JP2019012207A - Semiconductive roller - Google Patents

Abstract

To provide a semiconductive roller maintaining a simple structure without a coating film, equipped with a roller body having a lower-friction outer surface than conventional ones.SOLUTION: A semiconductive roller 1 is equipped with a roller body 2 made of crosslinked rubber composition comprising an epichlorohydrin rubber and a diene rubber as rubber, mixed with a silicone copolymer containing repeating units to constitute a resin compatible with the rubber in a molecule.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductive roller.

In an image forming apparatus using an electrophotographic method, the surface of the photoconductor can be charged with a voltage lower than that of corona discharge. Therefore, as a charging method, the charging roller is brought into direct contact with the surface of the photoconductor for charging. Charging methods are becoming popular.
Further, in an image forming apparatus using electrophotography, a non-magnetic one-component developing method is becoming mainstream as a developing method.

  In the non-magnetic one-component development method, toner is carried on the surface of the developing roller while passing between the developing roller and the toner amount regulating blade and frictionally charged, thereby forming a toner layer on the surface. Next, the formed toner layer is brought into direct contact with the surface of the photoreceptor on which the electrostatic latent image is formed, whereby the toner is selectively transferred from the toner layer to the electrostatic latent image and developed into a toner image. Alternatively, the toner layer and the surface of the photoreceptor are brought close to each other while maintaining a non-contact state, whereby the toner is selectively transferred (flyed) from the toner layer to the electrostatic latent image and developed into the toner image. In some cases.

As the charging roller and the developing roller, in particular, a semiconductive rubber composition is used in order to ensure a sufficient nip for contact with the surface of the photoreceptor and to make the function as each roller well. A semiconductive roller provided with a roller body formed into a cylindrical shape and crosslinked is preferably used.
In order to adjust the roller resistance value of the semiconductive roller to a range suitable for the charging roller and the developing roller, an ion conductive rubber such as epichlorohydrin rubber is used as a rubber for the rubber composition. There is a case.

  In addition, as rubber, the rubber composition is imparted with good processability, molded and cross-linked to improve the mechanical strength and durability of the roller body, or the roller body has good rubber properties. In some cases, diene rubber is used in combination with the ion conductive rubber in order to give the characteristic, that is, the softness and the characteristic that the compression set is small and hardly causes settling.

  However, since the outer peripheral surface of the roller body made of a rubber composition has a large coefficient of friction, when a semiconductive roller provided with the roller body is used as, for example, a charging roller, toner remaining on the surface of the photosensitive member Alternatively, external additives such as silica and titanium oxide that are externally added to the toner in order to improve the fluidity and chargeability of the toner adhere to and accumulate on the outer peripheral surface of the roller body, and the formed image has no charge. There are cases where uniform vertical stripes and dot-like density irregularities occur. In addition, the surface of the photoreceptor that is in direct contact may be affected.

Therefore, in the charging roller, in order to reduce the friction of the outer peripheral surface of the roller body, it has been studied to coat the outer peripheral surface with a coating film (see, for example, Patent Document 1).
On the other hand, when a semi-conductive roller made of a rubber composition and having a roller body having a large friction coefficient on the outer peripheral surface is used as a developing roller, for example, in combination with a toner amount regulating blade, and the toner is frictionally charged, the toner is crushed by friction As a result, the formed image may become gritty.

In addition, the fine particles of the external additive are embedded in the toner particles by friction, and the fluidity of the toner is impaired, resulting in uneven density in the formed image, and the toner amount regulating blade causes a so-called slip stick to form. In some cases, vertical stripe-like density unevenness occurs in the image.
Further, both end portions of the outer peripheral surface of the roller body may be sealed by a seal member in order to prevent the toner carried on the outer peripheral surface from leaking out of the developing device incorporating the developing roller. The seal member is formed of, for example, felt and is slidably contacted with both end portions of the outer peripheral surface of the roller body of the rotating developing roller in a state of being fixed to the housing or the like of the developing device.

However, when image formation is repeated, toner easily leaks from both ends that should have been sealed by the seal member. This is because the vicinity of both end portions of the outer peripheral surface of the roller body is worn by sliding contact with the seal member, and a gap is formed between the seal member and the seal member.
Therefore, in order to reduce the friction of the outer peripheral surface of the roller main body and to prevent these defects from occurring in the developing roller as well, it has been studied to coat the outer peripheral surface with a coating film (for example, Patent Document 2). Etc.).

JP 2000-267394 A JP 2001-222163 A

However, the coating film is formed by applying a liquid coating agent containing a binder resin as a base to the outer peripheral surface of the roller body by a coating method such as a spray method or a dipping method, and then drying the coating film. There is a problem that various defects such as contamination of dust and the like and occurrence of uneven thickness are likely to occur in the process.
In addition, an organic solvent that dissolves the binder resin is required to prepare the coating agent. However, the use of the organic solvent has a large environmental load and goes against the recent trend toward low VOC (volatile organic compounds). There is also a problem that it will be.

Furthermore, depending on the type of the binder resin, the coating film becomes hard, and coupled with the thickness of the coating film, there is another problem that the surface of the photoreceptor is easily damaged.
An object of the present invention is to provide a semiconductive roller having a roller body having a simpler structure in which the coating film is omitted, and having a lower outer peripheral surface than the current state.

  The present invention relates to a roller body comprising a crosslinked product of a rubber composition comprising epichlorohydrin rubber and diene rubber as rubber, and a silicone copolymer containing in its molecule a repeating unit constituting a resin compatible with the rubber. It is a semiconductive roller provided with.

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductive roller provided with the roller main body by which the outer peripheral surface made the friction low compared with the present condition can be provided, maintaining the simple structure which abbreviate | omitted the coating film.

It is a perspective view which shows an example of embodiment of the semiconductive roller of this invention.

The present invention relates to a roller body comprising a crosslinked product of a rubber composition comprising epichlorohydrin rubber and diene rubber as rubber, and a silicone copolymer containing in its molecule a repeating unit constituting a resin compatible with the rubber. It is a semiconductive roller provided with.
According to the present invention, for example, graphite and molybdenum disulfide are excellent in the effect of reducing the friction coefficient as compared with ordinary solid lubricants for rubber, but the silicone is not compatible with the rubber because of its low polarity. By introducing a repeating unit constituting a resin having good compatibility with the rubber, a silicone copolymer with improved compatibility with the rubber can be obtained while maintaining a good effect of reducing the friction coefficient. Can do.

