JP2010039455A - Electrophotographic photoreceptor and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoreceptor having good image characteristics with less change in sensitivity even under low temperature/low humidity conditions, and to provide an image forming apparatus equipped with the same. <P>SOLUTION: The electrophotographic photoreceptor includes an intermediate layer between a conductive support and a photosensitive layer, wherein the intermediate layer contains at least a binder resin and titanium oxide particles the surfaces of which are coated with alumina and silica, and the binder resin is a polyamide resin having a structural unit expressed by the general formula. In the formula, m represents an integer of 10 to 70, n represents an integer of 10 to 40, p represents an integer of 15 to 35, and q represents an integer from 5 to 35, satisfying m+n+p+q=100. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes an electrophotographic photosensitive member (also referred to as a “photosensitive member”) that includes an intermediate layer containing a polyamide resin having a specific structure and surface-treated titanium oxide, and that can realize good image characteristics with little sensitivity change even at low temperature and low humidity. And an image forming apparatus including the same.

2. Description of the Related Art An electrophotographic image forming apparatus (also referred to as “electrophotographic apparatus”) that forms an image using electrophotographic technology is widely used in copying machines, printers, facsimile machines, and the like.
A photoreceptor used in an electrophotographic process is configured by laminating a photosensitive layer containing a photoconductive material on a conductive support.
Conventionally, a photoconductor (also referred to as “inorganic photoconductor”) having a photosensitive layer mainly composed of an inorganic photoconductive material has been widely used. However, it is resistant to heat resistance, storage stability, human body and environment. It has defects in any of the aspects of toxicity, sensitivity, durability, occurrence of image defects, productivity, manufacturing cost, etc., and satisfactory products are not obtained in all points.

On the other hand, research and development of a photoreceptor (also referred to as “organic photoreceptor”) having a photosensitive layer mainly composed of an organic photoconductive material has progressed, and now it occupies the mainstream of photoreceptors.
Organic photoreceptors have some problems in sensitivity, durability, and environmental stability, but have many advantages over inorganic photoreceptors in terms of toxicity, manufacturing cost, and freedom of material design. Have. For example, an organic photoreceptor can form a photosensitive layer by an easy and inexpensive method typified by a dip coating method.

  As an organic photoreceptor, a single layer type photosensitive material in which a charge generation material and a charge transport material (also referred to as “charge transfer material”) are dispersed in a binder resin (also referred to as “binder resin” or “binder resin”). Layers are stacked on a conductive support, and a charge generation layer in which a charge generation material is dispersed in a binder resin and a charge transport layer in which a charge transport material is dispersed in a binder resin are formed in this order or in reverse order. A configuration in which the laminated photosensitive layer or the reverse laminated photosensitive layer is laminated on a conductive support has been proposed. Among these, the function-separated type photoconductor having a laminated type photosensitive layer and a reverse laminated type photosensitive layer is excellent in electrophotographic characteristics and durability, has a high degree of freedom in material selection, and can be designed in various ways. Widely used.

When the photosensitive layer is applied and formed directly on the conductive support in the production of an organic photoreceptor, the photosensitive layer is easily affected by the surface of the conductive support, and it is difficult to form a uniform and uniform film. For this reason, there has been a problem that film thickness unevenness occurs and causes various image defects and density unevenness.
In addition, in an organic photoreceptor having a laminated photosensitive layer, since the conductive support and the charge generation layer are in direct contact with each other, when an electric field is applied by charging, a charge is generated in a part of the charge generation material. However, when the charge generating substance is present nearby, the potential is locally lowered, and there is a problem that fogging or the like occurs on the white paper or the gray portion in the reversal development. This was particularly remarkable in a high temperature and high humidity environment.

As a countermeasure against the above problems, it is known that it is effective to provide a resin layer called an intermediate layer (also referred to as “undercoat layer”) between the conductive support and the photosensitive layer.
For example, a layer obtained by applying and drying an alcohol-soluble polyamide resin as an intermediate layer has been proposed (see, for example, JP-A-52-25638: Patent Document 1).
However, even if such an intermediate layer is provided, good electrical characteristics and image quality can be obtained in a normal environment, but these alcohol-soluble resins have a large resistance change due to the environment such as temperature and humidity. In addition, there is a problem that defects such as black spots, memory, and density unevenness occur on the image.

Therefore, a layer containing titanium oxide has been proposed as an intermediate layer (see, for example, JP-A-56-52757: Patent Document 2).
In addition, for the purpose of improving image characteristics, a technique is known that uses surface-treated titanium oxide to improve the dispersibility of titanium oxide in the intermediate layer coating solution.
For example, in JP-A-2-181158 (Patent Document 3), titanium oxide coated with alumina is disclosed in JP-A-9-152731 (Patent Document 4) and JP-A-2007-248560 (Patent Document 5). Titanium oxide coated with alumina and silica, and Japanese Patent No. 3617292 (Patent Document 6) proposes titanium oxide surface-treated with methylhydrogen polysiloxane.
On the other hand, Japanese Patent No. 2841720 (Patent Document 7) proposes a specific polyamide resin as a resin with little environmental change.

JP-A-52-25638 JP-A-56-52757 Japanese Patent Laid-Open No. 2-181158 Japanese Patent Laid-Open No. 9-152731 JP 2007-248560 A Japanese Patent No. 3617292 Japanese Patent No. 2841720

  However, by using a layer containing titanium oxide as an intermediate layer, environmental changes in the electrical characteristics and image characteristics of the photoreceptor are reduced, but the coating film becomes brittle and the adhesiveness deteriorates. Problems are likely to occur. Further, by using a specific polyamide resin as the intermediate layer, the environmental change is reduced, but the solubility in a solvent is deteriorated, and coating unevenness is likely to occur.

  Accordingly, it is an object of the present invention to provide a photoconductor capable of realizing good image characteristics with little change in sensitivity even at low temperature / low humidity, and an image forming apparatus including the photoconductor.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an intermediate layer containing titanium oxide particles whose surfaces are coated with alumina and silica and a specific polyamide resin is formed on the photoreceptor. The inventors have found that the dependency of the charging characteristics and sensitivity characteristics on humidity is improved, fog is not generated, and image defects such as black spots can be prevented, and the present invention has been completed.

