JPH11202526A - Electrophotographic photoreceptor and electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-resolution electrophotographic photoreceptor which has a surface protective layer of an optically uniform state free of light scattering and bleeding and with which the hydrophobic property of the surface, the mechanical characteristics, such as hardness and strength, and the electrical durability, such as arc discharge resistance, are made compatible and an electrophotographic image forming device using this electrophotographic photoreceptor. SOLUTION: This electrophotographic photoreceptor has the surface layer contg. colloidal silica and siloxane resin. The siloxane resin condensed in the presence of the colloidal silica in the surface layer contains the structure expressed by the following formula: RSiO3/2 ,(R is at least one group selected from 4-12C alkyl group, substd. or unsubstd. aryl group). This electrophotographic image forming device has the photoreceptor described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic system which is widely used in copiers, printers, facsimile machines, plate making systems, etc., and has excellent durability such as high image uniformity and abrasion resistance. The present invention also relates to an electrophotographic photoreceptor for electrophotography and an electrophotographic image forming apparatus having a surface protective layer excellent in anti-contamination property and slipperiness due to its hydrophobic surface, and more particularly, to a semiconductor laser or LED. An electrophotographic photoreceptor and an electrophotographic image forming apparatus capable of stably obtaining a higher resolution image than before by the digital system using the used spotlight, particularly a high gradation and full color image such as a conventional photograph. It concerns the device.

[0002]

2. Description of the Related Art Electrophotographic photoreceptors, of course, have the required sensitivity, electrical characteristics, optical characteristics, and the like according to the applied electrophotographic process.
The surface of a photoreceptor that is used repeatedly is subjected to electrical or mechanical influences directly by charging processes such as corona charging and roller charging, developing process, transfer process, and cleaning process, so that the durability against the Is required.

Specifically, the photoreceptor is required to have durability against abrasion and scratches on the surface of the photoreceptor due to rubbing and deterioration of the surface of the electric photoreceptor which is likely to occur when charged under high humidity. Particularly, in a charging system using a discharge phenomenon such as a roller charging system, durability against high-energy arc discharge is required.

In addition, there is a problem that toner adheres to the surface of the photoreceptor due to repetition of development and cleaning with the toner. For this purpose, improvement in the cleaning property of the surface of the photoreceptor is required.

Attempts have been made to provide a surface protective layer mainly composed of various resins on the photosensitive layer in order to satisfy the various characteristics required for the surface of the photosensitive member as described above. For example,
JP-A-57-30843 proposes a protective layer in which resistance is controlled by adding metal oxide particles as conductive particles.

It has also been studied to improve the physical properties of the photoreceptor surface by adding various substances to the charge transport layer as well as the protective layer. For example, the following are reported as additives focusing on low surface energy of silicone resins.

[0007] Silicone oil (JP-A-61-1329)
54), polydimethylsiloxane, silicone resin powder (JP-A-4-324454), crosslinked silicone resin, poly (carbonate silicon) block copolymer, silicone-modified polyurethane, silicone-modified polyester,
A thermosetting silicone resin (Japanese Patent Publication No. 5-46940) and a typical polymer having a low surface energy include a fluoropolymer, and the following can be added as the fluoropolymer.

[0008] Polytetrafluoroethylene powder Carbon fluoride powder

[0009]

However, a surface protective layer containing a metal oxide or the like can have a considerable hardness, but has a problem in cleaning properties because the surface is likely to be hydrophilic. Silicone resins are excellent in that they have low surface energy, but they do not show sufficient compatibility with other resins, so they tend to agglomerate in the additive system, causing light scattering or bleeding and biasing the surface. There is a problem that stable characteristics are not exhibited. In addition, when the silicone resin alone is used, the hardness is insufficient, and when a solvent system that does not attack the photoconductive layer, such as alcohol or water, is used, the surface of the silicone resin becomes hydrophilic. It has a problem in cleaning properties and the like.

In addition, since a fluorine-based polymer represented by polytetrafluoroethylene, which is a polymer having a low surface energy, is generally insoluble in a solvent and has poor dispersibility, it is difficult to obtain a smooth photoreceptor surface. Difficulty and low refractive index tend to cause light scattering, which causes a problem of deterioration of the latent image.

Further, polymer compounds such as polycarbonate, polyacrylester, polyester, and polytetrafluoroethylene generally have high hydrophobicity, but do not have sufficient arc discharge resistance, and the polymer main chain is cut by electric discharge. Therefore, there is a problem that it is easily deteriorated.

An object of the present invention is to provide a surface protective layer that is optically uniform without light scattering or bleeding and solves the above-mentioned problems, and provides hydrophobic properties of the surface and mechanical properties such as hardness and strength. Another object of the present invention is to provide a high-resolution electrophotographic photosensitive member having both electric durability such as arc discharge resistance and the like, and an electrophotographic image forming apparatus using the electrophotographic photosensitive member.

[0013]

Means for Solving the Problems A first invention of the present invention is:
In an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the outermost surface layer is a surface protective layer containing colloidal silica and a siloxane resin, and the outermost surface layer is condensed in the presence of colloidal silica. The siloxane resin obtained has a structure represented by the general formula (I): RSiO _3/2 (I) (R is a single or a plurality selected from an alkyl group having 4 to 12 carbon atoms or a substituted or unsubstituted aryl group.) It is an electrophotographic photosensitive member characterized by containing.

The siloxane resin described in the present invention has an OH group,
It means a silicone resin or a partially condensed oligomer obtained by condensation of a silicon compound having three hydrolyzable groups per silicon atom such as an OR group.

According to a second aspect of the present invention, a photoreceptor is charged in an image forming apparatus which forms a latent image by irradiating light onto the photoreceptor and develops the formed latent image to obtain an image. Means and a means for developing the obtained latent image with a toner, wherein the photosensitive body is an electrophotographic photosensitive body having a photosensitive layer on a conductive support, and contains the colloidal silica and a siloxane resin. Where the siloxane resin condensed in the presence of colloidal silica has a structure represented by the general formula (I) RSiO _3/2 (I) (R is a C 4-12 carbon atom) An electrophotographic photoreceptor containing an alkyl group or a single or a plurality of substituted or unsubstituted aryl groups). You.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The surface protective layer used in the present invention contains colloidal silica and a siloxane resin, and the composition for an electrophotographic photosensitive member surface protective layer is applied to the surface of an electrophotographic photosensitive member, dried and cured. It is formed by this. The composition for a surface protective layer of an electrophotographic photoreceptor of the present invention comprises at least the following three components (a) to (c). (A) colloidal silica (b) siloxane resin (R is an alkyl group having 4 to 12 carbon atoms, formed by partial condensation of R—Si (OR ′) ₃ ,
Alternatively, one or more selected from substituted or unsubstituted aryl groups. R ′ is an alkyl group having 1 to 3 carbon atoms,
One or a plurality of hydrogen atoms are selected. And (c) a solvent selected from one or more of lower aliphatic alcohols and water.

