阅读说明：本技术 显影辊 (Developing roller ) 是由 铃木大二朗 于 2019-05-13 设计创作，主要内容包括：本发明提供一种包括内层与外层这两层结构、而且即便重复进行图像形成,也无特别是纯黑部的图像浓度缓慢降低的担忧的显影辊。显影辊(1)包括辊本体,所述辊本体包括：筒状的内层(2),由弹性材料所形成；以及外层(4),由橡胶组合物的交联物所形成,所述橡胶组合物包含表氯醇橡胶、非极性的二烯系橡胶、及LIR,将极性的二烯系橡胶除外或者以未满橡胶的总量100质量份中的20质量份的比例包含极性的二烯系橡胶,且将碳黑除外或者以相对于橡胶的总量100质量份而未满10质量份的比例包含碘吸附量为40mg/g以下的碳黑。(The invention provides a developing roller which has a two-layer structure of an inner layer and an outer layer and has no fear of gradual reduction of image density of a pure black part even if image formation is repeatedly performed. The developing roller (1) includes a roller body including: a cylindrical inner layer (2) formed of an elastic material; and an outer layer (4) formed from a crosslinked product of a rubber composition containing epichlorohydrin rubber, a nonpolar diene rubber, and LIR, wherein the polar diene rubber is excluded or contained in an amount of 20 parts by mass out of 100 parts by mass of the total amount of the rubber, and the carbon black is excluded or contained in an amount of less than 10 parts by mass with respect to 100 parts by mass of the total amount of the rubber, the amount of iodine adsorbed being 40mg/g or less.)

1. A developer roller, comprising:

A roller body, the roller body comprising: a cylindrical inner layer formed of an elastic material; and an outer layer laminated on an outer peripheral surface of the inner layer and formed of an elastic material,

The outer layer is formed of a crosslinked product of a rubber composition containing epichlorohydrin rubber, nonpolar diene rubber, and liquid isoprene rubber as rubbers, wherein the polar diene rubber is excluded from or contains 20 parts by mass of the polar diene rubber in a proportion less than 100 parts by mass of the total amount of the rubbers, and carbon black is excluded from or contains carbon black having an iodine adsorption amount of 40mg/g or less in a proportion less than 10 parts by mass relative to 100 parts by mass of the total amount of the rubbers.

2. The developer roller according to claim 1, wherein:

The proportion of the carbon black is 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the total amount of the rubber.

3. The developing roller according to claim 1 or 2, wherein:

The proportion of the liquid isoprene rubber is 5 parts by mass or more and 15 parts by mass or less in 100 parts by mass of the total amount of the rubber.

4. The developing roller according to any one of claims 1 to 3, wherein:

The epichlorohydrin rubber is in a proportion of 20 parts by mass or more and 40 parts by mass or less in 100 parts by mass of the total amount of the rubber.

5. The developing roller according to any one of claims 1 to 4, wherein:

The nonpolar diene rubber is at least one selected from the group consisting of isoprene rubber, butadiene rubber, and styrene butadiene rubber.

Technical Field

The present invention relates to a developing roller used by being mounted to an image forming apparatus using an electrophotographic method.

Background

Recently, a roller body of a developing roller has been studied which has two layers, i.e., a cylindrical inner layer made of an elastic material and an outer layer made of an elastic material and laminated on an outer peripheral surface of the inner layer (see patent document 1 and the like).

In the developing roller described in patent document 1, the outer layer is formed by a crosslinked body of a rubber composition containing acrylonitrile butadiene rubber (NBR), epichlorohydrin rubber, and carbon black.

However, the developing roller including the outer layer tends to gradually decrease the image density of the pure black portion in the process of repeating image formation.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent laid-open No. 2016-95455

Disclosure of Invention

[ problems to be solved by the invention ]

The invention aims to provide a developing roller which comprises a two-layer structure of an inner layer and an outer layer and has no possibility of gradual reduction of image density of a pure black part even if image formation is repeatedly carried out.

[ means for solving problems ]

The present invention is a developing roller including a roller body, the roller body including: a cylindrical inner layer formed of an elastic material; and an outer layer laminated on an outer peripheral surface of the inner layer and formed of an elastic material,

The outer layer is formed from a crosslinked product of a rubber composition containing epichlorohydrin rubber, a nonpolar diene rubber, and a Liquid Isoprene Rubber (LIR) as rubbers, wherein the polar diene rubber is excluded or contained in an amount of 20 parts by mass out of 100 parts by mass of the total amount of the rubbers, and the carbon black is excluded or contained in an amount of less than 10 parts by mass of the total amount of the rubbers, and the carbon black having an iodine adsorption amount of 40mg/g or less.

[ Effect of the invention ]

According to the present invention, it is possible to provide a developing roller having a two-layer structure of an inner layer and an outer layer and free from a fear of a gradual decrease in image density particularly in a solid black portion even when image formation is repeated.

Drawings

Fig. 1A is a perspective view showing an entire appearance of an example of the developing roller of the present invention, and fig. 1B is an end view of the developing roller of the example.

