Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

The present invention provides an electrophotographic photoreceptor with high pressure resistance and low environmental sensitivity differences, a process cartridge equipped with the electrophotographic photoreceptor, and an image forming apparatus. [Solution] The electrophotographic photoreceptor comprises a conductive substrate, an intermediate layer provided on the conductive substrate, and a photosensitive layer provided on the intermediate layer, wherein the intermediate layer contains titanium dioxide that has not been surface-treated with an inorganic material and an intermediate layer resin, and the titanium dioxide content is 1.3 parts by mass or more and 1.7 parts by mass or less per 1.0 part by mass of the intermediate layer resin.

Description

Technical Field

[0001] The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an image forming apparatus.

Background Art

[0002] An electrophotographic photosensitive member is used as an image carrier in an electrophotographic image forming apparatus (e.g., a printer or a multifunction peripheral). The electrophotographic photosensitive member includes a conductive substrate and a photosensitive layer. In the case of a laminated electrophotographic photosensitive member, the photosensitive layer includes a charge generation layer and a charge transport layer. An intermediate layer may be provided between the conductive substrate and the photosensitive layer.

[0003] In recent years, particularly, cost reduction of image forming apparatuses has been desired. For cost reduction, it is necessary to design the photosensitive member at a low cost. Therefore, the photosensitive layer is thinned to achieve cost reduction. For example, Patent Document 1 describes an electrophotographic photosensitive member that has good electrical characteristics and enables thinning of the charge transport layer by using a predetermined triarylamine dimer compound in the photosensitive layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the photosensitive layer is thinned, the withstand voltage characteristics (hereinafter referred to as withstand voltage property) deteriorate. In order to suppress the deterioration of the withstand voltage property, it is effective to increase the electrical resistance by reducing the ratio of the content of conductive fine particles to the content of resin in the intermediate layer. However, in this case, particularly, the sensitivity difference due to environmental differences (hereinafter referred to as environmental sensitivity difference) becomes large, and image defects such as the image being faint in a low temperature and low humidity environment and the image being dark in a high temperature and high humidity environment may occur.

[0006] In view of the above circumstances, the object of the present invention is to provide an electrophotographic photoreceptor that has high pressure resistance and low environmental sensitivity differences, a process cartridge equipped with the electrophotographic photoreceptor, and an image forming apparatus. [Means for solving the problem]

[0007] To achieve the above objective, an electrophotographic photoreceptor according to one embodiment of the present invention comprises a conductive substrate, an intermediate layer provided on the conductive substrate, and a photosensitive layer provided on the intermediate layer. The above-mentioned intermediate layer includes titanium oxide that has not been surface-treated with an inorganic material, and an intermediate layer resin. The titanium dioxide content is 1.3 parts by mass or more and 1.7 parts by mass or less per 1.0 part by mass of the intermediate layer resin.

[0008] The electrophotographic photoreceptor described above, by including titanium oxide and a suitable resin in an appropriate ratio in its intermediate layer, can improve its electrical properties, increase its electrical resistance, and suppress environmental fluctuations. This makes it possible to reduce environmental sensitivity differences while ensuring good electrical properties and high voltage resistance.

[0009] The resin for the intermediate layer may be a polyamide resin.

[0010] The thickness of the above-mentioned intermediate layer may be 1.5 μm or more and 3.5 μm or less.

[0011] The titanium dioxide content may be 1.4 parts by mass or more and 1.6 parts by mass or less per 1.0 part by mass of the intermediate layer resin.

[0012] A process cartridge according to one embodiment of the present invention comprises at least one selected from the group consisting of a charging device, an exposure device, a developing device, a transfer device, a cleaning member, a rubbing roller, and a static elimination device, and the electrophotographic photoreceptor.

[0013] An image forming apparatus according to an embodiment of the present invention includes an image carrier, a charging device, an exposure device, a developing device, a transfer device, a cleaning member, and a charge removing device. The charging device charges the surface of the image carrier. The exposure device exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier. The developing device supplies toner to the surface of the image carrier and develops the electrostatic latent image as a toner image. The transfer device transfers the toner image from the image carrier to a transfer medium. The cleaning member cleans the surface of the image carrier. The charge removing device removes the charge from the surface of the image carrier. The image carrier is the electrophotographic photoreceptor.

[0014] The charging device may be a charging roller.

[0015] The developing device may adopt a two-component development system.

Advantages of the Invention

[0016] As described above, according to the present invention, it is possible to provide an electrophotographic photoreceptor having high pressure resistance and a small environmental sensitivity difference, a process cartridge including the electrophotographic photoreceptor, and an image forming apparatus.

Brief Description of the Drawings

[0017] [Figure 1] FIG. is a partial cross-sectional view of a laminated electrophotographic photoreceptor which is an example of the electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 2] FIG. is a partial cross-sectional view of a laminated electrophotographic photoreceptor which is an example of the electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 3] FIG. is a partial cross-sectional view of a single-layer electrophotographic photoreceptor which is an example of the electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 4]It is a diagram showing an example of an image forming apparatus according to a second embodiment of the present invention. [Figure 5] It is a diagram showing an example of the configuration of a developing device shown in FIG. 4.

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0019] First, the terms used in this specification will be explained. The number-average primary particle diameter is the number-average value of the equivalent circle diameter (Heywood diameter: the diameter of a circle having the same area as the projected area of the primary particle) of the primary particles measured using a scanning electron microscope, unless otherwise specified. The number-average primary particle diameter is, for example, the number-average value of the equivalent circle diameters of 100 primary particles. In some cases, the compound and its derivatives are comprehensively referred to by adding "system" after the compound name. Also, when "system" is added after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Also, "general formula" and "chemical formula" are collectively referred to as "formula". Each component described in this specification may be used alone or in combination of two or more, unless otherwise specified. The terms used in this specification have been explained above.

[0020] [First Embodiment: Electrophotographic Photoconductor] (Overall Configuration) Hereinafter, an electrophotographic photoconductor (hereinafter sometimes referred to as a photoconductor) according to a first embodiment of the present invention will be described. The photoconductor according to this embodiment includes a conductive substrate, an intermediate layer provided on the conductive substrate, and a photosensitive layer provided on the intermediate layer. The intermediate layer includes titanium oxide that has not been surface-treated with an inorganic material and a resin used for the intermediate layer (resin for intermediate layer). The content of the titanium oxide is 1.3 parts by mass or more and 1.7 parts by mass or less with respect to 1.0 part by mass of the resin for intermediate layer.

[0021] The photoreceptor according to this embodiment, by having the above configuration, can reduce the difference in environmental sensitivity while ensuring good electrical characteristics and high voltage resistance. The reason for this is presumed to be as follows.

[0022] Firstly, by ensuring a certain level of titanium dioxide content in the intermediate layer, the electrical properties (sensitivity characteristics) can be improved. Titanium dioxide tends to provide better sensitivity characteristics compared to other inorganic particles (such as metal oxides). If the titanium dioxide content is too low, good sensitivity characteristics cannot be obtained, so it is necessary to include a certain amount or more of titanium dioxide in the intermediate layer. Therefore, in the photoreceptor according to this embodiment, the titanium dioxide content is set to 1.3 parts by mass or more per 1.0 part by mass of the intermediate layer resin. This ensures good electrical properties.

[0023] Secondly, the pressure resistance can be increased by keeping the titanium dioxide content in the intermediate layer below a certain level. For example, when the photosensitive layer is made thin, the pressure resistance deteriorates. To improve pressure resistance, it is effective to increase the electrical resistance by reducing the content of titanium dioxide, which is a conductive fine particle. Therefore, in the photosensitive material according to this embodiment, the titanium dioxide content is set to 1.7 parts by mass or less per 1.0 part by mass of polyamide resin. This ensures high pressure resistance.

[0024] Thirdly, by not surface-treating the titanium dioxide with an inorganic material, it is possible to ensure high pressure resistance while reducing the difference in environmental sensitivity. Titanium dioxide that has not been surface-treated with an inorganic material does not contain conductive surface treatment agents, so its electrical resistance increases and it becomes less susceptible to environmental fluctuations. By including such titanium dioxide in the intermediate layer, it is possible to increase the electrical resistance while maintaining a state where the difference in environmental sensitivity is small. Therefore, in the photoreceptor according to this embodiment, titanium dioxide that has not been surface-treated with an inorganic material is included in the intermediate layer. This makes it possible to ensure high pressure resistance while reducing the difference in environmental sensitivity.

[0025] Therefore, by having the above configuration, the photoreceptor according to this embodiment can reduce the difference in environmental sensitivity while ensuring good electrical characteristics and high voltage resistance.

