JP2002202620A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which high image quality, long service life and high reliability are attained at a high level. SOLUTION: In the image forming device provided with a photoreceptor, an electrifier to uniformly electrify the surface of the photoreceptor, an image exposure device to form an electrostatic latent image by performing image exposure after uniformly electrifying the image, a developing device to develop the electrostatic latent image and a device to transfer a developed image, the photoreceptor is constituted of a photoreceptive layer 34 containing at least an electric charge generating substance and an electric charge transporting substance through an intermediate layer 33 on a conductive supporting body 32 and a protective layer 35 consisting of at least a filler and a binder resin, the total thickness of a photoreceptive layer film and a protective layer film is defined as <=25 μm, and the laser beam whose wavelength is <=670 nm is used in the image exposure device to be used for the image exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for performing an image forming operation using an electrophotographic process.
It is applied to copiers, facsimile machines, laser printers, direct digital plate making machines, etc.

[0002]

2. Description of the Related Art In general, an "electrophotographic process" means that a photoconductive photoreceptor is first charged in a dark place, for example, by corona discharge, and then image-exposed with a laser beam or the like to selectively charge only the exposed portion. To obtain an electrostatic latent image, develop the latent image portion with fine particles (toner) that consists of colorants such as dyes and pigments and a binder such as a polymer substance, and visualize the image. This is one of the image forming methods to be formed.

[0003] The basic characteristics required of the photoreceptor used in such an electrophotographic process are that it can be charged to an appropriate potential in a dark place, that there is little dissipation of electric charge in a dark place, and that the charge is quickly irradiated by light irradiation. Can be dissipated.

However, in the case of a so-called digital type electrophotographic process in which image exposure is performed by a currently mainstream laser beam even if the photoreceptor satisfies the above characteristics, if the laser beam has a long wavelength, It is difficult to reduce the diameter, and there is a limit in increasing the recording density with respect to the photoreceptor, and it cannot be said that it is sufficient to achieve high image quality.

In recent years, image forming apparatuses using an electrophotographic process, such as electrophotographic copying machines and electrophotographic printers, as well as high image quality, are required to have high speed, small size, and long life. The life of an image forming apparatus is often determined by the photoreceptor, which is caused by the deterioration of the photoreceptor due to mechanical and chemical actions during the repetition of charging, exposure, development, transfer, and cleaning in the electrophotographic process. I do. The mechanical deterioration causes wear and damage of the photoconductor, and the chemical deterioration causes oxidative deterioration of the binder resin and the charge transfer material due to the generated ozone, and lowers the image quality due to deposits. In addition, as described above, the photoreceptor is reduced in diameter as the speed and size are reduced, and the use conditions in the electrophotographic process are severe. In particular, a rubber blade is used in the cleaning section, and the rubber hardness is increased in order to perform sufficient cleaning. The contact pressure must be increased. This promotes abrasion of the photoreceptor, causing potential fluctuations and sensitivity fluctuations, thereby causing problems such as abnormal images, color balance of color images being lost, and problems in color reproducibility. For this reason, an attempt was made to increase the thickness of the photosensitive layer in order to increase the margin for abrasion. However, in the case of the currently mainstream photoreceptor having a laminated structure, the charge transport layer, which is responsible for charge transport, is used. By increasing the thickness, the charge is dissipated during charge transfer, causing disturbance of the latent image, resulting in problems such as a reduction in resolution, and potential fluctuation and sensitivity fluctuation due to film thickness fluctuation. The resulting problem remained.

For this purpose, techniques such as providing a protective layer or adding an inorganic filler to the photosensitive layer have been disclosed in Japanese Patent Laid-Open No. 1-20.
5171, JP-A-7-333881, JP-A-8-1
5887, JP-A-8-123053, JP-A-8-1
No. 46641 has been proposed. However, although the abrasion resistance is improved, the potential of the exposed portion is increased by continuous repetition for a long period of time, and image deterioration such as a decrease in image density occurs. The protective layer proposed in JP-A-8-179542 has a mechanical strength. Although the abrasion resistance was improved to a high degree, the image resolving power was reduced, and thick characters were observed, which was not sufficient to achieve high image quality.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus which achieves high image quality, long life and high reliability at a high level.