（式中、ｍは１０〜７０の整数であり、ｎは１０〜４０の整数であり、ｐは１５〜３５の整数であり、ｑは５〜３５の整数であり、但しｍ＋ｎ＋ｐ＋ｑ＝１００である）
で表される構造単位を有するポリアミド樹脂であることを特徴とする電子写真感光体が提供される。 Thus, according to the present invention, an intermediate layer is provided between the conductive support and the photosensitive layer,
The intermediate layer contains at least titanium oxide particles whose surface is coated with alumina and silica and a binder resin,
The binder resin has the general formula (I):

(In the formula, m is an integer of 10 to 70, n is an integer of 10 to 40, p is an integer of 15 to 35, q is an integer of 5 to 35, provided that m + n + p + q = 100. )
An electrophotographic photosensitive member is provided which is a polyamide resin having a structural unit represented by:

  According to the present invention, the electrophotographic photosensitive member described above, a charging unit that charges the electrophotographic photosensitive member, and an exposing unit that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image; An image comprising: a developing unit that develops and visualizes the electrostatic latent image formed by exposure; and a transfer unit that transfers the image visualized by the development onto a recording medium. A forming apparatus is provided.

According to the present invention, it is possible to provide a photoconductor capable of realizing good image characteristics with little change in sensitivity even at low temperature / low humidity, and an image forming apparatus including the photoconductor.
In addition, the coating liquid for coating and forming the intermediate layer of the photoreceptor of the present invention can maintain a desired dispersion state for a long period of time, and can form a coating film without coating unevenness even after long-term storage. it can.

  The photoreceptor of the present invention comprises an intermediate layer between the conductive support and the photosensitive layer, and the intermediate layer contains at least titanium oxide particles whose surfaces are coated with alumina and silica and a binder resin. The binder resin is a polyamide resin having a specific structural unit represented by the general formula (I).

The titanium oxide particles used in the intermediate layer of the photoreceptor of the present invention are not particularly limited as long as the particles are coated on the surface with alumina and silica.
As used herein, “particles surface-treated with a specific material” means “particles whose surfaces are coated with a specific material”.
The crystal form of titanium oxide includes anatase type, rutile type, and amorphous type. In the present invention, the crystal type of the titanium oxide particles may be any, and may be a mixture of two or more, but the stability of physical properties The rutile type is particularly preferable from the viewpoint of properties.

  Further, the shape of the titanium oxide particles includes dendrites, needles, and granules. In the present invention, any shape of the titanium oxide particles may be used, but in terms of achieving both film strength and electrical characteristics, Is particularly preferred.

The number average primary particle size of the titanium oxide particles is preferably 30 to 50 nm.
If the number average primary particle diameter of the titanium oxide particles is less than 30 nm, the dispersion efficiency of the titanium oxide is lowered, and minute black spots are easily generated in the image. Moreover, even if the number average primary particle diameter of the titanium oxide particles exceeds 50 nm, the dispersibility of the titanium oxide decreases, and the initial sensitivity tends to decrease in a low temperature and low humidity environment.

The titanium oxide particles used in the present invention are prepared by adding a slurry containing alumina, silica or an organic silicon compound component to a known method, for example, an aqueous dispersion (slurry) of untreated titanium oxide particles, and heating the titanium oxide particles. It can be obtained by forming a thin film of alumina and silica on the surface of the particles, but a commercially available product can also be used.
As such commercially available titanium oxide particles, for example, trade name: MT-500SA (average primary particle size: 35 nm) manufactured by Teika Co., Ltd. may be mentioned.

The binder resin used for the intermediate layer of the photoreceptor of the present invention is represented by the general formula (I):

(In the formula, m is an integer of 10 to 70, n is an integer of 10 to 40, p is an integer of 15 to 35, q is an integer of 5 to 35, provided that m + n + p + q = 100. )
It is a polyamide resin which has a structural unit represented by these.
That is, this polyamide resin is a quaternary copolymer obtained by polymerizing ε-caprolactam, 4,4′-diamino-dicyclohexylmethane, 1,6-hexamethylenediamine and adipic acid.
Q in the general formula (I) is preferably an integer of 5 to 30, and particularly preferably an integer of 10 to 25.

The number average molecular weight of the polyamide resin of the present invention is preferably from 5,000 to 80,000, particularly preferably from 10,000 to 60,000.
When the number average molecular weight of the polyamide resin is less than 5,000, the uniformity of the film thickness of the intermediate layer is deteriorated, and the effects of the present invention are not sufficiently exhibited. Further, when the number average molecular weight of the polyamide resin exceeds 80,000, the solubility of the resin in the solvent tends to be lowered, and an aggregated resin is likely to be generated in the intermediate layer, and image defects such as black spots are likely to occur. .

  In the present invention, the number average molecular weight was measured as follows. Using a GPC apparatus (trade name: HLC-8220GPC, manufactured by Tosoh Corporation), at a temperature of 40 ° C., a 0.25 wt% hexafluoroisopropanol solution of the sample is used as the sample solution, and the injection amount of the sample solution is 100 mL, and the molecular weight A distribution curve was determined. The molecular weight at the peak of the obtained molecular weight distribution curve was determined as the peak top molecular weight. Moreover, the number average molecular weight Mn was calculated | required from the obtained molecular weight distribution curve. The molecular weight calibration curve was prepared using standard polystyrene.

Examples of the polyamide resin used in the present invention include, for example, Tadahiro Miwa, “Chemistry of Basic Synthetic Resin (New Edition)”, Gihodo Publishing Co., Ltd., November 1975, p. It can be obtained by a general polyamide synthesis method described in 305-326 and the like.
The production method of the polyamide resin is not particularly limited, and a normal polyamide polycondensation method, a melt polymerization method, a solution polymerization method, an interfacial polymerization method and the like can be appropriately applied. In the polymerization, a monobasic acid such as acetic acid or benzoic acid, or a monoacid base such as hexylamine or aniline may be used as a molecular regulator.
The copolymerization ratio is not particularly limited, but the diamine component is preferably 5 to 40 mol%, particularly preferably 5 to 30 mol%.

