Thermosensitive recording material and phthalic acid derivatives for use in the same

A thermosensitive recording material comprising a support and a thermosensitive recording layer formed on said support, comprising a leuco dye and a color developer capable of inducing color formation in said leuco dye upon application of heat thereto, said color developer comprising at least one compound selected from the group consisting of compounds represented by formulas (I) to (IV);

• ##STR133## wherein R.sup.1 is a saturated or unsaturated chain hydrocarbon group having 1 to 10 carbon atoms which may be branched, a chain hydrocarbon group having 1 to 10 carbon atoms which may be substituted by hydroxyl group or interrupted by an ether linkage or carbonyl group, an aryl group selected from the group consisting of phenyl group and naphthyl group, which may have a substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, nitro group or a halogen, ##STR134## in which X is a saturated or unsaturated bivalent hydrocarbon group having 1 to 10 carbon atoms, or a bivalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted by hydroxyl group or interrupted by an ether linkage or carbonyl group;
• and Y is an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, nitro group or a halogen;
• and 1 is an integer of 0 to 5;
• ##STR135## wherein R.sup.2 is a saturated or unsaturated chain hydrocarbon group having 1 to 10 carbon atoms which may be branched, a chain hydrocarbon group having 1 to 10 carbon atoms which may be substituted by hydroxyl group or interrupted by an ether linkage or carbonyl group, an aryl group selected from the group consisting of phenyl group and naphthyl group, which may have a substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, nitro group or a halogen, ##STR136## in which X is a saturated or unsaturated bivalent hydrocarbon group having 1 to 10 carbon atoms, or a bivalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted by hydroxyl group or interrupted by an ether linkage or carbonyl group;
• and Y is an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, nitro group or a halogen;
• and 1 is an integer of 0 to 5;
• ##STR137## wherein R.sup.3 is a saturated or unsaturated chain hydrocarbon group having 1 to 10 carbon atoms which may be branched, a chain hydrocarbon group having 1 to 10 carbon atoms which may be substituted by hydroxyl group or interrupted by an ether linkage or carbonyl group, an aryl group selected from the group consisting of phenyl group and naphthyl group, which may have a substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, nitro group or a halogen, ##STR138## in which X is a saturated or unsaturated bivalent hydrocarbon group having 1 to 10 carbon atoms, or a bivalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted by hydroxyl group or interrupted by an ether linkage or carbonyl group;
• and Y is an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, nitro group or a halogen;
• and 1 is an integer of 0 to 5;
• and ##STR139## wherein R.sup.4 is a saturated or unsaturated chain hydrocarbon group having 1 to 10 carbon atoms which may be branched, a chain hydrocarbon group having 1 to 10 carbon atoms which may be substituted by hydroxyl group or interrupted by an ether linkage or carbonyl group, an aryl group selected from the group consisting of phenyl group and naphthyl group, which may have a substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, nitro group or a halogen, ##STR140## in which X is a saturated or unsaturated bivalent hydrocarbon group having 1 to 10 carbon atoms, or a bivalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted by hydroxyl group or interrupted by an ether linkage or carbonyl group;
• and Y is an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, nitro group or a halogen;
• and 1 is an integer of 0 to 5.