Elastic roller

Abstract

To provide an elastic roller which can suppress image fogging and roughness.SOLUTION: The present invention relates to an elastic roller 1 comprising a shaft 2, an elastic layer 3 provided on an outer periphery of the shaft 2, and a coating layer 4 provided on an outer periphery of the elastic layer 3, a surface of the coating layer 4 having an expanded area ratio Sdr in a range of 0.2 to 1.2, inclusive. The coating layer 4 contains a roughness material that may preferably be at least either of silicone particles and urethane resin particles.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an elastic roller. [Background technology]

[0002] Developing rollers used in electrophotographic image forming apparatuses such as copying machines, printers, and facsimiles have the function of applying a uniform frictional charge to toner and transporting a predetermined amount of toner stably to a development area. In recent years, efforts have been made to lower the melting point of toner used in electrophotographic copying machines in order to reduce power consumption and achieve high-speed printing.

[0003] Low melting point toner is easily melted by frictional heat caused by the pressure of the developing roller and other regulating members, and there is a problem that the melted toner adheres to the developing roller. Furthermore, in a high temperature and high humidity environment, the chargeability of the toner itself tends to decrease due to the influence of moisture, so at the end of the durability period, a phenomenon called fogging occurs in which the insufficiently charged toner adheres to the white part (background part) of the image.

[0004] In addition, the particle size distribution of the toner is broad, so that small and large particle toner particles are mixed together. When this pulverized toner is charged by friction and contact charging, the small particle toner particles, which are easily charged, are preferentially attached to the roller surface and consumed, so that as printing progresses, a large amount of large particle toner particles remain, causing roughness in the image quality and deteriorating the image quality.

[0005] In order to solve the adhesion and accumulation of toner and various problems caused by it, for example, Patent Document 1 discloses providing recesses in an elastic layer by using a laser. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-107147 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to meet the demand for higher speed image forming apparatuses, it is desired to improve image fog and roughness to a higher level than the invention described in Patent Document 1. The present invention has been made in view of the above circumstances, and has an object to provide an elastic roller capable of suppressing fog and roughness in an image. [Means for solving the problem]

[0008] The inventors discovered that by forming unevenness with high kurtosis on the surface of the roller and increasing the developed area ratio, the difference in the frequency of contact between small and large particle toners with the roller surface is eliminated, and the large particle toner also becomes charged. They also discovered that this allows the toner to adhere uniformly to the roller surface and be consumed, so that image quality does not decrease even as printing progresses, leading to the invention.

[0009] In other words, the present invention is an elastic roller comprising a shaft body, an elastic layer provided on the outer periphery of the shaft body, and a coating layer provided on the outer periphery of the elastic layer, wherein the developed area ratio Sdr of the surface of the coating layer is 0.2 or more and 1.2 or less.

[0010] The arithmetic mean height Sa of the surface is preferably 0.80 μm or more and 2.50 μm or less.

[0011] The surface kurtosis Sku is preferably 3 or more.

[0012] The coating layer preferably contains a urethane resin.

[0013] The coating layer contains a roughness material, and the roughness material is preferably at least one of silicone rubber particles or urethane resin particles.

[0014] The elastic roller is preferably a development roller. Effect of the Invention

[0015] According to the present invention, it is possible to provide an elastic roller capable of suppressing fog and roughness in an image. [Brief description of the drawings]

[0016] [Figure 1] 1 is a perspective view showing an embodiment of an elastic roller of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. [Elastic roller] 1, an elastic roller 1 of the present invention includes a shaft 2, an elastic layer 3 provided on the outside of the shaft 2, and a coating layer 4 provided on the outside of the elastic layer 3. Each of the components will be described in detail below.

[0018] <Shaft body> The shaft body 2 may preferably be a shaft body having conductive properties and used in a conventionally known elastic roller. The shaft body 2 is preferably made of at least one metal selected from the group consisting of iron, aluminum, stainless steel, and brass. Such a shaft body 2 is generally also known as a "core metal."

[0019] The shaft body 2 may contain an insulating resin. The insulating resin may be, for example, a thermoplastic resin or a thermosetting resin. The shaft body 2 may include, for example, a core body made of an insulating resin and a plating layer provided on the core body. Such a shaft body 2 can be obtained, for example, by plating a core body made of an insulating resin to make it conductive. The shaft body 2 is preferably a core bar in order to obtain good electrical conductivity.

