JP2006099036A - Semiconducting rubber member for electrophotography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconducting rubber member for electrophotography for a developing roller or the like, whose electrical resistance is uniform so that toner or the like is stuck evenly and uniformly, and which is highly superior in the imparting of electrifying characteristics to an adhesive matter, such as for toner and persistence. <P>SOLUTION: The semiconductive rubber member for electrophotography is a conductive rubber roller equipped with a conductive rubber layer including chloroprene rubber on its outermost layer, and its dielectric loss tangent, when AC voltage is applied, on the condition that the voltage be 5 V and the frequency be 100 Hz, is 0.1 to 1.8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductive rubber member used as a developing roller, a cleaning roller, a charging roller, a transfer roller and the like mounted on an electrophotographic apparatus, and more particularly, in an image forming mechanism of an electrophotographic apparatus such as a laser beam printer. As a non-magnetic one-component toner, the toner is preferably used for a developing roller that imparts high chargeability to the toner and adheres to the photoreceptor.

  In recent years, electrophotographic apparatuses such as laser printers are rapidly increasing in speed and image quality. In order to cope with this, the use of polymerized toners that are spherical and can be reduced in diameter has become widespread. As the polymerized toner, a one-component toner that does not use a carrier is used instead of a two-component toner composed of two types of carrier and toner made of ferrite powder or iron powder because the toner blending design is easy. It has been widely used. Accordingly, the developing roller that receives the toner and faithfully supplies the toner to the latent image drawn on the photoconductor is changing from the conventional magnet type to a semiconductive rubber roller having elasticity. is there.

  When a two-component toner using a carrier is used, it is relatively easy to convey the toner onto the photoreceptor due to electrical and magnetic action. However, when a non-magnetic one-component toner is used, the toner is magnetic. Such effects cannot be used for toner conveyance. For this reason, it is necessary that the surface of the developing roller serving as the electrode end face is uniformly formed. Further, in order to evenly adhere fine toner having a particle size of micron order evenly, an electrical characteristic represented by a resistance value is used so that a very uniform potential distribution is obtained when a bias potential is applied to the developing roller. The properties are required to be very uniform within the roller.

  In addition, since the one-component toner does not include a carrier, the developing roller is required to have a function of controlling the charging property of the toner. That is, in the developing roller, it is simultaneously required to impart chargeability to the toner and to maintain the imparted chargeability. If the charge amount of the toner is insufficient, the electrostatic force is insufficient and the toner cannot be faithfully conveyed to the latent image on the photoreceptor. Therefore, for example, various image defects such as density change due to the rotation of the developing roller, development ghost, and fogging may occur.

  Conventionally, various developing rollers have been proposed to meet the above requirements. For example, Japanese Patent Laid-Open No. 2002-194203 (Patent Document 1) proposes an electrophotographic rubber member made of a rubber material in which calcium carbonate having a limited particle diameter is dispersed in epichlorohydrin rubber, which is an ion conductive rubber. Yes. The rubber material improves uniformity by controlling electric resistance by ionic conduction rather than electronic conduction by a conductive filler, and further improves processing accuracy by a filler. However, it cannot be said that the chargeability to the toner and the sustainability of the chargeability are good, and there is a problem that a good image cannot be obtained when used as a developing roller.

  Japanese Patent Laid-Open No. 2001-357735 (Patent Document 2) proposes coating a treatment agent having an amine compound on the surface of a conductive member in order to control the chargeability of the toner. However, when a very high dimensional accuracy is required, such as a developing roller, not only a special device is required to perform surface treatment with high accuracy, but also the manufacturing yield becomes extremely low, resulting in an increase in manufacturing cost. Connected. Further, since the base material and the surface treatment coating agent are made of different materials, there is a problem of occurrence of peeling of the coating agent during production and use.

As described above, in order to impart high chargeability to the non-magnetic one-component toner, it is necessary to first maintain the ability of the developing roller to add charge to the toner and the added charge, but a coating layer is provided. Multi-layering leads to high costs, which is difficult in practice and causes the problem of peeling of the coating layer.
JP 2002-194203 A JP 2001-357735 A

  In the present invention, a coating layer is not provided to form a multilayer, and the electric resistance is uniform and the toner can be uniformly attached without unevenness. In addition, the charging property to the toner and the sustainability of the charging property are extremely high. It is an object to provide a semiconductive rubber member that is excellent and suitable for use as a developing roller at low cost.

  The present inventors have studied various materials. As a result, by using a rubber material containing chloroprene rubber as the outermost layer, an extremely high charge can be imparted to an adherent such as toner, and a voltage of 5 V and a frequency of It has been found that the leakage of charge applied to the toner can be prevented by adjusting the dielectric loss tangent when AC voltage is applied at 100 Hz to about 0.1 to 1.8.

A minute voltage of 5 V is applied as a dielectric tangent measurement condition when the semiconductive rubber member is a developing roller, when the developing roller holds the toner, or when the toner is conveyed to the photoreceptor. This is because a very small voltage fluctuation occurs.
The reason why the frequency is set to 100 Hz is that a low frequency of about 100 Hz matches the event extremely, considering the rotation speed of the developing roller, the nip with the photosensitive member, blade, and toner supply roller in contact with or close to the developing roller. is there.

By using chloroprene rubber using the conductive rubber layer as a rubber component, an extremely high charge can be imparted to the toner.
Chloroprene rubber is a polymer of chloroprene and is produced by emulsion polymerization, and is classified into a sulfur-modified type and a non-sulfur-modified type depending on the type of molecular weight regulator.
In the sulfur-modified type, a polymer obtained by copolymerizing sulfur and chloroprene is plasticized with thiuram disulfide or the like and adjusted to a predetermined Mooney viscosity.
Examples of non-sulfur-modified types include mercaptan-modified types and xanthogen-modified types. The mercaptan-modified type uses an alkyl mercaptan such as n-dodecyl mercaptan, tert-dodecyl mercaptan or octyl mercaptan as a molecular weight regulator. The xanthogen-modified type uses an alkyl xanthogen compound as a molecular weight regulator.
The chloroprene rubber is classified into a medium crystallization speed type, a low crystallization speed type, and a high crystallization speed type depending on the crystal acceleration of the produced chloroprene rubber.
In the present invention, any type may be used, but a type that is non-sulfur modified and has a low crystallization rate is preferred.
In the present invention, a rubber or elastomer having a structure similar to that of chloroprene rubber can be used as the chloroprene rubber. For example, a copolymer obtained by polymerizing a mixture of chloroprene and one or more other copolymerizable monomers may be used. Examples of monomers copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, sulfur, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene and acrylic. Examples include acids, methacrylic acid, and esters thereof.