In the composition for a surface protective layer of an electrophotographic photoreceptor of the present invention, colloidal silica is contained in an amount of 10 to 70% by weight, siloxane resin is contained in an amount of 30 to 90% by weight, and colloidal silica and siloxane resin are contained in an amount of 1 to 50% by weight. % Lower alcohol-water mixed solution is used. If the solid content exceeds 50 wt%, the composition is apt to deteriorate, and it is difficult to form a favorable coating film due to gelation and the like. If it is less than 1 wt%, there is a problem that the strength of the formed surface protective layer is not sufficient. The proportion of colloidal silica in the solid content is 10 to 70 wt%, and the proportion of the siloxane resin is 30 to 90 wt%. If the ratio of the siloxane resin to the solid content is less than 30% by weight, it becomes brittle and a good film is hardly formed, and cracks and the like tend to enter. There is.

As the colloidal silica used for the surface protective layer of the present invention, a commercially available aqueous dispersion type is used. (Product name "Ludox", "Nalcoag" etc.) Particle size is 5n
m to 150 nm, preferably 10 to 150 nm.
The particles have a particle size of nm to 30 nm, and are excellent in dispersion stability and optical characteristics. The colloidal silica of the present invention contains N
Those having a content of an alkali metal oxide such as a ₂ O of 2 wt% or less are used. As the dispersing solvent, a mixed solvent system of lower aliphatic alcohols such as methanol, ethanol, isopropanol, t-butanol, and n-butanol and water is used.Other glycols, and a water-soluble solvent such as acetone are further added. Is also good.

The composition for the surface protective layer of the electrophotographic photoreceptor of the present invention can be adjusted to pH by using an inorganic acid or an organic acid.
It is adjusted to an acidic state of 3.0 to 6.0. If a strong acid is used, the stability of the composition or the like is likely to be unfavorably affected. Therefore, a weak acid is more preferably used to adjust the pH to an acidic state of 4.0 to 5.5.

The composition of the present invention applied on the photosensitive layer of the electrophotographic photosensitive member is dried and then heat-cured to exhibit hardness, strength, surface hydrophobicity, and discharge resistance. Thermal curing proceeds more completely at higher temperatures, but is selected within a range that does not adversely affect the characteristics of the electrophotographic photosensitive member. Preferably 80
C. to 180.degree. C., more preferably 100.degree.
C. to 150.degree.

The longer the thermal curing time, the more the curing proceeds, but the thermal curing time is selected within a range that does not adversely affect the characteristics of the electrophotographic photosensitive member at the processing temperature. The heat curing treatment time is generally about 10 minutes to 12 hours.

After drying, the surface protective layer obtained by heat curing contains at least a component represented by SiO ₂ as colloidal silica and a siloxane resin represented by RSiO _3/2 .

In this case, R is a single or a plurality of R 4 to C 12 alkyl groups or substituted or unsubstituted aryl groups. The surface protective layer of the present invention is used in a thickness of 0.1 μm to 4 μm.
If the thickness is less than 0.1 μm, the surface hardness and strength are not sufficient, and there is a problem in durability. If it exceeds 4 μm, the contrast potential formed by the latent image during development deteriorates, which is not preferable. More preferably, it is used at a thickness of 0.2 μm or more and 3 μm or less.

The surface protective layer of the present invention needs to have a hydrophobic surface in order to satisfy cleaning properties and stain resistance. 90 as the hydrophobicity of the surface as measured by the contact angle of water
Degree is required. When the angle is 90 degrees or less, a charge product, a toner, and a dropping substance brought from paper are apt to adhere to the surface due to repeated use in the electrophotographic process, and a cleaning failure or a deterioration of a latent image (image deletion) due to a decrease in surface resistance is likely to occur. More preferably, a surface protective layer having a water contact angle of 95 degrees or more is used.

Further, as a feature of the surface protective layer of the present invention, by containing colloidal silica and a siloxane resin, an extremely high surface hardness can be obtained as compared with ordinary organic compounds. The surface hardness is appropriately selected from the balance with various physical properties depending on the content of colloidal silica and the structure of the siloxane resin, but the pencil hardness of the film formed on the glass plate is preferably 5H or more. If it is less than 5H, the toner and paper powder used in the electrophotographic process are apt to cause scratches and scraping, which is not preferable.

The volume resistivity of the surface protective layer of the present invention is 1 × 10
Those having a resistance of ⁹ Ωcm or more and 1 × 10 ¹⁵ Ωcm or less are used. If it is less than 1 × 10 ⁹ Ωcm, the electric charge of the formed latent image is diffused and deteriorated, which is not preferable. If it exceeds 1 × 10 ¹⁵ Ωcm, the charge may not be sufficiently transferred after the exposure as an electrophotographic photoreceptor until development, so that the apparent sensitivity may be reduced and the residual potential may be increased.

Further, not only the electric resistance but also the remaining hydrolyzable group such as a silanol group causes a problem that the residual potential is increased. Therefore, it is desirable that the residual potential is as low as possible. The ratio of the hydrolyzable group in terms of SiOH group is 0.1% by weight or less, more preferably 0.1% by weight.
It is used at not more than 01% by weight.

In the surface protective layer of the present invention, a resin composition containing colloidal silica and a siloxane resin as essential components is used.
Methods disclosed in U.S. Pat. No. 2,7073 and US Pat. No. 3,944,702 are disclosed.

The silicone-based hard coat resin comprises a hydrolytic condensate of a polyfunctional organosilicon compound having a hydrolyzable group in the molecule. The greater the number of functional groups, the higher the strength, and the resulting resin becomes harder. Among them, 4
In the case of using colloidal silica instead of functional organosilicon and using trifunctional organosilicon, the hardness is adjusted by controlling the particle size of colloidal silica, the amount of colloidal silica added, and the hydrolytic condensation of trifunctional organosilicon. A resin that is high and has excellent film-forming properties can be obtained. A preferred colloidal silica has an average particle size of 5 nm to 150 nm, which is dispersed in a lower alcohol containing water within the above-mentioned range, and a trifunctional organosilicon compound having a hydrolyzable group is acid or alkali. It is produced by hydrolysis in the presence. After completion of the reaction, a lower alcohol, a curing catalyst, a leveling agent and the like are further added as necessary. This is coated on a plastic substrate by dip, spray, bar coating, spin coating or the like. After removing the solvent, a coating is generally formed by heat-curing in the range of 80 to 150 degrees. The curing temperature is preferably performed at a temperature equal to or lower than the thermal deformation temperature of the coated substrate plastic. The siloxane resin thus formed can exhibit a pencil hardness of 5H or more.

The hard coat resin is subjected to a surface treatment with a silane compound called a silane coupling agent, or a chemical method, for the purpose of improving the adhesion to the substrate surface, depending on the substrate material to be applied. It is common practice to modify the surface by a physical method to improve the adhesion.

An example of producing an electrophotographic photosensitive member having a surface protective layer according to the present invention will be described below.

As the conductive support of the electrophotographic photosensitive member, a support having conductivity itself, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, chromium, titanium, nickel, magnesium, indium,
Gold, platinum, silver, iron and the like can be used. In addition, aluminum, indium oxide, tin oxide, gold, etc. are formed on a dielectric support such as plastic by vapor deposition or the like,
A conductive layer, a conductive fine particle mixed with plastic or paper, or the like can be used. For these conductive supports, uniform conductivity is required and a smooth surface is important. Since the surface smoothness greatly affects the uniformity of the undercoat layer, charge generation layer, and hole transport layer formed thereon, the surface roughness is used at 1.0 μm or less. Irregularities of 1.0 μm or more greatly change the local electric field applied to a thin layer such as an undercoat layer or a charge generation layer, so that the characteristics thereof are greatly changed, and defects such as charge injection and unevenness of residual charge are caused. This is not preferable because it is liable to occur.

