JP2017194564A - Semi-conductive roller and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semi-conductive roller that can suppress adhesion of toner and fine particles to an outer peripheral surface better than the present situation while maintaining a simple configuration where a coating film is omitted, and a method for manufacturing the same.SOLUTION: A semi-conductive roller 1 is formed of a crosslinking material of a rubber composition having epichlorohydrin rubber blended therein at a ratio of 15 to 80 mass%, and comprises an oxidizing flame treatment film 5 on an outer peripheral surface 4. The method for manufacturing the same includes a step of molding the rubber composition in a roller shape to be crosslinked and subsequently performing oxidizing flame treatment of bringing the outer peripheral surface into contact with oxidizing flame to form an oxidizing flame treatment film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductive roller particularly used as a charging roller or the like in an image forming apparatus using electrophotography such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, or a complex machine thereof. And its manufacturing method.

  In the image forming apparatus, a charging member for uniformly charging the surface of the photoreceptor, a developing member for developing an electrostatic latent image formed by exposing the surface of the charged photoreceptor to a toner image, and a formed toner image As a transfer member to be transferred to paper or the like, and a cleaning member to remove toner remaining on the surface of the photoconductor after the toner image is transferred to paper or the like, a contact nip with the photoconductor is particularly secured. In order to express each function satisfactorily, a semiconductive roller obtained by crosslinking a semiconductive rubber composition into a roller shape is preferably used.

The semiconductive roller is used by being incorporated in an image forming apparatus in a state in which a shaft made of metal or the like is inserted into and fixed to a central through hole.
In order to impart semiconductivity to the rubber composition that forms the semiconductive roller, an ion conductive rubber such as epichlorohydrin rubber may be used as the rubber component that forms the rubber composition. .

In addition, to improve the mechanical strength and durability of the semiconductive roller, or to give the semiconductive roller a characteristic as a rubber, that is, a characteristic that is flexible and has a small compression set and hardly causes settling. In addition, as the rubber component, a diene rubber may be used in combination with the ion conductive rubber.
Further, the outer peripheral surface of the semiconductive roller is generally coated with a coating film in order to adjust the surface state. However, in order to meet the recent demand for cost reduction of the image forming apparatus, the coating film is used. There is an increasing number of cases where the thickness is made as thin as possible or omitted at all.

  However, since the outer peripheral surface of the semiconductive roller made of a rubber composition has high friction and high adhesiveness, when it is not covered with a coating film, toner, or toner fluidity, chargeability, etc. are applied to the outer peripheral surface. In order to improve, fine particles of external additives such as silica and titanium oxide, which are externally added to the toner, and fine particles produced by finely pulverizing the toner by repeating image formation adhere to the above-mentioned image formation. It is easy to accumulate gradually by repeating.

The accumulated toner and fine particles may affect the characteristics of the semiconductive roller, for example, the charging characteristics of the photosensitive member in the charging roller, or may reattach to the formed image on the paper and cause image defects. . These problems are particularly remarkable in a charging roller that is always in contact with the surface of the photoreceptor.
Therefore, in order to suppress adhesion of toner and fine particles, the rubber composition constituting the outer peripheral surface is modified by adjusting the surface roughness of the outer peripheral surface of the semiconductive roller or by irradiating ultraviolet rays or electron beams. It has been proposed to improve the quality (Patent Document 1, etc.).

JP 2007-219085 A

However, in view of the recent demands for improving the process speed in the image forming apparatus, further improving the image quality of the formed image, or extending the life of each part constituting the image forming apparatus, the above-described conventional modified outer peripheral surface However, the current situation is that the effect is insufficient and adhesion of toner and fine particles cannot be sufficiently suppressed.
An object of the present invention is to provide a semiconductive roller capable of suppressing the adhesion of toner and fine particles to the outer peripheral surface better than the current state while maintaining a simple structure in which a coating film is omitted, and a method for manufacturing the same. It is in.

The present invention includes an epichlorohydrin rubber and a diene rubber as a rubber component, and a crosslinking component for crosslinking the rubber component, and the blending ratio of the epichlorohydrin rubber is 15% by mass or more in the total amount of the rubber component, It is a semiconductive roller comprising a cross-linked product of a rubber composition of 80% by mass or less and having an oxidation flame treatment film on the outer peripheral surface.
Further, the present invention provides a step of forming the rubber composition into a roller shape and crosslinking, and an oxidation flame treatment in which the outer circumferential surface of the crosslinked roller is brought into contact with the oxidation flame, and the oxidation flame treated film is formed on the outer circumferential surface. It is a manufacturing method of the semiconductive roller including the process to form.

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductive roller which can suppress the adhesion of a toner and a microparticle to an outer peripheral surface better than the present condition, and its manufacturing method 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. It is a figure explaining the method to measure the roller resistance value of a semiconductive roller.

The present invention includes an epichlorohydrin rubber and a diene rubber as a rubber component, and a crosslinking component for crosslinking the rubber component, and the blending ratio of the epichlorohydrin rubber is 15% by mass or more in the total amount of the rubber component, It is a semiconductive roller comprising a cross-linked product of a rubber composition of 80% by mass or less and having an oxidation flame treatment film on the outer peripheral surface.
Further, the present invention provides a step of forming the rubber composition into a roller shape and crosslinking, and an oxidation flame treatment in which the outer circumferential surface of the crosslinked roller is brought into contact with the oxidation flame, and the oxidation flame treated film is formed on the outer circumferential surface. It is a manufacturing method of the semiconductive roller including the process to form.

  According to the present invention, the outer peripheral surface of the roller composed of a crosslinked product of the rubber composition containing the above components is subjected to an oxidation flame treatment in which the outer peripheral surface is brought into contact with an oxidizing flame, for example, an external flame of a burner flame, so Mainly diene rubber constituting the exposed cross-linked product is oxidized to a higher degree than in the case of conventional treatment of irradiating ultraviolet rays, electron beams, etc. As is clear from the results, it is possible to form an oxide flame treatment film excellent in the effect of suppressing adhesion of toner and fine particles, which cannot be obtained by the conventional treatment.

