JP6524974B2 - Electrophotographic photosensitive member, process cartridge, and image forming apparatus - Google Patents

Description

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

  The electrophotographic photosensitive member is used in an electrophotographic image forming apparatus. The electrophotographic photosensitive member comprises a photosensitive layer. The photosensitive layer contains, for example, a charge generating agent, a charge transporting agent (for example, a hole transporting agent and an electron transporting agent), and a resin (binder resin) for binding them. The photosensitive layer may contain the charge generating agent and the charge transporting agent in the same layer, and have both the functions of charge generation and charge transport in the same layer. Such an electrophotographic photosensitive member is called a single layer type electrophotographic photosensitive member.

  The photosensitive layer provided in the electrophotographic photosensitive member described in Patent Document 1 contains a phenylbenzofuranone derivative (specifically, a naphthoquinone compound). Patent Document 1 discloses a compound represented by a chemical formula (ET-2).

Unexamined-Japanese-Patent No. 2013-117572

  However, in the electrophotographic photosensitive member described in Patent Document 1, the suppression of the generation of the sensitivity characteristic and the transfer memory is not sufficient.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic photosensitive member which is excellent in sensitivity characteristics and which suppresses the occurrence of transfer memory. In addition, another object of the present invention is to provide a process cartridge for suppressing the occurrence of image defects (in particular, image defects caused by deterioration of sensitivity characteristics and generation of transfer memory) by providing such an electrophotographic photosensitive member, and An image forming apparatus is provided.

  The electrophotographic photosensitive member of the present invention comprises a conductive substrate and a photosensitive layer. The photosensitive layer is a single layer type photosensitive layer. The photosensitive layer contains at least a charge generating agent, a hole transporting agent, an electron transporting agent, and a binder resin. The charge generating agent includes titanyl phthalocyanine represented by the following chemical formula (1). The electron transfer agent includes a quinone derivative represented by the following general formula (2).

In the general formula (2), R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

  The process cartridge of the present invention comprises the above-described electrophotographic photosensitive member.

  The image forming apparatus of the present invention includes an image carrier, a charging unit, an exposure unit, a developing unit, and a transfer unit. The image carrier is the above-described electrophotographic photosensitive member. The charging unit charges the surface of the image carrier. The charging polarity of the charging unit is positive. The exposure unit exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier. The developing unit develops the electrostatic latent image as a toner image. The transfer unit transfers the toner image from the image carrier to a transfer body.

  According to the electrophotographic photosensitive member of the present invention, the sensitivity characteristics are excellent, and the generation of transfer memory can be suppressed. Further, according to the process cartridge and the image forming apparatus of the present invention, the occurrence of an image defect can be suppressed by providing such an electrophotographic photosensitive member.

(A), (b), and (c) are each schematic sectional drawing which shows the structure of the electrophotographic photoreceptor which concerns on 1st embodiment. FIG. 7 is a schematic view showing a configuration of one aspect of an image forming apparatus according to a second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not at all limited to the following embodiments. The present invention can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, although description may be suitably abbreviate | omitted about the location where description overlaps, it does not limit the summary of invention.

  Hereinafter, “system” may be added after the compound name to generically generically refer to the compound and its derivative. Moreover, when a "system" is attached after a compound name and it represents a polymer name, it means that the repeating unit of a polymer originates in a compound or its derivative (s).

  Hereinafter, the alkyl group having 1 to 4 carbon atoms has the following meanings unless otherwise specified.

  The alkyl group having 1 or more and 4 or less carbon atoms is linear or branched and unsubstituted. As a C1-C4 alkyl group, a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, or t-butyl group is mentioned, for example.

First Embodiment: Electrophotographic Photoreceptor
The first embodiment relates to an electrophotographic photosensitive member (hereinafter sometimes referred to as a photosensitive member). The photosensitive member of the first embodiment will be described below with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the structure of the photosensitive member according to the first embodiment.

  As shown in FIG. 1A, the photosensitive member 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 is provided directly or indirectly on the conductive substrate 2. For example, as shown in FIG. 1A, the photosensitive layer 3 may be provided directly on the conductive substrate 2. As shown in FIG. 1B, the photoreceptor 1 may further include an intermediate layer, and the intermediate layer 4 may be provided between the conductive substrate 2 and the photosensitive layer 3. Further, as shown in FIGS. 1A and 1B, the photosensitive layer 3 may be exposed as the outermost layer. The photoreceptor 1 may further include a protective layer. As shown in FIG. 1 (c), a protective layer 5 may be provided on the photosensitive layer 3. The structure of the photosensitive member 1 has been described above with reference to FIG.

  The thickness of the photosensitive layer is not particularly limited as long as the photosensitive layer can sufficiently function. The thickness of the photosensitive layer is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

  The photosensitive layer contains at least a charge generating agent, a hole transporting agent, an electron transporting agent, and a binder resin. The charge generating agent includes titanyl phthalocyanine represented by the chemical formula (1) (hereinafter sometimes referred to as titanyl phthalocyanine (1)). An electron transport agent contains the quinone derivative (Hereinafter, it may describe as a quinone derivative (2)) represented by General formula (2). The photoreceptor according to the first embodiment has excellent electrical characteristics and suppresses the occurrence of transfer memory. The reason is presumed as follows.

