Abstract: A thermoreversibly thickening binder composition, comprises a resin latex wherein the amount of an emulsifier in the aqueous phase is smaller than 0.01 mmol/g, and a vinyl polymer having reversibility of hydrophilicity and hydrophobicity at a certain transition temperature. The resin latex is preferably prepared by using an emulsifier having a radically polymerizable group, and preferable as said vinyl polymer is a polymer having a cation-forming group. The binder composition exhibits an excellent chemical stability to factors other than heat without causing migration of the latex resin particles onto the surface of the coated layer even during the time of heat-drying, and thermoreversible thickening effects caused by a sharp heat-sensitive gelling properties. When applied to preparation of coated paper and pressure-sensitive recording sheet, the binder composition provides products excellent in gloss, printability and color producing properties.