Patent ID: 7081435

Claim:
A thermally sensitive recording medium comprising a thermally sensitive color developing layer containing colorless or pale colored basic leuco dye and a color developing agent as a main components on a substrate, wherein said thermally sensitive recording layer contains acrylic emulsion and colloidal silica, further contains at least one kind of diphenylsulfone bridgeable compound represented by general formula A as the color developing agent, wherein X and Y can be different or same and indicates a saturated or an unsaturated liner or grafted hydrocarbon group of carbon number 1–12 which can possess an ether bond, or indicate, wherein, R indicates a methylene group or an ethylene group, T indicates a hydrogen atom or an alkyl group of carbon number 1–4, and R 1 –R 6 independently a halogen atom, an alkyl group of carbon number 1–6, or an alkenyl group, further, m, n, p, q, r, t indicate an integer number of 0–4 and when are bigger than 2, R 1 –R 6 can be different, and a is an integer of 0–10 said diphenylsulfone bridgeable compound having an average particle diameter of 0.5 μm, said colloidal silica having a particle size of 10–25 nm and, said acrylic emulsion being blended to the thermally sensitive recording layer in a blending amount of 3–50 weight parts of the acrylic emulsion to 100 weight parts of the thermally sensitive recording layer.