For convenience, first, the transfer memory will be described. In electrophotographic image formation, for example, an image formation process including the following steps 1) to 4) is performed.
1) a charging step of charging the surface of an image carrier (corresponding to a photosensitive member);
2) exposing the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier,
3) a developing step of developing the electrostatic latent image as a toner image, and 4) a transferring step of transferring the formed toner image from the image carrier to a transfer member.
In such an image forming process, since the image carrier is used in rotation, transfer memory may occur due to the transfer process. Specifically, it is as follows. In the charging step, the surface of the image carrier is uniformly charged to a constant positive potential. Subsequently, through the exposure step and the development step, in the transfer step, a transfer bias of the reverse polarity (negative polarity) to the charging is applied to the image carrier through the transfer member. Specifically, the potential of the non-exposed area (non-image area) on the surface of the image carrier may be greatly reduced by the influence of the applied reverse polarity transfer bias, and the lowered state may be maintained. Under the influence of the potential drop, the non-exposed area is less likely to be charged to a desired positive potential in the next charging step on the basis of the circumference on which the photosensitive member forms an image. On the other hand, even when the transfer bias is applied, since the toner adheres to the exposed area and the transfer bias is difficult to be directly applied to the surface of the photosensitive member, the potential of the exposed area (image area) is hardly reduced. . For this reason, the exposed region is likely to be charged to a desired positive potential in the next peripheral charging step. As a result, the charging potential may be different between the exposed area and the non-exposed area, and it may be difficult to uniformly charge the surface of the image carrier to a constant positive potential. As described above, the chargeability of the unexposed area may be reduced due to the potential drop due to the transfer bias in the image forming process (image forming process) on the front side of the photosensitive member. Such a phenomenon that a potential difference occurs in the charging potential is called transfer memory.

  The quinone derivative (2) has a pi-conjugated system with a relatively large spatial extent. Therefore, the quinone derivative (2) is excellent in the carrier (electron) acceptability, and the moving distance of the carrier (electron) in the molecule of the quinone derivative (2) tends to be large. That is, the intramolecular migration distance of carriers (electrons) tends to be large. In addition, the plurality of quinone derivatives (2) in the photosensitive layer tends to overlap with each other in the π conjugated system, and the moving distance of carriers (electrons) between molecules of the plurality of quinone derivatives (2) tends to decrease. That is, the intermolecular migration distance of carriers (electrons) tends to decrease. Thus, the quinone derivative (2) is considered to improve the acceptability (injectability) and transportability of the carrier (electron) of the photoreceptor. Therefore, the photosensitive member according to the first embodiment is considered to be excellent in sensitivity characteristics and to be able to suppress the occurrence of transfer memory.

  The photosensitive layer contains titanyl phthalocyanine (1) as a charge generating agent. Since the lowest unoccupied molecular orbital (LUMO) of titanyl phthalocyanine (1) is slightly larger than that of quinone derivative (2), titanyl phthalocyanine tends to impart a carrier (electron) to quinone derivative (2). For this reason, the photoreceptor according to the first embodiment is considered to be excellent in sensitivity characteristics.

  Next, the elements of the photosensitive member will be described. Hereinafter, the conductive substrate, the charge generating agent, the hole transporting agent, the electron transporting agent, and the binder resin will be described. The photosensitive layer may further contain an additive. Further, the method for producing the additive, the intermediate layer, and the photoreceptor will be described.

[1. Conductive substrate]
The conductive substrate is not particularly limited as long as it can be used as the conductive substrate of the photoreceptor. The conductive substrate may be formed at least at a surface portion of a material having conductivity. An example of the conductive substrate is a conductive substrate formed of a conductive material. Another example of the conductive substrate is a conductive substrate coated with a material having conductivity. As a material which has electroconductivity, aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, or indium is mentioned, for example. These materials having conductivity may be used alone or in combination of two or more. As a combination of two or more, for example, an alloy (more specifically, an aluminum alloy, stainless steel, brass or the like) can be mentioned. Among these materials having conductivity, aluminum or an aluminum alloy is preferable because charge transfer from the photosensitive layer to the conductive substrate is good.

  The shape of the conductive substrate is appropriately selected in accordance with the structure of the image forming apparatus. Examples of the shape of the conductive substrate include a sheet or a drum. In addition, the thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

[2. Charge generator]
The charge generating agent includes titanyl phthalocyanine (1). The titanyl phthalocyanine (1) is represented by the chemical formula (1).

  Examples of crystals of titanyl phthalocyanine include α-type crystals, β-type crystals, and Y-type crystals of titanyl phthalocyanine. Hereinafter, α-type crystals, β-type crystals and Y-type crystals of titanyl phthalocyanine may be described as α-type titanyl phthalocyanine, β-type titanyl phthalocyanine and Y-type titanyl phthalocyanine, respectively. Among titanyl phthalocyanines, Y-type titanyl phthalocyanine is preferable because it has a high quantum yield in a wavelength range of 700 nm or more.

  Y-type titanyl phthalocyanine has a main peak at Bragg angle 2θ ± 0.2 ° = 27.2 ° in the CuKα characteristic X-ray diffraction spectrum. The main peak is any one of two peaks having the first and second largest peak intensities within the range where the Bragg angle 2θ ± 0.2 ° of the CuKα characteristic X-ray diffraction spectrum is 3 ° or more and 40 ° or less. Means the peak of

  The X-ray diffraction spectrum is measured as follows. A dispersion is prepared by dispersing 0.3 g of the sample (Y-type titanyl phthalocyanine) in 5.0 g of tetrahydrofuran. Subsequently, the prepared dispersion is stored for 7 days in a closed system under conditions of normal temperature and normal humidity (for example, temperature 23 ° C. ± 1 ° C. and humidity 50% RH to 60% RH). Subsequently, the dispersion after storage is filled into a sample holder of an X-ray diffractometer (for example, “RINT (registered trademark) 1100” manufactured by Rigaku Corporation), and the X-ray tube Cu, tube voltage 40 kV, tube current 30 mA And, the X-ray diffraction spectrum is measured under the condition of the wavelength 1.542 Å of the CuKα characteristic X-ray. 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.

  The charge generating agent may contain another charge generating agent in addition to the titanyl phthalocyanine (1). Other charge generating agents include, for example, phthalocyanine pigments (phthalocyanine pigments other than titanyl phthalocyanine (1)), perylene pigments, bisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squara Powders of line pigments, trisazo pigments, indigo pigments, azulenium pigments, cyanine pigments, inorganic photoconductive materials (more specifically, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, amorphous silicon, etc.), pyrylium salts, Ansanthrone pigments, triphenylmethane pigments, Sureren pigments, toluidine pigments, pyrazoline pigments, or quinacridone pigments can be mentioned. The charge generating agent may be used alone or in combination of two or more.