[ description of symbols ]

1: developing roller

2: inner layer

3: peripheral surface

4: outer layer

5: roller body

6: through hole

7: shaft

8: peripheral surface

9: oxide film

Detailed Description

As described above, the developing roller of the present invention is characterized in that: comprising a roller body, said roller body comprising: a cylindrical inner layer formed of an elastic material; and an outer layer laminated on an outer peripheral surface of the inner layer and formed of an elastic material,

The outer layer is formed of a crosslinked rubber composition containing epichlorohydrin rubber, a nonpolar diene rubber, and LIR as rubbers, wherein the polar diene rubber is excluded from the rubber composition or contains the polar diene rubber in a proportion of 20 parts by mass out of 100 parts by mass of the total amount of the rubbers, and the carbon black is excluded from the rubber composition or contains the carbon black having an iodine adsorption amount of 40mg/g or less in a proportion of less than 10 parts by mass with respect to 100 parts by mass of the total amount of the rubbers.

When image formation is repeated using a conventional developing roller having a two-layer structure such as that described in patent document 1, one of the factors that causes a decrease in the image density of a pure black portion, that is, a decrease in the durable image density is carbon black contained in the outer layer and polar diene rubber such as NBR.

Further, carbon black tends to decrease the durable image density as the specific surface area is larger or the ratio thereof to rubber is larger.

In contrast, according to the present invention, by not adding carbon black at all (excluding carbon black), or even if adding carbon black, adding a small amount of iodine adsorption at the above ratio to satisfy the above range and having a small specific surface area, it is possible to suppress a decrease in the durable image density.

Further, as the rubber, a polar diene rubber such as NBR is not blended at all (except for the polar diene rubber such as NBR), or even if blended, a small amount is blended at a ratio of 20 parts by mass out of 100 parts by mass of the total amount of the less than full rubber.

Further, by using a nonpolar diene rubber such as Isoprene Rubber (IR), Butadiene Rubber (BR), Styrene Butadiene Rubber (SBR) as the residual amount of the rubber, the decrease in the durable image density can be further suppressed.

Among them, a rubber composition in which carbon black is not blended at all or only a small amount of carbon black is poor in processability.

Further, when the rubber composition is extrusion-molded into a tubular body or the like which is a raw material of an outer layer, for example, an extruded skin of the extrusion-molded tubular body is rough, and unevenness may be generated on an outer peripheral surface of the tubular body or an inner peripheral surface of the through hole.

Even if the outer peripheral surface on which the irregularities are generated is polished or the like to finish the outer peripheral surface into a predetermined surface state, for example, traces of the irregularities may remain, which may cause image defects or the like in the formed image.

Further, if the inner peripheral surface is uneven, it may cause poor adhesion to the inner layer.

In contrast, according to the present invention, by blending LIR which has a low molecular weight before crosslinking and functions as a processing aid for a rubber composition, it is possible to improve the processability of the rubber composition, for example, to suppress the occurrence of irregularities on the outer peripheral surface of a cylindrical body or the inner peripheral surface of a through hole.

These cases are also clear from the results of the examples and comparative examples described below.

Fig. 1A is a perspective view showing an entire appearance of an example of the developing roller of the present invention, and fig. 1B is an end view of the developing roller of the example.

Referring to fig. 1A and 1B, a developing roller 1 of the above example includes a roller main body 5 having a two-layer structure in which an outer layer 4 made of an elastic material is directly laminated on an outer peripheral surface 3 of a cylindrical inner layer 2 made of an elastic material.

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

The shaft 7 is integrally formed of a material having good electrical conductivity, for example, a metal such as iron, aluminum, an aluminum alloy, or stainless steel.

The shaft 7 is electrically joined to the roller body 5 and mechanically fixed, for example, by an adhesive having conductivity, or is electrically joined to the roller body 5 and mechanically fixed by pressing a member having an outer diameter larger than the inner diameter of the through hole 6 into the through hole 6.

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

An oxide film 9 is formed on the surface of the outer layer 4, that is, the outer peripheral surface 8 of the roll main body 5, as shown in enlarged views in both figures.

By forming the oxide film 9 so that the oxide film 9 functions as a dielectric layer, the dielectric loss tangent of the developing roller 1 can be reduced, and the oxide film 9 can function as a low friction layer to favorably suppress the adhesion of toner.

Further, the oxide film 9 can be formed simply by, for example, simply oxidizing the rubber in the vicinity of the outer peripheral surface 8 by irradiating the outer peripheral surface 8 with ultraviolet rays or the like in an oxidizing environment, and therefore, a decrease in productivity of the developing roller 1 or an increase in manufacturing cost can be suppressed.

The oxide film 9 may be omitted.

The inner layer 2 and the outer layer 4 are preferably formed of a single non-porous layer in order to simplify the structure of each layer and improve durability.

The term "single layer" of the outer layer 4 means that the number of layers formed of the elastic material is a single layer.

The term "two layers" of the roll main body 5 also means that the number of layers formed by the elastic material of both the inner layer 2 and the outer layer 4 is two, and in any case, the oxide film 9 formed by irradiation of ultraviolet rays or the like is not included in the number of layers.

Rubber composition for outer layer 4

As described above, the rubber composition for the outer layer 4 includes epichlorohydrin rubber, nonpolar diene rubber, and LIR as rubbers, and the polar diene rubber is excluded or included in an amount of 20 parts by mass out of 100 parts by mass of the total amount of the less than full rubber, and the carbon black is excluded or included in an amount of less than 10 parts by mass with respect to 100 parts by mass of the total amount of the rubber, and the iodine adsorption amount is 40mg/g or less.

Epichlorohydrin rubber

Examples of the epichlorohydrin rubber include epichlorohydrin homopolymers, epichlorohydrin-ethylene oxide binary copolymers (ECO), epichlorohydrin-propylene oxide binary copolymers, epichlorohydrin-allyl glycidyl ether binary copolymers, epichlorohydrin-ethylene oxide-allyl glycidyl ether ternary copolymers (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether ternary copolymers, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymers, and epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymers.