The polyamide resin used in the present invention can be obtained as described above, but a commercially available product can also be used.
As such a commercially available polyamide resin, for example, trade name manufactured by BASF: Ultramid 1c and the like can be mentioned.

  The intermediate layer of the photoreceptor of the present invention mainly contains titanium oxide particles and a binder resin, and may contain additives such as an antioxidant and a conductive agent as necessary.

  The intermediate layer is prepared, for example, by dissolving or dispersing the titanium oxide particles of the present invention, the polyamide resin of the present invention and, if necessary, an additive in an organic solvent to prepare a coating solution for forming an intermediate layer. It can form by apply | coating to the surface of a support body and drying and removing an organic solvent.

Specifically, a coating solution for forming an intermediate layer can be prepared by dissolving the polyamide resin of the present invention in an organic solvent and adding the titanium oxide particles of the present invention to the resulting solution and dispersing it.
In order to disperse the titanium oxide particles in the solution, treatment may be performed using a ball mill, a sand mill, a roll mill, a paint shaker, an attritor, an ultrasonic disperser, or the like.

The content of titanium oxide in the intermediate layer is preferably 50 to 1000 parts by weight, more preferably 70 to 800 parts by weight, and more preferably 100 to 500 parts by weight with respect to 100 parts by weight of the polyamide resin as the binder resin. Is particularly preferred.
If the content of titanium oxide in the intermediate layer is within the above range, the balance between the dispersibility of titanium oxide and the electrical insulating property is improved, and the occurrence of fogging under high temperature and high humidity can be further reduced. it can.

Examples of the organic solvent include lower alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, tert-butanol and sec-butanol. Among these, methanol and ethanol are particularly preferable in terms of the solubility of the polyamide resin and the coating property of the prepared coating solution.
In the coating solution for forming the intermediate layer, the lower alcohol solvent is preferably 30 to 100% by weight, more preferably 40 to 100% by weight, and 50 to 100% by weight in all the solvents. Particularly preferred.

In preparation of the coating solution for forming the intermediate layer, toluene, methylene chloride, cyclohexanone, tetrahydrofuran or the like may be used in combination as a cosolvent for adjusting the solvent evaporation rate.
The cosolvent is about 5 to 30% by weight of the organic solvent.

The coating method for the intermediate layer forming coating solution may be appropriately selected in consideration of the physical properties and productivity of the coating solution, for example, dip coating method, spray method, nozzle method, bar coating method, Examples thereof include a roll coating method, a blade method, a ring method, and a dip coating method.
Among these coating methods, the dip coating method is a method of forming a layer on the surface of the substrate by immersing the substrate in a coating tank filled with a coating solution and then pulling it up at a constant speed or a speed that changes sequentially. Since it is relatively simple and excellent in terms of productivity and cost, it can be suitably used for the production of a photoreceptor. In order to stabilize the dispersibility of the coating liquid, the apparatus used for the dip coating method may be provided with a coating liquid dispersing apparatus represented by an ultrasonic generator.

  From the above, the intermediate layer of the photoreceptor of the present invention is preferably formed by a coating method using a coating solution in which titanium oxide particles and polyamide resin are dissolved or dispersed in a solvent composed of a lower alcohol.

Although it will not specifically limit if the temperature in the drying process of a coating film is the temperature which can remove the used organic solvent, 50-140 degreeC is suitable and 80-130 degreeC is especially preferable.
When the drying temperature is less than 50 ° C., the drying time may be long. On the other hand, if the drying temperature exceeds 140 ° C., the electrical characteristics during repeated use of the photoreceptor may deteriorate and the resulting image may deteriorate.
The temperature conditions in the production of such a photosensitive layer are common not only in the intermediate layer but also in the formation of layers such as a photosensitive layer described later and other processes.

  If the thickness of the intermediate layer is too thin, the effect on local charging failure will not be sufficient, and if it is too thick, the residual potential will increase or the adhesive strength between the conductive support and the photosensitive layer will decrease. . Therefore, the film thickness of the intermediate layer is preferably 0.1 to 10 μm, and more preferably 0.3 to 5 μm.

Next, the configuration of the photoreceptor of the present invention will be specifically described.
1 and 2 are schematic cross-sectional views showing the structure of the main part of the photoreceptor of the present invention.
In the photoreceptor 20b of FIG. 1, an intermediate layer 14b, a charge generation layer 11b, and a charge transport layer 12b are formed in this order on a conductive support 13b.
In the photoreceptor 20d of FIG. 2, an intermediate layer 14d, a charge generation layer 11d, a charge transport layer 12d, and a protective layer 15d are formed in this order on a conductive support 13d.

The photosensitive layer of the photoreceptor of the present invention includes a single-layer type photosensitive layer containing a charge generation material and a charge transport material, and a charge generation layer containing at least a charge generation material and a charge transport layer containing a charge transport material. Any of a laminated photosensitive layer laminated in order, a reverse laminated photosensitive layer in which a charge generating layer containing at least a charge generating substance and a charge transporting layer containing a charge transporting substance are laminated in reverse order may be used. From the viewpoint of abrasion resistance, a laminated photosensitive layer as shown in FIGS. 1 and 2 is particularly preferable.
The structure other than the intermediate layer in the photoreceptor of the present invention will be described.

[Conductive supports 13b and 13d]
The constituent material of the conductive support 13a is not particularly limited as long as it has a function as an electrode of the multilayer photoconductor 1 and a function as a support member and is a material used in this field.
Specifically, metallic materials such as aluminum, aluminum alloys, copper, zinc, stainless steel, and titanium: supports made of polymer materials such as polyethylene terephthalate, polyamide, polyester, polyoxymethylene, polystyrene, hard paper, glass, etc. Examples include those obtained by laminating a metal foil on the surface, those obtained by vapor-depositing a metal material, and those obtained by evaporating or applying a layer of a conductive compound such as a conductive polymer, tin oxide, or indium oxide.