Therefore, by blending the silicone-based copolymer into the rubber composition, the outer peripheral surface of the roller body without impairing the good rubber properties of the roller body made of a crosslinked product of the rubber composition. The friction can be reduced compared to the current situation.
In other words, according to the present invention, the semiconductivity provided with the roller body whose outer peripheral surface has a lower friction than the current state while maintaining a simple structure in which the coating film that may cause various problems described above is omitted. Roller can be provided.

  When the semiconductive roller of the present invention is used as, for example, a charging roller to form an image, toner and external additives remaining on the surface of the photoreceptor adhere to the outer peripheral surface of the roller body and accumulate. In this way, it is possible to suppress the occurrence of vertical streaks and dot-like density unevenness due to non-uniform charging in the formed image, and to influence the surface of the photoreceptor directly in contact with the image, thereby forming a good image. It becomes possible to do.

  Further, when an image is formed using the semiconductive roller of the present invention, for example, as a developing roller, the toner is pulverized by friction and the formed image is crushed, or fine particles of the external additive are contained in the toner particles. When the toner is buried and the fluidity of the toner is impaired, resulting in uneven density of the formed image, or when the toner amount regulation blade causes a slip stick to cause vertical streaky uneven density in the formed image, or when image formation is repeated Further, it is possible to suppress the occurrence of toner leakage due to wear of both end portions sealed by the sealing member, thereby forming a good image.

<Rubber composition>
<Rubber>
As described above, the rubber includes epichlorohydrin rubber and diene rubber.
(Epichlorohydrin rubber)
As the epichlorohydrin rubber, various polymers having epichlorohydrin as a repeating unit and having ionic conductivity can be used.

  Examples of the epichlorohydrin rubber include epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allyl glycidyl ether binary copolymer, epichlorohydrin-ethylene oxide- One or more of allylic glycidyl ether terpolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer, etc. Is mentioned.

Among them, when used in combination with a diene rubber, for example, a copolymer containing ethylene oxide, particularly an ECO, is effective in reducing the roller resistance value of a semiconductive roller to a range suitable for use as a charging roller or a developing roller. And / or GECO is preferred.
The ethylene oxide content in both copolymers is preferably 30 mol% or more, particularly preferably 50 mol% or more, and preferably 80 mol% or less.

Ethylene oxide serves to lower the roller resistance value of the semiconductive roller. However, when the ethylene oxide content is less than this range, such a function cannot be obtained sufficiently, and the roller resistance value may not be sufficiently reduced.
On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs and the segment motion of the molecular chain is hindered, so that the roller resistance value of the semiconductive roller tends to increase. In addition, the roller body after crosslinking may become too hard, or the viscosity of the rubber composition before crosslinking may increase when heated and melted, resulting in decreased processability of the rubber composition.

The epichlorohydrin content in ECO is the remaining amount of ethylene oxide content. That is, the epichlorohydrin content is preferably 20 mol% or more, preferably 70 mol% or less, and particularly preferably 50 mol% or less.
Further, the allylic glycidyl ether content in GECO is preferably 0.5 mol% or more, particularly 2 mol% or more, preferably 10 mol% or less, particularly 5 mol% or less.

The allyl glycidyl ether itself functions to secure a free volume as a side chain, thereby suppressing the crystallization of ethylene oxide and reducing the roller resistance value of the semiconductive roller. However, if the allyl glycidyl ether content is less than this range, such a function cannot be obtained sufficiently, and the roller resistance value may not be sufficiently reduced.
On the other hand, since allyl glycidyl ether functions as a crosslinking point during GECO crosslinking, when the allyl glycidyl ether content exceeds the above range, the GECO crosslinking density becomes too high, preventing the molecular chain segment movement. On the other hand, the roller resistance value tends to increase.

The epichlorohydrin content in GECO is the remaining amount of ethylene oxide content and allyl glycidyl ether content. That is, the epichlorohydrin content is preferably 10 mol% or more, particularly 19.5 mol% or more, preferably 69.5 mol% or less, particularly preferably 60 mol% or less.
As GECO, in addition to the above-described copolymer in the narrow sense obtained by copolymerization of the three types of monomers, a modification obtained by modifying epichlorohydrin-ethylene oxide copolymer (ECO) with allyl glycidyl ether. Any of these GECOs can be used in the present invention.
One or more of these epichlorohydrin rubbers can be used.

(Diene rubber)
As described above, the diene rubber imparts good processability to the rubber composition, improves the mechanical strength and durability of the roller body, or has good characteristics as rubber in the roller body, that is, flexible. In addition, it functions to impart a characteristic that the compression set is small and hardly causes settling.

In some cases, an oxide film is formed on the outer peripheral surface of the roller body, but the diene rubber is oxidized by the ultraviolet irradiation and becomes a material for forming the oxide film.
Examples of the diene rubber include natural rubber, isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR). Can be mentioned.
Among them, it is preferable to use SBR alone with epicudrhydrin rubber, or to use three types of SBR, CR and NBR together with epichlorohydrin rubber.

(SBR)
As the SBR, any of 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 crosslinkability can be used. .

As the SBR, any of SBR of high styrene type, medium styrene type, and low styrene type classified by styrene content can be used.
In addition, SBR is classified into an oil-extended type in which flexibility is adjusted by adding extender oil and a non-oil-extended type in which flexibility is not added, but when using a semiconductive roller as a charging roller or developing roller, In order to prevent contamination of the toner and the photoreceptor, it is preferable to use a non-oil-extended type SBR that does not contain an extending oil that can be a bleeding substance.
One or more of these SBRs can be used.

(CR)
CR is synthesized by emulsion polymerization of chloroprene, and is classified into a sulfur-modified type and a non-sulfur-modified type depending on the type of molecular weight modifier used.
Among these, the sulfur-modified CR is synthesized by plasticizing a polymer obtained by copolymerizing chloroprene and sulfur as a molecular weight adjusting agent with thiuram disulfide or the like to adjust to a predetermined viscosity.

Non-sulfur-modified CRs are classified into, for example, mercaptan-modified and xanthogen-modified types.
Among these, mercaptan-modified CR is synthesized in the same manner as sulfur-modified CR except that alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, octyl mercaptan, and the like are used as molecular weight regulators. .