Moreover, the oxidized flame-treated film is formed by oxidizing the crosslinked rubber composition itself exposed on the outer peripheral surface of the roller composed of the crosslinked rubber composition by oxidation flame treatment as described above. The conductive roller can maintain a simple structure in which the coating film is omitted.
Therefore, according to the present invention, it is possible to suppress adhesion of toner and fine particles to the outer peripheral surface better than the current situation while maintaining a simple structure in which the coating film is omitted.

<Rubber composition>
<Rubber>
As described above, the rubber component is composed of epichlorohydrin rubber and diene rubber, and the blending ratio of epichlorohydrin rubber among them is required to be 15% by mass or more and 80% by mass or less in the total amount of the rubber component.

  If the blending ratio of epichlorohydrin rubber is less than this range, there is a possibility that good semiconductivity, particularly as a charging roller, cannot be imparted to the semiconductive roller. That is, there is a possibility that the roller resistance value of the semiconductive roller cannot be sufficiently lowered to the value required for the charging roller. Further, the roller resistance value is not stable, and there is a possibility that the image resistance may be further increased from the initial value by repeating image formation.

  On the other hand, when the proportion of the epichlorohydrin rubber exceeds the above range, the proportion of the diene rubber that is oxidized mainly by the oxidation flame treatment to form the oxidation flame treatment film is relatively small, so that it is semiconductive. A good oxidation flame-treated film excellent in the effect of suppressing the adhesion of toner and fine particles cannot be formed on the outer peripheral surface of the roller, and the toner and fine particles may easily adhere to the outer peripheral surface.

In addition, since the ratio of the diene rubber that imparts rubber properties to the semiconductive roller is reduced, there is a possibility that the compression set of the semiconductive roller is increased and the settling is likely to occur.
On the other hand, by setting the blending ratio of epichlorohydrin rubber within the above range, toner and fine particles adhere to the outer peripheral surface of the semiconductive roller while maintaining good semiconductive properties and rubber properties. The adhesion can be satisfactorily suppressed by forming an oxide flame-treated film having an excellent suppressing effect.

In consideration of further improving this effect, the blending ratio of epichlorohydrin rubber is preferably 20% by mass or more, and preferably 70% by mass or less even in the above range.
(Epichlorohydrin rubber)
As the epichlorohydrin rubber, various polymers having epichlorohydrin as a repeating unit and having ionic conductivity can be used.

  Examples of such 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. 1 type or 2 types of allyl glycidyl ether terpolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer, etc. The above is mentioned.

Among them, a copolymer containing ethylene oxide, particularly ECO and / or GECO is preferable.
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 segment movement of the molecular chain is hindered, so that the roller resistance value tends to increase. In addition, the semiconductive roller 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.
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 preferably 2 mol% or more, more preferably 10 mol% or less, and particularly preferably 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.
As the epichlorohydrin rubber, GECO is particularly preferable. Since GECO has a double bond that functions as a crosslinking point due to allyl glycidyl ether in the main chain, the compression set of the semiconductive roller can be reduced by crosslinking between the main chains.

For this reason, for example, when a semiconductive roller is used as a charging roller and a portion that is kept in pressure contact with the photosensitive member when the image forming apparatus is stopped, the original state is maintained even if the pressure contact is released by rotating the semiconductive roller. There is an advantage that it is possible to suppress so-called settling that is not restored until the occurrence of image defects such as image unevenness in the formed image.
(Diene rubber)
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 or to use CR and SBR in combination, and the latter combined system is particularly preferable.
That is, as the rubber component, it is preferable to use three types of epichlorohydrin rubber, CR, and SBR in combination. As the three types of rubber, two or more types of different grades may be used in combination.

In such combined systems, CR contains many chlorine atoms in the molecule, so in addition to its function as a diene rubber, its charging characteristics are improved especially when the semiconductive roller of the present invention is used as a charging roller. Also works. Since CR is a polar rubber, it also functions to finely adjust the roller resistance value of the semiconductive roller.
The 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 regulator used at that time.

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. 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, as CR, there are an oil-extended type that adjusts flexibility by adding extension oil and a non-oil-extended type that does not add, but when using a semiconductive roller as a charging roller, etc., In order to prevent contamination of the photoreceptor, it is preferable to use a non-oil extended type CR.
One or more of these CRs can be used.
SBR has a function as a diene rubber, that is, a function that is oxidized by an oxidation flame treatment to form an oxidation flame treatment film excellent in the effect of suppressing adhesion of toner and fine particles on the outer peripheral surface of the semiconductive roller. Are better.

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 high styrene type, medium styrene type, and low styrene type SBR classified by styrene content can be used.

Furthermore, there are two types of SBR: an oil-extended type that adjusts flexibility by adding extension oil, and a non-oil-extended type that does not add flexibility. However, when using semi-conductive rollers as charging rollers, etc. In order to prevent contamination of the photoreceptor, it is preferable to use a non-oil-extended type SBR.
One or more of these SBRs can be used.

(Rubber content)
The blending ratio of epichlorohydrin rubber in the rubber component is limited to 15% by mass or more and 80% by mass or less in the total amount of the rubber component, and is preferably 20% by mass or more, and preferably 70% by mass or less. . The reason for this is as described above.
Further, in a system using the above-mentioned epichlorohydrin rubber, CR, and SBR in combination as the rubber component, the proportion of CR is preferably 10% by mass or more, particularly 40% by mass or less, particularly 30% in the total amount of the rubber component. It is preferable that it is below mass%.

When the blending ratio of CR is less than this range, the effects described above by blending the CR, that is, the effect of improving the charging characteristics when used as a charging roller and the effect of finely adjusting the roller resistance value are sufficiently obtained. There is a risk of not.
On the other hand, when the blending ratio of CR exceeds the above range, the ratio of epichlorohydrin rubber is relatively small, and there is a possibility that good semiconductivity as a charging roller cannot be imparted to the semiconductive roller. Further, the ratio of SBR is reduced, and there is a possibility that an oxidation flame treatment film excellent in the effect of suppressing adhesion of toner and fine particles cannot be formed on the outer peripheral surface of the semiconductive roller by the oxidation flame treatment.

