JP2007271659A - Conductive elastic roller, method for manufacturing the same, and electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive elastic roller to be used for an electrophotographic apparatus, in which a foamed rubber layer is tightly fixed in spite of no application of adhesive to a shaft core body, press fitting of the shaft core body into a foamed rubber tube and polishing on the surface of the foamed rubber layer can be easily performed in the manufacturing of the conductive elastic roller, and hardness variance and circumferential resistance variance can be eliminated as the result. <P>SOLUTION: The shaft core body is plated by electroless nickel plating, and the foamed rubber tube is obtained by cylindrically extruding a foamed rubber layer material composition composed of acrylonitrile-butadiene rubber and epichlorohydrin rubber as a rubber material added with at least a foaming agent and a vulcanizing agent to be subjected to vulcanization-foaming by microwaves, wherein the inner diameter (as a circle) of the foamed rubber tube is 80±10% of the outer diameter of the shaft core body to be press-fitted and sliding resistance in the inner surface of the tube against the press-fitted shaft core body is 0.6 to 0.9 Nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a conductive elastic roller used in an image forming apparatus such as an electrophotographic copying apparatus, a printer, and an electrostatic recording apparatus, and a manufacturing method thereof, and further relates to an electrophotographic apparatus using the conductive elastic roller as a transfer roller. .

  In electrophotographic image forming apparatuses such as copying machines and printers, various conductive elastic rollers are used as charging rollers, transfer rollers, developing rollers, and the like. In order to impart conductivity to the elastic layer of these rollers, a method of adding a conductive agent such as carbon black to the rubber material that is a raw material of the elastic layer, or the elastic layer itself is made of an ionic conductive material such as acrylonitrile butadiene rubber or epichlorohydrin rubber. There is a method of forming with a rubber material. These rollers are in contact with the electrophotographic photosensitive member (photosensitive drum) with a load applied, and are energized for a long time for the purpose of use. Therefore, it is desirable to use a rubber material having a small variation in conductivity (for example, resistance value), and acrylonitrile butadiene rubber, epichlorohydrin rubber, and the like are widely used in transfer rollers and charging rollers because of problems in the manufacturing method. For example, Patent Documents 1 and 2).

  The rubber material used for these rollers is a raw material composition obtained by kneading a vulcanizing agent, a foaming agent, a filler, and the like. A cylindrical molded body of sulfur is vulcanized and foamed by heating to form a cylindrical foam. Thereafter, a method is used in which a shaft core is press-fitted into a cylindrical foam, and the outer diameter is polished into a roller shape to form a conductive elastic roller. In the case of extrusion molding, it is cut into a predetermined length after vulcanization and foaming. Further, in molding by a mold, primary vulcanization / foaming is often performed in the mold.

  Several methods are known for press-fitting a shaft core into a cylindrical foam (for example, Patent Documents 3 to 5). That is, the amount of voids at the interface between the cylindrical foam and the shaft core is set such that the radial cross-sectional area of the cylindrical foam is 80% or more and less than 100% of the radial cross-sectional area of the shaft center body (Patent Document 3). (Patent Document 4) or the surface roughness Ra of the inner surface of the cylindrical foam is set to 20 μm to 100 μm, and the inner diameter of the cylindrical foam is 50% of the outer diameter of the shaft core body For example, a liquid adhesive is applied to the inner surface of a cylindrical foam (Patent Document 5).

However, in any case, the focus is only on the shape of the foam, and depending on the composition of the rubber raw material, the cylindrical foam (foamed rubber layer) cannot be firmly fixed to the shaft core body. In some cases, the foamed rubber layer may be distorted during polishing to adjust the outer shape. Also, the use of an adhesive is not preferable from the viewpoints of work, environment, and economy.
Japanese Patent Application Laid-Open No. 11-065269 Japanese Patent Laid-Open No. 2003-064224 JP 2003-323064 A Japanese Patent Laid-Open No. 2003-323065 JP 2004-237618 A

  Accordingly, an object of the present invention is a conductive elastic roller used in an electrophotographic apparatus, wherein a foamed rubber layer is firmly fixed regardless of whether an adhesive is applied to the shaft core, and In the production thereof, it is possible to easily press-fit the shaft core into the foamed rubber tube and polish the surface of the foamed rubber layer, and as a result, provide a conductive elastic roller having no hardness unevenness and resistance circumferential unevenness. Another object of the present invention is to provide a method for producing the conductive elastic roller, and to provide an electrophotographic apparatus capable of obtaining a good image by incorporating the conductive elastic roller as a transfer roller.

