developing roller

Abstract

The present invention provides a developing roller having a laminated structure and capable of forming an image with better quality than the existing one. The developing roller (1) includes an inner layer (2) and an outer layer (4), wherein the inner layer (2) is composed of a rubber composition containing epichlorohydrin rubber in a proportion of 21 parts by mass or more in 100 parts by mass of the total rubber, and the surface resistance value logR1 of the outer peripheral surface (8) is set to 7.0 to 8.5, and the roller resistance value logR2 of the entire roller body (5) is set to 6.3 to 8.5.

Description

Technical Field

[0001] The present invention relates to a developing roller mounted and used in an image forming apparatus utilizing an electrophotographic method. Background Art

[0002] Recently, as a developing roller, a developing roller has been studied, which includes a roller body and the roller body has a laminated structure. The laminated structure includes: a cylindrical inner layer composed of a cross-linked product of a rubber composition, and an outer layer that covers the outer peripheral surface of the inner layer and constitutes the outer peripheral surface of the roller body (see Patent Document 1, etc.).

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-95455 Summary of the Invention

[0006] [Problems to be solved by the invention]

[0007] An object of the present invention is to provide a developing roller having a laminated structure and capable of forming an image with higher quality than the conventional one.

[0008] [Technical means to solve the problem]

[0009] The present invention provides a developing roller comprising a roller body, the roller body comprising a cylindrical inner layer and a cylindrical outer layer, the cylindrical inner layer being composed of a crosslinked product of a rubber composition containing epichlorohydrin rubber and a diene rubber as rubber, the cylindrical outer layer covering the outer periphery of the inner layer, the proportion of the epichlorohydrin rubber being 21 parts by mass or greater in 100 parts by mass of the total amount of the rubber, and the surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface of the roller body, which is the outer peripheral surface of the outer layer, satisfies the formula (1):

[0010] 7.0≦logR1≦8.5 (1)

[0011] The overall roller resistance value R2 (Ω, when 400 V is applied) of the roller body satisfies the formula (2):

[0012] 6.3≦logR2≦8.5 (2).

[0013] [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a developing roller having a laminated structure and capable of forming an image with higher quality than conventional ones. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1(a) is a perspective view showing the overall appearance of an example of the developing roller of the present invention, Figure 1 (b) is an end view of the developing roller of the example.

[0016] Figure 2 This is a diagram explaining a method for measuring the roller resistance value of the roller body.

[0017] Figure 3 This is a diagram for explaining a method for measuring the contact angle of water on the outer peripheral surface of the roller body.

[0018] [Explanation of Symbols]

[0019] 1: Developing roller

[0020] 2: Inner layer

[0021] 3, 8: outer surface

[0022] 4: Outer layer

[0023] 5: Roller body

[0024] 6: Through hole

[0025] 7: Axis

[0026] 9: Oxide film

[0027] 10: Aluminum roller

[0028] 12: DC power supply

[0029] 13: Resistors

[0030] 14: Measurement circuit

[0031] 15: Droplets

[0032] F: Load

[0033] V: Detection voltage

[0034] θ W : Contact angle

[0035] h: height

[0036] r: radius. DETAILED DESCRIPTION

[0037] Examples of the image forming apparatus equipped with a developing roller include a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a multifunction peripheral thereof.

[0038] As one of the image evaluation criteria for image forming apparatuses such as laser printers, the solid black density and two-dot density of a formed image are known.

[0039] The so-called pure black density is the density of a so-called pure black image in which at least a portion of the paper surface is filled with black. The higher the pure black density, the higher the contrast of the image.

[0040] The so-called 2dot density is the density of an image of circles arranged side by side on a square grid with a grid length of about 80 μm, which is called an isolated 2dot. The higher the 2dot density, the more the reproducibility of fine lines or grayscale can be improved, forming a fine image.

[0041] However, the two image densities are in an opposite relationship and are difficult to coexist.

[0042] That is, there is a tendency that the lower the roller resistance of the developing roller, the higher the pure black density, but the higher the roller resistance of the developing roller, the higher the 2dot density. In the conventional single-layer developing roller, it is difficult to achieve these two contradictory characteristics.

[0043] As described above, it is considered that the roller body of the developing roller is structured to include two layers, an inner layer and an outer layer, both of which are made of a cross-linked rubber composition, and the resistance values ​​of the two layers are adjusted so that the two opposing characteristics can coexist.

[0044] That is, the solid black density is correlated with the resistance value near the surface of the roller body. If the resistance value near the surface is reduced, the solid black density can be increased.

[0045] On the other hand, the 2dot concentration is related to the overall roller resistance value of the roller body. As the overall roller resistance value increases, the 2dot concentration can be increased.

[0046] Therefore, if

[0047] As described above, the roller body is configured to include two layers, an inner layer and an outer layer, both of which are composed of a cross-linked product of a rubber composition.

[0048] The outer layer is set to a low resistance state in order to adjust the resistance value near the surface of the roller body to a range that can increase the density of pure black.

[0049] The inner layer below it is set to a high resistance state in order to adjust the roller resistance value of the entire roller body including the outer layer to a range that can increase the 2dot concentration.

[0050] Then the pure black concentration and the 2dot concentration can coexist.

[0051] However, according to the inventors' research, in the conventional developing roller including a roller body having a laminated structure described in Patent Document 1, etc., the setting ranges of the resistance value near the surface and the roller resistance value, or the composition of the rubber composition forming the two layers, are still uncertain.

[0052] Therefore, in the initial stage of image formation, the solid black density (initial solid black density) or the 2dot density (initial 2dot density) may be insufficient, or the 2dot density may be greatly reduced when image formation is repeated.

[0053] Furthermore, when image formation is repeated, density unevenness may occur in the formed image depending on the density of adjacent images in the lateral direction perpendicular to the paper feeding direction.

[0054] In addition, if image formation is performed repeatedly, white spots are likely to occur, especially when a pure black image is formed on the entire surface of the image-forming area of ​​the paper (entire surface pure black image), and sometimes a clean entire surface pure black image with uniform concentration cannot be formed.

[0055] Therefore, the inventors further studied the optimum ranges of the surface resistance value of the outer peripheral surface of the roller body and the roller resistance value of the roller body, which define the resistance value near the surface of the roller body, and the composition of the rubber composition forming the inner layer.

[0056] As a result, it was found that

[0057] The inner layer is formed of a cross-linked product of a rubber composition containing epichlorohydrin rubber and diene rubber, and the proportion of the epichlorohydrin rubber is set to 21 parts by mass or more in 100 parts by mass of the total amount of rubber.

[0058] The surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface of the roller body is set to satisfy the formula (1):

[0059] 7.0≦logR1≦8.5 (1)

[0060] range, and

[0061] The roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body is set to satisfy the formula (2):

[0062] 6.3≦logR2≦8.5 (2)

[0063] The range is ok.

[0064] That is, the developing roller of the present invention includes: a roller body, the roller body including a cylindrical inner layer and a cylindrical outer layer, the cylindrical inner layer is composed of a cross-linked product of a rubber composition containing epichlorohydrin rubber and diene rubber as rubber, the cylindrical outer layer covers the outer periphery of the inner layer, the proportion of the epichlorohydrin rubber is 21 parts by mass or more in 100 parts by mass of the total amount of rubber, the surface resistance value R1 (Ω, when 10V is applied) of the outer peripheral surface of the roller body as the outer peripheral surface of the outer layer satisfies the above formula (1), and the roller resistance value R2 (Ω, when 400V is applied) of the entire roller body satisfies the above formula (2).

[0065] According to the developing roller of the present invention, by adopting the above-mentioned configuration, both the pure black density and the 2-dot density can be increased simultaneously, thereby forming an image having excellent contrast, fine line reproducibility, and gradation.

[0066] Furthermore, it is possible to suppress the occurrence of density unevenness in an image that depends on the density of images adjacent in the horizontal direction, and to suppress a decrease in 2-dot density when image formation is repeated, that is, a decrease in durable 2-dot density.

[0067] Furthermore, it is possible to suppress the occurrence of white spots in a solid black image when image formation is repeated, and to make the solid black image have a clean state with uniform density.

[0068] The presence or absence of white blur can be evaluated using the density of the lowest density portion in the entire solid black image, that is, the entire solid black density.

[0069] These facts are also clear from the results of Examples, Comparative Examples, and Previous Examples described later.

[0070] Figure 1 (a) is a perspective view showing the overall appearance of an example of the developing roller of the present invention, Figure 1 (b) is an end view of the developing roller of the example.

[0071] Reference Figure 1 (a) Figure 1 (b) The developing roller 1 of the example includes a two-layer roller body 5 in which an outer layer 4 composed of an elastic material is directly laminated on an outer peripheral surface 3 of a cylindrical inner layer 2 composed of an elastic material.

[0072] A shaft 7 is inserted and fixed into a through hole 6 in the center of the inner layer 2 .

[0073] The shaft 7 is integrally formed of a highly conductive material, for example, a metal such as iron, aluminum, an aluminum alloy, or stainless steel.

[0074] The shaft 7 is electrically and mechanically fixed to the roller body 5 by, for example, being bonded to the roller body 5 via a conductive adhesive or by press-fitting a shaft having an outer diameter larger than an inner diameter of the through-hole 6 into the through-hole 6 .

[0075] Alternatively, the shaft 7 and the roller body 5 may be electrically joined and mechanically fixed by using both of the above methods.

[0076] The surface of the outer layer 4 , that is, the outer peripheral surface 8 of the roller body 5 , is covered with an oxide film 9 as shown in enlarged form in both figures.

[0077] By coating the outer peripheral surface 8 with the oxide film 9, the oxide film 9 functions as a dielectric layer, thereby reducing the dielectric loss factor tan δ of the developing roller 1. In addition, the oxide film 9 functions as a low friction layer, thereby effectively suppressing the adhesion of colorant.