On the other hand, by setting the blending ratio of CR within the above range, the charging characteristics when using a semiconductive roller as a charging roller are improved while maintaining the effect of using the other two types of rubber together. Or finely adjust the roller resistance.
The blending ratio of SBR is the remaining amount of epichlorohydrin rubber and CR. That is, when the blending ratio of epichlorohydrin rubber and CR is set to a predetermined value, the blending ratio of SBR may be set so that the total amount of rubber is 100% by mass.

<Crosslinking component>
As the crosslinking component, a thiourea-based crosslinking agent for mainly crosslinking epichlorohydrin rubber, a sulfur-based crosslinking agent for crosslinking GECO, etc. of diene rubber and epichlorohydrin rubber, and an accelerator for both crosslinking agents are used in combination. Is preferred.
(Thiourea crosslinking agent and accelerator)
As the thiourea-based crosslinking agent, various compounds having a thiourea group in the molecule and mainly functioning as a crosslinking agent for epichlorohydrin rubber can be used.

Examples of the thiourea-based crosslinking agent include tetramethylthiourea, trimethylthiourea, ethylenethiourea (also known as 2-mercaptoimidazoline), formula (1):
(C _n H _{2n + 1} NH) ₂ C = S (1)
[In formula, n shows the integer of 1-10. ] 1 type (s) or 2 or more types, such as thiourea represented by these. In particular, ethylene thiourea is preferable.

The blending ratio of the thiourea crosslinking agent takes into account that the epichlorohydrin rubber is well cross-linked and gives the semiconductive roller characteristics as a rubber, that is, a characteristic that is flexible and has a low compression set and is less likely to cause settling. Then, it is preferable that it is 0.3 mass part or more per 100 mass parts of total amounts of rubber, and it is preferable that it is 1 mass part or less.
Examples of accelerators for thiourea crosslinking agents include guanidines such as 1,3-diphenylguanidine (D), 1,3-di-o-tolylguanidine (DT), and 1-o-tolylbiguanide (BG). 1 type, or 2 or more types, such as an accelerator, are mentioned.

In consideration of sufficiently developing the effect of promoting the crosslinking of epichlorohydrin rubber, the blending ratio of the accelerator is preferably 0.3 parts by mass or more per 100 parts by mass of the total amount of rubber. Preferably there is.
(Sulfur-based crosslinking agent and accelerator)
As the sulfur-based crosslinking agent, at least one selected from the group consisting of sulfur and sulfur-containing crosslinking agents is used.

Among these, as the sulfur-containing crosslinking agent, various organic compounds that contain sulfur in the molecule and can function as a crosslinking agent for diene rubber or GECO can be used. Examples of the sulfur-containing crosslinking agent include 4,4′-dithiodimorpholine (R).
However, sulfur is particularly preferable as the sulfur-based crosslinking agent.
The mixing ratio of sulfur takes into account that the diene rubber and GECO are cross-linked well to give the semiconductive roller characteristics as a rubber, that is, a characteristic that is flexible and has a low compression set and is less likely to cause settling. Then, it is preferable that it is 1 mass part or more per 100 mass parts of total amounts of rubber, and it is preferable that it is 2 mass parts or less.

When a sulfur-containing crosslinking agent is used as the crosslinking agent, the blending ratio is adjusted so that the mass part of the sulfur contained in the molecule per 100 parts by mass of the total rubber content falls within the above range. preferable.
Examples of accelerators for sulfur-based crosslinking agents include sulfur-containing accelerators containing sulfur in the molecule, such as thiazole accelerators, thiuram accelerators, sulfenamide accelerators, and dithiocarbamate accelerators. 1 type or 2 types or more are mentioned.

Of these, it is preferable to use a thiazole accelerator and a thiuram accelerator in combination.
Examples of the thiazole accelerator include 2-mercaptobenzothiazole (M), di-2-benzothiazolyl disulfide (DM), zinc salt of 2-mercaptobenzothiazole (MZ), and cyclohexylamine of 2-mercaptobenzothiazole. 1 type or 2 types of salt (HM, M60-OT), 2- (N, N-diethylthiocarbamoylthio) benzothiazole (64), 2- (4'-morpholinodithio) benzothiazole (DS, MDB), etc. The above is mentioned. In particular, di-2-benzothiazolyl disulfide (DM) is preferable.

  Examples of the thiuram accelerator include tetramethylthiuram monosulfide (TS), tetramethylthiuram disulfide (TT, TMT), tetraethylthiuram disulfide (TET), tetrabutylthiuram disulfide (TBT), tetrakis (2-ethylhexyl) thiuram. One type or two or more types such as disulfide (TOT-N) and dipentamethylene thiuram tetrasulfide (TRA) can be used. Tetramethylthiuram monosulfide (TS) is particularly preferable.

  In the combined system of the above two sulfur-containing accelerators, considering that the effect of promoting the crosslinking of the diene rubber is sufficiently expressed, the blending ratio of the thiazole accelerator is 100 parts by mass of the total amount of rubber. It is preferably 1 part by mass or more and 2 parts by mass or less. Similarly, the blending ratio of the thiuram accelerator is preferably 0.3 parts by mass or more and 0.9 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 an accelerator, acid acceptor, plasticizer, processing aid, deterioration inhibitor, filler, scorch inhibitor, lubricant, pigment, ionic salt, antistatic agent, flame retardant, neutralizer, Examples thereof include a nucleating agent and a co-crosslinking agent.

These additives may be set in the type and the mixing ratio, paying attention to the balance between the resistance value of the semiconductive roller and the effect of suppressing the adhesion and accumulation of toner and fine particles on the outer peripheral surface. .
Examples of the acceleration aid include metal compounds such as zinc white (zinc oxide); fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and one or more conventionally known acceleration aids.

The proportion of the accelerator aid is individually 0.1 parts by mass or more, particularly 0.5 parts by mass or more, preferably 7 parts by mass or less, particularly 5 parts by mass or less, per 100 parts by mass of the total amount of rubber. Preferably there is.
The acid acceptor prevents chlorine-based gas generated from epichlorohydrin rubber or CR from remaining in the semiconductive roller during crosslinking of the rubber component, thereby preventing crosslinking inhibition or contamination of the photoreceptor. To work.