  As a phthalocyanine type pigment, metal free phthalocyanine or metal phthalocyanine (metal phthalocyanine other than titanyl phthalocyanine (1)) is mentioned, for example. Examples of crystals of metal-free phthalocyanine include, for example, X-type crystals of metal-free phthalocyanine (hereinafter sometimes referred to as X-type metal-free phthalocyanine). The metal-free phthalocyanine is represented, for example, by a chemical formula (CG-1).

  Examples of metal phthalocyanines include phthalocyanines coordinated with metals other than titanium oxide (more specifically, V-type hydroxygallium phthalocyanine or chlorogallium phthalocyanine etc.). The phthalocyanine pigment may be crystalline or non-crystalline. Further, chlorogallium phthalocyanin is represented by a chemical formula (CG-3). The V-type hydroxygallium phthalocyanine is represented, for example, by a chemical formula (CG-4).

  A charge generating agent having an absorption wavelength in a desired region may be used alone, or two or more charge generating agents may be used in combination. Furthermore, for example, in a digital optical image forming apparatus, it is preferable to use a photosensitive member having sensitivity in a wavelength region of 700 nm or more. Examples of digital optical image forming apparatuses include a laser beam printer using a light source such as a semiconductor laser, or a facsimile.

  In the case of applying a photoreceptor to an image forming apparatus using a short wavelength laser light source, anthanthrone based pigments or perylene based pigments are suitably used as the charge generating agent. The wavelength of the short wavelength laser light is, for example, 350 nm or more and 550 nm or less.

  The content of the charge generating agent is preferably 0.1 parts by mass to 50 parts by mass with respect to 100 parts by mass of the binder resin in the photosensitive layer, and 0.5 parts by mass to 30 parts by mass More preferable.

[3. Hole transport agent]
As the hole transport agent, for example, oxadiazole compounds such as 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole; 9- (4-diethylaminostyryl) anthracene Such styryl compounds; carbazole compounds such as polyvinylcarbazole; organic polysilane compounds; pyrazoline compounds such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline; hydrazone compounds; triphenylamine compounds; Nitrogen-containing cyclic compounds such as oxazole compounds, isoxazole compounds, thiazole compounds, imidazole compounds, pyrazole compounds, or triazole compounds; nitrogen-containing condensed polycyclic compounds such as indole compounds or thiadiazole compounds Compounds are mentioned. As the hole transfer agent, one type may be used alone, or two or more types may be used in combination.

  Among these hole transfer agents, hole transfer agents represented by the following chemical formulas (HT-1) to (HT-8) (hereinafter, hole transfer agents (HT-1) to (HT-8) respectively Is sometimes described)).

  Among these hole transfer agents, hole transfer agents (HT-2) to (HT-6) and (HT-8) are preferable from the viewpoint of improving the charge stability of the photoreceptor. Further, among these hole transfer agents, a hole transfer agent (HT-5) is preferable from the viewpoint of improving the sensitivity characteristics of the photoreceptor. And from a viewpoint of controlling generating of a transfer memory, hole transport agents (HT-2)-(HT-8) are preferred among these hole transport agents.

  The content of the hole transfer agent is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the binder resin in the photosensitive layer.

  The content of the triphenylamine derivative (1) in the hole transfer agent is preferably 80% by mass or more, and more preferably 90% by mass or more, based on the total mass of the hole transfer agent. Particularly preferred is 100% by mass.

[4. Electron transport agent]
Electron transport agents include quinone derivatives (2). The quinone derivative (2) is represented by the general formula (2).

In General Formula (2), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

In the general formula (2), the alkyl groups having 1 to 4 carbon atoms represented by R ¹ and R ² preferably each independently represent a methyl group, an isopropyl group or a t-butyl group, each of which is a methyl group It is more preferable to represent an isopropyl group or a t-butyl group, and it is further preferable to represent a t-butyl group.

Specific examples of the quinone derivative (2) include the quinone derivative (2) shown in Table 1.

  Among these quinone derivatives (2), quinone derivatives represented by the chemical formulas (2-1), (2-8) and (2-17) (hereinafter referred to as quinone derivatives (2-1) and (2- 8) and (2-17) may be mentioned, and in view of charge stability, quinone derivatives (2-17) are more preferred.

  The electron transfer agent may be used in combination with the quinone derivative (2) in combination with another electron transfer agent other than the quinone derivative (2). Another electron transport agent is suitably selected from well-known electron transport agents.

  As another electron transport agent, for example, quinone compounds other than quinone derivative (2), diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7 -Tetranitro-9-fluorenone compound, dinitroanthracene compound, dinitroacridine compound, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, or dibromoanhydride Maleic acid is mentioned. Examples of quinone compounds other than the quinone derivative (2) include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds. These electron transport agents may be used alone or in combination of two or more.

  The content of the electron transfer agent is preferably 5 parts by mass or more and 100 parts by mass or less, and more preferably 10 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the binder resin in the photosensitive layer.

  The content of the quinone derivative (2) in the electron transfer agent is preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass with respect to the total mass of the electron transfer agent. Being particularly preferred.

