Conductive roller, image forming apparatus, and detection method for conductive roller

Abstract

A conductive roller includes: a core member including an outer surface along and around an axis of the core member; and a surface layer disposed along the outer surface of the core member. The surface layer includes: a conductive portion formed of a conductive resin composition; and a surface roughness imparting material in the form of particles dispersed in the conductive portion. The average particle size of the surface roughness imparting material is in a range of greater than or equal to 6 micrometers and less than or equal to 10 micrometers. The number of particles of the surface roughness imparting material per unit area of the surface layer is in a range of greater than or equal to 1.0×10<supgt;4< / supgt> particles / mm<supgt;2< / supgt> and less than or equal to 2.0×10<supgt;6< / supgt> particles / mm<supgt;2< / supgt>. The average thickness of the surface layer is in a range of greater than or equal to 3.0 micrometers and less than or equal to 15.0 micrometers.

Description

Technical Field

[0001] The present invention relates to a conductive roller, an image forming apparatus, and a method for detecting a conductive roller. Background Art

[0002] A conductive roller (e.g., a charging roller) is generally used in an image forming apparatus (e.g., a printer or a copying machine), which is configured to form an image on a recording medium (e.g., paper) by an electrophotographic method using toner.

[0003] For example, the charging roller described in Patent Document 1 includes a core rod and a conductive rubber layer formed on the core rod.

[0004] To reduce charging non-uniformity, Patent Document 1 defines a range of the ten-point height Rz of the surface roughness of the charging roller and a range of the average spacing Sm between the peaks on the surface of the charging roller.

[0005] Related Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application with Publication No. 2012-14141 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] To roughen the surface of a conductive roller, for example, the following method is used: a surface roughness imparting material in the form of particles is dispersed on the surface of the conductive roller. When this method is applied to a charging roller, discharge occurs between the surface of the photosensor and the area of the surface of the charging roller that does not have the surface roughness imparting material. Image quality depends on the uniformity of charging or discharging on the surface of the photosensor; therefore, it is necessary to define a predetermined range of the discharge gap between the surface of the photosensor and the charging roller and a predetermined range of the distance between the discharge points.

[0010] However, the ten-point height Rz of the surface roughness and the average spacing Sm between the peaks defined in Patent Document 1 are each calculated values affected by the formed unevenness, regardless of the presence of the surface roughness imparting material; therefore, the ten-point height Rz of the surface roughness and the average spacing Sm between the peaks are not sufficiently related to the discharge gap or the distance between the discharge points. Therefore, even when the surface roughness imparting material is applied to the charging roller described in Patent Document 1, it is necessary to output an actual image to determine whether the desired image quality is obtained, which requires a lot of time and effort.

[0011] Means for Solving the Problems

[0012] To solve the above problems, a conductive roller according to one aspect of the present invention includes: a core member including an outer surface along and around the axis of the core member; and a surface layer disposed along the outer surface of the core member, wherein: the surface layer includes: a conductive portion; and a surface roughness imparting material in the form of particles dispersed in the conductive portion, the average particle size of the surface roughness imparting material being in the range of greater than or equal to 6 μm and less than or equal to 10 μm, and the number of particles of the surface roughness imparting material per unit area of the surface layer being in the range of greater than or equal to 1.0×10 4 particles / mm 2 and less than or equal to 2.0×10 6 particles / mm 2 and the average thickness of the surface layer is in the range of greater than or equal to 3.0 μm and less than or equal to 15.0 μm.

[0013] An image forming apparatus according to one aspect of the present invention includes: the conductive roller described above, and a photoreceptor in contact with or close to the conductive roller.

[0014] A detection method for a conductive roller according to one aspect of the present invention is a detection method for determining whether the characteristics of the conductive roller are good. The conductive roller includes: a core member including an outer surface along and around the axis of the core member; and a surface layer disposed along the outer surface of the core member. The surface layer includes: a conductive portion; and a surface roughness imparting material in the form of particles dispersed in the conductive portion, the average particle size of the surface roughness imparting material being in the range of greater than or equal to 6 μm and less than or equal to 10 μm, and the average thickness of the surface layer being in the range of greater than or equal to 3.0 μm and less than or equal to 15.0 μm. The detection method includes: calculating the number of particles of the surface roughness imparting material per unit area of the surface layer; and determining that the characteristics of the conductive roller are good based on the number of particles being in the range of greater than or equal to 1.0×10 4 particles / mm 2 and less than or equal to 2.0×10 6 particles / mm 2 and the range.

[0015] Effects of the Invention

[0016] According to the present invention, image non-uniformity can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram showing an example of the configuration of an image forming apparatus according to an embodiment. ​

[0018] Figure 2 Figure 2 is a cross-sectional view of a charging roller, which is an example of a conductive roller according to an embodiment.

[0019] Figure 3 Figure 3 is an enlarged cross-sectional view showing the surface layer of the charging roller. DETAILED DESCRIPTION

[0020] Preferred embodiments according to the present invention will be described with reference to the accompanying drawings. In the drawings, the dimensions and ratios of elements may be different from those of actual products, and some elements may be shown schematically for ease of understanding. The scope of the present invention is not limited to the embodiments described below, unless the following description includes a description specifically defining the scope of the present invention.

