JP2011048188A - Conductive roller and electrophotographic device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a conductive roller which has excellent flexibility that is substantially uniform over the circumferential surface and serves as a transfer roller, for example, while preventing unevenness and the like in an image formed on a surface of a paper sheet especially at a low temperature; and an electrophotographic device including the conductive roller as a transfer roller. <P>SOLUTION: The conductive roller 1 is provided with a plurality of ridges 7 and grooves 8 different in height h by 100 μm or more and in pitch w by 800 μm or less on the outer surface 6 of the roller body 2, and a plurality of hollows 9 and 10 of which area proportions are 10 to 80% in the body 2. The electrophotographic device includes the conductive roller as a transfer roller. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is incorporated in an electrophotographic apparatus such as a laser printer, and transfers a toner image formed on the surface of a photoreceptor or an image carrier of the electrophotographic apparatus onto the surface of paper (including a plastic film, etc.). The present invention relates to a conductive roller used as a transfer roller and the like, and an electrophotographic apparatus incorporating the conductive roller as a transfer roller.

  In an electrophotographic apparatus such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, or a complex machine of these, the surface of the photoconductor is exposed in a uniformly charged state to form a formed image on the surface. A corresponding electrostatic latent image is formed (charging process → exposure process), and the electrostatic latent image is developed into a toner image by selectively attaching a precharged toner (developing process), and then the toner The image is formed on the surface of the paper by transferring the image onto the surface of the paper (transfer process) and further fixing (fixing process).

In the transfer step, the toner image formed on the surface of the photoconductor may be transferred directly to the surface of the paper, or may be transferred once to the surface of the image carrier and then retransferred to the surface of the paper. .
The charging process of the above processes, the charging process of the developing process, the adhesion process to the electrostatic latent image, the transfer process, and the surface of the photoreceptor or image carrier after transferring the toner image to the paper surface. In the cleaning process for removing the toner remaining on the roller, conductive or semi-conductive rollers (hereinafter sometimes referred to as “conductive rollers”) are widely used.

For example, when a predetermined voltage is applied between the photosensitive member or the image carrier and a conductive roller as a transfer roller, paper is passed between the two, so that the surface of the photosensitive member or the image carrier is formed. The formed toner image can be transferred to the paper surface by electrostatic force between the transfer roller and an image can be formed on the paper surface.
Conventionally, the transfer roller is composed of a crosslinked (vulcanized) porous material of rubber, and the rubber is blended with a filler having electronic conductivity such as conductive carbon, or the rubber itself is ionically conductive. For example, a material imparted with conductivity by using a rubber having a property has been used. In recent years, it has also been studied to form a conductive roller using a thermoplastic elastomer composition that can be easily recycled instead of the vulcanized rubber.

  When the transfer roller is brought into contact with the surface of the photoreceptor or the image carrier, it is compressed and deformed in the radial direction by the contact pressure, and the paper is sandwiched between the surface of the photoreceptor or the image carrier. Therefore, flexibility that allows contact with a predetermined nip width is required. As a result, the paper can be brought into contact with the surface of the photoreceptor or the image carrier without any gap, and the toner image can be satisfactorily transferred from the surface of the photoreceptor or the image carrier to the surface of the paper.

However, in particular, non-porous conductive rollers made of a thermoplastic elastomer composition tend to be insufficient in flexibility as compared to those made of a vulcanized rubber porous body.
In Patent Documents 1 to 3, the shaft and the axial direction of the roller so as to surround the shaft inserted into the center of the roller inside the roller made of an elastic material such as the vulcanized rubber or the thermoplastic elastomer composition. It is described that a plurality of hollow portions are provided.

  According to such a configuration, even a non-porous conductive roller made of a thermoplastic elastomer composition is considered to be able to improve its flexibility. That is, when pressure is applied by contact with the photoreceptor or the image carrier, the hollow portion is deformed so as to be crushed, and the outer peripheral surface of the conductive roller is the surface of the photoreceptor or image carrier. Therefore, the flexibility of the conductive roller is improved.

However, due to the structure of the conductive roller, the hollow portion cannot be formed continuously over the entire circumference around the shaft. In order to integrally form the conductive roller and the shaft in a state where the respective central axes coincide with each other, in order to form the conductive roller and the shaft in a plurality of locations in the circumferential direction of the conductive roller, the outer peripheral surface of the conductive roller is extended from the outer peripheral surface of the shaft. A solid part must be provided.
Therefore, there is a difference in flexibility between the region corresponding to the solid portion of the conductive roller and the region including the other hollow portion. As a result, when the conductive roller is used as a transfer roller, the contact state (contact pressure, nip width, etc.) with the photosensitive member or image carrier varies between the two regions, and the surface of the paper is changed. There is a risk that unevenness due to the variation occurs in the formed image. In particular, the unevenness tends to occur under low temperature conditions where the flexibility of the thermoplastic elastomer composition is lowered.

  Patent Document 4 describes that a plurality of ridges and grooves are alternately provided in the circumferential direction on the outer peripheral surface of a roller. In such a configuration, it is considered that a certain degree of flexibility can be imparted to the conductive roller by compressive deformation of the ridges, but the compression deformation of the ridges is limited to a very small range (protrusions in the vicinity of the outer peripheral surface of the conductive roller). Therefore, the flexibility due to the compression deformation does not sufficiently satisfy the level required for the transfer roller.

Japanese Utility Model Publication No. 6-218868 Japanese Patent Laid-Open No. 10-299762 JP 2008-298855 A JP 2008-275669 A

  An object of the present invention is to have excellent flexibility and the flexibility is substantially constant over the entire circumference, for example, on an image formed on the surface of paper when used as a transfer roller, particularly under low temperature conditions. It is an object of the present invention to provide a conductive roller that does not cause unevenness and an electrophotographic apparatus incorporating the conductive roller as a transfer roller.

The present invention is a conductive roller, is formed in a cylindrical shape,
On the outer peripheral surface, a plurality of ridges and grooves are alternately provided in the circumferential direction, and a plurality of hollow portions are provided inside,
The height difference in the radial direction between the highest point of the ridge and the lowest point of the groove is 100 μm or more, the circumferential pitch between the highest points of adjacent ridges is 800 μm or less, and the conductive roller, From the cross-sectional area of the hollow portion in the cross section perpendicular to the axial direction and the cross-sectional area of the solid portion other than the hollow portion, the formula (1):

The area occupancy of the hollow portion determined by the above is 10% or more and 80% or less.
According to the present invention, the flexibility of the conductive roller as a whole can be increased by the function of the hollow portion having the area occupancy provided inside the conductive roller. Further, by compressing and deforming the protrusions having the height difference and the pitch provided on the outer peripheral surface of the conductive roller, the flexibility of the hollow portion is assisted, and the flexibility of the entire conductive roller is increased. It can also be made almost constant over the entire circumference.

  That is, when contacted with the photosensitive member or the image carrier, in the region including the hollow portion in the conductive roller, the hollow portion is mainly deformed to ensure flexibility, so that the solid state does not include the hollow portion. In the region, the lack of flexibility is compensated by compressive deformation of the ridges. Therefore, the flexibility of the entire conductive roller is made almost constant over the entire circumference in the circumferential direction. For example, an image formed on the surface of the paper when the conductive roller is used as a transfer roller, particularly at a low temperature. It is possible to suppress the occurrence of unevenness under conditions.

In the present invention, the height difference in the radial direction between the highest point of the ridge and the lowest point of the groove is limited to 100 μm or more for the following reason.
That is, if the height difference is less than the above range, when the conductive roller is brought into contact with the photosensitive member or the image carrier, the amount of compressive deformation of the ridge particularly in a solid region cannot be secured sufficiently. The effect of compensating for the lack of flexibility in the solid area due to compression deformation cannot be obtained, and an image formed on the surface of the paper when the conductive roller is used as a transfer roller, particularly under low temperature conditions The occurrence of unevenness cannot be suppressed.

