Heat-sensitive recording material

Claims

3. A heat-sensitive recording material as defined in claim 2 wherein X is oxygen atom.

5. A heat-sensitive recording material as defined in claim 1 wherein the color acceptor is used in an amount of 100 to 700 parts by weight per 100 parts by weight of the basic dye..Iadd.

6. In a heat-sensitive recording material comprising a substrate and a heat-sensitive recording layer deposited on said substrate, wherein the heat-sensitive recording layer comprises a colorless or pale-colored basic dye and a color acceptor which is thermally reactive with said dye to form a color record when thermally activated; the improvement comprising, in said heat-sensitive recording layer, at least one recording sensitivity enhancing compound according to the formula (I); ##STR5## wherein X is --O--, R.sub.1 to R.sub.4 are each hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl having 6 to 10 carbon atoms, aralkyl having 7 to 9 carbon atoms, chlorine atom, acetyl, propionyl, methoxy, methylthio, methoxycarbonyl, cyano, nitro or cyclohexenyl, substituents R.sub.1 and R.sub.2 and/or substituents R.sub.3 and R.sub.4 may link together to form aromatic ring(s), n is an integer of 1 to 10; wherein said basic dye, said color acceptor and said at least one recording sensitivity enhancing compound are deposited on the substrate in the form of fine particles..Iaddend..Iadd.7. In a color record, corresponding to a thermal contact with a thermally sensitive recording material comprising a substrate having a thermally sensitive recording layer disposed thereon; wherein said color record comprises the thermal reaction product of a colorless or pale-colored basic dye with a color acceptor thermally reactive therewith; the improvement comprising, in said thermally sensitive recording layer, a sensitivity enhancing quantity of at least one compound according to the formula (I); ##STR6## wherein X is --O--, R.sub.1 to R.sub.4 are each hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl having 6 to 10 carbon atoms, aralkyl having 7 to 9 carbon atoms, chlorine atom, acetyl, propionyl, methoxy, methylthio, methoxycarbonyl, cyano, nitro or cyclohexenyl, substituents R.sub.1 and R.sub.2 and/or substituents R.sub.3 and R.sub.4 may link together to form aromatic ring(s), n is an integer of 1 to 10.

.Iaddend..Iadd.8. In a heat-sensitive recording material, having improved recording sensitivity, consisting essentially of a substrate having deposited thereon a heat-sensitive recording layer comprising colorless or pale-colored basic dye, a color acceptor thermally reactive therewith; the improvement comprising, in said heat-sensitive recording layer, a sensitivity enhancing quantity of at least one compound according to the formula (I); ##STR7## wherein X is --O--, R.sub.1 to R.sub.4 are each hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl having 6 to 10 carbon atoms, aralkyl having 7 to 9 carbon atoms, chlorine atom, acetyl, propionyl, methoxy, methylthio, methoxycarbonyl, cyano, nitro or cyclohexenyl, substituents R.sub.1 and R.sub.2 and/or substituents R.sub.3 and R.sub.4 may link together to form aromatic ring(s), n is an integer of 1 to 10.

.Iaddend..Iadd.9. A heat sensitive recording material as claimed in claim 8 wherein said heat-sensitive recording layer further includes a binder..Iaddend..Iadd.10. A heat-sensitive recording material as claimed in claim 8 wherein said heat-sensitive recording layer further includes at least one auxiliary material in an amount which does not cause adverse effects.

.Iaddend..Iadd.11. A heat-sensitive recording material as claimed in claim 8, wherein each of said components of said heat-sensitive recording layer is separately dispersed as fine particles in said recording

material..Iaddend..Iadd.12. In a process of producing record images by:

coating a substrate with a heat-sensitive recording layer composition comprising a colorless or pale-colored basic dye and a color acceptor,

subjecting said coated substrate to a thermal recording, color forming reaction, and

recovering said substrate having thermally recorded images thereon;

the improvement which comprises:

including in said heat-sensitive recording layer at least one compound represented by the formula (I): ##STR8## wherein X is --O--, R.sub.1 to R.sub.4 are each hydrogen atom, alkyl having 1 to 8 carbon atoms, aryl having 6 to 10 carbon atoms, aralkyl having 7 to 9 carbon atoms, chlorine atom, acetyl, propionyl, methoxy, methylthio, methoxycarbonyl, cyano, nitro or cyclohexenyl, substituents R.sub.1 and R.sub.2 and/or substituents R.sub.3 and R.sub.4 may link together to form aromatic ring(s), n is an integer of 1 to 10, thereby providing a recording layer of enhanced recording sensitivity;

thermally recording images on said enhanced sensitivity recording layer; and

recovering from said thermal recording step said substrate and recording layer thereon of substantially undiminished whiteness having printed

thereon thermally recorded images..Iaddend..Iadd.13. A process of producing record images as claimed in claim 12 wherein said heat-sensitive recording layer further includes a binder..Iaddend..Iadd.14. A process of producing record images as claimed in claim 12 wherein said heat-sensitive recording layer further includes at least one auxiliary material in an

amount which does not cause adverse effects..Iaddend..Iadd.15. A process of producing record images as claimed in claim 12 wherein each of said components is separately dispersed as fine particles in said recording material..Iaddend.