[0020] The shape of the shaft body 2 is preferably, for example, rod-like, tubular, etc. The cross-sectional shape of the shaft body 2 may be, for example, circular, elliptical, or non-circular, such as polygonal. The outer peripheral surface of the shaft body 2 may be subjected to treatment such as cleaning treatment, degreasing treatment, and primer treatment.

[0021] The axial length of the shaft body 2 is not particularly limited, and may be adjusted as appropriate depending on the type of the image forming apparatus in which it is installed. The diameter (diameter of the circumscribing circle) of the shaft body 2 is also not particularly limited, and may be adjusted as appropriate depending on the type of the image forming apparatus in which it is installed.

[0022] <Elastic layer> The elastic layer 3 is provided on the outer periphery of the shaft body 2. For example, when the elastic roller 1 is a developing roller, the elastic layer 3 is provided in order to impart to the developing roller hardness and elasticity that allows it to be pressed against the photosensitive member with an appropriate nip width and nip pressure so that the toner can be supplied just enough to the electrostatic latent image formed on the surface of the photosensitive member. Various rubber materials can be used for the elastic layer 3. Examples of rubbers used for the rubber material include ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), fluororubber, silicone rubber, epichlorohydrin rubber, NBR hydride, and urethane rubber. These can be used alone or in combination of two or more. Among these, silicone rubber is preferable from the viewpoint of reducing damage to the toner and compressive stress distortion due to pressing. Examples of silicone rubber include polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polyphenylvinylsiloxane, and copolymers of these siloxanes. When the elastic layer 3 is made of silicone rubber, it may be a cured product of the rubber composition shown below.

[0023] (Rubber composition) The rubber composition preferably contains a rubber component that forms a silicone rubber by crosslinking, such as a silicone raw rubber such as organopolysiloxane.

[0024] As the organopolysiloxane, for example, there can be mentioned an organopolysiloxane represented by the following average composition formula. RnSiO (4-n) / 2 [R represents a monovalent hydrocarbon group which may be substituted. The number of carbon atoms in the hydrocarbon group is preferably 1 to 12, more preferably 1 to 8. Multiple R's may be the same or different. n represents a number of 1.95 to 2.05.]

[0025] Examples of R in the above formula include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl groups; cycloalkyl groups such as cyclohexyl groups; alkenyl groups such as vinyl, allyl, butenyl, and hexenyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as β-phenylpropyl groups; and organic groups in which some or all of the hydrogen atoms bonded to the carbon atoms of the above groups have been substituted with halogen atoms, cyano groups, or the like, such as chloromethyl, trifluoropropyl, and cyanoethyl groups.

[0026] The organopolysiloxane is preferably an organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule. For example, in the above formula, it is preferable that at least two R have the above alkenyl group. It is more preferable that the organopolysiloxane has a vinyl group.

[0027] Specific examples of organopolysiloxane include dimethylpolysiloxane, diphenylpolysiloxane, etc. It is preferable that the molecular chain terminals of the organopolysiloxane are blocked with a trimethylsilyl group, a dimethylvinylsilyl group, a dimethylhydroxysilyl group, a trivinylsilyl group, etc.

[0028] The rubber composition may contain various additives, such as an auxiliary agent such as a conductivity imparting agent, a chain extender, and a crosslinking agent, a catalyst such as an addition reaction catalyst, a reaction control agent, a dispersant, an antiaging agent, an antioxidant, a filler, a pigment, a colorant, a processing aid, a softener, a plasticizer, an emulsifier, a heat resistance improver, a flame retardant improver, an acid acceptor, a thermal conductivity improver, a release agent, and a solvent.

[0029] The rubber composition may be a liquid rubber composition or a millable type rubber composition.

[0030] The rubber composition for forming the elastic layer may contain various additives, such as an auxiliary such as a conductivity imparting agent, a chain extender, and a crosslinking agent, a catalyst such as an addition reaction catalyst, a reaction control agent, a dispersant, an antiaging agent, an antioxidant, a filler, a pigment, a colorant, a processing aid, a softener, a plasticizer, an emulsifier, a heat resistance improver, a flame retardant improver, an acid acceptor, a thermal conductivity improver, a release agent, and a solvent.

[0031] When forming the elastic layer 3 made of silicone rubber, it may be formed by a liquid silicone rubber composition using a LIMS (Liquid Injection Molding System) method, or it may be formed by injection molding using a millable silicone rubber composition. When a millable silicone rubber composition is used, it is preferable that the surface of the elastic layer is polished.

