Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Plural colors or plural diverse systems
Reexamination Certificate
2000-11-15
2003-07-22
Hess, B. Hamilton (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Plural colors or plural diverse systems
C503S201000, C503S216000
Reexamination Certificate
active
06596669
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to reversible two-color heat-sensitive recording materials in which formation of images and decolorization of the images can be carried out by controlling the heat energy. Moreover, the present invention relates to a recording method of the above-mentioned recording materials.
2. Prior Art
Heat-sensitive recording materials generally comprise a support and, provided thereon, a heat-sensitive recording layer mainly composed of a normally electron donating colorless or slightly colored dye precursor (hereinafter sometimes also referred to as “leuco dye”) and an electron accepting compound (hereinafter sometimes also referred to as “a color developer”) The dye precursor and the color developer instantaneously react upon application of heat by thermal head, thermal pen, laser beams or the like to form an image. Such heat-sensitive recording materials are disclosed in Japanese Patent Application Kokoku Nos. 43-4160, 45-14039 and the like.
In general, in the case of these heat-sensitive materials, when an image is once formed, it is impossible to erase the image and to restore the portion to the original state before forming the image. Therefore, for further recording of information, it is possible to make recording only in the portions where no image is formed. Accordingly, there is a problem that an area for heat-sensitive recording is limited and information to be recorded is restricted and not all of the necessary information can be recorded.
In recent years, reversible heat-sensitive recording materials capable of forming images and decolorizing the same repeatedly have been proposed for solving the above problems. For example, Japanese Patent Application Kokai Nos. 54-119377, 63-39377 and 63-41186 disclose heat-sensitive recording materials constituted by a matrix resin and an organic low molecular weight material dispersed in the matrix resin. However, in these methods, transparency of the heat-sensitive recording materials is reversibly changed and so the contrast between the image formed portion and the image unformed portion is insufficient.
Also, in the methods described in Japanese Patent Application Kokai Nos. 50-81157 and 50-105555, an image to be formed changes depending on the environmental temperatures, so that a temperature to maintain the image-formed state and a temperature to maintain the image-erased state are different from each other. Thus, these two states cannot be maintained for an optional period of time under normal temperature.
Further, Japanese Patent Application Kokai No. 59-120492 discloses a method for maintaining the image-formed state and the image-erased state by keeping the recording material in the region of the hysteresis temperatures utilizing the hysteresis characteristics of color forming components. However, this method requires a heat source and a cooling source for image formation and erasing the same and has the defects that the temperature region at which the image-formed state and the image-erased state can be maintained is limited to the region of the hysteresis temperature. Thus, this method is still not sufficient for using the materials in the temperature and environment of everyday life.
On the other hand, Japanese Patent Application Kokai Nos. 2-188293 and 2-188294 and International Patent Publication No. WO90/11898 disclose reversible heat-sensitive recording media comprising a leuco dye and a color developing and decolorizing agent which causes color formation of the leuco dye upon heating and causes decolorization of the color (or erases a formed color). The color developing and decolorizing agent is an amphoteric compound having an acidic group which causes color formation of the leuco dye and a basic group which causes decolorization of the leuco dye. It preferentially causes one of the color formation action of the acidic group and the decolorization action of the basic group by controlling the heat energy, thereby to perform the color formation and decolorization. However, according to this method, it is impossible to completely change the color forming reaction and the decolorizing reaction to each other only by controlling heat energy. Also, both of the reactions simultaneously take place with a certain ratio so that a sufficient color density cannot be obtained and the decolorization cannot be completely performed. For this reason, a sufficiently high contrast of the image cannot be obtained. Moreover, the decolorizing action of the basic group acts also on the color formed portion at room temperature, so that the density of the color formed portion inevitably decreases with a lapse of time. Furthermore, in Japanese Patent Application Kokai No. 5-124360, reversible heat-sensitive recording media which can form a color and erase the same by heating a leuco dye is described. Also, as an electron-accepting compound, there are exemplified by an organic phosphoric acid compound, &agr;-hydroxyaliphatic carboxylic acid, aliphatic dicarboxylic acid and a specific phenol compound such as an alkylthiophenol, an alkyloxyphenol, an alkylcarbamoylphenol and alkyl gallate each having a carbon number of 12 or more, etc. However, in this recording media, coloring density is low or decolorization of images is incomplete so that the two problems cannot be solved simultaneously and image stability with a lapse of time is also not practically satisfied.
The present applicants have previously proposed in Japanese Patent Application Kokai Nos. 7-108761, 7-179043 and 7-214907, etc., that a phenol compound having a specific connecting group as an electron-accepting compound is excellent in color-formation and decolorization contrast, image stability with a lapse of time and high speed decolorization properties.
On the other hand, there are great demands for a multi-color heat-sensitive recording, and a two-color heat-sensitive recording material has recently been in the region of practical use. This two-color heat-sensitive recording material comprises compositions having different color tones being laminated on a support and employs a method of forming respective images with low temperature energy and high temperature energy. More specifically, it has been accomplished by the two kinds of methods of a color mixing type wherein a high temperature color-formed image is added to a low temperature color-formed image, and a decolorization type wherein a low temperature color-formed image is erased by using a suitable erasing agent as soon as a high temperature color-formed image is obtained. However, in a color addition type, two-color image with good contrast can only be obtained as long as the high temperature color-formed image has a color tone which can sufficiently conceal the low temperature color-formed image. Also, in the decolorization type, a combination of color tones to be color-formed is free but there are problems in the points of color-formation and decolorization contrast, stability of the image with a lapse of time, or the like.
Recently, a method of utilizing a reversible heat-sensitive color-forming composition for an approach to a multi-color heat-sensitive recording material has been proposed. According to Japanese Patent Application Kokai Nos. 6-79970 and 6-305247, there are disclosed a material in which two or more kinds of reversible heat-sensitive color-forming compositions different in decolorization initiating temperatures are provided, and after forming all the mixed colors, a part of the image is erased at a suitable temperature to obtain an optional mixed color or a single color image. However, in this recording medium, differentiation of the decolorization initiating temperatures is carried out based on the length of an alkyl group possessed by an electron-accepting compound. Thus, there is a problem in a color-formation and decolorization contrast of a low temperature decolorizing layer containing a compound having a short alkyl group, or in stability of an image with a lapse of time. Also, its image forming system is a two step system of
Maruyama Jun
Sano Hidekazu
Hess B. Hamilton
Manelli Denison & Selter PLLC
Mitsubishi Paper Mills Limited
White, Jr. Paul E.
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