Among these, copolymers comprising ethylene oxide, in particular ECO and/or GECO, are preferred.

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

The ethylene oxide functions to lower the resistance value of the outer layer 4.

However, if the ethylene oxide content is less than the above range, the above-described effect cannot be sufficiently obtained, and therefore the resistance value of the outer layer 4 may not be sufficiently lowered.

On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs, and the chain motion of the molecular chain is inhibited, so that the resistance value of the outer layer 4 tends to increase conversely.

In addition, the outer layer 4 after crosslinking may become too hard, and the viscosity of the rubber composition before crosslinking at the time of heating and melting may increase, thereby deteriorating the processability of the rubber composition.

The epichlorohydrin content in the ECO is the remainder of the ethylene oxide content.

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

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

The allyl glycidyl ether functions to secure a free volume as a side chain, and thereby functions to suppress crystallization of ethylene oxide and to lower the resistance value of the outer layer 4.

However, if the allyl glycidyl ether content is less than the above range, the above effect cannot be sufficiently obtained, and therefore the resistance value of the outer layer 4 may not be sufficiently lowered.

On the other hand, allyl glycidyl ether functions as a crosslinking point at the time of crosslinking of GECO.

Therefore, when the allyl glycidyl ether content exceeds the above range, the crosslinking density of the GECO becomes too high, and the segmental motion of the molecular chain is inhibited, so that the electric resistance value of the outer layer 4 tends to be increased conversely.

The epichlorohydrin content in the GECO is the remainder of the ethylene oxide content, and the allyl glycidyl ether content.

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

Further, as the GECO, in addition to the copolymer having a narrow meaning of copolymerizing three monomers as described above, a modified product of modifying an epichlorohydrin-ethylene oxide copolymer (ECO) with allyl glycidyl ether is also known.

In the present invention, any of the above-described GECO may be used.

As the epichlorohydrin rubber, GECO is particularly preferable.

GECO is derived from allyl glycidyl ether and has a double bond in the main chain functioning as a crosslinking point, and therefore, the compression set after crosslinking can be reduced by crosslinking between the main chains.

Therefore, the outer layer 4 can be made to have a small compression set and be less likely to collapse.

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

Non-polar diene rubber

The diene rubber functions to impart good processability to the rubber composition, to improve mechanical strength and durability of the outer layer 4, or to impart good properties as a rubber, that is, properties of softness, small compression set and resistance to collapse to the outer layer 4.

The diene rubber is also oxidized by the ultraviolet irradiation to form an oxide film 9 on the surface of the outer layer 4, that is, the outer circumferential surface 8 of the roller body 5.

As the nonpolar diene rubber in the diene rubber, at least one selected from the group consisting of IR, BR, and SBR can be used as described above, and SBR is particularly preferable.

As described above, wet polishing is generally performed in the current step in order to finish the outer peripheral surface 8 of the outer layer 4 into a predetermined surface state.

However, in the case of IR, it is difficult to finish the outer peripheral surface 8 to a predetermined surface state even by wet polishing, and BR has high abrasion resistance, so that it takes time to perform wet polishing.

On the other hand, since SBR is easier to polish than IR or BR, the outer peripheral surface 8 of the outer layer 4 can be finished to a predetermined surface state with high efficiency by wet polishing in a short time.

In addition, epichlorohydrin rubber is also a polar rubber and still causes a reduction in the durable image density, but in the system in which epichlorohydrin rubber is used in combination with SBR, the proportion of epichlorohydrin rubber required to adjust the resistance value of the outer layer 4 to a predetermined range can be reduced as compared with the system in which epichlorohydrin rubber is used in combination with IR or BR.

Therefore, the decrease in the durable image density can be suppressed more efficiently.

(SBR)

As the SBR, various SBRs synthesized by copolymerizing styrene and 1, 3-butadiene by various polymerization methods such as an emulsion polymerization method and a solution polymerization method and having a crosslinking property can be used.

As the SBR, high styrene type, medium styrene type, and low styrene type SBRs classified according to the styrene content can be used.

Particularly preferably Mooney viscosity ML₁₊₄SBR having a temperature of (100 ℃) of 60 or less.

Further, as the SBR, there are an oil-extended SBR in which flexibility is adjusted by adding an extender oil and a non-oil-extended SBR in which flexibility is not adjusted, but in the present invention, it is preferable to use a non-oil-extended SBR which does not contain an extender oil that may be a bleeding substance in order to prevent contamination of the photoreceptor and the like.

One or two or more of these SBRs can be used.

(IR)

As the IR, various kinds of IR having a polyisoprene structure artificially reproducing the structure of natural rubber, having a crosslinking property, and having a solid shape at room temperature before crosslinking can be used.

Further, as the IR, there are oil-extended IR in which flexibility is adjusted by adding extender oil and non-oil-extended IR in which it is not added, but in the present invention, it is preferable to use non-oil-extended IR which does not contain extender oil that may be a bleeding substance, in order to prevent contamination of the photoreceptor.

One or two or more of these IR may be used.

(BR)

As BR, various types of BR having a polybutadiene structure in the molecule and having a crosslinking property can be used.

The high cis BR having a cis-1, 4 bond content of 95% or more, which can exhibit excellent characteristics as a rubber in a wide temperature range from low temperature to high temperature, is preferable.