The shape of the conductive support is not limited to a cylindrical shape (drum shape) as shown in FIGS. 1 to 3, and may be a sheet shape, a columnar shape, an endless belt shape, or the like.
If necessary, the surface of the conductive support is subjected to irregular reflection treatment such as anodizing film treatment, surface treatment with chemicals, hot water, coloring treatment, and surface roughening within a range that does not affect the image quality. May be given.

  The irregular reflection treatment is particularly effective when the photoreceptor according to the present invention is used in an electrophotographic process using a laser as an exposure light source. That is, in the electrophotographic process using a laser as an exposure light source, the wavelength of the laser beam is uniform, so the laser beam reflected on the surface of the photoconductor and the laser beam reflected inside the photoconductor cause interference, Interference fringes due to this interference may appear in the image and cause image defects. Therefore, by performing irregular reflection processing on the surface of the conductive support, it is possible to prevent image defects due to interference of laser light having a uniform wavelength.

[Charge generation layers 11b and 11d]
The charge generation layer contains a charge generation material that generates charges by absorbing light such as semiconductor laser light.

  Substances effective as a charge generating substance include azo pigments such as monoazo pigments, bisazo pigments and trisazo pigments; indigo pigments such as indigo and thioindigo; perylene pigments such as perylene imide and perylene anhydride; anthraquinone and Polycyclic quinone pigments such as pyrenequinone; metal phthalocyanines such as oxotitanium phthalocyanine and phthalocyanine pigments such as metal-free phthalocyanine; organic photoconductive materials such as squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes; and selenium Inorganic photoconductive materials such as amorphous silicon and the like can be used, and materials having sensitivity in the exposure wavelength region can be appropriately selected and used. These charge generation materials can be used alone or in combination of two or more.

In order to improve the function of the charge generation material, triphenylmethane dyes such as methyl violet, crystal violet, knight blue and victoria blue, erythrosine, rhodamine B, rhodamine 3R, acridine orange and frappeosin Sensitizing dyes such as acridine dyes, thiazine dyes typified by methylene blue and methylene green, oxazine dyes typified by capri blue and meldra blue, cyanine dyes, styryl dyes, pyrylium salt dyes or thiopyrylium salt dyes They can be used in combination.
The ratio of use of the sensitizing dye is not particularly limited, but is preferably 10 parts by weight or less, particularly preferably 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the charge generating material.

The charge generation layer may contain a binder resin for the purpose of improving the binding property.
As the binder resin, a resin having a binding property used in this field can be used, and a binder resin having excellent compatibility with the charge generation material is preferable.
Specifically, polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, polyarylate resin, phenoxy resin, polyvinyl butyral resin, polyvinyl Formal resins, copolymer resins containing two or more of the repeating units constituting these resins, and the like can be mentioned. Examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. The binder resin is not limited to these, and a resin generally used in this field can be used as the binder resin. These binder resins can be used alone or in combination of two or more.
The use ratio of the binder resin is not particularly limited, but is about 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the charge generation material.

  The charge generation layer is selected from hole transport materials, electron transport materials, antioxidants, ultraviolet absorbers, dispersion stabilizers, sensitizers, leveling agents, plasticizers, fine particles of inorganic compounds or organic compounds, as necessary. An appropriate amount of one or more of them may be included.

The charge generation layer can be formed by a known dry method and wet method.
Examples of the dry method include a method of vacuum-depositing a charge generating material on an intermediate surface formed on a conductive support.
As a wet method, for example, a charge generation material and, if necessary, a binder resin are dissolved or dispersed in an appropriate organic solvent to prepare a coating solution for forming a charge generation layer, and this coating solution is formed on a conductive support. The method of apply | coating to the surface of the intermediate | middle layer made and then drying and removing an organic solvent is mentioned.

  Examples of the solvent used in the charge generation layer coating solution include halogenated hydrocarbons such as dichloromethane and dichloroethane; ketones such as acetone, methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; tetrahydrofuran (THF) , Ethers such as dioxane; alkyl ethers of ethylene glycol such as 1,2-dimethoxyethane; aromatic hydrocarbons such as benzene, toluene and xylene; N, N-dimethylformamide, N, N-dimethylacetamide, etc. Examples include aprotic polar solvents. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment. These solvents can be used alone or in combination of two or more.

Prior to dissolving or dispersing the charge generation material in the solvent, the charge generation material may be previously pulverized by a pulverizer. Examples of the pulverizer used for the pulverization treatment include a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic disperser.
Dispersers such as paint shakers, ball mills, and sand mills can be used to dissolve or disperse the charge generating material in the solvent. At this time, it is preferable to appropriately set the dispersion condition so that impurities are generated from the container and the members constituting the disperser due to wear and the like and are not mixed into the coating liquid.
Other steps and conditions are in accordance with the formation of the intermediate layer.

The thickness of the charge generation layer is not particularly limited, but is preferably 0.05 to 5 μm, particularly preferably 0.1 to 1 μm.
If the thickness of the charge generation layer is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity of the photoreceptor may be lowered. On the other hand, if the thickness of the charge generation layer exceeds 5 μm, the charge transfer inside the charge generation layer becomes a rate-determining step in the process of erasing the charge on the surface of the photosensitive layer, which may reduce the sensitivity of the photoreceptor.

[Charge transport layers 12b, 12d]
The charge transport layer has a function of transporting charges generated in the charge generation layer to the surface of the photoreceptor.
The charge transport layer contains at least a charge transport material and a binder resin.
As the charge transport material, high molecular compounds such as polyvinyl carbazole, polyvinyl pyrene, and polyacenaphthylene, or low molecular compounds such as various pyrazoline derivatives, oxazole derivatives, hydrazone derivatives, stilbene derivatives, and arylamine derivatives can be used.
Binder resins include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylic ester, methacrylic ester, vinyl alcohol, ethyl vinyl ether, polyvinyl acetal, polycarbonate, polyester, polyamide, polyurethane, cellulose Examples include ether, phenoxy resin, silicon resin, and epoxy resin.

