JP2006227500A - Conductive roller, manufacturing method for the conductive roller, and transfer roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive rubber roller for an electrophotographic device whose formation performed is efficiently, which has minute cells, and with which satisfactory images of high image quality can be obtained, and to provide a manufacturing method for the conductive rubber roller. <P>SOLUTION: In the manufacturing method for the conductive rubber roller in which a foam rubber layer is formed on a conductive core material, the rubber material of the foam rubber layer contains acrylonitrile-butadiene rubber, epichlorohydrin rubber, or their mixture; and further, contains only azodicarbonamide as a foaming agent. The rubber material comprises a rubber composition formed, such that the decomposition temperature of the foaming agent is made 175° or below by a foaming assistant. The rubber material is subjected to a microwave vulcanization process, in which the rubber material is radiated with microwaves, and to a hot-air vulanization process which is carried out while blowing hot air onto the rubber material, and is vulcanized and foamed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a conductive rubber roller used in an electrophotographic image forming apparatus such as a copying apparatus, a printer, and an electrostatic recording apparatus, and a method of manufacturing the conductive rubber roller. The present invention relates to a roller for an electrophotographic image forming apparatus such as a transfer roller of a transfer apparatus for transferring a transferable image formed by a toner image formed and supported by an image forming means such as an electrorecording process onto a recording medium such as paper or a transfer material.

In many electrophotographic image forming apparatuses such as copying machines and printers, conductive rubber rollers such as a charging roller, a transfer roller, and a developing roller are used. These rubber rollers are required to maintain a uniform nip width by contact with the photoreceptor in order to respond to higher speed and higher image quality of the apparatus, and the density and uniformity of the foamed cells are desired. . Conventional production methods of these rubber rollers include vulcanization can vulcanization using high-pressure steam (Patent Document 1), vulcanization method using a mold (Patent Document 2), UHF vulcanization using microwave irradiation (Patent Document 3), and the like. Can be mentioned. In these methods, for example, it is easy to obtain relatively fine cells in vulcanization can vulcanization, but the cells of the foam are not uniform in the radial direction of the vulcanization tube, and the desired cells are brought to the surface. Therefore, there is a problem that a large amount of polishing is required. Further, in mold vulcanization, when a foam rubber roller is produced by an in-mold (split mold) foaming method, there is a joint between two molds. When a rubber composition containing a chemical foaming agent is vulcanized and foamed using such a split mold, leakage of the rubber composition (parting line) occurs from this joint, and the foamed rubber after demolding This effect appears, and abnormalities are likely to occur on this split mold joining surface, for example, in electrical resistance, hardness, cell shape, and the like. Therefore, in the foam rubber roller in which these characteristics are desired to be uniform, the heterogeneity of the characteristics becomes a big problem. Furthermore, it takes time to set up, and it is not suitable for making a large amount because it is necessary to clean the mold. Further, in UHF vulcanization, vulcanization foaming is performed continuously using microwaves immediately after extrusion, so that highly efficient production is possible. Furthermore, since the unvulcanized tube after extrusion is homogeneously heated using microwaves, a vulcanized tube having a uniform cell diameter in the radial direction can be obtained. In the above-mentioned patent document 3, in the detailed explanation of the invention, there is a description that the continuous vulcanization can make the foamed cell much finer than the batch type, but the control of the cell diameter is completely disclosed. Not. However, as described above, the conductive rubber roller for an electrophotographic image forming apparatus is required to have a fine and uniform foaming state, and a method for producing a conductive foam rubber roller having uniform fine cells is established. It is hoped that.
JP 11-114978 A JP 2002-115714 A Japanese Patent Laid-Open No. 2002-221859

  Accordingly, the present invention relates to a conductive rubber roller for an electrophotographic image forming apparatus such as a transfer roller, a charging roller, or a developing roller, and its molding is efficiently performed by a process of radiating microwaves and heating and vulcanizing and foaming in a short time. An object of the present invention is to provide a conductive rubber roller having fine cells and obtaining a good image with high image quality, and a method of manufacturing the conductive rubber roller.

