JP2007171531A - Image forming apparatus using two or more contact chargers - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of sufficiently preventing deterioration of the surface of an electrophotographic photoreceptor in the overlapping parts of contact charging members, that is, the overlapping parts of charging areas. <P>SOLUTION: The image forming apparatus includes the two or more contact charging members serving as charging means, which are disposed along a direction perpendicular to the direction of movement of the surface of the electrophotographic photoreceptor 1 such that the contact charging members have the overlapping parts for charging the surface of the electrophotographic photoreceptor 1 so that the charging areas overlap and non-overlapping parts for charging the surface of the electrophotographic photoreceptor 1 separately from one another. In the image forming apparatus, the load of contact between the electrophotographic photoreceptor 1 and a cleaning blade 7 is set to 3 to 10% higher in a part corresponding to each overlapping part than that in a part corresponding to the non-overlapping part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that charges a surface of an electrophotographic photosensitive member by bringing a plurality of charging members into contact with the surface of one electrophotographic photosensitive member. .

  Conventionally, in an electrophotographic image forming apparatus, an image is formed through processes such as charging, exposure, development, and transfer, and a charging system using a wire generally called corotron has been applied to the charging process. . However, there is a problem that ozone or the like is generated when charging is performed by the corotron.

  Under such a background, a contact charging method for charging a surface of an electrophotographic photosensitive member by applying a predetermined current while a roll-shaped or brush-shaped charging member (contact charging member) is in contact with the surface of the electrophotographic photosensitive member. Practical use is in progress.

  By the way, for example, when a contact charging member having the same width as that of the electrophotographic photosensitive member is used in a wide image forming apparatus having a charging surface width of about 1 m, the charging member is not flexible or has poor workability. It was difficult to perform uniform charging due to the influence of the above. Further, such a long contact charging member has not been practically available in terms of manufacturing cost.

  Therefore, various methods for uniformly charging the surface of the electrophotographic photosensitive member in a wide image forming apparatus to which the contact charging method is applied have been studied. For example, Patent Document 1 discloses a plurality of contact charging members. Discloses a charging device in which is distributed in the moving direction of the surface to be charged.

  However, when an image forming apparatus including such a charging device is used for a long time, toner adheres to the overlapping portion of the charged region, and the image is likely to be distorted. Therefore, Patent Document 2 proposes a method of controlling the alternating current applied to each of the contact charging members to 1.3 mA or less and a charge transport layer having a film thickness of 24 μm or more to eliminate these adverse effects. Has been.

JP-A-8-305128 JP 2000-91135 A

  However, even if such an image forming apparatus is used for a long time, the same phenomenon still occurs, so the electrophotographic photosensitive member must be replaced before the occurrence of image quality defects due to wear of the entire photosensitive layer. I didn't get it.

  The present invention has been made in view of the above-described problems of the prior art, and even when the electrophotographic photosensitive member is long, the surface of the photosensitive member can be sufficiently uniformly charged, and can be used for a long time. In this case, an object of the present invention is to provide an image forming apparatus capable of continuously obtaining sufficiently good image quality without causing poor cleaning of the surface of the photoreceptor.

  The configuration of the present invention is as follows.

  (1) An electrostatic latent image is formed by exposing the surface of the electrophotographic photosensitive member, a charging unit having a plurality of contact charging members for charging the surface of the electrophotographic photosensitive member, and the surface of the electrophotographic photosensitive member. An exposure unit, a developing unit that develops the electrostatic latent image with a developer, a transfer unit that transfers the developed image to a transfer medium, and the developer remaining on the surface of the electrophotographic photosensitive member are cleaned. A plurality of contact charging members, wherein the plurality of contact charging members include overlapping portions that charge the surface of the electrophotographic photosensitive member in an overlapping manner, and non-overlapping portions that individually charge the surface of the electrophotographic photosensitive member. The image forming apparatus is distributed along a direction orthogonal to the moving direction of the surface of the electrophotographic photosensitive member so that the cleaning member is in contact with the surface of the electrophotographic photosensitive member. The Contact load between the electrophotographic photosensitive member and the cleaning blade in a portion corresponding to the overlapping portion is included between the electrophotographic photosensitive member and the cleaning blade in a portion corresponding to the non-overlapping portion. An image forming apparatus, wherein the image forming apparatus is set to be 3 to 10% higher than a contact load.

  According to the image forming apparatus of the present invention, even when the electrophotographic photosensitive member is long, the surface of the electrophotographic photosensitive member can be charged sufficiently uniformly and without leakage, and the electrophotographic photosensitive member in the overlapping portion of the charged region can be charged. Even if partial wear of the body surface occurs, it can be sufficiently cleaned.

  Further, according to the image forming apparatus of the present invention, it is possible to sufficiently prevent the defective cleaning of the overlapping portion and obtain an excellent image quality over a long period until an image quality defect occurs due to film abrasion of the electrophotographic photosensitive member.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. 2A and 2B are a perspective view and a top view showing a positional relationship between the electrophotographic photosensitive member 1 and the contact charging members 2a to 2c in the image forming apparatus shown in FIG.

  In the apparatus shown in FIGS. 1, 2a and 2b, the electrophotographic photosensitive member 1 is supported by a support 9, and can rotate around the support 9 in the direction of the arrow at a predetermined rotational speed. . Then, along the rotation direction of the electrophotographic photosensitive member 1, three contact charging members 2a to 2c, an exposure device 3, a developing device 4, a transfer device 5, and a cleaning unit 7 are arranged in this order. The apparatus includes an image fixing device 6, and the transfer medium P is conveyed to the image fixing device 6 through the transfer device 5.

  The electrophotographic photosensitive member 1 has a photosensitive layer formed on a cylindrical conductive substrate, and the photosensitive layer contains a charge generating substance and a charge transporting substance. The electrophotographic photoreceptor 1 used in the embodiment shown in FIG. 1 is a laminate in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer) and laminated. Type photoconductors and single layer type photoconductors containing both the charge generation material and the charge transport material in the same layer, but are preferably laminated photoconductors. The charge generation material and the charge transport material are not particularly limited. For example, the structure of the electrophotographic photosensitive member 1 illustrated in FIG. 3 and the charge generation material and charge transport material described later can be used.

  In the electrophotographic photosensitive member 1 according to the embodiment of the present invention shown in FIG. 3, a cylindrical body having a diameter of 10 to 200 mm and a length of 250 to 1500 mm is usually used as the conductive substrate 21. The conductive base 21 is made of a metal material such as aluminum, stainless steel or nickel; electrically conductive with a polymer material such as polyethylene terephthalate, polybutylene terephthalate, polypropylene, nylon, polystyrene or phenol resin, or an insulating material such as hard paper. Examples include those obtained by dispersing a substance and conducting a conductive treatment; those obtained by laminating a metal foil on the above insulating material; those obtained by forming a metal vapor deposition film on the above insulating material, and the like.

  The conductive substrate 21 may be subjected to a surface treatment such as an anodizing treatment, rough grinding treatment, or honing treatment. By such surface treatment, the surface roughness of the conductive substrate is set within a predetermined range (preferably Ra is 0.05 to 0.5 μm, Rmax is 0.5 to 5 μm), thereby preventing light interference. be able to.

  Here, the surface roughness Ra is an arithmetic average roughness which is one of the measures of roughness, and a known stylus type surface roughness measuring machine (for example, Surfcom 1400A: manufactured by Tokyo Seimitsu Co., Ltd.) is used. Can be measured using.