As the binder resin, a transparent resin that does not absorb the light from the exposure light source of the image forming apparatus can be used among the resins having binding properties used in this field, and a resin similar to that contained in the charge generation layer can be used. One kind can be used alone or two or more kinds can be used in combination.
Among these, polystyrene, polycarbonate, polyarylate, and polyphenylene oxide are preferable because they have a volume resistance of 10 ¹³ Ω or more, excellent electrical insulation, and excellent film formability, potential characteristics, and the like, and polycarbonate is particularly preferable. .
The use ratio of the binder resin is not particularly limited, but is about 50 to 300 parts by weight with respect to 100 parts by weight of the charge transport material.

  The charge transport layer is selected from a hole transport material, an electron transport material, an antioxidant, an ultraviolet absorber, a dispersion stabilizer, a sensitizer, a leveling agent, a plasticizer, an inorganic compound, or an organic compound as necessary. An appropriate amount of one or more of them may be included.

Similarly to the charge generation layer, the charge transport layer can be formed by preparing a coating solution for forming a charge transport layer and using a wet method, particularly a dip coating method.
As the solvent used for the preparation of the coating solution for forming the charge transport layer, it is possible to use one kind of the same solvents as those used for the preparation of the coating solution for forming the charge generation layer alone or in combination of two or more kinds. it can.

Specifically, alcohols such as methanol, ethanol, isopropanol and butanol; aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; dichloromethane, dichloroethane and carbon tetrachloride , Halogenated hydrocarbons such as chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, propylene glycol monomethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone, cyclohexanone; ethyl acetate, acetic acid Esters such as methyl; dimethylformaldehyde, dimethylformamide, dimethylsulfoxide, etc. Among these, it is particularly preferable to use tetrahydrofuran and 1,3-dioxolane alone.
Other steps and conditions are in accordance with the formation of the intermediate layer and the charge generation layer.

Although the film thickness of a charge transport layer is not specifically limited, 5-40 micrometers is preferable and 10-30 micrometers is especially preferable.
When the thickness of the charge transport layer is less than 5 μm, the charge holding ability on the surface of the photoreceptor is lowered, and the contrast of the output image may be lowered. On the other hand, if the thickness of the charge transport layer exceeds 100 μm, the productivity of the photoreceptor may be lowered.

[Surface protective layer 15d]
As shown in FIG. 2, the photoreceptor of the present invention may have a surface protective layer on the photosensitive layer.
The protective layer has a function of improving the durability of the photoreceptor, is made of a binder resin, and may contain one or more of the same charge transport materials as those contained in the charge transport layer.
Examples of the binder resin include the same binders as those contained in the charge generation layer and the charge transport layer.

The surface protective layer can be formed by, for example, preparing a coating solution for forming a protective layer by dissolving a binder resin in an appropriate solvent, applying the coating solution to the surface of the photosensitive layer, and removing the organic solvent by drying. .
Other processes and conditions are in accordance with the formation of the intermediate layer, the charge generation layer, and the charge transport layer.

Although the film thickness of a protective layer is not specifically limited, 0.5-10 micrometers is preferable and 1-5 micrometers is especially preferable.
When the thickness of the protective layer is less than 0.5 μm, the scratch resistance on the surface of the photoreceptor is inferior and the durability may be insufficient. If it exceeds 10 μm, the resolution of the photoreceptor may be lowered.

The image forming apparatus of the present invention includes a photosensitive member of the present invention, a charging unit that charges the electrophotographic photosensitive member, an exposure unit that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image, The image forming apparatus includes a developing unit that develops and visualizes the electrostatic latent image formed by the exposure, and a transfer unit that transfers the image visualized by the development onto a recording medium.
The image forming apparatus of the present invention and the operation thereof will be described with reference to the drawings, but are not limited to the following description.
FIG. 3 is a schematic side view showing the configuration of the image forming apparatus of the present invention.

  An image forming apparatus (laser printer) 100 in FIG. 3 includes a photoreceptor 1 of the present invention, an exposure unit (semiconductor laser) 31, a charging unit (charging unit) 32, a developing unit (developing unit) 33, and a transfer unit. The image forming apparatus includes a (transfer charger) 34, a conveyance belt (not shown), a fixing unit (fixing unit) 35, and a cleaning unit (cleaner) 36. Reference numeral 51 indicates a transfer sheet.

  The photosensitive member 1 is rotatably supported by the main body of the image forming apparatus 100 (not shown), and is driven to rotate in the direction of the arrow 41 around the rotation axis 44 by a driving unit (not shown). The drive means includes, for example, an electric motor and a reduction gear, and transmits the driving force to a conductive support constituting the core of the photoconductor 1 to drive the photoconductor 1 to rotate at a predetermined peripheral speed. . The charger 32, the exposure unit 31, the developing unit 33, the transfer charger 34, and the cleaner 36 are arranged in this order from the upstream side in the rotation direction of the photosensitive member 1 indicated by an arrow 41 along the outer peripheral surface of the photosensitive member 1. It is provided toward the downstream side.

The charger 32 is a charging unit that uniformly charges the outer peripheral surface of the photoreceptor 1 to a predetermined potential.
The exposure unit 31 includes a blue semiconductor laser as a light source, and is charged by irradiating the surface of the single-layer type photoreceptor 1 between the charger 32 and the developer 33 with the light of the laser beam output from the light source. The outer peripheral surface of the single-layer type photoreceptor 1 is exposed according to image information. The light is repeatedly scanned in the main scanning direction in the direction in which the rotation axis 44 of the single-layer photoreceptor 1 extends, and these are imaged to form electrostatic latent images on the surface of the photoreceptor 1 in sequence. That is, the charge amount of the photoreceptor 1 uniformly charged by the charger 32 is different depending on whether the laser beam is irradiated or not, and an electrostatic latent image is formed.

  The developing unit 33 is a developing unit that develops an electrostatic latent image formed on the surface of the photoconductor 1 by exposure with a developer (toner), and is provided facing the photoconductor 1. A developing roller 33a for supplying toner to the toner, and a casing 33b for supporting the developing roller 33a so as to be rotatable about a rotation axis parallel to the rotation axis 44 of the photosensitive member 1 and containing a developer containing toner in the internal space thereof. Prepare.

