A heat-sensitive color-developing layer of a heat-sensitive recording medium and a coating liquid for forming the heat-sensitive color-developing layer each contain a leuco dye, a color developing agent and a polyvinyl alcohol resin containing an acetoacetyl group and a sulfonic acid group or a combination of a polyvinyl alcohol resin containing an acetoacetyl group and a polyvinyl alcohol resin containing a sulfonic acid group. Therefore, the heat-sensitive recording medium and the coating liquid for forming the heat-sensitive color-developing layer are excellent in light resistance, and free from unintended color development and discoloration even when exposed to ultraviolet radiation.

The present invention provides a heat-sensitive recording material which has improved thermal responsiveness and improved stability of the print part and the background in comparison to conventional heat-sensitive recording materials that contain a non-phenolic compound as a color developer. The present invention provides a heat-sensitive recording composition which contains a color former, a color developer and a stabilizer, wherein: N-[2-(3-phenylureido)phenyl] benzenesulfonamide or N-(p-toluenesulfonyl)-N-(3-p-toluenesulfonyloxyphenyl) urea is contained as the color developer, and 1,3-diphenyl urea is contained as the stabilizer.

A thermal recording medium includes: a transparent base material and a thermal recording layer on the base material. The thermal recording layer contains a dispersant having a carboxyl group and a crosslinking agent including an epichlorohydrin-modified polyamide polyamine resin or an organic compound containing an oxazoline group.

A heat-sensitive recording material including at least an undercoat layer and a heat-sensitive recording layer in this order on a support, the undercoat layer containing hollow particles and a binder, the heat-sensitive recording layer containing a leuco dye and a developer, the heat-sensitive recording material containing a compound represented by the following formula (1) as a first developer of the heat-sensitive recording layer:

##STR00001##

Disclosed is a heat-sensitive recording material comprising an undercoat layer and a heat-sensitive recording layer in this order on a support, the undercoat layer containing hollow particles, a binder, and an inorganic pigment I, the heat-sensitive recording layer containing a leuco dye, a developer, and an inorganic pigment II, and the heat-sensitive recording layer containing an N,N-diarylurea-based compound represented by the following formula (1): ##STR00001## wherein R.sub.2s may be the same or different, and each represents C.sub.1-12 alkyl, C.sub.7-12 aralkyl, or C.sub.6-12 aryl, and the aralkyl and the aryl may be each substituted with C.sub.1-12 alkyl, C.sub.1-12 alkoxy, C.sub.6-12 aryl, or halogen; A.sub.1s may be the same or different, and each represents hydrogen or C.sub.1-4 alkyl, as the developer, and a pigment with an oil absorption of 130 ml/100 g or less as the inorganic pigment II.

Iodonium salt initiator and processing-free thermally sensitive plate precursor containing thereof, and processing-free thermally sensitive plate and use thereof, At least one of two para positions of two benzene rings of the iodonium salt initiator is an alkene group containing a carbon or nitrogen or oxygen atom and a double bond at an end. The alkene group can increase a steric hindrance of the iodonium salt, improves compatibility of the iodonium salt, the thermosensitive resin and the crosslinkable prepolymer, reduces the surface migration of the iodonium salt in the imaging layer and improves the initiation efficiency. During the laser imaging, a double bond contained in a residual end of the iodonium salt can perform a crosslinking reaction with the thermosensitive resin and the crosslinkable prepolymer, and thus reduces damage to the imaging layer caused by small molecules. At the same time, substituents can be arranged at four meta positions of the two benzene rings to increase the steric hindrance of the iodonium salt, and therefore, the surface migration of the iodonium salt in the imaging layer is further reduced, and the initiation efficiency is improved and the performance of the processing-free thermally sensitive plate is further improved.

Provided is a thermosensitive recording medium including a support and a thermosensitive recording layer disposed on or above the support. The thermosensitive recording layer include a compound represented by General Formula (1) and a styrene-acryl resin, where, in General Formula (1), R.sub.2 is a C1-12 straight-chain, branched-chain, or alicyclic alkyl group, C7-12 aralkyl group that is substituted with a C1-12 alkyl group, a C1-12 alkoxy group, a C6-12 aryl group or a halogen atom, or a C6-12 aryl group that is unsubstituted or substituted with a C1-12 alkyl group, a C1-12 alkoxy group, a C6-12 aryl group, or a halogen atom, where two or more R.sub.2 may be identical to or different from each other; and A.sub.1 is a hydrogen atom or a C1-4 alkyl group, where two or more A.sub.1, may be identical to or different from each other. ##STR00001##