WO2019088465A1

WO2019088465A1 - Image forming apparatus

Info

Publication number: WO2019088465A1
Application number: PCT/KR2018/011716
Authority: WO
Inventors: Koichiro Takashima
Original assignee: Hp Printing Korea Co., Ltd.
Priority date: 2017-10-31
Filing date: 2018-10-04
Publication date: 2019-05-09
Also published as: JP2019082626A

Abstract

An image forming apparatus includes an image carrier, a cleaning blade to contact a surface of the image carrier, and a protective agent application member. The protective agent application member includes a rotatable shaft portion that extends along a rotary shaft of the image carrier, and an elastic body that is located on the shaft portion to apply a protective agent to a protective agent application region on the surface of the image carrier. The protective agent application region includes a contact portion and a non-contact portion in a direction along the rotary shaft. The elastic body contacts the contact portion without contacting the non-contact portion. A position of the contact portion and a position of the non-contact portion move in the direction along the rotary shaft in combination with a rotation of the image carrier.

Description

IMAGE FORMING APPARATUS

An image forming apparatus may include a rotatable image carrier and a cleaning blade that comes into contact with a surface of the image carrier to clean the surface. Additionally, a protective agent application member may be used to apply a protective agent to the surface of the image carrier, and a protective agent supply body allows the protective agent to be carried on the protective agent application member. The protective agent is applied to the surface of the image carrier by the protective agent application member to cover the surface of the image carrier with the protective agent and to reduce an abrasion of the surface of the image carrier.

FIG. 1 is a view schematically illustrating the periphery of a photoreceptor of an example image forming apparatus.

FIG. 2 is a side view illustrating an application roller and a protective agent supply body which are provided at the periphery of the photoreceptor.

FIG. 3 is a view schematically illustrating an elastic body formed region associated with developing a peripheral surface of a shaft portion of the application roller into a planar shape.

FIG. 4 is a graph showing a relationship of abrasion rates of a surface of the photoreceptor and a cleaning blade with respect to the amount of a protective agent.

FIG. 5 is a view schematically illustrating another example elastic body formed region.

In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted.

A protective agent may be used to reduce an abrasion of the surface of an image carrier. However, when the protective agent on the surface of the image carrier is modified, a frictional force on the surface of the image carrier increases. According to this, when a cleaning blade comes into contact with the surface of the image carrier in which the frictional force increases, the cleaning blade may become abraded. When the amount of the protective agent on the surface of the image carrier is increased, the frictional force on the surface of the image carrier increases.

An increased frictional force on the surface of the image carrier may result in a decreased operational lifespan of one or both of the image carrier and the cleaning blade.

An example image forming apparatus may include: a rotatable image carrier; a cleaning blade that comes into contact with a surface of the image carrier and cleans the surface of the image carrier; and a protective agent application member. The protective agent application member may include a rotatable shaft portion that extends along a rotary shaft of the image carrier, and an elastic body that is formed on the shaft portion and carries a protective agent. Additionally, the image forming apparatus may include a protective agent supply body that comes into contact with the elastic body of the protective agent application member and allows the protective agent to be carried on the elastic body. The protective agent application member is located upstream of the cleaning blade in a rotation direction of the image carrier. The elastic body comes into contact with the surface of the image carrier to apply the protective agent to a protective agent application region on the surface of the image carrier. The protective agent application region includes a contact portion with which the elastic body comes into contact and a non-contact portion with which the elastic body does not come into contact in a direction along the rotary shaft. A position of the contact portion and a position of the non-contact portion move in the direction along the rotary shaft in combination with a rotation of the image carrier.

The protective agent application region on the surface of the image carrier includes the contact portion and the non-contact portion in the direction along the rotary shaft. The elastic body that carries the protective agent comes into contact with the contact portion, and thus the protective agent is applied to the contact portion. The elastic body that carries the protective agent does not come into contact with the non-contact portion, and thus the protective agent is not applied to the non-contact portion. Accordingly, a contact area of the elastic body with respect to the surface of the image carrier is further reduced in comparison to a case where the elastic body that carries the protective agent comes into contact with the entirety of the protective agent application region on the surface of the image carrier. As a result, the amount of the protective agent that is applied to the surface of the image carrier may be decreased.

The protective agent that is applied to the surface of the image carrier is stretched on the surface of the image carrier by the cleaning blade that is located downstream of the protective agent application member in the rotation direction of the image carrier. The position of the contact portion and the position of the non-contact portion move in the direction along the rotary shaft in combination with rotation of the image carrier. Accordingly, a site to which the protective agent is applied with respect to the image carrier moves in the direction along the rotary shaft in accordance with rotation of the image carrier.

An amount of protective agent is uniformly applied to the entirety of the surface of the image carrier to suppress abrasion of the surface of the image carrier and/or the cleaning blade. In addition, since the contact portion exists in the protective agent application region in the direction along the rotary shaft, the elastic body comes into contact with an arbitrary site on the surface of the image carrier regardless of rotation of the image carrier. Accordingly, a torque fluctuation around the rotary shaft of the image carrier is further suppressed in comparison to a case where the elastic body comes into contact with the image carrier or does not come into contact with the image carrier depending on rotation of the image carrier, to stabilize rotation of the image carrier and to further suppress abrasion of the surface of the image carrier and/or the cleaning blade. Accordingly, the operational lifespan of one or both of the image carrier and the cleaning blade may be extended.

A ratio of a length of the contact portion in the direction along the rotary shaft to a length of the non-contact portion in the direction along the rotary shaft may be 1/9 to 9. For example, a ratio of 1/9 or greater may suppress abrasion of the surface of the image carrier. Additionally, a ratio of 9 or less may suppress abrasion of the cleaning blade.

At a position at which the surface of the image carrier and the elastic body come into contact with each other, a movement direction of the surface of the image carrier and a movement direction of the elastic body may be the same as each other, and a relative velocity difference between a movement velocity of the surface of the image carrier and a movement velocity of a surface of the elastic body may be 20% or less of the movement velocity of the surface of the image carrier. Such a configuration may operate to provide an efficient application of the protective agent with respect to the surface of the image carrier, and the surface of the image carrier may be less likely to be damaged in comparison to a case where the movement direction of the surface of the image carrier and the movement direction of the surface of the elastic body are different from each other at a position at which the surface of the image carrier and the surface of the elastic body come into contact with each other. Similarly, the surface of the image carrier may be less likely to be damaged in comparison to a case where the relative velocity difference between the movement velocity of the surface of the image carrier and the movement velocity of the surface of the elastic body is greater than 20% of the movement velocity of the surface of the image carrier.

The elastic body may be formed from raised fiber, and a fiber diameter of the fiber may be 2.5 denier to 6 denier. For example, a fiber diameter of the fiber that forms the elastic body of 2.5 denier or greater may be used to suppress settling of the elastic body. Additionally, a fiber diameter of the fiber that forms the elastic body of 6 denier or less may be used to avoid damaging the surface of the image carrier.

The elastic body may be formed from a foamed body, and a hardness of the foamed body may be 100 N to 400 N. A hardness of the foamed body that forms the elastic body of 100 N or greater may be used to suppress settling of the elastic body. A hardness of the foamed body that forms the elastic body of 400 N or less may be used to protect the surface of the image carrier.

A bulk density of the foamed body that forms the elastic body may be 25 kg/m³ to 65 kg/m³. A bulk density of the foamed body that forms the elastic body of 25 kg/m³ to 65 kg/m³ may be used to suppress application irregularity of the protective agent that is applied by the elastic body.

The protective agent supply body may be a molded body of a fatty acid metal salt. In this case, the protective agent supply body comes into contact with the elastic body and is decomposed into fine particles, and is carried on the elastic body as the fine particles. In addition, when the elastic body comes into contact with the surface of the image carrier, the fine particles carried on the elastic body are stretched between the elastic body and the surface of the image carrier, and adhere to the surface of the image carrier in a thin film shape. Accordingly, the application properties of the protective agent may be enhanced with respect to the surface of the image carrier.

The image forming apparatus may further include a pressing means that presses the protective agent supply body against the elastic body. The protective agent supply body may be pressed by the pressing means and may be brought into press contact with the elastic body. In this case, since the protective agent supply body is pressed by the pressing means and is brought into press contact with the elastic body, the protective agent may be carried on the elastic body.

The image carrier may include a plurality of layers which are stacked, an outermost layer, which is located on an outermost side, among the layers of the image carrier, may contain a filler, and an amount of the filler contained in the outermost layer may be 0.5 wt% to 15 wt%. In this case, when 0.5 wt% to 15 wt% of filler is contained in the outermost layer of the image carrier, hardness of the surface of the image carrier is raised, and abrasion resistance is improved. As a result, the amount of the protective agent applied to the surface of the image carrier may be decreased, thus further suppressing abrasion of the cleaning blade.

The image carrier may include a plurality of layers which are stacked, and an outermost layer, which is located on an outermost side, among the layers of the image carrier, may be formed from an acrylic resin. The outermost layer of the image carrier formed from an acrylic resin may be used to provide hardness of the surface of the image carrier and abrasion resistance. As a result, the amount of the protective agent applied to the surface of the image carrier may be decreased, thus further suppressing abrasion of the cleaning blade.