[5. Binder resin]
The binder resin disperses and fixes the charge generating agent and the like in the photosensitive layer. As binder resin, a thermoplastic resin, a thermosetting resin, or a photocurable resin is mentioned, for example. As a thermoplastic resin, for example, polycarbonate resin (more specifically, bisphenol Z type, bisphenol ZC type, bisphenol C type, or bisphenol A type, etc.), polyarylate resin, styrene-butadiene resin, styrene-acrylonitrile resin, Styrene-maleic acid resin, acrylic acid resin, styrene-acrylic acid resin, polyethylene resin, ethylene-vinyl acetate resin, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate resin, Alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, or polyether resins may be mentioned. As a thermosetting resin, a silicone resin, an epoxy resin, a phenol resin, a urea resin, a melamine resin, or the other crosslinkable thermosetting resin is mentioned, for example. As a photocurable resin, epoxy-acrylic acid type resin or urethane-acrylic acid type resin is mentioned, for example. Among these binder resins, polycarbonate resins are preferable, and bisphenol Z-type polycarbonate resins are more preferable. The bisphenol Z polycarbonate resin has a repeating unit represented by a chemical formula (Resin-1). Hereinafter, the binder resin which has a repeating unit represented by Chemical formula (Resin-1) may be described as bisphenol Z-type polycarbonate resin (Resin-1). In addition, binder resin may be used individually by 1 type, and may be used combining 2 or more types.

  The viscosity average molecular weight of the binder resin is preferably 40,000 or more, and more preferably 40,000 or more and 52,500 or less. When the viscosity average molecular weight of the binder resin is 40,000 or more, the abrasion resistance of the binder resin can be sufficiently enhanced, and the photosensitive layer becomes difficult to be abraded. In addition, when the viscosity average molecular weight of the binder resin is 52,500 or less, the binder resin is easily dissolved in the solvent when forming the photosensitive layer, and the viscosity of the coating solution for the photosensitive layer does not become too high. As a result, it becomes easy to form a photosensitive layer.

[6. Additive]
The photosensitive layer may contain various additives as long as the electrophotographic characteristics of the photoreceptor are not adversely affected. As the additive, for example, an antidegradant (more specifically, an antioxidant, a radical scavenger, a quencher, an ultraviolet absorber, etc.), a softener, a surface modifier, an extender, a thickener, Dispersion stabilizers, waxes, acceptors, donors, surfactants, plasticizers, sensitizers, or leveling agents may be mentioned. Examples of the antioxidant include hindered phenols, hindered amines, paraphenylene diamines, arylalkanes, hydroquinones, spirochromans, spiroindanones or derivatives thereof, organic sulfur compounds, or organic phosphorus compounds.

[7. Middle layer]
The intermediate layer contains, for example, inorganic particles and a resin (resin for an intermediate layer). Due to the presence of the intermediate layer, the flow of current generated when the photosensitive member is exposed is smoothed while maintaining the insulation state to a degree that can suppress the occurrence of leakage, and it becomes easy to suppress the rise in resistance.

  As the inorganic particles, for example, particles of metal (more specifically, aluminum, iron or copper etc.), metal oxides (more specifically, titanium oxide, alumina, zirconium oxide, tin oxide or zinc oxide) Etc., or particles of non-metallic oxides (more specifically, silica etc.). One of these inorganic particles may be used alone, or two or more thereof may be used in combination.

  The resin for the intermediate layer is not particularly limited as long as it is used as a resin for forming the intermediate layer.

  The intermediate layer may contain various additives as long as the electrophotographic characteristics of the photoreceptor are not adversely affected. The additives are the same as the additives of the photosensitive layer.

[8. Method of manufacturing photoreceptor]
Next, with reference to FIG. 1, an example of a method of manufacturing the photosensitive member 1 will be described. The method of manufacturing the photosensitive member 1 includes, for example, a photosensitive layer forming step. In the photosensitive layer forming step, the photosensitive layer coating solution is applied onto the conductive substrate 2 and the solvent contained in the applied photosensitive layer coating solution is removed to form the photosensitive layer 3. The coating solution for a photosensitive layer contains at least a titanyl phthalocyanine (1) as a charge generating agent, a hole transporting agent, a quinone derivative (2) as an electron transporting agent, a binder resin, and a solvent. The coating solution for a photosensitive layer is prepared by dissolving or dispersing titanyl phthalocyanine (1) as a charge generating agent, a hole transporting agent, a quinone derivative (2) as an electron transporting agent, and a binder resin in a solvent. Be prepared. If necessary, an electron transfer agent and various additives may be added to the coating solution for the photosensitive layer.

  The solvent contained in the coating solution for the photosensitive layer is not particularly limited as long as the components contained in the coating solution for the photosensitive layer can be dissolved or dispersed. As the solvent, for example, alcohols (more specifically, methanol, ethanol, isopropanol or butanol etc.), aliphatic hydrocarbons (more specifically, n-hexane, octane or cyclohexane etc.), aromatic Hydrocarbons (more specifically, benzene, toluene, or xylene etc.), halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride, or chlorobenzene etc.), ethers (more specifically, , Dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, or diethylene glycol dimethyl ether, etc., ketones (more specifically, acetone, methyl ethyl ketone, or cyclohexanone etc.), esters (more specifically, ethyl acetate, or acetic acid) Me Le etc.), dimethyl formaldehyde, N, N-dimethylformamide (DMF), or dimethylsulfoxide. These solvents may be used alone or in combination of two or more. Among these solvents, in order to improve the workability at the time of production of the photosensitive member 1, solvents other than halogenated hydrocarbons are preferable.

  The coating solution for the photosensitive layer is prepared by mixing the components and dispersing in a solvent. For mixing or dispersing, for example, a bead mill, a roll mill, a ball mill, an attritor, a paint shaker, or an ultrasonic disperser is used.

  The coating solution for photosensitive layer may contain, for example, a surfactant or a leveling agent in order to improve the dispersibility of each component or the surface smoothness of each layer to be formed.

  The method for applying the photosensitive layer coating solution is not particularly limited as long as it is a method capable of uniformly applying the photosensitive layer coating solution on the conductive substrate 2, for example. As a coating method, a dip coating method, a spray coating method, a spin coating method, or a bar coating method is mentioned, for example.

  The method of removing the solvent contained in the coating solution for photosensitive layer is not particularly limited as long as the solvent in the coating solution for photosensitive layer can be evaporated. Examples of the method for removing the solvent include 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 can be mentioned. The heat treatment conditions are, for example, a temperature of 40 ° C. to 150 ° C., and a time of 3 minutes to 120 minutes.

