Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or...
Reexamination Certificate
1998-11-25
2001-05-15
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
C427S150000, C503S204000, C503S209000
Reexamination Certificate
active
06232266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to a heat-sensitive recording material, more specifically to a heat-sensitive recording material containing a heat-sensitive recording component coloring characteristics such as a coloring temperature, etc. of which are controlled.
2. Prior art
A heat-sensitive material generally comprises a support and a heat-sensitive recording layer mainly comprising an electron-donative dye precursor generally colorless or pale colored and an electron-accepting developer as main component provided on the support. By heating the heat-sensitive material with a thermal head (heat head), a thermal pen, and a laser beam, etc., the dye precursor and the developer are immediately reacted to obtain a colored image. This is disclosed in, for example, Japanese Patent Publications No. 4160/1968 and No. 14039/1970, etc.
Recording by using such a heat-sensitive recording material can be carried out with a relatively simple device, and the device has advantages that maintenance is easy, no noise generates, etc. Thus, it is utilized in various fields such as an instrumental recorder, a facsimile machine, a printer, terminals of a computer, labeling, a ticket vending machine, etc.
On the other hand, in many uses of heat-sensitive recording materials, it has been desired to develop a multi-colored heat-sensitive recording material which can form two or more color tones by the difference of heating temperature. As a method for realizing such a multi-colored heat-sensitive recording material, the following methods have been known. One of them is a method in which color-forming temperatures are controlled by changing melting points of compounds constituting heat-sensitive recording components, and at low temperature heating, only a heat-sensitive recording component having a low color-forming temperature forms a color, while at a high temperature, the heat-sensitive recording component having a low color-forming temperature and a heat-sensitive recording component having a high color-forming temperature simultaneously produce colors to form a different color tone from that of the low-temperature heating as disclosed in Japanese Patent Publication No. 69/1974. As another method, several kinds of heat-sensitive recording components are contained in respective layers laminated on a support separately, and a heat-sensitive recording component contained in a surface layer which is close to a heat source is color-formed at a lower heating temperature, and a heat-sensitive recording component contained in a layer which is farthest from the heat source is color-formed at a higher heating temperature as disclosed in Japanese Patent Publication No. 27708/1974.
In the former method in which a color-forming temperature is controlled by changing a melting point of the compound constituting the heat-sensitive recording component, there are problems that raw materials which can be used in the method are limited and a balance with the other characteristics cannot sufficiently be obtained. In addition, to contain the heat-sensitive color-forming components different in a formed color tone in the same layer, it is necessary to prevent color formation by an interaction of the different kinds of heat-sensitive recording components to each other. Also, in the latter method in which respective kinds of heat-sensitive recording components are contained in a separate layer among the laminated layers, there is a problem that the layer constitution of the multi-colored heat-sensitive recording material becomes complex whereby productivity becomes worse, or the like.
Moreover, in the multi-colored heat-sensitive recording material, it is important that two kinds or more of color tones are formed within a narrow temperature range (a printing energy range), i.e., formed color tones are clearly separated to each other. To realize the above, it is required that, in a color-forming behavior of a high-temperature color-forming component, the difference between the highest temperature (the maximum energy) of a heating temperature (an applied energy) at which no color is formed and the lowest temperature (the minimum energy) at which color formation reaches saturation is small, that is, start of color-formation relative to the temperature (energy) is steep. By making start or raise of color formation of the high-temperature color-forming component steep, within a narrow temperature range (a printing energy range), the high-temperature color-forming component does not form a color at low-temperature heating but suddenly forms a color only at a certain temperature or more so that a color tone by low-temperature color-forming is sharp and color separation becomes clear.
However, in the above-mentioned conventional multi-colored heat-sensitive recording materials, start of color formation of the high-temperature color-forming component is generally gentle and color separation is unclear. Also, even if a color formation temperature of the high-temperature color-forming component is shifted to a higher temperature side by a certain means, whereas low-temperature color formation becomes sharp and color separation becomes clear with a certain extent, high energy is required for color-formation of the high-temperature color-forming component whereby it cannot be practically used. To solve these problems, it has been proposed a method of controlling color-forming characteristics such as a color-formation temperature, etc. by incorporating a compound constituting the heat-sensitive recording components into a microcapsule to have a role of a color-formation controlling layer to the wall of the microcapsule.
For example, in Japanese Provisional Patent Publication No. 282115/1996, it has been proposed a method in which a plural number of electron-donative dye precursors and electron-accepting compounds having different color tone to be color-formed are contained in the same layer, and at least one of said electron-donative dye precursors is contained in a microcapsule. According to this method, a color-forming temperature can be heightened by reacting the electron-donative dye precursor and the electron-accepting compound. Also, the electron-donative dye precursor incorporated into the microcapsule and the electron-donative dye precursor not incorporated therein are not interacted to each other so that two kinds or more of color tones to be color-formed can be obtained by one layer of the heat-sensitive recording layer.
Also, by incorporating a compound constituting the heat-sensitive recording component, e.g., an electron-donative dye precursor, in a microcapsule, in a heat-sensitive recording material having a heat-sensitive recording layer containing the microcapsule, control of color-forming characteristics such as a color-forming temperature can be realized. Moreover, even if an electron-donative dye precursor and an electron-accepting compound are used in combination, which cause background surface fogging when they are used in combination by not separating with each other, by separating the electron-donative dye precursor and the electron-accepting compound, a heat-sensitive recording material having good color-forming can be obtained without causing background fogging.
Moreover, even if a substance which color-forms a heat-sensitive recording material such as an organic solvent is attached to the heat-sensitive recording material, such an erroneous color-formation of the heat-sensitive recording material can be prevented by providing a characteristic of not dissolving a color-forming substance by an organic solvent, etc. to a color-formation controlling layer.
As a method for forming a color-formation controlling layer on the surface of the compound constituting the heat-sensitive recording components, various kinds of methods for making microcapsule can be applied to. Specific examples thereof may include the interfacial polymerization method, the coacervation method, the spray drying method, the emulsion evaporating solidification method, the emulsion cooling solidifica
Masuda Takao
Yokota Yasuro
Hess Bruce H.
Mitsubishi Paper Mills Limited
Pillsbury & Winthrop LLP
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