  The measurement of the surface roughness Ra in the conductive substrate 21 of this embodiment is based on JIS B0601-1994, using Surfcom 1400A, evaluation length Ln = 4 mm, reference length L = 0.8 mm, cut-off The measurement was performed under the measurement condition of value = 0.8 mm. Although it is possible to measure under other conditions, it is preferable to measure under conditions that can be correlated with the above-mentioned measurement conditions, and the measured values are converted to values evaluated under the above-described measurement conditions. It is evaluated by.

  Rmax is measured using, for example, Surfcom 1400A: manufactured by Tokyo Seimitsu Co., Ltd. in accordance with JIS B0601-1982.

  In addition, vibration noise can be suppressed by fitting a member obtained by processing metal, resin, rubber, or the like into a cylindrical shape or a columnar shape on the inner peripheral surface of the conductive base 21.

  The undercoat layer 22 is formed including a predetermined resin. Such resins include acrylic resins, vinyl chloride resins, vinyl acetate resins, epoxy resins, polyurethane resins, phenol resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins. These resins may be mixed with a zirconium compound, a titanium compound, or the like to form an undercoat layer. The thickness of the undercoat layer is preferably 0.1 to 3.0 μm.

  Thus, when an undercoat layer is provided on a conductive support, the following effects (1) to (6) can be obtained.

  (1) Image quality is improved by preventing unnecessary carrier injection from the conductive support to the photosensitive layer.

  (2) Stable image quality can be obtained by reducing the environmental dependence (temperature, humidity, etc.) of the light attenuation curve of the electrophotographic photosensitive member.

  (3) Due to an appropriate charge transport capability, charges are not accumulated even when used repeatedly over a long period of time, and the occurrence of sensitivity fluctuations is suppressed.

  (4) Occurrence of image defects due to dielectric breakdown is prevented by an appropriate pressure resistance against the charging voltage.

  (5) The photosensitive layer can be integrally held on the support as the adhesive layer.

  (6) Light reflection of the support is prevented.

  The charge generation layer 23 is formed including a charge generation material and a binder resin, and the charge generation material is dispersed in the binder resin and held in the charge generation layer 23. Such a charge generating material is not particularly limited, and specifically, an azo pigment, a disazo pigment, a quinone pigment, a quinocyanine pigment, a perylene pigment, an indigo pigment, a bisbenzimidazole pigment, a phthalocyanine pigment, a quinacridone pigment, a pyrylium salt, an azulenium. Examples thereof include salts and trigonal selenium. In addition, as the binder resin, polycarbonate, polyacrylate, polystyrene, polymethacrylic ester, styrene-methyl methacrylate copolymer, polysulfone, polyvinyl acetate, polyacrylonitrile, polyvinyl butyral, polyvinyl pyrrolidone, methyl cellulose, hydroxymethyl cellulose, cellulose esters Etc. can be used. The film thickness of the charge generation layer 23 is preferably 0.05 to 1.0 μm.

  The charge transport layer 24 is formed including a charge transport material and a binder resin, and the charge transport material is dispersed in the binder resin and held in the layer. Such a charge transport material is not particularly limited, and specifically, polycyclic aromatic compounds such as anthracene, pyrene, phenanthrene, coronene or derivatives thereof, indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, Examples thereof include nitrogen-containing heterocyclic compounds such as oxadiazole, pyrazoline, thiadiazole, triazole or derivatives thereof, and hole transport materials such as hydrazone. Further, as the binder resin, the same resin as that used as the binder resin of the charge generation layer can be used.

  Further, the thickness of the charge transport layer 24 is such that the surface can be charged sufficiently uniformly and without leakage even with a long electrophotographic photosensitive member, and the electrophotographic photosensitive member in the overlapping portion of the charged region is also provided. Considering the prevention of deterioration of the body surface, it is preferably 24 μm or more, more preferably 26 to 40 μm. When the thickness of the charge transport layer is less than 24 μm, when charging with the contact charging member, the toner adheres to the overlapping part and the image is disturbed, or the charging characteristic of the overlapping part is deteriorated and fogging occurs. May occur, and it may be difficult to obtain sufficiently good image quality over a long period of time.

  When forming the undercoat layer 22, the charge generation layer 23, and the charge transport layer 24, a coating obtained by dispersing a (binding) resin, or a charge generation material or a charge transport material in a predetermined solvent. It can be suitably obtained by applying the liquid on a predetermined layer (conductive support, undercoat layer, charge generation layer, etc.) and drying it.

  As the solvent, a solvent having high volatility and having a vapor density higher than that of air when the solvent is vaporized is preferable. Specifically, n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, N, N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, 4-methoxy-4-methylpentanone, dimethoxymethane, dimethoxyethane 2,4-pentadione, anisole, methyl 3-oxobutanoate, monochlorobenzene, toluene, xylene, chloroform, 1,2-dichloroethane, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, 1-butanol, ethyl acetate, acetic acid Examples include butyl, dimethyl sulfoxide, methyl cellosolve, ethyl cellosolve, and methyl cellosolve acetate. These organic solvents may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of a method for dispersing materials such as a binder resin, a charge transport material, and a charge generation material in the solvent include a sand mill, a colloid mill, an attritor, a ball mill, a dyno mill, a high-pressure homogenizer, an ultrasonic disperser, a coball mill, and a roll mill. Is mentioned.

  Examples of the method for applying the coating liquid include a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method.

  Further, as the electrophotographic photosensitive member in the embodiment of the present invention, the one further provided with a surface protective layer on the photosensitive layer for the purpose of more reliably preventing the deterioration of the surface of the electrophotographic photosensitive member and further improving the image quality. It may be used.

  Examples of the surface protective layer include a layer in which semiconductive fine particles such as titanium oxide and a low molecular compound having a charge transporting ability are dispersed in a binder resin, and a photofunctional polymer compound having a charge transporting ability (for example, specially Examples thereof include a layer containing an organosilicon compound described in Kaihei 9-190004, JP-A-11-38656, JP-A 2000-171990, and the like.

  In addition, the contact charging members 2a to 2c in the embodiment of the present invention have a cylindrical shape (roll shape), and an elastic layer, a resistance layer, and a protective layer are laminated in this order on the outer peripheral surface of the conductive core material. Consists of.

  As the core material, a conductive material such as iron, copper, brass, stainless steel, aluminum, nickel, or a resin molded product in which conductive particles are dispersed can be used.

The elastic layer is made of EPDM, polybutadiene, natural rubber, polyisobutylene, SBR, CR, NBR, silicone rubber, urethane rubber, epichlorohydrin rubber, SBS, thermoplastic elastomer, norbornene rubber, fluorosilicone rubber, ethylene oxide. For rubber materials such as rubber, carbon black, zinc, aluminum, copper, iron, nickel, chromium, titanium and other metals, ZnO—Al ₂ O ₃ , SnO ₂ —Sb ₂ O ₃ , In ₂ O ₃ —SnO ₂ , Conductive particles such as ZnO—TiO ₂ , MgO—Al ₂ O ₃ , FeO—TiO ₂ , TiO ₂ , SnO ₂ , Sb ₂ O ₃ , In ₂ O ₃ , ZnO, MgO, and other conductive particles or semiconductive A material in which conductive particles are dispersed is preferably used.

  As the material of the resistance layer and the protective layer, the conductive particles or semiconductive particles are acrylic resin, cellulose resin, polyamide resin, methoxymethylated nylon, ethoxymethylated nylon, polyurethane resin, polycarbonate resin, polyester resin, A resin which is dispersed in a polyethylene resin, a polyvinyl resin, a polyarylate resin, a polythiophene resin, a polyolefin resin such as PFA, FEP, or PET, or a styrene butadiene resin and whose resistance is controlled is preferably used.