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

The blending ratio of the acid acceptor is preferably 0.5 parts by mass or more, particularly 1 part by mass or more, preferably 6 parts by mass or less, particularly preferably 5 parts by mass or less, per 100 parts by mass of the total amount of rubber.
Examples of the plasticizer include various plasticizers such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), and tricresyl phosphate, and various waxes such as polar wax. Examples of the processing aid include fatty acids such as stearic acid.

The blending ratio of the plasticizer and / or processing aid is preferably 5 parts by mass or less, particularly 3 parts by mass or less, per 100 parts by mass of the total amount of rubber. For example, this is to prevent the photosensitive member from being contaminated when it is attached to the image forming apparatus or during operation. In view of this object, it is preferable to use a polar wax among the plasticizers.
Examples of the deterioration preventing agent include various antiaging agents and antioxidants.

  Of these, the antioxidant functions to reduce the environmental dependency of the roller resistance value of the semiconductive roller and to suppress an increase in the roller resistance value during continuous energization. Examples of the antioxidant include nickel diethyldithiocarbamate [NOCRACK (registered trademark) NEC-P manufactured by Ouchi Shinsei Chemical Co., Ltd.], nickel dibutyldithiocarbamate [NOCRACK NBC manufactured by Ouchi Shinsei Chemical Co., Ltd.] Etc.

Examples of the filler include one or more of zinc oxide, silica, carbon, carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, and the like.
By blending the filler, the mechanical strength of the semiconductive roller can be improved.
The blending ratio of the filler is preferably 5 parts by mass or more, preferably 25 parts by mass or less, particularly preferably 20 parts by mass or less, per 100 parts by mass of the total amount of rubber.

Further, a conductive filler such as conductive carbon black may be blended as a filler to impart electronic conductivity to the semiconductive roller.
As the conductive carbon black, for example, HAF and granular acetylene black are preferable. Since these conductive carbon blacks can be uniformly dispersed in the rubber composition, it is possible to impart as uniform electronic conductivity as possible to the semiconductive roller.

The blending ratio of the conductive carbon black is preferably 1 part by mass or more, particularly 3 parts by mass or more, preferably 8 parts by mass or less, particularly 6 parts by mass or less, per 100 parts by mass of the total amount of rubber.
Examples of the scorch inhibitor include one or more of N-cyclohexylthiophthalimide, phthalic anhydride, N-nitrosodiphenylamine, 2,4-diphenyl-4-methyl-1-pentene, and the like. . N-cyclohexylthiophthalimide is particularly preferable.

The blending ratio of the scorch inhibitor is preferably 0.1 parts by mass or more per 100 parts by mass of the total amount of rubber, and is preferably 5 parts by mass or less, particularly preferably 1 part by mass or less.
The co-crosslinking agent refers to a component that itself has a function of crosslinking and also having a function of crosslinking the rubber component to polymerize the whole.
Examples of co-crosslinking agents include methacrylic acid esters, or ethylenically unsaturated monomers represented by metal salts of methacrylic acid or acrylic acid, polyfunctional polymers using functional groups of 1,2-polybutadiene, Or 1 type, or 2 or more types, such as dioxime, is mentioned.

Among these, examples of the ethylenically unsaturated monomer include one or more of compounds represented by the following (a) to (h).
(a) Monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid.
(b) Dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid.
(c) Esters or anhydrides of unsaturated carboxylic acids of (a) (b).
(d) Metal salts of (a) to (c).
(e) Aliphatic conjugated dienes such as 1,3-butadiene, isoprene and 2-chloro-1,3-butadiene.
(f) Aromatic vinyl compounds such as styrene, α-methylstyrene, vinyl toluene, ethyl vinyl benzene and divinyl benzene.
(g) Vinyl compounds having a heterocyclic ring, such as triallyl isocyanurate, triallyl cyanurate, and vinylpyridine.
(h) Other vinyl cyanide compounds such as (meth) acrylonitrile or α-chloroacrylonitrile, acrolein, formylsterol, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone.

The ester of unsaturated carboxylic acids (c) is preferably an ester of monocarboxylic acids.
Examples of the esters of monocarboxylic acids include one or more of the following various compounds.
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, n-pentyl (meta ) Acrylate, i-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, i-nonyl (meth) ), Tert-butylcyclohexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, and other alkyl esters of (meth) acrylic acid.

Aminoalkyl esters of (meth) acrylic acid, such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and butylaminoethyl (meth) acrylate.
(Meth) acrylates having an aromatic ring, such as benzyl (meth) acrylate, benzoyl (meth) acrylate, and allyl (meth) acrylate.

(Meth) acrylates having an epoxy group, such as glycidyl (meth) acrylate, metaglycidyl (meth) acrylate, and epoxycyclohexyl (meth) acrylate.
(Meth) acrylate having various functional groups such as N-methylol (meth) acrylamide, γ- (meth) acryloxypropyltrimethoxysilane, and tetrahydrofurfuryl methacrylate.

Polyfunctional (meth) acrylates such as ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene dimethacrylate (EDMA), polyethylene glycol dimethacrylate, and isobutylene ethylene dimethacrylate.
The rubber composition containing each component demonstrated above can be prepared similarly to the past. First, a rubber component is blended at a predetermined ratio and kneaded, then various additives other than the crosslinking component are added and kneaded, and finally a crosslinking component is added and kneaded to obtain a rubber composition.

For kneading, for example, a closed kneader such as an intermix, a Banbury mixer, a kneader, an extruder, or an open roll can be used.
<Semiconductive roller and its manufacturing method>
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 is formed into a cylindrical shape by a rubber composition containing each component described above and is crosslinked, and a shaft 3 is inserted into a central through hole 2. Has been fixed.

Since the semiconductive roller 1 is composed of a crosslinked product of the rubber composition, it has excellent properties as a rubber, that is, it is flexible and has a small compression set and hardly causes settling.
The shaft 3 is formed of a metal such as aluminum, an aluminum alloy, or stainless steel.

The shaft 3 is electrically joined to the semiconductive roller 1 through a conductive adhesive and mechanically fixed, or has an outer diameter larger than the inner diameter of the through hole 2. By press-fitting into the through-hole 2, the semi-conductive roller 1 is electrically joined and mechanically fixed and rotated integrally.
An oxide flame treatment film 5 is provided on the outer peripheral surface 4 of the semiconductive roller 1 as shown in the enlarged view in the drawing.

