CHARGING MEMBER WITH COATING LAYER

BACKGROUND

[0001] Some image forming apparatuses include a photoreceptor, a charging device, an exposure device which forms an electrostatic latent image on the photoreceptor, a development device which applies a toner onto the electrostatic latent image to develop a toner image, and a transfer device to transfer the toner image formed on the photoreceptor to a transfer material. The charging device includes a charging member to charge the photoreceptor.

BRIEF DESCRIPTION OF DRAWINGS

[0002] FIG. 1 is a schematic cross-sectional view of an example charging member.

FIG. 2 is a schematic cross-sectional view illustrating an enlarged portion of the example charging member of FIG. 1.

DETAILED DESCRIPTION

[0003] Hereinafter, examples of a charging member will be described with reference to the drawings. In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. In addition, the dimensional ratio of each constituent is not limited to the illustrated ratio. In addition, a value noted with "approximately" indicates a range including the value and the vicinity of the value. Accordingly, the value

SUBSTITUTE SHEET (RULE 26) indicated with "approximately", in some exampies, may correspond to the exact value (excluding "approximately"). In addition, a numerical range indicated by using "to" indicates a range including numerical values before and after "to" as the minimum value and the maximum value, respectively.

[0004] Charging Member and Image Forming Apparatus

An example charging member includes a conductive support and a conductive body mounted on the conductive support. The conductive body includes an elastic layer located on the conductive support, a resin layer located on the elastic layer, and a coating layer located on the resin layer. The coating layer has a refractive index of approximately 1.10 to 1.42 and forms the outermost surface (a surface to be in contact with a photoreceptor) of the conductive body.

[0005] In an example image forming apparatus, the example charging member has a surface (an outermost surface) that is pressed against the surface of the photoreceptor. In such a case, abnormal electrical discharge may occur from the surface of the charging member, and in a case where ozone is generated due to the occurrence of the abnormal electrical discharge, the surface of the photoreceptor may be degraded by the ozone, and photoreceptor abrasion may be likely to occur. However, the coating layer having the refractive index described above forms the surface of the charging member, so as to suppress the occurrence of the abnormal electrical discharge. Consequently, the amount of ozone generated due to the abnormal electrical discharge is suppressed, and the degradation of the surface of the photoreceptor due to the ozone and the photoreceptor abrasion are thereby suppressed.

[0006] The reason that the occurrence of the abnormal electrical discharge is suppressed by the coating layer having the refractive index described above is assumed to be as follows. First, as described above, it is assumed that a coating layer having a tow refractive index has a porous structure in which a cohesive force of the structures forming the iayer is weak. Since a porous portion in the coating iayer is a iayer filled with air, it can be said that the coating iayer has a refractive index close to a refractive index (1.0) of air. It is assumed that electric properties of a iayer having such a porous structure are close to material properties of a low dielectric constant, and it is assumed that an abnormal electrical discharge amount is suppressed as a result of including such a layer as the outermost layer of the charging member.

[0007] Hereinafter, examples of the charging member will be described by with reference to an example charging roller 10 illustrated in FIG. 1.

[0008] The example charging roller (which is the example charging member) 10 includes a conductive body 5, and a conductive support 1 that forms a rotation axis for the conductive body 5. The conductive body 5 is in the shape of a roller to rotate about a rotation axis line L of the conductive support 1 . The conductive body 5 is rotationally symmetric about the rotation axis line L.

[0009] The conductive body 5 includes a conductive base 6 including an elastic layer 2 that is in contact with the outer circumferential surface of the conductive support 1 and a resin layer 3 that is in contact with the outer circumferential surface of the elastic layer 2, and a coating layer 4 that is in contact with the outer circumferential surface of the resin layer 3. The elastic layer 2 and the resin layer 3 generally have conductivity. Therefore, the elastic layer 2 may be referred to as a conductive elastic layer, and the resin layer 3 may be referred to as a conductive resin layer. The coating layer 4 is a layer formed by coating and has insulating properties. Therefore, the coating layer 4 may be referred to as an insulating coating layer.

[0010] The resin layer 3 may be located around the elastic layer 2 via other layers. For example, an intermediate layer such as a resistance adjustment layer for increasing voltage resistance (leakage resistance) may be interposed between the elastic layer 2 and the resin layer 3.

[0011] The coating layer 4 may be located around the resin layer 3 via the other layers. However, an oriented state of a polymer (for example, polysilexane) forming the coating layer 4 may be changed in accordance with the type of layer that is in contact with the coating Sayer 4, and thus, a physical state (an irregular state) and chemical properties (surface free energy or the like) of the outermost surface may be changed. In a case where the coating layer 4 is formed to be directly in contact with the outer circumferential surface of the resin layer 3, contamination on the surface of the conductive body 5 due to the contact with the photoreceptor (for example, contamination due to an external additive) is more easily suppressed.

[0012] Conductive Support

The conductive support 1 may be any suitable conductive support that is formed of a metal having conductivity. In some examples, the conductive support 1 may be a hollow body (e.g., in the shape of a pipe or of a circular tube), a solid body (e.g., in the shape of a rod), or the like that is formed of a metal including iron, copper, aluminum, nickel, stainless steel, and the like. The outer circumferential surface of the conductive support 1 may be subjected to a plating treatment, in order to rustproof the conductive support 1 , or to impart scratch resistance to the extent that the conductivity is not impaired. In addition, the outer circumferential surface of the conductive support 1 may be coated with an adhesive agent, a primer, or the like, in order to increase adhesiveness with respect to the elastic layer 2. In such cases, the adhesive agent, the primer, or the like may be selected to have a suitable conductivity, in order to increase the conductivity of the conductive support 1.

[0013] The conductive support 1 , for example, may be in the shape of a cylinder having a length of approximately 250 mm to 360 mm. A portion of the conductive support 1 that is covered with the elastic layer 2, for example, is formed into the shape of a cylinder or a circular tube that extends along a rotation axis line L direction of the conductive support 1 (an extending direction of the conductive support 1 ), and may have a diameter (an outer diameter) that is constant in the rotation axis line L direction (in the shape of a straight cylinder or a straight circular tube). The diameter of the portion of the conductive support 1 that is covered with the elastic layer 2, for example, may be approximately 8 mm or more, and may be approximately 10 mm or less.

[0014] A portion of the conductive support 1 that is not covered with the elastic layer 2, namely, opposite end portions of the conductive support 1 are supported by a support member. In some examples, the diameter of the portion of the conductive support 1 that is not covered with the elastic layer 2 may be less than the diameter of the portion that is covered with the elastic layer 2. The conductive support 1 rotates about the rotation axis line (a center line of a cylinder) L of the conductive support 1 , in a state of being supported on the support member.

[0015] The conductive support 1 is biased (or urged) toward a photoreceptor such that the surface of the coating layer 4 is in contact with the surface of the photoreceptor. Namely, in order to push the surface of the coating layer 4 against the surface of the photoreceptor, respective loads may be applied to the opposite end portions of the conductive support 1 toward the photoreceptor. In order to achieve a more suitable coherence of the charging roller 10 with respect to the rotating photoreceptor, a load to be applied to each of the end portions of the conductive support 1 , may be approximately 450 g or more, and may be approximately 750 g or less, depending on examples.

[0016] Elastic Layer The elastic layer 2 may be any suitable elastic layer that has a suitable elasticity in order to provide uniform cohesiveness with respect to the photoreceptor. The elastic layer 2, for example, may be formed by using: natural rubber; synthetic rubber such as ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR), silicone rubber, a polyurethane-based elastomer, epichlorohydrin rubber, isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR), and chloroprene rubber (CR); a synthetic resin such as a polyamide resin, a polyurethane resin, and a silicone resin; and the like. Namely, the elastic layer 2 may include an elastic body containing such base polymers or cross-linked bodies thereof. A single type of the materials may be used, and two or more types thereof may be used in combination. In order to achieve a more uniform cohesiveness with respect to the photoreceptor, the base polymer may contain a rubber component (natural rubber or synthetic rubber) as a main component. For example, the base polymer may contain approximately 50 mass% or more of the rubber component, and may contain approximately 80 mass% or more of the rubber component.

