The present invention relates to an image-forming material removing apparatus for peeling image-forming material from a recording medium on which an image has been formed using image-forming material containing hot-melt resin by means of the electrophotography method, the heat transfer method or the like, to render it reusable.
In recent years, an attempt has been made to reuse a large amount of sheets used by copying apparatuses, printers and the like for reasons of interest in environmental issues. Currently, a method is generally used to collect sheets once utilized as wastepaper, to beat them into fiber once in a paper mill to remove toner or ink, and thereafter to make paper as sheets again. This method, however, requires the same amount of energy as in making entirely new paper, and moreover energy and costs for transportation are added, and therefore, it does not necessarily follow that the load is small for the environment.
As an apparatus for solving such a problem, there has conventionally been known an image-forming material removing apparatus for peeling an image from a recording sheet to which image-forming material has been melted and adhered once. It is described in, for example, the Japanese Published Unexamined Patent Application Nos. 4-64472 and 7-36329.
In these apparatuses, there are used sheets, which have been processed so as to reduce the adhesive force with toner in advance, or toner is peeled from the recording sheets by coating the interior of the image-forming material removing apparatus with a solution for promoting the peeling property of toner to thereby reduce the adhesive force between recording sheets and toner, and by causing an image peeling medium having great adhesive force with toner to come into contact.
In the foregoing image-forming material peeling apparatus, a member obtained by layer-forming hot-melt resin on the base material in the same manner as toner is often used as an image peeling member. In this case, there is an advantage that the toner thus peeled can be used as it is as an image peeling medium in the next cycle, and the peeling process can be continuously performed.
In such an image-forming material removing apparatus, in such a roll-type image peeling member as disclosed in, for example, the Japanese Published Unexamined Patent Application No. 7-36329, there is provided a heating member at a place within the image peeling roll, and in such a belt-type image peeling member as disclosed in the Japanese Published Unexamined Patent Application No. 4-64472, there is provided a heating member at a place within a heat roll opposite to a pressing roll which presses the image peeling layer against the recording sheet. This heating member controls the image peeling layer so that the temperature at the portion of the image peeling layer, which is pressed against the recording sheet, becomes a desired temperature.
The property of the hot-melt resin constituting the image peeling layer varies with temperatures. More specifically, it is in a solidified state at temperatures of the glass transition point or less, in a rubber-like, softened state having elasticity at temperatures from the glass transition point to melting point, and in a molten state having the property of liquid at the melting temperature or more. Therefore, the temperature at the image peeling layer on causing it to come into contact with toner on the recording sheet must be set within an appropriate temperature range because when the temperature is too low and the image peeling layer is in a solidified state, no adhesive force is produced between the layer and toner on the recording sheet whereas when the temperature is too high, the image peeling layer including toner on the recording sheet enters a low-viscosity state, and permeates through the recording medium. When the image peeling layer is caused to come into contact in a softened state, the peeling property is usually high.
When such an image peeling layer is continuously used, toner peeled accumulates on the image peeling layer, the thickness of the layer entirely increases, and both a place where more toner accumulates and a place where less toner accumulates are formed, thus leading to a problem that projections and depressions on the surface increase.
When the thickness of the layer becomes thick, the temperature profile on the peeling layer in the direction of the thickness becomes large, the interior is in a molten state even if the surface is in a softened state, and defects such as the peeling layer shifting to the recording medium occur. Therefore, the image peeling layer, which has exceeded a certain thickness, is replaced with a new one, or as disclosed in the Japanese Published Unexamined Patent Application No. 4-116000, the sheet is caused to come into contact at a higher temperature than that of the image peeling layer to transfer it onto the sheet for thereby removing a part thereof.
Also, when projections and depressions occur on the surface of the peeling layer, the contact with the recording sheet becomes uneven, causing defective peeling. With respect to such a phenomenon, as disclosed in the Japanese Published Unexamined Patent Application No. 7-36329, a pressure member has been adapted to be pressed against the surface of the image peeling layer so as to smooth the projections and depressions of the toner.
In such an image removing apparatus, however, since the toner peeled by the image peeling layer is collected by causing the sheet to come into contact at high temperatures during the peeling operation to transfer a part of the image peeling layer onto the sheet, the thickness of the peeling layer greatly changes between before and after the transfer onto the sheet, and it was difficult to maintain the peeling performance. Also, it is difficult to separate the toner from a collection sheet, and the collection sheet cannot be reused, and therefore, the sheets are reused with a large amount of collection sheets ending up being scrapped, making it hardly suitable to say that the load on the environment is reduced. Also, timing at which the collection sheet is fed also must be set by detecting the thickness of the image peeling layer, and the apparatus will become complicated because a storage tray for collection sheets, a peeling layer thickness measuring device and the like are required.
Further, the surface properties of the image peeling member will be studied. As regards toner peeled from the recording sheet, the side, which adhered to the sheet on the image peeling member, is exposed to the surface. Therefore, on the portion, to which the peeled toner adhered, there exist projections and depressions corresponding to the thickness of the image (adhered toner) and further on the surface of the projections, there also exist projections and depressions of the recording material (for example, fiber of the sheet), which adhered thereto, as a replica. In a conventional image removing apparatus having a heating member only at one place, since, in order to satisfy the peeling condition, the highest temperature of resin in the image peeling layer in one cycle can be increased only up to the softened state at a point of time whereat it is pressed against the recording sheet, it is not much more than large undulation in an image level that can be smoothed even if the pressure member is pressed against the surface of the image peeling layer, and such microscopic projections and depressions as seen in the projections and depressions on the surface of paper could not be completely smoothed. Therefore, in the image peeling layer in a portion from which toner has been once peeled, the surface smoothness could not be completely restored before the next cycle, and no sufficient adhesive force was generated, possibly causing defective peeling.
The present invention has been achieved in the light of the foregoing, and is aimed to provide an image-forming material removing apparatus capable of continuously peeling toner from a recording medium while, with simple structure, maintaining the material's high quality.