JP2009031758A - Charging roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging roll that is low in hardness, while having superior sag resistance, and capable of advantageously exhibiting the conductivity demanded. <P>SOLUTION: In this charging roll provided by forming a conductive elastic body layer around a shaft body, the conductive elastic body layer is formed of a rubber composition, prepared by mixing 0.7-1.0 pts.wt. of a peroxide cross-linking agent in 100 pts.wt. of epichlorohydrin rubber and/or nitrile rubber which is ion-conducting rubber, without mixing an electron conductive agent, and the abundance ratio of the rubber components in the conductive elastic body layer by thermogravimetric measurement is set to be not smaller than 90 wt.%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roll used for charging an image carrier made of an electrophotographic photosensitive member or an electrostatic recording dielectric in an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system. It is.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system, an image carrier such as a photoconductor (drum) is brought into contact with the outer peripheral surface of the charging roll, and the image carrier and the charging roll A so-called roll charging method is widely adopted in which the surfaces of the image carrier are charged by rotating the image bearing members mutually.

  In addition, as a charging roll used in a roll charging method related to such a contact charging method, those having various structures have been proposed and used conventionally. For example, a shaft body (core metal) as a conductor is proposed. ) Is provided with a conductive elastic layer made of a low-hardness rubber layer, and if necessary, a resistance adjusting layer and a protective layer are sequentially laminated on the outer peripheral surface of the conductive elastic layer. The thing of the structure which becomes is adopted.

  Conventionally, the conductive elastic layer of the charging roll having such a structure uses a rubber composition formed by blending various additives including an electronic conductive agent such as carbon black with natural rubber and various synthetic rubbers. Have been made. Specifically, using such a rubber composition as a molding material, an unvulcanized (uncrosslinked) rubber composition layer having a predetermined thickness is formed around a shaft body according to various molding methods, By vulcanizing or crosslinking the rubber composition layer, the conductive elastic layer is formed.

  In such a conductive elastic layer, the charging roll can efficiently charge the surface of the image carrier, and the contact property with the image carrier can be advantageously ensured. It is required to have excellent resistance to settling and uniformity of charging, and to keep the hardness as low as possible.

  By the way, in recent years, a rubber composition having an ion conductive rubber such as epichlorohydrin rubber as a rubber component has been used in producing a conductive elastic layer of a charging roll. If the molding is performed according to an existing injection molding method (mold injection molding method), the resulting molded product (unvulcanized (uncrosslinked) rubber composition layer) has problems such as poor surface properties. An extrusion method is widely employed when molding a rubber composition containing an ion conductive rubber as a rubber component. Further, in such a rubber composition, Patent Document 1 (Japanese Patent No. 3724465) is provided in order to ensure moldability during extrusion molding and to facilitate grinding of a finally obtained vulcanized (crosslinked) product. In general, inorganic fillers (fillers) such as calcium carbonate and silica are blended and used.

  However, in a conductive elastic layer obtained by vulcanization (crosslinking) after extrusion molding using a rubber composition in which inorganic fillers (fillers) such as calcium carbonate and silica are blended, the filler Due to the presence of this, there is a problem that the hardness of the conductive elastic layer, and consequently the hardness of the entire charging roll inevitably increases. In order to solve this problem, for example, it is known to form a conductive elastic layer using a rubber composition containing a liquid polymer or the like. An image forming apparatus such as a copying machine using an electrophotographic system is known. In the present situation where further miniaturization and higher functionality are required, and accordingly, more severe characteristics are required for the charging roll, it has excellent sag resistance. However, development of a charging roll that has low hardness and that can advantageously exhibit the required conductivity is desired.

Japanese Patent No. 3724465

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is that the hardness is low while having excellent sag resistance and the required conductivity. An object of the present invention is to provide a charging roll that can exhibit its properties in an advantageous manner.

  Then, the present inventors have made extensive studies on a rubber composition containing epichlorohydrin rubber and / or nitrile rubber (NBR), which are ionic conductive rubbers, as well as improvement of injection molding (mold injection molding) technology. However, in a charging roll having a conductive elastic layer formed using a rubber composition having a predetermined composition, the present inventors have found that the above-mentioned problems are solved and the present invention has been completed. .

