Developing roller

Abstract

To provide a developing roller having good surface smoothness in spite of low hardness.SOLUTION: The present invention is a developing roller 1 including a shaft 2 and an elastic layer 3 on the outer periphery of the shaft 2, wherein the elastic layer 3 is formed of an elastic layer composition containing (a) an organopolysiloxane, (b) a silicone ball, (c) a conductivity imparting agent, (d) a filler, and (e) a vulcanizing agent, and the elastic layer has an MD-1 hardness of 40 or less and a surface roughness Ra of 1 μm or more and 5 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a developing roller. [Background technology]

[0002] Various image forming devices using electrophotography are employed in printers such as laser printers and video printers, copiers, facsimiles, and multifunction machines thereof. Electrophotographic image forming devices include various elastic rollers, such as developing rollers, transfer rollers, toner supply rollers, and cleaning rollers, each having an elastic layer provided on the outer periphery of a shaft. The elastic layer can be formed by coating the outer periphery of the shaft with a rubber composition using, for example, a crosshead extrusion molding machine, followed by vulcanization (see, for example, Patent Document 1).

[0003] For example, since the developing roller rotates in contact with the image carrier, if the hardness of the elastic layer is too high, the developer may be damaged between the developing roller and the image carrier. To address this problem, it is conceivable to add a silicone rubber to the composition for the elastic layer to reduce the hardness of the elastic layer and thereby reduce damage to the developer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-224378 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the hardness of the composition for the elastic layer is low, the surface smoothness during extrusion molding will be poor, resulting in problems such as low durability and reduced image quality. The present invention has been made in view of the above circumstances, and has as its object to provide a developing roller that has low hardness but good surface smoothness. [Means for solving the problem]

[0006] After extensive research, the inventors discovered that by incorporating low-hardness, high-resilience ricone balls into the composition for the elastic layer, it is possible to reduce the hardness of the elastic layer while maintaining surface smoothness during extrusion molding, and thus arrived at the present invention.

[0007] That is, the present invention is a developing roller comprising a shaft body and an elastic layer on the outer periphery of the shaft body, wherein the elastic layer is formed from a composition for an elastic layer containing (a) organopolysiloxane, (b) silicone balls, (c) a conductivity imparting agent, (d) a filler, and (e) a vulcanizing agent, and the MD-1 hardness of the elastic layer is 40 or less, and the surface roughness Ra is 1 μm or more and 5 μm or less.

[0008] The elastic layer composition may further contain crude rubber.

[0009] The content of the silicone balls in the composition for the elastic layer is preferably 3% by mass or more and 10% by mass or less, relative to 100% by mass of the total of (a) organopolysiloxane and (b) silicone balls.

[0010] (b) The average particle size of the silicone balls is preferably 2 μm or more and 20 μm or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a developing roller that has low hardness and good surface smoothness. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view illustrating an embodiment of a developing roller of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Developing roller] As shown in FIG. 1, the developing roller 1 of this embodiment includes a shaft 2 and an elastic layer 3 on the outer periphery of the shaft 2. Each component will be described in detail below.

[0014] (shaft body) The shaft 2 can preferably be a conductive shaft used in a conventionally known developing roller. The shaft 2 is preferably made of at least one metal selected from the group consisting of iron, aluminum, stainless steel, and brass. Such a shaft 2 is also generally known as a "core metal."

[0015] 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 include, for example, a core made of an insulating resin and a plating layer provided on the core. Such a shaft 2 can be obtained, for example, by plating the core made of an insulating resin to make it conductive. The shaft 2 is preferably a cored bar in order to obtain good electrical conductivity.

[0016] The shape of the shaft 2 is preferably, for example, rod-like or tubular. The cross-sectional shape of the shaft 2 may be, for example, circular or elliptical, or may be non-circular such as polygonal. The outer peripheral surface of the shaft 2 may be subjected to treatment such as cleaning, degreasing, or primer treatment.

[0017] The axial length of the shaft 2 is not particularly limited and may be adjusted appropriately depending on the type of the image forming apparatus in which it is installed. The diameter of the shaft 2 (diameter of the circumscribing circle) is also not particularly limited and may be adjusted appropriately depending on the type of the image forming apparatus in which it is installed.