[0078] Furthermore, the oxide film 9 can be easily formed by, for example, irradiating the outer peripheral surface 8 with ultraviolet rays to oxidize the rubber near the outer peripheral surface 8 , thereby suppressing a decrease in productivity of the developing roller 1 or an increase in manufacturing cost.

[0079] However, the oxide film 9 may be omitted.

[0080] The inner layer 2 and the outer layer 4 are preferably both formed as non-porous single layers in order to simplify their respective structures and improve durability.

[0081] Furthermore, the term "single layer" for the inner layer 2 and the outer layer 4 means that the number of layers including the elastic material is a single layer.

[0082] The “two layers” of the roller body 5 also means that the inner layer 2 and the outer layer 4 both contain two elastic materials. In any case, the oxide film 9 formed by ultraviolet irradiation or the like is not included in the number of layers.

[0083] In the present invention, the surface resistance value R1 (Ω, when 10V is applied) of the outer peripheral surface 8 of the roller body 5 and the roller resistance value R2 (Ω, when 400V is applied) of the entire roller body 5 are limited to the ranges satisfying the above-mentioned formula (1) and formula (2) respectively for the following reasons.

[0084] That is, if the surface resistance value R1 (Ω, when 10V is applied) of the outer peripheral surface 8 of the roller body 5 is less than 7.0, expressed as the common logarithm logR1, the resistance value near the surface of the roller body 5 may be too low, and for example, image defects may occur due to overcurrent.

[0085] On the other hand, when the surface resistance R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 expressed as the common logarithm logR1 exceeds 8.5, the resistance near the surface of the roller body 5 cannot be sufficiently reduced to a range where the pure black density can be increased.

[0086] Therefore, the initial pure black density may be insufficient and the image contrast may be reduced, or in particular, white spots may appear on the entire pure black image and the pure black density may be reduced.

[0087] In addition, if the overall roller resistance value R2 (Ω, when 400V is applied) of the roller body 5 is expressed as the common logarithm logR2 and is less than 6.3, the initial 2dot density may be insufficient, the durable 2dot density may be significantly reduced, or the reproducibility of fine lines or grayscale may be reduced, thereby reducing the fineness of the image.

[0088] On the other hand, when the overall roller resistance value R2 (Ω, when 400V is applied) of the roller body 5 expressed as the common logarithm logR2 exceeds 8.5, density unevenness may sometimes occur in the image depending on the density of adjacent images in the horizontal direction perpendicular to the paper feeding direction.

[0089] The reason why the proportion of the epichlorohydrin rubber in the rubber composition forming the inner layer 2 is limited to 21 parts by mass or more in 100 parts by mass of the total amount of the rubber is as follows.

[0090] That is, if the proportion of epichlorohydrin rubber is less than 21 parts by mass, the initial 2dot concentration may be insufficient or the durable 2dot concentration may be significantly reduced regardless of the roller resistance value R2 (Ω, when 400V is applied) of the entire roller body 5 .

[0091] In contrast, by setting the surface resistance value R1 (Ω, when 10 V is applied) to the range satisfying formula (1), setting the roller resistance value R2 (Ω, when 400 V is applied) to the range satisfying formula (2), and setting the proportion of epichlorohydrin rubber in the rubber composition forming the inner layer 2 to the above range, the occurrence of the above-mentioned various defects can be suppressed.

[0092] Furthermore, it is possible to provide a developing roller capable of forming images with higher quality than conventional ones over a long period of time.

[0093] The developing roller 1 of the present invention also depends on the composition of the rubber composition forming the outer layer 4 constituting the outer peripheral surface 8 of the roller body 5, but the contact angle θ of water on the outer peripheral surface 8 is preferably W (°) is 50° or more.

[0094] If the water contact angle θ of the outer peripheral surface 8 of the roller body 5 is W When the angle (°) is within the above range, the outer peripheral surface 8 exhibits water repellency, thereby improving the releasability of the toner.

[0095] Therefore, the initial solid black density can be further increased, and the occurrence of white blur in the entire solid black image can be more effectively suppressed, thereby reducing the entire solid black density.

[0096] Furthermore, if the above effect is to be further enhanced, the contact angle θ of water is W (°) is more preferably 60° or more even within the above range.

[0097] In order to set the water contact angle θ of the outer peripheral surface 8 of the roller body 5 W (°) is adjusted to the above range. For example, in order to form the oxide film 9 covering the outer peripheral surface 8, it is only necessary to adjust the cumulative light intensity (mJ / cm 2 )

[0098] Specifically, the smaller the integrated light intensity (mJ / cm 2 ), the greater the water contact angle θ W (°).

[0099] What is the cumulative light intensity (mJ / cm 2 ) refers to the irradiation intensity per unit area of ​​ultraviolet rays irradiated to the outer peripheral surface 8 of the roller body 5 (mW / cm 2 The total amount of ultraviolet light irradiated to the outer peripheral surface 8 is obtained by multiplying the irradiation time (seconds) by the irradiation time (seconds).

[0100] Furthermore, the contact angle θ of water W The upper limit of (°) is not particularly limited, and includes the contact angle θ of water on the outer peripheral surface 8 that is not irradiated with ultraviolet rays and is therefore not covered with the oxide film 9. W (°) until.

[0101] <Measurement of the cumulative amount of ultraviolet light>

[0102] Cumulative light intensity (mJ / cm 2 ) is measured using an integrated light quantity measuring device.

[0103] Specifically, for example, a cumulative light quantity measuring device is installed at a position where the roller body 5 is installed in a device (UV treatment device) that actually irradiates the outer peripheral surface 8 of the roller body 5 with ultraviolet rays.

[0104] Next, the UV treatment device is operated in the same manner as when the outer peripheral surface 8 of the roller body 5 is irradiated with ultraviolet rays, and the light receiving part of the integrated light quantity measuring device is irradiated with ultraviolet rays, and the integrated light quantity (mJ / cm 2 ) The operating conditions of the UV treatment device required to achieve the target value.

[0105] As operating conditions, for example, in addition to the wavelength, irradiation intensity, and irradiation time of the irradiated ultraviolet rays, in the case of a UV treatment device that irradiates the outer peripheral surface 8 with ultraviolet rays while rotating the roller body 5, the rotation speed of the roller body 5 can be listed.

[0106] Furthermore, if the roller body 5 is installed in the same UV treatment device and operated under the operating conditions obtained by the previous measurement, the same cumulative light amount (mJ / cm 2 ) The outer peripheral surface 8 of the roller body 5 is irradiated with ultraviolet rays.

[0107] Rubber composition for inner layer 2

[0108] As described above, the inner layer 2 is formed of a cross-linked product of a rubber composition containing epichlorohydrin rubber and diene rubber as rubber and imparted with ion conductivity.

[0109] <Epichlorohydrin rubber>

[0110] Examples of the epichlorohydrin rubber include epichlorohydrin homopolymers, epichlorohydrin-ethylene oxide copolymers (ECO), epichlorohydrin-propylene oxide copolymers, epichlorohydrin-allyl glycidyl ether copolymers, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymers (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymers, and epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether tetrapolymers.

[0111] Among them, copolymers containing ethylene oxide, particularly ECO and / or GECO, are preferred.

[0112] The ethylene oxide content in ECO and / or GECO is preferably 30 mol% or more, particularly 50 mol% or more, and preferably 80 mol% or less.

[0113] Ethylene oxide plays a role in reducing the resistance value of the inner layer 2 and, consequently, reducing the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 .

[0114] However, if the ethylene oxide content is below the above range, the above effect cannot be fully obtained, and therefore the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 may not be sufficiently reduced.

[0115] On the other hand, when the ethylene oxide content exceeds the above range, ethylene oxide crystallization occurs and the segment motion of the molecular chain is inhibited, so the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 tends to increase.

[0116] In addition, the inner layer 2 may become too hard after crosslinking, or the viscosity of the rubber composition before crosslinking may increase during heating and melting, thereby reducing the processability of the rubber composition.

[0117] The epichlorohydrin content in ECO is the residual of the ethylene oxide content.

[0118] That is, the epichlorohydrin content is preferably 20 mol% or more, preferably 70 mol% or less, and particularly preferably 50 mol% or less.

[0119] The allyl glycidyl ether content in GECO is preferably 0.5 mol% or more, particularly 2 mol% or more, and is preferably 10 mol% or less, particularly 5 mol% or less.

[0120] Allyl glycidyl ether functions to ensure free volume as a side chain, thereby suppressing crystallization of ethylene oxide and reducing the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 .

[0121] However, if the allyl glycidyl ether content is below the above range, the above effect cannot be fully achieved, and thus the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 may not be sufficiently reduced.

[0122] On the other hand, allyl glycidyl ether functions as a crosslinking point during crosslinking of GECO.

[0123] Therefore, when the allyl glycidyl ether content exceeds the above range, the crosslinking density of GECO becomes too high, thereby hindering the segmental movement of the molecular chain, and the roller resistance value R2 (Ω, when 400V is applied) of the entire roller body 5 tends to increase.

[0124] The epichlorohydrin content in GECO is the residual amount of ethylene oxide and allyl glycidyl ether.

[0125] That is, the epichlorohydrin content is preferably 10 mol% or more, particularly 19.5 mol% or more, and is preferably 69.5 mol% or less, particularly 60 mol% or less.

[0126] Furthermore, as GECO, in addition to the copolymer in the narrow sense in which three monomers are copolymerized as described above, there is also known a modified product obtained by modifying an epichlorohydrin-ethylene oxide copolymer (ECO) with allyl glycidyl ether.

[0127] In the present invention, any of the GECOs can be used.

[0128] As the epichlorohydrin rubber, GECO is particularly preferred.