[0026] The above explains why the photoreceptor according to this embodiment can minimize environmental sensitivity differences while ensuring good electrical characteristics and high voltage resistance. The photoreceptor will be described further below.

[0027] The photoreceptor is, for example, a single-layer electrophotographic photoreceptor (hereinafter sometimes referred to as a single-layer photoreceptor) or a multilayer electrophotographic photoreceptor (hereinafter sometimes referred to as a multilayer photoreceptor).

[0028] The structure of a stacked photoreceptor 1, an example of a photoreceptor, will be described below with reference to Figures 1 and 2. Figures 1 and 2 show partial cross-sectional views of the stacked photoreceptor 1, respectively.

[0029] As shown in Figure 1, the stacked photoreceptor 1 according to this embodiment comprises a conductive substrate 2, an intermediate layer 3, and a photosensitive layer 4. The intermediate layer 3 is provided on the conductive substrate 2. The photosensitive layer 4 is provided on the intermediate layer 3. The photosensitive layer 4 includes a charge generation layer 4a and a charge transport layer 4b. In other words, the stacked photoreceptor 1 comprises a charge generation layer 4a and a charge transport layer 4b as the photosensitive layer 4.

[0030] As shown in Figure 1, a charge generation layer 4a may be provided on the intermediate layer 3, and a charge transport layer 4b may be provided on the charge generation layer 4a. Alternatively, as shown in Figure 2, a charge transport layer 4b may be provided on the intermediate layer 3, and a charge generation layer 4a may be provided on the charge transport layer 4b.

[0031] The stacked photoreceptor 1 may further include a protective layer (not shown) in addition to the conductive substrate 2, the intermediate layer 3, and the photosensitive layer 4. The protective layer is provided on the photosensitive layer 4. As shown in Figures 1 and 2, the photosensitive layer 4 (for example, a charge transport layer 4b or a charge generation layer 4a) may be provided as the outermost layer of the stacked photoreceptor 1. Alternatively, the protective layer may be provided as the outermost layer of the stacked photoreceptor 1.

[0032] The structure of a stacked photoreceptor 1, which is an example of a photoreceptor, has been described above with reference to Figures 1 and 2.

[0033] The structure of a single-layer photoreceptor 10, an example of a photoreceptor, will be described below with reference to Figure 3. Figure 3 shows a partial cross-sectional view of the single-layer photoreceptor 10.

[0034] As shown in Figure 3, the single-layer photoreceptor 10 according to this embodiment comprises a conductive substrate 2, an intermediate layer 3, and a photosensitive layer 4. The intermediate layer 3 is provided on the conductive substrate 2. The photosensitive layer 4 is provided on the intermediate layer 3. The photosensitive layer 4 is a single layer. Hereinafter, the single-layer photosensitive layer 4 may be referred to as a single-layer photosensitive layer 4c.

[0035] The photoreceptor 10 may further include a protective layer (not shown) in addition to the conductive substrate 2, the intermediate layer 3, and the single-layer photosensitive layer 4c. The protective layer is provided on the single-layer photosensitive layer 4c. As shown in Figure 3, the single-layer photosensitive layer 4c may be provided as the outermost layer of the photoreceptor 10. Alternatively, the protective layer may be provided as the outermost layer of the photoreceptor 10.

[0036] The structure of a single-layer photoreceptor 10, which is an example of a photoreceptor, has been described above with reference to Figure 3.

[0037] Next, the parts constituting the photoreceptor according to this embodiment and their constituent materials will be described.

[0038] (Conductive substrate) The conductive substrate is not particularly limited and only needs to be composed of a material whose surface is conductive. An example of a conductive substrate is a conductive substrate composed of a conductive material. Another example of a conductive substrate is a conductive substrate coated with a conductive material. Examples of conductive materials include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. These conductive materials may be used individually or in combination of two or more (for example, as an alloy). Among these conductive materials, aluminum and aluminum alloys are preferred because they allow for good charge transfer from the photosensitive layer to the conductive substrate.

[0039] The shape of the conductive substrate is appropriately selected according to the structure of the image forming apparatus, etc. Examples of conductive substrate shapes include sheet-like and drum-like shapes. The thickness of the conductive substrate is also appropriately selected according to its shape.

[0040] (Middle class) The intermediate layer contains a specified titanium oxide and a resin used in the intermediate layer (intermediate layer resin).

[0041] The specified titanium oxide described above is titanium oxide that has not been surface-treated with an inorganic material. Examples of inorganic materials include alumina, silica, zinc, and zirconium. Furthermore, the content of the specified titanium oxide in the intermediate layer is preferably 1.3 parts by mass or more and 1.7 parts by mass or less, and more preferably 1.4 parts by mass or more and 1.6 parts by mass or less, per 1 part by mass of the resin for the intermediate layer.

[0042] Examples of resins for the intermediate layer include thermoplastic resins (more specifically, polyarylate resins, polycarbonate resins, styrene-based resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, acrylic copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomers, vinyl chloride-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyvinyl acetal resins, and polyether resins), and thermosetting resins (more specifically, silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins). These resins may be used individually or in combination of two or more. Among the resins mentioned above, polyamide resins are particularly preferred. Furthermore, in order to properly form the intermediate layer and the photosensitive layer, it is preferable that the resin for the intermediate layer is different from the binder resin contained in the photosensitive layer.

[0043] The intermediate layer may contain additives. Examples of additives include UV absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, bulking agents, thickening agents, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, electron acceptor compounds, and leveling agents. Silicone oil is preferred as the leveling agent, and silicone oil having a dimethylpolysiloxane structure is more preferred.

[0044] Furthermore, it is preferable that the thickness of the intermediate layer be within the range of 1.5 μm to 3.5 μm. A thickness within this range is preferable from the viewpoint of obtaining the desired pressure resistance. A thickness of less than 1.5 μm is undesirable from the viewpoint of pressure resistance. On the other hand, a thickness exceeding 3.5 μm is undesirable from the viewpoint of cost reduction.

[0045] (Photosensitive layer) The photosensitive layer contains a charge generating agent, a hole transporter, and a binder resin. When the photoreceptor is a single-layer photoreceptor, the single-layer photosensitive layer contains a charge generating agent, a hole transporter, and a binder resin. Preferably, the single-layer photosensitive layer further contains an electron transporter. The single-layer photosensitive layer may further contain additives as needed.

[0046] If the photoreceptor is a multilayer photoreceptor, the charge generation layer included in the photosensitive layer contains a charge generating agent. The charge transport layer included in the photosensitive layer contains a hole transport agent and a binder resin. The charge generation layer may further contain a base resin as needed. The charge generation layer and the charge transport layer may each further contain additives as needed. The charge generation layer and the charge transport layer may each contain a radical acceptor compound. However, the charge generation layer and the charge transport layer do not each contain a radical acceptor compound.

[0047] (Charge-generating agent) Examples of charge generating agents include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metallic naphthalocyanine pigments, squaline pigments, indigo pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium, selenium-tellurium, selenium-arsenide, cadmium sulfide, and amorphous silicon), pyryllium pigments, ancencelon pigments, triphenylmethane pigments, surene pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments.

[0048] Phthalocyanine pigments have a phthalocyanine structure. Examples of phthalocyanine pigments include metallic phthalocyanines and metal-free phthalocyanines. Examples of metallic phthalocyanines include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. Titanyl phthalocyanine is preferred as the metallic phthalocyanine. Titanyl phthalocyanine is represented by formula (CG-1). Metal-free phthalocyanines are represented by formula (CG-2).

[0049] [ka]

[0050] Phthalocyanine pigments may be crystalline or amorphous. Examples of metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter sometimes referred to as X-type metal-free phthalocyanine). Examples of titanyl phthalocyanine crystals include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter sometimes referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively).

[0051] For example, in digital optical image forming apparatuses (e.g., laser beam printers or facsimile machines using light sources such as semiconductor lasers), it is preferable to use a photoreceptor that is sensitive to wavelengths of 700 nm or more. As a charge generating agent, phthalocyanine-based pigments are preferred because they have a high quantum yield in the wavelength range of 700 nm or more, with titanyl phthalocyanine or metal-free phthalocyanine being more preferred, and Y-type titanyl phthalocyanine or X-type metal-free phthalocyanine being particularly preferred.