[0017] In the base polymer, additives such as a conductive agent, a vulcanizing agent, a vulcanization promoter, a lubricant, and an auxiliary agent may be suitably compounded in order to impart suitable properties to the elastic layer 2. In order to form a more stable resistance, the elastic layer 2 (the elastic body) may contain epichlorohydrin rubber and a cross-linked body thereof as a main component. Namely, the elastic layer 2 may contain approximately 50 mass% or more of epichlorohydrin rubber or the cross-linked body thereof, and may contain approximately 80 mass% or more of epichlorohydrin rubber or the cross-linked body thereof.

[0018] Examples of the conductive agent include carbon black, graphite, potassium titanate, iron oxide, conductive titanium oxide (c-TiCh), conductive zinc oxide (c-ZnO), conductive tin oxide (c-SnCh), quaternary ammonium sait, and the like. Sulfur and the like may be used as the vulcanizing agent. Tetramethyl thiuram disulfide (CZ) and the like may be used as the vulcanization promoter. A stearic acid and the like may be used as the lubricant. Zinc flower (ZnO) and the like may be used as the auxiliary agent.

[0019] The thickness of the elastic layer 2 may be approximately 1.25 mm or more, and may be approximately 3.00 mm or less, in order to exhibit suitable elasticity.

[0020] Resin Layer

The resin layer 3 is a layer containing a resin. The resin layer 3 is a layer that is harder than the elastic layer, and for example, an elastic modulus of the resin layer 3 that is measurable on the basis of JIS K7162 is greater than the elastic modulus of the elastic layer. The resin layer 3 Is located on the elastic layer 2, so as to suppress the bleeding of a plasticizer or the like from the elastic layer 2 to the surface of the conductive body 5.

[0021] The resin layer 3 may form an irregular surface. Namely, the outer circumferential surface of the resin layer 3 may have an irregularity due to the resin layer 3. In a case where the resin layer 3 forms the irregular surface, the coating layer covers the irregular surface, and thus, the surface of the conductive body has an irregularity. Consequently, a discharge point can be sufficiently provided, and image quality can be improved. On the other hand, in a case where the surface of the conductive body has an irregularity, the abnormal electrical discharge is likely to occur in the convexities of the surface, and the degradation of the surface of the photoreceptor due to the ozone that is generated due to the abnormal electrical discharge and the photoreceptor abrasion thereby may be more likely to occur. However, in the charging roller 10, the surface is covered with the coating layer having a refractive index of approximately 1.10 to 1.42, and thus, the abnormal electrical discharge is less likely to occur, and the generation of the ozone due to the abnormal electrical discharge is also suppressed. Accordingly, in a case of using the charging roller 10, it is possible to suppress the degradation of the surface of the photoreceptor due to the ozone and the photoreceptor abrasion thereby while improving the image quality.

[0022] The resin layer 3, for example, as illustrated in FIG. 2, may contain a matrix material 30, and particles dispersed in the material. In FIG. 2, the particles include first particles 31 , and second particles 32 having a type different from that of the first particles 31. In FIG. 2, the resin layer 3 forms the irregular surface by containing the particles. In the present disclosure, such different types of particles refer to particles having different materials, different shapes, and the like. For example, even in a case where the material of the first particles 31 and the material of the second particles 32 are identical to each other, the first particles 31 and the second particles 32 are considered to be of different types when the shapes thereof are different from each other. According to some examples, the particles contained in the resin layer 3 may be of a same type of particles, or may be of three or more types of particles.

[0023] The matrix material 30 may contain a base polymer. For example, a polymer such as a fluorine resin, a polyamide resin, an acrylic resin, a nylon resin, a polyurethane resin, a silicone resin, a butyral resin, a styrene-ethylene-butylene-olefin copolymer (SEBC), and an olefin-ethylene-butylene-olefin copolymer (CEBC) may be used as the base polymer. A single type of the materials may be used, or two or more types thereof may be used together. In order to increase ease of handling, the freedom degree of material design (e.g., the range of materials that may be selected), or the like, the base polymer may be of at least one type selected from the group consisting of a fluorine resin, an acrylic resin, a nylon resin, a polyurethane resin, and a silicone resin according to some examples, or may be of at least one type selected from the group consisting of a nylon resin and a polyurethane resin according to other examples.

[0024] The content of the base polymer in the resin layer 3, for example, may be approximately 30 mass% or more, and may be approximately 90 mass% or less, relative to the total amount of the resin layer.

[0025] The matrix material 30 may further contain various conductive agents (conductive carbon, graphite, copper, aluminum, nickel, an iron powder, conductive tin oxide, conductive titanium oxide, an ion conductive agent, and the like), a charging control agent, and the like.

[0026] The particles (for example, the first particles 31 and the second particles 32) may be insulating particles. The particles may be resin particles, or may be inorganic particles. The particles may be any suitable particles that are capable of forming an irregularity with respect to the surface of the resin layer in order to sufficiently provide a discharge point. Examples of the material of the resin particles include a urethane resin, a polyamide resin, a fluorine resin, a nylon resin, an acrylic resin, a urea resin, and the like. Examples of the material of the inorganic particles include silica, alumina, and the like. A single type of the materials may be used in some examples, or two or more types thereof may be used in combination in other examples. In order to increase compatibility with respect to the matrix material, dispersion retainability after the particles are added, stability after forming a coating material (pot life), or the like, the particles may be of at least one type selected from the group consisting of nylon resin particles, acrylic resin particles, and polyamide resin particles, or may be of at least one type selected from the group consisting of nylon resin particles and acrylic resin particles.

[0027] The shape of the particles may be a shape that is capable of forming an irregularity with respect to the surface of the resin layer 3. The shape of the particles may be a spherical shape and an ovoidal shape, an amorphous shape, and/or the like, depending on examples.

[0028] In a case where the particles include the first particles 31 and the second particles 32, a ratio of the content of the first particles 31 to the content of the second particles 32, for example, may be approximately 5 : 1 to 1 : 5, or may be approximately 3 : 1 to 1 : 3, in order to more easily achieve a suitable charging performance.

[0029] The content of the particles, for example, may be approximately 5 mass% to 50 mass%, relative to the total mass of the resin layer 3. The charging performance tends to be more easily satisfied by setting the content of the particles to be approximately 5 mass% or more, and the control of particle precipitation at the time of being a coating material is further facilitated and coating material stability is better maintained by setting the content of the particles to be approximately 50 mass% or less. According to examples, the content of the particles may be approximately 10 mass% to 40 mass% or may be approximately 20 mass% to 30 mass%, relative to the total mass of the resin layer 3. In a case where there are a plurality of types of particles as the particles contained in the resin layer 3, the content of the particles described above indicates the total amount of the plurality of types of particles. The content of the particles contained in the resin layer 3, for example, can be quantified by sampling the resin layer 3 from the charging member, and by measuring a weight change (TG), differential heat (DTA), calory (DSC), and the mass (MS) of a volatile component, which occur by heating the sampled resin layer (TG-DTA-MS, DSC (heat analysis)). [0030] With reference to FIG. 2, in the cross-section of the resin layer 3, a layer thickness A of a portion containing the matrix material 30 exclusively, without containing the particles in a thickness direction (e.g., a radial direction of the conductive body 5), may be within a range having a minimum of approximately 1.0 pm, of approximately 2.0 pm, or of approximately 3.0 pm, and having a maximum of approximately 7.0 pm, of approximately 6.0 pm, or of approximately 5.0 pm. In a case where the resin layer 3 contains the particles, the layer thickness A corresponds to a thickness of the resin layer 3 at a middle point between the nearest particles. By setting the layer thickness A to be approximately 1.0 pm or more, the resin particles to be added are more easily continuously retained without having any dropout of the resin particles for a long period of time. By setting the layer thickness A to be approximately 7.0 pm or less, the charging performance is more easily maintained. The layer thickness A may be measured by cutting out a sectional surface of the conductive body 5 with a sharp blade, and by observing the sectional surface with an optical microscope or an electronic microscope.