[0021] 1. Image forming apparatus 100

[0022] Figure 1 Figure 1 is a schematic diagram showing an example of the configuration of an image forming apparatus 100 having a conductive roller according to an embodiment. The image forming apparatus 100 is an apparatus for forming an image on a recording medium M (e.g., paper for printing) by an electrophotographic method, such as a copying machine or a printer.

[0023] As shown in Figure 1 , the image forming apparatus 100 includes a photoreceptor 10, a charging device 20, an exposure device 30, a developing device 40, a transfer device 50, a cleaning device 60, and a fixing device (not shown). Among these devices, the charging device 20, the exposure device 30, the developing device 40, the transfer device 50, and the cleaning device 60 are arranged in this order along the outer surface of the photoreceptor 10 in the circumferential direction of the photoreceptor 10.

[0024] The photoreceptor 10 includes a photosensitive layer as the outermost layer, which is formed of a photoconductive insulating material (e.g., an organic photoreceptor (OPC: Organic Photoreceptor)), for example, Figure 1 Figure 1 the photoreceptor 10 in

[0025] The charging device 20 is a device configured to uniformly charge the outer surface of the photoreceptor 10 by discharging (e.g., corona discharge). In the example shown in Figure 1 , the charging device 20 includes a charging roller 21, which is an example of a conductive roller. In addition, the charging device 20 is configured to generate a discharge, such as a corona discharge, between the charging roller 21 and the photoreceptor 10. The charging roller 21 contacts the outer surface of the photoreceptor 10. Therefore, a discharge occurs in the region R1 or R2 near the nip N formed by the contact.​​

[0026] The exposure device 30 is a device configured to form an electrostatic latent image on the outer surface of the photoreceptor 10 by exposing the charged outer surface of the photoreceptor 10 using light (such as laser) according to image information from an external device (such as a personal computer).

[0027] The developing device 40 applies toner T to the electrostatic latent image formed on the outer surface of the photoreceptor 10 to visualize the latent image as a toner image. For example, in Figure 1 the developing device 40 shown in includes: a container 41 configured to contain toner T therein; a developing roller 42 configured to carry toner T; a toner supply roller 43 configured to supply toner T to the developing roller 42; and a regulating blade 44 configured to regulate the amount of toner T carried by the developing roller 42.

[0028] The transfer device 50 is a device configured to transfer the toner image formed on the photoreceptor 10 to the recording medium M. In the example shown in Figure 1 the transfer device 50 includes a transfer roller 51, and a predetermined bias voltage is applied to the transfer roller 51 to transfer the toner image on the photoreceptor 10 to the recording medium M, and the recording medium is conveyed between the photoreceptor 10 and the transfer roller 51.

[0029] The recording medium M on which the toner image has been transferred is heated and pressed by a fixing device (not shown). Through the heating and pressing steps, the toner image is fixed to the recording medium M. The fixing device is not particularly limited, and the fixing device can be one of various known fixing devices, and various known fixing devices include a fixing device using a roller fixing method, a fixing device using a film fixing method, a fixing device using a flash fixing method, etc.

[0030] The cleaning device 60 is a device configured to remove the toner T remaining on the outer surface of the photoreceptor 10 after the transfer process. In the example shown in Figure 1 the cleaning device 60 includes: a cleaning blade 61 configured to scrape toner T from the outer surface of the photoreceptor 10; and a collector 62 configured to collect the toner T scraped by the cleaning blade 61. The cleaning device 60 may include a cleaning brush instead of the cleaning blade 61, or may include a cleaning brush in addition to the cleaning blade 61.

[0031] 2. Charging roller 21

[0032] Figure 2 is a cross-sectional view of the charging roller 21, which is an example of a conductive roller according to an embodiment. As shown in Figure 2As shown in the figure, the charging roller 21 includes a core member 21a, an elastic layer 21b, and a surface layer 21c. In addition, the charging roller 21 has a structure in which the elastic layer 21b is sandwiched between the core member 21a and the surface layer 21c. Each element of the charging roller 21 will be described in turn.

[0033] 2-1. Core member 21a

[0034] The core member 21a is a columnar or cylindrical conductive member. The core member includes an outer surface that extends along and around the axis AX of the core member 21a. The core member 21a has two ends, and each of the two ends may be appropriately provided with a shaft member for a bearing.

[0035] The core member 21a is formed of a material having excellent thermal conductivity and mechanical strength. The material is not particularly limited, and examples of the material include metal materials (such as stainless steel materials, nickel (Ni) materials, nickel alloy materials, iron (Fe) materials, magnetic stainless steel materials, cobalt-nickel (Co-Ni) alloy materials, etc.) and resin materials (such as polyimide resin (PI) materials, etc.). In addition, one of these materials may be used alone, or alternatively, a combination of two or more of these materials may be used in the form of a mixture, laminate, or alloy.

[0036] The core member 21a is manufactured by known machining techniques such as cutting, for example. The surface of the core member 21a may be appropriately subjected to surface treatment such as sandblasting or electroplating.

