JP2015114349A - Electrophotographic photoreceptor, and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor that has excellent abrasion resistance and achieves both good electrical characteristics.SOLUTION: There is provided an electrophotographic photoreceptor having a lamination type photosensitive layer, laminated on a conductive substrate, in which at least a charge generating layer including a charge generating material and a charge transport layer including a charge transport material are laminated in this order, or having a single-layer type photosensitive layer including a charge generating material and charge transport material laminated on a conductive substrate, where the photoreceptor has an outermost surface layer including at least a charge transport material, binder resin, and fluororesin fine particles; the binder resin shows a surface free energy value in a range of 25 to 35 mJ/mmin a charge transport layer formed by using a coating liquid for forming a charge transport layer having excluded the fluororesin fine particles; and the charge generating material is crystalline titanyl phthalocyanine showing first and second strong peaks, respectively, at a Bragg angle of (2θ±0.2°)9.4° or 9.7° and showing diffraction peaks at least at 7.3°, 9.4°, 9.7°, and 27.3°.

Description

  The present invention relates to an electrophotographic photosensitive member and an image forming apparatus including the same. More specifically, the present invention is specified as a charge transport layer including a binder resin exhibiting a specific surface free energy after curing, a specific particle size and a specific ratio of tetrafluoroethylene resin fine particles, and a charge generation material. The present invention relates to an electrophotographic photosensitive member including the crystal type of the above and an electrophotographic image forming apparatus (also referred to as “image forming apparatus”) including the electrophotographic photosensitive member.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile machine, an image is formed by the following electrophotographic process.

  First, a photosensitive layer of an electrophotographic photosensitive member (also referred to as “photosensitive member”) provided in the image forming apparatus is uniformly charged to a predetermined potential by a charger. Next, the photosensitive member is exposed to light (for example, laser light) emitted from the exposure unit according to the image information, and an electrostatic latent image is formed on the photosensitive member. A developer is supplied from the developing means to the formed electrostatic latent image, and the electrostatic latent image is developed by attaching colored fine particles called toner, which is a component of the developer, to the surface of the photoreceptor, Visualize as a toner image. Further, the formed toner image is transferred from the surface of the photoreceptor to a transfer material such as recording paper by a transfer unit, and fixed by a fixing unit.

  However, not all the toner on the surface of the photoconductor is transferred to the recording paper and transferred during the transfer operation by the transfer means, but a part of the toner remains on the surface of the photoconductor. Further, the paper dust of the recording paper that comes into contact with the photoconductor during transfer may remain attached to the surface of the photoconductor. Such foreign matters such as residual toner and adhering paper dust on the surface of the photosensitive member adversely affect the quality of the formed image and are removed by the cleaning device.

  In recent years, cleaner-less technology has advanced, and there is also a method of removing the foreign matter by a system (so-called development and cleaning system) that collects residual toner by a cleaning function added to the developing unit without having an independent cleaning unit. . In this method, after the surface of the photosensitive member is cleaned, the surface of the photosensitive layer is neutralized by a static eliminator or the like so that the electrostatic latent image disappears.

  A photoreceptor 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 photoconductor include an inorganic photoconductor using an inorganic photoconductive material, and an organic photoconductor using an organic photoconductive material (organic photoconductor “Organic Photoconductor; OPC”). However, due to recent research and development, the sensitivity and durability of organic photoreceptors have improved, and organic photoreceptors are now often used.

  Further, in recent years, a laminated type photoreceptor in which a photosensitive layer is functionally separated into a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material has become mainstream. In many cases, a charge transport layer in which a charge transport material having a charge transport capability is dispersed in a molecular form in a binder resin is formed on a charge generation layer in which a charge generation material is deposited or dispersed in a binder resin. This is a negatively charged photosensitive member laminated. 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 has also been proposed. Further, in order to improve the print image quality, an undercoat layer is provided between the conductive substrate and the photosensitive layer.

  As a drawback of the organic photoconductor described above, surface wear due to slid printing of a cleaner or the like around the photoconductor due to the nature of the organic material. In order to overcome this drawback, efforts have been made to improve the mechanical properties of the material on the surface of the photoreceptor.

For example, Patent Documents 1 and 2 are cited as documents showing techniques for improving the mechanical properties of the material on the surface of the photoreceptor.
Patent Document 1 discloses that the protective layer contains filler particles.
Further, studies have been made to add fluorine-based particles (fluorine resin particles) to the surface as a filler (for example, Patent Document 2).

Fluorine-based particles are characterized by a high lubrication function derived from the material, as well as improving the mechanical properties of the photoconductor as a filler, as well as frictional force with the member that contacts the photoconductor process by providing lubricity This contributes to the improvement of printing durability on the surface of the photoreceptor by reducing the above.
On the other hand, when forming a laminated type photoreceptor, various crystal types have been proposed because the charge generation efficiency of the charge generation material or the charge injection efficiency into the charge transport layer affects the photoreceptor characteristics. (For example, Patent Document 3)

JP-A-1-172970 Japanese Patent No. 3148571 Japanese Patent Publication No. 6-29975

As described above, conventionally, when fluorine-based fine particles are added to the surface layer of the photoreceptor, good electrical characteristics cannot be obtained in initial sensitivity and repeated use.
SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photosensitive member that maintains both wear resistance and achieves good electrical characteristics.

  As a result of intensive studies to solve the above problems, the present inventors have found that the outermost surface layer of the photoreceptor is a binder resin exhibiting a specific surface free energy after the drying step, and a fluorine-based resin having a specific particle size and a specific ratio. It has been found that by using oxo titanyl phthalocyanine containing resin fine particles and having a specific crystal form as a charge generation material, an electrophotographic photoreceptor having both wear resistance and good electrical characteristics can be provided, and the present invention is completed. It came to.

However, according to the present invention, on the conductive substrate, the charge generating layer containing at least the charge generating material and the charge transporting layer containing the charge transporting material are laminated in this order, or on the conductive substrate. An electrophotographic photosensitive member in which a single-layer type photosensitive layer containing a charge generating material and a charge transporting material is laminated, wherein the outermost surface layer of the photosensitive member contains at least a charge transporting material, a binder resin, and fluororesin fine particles. ,
The binder resin has a surface free energy value in the range of 25 to 35 mJ / mm ² in the charge transport layer formed using the charge transport layer forming coating liquid excluding the fluorine resin fine particles,
The charge generating material exhibits first and second strong peaks at a Bragg angle (2θ ± 0.2 °) of 9.4 ° or 9.7 ° in the X-ray diffraction spectrum, respectively, and at least 7.3 ° , 9.4 °, 9.7 °, and 27.3 °, a crystalline form of titanyl phthalocyanine that exhibits diffraction peaks is provided.