  Moreover, antioxidants, such as hindered phenol and hindered amine, fillers, such as clay and kaolin, and lubricants, such as silicone oil, can be added to the said resistance layer and protective layer as needed. As a method for forming these layers, a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like can be used.

The resistivity of the resistance layer and the protective layer is preferably 10 ³ to 10 ¹⁴ Ωcm, more preferably 10 ⁶ to 10 ¹² Ωcm, and further preferably 10 ⁷ to 10 ¹² Ωcm. The thicknesses of the resistance layer and the protective layer are each preferably 0.01 to 1000 μm, more preferably 0.1 to 500 μm, and still more preferably 0.5 to 100 μm.

  As shown in FIGS. 2a and 2b, in the present embodiment, for example, the contact charging member is used as a contact charging member so that the contact charging member has a length that does not bend and can be manufactured inexpensively. It is arranged on the surface of the electrophotographic photosensitive member 1 by being divided into three parts 2a to 2c.

  Further, the contact charging members 2a, 2b, and 2c are along a direction (in the direction of the rotation axis of the electrophotographic photosensitive member 1) orthogonal to the moving direction of the surface of the electrophotographic photosensitive member 1 (the arrow direction in FIG. 2a or 2b). They are arranged at a predetermined interval. The contact charging members 2a and 2c are disposed at both ends of the electrophotographic photosensitive member 1, respectively. On the other hand, the contact charging member 2b is provided at the center of the electrophotographic photosensitive member 1 so as to be positioned between the contact charging members 2a and 2c. It arrange | positions so that it may overlap with the edge part of the charging region by the members 2a and 2c. That is, the contact charging members 2a, 2b, and 2c include an overlapping portion that charges the surface of the electrophotographic photosensitive member 1 in an overlapping manner, and a non-overlapping portion that charges the surface of the electrophotographic photosensitive member 1 independently without overlapping. , Distributed to have.

  The diameter-shaped contact charging members 2a, 2b, and 2c may be produced by, for example, adhering or covering a sheet-like or tube-like layer formed in advance to a predetermined thickness, It may be performed by a conventionally known method such as dipping coating or the like. Further, it may be a method of roughly forming a layer by extrusion molding and then adjusting the shape by polishing or the like, or a method of curing and molding a material into a predetermined shape in a mold.

  When charging the surface of the electrophotographic photosensitive member 1 to the contact charging members 2a to 2c, the AC current value applied to each contact charging member is not particularly limited, but a long electrophotographic photosensitive member is sufficiently used. From the viewpoint of charging uniformly and without leakage, and from the viewpoint of preventing deterioration of the surface of the electrophotographic photosensitive member in the overlapping portion of the charging region, it is preferably 1.3 mA or less. In view of the property and the ease of occurrence of image fogging, it is more preferably 0.7 to 1.3 mA.

  When the alternating current value is 1.3 mA or less, it is possible to more reliably prevent the phenomenon that the toner adheres to the overlapping portion and the image is disturbed, or the charging characteristic of the overlapping portion is deteriorated to cause fogging. The image quality can be further improved.

  Moreover, it is preferable that the frequency at the time of applying an alternating current to the contact charging members 2a-2c is 400-2000 Hz. When the frequency is less than 400 Hz, the surface of the electrophotographic photosensitive member 1 is unevenly charged and tends to cause fogging. On the other hand, when the frequency exceeds 2000 Hz, vibration noise tends to be easily generated. .

  The contact charging members 2a to 2c shown in FIG. 1, FIG. 2a and FIG. 2b can rotate at the same peripheral speed as the electrophotographic photosensitive member 1 by being brought into contact with the electrophotographic photosensitive member 1. A predetermined driving means may be attached to each of the charging members 2 a to 2 c and rotated at a peripheral speed different from the peripheral speed of the electrophotographic photosensitive member 1.

  Further, the image forming apparatus shown in FIG. 1 includes three contact charging members 2a to 2c. In the embodiment of the present invention, the number of contact charging members included in the image forming apparatus is an electrophotographic number. It can be appropriately selected according to the size of the photoreceptor and the processability of the contact charging member.

  An electrostatic latent image is formed by irradiating the surface of the electrophotographic photosensitive member 1 thus charged with exposure light from the exposure device 3. As the exposure device 3, an optical system device such as a semiconductor laser, an LED (light emitting diode), a liquid crystal shutter, or the like can be used.

  Next, the electrostatic latent image formed on the surface of the electrophotographic photoreceptor 1 is developed by the developing device 4 to form a toner image. As the developing device 4, known developing means using a regular or reversal developer such as a one-component system or a two-component system can be used. Further, the shape of the toner to be used is not particularly limited, and for example, an irregular shaped toner by a pulverization method or a spherical or granular toner by a polymerization method is preferably used.

  The toner image on the surface of the electrophotographic photoreceptor 1 is transferred to the transfer medium P by the transfer device 5. Examples of the transfer device 5 include a contact transfer charger using a belt, a roller, a film, a rubber blade, and the like, a scorotron transfer charger using a corona discharge, a corotron transfer charger, and the like, from the viewpoint of preventing ozone generation. It is preferable to use a contact type transfer charger.

  The transfer medium P is conveyed to the image fixing device 6, and the toner image is fixed to the transfer medium by heating or pressurization and printed out.

  On the other hand, since the residual toner usually adheres to the surface of the electrophotographic photoreceptor 1 after the transfer process, the residual toner is removed by a cleaning device. The electrophotographic photosensitive member 1 thus cleaned is repeatedly used for the image forming process.

  The cleaning device includes a cleaning member that removes toner adhering to the electrophotographic photosensitive member, and a support member that supports the cleaning member. A cleaning blade is preferably used as the cleaning member. As a material of the cleaning blade, urethane rubber, silicone rubber, fluorine rubber, chloroprene rubber, butadiene rubber, or the like can be used. Among them, it is particularly preferable to use a polyurethane elastic body because of its excellent wear resistance. As the polyurethane elastic body, a polyurethane generally synthesized through an addition reaction between an isocyanate and a polyol and various hydrogen-containing compounds is used. As a polyol component, a polyether-based polyol such as polypropylene glycol or polytetramethylene glycol, Polyester polyols such as adipate polyols, polycaprolactam polyols, polycarbonate polyols are used, and polyisocyanate components include aromatics such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, toluidine diisocyanate, etc. Group polyisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicycle Manufactured by preparing a urethane prepolymer using an aliphatic polyisocyanate such as hexylmethane diisocyanate, adding a curing agent to the urethane prepolymer, pouring it into a predetermined mold, crosslinking and curing, and then aging at room temperature. ing. As the curing agent, a dihydric alcohol such as 1,4-butanediol and a trihydric or higher polyhydric alcohol such as trimethylolpropane or pentaerythritol are usually used in combination.