[0052] Y-type titanyl phthalocyanine has a major peak at, for example, 27.2° of the Bragg angle (2θ±0.2°) in its CuKα-characterized X-ray diffraction spectrum. The major peak in a CuKα-characterized X-ray diffraction spectrum is the peak with the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is between 3° and 40°. Y-type titanyl phthalocyanine does not have a peak at 26.2° in its CuKα-characterized X-ray diffraction spectrum.

[0053] The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, the sample (titanyl phthalocyanine) is placed in the sample holder of an X-ray diffractometer (for example, RIGAK Corporation's "RINT(registered trademark) 1100"), and the X-ray diffraction spectrum is measured under the following conditions: X-ray tube Cu, tube voltage 40kV, tube current 30mA, and CuKα characteristic X-ray wavelength 1.542Å. The measurement range (2θ) is, for example, 3° to 40° (start angle 3°, stop angle 40°), and the scanning speed is, for example, 10° / min. The main peak is determined from the obtained X-ray diffraction spectrum, and the Bragg angle of the main peak is read.

[0054] When the photoreceptor is a single-layer photoreceptor, the content of the charge generating agent in the single-layer photoreceptor layer is preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 30 parts by mass or less, per 10 parts by mass of the binder resin. When the photoreceptor is a multilayer photoreceptor, the content of the charge generating agent in the photoreceptor layer (specifically the charge generating layer) is preferably 10 parts by mass or more and 30 parts by mass or less, and more preferably 10 parts by mass or more and 20 parts by mass or less, per 10 parts by mass of the base resin.

[0055] (Hole transport agent) Examples of hole transporters include triphenylamine derivatives, diamine derivatives (e.g., N,N,N',N'-tetraphenylbenzidine derivatives, N,N,N',N'-tetraphenylphenylenediamine derivatives, N,N,N',N'-tetraphenylnaphthylenediamine derivatives, N,N,N',N'-tetraphenylphenantolylenediamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazo Examples include oxymethylcellulose, styryl compounds (e.g., 9-(4-diethylaminostyryl)anthracene), carbazole compounds (e.g., polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

[0056] When the photoreceptor is a single-layer photoreceptor, the content of the hole transporter in the single-layer photoreceptor, which is the photosensitive layer, is preferably 10 parts by mass or more and 20 parts by mass or less, and more preferably 40 parts by mass or more and 130 parts by mass or less, per 10 parts by mass of the binder resin.

[0057] To improve the sensitivity characteristics of the photoreceptor, when the photoreceptor is a single-layer photoreceptor, the total content of hole transporters and electron transporters in the single-layer photoreceptor layer is preferably 40% by mass or more, and more preferably 40% by mass or more and 60% by mass or less, relative to the mass of the single-layer photoreceptor layer.

[0058] When the photoreceptor is a single-layer photoreceptor, the thickness of the single-layer photoreceptor is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0059] When the photoreceptor is a laminated photoreceptor, the content of the hole transporter in the photosensitive layer (specifically the charge transport layer) is preferably 10 to 20 parts by mass, and more preferably 50 to 10 parts by mass, per 10 parts by mass of the binder resin.

[0060] To improve the sensitivity characteristics of the photoreceptor, when the photoreceptor is a multilayer photoreceptor, the content of the hole transporter in the charge transport layer is preferably 40% by mass or more, and more preferably 40% by mass or more and 60% by mass or less, relative to the mass of the charge transport layer.

[0061] When the photoreceptor is a multilayer photoreceptor, the thickness of the charge generation layer is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 3 μm or less.

[0062] When the photoreceptor is a multilayer photoreceptor, the thickness of the charge transport layer is not particularly limited, but is preferably 2 μm to 100 μm, and more preferably 5 μm to 50 μm.

[0063] (Electron transport agent) Examples of electron transport agents include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Examples of quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds.

[0064] When the photoreceptor is a single-layer photoreceptor, the content of the electron transport agent in the single-layer photoreceptor layer is preferably 5 parts by mass or more and 150 parts by mass or less, and preferably 10 parts by mass or more and 50 parts by mass or less, per 10 parts by mass of the binder resin.

[0065] (Binder resin) Examples of binder resins include thermoplastic resins (more specifically, polyarylate resins, polycarbonate resins, styrene-based resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, acrylic copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomers, vinyl chloride-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyvinyl acetal resins, and polyether resins), thermosetting resins (more specifically, silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins), and photocurable resins (more specifically, epoxy-acrylic acid resins and urethane-acrylic acid copolymers).

[0066] Among these resins, polycarbonate resin is preferred because it provides a single-layer photosensitive layer and charge transport layer with an excellent balance of processability, mechanical strength, optical properties, and abrasion resistance. Examples of polycarbonate resins include bisphenol Z type polycarbonate resin, bisphenol B type polycarbonate resin, bisphenol ZC type polycarbonate resin, bisphenol C type polycarbonate resin, and bisphenol A type polycarbonate resin. As the binder resin, bisphenol Z type polycarbonate resin or bisphenol B type polycarbonate resin is preferred. Bisphenol Z type polycarbonate resin is a resin having repeating units represented by the formula (BisZ). Bisphenol B type polycarbonate resin is a resin having repeating units represented by the formula (BisB).

[0067] [ka]

[0068] (Base resin) The base resin contained in the charge generation layer is the same as the binder resin contained in the charge transport layer. However, in order to suitably form the charge generation layer and the charge transport layer, it is preferable to select a resin as the base resin that is different from the resin used as the binder resin from the above examples of binder resins. The base resin is, for example, polyvinyl acetal resin.

[0069] (Additives) Examples of additives include UV absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, bulking agents, thickening agents, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, electron acceptor compounds, and leveling agents. As leveling agents, silicone oil is preferred, and silicone oil having a dimethylpolysiloxane structure is more preferred.

[0070] According to this embodiment, a photoreceptor with good electrical characteristics, high voltage resistance, and small environmental sensitivity differences can be obtained. In other words, the photoreceptor according to this embodiment can prevent image defects caused by environmental sensitivity differences, such as images becoming fainter in low-temperature, low-humidity environments and darker in high-temperature, high-humidity environments.

[0071] The electrophotographic photoreceptor according to the first embodiment of the present invention has been described above.

[0072] (Method of manufacturing a photosensitive material) Next, an example of a method for manufacturing a photoreceptor according to the first embodiment will be described. The method for manufacturing a photoreceptor according to the first embodiment includes, for example, an intermediate layer formation step and a photosensitive layer formation step.

[0073] (Intermediate layer formation process) In the intermediate layer formation process, a coating solution for forming the intermediate layer (hereinafter sometimes referred to as the intermediate layer coating solution) is prepared. The intermediate layer coating solution contains a predetermined titanium dioxide, an intermediate layer resin, a solvent, and additives as needed. The intermediate layer coating solution is prepared by mixing these components. Next, the intermediate layer coating solution is applied onto a conductive substrate. Then, at least a portion of the solvent contained in the applied intermediate layer coating solution is removed to form the intermediate layer.

[0074] (Photosensitive layer formation process for stacked photoreceptors) The photosensitive layer formation process for a stacked photoreceptor will be described below. The photosensitive layer formation process for a stacked photoreceptor includes a charge generation layer formation process and a charge transport layer formation process.

[0075] In the charge generation layer formation step, a coating solution for forming the charge generation layer (hereinafter sometimes referred to as the charge generation layer coating solution) is prepared. The charge generation layer coating solution includes, for example, a charge generating agent, a base resin, a solvent, and additives as needed. The charge generation layer coating solution is prepared by mixing these components. Next, the charge generation layer coating solution is applied onto the intermediate layer. Then, at least a portion of the solvent contained in the applied charge generation layer coating solution is removed to form the charge generation layer.

[0076] In the charge transport layer formation process, a coating solution for forming the charge transport layer (hereinafter sometimes referred to as the charge transport layer coating solution) is prepared. The charge transport layer coating solution contains a hole transport agent, a binder resin, a solvent, and additives as needed. The charge transport layer coating solution is prepared by mixing these components. Next, the charge transport layer coating solution is applied onto the charge generating layer. Then, at least a portion of the solvent contained in the applied charge transport layer coating solution is removed to form the charge transport layer.

[0077] (Photosensitive layer formation process for single-layer photoreceptors) The photosensitive layer formation process for a single-layer photoreceptor is described below. The photosensitive layer formation process for a single-layer photoreceptor includes a single-layer photosensitive layer formation process. In the single-layer photosensitive layer formation process, a coating solution for forming a single-layer photosensitive layer (hereinafter sometimes referred to as a single-layer photosensitive layer coating solution) is prepared. The single-layer photosensitive layer coating solution contains, for example, a charge generating agent, a hole transporter, a binder resin, a solvent, an electron transporter if necessary, and additives if necessary. The single-layer photosensitive layer coating solution is prepared by mixing these. Next, the single-layer photosensitive layer coating solution is applied onto the intermediate layer. Then, at least a portion of the solvent contained in the applied photosensitive layer coating solution is removed to form a single-layer photosensitive layer.