[0037] 2-2. Elastic layer 21b

[0038] The elastic layer 21b is disposed on the entire outer surface of the core member 21a. In addition, the elastic layer 21b is a layer having conductivity and elasticity. The elastic layer 21b is elastically deformed by the contact between the charging roller 21 and the photoreceptor 10. In the region R1 or R2 close to the imprint portion N formed by the contact between the charging roller 21 and the photoreceptor 10, the elastic deformation makes the distance between the outer surface of the charging roller 21 and the outer surface of the photoreceptor 10 equal in the direction along the axis AX.

[0039] In Figure 3 the example shown, the elastic layer 21b is a single layer; however, the elastic layer 21b may be a laminate having two or more layers. Another layer may be appropriately inserted between the core member 21a and the elastic layer 21b, such as an adhesive layer that bonds these layers to each other, a sealing layer that improves the sealing of these layers, or an adjustment layer that adjusts the surface condition of the core member 21a.

[0040] The thickness of the elastic layer 21b is appropriately determined according to the material of the elastic layer 21b. The thickness of the elastic layer is not particularly limited, and in order to achieve appropriate elasticity of the elastic layer 21b, the thickness of the elastic layer can be, for example, in the range of greater than or equal to 0.5 mm and less than or equal to 5 mm, and can preferably be in the range of greater than or equal to 1 mm and less than or equal to 3 mm. When the non-contact method is applied to the image forming apparatus 100, the elastic layer 21b can be omitted, in the non-contact method, the charging roller 21 does not contact the photoreceptor 10.

[0041] The elastic layer 21b is formed, for example, of a rubber composition in which a conductivity-imparting agent is added to a rubber material. The elastic layer 21b can be a dense member formed of a rubber composition, or can be a foam member formed of a rubber composition.

[0042] The rubber material is not particularly limited, and can be, for example, a synthetic rubber material such as a polyurethane rubber (PUR) material, a chlorinated ether rubber (ECO) material, a nitrile rubber (NBR) material, a styrene rubber (SBR) material, or a chloroprene rubber (CR) material, etc. In addition, one of these materials can be used alone, or alternatively, a combination of two or more of these materials can be used in the form of a copolymer or a blend, etc.

[0043] The rubber material is not limited to synthetic rubber materials, and the rubber material can be a thermoplastic elastomer material. Additives such as a crosslinking agent or a crosslinking aid can be appropriately added to the rubber material. The crosslinking agent is not particularly limited, and examples of the crosslinking agent include sulfur and peroxide vulcanizing agents, etc. Examples of the crosslinking aid include inorganic materials (such as zinc oxide and magnesium oxide) and organic materials (such as stearic acid and amines).

[0044] The conductivity-imparting reagent is not particularly limited. Examples of the conductivity-imparting reagent include an electron conductivity-imparting reagent and an ion conductivity-imparting reagent. In addition, a combination of two or more of these reagents can be used in the form of a mixture or the like. The electron conductivity-imparting reagent is not particularly limited. Examples of the electron conductivity-imparting reagent include carbon black and metal powder, etc. In addition, one electron conductivity-imparting reagent in the electron conductivity-imparting reagents can be used alone, or a combination of two or more electron conductivity-imparting reagents in the electron conductivity-imparting reagents can be used. The ion conductivity-imparting reagent is not particularly limited. Examples of the ion conductivity-imparting reagent include organic salts, inorganic salts, metal complexes, and ionic liquids. Examples of the organic salt include sodium trifluoroacetate materials, etc. Examples of the inorganic salt include lithium perchlorate materials and quaternary ammonium salts, etc. Examples of the metal complex include iron halide-ethylene glycol materials, as shown in the Japanese Patent with Patent No. 3655364. An ionic liquid is a molten salt that is liquid at room temperature. The melting point of the ionic liquid is 70 degrees Celsius or lower, preferably 30 degrees Celsius or lower, as shown in the Japanese Patent Application with Publication No. 2003-202722.

[0045] Since the surface layer 21c described below is very thin, the shape of the surface of the elastic layer 21b tends to present as the shape of the surface of the charging roller 21. Therefore, preferably, the surface of the elastic layer 21b is as smooth as possible. Specifically, preferably, the surface roughness Rz of the elastic layer 21b is equal to or less than 8.5 micrometers, and more preferably, equal to or less than 6 micrometers. The surface roughness Rz within this range enables the effect of the shape of the surface layer 21c described below to be appropriately achieved. According to JIS B 0601 (1994), the surface roughness Rz represents the ten-point height of the micro-irregularities.

[0046] Preferably, the durometer hardness of the elastic layer 21b is in the range of greater than or equal to 50° and less than or equal to 64°. The durometer hardness of the elastic layer 21b within this range enables the effect of the shape of the surface layer 21c described below to be appropriately achieved. The durometer hardness is measured using a "Type A" durometer according to JIS K 6253 or ISO 7619.