As the physical properties of the cleaning blade, for example, hardness (durometer hardness obtained by a type A durometer specified in JIS K 6253 “Hardness test method of vulcanized rubber and thermoplastic rubber”) A50 / S to A90 / S, Young's modulus About 3.92 × 10 ⁴ to about 8.82 × 10 ⁴ N / m ² (40 to 90 kgf / cm ² ), 100% modulus (according to JIS K6261 “Low temperature test method for vulcanized rubber and thermoplastic rubber”) About 1.96 × 10 ⁴ to about 6.37 × 10 ⁴ N / m ² (20 to 65 kgf / cm ² ), 300% modulus (according to JIS K6261 “Low temperature test method for vulcanized rubber and thermoplastic rubber”) About 6.86 × 10 ⁴ to about 1.36 × 10 ⁵ N / m ² (70 to 150 kgf / cm ² ), tensile strength (according to JIS K6251) about 2.35 × 10 ⁵ to about 4.9 × 10 ⁵ N / m ² (240 to 500 kgf / cm ² ), elongation (elongation at break as defined in JIS K6251 “Tensile test method of vulcanized rubber”) 290 to 500%, impact resilience ( 30% to 70%, according to JIS K6255 “Repulsive Elasticity Test Method for Vulcanized Rubbers and Thermoplastic Rubbers”, Tear Strength (according to JIS K6252 “Vulcanized Rubbers and Thermoplastic Rubbers—How to Determine Tear Strength”) About 2 4.46 × 10 ⁴ to about 7.35 × 10 ⁴ N / m ² (25-75 kgf / cm ² ), permanent elongation (according to JIS K6262 “Testing method for permanent strain of vulcanized rubber and thermoplastic rubber”) A material having a content of 0% or less can be used, but the present invention is not limited to this. The pressure contact force of the blade is preferably about 0.98 to about 5.88 N / m (10 to 60 gf / cm), and the contact angle is preferably 17 to 30 °.

  The support member that supports the cleaning blade may be any member that has higher rigidity than the cleaning blade. Specifically, it is desirable to form from metal members, such as aluminum, a mild steel plate, and a SUS board, or the resin molding member which mixed carbon and glass fiber. Further, these support members may have a shape for obtaining high rigidity, for example, an L shape.

  The load N when the cleaning blade 30 illustrated in FIG. 4A is brought into contact with the surface of the electrophotographic photosensitive member 1 to be in the state shown in FIG. 4B is only one of the support members 32. Can be regarded as a fixed cantilever beam, and can generally be expressed by the following equation.

^{N = K × S, K =} 3EI / L 3, I = Bt 3/12
However, N: Load (N (Newton)), K: Spring constant (N / m), S: Biting amount (m), E: Young's modulus (Pa (Pascal) or N / m ² ), I: Cross section Next moment (m ⁴ ), L: Free length (m), B: Longitudinal length (m), t: Thickness (m), X: Set angle (degree (°)), Y: Contact angle (Degree (°)) is shown respectively (see FIGS. 4A and 4B).

  Here, the load N at which the cleaning member and the electrophotographic photosensitive member 1 are in contact with each other is set non-uniformly in the axial direction of the electrophotographic photosensitive member 1 so that the load N is increased by 3 to 10% for the overlapping portion of the charging region of the contact charging member. By doing so, the long electrophotographic photosensitive member 1 can be cleaned sufficiently uniformly and without leakage. Accordingly, it is possible to obtain excellent image quality over a long period of time without causing a phenomenon in which the toner adheres to the overlapping portion and the image is disturbed or the charging characteristic of the overlapping portion is deteriorated to cause fogging.

  On the other hand, the increment of the “load where the cleaning member and the electrophotographic photosensitive member 1 are in contact” in the overlapping portion of the charging region formed by the plurality of contact charging members is the “contact between the cleaning member and the electrophotographic photosensitive member 1 in the non-overlapping portion. If the load is less than 3%, the above effect cannot be obtained sufficiently. In addition, the increment of the “load where the cleaning member and the electrophotographic photosensitive member 1 are in contact” in the overlapping portion of the charging region formed by the plurality of contact charging members is the “contact between the cleaning member and the electrophotographic photosensitive member 1 in the non-overlapping portion. If the load exceeds 10%, the cleaning performance in the vicinity of the boundary between the normal portion and the normal portion becomes relatively low, and defective cleaning occurs, resulting in an image forming apparatus that cannot withstand practical use.

  Accordingly, by operating the various parameters described above so that they are different between the overlapping portion and the non-overlapping portion, “the cleaning member and the electrophotographic photosensitive member 1 are in contact with each other in the overlapping portion of the charging region of the contact charging member. "Load" can be partially varied. For example, since the load N of the cleaning blade 30 is proportional to the cube of the thickness t of the cleaning blade 30, the increment of the “load where the cleaning member and the electrophotographic photosensitive member 1 are in contact” at the overlapping portion is set to 3%. Then, it can be seen that the thickness t may be increased by about 0.99% with respect to the non-overlapping portion. Similarly, if the increment of “the load at which the cleaning member and the electrophotographic photosensitive member 1 are in contact” is increased to 10% in the overlapping portion, the thickness t is increased by about 3.23% relative to the non-overlapping portion. I know it ’s good.

  Similarly, the end of the charging region of the contact charging member is set so that the load at which the cleaning member and the electrophotographic photosensitive member 1 are in contact is increased by 3 to 10% with respect to the overlapping region of the charging region by the plurality of contact charging members. For example, any method may be employed such as partially changing the free length L of the cleaning blade 30 or changing the amount of biting S in the portion corresponding to the overlapping portion of the charged region. May be.

  In the present specification, to increase the load for contacting only the overlapping portion of the charging region by only a plurality of contact charging members by 3 to 10% means that the contact load is at the boundary between the overlapping portion and the non-overlapping portion of the charging region. However, the present invention is not limited to this. For example, the load may be changed stepwise with a certain predetermined width. The predetermined width allowed at this time is about 10 mm regardless of the total length or the width of the overlapping portions of the charging regions formed by the plurality of contact charging members.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Production of contact charging member]
As a charging roll as a contact charging member, an epichlorohydrin rubber layer is formed on the surface of a metal (SUS304) shaft, and the surface of the epichlorohydrin rubber layer is coated with about 3 μm of polyamide containing conductive oxide powder. used.

  The total length of the charging roll was 330 mm, which is a part compatible with A3 Novi. As described above, in order to sufficiently charge the effective photosensitive area (920 mm) of the electrophotographic photosensitive member, the charging area was set to 930 mm with a slight margin. Accordingly, three charging rolls are required, and the overlapping portion is set to be (330 × 3-930) / 2 = 30 mm (see FIGS. 2a and 2b).

  In this example, the diameter shape of the charging roll was a conventionally known so-called crown shape. The charging member was polished by using a grindstone having a width approximately equal to the length of the charging roll and pressing it once.

[Production of Cleaning Member (1)]
A polyurethane cleaning blade used as a cleaning member was prepared. Polyurethane having a rubber hardness of A70 / S (durometer hardness obtained by a type A durometer specified in JIS K 6253) and Young's modulus of 6.6 MPa was used. The shape of the cleaning blade is a conventionally known shape, and has a substantially rectangular parallelepiped shape with a thickness of 2 mm and a total length of 930 mm (see FIG. 5A). A cold rolled steel plate (SPCC) having substantially the same shape as the cleaning blade shown in FIG. 5A was used as a support member to which this was attached (see FIG. 5B). The cleaning blade 30 and the support member 32 were pasted with a hot melt adhesive to obtain a cleaning member (1) as shown in FIG. 5C in which the free length L of the cleaning blade 30 was 20 mm.

Blade at a portion in the thus obtained cleaning member (1), a blade load N ₁ at the portion corresponding to the non-overlapping portion not overlapping the charged area by the plurality of the charging roll, which corresponds to the overlapping portion where the charged regions overlap the load _{N 2} is exactly the same.