[0078] The solvents contained in the above-mentioned intermediate layer coating solution, charge generation layer coating solution, charge transport layer coating solution, and single-layer photosensitive layer coating solution (hereinafter, these may be collectively referred to as "coating solution") are not particularly limited as long as they can dissolve or disperse each component contained in the coating solution. Examples of solvents include alcohols (more specifically methanol, ethanol, isopropanol, and butanol), aliphatic hydrocarbons (more specifically n-hexane, octane, and cyclohexane), aromatic hydrocarbons (more specifically benzene, toluene, and xylene), halogenated hydrocarbons (more specifically methylene chloride, chloroform, ethylene chloride, dichloromethane, dichloroethane, carbon tetrachloride, and chlorobenzene), ethers (more specifically dioxane, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, and diethylene glycol dimethyl ether), ketones (more specifically acetone, methyl ethyl ketone, 2-butanone, and cyclohexanone), esters (more specifically ethyl acetate and methyl acetate), dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide.

[0079] It is preferable that the solvent contained in the coating solution for the charge transport layer is different from the solvent contained in the coating solution for the charge generation layer. This is because, when the coating solution for the charge transport layer is applied to the charge generation layer, it is preferable that the charge generation layer does not dissolve in the solvent of the coating solution for the charge transport layer.

[0080] The coating solution is prepared by mixing each component and dispersing them in a solvent. For mixing or dispersion, for example, a bead mill, roll mill, ball mill, attritor, paint shaker, or ultrasonic disperser can be used.

[0081] The method of applying the coating solution is not particularly limited, as long as it allows for uniform application of the coating solution. Examples of application methods include dip coating, spray coating, spin coating, and bar coating.

[0082] Methods for removing at least a portion of the solvent contained in the coating solution include, for example, heating, reduced pressure, or a combination of heating and reduced pressure. More specifically, a method of heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer is used. The heat treatment temperature is, for example, 40°C to 150°C. The heat treatment time is, for example, 3 minutes to 120 minutes.

[0083] The method for manufacturing a photoreceptor according to the first embodiment may further include a step of forming a protective layer, if necessary. The step of forming the protective layer may be carried out by appropriately selecting a known method.

[0084] [Second Embodiment: Image Forming Apparatus] Next, with reference to Figure 4, an image forming apparatus 100, which is an example of an image forming apparatus of a second embodiment of the present invention, will be described. Figure 4 is a diagram showing an example of the configuration of the image forming apparatus 100. The image forming apparatus 100 is, for example, a tandem-type color printer.

[0085] As shown in Figure 4, the image forming apparatus 100 comprises a control unit 15, an operating unit 20, a paper feeding unit 30, a transport unit 40, a toner supply unit 50, an image forming unit 60, a transfer device 70, a fixing device 80, and a discharge unit 90.

[0086] The control unit 15 controls the operation of each part of the image forming apparatus 100. The control unit 15 includes a processor (not shown) and a storage unit (not shown). The processor includes, for example, a CPU (Central Processing Unit). The storage unit includes memory such as semiconductor memory, and may also include an HDD (Hard Disk Drive). The processor controls the operation of the image forming apparatus 100 by executing a control program. The storage unit stores the control program.

[0087] The control unit 20 receives instructions from the user. Upon receiving instructions from the user, the control unit 20 transmits a signal indicating the user's instructions to the control unit 15. As a result, the image forming operation by the image forming apparatus 100 begins.

[0088] The paper feeding unit 30 includes a paper feeding cassette 31 and a group of paper feeding rollers 32. The paper feeding cassette 31 can accommodate multiple recording media P (for example, paper). The group of paper feeding rollers 32 feeds the recording media P stored in the paper feeding cassette 31 one sheet at a time to the transport unit 40.

[0089] The transport unit 40 is equipped with rollers and guide members. The transport unit 40 extends from the paper feeding unit 30 to the discharge unit 90. The transport unit 40 transports the recording medium P from the paper feeding unit 30 to the discharge unit 90, passing through the image forming unit 60 and the fixing device 80.

[0090] The toner supply unit 50 supplies toner to the image forming unit 60. The toner supply unit 50 comprises a first mounting unit 51Y, a second mounting unit 51C, a third mounting unit 51M, and a fourth mounting unit 51K.

[0091] The first toner container 52Y is mounted in the first mounting section 51Y. Similarly, the second toner container 52C is mounted in the second mounting section 51C, the third toner container 52M is mounted in the third mounting section 51M, and the fourth toner container 52K is mounted in the fourth mounting section 51K.

[0092] The first toner container 52Y, the second toner container 52C, the third toner container 52M, and the fourth toner container 52K each contain toner. In the second embodiment, the first toner container 52Y contains yellow toner. The second toner container 52C contains cyan toner. The third toner container 52M contains magenta toner. The fourth toner container 52K contains black toner.

[0093] The image forming unit 60 comprises an exposure apparatus 61, a first image forming unit 62Y, a second image forming unit 62C, a third image forming unit 62M, and a fourth image forming unit 62K.

[0094] Each of the first image forming units 62Y to the fourth image forming unit 62K includes a charging device 63, a developing device 64, an image carrier 65, a cleaning device 66, and a static elimination device 67.

[0095] Note that the configurations of the first image forming unit 62Y to the fourth image forming unit 62K are the same except for the type of toner supplied from the toner supply unit 50. Therefore, in Figure 4, the reference numerals are omitted for the components of the second image forming unit 62C to the fourth image forming unit 62K.

[0096] The image carrier 65 is the photoreceptor of the first embodiment (more specifically, the stacked photoreceptor 1 and the single-layer photoreceptor 10). As described in the first embodiment, the photoreceptor of the first embodiment can prevent the occurrence of image defects due to environmental sensitivity differences, such as the image being fainter in low-temperature, low-humidity environments and darker in high-temperature, high-humidity environments. Therefore, the image forming apparatus 100 of the second embodiment can prevent the occurrence of image defects due to environmental sensitivity differences, such as the image being fainter in low-temperature, low-humidity environments and darker in high-temperature, high-humidity environments.

[0097] In the second embodiment, the image carrier 65 rotates in the direction indicated by arrow R1 in Figure 4 (clockwise in Figure 4). The charging device 63, developing device 64, cleaning device 66, and static elimination device 67 are arranged along the circumferential surface of the image carrier 65 in the order listed from the upstream side in the rotational direction of the image carrier 65.

[0098] The charging device 63 charges the surface (circumferential surface) of the image carrier 65. The charging device 63 uniformly charges the image carrier 65 to a predetermined polarity by discharge. The charging device 63 is, for example, a charging roller.

[0099] The exposure apparatus 61 exposes the surface of the charged image carrier 65. More specifically, the exposure apparatus 61 irradiates the surface of the charged image carrier 65 with laser light. As a result, an electrostatic latent image is formed on the surface of the image carrier 65.

[0100] The developing device 64 receives toner from the toner supply unit 50. The developing device 64 supplies the toner supplied from the toner supply unit 50 to the surface of the image carrier 65. As a result, the electrostatic latent image formed on the surface of the image carrier 65 is developed as a toner image.

[0101] In the second embodiment, the developing device 64 of the first image forming unit 62Y is connected to the first toner container 52Y. Therefore, yellow toner is supplied to the developing device 64 of the first image forming unit 62Y. As a result, a yellow toner image is formed on the surface of the image carrier 65 of the first image forming unit 62Y.

[0102] Similarly, the developing device 64 of the second image forming unit 62C, the developing device 64 of the third image forming unit 62M, and the developing device 64 of the fourth image forming unit 62K are connected to the second toner container 52C, the third toner container 52M, and the fourth toner container 52K, respectively. Therefore, the developing devices 64 of the second image forming unit 62C, the third image forming unit 62M, and the fourth image forming unit 62K are supplied with cyan toner, magenta toner, and black toner, respectively. As a result, cyan toner images, magenta toner images, and black toner images are formed on the surfaces of the image carrier 65 of the second image forming unit 62C, the third image carrier 65 of the third image forming unit 62M, and the fourth image carrier 65 of the fourth image forming unit 62K, respectively.