[0031] In a case where the resin layer 3 contains the first particles 31 and the second particles 32, the average of particle diameters (an average particle diameter B) of the first particles 31 (a "B" portion in FIG. 2) may be approximately 15.0 pm to 40.0 pm, in order to suppress charging unevenness which is an initial image defect. In addition, the average of particle diameters (an average particle diameter C) of the second particles 32 (a "C" portion in FIG. 2) may be approximately 15.0 pm or more, and may be approximately 40.0 pm or less, in order to suppress the charging unevenness which is the initial image defect. In addition, in order to suppress the charging unevenness, the average particle diameter B of the first particles 31 may be greater than the average particle diameter C of the second particles 32. In some examples, the average particle diameter B of the first particles 31 may be greater than the average particle diameter C of the second particles 32 by approximately 10 urn or more.

[0032] In a case where the resin layer 3 contains the first particles exclusively, as the particles, the average of the particle diameters of the first particles (the average particle diameter of the first particles) may be approximately 5.0 pm to 50.0 pm, and may be approximately 15.0 pm to 30.0 pm, in order to suppress the charging unevenness which is the initial image defect.

[0033] In the present disclosure, the average particle diameter of the particles can be derived by extracting 100 particles randomly, from a population of a plurality of particles with SEM observation, and by obtaining an average value of particle diameters. However, in a case where a particle shape is not a spherical shape, but rather a shape having a variable diameter or non-uniform dimensions, such as an ovoidal shape (having an oval cross-section) or an amorphous shape, an average value of the longest diameter (or longest transverse dimension) and the shortest diameter (or shortest transverse dimension) may be considered as the particle diameter of the particles.

[0034] A ratio (B/A) of the average particle diameter B of the first particles 31 to the layer thickness A of the resin layer 3 may be approximately 5.0 to 30.0. The ratio B/A may be set to approximately 5.0 or more, to more easily increase a charging evenness. The ratio B/A may be set to approximately 30.0 or less, in order to achieve suitable coating properties of a coating liquid for forming a resin layer and to suppress particle dropout. According to examples, the ratio B/A may be approximately 7.5 to 20.0, or may be approximately 8.0 to 12.5.

[0035] An interparticle distance in the resin layer 3 (namely, an interparticle distance of all of the particles including the first particles 31 and the second particles 32 included in accordance with a case) may be approximately 50 pm to 400 pm. The surface roughness of the resin layer 3 and the particle dropout are more easily suppressed by setting the interpartide distance to be approximately 50 urn or more. The particle dropout is more easily suppressed by setting the interpartide distance to be approximately 400 pm or less. According to examples, the interparticle distance may be approximately 75 pm to 300 pm, or may be approximately 100 pm to 250 pm. The interpartide distance can be measured on the basis of JIS B0601-1994.

[0036] The resin layer 3 may be formed by impregnating the surface of the originally existing elastic layer with a solution containing an isocyanate compound, and then, by curing the solution. In this case, a cured portion on the surface side of the originally existing elastic layer is the resin layer 3, and other uncured portions are the elastic layer 2. In such a method, the elastic layer may be formed by grinding, and thus, an irregularity may be formed on the surface of the elastic layer such that the resin layer 3 to be formed after solution impregnation forms the irregular surface.

[0037] The isocyanate compound, for example, may be 2,6-tolylene diisocyanate (TDI), 4,4‘~diphenyl methane diisocyanate (MDI), paraphenylene diisocyanate (PPDI), 1 ,5-naphthalene diisocyanate (NDI), and 3,3-dimethyl diphenyl"4,4'"diisocyanate (TODI), multimers and modified bodies thereof, and the like.

[0038] A solvent of the solution containing the isocyanate compound may be any suitable solvent that is an organic solvent in which the isocyanate compound can be dissolved. The organic solvent may be ethyl acetate or the like. The solution may further contain carbon black, at least one type of polymer selected from an acrylic fluorine-based polymer and an acrylic silicone-based polymer, a conductivity imparting agent, and the like.

[0039] The resin layer formed by impregnating the elastic layer with the solution containing the isocyanate compound, and then, by curing the solution, for example, may contain the elastic body forming the elastic layer 2, and a resin derived from the isocyanate compound. In this case, the elastic body may be formed of a base polymer containing acrylonitrile-butadiene rubber (NBR) or epichlorohydrin rubber as a main component, in order to impart suitable binding properties with respect to the resin derived from the isocyanate compound. For example, the base polymer may contain 50 mass% or more of acrylonitrile-butadiene rubber (NBR) or epichlorohydrin rubber in some examples, or may contain 80 mass% or more of acrylonitrile-butadiene rubber (NBR) or epichlorohydrin rubber in other examples. The resin derived from the isocyanate compound, may be a resin having a urea bond, a urethane bond, or the like (a urea resin, a urethane resin, or the like). The resin derived from the isocyanate compound may be bonded to the base polymer and/or the cross-linked body in the elastic body by a urethane bond or the like.

[0040] In a case where the resin layer 3 is formed by the above method for impregnating the elastic layer with the solution containing the isocyanate compound, the thickness of the resin layer 3 may be within a range having a minimum of approximately 1.0 pm, of approximately 10.0 pm, or of approximately 20.0 pm, depending on examples, and having a maximum of approximately 250.0 pm, of approximately 200.0 pm, or of approximately 150.0 pm, depending on examples.

[0041] Coating Layer

The coating layer 4 has a refractive index of approximately 1 .10 to 1 .42. The refractive index of the coating layer 4, depending on examples, may be approximately 1.40 or less, approximately 1.38 or less, approximately 1.37 or less, approximately 1.36 or less, approximately 1.35 or less, approximately 1.34 or less, approximately 1.33 or less, approximately 1.32 or less, approximately 1.31 or less, approximately 1.30 or less, approximately 1.28 or less, approximately 1 .26 or less, approximately 1 .23 or less, or approximately 1 .20 or less. The abnormal electrical discharge is less likely to occur as the refractive index of the coating layer 4 decreases. The refractive index of the coating layer 4, depending on examples, may be approximately 1.15 or more, approximately 1 .20 or more, approximately 1 .23 or more, approximately 1 .26 or more, approximately 1.28 or more, approximately 1.30 or more, approximately 1.31 or more, approximately 1.32 or more, approximately 1.33 or more, approximately 1.34 or more, approximately 1.35 or more, approximately 1.36 or more, approximately 1.37 or more, or approximately 1.38 or more. The denseness of the structures forming the layer increases and a surface hardness increases, as the refractive index of the coating layer 4 increases. Consequently, the contamination due to the external additive is less likely to occur.

[0042] The coating layer 4, for example, contains polysiloxane. In the present disclosure, the "polysiloxane" indicates a compound having a plurality of Si-O-Si bonds (siloxane bonds) in a molecular structure. Three or four oxygen atoms may be bonded to the Si of the Si-O-Si bond. The polysiloxane, for example, is a condensate of a monomer component containing hydrolyzable silane or a derivative thereof, and includes a monomer unit derived from a compound having a hydrolyzable silyl group represented by Formula (1) described below (hereinafter, referred to as "hydrolyzable silane").

[Formula 1]

[0043] In Formula (1 ), R ³¹ to R ³³ each independently indicates a hydrocarbon group. The hydrocarbon group, for example, is an alkyl group having 1 to 4 carbon atoms.

[0044] The polysiloxane, for example, has a Si-O-Zr bond in the molecular structure. The Si-O-Zr bond, for example, is a bond to be formed between a zirconium chelate compound and hydrolyzable silane at the time of polymerizing (self-condensing) the hydrolyzable silane in the presence of the zirconium chelate compound. Namely, the polysiloxane having a Si-O-Zr bond in the molecular structure is also capable of including a monomer unit derived from the zirconium chelate compound, in addition to the monomer unit derived from the hydrolyzable silane. The Si of the Si-O-Zr bond can be the same as the Si of the Si-O-SI bond. Three or four oxygen atoms may be bonded to the Si of the Si-O-Zr bond.

