Electrophotographic photoreceptor, method for manufacturing the same, and image forming apparatus equipped therewith

Abstract

The objective is to provide an electrophotographic photoreceptor with excellent crack resistance due to long-term contact with charged materials, a method for manufacturing the same, and an image forming apparatus equipped therewith. [Solution] The above problems are solved by an electrophotographic photoreceptor comprising at least a laminated photosensitive layer on a conductive support, in which a charge generating layer containing a charge generating material and a charge transport layer containing a charge transport material are laminated in this order, wherein the charge transport layer contains a specific polycarbonate resin having a biphenyl structure as a binder resin, and the outermost layer of the electrophotographic photoreceptor that contacts the charging member of an image forming apparatus has an elastic power W of 52% or more and a creep value C of 2.70% or less when loaded with a Vickers square pyramidal diamond indenter with a facing angle of 136° under the conditions of a maximum indentation load of 5mN, a loading time to reach the maximum indentation load of 10 seconds, a load holding time of 5 seconds, and an unloading time of 10 seconds in an environment of temperature 25°C and relative humidity 50%, using a Vickers square pyramidal diamond indenter, and having an elastic power W of 52% or more and a creep value C of 2.70% or less.

Description

[Technical Field]

[0001] This disclosure relates to an electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor"), a method for manufacturing the same, and an image forming apparatus equipped with the same. [Background technology]

[0002] Electrophotographic image forming machines, which use electrophotographic technology to form images, are widely used in photocopiers, printers, and facsimile machines. The photoreceptor in these machines is often a photoreceptor with a photosensitive layer primarily composed of organic photoconductive materials (also called an "organic photoreceptor"), and for environmental reasons, contact-type charging devices (charging devices) that do not generate ozone, such as contact roller chargers (charging rollers), are widely used. However, the photoreceptor and the contact roller are always in contact under constant pressure. If this condition is left unattended for a long period, i.e., if the image forming apparatus is stopped, the material from the charging roller may seep into the photoreceptor, causing cracks to form. As a result, image defects due to cracks may occur.

[0003] Therefore, a method has been proposed to suppress crack formation by separating the charging roller and the photoreceptor when the image forming apparatus is stopped, thereby suppressing the seepage of the charging roller material into the photoreceptor (see, for example, Japanese Patent Application Publication No. 2000-231243: Patent Document 1). However, this necessitates that the image forming apparatus be equipped with a separation mechanism, which makes the apparatus itself more complex and leads to increased costs.

[0004] Furthermore, a method has been proposed in which a crosslinked charge transport layer with a high crosslinking density is provided on the surface of the photoreceptor to strengthen the surface of the photoreceptor and to suppress the leakage of the charging roller material into the photoreceptor (for example, Japanese Patent Publication No. 2006-030985: Patent Document 2). However, in the manufacturing of photoreceptors, a process involving the creation of a crosslinked charge transport layer, including a crosslinking process, is required, which leads to decreased productivity and increased costs.

[0005] Furthermore, a method has been proposed in which multiple polycarbonate resins are used as the binder resin for the photosensitive layer, and specific plasticizer components are added. Through the interaction of these components, it is possible to maintain excellent durability, abrasion resistance, and sensitivity characteristics while effectively preventing crack formation and crystallization caused by the adhesion of finger oils, etc. (Japanese Patent Publication No. 2007-102199: Patent Document 3). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2000-231243 [Patent Document 2] Patent No. 2006-030985 [Patent Document 3] Patent No. 2007-102199 [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, the present disclosure aims to provide an electrophotographic photoreceptor with excellent crack resistance due to long-term contact with a charged member, a method for manufacturing the same, and an image forming apparatus equipped therewith. [Means for solving the problem]

[0008] The present inventors, through diligent research to solve the above problems, have found that by including a polycarbonate resin having a specific biphenyl structure as the binder resin of the photosensitive layer, and by having the outermost layer of the photoreceptor have a specific elastic power W and creep value C, it is possible to provide a photoreceptor and an image forming apparatus equipped therewith that have improved crack resistance due to long-term contact with a charged member. Furthermore, they have found that by slowly cooling the photosensitive layer under specific conditions during the cooling process of the photoreceptor during manufacturing, it is possible to produce a photoreceptor that has an increased elastic power and a reduced creep value, thereby completing the present invention. The present inventors have confirmed that in the photoreceptor of Patent Document 3 using a binder resin similar to that of the present invention, the effect of suppressing crack generation is insufficient. The present inventors consider that this is because natural cooling (rapid cooling) is performed in the cooling step of the photosensitive layer during photoreceptor production, and it does not have the physical properties of the photoreceptor surface defined in the present invention, similar to Comparative Example 1 described later. Further, Patent Document 3 does not describe the cooling step during layer formation as described above.

[0009] Thus, according to the present disclosure, there is provided an electrophotographic photoreceptor comprising at least a laminated photosensitive layer in which a charge generation layer containing a charge generating substance and a charge transport layer containing a charge transport substance are laminated in this order on a conductive support, wherein the charge transport layer comprises a polycarbonate resin represented by the general formula (I) consisting of structural units (A) and (B) or structural unit (B) alone as a binder resin:

Chemical formula

[0010] (In the formula, R1 to R6 are the same or different and are a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a fluoroalkyl group having 1 to 3 carbon atoms, and the carbon atom of R3 and the carbon atom of R4 may be bonded to each other to form a cyclo ring, and m and n are exponents satisfying the relationship of 0 ≦ m < 1, 0 < n ≦ 1, and m + n = 1) and having an elastic work rate W of 52% or more and a creep value C of 2.70% or less when loaded under the conditions of a maximum indentation load of 5 mN using a Vickers square pyramid diamond indenter with an included angle of 136° in an environment of a temperature of 25°C and a relative humidity of 50%, a load application time required to reach the maximum indentation load of 10 seconds, a load holding time of 5 seconds, and an unloading time of 10 seconds. The electrophotographic photoreceptor is provided.

[0011] ​Also, according to the present disclosure, the above electrophotographic photoreceptor, charging means for charging the electrophotographic photoreceptor, exposure means for exposing the charged electrophotographic photoreceptor to form an electrostatic latent image, development means for developing the electrostatic latent image to form a toner image, transfer means for transferring the toner image onto a recording medium, and cleaning means for removing and recovering the toner remaining on the electrophotographic photoreceptor are provided, An image forming apparatus is provided, wherein the cleaning means includes a blade having an angle of 5° or more and 20° or less with respect to the outer peripheral surface of the electrophotographic photoreceptor.

[0012] Furthermore, according to the present disclosure, there is provided a method for manufacturing the above electrophotographic photoreceptor, A method for manufacturing an electrophotographic photoreceptor is provided, which includes a step of applying a coating solution, heating and drying it, and gradually cooling it at a cooling rate of less than 1°C / min when forming the charge transport layer of the electrophotographic photoreceptor.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide an electrophotographic photoreceptor excellent in crack resistance due to long-term contact with a charging member, a method for manufacturing the same, and an image forming apparatus including the same.

Brief Description of the Drawings

[0014] [Figure 1] It is a diagram for explaining a method for obtaining the creep value C and the elastic work rate W of the outermost surface layer of the photoreceptor. [Figure 2] It is a schematic cross-sectional view showing the configuration of the main part of the photoreceptor F01 of the present disclosure. [Figure 3] It is a schematic side view showing the configuration of the main part of the image forming apparatus 50 of the present disclosure. [Figure 4] It is a diagram for explaining the relationship between the spring pressure of the elastic body of the charging means and the occurrence of cracks. [Figure 5] It is a diagram for explaining the relationship between the hardness of the charging means and the occurrence of cracks. [Figure 6]This is a diagram for explaining the angle (blade angle) θ2 formed between the blade of the cleaning means and the outer peripheral surface of the photoreceptor.

Embodiments for Carrying Out the Invention

[0015] The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor comprising at least a laminated photosensitive layer in which a charge generation layer containing a charge generating substance and a charge transport layer containing a charge transport substance are laminated in this order on a conductive support. The charge transport layer consists of structural units (A) and (B) as a binder resin, or a general formula (I) consisting of structural unit (B) alone:

Chemical formula

[0016] (In the formula, R1 to R6 are the same or different and are a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a fluoroalkyl group having 1 to 3 carbon atoms. The carbon atom of R3 and the carbon atom of R4 may be bonded to each other to form a cyclo ring. m and n are exponents satisfying the relationship of 0 ≦ m < 1, 0 < n ≦ 1, and m + n = 1) and contains a polycarbonate resin represented by When the outermost surface layer of the electrophotographic photoreceptor is loaded under the conditions of a maximum indentation load of 5 mN using a Vickers square pyramid diamond indenter with an opposing angle of 136° in an environment of a temperature of 25°C and a relative humidity of 50%, a load required time of 10 seconds until the maximum indentation load, a load holding time of 5 seconds, and an unloading time of 10 seconds, it has an elastic work rate W of 52% or more and a creep value C of 2.70% or less. This is the feature. Hereinafter, the constituent elements characteristic of the photoreceptor of the present disclosure will be described, and then (1) the photoreceptor, (2) the manufacturing method of the photoreceptor, and (3) the image forming apparatus will be described.

[0017] <Binder resin (polycarbonate resin)> The binder resin contained in the charge transport layer of the photoreceptor of the present disclosure is a polycarbonate resin represented by the above general formula (I), which consists of structural units (A) and (B), or structural unit (B) alone. The substituents and exponents in the general formula (I) will be described. Examples of the alkyl group having 1 to 3 carbon atoms for the substituents R1 to R6 include methyl, ethyl, n-propyl, and isopropyl. Examples of the fluoroalkyl group having 1 to 3 carbon atoms for the substituents R1 to R6 include fluoromethyl, difluoromethyl, trifluoromethyl, fluoroethyl, difluoroethyl, trifluoroethyl, fluoropropyl, difluoropropyl, and trifluoropropyl. Examples of the cyclo ring formed by bonding the carbon atom of the substituent R3 and the carbon atom of the substituent R4 to each other include cyclopropylene, cyclobutylene, cyclopentylene, and cyclohexylene.

[0018] The exponents m and n satisfy the relationship of 0 ≦ m < 1, 0 < n ≦ 1, and m + n = 1. In the polycarbonate resin, the structural unit (A) is considered to contribute to the improvement of the resistance to electrical fatigue on the surface of the laminated photosensitive layer. In addition, the biphenyl structure of the structural unit (B) is chemically stable, making it difficult for the crack-causing substances that bleed out from the members of the charging means of the image forming apparatus described later to penetrate into the photoreceptor. Also, by setting the elastic work rate and creep value within the above numerical ranges, the influence of external forces is reduced, so it is considered to contribute to the improvement of printing resistance and crack resistance. The structural unit (B) is essential (n ≠ 0), and particularly when n ≧ 0.35, the crack resistance is further improved. When the exponent n becomes small, the resistance to charging deterioration decreases, so preferably 0.4 ≦ n ≦ 0.65.

[0019] The polycarbonate resin binder resin of the photoreceptor in this disclosure preferably has chain-end groups consisting of monovalent aromatic groups, that is, the chain ends of the polycarbonate resin are sealed by monovalent aromatic groups. The chain-end groups of the polycarbonate resin have the function of improving the lubricity of the surface of the photosensitive layer. Furthermore, the chain-end groups may be monovalent fluorine-containing aliphatic groups. In this case, even if the surface of the outermost layer of the photoreceptor is scraped, a certain amount of fluorine-containing aliphatic groups of the chain-end groups incorporated into the polycarbonate resin will remain on the surface, allowing for control of the lubricity of the photosensitive layer surface and suppression of blade reversal.

