conductive roller

Abstract

The present invention provides a conductive roller that can reduce frictional force without drastically increasing the hardness of the surface layer. [Solution] The present invention provides a conductive roller 1 comprising a shaft 2, an elastic layer 3 provided on the outer circumference of the shaft 2, and a surface layer 4 provided on the outer circumference of the elastic layer 3, wherein the surface layer 4 has an area ratio of 40% or more of the histogram portion where the adhesion force to the entire histogram measured using an atomic force microscope is 6 nN or less, and an area ratio of 30% or more of the histogram portion where the adhesion force to the entire histogram is 8 nN or more.

Description

[Technical Field]

[0001] This invention relates to a conductive roller. [Background technology]

[0002] Developing rollers used in image forming devices such as photocopiers, printers, and facsimile machines employing electrophotography have the function of transporting toner to an image carrier on which an electrostatic latent image has been formed. In recent years, with the miniaturization of image forming devices, the motors that rotate the rollers have also become smaller. To reduce the load on these small motors, it is necessary to reduce the frictional force (adhesion force) on the surface of the developing roller. For example, Patent Document 1 discloses a cleaning blade in which the adhesion force of the surface near the contact portion, including at least the portion that contacts the image carrier, is set to 2.5 nN or more and 3.9 nN or less, thereby improving cleaning performance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2007-102129 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, hardness and friction are in a trade-off relationship, so to reduce surface friction, the hardness must be increased. When hardness increases, the silica added to the toner detaches as it rolls on the roller, accumulates on the blade, and scrapes off the toner, making it more prone to vertical streaks in the image. This invention has been made in view of the above circumstances, and aims to provide a conductive roller that can reduce frictional force without drastically increasing the hardness of the surface layer. [Means for solving the problem]

[0005] The inventor of the present invention has found that the above problems can be solved by adding a predetermined amount of a reactive additive having a graft structure to the resin composition for the surface layer, and thus the present invention has been achieved. That is, the present invention is as follows. [1] The present invention provides a conductive roller including a shaft body, an elastic layer provided on the outer periphery of the shaft body, and a surface layer provided on the outer periphery of the elastic layer, wherein the surface layer has an area ratio of a histogram portion having an adhesion force of 6 nN or less with respect to the entire histogram measured using an atomic force microscope of 40% or more, and an area ratio of a histogram portion having an adhesion force of 8 nN or more with respect to the entire histogram of 30% or more. [2] The conductive roller according to [1] above, wherein the surface layer contains a silicone urethane resin. [3] The conductive roller according to [1] above, wherein the surface layer has a sea-island structure. [4] The conductive roller according to [1] above, wherein the resin composition for the surface layer for forming the surface layer contains an acrylic-based or fluorine-based reactive additive having a graft structure. [5] The conductive roller according to [1] above, wherein the static friction coefficient of the surface layer is 0.8 or more and 1.2 or less. [Advantages of the Invention]

[0006] According to the present invention, it is possible to provide a conductive roller capable of reducing the frictional force without extremely increasing the hardness of the surface layer. [Brief Description of the Drawings]

[0007] [Figure 1] It is a perspective view showing an embodiment of the conductive roller of the present invention. [Figure 2] It is a histogram showing the adhesion force of the surface layer of the developing roller of Example 1. [Figure 3] It is a photograph of an atomic force microscope of the surface layer of the developing roller of Example 1. [Figure 4] It is a histogram showing the adhesion force of the surface layer of the developing roller of Example 2. [Figure 5] It is a photograph of an atomic force microscope of the surface layer of the developing roller of Example 2. [Figure 6] This is a histogram showing the adhesion force of the surface layer of the developing roller in Example 3. [Figure 7] This is an atomic force microscope image of the surface layer of the developing roller in Example 3. [Figure 8] This is a histogram showing the adhesion force on the surface of the developing roller in Comparative Example 1. [Figure 9] This is an atomic force microscope image of the surface layer of the developing roller in Comparative Example 1. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0009] [Conductive roller] As shown in Figure 1, the conductive roller 1 of the present invention comprises a shaft 2, an elastic layer 3 provided on the outer circumference of the shaft 2, and a surface layer 4 provided on the outer circumference of the elastic layer 3. The surface layer 4 has an area ratio of 40% or more of the histogram portion where the adhesion force to the entire histogram, as measured using an atomic force microscope, is 6 nN or less, and an area ratio of 30% or more of the histogram portion where the adhesion force to the entire histogram is 8 nN or more. The following describes each component.

[0010] (Axis) The shaft 2 is preferably a conductive shaft used in conventionally known conductive rollers. The shaft 2 is preferably made of at least one metal selected from the group consisting of, for example, iron, aluminum, stainless steel, and brass. A shaft 2 made of such a metal is generally also known as a "core metal".

[0011] The shaft 2 may contain an insulating resin. The insulating resin may be, for example, a thermoplastic resin or a thermosetting resin. The shaft 2 may comprise, for example, a core made of an insulating resin and a plating layer provided on this core. Such a shaft 2 can be obtained, for example, by plating a core made of an insulating resin to make it conductive. The shaft 2 is preferably a core metal in order to obtain good conductivity.

[0012] The shape of the shaft 2 is preferably, for example, rod-shaped or tubular. The cross-sectional shape of the shaft 2 may be, for example, circular or elliptical, or non-circular, such as a polygon. The outer surface of the shaft 2 may be treated with cleaning, degreasing, priming, etc., to improve adhesion with the elastic layer 3.