According to the present invention, the fluororesin fine particles are tetrafluoroethylene resin fine particles,
(1) It is composed of primary particles having an average particle diameter of 0.1 to 0.5 μm and secondary particles that are aggregates of secondary particles that are aggregates of primary particles.
(2) included in the range of 1 to 30% by weight of the binder resin component in the outermost surface layer,
(3) including primary particles and secondary particles having a particle diameter of less than 1 μm in a content ratio of less than 80% by weight;
(4) The electrophotographic photosensitive member is provided, which contains secondary particles of 3 μm or more at a content ratio of 5% by weight or less.

  Further, according to the present invention, there is provided the electrophotographic photosensitive member, wherein the tetrafluoroethylene resin fine particles include primary particles having an average particle diameter of 0.2 to 0.4 μm.

  Further, according to the present invention, there is provided the electrophotographic photosensitive member, wherein the tetrafluoroethylene resin fine particles are contained in a range of 5 to 15% by weight of the binder resin component.

  In addition, according to the present invention, there is provided the electrophotographic photosensitive member, wherein the tetrafluoroethylene resin fine particles are contained in an amount of 8 to 12% by weight of the binder resin component.

In addition, according to the present invention, there is provided the electrophotographic photosensitive member, wherein the surface free energy value is in a range of 27 to 32 mJ / mm ² .

  Further, according to the present invention, there is provided the electrophotographic photosensitive member, wherein a laminated photosensitive layer is laminated on the conductive substrate via an undercoat layer.

  Further, according to the present invention, the multilayer photosensitive layer is formed of two charge transport layers having different charge transport substance concentrations, and the outermost surface charge transport layer contains tetrafluoroethylene resin fine particles. The electrophotographic photosensitive member is provided.

  Further, according to the present invention, the electrophotographic photosensitive member, 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; 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 for fixing the transferred toner image on the recording material An image forming apparatus including the means is provided.

  According to the present invention, an electrophotographic photosensitive member capable of producing an electrophotographic photosensitive member having both good electric characteristics and dispersibility, having excellent wear resistance, and having both good dispersibility and good electric characteristics. Can be provided.

It is a schematic diagram which shows the cross section of the electrophotographic photoreceptor which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the cross section of the electrophotographic photoreceptor which concerns on Embodiment 2 of this invention. It is a schematic diagram which shows the cross section of the electrophotographic photoreceptor which concerns on Embodiment 3 of this invention. It is a schematic diagram which shows the cross section of the structure of the image forming apparatus which concerns on Embodiment 4 of this invention.

The electrophotographic photoreceptor according to the present invention contains at least a specific binder resin and fluorine-based resin fine particles having a specific particle diameter, preferably tetrafluoroethylene resin fine particles in a specific ratio, has good dispersibility, and A charge generation material having a specific crystal type is contained in the charge generation layer.
Further, the electrophotographic photoreceptor according to the present invention (hereinafter sometimes simply referred to as “photoreceptor”) has a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material on a conductive substrate. It is a laminated type photoreceptor in which a photosensitive layer is formed by sequentially laminating.

Further, the laminated photoreceptor may be provided with a protective layer as an additional outermost layer. In this case, it is preferable that the protective layer contains the above-mentioned tetrafluoroethylene resin fine particles.
The laminated photoreceptor can be further electrically stabilized by using an undercoat layer.

  The image forming apparatus (electrophotographic image forming apparatus) of the present invention is configured to expose the electrophotographic photosensitive member, charging means for charging the electrophotographic photosensitive member, and electrostatically expose the charged electrophotographic photosensitive member. An exposure unit that forms a latent image; a developing unit that develops the electrostatic latent image with toner to form a toner image; a transfer unit that transfers the toner image onto a recording material; and the transferred toner image The image forming apparatus includes a fixing unit that fixes the recording material, and further includes a cleaning unit that removes and collects toner remaining on the electrophotographic photosensitive member, and a surface charge remaining on the electrophotographic photosensitive member. Neutralizing means. 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 described in detail with reference to FIGS. Note that 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 view showing a cross section of the electrophotographic photosensitive member according to the present exemplary embodiment. The electrophotographic photosensitive member 1 according to this exemplary embodiment includes a cylindrical conductive base 11 made of a conductive material, an undercoat layer (intermediate layer) 15 formed on the outer peripheral surface of the conductive base 11, and an undercoat. And a photosensitive layer 14 formed on the outer peripheral surface of the layer 15.
As shown in FIG. 1, the photosensitive layer 14 includes a charge generation layer 12 and a charge transport layer 13. The charge generation layer 12 is laminated on the outer peripheral surface of the undercoat layer 15 and contains a charge generation material. The charge transport layer 13 is laminated on the outer peripheral surface of the charge generation layer 12 and contains a charge transport material.
In the example of FIG. 1, the charge transport layer 13 among the layers constituting the photosensitive layer 14 corresponds to the surface layer of the photoreceptor 1.

Conductive substrate 11
The conductive substrate 11 serves as an electrode of the photoreceptor 1 and also functions as a support member for the layers (ie, the undercoat layer 15 and the photosensitive layer 14) disposed on the outside.
The shape of the conductive substrate 11 is cylindrical in the present embodiment, but is not limited to a cylindrical shape, and may be a columnar shape, a sheet shape, an endless belt shape, or the like.

  Examples of the conductive material constituting the conductive substrate 11 include a conductive metal such as aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum, or the conductive material. An alloy material of a conductive metal. Alternatively, as the conductive material, a conductive metal such as aluminum, tin oxide, gold, or indium oxide, or an alloy material or metal oxide of the conductive metal may be used.

In addition, the conductive material is obtained by laminating or vapor-depositing a metal foil made of the conductive metal on the surface of a polymer material (polyethylene terephthalate, nylon, polyester, polyoxymethylene, polystyrene, etc.), hard paper or glass. It is good.
Alternatively, a material obtained by depositing or applying a layer of a conductive compound such as a conductive polymer, tin oxide, or indium oxide on the surface of the polymer material, hard paper, or glass may be used as the conductive material. The conductive substrate 11 is formed by processing the above conductive material into a predetermined shape.

If necessary, the surface of the conductive substrate 11 is irregularly reflected within a range that does not affect the image quality, such as anodic oxide film treatment, surface treatment with chemicals or hot water, coloring treatment, or roughening the surface. It is preferable to perform the treatment.
In an electrophotographic process using a laser as an exposure light source, the wavelengths of the laser light are uniform, so the laser light reflected on the surface of the photoconductor and the laser light reflected inside the photoconductor cause interference, and the interference due to this interference occurs. Stripes may appear on the image and cause image defects. However, by performing the above-described treatment on the surface of the conductive substrate 11, it is possible to prevent image defects due to interference of laser light having the same wavelength.

