COLOR DEVELOPING COMPOSITION, ITS MANUFACTURE, AND HEAT-SENSITIVE RECORDING MATERIAL

PROBLEM TO BE SOLVED: To reduce fogging by a method wherein 4-hydroxy-4'-isopropoxy diphenyl sulfone which is a color developing compound is wet-ground and dispersed together with a styrene/acrylic copolymer ammonium salt. SOLUTION: When 4-hydroxy-4'-isopropoxy diphenyl sulfone is wet-ground in water, the solid component concentration of the 4-hydroxy-4'-isopropoxy diphenyl sulfone is approx. 5-70 wt.%, and the grinding is performed with the existence of approx. 0.1-50 pts.wt. of a styrene/acrylic copolymer ammonium salt based on 100 pts.wt. of the 4-hydroxy-4'-isopropoxy diphenyl sulfone. By this method, the stability of the water-soluble dispersion liquid is increased, and a heat-sensitive recording material having a high sensitity and less fogging can be obtained.