[0129] GECO has double bonds functioning as crosslinking points in the main chain due to allyl glycidyl ether. Therefore, crosslinking between main chains can reduce the compression permanent strain after crosslinking.

[0130] Therefore, the compressive permanent strain of the inner layer 2 can be reduced and collapse is less likely to occur.

[0131] One or two or more of these epichlorohydrin rubbers may be used.

[0132] Diene rubber

[0133] The diene rubber functions to impart good processability to the rubber composition, to improve the mechanical strength and durability of the inner layer 2, or to impart good rubber properties to the inner layer 2, namely, properties such as softness, small compression set, and resistance to collapse.

[0134] Examples of the diene rubber include natural rubber, isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (BR), and chloroprene rubber (CR).

[0135] Among them, the diene rubber is preferably a non-polar diene rubber, specifically at least one of IR, BR, and SBR, and particularly preferably both IR and BR, or both IR and SBR.

[0136] In addition, CR and / or NBR may be used in combination in the above-mentioned combined system.

[0137] (IR)

[0138] As the IR, various IRs having a polyisoprene structure that artificially reproduces the structure of natural rubber can be used.

[0139] IR includes oil-filled IR to which extender oil is added to adjust flexibility, and non-oil-filled IR to which no extender oil is added. However, in the present invention, non-oil-filled IR containing no extender oil that may cause bleeding is preferably used to prevent contamination of the photoreceptor.

[0140] One or two or more of these IRs may be used.

[0141] (BR)

[0142] As BR, various BRs including a polybutadiene structure in the molecule and having crosslinking properties can be used.

[0143] In particular, high-cis BR having a cis-1,4 bond content of 95% or more is preferred, as it can exhibit good properties as a rubber over a wide temperature range from low to high temperatures.

[0144] BR includes oil-extended BR to which extender oil is added to adjust flexibility, and non-oil-extended BR to which no extender oil is added. However, in the present invention, non-oil-extended BR containing no extender oil that may cause bleeding is preferably used to prevent contamination of the photoreceptor.

[0145] One or two or more of these BRs may be used.

[0146] (SBR)

[0147] As the SBR, various SBRs synthesized by copolymerizing styrene and 1,3-butadiene by various polymerization methods such as emulsion polymerization and solution polymerization can be used.

[0148] In addition, SBR is classified into high styrene type, medium styrene type, and low styrene type SBR according to the styrene content, and any of them can be used.

[0149] Furthermore, as SBR, there are oil-extended SBR to which extender oil is added to adjust the flexibility, and non-oil-extended SBR to which no extender oil is added. However, in the present invention, in order to prevent contamination of the photoreceptor, etc., it is still preferable to use non-oil-extended SBR that does not contain extender oil that may become a bleed-out substance.

[0150] One or two or more of these SBRs may be used.

[0151] (CR)

[0152] CR is a diene rubber having polarity, and functions to finely adjust the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 .

[0153] CR is synthesized by emulsion polymerization of chloroprene and is classified into sulfur-modified and non-sulfur-modified types depending on the type of molecular weight modifier used.

[0154] Among them, sulfur-modified CR can be synthesized by plasticizing a polymer obtained by copolymerizing chloroprene with sulfur as a molecular weight modifier using thiuram disulfide or the like to adjust the polymer to a predetermined viscosity.

[0155] Furthermore, non-sulfur-modified CR is classified into, for example, mercaptan-modified CR and xanthogen-modified CR.

[0156] Among them, mercaptan-modified CR was synthesized in the same manner as sulfur-modified CR except that alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and octyl mercaptan were used as molecular weight modifiers.

[0157] Furthermore, xanthogen-modified CR was synthesized in the same manner as sulfur-modified CR except that an alkylxanthogen compound was used as a molecular weight modifier.

[0158] CR is classified into slow crystallization rate type, medium crystallization rate type, and fast crystallization rate type based on its crystallization rate.

[0159] In the present invention, any type of CR can be used, but among them, non-sulfur-modified CR with a slow crystallization rate is preferred.

[0160] In addition, copolymers of chloroprene and other copolymer components can also be used as CR. Examples of other copolymer components include one or more of 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, acrylic acid, acrylic acid esters, methacrylic acid, and methacrylic acid esters.

[0161] Furthermore, as CR, there are oil-filled CR that adds extender oil to adjust the flexibility, and non-oil-filled CR that does not add extender oil. However, in order to prevent contamination of the photoreceptor, it is still preferable to use non-oil-filled CR that does not contain extender oil that may cause bleeding.

[0162] One or two or more of these CRs may be used.

[0163] (NBR)

[0164] NBR is also a diene rubber having polarity, and functions to finely adjust the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 .

[0165] As NBR, any of low nitrile NBR having an acrylonitrile content of 24% or less, medium nitrile NBR having an acrylonitrile content of 25% to 30%, medium-high nitrile NBR having an acrylonitrile content of 31% to 35%, high nitrile NBR having an acrylonitrile content of 36% to 42%, and very high nitrile NBR having an acrylonitrile content of 43% or more can be used.

[0166] In addition, as NBR, there are oil-extended NBRs to which extender oil is added to adjust the flexibility, and non-oil-extended NBRs to which no extender oil is added. However, in the present invention, in order to prevent contamination of photoreceptors, etc., it is still preferable to use non-oil-extended NBRs that do not contain extender oil that may become a bleed-out substance.

[0167] One or two or more of these NBRs may be used.

[0168] (Rubber ratio)

[0169] The rubber ratio can be arbitrarily set according to various properties required of the inner layer 2 , particularly the resistance value of the inner layer 2 , the roller resistance value R2 (Ω, when 400V is applied) of the entire roller body 5 , and the flexibility of the inner layer 2 .

[0170] However, the proportion of the epichlorohydrin rubber must be 21 parts by mass or more in 100 parts by mass of the total amount of the rubber.

[0171] The reason is as explained above.

[0172] Furthermore, the proportion of the epichlorohydrin rubber is preferably 30 parts by mass or less in 100 parts by mass of the total amount of the rubber also within the above range.

[0173] When the ratio of epichlorohydrin rubber exceeds the above range, depending on the composition of the rubber composition, the roller resistance value R2 (Ω, when 400 V is applied) of the roller body 5 as a whole may be less than the range of formula (2), resulting in insufficient initial 2dot concentration or significantly reduced durable 2dot concentration.

[0174] On the other hand, by setting the proportion of the epichlorohydrin rubber to 30 parts by mass or less in 100 parts by mass of the total amount of the rubber, it is possible to suppress a decrease in these characteristics.

[0175] The proportion of CR and / or NBR is preferably 1 part by mass or more, and preferably 15 parts by mass or less, in 100 parts by mass of the total amount of rubber.

[0176] If the ratio of CR and / or NBR is below the above range, the effect of blending these rubbers, namely, the effect of finely adjusting the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 , may not be fully achieved.

[0177] On the other hand, when the ratio of these rubbers exceeds the above range, the amount of epichlorohydrin rubber becomes relatively small, and the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 may not be sufficiently reduced to the range satisfying the above formula (2).

[0178] The ratio of the non-polar diene rubber other than CR and / or NBR is the residual amount of epichlorohydrin rubber or epichlorohydrin rubber and CR and / or NBR.

[0179] That is, when the ratio of epichlorohydrin rubber or epichlorohydrin rubber to CR and / or NBR is set to a predetermined value within the above range, the ratio of the nonpolar diene rubber may be set so that the total amount of rubber becomes 100 parts by mass.

[0180] <Cross-linking ingredients>

[0181] A cross-linking component for cross-linking the rubber is blended into the rubber composition for the inner layer 2 .

[0182] As the crosslinking component, it is preferred to use a crosslinking agent for crosslinking the rubber and a crosslinking accelerator for accelerating the crosslinking of the rubber by the crosslinking agent.

[0183] Among these, examples of the crosslinking agent include sulfur-based crosslinking agents, thiourea-based crosslinking agents, triazine derivative-based crosslinking agents, peroxide-based crosslinking agents, and various monomers. Among them, sulfur-based crosslinking agents are particularly preferred.

[0184] (Sulfur-based crosslinking agent)

[0185] Examples of the sulfur-based crosslinking agent include sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersed sulfur; and organic sulfur-containing compounds such as tetramethylthiuram disulfide and N,N-dithiobismorpholine. Sulfur is particularly preferred.

[0186] In consideration of imparting good rubber properties to the roller body, the proportion of sulfur is preferably 0.5 parts by mass or more and preferably 2 parts by mass or less relative to 100 parts by mass of the total amount of rubber.

[0187] In addition, when oil-treated powdered sulfur, dispersed sulfur, etc. are used as sulfur, the above ratio is set as the ratio of sulfur itself as an effective component contained in each.

[0188] When an organic sulfur-containing compound is used as the crosslinking agent, the ratio thereof is preferably adjusted so that the ratio of sulfur contained in the molecule relative to 100 parts by mass of the total amount of the rubber falls within the above range.

[0189] (Crosslinking accelerator)

[0190] Examples of the crosslinking accelerator for accelerating crosslinking of rubber include one or more of thiuram-based accelerators, thiazole-based accelerators, thiourea-based accelerators, guanidine-based accelerators, sulfenamide-based accelerators, and dithiocarbamate-based accelerators.

[0191] Among these, it is preferable to use a thiuram-based accelerator, a thiazole-based accelerator, a thiourea-based accelerator, and a guanidine-based accelerator in combination.

[0192] Examples of the thiuram-based accelerator include one or more of tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, and dipentamethylenethiuram tetrasulfide. Among them, tetramethylthiuram monosulfide is preferred.

[0193] Examples of the thiazole accelerator include one or more of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and 2-(4′-morpholinyldithio)benzothiazole. Di-2-benzothiazolyl disulfide is particularly preferred.

[0194] As the thiourea-based accelerator, various thiourea compounds having a thiourea structure in the molecule can be used.

