As particles other than the fluororesin, an acrylic resin is preferable. This is because the acrylic resin has a certain degree of hardness, so that it is possible to expect the effect of slidability. Meanwhile, the shape of particles is not particularly limited, and can be appropriately selected according to the purpose, but is preferably spherical. Such a shape is preferable because it is possible to prevent a failure in which particles other than the fluororesin, detached from the covering layer will damage the image bearer or the blade substrate in the cleaning blade.

The acrylic resin is not particularly limited, and can be appropriately selected according to the purpose. Examples of the acrylic resin include polymethyl (meta) acrylic acid, a styrene-(meta) acrylic acid methyl copolymer, and a styrene-(meta) acrylic acid ethyl copolymer. The acrylic resin may be in the form of acrylic resin particles.

The volume average particle diameter (50% volume diameter, median diameter) of the particles other than the fluororesin is not particularly limited and can be appropriately selected according to the purpose. Meanwhile, the volume average particle diameter of the particles other than the fluororesin is preferably 0.1 [μm] or more and 1 [μm] or less, more preferably 0.5 [μm] or less, and still more preferably 0.3 [μm] or less. When the volume average particle diameter of the particles is 1 [μm] or less, the particles easily settle in a solvent. Therefore, it is possible to prevent a failure in which it is difficult for the particles to stably disperse. When the volume average particle diameter of the particles is 0.5 [μm] or less, the particles can be more stably dispersed in a nonaqueous solvent.

The method for producing the covering layer is not particularly limited, and can be appropriately selected according to the purpose. For example, it is possible to obtain the covering layer by adding particles to a mixture of a solvent and a binding component, and applying a particle dispersion obtained from the mixture to a blade substrate in the cleaning blade.

The solvent is not particularly limited, and can be appropriately selected according to the purpose. For example, in the case of fluorine-based particles and a binding component, a fluorine-containing organic solvent can be cited as an example as the solvent. Examples of the fluorine-containing organic solvent include hydrofluoroether (HFE), perfluorocarbon (PFC), and perfluoroether (PFE). One of these options may be used alone, or two or more of these options may be used in combination.

In the present embodiment, the average particle diameter of the particles in the binding component based on a dynamic light scattering method (average particle diameter of cumulant analysis in scattering intensity distribution) is preferably 1 [μm] or less, more preferably 0.5 [μm] or less, and still more preferably 0.3 [μm] or less from the viewpoint of obtaining a uniform dispersion. Generally, even when fine particles having a volume average particle diameter of 1 [μm] or less are used, the particles are aggregated to form secondary particles. As a result, fine particles having a volume average particle diameter of 1 [μm] or more are formed. Even when the fluororesin dispersion is stored at a low viscosity for a long period of time, it is possible to obtain a stable dispersion by dispersing fine particles aggregated to form secondary particles, in such a way as to achieve a particle diameter of 1 [μm] or less. The dispersion method is not particularly limited, and can be appropriately selected according to the purpose. Examples of the dispersion method include a method using a disperser such as an ultrasonic disperser, a triple roll mill, a ball mill, a bead mill, or a jet mill.

The method for forming the covering layer is not particularly limited, and can be appropriately selected according to the purpose. Examples of the method for forming the covering layer include dipping in which the entire blade substrate in the cleaning blade or a part of the blade substrate is immersed in a particle dispersion and treated. In addition to the dipping, a coating method such as spray coating or a dispenser may be used.

Blade Substrate

In the present embodiment, the blade substrate in the cleaning blade may be referred to as a “blade substrate” or a “substrate”. The shape of the blade substrate can be appropriately selected according to the purpose as long as the blade substrate has a structure that allows the residue on the image bearer to be removed. Meanwhile, it is preferable for the blade substrate to have a structure in which the contact side of the contact portion for contact between the blade substrate and the image bearer is linear. Examples of the shape of the blade substrate include a plate shape.

The structure of the blade substrate is not particularly limited, and can be appropriately selected according to the purpose. Examples of the structure of the blade substrate include a single-layer structure, a layered structure, and a layered structure in which multiple members is combined. Among these options, a single-layer structure and a layered structure including multiple members stacked in layers are preferable from the viewpoint of easy processing into the cleaning blade. When the blade substrate has a layered structure, a layer in contact with the image bearer may be referred to as an edge layer, and a layer that is not the edge layer may be referred to as a base layer. When the blade substrate is single-layered, the blade substrate includes only an edge layer. The multiple members in the layered structure more preferably differ in Martens hardness from each other.

