JP2008176030A - Method for manufacturing conductive rubber roller and roller for electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a conductive rubber roller useful as a roller for an electrophotographic apparatus, such as a transfer roller, a charging roller or a developing roller, having a uniform horizontal to vertical ratio and a uniform cell distribution of a tube thereof, free of unevenness in hardness and resistance, and having good grindability. <P>SOLUTION: A rubber composition for a foam rubber layer contains at least 10-60 pts.mass of a carbon black having a DBP oil absorption value of 30-60 ml/100 g based on 100 pts.mass of base rubber in combination with a chemical foaming agent, and a tube of the rubber composition is irradiated with microwaves at an intensity of 0.5-2.5 kW within a length of an irradiation zone of 2 m. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  In many electrophotographic image forming apparatuses (hereinafter referred to as electrophotographic apparatuses) such as copying machines and printers, conductive rollers such as a charging roller, a transfer roller, and a developing roller are used.

  Conventionally, conductive rubber rollers for these applications are manufactured by forming a conductive foamed or solid rubber layer around a core material by various methods. Among them, a foam rubber layer is often used due to flexibility and the like.

  There are various methods for forming the foam rubber layer around the core material. However, the rubber composition for the foam rubber layer is formed in advance as a foam rubber tube, and this is covered with the core material. . In producing this foam rubber tube, the rubber composition for the foam rubber layer is vulcanized and foamed. Known vulcanization foaming methods include vulcanization can vulcanization using high-pressure steam (Patent Document 1), mold vulcanization using a cylindrical mold (Patent Document 2), and microwave vulcanization using microwave irradiation (Patent Document 3). It has been.

  In these methods, for example, in the vulcanization can vulcanization, the foam cells are uneven and a large amount of polishing must be performed to bring the desired cells to the surface. In addition, since it is necessary to perform mold cleaning, it is not suitable for making a large amount.

  Microwave vulcanization is well set up and the cells are uniform, but when the rubber is softened, the tube is crushed and the aspect ratio of the inner and outer diameters of the tube is non-uniform. Furthermore, due to the non-uniformity of the tube, circumferential hardness unevenness and resistance unevenness were caused.

  In order to eliminate this non-uniformity of the tube, a method of connecting a plurality of short UHF devices and providing a gradient in the microwave irradiation output is known as a known technique. However, since it is a long device, the elapsed time becomes long, microwaves are excessively applied, the epichlorohydrin rubber, acrylonitrile butadiene rubber, etc. of the rubber material change in quality, and the volume specific resistance value of the rubber material is reduced. It will be high.

  When a large amount of carbon black is added to the rubber material, the microwave absorption efficiency, grindability and shape stability are improved, but the volume resistivity of the rubber material varies depending on the applied voltage and processing conditions. It becomes difficult to handle as a conductive rubber roller. As a result, usage has decreased in recent years.

  As described above, the conductive rubber rollers prepared by these methods are not suitable for conductive rubber rollers used in copying machines and printers, and such short diameters that require fine performance such as resistance values are required. There was nothing to introduce the technology deployment to Laura.

With this background, the rollers used in future copying machines and printers have uniform foam cell and tube inside / outside diameter aspect ratios, no circumferential hardness and uneven resistance, and better setup and productivity. There is a need for a manufacturing method.
JP 11-114978 A Japanese Patent Laid-Open No. 2002-221859 JP-A-11-201140

  Accordingly, an object of the present invention is to provide a conductive rubber roller useful as a roller for an electrophotographic apparatus such as a transfer roller, a charging roller, and a developing roller. It is an object of the present invention to provide a method for producing a conductive rubber roller having no unevenness and good grindability and a roller for an electrophotographic apparatus.

  The present inventors have intensively studied to solve the above problems, and found that the above problems can be achieved if a specific amount of specific carbon black is used and specific microwave vulcanization conditions are taken. Invented.

  That is, the present invention provides a method for producing a conductive rubber roller in which a foam rubber layer made of a rubber composition is molded on a conductive core material, and the rubber composition is at least based on 100 parts by mass of the main rubber. It contains 10 parts by mass or more and 60 parts by mass or less of carbon black having a DBP oil absorption of 30 ml / 100 g or more and 60 ml / 100 g or less, further contains a chemical foaming agent, and the rubber composition has a microwave irradiation section length of 2 m. The foam rubber layer is formed by irradiating with a microwave having an intensity of 0.5 kW or more and 2.5 kW or less, and a method for producing a conductive rubber roller.