[0008]

As a result of repeated studies, the present inventors have achieved a small beam diameter by limiting the wavelength of an image exposure laser beam in an electrophotographic process to 670 nm or less, and have achieved a high recording density. At the same time as achieving higher image quality, a photosensitive layer formed on this intermediate layer is provided via an intermediate layer provided to suppress charge injection from the support side to prevent image defects. By reducing the thickness, the image quality is prevented from deteriorating due to the diffusion of electric charges during the formation of an electrostatic latent image, and a latent image is formed on the photoreceptor surface without impairing high-resolution writing using a small-diameter beam.
At the same time as the transfer, an image forming apparatus is provided by providing at least a protective layer comprising a filler and a binder resin in order to improve a reduction in the life due to the thinning of the photosensitive layer, and limiting the sum of the photosensitive layer thickness and the protective layer thickness. It has been found that both high image quality due to high resolution reproduction and remarkable long life can be achieved.

In addition, when toner is developed by the reversal (negative / positive) development method using the image forming apparatus of the present invention, the background stain is D which is the sum of the thickness of the photosensitive layer and the thickness of the protective layer.
(Μm) and the electric field strength (V / D) obtained from the charged potential V (V) on the surface of the photoconductor. This abnormal image has an electric field strength of 40 V / μm regardless of the film thickness.
It was found that this would occur. On the other hand, it is known that when the electric field strength of the photoreceptor decreases, the charge transport ability in the photosensitive layer decreases, and accordingly, the photosensitivity decreases. From the examination results, the electric field strength applied to the photoconductor is
If it is 12 V / μm or less, the photosensitivity of the photoreceptor decreases, the potential of the exposed portion is hardly reduced, and the density of the image decreases.
It was found that the resolution was reduced. That is, 12
(V / μm) ≦ V / D ≦ 40 (V / μm) It is clear that it is preferable to form an image.

It is apparent that the above-mentioned effects become more apparent by stacking the photosensitive layer, specifying the filler and binder resin materials to be used, and specifying the composition of the intermediate layer. It became.

According to the present invention, (1) a photosensitive member, a charging device for uniformly charging the surface of the photosensitive member, and an image exposing device for forming an electrostatic latent image by performing image exposure after uniform charging. An image forming apparatus comprising: a developing device for developing the electrostatic latent image; and a device for transferring a developed image, wherein the photoconductor is at least a charge generating material and a charge transport material on a conductive support via an intermediate layer. And a protective layer comprising at least a filler and a binder resin, wherein the sum of the thickness of the photosensitive layer and the thickness of the protective layer is 25 μm or less, and the image exposure used for the image exposure is performed. An image forming apparatus, wherein the apparatus uses a laser beam having a wavelength of 670 nm or less;

(2) In the image forming apparatus described in (1), the sum of the thickness of the photosensitive layer and the thickness of the protective layer is D (μm), and the absolute value of the surface potential of the photosensitive member due to charging is V (V). The image forming apparatus satisfies a relationship of 12 (V / μm) ≦ V / D ≦ 40 (V / μm),

(3) The image forming apparatus according to the above (1), wherein the photosensitive layer comprises a laminate of a charge generation layer and a charge transport layer.

(4) The image forming apparatus according to any one of (1) to (3), wherein the filler is an inorganic pigment.

(5) The image forming apparatus according to (4), wherein the inorganic pigment is a metal oxide.

(6) The image forming apparatus according to (5), wherein the metal oxide is one selected from silica, alumina, and titanium oxide.

(7) The image forming apparatus according to any one of (1) to (6), wherein the protective layer contains a charge transport material.

(8) The image forming apparatus according to any one of (1) to (6), wherein the binder resin used for the protective layer is polycarbonate.

(9) The image forming apparatus according to any one of (1) to (8), wherein the intermediate layer comprises an inorganic filler, an alkyd resin, and a melamine resin.

(10) The image forming apparatus according to (9), wherein the inorganic filler used for the intermediate layer is titanium oxide.

First, the photosensitive member used in the image forming apparatus of the present invention will be described. FIG. 1 is a cross-sectional view showing a configuration example of a photoreceptor used in the image forming apparatus of the present invention, in which an intermediate layer 33, a photosensitive material containing at least a charge generating substance and a charge transporting substance on a conductive support 32. Layer 34, protective layer 3 comprising at least filler and binder resin on photosensitive layer
5 are provided. The sum of the thicknesses of the photosensitive layer 34 and the protective layer 35, that is, the total thickness of the two layers 37 is 25 μm or less. Further, the photosensitive layer 34 may be constituted by a laminate of a charge generation layer and a charge transport layer.