A material of the blade substrate is not particularly limited, and can be appropriately selected according to the purpose. Meanwhile, the material of the blade substrate preferably has appropriate elasticity and hardness from a viewpoint of preventing wear of the blade substrate and a viewpoint of sufficiently removing the residue on the intermediate transfer body. Examples of the material of the blade include an elastic material. As long as the elastic material is highly elastic, the elastic material is not particularly limited, and can be appropriately selected according to the purpose. Examples of the elastic material include polyurethane rubber, silicone rubber, fluororubber, nitrile rubber (NBR), and ethylene propylene diene rubber (EPDM). Among these options, polyurethane rubber is preferable from the viewpoint of durability and anti-staining properties. The size of the blade substrate is not particularly limited, and can be appropriately selected according to the size of the image bearer.

The Martens hardness of the polyurethane rubber in the cleaning blade of the present embodiment is not particularly limited, and can be appropriately selected according to the purpose, but is preferably 0.5 [N/mm²] or more and 2 [N/mm²] or less. A cleaning failure occurs when it is difficult to obtain a blade linear pressure and an area of a contact portion for contact with the image bearer is likely to increase. A chip is caused when the blade substrate is excessively hard. However, when the Martens hardness of the polyurethane rubber in the cleaning blade is in a desired range, it is possible to eliminate faults such as the cleaning failure and the chip.

The method for producing the blade substrate is not particularly limited, and can be appropriately selected according to the purpose. Meanwhile, for example, it is possible to obtain the blade substrate by preparing a polyurethane prepolymer by use of a polyol compound and a polyisocyanate compound, adding a curing agent and a curing catalyst as necessary to the polyurethane prepolymer, centrifugally molding the polyurethane prepolymer by use of a predetermined mold, and leaving the polyurethane prepolymer to stand at normal temperature to age (cure) the polyurethane prepolymer, and cutting the cured polyurethane prepolymer into a flat plate shape with predetermined dimensions. The polyol compound is not particularly limited, and can be appropriately selected according to the purpose. Examples of the polyol compound include a high-molecular weight polyol and a low-molecular weight polyol.

Examples of the high-molecular weight polyol include a polyester polyol which is a condensate of an alkylene glycol and an aliphatic dibasic acid; polyester-based polyols such as polyester polyols of alkylene glycols and adipic acid, such as ethylene adipate ester polyols, butylene adipate ester polyols, hexylene adipate ester polyols, ethylene propylene adipate ester polyols, ethylene butylene adipate ester polyols, and ethylene neopentylene adipate ester polyols; polycaprolactone-based polyols such as polycaprolactone ester polyols obtained by ring-opening polymerization of caprolactone; and polyether-based polyols such as poly (oxytetramethylene) glycol and poly (oxypropylene) glycol. One of these options may be used alone, or two or more of these options may be used in combination.

Examples of the low-molecular weight polyol include dihydric alcohols such as 1,4-butanediol, ethylene glycol, neopentyl glycol, hydroquinone-bis (2-hydroxyethyl) ether, 3,3′-dichloro-4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenylmethane; and trihydric or higher polyhydric alcohols such as 1,1,1-trimethylolpropane, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, trimethylolethane, 1,1,1-tris (hydroxyethoxymethyl) propane, diglycerin, and pentaerythritol. One of these options may be used alone, or two or more of these options may be used in combination.

The polyisocyanate compound is not particularly limited, and can be appropriately selected according to the purpose. Examples of the polyisocyanate compound include methylene diphenyl diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), naphthylene 1,5-diisocyanate (NDI), tetramethylxylene diisocyanate (TMXDI), isophorone diisocyanate (IPDI), hydrogenated xylylene diisocyanate (H6XDI), dicyclohexylmethane diisocyanate (H12MDI), hexamethylene diisocyanate (HDI), dimer acid diisocyanate (DDI), norbornene diisocyanate (NBDI), and trimethylhexamethylene diisocyanate (TMDI). One of these options may be used alone, or two or more of these options may be used in combination.

The curing agent is not particularly limited, and can be appropriately selected according to the purpose. Examples of the curing agent include amines and alcohols. One of these options may be used alone, or two or more of these options may be used in combination. The curing agent is used, for example, for adjusting the hardness of the blade substrate.

The curing catalyst is not particularly limited, and can be appropriately selected according to the purpose. Examples of the curing catalyst include 2-methylimidazole and 1,2-dimethylimidazole. The amount of contained curing catalyst is not particularly limited, and can be appropriately selected according to the purpose. Meanwhile, the amount of contained curing catalyst is preferably 0.01 mass % or more and 0.5 mass % or less, and more preferably 0.05 mass % or more and 0.3 mass % or less with respect to the sum of the mass of prepolymer and curing agent.