In particular, a conductive layer obtained by dispersing and coating conductive fine particles in a polymer binder is easy to form and is suitable for forming a uniform surface.
The primary particle size of the conductive fine particles used at this time is 100 n.
m, more preferably 50 nm or less. As the conductive fine particles, conductive zinc oxide, conductive titanium oxide, Al, Au, Cu, Ag, Co, N
i, Fe, carbon black, ITO, tin oxide, indium oxide, indium, and the like are used, and these may be used by coating the surface of the insulating fine particles. The content of the conductive fine particles is used so that the volume resistance is sufficiently low, and is preferably added so as to have a resistance of 1 × 10 ¹⁰ Ωcm or less. More preferably, 1 × 10 ⁸ Ωc
m or less.

When exposure is performed using a coherent light source such as a laser, it is possible to form irregularities on the surface of the conductive support in order to prevent image deterioration due to interference. In this case, irregularities having a wavelength of about 1 / 2λ used for dispersing insulators such as silica beads having a diameter of several μm or less are formed at a period of 10 μm or less so that defects such as charge injection and residual potential unevenness are unlikely to occur. It can be formed and used.

An undercoat layer having an injection blocking function and an adhesive function can be provided between the conductive support and the photosensitive layer.
The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, polyamide, polyurethane, gelatin, or the like. The thickness of the undercoat layer is 0.1 μm to 10 μm, preferably 0.3 μm to 3 μm.

The photosensitive layer may be of a function-separated type comprising a charge generation layer and a charge transport layer, or a single layer type in which charge generation and charge transport are performed in the same layer.

As the charge generating material, for example, selenium
Tellurium, pyrylium-based dye, thiopyrylium-based dye, phthalocyanine-based pigment, anthantrone-based pigment, dibenzpyrenequinone-based pigment, pyranthrone-based pigment, trisazo-based pigment, disazo-based pigment, azo-based pigment, indigo-based pigment, quinacridone-based pigment, Cyanine pigments and the like can be used.

The charge transporting compound is roughly classified into an electron transporting compound and a hole transporting compound.

As the electron transporting compound, 2,4,7-
Examples thereof include electron accepting compounds such as trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil, tetracyanoquinodimethane, and alkyl-substituted diphenoquinone, and those obtained by polymerizing these electron accepting compounds. . Examples of the hole-transporting compound include pyrene, and a polycyclic aromatic compound such as anthracene, carbazole,
Heterocyclic compounds such as indole, oxazole, thiazole, oxathiazole, pyrazole, pyrazoline, thiadiazole and triazole p-diethylaminobenzaldehyde-N, N-diphenylhydrazone and N, N-diphenylhydrazino-3-methylidene-9-
Hydrazone compounds such as ethylcarbazole, α-phenyl-4′-N, N-diphenylaminostilbene and 5- (4- (di-p-tolylamino) benzylidene)
Styryl-based compounds such as -5H-dibenzo (a, d) cycloheptene, benzidine-based compounds, triarylamine-based compounds or polymer compounds having a group consisting of these compounds in the main chain or side chain (poly-N-vinylcarbazole) , Polyvinyl anthracene, etc.).

Next, specific examples of the charge transporting compound are shown below.

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Embedded image As the charge generation material and the charge transport material, a binder polymer is used as needed. Examples of binder polymers include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylates, methacrylates, vinylidene fluoride, trifluoroethylene, and the like, polyvinyl alcohol, polyvinyl acetal, and polycarbonate. , Polyester, polysulfone, polyphenylene oxide, polyurethane, cellulose resin, phenol resin, melamine resin, silicon resin, epoxy resin, and the like.

In particular, as the polymer compound for the charge transport layer used in the present invention, those which are compatible with the charge transport compound of the present invention are used. Representative polymer compounds include polyester, polycarbonate, polystyrene, polymethacrylate, and polyacrylate.

The charge transporting compound used in the charge transporting layer is 20 wt% or more and 70 w
t% or less is preferable. If the content is less than 20% by weight, sufficient charge transfer ability cannot be obtained, so that the residual potential increases and the like, which is not preferable. If the content is 70% by weight or more, sufficient durability cannot be obtained because the mechanical strength of the charge transport layer is reduced. The amount of the polymer compound used in the charge transport layer is preferably 20% by weight or more and 80% by weight or less based on the solid content of the charge transport layer.
If the content is 80% by weight or more, sufficient charge transfer ability cannot be obtained, resulting in an increase in residual potential, a decrease in electrical durability, a reduction in the effect of surface hydrophobicity, and the like. If the content is less than 20% by weight, the mechanical strength of the charge transport layer is reduced, so that sufficient durability cannot be obtained.

When used as a single-layer photoreceptor, good properties can be obtained by using a composition comprising a combination of the above-mentioned charge generating material, a charge transporting compound and a polymer compound.

Additives other than the above compounds can be used in the photosensitive layer in order to improve mechanical properties and durability. As such additives, an antioxidant, an ultraviolet absorber, a stabilizer, a crosslinking agent, a lubricant, a conductivity controlling agent, and the like are used.

The above-mentioned surface protective layer of the present invention is formed on the photosensitive layer formed as described above. The solvent used in the composition for forming the surface protective layer preferably does not attack the photosensitive layer, and is applied by a dipping method, a blade coating method, a roll coating method, or the like. Even in the case of using a solvent that immerses the photosensitive layer, the effect can be reduced by using a spray coating method or the like.

Next, an electrophotographic image forming apparatus using the electrophotographic photosensitive member of the present invention will be described.

By forming a latent image on the electrophotographic photosensitive member of the present invention by charging and exposing the same, it is possible to always obtain high-quality images with excellent durability. As a high-speed, low-noise printer, a laser beam printer adopting an electrophotographic system or a digital copying machine, Fax, etc., has a great effect of improving image quality and durability.

A laser beam printer adopting an electrophotographic system or a digital copying machine, Fax, etc. is a binary recording in which images such as characters and figures are formed by applying or not applying a laser beam to a photosensitive member. In general, printing of characters, figures, and the like does not require a halftone, so that the structure of the printer can be simplified.

However, there is a printer capable of expressing halftones even with such a binary recording system. As such a printer, a printer employing a dither method, a density pattern method, or the like is well known. However, as is well known, high resolution cannot be obtained with a printer employing a dither method, a density pattern method, or the like. Therefore, in recent years, a method (PWM method) of forming a halftone in each pixel with high resolution without lowering the recording density has been proposed. In this method, a halftone pixel is formed by modulating a laser beam irradiation time by an image signal. According to this method, a high-resolution and high-gradation image can be formed. It is particularly suitable for a color image forming apparatus requiring high gradation. That is, according to this method, 1
Area gradation of dots formed by the beam spot can be performed for each pixel, and halftone can be expressed without lowering the resolution.