  The present invention is also the method for producing the conductive rubber roller, wherein the main rubber is selected from epichlorohydrin rubber, acrylonitrile butadiene rubber and a mixture thereof.

  And this invention is a manufacturing method of the said conductive rubber roller, wherein a chemical foaming agent is selected from p, p'-oxybisbenzenesulfonylhydrazide and azodicarbonamide.

  Furthermore, the present invention is a roller for an electrophotographic apparatus, which is a conductive rubber roller manufactured by any one of the above manufacturing methods.

  Furthermore, the present invention provides the above-mentioned roller for an electrophotographic apparatus, wherein a surface layer is formed on the foam rubber layer.

  In addition, the present invention provides the above-mentioned electrophotographic apparatus roller, wherein the electrophotographic apparatus roller is a transfer roller.

  According to the present invention, the aspect ratio of the inner and outer diameters and the cell distribution are uniform, and as a result of manufacturing the foamed rubber tube, the foam rubber layer has no unevenness in hardness or resistance in the circumferential direction, and the volume resistivity is applied voltage. It is possible to provide a conductive rubber roller that does not easily vary depending on the processing conditions and the like, and has good grindability.

  The conductive rubber roller produced according to the present invention can be suitably used as a roller for an electrophotographic apparatus, particularly as a transfer roller.

  The present invention relates to a method for producing a conductive rubber roller in which a foam rubber layer made of a rubber composition is formed on a conductive core material. The rubber composition has a DBP oil absorption amount per 100 parts by mass of the main rubber. Of carbon black of 30 ml / 100 g or more and 60 ml / 100 g or less, further including a chemical foaming agent, and the rubber composition has a microwave irradiation section length of 2 m or less. Thus, the foam rubber layer is formed by irradiating a microwave having an intensity of 0.5 kW or more and 2.5 kW or less. In addition, the electrophotographic apparatus roller is a conductive rubber roller manufactured by the above manufacturing method.

  Hereinafter, the present invention will be described in detail.

(Electrophotographic equipment)
FIG. 2 is an explanatory diagram showing an example in which the conductive rubber roller according to the present invention is used in an electrophotographic apparatus.

  The electrophotographic apparatus shown in FIG. 2 is a laser printer using a process cartridge, and the figure shows a schematic configuration thereof. The apparatus is equipped with a transfer apparatus having a transfer roller.

  The apparatus 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, and is driven to rotate in the direction of arrow R2 as the photosensitive drum 1 rotates in the direction of arrow R1. An oscillation 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). As a result, the surface of the photosensitive drum 1 is uniformly charged to −600 V (dark portion potential Vd). The surface of the photosensitive drum 1 after charging 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 with negatively charged toner 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 supply unit (not shown) is guided by a transfer guide, and is 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 a transfer bias applied to the transfer roller 6 by a transfer bias application power source. At this time, the toner (residual toner) that is not transferred to the transfer material 7 and remains on the surface of the photosensitive drum 1 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 fixed, and an electrophotographic apparatus main body (not shown) is formed as an image formed product (print). It is discharged outside.

  Here, the conductive rubber roller manufactured by the manufacturing method of the present invention is provided with a surface layer if necessary, and is used as a charging roller, a developing sleeve, a transfer roller, or the like. In particular, it is useful as a transfer roller.

(Manufacture of conductive rubber roller)
The rubber composition of the foam rubber layer is selected from epichlorohydrin rubber, acrylonitrile butadiene rubber and a mixture thereof as the main rubber, and carbon black having a DBP oil absorption of 30 ml / 100 g or more and 60 ml / 100 g or less is disposed on the rubber composition. Further, a chemical foaming agent or the like is arranged. If necessary, conductive materials, fillers such as calcium carbonate, other auxiliaries and sulfur, organic peroxides, vulcanizing agents such as triazine, polyamine, thiuram, thiazole, guanidine, sulfenamide, Dithiocarbamate, thiourea, or a mixture of several kinds thereof is mixed.

