas pressure adjusting valve 28 while spraying the liquid onto the support 17.

Factors for controlling the thickness of the photosensitive layer and its uniformity include atomizing air pressure, atomizing air flow rate, nozzle opening of the outlet, scan speed, number of scans,
Examples include the control value of the coating liquid feeding pump.
By setting the maximum thickness difference and surface roughness of the photosensitive layer to the conditions included in the claims, an electrophotographic photoreceptor that does not generate uneven shading and interference fringes in a halftone image even by using a spray coating method. Obtainable.

Next, the photosensitive layer used in the present invention will be described. FIG. 1 is a schematic cross-sectional view of an electrophotographic photoreceptor of the present invention, in which an undercoat layer is inserted between a charge generation layer and a charge transport layer of a conductive substrate and a function-separated type photosensitive layer.

In the present invention, the conductive support used for the electrophotographic photoreceptor may be a conductor or an insulator subjected to a conductive treatment, for example, a metal such as Al, Ni, Fe, Cu, Au, or an alloy thereof. In addition, on an insulating substrate such as polyester, polycarbonate, polyimide, PET, or glass, a metal such as Al, Ag,
Those formed with a thin film of a conductive material such as ₂ O ₃ and SnO ₂ , and paper subjected to a conductive treatment can be used. The shape of the conductive support is not particularly limited, and any of a plate shape, a drum shape, and a belt shape can be used. Above all, a seamless nickel belt, a metal-deposited endless belt, a bonded aluminum-deposited PET, and a seamless aluminum-deposited PET that do not require a surface roughening step by surface treatment and have a high degree of freedom in layout in an image forming apparatus An endless belt using a film is preferable.

An undercoat layer may be provided between the conductive support and the photosensitive layer, if necessary. The provided undercoat layer is provided for the purpose of improving adhesiveness, preventing interference fringes, improving the coating property of the upper layer, reducing residual potential, and the like. The undercoat layer generally contains a resin as a main component. However, considering that the photosensitive layer is coated thereon with a solvent, these resins are resins having high solubility resistance to general organic solvents. It is desirable. Examples of such a resin include water-soluble resins such as polyvinyl alcohol, casein and sodium polyacrylate, alcohol-soluble resins such as copolymerized nylon and methoxymethylated nylon, polyurethane, melamine resin, alkyd-melamine resin, and epoxy resin. And the like, a curable resin forming a three-dimensional network structure. Further, fine powders such as metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide, and the like, or metal sulfides and metal nitrides may be dispersed and contained. These undercoat layers can be formed using an appropriate solvent and a coating method.

Further, as the undercoat layer of the present invention, a metal oxide layer formed by a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent or the like is also useful.

In addition, the undercoat layer of the present invention has_TwoO_Three
Provided by anodic oxidation, or polyparaxylylene (P
Organic matter such as rylene) and SnO_Two, TiO_Two, ITO, C
eO _TwoInorganic substances such as those provided by vacuum thin film production method are also good.
Can be used well. The thickness of the undercoat layer is suitably 1 to 20 μm.
And preferably 2 to 10 μm.

Next, the photosensitive layer provided on the conductive support via an undercoat layer will be briefly described below.

First, the charge generation layer will be described.
The charge generation layer is a layer containing a charge generation substance as a main component, and a binder resin may be used as needed. Known materials can be used as the charge generating substance. For example, phthalocyanine pigments such as metal phthalocyanine and non-metal phthalocyanine, azulhenium salt pigment, methine squaric acid pigment, azo pigment having a carbazole skeleton, azo pigment having a triphenylamine skeleton, azo pigment having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigment having a fluorenone skeleton, azo pigment having an oxadiazole skeleton, azo pigment having a bisstillene skeleton, azo pigment having a distyryl oxadiazole skeleton, azo pigment having a distyryl carbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinone imine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, i Jigoido based pigments, and bisbenzimidazole pigments. These charge generating materials are
They can be used alone or as a mixture of two or more. As the binder resin used as needed for the charge generation layer, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin,
Acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-
Vinyl carbazole, polyacrylamide and the like are used. These binder resins can be used alone or as a mixture of two or more.