Further, the groove between the ridges works to take in paper dust that is separated from the paper and affects the formed image, but if the height difference is less than the above range, the amount of paper powder that can be taken into the groove Further, since the size of the paper dust is limited, it is also impossible to prevent the paper dust once detached from the paper from adhering to the paper together with the toner image and causing an image defect in the formed image.
The reason why the circumferential pitch between the highest points of adjacent ridges is limited to 800 μm or less is as follows.

For example, when a conductive roller is used as a transfer roller, the electrostatic force generated by applying a voltage between the photosensitive member or the image carrier has a strength difference based on the uneven shape. That is, the electrostatic force is strong at the convex portion where the photosensitive member or the image carrier is in contact with the paper and the electrostatic force is weak at the concave groove portion away from the photosensitive member or the image carrier.
If the pitch is 800 μm or less, the difference in strength of the electrostatic force can be reduced by supplementing the electrostatic force in the concave groove by overlapping the strong electrostatic force in the adjacent ridges, so that the formed image is hardly affected. Absent.

However, when the pitch exceeds the above range, the difference in strength of the electrostatic force based on the uneven shape increases, and the toner image transferred from the photosensitive member or the image carrier to the surface of the paper can be visually recognized. Unevenness may occur.
The reason why the area occupancy ratio of the hollow portion obtained by the formula (1) is limited to 10% or more and 80% or less is as follows.

That is, when the area occupancy ratio of the hollow portion is less than the above range, the hollow portion cannot provide an effect of imparting good flexibility to the entire conductive roller. For example, when used as a transfer roller, the transfer roller Cannot be brought into contact with the photosensitive member or the image carrier with a predetermined nip width, so that a good image cannot be formed on the surface of the paper.
On the other hand, it is difficult to produce a conductive roller having an area occupancy ratio of the hollow portion exceeding the above range by, for example, an extrusion molding method described later.

In the conductive roller of the present invention, in a resin matrix containing a styrene-based thermoplastic elastomer and polypropylene,
A cross-linked product of at least one rubber selected from the group consisting of diene rubber and ethylene propylene rubber;
It is preferably formed by a thermoplastic elastomer composition in which an ion conductive resin type antistatic agent containing an ion conductive elastomer and an ion conductive salt is dispersed.

Thereby, the conductive roller having the complicated shape can be easily manufactured with high productivity by extrusion molding or the like. In addition, the recyclability of the formed conductive roller can be improved.
The thermoplastic elastomer composition is preferably prepared through a dynamic crosslinking step in which a mixture containing a resin matrix and an uncrosslinked rubber component is kneaded while heating to crosslink the rubber component.

As a result, the cross-linked product of rubber can be dispersed more finely and uniformly in the resin matrix, so that a thermoplastic elastomer composition having uniform characteristics, and thus a conductive roller can be obtained.
The conductive roller of the present invention includes the thermoplastic elastomer composition, a base, and a plurality of concave portions and convex portions that are the basis of the convex strips and the concave grooves on the inner peripheral surface of the base in the circumferential direction. It is possible to manufacture by alternately extruding into a cylindrical shape using an extrusion molding machine provided with a die provided with a plurality of pins that are the basis of the hollow portion inside the base. As a result, the productivity of the conductive roller can be improved as described above.

The conductive roller of the present invention is incorporated in the electrophotographic apparatus in a state where the outer peripheral surface on which the ridges and the grooves are formed is in contact with the surface of the electrophotographic apparatus or the image carrier. Alternatively, it can be used as a transfer roller for transferring the toner image formed on the surface of the image carrier onto the surface of the paper.
The present invention is an electrophotographic apparatus comprising the conductive roller of the present invention as a transfer roller, and the surface of the paper is free of unevenness especially under low temperature conditions by the function of the conductive roller. A good image can be formed.

  According to the present invention, the flexibility is excellent and the flexibility is substantially constant over the entire circumference, for example, an image formed on the surface of the paper when used as a transfer roller, particularly under low temperature conditions. Thus, it is possible to provide a conductive roller that does not cause unevenness and an electrophotographic apparatus incorporating the conductive roller as a transfer roller.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows the whole example of embodiment of the electroconductive roller of this invention, and expands and shows the one part. It is the end elevation which expanded a part of conductive roller of the example of Drawing 1 further. It is sectional drawing of a roller main body among the electroconductive rollers of the example of FIG. It is a perspective view which expands and shows the die die used in order to form the electroconductive roller of the example of FIG. 1 by extrusion molding, and its part. FIG. 5 is a partially enlarged perspective view illustrating one process of forming the conductive roller of the example of FIG. 1 by extrusion molding using a die having the die of FIG. 4.

<Thermoplastic elastomer composition>
As described above, the conductive roller of the present invention is
In a resin matrix containing a styrenic thermoplastic elastomer and polypropylene,
A cross-linked product of at least one rubber selected from the group consisting of diene rubber and ethylene propylene rubber;
It is preferably formed by a thermoplastic elastomer composition having a dispersed structure in which an ion conductive resin type antistatic agent containing an ion conductive elastomer and an ion conductive salt is dispersed.

The thermoplastic elastomer composition is obtained by, for example, mixing a rubber component in the resin matrix by dynamic crosslinking in which a mixture containing a resin matrix and an uncrosslinked rubber component is kneaded while heating to crosslink the rubber component. After the dispersion, it can be prepared by blending an ion conductive resin type antistatic agent.
Of these, the styrene thermoplastic elastomer is preferably a hydrogenated styrene thermoplastic elastomer. The hydrogenated styrenic thermoplastic elastomer has low hardness and excellent flexibility because the double bond is saturated by hydrogenation, and also has excellent durability. Therefore, the occurrence of settling or the like can be effectively suppressed, and the durability of the conductive roller can be improved.

Further, since the hydrogenated styrene thermoplastic elastomer does not contain a double bond, there is no risk of inhibiting the crosslinking when dynamically crosslinking the rubber component, and since the rubber itself is not crosslinked, Desired plasticity and flexibility can be imparted to the plastic elastomer composition.
Examples of the hydrogenated styrene thermoplastic elastomer include styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene / propylene copolymer (SEP), and styrene-ethylene. / Propylene-styrene copolymer (SEPS), styrene-ethylene / butylene-styrene copolymer (SEBS), and at least one selected from the group consisting of styrene-ethylene-ethylene / propylene-styrene copolymer (SEEPS) A hydrogenated product of a particular styrenic thermoplastic elastomer is preferred. In particular, a hydrogenated product of SEEPS is preferable.

  Polypropylene functions to improve the processability of the thermoplastic elastomer composition during extrusion. As the polypropylene, in addition to a homopolymer type obtained by polymerizing only propylene, a random or block copolymer obtained by copolymerizing some amount of other olefins such as ethylene in order to improve low temperature brittleness of the homopolymer type polypropylene. One type or two or more types of various types of polypropylene may be mentioned.

  Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), chloroprene rubber (CR), and acrylonitrile-butadiene copolymer rubber (NBR). Etc. Examples of the ethylene propylene rubber include ethylene-propylene copolymer rubber (EPM) and ethylene-propylene-diene copolymer rubber (EPDM). As the rubber component, any one of the above rubbers may be used alone, or two or more may be used in combination.

  EPDM is particularly preferable. In EPDM, the main chain is composed of saturated hydrocarbons and does not contain double bonds. Therefore, even when exposed to an environment such as high-concentration ozone atmosphere or light irradiation including ultraviolet rays, the main chain is hardly broken. Therefore, the ozone resistance, ultraviolet resistance, heat resistance, etc. of the conductive roller can be improved. EPDM is preferably used alone, but EPDM may be used in combination with other rubber components, in which case the proportion of EPDM in the total rubber content is 50% by mass or more, particularly 80% by mass or more. Is preferred.

