JP7205115B2 - Electrophotographic photoreceptor and process cartridge using the same - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor (hereinafter also simply referred to as a "photoreceptor"), and more specifically, an electrophotographic photoreceptor used in image forming apparatuses such as electrophotographic printers, copiers and facsimiles, and and a process cartridge detachable from an image forming apparatus main body.

In the electrophotographic process, in order to keep the print density constant, it is necessary to control the distance between the photoreceptor, which is an image carrier, and the developing sleeve, which supplies the toner to the surface of the photoreceptor, at a constant distance. One method for this is to provide a gap ensuring member called a developing roller at the end position of the developing sleeve, and rotate both while keeping the outer peripheral portion of the developing roller in contact with the outer peripheral portion of the photoreceptor. , a method of controlling the gap between the developing sleeve and the photoreceptor to a proper distance by setting the thickness of the gap guarantee member to a predetermined value.

If the gap is smaller than the appropriate range, image defects such as white background fogging and black spots are likely to occur, especially when the charging method is a contact charging method using a charging roller. Therefore, in order to suppress changes in the gap due to rotation as much as possible, the gap assurance member is generally firmly fixed to the developing sleeve or a frame member provided with a rotation shaft hole of the developing sleeve.

With respect to such a gap guarantee member, for example, Japanese Patent Application Laid-Open No. 2002-100001 discloses a cylindrical roller for the purpose of suppressing deterioration in recorded image quality due to fluctuations in the gap between the surfaces of an image bearing member and a developing roller caused by wear of the gap guarantee member. A drum-shaped image carrier is used in which flanges are press-fitted into both edges of a photosensitive tube, and a rotating shaft is inserted through the center of both flanges. Cylindrical exposure that occurs when the flange is press-fitted in an image forming apparatus that positions the developing device, visualizes the latent image on the image carrier with the developing device, transfers the visible image, and records it on paper. A technique is disclosed for forming a taper at the abutting portion in accordance with the taper of the outer periphery of both end edges of the pipe.

JP-A-10-63142

In recent years, for the purpose of reducing printing costs and reducing waste, photoreceptors are required to have a longer life. Since the photosensitive layer of the photoreceptor wears due to contact with peripheral members such as a developing sleeve and a cleaning blade, a method of increasing the film thickness of the photosensitive layer is known as a means for extending the life of the photosensitive layer.

On the other hand, when a photoreceptor with a thick photosensitive layer is mounted in a process cartridge or an electrophotographic apparatus having a developing process equipped with the above-described gap guarantee member, the contact area with the gap guarantee member on the surface of the photosensitive layer is selectively worn, or peeling of the photosensitive layer occurs, the gap between the developing sleeve and the photosensitive member becomes small, and image defects such as white background fogging and black spots may occur. In particular, when the charging method is a contact charging method using a charging roller, increasing the film thickness of the photosensitive layer deteriorates charging uniformity, and image defects such as black spots may occur.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrophotographic photoreceptor that is used in a process cartridge having a development process that includes a gap guarantee member. An object of the present invention is to provide an electrophotographic photoreceptor capable of suppressing the occurrence of image defects, and a process cartridge using the same.

The present inventors have made intensive studies to solve the above problems, and found that the outer diameter of the central portion including the image forming area and the plurality of outer end portions of the conductive substrate used for the photoreceptor The inventors have found that the above problems can be solved by satisfying a predetermined relationship between the respective outer diameters, and have completed the present invention.

That is, a first aspect of the present invention is an electrophotographic photoreceptor comprising a cylindrical conductive substrate and an organic photosensitive layer provided on the conductive substrate,
The conductive substrate has, in the rotation axis direction, a cylindrical central portion having an outer diameter D0 including an image forming area and two cylindrical end portions having an outer diameter D1 located outside the central portion. ,
The organic photosensitive layer is formed on the periphery of the central portion,
The thickness of the organic photosensitive layer is 26 to 34 μm (the thickness of the organic photosensitive layer includes the thickness of the undercoat layer when an undercoat layer is provided),
The outer diameter D0 of the central portion and the outer diameter D1 of each of the two ends are determined by the following formula,
50 μm≦(D1−D0)/2≦90 μm (1)
It satisfies the relationship shown by Here, preferably, slope portions are provided between the central portion and the two end portions.

A second aspect of the present invention provides a process cartridge detachable from an electrophotographic image forming apparatus main body,
an electrophotographic photoreceptor according to the first aspect;
a developing sleeve for developing the electrostatic latent image formed on the electrophotographic photoreceptor using a developer;
a gap guarantee member that is supported by the developing sleeve and defines a gap between the electrophotographic photoreceptor and the developing sleeve;
The gap guarantee member is in contact with the outer peripheral surface of the end portion of the electrophotographic photoreceptor.