  When the semiconductive rubber member of the present invention having the chloroprene rubber as a rubber component is used as a developing roller, the charge amount of the toner on the surface of the developing roller before contact with the photoreceptor can be maintained at a high level, and a high quality image can be obtained. Can be formed. Furthermore, the conductive rubber roller does not need to be provided with a surface coating layer to be multi-layered, and therefore can be manufactured at low cost without requiring special equipment and without reducing the yield of the product.

The content of the chloroprene rubber can be appropriately selected within a range of about 1 to 100 parts by weight with respect to 100 parts by weight of the rubber component. However, in view of the effect of imparting charging properties, it is preferable that the chloroprene rubber is contained in an amount of about 5 parts by weight or more with respect to 100 parts by weight of the rubber component. Furthermore, it is more preferable that it is contained in an amount of about 10 parts by weight or more from the viewpoint of rubber uniformity.
When the conductive rubber layer is a blend rubber of chloroprene rubber and other rubber, the other rubber includes epihalohydrin rubber (especially epichlorohydrin rubber), urethane rubber, acrylonitrile rubber, butadiene rubber, acrylonitrile butadiene rubber (NBR), styrene. Examples thereof include butadiene rubber, butyl rubber, fluorine rubber, isoprene rubber, rubber alone such as polyether rubber containing silicone rubber and ethylene oxide, or blended rubber thereof. Of these, blending with polar rubber, particularly NBR, is preferable from the viewpoint of suppressing the increase in hardness and reducing the temperature dependence.
Also, it is extremely preferable to blend an epihalohydrin rubber having high electrical conductivity and ionic conductivity or a polyether polymer containing ethylene oxide from the viewpoint of controlling to a predetermined resistance value.

  When NBR is blended with chloroprene rubber as a rubber component, the NBR content is about 5 to 50 parts by weight with respect to 100 parts by weight of the total rubber component. Since the toner charge amount is reduced, the NBR content is preferably about 50 parts by weight or less. In order to substantially suppress the increase in hardness and reduce the temperature dependence, the NBR content is about 5 parts. It is preferable that it is -20 weight part.

In particular, the semiconductive rubber member of the present invention suitably used as a developing roller has a dielectric loss tangent of about 0.1 to 1.8 when an AC voltage is applied at a voltage of 5 V and a frequency of 100 Hz, as described above.
In the electrical characteristics of a rubber roller, the dielectric loss tangent is an index indicating the degree of influence of electric flow (conductivity) and the capacitor component (capacitance), and is also a parameter indicating the phase delay when an alternating current is applied. The size of the capacitor component ratio when a voltage is applied is shown.
In other words, the dielectric loss tangent is expressed by the amount of charge generated when the toner contacts the developing roller at a high pressure by the amount regulating blade and the amount of charge that escapes onto the roller before being conveyed to the photosensitive member. It becomes an index indicating the charge amount.
When the dielectric loss tangent is large, it is easy to pass electricity (electric charge) and the polarization does not proceed easily. Conversely, when the dielectric loss tangent is small, it is difficult for electricity (electric charge) to pass therethrough and the polarization proceeds. Therefore, the smaller the dielectric loss tangent, the higher the capacitor-like characteristics of the roll, and the charge on the toner generated by frictional charging can be maintained without escaping from the roll. That is, chargeability can be added to the toner, and the added chargeability can be maintained. In order to obtain such an effect, the dielectric loss tangent is set to about 1.8 or less. In addition, in order to prevent the charge amount from being excessively increased and the printing density from being excessively decreased, and further to prevent the amount of the additive for adjusting the dielectric loss tangent from increasing and becoming hard, the dielectric loss tangent is set to about 0.1 or more. Yes.
More preferably, it is 0.3 or more, more preferably 0.5 or more, and a preferable upper limit is 1.5 or less, further 1.0 or less, and most preferably 0.8 or less.
The dielectric loss tangent is measured by the method described in the examples described later.

In order to control the dielectric loss tangent of the conductive rubber roller within the predetermined range, 5 to 70 parts by weight of carbon black is preferably mixed with 100 parts by weight of the rubber component of the conductive rubber layer.
Known carbon black is used as the carbon black, but it is preferable to use weakly conductive carbon black from the viewpoint of obtaining ionic conductivity.

The weakly conductive carbon black is a carbon black that has a large particle size, a small structure development, and a small contribution to conductivity, and by combining it, it acts as a capacitor by polarization without increasing conductivity. The chargeability can be controlled without impairing the uniformity of the electrical resistance.
If the weak conductive carbon black has a primary particle size of about 80 nm or more, preferably about 100 nm or more, the above effect can be obtained more effectively. Further, when the primary particle size is about 500 nm or less, preferably about 250 nm or less, the surface roughness can be extremely reduced. The weakly conductive carbon black is preferably spherical or nearly spherical because of its small surface area.
Various types of weakly conductive carbon black can be selected. Among them, carbon black produced by a furnace method or a thermal method that easily obtains a large particle size is preferable, and furnace carbon black is more preferable. In terms of carbon classification, SRF, FT, and MT are preferable. Carbon black used as a pigment may also be used.

