JP3481380B2 - Conductive roller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roller used as a charging roller, a developing roller or a transfer roller of a developing device in an electronic copying machine or a laser beam printer. About. 2. Description of the Related Art An electrophotographic plain paper copying machine, a so-called electronic copying machine, forms an electrostatic latent image on a photosensitive drum using a photosensitive member that generates electric charges by light, and forms the electrostatic latent image on the photosensitive drum. There is known a system in which a toner, which is a colored charged powder, is adhered to an electrostatic latent image to develop or visualize the image, and the image is fixed on recording paper by heat. In forming an electrostatic latent image on the surface of the photoconductor drum, the surface of the photoconductor drum is charged in advance, and an original image is projected onto the charged portion via an optical system to eliminate the charging of the portion that has been exposed to light. That is being done. [0003] With the remarkable spread of copying machines in recent years, there has been an increasing demand for simplification of equipment, that is, reduction in cost and size. In order to respond to such demands, we have been developing organic photoconductive materials as photoreceptors and adopting a simpler one-component development method with a mechanism as a development method, or a method of charging the surface of a photoreceptor drum,
Improvements have been made in various directions, such as adoption of a contact roller charging method that makes it easier to reduce the size of the device than a conventional corona discharge method. In this contact roller charging system, a conductive elastic roller is installed so that its surface is in contact with the surface of the photosensitive drum, and the surface of the photosensitive drum is charged by rotation of the roller. Also, a conductive elastic roller is often used as a cleaning roller. For such a conductive roller, it has a stable volume resistivity of about 10 ⁵ to 10 ¹² Ω · cm, has a suitable elasticity, has a small compression set and is unlikely to cause creep, Further, it is required that the photoconductor is not contaminated. As a roller which can meet such a demand,
For example, a synthetic rubber material such as nitrile butadiene rubber (NBR) or silicone rubber is used, its volume resistivity and rubber hardness are adjusted to desired values, and a conductive elastic layer made of these rubber materials is provided on the outer periphery of the roller core shaft. Formed single-layer rollers are known. For rubber materials, usually the addition of a plasticizer or softener to reduce rubber hardness,
In order to adjust the conductivity, mixing of a conductive powder such as carbon black is performed. [0006] However, such a single-layer roller has a problem that when a vulcanizing agent composed of sulfur or its derivative is used for a rubber material, the vulcanizing agent remains on the photosensitive member due to the residual vulcanizing agent. There was a drawback that contamination could occur. Alternatively, in the case of a rubber material such as NBR that requires a large amount of a softening agent to be reduced to a desired rubber hardness, the so-called bleeding that the softening agent leaks out onto the roller surface and contaminates the photoreceptor. However, there is a drawback that liable to occur. Further, in the case of a conductive roller having a silicone rubber elastic layer, when used as a developing roller or a charging roller, there is a problem that a white spot phenomenon easily occurs in an image. [0007] In order to solve the difficulties of these single-layer rollers,
A conductive elastic layer having a low rubber hardness on the outer periphery of the roller core shaft,
