A thermal recording material having both of excellent coloring property and storage stability with a low cost is provided. The thermal recording material contains a leuco dye and a developer in a coloring layer, and the developer contains 2,4′-dihydroxydiphenylsulfone and 4,4′-dihydroxydiphenylsulfone with a specific ratio, and the above-mentioned two kinds of the dihydroxydiphenylsulfones are made a material obtained by sequentially undergoing a separating step for heightening the weight ratio of a 2,4′ material from a dichlorodiphenylsulfone mixture containing the 2,4′ material and a 4,4′ material, a reaction step of hydrolyzing the mixture to obtain a dihydroxydiphenylsulfone mixture, and a post-treatment step of subjecting to decolorization and purification.
提供了一种具有优异的着色性能和储存稳定性且成本低廉的热记录材料。该热记录材料包含一个显色层中的亚乙基
染料和显影剂,显影剂包含2,4'-二羟基二苯基砜和4,4'-二羟基二苯基砜,并具有特定比例,上述两种二羟基二苯基砜是通过依次经历提高2,4'材料的重量比的分离步骤,
水解混合物以获得二羟基二苯基砜混合物的反应步骤和经过脱色和纯化的后处理步骤而获得的材料。