Undercoat layer (intermediate layer) 15
When the undercoat layer 15 is not provided between the conductive substrate 11 and the photosensitive layer 14, the chargeability is reduced in a minute region due to defects in the conductive substrate 11 or the photosensitive layer 14, and black spots or the like are caused. Image fogging may occur, resulting in significant image defects.
On the other hand, when the undercoat layer 15 is provided, injection of charges from the conductive substrate 11 to the photosensitive layer 14 can be prevented. Therefore, it is possible to prevent the chargeability of the photosensitive layer 14 from being lowered, to suppress the reduction of the surface charge other than the portion to be erased by exposure, and to prevent the occurrence of defects such as fogging on the image.

  Further, by providing the undercoat layer 15, it is possible to cover the unevenness of the surface of the conductive substrate 11 and obtain a uniform surface, so that the film formability of the photosensitive layer 14 can be improved. Further, peeling of the photosensitive layer 14 from the conductive substrate 11 can be suppressed, and adhesion between the conductive substrate 11 and the photosensitive layer 14 can be improved.

  For the undercoat layer 15, a resin layer or an alumite layer made of various resin materials is used. As the resin material constituting the resin layer, polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, silicone resin, polyvinyl butyral resin, Examples thereof include resins such as polyvinyl pyrrolidone resin, polyacrylamide resin and polyamide resin, and copolymer resins containing two or more of repeating units constituting these resins. Further, casein, gelatin, polyvinyl alcohol, cellulose, nitrocellulose, ethylcellulose and the like are also included.

Among these resins, it is preferable to use a polyamide resin, and it is particularly preferable to use an alcohol-soluble nylon resin.
Preferred alcohol-soluble nylon resins include 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 Examples thereof include resins obtained by chemically modifying nylon such as N-alkoxyethyl-modified nylon.

  In order to give the undercoat layer 15 a charge adjusting function, a filler is added to the undercoat layer 15. As the filler added to the undercoat layer 15, metal oxide fine particles are applied. Examples thereof include particles such as titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide. The average particle diameter of the metal oxide is suitably 0.01 to 0.3 μm, preferably 0.02 to 0.1 μm.

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

  As the solvent for the coating solution for the undercoat layer, water, various organic solutions, or a mixed solution thereof is used. For example, a single solvent such as water, methanol, ethanol or butanol, a mixed solution of water and alcohols, a mixed solution of two or more alcohols, a mixed solution of acetone or dioxolane and alcohols, dichloroethane, chloroform or trichloroethane, etc. A mixed solvent of a halogen type organic solvent and alcohol is used. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.

  A general method using a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, a paint shaker, or the like is used as a method of dispersing the metal oxide fine particles in the resin solution (coating solution for the undercoat layer). it can. In addition, it is possible to produce a more stable dispersion coating liquid by using a media-less type dispersion device that uses a very strong shearing force that is generated by passing the dispersion liquid through ultra-high pressures in a minute gap. It becomes.

Examples of the coating method for the coating solution for the undercoat layer 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, the dip coating method is relatively simple and excellent in terms of productivity and cost, and is therefore often used when the undercoat layer 15 is formed.
The thickness of the undercoat layer 15 is preferably 0.01 to 20 μm, more preferably 0.05 to 10 μm.

  If the thickness of the undercoat layer 15 is less than 0.01 μm, the undercoat layer 15 does not substantially function as the undercoat layer 15, and it is impossible to obtain a uniform surface property by covering the unevenness of the conductive substrate 11. It becomes impossible to prevent the injection of charges from the photosensitive substrate 11 to the photosensitive layer 14 and the chargeability of the photosensitive layer 14 is lowered. In addition, when the thickness of the undercoat layer 15 is greater than 20 μm, it is difficult to form the undercoat layer 15 when the undercoat layer 15 is formed by a dip coating method. Since the photosensitive layer 14 cannot be formed uniformly, the sensitivity of the photoreceptor is lowered, which is not preferable. Therefore, it was determined that 0.01 to 20 μm was appropriate for the preferable range of the thickness of the undercoat layer 15.

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

  Examples of the organic photoconductive materials include azo pigments such as monoazo pigments, bisazo pigments and trisazo pigments, indigo pigments such as indigo and thioindigo, perylene pigments such as peryleneimide and perylene anhydride, anthraquinone and Organic photoconductive materials such as polycyclic quinone pigments such as pyrenequinone, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, squarylium dyes, pyrylium salts, thiopyrylium salts, and triphenylmethane dyes.

Examples of the inorganic photoconductive material include selenium, selenium alloy, arsenic-selenium, cadmium sulfide, zinc oxide, amorphous silicon, and other inorganic photoconductors.
However, the charge generation material in the present invention is preferably titanyl phthalocyanine. However, in the X-ray diffraction spectrum, the first and second strongest at a Bragg angle (2θ ± 0.2 °) of 9.4 ° or 9.7 °. A crystalline form of titanyl phthalocyanine, each showing a peak and showing diffraction peaks at least at 7.3 °, 9.4 °, 9.7 ° and 27.3 °, is achieved in combination with other components of the invention. From the viewpoint of the effect to be achieved, it is particularly preferable.

  Charge generation materials include triphenylmethane dyes represented by methyl violet, crystal violet, knight blue and Victoria blue, erythrosine, rhodamine B, rhodamine 3R, acridine dyes represented by acridine orange and frapeosin, methylene blue and methylene They may be used in combination with sensitizing dyes such as thiazine dyes typified by green, oxazine dyes typified by capri blue and meldra blue, cyanine dyes, styryl dyes, pyrylium salt dyes or thiopyrylium salt dyes.

As a method of forming the charge generation layer 12, the charge generation material is vacuum-deposited on the surface of the conductive substrate 11, or the charge generation layer is obtained by dispersing the charge generation material in a suitable solvent. A method of applying the liquid to the surface of the conductive substrate 11 is used.
In particular, it is obtained by dispersing a charge generating substance in a binder resin solution obtained by mixing a binder resin as a binder in a solvent by a conventionally known method to prepare a coating solution for a charge generating layer. A method of applying the applied coating solution (coating solution) to the surface of the conductive substrate 11 is preferably used. 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, and 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 repeating units constituting these resins.

Specific 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. be able to.
The binder resin is not limited to these, and a commonly used resin can be used as the binder resin. These resins may be used alone or in combination of two or more.

Examples of the solvent for the charge generation layer coating solution include halogenated hydrocarbons such as dichloromethane or dichloroethane; alcohols such as methanol and ethanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; Ethers such as tetrahydrofuran or dioxane; alkyl ethers of ethylene glycol such as 1,2-dimethoxyethane; aromatic hydrocarbons such as benzene, toluene or xylene; or N, N-dimethylformamide or N, N-dimethylacetamide An aprotic polar solvent such as is used.
Among the above solvents, non-halogen organic solvents are preferably used in consideration of the global environment. One of the above solvents may be used alone, or a mixed solvent of two or more may be used.

