Thermal recording sheet

A thermal recording sheet having a thermal recording layer containing a colorless or pale colored dye precursor and a color developer reactable with said dye precursor upon heating to develop a color, wherein said color developer is a urea compound of Formula (2), (3), or (4), and the thermal recording layer contains at least one of said urea compounds:

• ##STR15## wherein X is alkyl group having 1 to 12 carbon atoms, halogenated alkyl group having 1 to 6 carbon atoms, aralkyl group having 7 to 14 carbon atoms, alkoxy group having 1 to 12 carbon atoms, aryloxy group having 6 to 12 carbon atoms, alkoxycarbonyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, dialkylamino group having 1 to 12 carbon atoms, arylalkylamino group having 7 to 12 carbon atoms, arylamino group having 6 to 12 carbon atoms, acylamino group having 1 to 12 carbon atoms, nitro group, cyano group, halogen group, or hydrogen group, A denotes a divalent group comprising 30 or less carbon atoms, and B denotes a trivalent group comprising 30 or less carbon atoms, n is an integer from 1 to 3.

A thermal recording sheet having a thermal recording layer containing a colorless or pale colored dye precursor and a color developer reactable with said dye precursor upon heating to develop a color, wherein said color developer is a urea compound of Formula (5), and the thermal recording layer contains at least one of said urea compound:

• ##STR16## wherein X is alkyl group having 1 to 12 carbon atoms, halogenated alkyl group having 1 to 6 carbon atoms, aralkyl group having 7 to 14 carbon atoms, alkoxy group having 1 to 12 carbon atoms, aryloxy group having 6 to 12 carbon atoms, alkoxycarbonyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, dialkylamino group having 1 to 12 carbon atoms, arylalkylamino group having 7 to 12 carbon atoms, arylamino group having 6 to 12 carbon atoms, acylamino group having 1 to 12 carbon atoms, nitro group, cyano group, halogen group, or hydrogen group, n is an integer from 1 to 3, and m is an integer from 1 to 12.

A thermal recording sheet having a thermal recording layer containing a colorless or pale colored dye precursor and a color developer reactable with said dye precursor upon heating to develop a color, wherein said color developer is a urea compound of Formula (2), and the thermal recording layer contains at least one of said urea compound:

• ##STR17## wherein X is alkyl group having 1 to 12 carbon atoms, halogenated alkyl group having 1 to 6 carbon atoms, aralkyl group having 7 to 14 carbon atoms, alkoxy group having 1 to 12 carbon atoms, aryloxy group having 6 to 12 carbon atoms, alkoxycarbonyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, dialkylamino group having 1 to 12 carbon atoms, arylalkylamino group having 7 to 12 carbon atoms, arylamino group having 6 to 12 carbon atoms, acylamino group having 1 to 12 carbon atoms, nitro group, cyano group, halogen group, or hydrogen group.

A thermal recording sheet having a thermal recording layer containing a colorless or pale colored dye precursor and a color developer reactable with said dye precursor upon heating to develop a color, wherein said color developer is a urea compound of Formula (3), and the thermal recording layer contains at least one of said urea compound:

• ##STR18## wherein X is alkyl group having 1 to 12 carbon atoms, halogenated alkyl group having 1 to 6 carbon atoms, aralkyl group having 7 to 14 carbon atoms, alkoxy group having 1 to 12 carbon atoms, aryloxy group having 6 to 12 carbon atoms, alkoxycarbonyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, dialkylamino group having 1 to 12 carbon atoms, arylalkylamino group having 7 to 12 carbon atoms, arylamino group having 6 to 12 carbon atoms, acylamino group having 1 to 12 carbon atoms, nitro group, cyano group, halogen group, or hydrogen group, A denotes a divalent group comprising 30 or less carbon atoms, and n is an integer from 1 to 3.

A thermal recording sheet having a thermal recording layer containing a colorless or pale colored dye precursor and a color developer reactable with said dye precursor upon heating to develop a color, wherein said color developer is a urea compound of Formula (4), and the thermal recording layer contains at least one of said urea compound:

• ##STR19## wherein X is alkyl group having 1 to 12 carbon atoms, halogenated alkyl group having 1 to 6 carbon atoms, aralkyl group having 7 to 14 carbon atoms, alkoxy group having 1 to 12 carbon atoms, aryloxy group having 6 to 12 carbon atoms, alkoxycarbonyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, dialkylamino group having 1 to 12 carbon atoms, arylalkylamino group having 7 to 12 carbon atoms, arylamino group having 6 to 12 carbon atoms, acylamino group having 1 to 12 carbon atoms, nitro group, cyano group, halogen group, or hydrogen group, B denotes a trivalent group comprising 30 or less carbon atoms, and n is an integer from 1 to 3.