JP2005240948A - Conductive rubber roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive rubber roller in which variations in resistance caused by the deterioration of a hydrin rubber occurring by long-term energization and further the mounting properties of a roller surface are reduced, especially the conductive rubber roller made of foam, in the conductive rubber roller, such as a transfer roller, a conductive one, or a development one. <P>SOLUTION: The conductive rubber roller in which a rubber layer made of foam is formed on a conductive core contains 1.0-10.0 pts.mass magnesium oxide to 100 pts.mass polymer content in the rubber material of the rubber layer, 1.2-3.0 pts.mass active zinc oxide, 2.0-5.0 pts.mass 2-mercapto benzimidazole, and 5-100 pts.mass epichlorohydrin rubber in 100 pts.mass polymer content in the rubber material of the rubber layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a conductive roller used in an image forming apparatus such as an electrophotographic copying apparatus, a printer, and an electrostatic recording apparatus.

  In many electrophotographic image forming apparatuses such as copying machines and printers, conductive rollers such as a charging roller, a transfer roller, and a developing roller are used. Conventionally, in order to impart conductivity to these rubber rollers, a method of adding a conductive filler such as carbon black or a method of blending an ion conductive rubber material such as acrylonitrile butadiene rubber or epichlorohydrin rubber can be cited (patent) Reference 1). The method of adding a conductive filler such as carbon black to impart conductivity to the roller is relatively stable because the resistance value depends on the voltage value and the resistance value varies greatly from lot to lot. Means using the latter ion-conductive acrylonitrile butadiene rubber, epichlorohydrin rubber, or a rubber material to which an ionic conductive agent is added have become mainstream (for example, Patent Document 2).

However, when these materials are energized for a long time, there is a problem that the resistance fluctuation becomes large due to deterioration of acrylonitrile butadiene rubber, epichlorohydrin rubber or the like. In particular, in the case of epichlorohydrin rubber, it is known that zinc oxide added as an acid acceptor becomes zinc chloride during the crosslinking reaction, which breaks the ether bond in the epichlorohydrin rubber and softens and deteriorates (Patent Document 3). Since the resistance fluctuations described above and the low molecular weight epichlorohydrin rubber migrate to the roller surface due to the breakage of the ether bond and stick to the photosensitive drum, there is a problem. Due to demands for higher speeds and printers, conductive rubber rollers are required to have characteristics that reduce the change in electrical characteristics due to further rubber deterioration, and characteristics that reduce sticking to photosensitive drums, etc. .
JP 2004-20800 A JP 2001-214925 A Japanese Patent Laid-Open No. 1-261436

  The object of the present invention is to reduce the resistance fluctuation caused by the deterioration of the hydrin rubber caused by energization for a long time in a conductive rubber roller such as a transfer roller, a charging roller or a developing roller, and further reduce the sticking property of the roller surface. It is to provide a conductive rubber roller, particularly a conductive rubber roller made of a foam.

  According to the present invention, in a conductive rubber roller in which a foam rubber layer is molded on a conductive core material, magnesium oxide is added in an amount of 1.0 to 100 parts by mass with respect to 100 parts by mass of the polymer content in the rubber material of the rubber layer. 10.0 parts by mass, 1.2 to 3.0 parts by mass of active zinc oxide, 2.0 to 5.0 parts by mass of 2-mercaptobenzimidazole, and a polymer content of 100 in the rubber material of the rubber layer There is provided a conductive rubber roller characterized by containing 5 to 100 parts by mass of epichlorohydrin rubber in a part by mass.

  As described above, according to the present invention, it is possible to provide a conductive rubber roller having a reduced resistance fluctuation amount, improved heat aging resistance, and further improved contamination.

  Accordingly, the conductive roller using the conductive rubber roller can be suitably used as a transfer roller used for image formation in electrophotographic technology.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 2 shows an example in which the conductive roller according to the present invention is used in an image forming apparatus. Although the transfer roller is described here, it can also be applied to other roller type members such as a charging roller or a developing roller. 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). Is done. The charged photosensitive drum 1 surface 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 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 synchronization 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 subjected to fixing processing, and an image forming apparatus main body (not shown) as an image formed product (print). It is discharged outside.