  That is, according to the present invention, in the charging roll in which the conductive elastic layer is provided around the shaft body, the conductive elastic layer is added to 100 parts by weight of the epichlorohydrin rubber and / or nitrile rubber which is an ion conductive rubber. The conductive elastic body is formed of a rubber composition containing 0.7 to 1.0 part by weight of a peroxide crosslinking agent and not containing an electronic conductive agent, and is measured by thermogravimetry. The gist of the present invention is a charging roll characterized in that the abundance of the rubber component in the layer is 90% by weight or more.

  In one preferred embodiment of the charging roll according to the present invention, the ion conductive rubber constituting the rubber composition is an epichlorohydrin rubber, and is 0.5 weight with respect to 100 parts by weight of the epichlorohydrin rubber. Further less than or equal to an ionic conductive agent is further blended.

  In another preferred embodiment of the charging roll according to the present invention, the ion conductive rubber constituting the rubber composition is a nitrile rubber, and is 1 to 100 parts by weight of the nitrile rubber. 2 parts by weight of an ionic conductive agent is further blended.

  Furthermore, in the charging roll of the present invention as described above, advantageously, the conductive elastic body layer is formed of the shaft body disposed on the central axis in a mold having a cylindrical molding cavity. A layer made of the rubber composition provided by injecting or injecting the rubber composition into the mold is peroxide-crosslinked.

  As described above, in the charging roll according to the present invention, the conductive elastic layer is formed by peroxide-crosslinking a rubber composition obtained by blending a predetermined ion conductive rubber with a peroxide crosslinking agent. Since it is formed and is composed of a crosslinked product having a rubber component ratio of 90% by weight or more by thermogravimetry, a conventional inorganic filler (filler) such as silica is blended. Compared to a charging roll having a conductive elastic layer obtained by using a rubber composition, it has a low hardness while having excellent settling resistance.

  Further, the conductive elastic body layer in such a charging roll is formed by peroxide crosslinking using a peroxide as a crosslinking agent in place of the conventional sulfur vulcanization. The formation of the conductive elastic body layer by peroxide crosslinking also greatly contributes to the excellent anti-sag resistance.

  Furthermore, the conductive elastic body layer in the charging roll of the present invention is formed using a rubber composition comprising an epichlorohydrin rubber and / or nitrile rubber as an ion conductive rubber, and the epichlorohydrin rubber and nitrile rubber. Since both have a relatively low volume resistivity as rubber, it is possible to advantageously develop the conductivity required for the charging roll.

  Furthermore, when better conductivity is required for the conductive elastic layer, the conductive elastic layer may be formed using a rubber composition containing an ionic conductive agent. When only epichlorohydrin rubber is used as the ion conductive rubber, 0.5 parts by weight or less of ionic conductive agent is used with respect to 100 parts by weight of the epichlorohydrin rubber, and when only nitrile rubber is used. It is advantageous to improve conductivity by forming a conductive elastic layer using a rubber composition obtained by blending 1-2 parts by weight of an ionic conductive agent with respect to 100 parts by weight of nitrile rubber. It is possible to plan.

  In addition, the conductive elastic layer formed using a rubber composition containing a conventional conductive carbon black has an axial direction in order to prevent leakage between the rubber layer and the image carrier surface. The so-called C-plane treatment was required at both ends, but the conductive elastic body layer of the charging roll according to the present invention uses ionic conductive rubber as a rubber component, and conductive carbon. Since it does not contain an electronic conductive agent such as black, the conductive elastic layer in the charging roll of the present invention does not require the C-side treatment that has been conventionally required.

  Further, among the charging rolls according to the present invention, in particular, the conductive elastic layer has a shaft disposed on the central axis in a mold having a cylindrical molding cavity, and the rubber described above is included in the mold. In the charging roll formed by injecting or injecting the composition to provide a rubber composition layer around the shaft body and then peroxide-crosslinking the rubber composition layer, the above-described excellent charge roll is obtained. Of course, the surface property of the conductive elastic layer is very excellent as well as exhibiting the characteristics, and the cross-linking ( No grinding or polishing step after vulcanization) is required.

  By the way, when manufacturing the charging roll according to the present invention, first, a shaft body (core metal) made of a conductor having a predetermined length is prepared, and a conductive elastic layer is formed on the shaft body. A rubber composition will be prepared. For the preparation of such a rubber composition, epichlorohydrin rubber and / or nitrile rubber, which is an ion conductive rubber, is used as the main rubber component.