  In order to solve the above-mentioned problems, the present inventors have intensively studied the shaft core body and the foamed rubber layer of the conductive elastic roller. First, the surface of the shaft core body is nickel-plated and used as the foamed rubber layer. The present inventors have found that it is important for the foamed rubber tube to specify the raw material and the foaming process, and have further studied to arrive at the present invention.

  That is, the present invention is achieved by the following configuration.

(1) A conductive elastic roller having a foam rubber layer formed by press-fitting a shaft core body into a foam rubber tube,
The shaft core is electroless nickel plated,
A foamed rubber tube has at least a foaming agent and a vulcanizing agent disposed in a rubber raw material, and the rubber raw material is extruded from a foamed rubber layer raw material composition comprising acrylonitrile butadiene rubber and epichlorohydrin rubber, and vulcanized by microwaves. The foamed rubber tube has an inner diameter (as a perfect circle) of 80% ± 10% of the outer diameter of the shaft core body to be press-fitted,
The conductive elastic roller is characterized in that the sliding resistance of the inner surface of the tube relative to the shaft core is 0.6 N · m or more and 0.9 N · m or less.

(2) The electroconductive elastic roller in which vulcanization foaming by microwaves is performed in a microwave vulcanization furnace having an effective irradiation section of 2 m or less and an output of 1.0 kW to 2.0 kW.

(3) A method for producing a conductive elastic roller in which a shaft core body is press-fitted into a foamed rubber tube to form a foamed rubber layer, comprising at least the following steps:
A step of preparing a foamed rubber layer raw material composition by arranging at least a foaming agent and a vulcanizing agent on a rubber raw material comprising acrylonitrile butadiene rubber and epichlorohydrin rubber;
A step of extruding the foam rubber layer raw material composition into a cylindrical shape to produce a foam rubber layer raw material composition tube;
The foam rubber layer material composition tube is foam vulcanized in a microwave vulcanization furnace having an effective irradiation section of 2 m or less and an output of 1.0 kW to 2.0 kW, and the inner diameter (as a perfect circle) is Obtaining a foamed rubber tube that is 80% ± 10% of the outer diameter of the press-fitted shaft core;
A step of cutting the foam rubber tube; and a step of press-fitting a shaft core body having an electroless nickel plating surface into the cut foam rubber tube.

(4) The manufacturing method of the said conductive elastic roller whose sliding resistance of the foam rubber tube inner surface with respect to a shaft core body is 0.6 N * m or more and 0.9 N * m or less.

(5) The transfer roller is vulcanized by microwave after a foamed rubber layer raw material composition in which at least a foaming agent and a vulcanizing agent are arranged on a rubber raw material made of acrylonitrile butadiene rubber and epichlorohydrin rubber is extruded into a cylindrical shape. Manufactured by press-fitting a shaft core body having an electroless nickel plating surface into a foamed rubber tube whose inner diameter (as a perfect circle) is 80% ± 10% of the outer diameter of the shaft core body. An electrophotographic apparatus characterized by being a conductive elastic roller having a sliding resistance of an inner surface of a foam rubber tube with respect to the shaft core body of 0.6 N · m or more and 0.9 N · m or less.

(6) The electrophotographic apparatus described above, wherein the microwave vulcanization foaming is performed in a microwave vulcanization furnace having an effective irradiation section of 2 m or less and an output of 1.0 kW to 2.0 kW.

  According to the present invention, even if the shaft core body is not coated with an adhesive, the foamed rubber layer is firmly fixed. Polishing can be easily performed. As a result, a conductive elastic roller having no hardness unevenness and resistance circumferential unevenness is provided.

  The conductive roller can be suitably used as a roller for an electrophotographic apparatus, particularly as a transfer roller.

  The best mode for carrying out the present invention will be described in detail below.

  In FIG. 1, the perspective view of an example of the electroconductive elastic roller of this invention is shown.

  The conductive elastic roller of the present invention has a conductive foam rubber layer 2 formed around a conductive shaft core 1 having at least a surface plated with electroless nickel. A surface layer may be formed on the surface of the foamed rubber layer in order to provide a function necessary as a roller of an electrophotographic apparatus.