[0013] The axial length of the shaft 2 is not particularly limited and may be adjusted as appropriate depending on the configuration of the image forming apparatus in which it is installed. For example, if the printing target is A4 size, the axial length of the shaft 2 is preferably 250 mm to 320 mm, and more preferably 260 mm to 310 mm. The diameter of the shaft 2 (diameter of the circumscribed circle) is also not particularly limited and may be adjusted as appropriate depending on the configuration of the image forming apparatus in which it is installed. For example, the outer diameter (diameter of the circumscribed circle) of the shaft 2 is preferably 4 mm to 14 mm, and more preferably 6 mm to 10 mm.

[0014] (Elastic layer) The elastic layer 3 is formed by heat-curing a rubber composition on the outer surface of the shaft 2. The rubber composition for forming the elastic layer 3 preferably contains rubber, a conductivity imparting agent, and various additives, if desired.

[0015] Examples of rubbers used in rubber compositions include silicone or silicone-modified rubber, nitrile rubber, ethylene propylene rubber (including ethylene propylene diene rubber), styrene-butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, acrylic rubber, chloroprene rubber, butyl rubber, epichlorohydrin rubber, urethane rubber, and fluororubber. Silicone, silicone-modified rubber, or urethane rubber are preferred, with silicone or silicone-modified rubber being particularly preferred because it can reduce compression set, has excellent flexibility in low-temperature environments, and also has excellent heat resistance and electrostatic properties. Examples of silicone rubbers include crosslinked organopolysiloxanes such as dimethylpolysiloxane and diphenylpolysiloxane. Examples of silicone rubber compositions include addition-curing type millable conductive silicone rubber compositions and addition-curing type liquid conductive silicone rubber compositions.

[0016] -Addition-curing type millable conductive silicone rubber composition- The addition-curing millable conductive silicone rubber composition may contain, for example, (A) an organopolysiloxane represented by the following average composition formula (1), (B) a filler, and (C) a conductivity imparting agent. R 1 n SiO (4-n) / 2 …(1) In equation (1), n ​​is a positive number between 1.95 and 2.05. Also, R 1 This represents a substituted or unsubstituted monovalent hydrocarbon group, which may be the same or different. The number of carbon atoms in the hydrocarbon group is preferably 1 to 12, and more preferably 1 to 8.

[0017] R 1 Examples 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, and aralkyl groups such as β-phenylpropyl groups.1 These hydrocarbon groups may be groups in which some or all of the hydrogen atoms are substituted with substituents. The substituents may be, for example, halogen atoms, cyano groups, etc. Examples of hydrocarbon groups with substituents include chloromethyl groups, trifluoropropyl groups, and cyanoethyl groups.

[0018] (A) It is preferable that the molecular chain ends of the organopolysiloxane are sealed with trialkylsilyl groups such as trimethylsilyl groups, dialkylaralkylsilyl groups such as dimethylvinylsilyl groups, dialkylhydroxysilyl groups such as dimethylhydroxysilyl groups, trialkylaralkylsilyl groups such as trivinylsilyl groups, etc.

[0019] (A) The organopolysiloxane preferably has two or more alkenyl groups in its molecule. (A) The organopolysiloxane is R 1 It is preferable that the organopolysiloxane has 0.001 mol% to 5 mol% (more preferably 0.01 mol% to 0.5 mol%) of alkenyl groups. (A) Vinyl groups are particularly preferred as the alkenyl groups of the organopolysiloxane.

[0020] (A) Organopolysiloxanes can be obtained, for example, by co-hydrolysis condensation of one or more organohalosilanes, or by ring-opening polymerization of cyclic polysiloxanes such as trimers or tetramers of siloxanes. (A) Organopolysiloxanes may basically be linear diorganopolysiloxanes, or they may be partially branched. Furthermore, (A) organopolysiloxanes may be a mixture of two or more types with different molecular structures.

[0021] (A) The organopolysiloxane preferably has a kinematic viscosity of 100 cSt or more at 25°C, and more preferably 100,000 cSt or more and 10,000,000 cSt or less. Furthermore, the degree of polymerization of (A) organopolysiloxane is preferably 100 or more, and more preferably 3,000 or more and 10,000 or less.

[0022] (B) As the filler, for example, silica-based fillers can be mentioned. Examples of silica-based fillers include fumed silica, precipitated silica, etc.

[0023] As the silica-based filler, R 2 Si(OR 3 )3, a surface-treated silica-based filler surface-treated with a silane coupling agent can be preferably used. Here, R 2 may be a group having a vinyl group or an amino group, and for example, a glycidyl group, a vinyl group, an aminopropyl group, a methacryloxy group, an N-phenylaminopropyl group, a mercapto group, etc. may be used. R 3 may be an alkyl group, for example, a methyl group, an ethyl group, etc. The silane coupling agent can be easily obtained, for example, under the trade names "KBM-1003", "KBE-402", etc. manufactured by Shin-Etsu Chemical Co., Ltd. The surface-treated silica-based filler can be obtained by treating the surface of the silica-based filler with a silane coupling agent according to a conventional method. As the surface-treated silica-based filler, commercially available products may be used, for example, products under the trade name "Zeothix 95" manufactured by J.M. HUBER Co., Ltd.