In order to substantially exhibit the effect of reducing the dielectric loss tangent, the amount of carbon black is preferably about 5 parts by weight or more with respect to 100 parts by weight of the rubber component, as described above, and the hardness increases. In order to avoid the possibility of damaging other members that come into contact and to avoid a decrease in wear resistance, it is preferable that the amount is about 70 parts by weight or less as described above.
Further, in order to obtain a so-called ionic conductivity characteristic in which the voltage fluctuation of the roll resistance is small with respect to the applied voltage, the blending of about 70 parts by weight or less is preferable.

In the rubber roller as the developing roller of the present invention, as the electronic conductive agent, in addition to the above-described carbon black, carbon black having a particle diameter smaller than the carbon black, zinc oxide, potassium titanate, antimony-doped titanium oxide, tin oxide or Examples thereof include conductive metal oxides such as graphite or carbon fibers.
In order for the rubber roller of the present invention to obtain electronic conductive properties, it is not preferable to use the aforementioned weakly conductive carbon black. This is because the conductivity is extremely low. However, you may use together with the said electronic conductive agent for the purpose of lowering | hanging a dielectric loss tangent more, and improving grindability and extrudability.

In order to make the resistance value of the conductive rubber layer uniform, a rubber component having ionic conductivity is preferably used. In that case, weakly conductive carbon black is used as the carbon black, and its blending amount is 100 weight of the rubber component. About 10 to 70 parts by weight, preferably about 20 to 65 parts by weight, more preferably about 25 to 60 parts by weight of furnace carbon black based on 100 parts by weight of the rubber component.
Since such carbon has a relatively large particle size and a spherical shape, it is nano-dispersed uniformly within the rubber. Therefore, even if the rubber is not coated, it can be made uniform and highly dielectric.
On the other hand, when the conductive rubber layer is not ionic conductive, it is preferable to use a known conductive carbon black such as ketjen black, furnace black or acetylene black and the aforementioned weak conductive carbon black in combination. . Of these, the blending amount of the conductive carbon black is preferably about 10 to 20 parts by weight with respect to 100 parts by weight of the rubber component.

  The dielectric loss tangent can also be controlled within the predetermined range by blending the conductive rubber layer with calcium carbonate treated with fatty acid. The fatty acid-treated calcium carbonate has a higher activity than ordinary calcium carbonate due to the presence of the fatty acid at the interface of calcium carbonate, and is easily slippery, so that high dispersion can be realized easily and stably. When the polarization action is promoted by the fatty acid treatment, the function of the capacitor in the rubber is strengthened by the action of the two actions, so that the dielectric loss tangent can be efficiently reduced. As the calcium carbonate subjected to the fatty acid treatment, those in which a fatty acid such as stearic acid is coated on the entire surface of the calcium carbonate particles are preferable. The compounding amount of the fatty acid-treated calcium carbonate is about 30 to 80 parts by weight, preferably about 40 to 70 parts by weight with respect to 100 parts by weight of the rubber component. In order to substantially exhibit the effect of reducing the dielectric loss tangent, the amount is preferably about 30 parts by weight or more, and in order to avoid an increase in hardness and a variation in resistance, it is preferably about 80 parts by weight or less.

As described above, the conductive rubber layer in the present invention may have either ionic conductivity, electronic conductivity, or a combination of both. Since the rubber component of the conductive rubber layer in the present invention is ionic conductive from the viewpoint that more uniform electrical characteristics can be obtained, the resistance value when applying 500V is R500, and the resistance value when applying 100V is R100. More preferably, R100) −log (R500) <about 0.5. This clarifies the uniformity of the electrical characteristics of the conductive rubber roller by using the difference from the resistance value when a voltage of 100 V is applied as an index with reference to the resistance value when a voltage of 500 V is applied, which is close to the developing bias. Thus, it is preferable that the conductive rubber layer in the present invention has ionic conductivity with small voltage dependency.
Usually, the value of the above formula is 1 or more when depending on electronic conduction such as carbon black. In addition, the measuring method of resistance value is as having described in the following Example.

In order to make the rubber component of the conductive rubber layer ion conductive, a known method such as a method of blending an ion conductive rubber or a method of adding an ion conductive agent is used. Examples of the ion conductive rubber include a rubber material having a polar group in the composition. Specifically, the above-described epihalohydrin rubber (particularly epichlorohydrin rubber) and an elastomer containing ethylene oxide are preferably used. Specifically, epichlorohydrin (EP) homopolymer rubber, epichlorohydrin-ethylene oxide (EO) copolymer, epichlorohydrin-propylene oxide (PO) copolymer, epichlorohydrin-allyl glycidyl ether (AGE) copolymer, epichlorohydrin-ethylene Examples thereof include an oxide-allyl glycidyl ether copolymer, an epichlorohydrin-propylene oxide-allyl glycidyl ether copolymer, an epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether copolymer, and the like.
When blending such an ion conductive rubber, the content of chloroprene rubber is preferably about 90 parts by weight or less, more preferably about 75 parts by weight or less, and still more preferably about 60 parts by weight with respect to 100 parts by weight of the rubber component. It is as follows. Further, from the viewpoint of the charging effect, the content of the chloroprene rubber is about 5 parts by weight or more, preferably about 10 parts by weight or more with respect to 100 parts by weight of the rubber component. The above is preferable.

As described above, it is preferable that the conductive rubber layer includes a rubber in which the constituent monomer includes ethylene oxide and epichlorohydrin is selectively blended.
In that case, it is preferable that the total mol% of the chloroprene monomer and epichlorohydrin constituting the chloroprene rubber is larger than the mol% of ethylene oxide.
Moreover, it is preferable that mol% of the chloroprene monomer constituting the chloroprene rubber is larger than mol% of epichlorohydrin.
Furthermore, it is preferable that mol% of the chloroprene monomer constituting the chloroprene rubber is larger than mol% of ethylene oxide.

  Further, the semiconductive rubber member used as the developing roller or the like of the present invention is not particularly limited as long as it has at least the conductive rubber layer as the outermost layer, and has a multilayer structure such as two layers according to the required performance. However, a structure composed of a single layer of a conductive rubber layer is preferable because it can be manufactured at low cost with little variation in physical properties.

