JPH06149097A - Transfer roller and it production - Google Patents

Abstract

PURPOSE:To obtain a transfer roller for an electrophotographic device which does not contaminate a photosensitive drum. CONSTITUTION:The transfer roller is formed to have surface roughness larger than the average particle size of the toner, and the roller surface is partly coated with fluorinated resin in fine spots. This roller is produced by winding an elastic material containing a foaming agent on the core metal, foaming the elastic material in a die in a manner that the average size of the foam is not smaller than the average particle size of the toner, then removing a skin layer formed on the outer surface to obtain surface roughness not smaller than the average particle size of the toner, and then partly coating the surface with fluorinated resin in fine spots. Spray coating is preferably used. By this method, bleeding of contaminant to the roller surface is extremely little so that deterioration of the photosensitive drum can be prevented, deposition of toner is very little, and no cleaning is required.

Description

Detailed Description of the Invention

[0001]

2. Description of the Related Art In an electrophotographic copying machine or the like, a method of transferring a toner image formed on a photosensitive drum or the like to a paper or the like includes a corona transfer method using a corona charger and a transfer having an elastic layer. A transfer roller system has been put into practical use, in which a sheet or the like to be transferred by a roller is dynamically pressed against a toner image carrier or a bias voltage is applied to press the paper. The transfer roller used in the transfer roller system is usually composed of a cored bar, an elastic body layer wound around the cored bar, and a surface coating layer that covers the surface of the elastic body layer as necessary. Recently, the technology of the transfer roller system has been improved, and this transfer roller is also disclosed in Japanese Patent Laid-Open No.
-154086, Japanese Patent Laid-Open No. 3-202885, Japanese Patent Laid-Open No. 4-163097, and Japanese Patent Laid-Open No. 4-2.
Various proposals have been made in Japanese Patent Publication No. 08973.

[0002]

By the way, in the transfer roller system, a trace amount of contaminants such as siloxane and a plasticizer are exuded from a polymer foam or the like which has been a constituent of the transfer roller for a long time to contaminate the surface of the photosensitive drum. However, there are problems such as deterioration and the problem that toner adheres to the transfer roller to stain the paper. The present invention has been completed by studying these problems of the transfer roller system, that is, a transfer roller that does not contaminate the photosensitive drum and does not adhere with toner.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a transfer roller used in an electrophotographic apparatus having a foamed elastic body wound around a cored bar, and the surface roughness of the roller surface is the average particle size of the toner used. Provided is a transfer roller having a diameter larger than that of the transfer roller, and the roller surface is partially coated with a fluororesin or a silicone resin in fine spots. In addition, an elastic body containing a foaming agent wrapped around a core metal is foamed to a size in which the average bubble diameter does not fall below the average diameter of the toner used in the mold, and is taken out from the mold and the outer circumference To the extent that the skin layer formed on the surface is deleted to form a surface roughness that does not fall below the average particle size of the toner used, and the surface to be removed is partially covered with fluororesin or silicone resin in fine spots. A method for manufacturing a transfer roller is provided, which is characterized in that the transfer roller is coated.
Spray coating is suitable for coating a fluororesin or a silicone resin.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION In the research for solving the above-mentioned problems, the present inventor has found a surprising fact that is completely different from what has been conventionally considered. That is, conventionally, for example, JP-A-3-154086 and JP-A-3-202.
For the purpose of preventing toner from adhering to the transfer roller and contaminating the photosensitive drum to make cleaning of the toner difficult, as in the transfer roller disclosed in Japanese Patent Laid-Open No. 885 and Japanese Patent Application Laid-Open No. 4-208973. The surface roughness is smaller than that of the toner. If necessary, a uniform resin coating layer is provided on the surface in order to adjust the conductivity and facilitate the separation of the paper. However,
As a result of research, they have found that it is not necessarily the case that the surface roughness of the transfer roller is smaller or that the resin layer on the surface is uniformly coated. Based on this fact, the transfer roller of the present invention has an improved microscopic surface shape and structure of a known transfer roller used in an electrophotographic apparatus, which is formed by winding a foamed elastic body around a cored bar. By doing so, a slight amount of contaminants oozes out from the transfer roller, the photosensitive drum is contaminated and deteriorated, and toner adhesion is prevented.