The process cartridge may further include a charging roller for charging the electrophotographic photoreceptor. Further, the distance between the surface of the organic photosensitive layer of the electrophotographic photoreceptor and the surface of the developing sleeve is preferably in the range of 220 to 260 μm.

According to the present invention, in an electrophotographic photoreceptor used in a process cartridge having a developing process with a gap guarantee member, even if the photosensitive layer is made thicker to extend the life, image quality can be ensured. It is possible to provide an electrophotographic photoreceptor and a process cartridge that can suppress the occurrence of defects.

1 is an explanatory view showing one configuration example of an electrophotographic photoreceptor of the present invention; FIG. FIG. 2 is an explanatory view showing an example of the arrangement configuration of the electrophotographic photoreceptor, developing sleeve and charging roller of the present invention when incorporated in an electrophotographic apparatus or process cartridge; FIG. 1 is a schematic cross-sectional view showing a negative charging laminated electrophotographic photoreceptor, which is an example of the electrophotographic photoreceptor of the present invention. FIG. 2 is a schematic cross-sectional view showing a positive charging type single-layer electrophotographic photoreceptor as another example of the electrophotographic photoreceptor of the present invention. FIG. 2 is a schematic cross-sectional view showing a positively charged laminated electrophotographic photoreceptor as still another example of the electrophotographic photoreceptor of the present invention. FIG. 2 is an explanatory view showing an example of arrangement configuration of a conventional electrophotographic photoreceptor, a developing sleeve, and a charging roller;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Photoreceptor for electrophotography)
FIG. 1 is an explanatory view showing one structural example of the electrophotographic photoreceptor of the present invention. As illustrated, an electrophotographic photoreceptor 10 according to an embodiment of the present invention includes a cylindrical conductive substrate 1 and an organic photosensitive layer 2 provided on the conductive substrate 1 . The conductive substrate 1 may have a rotation axis, and may include a combination of two or more cylinders having a common rotation axis and different diameters.

FIG. 2 is an explanatory diagram showing an example of the arrangement configuration of the electrophotographic photoreceptor 10, developing sleeve 20 and charging roller 30 of the present invention when incorporated into an electrophotographic apparatus or process cartridge. Cylindrical gap assurance members 40 are attached to both ends of the developing sleeve 20 in the axial direction, and are pressed against the photoreceptor 10 with a predetermined pressing force. Here, the process cartridge is a cartridge integrally formed of a developing unit including members such as a photosensitive member, a developing sleeve, and a charging roller, and is detachably formed in the main body of the electrophotographic image forming apparatus. A process cartridge also includes a combination of a plurality of cartridges.

As shown in FIG. 1, the conductive substrate 1 has a central portion 1C including an image forming area and two end portions 1E located outside the central portion 1C in the rotation axis direction. As shown, the center portion 1C has one end and the other end opposite to the one end, and the two ends 1E may be arranged one on one end side and the other on the other end side of the center portion 1C. . The organic photosensitive layer 2 can be formed on the periphery of the central portion 1C and not formed on the end portions 1E of both ends. Further, the outer diameter D0 of the central portion 1C and the outer diameter D1 of the two end portions 1E of the conductive substrate 1 are determined by the following formula,
50 μm≦(D1−D0)/2 (1)
satisfies the relationship shown by
The shape of the central portion 1C and the two ends 1E may be substantially cylindrical with outer diameters D0 and D1, respectively. The two ends 1E share the axis of rotation with the central portion 1C and may be arranged to sandwich the central portion 1C.

FIG. 6 is an explanatory view showing an example of the arrangement configuration of a conventional electrophotographic photoreceptor 50, developing sleeve 20 and charging roller 30. As shown in FIG. As shown in the figure, when a conventional photoreceptor 50 using a conductive substrate 51 having no outer diameter difference is used, the distance (gap) G between the surface of the developing sleeve 20 and the surface of the photoreceptor 50 is It is defined only by the thickness of the gap assurance member 40 .
On the other hand, in the photoreceptor of the embodiment of the present invention, when the thickness of the organic photoreceptor layer is constant, the gap between the surface of the developing sleeve 20 and the surface of the photoreceptor 10 is equal to the thickness of the gap guarantee member 40 , and the outer diameter difference between the central portion 1C and the end portion 1E of the photosensitive member. Specifically, the thickness (D4-D3)/2 of the clearance guarantee member 40, which is half the difference between the outer diameter D3 of the developing sleeve 20 and the outer diameter D4 of the clearance guarantee member, and the photosensitive It is determined by (D1-D0)/2, which is half the difference between the outer diameter D0 of the central portion 1C of the body 10 and the outer diameter D1 of the end portion 1E. Therefore, by using the photoreceptor of the embodiment of the present invention, the gap G between the surface of the developing sleeve 20 and the surface of the photosensitive layer of the photoreceptor 50 can be set regardless of the thickness of the gap assurance member 40. It is possible to control by the difference in outer diameter between the central portion 1C and the end portion 1E. The value of (D1-D0)/2 is preferably 50 μm or more, more preferably 50 μm or more and 90 μm or less, particularly 60 μm or more and 90 μm or less, or 60 μm or more and 80 μm or less.