An image forming apparatus may therefore be produced having a long operational lifespan of both the image carrier and the cleaning blade.

An example image forming apparatus may be used to form a color image, for example, by using respective colors of magenta, yellow, cyan, and black. As illustrated in FIG. 1, an example image forming apparatus 1 includes a photoreceptor 2 (image carrier), a charging roller 3, a development device 4, an application roller 5 (protective agent application member), a protective agent supply body 6, and a cleaning blade 7. The image forming apparatus 1 may further include a conveying device that conveys paper, and an exposure device that exposes a surface 2b of the photoreceptor 2, a transfer device that secondarily transfers a toner image to the paper, a fixing device that fixes the toner image to the paper, an ejection device that ejects the paper, and the like.

Four photoreceptors 2 are provided in the image forming apparatus 1 in correspondence with respective colors which may used in a color image. Each of the photoreceptors 2 is a drum-shaped electrostatic latent image carrier (photosensitive drum) in which an image is formed on a peripheral surface (surface 2b). For example, the photoreceptor 2 is constituted by an organic photoconductor (OPC). The photoreceptor 2 is driven to rotate in a direction of an arrow Ra at a constant speed by a driving motor (not illustrated). A detailed configuration of the photoreceptor 2 will be described later.

The charging roller 3 is provided at the periphery of the photoreceptor 2. The charging roller 3 is a charging means that uniformly charges a surface of the photoreceptor 2 to a predetermined potential. The charging roller 3 rotates in a direction of an arrow Rb in conformity to rotation of the photoreceptor 2. The surface of the photoreceptor 2, which is charged by the charging roller 3, is exposed by an exposure device in correspondence with an image that is formed on paper. A potential of an exposed portion on the surface of the photoreceptor 2 varies, and an electrostatic latent image is formed. A cleaning roller 8 is provided at the periphery of the charging roller 3. The cleaning roller 8 is a cleaning means that cleans the surface of the charging roller 3. A detailed configuration of the charging roller 3 will be described later.

Four development devices 4 are provided in the image forming apparatus 1 in correspondence with respective colors that may be used in a color image. Each of the development devices 4 includes a development roller 9 that is provided at the periphery of the photoreceptor 2. The development roller 9 rotates in a direction of an arrow Rc in conformity to rotation of the photoreceptor 2. The development device 4 develops an electrostatic latent image formed on the photoreceptor 2 with a toner supplied from a toner tank (not illustrated), and generates a toner image. The development device 4 mixes and stirs a toner and a carrier, and charges the mixed toner and carrier. Then, the development device 4 allows the developer generated by mixing the toner and the carrier to be carried on the development roller 9. In addition, when the developer is conveyed to a region that faces the photoreceptor 2 due to rotation of the development roller 9, the toner in the developer carried on the development roller 9 moves to an electrostatic latent image formed on the peripheral surface of the photoreceptor 2, and the electrostatic latent image is developed.

The application roller 5 is provided at the periphery of the photoreceptor 2. The application roller 5 is located between the development roller 9 and the cleaning blade 7 at the periphery of the photoreceptor 2. The application roller 5 is located upstream of the cleaning blade 7 in a rotation direction of the photoreceptor 2. The application roller 5 rotates in a direction of an arrow Rd in conformity to rotation of the photoreceptor 2. The application roller 5 carries a protective agent that is supplied from the protective agent supply body 6. The application roller 5 applies the protective agent that is carried thereon to the surface 2b of the photoreceptor 2. A detailed configuration of the application roller 5 will be described later.

The protective agent supply body 6 is provided to be in contact with the application roller 5. The protective agent supply body 6 comes into contact with an elastic body 14 (refer to FIG. 2) of the application roller 5 to allow the protective agent to be carried on the application roller 5. For example, the protective agent supply body 6 is a shaped body that is obtained by molding the protective agent into a predetermined shape (a rod shape, a square column shape, a circular column shape, and the like). Examples of a method of molding the protective agent into a predetermined shape includes a compression molding method, a melting molding method, a powder molding method, a cold isotropic pressing method (CIP), and a hot isotropic pressing method (HIP). Furthermore, the protective agent supply body 6 that is molded can be used in a state of being stuck on a base material such as a metal, an alloy, and plastic with an adhesive and the like.

The image forming apparatus 1 further includes an elastic member 10 (pressing means) that presses the protective agent supply body 6 against the elastic body 14 (refer to FIG. 2) of the application roller 5. When being pressed by the elastic member 10, the protective agent supply body 6 can be brought into press contact with the elastic body 14 of the application roller 5. When being brought into press contact with the elastic body 14, the material of the protective agent supply body 6 is crushed into fine particles by friction, and the fine particles are stretched between the elastic body 14 and the surface 2b of the photoreceptor 2, and adhere to the surface 2b of the photoreceptor 2 in a thin film shape. In some examples, the protective agent supply body 6 is a molded body of a fatty acid metal salt.

Examples of the fatty acid metal salt include barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, zinc stearate, zinc oleate, magnesium oleate, iron oleate, cobalt oleate, copper oleate, lead oleate, manganese oleate, zinc palmitate, cobalt palmitate, lead palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, lead caprylate, lead caprate, zinc linolenate, cobalt linolenate, calcium linolenate, zinc ricinoleate, cadmium ricinoleate, zinc laurate, cobalt laurate, lead laurate, and magnesium laurate. These may be used alone or in combination of two or more kinds. For example, one or more of zinc stearate, calcium stearate, or zinc laurate may be used as the fatty acid metal salt.

The protective agent supply body 6 may have a configuration in which an inorganic lubricant, a silicone resin, or the like is contained in the fatty acid metal salt in a constant amount so as to provide a lubricating property of the surface 2b of the photoreceptor 2. The inorganic lubricant is a compound that is cleft and lubricates or causes inner sliding. Examples of the inorganic lubricant include mica, boron nitride, molybdenum disulfide, tungsten disulfide, talc, kaolin, montmorillonite, calcium fluoride, graphite, other like materials, or any combination thereof.

The cleaning blade 7 recovers a toner (residual toner) that remains on the photoreceptor 2 even after the toner image is primarily transferred from the photoreceptor 2 to an intermediate transfer body. The cleaning blade 7 is formed from an elastic body such as a urethane rubber. The cleaning blade 7 is swingably held by a holding member 11, and is pressed to the surface 2b of the photoreceptor 2 when a load is applied to the holding member 11 with an elastic force of the elastic member 12. The cleaning blade 7 comes into contact with the surface 2b of the photoreceptor 2 to scrape off the residual toner on the surface 2b of the photoreceptor 2. In addition, the cleaning blade 7 stretches the protective agent that is applied to the surface 2b of the photoreceptor 2 by the application roller 5, and spreads the protective agent into a uniform state on the surface 2b of the photoreceptor 2.

Next, a detailed configuration of the application roller 5 will be described with reference to FIG. 2. FIG. 2 is a side view illustrating the application roller 5, and the protective agent supply body 6 which are provided at the periphery of the photoreceptor 2.

As illustrated in FIG. 2, the application roller 5 includes a rotatable shaft portion 13 that can rotate, and the elastic body 14 that is formed on a peripheral surface 13a of the shaft portion 13. The shaft portion 13 is rotatably supported to the inside of the image forming apparatus 1. For example, the shaft portion 13 is formed from a resin (an epoxy resin, a phenolic resin, and the like), and/or a metal (iron, aluminum, stainless steel, and the like). For example, the shaft portion 13 has a circular column shape, or a cylindrical shape. The shaft portion 13 extends along a rotary shaft 2a of the photoreceptor 2. Hereinafter, a direction along the rotary shaft 2a of the photoreceptor 2 is simply referred to as "axial direction A". Furthermore, an adhesive layer may be formed on the peripheral surface 13a of the shaft portion 13. For example, the application roller 5 may include an adhesive layer that is located between the shaft portion 13 and the elastic body 14.

The elastic body 14 is formed to protrude from the peripheral surface 13a of the shaft portion 13. The elastic body 14 is formed to cover a part of the peripheral surface 13a of the shaft portion 13 instead of covering the entirety of the peripheral surface 13a of the shaft portion 13. For example, the elastic body 14 has a shape which may be wound around the peripheral surface 13a of the shaft portion 13 in a spiral shape.

FIG. 3 is a view schematically illustrating an elastic body formed region 5a as a development view when developing the peripheral surface 13a of the shaft portion 13 of the application roller 5 into a planar shape. The elastic body formed region 5a is a region representing a range, in which the elastic body 14 is formed, on the peripheral surface 13a of the shaft portion 13 of the application roller 5. In FIG. 3, the elastic body formed region 5a is indicated by a two-dot chain line, and a portion in which the elastic body 14 exists is indicated by being painted out with a gray color. The elastic body formed region 5a includes a portion in which the elastic body 14 exists, and a portion in which the elastic body 14 does not exist. As illustrated in FIG. 3, in a state in which the peripheral surface 13a of the shaft portion 13 is developed, the elastic body formed region 5a shows a rectangular shape that extends along an axial direction (for example, an axial direction A) of the application roller 5 and a peripheral direction B of the application roller 5.