  Carbon black having a DBP oil absorption of 30 ml / 100 g or more and 60 ml / 100 g or less is used in an amount of 10 to 60 parts by mass with respect to 100 parts by mass of the main rubber. If it is less than 10 parts by mass, the electrical resistance becomes large. On the other hand, if it exceeds 60 parts by mass, the electric resistance becomes too small and the current becomes excessive. Therefore, the blending amount of carbon black having a DBP oil absorption of 30 ml / 100 g or more and 60 ml / 100 g or less is within the above range. When the DBP oil absorption amount of the carbon black is in the above range, the conductivity becomes a desired magnitude, which is preferable.

  As the chemical foaming agent used in the present invention, any chemical foaming agent can be used as long as it is used for producing foamed rubber. For example, p, p′-oxybisbenzenesulfonylhydrazide, azodicarbonamide Can be mentioned as preferred.

  In the present invention, the rubber composition is extruded into a tube shape from an extruder and foamed and vulcanized in a microwave vulcanizing furnace. The outline of the apparatus is shown in FIG.

  In FIG. 3, 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 regular cutter.

  The rubber composition is kneaded using a closed kneader such as a Banbury mixer, a kneader, etc., then formed into a ribbon shape with an open roll and a ribbon forming dispenser, and then charged into the extruder 11. The rubber composition extruded from the extruder 11 in a tube shape is conveyed to the UHF 12 by a mesh-coated belt or a fluororesin-coated roller. Thereafter, the rubber composition vulcanized with UHF 12 is conveyed to HAV 13 with a fluororesin-coated roller and foamed and vulcanized. The UHF 12 and the HAV 13 are connected by a fluororesin-coated roller.

  In addition, the length of UHF12, HAV13, and the take-up machine 14 can be 4m, 6m, 1m in order, for example. Further, the distance between the UHF 12 and the HAV 13 and the distance between the HAV 13 and the take-up machine 14 are normally set to 0.1 m or more and 1.0 m or less. With such a configuration, the distance from the UHF to the take-up machine can be as short as about 13 m.

  In the manufacturing apparatus by continuous vulcanization using the microwave, the rubber composition extruded into a tube shape from the extruder 11 is conveyed into the UHF 12 immediately after being extruded, and has a strength of 0.5 kW to 2.5 kW. Microwave is irradiated within an irradiation section length of 2 m within a microwave irradiation time of 0.6 min to 3.6 min, vulcanized and foamed, and then conveyed to HAV 13 to complete vulcanization. The vulcanization in the HAV 13 is preferably performed in hot air between 4 min and 10 min and between 150 ° C. and 300 ° C.

  Note that the microwave is operated with an intensity of 0.5 kW to 2.5 kW. When the output is smaller than 0.5 kW, the vulcanization foaming is insufficient with such a short apparatus configuration, and when the power is larger than 2.5 kW, the tube of the rubber composition is excessively heated, and the fineness as in the present invention is not achieved. For the production of a short diameter rubber roller, the control becomes very difficult.

  The foamed rubber tube, which has been completely vulcanized and foamed, is cut into a desired size by a fixed length cutting machine 15 immediately after being discharged from the take-up machine 14.

  To the cut foamed rubber tube, if necessary, after removing the distortion, a hot melt adhesive or a vulcanized adhesive applied to a desired region is pressed into an inner diameter portion of a conductive core material of φ4 mm or more and 10 mm or less, A roller-shaped molded body is used. This molded body is set in a polishing machine (not shown) equipped with a polishing grindstone GC80, polished at a rotation speed of 2000 rpm and a feed speed of 500 mm / min. An elastic rubber roller is created.

  The conductive rubber roller manufactured in this way is, for example, as shown in the perspective view of FIG. In FIG. 1, 61 is a conductive core material, and a foam rubber layer 62 is formed around it. In the present invention, the surface of the foam rubber layer 62 may be further treated with energy rays such as ultraviolet rays and electron beams, and a functional surface layer may be formed on the surface. .

  The conductive rubber roller thus produced can be used as it is, or after surface treatment, as a roller for an electrophotographic apparatus.

  Hereinafter, the present invention will be described by way of examples.

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

1) Main rubber / NBR: Acrylonitrile butadiene rubber [Brand name: Nipol DN401, manufactured by Nippon Zeon Co., Ltd.]
CHR: Epichlorohydrin rubber [Brand name: Hydrin T3106, manufactured by Nippon Zeon Co., Ltd.]

