Microsencapsulated system for thermal paper
First Claim
Patent Images
1. A coating formulation which provides thermal sensitive coatings for thermal paper, said coating formulation comprising:
- (a) microcapsules containing solid particles of a homogenous blend of a colorless dye and a sensitizer, said sensitizer which is free of color develops having a melting point below that of the colorless dye, wherein the homogenous blend melts at a temperature below the melting point of the colorless dye and below the operating temperature of a thermal print head of a thermal printer in the range of 50°
C. to 250°
C.;
(b) solid particles of a color developer; and
(c) a liquid vehicle for the microcapsules of (a), and particles of (b);
wherein the colorless dye develops color when exposed and reacted with the color developer; and
wherein the microcapsule is impermeable to said colorless dye at room temperature but ruptures to expose and react the colorless dye with the color developer at the operating temperature of a thermal print head of a thermal printer in the range of 50°
C. to 250°
C.
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Abstract
A coating formulation which forms a heat sensitive coating and a thermal recording material with such a coating are disclosed. The heat sensitive coating shows improved prerecording shelf life and improved record stability and consists of microcapsules containing a solid blend of dye and sensitizer, with the exterior of the capsules consisting of color developer and other coating materials such as pigment, binder and additives. Application of heat during printing renders the microcapsule walls permeable to the dye resulting in color development upon reaction of the dye and color developer.
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Citations
14 Claims
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1. A coating formulation which provides thermal sensitive coatings for thermal paper, said coating formulation comprising:
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(a) microcapsules containing solid particles of a homogenous blend of a colorless dye and a sensitizer, said sensitizer which is free of color develops having a melting point below that of the colorless dye, wherein the homogenous blend melts at a temperature below the melting point of the colorless dye and below the operating temperature of a thermal print head of a thermal printer in the range of 50°
C. to 250°
C.;(b) solid particles of a color developer; and (c) a liquid vehicle for the microcapsules of (a), and particles of (b); wherein the colorless dye develops color when exposed and reacted with the color developer; and wherein the microcapsule is impermeable to said colorless dye at room temperature but ruptures to expose and react the colorless dye with the color developer at the operating temperature of a thermal print head of a thermal printer in the range of 50°
C. to 250°
C. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification