| 摘要 |
PROBLEM TO BE SOLVED: To form an image having sufficient second color developing sensitivity and density in practical use by incorporating metal salt of strong acid in a thermal recording material having a thermal recording material having a thermal recording layer containing developer of electron donative dye precursor having a functional group represented by a formula and aromatic carboxylic acid compound or its metal salt. SOLUTION: The thermal recording material having a thermal recording layer containing developer of phthalide group and dye precursor having a functional group represented by a formula (R1 is 1-14C monovalent group containing ether bond, thioether bond, halogen atom and the like) and aromatic carboxylic acid compound or its metal salt contains metal salt of strong acid. The metal salt of the acid represents metal salt of inorganic or organic acid in which logarithmic value pKa of reciprocal number of acid dissociation constant Ka is 3 or less or preferably 0 or less. As such metal salt of the acid, cobalt chloride (II), cobalt bromide (II), cobalt fluoride (II), the like, and their hydrates are used, but the metal salt is not limited to these. And, an adding amount of each of them is preferably 0.1 to 7.0 pts.wt. or particularly 0.3 to 5.0 pts.wt. to 1 pt.wt. of the precursor. |