[0032] The elastic layer 3 is preferably a solid layer, and preferably has no hollow space inside the layer. In this specification, "solid" means that the layer has a hollow space of 0.1 mm or less inside. 2 This means that the material does not have more than one hollow space.

[0033] The JIS A hardness (JIS K 6301) of the elastic layer 3 is preferably 20 or more and 55 or less. When the JIS A hardness of the elastic layer 3 is within the above range, the contact area (nip width) between the elastic roller 1 and the contacted body (for example, an image carrier such as a photoconductor) becomes large, which tends to further improve the transfer efficiency, charging efficiency, development efficiency, and other performances. In addition, the possibility of mechanically damaging the contacted body is reduced.

[0034] The thickness of the elastic layer 3 is preferably 0.5 mm or more and 10 mm or less, and more preferably 1 mm or more and 5 mm or less, from the viewpoint of ensuring a uniform nip width with the contacted body when in contact with the contacted body. In the present invention, the "thickness" refers to the thickness of the elastic roller 1 in a direction perpendicular to the axial direction. The outer diameter of the elastic layer 3 is not particularly limited. The outer diameter may be, for example, 5 mm or more and 20 mm or less. In this specification, the "outer diameter" refers to the outer diameter of the elastic roller 1 in a cross section perpendicular to the axial direction. The thickness and outer diameter of the elastic layer 3 can be adjusted by methods such as adjusting the amount of rubber composition used when forming the elastic layer 3, or polishing or grinding the outer peripheral surface of the elastic layer 3 after forming the elastic layer 3.

[0035] The outer peripheral surface of the elastic layer 3 may be subjected to a surface treatment such as a primer treatment, a corona treatment, a plasma treatment, an excimer treatment, a UV treatment, an ITO treatment, or a frame treatment.

[0036] (Resistance value of elastic layer) The resistance value of the elastic layer 3 is 1×10 1 Ω or more 1×10 7 By adjusting the resistance value of the elastic layer 3 to fall within this range, it is possible to stabilize the chargeability of the developer, particularly in the initial stage (for example, from 1 to 500 sheets), and to suppress a decrease in print density. The resistance value of the elastic layer 3 is 1×10 3 Ω or more 1×10 7 Ω or less is preferable, and 1×10 4 Ω or more 5×10 6It is more preferable that it is Ω or less. The resistance value of the elastic layer is measured by the measurement method in the examples described later.

[0037] <Coating layer> The coating layer 4 can be formed by applying and curing a resin composition for forming a coating layer, which contains the following (A) polyol, (B) isocyanate compound, (C) roughness material, and (D) dilution solvent.

[0038] (A) Polyol As the polyol, an acrylic polyol, a silicone polyol, or the like can be used. The carbonate polyol, the fluorine polyol, and the hydrogenated butadiene polyol react with the first isocyanate compound described above or the second isocyanate compound described below to form a polyurethane. In the present invention, these polyols may be used alone or in combination. As the polyols to be used, it is preferable to use the carbonate polyol and the fluorine polyol alone or in combination.

[0039] The carbonate polyol and / or the fluorine polyol is preferably 5 parts by mass or more and 40 parts by mass or less, more preferably 15 parts by mass or more and 25 parts by mass or less, based on 100 parts by mass of the both-end-modified silicone oil. As these polyols, commercially available products can be used.

[0040] (B) Isocyanate compound As the (B) isocyanate compound used in the resin composition for forming the coating layer, various isocyanate compounds (e.g., aromatic isocyanate compounds, aliphatic isocyanate compounds, alicyclic isocyanate compounds) that are usually used in the preparation of polyurethane can be used. Examples of aromatic isocyanate compounds include 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, polymethylene polyphenylene polyisocyanate, tolidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), and 3,3'-dimethylbiphenyl-4,4'-diisocyanate. Examples of the aliphatic isocyanate compound include hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornene diisocyanate methyl (NBDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), etc. Examples of the alicyclic polyisocyanate include transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), H12MDI (hydrogenated MDI), 4,4'-dicyclohexylmethane diisocyanate, etc.

[0041] In the present invention, the amount of the (B) isocyanate compound in the mixed liquid used to form the coating layer 4 is preferably used so that the reaction rate of the isocyanate compound is 80% or more and 126% or less, preferably 95% or more and 112% or less.