As the conductive support of the photoreceptor used in the image forming apparatus of the present invention, a conductor or an insulator subjected to a conductive treatment, for example, a metal such as Al, Fe, Cu, Au, etc.
Alternatively, other than their alloys, polyester, polycarbonate, polyimide, Al,
A thin film made of a metal such as Ag or Au, or a conductive material such as In ₂ O ₃ or SnO _2, or a paper subjected to a conductive treatment can be used. The shape of the conductive support is not particularly limited and is plate-like,
Any of a drum shape and a belt shape can be used.

The intermediate layer of the photoreceptor used in the image forming apparatus of the present invention is generally composed of a resin as a main component. Is considered to be applied using a solvent, it is preferable that the resin is a resin having high solubility resistance to a general organic solvent. 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 resin, melamine resin, and epoxy resin. etc,
Curable resins that form a three-dimensional network structure are exemplified. Above all, when an alkyd resin or a melamine resin is used, a high-quality image without defects can be obtained.

Further, by adding a fine powder of a metal oxide such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide, or the like, or a metal sulfide or a metal nitride as a filler, the composition becomes more stable. It is preferable to use titanium oxide while maintaining the chargeability. These intermediate layers can be formed using an appropriate solvent and a coating method, and have a thickness of 0.1 to 10
μm, preferably 0.2 to 6 μm is suitable.

Next, the photosensitive layer of the photosensitive member used in the image forming apparatus of the present invention will be described. The photosensitive layer of the photoreceptor used in the image forming apparatus of the present invention may be a single layer type or a laminated type, but here, for convenience of explanation, first, a charge transport layer, and a laminated type photosensitive layer composed of a charge generation layer. State.

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. As the charge generating substance, any of inorganic and organic materials having sensitivity to a laser beam of 670 nm or less used in the image forming apparatus of the present invention can be used.

Examples of the inorganic material include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compounds, and amorphous silicon. As amorphous silicon, a material obtained by terminating a dangling bond with a hydrogen atom or a halogen atom, or a material doped with a boron atom, a phosphorus atom, or the like is preferably used.

On the other hand, a known material can be used as the organic material. 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 substances can be used alone or as a mixture of two or more kinds.

The binder resin used as needed in the charge generation layer includes 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
It can be used as a mixture of more than one species. Further, a low molecular charge transport material may be added as needed.

As a method for forming the charge generation layer, a vacuum thin film preparation method and a casting method from a solution dispersion system can be used. The former method includes a vacuum deposition method, a glow discharge decomposition method, an ion plating method, a sputtering method,
Reactive sputtering, CVD, or the like is used, and the above-described inorganic and organic materials can be formed favorably.

In order to provide a charge generation layer by the casting method described below, the above-mentioned inorganic or organic charge generation material is used together with a binder resin, if necessary, using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane or butanone. It can be formed by dispersing with a ball mill, an attritor, a sand mill, or the like, diluting the dispersion liquid appropriately, and applying. The coating can be performed by a dip coating method, a spray coating method, a bead coating method, or the like. The thickness of the charge generation layer provided as described above is appropriately about 0.01 to 5 μm, and preferably 0.05 to 2 μm.

Next, the charge transport layer will be described. The charge transport layer is dissolved and coated together with a charge transport material and a binder resin, and can be used as the charge transport layer. As the binder resin, polycarbonate having good film properties (bisphenol A type, bisphenol Z type, bisphenol C type, or a copolymer thereof) ), Polyarylate, polysulfone, polyester, methacrylic resin,
Polystyrene, polyvinyl acetate, epoxy resin, phenoxy resin and the like are used. These binders can be used alone or as a mixture of two or more.

The charge transporting material used in the charge transporting layer is
Oxazole derivatives, oxadiazole derivatives (described in JP-A-52-139065 and 52-139066), imidazole derivatives, triphenylamine derivatives (described in Japanese Patent Application No. 1-77839), benzidine derivatives (described in JP-B-58-32372). No.), α-phenylstilbene derivatives (described in JP-A-57-73075),
Hydrazone derivatives (Japanese Patent Application Laid-Open Nos.
156954, 55-52063, 56-81850, etc.), triphenylmethane derivatives (described in JP-B-51-10983), anthracene derivatives (described in JP-A-51-94829), styryl derivatives (described in JP-A-51-94829). 56-29245, 58-198043),
Carbazole derivatives (described in JP-A-58-58552), pyrene derivatives (described in Japanese Patent Application No. 2-94812)
Etc. can be used.