[0045] The coating layer 4 having the refractive index described above, for example, contains polysiloxane including a monomer unit derived from hydrolyzable silane having an epoxy group, a monomer unit derived from a compound having an oxetane group, and optionally, a monomer unit derived from a zirconium chelate compound. Such polysiloxane has a bond (a cross-linkage) to be formed by a reaction between an epoxy group and an oxetane group, in addition to a Si-O-Si bond to be formed by the condensation of hydrolyzable silane, and further has a Si-O-Zr bond in accordance with a case. The oxetane group is a monovalent or divalent group having a 4-membered ring ether structure, and as with the epoxy group, has cationic polymerizability. A structure to be formed by the reaction between the epoxy group and the oxetane group has a weaker cohesive force than a structure to be formed by a reaction between epoxy groups, and thus, it is possible to decrease the denseness of the structures forming the coating layer 4 by introducing a monomer unit derived from a compound having an oxetane group in polysiloxane. Accordingly, in a case where the coating layer 4 contains the polysiloxane described above, a porous structure is more easily formed in the coating iayer 4, so that the refractive index in the range described above can be more easily obtained.

[0046] The hydrolyzable silane having an epoxy group may be a monofunctional hydrolyzable silane, or may be a difunctional or higher hydrolyzable silane. Namely, there may be one epoxy group, or there may be a plurality of epoxy groups, depending on examples. The equivalent of the epoxy group (the molecular weight per 1 mol of the epoxy group) of the hydrolyzable silane having an epoxy group, for example, is approximately 100.0 g/mol to 300.0 g/mol.

[0047] The hydrolyzable silane having an epoxy group, for example, may be a compound represented by Formula (2) or Formula (3) described below, in order to suppress the occurrence of polymerization inhibition due to oxygen at the time of forming the polysiloxane and to easily obtain the coating layer excellent in the surface hardness by improving surface curing properties.

[Formula 2]

[0048] In Formula (2), R ¹ to R ³ each independently indicates one among a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyl group, a carboxyl group, or an amino group, X indicates a single bond or a divalent organic group, and Q indicates the hydrolyzable siiyl group represented by Formuia (1) described above.

[0049] In Formula (3), R ⁴ to R ⁵ each independently indicates one among a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyl group, a carboxyl group, or an amino group, R ⁶ to R ⁷ each independently indicates one among a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxyl group having 1 to 4 carbon atoms, and m indicates an integer of 4 to 12, and Q indicates the hydrolyzable silyl group represented by Formula (1 ) described above.

[0050] A divalent organic group of X, for example, may be a divalent hydrocarbon group having 1 to 16 carbon atoms. A part of the carbon atoms of the hydrocarbon group may be substituted with an oxygen atom. The hydrocarbon group may be linear or branched, and may be saturated or unsaturated. For example, the divalent organic group may be a group represented by Formula (4) or Formula (5) described below.

[Formula 4]

[Formula 5]

[0051] In Formula (4), R ⁸ to R ³ each independently indicates a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and I indicates an integer of 1 to 8. In Formula (5), R ¹⁰ to R ¹³ each independently indicates a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and p and q each independently indicates an integer of 1 to 8. In Formula (4) and Formula (5), * indicates a bonding hand with respect to Q.

[0052] According to some examples, the hydrolyzable silane having an epoxy group may be (3-glycidoxypropyl) trimethoxysilane, (3-glycidoxypropyl) triethoxysilane, 2~(3,4~epoxy cyclohexyl) ethyl trimethoxysilane, 2-(3,4-epoxy cyclohexyl) ethyl triethoxysilane, or the like. A single type of the hydrolyzable silane having an epoxy group may be used, and a plurality of types of the hydrolyzable silanes having an epoxy group may be used in combination.

[0053] In a case where the hydrolyzable silane having an epoxy group is the compound represented by Formula (2) described above, the monomer unit derived from the hydrolyzable silane having an epoxy group can be represented by Formula (6) described below.

[Formula 6]

[0054] R ¹ to R ³ and X in Formula (6) respectively correspond to the same as R ¹ to R ³ and X in Formula (2), and n indicates 0 or 1 .

[0055] In some examples, the monomer unit having the structure represented by Formula (6) described above may be a monomer unit having a structure represented by Formula (7) or Formula (8) described below. [Formula 7]

[0056] In Formula (7) and Formula (8), n corresponds to the same as n in Formula (6). In Formula (7), I corresponds to the same as I in Formula (4), and in Formula (8), p and q correspond to the same as p and q in Formula (5).

[0057] In a case where the hydrolyzable silane having an epoxy group is the compound represented by Formula (3) described above, the monomer unit derived from the hydrolyzable silane having an epoxy group has a structure represented by Formula (9) described below.

[Formula 9]

[0058] R ⁴ to R ⁷ , m, and X in Formula (9) respectively correspond to the same as R ⁴ to R ⁷ m, and X in Formula (3).

[0059] The monomer unit having the structure represented by Formula (9) described above may be a monomer unit having a structure represented by Formula (10) or Formula (11) described below.

[Formula 10]

[Formula 11]

[0060] In Formula (10), I corresponds to the same as I in Formula (4), and in Formula (11), p and q correspond to the same as p and q in Formula (5).

[0061] The content of the monomer unit derived from the hydrolyzable silane having an epoxy group may be, depending on examples, approximately 60.0 mol% or more, approximately 64.0 mol% or more, or approximately 74.0 mol% or more, relative to the total amount of the monomer units included in the polysiloxane, in order to achieve a more suitable surface hardness of the coating layer. The content of the monomer unit derived from the hydrolyzable silane having an epoxy group may be, depending on examples, approximately 95.0 mol% or less, approximately 93.0 mol% or less, or approximately 90.0 mol% or less, relative to the total amount of the monomer units included in the polysiloxane, in order to more easily suppress the occurrence of the abnormal electrical discharge by decreasing the refractive index of the coating layer. According to examples, the content of the monomer unit derived from the hydrolyzable silane having an epoxy group may be approximately 60.0 mol% to 95.0 mol%, may be approximately 64.0 mol% to 93.0 mol%, or may be approximately 74.0 mol% to 90.0 mol%, relative to the total amount of the monomer units included in the polysiloxane.

[0062] The compound having an oxetane group may be a monofunctional compound, or may be a difunctional or higher compound. Namely, there may be one oxetane group, or there may be a plurality of oxetane groups. The equivalent of the oxetane group (the molecular weight per 1 mol of the oxetane group) of the compound having an oxetane group, for example, is approximately 100.0 g/mol to 300.0 g/mol.

[0063] The compound having an oxetane group, for example, may be a compound represented by Formula (12) or Formula (13) described below, in order to further decrease the refractive index of the coating layer.

[Formula 12]

[Formula 13]

[0064] In Formula (12), R ²¹ indicates a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ²² indicates a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. The alkyl group having 1 to 4 carbon atoms and the alkyl group having 1 to 12 carbon atoms may be linear or branched. In a case where R ²² is the alkyl group having 1 to 12 carbon atoms, a lower refractive index can be easily obtained.

[0065] In Formula (13), R ²³ to R ²⁴ each independently indicates a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ²⁵ indicates a divalent organic group, and s indicates an integer of 0 to 3. The alkyl group having 1 to 4 carbon atoms and the alkyl group having 1 to 12 carbon atoms may be linear or branched. The divalent organic group, for example, may be a divalent hydrocarbon group having 1 to 16 carbon atoms. The hydrocarbon group may be linear or branched, and may be saturated or unsaturated. The hydrocarbon group may have an aromatic ring. Examples of such a hydrocarbon group include an arylene group such as a phenylene group, an arylene alkylene group such as a phenylene methylene group and a phenylene ethylene group, an arylene dialkylene group such as a phenylene dimethylene group and a phenylene diethylene group, and the like. In a case where s is 0, a lower refractive index can be easily obtained.

