JP2007138034A - Conductive elastomer member for electrophotography apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive member for electrophotography, which can control the formation of compression set despite low hardness, can prevent the formation of image defects in an electrophotographic apparatus, can improve the irregularity of electric resistance, when containing a conductive filler, can maintain low hardness, can inhibit increase in viscosity in an unvulcanized state, and can improve processability, and to provide a method for producing the same. <P>SOLUTION: This conductive elastomer member for the electrophotography is characterized by comprising a conductive elastomer which comprises a matrix phase containing an elastomer and a domain phase containing rubber particles obtained by a radiation crosslinking treatment. The rubber particles preferably have an average particle diameter of 50 to 500 nm, and preferably contains an adhesion-preventing agent close to the surfaces. The matrix phase preferably contains a conductive filler, and the conductive elastomer preferably has a highly releasable layer on the surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive elastic member for an electrophotographic apparatus such as a roller, a blade, a brush, a belt, a sheet, and a chip used for a developing member, a charging member, a transfer member, and the like used in an electrophotographic apparatus.

  Conventionally, various methods are known as electrophotographic methods. Generally, in an electrophotographic apparatus, an electric latent image is formed on a charged body (photosensitive body) such as a photosensitive drum using a photoconductive substance. Then, the latent image is developed with toner to form a visible image (development process), and the toner is transferred to a transfer material such as paper as necessary (transfer process). Thereafter, the toner on the transfer material is fixed by heat, pressure or the like (fixing step) to form an image. In addition, it is known that an image is formed with a main process of removing toner particles remaining on a charged body without being transferred onto a transfer material from the charged body by various means (cleaning process). Yes.

  In such an electrophotographic apparatus, various conductive members such as a roller, a blade, a brush, a belt, a film, a sheet, and a chip are formed in a process such as formation of a latent image and charging, development, and transfer accompanied by toner movement. It is used facing the surface of the object to be charged (contact or proximity).

  In particular, the electrophotographic apparatus conductive member used in contact with the member to be charged is preferably an elastic body satisfying an appropriate low hardness and low compressive strain. If the hardness of the electroconductive elastic member for the electrophotographic apparatus is high, the object to be charged is scraped. Also, the electroconductive elastic member is soiled by toner or an external additive, and the object to be charged and the electroconductive elastic member are not driven, and stick. This causes a problem such as slipping, and an adverse effect such as failure to obtain an appropriate nip for causing electric discharge between the member to be charged and the conductive elastic member, which causes image defects. Further, if the compression set of the conductive elastic member is large, when the rest or stop time of the electrophotographic apparatus becomes long, the deformation of the press contact portion of the conductive elastic member with the charged body cannot be restored, Image defects occur due to “dents”.

Further, in order to be suitably used as a conductive elastic member for an electrophotographic apparatus, an electrical resistance of a semiconductive region of about 10 ⁴ to 10 ¹¹ Ωcm is necessary. The conductive development mechanism of the conductive rubber is roughly divided into an ion conductive mechanism and an electronic conductive mechanism. Among them, conductive rubbers based on ionic conduction mechanisms include cationic surfactants such as lauryltrimethylammonium, anionic surfactants such as aliphatic sulfonates, zwitterionic surfactants such as various betaines, and higher alcohol ethylene oxide. It is obtained by dispersing an ionic conductive agent such as a nonionic antistatic agent or an antistatic agent of a metal salt. In particular, by applying to polar rubbers such as epichlorohydrin rubber, chloroprene rubber, acrylonitrile-butadiene rubber, low electrical resistance can be achieved. However, conductive rubber with an ionic conduction mechanism is highly environment-dependent, and it is difficult to reduce the resistance to 10 ⁶ Ωcm or less. Easy to wake up. On the other hand, a conductive rubber by an electronic conductive mechanism can be obtained by dispersing a conductive filler such as carbon black, carbon fiber, graphite, metal fine powder, and metal oxide in the rubber and combining them. Conductive rubber with an electronic conductive mechanism is easier to reduce to 10 ⁶ Ωcm or less than conductive rubber with an ionic conductive mechanism, is less dependent on temperature and humidity, is inexpensive, and has no bleed or bloom. There are advantages such as fewer. However, since it is a dispersed composite material, the physical properties vary greatly depending not only on the filling amount but also on the dispersion state. Conductivity also varies greatly depending on the dispersion state because it is expressed by a conductive channel formed by a series of conductive fillers. For this reason, there is a problem that electric resistance varies greatly not only in one member but for each production lot, and it is difficult to control. Moreover, in order to obtain desired conductivity, it is necessary to add a certain amount or more of a conductive filler, and there is a tendency that the hardness becomes higher than a hardness preferable as a conductive elastic member for an electrophotographic apparatus.

  A conductive elastic member for an electrophotographic apparatus using conductive rubber by such an electronic conductive mechanism has a uniform electrical resistance in the semiconductive region and a moderately low hardness. Various ideas have been made for this purpose. As one of the methods, a domain structure (sea island structure) in which several kinds of rubbers with different affinity with the conductive filler are blended and the conductive filler is unevenly distributed in the rubber phase with high affinity with the conductive filler. ) Has been made. In this method, among the plurality of types of rubber phases blended with the conductive filler, by being unevenly distributed in one rubber phase, the electrical resistance of the semiconductive region can be obtained even with a small amount of conductive filler, In addition, since the filling amount is small, a low hardness electroconductive elastic member for an electrophotographic apparatus can be obtained (Patent Document 1). However, in this method, it is difficult to control the conductive particles to be unevenly distributed. Furthermore, it is virtually impossible to make all conductive fillers added to one rubber phase out of the blended rubber phases unevenly distributed.