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

[Conductive roller]
The rubber composition contains 1.0 to 10.0 parts by mass of magnesium oxide, 1.2 to 3.0 parts by mass of active zinc oxide, and 2-mercaptobenzoimidazole with respect to 100 parts by mass of the polymer component of the rubber main component. A mixture of 2.0 to 5.0 parts by mass and 100 parts by mass of the polymer content in the rubber material of the rubber layer containing 5 to 100 parts by mass of epichlorohydrin rubber, and a conductive material such as carbon black. And other auxiliaries, a vulcanizing agent such as sulfur, a sulfide-based vulcanization accelerator, and a foaming agent.

  In the above, when magnesium oxide is less than 1.0 part by mass, it acts as a foaming aid before acting as a vulcanization accelerating aid, and the effect as a vulcanization accelerating aid is diminished and vulcanization does not occur. If the amount exceeds 0.0 parts by mass, the effect as a vulcanization accelerating aid appears too much, and there is a concern about the problem of vulcanizing before foaming and not forming a foam. Further, if the active zinc oxide is less than 1.2 parts by mass, there is a concern that the active zinc oxide does not work as a vulcanization accelerating agent but works as a foaming aid and becomes unvulcanized, exceeding 3.0 parts by mass. And the effect as a vulcanization | cure acceleration | stimulation adjuvant appears like magnesium oxide, and possibility that the problem that it vulcanizes before foaming and does not become a foam will become high.

  If the particle size of the activated zinc oxide, which increases the specific surface area and increases the activity by reducing the particle size of the zinc oxide, is less than 0.05 μm, the activity increases too much and conversely the ether bond of the hydrin rubber is cleaved. If the thickness exceeds 0.2 μm, there is a problem that the activity is lowered and the role of the vulcanization accelerating agent cannot be fulfilled.

  Moreover, when the epichlorohydrin rubber is less than 5 parts by mass, the effect of deterioration of other polymers becomes larger than that of hydrin, and the effect is not exhibited.

  Further, if the amount of 2-mercaptobenzimidazole is less than 2.0 parts by mass, the effect on deterioration is reduced, and if it exceeds 5.0 parts by mass, bloom is generated and the contamination may be increased. The

  After extruding the rubber composition using an extruder (not shown) to obtain an unvulcanized tube-shaped conductive rubber molded product, vulcanization is carried out at 160 ° C. for 30 minutes in a vulcanizing can. A conductive rubber molded product was prepared, and then a conductive core material having a diameter of 4 to 10 mm was press-fitted into the inner diameter portion of the tube-shaped conductive rubber molded product to obtain a roller-shaped molded product. This molded body is set in a polishing machine (not shown) to which a grinding wheel GC80 is attached, and is polished so that the outer diameter is 14 mm at a rotation speed of 2000 RPM and a feed speed of 500 m / min as polishing conditions. Was made.

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

Further, in the examples and comparative examples, a low nitrile acrylonitrile butadiene rubber having a bound acrylonitrile level of 25% or less is described, but the present invention is not limited to this.
・ Epichlorohydrin rubber [trade name: Zeklon 3106, manufactured by Nippon Zeon Co., Ltd.]
・ Acrylonitrile butadiene rubber [trade name: DN401, manufactured by Nippon Zeon Co., Ltd.]
・ Magnesium oxide [Product name: Kyowa Mag 150 Kyowa Chemical Industry Co., Ltd.]
・ Activated zinc oxide [trade name: AZO Shodo Chemical Industry Co., Ltd.]
・ 2-Mercaptobenzimidazole [Brand name: NOCRACK MB Ouchi Shinsei Chemical Co., Ltd.]