[0024] The blending amount of the silica-based filler is preferably 11 parts by mass or more and 39 parts by mass or less, more preferably 15 parts by mass or more and 35 parts by mass or less, with respect to 100 parts by mass of (A) organopolysiloxane. Also, the average particle diameter of the silica-based filler is preferably 1 μm or more and 80 μm or less, more preferably 2 μm or more and 40 μm or less. Note that the average particle diameter of the silica-based filler can be measured as the median diameter using a particle size distribution measuring device by the laser light diffraction method.

[0025] Examples of conductivity imparters include carbon, metals, metal oxides, metal compounds, conductive polymers, and ionic liquids. (C) The amount of conductivity imparter is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of (A) organopolysiloxane. Furthermore, the amount of conductivity imparter is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of (A) organopolysiloxane.

[0026] The addition-curing millable conductive silicone rubber composition may further contain additives other than (A) to (C). Examples of additives include auxiliary agents (chain extenders, crosslinking agents, etc.), catalysts, dispersants, foaming agents, anti-aging agents, antioxidants, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, ionic conductive agents, heat resistance improvers, flame retardancy improvers, acid acceptors, thermal conductivity improvers, mold release agents, solvents, and the like.

[0027] Specific examples of additives include (A) dimethylsiloxane oil, polyether-modified silicone oil, silanol, diphenylsilanediol, and α,ω-dimethylsiloxanediol, which have a lower degree of polymerization than organopolysiloxane, as well as dispersants such as silanes and other low molecular weight siloxanes with silanol groups encapsulated at both ends. Other specific examples of additives include heat-resistant agents such as iron octoate, iron oxide, and cerium oxide. Furthermore, various carbon functional silanes and various olefin-based elastomers may be used as additives to improve adhesion, moldability, etc.

[0028] -Addition-curing liquid conductive silicone rubber composition- The addition-curing liquid conductive silicone rubber composition may contain, for example, (D) an organopolysiloxane having two or more alkenyl groups in its molecule, (E) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in its molecule, (F) a filler, (G) a conductivity imparting agent, and (H) an addition reaction catalyst.

[0029] (D) As the organopolysiloxane, the compound shown in the following average composition formula (2) is preferred. R 4 a SiO (4-a) / 2 …(2) In equation (2), a represents a positive number between 1.5 and 2.8, preferably between 1.8 and 2.5, and more preferably between 1.95 and 2.05. Also, R 4 R represents a monovalent hydrocarbon group, which may be the same or different, substituted or unsubstituted. However, R in one molecule 4 At least two of these are alkenyl groups. The number of carbon atoms in the hydrocarbon group is preferably 1 to 12, and more preferably 1 to 8.

[0030] R 4 As for the above R 1 The same group as the example group can be used as an example. Also, the R in one molecule 4 At least two of them are alkenyl groups, and the other R 4 It is preferable that the alkyl group is an alkyl group. The alkenyl group is preferably a vinyl group, and the alkyl group is preferably a methyl group. Also, R 4 Of these, for example, 90% or more may be alkyl groups (preferably methyl groups). (D) The content of alkenyl groups in the organopolysiloxane is, for example, 1.0 × 10 -6 mol / g or more 5.0×10 -3 It is preferable that the amount is mol / g or less, and 5.0 × 10 -6 mol / g or more 1.0×10 -3 It is more preferable that the concentration be mol / g or less.

[0031] (D) The organopolysiloxane is preferably liquid at 25°C, and its viscosity at 25°C is preferably 100 mPa·s to 1,000,000 mPa·s, and more preferably 200 mPa·s to 100,000 mPa·s. Furthermore, the average degree of polymerization of (D) organopolysiloxane is preferably 100 to 800, and more preferably 150 to 600.

[0032] (E) As the organohydrogenpolysiloxane, the compound shown in the following average composition formula (3) is preferred. R 5 b H c SiO (4-b-c) / 2 …(3) In equation (3), b is a positive number between 0.7 and 2.1, c is a positive number between 0.001 and 1.0, and bc is between 0.8 and 3.0. Also, R 5 R represents a substituted or unsubstituted monovalent hydrocarbon group, which may be the same or different. The number of carbon atoms in the hydrocarbon group is preferably 1 to 10. 5 As for the above R 1 The same group exemplified as above can be used as an example.

[0033] (E) The organohydrogenpolysiloxane has two or more hydrogen atoms (Si-H) bonded to silicon atoms in one molecule, preferably three or more. Furthermore, the number of hydrogen atoms bonded to silicon atoms in one molecule of (E) organohydrogenpolysiloxane is preferably 200 or less, and more preferably 100 or less.

[0034] (E) In the organohydrogenpolysiloxane, the content of hydrogen atoms bonded to silicon atoms is preferably 0.001 mol / g or more and 0.017 mol / g or less, and more preferably 0.002 mol / g or more and 0.015 mol / g or less.

[0035] (E) Examples of organohydrogenpolysiloxanes include methylhydrogenpolysiloxane with trimethylsiloxy group blockade at both ends, dimethylsiloxane-methylhydrogensiloxane copolymer with trimethylsiloxy group blockade at both ends, dimethylpolysiloxane with dimethylhydrogensiloxy group blockade at both ends, dimethylsiloxane-methylhydrogensiloxane copolymer with dimethylhydrogensiloxy group blockade at both ends, methylhydrogensiloxane-diphenylsiloxane copolymer with trimethylsiloxy group blockade at both ends, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer with trimethylsiloxy group blockade at both ends, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 Copolymers consisting of units, and (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 Units and (C6H5)SiO 3 / 2 Examples include copolymers consisting of units.

