Abstract: A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a leuco dye and a developer, formed on one side of the support, wherein the heat-sensitive recording layer contains an ultraviolet ray-absorbing agent, said ultraviolet ray-absorbing agent being a dimer ultraviolet ray-absorbing agent.

Abstract: The heat-sensitive recording material disclosed comprises a colorless or pale colored dyestuff precursor, one or more salicylic acid derivative of the formula (1) or metal salt of the derivative and an aliphatic amide compound having 18.about.60 carbon atoms in molecular structure, and is excellent in thermal response and preservation stability of white portions and images. ##STR1## wherein X.sub.1 and X.sub.2 are a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aralkyl group or an aryl group, Y.sub.1 and Y.sub.2 are an oxygen atom or a sulfur atom, R.sub.1 is a hydrogen atom, an alkyl group, an aralkyl group or an aryl group, and R.sub.2 is an alkyl group, an alkenyl group, an aralkyl group or an aryl group.

Abstract: A heat-sensitive recording material comprising a color forming, electron donating compound and a salicylic acid derivative represented by the formula (1): ##STR1## wherein X.sub.1 and X.sub.2 are a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group or a halogen atom, Y.sub.1 and Y.sub.2 are an oxygen atom or a sulfur atom, R.sub.1 is a hydrogen atom, an alkyl group, an aralkyl group or an aryl group , and R.sub.2 is an alkyl group, an alkenyl group, an aralkyl group or an aryl group, and/or a metal salt of the salicylic acid derivative as an electron accepting compound, is disclosed.

Abstract: There is disclosed a thermosensitive recording material, comprising a support, a thermosensitive recording layer coated on said support and comprising a dye precursor and a color developer capable of developing a color of said dye precursor upon heating, and an porous undercoat layer comprising any one selected from water soluble polymers and latex resins and coated between said support and said thermosensitive recording layer.

Abstract: A thermosensitive recording material bearing an undercoat layer comprising fine organic hollow particles having a specific ratio of its wall thickness to its particle diameter provides excellent thermal response and minimizes foreign matters adhered to a thermal head.

Abstract: A heat-sensitive recording material is disclosed. The material comprises a support and a heat-sensitive recording layer, between which is provided an undercoat layer which comprises a first layer comprising urea-formaldehyde resin and a second layer comprising a pigment provided on the first layer. The first layer may additionally contain a pigment.

Abstract: There is disclosed a good thermosensitive recording material, having excellent thermal response and having minimal adhesion to a thermal head, which comprises a support having provided thereon a thermosensitive recording layer comprising:(1) a substantially colorless dye precursor,(2) an electron donating developer capable of developing a color of the dye precursor, and,(3) as an additive, 2-benzyloxynaphthalene and p-benzylbiphenyl in a mixing ratio of 95:5 to 70:30 (by weight).

Abstract: There is disclosed a thermosensitive recording material improved in thermal response and image retention which comprises a support and, provided thereon, a thermosensitive recording layer containing a generally colorless or slightly colored dye precursor and a developer which, upon being heated, reacts with said dye precursor to develop color, wherein said thermosensitive recording layer contains as sensitizer a compound selected from a group consisting of p-benzylbiphenyl, diaryl esters of adipic acid, ##STR1## (wherein R represents a substituted or unsubstituted aralkyl group, ##STR2## (wherein R.sub.1 and R.sub.2 each represents an alkyl, aralkyl, or aryl group), and ##STR3## and said developer is bis(3-allyl-4-hydroxyphenyl)sulfone.

Abstract: There is disclosed a thermosensitive recording material improved in thermal response and image retention which comprises a support and, provided thereon, a thermosensitive recording layer containing a generally colorless or slightly colored dye precursor and a developer which, upon being heated, reacts with said dye precursor to develop color, wherein said thermosensitive recording layer contains as sensitizer a compound selected from a group consisting of p-benzylbiphenyl, diaryl esters of adipic acid, ##STR1## (wherein R represents a substituted or unsubsitituted aralkyl group), ##STR2## (wherein R.sub.1 and R.sub.2 each represents an alkyl, aralkyl, or aryl group), and ##STR3## and said developer is bis(3-allyl-4-hydroxyphenyl)sulfone.

Abstract: A thermosensitive recording sheet containing in its thermosensitive layer dimethyl 4-hydroxy-phthalate as color developer and further containing if desired dimethyl terephthalate and/or a 2-tert-butylphenol derivative is excellent in color development sensitivity characteristic and recorded image stability.

Abstract: In ordinary heat-sensitive sheets using a colorless to light-colored dye precursor and a color developer which causes said dye precursor to develop a color by reacting with the dye precursor when heated, printability can be improved by establishing the maximum peaks of their void distribution curves at a void diameter of 1.0 .mu.m or less.