[0066] In some examples, the compound having an oxetane group may be 3-ethyl-3-hydroxymethyl oxetane, 2-ethyl hexyl oxetane, 3-ethyl-3-{[(3-ethyl oxetan-3-yl) methoxy]methyl} oxetane, 1 ,4-bis[{(3-ethyl oxetan-3-yl) methoxy}methyl] benzene (also referred to as "xylene bisoxetane"), or the like. Among them, in a case where the compound having an oxetane group is the 3-ethyl-3-{[(3-ethyl oxetan-3-yl) methoxy]methyl} oxetane, a lower refractive index can be easily obtained. A single type of the compound having an oxetane group may be used, and a plurality of types of the compounds having an oxetane group may be used in combination.

[0067] In a case where the compound having an oxetane group is the compound represented by Formula (12) described above, the monomer unit derived from the compound having an oxetane group can be represented by Formula (14) described below. [0068] R ²¹ to R ²² in Formula (14) respectively correspond to the same as R ²¹ to

R ²² in Formula (12).

[0069] In a case where the compound having an oxetane group is the compound represented by Formula (13) described above, the monomer unit derived from the compound having an oxetane group can be represented by

Formula (15) described below.

[Formula 15]

[0070] R ²³ to R ²⁵ in Formula (15) respectively correspond to the same as R ²³ to

R ²⁵ in Formula (13).

[00/1 ] The content of the monomer unit derived from the compound having an oxetane group may be, depending on examples, approximately 3.0 mol% or more, approximately 5.0 mol% or more, approximately 7.5 mol% or more, or approximately 10.0 mol% or more, relative to the total amount of the monomer units included in the polysiloxane, in order to further decrease the refractive index of the coating layer. The content of the monomer unit derived from the compound having an oxetane group may be, depending on examples, approximately 30.0 mol% or less, approximately 25.0 mol% or less, or approximately 20.0 mol% or less, relative to the total amount of the monomer units included in the polysiloxane, in order to increase the surface hardness of the coating layer. According to examples, the content of the monomer unit derived from the compound having an oxetane group may be approximately 3.0 mol% to 30.0 mol%, may be approximately 5.0 mol% to 30.0 mol%, may be approximately 7.5 mol% to 25.0 mol%, or may be approximately 10.0 mol% to 20.0 mol%, relative to the total amount of the monomer units included in the polysiloxane.

[0072] The zirconium chelate compound has a zirconium atom (Zr) that is a central metal, and 1 to 4 chelate ligands (polydendate ligands) that are coordinated to the zirconium atom. The zirconium chelate compound accelerates a polymerization (self-condensation) reaction of the hydrolyzable silane, and contributes to the formation of a coating layer having low surface free energy.

[0073] The chelate ligand, for example, may be a bidentate ligand or a tridentate ligand. An example of a ligand atom of the chelate ligand includes an oxygen atom. In some examples, the chelate ligand may be an acetylacetonate group or an alkyl acetoacetate group. Alkyl of the alkyl acetoacetate group, for example, may be alkyl having 1 to 10 carbon atoms.

[0074] The zirconium chelate compound may have a monodentate ligand. An example of the monodentate ligand includes an alkoxy group. The number of carbon atoms of the alkoxy group, for example, may be 1 to 10.

[0075] The zirconium chelate compound, for example, may be zirconium tributoxymonoacetylacetonate, zirconium dibutoxybis(acetylacetonate), zirconium dibutoxybis(ethyl acetoacetate), or the like. Among them, in a case where the zirconium chelate compound is the zirconium dibutoxybis(acetylacetonate), a higher reaction efficiency can be easily obtained at the time of synthesizing the polysiloxane. Accordingly, in a case where the polysiloxane includes a monomer unit derived from the zirconium dibutoxybis(acetylacetonate), a lower refractive index can be easily obtained, and the contamination due to the external additive is less likely to occur. A single type of the zirconium chelate compound may be used, and a plurality of types of the zirconium chelate compounds may be used in combination.

[0076] The content of the monomer unit derived from the zirconium chelate compound may be adjusted according to a reaction time, a condensation rate, and/or the like. The reaction time tends to decrease as the used amount of the zirconium chelate compound increases, and the condensation rate tends to increase as the used amount of the zirconium chelate compound decreases. The content of the monomer unit derived from the zirconium chelate compound may be within a range having a minimum of approximately 2.0 mol%, of approximately 3.0 mol%, or of approximately 4.0 mol%, and a maximum of approximately 10.0 mol%, of approximately 8.0 mol%, or of approximately 6.0 mol%, relative to the total amount of the monomer units included in the polysiloxane, depending on examples.

[0077] The polysiloxane may further include monomer units other than the monomer units described above. The polysiloxane, for example, may further include a monomer unit derived from hydrolyzable silane not having an epoxy group.

[0078] The content of the polysiloxane, depending on examples, may be 90 mass% or more, may be 95 mass% or more, or may be 98 mass% or more, relative to the total mass of the coating layer.

[0079] The coating layer containing the polysiloxane described above, for example, may be a layer containing a cured product of a curable composition containing the polymerizable polysiloxane having an epoxy group and the compound having an oxetane group, or polymerizable polysiloxane having an epoxy group and an oxetane group, the zirconium chelate compound, and an acid generating agent. The coating layer may further contain components other than the components derived from the curable composition (for example, the polysiloxane described above). In the coating layer, the content of the components other than the components derived from the curable composition, for example, may be 5 mass% or less, may be 1 mass% or less, or may be 0.5 mass% or less, relative to the total mass of the coating layer.

[0080] The polymerizable polysiloxane having an epoxy group, for example, is a condensate of the hydrolyzable silane having an epoxy group described above. The polymerizable polysiloxane having an epoxy group and an oxetane group, for example, is a condensate of the hydrolyzable silane having an epoxy group described above and the compound having an oxetane group which is a compound to be condensable by a reaction with a hydrolyzable silyl group (for example, a compound having an oxetane group and a hydroxyl group).

[0081] The acid generating agent may be a photo-acid generating agent, or may be a thermal-acid generating agent. A single type of the acid generating agent may be used in some examples, or a plurality of types of the acid generating agents may be used in combination in other examples.

[0082] The photo-acid generating agent may be a photo-acid generating agent that can be activated with light having a wavelength of 365 nm to 405 nm from a UV-LED light source, in order to suppress damage to a base due to heat from a light source and oxidation degradation of the coating layer. The photo-acid generating agent, for example, may be a triarylsulfonium salt-based photo-acid generating agent or the like.

[0083] The thermal-acid generating agent may be a thermal-acid generating agent that can be activated at a tow temperature (for example, 250°C or less), in order to suppress the damage to the base due to heat and the oxidation degradation of the coating layer. The thermal-acid generating agent, for example, may be an aromatic sulfonium salt-based thermal-acid generating agent, an aromatic iodonium salt-based thermal-acid generating agent, or the like. A counter anion of such a thermal-acid generating agent, for example, may be a hexafluorophosphoric acid, a tritrifluoromethane sulfonic acid, a perfluorobutane sulfonic acid, or the like.

[0084] The content of the acid generating agent may be adjusted in order to achieve a suitable reaction time and/or the like. Depending on examples, the content of the acid generating agent may be 1 .0 parts by mass or more, may be 3.0 parts by mass or more, or may be 5.0 parts by mass or more, and may be 10.0 parts by mass or less, may be 8.0 parts by mass or less, or may be 7.0 parts by mass or less, with respect to 100 parts by mass of the total amount of a cationic polymerizable compound and the zirconia chelate compound (for example, the total amount of the compound having an epoxy group, the compound having an oxetane group, and the zirconia chelate compound).