[0036] The amount of (E) organohydrogenpolysiloxane blended is preferably 0.1 parts by mass or more and 30 parts by mass or less, and more preferably 0.3 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of (D) organohydrogenpolysiloxane. Furthermore, the molar ratio of Si-H of (E) organohydrogenpolysiloxane to the alkenyl groups of (D) organohydrogenpolysiloxane is preferably 0.3 or more and 5.0 or less, and more preferably 0.5 or more and 2.5 or less.

[0037] (F) The filler may be, for example, an inorganic filler. By incorporating (F) the filler into the addition-curing liquid conductive silicone rubber composition, the compression set is reduced, the volume resistivity stabilizes over time, and sufficient roller durability is obtained.

[0038] (F) The average particle diameter of the filler is preferably 1 μm or more and 30 μm or less, and more preferably 2 μm or more and 20 μm or less. If the average particle diameter of the filler is 1 μm or more, the change in volume resistivity over time is further suppressed. Furthermore, if the average particle diameter of the filler is 30 μm or less, an elastic layer 3 with even greater durability can be obtained. The average particle diameter of the filler can be measured as the median diameter using a particle size distribution analyzer that measures by laser diffraction.

[0039] (F) The bulk density of the filler is 0.1 g / cm³. 3 More than 0.5g / cm 3 Preferably, it is 0.15 g / cm³. 3 More than 0.45g / cm 3 The following is more preferable: (F) By adjusting the bulk density of the filler to the above range, the compression set can be further reduced, the change in volume resistivity over time is further suppressed, and an elastic layer 3 with even greater durability can be obtained. (F) The bulk density of the filler can be determined based on the method for measuring apparent specific gravity in JIS K 6223.

[0040] (F) Examples of fillers include diatomaceous earth, perlite, mica, calcium carbonate, glass flakes, and hollow fillers. Among these, diatomaceous earth, perlite, and crushed foamed perlite can be suitably used as fillers (F).

[0041] (F) The amount of filler added is preferably 5 parts by mass or more and 100 parts by mass or less, and more preferably 10 parts by mass or more and 80 parts by mass or less, per 100 parts by mass of (D) organopolysiloxane.

[0042] Examples of conductivity imparters include carbon, metals, metal oxides, metal compounds, conductive polymers, and ionic liquids. (G) The amount of conductivity imparter is preferably 0.5 parts by mass or more and 15 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less, per 100 parts by mass of (D) organopolysiloxane.

[0043] (H) The addition catalyst can be any catalyst capable of activating the addition reaction between (D) organopolysiloxane and (E) organohydrogenpolysiloxane. (H) Examples of addition catalysts include catalysts containing platinum group elements. Examples of catalysts containing platinum group elements include platinum-based catalysts (e.g., platinum black, dic platinum chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetate, etc.), palladium-based catalysts, rhodium-based catalysts, etc.

[0044] (H) The amount of addition catalyst may be catalytic. For example, the amount of addition catalyst (H) is preferably such that the amount of platinum group elements is 0.5 ppm to 1000 ppm relative to the total mass of (D) organopolysiloxane and (E) organohydrogenpolysiloxane, and more preferably 1 ppm to 500 ppm relative to the total mass.

[0045] The elastic layer 3 is formed on the outer surface of the shaft 2 by a known molding method, which involves simultaneous or continuous heat curing and molding. The curing method for the rubber composition is not limited to any method that applies the heat necessary for curing the rubber composition, and the molding method for the elastic layer 3 is not particularly limited, including continuous vulcanization by extrusion molding, pressing, injection molding, etc. For example, if the rubber composition is an addition-curing type millable conductive silicone rubber composition, extrusion molding can be selected, and if the rubber composition is an addition-curing type liquid conductive silicone rubber composition, a molding method using a mold can be selected, for example. Alternatively, the elastic layer 3 may be formed by grinding or polishing the elastic body (cured product of the silicone rubber composition) formed on the shaft 2.

[0046] For addition-curing type millable conductive silicone rubber compositions, the heating temperature is preferably 100°C to 500°C, and more preferably 120°C to 300°C. The heating time is preferably several seconds to 1 hour, and more preferably 10 seconds to 35 minutes. For addition-curing type liquid conductive silicone rubber compositions, the heating temperature is preferably 100°C to 300°C, and more preferably 110°C to 200°C. The heating time is preferably 5 minutes to 5 hours, and more preferably 1 hour to 3 hours. Secondary vulcanization may also be performed as needed. For addition-curing type millable conductive silicone rubber compositions, for example, curing conditions of approximately 100°C to 200°C for 1 hour to 20 hours are selected. For addition-curing type liquid conductive silicone rubber compositions, for example, curing conditions of approximately 120°C to 250°C for 2 hours to 70 hours are selected. Furthermore, the rubber composition can be easily formed into a sponge-like elastic layer with bubbles by foam curing using a known method.