In the charge generation layer 12 including the charge generation material and the binder resin, the ratio W1 / W2 between the weight W1 of the charge generation material and the weight W2 of the binder resin is 10/100 (10/100). It is preferable that it is 400/100 (400/100).
When the ratio W1 / W2 is less than 10/100, the sensitivity of the photoreceptor 1 may be lowered.
On the other hand, when the ratio W1 / W2 exceeds 400/100, not only the film strength of the charge generation layer 12 decreases, but also the dispersibility of the charge generation material decreases and coarse particles increase. The surface charge other than the portion to be reduced is reduced, and image defects, particularly the fogging of images called black spots where toner adheres to a white background and minute black spots are formed may increase.
Therefore, it was determined that the preferable range of the ratio W1 / W2 is 10/100 to 400/100.

The charge generation material may be pulverized in advance by a pulverizer before being dispersed in the binder resin solution.
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.
Examples of the disperser used when dispersing the charge generating substance in the binder resin solution include a paint shaker, a ball mill, and a sand mill. As a dispersion condition at this time, it is preferable to select an appropriate condition so that impurities are not mixed due to wear of a container used and a member constituting the disperser.

Examples of the coating method for the charge generation 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 application methods, an optimum method can be selected in consideration of the physical properties and productivity of the application.
Among these coating methods, in particular, 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 is often used in the production of photoreceptors.
In addition, in order to stabilize the dispersibility of a coating liquid, the apparatus used for the dip coating method may be provided with a coating liquid dispersing apparatus represented by an ultrasonic generator.

The film thickness of the charge generation layer 12 is preferably 0.05 to 5 μm, more preferably 0.1 to 1 μm.
If the thickness of the charge generation layer 12 is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity of the photoreceptor 1 may be lowered.
On the contrary, when the film thickness of the charge generation layer 12 exceeds 5 μm, the charge transfer inside the charge generation layer 12 becomes a rate-determining step in the process of erasing the surface charge of the photosensitive layer 12, and the sensitivity of the photoreceptor 1 is lowered. Sometimes.
Therefore, the thickness of the charge generation layer 12 was determined to be 0.05 to 5 μm.

Charge transport layer 13
A charge transport layer 13 is provided on the outer peripheral surface of the charge generation layer 12. The charge transport layer 13 includes a charge transport material having an ability to accept and transport the charge generated by the charge generation material contained in the charge generation layer 12, and a binder resin that binds the charge transport material.
In addition, filler particles can be added to the charge transport layer 13 for the purpose of improving wear resistance and the like.
Furthermore, an antioxidant, a sensitizer, and various additives such as a plasticizer or a leveling agent can be added to the charge transport layer 13 as necessary.

  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 the film formability, flexibility, or surface smoothness. Examples of the plasticizer include dibasic acid esters such as phthalate esters, fatty acid esters, phosphate esters, chlorinated paraffins, and epoxy type plasticizers. Moreover, as said leveling agent, a silicone type leveling agent etc. can be mentioned, for example.

  Examples of the charge transport material 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, hydrazone compounds. , Polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, Examples thereof include stilbene derivatives and benzidine derivatives.

As the binder resin constituting the charge transport layer 13, a polycarbonate resin mainly composed of polycarbonate known in the art is suitably selected for reasons such as excellent transparency and printing durability.
In addition to the above polycarbonate resin, as the binder resin as the second component, for example, a vinyl polymer resin such as a polymethyl methacrylate resin, a polystyrene resin, a polyvinyl chloride resin, or two of repeating units constituting them. Copolymer resin containing two or more, or polyester resin, polyester carbonate resin, polysulfone resin, phenoxy resin, epoxy resin, silicone resin, polyarylate resin, polyamide resin, polyether resin, polyurethane resin, polyacrylamide resin and phenol resin Alternatively, a copolymer resin having a polycarbonate skeleton and a polydimethylsiloxane skeleton can be used.

Further, a thermosetting resin obtained by partially cross-linking these resins may be used.
These resins may be used alone, or a mixture of two or more kinds may be used.
The above-mentioned polycarbonate resin is the main component means that the weight percent of the polycarbonate resin in the total binder resin constituting the charge transport layer occupies the highest proportion, preferably 50 to 90 wt%. It means that it is in the range.
The binder resin as the second component is lower than the content of the polycarbonate resin with respect to the total weight of the binder resin constituting the charge transport layer 13, and is in the range of 10 to 50% by weight. It means a binder resin that can be used.

  The ratio of the charge transport material and the binder resin in the charge transport layer is preferably in the range of 10/10 to 10/18 by weight ratio.

The filler particles are roughly classified into organic filler particles and inorganic filler particles mainly composed of metal oxides, but have the following restrictions as basic requirements. That is, when the relative dielectric constant of the charge transport layer 13 becomes significantly large as εr> 10 as compared with the average relative dielectric constant (εr≈3) of the organic photoreceptor, the charge transport layer 13 is not uniform. Therefore, it is considered that the electrical characteristics are adversely affected, so that the relative dielectric constant of the charge transport layer 13 should be relatively small.
Considering this point, organic filler particles are more advantageous than metal oxides.
Furthermore, among organic filler particles, fluorine fine particles (fluorine resin fine particles) are excellent in lubricity.

Therefore, the present invention is characterized in that tetrafluoroethylene resin (PTFE: polytetrafluoroethylene) fine particles are mainly used as the fluorine-based particles that are filler particles added to the charge transport layer 13.
The tetrafluoroethylene resin fine particles are
(1) It is composed of primary particles having an average particle diameter of 0.1 to 0.5 μm and secondary particles that are aggregates of secondary particles that are aggregates of primary particles.
(2) included in the range of 1 to 30% by weight of the binder resin component of the charge transport layer,
(3) including primary particles and secondary particles having a particle diameter of less than 1 μm in a content ratio of less than 80% by weight;
(4) It contains secondary particles of 3 μm or more in a content ratio of 5% by weight or less.

  When the tetrafluoroethylene resin fine particles are added to the charge transport layer, the tetrafluoroethylene resin having a small particle diameter is used in order to minimize the adverse effects on light scattering and electrical carriers in the charge transport layer 13. It is preferable to use fine particles. Therefore, in the present invention, PTFE fine particles having an average primary particle diameter of 0.1 to 0.5 μm, more preferably 0.2 to 0.4 μm are preferably used.

When the average primary particle diameter of the PTFE fine particles is smaller than 0.1 μm, aggregation of the primary particles becomes remarkable and light scattering increases.
Further, when the average primary particle of the PTFE fine particles is larger than 0.5 μm, the light scattering by the primary particles increases accordingly.
Therefore, the average primary particle size of the PTFE fine particles was determined to be within a proper range of 0.1 to 0.5 μm.

  The tetrafluoroethylene resin fine particles are preferably contained in the range of 1 to 30% by weight of the binder resin component in the charge transport layer.