  The transfer charger 34 transfers a toner image, which is a visible image formed on the outer peripheral surface of the photoreceptor 1 by development, between the single-layer photoreceptor 1 and the transfer charger 34 from the direction of the arrow 42 by a conveying unit (not shown). It is a transfer means for transferring onto a transfer paper 51 which is a recording medium supplied in between. The transfer charger 34 is, for example, a non-contact type transfer unit that includes a charging unit and transfers the toner image onto the transfer paper 51 by giving the transfer paper 51 a charge having a polarity opposite to that of the toner.

  The cleaner 36 is a cleaning unit that removes and collects toner remaining on the outer peripheral surface of the photoconductor 1 after the transfer operation by the transfer charger 34, and removes the toner remaining on the outer peripheral surface of the single-layer type photoconductor 1. 36a and a recovery casing 36b for storing the toner separated by the cleaning blade 36a. The cleaner 36 is provided together with a static elimination lamp (not shown).

Further, the image forming apparatus 100 is provided with a fixing device 35 as fixing means for fixing the transferred image on the downstream side where the transfer paper 51 that has passed between the photoreceptor 1 and the transfer charger 34 is conveyed. It is done. The fixing device 35 includes a heating roller 35a having a heating unit (not shown), and a pressure roller 35b that is provided facing the heating roller 35a and is pressed by the heating roller 35a to form a contact portion.
Reference numeral 37 denotes a separating means for separating the transfer paper and the photosensitive member, and 38 denotes a casing for housing each means of the image forming apparatus.

The image forming operation by the electrophotographic apparatus 100 is performed as follows.
First, when the photosensitive member 1 is rotationally driven in the direction of the arrow 41 by the driving unit, the photosensitive member 1 is provided by the charger 32 provided on the upstream side in the rotational direction of the photosensitive member 1 with respect to the light imaging point by the exposure unit 31. Are uniformly charged to a predetermined positive potential.

Next, light corresponding to image information is irradiated from the exposure unit 32 to the surface of the photoreceptor 1. In this exposure, the surface charge of the portion irradiated with light is removed by this exposure, and a difference occurs between the surface potential of the portion irradiated with light and the surface potential of the portion not irradiated with light. A latent image is formed.
Toner is supplied to the surface of the photosensitive member 1 on which the electrostatic latent image is formed from a developing device 33 provided on the downstream side in the rotation direction of the photosensitive member 1 with respect to the light image formation point by the exposure means 33, and the electrostatic latent image. Is developed to form a toner image.

In synchronization with the exposure of the photoreceptor 1, the transfer paper 51 is supplied between the photoreceptor 1 and the transfer charger 34. The transfer charger 34 applies a charge having a polarity opposite to that of the toner to the supplied transfer paper 51, and the toner image formed on the surface of the photoreceptor 1 is transferred onto the transfer paper 51.
The transfer paper 51 onto which the toner image has been transferred is conveyed to the fixing device 35 by the conveying means, and is heated and pressurized when passing through the contact portion between the heating roller 35a and the pressure roller 35b of the fixing device 35, and the toner The image is fixed on the transfer paper 51 and becomes a robust image. The transfer paper 51 on which the image is formed in this manner is discharged to the outside of the electrophotographic apparatus 100 by the conveying means.

  On the other hand, the toner remaining on the surface of the photoreceptor 1 even after the transfer of the toner image by the transfer charger 34 is separated from the surface of the single-layer photoreceptor 1 by the cleaner 36 and collected. The charge on the surface of the photoreceptor 1 from which the toner has been removed in this manner is removed by the light from the static elimination lamp, and the electrostatic latent image on the surface of the photoreceptor 1 disappears. Thereafter, the photosensitive member 1 is further driven to rotate, and a series of operations starting from charging is repeated to form images continuously.

  The present invention will be specifically described below with reference to production examples, examples and comparative examples, but the present invention is not limited to these production examples and examples.

(Production Example 1)
A polyamide resin of the present invention was produced.
64 parts by weight of ε-caprolactam, 73 parts by weight of 4,4′-diamino-dicyclohexylmethane, 27 parts by weight of 1,6-hexamethylenediamine, 68 parts by weight of adipic acid and 7 parts by weight of water were placed in an autoclave equipped with a stirrer. Heating was started after the inside was sufficiently purged with nitrogen. Stirring was started when the system temperature reached 100 ° C., and heating was performed until the system pressure reached 13 kg / cm ² . After system pressure has reached 13 kg / cm ^2, system pressure is to distill water to a 13 kg / cm ^2. Next, the valve of the autoclave was closed, and after reacting for 2 hours, the valve was opened and the system was returned to normal pressure. Then, after making it react at 290 degreeC for further 2 hours, the produced | generated molten polymer was extracted and it wash | cleaned 5 times with 10 times amount boiling water. The obtained polymer was dried at 120 ° C. under reduced pressure for 3 days to obtain 116 g of a copolymerized polyamide resin.
The copolymer composition was determined by C ¹³ -NMR and found to be the following composition. The number average molecular weight of the copolymerized polyamide resin measured by GPC method under the above conditions was 15000.

（式中、ｍ＝３４、ｎ＝２０、ｐ＝３３、ｑ＝１３、ｍ＋ｎ＋ｐ＋ｑ＝１００である）

(Where m = 34, n = 20, p = 33, q = 13, m + n + p + q = 100)

Example 1
The photoreceptor shown in FIG. 1 was produced.
Titanium oxide particles surface-treated with only alumina and silica (trade name: MT-500SA, manufactured by Teika Co., Ltd., rutile crystal, average primary particle size 35 nm) and 400 parts by weight of a commercially available polyamide resin (trade name: Ultramid ( Ultramid) 1c, manufactured by BASF, m = 25, n = 25, p = 25, q = 25) 100 parts by weight is added to 265 parts by weight of methyl alcohol and dispersed for 8 hours with a paint shaker to form an intermediate layer A coating solution was prepared.
The obtained coating solution for forming an intermediate layer is filled in a coating tank, and an aluminum drum-like support having a diameter of 30 mm and a total length of 340 mm is immersed as a conductive support, and then pulled up and dried naturally to form an intermediate layer having a thickness of 1 μm. Formed.