[Preparation of Cleaning Member (2-1)]
Instead of using the support member 32 having the shape shown in FIG. 6B instead of the support member 32 shown in FIG. 5B, the cleaning member (2-1) is used in the same manner as the cleaning member 1. Produced. The support member shown in FIG. 6B has a shape in which a portion corresponding to the overlapping portion of the charging region by the three contact charging members is extended in the length direction. The length of the extended part was set higher by 0.05 mm in the free height L direction than the other parts. The cleaning blade free height L after adhering the cleaning blade and the support member was 19.95 mm at a portion corresponding to the overlapping portion of the charged region, and 20 mm at the other portions.

In the thus obtained cleaning member (2-1), the blade load N ₁ at the portion corresponding to the non-overlapping portion not overlapping the charged area by the plurality of the charging roll, which corresponds to the overlapping portion where the charged regions overlap portion In comparison with the blade load N ₂ , N ₂ is about 0.8% higher than N ₁ .

[Preparation of Cleaning Member (2-2)]
In the support member shown in FIG. 6 (b), the portion extending in the length direction corresponding to the overlapping portion of the charging region by the three contact charging members is in the free height L direction compared to the other portions. A cleaning member (2-2) was prepared in the same manner as the cleaning member 2-1, except that a material set higher by 0.20 mm was used. The cleaning blade free height L after adhering the cleaning blade and the support member was 19.80 mm in the portion corresponding to the overlapping portion of the charged region, and 20 mm in the other portions.

In the thus obtained cleaning member (2-2), the blade load N ₁ at the portion corresponding to the non-overlapping portion not overlapping the charged area by the plurality of the charging roll, which corresponds to the overlapping portion where the charged regions overlap portion comparing the blade load _{N 2} in, towards the _{N 2} is about 3.1% higher than _{N 1.}

[Preparation of Cleaning Member (2-3)]
In the support member shown in FIG. 6 (b), the portion extending in the length direction corresponding to the overlapping portion of the charging region by the three contact charging members is in the free height L direction compared to the other portions. A cleaning member (2-3) was prepared in the same manner as the cleaning member (2-1) except that a material set higher by 0.4 mm was used. The cleaning blade free height L after bonding the cleaning blade and the support member was 19.6 mm at a portion corresponding to the overlapping portion of the charged region, and 20 mm at the other portions.

In the thus obtained cleaning member (2-3), the blade load N ₁ at the portion corresponding to the non-overlapping portion not overlapping the charged area by the plurality of the charging roll, which corresponds to the overlapping portion where the charged regions overlap portion In comparison with the blade load N _{2 at} , N ₂ is about 6.4% higher than N ₁ .

[Preparation of Cleaning Member (2-4)]
In the support member shown in FIG. 6 (b), the portion extending in the length direction corresponding to the overlapping portion of the charging region by the three contact charging members is in the free height L direction compared to the other portions. A cleaning member (2-4) was prepared in the same manner as the cleaning member (2-1) except that a material set higher by 0.6 mm was used. The cleaning blade free height L after adhering the cleaning blade and the supporting member was 19.4 mm at a portion corresponding to the overlapping portion of the charged region, and 20 mm at the other portions.

In the thus obtained cleaning member (2-4), the blade load N ₁ at the portion corresponding to the non-overlapping portion not overlapping the charged area by the plurality of the charging roll, which corresponds to the overlapping portion where the charged regions overlap portion comparing the blade load _{N 2} in, towards the _{N 2} is about 9.6% higher than _{N 1.}

[Preparation of Cleaning Member (2-5)]
In the support member shown in FIG. 6 (b), the portion extending in the length direction corresponding to the overlapping portion of the charging region by the three contact charging members is in the free height L direction compared to the other portions. A cleaning member (2-5) was produced in the same manner as the cleaning member (2-1) except that a material set higher by 0.7 mm was used. The cleaning blade free height L after bonding the cleaning blade and the support member was set to 19.3 mm at a portion corresponding to the overlapping portion of the charged region, and 20 mm at the other portions.

In the thus obtained cleaning member (2-5), the blade load N ₁ at the portion corresponding to the non-overlapping portion not overlapping the charged area by the plurality of the charging roll, which corresponds to the overlapping portion where the charged regions overlap portion In comparison with the blade load N _{2 at} , N ₂ is about 11.3% higher than N ₁ .

[Preparation of Cleaning Member (3)]
The cleaning member (3) is manufactured in the same manner as the cleaning member (1) except that a cleaning blade having the shape shown in FIG. 7 (a) is used instead of the cleaning blade shown in FIG. 5 (a). did. The cleaning blade shown in FIG. 7A has a shape in which the thickness is increased at a portion corresponding to the overlapping portion of the charging region by the three contact charging members. Specifically, the thickness of the portion corresponding to the overlapping portion of the charging region was 2.04 mm, and the thickness in the other portion was 2 mm. Affixed to the support member shown in FIG. 7B to obtain a cleaning member (3) shown in FIG. In the cleaning member (3), the free length of the cleaning blade was 20 mm.

Blade at a portion in the thus obtained cleaning member (3), the blade load N ₁ at the portion corresponding to the non-overlapping portion not overlapping the charged area by the plurality of the charging roll, which corresponds to the overlapping portion where the charged regions overlap comparing load _{N 2,} towards the _{N 2} is about 6.4% higher than _{N 1.}

[Preparation of Cleaning Member (4)]
The member made from SPCC shown in FIG.8 (b) was used as a supporting member. The support member shown in FIG. 8B has a shape bent so as to have the convex surfaces 40 and 42. The convex surfaces 40 and 42 of the support member shown in FIG. 8B have a length (here, 30 mm) corresponding to the overlapping portion of the charging region, and the convex amount on the convex surfaces 40 and 42 is the convex surfaces 40 and 42. Is set to be higher by 0.13 mm in the thickness direction than the plane 44 parallel to.

  8C is attached to the convex surfaces 40 and 42 of the supporting member shown in FIG. 8B while being deformed so that the cleaning blade shown in FIG. A cleaning member (4) shown in FIG. The free length of the cleaning blade was 20 mm.

Blade at a portion in the thus obtained cleaning member (4), the blade load N ₁ at the portion corresponding to the non-overlapping portion not overlapping the charged area by the plurality of the charging roll, which corresponds to the overlapping portion where the charged regions overlap comparing load _{N 2,} towards the _{N 2} is about 6.5% higher than _{N 1.}

The blade loads N ₁ and N ₂ in the cleaning members (1) to (4) are the cleaning members shown in FIGS. 5 (c), 6 (c), 7 (c), and 8 (c). The load when the ridge 36 of (1) to (4) is brought into contact with the electrophotographic photosensitive member 1 prior to other parts of the cleaning blade 30 in the direction of the arrow 34, that is, the cleaning blade 30. And the contact load between the electrophotographic photosensitive member 1 (see FIG. 4).

[Preparation of electrophotographic photoreceptor (1)]
A cylindrical aluminum (6063; JIS H4080) substrate having a length of 965 mm in the central axis direction, an inner diameter of φ78 mm, and an outer diameter of φ84 mm was subjected to honing treatment to roughen it to Ra 0.2 μm. Next, brush cleaning using a surfactant and cleaning with pure water were sequentially performed and dried at 135 ° C. for 5 minutes. Further, 24 ° C. cooling air was blown onto the surface of the substrate at 10 m / sec for 5 minutes.