  In the present invention, the conductive foam rubber layer is a foam rubber tube in which at least a foaming agent and a vulcanizing agent are disposed on a rubber raw material made of acrylonitrile butadiene rubber and epichlorohydrin rubber, extruded into a cylindrical shape, and then vulcanized and foamed. The foamed rubber tube cut into a roller length is formed by covering the shaft core body. In addition, since acrylonitrile butadiene rubber and epichlorohydrin rubber have ionic conductivity, the foamed rubber layer exhibits conductivity, but in order to lack conductivity or stabilize conductivity, It is preferable to arrange the conductive material.

  In the present invention, acrylonitrile butadiene rubber and epichlorohydrin rubber are used in combination as rubber raw materials. In addition, polymer materials such as polystyrene polymer materials, polyolefin polymer materials, polyester polymer materials, polyurethane polymer materials, thermoplastic elastomers such as RVC, acrylic resins, and styrene vinyl acetate copolymers are required. Can also be used by mixing. The mixing ratio of acrylonitrile butadiene rubber and epichlorohydrin rubber is suitably in the range of 1/99 to 99/1 by mass ratio.

  In the present invention, a foaming agent is used for forming the foamed rubber layer. Organic foaming agents such as azodicarbonamide (ADCA), dinitrosopentamethylenetetraamine (DPT), p-toluenesulfonyl hydrazide (TSH), oxybisbenzenesulfonyl hydrazide (OBSH) are used as the foaming agent. These can be used alone or in combination. The amount of the foaming agent is set to an appropriate amount in order to achieve the elasticity required of the foamed rubber layer, but it is suitably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the rubber raw material.

  Further, the decomposition temperature of the foaming agent can be lowered by adding urea, zinc oxide or the like as a foaming aid. Examples of the foaming aid include urea compounds; metal oxides such as zinc oxide and lead oxide; compounds mainly composed of salicylic acid, stearic acid, and the like, which are selected and used according to the foaming agent.

  As the vulcanizing agent, sulfur, metal oxides and the like can be used, and sulfur is particularly preferable. The vulcanizing agent has an appropriate amount to achieve the elasticity and strength required by the foamed rubber layer, but 0.1 parts by weight or more and 5.0 parts by weight or less with respect to 100 parts by weight of the rubber raw material Is appropriate.

  Moreover, in this invention, it is preferable to use a vulcanization accelerator with a vulcanizing agent. Various vulcanization accelerators are known, and thiazole vulcanization accelerators and thiuram vulcanization accelerators can be used. And, it is generally known that the combined use of a thiazole vulcanization accelerator and a thiuram vulcanization accelerator has an effect on the C setting property, so it is preferable to use them together.

  Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and the like, and dibenzothiazyl disulfide that is used in combination with a thiuram-based vulcanization accelerator is preferable. Examples of the thiuram vulcanization accelerator include tetramethylthiuram monosulfide, tetraethylthiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, dipentamethylenethiuram tetrasulfide and the like. It is preferable to use tetrakis (2-ethylhexyl) thiuram disulfide having excellent scorch properties. In addition, other thiazole vulcanization accelerators and thiuram vulcanization accelerators can be used by adjusting the use conditions.

  Although it is preferable to use sulfur as a vulcanizing agent, this is not only an effect as a normal vulcanizing agent, but also an effect of improving the adhesion due to chemical interaction with the conductive shaft core. There is also.

  Moreover, in this invention, it is possible to mix | blend conductive agents, such as carbon black, fillers, such as a calcium carbonate, and anti-aging agent with a foaming agent and a vulcanizing agent as needed.

As the conductive agent, a known conductive substance can be used. For example, as an electronic conductive agent, conductive carbon black, TiO ₂ , SnO ₂ , ZnO, a metal oxide such as a solid solution of SnO ₂ and SbO ₃ , a metal powder such as Cu and Ag, and the like, and as an ionic conductive agent, LiCIO ₄ , NaSCN, etc. are mentioned, and are added to a rubber raw material alone or plurally and dispersed. In addition, the kind and usage-amount are suitably determined from required electroconductivity. Further, in order to obtain the conductivity of the foamed rubber layer, it is possible to introduce a functional group having polarity into the main chain or side chain of the rubber raw material.