Further, a charge transport material may be added as required. Further, in addition to the binder resin described above, a polymer charge transport material is preferably used as the binder resin for the charge generation layer.

If necessary, these organic charge generating substances are dispersed together with a binder resin using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane or butanone by a ball mill, an attritor, a sand mill or the like, and the dispersion is diluted appropriately. A coating liquid for forming a charge generation layer is prepared.

The thickness of the charge generation layer provided as described above is suitably about 0.01 to 5 μm, and preferably 0.05 to 2 μm.

The charge transporting layer is a layer intended to hold the charged charges and to move the charges generated and separated in the charge generating layer by exposure to combine with the charged charges held therein. High electrical resistance is required to achieve the purpose of retaining the charged charge, and in order to achieve the purpose of obtaining a high surface potential with the retained charged charge, the dielectric constant is small and the charge mobility is good. Is required.

The charge transport layer for satisfying these requirements is composed of a charge transport material and a binder resin used as required. The charge transport material and the binder resin can be formed by dissolving or dispersing in a suitable solvent, and then applying and drying the solution. If necessary, a plasticizer, an antioxidant, a leveling agent and the like can be added in an appropriate amount in addition to the charge transport material and the binder resin.

The charge transport material includes a hole transport material and an electron transport material. Examples of the electron transporting substance include chloranil, bromanil, tetracyanoethylene,
Tetracyanoquinodimethane, 2,4,7-trinitro-
9-fluorenone, 2,4,5,7-tetranitro-9
Fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,
Electron accepting substances such as 6,8-trinitro-4H-indeno [1,2-b] thiophen-4one and 1,3,7-trinitrodibenzothiophene-5,5-dioxide are exemplified. These electron transport materials can be used alone or
It can be used as a mixture of more than one species.

As the hole transporting substance, the following electron donating substances can be used, and are preferably used. For example, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9-
(P-diethylaminostyrylanthracene), 1,1
-Bis- (4-dibenzylaminophenyl) propane,
Styryl anthracene, styryl pyrazoline, phenylhydrazone, α-phenylstilbene derivative, thiazole derivative, triazole derivative, phenazine derivative,
Examples include acridine derivatives, benzofuran derivatives, benzimidazole derivatives, and thiophene derivatives. These hole transport materials can be used alone or as a mixture of two or more.

The polymer charge transport layer material has the following structure. (A) Polymer having a carbazole ring For example, poly-N-vinylcarbazole,
No. 82056, JP-A-54-9632, JP-A-54-11737, JP-A-4-175337, JP-A-4-183719, JP-A-6-23
Compounds described in JP-A-4841 are exemplified.

(B) Polymer having a hydrazone structure For example, JP-A-57-78402, JP-A-61-78402
JP-A-20953, JP-A-61-296358,
JP-A-1-134456, JP-A-1-17916
No. 4, JP-A-3-180851, JP-A-3-180851
180852, JP-A-3-50555, JP-A-5-310904, JP-A-6-234840
And the like.

(C) Polysilylene polymer For example, JP-A-63-285552,
88461, JP-A-4-264130, JP-A-4-264131, JP-A-4-264132
JP, JP-A-4-264133, JP-A-4-4-2
Compounds described in JP-A-89867 are exemplified.

(D) Polymer having a triarylamine structure For example, N, N-bis (4-methylphenyl) -4-aminopolystyrene, JP-A-1-134457, JP-A-2-282264, Kaihei 2-304456
JP, JP-A-4-133065, JP-A-4-13-1
Compounds described in JP-A-33066, JP-A-5-40350, and JP-A-5-202135 are exemplified.

(E) Other Polymers For example, a formaldehyde condensation polymer of nitropyrene, JP-A-51-73888, JP-A-56-15074
9, JP-A-6-234836 and JP-A-6-34836.
Compounds described in JP-A-234837 are exemplified.