Further, as another method for obtaining a conductive elastic member for an electrophotographic apparatus having a uniform electric resistance in the semiconductive region and having an appropriate low hardness, a previously crosslinked rubber composition is pulverized. There is a method of forming a domain structure using the rubber particles as a domain phase (Patent Document 2). In this case, all the conductive fillers can be unevenly distributed in either the domain phase or the matrix phase. However, since it contains cross-linked rubber particles, the viscosity of the unvulcanized mixture becomes high and the processability is poor, and a process for obtaining rubber particles by pulverization is necessary, the number of manufacturing steps is increased, and the particles of rubber particles The variation in diameter is large, and coarse particles may cause image defects.
JP-A-11-45013 Japanese Patent No. 3593402

  An object of the present invention is to suppress the occurrence of image defects in an electrophotographic apparatus due to high hardness and large compression set, and is unique to a composition containing a conductive filler. It is possible to suppress the occurrence of image defects in the electrophotographic apparatus due to variations in electrical resistance, and to reduce the increase in viscosity in the unvulcanized state unique to the composition containing crosslinked rubber particles, thereby improving workability. It is to obtain an electrophotographic conductive member that can be improved and a method for producing the same.

  In order to solve the above-mentioned problems, the present inventors have included the fine rubber particles obtained by radiation crosslinking having a low hardness as the domain phase in the matrix phase containing the elastomer, so that the elastomer is a cause of high hardness. Therefore, it is possible to suppress the occurrence of compression set while having a low hardness, and to suppress the occurrence of image defects in the electrophotographic apparatus caused by coarse particles. The domain phase can be made to exist uniformly in the matrix phase, the variation in electric resistance can be suppressed, and the conductive elastic member of the electrophotographic apparatus can have an appropriate electric resistance. . In addition, the conductive filler can be uniformly contained only in the matrix phase, the variation in electrical resistance can be improved, and even when the electrical resistance is lowered by containing a large amount of conductive material, the electrical resistance can be reduced. The knowledge that the hardness can be maintained was obtained. Furthermore, when the rubber particles contain an anti-sticking agent near the surface, it is possible to suppress an increase in viscosity that is characteristic of a rubber composition in an unvulcanized state in which fine crosslinked rubber particles are mixed, thereby improving processability. Based on these findings, the present invention has been completed.

  That is, the present invention relates to a conductive elastic member for an electrophotographic apparatus, comprising a conductive elastic body composed of a matrix phase containing an elastomer and a domain phase containing rubber particles obtained by radiation crosslinking.

  The present invention also provides a mixture obtained by mixing rubber particles obtained by radiation crosslinking, a conductive filler, and an elastomer, and curing the mixture to form a domain phase composed of rubber particles and an elastomer matrix phase. The present invention relates to a method for manufacturing a conductive elastic member for an electrophotographic apparatus, wherein the domain structure is formed.

  The conductive elastic member for an electrophotographic apparatus of the present invention and the method for producing the same can suppress the occurrence of compression set even though the hardness is low because the elastomer does not require a filler that causes high hardness. Moreover, the occurrence of image defects in the electrophotographic apparatus can be suppressed. Moreover, even when a conductive filler is contained in the matrix phase, variation in electric resistance can be improved, and even when the electric resistance is lowered, low hardness can be maintained. Furthermore, the viscosity increase peculiar to the rubber composition in the unvulcanized state in which fine crosslinked rubber particles are mixed can be suppressed, and processability can be improved.

  The electroconductive elastic member for an electrophotographic apparatus of the present invention is particularly limited as long as it includes a conductive elastic body composed of a matrix phase containing an elastomer and a domain phase containing rubber particles obtained by radiation crosslinking. It is not something to receive.

  The conductive elastic body in the conductive elastic body member for an electrophotographic apparatus of the present invention is schematically represented by a matrix phase (sea phase) 11 of continuous phases and radiation crosslinking as shown in FIG. It has a domain structure having a domain phase (island phase) 12 of a discontinuous phase containing the obtained rubber particles. In the present invention, the domain structure (sea-island structure) is completely incompatible when two or more types of polymers are blended, and includes a continuous phase (matrix phase / sea phase) and a discontinuous phase ( A domain phase / island phase). Moreover, as will be described later, a structure in which the average particle size of the discontinuous phase is 50 μm or more is preferable. Examples of the elastomer contained in the matrix phase include rubbers and thermoplastic elastomers conventionally used as elastic bodies for electrophotographic conductive members. Specifically, polyurethane rubber, silicone rubber, butadiene rubber , Rubbers such as acrylonitrile-butadiene rubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, polynorbornene rubber, epichlorohydrin rubber, and thermoplastic elastomers such as general-purpose styrene elastomers and olefin elastomers. Can do. These can be used as a composition of one kind or a combination of two or more kinds.

The matrix phase preferably has a conductivity of about 10 ⁴ to 10 ¹¹ Ωcm by containing a conductive substance. As the conductive substance contained in the matrix phase, any of an ionic conduction mechanism and an electronic conduction mechanism can be applied.
Examples of ionic conductive agents based on the ionic conductive mechanism include lauryl trimethyl ammonium, stearyl trimethyl ammonium, octadodecyl trimethyl ammonium, dodecyl trimethyl ammonium, hexadecyl trimethyl ammonium, modified fatty acid / dimethyl ethyl ammonium perchlorate, chlorate, Cationic surfactants such as quaternary ammonium salts such as halogenated benzyl salts such as borofluoride, ethosulfate, benzyl bromide, benzyl chloride, aliphatic sulfonates, higher alcohol sulfates, Anionic surfactants such as higher alcohol ethylene oxide addition sulfate ester salt, higher alcohol phosphate ester salt, higher alcohol ethylene oxide addition phosphate ester salt, and zwitterionic interfaces such as various betaines Sexual agents, higher alcohol ethylene oxide, polyethylene glycol fatty acid esters, antistatic agents such as nonionic antistatic agents such as polyhydric alcohol fatty acid _{esters, LiCF 3 SO 3, NaClO 4} , LiAsF 6, LiBF 4, NaSCN, KSCN, Periodic table group 1 metal salts such as Li ⁺ , Na ⁺ , K ^+, etc., such as NaCl, electrolytes such as NH ₄ ⁺ salts, periods of Ca ²⁺ , such as Ca (ClO ₄ ) ₂ , Ba ^2+, etc. List 2 group metal salts, and those having antistatic agents having at least one group having an active hydrogen that reacts with isocyanate such as hydroxyl group, carboxyl group, primary or secondary amine group, etc. be able to. Furthermore, with them, complexes of polyhydric alcohols such as 1,4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol and polyethylene glycol and their derivatives, or monools such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether An ionic conductive agent such as a complex of These ionic conductive agents are easily dispersed in the matrix phase, especially when polar rubber typified by epichlorohydrin rubber, chloroprene rubber, acrylonitrile-butadiene rubber is used as the elastomer constituting the matrix phase, and low electrical resistance. Can be applied uniformly.

