JPH08292625A - Roller member - Google Patents

Abstract

PURPOSE: To provide such a roller member to be disposed in contact with a photoreceptor that a rubber material is used and contamination of a photoreceptor can be improved. CONSTITUTION: This roller member is used as a transferring roller 1 which is brought into contact with a photoreceptor 3 to transfer an image on the photoreceptor 3 to a transfer material passing through the contact part with the photosensitive body 3, or as an electrifying roller 4 which touches the photoreceptor 3 to electrify the photoreceptor 3. This roller member is produced by forming a rubber layer around a core comprising a metal material. The rubber layer is a sponge-like elastic material comprising a butadiene rubber which is vulcanized with a peroxide vulcanizing agent. Namely, by vulcanizing a butadiene rubber with a peroxide vulcanizing agent, the total amt. of chemicals added to the rubber can be decreased and the crosslinking degree can be increased compared to vulcanization with sulfur which is usually used. Therefore, the amt. of chemicals or molecules which do not react can be decreased, which improves contamination of a photoreceptor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller member used for a transfer roller, a charging roller or the like of an electrophotographic image forming apparatus such as a copying machine, a facsimile or a printer.

[0002]

2. Description of the Related Art In recent years, OA equipment has been aiming to be ozoneless,
Charging and transfer in an electrophotographic image forming apparatus such as a copying machine is changing from a conventional charger method to a roller method, and a transfer material that contacts a photoconductor and passes through a contact portion with the photoconductor is transferred onto the photoconductor. Transfer roller that transfers the image of
A charging roller or the like that contacts a photoconductor and charges the photoconductor is known. For the transfer roller, the charging roller, etc., a roller member formed by forming rubber around a cored bar made of a metal material such as iron is used.

[0003]

The conventional charging method using a charging charger or a transfer charger has a drawback that a large amount of ozone is generated because it discharges in the air, but it is not in contact with the photoreceptor. There was no problem of photoconductor contamination by the charger. On the other hand, the roller system using a transfer roller or a charging roller has an advantage that the amount of ozone generated is small, but since it is contact charging to contact the photosensitive member, there is a problem of contamination of the photosensitive member by the roller. The problem due to the contamination of the photoconductor is that density unevenness occurs in the image on the transfer paper. Specifically, a light density portion is generated on the transfer paper corresponding to the surface of the photoconductor that was in contact with the roller. Especially in halftone, this phenomenon is remarkable. Further, this density unevenness may gradually disappear when the paper is passed.

The contamination of the photoconductor is caused by migration of unreacted chemicals such as vulcanizing agent and vulcanization accelerator and unreacted molecules of the rubber material from the rubber material constituting the surface of the roller to the surface of the photoconductor, and these substances are It seems that it is attached to the surface. Therefore, in order to prevent contamination of the photoconductor, it is necessary to keep the roller in a non-contact state with the photoconductor except when in use, or to form a barrier layer on the surface of the roller to prevent migration from the roller material. However, in order to keep the roller in a non-contact state with the photoconductor except when the roller is in use, a mechanism (contact / separation mechanism, etc.) for ensuring the non-contact is required, so that the unit becomes large,
The cost will increase. Further, in order to form the barrier layer on the roller surface, it is necessary to add a process such as painting, which makes it difficult to secure stable roller quality.

In order to solve the above problems, it is conceivable to use a thermoplastic elastomer, which does not use a vulcanizing agent or an accelerator as a rubber material, as a constituent material of the surface layer of the roller. The strain resistance is poorer than that of the material, and the roller is likely to be deformed when pressed against the photoconductor for a long time, resulting in charging failure and the like. Further, although it is possible to remove the low molecular weight of the rubber material, the material cost becomes bulky and it becomes unworthy of practical use.

The present invention has been made in view of the above circumstances, and an object thereof is to use a rubber material in a roller member used for a transfer roller, a charging roller, etc. installed in contact with a photosensitive member, and Provided is a roller member with improved contamination of a photoconductor.

[0007]

In order to achieve the above object, a roller member according to the present invention is formed by forming rubber around a cored bar made of a metal material, and the rubber is vulcanized by a peroxide vulcanizing agent. It is characterized in that it is a sponge-like elastic body made of butadiene rubber.

[0008]

[Function] When butadiene rubber is vulcanized with a peroxide vulcanizing agent, the total amount of chemicals added can be reduced and the degree of cross-linking can be increased compared to normal sulfur vulcanization, so unreacted chemicals and unreacted molecules can be reduced. It is possible to improve the contamination of the photoconductor.