The xanthogen-modified CR is synthesized in the same manner as the sulfur-modified CR except that an alkyl xanthogen compound is used as a molecular weight modifier.
Further, CR is classified into a type having a low crystallization rate, a type having a moderate rate, and a type having a high rate based on the crystallization rate.
In the present invention, any type of CR may be used, but among them, a non-sulfur modified type and a slow crystallization rate type CR are preferable.

  As CR, a copolymer of chloroprene and other copolymer components may be used. Examples of such other copolymerization components include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, acrylic acid, and acrylate esters. , Methacrylic acid, and one or more of methacrylic acid esters.

Furthermore, there are two types of CRs: oil-extended types that have been adjusted for flexibility by adding extender oils, and non-oil-extended types that do not, but use semi-conductive rollers as charging rollers and developing rollers. In order to prevent contamination of the toner and the photoconductor, it is preferable to use a non-oil-extended type CR that does not contain an extending oil that can be a bleeding material.
One or more of these CRs can be used.

(NBR)
NBR includes low nitrile NBR having an acrylonitrile content of 24% or less, medium nitrile NBR having 25 to 30%, medium to high nitrile NBR having 31 to 35%, high nitrile NBR having 36 to 42%, 43% or more Any of the very high nitrile NBRs may be used.

NBR is also classified into an oil-extended type that adjusts flexibility by adding extender oil, and a non-oil-extended type that does not add NBR, but when semi-conductive rollers are used as charging rollers or developing rollers In order to prevent contamination of the toner and the photoreceptor, it is preferable to use a non-oil-extended type NBR that does not contain an extending oil that can become a bleeding material.
One or more of these NBRs can be used.

(Rubber mixing ratio)
The blending ratio of the rubber can be arbitrarily set according to various characteristics required for the semiconductive roller, in particular, the roller resistance value and the flexibility of the roller body.
However, the blending ratio of the epichlorohydrin rubber is preferably 15 parts by mass or more, particularly 30 parts by mass or more, and preferably 90 parts by mass or less, particularly 80 parts by mass or less, in 100 parts by mass of the total amount of rubber.

If the blending ratio of epichlorohydrin rubber is less than this range, the roller resistance value of the semiconductive roller may not be sufficiently reduced to a range suitable for use as a charging roller or a developing roller.
On the other hand, when the proportion of the epichlorohydrin rubber exceeds the above range, the proportion of the diene rubber is relatively reduced, so that the rubber composition is imparted with good processability or the above-mentioned rubber is added to the roller body. As a result, it may not be possible to impart good characteristics.

On the other hand, by setting the blending ratio of the epichlorohydrin rubber in the above range, the roller resistance value of the semiconductive roller can be set as a charging roller or a developing roller while maintaining the above effect by using the diene rubber together. Can be sufficiently reduced to a range suitable for use.
The blending ratio of the diene rubber is the remaining amount of epichlorohydrin rubber. That is, the blending ratio of epichlorohydrin rubber is set within a predetermined range, and the blending ratio of the diene rubber may be set so that the total amount of rubber including the diene rubber is 100 parts by mass.

<Silicone copolymer>
As the silicone-based copolymer, various silicone-based copolymers containing a repeating unit constituting a resin compatible with rubber can be used in the molecule as described above.
Examples of the resin that is compatible with rubber constituting the silicone copolymer include polypropylene (PP), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and ethylene-ethyl acrylate copolymer resin. 1 type or 2 types or more, such as (EEA), ethylene-methyl methacrylate copolymer resin (EMMA), ethylene-vinyl acetate copolymer resin (EVA), (meth) acrylic acid alkyl ester copolymer, etc. are mentioned.

  Examples of the silicone copolymer include a block copolymer, a graft copolymer, or a polysiloxane having a structure in which a silicone moiety such as polysiloxane is bonded to the end of the main chain of the resin or as a side chain. Examples thereof include one or more of a block copolymer having a structure in which a portion corresponding to the above resin is bonded to the terminal of the main chain of the silicone or the like as a side chain, or a graft copolymer.

  Specific examples of the silicone-based copolymer include BY27-201 manufactured by Toray Dow Corning Co., Ltd. synthesized by graft polymerization of a reactive polyorganosiloxane to a resin [resin: PP, silicone content: 40%], BY27-201C [resin: PP, silicone content: 40%], BY27-202H [resin: LDPE, silicone content: 60%], BY27-213 [resin: LLDPE, silicone content: 40%] ], BY27-218 [resin: EEA, silicone content: 50%], BY27-219 [resin: EMMA, silicone content: 60%], BY27-220 [resin: EVA, silicone content: 60%], etc. Is mentioned.

  Further, specific examples of the silicone copolymer include, for example, Charine (registered trademark) manufactured by Nissin Chemical Industry Co., Ltd., which is a graft copolymer of a polyalkylsiloxane and a (meth) acrylic acid alkyl ester copolymer. R-170 [silicone content: 70%, amorphous powder, average particle size 350 μm, primary particle size: 0.2 to 0.3 μm], R-170S [silicone content: 70%, spherical, average particle size 30 μm, primary particle size: 0.2 to 0.3 μm] and the like.

One or more of these silicone copolymers can be used.
The blending ratio of the silicone-based copolymer is preferably 1 part by mass or more, preferably 40 parts by mass or less, particularly preferably 30 parts by mass or less, per 100 parts by mass of the total amount of rubber.
When the blending ratio of the silicone copolymer is less than this range, the outer peripheral surface of the roller body is lower than the current state while maintaining a simple structure by omitting the coating film by blending the silicone copolymer. There is a possibility that the effect of rubbing cannot be obtained sufficiently.

When an image is formed using the semiconductive roller of the present invention as a charging roller, toner and external additives remaining on the surface of the photoreceptor adhere to and accumulate on the outer peripheral surface of the roller body, There is a risk that the formed image may have vertical streak-like or spot-like density unevenness due to non-uniform charging, or may affect the surface of the photoreceptor directly in contact with the formed image.
In addition, when an image is formed using the semiconductive roller of the present invention as a developing roller, the toner is crushed by friction and the formed image is crushed, or fine particles of the external additive are embedded in the toner particles. The flowability of the toner is impaired, resulting in uneven density of the formed image, or the toner amount regulating blade causes a slip stick to cause vertical streaky uneven density in the formed image, or when image formation is repeated, There is a possibility that both ends sealed by the seal member are worn and toner leakage occurs.