Further, BR includes oil-extended BR whose flexibility is adjusted by adding extender oil and non-oil-extended BR whose flexibility is not added, but in the present invention, it is preferable to use non-oil-extended BR which does not contain extender oil which may be a bleeding substance, in order to prevent contamination of the photoreceptor.

One or two or more of these BR may be used.

〈LIR〉

Since LIR has a low molecular weight before crosslinking and functions as a processing aid for the rubber composition as described above, the processability of the rubber composition can be improved by blending LIR, and for example, the occurrence of irregularities on the outer peripheral surface of the cylindrical body or the inner peripheral surface of the through-hole can be suppressed.

In addition, since LIR is taken into a crosslinked product by a crosslinking reaction with rubber when the rubber composition is molded into the shape of the outer layer and crosslinked, the LIR is also prevented from bleeding out to the outer peripheral surface of the outer layer to cause contamination of the photoreceptor and the like.

As LIR, various LIRs which are liquid at room temperature before crosslinking and have crosslinking properties can be used.

Particularly, it is preferable to use LIR having a number average molecular weight Mn of 28000 or more and 58000 or less.

LIR having a number average molecular weight Mn less than the above range tends to have too low a viscosity and to be difficult to knead with epichlorohydrin rubber and nonpolar diene rubber.

Therefore, it is sometimes difficult to sufficiently obtain the effect of improving the processability of the rubber composition by causing LIR to function as a processing aid.

in addition, the LIR remaining in the roller body in a state where the molecular weight is low even after crosslinking may increase, and the LIR may bleed out to the outer peripheral surface of the outer layer 4 to cause contamination of the photoreceptor.

On the other hand, LIR having a number average molecular weight Mn exceeding the above range has too high a viscosity and is in a state that it is difficult to say that it is liquid at room temperature, and therefore, there is a case where the effect of improving the processability of the rubber composition by causing LIR to function as a processing aid cannot be sufficiently obtained.

In contrast, by selectively using LIR having the number average molecular weight Mn in the range, contamination of the photoreceptor due to bleeding can be suppressed, and the processability of the rubber composition can be further improved.

LIR is classified as a nonpolar diene rubber, but in the present invention, LIR is treated as a processing aid that is regarded as a function of importance and is different from other nonpolar diene rubbers.

Polar diene rubber

The rubber may further be a polar diene rubber such as NBR or CR.

the polar diene rubber cannot be blended in a large amount because it lowers the durable image density, but in the case of blending in a small amount, it functions to finely adjust the resistance value of the outer layer 4.

(NBR)

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

The NBR includes an oil-extended NBR whose flexibility is adjusted by adding an extender oil, and a non-oil-extended NBR which is not added, but in the present invention, it is preferable to use a non-oil-extended NBR which does not contain an extender oil that may be a bleeding substance in order to prevent contamination of the photoreceptor and the like.

One or two or more of these NBRs may be used.

(CR)

CR is synthesized by emulsion polymerization of chloroprene, and is classified into sulfur-modified type and non-sulfur-modified type according to the type of molecular weight regulator used at this time.

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

Further, the non-sulfur-modified CR is classified into, for example, a thiol-modified CR and a xanthane-modified CR.

Among them, the thiol-modified CR is synthesized in the same manner as the sulfur-modified CR, except that alkylthiols such as n-dodecylthiol, t-dodecylthiol, and octylthiol are used as a molecular weight modifier.

Further, the xanthate-modified CR was synthesized in the same manner as the sulfur-modified CR, except that an alkylxanthate compound was used as a molecular weight modifier.

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

In the present invention, any type of CR may be used, but among them, a non-sulfur-modified CR having a slow crystallization rate is preferable.

In addition, as CR, a copolymer of chloroprene and other copolymerization components may also be used. Examples of the other copolymerizable component include one or more of 2, 3-dichloro-1, 3-butadiene, 1-chloro-1, 3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, acrylic acid ester, methacrylic acid, and methacrylic acid ester.

Further, as CR, there are oil-extended CR in which flexibility is adjusted by adding extender oil and non-oil-extended CR in which CR is not added, but in the present invention, it is preferable to use non-oil-extended CR not containing extender oil which may be a bleeding substance, in order to prevent contamination of the photoreceptor.

one or two or more of these CR may be used.

Proportion of rubber

The proportion of the rubber can be arbitrarily set in accordance with various characteristics required for the outer layer 4, particularly, the durable image density, the resistance value, the flexibility, and the like.

In consideration of adjusting the resistance value of the outer layer 4 to a range suitable for the outer layer 4 and suppressing the reduction in the durable image density, the proportion of the epichlorohydrin rubber is preferably 20 parts by mass or more and preferably 40 parts by mass or less of the total 100 parts by mass of the rubber.

The ratio of LIR is preferably 5 parts by mass or more, particularly 7 parts by mass or more, and preferably 15 parts by mass or less, particularly 12 parts by mass or less, of the total 100 parts by mass of the rubber.

By setting the ratio of LIR in the above range, the increase in the amount of LIR remaining in the roll body in a state where the molecular weight is also low after crosslinking can be suppressed, and the processability of the rubber composition before crosslinking can be improved.

As described above, the polar diene rubber is not blended at all (except for the above-mentioned rubber), or even if blended, it is necessary to blend the polar diene rubber in a range of less than 20 parts by mass out of 100 parts by mass of the total amount of the rubber.

The reason for this is as described above.