However, even in this PWM method, if the pixel density is further increased, the pixels become relatively small with respect to the exposure spot diameter, so that it is not possible to obtain a sufficient gradation by exposure time modulation. There is a point. Therefore, in order to improve the resolution while maintaining the gradation, it is necessary to make the exposure spot diameter smaller. For this purpose, for example, when a scanning optical system using a laser is used, it is necessary to shorten the wavelength of the laser light, increase the NA of the f-θ lens, and the like. If used, the use of expensive lasers, the enlargement of lenses and scanners, the increase in required mechanical precision due to the decrease in the depth of focus, and the like, inevitably increase the size and cost of the apparatus.

Further, in solid-state scanners such as LED arrays and liquid crystal shutter arrays, it is inevitable that the price of the scanner itself, the mounting accuracy, and the cost of the electric drive circuit will increase.

Further, even if the light spot is miniaturized as described above, it is difficult to obtain good gradation reproducibility in the electrophotographic method, and the gradation is reproduced in a pseudo manner by electrical processing. It was just doing.

In spite of the above-mentioned problems, the resolution and gradation required of the image forming apparatus using the electrophotographic method have been increasing more and more in recent years.

Under such circumstances, attempts have been made to improve the resolution and gradation by reducing the particle size of the toner used for development, and to improve the uniformity of the development conditions.

However, even if such an improvement is made, the reproducibility of gradation data such as full-color image data of 256 gradations of 400 to 600 lines recognizable by the naked eye and the high resolution of binary images such as characters. Reproduction was not enough.

As described above, an image which can be normally discriminated by the naked eye is about 400 dpi and about 256 gradations. In this case, the minimum resolution area is about 16 μm ² and 5000
This corresponds to a resolution higher than dpi.

In order to realize such a high resolution, it is necessary to reduce the spot area of the light beam. However, simply by reducing the spot area, the above-described high image quality can be realized. Did not. After examining such problems, the product of the thickness of the photosensitive layer of the photoconductor and the irradiated spot area and the gradation reproducibility in an electrophotographic image forming apparatus that forms a latent image by irradiating a light beam It is found that there is a certain relationship between the two, and when the product of the spot area and the film thickness of the photosensitive layer of the photosensitive member is 20,000 μm ³ or less, an extremely excellent image quality that realizes 400 dpi and 256 gradations is obtained. Made it possible.

It is considered that this is because, in the conventional electrophotographic image forming apparatus, the conditions of the latent image formed on the photoreceptor and the development conditions are not sufficient despite the miniaturization of the light spot area. . That is, the phenomenon that the image information given by the light spot is degraded due to the diffusion of the optical carrier for forming the latent image while traveling through the photosensitive layer and the contrast of the potential potential caused by the formed latent image are reduced. It is conceivable that the phenomenon of deterioration caused by the space existing up to the conductive substrate causes the image information given by the light spot at the initial stage to be largely deteriorated, thereby causing the deterioration of the image quality.

As described above, by setting the product of the spot area of the light beam and the thickness of the photosensitive layer of the photosensitive member to 20,000 μm ³ or less, a good image can be formed without causing the above-mentioned carrier diffusion and deterioration in developability. It enables formation.

This indicates that the film thickness of the photosensitive layer of the photoreceptor used at the spot area determined from the generally achievable minute light spot diameter, mainly the film thickness of the hole transport layer, is preferably 12 μm or less. ing. As described above, it is desirable that the thickness of the photosensitive layer be thin, but a thickness of 1 μm or more is desirable because pinholes and a decrease in sensitivity occur at the same charging potential. More preferably, it is used with a film thickness of 3 μm or more.

FIG. 1 is a plan view showing a schematic cross section of the electrophotographic photosensitive member of the present invention.

The surface protective layer of the present invention can be used as shown in FIG. 1A as a surface protective layer of an electrophotographic photosensitive member formed by applying the surface protective layer on the charge transport layer and drying by heating. It is also possible to use it as shown in FIG.

In order to perform high-resolution recording, the thickness (L) of the charge transport layer and the resolution (S) of the recorded image shown in FIG.
It is necessary to increase the ratio (S / L), and if the ratio is small, the latent image is blurred due to the diffusion of the photocarrier,
Good images cannot be obtained. The ratio (S / L) is preferably 4 or more, and more preferably 5 or more.

In the step of visualizing the latent image formed on the electrophotographic photosensitive member with a developer, the potential potential contrast obtained is also affected by the above ratio. Similarly, it is preferable that the ratio is large, and it is required to reduce the thickness of the charge transport layer in order to improve the resolution.

At present, the required resolution is 400 dp.
i or more, more preferably 500 dpi or more, and the thickness of the charge transport layer used is 15 μm or less, more preferably 12 μm or less.

FIG. 2 shows the light intensity distribution of the irradiation light and the light intensity distribution of the light reaching the conductive substrate in the electrophotographic image forming apparatus using the electrophotographic photosensitive member of the present invention.

The spot area of the light beam is represented by a portion until it decreases to 1 / e2 of the peak intensity.

The light beam used includes a scanning optical system using a semiconductor laser, a solid-state scanner such as an LED or a liquid crystal shutter, and the like. The light intensity distribution also includes a Gaussian distribution, a Lorentz distribution, and the like. The area up to 1 / e2 is defined as the spot area.

The light spot generally has an elliptical shape as shown in FIG.

The spot area of the light beam is 4000 μm ²
Used below. 400dp over 4000μm ²
When an image signal of i, 256 gradations is given, the influence of overlapping of adjacent pixels increases, and gradation reproducibility becomes unstable, which is not preferable.

The gradation reproducibility in the present invention is 400 dp.
When the irradiation amount of the light beam is linearly changed by 256 gradations at the resolution of i, the image density is defined by a portion proportional to the irradiation amount. FIG. 3 shows a schematic diagram of the measurement of gradation reproducibility in the present invention.

The image evaluation was performed using the image forming apparatus of the present invention.

A digital full-color copying machine and a laser beam printer were modified as an image forming apparatus of the present invention, and a semiconductor laser of 680 nm and 100 mW was used, and the spot diameter on the photosensitive member was 400 at 1 / e2 in the sub-scanning direction.
1 / e in the main scanning direction, assuming a constant of 63.5 μm corresponding to the line
(2) The spot diameter is set to 20 μm.
An image was output after performing PWM modulation of 56 gradations or pixel modulation corresponding to 600 dpi, and evaluation and measurement were performed. The spot area of the light spot is about 1000 μm ² .