  The content of these ionic conductive agents in the matrix phase is such that the conductive elastic member has a desired electrical resistance depending on the type of conductive elastic member, elastomer, or conductive agent of the electrophotographic apparatus. For example, it can be 0.1 to 20 parts by mass, preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the elastomer.

Examples of the conductive filler by the electronic mechanism include conductive carbon such as ketjen black EC and acetylene black, rubber carbon such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT, and oxidation treatment. Examples thereof include carbon for color (ink), pyrolytic carbon, natural graphite, synthetic graphite, tin oxide, titanium oxide, zinc oxide, copper, silver, and other metals and metal oxides. These conductive fillers are less temperature-dependent than ionic conductive agents, can easily have a low electrical resistance of 10 ⁶ Ωcm or less, have few bleeds and blooms, and are inexpensive. Therefore, an electrophotographic conductive elastic member using a conductive rubber using a conductive filler has a wide usage environment, low contamination to the photoreceptor, and in an electrophotographic apparatus aimed at low cost, More preferred.

  The content of these conductive fillers in the matrix phase is such that the conductive elastic member has a desired electrical resistance depending on the type of the conductive elastic member, elastomer, or conductive agent of the electrophotographic apparatus. For example, it can be 0.5 to 100 parts by mass, preferably 2 to 50 parts by mass with respect to 100 parts by mass of the elastomer.

  The above matrix phase is generally used as an elastomer compounding agent within a range that does not lose low hardness and low compression set, processing aid, crosslinking agent, crosslinking accelerator, crosslinking accelerator, crosslinking retarder, filling An agent, a dispersant, a foaming agent, a lubricant, an anti-aging agent, an ozone deterioration preventing agent, an antioxidant, a conductive agent, and the like can be added. As crosslinking agents, sulfur, organic sulfur-containing compounds, organic peroxides, etc., and as crosslinking accelerators, aldehyde ammonias, aldehyde amines, guanidines, thiazoles, sulfenamides, thiurams, dithiocarbamates , Xanthates, etc., as crosslinking accelerators, metal oxides, fatty acids, etc., as crosslinking retarders, organic acids, nitroso compounds, N-cyclohexylthiophthalimide, etc., as lubricants, stearic acid metal salts As an anti-aging agent, an amine ketone type, aromatic secondary amine type, monophenol type, bisphenol type, benzimidazole type, thiocarbamic acid type, thiourea type anti-aging agent, etc., as an antioxidant, Phenol-based, phosphite-based and thioether-based antioxidants can be exemplified.

  The radiation-crosslinked rubber particles contained in the domain phase are not completely compatible when two types of polymers are blended, and can also be referred to as a polymer phase contained as a particle state. Specific examples of radiation-crosslinked rubber particles include styrene-butadiene rubber (SBR), acrylic rubber, acrylonitrile-butadiene rubber (NBR), carboxylic acid-modified acrylonitrile-butadiene rubber (XNBR), chloroprene rubber (CR), silicone rubber, butadiene -Radiation-crosslinked rubber particles such as styrene-vinyl pyridine terpolymers. As the average particle diameter of the rubber particles, a very small particle size of 50 to 500 nm is preferable because image defects can be suppressed in the electrophotographic apparatus. When the average particle diameter of the crosslinked rubber particles is 500 nm or less, the occurrence of black spots on the image due to coarse particles or aggregates can be suppressed, and the occurrence of image defects can be suppressed. When the average particle diameter of the crosslinked rubber particles is 50 nm or more, the particles can be easily dispersed, and the residual aggregated particles can be suppressed. When the crosslinked rubber particles are 50 nm or more and 200 nm or less, the above effect can be obtained more remarkably, and it is more preferable.

  Here, the average particle diameter of the radiation-crosslinked rubber particles can be determined by the following method. A section is cut out from the molded electroconductive elastic member for an electrophotographic apparatus, and the cut surface is observed with an SEM or TEM. The obtained image is image processing software (trade name “Image-Pro Plus”: manufactured by Planetron Co., Ltd.). ) And automatically extract the diameter (average) of the crosslinked rubber particles according to the count / size. The diameter (average) at this time is a value obtained by measuring the diameter passing through the center of gravity of the counted object in increments of 2 ° and averaging it. Next, the measurement data of this diameter (average) is taken into spreadsheet software, and the value of 50 nm or less in the measurement data is deleted as noise, and the remaining value is only when there are 100 or more remaining values. Is determined as the average particle size. When the remaining value is less than 100, the measurement is repeated again, and the obtained value can be used as the average particle diameter.

  The content of the crosslinked rubber particles is not particularly limited as long as the desired elastic permanent deformation is low in the conductive elastic body and low hardness is obtained, but it is 1 part by mass or more with respect to 100 parts by mass of the elastomer. 200 parts by mass or less is preferable. When the content of the crosslinked rubber particles is 1 part by mass or more, the electroconductive elastic member for an electrophotographic apparatus has a low compression set and a low hardness. Further, if the content of the crosslinked rubber particles is 100 parts by mass or less, the Mooney viscosity of the conductive elastic body can be lowered, the processability is good, and the compression elastic strain is not generated in the conductive elastic member for an electrophotographic apparatus. Less.

