JP6426490B2 - Method of manufacturing electrophotographic photosensitive member - Google Patents

Description

The present invention relates to a method of manufacturing an electrophotographic photosensitive member. More specifically, according to the present invention, the surface layer of the photoreceptor contains fine particles and a high boiling point solvent-containing dispersant as a dispersant therefor, and further, another high boiling point solvent is used as an auxiliary solvent for the surface layer coating solution The present invention relates to a method for producing an electrophotographic photosensitive member produced using the coating for forming a surface layer contained therein.

  In an electrophotographic image forming apparatus (hereinafter, also referred to as an electrophotographic apparatus) used as a copying machine, a printer or a facsimile machine, an image is formed through the following electrophotographic process.

First, the photosensitive layer of an electrophotographic photosensitive member (hereinafter, also simply referred to as a photosensitive member) included in the apparatus is uniformly charged to a predetermined potential by a charger.
Next, exposure is performed with light such as laser light emitted from the exposure means according to the image information to form an electrostatic latent image.

The developer is supplied from the developing means to the formed electrostatic latent image, and the electrostatic latent image is developed by depositing colored fine particles called toner, which is a component of the developer, on the surface of the photoreceptor. Visualize as a toner image.
The formed toner image is transferred from the surface of the photosensitive member by a transfer unit onto a transfer material such as recording paper and fixed by a fixing unit to form an image.

However, during the transfer operation by the transfer means, not all the toner on the surface of the photosensitive member is transferred to the recording paper and transferred, but a part thereof remains on the surface of the photosensitive member. In addition, paper dust of the recording paper, which comes in contact with the photosensitive member at the time of transfer, may remain attached to the photosensitive member surface.
Such foreign matters such as residual toner and adhered paper dust on the surface of the photosensitive member adversely affect the quality of the formed image, and are therefore removed by the cleaning device.

In recent years, cleanerless technology has advanced, and there is also a method of removing the above-mentioned foreign matter with a so-called development and cleaning system in which residual toner is recovered by a cleaning function added to the developing means without having an independent cleaning means.
In this method, after the surface of the photosensitive member is cleaned, the surface of the photosensitive layer is removed by a charge removing device or the like, and the remaining electrostatic latent image is lost.

An electrophotographic photosensitive member used in such an electrophotographic process is configured by laminating a photosensitive layer containing a photoconductive material on a conductive substrate made of a conductive material.
Examples of the electrophotographic photosensitive member include inorganic photoconductive materials and organic photoconductive materials (hereinafter, organic photoconductors (OPCs)). According to recent research and development, organic photosensitive materials are used. At present, organic photoreceptors are often used because the sensitivity and durability of the body have been improved.

  In recent years, in the construction of this electrophotographic photosensitive member, a laminated type photosensitive member in which a photosensitive layer is functionally separated into a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance has become mainstream. ing. In many cases, a charge transport layer in which a charge transport substance having charge transport ability is dispersed in a molecular form in a binder resin is laminated on a charge generation layer in which a charge generation substance is vapor deposited or dispersed in a binder resin. It is a negatively charged photosensitive member.

In addition, a single-layer type photoreceptor in which a charge generation material and a charge transport material are uniformly dispersed and dissolved in the same binder resin is also proposed.
In order to further improve the quality of printed images, it is also practiced to provide an undercoat layer between the conductive substrate and the photosensitive layer.

  As a drawback of organic photoreceptors, the nature of organic materials causes the surface to be worn away by rubbing with a cleaner around the photoreceptor. As a means of overcoming this drawback, it has been done up to now to improve the mechanical properties of the material of the photoreceptor surface.

  As a previous approach, a protective layer is provided on the outermost surface layer of the photosensitive member to impart lubricity (for example, JP-A 1-23259: Patent Document 1), and filler particles are contained in the protective layer (for example, Methods, such as Unexamined-Japanese-Patent No. 1-172970: patent document 2), are known. Among them, studies have also been made to add fluorine-based particles to the surface as a filler (for example, Patent No. 3416310: Patent Document 3). In addition, as a feature of the fluorine-based particles, the high lubricant function derived from the material allows the fluorine-based particles not only to improve the mechanical properties of the photoreceptor as a filler but also to contact during the photoreceptor process by imparting lubricity. The reduction of the frictional force with the member which also contributes to the improvement of the printing durability of the photosensitive member surface.

  On the other hand, fluorine-based fine particles, for example, polytetrafluoroethylene (PTFE) fine particles, while having an excellent lubricating function as a material, have the disadvantage that the cohesion of the particles is very large and the dispersibility is extremely poor because they have no polarity is there. Therefore, when dispersing PTFE fine particles for a photosensitive member, it has been proposed to use a dispersing agent (for example, JP-A-2011-118054: Patent document 4), but as a result, the photosensitive member electrical characteristics deteriorate. It will

Unexamined-Japanese-Patent No. 1-23259 Unexamined-Japanese-Patent No. 1-172970 Patent No. 3416310 JP, 2011-118054, A

As described above, when fluorine fine particles are added to the photoreceptor surface layer, the use of a dispersant is inevitable, and the addition of the dispersant causes deterioration of the photoreceptor electrical characteristics. In addition, high boiling point solvents tend to remain in the system even after drying, but many of them have high affinity for the dispersant of the above-mentioned fine particles, and have the effect of improving dispersibility and dispersion stability.
Therefore, it is an object of the present invention to provide an electrophotographic photosensitive member having stable photosensitive member electrical characteristics over a long period despite the inclusion of a dispersant causing deterioration of the electrical characteristics.

  As a result of intensive studies to solve the above problems, the present inventor added as a high boiling point solvent or an auxiliary solvent which is usually contained in a dispersant, in an electrophotographic photosensitive member having a photosensitive layer formed on a conductive substrate. By containing the residual amount of high boiling point solvent in the outermost surface layer of the photosensitive member after formation of the photosensitive layer manufactured using the coating solution for forming the surface layer of the photosensitive member containing the high boiling point solvent in a specific range It has been found that a photoreceptor excellent in abrasion resistance and electrically stable can be provided, and the present invention has been completed.

Thus, according to the present invention, an electrophotographic photosensitive member is provided in which a laminated photosensitive layer is provided on a conductive substrate, in which a charge generation layer containing at least a charge generation substance and a charge transport layer containing a charge transport substance are laminated in this order. A method of manufacturing the body,
Applying a coating solution for forming a charge transport layer on the surface of the charge generation layer and drying it to form the charge transport layer as the outermost surface layer of the electrophotographic photosensitive member,
The coating liquid for forming a charge transport layer is at least a charge transport substance ; a binder resin ; a polytetrafluoroethylene particle as a filler ; a dispersant for the polytetrafluoroethylene particle ; a boiling point of 100 to 160 ° C. derived from the dispersant. A suspension having a solid concentration of 21% by weight, which comprises a high boiling point solvent having : and a mixed solvent of tetrahydrofuran and toluene as a main solvent ,
The weight ratio of said tetrahydrofuran to toluene is from 9.0: 1 to 23.8: 1, and said tetrahydrofuran is 0.05% by weight of 2,6-di-t-butyl-4-4 as an antioxidant. Contains methylphenol,
When the amount of residual solvent at a thermal desorption temperature of 200 ° C. or lower is analyzed by thermal desorption gas chromatography using the thermal desorption gas chromatography, the integrated intensity ratio of the 2,6-di-t-butyl-4-methylphenol The integrated intensity ratio of the high-boiling point solvent and toluene to the above is 10 to 70%,
The method of producing an electrophotographic photosensitive member is provided, wherein the charge transport layer has a thickness of 10 to 30 μm.