That is, in the conductive substrate 1, the central portion 1C including the image forming area for forming the organic photosensitive layer 2 and the end portion 1E outside the image forming area and serving as the portion to which the gap assurance member 40 is brought into contact are the above-mentioned By having different outer diameters that satisfy the relationship, even if the thickness of the photosensitive layer is increased, abrasion and peeling of the photosensitive layer due to the gap assurance member 40 do not occur. It is possible to suppress the occurrence of image defects such as white background fogging and black spots by suppressing the change in the gap G between the photoreceptor. Further, even when a contact charging method using the charging roller 30 is adopted for a photoreceptor having a thick photosensitive layer, charging uniformity can be maintained and good image quality can be obtained. Therefore, it is possible to obtain a photoreceptor that suppresses the occurrence of image defects such as white background fogging and black spots while maintaining the print density even if the life of the photoreceptor is increased by increasing the thickness of the photosensitive layer. In the photoreceptor of the embodiment of the present invention, the film thickness of the organic photosensitive layer 2 can be 24 μm or more, preferably 26 to 34 μm. The film thickness of the organic photosensitive layer 2 referred to here includes the film thickness of the undercoat layer when the photoreceptor is provided with the undercoat layer, which will be described later. Further, the outer diameter D2 of the photoreceptor in the image forming area is a value obtained by adding the film thickness of the organic photosensitive layer 2 to the outer diameter D0 of the conductive substrate 1 .

In the illustrated example, the conductive substrate 1 has a slope portion for reducing a step in the outer diameter between a center portion 1C having an outer diameter D0 and an end portion 1E having an outer diameter D1 in the rotation axis direction. 1S. The length and the angle of inclination of the slope portion 1S are not particularly limited as long as they are provided so as not to affect the image quality, and the slope portion 1S may not be provided. Specifically, the length L1 of the slope portion 1S in the rotation axis direction can be, for example, 10 mm or less, and particularly can be 7 to 3 mm. In addition, although the organic photosensitive layer 2 is provided only in the central portion 1C in the illustrated example, it may be provided across from the central portion 1C to the slope portion 1S. Furthermore, an undercoat layer, which will be described later, of the organic photosensitive layer 2 may be formed from the central portion 1C to the end portion 1E. It may be formed from the central portion 1C to the slope portion 1S. The imaging areas may be defined in an organic photosensitive layer 2 provided on the central portion 1C.

The conductive substrate 1 serves not only as an electrode of the photoreceptor but also as a support for each layer constituting the photoreceptor. As the material of the conductive substrate 1, metals such as aluminum alloy, stainless steel, and nickel, or glass, resin, or the like whose surface is subjected to conductive treatment can be used. The conductive substrate 1 can be formed into a cylindrical shape by extrusion or drawing in the case of an aluminum alloy, or by injection molding in the case of a resin, and then finished to the predetermined shape and dimensions by cutting or the like. . The surface of the conductive substrate 1 is processed to have an appropriate surface roughness by cutting with a diamond bit or the like, if necessary. Thereafter, the surface is cleaned by degreasing and washing with an aqueous detergent such as a weakly alkaline detergent.

The layer structure of the organic photosensitive layer 2 provided on the conductive substrate 1 is not particularly limited. Photoreceptors for electrophotography are divided into layered (function-separated) photoreceptors, so-called negatively charged layered photoreceptors and positively charged layered photoreceptors, and single-layer photoreceptors that are mainly used for positive charging. separated. FIG. 3 is a schematic cross-sectional view showing a negative charging laminated electrophotographic photoreceptor as an example of the electrophotographic photoreceptor of the present invention. FIG. 4 is a schematic cross-sectional view showing a positive charging type single-layer electrophotographic photoreceptor as another example of the electrophotographic photoreceptor of the present invention. Further, FIG. 5 is a schematic cross-sectional view showing a positive charging type laminated electrophotographic photoreceptor as still another example of the electrophotographic photoreceptor of the present invention.