[0042] (C) Roughness material The resin composition for forming the coating layer contains (C) a roughness material. The roughness material contains silicone rubber particles and / or acrylic particles. The particle diameter of the silicone rubber particles and acrylic particles is preferably 0.2 μm or more and 10 μm or less, and more preferably 0.8 μm or more and 5 μm or less. By making the particle diameter of the silicone rubber particles and acrylic particles within the above range, the surface roughness of the elastic roller 1 is appropriately maintained, and the developer transportability is kept good, while the resolution is maintained at a high level, and deterioration of the image quality can be prevented. The particle diameter of the silicone rubber particles and acrylic particles can be measured by observing the cross section with a microscope after cutting the elastic roller 1.

[0043] The roughness material used in the present invention, silicone rubber particles and acrylic particles, preferably have heat resistance such that they do not deform or melt even at temperatures of 100° C. or higher, and more preferably have heat resistance at temperatures from 130° C. to 180° C. This makes it possible to prevent the silicone rubber particles and acrylic particles from deforming even at the crosslinking temperature of the coating layer 4. The heat resistance of the silicone rubber particles and acrylic particles can be evaluated by confirming that the silicone rubber particles and acrylic particles do not melt and flow out even when pressure and heat are applied in a melt flow indexer.

[0044] The silicone rubber particles and the acrylic particles may be present (embedded) in the coating layer 4, or a part of them may protrude from the surface of the coating layer 4. In addition, the silicone rubber particles and the acrylic particles may be unevenly dispersed in the coating layer 4, or may be unevenly distributed on the surface side of the coating layer 4.

[0045] Of the silicone rubber particles and the acrylic particles, the silicone rubber particles are preferably those having a structure in which organopolysiloxane such as dimethylpolysiloxane or polyorganosilsesquioxane is crosslinked, and the acrylic particles may be commercially available acrylic particles.

[0046] It is preferable that the silicone rubber particles are prepared from an organopolysiloxane or organopolysilsesquioxane having, as an organic group, one or more monovalent organic groups having 1 to 20 carbon atoms selected from the following: alkyl groups, such as methyl groups, ethyl groups, propyl groups, and butyl groups; aryl groups, such as phenyl groups and tolyl groups; alkenyl groups, such as vinyl groups and allyl groups; aralkyl groups, such as β-phenylethyl groups and β-phenylpropyl groups; monovalent halogenated hydrocarbon groups, such as chloromethyl groups and 3,3,3-trifluoropropyl groups; and reactive group-containing organic groups, such as epoxy groups, amino groups, mercapto groups, acryloxy groups, and methacryloxy groups. The particles prepared from these organopolysiloxanes or organopolysilsesquioxanes may be surface-treated with an organoalkoxysilane. Examples of such silicone rubber particles that can be used include "KMP-597" manufactured by Shin-Etsu Chemical Co., Ltd., and "EP-5500", "EP-2600", "EP-2601", "E-2720", "DY 33-430M", "EP-2720", "EP-9215 Cosmetic Powder", and "9701 Cosmetic Powder" manufactured by Dow Corning Toray Co., Ltd.

[0047] The amount of silicone rubber particles and / or acrylic particles used is preferably 15 parts by mass or more and 40 parts by mass or less, and more preferably 20 parts by mass or more and 35 parts by mass or less, relative to 100 parts by mass of the resin composition for forming the coating layer. By setting the amount of silicone rubber particles and / or acrylic particles used within the above range, the surface roughness of the elastic roller 1 is appropriately maintained, developer transportability is kept good, while the resolution is maintained at a high level, and deterioration of image quality can be prevented.

[0048] (D) Diluent solvent As the dilution solvent, aqueous solvents and organic solvents can be used, and low-boiling point solvents and high-boiling point solvents can be used in combination depending on the required drying speed.

[0049] In the present invention, the solid content concentration in the resin composition for forming a coating layer is preferably in the range of 10% by mass to 50% by mass, more preferably in the range of 20% by mass to 40% by mass, based on the total amount of the resin composition for forming a coating layer. If the solid content concentration is low, dripping is likely to occur during application and drying takes a long time, while if the solid content concentration is high, the coating surface becomes rough and thickness control becomes difficult.

[0050] In the present invention, it is preferable to use a dilution solvent that swells the above-mentioned silicone rubber particles or acrylic particles, which allows the silicone rubber particles or acrylic particles to swell in the mixed liquid, making it possible to form a coating layer 4 that is free of repellency or dents, and also to suppress the sedimentation of the silicone rubber particles or acrylic particles in the mixed liquid.