[0018] (elastic layer) The elastic layer 3 is preferably made of silicone rubber. For example, the elastic layer is formed by extruding the following composition for the elastic layer onto the outer peripheral surface of the shaft 2, followed by vulcanization and polishing. The composition for the elastic layer contains at least (a) organopolysiloxane, (b) silicone balls, (c) a conductivity imparting agent, (d) a filler, and (e) a vulcanizing agent.

[0019] (a) Organopolysiloxane The organopolysiloxane is preferably an organopolysiloxane having a degree of polymerization of 100 or more and represented by the following average composition formula (I). R 1 a SiO (4-a) / 2 (I) (In the formula, R 1 represent the same or different unsubstituted or substituted monovalent hydrocarbon groups, and a is a positive number of 1.95 or more and 2.05 or less.

[0020] R 1 Examples of the alkyl group 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 may be groups in which some or all of the hydrogen atoms of these hydrocarbon groups have been substituted with a substituent. The substituent may be, for example, a halogen atom, a cyano group, etc. Examples of hydrocarbon groups having a substituent include a chloromethyl group, a trifluoropropyl group, and a cyanoethyl group.

[0021] The molecular chain terminals of the organopolysiloxane are preferably blocked with a trialkylsilyl group such as a trimethylsilyl group, a dialkylaralkylsilyl group such as a dimethylvinylsilyl group, a dialkylhydroxysilyl group such as a dimethylhydroxysilyl group, or a trialalkylsilyl group such as a trivinylsilyl group.

[0022] The organopolysiloxane preferably has two or more alkenyl groups in the molecule. 1 Of these, it is preferable that the alkenyl group account for 0.001 mol % or more and 5 mol % or less (more preferably 0.01 mol % or more and 0.5 mol % or less).Vinyl groups are particularly preferable as the alkenyl groups contained in the organopolysiloxane.

[0023] Organopolysiloxanes can be obtained, for example, by co-hydrolysis and condensation of one or more organohalosilanes, or by ring-opening polymerization of cyclic polysiloxanes such as siloxane trimers or tetramers. The organopolysiloxane may basically be a linear diorganopolysiloxane, or may be partially branched. Furthermore, the organopolysiloxane may be a mixture of two or more organopolysiloxanes with different molecular structures.

[0024] The organopolysiloxane preferably has a kinematic viscosity of 100 cSt or more, more preferably 100,000 cSt or more and 10,000,000 cSt or less at 25° C. The degree of polymerization of the organopolysiloxane is preferably, for example, 100 or more, more preferably 3,000 or more and 10,000 or less.

[0025] (b) Silicone ball In this specification, silicone balls refer to fine particles made of silicone. The average particle size of the silicone balls is preferably 5 μm or more and 20 μm or less. The hardness (Durometer A) of the silicone balls is preferably 25 or more and 75 or less, and more preferably 30 or more and 75 or less. Examples of commercially available products include those under the trade name "KMP-597" (manufactured by Shin-Etsu Chemical Co., Ltd.) and those under the trade name "KMP-598" (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0026] From the viewpoint of improving distortion, the content of the silicone balls in the elastic layer composition is preferably 3% by mass or more and 10% by mass or less, relative to 100% by mass of the total of (a) organopolysiloxane and (b) silicone balls.

[0027] The elastic layer containing silicone balls has low hardness and good surface smoothness during extrusion molding, resulting in a highly durable developing roller that can produce high-quality images when incorporated into an image forming apparatus.

[0028] (c) Conductive agent Examples of the conductivity imparting agent include conductive powders containing conductive carbon, rubber carbons, metals, conductive polymers, etc. Carbon black is preferably used as the conductive powder, and examples of carbon black include furnace black such as Ketjenblack (registered trademark), acetylene black, channel black, and thermal black. The resistance value of the elastic layer is preferably adjusted to the range of 4 to 9 (log Ω).

[0029] (d) Filler Examples of the filler include silica-based fillers, such as fumed silica and precipitated silica.