As shown in the figure, in the negative charging laminated photoreceptor, a charge generating layer 4 having a charge generating function and a charge transporting layer having a charge transporting function are formed on a conductive substrate 1 with an undercoat layer 3 interposed therebetween. 5 are laminated in sequence. In the positive charging single-layer type photoreceptor, a single-layer type photosensitive layer 7 having both functions of charge generation and charge transport is laminated on the conductive substrate 1 with an undercoat layer 3 interposed therebetween. . Further, in the positive charging multilayer photoreceptor, a charge transport layer 5 having a charge transporting function and a charge transporting function are provided on the conductive substrate 1 via the undercoat layer 3. A laminated photosensitive layer 8 having a charge generation layer 4 is laminated in sequence. In any type of photoreceptor, the undercoat layer 3 may be provided as required.

The undercoat layer 3 is made of a layer containing resin as a main component or a metal oxide film such as alumite. The purpose of the undercoat layer 3 is to control charge injection from the conductive substrate 1 to the photosensitive layer, cover defects on the surface of the conductive substrate 1, and improve adhesion between the photosensitive layer and the conductive substrate 1. and provided as needed. Resin materials used for the undercoat layer 3 include insulating polymers such as casein, polyvinyl alcohol, polyamide, melamine, and cellulose, and conductive polymers such as polythiophene, polypyrrole, and polyaniline. , or can be used in combination and mixed as appropriate. Moreover, these resins may be used by containing metal oxides such as titanium dioxide and zinc oxide.

[Negative charging multilayer photoreceptor]
As described above, in the negatively charged layered photoreceptor, the photosensitive layer 6 has the charge generation layer 4 and the charge transport layer 5 .

In the negative charging laminated photoreceptor, the charge generation layer 4 is formed by applying a coating liquid in which particles of a charge generation material are dispersed in a resin binder, and receives light to generate charges. It is important that the charge generation layer 4 has a high charge generation efficiency as well as an ability to inject generated charges into the charge transport layer 5. It is desirable that the charge generation layer 4 has little electric field dependence and good injection even in a low electric field.

Specific examples of the charge generation material for the charge generation layer 4 include X-type metal-free phthalocyanine, τ-type metal-free phthalocyanine, α-type titanyl phthalocyanine, Y-type titanyl phthalocyanine, γ-type titanyl phthalocyanine, amorphous titanyl phthalocyanine, and hydroxygallium phthalocyanine. , chlorogallium phthalocyanine, phthalocyanine compounds such as ε-type copper phthalocyanine, various azo pigments, anthanthrone pigments, thiapyrylium pigments, perylene pigments, perinone pigments, squarylium pigments, quinacridone pigments, and the like can be used alone or in appropriate combination. A suitable material can be selected according to the light wavelength region of the exposure light source used for formation. In particular, phthalocyanine compounds can be preferably used. The charge-generating layer 4 may be mainly composed of a charge-generating material, and may be used by adding a charge-transporting material or the like.

Resin binders for the charge generation layer 4 include polycarbonate resins, polyester resins, polyamide resins, polyurethane resins, vinyl chloride resins, vinyl acetate resins, phenoxy resins, polyvinyl acetal resins, polyvinyl butyral resins, polystyrene resins, polysulfone resins, and diallyl phthalate. Resins, polymers and copolymers of methacrylic acid ester resins, and the like can be used in appropriate combinations.

The content of the charge generation material in the charge generation layer 4 is preferably 20 to 80 mass %, more preferably 30 to 70 mass %, based on the solid content in the charge generation layer 4 . The content of the resin binder in the charge generation layer 4 is preferably 20-80 mass %, more preferably 30-70 mass %, based on the solid content in the charge generation layer 4 . Moreover, since the charge generation layer 4 only needs to have a charge generation function, its film thickness is generally 0.01 to 1 μm, preferably 0.05 to 0.5 μm.

In the negative charging laminated photoreceptor, the charge transport layer 5 is mainly composed of a charge transport material and a resin binder.

As the charge transport material for the charge transport layer 5, various hydrazone compounds, styryl compounds, diamine compounds, butadiene compounds, indole compounds, arylamine compounds and the like can be used singly or in combination as appropriate.