In the elastic body formed region 5a, the elastic body 14 is formed so that a set of spirals is formed in one pitch. In a state in which the peripheral surface 13a of the shaft portion 13 is developed, the elastic body 14 includes a plurality of (three, for example) oblique line portions 14a, which extend in a direction intersecting the axial direction A and the peripheral direction B, on the elastic body formed region 5a. On the peripheral surface 13a of the shaft portion 13, the three oblique line portions 14a are connected to each other to form a set of spirals.

As illustrated in FIG. 2, the elastic body 14 is a portion that comes into contact with the protective agent supply body 6 and the surface 2b of the photoreceptor 2 in the application roller 5. The elastic body 14 comes into contact with the protective agent supply body 6 to acquire the protective agent from the protective agent supply body 6, and carries the protective agent. The elastic body 14 comes into contact with the surface 2b of the photoreceptor 2 to apply the carried protective agent to a protective agent application region 20 on the surface 2b of the photoreceptor 2. The protective agent application region 20 is a region, to which the protective agent is applied by the application roller 5, on the surface 2b of the photoreceptor 2. The protective agent application region 20 extends along the axial direction A to face the elastic body formed region 5a of the application roller 5, and extends to the entire region in the peripheral direction of the photoreceptor 2 when the surface 2b moves due to rotation of the photoreceptor 2.

Since the elastic body 14 is formed to cover a part of the peripheral surface 13a of the shaft portion 13, the application roller 5 comes into contact with a part of a region Sa, which faces the application roller 5, on the surface 2b of the photoreceptor 2 instead of the entirety of the region Sa. Accordingly, the application roller 5 forms a contact portion 21 with which the elastic body 14 comes into contact, and a non-contact portion 22 with which the elastic body 14 does not come into contact with respect to the protective agent application region 20 in the axial direction A. The protective agent application region 20 includes the contact portion 21 with which the elastic body 14 comes into contact and the non-contact portion 22 with which the elastic body 14 does not come into contact in the axial direction A.

When the elastic body 14 on which the protective agent is carried comes into contact with the contact portion 21, the protective agent is applied to the contact portion 21. The elastic body 14 on which the protective agent is carried does not come into contact with the non-contact portion 22, and thus the protective agent is not applied to the non-contact portion 22. In some examples, a plurality of the contact portions 21 and a plurality of the non-contact portions 22 are provided. The contact portions 21 and the non-contact portions 22 are alternately arranged along the axial direction A. The contact portion 21 exists in the entire region in a peripheral direction in the protective agent application region 20. For example, the elastic body 14 comes into contact with an arbitrary site on the surface 2b of the photoreceptor 2 regardless of rotation of the photoreceptor 2. A position of the contact portion 21 and a position of the non-contact portion 22 move in the axial direction A in combination with rotation of the photoreceptor 2. The position of the contact portion 21 corresponds to a contact position P1 between the surface 2b of the photoreceptor 2 and the elastic body 14. "The position of the contact portion 21 and the position of the non-contact portion 22 move in the axial direction A in combination with rotation of the photoreceptor 2" represents that the contact position P1 moves in the axial direction A in accordance with rotation of the photoreceptor 2. The protective agent application region 20 is a site with which the elastic body 14 comes into contact, and is a site to which the protective agent is applied in the protective agent application region 20. Accordingly, the protective agent application region 20 moves in the axial direction A in accordance with rotation of the photoreceptor 2.

For example, a ratio L_A/L_B of a length L_A of the contact portion 21 in the axial direction A to a length L_B of the non-contact portion 22 in the axial direction A is 1/9 to 9. The length L_B is the total sum of a length Lb of each of the plurality of non-contact portions 22. The length L_A is the total sum of a length La of each of the plurality of contact portions 21. The ratio L_A/L_B of 1/9 or greater may be used to suppress an abrasion of the photoreceptor 2. A ratio L_A/L_B of 9 or less may be used to suppress abrasion of the cleaning blade 7. In addition, in one pitch of the elastic body 14 having a spiral shape, a ratio La/Lb of a length La of one contact portion 21 to a length Lb of one non-contact portion 22 is 1/9 to 9. The length La of the contact portion 21 corresponds to a length Lc of each of the oblique line portions 14a illustrated in FIG. 3 in the axial direction A. The length Lb of the non-contact portion 22 corresponds to an interval Ld between the oblique line portions 14a along the axial direction A.

The photoreceptor 2 rotates in a direction indicated by the arrow Ra, and the application roller 5 rotates in a direction indicated by the arrow Rd opposite to the arrow Ra. For example, the photoreceptor 2 and the application roller 5 rotate in directions opposite to each other to be close to each other in accordance with rotation. Accordingly, at the contact position P1 between the surface 2b of the photoreceptor 2 and a surface 14s of the elastic body 14, both a movement direction of the surface 2b of the photoreceptor 2 and a movement direction of the surface 14s of the elastic body 14 are directions which face a depth side of a paper plane from a front side of the paper plane in FIG. 2. For example, at the contact position P1, the movement direction of the surface 2b of the photoreceptor 2 and the movement direction of the surface 14s of the elastic body 14 are the same as each other. In addition, at the contact position P1, a relative velocity difference between a movement velocity of the surface 2b of the photoreceptor 2 and a movement velocity of the surface 14s of the elastic body 14 is set to, for example, 20% or less of the movement velocity of the surface 2b of the photoreceptor 2. In some examples, at the contact position P1, the movement velocity of the surface 2b of the photoreceptor 2 and the movement velocity of the surface 14s of the elastic body 14 are the same as each other, and the relative velocity difference is set to 0% of the movement velocity of the surface 2b of the photoreceptor 2.

The elastic body 14 may be formed from raised fiber. Additionally, the elastic body 14 may comprise a brush-shaped elastic body. In some examples, the raised fiber has flexibility to suppress mechanical stress applied to the surface 2b of the photoreceptor 2. Examples of the raised fiber having flexibility include a polyolefin resin (for example, polyethylene or polypropylene), a polyvinyl resin or a polyvinylidene resin (for example, polystyrene, an acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, or polyvinyl ketone), a vinyl chloride-vinyl acetate copolymer, a styrene-acrylic acid copolymer, a styrene-butadiene resin, a fluororesin (for example, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, or polychlorotrifluoroethylene), polyester, nylon, acryl, rayon, polyurethane, polycarbonate, a phenolic resin, an amino resin (for example, a urea-formaldehyde resin, a melamine resin, a benzoguanamine resin, a urea resin, or a polyamide resin), other like materials, or any combination thereof.

Furthermore, for example, a diene-based rubber, a styrene-butadiene rubber (SBR), an ethylene propylene rubber, an isoprene rubber, a nitrile rubber, a urethane rubber, a silicone rubber, a hydrin rubber, a norbornene rubber, and the like may be compositely added to the fiber material to adjust the degree of bending.

Examples of a method of forming the elastic body 14 as the brush-shaped elastic body include a method of fixing a resin and the like implanted with the fiber to a core material or fixing the fiber to the core material with electrostatic implantation, and a method of winding a tape obtained by making the fiber into pile fabric around the core material in a spiral shape. In some examples, the fiber that constitutes the blush-shaped elastic body has a length of 1 mm to 4 mm, and a density of 10,000 pieces/inch² to 100,000 pieces/inch². In other examples, the density is 20,000 pieces/inch² to 50,000 pieces/inch². In addition examples, a fiber diameter (fineness) of the fiber that constitutes the brush-shaped elastic body is 2.5 denier to 6 denier (2.8 decitex to 6.7 decitex). A fiber diameter of 2.5 denier or greater may be used to suppress settling of the elastic body 14. A fiber diameter of 6 denier or less may be used to protect the surface 2b of the photoreceptor 2.

The elastic body 14 is not limited to the raised fiber, and may be formed from, for example, a foamed body (foamed body layer). For example, the elastic body 14 may be a sponge-shaped elastic body. Examples of the foamed body include foamed polyurethane, a foamed nitrile butadiene rubber, a foamed ethylene propylene diene rubber, other like materials, or any combination thereof. Examples of a raw material of the foamed polyurethane include polyol, polyisocyanate, a catalyst, a foaming agent, a foam stabilizer, other like materials, or any combination thereof.

As a method of molding the sponge-shaped elastic body, the raw material of the foamed polyurethane is foamed and cured to form a block-shaped foamed polyurethane. Next, the block-shaped foamed polyurethane is cut into a cylindrical shape, and a core material is inserted into the cylindrical shape. In addition, the foamed polyurethane is rotated and is brought into contact with a polishing blade and the like by using a polishing machine and a cutting machine to cut the foamed polyurethane to a predetermined thickness (traverse grinding). According to this, a cylindrical elastic body having a cell opened to a surface is obtained. Additionally, a method of obtaining a cylindrical foamed roller may comprise foaming and curing the raw material of the foamed polyurethane in a state of allowing a core material to pass through a cylindrical mold. Examples of a structure of the foamed body include a closed cell type, a continuous cell type, a mixed type thereof, and the like.