Next, 1 part by weight of titanyl phthalocyanine having an X-ray diffraction spectrum in which the Bragg angle (2θ ± 0.2 °) with respect to X-ray of CuKα1.541Å as a charge generation material shows a main peak at 27.3 ° and a binder resin 1 part by weight of butyral resin (trade name: # 6000-C, manufactured by Denki Kagaku Kogyo Co., Ltd.) was mixed with 98 parts by weight of methyl ethyl ketone and dispersed for 8 hours with a paint shaker to prepare a coating solution for forming a charge generation layer. .
The obtained coating solution for forming a charge generation layer was applied to the surface of the intermediate layer previously provided by the same method as that for forming the intermediate layer, and then naturally dried to form a charge generation layer having a thickness of 0.4 μm.

Next, 100 parts by weight of a triphenylamine compound having the following structure as a charge transport material, 150 parts by weight of a polycarbonate resin (trade name: PCZ-400, manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a binder resin, and 0.02 part by weight of silicon oil Then, a coating solution for forming a charge transport layer having a solid content of 25% by weight was prepared using tetrahydrofuran as a solvent.
The obtained charge transport layer forming coating solution was applied to the surface of the charge generation layer previously provided in the same manner as in the intermediate layer formation, and dried at 130 ° C. for 1 hour to form a charge transport layer having a thickness of 25 μm. Formed.
In this way, the photoreceptor shown in FIG. 1 was produced.

(Example 2)
A photoconductor shown in FIG. 1 was produced in the same manner as in Example 1 except that the polyamide resin produced in Production Example 1 was used in place of the commercially available polyamide resin in the preparation of the intermediate layer forming coating solution.

(Example 3)
A photoconductor shown in FIG. 1 was prepared in the same manner as in Example 1 except that n-propyl alcohol was used instead of methyl alcohol as a solvent in the preparation of the intermediate layer forming coating solution.

(Comparative Example 1)
In the preparation of the coating solution for forming the intermediate layer, the same procedure as in Example 1 was used except that titanium oxide particles (trade name: MT-500B, manufactured by Teika Co., Ltd., average primary particle size: 35 nm) were used as titanium oxide particles. Thus, the photoreceptor shown in FIG. 1 was produced.

(Comparative Example 2)
Example except that alumina-treated titanium oxide particles (trade name: TTO-55A, manufactured by Ishihara Sangyo Co., Ltd., rutile crystal, average primary particle size 35 nm) are used as titanium oxide particles in the preparation of the intermediate layer forming coating solution. 1 was produced in the same manner as in FIG.

(Comparative Example 3)
Examples except that silica-treated titanium oxide particles (trade name: TS-04, manufactured by Showa Denko KK, rutile crystals, average primary particle size 35 nm) are used as titanium oxide particles in the preparation of the intermediate layer forming coating solution. 1 was produced in the same manner as in FIG.

(Comparative Example 4)
Titanium oxide particles (trade name: SMT-500SAS, Teika Co., Ltd.) surface-treated with alumina and silica as titanium oxide particles in the preparation of the intermediate layer forming coating solution and then surface-treated with silicone (methyl hydrogen polysiloxane) The photoconductor shown in FIG. 1 was produced in the same manner as in Example 1 except that the product used was a rutile-type crystal and an average primary particle diameter of 35 nm.

(Comparative Example 5)
The photoreceptor shown in FIG. 1 is produced in the same manner as in Example 1 except that alcohol-soluble copolymer nylon (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.) is used as the polyamide resin in the preparation of the intermediate layer forming coating solution. did.

The electrical characteristics of the photoreceptors of Examples 1 to 3 and Comparative Examples 1 to 5 produced as described above were evaluated.
Further, the dispersibility and coating solution stability of the coating solution for forming an intermediate layer used in the production of each photoreceptor were evaluated.

<Electrical characteristics>
The light attenuation characteristics of each of the photoreceptors of Examples 1 to 3 and Comparative Examples 1 to 5 were measured.
Using a drum sensitivity tester (model: CYNTHIA60, manufactured by Gentec Co., Ltd.), the surface of the photoreceptor is charged to −600 ± 20 V with a scorotron charger, and the light intensity is adjusted with an ND filter as an exposure light source. Laser light (wavelength 780 nm) was irradiated on the surface of the photoreceptor, and the surface potential (V) of each photoreceptor at each light intensity was measured.

The surface potential is the surface potential of the photoconductor immediately after the charging operation by the charger in a normal temperature / normal humidity (N / N) environment at a temperature of 25 ° C. and a relative humidity of 50%. ) Was measured.
Further, the surface potential of the photoconductor immediately after being exposed to the laser beam was measured as a residual potential VL (V), and this was defined as a residual potential VL (N / N) in an N / N environment.
The larger the absolute value of the charging potential V0, the better the charging property, and the smaller the absolute value of the residual potential VL (N / N), the better the photoresponsiveness.

Similarly to the N / N environment, the residual potential VL (V) is measured in a low temperature / low humidity (L / L) environment at a temperature of 5 ° C. and a relative humidity of 20%. Was defined as a residual potential VL (L / L) in an L / L environment.
The absolute value of the difference between the residual potential VL (N / N) in the N / N environment and the residual potential VL (L / L) in the L / L environment is expressed as potential fluctuation ΔVL (= | VL (L / L) -VL (N / N) |).
It was evaluated that the smaller the potential fluctuation ΔVL (environmental characteristics), the better the stability of the electrical characteristics.

The electrical characteristics were evaluated according to the following criteria.
A: Very good ΔVL Less than 80V.
○: Good ΔVL 80V or more and less than 95V.
Δ: Slightly poor ΔVL 95V or more and less than 110V.
X: Defect ΔVL 110V or more.
The obtained results are shown in Table 1. Further, the light attenuation characteristics of the photoconductors of Example 1 and Comparative Example 5 are shown in FIG. In the figure, the horizontal axis represents the exposure amount (Laser Power, μJ / cm ² ), and the vertical axis represents the surface potential (Surface Potential, V).