A function-separated type multi-layer roller in which a resistance adjusting layer having a desired volume specific resistance value is formed in order has also been developed. However, such a function-separated type multi-layer roller naturally has the disadvantage that the number of manufacturing steps is increased and the price is higher than that of a single-layer roller. Therefore, as the conductive roller, a single-layer roller which is advantageous in terms of cost and which does not cause contamination of the photoreceptor has been demanded. The present invention has been made to solve the above-mentioned demands by solving the problems of the conventional conductive roller. As a conductive rubber material, ethylene propylene rubber (EPM or EPDM). According to the present invention, as a material for forming a conductive elastic layer of a single-layer conductive roller, a conductive rubber composition mainly composed of conductive ethylene propylene rubber and having no risk of causing contamination of a photoreceptor is used. An object of the present invention is to provide a conductive roller provided by appropriately selecting the conductive rubber composition and using the conductive rubber composition to form a conductive elastic layer. The conductive rubber composition of the conductive roller according to the present invention comprises a conductive ethylene propylene rubber as a main component and a crosslinking agent limited to three kinds of organic peroxides. It is. That is, the conductive roller of the present invention,
Mainly conductive ethylene propylene rubber, 1,1-bis (tert-butylperoxy)-as a crosslinking agent
3,3,5-trimethylcyclohexane, n-butyl-
At least one selected from 4,4-bis (tert-butylperoxy) valerate and ethyl-3,3-bis (tert-butylperoxy) butyrate
20% by weight or less of charcoal containing seeds and as a softener
An elastic layer made of a conductive rubber composition containing a hydride-based process oil is formed on the outer periphery of the roller core shaft. These crosslinking agents used in the present invention include, for example, "Lupaco 231XL" (trade name of 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, manufactured by Yoshitomi Pharmaceutical Co., Ltd.) ), “Trigonox 17/40” (trade name of n-butyl-4,4-bis (tert-butylperoxy) valerate)
Kayaku Nouri) or "Lupaco 233XL"
(Ethyl-3,3-bis (tert-butylperoxy) butyrate, trade name, manufactured by Yoshitomi Pharmaceutical Co., Ltd.) and the like, and can be easily obtained. The conductive rubber composition according to the present invention does not particularly limit the type and characteristics of the main component ethylene propylene rubber, but by appropriately selecting the characteristics, the low creep property of the elastic layer can be obtained. It is also possible to better meet strict requirements such as. For example, the low creep property of the conductive roller is 7
The value of the permanent compression set under the test conditions of 0 ° C. × 22 hours is usually required to be 10% or less, and particularly to 5% or less in severe cases. According to the present invention, such a demand can be satisfied by improving the degree of crosslinking by using an ethylene propylene rubber having an iodine value of 20 or more and a Mooney viscosity of ML _{1 +} 460 or more, for example. Have also gained. Similarly, from the viewpoint of improving the degree of crosslinking, it is also preferable to use a vulcanization aid or a vulcanization accelerator.
In the present invention, it is not preferable to use a vulcanization aid which is a liquid or a contaminant which easily causes bleed or bloom. Examples of the vulcanization aid usable in the present invention include N, N'-m-phenylenedimaleimide (manufactured by Ouchi Shinko Chemical Co., Ltd., trade name: Barnock P
M), zinc methacrylate (manufactured by Asada Chemical Industry Co., Ltd.,
Trade name R-20S). In the conductive rubber composition according to the present invention, it is preferable to use carbon black as a conductivity-imparting agent for ethylene propylene rubber. Although the type of carbon black is not particularly limited, in order for the roller of the present invention to exhibit a stable volume resistivity in a medium resistance region required as a conductive roller,
More preferably, the type of carbon black is appropriately selected. In general, carbon black has a smaller particle diameter, and a three-dimensional structure in which the particles are connected in a chain, that is, a structure in which a so-called structure is more developed,
It is known to provide high conductivity. However, carbon black with a developed structure may show a sudden change in resistance value in the medium resistance region required for the conductivity of the conductive roller, and may also be subjected to operations such as kneading when compounding the rubber material. The chains are easily broken, and as a result, the conductivity is easily damaged. As described above, carbon black having a developed structure is easily affected by the resistance value from the outside. Therefore, in the present invention, it is preferable to select carbon black while paying attention to the particle diameter and structure, and to adjust the volume specific resistance so as to be in the range of 10 ⁶ to 10 ⁹ Ω · cm. In general, the magnitude of the particle size of carbon black is represented by the magnitude of the iodine adsorption amount, and the quality of the structure development is represented by the magnitude of the DBP oil absorption. In the roller of the present invention, for example, the iodine adsorption Is 70 mg / g or more and DBP oil absorption is 100 ml / 10