On the other hand, when the blending ratio of the silicone-based copolymer exceeds the above range, the rubber ratio is relatively reduced, so that the processability of the rubber composition is lowered, and the extruded cylindrical body is The extruded skin on the outer peripheral surface tends to be rough.
When the extruded skin is rough, there is a risk that density unevenness is likely to occur in the formed image when the image is formed using, for example, a developing roller, although the outer peripheral surface is polished in the subsequent process. .

In addition, the roller resistance value of the semiconductive roller cannot be sufficiently lowered to a range particularly suitable for use as a developing roller, and the density of the formed image may be lowered.
On the other hand, by setting the blending ratio of the silicone-based copolymer in the above-described range, it is possible to suppress the occurrence of these various problems and form a better image.
<Crosslinking component>
The rubber composition contains a crosslinking component for crosslinking the rubber. As the crosslinking component, it is preferable to use a thiourea crosslinking agent and a sulfur crosslinking agent in combination.

(Thiourea based crosslinking agent)
As the thiourea-based crosslinking agent, various thiourea compounds having a thiourea structure in the molecule and mainly functioning as a crosslinking agent for ECO and / or GECO can be used.
Examples of the thiourea-based crosslinking agent include ethylene thiourea, N, N′-diphenylthiourea, trimethylthiourea, formula (1):
(C _n H _{2n + 1} NH) ₂ C = S (1)
[In formula, n shows the integer of 1-12. Or one or more of thiourea and tetramethylthiourea represented by the formula: In particular, ethylene thiourea is preferable.

The blending ratio of the thiourea-based crosslinking agent is preferably 0.1 parts by mass or more per 100 parts by mass of the total amount of rubber in consideration of imparting the above-mentioned good characteristics as rubber to the roller body. It is preferably less than or equal to parts by mass.
(Crosslinking accelerator)
The thiourea crosslinking agent may be used in combination with various crosslinking accelerators that promote the crosslinking reaction of ECO and / or GECO with the thiourea crosslinking agent.

Examples of the crosslinking accelerator include one or more guanidine accelerators such as 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and the like. In particular, 1,3-di-o-tolylguanidine is preferable.
The blending ratio of the crosslinking accelerator is preferably 0.1 parts by mass or more and preferably 1 part by mass or less per 100 parts by mass of the total amount of rubber in consideration of sufficiently developing the effect of promoting the crosslinking reaction. Is preferred.

(Sulfur-based crosslinking agent)
As sulfur-based crosslinking agents mainly for crosslinking diene rubber and GECO, for example, sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, dispersible sulfur, or tetramethylthiuram disulfide, N, Examples thereof include organic sulfur-containing compounds such as N-dithiobismorpholine, and sulfur is particularly preferable.

The mixing ratio of sulfur is preferably 1 part by mass or more and 100 parts by mass or less per 100 parts by mass of the total amount of rubber in consideration of imparting the above-mentioned good characteristics as rubber to the roller body. Is preferred.
For example, when oil-treated powder sulfur, dispersible sulfur, or the like is used as sulfur, the blending ratio is the ratio of sulfur itself as an active ingredient contained therein.

Moreover, when using an organic sulfur-containing compound as a crosslinking agent, it is preferable to adjust the blending ratio so that the ratio of sulfur contained in the molecule per 100 parts by mass of the rubber is within the above range.
(Crosslinking accelerator)
The sulfur-based crosslinking agent may be used in combination with various crosslinking accelerators that accelerate the crosslinking reaction of the diene rubber or the like with the sulfur-based crosslinking agent.

Examples of such crosslinking accelerators include one or more of thiazole accelerators, thiuram accelerators, sulfenamide accelerators, dithiocarbamate accelerators, and the like. Among these, it is preferable to use a thiazole accelerator and a thiuram accelerator in combination.
Examples of thiazole accelerators include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2- (N, N- Examples thereof include one or more of diethylthiocarbamoylthio) benzothiazole, 2- (4′-morpholinodithio) benzothiazole and the like. Di-2-benzothiazolyl disulfide is particularly preferable.

  Examples of the thiuram accelerator include one or two of tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, dipentamethylenethiuram tetrasulfide and the like. More than species. Tetramethylthiuram monosulfide is particularly preferable.

  In consideration of sufficiently developing the effect of promoting the crosslinking reaction in the combined system of the two types of crosslinking accelerators, the blending ratio of the thiazole accelerator is 0.1 parts by mass or more per 100 parts by mass of the total amount of rubber. 1 part by mass or less is preferable. The blending ratio of the thiuram accelerator is preferably 0.1 parts by mass or more and 1 part by mass or less per 100 parts by mass of the total amount of rubber.

<Conductive agent>
In particular, the rubber composition forming the charging roller may further contain a salt (ionic salt) of an anion having a fluoro group and a sulfonyl group in the molecule and a cation as a conductive agent.
By blending an ionic salt as a conductive agent, the ionic conductivity of the rubber composition can be further improved, and the roller resistance value of the charging roller can be further reduced.
Examples of the anion having a fluoro group and a sulfonyl group in the molecule constituting the ionic salt include one or two of fluoroalkylsulfonic acid ion, bis (fluoroalkylsulfonyl) imide ion, tris (fluoroalkylsulfonyl) methide ion, etc. The above is mentioned.

Of these, examples of the fluoroalkylsulfonic acid ion include one or more of CF ₃ SO ₃ ^— , C ₄ F ₉ SO ₃ ^{—, and the} like.
Examples of bis (fluoroalkylsulfonyl) imide ions include (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) N ^−. , (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) N ⁻ , (C ₈ F ₁₇ SO ₂ ) (CF ₃ SO ₂ ) N ⁻ , (CF ₃ CH ₂ OSO ₂ ) ₂ N ⁻ , (CF _{3 CF 2 CH 2 OSO 2) 2} N -, (HCF 2 CF 2 CH 2 OSO 2) 2 N - include one or more of such ^{_{-, [(CF 3) 2}} CHOSO 2] 2 N.

Further, examples of the tris (fluoroalkylsulfonyl) methide ion include one or more of (CF ₃ SO ₂ ) ₃ C ⁻ , (CF ₃ CH ₂ OSO ₂ ) ₃ C ^{− and the} like.
Examples of the cation include 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, One kind or two or more kinds such as a quaternary ammonium ion and an imidazolium cation may be mentioned.