[0020] Examples of monovalent aromatic groups at the end of a chain include p-tert-butylphenonyl, p-phenylphenonyl, and p-cumylphenonyl. Examples of monovalent fluorine-containing aliphatic groups at the end of the chain include 2,2-difluoro-2-(perfluorohexyloxy)ethoxy and F1 to F4 listed below. Among these chain-end groups, p-tert-butyl-phenonyl is preferred because introducing a fluorine-containing aliphatic group may result in an excessively high contact angle between the photosensitive layer surface and pure water. By selecting the chain-end groups, it is possible to control the lubricity of the photoreceptor surface, and the above-mentioned chain-end groups are preferred from the viewpoint of improving electrical properties and wear resistance.

[0021] [ka]

[0022] A polycarbonate resin having a specific structure contained in the photosensitive layer of the photoreceptor of the present disclosure can be synthesized, for example, by the method described in Japanese Patent No. 6893205. The above-mentioned chain end groups originate from the end-capturing agent used during resin synthesis. Examples of end-capturing agents include monovalent carboxylic acids and their derivatives and monovalent phenols, specifically p-tert-butylphenol, p-phenylphenol, p-cumylphenol, 2,2-difluoro-2-(perfluorohexyloxy)ethanol, and fluorine-containing alcohols corresponding to (F1) to (F4) above.

[0023] The repeating units (constituent units (A) and (B)) of polycarbonate resin represented by general formula (I) are as follows, but are not limited to these, and two or more types of these resins can also be used in combination.

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] As for the polycarbonate resin, among the polymers (1) to (11) above, polymers (1) and (2) having p-tert-butyl-phenonyl as a chain end group are preferred, with polymer (1) being particularly preferred, from the viewpoint of balancing coating properties during production and print resistance during use.

[0028] <Viscosity-average molecular weight of polycarbonate resin> From the viewpoint of improving crack resistance, polycarbonate resin is preferably made of a viscosity-average molecular weight of 40,000 or more. If the viscosity-average molecular weight is less than 40,000, the print resistance may be insufficient. On the other hand, if the viscosity-average molecular weight exceeds 80,000, the viscosity of the coating solution becomes too high during preparation, which not only reduces the production efficiency of coating film (layer) formation but also increases the risk of coating defects during application. A more preferable viscosity-average molecular weight for polycarbonate resin is approximately 45,000 to 70,000.

[0029] <Creep value C of the outermost surface layer of the photoreceptor> Generally, even under relatively low loads, solid materials gradually undergo a continuous deformation phenomenon, known as creep, as the duration of the applied load increases. Creep is particularly pronounced in organic polymer materials. Creep broadly consists of delayed elastic deformation and plastic deformation components, and is used as an indicator of the flexibility, or viscoelasticity, of a material, with a particularly large contribution to viscosity. Figure 1 illustrates a method for determining the creep value C and elastic power W of the outermost layer of a photoreceptor. The creep value C is a parameter that evaluates the degree of relaxation of the photoreceptor surface film in response to an indentation load, i.e., the change in the amount of indentation of the indenter when a predetermined load is applied to the surface of the photoreceptor via the indenter for a certain period of time.

[0030] The hysteresis line shown in Figure 1 represents the predetermined maximum indentation load F applied when an indentation load is started on the surface of the photoreceptor. max The pushing process until it reaches (A→B), maximum pushing load F max The deformation history (change in indentation depth) is shown for the load holding process (B→C) where the load is held for a certain period of time t, and the unloading process (C→D) from the start of unloading until the load reaches zero and unloading is completed. The creep value C is given by the change in the amount of indentation during the load-holding process (B→C). In this embodiment, the creep value C is measured in an environment of 25°C and 50% relative humidity using a Vickers square pyramidal diamond indenter with a facing angle of 136°, under the conditions of a maximum indentation load of 5mN, a loading time to reach the maximum indentation load of 10 seconds, a load holding time of 5 seconds, and an unloading time of 10 seconds, and is calculated by the following formula (1). C = [(h2-h1) / h1] × 100 (%) (1) (In the formula, h1 is the indentation depth at the point when the maximum load of 5mN is reached (B), and h2 is the indentation depth at the point when the maximum load of 5mN is held for time t (C).)

[0031] In the photoreceptor of this disclosure, the outermost surface layer of the photoreceptor has a creep value C of 2.70% or less, and by reducing the flexibility of the photoreceptor, resistance to cracking can be improved. The lower limit is approximately 2.50%.

[0032] <Elastic power W(ηHU) of the outermost surface layer of the photoreceptor> Generally, when a load is applied to a solid material, the amount of mechanical work W spent during the indentation is... total Of this, only a portion is used as the plastic deformation work Wp, and the remainder is released as the elastic recovery work (elastic deformation work) We when the load is removed. Furthermore, the elastic recovery work We includes both an instantaneous elastic deformation component and a delayed elastic deformation component. Elastic power W, like the creep value C, is used as an indicator of the viscoelasticity of the material, and is a parameter that particularly contributes to elastic recovery.

[0033] In this embodiment, the elastic power W(ηHU) is the mechanical work W, as shown in equation (2) below, from the hysteresis line 8 used to determine the creep value C. total It is determined by the ratio of the work done to restore elasticity We. Mechanical work W total The coefficient of force is given by W = ∫Fdh, and is represented by the area enclosed by the indentation depth curve (A→B) during load increase and the indentation depth h1. The elastic recovery work We within this coefficient is represented by the area enclosed by the indentation depth curve (C→D) during load removal and the indentation depth h2. In this case, the indentation during the load holding process (B→C), i.e., creep, is not included. W(ηHU)=[We / W total ×100(%) (2) (However, W total =We + Wp)

[0034] Since the photoreceptor of the present disclosure is composed of a mixture of a resin and a low-molecular substance, it cannot become a complete plastic body and always contains some elastic components. The direction in which W decreases is considered to be such that the elastic recovery when an external stress is applied is small, that is, it approaches a plastic body. In the photoreceptor of the present disclosure, the outermost surface layer of the photoreceptor has an elastic work rate W of 52% or more, and the resistance to cracks can be improved. When the elastic work rate W is less than 52%, the elastic recovery with respect to an external stress is small, and the applied force is likely to directly lead to surface deformation and is likely to cause cracks. A preferable elastic work rate W is 52% or more, and the upper limit is about 58%.

[0035] [[ID=2D]]<Binder resin (polyarylate resin)> In the photoreceptor of the present disclosure, it is preferable that the charge transport layer further contains a polyarylate resin as a binder resin. By further containing a polyarylate resin, the film strength of the charge transport layer can be increased and the crack resistance can be improved.

[0036] The polyarylate resin is a polycondensate of a divalent phenol and a dibasic acid component, and is composed of, for example, structural units (C) and (D) as shown in the following formula.

Chemical formula

[0037] (In the formula, R 1 , R 2 , R 3 and R 4 are the same or different and are a hydrogen atom or a methyl group, R 5 and R 6 are the same or different and are a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X 1These are given by the following equations (D1), (D2), and (D3): [ka] (Selected from) Examples of the C1-C4 alkyl groups mentioned above include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl.

[0038] Examples of polyarylate resins include polymers (PAR-1) to (PAR-4) as shown in the following formulas. [ka] Among these, a polyarylate resin, such as the polymer (PAR-1) used in the examples (for example, Mitsubishi Chemical Corporation, product name: E2-400), is preferred in terms of ease of preparation of the coating solution.

[0039] The polyarylate resin is preferably included as the binder resin in the charge transport layer at a ratio of 10 to 50% by mass. If the polyarylate resin content is less than 10% by mass, the crack resistance improvement effect may be small. On the other hand, if the polyarylate resin content exceeds 50% by mass, the resin may become difficult to dissolve, making it difficult to liquefy the coating. A more preferable polyarylate resin content is 20-40% by mass.

[0040] <Terphenyl compounds> In the photoreceptor of this disclosure, the charge transport layer preferably further comprises a compound having a terphenyl structure. By further including compounds having a terphenyl structure, these compounds exhibit properties similar to the binder resin's skeleton and readily interact with it. This makes it difficult for crack-causing substances to penetrate into the photoreceptor, while maintaining excellent durability, abrasion resistance, and sensitivity characteristics, thereby effectively preventing crack formation and crystallization.

[0041] Examples of compounds having a terphenyl structure include o-terphenyl, m-terphenyl, p-terphenyl, triphenylbenzene, and p-quaterphenyl (each represented by (TP1) to (TP5) in the formulas below). Among these, o-terphenyl (TP1) is particularly preferred for its ability to enhance crack resistance.

[0042] [ka]

[0043] The compound having a terphenyl structure is preferably included in a proportion of 3 to 18% by mass relative to the charge transport material. If the content of compounds having a terphenyl structure is less than 5% by mass, the effect against cracking may be reduced. On the other hand, if the content of compounds having a terphenyl structure exceeds 15% by mass, the proportion of binder resin in the charge transport layer decreases, which may reduce print resistance. The content of compounds having a more preferable terphenyl structure is 5 to 15% by mass.

[0044] (1) Electrophotographic photoreceptor The photoreceptor of this disclosure is a stacked photoreceptor (also called a "functionally separated photoreceptor") comprising at least a stacked photoreceptor layer on a conductive support, in which a charge generating layer containing a charge generating material and a charge transport layer containing a charge transport material are stacked in that order. Figure 2 is a schematic cross-sectional view showing the configuration of the main parts of the photoreceptor F01 of this disclosure. The photoreceptor F01 comprises a laminated photoreceptor layer on a conductive support F1, in which an undercoat layer F21, a charge generating layer F22 containing a charge generating material, and a charge transport layer F23 containing a charge transport material are laminated in that order. Figure number Fa represents the surface of the photoreceptor. The photoreceptor of this disclosure may include an undercoat layer F21 between the conductive support F1 and the multilayer photosensitive layer, as described below, and may also include a surface protection layer on the multilayer photosensitive layer.

[0045] <Conductive support F1> The conductive support (also called the "conductive substrate" or "substrate") has the function of both an electrode for the photoreceptor and a support member, and its constituent material is not particularly limited as long as it is a material used in the art.

[0046] Specifically, examples include metallic materials such as aluminum, aluminum alloys, copper, zinc, stainless steel, and titanium, as well as polymer materials such as polyethylene terephthalate, nylon, and polystyrene, rigid paper, and glass, which have a metal foil laminate, metal vapor deposition treatment, or a layer of conductive polymer, tin oxide, indium oxide, or other conductive compound vapor deposition or coating on their surface. Among these, aluminum is preferred in terms of ease of processing, and aluminum alloys such as JIS 3003, JIS 5000, and JIS 6000 series are particularly preferred.

[0047] The shape of the conductive support is not limited to a cylindrical (drum-shaped) form as shown in Figure 3, but may also be sheet-shaped, columnar, endless belt-shaped, etc. Furthermore, the surface of the conductive support may, if necessary, be subjected to a diffuse reflection treatment such as anodizing, surface treatment with chemicals or hot water, coloring, or surface roughening, to prevent interference fringes caused by laser light, within a range that does not affect image quality.