When the tetrafluoroethylene resin particles are contained in the range of 1 to 30% by weight, more preferably 5 to 15% by weight of the binder resin component in the charge transport layer, the printing durability is excellent and the Provided is a photoreceptor that can achieve both stabilization of characteristics.
When the content concentration of the tetrafluoroethylene resin fine particles in the charge transport layer is less than 1% by weight, the effect of improving the abrasion resistance of the photoreceptor by adding the tetrafluoroethylene resin fine particles is not observed.
In addition, when the content concentration of the tetrafluoroethylene resin fine particles in the charge transport layer is 30% by weight or more, the electrical characteristics of the photosensitive member are significantly deteriorated and cannot be used in actual use in the image forming apparatus.

  Further, as a method of dispersing the tetrafluoroethylene resin particles as filler particles, a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, a paint shaker, or the like is used in the same manner as the oxide fine particles added to the undercoat layer. The general method used can be used. In addition, it is possible to produce a more stable dispersion coating liquid by using a media-less type dispersion device that uses a very strong shearing force that is generated by passing the dispersion liquid through a micro gap at an ultrahigh pressure. It becomes.

  As in the case where the charge generation layer 12 is formed by coating, the charge transport layer 13 is formed by, for example, dissolving a charge transport material, a binder resin, the filler particles, and / or the additive in an appropriate solvent. It is formed by dispersing and preparing a coating liquid for forming a charge transport layer and coating the obtained coating liquid (coating liquid) on the outer peripheral surface of the charge generation layer 12.

  Examples of the solvent for the coating solution for forming the charge transport layer include aromatic hydrocarbons such as benzene, toluene, xylene and monochlorobenzene, halogenated hydrocarbons such as dichloromethane and dichloroethane, ethers such as tetrahydrofuran, dioxane and dimethoxymethyl ether, And aprotic polar solvents such as N, N-dimethylformamide. One of these solvents may be used alone, or two or more thereof may be mixed and used.

In addition, a solvent such as alcohols, acetonitrile, or methyl ethyl ketone can be further added to the above solvent as necessary. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.
Examples of the coating method for the charge transport layer forming coating solution 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, the dip coating method is particularly excellent in various respects as described above, and is often used when the charge transport layer 13 is formed.

The film thickness of the charge transport layer 13 is 5 to 40 μm, more preferably 10 to 30 μm.
If the thickness of the charge transport layer 13 is less than 5 μm, the charge retention ability is lowered, which is not preferable.
On the other hand, if the thickness of the charge transport layer 13 exceeds 40 μm, the resolution of the photoreceptor 1 is lowered, which is not preferable.
Therefore, the suitable range of the film thickness of the charge transport layer 13 was determined to be 5 to 40 μm.

Additives to photosensitive layer 14 Each layer of the photosensitive layer 14 (charge generation layer 12 and charge transport layer 13) has an electron accepting material in order to improve sensitivity and to suppress a rise in residual potential and fatigue due to repeated use. In addition, one or more sensitizers such as dyes may be added.
Examples of the electron acceptor include acid anhydrides such as succinic anhydride, maleic anhydride, phthalic anhydride, 4-chloronaphthalic anhydride, cyano compounds such as tetracyanoethylene and terephthalmalondinitrile, 4-nitrobenzaldehyde, and the like. Aldehydes, anthraquinones such as anthraquinone and 1-nitroanthraquinone, polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, and diphenoquinone compounds The electron-withdrawing material can be used. Moreover, what polymerized these electron-withdrawing materials can also be used.

As the dye, for example, an organic photoconductive compound such as xanthene dye, thiazine dye, triphenylmethane dye, quinoline pigment or copper phthalocyanine can be used. These organic photoconductive compounds function as optical sensitizers.
Further, an antioxidant or an ultraviolet absorber may be added to each layer of the photosensitive layer 14. In particular, it is preferable to add an antioxidant or an ultraviolet absorber to the charge transport layer 14b, and the stability of the coating solution when forming each layer by coating can be improved.

  Furthermore, the addition of an antioxidant to the charge transport layer 13 can reduce deterioration of the photosensitive layer with respect to an oxidizing gas such as ozone or nitrogen oxide. Examples of the antioxidant include phenol compounds, hydroquinone compounds, tocopherol compounds, and amine compounds. Among these, a hindered phenol derivative or a hindered amine derivative, or a mixture thereof is preferably used.

Embodiment 2
In the first embodiment, the mode in which the photosensitive layer 14 includes the charge generation layer 12 and the charge transport layer 13 has been described. However, the photosensitive layer 14 is a single layer as in the photoreceptor 1 shown in FIG. May be formed. That is, it is formed of 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 transport substance. Also good. In this case, the charge generating material can be added and dispersed in the charge transport layer forming coating solution according to the present invention to obtain a single layer type photosensitive layer coating solution.
In the configuration of FIG. 2, the entire photosensitive layer 14 is a surface layer of the photoreceptor 1, and the above-described tetrafluoroethylene resin fine particles are added to the photosensitive layer 14.

Embodiment 3
As shown in FIG. 3, a plurality of charge transport layers may be formed. 3 includes a conductive substrate 11 and a photosensitive layer 14 formed on the outer peripheral surface of the conductive substrate 11. The photosensitive layer 14 includes a charge generation layer 12 formed on the outer peripheral surface of the conductive substrate 11, a first charge transport layer 13A formed on the outer peripheral surface of the charge generation layer 12, and an outer peripheral surface of the first charge transport layer 13A. The second charge transport layer 13B is formed. 3 is formed so that the content of the charge transport material in the first charge transport layer 13A is different from the content of the second charge transport layer 13B. Further, in the configuration of FIG. 3, the second charge transport layer 13B corresponds to the outermost surface layer among the layers constituting the photosensitive layer 14, and the tetrafluoroethylene resin fine particles are compared with the second charge transport layer 13B. Is added.

  In addition, a protective layer is formed on the outer peripheral surface of the photosensitive layer, and one embodiment of the present invention can be applied to a photoreceptor having the protective layer as a surface layer. In this embodiment, it is preferable to add tetrafluoroethylene resin fine particles to the binder resin of the protective layer.

Surface Free Energy of Photoreceptor Surface free energy (γ) is often used as an index representing the surface wettability of the photoreceptor. In order to deteriorate wettability, that is, to improve surface repellency, a material having a low surface free energy is used. PTFE fine particles are typical and widely used. In addition, the γ value on the surface of the photosensitive layer can be lowered by mixing a component having a low surface free energy with the binder resin used on the surface of the photoreceptor (most of which is a charge transport layer).
For example, a repeating structure having a siloxane skeleton may be used as a copolymer. A copolymer binder resin containing a fluorinated ethylene skeleton may be used.
By changing the component ratio of these copolymers, the surface free energy on the surface of the formed photosensitive layer can be controlled.