The modulus of repulsion elasticity of the blade substrate in conformity with JIS K6255 standard is not particularly limited, and can be appropriately selected according to the purpose, but is preferably 10% to 80% at 23° C. When the modulus of repulsion elasticity is within a desired range, it is possible to eliminate a cleaning failure caused by inflexibility of the entire blade substrate and inability to follow the shake and roughness of the image bearer and a defect such as blade squeal (abnormal noise) caused by too strong repulsion. For example, it is possible to measure the modulus of repulsion elasticity of the blade substrate in conformity with JIS K6255 standard at 23° C. by using Resilience tester No. 221 manufactured by Toyo Seiki Seisaku-sho, Ltd.

Average Value of Luminance Histogram

In the cleaning blade of the present embodiment, the average value of the luminance histogram is 15,000 or more and 25,000 or less at the point located inward from the tip ridge in the covering layer on the lower surface of the cleaning blade substrate, the point being located at a distance of 100 μm from the tip ridge. Note that the “point located inward from the tip ridge, the point being located at a distance of 100 μm from the tip ridge” refers to, for example, a measurement point illustrated in FIG. 3. When the average value of the luminance histogram is 15,000 or more and 25,000 or less, it is possible to sufficiently obtain the effect of enabling the covering layer to be easily collapsed. The average value of the luminance histogram can be acquired from a luminance image by a confocal laser microscope. The luminance histogram acquired from the luminance image of the confocal microscope is a histogram of the intensity of light reflected from the surface of the covering layer. The covering layer of the present embodiment includes particles and a binding component. The fact that the covering layer is likely to collapse indicates a state in which the binding component around the particles is relatively small in amount, and indicates that since voids between the particles are relatively large, the light reflected from the surface of the covering layer increases. As a result, the average value of the luminance histogram increases. In the cleaning blade of the present embodiment, the average value of the luminance histogram is preferably 18,000 or more and 22,000 or less at a point located inward from a tip ridge of the edge layer, the point being located at a distance of 100 μm from the tip ridge, from the viewpoint of achieving both the sliding effect and good cleaning performance due to the easy collapse of a film. When the average value of the luminance histogram is 15,000 or more at the point located inward from the tip ridge of the edge layer in the cleaning blade, the point being located at a distance of 100 μm from the tip ridge, the covering layer is likely to collapse. This is advantageous in that cleaning performance can be maintained even when high-density images are continuously printed. When the average value of the luminance histogram is less than 15,000 at the point located inward from the tip ridge of the edge layer in the cleaning blade, the point being located at a distance of 100 μm from the tip ridge, the covering layer is less likely to collapse. Therefore, cleaning performance cannot be maintained when high-density images are continuously printed. In contrast, when the average value of the luminance histogram exceeds 25,000, the covering layer is too likely to collapse. This causes the following disadvantages: the slidability cannot be maintained, or the covering layer falls off from the cleaning blade on its own when not in use. Note that the measurement of the average value of the luminance histogram in the present embodiment is performed on a product processed into a cleaning blade.

Measurement of Average Value of Luminance Histogram

Using a confocal laser microscope (OLS-4100 manufactured by Olympus Corporation), a luminance image of the surface of the covering layer was acquired by means of a 100-fold magnification objective lens. A luminance histogram at 100 μm from the tip was acquired by an attached analysis application, and the mean thereof was adopted.

Measurement of Martens Hardness

The location of measurement of the Martens hardness in the base layer of the cleaning blade is not particularly limited, but was set to a point located inward from an end portion of the base layer, the point being located at a distance of 20 [μm] from the end portion for ease of measurement. The Martens hardness indicates the median of numerical values obtained by measurement at four to six points at each measurement location. It is possible to measure the Martens hardness in conformity with ISO14577 by continuously pushing a Berkovich indenter for 10 seconds by means of a nanoindenter (ENT-3100, manufactured by Elionix Inc.) until a maximum load reaches 1,000 μN, holding the indenter for 5 seconds, and unloading the indenter at the same loading speed for 10 seconds.

Image Forming Apparatus and Image Forming Method

The image forming apparatus according to the present embodiment includes at least: an image bearer; a charger that charges a surface of the image bearer, an exposing device that exposes the charged image bearer to form an electrostatic latent image, a developer that develops the electrostatic latent image by means of toner to form a visible image, a transferring device that transfers the visible image to a recording medium via an intermediate transfer body; a fixing device that fixes the transfer image transferred to the recording medium; and a cleaner that removes toner remaining on the intermediate transfer body, and further includes other means appropriately selected as necessary. The charger and the exposing device may be collectively referred to as an electrostatic latent image forming means. Each of the cleaner includes the cleaning blade of the present embodiment. An image forming method used in the present embodiment includes at least a charging step, an exposure step, a developing step, a transfer step, a fixing step, and a cleaning step, and further includes other steps appropriately selected as necessary. The charging step and the exposure step may be collectively referred to as an electrostatic latent image forming step. The image forming method used in the present embodiment can be more suitably performed by the image forming apparatus of the present embodiment. The charging step can be performed by the charger. The exposure step can be performed by the exposing device. The developing step can be performed by the developer. The transfer step can be performed by the transferring device. The fixing step can be performed by the fixing device. The cleaning step can be performed by the cleaner. The cleaner includes the cleaning blade of the present embodiment. The other steps can be performed by the other means.