[0048] <Underlayment F21> The photoreceptor F01 of this disclosure preferably comprises an undercoat layer (also called an "intermediate layer") F21 between a conductive support F1 and a multilayer photosensitive layer (also simply called a "photosensitive layer"). The undercoat generally covers and smooths the uneven surface of the conductive support, improving film formation with the charge generation layer of the photosensitive layer, suppressing delamination of the photosensitive layer from the conductive support, and improving adhesion between the conductive support and the photosensitive layer. Specifically, it prevents charge injection from the conductive support into the photosensitive layer, prevents a decrease in the photosensitive layer's chargeability, prevents image fringing (so-called black spots), and maintains good electrophotographic properties such as chargeability throughout its lifecycle. The undercoat can be formed, for example, by dissolving a binder resin in a suitable solvent to prepare an undercoat coating solution, applying this coating solution to the surface of a conductive support, and removing the organic solvent by drying.

[0049] Examples of binder resins include those similar to those contained in the photosensitive layer described later, as well as natural polymer materials such as casein, gelatin, polyvinyl alcohol, and ethylcellulose. These can be used individually or in combination of two or more. The binder resin is required to have properties such as not dissolving or swelling when used in solvents to form the photosensitive layer on the undercoat, excellent adhesion to the conductive support, and flexibility. Among the above binder resins, polyamide resin is preferred, and alcohol-soluble nylon resin is particularly preferred. Examples of alcohol-soluble nylon resins include homopolymerized or copolymerized nylons such as 6-nylon, 66-nylon, 610-nylon, 11-nylon, and 12-nylon, as well as resins in which nylon has been chemically modified, such as N-alkoxymethyl-modified nylon.

[0050] Examples of solvents for dissolving or dispersing resin materials include water; alcohols such as methanol, ethanol, and butanol; glycyles such as methyl carbitol and butyl carbitol; chlorinated solvents such as dichloroethane, chloroform, or trichloroethane; acetone, dioxolane, and mixed solvents obtained by mixing two or more of these solvents. Among these solvents, non-halogenated organic solvents are preferably used out of consideration for the global environment.

[0051] Furthermore, the coating liquid for the undercoat layer may contain inorganic compound fine particles. Inorganic compound fine particles allow for easy adjustment of the volume resistivity of the undercoat layer, further suppression of charge injection into the multilayer photosensitive layer, and maintenance of the photoreceptor's electrical properties under various environmental conditions. Examples of inorganic compound fine particles include titanium dioxide, aluminum oxide, aluminum hydroxide, and tin oxide. To disperse inorganic compound fine particles in the coating liquid for the undercoat layer, known devices such as ball mills, sand mills, attritors, vibration mills, ultrasonic dispersers, and paint shakers may be used.

[0052] In the coating solution for the undercoat layer, the ratio A / B of the total mass A of the binder resin and inorganic compound fine particles to the mass B of the solvent is preferably 1 / 99 to 40 / 60, and particularly preferably 2 / 98 to 30 / 70. Furthermore, the ratio C / D of the mass C of the binder resin to the mass D of the inorganic compound fine particles is preferably 1 / 99 to 90 / 10, and particularly preferably 5 / 95 to 70 / 30.

[0053] The application method for the undercoat coating solution should be appropriately selected considering the physical properties of the coating solution and productivity, and examples include the spray method, bar coating method, roll coating method, blade method, ring method, and immersion coating method. Among these methods, the immersion coating method is a method in which a conductive support is immersed in a coating tank filled with a coating solution, and then pulled out at a constant speed or a sequentially changing speed to form a layer on the surface of the conductive support. It is relatively simple and excellent in terms of productivity and cost, and is therefore suitable for use in the manufacture of photoreceptors. The apparatus used in the immersion coating method may be equipped with a coating solution dispersion device, such as an ultrasonic generator, to stabilize the dispersibility of the coating solution.

[0054] The solvent in the coating can be removed by natural drying, or it can be forcibly removed by heating. The temperature in this drying process is not particularly limited as long as it is a temperature that can remove the solvent used, but a temperature of about 50 to 140°C is appropriate, and a temperature of about 80 to 130°C is particularly preferred. If the drying temperature is below 50°C, the drying time may be prolonged, and the solvent may not evaporate sufficiently, remaining in the photoreceptor layer. Furthermore, if the drying temperature exceeds approximately 140°C, the electrical properties of the photoreceptor may deteriorate during repeated use, resulting in a degradation of the resulting image. These temperature conditions are common not only to the undercoat layer but also to the layer formation of the multilayer photosensitive layer described later and to other processing steps.

[0055] The thickness of the undercoat is not particularly limited, but is preferably 0.01 to 20 μm, and more preferably 0.05 to 10 μm. If the thickness of the undercoat layer is less than 0.01 μm, it will not function effectively as an undercoat layer, making it impossible to cover defects in the conductive support and obtain a uniform surface, which may prevent charge injection from the conductive support into the multilayer photosensitive layer. On the other hand, if the thickness of the undercoat layer exceeds 20 μm, it will be difficult to form a uniform undercoat layer, and the sensitivity of the photoreceptor may also decrease. Furthermore, if the constituent material of the conductive support is aluminum, a layer containing anodized aluminum (anodized layer) can be formed and used as the undercoat layer.

[0056] <Charge generation layer F22> The charge generation layer, used in image forming apparatuses and the like, has the function of generating electric charge by absorbing irradiated light such as semiconductor laser light. It mainly consists of a charge generation material and contains binder resins and additives as needed.

[0057] As charge-generating materials, compounds used in the field can be used, specifically azo pigments such as monoazo pigments, bisazo pigments, and trisazo pigments; indigo pigments such as indigo and thioindigo; perylene pigments such as peryleneimide and perylene anhydride; polycyclic quinone pigments such as anthraquinone and pyrenequinone; phthalocyanine pigments such as metallic phthalocyanines such as titanyl phthalocyanine and metal-free phthalocyanines; organic photoconductive materials such as squarylium dyes, pyryllium salts, thiopyrillium salts, and triphenylmethane dyes; and inorganic photoconductive materials such as selenium and amorphous silicon. Those with sensitivity to the exposure wavelength range can be appropriately selected and used. These charge-generating materials can be used individually or in combination of two or more. Among these charge-generating materials, the following general formula (A):

[0058] [ka]

[0059] (In the formula, X 1 , X 2 , X 3 and X 4 (The elements are the same or different halogen atoms, alkyl groups, or alkoxy groups, and r, s, y, and z are the same or different integers from 0 to 4.) It is preferable to use titanylphthalocyanine represented by . Titanyl phthalocyanine is a charge-generating material that exhibits high charge generation and charge injection efficiency in the emission wavelength range (near-infrared light) of laser and LED light currently in common use. It generates a large amount of charge by absorbing light and can efficiently inject the generated charge into charge transport materials without accumulating it internally.

[0060] Titanyl phthalocyanine represented by general formula (A) can be produced by known manufacturing methods, such as the method described in Phthalocyanine Compounds by Moser, Frank H and Arthur L. Thomas, Reinhold Publishing Corp., New York, 1963. For example, in the case of unsubstituted titanylphthalocyanine compounds represented by general formula (A), where r, s, y, and z are 0, dichlorotitanylphthalocyanine is synthesized by heating and melting phthalonitrile and titanium tetrachloride, or by heating and reacting them in a suitable solvent such as α-chloronaphthalene, and then hydrolyzing with a base or water. Furthermore, a titanylphthalocyanine composition can also be produced by heating isoindoline and a titanium tetraalkoxide such as tetrabutoxytitanium in a suitable solvent such as N-methylpyrrolidone.

[0061] Methods for forming a charge generation layer include vacuum deposition of a charge generation material onto a conductive support, and coating a charge generation layer solution obtained by dispersing a charge generation material in a solvent onto a conductive support. Among these, the method of dispersing a charge generation material in a binder resin solution obtained by mixing a binder resin in a solvent using a known method, and then coating the charge generation layer solution onto the conductive support (on the undercoat layer), is preferred. This method will be described below.

[0062] The binder resin is not particularly limited, and any resin known in the field can be used. Specifically, examples include resins such as polyester, polystyrene, polyurethane, phenolic resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate, polyarylate, polyphenoxy, polyvinyl butyral, and polyvinyl formal, as well as copolymer resins containing two or more of the repeating units that constitute these resins. Examples of copolymer resins include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. These resins can be used individually or in combination of two or more.

[0063] Examples of solvents include halogenated hydrocarbons such as dichloromethane and dichloroethane; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as tetrahydrofuran (THF) and dioxane; alkyl ethers of ethylene glycol such as 1,2-dimethoxyethane; aromatic hydrocarbons such as benzene, toluene, and xylene; and aprotic polar solvents such as N,N-dimethylformamide and N,N-dimethylacetamide. These solvents can be used individually or in combination of two or more.

[0064] The ratio E / F of the mass E of the charge-generating material to the mass F of the binder resin is preferably 10 / 90 to 99 / 1, and particularly preferably 55 / 45 to 80 / 20. When the E / F ratio is less than 10 / 90 and the proportion of charge-generating material is low, sensitivity may decrease. On the other hand, when the E / F ratio exceeds 99 / 1 and the proportion of charge-generating material is high, not only does the film strength of the charge-generating layer decrease, but the dispersibility of the charge-generating material decreases, leading to an increase in coarse particles. This reduces the surface charge in areas other than those that should be erased by exposure, which can result in many image defects, especially black spots, where toner adheres to a white background, forming tiny black dots.

[0065] Before dispersing the charge-generating material in the binder resin solution, the charge-generating material may be pre-treated by grinding it using a grinder. Examples of grinders used for this treatment include ball mills, sand mills, attritors, vibratory mills, and ultrasonic dispersers. Dispersers used to disperse charge-generating substances in a binder resin solution include paint shakers, ball mills, and sand mills. The dispersion conditions should be selected appropriately to prevent contamination by impurities due to wear of the container and components of the disperser. The coating method for the charge generation layer is the same as the coating method for the undercoat layer, and the immersion coating method is particularly preferred.

[0066] The thickness of the charge generation layer is not particularly limited, but is preferably 0.05 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 1 μm or less. If the thickness of the charge generation layer is less than 0.05 μm, the efficiency of light absorption decreases, which can reduce the sensitivity of the photoreceptor. On the other hand, if the thickness of the charge generation layer exceeds 5 μm, charge transfer within the charge generation layer becomes the rate-limiting step in the process of erasing the charge on the surface of the stacked photosensitive layer, which can reduce the sensitivity of the photoreceptor.

[0067] <Charge transport layer F23> The charge transport layer has the function of receiving the charge generated by the charge generating material and transporting it to the surface of the photoreceptor. It contains the aforementioned polycarbonate resin as the charge transport material and binder resin, and contains additives as needed.

[0068] The charge transport material is not particularly limited, and compounds used in the art can be used. Specifically, examples include carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolon derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene derivatives, enamine derivatives, benzidine derivatives, polymers having groups derived from these compounds in their main chain or side chain (such as poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly-9-vinylanthracene, etc.), and polysilanes. These charge transport materials can be used individually or in combination of two or more types. Among these various charge transport materials, stilbene derivatives, butadiene derivatives, enamine derivatives, and compounds in which multiple types of these are bonded together are preferred in terms of electrical properties, durability, and chemical stability, with stilbene derivatives being more preferred.