As described above, the oxidized flame-treated film 5 is subjected to an oxidized flame treatment that brings the outer peripheral surface 4 into contact with the oxidized flame. It is formed with a higher degree of oxidation than in the case of the conventional process of irradiation.
Therefore, by providing the oxide flame treatment film 5, when the semiconductive roller 1 is used as a charging roller in particular, it is possible to suppress the adhesion of toner and fine particles to the outer peripheral surface 4 better than the current situation.

Moreover, the oxidized flame treated film 5 is formed by oxidizing the crosslinked product of the rubber composition itself exposed on the outer peripheral surface 4 of the roller composed of the crosslinked product of the rubber composition as described above by the oxidized flame treatment. The semiconductive roller 1 can maintain a simple structure in which the coating film is omitted.
Accordingly, it is possible to suppress adhesion of toner and fine particles to the outer peripheral surface 4 better than the current state while maintaining a simple structure in which the coating film is omitted.

The outer peripheral surface 4 has an arithmetic average roughness Ra of a roughness curve defining the surface roughness of 1.0 μm or more and 3.0 μm or less, and an actual surface area measured value S per unit area, and the outer peripheral surface is smooth. It is preferably finished so that the ratio S / S ₀ to the theoretical value S ₀ of the surface area per unit area when it is assumed to be a plane is 2.0 or more and 3.3 or less.
When the arithmetic average roughness of the outer peripheral surface 4 is less than this range or exceeds the above range, in any case, the oxidation treatment film 5 is formed on the outer peripheral surface 4, There is a possibility that toner and fine particles are likely to adhere to the outer peripheral surface 4.

On the other hand, by setting the arithmetic average roughness Ra of the outer peripheral surface 4 in the above range, the toner and fine particles adhere to the outer peripheral surface 4 in combination with the formation of the oxide flame treatment film 5. It can be suppressed even better.
In consideration of further improving this effect, the arithmetic average roughness Ra of the outer peripheral surface 4 is preferably 1.5 μm or more, and preferably 2.5 μm or less, even in the above range.

The arithmetic average roughness Ra is calculated based on the surface properties of the outer peripheral surface measured using an ultra-deep color 3D shape measuring microscope [VK-9510 manufactured by Keyence Corporation]. Japanese Industrial Standard JIS B0601 _{: 2013} “Product Geometric Properties” The specification (GPS) -surface property: contour curve method-term, definition, and surface property parameter "are used to express the value.
Further, when the ratio S / S ₀ is less than the above range, the outer peripheral surface 4 is too smooth, and the surface of the photoreceptor cannot be uniformly charged particularly when used as a charging roller. There is a risk of causing defects.

On the other hand, when the ratio S / S ₀ exceeds the above range, the undulation of the outer peripheral surface 4 is too large, and the surface of the photoreceptor cannot be uniformly charged when used as a charging roller. In addition, image defects such as density unevenness are likely to occur.
On the other hand, by setting the ratio S / S ₀ within the above range, the surface of the photosensitive member can be uniformly charged, particularly when used as a charging roller, and image defects such as density unevenness can be hardly generated in the formed image.

In consideration of further improving this effect, the ratio S / S ₀ is particularly preferably 2.2 or more even in the above range, and is preferably 3.0 or less.
The actual measured value S of the surface area that is the basis of S / S ₀ is represented by the value measured at the measurement area: 0.054 mm ² using the above-described ultra-depth color 3D shape measuring microscope.
In order to manufacture the semiconductive roller 1, the rubber composition prepared first is extruded into a cylindrical shape using an extruder, then cut into a predetermined length and heated in a vulcanizing can. To crosslink the rubber.

Next, the crosslinked cylindrical body is heated using an oven or the like to be secondarily crosslinked, cooled, and then polished so as to have a predetermined outer diameter.
As the polishing method, various polishing methods such as dry traverse grinding can be employed. However, the arithmetic average roughness Ra of the outer peripheral surface 4 and the surface area ratio S / S ₀ per unit area are within the ranges described above. It is preferable to finish so that it becomes.

Then, when the polished cylindrical body is rotated at a constant speed, for example, around its central axis, the outer peripheral surface 4 is brought into contact with the oxidizing flame from the burner, and the oxidizing flame treatment is performed on the outer peripheral surface 4. The treatment film 5 is formed, and the semiconductive roller 1 shown in FIG. 1 is manufactured.
Although the conditions for the oxidation flame treatment can be arbitrarily set, it is preferable to set the temperature of the oxidation flame at a position in contact with the outer peripheral surface 4 to 1300 ° C. or more and 1700 ° C. or less.

If the temperature of the oxidation flame is less than this range, a good oxidation flame treatment film 5 excellent in the effect of suppressing the adhesion of toner and fine particles cannot be formed on the outer peripheral surface 4. There is a possibility that particles are likely to adhere.
On the other hand, if the temperature of the oxidation flame exceeds the above range, the thickness of the oxidation flame treatment film 5 becomes non-uniform, and the photoreceptor is uniformly charged when the semiconductive roller 1 is used as a charging roller, for example. It becomes impossible to perform density unevenness in a formed image, particularly a halftone image or a solid image.

On the other hand, by setting the temperature of the oxidation flame within the above range, it is possible to form a good oxidation flame treatment film 5 having a uniform thickness and excellent effect of suppressing adhesion of toner and fine particles on the outer peripheral surface 4. .
In consideration of further improving this effect, the temperature of the oxidation flame is preferably 1400 ° C. or higher, and preferably 1500 ° C. or lower, even in the above range.

The shaft 3 can be fixed by being inserted into the through-hole 2 at an arbitrary time after the cylindrical body is cut and after polishing.
However, after the cut, it is preferable to first perform secondary crosslinking, polishing, and oxidation flame treatment with the shaft 3 inserted through the through hole 2.
Thereby, the curvature and deformation | transformation of the semiconductive roller 1 by the expansion / contraction at the time of secondary bridge | crosslinking can be prevented.