In some examples, an average cell diameter of the foamed body roller is 200 ㎛ to 800 ㎛ from the viewpoints of improving grinding performance with respect to the protective agent and of uniformly supplying the protective agent to the surface of the photoreceptor 2. In other examples, the average cell diameter may be 300 ㎛ to 600 ㎛. The average cell diameter of the foamed body roller can be obtained from a value obtained by dividing one inch (= 25.4 mm) by the number of measured cells. For example, with respect to a surface of a foamed body, a photograph screen of each measurement site is observed by using a microscope. In addition, a line having a length corresponding to one inch is drawn on the central portion of the photograph screen, and measures the number of cells which exist within the line. In the measurement, a cell that is slightly in contact with the line of one inch is regarded as one cell.

In some examples, an average thickness of the foamed body is 1 mm to 4 mm. An average thickness of the foamed body of 1 mm or greater may be less susceptible to the core material. Additionally, an average thickness of the foamed body of 4 mm or less may be used to prevent useless consumption of the protective agent.

In some examples, the hardness of the foamed body is 50 N to 600 N. In other examples, the hardness may be 100 N to 400 N. A hardness is 50 N or greater may be used to stabilize the supply of the protective agent, and a hardness of 600 N or less may be used to prevent abrasion of the surface 2b of the photoreceptor 2. Similarly, a hardness of 100 N or greater may be used to stabilize the supply of the protective agent, and a hardness of 400 N or less may be used to protect the surface 2b of the photoreceptor 2. The hardness is a value that is obtained by measuring the foamed body on the basis of JIS K 6400 2D.

In some examples, a bulk density of the foamed body is 15 kg/m³ to 75 kg/m³ from the viewpoint of uniformly supplying the protective agent without irregularity, and in other examples the bulk density may be 25 kg/m³ to 65 kg/m³. With regard to a measurement method, a volume of a test specimen that is cut out in dimensions of 12.5 mm × 100 mm × 100 mm, and the bulk density is calculated from the weight of the test specimen.

Next, a detailed configuration of the photoreceptor 2 will be described.

The photoreceptor 2 has a configuration in which a plurality of layers are stacked. For example, the photoreceptor 2 includes a conductive support and a photosensitive layer that is formed on the conductive support.

The conductive support is formed from a material having conductivity. Examples of the material having conductivity include a metal such as aluminum, copper, chromium, nickel, zinc, and stainless steel. For example, the conductive support is obtained by shaping the metal into a drum shape, a sheet shape, or a belt shape. The conductive support may be obtained by laminating metal foil of aluminum, copper, or the like on a plastic film. The conductive support may be obtained by depositing aluminum, indium oxide, tin oxide, or the like on a plastic film. The conductive support may be a conductive layer that is provided by applying a conductive material alone or in combination with a binder resin on a metal, a plastic film, paper, or the like.

The photosensitive layer may be any one of a negatively-charged stacked type or a positively-charged single-layer type. In some examples, the photosensitive layer is a negatively-charged stacked type, and includes a charge generation layer formed on the conductive support and a charge transport layer that is formed on the charge generation layer.

The charge generation layer is a layer containing a charge generation material having a charge generation function as a main component. Examples of the charge generation material include a monoazo pigment, a disazo pigment, an asymmetric disazo pigment, a trisazo pigment, an azo pigment having a carbazole skeleton, an azo pigment having a distyrylbenzene skeleton, an azo pigment having a triphenylamine skeleton, an azo pigment having a diphenylamine skeleton, a perylene pigment, a phthalocyanine pigment, other like materials, or any combination thereof. The charge generation materials may be used alone or as a mixture of two or more kinds thereof. The charge generation material may include at least one kind of material selected from the group of materials consisting of oxotitanyl phthalocyanine and gallium phthalocyanine based, at least in part, on their electrical characteristics.

The charge generation layer may contain a binder resin. Examples of the binder resin include polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, a silicone resin, an acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, and the like. The binder resins may be used alone or as a mixture of two or more kinds thereof.

The charge generation material may be dispersed in a solvent by using a dispersion method to obtain a coating solution for forming the charge generation layer on the conductive support. In a case where the binder resin is contained in the charge generation layer, the binder resin is dispersed in the solvent in combination with the charge generation material. As a dispersion method, for example, a ball mill, an attritor, a sand mill, a bead mill, ultrasonic waves, and the like can be used. In some examples, a layer thickness of the charge generation layer is 0.01 ㎛ to 5 ㎛, and in other examples the layer thickness may be 0.05 ㎛ to 3 ㎛.

The charge transport layer is a layer that has a charge transport structure, and contains a charge transport material and a binder resin as a main component. For example, the charge transport material is a hole transport material. Examples of the hole transport material include materials such as poly(N-vinylcarbazole) and derivatives thereof, poly(g-carbazolylethyl glutamate) and derivatives thereof, pyrene-formaldehyde condensate and derivatives thereof, polyvinyl pyrene, polyvinyl phenanthrene, polysilane, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, a-phenylstilbene derivatives, aminobiphenyl derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazoline derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, bisstilbene derivatives, distyrylbenzene derivatives, and enamine derivatives. The hole transport material may be used alone or as a mixture of two or more kinds thereof.

The charge transport material may contain an electron transport material in addition to the hole transport material. Examples of the electron transport material include a benzoquinone-based compound, a cyanoethylene-based compound, a cyanoquinodimethane-based compound, a fluorenone-based compound, a phenantraquinone-based compound, a phthalic anhydride-based compound, a thiopyran-based compound, a naphthalene-based compound, a diphenoquinone-based compound, and a stilbenequinone-based compound. Specific examples thereof include electron acceptable substances such as chloranil, bromanil, tetracyanoethylene, tetracyanoquinodimethane, and 7-trinitro-9-fluorenone. The electron transport materials may be used alone or as a mixture of two or more kinds thereof.

The charge transport layer may comprise an outermost layer that is located on the outermost side among layers of the photoreceptor 2. The charge transport layer contains filler particles (filler). The amount of the filler particles contained in the outermost layer is, for example, 0.5 wt% to 15 wt%. For example, the filler particles are organic filler particles or inorganic filler particles. As the filler particles, a material that is less susceptible to discharging by the charging roller 3 in comparison to an organic compound contained may be selected as a main component of the charge transport layer to improve abrasion resistant characteristics of the surface of the photoreceptor 2. Examples of the material include silica, alumina, titanium oxide, and the like as the inorganic filler particles, and a fluorine-based polymer as the organic filler particles. Examples of the fluorine-based polymer include a tetrafluoroethylene·ethylene copolymer (ETFE), a tetrafluoroethylene·perfluoroalkyl·vinyl ether copolymer (PFA), a trifluorochloroethylene·ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polytrifluoroethylene chloride (PCTFE), polyvinyl fluoride (PVF), ethylene tetrafluoride·hexafluoropropylene (FEP), tetrafluoroethylene·hexafluoropropylene·perfluoroalkyl·vinyl ether copolymer (EPE), other like polymers, or any combination thereof.

The charge transport material and the binder resin are dissolved in a solvent to obtain a coating solution for forming the charge transport layer on the charge generation layer. In some examples, a layer thickness of the charge transport layer is 5 ㎛ to 40 ㎛, and in other examples the layer thickness is 10 ㎛ to 35 ㎛.

Next, additional details of the charging roller 3 will be described.

A DC discharging contact charging roller type, an AC discharging non-contact charging roller type, or a scorotron type may be used to reduce abrasion of the surface 2b of the photoreceptor 2 due to an influence of discharging. Hereinafter, example types of charging rollers will be described in further detail.

DC Discharging Contact Charging Roller Type

The charging roller 3 of this type is rotatably supported to a unit, and includes a conductive support that becomes a rotary shaft, a conductive elastic body layer that is formed on the conductive support, and a resin layer that is formed on the conductive elastic body layer. The charging roller 3 is pressed to the surface 2b of the photoreceptor 2 with a predetermined load (1 kgf), and forms a contact surface with respect to the photoreceptor 2. In addition, when the photoreceptor 2 rotates, the charging roller 3 also rotates due to a frictional force of the contact surface. In this state, when approximately -1 kV of DC current is applied to the conductive support, the surface 2b of the photoreceptor 2 is charged due to discharging. In DC discharging of this type, a discharging opportunity is less in comparison to AC discharging, and thus a discharging stress is less. Accordingly, the DC discharging of this type may be used to reduce an amount of abrasion of the surface 2b of the photoreceptor 2.

The conductive support is formed from a material having conductivity. Examples of the material having conductivity include metals such as iron, copper, aluminum, nickel, stainless steel, other like materials, or any combination thereof. For example, the conductive support is obtained by shaping the metals into a hollow body (pipe shape) or a solid body (rod shape). The outer peripheral surface of the conductive support may be subjected to a plating treatment to a certain extent in which conductivity is not damaged for application of rust prevention and scratch resistance. In addition, an adhesive, a primer, and the like may be applied to the outer peripheral surface of the conductive support to enhance adhesiveness with the conductive elastic body layer. At this time, the adhesive, the primer, and the like may be made to have conductivity. For example, the conductive support has a circular column shape in which a diameter is 5 mm to 10 mm, and a length is 250 mm to 360 mm.