As the resin binder for the charge transport layer 5, various polycarbonate resins such as polyarylate resin, bisphenol A type, bisphenol Z type, bisphenol C type, bisphenol A type-biphenyl copolymer, bisphenol Z type-biphenyl copolymer, etc. are used alone. or a mixture of two or more of them can be used. Moreover, you may mix and use the resin of the same kind with which molecular weight differs. In addition, polyphenylene resin, polyester resin, polyvinyl acetal resin, polyvinyl butyral resin, polyvinyl alcohol resin, vinyl chloride resin, vinyl acetate resin, polyethylene resin, polypropylene resin, acrylic resin, polyurethane resin, epoxy resin, melamine resin, silicone resin, polyamide Resins, polystyrene resins, polyacetal resins, polysulfone resins, polymers of methacrylic acid esters, copolymers thereof, and the like can be used. The weight average molecular weight of the resin binder is preferably 5,000 to 250,000, more preferably 10,000 to 200,000 in GPC (gel permeation chromatography) analysis in terms of polystyrene.

The content of the charge transport material in the charge transport layer 5 is preferably 10-80 mass %, more preferably 20-70 mass %, based on the solid content of the charge transport layer 5 . The content of the resin binder in the charge transport layer 5 is preferably 20 to 90 mass %, more preferably 30 to 80 mass %, based on the solid content of the charge transport layer 5 . The film thickness of the charge transport layer 5 is preferably in the range of 3 to 50 μm, more preferably in the range of 15 to 40 μm, in order to maintain a practically effective surface potential.

[Positive charging single-layer photoreceptor]
In the positive charging single-layer type photoreceptor, the single-layer type photosensitive layer 7 is mainly composed of a charge generating material, a hole transporting material and an electron transporting material (acceptor compound) as charge transporting materials, and a resin binder.

Specific examples of charge generating materials for the single-layer photosensitive layer 7 include phthalocyanine pigments, azo pigments, anthantrone pigments, perylene pigments, perinone pigments, polycyclic quinone pigments, squarylium pigments, thiapyrylium pigments, and quinacridone pigments. can be used. These charge generation materials can be used alone or in combination of two or more. In particular, azo pigments include disazo pigments and trisazo pigments, and perylene pigments include N,N'-bis(3,5-dimethylphenyl)-3,4:9,10-perylene-bis(carboximide) and phthalocyanine. Metal-free phthalocyanine, copper phthalocyanine, and titanyl phthalocyanine are preferably used as the system pigment. In addition, X-type metal-free phthalocyanine, τ-type metal-free phthalocyanine, ε-type copper phthalocyanine, α-type titanyl phthalocyanine, Y-type titanyl phthalocyanine, amorphous titanyl phthalocyanine, JP-A-8-209023, US Pat. CuKα described in U.S. Pat. No. 5,874,570: Using titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine having a maximum peak at a Bragg angle 2θ of 9.6° in the X-ray diffraction spectrum improves sensitivity and durability. It is preferred because it shows a significantly improved effect in terms of image quality.

Examples of hole-transporting materials for the single-layer photosensitive layer 7 include hydrazone compounds, pyrazoline compounds, pyrazolone compounds, oxadiazole compounds, oxazole compounds, arylamine compounds, benzidine compounds, stilbene compounds, styryl compounds, poly- N-vinylcarbazole, polysilane, and the like can be used. These hole transport materials can be used alone or in combination of two or more. As the hole-transporting material, those having excellent transportability of holes generated upon irradiation with light and suitable in combination with the charge-generating material are preferable.

Electron transport materials (acceptor compounds) for the single-layer photosensitive layer 7 include succinic anhydride, maleic anhydride, dibromo succinic anhydride, phthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, pyromellitic acid, pyromellitic acid, trimellitic acid, trimellitic anhydride, phthalimide, 4-nitrophthalimide, tetracyanoethylene, tetracyanoquinodimethane, chloranyl, bromanyl, o-nitrobenzoic acid, malononitrile, trinitrofluorenone, Trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, thiopyran compound, quinone compound, benzoquinone compound, diphenoquinone compound, naphthoquinone compound, anthraquinone compound, stilbenequinone compound, azoquinone compound etc. can be mentioned. These electron transport materials can be used alone or in combination of two or more.

As the resin binder for the single-layer type photosensitive layer 7, other various polycarbonate resins such as bisphenol A type, bisphenol Z type, bisphenol A type-biphenyl copolymer, bisphenol Z type-biphenyl copolymer, etc., polyphenylene resin, and polyester resin can be used. , polyvinyl acetal resin, polyvinyl butyral resin, polyvinyl alcohol resin, vinyl chloride resin, vinyl acetate resin, polyethylene resin, polypropylene resin, acrylic resin, polyurethane resin, epoxy resin, melamine resin, silicone resin, polyamide resin, polystyrene resin, polyacetal resin , polyarylate resins, polysulfone resins, polymers of methacrylic acid esters, copolymers thereof, and the like can be used. Further, resins of the same type with different molecular weights may be mixed and used.