The polymer having an electron donating group used in the present invention includes not only the above-mentioned polymers but also copolymers of known monomers, block polymers, graft polymers, star polymers, and the like. For example, it is also possible to use a crosslinked polymer having an electron donating group as disclosed in JP-A-3-109406.

The following compounds are exemplified as polycarbonates, polyurethanes, polyesters, and polyethers having a triarylamine structure which are more useful as the polymer charge transporting material used in the present invention.

For example, JP-A-64-1728, JP-A-64-13061, and JP-A-64-19049
JP, JP-A-4-11627, JP-A-4-22
5014, JP-A-4-230767, JP-A-4-320420, JP-A-5-232727, JP-A-7-56374, JP-A-9-127
713, JP-A-9-222740, JP-A-9-265197, JP-A-9-212877, JP-A-9-309495, and the like.

As the binder resin that can be used in combination with the charge transport layer, polycarbonate, polyester, methacrylic resin, acrylic resin, polyethylene, polyvinyl chloride, polyvinyl acetate, polystyrene, phenol resin, epoxy resin, polyurethane, polyvinylidene chloride, Alkyd resin, silicon resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, polyacrylate, polyacrylamide, phenoxy resin, and the like are used. These binders can be used alone or as a mixture of two or more.

In the charge transport layer of the present invention, other antioxidants and plasticizers used for rubbers, plastics, oils and the like may be added.

A leveling agent may be added to the charge transport layer. As the leveling agent, silicone oils such as dimethyl silicone oil and methyl phenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in the chain measurement are used, and the amount used is based on 100 parts by weight of the binder resin. 0 to 1 part by weight is suitable. This charge transport layer can be formed using a suitable solvent and a coating method. The thickness of the charge transport layer is
About 5 to 100 μm is suitable, preferably about 20 to 3 μm.
0 μm.

FIG. 2 is a schematic view for explaining the image forming apparatus of the present invention, and the present invention is not limited to this.
In FIG. 2, a photoconductor 1 is provided with an endless belt-shaped electrophotographic photoconductor manufactured according to the present invention. The endless belt-shaped electrophotographic photosensitive member is driven and driven by three driven, driven, and tension rollers. The driven roller and the tension roller may also be used, and the photoconductor may be supported and driven by two drive rollers. The length of each roller in contact with the back surface of the endless photoconductor is longer than the width of the image forming area and equal to or less than the width of the endless belt-shaped photoconductor.

As the charging charger 2 and the transfer charger 7, known means such as a corotron, a scorotron, a solid state charger (solid state charger), and a charging roller are used.

As another transfer means, a method may be used in which an intermediate transfer belt is used, a toner image on a photoreceptor is transferred to the intermediate transfer belt, and a secondary transfer transfer is performed on paper. Also,
The toner images of different colors may be superimposed on the intermediate transfer belt and then secondarily transferred to paper.

Light sources such as the image exposure unit 3 and the static elimination lamp 10 include a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, and a light emitting diode (LE).
D), semiconductor lasers (LD), electroluminescence (EL), and other general light-emitting materials can be used.
To irradiate only light in a desired wavelength range, various filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used.

The light source and the like are provided with a transfer step, a charge removal step, a cleaning step, and a pre-exposure step using light irradiation in addition to the step shown in FIG.
Light is applied to the photoconductor.

The toner developed on the photoreceptor belt 1 by the developing unit 4 is transferred to the transfer paper 9, but not all is transferred, and some toner remains on the photoreceptor 1. Such toner is removed from the photoconductor by cleaning 9. The cleaning may be performed only by the cleaning blade, or may be performed only by the cleaning brush or in combination with the blade.

When the electrophotographic photosensitive member is negatively charged and subjected to image exposure, a negative electrostatic latent image is formed on the surface of the photosensitive member. If this is developed with a negative polarity toner, a positive image is obtained, and if it is developed with a positive polarity toner, a negative image is obtained.

A known method is applied to the developing means, and a known method is also used for the charge removing means.