[0085] Depending on examples, a layer thickness D (a "D" portion in FIG. 2) of the coating layer 4, may be approximately 50 nm or more, or may be approximately 70 nm or more, and may be approximately 500 nm or less, may be approximately 400 nm or less, or may be approximately 300 nm or less. In a case where the layer thickness of the coating layer 4 increases, stress resistance of the coating layer 4 increases, and thus, even in a case where the refractive index is tow, the contamination due to the external additive is less likely to occur.

[0086] The surface of the coating layer 4, namely, an outermost surface S of the conductive body 5 may have an irregularity to be formed by the resin layer 3.

[0087] Depending on exampies, an average interval (Sm) of the irregularities of the outermost surface S of the conductive body 5 may be approximately 50 pm to 400 pm, may be approximately 75 pm or more, or may be approximately 100 pm or more, and may be approximately 300 pm or less, or may be approximately 250 pm or less, in order to obtain more suitable image quality.

[0088] Depending on examples, a ten-point average roughness (Rzjis) of the outermost surface S of the conductive body 5 may be 11 .5 pm or more, may be 15.0 pm or more, may be 18.0 pm or more, may be 20.0 pm or more, may be 22.0 pm or more, may be 22.5 pm or more, or may be 23.0 pm or more, in order to suppress the charging unevenness. Depending on examples, the ten-point average roughness (Rzjis) of the outermost surface of the conductive body 5 may be 32.0 pm or less, may be 30.0 pm or less, may be 29.0 pm or less, may be 28.0 pm or less, may be 27.5 pm or less, may be 27.0 pm or less, may be 26.5 pm or less, or may be 26.0 pm or less, in order to suppress rotation unevenness (a circumferential speed deviation) of the charging roller 10.

[0089] Depending on examples, the average interval (Sm) of the irregularities and the ten-point average roughness (Rzjis) are measured on the basis of JIS B0601-2001 by using a surface roughness meter SE-3400 manufactured by Kosaka Laboratory Ltd. The average interval (Sm) of the irregularities and the ten-point average roughness (Rzjis), and other surface properties of the conductive body can be adjusted by changing the size, the shape, the amount, and the interparticle distance of the particles to be contained in the resin layer 3, the layer thickness of the coating layer 4, and the like.

[0090] The conductive body 5 may include a surface that is curved with respect to the rotation axis line L. Namely, the surface of the coating layer 4 may be curved with respect to the rotation axis line L. The radius (corresponding to 1/2 the diameter) of the conductive body 5, which is the shortest distance from the rotation axis line L to the surface of the conductive body 5 (the surface of the coating layer 4) varies along the direction of the rotation axis line L (a longitudinal direction). The radial distance is the greatest (maximum) at a center point of the conductive body 5 on the rotation axis line L (a center point of the conductive body 5 in the longitudinal direction), and decreases toward each of the opposite end portions of the conductive body 5.

[0091] A crown amount can be used as an index expressing a roller shape of the conductive body 5. The crown amount of the conductive body 5 is defined as follows.

Crown Amount = d2 - (d1 + d3)/2

In the above expression, d1 indicates the outer diameter of the conductive body 5 in a position that is 30 mm separated from a first end of the conductive body 5 in the longitudinal direction (a rubber length) toward the center point, d2 indicates the outer diameter of the conductive body 5 at the center point of the conductive body 5 in the longitudinal direction (the rubber length), and d3 indicates the outer diameter of the conductive body 5 in a position that is offset from the second end of the conductive body 5 by 30 mm, in the longitudinal direction (the rubber length) toward the center point.

[0092] Depending on examples, the crown amount of the conductive body 5 may be 50 pm or more, may be 60 pm or more, or may be 70 pm or more, and may be 130 pm or less, may be 120 pm or less, or may be 110 pm or less, to achieve a stable charging evenness for a long period of time while allowing the charging roller 10 to suitably cohere to the photoreceptor, and of maintaining the granularity of image quality.

[0093] The charging member described above may be provided in an example image forming apparatus, as a charging means to charge the photoreceptor. For example, the charging member may perform a charging treatment with respect to the surface of the photoreceptor that is an image carrier. Accordingly, the example image forming apparatus may include the photoreceptor, and the charging member to charge the photoreceptor.

[0094] In the example image forming apparatus, a direct-current voltage exclusively, may be applied to the charging member. In such a case, a bias voltage to be applied while an image is output may be -1000 V to -1500 V.

[0095] Manufacturing Method of Charging Member

Hereinafter, an example manufacturing method of a charging member will be described based on a manufacturing method of the charging roller 10 as an example.

[0096] The manufacturing method of the charging roller 10 includes preparing the conductive base 6 that is mountable on the conductive support 1 , preparing a coating liquid containing a curable composition, spraying the coating liquid onto the surface of the conductive base 6, and curing the curable composition to form the coating layer 4 having a refractive index of approximately 1.10 to 1.42 on the conductive base 6.

[0097] The conductive base 6, for example, can be prepared as follows. Namely, first, a material for forming an elastic layer and a coating liquid for forming a resin layer are prepared. The material for forming an elastic layer can be prepared by kneading a material for the elastic layer 2 with a kneading machine such as a kneader. In addition, the coating liquid for forming a resin layer can be prepared by kneading a material for the resin layer 3 with a kneading machine such as a roller, by adding an organic solvent to the mixture, and by performing mixing and stirring. Next, a metal mold for injection molding in which a core bar that is the conductive support 1 is set is filled with the material for forming an elastic layer, and is thermally crosslinked in a predetermined condition. Subsequently, demolding is performed, and thus, a base roll is manufactured in which the elastic layer is formed along the outer circumferential surface of the conductive support 1 . Next, the coating liquid for forming a resin layer is applied onto an outer circumferential surface of the base roll described above, so as to form the resin layer 3. As described above, it is possible to prepare the conductive base 6 including the elastic layer 2 formed on the outer circumferential surface of the conductive support 1 , and the resin layer 3 formed on the outer circumferential surface of the elastic layer 2.

[0098] In addition to an injection molding method, the formation method of the elastic layer may include a cast molding method, or a method in which press molding and grinding are combined together. In addition, a coating method of the coating liquid for forming a resin layer may include a suitable method such as a dipping method, a roll coating method, and the like.

[0099] The coating liquid, for example, contains the curable composition, and a liquid medium (a solvent or a dispersion medium) in which the components of the composition are dissolved or dispersed. The curable composition, for example, contains polymerizable polysiloxane having an epoxy group and a compound having an oxetane group, or a polymerizable polysiloxane having an epoxy group and an oxetane group, and an acid generating agent.

[0100] The liquid medium, for example, may contain water. The liquid medium may further contain an alcohol solvent. Namely, the liquid medium may be a mixed liquid of water and the alcohol solvent. In this case, depending on examples, the content of water in the liquid medium may be 10.0 mass% or more, and may be 60.0 mass% or less, relative to the total mass of the liquid medium. Methanol, ethanol, isopropyl alcohol, or the like may be used as the alcohol solvent.

[0101 ] The content of the liquid medium, for example, may be adjusted in order to achieve a suitable viscosity of the coating liquid. The content of the liquid medium, for example, may be 95.0 mass% to 99.9 mass%, relative to the total mass of the coating liquid.

[0102] The coating liquid described above can be obtained by the following method. First, curable components including the hydrolyzable silane having an epoxy group, the compound having an oxetane group, and in some examples, the zirconium chelate compound are heated to reflux in the presence of a solvent, and the polymerizable polysiloxane having an epoxy group and the compound having an oxetane group, or the polymerizable polysiloxane having an epoxy group and an oxetane group are obtained as a reaction product. In the present, the curable components indicate components to be Incorporated in the structure of polysiloxane that is generated after curing. The solvent may be water, may be alcohol such as ethanol, or may be a mixture thereof, or the like. Next, the obtained reaction product, the acid generating agent, and the liquid medium are mixed. In such a case, the reaction product and the acid generating agent may be mixed by being dissolved in advance in the liquid medium.