The content of the charge-generating material in the single-layer type photosensitive layer 7 is preferably 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, based on the solid content of the single-layer type photosensitive layer 7. is. The content of the hole-transporting material in the single-layer type photosensitive layer 7 is preferably 3-80% by weight, more preferably 5-60% by weight, based on the solid content of the single-layer type photosensitive layer 7 . The content of the electron-transporting material in the single-layer photosensitive layer 7 is preferably 1-50% by weight, more preferably 5-40% by weight, based on the solid content of the single-layer photosensitive layer 7 . The content of the resin binder in the single-layer type photosensitive layer 7 is preferably 10-90% by weight, more preferably 20-80% by weight, based on the solid content of the single-layer type photosensitive layer 7 . In order to maintain a practically effective surface potential, the film thickness of the monolayer type photosensitive layer 7 is preferably in the range of 3 to 100 μm, more preferably in the range of 5 to 40 μm.

[Positive charging multilayer photoreceptor]
As described above, in the positively charged layered photoreceptor, the photosensitive layer 8 has the charge transport layer 5 and the charge generation layer 4 .

In the positive charging laminated photoreceptor, the charge transport layer 5 is mainly composed of a charge transport material and a resin binder. As such a charge transport material and a resin binder, the same materials as those mentioned for the charge transport layer 5 of the negative charge laminated photoreceptor can be used. The content of each material and the film thickness of the charge transport layer 5 can also be the same as those of the negative charging multilayer photoreceptor.

The charge-generating layer 4 provided on the charge-transporting layer 5 is mainly composed of the charge-generating material, the hole-transporting material and the electron-transporting material (acceptor compound) as the charge-transporting material, and a resin binder. As the charge generating material, the hole transporting material, the electron transporting material and the resin binder, materials similar to those mentioned for the single layer type photosensitive layer 7 of the single layer type photoreceptor can be used. The content of each material and the film thickness of the charge generating layer 4 can be the same as those of the single-layer photosensitive layer 7 of the single-layer photosensitive body.

In the embodiment of the present invention, silicone oil, fluorine-based oil, or the like may be added to the photosensitive layer of either the laminated type or the single layer type for the purpose of improving the leveling property of the formed film and imparting lubricity. A leveling agent can be included. In addition, metal oxides such as silica, titanium oxide, zinc oxide, calcium oxide, alumina, and zirconium oxide, and metals such as barium sulfate and calcium sulfate are used for the purpose of adjusting film hardness, reducing friction coefficient, and imparting lubricity. Fine particles of metal nitrides such as sulfates, silicon nitrides and aluminum nitrides, fluororesin particles such as ethylene tetrafluoride resin, fluorine-based comb-type graft polymerized resins, and the like may also be contained. Further, if necessary, other known additives may be added within a range that does not significantly impair the electrophotographic properties.

Further, the photosensitive layer may contain an anti-deterioration agent such as an antioxidant and a light stabilizer for the purpose of improving environmental resistance and stability against harmful light. Compounds used for such purposes include chromanol derivatives and esterified compounds such as tocopherol, polyarylalkane compounds, hydroquinone derivatives, etherified compounds, dietherified compounds, benzophenone derivatives, benzotriazole derivatives, thioether compounds, and phenylenediamine derivatives. , phosphonates, phosphites, phenol compounds, hindered phenol compounds, linear amine compounds, cyclic amine compounds, hindered amine compounds, and the like.

The electrophotographic photoreceptor of the embodiment of the present invention can obtain desired effects by applying it to various machine processes. Specifically, charging processes such as a contact charging method using a charging member such as a roller or a brush, a non-contact charging method using a corotron or scorotron, etc. Sufficient effects can also be obtained in development processes such as contact development using a development system and non-contact development system.

The photoreceptor according to the embodiment of the present invention is formed by sequentially laminating each layer as described above on a conductive substrate 1, optionally with an undercoat layer 3 interposed therebetween, according to a conventional method. can be manufactured. Each layer is formed by applying a coating liquid obtained by dispersing and dissolving each constituent material in an appropriate organic solvent by a usual method such as a dip coating method, followed by drying. The type of solvent, coating conditions, drying conditions, and the like used to prepare the coating liquid can be appropriately selected according to conventional methods, and are not particularly limited.