[0103] The cleaning device 66 includes a cleaning member 661 and a scraping roller 662. After transfer by the primary transfer roller 71, which will be described later, the cleaning member 661 is pressed against the surface of the image carrier 65 to collect toner adhering to the surface of the image carrier 65. The cleaning member 661 is, for example, a cleaning blade. The scraping roller 662 scrapes the surface of the image carrier 65 to polish the surface of the image carrier 65.

[0104] The static elimination device 67 irradiates the surface of the image carrier 65 with static elimination light to eliminate static electricity from the surface of the image carrier 65.

[0105] The transfer device 70 transfers the toner image from the image carrier 65 to the recording medium P, which is the object to be transferred. Specifically, the transfer device 70 transfers each toner image formed on the surface of each image carrier 65 of the first image forming unit 62Y to the fourth image forming unit 62K onto the recording medium P. In the second embodiment, the transfer device 70 transfers each toner image onto the recording medium P using a secondary transfer method (intermediate transfer method). The transfer device 70 has four primary transfer rollers 71, an intermediate transfer belt 72, a drive roller 73, a driven roller 74, and a secondary transfer roller 75.

[0106] The intermediate transfer belt 72 is an endless belt stretched over four primary transfer rollers 71, a drive roller 73, and a driven roller 74. The intermediate transfer belt 72 is driven in accordance with the rotation of the drive roller 73. The intermediate transfer belt 72 rotates counterclockwise in Figure 4. The driven roller 74 is rotationally driven in accordance with the drive of the intermediate transfer belt 72.

[0107] The first image forming unit 62Y to the fourth image forming unit 62K are arranged facing the lower surface of the intermediate transfer belt 72. In the second embodiment, the first image forming unit 62Y to the fourth image forming unit 62K are arranged in the order of the first image forming unit 62Y to the fourth image forming unit 62K from the upstream side to the downstream side in the driving direction D of the lower surface of the intermediate transfer belt 72.

[0108] Each primary transfer roller 71 is positioned opposite each image carrier 65 via an intermediate transfer belt 72 and is pressed toward each image carrier 65. As a result, the toner images formed on the surface of each image carrier 65 are sequentially transferred to the intermediate transfer belt 72 by each primary transfer roller 71. In the second embodiment, yellow toner images, cyan toner images, magenta toner images, and black toner images are transferred to the intermediate transfer belt 72 in this order. Hereinafter, the toner image formed by the superimposition of yellow toner images, cyan toner images, magenta toner images, and black toner images may be referred to as a "layered toner image".

[0109] The secondary transfer roller 75 is positioned opposite the drive roller 73 via the intermediate transfer belt 72. The secondary transfer roller 75 is pressed toward the drive roller 73. This forms a transfer nip between the secondary transfer roller 75 and the drive roller 73. As the recording medium P passes through the transfer nip, the secondary transfer roller 75 transfers the laminated toner image on the intermediate transfer belt 72 to the recording medium P. In the second embodiment, the yellow toner image, cyan toner image, magenta toner image, and black toner image are transferred to the recording medium P in this order, from top to bottom. The recording medium P on which the laminated toner image has been transferred is transported toward the fuser 80 by the transport unit 40.

[0110] The fixing device 80 includes a heating element 81 and a pressurizing element 82. The heating element 81 and the pressurizing element 82 are arranged facing each other to form a fixing nip. The recording medium P, transported from the image forming unit 60, is heated to a predetermined fixing temperature and pressurized as it passes through the fixing nip. As a result, the stacked toner image is fixed to the recording medium P. The recording medium P is transported from the fixing device 80 to the discharge unit 90 by the transport unit 40.

[0111] The discharge unit 90 includes a pair of discharge rollers 91 and a discharge tray 93. The pair of discharge rollers 91 transports the recording medium P to the discharge tray 93 via a discharge port 92. The discharge port 92 is formed on the upper part of the image forming apparatus 100.

[0112] Next, the configuration of the developing apparatus 64 will be described in detail with reference to Figure 5. Figure 5 is a diagram showing an example of the configuration of the developing apparatus 64. Specifically, Figure 5 shows the developing apparatus 64 of the first image forming unit 62Y. In Figure 5, the image carrier 65 is shown with a dashed line for ease of understanding. In the second embodiment, the developing apparatus 64 employs a two-component developing method using a two-component developer and a touchdown developing method.

[0113] As already explained with reference to Figure 4, the developing container 640 of the developing device 64 is connected to the first toner container 52Y. Therefore, yellow toner is supplied to the developing container 640 of the developing device 64 through the toner supply port 640h.

[0114] As shown in Figure 5, the developing apparatus 64 has a developing roller 641, a magnetic roller 642, a first stirring screw 643, a second stirring screw 644, and a blade 645 inside the developing container 640. Specifically, the developing roller 641 is positioned opposite the magnetic roller 642. The magnetic roller 642 is positioned opposite the second stirring screw 644. The blade 645 is positioned opposite the magnetic roller 642.

[0115] The developing container 640 is divided into a first stirring chamber 640a and a second stirring chamber 640b by a partition wall 640c. The partition wall 640c extends in the axial direction of the developing roller 641. The first stirring chamber 640a and the second stirring chamber 640b are in communication with each other at the outer ends of the longitudinal direction of the partition wall 640c.

[0116] The first stirring chamber 640a houses the first stirring screw 643. The first stirring chamber 640a contains a carrier, which is a magnetic material. The first stirring chamber 640a is supplied with toner, which is a non-magnetic material, through the toner supply port 640h. In the example shown in Figure 5, yellow toner is supplied to the first stirring chamber 640a.

[0117] The second stirring chamber 640b houses the second stirring screw 644. The second stirring chamber 640b contains a carrier which is a magnetic material.

[0118] The yellow toner is agitated with the carrier by the first agitation screw 643 and the second agitation screw 644. As a result, a two-component developer containing the carrier and the yellow toner is formed. This two-component developer is then placed in the developing container 640 (more specifically, the first agitation chamber 640a and the second agitation chamber 640b).

[0119] The first stirring screw 643 and the second stirring screw 644 agitate the two-component developer between the first stirring chamber 640a and the second stirring chamber 640b while circulating it. As a result, the toner becomes charged to a predetermined polarity due to friction with the carrier.

[0120] Furthermore, if the image carrier 65 is a stacked photoreceptor 1, the surface of the image carrier 65 and the toner are charged with, for example, a positive polarity. If the image carrier 65 is a single-layer photoreceptor 10, the surface of the image carrier 65 and the toner are charged with, for example, a negative polarity.

[0121] The magnetic roller 642 consists of a non-magnetic rotating sleeve 642a and a magnet body 642b. The magnet body 642b is fixedly positioned inside the rotating sleeve 642a. The magnet body 642b contains multiple magnetic poles. The two-component developer is attracted to the magnetic roller 642 by the magnetic force of the magnet body 642b. As a result, magnetic brushes are formed on the surface of the magnetic roller 642.

[0122] The blade 645 is positioned upstream of the magnetic roller 642 in the direction of rotation of the magnetic roller 642, above the position where the magnetic roller 642 and the developing roller 641 face each other. In the second embodiment, the magnetic roller 642 rotates in the direction indicated by arrow R3 in Figure 5 (counterclockwise in Figure 5). By rotating, the magnetic roller 642 transports the magnetic brush to a position facing the blade 645. The blade 645 is positioned such that a gap is formed between it and the magnetic roller 642. The blade 645 is made of a magnetic material. Therefore, the thickness of the magnetic brush is regulated by the magnetic force of the blade 645.

[0123] After the thickness of the magnetic brush on the magnetic roller 642 is regulated, a predetermined voltage is applied to the magnetic roller 642 and the developing roller 641. When the predetermined voltage is applied and a predetermined potential difference is reached between the magnetic roller 642 and the developing roller 641, the yellow toner contained in the two-component developer is transferred to the developing roller 641. As a result, a thin layer of yellow toner is formed on the surface of the developing roller 641.

[0124] The developing roller 641 rotates in the direction indicated by arrow R2 in Figure 5 (counterclockwise in Figure 5). This transports the thin layer of toner formed on the surface of the developing roller 641 to a position facing the image carrier 65, where it adheres to the image carrier 65. In this way, the developing device 64 supplies toner, which has been charged by friction with the carrier, to the surface of the image carrier 65.

[0125] The developing device 64 of the first image forming unit 62Y has been described above with reference to Figure 5. The configuration of the developing device 64 of each of the first image forming units 62Y to the fourth image forming unit 62K is the same except for the type of toner supplied from the toner supply unit 50. Therefore, the configuration of the developing device 64 of the second image forming unit 62C to the fourth image forming unit 62K will not be described.