As the ionic salt, a lithium salt using lithium ion as a cation or a potassium salt using potassium ion is particularly preferable.
Among them, (CF ₃ SO ₂ ) ₂ NLi [lithium bis (trifluoromethanesulfonyl) imide Li-TFSI] in terms of the effect of improving the ionic conductivity of the rubber composition and reducing the roller resistance value of the charging roller, And / or (CF ₃ SO ₂ ) ₂ NK [potassium bis (trifluoromethanesulfonyl) imide, K-TFSI] is preferred.

The blending ratio of the ionic salt is preferably 0.5 parts by mass or more and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.
<Others>
You may mix | blend various additives with a rubber composition further as needed. Examples of the additive include a crosslinking acceleration aid, an acid acceptor, a filler, a plasticizer, a processing aid, and a deterioration inhibitor.

Among these, examples of the crosslinking accelerating aid include metal compounds such as zinc oxide (zinc white); fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and one or more conventionally known crosslinking accelerating aids. Can be mentioned.
The blending ratio of the crosslinking accelerating aid is preferably individually 0.1 parts by mass or more and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.

The acid acceptor functions to prevent the chlorine-based gas generated from epichlorohydrin rubber or CR during crosslinking from remaining in the roller body, thereby inhibiting crosslinking and contamination of the photoreceptor.
As the acid acceptor, various substances acting as an acid acceptor can be used. Among them, hydrotalcite or magsarat having excellent dispersibility is preferable, and hydrotalcite is particularly preferable.

Further, when hydrotalcites or the like are used in combination with magnesium oxide or potassium oxide, a higher acid-receiving effect can be obtained, and contamination of the photoreceptor can be prevented even better.
The blending ratio of the acid acceptor is preferably 0.1 parts by mass or more and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.
Examples of the filler include one or more of zinc oxide, silica, carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, and the like.

By blending the filler, the mechanical strength of the charging roller and the developing roller can be improved.
In addition, when conductive carbon black is used as a filler, electronic conductivity can be imparted to the roller body.
Examples of the conductive carbon black include acetylene black.
The blending ratio of the conductive carbon black is preferably 1 part by mass or more per 100 parts by mass of the total amount of rubber, and is preferably 10 parts by mass or less.

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.
The blending ratio of the plasticizer and / or processing aid is preferably 3 parts by mass or less per 100 parts by mass of the total amount of rubber.

Examples of the deterioration preventing agent include various antiaging agents and antioxidants.
Among these, the anti-aging agent functions to reduce the environmental dependency of the roller resistance value of the charging roller and the developing roller and to suppress an increase in the roller resistance value during continuous energization. Examples of the antiaging agent include nickel diethyldithiocarbamate and nickel dibutyldithiocarbamate.

The blending ratio of the anti-aging agent is preferably 0.1 parts by mass or more and preferably 1 part by mass or less per 100 parts by mass of the total amount of rubber.
As additives, various additives such as a scorch inhibitor, a lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizing agent, a nucleating agent, and a co-crosslinking agent may be further blended in an arbitrary ratio.

《Semiconductive roller》
FIG. 1 is a perspective view showing an example of an embodiment of a semiconductive roller of the present invention.
Referring to FIG. 1, a semiconductive roller 1 of this example includes a roller body 2 formed in a cylindrical shape having a non-porous and single layer structure by using a rubber composition containing the above-described components. A shaft 4 is inserted into and fixed to the through hole 3 at the center of the roller body 2.
The shaft 4 is integrally formed of a metal such as aluminum, an aluminum alloy, or stainless steel.

The shaft 4 is electrically bonded and mechanically fixed to the roller body 2 through, for example, a conductive adhesive, or a through-hole having an outer diameter larger than the inner diameter of the through-hole 3. By press-fitting into the roller 3, the roller body 2 is electrically joined and mechanically fixed.
Although not shown, an oxide film may be formed on the outer peripheral surface 5 of the roller body 2.

When the oxide film is formed, the oxide film functions as a dielectric layer, and the dielectric loss tangent of the semiconductive roller 1 can be reduced. Further, since the oxide film functions as a low friction layer, there is a possibility that the outer peripheral surface 5 can be further reduced in friction.
However, in the present invention, the outer peripheral surface 5 of the roller body 2 can be satisfactorily reduced in friction by blending the above-described silicone copolymer into the rubber composition forming the roller body 2. In order to further simplify the structure of the roller and the manufacturing process, the oxide film may be omitted.

In order to manufacture the semiconductive roller 1, the prepared rubber composition is first extruded into a cylindrical shape using an extruder, then cut into a predetermined length, and pressed and heated in a vulcanizing can. To crosslink.
Next, the crosslinked cylindrical body is heated and secondarily crosslinked using an oven or the like, cooled, and then polished to have a predetermined outer diameter to form the roller body 2.
As a polishing method, various polishing methods such as dry traverse polishing can be employed.

In addition, mirror polishing or wet polishing may be performed at the end of the polishing process. In that case, the mold releasability of the outer peripheral surface 5 can be improved, and the outer peripheral surface 5 can be further reduced in friction. Further, it is possible to effectively prevent contamination of the photoconductor.
The shaft 4 can be inserted through the through hole 3 and fixed at an arbitrary time from after the cylindrical body is cut to after polishing.

However, after the cut, it is preferable to first perform secondary crosslinking and polishing in a state where the shaft 4 is inserted into the through hole 3. Thereby, the curvature and deformation | transformation of the roller main body 2 by the expansion-contraction at the time of secondary bridge | crosslinking can be suppressed. Further, by polishing while rotating around the shaft 4, the workability of the polishing can be improved, and the deflection of the outer peripheral surface 5 can be suppressed.
As described above, the shaft 4 is either press-fitted into the through-hole 3 having an outer diameter larger than the inner diameter of the through-hole 3 or before the secondary crosslinking through a conductive thermosetting adhesive. What is necessary is just to insert in the through-hole 3 of this cylindrical body.

In the former case, electrical joining and mechanical fixing are completed simultaneously with the press-fitting of the shaft 4.
In the latter case, the thermosetting adhesive is cured at the same time as the cylindrical body is secondarily crosslinked by heating in the oven, and the shaft 4 is electrically joined to the roller body 2. Fixed mechanically.
The semi-conductive roller 1 having a non-porous and single-layer structure preferably has a roller A 2 having a type A durometer hardness of 52 or more, and preferably 56 or less.