[0195] Examples of the thiourea-based accelerator include ethylene thiourea, N,N'-diphenylthiourea, trimethylthiourea, and the compound of formula (5):

[0196] (C n H 2n+1NH)2C=S (5)

[0197] [wherein n represents an integer of 1 to 12], one or more of thiourea, tetramethylthiourea, etc. represented by [wherein n represents an integer of 1 to 12], and ethylenethiourea is particularly preferred.

[0198] Examples of the guanidine-based accelerator include one or more of 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, and 1-o-tolylbiguanide. 1,3-di-o-tolylguanidine is particularly preferred.

[0199] In the four combined use systems, the proportion of the thiuram accelerator is preferably 0.3 parts by mass or more and 1 part by mass or less relative to 100 parts by mass of the total amount of rubber, in consideration of sufficient effect of promoting crosslinking of the rubber.

[0200] The proportion of the thiazole-based accelerator is preferably 0.3 parts by mass or more and preferably 2 parts by mass or less relative to 100 parts by mass of the total amount of the rubber.

[0201] The proportion of the thiourea-based accelerator is preferably 0.3 parts by mass or more and preferably 1 part by mass or less relative to 100 parts by mass of the total amount of the rubber.

[0202] Furthermore, the proportion of the guanidine-based accelerator is preferably 0.2 parts by mass or more and preferably 1 part by mass or less relative to 100 parts by mass of the total amount of the rubber.

[0203] Furthermore, the thiourea-based accelerator also functions as a cross-linking agent for ECO that does not have sulfur cross-linking properties, and the guanidine-based accelerator also functions as an accelerator for cross-linking of ECO by the thiourea-based accelerator.

[0204] Ionic conductive agent

[0205] An ion conductive agent may be further formulated into the rubber composition for the inner layer 2 .

[0206] As the ion conductive agent, a salt (ionic salt) of an anion and a cation having a fluorine group and a sulfonyl group in the molecule is preferable.

[0207] By adding the ion conductive agent, the ion conductivity of the rubber composition can be further improved, and the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 can be further reduced.

[0208] Examples of the anion having a fluorine group and a sulfonyl group in the molecule constituting the ionic salt include one or more of fluoroalkylsulfonate ion, bis(fluoroalkylsulfonyl)imide ion, and tris(fluoroalkylsulfonyl)methide ion.

[0209] Among them, examples of fluoroalkylsulfonate ions include CF3SO3 -、C4F9SO3 - One or more of the above.

[0210] In addition, examples of bis(fluoroalkylsulfonyl)imide ions include (CF3SO2)2N - 、(C2F5SO2)2N - 、(C4F9SO2)(CF3SO2)N - 、(FSO2C6F4)(CF3SO2)N - 、(C8F 17 SO2)(CF3SO2)N - 、(CF3CH2OSO2)2N - 、(CF3CF2CH2OSO2)2N - 、(HCF2CF2CH2OSO2)2N - 、[(CF3)2CHOSO2]2N - One or more of the above.

[0211] Furthermore, as tris(fluoroalkylsulfonyl)methide ions, for example, (CF3SO2)3C - 、(CF3CH2OSO2)3C - One or more of the above.

[0212] In addition, examples of cations include one or more of alkali metal ions such as sodium, lithium, and potassium, ions of Group 2 elements such as beryllium, magnesium, calcium, strontium, and barium, ions of transition elements, cations of amphoteric elements, quaternary ammonium ions, and imidazolium cations.

[0213] As the ionic salt, a lithium salt using lithium ions as cations or a potassium salt using potassium ions is particularly preferred.

[0214] Among them, in terms of the effect of improving the ionic conductivity of the rubber composition and reducing the overall roller resistance value R2 (Ω, when 400V is applied) of the roller body 5, (CF3SO2)2NLi [lithium·bis(trifluoromethanesulfonyl)imide Li-TFSI] and / or (CF3SO2)2NK [potassium·bis(trifluoromethanesulfonyl)imide, K-TFSI] are preferred.

[0215] The ratio of the ion conductive agent such as the ion salt is preferably 0.1 parts by mass or more and preferably 2 parts by mass or less relative to 100 parts by mass of the total amount of the rubber.

[0216] Carbon black

[0217] Carbon black may be further formulated into the rubber composition for the inner layer 2 as a filler.

[0218] By adding carbon black, the mechanical strength of the developing roller can be improved.

[0219] Examples of carbon black include SAF, ISAF, HAF, and FEF.

[0220] Furthermore, when conductive carbon black is used as carbon black, electronic conductivity can be imparted to the inner layer 2 .

[0221] Examples of the conductive carbon black include acetylene black.

[0222] The proportion of carbon black is preferably 3 parts by mass or more and preferably 10 parts by mass or less relative to 100 parts by mass of the total amount of rubber.

[0223] <Other>

[0224] The rubber composition for the inner layer 2 may further contain various additives as needed.

[0225] Examples of the additives include a cross-linking accelerator, an acid scavenger, a plasticizer, and a processing aid.

[0226] Examples of the cross-linking accelerator include metal compounds such as zinc oxide; fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid; and one or more of other conventionally known cross-linking accelerators.

[0227] The proportion of the cross-linking accelerator is preferably 0.1 parts by mass or more and preferably 7 parts by mass or less, based on 100 parts by mass of the total amount of the rubber.

[0228] The acid absorber functions to prevent chlorine-based gas generated from epichlorohydrin rubber or CR during crosslinking from remaining in the inner layer 2 and thereby causing crosslinking inhibition or contamination of the photoreceptor.

[0229] As the acid scavenger, various substances that function as an acid acceptor can be used, and among them, hydrotalcites and MAGSARAT having excellent dispersibility are preferred, and hydrotalcites are particularly preferred.

[0230] Furthermore, when hydrotalcites and the like are used in combination with magnesium oxide or potassium oxide, a higher acid-absorbing effect can be obtained, and contamination of the photoreceptor can be more reliably prevented.

[0231] The proportion of the acid scavenger is preferably 0.1 parts by mass or more and preferably 7 parts by mass or less relative to 100 parts by mass of the total amount of the rubber.

[0232] Examples of the plasticizer include various plasticizers such as dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate, and various waxes such as polar wax. Examples of the processing aid include fatty acid metal salts such as zinc stearate.

[0233] The proportion of the plasticizer and / or processing aid is preferably 3 parts by mass or less relative to 100 parts by mass of the total amount of the rubber.

[0234] Furthermore, various additives such as fillers other than carbon black, degradation inhibitors, scorch retardants, lubricants, pigments, antistatic agents, flame retardants, neutralizers, nucleating agents, and co-crosslinking agents may be further formulated in arbitrary proportions as additives.

[0235] Examples of fillers other than carbon black include one or more of zinc oxide, silica, talc, calcium carbonate, magnesium carbonate, and aluminum hydroxide.

[0236] <Preparation of rubber composition>

[0237] The rubber composition for the inner layer 2 containing the above-described components can be prepared in the same manner as conventionally.

[0238] First, the rubber is masticated, then the components other than the cross-linking component are added and kneaded, and finally the cross-linking component is added and kneaded, thereby obtaining a rubber composition for the inner layer 2 .

[0239] For kneading, for example, a kneader, a Banbury mixer, an extruder, or the like can be used.

[0240] Rubber composition for outer layer 4

[0241] The outer layer 4 can be formed of various elastic materials that can adjust the surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 to be within the above range.

[0242] In particular, the outer layer 4 is preferably formed of a cross-linked product of a rubber composition containing epichlorohydrin rubber and diene rubber.

[0243] <Epichlorohydrin rubber>

[0244] As the epichlorohydrin rubber, one or two or more of the same epichlorohydrin rubbers as used in the inner layer 2 can be used.

[0245] Among them, ECO and / or GECO are preferred, and GECO is particularly preferred.

[0246] The reason is the same as that of the inner layer 2.

[0247] That is, by using GECO as the epichlorohydrin rubber, the compressive permanent strain of the outer layer 4 can be reduced and collapse is less likely to occur.

[0248] Diene rubber

[0249] The diene rubber functions to impart good processability to the rubber composition, to improve the mechanical strength and durability of the outer layer 4 , or to impart good properties as rubber to the outer layer 4 .

[0250] Furthermore, the diene rubber is also a material that is oxidized by ultraviolet irradiation to form an oxide film 9 on the surface of the outer layer 4 , that is, on the outer peripheral surface 8 of the roller body 5 .

[0251] As the diene rubber, one or two or more of the same diene rubbers as used in the inner layer 2 can be used.

[0252] Specifically, examples of the diene rubber include natural rubber, IR, NBR, SBR, BR, and CR.

[0253] Among them, as the diene rubber, it is preferred to use a non-polar diene rubber, specifically at least one of IR, BR, and SBR, and particularly SBR.

[0254] Furthermore, in order to finely adjust the surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 , CR and / or NBR may be used in combination with the non-polar diene rubber.

[0255] Specific examples of these diene rubbers are as described above.

[0256] (Rubber ratio)

[0257] The proportion of rubber can be arbitrarily set according to various properties required of the outer layer 4 , particularly the surface resistance R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 and the flexibility of the outer layer 4 .

[0258] However, the proportion of the epichlorohydrin rubber is 20 parts by mass or more, preferably 25 parts by mass or more, and preferably 50 parts by mass or less, in 100 parts by mass of the total amount of the rubber.

[0259] If the proportion of epichlorohydrin rubber is less than the above range, the surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 may exceed the range of the above formula (1), depending on the composition of the rubber composition.

[0260] Furthermore, sometimes the initial pure black density is insufficient and the image contrast is reduced, or white spots appear on the entire pure black image and the pure black density is reduced.

[0261] On the other hand, when the proportion of epichlorohydrin rubber exceeds the above range, the surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 may be less than the range of the above formula (1), and the resistance value near the surface of the roller body 5 may be too low, resulting in image defects caused by overcurrent.