[0051] As such a dilution solvent, it is preferable to use an organic solvent such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), tetrahydrofuran (THF), acetone, ethyl acetate, butyl acetate, toluene, xylene, heptane, cyclohexanone, or isophorone.

[0052] (Sdr: development area ratio) The surface area ratio Sdr of the coating layer 4 is 0.2 or more and 1.2 or less. By setting the surface area ratio Sdr to 0.2 or more and 1.2 or less, the contact frequency with the large particle size toner can be improved, and the contact frequency with the small particle size toner can be obtained. It is more preferable that Sdr is 0.4 or more and 1.0 or less. The developed area ratio Sdr can be measured by the following method. <Measurement method> The coating layer 4 of each sample at the center of the roller longitudinal direction was photographed using a non-contact laser microscope "VK-X1000" manufactured by Keyence Corporation. The magnification was 1200x. Next, the geometric data obtained from the photograph was corrected for quadratic curves using Version 3.8.0.0 of the multi-file analysis application "VK-H1XA" manufactured by Keyence Corporation, and the developed area ratio Sdr of the surface properties was calculated based on the obtained data in the photographed field of view. The cutoff values ​​λs and λc were set to "none" for the calculation.

[0053] (Sa: arithmetic mean roughness) The arithmetic mean roughness Sa of the surface of the coating layer 4 is preferably 0.80 μm or more and 2.50 μm or less, and more preferably 1.00 μm or more and 2.20 μm or less. By having the arithmetic mean roughness Sa of 0.80 μm or more and 2.50 μm or less, the toner transport amount is 0.45 mg / cm, which is an appropriate value. 2 More than 0.60mg / cm 2 The result is as follows. The arithmetic mean roughness Sa can be measured by the following method. <Measurement method> The coating layer 4 of each sample at the center of the roller longitudinal direction was photographed using a non-contact laser microscope "VK-X1000" manufactured by Keyence Corporation. The magnification was 1200x. Next, the geometric data obtained from the photograph was corrected for quadratic curves using Version 3.8.0.0 of the multi-file analysis application "VK-H1XA" manufactured by Keyence Corporation, and the surface roughness parameter surface roughness Sa was calculated based on the obtained data in the photographed field of view. The cutoff values ​​λs and λc were set to "none" for the calculation.

[0054] (Sku: Kurtosis) The surface kurtosis Sku is preferably 3 or more, more preferably 3.5 or more. When the kurtosis Sku is 3 or more, unevenness with large kurtosis is formed, so that the contact with small particle size toner and large particle size toner is good. Therefore, the toner can be uniformly attached to the roller surface, and a high quality image can be obtained. Kurtosis Sku can be measured by the following method. <Measurement method> The coating layer 4 at the center of the roller longitudinal direction of each sample was photographed using a non-contact laser microscope "VK-X1000" manufactured by Keyence Corporation. The magnification was 1200x. Next, quadratic curve correction was performed on the geometric data obtained from the photograph using Version 3.8.0.0 of the multi-file analysis application "VK-H1XA" manufactured by Keyence Corporation, and the surface roughness parameter kurtosis Sku was calculated based on the obtained data in the photographed field of view. The cutoff values ​​λs and λc were also set to "none" for the calculation.

[0055] The elastic roller of the present invention has a surface development area ratio Sdr of 0.2 or more and 1.2 or less, thereby eliminating the difference in frequency of contact between small particle size toner and large particle size toner with the roller surface, and since large particle size toner is charged as well as small particle size toner, the toner adheres uniformly to the roller surface and is consumed, so that even as printing progresses, a good image free of fogging and roughness can be obtained. EXAMPLES

[0056] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below.

[0057] [Examples 1 to 12 and Comparative Examples 1 to 6] A developing roller was produced as an example of an elastic roller by the following procedure.

[0058] (Formation of primer layer) The electroless nickel-plated shaft (made of SUM22, diameter 7.5 mm, length 274.1 mm) was washed with ethanol, and its surface was coated with a silicone primer (product name "Primer No. 16", made by Shin-Etsu Chemical Co., Ltd.). The primer-treated shaft was baked in a gear oven at 150°C for 10 minutes and then cooled at room temperature for 30 minutes or more to form a primer layer on the outer circumferential surface of the shaft.