2) Chemical foaming agent / ADCA: Azodicarbonamide [Brand name: VINYHALL AC, manufactured by Eiwa Chemical Industry Co., Ltd.]
OBSH: p, p′-oxybisbenzenesulfonyl hydrazide [trade name: Neocerbon N, manufactured by Eiwa Kasei Kogyo Co., Ltd.]

3) Carbon black carbon (DBP oil absorption amount: 30 ml / 100 g) [trade name: Asahi # 8, manufactured by Asahi Carbon Co., Ltd.]
Carbon (DBP oil absorption; 40 ml / 100 g) [trade name: Asahi # 15, manufactured by Asahi Carbon Co., Ltd.]
Carbon (DBP oil absorption amount: 60 ml / 100 g) [trade name: Asahi # 35, manufactured by Asahi Carbon Co., Ltd.]
・ Carbon (DBP oil absorption: 80 ml / 100 g) [trade name: Asahi # 90, manufactured by Asahi Carbon Co., Ltd.]

  Measurement methods and evaluation methods for various data in Examples and Comparative Examples are shown below.

(Aspect ratio measurement method for tube inner and outer diameters)
The tube is cut at an arbitrary location, and the cross section is measured with a projector (trade name: Nikon Profile Projector V-12B, manufactured by Nikon Corporation), and the maximum part (a) and minimum part (b) of each of the inner and outer diameters are measured. did. The ratio (= a / b) was calculated from the obtained measurement values, and was used as the aspect ratio. At this time, it is preferable that a / b is closer to 1.

(Measurement method of hardness unevenness)
Using a rubber hardness tester (trade name: Asker rubber hardness tester C type, manufactured by Kobunshi Keiki Co., Ltd.), with a load of 4.9 N, any place on the conductive rubber roller in the circumferential direction at four locations of 90 ° Asker C hardness Was measured. The difference between the maximum value and the minimum value of these measured values was regarded as hardness unevenness. The hardness unevenness is preferably 0 °.

(Measurement method of roller resistance unevenness)
After the production, the load of 4.9N on one side is applied to both of the core material of the conductive rubber roller placed in N / N (23 ° C x 55% RH) environment for 48 hours, and it is crimped to an aluminum drum with an outer diameter of 30mm. And rotated. In the rotated state, a voltage of 2 kV was applied between the core material and the aluminum drum, and the resistance value of the roller was measured. The logarithm of the ratio between the maximum value and the minimum value of the resistance value at this time was defined as resistance unevenness. The resistance unevenness is preferably less than 1.2.

(Measurement method of roller resistance depending on applied voltage)
Similarly to the measurement of the resistance unevenness of the roller, a voltage of 0.5 kV or 2.5 kV was applied between the core material and the aluminum drum, and the resistance value at each applied voltage was measured. The logarithm of the ratio of resistance values at this time was calculated. It is preferable that this calculated value falls within ± 0.3.

(Confirmation method of cell diameter distribution)
The foamed rubber tube is cut at an arbitrary location, and the cross section is observed with a video microscope (trade name: Digital Microscope VH-8000, manufactured by Keyence Corporation). The cell diameter on the outer diameter side and the cell diameter on the inner diameter side are measured. The difference in size was confirmed. At this time, it is preferable that there is no difference between the cell diameter on the outer diameter side and the cell diameter on the inner diameter side, and “◯” indicates that there is no difference, “X” indicates that there is a difference, and “Δ” indicates that there is a slight difference.

  In the following Examples and Comparative Examples, foam vulcanization was performed as follows unless otherwise specified. That is, the manufacturing apparatus shown in FIG. 3 was used. The total length excluding the extruder 11 is about 13 m, the UHF 12 is 4 m, the HAV 13 is 6 m, and the take-up machine 14 is 1 m. And between each apparatus can be adjusted between 0.1 m and 1 m, and the regular cutting machine 15 is provided in contact with the take-up machine 14. Between the extruder 11 and the UHF 12, the mesh belt covered with the fluororesin in the UHF 12 receives the tubular rubber composition extruded from the extruder 11. Further, a roller whose surface is coated with a fluororesin is provided between the UHF 12 and the HAV 13, and a cylindrical rubber molded body vulcanized and foamed in the UHF 12 is conveyed on the roller. Yes. Here, a microwave transmitter is installed in the UHF 12, and the irradiation section length is about 2 m. Also, heated air is fed into the HAV 13 and kept at 200 ° C.