[0069] A preferred method for forming the charge transport layer is to disperse a charge transport substance in a binder resin solution obtained by mixing a binder resin in a solvent using a known method, prepare a coating solution for the charge transport layer, and then apply this solution onto the charge generating layer. This method will be described below.

[0070] The binder resin is not particularly limited, and any resin known in the field can be used, but one with excellent compatibility with charge transport material is preferred. Specifically, examples include vinyl polymer resins such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymer resins thereof, as well as resins such as polycarbonate, polyester, polyester carbonate, polysulfone, phenoxy resin, epoxy resin, silicone resin, polyarylate, polyphenylene oxide, polyamide, polyether, polyurethane, polyacrylamide, and phenolic resin. These binder resins can be used individually or in combination of two or more types. Among these, polystyrene, polycarbonate, polyarylate, and polyphenylene oxide have a volume resistivity of 10 13 It is particularly preferable because it has a resistance of Ω or more, excellent electrical insulation properties, and also excellent film-forming properties and potential characteristics.

[0071] The ratio G / H of the mass G of the charge transport material to the mass H of the binder resin is preferably 10 / 30 to 10 / 12, and particularly preferably 10 / 20 to 10 / 14. When the G / H ratio is less than 10 / 30 and the binder resin ratio is high, the viscosity of the coating solution increases when forming the charge transport layer by immersion coating, leading to a decrease in coating speed and a significant reduction in productivity. Furthermore, if the amount of solvent in the coating solution is increased to suppress the increase in viscosity, a brushing phenomenon may occur, causing clouding of the formed charge transport layer. On the other hand, when the G / H ratio exceeds 10 / 12 and the binder resin ratio is low, the print resistance decreases compared to when the binder resin ratio is high, and the amount of wear on the photosensitive layer may increase.

[0072] The charge transport layer may have a cross-linked structure to enhance its mechanical strength and improve its electrical properties. Methods for forming a cross-linked structure include formulations containing a curable binder resin, and methods containing a charge transporter having a cross-linkable functional group and a curable binder resin. The curable binder resin preferably includes a resin that forms a three-dimensional network structure through a crosslinking reaction. Examples include a resin containing at least one of an alkyd resin and a thermosetting acrylic resin, and at least one of a guanamine resin and a melamine resin, or a thermosetting polyurethane resin, or a curable siloxane resin formed by heating and crosslinking an organosilicon compound having either a hydroxyl group or a hydrolyzable group. Examples of charge transporters having crosslinkable functional groups include charge transporters with functional groups such as hydroxyl groups, mercapto groups, isocyanate groups, and amine groups, and their mechanical strength can be enhanced by crosslinking them with binder resins.

[0073] The charge transport layer may contain inorganic compound particles or fluorine-based particles to enhance mechanical strength and improve electrical properties. When the charge transport layer is the surface layer of the photosensitive layer, the content of inorganic particles / fluorine-based resin particles is preferably about 5 to 25% by mass relative to the total solid content of the charge transport layer.

[0074] Silica particles and alumina particles are preferably used as inorganic particles. Examples of fluorine-based resin particles include polytetrafluoroethylene resin, polychlorotrifluoroethylene resin, polytetrafluoroethylene propylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, or polydichlorodifluoroethylene resin. Among these, polytetrafluoroethylene particles containing polytetrafluoroethylene resin are preferably used from the viewpoint of improving dispersibility. The charge transport layer may contain additives such as plasticizers and leveling agents, as needed, to improve film formation, flexibility, and surface smoothness.

[0075] Examples of plasticizers include dibasic acid esters such as phthalate esters, fatty acid esters, phosphate esters, chlorinated paraffins, and epoxy plasticizers. Examples of leveling agents include silicon-based leveling agents.

[0076] Examples of solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as dichloromethane, dichloroethane, and monochlorobenzene; ethers such as THF, dioxane, and dimethoxymethyl ether; and aprotic polar solvents such as N,N-dimethylformamide. Alcohols, acetonitrile, and methyl ethyl ketone may also be added as needed. Among these solvents, non-halogenated organic solvents are preferred due to considerations for the global environment. These solvents may be used individually or in combination of two or more.

[0077] The thickness of the charge transport layer is not particularly limited, but is preferably 5 μm to 50 μm, and more preferably 10 μm to 40 μm. If the thickness of the charge transport layer is less than 5 μm, the charge retention ability of the photoreceptor surface may decrease. On the other hand, if the thickness of the charge transport layer exceeds 50 μm, the resolution of the photoreceptor may decrease.

[0078] <Surface protective layer (not shown in Figure 2)> The photoreceptor of this disclosure may include a surface protective layer on a stacked photosensitive layer. The constituent materials of the surface protective layer, their content and proportion, and the formation method are the same as those for the <charge transport layer F23>. The surface protective layer may contain one or more charge transport substances to stabilize electrical properties. Filler materials may be included to improve wear resistance. Examples of such filler materials include organic filler materials such as fluororesin powder such as polytetrafluoroethylene, silicone resin powder, and α-carbon powder; metal powders such as copper, tin, aluminum, and indium; metal oxides such as silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide, and tin-doped indium oxide; and inorganic filler materials such as potassium titanate. Inorganic filler materials are particularly preferred in terms of filler hardness. The thickness of the surface protective layer is not particularly limited, but is preferably 0.5 to 10 μm, and more preferably 1 to 7 μm.

[0079] (2) Method for manufacturing an electrophotographic photoreceptor The method for manufacturing a photoreceptor according to the present disclosure is characterized by including a step of applying and heating a coating solution to form the charge transport layer of the photoreceptor according to the present disclosure, and then slowly cooling it at a cooling rate of less than 1°C / min. The method for manufacturing the photoreceptor of this disclosure is not particularly limited, but according to this method, a photoreceptor having a specific elastic power W and creep value C in its outermost layer, which is a characteristic of the photoreceptor of this disclosure, can be suitably manufactured.

[0080] Although the mechanism is not clear, the inventors believe that when the charge transport layer is slowly cooled under the above conditions after the coating is formed, while rapid cooling leaves a small amount of solvent remaining in the coating, making it prone to cracking in this area, slow cooling allows the remaining solvent in the coating to evaporate over a sufficient period of time, resulting in a uniform distribution of resin within the film, thus improving resistance to cracking.

[0081] (3) Image forming apparatus The image forming apparatus of the present disclosure comprises at least a photoreceptor of the present disclosure, a charging means for charging the electrophotographic photoreceptor, an exposure means for exposing the charged electrophotographic photoreceptor to form an electrostatic latent image, a developing means for developing the electrostatic latent image to form a toner image, a transfer means for transferring the toner image onto a recording medium, and a cleaning means for removing and recovering toner remaining on the electrophotographic photoreceptor. The cleaning means is characterized by comprising a blade having an angle of 5° to 20° with respect to the outer surface of the electrophotographic photoreceptor. The image forming apparatus of this disclosure may include means selected from fixing means for fixing a transferred toner image onto a recording medium to form an image, and means for removing residual surface charge from a photoreceptor. The image forming apparatus and its operation will be described below with reference to the drawings, but the image forming apparatus of the present invention is not limited thereto.

[0082] Figure 3 is a schematic side view of the main components of the image forming apparatus 50 of the present disclosure. The image forming apparatus 50 comprises at least a photoreceptor 2 (corresponding to F01 in Figure 2), a charging means 7 for charging the surface of the photoreceptor, an exposure means 11 for irradiating the charged surface of the photoreceptor with light to form an electrostatic latent image, a developing means 12 for developing the electrostatic latent image formed by exposure to form a toner image, a transfer means 13 for transferring the toner image formed by development onto a recording medium 26, a fixing means 19 for fixing the transferred toner image onto the recording medium to form an image, and a cleaning means 14 for removing and recovering residual toner from the surface of the photoreceptor. The charging means 7, exposure means 11, developing means 12, transfer means 13, and cleaning means 14 are provided in this order along the outer circumferential surface of the photoreceptor 2, from the upstream side to the downstream side in the rotational direction of the photoreceptor 2. Each of these components constituting the image forming apparatus 50 is housed in a housing 23.

[0083] The image forming apparatus 50 is an electrophotographic image forming apparatus that forms images using electrophotographic technology. The image forming apparatus 50 may be a monochrome image forming apparatus capable of forming monochrome images as shown in Figure 3, or it may be an intermediate transfer type color image forming apparatus capable of forming color images. The color image forming apparatus is, for example, a so-called tandem type full-color image forming apparatus having a configuration in which a plurality of photoreceptors on which toner images are formed are arranged in a predetermined direction (for example, horizontal or vertical). The image forming apparatus 50 may also be another color image forming apparatus, a copier, a multifunction printer, or a facsimile machine.

[0084] (3-1) Photoreceptor 2 The photoreceptor 2 is a component on which an electrostatic latent image and a toner image are formed, and an image is continuously formed as the photoreceptor 2 rotates. The photoreceptor 2 is, for example, a photoreceptor drum. The photoreceptor 2 is rotatably supported on the main body (not shown) of the image forming apparatus 50 and is rotationally driven in the direction of the arrow by a driving means (not shown). The driving means, for example, comprises an electric motor and a reduction gear, and transmits its driving force to the conductive support 3 that constitutes the core of the photoreceptor 2, thereby rotating the photoreceptor 2 at a predetermined peripheral speed.

[0085] (3-2) Charging means 7 The charging means ("charger" or "charging roller") 7 is a device that uniformly charges the surface (outer surface) of the photoreceptor 2 to a predetermined potential using a DC voltage from a charging bias power supply or a voltage obtained by superimposing an AC voltage. As the charger 7, for example, a contact charger such as a roller shape, belt shape, or blade shape can be used. In the image forming apparatus of this disclosure, a contact roller charger is preferred among these. The contact roller charger 7 has a conductive support 28 as its base, and on its outer surface, it may have an elastic layer 29 and a resistive layer 30 in that order as coating layers. The method for forming the charging means will be described in detail in the examples.

[0086] (3-2-1) Conductive support 28 The conductive support (conductive substrate) 28 is not particularly limited as long as it has conductivity and can maintain strength as a charging means material. Examples of its constituent materials include metals such as iron, copper, aluminum, and nickel, and alloys such as stainless steel and brass. As long as conductivity is not impaired, its surface may be plated to prevent rust and provide scratch resistance. In this embodiment, a cylindrical (round bar) member is used, but its shape may be hollow or belt-shaped.

[0087] (3-2-2) Elastic layer 29 The elastic layer (conductive elastic layer) 29 is not particularly limited as long as it has appropriate conductivity and elasticity to ensure power supply to the photoreceptor as the charged object and good uniform adhesion of the charging means to the photoreceptor. In order to ensure uniform adhesion between the charging roller and the photoreceptor, it is preferable that the elastic layer 29 be polished so that its center is the thickest part and it tapers from the center to both ends (a so-called crown shape).

[0088] Generally, contact roller chargers come into contact with the photoreceptor by applying a predetermined pressing force to both ends of the conductive support. As a result, the pressing force is small in the center and large towards the ends. Therefore, there is no problem if the straightness of the contact roller charger is sufficient, but if it is not sufficient, there is a problem that density unevenness will occur in the image corresponding to the center and the ends. In addition, as the number of models that support only A3 and the number of color machines have increased, the charging area has expanded, so the contact roller charger itself is more prone to bending due to the pressing force applied only to the ends of the conductive support, causing problems such as gaps in the center. For these reasons, in order to ensure uniform adhesion between the charging means and the photoreceptor, it is preferable to polish the elastic layer so that it is thickest in the center and tapers from the center to the ends (a so-called crown shape).