  Further, according to the present invention, the electrophotographic photosensitive member is provided, wherein the analysis of the amount of residual solvent by the thermal desorption gas chromatography is an analysis by comparing the integrated intensity of the amount of residual solvent at a thermal desorption temperature of 200 ° C. or less. .

  Further, according to the present invention, in the analysis of the amount of residual solvent by the thermal desorption gas chromatography, the electrophotographic photosensitive member in which the outermost surface layer contains 10 to 40% of integrated intensity ratio of the high boiling point solvent. Provided.

  Further, according to the present invention, in the analysis of the amount of residual solvent by the thermal desorption gas chromatography, the electrophotographic photosensitive member in which the outermost surface layer contains 10 to 20% of integrated intensity ratio of the high boiling point solvent. Provided.

  Further, according to the present invention, there is provided a coating liquid for charge transport layer comprising a charge transport substance, a binder resin, polytetrafluoroethylene particles, a dispersant and a 0 to 45% by weight toluene solution in toluene. Provided.

  Further, according to the present invention, a coating liquid for charge transport layer containing a charge transport substance, a binder resin, polytetrafluoroethylene particles, a dispersant and a 0 to 45% by weight toluene solution in toluene is used. There is provided a process for producing an electrophotographic photosensitive member containing the above-mentioned high boiling point solvent.

  Further, the electrophotographic photosensitive member, a charging unit for charging the electrophotographic photosensitive member, an exposing unit for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image, and the electrostatic latent image An image forming apparatus comprising: developing means for developing a toner image with toner to form a toner image; transfer means for transferring the toner image onto a recording material; and fixing means for fixing the transferred toner image onto the recording material Is provided.

  The inventors of the present invention found that the outermost surface layer of the electrophotographic photosensitive member according to the present invention was used as a high boiling solvent and a secondary solvent derived from a dispersant containing a specific fine particle and a high boiling solvent and containing a specific polymer. The total residual amount of the solvent is the tetrahydrofuran-containing 2, 6-di used as the main solvent in the coating liquid for forming the outermost surface layer in the analysis of the amount of residual solvent using thermal desorption gas chromatography of the outermost surface layer. By including in a specific range with respect to the integrated strength of -t-butyl-4-methylphenol, an electrophotographic photosensitive member having high abrasion resistance and long-term electrical stability and an image forming including the photosensitive member It became possible to provide equipment.

FIG. 1 is a schematic cross-sectional view showing a configuration of an electrophotographic photosensitive member according to Embodiment 1 of the present invention. FIG. 6 is a schematic cross-sectional view showing the configuration of an electrophotographic photosensitive member according to Embodiment 2 of the present invention. FIG. 6 is a schematic cross-sectional view showing a configuration of an electrophotographic photosensitive member according to Embodiment 3 of the present invention. FIG. 10 is a schematic cross-sectional view showing a configuration of an image forming apparatus according to Embodiment 4 of the present invention.

  In the electrophotographic photosensitive member of the present invention (hereinafter also referred to as a photosensitive member), the outermost surface layer of the electrophotographic photosensitive member in which a photosensitive layer is provided on a conductive substrate is a specific particle, that is, polytetrafluoroethylene (PTFE) particles And the amount of a specific polymer containing a high boiling point solvent, that is, the residual amount of a high boiling point solvent derived from a dispersant containing a fluorine-containing copolymer and other high boiling point solvents is the residual solvent using thermal desorption gas chromatography of the outermost surface layer In the specific range with respect to the integrated strength of tetrahydrofuran-containing 2,6-di-t-butyl-4-methylphenol used as the main solvent in the coating liquid for forming the outermost surface layer in the analysis of the amount It is characterized by

  The photosensitive member according to the present invention is provided with a photosensitive layer on a conductive substrate, and the photosensitive layer may be of either single layer type or laminated type. In addition, a charge transport layer may be provided as the outermost surface layer, or a protective layer may be separately provided as the outermost surface layer. Further, the charge transport layer may be composed of a first charge transport layer and a second charge transport layer, and the second charge transport layer may be the outermost surface layer. In addition, it is possible to further stabilize electrically by using the undercoat layer.

The term "high-boiling point solvent" used in the present invention refers to a solvent for a charge transport layer coating solution, which is contained in a PTFE particle dispersant used for a charge transport layer coating solution, or 100 to 160 By solvents are meant having a boiling point between 0 ° C.
As such high boiling point solvents, for example, methyl isobutyl ketone, n-butyl acetate, n-butyl acetate, s-butyl acetate, pentyl acetate, isopentyl acetate, cyclohexanone, toluene, o-xylene, m-xylene and p-xylene, N, N -Dimethylformamide may be used alone or in combination of these solvents.

Moreover, as a specific polymer which said dispersion agent for PTFE particles contains, a fluorine-containing copolymer is mentioned.
As the above-mentioned fluorine-containing copolymer, a fluorine-based graft polymer having a matrix compatible side chain arranged in a fluorine-based main chain, for example, GF-400 manufactured by Toagosei Co., Ltd .; a fluorine-based segment and a compatible segment alternately arranged A block copolymerization type, for example, F-200 manufactured by NOF Corporation; an oligomer type in which a fluorine-based resin is suspended as a pendant from a compatible resin, for example, F-561 manufactured by Dainippon Ink and Chemicals, Inc. can be mentioned.
Therefore, examples of the dispersant for PTFE particles contained in the outermost surface layer of the electrophotographic photosensitive member according to the present invention include dispersants containing any of the above-mentioned fluorine-containing copolymer and the above-mentioned high boiling point solvent.

  The outermost surface layer of the electrophotographic photosensitive member according to the present invention is subjected to analysis by thermal desorption chromatography, and the residual amount of the high boiling point solvent contained in the PTFE particle dispersant contained in the outermost surface layer is measured . For this analysis, a section prepared by peeling and cutting the above outermost surface layer for the above analysis is provided as a sample.

  The outermost surface layer of the electrophotographic photosensitive member according to the present invention is a tetrahydrofuran used as a main solvent in the coating solution for the outermost surface layer in comparison of integrated intensity of analysis of the amount of residual solvent by thermal desorption gas chromatography using the above-mentioned material Characterized in that it comprises 10 to 70% of the integral strength ratio of the high-boiling point solvent in proportion to the integral strength of 2,6-di-t-butyl-4-methylphenol (butylated hydroxytoluene: BHT) containing THF) .

The ratio of the total of the high boiling point solvents contained in the outermost surface layer to the BHT integrated strength is preferably 10 to 40%, and more preferably 10 to 20%.
The heat treatment or the heat treatment for a long time such that the total of the content of the high-boiling point solvent to BHT is less than 10% when the electrophotographic photoreceptor outermost surface layer according to the present invention is prepared It is not preferable because it also causes the component deterioration of

  Further, when the drying conditions at the time of preparation of the outermost surface layer of the electrophotographic photosensitive member according to the present invention are the heat treatment and processing time at a temperature such that the total content of high boiling point solvent to BHT exceeds 70%, The surface layer is not sufficiently dried, and the high boiling point solvent remains in the outermost surface layer, the hardness of the outermost surface layer is not obtained, and trapping due to the remaining high boiling point solvent occurs, resulting in good electrical characteristics. It is not preferable because it can not be obtained.