The image forming apparatus as described above may be fixedly incorporated in a copying machine, a facsimile, or a printer, or may be incorporated in the apparatus in the form of a process cartridge. The process cartridge is one device (part) that includes a photoconductor and further includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and a charge removing unit. There are many shapes and the like of the process cartridge. As a general example, the one shown in FIG. The photoreceptor 30 has an electrophotographic photoreceptor manufactured by the present invention on a conductive support.

It has been found that a good image can be provided by using the image forming apparatus according to the present invention described above.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to examples, but the embodiments of the present invention are not limited thereto. All parts are by weight.

Example 1 An alkyd resin (Veccosol 1307-60-EL)
15 parts by weight (manufactured by Dainippon Ink and Chemicals, Inc.) and 10 parts by weight of melamine resin (Super Beckamine G-821-60 (manufactured by Dainippon Ink and Chemicals, Inc.)) are dissolved in 150 parts by weight of methyl ethyl ketone and oxidized. 90 parts by weight of titanium powder (Taipal CR-EL (manufactured by Ishihara Sangyo Co., Ltd.)) was added and dispersed by a ball mill for 12 hours. This was taken out into a container and diluted with cyclohexanone so as to have a solid content of 25% by weight to prepare a coating liquid for an undercoat layer.

This was applied to a nickel seamless belt having a diameter of 92 mm, a length of 410 mm, a thickness of 30 μm, and a maximum surface roughness of 0.05 μm by a spray coating method.
After drying for 20 minutes, an undercoat layer having a thickness of 6.5 μm and a maximum thickness difference of 0.9 μm in the effective image area was formed.

Next, 4 parts by weight of a polyvinyl butyral resin (S-LEC HL-S (manufactured by Sekisui Chemical Co., Ltd.)) was dissolved in 150 parts by weight of cyclohexanone, and this was dissolved in a structural formula (1).
Of trisazo pigment shown in (1) was added and dispersed in a ball mill for 48 hours, and then 210 parts by weight of cyclohexanone was added and dispersed for 3 hours.

[0058]

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This was taken out into a container and diluted with cyclohexanone so that the solid content was 1.5% by weight. The coating liquid for a charge generation layer thus obtained is applied on the intermediate layer by a spray coating method, and then dried at 130 ° C. for 20 minutes. The transmittance at a wavelength of 690 nm is 4% and the maximum transmittance difference in the effective image area is 0. An 8% charge generation layer was formed.

Next, in 83 parts of tetrahydrofuran, 10 parts of a bisphenol A type polycarbonate resin and 0.0 of silicone oil (KF-50 (manufactured by Shin-Etsu Chemical Co., Ltd.))
Of the charge transporting material 8 of the structural formula (2)
Was added and dissolved, and diluted with cyclohexanone so as to have a solid content of 8% by weight to prepare a charge transport layer coating solution.

[0061]

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After the thus obtained coating solution for a charge transport layer is applied on the charge generation layer by a spray coating method,
After drying at 20 ° C. for 20 minutes, a charge transport layer having a thickness of 25 μm and a maximum thickness difference of 1.2 μm in the effective image area was formed. afterwards,
Both ends were cut so that the length of the endless belt-shaped photosensitive member was 367 mm. As described above, the electrophotographic photosensitive member of Example 1 was manufactured. The surface roughness of this photoconductor is
It was 0.51 μm.

The measurement of the maximum surface roughness of the conductive support and the electrophotographic photosensitive member obtained in Example 1 was performed using a surface roughness measuring device Surfcom (manufactured by Tokyo Seimitsu Co., Ltd.). The difference between the thickness of the undercoat layer and the thickness of the charge transport layer was determined by providing a single film on the support in the same manner as in Example 1 and measuring 80 points at any measurement points using an eddy current film thickness meter (manufactured by Fischer). Was measured, and the difference between the maximum value and the minimum value was determined. The transmittance difference of the charge generation layer was determined by measuring the transmittance at 690 nm at 60 arbitrary measurement points by spectrophotometry using a single film on a transparent PET film, and defining the difference between the maximum value and the minimum value. .