The transfer roller and the method of manufacturing the transfer roller of the present invention will be described in detail. First, an unfoamed elastomer such as silicone rubber or urethane rubber is added with a filler for adjusting conductivity and hardness such as carbon black or metal oxide, and a required foaming agent or vulcanizing agent. The kneaded material of the foamed elastic body is extruded by, for example, an extruder, and wound around the core metal fed to the extruder and the crosshead. A cored bar around which a foamed elastic material is wound is set in a mold, heated, foamed, and fixed to the cored bar. In the present invention, in addition to the hardness and conductivity of the resulting foamed elastic body, the amount of the foaming agent and the foaming conditions may be adjusted so that the average bubble diameter does not become smaller than the average particle diameter of the toner used. is important. The foamed roller is removed from the mold, and the non-foamed or less foamed skin layer formed on the surface is usually removed to expose the foamed layer. Depending on the manufacturing method and conditions, when the surface roughness of the foamed roller is larger than the average particle size of the toner used, the surface may not be deleted.

In this way, a roller whose surface roughness is larger than the average particle diameter of the toner used is manufactured. The surface of this roller is further coated with a fluororesin or a silicone resin (hereinafter, abbreviated as “fluororesin”).
Partially applied in fine patches. For this fluororesin,
A conductive material such as carbon is often added in order to have conductivity. In the present invention, it is not preferable that the roller surface is uniformly covered with fluororesin or the like. It is necessary that the fluororesin or the like partially adheres to the roller surface in the form of fine spots. The fine range here is on the order of submicrons to hundreds of microns.
The mottled shape may be any of mottled shape, sea-island shape, mesh shape, interdigital shape, and may be regular or irregular. Partially coated means that the coated part and the uncoated part are not separated into a large area, but the two are finely intermingled with each other. It means that you are in a living state. A preferable mode of coating is that a large amount of resin adheres to the crests of the roller surface and does not adhere to the valleys, or even a small amount of resin adheres to the valleys.

For the coating, a resin containing a fibrous conductive substance is dispersed in an appropriate solvent and transferred by a roll coater, a method using a gravure coater, a screen coater, a reverse roll coater, etc.,
Alternatively, it can be carried out by using a spray or the like, and is not particularly limited, but it is preferable to use the spray method because it is necessary to control the coating amount to be small in the present invention. Using such a coating method, coat an appropriate small amount of resin according to the characteristics of the resin and the surface condition of the roller.A large amount of resin adheres to the ridges of the roller surface, and does not adhere to the valleys. Even if you do it, you can make it very small.

[0008]

The transfer roller according to the present invention has a very small amount of contaminants oozing out from the surface of the transfer roller, so that surface contamination of the photosensitive drum can be minimized. In addition to this, since there is no toner that easily separates, cleaning of the photosensitive drum is easy or unnecessary. The reason for this is that the surface roughness of the transfer roller is larger than the toner particle size,
Moreover, since the valley portion of the surface is not coated with fluororesin or the like, it is considered that a small amount of toner enters the valley portion and is fixed to prevent the contaminant from leaking through the bubbles. Further, since it is difficult for the toner to adhere to the peaks and the toner coated with the fluororesin, it is considered that the cleaning of the photosensitive drum becomes less necessary.

Claims (3)

[Claims] 1. A transfer roller for use in an electrophotographic apparatus, comprising a foamed elastic body wound around a cored bar, wherein the surface roughness of the roller surface is larger than the average particle diameter of the toner used, and the roller. A transfer roller, the surface of which is partially coated with a fluororesin or a silicone resin in the form of fine spots. 2. A core metal around which an elastic body containing a foaming agent is wound is foamed to a size such that the average bubble diameter is not smaller than the average diameter of the toner used in the mold, Remove and remove the skin layer formed on the outer peripheral surface to form a surface roughness that does not fall below the average particle size of the toner to be used. A method of manufacturing a transfer roller, which comprises coating to such an extent that it covers the transfer roller. 3. The method for producing a transfer roller according to claim 2, wherein spray coating is used for the coating according to claim 2. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer roller for transferring a toner image onto paper or the like in an electrophotographic copying machine, a laser printer, a plain paper facsimile or the like.