<Dispersibility>
The coating solution for forming the intermediate layer used in the production of each of the photoreceptors of Examples 1 to 3 and Comparative Examples 1 to 5 was put into a 2 mm thick cell, and the turbidity immediately after the preparation was measured using an integrating sphere turbidimeter (Mitsubishi Chemical). Measurement was performed using SEP-PT-501D).
The dispersibility of the intermediate layer forming coating solution was evaluated according to the following criteria.
A: Very good Turbidity is less than 80.
○: Good Turbidity 80 or more and less than 120.
Δ: Slightly poor Turbidity 120 or more and less than 200
X: Poor turbidity 200 or more The results obtained are shown in Table 1.

<Coating solution stability>
After evaluating the dispersibility, the intermediate layer forming coating solution was allowed to stand at room temperature for 90 days, and then the turbidity was measured in the same manner as described above, and the difference from the turbidity at the time of dispersibility evaluation (turbidity change value). Asked.
The coating solution stability of the coating solution for forming an intermediate layer was evaluated according to the following criteria.
A: Very good Turbidity change value of less than 10.
○: Good Turbidity change value of 10 or more and less than 40.
Δ: Slightly poor Turbidity change value of 40 or more and less than 100.
X: Poor turbidity change value of 100 or more.
The obtained results are shown in Table 1.

From the evaluation results in Table 1, the following can be understood.
The photoconductor using the polyamide resin of the present invention (Examples 1 and 2) has a smaller sensitivity change even at low temperature / low humidity than the conventional photoconductor using the polyamide resin (Comparative Example 5). The coating solution for forming an intermediate layer used in the production maintains a good dispersion state even after standing for 90 days.
In the preparation of the coating solution for forming the intermediate layer, the photoreceptor (Example 3) using n-propyl alcohol has a small sensitivity change at low temperature / low humidity in the initial stage, and the dispersion of the coating solution for forming the intermediate layer is good. However, the dispersion state deteriorates after standing for 90 days.

The sensitivity change in the photoconductor (comparative example 1) using the titanium oxide particles that have not been surface-treated is large. This is thought to be because the dispersion state of the coating liquid for forming the intermediate layer was poor and the titanium oxide particles settled.
Photosensitive materials (comparative examples 2 to 3) using alumina-treated or silica-treated titanium oxide particles have a large sensitivity change. Moreover, it is inferior to the storage stability of the coating liquid for intermediate | middle layer formation.
A photoreceptor (comparative example 4) using titanium oxide particles surface-treated with alumina and silica and then surface-treated with silicone is inferior in electrical properties, although the dispersion state of the coating liquid for forming the intermediate layer is improved.

From the above, it can be seen that the photoreceptor of the present invention can realize good image characteristics with little sensitivity change even at low temperature / low humidity.
It can also be seen that the coating solution for forming an intermediate layer used in the production of the photoreceptor of the present invention can maintain a desired dispersion state for a long period of time, and can form a coating film without coating unevenness even after long-term storage.

FIG. 2 is a schematic cross-sectional view showing a configuration of a main part of the electrophotographic photosensitive member of the present invention. FIG. 2 is a schematic cross-sectional view showing a configuration of a main part of the electrophotographic photosensitive member of the present invention. 1 is a schematic side view illustrating a configuration of an image forming apparatus of the present invention. It is a figure which shows the light attenuation characteristic of an electrophotographic photoreceptor (Example 1 and Comparative Example 5).

Explanation of symbols

1, 20b, 20d Electrophotographic photoreceptor 11 Conductive support 11b, 11d Charge generation layer 12b, 12d Charge transport layer 13b, 13d Conductive support 14b, 14d Intermediate layer 15d Surface protective layer

31 Exposure means (semiconductor laser)
32 Charging means (charger)
33 Developing means (developer)
33a Developing roller 33b Casing 34 Transfer means (transfer charger)
35 Fixing means (fixing device)
35a Heating roller 35b Pressure roller 36 Cleaning means (cleaner)
36a Cleaning blade 36b Recovery casing 37 Separating means 38 Housing 41, 42 Arrow 44 Rotating axis 51 Transfer paper 100 Electrophotographic apparatus (laser printer)

Claims (8)

Comprising an intermediate layer between the conductive support and the photosensitive layer;
The intermediate layer contains at least titanium oxide particles whose surface is coated with alumina and silica and a binder resin,
The binder resin has the general formula (I):

(In the formula, m is an integer of 10 to 70, n is an integer of 10 to 40, p is an integer of 15 to 35, q is an integer of 5 to 35, provided that m + n + p + q = 100. )
An electrophotographic photoreceptor, which is a polyamide resin having a structural unit represented by:   The electrophotographic photosensitive member according to claim 1, wherein q in the general formula (I) is an integer of 10 to 25.   The electrophotographic photosensitive member according to claim 1, wherein the titanium oxide particles have a number average primary particle size of 30 to 50 nm.   The electrophotographic photosensitive member according to claim 1, wherein the polyamide resin has a number average molecular weight of 5,000 to 80,000.   The electrophotographic photosensitive member according to claim 1, wherein the titanium oxide particles are contained in a proportion of 50 to 1000 parts by weight with respect to 100 parts by weight of the polyamide resin.   The said intermediate | middle layer is formed by the apply | coating method using the coating liquid which melt | dissolved or disperse | distributed the said titanium oxide particle and the said polyamide resin in the solvent which consists of a lower alcohol. Electrophotographic photoreceptor.   The photosensitive layer according to any one of claims 1 to 6, wherein the photosensitive layer is a laminated photosensitive layer in which a charge generation layer containing at least a charge generation material and a charge transport layer containing a charge transport material are laminated in this order. The electrophotographic photosensitive member described.   An electrophotographic photosensitive member according to claim 1, a charging means for charging the electrophotographic photosensitive member, and the charged electrophotographic photosensitive member is exposed to form an electrostatic latent image. An exposure unit, a development unit that develops and visualizes the electrostatic latent image formed by the exposure, and a transfer unit that transfers the image visualized by the development onto a recording medium. An image forming apparatus.

Images