Embodiment 4
Image Forming Apparatus Next, an electrophotographic image forming apparatus provided with the photoreceptor according to the present invention will be described.
FIG. 4 is a schematic cross-sectional view showing the inside of the image forming apparatus 30 of the present embodiment.
The image forming apparatus 30 is a laser printer. The image forming apparatus 30 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, a developing device 37, a transfer paper cassette 38, a paper feed roller 39, a registration roller 40, A transfer charger 41, a separation charger 42, a transport belt 43, a fixing device 44, a paper discharge tray 45, and a cleaner 46 are provided.

  The photoreceptor 1 is mounted on the image forming apparatus 30 so as to be rotatable in the direction of an arrow 47 by a driving unit (not shown). The laser beam 33 emitted from the semiconductor laser 31 is scanned by the rotary polygon mirror 32. The imaging lens 34 has f-θ characteristics, and reflects the laser beam 33 by the mirror 35 to form an image on the surface of the photoreceptor 1. As the photosensitive member 1 is rotated, the laser beam 33 is scanned and imaged as described above, and an electrostatic latent image corresponding to image information is formed on the surface of 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 rotation direction of the photosensitive member 1 indicated by an arrow 47. The corona charger 36 is provided upstream of the image forming point of the laser beam 33 in the rotation direction of the photoconductor 1 and uniformly charges the surface of the photoconductor 1. By irradiating (exposing) the laser beam 33 to the uniformly charged surface of the photosensitive member 1, a difference in charge amount occurs between the irradiated portion and other portions, and the above-described electrostatic latent image is formed. .

  The developing device 37 is provided on the downstream side in the rotation direction of the photosensitive member 1 with respect to the image forming point of the laser beam 33, and supplies toner to the electrostatic latent image formed on the surface of the photosensitive member 1. Develop as a toner image. The transfer paper 48 accommodated in the transfer paper cassette 38 is taken out one by one by a paper feed roller 39 and given to a transfer charger 41 by a registration roller 40. The toner image is transferred to the transfer paper 48 by the transfer charger 41. The separation charger 42 neutralizes the transfer paper on which the toner image is transferred and separates it from the photoreceptor 1.

  The transfer paper 48 separated from the photoreceptor 1 is conveyed to the fixing device 44 by the conveying belt 43, and an image is formed by fixing the toner image by the fixing device 44 and is discharged to the paper discharge tray 45. In addition, after the transfer paper 48 is separated by the separation charger 42, the photosensitive member 1 that continues to rotate is cleaned by a cleaner 46 of toner and paper dust remaining on the surface thereof. The cleaned portion of the photoreceptor 1 is neutralized by a static eliminator (static elimination lamp) 50. Such a series of image forming processes is repeated by the rotation of the photoreceptor 1.

  The image forming apparatus 30 is not limited to the configuration shown in FIG. 4 and may be either a monochrome printer or a color printer as long as it uses a photoconductor. In addition, the image forming apparatus 30 can be various printers, copiers, facsimiles, multi-function machines, and the like that use an electrophotographic process.

  Hereinafter, although this embodiment is described further in detail using an example, this embodiment is not limited to the following description.

Example 1
Preparation of undercoat layer (intermediate layer) 3 parts by weight of titanium oxide (trade name: Tybak TTO-D-1, manufactured by Ishihara Sangyo Co., Ltd.) and 2 parts of commercially available polyamide resin (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.) The mixture was mixed with 25 parts by weight of methyl alcohol, and the mixture was subjected to dispersion treatment for 8 hours with a paint shaker to prepare 3 kg of coating solution for forming an undercoat layer (the mixture after dispersion treatment was used as the coating solution). did). And the coating liquid was apply | coated to the electroconductive support body by the dip coating method. Specifically, the obtained coating solution is filled in a coating tank, and an aluminum drum-shaped support having a diameter of 30 mm and a length of 357 mm is immersed in the coating solution as a conductive support, and then pulled up, and the film thickness is reduced to 1 μm. A pulling layer (intermediate layer) was formed.

Preparation of charge generation layer As a charge generation material, the Bragg angle (2θ ± 0.2 °) with respect to X-ray of CuKα 1.541Å shows first and second strong peaks at 9.4 ° or 9.7 °, respectively. In addition, oxo titanyl phthalocyanine having diffraction peaks at 7.3 °, 9.4 °, 9.7 ° and 27.3 ° is used as a charge generation material, butyral resin (trade name: ESREC BM-2, Sekisui Chemical Co., Ltd.) Co., Ltd.) is a binder resin (binder resin). Then, 1 part by weight of the charge generation material and 1 part by weight of the binder resin are mixed with 98 parts by weight of methyl ethyl ketone, and the mixture is dispersed for 8 hours with a paint shaker to prepare 3 liters of coating solution for forming the charge generation layer. (The mixture after the dispersion treatment was used as a coating solution). Then, as in the case of forming the undercoat layer, a coating solution for forming a charge generation layer was applied to the surface of the undercoat layer by a dip coating method. That is, the obtained coating solution for forming the charge generation layer is filled in a coating tank, and the drum-like support with the undercoat layer formed is dipped in the coating solution, then pulled up, and naturally dried to obtain a charge having a thickness of 0.3 μm. A generation layer was formed.

Preparation of charge transport layer Add 0.12 parts by weight of GF-400 (Toagosei Co., Ltd.) as a particle dispersant to 6 parts by weight of tetrafluoropolyethylene fine particles (Lublon L2, Daikin Industries) having an average primary particle size of about 0.2 μm. Furthermore, as a charge transport layer binder, TS2040 (Teijin Chemicals) 55 parts by weight, and the following formula:
35 parts by weight of the compound 1 (T2269: manufactured by Tokyo Chemical Industry Co., Ltd., N, N, N ′, N ′,-tetrakis (4-methylphenyl) benzidine) was used as a charge transport material.

  Then, a suspension having a solid content of 21% by weight was prepared by mixing tetrahydrofuran as a solvent. Then, using a wet emulsifying dispersion device (NVL-AS160: manufactured by Yoshida Kikai Kogyo Co., Ltd.), a dispersion treatment was performed by performing a 5 pass operation under a setting pressure of 100 MPa. Thus, 3 kg of a coating liquid for forming a charge transport layer was prepared (the dispersion-treated liquid was used as the coating liquid).

And the coating liquid for charge transport layer formation was apply | coated to the charge generating layer surface by the dip coating method. That is, the obtained coating liquid for forming a charge transport layer is filled in a coating tank, the drum-like support on which the charge generation layer is formed is dipped in the coating liquid, pulled up, dried at 120 ° C. for 1 hour, and a film thickness of 28 μm. The charge transport layer was formed. In this manner, a photoreceptor having the structure shown in FIG. 1 was produced.
At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 41.6 mJ / mm ² .