When the rubber component is dynamically crosslinked as described above, a crosslinking agent for crosslinking the rubber component is blended in the mixture of the rubber component and the matrix resin. As the crosslinking agent, a resin crosslinking agent is preferable.
The resin cross-linking agent is a synthetic resin that can cause a cross-linking reaction to the rubber component by heating or the like, and does not generate bloom like a normal sulfur cross-linking system (combined system of sulfur and vulcanization accelerator). The rubber has a merit that it can reduce the compression set and mechanical properties of the rubber after crosslinking, and can improve durability.

Moreover, according to the resin crosslinking agent, the crosslinking time can be shortened as compared with the sulfur crosslinking system. Therefore, for example, when kneading a mixture of each component containing a rubber component while heating in an extruder for dynamic crosslinking, the dynamic crosslinking can be sufficiently advanced within a short time staying in the extruder. it can.
The resin crosslinking agent is preferably at least one selected from the group consisting of phenol resins, melamine / formaldehyde resins, triazine / formaldehyde condensates, and hexamethoxymethyl / melamine resins, and phenol resins are particularly preferable.

  As the phenol resin, various phenol resins synthesized by reaction of phenols such as phenol, alkylphenol, cresol, xylenol or resorcin with aldehydes such as formaldehyde, acetaldehyde or furfural are preferable. A halogenated phenol resin in which at least one halogen atom is bonded to the aldehyde unit of the phenol resin can also be used.

In particular, alkylphenol-formaldehyde resins obtained by the reaction of alkylphenols with an alkyl group bonded to the ortho or para position of benzene and formaldehyde have excellent compatibility with rubber components and are highly reactive. It is preferable because it can be done quickly.
The alkyl group of the alkylphenol / formaldehyde resin is preferably an alkyl group having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, a propyl group or a butyl group. Further, a halide of an alkylphenol / formaldehyde resin is also preferably used.

Furthermore, modified alkylphenol resins obtained by addition condensation of sulfurized p-tert-butylphenol and aldehydes, and alkylphenol / sulfide resins can also be used as a resin crosslinking agent.
In order to appropriately perform dynamic crosslinking, a crosslinking assistant (crosslinking activator) may be blended in the mixture of the resin matrix and the rubber component. Examples of the crosslinking aid include metal oxides such as zinc oxide and zinc carbonate, and zinc oxide (zinc white) is particularly preferable.

Moreover, you may mix | blend a softener with the said mixture. The softening agent facilitates kneading of the mixture when dynamically crosslinking the rubber component, and functions to disperse the rubber crosslinked product more finely and uniformly in the resin matrix, and also improves the flexibility of the conductive roller. Work to raise.
The softener is preferably oil or a plasticizer. Of these, the oil is preferably at least one selected from the group consisting of paraffinic, naphthenic, aromatic and other mineral oils, synthetic oils composed of hydrocarbon oligomers, and process oils. The synthetic oil is preferably at least one selected from the group consisting of oligomers of α-olefins, butene oligomers, and amorphous oligomers of ethylene and α-olefins.

The plasticizer is preferably at least one selected from the group consisting of dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl separate, and dioctyl adipate, for example.
In particular, paraffinic oil is preferable, and as the paraffinic oil, any of various paraffinic oils refined from mineral oil (crude oil) and having a paraffinic base oil can be used.

  As the ion conductive elastomer constituting the ion conductive resin type antistatic agent, ethylene oxide-propylene oxide copolymer (hereinafter sometimes abbreviated as “EO-PO copolymer”), and ethylene oxide-propylene oxide are used. -At least 1 sort (s) selected from the group which consists of an allyl glycidyl ether copolymer (it may abbreviate as "EO-PO-AGE copolymer" hereafter) is used.

The two types of copolymers stabilize the ions derived from the ion conductive salt by the functions of ethylene oxide (EO) units and propylene oxide (PO) units, particularly EO units, contained in the molecule, and thus become conductive. It works to reduce the electrical resistance of the roller.
The EO-PO copolymer preferably has an EO unit content of 55 mol% to 95 mol%, particularly 65 mol% to 92 mol%.

If the content of the EO unit is less than the above range, the effect of stabilizing the ions derived from the ion conductive salt by the function of the EO unit described above may not be sufficiently obtained. If the content exceeds the above range, the EO unit may crystallize, and the effect of stabilizing ions derived from the ion conductive salt may not be sufficiently obtained.
The EO-PO-AGE copolymer preferably has an EO unit content of 55 mol% or more and 95 mol% or less, particularly 65 mol% or more and 92 mol% or less.

If the content of the EO unit is less than the above range, the effect of stabilizing the ions derived from the ion conductive salt by the function of the EO unit described above may not be sufficiently obtained. If the content exceeds the above range, the EO unit may crystallize, and the effect of stabilizing ions derived from the ion conductive salt may not be sufficiently obtained.
The EO-PO-AGE copolymer has a content of 1 mol% of allyl glycidyl ether (AGE) units containing an allyl group that functions as a crosslinkable functional group when a crosslinking reaction is performed with a peroxide crosslinking agent described later. The content is preferably 10 mol% or less, more preferably 2 mol% or more and 8 mol% or less.

  If the AGE unit content is less than the above range, the EO-PO-AGE copolymer cannot be crosslinked well, and the uncrosslinked or insufficiently crosslinked copolymer bleeds to the surface of the conductive rubber layer. Alternatively, the ionic conductive salt tends to bloom or bleed on the surface of the conductive rubber layer along with the bleed or bloom, which may contaminate the photoreceptor or toner.

Further, when the content exceeds the above range, the crosslinking density becomes too high, so that the tensile strength, fatigue characteristics, flex fatigue resistance, etc. of the EO-PO-AGE copolymer may be lowered.
The number average molecular weight Mn of the EO-PO copolymer and the EO-PO-AGE copolymer is preferably 10,000 or more, particularly preferably 50,000 or more. When the number average molecular weight Mn is less than the above range, the copolymer bleeds or blooms on the surface of the conductive rubber layer, or the ion conductive salt blooms on the surface of the conductive rubber layer along with the bleed or bloom. Or bleed, which may contaminate the photoreceptor or toner.

As the ion conductive salt, a salt of an anion having a fluoro group and a sulfonyl group and a cation is preferable. The salt is further excellent in the effect of further improving the ionic conductivity of the ionic conductive rubber and reducing the electrical resistance value of the conductive rubber layer.
Examples of the anion having a fluoro group and a sulfonyl group constituting the ion conductive salt include a fluoroalkylsulfonic acid ion, a bis (fluoroalkylsulfonyl) imide ion, and a tris (fluoroalkylsulfonyl) methide ion.

  In addition, as the cation constituting the ion conductive salt together with the anion, ions of alkali metals such as sodium, lithium and potassium, ions of group 2 elements such as beryllium, magnesium, calcium, strontium and barium, transition elements Ions, amphoteric element cations, quaternary ammonium ions, imidazolium cations, and the like. Particularly preferred is a lithium salt in combination with lithium ions.

Examples of the lithium salt include CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) ₂ NLi, (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) NLi, (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) NLi, (C ₈ F ₁₇ SO ₂ ) (CF ₃ SO ₂ ) NLi, (CF ₃ CH ₂ OSO ₂ ) ₂ NLi, (CF ₃ CF ₂ CH ₂ OSO ₂ ) ₂ NLi, (HCF ₂ CF ₂ CH ₂ OSO ₂ ) ₂ NLi, [(CF ₃ ) ₂ CHOSO ₂ ] ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, and (CF ₃ CH ₂ OSO ₂ ) ₃ CLi is preferably at least one selected from the group consisting of

Of these, CF ₃ SO ₃ Li (lithium trifluoromethanesulfonate) and (CF ₃ SO ₂ ) ₂ NLi [bis (trifluoromethanesulfonyl) imidolithium] are preferable, and lithium trifluoromethanesulfonate is particularly preferable.
The ion conductive salt is blended in a resin matrix in which a crosslinked product of rubber is dispersed in the state of an ion conductive resin type antistatic agent dispersed in advance in an ion conductive elastomer. As a result, the ion conductive salt can be finely dispersed in the resin matrix in a state of being well-distributed in the ion conductive elastomer.