[Examples 1 to 6]
Magnesium oxide is contained in an amount of 1.0 to 10.0 parts by mass with respect to 100 parts by mass of the polymer in the rubber material, and 1.2% of active zinc oxide is added to 100 parts by mass of the polymer in the rubber material of the rubber layer. It is characterized by containing -3.0 parts by mass, and further comprising 5-100 parts by mass of epichlorohydrin rubber in 100 parts by mass of the polymer in the rubber material of the rubber layer, and the active oxidation in the rubber material The zinc particle size is 0.05 to 0.2 μm, and 2-mercaptobenzimidazole is contained in an amount of 2.0 to 5.0 parts by mass with respect to 100 parts by mass of the polymer in the rubber material of the rubber layer. It was set as Examples 1-6, and evaluation was performed as follows. The results are shown in Table 1.

[Comparative Examples 1-3]
As a comparative example, when magnesium oxide is contained in an amount of less than 1.0 part by mass, and active zinc oxide is contained in an amount of less than 1.2 parts by mass and more than 3.0 parts by mass as comparative examples 1 to 3, Evaluation was performed as follows. The results are shown in Table 2.

<Roller energization durability test method>
In the roller energization durability test, the conductive roller was placed in an environment of 50 ° C., and the shaft was pressure-bonded to an aluminum drum having an outer diameter of 30 mm and rotated so that a load of 4.9 N on one side was applied to both. In this state, a constant current of 80 μA was continuously applied between the shaft body and the aluminum drum for 25 hours. Then, after returning to N / N environment and leaving it to stand for 24 hours or more, roller resistance was measured again. Here, a value representing the difference between the initial resistance value and the resistance value after durability in terms of the number of digits was defined as the energization durability. It can be said that the smaller this is, the better the current-carrying durability of the conductive rubber roller. The fluctuation amount is preferably less than 0.1 digit.

<Method of heat aging test>
It measured based on JIS K-6257.

<Adhesiveness>
A conductive roller molded and polished to 15 mm in diameter and 250 mm in length is brought into contact with a photoreceptor used in a laser printer (Laser Jet 4000N HP), a load of 1000 g is applied to both ends, and the environment is 40 ° C./95% RH. I left it for a month. After leaving, the load was removed, and the one that was not attached to the photoconductor was evaluated as A, the one that was attached but removed from the photoconductor due to the weight of the roller was evaluated as B, and the one that did not come off due to the weight of the roller was evaluated as C (evaluation device) (The figure is not shown).

<Contamination>
The photoconductor that has been evaluated for stickiness is incorporated into the cartridge of the laser printer, and 30 sheets of solid black are printed. The image has no white traces of contact traces. An object was evaluated as B, and an object in which white streaks did not disappear until the end was evaluated as C.

  From these results, 1.0 to 10.0 parts by mass of magnesium oxide, 1.2 to 3.0 parts by mass of active zinc oxide, and 2.mercaptobenzimidazole to 2.100 parts by mass of the polymer content in the rubber material. 0 to 5.0 parts by mass, and 5 to 100 parts by mass of epichlorohydrin rubber in 100 parts by mass of the polymer in the rubber material of the rubber layer. It can be seen that the heat aging resistance is improved and the sticking property and the contamination property are also improved. Further, when the value is out of the range of the present invention, the resistance fluctuation amount becomes large, the heat aging resistance is deteriorated, and the sticking property and the contamination property are also deteriorated.

It is the schematic sectional drawing which used the conductive rubber roller of the present invention for the transfer roller. It is a schematic sectional drawing of the image forming apparatus which comprises the conductive rubber roller of 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 61 Core metal 62 Elastic layer

Claims (2)

  In a conductive rubber roller in which a rubber layer made of a foam is formed on a conductive core material, magnesium oxide is added in an amount of 1.0 to 10.0 mass with respect to 100 mass parts of the polymer in the rubber material of the rubber layer. In an amount of 1.2 to 3.0 parts by mass of active zinc oxide, 2.0 to 5.0 parts by mass of 2-mercaptobenzimidazole, and 100 parts by mass of the polymer in the rubber material of the rubber layer A conductive rubber roller comprising 5 to 100 parts by mass of epichlorohydrin rubber.   2. The conductive rubber roller according to claim 1, wherein a particle diameter of the active zinc oxide in the rubber material is 0.05 to 0.2 μm.

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