  The method of manufacturing the photoreceptor 1 may further include the step of forming the intermediate layer 4 and / or the step of forming the protective layer 5 as necessary. In the step of forming the intermediate layer 4 and the step of forming the protective layer 5, known methods are appropriately selected.

  The photoreceptor 1 is used, for example, as an image carrier in an image forming apparatus. The image forming apparatus described later in the second embodiment includes a charging unit that contacts the image carrier and applies a DC voltage to the image carrier.

  The photoconductor 1 according to the first embodiment has been described above with reference to FIG. According to the photosensitive member 1 according to the first embodiment, the sensitivity characteristic is excellent, and the generation of the transfer memory can be suppressed.

Second Embodiment Image Forming Apparatus
The second embodiment relates to an image forming apparatus. The image forming apparatus according to the second embodiment includes an image carrier, a charging unit, an exposure unit, a developing unit, and a transfer unit. The charging unit charges the surface of the image carrier. The exposure unit exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier. The developing unit develops the electrostatic latent image as a toner image. The transfer unit transfers the toner image from the image carrier to the transfer body. The image carrier is the electrophotographic photosensitive member according to the first embodiment. The charging polarity of the charging unit is positive.

  The image forming apparatus according to the second embodiment can suppress image defects. Such image defects include, for example, image defects caused by deterioration of sensitivity characteristics and generation of transfer memory. The reason is presumed as follows. The image forming apparatus according to the second embodiment includes the photosensitive member according to the first embodiment as an image carrier. The photoreceptor according to the first embodiment has excellent sensitivity characteristics, and can suppress the occurrence of transfer memory. Thus, the image forming apparatus according to the second embodiment can suppress image defects.

  Hereinafter, an image forming apparatus 100 according to the second embodiment will be described with reference to FIG. FIG. 2 is a schematic view showing the configuration of one aspect of the image forming apparatus 100 according to the second embodiment.

  The image forming apparatus 100 is not particularly limited as long as it is an electrophotographic image forming apparatus. The image forming apparatus 100 may be, for example, a monochrome image forming apparatus or a color image forming apparatus. When the image forming apparatus 100 is a color image forming apparatus, the image forming apparatus 100 employs, for example, a tandem system. Hereinafter, the tandem type image forming apparatus 100 will be described as an example.

  The image forming apparatus 100 includes image forming units 40 a, 40 b, 40 c and 40 d, a transfer belt 50, and a fixing unit 52. Hereinafter, each of the image forming units 40 a, 40 b, 40 c, and 40 d will be referred to as an image forming unit 40 if it is not necessary to distinguish.

  The image forming unit 40 includes an image carrier, a charging unit 42, an exposure unit 44, a developing unit 46, and a transfer unit 48. An image carrier is provided at a central position of the image forming unit 40. The image carrier is provided rotatably in the arrow direction (counterclockwise). A charging unit 42, an exposure unit 44, a developing unit 46, and a transfer unit 48 are provided around the image carrier sequentially from the upstream side of the rotation direction of the image carrier with respect to the charging unit 42. The image forming unit 40 may further include one or both of a cleaning unit (not shown) and a charge removing unit (not shown).

  The charging unit 42 charges the surface of the image carrier. The charging polarity of the charging unit is positive. The charging unit 42 is a non-contact or contact charging unit. As the non-contact type charging unit 42, for example, a corotron charger or a scorotron charger may be mentioned. Examples of the contact type charging unit 42 include a charging roller or a charging brush.

  The exposure unit 44 exposes the charged surface of the image carrier. Thereby, an electrostatic latent image is formed on the surface of the image carrier. The electrostatic latent image is formed based on the image data input to the image forming apparatus 100.

  The developing unit 46 supplies toner to the surface of the image carrier and develops the electrostatic latent image as a toner image.

  The transfer belt 50 conveys the recording medium P between the image carrier and the transfer unit 48. The transfer belt 50 is an endless belt. The transfer belt 50 is provided rotatably in the arrow direction (clockwise).

  The transfer unit 48 transfers the toner image developed by the developing unit 46 to the recording medium P from the surface of the image carrier. When the toner image is transferred from the image carrier to the recording medium P, the image carrier is in contact with the recording medium P. That is, the image forming apparatus 100 adopts a so-called direct transfer method. Examples of the transfer unit 48 include a transfer roller.

  The toner images of a plurality of colors (for example, four colors of black, cyan, magenta and yellow) are sequentially superimposed on the recording medium P on the transfer belt 50 by each of the image forming units 40a to 40d. When the image forming apparatus 100 is a monochrome image forming apparatus, the image forming apparatus 100 includes the image forming unit 40a, and the image forming units 40b to 40d are omitted.

  The fixing unit 52 heats and / or pressurizes the unfixed toner image transferred to the recording medium P by the transfer unit 48. The fixing unit 52 is, for example, a heating roller and / or a pressure roller. The toner image is fixed on the recording medium P by heating and / or pressurizing the toner image. As a result, an image is formed on the recording medium P.

  The image forming apparatus 100 can include a charging roller as the charging unit 42. When charging the surface of the image carrier, the charging roller contacts the surface of the image carrier. Usually, in an image forming apparatus provided with a charging roller, a transfer memory tends to occur. However, the image forming apparatus 100 includes the photosensitive member according to the first embodiment as an image carrier. The photoreceptor according to the first embodiment can suppress the occurrence of transfer memory. Therefore, even when the image forming apparatus according to the second embodiment includes the charging roller as the charging unit 42, it is possible to suppress the occurrence of the image defect caused by the generation of the transfer memory.

  The voltage applied by the charging unit 42 is not particularly limited, and examples thereof include a DC voltage, an AC voltage, or a superimposed voltage in which a DC current is superimposed on an AC current. When the charging unit 42 applies only a DC voltage, the surface of the image carrier is likely to be uniformly charged to a constant potential because the voltage value applied to the image carrier is constant. In addition, when the charging unit 42 applies only a DC voltage, the amount of abrasion of the photosensitive layer 3 tends to decrease. As a result, a suitable image can be formed.