Therefore, the semiconductive rubber member used as the developing roller or the like of the present invention is composed of a single layer composed of only the conductive rubber layer, and the outermost surface of the conductive rubber layer is formed into an oxide film by ultraviolet irradiation or / and ozone irradiation. It is preferable.
Since the oxide film becomes a dielectric layer and the dielectric loss tangent of the rubber roller can be reduced, the dielectric loss tangent can be easily controlled within a predetermined range. Further, since the oxide film becomes a low friction layer, toner separation is improved and image formation is easily performed, and as a result, a better image can be obtained.
As the oxide film, an oxide film having many C═O groups or C—O groups is preferable. As described above, the oxide film is formed by subjecting the surface of the conductive rubber layer to a treatment such as ultraviolet irradiation and / or ozone irradiation to oxidize the surface layer portion of the conductive rubber layer. In particular, it is preferable to form an oxide film by ultraviolet irradiation because the processing time is fast and the cost is low.
The treatment for forming the oxide film can be performed according to a known method. For example, in the case of performing ultraviolet irradiation, although depending on the distance between the surface of the rubber layer and the ultraviolet lamp, the type of rubber, and the like, the wavelength of the ultraviolet light is about 100 to 400 nm, more preferably about 100 to 200 nm. It is preferable to irradiate while rotating the rubber roller for about 1 minute, preferably about 1 to 10 minutes. However, the intensity of ultraviolet rays and the irradiation conditions (time, bath temperature, distance) must be selected so that the dielectric loss tangent can be controlled within the range defined by the present invention.
In addition, when ultraviolet irradiation is performed, it is preferable to mix 50 parts by weight or less of rubber that is easily deteriorated by ultraviolet rays such as NBR. Addition of chloroprene and chloroprene rubber is particularly effective when irradiated with ultraviolet rays.

  Log resistance (R50a) −log (R50) = approx. R50 when the roller resistance when the voltage 50V is applied to the conductive rubber roller before the oxide film formation is R50 and the roller resistance at the applied voltage 50V after the oxide film formation is R50a. A value of about 0.2 to 1.5 is preferable from the viewpoints of improvement in durability, reduction in resistance change when the roller is used, reduction in stress on the toner, and measures against collapse of the photoreceptor. Since the roller resistance at a low voltage of 50 V, at which a voltage can be stably loaded, is used as an index value, a minute increase in resistance due to oxide film formation can be accurately captured. The lower limit is preferably 0.3, particularly 0.5, and the upper limit is preferably 1.2, particularly 1.0.

  The conductive rubber layer in the present invention preferably contains an acid acceptor so as not to leave chlorine-based gas such as HCl generated during rubber vulcanization and to prevent contamination of the photoreceptor. As the acid acceptor, various substances acting as an acid acceptor can be used, but hydrotalcite is preferable because of its excellent dispersibility. Further, when used in combination with magnesium oxide or potassium oxide, a high acid receiving effect can be obtained, and contamination of the photoreceptor can be more reliably prevented. The hydrotalcite is preferably blended at a ratio of about 1 part by weight or more and about 10 parts by weight or less with respect to 100 parts by weight of the rubber component. The amount of the acid acceptor is preferably about 1 part by weight or more in order to effectively exhibit the above effect, and about an amount of about 10% by weight in order to prevent an increase in hardness and to prevent a large amount of chlorine-based gas and unreacted acid acceptor from remaining. The amount is preferably 10 parts by weight or less.

Various additives may be included as long as the object of the present invention is not adversely affected. Examples of the additives include vulcanizing agents, processing aids, plasticizers, anti-aging agents such as anti-aging agents, and ionic conductive agents.
As the vulcanizing agent, sulfur, thiourea, triazine derivative, peroxide, various monomers and the like can be used. These may be used alone or in combination of two or more. Examples of the sulfur-based vulcanizing agent include powdered sulfur, organic sulfur-containing compounds such as tetramethylthiuram disulfide or N, N-dithiobismorpholine. The thiourea vulcanizing agent is selected from the group consisting of tetramethylthiourea, trimethylthiourea, ethylenethiourea, and (CnH2n + 1NH) 2C = S (wherein n represents an integer of 1 to 10). One or more thioureas can be used. Examples of the peroxide include benzoyl peroxide. The addition amount of the vulcanizing agent is preferably about 0.2 parts by weight or more and about 5 parts by weight or less, more preferably about 1 part by weight or more and about 3 parts by weight or less with respect to 100 parts by weight of the rubber component.

  In the present invention, a thiourea vulcanizing agent is preferably used as the vulcanizing agent, and ethylene thiourea is more preferably used. By vulcanizing with a thiourea vulcanizing agent, particularly ethylene thiourea, and adjusting the compression set to about 10% or less, preferably about 5% or less, it is possible to easily ensure accuracy during polishing. In addition, a product that can withstand storage in a high temperature environment with little sag during transportation is obtained. Furthermore, there is an advantage that an oxide film can be easily formed by ultraviolet rays. In this case, the thiourea vulcanizing agent or the triazine vulcanizing agent is preferably about 0.2 parts by weight or more and about 3 parts by weight or less, more preferably about 1 part by weight or more and about 2 parts by weight with respect to 100 parts by weight of the rubber component. It mix | blends in the following ratios.

Examples of the plasticizer include various plasticizers and waxes such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), and tricresyl phosphate, and examples of the processing aid include fatty acids such as stearic acid.
These plastic components are preferably blended at a ratio of about 5 parts by weight or less with respect to 100 parts by weight of the rubber component of the rubber layer. This is to prevent bleeding when forming the oxide film and contamination of the photoconductor when the printer is mounted or operated. For this reason, the use of polar wax is most preferred.
Examples of the deterioration preventing agent include various anti-aging agents. In particular, when NBR rubber or the like is added to adjust rubber hardness or improve workability, it is preferable to add an antioxidant as an anti-aging agent according to the amount added. In the case of using an antioxidant, it is preferable to appropriately select the blending amount so that the formation of an oxide film on the surface layer portion to be applied as desired proceeds efficiently. In contrast to the addition of these various additives, surface treatment such as UV irradiation is effective in preventing exudation of the various additives added.