[0089] The elastic layer can be formed by appropriately adding conductive agents having an electron conduction mechanism, such as carbon black, graphite, and conductive metal oxides, as well as conductive agents having an ion conduction mechanism, such as alkali metal salts and quaternary ammonium salts, to an elastic material such as rubber, using known methods. Its volume resistivity is 1 × 10⁻⁶ 10 It is preferable that the conductivity be adjusted to be less than Ωcm.

[0090] Conductive materials include carbon black, conductive tin oxide, conductive zinc oxide, conductive titanium oxide, quaternary ammonium salts, surfactants, and other ionic conductive materials, and mixtures thereof may also be used. Examples of elastic materials include natural rubber, ethylene propylene rubber (EPDM), ethylene-propylene-diene rubber, styrene-butadiene rubber (SBR), silicone rubber, urethane rubber, epichlorohydrin rubber, epichlorohydrin-ethylene oxide rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether rubber, acrylonitrile-butadiene rubber, isoprene rubber (IR), butadiene rubber (BR), nitrile-butadiene rubber (NBR), and chloroprene rubber (CR), as well as polyamide resins, polyurethane resins, and silicone rubbers, and may also be mixtures thereof.

[0091] Furthermore, in order to impart the desired properties, the conductive elastic layer may contain additives such as a curing agent, a softening agent such as ricinoleic acid, a vulcanizing agent such as sulfur, a vulcanization accelerator such as tetrabenzyl thiuram disulfide, an antioxidant, a crosslinking agent, a dispersant, and a plasticizer. The thickness of the elastic layer is not particularly limited, but is preferably 1 to 3 mm, more preferably 1.5 to 2 mm.

[0092] (3-2-3) Resistance layer 30 The resistive layer (surface layer) is formed in contact with the elastic layer and is provided to prevent the bleed-out of softening oils, plasticizers, and other substances contained in the elastic layer to the surface of the charger, as well as to adjust the overall electrical resistance of the charger. Examples of materials for forming the resistance layer (hereinafter also referred to as "rubber substrate") include epichlorohydrin rubber, nitrile butadiene rubber (NBR), polyolefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, polystyrene-based thermoplastic elastomers, fluororubber-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polybutadiene-based thermoplastic elastomers, ethylene vinyl acetate-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, and chlorinated polyethylene-based thermoplastic elastomers. One of these can be used alone, or two or more can be used as a mixture or copolymer.

[0093] The resistive layer is conductive or semiconductive. Therefore, it is formed by appropriately adding a conductive agent having an electron conduction mechanism (e.g., conductive carbon, graphite, conductive metal oxide, copper, aluminum, nickel, iron powder, etc.) or a conductive agent having an ion conduction mechanism (e.g., alkali metal salts, ammonium salts, etc.) to the above material. In this case, two or more conductive agents may be used in combination to obtain the desired electrical resistance. However, considering environmental fluctuations and contamination of the photoreceptor, it is preferable to use a conductive agent that has an electron conduction mechanism.

[0094] The resistive layer may contain fillers (particles that form irregularities) as long as they do not significantly impair the effect of the image forming apparatus of this disclosure. The fillers are not particularly limited and include, for example, calcium carbonate, talc, mica, silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, zinc oxide, zeolite, wollonite, diatomaceous earth, glass beads, bentonite, montmorillonite, asbestos, hollow glass spheres, graphite, molybdenum disulfide, titanium oxide, aluminum fibers, stainless steel fibers, brass fibers, aluminum powder, wood powder, rice husks, graphite, metal powder, conductive metal oxides, organometallic compounds, organometallic salts, etc., and one of these can be used alone or in combination of two or more. The thickness of the resistive layer is not particularly limited, but is preferably 5 to 100 μm, and more preferably 5 to 20 μm. By incorporating particles that form irregularities in the resistance layer (surface layer) and further changing the shape of the particles, a charging roller having the desired surface roughness according to this disclosure can be manufactured.

[0095] <Stretchable body (not shown in Figure 3)> The charging means includes support members that support it at both ends and an expandable / contractible body that expands and contracts in the direction toward the photoreceptor from the support members, and the linear pressure on the photoreceptor can be changed by the spring pressure of the expandable / contractible body. The pressure between the charging means and the photoreceptor is kept to a level that does not cause image defects due to slippage, making image defects less likely to occur. In the charging means of the image forming apparatus disclosed herein, it is preferable that the expandable body has a spring pressure of 400 gF or more and 750 gF or less.

[0096] Figure 4 is a diagram illustrating the relationship between the spring pressure of the expandable body of the charging mechanism and crack occurrence. In the figure, figures 2 and 7 represent the photoreceptor and the charging mechanism, respectively, and the spiral spring indicates the strength of the spring pressure. When the spring pressure of the expandable body is less than 400gF, as shown in Figure 4(b), the pressure on the photoreceptor is weak, making it easier for image defects due to slippage to occur. On the other hand, when the spring pressure of the expandable body exceeds 750gF, as shown in Figure 4(a), the pressure on the photoreceptor becomes strong, making it easier for cracks to occur. A more preferable spring pressure for the expandable body is between 500gF and 680gF.

[0097] <Surface hardness of the charging device> The charging means of this disclosure preferably has a surface with a hardness of 65 degrees or more under a 1 kg load, as defined in JIS K7312. More preferably, it has a hardness of 75 degrees or more, with an upper limit of about 90 degrees. Figure 5 illustrates the relationship between the hardness of the charging means and crack initiation. As shown in Figure 5(b), the higher the hardness of the charging means, the less deformable it becomes, resulting in fewer contact points with the photoreceptor. Consequently, less crack-causing material seeps out, making crack initiation less likely. On the other hand, as shown in Figure 5(a), the lower the hardness of the charging means, the more easily it deforms, resulting in more contact points with the photoreceptor. Consequently, more crack-causing material seeps out, making crack initiation more likely.

[0098] <Charging Method> The charging means of the image forming apparatus is preferably a charging roller having an AC superposition of 1.80kV or less. While charging becomes more stable as the peak-to-peak voltage of the AC voltage applied to the charging means increases, fatigue on the photoreceptor increases, raising the risk of crack formation. Therefore, from the viewpoint of suppressing crack formation, it is desirable that Vpp be 1.75kV or less, more preferably 1.40 to 1.75kV. By setting the applied voltage to the charging means for the photoreceptor in this disclosure to 1.75kV or less, the photoreceptor becomes less susceptible to scratches and cracks can be suppressed.

[0099] (3-3) Exposure means 11 The exposure means 11 is a device that emits light modulated based on image information (data) to be printed. The exposure means 11 can be equipped with a semiconductor laser or a light-emitting diode as a light source, and by irradiating the surface (outer surface) of the photoreceptor 2 between the charger 7 and the developer 12 with the laser beam light output from the light source, exposure is performed on the charged surface of the photoreceptor 2 according to the image information. The light is repeatedly scanned in the direction in which the rotation axis of the photoreceptor 2 extends, which is the main scanning direction, and these images are formed to sequentially create an electrostatic latent image on the surface of the photoreceptor 2. That is, the amount of charge on the photoreceptor 2, which is uniformly charged by the charger 7, differs depending on whether it is irradiated with the laser beam or not, and an electrostatic latent image is formed.

[0100] (3-4) Developing means 12 The developing means (developer) 12 is a device that develops the electrostatic latent image formed on the surface of the photoreceptor 2 by exposure using a developer (toner) 25. It is provided opposite the photoreceptor 2 and comprises a developing roller 31 that supplies toner to the surface of the photoreceptor 2, and a casing 32 that supports the developing roller 31 so as to be rotatable around a rotation axis parallel or substantially parallel to the rotation axis of the photoreceptor 2 and houses a developer containing toner in its internal space. Furthermore, this disclosure is not limited to an image forming apparatus 100 that prints monochrome images, but can also be applied to an image forming apparatus 100 that prints full-color images.

[0101] (3-5) Transfer means 13 The transfer means ("transfer charger" and "transfer roller") 13 is a device that transfers the toner image, which is a visible image formed on the surface of the photoreceptor 2 by development, onto the transfer paper, which is a recording medium 26 supplied between the photoreceptor 2 and the transfer charger 13 from a predetermined transport direction (direction of the arrow) by a transport means (not shown). The transfer means applies a predetermined high voltage to the transfer nip portion formed between the photoreceptor 2 and the transfer charger 13 by a power supply unit (high voltage application device) 18b. The transfer means 13 can be configured in the same way as the charging means 7 described above, and is, for example, a contact-type transfer means that transfers the toner image onto the recording medium 26 by applying a charge of opposite polarity to the toner 25 to the recording medium 26.

[0102] (3-6) Fixing means 19 The fixing means (fuser) 19 is a device that fixes the toner image transferred to the recording medium 26 by the transfer means 13 onto the recording medium 26. The fixing means 19 is located downstream of the transfer nip between the photoreceptor 2 and the transfer means 13 in the transport direction of the recording medium 26. For example, the fixing means 19 comprises a heating roller and a pressure roller provided opposite it, and the pressure roller is pressed by the heating roller to form the fixing nip.

[0103] (3-7) Cleaning method 14 The cleaning means (cleaner) 14 is a cleaning device that removes and recovers the toner 25 remaining on the surface of the photoreceptor 2 after the transfer operation by the transfer means 13. The cleaner 14 comprises a cleaning blade (also simply called a "blade") 34 that peels off the toner 25 remaining on the surface of the photoreceptor 2, and a recovery casing 35 that contains the toner 25 that has been peeled off.

[0104] <Angle of blade 34 relative to photoreceptor 2> Figure 6 shows the detailed positional relationship between the photoreceptor 200 and the blade 301, and is a diagram for explaining the angle (hereinafter also referred to as "blade angle θ2") that the cleaning means's blade 301 makes with the outer surface of the photoreceptor 200. The blade 301 is positioned so as to slope downward toward the photoreceptor 200, with its tip in contact with the photoreceptor 200. The blade 301 scrapes off the remaining toner from the circumferential surface of the photoreceptor 200 that has been transferred to the printing paper. In this process, the photosensitive layer on the circumferential surface of the photoreceptor 200 is worn away by being scraped by the blade 301. In the figure, figure no. 204 indicates the axis of rotation of the photoreceptor 200.

[0105] The angle between the blade 301 and the outer surface of the photoreceptor 200 is defined as the angle between the tangent at the point of contact 205 between the photoreceptor 200 and the blade 301 and the blade 301 itself. The cleaning means includes a blade whose angle with respect to the outer surface of the photoreceptor is between 5° and 20°. When the blade angle θ2 is less than 5°, the amount of toner removed by the blade decreases, making image defects more likely. On the other hand, when the blade angle θ2 exceeds 20°, the frictional force between the photoreceptor and the blade increases, making the photoreceptor more susceptible to scratches and consequently cracks. Therefore, when the blade angle θ2 is between 5° and 20°, the machine can operate without compromising cleaning and removal capabilities and without placing excessive stress on the photoreceptor, thus achieving both suppression of image defects and crack formation. A more preferable blade angle θ2 is between 8° and 18°.