  An object of the present invention is to provide a method for producing a conductive rubber roller in which a foam rubber layer is formed on a conductive core material, wherein the rubber material of the foam rubber layer contains acrylonitrile butadiene rubber, epichlorohydrin rubber, or a mixture thereof. Further, the rubber material containing only azodicarbonamide as a foaming agent, and composed of a rubber composition in which the decomposition temperature of the foaming agent is set to 175 ° C. or less with a foaming auxiliary agent, is used to vulcanize the rubber material. The foaming step is achieved by a method for producing a conductive rubber roller including a microwave vulcanization step performed under microwave irradiation and a hot air vulcanization step performed while blowing hot air.

  In addition, this is achieved by the use of a urea auxiliary agent as the foaming auxiliary agent.

  Further, the conductive rubber roller used in the electrophotographic image forming apparatus is achieved by the one formed by the above-described method for manufacturing a conductive rubber roller.

  In the present invention, a conductive rubber roller for an electrophotographic image forming apparatus such as a transfer roller, a charging roller, or a developing roller is efficiently formed by a process of radiating microwaves, heating in a short time, and performing vulcanization foaming. In addition, it is possible to provide a conductive rubber roller having fine cells and capable of obtaining a good image with high image quality and a method for producing the conductive rubber roller, and an excellent image can be obtained.

  The present invention relates to a method for producing a conductive rubber roller in which a foam rubber layer is formed on a conductive core material, wherein the rubber material of the foam rubber layer includes acrylonitrile butadiene rubber, epichlorohydrin rubber, or a mixture thereof, Vulcanization and foaming step of the rubber material using only a rubber composition containing only azodicarbonamide as a foaming agent, and comprising a rubber composition having a decomposition temperature of the foaming agent of 175 ° C. or less by a foaming aid As a method for producing a conductive rubber roller, the method includes a microwave vulcanization step performed under microwave irradiation and a hot air vulcanization step performed while blowing hot air.

  Hereinafter, it demonstrates in detail, using a figure.

  FIG. 1 is a perspective view of a transfer roller according to the present invention. The core metal is indicated by 61, and the elastic layer (foam rubber layer) is indicated by 62.

  FIG. 2 shows an example in which the conductive rubber roller according to the present invention is used in an image forming apparatus. The image forming apparatus shown in the figure is a laser printer using an electrophotographic process cartridge, and the figure is a longitudinal sectional view showing a schematic configuration thereof. Further, the image forming apparatus shown in the figure is equipped with a transfer device having a transfer roller.

  The image forming apparatus shown in FIG. 1 includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier. In the photosensitive drum 1, a photosensitive layer made of an organic photoconductor (OPC) is provided on the outer peripheral surface of a grounded cylindrical aluminum substrate. The photosensitive drum 1 is driven to rotate at a predetermined process speed (circumferential speed), for example, 50 mm / sec, in the direction of arrow R1 by a driving means (not shown).

  The surface of the photosensitive drum 1 is uniformly charged by a charging roller 2 as a contact charging member. The charging roller 2 is disposed in contact with the surface of the photosensitive drum 1 and is driven to rotate in the direction of arrow R2 as the photosensitive drum 1 rotates in the direction of arrow R1. An oscillating voltage (AC voltage VAC + DC voltage VDC) is applied to the charging roller 2 by a charging bias application power source (high voltage power source), whereby the surface of the photosensitive drum 1 is uniformly charged to −600 V (dark portion potential Vd). It is processed. The surface of the charged photosensitive drum 1 is scanned and exposed by laser light 3 output from a laser scanner and reflected by a mirror, that is, laser light modulated in accordance with a time-series electric digital image signal of target image information. Receive. As a result, an electrostatic latent image corresponding to the target image information (bright part Vl = −150 V) is formed on the surface of the photosensitive drum 1.

  The electrostatic latent image is reversely developed as a toner image by the negatively charged toner 5 attached thereto by a developing bias applied to the developing sleeve of the developing device 4.

  On the other hand, a transfer material 7 such as paper fed from a paper feed unit (not shown) is guided by a transfer guide and transferred to a transfer unit (transfer nip unit) T between the photosensitive drum 1 and the transfer roller 6. The toner image is supplied in synchronism with the toner image on the photosensitive drum 1. The toner image on the photosensitive drum 1 is transferred to the surface of the transfer material 7 supplied to the transfer portion T by the transfer bias applied to the transfer roller 6 by the transfer bias application power source. At this time, toner remaining on the surface of the photosensitive drum 1 without being transferred to the transfer material 7 (residual toner) is removed by the cleaning device 9.