  Here, in the present invention, any of epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide copolymer, and those obtained by further copolymerizing allyl glycidyl ether with these copolymers can be used as the epichlorohydrin rubber. Moreover, it is also possible to use these 2 or more types together.

  In addition, it is possible in the present invention to use one or two or more kinds of epichlorohydrin rubber and nitrile rubber (NBR) in combination, or to use nitrile rubber alone.

  In the present invention, a peroxide crosslinking agent is used as a crosslinking agent for crosslinking the ion conductive rubber such as epichlorohydrin rubber. By cross-linking the ionic conductive rubber with a peroxide instead of sulfur which has been widely used conventionally, the obtained conductive elastic layer and thus the anti-sag property of the charging roll is excellent.

  Here, in this invention, a peroxide crosslinking agent is mix | blended in the ratio which will be 0.7-1.0 weight part with respect to 100 weight part of ion conductive rubber. When the amount of the peroxide cross-linking agent is less than 0.7 parts by weight, the cross-linking of the ion conductive rubber does not proceed sufficiently, and as a result, the obtained conductive elastic layer can exhibit sufficient settling resistance. On the other hand, if the blending amount exceeds 1.0 parts by weight, the hardness of the conductive elastic layer may be too high.

  As the peroxide crosslinking agent used in the present invention, any conventionally known crosslinking agent can be used. Specifically, peroxyketal crosslinkers such as perhexa HC, perhexa V and perhexa C (all trade names, manufactured by Nippon Oil & Fats Co., Ltd.), perhexa 25B, peroximon F, park mill D, perbutyl C, perhexyl D and perbutyl Dialkyl peroxide crosslinking agents such as D (both trade names, manufactured by NOF Corporation), peroxyester crosslinking agents such as perbutyl E, perbutyl I and perbutyl Z (all trade names, manufactured by NOF Corporation) Ketone peroxide crosslinking agents, peroxydicarbonate crosslinking agents, diacyl peroxide crosslinking agents, hydroperoxide crosslinking agents and the like can be exemplified. Among these known peroxide crosslinking agents, one or two or more types according to the purpose are appropriately selected and used.

  By the way, the epichlorohydrin rubber and the nitrile rubber, both of which are the ion conductive rubbers described above, have a relatively low volume resistivity as a rubber, but when a charging roll having higher conductivity is required, the ion conductive An agent (ionic conductive system conductive agent) is further blended in the rubber composition comprising the ion conductive rubber and the peroxide crosslinking agent.

  Such ionic conductive agent, if the blending amount is too small, the blending effect is not recognized, on the other hand, no significant improvement in conductivity is observed even if blended in a large amount, rather the probability of occurrence of bleeding and the like increases. Therefore, the blending amount according to the conductivity required for the target charging roll is appropriately determined. Preferably, when the rubber component that constitutes the rubber composition is epichlorohydrin rubber, the rubber component that constitutes the rubber composition at a ratio of 0.5 parts by weight or less with respect to 100 parts by weight of the epichlorohydrin rubber. Is a nitrile rubber, the ionic conductive agent is blended in the rubber composition in a ratio of 1 to 2 parts by weight with respect to 100 parts by weight of the nitrile rubber. As the ionic conductive agent usable in the present invention, various conventionally known ionic conductive agents, for example, tributylethylammonium ethyl sulfate, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide and tetrabutylammonium Examples include quaternary ammonium salts such as perchlorate, perchlorates such as lithium perchlorate and potassium perchlorate, and organic boron complexes.

  However, when the conductive elastic layer of the charging roll according to the present invention is produced, an electronic conductive agent (electroconductive agent) such as conductive carbon black is not used. This is because when such conductive carbon black or the like is blended in the rubber composition, the hardness of the resulting conductive elastic body layer is increased, and there is a risk of deterioration of the sag resistance.

  As described above, in the charging roll according to the present invention, the conductive elastic body layer is blended with an electronic conductive agent such as conductive carbon black using an ion conductive rubber such as epichlorohydrin rubber as a rubber component. It is formed with no rubber composition. Therefore, in a conductive elastic layer formed of a rubber composition containing a conventional electronic conductive agent, in many cases, such an elastic layer is used to prevent leakage between the surface and the surface of the image carrier. However, this C surface treatment is not necessary for the conductive elastic layer in the charging roll of the present invention.