[0106] (3-8) Static elimination means (not shown in Figure 3) The image forming apparatus 50 preferably further includes a static elimination means for removing residual surface charge from the photoreceptor 2, and preferably is provided together with the cleaning means 14. As a means of eliminating static electricity, devices known in the art can be used. Furthermore, it is preferable that the image forming apparatus of this disclosure further comprises a separation means (separation claws) 20 for separating the recording medium 26 from the photoreceptor 2.

[0107] (3-9) Control means 15 The control means 15 is the part that controls the image forming apparatus 50 and includes, for example, a microcontroller having a CPU, memory, timer, input / output ports, etc. The memory of the control means 15 stores control software for controlling the image forming apparatus 50. Furthermore, the image forming apparatus 50 may be equipped with a temperature and humidity sensor that can detect the operating environment of the image forming apparatus 50.

[0108] (3-10) Operation of the image forming apparatus The operation of the image forming apparatus of this disclosure will be explained using the image forming apparatus 50 described above. First, when the photoreceptor 2 is driven to rotate in a predetermined direction (direction of the arrow) by the drive unit, a negative charge is supplied to the surface of the photoreceptor 2 from the charger 7, which is located upstream of the image point of the light formed by the exposure means 11 in the direction of rotation of the photoreceptor 2, and the surface of the photoreceptor 2 is uniformly charged to a predetermined potential. For example, as shown in Figure 3, negative charges accumulate on the surface of the photoreceptor 2, causing the surface of the photoreceptor 2 to become charged. Meanwhile, on the surface of the conductive support 3 facing the charged surface of the photoreceptor 2, positive charges are generated due to the Coulomb force of the negative charges on the surface of the photoreceptor 2. This stabilizes the negative charges on the surface of the photoreceptor 2, resulting in a uniform charge distribution across the surface. Therefore, to suppress uneven charging, it is important to rapidly generate positive charges on the surface of the conductive support 3 due to the Coulomb force of the negative charges on the surface of the photoreceptor 2.

[0109] Next, the exposure means 11 irradiates the uniformly charged photoreceptor surface (Fa in Figure 2) with light corresponding to the image information. This exposure removes the surface charge from the irradiated portion of the photoreceptor 2, creating a difference in surface potential between the irradiated portion and the unirradiated portion, thus forming an electrostatic latent image. Toner 25 is supplied from a developing means 12 located downstream of the image point of light formed by the exposure means 11 in the rotational direction of the photoreceptor 2 to the surface of the photoreceptor 2 on which an electrostatic latent image has been formed, thereby developing the electrostatic latent image and forming a toner image.

[0110] Synchronized with the exposure of the photoreceptor 2, the recording medium 26 is supplied to the transfer nip between the photoreceptor 2 and the transfer means 13 from the transport direction of the transfer paper (arrow direction). The transfer means 13 applies a charge of opposite polarity to the toner 25 to the supplied recording medium 26, and the toner image formed on the surface of the photoreceptor 2 is transferred onto the recording medium 26. The recording medium 26 onto which the toner image has been transferred is transported by the transport unit to the fixing unit 19. As it passes through the contact area between the heating roller and the pressure roller of the fixing unit 19, and the fixing nip, the toner image is heated and pressurized, fixing it to the recording medium 26 to form a robust image. The recording medium 26 with the image formed in this way is then discharged from the image forming apparatus 50 by the transport unit.

[0111] On the other hand, any toner 25 remaining on the surface of the photoreceptor 2 after the transfer of the toner image by the transfer means 13 is peeled off from the surface of the photoreceptor 2 by the cleaning blade 34 of the cleaning means 14 and collected in the recovery casing 35. In this way, the charge on the surface of the photoreceptor 2 from which the toner 25 has been removed is removed, and the electrostatic latent image on its surface disappears. Subsequently, the photoreceptor 2 is further rotated, and the series of operations starting again with charging is repeated, so that an image is continuously formed. If the image forming apparatus 50 is equipped with an anti-static means downstream of the cleaning means 14 and before reaching the charging means 7, the light from the anti-static lamp of the anti-static means efficiently and more reliably removes the charge from the surface of the photoreceptor 2, causing the electrostatic latent image on the surface of the photoreceptor 2 to disappear. [Examples]

[0112] The present disclosure will be specifically described below with reference to examples and comparative examples, but the present invention is not limited by these examples unless they exceed the gist of the invention. In the examples and comparative examples, a laminated photoreceptor with only a laminated photosensitive layer on the surface side of the photoreceptor was used, but similar results can be obtained even if a laminated photoreceptor further has a surface protective layer on top of the laminated photosensitive layer. The physical properties of the photoreceptor (drum) and charging means (roll) obtained in the examples and comparative examples were measured by the following method.

[0113] [Creep value and elastic power of the photosensitive layer] Using a microhardness tester (manufactured by Fischer Instruments Co., Ltd., model: Fischerscope® H100V), measurements were obtained under the following conditions: a maximum indentation load of 5 mN, a loading time to reach the maximum indentation load of 10 seconds, a load holding time of 5 seconds, and an unloading time of 10 seconds, all within a temperature of 25°C and a relative humidity of 50%. The creep value and elastic power were calculated based on the aforementioned formulas.

[0114] [Surface hardness of the charging means] The surface hardness of the charging means was measured using a rubber hardness tester (manufactured by Polymer Instruments Co., Ltd., model: Asker rubber hardness tester type C) in an environment of 25°C and 50% relative humidity. The charging roller was fixed on the measurement base so that the measurement position was at the axial center of the charging means and the charging roller did not roll. A load of 1 kg was applied to the center of the roller using the hardness tester, and the value at the position where the hardness tester needle came to rest was read as the surface hardness of the charging roller.

[0115] (Example 1) (Fabrication of the photosensitive material) (Formation of the underlayer) Three parts by mass of titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd., product name: Typeque® TTO-D-1) and two parts by mass of copolymerized polyamide (nylon) (manufactured by Toray Industries, Inc., product name: Amiran® ​​Grade: CM8000) were added to 25 parts by mass of methyl alcohol and dispersed in a paint shaker for 8 hours to prepare 3 liters of coating solution for the undercoat layer. The obtained undercoat coating solution was filled into a coating tank, and a drum-shaped aluminum support with a diameter of 30 mm and a length of 354 mm was immersed as a conductive support F1. After immersion, the drum was removed, and the resulting coating film was allowed to air dry to form an undercoat layer F21 with a thickness of 1 μm on the conductive support F1.

[0116] (Formation of a charge generation layer) Prior to use as a charge-generating substance, oxotitanylphthalocyanine, represented by the following structural formula, was prepared. [ka]

[0117] 29.2 g of diiminoisoindoline and 200 ml of sulfolane were mixed, and 17.0 g of titanium tetraisopropoxide was added. The mixture was reacted under a nitrogen atmosphere at 140°C for 2 hours. After the reaction mixture was allowed to cool, the precipitate was filtered and washed sequentially with chloroform and 2% hydrochloric acid aqueous solution, then sequentially with water and methanol, and dried to obtain 25.2 g of blue-violet crystals. Chemical analysis of the obtained compound confirmed that it was oxotitanylphthalocyanine, as shown in the above structural formula (yield 88.5%).

[0118] One part by mass of the obtained titanyl phthalocyanine and one part by mass of butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: Esrec BM-2) were added to 98 parts by mass of methyl ethyl ketone and dispersed in a paint shaker for 2 hours to prepare 3 liters of coating solution for the charge generation layer. The obtained charge generation layer coating solution was applied onto the base layer F21 using the same immersion method as in the case of base layer formation, and the resulting coating film was allowed to air dry to form a charge generation layer F22 with a thickness of 0.3 μm.

[0119] (Formation of a charge transport layer) 5 g of an enamine compound represented by the following structural formula as a charge transport material, 10 g of polycarbonate resin of polymer (1) [index (m,n) = (0.75,0.25), chain end group: p-tert-butylphenyl, viscosity-average molecular weight 45,000] and 68 g of tetrahydrofuran were added to a 100 mL polypropylene (PP) container and mixed. The resulting mixture was stirred for 15 hours using a ball mill (manufactured by Eishin Co., Ltd., model: benchtop ball mill BM-15) to prepare 60 g of a coating solution for the charge transport layer. The obtained charge transport layer coating solution was applied onto the charge generation layer F22 by blade coating under conditions of a 2 mm gap and a coating speed of 1.9 mm / sec. The resulting coating film was dried at a temperature of 130°C for 1 hour, and then cooled to room temperature at a cooling rate of 0.17°C / min to form a charge transport layer F23 with a thickness of 34 μm, thereby obtaining the photoreceptor F01 of Example 1, as shown in Figure 2.

[0120] [ka]

[0121] (Creation of a charging roller) (Preparation of conductive elastic layer material) 100 parts by mass of acrylonitrile butadiene rubber (NBR, manufactured by Nippon Zeon Co., Ltd., product name: Nipol® DN219) as a rubber component, 1 part by mass of tetrabutylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) as a conductive material, 5 parts by mass of ricinoleic acid (manufactured by Tokyo Chemical Industry Co., Ltd., Nicinoleic Acid) as a softening agent, 1.2 parts by mass of sulfur (manufactured by Tsurumi Chemical Industries, Ltd., product name: Sulfur-SULFAX® PTC) as a vulcanizing agent, and 3 parts by mass of tetrabenzylthioram disulfide (TBzTD, manufactured by Sanshin Chemical Industry Co., Ltd., product name: Sunceller TBZTD) as a vulcanization accelerator were kneaded to obtain 50 g of a conductive rubber composition.

[0122] (Preparation of surface (resistive layer) material) 100 parts by mass of N-methoxymethylated nylon 1 (manufactured by Enshi Co., Ltd., product name: FR101) as a binder resin, 20 parts by mass of carbon black (manufactured by Lion Corporation, product name: Ketjenblack EC600JD) as a conductive material, and 30 parts by mass of irregularly shaped nylon resin particles (average particle size 20 μm, manufactured by Arkema, Orgasol series) as texture-forming particles were diluted with 200 parts by mass of methanol, soda-lime glass (manufactured by AS ONE Corporation, product name: soda glass beads) was added, and the mixture was stirred in a ball mill for 60 minutes to obtain 500 g of a rubber composition for the surface layer material.

[0123] (Manufacturing of a statically charged roller) A core metal (a conductive support made of SUM23 (free-cutting steel) with a diameter of 9 mm and a length of 355 mm) was set in a molding die as a conductive support 28, the prepared conductive rubber composition was injected, and after heating at a temperature of 160°C for 50 minutes, it was cooled to form an elastic layer 29 with a thickness of 1.5 mm. Subsequently, the prepared rubber composition of the surface material was applied to the surface of the elastic layer 29 by a blade coating method, heated at 160°C for 25 minutes, and then cooled to form a surface layer (resistive layer 30) with a thickness of 10 μm, obtaining the charging roller 7 of Example 1, which was then evaluated in combination with the photoreceptor 2.

[0124] (Example 2) In forming the charge transport layer, the photoreceptor and charging roller of Example 2 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of polymer (2) [exponents (m,n) = (0.75,0.25), chain end group: p-tert-butylphenyl, viscosity-average molecular weight 45,000].

[0125] (Example 3) In forming the charge transport layer, the photoreceptor and charging roller of Example 3 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of polymer (1) [exponents (m,n) = (0.60,0.40), viscosity-average molecular weight 50,000].