[0126] The image forming apparatus 100, an example of an image forming apparatus of the second embodiment, has been described above with reference to Figures 4 and 5. However, the image forming apparatus of the second embodiment is not limited to the image forming apparatus 100. For example, the image forming apparatus may be a monochrome image forming apparatus. In this case, the image forming apparatus only needs to have one image forming unit. The image forming apparatus may employ a rotary system. The charging device may be a charging device other than a charging roller (for example, a scorotron charger, a charging brush, or a scorotron charger). The image forming apparatus may employ a one-component development method using a one-component developer. The image forming apparatus may employ a development method other than the touchdown development method (for example, a development method in which there is no development roller and the magnetic roller also serves as the development roller). The image forming apparatus may employ a direct transfer method. When the image forming apparatus employs a direct transfer method, the toner image is directly transferred from the image carrier to the recording medium while the image carrier is in contact with the recording medium. The image forming apparatus does not need to be equipped with a cleaning device. The image forming apparatus does not need to be equipped with a static elimination device. The image forming apparatus of the second embodiment has been described above.

[0127] [Third Embodiment: Process Cartridge] Next, with continued reference to Figure 4, a first process cartridge 101, a second process cartridge 102, a third process cartridge 103, and a fourth process cartridge 104, which are examples of process cartridges according to a third embodiment of the present invention, will be described. The first to fourth process cartridges 101 to 104 of the third embodiment correspond to the first to fourth image forming units 62Y to 62K, respectively. Each of the first to fourth process cartridges 101 to 104 comprises an image carrier 65. The image carrier 65 is a photoreceptor according to the first embodiment (more specifically, a stacked photoreceptor 1 and a single-layer photoreceptor 10).

[0128] As described in the first embodiment, the photoreceptor of the first embodiment can prevent image defects caused by differences in environmental sensitivity, such as faint images in low-temperature, low-humidity environments and darker images in high-temperature, high-humidity environments. Therefore, the process cartridge of the third embodiment, which is equipped with the photoreceptor of the first embodiment, can prevent image defects caused by differences in environmental sensitivity, such as faint images in low-temperature, low-humidity environments and darker images in high-temperature, high-humidity environments.

[0129] The process cartridge of the third embodiment may further include, in addition to the image carrier 65, at least one (for example, one to seven) selected from the group consisting of a charging device 63, an exposure device 61, a developing device 64, a transfer device 70 (particularly a primary transfer roller 71), a cleaning member 661, a rubbing roller 662, and a static elimination device 67.

[0130] The first process cartridge 101, second process cartridge 102, third process cartridge 103, and fourth process cartridge 104 shown in Figure 4 each include an image carrier 65, a charging device 63, a developing device 64, a cleaning device 66 having a cleaning member 661 and a rubbing roller 662, and a static elimination device 67, similar to the first image forming unit 62Y, second image forming unit 62C, third image forming unit 62M, and fourth image forming unit 62K. However, the process cartridges of the third embodiment are not limited to the first process cartridge 101 to the fourth process cartridge 104. As described above, the process cartridge of the third embodiment may further include at least one of the exposure device 61 and the transfer device 70, or it may include only one of the cleaning member 661 and the rubbing roller 662 (for example, only the cleaning member 661). In any case, the process cartridge of the third embodiment only needs to include the photoreceptor of the first embodiment as the image carrier 65.

[0131] The process cartridge of the third embodiment is designed to be detachably attached to the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and if the sensitivity characteristics of the image carrier 65 deteriorate, the process cartridge, including the image carrier 65, can be easily and quickly replaced. The process cartridge of the third embodiment has been described above with reference to Figure 4.

[0132] [Other embodiments] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made.

[0133] [Examples and Comparative Examples] The following describes examples of the present invention, but the present invention is not limited to these examples.

[0134] (Manufacturing of stacked photoreceptors for evaluation) A stacked photoreceptor for evaluation (the photoreceptor according to Example 1) was manufactured as follows.

[0135] First, a drum-shaped aluminum support with a diameter of 30 mm was prepared as a conductive substrate. Next, 1.5 parts by mass of titanium dioxide (MTX-00S, manufactured by Teika Co., Ltd., number mean primary particle size 10 nm), which had been surface-treated with methyl hydrogen polysiloxane while wet-dispersed, 1 part by mass of polyamide resin (Amiran® ​​CM8000, manufactured by Toray Industries, Inc., a quaternary copolymer polyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610), 10 parts by mass of methanol, 1 part by mass of butanol, and 1 part by mass of toluene were mixed using a bead mill for 5 hours to obtain an intermediate layer coating solution. The obtained intermediate layer coating solution was filtered using a filter with a mesh size of 5 μm. Subsequently, the obtained filtrate was applied to the surface of the conductive substrate by the dip-coating method. Then, the applied filtrate was dried at 130°C for 30 minutes. In this way, an intermediate layer (film thickness: 2.5 μm) was formed on the conductive substrate.

[0136] Next, 1.5 parts by mass of Y-type titanyl phthalocyanine, a charge-generating agent, 1.0 part by mass of polyvinyl acetal resin (Sekisui Chemical Co., Ltd.'s "Eslec BX-5") as a base resin, 40.0 parts by mass of propylene glycol monomethyl ether, and 40.0 parts by mass of tetrahydrofuran were mixed using a bead mill for 12 hours to obtain a coating solution for the charge-generating layer. The obtained coating solution for the charge-generating layer was filtered using a filter with a mesh size of 3 μm. Subsequently, the obtained filtrate was applied onto the intermediate layer by the dip-coating method. The applied filtrate was then dried at 50°C for 5 minutes. In this way, a charge-generating layer (film thickness: 0.3 μm) was formed on the intermediate layer.

[0137] Next, 60.0 parts by mass of a compound represented by the following formula (HTM-1) as a hole transport agent, 100.0 parts by mass of polycarbonate resin (PCZ-500, manufactured by Mitsubishi Gas Chemical Co., Ltd., viscosity-average molecular weight 50,000) as a binder resin, 0.05 parts by mass of silicone oil (KF96-50cs, manufactured by Shin-Etsu Chemical Co., Ltd., silicone oil having a dimethylpolysiloxane structure) as a leveling agent, 340.0 parts by mass of tetrahydrofuran as a solvent, and 60.0 parts by mass of toluene were mixed to obtain a coating solution for the charge transport layer. The obtained coating solution for the charge transport layer was applied onto the charge generation layer by the dip-coating method. Subsequently, the applied coating solution for the charge transport layer was dried at 120°C for 40 minutes. In this way, a charge transport layer (film thickness: 24.7 μm or 12.7 μm) was formed on the charge generation layer.

[0138] [ka]

[0139] As described above, a stacked electrophotographic photoreceptor according to Example 1 was manufactured, comprising a photosensitive layer with a thickness of 25 μm (0.3 μm + 24.7 μm) or a photosensitive layer with a thickness of 13 μm (0.3 μm + 12.7 μm). To evaluate the electrical characteristics and environmental sensitivity differences, a stacked electrophotographic photoreceptor with a 25 μm thick photosensitive layer was used. To evaluate the voltage resistance, a stacked electrophotographic photoreceptor with a 13 μm thick photosensitive layer was used.

[0140] Except for the following changes, the photoreceptors for Examples 2 to 9 and Comparative Examples 1 to 9 were manufactured in the same manner as the photoreceptor for Example 1.

[0141] Example 2 differs from Example 1 in that the titanium dioxide content in the intermediate layer is 1.3 parts by mass.

[0142] Example 3 differs from Example 1 in that the titanium dioxide content in the intermediate layer is 1.7 parts by mass.

[0143] Example 4 differs from Example 1 in that the thickness of the intermediate layer was set to 1.5 μm.

[0144] Example 5 differs from Example 1 in that the thickness of the intermediate layer was set to 2.0 μm.

[0145] Example 6 differs from Example 1 in that the thickness of the intermediate layer was set to 3.0 μm.

[0146] Example 7 differs from Example 1 in that the thickness of the intermediate layer was set to 3.5 μm.

[0147] Example 8 differs from Example 1 in that it uses untreated fine-particle titanium dioxide (MT-500B manufactured by Teika Co., Ltd., with a number-average primary particle size of 35 nm) instead of MTX-00S.

[0148] Example 9 differs from Example 1 in that it uses the largest particle size titanium dioxide (MT-700BS, manufactured by Teika Co., Ltd., with a number-average primary particle size of 80 nm) surface-treated with methylhydrogenpolysiloxane instead of MTX-00S.

[0149] Comparative Example 1 differs from Example 1 in that the titanium dioxide content in the intermediate layer is 1.0 part by mass.