[0030] Silica-based fillers include R 2 Si(OR 3 A surface-treated silica-based filler that has been surface-treated with a silane coupling agent represented by formula (R) 3 can be preferably used. 2 may be a group having a vinyl group or an amino group, such as a glycidyl group, a vinyl group, an aminopropyl group, a methacryloxy group, an N-phenylaminopropyl group, or a mercapto group. 3may be an alkyl group, such as a methyl group or an ethyl group. Silane coupling agents are readily available, for example, under the trade names "KBM1003" and "KBE402" manufactured by Shin-Etsu Chemical Co., Ltd. The surface-treated silica-based filler can be obtained by treating the surface of a silica-based filler with a silane coupling agent according to a standard method. Commercially available surface-treated silica-based fillers may be used, such as "Zeothix 95" manufactured by JMHUBER Corporation.

[0031] The amount of silica-based filler blended is preferably 11 parts by mass or more and 39 parts by mass or less, and more preferably 15 parts by mass or more and 35 parts by mass or less, per 100 parts by mass of (a) organopolysiloxane. The average particle size of the silica-based filler is preferably 1 μm or more and 80 μm or less, and more preferably 2 μm or more and 40 μm or less. The average particle size of the silica-based filler can be measured as the median size using a particle size distribution measuring device based on the laser diffraction method.

[0032] (e) Vulcanizing agent Examples of the vulcanizing agent include an addition vulcanizing agent and an organic peroxide vulcanizing agent. Suitable examples of the addition vulcanizing agent include organohydrogenpolysiloxanes, which are known as addition reaction type vulcanizing agents having two or more SiH groups (SiH bonds) in one molecule. The addition vulcanizing agents can be used alone or in combination of two or more. The amount of the addition vulcanizing agent is usually preferably 0.1 to 10 parts by mass, more preferably 2 to 5 parts by mass, per 100 parts by mass of the elastic layer composition.

[0033] When an addition vulcanizing agent is used, the organic peroxide vulcanizing agent can crosslink the millable silicone rubber alone, but when used in combination with the addition vulcanizing agent as an auxiliary vulcanizing agent, the physical properties of the resulting roller, such as strength and distortion, can be further improved.

[0034] Examples of organic peroxide vulcanizing agents include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane. The amount of the organic peroxide vulcanizing agent is usually preferably 0.1 to 10 parts by mass, more preferably 2 to 8 parts by mass, per 100 parts by mass of the composition for the elastic layer.

[0035] The addition vulcanizing agent is preferably used in combination with an addition reaction catalyst. Examples of the addition reaction catalyst include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins, platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. The amount of the addition reaction catalyst to be added can be a catalytic amount.

[0036] (Other ingredients) (f) Reaction control agent The composition for the elastic layer may contain a reaction inhibitor. The reaction inhibitor is a component that inhibits the crosslinking reaction of the silicone raw rubber at room temperature (e.g., 23°C). The reaction inhibitor may be, for example, a component that is deactivated or volatilized by heating. By including a reaction inhibitor, the pot life of the composition for the elastic layer is extended, and the composition for the elastic layer has excellent workability.

[0037] The reaction inhibitor can be appropriately selected from components that can inhibit the crosslinking reaction of the silicone raw rubber at room temperature, depending on the types of silicone raw rubber, vulcanizing agent, and curing accelerator blended in the elastic layer composition. For example, when the elastic layer composition contains a platinum catalyst, suitable reaction inhibitors that can be used include methylvinylcyclotetrasiloxane, acetylene alcohols, siloxane-modified acetylene alcohols, and hydroperoxides.

[0038] The amount of the reaction inhibitor is not particularly limited and can be adjusted appropriately depending on the desired pot life, curing temperature, curing speed, etc. The amount of the reaction inhibitor is, for example, preferably 0.5% by mass or more and 8.0% by mass or less, and more preferably 1.0% by mass or more and 6.0% by mass or less, based on the total amount of the composition for the elastic layer.