  In producing the conductive elastic layer of the charging roll according to the present invention, the same as the conventional rubber composition with respect to the above-described ionic conductive rubber and peroxide crosslinking agent (and ionic conductive agent if necessary). It is possible to add a crosslinking aid, a crosslinking accelerator and other various additives. However, these additives are blended only in such an amount that the conductive elastic layer obtained by crosslinking the rubber composition has a rubber component content of 90% by weight or more by thermogravimetry (TG). It is possible.

  That is, in the charging roll according to the present invention, the conductive elastic layer is composed of a crosslinked product having a rubber component content of 90% by weight or more as measured by thermogravimetry. Since the rubber component is present in a higher proportion than the elastic elastic layer, the hardness is kept low while having excellent anti-sagging properties.

  Here, the abundance ratio of the rubber component by thermogravimetry in the present invention is calculated according to the following method.

  First, a conductive elastic layer obtained by peroxide crosslinking of a rubber composition (or a rubber composition having the same composition is crosslinked and molded under the same conditions as those for forming the conductive elastic layer. A sample is sampled from the cross-linked product obtained as described above. Using this sample, quantitative analysis of the extract (volatile components such as trace additives) contained in the sample is performed. Specifically, after 1) measuring the weight of the sample, 2) extracting volatile components from the sample according to the Soxhlet extraction method (conditions: 80 ° C. × 16 hours) using acetone or the like as the solvent, and 3) after extraction After the sample was air-dried, it was placed in a vacuum dryer set at 70 ° C. overnight and dried, and 4) the weight of the sample was measured after such drying. From the weight of the sample before extraction of the volatile components and the weight of the sample after extraction, the ratio of the volatile components in the sample (A [wt%]) is calculated.

  On the other hand, the other sampled samples are subjected to thermogravimetry using a thermogravimetric measuring device (thermobalance) at a heating rate of 20 ° C./min. At this time, the temperature is increased in a nitrogen atmosphere (in a nitrogen stream) from room temperature to 600 ° C., and the temperature is increased in an oxidizing atmosphere (in an air stream) from 600 ° C. to 900 ° C. The weight loss in the nitrogen atmosphere is due to the vaporization of the volatile components contained in the sample and the rubber component decomposition, and the weight loss in the oxidizing atmosphere is due to the oxidative decomposition of the carbon, and further increases to 900 ° C. The amount remaining after heating is assumed to be ash. After such measurement, the abundance ratio (% by weight) of “volatile component and rubber component”, “carbon component” and “ash component” is quantified from each weight decrease. And the existence ratio of the rubber component is obtained by subtracting the existence ratio (A [wt%]) of the volatile component in the sample calculated separately from the existence ratio of the “volatile component and the rubber component” determined by thermogravimetry. (% By weight).

  By the way, when the charging roll according to the present invention is manufactured, the rubber composition layer (core metal) around the shaft body (core metal) is advantageously used in accordance with the above-described rubber composition, preferably in accordance with an injection molding method (mold injection molding method). A conductive elastic layer before crosslinking) is formed. Specifically, a shaft body (core metal) is disposed on a central axis in a mold having a cylindrical molding cavity, and in this state, a rubber composition is injected or injected into the mold, A rubber composition layer is formed around the body (core metal). And the conductive roll of this invention is obtained by performing bridge | crosslinking operation with respect to this rubber composition layer. In the charging roll thus obtained, the surface property of the conductive elastic layer is very excellent. Note that various conditions in injection molding, temperature conditions in cross-linking, and the like according to the composition of the rubber composition and the like are appropriately selected.

In addition, a protective layer is further formed on the surface of the conductive roll thus manufactured (the outer peripheral surface of the conductive elastic layer) as necessary. This protective layer is provided in order to prevent toner or the like from adhering to or accumulating on the roll surface. For example, a resin composition material containing a fluorine-based resin such as a fluorine-modified acrylate resin, N-methoxy Conductive agents such as carbon black and metal oxides are blended with nylon materials such as methylated nylon so that the volume resistivity is generally about 1 × 10 ⁵ to 1 × 10 ¹³ Ω · cm. It is formed. The production of such a protective layer is performed according to a known coating technique such as dipping, and the thickness thereof is appropriately set according to the size (diameter, length) of the conductive roll. However, it is usually about 1 to 20 μm.

  Further, in the conventional charging roll, a resistance intended to increase the voltage resistance (leakage resistance) by controlling the electrical resistance of the entire charging roll between the conductive elastic layer and the protective layer. Generally, an adjustment layer is provided. However, in the charging roll of the present invention, such a resistance adjustment is performed because the conductive elastic body layer uses an ion conductive rubber as a rubber component. Layers are generally not required.