[0103] The used amount of the curable components and the acid generating agent to be used for manufacturing the coating liquid described above may be adjusted such that the content of the monomer unit derived from each of the components is in the range described above. For example, the used amount of the hydrolyzable silane having an epoxy group may be approximately 60.0 mol% to 95.0 mol%, relative to the total amount of the curable components. According to examples, the used amount of the compound having an oxetane group may be approximately 3.0 mol% to 30.0 mol%, relative to the total amount of the curable components. For example, the used amount of the zirconium chelate compound may be approximately 2.0 mol% to 10.0 mol%, relative to the total amount of the curable components.

[0104] An application method of the coating liquid may include a suitable method such as a dipping method, a spray coating method, a roll coating method, and the like.

[0105] Drying or the like may be performed after the coating liquid is applied and before the curable composition is cured so that the solvent in the formed coating may be removed. The drying may be performed at 130°C to 220°C.

[0106] A curing method of the curable composition is not particularly limited. In a case where the curable composition contains the acid generating agent, suitable curing means (heating, light irradiation, or the like) may be adopted, in accordance with the type of acid generating agent. The heating and the light irradiation may be used together as the curing means. In a case of using the photo-acid generating agent, the curable composition may be cured by being irradiated with light having a wavelength of 365 nm to 405 nm from the UV-LED light source, in order to suppress the damage on the base due to heat generated from the light source and the oxidation degradation of the coating layer. The UV-LED light source, for example, may be a UV-LED light source manufactured by Hamamatsu Photonics K.K., a UV-LED light source manufactured by HOYA Corporation, a UV-LED light source manufactured by Iwasaki Electric Co., Ltd., a UV-LED light source manufactured by Ushio Inc., a UV-LED light source manufactured by Heraeus K.K., a UV-LED light source manufactured by AITEC SYSTEM Co., Ltd., a UV-LED light source manufactured by Micro-Sphere S.A., and the like. In addition, in a case of using the thermal-acid generating agent, the curable composition may be cured by heating to 250°C or less, in order to suppress the damage to the base due to heat and the oxidation degradation of the coating layer.

Test Examples [0107] Hereinafter, Test Examples of the charging member will be described, although it will be understood that the charging member is not limited to these Test Examples.

[0108] Comparative Test Example 1

Preparation of Material for Forming Elastic Layer

A material for forming an elastic layer was prepared by compounding together and subsequently kneading with a roller, 100.00 parts by mass of epichlorohydrin rubber ("EPICHLOMER CG-102", manufactured by DAISO CHEMICAL CO., LTD.) as a rubber component, 5.00 parts by mass of sorbitan fatty acid ester ("SPLENDER R-300", manufactured by Kao Corporation) as a lubricant, 5.00 parts by mass of a ricinoleic acid as a softener, 0.50 part by mass of a hydrotalcites compound ("DHT-4A", manufactured by Kyowa Chemical Industry Co., Ltd.) as an acid acceptor, 1.00 part by mass of tetrabutyl ammonium chloride (''tetrabutyl ammonium chloride”, manufactured by Tokyo Chemical Industry Co., Ltd.) as a conductive agent (an ion conductive agent), 50.00 parts by mass of silica ("Nipsil ER”, manufactured by Tosoh Silica Corporation) as a filler, 5.00 parts by mass of zinc oxide as a cross-linking promoter, 1.50 parts by mass of dibenzothiazole sulfide, 0.50 part by mass of tetramethyl thiuram monosulfide, and 1.05 parts by mass of sulfur as a cross-linking agent. Consequently, the material for forming an elastic layer was obtained.

[0109] Preparation of Coating Liquid for Forming Resin Layer

A mixed liquid was prepared by mixing into tetrahydrofuran (THF), 100.00 parts by mass of thermoplastic N-methoxy methylated 6-nylon ("Toresin F-30K”, manufactured by Nagase ChemteX Corporation) as a polymer component, 5.00 parts by mass of methylene bisethyl methyl aniline ("CUREHARD-MED”, manufactured by lhara Chemical Industry Co., Ltd.) as a curing agent, and 18.00 parts by mass of carbon black ("Denka Black HS100”, manufactured by Denka Company Limited) as a conductive agent (an electronic conductive agent). In the mixed liquid, two types of amorphous nylon resin particles having different average particle diameters (25.0 pm and 5.0 pm) ("Orgasol Series", manufactured by Arkema S.A.) were added as the first particles 31 and the second particles 32, and were sufficiently stirred until the solution became uniform. An additive amount was adjusted based on the total amount of the resin layer 3 to be obtained such that the content of the first particles 31 was 25 mass% and the content of the second particles 32 was 5 mass%. Subsequently, each component in the solution was dispersed by using a double roll. Accordingly, a coating liquid for forming a resin layer was obtained.

[0110] The average particle diameter of the first particles 31 and the second particles 32 was measured as follows. Namely, 100 particles were extracted randomly from a population of a plurality of particles with SEM observation, and an average value of particle diameters was set to the average particle diameter of the resin particles. A particle shape of the used resin particles was an amorphous shape, and thus, an average value of the longest diameter (longest transverse dimension) and the shortest diameter (shortest transverse dimension) of the observed particles was set as the particle diameter of the respective particles.

[0111] Preparation of Conductive Base

A roll molding metal mold including a cylindrical roll molding space was prepared, and a core bar having a diameter of 8 mm (the conductive support 1 ) onto which a conductive adhesive agent was applied was set to be coaxial with the roll molding space. The material for forming an elastic layer prepared as described above, was injected into the roll molding space in which the core bar was set, was subsequently heated at 170°C for 30 minutes, and then, was cooied, and was further demolded. Accordingly, a base roll including the conductive support 1 as a conductive axis body, and the elastic layer 2 having a thickness of 2 mm (a thickness in the central position in the rotation axis line L direction) that was formed along the outer circumferential surface of the conductive support 1 was obtained.

[0112] Next, the coating liquid for forming a resin layer prepared as described above, was applied onto the surface of the elastic layer 2 of the base roll by a roll coating method. At this time, the coating was performed while an excess coating liquid was scraped with a scraper to achieve a suitable film thickness. After a coated film was formed, the film was heated at 150°C for 30 minutes so as to form the resin layer 3 having a layer thickness A of 5.0 pm. Accordingly, a conductive base including the elastic layer 2 formed along the outer circumferential surface of the axis body (the conductive support 1 ), and the resin layer 3 formed along the outer circumferential surface of the elastic layer 2 was obtained.

[0113] According to the above preparation, a roller including the axis body (the conductive support 1 ) and the conductive base (the elastic layer 2 and the resin layer 3) was obtained. In the following evaluation, this roller was used as a charging roller of Comparative Test Example 1.

[0114] Test Examples 1 to 22 and Comparative Test Example 2

Preparation of Coating Liquid

In Test Examples 1 to 22, first, hydrolyzable silane having an epoxy group (Ep silane), a compound having an oxetane group (an Ox compound), a zirconium chelate compound (a Zr compound), and water and ethanol as a solvent were mixed in combination shown in Tables 1 to 4, and then, were stirred at a room temperature, and then, were heated to reflux for 24 hours, and thus, a reaction product containing a condensate of hydrolyzable siiane (polysiloxane having a Si-O-Zr bond in a moiecuiar structure) was obtained. The reaction product obtained was added to a mixed solvent of 2-butanol and ethanol, so as to obtain a condensate-containing alcohol solution having a solid content shown in Tables 1 to 4. In such a case, curable components (the hydrolyzable silane having an epoxy group, the compound having an oxetane group, and the zirconium chelate compound) were compounded at a compounding ratio shown in Tables 1 to 4 such that the total amount was 100 mol%. In addition, a compounding amount of water was adjusted such that R _OR was a value shown in Tables 1 to 4. Here, R _OR indicates a molar number ratio of water with respect to a condensation point of the hydrolyzable silane to be used. For example, the minimum number of water molecules for condensing one molecule of hydrolyzable silane having a trimethoxy group is 3. Such a relationship is set to R _OR = 1.0. In some examples, a range of R _OR is set to satisfy the following relationship: 1.0 < R _OR ≤ 2.0.