Image Bearer

The image bearer is not particularly limited in terms of structure, size, and the like, and can be appropriately selected from known ones. The shape of the image bearer is not particularly limited, and can be appropriately selected according to the purpose. Examples of the shape of the image bearer include a drum-like shape and a belt-like shape. The material of the image bearer is not particularly limited, and can be appropriately selected according to the purpose. Examples the material of the image bearer include inorganic photoconductors such as amorphous silicon and selenium, and organic photoconductors (OPC) such as polysilane and phthalopolymethine.

Examples of the organic photoconductor include a layered photoconductor and a single-layer photoconductor. The layered photoconductor has a layered structure in which a layer (charge generation layer) obtained by dispersion of a charge generation material such as metal-free phthalocyanine or titanyl phthalocyanine in a binder resin and a layer (charge transport layer) obtained by dispersion of a charge transport material in a binder resin are stacked on a support such as an aluminum drum. The single-layer photoconductor includes a photosensitive layer having a single-layer structure in which both a charge generation material and a charge transport material are dispersed in a binder resin on a support. It is also possible to add, to the photosensitive layer, a hole transport agent and an electron transport agent as charge transport materials in the single-layer photoconductor.

In addition, an undercoat layer may be provided between the support and the charge generation layer in the layered structure or the photosensitive layer in the single-layer structure.

Charging Step and Charger

The charging step is a step of charging the surface of the image bearer, and is performed by the charger. As long as the charger can charge the surface of the image bearer, the charger is not particularly limited, and can be appropriately selected according to the purpose. Examples of the charger include contact chargers known per se including a conductive or semiconductive roller, brush, film, rubber blade, and the like, and non-contact chargers using corona discharge, such as corotron and scorotron. With regard to the shape of the charger, the charger may have any form such as a roller, a magnetic brush, or a fur brush, and the form of the charger can be selected according to the specifications and form of an electrophotographic image forming apparatus. In the case of using a magnetic brush, the magnetic brush uses various ferrite particles such as Zn-Cu ferrite as a charger, and includes a nonmagnetic conductive sleeve for supporting the charger, and a magnet roll included in the conductive sleeve. In the case of using a brush, it is possible to use the brush as a charger by, for example, using, as a material of a fur brush, a fur subjected to conductive treatment with carbon, copper sulfide, metal, or a metal oxide, and by winding or sticking the fur around a metal or a cored bar subjected to other conductive treatment

The charger is not limited to the contact-type charger as described above. Meanwhile, it is preferable to use such a charger because an image forming apparatus can be obtained in which ozone generated from the charger is reduced. The charger is preferably disposed in a state of being in contact with or not in contact with the image bearer, and preferably charges the surface of the image bearer by superimposing direct-current and alternating-current voltages. In addition, the charger is also preferably a charging roller that is disposed, in a non-contact manner, close to the image bearer with a gap tape, and charges the surface of the image bearer by superimposing direct-current and alternating-current voltages on the charging roller.

Exposure Step and Exposing device

The exposure step is a step of exposing the charged surface of the image bearer, and is performed by the exposing device. It is possible to perform the exposure by, for example, imagewise exposure of the surface of the image bearer by means of the exposing device. An optical system in the exposure is roughly divided into an analog optical system and a digital optical system. The analog optical system is an optical system that directly projects a document onto the surface of the image bearer by an optical system. The digital optical system is an optical system that receives image information as an electric signal, converts the electric signal into an optical signal, and exposes the image bearer to form an image.

As long as it is possible to form an electrostatic latent image by exposing the charged image bearer, the exposing device is not particularly limited, and can be appropriately selected according to the purpose. Examples of the exposing device include various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, a liquid crystal shutter optical system, and a light-emitting diode (LED) optical system. Note that an optical backplane method in which imagewise exposure is performed from a back surface side of the image bearer may be adopted in the present embodiment.