[0111]

EXAMPLES The composition for a surface protective layer of an electrophotographic photosensitive member used in the present invention will be described in detail below. Liquid Preparation Example 1 8.7 g of an aqueous dispersion of colloidal silica (40% solid) was placed in a flask, and stirred while stirring.
00.5 solid) isopropyl alcohol dispersion 20.5
g, 34.5 g of phenyltriethoxysilane, 2.9 g of butyltrimethoxysilane, and 3.2 g of acetic acid.
After the addition, the mixed solution was heated to 65 to 70 ° C. and reacted for 2 hours. Thereafter, the mixture was diluted with 21.7 g of isopropyl alcohol, 2.4 g of benzyltrimethylammonium acetate was added as a curing catalyst, and a 0.1% ethanol solution of 10% polyether modified dimethyl silicone was added.
g was added. Preparation Example 2 3.9 g of an aqueous dispersion of colloidal silica (40% solid) was placed in a flask, and stirred while stirring.
06.8% solid) isopropyl alcohol dispersion 26.8
g, phenyltriethoxysilane 2.0 g, butyltrimethoxysilane 1.4 g, 3,3,4,4,5,5
6,6,6-Nonafluorohexyltrimethoxysilane 2.4 g and acetic acid 3.1 g were added. After the addition, the mixed solution was heated to 65 to 70 ° C. and reacted for 2 hours. afterwards,
Diluted with 23.3 g of isopropyl alcohol, benzyltrimethylammonium acetate as curing catalyst
4 g were added, and further 0.16 g of a 10% ethanol solution of polyether modified dimethyl silicone was added. Preparation Example 3 30.0 g of an aqueous dispersion of colloidal silica (40% solid) was placed in a flask, and 1/3 of the mixture of 28.9 g of phenyltrimethoxysilane and 3.5 g of acetic acid was stirred.
Was added. After the addition, the remaining mixture was added while maintaining the mixed solution at 50-60 ° C. Cool the reaction solution to 20 ° C. and stir for 30 minutes when the temperature stabilizes. Thereafter, the reaction solution was diluted with 17.8 g of isopropyl alcohol,
2.8 g of dibutyltin di-2-ethylhexoate was gradually added, and 0.16 g of a 10% ethanol solution of polyether-modified dimethyl silicone was further added. The resulting reaction mixture was free of precipitate.

Hereinafter, the present invention will be described in more detail with reference to specific examples. Example 1 An aluminum cylinder having an outer diameter of 30 mm formed by mirror polishing and having anodized aluminum formed by anodization was used as a support.

Next, as a charge generation layer, 5 parts of the following bisazo pigment was added to a solution prepared by dissolving 2 parts of polyvinyl benzal (degree of benzalization of 75% or more) in 95 parts of cyclohexanone, and dispersed in a sand mill for 20 hours. This dispersion was applied on a support by a dip coating method so that the film thickness after drying was 0.2 μm.

[0114]

Embedded image Then, 5 parts of a triarylamine compound having the following structural formula and a polycarbonate resin (trade name: Z-40)
0, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was dissolved in 70 parts of tetrahydrofuran, and a solution for the charge transport layer was dried on the charge generation layer by a dip coating method and then applied to a thickness of 10 μm. .

[0115]

Embedded image Next, the composition for the surface layer of Preparation Example 1 was applied on the above-mentioned intermediate layer by a dip coating method, and dried at 110 ° C. for 4 hours to give a film thickness of 1.0 μm.

The electrophotographic characteristics were measured at a wavelength of 680 nm after being charged to -700 V. As a result, E1 / 2 (exposure amount at which the charged potential decreased to -350 V) = 1.2 μJ / cm ² ,
The residual potential was 28 V, which was good.

The electrophotographic photoreceptor was charged at an initial charge of −60 by an evaluation machine obtained by modifying a digital copying machine GP215 (roller charging system) manufactured by Canon to have the above-mentioned irradiation spot diameter.
When the image was evaluated at 0 V, the initial and 5000
Even after the sheet durability test, an image output with excellent uniformity was obtained, the tone reproducibility was very good at 256 gradations at 400 dpi, and the abrasion amount of the photoconductor was 0.1 μm per 5,000 sheet durability test. There were few.

When the contact angle of water on the surface of the photoreceptor was measured, the initial value was 98 deg, which was as good as 94 deg even after the 5,000-sheet durability test. Example 2 A charge generation layer and a charge transport layer were coated under the same conditions as in Example 1 by using an aluminum cylinder having an outer diameter of 80 mm formed by mirror polishing and having anodized aluminum formed by anodic oxidation.

Next, the composition for the surface layer of Preparation Example 1 was applied on the intermediate layer by a spray coating method.
After drying and heat treatment at 4 ° C. for 4 hours, a film thickness of 1.0 μm was obtained.

The electrophotographic photoreceptor was subjected to image evaluation at an initial charge of -500 V using an evaluator modified from a Canon digital color copying machine CLC500 (corona charging system) to have the above-mentioned irradiation spot diameter. Initial and 5
Even after the durability test for 000 sheets, an image output with excellent uniformity was obtained, the tone reproducibility was extremely good at 256 gradations at 400 dpi, and the wear amount of the photoconductor was 0.1 μm per the durability test for 5000 sheets. There were very few:

When the contact angle of water on the surface of the photoreceptor was measured, it was as good as 92 deg at the initial stage and 92 deg after the durability test for 5000 sheets. Example 3 A phenol resin (trade name: Plyofen, manufactured by Dainippon Ink and Chemicals, Inc.) as a conductive layer was dissolved in 100 parts of methyl cellosolve as a conductive layer using an aluminum cylinder having an outer diameter of 30 mm obtained by drawing. Conductive barium sulfate ultrafine particles (primary particle size 50
nm) 200 parts and a dispersion of 3 parts of silicone resin particles having an average particle size of 2 μm were dispersed by a dip coating method.
Coating was performed so that the film thickness after drying was 15 μm.

As an undercoat layer, alcohol-soluble copolymerized nylon (trade name: Amilan CM-8000, manufactured by Toray Industries, Inc.)
(5 parts) in 95 parts of methanol was applied by dip coating. After drying at 80 ° C. for 10 minutes, an undercoat layer having a thickness of 1 μm was formed.

Next, as a charge generating layer, 5 parts of an oxytitanium phthalocyanine pigment was added to a solution of 2 parts of polyvinyl benzal (a degree of benzalization of 75% or more) dissolved in 95 parts of cyclohexanone, and dispersed by a sand mill for 2 hours.

This dispersion was applied on the undercoat layer formed previously by dip coating so that the film thickness after drying was 0.2 μm.

Then, 5 parts of the triarylamine compound used in Example 1 and a polycarbonate resin (trade name Z-
400, manufactured by Mitsubishi Gas Chemical Co., Ltd.) 5 parts of a solution for the charge transport layer in which 70 parts of tetrahydrofuran was dissolved was dried on the above-mentioned charge generation layer by a dip coating method, and then dried to 10 μm.
Was applied.

Next, the composition for the surface layer of Preparation Example 3 was applied onto the intermediate layer by a dip coating method.
After a drying heat treatment for 4 hours, a film thickness of 0.4 μm was obtained.

[0127] The contact angle of water was 97 degrees.

When the electrophotographic characteristics were measured at a wavelength of 680 nm after charging at -700 V, E1 / 2 (exposure amount at which the charging potential decreased to -350 V) = 0.1 μJ / cm ² ,
The residual potential was 55 V, which was good.