Examples 2 to 8 and Comparative Examples 1 to 5 Using a Ni seamless belt having the surface roughness shown in Table 1, atomizing air pressure of air spray at the time of coating an undercoat layer, a charge generation layer and a charge transport layer. The electrophotographic photoreceptors of Examples 2 to 8 and Comparative Examples 1 to 5 were prepared in the same manner as in Example 1 except that the flow rate of the atomizing air and the scanning speed were changed to ΔUL, ΔTG, and ΔCTL shown in Table 1, respectively. Produced. The surface roughness of each photoconductor was as shown in Table 1.

Examples 1 to 8 and Comparative Example 1 thus obtained
To 5 photoconductors are full-color laser printers IPSIO Co
lor 5000 (manufactured by Ricoh (λ = 780 nm, 600 dp
i, an image forming test was performed using a modified machine having a beam spot of 4.5 × 10 ⁻³ mm ² ). Defects in the halftone image were visually determined. Table 1 shows the results.

Example 9 The charge generating substance was converted from the above structural formula (1) to the following structural formula (3)
Of bisazo pigments, 4% transmittance at a wavelength of 610 nm
And that a charge generation layer having a maximum transmittance difference of 0.4% in the effective image area was formed, a Ni seamless belt having a surface roughness shown in Table 1 was used, and an undercoat layer and a charge transport layer were coated. The electrophotographic photoreceptor of Example 9 was manufactured in the same manner as in Example 1 except that the atomizing air pressure, the atomizing air flow rate, and the scanning speed of the air spray were changed to ΔUL, ΔTG, and ΔCTL shown in Table 1, respectively. Produced.

[0067]

Embedded image

Examples 10 to 16 and Comparative Examples 6 to 12 and 15 Using a Ni seamless belt having the surface roughness shown in Table 1, atomization of air spray when coating the undercoat layer, the charge generation layer and the charge transport layer. Examples 10 to 16 and Comparative Examples 6-1 were performed in the same manner as in Example 9 except that the air pressure, the atomizing air flow rate, and the scan speed were changed to ΔUL, ΔTG, and ΔCTL shown in Table 1, respectively.
No. 0 electrophotographic photosensitive member was produced. The surface roughness of each photoconductor was as shown in Table 1.

Comparative Examples 13 and 14 To 83 parts of tetrahydrofuran, 10 parts of a bisphenol A type polycarbonate resin and silicone oil (KF-5)
0 (manufactured by Shin-Etsu Chemical Co., Ltd.), 0.002 parts, and 8 parts of the charge transport material of the structural formula (2) are added thereto to prepare a charge transport layer coating solution, and the charge transport layer is immersed. Comparative Example 1 was performed in the same manner as in Example 10 except that the coating was formed by a coating method.
Electrophotographic photosensitive members Nos. 3 and 14 were produced.

Comparative Example 16 At the stage of producing a seamless nickel belt as a conductive support, the surface roughness was reduced to 0.31 by a step of roughening the surface.
An electrophotographic photosensitive member of Comparative Example 14 was produced in the same manner as in Example 10, except that the thickness was changed to μm.

The photoreceptors of Examples 10 to 16 and Comparative Examples 6 to 16 obtained as described above were applied to a full-color laser printer IP.
Modified SIO Color 5000 (Ricoh (λ = 655n)
m, 1200 dpi, beam spot 2.7 × 10 ^-3 m
with m ² to remodeling), image formation was performed test. Defects in the halftone image were visually determined. Table 1 shows the results.

[0072]

[Table 1]

FIG. 5 shows the results of analysis of Examples 1 to 16 and Comparative Examples 1 to 12. Regarding the occurrence of shading in the halftone image, the maximum thickness difference of the undercoat layer was 2 μm.
It can be seen that Examples 1 to 16 and Comparative Examples 1 to 10 which are equal to or less than m are divided into two by the solid line in the figure. Region that does not occur in the halftone uneven shading can be well approximated by the proposed formula of the present invention ^{(7 · ΔTG) -2 + (} 5 · ΔCTL) -2 ≦ 10 -2 ...... (1). △ in the graph 1 satisfies the expression (1) but ΔUL is 2 μm or more, and halftone shading unevenness occurs. Therefore, in order to prevent the halftone shading unevenness, the undercoating layer, the charge generating layer and the charge transporting layer are required to have ΔUL ≦ 2 μm and (7 · ΔTG) ⁻² + (5 · ΔCTL)
^It can be said that it is necessary to satisfy ⁻² ≦ 10 ⁻² .