In order to adjust the resistance value, an ionic conductive agent may be added in addition to the addition of the electronic conductive agent and the blend of the ionic conductive rubber.
Various ion conductive agents can be selected, and addition of 0.1 to 5 parts is preferable. For example, as a salt having an anion having a fluoro group (F—) and a sulfonyl group (—SO ₂ —), bisfluoroalkylsulfonyl It preferably contains at least one salt selected from the group consisting of an imide salt, a tris (fluoroalkylsulfonyl) methane salt, or a fluoroalkylsulfonic acid salt.
The salt described above has a high degree of dissociation in polyethylene oxide since the anion is stable because charges are delocalized by a strong electron-attracting effect, and a particularly high ionic conductivity can be realized. Thus, by blending a salt having an anion having a fluoro group (F—) and a sulfonyl group (—SO ₂ —), it becomes possible to efficiently realize a low electric resistance. By appropriately adjusting the blending of these, it is possible to suppress the problem of photoconductor contamination while maintaining low electrical resistance.

In addition, as a salt having an anion having an upper fluoro group (F—) and a sulfonyl group (—SO ₂ —), a lithium salt is preferable, but a salt of an alkali metal, a group 2A, or other metal, etc. However, a salt having an anion as shown by the following chemical formulas (Chemical Formula 1 and Chemical Formula 2) may be used.
In the following formula, R _{1 to} R ₆ are each an alkyl group having 1 to 20 carbon atoms or a derivative thereof, and R _{1 to} R ₄ , and R ₅ and R ₆ may be the same or different. Among these, a quaternary ammonium cation of trimethyl type in which three of R _{1 to} R ₄ are methyl groups, and the other is an alkyl group having 4 to 20 carbon atoms, preferably 8 to 20 carbon atoms, or a derivative thereof. The salt consisting of is particularly preferred because the positive charge on the nitrogen atom can be stabilized by three methyl groups having strong electron donating properties, and the compatibility with the polymer can be improved by other alkyl groups or derivatives thereof. In addition, in the cation of the formula 2, it is desirable that R ₅ or R ₆ is a methyl group or an ethyl group because it is easier to stabilize the positive charge on the nitrogen atom if it has an electron donating property. In this way, by stabilizing the positive charge on the nitrogen atom, the stability as a cation can be increased, and the salt can have a higher degree of dissociation and thus excellent conductivity imparting performance.

Specifically, a fluoro group (F-) and a sulfonyl group (-SO ₂ -) Salts having anions having, for _{example, LiCF 9 SO 3, LiN (} SO 2 CF 3) 2, LiC (SO _{2 CF 3), LiCH (SO} 2 CF 3) 2, LiSF 6 CF 2 SO 3 and the like.

Incidentally, a fluoro group (F-) and a sulfonyl group (-SO 2 _-) salts with anions with are preferably uniformly dispersed in the conductive elastomer braid. Of the above-mentioned salts, bisfluoroalkylsulfonylimide salts such as LiN (S0 ₂ CF ₃ ) ₂ have extremely good solubility in polyethylene oxide chains and the like, and can further plasticize polyethylene oxide chains and the like. Therefore, the addition can reduce the hardness and can reduce the ring-ring dependency of the volume resistivity, which is very preferable. In particular, lithium-bis (trifluoromethanesulfonylimide (LiN (SO ₂ CF ₃ ) ₂ ) can be easily and uniformly dispersed by adding it directly to an ion conductive rubber such as an epihalohydrin rubber. Can be improved, and the hardness is hardly affected.
In addition to the above, borates, lithium salts, ammonium salts and the like can also be added. In particular, by using chloroprene, compatibility with chlorine-based and halogen-based salts is good. For example, it is highly stabilized with aumonium perchlorate, boron-based salt, and imidolithium salt. Can be suppressed and contamination of the photoreceptor can be prevented. In addition, surface treatment such as UV irradiation increases the hardness of the surface layer, and the density increases due to oxidation or the like. Further, the exudation of these additives can be prevented, and an extremely good rubber roller can be obtained. Can be formed.

When the semiconductive rubber member of the present invention is used as a developing roller, the roller resistance value at an applied voltage of 500 V is about 10 ⁵ to 10 ⁸ Ω, preferably about 10 ⁵ to 10 ⁷ Ω.
The roller resistance is preferably about 10 ⁵ Ω or more in order to control the flowing current to suppress the occurrence of image defects and prevent discharge to the photoreceptor. In order to maintain the efficiency of toner supply and the like, and to prevent the toner from being reliably transferred from the developing roll to the photosensitive member after the voltage drop of the developing roller occurs when the toner moves to the photosensitive member, a roller is used. The resistance value is preferably about 10 ⁸ Ω or less. Further, if it is 10 ⁷ Ω or less, it can be used in a wider range of environments and is extremely useful.

Further, when the semiconductive rubber member of the present invention is used as a developing roller, the JIS A (K-6253) hardness is preferably about 75 degrees or less, more preferably about 70 degrees or less, and low hardness. However, it is preferably 50 degrees or more from the viewpoint of ensuring wear resistance and polishing accuracy because it is used without being coated. However, when surface treatment such as UV irradiation is performed, even lower hardness is possible, and good characteristics are obtained in terms of wear resistance even at 40 degrees or more.
Further, the compression set in a standing test under a high temperature environment of 50 ° C. is preferably about 10% or less, and more preferably about 5% or less. If the compression set is within the above range, a nip mark hardly remains in the nip portion between the regulating blade and the developing roll.
Furthermore, the charge amount in the measurement described later is 20 μC / g or more, more preferably 28.5 μC / g or more.