[0115] In Comparative Test Example 2, condensate-containing alcohol was prepared similarly to the described above method, except that the compound having an oxetane group was not used and the compounding ratio of the curable component was set to a compounding ratio shown in Table 4.

[0116] Next, an acid generating agent shown in Tables 1 to 4 was added to the condensate-containing alcohol solution. In such a case, an additive amount of the acid generating agent was 5 parts by mass with respect to 100 parts by mass of the solid content in the condensate-containing alcohol solution. Accordingly, coating liquids of Test Examples 1 to 22 and Comparative Test Example 2 were obtained, respectively.

[0117] Manufacturing of Charging Roller 10

The prepared coating liquid was applied onto the surface of a conductive base of a roller prepared as with Comparative Test Example 1 by a roll coating method, so as to form a coated film. After the coated film was formed, in a case where a thermal-acid generating agent was used as the acid generating agent, the coated film was cured by being heated in a condition shown in Tables 1 to 4, and in a case of using a photo-acid generating agent as the acid generating agent, the coated film was cured by being irradiated with light in a condition shown in Tables 1 to 3 by using a UV irradiation device (manufactured by Heraeus K.K.) including a UV-LED light source. Accordingly, the coating layer 4 having a layer thickness shown in Tables 1 to 4 was formed. In Tables 1 to 3, a wavelength of 365/405 nm indicates using a UV-LED having a wavelength peak at 365 nm and at 405 nm.

[0118] According to the above-described manufacturing method, the charging roller 10 including the axis body (the conductive support 1), and the conductive body 5 including the elastic layer 2 formed along the outer circumferential surface of the axis body, the resin layer 3 formed along the outer circumferential surface of the elastic layer 2, and the coating layer 4 formed along the outer circumferential surface of the resin layer 3 was prepared.

[0119] Measurement of Refractive Index of Coating Layer

A sample for measuring a refractive index was prepared by using the coating liquid obtained as described above. Namely, first, the coating liquid was applied onto an aluminum sheet having a diameter of 10.0 cm and a thickness of 0.1 mm by using a spin coater (ASC150II, manufactured by ASUMI GIKEN, Limited). Next, the obtained coated film was cured by the same curing means as that in the manufacturing of the charging roller 10 described above, so as to obtain a sample for measuring a refractive index Including a coating layer. According to the method described above, a plurality of samples for measuring a refractive index having different film thicknesses were prepared by using the same coating liquid. Next, a reflective index of each of the samples at a wavelength of 400.0 nm to 1000.0 nm was measured by using a reflection spectroscopic film thickness meter (manufactured by ASUMI GIKEN, Limited), and a refractive index at a layer thickness shown in Tables 1 to 4 was obtained by using a Fresnel equation. Results are shown in Tables 1 to 4.

[0120] [Table 1]

121] [Table 2]

0122] [Table 3]

123] [Table 4]

[0124] The details of the compounds shown in Tables 1 to 4 are as follows.

• KBM-303: Product Name, manufactured by Shin-Etsu Chemical Co., Ltd., 2-(3,4-Epoxy Cyclohexyl) Ethyl Trimethoxysilane

• KBM-403: Product Name, manufactured by Shin-Etsu Chemical Co., Ltd., (3-Glycidoxypropyl) Trimethoxysilane

• OXT-101 : Product Name, manufactured by Toagosei Co., Ltd., 3-Ethyl-3-Hydroxym ethyl Oxetane

• OXT-212: Product Name, manufactured by Toagosei Co., Ltd., 2-Ethyl Hexyl Oxetane

• OXT-121 : Product Name, manufactured by Toagosei Co., Ltd., Xylene Bisoxetane (Number of Repetitions of Xylene: 1 to 3)

• OXT-221 : Product Name, manufactured by Toagosei Co., Ltd., 3-Ethyl~3~{[(3~Ethyl Oxetan-3-YI) Methoxy]Methyl} Oxetane

• ZC-580: Product Name, manufactured by Matsumoto Fine Chemical Co., Ltd., Solution of Zirconium Dibutoxybis(Ethyl Acetoacetate) (Solid Content of 70 mass%)

• AKZ947: Product Name, manufactured by Gelest, Inc., Solution of Zirconium Dibutoxybis(Acetylacetonate) (Solid Content of 25 mass%)

• ZC-540: Product Name, manufactured by Matsumoto Fine Chemical Co., Ltd., Solution of Zirconium Tributoxymonoacetylacetonate (Solid Content of 70 mass%)

• CPI-31 OS: Product Name, manufactured by San-Apro Ltd.,

Triarylsulfonium Salt-Based Photo-Acid Generating Agent

• CPI-41 OS: Product Name, manufactured by San-Apro Ltd.,

Triarylsulfonium Salt-Based Photo-Acid Generating Agent

• SI-B3: Product Name, manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD., Aromatic Sulfonium Salt-Based Thermal-Acid Generating Agent

• SI-B5: Product Name, manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD., Aromatic Sulfonium Salt-Based Thermal-Acid Generating Agent

[0125] Evaluation

Endurance Test

The charging member (the charging roller) obtained as described above was incorporated in Multixpress C8640 ND manufactured by Samsung Electronics Co., Ltd., to obtain an image forming apparatus, and an endurance test (the formation of an image) was performed in accordance with the following condition.

Image Forming Condition

• Printing Environment: in Low Temperature Low Humidity Environment (15°C/10%RH)

• Printing Condition: General Printing Speed of 305 mm/sec and Half Speed thereof, Number of Printed Sheets (80 kPV), Type of Sheet (Office Paper EC)

• Load with respect to Conductive Support End Portion: 5.88 N on One Side

• Applied Bias: Suitably adjusted and Determined such that Photoreceptor Surface Potential Becomes -600 V

[0126] Evaluation of Photoreceptor Abrasion

Photoreceptor abrasion after the endurance test described above was evaluated. Namely, a film thickness (Unit: nm) of the photoreceptor before the endurance test and a film thickness (Unit: nm) of the photoreceptor after the endurance test were measured by using an eddy current type film thickness meter Fischerscope MMS, and the degree of abrasion was evaluated by comparing values obtained by dividing a difference between the film thicknesses by the number of rotations (unit: kcycle) of the photoreceptor in the endurance test.

[0127] Evaluation of Surface Contamination

Surface contamination of the charging roller after the endurance test described above was evaluated. The surface contamination of the charging roller was mainly derived from silica of an external additive to be used in a toner, and thus, was evaluated by quantifying an element Si on the surface of the charging roller with a fluorescence X-ray measurement device (EDXL300: manufactured by Rigaku Corporation). Namely, In a chamber of the fluorescence X-ray measurement device, the charging roller was arranged such that the center of the charging roller was aligned with a detector, and the element Si on the surface of the charging roller was quantified. Such measurement was performed with respect to the charging roller before the image was formed and after the image was formed (for each 20 kPV), to calculate a difference ASi [cps/mA] in the amount of Si (= Amount of Si [cps/mA] after Endurance Test - Amount of Si [cps/mA] before Endurance Test). Next, the difference ASi was plotted on a vertical axis, the total number of rotations of the photoreceptor was plotted on a horizontal axis, and the surface contamination was evaluated based on the following standards, by using the slope of the obtained graph as an index.

Evaluation A: ASi < 1000 [cps/mA]

Evaluation B: 1000 [cps/mA] < ASi < 2000 [cps/mA]

Evaluation C: 2000 [cps/mA] < ASi < 3000 [cps/mA]

Evaluation D: 3000 [cps/mA] < ASi

The A Si compared to the number of rotations of the photoreceptor decreases with a decrease of the slope of the obtained graph, so that the contamination due to the external additive is less likely to occur. Results are shown in Table 5.

[0128] [Table 5]

[0129] It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail is omitted.