[0039] The elastic layer composition may also contain various additives. Examples of the various additives include auxiliary agents such as chain extenders, catalysts, dispersants, antioxidants, antioxidants, and non-silica fillers such as glass beads, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardancy improvers, acid acceptors, thermal conductivity improvers, mold release agents, and solvents. These various additives may be commonly used additives or may be additives specially used depending on the application.

[0040] The heating temperature when vulcanizing the composition for the elastic layer is preferably 100°C or higher and 500°C or lower, more preferably 120°C or higher and 300°C or lower. The heating time is preferably several seconds to 1 hour, more preferably 10 seconds to 35 minutes. If necessary, secondary vulcanization may be performed. Further, tertiary vulcanization may be performed at 180 to 280°C, particularly 200 to 250°C, for 1 to 15 minutes.

[0041] The developing roller thus obtained is polished to the desired product outer diameter. In the polishing process, the shape of the developing roller formed on the outer surface of the shaft is adjusted to a straight shape, a shape in which the thickness of the developing roller in the axial direction of the shaft gradually increases toward the center of the shaft and gradually decreases from the center to the tip of the shaft (i.e., an inverted crown shape), or a shape in which the thickness of the developing roller increases from the center of the shaft toward both ends of the shaft (i.e., an inverted crown shape).

[0042] The outer diameter of the elastic layer 3 is not particularly limited, and is preferably, for example, 6 mm or more and 25 mm or less, and more preferably 7 mm or more and 21 mm or less.

[0043] The thickness of the elastic layer 3 is not particularly limited, but is preferably 0.1 mm to 6 mm, and more preferably 1 mm to 4 mm. Note that the thickness in this specification refers to the thickness in the direction perpendicular to the axial direction of the developing roller 1.

[0044] A coating layer may be provided on the outer peripheral surface of the elastic layer 3. For the purpose of improving adhesion to the coating layer, the elastic layer 3 may be subjected to surface treatment such as primer treatment, corona treatment, plasma treatment, excimer treatment, UV treatment, itro treatment, or flame treatment.

[0045] (MD-1 hardness of elastic layer) The MD-1 hardness of the elastic layer 3 in the developing roller 1 is low, and is therefore preferably 40° or less, and more preferably 37° or less. By adjusting the MD-1 hardness of the elastic layer within the above range, it is possible to maintain the amount of developer transport while reducing the load on the developer. The MD-1 hardness can be measured using an MD-1 hardness tester (Micro Rubber Hardness Tester MD-1, manufactured by Kobunshi Keiki Co., Ltd.). In the present invention, the MD-1 hardness is determined by pressing the indenter of the MD-1 hardness tester against the roller surface and reading the value in peak hold mode. In principle, the MD-1 hardness tester conforms to the Type A durometer specified in JIS K6253.

[0046] (JIS A hardness of elastic layer) The JIS A hardness of the elastic layer 3 in the developing roller 1 is low, so it is preferably 45 or less, and more preferably 41 or less. The lower limit is preferably 28 or more, and more preferably 30 or more.

[0047] (Surface roughness of elastic layer) The surface roughness Ra of the elastic layer 3 is preferably 1 μm or more and 5 μm or less. When the surface roughness Ra is in the above range, the smoothness is high, and therefore the durability is high and high-quality images can be provided. In the present invention, the surface roughness Ra is measured using a contact type surface roughness measuring instrument Surfcom 1400G (manufactured by Tokyo Seimitsu) in accordance with JIS B 0601:1994.

[0048] The developing roller of the present invention can be used as a developing roller for an image forming apparatus. Such a developing roller has excellent flatness and smoothness even though it has a low hardness, and therefore can provide high image quality. [Example]

[0049] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0050] [Example 1] The developing roller of Example 1 was produced by the following procedure: Table 1 shows the formulation of the elastic layer composition of each Example and Comparative Example. (Formation of primer layer) An electroless nickel-plated shaft (made of SUM23, diameter 10 mm, length 274.2 mm) was washed with ethanol, and its surface was coated with a silicone primer (product name "Primer No. 16", manufactured by Shin-Etsu Chemical Co., Ltd.). The primer-treated shaft was baked in a gear oven at 150°C for 10 minutes and then cooled at room temperature for at least 30 minutes, forming a primer layer on the outer surface of the shaft.