  And in the charging roll obtained in this way, the electroconductive elastic body layer has a low hardness while having excellent settling resistance.

  Some examples of the present invention will be shown below to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. Needless to say. In addition to the following examples, the present invention includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the specific description described above. It should be understood that improvements and the like can be added.

  First, 16 types of rubber compositions (rubber compositions No. 1 to 16) having different compositions were prepared according to the blending ratios shown in Tables 1 and 2 below. In this preparation, Epichroma CG102 (trade name) manufactured by Daiso Corporation is used as the epichlorohydrin rubber, Nipol 3335 (trade name) manufactured by Nippon Zeon Co., Ltd. is used as the nitrile rubber, and hydrotalcite serving as the acid acceptor is used as the hydrotalcite. DHT4A (trade name) manufactured by Kyowa Chemical Industry Co., Ltd., dicumyl peroxide (trade name: Park Mill D, manufactured by NOF Corporation) as the peroxide crosslinking agent, and quaternary ammonium salt as the ionic conductive agent. , Respectively. In Table 1 below, vulcanization accelerator A is Sunseller CZ (trade name) manufactured by Sanshin Chemical Industry Co., Ltd., and vulcanization accelerator B is Noxeller TRA (trade name) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. And Vulcanization Accelerator C indicate Noxeller TT (trade name) manufactured by Ouchi Shinsei Chemical Co., Ltd., respectively.

  Using the prepared 16 types of rubber compositions, first, the following physical properties were measured according to the respective methods. The measurement results are shown as material characteristics in Tables 3 and 4 below.

-Rubber fraction-
Using a cross-linked product (vulcanized product) obtained by cross-linking (vulcanizing) each rubber composition as a sample, the abundance ratio (rubber fraction) of the rubber component in the sample is determined according to the method described above. Thermogravimetry was performed and calculated.

-Compression set-
Each rubber composition was subjected to press crosslinking (vulcanization) molding at 160 ° C. for 30 minutes to obtain a crosslinked product (vulcanized product) sample having a predetermined shape. Using the obtained sample, compression set (%) was measured according to JIS-K-6262.

-Volume resistivity-
Each rubber composition was subjected to press crosslinking (vulcanization) molding at 160 ° C. for 30 minutes to obtain a sheet-like sample having a thickness of 2 mm. By applying a silver paste on one surface of the obtained sheet-like sample, an electrode having a size of 10 mm × 10 mm is provided (with a guard electrode), while a counter electrode is provided on the surface opposite to the surface on which the electrode is provided. The resistance between both electrodes under the condition of applied voltage: 100 V was measured according to the method described in JIS-K-6911, and the volume resistivity (Ω · cm) was calculated.

  Next, charging rolls were produced using the obtained rubber compositions according to the following method.

  That is, a mold (mold) having a predetermined cylindrical molding cavity is prepared, a shaft body (core metal) is disposed on the central axis in the mold, and a rubber composition is injected into the mold. did. Thereafter, a conductive elastic body layer was formed on the shaft body by performing a predetermined crosslinking (vulcanization) operation. Further, the surface of the conductive elastic layer was spray-coated with a protective layer-forming resin solution consisting of 100 parts by weight of N-methoxymethylated nylon and 8 parts by weight of conductive carbon black, and then dried. Thus, using each rubber composition, it has a conductive elastic body layer (thickness: 3 mm) around a metal core (diameter: 6 mm), and further protects the surface of the conductive elastic body layer. A charging roll having a layer (thickness: 10 μm) was produced.

  Various properties were measured and evaluated for the charging rolls using the rubber compositions thus obtained. Evaluation and measurement of such physical properties are carried out according to the following methods, respectively, and the evaluation (measurement) results are shown in Table 3 and Table 4 below as roll evaluation.

-Micro rubber hardness-
Both ends are supported by a V block using a spring-type hardness tester (micro rubber hardness tester, MD-1 type, manufactured by Kobunshi Keiki Co., Ltd.) using a cantilever leaf spring type load system. The tip of the push needle of the spring type hardness tester is brought into contact with the surface of the central portion in the axial direction of each conductive roll held in a horizontal state, and the tester is placed vertically with a load of 33.85 g. Measurement was performed by pressing and immediately reading the scale.