If the type A durometer hardness is less than this range, the compression set of the roller body 2 is increased, and there is a risk of causing settling.
On the other hand, when the type A durometer hardness exceeds the above range, the roller body 2 becomes too hard. For example, with a charging roller, the surface of the directly contacting photoreceptor may be easily damaged. In addition, the developing roller tends to crush the toner and cause the formed image to become crushed, or the fine particles of the external additive are embedded in the toner particles, and the fluidity of the toner is impaired, resulting in uneven density of the formed image. There is a risk.

On the other hand, by setting the type A durometer hardness within the above range, the roller body 2 has a small permanent compression set and hardly causes settling, and is flexible and does not easily crush the toner or damage the surface of the photoreceptor. A semiconductive roller 1 can be obtained.
In order to adjust the type A durometer hardness within the above range, the type and blending ratio of each component described above may be appropriately changed within the above range.

  The semiconductive roller 1 of the present invention is used as a charging roller or a developing roller in an image forming apparatus using electrophotography such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a complex machine of these. In addition to being suitable, it can also be used as a transfer roller, a cleaning roller, or the like.

The present invention will be further described below based on examples and comparative examples, but the configuration of the present invention is not limited by these examples and comparative examples.
<Charging roller>
<Example 1-1>
(Preparation of rubber composition)
As rubber, GECO [HYDRIN (registered trademark) T3108 manufactured by Nippon Zeon Co., Ltd.] 40 parts by mass, SBR [JSR (registered trademark) 1502 manufactured by JSR Co., Ltd., emulsion polymerization method, non-oil-extended] 40 parts by mass , CR [Showen (registered trademark) WRT manufactured by Showa Denko KK, non-oil extended] 10 parts by mass, and NBR (Nipol (registered trademark) DN401LL manufactured by Nippon Zeon Co., Ltd., low nitrile NBR, acrylonitrile content: 18 %, Non-oil extended] 10 parts by mass were blended.

  Then, while kneading 100 parts by mass of the total amount of the four types of rubber using a Banbury mixer, a silicone copolymer [BY27-220 manufactured by Toray Dow Corning Co., Ltd., resin: EVA, silicone content: 60% 7 parts by mass and the following components were blended and kneaded.

Each component in Table 1 is as follows. Moreover, the mass part in a table | surface is a mass part per 100 mass parts of total amounts of rubber | gum.
Ion salt: Potassium bis (trifluoromethanesulfonyl) imide [EF-N112, K-TFSI manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd.]
Cross-linking accelerator: 2 types of zinc oxide [manufactured by Sakai Chemical Industry Co., Ltd.]
Acid acceptor: Hydrotalcite [DHT-4A (registered trademark) -2 manufactured by Kyowa Chemical Industry Co., Ltd.]
Filler: Conductive carbon black [Denka Black (registered trademark), acetylene black, granular, manufactured by Denki Kagaku Kogyo Co., Ltd.]
Next, while continuing kneading, the following crosslinking components were blended and further kneaded to prepare a rubber composition.

Each component in Table 2 is as follows. Moreover, the mass part in a table | surface is a mass part per 100 mass parts of total amounts of rubber | gum.
Thiourea-based cross-linking agent: ethylenethiourea [Axel (registered trademark) 22-S, 2-mercaptoimidazoline manufactured by Kawaguchi Chemical Industry Co., Ltd.]
Accelerator DT: 1,3-di-o-tolylguanidine [Sunseller (registered trademark) DT, guanidine-based accelerator manufactured by Sanshin Chemical Industry Co., Ltd.]
Sulfur-based crosslinking agent: sulfur containing 5% oil (manufactured by Tsurumi Chemical Co., Ltd.)
Accelerator DM: Di-2-benzothiazolyl disulfide [Noxeller (registered trademark) DM, thiazole accelerator manufactured by Ouchi Shinsei Chemical Co., Ltd.]
Accelerator TS: Tetramethylthiuram monosulfide [Sunseller TS, thiuram accelerator made by Sanshin Chemical Industry Co., Ltd.]
(Manufacture of charging roller)
The prepared rubber composition is supplied to an extruder, extruded into a cylindrical shape having an outer diameter of 11.0 mm and an inner diameter of 5.0 mm, mounted on a temporary shaft for crosslinking, and 160 ° C. × 1 in a vulcanizing can. Cross-linked for hours.

Next, the cross-linked cylindrical body was reattached to a metal shaft having an outer diameter of φ6.0 mm with a conductive thermosetting adhesive (polyamide type) applied to the outer peripheral surface, and heated to 160 ° C. in an oven. And adhered to the metal shaft.
Then, both ends were shaped, and then the outer peripheral surface was traverse-polished using a cylindrical grinder, and finished by wet grinding so that the outer diameter was 9.50 mm (tolerance 0.05), and integrated with the shaft. A roller body was formed to produce a charging roller.

<Example 1-2>
A rubber composition in the same manner as in Example 1-1 except that BY27-202H [resin: LDPE, silicone content: 60%] manufactured by Toray Dow Corning Co., Ltd. was blended in the same amount as the silicone copolymer. The product was prepared and a charging roller was manufactured.
<Example 1-3>
A rubber composition in the same manner as in Example 1-1, except that BY27-201 (resin: PP, silicone content: 40%) manufactured by Toray Dow Corning Co., Ltd. was blended in the same amount as the silicone copolymer. The product was prepared and a charging roller was manufactured.

<Example 1-4>
As a silicone copolymer, the same amount of Charine R-170S manufactured by Nissin Chemical Industry Co., Ltd. [silicone content: 70%, spherical, average particle size 30 μm, primary particle size: 0.2 to 0.3 μm] Except for blending, a rubber composition was prepared in the same manner as in Example 1-1 to produce a charging roller.

<Examples 1-5, 1-6, 1-7>
As a silicone copolymer, the blending ratio of BY27-202H [resin: LDPE, silicone content: 60%] manufactured by Toray Dow Corning Co., Ltd. is 1 part by mass per 100 parts by mass of rubber (Examples). 1-5) A rubber composition was prepared in the same manner as in Example 1-2 except that 30 parts by mass (Example 1-6) and 40 parts by mass (Example 1-7) were used. Manufactured.