By incorporating an appropriate amount of a dispersant having a boiling point of 100 to 160 ° C. and a fluorine-containing graft copolymer in a coating solution for the surface layer of a photosensitive layer containing tetrahydrofuran as a main solvent, polytetrafluoroethylene in a coating film It is possible to maintain good electrical characteristics as a photoreceptor while maintaining the dispersibility of ethylene particles.
An organic solvent having a boiling point of less than 100 ° C. is not suitable in terms of a good solvent and storage stability of the dispersant, resulting in the failure to obtain sufficient fine particle dispersibility.
Therefore, using a solvent having a boiling point of 100 to 160 ° C. as an auxiliary solvent and further using THF as a surface layer coating solution is more excellent in the dispersibility because the affinity between the above-mentioned dispersant and a high boiling point solvent is excellent. Preferred to hold
In addition, with respect to the use of a solvent having a boiling point higher than 160 ° C., since the boiling point is obviously higher than the substantial photosensitive member drying temperature, the residual amount of the solvent after drying is extremely large. The impact will be significantly worse.

  In order to keep the amount of the contained high boiling point solvent in a desired range, it is necessary to control the drying conditions after the application of the coating liquid or the original addition amount of the dispersant. That is, the formation of the photosensitive film by relatively high temperature drying or the loss of the dispersing agent ensures the desired integrated intensity ratio by analysis.

Although the details are not clear, the following is considered to be able to obtain the correlation between the definition of the high boiling point solvent amount according to the present invention and the stability of the electrical characteristics of the photoreceptor.
That is, it is presumed that the high boiling point solvent detected (desorbed) at 200 ° C. or lower set at the time of the analysis is contained in the photosensitive system with a certain cluster size.
On the other hand, in these solvents, it seems that there are other solvent components completely dissolved in the system as a monomolecular state. Therefore, it is presumed that the desorbed solvent molecular weight defined by the present invention, not the amount originally added to the system, contributes to the electrical stability of the photoreceptor.

  In the image forming apparatus according to the present invention, the electrophotographic photosensitive member, a charging unit for charging the electrophotographic photosensitive member, and an exposure unit for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image Developing means for developing the electrostatic latent image with toner to form a toner image, transfer means for transferring the toner image onto a recording material, and fixing the transferred toner image onto the recording material The image forming apparatus further comprises a cleaning unit that removes and recovers the toner remaining on the electrophotographic photosensitive member, and a charge removing unit that discharges the surface charge remaining on the electrophotographic photosensitive member. It is also good. The image forming apparatus of the present invention may be configured to include the electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a transfer unit.

  Hereinafter, embodiments and examples of the present invention will be specifically described with reference to FIGS. The embodiments and examples described below are merely specific examples of the present invention, and the present invention is not limited thereto.

Embodiment 1
FIG. 1 is a schematic cross-sectional view showing the configuration of the electrophotographic photosensitive member according to Embodiment 1 of the present invention.
The electrophotographic photosensitive member 1 (hereinafter also referred to as the photosensitive member 1) according to the first embodiment contains an undercoat layer 15 and a charge generation material on a cylindrical conductive substrate 11 made of a conductive material. It is a multi-layered photoreceptor comprising a photosensitive layer 14 in which a charge generation layer 12 and a charge transport layer 13 containing a charge transport material are laminated in this order.

Conductive Substrate The conductive substrate 11 not only functions as an electrode of the photosensitive member 1 but also functions as a layer disposed thereon, ie, a support member for the undercoat layer 15 and the photosensitive layer 14.
Although the shape of the conductive substrate 11 is cylindrical in the first embodiment, the shape of the conductive substrate 11 is not limited to this, and may be cylindrical, sheet-like or endless belt-like.

  The conductive material constituting the conductive substrate 11 includes, for example, conductive metals such as aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum and the like; or aluminum alloy etc. , Metal oxides such as tin oxide and indium oxide, and the like.

Also, without being limited to these metal materials, polymeric materials such as polyethylene terephthalate, nylon, polyester, polyoxymethylene or polystyrene, the above-mentioned metal foil laminated on the surface of hard paper or glass, etc .; It is also possible to use one deposited or coated or coated with a layer of a conductive compound such as a conductive polymer, tin oxide or indium oxide.
These conductive materials are processed into a predetermined shape and used.

  The surface of the conductive substrate 11 may be subjected to anodized film treatment, surface treatment with chemicals or hot water, coloring treatment, roughing of the surface, or the like, as needed, within the range not affecting image quality. You may process.

In an electrophotographic process using a laser as an exposure light source, the wavelengths of the laser light are uniform, so that the laser light reflected on the surface of the photosensitive member and the laser light reflected on the inside of the photosensitive member cause interference and interference due to this interference Stripes may appear on the image resulting in image defects.
However, by applying the above-described treatment to the surface of the conductive substrate 11, it is also possible to prevent an image defect due to the interference of the laser light having the same wavelength.

Subbing layer 15 (also referred to as intermediate layer)
When the undercoat layer 15 is not provided between the conductive substrate 11 and the photosensitive layer 14, the chargeability of the minute region is lowered due to the defect of the conductive substrate 11 or the photosensitive layer 14, and black spots and the like are produced. Image fogging may occur, resulting in significant image defects. By providing the undercoat layer 15, the injection of charges from the conductive substrate 11 to the photosensitive layer 14 can be prevented.

  Therefore, by providing the undercoating layer 15, it is possible to prevent the decrease in the chargeability of the photosensitive layer 14, to suppress the decrease in surface charge other than the portion to be erased by exposure, and to generate defects such as fogging in the image. Can be prevented.

Further, by providing the undercoating layer 15, it is possible to cover the unevenness of the surface of the conductive substrate 11 to obtain a uniform surface, so that the film forming property of the photosensitive layer 14 is enhanced and the conductive substrate 11 of the photosensitive layer 14 is formed. It is possible to suppress the peeling from the surface and to improve the adhesion between the conductive substrate 11 and the photosensitive layer 14.
For the undercoat layer 15, a resin layer or an alumite layer made of various resin materials is used.

  The resin material constituting the resin layer as the undercoat layer 15 is polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, silicone resin And resins such as polyvinyl butyral resin, polyvinyl pyrrolidone resin, polyacrylamide resin, and polyamide resin, and copolymer resins containing two or more of the repeating units constituting these resins.

  Other examples include casein, gelatin, polyvinyl alcohol, cellulose, nitrocellulose and ethyl cellulose.

Among these resins, polyamide resins are preferably used, and in particular, alcohol-soluble nylon resins are preferably used.
Preferred alcohol-soluble nylon resins include, for example, so-called nylons such as 6-nylon, 6,6-nylon, 6,10-nylon, 11-nylon, 2-nylon and 12-nylon, and N-alkoxymethyl-modified nylon and Resin which chemically modified nylon, etc. can be mentioned like N- alkoxy ethyl modified nylon.

  Then, in order to give the undercoat layer a charge control function, a filler which is metal oxide fine particles is added. Examples of such fillers include particles of titanium oxide, aluminum oxide, aluminum hydroxide and tin oxide. The particle size of the metal oxide is suitably about 0.01 to 0.3 μm, preferably about 0.02 to 0.1 μm.

The undercoat layer 15 is formed, for example, by dissolving or dispersing the above-described resin in a suitable solvent to prepare a coating solution for an intermediate layer, and applying the coating solution to the surface of the conductive substrate 11. Be done.
When the undercoat layer 15 contains particles such as the metal oxide fine particles, for example, metal oxide fine particles such as titanium oxide are dispersed in a resin solution obtained by dissolving the resin in an appropriate solvent. The undercoat layer 15 can be formed by preparing a coating liquid for undercoat layer and applying the coating liquid to the surface of the conductive substrate 11.