Therefore, the ionic conductivity of the conductive roller can be further improved, and the ion conductive salt is prevented from moving to the surface even when an electric field is continuously applied to the conductive roller, for example, and the ion conductive salt blooms. It is possible to prevent the photoreceptor and toner from being contaminated.
You may mix | blend a compatibilizing agent with the compound of the said resin matrix and an ion conductive resin type | mold antistatic agent further.

The compatibilizing agent finely disperses the ion conductive elastomer in the resin matrix and makes the ion conductive salt unevenly distributed in the ion conductive elastomer based on a good affinity with the ion conductive elastomer. In the state, it functions to be further finely dispersed in the resin matrix.
Examples of the compatibilizer include at least one selected from the group consisting of an ethylene-acrylic ester-maleic anhydride copolymer and an ethylene-acrylic ester-glycidyl methacrylate copolymer.

  The ethylene-acrylic acid ester-maleic anhydride copolymer and / or the ethylene-acrylic acid ester-glycidyl methacrylate copolymer has an acrylic acid ester unit content of 0.1% by mass to 30% by mass, Among them, it is preferably 1% by mass or more and 20% by mass or less, particularly 3% by mass or more and 15% by mass or less. The maleic anhydride unit content is preferably 0.05% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 15% by mass or less, and particularly preferably 1% by mass or more and 10% by mass or less. The content of the glycidyl methacrylate unit is preferably 0.05% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 15% by mass or less, and particularly preferably 1% by mass or more and 10% by mass or less.

Examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate. 1 type, or 2 or more types, etc. are mentioned.
You may mix | blend a peroxide crosslinking agent with the said mixture further.

The peroxide cross-linking agent functions to dynamically cross-link the ion conductive elastomer in the resin matrix.
Examples of the peroxide crosslinking agent include benzoyl peroxide, 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (benzoylperoxy). ) Hexane, di (tert-butylperoxy) diisopropylbenzene, 1,4-bis [(tert-butyl) peroxyisopropyl] benzene, di (tert-butylperoxy) benzoate, tert-butylperoxybenzoate, dicumyl Peroxide, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, ditert-butyl peroxide and 2,5-dimethyl-2,5-di (tert -Butylperoxy) -3-hexene selected from the group consisting of Kutomo one is preferable. In particular, di (tert-butylperoxy) diisopropylbenzene is preferable.

A crosslinking aid may be used in combination with the peroxide crosslinking agent. The cross-linking aid functions to cross-link with the ion conductive elastomer and to polymerize the whole as a whole. The crosslink density can be improved by co-crosslinking with the crosslinking aid.
Crosslinking aids include metal salts of methacrylic acid or acrylic acid, methacrylic acid esters, aromatic vinyl compounds, heterocyclic vinyl compounds, allyl compounds, polyfunctional polymers using functional groups of 1,2-polybutadiene, and dioximes. At least one selected from the group consisting of the above is preferred.

  Specifically, triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), trimethylolpropane trimethacrylate (TMPT), ethylene glycol dimethacrylate (EDMA), p-quinone dioxime, p, p'-dibenzoylquinone di At least one selected from the group consisting of oxime and N, N′-m-phenylenebismaleimide is preferred. In particular, N, N′-m-phenylene bismaleimide is preferable.

A filler may be further blended in the thermoplastic elastomer composition containing the above components. The filler functions to increase the mechanical strength of the conductive roller.
Examples of the filler include at least one selected from the group consisting of silica, carbon black, clay, talc, calcium carbonate, dibasic phosphite (DLP), basic magnesium carbonate, and alumina, calcium carbonate, and Carbon black is preferred.

The thermoplastic elastomer composition also includes a group consisting of a foaming agent, an anti-aging agent, an antioxidant, an ultraviolet absorber, a lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizing agent, a nucleating agent, and an anti-bubble agent. You may mix | blend the at least 1 sort (s) of additive selected more.
The blending ratio of each component can be arbitrarily set.
For example, the blending ratio of the resin matrix containing styrene-based thermoplastic elastomer and polypropylene is preferably 10 parts by mass or more, particularly 20 parts by mass or more, preferably 100 parts by mass or less, particularly 75 parts by mass or less per 100 parts by mass of rubber. Is preferred.

If the blending ratio of the resin matrix is less than the above range, the amount of the resin matrix as the thermoplastic component is too small, and therefore there is a possibility that good thermoplasticity cannot be imparted to the thermoplastic elastomer composition. Moreover, there is a possibility that the rubber cross-linked product or the ion conductive resin type antistatic agent cannot be dispersed well in the resin matrix.
On the other hand, when the blending ratio of the resin matrix exceeds the above range, the amount of the cross-linked product of the rubber becomes relatively small, and there is a possibility that good rubber elasticity cannot be imparted to the conductive roller. Further, since the amount of the ion conductive resin-type antistatic agent is relatively small, there is a possibility that good ion conductivity cannot be imparted to the conductive roller.

The blending ratio of the resin matrix is the total blending ratio of these two kinds when the styrenic thermoplastic elastomer and polypropylene are used in combination as the resin matrix.
In the two types of combined systems, the blending ratio of polypropylene per 100 parts by mass of the styrenic thermoplastic elastomer is preferably 10 parts by mass or more, particularly preferably 30 parts by mass or more, and 100 parts by mass or less, particularly 50 parts by mass or less. Preferably there is.

  If the blending ratio of polypropylene is less than the above range, the effect of improving the processability at the time of extrusion molding of the thermoplastic elastomer composition described above due to blending of the polypropylene may not be sufficiently obtained. When the blending ratio of polypropylene exceeds the above range, the amount of the styrene-based thermoplastic elastomer is relatively small, so that the flexibility of the conductive roller may be lowered.

The blending ratio of the resin crosslinking agent is preferably 2 parts by mass or more, particularly 5 parts by mass or more, preferably 20 parts by mass or less, particularly 15 parts by mass or less, per 100 parts by mass of rubber.
If the blending ratio of the resin cross-linking agent is less than the above range, the rubber component is not sufficiently cross-linked, so that there is a possibility that good mechanical properties and durability cannot be imparted to the conductive roller. On the other hand, when the blending ratio of the resin cross-linking agent exceeds the above range, the rubber component becomes too hard, and the flexibility of the conductive roller may be reduced.

The blending ratio of the crosslinking aid (crosslinking activator) is preferably 0.01 parts by mass or more, particularly preferably 0.1 parts by mass or more, especially 10 parts by mass or less, particularly 5 parts by mass or less, per 100 parts by mass of the rubber component. Preferably there is.
The blending ratio of the softening agent is preferably 50 parts by mass or more, particularly 80 parts by mass or more, and preferably 250 parts by mass or less, particularly 200 parts by mass or less, per 100 parts by mass of rubber.

If the blending ratio of the softening agent is less than the above range, the effects described above due to the blending of the softening agent may not be sufficiently obtained. In addition, if the blending ratio exceeds the above range, not only the effect is not obtained, but also an excessive softener bleeds on the surface of the conductive roller to contaminate the photoreceptor and toner, and to contaminate the paper. There is a risk.
The blending ratio of the ion conductive elastomer constituting the ion conductive resin type antistatic agent is preferably 50 parts by mass or more, particularly preferably 70 parts by mass or more, particularly 150 parts by mass or less, particularly 120 parts by mass, per 100 parts by mass of rubber. It is preferably less than or equal to parts.