<Example 1-8>
Except for using two types of rubber, 80 parts by mass of GECO [HYDRIN T3108 manufactured by Nippon Zeon Co., Ltd.] and 20 parts by mass of SBR [JSR1502 manufactured by JSR Corporation, emulsion polymerization method, non-oil-extended] A rubber composition was prepared in the same manner as in Example 1-2 to produce a charging roller.
<Comparative Example 1-1>
A rubber composition was prepared in the same manner as in Example 1-1 except that no silicone copolymer was blended, and a charging roller was produced.

<Comparative Example 1-2>
Instead of the silicone copolymer, a rubber composition was prepared in the same manner as in Example 1-1, except that the same amount of graphite (UP-5N manufactured by Nippon Graphite Industry Co., Ltd.) was blended. A charging roller was manufactured.
<Comparative Example 1-3>
A rubber composition was prepared in the same manner as in Comparative Example 1-2, except that the blending ratio of graphite was 30 parts by mass per 100 parts by mass of the total amount of rubber, and a charging roller was produced.

<Comparative Example 1-4>
Instead of the silicone copolymer, a rubber composition was prepared in the same manner as in Example 1-1 except that the same amount of molybdenum disulfide [Moly powder PS manufactured by Sumiko Lubricant Co., Ltd.] was blended. A charging roller was manufactured.
<Comparative Example 1-5>
A rubber composition was prepared in the same manner as in Comparative Example 1-4, except that the blending ratio of molybdenum disulfide was 30 parts by mass per 100 parts by mass of the total amount of rubber, and a charging roller was manufactured.

<Processability evaluation>
In Examples and Comparative Examples, the cylindrical body formed by extruding the rubber composition was observed for the extruding skin on the outer peripheral surface. Things were evaluated as bad (x).
<Real machine test>
A genuine photoconductor unit (manufactured by Lexmark International), which is provided with a photoconductor and a charging roller that is always in contact with the surface of the photoconductor and is detachable from the laser printer body, Instead of the charging roller, the charging roller manufactured in Examples and Comparative Examples was incorporated.

  The assembled photoconductor unit is loaded into a color laser printer (color laser printer CS510de manufactured by Lexmark International), and a 30% density, 300 lpi black solid image is printed at 30000 sheets at a rate of 2 sheets / 25 seconds. In the image of 30000 images formed continuously over the period, even if one image has vertical streak-like or dot-like density unevenness due to non-uniform charging, it is defective (x), and no image has occurred at all (good) ○).

In addition, after the continuous image formation, the charging roller is taken out and the outer peripheral surface is visually observed. If the toner or whitening agent is whitened due to the adhesion of the toner or the external additive, the whitening is defective (x), and the whitening is not good. ).
The above results are shown in Tables 3 to 5.

  From the results of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-5 in Tables 3 to 5, it is compatible with rubber instead of graphite and molybdenum disulfide which are conventional solid lubricants. By blending a silicone-based copolymer containing the repeating unit constituting the resin in the molecule, the friction coefficient of the outer peripheral surface of the roller body of the charging roller is greatly reduced, so that the toner remaining on the photoreceptor and the external additive It has been found that the agent can be prevented from adhering and accumulating on the outer peripheral surface of the roller main body, and causing vertical stripes and dot-like density unevenness in the formed image due to non-uniform charging.

In particular, from the results of Examples 1-1 and 1-5 to 1-7, when considering that the above effects can be further improved while maintaining good processability of the rubber composition, the silicone copolymer It has been found that the blending ratio of the coalescence is preferably 1 part by mass or more with respect to 100 parts by mass of the total amount of rubber, preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less.
<Development roller>
<Example 2-1>
(Preparation of rubber composition)
As rubber, GECO [HYDRIN T3108 manufactured by Nippon Zeon Co., Ltd.] 40 parts by mass, SBR [JSR 1502 manufactured by JSR Co., Ltd., emulsion polymerization method, non-oil exhibition] 40 parts by mass, CR [manufactured by Showa Denko Co., Ltd.] And 10 parts by mass of NBR [Nipol DN401LL, low nitrile NBR, acrylonitrile content: 18%, non-oil extended] manufactured by Nippon Zeon Co., Ltd.].

  Then, while kneading 100 parts by mass of the total amount of the four types of rubber using a Banbury mixer, a silicone copolymer [BY27-220 manufactured by Toray Dow Corning Co., Ltd., resin: EVA, silicone content: 60% 7 parts by mass and the following components were blended and kneaded.

Each component in Table 6 is as follows. Moreover, the mass part in a table | surface is a mass part per 100 mass parts of total amounts of rubber | gum.
Cross-linking accelerator: 2 types of zinc oxide [manufactured by Sakai Chemical Industry Co., Ltd.]
Acid acceptor: Hydrotalcite [DHT-4A-2 manufactured by Kyowa Chemical Industry Co., Ltd.]
Filler: Conductive carbon black [Denka black, acetylene black, granular, manufactured by Denki Kagaku Kogyo Co., Ltd.]
Next, while continuing kneading, the following crosslinking components were blended and further kneaded to prepare a rubber composition.

Each component in Table 7 is as follows. Moreover, the mass part in a table | surface is a mass part per 100 mass parts of total amounts of rubber | gum.
Thiourea-based crosslinking agent: ethylenethiourea [Axel 22-S, 2-mercaptoimidazoline manufactured by Kawaguchi Chemical Industry Co., Ltd.]
Accelerator DT: 1,3-di-o-tolylguanidine (Sunseller DT manufactured by Sanshin Chemical Industry Co., Ltd., guanidine accelerator)
Sulfur-based crosslinking agent: sulfur containing 5% oil (manufactured by Tsurumi Chemical Co., Ltd.)
Accelerator DM: Di-2-benzothiazolyl disulfide [Noxeler DM, thiazole accelerator manufactured by Ouchi Shinsei Chemical Co., Ltd.]
Accelerator TS: Tetramethylthiuram monosulfide [Sunseller TS, thiuram accelerator made by Sanshin Chemical Industry Co., Ltd.]
(Manufacture of developing roller)
The prepared rubber composition is supplied to an extruder, extruded into a cylindrical shape having an outer diameter of 20.0 mm and an inner diameter of 7.0 mm, mounted on a temporary shaft for crosslinking, and 160 ° C. × 1 in a vulcanizing can. Cross-linked for hours.