[0262] In contrast, by setting the ratio of epichlorohydrin rubber within the above range and setting the surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 within the range of formula (1), the degradation of these characteristics can be suppressed.

[0263] The proportion of CR and / or NBR is preferably 1 part by mass or more, particularly 2.5 parts by mass or more, and preferably 10 parts by mass or less, in 100 parts by mass of the total amount of rubber.

[0264] If the ratio of CR and / or NBR is below the above range, the effect of finely adjusting the surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 may not be fully achieved by blending these rubbers.

[0265] On the other hand, when the ratio of these rubbers exceeds the above range, the amount of epichlorohydrin rubber may be relatively small, and the surface resistance value R1 (Ω, when 10V is applied) of the outer peripheral surface 8 of the roller body 5 may not be sufficiently reduced to the range satisfying the above formula (1).

[0266] The ratio of the non-polar diene rubber other than CR and / or NBR is the residual amount of epichlorohydrin rubber or epichlorohydrin rubber and CR and / or NBR.

[0267] That is, when the ratio of epichlorohydrin rubber or epichlorohydrin rubber to CR and / or NBR is set to a predetermined value within the above range, the ratio of the nonpolar diene rubber may be set so that the total amount of rubber becomes 100 parts by mass.

[0268] <Cross-linking ingredients>

[0269] As the crosslinking component, it is preferable to use in combination the same crosslinking agent and crosslinking accelerator as those used in the inner layer 2 .

[0270] Specifically, the crosslinking agent is preferably a sulfur-based crosslinking agent, particularly sulfur, and the crosslinking accelerator used in combination with the sulfur-based crosslinking agent is preferably a combination of four accelerators: a thiuram-based accelerator, a thiazole-based accelerator, a thiourea-based accelerator, and a guanidine-based accelerator.

[0271] The ratios of the sulfur-based crosslinking agent and the four crosslinking accelerators are also preferably similar to those in the inner layer 2 .

[0272] Ionic conductive agent

[0273] An ion conductive agent may be further formulated into the rubber composition for the outer layer 4 .

[0274] By adding the ion conductive agent, the ion conductivity of the rubber composition can be further improved, and the surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 can be further reduced.

[0275] The ion conductive agent is preferably a salt (ionic salt) of an anion and a cation having a fluorine group and a sulfonyl group in the molecule, which is the same as that used in the inner layer 2 .

[0276] The ratio of the ion conductive agent is preferably similar to that in the inner layer 2 .

[0277] <Other>

[0278] The rubber composition for the outer layer 4 may further contain various additives as needed.

[0279] Examples of additives include the same additives as those used in the inner layer 2, such as crosslinking accelerators, acid scavengers, fillers, plasticizers, processing aids, degradation inhibitors, scorch retardants, lubricants, pigments, antistatic agents, flame retardants, neutralizers, nucleating agents, co-crosslinking agents, and the like.

[0280] As the filler, carbon black such as thermal black is preferable, for example.

[0281] The ratio of the additive is preferably similar to that of the inner layer 2 .

[0282] <Preparation of rubber composition>

[0283] The rubber composition for the outer layer 4 containing the above-described components can be prepared in the same manner as before.

[0284] Specifically, the rubber is first masticated, then the components other than the cross-linking component are added and kneaded, and finally the cross-linking component is added and kneaded, thereby obtaining the rubber composition for the outer layer 4 .

[0285] For kneading, for example, a kneader, a Banbury mixer, an extruder, or the like can be used.

[0286] Manufacturing of Developing Roller 1

[0287] In order to manufacture the rubber composition for the inner layer 2 and the outer layer 4, Figure 1 (a) Figure 1 The developing roller 1 shown in (b) is formed by, for example, supplying two rubber compositions to a two-layer extruder, co-extruding them into a cylindrical shape of a laminated two-layer structure, and then crosslinking the entire structure to form the inner layer 2 and the outer layer 4 .

[0288] Alternatively, the rubber composition for the inner layer 2 is extruded into a cylindrical shape and cross-linked to form the inner layer 2, and then a sheet of the rubber composition for the outer layer 4 is wrapped around its outer peripheral surface 3, formed into a cylindrical shape by press molding, cross-linked, and integrated with the inner layer 2 to form the outer layer 4.

[0289] Next, the formed laminate of the inner layer 2 and the outer layer 4 is heated in an oven or the like to undergo secondary crosslinking, and after cooling, is ground to a predetermined outer diameter, thereby forming a roller body 5 including the laminate.

[0290] The thickness of the inner layer 2 can be arbitrarily set according to the structure and size of the image forming apparatus to be installed.

[0291] The thickness of the outer layer 4 can also be set arbitrarily, but is preferably 0.1 mm or more and preferably 2 mm or less.

[0292] By setting the thickness of the outer layer 4 within the said range, when the inner layer 2 and the outer layer 4, each containing the said specified rubber composition, are combined, the surface resistance value R1 (Ω, when 10V is applied) of the outer peripheral surface 8 of the roller body 5 and the overall roller resistance value R2 (Ω, when 400V is applied) can be adjusted to be within the said range.

[0293] Therefore, both the pure black density and the 2-dot density can be increased simultaneously, thereby forming an image with excellent contrast, fine line reproducibility, and gradation.

[0294] Furthermore, it is possible to suppress the occurrence of density unevenness in an image that depends on the density of adjacent images in the horizontal direction, and it is also possible to suppress a decrease in the durable 2-dot density or the entire surface solid black density.

[0295] As the grinding method, various grinding methods such as dry longitudinal grinding can be adopted, and mirror grinding can be performed at the end of the grinding step to perform finishing.

[0296] In this case, the releasability of the outer peripheral surface 8 is improved, and the oxide film 9 is not formed, or the adhesion of the toner is further suppressed by the synergistic effect of the oxide film 9, and contamination of the photoreceptor and the like can be effectively prevented.

[0297] The shaft 7 can be inserted into and fixed to the through hole 6 at any time from after the cylindrical body serving as the base of the roller body 5 is cut to after it is ground.

[0298] However, after cutting, it is preferred to first perform secondary cross-linking and grinding with the shaft 7 inserted into the through-hole 6. This can suppress warping or deformation of the roller body 5 caused by expansion and contraction during secondary cross-linking.

[0299] Furthermore, by performing grinding while rotating about the shaft 7 , the workability of the grinding can be improved and the runout of the outer peripheral surface 8 can be suppressed.

[0300] As described above, the shaft 7 can be inserted into the through hole 6 of the cylindrical body before secondary crosslinking via a conductive adhesive, especially a conductive thermosetting adhesive, and then secondary crosslinked, or a shaft having an outer diameter larger than the inner diameter of the through hole 6 can be press-fitted into the through hole 6.

[0301] In the former case, the cylindrical body is secondarily cross-linked by heating in an oven, and the thermosetting adhesive is cured, so that the shaft 7 and the roller body 5 are electrically bonded and mechanically fixed.

[0302] In the latter case, electrical bonding and mechanical fixation are simultaneously achieved during press-fitting.

[0303] Furthermore, as described above, the shaft 7 and the roller body 5 may be electrically joined and mechanically fixed by using both of the above methods.

[0304] As described above, the oxide film 9 is preferably formed by irradiating the outer peripheral surface 8 of the roller body 5 , which is the surface of the outer layer 4 , with ultraviolet rays.

[0305] That is, by irradiating the outer peripheral surface 8 of the roller body 5 with ultraviolet rays of a predetermined wavelength for a predetermined time, only the rubber constituting the vicinity of the outer peripheral surface 8 can be oxidized to form the oxide film 9 .

[0306] Therefore, the step of forming the oxide film 9 is simple and efficient, and a decrease in productivity of the developing roller 1 or an increase in manufacturing cost can be suppressed.

[0307] In addition, as mentioned above, by adjusting the integrated light intensity of ultraviolet rays (mJ / cm 2 ), the contact angle θ of water on the outer peripheral surface 8 covered by the formed oxide film 9 can also be adjusted W (°).

[0308] Furthermore, the oxide film 9 formed by ultraviolet irradiation does not cause problems such as a coating film formed by applying a coating agent, and is excellent in thickness uniformity and adhesion to the roller body 5 .

[0309] The wavelength of the irradiated ultraviolet rays is preferably 100 nm or more, 400 nm or less, and particularly 300 nm or less, in order to efficiently oxidize the diene rubber in the rubber composition for the outer layer 4 and form the functionally excellent oxide film 9 .

[0310] In addition, the irradiation time can be based on the cumulative amount of ultraviolet light (mJ / cm 2 ) of water contact angle θ W (°) The method of falling within the above-mentioned predetermined range is arbitrarily set.

[0311] However, the oxide film 9 may be formed by other methods, or may not be formed as described above.

[0312] One or two or more arbitrary intermediate layers may be interposed between the inner layer 2 and the outer layer 4 .

[0313] However, if the structure of the roller body 5 is simplified, the roller body 5 is preferably as follows: Figure 1 (a) Figure 1 (b) shows a two-layer structure in which the inner layer 2 and the outer layer 4 are directly laminated.

[0314] The developing roller 1 of the present invention can be used by being incorporated into various image forming apparatuses utilizing electrophotography, such as laser printers, electrostatic copying machines, plain paper facsimile machines, and multifunction peripherals thereof.

[0315] [Example]

[0316] Hereinafter, the present invention will be described based on Examples and Comparative Examples, but the configuration of the present invention is not necessarily limited to these examples.