By using about 0 g or less of carbon black,
More favorable conductivity is obtained. In the conductive rubber composition according to the present invention, in addition to the above components, a softener, a filler and other compounding agents which are usually added to ethylene propylene rubber are required as long as the effects of the present invention are not impaired. Can be blended according to In the conductive rubber composition according to the present invention, as a softening agent for adjusting the hardness of the ethylene propylene rubber, for example, a hydrocarbon-based process oil such as a paraffin-based oil can be added. It is preferable that the addition amount be 20% by weight or less. If process oil is not added or is insufficient, fluidity is reduced and moldability is impaired. If the amount exceeds 20% by weight, process oil spouts on the surface and contamination of the photoreceptor is observed. Is not preferred. Since ethylene propylene rubber has excellent heat resistance, ozone resistance and weather resistance, an antioxidant does not need to be particularly blended in the conductive rubber composition of the present invention. The conductive rubber composition of the present invention can be produced by using a usual kneading machine such as a mixing roll or a Banbury mixer. Further, the conductive roller of the present invention having the rubber elastic layer made of the above-mentioned conductive rubber composition can be manufactured according to a general manufacturing method of a rubber roller. For example, after the conductive rubber composition of the present invention is wound around the outer periphery of a roller core shaft, it is housed in a cylindrical mold and heated and pressurized for vulcanization, or a cylindrical mold in which a roller core shaft is attached in advance. Various methods such as injection molding and extrusion using the same can be applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Example 1 In order to obtain a conductive rubber composition according to the present invention, ethylene propylene rubber (trade name: EP manufactured by Mitsui Petrochemical Co., Ltd.)
12 parts by weight of n-butyl-4,4-bis (tert-butylperoxy) valerate (trade name: Trigonox 17/40, manufactured by Kayaku Nuuri Co.) as a crosslinking agent with respect to 120 parts by weight of TPx-019) Carbon black (made by Tokai Carbon Co., Ltd., Seast #
3) 65 parts by weight, 5 parts by weight of zinc white (manufactured by Nippon Chemical Industry Co., Ltd.) as a vulcanization accelerator, 15 parts by weight of factice as a softening agent, and 50 parts by weight of paraffin-based process oil (manufactured by Esso Oil Co., trade name: Purex 400) 50 parts by weight of heavy calcium carbonate (manufactured by Maruo Calcium Co., Ltd., trade name: Shige Cal Super SSS) as an inorganic filler, and 1.5 parts by weight of a vulcanization aid Barnock PM are mixed and kneaded according to the present invention. A conductive rubber composition was obtained. The carbon black used (made by Tokai Carbon Co., Ltd., trade name: Seast #
The iodine adsorption amount of 3) is 80 mg / g, and the DBP oil absorption amount is 1
It was 01 ml / 100 g. The above conductive rubber composition was vulcanized and formed into a sheet, and then subjected to secondary vulcanization at 120 ° C. × 4 hours. When the vulcanization properties were examined, the tensile strength was 63 kg / cm.
² , elongation 180%, Shore hardness 59, compression set (7
(0 ° C. × 24 hours) was 5.0%. The volume resistivity was 5 × 10 ⁶ Ω · cm. Then, a photoreceptor having a weight of 500 g on each end is pressed against the obtained vulcanized rubber sheet and left for 24 hours in an environment of a temperature of 55 ° C. and a relative humidity of 85%. An image was taken using the photoreceptor, and the presence or absence of contamination on the photoreceptor was examined. As a result, no contamination was observed. Example 2 Ethylene propylene rubber (trade name E, manufactured by Mitsui Petrochemical Co., Ltd.)