  As the electronic conductive agent, it is preferable to use conductive carbon black because sufficient conductivity can be obtained with a small amount of use, and the amount used is usually 5 parts by mass with respect to 100 parts by mass of the rubber raw material. The amount of 95 parts by mass or more is appropriate.

  In the present invention, the shaft core body is made of a conductive rod-shaped or cylindrical metal or resin, and its surface needs to be electrolessly nickel-plated. In addition, it is preferable that the shaft core body is made of metal, and as the metal, iron, steel, cast iron, rust-free steel, brass, copper, etc. can be used, but these metals are vulcanized rubber raw materials. Since there is no resistance to sulfur and peroxide used in the electroless plating, electroless nickel plating is used as the surface. In addition to electroless nickel plating, chrome plating, tin plating, and the like can be cited as the type of plating, but electroless nickel plating is particularly preferable in terms of cost and adhesion to the foamed rubber layer. If the vulcanizing agent is sulfur, the adhesion with the foamed rubber layer is further improved.

  The outer diameter of the shaft body may be appropriately determined depending on the purpose of use of the conductive elastic roller. For example, in the case of a transfer roller, it is 2 mm or more and 20 mm or less, preferably 3 mm or more and 15 mm or less, more preferably 4 mm or more and 10 mm or less. Is appropriate. In addition, when an outer diameter is 8 mm or more, it can also be reduced in weight by using the cylindrical shape which has the thickness of the range of 2 mm to 3 mm.

  The conductive elastic roller of the present invention can be manufactured as follows.

  In the present invention, first, a foam rubber tube is manufactured. The outline of the vulcanization foaming apparatus used for manufacture is shown in FIG.

  That is, after the above foam rubber layer raw material composition is kneaded in a closed kneader such as a Banbury mixer or kneader, it is molded into a ribbon shape by an open roll or a ribbon molding dispenser, and is put into the extruder 11. The extruded rubber layer raw material composition tube is extruded into a cylindrical shape and is unvulcanized and unfoamed.

  The unvulcanized and unfoamed foam rubber layer raw material composition tube formed by the extruder 11 is introduced into a vulcanizer (microwave vulcanizer, UHF) 12 by microwave heating. The foamed rubber layer raw material composition tube that is unvulcanized and unfoamed with UHF 12 is heated to perform foaming and vulcanization. The heating section (effective microwave irradiation section) of the UHF 12 is preferably 2 m or less. Even if the heating section exceeds 2 m, there is no problem with vulcanization foaming, but it is not preferable because it only increases the size of the apparatus and takes up installation space and reduces the economy. The output of the UHF 12 is suitably from 1.0 kW to 2.0 kW. When the output of UHF12 is less than 1.0 kW, the unvulcanized and unfoamed foam rubber layer raw material composition tube is not sufficiently vulcanized / foamed, and when it exceeds 2.0 kW, heating is too early, Too much foaming, control is not possible, and the tube is not cylindrical. There is also a risk that the foam rubber layer material composition may ignite.

  The foam rubber layer raw material composition tube vulcanized and foamed with UHF 12 is conveyed to a hot-air vulcanizer (HAV) 13 following UHF 12 and vulcanization is completed to obtain a foam rubber tube. In addition, although the temperature of the hot air sent to HAV13 changes with compositions of a foamed rubber layer raw material composition, a foaming ratio, a vulcanization degree, etc., it is suitable that it is normally 100 degreeC or more and 250 degrees C or less. Also, the blowing rate is appropriately set depending on the composition of the foamed rubber layer raw material composition, the expansion ratio, the degree of vulcanization, and the like. The thickness of the foamed rubber tube to be manufactured varies depending on the purpose of use of the conductive elastic roller to be manufactured, the presence or absence of surface polishing after inserting the shaft core, etc., but usually 2 mm or more and 20 mm or less, preferably 3 mm or more and 15 mm. Hereinafter, it is particularly preferably 4 mm or more and 12 mm or less.

  The foamed rubber tube that has been completely vulcanized and foamed is taken up by the take-up machine 14, and then sent to the fixing and cutting machine 15 to be cut into a predetermined length.