[0126] (Example 4) In forming the charge transport layer, the photoreceptor and charging roller of Example 4 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of polymer (1) [exponents (m,n) = (0.60,0.40), viscosity-average molecular weight 40,000].

[0127] (Example 5) In forming the charge transport layer, the photoreceptor and charging roller of Example 5 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of polymer (1) [exponents (m,n) = (0.75,0.25), viscosity-average molecular weight 35,000].

[0128] (Example 6) In forming the charge transport layer, the photoreceptor and charging roller of Example 6 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to 8 g of polycarbonate resin of polymer (1) [exponents (m,n) = (0.75,0.25), viscosity-average molecular weight 45,000] and 2 g of polyarylate resin of polymer (PAR-1) (manufactured by Mitsubishi Chemical Corporation, product name: E2-400) (20% by mass in the binder resin).

[0129] (Example 7) In forming the charge transport layer, 0.15 g of o-terphenyl (manufactured by Tokyo Chemical Industry Co., Ltd., product code: T0019) (3% by mass relative to the charge transport material) was added as an additive, and the amount of tetrahydrofuran was changed from 68 g to 69 g. Except for these changes, the photoreceptor and charging roller of Example 7 were obtained and evaluated in the same manner as in Example 1.

[0130] (Example 8) The photoreceptor and charging roller of Example 8 were obtained and evaluated in the same manner as in Example 7, except that the additive o-terphenyl was changed from 0.15 g to 0.25 g (5% by mass relative to the charge transport material) in the formation of the charge transport layer.

[0131] (Example 9) The photoreceptor and charging roller of Example 9 were obtained in the same manner as in Example 7, except that the additive was changed from 0.15 g of o-terphenyl to 0.75 g (15% by mass relative to the charge transport material) in the formation of the charge transport layer.

[0132] (Example 10) The photoreceptor and charging roller of Example 10 were obtained and evaluated in the same manner as in Example 7, except that the additive o-terphenyl was changed from 0.15 g to 1.0 g (20% by mass relative to the charge transport material) in the formation of the charge transport layer.

[0133] (Example 11) The photoreceptor and charging roller of Example 11 were obtained and evaluated in the same manner as in Example 7, except that o-terphenyl was replaced with m-terphenyl (manufactured by Tokyo Chemical Industry Co., Ltd., product code: T0018) in the formation of the charge transport layer.

[0134] (Example 12) The photoreceptor and charging roller of Example 12 were obtained and evaluated in the same manner as in Example 7, except that o-terphenyl was replaced with p-terphenyl (manufactured by Tokyo Chemical Industry Co., Ltd., product code: T0020) in the formation of the charge transport layer.

[0135] (Example 13) The photoreceptor and charging roller of Example 13 were obtained and evaluated in the same manner as in Example 7, except that o-terphenyl was replaced with triphenylbenzene (manufactured by Tokyo Chemical Industry Co., Ltd., product code: T0509) in the formation of the charge transport layer.

[0136] (Example 14) The photoreceptor and charging roller of Example 14 were obtained and evaluated in the same manner as in Example 7, except that o-terphenyl was replaced with p-quaterphenyl (manufactured by Tokyo Chemical Industry Co., Ltd., product code: Q0001) in the formation of the charge transport layer.

[0137] (Example 15) The photoreceptor and charging roller of Example 15 were obtained in the same manner as in Example 1, and in the evaluation of the image forming apparatus described later, the photoreceptor and charging roller were evaluated in the same manner as in Example 1, except that the angle θ2 between the cleaning means blade and the outer surface of the photoreceptor (blade angle) was changed from 10° to 3°.

[0138] (Example 16) The photoreceptor and charging roller of Example 16 were obtained in the same manner as in Example 1, and in the evaluation of the image forming apparatus described later, the photoreceptor and charging roller were evaluated in the same manner as in Example 1, except that the angle θ2 between the cleaning means blade and the outer surface of the photoreceptor (blade angle) was changed from 10° to 5°.

[0139] (Example 17) The photoreceptor and charging roller of Example 17 were obtained in the same manner as in Example 1, and in the evaluation of the image forming apparatus described later, the photoreceptor and charging roller were evaluated in the same manner as in Example 1, except that the angle θ2 between the cleaning means blade and the outer surface of the photoreceptor (blade angle) was changed from 10° to 20°.

[0140] (Example 18) The photoreceptor and charging roller of Example 18 were obtained in the same manner as in Example 1, and in the evaluation of the image forming apparatus described later, the photoreceptor and charging roller were evaluated in the same manner as in Example 1, except that the angle θ2 between the cleaning means blade and the outer surface of the photoreceptor (blade angle) was changed from 10° to 23°.

[0141] (Example 19) The photoreceptor and charging roller of Example 19 were obtained in the same manner as in Example 1. In the evaluation of the image forming apparatus described later, the photoreceptor and charging roller of Example 19 were obtained and evaluated in the same manner as in Example 1, except that the charging AC voltage (AC superimposed) Vpp of the charging means was changed from 1.75kV to 1.65kV.

[0142] (Example 20) In preparing the electrostatic roller, the photoreceptor and electrostatic roller of Example 20 were obtained and evaluated in the same manner as in Example 1, except that the softening agent was changed from 5 parts by mass of ricinoleic acid to 2.5 parts by mass. By reducing the amount of ricinoleic acid added, the surface hardness of the electrostatic roller was increased (the same applies to Examples 29 and 30 described later).

[0143] (Example 21) The photoreceptor and charging roller of Example 21 were obtained in the same manner as in Example 1, and in the evaluation of the image forming apparatus described later, the photoreceptor and charging roller were evaluated in the same manner as in Example 1, except that the spring pressure of the expandable body supporting the charging roller was changed from 680gF to 350gF.

[0144] (Example 22) The photoreceptor and charging roller of Example 22 were obtained in the same manner as in Example 1, and in the evaluation of the image forming apparatus described later, the photoreceptor and charging roller were evaluated in the same manner as in Example 1, except that the spring pressure of the expandable body supporting the charging roller was changed from 680gF to 450gF.

[0145] (Example 23) The photoreceptor and charging roller of Example 23 were obtained in the same manner as in Example 1, and in the evaluation of the image forming apparatus described later, the photoreceptor and charging roller were evaluated in the same manner as in Example 1, except that the spring pressure of the expandable body supporting the charging roller was changed from 680gF to 750gF.

[0146] (Example 24) The photoreceptor and charging roller of Example 24 were obtained in the same manner as in Example 1, and in the evaluation of the image forming apparatus described later, the photoreceptor and charging roller were evaluated in the same manner as in Example 1, except that the spring pressure of the expandable body supporting the charging roller was changed from 680gF to 900gF.

[0147] (Example 25) In forming the charge transport layer, the photoreceptor and charging roller of Example 25 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to the polycarbonate resin of the aforementioned structural polymer (2) [index (m,n) = (0.40,0.60), viscosity-average molecular weight 45,000].

[0148] (Example 26) In forming the charge transport layer, the photoreceptor and charging roller of Example 26 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of polymer (2) [exponent (m,n) = (0,1.00), viscosity-average molecular weight 45,000].

[0149] (Example 27) In forming the charge transport layer, the photoreceptor and charging roller of Example 27 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of polymer (1) [exponents (m,n) = (0.75,0.25), viscosity-average molecular weight 65,000].

[0150] (Example 28) In forming the charge transport layer, the photoreceptor and charging roller of Example 28 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of polymer (1) [exponents (m,n) = (0.75,0.25), viscosity-average molecular weight 80,000].

[0151] (Example 29) In preparing the electrostatic roller, the photoreceptor and electrostatic roller of Example 29 were obtained and evaluated in the same manner as in Example 1, except that the softening agent was changed from 5 parts by mass of ricinoleic acid to 1.5 parts by mass.

[0152] (Example 30) In preparing the electrostatic roller, the photoreceptor and electrostatic roller of Example 30 were obtained and evaluated in the same manner as in Example 1, except that the softening agent was changed from 5 parts by mass of ricinoleic acid to 0.5 parts by mass.

[0153] (Example 31) The photoreceptor and charging roller of Example 31 were obtained in the same manner as in Example 1. In the evaluation of the image forming apparatus described later, the photoreceptor and charging roller of Example 31 were obtained and evaluated in the same manner as in Example 1, except that the AC charging voltage Vpp of the charging means was changed from 1.75kV to 1.50kV.

[0154] (Example 32) In forming the charge transport layer, the charge transport layer coating solution was applied onto the charge generation layer, the resulting coating film was dried at 130°C for 1 hour, and then cooled to room temperature at a cooling rate of 0.5°C / minute. Aside from these steps, the photoreceptor and charging roller of Example 32 were obtained and evaluated in the same manner as in Example 1.

[0155] (Example 33) In preparing the electrostatic roller, the photoreceptor and electrostatic roller of Example 33 were obtained and evaluated in the same manner as in Example 1, except that the softening agent was changed from 5 parts by mass to 7 parts by mass of ricinoleic acid.

[0156] (Comparative Example 1) In forming the charge transport layer, the charge transport layer coating solution was applied onto the charge generation layer, the resulting coating film was dried at 130°C for 1 hour, and then cooled to room temperature at a cooling rate of 10°C / minute. Aside from these steps, the photoreceptor and charging roller of Comparative Example 1 were obtained and evaluated in the same manner as in Example 1.

[0157] (Comparative Example 2) In forming the charge transport layer, the charge transport layer coating solution was applied onto the charge generation layer, the resulting coating film was dried at 130°C for 1 hour, and then cooled to room temperature at a cooling rate of 1°C / minute. Aside from these steps, the photoreceptor and charging roller of Comparative Example 2 were obtained and evaluated in the same manner as in Example 1.

[0158] (Comparative Example 3) In forming the charge transport layer, the photoreceptor and charging roller of Comparative Example 3 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of polymer (1) [exponent (m,n)=(1.0,0), viscosity-average molecular weight 50,000].

[0159] (Comparative Example 4) In forming the charge transport layer, the photoreceptor and charging roller of Comparative Example 4 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of the following polymer (12) [exponents (m,n) = (0.75,0.25), chain end group: p-tert-butylphenyl, viscosity-average molecular weight 45,000]. [ka]

[0160] (Comparative Example 5) In forming the charge transport layer, the photoreceptor and charging roller of Comparative Example 5 were obtained and evaluated in the same manner as in Example 1, except that the binder resin was changed to a polycarbonate resin of the following polymer (13) [exponents (m,n) = (0.75,0.25), chain end group: p-tert-butylphenyl, viscosity-average molecular weight 45,000]. [ka]

[0161] [evaluation] The photoreceptors and charging rollers of Examples 1-33 and Comparative Examples 1-5 were prepared, and their crack resistance and print resistance were evaluated.

[0162] (1) Crackability evaluation The fabricated photoreceptor and charging roller were mounted in a digital copier unit (Sharp Corporation, model: BP70M65) modified for testing. Under room temperature conditions of 24°C and 60% relative humidity, the blade angle θ2, the superimposed AC voltage (AC) Vpp, and the spring pressure of the expandable body supporting the charging roller were set to the conditions described in Tables 1 and 2. A character test chart (ISO19752) was printed on 1000 sheets of recording paper to perform a print durability test. Afterwards, the unit was removed and left for 1 hour in a low-temperature, low-humidity environment of 5°C and 10% relative humidity. Immediately afterwards, it was moved to a high-temperature, high-humidity environment of 50°C and 85% relative humidity and stored for 2 weeks. After removal, the contact area of ​​the charging roller was visually inspected, and the number of cracks in the drum axis direction was measured. The crack resistance was evaluated from the obtained measurement values ​​according to the following criteria.