  In general, direct-current voltage tends to generate transfer memory more easily than alternating-current voltage. However, the image forming apparatus 100 according to the second embodiment includes the photosensitive member according to the first embodiment as an image carrier. The photoreceptor according to the first embodiment can suppress the occurrence of transfer memory. Therefore, the image forming apparatus 100 according to the second embodiment can suppress the occurrence of the image defect caused by the transfer memory even if the image forming apparatus 100 includes the charging unit which applies the DC voltage in contact with the image holding member.

  The image forming apparatus 100 employs a direct transfer method. Usually, in an image forming apparatus adopting a direct transfer method, since an image carrier is easily influenced by a transfer bias, a transfer memory is usually easily generated. However, the image forming apparatus 100 according to the second embodiment includes the photoconductor 1 according to the first embodiment as an image carrier. The photoreceptor according to the first embodiment can suppress the occurrence of transfer memory. Therefore, it is considered that when the photosensitive member 1 according to the first embodiment is provided as the image carrier, the occurrence of image defects caused by the transfer memory can be suppressed even when the image forming apparatus 100 adopts the direct transfer method. Be

  The image forming apparatus according to the second embodiment has been described above. The image forming apparatus according to the second embodiment can suppress the occurrence of image defects by including the photosensitive member according to the first embodiment as an image carrier.

Third Embodiment Process Cartridge
The third embodiment relates to a process cartridge. The process cartridge according to the third embodiment includes the photosensitive member according to the first embodiment. Continuing, with reference to FIG. 2, the process cartridge according to the third embodiment will be described. The process cartridge comprises a unitized image carrier. The process cartridge adopts a configuration in which at least one unit selected from the group consisting of a charging unit 42, an exposure unit 44, a developing unit 46, and a transfer unit 48 in addition to an image carrier is unitized. The process cartridge corresponds to, for example, each of the image forming units 40 a to 40 d. The process cartridge may further include one or both of a cleaning device (not shown) and a static eliminator (not shown). The process cartridge is designed to be removable from the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and can be easily and quickly replaced including the image carrier when the sensitivity characteristic of the image carrier is deteriorated.

  The process cartridge according to the third embodiment has been described above. The process cartridge according to the third embodiment can suppress the occurrence of image defects by including the photosensitive member according to the first embodiment as an image carrier.

  Hereinafter, the present invention will be more specifically described using examples. In addition, this invention is not limited at all to the range of an Example.

<1. Material of Photoreceptor>
(1-1. Charge generating agent)
As materials for forming the photosensitive layer of the photosensitive member, the following charge generating agent, hole transporting agent, electron transporting agent, and binder resin were prepared. The charge generating agents (CG-1) to (CG-4) described in the first embodiment were prepared as charge generating agents. The charge generating agent (CG-1) was a metal-free phthalocyanine represented by a chemical formula (CG-1) (hereinafter sometimes referred to as metal-free phthalocyanine (CG-1)). The crystal structure of metal-free phthalocyanine (CG-1) was of type X.

  The charge generating agent (CG-2) is titanyl phthalocyanine (1). The crystal structure of titanyl phthalocyanine (1) was Y-type. The X-ray diffraction spectrum had peaks at 9.7 °, 11.7 °, 15.0 °, 23.5 °, 27.3 °. The main peak was 27.3 °.

  The charge generating agent (CG-3) was chlorogallium phthalocyanine represented by a chemical formula (CG-3) (hereinafter sometimes referred to as chlorogallium phthalocyanine (CG-3)). The main peaks in the X-ray diffraction spectrum were at 7.4 °, 16.6 °, 25.5 ° and 28.3 °, and the maximum peak was at 7.4 °.

  The charge generating agent (CG-4) was hydroxygallium phthalocyanine represented by a chemical formula (CG-4) (hereinafter sometimes referred to as hydroxygallium phthalocyanine (CG-4)). The crystal structure of hydroxygallium phthalocyanine (CG-4) was of type V. The main peaks in the X-ray diffraction spectrum are 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 °, 25.1 °, 28.3 °, and the maximum peak is 7. It was 5 °.

(1-2. Hole transport agent)
The hole transport agent prepared the hole transport agents (HT-1) to (HT-8) among the hole transport agents described in the first embodiment.

(1-3. Electron transport agent)
Among the quinone derivatives (2) described in the first embodiment, quinone derivatives (2-1), (2-8), and (2-17) were prepared as the electron transfer agent. In addition, a compound represented by a chemical formula (ET-2) (hereinafter sometimes referred to as a compound (ET-2)) was prepared as an electron transfer agent.

(1-4. Binder resin)
As a binder resin, bisphenol Z-type polycarbonate resin (Resin-1) described in the first embodiment was prepared.

<2. Production of photoconductor>
Photosensitive members (A-1) to (A-12) and (B-1) to (B-8) were manufactured using the materials for forming the photosensitive layer of the prepared photosensitive member.

(2-1. Manufacture of photoconductor (A-1))
In a container, 5 parts by mass of a charge generating agent (CG-2), 50 parts by mass of a hole transporting agent (HT-1), 35 parts by mass of an electron transporting agent (2-1), and a binder resin (Resin-1) 100 parts by mass and 750 parts by mass of tetrahydrofuran as a solvent were charged. The contents of the container were mixed and dispersed for 50 hours using a ball mill to prepare a coating solution for photosensitive layer.

  The coating solution for photosensitive layer was applied onto the conductive substrate by dip coating to form a coating film on the conductive substrate. Subsequently, it was dried at 100 ° C. for 40 minutes to remove tetrahydrofuran from the coating film. Thus, a photosensitive member (A-1) including a photosensitive layer with a thickness of 35 μm on a conductive substrate was obtained.