That is, when the proportion of the polar diene rubber is 20 parts by mass or more in 100 parts by mass of the total amount of the rubber, the durable image density is greatly reduced.

On the other hand, by not blending the polar diene rubber or blending the polar diene rubber in a proportion of 20 parts by mass out of 100 parts by mass of the total amount of the less than all rubbers, the decrease in the durable image density can be suppressed.

In order to further improve the above effect, the proportion of the polar diene rubber is preferably 10 parts by mass or less in the above range.

In addition, in view of the effect of blending the polar diene rubber, the proportion of the polar diene rubber is preferably 1 part by mass or more of 100 parts by mass of the total amount of the rubber in the above range.

In the present invention, as described above, the polar diene rubber is not blended, that is, the proportion of the polar diene rubber is in the range of 0 part by mass out of 100 parts by mass of the total amount of the rubber.

The proportion of the nonpolar diene rubber is the residual amounts of the epichlorohydrin rubber and the LIR or the epichlorohydrin rubber, the LIR and the polar diene rubber.

That is, when the proportions of epichlorohydrin rubber and LIR, or epichlorohydrin rubber and LIR and polar diene rubber are set to predetermined values within the above ranges, the proportion of nonpolar diene rubber may be set so that the total amount of rubber is 100 parts by mass.

When two or more kinds of epichlorohydrin rubber, LIR, nonpolar diene rubber, or polar diene rubber are used in combination, the ratio is the total ratio of the two or more kinds of rubbers used in combination.

Carbon black

As described above, it is necessary to add carbon black having an iodine adsorption amount of 40mg/g or less to the total amount of rubber 100 parts by mass but less than 10 parts by mass, if any, without adding carbon black at all (excluding carbon black).

the reason for this is as described above.

That is, carbon black having a large specific surface area and an iodine adsorption amount of more than 40mg/g significantly lowers the durable image density even when a small amount of carbon black is blended.

Even when carbon black having an iodine adsorption amount of 40mg/g or less is used, the durable image density is significantly reduced when the carbon black is used in an amount of 10 parts by mass or more based on 100 parts by mass of the total amount of the rubber.

On the other hand, by not blending carbon black, or blending carbon black having an iodine adsorption amount of 40mg/g or less at a ratio of less than 10 parts by mass to 100 parts by mass of the total amount of the rubber, it is possible to suppress a decrease in the density of the durable image.

In view of further improving the above effect, the amount of iodine adsorbed by carbon black is preferably 10mg/g or more, and preferably 30mg/g or less in the above range.

Further, the proportion of carbon black having an iodine adsorption amount of 40mg/g or less is preferably 5 parts by mass or less with respect to 100 parts by mass of the total amount of the rubber.

In view of the good effect of blending carbon black having an iodine adsorption amount of 40mg/g or less, the proportion of carbon black is preferably 1 part by mass or more in the above range with respect to 100 parts by mass of the total amount of the rubber.

In the present invention, as described above, the carbon black is not blended, that is, the proportion of the carbon black having an iodine adsorption amount of 40mg/g or less is included in the range of 0 part by mass with respect to 100 parts by mass of the total amount of the rubber.

As the carbon black having an iodine adsorption amount of 40mg/g or less, for example, asahi #60U manufactured by asahi carbon (stock asahi) (iodine adsorption amount: 40 mg/g), Asahi #55 [ iodine adsorption amount: 25mg/g, Asahi #50HG [ iodine adsorption: 20 mg/g), Asahi #52 [ iodine adsorption amount: 19 mg/g), Asahi #51 [ iodine adsorption amount: 17 mg/g), Asahi #50U [ iodine adsorption amount: 26 mg/g), Asahi #50 [ iodine adsorption amount: 23 mg/g), Asahi #35 [ iodine adsorption amount: 23 mg/g), Asahi #22K [ iodine adsorption: 19 mg/g), Asahi #15HS [ iodine adsorption amount: 13 mg/g), Asahi #15 [ iodine adsorption amount: 11 mg/g), Asahi #8 [ iodine adsorption amount: 12 mg/g), Asahi fever (Asahi thermal) [ iodine adsorption amount: 27mg/g, and the like.

Further, when the rubber composition for the outer layer 4, in which carbon black is not blended or the ratio thereof is within the above range, is combined with the rubber composition for the inner layer 2, for example, in an amount of standard carbon black, visibility of both compositions can be improved depending on the shade of color.

Therefore, there is also an advantage that, for example, adjustment at the time of coextrusion molding can be facilitated.

Crosslinked component

A crosslinking component for crosslinking the rubber is blended in the rubber composition for the outer layer 4.

As the crosslinking component, it is preferable to use a crosslinking agent for crosslinking the rubber and a crosslinking accelerator for accelerating crosslinking of the rubber by the crosslinking agent in combination.

Among these, examples of the crosslinking agent include a sulfur-based crosslinking agent, a thiourea-based crosslinking agent, a triazine derivative-based crosslinking agent, a peroxide-based crosslinking agent, and various monomers, and particularly a sulfur-based crosslinking agent is preferable.

(Sulfur-based crosslinking agent)

Examples of the sulfur-based crosslinking agent include: powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, dispersible sulfur, or an organic sulfur-containing compound such as tetramethylthiuram disulfide or N, N-dithiodimorpholine, and the like, and sulfur is particularly preferable.

In view of imparting good properties as rubber to the roll body, the proportion of sulfur is preferably 0.5 parts by mass or more and preferably 2 parts by mass or less with respect to 100 parts by mass of the total amount of rubber.