[0317] Preparation of rubber composition

[0318] <Rubber composition (A) for inner layer 2>

[0319] As rubber, 16 parts by mass of GECO [EPION (registered trademark) 301L manufactured by OSAKA SODA Co., Ltd., EO / EP / AGE = 73 / 23 / 4 (molar ratio)], 77 parts by mass of IR [Nipol (registered trademark) IR2200 manufactured by ZEON Co., Ltd., non-oil extended], 6 parts by mass of SBR [JSR 1502 manufactured by JSR Co., Ltd., bonded styrene: 23.5%, non-oil extended], and 1 part by mass of CR [SHOPRENE (registered trademark) WRT manufactured by Showa Denko Co., Ltd., non-oil extended] were used.

[0320] While masticating the rubber in an amount of 100 parts by mass using a Banbury mixer, the following components were blended and kneaded.

[0321] [Table 1]

[0322] Element parts by mass Ionic salts 0.1 Cross-linking accelerator 2.5 Fillers 5.0 acid absorbents 3.0 Processing aids 0.5

[0323] The components in Table 1 are as follows, and the parts by mass in the table are parts by mass relative to 100 parts by mass of the total amount of rubber.

[0324] Ionic salt: Potassium bis(trifluoromethanesulfonyl)imide [K-TFSI, EF-N112 manufactured by Mitsubishi Materials Electronics Co., Ltd.]

[0325] Cross-linking accelerator: Two types of zinc oxide [manufactured by Sakai Chemical Industry Co., Ltd.]

[0326] Filler: Carbon black FEF [SEAST (registered trademark) SO manufactured by Tokai Carbon Co., Ltd.]

[0327] Acid scavenger: Hydrotalcite [DHT-4A (registered trademark)-2 manufactured by Kyowa Chemical Industry Co., Ltd.]

[0328] Processing aid: Zinc stearate [SZ-2000 manufactured by Sakai Chemical Industry Co., Ltd.]

[0329] Next, while kneading is continued, the following cross-linking components are blended and kneaded further to prepare a rubber composition (A) for the inner layer 2 .

[0330] [Table 2]

[0331] Element parts by mass crosslinking agent 1.05 Accelerator DM 1.5 Accelerator TS 0.5 Accelerator 22 0.3 Accelerator DT 0.2

[0332] The components in Table 2 are as follows, and the parts by mass in the table are parts by mass relative to 100 parts by mass of the total amount of rubber.

[0333] Cross-linking agent: Oil-treated powdered sulfur [Tsurumi Chemical Co., Ltd., Kinkain 5% oil-impregnated micronized sulfur]

[0334] Accelerator DM: Di-2-benzothiazolyl disulfide [Nocceler (registered trademark) DM, thiazole-based accelerator manufactured by Ouchi Shinko Chemical Industry Co., Ltd.]

[0335] Accelerator TS: Tetramethylthiuram monosulfide [SANCELER (registered trademark) TS, thiuram-based accelerator manufactured by Sanshin Chemical Industry Co., Ltd.]

[0336] Accelerator 22: Ethylene thiourea [2-mercaptoimidazoline, Accel 22-S manufactured by Kawaguchi Chemical Industry Co., Ltd., thiourea-based accelerator]

[0337] Accelerator DT: 1,3-di-o-tolylguanidine [Nocceler DT, guanidine-based accelerator manufactured by Ouchi Shinko Chemical Industry Co., Ltd.]

[0338] <Rubber composition for inner layer 2 (B)>

[0339] A rubber composition (B) for the inner layer 2 was prepared in the same manner as in the rubber composition (A) except that the amount of GECO was 18 parts by mass and the amount of IR was 75 parts by mass.

[0340] <Rubber composition (C) for inner layer 2>

[0341] A rubber composition (C) for the inner layer 2 was prepared in the same manner as in the rubber composition (A) except that the amount of GECO was 21 parts by mass and the amount of IR was 72 parts by mass.

[0342] <Rubber composition for inner layer 2 (D)>

[0343] A rubber composition (D) for the inner layer 2 was prepared in the same manner as in the rubber composition (A) except that the amount of GECO was 23 parts by mass and the amount of IR was 70 parts by mass.

[0344] <Rubber composition for inner layer 2 (E)>

[0345] A rubber composition (E) for the inner layer 2 was prepared in the same manner as in the rubber composition (A) except that the amount of GECO was 26 parts by mass and the amount of IR was 67 parts by mass.

[0346] <Rubber composition (F) for inner layer 2>

[0347] A rubber composition (F) for the inner layer 2 was prepared in the same manner as in the rubber composition (A) except that the amount of GECO was 28 parts by mass and the amount of IR was 65 parts by mass.

[0348] <Rubber composition for inner layer 2 (G)>

[0349] A rubber composition (G) for the inner layer 2 was prepared in the same manner as in the rubber composition (A) except that the amount of GECO was 30 parts by mass and the amount of IR was 63 parts by mass.

[0350] <Rubber composition for inner layer 2 (H)>

[0351] A rubber composition (H) for the inner layer 2 was prepared in the same manner as in the rubber composition (A) except that the amount of GECO was 32 parts by mass and the amount of IR was 61 parts by mass.

[0352] <Rubber composition for inner layer 2 (I)>

[0353] A rubber composition (I) for the inner layer 2 was prepared in the same manner as the rubber composition (A) except that 26 parts by mass of GECO [EPION 301L manufactured by OSAKA SODA Co., Ltd. mentioned above], 59 parts by mass of BR [UBEPOL (registered trademark) BR130B manufactured by Ube Industries, Ltd., non-oil extended], 10 parts by mass of CR [SHOPRENE WRT manufactured by Showa Denko Co., Ltd. mentioned above], and 5 parts by mass of NBR [Nipol DN401LL manufactured by ZEON Co., Ltd., acrylonitrile content: 18.0%, non-oil extended] were used as the rubbers, and no ionic salt was added.

[0354] <Rubber composition for inner layer 2 (J)>

[0355] A rubber composition (J) for the inner layer 2 was prepared in the same manner as the rubber composition (A) except that 17.5 parts by mass of GECO [EPION 301L manufactured by OSAKA SODA Co., Ltd. mentioned above], 36.25 parts by mass of IR [Nipol IR2200 manufactured by ZEON Co., Ltd. mentioned above], 36.25 parts by mass of SBR [JSR 1502 manufactured by JSR Co., Ltd. mentioned above], 5 parts by mass of CR [SHOPRENE WRT manufactured by Showa Denko Co., Ltd. mentioned above], and 5 parts by mass of ethylene propylene diene rubber [EPDM, Esprene (registered trademark) 505A manufactured by Sumitomo Chemical Co., Ltd.] as a non-diene rubber were used.

[0356] <Rubber composition (K) for inner layer 2>

[0357] A rubber composition (K) for the inner layer 2 was prepared in the same manner as the rubber composition (A), except that 5 parts by mass of GECO [EPION 301L manufactured by OSAKA SODA Co., Ltd. mentioned above], 45 parts by mass of IR [Nipol IR2200 manufactured by ZEON Co., Ltd. mentioned above], 40 parts by mass of BR [UBEPOL BR130B manufactured by Ube Industries, Ltd. mentioned above], and 10 parts by mass of CR [SHOPRENE WRT manufactured by Showa Denko Co., Ltd. mentioned above] were used as the rubbers and the amount of the ionic salt was changed to 1 part by mass.

[0358] <Rubber composition for inner layer 2 (L)>

[0359] A rubber composition (L) for the inner layer 2 was prepared in the same manner as the rubber composition (K) except that the amount of GECO was 10 parts by mass, the amount of IR was 42.5 parts by mass, and the amount of BR was 37.5 parts by mass.

[0360] <Rubber composition for inner layer 2 (M)>

[0361] A rubber composition (M) for the inner layer 2 was prepared in the same manner as the rubber composition (K) except that the amount of GECO was 12.5 parts by mass, the amount of IR was 41.25 parts by mass, and the amount of BR was 36.25 parts by mass.

[0362] <Rubber composition for inner layer 2 (N)>

[0363] A rubber composition (N) for the inner layer 2 was prepared in the same manner as the rubber composition (K) except that the amount of GECO was 15 parts by mass, the amount of IR was 40 parts by mass, and the amount of BR was 35 parts by mass.

[0364] <Rubber composition for inner layer 2 (O)>

[0365] A rubber composition (O) for the inner layer 2 was prepared in the same manner as the rubber composition (K) except that the amount of GECO was 20 parts by mass, the amount of IR was 37.5 parts by mass, and the amount of BR was 32.5 parts by mass.

[0366] <Rubber composition for inner layer 2 (P)>

[0367] A rubber composition (P) for the inner layer 2 was prepared in the same manner as the rubber composition (K) except that the amount of GECO was 30 parts by mass, the amount of IR was 32.5 parts by mass, and the amount of BR was 27.5 parts by mass.

[0368] <Rubber composition for inner layer 2 (Q)>

[0369] A rubber composition (Q) for the inner layer 2 was prepared in the same manner as for the rubber composition (A), except that 28 parts by mass of GECO [EPION 301L manufactured by OSAKA SODA Co., Ltd. mentioned above], 60 parts by mass of IR [Nipol IR2200 manufactured by ZEON Co., Ltd. mentioned above], 6 parts by mass of SBR [JSR 1502 manufactured by JSR Co., Ltd. mentioned above], 1 part by mass of CR [SHOPRENE WRT manufactured by Showa Denko Co., Ltd. mentioned above], and 5 parts by mass of EPDM [Esprene 505A manufactured by Sumitomo Chemical Co., Ltd. mentioned above] were used as the rubber.

[0370] <Rubber composition for outer layer 4 (i)>

[0371] As rubber, 15 parts by mass of GECO [EPION 301L manufactured by OSAKA SODA Co., Ltd. mentioned above], 75 parts by mass of SBR [JSR 1502 manufactured by JSR Co., Ltd. mentioned above], and 10 parts by mass of CR [SHOPRENE WRT manufactured by Showa Denko Co., Ltd. mentioned above] were used.

[0372] While masticating the rubber in an amount of 100 parts by mass using a Banbury mixer, the following components were blended and kneaded.