  The radiation-crosslinked rubber particles can be obtained by irradiating the rubber latex exemplified above with radiation and crosslinking. The latex contains a cross-linking agent such as polyfunctional acrylates such as trimethanolpropane triacrylate (TMPTA) and isooctyl acrylate (OMA), polythiol, and polyhalides such as hexachloroethane in order to improve the crosslinking efficiency. Can be made. As the radiation to be irradiated, γ rays, electron beams, and the like can be used. As the irradiation dose, 10 kGy to 10000 kGy can be mentioned. The crosslinked rubber particles produced by this method are preferable because they have a small particle size of 50 to 500 nm, which is about the same as the particle size of the rubber before crosslinking existing in the latex, and the particle size distribution is narrow. By using such cross-linked rubber particles in the domain phase, the hardness of the conductive elastic body is increased as compared with generally used inorganic fillers such as calcium carbonate, clay, talc, diatomaceous earth, and silica. Since it can suppress and generation | occurrence | production of a compression set can be suppressed, it is preferable as an electroconductive elastic body member for electrophotographic apparatuses. Further, generally used organic fillers such as powder rubber, it is difficult to reduce the particle size, and there are harmful effects due to bleed and bloom of various compounding agents, but by using the radiation-crosslinked rubber particles, Bleed bloom can be suppressed. Further, since the conductive filler does not enter the radiation-crosslinked rubber particles, the conductive filler contained in the matrix phase also stays in the matrix phase and is unevenly distributed. For this reason, even if the conductive filler is less dispersible than the ionic conductive agent, it is uniformly dispersed in the matrix phase, the conductive channel of the conductive particles is stabilized, and the variation in electric resistance in the matrix phase is reduced. Moreover, since a low electrical resistance can be realized even if the volume fraction of the conductive filler is small, a conductive elastic body having a low hardness can be obtained.

  Such radiation-crosslinked rubber particles preferably contain an anti-sticking agent in the vicinity of the surface. In a composition in which a radiation-crosslinked rubber and an elastomer are mixed, the molecular chains of the two tend to be entangled and the viscosity tends to increase. For this reason, molding processability such as extrusion may be deteriorated. When the radiation-crosslinked rubber particles contain an anti-sticking agent in the vicinity of the surface, an increase in viscosity in the composition can be suppressed. Specific examples of such surface adhesion preventing agents include inorganic fine particles such as calcium carbonate, titanium oxide, silica, clay, and talc, and the particle size thereof is smaller than the rubber particle size. Is preferable, and examples thereof include 10 nm to 100 nm. The anti-sticking agent is preferably attached to the surface of the radiation-crosslinked rubber particles at a ratio of 1 to 20% by mass relative to the mass of the radiation-crosslinked rubber particles.

  In order to fix the anti-sticking agent on the surface of such a radiation-crosslinked rubber particle, the anti-sticking agent and the radiation-crosslinking rubber particle are mixed by mixing the non-crosslinked latex with an anti-sticking agent, and a wet disperser. Examples thereof include a method of curing the material dispersed in (1) and a method of fixing the crosslinked rubber particles to the crosslinked rubber particles with a dry disperser.

  As a method for producing the electroconductive elastic member for an electrophotographic apparatus, the rubber particles obtained by the radiation crosslinking, a conductive filler and an elastomer are mixed to obtain a mixture, and the mixture is cured to obtain rubber particles. As a preferred method, a method of forming a conductive elastic body composed of a domain phase composed of the above and an elastomer matrix phase can be mentioned. The mixture of rubber particles, conductive filler, and elastomer obtained by the above-mentioned radiation cross-linking includes, in addition to the above-mentioned radiation cross-linked rubber particles, conductive fillers, ionic conductive agents, and fillers as long as these functions are not impaired. , Processing aids, crosslinking agents, crosslinking aids, crosslinking accelerators, crosslinking accelerators, crosslinking retarders, dispersants, foaming agents, lubricants, anti-aging agents, ozone degradation inhibitors, antioxidants, etc. Can do. Examples of these mixing methods include a method using a closed mixer such as a Banbury mixer, intermix or pressure kneader, or a method using an open mixer such as an open roll. Examples of the curing method of the obtained mixture include mold vulcanization, can vulcanization, and continuous vulcanization.

  Moreover, about the electroconductive elastic body obtained by hardening | curing a mixture, the high mold release layer can be shape | molded by irradiating the surface with an ultraviolet-ray as needed. When the conductive elastic body has a high release layer on the surface, it is possible to suppress adhesion of the toner and the external additive and to suppress contamination of the charged body. Examples of a method for forming the highly release layer on the surface of the conductive elastic body include a method of coating a material having a composition different from that of the conductive elastic body, such as coating. In this case, it is possible to select a material having low adhesion, non-contamination, conductivity, setability, etc. as a coating material and share different functions between the coating layer and the conductive elastic body. A high-performance electroconductive elastic member for an electrophotographic apparatus with a high degree of freedom of selection can be obtained.

  Examples of the method for forming the surface release layer include a method of irradiating energy rays typified by electron beam, ultraviolet ray, X-ray, infrared ray, plasma and the like. In this case, the material cost is unnecessary, the processing process is short, and the process can be performed more easily than the coating. In the high release layer by irradiation with energy rays, it is possible to control the electrical properties as desired, to reduce the adhesiveness and friction coefficient, and to prevent the toner and external additives from sticking to the conductive elastic member. A good image can be obtained. As an energy ray used for forming a high release layer, ultraviolet rays are preferable. As the irradiation condition of ultraviolet rays, light having a wavelength of 200 nm to 450 nm is used, and as the light source, those capable of irradiating ultraviolet rays in the wavelength range can be used. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury A light source such as a lamp, a metal halide lamp, or an excimer lamp can be used. It is preferable to use a lamp with a lamp output of 80 W / cm and a rated power of 4000 W. In the conductive elastic body at the time of irradiation, the closer to the lamp, the better the irradiation efficiency, and the rotation can uniformly irradiate the surface of the elastic body, and the high release layer is uniformly formed over the entire surface. Can do. As the irradiation time, an optimum range can be selected depending on the type of lamp, irradiation distance, and the like, but it can be, for example, several seconds to several tens of minutes.

  Specific examples of the electroconductive elastic member for an electrophotographic apparatus of the present invention include rollers, blades, brushes, belts, sheets, chips and the like used for developing members, charging members, transfer members and the like. As an example, as shown in FIG. 2, a conductive elastic body 22 including the conductive elastic body provided on the outer periphery of a conductive support (shaft) 21 can be cited. The thing which has the type | molding layer 23 can be mentioned.