(2-2. Production of photoreceptors (A-2) to (A-15), (A-22) to (A-30) and (B-1) to (B-24))
Photosensitive members (A-2) to (A-15), (A-22) to (A-30), and (A-22) and (A-30) and in the same manner as in the production of photosensitive member (A-1) except that the following points were changed. (B-1) to (B-24) were produced. Compounds represented by the charge generating agent (CG-2), the hole transporting agent (HT-1), and the quinone derivative (2-1) as an electron transporting agent used for producing the photosensitive member (A-1) Instead, charge generating agents (CGM), hole transport agents (HTM), and electron transport agents (ETM) of the types shown in Table 2 and Table 3, respectively, were used.

<3. Evaluation of photoconductor>
(3-1. Charge stability evaluation)
The stability of the surface potential during charging for each of the photosensitive members (A-1) to (A-15), (A-22) to (A-30) and (B-1) to (B-24) The evaluation of (charging stability) was performed.

  The photosensitive member was attached to an image forming apparatus ("FS-C5250 DN" manufactured by KYOCERA Document Solutions Inc.). The image forming apparatus is provided with a contact type charging roller that applies a DC voltage as a charging unit. The chargeable sleeve was formed of a chargeable rubber in which conductive carbon is dispersed in epichlorohydrin resin. The charging voltage of the charging unit was set to +1.4 kV.

The charging voltage was kept applied to the photosensitive member for 30 minutes using the charging unit. The surface potential of the photoreceptor was continuously measured during the application of the charging voltage to the photoreceptor for 30 minutes. The surface potential of the photosensitive member immediately after the application of the charging voltage was started was + 570 ± 30 V. The maximum value of the surface potential of the photosensitive member measured in the application of the charging voltage is V ₀ (unit: V), and the minimum value is V ₁ (unit: V). The measurement environment was a temperature of 23 ° C. and a relative humidity of 50% RH.

From the measured maximum value V ₀ and minimum value V ₁ of the surface potential of the photosensitive member, the difference ΔV _{0 of the} surface potential was obtained using the formula “ΔV ₀ = V ₁ −V ₀ ”. The difference ΔV ₀ of the surface potential of the photosensitive member is shown in Table 2. The smaller the absolute value of the surface potential difference ΔV ₀ of the photosensitive member, the more stable the surface potential of the photosensitive member is at the time of charging.

(3-2. Evaluation of sensitivity characteristics and transfer memory)
The charging stability was evaluated for each of the photosensitive members (A-1) to (A-15), (A-22) to (A-30) and (B-1) to (B-24). .

  The photosensitive member was attached to an image forming apparatus ("FS-C5250 DN" manufactured by KYOCERA Document Solutions Inc.). The image forming apparatus is provided with a contact type charging roller that applies a DC voltage as a charging unit. Further, this image forming apparatus adopts a direct transfer method in which a toner image is directly put on an intermediate transfer belt. The chargeable sleeve is provided on the surface of the charge roller, and is formed of a chargeable rubber whose main constituent material is epichlorohydrin resin. The charging voltage of the charging portion was adjusted, and the charging potential (white sheet portion potential Vs) of the photosensitive member corresponding to the developing portion position at non-exposure was set to 570 V ± 10 V.

Next, monochromatic light was extracted from the white light of the halogen lamp using a band pass filter. The monochromatic light thus extracted was measured for the charging potential of the photosensitive member corresponding to the development position when exposed to a laser beam having a wavelength of 780 nm, a half width of 20 nm, and a light energy of 1.16 μJ / cm ² . The surface potential of the measured exposure area was taken as the sensitivity potential V _L (unit: V). The surface potential of the non-exposed area measured was taken as the blank portion potential V ₃ (unit: V). The sensitivity potential V _L and the white sheet portion potential V ₃ were measured with the transfer bias turned off. Subsequently, a transfer bias of −2 kV was applied, and the surface potential of the non-exposed area (white paper portion) was measured in a state where the transfer bias was turned on. The surface potential of the unexposed areas obtained (blank section) and a blank portion potential V _4. From the resulting V ₃ and V ₄ Metropolitan using Equation "transfer memory potential ΔVtc = V ₄ -V _3" transfer memory potential DerutaVtc (Unit: V) was obtained. The measurement environment was a temperature of 23 ° C. and a relative humidity of 50% RH.

Tables 2 and 3 show the obtained sensitivity potential V _L and transfer memory potential ΔVtc. The smaller the value of the sensitivity potential V _L, the better the sensitivity characteristics of the photosensitive member. The smaller the absolute value of the transfer memory potential ΔVtc, the more the generation of the transfer memory is suppressed.

  In Tables 2 and 3, CGM, HTM, and ETM in the “material” column indicate a charge generator, a hole transfer agent, and an electron transfer agent, respectively.

  As shown in Table 2, in the photosensitive members (A-1) to (A-15) and (A-22) to (A-30), the photosensitive layer is a quinone derivative (2-1) as an electron transfer agent, Any of (2-8) and (2-17) is included. The quinone derivatives (2-1), (2-8), and (2-17) are quinone derivatives represented by the general formula (2). In the photosensitive members (A-1) to (A-15) and (A-22) to (A-30), the photosensitive layer contains a charge generating agent (CG-2). The charge generating agent (CG-2) is a titanyl phthalocyanine represented by the chemical formula (1).

As shown in Table 2, in the photosensitive members (A-1) to (A-15) and (A-22) to (A-30), the sensitivity potential (V _L ) is +82 V or more and +122 V or less. The transfer memory potential difference (ΔVtc) is −45 V or more and −28 V or less.