Further, by polishing while rotating about the shaft 3, the workability of the polishing can be improved, and the flare of the outer peripheral surface 4 can be suppressed.
Furthermore, the oxide flame treatment film 5 having a more uniform thickness can be formed on the outer peripheral surface 4 by performing the oxidation flame treatment while rotating around the shaft 3.
As described above, the shaft 3 is inserted into the through-hole 2 of the tubular body before the secondary cross-linking through a conductive adhesive, particularly a thermosetting adhesive, and then secondary cross-linked. What is necessary is just to press-fit into the through-hole 2 what is larger in outer diameter than the inner diameter of the hole 2.

In the former case, the thermosetting adhesive is cured simultaneously with the secondary cross-linking of the cylindrical body by heating in the oven, and the shaft 3 is electrically joined to the semiconductive roller 1 and the machine. Fixed.
In the latter case, electrical joining and mechanical fixing are completed simultaneously with press-fitting.
The semiconductive roller 1 press-molds the rubber composition into a cylindrical shape by press molding using a mold in which the mold surface corresponding to the outer peripheral surface 4 is formed into the predetermined planar shape by laser processing or the like. In addition, after the crosslinking, it is possible to manufacture the outer peripheral surface 4 by further forming an oxidation flame treated film 5 by an oxidation flame treatment.

For example, the shaft 3 is molded and crosslinked by setting a predetermined position of the press molding die in a state where a conductive thermosetting adhesive is applied to the outer periphery and press molding. At the same time, the semiconductive roller 1 can be electrically joined and mechanically fixed.
Similarly to the previous example, the shaft 3 is inserted into the through hole 2 of the semiconductive roller 1 press-molded into a cylindrical shape later, and is electrically connected to the semiconductive roller 1 via, for example, a conductive adhesive. May be mechanically fixed and mechanically fixed, or a member having an outer diameter larger than the inner diameter of the through-hole 2 may be press-fitted into the through-hole 2 to electrically join the semiconductive roller 1 and the machine May be fixed.

For example, the semiconductive roller 1 may be formed in a two-layer structure of an outer layer on the outer peripheral surface 4 side and an inner layer on the shaft 3 side. The semiconductive roller 1 may have a porous structure.
However, considering the fact that the structure is simplified and the production is as low as possible and the productivity is low, and the durability, compression set characteristics, etc. are improved, the semiconductive roller 1 is non-porous and simple. It is preferable to form a layer structure.

Here, the single layer structure means that the number of layers made of rubber is a single layer, and the oxidation flame treatment film 5 formed by the oxidation flame treatment is not included in the number of layers.
When the semiconductive roller 1 is used as a charging roller, the roller resistance value is preferably 10 ⁷ Ω or less. The roller resistance value is a measured value in a state where the oxide flame treatment film 5 is formed on the outer peripheral surface 4.

<Measurement method of roller resistance value>
FIG. 2 is a diagram for explaining a method of measuring the roller resistance value of the semiconductive roller 1.
With reference to FIGS. 1 and 2, in the present invention, the roller resistance value of the semiconductive roller 1 is measured by the following method under the condition of an applied voltage of 200 V under a normal temperature and humidity environment of a temperature of 23 ° C. and a relative humidity of 55%. It shall be expressed by the value that was made.

That is, an aluminum drum 6 that can be rotated at a constant rotational speed is prepared, and an oxide flame treatment film 5 of the semiconductive roller 1 that measures the roller resistance value from above is formed on the outer peripheral surface 7 of the aluminum drum 6. The outer peripheral surface 4 thus made is brought into contact.
A DC power supply 8 and a resistor 9 are connected in series between the shaft 3 of the semiconductive roller 1 and the aluminum drum 6 to constitute a measuring circuit 10. The DC power source 8 is connected to the shaft 3 on the (−) side and to the resistor 9 on the (+) side. The resistance value r of the resistor 9 is 100Ω.

Next, while applying a load F of 450 g to both ends of the shaft 3 so that the semiconductive roller 1 is pressed against the aluminum drum 6, the aluminum drum 6 is rotated (rotation speed: 40 rpm) while a direct current is applied therebetween. The detection voltage V applied to the resistor 9 when the applied voltage E of 200 V DC is applied from the power supply 8 is measured.
From the detection voltage V and the applied voltage E (= 200 V), the roller resistance value R of the semiconductive roller 1 is basically the formula (i ′):
R = r × E / V−r (i ′)
Sought by. However, since the -r term in the formula (i ′) can be regarded as minute, in the present invention, the formula (i):
R = r × E / V (i)
It is assumed that the roller resistance value of the semiconductive roller 1 is the value obtained by the above. As described above, the measurement conditions are a temperature of 23 ° C. and a relative humidity of 55%.

  Moreover, the semiconductive roller 1 can be adjusted so as to have an arbitrary hardness and compression set according to its use. In order to adjust the hardness, compression set, roller resistance, etc., for example, the mass ratio of epichlorohydrin rubber, CR and SBR is adjusted within the range described above, or the type and amount of the crosslinking component are adjusted. Or whether or not carbon black, a filler, an ionic salt and other components are blended, and the type and amount thereof may be adjusted.

  The semiconductive roller 1 of the present invention can be suitably used as a charging roller in an image forming apparatus using an electrophotographic method such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a composite machine thereof. For example, it can also be used as a developing roller, a transfer roller, a cleaning roller, or the like.

<Example 1>
(Preparation of rubber composition)
The following rubber components were blended.
(A) GECO [Epion (registered trademark) -301L manufactured by Daiso Corporation, EO / EP / AGE = 73/23/4 (molar ratio)] 60 parts by mass
(B) 20 parts by mass of CR [Showen (registered trademark) WRT manufactured by Showa Denko KK]
(C) SBR [Emulsion polymerization method, non-oil-extended, JSR (registered trademark) 1502 manufactured by JSR Corporation] 20 parts by mass The mixing ratio of GECO was 60% by mass in the total amount of rubber.

First, hydrotalcites [DHT-4A (registered by Kyowa Chemical Industry Co., Ltd.) as an acid-accepting agent were used while masticating 100 parts by mass of the above rubber components (A) to (C) using a Banbury mixer. Trademark) -2] 5 parts by mass and 2 parts by mass of zinc oxide as a crosslinking aid (Mitsui Metal Mining Co., Ltd.) 5 parts by mass were mixed and kneaded.
Next, while continuing kneading, the following crosslinking components were blended and further kneaded to prepare a rubber composition.