  The transfer material 7 that has passed through the transfer portion T is separated from the photosensitive drum 1 and introduced into the fixing device 10, where the toner image is subjected to fixing processing, and an image forming apparatus main body (not shown) as an image formed product (print). It is discharged outside. The above is the outline of the operation of the image forming apparatus.

    A conductive rubber roller (FIG. 1) demonstrating the present invention was produced as follows.

[Conductive rubber roller]
A rubber composition comprising acrylonitrile butadiene rubber, epichlorohydrin rubber, or a mixture thereof, containing only azodicarbonamide as a foaming agent, and having a decomposition temperature of the foaming agent set to 175 ° C. or less by a foaming aid It consists of a composition, which includes zinc oxide, stearic acid, carbon black, fillers such as calcium carbonate, vulcanizing agents such as sulfur, thiuram, thiazole, guanidine, sulfenamide, dithiocarbamate , Thiourea, or a mixture of several of them, and a vulcanization accelerator. The rubber material vulcanization and foaming step includes a microwave vulcanization step performed under microwave irradiation and a hot air vulcanization step performed while blowing hot air.

  In the above, when a foaming agent other than azodicarbonamide such as 4,4′-oxybis (benzenesulfonylhydrazide) is used, problems such as contamination of the photosensitive drum occur. Further, when the decomposition temperature of the foaming agent is 175 ° C. or higher, the foam cell becomes too large, which causes a problem that it is not suitable for practical use.

  The acrylonitrile butadiene rubber and epichlorohydrin rubber in the rubber composition can be used singly or in combination. When the polymer content in the rubber composition is 100 parts by mass, the acrylonitrile butadiene rubber is 100 to 0 parts by mass, epichlorohydrin. It is the range of 0-100 mass parts of rubber | gum.

  The blending ratio of the foaming agent is not particularly limited, but is usually 0.5 to 20 parts by mass, preferably 0.7 to 16 parts by mass, more preferably 100 parts by mass of the polymer in the rubber composition. Is in the range of 1-10 parts by weight.

  The foaming assistant is a compounding agent generally used for the purpose of lowering the decomposition temperature of the foaming agent, and the decomposition behavior of the foaming agent can be adjusted by adding and mixing with the foaming agent. The blending ratio of the foaming aid is not particularly limited, but is usually 0.3 to 20 parts by weight, preferably 0.5 to 16 parts by weight, more preferably 100 parts by weight of the polymer in the rubber composition. Is in the range of 1-10 parts by weight.

  A vulcanization accelerator is a compounding agent generally used in combination with a vulcanizing agent for the purpose of shortening the vulcanization time. Vulcanization accelerators may be used alone or in combination of two or more. The blending ratio of the vulcanization accelerator is not particularly limited, but is usually 0.1 to 15 parts by weight, preferably 0.3 to 12 parts by weight, with respect to 100 parts by weight of the polymer in the rubber composition. Preferably it is the range of 0.5-10 mass parts.

  FIG. 3 shows a manufacturing apparatus by continuous vulcanization using microwaves of conductive rollers. The extrusion vulcanizer used in this experiment has a total length of 13 m, 11 is an extruder, 12 is a microwave vulcanizer (UHF), 13 is a hot air vulcanizer (HAV), 14 is a take-up machine, and 15 is a standard. Consists of cutting machine.

  After kneading using a closed kneader such as a Banbury mixer or a kneader, the rubber composition molded into a ribbon shape with an open roll and a ribbon molding dispenser is put into the extruder 11. The microwave vulcanizer (UHF) 12 conveys a rubber tube extruded from the extruder 11 with a mesh belt coated with Teflon (registered trademark) or a roller coated with Teflon (registered trademark) resin. The hot air vulcanizer (HAV) 13 is transported by a roller coated with Teflon (registered trademark) resin. The microwave vulcanizer (UHF) 12 and the hot air vulcanizer (HAV) 13 are connected by a roller coated with Teflon (registered trademark) resin.

  The lengths of the devices 12, 13, and 14 are as shown in the figure, and in this embodiment, the lengths are 4m, 6m, and 1m, respectively. The space between the microwave vulcanizer (UHF) 12 and the hot air vulcanizer (HAV) 13 and between the hot air vulcanizer (HAV) 13 and the take-up machine 14 are set to be 0.1 to 1.0 m. .

