(1) A 4-hydroxy-4'-isopropoxydiphenylsulfone developer dispersion
characterized by being obtained by wet grinding a
4-hydroxy-4'-isopropoxydiphenylsulfone developer in the presence of at
least one compound selected from the group consisting of
1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane and
1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, or in the
presence of
1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid;
(2) a method for wet grinding a 4-hydroxy-4'-isopropoxydiphenylsulfone
developer, characterized by wet grinding a
4-hydroxy-4'-isopropoxydiphenylsulfone developer in the presence of at
least one compound selected from the group consisting of
1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane and
1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, or in the
presence of
1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid;
and (3) a heat-sensitive recording material having a heat-sensitive
recording layer containing the developer dispersion.