  Next, 170 parts by mass of n-butyl alcohol in which 4 parts by mass of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) is dissolved, 20 parts by mass of an organic zirconium compound (acetylacetone zirconium butyrate) and an organic silane compound (γ -Aminopropyltrimethoxysilane) 10 parts by mass was mixed and stirred to prepare a coating solution for the undercoat layer. This coating solution is applied to the outer peripheral surface of the substrate, air-dried at room temperature for 5 minutes, heated to 50 ° C. for 10 minutes, and placed in a constant temperature and humidity chamber of 50 ° C. and 85% RH. The humidification hardening acceleration process was performed for 20 minutes. Furthermore, the drying process was performed for 10 minutes at 150 degreeC in the hot air dryer, and the undercoat layer of film thickness of 1 micrometer was formed into a film.

  Furthermore, a mixture of 15 parts by mass of chlorogallium phthalocyanine as a charge generation material, 10 parts by mass of vinyl chloride vinyl acetate copolymer resin (VMCH, manufactured by Nihon Unicar), and 300 parts by mass of n-butyl alcohol was added to a mixture using a sand mill. The coating solution for the charge generation layer was prepared by dispersing for a time. This coating solution was dip-coated on the undercoat layer and dried to form a charge generation layer having a thickness of 0.2 μm.

  And 4 mass parts of N, N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine and bisphenol Z polycarbonate resin (viscosity average molecular weight: 40,000) 6 parts by mass was dissolved in 80 parts by mass of chlorobenzene to prepare a coating solution for the charge transport layer. This coating solution was applied onto the charge generation layer using a dip coating apparatus, and dried at 110 ° C. for 40 minutes. In this way, a charge transport layer having a film thickness of 22 μm was formed, and an electrophotographic photosensitive member (1) having the structure shown in FIG. 3 was obtained.

[Preparation of electrophotographic photoreceptor (2)]
An electrophotographic photosensitive member (2) was obtained in the same manner as the electrophotographic photosensitive member (1) except that the thickness of the charge transport layer was 24 μm.

[Preparation of electrophotographic photoreceptor (3)]
An electrophotographic photosensitive member (3) was obtained in the same manner as in the electrophotographic photosensitive member (1) except that the thickness of the charge transport layer was 26 μm.

[Preparation of electrophotographic photoreceptor (4)]
An electrophotographic photosensitive member (4) was obtained in the same manner as the electrophotographic photosensitive member (1) except that the thickness of the charge transport layer was 30 μm.

[Preparation of electrophotographic photoreceptor (5)]
An electrophotographic photosensitive member (5) was obtained in the same manner as the electrophotographic photosensitive member (1) except that the thickness of the charge transport layer was 40 μm.

[Preparation of electrophotographic photoreceptor (6)]
An electrophotographic photosensitive member (6) was obtained in the same manner as the electrophotographic photosensitive member (1) except that the thickness of the charge transport layer was 42 μm.

  The effective photosensitive areas of the obtained electrophotographic photoreceptors (1) to (6) were all 920 mm, and included 36 inches (≈914.4 mm) that is common in drawing related systems.

[Production of Image Forming Apparatus (1)]
Using the electrophotographic photosensitive member (1), the three contact charging members were arranged as shown in FIGS. 2A and 2B to produce an image forming apparatus having the configuration shown in FIG. The exposure device 3 is an LED, the developing device 4 is a one-component developing device, the transfer device 5 is a transfer roller, the image fixing device is a heating roller and a pressure roller, and the cleaning device 7 is a cleaning member (1). The setting angle X of the cleaning member (1) with respect to the electrophotographic photosensitive member (1) was set to 22 °, and the biting amount S was set to 2 mm (see FIG. 4). This is the image forming apparatus (1).

[Production of Image Forming Apparatus (2)]
An image forming apparatus (2) having the same configuration as the image forming apparatus (1) except that the cleaning member (2-1) was used as the cleaning apparatus 7 was produced. The setting angle X of the cleaning member (2-1) with respect to the electrophotographic photosensitive member (1) was set to 22 ° and the biting amount S was set to 2 mm (see FIG. 4).

[Production of Image Forming Apparatus (3)]
An image forming apparatus (3) having the same configuration as the image forming apparatus (1) except that the cleaning member (2-2) was used as the cleaning apparatus 7 was produced. The setting angle X of the cleaning member (2-2) with respect to the electrophotographic photosensitive member (1) was set to 22 °, and the biting amount S was set to 2 mm (see FIG. 4).

[Production of Image Forming Apparatus (4)]
An image forming apparatus (4) having the same configuration as the image forming apparatus (1) except that the cleaning member (2-3) was used as the cleaning apparatus 7 was produced. The setting angle X of the cleaning member (2-3) with respect to the electrophotographic photosensitive member (1) was set to 22 °, and the biting amount S was set to 2 mm (see FIG. 4).

[Production of Image Forming Apparatus (5)]
An image forming apparatus (5) having the same configuration as that of the image forming apparatus (1) except that a cleaning member (2-4) was used as the cleaning apparatus 7 was produced. The setting angle X of the cleaning member (2-4) with respect to the electrophotographic photosensitive member (1) was set to 22 ° and the biting amount S was set to 2 mm (see FIG. 4).

[Production of Image Forming Apparatus (6)]
An image forming apparatus (6) having the same configuration as that of the image forming apparatus (1) except that a cleaning member (2-5) was used as the cleaning apparatus 7 was produced. The setting angle X of the cleaning member (2-5) with respect to the electrophotographic photosensitive member (1) was set to 22 °, and the biting amount S was set to 2 mm (see FIG. 4).

[Production of Image Forming Apparatus (7)]
An image forming apparatus (7) having the same configuration as the image forming apparatus (1) except that the cleaning member (3) was used as the cleaning apparatus 7 was produced. The setting angle X of the cleaning member (3) with respect to the electrophotographic photosensitive member (1) was set to 22 °, and the biting amount S was set to 2 mm (see FIG. 4).

[Production of Image Forming Apparatus (8)]
An image forming apparatus (8) having the same configuration as that of the image forming apparatus (1) except that the cleaning member (4) was used as the cleaning apparatus 7 was produced. The setting angle X of the cleaning member (4) with respect to the electrophotographic photosensitive member (1) was set to 22 °, and the biting amount S was set to 2 mm (see FIG. 4). At this time, the overlapping amount of the contact charger has a biting amount of 2.0 + 0.13 mm, and the biting amount which is difficult to be gradually changed in the length direction of the cleaning member (4) is changed.

[Production of Image Forming Apparatus (9)]
An image forming apparatus (9) having the same configuration as the image forming apparatus (4) except that the electrophotographic photosensitive body (2) was used instead of the electrophotographic photosensitive body (1) was produced.

[Production of Image Forming Apparatus (10)]
An image forming apparatus (10) having the same configuration as the image forming apparatus (4) except that the electrophotographic photoreceptor (3) was used in place of the electrophotographic photoreceptor (1) was produced.

[Production of Image Forming Apparatus (11)]
An image forming apparatus (11) having the same configuration as that of the image forming apparatus (4) except that the electrophotographic photosensitive body (4) was used in place of the electrophotographic photosensitive body (1) was produced.

[Production of Image Forming Apparatus (12)]
An image forming apparatus (12) having the same configuration as that of the image forming apparatus (4) was produced except that the electrophotographic photosensitive body (5) was used in place of the electrophotographic photosensitive body (1).

[Production of Image Forming Apparatus (13)]
An image forming apparatus (13) having the same configuration as that of the image forming apparatus (4) was produced except that the electrophotographic photosensitive body (6) was used instead of the electrophotographic photosensitive body (1).

  The image forming apparatuses (1) to (13) thus obtained are summarized in Table 1.

