| abstract |
According to the present invention, the contained amount of a compound measured by mass spectrometry to have a molecular weight of 650-670, typically a molecular weight of 660, is reduced to 0.5 mass% or less in a heat-sensitive recording material containing 3,3'-diallyl-4,4'-dihydroxy diphenylsulfone, or in a diphenylsulfone or a color developer. Accordingly, a heat-sensitive recording material, a color developer, or a diphenylsulfone is provided which is less susceptible to background fogging under moisture and heat and which has excellent color-developed image preservation stability. |