  Further, when the semiconductive rubber member of the present invention is used as a developing roller, a cleaning roller, a charging roller, or a transfer roller, a cored bar is attached and used. Examples of the core metal include a metal core made of metal such as aluminum, aluminum alloy, SUS or iron, or ceramic. In the developing roller, the thickness of the conductive rubber layer is preferably about 0.5 to 10 mm, more preferably about 1 to 7 mm. In order to obtain an appropriate nip and rubber elasticity effect, the wall thickness is preferably about 0.5 mm or more, and in order to reduce the size and weight, the wall thickness is preferably about 10 mm or less.

The developing roller of the present invention is used in an image forming mechanism of an electrophotographic apparatus in OA equipment such as a laser beam printer, an ink jet printer, a copying machine, a facsimile, or an ATM.
Specifically, it is suitably used as a developing roller for adhering non-magnetic one-component toner having positive charging property to the photoreceptor.
Since chloroprene contained in the conductive rubber layer of the developing roller of the present invention has a very high positive charge imparting property due to its rubber structure, it is preferably used for toner having positive chargeability. The developing method in the image forming mechanism of the electrophotographic apparatus is roughly classified into a contact type or a non-contact type when classified according to the relationship between the photosensitive member and the developing roll, but the conductive roller of the present invention can be used in any method. In particular, it is preferable that the developing roller of the present invention is almost in contact with the photoreceptor.
In addition to the developing roller, a charging roll for uniformly charging the photosensitive drum, a transfer roll for transferring the toner image from the photosensitive member to a transfer belt or paper, a toner supply roll for transferring the toner, a transfer It can also be used as a drive roll for driving the belt from the inside.
When used for a cleaning roller that cleans toner on the photoreceptor or transfer belt, the toner to be cleaned can be electrostatically adsorbed and discharged, and is especially suitable for a mechanism that collects toner in a collecting machine using electrostatic force. .
Furthermore, it can be suitably used as a cleaning blade and a transfer drum.

  In the semiconductive rubber member used as the developing roller or the like of the present invention, a rubber material containing chloroprene rubber can be used for the outermost layer, so that an extremely high charge can be imparted to an adherent such as toner, and a voltage of 5 V, frequency By adjusting the dielectric loss tangent when an AC voltage is applied at 100 Hz to about 0.1 to 1.8, leakage of charges applied to the toner can be prevented. As a result, the charge amount on the deposit such as toner can be maintained at a high level, and the electrophotographic apparatus provided with the semiconductive rubber member such as the developing roller of the present invention can form a high quality image. Further, the developing roller can be manufactured at low cost without requiring special equipment as in the case of surface multi-layer technology such as surface coating and without reducing the yield of products.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, a conductive rubber roller 10 used as a developing roller includes a cylindrical rubber layer 1 having a thickness of 10 mm and a cylindrical core metal (shaft) 2 having a diameter of 10 mm that is press-fitted into the hollow portion. It has.
The rubber layer 1 and the core metal 2 are joined with a conductive adhesive. An oxide film 1a is formed on the surface layer of the rubber layer 1 by irradiating the rubber with ultraviolet rays.

The rubber layer 1 contains about 10 to 90 parts by weight of chloroprene rubber as a rubber component with respect to 100 parts by weight of the total rubber component, and blends epichlorohydrin rubber having ionic conductivity.
Furthermore, carbon black is blended in order to adjust the dielectric loss tangent within a predetermined range, and the blending amount is 20 to 70 parts by weight with respect to 100 parts by weight of the rubber component.
Further, a thiourea vulcanizing agent (ethylene thiourea) is blended as a vulcanizing agent, and 1 to 10 parts by weight is blended with respect to 100 parts by weight of the rubber component using hydrosartite as an acid acceptor. Prevents contamination.

  The conductive rubber roller used as the developing roller of the present invention is manufactured by the following method. After kneading the above rubber composition, it is extruded into a cylindrical shape with an extruder and preformed, and this is cut into a predetermined size to obtain a preform. This preform is put into a vulcanizing can and vulcanized at a temperature at which the rubber component is crosslinked. After vulcanization, the cored bar is mounted in a cylindrical rubber layer to form a roller.

Further, an oxide film 1a is formed on the surface layer portion of the conductive rubber layer. Note that the oxide film is not necessarily provided.
The oxide film 1a is polished on a roller surface with a cylindrical polishing machine, mirror-finished so that the roller surface roughness Rz is about 6.5 μm or less, preferably about 3 to 5 μm, washed with water, and then irradiated with ultraviolet rays. The film is irradiated with ultraviolet rays (184.9 nm) to form an oxide film.
Specifically, ultraviolet rays are irradiated every 90 degrees in the circumferential direction of the roller for a predetermined time, preferably about 1 to 15 minutes, more preferably about 5 to 10 minutes, and the roller is rotated four times in total in the circumferential direction. An oxide film is formed.

The developing roller made of the conductive rubber roller of the present invention obtained as described above has a dielectric loss tangent of about 0.1 to 1.8 when an AC voltage is applied at a voltage of 5 V and a frequency of 100 Hz.
Further, the roller resistance value at an applied voltage of 500 V is set to about 10 ⁵ to 10 ⁸ Ω, and the JISA hardness is set to about 65 degrees or less. Further, the compression set in a standing test under a high temperature environment of 50 ° C. is about 10% or less, and the charge amount measured by the method described in the following examples is about 20 μC / g or more.

"Examples 1-8, Comparative Examples 1-3"
The compounding materials described below and in Table 1 (the values in the table indicate parts by weight) were kneaded with a Banbury mixer, and then extruded into a tube shape having an outer diameter of φ22 mm and an inner diameter of φ9.5 mm using an extruder. . The tube is attached to a vulcanizing shaft, vulcanized in a vulcanizing can at 160 ° C. for 1 hour, and then attached to a φ10 mm shaft coated with a conductive adhesive and adhered in an oven at 160 ° C. did. Thereafter, the end portion was molded, traverse polishing was performed with a cylindrical polishing machine, and then mirror polishing was performed as final polishing to obtain a conductive rubber roller having a diameter of 20 mm (tolerance 0.05). The surface roughness Rz of the obtained conductive rubber roller was 3 to 5 μm. The surface roughness Rz was measured according to JIS B 0601 (1994).