[0047] The addition-curing liquid conductive silicone rubber composition may further contain additives in addition to components (D) to (H). Examples of additives include auxiliary agents (chain extenders, crosslinking agents, etc.), foaming agents, dispersants, anti-aging agents, antioxidants, ionic conductive agents, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardancy improvers, acid acceptors, thermal conductivity improvers, mold release agents, diluents, reactive diluents, solvents, and the like.

[0048] Specific examples of additives include dispersants such as low molecular weight siloxane esters, polyether-modified silicone oils, silanols, and phenylsilanediols. Heat-resistant agents such as iron octoate, iron oxide, and cerium oxide are also used. Furthermore, various carbon functional silanes and olefin-based elastomers may be used to improve adhesion, moldability, etc. Halogen compounds may also be used to impart flame retardancy.

[0049] The viscosity of the addition-curing liquid conductive silicone rubber composition at 25°C is preferably 5 Pa·s or more and 500 Pa·s or less, and more preferably 5 Pa·s or more and 200 Pa·s or less.

[0050] The thickness of the elastic layer 3 is not particularly limited, but is preferably 0.1 mm or more and 6 mm or less, and more preferably 1 mm or more and 4 mm or less. In this specification, the thickness refers to the thickness in the direction perpendicular to the axial direction of the conductive roller 1.

[0051] The outer diameter of the elastic layer 3 is not particularly limited, but is preferably 6 mm or more and 25 mm or less, and more preferably 7 mm or more and 21 mm or less.

[0052] The outer surface of the elastic layer 3 may be subjected to surface treatments such as primer treatment, corona treatment, plasma treatment, excimer treatment, UV treatment, itro treatment, or flame treatment for purposes such as improving adhesion with the surface layer 4.

[0053] The method for forming the elastic layer 3 is not particularly limited. For example, the elastic layer 3 may be formed by methods such as extrusion molding or LIMS molding of the silicone rubber composition. Alternatively, the elastic layer 3 may be formed by grinding or polishing the elastic body (cured product of the silicone rubber composition) formed on the shaft 2.

[0054] -Other ingredients- The rubber composition may further contain various additives other than those listed above. Examples of such additives include auxiliary agents (chain extenders, crosslinking agents, etc.), catalysts, dispersants, foaming agents, anti-aging agents, antioxidants, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardancy improvers, acid acceptors, thermal conductivity improvers, mold release agents, solvents, and the like.

[0055] (surface) The surface layer 4 is located on the outer periphery of the elastic layer 3 and is provided on the outermost surface of the conductive roller 1. The surface layer 4 preferably contains a silicone urethane resin. For example, the surface layer 4 can be formed from a surface resin composition containing at least (a) a silicone-modified polyol, (b) an isocyanate, and (c) a reactive additive. The surface layer 4 is formed by coating the outer periphery of the elastic layer 3, or optionally a primer layer, with the surface resin composition, and then heat-curing the coated surface resin composition. The components of the surface resin composition are described below.

[0056] (a) Silicone-modified polyol Silicone-modified polyols are prepolymerized by polymerizing a composition consisting of modified silicone oil and isocyanate. The details of the modified silicone oils and isocyanates used in the synthesis of silicone-modified polyols are described below. Modified silicone oils include double-ended modified silicone oils and single-ended modified silicone oils.

[0057] - Modified silicone oil at both ends - Double-ended modified silicone oils are a type of so-called reactive silicone oil and have the property of polymerizing with isocyanates. Therefore, it is preferable that both ends of the silicone chain of the double-ended modified silicone oil are modified with ether groups, amino groups (primary or secondary amino groups), mercapto groups, or hydroxyl groups. These double-ended modified silicone oils are commercially available as double-ended ether-modified silicone oils, double-ended amino-modified silicone oils, double-ended mercapto-modified silicone oils, double-ended carboxyl-modified silicone oils, double-ended phenol-modified silicone oils, and double-ended carbinol-modified silicone oils.

[0058] In this invention, preferred double-ended modified silicone oils used in this invention include the double-ended modified silicone oil represented by the following general formula (1).

[0059] [ka]

[0060] In general formula (1), R represents -C3H6OC2H4OH or -C3H6OCH2-C(CH2OH)2C2H5, and n represents an integer less than or equal to 20.

[0061] Among the double-ended modified silicone oils represented by general formula (1), it is particularly preferable to use a silicone oil in which the R at both ends is -C3H6OC2H4OH and n is approximately 10. Such silicone oils can be appropriately obtained from the market.

[0062] In general formula (1), the functional group bonded to the silicon atom is a methyl group, but this methyl group may be replaced with a hydrogen atom in a modified silicone oil with modified ends.

[0063] By including modified silicone oil at both ends in the composition for forming the surface layer 4, it is possible to impart appropriate elasticity to the surface layer 4, adjust the electrical properties of the surface layer 4, and effectively suppress the occurrence of filming.

[0064] -Partially modified silicone oil- As the single-ended modified silicone oil, a single-ended diol modified silicone oil is preferred. A single-ended diol modified silicone oil is a reactive silicone oil, similar to a double-ended modified silicone oil, but it has two hydroxyl groups bonded to one end of the silicone chain. Normally, when a double-ended modified silicone oil is polymerized with an isocyanate, a linear polyurethane is produced. However, by using a single-ended diol modified silicone oil in combination, branched chains are introduced into the polyurethane, which can improve the nanoscale fine roughness of the conductive roller 1.