An antioxidant can be added for the purpose of improving environmental resistance, especially for the purpose of preventing a decrease in sensitivity and an increase in residual potential. The antioxidant may be added to any layer containing an organic substance, but good results can be obtained by adding it to a layer containing a charge transporting substance. The antioxidants that can be used in the present invention include the following.

Monophenolic compounds 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, stearyl-β- (3,5- Di-t-
(Butyl-4-hydroxyphenyl) propionate and the like.

Bisphenolic compounds 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-
Ethyl-6-t-butylphenol), 4,4′-thiobis- (3-methyl-6-t-butylphenol),
4,4'-butylidenebis- (3-methyl-6-t-butylphenol) and the like.

High molecular phenolic compound 1,1,3-tris- (2-methyl-4-hydroxy-
5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-
4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis (4′-hydroxy -3'-t-butylphenyl) butyric acid] crylic ester, tocopherols and the like.

Paraphenylenediamines N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-
Phenylenediamine, N, N'-di-isopropyl-p
-Phenylenediamine, N, N'-dimethyl-N, N '
-Di-t-butyl-p-phenylenediamine and the like.

Hydroquinones 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t
-Octyl-5-methylhydroquinone, 2- (2-octadecenyl) -5-methylhydroquinone and the like.

Organic sulfur compounds: dilauryl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate and the like.

Organic phosphorus compounds: triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine and the like.

These compounds are known as antioxidants for rubber, plastics, oils and the like, and commercially available products can be easily obtained.

The addition amount of the antioxidant in the present invention is 0.1 to 100 parts by weight, preferably 2 to 30 parts by weight, based on 100 parts by weight of the charge transporting substance.

Next, the single-layer type photosensitive layer will be described. When a single-layer photosensitive layer is provided by a casting method or the like, a single-layer structure may be formed by using the above-described materials such as the above-described charge generation substance, charge transport substance, and binder resin.

If necessary, a plasticizer or a leveling agent may be added. As the binder resin, in addition to using the binder resin described above for the charge transport layer as it is, a mixture of the binder resin described for the charge generation layer may be used. The total thickness of the single-layer photosensitive layer and the protective layer provided thereon may be 25 μm or less, and preferably about 10 to 15 μm.

Next, the protective layer of the photosensitive member used in the image forming apparatus of the present invention will be described. The protective layer of the photoreceptor used in the image forming apparatus of the present invention comprises at least a filler and a binder resin.

As the filler material, first, as the organic filler material, a fluororesin powder such as polytetrafluoroethylene, a silicone resin powder, an a-carbon powder and the like can be mentioned. Examples of the inorganic filler material include metal powders such as copper, tin, aluminum, and indium, silica, tin oxide, zinc oxide, titanium oxide, alumina, indium oxide, antimony oxide, bismuth oxide, and tin oxide and tin doped with antimony. Examples thereof include metal oxides such as doped indium oxide, and inorganic materials such as potassium titanate. Particularly, from the viewpoint of the hardness of the filler, it is advantageous to use an inorganic material among them. In particular, silica, titanium oxide, and alumina can be used effectively. These filler materials are used alone or in combination of two or more.
These inorganic fillers may be surface-treated with an inorganic or organic substance for reasons such as improvement in dispersibility.

In general, water-repellent treatments include those treated with a silane coupling agent, those treated with a fluorine-based silane coupling agent, and those treated with a higher fatty acid. As an inorganic material treatment, a material obtained by treating a filler surface with alumina, zirconia, tin oxide, or silica is known. These filler materials are pulverized and dispersed using a ball mill, a sand mill, a vibration mill or the like. The conditions for pulverization and dispersion are such that the average particle size is 0.05 to 1.0 μm, preferably 0.0
When the particle size is large, the cueing cleaning blade is damaged on the surface and poor cleaning occurs. The addition amount of the filler is 5% by weight to 50% by weight, preferably 10% by weight to 40% by weight. If the content is less than 5% by weight, the abrasion resistance is sufficient but not sufficient.
If it is 0% by weight or more, the transparency of the protective layer is impaired.

As the binder resin for the protective layer, acrylic resin, polyester, polycarbonate, polyamide,
Examples include polyurethane, polystyrene, and epoxy resin. Among them, polycarbonate is particularly preferred.