[0047] The elastic layer 21b described above is formed, for example, by extrusion molding. This molding can be insert extrusion molding, in which the core member 21a is used as an insert. In this case, the joining of the core member 21a and the elastic layer 21b is performed simultaneously with the formation of the elastic layer 21b. Alternatively, the elastic layer 21b can be formed by bonding a sheet-like or tubular member formed of the rubber composition described above to the outer surface of the core member 21a. When forming the elastic layer 21b, the thickness and surface roughness of the elastic layer 21b can be appropriately adjusted by grinding the outer surface of the elastic layer 21b using a grinding machine or the like.

[0048] 2-3. Surface layer 21c

[0049] The surface layer 21c disposed on the entire outer surface of the elastic layer 21b is a conductive layer having a rough surface. The surface layer 21c is disposed along the outer surface of the core member 21a as the outermost layer of the charging roller 21. Therefore, the surface layer 21c includes a rough surface such that corona charging is generated uniformly between the charging roller 21 and the photoreceptor 10 as compared with a configuration in which the surface of the surface layer 21c is a smooth surface, and the surface layer is disposed as the outermost layer of the charging roller 21.

[0050] Figure 3 is an enlarged cross-sectional view showing the surface layer 21c of the charging roller 21. As shown in Figure 3 shown, the surface layer 21c includes a conductive portion 21c1 and a surface roughness imparting material 21c2 in the form of particles. The conductive portion 21c1 is used to generate discharge in the region R1 or R2 between the conductive portion 21c1 and the outer surface of the photoreceptor 10, and serves as an adhesion portion that fixes the surface roughness imparting material 21c2 in a dispersed state to the elastic layer 21b. On the other hand, the surface roughness imparting material 21c2 is used to roughen the surface of the surface layer 21c. The conductive portion 21c1 and the surface roughness imparting material 21c2 will be described in detail in sequence.

[0051] The conductive portion 21c1 is formed of a conductive resin composition in which a conductive reagent is added to a resin material as a base material. The resin composition may include another additive, such as a modifier or the like.

[0052] The resin material is not particularly limited. Examples of the resin material include urethane resin materials, acrylic resin materials, acrylic urethane resin materials, amino resin materials, silicone resin materials, fluororesin materials, polyamide resin materials, epoxy resin materials, polyester resin materials, polyether resin materials, phenolic resin materials, urea-formaldehyde resin materials, polyvinyl butyral resin materials, melamine resin materials, and nylon resin materials, etc. One of these base materials can be used alone, or alternatively, two or more of these materials can be used in the form of a copolymer or a blend, etc.

[0053] The conductive reagent is not particularly limited. Examples of the conductive reagent include carbon black (such as acetylene black, Ketjen black, and Tokablack, etc.), carbon nanotubes, lithium salts (such as lithium perchlorate materials, etc.), ionic liquids (such as 1-butyl-3-methylimidazolium hexafluorophosphate, etc.), metal oxide materials (such as tin oxide materials, etc.), and conductive polymers. One of these conductive reagents can be used alone, or alternatively, a combination of two or more of these conductive reagents can be used in the form of a mixture, etc.

[0054] The surface roughness imparting material 21c2 is not particularly limited. Examples of the surface roughness imparting material 21c2 include acrylic particles, urethane particles, polyamide resin particles, silicone resin particles, fluororesin particles, styrene resin particles, phenolic resin particles, polyester resin particles, olefin resin particles, epoxy resin particles, nylon resin particles, carbon particles, graphite particles, carbon spheres, silica particles, alumina particles, titanium oxide particles, zinc oxide particles, magnesium oxide particles, zirconium oxide particles, calcium sulfate particles, calcium carbonate particles, magnesium carbonate particles, calcium silicate particles, aluminum nitride particles, boron nitride particles, talc particles, kaolin particles, diatomaceous earth particles, glass beads, and hollow glass spheres, etc. One of these types of particles can be used alone, or alternatively, two or more of these types of particles can be used in combination.

[0055] As described above, the charging roller 21 is an example of a conductive roller. The charging roller includes a core member 21a and a surface layer 21c disposed along the outer surface of the core member 21a. The core member includes an outer surface along and around the axis AX. As described above, the surface layer 21c includes a conductive portion 21c1 having conductivity and a surface roughness imparting material 21c2, and the surface roughness imparting material is in the form of particles dispersed in the conductive portion 21c1.

[0056] The average particle size of the surface roughness imparting material 21c2 is within a range of 6 μm or more and 10 μm or less. The number of particles of the surface roughness imparting material 21c2 per unit area of ​​the surface layer 21c is within a range of 1.0×10 4 Particles / mm 2 and less than or equal to 2.0×10 6 Particles / mm 2 The average thickness of the surface layer 21c is within a range of greater than or equal to 3.0 micrometers and less than or equal to 15.0 micrometers.

[0057] The range of the average particle size of the surface roughness imparting material 21c2, the range of the number of particles of the surface roughness imparting material 21c2 per unit area of ​​the surface layer 21c, and the range of the average thickness of the surface layer 21c are defined as described above, so that by using the charging roller 21, electricity can be uniformly charged or discharged to the outer surface of the photoreceptor 10.