Next, the cross-linked cylindrical body was reattached to a metal shaft having an outer diameter of φ7.5 mm and coated with a conductive thermosetting adhesive (polyamide) on the outer peripheral surface, and heated to 160 ° C. in an oven. And adhered to the metal shaft.
Then, both ends were shaped, and then the outer peripheral surface was traverse-polished using a cylindrical grinder, and finished to have an outer diameter of φ20.00 mm (tolerance 0.05) by mirror polishing, and integrated with the shaft. A roller body was formed to produce a developing roller.

<Example 2-2>
A rubber composition in the same manner as in Example 2-1, except that BY27-202H [resin: LDPE, silicone content: 60%] manufactured by Toray Dow Corning Co., Ltd. was blended in the same amount as the silicone copolymer. The product was prepared and a developing roller was manufactured.
<Example 2-3>
A rubber composition in the same manner as in Example 2-1, except that BY27-201 (resin: PP, silicone content: 40%) manufactured by Toray Dow Corning Co., Ltd. was blended in the same amount as the silicone copolymer. The product was prepared and a developing roller was manufactured.

<Example 2-4>
As a silicone copolymer, the same amount of Charine R-170S manufactured by Nissin Chemical Industry Co., Ltd. [silicone content: 70%, spherical, average particle size 30 μm, primary particle size: 0.2 to 0.3 μm] Except for blending, a rubber composition was prepared in the same manner as in Example 2-1, and a developing roller was produced.

<Examples 2-5, 2-6, 2-7>
As a silicone copolymer, the blending ratio of BY27-202H [resin: LDPE, silicone content: 60%] manufactured by Toray Dow Corning Co., Ltd. is 1 part by mass per 100 parts by mass of rubber (Examples). 2-5), a rubber composition was prepared in the same manner as in Example 2-2 except that 30 parts by mass (Example 2-6) and 40 parts by mass (Example 2-7) were used. Manufactured.

<Example 2-8>
Except for using two types of rubber, 80 parts by mass of GECO [HYDRIN T3108 manufactured by Nippon Zeon Co., Ltd.] and 20 parts by mass of SBR [JSR1502 manufactured by JSR Corporation, emulsion polymerization method, non-oil-extended] A rubber composition was prepared in the same manner as in Example 2-2 to produce a developing roller.
<Comparative Example 2-1>
A rubber composition was prepared in the same manner as in Example 2-1, except that no silicone copolymer was blended, and a developing roller was produced.

<Comparative Example 2-2>
Instead of the silicone copolymer, a rubber composition was prepared in the same manner as in Example 2-1, except that the same amount of graphite (UP-5N manufactured by Nippon Graphite Industry Co., Ltd.) was blended. A developing roller was produced.
<Comparative Example 2-3>
A rubber composition was prepared in the same manner as in Comparative Example 2-2 except that the proportion of graphite was 30 parts by mass per 100 parts by mass of the total amount of rubber, and a developing roller was produced.

<Comparative Example 2-4>
Instead of the silicone copolymer, a rubber composition was prepared in the same manner as in Example 2-1, except that the same amount of molybdenum disulfide [Moly powder PS manufactured by Sumiko Lubricant Co., Ltd.] was blended. A developing roller was produced.
<Comparative Example 2-5>
A rubber composition was prepared in the same manner as in Comparative Example 2-4 except that the blending ratio of molybdenum disulfide was 30 parts by mass per 100 parts by mass of the total amount of rubber, and a developing roller was produced.

<Processability evaluation>
In Examples and Comparative Examples, the cylindrical body formed by extruding the rubber composition was observed for the extruding skin on the outer peripheral surface. Things were evaluated as bad (x).
<Real machine test>
To a genuine developer roller of a new cartridge (manufactured by Brother Industries, Ltd.), which has a toner container containing toner, a photoconductor, and a developing roller in contact with the photoconductor, and is detachable from the main body of the laser printer. Instead, the developing rollers manufactured in the examples and comparative examples were incorporated.

  Then, the assembled cartridge is loaded into a laser printer (HL-6180D manufactured by Brother Industries, Ltd.), and 6500 images of 5% density are printed on plain paper in an environment of a temperature of 23 ± 1 ° C. and a relative humidity of 55 ± 1%. Consecutively formed sheets, and 6500 images formed were defective (x) where even one sheet was not smooth, density unevenness, or vertical streak-like density unevenness was found. Was evaluated as good (◯).

Further, the density of the black solid portion of the 6500th formed image was measured using a reflection densitometer [Model 939 manufactured by X-Rite Co., Ltd.], and the density was evaluated according to the following criteria.
○: The concentration was 1.3 or more. Good.
(Triangle | delta): The density | concentration was 1.2 or more and less than 1.3. Intermediate level.
X: The concentration was less than 1.2. Bad.

Further, the cartridge was observed after 6500 images were formed, and toner leakage was evaluated according to the following criteria.
○: No toner leakage was observed. Good.
X: Leakage of toner was observed. Bad.
The above results are shown in Tables 8 to 10.

  From the results of Examples 2-1 to 2-8 and Comparative Examples 2-1 to 2-5 in Tables 8 to 10, it is compatible with rubber instead of graphite or molybdenum disulfide which are conventional solid lubricants. By blending a silicone-based copolymer containing the repeating unit constituting the resin in the molecule, the coefficient of friction of the outer peripheral surface of the roller body of the developing roller is greatly reduced, and the formed image is crushed, density unevenness, vertical It was found that streaky density unevenness can be suppressed and toner leakage can be suppressed.

  In particular, from the results of Examples 2-1 and 2-5 to 2-7, while maintaining the good processability of the rubber composition, the above effect is further improved, and the decrease in the density of the formed image is suppressed. In consideration of this, the blending ratio of the silicone-based copolymer is preferably 1 part by mass or more, preferably 40 parts by mass or less, particularly preferably 30 parts by mass or less with respect to 100 parts by mass of the total amount of rubber. I found out.

1 Semiconductive roller 2 Roller body 3 Through hole 4 Shaft 5 Outer peripheral surface

Claims (3)

Epichlorohydrin rubber and diene rubber as rubber, and a silicone copolymer containing in its molecule a repeating unit constituting a resin compatible with the rubber,
A semiconductive roller provided with a roller body made of a cross-linked product of a rubber composition.   2. The semiconductive roller according to claim 1, wherein the copolymer is contained at a ratio of 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the total amount of the rubber.   The semiconductive roller according to claim 1 or 2, wherein the semiconductive roller is incorporated in an image forming apparatus using an electrophotographic method and used as a charging roller or a developing roller.

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