[0059] (Formation of elastic layer) An elastic body made of a rubber material was molded on the outer circumferential surface of the shaft by extrusion molding using a rubber composition made of silicone rubber. In the extrusion molding, the rubber composition made of silicone rubber was heated at 360°C for 5 minutes using an infrared heating furnace (IR furnace), and then heated at 200°C for 4 hours using a gear oven to harden it. As a result, an elastic layer made of a hardened product of the rubber composition was formed on the outer circumferential surface of the shaft treated with the primer. The elastic layer was a solid layer and the thickness of the elastic layer was 4.25 mm.

[0060] (Formation of coating layer) -Preparation of resin composition for forming coating layer- (A) Polyol: Product name "Kuraray Polyol P-2010" (manufactured by Kuraray Co., Ltd.) (B) Isocyanurate: Trade name "Duranate TPA-100" (manufactured by Asahi Kasei Corporation) (C) Roughness material: silicone rubber particles (DOWSIL EP-2601 TM Powder, average particle size 2μm, manufactured by Dow Toray Co., Ltd.) (D) n-Butyl acetate

[0061] The resin composition for the covering layer was applied to the outer peripheral surface of the elastic layer by spray coating, and heated at 170° C. for 20 minutes to form a covering layer having a thickness of 10 μm. In this manner, a developing roller having a shaft body, an elastic layer, and a covering layer was manufactured.

[0062] [evaluation] The following evaluations were carried out for the above-mentioned Examples and Comparative Examples. The evaluation results are shown in Table 1.

[0063] (Measurement of Sdr, Sa, Sku) The coating layer 4 at the center of the longitudinal direction of the developing rollers produced in the above examples and comparative examples was photographed at a magnification of 1200 times using a non-contact laser microscope "VK-X1000" manufactured by Keyence Corporation. Next, quadratic curve correction was performed on the geometric data obtained by the photographing using Version 3.8.0.0 of the multi-file analysis application "VK-H1XA" manufactured by Keyence Corporation, and based on the obtained data, the cutoff values ​​λs and λc were set to "none" in the photographed field of view, and the developed area ratio Sdr, surface roughness Sa, and kurtosis Sku were calculated.

[0064] (Rough printing) The developing rollers prepared in the above examples and comparative examples were mounted on an image forming apparatus "HL-L2360DN (manufactured by Brother Industries, Ltd.)" and printed 4000 sheets at 1.0% duty in a low temperature and low humidity environment (10°C 20% RH), after which a solid black print was performed to confirm the print density. The density was measured using an X-Rite504 spectrodensitometer manufactured by X-Rite Corporation. For the evaluation of roughness, a print density of 1.44 or less was rated as A, 1.45 to 1.48 was rated as B, and 1.49 or more was rated as C, with a rating of A or above being considered a pass. A: 1.44 or less B: 1.45 or more and 1.48 or less C:1.49 or higher

[0065] (Method of evaluating fogging) The developing rollers prepared in the above examples and comparative examples were mounted on an image forming apparatus "HL-2360DN (manufactured by Brother Industries, Ltd.)" and solid white printing was performed in a high temperature and high humidity environment (32°C, 80% RH). The solid white printing was instantly stopped, and tape was attached to the photosensitive drum and transferred onto white paper. Tape was attached to a reference paper, and the color difference ΔE between the reference value and the transferred portion was measured. A: ΔE is less than 1.0 B: ΔE is 1.0 or more and less than 1.5 C: ΔE is 1.5 or more

[0066] [Table 1]

[0067] [Table 2]

[0068] As shown in Tables 1 and 2, the examples in which the developed surface area ratio Sdr of the coating layer was 0.2 or more and 1.2 or less were favorable in the evaluation of rough printing and fogging. [Explanation of symbols]

[0069] 1 Elastic roller 2-axis body 3 Elastic layer 4 Covering layer

Claims

1. The shaft body includes an elastic layer provided on an outer periphery of the shaft body, and a coating layer provided on an outer periphery of the elastic layer, The elastic roller has a developed surface area ratio Sdr of the coating layer of 0.2 or more and 1.2 or less.

2. 2. The elastic roller according to claim 1, wherein the arithmetic mean height Sa of the surface is 0.80 μm or more and 2.50 μm or less.

3. 2. The elastic roller according to claim 1, wherein the kurtosis Sku of the surface is 3 or more.

4. 2. The elastic roller according to claim 1, wherein the coating layer contains a urethane resin.

5. The coating layer contains a roughness material, 2. The elastic roller according to claim 1, wherein the roughness material is at least one of silicone rubber particles and urethane resin particles.

6. 2. The elastic roller according to claim 1, wherein the elastic roller is a developing roller.

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