[0373] [Table 3]

[0374] Element parts by mass Ionic salts 1.0 Cross-linking accelerator 2.5 Fillers 5.0 acid absorbents 3.0 Processing aids 0.5

[0375] The components in Table 3 are as follows: Parts by mass in the table are parts by mass relative to 100 parts by mass of the total amount of rubber.

[0376] Ionic salt: Potassium bis(trifluoromethanesulfonyl)imide [K-TFSI, EF-N112 manufactured by Mitsubishi Materials Electronics Co., Ltd. mentioned above]

[0377] Cross-linking accelerator: Two types of zinc oxide [manufactured by Sakai Chemical Industry Co., Ltd.]

[0378] Filler: Carbon black [thermal black, Asahi #15 manufactured by Asahi Carbon Black Co., Ltd.]

[0379] Acid scavenger: Hydrotalcite [DHT-4A-2 manufactured by Kyowa Chemical Industry Co., Ltd. mentioned above]

[0380] Processing aid: Zinc stearate [SZ-2000 manufactured by Sakai Chemical Industry Co., Ltd. mentioned above]

[0381] Next, while kneading is continued, the following cross-linking components are blended and kneaded further to prepare a rubber composition (i) for the outer layer 4 .

[0382] [Table 4]

[0383] Element parts by mass crosslinking agent 1.05 Accelerator DM 1.5 Accelerator TS 0.5 Accelerator 22 0.3 Accelerator DT 0.2

[0384] The components in Table 4 are as follows: In addition, the mass parts in the table are mass parts relative to 100 mass parts of the total amount of rubber.

[0385] Cross-linking agent: Oil-treated powdered sulfur [Tsurumi Chemical Co., Ltd.'s Kinkain 5% oil-impregnated micronized sulfur mentioned above]

[0386] Accelerator DM: Di-2-benzothiazolyl disulfide [Nocceler DM, thiazole-based accelerator manufactured by Ouchi Shinko Chemical Co., Ltd., mentioned above]

[0387] Accelerator TS: Tetramethylthiuram monosulfide [SANCELER TS, a thiuram-based accelerator manufactured by Sanshin Chemical Industries Co., Ltd., mentioned above]

[0388] Accelerator 22: Ethylene thiourea [2-mercaptoimidazoline, Accel 22-S manufactured by Kawaguchi Chemical Industries, Ltd., mentioned above, thiourea-based accelerator]

[0389] Accelerator DT: 1,3-di-o-tolylguanidine [Nocceler DT and guanidine-based accelerators manufactured by Ouchi Shinko Chemical Co., Ltd. mentioned above]

[0390] <Rubber composition for outer layer 4 (ii)>

[0391] A rubber composition (ii) for the outer layer 4 was prepared in the same manner as the rubber composition (i) except that the amount of GECO was changed to 20 parts by mass and the amount of SBR was changed to 70 parts by mass.

[0392] <Rubber composition for outer layer 4 (iii)>

[0393] A rubber composition (iii) for the outer layer 4 was prepared in the same manner as in the rubber composition (i) except that the amount of GECO was changed to 25 parts by mass and the amount of SBR was changed to 65 parts by mass.

[0394] <Rubber composition for outer layer 4 (iv)>

[0395] A rubber composition (iv) for the outer layer 4 was prepared in the same manner as in the rubber composition (i) except that the amount of GECO was changed to 30 parts by mass and the amount of SBR was changed to 60 parts by mass.

[0396] <Rubber composition for outer layer 4 (v)>

[0397] A rubber composition (v) for the outer layer 4 was prepared in the same manner as in the rubber composition (i) except that the amount of GECO was 50 parts by mass and the amount of SBR was 40 parts by mass.

[0398] <Rubber composition for outer layer 4 (vi)>

[0399] A rubber composition (vi) for the outer layer 4 was prepared in the same manner as the rubber composition (i) except that the amount of GECO was 30 parts by mass, the amount of SBR was 67.5 parts by mass, and the amount of CR was 2.5 parts by mass.

[0400] <Rubber composition for outer layer 4 (vii)>

[0401] A rubber composition (vii) for the outer layer 4 was prepared in the same manner as the rubber composition (vi) except that no ionic salt was formulated.

[0402] <Rubber composition for outer layer 4 (viii)>

[0403] A rubber composition (viii) for the outer layer 4 was prepared in the same manner as in the rubber composition (vii) except that the amount of GECO was 40 parts by mass and the amount of SBR was 57.5 parts by mass.

[0404] <Rubber composition for outer layer 4 (ix)>

[0405] A rubber composition (ix) for the outer layer 4 was prepared in the same manner as in the rubber composition (vii) except that the amount of GECO was changed to 25 parts by mass and the amount of SBR was changed to 72.5 parts by mass.

[0406] Examples 1 to 9, Comparative Examples 1 to 10

[0407] The rubber compositions (B) to (P) for the inner layer 2 and the rubber compositions (i) to (v) for the outer layer were supplied to a two-layer extruder in the combinations shown in Tables 5 to 8, extruded into a two-layer cylindrical structure having an outer diameter of φ16 mm and an inner diameter of φ6.5 mm, mounted on a temporary shaft for crosslinking, and crosslinked in a vulcanizing tank at 160°C for 1 hour.

[0408] Next, the cross-linked cylindrical body was remounted on a metal shaft 7 having an outer diameter of 7.5 mm and coated with a conductive thermosetting adhesive on the outer peripheral surface, and heated to 160° C. in an oven to be bonded to the shaft 7 .

[0409] Next, both ends of the cylindrical body are shaped, and the outer peripheral surface 8 is longitudinally ground using a cylindrical grinder, and then mirror-polished to an outer diameter of φ16 mm as a finishing process, thereby forming a roller body 5 having a two-layer structure of an inner layer 2 and an outer layer 4 and integrated with the shaft 7.

[0410] The thickness of the outer layer 4 after grinding is about 0.1 mm to 2 mm.

[0411] Next, the outer peripheral surface 8 of the formed roller body 5 was wiped with alcohol, and then the distance from the outer peripheral surface 8 to the UV lamp was set to 50 mm, and the roller body 5 was placed in an ultraviolet irradiation device [PL21-200 manufactured by SEN Special Light Source Co., Ltd.].

[0412] Then, the outer peripheral surface 8 is coated with the oxide film 9 by irradiating ultraviolet rays having wavelengths of 184.9 nm and 253.7 nm while rotating in units of 90° about the axis, thereby manufacturing the developing roller 1 .

[0413] The cumulative amount of ultraviolet light is 100mJ / cm 2 .

[0414] Characteristic Determination

[0415] The developing rollers 1 manufactured in the above-described examples and comparative examples were subjected to the following tests to determine their characteristics.

[0416] In addition, each test was performed in an environment of a temperature of 23° C. and a relative humidity of 55%.

[0417] <Measurement of surface resistance value R1>

[0418] The surface resistance value R1 (Ω, when 10 V is applied) of the outer peripheral surface 8 of the roller body 5 was measured in the surface resistance mode using a resistivity meter [Hiresta (registered trademark) UP MCP-HT800 manufactured by Mitsubishi Chemical Analytech Co., Ltd.] and a dedicated MCP probe (UA type) manufactured by the same company.

[0419] Specifically, a load of 480 g was applied to the MCP probe, pressing it against the axial center of the outer peripheral surface 8 of the roller body 5 , and the value after 10 seconds was taken as the surface resistance R1 (Ω, when 10 V was applied) of the outer peripheral surface 8 of the roller body 5 .

[0420] The measurement conditions were RCF(S): 1.050 and applied voltage: 10V.

[0421] Regarding the surface resistance value R1 (Ω, when 10 V is applied), as described above, a common logarithm value logR1 of 7.0 or more and 8.5 or less was considered acceptable (○), and the others were considered unacceptable (×).

[0422] <Measurement of Roller Resistance R2>

[0423] use Figure 2 The roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 is measured by the method shown.

[0424] That is, refer to Figure 1 (a) Figure 1 (b) Figure 2 First, an aluminum drum 10 that can rotate at a fixed rotational speed is prepared, and the outer peripheral surface 8 of the roller body 5 is brought into contact with the outer peripheral surface 11 of the prepared aluminum drum 10 from above.

[0425] Furthermore, a DC power supply 12 and a resistor 13 are connected in series between the shaft 7 and the aluminum drum 10 to form a measurement circuit 14 .

[0426] The (-) side of the DC power supply 12 is connected to the shaft 7 , and the (+) side is connected to the resistor 13 . The resistance value r′ of the resistor 13 is set to 100Ω.

[0427] Next, a load F of 450 g was applied to both ends of the shaft 7 , and the aluminum drum 10 was rotated at 40 rpm in a state where the roller body 5 was brought into pressure contact with the aluminum drum 10 .

[0428] Then, while the rotation is continued, when a DC 400 V applied voltage E is applied between the roller body 5 and the aluminum drum 10 from the DC power supply 12 , a detection voltage V applied to the resistor 13 is measured.

[0429] Based on the detection voltage V and the applied voltage E (=400 V), the roller resistance value R2 of the entire roller body 5 is basically calculated using the formula (3):

[0430] R2=r'×E / V-r' (3)

[0431] And seek out.

[0432] However, the term -r' in formula (3) can be considered small, so the present invention uses formula (3a):

[0433] R2=r'×E / V (3a)

[0434] The obtained value is the roller resistance value R2 (Ω, when 400 V is applied) of the entire roller body 5 .

[0435] As described above, regarding the roller resistance value R2 (Ω, when 400 V was applied), a common logarithm value logR2 of 6.3 or more and 8.5 or less was considered acceptable (○), and other values ​​were considered unacceptable (×).