Example 2
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a coating solution for forming a charge transport layer was prepared in the same manner as in Example 1 except that 8 parts by weight of tetrafluoroethylene resin fine particles and 0.16 part by weight of GF-400 (Toagosei) were added as a particle dispersant. Subsequently, a photoreceptor was prepared using the coating solution.

Example 3
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a coating liquid for forming a charge transport layer was prepared in the same manner as in Example 1 except that 10 parts by weight of tetrafluoroethylene resin fine particles and 0.2 part by weight of GF-400 (Toagosei) were added as a particle dispersant. Subsequently, a photoreceptor was prepared using the coating solution.

Example 4
In the same manner as in Example 3, an undercoat layer and a charge generation layer were prepared. Thereafter, perfluoroalkoxyethylene (PFA) particles (average primary particle size: 2 μ, MP101, manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) were used as fine particles for the charge transport layer instead of tetrafluoroethylene particles. A coating solution was prepared in the same manner as in Example 3 to prepare a photoreceptor.

Example 5
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a coating liquid for forming a charge transport layer was prepared in the same manner as in Example 1 except that 12 parts by weight of tetrafluoroethylene resin fine particles and 0.24 part by weight of GF-400 (Toagosei) were added as a particle dispersant. Subsequently, a photoreceptor was prepared using the coating solution.

Example 6
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a coating solution for forming a charge transport layer was prepared in the same manner as in Example 1 except that 14 parts by weight of tetrafluoroethylene resin fine particles and 0.28 part by weight of GF-400 (Toagosei) were added as a particle dispersant. Subsequently, a photoreceptor was prepared using the coating solution.

Example 7
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, as the charge transport layer binder resin, 49.5 parts by weight of TS2040 (Teijin Chemicals), low surface free energy (γ) polycarbonate resin: (copolymer having polycarbonate skeleton and polydimethylsiloxane skeleton, viscosity average molecular weight (Mv ): About 50,000) A coating solution for forming a charge transport layer was prepared in the same manner as in Example 3 except that 5.5 parts by weight were added, and then a photoreceptor was prepared using the coating solution.
At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 31.5 mJ / mm ² .

Example 8
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a charge transport layer forming coating solution was prepared in the same manner as in Example 3 except that 33 parts by weight of TS2040 (Teijin Kasei) and 22 parts by weight of the low γ polycarbonate resin were added as the charge transport layer binder resin. Next, a photoreceptor was prepared using the coating solution.
At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 28.2 mJ / mm ² .

Example 9
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a coating solution for forming a charge transport layer was formed in the same manner as in Example 3 except that 16.5 parts by weight of TS2040 (Teijin Chemicals) and 38.5 parts by weight of the above low γ polycarbonate resin were added as the charge transport layer binder resin. Then, a photoreceptor was prepared using the coating solution.
At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 25.9 mJ / mm ² .

Comparative Example 1
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, the tetrafluoroethylene fine particles and the dispersant were not added to the charge transport layer coating solution, and the charge transport layer coating solution was prepared by mixing and stirring with tetrahydrofuran as a solvent.

Comparative Example 2
As a material for charge transport layer, Bragg angles (2θ ± 0.2 °) with respect to X-ray of CuKα 1.541Å show diffraction peaks at 7.3 °, 9.4 °, 9.7 ° and 27.2 °. A photoconductor was prepared in the same manner as in Example 3 except that oxotitanylphthalocyanine having a maximum diffraction peak of 27.2 ° was used.

Comparative Example 3
As a material for the charge transport layer, Bragg angles (2θ ± 0.2 °) of CuKα 1.541５４ with respect to X-rays are 7.5 °, 12.3 °, 16.3 °, 25.3 ° and 28.7 °. A photoconductor was prepared in the same manner as in Example 3 except that oxo titanyl phthalocyanine having a diffraction peak at 28.7 ° and a peak at 28.7 ° being the maximum diffraction peak was used.

Evaluation of surface free energy in Examples and Comparative Examples Measurement of surface free energy on the surface of the photoconductor in a state not including the fluorine fine particles used in Examples 1 to 9 and Comparative Examples 1 to 3, and contact angle manufactured by Kyowa Interface Science Co., Ltd. It calculated using the meter.

Evaluation of actual film slip amount The photoconductor obtained in Examples 1 to 9 and Comparative Examples 1 to 3 was used as a test copying machine obtained by modifying a digital copying machine (trade name: MX-2600, manufactured by Sharp Corporation). A photoconductor was mounted. Then, a surface potential meter (manufactured by TREK JAPAN, mode 1344) was provided so that the surface potential of the photoreceptor in the image forming process could be measured. A laser light source having a wavelength of 780 mm was used as a light source for exposing the photosensitive member.

For each evaluation photoconductor drum, the amount of change in the photoconductor film thickness after 100,000 (100k) photo-taking (difference between the photo-sensitive photoconductor film thickness before 100,000 photo-taking and the photoconductor film thickness after 100,000 photo-taking) Was measured using an eddy current film thickness meter (Fischer), and the measured value was converted into the amount of film slip per 100,000 rotations of the photoreceptor. In other words, the amount of change was directly used as the amount of film slip. The film slip evaluation was performed as follows based on the film slip amount per 100,000 rotations of the photoreceptor.
VG: Very good (film slippage <0.8 μm).
G: Good (0.8 μm ≦ film slippage <1.0 μm).
NB: Slightly good (1.0 ≦ film slippage <2.0 μm)
B: Not good (2.0 μm <film slip amount).

Evaluation of electrical characteristics The electrical characteristics (sensitivity) of the photoreceptors of Examples 1 to 9 and Comparative Examples 1 to 3 were evaluated as follows.
The photoconductors produced in Examples 1 to 9 and Comparative Examples 1 to 3 were tested at normal temperature / normal using a test copier modified from the above digital copier (trade name: MX-2600, manufactured by Sharp Corporation). In a wet (N / N) environment, the surface potential VL of the initial photoreceptor (before printing) and the surface potential VL of the photoreceptor after continuous printing of 100,000 sheets were measured. In the present embodiment, the N / N environment indicates 25 ° C. and 50% RH (relative humidity). Further, the surface potential VL indicates the surface potential of the photosensitive member at the black background at the time of exposure, that is, the surface potential of the photosensitive member at the developing portion.

Next, for Examples 1 to 9 and Comparative Examples 1 to 7, a value ΔVL obtained by subtracting the initial surface potential VL from the surface potential VL after continuous printing of 100,000 sheets was calculated. Then, the electrical characteristics of the photoconductor were evaluated as follows.
VG: Very good (0 ≦ ΔVL <50).
G: Good (50 ≦ ΔVL <100).
NB: No problem in actual use (100 ≦ ΔVL <150).
B: Actual use is not possible (150 ≦ ΔVL).