  Examples of the method for producing the roller include the following methods, but are not limited thereto. First, a composition containing an elastomer and rubber particles obtained by radiation crosslinking is extruded into a tube shape with an extruder, and steam vulcanized with a vulcanizer. A cylindrical shaft made of SUS or aluminum with a hot melt adhesive applied on the surface is press-fitted into this tube. Then, the shaft and the tube are bonded by heating in a hot air furnace. And the both ends of a tube are cut | disconnected to desired length, The tube surface can be grind | polished and a rubber roller can be obtained.

  An example in which the electroconductive elastic member for an electrophotographic apparatus of the present invention is applied to an electrophotographic apparatus will be described with reference to the drawings. In the electrophotographic apparatus to which the electrophotographic conductive member of the present invention is applied as a charging roller, as shown in FIG. 3, the image rotates at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow in the figure. A rotating drum type electrophotographic photosensitive member (charged member) 31 as a carrier is provided. The photoreceptor 31 has, for example, a photosensitive layer containing an inorganic photosensitive material or an organic photosensitive material on its surface, and further has a charge injection layer for charging the surface of the charged body to a predetermined polarity and potential. Also good. Around such a photoreceptor, a charging device, an exposure device, a developing device, a transfer device, a fixing device, and a cleaning device are sequentially provided. The charging device includes a charging roller 32 that is a conductive elastic member for an electrophotographic apparatus of the present invention disposed in contact with the photoreceptor 31 with a predetermined pressing force, and a charging bias that applies a charging bias to the charging roller 32. An applied power source S1 is provided. A charging roller 32 to which a predetermined DC voltage, for example, -1200 V, is applied from the charging bias application power source S1 contacts the photoconductor 31 and rotates counterclockwise so that the surface of the photoconductor 31 has a predetermined polarity potential, for example, In addition, it is uniformly charged to a dark part potential of −600 V (DC charging). As charging of the photosensitive member, charging such as AC / DC superimposed charging or injection charging can be used.

  In the exposure apparatus, for example, an exposure means 33 such as a laser beam scanner is provided. When image exposure corresponding to target image information is performed on the charging surface of the photoreceptor 31 by the exposure means, the exposure bright portion of the charging surface is set. The potential is selectively lowered (attenuated), for example, to a bright part potential of −350 V, so that an electrostatic latent image is formed.

  The developing device includes, for example, a developing roller 34a that is a toner carrying member that is disposed in an opening of a developing container that contains toner and carries and conveys the toner, an agitating member 34b that agitates the contained toner, and a developing device. A developing unit 34 is provided having a blade 34c which is a toner regulating member that makes the toner carrying amount (toner layer thickness) of the roller 34a constant. In the developing means 34, the electrostatic latent image on the surface of the photoconductor 31 is attached with a toner (negative toner) charged with the same polarity as the charge polarity of the photoconductor 31, for example, charged with a developing bias 350V, thereby causing an electrostatic latent image. Visualize the image as a toner image. There is no particular limitation on the developing method, and for example, existing methods such as a jumping developing method, a contact developing method, and a magnetic brush method can be used. However, particularly in a developing device that outputs a color image, toner scattering properties are improved. Therefore, a contact developing type developing roller is preferable. The electroconductive elastic member for electrophotographic apparatus of the present invention can also be suitably used for this developing roller.

  In the transfer device, a transfer roller 35 disposed in contact with the photosensitive member 31 with a predetermined pressing force to form a transfer nip portion, and a transfer bias having a polarity opposite to the toner charging characteristic are applied to the transfer roller 35. A transfer bias application power source S2. The electroconductive elastic member for an electrophotographic apparatus of the present invention can be applied to the transfer roller, and the transfer roller 35 that contacts the photoconductor 31 and rotates counterclockwise at substantially the same peripheral speed as its peripheral speed. A voltage having a polarity opposite to the charging polarity of the toner applied to the developing roller is applied from the back side of the transfer material P conveyed at a predetermined timing from a sheet feeding mechanism (not shown) between the toner and the photosensitive member 31. As a result, the toner adhering to the surface of the photoreceptor 31 is electrostatically transferred to the surface side of the transfer material P.

  The fixing device (not shown) is provided with known toner image fixing means such as a heating means so that the toner transferred onto the transfer material P is fixed and output as an image formed product. In the case of the double-sided image forming mode or the multiple image forming mode, the image formed product is introduced into a recirculation conveyance mechanism (not shown) and reintroduced into the transfer nip portion.

  The cleaning device is provided with a blade-type cleaning means 36 that removes toner remaining on the photoconductor 31 without being transferred by the transfer device, and collects residual toner on the photoconductor.

  Further, if necessary, if a charge remains on the photosensitive member, a charge removing unit 37 such as a pre-exposure unit is provided to remove the charge before charging by the charging member 32 for the next printing. Further, the residual charge may be removed by the pre-exposure means, and the charging of the photosensitive member 31 by the charging member 32 may be made uniform to suppress the occurrence of image defects.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, the technical scope of this invention is not limited to the following.

[Example 1]
As an elastomer that forms a matrix phase, 100 parts by mass of epichlorohydrin rubber (trade name “Epichromer CG105” manufactured by Daiso Corporation), and as a radiation-crosslinked rubber particle that forms a domain phase, crosslinked NBR crosslinked with ⁶⁰ Co γ rays. 50 parts by mass of nanoparticles (trade name “Narpow VP-401”: manufactured by Beijing Chemical Research Institute), 40 parts by mass of carbon black (trade name “Asahi HS-500”: manufactured by Asahi Carbon) as conductive particles, 5 parts by mass of zinc oxide 10 parts by mass of liquid epoxidized polybutadiene (trade name “BF-1000”: manufactured by Asahi Denka Kogyo Co., Ltd.) for 20 minutes with an open roll, and further dibenzothiazolyl disulfide (trade name “Noxeller DM-P”) : Ouchi Shinsei Chemical Co., Ltd.) 1 part by mass, tetramethylthiuram monosulfide (trade name “Noxeller”) “TS” (manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1 part by mass and 1.2 parts by mass of sulfur as a vulcanizing agent were added and further kneaded with an open roll for 15 minutes.