  In the manufacturing apparatus by continuous vulcanization using the microwave, the rubber tube formed and extruded into a tube shape having an outer diameter of φ8 to φ15 mm and an inner diameter of φ2 to 8 mm from the extruder 11 is immediately extruded from the extruder 11. Is transferred to a microwave vulcanizer (UHF) 12 set at a microwave intensity of 0.5 to 3.0 kW, a furnace temperature of 160 to 230 ° C., and a transfer speed of 0.5 to 3.0 m / min. Then, it is conveyed to a hot air vulcanizer (HAV) 13 set at 160 to 230 ° C. to complete vulcanization foaming.

  Immediately after being discharged from the take-up machine 14 after vulcanization and foaming, it was cut into a desired size by a regular cutting machine 15 to produce a tubular conductive rubber molded product. Next, a φ4 to 10 mm conductive core material coated with a hot melt adhesive or vulcanized adhesive in a desired region is press-fitted into the inner diameter portion of the tube-shaped conductive rubber molded product to obtain a roller-shaped molded body. It was. This molded body is set in a polishing machine (not shown) to which a polishing grindstone GC80 is attached, and polished as polishing conditions so that the outer diameter is 15 mm at a rotation speed of 2000 RPM and a feed speed of 500 m / min. Produced.

  In addition, the material used by each Example and the comparative example is as follows.

Acrylonitrile butadiene rubber [trade name: Nipol DN401LL Nippon Zeon Co., Ltd.]
Epichlorohydrin rubber [Brand name: Zeklon G3106 Nippon Zeon Co., Ltd.]
Azodicarbonamide (ADCA): Foaming agent [Brand name: VINYHALL AC Eiwa Chemical Industry Co., Ltd.]
Urea: Foaming aid [Product name: Cell paste K5, Eiwa Kasei Kogyo Co., Ltd.]
Dibenzothiazyl disulfide (DM)
[Product Name: Noxeller DM-P Ouchi Shinsei Chemical Co., Ltd.]
Tetrakis (2-ethylhexyl) thiuram disulfide (TOT)
[Product name: Noxeller TOT-N Ouchi Shinsei Chemical Co., Ltd.]
Tetraethylthiuram disulfide (TET)
[Product Name: Noxeller TET-G Ouchi Shinsei Chemical Co., Ltd.]
Dipentamethylene thiuram tetrasulfide (TRA)
[Product Name: Noxeller TRA Ouchi Shinsei Chemical Co., Ltd.]
Sulfur (S)
[Product name: Sulfax PMC Tsurumi Chemical Co., Ltd.]
(Measurement method of foaming agent decomposition temperature)
Using a gas tracer (Eiwa Chemical Industry Gas Tracer 250), an arbitrary amount of unvulcanized rubber to be used is weighed and placed in a test tube, and the whole test tube is immersed in an oil bath. The decomposition temperature of the foaming agent was measured by increasing the temperature of the oil bath from about 80 ° C. to about 220 ° C. at a rate of 2 ° C./minute and reading the temperature at which gas was generated.

(Confirmation method of cell diameter distribution)
The roller surface was confirmed with a video microscope (Keyence Digital Microscope VH-8000), and the average cell diameter was calculated. The average cell diameter is preferably 150 μm or less.

Examples As shown in Table 1, in Examples 1 to 7, the rubber material of the foam rubber layer contains acrylonitrile butadiene rubber, epichlorohydrin rubber, or a mixture thereof, and further contains only azodicarbonamide as a foaming agent. And a rubber composition characterized in that the decomposition temperature of the foaming agent is set to 175 ° C. or less by the foaming aid, and the vulcanization and foaming step of the rubber material is performed by microwave vulcanization performed under microwave irradiation. It includes a hot air vulcanization step that is performed while blowing a process and hot air.

  In Example 1, the decomposition temperature of the foaming agent was as low as 150 ° C., and the average cell diameter was 90 μm, and good results could be obtained.

  In Examples 2 to 4, the amount of urea added as a foaming aid gradually decreases, and at the same time, the decomposition temperature of the foaming agent increases. However, since the decomposition temperature of the foaming agent is 175 ° C. or less, a good conductive rubber roller having a fine cell diameter could be obtained.