Water, various organic solvents, or a mixed solvent thereof is used as a solvent for the undercoat layer coating liquid. For example, water or an alcohol such as methanol, ethanol or butanol alone, or a mixture of water and alcohol, a mixture of two or more alcohols, acetone or dioxolane and the like, alcohol, a halogenated organic solvent such as dichloroethane, chloroform or trichloroethane and the like Mixed solvents are used.
Among these solvents, non-halogen based organic solvents are preferably used in consideration of global environment.

As a method of dispersing the particles in the resin solution, a general dispersion method using a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, a paint shaker or the like can be used.
In addition, a more stable dispersion coating liquid can be produced by utilizing a medialess type dispersion apparatus utilizing a very strong shear force generated by passing the above-mentioned dispersion liquid at ultra-high pressure into micro voids. It becomes possible.

Examples of the coating method for the undercoating layer coating liquid include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method.
Among these coating methods, in particular, the dip coating method forms a layer on the surface of the substrate by immersing the substrate in a coating tank filled with the coating liquid and then pulling it at a constant speed or a gradually changing speed. It is a method, is relatively easy, and is excellent in productivity and cost, so it is often used in the manufacture of an electrophotographic photosensitive member. In addition, in order to stabilize the dispersibility of a coating liquid, you may provide the coating liquid dispersion apparatus represented by the ultrasonic wave generation apparatus in the apparatus used for the dip coating method.

The thickness of the undercoat layer 15 is preferably 0.01 to 20 μm, and more preferably 0.05 to 10 μm.
When the film thickness of the undercoat layer 15 is thinner than 0.01 μm, it is not possible to cover the unevenness of the conductive substrate 11 to obtain uniform surface properties, and it does not substantially function as the undercoat layer 15 and it is conductive. It is not preferable because the chargeability of the photosensitive layer 14 is lowered because the charge injection from the porous substrate 11 to the photosensitive layer 14 can not be prevented.

If the film thickness of the undercoat layer 15 is more than 20 μm, the formation of the undercoat layer 15 by dip coating becomes difficult, and the photosensitive layer 14 can not be uniformly formed on the undercoat layer 15, and thus the photosensitive member Is not preferable because the sensitivity of the
Therefore, the preferable range of the film thickness of the undercoat layer 15 is preferably 0.01 to 20 μm.

Charge generation layer 12
The charge generation layer 12 contains, as a main component, a charge generation substance that generates charges by absorbing light.
Examples of the charge generating material include organic photoconductive materials including organic pigments and inorganic photoconductive materials including inorganic pigments.

Examples of the organic photoconductive material 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 pyrene quinone, phthalocyanine pigments such as metal phthalocyanine and metal free phthalocyanine, and organic photoconductive materials such as squalilium dyes, pyrylium salts and thiopyrylium salts, and triphenylmethane dyes.
In addition, examples of the above-mentioned inorganic photoconductive material include selenium and its alloy, arsenic-selenium, cadmium sulfide, zinc oxide, amorphous silicon and other inorganic photoconductors.

  Examples of the charge generating material include triphenylmethane dyes such as methyl violet, crystal violet, night blue and victoria blue, erythrosine, rhodamine B, rhodamine 3R, acridine dyes such as acridine orange and flapeocin, methylene blue and methylene It may be used in combination with sensitizing dyes such as thiazine dyes represented by green and the like, oxazine dyes represented by capri blue and meldola blue, cyanine dyes, styryl dyes, pyrylium salt dyes or thiopyrylium salt dyes.

As a method of forming the charge generation layer 12, a method of vacuum depositing the charge generation material on the surface of the conductive substrate 11, or a coating for charge generation layer obtained by dispersing the charge generation material in a suitable solvent A method of applying a processing solution to the surface of the conductive substrate 11 or the like is used.
Among these, a charge generation material is dispersed by a conventionally known method in a binder resin solution obtained by mixing a binder resin as a binder in a solvent to prepare a coating solution for charge generation layer. The method of apply | coating the obtained coating liquid on the surface of the electroconductive base 11 is used suitably. Hereinafter, this method will be described.

  Examples of the binder resin used for the charge generation layer 12 include polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, polyarylate resin And resins such as phenoxy resin, polyvinyl butyral resin, polyvinyl chloride resin and polyvinyl formal resin, and copolymer resins containing two or more of the repeating units constituting these resins.

Specific examples of the copolymer resin include, for example, insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, acrylonitrile-styrene copolymer resin, etc. be able to.
The binder resin is not limited to these, and a commonly used resin can be used as the binder resin. One of these resins may be used alone, or two or more thereof may be mixed and used.

  Examples of the solvent for the coating liquid for charge generation layer include halogenated hydrocarbons such as dichloromethane and dichloroethane, alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone or cyclohexanone, and esters such as ethyl acetate or butyl acetate , Ethers such as tetrahydrofuran or dioxane, alkyl ethers of ethylene glycol such as 1,2-dimethoxyethane, benzene, aromatic hydrocarbons such as toluene or xylene, or N, N-dimethylformamide or N, N-dimethyl An aprotic polar solvent such as acetamide is used.

  Among the above solvents, non-halogen based organic solvents are preferably used in consideration of global environment. The above solvents may be used alone or in combination of two or more.

In the charge generation layer 12 including the charge generation substance and the binder resin, the ratio W1 / W2 of the weight W1 of the charge generation substance to the weight W2 of the binder resin is 10/100 to 400/100. Is preferred.
When the ratio W1 / W2 is less than 10/100, the sensitivity of the photosensitive member 1 is likely to decrease.

Conversely, when the ratio W1 / W2 exceeds 400/100, not only the film strength of the charge generation layer 12 is reduced, but also the dispersibility of the charge generation material is reduced and coarse particles are increased. The surface charge of portions other than the portion to be reduced is reduced, and image defects, in particular, fogging of an image called black spots in which toner adheres to a white background and minute black spots are formed, are increased.
Therefore, the preferable range of the ratio W1 / W2 is preferably 10/100 to 400/100.

The charge generation material may be previously crushed by a grinder before being dispersed in the binder resin solution.
As a grinder used for a grinding process, a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic dispersion machine, etc. can be mentioned.
Moreover, as a disperser used when dispersing the charge generation material in the binder resin solution, a paint shaker, a ball mill, a sand mill and the like can be mentioned. As the dispersion condition at this time, an appropriate condition is selected so that mixing of impurities due to abrasion of the container used and members constituting the dispersing machine does not occur.

As a method of applying the coating liquid for charge generation layer, a spray method, a bar coat method, a roll coat method, a blade method, a ring method, a dip coating method and the like can be mentioned.
Among these coating methods, the optimum method can be selected in consideration of the physical properties of the coating, productivity, and the like.
Among these coating methods, the dip coating method described in the coating method of the undercoat layer is particularly preferable.

The film thickness of the charge generation layer 12 is preferably 0.05 to 5 μm, and more preferably 0.1 to 1 μm.
When the film thickness of the charge generation layer 12 is less than 0.05 μm, the charge generation efficiency by light absorption is reduced, and the sensitivity of the photosensitive member 1 is reduced.
Conversely, when the film thickness of the charge generation layer 12 exceeds 5 μm, the light absorption efficiency decreases, and charge transfer in the charge generation layer 12 becomes the rate-limiting step in the process of erasing the surface charge of the photosensitive layer 14. The sensitivity of the photosensitive member 1 is reduced.
Therefore, the preferable range of the film thickness of the charge generation layer 12 is preferably 0.05 to 5 μm.

Charge Transport Layer The charge transport layer 13 is provided on the charge generation layer 12. The charge transport layer 13 includes a charge transport material that receives the charge generated by the charge generation material contained in the charge generation layer 12 and transports the charge, and a binder resin that binds the charge transport material.