  Next, the foamed rubber tube cut to a predetermined length is taken up if necessary, and after the distortion caused by cutting or the like is removed, the shaft core body whose surface is electroless nickel plated is press-fitted, and the conductive property of the present invention An elastic roller is manufactured. Here, it is important that the inner diameter (as a perfect circle) of the foam rubber tube is 80% ± 10% of the outer diameter of the press-fitted shaft core body. When the inside diameter of the foam rubber tube is within such a range, the adhesion between the press-fitted shaft core body and the foam rubber layer is improved. When the foamed rubber tube has a diameter exceeding this range, the adhesiveness with the shaft core is insufficient, and the foamed rubber layer is distorted during use or processing as required, which is not preferable. On the other hand, if it is smaller than this range, the foamed rubber layer is distorted when the shaft body is press-fitted, which is not preferable.

  In the obtained conductive elastic roller, the sliding resistance of the foam rubber tube inner surface with respect to the shaft core, that is, the adhesion strength between the shaft core and the foam rubber layer is 0.6 N · m or more and 0.9 N · m or less. Is essential. If the sliding resistance is less than 0.6 N · m, the adhesiveness between the shaft core and the foamed rubber layer is insufficient, and distortion is generated in the foamed rubber layer during use or as required, which is not preferable. On the other hand, if it exceeds 0.9 N · m, the reaction between the sulfur in the foamed rubber layer and the electroless nickel plating has advanced. In such a case, the shaft core body is corroded during storage or use of the conductive elastic roller, the shaft core body strength decreases, the adhesion between the shaft core body and the foam rubber layer decreases, and irregularities occur on the surface of the foam rubber layer. This is also not preferable because it tends to cause problems such as the above.

  As for a specific example of a line for producing a foam rubber tube, the total length from the UHF 12 excluding the extruder 11 to the regular cutting machine 15 is about 13 m, the UHF 12 is about 4 m in order, the HAV 13 is about 6 m, The take-up machine 14 and the standard cutting machine 15 are about 1 m in total, and an interval of 0.1 m or more and 1.0 m is provided between them. The UHF 12 is provided with a mesh belt whose surface is coated with a fluororesin, on which the unvulcanized unfoamed rubber layer raw material composition tube from the extruder is conveyed and vulcanized and foamed. . The microwave irradiation area in the UHF 12 is 2 m or less. The foamed rubber layer raw material composition tube vulcanized and foamed in UHF 12 is transported to HAV 13 by placing it on a roller coated with a fluororesin. Be transported. In this case, the belt or roller coated with fluororesin is used because the foam rubber layer raw material composition tube that has not been vulcanized and foamed adheres to the belt or roller, causing the tube surface to peel off or cause distortion. This is in order not to let them.

  The shaft core body is press-fitted into a foamed rubber tube cut to a predetermined length to form a roller-shaped molded body, which can be used as a conductive elastic roller as it is. It is polished with a grindstone or blasted with abrasive grains, and the roller diameter and surface are made to have a size and surface roughness according to the purpose of use.

  Here, the polishing of the surface is performed, for example, by setting the conductive elastic roller on which the foamed rubber layer produced as described above is formed in a polishing machine equipped with a polishing grindstone, and setting the rotation speed of the polishing grindstone to 2000 rpm. The feeding speed can be set to 500 m / min. In this polishing, if the adhesion strength between the foamed rubber layer and the shaft core is less than 0.6 N · m, the foamed rubber layer is peeled off and uniform polishing cannot be performed.

  The conductive elastic roller of the present invention produced as described above can further be formed with a resin layer in order to obtain a surface state corresponding to the purpose of use.

  Next, an image forming apparatus in which the conductive elastic roller of the present invention is incorporated in a transfer roller or the like will be described.

  FIG. 3 is a schematic configuration diagram illustrating an example of an electrophotographic image forming apparatus using a process cartridge.

  The image forming apparatus includes a drum-type electrophotographic photosensitive member (photosensitive drum) 21 as an image carrier. The photosensitive drum 21 is obtained by providing a photosensitive layer made of an organic photoconductor (OPC) on the outer peripheral surface of a grounded cylindrical aluminum substrate. This photosensitive drum 21 is rotationally driven by a driving means (not shown) at a predetermined process speed (circumferential speed), for example, 50 mm / sec, in the direction of arrow R1.