[0058] In particular, the number of particles of the surface roughness imparting material 21c2 per unit area of ​​the surface layer 21c has a higher correlation with the distance between the protrusions due to the surface roughness imparting material 21c2 than the average spacing Sm between the peaks. Therefore, compared with the conventional technology that defines the average spacing Sm between the peaks, the variation in the distance L between the discharge points is reduced regardless of the shape of the conductive portion 21c1.

[0059] Compared with the micro-roughness ten-point height RZ, the average particle size of the surface roughness imparting material 21c2 has a higher correlation with the height of the protrusion caused by the surface roughness imparting material 21c2. Therefore, compared with the conventional technology of defining the micro-roughness ten-point height RZ, the variation of the discharge gap G is reduced regardless of the shape of the conductive portion 21c1. In order to reduce the variation of the discharge gap G, preferably, the standard deviation (variation) of the particle size of the surface roughness imparting material 21c2 is as small as possible; specifically, the standard deviation of the particle size is preferably equal to or less than 1.5 micrometers, and more preferably equal to or less than 1 micrometer.

[0060] Furthermore, since the relationship between the average thickness of the surface layer 21c and the average particle size of the surface roughness imparting material 21c2 is defined, it is possible to obtain protrusions each of which has a desired height due to the surface roughness imparting material 21c2. Therefore, it is possible to obtain a discharge gap G having a desired length.

[0061] As described above, the range of the average particle size of the surface roughness-imparting material 21c2, the range of the number of particles of the surface roughness-imparting material 21c2 per unit area of the surface layer 21c, and the range of the average thickness of the surface layer 21c are defined. Thus, a desired discharge gap G and a desired distance L between the discharge points can be obtained. As a result, by using the charging roller 21, electricity can be uniformly charged or discharged to the outer surface of the photoreceptor 10.

[0062] When measuring the average particle size of the surface roughness-imparting material 21c2, the average thickness of the surface layer 21c, and the number of particles of the surface roughness-imparting material 21c2 per unit area of the surface layer 21c, it is possible to determine whether the characteristics of the charging roller 21 are good based on the measurement results. In other words, it is determined that the characteristics of the charging roller 21 are good within the range described above based on the measurement results. As described above, a detection method can be provided that can determine whether the charging roller 21 is good without evaluating the quality of an image output from the image forming apparatus 100 in which the charging roller 21 is actually installed.

[0063] As described above, the charging roller 21 according to the present embodiment includes a conductive elastic layer 21b disposed between the core member 21a and the surface layer 21c. With this configuration, based on the charging roller 21 being in contact with the outer surface of the photoreceptor 10, the distance between the outer surface of the photoreceptor 10 and the outer surface of the charging roller 21 can be uniform in the direction along the axis AX.

[0064] Preferably, the surface roughness-imparting material 21c2 is formed of insulating particles. In this case, it is possible to reduce the discharge to the protrusions caused by the surface roughness-imparting material 21c2. In the example shown in Figure 3 , the surface roughness-imparting material 21c2 is partially exposed to the outside from the conductive portion 21c1; however, the surface roughness-imparting material 21c2 can be completely embedded in the conductive portion 21c1.

[0065] As described above, the conductive portion 21c1 is formed of a resin composition including a resin material and a conductive agent. Thus, the conductive portion 21c1 is suitably used to generate a discharge at the regions R1 or R2 between the conductive portion 21c1 and the outer surface of the photoreceptor 10, and to fix the surface roughness-imparting material 21c2 in a dispersed state to the elastic layer 21b.

[0066] As described above, in the image forming apparatus 100 including the charging roller 21 and the photoreceptor 10, the charging roller 21 charges the outer surface of the photoreceptor 10 by applying a voltage between the charging roller 21 and the outer surface of the photoreceptor 10. The voltage (in other words, the charging voltage) may be a DC voltage, or may be a voltage obtained by superimposing an AC voltage on the DC voltage. In the case where the charging voltage is a DC voltage, charging unevenness is generally likely to occur as compared with the case where the charging voltage is a voltage obtained by superimposing an AC voltage on the DC voltage; however, according to the present invention, even when the charging voltage is a DC voltage, charging unevenness can be reduced.

[0067] The surface layer 21c described above is formed from a coating liquid in which the resin composition described above is dissolved in a solvent, and in addition, the surface roughness imparting material described above is dispersed in the coating liquid. Specifically, the coating liquid is applied to the outer surface of the elastic layer 21b and then hardened or cured to form the surface layer 21c.

[0068] The method of applying the coating liquid is not particularly limited, and examples of the method include a dipping coating method, a roller coating method, a spraying method, and the like. In order to cure or harden the coating liquid, heat treatment, ultraviolet irradiation treatment, etc. can be appropriately performed.

[0069] The solvent for the coating liquid is not particularly limited, and examples of the solvent include water-based solvents (such as water, etc.), ester-based solvents (such as methyl acetate, ethyl acetate, or butyl acetate, etc.), ketone-based solvents (such as methyl ethyl ketone (MEK) or methyl isobutyl ketone (MIBK), etc.), alcohol-based solvents (such as methanol, ethanol, butanol, or 2-propanol (IPA), etc.), hydrocarbon-based solvents (such as acetone, toluene, xylene, hexane, or heptane, etc.), and halogenated solvents (such as chloroform, etc.). One of these solvents can be used alone, or alternatively, a combination of two or more of these solvents can be used in the form of a mixture, etc.