When the blending ratio of the ion conductive elastomer is less than the above range, the effect of stabilizing the ions derived from the ion conductive salt described above by the ion conductive elastomer cannot be sufficiently obtained, and the thermoplastic elastomer composition is good. May not be able to impart sufficient ionic conductivity. Moreover, even if it exceeds the said range, there exists a possibility that the addition effect beyond it may not be acquired.
The blending ratio of the ion conductive salt is preferably 0.1 parts by mass or more, particularly 1 part by mass or more, preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, per 100 parts by mass of rubber.

When the blending ratio of the ion conductive salt is less than the above range, there is a possibility that good ion conductivity cannot be imparted to the thermoplastic elastomer composition. Further, if the amount exceeds the above range, not only the addition effect is not obtained, but also the excessive ionic conductive salt blooms or bleeds on the surface of the conductive roller to contaminate the surface of the photoreceptor or the image carrier. There is a fear.
The blending ratio of the compatibilizer is preferably 1 part by mass or more, particularly 5 parts by mass or more, preferably 20 parts by mass or less, particularly preferably 10 parts by mass or less, per 100 parts by mass of the rubber component.

If the blending ratio is less than the above range, the function as a compatibilizing agent is insufficient, and the ion conductive elastomer cannot be finely dispersed in the resin matrix, and in the extrusion direction in the surface layer portion of the conductive roller during extrusion molding. There is a risk of separation along the lines.
On the other hand, even if the blending ratio exceeds the above range, not only the effect of addition is not obtained, but there is a possibility that the strength of the conductive roller may decrease or the hardness may increase.

When dynamically crosslinking the ion conductive elastomer, the blending ratio of the peroxide crosslinking agent is preferably 0.1 parts by mass or more, particularly 0.1 parts by mass or more per 100 parts by mass of the ion conductive elastomer, It is preferably 10 parts by mass or less, particularly 5 parts by mass or less.
When the blending ratio of the peroxide crosslinking agent is less than the above range, crosslinking is insufficient, and the crosslinking effect described above cannot be sufficiently obtained. On the other hand, when the blending ratio exceeds the above range, the mechanical properties are lowered due to molecular cutting, or dispersion failure occurs, which makes processing difficult.

The blending ratio of the crosslinking aid is preferably 0.1 parts by mass or more per 100 parts by mass of the ion conductive elastomer, preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.
The blending ratio of the filler is preferably 10 parts by mass or more, particularly 20 parts by mass or more, preferably 100 parts by mass or less, particularly 50 parts by mass or less, per 100 parts by mass of rubber.
If the blending ratio of the filler is less than the above range, the effects explained above due to blending of the filler may not be sufficiently obtained. Moreover, when a mixture ratio exceeds the said range, there exists a possibility that the softness | flexibility of an electroconductive roller may fall.

The blending ratio is the total blending ratio when two or more fillers are used in combination as the filler.
In order to prepare the thermoplastic elastomer composition, first, a kneaded material in which a crosslinked product of rubber is dispersed in a resin matrix is prepared.
For example, when using dynamic crosslinking, as described above, a mixture in which a resin crosslinking agent, a crosslinking assistant (crosslinking activator), a softening agent, and the like are further blended with the resin matrix and the uncrosslinked rubber component. A kneaded product is obtained by kneading while heating and dynamically crosslinking the rubber component while finely dispersing it in the resin matrix.

  For the kneading, an extruder, a Banbury mixer, a kneader or the like can be used, and an extruder is particularly preferable. When using an extruder, a kneaded product can be prepared by kneading the mixture while continuously heating in the screw part of the extruder to dynamically crosslink the rubber component, and continuously extruding the kneaded product from the nozzle tip. In particular, since it can be sent to the next step (for example, a pelletizing step), the productivity of the kneaded product can be improved.

The rubber component is preferably dynamically crosslinked in the presence of halogen. For this purpose, a halogenated resin crosslinking agent may be used. In addition, halogen donating substances such as stannic chloride, ferric chloride, and cupric chloride may be added.
Next, an ion conductive resin-type antistatic agent prepared by kneading an ion conductive salt in an ion conductive elastomer in advance, the kneaded material, and a compatibilizing agent and a filler as necessary A thermoplastic elastomer composition is prepared by kneading a mixture of the above and the like while heating and finely dispersing the ion conductive resin-type antistatic agent in the base resin.

In this case, a peroxide cross-linking agent and a cross-linking aid are blended into the mixture, and the dynamic cross-linking is performed while finely dispersing the ion conductive elastomer constituting the ion conductive resin type antistatic agent in the base resin. You may let them.
For this kneading, an extruder, a Banbury mixer, a kneader or the like can be used, and an extruder is particularly preferable. When an extruder is used, a thermoplastic elastomer composition can be prepared by kneading the mixture while continuously heating in the screw portion of the extruder, and the thermoplastic elastomer composition is successively extruded from the nozzle tip to continuously. Since it can send to the following process (for example, process of pelletization etc.), the productivity of the said thermoplastic elastomer composition can be improved.

Thereafter, the prepared thermoplastic elastomer composition is supplied to an extrusion molding machine for extruding the cylindrical body that is the basis of the conductive roller of the present invention, and is attached to the tip of the screw portion of the extrusion molding machine. The conductive roller of the present invention is manufactured by extruding into a cylindrical shape through a die die connected to the die.
The conditions for extrusion molding may be the same as in the prior art. For example, the extrusion temperature (set temperature at the tip of the screw part) is preferably 160 ° C. or higher, particularly preferably 180 ° C. or higher, and is preferably 250 ° C. or lower, particularly 230 ° C. or lower. The extrusion speed is preferably 0.5 m / min or more, particularly preferably 0.8 m / min or more, more preferably 7 m / min or less, and particularly preferably 5 m / min or less.

The ion conductive resin type antistatic agent, kneaded product, compatibilizing agent, filler, etc. may be directly fed to the extruder and extruded while being kneaded in the screw part of the extruder. Good. Extrusion conditions may be the same as described above.
<Conductive roller and electrophotographic apparatus>
FIG. 1 is a perspective view showing an entire embodiment of the conductive roller of the present invention and an enlarged part thereof. FIG. 2 is an end view in which a part of the conductive roller in the example of FIG. 1 is further enlarged. FIG. 3 is a cross-sectional view of the roller body of the conductive roller of the example of FIG. FIG. 4 is an enlarged perspective view showing a die die used for forming the conductive roller of the example of FIG. 1 by extrusion molding and a part thereof. Further, FIG. 5 is a partially enlarged perspective view for explaining one process of forming the conductive roller of the example of FIG. 1 by extrusion molding using a die having the die of FIG.

Referring to FIG. 1, a conductive roller 1 of this example includes a cylindrical roller body 2 made of the thermoplastic elastomer composition and the like, and a shaft 4 inserted through a through hole 3 at the center of the roller body 2. Is included. Among these, the roller body 2 is formed by cutting a cylindrical body 5 (see FIG. 5) formed by extruding a thermoplastic elastomer composition into a predetermined length, for example.
1 and 2, a plurality of ridges 7 and grooves 8 are alternately provided in the circumferential direction on the outer peripheral surface 6 of the roller body 2.

In the example shown in the figure, the ridges 7 and the grooves 8 are formed by making the outer peripheral surface 6 substantially sinusoidal. That is, the portion of the mountain that protrudes outward in the radial direction of the roller body 2, which constitutes a substantially sine wave, is the ridge 7, and the valley that is recessed inward in the radial direction between the adjacent peaks is the groove 8. Yes.
Referring to FIGS. 1 and 3, a plurality of hollow portions 9 and 10 are provided inside the roller body 2.