The surface of the photosensitive drum 21 is uniformly charged by a charging roller 22 as a contact charging member. The charging roller 22 is disposed in contact with the photosensitive drum 21 and is driven to rotate in the direction of the arrow R2 as the photosensitive drum 21 rotates. An oscillating voltage (AC voltage VAC + DC voltage VDC) is applied to the charging roller 22 by a charging bias applying power source (high voltage power source), whereby the surface of the photosensitive drum 21 is uniformly at a dark portion potential V _d (for example, −600 V). Is charged. The surface of the charged photosensitive drum 21 is scanned and exposed by a laser beam 23 output from a laser scanner and reflected by a mirror, that is, a laser beam modulated in accordance with a time-series electric digital image signal of target image information. receive. As a result, an electrostatic latent image (bright part V ₁ , for example, −150 V) corresponding to the target image information is formed on the surface of the photosensitive drum 21.

  The electrostatic latent image is reversely developed as a toner image by attaching negatively charged toner by a developing bias applied to the developing roller 24a of the developing device 24.

  On the other hand, the transfer material 27 such as paper fed from the paper supply unit is guided by the transfer guide, and is transferred to the transfer unit (transfer nip unit) T between the photosensitive drum 21 and the transfer roller 26. The toner image is supplied so as to match the timing of the upper toner image. The toner image is transferred to the transfer material 27 supplied to the transfer portion T by the transfer bias applied to the transfer roller 26 by the transfer bias application power source. At this time, toner remaining on the surface of the photosensitive drum 21 without being transferred to the transfer material 27 (residual toner) is removed by the cleaning device 29.

  The transfer material 27 that has passed through the transfer portion T is separated from the photosensitive drum 21 and introduced into the fixing device 30, where the toner image is subjected to fixing processing, and is discharged out of the image forming apparatus main body as an image formed product (print). The

  Here, the conductive elastic roller of the present invention is used as a charging roller, a developing roller, and a transfer roller, and is particularly useful as a transfer roller.

  The measurement of the inner surface of the foamed rubber tube and the sliding resistance (adhesion degree between the foamed rubber layer and the shaft core body), which is an important evaluation item in the present invention, was performed by the following method.

〔Rotation torque〕
That is, after the shaft core body is press-fitted into the foam rubber tube, the conductive elastic roller placed in a N / N environment of 23 ° C. and 55% RH for 48 hours is clamped until the distortion of the foam rubber layer is relieved. Hold it. Then, attach a motor to the shaft core and rotate the motor. The sandwiching of the conductive elastic roller does not slide between the foamed rubber layer and the clamp due to the rotation of the motor, but it is necessary that the deformation due to the clamping does not reach the new shaft load. The load applied when the motor is rotated is measured with a sliding torque detector “Ceder DI-12” (trade name) manufactured by Sugisaki Keiki Co., Ltd. Then, the load at the time when the new shaft starts to slide with respect to the foam rubber layer is measured, and the inner surface of the foam rubber tube with respect to the shaft core body and the sliding resistance (adhesion degree between the foam rubber layer and the shaft core body) are measured as rotational torque N · m).

  Further, the hardness unevenness and the electrical resistance unevenness of the foamed rubber layer of the conductive elastic roller are also evaluated as follows.

[Hardness unevenness]
The Asker C hardness is measured with an Asker C-type hardness meter (4.9 N load) at an arbitrary location on the surface of the foamed rubber layer of the obtained conductive elastic roller at 90 ° intervals in the circumferential direction. The difference in hardness between the maximum value and the minimum value of the obtained values is obtained and used as an index representing the degree of hardness unevenness. That is, when the difference in hardness is 0, it means that there is no unevenness at all, and as the hardness difference is closer to 0, it means that there is no unevenness and is preferable.

[Electric resistance unevenness]
The obtained conductive elastic roller was placed in an N / N environment of 23 ° C. and 55% RH for 48 hours, and then a load of 4.9 N was applied to the end portion of the shaft core so that the outer diameter was 30 mm. Then, the aluminum drum is rotated at 30 rpm, and the conductive elastic roller is also driven to rotate. In this state, a voltage of 2 kV is applied between the shaft core and the aluminum drum, and the electrical resistance is continuously measured for one rotation of the conductive elastic roller. Next, logarithmic values of the maximum value and the minimum value of the measured electric resistance are obtained, and the difference is used as an index of the electric resistance unevenness. This difference is preferably less than 1.2.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to this transfer roller, but can be developed to a charging roller and a developing roller.