The electrophotographic photoreceptor was modified with a laser beam printer (LBP-8 Mark II) manufactured by Canon (modified to the irradiation spot conditions described above, using an AC roller charger).
When image evaluation was performed at -500 V at initial charging,
The wear amount of the photoconductor after the durability test of 4000 sheets is 0.1 μm.
The contact angle of water after durability was as good as 95 degrees, and the image was not deteriorated. The reproducibility of one pixel of a highlight portion in an input signal equivalent to 600 dpi was sufficient. Comparative Example 1 Triarylamine compound 10 used in Example 1
Of a charge transport layer in which 70 parts of chlorobenzene and 10 parts of a polycarbonate resin (trade name: Z-400, manufactured by Mitsubishi Gas Chemical Co., Ltd.) are dissolved, and dried by dip coating on the above-described charge generation layer to obtain a layer having a thickness of 18 μm. When the image was evaluated with the same Canon laser beam printer as in Example 3 after the endurance test of 4000 sheets, interference fringes and black spots were observed, and the wear amount was as large as 5 μm.
The water contact angle was as small as 72 degrees, which was poor.
The reproduction of one pixel of the highlight portion at dpi was also insufficient, resulting in unevenness. Example 4 An outer diameter of 30 obtained by drawing in the same manner as in Example 3
167 parts of a phenol resin (trade name: Plyofen, manufactured by Dainippon Ink and Chemicals, Inc.) as a conductive layer using an aluminum cylinder having a thickness of 1 mm.
A solution prepared by dispersing 200 parts of conductive barium sulfate ultrafine particles (primary particle size: 50 nm) in a solution dissolved in 00 parts was applied by a dip coating method so that the film thickness after drying was 10 μm. 1 μm was applied to this support in the same manner as in Example 10.
, A 0.2 μm charge generation layer was formed.

Next, 5 parts of the triarylamine compound used in Example 1 and a polycarbonate resin (trade name Z
A solution for a charge transport layer, in which 5 parts of -400, manufactured by Mitsubishi Gas Chemical Co., Ltd.) were dissolved in 70 parts of chlorobenzene, was dried on the charge generation layer by a dip coating method and then applied to a thickness of 10 μm.

Next, the resin solution prepared in Preparation Example 2 was dried on the intermediate layer by a spray coating method.
It was applied to a thickness of μm. Drying at 110 ° C. for 4 hours,
It was thermoset and the contact angle of water was 98 degrees. Electrophotographic properties were measured at a wavelength of 680 nm after charging at -700 V. As a result, E1 / 2 (exposure amount at which the charging potential decreased to -350 V) = 0.14 μJ / cm ² and a residual potential of 51 V were satisfactory.

The electrophotographic photoreceptor was converted to a modified laser beam printer (LBP-8 Mark IV) (78).
Using a semiconductor laser of 0 nm and 100 mW, the optical system was changed to a laser spot diameter of 60 × 20 μm ² ).
The wear amount of the photoreceptor after the durability test of the sheet is extremely small as 0.1 μm, the contact angle of water is as good as 94 °, there is no deterioration of the image due to charge injection such as black spots and interference fringes, and 600 dpi
The reproducibility of one pixel in the highlight portion for a considerable input signal was also sufficient. Example 5 Using an aluminum cylinder having an outer diameter of 30 mm obtained by drawing, 167 parts of a phenol resin (trade name: Plyofen, manufactured by Dainippon Ink and Chemicals, Inc.) was dissolved in 100 parts of methyl cellosolve as a conductive layer. Conductive barium sulfate ultrafine particles (primary particle size 50
(nm) 200 parts and a dispersion of 3 parts of silicone resin particles having an average particle diameter of 2 μm were applied by a dip coating method so that the film thickness after drying was 15 μm.

As an undercoat layer, an alcohol-soluble copolymerized nylon (trade name: Amilan CM-8000, manufactured by Toray Industries, Inc.)
(5 parts) in 95 parts of methanol was applied by dip coating. After drying at 80 ° C. for 10 minutes, an undercoat layer having a thickness of 1 μm was formed.

Next, as a charge generation layer, 5 parts of an oxytitanium phthalocyanine pigment was added to a solution prepared by dissolving 2 parts of polyvinyl benzal (a degree of benzalization of 75% or more) in 95 parts of cyclohexanone, and dispersed by a sand mill for 2 hours. This dispersion was applied by dip coating on the previously formed undercoat layer so that the film thickness after drying was 0.2 μm.

Then, 5 parts of the triarylamine compound used in Example 1 and a polycarbonate resin (trade name Z-
400, manufactured by Mitsubishi Gas Chemical Co., Ltd.) 5 parts of a solution for the charge transport layer in which 70 parts of tetrahydrofuran was dissolved was dried on the above-mentioned charge generation layer by a dip coating method, and then dried to 10 μm.
Was applied.

Next, the composition of Preparation Example 2 was applied on the charge transport layer by a dip coating method, and dried at 110 ° C. for 4 hours to form a film having a thickness of 1.5 μm.

The contact angle of water was 97 degrees.

Electrostatic properties were measured at a wavelength of 680 nm after charging to -700 V. E1 / 2 (exposure amount at which the charging potential decreases to -350 V) = 0.11 μJ / c.
m ² and a residual potential of 42 V were good.

This electrophotographic photoreceptor was initially charged by a remodeling machine of a Canon laser beam printer P270 (remodeled to the above-mentioned irradiation spot conditions, using an AC roller charger).
When the image was evaluated at 00 V, the wear amount of the photoconductor after the durability test of 4000 sheets was extremely small at 0.2 μm.
The contact angle of water after endurance was as good as 95 degrees, and the image was not deteriorated. However, the reproducibility of one pixel of a highlight portion in an input signal corresponding to 600 dpi was slightly insufficient. Comparative Example 2 Using an aluminum cylinder having an outer diameter of 30 mm obtained by drawing, 167 parts of a phenol resin (trade name: Plyofen, manufactured by Dainippon Ink and Chemicals, Inc.) was dissolved as a conductive layer in 100 parts of methyl cellosolve. Conductive barium sulfate ultrafine particles (primary particle size 50
(nm) 200 parts and a dispersion of 3 parts of silicone resin particles having an average particle diameter of 2 μm were applied by a dip coating method so that the film thickness after drying was 15 μm.

As an undercoat layer, alcohol-soluble copolymerized nylon (trade name: Amilan CM-8000, manufactured by Toray Industries, Inc.)
A solution prepared by dissolving 5 parts in 95 parts of methanol was applied by dip coating. Dry at 80 ° C for 10 minutes,
An undercoat layer having a thickness of 1 μm was formed.

Next, as a charge generating layer, 5 parts of an oxytitanium phthalocyanine pigment was added to a solution of 2 parts of polyvinyl benzal (a degree of benzalization of 75% or more) dissolved in 95 parts of cyclohexanone, and dispersed by a sand mill for 2 hours.

This dispersion was applied by dip coating on the previously formed undercoat layer so that the film thickness after drying was 0.2 μm.

On the charge generation layer, 5 parts of the triarylamine compound used in Example 1 and a polycarbonate resin (trade name: Z-400, manufactured by Mitsubishi Gas Chemical Co., Ltd.) 5
Parts and 0.5 parts of Teflon microparticles in chlorobenzene 70
The solution for the charge transport layer dispersed and dissolved in the portion was dried by a dip coating method, applied to a thickness of 20 μm, and evaluated with the same Canon laser beam printer as in Example 3. 4μ after wear test
m and the contact angle of water was 89 degrees, and the surface was slightly hydrophobic. However, the reproduction of one pixel of the highlight portion at 600 dpi was insufficient from the initial stage of durability and was uneven.

FIG. 4 briefly describes an image forming apparatus according to an embodiment of the present invention.