  This was extruded into a cylindrical shape with an outer diameter of 15 mm and an inner diameter of 5.5 mm with a rubber extruder, cut into a length of 250 mm, and primary vulcanized with steam at 160 ° C. for 40 minutes in a vulcanizing can, and conductive elastic A primary vulcanization tube was obtained. Next, a hot melt adhesive was applied to the central portion 231 mm in the axial direction of the cylindrical surface of a cylindrical conductive support (steel surface industrial nickel plating) having a diameter of 6 mm and a length of 256 mm, and dried. This support was inserted into the conductive elastic body primary vulcanization tube, then placed in an electric oven, subjected to secondary vulcanization and adhesive curing at 160 ° C. for 2 hours to obtain an unpolished conductive member. . After cutting both ends of the rubber part of this unpolished product to make the length of the rubber part 231 mm, the rubber part is polished with a rotating grindstone, and the crown shape with an end diameter of 8.3 mm and a central part of 8.5 mm is used. A conductive member having an average roughness Rz of 4 μm and a deflection of 40 μm was obtained.

A low-pressure mercury lamp was used as the conductive member, and the roller was manufactured by uniformly irradiating the conductive member while rotating the conductive member so that the light intensity of the ultraviolet ray became 8000 mJ / cm ² with the sensitivity of the sensor of 254 nm.

  About the produced roller, physical properties, such as an average particle diameter of a crosslinked rubber particle, a compression set, and hardness, were measured, and the processability and evaluation when mounted in a practical machine were performed as follows. The results are shown in Table 1.

<Average particle diameter of crosslinked rubber particles>
The average particle size of the crosslinked rubber particles was measured as follows.
A section was cut out from the produced roller, the cut surface was observed with SEM or TEM, and the domain structure was photographed. The image obtained here was taken into image processing software (trade name “Image-Pro Plus” manufactured by Planetron Co., Ltd.), and the diameter (average) of the crosslinked rubber particles was automatically extracted based on the count / size. The “diameter (average)” is a value obtained by measuring the diameter passing through the center of gravity of the counted object in increments of 2 ° and averaging it. Next, the measurement data of this diameter (average) is taken into spreadsheet software, and the value of 50 nm or less in the measurement data is deleted as noise, and only when the remaining value count number is 100 or more The average value of the remaining values was defined as the average particle size. When the count number was less than 100, retesting was performed again from observation by SEM or TEM. The particle diameter of the crosslinked NBR nanoparticles measured by the method as described above was 74 nm.

<Mooney viscosity>
The Mooney viscosity was measured according to JIS K6300-1 as a guideline for extrudability of the unvulcanized composition used for the production of the roller. As a result, it was 69.5 ML (1 + 4) 100 ° C. Here, 69.5M indicates Mooney viscosity, L indicates that it is measured with an L-shaped rotor, (1 + 4) indicates a 1 minute preheating time and a 4 minute rotor rotation time, and 100 ° C. indicates a test temperature. Yes.

<Compression set test>
This unvulcanized composition was vulcanized in a mold at 160 ° C., and then subjected to a compression set test in accordance with JIS K6262 for the vulcanized rubber that had been vulcanized in an oven at 160 ° C. As a test procedure, first, the thickness of a test piece is measured, and it is left in a state where it is deformed by 25% in an environment of 70 ° C. for 22 hours. Was measured. As a result, the compression set was 9.9%.

<Micro rubber hardness measurement>
The micro rubber hardness of the test piece produced by the same method as the vulcanized rubber used in the compression set test was measured using MD-1 type manufactured by Kobunshi Keiki Co., Ltd. As a result, it was 64.0 °.

<Volume resistance measurement>
A vulcanized sheet having a thickness of 2 mm was prepared in the same manner as the vulcanized rubber used in the compression set test, and the volume resistance was measured in accordance with JIS K6271. The average of five points at the four corners and the center of the test piece was obtained as volume resistance, and the maximum volume resistance value / minimum volume resistance value was calculated for the maximum value and the minimum value of the five points, and the resistance variation in the sheet was determined. As a result, the volume resistance was 1.54 × 10 ⁵ Ωcm, and the resistance variation in the sheet was 1.5.

<Processability evaluation>
When the Mooney viscosity is high, the processability was evaluated. From the viewpoint of extrudability, using this as an index, bad effects such as poor extruding skin, poor voids, and high extruding pressure appear. . Three-stage evaluation was performed, with A being a very good extrudability, B being a good extrudability, and C being a poor extrudability. If it is B or more of this evaluation, it can be judged that there is productivity. The obtained roller had an increased Mooney viscosity and an extrusion moldability of B because the polarity of the epichlorohydrin rubber in the matrix phase and the cross-linked NBR nanoparticles in the domain phase were close.

<Evaluation in electrophotographic apparatus>
The roller obtained in Example 1 is attached to the electrophotographic apparatus (LBP5500: manufactured by Canon Inc.) having the configuration shown in FIG. 3 as a charging roller, and a halftone image is obtained in an environment of temperature 15 ° C. and humidity 10% RH. Output. At this time, the dot-like black defects (image spots) on the image generated due to the large cross-linked rubber particles present on the surface do not exist at all on the basis of the frequency of occurrence (A), and exist very rarely. (B), it evaluated in 3 steps | paragraphs of (C) which exists in large quantities. In a practical machine, if it is B rank or higher, it can be used without any problem. As a result, the image spot evaluation of the obtained roller was B. The reason for this evaluation seems to be that although the primary particle size of the crosslinked rubber particles is small, the aggregation thereof is slightly caused.

  In addition, in this halftone image, irregular “image density unevenness” due to resistance unevenness of the charging roller was evaluated. Based on the density difference between the bright part and the dark part, the evaluation was made in three stages: A for no density difference, B for slight density difference, and C for clear density difference. In a practical machine, if it is B rank or higher, it can be used without any problem. As a result, the resistance unevenness was small and the image density unevenness evaluation was A.