It is particularly preferable that the inorganic filler is dispersed together with a binder resin. As a method for forming the protective layer, a usual coating method is employed. Among them, the spray method is an effective means.

The thickness of the protective layer may be such that the sum of the thickness of the protective layer and the photosensitive layer provided thereunder is 25 μm or less.
About 1 to 5 μm is appropriate.

Further, a charge transport material may be added to the protective layer in order to provide a charge transport function. As the charge transporting material, the charge transporting material used in the above-described charge transporting layer can be used.

Next, the overall image forming apparatus of the present invention will be described. FIG. 2 is a schematic diagram for explaining an electrophotographic process of the image forming apparatus of the present invention, and the following modified examples also belong to the category of the present invention.

In FIG. 2, the photosensitive member 1 has a drum shape, but may have a sheet shape or an endless belt shape. Known means such as a corotron, a scorotron, a solid state charger (solid state charger), and a charging roller are used for the charging charger 3, the pre-transfer charger 7, the transfer charger 10, the separation charger 11, and the pre-cleaning charger 13. Can be

As the transfer means, generally, the above-mentioned charger can be used, but as shown in the figure, a combination of a transfer charger and a separation charger is effective.

The light source of the (image) image exposure unit 5 has a wavelength of 6
A laser beam of 70 nm or less can be used.

The light source such as the neutralizing lamp 2 is a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp,
Light emitting diode (LED), semiconductor laser (LD),
A general light-emitting material such as electroluminescence (EL) can be used.

The photosensitive member is irradiated with various lights by providing a transfer step, a charge removal step, a cleaning step, or a pre-exposure step using light irradiation in addition to the step shown in FIG.

The toner developed on the photosensitive member 1 by the developing unit 6 is transferred to the transfer paper 9, but not all of the toner is transferred, and toner remaining on the photosensitive member 1 is generated. Such toner is removed from the photoconductor by the fur brush 14 and the blade 15. Cleaning may be performed only with a cleaning brush, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush.

When a positive (negative) charge is applied to the electrophotographic photosensitive member and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photosensitive member.

If this is developed with a negative (positive) polarity toner (electrostatic detection fine particles), a positive image can be obtained, and if it is developed with a positive (negative) polarity toner, a negative image can be obtained.

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

The above illustrated electrophotographic process is an example of the embodiment of the present invention, and other embodiments are of course possible.

The image forming apparatus as described above may be fixedly incorporated in a copying apparatus, a facsimile, or a printer, or may be incorporated in the apparatus in the form of a process cartridge. The process cartridge includes a photoreceptor, and further includes a charging unit, an exposing unit, a developing unit, a transferring unit, a cleaning unit, and a discharging unit.
Devices (parts). Although there are many shapes and the like of the process cartridge, a general example is shown in FIG.

[0065]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples. All parts used in the examples are parts by weight.

Example 1 First, an electrophotographic photosensitive member used in Example 1 was obtained in the following manner. The following components were mixed in a φ30 mm aluminum drum as a conductive support, pulverized by a ball mill, coated by a dipping method, and dried by heating to form a 3.5 μm intermediate layer.

[Coating Liquid for Intermediate Layer] Alkyd resin (Beccosol 1307-60-EL, manufactured by Dainippon Ink and Chemicals) 6 parts Melamine resin (Super Becamine G-821-60, manufactured by Dainippon Ink and Chemicals) 4 Part Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd.) 40 parts Methyl ethyl ketone 200 parts The following charge generation layer coating solution is applied on this intermediate layer by a dipping method, and heated and dried to form a 0.2 μm-thick charge. A generating layer was formed.

[Coating Liquid for Charge Generating Layer] The following components were mixed and dispersed by a ball mill. Disazo compound having the following structure (1) 5 parts τ-type metal-free phthalocyanine 2.5 parts Polyvinyl butyral (Eslec BL-S: manufactured by Sekisui Chemical) 1.5 parts Cyclohexanone 120 parts Methyl ethyl ketone 120 parts This dispersion is coated for a charge generation layer. It was a working liquid.

[0069]

Embedded image

The following charge transport layer coating solution is applied on the charge generation layer by a dipping method, and is dried by heating.
A μm charge transport layer was formed.