In the case of using oil-treated powdered sulfur, dispersed sulfur, or the like as the sulfur, the above-mentioned ratio is defined as the ratio of the sulfur itself as the active ingredient contained in each.

In the case where the organic sulfur-containing compound is used as the crosslinking agent, the proportion thereof is preferably adjusted so that the proportion of sulfur contained in the molecule with respect to 100 parts by mass of the total amount of the rubber falls within the above-mentioned range.

(crosslinking accelerator)

Examples of the crosslinking accelerator for accelerating crosslinking of the rubber include one or two or more of thiuram accelerators, thiazole accelerators, thiourea accelerators, guanidine accelerators, sulfenamide accelerators, and dithiocarbamate accelerators.

Among them, it is preferable to use a thiuram-based accelerator, a thiazole-based accelerator, a thiourea-based accelerator, and a guanidine-based accelerator in combination.

The thiuram-based accelerator includes, for example, one or more of tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide, and the like, and tetramethylthiuram monosulfide is particularly preferable.

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' -morpholinodithio) benzothiazole, and di-2-benzothiazolyl disulfide is particularly preferable.

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

Examples of the thiourea-based accelerator include: ethylenethiourea, N' -diphenylthiourea, trimethylthiourea, formula (1):

(C_nH_2n+1NH)₂C＝S (1)

In the formula, n represents an integer of 1 to 12, one or more of thiourea, tetramethylthiourea and the like, and ethylenethiourea is particularly preferable.

Examples of the guanidine-based accelerator include one or two or more of 1, 3-diphenylguanidine, 1, 3-di-o-tolylguanidine, 1-o-tolylbiguanide, and the like, and 1, 3-di-o-tolylguanidine is particularly preferable.

In the above-described system of four types in combination, the proportion of the thiuram-based accelerator is preferably 0.3 parts by mass or more and preferably 1 part by mass or less with respect to 100 parts by mass of the total amount of the rubber, in consideration of the effect of accelerating crosslinking of the rubber and the like being sufficiently exhibited.

The proportion of the thiazole accelerator is preferably 0.3 part by mass or more and preferably 2 parts by mass or less with respect to 100 parts by mass of the total amount of the rubber.

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

Further, the proportion of the guanidine-based accelerator is preferably 0.2 parts by mass or more and preferably 1 part by mass or less with respect to 100 parts by mass of the total amount of the rubber.

The thiourea-based accelerator also functions as a crosslinking agent for ECO that does not have sulfur crosslinking properties, and the guanidine-based accelerator also functions as an accelerator for crosslinking ECO that is performed by the thiourea-based accelerator.

Ionic conductive agent

An ion conductive agent may be further blended in the rubber composition for the outer layer 4.

By blending the ion conductive agent, the ion conductivity of the rubber composition can be further improved, and the resistance value of the outer layer 4 itself can be further reduced.

The ion conductive agent is preferably an anion having a fluoro group and a sulfonyl group in the molecule, or a salt (ionic salt) with a cation.

Examples of the anion constituting the ionic salt, which has a fluoro group and a sulfonyl group in the molecule, include one or two or more kinds of a fluoroalkyl sulfonate ion, a bis (fluoroalkylsulfonyl) imide ion, a tris (fluoroalkylsulfonyl) methide ion, and the like.

Among them, as the fluoroalkyl sulfonate ion, for example, CF is cited₃SO₃ ^-、C₄F₉SO₃ ^-And the like, or two or more thereof.

Further, the bis (fluoroalkylsulfonyl) imide ion may be, for example, (CF)₃SO₂)₂N^-、(C₂F₅SO₂)₂N^-、(C₄F₉SO₂)(CF₃SO₂)N^-、(FSO₂C₆F₄)(CF₃SO₂)N^-、(C₈F₁₇SO₂)(CF₃SO₂)N^-、(CF₃CH₂OSO₂)₂N^-、(CF₃CF₂CH₂OSO₂)₂N^-、(HCF₂CF₂CH₂OSO₂)₂N^-、[(CF₃)₂CHOSO₂]₂N^-And the like, or two or more thereof.

Further, the tris (fluoroalkylsulfonyl) methide ion may be, for example, (CF)₃SO₂)₃C^-、(CF₃CH₂OSO₂)₃C^-And the like, or two or more thereof.

Examples of the cation include one or more of ions of alkali metals 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.

The ionic salt is particularly preferably a lithium salt using a lithium ion as a cation or a potassium salt using a potassium ion.

Among them, (CF) is preferable in terms of the effect of improving the ionic conductivity of the rubber composition and reducing the resistance value of the outer layer 4₃SO₂)₂NLi [ lithium bis (trifluoromethanesulfonyl) imide, Li-TFSI ], and/or (CF)₃SO₂)₂NK [ potassium bis (trifluoromethanesulfonyl) imide, K-TFSI ].

The proportion of the ionic salt plasma conductive agent is preferably 0.5 parts by mass or more and preferably 2 parts by mass or less with respect to 100 parts by mass of the total amount of the rubber.

Other

Various additives may be further blended as necessary in the rubber composition for the outer layer 4.

Examples of the additives include a crosslinking accelerating aid, an acid acceptor, a plasticizer, and a processing aid.

Among them, examples of the crosslinking acceleration aid include metal compounds such as zinc oxide (zinc white); one or more of fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and other conventionally known crosslinking accelerating aids.