  Subsequently, an image output durability test was performed. Continuously pass through 6,000 sheets, and based on the occurrence frequency of the toner adhering to the charging roller at this time and the dot-like or linear image defect (durable stain) due to the external additive, In very rare cases, B was evaluated as being present, and C being present as being present in a large amount. This durable stain occurs when the toner and the external additive are crushed between the charging roller and the member to be charged, and the elastic body of the charging roller is more likely to adhere as the hardness increases. The obtained roller had a durable stain evaluation of A. This evaluation is considered to be because an elastic body having a low hardness was obtained because the crosslinked rubber particles had a low hardness.

  The roller was applied to each end of the conductive support at a load of 500 g, abutted against the member to be charged, and left in a constant temperature and humidity chamber at room temperature of 40 ° C. and humidity of 95% for 1 week. The roller and the member to be charged (photosensitive member) were taken out from the constant temperature and humidity chamber and incorporated in the electrophotographic apparatus shown in FIG. 3 to output a halftone image. In the halftone image, it was evaluated whether a white image defect (deformed portion due to contact with a charged body) appeared as a severely left-over roller deformation trace in the circumferential cycle of the roller. The evaluation was A when the image defect could not be recognized on the image, and C when the image defect could be recognized. As a result, the evaluation of the roller was A. This evaluation is considered to be because an elastic body having a small compression set was obtained because the crosslinked rubber particles have low compression strain characteristics and a large interaction at the interface with epichlorohydrin forming the matrix phase.

[Example 2]
A roller was produced in the same manner as in Example 1 except that the ultraviolet irradiation of Example 1 was not performed. About the produced roller, the measurement of physical properties and the evaluation of workability were performed in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]
A roller was produced in the same manner as in Example 1 except that the amount of ultraviolet light in Example 1 was set to 1000 mJ / cm ² . About the produced roller, the measurement of physical properties and the evaluation of workability were performed in the same manner as in Example 1. The results are shown in Table 1.

[Example 4]
A roller was produced in the same manner as in Example 1 except that the amount of ultraviolet light in Example 1 was changed to 100,000 mJ / cm ² . About the produced roller, the measurement of physical properties and the evaluation of workability were performed in the same manner as in Example 1. The results are shown in Table 1.

[Example 5]
Other than using 50 parts by mass of crosslinked carboxyl-modified NBR nanoparticles (trade name “Narpow VP-502” manufactured by Beijing Chemical Research Laboratories) as radiation-crosslinked rubber particles instead of the crosslinked NBR nanoparticles in the material composition of Example 1 A roller was produced in the same manner as in Example 1. About the produced roller, the measurement of physical properties and the evaluation of workability were performed in the same manner as in Example 1. The results are shown in Table 1.

[Example 6]
Example except that 50 parts by mass of crosslinked CR nanoparticles (trade name “Narpow VP-801”: manufactured by Beijing Chemical Research Institute) were used as radiation crosslinked rubber particles in place of the crosslinked NBR nanoparticles in the material composition of Example 1. A roller was prepared as in 1. About the produced roller, the measurement of physical properties and the evaluation of workability were performed in the same manner as in Example 1. The results are shown in Table 1.

[Example 7]
Cross-linked SBR nanoparticles containing 5% by mass of calcium carbonate (trade name “Narpow VP-121”: manufactured by Beijing Chemical Research Institute) as radiation cross-linked rubber particles instead of the cross-linked NBR nanoparticles in the material composition of Example 50 A roller was prepared in the same manner as in Example 1 except that the part was used. About the produced roller, the measurement of physical properties and the evaluation of workability were performed in the same manner as in Example 1. The results are shown in Table 1.

[Example 8]
A roller was prepared in the same manner as in Example 1 except that 50 parts by mass of crosslinked NBR nanoparticles containing 5% by mass of calcium carbonate was used instead of the crosslinked NBR nanoparticles in the material composition of Example 1. About the produced roller, the measurement of physical properties and the evaluation of workability were performed in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
A roller was prepared in the same manner as in Example 1 except that the crosslinked NBR nanoparticles in the material composition of Example 1 were excluded, and the physical properties were measured and the processability was evaluated in the same manner as in Example 1 for the prepared roller. It was done. The results are shown in Table 1.

[Comparative Example 2]
A roller was produced in the same manner as in Example 1 except that 50 parts by mass of pulverized rubber particles produced in the following procedure was used instead of the crosslinked NBR nanoparticles in the material composition of Example 1, and the physical properties of the produced roller were as follows. Measurement and processability evaluation were performed in the same manner as in Example 1. The results are shown in Table 1.

<Preparation of crushed rubber particles>
Acrylonitrile butadiene rubber (trade name “DN219” manufactured by Nippon Zeon Co., Ltd.) 100 parts by mass, zinc oxide 5 parts by mass with an open roll for 20 minutes, and dibenzothiazolyl disulfide (trade name “Noxeller DM-P”) : Ouchi Shinsei Chemical Co., Ltd.) 1 part by mass, tetramethylthiuram monosulfide (trade name “Noxeller TS”: Ouchi Shinsei Chemical Co., Ltd.) 1 part by mass, sulfur as a vulcanizing agent 1.2 parts by mass And kneaded with an open roll for another 15 minutes.

  This unvulcanized composition was vulcanized in a 160 ° C. mold and then vulcanized in an oven at 160 ° C. This vulcanized rubber was cut into 2 mm squares and pulverized with a mill to obtain pulverized rubber particles.

[Comparative Example 3]
50 parts by mass of crosslinked silicone particles (trade name “Trefil E600” manufactured by Toray Dow Corning Silicone Co., Ltd.) made by heating latex instead of crosslinked NBR nanoparticles in the material composition of Example 1 A roller was produced in the same manner as in Example 1 except that it was used, and physical properties were measured and processability was evaluated in the same manner as in Example 1 for the produced roller. The results are shown in Table 1.