The conductive elastic body layer has elasticity to secure uniform adhesiveness with respect to the photoreceptor 2. The conductive elastic body layer is formed by using, for example, a natural rubber, a synthetic rubber, a synthetic resin, and the like as a base polymer. Examples of the synthetic rubber include an ethylene-propylene-diene rubber (EPDM), a styrene-butadiene rubber (SBR), a silicone rubber, a polyurethane-based elastomer, an epichlorohydrin rubber, an isoprene rubber (IR), a butadiene rubber (BR), an acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR), chloroprene rubber (CR), and the like. Examples of the synthetic resin include a polyamide resin, a polyurethane resin, a silicone resin, and the like. The conductive elastic body layer may comprise a single material selected from the above, or may comprise a mixture of two or more kinds of materials.

An additive such as a conducting agent, a vulcanizing agent, a vulcanization accelerator, a lubricant, and an auxiliary agent may be appropriately blended to the base polymer in order to apply desired characteristics to the conductive elastic body layer. Examples of the conducting agent include carbon black, graphite, potassium titanate, iron oxide, conductive titanium oxide (c-TiO₂), conductive zinc oxide (c-ZnO), conductive tin oxide (c-SnO₂), quaternary ammonium salt, other like materials, or any combination thereof. Examples of the vulcanizing agent include sulfur, and the like. Examples of the vulcanization accelerator include tetramethylthiuram disulfide (CZ), and the like. Examples of the lubricant include stearic acid, and the like. Examples of the auxiliary agent include zinc oxide (ZnO). In some examples, the thickness of the conductive elastic body layer is approximately 1.25 mm to 3.00 mm to exhibit elasticity.

The resin layer contains a matrix material as a main component. The matrix material is not particularly limited as long as the matrix material does not contaminate the photoreceptor that is an object to be charged. Examples of the matrix material include a base polymer such as a fluororesin, a polyamide resin, an acrylic resin, a nylon resin, a polyurethane resin, a silicone resin, a butyral resin, a styrene-ethylene·butylene-olefin copolymer (SEBC), and an olefin-ethylene·butylene-olefin copolymer (CEBC). The matrix layer may comprise a single material selected from the above, or may comprise a mixture of two or more kinds of materials. From the viewpoints of ease of handling, the magnitude of the degree of freedom of material design, and the like, the matrix material may comprise at least one kind of material that is selected from the group of materials consisting of fluororesin, acrylic resin, nylon resin, polyurethane resin, and silicone resin, and in other examples at least one kind of material that is selected from the group of materials consisting of nylon resin and polyurethane resin.

The thickness of the resin layer, that is, a layer thickness (thickness of a layer) of a portion that is formed from the matrix material alone, may be 1.0 ㎛ to 15.0 ㎛. Furthermore, the thickness of the resin layer can be measured by cutting a roller cross-section with a sharp-edged tool and by observing the cross-section with an optical microscope or an electron microscope.

The resin layer contains filler particles. The filler particles form unevenness with respect to a surface of the resin layer to secure discharging points. The filler particles are organic filler particles or inorganic filler particles. Examples of organic filler particles include a urethane resin, a polyamide resin, a fluororesin, a nylon resin, an acrylic resin, a urea resin, other like resins, or any combination thereof. Examples of suitable inorganic filler particles include silica, alumina, other like materials, or any combination thereof. The filler particles may comprise a single material selected from the above, or may comprise a mixture of two or more kinds of materials.

A shape of the filler particles is not particularly limited as long as unevenness can be formed with respect to a surface of the resin layer, and may be, for example, a spherical shape, an elliptical spherical shape, an irregular shape, and the like. Furthermore, in addition to the filler particles, various conducting agents (conductive carbon, graphite, copper, aluminum, nickel, iron particles, conductive tin oxide, conductive titanium oxide, ion conducting agent, other like materials, or any combination thereof), a charging control agent, and the like may be contained in the base polymer.

The charging roller 3 may be provided with a rough surface to maintain uniformity of charging with DC current application. For example, a ten-point average roughness Rzjis of the surface of the resin layer may be approximately 5 ㎛ to 30 ㎛, and an average length Sm of a roughness curve element may be approximately 30 ㎛ to 500 ㎛. Furthermore, A surface may be roughened by polishing an elastic rubber, but a cord-shaped charging irregularity due to a polishing trace may occur using this method. Filler particles may be added to the surface of the charging roller 3. When the filler particles are added to the surface of the charging roller 3, discharging may occur at a particle portion, and when the filler particles are added uniformly, discharging becomes uniform and the cord-shaped charging irregularity may be suppressed. Measurement of the surface roughness can be performed by using a surface roughness measurement device SE-3400 manufactured by Kosaka Laboratory Ltd. in conformity to JIS B0601-2001.

The charging roller 3 can be manufactured as follows. First, a material for a conductive elastic body layer is kneaded by using a kneading machine such as a kneader to prepare the material for the conductive elastic body layer. In addition, a material for a resin layer is kneaded by using a kneading machine such as roller, an organic solvent is added to the mixture, and the mixture is mixed and stirred, thereby preparing an application solution for the resin layer. Next, an injection mold, in which a core metal that becomes the conductive support is set, is filled with the material for the conductive elastic body layer, and heating and crosslinking are performed under predetermined conditions. Then, the mold is removed. According to this, a base roll in which the conductive elastic body layer is formed along an outer peripheral surface of the conductive support is manufactured. Then, the outer peripheral surface of the base roll is coated with the application solution for the resin layer to form the resin layer. In this manner, the charging roller 3 may be manufactured to include the conductive support, the conductive elastic body layer formed on the conductive support, and the resin layer formed on the conductive elastic body.

Furthermore, the method of forming the conductive elastic body layer is not limited to an injection molding method, and a casting molding method, a press molding method, a roll coating method, and a method combined with polishing may be employed. In addition, the coating method of the application solution for the resin layer is not particularly limited, and a dipping method, a spray coating method, a roll coating method, and the like, may be employed.

AC Discharging Non-Contact Charging Roller Type

As in the DC discharging contact charging roller type, a charging roller 3 of this type includes a conductive support, a conductive elastic body layer, and a resin layer, and is pressed to the surface of the photoreceptor 2 with a predetermined load (1 kgf) and forms a contact surface with respect to the photoreceptor 2. A gap regulation rotator having an outer diameter greater than an outer diameter of the charging roller 3 by 200 ㎛ is provided on an outer side of both ends of the conductive elastic body layer in a direction along a rotary shaft of the conductive elastic body layer, and a gap of approximately 100 ㎛ is formed between the charging roller 3 and the surface of the photoreceptor 2. The charging roller 3 rotates by a driving force that rotates the conductive support. Approximately -500 V of DC current is applied to the conductive support, an amplitude voltage of an AC current is set to approximately 1.8 kV, and a frequency is set to approximately 3 kHz. Accordingly, the surface of the photoreceptor 2 is charged with discharging.

Furthermore, a hardness of the conductive elastic layer may be set to a high hardness as in the resin. However, there is a possibility that the conductive elastic body comes into slight contact with the photoreceptor 2. Accordingly, in both the AC discharging non-contact charging roller type and the DC discharging contact charging type, the hardness of the charging roller may be set to 78° in terms of ASKER-C hardness. A constituent material of the charging roller 3 of this non-contact charging type is the same as in the DC discharging contact charging type. The non-contact charging of this type is discharged in a narrow region of an adjacent portion with the photoreceptor 2, but the contact charging is discharged in a relatively wide region of an adjacent portion in the vicinity of a contact with the photoreceptor 2. In the non-contact charging type, a discharging opportunity is less, and thus a discharging stress is less. Accordingly, the non-contact charging type may be used to provide for a reduction in abrasion of the surface 2b of the photoreceptor 2.

Scorotron Type

In the scorotron type, a wire that generates a charge is set as the center, and a casing and a grid electrode are disposed to surround the wire at a position distant from the wire by 6 mm. The grid electrode is made to be adjacent to the photoreceptor 2, and is fixed at a position that is distant from the photoreceptor 2 by 700 ㎛. In some examples, -6 kV to -7 kV is applied to the wire, and approximately -500 V is applied to the grid electrode and the casing to charge the surface of the photoreceptor. In this scorotron type, discharging is performed to the grid electrode and the casing, and direct discharging is not performed to the surface 2b of the photoreceptor 2, and thus a discharging stress to the surface 2b of the photoreceptor 2 does not exist. Accordingly, this scorotron type may be used to provide a reduction in abrasion of the surface 2b of the photoreceptor 2.

Next, with reference to FIG. 4, a description will be given of an operation of the example image forming apparatus 1 in comparison to other image forming apparatus.

In other image forming apparatus, the elastic body (portion that comes into contact with the surface of the photoreceptor) of the application roller is formed to cover the entirety of the shaft portion, and the elastic body comes into contact with the entirety of the protective agent application region on the surface of the photoreceptor. The amount of the protective agent on the surface of the photoreceptor may be excessive.

