| 摘要 |
PURPOSE:To enhance sensitivity and prevent fading or whitening of recorded images from occurring, by a method wherein dimethyl 4-hydroxyphthalate or a specified bisphenol compound is used as a color developer, and an undercoat layer comprising a specified bisphenol derivative is provided between a base and a thermal color forming layer. CONSTITUTION:Dimethyl 4-hydroxyphthalate or a bisphenol compound of formula I , whrein n is 1 or 2, is used as a color developer. This compound has a high color-developing capability, and high heat response characteristics, and color images developed thereby are excellent in uniformity. The undercoat layer comprising a bisphenol derivative of formula II, wherein X is halogen, Y is -SO2 or -C(CH3)2-, m is 1 or 2, and the groups X in the left and right benzene rings are substituted at positions symmetrical with respect to the group Y, is provided between the base and the thermal color forming layer. Although the melting point of the bisphenol derivative is considerably high, recrystallization at a developed color part is prevented when the dericative is melted together with the dimethyl ester and the bisphenol compound of formula I , so that fading and whitening can be prevented. |
