Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-08-03
2001-03-20
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031170, C106S031230, C106S031320, C106S031360
Reexamination Certificate
active
06203603
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image forming material that is used in electrophotography of, e.g., printers, plain paper copiers, and facsimile machines, thermal transfer recording, writing tools, and printing and can be erased after image formation.
With the recent progress of office automation, the amounts of various pieces of information are significantly increasing, and information output is increasing accordingly. Information output is represented by display output and hard copy output from printers to paper sheets. Display output requires large-scale circuit boards in display units and hence has problems in portability and cost. Hard copy output is the most basic image display means and superior in versatility and storage stability. However, hard copy output uses large amounts of paper as a recording medium when the information amount increases, and this leads to an increase in deforestation. Forest resources are very important to maintain the terrestrial environment and suppress the greenhouse effect caused by carbon dioxide. Therefore, it is an important subject to minimize future deforestation and efficiently use the paper resources that we presently possess.
Conventionally, paper resources are recycled by processing sheets of paper on which image forming materials are printed using large amounts of a bleaching agent and water and remaking paper fibers to manufacture recycled paper with low paper quality. This method raises the cost of recycled paper and causes new environmental pollution resulting from waste liquor disposal.
Formerly, paper sheets are reused by correcting images using rubber erasers to pencils and ink erasers to writing inks. However, these methods have low correction efficiency, and the reuse itself has its limit. Recently, rewritable paper has been proposed to reuse hard copy paper sheets. Unfortunately, this rewritable paper is applicable only to thermal recording and is not recyclable, although it is reusable, because it is special paper.
The present inventors are developing an image forming material that contains a color former, a developer, and a decolorizer compatible with these components, can form images in the same manner as common image forming materials, and allows formed images to be erased by processing the material with heat or a solvent. Use of this erasable image forming material makes it possible to repeatedly reuse paper sheets any number of times by returning the paper sheets to blank paper sheets by erasing images, with minimum degradation of paper quality. Since recycle need only be done when the paper quality significantly degrades by the reuse, the use efficiency of paper resources greatly improves. In this manner, the essential paper use amount can be reduced, so deforestation can be minimized. Additionally, it is possible to minimize any increase in cost of recycle paper and the environmental pollution by waste liquor disposal, that are problems in the present recycle system.
The image forming material being developed by the present inventors and containing a color former, a developer, a decolorizer, and a binder resin can form images in the same manner as common electrophotographic toner and can be erased by a solvent or heating. However, this image forming material sometimes varies the image reflection density depending on the manufacturing lots or causes defective fixation (offset) when images are thermally fixed. Also, when images are erased with a solvent, marks of a flow of the image forming material or blurred images partially form, and unerased images sometimes remain. Since these unerased images limit the reuse of paper sheets, the material must be improved to be able to decolor formed images as completely as possible.
Also, depending on the intended use of the image forming material, it is preferable to be able not only to completely erase images but also to repeatedly write and erase images. Accordingly, an image forming material applicable to such a use is also being demanded.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming material that can form sharp images, can erase images by heat processing or solvent processing, and can be erased well without any defect.
It is another object of the present invention to provide an image forming material capable of repetitively writing and erasing images as well as completely erasing them.
The first erasable image forming material of the present invention comprises a color former, a developer, a matrix agent, and a polymer decolorizer having an electron donating group capable of physically or chemically adsorbing the developer.
The polymer decolorizer is preferably at least one compound selected from the group consisting of a polymer compound having a sugar skeleton, polyamino acid, a polymer compound having a hydroxyl group, a polymer compound having an amino group, polyvinylacetal, polyacrylonitrile, and their copolymers.
The second erasable image forming material of the present invention comprises a color former, a developer, a matrix agent in which a total number of electron donating groups is 5% or less of a total number of carbon atoms, and a decolorizer, wherein the color former and the developer are separated from the decolorizer by a microcapsule.
The third erasable image forming material of the present invention comprises a color former, a developer, a matrix agent in which a total number of electron donating groups is 5% or less of a total number of carbon atoms, a decolorizer, and a polymer filler having a glass transition point or softening point higher by 20° C. or more that of the matrix agent, wherein the color former and the developer are phase-separated from or co-dispersed in the polymer filler.
The fourth erasable image forming material of the present invention comprises a core containing a color former, a developer, and a matrix agent in which a total number of electron donating groups is 5% or less of a total number of carbon atoms, a polymer filler externally added to the core, and a decolorizer contained in at least one of the core and the polymer filler.
The first to fourth image forming materials are used in applications in which an image is formed on a paper sheet (image recording medium) by a colored image forming material and completely decolored to allow the paper sheet to be reused.
The fifth erasable image forming material of the present invention comprises a color former, a developer, a decolorizer, a matrix agent in which a total number of electron donating groups is 5% or less of a total number of carbon atoms, and an organic solvent having a boiling point of 150° C. or more.
The sixth erasable image forming material of the present invention comprises a microcapsule containing a color former, a developer, and an organic solvent having an electron donating group, a decolorizer, and a matrix agent in which a total number of electron donating groups is 5% or less of a total number of carbon atoms.
The seventh erasable image forming material of the present invention comprises a microcapsule containing a color former, a microcapsule containing a developer, a matrix agent in which a total number of electron donating groups is 5% or less of a total number of carbon atoms, and a decolorizer.
The eighth erasable image forming material of the present invention comprises a color former, a developer, a reversible decolorizer, one of a compatible decolorizer and a phase separation inhibitor, and a matrix agent in which a total number of electron donating groups is 5% or less of a total number of carbon atoms.
The fifth to eighth image forming materials are used in applications in which reversible coloration and decoloration of an image forming material on a paper sheet (image recording medium) are used. The paper sheet can be reused after an image is finally erased.
An image recording/erasing method of the present invention comprises the steps of forming a colorless image on an image recording medium by using the fifth, sixth, or seventh image forming material, coloring
Machida Shigeru
Sano Kenji
Sato Shuitsu
Takayama Satoshi
Tsunemi Koichi
Bell Mark L.
Faison Veronica F.
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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