[Coating solution for charge transport layer] The following components were mixed and dissolved to prepare a coating solution for charge transport layer. 7 parts of a charge transport material having the following structure (2)

[0072]

Embedded image

Polycarbonate 10 parts Methylene chloride 100 parts 1% silicone oil (KF50 Shin-Etsu Silicone Co., Ltd.) Methylene chloride solution 1 part

The following components were pulverized on the charge transport layer with a paint shaker using zirconia beads for 2 hours to obtain a coating liquid for a protective layer. This liquid was applied by a spray method to provide a 2.5 μm protective layer to obtain an electrophotographic photosensitive member of the present invention.

Polycarbonate resin (Z polycarbonate: Mv50,000, manufactured by Teijin Chemicals Ltd.) 5 parts Titanium oxide (CR97: manufactured by Ishihara Sangyo Co., Ltd.) 2 parts Charge transporting material having the following structure (3): 3 parts

Embedded image Cyclohexanone 200 parts

The electrophotographic photoreceptor thus produced was subjected to image formation using an image forming apparatus based on an electrophotographic copier Imagio MF2200 (manufactured by Ricoh Co., Ltd.) having a writing laser beam wavelength of 655 nm for image exposure. T
A paper passing test was performed on up to 0000 sheets.

Initial stage of paper-passing test and 120,000 paper-passing test
After the test, the following items were evaluated.

The amount of decrease in the thickness of the photoreceptor The amount of decrease in the film thickness after the paper passing test was measured using an eddy current film thickness meter, Fischer Corp. MMS manufactured by Fischer.

In-machine potential The transition of the charging (dark portion) potential and the exposure portion potential when the initial charging potential was -600 V was evaluated.

Image quality Three levels of "good", "slightly low quality", and "poor quality" by comprehensively evaluating the solid density of the output image, local defects such as black spots, background contamination, abnormal images, etc. Classified.

An image of one independent dot is formed at a resolution of 1200 dpi,
The reproducibility of the dots on the image was evaluated by microscopic observation and classified into three levels of "good", "slightly reduced reproducibility" and "poor reproducibility". The evaluation results are shown in Table 1 below.

[0082]

[Table 1]

Example 2 Evaluation was performed in the same manner as in Example 1 except that titanium oxide (RB11 manufactured by Nippon Aerosil Co., Ltd.) was used as the component of the coating solution for the protective layer of the photoreceptor used in Example 1. I did it.

Example 3 Titanium oxide in the components of the coating solution for the protective layer of the photoreceptor used in Example 1 was converted to alumina (Sumicorundum AA-03:
Evaluation was performed in the same manner as in Example 1 except that Sumitomo Chemical Co., Ltd.) was used.

Example 4 Evaluation was performed in the same manner as in Example 1 except that the thickness of the charge transport layer of the photoreceptor used in Example 1 was changed to 13.0 μm.

Example 5 Evaluation was made in the same manner as in Example 1 except that the thickness of the charge transport layer of the photoreceptor used in Example 1 was changed to 22.0 μm.

Example 6 Titanium oxide in the components of the coating solution for the protective layer of the photoreceptor used in Example 1 was replaced with calcium carbonate (CS 3NA:
The evaluation was performed in the same manner as in Example 1 except that the sample was replaced with Ube Materials Co., Ltd.).

Example 7 The procedure of Example 1 was repeated, except that the coating solution for the intermediate layer of the photoreceptor used was changed as follows, and the coating was applied by dipping and dried by heating to form a 0.5 μm intermediate layer. Are all Example 1.
The evaluation was performed in the same manner as described above.

Nylon resin (CM8000: manufactured by Toray) 10 parts by weight Methanol 140 parts by weight n-butanol 73 parts by weight

Example 8 A photosensitive layer having a thickness of 16.5 μm was provided using the following photosensitive layer coating solution instead of providing the charge generating layer and the charge transporting layer of the photoreceptor used in Example 1, respectively. Example 1
The evaluation was performed in exactly the same manner as in the above.

[Coating Liquid for Photosensitive Layer] The following components were mixed and dispersed by a ball mill. 5 parts of the disazo compound of the above (1) 50 parts of the charge transporting substance of the above (2) 97 parts of a Z-type polycarbonate (molecular weight of 60,000) 97 parts 328 parts of tetrahydrofuran

Comparative Example 1 Evaluation was performed in the same manner as in Example 1 except that the thickness of the charge transport layer of the photosensitive member used was changed to 27 μm.