[0436] <Contact angle of water θ W Determination of

[0437] The contact angle θ of water on the outer peripheral surface 8 of the roller body 5 W (°) Measured using an automatic contact angle meter [DMo-501 manufactured by Kyowa Interface Science Co., Ltd.] under the conditions of a droplet volume of 2 μL and a measurement start time after droplet placement of 1000 ms.

[0438] Specifically, refer to Figure 3 First, 2 μL of pure water filled in a micro syringe is dripped onto the outer peripheral surface 8 of the roller body 5. According to the shape of the droplet 15 1000 ms after the dripping, the following equation (4) is used:

[0439] θ W=2arctan(h / r) (4)

[0440] Calculate the contact angle θ of water W (°).

[0441] Furthermore, the symbols in formula (4) are as follows Figure 3 As shown, h is the height of the liquid drop 15 dropped onto the outer peripheral surface 8 of the roller body 5 , and r is the radius of the liquid drop 15 .

[0442] The measurement was performed by dripping the liquid droplets 15 at three locations, 5 cm from both ends in the axial direction and the center in the axial direction, on the outer peripheral surface 8 of the roller body 5 of the same sample, and the average value was taken as the measured value.

[0443] The contact angle of water θ W A value less than 50° was considered poor (×), a value of 50° or more and less than 60° was considered good (△), and a value of 60° or more was considered particularly good (○).

[0444] Actual Machine Test

[0445] The manufactured developing roller 1 was installed in a laser printer [HL-2240D manufactured by Brother Industries, Ltd.], and the following tests were carried out to evaluate the quality of the formed images.

[0446] In addition, each test was performed in an environment of a temperature of 23.5° C. and a relative humidity of 55%.

[0447] <Measurement of initial pure black density>

[0448] Immediately after a 1% density image was continuously formed on 30 sheets of plain paper, a solid black image of 3 cm square was formed on one sheet.

[0449] The image density was then measured at five random points on the formed solid black image using a reflection densitometer manufactured by Videojet X-Rite Co., Ltd. The average value was determined as the initial solid black density. An initial solid black density of 1.30 or greater was considered acceptable (○), while an initial solid black density of less than 1.30 was considered unacceptable (×).

[0450] <Measurement of initial 2dot concentration>

[0451] Immediately after a 1% density image was continuously formed on 30 sheets of plain paper, an isolated 2-dot image consisting of circles arranged side by side on a square grid with a grid length of approximately 80 μm was formed on one sheet.

[0452] Then, the image density was measured at five arbitrary points on the formed isolated 2-dot image using the same reflection densitometer, and the average value was determined and used as the initial 2-dot density.

[0453] An initial 2-dot concentration exceeding 0.02 was evaluated as acceptable (○), and an initial 2-dot concentration of 0.02 or less was evaluated as unacceptable (×).

[0454] <Measurement of concentration unevenness>

[0455] Immediately after continuously forming an image of 1% density on 3000 sheets of plain paper, a 3 cm wide halftone portion and the halftone portion were adjacent to each other with a 5 mm gap in the lateral direction perpendicular to the paper feeding direction, and an image of a 3 cm square image having a pure black portion was formed.

[0456] The halftone portion of the formed image was observed, and the image with no unevenness was evaluated as good (○), while the image with unevenness was evaluated as poor (×). The image with poor (×) was not subjected to the subsequent tests.

[0457] In addition, those with an initial pure black density of 1.1 or less and / or an initial 2-dot density of 0.01 or less were not subjected to subsequent tests.

[0458] <Determination of durable 2dot concentration>

[0459] Immediately after continuously forming 1% density images on 3000 sheets of plain paper, an isolated 2-dot image was formed on one sheet in the same manner as in the measurement of the initial 2-dot density.

[0460] Then, the image density was measured at five arbitrary points on the formed isolated 2-dot image using the same reflection densitometer, and the average value was determined and used as the durable 2-dot density.

[0461] A durable 2-dot concentration exceeding 0.02 was evaluated as acceptable (○), and a durable 2-dot concentration of 0.02 or less was evaluated as unacceptable (×).

[0462] The difference between the initial 2dot concentration and the durable 2dot concentration was determined as a change (Δ2dot concentration), and a Δ2dot concentration of 0.03 or less was considered acceptable (○), while a concentration exceeding 0.03 was considered unacceptable (×).

[0463] <Measurement of the density of pure black on the entire surface>

[0464] Immediately after 1% density images were continuously formed on 3,000 sheets of plain paper, a solid black image was formed on one sheet.

[0465] Furthermore, the density of the lowest density portion of the formed solid black image was measured using the same reflection densitometer, and this was taken as the solid black density.

[0466] A full-surface pure black density of less than 1.13 was rated as poor (×), 1.13 or more and less than 1.2 was rated as good (△), and 1.2 or more was rated as particularly good (○).

[0467] The above results are shown in Tables 5 to 8.

[0468] [Table 5]

[0469]

[0470] [Table 6]

[0471]

[0472] [Table 7]

[0473]

[0474] [Table 8]

[0475]

[0476] The results in Tables 5 to 8 show that a developing roller capable of forming images of superior quality to the conventional development roller can be obtained by having a two-layer structure of an inner layer 2 and an outer layer 4, setting the proportion of epichlorohydrin rubber in the inner layer 2 to 21 parts by mass or more in 100 parts by mass of the total amount of rubber, setting the surface resistance value log R1 of the outer peripheral surface 8 to 7.0 to 8.5, and setting the overall roller resistance value log R2 of the roller body 5 to 6.3 to 8.5.

[0477] Examples 10 to 19, Comparative Examples 11 to 14

[0478] The rubber compositions (A) to (H) (Q) for the inner layer 2 and the rubber compositions (vi) to (ix) for the outer layer were supplied to a two-layer extruder in the combinations shown in Tables 9 to 11, extruded into a two-layer cylindrical structure having an outer diameter of φ16 mm and an inner diameter of φ6.5 mm, mounted on a temporary shaft for crosslinking, and crosslinked in a vulcanizing tank at 160°C for 1 hour.

[0479] Next, the cross-linked cylindrical body was remounted on a metal shaft 7 having an outer diameter of 7.5 mm and coated with a conductive thermosetting adhesive on the outer peripheral surface, and heated to 160° C. in an oven to be bonded to the shaft 7 .

[0480] Next, both ends of the cylindrical body are shaped, and the outer peripheral surface 8 is longitudinally ground using a cylindrical grinder, and then mirror-polished to an outer diameter of φ16 mm as a finishing process, thereby forming a roller body 5 having a two-layer structure of an inner layer 2 and an outer layer 4 and integrated with the shaft 7.

[0481] The thickness of the outer layer 4 after grinding is about 0.1 mm to 2 mm.

[0482] Next, the outer peripheral surface 8 of the formed roller body 5 was wiped with alcohol, and then the distance from the outer peripheral surface 8 to the UV lamp was set to 50 mm, and the roller body 5 was placed in an ultraviolet irradiation device [PL21-200 manufactured by SEN Special Light Source Co., Ltd.].

[0483] Then, the outer peripheral surface 8 is coated with the oxide film 9 by irradiating ultraviolet rays having wavelengths of 184.9 nm and 253.7 nm while rotating in units of 90° about the axis, thereby manufacturing the developing roller 1 .

[0484] The integrated light amounts of ultraviolet rays were set to the values ​​shown in Tables 9 to 11, respectively.

[0485] The developing rollers 1 manufactured in the above-mentioned examples and comparative examples were subjected to the above-mentioned tests to evaluate their characteristics.

[0486] The results are shown in Tables 9 to 11.

[0487] [Table 9]

[0488]

[0489] [Table 10]

[0490]

[0491] [Table 11]

[0492]

[0493] As can be seen from the results of Tables 9 to 11, the above-described configuration can provide a developing roller capable of forming an image with a higher quality than the conventional one.

[0494] Furthermore, the results of Examples 1 to 19 and Comparative Examples 1 to 14 further show that the water contact angle θ of the outer peripheral surface 8 of the roller body 5 is W (°) is preferably 50° or more, particularly 60° or more.

Claims

1. A developing roller comprising a roller body, the roller body comprising a cylindrical inner layer and a cylindrical outer layer, the cylindrical inner layer being composed of a crosslinked product of a rubber composition containing epichlorohydrin rubber and a diene rubber as rubber, the cylindrical outer layer covering the outer periphery of the inner layer, the proportion of the epichlorohydrin rubber being 21 parts by mass or greater in 100 parts by mass of the total amount of the rubber, and the outer peripheral surface of the roller body, which is the outer peripheral surface of the outer layer, having a surface resistance value R1 when 10 V is applied, satisfying the formula (1): 7.0≦logR1≦8.5(1) The roller resistance value R2 of the entire roller body when 400V is applied satisfies the formula (2): 6.3≦logR2≦8.5(2) The outer layer comprises epichlorohydrin rubber and chloroprene rubber and / or acrylonitrile butadiene rubber as rubber, The ratio of the chloroprene rubber and / or acrylonitrile butadiene rubber contained in the outer layer is 1 part by mass or more and 10 parts by mass or less in 100 parts by mass of the total amount of the rubber.

2. The developing roller according to claim 1, wherein the inner layer further comprises chloroprene rubber and / or acrylonitrile butadiene rubber as the rubber, The ratio of the chloroprene rubber and / or acrylonitrile butadiene rubber contained in the inner layer is 1 part by mass or more and 15 parts by mass or less in 100 parts by mass of the total amount of the rubber. 3 . The developing roller according to claim 1 , wherein the rubber composition forming the inner layer contains at least one selected from the group consisting of isoprene rubber and butadiene rubber as the diene rubber. 4 . The developing roller according to claim 1 , wherein the outer peripheral surface of the roller body is coated with an oxide film.

5. The developing roller according to claim 1 or 2, wherein the contact angle θ of water on the outer peripheral surface of the roller body is W More than 50°.

Images