-Roll resistance-
As shown in FIG. 1, in a state where both ends of the produced conductive roll are pressed against a metal roll (diameter: 24 mm) with a predetermined load, the metal roll is rotated at a predetermined rotational speed in the direction of the arrow in the figure. As a result, the conductive roll was rotated. While maintaining this state (while rotating both the metal roll and the conductive roll), a voltage of 300 V is applied between the ends of the conductive roll and the metal roll, the flowing current value is measured, and the electric resistance value (roll Resistance: Ω) was obtained.

-Sag amount, evaluation-
The prepared charging roll was placed on a metal roll (diameter: 24 mm), and a load of 500 g was applied to each of the shaft bodies (core metal) at both ends of the charging roll. Humidity: left in an atmosphere of 95% for 2 weeks. Thereafter, the charging roll was taken out from the atmosphere and allowed to stand in the room for 30 minutes, and then a dent (mm) generated on the surface of the charging roll was measured to obtain a set amount. The charging roll was attached to an actual machine (trade name: CNJ3000, manufactured by Hewlett-Packard Company), and a predetermined image (test pattern) was output from the actual machine. The output image was visually observed, and the evaluation was performed based on the presence or absence of deformation stripes due to the dent (sagging) of the charging roll. The evaluation criteria are as follows.
○: No deformation streak exists in the output image.
X: Deformed streaks exist in the output image.

-Durable dirt evaluation-
The prepared charging roll is attached to an actual machine (Fuji Xerox Co., Ltd., trade name: DocuPrint C3530), and using this actual machine, a print test of 5000 sheets in an environment of temperature: 32.5 ° C. and humidity: 83% ( Printing rate: 5%). Thereafter, the charging roll was taken out from the actual machine, and the fixing state of the toner or the external additive on the surface was visually observed and evaluated. The evaluation criteria are as follows.
○: The toner and external additives are hardly fixed on the roll surface.
Δ: Slight adhesion of toner or external additive is present on the roll surface.
X: Toner or external additives are adhered to the roll surface to a degree that significantly affects the image.

-Bleed evaluation-
The produced charging roll was left in an atmosphere of temperature: 50 ° C. × humidity: 90% for 2 weeks, and then the presence or absence of bleeding on the roll surface was visually observed. Next, the charging roll was attached to an actual machine (trade name: CNJ3000, manufactured by Hewlett-Packard Company), a predetermined image (test pattern) was output with this actual machine, and the output image was visually observed. And bleed evaluation was performed based on the observation result of the roll surface before image output, and the observation result of the output image. The evaluation criteria are as follows.
○: Bleed is not recognized on the roll surface, and there is no image defect in the output image.
(Triangle | delta): Although bleeding is recognized on the roll surface, an image defect does not exist in an output image.
X: Bleed is observed on the roll surface, and image defects exist in the output image.

  As is apparent from the results of Table 2, the anti-sag resistance is excellent in the charging roll according to the present invention (the charging roll in which the conductive elastic layer is formed using the rubber compositions No. 1 to 11). It has been confirmed that the required conductivity can be advantageously exerted by changing the blending amount of the ionic conductive agent while exhibiting the properties.

It is explanatory drawing which shows typically the measuring method of the resistance value (roll resistance) of the charging roll in an Example.

Claims (4)

In a charging roll in which a conductive elastic layer is provided around a shaft body,
An electronic conductive agent, wherein the conductive elastic layer is formed by blending 0.7 to 1.0 parts by weight of a peroxide crosslinking agent with 100 parts by weight of epichlorohydrin rubber and / or nitrile rubber which is an ion conductive rubber. And a rubber component in the conductive elastic body layer by thermogravimetry is 90% by weight or more.   2. The ion conductive rubber constituting the rubber composition is epichlorohydrin rubber, and 0.5 parts by weight or less of an ionic conductive agent is further blended with 100 parts by weight of the epichlorohydrin rubber. Charging roll.   The ion conductive rubber which comprises the said rubber composition is a nitrile rubber, Comprising: The ion conductive agent of 1-2 weight part is further mix | blended with respect to 100 weight part of this nitrile rubber. Charging roll. By injecting or injecting the rubber composition into the mold around the shaft disposed on the central axis in the mold having the cylindrical molding cavity, the conductive elastic layer. The charging roll according to any one of claims 1 to 3, wherein the layer made of the rubber composition is formed by peroxide crosslinking.

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