[Image quality evaluation test]
In the image forming apparatuses (1) to (13), a test was performed in which an A0 size print was continuously printed by applying an alternating current to each contact charging member at a rotational peripheral speed of the electrophotographic photosensitive member of 60 mm / sec. . The print was a pattern in which a white background and a portion where nothing was printed, a halftone, and a black portion called a solid were mixed (see FIG. 9).

  The presence or absence of fogging of the white background portion of the print sample after the test conducted under each condition was confirmed by visual observation, and the number of prints at the time when a print that was judged unusable was recorded.

<Example 1>
An image quality evaluation test was performed using the image forming apparatus (3) and setting the alternating current applied to the contact charging member to 0.5 mA. The obtained results are shown in Table 2. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 2>
An image quality evaluation test was performed in the same manner as in Example 1 except that the AC current value applied to the contact charging member was 0.7 mA. The obtained results are shown in Table 2.

<Example 3>
An image quality evaluation test was performed in the same manner as in Example 1 except that the AC current value applied to the contact charging member was 1.1 mA. The obtained results are shown in Table 2.

<Example 4>
An image quality evaluation test was performed in the same manner as in Example 1 except that the AC current value applied to the contact charging member was 1.3 mA. The obtained results are shown in Table 2.

<Example 5>
An image quality evaluation test was performed in the same manner as in Example 1 except that the AC current value applied to the contact charging member was 1.5 mA. The obtained results are shown in Table 2.

<Example 6>
Using the image forming apparatus (4), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. The obtained results are shown in Table 3. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 7>
An image quality evaluation test was performed in the same manner as in Example 6 except that the AC current value applied to the contact charging member was 0.7 mA. The obtained results are shown in Table 3.

<Example 8>
An image quality evaluation test was performed in the same manner as in Example 6 except that the alternating current value applied to the contact charging member was 1.1 mA. The obtained results are shown in Table 3.

<Example 9>
An image quality evaluation test was performed in the same manner as in Example 6 except that the AC current value applied to the contact charging member was 1.3 mA. The obtained results are shown in Table 3.

<Example 10>
An image quality evaluation test was performed in the same manner as in Example 6 except that the AC current value applied to the contact charging member was 1.5 mA. The obtained results are shown in Table 3.

<Example 11>
Using the image forming apparatus (5), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. Table 4 shows the obtained results. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 12>
An image quality evaluation test was performed in the same manner as in Example 11 except that the alternating current value applied to the contact charging member was 0.7 mA. Table 4 shows the obtained results.

<Example 13>
An image quality evaluation test was performed in the same manner as in Example 11 except that the alternating current value applied to the contact charging member was 1.1 mA. Table 4 shows the obtained results.

<Example 14>
An image quality evaluation test was performed in the same manner as in Example 11 except that the AC current value applied to the contact charging member was 1.3 mA. Table 4 shows the obtained results.

<Example 15>
An image quality evaluation test was performed in the same manner as in Example 11 except that the AC current value applied to the contact charging member was 1.5 mA. Table 4 shows the obtained results.

<Example 16>
Using the image forming apparatus (7), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. The results obtained are shown in Table 5. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 17>
An image quality evaluation test was performed in the same manner as in Example 16 except that the alternating current value applied to the contact charging member was 0.7 mA. The results obtained are shown in Table 5.

<Example 18>
An image quality evaluation test was performed in the same manner as in Example 16 except that the alternating current value applied to the contact charging member was 1.1 mA. The results obtained are shown in Table 5.

<Example 19>
An image quality evaluation test was performed in the same manner as in Example 16 except that the alternating current value applied to the contact charging member was set to 1.3 mA. The results obtained are shown in Table 5.

<Example 20>
An image quality evaluation test was performed in the same manner as in Example 16 except that the AC current value applied to the contact charging member was 1.5 mA. The results obtained are shown in Table 5.

<Example 21>
An image forming apparatus (8) was used, and an image quality evaluation test was performed with an alternating current value applied to the contact charging member being 0.5 mA. The results obtained are shown in Table 6. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 22>
An image quality evaluation test was performed in the same manner as in Example 21 except that the alternating current value applied to the contact charging member was 0.7 mA. The results obtained are shown in Table 6.

<Example 23>
An image quality evaluation test was performed in the same manner as in Example 21 except that the alternating current value applied to the contact charging member was 1.1 mA. The results obtained are shown in Table 6.

<Example 24>
An image quality evaluation test was performed in the same manner as in Example 21 except that the AC current value applied to the contact charging member was 1.3 mA. The results obtained are shown in Table 6.

<Example 25>
An image quality evaluation test was performed in the same manner as in Example 21 except that the AC current value applied to the contact charging member was 1.5 mA. The results obtained are shown in Table 6.

<Example 26>
Using the image forming apparatus (9), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. The results obtained are shown in Table 7. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 27>
An image quality evaluation test was performed in the same manner as in Example 26 except that the alternating current value applied to the contact charging member was 0.7 mA. The results obtained are shown in Table 7.

<Example 28>
An image quality evaluation test was performed in the same manner as in Example 26 except that the alternating current value applied to the contact charging member was 1.1 mA. The results obtained are shown in Table 7.

<Example 29>
An image quality evaluation test was performed in the same manner as in Example 26 except that the value of the alternating current applied to the contact charging member was 1.3 mA. The results obtained are shown in Table 7.

<Example 30>
An image quality evaluation test was performed in the same manner as in Example 26 except that the AC current value applied to the contact charging member was 1.5 mA. The results obtained are shown in Table 7.

<Example 31>
Using the image forming apparatus (10), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. Table 8 shows the obtained results. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 32>
An image quality evaluation test was performed in the same manner as in Example 31 except that the alternating current value applied to the contact charging member was 0.7 mA. Table 8 shows the obtained results.

<Example 33>
An image quality evaluation test was performed in the same manner as in Example 31 except that the alternating current value applied to the contact charging member was 1.1 mA. Table 8 shows the obtained results.

<Example 34>
An image quality evaluation test was performed in the same manner as in Example 31 except that the value of the alternating current applied to the contact charging member was 1.3 mA. Table 8 shows the obtained results.

<Example 35>
An image quality evaluation test was performed in the same manner as in Example 31 except that the alternating current value applied to the contact charging member was 1.5 mA. Table 8 shows the obtained results.

<Example 36>
Using the image forming apparatus (11), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. Table 9 shows the obtained results. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 37>
An image quality evaluation test was performed in the same manner as in Example 36 except that the alternating current value applied to the contact charging member was 0.7 mA. Table 9 shows the obtained results.

<Example 38>
An image quality evaluation test was performed in the same manner as in Example 36 except that the AC current value applied to the contact charging member was 1.1 mA. Table 9 shows the obtained results.

<Example 39>
An image quality evaluation test was performed in the same manner as in Example 36 except that the AC current value applied to the contact charging member was 1.3 mA. Table 9 shows the obtained results.

<Example 40>
An image quality evaluation test was performed in the same manner as in Example 36 except that the AC current value applied to the contact charging member was 1.5 mA. Table 9 shows the obtained results.

<Example 41>
Using the image forming apparatus (12), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. Table 10 shows the obtained results. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 42>
An image quality evaluation test was performed in the same manner as in Example 41 except that the alternating current value applied to the contact charging member was 0.7 mA. Table 10 shows the obtained results.

<Example 43>
An image quality evaluation test was performed in the same manner as in Example 41 except that the alternating current value applied to the contact charging member was 1.1 mA. Table 10 shows the obtained results.