The rubber materials used in each example and comparative example are as follows.
・ NBR: Acrylonitrile butadiene rubber “NIPOL DN401LL” (trade name, manufactured by Nippon Zeon Co., Ltd.)
GECO: Epichlorohydrin rubber “Hydrin G3106” (trade name, manufactured by Nippon Zeon Co., Ltd.)
DM: Dibenzothiazyl disulfide “Noxeller DM-P” (trade name, thiazole vulcanization accelerator, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
-TOT: Tetrakis (2-ethylhexyl) thiuram disulfide "Noxeller TOT-N" (trade name, thiuram disulfide vulcanization accelerator, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Sulfur: Sulfur “Salfax PMC” (trade name, manufactured by Tsurumi Chemical Co., Ltd.)
・ ADCA: Azodicarbonamide “Vinihol AC” (trade name, manufactured by Eiwa Kasei Kogyo Co., Ltd.)

Examples 1-4
As raw rubber, 80 parts by mass of NBR and 20 parts by mass of GECO were used, and 4.0 parts by mass of ADCA as a foaming agent, 1.5 parts by mass of sulfur as a vulcanizing agent and 1.5 parts by mass of DM as a vulcanization accelerator. And 2.0 parts by mass of TOT were kneaded with a Banbury mixer, and then molded into a ribbon shape using an open roll and a ribbon molding dispenser to obtain a foamed rubber layer raw material composition.

  Next, using a vulcanization foaming apparatus as shown in FIG. 2, this foamed rubber layer raw material composition was put into an extruder and extruded into a tube shape. This foamed rubber layer raw material composition tube was placed on a mesh belt coated with a fluororesin, introduced into UHF whose microwave output was adjusted from 1.0 kW to 2.0 kW, and vulcanized and foamed. At this time, the rate of introduction of the foamed rubber layer raw material composition tube into UHF was 2.5 m / min. Moreover, the distance (irradiation effective area) to which the microwave was applied was 1.8 m.

  The foamed rubber tube vulcanized and foamed with UHF was further conveyed by a roller coated with a fluororesin and introduced into HAV maintained at a temperature of 180 ° C. with hot air to complete the vulcanization. Note that the length of the HAV was 6 m. Next, the foamed rubber tube exiting the HAV was taken up by a take-up machine, and further cut into a length of 250 mm by a cutting machine to obtain a foamed rubber tube having a length for the foamed rubber layer. The extruder die was appropriately changed so that the inner diameter of the tube after vulcanization and foaming was 80% ± 10% of the outer diameter of the shaft core (6 mm). Moreover, the tube outer diameter after foaming was about 20 mm (thickness of the foamed rubber tube was about 7.5 mm).

  An iron shaft core with a diameter of 6 mm having an electroless nickel plating layer on the surface is press-fitted into the cut foam rubber tube, then the surface is polished, and then both ends are cut off to produce a conductive elastic roller with an outer diameter of 17 mm. did. The obtained conductive elastic roller was measured for hardness unevenness and electrical resistance unevenness. On the other hand, the conductive elastic roller before surface polishing was placed in an N / N environment (23 ° C., 55% RH) for 48 hours, and the sliding resistance between the shaft core and the foamed rubber layer was measured. The obtained results are shown in Table 1.

Comparative Examples 1-6
A foamed rubber tube is produced in the same manner as in Examples 1 to 4 except that the output of UHF microwaves or the inner diameter of the obtained foamed rubber tube is as shown in Table 2. A rubber roller was produced. In Comparative Example 5, since the inner diameter of the rubber tube was set to 65% of the outer diameter of the shaft core body, the shaft core body could not be press-fitted into the foamed rubber tube. The obtained conductive rubber roller was evaluated in the same manner as in Examples 1 to 4. The results are shown in Table 1.

  Obtained when the inner diameter of the foam rubber tube to be press-fitted is 80% ± 10% with respect to the outer diameter of the conductive shaft body, and when the microwave output of UHF is 1.0 kW or more and 2.0 kW or less. The sliding resistance between the shaft core of the conductive elastic roller and the foamed rubber layer is 0.6 N · m or more and 0.9 N · m in terms of rotational torque, and the hardness unevenness and resistance unevenness of the roller are also good.