  As shown in Table 3, in the photosensitive members (B-1) to (B-24), the photosensitive layer contains a quinone derivative (2-17) or a compound (ET-2) as an electron transfer agent, and the charge generating agent (CG-1), (CG-2), (CG-3), or (CG-4) is included. Specifically, in the photosensitive members (B-1) to (B-5), (B-7) to (B-18), and (B-20) to (B-24), the photosensitive layer serves as an electron transfer agent. It contains a compound (ET-2). The compound (ET-2) is not a quinone derivative represented by the general formula (2). In the photosensitive members (B-1) to (B-6), the photosensitive layer contains a charge generating agent (CG-1). In the photosensitive members (B-12) to (B-13) and (B-23), the photosensitive layer contains a charge generating agent (CG-3). In the photosensitive members (B-14) to (B-15) and (B-24), the photosensitive layer contains a charge generating agent (CG-4). The charge generating agents (CG-1) and (CG-3) to (CG-4) are not charge generating agents represented by the chemical formula (1).

As shown in Table 3, in the photosensitive members (B-1) to (B-24), the sensitivity potential (V _L ) is +142 V or more and +176 V or less. In the photosensitive members (B-1) to (B-24), the transfer memory potential difference (ΔVtc) is −82 V or more and −45 V or less.

Therefore, the photosensitive members (A-1) to (A-15) and (A-22) to (A-30) have sensitivity potentials V _L compared to the photosensitive members (B-1) to (B-24). It is apparent that the absolute value of the difference ΔVtc of the transfer memory potential is small. From the above, it is clear that the photosensitive member according to the present invention has excellent sensitivity characteristics and suppresses the occurrence of transfer memory.

As shown in Table 2, in the photoreceptor (A-15), the photosensitive layer contains a quinone derivative (2-17) as an electron transfer agent. The surface potential difference ΔV ₀ is −46V.

As shown in Table 2, in the photoreceptors (A-13) and (A-14), the photosensitive layer contains a quinone derivative (2-1) or (2-8) as an electron transfer agent. The surface potential difference ΔV ₀ is -75 V and -50 V, respectively.

  The tendency of such photosensitive members (A-13) to (A-15) is the same as that of photosensitive members (A-1) to (A-3) and (A-4) to (A-6) and (A-7). ) To (A-9), (A-10) to (A-12), (A-22) to (A-24), (A-25) to (A-27), and (A-28) It is confirmed also in (A-30).

  From the above, it is clear that the quinone derivative (2-17) has superior charge stability as compared to the quinone derivatives (2-1) and (2-8).

As shown in Table 2, in the photoreceptors (A-4) to (A-15), (A-22) to (A-24), and (A-28) to (A-30), the hole transport Agents (HT-2), (HT-3), (HT-4), (HT-5), (HT-6), or (HT-8). The surface potential difference ΔV ₀ is -82 V or more and -40 V or less.

As shown in Table 2, in the photosensitive members (A-1) to (A-3) and (A-25) to (A-27), the hole transfer agent (HT-1) or (HT-7) was used. Including. The surface potential difference ΔV ₀ is -120 V or more and -103 V or less.

  From the above, photoreceptors (A-4) to (A-15) and (A-22) to (A-24) containing hole transfer agents (HT-2) to (HT-6) or (HT-8). ), And (A-28) to (A-30) are photoreceptors (A-1) to (A-3) and (A-) containing a hole transfer agent (HT-1) or (HT-7). It is apparent that the charging stability is superior to (25) to (A-27).

  As shown in Table 2, in the photosensitive members (A-4) to (A-15) and (A-22) to (A-30), the photosensitive layers were formed of hole transport agents (HT-2) to (HT) -8). In the photosensitive members (A-4) to (A-15) and (A-22) to (A-30), the potential difference (ΔVtc) of the transfer memory is −39 V or more and −28 V or less.

  As shown in Table 2, in the photoreceptors (A-1) to (A-3), the photosensitive layer contains a hole transfer agent (HT-1). In the photosensitive members (A-1) to (A-3), the potential difference (ΔVtc) of the transfer memory is −45 V or more and −42 V or less.

  From the above, the photoreceptors (A-4) to (A-15) and (A-22) to (A-30) containing the hole transfer agents (HT-2) to (HT-8) It is apparent that the generation of transfer memory is further suppressed as compared with the photoreceptors (A-1) to (A-3) containing the agent (HT-1).

  The photoreceptor according to the present invention can be suitably used as an electrophotographic photoreceptor.

1 electrophotographic photosensitive member 2 conductive substrate 3 photosensitive layer

Claims (7)

An electrophotographic photosensitive member comprising a conductive substrate and a photosensitive layer,
The photosensitive layer is a single layer type photosensitive layer,
The photosensitive layer contains at least a charge generating agent, a hole transporting agent, an electron transporting agent, and a binder resin,
The charge generating agent includes titanyl phthalocyanine represented by the following chemical formula (1),
The electron transport agent, see contains the quinone derivative represented by the following general formula (2),
The electrophotographic photosensitive member, wherein the hole transport agent comprises a compound represented by a chemical formula (HT-6) or a chemical formula (HT-8) .

In the general formula (2),
Each of R ¹ and R ² independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

In the general formula (2),
The electrophotographic photosensitive member according to claim ^1, wherein R ¹ and R ² each represent a methyl group, an isopropyl group or a t-butyl group. In the general formula (2),
The electrophotographic photosensitive member according to claim ^1, wherein R ¹ and R ² each represent a t-butyl group. A process cartridge comprising the electrophotographic photosensitive member according to any one of claims 1 to 3 . An image carrier,
A charging unit that charges the surface of the image carrier;
An exposure unit for exposing the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier;
A developing unit for developing the electrostatic latent image as a toner image;
An image forming apparatus including: a transfer unit configured to transfer the toner image from the image carrier to a transfer body;
The charging polarity of the charging unit is positive,
The image forming apparatus according to any one of claims 1 to 3 , wherein the image carrier is an electrophotographic photosensitive member. The image forming apparatus according to claim 5 , wherein the charging unit contacts the image carrier and applies a DC voltage to the image carrier. The transfer member is a recording medium, the image forming apparatus according to claim 5 or 6.

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