  Examples of the charge transport substance include enamine derivatives, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazones Compound, polycyclic aromatic compound, indole derivative, pyrazoline derivative, oxazolone derivative, benzimidazole derivative, quinazoline derivative, benzofuran derivative, acridine derivative, phenazine derivative, aminostilbene derivative, triarylamine derivative, triarylmethane derivative, phenylenediamine derivative And stilbene derivatives and benzidine derivatives.

As the binder resin constituting the charge transport layer 13, a resin containing polycarbonate as a main component, which is well known in the relevant field, is preferably selected because of its excellent transparency and printing durability.
In addition, as a second component, for example, vinyl polymer resins such as polymethyl methacrylate resin, polystyrene resin, polyvinyl chloride resin and the like, copolymer resins containing two or more of repeating units constituting them, and polyester resins And polyester carbonate resin, polysulfone resin, phenoxy resin, epoxy resin, silicone resin, polyarylate resin, polyamide resin, polyether resin, polyurethane resin, polyacrylamide resin and phenol resin.

Moreover, the thermosetting resin which partially bridge | crosslinked these resin is also mentioned.
These resins may be used alone, or a mixture of two or more may be used.
The above main component means that the weight% of the polycarbonate resin accounts for the highest proportion in the total binding resin constituting the charge transport layer, and more preferably in the range of 50 to 90 weight%. It means that.

The resin as the second component may be used in an amount of 10 to 50% by weight based on the total binder resin.
The ratio of the charge transport material to the binder resin in the charge transport layer is preferably in the range of 10/18 to 10/10 in weight ratio.

When the charge transport layer 13 is the outermost layer of the photoreceptor, filler particles can be added for the purpose of improving the abrasion resistance and the like of the transport layer.
Filler particles are roughly classified into organic filler particles and inorganic filler particles centering on metal oxides.
From the viewpoint of mechanical properties for improving the wear resistance of the charge transport layer 13, it is often advantageous to use a metal oxide having a relatively high hardness as the filler particle.

However, when the filler particles are added to the charge transport layer 13, the following requirements such as not to impair the electrical characteristics of the charge transport layer 13 are required of the filler particles.
That is, when using a filler particle in which the relative dielectric constant in the charge transport layer 13 is significantly larger than the average relative dielectric constant (.di-elect cons. It is considered that the dielectric properties become nonuniform to adversely affect the electrical characteristics.

Therefore, it is considered that filler particles having a relatively small relative dielectric constant can be suitably used for the charge transport layer without causing a great adverse effect on the electrical properties of the charge transport layer.
Therefore, as filler particles to be added to the charge transport layer 13, organic filler particles are generally more advantageous than metal oxides having a high dielectric constant.
In addition, in order to impart lubricity to the outermost layer of the photosensitive member, selection of a material such as fluorine particles is advantageous.

  Further, in order to minimize the adverse effect on light carriers and electrical carriers in the charge transport layer 13, it is preferable to use one having a small filler particle size. Specifically, filler particles having a median diameter (D50) of primary particles of 0.1 to 2 μm are preferable from the viewpoint of dispersion stability of a coating liquid containing the filler particles.

The addition amount of the filler particles is 1 to 40 wt%, preferably 1.5 to 35 wt%, with respect to the total weight of the charge transport material and the binder resin (solid content of the charge transport layer).
When the addition amount of the filler particles is less than 1 wt%, the resin does not function as a filler and the printing durability is not improved.
If it exceeds 40 wt%, the electrical characteristics of the photoreceptor deteriorate as a negative effect of the addition of insulating filler fine particles, sufficient image density can not be obtained, and image quality defects occur, which is a problem in practical use It becomes.

As a method of dispersing the filler particles, a general method using a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic dispersion machine, a paint shaker or the like can be used similarly to the oxide fine particles added to the undercoat layer. .
In addition, it is also possible to produce a more stable dispersion coating liquid by using a medialess type dispersing device utilizing a very strong shear force generated by passing the above-mentioned dispersion liquid at an ultra-high pressure into the microvoids. it can.

  In addition, various additives may be added to the charge transport layer 13 as necessary. That is, a plasticizer or a leveling agent may be added to the charge transport layer 13 in order to improve film forming property, flexibility or surface smoothness.

Examples of the plasticizer include dibasic acid esters such as phthalic acid esters, fatty acid esters, phosphoric acid esters, chlorinated paraffins and epoxy type plasticizers.
Moreover, as said leveling agent, a silicone type leveling agent etc. can be mentioned, for example.

  The charge transport layer 13 may be, for example, a charge transport material, a binder resin, the filler particles and, if necessary, the additive, in a suitable solvent, as in the case of forming the charge generation layer 12 by coating. It is formed by dissolving or dispersing to prepare a coating liquid for charge transport layer, and coating the obtained coating liquid on the charge generation layer 12.

  As a solvent for the coating liquid for charge transport layer, generally, for example, aromatic hydrocarbons such as benzene, toluene, xylene and monochlorobenzene, halogenated hydrocarbons such as dichloromethane and dichloroethane, tetrahydrofuran, dioxane and dimethoxymethyl ether And an aprotic polar solvent such as N, N-dimethylformamide. These solvents may be used alone or in combination of two or more.

If necessary, solvents such as alcohols, acetonitrile or methyl ethyl ketone may be further added to the above-mentioned solvents.
Among these solvents, non-halogen based organic solvents are preferably used in consideration of global environment.

  Among them, in the present invention, tetrahydrofuran (THF) is used as a main solvent of the coating liquid for charge transport layer. However, THF contains 0.05 wt% of 2,6-di-t-butyl-4-methylphenol (BHT) as an antioxidant in the solvent, and this BHT is thermally desorbed after charge transport layer formation. It becomes an internal standard substance at the time of residual amount measurement of the high boiling point solvent after photosensitive layer formation specified by gas chromatography.

  In the present invention, as a main solvent of the coating liquid for charge transport layer, a toluene-containing tetrahydrofuran solution of 0 to 45% by weight is preferable from the viewpoint of the temporal dispersion stability of the coating liquid.

  Thermal desorption gas chromatography is generally a widely used method for extracting and separating volatile and semivolatile compounds from various matrices. In the present invention, high-boiling point solvent components leading to deterioration of the properties are selectively extracted from the matrix of the photosensitive layer.

  Examples of the coating method for the charge transport layer coating liquid include a spray method, a bar coating method, a roll coating method, a blade method, a ring method and a dip coating method. Among these coating methods, in particular, the dip coating method is excellent in various points as described above, and therefore, can be used also when forming the charge transport layer 13.

The film thickness of the charge transport layer 13 is preferably 5 to 40 μm, and more preferably 10 to 30 μm.
If the film thickness of the charge transport layer 13 is less than 5 μm, the charge retention ability is reduced, and a clear image is difficult to obtain, which is not preferable.
When the film thickness of the charge transport layer 13 exceeds 40 μm, the resolution of the photosensitive member 1 is reduced.
Therefore, the preferable range of the film thickness of the charge transport layer 13 is 5 to 40 μm.

  Each layer of the photosensitive layer 14 is added with one or more kinds of sensitizers such as an electron accepting substance and a dye in order to improve sensitivity and to suppress residual potential increase and fatigue due to repeated use. It is also good.

  Examples of the electron accepting substance include acid anhydrides such as succinic anhydride, maleic anhydride, phthalic anhydride and 4-chloronaphthalic anhydride, cyano compounds such as tetracyanoethylene and terephthalmalononitrile, 4-nitrobenzaldehyde and the like Aldehydes, anthraquinones, anthraquinones such as 1-nitroanthraquinone, polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, or diphenoquinone compounds Electron-withdrawing materials, etc. can be used. Further, those obtained by polymerizing these electron-withdrawing materials can also be used.