Here, as described above, the end portion 1E of the conductive substrate 1 is outside the image forming area and is a portion with which the gap assurance member 40 is brought into contact, so the organic photosensitive layer 2 is usually not provided. For example, when the organic photosensitive layer 2 is formed by a dip coating method, the conductive substrate 1 is immersed in the coating liquid so that the axial direction is vertical. The upper end portion 1E where the layer 2 is not provided can be formed by providing an unapplied region of the coating liquid by controlling the immersion position. On the other hand, the lower end portion 1E of the conductive substrate 1 is immersed in a coating liquid to form a coating film of the organic photosensitive layer 2, and then the coating film is removed from a portion corresponding to this end portion 1E. Thus, an uncoated film forming portion can be provided. The coating film can be removed using a solvent capable of dissolving the coating film (a coating-soluble solvent). A cleaning tape made of nonwoven fabric impregnated with a coating-film-soluble solvent can also be used. Examples of coating-film-soluble solvents include dichloromethane, tetrahydrofuran, and dioxane.

(process cartridge)
The process cartridge of the embodiment of the present invention comprises the electrophotographic photoreceptor 10, a developing sleeve 20 for developing the electrostatic latent image formed on the electrophotographic photoreceptor 10 using a developer, and the developing sleeve 20. and a gap guarantee member 40 supported by and defining a gap between the electrophotographic photoreceptor 10 and the developing sleeve 20 . The gap guarantee members 40 may be provided at both ends of the developing sleeve 20, respectively. As shown in FIG. 2, a charging roller 30 for charging the electrophotographic photoreceptor 10 may also be provided.

In the process cartridge of the embodiment of the present invention, the two gap guarantee members 40 are in contact with the outer peripheral surface of the end portion 1E of the electrophotographic photoreceptor 10, respectively. With such a configuration, the organic photosensitive layer 2 is not worn or peeled off due to the gap guarantee member 40. Therefore, the change in the gap between the developing sleeve and the photosensitive member is suppressed, and white background fogging is prevented. It is possible to suppress the occurrence of image defects such as black spots and black spots. Further, since the gap between the developing sleeve and the photoreceptor can be kept constant by the gap guarantee member 40, even if the photoreceptor with a thick photosensitive layer is subjected to a contact charging method using the charging roller 30, charging uniformity can be maintained, and good image quality can be obtained. Therefore, it is possible to obtain a process cartridge capable of suppressing the occurrence of image defects such as white background fogging and black spots while maintaining the print density even if the photosensitive layer is made thicker to extend the life of the cartridge.

In the process cartridge of the embodiment of the present invention, the specific configurations of the developing sleeve 20, the charging roller 30 and the gap ensuring member 40 are not particularly limited, and can be appropriately selected according to a conventional method. For example, since both the central portion 1C and the end portion 1E of the conductive substrate 1 are formed to have a substantially constant outer diameter along the direction of the rotating shaft, the gap guarantee contacting the outer peripheral surface of the end portion 1E among them The outer peripheral surface of the member 40 also has a substantially constant outer diameter along the direction of the rotation axis, so that the outer peripheral surface of the end portion 1E and the outer peripheral surface of the gap assurance member 40 are in contact with each other in parallel to the direction of the rotation axis. . Note that the distance G between the surface of the organic photosensitive layer 2 of the photoreceptor 10 and the surface of the developing sleeve 20 is preferably It ranges from 220 to 260 μm, more preferably from 234 to 260 μm. Further, the outer diameter D4 of the gap assurance member 40 is generally in the range of 15-30 mm.
The process cartridge described above includes two sets of the end portion 1E and the clearance guarantee member 40 contacting the end portion 1E. It may contain only pairs.

Specific embodiments of the present invention will be described in more detail below using examples. The present invention is not limited by the following examples as long as the gist thereof is not exceeded.

Using conductive substrates having the conditions shown in the table below, electrophotographic photoreceptors of Examples and Comparative Examples were produced. The conductive substrate is made of aluminum and has a cylindrical shape. It was machined into a shape with two located ends. The total length of the conductive substrate was 357.5 mm. Also, the length L1 of the slope portion in the rotation axis direction was set to 5 mm.

First, 5 parts by mass of alcohol-soluble nylon (manufactured by Toray Industries, Inc., trade name "CM8000") and 5 parts by mass of aminosilane-treated titanium oxide fine particles are dissolved and dispersed in 90 parts by mass of methanol to form an undercoat layer. A forming coating liquid was prepared. This undercoat layer-forming coating liquid was dip-coated on the periphery of the central portion of the conductive substrate and dried at 100° C. for 30 minutes to form an undercoat layer having a thickness of 3 μm.

1.5 parts by mass of Y-type titanyl phthalocyanine (Y-TiOPc) as a charge generating material and 1 part by mass of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd., trade name "S-Lec BM-1") as a resin binder. , and 60 parts by mass of dichloromethane to prepare a charge generating layer coating solution. This charge generation layer coating solution was dip-coated on the undercoat layer and dried at a temperature of 80° C. for 30 minutes to form a charge generation layer having a thickness of 0.3 μm.