[result]
<Processability and image evaluation>
Since the cross-linked rubber particles in the domain phase have a higher resistance than the matrix phase, if the cross-linked rubber particles present on the surface are excessively large, an image is produced. Therefore, in Comparative Example 2, rubber produced by pulverization The particles contain coarse particles, and this causes the image spot to be evaluated as C. Further, in Comparative Example 1, since the crosslinked rubber particles are not contained, the image spot is A evaluation. In Examples 7 and 8, since the particle diameter of the crosslinked rubber particles is sufficiently small and the anti-sticking agent is contained, it is difficult to agglomerate, and the evaluation is A. On the other hand, in Examples 1 to 6 and Comparative Example 3, since no anti-sticking agent was contained, an agglomerated lump was rarely generated and B evaluation was made.

  The Mooney viscosity decreases as the compatibility between the elastomer forming the matrix phase and the crosslinked rubber particles forming the domain phase decreases. Therefore, it is preferable to select materials having greatly different SP values. Further, as a method for reducing Mooney viscosity, there is a method using crosslinked rubber particles in which inorganic fine particles such as talc and calcium carbonate are mixed as a sticking prevention agent around the crosslinked rubber particles. Due to the presence of the anti-sticking agent, the interaction between the matrix phase and the domain phase is weakened and the Mooney viscosity is lowered. Because of this effect, in Examples 7 and 8, the Mooney viscosity is low, and the evaluation of extrusion moldability is also good.

  The micro rubber hardness varies depending on the polymer and production method of the crosslinked rubber particles forming the domain phase. When radiation-cured crosslinked NBR / SBR is used, the hardness of the elastic body is most reduced, and then the radiation-cured crosslinked carboxyl-modified NBR / CR is good, and the hardness of the elastic body is hardly decreased. Cross-linked silicone particles. In the case of pulverized rubber particles, an arbitrary hardness can be obtained by selecting a rubber vulcanizate before pulverization, but a composition having a lower hardness tends to be difficult to pulverize. From the tendency of the micro rubber hardness, the durability stains were evaluated as A in Examples 1, 7, and 8, evaluated as B in Examples 5, 6, and Comparative Example 2, and evaluated as C in Comparative Examples 1 and 3. Further, in Examples 2 and 3, since the high release by ultraviolet irradiation is insufficient, in Example 5, the amount of ultraviolet irradiation is too large and the elastic body surface deteriorates. Since it became easy to adhere to the surface, it was B evaluation.

  The volume resistance is determined by the resistance of the matrix phase and the resistance of the domain phase of the crosslinked rubber particles. In the case of Comparative Example 1 that does not include the crosslinked rubber particles, the resistance is determined only by the dispersion state of the carbon, so that it is difficult to control and the resistance variation is large. When NBR, carboxyl-modified NBR, CR, or epichlorohydrin rubber having a relatively low resistance as the crosslinked rubber particles is used in the composition of Comparative Example 1, the electric resistance is moderately proportional to the content of the crosslinked rubber particles. Because it changes, it is easy to control. However, when SBR or silicone having a relatively high electrical resistance is used, the resistance changes abruptly depending on the content of the crosslinked rubber particles, which makes it difficult to control. Therefore, in Example 6 and Comparative Example 3, the resistance variation in the sheet is large. Since image density unevenness also occurs in correlation with the resistance variation in the sheet, Examples 1 to 5 and 7 and Comparative Example 2 are evaluated as A, Example 6 and Comparative Example 3 are evaluated as B, and Comparative Example 1 is evaluated as C. It has been evaluated.

  The compression set varies depending on the polymer of the crosslinked rubber particles and the production method. When it contains radiation-cured crosslinked NBR particles, crosslinked carboxyl-modified NBR particles, crosslinked CR particles, crosslinked SBR particles, and thermally cured crosslinked silicone particles, compared to crosslinked rubber particles prepared by pulverization of the vulcanizate Since there are few non-polymer components that cause deterioration of compression set, compression set is small and good. For this reason, severely neglected roller deformation marks, which are image defects caused by a large compression set, are not generated in Examples 1 to 8 and Comparative Example 3, but are generated in Comparative Examples 2 and 3.

It is a figure which shows the structure schematic diagram of an example of the electroconductive elastic body member for electrophotographic apparatuses of this invention. It is a figure which shows the schematic of an example of the electroconductive elastic body member for electrophotographic apparatuses of this invention. It is a figure which shows the schematic of an example of the electrophotographic apparatus using the electroconductive elastic body member for electrophotographic apparatuses of this invention.

Explanation of symbols

11 ... Matrix phase 12 ... Domain phase 21 ... Conductive support (shaft)
22... Conductive elastic body 23... High release layer 31 .. Electrophotographic photosensitive member (charged body)
32 ... Charging member (charging roller)
33 ... Exposure means 34 ... Development means 34a ... Toner carrier 34b ... Stirring member 34c ... Toner regulating member 35 ... Transfer means 36 ... Cleaning means 37 ... Pre-exposure means L ... Laser light S1, S2 Bias applied power supply P Transfer material

Claims (7)

  A conductive elastic member for an electrophotographic apparatus, comprising a conductive elastic body comprising a matrix phase containing an elastomer and a domain phase containing rubber particles obtained by radiation crosslinking.   2. The electroconductive elastic member for an electrophotographic apparatus according to claim 1, wherein the rubber particles have an average particle diameter of 50 nm or more and 500 nm or less.   The conductive elastic member for an electrophotographic apparatus according to claim 1, wherein the rubber particles contain an anti-sticking agent in the vicinity of the surface.   The electroconductive elastic member for an electrophotographic apparatus according to claim 1, wherein the matrix phase contains an electroconductive filler.   The electroconductive elastic member for an electrophotographic apparatus according to any one of claims 1 to 4, wherein the electroconductive elastic body has a high release layer on the surface.   Rubber particles obtained by radiation crosslinking, conductive filler and elastomer are mixed to obtain a mixture, and the mixture is cured to form a domain structure having a domain phase composed of rubber particles and an elastomer matrix phase. A method for producing a conductive elastic member for an electrophotographic apparatus.   7. The method for producing a conductive elastic member for an electrophotographic apparatus according to claim 6, wherein after the curing, the surface is irradiated with ultraviolet rays to form a highly release layer.

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