Each component in Table 1 is as follows. In addition, the mass part in a table | surface is a mass part per 100 mass parts of total amounts of a rubber part.
Thiourea-based cross-linking agent: ethylenethiourea [2-mercaptoimidazoline, Axel (registered trademark) 22-S manufactured by Kawaguchi Chemical Co., Ltd.]
Accelerator DT: 1,3-di-o-tolylguanidine [Guanidine accelerator, NOCELLER (registered trademark) DT manufactured by Ouchi Shinsei Chemical Co., Ltd.]
Powdered sulfur: Cross-linking agent [manufactured by Tsurumi Chemical Co., Ltd.]
Accelerator DM: Di-2-benzothiazolyl disulfide [Thiazole accelerator, Noxeller DM manufactured by Ouchi Shinsei Chemical Co., Ltd.]
Accelerator TS: Tetramethylthiuram monosulfide [Thiuram accelerator, NOCELLER TS manufactured by Ouchi Shinsei Chemical Co., Ltd.]
(Manufacture of semi-conductive rollers)
The prepared rubber composition is supplied to an extrusion molding machine having a diameter of 60 mm, extruded into a cylindrical shape having an outer diameter of 10 mm and an inner diameter of 5 mm, mounted on a temporary shaft for crosslinking, and crosslinked at 160 ° C. for 30 minutes in a vulcanizing can. I let you.

Next, the cross-linked cylindrical body is reattached to a shaft having an outer diameter of φ6 mm whose outer peripheral surface is coated with a conductive thermosetting adhesive (polyamide type) and heated in an oven at 150 ° C. for 60 minutes. Then, both ends were cut, and the outer peripheral surface was dry-polished using a wide polishing machine until the outer diameter reached 8.5 mm.
Then, after wiping alcohol on the outer peripheral surface after polishing, the cylindrical body was set on a rotating jig and rotated at 30 rpm around the shaft, while a burner [power torch made by Shin Fuji Burner Co., Ltd. RZ-710] was brought into contact with an external flame (oxidation flame) and subjected to an oxidation flame treatment to produce a semiconductive roller.

In the oxidation flame treatment, the contact position is adjusted to one end in the axial direction of the outer peripheral surface in a state where the distance between the burner and the outer peripheral surface is adjusted so that the temperature of the oxidation flame at the position in contact with the outer peripheral surface is 1500 ° C. It was carried out while gradually moving from one end to the other.
<Examples 2 and 3>
Oxidation flame treatment was performed by adjusting the distance between the burner and the outer peripheral surface so that the temperature of the oxidation flame at the position in contact with the outer peripheral surface was 1200 ° C. (Example 2) and 1800 ° C. (Example 3). A semiconductive roller was produced in the same manner as in Example 1 except for the above.

<Comparative example 1>
A semiconductive roller was produced in the same manner as in Example 1 except that the outer peripheral surface was irradiated with ultraviolet rays instead of the oxidation flame treatment.
That is, after wiping alcohol on the outer peripheral surface after polishing, the distance from the UV light source to the outer peripheral surface is set to 50 mm and set in an ultraviolet irradiation device [PL-200 manufactured by Sen Special Light Source Co., Ltd.] While rotating at 30 rpm, the outer peripheral surface was irradiated with ultraviolet rays for 5 minutes.

<Example 4>
Example 1 except that the amount of GECO is 15 parts by mass, the amount of CR is 40 parts by mass, the amount of SBR is 45 parts by mass, and the blending ratio of GECO is 15% by mass in the total amount of rubber. Thus, a semiconductive roller was manufactured.
<Example 5>
Example 1 except that the amount of GECO is 80 parts by mass, the amount of CR is 10 parts by mass, the amount of SBR is 10 parts by mass, and the blending ratio of GECO is 80% by mass in the total amount of rubber. Thus, a semiconductive roller was manufactured.

<Comparative example 2>
Example 1 except that the amount of GECO is 10 parts by mass, the amount of CR is 45 parts by mass, the amount of SBR is 45 parts by mass, and the blending ratio of GECO is 10% by mass in the total amount of rubber. Thus, a semiconductive roller was manufactured.
<Comparative Example 3>
Example 1 except that the amount of GECO is 85 parts by mass, the amount of CR is 5 parts by mass, the amount of SBR is 10 parts by mass, and the blending ratio of GECO is 85% by mass in the total amount of rubber. Thus, a semiconductive roller was manufactured.

<Roller resistance measurement>
The roller resistance values of the semiconductive rollers manufactured in Examples and Comparative Examples were measured by the method described above in an environment of a temperature of 23 ° C. and a relative humidity of 55%. In Tables 2 and 3, the roller resistance value R is represented by a logR value.
A roller resistance value of 10 ⁷ Ω or less was evaluated as good (A) and a value exceeding 10 ⁷ Ω as defective (C) in consideration of use as a charging roller.

<Surface property evaluation>
The arithmetic average roughness Ra of the roughness curve defining the surface roughness of the outer peripheral surface 4 of the semiconductive roller manufactured in the examples and comparative examples, and the actual measured value S of the surface area per unit area of the outer peripheral surface 4 Then, the ratio S / S ₀ to the theoretical value S ₀ of the surface area per unit area when the outer peripheral surface 4 is assumed to be a smooth surface was measured by the method described above.

<Real machine test>
(Evaluation of initial image)
A toner comprising a photoconductor that is detachable from a main body of a laser printer (HP Color LaserJet 3800 manufactured by Hewlett-Packard Japan), and a charging roller that is always in contact with the surface of the photoconductor. Instead of the genuine charging roller of the cartridge, a toner cartridge was constructed by incorporating the semiconductive roller manufactured in the example and the comparative example as a charging roller.

Then, in an environment of a temperature of 23 ° C. and a relative humidity of 55%, immediately after the toner cartridge is loaded in the laser printer, a halftone image and a solid image are printed and visually observed. The state of unevenness was evaluated.
A: Density unevenness was not seen at all. Good.
B: Slight density unevenness was observed, but the allowable range.