で示される化合物８質量部と、樹脂バインダとしての下記構造式、

で示される繰り返し単位を有する樹脂１２質量部とを、テトラヒドロフラン８０質量部に溶解して、電荷輸送層形成用塗布液を作製した。上記電荷発生層上に、この電荷輸送層形成用塗布液を浸漬塗工し、温度１２０℃で６０分間乾燥して、下記の表中に示す有機感光層膜厚となるような膜厚で電荷輸送層を形成し、負帯電積層型感光体を作製した。 The following structural formula as a charge transport material (CTM),

8 parts by mass of the compound represented by the following structural formula as a resin binder,

was dissolved in 80 parts by mass of tetrahydrofuran to prepare a coating liquid for forming a charge transport layer. This coating solution for forming a charge transport layer was dip-coated on the charge generation layer and dried at a temperature of 120° C. for 60 minutes. A transport layer was formed to prepare a negatively charged laminated photoreceptor.

The photoreceptor obtained in each example and comparative example was incorporated into a process cartridge comprising a developing sleeve, a gap guarantee member fixed to both ends of the sleeve, and a charging roller. It was mounted on the printer image RUNNER 2545. In this process cartridge, the gap assurance member is pressed against the outer peripheral surface of both ends of the photoreceptor with a predetermined pressing force. The outer diameter D3 of the developing sleeve was 20 mm, and the outer diameter D4 of the gap assurance member was 20.4 mm. The charging roller had an outer diameter of 14 mm.

Printing was performed with this printer under normal temperature and humidity (24° C., 50%) environment, and the black spot generation level on the blank image was evaluated in increments of 0.5, and the print density was measured. If the black dot level is 4 or higher, it is indicated by x, if it is 3.5, it is indicated by △, if it is 3 or lower, it is indicated by o, if the print density is 1.33 or higher, it is indicated by o, and if it is 1.32 or lower, it is indicated by x. When the evaluation was x, it was determined as x, when there was no x but there was △, it was determined as △, and when only ○ was evaluated, it was determined as ○. The results are also shown in the table below.

As shown in the above table, the photoreceptor of each example using a conductive substrate satisfying predetermined conditions for the outer diameter D0 of the central portion and the outer diameter D1 of the end portion was obtained by increasing the thickness of the photosensitive layer. It was confirmed that even if the life span was extended, image defects could be suppressed while maintaining image quality when incorporated in a process cartridge having a developing process with a gap guarantee member.

1, 51 conductive substrate 1C central portion 1E end portion 1S slope portion 2 organic photosensitive layer 3 undercoat layer 4 charge generation layer 5 charge transport layers 6, 8 laminated photosensitive layer 7 single layer photosensitive layer 10, 50 electrons Photosensitive member 20 Developing sleeve 30 Charging roller 40 Gap ensuring member

Claims (5)

An electrophotographic photoreceptor comprising a cylindrical conductive substrate and an organic photosensitive layer provided on the conductive substrate,
The conductive substrate has, in the rotation axis direction, a cylindrical central portion having an outer diameter D0 including an image forming area and two cylindrical end portions having an outer diameter D1 located outside the central portion. ,
The organic photosensitive layer is formed on the periphery of the central portion,
The thickness of the organic photosensitive layer is 26 to 34 μm (the thickness of the organic photosensitive layer includes the thickness of the undercoat layer when an undercoat layer is provided) ,
The outer diameter D0 of the central portion and the outer diameter D1 of each of the two ends are determined by the following formula,
50 μm≦(D1−D0)/2≦90 μm (1)
An electrophotographic photoreceptor that satisfies the relationship represented by: 2. The electrophotographic photoreceptor according to claim 1, wherein slope portions are provided between said central portion and said two end portions. In the process cartridge detachable to the main body of the electrophotographic image forming apparatus,
an electrophotographic photoreceptor according to claim 1 or 2;
a developing sleeve for developing the electrostatic latent image formed on the electrophotographic photoreceptor using a developer;
a gap guarantee member that is supported by the developing sleeve and defines a gap between the electrophotographic photoreceptor and the developing sleeve;
A process cartridge in which the gap guarantee member is in contact with the outer peripheral surface of the end portion of the electrophotographic photoreceptor. 4. A process cartridge according to claim 3, further comprising a charging roller for charging said electrophotographic photosensitive member. 5. A process cartridge according to claim 3, wherein the distance between the surface of said organic photosensitive layer of said electrophotographic photosensitive member and the surface of said developing sleeve is in the range of 220 to 260 μm.

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