FIG. 4 is a graph showing a relationship of abrasion rates of surface 2b of the photoreceptor 2 and a cleaning blade 7 with respect to the amount of the protective agent. The horizontal axis of FIG. 4 represents the amount of the protective agent [cps/mA], which is measured by a fluorescent X-ray device, on the surface 2b of the photoreceptor 2. The vertical axis of FIG. 4 represents an abrasion rate, a left axis represents an abrasion ratio of the surface 2b of the photoreceptor 2, and a right axis represents an abrasion rate of the cleaning blade 7.

Graphs

4a and 4b illustrate a variation of the abrasion rate of the surface 2b of the photoreceptor 2 with respect to the amount of the protective agent, and a graph 4c is a graph illustrating a variation of the abrasion rate of the cleaning blade 7 with respect to the amount of the protective agent. The graph 4a illustrates a case where the outermost layer of the photoreceptor 2 does not contain filler particles, and the graph 4b illustrates a case where the outermost layer of the photoreceptor 2 contains filler particles.

As shown in FIG. 4, when the amount of the protective agent on the surface 2b of the photoreceptor 2 increases, the amount of abrasion of the photoreceptor 2 is suppressed, and abrasion of the cleaning blade 7 deteriorates. In other image forming apparatus, the amount of the protective agent on the surface 2b of the photoreceptor 2 may be excessive in some cases, and thus suppression of the abrasion of the surface 2b of the photoreceptor 2 and suppression of the abrasion of the cleaning blade 7 may not be compatible with each other. As is clear from the graphs shown in FIG. 4, the amount of protective agent on the surface 2b of the photoreceptor 2 effects the ability of the suppression of the abrasion of the surface 2b of the photoreceptor 2 and suppression of the abrasion of the cleaning blade 7 to be compatible with each other.

In some examples, the protective agent application region 20 on the surface 2b of the photoreceptor 2 includes the contact portion 21 and the non-contact portion 22 in the axial direction A. The elastic body 14 on which the protective agent is carried comes into contact with the contact portion 21, and thus the protective agent is applied thereto. The elastic body 14 on which the protective agent is carried does not come into contact with the non-contact portion 22, and thus the protective agent is not applied thereto. Accordingly, a contact area of the elastic body 14 with respect to the surface 2b of the photoreceptor 2 is further reduced in comparison to other image forming apparatus to decrease the amount of the protective agent that is applied to the surface 2b of the photoreceptor 2. The protective agent applied to the surface of the photoreceptor 2 is stretched on the surface 2b of the photoreceptor 2 by the cleaning blade 7 located downstream of the application roller 5 in a rotation direction of the photoreceptor 2. The position of the contact portion 21 and the position of the non-contact portion 22 move in the axial direction A in accordance with rotation of the photoreceptor 2. Accordingly, a site to which the protective agent is applied with respect to the photoreceptor 2 moves in the axial direction A in accordance with rotation of the photoreceptor 2. As a result, an amount of protective agent is uniformly applied to the surface 2b of the photoreceptor 2 without performing complicated application control with respect to the entirety of the surface 2b of the photoreceptor 2. Accordingly, the protective agent may be set on the surface 2b of the photoreceptor 2 in an amount that suppresses abrasion of the surface 2b of the photoreceptor 2 and suppresses abrasion of the cleaning blade 7. In addition, in the protective agent application region 20, the contact portion 21 exists in the axial direction A, and thus the elastic body 14 comes into contact with an arbitrary site on the surface 2b of the photoreceptor 2 regardless of rotation of the photoreceptor 2. Here, for example, in a case where the elastic body 14 comes into contact with the photoreceptor 2 or does not come into contact with the photoreceptor 2 depending on rotation of the photoreceptor 2, a torque fluctuation may occur such that a rotation of the photoreceptor 2 may not be stable. Accordingly, a torque fluctuation around the rotary shaft 2a of the photoreceptor 2 may be further suppressed to stabilize rotation of the photoreceptor 2 and to suppress abrasion of the surface 2b of the photoreceptor 2 and the cleaning blade 7. As a result, the operational lifespan of both the photoreceptor 2 and the cleaning blade 7 may be made longer.

In some examples, the ratio L_A/L_B of the length L_A of the contact portion 21 to the length L_B of the non-contact portion 22 is 1/9 or greater to obtain the effect of suppressing abrasion of the surface 2b of the photoreceptor 2. Additionally, a ratio L_A/L_B of the length L_A of the contact portion 21 to the length L_B of the non-contact portion 22 of 9 or less may be used to suppress an abrasion of the cleaning blade 7.

In some examples, at the contact position P1 at which the surface 2b of the photoreceptor 2 and the elastic body 14 come into contact with each other, the movement direction of the surface 2b of the photoreceptor 2 and the movement direction of the elastic body 14 are the same as each other, and a relative velocity difference between the movement velocity of the surface 2b of the photoreceptor 2 and the movement velocity of the surface 14s of the elastic body 14 is 20% or less of the movement velocity of the surface 2b of the photoreceptor 2. Accordingly, at the contact position P1, the application efficiency of the protective agent with respect to the surface 2b of the photoreceptor 2 may be realized, and the surface 2b of the photoreceptor 2 is less likely to be damaged in comparison to a case where the movement direction of the surface 2b of the photoreceptor 2 and the movement direction of the surface 14s of the elastic body 14 are different from each other. Similarly, the surface 2b of the photoreceptor 2 is less likely to be damaged in comparison to a case where the relative velocity difference between the movement speed of the surface 2b of the photoreceptor 2 and the movement speed of the surface 14s of the elastic body 14 is greater than 20% of the movement speed of the surface 2b of the photoreceptor 2.

In some examples, the elastic body 14 is formed from raised fiber, and the fiber diameter of the fiber is 2.5 denier to 6 denier. A fiber diameter of 2.5 denier or greater may be used to suppress settling of the elastic body 14. A fiber diameter of 6 denier or less may be used to protect the surface 2b of the photoreceptor 2.

In some examples, the elastic body 14 may be formed from a foamed body having hardness of 100 N to 400 N. A hardness of the foamed body of 100 N or greater may be used to stabilized the supply of the protective agent, and settling of the elastic body 14 may be suppressed. A hardness of the foamed body of 400 N or less may be used to protect the surface 2b of the photoreceptor 2.

In some examples, the bulk density of the foamed body that forms the elastic body 14 is 25 kg/m³ to 65 kg/m³ to suppress application irregularity of the protective agent that is applied by the elastic body 14.

In some examples, the protective agent supply body 6 is a molded body of a fatty acid metal salt. Accordingly, when coming into contact with the elastic body 14, the protective agent supply body 6 is decomposed into fine particles, and is carried on the elastic body 14 as fine particles. In addition, when the elastic body 14 comes into contact with the surface 2b of the photoreceptor 2, the fine particles carried on the elastic body 14 are stretched between the elastic body 14 and the surface 2b of the photoreceptor 2, and adhere to the surface 2b of the photoreceptor 2 in a thin film shape. Accordingly the application properties of the protective agent may be enhanced with respect to the surface 2b of the photoreceptor 2.

When being pressed by the elastic member 10, the protective agent supply body 6 can be brought into press contact with the elastic body 14, and thus the protective agent can be carried on the elastic body 14.

In some examples, 0.5 wt% to 15 wt% of filler particles are contained in the outermost layer of the photoreceptor 2, and thus the hardness of the surface 2b of the photoreceptor 2 is raised, and abrasion resistance is improved. Accordingly, as shown in graph 4b of FIG. 4, even in a case where the amount of the protective agent on the surface 2b of the photoreceptor 2 is smaller in comparison to the graph 4a in which the filler particles are not contained in the outermost layer of the photoreceptor 2, an abrasion rate of the surface 2b of the photoreceptor 2 may be suppressed. As a result, the amount of the protective agent that is applied to the surface 2b of the photoreceptor 2 may be decreased to further suppress abrasion of the cleaning blade 7.

It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail.

FIG. 5 is a view schematically illustrating another elastic body formed region 5a as a development view. The elastic body 14 is formed on the elastic body formed region 5a, so that a set of spirals is formed in one pitch. For example, as illustrated in FIG. 5(a), the elastic body 14 may be formed so that two sets of spirals are formed in one pitch, or the elastic body 14 may be formed so that a plurality of sets of spirals greater than two sets are formed in one pitch. In a case illustrated in FIG. 5(a), in a state in which the peripheral surface 13a of the shaft portion 13 is developed, on the elastic body formed region 5a, the elastic body 14 includes three oblique line portions 14a and three oblique line portions 14b which extend to respectively intersect the oblique line portions 14a. Actually, on the peripheral surface 13a of the shaft portion 13, the three oblique line portions 14a are connected to each other to construct a set of spirals, and the three oblique line portions 14b are connected to each other to construct a set of spirals, and thus a total of two sets of spirals are constructed.