[0150] Comparative Example 2 differs from Example 1 in that the titanium dioxide content in the intermediate layer is 2.0 parts by mass.

[0151] Comparative Example 3 differs from Example 1 in that it uses fine titanium oxide particles (MT-05, manufactured by Teika Co., Ltd., with a number-average primary particle size of 10 nm) surface-treated with alumina and silica instead of MTX-00S.

[0152] Comparative Example 4 differs from Example 1 in that it uses fine titanium oxide particles (MT-05, manufactured by Teika Co., Ltd., with a number-mean primary particle size of 10 nm) surface-treated with alumina and silica instead of MTX-00S, and the thickness of the intermediate layer is 5.0 μm.

[0153] Comparative Example 5 differs from Example 1 in that it uses fine-particle titanium oxide (SMT-A, manufactured by Teika Co., Ltd., with a number-mean primary particle size of 10 nm) surface-treated with alumina, silica, and methylhydrogenpolysiloxane instead of MTX-00S, and the thickness of the intermediate layer is 0.5 μm.

[0154] Comparative Example 6 differs from Example 1 in that it uses fine-particle titanium oxide (SMT-A, manufactured by Teika Co., Ltd., with a number-average primary particle size of 10 nm) surface-treated with alumina, silica, and methylhydrogenpolysiloxane instead of MTX-00S.

[0155] Comparative Example 7 differs from Example 1 in that it uses fine titanium oxide particles (MT-500SA, manufactured by Teika Co., Ltd., with a number-average primary particle size of 35 nm) surface-treated with alumina and silica instead of MTX-00S.

[0156] Comparative Example 8 differs from Example 1 in that it uses fine-particle titanium oxide (MT-500SAS, manufactured by Teika Co., Ltd., with a number-average primary particle size of 35 nm) surface-treated with alumina, silica, and methylhydrogenpolysiloxane instead of MTX-00S.

[0157] Comparative Example 9 differs from Example 1 in that it uses fine-particle zinc oxide (MZY-303S, manufactured by Teika Co., Ltd., with a number-average primary particle size of 35 nm) surface-treated with methylhydrogenpolysiloxane instead of MTX-00S, and the zinc oxide content (titanium dioxide in Example 1) in the intermediate layer is 1.0 part by mass.

[0158] (Manufacturing of single-layer photoreceptors for evaluation) A single-layer photoreceptor for evaluation (the photoreceptor according to Example 10) was manufactured as follows.

[0159] First, a drum-shaped aluminum support with a diameter of 30 mm was prepared as a conductive substrate. Next, 1.5 parts by mass of titanium dioxide (MTX-00S, manufactured by Teika Co., Ltd., number mean primary particle size 10 nm), which had been surface-treated with methyl hydrogen polysiloxane while wet-dispersed, 1 part by mass of polyamide resin (Amiran® ​​CM8000, manufactured by Toray Industries, Inc., a quaternary copolymer polyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610), 10 parts by mass of methanol, 1 part by mass of butanol, and 1 part by mass of toluene were mixed using a bead mill for 5 hours to obtain an intermediate layer coating solution. The obtained intermediate layer coating solution was filtered using a filter with a mesh size of 5 μm. Subsequently, the obtained filtrate was applied to the surface of the conductive substrate by the dip-coating method. Then, the applied filtrate was dried at 130°C for 30 minutes. In this way, an intermediate layer (film thickness: 2.5 μm) was formed on the conductive substrate.

[0160] Next, 2.85 parts by mass of Y-type titanylphthalocyanine as a charge generator, 70.0 parts by mass of a compound represented by formula (HTM-1) as a hole transporter, 40.0 parts by mass of a compound represented by the following formula (ETM-1) as an electron transporter, 100.0 parts by mass of polycarbonate resin (PCZ-500, manufactured by Mitsubishi Gas Chemical Co., Ltd., viscosity-average molecular weight 50,000) as a binder resin, 0.02 parts by mass of silicone oil (KF96-50cs, manufactured by Shin-Etsu Chemical Co., Ltd., silicone oil having a dimethylpolysiloxane structure) as a leveling agent, and 500.0 parts by mass of tetrahydrofuran as a solvent were mixed for 20 minutes using a rod-shaped ultrasonic oscillator to obtain a coating solution for the photosensitive layer. The obtained coating solution for the photosensitive layer was filtered using a filter with a mesh size of 5 μm. Then, the obtained filtrate was applied to the intermediate layer by the dip-coating method. Subsequently, the applied filtrate was dried at 110°C for 60 minutes. In this way, a photosensitive layer (film thickness: 25 μm or 13 μm) was formed on the intermediate layer.

[0161] [ka]

[0162] As described above, a single-layer electrophotographic photoreceptor according to Example 10, comprising a photosensitive layer with a thickness of 25 μm or a photosensitive layer with a thickness of 13 μm, was manufactured. To evaluate the electrical characteristics and environmental sensitivity differences, a single-layer electrophotographic photoreceptor with a photosensitive layer with a thickness of 25 μm was used. To evaluate the voltage resistance, a single-layer electrophotographic photoreceptor with a photosensitive layer with a thickness of 13 μm was used.

[0163] (Evaluation of electrical properties of stacked photoreceptors) To evaluate the electrical properties of the manufactured stacked photoreceptor, the post-exposure potential of the photoreceptor was measured using a drum sensitivity tester (manufactured by GENTEC) under conditions of 23°C and 50% RH relative humidity. First, the surface of the photoreceptor was charged so that its surface potential was -600V. Then, monochromatic light (exposure wavelength: 780nm) was used for exposure at an exposure dose of 0.87 μJ / cm². 2The surface of the photoreceptor was exposed by irradiating it with a light source. The surface potential of the exposed area of ​​the photoreceptor was measured 50 milliseconds after exposure. The measured surface potential was defined as the post-exposure potential.

[0164] (Evaluation of electrical characteristics of single-layer photoreceptors) To evaluate the electrical properties of the manufactured single-layer photoreceptor, the post-exposure potential of the photoreceptor was measured using a drum sensitivity tester (manufactured by GENTEC) under conditions of 23°C and 50% RH relative humidity. First, the surface of the photoreceptor was charged so that its surface potential was +600V. Then, monochromatic light (exposure wavelength: 780nm) was used for exposure at an exposure dose of 0.87 μJ / cm². 2 The surface of the photoreceptor was exposed by irradiating it with a light source. The surface potential of the exposed area of ​​the photoreceptor was measured 50 milliseconds after exposure. The measured surface potential was defined as the post-exposure potential.

[0165] Furthermore, a smaller post-exposure potential value (but above 0V) indicates superior sensitivity of the photoreceptor. The sensitivity of each photoreceptor was evaluated according to the following criteria. Evaluation A: The absolute value of the post-exposure potential was 130V or less. Evaluation B: The absolute value of the post-exposure potential exceeded 130V.

[0166] (Evaluation of environmental sensitivity differences in stacked photoreceptors) To evaluate the environmental sensitivity differences of the manufactured stacked photoreceptor, the post-exposure potential of the photoreceptor was measured using a drum sensitivity tester (manufactured by GENTEC) under conditions of 10°C and 15% RH relative humidity, as follows: First, the surface of the photoreceptor was charged so that its surface potential was -600V. Then, monochromatic light (exposure wavelength: 780nm) was used for exposure at an exposure dose of 0.15 μJ / cm². 2 The surface of the photoreceptor was exposed by irradiating it with a light source. The surface potential of the exposed area of ​​the photoreceptor was measured 50 milliseconds after exposure. The measured surface potential was defined as the post-exposure potential.

[0167] The measurement environment was changed to a temperature of 32°C and a relative humidity of 80% RH, and the post-exposure potential of the photoreceptor was measured in the same manner as described above. Of the post-exposure potentials obtained in this way, the post-exposure potential of one was subtracted from the post-exposure potential of the other, and the absolute value of the difference was defined as the environmental sensitivity difference.

[0168] (Evaluation of environmental sensitivity differences in single-layer photoreceptors) To evaluate the environmental sensitivity differences of the manufactured single-layer photoreceptor, the post-exposure potential of the photoreceptor was measured using a drum sensitivity tester (manufactured by GENTEC) under conditions of 10°C and 15% RH relative humidity, as follows: First, the surface of the photoreceptor was charged so that its surface potential was +600V. Then, monochromatic light (exposure wavelength: 780nm) was used for exposure at an exposure dose of 0.15 μJ / cm². 2 The surface of the photoreceptor was exposed by irradiating it with a light source. The surface potential of the exposed area of ​​the photoreceptor was measured 50 milliseconds after exposure. The measured surface potential was defined as the post-exposure potential.