  After washing the roller surface with water, in Examples 2, 3, 5, 6, 7 and Comparative Examples 1 and 3, ultraviolet rays were irradiated to form an oxide layer on the surface layer portion. This uses an ultraviolet irradiator (“PL21-200” manufactured by Sen Special Light Source Co., Ltd.), and the distance between the roller and the ultraviolet lamp is 10 cm, and ultraviolet rays (wavelengths 184.9 nm and 253.7 nm) are emitted every 90 degrees in the circumferential direction. Irradiation was performed for a predetermined time, and the roller was rotated four times by 90 degrees to form an oxide film on the entire circumference of the roller (360 degrees). The irradiation time in Table 1 and Table 2 refers to the irradiation time per surface (90 degree range).

The following components were used as constituent components in the conductive rubber rollers of the examples and comparative examples.
(A) Rubber component, chloroprene rubber; “Shoprene WRT” manufactured by Showa Denko K.K.
Epichlorohydrin rubber (GECO); “Epichromer CG102” manufactured by Daiso Corporation (the rubber component is ethylene oxide (EO) / epichlorohydrin (EP) / allyl glycidyl ether (AGE) copolymerization ratio of 56 mol% / 40 mol%) / 4 mol% epichlorohydrin polymer)
・ Epichlorohydrin rubber (ECO); “Epichromer D” manufactured by Daiso Corporation
EO (ethylene oxide) / EP (epichlorohydrin) = 61 mol% / 39 mol%)
-Acrylonitrile butadiene rubber (NBR); "Nippol 401 LL" manufactured by Nippon Zeon Co., Ltd.
-Polyether polymer: "Zeospan ZSN8030" manufactured by Nippon Zeon Co., Ltd.
EO (ethylene oxide) / PO (propylene oxide) / AGE (allyl glycidyl ether) = 90 mol% / 4 mol% / 6 mol%
(B) Other components, powdered sulfur (vulcanizing agent)
・ Ethylenethiourea (vulcanizing agent); “Axel 22-S” manufactured by Kawaguchi Chemical Industry Co., Ltd.
-Hydrotalcite (acid acceptor); "DHT-4A-2" manufactured by Kyowa Chemical Industry Co., Ltd.
Conductive carbon black; “Seast 3” manufactured by Tokai Carbon Co., Ltd. (Example 1)
Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd. (Comparative Example 3)
・ Low-electricity carbon black: “Asahi # 15 (average primary particle size 122 nm)” manufactured by Asahi Carbon Co., Ltd.
・ Calcium carbonate: Maruo Calcium Co., Ltd. “Super S”

  The following characteristic measurements were performed on the conductive rubber rollers of the above examples and comparative examples. The results are shown in Tables 1 and 2.

"Measurement of roller electrical resistance"
As shown in FIG. 2, the rubber layer 1 through the metal core 2 is abutted and mounted on the aluminum drum 3, and the tip of the lead wire of the internal resistance r (100Ω) connected to the + side of the power source 4 is connected to the aluminum drum 3 Measurement was performed by connecting the end of the conductive wire connected to the end face and connected to the negative side of the power source 4 to the other end face of the conductive roller 1.
The voltage applied to the internal resistance r of the wire was detected and used as the detection voltage V. Assuming that the applied voltage is E in this apparatus, the roller resistance R is R = r × E / (V−r), but this time the term −r is regarded as very small and R = r × E / V. Measure 100 detection voltages V over 4 seconds when applied voltage E is 500V or 100V with 500g load F applied to both ends of core 2 and rotate at 30rpm, and calculate R by the above formula did. The above measurement was performed under constant temperature and humidity conditions of a temperature of 23 ° C. and a relative humidity of 55%.

"Measurement of dielectric loss tangent"
As shown in FIG. 3, the metal plate 53 on which the rubber roller 51 is placed and the shaft 52 are used as electrodes, an AC voltage of 5V and 100 Hz is applied to the rubber roller 51, and an LCR meter (“AG” manufactured by Ando Electric Co., Ltd.) is applied. -4311B "), the R (resistance) component and the C (capacitor) component were separated and measured. From the values of R and C, the dielectric loss tangent was obtained by the following equation. The measurement temperature was 23 ° C. to 24 ° C. (room temperature).
Dissipation factor (tan δ) = G / (ωC)
G = 1 / R
Thus, the dielectric loss tangent is a value obtained as G / ωC when the electrical characteristics of one roller are modeled as two types of parallel equivalent circuits of a roller resistance component and a capacitor component.

"Evaluation of toner chargeability"
In order to investigate toner separation, toner charging uniformity and stability over time (durability), each rubber roller of the examples and comparative examples was developed on a commercially available laser printer (commercial printer using a non-magnetic one-component toner) as a developing roller. As a result, the performance was evaluated. Specifically, a 25% halftone image was printed after 5% printing of 100 sheets, and the uneven density was observed. In addition, a decrease in density due to the rotation of the roller was also observed.
After printing a 25% halftone image, the charge amount of the toner at that stage was measured and used as an evaluation parameter. Specifically, after printing a 25% halftone image, the cartridge is removed from the laser printer, and a suction-type charge measuring machine (Q / m METER Model 210HS manufactured by Trek Co., Ltd.) is applied from above to the developing roller mounted on the cartridge. -2 "), the toner was sucked, and the charge amount (μC) and the toner weight (g) were measured. The amount of static electricity per weight was calculated as the toner charge amount (μC / g). That is, toner charge amount (μC / g) = charge amount (μC) / toner weight (g).