[0070] As described above, the surface layer 21c is formed by curing or hardening a coating reagent including a surface roughness-imparting material 21c2. Based on the area of the surface layer 21c, the inclusion rate of the surface roughness-imparting material 21c2 in the coating reagent, the mass of the coating reagent used to form the surface layer 21c, and the average mass of each particle of the surface roughness-imparting material 21c2, the number of particles of the surface roughness-imparting material 21c2 per unit area of the surface layer 21c can be calculated. Therefore, even without using a device such as a microscope, the number of particles of the surface roughness-imparting material 21c2 per unit area of the obtained surface layer 21c can be determined. Therefore, when the thickness of the surface layer 21c and the average particle size of the surface roughness-imparting material 21c2 are known, it is possible to determine whether the characteristics of the charging roller 21 are good by using the detection method described above.

[0071] For example, the average mass of each particle of the surface roughness-imparting material 21c2 is calculated based on the density of the material constituting the surface roughness-imparting material 21c2 and the volume of each particle of the surface roughness-imparting material 21c2. For example, the volume of each particle of the surface roughness-imparting material 21c2 is calculated based on the average particle size of the surface roughness-imparting material 21c2.

[0072] 3. Variations

[0073] Various variations can be made to the embodiments described above. Specific variations that can be applied to the embodiments described above are described below. Two or more variations freely selected from the following variations can be combined as long as such a combination does not cause a conflict.

[0074] 3-1. First Variation

[0075] In the embodiments described above, an example is shown in which the conductive roller according to the present invention is applied to a charging roller; however, the present invention is not limited to this example. The conductive roller according to the present invention is applicable not only to the charging roller of an image forming apparatus (such as an electrophotographic copying machine or a printer), but also to, for example, a developing roller, a transfer roller, an electrostatic charge eliminating roller, a toner supply roller, and the like.

[0076] 3-2. Second Variation

[0077] In the embodiments described above, a configuration in which the charging roller is in contact with the outer surface of the photoreceptor is shown; however, the present invention is not limited to this configuration, and a configuration in which the conductive roller is close to the outer surface of the photoreceptor can be used. For example, when the conductive roller is a developing roller, the developing method can be a contact method or a non-contact method.

[0078] 3-3. Third Variation

[0079] In the embodiments described above, an example of an image forming apparatus according to the present invention is shown as a monochrome image forming apparatus; however, the image forming apparatus is not limited to this example. For example, the image forming apparatus according to the present invention is applicable not only to a monochrome image forming apparatus but also to a color image forming apparatus. The color image forming apparatus may use a rotary development method or a tandem development method. In the case where the image forming apparatus includes an intermediate transfer member, a conductive roller may be applied to a primary transfer roller or a secondary transfer roller. Further, the image forming apparatus may use wet toner or dry toner, and the toner may be a magnetic or non-magnetic one-component developer or two-component developer.

[0080] Example

[0081] Specific examples of the present invention will be described below. The present invention is not limited to the following examples.

[0082] A. Manufacture of Conductive Roller

[0083] A-1. First Example

[0084] Manufacture of Elastic Layer

[0085] First, a rubber composition is kneaded using a roller mixer. The rubber composition includes the following components.

[0086] Chlorinated ether rubber used as a rubber material (“Epichlomer(エピクロマ)-CG-102” manufactured by Osaka Soda Co., Ltd.): 100 parts by mass

[0087] Sodium trifluoroacetate used as a conductivity-imparting reagent: 0.5 part by mass

[0088] Zinc oxide used as a crosslinking aid: 3 parts by mass

[0089] Stearic acid used as a crosslinking aid: 2 parts by mass

[0090] Crosslinking reagent: 1.5 parts by mass

[0091] The kneaded rubber composition is formed into a sheet material, and then the kneaded rubber composition is wound around the surface of a core member made of stainless steel and having a diameter of 8 mm, and then the kneaded rubber composition is compression-molded to form a layer made of crosslinked chlorinated ether rubber. Then, a grinding machine is used to grind the surface of the layer to form an elastic layer having a thickness of 2.0 mm. During the grinding process, after the thickness of the elastic layer becomes a predetermined thickness, the rotational speed of the grinding wheel of the grinding machine is sequentially increased from 1000 rpm to 2000 rpm and 3000 rpm to grind the surface of the elastic layer by dry grinding, thereby minimizing the surface roughness of the elastic layer.

[0092] The hardness of the obtained elastic layer is measured using a "Type A" durometer in accordance with JIS K 6253 or ISO 7619; as a result, the measured hardness is in the range of 50° to 64°.

[0093] Manufacture of the surface layer

[0094] First, a coating liquid for forming the surface layer is prepared. The coating liquid includes the following components.