  In Examples 5 and 6, tetrakis (2-ethylhexyl) thiuram disulfide having a relatively weak vulcanization promoting effect is used. However, since the decomposition temperature of the blowing agent is 175 ° C. or less, a good average cell diameter value is obtained. I was able to.

  In Examples 7 and 8, dipentamethylene thiuram tetrasulfide, which has a relatively high vulcanization acceleration effect, is used. However, since the decomposition temperature of the blowing agent is 175 ° C. or lower, a good average cell diameter value can be obtained. It was.

  In Example 9, the content of epichlorohydrin rubber is as high as 80 parts by mass, but since the decomposition temperature of the foaming agent is as low as 149 ° C., the average cell diameter is as small as 88 μm.

Comparative Example The comparative example is also shown in Table 2.

  As comparative examples, several foaming agents having a decomposition temperature of 175 ° C. or higher were selected and used as comparative examples.

  In Comparative Example 1, since the content of urea as a foaming aid was too small, the decomposition temperature of the foaming agent was as high as 177 ° C., and the average cell diameter was too large as 190 μm.

  Similarly, in Comparative Example 2, since the content of the foaming aid is small, the decomposition temperature of the foaming agent is high and the cell diameter is large.

  In Comparative Examples 3 and 4, since the foaming aid was not included, the decomposition temperature of the foaming agent was high, and the cell diameter was also large.

  In Comparative Examples 5 and 6, tetrakis (2-ethylhexyl) thiuram disulfide having a relatively weak vulcanization promoting effect is used. However, since the content of the foaming aid is small or not contained, the decomposition temperature of the foaming agent is high. The average cell diameter also increased.

  In Comparative Examples 7 and 8, dipentamethylene thiuram tetrasulfide having a high vulcanization accelerating effect is used, but since the content of the foaming aid is small or not contained, the decomposition temperature of the foaming agent is high, and the average cell diameter The value of became larger.

  From this result, in the conductive rubber roller in which the foam rubber layer is formed on the conductive core material, the rubber material of the foam rubber layer contains acrylonitrile butadiene rubber, epichlorohydrin rubber, or a mixture thereof, and azo as a foaming agent. It comprises a rubber composition containing only dicarbonamide and having a foaming agent having a decomposition temperature of 175 ° C. or lower with a foaming aid. The rubber material is vulcanized and foamed by microwave irradiation and heated air. It can be seen that a conductive rubber roller having a fine cell diameter can be obtained when the process is performed by a process using a microwave vulcanizing furnace. The results are shown in Table 1.

  Moreover, in the case of the range of a comparative example, it turns out that a cell diameter will become large. The results are shown in Table 2.

  The present invention has the effects as described above, and is expected to be used as a conductive rubber roller for an electrophotographic image forming apparatus.

FIG. 3 is a perspective view of a transfer roller according to the present invention. 1 is an overall cross-sectional view of an image forming apparatus according to the present invention. 1 is an overall cross-sectional view of a vulcanization molding apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Laser beam 4 Developing device 5 Toner 6 Transfer roller 7 Transfer material 8 Cleaning blade 9 Cleaning device 10 Fixing device 11 Extruder 12 Microwave vulcanizing device (UHF)
13 Hot air vulcanizer (HAV)
14 Picking Machine 15 Standard Cutting Machine 61 Core Bar 62 Elastic Layer

Claims (4)

  In the method for producing a conductive rubber roller in which a foam rubber layer is formed on a conductive core material, the rubber material of the foam rubber layer contains acrylonitrile butadiene rubber, epichlorohydrin rubber, or a mixture thereof, and azo as a foaming agent. As the rubber material containing only dicarbonamide and composed of a rubber composition in which the decomposition temperature of the foaming agent is 175 ° C. or less by a foaming aid, A method for producing a conductive rubber roller, comprising a microwave vulcanization step performed under irradiation and a hot air vulcanization step performed while blowing hot air.   The method for producing a conductive rubber roller according to claim 1, wherein the foaming aid includes a urea-based aid.   A conductive rubber roller, wherein the conductive rubber roller used in the electrophotographic image forming apparatus is formed by the method for producing a conductive rubber roller according to claim 1. The transfer roller used for an electrophotographic image forming apparatus is the conductive rubber roller according to claim 3.

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