The proportion of the crosslinking accelerating assistant is preferably 0.1 part by mass or more and preferably 7 parts by mass or less, respectively, with respect to 100 parts by mass of the total amount of the rubber.

The acid-absorbing agent functions to prevent chlorine-based gas generated from epichlorohydrin rubber or CR during crosslinking from remaining in the outer layer 4, and to prevent crosslinking inhibition and contamination of the photoreceptor caused by the chlorine-based gas.

As the acid acceptor, various substances which function as acid acceptors can be used, but among them, hydrotalcite and magarat (magaraat) having excellent dispersibility are preferable, and hydrotalcite is particularly preferable.

Further, when hydrotalcite or the like is used in combination with magnesium oxide or potassium oxide, a higher acid absorption effect can be obtained, and contamination of the photoreceptor can be further reliably prevented.

The proportion of the acid scavenger is preferably 0.1 part by mass or more and preferably 7 parts by mass or less with respect to 100 parts by mass of the total amount of the rubber.

Examples of plasticizers include: various plasticizers such as dibutyl phthalate, dioctyl phthalate and tricresyl phosphate, and various waxes such as polar waxes, and examples of the processing aid include fatty acid metal salts such as zinc stearate.

The proportion of the plasticizer and/or the processing aid is preferably 3 parts by mass or less with respect to 100 parts by mass of the total amount of the rubber.

Further, as the additive, various additives such as a filler other than carbon black, a deterioration inhibitor, a scorch retarder, a lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizer, a nucleating agent, and a co-crosslinking agent may be further blended at an arbitrary ratio.

Examples of the filler other than carbon black include one or two or more of zinc oxide, silica, talc, calcium carbonate, magnesium carbonate, and aluminum hydroxide.

Preparation of rubber composition

The rubber composition for the outer layer 4 containing the above-described components can be prepared in the same manner as in the conventional case.

First, the rubber composition for the outer layer 4 is obtained by masticating the rubber, adding and kneading the components other than the crosslinking component, and finally adding and kneading the crosslinking component.

The kneading may be carried out by, for example, a kneader, a Banbury mixer, an extruder, or the like.

Rubber composition for inner layer 2

The inner layer 2 may be formed using various elastic materials.

Particularly preferably, the inner layer 2 is formed by a crosslinked product of a rubber composition containing epichlorohydrin rubber and diene rubber.

Epichlorohydrin rubber

As the epichlorohydrin rubber, one or two or more of the same epichlorohydrin rubbers as used in the outer layer 4 can be used.

Among these, ECO and/or GECO are preferable, and GECO is particularly preferable.

The reason for this is the same as in the case of the outer layer 4.

That is, when GECO is used as the epichlorohydrin rubber, the inner layer 2 can be made to have a small compression set and to be less likely to collapse.

Diene rubber

The diene rubber functions to impart good processability to the rubber composition, to improve mechanical strength, durability, and the like of the inner layer 2, or to impart good properties as a rubber to the inner layer 2.

Examples of the diene rubber include natural rubber, IR, NBR, SBR, BR, and CR.

Among these, it is preferable to use a nonpolar diene rubber, specifically at least one of IR, BR, and SBR, and particularly two of IR and BR, in combination.

As the IR, one or two or more kinds of the same IR as used in the outer layer 4 may be used, and as the BR, one or two or more kinds of the same BR as used in the outer layer 4 may be used.

Further, as the diene rubber, CR may be further compounded.

CR is a polar diene rubber as described above, and thus functions to finely adjust the resistance value of the inner layer 2 itself.

As CR, one or two or more of the same CR as used in the outer layer 4 can be used.

(proportion of rubber)

The rubber ratio can be arbitrarily set according to various characteristics such as the resistance value and flexibility required for the inner layer 2.

For example, the proportion of the epichlorohydrin rubber is preferably 12 parts by mass or more and preferably 20 parts by mass or less of the total 100 parts by mass of the rubber.

The ratio of CR is preferably 5 parts by mass or more and preferably 12 parts by mass or less in 100 parts by mass of the total amount of rubber.

The proportion of the nonpolar diene rubber other than CR is epichlorohydrin rubber or the residual amount of epichlorohydrin rubber and CR.

That is, when the epichlorohydrin rubber or the ratio of the epichlorohydrin rubber to CR 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 the rubber is 100 parts by mass.

Crosslinked component

As the crosslinking component, it is preferable to use the same crosslinking agent and crosslinking accelerator in combination as those used for the outer layer 4.

That is, the crosslinking agent is preferably a sulfur-based crosslinking agent, particularly sulfur, and the crosslinking accelerator combined with the sulfur-based crosslinking agent is preferably a combination of four of a thiuram-based accelerator, a thiazole-based accelerator, a thiourea-based accelerator, and a guanidine-based accelerator.

The proportions of the sulfur-based crosslinking agent and the four crosslinking accelerators are also preferably set to the same extent as in the case of the outer layer 4.

Ionic conductive agent

An ion conductive agent may be further blended in the rubber composition for the inner layer 2.

By blending the ion conductive agent, the ion conductivity of the rubber composition can be further improved, and the resistance value of the inner layer 2 itself can be further reduced.

As the ion conductive agent, it is preferable to use the same anion having a fluorine group and a sulfonyl group in the molecule and a salt (ionic salt) with a cation as in the outer layer 4.

The proportion of the ion conductive agent is also preferably set to the same extent as in the case of the outer layer 4.

Other

Various additives may be further compounded in the rubber composition for the inner layer 2 as required.