In addition, for example as illustrated in FIG. 5(b), the elastic body 14 may be formed on the elastic body formed region 5ain a dot shape. In a case illustrated in FIG. 5(b), the elastic body 14 has a plurality of rectangular dots 14c. Furthermore, in the example illustrated in FIG. 5(b), the dots 14c have a rectangular shape, but may have a circular shape instead of a rectangular shape. In addition, in the example illustrated in FIG. 5(b), the dots are arranged so that a screen angle thereof becomes 45°. However, the screen angle may be changed to uniformly apply the protective agent.

In of the examples illustrated in FIGS. 5(a) and 5(b), the protective agent application region 20 on the surface 2b of the photoreceptor 2 includes the contact portion 21 and the non-contact portion 22 which are arranged in the axial direction A, and the position of the contact portion 21 and the position of the non-contact portion 22 move in the axial direction A in combination with rotation of the photoreceptor 2. Accordingly, an amount of protective agent is uniformly applied to the surface 2b of the photoreceptor 2 with respect to the entirety of the surface 2b of the photoreceptor 2.

A description has been given of a case where the photosensitive layer included in the photoreceptor 2 is the negatively-charged stacked type as an example. However, in a case where the photosensitive layer is the positively-charged single-layer type, the photosensitive layer has a configuration in which at least the charge generation material and the charge transport material are dispersed in a single layer formed from a binder resin. As in the negatively-charged stacked type, the materials may be used alone or as a mixture of two or more kinds. Even in the positively-charged stacked type, a coating solution may be obtained by the same method as in the negatively-charged stacked type. The coating solution is applied to the conductive support, and the binder resin is solidified to form the photosensitive layer.

In addition, a description has been given of an example in which the charge transport layer included in the photosensitive layer is the outermost layer of the photoreceptor 2. However, a protective layer formed from an acrylic resin, and the like may be further formed on the charge transport layer. For example, the outermost layer of the photoreceptor 2 may be formed from an acrylic resin. Even in this case, the hardness of the surface 2b of the photoreceptor 2 is raised, and abrasion resistance is improved. As a result, the amount of the protective agent applied to the surface 2b of the photoreceptor 2 may be decreased to further suppress abrasion of the cleaning blade 7. The filler particles may not be contained in the photosensitive layer, and the filler particles may be contained in the protective layer that is the outermost layer. In the case of adding the filler particles, the same filler particles as those added to the photosensitive layer can be added.

For example, the protective layer includes a curable resin obtained by curing a compound including a plurality of polymerizable functional groups. The protective layer may be formed as follows. A compound including at least a polymerizable functional group is dissolved in a solvent, and the filler particles are contained in the resultant dissolved compound to obtain an application solution for the protective layer. A coating film is obtained from the application solution for the protective layer, and the coating film is cured (polymerized) by using crosslinking or a polymerization reaction, thereby obtaining the protective layer. The compound including the polymerizable functional group may be a polymerizable monomer, or an oligomer of a dimer or the like in which a plurality of the polymerizable monomers are connected. Examples of the compound including the polymerizable functional group include compounds that include a chain polymerizable functional group such as an acryloyloxy group, a methacryloyloxy group, and a styryl group. In addition, compounds including a successive polymerizable function group such as a hydroxyl group, an alkoxysilyl group, an isocyanate group, and an epoxy group may be used. In a curing reaction, for example, radical polymerization, ionic polymerization, thermal polymerization, photopolymerization, radiation polymerization (electron beam polymerization), a plasma CVD method, an optical CVD method, other like methods, or any combination thereof can be used.

A charge transport material may be added to the application solution for the protective layer to provide additional charge transport capabilities of the protect layer. The same material as previously described can be used. In addition, an additive may be added to improve various functions. Examples of the additive include conductive particles, an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, other like materials, or any combination thereof. In some examples, a layer thickness of the protective layer is 0.1 ㎛ 10 ㎛, and in other examples the layer thickness may be 1 ㎛ to 7 ㎛.

Description will now be given of results of examples and comparative examples for evaluation of an operational lifespan of the photoreceptor 2 and the cleaning blade 7. In the following examples and comparative examples, the image forming apparatus was coupled to "MultiXpress X7600LX (manufactured by Samsung Electronics)", and image formation was repetitively performed under the following conditions.

Common Conditions of Image Formation

A printing environment was set to an environment under room temperature and room humidity (23°C/60% RH). As printing conditions, a printing speed was set to A4 transverse feed of 60 sheets/minute, and the number of printing sheets was set to 100,000 sheets. A charging application voltage was set to a DC voltage of -1400 V. An initial film thickness of a photoreceptor was set to 30 ㎛. The cleaning blade 7 was formed from a urethane rubber, and a contact pressure thereof was set to 30 gf/cm. The contact pressure of the cleaning blade 7 was obtained as follows. A load cell was disposed at a position at which the load cell comes into contact with the cleaning blade 7 on the surface 2b of the photoreceptor 2 to measure a load, and the measured load was divided by a contact length between the load cell and the cleaning blade 7 in a direction of the rotary shaft 2a to measure a linear pressure. Accordingly, the contact pressure was obtained. Furthermore, 100,000 printing sheets correspond to 5 km as a travel distance of the surface 2b of the photoreceptor 2. Polycarbonate was used as the binder resin contained in the charge transport layer of the photoreceptor 2.

In the following examples and comparative examples, the amount of abrasion of the surface 2b of the photoreceptor 2, the amount of abrasion of the cleaning blade 7, and the amount of the protective agent on the surface 2b of the photoreceptor 2 were measured by the following method, and evaluation of the operational lifespan of the photoreceptor 2 and the cleaning blade 7 was performed.

Measurement of Amount of Abrasion of Surface 2b of Photoreceptor 2

A film thickness including the thickness of the photosensitive layer staked on the photosensitive support in an image forming region was measured by ISOSCOPE FMP30 manufactured by Fischer Technology Inc., and image formation was repetitively performed to obtain the amount of abrasion of the surface 2b of the photoreceptor 2 from a film thickness variation amount before and after performing the repetitive image formation. The value was divided by the travel distance of the surface 2b of the photoreceptor 2 in accordance with rotation of the photoreceptor 2 to calculate an abrasion rate of the surface 2b of the photoreceptor 2.

Measurement of Amount of Abrasion of Cleaning Blade 7

A cross-sectional shape of the cleaning blade 7 was measured by VK100 manufactured by KEYENCE CORPORATION, the amount of abrasion of the cleaning blade 7 was obtained from a cross-sectional area variation amount before and after performing repetitive image formation. This value was divided by the travel distance of the surface 2b in accordance with rotation of the photoreceptor 2 to calculate an abrasion rate of the cleaning blade 7.

(Measurement of Amount of Protective Agent on Surface 2b of Photoreceptor 2)

The amount of zinc in zinc stearate, which is a main component of the protective agent, was measured by EDXL 300 manufactured by Rigaku Corporation. Specifically, Zn-Ka rays were counted, and the amount of the protective agent on the surface 2b of the photoreceptor 2 was obtained from a result of differentiation of the counted number before and after performing repetitive image formation.

Example 1

In Example 1, a photoreceptor 2 in which PTFE was contained in the outermost layer as a filler was used. A molded body of zinc stearate was used as the protective agent supply body 6. A brush-shaped elastic body formed in a dot shape on the peripheral surface 13a of the shaft portion 13 was used As the elastic body 14. Additionally, an elastic body in which fineness was 5.7 denier and the number of fibers was 50 kilo-filament was used as the brush-shaped elastic body. In addition, in Example 1, the ratio L_A/L_B of the length L_A of the contact portion 21 to the length L_B of the non-contact portion 22 was set to 1/1. The elastic body 14 was brought into contact with the surface 2b of the photoreceptor 2 to apply the protective agent to the surface 2b of the photoreceptor 2.

Example 2

As in Example 1, in Example 2 a photoreceptor 2 in which PTFE was contained in the outermost layer as a filler was used, and a molded body of zinc stearate was used as the protective agent supply body 6. Additionally, a brush-shaped elastic body formed to be wound around the peripheral surface 13a of the shaft portion 13 in a spiral shape was used as the elastic body 14, differently from Example 1. The fineness of the brush-shaped elastic body and the number of fibers were set to be the same as in Example 1. The ratio L_A/L_B of the length L_A of the contact portion 21 to the length L_B of the non-contact portion 22 was set to 1/3. The elastic body 14 was brought into contact with the surface 2b of the photoreceptor 2 to apply the protective agent to the surface 2b of the photoreceptor 2.

Example 3

As in Example 1, in Example 3 a photoreceptor 2 in which PTFE was contained in the outermost layer as a filler was used, and a molded body of zinc stearate was used as the protective agent supply body 6. In Example 3, a sponge-shape elastic body (for example, a foamed body) formed to be wound around the peripheral surface 13a of the shaft portion 13 in a spiral shape was used as the elastic body 14, differently from Examples 1 and 2. Additionally, a foamed body having a hardness of 250 N and a bulk density of 45 kg/m³ was used as the foamed body. The ratio L_A/L_B of the length L_A of the contact portion 21 to the length L_B of the non-contact portion 22 was set to 1/1.

