| abstract |
Compounds of formula (I) :n n wherein A is hydrogen, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy or nitro; R₁, R₂, and R₃, which may be the same or different, are each hydrogen, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy or nitro, or R₁ and R₂ form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulphur or oxygen atom; and formula (II) :n n wherein B is hydrogen, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy or nitro; R₁, R₂, and R₃, which may be the same or different, are each hydrogen, C₁-C₄ alkyl, C₁-C₄ alkoxy, hydroxy or nitro, or R₁ and R₂ form, together with the carbon atoms to which they are attached, an aromatic ring; and Y is a sulphur of oxygen atom; are used in the color developing layer of a thermal recording sheet which comprises a basic colorless dye and an organic color developer. |