[0065] Examples of one-ended diol-modified silicone oils include the one-ended modified silicone oil represented by the following general formula (2).

[0066] [ka]

[0067] In general formula (2), R' represents -C3H6OCH2-C(CH2OH)2C2H5, and n represents an integer less than or equal to 20.

[0068] Among the one-terminated diol-modified silicone oils represented by general formula (2), it is particularly preferable to use a silicone oil in which n is approximately 10. In general formula (2), the functional group bonded to the silicon atom is a methyl group, but a silicone oil in which this methyl group is substituted with a hydrogen atom may also be used.

[0069] In the present invention, the amount of one-ended diol-modified silicone oil used for preparing the silicone-modified polyol is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, per 100 parts by mass of the double-ended modified silicone oil. By adjusting the amount of one-ended diol-modified silicone oil used relative to the double-ended modified silicone oil within the above range, the surface roughness of the surface layer 4 can be adjusted, thereby effectively preventing filming while maintaining good developing performance.

[0070] -Isocyanate- In the present invention, the isocyanate used for prepolymerizing the silicone-modified polyol is not particularly limited as long as it has reactivity with the reactive group introduced into the silicone oil. Examples include diisocyanates such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), and hexamethylene diisocyanate (HDI), as well as modified forms of these isocyanates, such as adduct type, burette type, isocyanurate type, and allophanate type. Among these isocyanates, bifunctional isocyanates, isocyanurate type isocyanates, and adduct type isocyanates are preferred, and these may be used individually or in combination. The longer the molecular chain of the isocyanate, the more flexible the polyurethane that can be produced.

[0071] (b) Isocyanates For curing the silicone-modified polyol, various isocyanates commonly used in the preparation of polyurethanes, such as aromatic isocyanates, aliphatic isocyanates, and alicyclic isocyanates, can be used as isocyanates.

[0072] Examples of aromatic isocyanates include xylylene diisocyanate (XDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (also called tolylene diisocyanate, TDI), 3,3'-vitrylene-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 2,4-tolylene diisocyanate uretidinedione (a dimer of 2,4-TDI), xylylene diisocyanate, naphthalene diisocyanate (NDI), paraphenylenedi diisocyanate (PDI), tolidine diisocyanate (TODI), and metaphenylenedi diisocyanate.

[0073] Examples of aliphatic isocyanates include hexamethylene diisocyanate (HDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), orthotoluidine diisocyanate, lysine diisocyanate methyl ester, isophorone diisocyanate (IPDI), norbornane diisocyanate methyl, transcyclohexane-1,4-diisocyanate, and triphenylmethane-4,4',4''-triisocyanate.

[0074] Furthermore, examples of alicyclic isocyanates include transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), H12MDI (hydrogenated MDI), and 4,4'-dicyclohexylmethane diisocyanate.

[0075] The (b) isocyanate used in the surface resin composition is preferably a polyisocyanate. The number of isocyanate groups in one molecule of (b) isocyanate is preferably more than 2, more preferably 2.5 or more, and even more preferably 3 or more. The mixing ratio of silicone-modified polyol and polyisocyanate is not particularly limited, but it is generally preferable that the molar ratio (NCO / OH, hereinafter sometimes referred to as the "isocyanate index") of hydroxyl groups (OH) contained in the silicone-modified polyol to isocyanate groups (NCO) contained in the polyisocyanate is 0.7 or more and 1.15 or less. A molar ratio (NCO / OH) of 0.85 or more and 1.10 or less is more preferable in that it can prevent hydrolysis of the polyurethane. In practice, however, considering the working environment and operational errors, an amount equivalent to 3 to 4 times the appropriate molar ratio may be added.

[0076] (c) Reactive additives The surface resin composition in the present invention preferably contains an acrylic or fluorine-based reactive additive having a graft structure. By adding acrylic or fluorine-based reactive additives having a graft structure, areas with low adhesion can be formed on the surface layer 4. As a result, areas of relatively low hardness and high hardness are formed within the polyurethane resin of the surface layer 4, making it possible to reduce adhesion (friction) without drastically increasing hardness. The hydroxyl value of the acrylic or fluorine-based reactive additive having a graft structure is preferably 80 mg KOH / g or more and 150 mg KOH / g or less. Commercially available acrylic-based reactive additives include "GS-1015" (manufactured by Toagosei Co., Ltd.). Additionally, fluorine-based reactive additives include "ZX-022" (manufactured by T&K TOKA Corporation) and "ZX-022-H" (manufactured by T&K TOKA Corporation).

[0077] Preferably, the surface layer 4 has a sea-island structure formed by the difference in compatibility between the base resin silicone urethane resin and the reactive additive. Having a sea-island structure in the surface layer 4 allows for a moderate distribution of low-hardness and high-hardness regions, making it easier to adjust the hardness and adhesive strength.

[0078] The surface resin composition may contain (a) a silicone-modified polyol, (b) an isocyanate, and (c) a reactive additive, as well as a surface material, an ionic conductive agent, etc. Furthermore, auxiliary agents commonly used in the reaction between (a) the silicone-modified polyol and (b) the isocyanate, such as chain extenders and crosslinking agents, may be used in combination. Examples of chain extenders and crosslinking agents include glycols, hexanetriol, trimethylolpropane, and amines.