  Among these, the hollow portions 9 are arranged at equal intervals around the through hole 3 at the center of the roller body 2 at six locations in the circumferential direction of the roller body 2. The cross-sectional shape of each hollow portion 9 in the direction perpendicular to the axial direction of the roller body 2 is an arc shape in which the radially inner edge of the roller body 2 is along the inner peripheral surface of the through-hole 3 and radially outward. The edge part of this is made into the circular arc shape which follows the outer peripheral surface 6, and is made into the substantially sector shape whose opening width of outer side is wider than inner side of radial direction.

Further, the hollow portions 10 are arranged at equal intervals in the circumferential direction of the roller main body 2 so as to surround the through holes 3 at six locations between the hollow portions 9. The cross-sectional shape in the orthogonal direction of each hollow portion 10 is a substantially rectangular shape with a constant width.
The adjacent hollow portions 9 and 10 are separated by a solid connecting portion 11 that reaches the outer peripheral surface 6 of the roller body 2 from the outer peripheral surface of the shaft 4 inserted through the through hole 3. Each of the connecting portions 11 is formed in a substantially plate shape having a constant width, and each of the two sandwiching one hollow portion 10 is parallel to each other, and as a whole, is substantially radially centered on the central axis L of the roller body 2. It is arranged.

  A space between the hollow portions 9 and 10 and the through hole 3 is a solid inner cylindrical portion 12 that constitutes the inner peripheral surface of the through hole 3 and partitions the through hole 3 and the hollow portions 9 and 10. Between the portions 9 and 10 and the outer peripheral surface 6, the outer peripheral surface 6, that is, the solid outer cylindrical portion 13 constituting the outer shape of the roller body 2 is formed. The plurality of connecting portions 11 connect the inner cylindrical portion 12 and the outer cylindrical portion 13 concentrically with their respective central axes L aligned.

  Referring to FIGS. 4 and 5, the roller body 2 having the above-described parts is composed of the thermoplastic elastomer composition in which a plurality of concave portions 16 and convex portions 17 are alternately arranged on the inner peripheral surface 15 of the base 14 in the circumferential direction. And a die provided with a plurality of pins (mandrels) 18 and 19 on which the hollow portions 9 and 10 are based and a mandrel 20 on which the through-hole 3 is based on the inside of the base 14. The cylindrical body 5 formed by extrusion using the provided extrusion molding machine is cut into a predetermined length and formed.

On the outer peripheral surface 6 of the extruded cylindrical body 5, a ridge 7 is formed corresponding to the concave portion 16, and a concave groove 8 is formed corresponding to the convex portion 17. Since the concave portion 16 and the convex portion 17 are alternately provided on the inner peripheral surface 15 of the base 14 in the circumferential direction, the outer peripheral surface 6 of the extruded cylindrical body 5 has a corresponding convex strip. 7 and the groove 8 are formed alternately in the circumferential direction.
Further, since the thermoplastic elastomer composition is extruded through the opening between the pins 18 and 19 and the mandrel 20 in the inner peripheral surface 15 of the base 14, the inside of the extruded cylindrical body 5 is not formed. The hollow portions 9 and 10 corresponding to the pins 18 and 19 and the through holes 3 corresponding to the mandrels 20 are formed.

  That is, the connecting portion 11 is formed by the thermoplastic elastomer composition extruded through the opening between the pins 18 and 19, and the thermoplastic elastomer composition extruded through the opening between the pins 18 and 19 and the mandrel 20. The inner cylindrical portion 12 is formed by the object, and the outer cylindrical portion 13 is formed by the thermoplastic elastomer composition extruded through the opening between the pins 18 and 19 and the inner peripheral surface 15 of the base 14. Hollow portions 9 and 10 and through holes 3 are provided between the respective portions.

Referring to FIG. 2, in the present invention, the radial height difference h between the highest point of the ridge 7 and the lowest point of the groove 8 is 100 μm or more, and between the highest points of adjacent ridges 7. The circumferential pitch w must be 800 μm or less.
That is, when the height difference h is less than 100 μm, the solid roller region (the inner cylindrical portion 12 and the outer cylindrical portion 13 are connected by the connecting portion 11 when the conductive roller 1 is brought into contact with the photosensitive member or the image carrier. The amount of compressive deformation of the ridges 7 in the region) cannot be sufficiently secured, so that the effect of compensating the lack of flexibility in the solid region due to the compression deformation of the ridges 7 cannot be obtained, and the conductivity When the roller 1 is used as a transfer roller, it is not possible to suppress the occurrence of unevenness in the image formed on the paper surface, particularly under low temperature conditions.

Further, the concave grooves 8 between the ridges 7 function to take in paper dust that is separated from the paper and affects the formed image. However, if the height difference is less than the above range, the paper that can be taken into the concave grooves 8. Since the amount of powder and the size of the paper powder are limited, it is also impossible to prevent the paper powder once detached from the paper from adhering to the paper together with the toner image and causing an image defect in the formed image.
The reason why the pitch w is limited to 800 μm or less is as follows.

For example, when the conductive roller 1 of the present invention is used as a transfer roller, the electrostatic force generated by applying a voltage between the photosensitive member or the image carrier has a difference in strength based on the uneven shape. That is, the electrostatic force is increased at the portion of the ridge 7 that is in contact with the photoconductor or the image carrier with the paper interposed therebetween, and the electrostatic force is reduced at the portion of the groove 8 that is separated from the photoconductor or the image carrier.
If the pitch w is 800 μm or less, the difference in strength of the electrostatic force can be reduced by compensating for the electrostatic force in the groove 8 by overlapping the strong electrostatic force in the adjacent ridges 7. There is no impact.

However, when the pitch w exceeds the above range, the difference in strength of the electrostatic force based on the concavo-convex shape becomes large, and the toner image transferred from the photoreceptor or the image carrier to the surface of the paper can be visually recognized. Density unevenness may occur.
The height difference h is 200 μm or more, particularly 300 μm or more, preferably 1 mm or less, particularly 800 μm or less, even within the above range.

When the height difference h exceeds the above range, in order to form the ridge 7 having a predetermined height difference h by sufficiently spreading the thermoplastic elastomer composition in the concave portion 16 of the base 14, the extrusion speed is decreased. It is necessary to increase the extrusion temperature to improve the fluidity of the thermoplastic elastomer composition.
In the former case, in order to prevent the strips 7 from being peeled off, the extrusion speed must be greatly reduced. In that case, there is a possibility that the productivity of the conductive roller 1 is significantly reduced. is there.

In the latter case, in order to prevent the strips 7 from being peeled off, the extrusion temperature must be significantly increased. In this case, the components constituting the thermoplastic elastomer composition deteriorate and become conductive. There is a risk that the flexibility, wear resistance, durability, and the like of the roller 1 are significantly reduced.
Further, the high ridges 7 whose height difference h exceeds the above range are likely to be deformed or chipped, and the durability of the conductive roller 1 may be lowered. Furthermore, when the width of the ridges 7 is increased in order to improve the durability, the pitch w must be increased beyond the above range, which may cause density unevenness.

Further, the pitch w is preferably 200 mm or more, particularly 300 mm or more, even within the above range.
When the pitch w is less than the above range, the amount of paper powder that can be taken into the groove 8 and the size of the paper powder are limited, so that the above-described effect by providing the uneven shape can be obtained. There is a risk of not. Further, the thin ridges having the pitch w less than the above range and the height difference h within the above range are likely to be deformed or chipped, and the durability of the conductive roller 1 may be lowered.

  With reference to FIG. 3, in this invention, the cross-sectional area (the outer peripheral surface 6 in a figure is shown) of the said hollow parts 9 and 10 in the cross section (cross section of FIG. 3) orthogonal to an axial direction of the roller main body 2. FIG. The cross-sectional area of the portion shown in white in the circle and the hatched area outside the circle indicating the through-hole 3), and the cross-sectional area of the solid portion other than the hollow portions 9 and 10 (the above-mentioned The area occupancy ratio of the hollow portions 9 and 10 obtained by the above equation (1) needs to be 10% or more and 80% or less from the cross-sectional area of the hatched region.