C: Density unevenness was observed. Bad.
(Evaluation of images after passing)
The same toner cartridge prepared separately is loaded into the same laser printer, and after passing through 2000 sheets / day for 7 days in an environment with a temperature of 10 ° C and a relative humidity of 20%, halftone images and solid images are printed. And evaluated the state of density unevenness after paper feeding according to the following criteria.

Density unevenness after passing paper is caused by toner and fine particles adhering to the outer peripheral surface due to paper passing and accumulating, and the roller resistance value is not stable and the roller resistance value increases due to paper passing. From the state of density unevenness after paper passing, it is possible to evaluate the presence or absence of adhesion of toner or fine particles, or the stability of the roller resistance value.
A: Density unevenness was not seen at all. Good.

B: Slight density unevenness was observed, but the allowable range.
C: Density unevenness was observed. Bad.
(Evaluation of photoconductor contamination)
The same toner cartridge prepared separately was allowed to stand for 14 days in an environment with a temperature of 50 ° C. and a relative humidity of 90%, and then loaded into the same laser printer, and a halftone image and a solid image in an environment with a temperature of 23 ° C. and a relative humidity of 55% Were continuously printed and visually observed, and the presence or absence of contamination of the photoreceptor was evaluated according to the following criteria.

A: From the first sheet, no image defect due to contamination of the photoreceptor was observed. Good.
B: Streaky image defects were observed on the first several sheets at the position where the semiconductive roller was in contact with the surface of the photoconductor when it was allowed to stand. The image defect was thought to be caused by contamination with absorbed moisture. Tolerance.
C: A streak-like image defect was observed at the above position from the first sheet, and this was not resolved even after continuous printing of 20 sheets or more. The image defect was considered to be caused by contamination due to a bleed or bloom component on the outer peripheral surface of the semiconductive roller. Bad.

  The above results are shown in Tables 2 and 3.

From the result of Comparative Example 1 in Table 3, although the blending ratio of epichlorohydrin rubber is composed of a crosslinked product of a rubber composition that is 15% by mass or more and 80% by mass or less in the total amount of rubber, the outer peripheral surface is not an oxidation flame. It was found that the semiconductive roller treated by the irradiation of ultraviolet rays causes density unevenness in the formed image after passing the paper.
Therefore, when the outer peripheral surface was observed, toner and fine particles adhered and accumulated, and from this, it was confirmed that the effect of preventing the above adhesion was insufficient when irradiated with ultraviolet rays compared to the oxidized flame-treated film. It was.

Further, from the result of Comparative Example 2, the semiconductive roller made of a crosslinked product of the rubber composition in which the blending ratio of epichlorohydrin rubber is less than 15% by mass in the total amount of the rubber has a high initial roller resistance value, and paper passing It was found that density unevenness occurred in the later formed image.
Accordingly, when the roller resistance value after passing the paper was confirmed, it was further increased from the initial value, and it was confirmed that the stability of the roller resistance value was lowered when the blending ratio of epichlorohydrin rubber was less than the above range.

Furthermore, from the result of Comparative Example 3, the semiconductive roller composed of a crosslinked product of the rubber composition in which the blending ratio of epichlorohydrin rubber exceeds 80% by mass in the total amount of the rubber causes contamination of the photoreceptor and after passing the paper. It has been found that density unevenness occurs in the formed image.
Therefore, when the outer peripheral surface was observed, toner and fine particles adhered and accumulated, and from this, when the proportion of epichlorohydrin rubber exceeds the above range, the proportion of diene rubber is relatively insufficient. It was confirmed that a good oxidation flame treated film could not be formed on the outer peripheral surface.

  On the other hand, from the results of Examples 1 to 5 in Table 2, the blending ratio of the epichlorohydrin rubber is 15% by mass to 80% by mass in the total amount of the rubber component, and the outer peripheral surface. According to the semiconductive roller having an oxide flame treatment film formed thereon, the roller resistance value is low, the roller resistance value is stable, and the outer peripheral surface is maintained while maintaining a simple structure in which the coating film is omitted. It was found that the adhesion of toner and fine particles to the toner can be suppressed better than the current situation.

DESCRIPTION OF SYMBOLS 1 Semiconductive roller 2 Through-hole 3 Shaft 4 Outer peripheral surface 5 Oxidation flame treatment film 6 Aluminum drum 7 Outer peripheral surface 8 DC power supply 9 Resistance 10 Measuring circuit F Load V Detection voltage

Claims (6)

  Epichlorohydrin rubber and diene rubber as a rubber component, and a crosslinking component for crosslinking the rubber component, and the blending ratio of the epichlorohydrin rubber is 15% by mass or more and 80% by mass or less in the total amount of the rubber component A semiconductive roller comprising a cross-linked product of the rubber composition and having an oxide flame treatment film on the outer peripheral surface.   The semiconductive roller according to claim 1, wherein the crosslinking component is a thiourea crosslinking agent, a sulfur crosslinking agent, and an accelerator for both crosslinking agents. The outer peripheral surface has an arithmetic mean roughness Ra of a roughness curve defining surface roughness of 1.0 μm or more and 3.0 μm or less, an actual measurement value S of the surface area per unit area of the outer peripheral surface, and the outer peripheral surface 3. The semiconductive roller according to claim 1, wherein a ratio S / S ₀ to a theoretical value S ₀ of a surface area per unit area when assuming a smooth surface is 2.0 or more and 3.3 or less. .   The semiconductive roller according to any one of claims 1 to 3, wherein the semiconductive roller is incorporated in an image forming apparatus using an electrophotographic method and used as a charging roller for charging the surface of the photoreceptor.   The method for producing a semiconductive roller according to any one of claims 1 to 4, wherein the rubber composition is formed into a roller shape and crosslinked, and the outer peripheral surface of the crosslinked roller is oxidized. A method for producing a semiconductive roller, comprising a step of forming the oxidation flame-treated film on the outer peripheral surface by an oxidation flame treatment brought into contact with a flame.   The method for producing a semiconductive roller according to claim 5, wherein the oxidation flame treatment is performed by setting a temperature of the oxidation flame at a position in contact with the outer peripheral surface to 1300 ° C or higher and 1700 ° C or lower.

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