[0051] (Formation of elastic layer) First, a composition for the elastic layer was prepared. Details of the composition for the elastic layer are as follows. Conductive silicone compound (product name "KE-3711-U", manufactured by Shin-Etsu Chemical Co., Ltd.) 95 parts by weight Silicone ball (product name (KMP-598), manufactured by Shin-Etsu Chemical Co., Ltd.) 5 parts by mass Peroxide vulcanizing agent (product name "C-3", manufactured by Shin-Etsu Chemical Co., Ltd.) 1.5 parts by mass Vulcanizing agent (product name "C-153A", manufactured by Shin-Etsu Chemical Co., Ltd.) 3.5 parts by mass 0.75 parts by mass of catalyst (product name "C-25A", manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass of control agent (product name "X93-1242", manufactured by Shin-Etsu Chemical Co., Ltd.)

[0052] The elastic layer composition was used to form an elastic layer on the outer peripheral surface of the elastic layer using an extrusion molding machine, and the layer was heated in an infrared heating furnace (IR furnace) at 270°C for 5 minutes, and then heated in a gear oven at 200°C for 4 hours for vulcanization. In this way, an elastic layer was formed on the outer peripheral surface of the elastic layer, and a developing roller was produced. The thickness of the elastic layer was 4 mm.

[0053] [Example 2, Example 3, Comparative Example 1 and Comparative Example 2] A developing roller was produced in the same manner as in Example 1, except that the contents of the conductive silicone compound (product name "KE-3711-U") and silicone balls in the composition for the elastic layer were changed as shown in Table 1.

[0054] [evaluation] The hardness and surface roughness Ra at the time of molding of the developing rollers manufactured in the above examples and comparative examples were measured. The evaluation results are shown in Table 1.

[0055] (MD-1 hardness) The MD-1 hardness of the elastic layer was measured using an MD-1 hardness tester ("Micro Rubber Hardness Tester MD-1 Hardness Type", manufactured by Kobunshi Keiki Co., Ltd.) The needle of the MD-1 hardness tester was pressed against the roller surface, and the value read in peak hold mode was taken as the MD-1 hardness.

[0056] (JIS A hardness) The JIS A hardness of the elastic layer was measured using a type A durometer in accordance with JIS K6253.

[0057] (Surface roughness Ra during molding) The surface roughness Ra of the elastic layer after molding was measured in the circumferential direction of the roller. The calculation standard was JIS B 0601:1994. The measurement length was 2.4 mm, and the measurement speed was 0.15 mm / s. A contact-type surface roughness measuring instrument (product name "Surfcom 1400G", manufactured by Tokyo Seimitsu Co., Ltd.) was used for the measurement. The average value of N = 5 measurements was used as the measurement value.

[0058] [Table 1]

[0059] As shown in Table 1, the developing rollers of Examples 1 to 3 have a low surface roughness Ra at the time of molding, despite the low hardness of the elastic layer. In other words, the developing roller of the present invention has a high surface smoothness and can provide high durability. [Explanation of symbols]

[0060] 1 Developing roller 2-axis body 3 Elastic layer

Claims

1. A developing roller including a shaft body and an elastic layer on the outer periphery of the shaft body, the elastic layer is formed from a composition for an elastic layer containing (a) an organopolysiloxane, (b) silicone balls, (c) a conductivity imparting agent, (d) a filler, and (e) a vulcanizing agent; The developing roller has an MD-1 hardness of the elastic layer of 40 or less, and a surface roughness Ra of 1 μm or more and 5 μm or less.

2. 2. The developing roller according to claim 1, wherein the content of the silicone balls in the composition for the elastic layer is 3% by mass or more and 10% by mass or less, relative to 100% by mass of the total of the organopolysiloxane (a) and the silicone balls (b).

3. 2. The developing roller according to claim 1, wherein the average particle size of the silicone balls (b) is 2 [mu]m or more and 20 [mu]m or less.

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