  As seen in Comparative Examples 5 and 6, when the inner diameter of the foam rubber tube to be press-fit is outside the range of 80% ± 10% with respect to the outer diameter of the conductive shaft core, the shaft core can be press-fitted well. Even if it can be press-fitted, uneven hardness or electrical resistance of the roller may be seen. Moreover, when the microwave output of UHF was less than 1.0 kW, vulcanization foaming was not performed well, and in Comparative Example 1, vulcanization was not performed at all. Even when foam vulcanization is performed, as seen in Comparative Example 2, the sliding resistance between the shaft core and the foamed rubber layer is insufficient, and uneven hardness and electrical resistance of the roller are observed. Furthermore, when the microwave output of UHF is over 2.0 kW, the vulcanization and firing progresses excessively as seen in Comparative Examples 3 and 4, and the sliding resistance between the shaft core body and the foamed rubber layer of the obtained conductive elastic roller Is insufficient, and roller hardness unevenness and resistance unevenness are observed.

It is a perspective view of an example of a conductive elastic roller concerning the present invention. It is a schematic diagram of the vulcanization foaming apparatus concerning the present invention. 1 is a schematic diagram of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft core body 2 Foam rubber layer 11 Extruder 12 Microwave vulcanizer (UHF)
13 Hot air vulcanizer (HAV)
14 Take-up machine 15 Standard cutting machine 21 Electrophotographic photosensitive member (photosensitive drum)
22 charging device 23 exposure means 24 developing device 24a developing roller 25 toner 26 transfer roller 27 recording medium 28 cleaning blade 29 waste toner container 30 fixing device

Claims (6)

A conductive elastic roller having a foam rubber layer formed by press-fitting a shaft core into a foam rubber tube,
The shaft core is electroless nickel plated,
A foamed rubber tube has at least a foaming agent and a vulcanizing agent disposed in a rubber raw material, and the rubber raw material is extruded from a foamed rubber layer raw material composition comprising acrylonitrile butadiene rubber and epichlorohydrin rubber, and vulcanized by microwaves. The foamed rubber tube has an inner diameter (as a perfect circle) of 80% ± 10% of the outer diameter of the shaft core body to be press-fitted,
The conductive elastic roller is characterized in that the sliding resistance of the inner surface of the tube relative to the shaft core is 0.6 N · m or more and 0.9 N · m or less.   The vulcanization foaming by the microwave is performed in a microwave vulcanization furnace having an effective irradiation section of 2 m or less and an output of 1.0 kW or more and 2.0 kW or less. Conductive elastic roller. A method for producing a conductive elastic roller having a foam rubber layer formed by press-fitting a shaft core into a foam rubber tube, comprising at least the following steps:
A step of preparing a foamed rubber layer raw material composition by arranging at least a foaming agent and a vulcanizing agent on a rubber raw material comprising acrylonitrile butadiene rubber and epichlorohydrin rubber;
A step of extruding the foam rubber layer raw material composition into a cylindrical shape to produce a foam rubber layer raw material composition tube;
The foam rubber layer material composition tube is foam vulcanized in a microwave vulcanization furnace having an effective irradiation section of 2 m or less and an output of 1.0 kW to 2.0 kW, and the inner diameter (as a perfect circle) is Obtaining a foamed rubber tube that is 80% ± 10% of the outer diameter of the press-fitted shaft core;
A step of cutting the foam rubber tube; and a step of press-fitting a shaft core body having an electroless nickel plating surface into the cut foam rubber tube.   4. The method for producing a conductive elastic roller according to claim 3, wherein the sliding resistance of the inner surface of the foam rubber tube relative to the shaft core is 0.6 N · m or more and 0.9 N · m or less.   The transfer roller was vulcanized and foamed by microwaves after a foamed rubber layer raw material composition in which at least a foaming agent and a vulcanizing agent were arranged on a rubber raw material made of acrylonitrile butadiene rubber and epichlorohydrin rubber was extruded into a cylindrical shape. The shaft produced by press-fitting a shaft core body having an electroless nickel plating surface into a foamed rubber tube whose inner diameter (as a perfect circle) is 80% ± 10% of the outer diameter of the shaft core body to be press-fitted An electrophotographic apparatus comprising a conductive elastic roller having a sliding resistance of an inner surface of a foam rubber tube with respect to a core body of 0.6 N · m or more and 0.9 N · m or less.   6. The microwave vulcanization foaming is performed in a microwave vulcanization furnace having an effective irradiation section of 2 m or less and an output of 1.0 kW to 2.0 kW. Electrophotographic equipment.

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