Comparative Example 2 Evaluation was performed in the same manner as in Example 1 except that the thickness of the charge transport layer of the photosensitive member used was changed to 25 μm.

Comparative Example 3 Evaluation was performed in the same manner as in Example 1 except that the wavelength of the writing laser beam for image exposure was changed to 780 nm.

Comparative Example 4 Evaluation was performed in the same manner as in Example 1 except that no intermediate layer of the photosensitive member used in Example 1 was provided.

Comparative Example 5 Evaluation was performed in the same manner as in Example 1 except that the protective layer of the photoreceptor used in Example 1 was not provided.

Comparative Example 6 Example 1 was repeated except that titanium oxide (CR97: manufactured by Ishihara Sangyo Co., Ltd.) was not added to the coating solution for the protective layer of the photoreceptor used in Example 1, and the film thickness was 1.3 μm. The evaluation was performed in exactly the same manner as in the above. Table 2 shows the evaluation results of Example 2 to Comparative Example 6.
Shown in

[0098]

[Table 2]

As is clear from Table 2, the image forming apparatuses of Examples 1 to 8 satisfying the claims of the present invention have excellent potential stability after repeated use (paper passing test), and have high image quality. It can be seen that a hard copy can be obtained stably for a long time.

On the other hand, in the image forming apparatuses of Comparative Examples 1 to 6, any or all of the electrical characteristics, image quality, and resolution are greatly deteriorated, and the superiority of the image forming apparatus of the present invention is apparent.

[0101]

As described above, according to the present invention, a highly durable image forming apparatus having excellent image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a layer configuration of a photoconductor of the present invention.

FIG. 2 is an explanatory diagram of an electrophotographic process illustrating an embodiment of the present invention.

FIG. 3 is an explanatory diagram of an example of a process cartridge.

[Explanation of symbols]

 32 conductive support 33 intermediate layer 34 photosensitive layer 35 protective layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) G03G 5/147 503 G03G 5/147 503 504 504 (72) Inventor Akihiko Matsuyama 1-chome Nakamagome, Ota-ku, Tokyo No. 3-6 Ricoh Co., Ltd. (72) Inventor Nozomu Nozomu 1-3-6 Nakamagome, Ota-ku, Tokyo Incorporation Ricoh Co., Ltd. (72) Inventor Shimizu 1-3-6 Nakamagome, Ota-ku, Tokyo No. F-term in Ricoh Co., Ltd. (reference) 2H068 AA03 AA04 AA37 AA43 BB25 BB37 BB50 CA06 CA29 CA33 FB07 FC01 FC05

Claims (10)

[Claims] 1. A photoreceptor, a charging device for uniformly charging the surface of the photoreceptor, an image exposure device for forming an electrostatic latent image by performing image exposure after uniform charging, and A developing device for developing, and an image forming apparatus including a device for transferring a developed image, wherein the photosensitive member contains at least a charge generating substance and a charge transporting substance via a middle layer on a conductive support, A laser beam having a wavelength of 670 nm or less is used for an image exposing device used for the image exposure, wherein the image exposing device is composed of at least a protective layer including a filler and a binder resin, and has a sum of the photosensitive layer thickness and the protective layer thickness of 25 μm or less. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein
When the sum of the thickness of the photosensitive layer and the thickness of the protective layer is D (μm), and the absolute value of the surface potential of the photosensitive member due to charging is V (V), 12
An image forming apparatus satisfying a relationship of (V / μm) ≦ V / D ≦ 40 (V / μm). 3. The image forming apparatus according to claim 1, wherein the photosensitive layer is formed by laminating a charge generation layer and a charge transport layer. 4. The image forming apparatus according to claim 1, wherein the filler in the protective layer is an inorganic pigment. 5. The image forming apparatus according to claim 4, wherein the inorganic pigment is a metal oxide. 6. The method according to claim 1, wherein the metal oxide is silica, alumina,
The image forming apparatus according to claim 5, wherein the type is one selected from titanium oxide. 7. The image forming apparatus according to claim 1, wherein the protective layer contains a charge transport material. 8. The method according to claim 1, wherein the binder resin used for the protective layer is polycarbonate.
7. The image forming apparatus according to any one of 6. 9. The image forming apparatus according to claim 1, wherein said intermediate layer comprises an inorganic filler, an alkyd resin, and a melamine resin. 10. The image forming apparatus according to claim 9, wherein the inorganic filler used for the intermediate layer is titanium oxide.