Examples of the additives include the same additives used in the outer layer 4, for example, crosslinking acceleration aids, acid absorbers, fillers, plasticizers, processing aids, deterioration inhibitors, scorch retarders, lubricants, pigments, antistatic agents, flame retardants, neutralizing agents, nucleating agents, and co-crosslinking agents.

Examples of the filler include one or more of zinc oxide, carbon black, silica, talc, calcium carbonate, magnesium carbonate, and aluminum hydroxide.

As the carbon black, conductive carbon black may be used.

By using the conductive carbon black, the inner layer 2 can be given electronic conductivity.

Examples of the conductive carbon black include acetylene black.

Preparation of rubber composition

The rubber composition for the inner layer 2 containing the above-described components can be prepared in the same manner as in the conventional case.

That is, the rubber composition for the inner layer 2 is obtained by kneading the rubber, adding the components other than the crosslinking component, and kneading the kneaded mixture, and finally adding the crosslinking component and kneading the kneaded mixture.

The kneading may be carried out by, for example, a kneader, a Banbury mixer, an extruder, or the like.

Production of developing roller 1

When the developing roller 1 shown in fig. 1A and 1B is manufactured using the rubber compositions for the inner layer 2 and the outer layer 4, for example, both the rubber compositions are supplied to a two-layer extruder, and are co-extruded and molded into a cylindrical shape having a laminated two-layer structure, and then the entire structure is crosslinked to form the inner layer 2 and the outer layer 4.

Alternatively, the rubber composition for the inner layer 2 is extruded into a cylindrical shape and crosslinked to form the inner layer 2, and then a sheet of the rubber composition for the outer layer 4 is wound around the outer peripheral surface 3 thereof, and is molded into a cylindrical shape by press molding or the like and crosslinked, and is integrated with the inner layer 2 to form the outer layer 4.

Then, the formed laminate of the inner layer 2 and the outer layer 4 is heated in an oven or the like to be secondarily crosslinked, and is ground to have a predetermined outer diameter after being cooled, thereby forming the roller body 5 including the laminate.

The thickness of the inner layer 2 can be arbitrarily set according to the structure, size, and the like of the image forming apparatus to be mounted.

The thickness of the outer layer 4 may be arbitrarily set, but is preferably 0.1mm or more, and preferably 2mm or less.

As the polishing method, various polishing methods such as dry longitudinal polishing can be used, or mirror polishing can be performed at the end of the polishing step to finish the polishing.

In this case, the releasability of the outer peripheral surface 8 is improved, and when the oxide film 9 is not formed or by a synergistic effect with the formation of the oxide film 9, the adhesion of the toner can be further suppressed more favorably, and the contamination of the photoreceptor and the like can be effectively prevented.

The shaft 7 can be inserted and fixed into the through hole 6 at any time from the cutting of the cylindrical body as a raw material of the roller body 5 to the polishing.

After the cutting, the shaft 7 is preferably first subjected to secondary crosslinking and polishing in a state inserted into the through hole 6. This can suppress the warping or deformation of the roller body 5 due to expansion and contraction during secondary crosslinking.

Further, by performing polishing while rotating about the shaft 7, the workability of the polishing can be improved, and the run-out of the outer peripheral surface 8 can be suppressed.

As described above, the shaft 7 may be inserted into the through hole 6 of the tubular body before secondary crosslinking via an adhesive having conductivity, particularly a thermosetting adhesive having conductivity, and then secondary crosslinking is performed, or a shaft having an outer diameter larger than the inner diameter of the through hole 6 may be press-fitted into the through hole 6.

In the former case, the cylindrical body is secondarily crosslinked by heating in the oven, and at the same time, the thermosetting adhesive is cured, and the shaft 7 is mechanically fixed while being electrically bonded to the roller main body 5.

In addition, in the latter case, the electrical bonding and the mechanical fixing are completed simultaneously with the press-fitting.

Alternatively, the shaft 7 and the roller body 5 may be electrically joined and mechanically fixed by the above-described two methods.

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

That is, the outer peripheral surface 8 of the roller body 5 is irradiated with ultraviolet rays of a predetermined wavelength for a predetermined time, and only the rubber constituting the vicinity of the outer peripheral surface 8 is oxidized to form the oxide film 9, so that the operation is simple and efficient.

Further, the oxide film 9 formed by irradiation with ultraviolet rays does not cause a problem such as a coating film formed by coating a conventional coating agent, and is excellent in uniformity of thickness, adhesion to the roller body 5, and the like.

the wavelength of the ultraviolet rays to be irradiated is preferably 100nm or more, more preferably 400nm or less, and particularly 300nm or less, in consideration of efficiently oxidizing the diene rubber in the rubber composition for the outer layer 4 to form the oxide film 9 having excellent functions.

The irradiation time is preferably 30 seconds or more, particularly 1 minute or more, and preferably 30 minutes or less, particularly 20 minutes or less.

The oxide film 9 may be formed by other methods, or may not be formed in some cases.

One or more optional intermediate layers may be interposed between the inner layer 2 and the outer layer 4.

However, considering the simplification of the structure of the roller body 5, the roller body 5 is preferably formed in a two-layer structure in which the inner layer 2 and the outer layer 4 are directly laminated as shown in fig. 1A and 1B.

The developing roller 1 of the present invention can be used by being attached to various image forming apparatuses using electrophotography, such as a laser printer, an electrostatic copier, a plain paper facsimile machine, and a multifunction machine thereof.