From Comparative Examples 13 to 15, when a photosensitive layer is formed on a conductive support having a surface roughness of 0.02 to 0.20 μm as used in the present invention, the surface roughness of the photosensitive layer is preferably 0.2 μm or less. If an interference fringe occurs and exceeds 0.6 μm,
It can be seen that the reproducibility of one dot is deteriorated. Therefore, using a conductive support having a surface roughness of 0.02 to 0.20 μm,
In order to prevent the occurrence of interference fringes and crushed dots, it can be said that the surface roughness of the photoconductor should be set to 0.2 to 0.6 μm.

Further, when the conductive support having such a surface close to the mirror surface is roughened, the background stain as shown in Comparative Example 16 is undesirably generated.

[0076]

As is evident from the above description, even in an electrophotographic photosensitive member produced by a spray coating method using a conductive support having a small surface roughness, the occurrence of density unevenness and interference fringes in a halftone image. And an image forming apparatus using the electrophotographic photosensitive member.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a layer configuration of an electrophotographic photoreceptor of the present invention.

FIG. 2 is a schematic view illustrating the image forming apparatus of the present invention.

FIG. 3 is a schematic view showing an example of an apparatus for applying and forming a belt-shaped photoconductor of the present invention.

FIG. 4 is a schematic view illustrating a process cartridge incorporated in the image forming apparatus of the present invention.

FIG. 5 is a graph showing the results of analyzing the examples and comparative examples.

[Explanation of symbols]

 Reference Signs List 6 registration roller 7 transfer unit 8 fixing unit 9 cleaning 10 static elimination unit 11 drive roller 12 driven roller 13 tension roller 14 potential detector 16 support 17 support 18 central shaft 19 pulley 20 belt 21 spray gun 22 pedestal 23 scanning device 24 ejection Nozzle 25 Pipe 26 Tank 27 Pipe 28 Gas pressure regulating valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Michio Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Toshiyuki Kahata 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (72) Inventor Akihiro Sugino 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2H035 CA05 CB06 2H068 AA28 AA29 AA48 AA52 AA55 AA58 CA46

Claims (7)

[Claims] 1. An undercoat layer on a conductive support,
An electrophotographic photosensitive member comprising a charge generation layer and a charge transport layer, wherein at least the charge transport layer is formed by a spray coating method and satisfies the following formula. ΔUL ≦ 2 and ^{(7 · ΔTG) -2 + (} 5 · ΔCTL) -2 ≦
^10-2 Here, ΔUL: maximum film thickness difference of the undercoat layer in the effective image area ([mu] m)? Tg: Maximum transmittance difference of the charge generating layer in the effective image area (%) (measurement wavelength of the transmittance of the charge generating agent ΔCTL: Maximum thickness difference of the charge transport layer in the effective image area (μm) 2. The electrophotographic photosensitive member has a maximum surface roughness of 0.2.
2. The electrophotographic photosensitive member according to claim 1, wherein the thickness is not less than μm and not more than 0.6 μm. 3. The conductive support has a maximum surface roughness of 0.02.
3. The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor has a thickness of not less than μm and not more than 0.20 μm. 4. The electrophotographic photosensitive member according to claim 1, wherein the conductive support is a nickel seamless belt. 5. An image forming apparatus for repeatedly performing at least charge, exposure with coherent light, development, and transfer on an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member is provided with the electrophotographic photosensitive member according to claim 1. Characteristic image forming apparatus. 6. The exposure resolution by coherent light is 600 dp.
The image forming apparatus according to claim 1, wherein the number is i or more. 7. A process cartridge for an image forming apparatus, comprising the electrophotographic photosensitive member according to claim 1.