As the dye, for example, organic photoconductive compounds such as xanthene dyes, thiazine dyes, triphenylmethane dyes, quinoline pigments or copper phthalocyanine can be used. These organic photoconductive compounds function as optical sensitizers.
Further, an antioxidant or a UV absorber may be added to each of the layers 12 and 13 of the photosensitive layer 14. In particular, it is preferable to add an antioxidant or a UV absorber to the charge transport layer 13, and the stability of the coating liquid when forming each layer by coating can be enhanced. Furthermore, it is particularly preferable to add an antioxidant to the charge transport layer 13. The addition of this antioxidant to the charge transport layer can reduce the deterioration of the photosensitive layer against oxidizing gases such as ozone and nitrogen oxides.

As said antioxidant, a phenol type compound, a hydroquinone type compound, a tocopherol type compound, an amine type compound etc. are mentioned. Among these, a hindered phenol derivative or a hindered amine derivative, or a mixture thereof is suitably used.
In addition, if necessary, a surface protective layer may be provided.

Embodiment 2
In the first embodiment described above, the form of the laminated type photosensitive layer in which the photosensitive layer 14 is formed of the charge generation layer 12 and the charge transport layer 13 has been described, but as shown in FIG. It may be in the form of a single layer, that is, a single-layer type photosensitive layer containing both of the generating material and the charge transport layer.
That is, the photosensitive member 1 is a cylindrical conductive substrate 11 made of a conductive material, and a photosensitive layer 14 which is a layer laminated on the outer peripheral surface of the conductive substrate 11 and contains a charge generating substance and a charge transporting substance. And may be formed by

Third Embodiment
Further, as shown in FIG. 3, the charge transport layer 13 may be formed of a plurality of layers.
That is, the charge transport layer is formed by laminating two layers including different charge transport layers 13A and 13B, and a polytetrafluoroethylene particle is added to the charge transport layer 13B on the outermost surface. That is, in FIG. 3, the charge transport layer 13 is composed of the first charge transport layer 13A and the second charge transport layer 13B, and the content of the charge transport substance in the first charge transport layer 13A and the second charge transport layer 13B. The second charge transport layer 13B is formed to contain polytetrafluoroethylene particles.
As described above, when the charge transport layer 13 is formed by laminating a plurality of layers, it is preferable that the layer on the surface side of the charge transport layer 13 contain polytetrafluoroethylene particles.

Fourth Embodiment
FIG. 4 is a schematic cross-sectional view showing the configuration of the image forming apparatus 30 according to the present invention.
The image forming apparatus according to the present invention is not limited to the configuration of the image forming apparatus shown in FIG. 4, and any type of monochrome or color electrophotography can be used as long as the photoreceptor according to the present invention can be used. It may be various printers, copiers, facsimiles, multifunction machines, etc. that use the process.
The configuration and the image forming operation of the laser printer 30 on which the photosensitive member 1 according to the first embodiment of the present invention is mounted will be described below with reference to FIG.
The laser printer 30 shown in FIG. 4 is one example of the image forming apparatus of the present invention, and the image forming apparatus of the present invention is not limited by the following description.

The laser printer 30, which is an image forming apparatus, includes a photosensitive member 1, a semiconductor laser 31, a rotary polygon mirror 32, an imaging lens 34, a mirror 35, a corona charger 36, which is a charging unit, a developing unit 37, which is a developing unit, and a transfer sheet. A cassette 38, a sheet feeding roller 39, a registration roller 40, a transfer charger 41 as a transfer means, a separation charger 42, a conveyance belt 43, a fixing device 44, a sheet discharge tray 45 and a cleaner 46 as a cleaning means.
The semiconductor laser 31, the rotating polygon mirror 32, the imaging lens 34 and the mirror 35 constitute an exposure unit 49.

  The photosensitive member 1 is mounted on the laser printer 30 so as to be rotatable in the direction of the arrow 47 by driving means (not shown). The laser beam 33 emitted from the semiconductor laser 31 is repeatedly scanned by the rotating polygon mirror 32 in the longitudinal direction (main scanning direction) with respect to the surface of the photosensitive member 1. The imaging lens 34 has an f-θ characteristic, and the laser beam 33 is reflected by the mirror 35 to form an image on the surface of the photosensitive member 1 for exposure. An electrostatic latent image corresponding to image information is formed on the surface of the photosensitive member 1 by scanning the laser beam 33 as described above and forming an image while rotating the photosensitive member 1.

The corona charger 36, the developing device 37, the transfer charger 41, the separation charger 42 and the cleaner 46 are provided in this order from the upstream side to the downstream side in the rotational direction of the photosensitive member 1 indicated by the arrow 47.
In addition, the corona charger 36 is provided on the upstream side in the rotational direction of the photosensitive member 1 with respect to the imaging point of the laser beam 33, and uniformly charges the surface of the photosensitive member 1. Therefore, when the laser beam 33 exposes the surface of the photosensitive member 1 uniformly charged, a difference occurs between the charge amount of the portion exposed by the laser beam 33 and the charge amount of the portion not exposed. An electrostatic latent image is formed.

  The developing unit 37 is provided downstream of the image forming point of the laser beam 33 in the rotational direction of the photosensitive member 1, supplies toner to the electrostatic latent image formed on the surface of the photosensitive member 1, and converts the electrostatic latent image into toner. Develop as an image. The transfer paper 48 accommodated in the transfer paper cassette 38 is taken out one by one from the transfer paper cassette by the paper feed roller 39 and given to the transfer charger 41 in synchronization with the exposure to the photosensitive member 1 by the registration roller 40. The toner image is transferred to the transfer paper 48 by the transfer charger 41. A separation charger 42 provided close to the transfer charger 41 separates the transfer sheet on which the toner image has been transferred from the photosensitive member 1 by discharging.

  The transfer paper 48 separated from the photosensitive member 1 is conveyed by the conveyance belt 43 to the fixing device 44, and the toner image is fixed by the fixing device 44. The transfer paper 48 on which the image is formed in this manner is discharged toward the discharge tray 45. Incidentally, after the transfer paper 48 is separated by the separation charger 42, in the photoreceptor 1 which continues to rotate, foreign matters such as toner and paper dust remaining on the surface thereof are cleaned by the cleaner 46. The photoreceptor 1 whose surface has been cleaned by the cleaner 46 is discharged by a discharge lamp (not shown) provided together with the cleaner 46, and is further rotated to repeat a series of image forming operations starting from the charging of the photoreceptor 1 described above. .

  Therefore, according to the present invention, there is provided an image forming apparatus comprising the electrophotographic photosensitive member according to the present invention, a charging unit, an exposure unit, a developing unit and a transfer unit.

  The image forming apparatus 30 according to the present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the spirit of the present invention. And can be easily understood from the description of the drawings.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following description contents.
Examples 1, 2, 4 and 6 are reference examples.

Example 1
Preparation of Intermediate Layer 3 parts by weight of titanium oxide (trade name: Thaibake TTO-D-1, manufactured by Ishihara Sangyo Co., Ltd.) and 2 parts by weight of a commercially available polyamide resin (trade name: Amilan CM 8000, manufactured by Toray Industries, Inc.) The resulting mixture was added to 25 parts by weight and dispersed for 8 hours with a paint shaker to prepare 3 kg of a coating liquid for forming an intermediate layer. The obtained coating solution for an intermediate layer was filled in a coating tank, and an aluminum drum-like support having a diameter of 30 mm and a length of 357 mm was immersed and pulled up as a conductive support to form an intermediate layer with a thickness of 1 μm.