[0095] Ethyl acetate used as a diluting solvent

[0096] A urethane resin (polyol ("T5650E" manufactured by Asahi Kasei Chemicals Corporation) and isocyanurate ("TPA-100" manufactured by Asahi Kasei Chemicals Corporation)) used as a resin material

[0097] A carbon dispersion liquid used as a conductive material ("MHI-BK" manufactured by Mikuni Shikiso Co., Ltd. (carbon content by mass is 20% to 30%))

[0098] An acrylic silicone resin polymer used as an additive ("Modifier FS700" manufactured by NOF Corporation)

[0099] Urethane beads used as a surface roughness imparting agent ("C-600" manufactured by Negami Chemical Industry Co., Ltd.), with an average particle size of 10 microns and a density of 1160 kg / m 3

[0100] The coating liquid is stirred for 3 hours using a ball mill, and the coating liquid has the above-described components in an appropriate combined ratio.

[0101] A conductive roller is formed by forming a surface layer on the outer surface of the above-described elastic layer using the coating liquid. Specifically, the stirred coating liquid is applied to the outer surface of the elastic layer by spraying, and then the stirred coating liquid is dried in an electric furnace at 120 °C for 60 minutes to form a surface layer with an average thickness of 4.5 microns.

[0102] The amount of the coating liquid for each conductive roller is 2.1 g. Therefore, based on the amount of the coating liquid used and the combined ratio of the surface roughness imparting material in the above-described coating liquid, the number of particles of the surface roughness imparting material included in the surface layer of a single conductive roller is calculated; as a result, the calculated value is 1×10 8 particles per roller.

[0103] The outer diameter of the elastic layer is 9.5 mm, and the coating liquid is applied to an area of the elastic layer that has a length of 225 mm in the axial direction of the elastic layer. Accordingly, based on the area to which the coating liquid is applied (in other words, the area of the surface layer becomes 9.5×π×225 [mm 2 ), the number of particles of the surface roughness imparting material per unit area of the surface layer is calculated; as a result, the calculated value is 1.5×10 4 [particles / mm 2 .

[0104] The average thickness of the surface layer is measured by the following method: First, the cross-section of the elastic layer and the cross-section of the surface layer (the cross-section of the elastic layer and the cross-section of the surface layer are taken along a line in the thickness direction of the elastic layer and the surface layer) are observed with a laser microscope (“VK-X200” manufactured by Keyence Corporation), then the distances from the surface of the conductive roller to the boundary between the surface layer and the elastic layer are measured at 20 different points in the circumferential direction of the conductive roller, and then the average value of the measured distances is calculated.

[0105] A-2. Second to Seventh Examples, and First to Third Comparative Examples

[0106] The conductive rollers according to the Second to Seventh Examples and the conductive rollers according to the First to Third Comparative Examples are manufactured in substantially the same manner as in the First Example, except that the combined ratio of the components of the coating reagent is changed so that the average particle size of the surface roughness imparting material, the number of particles of the surface roughness imparting material, and the average thickness of the surface layer in the surface layer are the values listed in Table 1. The combined ratio of the components of the coating reagent is adjusted so that the amount of the coating liquid used for each conductive roller is 2.1 g.

[0107] [Table 1]

[0108] Table 1

[0109]

[0110] Table 1 lists the average particle size of the surface roughness imparting material, the number of particles of the surface roughness imparting material, and the average thickness of the surface layer for each of the Examples and each of the Comparative Examples, and the results of the evaluations described below.

[0111] In the fourth, fifth, and seventh examples, urethane beads ("C-800" manufactured by Negami Chemical Industry Co., Ltd.) were used as the surface roughness imparting material with an average particle size of 6 μm. In the second and third examples, urethane beads ("C-400" manufactured by Negami Chemical Industry Co., Ltd.) were used as the surface roughness imparting material with an average particle size of 15 μm.

[0112] B. Evaluation of the conductive roller

[0113] The image non-uniformity of the images printed by a copying machine ("bizhub C3850" manufactured by Konica Minolta, Inc.) was evaluated. The copying machine used the conductive roller according to each example in the examples or each comparative example in the comparative examples as the charging roller. The copying machine is a color multifunctional printer (MFP, multifunctional printer), and the color multifunctional printer is configured to use a voltage that is a DC voltage as the charging voltage.

[0114] In the evaluation described below, the normal charging voltage was measured with a tester, and then a voltage 100 V lower than the normal charging voltage was applied to the charging roller as the charging voltage through an external power supply. Printing was performed at a printing rate of 38 sheets per minute at an ambient temperature of 23°C and a humidity of 55%.

[0115] B-1. Whether there is image non-uniformity caused by partial discharge

[0116] A halftone image was printed, and then the evaluation was performed by visually determining whether there were white dots, black dots, white streaks, or black streaks based on the following criteria. The white dots, black dots, white streaks, or black streaks appeared as image non-uniformity caused by partial discharge on the printed image. A summary of the evaluation results is shown in Table 1 described above.

[0117] <Standard>

[0118] P: There is no image non-uniformity caused by partial discharge.

[0119] F: There is image non-uniformity caused by partial discharge.

