| 摘要 |
PROBLEM TO BE SOLVED: To improve optical character reading suitability in a specific wavelength range by using one type of indolylazaphthalide derivatives of a specific structure as a basic bye in a recording layer, and incorporating 1,1-bis(4- hydroxyphenyl)-1-phenylethane as a colorant. SOLUTION: In the thermal recording medium comprising a recording layer containing a colorless or pale basic dye and a colorant on a support with excellent optical character reading(OCR) suitability in a wavelength range of 650 to 700nm, at least one type of indolylazaphthalide derivatives rephresented by the formula is used as the basic bye and 1,1-bis(4-hydroxypenyl)-1- phenylethane is contained as a colorant in the recording layer. In the formula, R1 indicates a 1-8C alkyl group, R2 indicates a 1-6 alkyl group, and R3 , R4 indicate 1-6C alkyl groups. The R3 , R4 may form a heatero ring together with adjacent nitrogen atom. |