[0163] <Judgment criteria> VG: No cracks have occurred. It can be used without problems even in multifunction printers and printers that require long battery life and high image quality. G: There are 1 to 5 cracks of about 3 mm or less. It can be used without any problems for all types of printers and devices except for multifunction printers and printers that require long battery life or high image quality. NB: There are 6 to 10 cracks less than 3mm in diameter. Inexpensive multifunction printers and printers are usable. B: There are 11 or more cracks, or one or more cracks that are approximately 5 mm or larger. Problematic in practical use (difficult to use)

[0164] (2) Durability evaluation The fabricated photoreceptor and charging roller were mounted in a digital copier unit (Sharp Corporation, model: BP30C25) modified for testing. Under low temperature and low humidity conditions of 5°C and 10% relative humidity, the blade angle θ2, the AC superimposed charging voltage Vpp, and the spring pressure of the expandable body supporting the charging roller were set to the conditions described in Tables 1 and 2. A character test chart (ISO19752) was printed on 50,000 sheets of recording paper to conduct a print durability test. The thickness of the photosensitive layer at the start of the print durability test and after 50,000 images had been formed was measured using a film thickness measuring device (Filmetrics, model: F-20-EXR). The amount of film abrasion (film loss) per 100,000 rotations of the photoreceptor drum was determined from the difference between the film thickness at the start of the print durability test and the film thickness after 50,000 images were formed. The print durability was then evaluated based on the obtained abrasion amount according to the following criteria. A higher abrasion amount was considered to indicate poorer print durability.

[0165] <Judgment criteria> VG: Abrasion amount <1.00 μm / 100,000 rpm It can be used without problems even in multifunction devices or printers that require a long lifespan. G: 1.00 μm / 100,000 rpm ≤ amount of material removed < 1.50 μm / 100,000 rpm Although the amount of wear is slightly higher than average, it can be used without problems unless you are using a multifunction printer or printer that requires a long lifespan. NB: 1.50 μm / 100,000 rpm ≤ amount of material removed < 2.00 μm / 100,000 rpm Although it wears down considerably, it can be used without problems in the case of inexpensive multifunction printers or printers. B: 2.00 μm / 100,000 rpm ≤ amount of material removed The amount of material worn down is excessive, posing a problem for practical use (making it difficult to use).

[0166] (3) Image evaluation For the drums that underwent the print durability evaluation in (2), halftone images were acquired and the images were visually inspected. Those with no noticeable problems were marked with "-", and those with minor defects were marked with "minor defects".

[0167] Tables 1 and 2 show the production and setting conditions of the photoreceptor and the image forming apparatus, as well as their physical properties and evaluation results. The abbreviations in Table 1 have the following meanings. (1): Polymer (1) (2): Polymer (2) PAR: Polyarylate resin o-TPh: o-Terphenyl m-TPh: m-Terphenyl p-TPh: p-Terphenyl TPhB: Triphenylbenzene p-QPh: p-Quaterphenyl In addition, for the binder resin / additive type and blending amount in the table, "-" means no blending or no addition. * / The "-" for the type and blending amount of the additive means no blending or no addition.

[0168]

Table 1

[0169]

Table 2

[0170] The following can be understood from Tables 1 and 2. (1) The photoreceptors of Examples 1 to 33 that satisfy the constituent requirements of the present disclosure can significantly suppress crack generation compared with the photoreceptors of Comparative Examples 1 to 5 that do not satisfy the constituent requirements of the present disclosure. (2) The photoreceptors of Examples 3, 4, 25, and 26 using a resin with an n value of 0.35 or more for the structural unit (B) of the polycarbonate resin tend to further suppress crack generation compared with the photoreceptor of Example 1 using a resin with an n value less than 0.35 (0.25). (3) The photoreceptors of Examples 1, 27, and 28 using a resin with a viscosity average molecular weight of 40,000 or more for the polycarbonate resin can further suppress crack generation compared with the photoreceptor of Example 5 using a resin with a viscosity average molecular weight less than 40,000 (35,000).

[0171] (4) The photoreceptor of Example 6 further containing a polyarylate resin as a binder resin can suppress crack generation as compared with the photoreceptor of Example 1 not containing the polyarylate resin. (5) The photoreceptors of Examples 7 to 14 to which a compound having a terphenyl structure is added, particularly the photoreceptors of Examples 8 to 14 in which the addition amount thereof is 5% by mass or more with respect to the charge transport material, can further suppress crack generation as compared with the photoreceptor of Example 1 to which a compound having a terphenyl structure is not added. However, the photoreceptor of Example 10 in which the addition amount of the compound having a terphenyl structure is 18% by mass or more (20) with respect to the charge transport material has slightly inferior printing durability.

[0172] (6) The image forming apparatuses of Examples 15 to 17 in which the angle (blade angle θ2) formed between the blade of the cleaning means and the outer peripheral surface of the photoreceptor is set to 20° or less can suppress crack generation as compared with the image forming apparatus of Example 18 in which the blade angle θ2 is set to exceed 20°. However, the image forming apparatus of Example 15 in which the blade angle θ2 is set to 5° or less (3°) has minor image defects. (7) The image forming apparatus having a charging means with an AC superposition (Vpp) of 1.80 kV or less can suppress crack generation. The image forming apparatuses of Examples 19 and 31 (1.65 kV and 1.50 kV) having a charging roller with a lower AC superposition (Vpp) can further suppress crack generation. (8) The image forming apparatuses of Examples 1, 20, 29, and 30 in which the charging means (charging roller) has a surface with a hardness of not less than 68 degrees at a load of 1 kg as defined in JIS K7312 can further suppress crack generation as compared with the image forming apparatus of Example 33 having a hardness of less than 68 degrees (63). (9) The image forming apparatus in which the spring pressure of the elastic body supporting the elastic body of the charging means (charging roller) is 750 gF or less can further suppress crack generation as compared with the image forming apparatus of Example 24 in which the spring pressure is set to exceed 750 gF (900). However, the image forming apparatus of Example 21 in which the spring pressure of the elastic body is less than 400 gF (350) has minor image defects.

[0173] (10) In the method for manufacturing a photoreceptor according to the present disclosure, which includes a step of applying and heating a coating solution to form the charge transport layer of the photoreceptor and then slowly cooling it at a cooling rate of less than 1°C / min, the photoreceptors of Examples 1 and 32 were obtained in which the elastic power was increased and the creep value was reduced, and crack occurrence was suppressed. In contrast, the photoreceptors of Comparative Examples 1 and 2, obtained under the conditions of cooling rates of 10°C / min and 1°C / min, did not have suppressed crack occurrence. [Explanation of Symbols]

[0174] F01 Electrophotographic Photoconductor F1 conductive support F21 Lower layer F22 Charge Generation Layer F23 Charge transport layer Fa Electrophotographic photoreceptor surface

[0175] 50 Image forming apparatus 23. Enclosure (Housing) 2. Electrophotographic photoreceptor 3. Conductive support 4. Photosensitive layer (stacked photosensitive layer) Arrow indicates the rotation direction of the electrophotographic photoreceptor. 7. Charging means (charging roller) 28 Conductive support 29 Elastic layer 30 resistance layer 18a Power supply unit (high voltage application device) 11 Exposure means 12. Developing means (developer) 31 Developing roller 32 Casing 25. Developer (including toner) 13. Transfer means (transfer charger) 18b Power supply unit (high voltage application device) 26 Recording media (recording paper or transfer paper) 19 Fixing means (fuser) 14. Cleaning methods (cleaners) 34 Cleaning Blades 35 Recovery casing 15 Control means 20 Separation means (separation claw)

[0176] 8. Hysteresis lines A, B, C, D: Each component of the hysteresis line F max Maximum indentation load 200 electrophotographic photoreceptors 204 Rotation axis of the electrophotographic photoreceptor 205 contacts 301 Blade θ2 blade angle

Claims

1. An electrophotographic photoreceptor comprising at least a stacked photosensitive layer on a conductive support, in which a charge generating layer containing a charge generating material and a charge transport layer containing a charge transport material are stacked in that order, The charge transport layer is a binder resin consisting of structural units (A) and (B), or structural unit (B) alone, according to general formula (I): 【Chemistry 1】 (In the formula, R 1 ~R 6 R is the same or different hydrogen atom, a C1-C3 alkyl group, or a C1-C3 fluoroalkyl group, 3 The carbon atoms and R 4 The carbon atoms may bond with each other to form a cyclo ring, and m and n are indices that satisfy the relationships 0 ≤ m < 1, 0 < n ≤ 1, and m + n = 1. It contains polycarbonate resin represented by The outermost layer of the electrophotographic photoreceptor, when subjected to a Vickers square pyramidal diamond indenter with a facing angle of 136° under the conditions of a maximum indentation load of 5 mN, a loading time to reach the maximum indentation load of 10 seconds, a load holding time of 5 seconds, and an unloading time of 10 seconds, has an elastic power W of 52% or more and a creep value C of 2.70% or less. An electrophotographic photoreceptor characterized by the following features.

2. The electrophotographic photoreceptor according to claim 1, wherein the polycarbonate resin satisfies the relationship n≧0.35 in general formula (I).

3. The electrophotographic photoreceptor according to claim 1 or 2, wherein the polycarbonate resin has a viscosity-average molecular weight of 40,000 or more.

4. The electrophotographic photoreceptor according to claim 1 or 2, wherein the charge transport layer further comprises a polyarylate resin as a binder resin.

5. The electrophotographic photoreceptor according to claim 1 or 2, wherein the charge transport layer further comprises a compound having a terphenyl structure.

6. The electrophotographic photoreceptor according to claim 5, wherein the compound having the terphenyl structure is contained in a proportion of 3 to 18% by mass relative to the charge transport material.

7. The invention provides at least an electrophotographic photoreceptor according to claim 1 or 2, a charging means for charging the electrophotographic photoreceptor, an exposure means for exposing the charged electrophotographic photoreceptor to an electrostatic latent image, a developing means for developing the electrostatic latent image to form a toner image, a transfer means for transferring the toner image onto a recording medium, and a cleaning means for removing and recovering toner remaining on the electrophotographic photoreceptor. The image forming apparatus is characterized in that the cleaning means comprises a blade having an angle of 5° or more and 20° or less with respect to the outer surface of the electrophotographic photoreceptor.

8. The image forming apparatus according to claim 7, wherein the charging means is a charging roller having AC superposition of 1.80 kV or less.

9. The image forming apparatus according to claim 7, wherein the charging means has a surface with a hardness of 65 degrees or more when a 1 kg load is applied, as defined in JIS K7312.

10. The image forming apparatus according to claim 7, comprising a support member supported at both ends thereof by the charging means and an expandable body that expands and contracts in a direction toward the electrophotographic photoreceptor from the support member, wherein the expandable body has a spring pressure of 400 gF or more and 750 gF or less.

11. A method for manufacturing an electrophotographic photoreceptor according to claim 1 or 2, A method for manufacturing an electrophotographic photoreceptor, characterized by including a step of applying a coating solution, heating and drying it, and slowly cooling it at a cooling rate of less than 1°C / min when forming the charge transport layer of the electrophotographic photoreceptor.

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