Developing Step and Developer

The developing step is a step of developing the electrostatic latent image into the toner image, and is performed by the developer. As long as it is possible to develop the electrostatic latent image into a toner image, the developer is not particularly limited, and can be appropriately selected according to the purpose. For example, the developer includes at least a developing device that stores the toner and can apply the toner to the electrostatic latent image in a contact or non-contact manner. The developing device may be of a dry developing type or a wet developing type, or may be a monochromatic developing device or a multicolor developing device. Examples of the developing device include a device including a stirrer that frictionally stirs and charges the toner and a rotatable magnet roller. In the developing device, for example, the toner and a carrier are mixed and stirred as necessary, the toner is charged by friction generated at that time, and the toner is held on a surface of the rotating magnet roller in a napped state to form a magnetic brush. Since the magnet roller is disposed in the vicinity of the image bearer, a part of the toner included in the magnetic brush formed on the surface of the magnet roller moves to the surface of the image bearer by an electric attraction force of the electrostatic latent image. As a result, the electrostatic latent image is developed by the toner, and the toner image is formed on the surface of the image bearer. The toner to be stored in the developing device may be a developer containing the toner, and the developer may be a one-component developer or a two-component developer. Note that the toner can also be used as a one-component magnetic toner that uses no carrier, or a nonmagnetic toner. As a developing method, a premix developing method may be adopted which is a method for supplying a premix developer in which toner and a carrier are mixed in advance. In the premix developing method, increased carriers in the developing device are discharged as excess developer. Accordingly, the developer in the developing device is gradually refreshed. Therefore, it is possible to extend the cycle of replacement accompanying deterioration of the developer and to save time and effort for replacing the developer.

Transfer Step and Transferring device

The transfer step is a step of transferring the toner image to a recording medium, and is performed by the transferring device. The transfer step preferably includes, for example, a primary transfer step of using an intermediate transfer body and transferring the toner image to a surface of the intermediate transfer body to form a composite transfer image, and a secondary transfer step of transferring the composite transfer image to a recording medium. As long as it is possible to transfer the toner image to a recording medium, the transferring device is not particularly limited, and can be appropriately selected according to the purpose. The transferring device preferably includes a primary transferring device of transferring the toner image to the surface of the intermediate transfer body to form a composite transfer image, and a secondary transferring device of transferring the composite transfer image to a recording medium. The primary transferring device and the secondary transferring device preferably include, for example, at least a transfer device that peels, from the surface of the image bearer, the toner image formed on the surface of the image bearer and transfers the toner image to a recording medium. The transfer device is not particularly limited, and can be appropriately selected according to the purpose. Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device. The number of the transfer devices may be one, or two or more.

As long as the recording medium can transfer the toner image that has not yet been fixed after development, the recording medium is not particularly limited, and can be appropriately selected according to the purpose. Meanwhile, plain paper is typically used, but for example, a polyethylene terephthalate (PET) base for an overhead projector (OHP) can also be used.

Fixing Step and Fixing device

The fixing step is a step of fixing the toner image transferred to the recording medium, and is performed by the fixing device. In a case where two or more colors of toner are used, the toner of each color may be fixed every time the toner of each color is transferred to the recording medium. Alternatively, the toner of all colors may be fixed in the state of being transferred to the recording medium and layered. As long as the fixing device can fix the toner image transferred to the recording medium, the fixing device is not particularly limited, and can be appropriately selected according to the purpose. A heat fixing system using a known heating and pressurizing means can be adopted as the fixing device. The heating and pressurizing means is not particularly limited, and can be appropriately selected according to the purpose. Examples of the heating and pressurizing means include a combination of a heating roller and a pressurizing roller, and a combination of a heating roller, a pressurizing roller, and an endless belt. Heating temperature is not particularly limited, and can be appropriately selected according to the purpose. Meanwhile, heating is preferably performed at a temperature of 80° C. to 200° C. Note that, for example, a known optical fixing device may be used together with the fixing device as necessary.

Cleaning Step and Cleaner

The cleaning step is a step of removing the toner remaining on the surface of the image bearer, and is performed by the cleaner. One in which the cleaning blade of the present embodiment is secured to a support is used as the cleaner.

The linear pressure to be applied to the surface of the image bearer by the blade substrate in the cleaning blade of the present embodiment is not particularly limited, and can be appropriately selected according to the purpose. Meanwhile, the linear pressure is preferably 10 N/m or more and 100 N/m or less, and more preferably 10 N/m or more and 50 N/m or less. When the linear pressure is 10 N/m or more and 100 N/m or less, a cleaning failure in which the toner slips between the contact portion and the image bearer is less likely to occur, and it is possible to easily prevent the turning-up of the elastic body. It is possible to measure the linear pressure by using, for example, a measuring device incorporating a compact compression type load cell manufactured by Kyowa Electronic Instruments Co., Ltd.

An angle (hereinafter, referred to as a “cleaning angle”) formed by a tangent line of the image bearer and the tip surface of the free end in the blade substrate at a position where the contact portion of the blade substrate in the cleaning blade of the present embodiment is in contact with the image bearer is not particularly limited, and can be appropriately selected according to the purpose. Meanwhile, the angle is preferably 65° or more and 85° or less. When the cleaning angle is 65° or more and 85° or less, occurrence of the turning-up of the blade substrate can be easily prevented, and occurrence of cleaning failure can also be easily reduced.