[0009]

Embodiments of the present invention will be described below. Table 1 shows the composition of materials for forming the rubber used for the roll member. In addition, compound Nos. 1 to 4 are peroxide vulcanization, compound N
o.5 is sulfur vulcanization.

[0010]

[Table 1]

First, based on the composition table shown in Table 1, rubber was kneaded with an open roll, and this rubber was formed around a core metal made of a metal material such as iron to which an adhesive was applied in advance by using an extruder. Next, this was foamed (vulcanized) in a pipe mold. The foaming (vulcanization) temperature was 150 ° C./40 minutes. After foaming (vulcanization), the outer diameter is 16mm with a cylindrical grinder.
Finished.

Next, this roller is assembled as a transfer roller 1 in an actual machine such as a copying machine as shown in FIG. 1, and is brought into contact with a photoconductor 3 for 2 hours, and then charged by a charging roller 4 and an optical writing device (not shown). No.), the development with the developing roller 2, the transfer roller 1 and the transfer roller 1 to the transfer sheet were repeatedly performed, and a large number of halftone images were produced.
The roller was pressed against the photoconductor 3 by applying a load of 700 gf to both journals with springs. Table 2 shows the results of density unevenness on the transfer paper.

[0013]

[Table 2]

Although concentration unevenness occurred in all the blends, in the peroxide vulcanization, the vulcanizing agent was added in an amount of 3 phr or more (No.
In No. 3, No. 4), the uneven density disappeared after 8 to 9 sheets were continuously fed. On the other hand, in the case where the amount of the peroxide vulcanizing agent is small and the sulfur vulcanization is performed, the uneven density does not disappear even when 20 sheets are continuously fed. The number of sheets passed was 20 for each.

Next, Table 3 shows the swelling ratio of toluene for each formulation. Immersion in toluene is room temperature / 72 hours. This toluene swelling ratio serves as a surrogate characteristic of the degree of crosslinking of rubber. Therefore, it is shown that the smaller the toluene swelling rate is, the higher the degree of crosslinking is, which means that the rubber material contains less unreacted molecules. As can be seen from the results shown in Table 3, the swelling ratio of toluene was small in the case of blends No. 3 and No. 4, suggesting the results in Table 2.

[0016]

[Table 3]

When the peroxide vulcanizing agent is used as described above, the total amount of chemicals to be added can be reduced and the degree of crosslinking can be increased as compared with sulfur vulcanization, so that unreacted chemicals and unreacted molecules can be reduced. As a result, substances that migrate from the rubber material to the surface of the photoconductor are reduced, and the contamination of the photoconductor can be improved.

Even in sulfur vulcanization, it is possible to increase the degree of cross-linking by increasing the amount of sulfur added, but as the amount of sulfur added increases, precipitation of compound chemicals after vulcanization called bloom increases. However, it will accelerate the contamination of the photoconductor. Silicone rubber and ethylene propylene rubber are examples of rubber materials that often use a peroxide vulcanizing agent. As a result of similar tests, these rubber materials did not have the effects found in butadiene rubber.

[0019]

As described above, the roller member according to the present invention is formed by forming rubber around a metal core made of a metal material, and the rubber is made of butadiene rubber vulcanized by a peroxide vulcanizing agent. It is characterized in that it is a sponge-like elastic body consisting of a vulcanized butadiene rubber with a peroxide vulcanizing agent in this way, the total amount of chemicals added can be reduced compared to normal sulfur vulcanization, and the degree of crosslinking can be reduced. Because it can be big
Unreacted chemicals and unreacted molecules can be reduced. As a result, substances that migrate from the rubber material to the surface of the photoconductor are reduced, and the contamination of the photoconductor can be improved. Therefore,
According to the present invention, it is possible to provide a transfer roller and a charging roller in which the problem of photoconductor contamination is improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an arrangement example of roller members around a photoconductor in an image forming apparatus.

[Explanation of symbols]

 1: Transfer roller 2: Developing roller 3: Photoconductor 4: Charging roller

Claims (1)

[Claims] 1. A transfer roller for transferring an image on a photoconductor to a transfer material which comes into contact with the photoconductor and passes through a contact portion with the photoconductor,
In a roller member used for a charging roller or the like that contacts a photoconductor and charges the photoconductor, a rubber is formed around a metal core made of a metal material, and the rubber is vulcanized by a peroxide vulcanizing agent. A roller member comprising a sponge-like elastic body made of butadiene rubber.