First, the document G is set on the document table 10 with the surface to be copied facing downward. Next, copying is started by pressing the copy button. A unit 9 in which a document irradiation lamp, a short focus lens array, and a CCD sensor are integrated scans the document while irradiating the document. The irradiation scan light is imaged by the short focus lens array and is incident on the CCD sensor. The CCD sensor is a light receiving unit, a transfer unit,
It consists of an output unit. The optical signal is converted into an electric signal in the CCD light receiving unit, and is sequentially transferred to the output unit in synchronization with the clock pulse in the transfer unit. The output unit converts the charge signal into a voltage signal, amplifies the voltage signal, reduces the impedance, and outputs the signal. The analog signal obtained in this way is converted into a digital signal, and further converted into a digital signal for performing image processing for optimizing the resolution and gradation according to the characteristics of the image and outputting the digital signal. Sent to the department. When outputting from a computer or the like, resolution, gradation reproduction method and the like are selected, processed and converted so as to obtain a desired image, and sent to a printer unit. The printer unit receives the image signal and forms an electrostatic latent image as follows. The photosensitive drum 1 of the present invention is driven to rotate around a center support shaft at a predetermined peripheral speed, and receives a uniform positive or negative charging process of a predetermined voltage by a charger 3 during the rotation process. O corresponding to the image signal on the uniformly charged surface
By scanning the light of the solid-state laser element that emits N, OFF light with a rotating polygon mirror rotating at a high speed, an electrostatic latent image corresponding to the original image is sequentially formed on the surface of the photosensitive drum 1.

FIG. 5 shows a schematic mechanism of a laser scanning unit 300 (100 in FIG. 4) for scanning a laser beam in the above-described apparatus.

When the laser beam is scanned by the laser scanning unit 300, the solid-state laser element 30 is first emitted by the light emission signal generator 301 based on the input image signal.
The laser light emitted from 2 is converted into a substantially parallel light beam by a collimator lens system 303, and further scanned in a direction of an arrow c by a rotating polygon mirror 304 rotating in a direction of an arrow b, and fθ lens groups 305a, 305b, 30
5ac forms an image in a spot shape on the surface to be scanned 306 such as a photosensitive drum. By such scanning of the laser beam, an exposure distribution for one scan of an image is formed on the surface to be scanned 306. If the surface to be scanned 306 is scrolled by a predetermined amount perpendicularly to the scanning direction, the scanned surface is scanned. An exposure distribution according to the image signal is obtained on the surface 306. In this embodiment,
Since the multi-level recording based on the area gradation of one pixel was performed using the laser PWM method (pulse width modulation), the PWM method will be briefly described.

FIG. 6 is a circuit block diagram showing an example of the pulse width modulation circuit, and FIG. 7 is a timing chart showing the operation of the pulse width modulation circuit.

In FIG. 6, reference numeral 401 denotes a TTL latch circuit for latching an 8-bit digital image signal;
A high-speed level converter 403 for converting the L logic level to the ECL logic level, and a high-speed D / A converter 403 for converting the ECL logic level to an analog signal. 404 is PWM
ECL comparator for generating signal, 405 is ECL comparator
A level converter for converting the logic level to a TTL logic level, a clock oscillator 406 for oscillating the clock signal 2f, a reference numeral 407 for generating a substantially ideal triangular wave signal in synchronization with the clock signal 2f, and a reference numeral 408 for the clock signal 2f Is a 分 frequency divider that generates the image clock signal f by dividing the frequency by １ ／. Thus, the clock signal 2f has a cycle twice as long as the image clock signal f. In order to operate the circuit at high speed, ECL is used everywhere.
A logic circuit is provided.

The operation of the circuit having the above configuration will be described with reference to the timing chart of FIG. The signal (a) shows the clock signal 2f and the signal (b) shows the image clock signal f, which are related to the image signal as shown in the figure. Also, inside the triangular wave generator, the clock signal 2f is once frequency-divided by か ら to generate the triangular wave signal (c) in order to keep the duty ratio of the triangular wave signal at 50%. Further, this triangular wave signal (c) is converted into an ECL level to become a triangular wave signal (d).

On the other hand, the image signal is from 00h (white) to FFh
It changes at 256 gradation levels up to (black). In addition, signal '
h 'indicates hexadecimal notation. And the image signal (e) is D / A for some image signal values.
The converted ECL voltage level is shown. For example, the first
The pixel indicates a black pixel level FFh, the second pixel indicates a halftone level 80h, the third pixel indicates a halftone level 40h, and the fourth pixel indicates a halftone level 20h. The comparator generates a PWM signal having a pulse width T, t2, t3, t4 or the like corresponding to the pixel density to be formed by comparing the triangular wave signal (d) with the image signal (e). Then, this PWM signal is converted into a TTL level of 0 V or 5 V, becomes a PWM signal (f), and is input to the laser driver circuit. By changing the exposure time per pixel corresponding to the PWM signal value obtained in this way, it is possible to obtain a maximum of 256 gradations per pixel.

Although the present embodiment uses the gradation control by the PWM method, it is also possible to use an area gradation method such as a dither method or laser light intensity modulation, and these may be combined.

The electrostatic latent image formed on the photosensitive drum 1 is developed by the developing device 4 and the formed toner image is electrostatically transferred onto a transfer material by the transfer charger 7. Thereafter, the transfer material is electrostatically separated by the separation charger 8, conveyed to the fixing device 6, and thermally fixed to output an image.

On the other hand, the surface of the photosensitive drum 1 after the transfer of the toner image is subjected to removal of adhered contaminants such as untransferred toner by the cleaner 5 and is repeatedly used for image formation.

FIG. 8 is a schematic view of a color copying machine according to the present invention.

In FIG. 8, reference numeral 201 denotes an image scanner, which reads an original and performs digital signal processing. Reference numeral 200 denotes a printer unit which prints out an image corresponding to the document image read by the image scanner 201 on a sheet in full color.

In the image scanner section 201, 20
Reference numeral 2 denotes an original plate, and an original platen glass (hereinafter, platen) 2
This is used to fix the original 204 on the document 03. The document 204 is irradiated with light from a halogen lamp 205. The light reflected from the document 204 is guided to mirrors 206 and 207, and forms an image on a three-line sensor (hereinafter, referred to as a CCD) 210 including three CCD line sensors by a lens 208. The CCD 210 separates the light information from the document into colors and sends it to the signal processing unit 209 as red (R), green (G), and blue (B) components of the fel color information. Note that 205 and 206 are speeds v, and 207 is 1
/ 2v, the entire surface of the document is scanned by mechanically moving in a direction perpendicular to the electrical scanning direction (hereinafter, main scanning direction) of the line sensor (hereinafter, main scanning direction).

Reference numeral 211 denotes a standard white plate, which is used to generate data for correcting read data corresponding to the R, G, and B component line sensors at the time of shading correction. Used.

The standard white plate has a substantially uniform reflection characteristic with respect to visible light.

The standard white plate is used to correct the output data of the R, G, B visible sensors 210-2 to 210-4.

In the signal processing unit 209, the read signal is electrically processed, decomposed into magenta (M), cyan (C), yellow (Y), and black (BK) components, and sent to the printer unit 200. .

Further, M, C, Y, and BK per one scan of the original in the image scanner unit 201 (scan).
Is sent to the printer 200 in a frame-sequential manner,
One color image formation is completed by a total of four document scans.