(PT4095) 100 parts by weight of ethyl-3,3-bis (tert-butylperoxy) butyrate (trade name: Luparco 233XL, manufactured by Yoshitomi Pharmaceutical Co.) as a crosslinking agent
8 parts by weight, carbon black (trade name: Toka Black 7360SB, manufactured by Tokai Carbon Co., Ltd.) 70 as a conductive substance
Parts by weight, 3 parts by weight of triallyl isocyanate (manufactured by Nippon Kasei Co., Ltd., trade name: Tyke) as a vulcanization aid, 5 parts by weight of zinc white (manufactured by Nippon Chemical Industry Co., Ltd.) as a vulcanization accelerator, and a paraffin-based process as a softening agent 50 parts by weight of oil (Purex 400, manufactured by Esso Oil Co., Ltd.), 50 parts by weight of heavy calcium carbonate (manufactured by Maruo Calcium Co., Ltd., product name: Cal Super SSS), and stearic acid (Nippon Seisaku) as a release agent 1 part by weight (Kakosha Co., Ltd.) was mixed and kneaded to obtain a conductive rubber composition according to the present invention. The ratio of the softening agent in the above composition was 14.4% by weight, the iodine value of the ethylene propylene comb used was 30, the Mooney viscosity ML 1 _{+ 4} (100 ° C.) was 76, and carbon black (Tokai Carbon Co., Ltd.) was used. Made by Toka Black 73
60SB) had an iodine adsorption of 81 mg / g and a DBP oil absorption of 87 ml / 100 g. Next, using the conductive rubber composition,
When a rubber sheet was prepared in the same manner as in Example 1, and the presence or absence of contamination of the photoreceptor was examined, no contamination was found. Further, using a high resistance measuring instrument R8340A (manufactured by Advantest Co.), an applied voltage of 250 V, a circular electrode having a diameter of 2 mm was used, and the resistance was determined based on measurement data of 9 places per 2 mm thick rubber sheet, a total of 36 places. An analysis on the variation of the values was performed. A numerical value of 23.88 was obtained as the analysis result (db). The larger the value, the smaller the variation. The compression set (70 ° C. × 22)
Hr) was 7.5%. Example 3 Instead of carbon black (manufactured by Tokai Carbon Co., Ltd., trade name: Toka Black 7360SB), carbon black (manufactured by Tokai Carbon Co., trade name: Seast # 3), iodine adsorption amount 80 mg / g, DBP oil absorption 101 ml / Except for using 100 g), a conductive rubber composition according to the present invention was obtained in the same manner as in Example 2. Next, using the conductive rubber composition,
When a rubber sheet was prepared in the same manner as in Example 1, and the presence or absence of contamination of the photoreceptor was examined, no contamination was found. Further, in the same manner as in Example 2, an analysis regarding the variation of the resistance value was performed. The analysis result (db) was 20.05. The compression set (70 ° C. × 22 hours) was 6.9%. Example 4 Instead of 70 parts by weight of carbon black (manufactured by Tokai Carbon Co., trade name: Toka Black 7360SB), carbon black (manufactured by Denka Co., Ltd., trade name: Denka Black, iodine adsorption 90 mg / g, DBP oil absorption 190 ml) / 100g) 6
A conductive rubber composition according to the present invention was obtained in the same manner as in Example 2 except that 0 parts by weight was used. The softener ratio is 15.
It was 0% by weight. Next, using the conductive rubber composition,
When a rubber sheet was prepared in the same manner as in Example 1, and the presence or absence of contamination of the photoreceptor was examined, no contamination was found. Further, in the same manner as in Example 2, an analysis regarding the variation of the resistance value was performed. The analysis result (db) was 18.40. The compression set (70 ° C. × 22 hours) was 7.8%. Example 5 Ethylene propylene rubber (trade name E, manufactured by Mitsui Petrochemical Co., Ltd.)