Preparation of Charge Generation Layer Next, titanyl phthalocyanine 1 having an X-ray diffraction spectrum showing a main peak at 27.3 ° with Bragg angle (2θ ± 0.2 °) to X-ray of CuKα 1.541 Å as a charge generation material. 1 part by weight of butyral resin (trade name: S-Lec BM-2, manufactured by Sekisui Chemical Co., Ltd.) as binder resin and 98 parts by weight of methyl ethyl ketone are mixed and dispersed for 8 hours with a paint shaker to form a charge generation layer Three liters of the coating solution was prepared.
The obtained coating liquid for forming a charge generation layer is applied to the surface of the undercoat layer previously provided in the same manner as in the formation of the undercoat layer, and naturally dried to form a charge generation layer having a thickness of 0.3 μm. It formed.

As a charge transport material, the following formula:

100 parts by weight of a compound 1 (T2269: made by Tokyo Chemical Industry Co., Ltd.), 180 parts by weight of a polycarbonate resin (TS2050: made by Teijin Chemicals, Ltd.), Lubron L-2 (Daikin Industries, Ltd.) which is a polytetrafluoroethylene (PTFE) particle 30 parts by weight of a primary particle size of 200 to 300 nm, and GF-400 (manufactured by Toagosei Co., Ltd., solid content: solid content: 25% of fluorine-based graft polymer, 57% of methyl isobutyl ketone and n-acetic acid 2.4 parts by weight of butyl (18%) is mixed and dispersed in 817 parts by weight of tetrahydrofuran and 350 parts by weight of toluene as a solvent, that is, a 30% by weight solution of toluene in tetrahydrofuran, After preparation, wet emulsification and dispersion device Microfluidizer M-110 Microfluidi Using s manufactured device, and 5pass operations carried out under conditions of set pressure 100 MPa, the solid concentration of 21 wt% of the charge transport layer coating liquid 3Kg of surface layer coating for suspension were prepared.
The coating liquid for forming a charge transport layer was applied to the surface of the charge generation layer provided earlier by a dipping method, and dried at 130 ° C. for 1 hour to form a charge transport layer having a thickness of 28 μm. In this way, a multi-layered photosensitive member shown in FIG. 1 was produced.

  Hereinafter, the solid content concentration of the suspension liquid for surface layer coating in Examples and Comparative Examples is standardized to 21 wt% as in Example 1. Thereby, when it coats with the same film thickness, in this example, the amount of residual THF contained immediately after coating film formation, and the amount of 2, 6- di-t- butyl -4- methyl phenols (BHT) are It was considered to be a constant value.

Example 2
As in Example 1, an intermediate layer and a charge generation layer were formed. Thereafter, the procedure is carried out in the same manner as in Example 1 except that 934 parts by weight of tetrahydrofuran and 233 parts by weight of toluene, that is, a 24 wt% toluene-containing tetrahydrofuran solution is used as a solvent for the coating liquid for forming the charge transport layer. The photoreceptor of Example 2 was made.

Example 3
As in Example 1, an intermediate layer and a charge generation layer were formed. Thereafter, the same procedure as in Example 1 was carried out except that 1050 parts by weight of tetrahydrofuran and 117 parts by weight of toluene, that is, a 11% by weight solution of toluene in toluene was used as a solvent for the coating liquid for forming the charge transport layer. The photoreceptor of Example 3 was made.

Example 4
As in Example 1, an intermediate layer and a charge generation layer were formed. Thereafter, a photoreceptor of Example 4 was produced in the same manner as Example 1, except that only 1,167 parts by weight of tetrahydrofuran was used as a solvent for the charge transport layer forming coating solution.

Example 5
As in Example 1, an intermediate layer and a charge generation layer were formed. Thereafter, the same procedure as in Example 1 was carried out except that 1120 parts by weight of tetrahydrofuran and 47 parts by weight of toluene, that is, a 4 wt% toluene-containing tetrahydrofuran solution was used as a solvent for the coating liquid for forming the charge transport layer. The photoreceptor of Example 5 was made.

Example 6
As in Example 1, an intermediate layer and a charge generation layer were formed. Thereafter, the procedure is carried out in the same manner as in Example 1 except that 700 parts by weight of tetrahydrofuran and 467 parts by weight of toluene, that is, a 40 wt% toluene-containing tetrahydrofuran solution is used as a solvent for the coating liquid for forming the charge transport layer. The photoreceptor of Example 6 was made.

Comparative Example 1
A photoconductor was prepared in the same manner as in Example 1 except that the PTFE fine particles and the dispersant were not added to the charge transport layer.

Comparative example 2
As in Example 1, an intermediate layer and a charge generation layer were formed. Thereafter, a photoreceptor of Comparative Example 2 was produced in the same manner as in Example 1 except that 584 parts by weight of tetrahydrofuran and 583 parts by weight of toluene were used as solvents for the coating liquid for forming the charge transport layer.

Comparative example 3
As in Example 1, an intermediate layer and a charge generation layer were formed. Thereafter, the same charge transport layer forming coating solution was applied to the surface of the charge generation layer provided earlier by a dipping method, and dried at 110 ° C. for 1 hour to form a charge transport layer having a thickness of 28 μm.

Comparative example 4
As in Example 1, an intermediate layer and a charge generation layer were formed. Thereafter, the same charge transport layer-forming coating solution was applied to the surface of the charge generation layer provided earlier by a dipping method, and dried at 150 ° C. for 1 hour to form a charge transport layer having a thickness of 28 μm.

Comparative example 5
As in Example 4, an intermediate layer and a charge generation layer were formed. Thereafter, the same charge transport layer-forming coating solution was applied to the surface of the charge generation layer provided earlier by a dipping method, and dried at 150 ° C. for 1 hour to form a charge transport layer having a thickness of 28 μm.

Evaluation 1. Evaluation of residual amount of high-boiling point solvent The thermal desorption gas chromatography in the present invention selects thermal desorption conditions at or below the boiling point of BHT as a reference substance and above the boiling point of the high-boiling point solvent. That is, the surface layer peeled off from the photosensitive layer is used as a sample and thermally desorbed under the temperature rising condition set at 180 ° C. to 200 ° C. using EGA-PY 3030D manufactured by Frontier Lab, and then the liquid nitrogen temperature ( The residual high boiling point solvent and BHT were detected and analyzed by an Agilent Technologies 7890A GC system and a 5975C mass detection system which were trapped at 193 ° C. and arranged at 40 ° C. to 180 ° C. heating conditions arranged at the latter stage.

2. Evaluation of Electrical Properties: The photoconductors prepared in the example / comparative example are mounted on a test copying machine obtained by modifying a digital copying machine (trade name: MX-2600, manufactured by Sharp Corporation) to the obtained photoconductors, In order to measure the surface potential of the photosensitive member in the image forming process, a surface voltmeter (model 344 manufactured by TRECJAPAN) was provided to evaluate the electrical characteristics and the image quality of each photosensitive member. In addition, the light source used the laser beam of wavelength 780 nm.

  First, using the above-mentioned copying machine, the surface potential of the photosensitive member at the developing portion, specifically, the surface potential VL of the photosensitive member at the black background at the time of exposure was measured in order to check the sensitivity of the photosensitive member. These surface potentials VL were measured at an initial temperature of 25 ° C./50% RH (relative humidity) under normal temperature / normal humidity (abbreviated as “N / N”) environment and immediately after 100 k continuous copying.

