A heat-sensitive recording material having i) a supporting substrate and ii) a heat-sensitive recording layer, where the heat-sensitive recording layer comprises a colour former and a colour developer mixture and the colour developer mixture comprises a) N-[2-(3-phenylureido)phenyl]benzenesulfonamide (compound of the formula (I)), where the compound of the formula (I) is in a crystalline form having an absorption band at 3401 20 cm 1 in the IR spectrum, and b) N-(4-methylphenylsulfonyl)-N-(3-(4-methylphenylsulfonyloxy)phenyl) urea (compound of the formula (II)), where the mass ratio between the compound of the formula (I) and the compound of the formula (II) is 0.5:99.5 to 35:65 or 99.5:0.5 to 65:35.

A heat-sensitive recording material eempri waff-having i) a carrier substrate and ii) a heat-sensitive recording lavcrr-wheKH-fth*. The heat-sensitive recording layer contains a color former and a color developer mixture and the color developer mixture contains a) N-[2 -(3- phenylureido)phenyl]benzole sulfonamide (compound of formula (1)). wherein tlw. The compound of formula (I) is present in a crystalline form, which has an absorption band in the IR spectrum at 3401cm-1. and b) N-(4-methylphenylsulfonyl)-N-(3-(4- methylphenylsulfonyloxy)phenyl)urea (compound of formula (II)).

The objective of the present invention is to provide a thermosensitive recording medium excellent in color developing property, especially excellent in bar code readability, under severe environment. Provided is a thermosensitive recording medium having a thermosensitive recording layer comprising a colorless or pale colored electron donating leuco dye and an electron accepting color developing agent on a substrate, wherein the thermosensitive recording layer contains a specific sulfone compound and a specific urea-urethane-based compound in a specific ratio.

A recording material and a recording sheet having better color-developing performance, storage stability, etc. A recording material which contains (A) at least one color former, (B) at least one compound selected from the group including compounds represented by the following formula (I), and (C) at least one compound selected from the group including compounds represented by the following formula (II)

(wherein R.sup.1 to R.sup.3 each represent a halogen atom, a nitro group, a C.sub.1 to C.sub.6 alkyl group, a C.sub.1 to C.sub.6 alkoxy group, a C.sub.2 to C.sub.6 alkenyl group or a C.sub.1 to C.sub.6 haloalkyl group, n1 and n3 each independently represent any integer of 0 to 5, n2 represents any integer of 0 to 4, and X represents SO.sub.2O or OSO.sub.2).

##STR00001##

The invention relates to a color developer of formula (I), (Ar.sup.1SO.sub.2NH)m-Y(NHC(O)NHSO.sub.2Ar.sub.2)n (I), wherein Ar.sup.1 is an unsubstituted or substituted aromatic moiety, Ar.sup.2 is an unsubstituted or substituted phenyl moiety, Y is at least an (m+n)-times substituted benzene group or naphthalene group, and Y is substituted in such a way that at least one Ar.sub.2SO.sub.2NHC(O)NH group is in ortho-position with respect to at least one Ar.sup.1SO.sub.2NH group. The invention further relates to a heat-sensitive recording material, comprising a carrier substrate and a heat-sensitive color-forming layer, which contains at least one color former and at least one phenol-free color developer, the at least one color developer being the compound of formula (I). The invention further relates to a method for producing said heat-sensitive recording material.

Provided is a thermosensitive recording medium having excellent oil resistance among various performances required for the thermosensitive recording medium. The thermosensitive recording medium has a thermosensitive recording layer comprising a colorless or pale colored electron donating leuco dye and an electron accepting color developing agent on a substrate, wherein the thermosensitive recording layer contains N-[2-(3-phenylureido)phenyl] benzenesulfonamide and an urea-based compound represented by the general formula 1 as the electron accepting color developing agents, ##STR00001##
wherein R.sup.1 represents a substituted or unsubstituted alkyl group, aralkyl group or aryl group, and R.sup.2 represents a hydrogen atom or an alkyl group.

Non-phenolic direct thermal recording media have a thermally responsive layer containing a leuco dye and a plurality of diarylurea acidic developers selected to improve the quality and readability of the image produced in such media, particularly after being contacted with oils such as vegetable oil. The diarylurea developers preferably include, or consist essentially of, or consist of, N,N-diphenylurea (DPU) and a derivative of DPU. An exemplary combination is DPU together with a developer known commercially as TGMD.

As a thermosensitive recording medium utilizes a coloring reaction between a colorless or pale colored electron donating leuco dye and an electron accepting color developing agent, a thermosensitive recording medium using an environment-friendly color developing agent is provided. Provided is a thermosensitive recording medium having a thermosensitive recording layer comprising a colorless or pale colored electron donating leuco dye and an electron accepting color developing agent on a substrate, wherein the thermosensitive recording layer comprises a gluconolactone as the electron accepting color developing agent.

The invention relates to a color developer of the formula (I), wherein m and n independently of one another are ?1, Ar.sup.1 is an unsubstituted or substituted (hetero) aromatic radical, Ar.sup.2 is an unsubstituted or substituted phenyl radical, and Y is at least one (m+n)-times substituted benzene or naphthalene group, and to a heat-sensitive recording material, comprising a supporting substrate and a heat-sensitive color-forming layer containing at least one color former and at least one phenol-free color developer, wherein the at least one color developer is the compound of the formula (I). The invention further relates to a method for producing said heat-sensitive recording material. ##STR00001##

Disclosed is a heat-sensitive recording material comprising an undercoat layer and a heat-sensitive recording layer formed in this order on a support, the undercoat layer containing hollow plastic particles and a binder, the heat-sensitive recording layer containing a leuco dye and a developer, and the heat-sensitive recording material having an elastic modulus of 200 N/mm.sup.2 or less as measured by a nanoindentation method.