Other Steps and Other Means

Examples of the other steps include a static elimination step, a recycling step, and a control step. Examples of the other means include a static elimination means, a recycling means, and a control means.

Static Elimination Step and Static Elimination Means

The static elimination step is a step of applying a static elimination bias voltage to the image bearer to perform static elimination, and is performed by the static elimination means. As long as a static elimination bias voltage can be applied to the image bearer, the static elimination means is not particularly limited, and can be appropriately selected according to the purpose. Examples of the static elimination means include a static elimination lamp.

Recycling Step and Recycling Means

The recycling step is a step of causing the developer to recycle the toner removed in the cleaning step, and is performed by the recycling means. The recycling means is not particularly limited, and can be appropriately selected according to the purpose. Examples of the recycling means include a known conveyance means.

Control Step and Control Means

The control step is a step of controlling each of the steps, and is performed by the control means. As long as movement of each means can be controlled, the control means is not particularly limited, and can be appropriately selected according to the purpose. Examples the control means include devices such as a sequencer and a computer.

An example of the image forming apparatus according to the present embodiment is described with reference to the drawings. However, an application of the cleaning blade is not limited to these embodiments. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted. Furthermore, the number, position, shape, and so forth of each constituent member to be described below are not limited to those described in the present embodiment, and may be set to a number, a position, a shape, and so forth suitable to implement the present embodiment.

FIG. 5 is a schematic configuration diagram illustrating an exemplary configuration of the image forming apparatus of the present embodiment. The image forming apparatus includes four image forming units for yellow, magenta, cyan, and black (hereinafter, may be abbreviated as Y, M, C, and BK, respectively). The Y, M, C, and BK toners having different colors are used as image forming substances for forming an image. Except for this point, the Y, M, C, and BK toners have the same configuration.

Each image forming unit includes a photoconductor drum 21 (cyan photoconductor drum 21C, yellow photoconductor drum 21Y, magenta photoconductor drum 21M, or black photoconductor drum 21BK), a charger, an exposure device 12, a developing device 20 (cyan developing device 20C, yellow developing device 20Y, magenta developing device 20M, or black developing device 20BK), a transfer charger, a cleaning device 13, and a static elimination lamp. The charger uniformly charges the photoconductor drum 21. The exposure device 12 exposes the photoconductor drum 21, and forms a latent image of each color on the photoconductor drum 21, on the basis of image information on each color. The developing device 20 is a developer that develops the latent image with a developer of each color, and forms a toner image of each color. The transfer charger transfers the toner image onto an intermediate transfer belt 22. The charger is a charging member included in a charging device serving as a charger. The developing device 20 is a developer that converts a latent image formed on the surface of the photoconductor drum 21 into a toner image. The cleaning device 13 is a cleaner that cleans toner remaining on the photoconductor drum 21 from which the toner image has been transferred to the intermediate transfer belt 22. The static elimination lamp is a static elimination means that neutralizes the surface potential of the photoconductor drum 21 that has been cleaned. Although the photoconductor drum 21 has a drum-like shape, the photoconductor drum may have a sheet-like shape or an endless belt-like shape.

EXAMPLES

Hereinafter, examples and reference examples of the present embodiment will be described, but the present embodiment is not limited to these examples at all. Note that the term “part(s)” refers to “part(s) by mass” unless otherwise specified. Hereinafter, a description will be given of an embodiment in which the cleaning blade substrate illustrated in FIG. 4 includes an elastic edge layer and a base layer.

Preparation of Particle Dispersion for Forming Covering Layer, Preparation of Particle Dispersion A

The following were put in a screw tube and stirred with a stirrer or the like to prepare [particle dispersion A]: 6.8 parts of polytetrafluoroethylene (PTFE) micro powder (TF9201Z, manufactured by 3M Company, volume average particle diameter of 200 nm) as particles, 0.2 parts of a VdF-HFP-TFE terpolymer containing vinylidene fluoride (VdF), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE) as a binding component, and 93.0 parts of 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (HFE-347, manufactured by Tokyo Chemical Industry Co., Ltd.) as fluorine dispersion solvent.

Preparation of Particle Dispersion B

The following were put in a screw tube and stirred with a stirrer or the like to prepare [particle dispersion B]: 6.9 parts of polytetrafluoroethylene (PTFE) micro powder (TF9201Z, manufactured by 3M Company, volume average particle diameter of 200 nm) as particles, 0.1 parts of a VdF-HFP-TFE terpolymer as a binding component, and 93.0 parts of 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (HFE-347, manufactured by Tokyo Chemical Industry Co., Ltd.) as fluorine dispersion solvent.