[0079] The content of (c) reactive additive in the surface resin composition is preferably 1% by mass to 15% by mass, and more preferably 2% by mass to 10% by mass, from the viewpoint of setting the MD-1 hardness in the range of 30 to 40 and the adhesive force to 6 nN or less.

[0080] - Area ratio of the histogram portion - The surface layer 4 of the conductive roller 1 of the present invention has an area ratio of 40% or more of histogram portions where the adhesion force to the entire histogram, as measured using an atomic force microscope, is 6 nN or less, and an area ratio of 30% or more of histogram portions where the adhesion force to the entire histogram is 8 nN or more. Furthermore, it is more preferable that the area ratio of the histogram portions where the adhesion force to the entire histogram of the surface layer 4 is 6 nN or less is 45% or more, and the area ratio of the histogram portions where the adhesion force to the entire histogram is 8 nN or more is 35% or more. The histogram shall be measured using the measurement method described in the examples below.

[0081] -hardness- The hardness of the surface layer 4 is preferably in the range of 30 to 40 on the MD-1 hardness scale. The MD-1 hardness of surface layer 4 shall be determined by the measurement method described in the examples below.

[0082] - Static friction coefficient - From the viewpoint of suppressing longitudinal reinforcement, the static friction coefficient of the surface layer 4 is preferably 0.5 or more and 2.0 or less. The coefficient of static friction shall be determined by the measurement method described in the examples below.

[0083] -Coefficient of kinetic friction- From the viewpoint of suppressing longitudinal reinforcement, the coefficient of dynamic friction of the surface layer 4 is preferably 0.3 or more and 1.5 or less. The coefficient of dynamic friction shall be determined by the measurement method described in the examples below.

[0084] (Other configurations) The conductive roller 1 of the present invention may include an adhesive layer or a primer layer between the shaft 2 and the elastic layer 3, and between the elastic layer 3 and the surface layer 4. As the primer layer, one that is normally used as a primer layer for conductive rollers can be used, but for example, by forming a primer layer made of a urethane resin having an ester group, the developing performance of the conductive roller 1 can be maintained well.

[0085] The conductive roller of the present invention has a histogram area ratio of 40% or more in which the adhesion force relative to the entire histogram is 6 nN or less, as measured using an atomic force microscope, and a histogram area ratio of 30% or more in which the adhesion force relative to the entire histogram is 8 nN or more. This makes it possible to achieve low friction without drastically increasing the hardness of the surface layer 4. Therefore, it is possible to reduce the load on a small motor without worsening the longitudinal grooves. [Examples]

[0086] The present invention will be described in detail below with reference to examples. However, the present invention is not limited in any way to the examples shown below.

[0087] [Examples 1 to 3, Comparative Example 1] The developing rollers for the examples and comparative examples were prepared using the following procedure. (Formation of primer layer) An iron shaft (φ13mm) that had been electroless nickel plated was cleaned with ethanol, and a silicone-based primer (product name "Primer No. 16", manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to its surface. The primer-treated shaft was then baked in a gear oven at 150°C for 10 minutes, and then cooled at room temperature for more than 30 minutes to form a primer layer on the outer surface of the shaft.

[0088] (Formation of an elastic layer) An elastic body made of rubber material was formed on the outer surface of a shaft by extrusion molding using a millable-type rubber composition (a composition containing conductive carbon) containing silicone rubber. In the extrusion molding process, the millable-type silicone rubber composition was heated at 270°C for 5 minutes using an infrared heating furnace (IR furnace), and then cured by heating at 200°C for 4 hours using a gear oven. This formed an elastic layer made of the cured rubber composition on the outer surface of the primer-treated shaft. The elastic layer was a solid layer, and its thickness was 2.5 mm.

[0089] (Formation of the surface layer) Using the following materials, the surface resin compositions for the examples and comparative examples were prepared according to the formulations shown in Table 1.

[0090] -Resin composition for surface layer- • Silicone-modified polyol (product name "KF-6002", manufactured by Shin-Etsu Chemical Co., Ltd.) • Isocyanate (product name "TPA-100", manufactured by Asahi Kasei Corporation) • Reactive acrylic additive: (Product name "8BS-9000", manufactured by Taisei Fine Chemical Co., Ltd.) • Reactive fluorine-based additive 1: (Product name "Futajont 650AC", manufactured by Neos Co., Ltd.) • Reactive fluorine-based additive 2: (Product name "Futajont 681", manufactured by Neos Co., Ltd.) • Solvent: Butyl acetate (manufactured by Kanto Chemical Co., Ltd.)

[0091] Next, the outer surface of the elastic layer was UV treated. Then, a surface resin composition was applied onto the UV-treated elastic layer. The applied composition was heated at 150°C to 160°C for 30 minutes to obtain a developing roller. The thickness of the surface layer after drying was 20 μm.

[0092] [evaluation] The conductive rollers of the above examples and comparative examples were evaluated as follows. The evaluation results are shown in Table 1.

[0093] (sea-island structure) The presence or absence of sea-island structures was observed on the surface of the layer using image data obtained from adhesion force measurements with an atomic force microscope. Figures 2 to 5 show atomic force microscope images of the surface layers in Examples 1 to 3 and Comparative Example 1. The black areas in the images represent the parts containing the reactive additive.