Image evaluation after 100k images were actually performed Image evaluation after 100,000 images were actually performed on the photoreceptors of Examples 1 to 9 and Comparative Examples 1 to 3 was described below.
After the above N / N environment shooting, black and white images were printed on each photoconductor to evaluate the degree of occurrence of image defects.
VG: Good density level with no black spots or white spots.
G: Level at which some black spots or white spots are not a problem.
NB: Black spots and white spots are observed, but the density fluctuation is small and the level can be actually used.
B: Many black spots and white spots occur, or the density fluctuation is so large that it cannot be used.

Comprehensive evaluation In consideration of the evaluation results of the actual film slip amount, the electrical characteristics, and the image evaluation, a comprehensive determination was made based on the following judgment.
VG: Very good (two or more of the above three types of individual determinations are VG and the remaining G).
G: Good (all three of the above three individual determinations are G, or two are G or more and one is NB).
NB: Actually usable (one of the above three types of individual determination is G, the remaining NB)
B: Actual use is not possible (including one or more B among the above three types of individual determination).

  As shown above, in the case where fluorine fine particles are introduced into the outermost surface layer of the photoconductor, when the oxotitanyl phthalocyanine having a specific crystal type is used as a charge generating material, the fluorine fine particles It has been found that a long life photoreceptor can be realized by improving the abrasion resistance by the addition and obtaining stable electric characteristics by the charge generation layer.

  In the charge generation layer, the oxotitanyl phthalocyanine molecule has a form in which planar molecules are stacked. When the diffraction pattern corresponds to the oxotitanyl phthalocyanine molecule, the peak at 9.4 ° corresponds to the spacing of the molecules on the plane, and 27 The 2 ° peak corresponds to the stacking direction of the molecules. Therefore, although details are not known, the fact that the one with a strong peak at 9.4 ° is good is that the crystal grains in which planar molecules are arranged more preferentially promote better charge generation. It seems that it will be. In other words, at the interface between the charge generation layer and the charge transport layer where the fine fluorine particles are present, qualitatively, the direction in which the molecular planes are aligned is more advantageous for charge generation than the alignment in the stacking direction.

  The present invention can be used for an electrophotographic photosensitive member used in an image forming apparatus such as an electrophotographic printer, a copying machine, a multifunction machine, and a facsimile.

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 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)
DESCRIPTION OF SYMBOLS 31 Semiconductor laser 32 Rotating polygon mirror 33 Laser beam 34 Imaging lens 35 Mirror 36 Corona charger 37 Developer 38 Transfer paper cassette 39 Paper feed roller 40 Registration roller 41 Transfer charger 42 Separation charger 43 Conveyor belt 44 Fixer 45 Exhaust Paper tray 46 Cleaner 47 Arrow 48 Transfer paper 49 Exposure means 50 Static eliminator

Further, according to the present invention, the fluorine resin particles is a tetrafluoroethylene resin fine particles,
(1) is composed of a primary particle having an average particle diameter of 0.1 to 0.5 [mu] m, secondary particle Ru aggregates der of the primary particles,
(2) included in the range of 1 to 30% by weight of the binder resin component in the outermost surface layer,
(3) including primary particles and secondary particles having a particle diameter of less than 1 μm in a content ratio of less than 80% by weight;
(4) The electrophotographic photosensitive member is provided, which contains secondary particles of 3 μm or more at a content ratio of 5% by weight or less.

Therefore, the present invention is characterized in that tetrafluoroethylene resin (PTFE: polytetrafluoroethylene) fine particles are mainly used as the fluorine-based particles that are filler particles added to the charge transport layer 13.
The tetrafluoroethylene resin fine particles are
(1) is composed of a primary particle having an average particle diameter of 0.1 to 0.5 [mu] m, secondary particle Ru aggregates der of the primary particles,
(2) included in the range of 1 to 30% by weight of the binder resin component of the charge transport layer,
(3) including primary particles and secondary particles having a particle diameter of less than 1 μm in a content ratio of less than 80% by weight;
(4) It is characterized by containing secondary particles of 3 μm or more at a content ratio of 5% by weight or less .

Claims (9)

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 on a conductive substrate, or a charge generation material and a charge transport material on a conductive substrate. An electrophotographic photosensitive member in which a single-layer type photosensitive layer is laminated, wherein the outermost surface layer of the photosensitive member includes at least a charge transport material, a binder resin, and fluororesin fine particles,
The binder resin has a surface free energy value in the range of 25 to 35 mJ / mm ² in the charge transport layer formed using the charge transport layer forming coating liquid excluding the fluorine resin fine particles,
The charge generating material exhibits first and second strong peaks at a Bragg angle (2θ ± 0.2 °) of 9.4 ° or 9.7 ° in the X-ray diffraction spectrum, respectively, and at least 7.3 ° An electrophotographic photoreceptor characterized by being a crystalline titanyl phthalocyanine having diffraction peaks at 9.4 °, 9.7 ° and 27.3 °. The fluorine resin fine particles are tetrafluoroethylene resin fine particles,
(1) It is composed of primary particles having an average particle diameter of 0.1 to 0.5 μm and secondary particles that are aggregates of secondary particles that are aggregates of primary particles.
(2) included in the range of 1 to 30% by weight of the binder resin component in the outermost surface layer,
(3) including primary particles and secondary particles having a particle diameter of less than 1 μm in a content ratio of less than 80% by weight;
(4) The electrophotographic photosensitive member according to claim 1, comprising secondary particles having a content of 5% by weight or less and 3 μm or more.   The electrophotographic photosensitive member according to claim 1, wherein the tetrafluoroethylene resin fine particles include primary particles having an average particle diameter of 0.2 to 0.4 μm.   The electrophotographic photosensitive member according to claim 1, wherein the tetrafluoroethylene resin fine particles are contained in a range of 5 to 15 wt% of the binder resin component.   The electrophotographic photosensitive member according to claim 1, wherein the tetrafluoroethylene resin fine particles are contained in an amount of 8 to 12% by weight of the binder resin component. The electrophotographic photosensitive member according to claim 1, wherein the surface free energy value is in a range of 27 to 32 mJ / mm ² .   The electrophotographic photosensitive member according to claim 1, wherein a laminated photosensitive layer is laminated on the conductive substrate via an undercoat layer.   The multilayer photosensitive layer is formed of two charge transport layers having different charge transport substance concentrations, and the outermost charge transport layer contains tetrafluoroethylene resin fine particles. The electrophotographic photosensitive member according to any one of the above.   9. The electrophotographic photosensitive member according to claim 1; a charging unit that charges the electrophotographic photosensitive member; and the charged electrophotographic photosensitive member is exposed to form an electrostatic latent image. An exposure unit; a developing unit that develops the electrostatic latent image with toner to form a toner image; a transfer unit that transfers the toner image onto a recording material; and the transferred toner image on the recording material. An image forming apparatus including fixing means for fixing.