Comparative Example 1

As in Examples 1 to 3, in Comparative Example 1a photoreceptor 2 in which PTFE was contained in the outermost layer as a filler was used. The protective agent was not applied to the surface 2b of the photoreceptor 2 differently from Examples 1 to 3.

Comparative Example 2

In Comparative Example 2, a photoreceptor 2 in which a filler was not contained in the outermost layer was used differently from Examples 1 to 3. As in Examples 1 to 3, in Comparative Example 2 a molded body of zinc stearate was used as the protective agent supply body 6. In Comparative Example 2, an elastic body (portion that comes into contact with the surface 2b of the photoreceptor 2) formed to cover the entirety of the shaft portion 13 in the application roller 5 was brought into contact with the surface 2b of the photoreceptor 2 to apply the protective agent to the surface 2b of the photoreceptor 2 differently from Examples 1 to 3. For example, the elastic body of the application roller 5 was brought into contact with the entirety of the protective agent application region 20 on the surface 2b of the photoreceptor 2 to apply the protective agent to the surface 2b of the photoreceptor 2.

Results

Results of Examples 1 to 3, and Comparative Examples 1 and 2 are shown in Table 1 and Table 2.

		Unit	Example 1	Example 2	Example 3
Photoreceptor	Charge transport layer binder		Polycarbonate
Photoreceptor	Filler		PTFE
Charging unit	Type		DC contact discharging
Cleaning blade	Rubber material		Urethane
Cleaning blade	Load	gf/cm	30
Protective Agent			Zinc stearate
Application roller	Elastic body		Brush	Brush	Sponge
	Fineness	denier	5.7	5.7	-
	Number of fibers	k filament	50	50	-
	Hardness	N	-	-	250
	Bulk density	kg/m³	-	-	45
	Shape of elastic body		Dot	Spiral	Spiral
	Contact length/non-contact length ratio		1/1	1/3	1/1
X-ray count increase		cps/mA	4.2	2	3.6
Abrasion rate of photoreceptor		10^-7	1.8	3.3	1.7
Abrasion rate of blade		10^-15 m	4	2.4	3

		Unit	Comparative Example 1	Comparative Example 2
Photoreceptor	Charge transport layer binder		Polycarbonate
Photoreceptor	Filler		PTFE	-
Charging unit	Type		DC contact discharging
Cleaning blade	Rubber material		Urethane
Cleaning blade	Load	gf/cm	30
Protective Agent			-	Zinc stearate
Application roller	Elastic body			Brush
	Fineness	denier	-	5.7
	Number of fibers	k filament	-	50
	Hardness	N	-	-
	Bulk density	kg/m³	-	-
	Shape of elastic body		-	-
	Contact length/non-contact length ratio		-	-
X-ray count increase		cps/mA	0	8.3
Abrasion rate of photoreceptor		10^-7	8.6	8.1
Abrasion rate of blade		10^-15 m	2.2	9.6

As shown in Table 1 and Table 2, in the case of Comparative Example 1, since the protective agent was not applied to the surface 2b of the photoreceptor 2, the abrasion rate of the surface 2b of the photoreceptor 2 was as high as 8.6×10^-7. In the case of Comparative Example 2, the X-ray count increase was as high as 8.3 cps/mA, and the amount of the protective agent applied to the surface 2b of the photoreceptor 2 was excessively large. According to this, the abrasion rate of the cleaning blade 7 was as high as 9.6×10^-7.

In contrast, in the case of Examples 1 to 3, since the elastic body 14 was formed on the shaft portion 13 in a dot shape or a spiral shape, the elastic body 14 includes a portion that comes into contact with the surface 2b of the photoreceptor 2 and a portion that does not come into contact with the surface 2b of the photoreceptor 2. Since the protective agent application region 20 on the surface 2b of the photoreceptor 2 includes the contact portion 21 and the non-contact portion 22, the X-ray count increase is lower in comparison to Comparative Example 2, and the amount of application of the protective agent is suppressed. Accordingly, compatibility between suppression of the abrasion rate of the surface 2b of the photoreceptor 2 and suppression of the abrasion rate of the cleaning blade 7 was realized. Accordingly, in the case of Examples 1 to 3, it can be seen that a long operational lifespan of the photoreceptor 2 and a long operational lifespan of the cleaning blade 7 may be realized in combination with each other.

List of Reference Numbers

1 image forming apparatus, 2 photoreceptor (image carrier), 2a rotary shaft, 2b surface, 7 cleaning blade, 5 application roller (protective agent application member), 6 protective agent supply body, 10 elastic member (pressing means), 13 shaft portion, 14 elastic body, 14s surface, 20 protective agent application region, 21 contact portion, 22 non-contact portion, A axial direction, P1 contact position.

Claims

An image forming apparatus, comprising:

a rotatable image carrier;

a cleaning blade to contact and clean a surface of the image carrier;

a protective agent application member located upstream of the cleaning blade in a rotation direction of the image carrier and including:

a rotatable shaft portion that extends along a rotary shaft of the image carrier, and

an elastic body that is located on the shaft portion to carry a protective agent, the elastic body to contact the surface of the image carrier and to apply the protective agent to a protective agent application region on the surface of the image carrier; and

a protective agent supply body to contact the elastic body of the protective agent application member and to allow the protective agent to be carried on the elastic body,

wherein the protective agent application region includes a contact portion and a non-contact portion in a direction along the rotary shaft, the elastic body to contact the contact portion and not contact the non-contact portion, and a position of the contact portion and a position of the non-contact portion to move in the direction along the rotary shaft in combination with a rotation of the image carrier.
The image forming apparatus according to claim 1, wherein a ratio of a length of the contact portion in the direction along the rotary shaft to a length of the non-contact portion in the direction along the rotary shaft is approximately 1/9 to 9.
The image forming apparatus according to claim 1, wherein at a position at which the surface of the image carrier and the elastic body come into contact with each other, a movement direction of the surface of the image carrier and a movement direction of the elastic body are the same as each other, and a relative velocity difference between a movement velocity of the surface of the image carrier and a movement velocity of a surface of the elastic body is approximately 20% or less of the movement velocity of the surface of the image carrier.
The image forming apparatus according to claim 1, wherein the elastic body comprises raised fiber, and a fiber diameter of the fiber is approximately 2.5 denier to 6 denier.
The image forming apparatus according to claim 1, wherein the elastic body comprises a foamed body, and a hardness of the foamed body is approximately 100 N to 400 N.
The image forming apparatus according to claim 5, wherein a bulk density of the foamed body is approximately 25 kg/m³ to 65 kg/m³.
The image forming apparatus according to claim 1, wherein the protective agent supply body comprises a molded body of a fatty acid metal salt.
The image forming apparatus according to claim 1, further comprising a pressing member to press the protective agent supply body against the elastic body, wherein the protective agent supply body is pressed by the pressing member and is brought into press contact with the elastic body.
The image forming apparatus according to claim 1, wherein the image carrier includes a plurality of layers which are stacked,

wherein an outermost layer, which is located on an outermost side, among the layers of the image carrier, contains a filler, and

wherein an amount of the filler contained in the outermost layer is approximately 0.5 wt% to 15 wt%.
The image forming apparatus according to claim 1, wherein the image carrier includes a plurality of layers which are stacked, and

wherein an outermost layer, which is located on an outermost side, among the layers of the image carrier, comprises an acrylic resin.
An image forming apparatus, comprising:

an image carrier;

a cleaning blade to contact a surface of the image carrier; and

a protective agent application member including:

a rotatable shaft portion that is substantially parallel to a rotary shaft of the image carrier, and

an elastic body that is located on the shaft portion to apply a protective agent to a protective agent application region on the surface of the image carrier,

wherein the protective agent application region includes a contact portion and a non-contact portion in a direction along the rotary shaft, the elastic body to contact the contact portion without contacting the non-contact portion, and a position of the contact portion and a position of the non-contact portion to move in the direction along the rotary shaft in combination with a rotation of the image carrier.
The image forming apparatus according to claim 11, wherein a ratio of a length of the contact portion in the direction along the rotary shaft to a length of the non-contact portion in the direction along the rotary shaft is approximately 1/9 to 9, and

wherein at a position at which the surface of the image carrier and the elastic body come into contact with each other, a movement direction of the surface of the image carrier and a movement direction of the elastic body are the same as each other, and a relative velocity difference between a movement velocity of the surface of the image carrier and a movement velocity of a surface of the elastic body is approximately 20% or less of the movement velocity of the surface of the image carrier.
The image forming apparatus according to claim 11, further comprising a protective agent supply body to contact the elastic body of the protective agent application member and to allow the protective agent to be carried on the elastic body.
The image forming apparatus according to claim 13, further comprising a pressing member to press the protective agent supply body against the elastic body.
The image forming apparatus according to claim 1, wherein the image carrier comprises a photoreceptor including a plurality of layers which are stacked,

wherein an outermost layer, which is located on an outermost side, among the layers of the photoreceptor, contains a filler, and

wherein an amount of the filler contained in the outermost layer is approximately 0.5 wt% to 15 wt%.