[0094] (Static friction coefficient and kinetic friction coefficient) The static friction coefficient and kinetic friction coefficient were measured using the following method. Equipment: Probe-type friction measuring machine Handy Rub Tester TL701 (manufactured by Trinity Lab Co., Ltd.) Vertical load: 100g Roller rotation speed: 60 rpm Contact element: R contact element (accessory for the Handy Rub Tester TL701 probe-type friction measuring instrument; contact wire length: 8.0 mm, width: 8.0 mm, arc length: 8.8 mm)

[0095] <Calibration method for friction measuring instruments> Following the instructions in the equipment manual, a simulated input signal was generated from the dynamic distortion amplifier, and the amplifier's amplification factor was obtained and calibrated based on the no-load point output and the simulated input signal equivalent to approximately +0.1mV / V.

[0096] <Method for measuring the coefficient of friction> A fluororesin adhesive tape (product name "NITOFLON", part number "No.903UL", thickness 0.13 mm, width 8 mm, length 9 mm) was attached to the R contact, and after calibrating the friction measuring instrument, the shaft portions at both ends of the roller were held down with a metal jig, and the contact portion of the friction measuring instrument was applied perpendicularly to the surface of the roller. Simultaneously with the start of the friction coefficient measurement, the roller was rotated at 60 rpm and the measurement was performed for 10 seconds.

[0097] -Method for calculating the coefficient of static friction- The maximum value of the friction coefficient at the moment the roller started rotating immediately after the friction coefficient measurement was started was defined as the static friction coefficient.

[0098] -Method for calculating the coefficient of kinetic friction- The average coefficient of friction for the first 3 to 9 seconds after the start of measurement was defined as the coefficient of kinetic friction.

[0099] (Surface MD-1 hardness) Using an MD-1 hardness tester ("Micro Rubber Hardness Tester MD-1" manufactured by Polymer Instruments Co., Ltd.), the indenter of the MD-1 hardness tester was pressed against the surface of the developing roller, and the MD-1 hardness was measured in peak hold mode with a hold time of 3 seconds.

[0100] (Method for measuring adhesive strength) The adhesion force of the developing rollers of the above examples and comparative examples, which were prepared down to the surface, was measured using an atomic force microscope in the following procedure. 1. The force curve was measured using a standard Bruker SAPPHIRE-12M (sapphire) sample, and the cantilever spring constant was corrected. 2. The surface shape of the standard sample RS-12M (titanium) manufactured by Bruker and the indentation depth of the standard sample PDMS-SOFT-2-12M were measured, and the radius of the cantilever probe tip was calculated and corrected. 3. The coated developing roller was placed flat on the measuring table, and the adhesion force was measured using a corrected cantilever.

[0101] <Atomic force microscope and measurement conditions> Manufacturer: Bruker Device name: Dimension Icon Cantilever: RTESPA-300 Measurement mode: PeakForce QNM (Quantitative Nanomechanics) Measurement area: 10μm×10μm Measurement atmosphere: Under air <Detailed specifications for the cantilever RTESPA-300> Tip radius: 8nm Probe height D: 12.5μm Lever length L: 125 μm Lever thickness T: 3.4 μm Lever width W: 40 μm Spring constant: 40 N / m Resonance frequency: 300kHz

[0102] (Area ratio of the histogram portion) A histogram was created from the data obtained from the above adhesion force measurement (n=128), and the area ratio was determined. The histogram and atomic force microscope image of the surface of Example 1 are shown in Figures 2 and 3, respectively; the histogram and atomic force microscope image of the surface of Example 2 are shown in Figures 4 and 5, respectively; the histogram and atomic force microscope image of the surface of Example 3 are shown in Figures 6 and 7, respectively; and the histogram and atomic force microscope image of the surface of Comparative Example 1 are shown in Figures 8 and 9, respectively.

[0103] [Table 1]

[0104] As shown in Table 1, Examples 1 to 3, in which the surface layer had an area ratio of 40% or more of the histogram portion where the adhesion force to the entire histogram measured using an atomic force microscope was 6 nN or less, and an area ratio of 30% or more of the histogram portion where the adhesion force to the entire histogram was 8 nN or more, were able to lower both the hardness and the coefficient of friction (i.e., reduce the adhesion force). On the other hand, in Comparative Example 1, where the area ratio of the histogram fell outside the scope of the present invention, the hardness was reduced, but the coefficient of friction became high. [Explanation of symbols]

[0105] 1. Conductive roller 2-axis body 3. Elastic layer 4 Surface layer

Claims

1. The device comprises a shaft, an elastic layer provided on the outer circumference of the shaft, and a surface layer provided on the outer circumference of the elastic layer. A conductive roller wherein the surface layer has an area ratio of 40% or more of the histogram portion where the adhesion force to the entire histogram, as measured using an atomic force microscope, is 6 nN or less, and an area ratio of 30% or more of the histogram portion where the adhesion force to the entire histogram is 8 nN or more.

2. The conductive roller according to claim 1, wherein the surface layer contains a silicone urethane resin.

3. The conductive roller according to claim 1, wherein the surface layer has a sea-island structure.

4. The conductive roller according to claim 1, wherein the surface resin composition for forming the surface layer contains an acrylic or fluorine-based reactive additive having a graft structure.

5. The conductive roller according to claim 1, wherein the static friction coefficient of the surface layer is 0.8 or more and 1.2 or less.

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