<Example 44>
An image quality evaluation test was performed in the same manner as in Example 41 except that the value of the alternating current applied to the contact charging member was 1.3 mA. Table 10 shows the obtained results.

<Example 45>
An image quality evaluation test was conducted in the same manner as in Example 41 except that the alternating current value applied to the contact charging member was 1.5 mA. Table 10 shows the obtained results.

<Example 46>
An image forming apparatus (13) was used, and an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. The obtained results are shown in Table 11. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Example 47>
An image quality evaluation test was performed in the same manner as in Example 46 except that the AC current value applied to the contact charging member was 0.7 mA. The obtained results are shown in Table 11.

<Example 48>
An image quality evaluation test was performed in the same manner as in Example 46 except that the AC current value applied to the contact charging member was 1.1 mA. The obtained results are shown in Table 11.

<Example 49>
An image quality evaluation test was performed in the same manner as in Example 46 except that the AC current value applied to the contact charging member was 1.3 mA. The obtained results are shown in Table 11.

<Example 50>
An image quality evaluation test was performed in the same manner as in Example 46 except that the AC current value applied to the contact charging member was 1.5 mA. The obtained results are shown in Table 11.

<Comparative Example 1>
Using the image forming apparatus (1), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. The results obtained are shown in Table 12. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Comparative example 2>
An image quality evaluation test was performed in the same manner as in Comparative Example 1 except that the AC current value applied to the contact charging member was 0.7 mA. The results obtained are shown in Table 12.

<Comparative Example 3>
An image quality evaluation test was performed in the same manner as in Comparative Example 1 except that the AC current value applied to the contact charging member was 1.1 mA. The results obtained are shown in Table 12.

<Comparative example 4>
An image quality evaluation test was performed in the same manner as in Comparative Example 1 except that the value of the alternating current applied to the contact charging member was 1.3 mA. The results obtained are shown in Table 12.

<Comparative Example 5>
An image quality evaluation test was performed in the same manner as in Comparative Example 1 except that the AC current value applied to the contact charging member was 1.5 mA. The results obtained are shown in Table 12.

<Comparative Example 6>
An image quality evaluation test was performed using the image forming apparatus (2) and setting the alternating current applied to the contact charging member to 0.5 mA. The obtained results are shown in Table 13. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Comparative Example 7>
An image quality evaluation test was performed in the same manner as in Comparative Example 6 except that the AC current value applied to the contact charging member was 0.7 mA. The obtained results are shown in Table 13.

<Comparative Example 8>
An image quality evaluation test was performed in the same manner as in Comparative Example 6 except that the alternating current value applied to the contact charging member was 1.1 mA. The obtained results are shown in Table 13.

<Comparative Example 9>
An image quality evaluation test was performed in the same manner as in Comparative Example 6 except that the value of the alternating current applied to the contact charging member was 1.3 mA. The obtained results are shown in Table 13.

<Comparative Example 10>
An image quality evaluation test was performed in the same manner as in Comparative Example 6 except that the AC current value applied to the contact charging member was 1.5 mA. The obtained results are shown in Table 13.

  In the image evaluation tests of Comparative Examples 1 to 10, the image defects that cannot be used were fog generated in overlapping portions of the contact charging roll members except for Comparative Examples 1 and 6.

<Comparative Example 11>
Using the image forming apparatus (6), an image quality evaluation test was performed with an alternating current value applied to the contact charging member of 0.5 mA. The results obtained are shown in Table 14. From the initial stage, a defect that was determined to be unusable occurred in the halftone image.

<Comparative Example 12>
An image quality evaluation test was performed in the same manner as in Comparative Example 11 except that the AC current value applied to the contact charging member was 0.7 mA. The results obtained are shown in Table 14.

<Comparative Example 13>
An image quality evaluation test was performed in the same manner as in Comparative Example 11 except that the AC current value applied to the contact charging member was 1.1 mA. The results obtained are shown in Table 14.

<Comparative example 14>
An image quality evaluation test was performed in the same manner as in Comparative Example 11 except that the value of the alternating current applied to the contact charging member was 1.3 mA. The results obtained are shown in Table 14.

<Comparative Example 15>
An image quality evaluation test was performed in the same manner as in Comparative Example 11 except that the AC current value applied to the contact charging member was 1.5 mA. The results obtained are shown in Table 14.

  In addition, when the image evaluation test of Comparative Example 11 to Comparative Example 15 was started, a so-called blade squeal occurred with several tens of sheets, and it was in a state where it could not withstand actual use.

  According to the image forming apparatus of the present invention, even when the electrophotographic photosensitive member is long, the surface of the electrophotographic photosensitive member can be charged sufficiently uniformly and without leakage, and the overlapping portion of the contact charging member, That is, it can be used for an application of an image forming method in which it is necessary to sufficiently prevent deterioration of the surface of the electrophotographic photosensitive member in the overlapping portion of the charged region.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view showing a positional relationship between an electrophotographic photosensitive member and a contact charging member in the image forming apparatus shown in FIG. 1. FIG. 2 is a top view showing a positional relationship between an electrophotographic photosensitive member and a contact charging member in the image forming apparatus shown in FIG. 1. 1 is a schematic cross-sectional view showing an electrophotographic photoreceptor 1 in an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing a state of contact between the electrophotographic photoreceptor 1 and the cleaning blade in the embodiment of the present invention. It is a schematic cross section which shows the shape of a cleaning blade (a), a supporting member (b), and a cleaning blade (c). It is a schematic cross section which shows the shape of a cleaning blade (a), a supporting member (b), and a cleaning blade (c). It is a schematic cross section which shows the shape of a cleaning blade (a), a supporting member (b), and a cleaning blade (c). It is a schematic cross section which shows the shape of a cleaning blade (a), a supporting member (b), and a cleaning blade (c). It is a schematic diagram of the print pattern used for the image quality evaluation test of an Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Electrophotographic photosensitive member, 2a, 2b, 2c Contact charging member, 3 Exposure apparatus, 4 Developing apparatus, 5 Transfer apparatus, 6 Image fixing apparatus, 7 Cleaning apparatus, 9 Support body, 20 Photosensitive layer, 21 Conductive substrate, 22 Undercoat layer, 23 charge generation layer, 24 charge transport layer, 30 cleaning blade, 32 support member, 34 contact direction, 36, 36a, 36b ridge, 40, 42 convex surface, 44 plane.

Claims (1)

An electrophotographic photoreceptor;
Charging means having a plurality of contact charging members for charging the surface of the electrophotographic photosensitive member;
Exposure means for exposing the surface of the electrophotographic photosensitive member to form an electrostatic latent image;
Developing means for developing the electrostatic latent image with a developer;
Transfer means for transferring the developed image to a transfer medium;
A cleaning member for cleaning the developer remaining on the surface of the electrophotographic photosensitive member;
With
The plurality of contact charging members are:
An overlapping portion for overlappingly charging the surface of the electrophotographic photosensitive member;
A non-overlapping portion for charging the surface of the electrophotographic photoreceptor alone;
An image forming apparatus distributed along a direction perpendicular to the moving direction of the surface of the electrophotographic photosensitive member,
The cleaning member includes a cleaning blade that contacts the surface of the electrophotographic photosensitive member,
In the portion corresponding to the overlapping portion, the contact load between the electrophotographic photosensitive member and the cleaning blade is:
An image forming apparatus, wherein the image forming apparatus is set to be 3 to 10% higher than a contact load between the electrophotographic photosensitive member and the cleaning blade in a portion corresponding to the non-overlapping portion.

Images