Preparation of Particle Dispersion C

The following were put in a screw tube and stirred with a stirrer or the like to prepare [particle dispersion C]: 5.8 parts of polytetrafluoroethylene (PTFE) micro powder (TF9201Z, manufactured by 3M Company, volume average particle diameter of 200 nm) as particles, 1.2 parts of a VdF-HFP-TFE terpolymer as a binding component, and 93.0 parts of 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (HFE-347, manufactured by Tokyo Chemical Industry Co., Ltd.) as fluorine dispersion solvent.

Preparation of Particle Dispersion D

The following were put in a screw tube and stirred with a stirrer or the like to prepare [particle dispersion D]: 97.0 parts of a polymethyl methacrylate (PMMA) aqueous dispersion (MX100W, manufactured by Nippon Shokubai Co., Ltd., volume average particle diameter of 150 nm) as particles, and 3.0 parts of a polyvinyl butyral (PVB) resin (S-LEC KW-10, manufactured by Sekisui Chemical Co., Ltd., acetalization degree of 9±2 mol %) as a binding component.

Preparation of Particle Dispersion E

The following were put in a screw tube and stirred with a stirrer or the like to prepare [particle dispersion E]: 95.0 parts of a polymethyl methacrylate (PMMA) aqueous dispersion (MX100W, manufactured by Nippon Shokubai Co., Ltd., volume average particle diameter of 150 nm) as particles, and 5.0 parts of a polyvinyl alcohol (PVA) resin (Poval JP-03, manufactured by Japan Vam & Poval Co., Ltd., degree of saponification of 88±2 mol %) as a binding component.

Example 1
Preparation of Blade Substrate in Cleaning Blade

A polyurethane elastomer sheet obtained by centrifugal molding, curing, and post-crosslinking was used for the edge layer and the base layer. The average thickness and Martens hardness (HM) of the edge layer and the base layer are as follows.

- Average thickness: 2.0 [mm]
- Martens hardness (HM) of edge layer: 0.5 [N/mm²]
- Martens hardness (HM) of base layer: 1.1 [N/mm²]

The edge layer and the base layer were bonded to each other to produce a blade substrate. The blade substrate was bonded to a metal plate.

Formation of Covering Layer: Dipping

One end surface (hereinafter, may be referred to as a cleaning blade tip end surface) of a peripheral side surface used as the tip of the cleaning blade was immersed in the [particle dispersion A] by a depth of 2 [mm] from the cleaning blade tip end surface at right angles to a horizontal plane, and was pulled up at a pulling speed of 1 [mm/s]. For the purpose of collecting PTFE particles necessary for the cleaning function in a portion including the contact side on the cleaning blade tip end surface, the cleaning blade of Example 1 was produced by being inclined by about 45° as illustrated in FIG. 6 and dried at normal temperature (25° C.) for 30 minutes.

The average thickness of the covering layer was 0.5 μm.

Examples 2 to 7 and Comparative Examples 1 to 3

Cleaning blades of Examples 2 to 7 and Comparative Examples 1 to 3 were produced in the same manner as in Example 1 except that the type of particle dispersion, the Martens hardness of the base layer, and the average thickness of the covering layer of Example 1 were changed as illustrated in Table 1.

The thickness of the covering layer was controlled by a pulling speed at the time of dipping. Increasing the pulling speed increases the thickness.

Comparative Example 1 is a cleaning blade including a blade substrate on which no covering layer is provided.

Assembly of Image Forming Apparatus

The cleaning blades obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were attached to an image bearer unit of a color multifunction peripheral (imagio MP C4500, manufactured by Ricoh Co., Ltd.), and an image forming apparatus was assembled. A printer unit of the color multifunction peripheral has a configuration similar to the configuration of an image forming apparatus 500 illustrated in FIG. 4. The cleaning blades were attached to the image forming apparatus in such a way as to achieve a linear pressure of 20 g/cm and a cleaning angle of 81°.

Measurement of Average Value of Luminance Histogram

The means of the luminance histograms of the cleaning blades obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were measured. The measurement method described above in the section “Average value of luminance histogram” was adopted as a method for measuring the means of the luminance histograms. The average value of the luminance histogram illustrated in Table 1 shows the median of values measured at four to six points at each measurement location.

Measurement of Martens Hardness

The Martens hardness of the base layer of each of the cleaning blades obtained from Examples 1 to 7 and Comparative Examples 1 to 3 was measured. The Martens hardness (HM) was measured under the same conditions as the measurement conditions described above in the section “Measurement of Martens Hardness”. Specifically, measurement was performed in conformity with ISO14577 as follows: a Berkovich indenter was continuously pushed for 10 seconds by means of a nanoindenter (ENT-3100, manufactured by Elionix Inc.) until the maximum load reached 1,000 μN, held for 5 seconds, and unloaded for 10 seconds at the same loading speed. Results are illustrated in Table 1. The location of measurement of the Martens hardness in the base layer was set to the point located inward from the end portion of the base layer, the point being located at a distance of 20 μm. The Martens hardness indicates the median of values measured at four to six points at each measurement location.

