Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Identified reactant isolating material or capsule wall...
Reexamination Certificate
2002-06-18
2004-03-09
Hess, B. Hamilton (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Identified reactant isolating material or capsule wall...
C503S226000
Reexamination Certificate
active
06703344
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal recording material, more precisely to a thermal recording material having good lightfastness and in particular to a thermal recording material having the advantages of good lightfastness and image fixation.
2. Description of the Related Art
Relatively inexpensive and capable of being processed in simple and reliable recording appliances not requiring maintenance, thermal recording materials for forming an image upon being provided with a heat by a thermal head, and the like are widely used in the art. Heretofore, there has been a high demand for high-performance thermal recording materials,for example, with improved high image quality or storage stability and the like. Thus, research relating to color density, image quality, storability, and the like has been performed.
Various types of thermal recording materials have been heretofore known, including, for example, those in which electron-donating leuco-dyes and electron-accepting compounds in which they are reacted to form colors, and those in which diazo compounds such as diazonium salts and couplers in which they are reacted to form colors.
The recent development in the art toward full-color thermal recording materials is noticeable. In general, full-color thermal recording materials have a laminate structure of yellow, magentaand cyan-coloring layers, in which the respective layers are thermally colored to form full-color images.
One example of such full-color thermal recording materials has a laminate structure of color-forming layers (thermal recording layers) comprising an electron-donating leuco-dye and an electron-accepting compound and color-forming layers comprising a diazo compound and a coupler, in which yellow, magenta and cyan color-forming layers are laminated in that order from its top.
One method of improving the storability and the image stability against light and heat of thermal recording materials is to encapsulate the electron-donating leuco-dyes and the diazo compounds in microcapsules. According to this method, the electron-donating leuco-dyes and the diazo compounds in thermal recording materials are isolated from water and bases that may promote their decomposition, and, as a result, the shelf life of the thermal recording materials is prolonged (Tomomasa Usami, et al., “
The Journal of the Electrophotography Society of Japan”
, Vol. 26, No. 2, 1987, pp. 115-125).
In heat-responsive microcapsules, a type of microcapsules in which the glass transition point of the capsule wall is slightly higher than room temperature, the capsule wall is substance-impervious at room temperature but is substance-pervious at a temperature not lower than its glass transition point. Accordingly, when electron-donating leuco-dyes or diazo compounds are encapsulated with this capsule wall and electron-accepting compounds, couplers or bases are outside the microcapsules in the thermal recording material, then the encapsulated electron-donating leuco-dyes or diazo compounds can be kept stable for a long time and a color image can be readily formed by heating the material. In addition, the color image thus formed on the material can be readily fixed thereon through exposure to light (photofixation).
One general method of encapsulating a core substance of electron-donating dye precursors or diazo compounds into microcapsules comprises dissolving the core substance in a hydrophobic solvent (oily phase), followed by emulsifying and dispersing this mixture in an aqueous solution having a water-soluble polymer dissolved therein (aqueous phase) using a homogenizer or the like, with a monomer or a prepolymer, which will be the microcapsule wall, being added to one or both of the oily phase and the aqueous phase, to thereby polymerize the monomer or the prepolymer in the interface between the oily phase and the aqueous phase or precipitate the polymer to form a wall of the polymer compound. The method is described in detail, for example, in “
Microcapsules”
(by Tomoji Kondo, Nikkan Kogyo Shinbun Publishing, 1970); and “
Microcapsules”
(by Tamotsu Kondo, et al., Sankyo Publishing, 1977).
However, the above method of microcapsule formation is problematic in that the aqueous solution used forms a lot of bubbles. The bubbles often enter exhaust dusts and therefore lower the production efficiency, and also lower the properties such as the stability of the photographic materials that contain the microcapsules formed according to the method. Therefore, a surfactant that serves as a defoaming agent is generally added to the system of forming microcapsules according to the method. One typical example of the surfactant is sodium dodecylbenzenesulfonate. However, this is still unsatisfactory for completely preventing the generation of bubbles in forming microcapsules when the conditions of this method.
The sensitivity to heat of the microcapsules mentioned above is one important factor thereof. Therefore, if the sensitivity to heat of the microcapsules in one layer of a thermal photographic material is not stable, the quality of the photographic material decreases.
Moreover, when a full color thermal recording material, which is formed by stacking multiple thermal recording layers, uses highly sensitive microcapsules, a problem in that the thermal recording layers comprising microcapsules may generate colors by heat, which is added to cause a color forming reaction in the upper layers. This can cause a mixing of colors and an inferior thermal differation. Thus, when thermal recording layers are superimposed, it is preferable to use microcapsules having low heat sensitivity in the lower layers by the support.
For controlling the sensitivity of microcapsules, the reaction temperature in forming the microcapsules is particularly important. In addition, for satisfactorily preventing the generation of bubbles in microcapsule formation, the surfactant alone is unsatisfactory. Therefore, the reaction condition including the reaction temperature in microcapsule formation must be suitably controlled. However, it is difficult to stably form microcapsules of low sensitivity under the reaction conditions which prevent bubbles from being formed, and it has heretofore been difficult to produce full-color thermal recording materials of good thermal differentiation.
SUMMARY OF THE INVENTION
The present invention is to solve the problems in the prior art noted above, and its object is to provide a thermal recording material having the advantages of superior production suitability, production stability and thermal differentiation.
The means of the invention for solving the problems as above are mentioned below.
Specifically, the invention provides a thermal recording material comprising a support and at least one thermal recording layer disposed on the support, wherein the layer comprises at least one electron-accepting compound, and microcapsules, which encapsulate an electron-donating dye precurser and are formed using a compound represented by the following general formula (I) and a compound represented by the following general formula (II):
wherein each of R
1
and R
2
represents an alkyl group; n is an integer selected from 0 to 3; and M represents Na, Mg, K or Ca.
The invention also provides a thermal recording material comprising a support and at least one thermal recording layer disposed on the support, wherein the layer comprises at least microcapsules, which encapsulate a diazo compound, and a coupler, for reacting with the diazo compound to produce a color, which microcapsules are formed using a compound represented by the following general formula (I) and a compound represented by the following general formula (II):
wherein each of R
1
and R
2
represents an alkyl group; n is an integer selected from 0 to 3; and M represents Na, Mg, K or Ca.
Moreover, the present invention provides the thermal recording material comprising a support and at least one thermal recording layer disposed on the support, the layer including at least an electron-accepting c
Minami Kazumori
Ueki Shiki
Fuji Photo Film Co. , Ltd.
Hess B. Hamilton
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