Heat-sensitive recording material

Abstract

In a heat-sensitive recording material incorporating a colorless or pale-colored basic dye and a color acceptor which is reactive with the basic dye to form a color when contacted therewith, the recording material characterized in that at least one compound represented by the formula [I] is contained in a heat-sensitive recording layer wherein X is -O- or -COO-, R1 to R4 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 R1 and/or R2 or substituents R3 and R4 may link together to form aromatic ring(s), n is an integer of 1 to 10.

We claim: 
     
       1. In a heat-sensitive recording material .Iadd.comprising a heat-sensitive recording layer .Iaddend.incorporating a colorless or pale-colored basic dye.Iadd., .Iaddend.and a color acceptor which is reactive with the basic dye to form a color when contacted therewith, the recording material characterized in that at least one compound represented by the formula  I! is contained in the heat-sensitive recording layer ##STR4## wherein X is --O-- . .or --COO--.!., R 1  to R 4  are each a 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 1  and. ./or.!. R 2  .Iadd.and/.Iaddend.or substituents R 3  and R 4  may link together to form aromatic ring(s), and n is an integer of 1 to 10.Iadd., wherein said recording layer is deposited on a substrate.Iaddend.. 
     
     
       2. A heat-sensitive recording material as defined in claim 1 wherein X is --O-- . .or --COO--.!., R 1  to R 4  are each hydrogen atom, alkyl having 1 to 4 carbon atoms, phenyl, benzyl, chlorine atom, methoxy, methylthio, cyano or nitro, substituents R 1  and R 2  and/or substituents R 3  and R 4  may link together to form aromatic ring(s). 
     
     
       3. A heat-sensitive recording material as defined in claim 2 wherein X is oxygen atom. 
     
     
       4. A heat-sensitive recording material as defined in claim 1 wherein the compound represented by the formula  I! is used in an amount of 10 to 1000 parts by weight per 100 parts by weight of the color acceptor. 
     
     
       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 1  to R 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 1  and R 2  and/or substituents R 3  and R 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 1  to R 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 1  and R 2  and/or substituents R 3  and R 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 1  to R 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 1  and R 2  and/or substituents R 3  and R 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 1  to R 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 1  and R 2  and/or substituents R 3  and R 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.