[0120] B-2. Whether there is image non-uniformity caused by fouling

[0121] A pure white image was printed, and then the L* value (brightness) was measured at seven points of each pure white image with a colorimeter ("CR-400" manufactured by Konica Minolta, Inc.). Then, based on the measurement results, the evaluation was performed by determining whether there was image non-uniformity caused by fouling according to the following criteria. A summary of the evaluation results is shown in Table 1 described above.

[0122] <Standard>

[0123] P: No fouling (L* is equal to or greater than 95.5)

[0124] F: Fouling exists (L* is less than 95.5)

[0125] "Fouling" is also referred to as "fog" and means printing on non-printing areas. When fouling appears on a printed pure white image, the brightness of the printed image decreases.

[0126] B-3. Overall evaluation

[0127] When the evaluations in B-1 described above and the evaluations in B-2 described above are both P, the overall evaluation is limited to P, and in cases other than those described above, the overall evaluation is limited to F. A summary of the evaluation results is shown in Table 1 described above.

[0128] From the above evaluation results, it can be understood that image non-uniformity can be reduced in each of the examples shown in Table 1. In contrast, image non-uniformity appears in each of the comparative examples.

[0129] Description of reference numerals

[0130] 10… Photosensor, 20… Charging device, 21… Charging roller, 21a… Core member, 21b… Elastic layer, 21c… Surface layer, 21c1… Conductive part, 21c2… Surface roughness imparting material, 30… Exposure device, 40… Developing device, 41… Container, 42… Developing roller, 43… Toner supply roller, 44… Regulation blade, 50… Transfer device, 51… Transfer roller, 60… Cleaning device, 61… Cleaning blade, 62… Collector, 100… Image forming apparatus, AX… Axis, G… Discharge gap, L… Distance between discharge points, M… Recording medium, N… Imprinting part, R1… Area, Sm… Average spacing between peaks, T… Toner.

Claims

1. A detection method for a conductive roller, the detection method being a detection method for determining whether the characteristics of the conductive roller are good, the conductive roller comprising: A core member, the core member including an outer surface that extends along and around an axis of the core member; and a surface layer disposed along the outer surface of the core member, the surface layer including: a conductive portion; and a surface roughness imparting material in the form of particles dispersed in the conductive portion, the surface roughness imparting material having an average particle size in a range greater than or equal to 6 micrometers and less than or equal to 10 micrometers, and the surface layer having an average thickness in a range greater than or equal to 3.0 micrometers and less than or equal to 15.0 micrometers, the detecting method comprising: calculating a number of particles of the surface roughness imparting material per unit area of the surface layer; and Based on the number of the particles being greater than or equal to 1.0×10 4 particles / mm 2 and less than or equal to 2.0×10 6 particles / mm 2 within the range, it is determined that the characteristics of the conductive roller are good.

2. The detecting method for a conductive roller according to claim 1, wherein: the surface layer is formed by curing or hardening a coating reagent including the surface roughness imparting material, calculating the number of particles includes calculating the number of particles of the surface roughness imparting material per unit area of the surface layer based on: the area of the surface layer; the inclusion rate of the surface roughness imparting material in the coating reagent, the mass of the coating reagent for forming the surface layer, and the average mass of each particle of the surface roughness imparting material.

3. A manufacturing method of a conductive roller, the conductive roller comprising: A core member, the core member including an outer surface that extends along and around an axis of the core member; and a surface layer disposed along the outer surface of the core member, the surface layer including: a conductive portion; and a surface roughness imparting material in the form of particles dispersed in the conductive portion, wherein the manufacturing method of the conductive roller includes: a step of forming the surface layer; and a step of determining whether the conductive roller is good, the surface roughness imparting material having an average particle size in a range greater than or equal to 6 micrometers and less than or equal to 10 micrometers, and the surface layer having an average thickness in a range greater than or equal to 3.0 micrometers and less than or equal to 15.0 micrometers, the step of determining whether the conductive roller is good includes: calculating a number of particles of the surface roughness imparting material per unit area of the surface layer; and Based on the particles of the material imparted by the surface roughness per unit area of the surface layer being greater than or equal to 1.0×10 4 particles / mm 2 and less than or equal to 2.0×10 6 particles / mm 2 within the range, it is determined that the characteristics of the conductive roller are good.

4. The manufacturing method of the conductive roller according to claim 3, wherein, the surface layer is formed by curing or hardening a coating reagent including the surface roughness imparting material, calculating the number of particles of the surface roughness imparting material per unit area of the surface layer based on: the area of the surface layer; the inclusion rate of the surface roughness imparting material in the coating reagent; the mass of the coating reagent for forming the surface layer; and the average mass of each particle of the surface roughness imparting material.

5. The manufacturing method of the conductive roller according to claim 3 or 4, wherein, The conductive roller further includes a conductive elastic layer disposed between the core member and the surface layer.

6. The manufacturing method of the conductive roller according to claim 3 or 4, wherein, The surface roughness imparting material is formed of an insulating material.

7. The manufacturing method of the conductive roller according to claim 3 or 4, wherein, The conductive portion is formed of a resin composition including a resin material and a conductive reagent.

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