That is, when the area occupancy is less than 10%, the provision of the hollow portions 9 and 10 does not provide an effect of imparting good flexibility to the entire conductive roller 1, and for example, when used as a transfer roller Since the transfer roller cannot be brought into contact with the photosensitive member or the image carrier with a predetermined nip width, a good image cannot be formed on the surface of the paper.
On the other hand, it is difficult to manufacture the roller body 2 of the conductive roller 1 in which the area occupation ratio of the hollow portions 9 and 10 exceeds the above range by the extrusion method or the like.

Note that the area occupancy ratio of the hollow portions 9 and 10 is 30% or more even within the above range in consideration of further improving the overall flexibility of the conductive roller 1 while ensuring good extrudability. Is preferable, and it is preferable that it is 75% or less.
The shaft 4 is made conductive to constitute the conductive roller 1. Examples of the conductive shaft 4 include those integrally formed of a metal such as aluminum, an alloy thereof, and stainless steel. Alternatively, a composite structure shaft 4 formed of ceramic, hard resin, or the like and provided with a conductive film or the like electrically connected to the roller body 2 on its outer peripheral surface can be used.

  The outer peripheral surface 6 of the roller body 2 may be covered with a coating layer. The coating layer can be formed, for example, by applying a coating agent in which a fluororesin powder or the like is dispersed in an emulsion or solution such as urethane resin or acrylic resin, or rubber latex, and then drying. By covering with the coating layer, the surface energy of the outer peripheral surface 6 is controlled to prevent paper dust and toner from adhering to the outer peripheral surface 6 or to adjust the friction coefficient. be able to.

  The electroconductive roller 1 of the present invention includes a charging roller for charging the surface of the photoreceptor in the charging process of the electrophotographic apparatus, a charging roller for charging the toner while stirring in the charging process of the toner in the developing process, A developing roller that selectively attaches the toner charged in the process of attaching to the latent image to the electrostatic latent image on the surface of the photoreceptor to develop the toner image, and the toner image is applied to the surface of the paper or the image carrier in the transfer process. It can be used as a transfer roller for transferring, a cleaning roller for removing toner remaining in the cleaning process, or the like.

In particular, the conductive roller 1 of the present invention is preferably used as a transfer roller that is in direct contact with paper and is likely to cause various problems associated with the adhesion of paper dust.
When the conductive roller 1 is used as a transfer roller, the resistance value of the roller body 2 is about 10 ⁴ Ω or more and 10 ⁹ Ω or less, particularly about 10 ⁶ Ω or more and 10 ⁸ Ω or less at an applied voltage of 1000V. preferable.

In order to adjust the resistance value within the above range, for example, the types and blending ratios of the ion conductive elastomer and the ion conductive salt may be appropriately adjusted within the range described above.
The roller body 2 of the conductive roller 1 to be used as the transfer roller, the peripheral surface 6 the hardness of the central axis L direction, the Japanese Industrial Standard JIS K7312 _{-1 996} of "physical test method for thermosetting polyurethane elastomer molded product" In accordance with the spring hardness test type C test method defined in Appendix 2, the spring type C hardness measured under the conditions of a temperature of 23 ± 1 ° C. and a relative humidity of 55 ± 1% is 55 or less, especially 40 It is preferable that:

If the hardness is within this range, the roller body 2 is provided with good flexibility, and when the conductive roller 1 is used as a transfer roller, it is possible to reliably prevent unevenness, particularly under low temperature conditions. it can. Further, it is possible to increase the coefficient of friction with respect to the paper, thereby making it difficult to cause a paper feed failure.
Since the electrophotographic apparatus of the present invention incorporates the conductive roller of the present invention as a transfer roller, the function of the conductive roller forms a good image with no unevenness on the paper surface, particularly under low temperature conditions. can do. Examples of the electrophotographic apparatus include a laser printer, an electrostatic copying machine, a plain paper facsimile machine, or a complex machine thereof.

The present invention is not limited to the examples described above.
For example, by forming the outer peripheral surface 6 into an arbitrary irregular shape other than the substantially sine wave shape shown in FIG. 2 (for example, a substantially triangular wave shape, a substantially rectangular wave shape, etc.), a cross section corresponding to the peaks and valleys of the irregular shape You may form the protruding item | line 7 and the ditch | groove 8 which have a shape.
Moreover, the cross-sectional shape of a hollow part is not limited to the substantially fan shape and substantially rectangular shape shown in FIG. 3, For example, it can form in arbitrary cross-sectional shapes, such as the circular shape currently disclosed by patent documents 1-3.

  In addition, various design changes can be made without departing from the paper of the present invention.

Production and testing of conductive rollers in the following examples and comparative examples were conducted in an environment of a temperature of 23 ± 1 ° C. and a relative humidity of 55 ± 1%, unless otherwise specified.
<Example 1>
(Preparation of thermoplastic elastomer composition)
Hydrogenated styrenic thermoplastic elastomer (SEEPS, Kuraray Co., Ltd. Septon (registered trademark) 4077) and polypropylene (Nippon Polypro Co., Ltd. Novatec (registered trademark) PP) as a resin matrix EPDM [Esprene (registered trademark) EPDM505A manufactured by Sumitomo Chemical Co., Ltd.], paraffinic oil [Diana (registered trademark) process oil PW-380 manufactured by Idemitsu Kosan Co., Ltd.], resin crosslinking agent [brominated alkylphenol / formaldehyde resin Tacchiol (registered trademark) 250-III] manufactured by Taoka Chemical Industry Co., Ltd., and zinc oxide [Zinc Hana 1 manufactured by Mitsui Metal Mining Co., Ltd.] as a crosslinking assistant (crosslinking activator) were blended.

Each of the above components is kneaded while being heated to 200 ° C. in the screw part of a twin screw extruder and extruded from the nozzle tip while dynamically crosslinking the rubber component, and then continuously cut into a predetermined length to be pelletized. A kneaded material in which a crosslinked product of EPDM was dispersed in the resin matrix was prepared.
Also, bis (trifluoromethanesulfonyl) imidolithium as a lithium salt and an EO-PO-AGE copolymer [Zeospan (registered trademark) 8010 manufactured by Nippon Zeon Co., Ltd.] are kneaded to obtain an ion conductive resin type antistatic agent. An agent was prepared.

Next, after dry blending the ion conductive resin-type antistatic agent and the previous kneaded product using a tumbler, the mixture is extruded from the tip of the nozzle while kneading while being heated to 200 ° C. in the screw portion of a twin screw extruder, A thermoplastic elastomer composition was prepared by continuously cutting to a predetermined length and pelletizing.
The blending ratio of each component constituting the thermoplastic elastomer composition was as shown in Table 1.

(Manufacture of conductive rollers)
The pellets of the thermoplastic elastomer composition are kneaded while being heated in the screw portion of an extruder, and extruded into a cylinder through a die base connected to the tip of the screw portion. A cylindrical body 5 was produced.
There are two conditions for extrusion molding: extrusion temperature (set temperature at the tip of the screw part) 200 ° C., low speed condition at an extrusion speed of about 1 m / min, and high speed condition at the same extrusion temperature and an extrusion speed of about 3 m / min. Set.

The cylindrical body 5 had an outer diameter of 12.5 mm and an inner diameter of 4.6 mm. Also, as shown in FIGS. 4 and 5, by providing a substantially sinusoidal uneven shape on the inner peripheral surface 15 of the base 14, the outer peripheral surface 6 of the extruded cylindrical body 5 is formed on the concave portion 16 having the uneven shape. The ridges 7 corresponding to the sine wave and the concave grooves 8 corresponding to the ridges 17 were alternately arranged in a sine wave-like concavo-convex shape.
The concave portion 16 and the convex portion 17 have a radial height difference h of 700 μm between the highest point of the protruding ridge 7 of the extruded cylindrical body 5 and the lowest point of the recessed groove 8, and the adjacent protruding ridges 7. The circumferential pitch w between the highest points was set to 400 μm.