In the same manner as in Example 2 except that ethylene propylene rubber (trade name: EPT3045, manufactured by Mitsui Petrochemical Co., Ltd., iodine value: 13, Mooney viscosity: ML _{1 +} 440) was used instead of (PT4095), the conductive material according to the present invention was used. A rubber composition was obtained. At this time, the ratio of the softener was 14.4% by weight. Next, using the above conductive rubber composition,
When a rubber sheet was prepared in the same manner as in Example 1, and the presence or absence of contamination of the photoreceptor was examined, no contamination was found. The compression set (70 ° C. × 22 hours) was 12.3%. Example 6 Instead of ethyl-3,3-bis (tert-butylperoxy) butyrate (Lupaco 233XL, manufactured by Yoshitomi Pharmaceutical Co., Ltd.) as a crosslinking agent, 1,1-bis (tert-butylperoxy) was used. ) -3,3-, 5-trimethylcyclohexane (manufactured by Yoshitomi Pharmaceutical Co., Ltd., trade name: Luparco 231XL) was used in the same manner as in Example 2 to obtain a conductive rubber composition according to the present invention. Next, using the conductive rubber composition,
When a rubber sheet was prepared in the same manner as in Example 1, and the presence or absence of contamination of the photoreceptor was examined, no contamination was found. COMPARATIVE EXAMPLE 1 Instead of ethyl-3,3-bis (tert-butylperoxy) butyrate (Lupaco 233XL, manufactured by Yoshitomi Pharmaceutical Co., Ltd.) as a crosslinking agent, dicumyl peroxide (manufactured by Kayaku Akzo) was used. A conductive rubber composition was obtained in the same manner as in Example 2 except that KAYAKUMIRU D-40) was used. Next, using this conductive rubber composition,
When a rubber sheet was prepared in the same manner as in Example 1, and the presence or absence of contamination of the photoconductor was examined, contamination of the photoconductor was found. Comparative Example 2 Instead of ethyl-3,3-bis (tert-butylperoxy) butyrate (Lupaco 233XL, manufactured by Yoshitomi Pharmaceutical Co., Ltd.) as a crosslinking agent, 1,3-bis (tert-butylperoxy) was used. A conductive rubber composition was obtained in the same manner as in Example 2 except that isopropyl) benzene (manufactured by Kayaku Akzo Co., Ltd., trade name: Parkadox 14/40) was used. Next, using this conductive rubber composition,
When a rubber sheet was prepared in the same manner as in Example 1, and the presence or absence of contamination of the photoconductor was examined, contamination of the photoconductor was found. Example 7 The conductive rubber composition of Example 1 was wound around the outer periphery of a primer-treated metal core shaft (body length: 320 mm, outer diameter: φ10 mm), vulcanized in a mold, and polished to a thickness of 5 mm. A conductive ethylene propylene rubber layer was formed. When the obtained conductive roller was used as a developing roller, an image with less unevenness could be obtained for a long time without causing contamination of the photosensitive member. As described above, according to the present invention,
A low-creep conductive rubber composition that does not contaminate the photoreceptor and has little variation in resistance value in a medium resistance region is obtained, and an excellent conductive roller is provided using the same. [0041]

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuhisa Ishikawa 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Showa Electric Wire & Cable Co., Ltd. Chome 1-1 Showa Electric Wire & Cable Co., Ltd. (56) References JP-A-7-330989 (JP, A) JP-A-5-178944 (JP, A) JP-A-6-128429 (JP, A) Kaihei 8-6354 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/02 F16C 13/00 G03G 15/08 501 G03G 15/16 103 G03G 15/20 103

Claims (1)

(57) [Claims] 1. A conductive ethylene propylene rubber as a main component, and as a crosslinking agent, 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane,
contains at least one selected from n-butyl-4,4-bis (tert-butylperoxy) valerate and ethyl-3,3-bis (tert-butylperoxy) butyrate , and is softened As an agent, 20 layers
An electroconductive roller, wherein an elastic layer made of an electroconductive rubber composition containing not more than 5% by weight of a hydrocarbon-based process oil is formed on the outer periphery of a roller core shaft.