Examples 1-5, Comparative Examples 1-5
NBR or CHR was used, and carbon black shown in Table 12 was used in the amount shown in Table 1, and kneaded with a chemical foaming agent and the like by a Banbury mixer. Thereafter, a rubber composition is obtained by forming into a ribbon shape with an open roll and a ribbon forming / dispensing machine, and the rubber composition is charged into the extruder 11 so that the outer diameter after vulcanization and foaming from the extruder 11 is 20 mm and the inner diameter is 5 mm. Extruded into a cylindrical shape. Subsequently, the cylindrical rubber composition molded body was carried into UHF 12 in which the microwave transmitter was adjusted so that the microwave irradiation amount became 0.3 kW to 3.0 kW, and vulcanized and foamed. Next, vulcanization and foaming was completed in the HAV 13 to form a foamed rubber tube, which was taken up by the take-up machine 14 and cut by a regular cutting machine 15 at a length of 230 mm.

  A conductive core material in which a hot-melt adhesive was applied to an iron rod whose surface was 6 mm in outer diameter and 250 mm in length and was chemically nickel-plated was press-fitted into the cut rubber foam tube. Then, it was placed at a temperature at which the hot melt adhesive was dissolved, and further cooled to room temperature to obtain a roller-shaped molded body. Both ends of the foam rubber layer of this molded body are cut off so that the length of the foam rubber layer is 220 mm, and then the surface is rotated with a grinding machine equipped with a grinding wheel GC80, the rotational speed of the workpiece is 500 rpm, Polishing was performed at a rotation speed of 2000 rpm and a feed speed of 500 mm / min to obtain a conductive rubber roller having an outer diameter of 17 mm. In the polishing of the foam rubber layer, in Examples 1 to 5, the foamed cells were uniform and the uniform grindability was good.

  In Examples 1 to 5 and Comparative Examples 1 to 5, the inner diameter of the manufactured foam rubber tube, the aspect ratio of the outer diameter, the cell diameter distribution, and the hardness unevenness, resistance unevenness, and voltage dependency of the obtained conductive rubber roller The above was investigated. The results are shown in Table 1.

It is a perspective view of an example of a conductive rubber roller concerning the present invention. It is explanatory drawing of an example of the electrophotographic apparatus which concerns on this invention. It is explanatory drawing of an example of the vulcanization molding apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Exposure means 4 Developing device 5 Toner 6 Transfer roller 7 Recording medium 8 Cleaning blade 9 Waste toner container 10 Fixing device 11 Extruder 12 Microwave vulcanizing device (UHF)
13 Hot air vulcanizer (HAV)
14 Take-up machine 15 Standard cutting machine 61 Core material 62 Foam rubber layer

Claims (6)

In a method for producing a conductive rubber roller in which a foam rubber layer made of a rubber composition is molded on a conductive core material,
The rubber composition contains at least 10 parts by mass and 60 parts by mass of carbon black having a DBP oil absorption of 30 ml / 100 g or more and 60 ml / 100 g or less with respect to 100 parts by mass of the main rubber. Containing agents,
The foam rubber layer is formed by irradiating the rubber composition with microwaves having a microwave irradiation section length of 2 m or less and having an intensity of 0.5 kW or more and 2.5 kW or less. Manufacturing method of rubber roller.   2. The method for producing a conductive rubber roller according to claim 1, wherein the main rubber is selected from epichlorohydrin rubber, acrylonitrile butadiene rubber and a mixture thereof.   The method for producing a conductive rubber roller according to claim 1 or 2, wherein the chemical foaming agent is selected from p, p'-oxybisbenzenesulfonylhydrazide and azodicarbonamide.   A roller for an electrophotographic apparatus, which is a conductive rubber roller formed by the method for producing a conductive rubber roller according to claim 1.   The roller for an electrophotographic apparatus according to claim 4, wherein a surface layer is further formed on the foam rubber layer.   6. The roller for an electrophotographic apparatus according to claim 4, wherein the roller for the electrophotographic apparatus is a transfer roller.

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