Measurement of Average Thickness of Covering Layer

The average thickness of the covering layer on each of the cleaning blades obtained from Examples 1 to 7 and Comparative Examples 1 to 3 was measured. Results are illustrated in Table 1. The average thickness was measured as follows: a part of the covering layer was scraped with a spatula, a cotton swab, or the like, and shape measurement was performed by means of a contact-type surface roughness meter (Surftest SJ-500: manufactured by Mitutoyo Corporation).

Evaluation of Torque Increase Rate

Output was performed by use of the image forming apparatus under the following conditions, and the rate of change of increase in the driving torque of the image bearer was measured. After the output, the tip portion of the cleaning blade was observed with a laser microscope (LEXT OLS4100, manufactured by Olympus Corporation), and the rate of increase in torque was evaluated based on the following evaluation criteria. Evaluation results are illustrated in Table 1. Note that the term “initial” in the evaluation criteria refers to a period during which first to 500th sheets were output.

- Environment: 23° C./45% RH
- Paper feeding condition: blank chart
- Number of output sheets: 5,000 sheets (A4 size horizontal)

Evaluation Criteria

- ⊚: Torque increased by 50% or less of an initial value, and there was no stop of the image bearer due to the driving torque increase. Furthermore, even when the tip portion of the cleaning blade was observed after the output, there was no trace of being turned up.
- ◯: Torque increased by 50% or less of the initial value, and there was no stop of the image bearer due to the driving torque increase. When the tip portion of the cleaning blade was observed after the output, there was a trace of being turned up. However, since the tip portion of the cleaning blade was not turned up to such a degree that the toner might come out, there is no problem in practical use.
- ×: There was a stop of the image bearer due to an increase in torque, and when the tip portion of the cleaning blade was observed after the output, there was a trace of being turned up to such a degree that the toner might come out, which may cause a problem in practical use.

Image Quality Evaluation (Cleaning Performance)

Output was performed by use of the image forming apparatus under the following conditions. Thereafter, the tip portion of the cleaning blade and the surface of the image bearer were observed with a laser microscope (LEXT OLS4100, manufactured by Olympus Corporation) and evaluated on the basis of the following evaluation criteria. Evaluation results are illustrated in Table 1.

- Environment: 27° C./80% RH
- Paper feeding condition: full solid images are continuously fed
- Number of output sheets: 2,000 sheets (A4 size horizontal)

Evaluation Criteria

- GOOD: Toner that has passed through due to a cleaning failure cannot be found on the printing paper or the image bearer by a visual check, and even when the image bearer is observed with a microscope in the longitudinal direction, the streak-like passing through of toner cannot be found.
- FAIR: Toner that has passed through due to a cleaning failure cannot be found on the printing paper or the image bearer by a visual check, but when the image bearer is observed with a microscope in the longitudinal direction, the streak-like passing through of toner can be found.
- POOR: Toner that has passed through due to a cleaning failure can be found on both the printing paper and the image bearer by a visual check.

TABLE 1

Examples

1
2
3
4
5
6
7

Covering
Particle dispersion used for
A
B
C
A
B
D
E

layer
forming covering layer

Particles
PTFE (particle
6.8
6.9
5.8
6.8
6.9
—
—

diameter: 0.200

[μm])

PMMA (particle
—
—
—
—
—
97.0
95.0

diameter: 0.150

[μm])

Binding
VdF/HFP/TFE
0.2
0.1
1.2
0.2
0.1
—
—

component
Polyvinyl butyral
—
—
—
—
—
3.0
—

Polyvinyl alcohol
—
—
—
—
—
—
5.0

Dispersion
1,1,2,2-
93.0
93.0
93.0
93.0
93.0
92.0
92.0

solvent
tetrafluoroethyl

2,2,2-trifluoroethyl

ether

Average thickness [μm]
0.5
6.5
4.0
4.0
10.0
7.5
7.0

Average value of luminance
15,000
21,600
16,900
20,500
25,000
22,100
23,200

histogram

Blade
Martens hardness [N/mm²]
2.0
2.0
2.0
0.5
1.5
0.5
0.5

substrate
in base layer

Evaluation
Torque increase rate
FAIR
GOOD
FAIR
GOOD
GOOD
FAIR
FAIR

Cleaning performance
GOOD
FAIR
FAIR
GOOD
FAIR
FAIR
FAIR

Comparative examples

1
2
3

Covering
Particle dispersion used for
—
B
C

layer
forming covering layer

Particles
PTFE (particle
—
6.9
5.8

diameter: 0.200

[μm])

PMMA (particle
—
—
—

diameter: 0.150

[μm])

Binding
VdF/HFP/TFE
—
0.1
1.2

component