[0169] The measurement environment was changed to a temperature of 32°C and a relative humidity of 80% RH, and the post-exposure potential of the photoreceptor was measured in the same manner as described above. Of the post-exposure potentials obtained in this way, the post-exposure potential of one was subtracted from the post-exposure potential of the other, and the absolute value of the difference was defined as the environmental sensitivity difference.

[0170] The environmental sensitivity differences of each photoreceptor were evaluated according to the following criteria. Evaluation A: The environmental sensitivity difference was 60V or less. Rating B: The environmental sensitivity difference exceeded 60V.

[0171] (Evaluation of pressure resistance of stacked photoreceptors) To evaluate the voltage resistance of the manufactured stacked photoreceptor, a modified unit was used in which a high-voltage power supply was connected to the charging roller in the process unit of a multifunction printer (Taskalfa356ci, manufactured by Kyocera Document Solutions Inc.). The voltage (unit: +kV) at which leakage occurred in the photoreceptor was measured as follows. First, the photoreceptor was set in the process unit. In a dark environment with a temperature of 23°C and a relative humidity of 50%RH, a voltage of 2.0kV was applied to the charging roller for 3 minutes, and then a negative voltage was applied at a step-down rate of -0.2kV / 3 minutes. The voltage at which leakage occurred in the photoreceptor was then measured. The position of the measurement surface was shifted after each measurement, and the voltage was measured a total of three times. The absolute value of the average of the values ​​obtained from the three measurements was taken as the voltage resistance measurement. The measured values ​​are shown in the "Battery Resistance" column of Table 1. A higher measured value indicates higher voltage resistance of the photoreceptor. Note that static electricity removal was not performed during the voltage resistance measurement.

[0172] (Evaluation of pressure resistance of single-layer photoreceptors) To evaluate the voltage resistance of the manufactured single-layer photoreceptor, a modified unit was used in which a high-voltage power supply was connected to the charging roller in the process unit of a multifunction printer (Taskalfa356ci, manufactured by Kyocera Document Solutions Inc.). The voltage (in units of +kV) at which leakage occurred in the photoreceptor was measured as follows: First, the photoreceptor was set in the process unit. In a dark environment with a temperature of 23°C and a relative humidity of 50%RH, a voltage of 2.0kV was applied to the charging roller for 3 minutes, and then a positive voltage was applied at a boost rate of +0.2kV / 3 minutes. The voltage at which leakage occurred in the photoreceptor was then measured. The position of the measurement surface was shifted after each measurement, and the voltage was measured a total of three times. The absolute value of the average of the values ​​obtained from the three measurements was taken as the voltage resistance measurement. The measured values ​​are shown in the "Battery Resistance" column of Table 1. A higher measured value indicates higher voltage resistance of the photoreceptor. Note that static electricity removal was not performed during the voltage resistance measurement.

[0173] The pressure resistance of each photoreceptor was evaluated according to the following criteria. Evaluation A: The measured value was 2.6kV or higher. Evaluation B: The measured value was less than 2.6kV.

[0174] [Table 1]

[0175] (Evaluation of the Examples and Comparative Examples) As shown in Table 1, the photoreceptors in Examples 1 to 10 all exhibited good electrical properties, high voltage resistance, and small differences in environmental sensitivity. This is thought to be because the intermediate layer contained appropriate titanium oxide and appropriate resin in appropriate ratios, thereby improving electrical properties, increasing electrical resistance, and suppressing environmental fluctuations.

[0176] As shown in Table 1, the photoreceptor in Comparative Example 1 had high pressure resistance, but exhibited a large difference in environmental sensitivity. This is thought to be because the titanium dioxide content was 1.0 part by mass per 1.0 part by mass of polyamide resin, which is less than 1.3 parts by mass, and therefore the effect of reducing the difference in environmental sensitivity by titanium dioxide was not sufficiently obtained.

[0177] As shown in Table 1, the photoreceptor in Comparative Example 2 had a small difference in environmental sensitivity, but low pressure resistance. This is thought to be because the titanium dioxide content was 2.0 parts by mass per 1.0 part by mass of polyamide resin, which is more than 1.7 parts by mass, and therefore the effect of increasing electrical resistance by reducing the amount of titanium dioxide was not sufficiently obtained.

[0178] As shown in Table 1, the photoreceptor in Comparative Example 3 had a small difference in environmental sensitivity, but low pressure resistance. This is thought to be because the titanium oxide was surface-treated with inorganic materials such as alumina and silica, which reduced its electrical resistance.

[0179] As shown in Table 1, the photoreceptor in Comparative Example 4 had a small difference in environmental sensitivity, but low pressure resistance. This is thought to be because the titanium oxide was surface-treated with inorganic materials such as alumina and silica, which reduced its electrical resistance.

[0180] As shown in Table 1, the photoreceptor in Comparative Example 5 exhibited a small difference in environmental sensitivity and low pressure resistance. This is thought to be due to the fact that titanium oxide is surface-treated with inorganic materials such as alumina and silica, making it susceptible to environmental fluctuations, and also because the thickness of the intermediate layer is too thin.

[0181] As shown in Table 1, the photoreceptor in Comparative Example 6 had high pressure resistance, but showed little difference in environmental sensitivity. This is thought to be because titanium oxide is surface-treated with inorganic materials such as alumina and silica, making it susceptible to environmental fluctuations.

[0182] As shown in Table 1, the photoreceptor in Comparative Example 7 had a small difference in environmental sensitivity, but low pressure resistance. This is thought to be because the titanium oxide was surface-treated with inorganic materials such as alumina and silica, which reduced its electrical resistance.

[0183] As shown in Table 1, the photoreceptor in Comparative Example 8 exhibited a small difference in environmental sensitivity and low pressure resistance. This is thought to be due to the fact that titanium oxide was surface-treated with inorganic materials such as alumina and silica, making it susceptible to environmental fluctuations and resulting in reduced electrical resistance.

[0184] As shown in Table 1, the photoreceptor in Comparative Example 9 had high pressure resistance, but exhibited a large difference in environmental sensitivity. This is thought to be because zinc oxide was used instead of titanium dioxide, which prevented a sufficient reduction in the difference in environmental sensitivity. [Explanation of symbols]

[0185] 1…Stacked photoreceptor 10…Single-layer photoreceptor 2…Conductive substrate 3…Middle class 4…Photosensitive layer 4a... Charge generation layer 4b...Charge transport layer 4c... Single-layer photosensitive layer 100…Image forming apparatus 64…Developing equipment

Claims

1. A conductive substrate, An intermediate layer provided on the conductive substrate, A photosensitive layer provided on the intermediate layer and It is equipped with, The aforementioned intermediate layer comprises titanium oxide that has not been surface-treated with an inorganic material and an intermediate layer resin. The titanium oxide content is 1.3 parts by mass or more and 1.7 parts by mass or less per 1.0 part by mass of the intermediate layer resin. Electrophotographic photoreceptor.

2. The electrophotographic photoreceptor according to claim 1, The resin for the intermediate layer is a polyamide resin. Electrophotographic photoreceptor.

3. An electrophotographic photoreceptor according to claim 1 or 2, The thickness of the intermediate layer is 1.5 μm or more and 3.5 μm or less. Electrophotographic photoreceptor.

4. An electrophotographic photoreceptor according to claim 1 or 2, The titanium oxide content is 1.4 parts by mass or more and 1.6 parts by mass or less per 1.0 part by mass of the intermediate layer resin. Electrophotographic photoreceptor.

5. At least one selected from the group consisting of a charging device, an exposure device, a developing device, a transfer device, a cleaning member, a friction roller, and a static elimination device, The electrophotographic photoreceptor according to claim 1 and Equipped with Process cartridge.

6. Image carrier and, A charging device for charging the surface of the image carrier, An exposure apparatus for exposing the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier, A developing apparatus that supplies toner to the surface of the image carrier and develops the electrostatic latent image as a toner image, A transfer device for transferring the toner image from the image carrier to the transfer target, A cleaning member for cleaning the surface of the image carrier, A static elimination device for removing static electricity from the surface of the image carrier and It is equipped with, An image forming apparatus wherein the image carrier is the electrophotographic photoreceptor described in claim 1.

7. An image forming apparatus according to claim 6, The charging device is a charging roller. Image forming apparatus.

8. An image forming apparatus according to claim 6 or 7, The aforementioned developing apparatus employs a two-component developing method. Image forming apparatus.

Images