| 摘要 |
PURPOSE:To enhance head matching properties by using high purity silica wherein the content of an Na<+> ion and a Cl<-> ion is a predetermined value or less as pigment in a protective layer. CONSTITUTION:A protective layer based on a resin and pigment is provided on a thermal color forming layer based on a leuco dye and a coupler. As the pigment in the projective layer, high purity silica wherein the content of an Na<+> ion and a Cl<-> ion is 1ppm or less is sued. This high purity silica is amorphous and the average particle size thereof is set to 0.5mum or less. By this constitution, effect is developed in thermal head abrasion resistance. As a resin added to the protective layer, a water-soluble polymer emulsion of polyvinyl alcohol or the like is used. |