As shown in Table 1, the rubber rollers of Examples 1 to 8 have very small values of dielectric loss tangent values in the range of 0.1 to 1.8. For this reason, there was no problem in the result of image evaluation, the value of the charge amount was large, and it was confirmed that the developing roller showed good charging characteristics and was excellent in practicality.
On the other hand, Comparative Examples 1 to 3 did not use chloroprene rubber as the rubber component, and only epichlorohydrin rubber (ECO) was used, so that the toner chargeability was low. Further, in Comparative Example 2, since ordinary calcium carbonate was used as the filler, the toner charge amount was reduced, and as a result, the density of one round of the roller was extremely high, and the density was greatly reduced as the roller was cycled. In Comparative Example 2, the dielectric loss tangent was 1.7, which was within the range of the present invention, but the toner chargeability was low because chloroprene rubber was not blended.
In Comparative Example 3, in which only carbon black was used as the conductive agent, the value of the dielectric loss tangent was as small as 0.48, and as a result, although the toner charge amount was large, unevenness in density on the printed surface was generated and the image evaluation was It was not good.
From the above results, it was confirmed that the toner charge amount can be improved by increasing the content of chloroprene. On the other hand, by blending with epichlorohydrin rubber, it can be confirmed that the resistance value of the rubber can be homogenized and density unevenness can be reduced. Particularly, when it is made ionic conductive, the density unevenness can be almost eliminated, and an extremely good developing roller. Was created.

"Tensile strength"
For the conductive rubber materials of Examples 2 to 4 and Comparative Example 1, tensile strength was measured according to JIS K 6251. As a result, while the tensile strength of the conductive rubber material of Comparative Example 1 was 9 MPa, the tensile strengths of the conductive rubber materials of Examples 2 to 4, 6, and 7 were as extremely high as 12 to 17 MPa. It was confirmed that the use of chloroprene was very useful in terms of durability in terms of strength.

Further, from Examples 7 and 8 in which chloroprene rubber constituting chloroprene rubber, epichlorohydrin rubber (ECO) and polyether polymer were blended, when the above components were blended in three ways, for example, a binary blend of chloroprene rubber and epichlorohydrin was obtained. On the other hand, the dispersion state of the rubber as an island was good and uniform.
The mixing degree of the filler, in particular, the dielectric loss tangent adjusting material varies depending on the rubber type blended. That is, by making the dispersibility of the rubber good, even if the dielectric loss tangent adjusting material is blended with rubber, the rubber can be uniformly dispersed throughout the rubber, and the rubber roller can be evenly and highly designed as designed. Furthermore, it was confirmed that the wear resistance was extremely good because the rubber was well dispersed.

  Further, in Example 5 in which chloroprene rubber, epichlorohydrin rubber (GECO) and NBR were blended, NBR having the same polarity was blended with chloroprene and epichlorohydrin rubber, so that the three are extremely easy to cross. As a result, a uniform rubber dispersion state was realized, and the same or higher wear resistance as in Examples 7 and 8 was obtained. It was also confirmed that the processability was excellent because the viscosity of the rubber could be reduced.

In Examples 2, 3, 7, and 8, the total mol% of the chloroprene monomer and epichlorohydrin constituting the chloroprene rubber is set larger than the mol% of ethylene oxide.
In Examples 3, 7, and 8, the mol% of the chloroprene monomer constituting the chloroprene rubber is set larger than the mol% of epichlorohydrin.
In Examples 3 and 8, the mol% of the chloroprene monomer constituting the chloroprene rubber is larger than the mol% of ethylene oxide.
In Examples 2, 3, 7, and 8, it was confirmed that the toner charge amount can be increased by employing the above-described configuration.
Specifically, in Example 2, at least a sufficient chargeability was obtained with the addition amount of chloroprene rubber.
In Example 3, UV irradiation was performed, but extremely high chargeability was obtained.
In Example 7, chargeability higher than that in Example 2 was easily obtained.
In Example 8, high chargeability as in Example 7 was obtained without UV irradiation.

  Although not exemplified as an example, when liquid NBR (for example, “Nippol DN223” manufactured by Nippon Zeon Co., Ltd.) or a polyether polymer is blended, in Example 6 to which salt is added, the liquid NBR is extremely increased. It has been found that the durability of the seal portion becomes extremely high due to the effect of lowering the hardness by the addition of and the effect of lowering the density by a polyether polymer having a low density. In this experiment, it is preferable to add 3 to 25 parts by weight, more preferably 5 to 20 parts by weight, and most preferably 5 to 15 parts by weight to optimize the balance between durability and chargeability. I found something I could do.

It is the schematic of the conductive rubber roller of this invention. It is a figure which shows the measuring method of the electrical resistance of a conductive rubber roller. It is a figure which shows the measuring method of the dielectric loss tangent of a conductive rubber roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive rubber layer 2 Core metal 10 Conductive rubber roller

Claims (9)

  A conductive rubber layer containing chloroprene rubber is provided on the outermost layer, and a dielectric loss tangent when an AC voltage is applied at a voltage of 5 V and a frequency of 100 Hz is 0.1 to 1.8. Rubber material.   The semiconductive rubber member according to claim 1, wherein the conductive rubber layer contains 5 to 70 parts by weight of carbon black with respect to 100 parts by weight of the rubber component.   The semiconductive rubber member according to claim 1 or 2, wherein the rubber component of the conductive rubber layer has ionic conductivity.   4. The conductive rubber layer according to claim 1, wherein the conductive rubber layer is a single layer, and an outermost surface of the conductive rubber layer is an oxide film by ultraviolet irradiation or / and ozone irradiation. Semiconductive rubber member.   The semiconductive rubber member according to any one of claims 1 to 4, wherein the conductive rubber layer contains 1 to 10 parts by weight of hydrosartite with respect to 100 parts by weight of the rubber component.   The semiconductive rubber according to any one of claims 1 to 5, wherein the conductive rubber layer contains a rubber in which a monomer constituting the oxide contains ethylene oxide and epichlorohydrin is selectively blended. Element. The semiconductive rubber member according to any one of claims 1 to 6, which has a resistance value of 10 ⁵ to 10 ⁸ Ω.   The semiconductive rubber member according to any one of claims 1 to 7, wherein the semiconductive rubber member is a developing roller, a cleaning roller, a charging roller, a transfer roller, a cleaning blade, or a transfer drum.   The semiconductive rubber member according to claim 8, wherein the developing roller adheres a non-magnetic one-component toner having a positive charging property to the photosensitive member.

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