The measurement results of the surface potential were evaluated by the following criteria.
VG: The initial VL is −100 V or more, and the fluctuation range ΔVL after 100 k actual shooting is 20 V or less.
G: The initial VL is −100 V or more, and the fluctuation range ΔVL after the actual shooting of 100 k sheets is more than 20 V and 40 V or less.
NB: The initial VL is −100 V or more, and the fluctuation range ΔVL after the actual shooting of 100 k sheets is more than 40 V and 70 V or less.
B: Initial VL is less than −100, or variation width ΔVL after 100 k actual copying is greater than 70 V.

3. Evaluation of image After photographing 100 k sheets of the photosensitive member, 10 sheets of plain images are printed, and the periodicity of black spot generation per hard copy A3 plate corresponds to the period of the photosensitive member and the visible diameter is 0. The number of black spots having a size of 4 mm or more was measured, and the results were judged based on the following criteria.
VG: Good for all hard copies when the frequency of occurrence of image defects is 3 or less per sheet.
G: The frequency of occurrence of image defects in all hard copies is 4 to 7 per sheet, but there is no problem in practical use.
NB: The occurrence frequency of image defects in all hard copies is 8 to 10 per sheet, but it is a practicable level.
B: There is a problem in practical use because there are one or more hard copies of which 11 or more of the image defects occur.

4. Evaluation of film thickness change The film thickness change before and after the actual copying evaluation and after 100k actual copying was measured using an eddy current film thickness meter (manufactured by Fisher), and the film thickness per 100 k of the photosensitive member on the copying machine It converted into quantity and evaluated.
VG: Improved level very good (film weight is less than 0.5 μm / 100 k rotation)
G: Improved level good (film weight is 0.5 or more and 0.8 μm / 100 k or less)
NB: Improvement is seen (film weight is 0.8 or more and less than 1.0 μm / 100 k times)
B: No improvement is observed (film thickness is 1.0 μm or more)

5. Coating liquid dispersion stability evaluation About the stability (dispersion stability) of the dispersion state of the tetrafluoroethylene resin particle in the coating liquid for charge transport layers used about Examples 1-6 and Comparative Examples 2-5, It evaluated using laser diffraction type particle size distribution measuring apparatus (Microtrac MT-3000II, Nikkiso Co., Ltd. make).
Specifically, after dispersion of each coating liquid, 40 ml was immediately transferred into a sample tube (50 ml) and the aggregate particle diameter (median diameter) of aggregate particles after storage for 3 months in a constant temperature storage (20 ° C.) D50) was measured.

And evaluation of dispersion stability was performed as follows using the aggregation particle diameter (particle diameter after stirring) measured here.
VG: very good (aggregated particle size <0.8 μm).
G: Good (0.8 ≦ aggregate particle size <1.5 μm).
NB: It is a level which can be practically used (1.5 凝集 agglomerated particle size <4.0 μm).
B: It can not be actually used (4.0 μm ≦ aggregated particle diameter).

6. Overall Evaluation The items from "2" to "4" above were comprehensively evaluated and classified as follows.
VG: G is good at all items, and it is very good without any problem in actual use.
G: Even if the item is bad, it is NB, and it is good without any problem in practical use.
NB: There are two or more NBs, but there is no B, and it can be used practically.
B: There is more than one item B, making actual use difficult.

From the above results, all of the photoreceptors obtained in Examples 1 to 6 are superior to the photoreceptors obtained in Comparative Examples 1 to 5 in the electrical characteristics and the overall judgment, and for a long period of time, It has been found that the characteristics are stable and excellent also for the abrasion of the surface of the photoreceptor.
That is, the photosensitive members obtained in Examples 1 to 6 in which the integrated intensity ratio of the high-boiling point solvent to the BHT in thermal desorption chromatography is in the range of 10 to 70% have stable electrical characteristics in the evaluation test. showed that. Further, among them, a more stable transition was shown in Example 2 in which the integrated intensity ratio to BHT is 40% or less, and further in Example 3 in which the integrated intensity ratio to 20% or less.

On the other hand, Comparative Examples 2 and 3 in which the total of the integrated intensity ratio of the solvent was more than 70% showed significant deterioration of the electrical characteristics. Further, in Comparative Examples 4 and 5 in which the total integrated strength of the solvent is less than 10% in the ratio to BHT, thermal deterioration of the components was caused by the influence of high drying temperature, and the electrical characteristics already deteriorated at the initial stage.
In addition, focusing on the dispersion stability as a coating liquid, it was confirmed that the dispersed particles can maintain the relatively stable small particle diameter depending on the amount of the high boiling point solvent added.

  The outermost surface layer of the electrophotographic photosensitive member according to the present invention contains the specific fine particles and the high boiling point solvent, and the remaining amount of the high boiling point solvent derived from the dispersant including the specific polymer in the specific range, thereby the abrasion resistance. It is possible to provide an electrophotographic photosensitive member which is electrically stable over a long period of time and an image forming apparatus provided with the photosensitive member.

Reference Signs List 1 electrophotographic photosensitive member 11 conductive substrate 12 charge generation layer 13, 13A, 13B charge transport layer 14 photosensitive layer 15 undercoat layer (intermediate layer)
30 Laser Printer (Image Forming Device)
Reference Signs List 31 semiconductor laser 32 rotary polygon mirror 34 imaging lens 35 mirror 36 corona charger 37 developing device 38 transfer paper cassette 39 sheet feeding roller 40 registration roller 41 transfer charger 42 separation charger 43 transport belt 44 fixing device 45 paper discharge tray 46 Cleaner 47 Arrow mark 48 Transfer paper 49 Exposure unit 50 Electrostatic discharger

Claims (5)

A method for producing an electrophotographic photosensitive member , comprising: a conductive layer; and 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.
Applying a coating solution for forming a charge transport layer on the surface of the charge generation layer and drying it to form the charge transport layer as the outermost surface layer of the electrophotographic photosensitive member,
The coating liquid for forming a charge transport layer is at least a charge transport substance ; a binder resin ; a polytetrafluoroethylene particle as a filler ; a dispersant for the polytetrafluoroethylene particle ; a boiling point of 100 to 160 ° C. derived from the dispersant. A suspension having a solid concentration of 21% by weight, which comprises a high boiling point solvent having : and a mixed solvent of tetrahydrofuran and toluene as a main solvent ,
The weight ratio of said tetrahydrofuran to toluene is from 9.0: 1 to 23.8: 1, and said tetrahydrofuran is 0.05% by weight of 2,6-di-t-butyl-4-4 as an antioxidant. Contains methylphenol,
When the amount of residual solvent at a thermal desorption temperature of 200 ° C. or lower is analyzed by thermal desorption gas chromatography using the thermal desorption gas chromatography, the integrated intensity ratio of the 2,6-di-t-butyl-4-methylphenol The integrated intensity ratio of the high-boiling point solvent and toluene to the above is 10 to 70%,
The film thickness of the said charge transport layer is 10-30 micrometers , The manufacturing method of the electrophotographic photosensitive member characterized by the above-mentioned. The method for producing an electrophotographic photosensitive member according to claim 1, wherein an integrated intensity ratio of the high boiling point solvent and toluene is 10 to 40%. The method for producing an electrophotographic photosensitive member according to claim 1 or 2, wherein an integrated intensity ratio of the high-boiling point solvent and toluene is 10 to 20%. The high boiling point solvent is selected from methyl isobutyl ketone, n-butyl acetate, n-butyl acetate, s-butyl acetate, pentyl acetate, isopentyl acetate, cyclohexanone, o-xylene, m-xylene, m-xylene, p-xylene and N, N-dimethylformamide The method for producing an electrophotographic photosensitive member according to any one of claims 1 to 3, which is at least one type. The method for producing an electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the high boiling point solvent is methyl isobutyl ketone and n-butyl acetate.

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