Further, by providing a plurality of pins 18 and 19 and a mandrel 20 inside the base 14, a plurality of hollow portions 9 and 10 having a cross-sectional shape shown in FIG. 3 are formed inside the extruded cylindrical body 5. The through hole 3 was formed.
In the cross section of FIG. 3, the area occupancy ratio of the hollow portions 9 and 10 determined by the above equation (1) from the cross sectional area of the hollow portions 9 and 10 and the cross sectional area of the solid portion other than the hollow portions 9 and 10. Was 30%.

The extruded cylindrical body 5 is cooled while being maintained so as not to rotate in the circumferential direction around the central axis L, and then inserted into the through-hole 3 and cut into a length of 216 mm to cut the roller body 2. To form a conductive roller 1.
<Examples 2 to 4>
By changing the cross-sectional area of the pins 18 and 19 provided inside the base 14, the area occupancy of the hollow portions 9 and 10 is 10% (Example 2), 50% (Example 3), and 75% (implementation). A conductive roller 1 was produced in the same manner as in Example 1 except that Example 4) was used.

<Comparative example 1>
Except that the concave portion 16 and the convex portion 17 are not provided on the inner peripheral surface 15 of the base 14, and thus the convex strip 7 and the concave groove 8 are not formed on the outer peripheral surface 6 of the roller body 2, the same as in the first embodiment. Thus, the conductive roller 1 was manufactured.
<Comparative example 2>
The concave portion 16 and the convex portion 17 are formed such that the height difference h in the radial direction between the highest point of the protruding ridge 7 of the extruded cylindrical body 5 and the lowest point of the recessed groove 8 is 70 μm. The conductive roller 1 was manufactured in the same manner as in Example 1 except that the circumferential pitch w between the highest points was set to 400 μm.

<Example 5>
The concave portion 16 and the convex portion 17 are formed so that the height difference h in the radial direction between the highest point of the protruding ridge 7 of the cylindrical body 5 and the lowest point of the recessed groove 8 is 100 μm. The conductive roller 1 was manufactured in the same manner as in Example 1 except that the circumferential pitch w between the highest points was set to 400 μm.

<Comparative Example 3>
The concave portion 16 and the convex portion 17 are formed so that the height difference h in the radial direction between the highest point of the protruding protrusion 7 of the cylindrical body 5 and the lowest point of the recessed groove 8 is 700 μm, The conductive roller 1 was manufactured in the same manner as in Example 1 except that the circumferential pitch w between the highest points was set to 850 μm.

<Comparative example 4>
The conductive roller 1 was manufactured in the same manner as in Example 1 except that the pins 18 and 19 were not provided on the inner side of the base 14 and therefore the hollow portions 9 and 10 were not formed inside the roller body 2.
<Comparative Example 5>
Six pins having a circular cross section are arranged at equal intervals in the circumferential direction inside the base 14 and around the mandrel 20, and the cross-sectional area thereof is adjusted so that the area occupation ratio of the hollow portions 9 and 10 is 8%. A conductive roller 1 was produced in the same manner as in Example 1 except that.

<Comparative Example 6>
When the cross-sectional areas of the pins 18 and 19 provided inside the base 14 were changed so that the area occupation ratio of the hollow portions 9 and 10 was 85%, the cylindrical body 5 could not be extruded.
<Hardness measurement>
Examples of the roller body 2 Comparative conductive roller prepared in Example 1, the central axis L direction stiffness from the outer peripheral surface 6, at a plurality of positions on the outer circumferential surface 6, the attendant JIS K7312 _-1,996 supra Measurement was performed in accordance with the spring hardness test type C test method defined in the document 2, and the average value was defined as the hardness of the roller body 2.

<Image evaluation test>
The conductive roller manufactured in the example and the comparative example is assembled in a laser printer (LaserJet (registered trademark) P1006 manufactured by Hewlett-Packard Co., Ltd.) by betting the transfer roller, and in an environment of a temperature of 10 ° C. and a relative humidity of 20 ± 1%. Twenty halftone images were continuously printed on A4 size paper (PPC paper manufactured by Fuji Xerox Office Supply Co., Ltd.).

Subsequently, 20 prints were visually observed, and the presence or absence of unevenness under low temperature conditions was evaluated according to the following criteria.
A: Image defects such as unevenness and streaks that were uneven in strength were not observed on 20 sheets of printing.
○: Image defects such as slight unevenness and streaks were observed on about 1 to 2 out of 20 sheets, but these image defects are those that cannot be understood unless the images are carefully looked at, and at a level with no problem. there were.

X: Image defects such as obvious unevenness and streaks were observed in 2 or more of 20 sheets.
The above results are shown in Tables 2 and 3.

According to both tables, the outer peripheral surface 6 of the roller body 2 is provided with a plurality of ridges 7 and grooves 8 having a height difference h of 100 μm or more and a pitch w of 800 μm or less, and an area occupancy rate of 10%. As described above, it was found that by providing the hollow portions 9 and 10 that are 80% or less, it is possible to form a good image without image defects such as unevenness and streaks, particularly in a low temperature environment.
It was also found that the area occupancy is preferably 30% or more and 75% or less even within the above range.

DESCRIPTION OF SYMBOLS 1 Conductive roller 2 Roller main body 3 Through-hole 4 Shaft 5 Cylindrical body 6 Outer peripheral surface 7 Convex 8 Concave groove 9 Hollow part 10 Hollow part 11 Connection part 12 Inner cylindrical part 13 Outer cylindrical part 14 Base 15 Inner peripheral surface 16 Concave part 17 Convex 18 and 19 Pin 20 Mandrel

Claims (6)

A conductive roller formed in a cylindrical shape;
On the outer peripheral surface, a plurality of ridges and grooves are alternately provided in the circumferential direction, and a plurality of hollow portions are provided inside,
The height difference in the radial direction between the highest point of the ridge and the lowest point of the groove is 100 μm or more, the circumferential pitch between the highest points of adjacent ridges is 800 μm or less, and the conductive roller, From the cross-sectional area of the hollow portion in the cross section perpendicular to the axial direction and the cross-sectional area of the solid portion other than the hollow portion, the formula (1):

The conductive roller is characterized in that the area occupancy of the hollow portion determined by the above is 10% or more and 80% or less. In a resin matrix containing a styrenic thermoplastic elastomer and polypropylene,
A cross-linked product of at least one rubber selected from the group consisting of diene rubber and ethylene propylene rubber;
2. The conductive roller according to claim 1, wherein the conductive roller is formed of a thermoplastic elastomer composition in which an ion conductive resin-type antistatic agent containing an ion conductive elastomer and an ion conductive salt is dispersed.   3. The thermoplastic elastomer composition according to claim 2, wherein the thermoplastic elastomer composition is prepared through a dynamic crosslinking step in which a mixture containing a resin matrix and an uncrosslinked rubber component is kneaded while heating to crosslink the rubber component. Conductive roller.   The thermoplastic elastomer composition is provided with a base, and on the inner peripheral surface of the base, a plurality of concave portions and convex portions that are the basis of the convex stripes and concave grooves are alternately provided in the circumferential direction, and the base 4. The conductive roller according to claim 2, wherein the conductive roller is manufactured by extrusion molding into a cylindrical shape using an extrusion molding machine provided with a die provided with a plurality of pins on which the hollow portion is based. .   The toner image formed on the surface of the photoconductor or image carrier is incorporated into the electrophotographic device in a state where the outer peripheral surface is in contact with the surface of the photoconductor or image carrier of the electrophotographic device. The conductive roller according to claim 1, wherein the conductive roller is used as a transfer roller to be transferred to a roller.   An electrophotographic apparatus comprising the conductive roller according to claim 1 as a transfer roller.

Images