The M, C, Y, and BK image signals sent from the image scanner unit 201 are transmitted to the laser driver 21.
Sent to 2. The laser driver 212 modulates and drives the semiconductor laser 213 according to the image signal. The laser light is reflected by a polygon mirror 214, an f-θ lens 215, and a mirror 21.
6, the photosensitive drum 217 is scanned.

Reference numerals 219 to 222 denote developing units, which are a magenta developing unit 219, a cyan developing unit 220, and a yellow developing unit 2
21; a black developing device 222; four developing devices alternately contact the photosensitive drum, and develop M, C, Y, and BK electrostatic latent images formed on the photosensitive drum 217 with corresponding toners; I do.

Reference numeral 223 denotes a transfer drum.
4 or 225 to the transfer drum 2
23, and the toner image developed on the photosensitive drum 217 is transferred to a sheet. Thus, M, C, Y, B
After the four colors K are sequentially transferred, the sheet is fixed to the fixing unit 2.
After passing through 26 and being fixed, the sheet is discharged.

The above-mentioned electrophotographic image forming apparatus uses a semiconductor laser to expose a photosensitive member by a polygonal scanning optical system. However, an LED printer is used as a solid-state scanner having no mechanical driving unit such as a polygon. A head is used. The LED printer head is one in which light-emitting diodes are integrated in a substantially linear shape, and one having a high resolution of 400 dpi or more is also produced. Since there is no driving part, it is advantageous for miniaturization. The spot light from the LED printer head is imaged on the photoreceptor by the converging rod lens array. At this time, the resolution in the main scanning direction is LED
Determined by the degree of integration of the printer head, 400dp
i, that is, a resolution higher than the 63.5 μm interval is used, but the sub-scanning direction is determined by the light condensing performance of the rod lens array and the moving speed of the photoconductor.

The intensity distribution of the light emission of the LED has a more rectangular distribution than the Gaussian distribution, but the area of a portion having 1 / e2 of the peak intensity may be considered.

[0168]

As described above, by using the composition containing the colloidal silica and the siloxane resin of the present invention as the surface protective layer of the photosensitive layer, it has high hardness and is hardly deteriorated by electric discharge. Excellent in nature,
In addition, an electrophotographic photoreceptor having less contamination due to its hydrophobic surface, excellent cleaning properties, and excellent electric properties such as residual potential is realized.

Further, since the electrophotographic photosensitive member has little light scattering, an electrophotographic image forming apparatus using the same can not only have excellent durability but also provide a good image after the durability. did. In particular, in a digital electrophotographic image forming apparatus using a spot light such as a laser beam, it is possible to reduce the thickness of the photosensitive layer while maintaining durability.
It has become possible to obtain an even, high-quality image output having excellent gradation reproducibility of six gradations.

[Brief description of the drawings]

FIG. 1A is a schematic cross-sectional view of an electrophotographic photoreceptor of the present invention using a composition containing the colloidal silica and a siloxane resin of the present invention for a surface protective layer of a charge transport layer. (B) is a schematic cross-sectional view of an electrophotographic photoreceptor of the present invention using a composition containing the colloidal silica and a siloxane resin of the present invention for a surface protective layer of a charge generation layer.

FIG. 2 is a schematic diagram showing a spot shape of an irradiation light beam and an intensity distribution of the light beam reaching a conductive substrate in the electrophotographic photosensitive member of the present invention.

FIG. 3 is a schematic diagram showing a relationship between a light irradiation amount and an image density in a method of measuring gradation reproducibility.

FIG. 4 is a schematic view of an electrophotographic image forming apparatus of the present invention.

FIG. 5 is a schematic diagram of a laser beam scanning unit of the present invention.

FIG. 6 is a circuit block diagram of a pulse width modulation circuit for controlling laser light according to the present invention.

FIG. 7 is a timing chart showing an operation of a pulse width modulation circuit for controlling laser light according to the present invention.

FIG. 8 is a configuration diagram of a color copying machine of the electrophotographic image forming apparatus of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keiko Hiraoka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (13)

[Claims] 1. An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the surface protective layer contains colloidal silica and a siloxane resin, and the surface protective layer generally comprises a siloxane resin condensed in the presence of colloidal silica. It contains a structure represented by the formula (I) RSiO _3/2 (I) (R is singly or plurally selected from an alkyl group having 4 to 12 carbon atoms or a substituted or unsubstituted aryl group.) An electrophotographic photosensitive member characterized by the following. 2. The electrophotographic photoreceptor according to claim 1, wherein said photosensitive layer comprises a charge generation layer and a charge transport layer. 3. The electrophotographic photoconductor according to claim 1, wherein the contact angle of water of the surface protective layer is 95 degrees or more. 4. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer formed on the conductive support in the electrophotographic photosensitive member has a thickness of 12 μm or less. 5. The volume resistance of the surface protective layer is 1 × 10 ^9.
2. The electrophotographic photoreceptor according to claim 1, wherein said electrophotographic photoreceptor is not less than Ωcm and not more than 1 × 10 ¹⁵ Ωcm. 6. The electrophotographic photosensitive member according to claim 1, wherein the pencil hardness of the surface protective layer is 5H or more. 7. The electrophotographic photosensitive member according to claim 1, wherein the thickness of the surface protective layer is 0.2 μm or more and 3 μm or less. 8. An image forming apparatus for forming a latent image on an electrophotographic photoreceptor by exposure and developing the formed latent image to obtain an image, wherein the image forming apparatus charges the photoreceptor, and Means for developing the obtained latent image with toner, and wherein the photosensitive member is an electrophotographic photosensitive member having a photosensitive layer on a conductive support, and wherein the surface protective layer of the photosensitive member has colloidal silica and The surface protective layer contains a siloxane resin, and in the surface protective layer, a siloxane resin condensed in the presence of colloidal silica has a structure represented by the general formula (I): RSiO _3/2 (I) (R is an alkyl group having 4 to 12 carbon atoms; Or a single or a plurality of substituted or unsubstituted aryl groups). 9. An image forming apparatus for forming a latent image by irradiating a light beam modulated by an input signal onto a photosensitive member and scanning the same, and developing the formed latent image to obtain an image. The image forming apparatus includes a unit that controls an exposure amount of the light beam to the photoconductor according to a resolution and a gradation of a recorded image, a unit that charges the photoconductor, and a unit that develops the obtained latent image with toner. Having, and the photoreceptor is an electrophotographic photoreceptor having a photosensitive layer on a conductive support, and the surface protective layer of the photoreceptor contains colloidal silica and a siloxane resin, in the surface protective layer, colloidal silica condensed siloxane resin in the presence general formula structure RSiO _3/2 represented by (I) (I) (R is an alkyl group having 4 to 12 carbon atoms or a substituted or unsubstituted aryl group, Are German or multiple selection.) Electrophotographic image forming apparatus characterized by containing the. 10. The electrophotographic image forming apparatus according to claim 9, wherein the product of the spot area of the light beam and the thickness of the photosensitive layer is 20,000 μm ³ or less. 11. An electrophotographic image forming apparatus according to claim 9, wherein said means for controlling the amount of exposure includes exposure time modulation. 12. An electrophotographic image forming apparatus according to claim 9, wherein said light beam is obtained by a semiconductor laser. 13. An electrophotographic image forming apparatus according to claim 9, wherein said light beam is obtained by an LED array.