Kanzaki Paper Manufacturing Co., Ltd.

Fumio Hama

Mitsuru Kondo

Toshitake Suzuki

Nobuo Kanda

Masayuki Omatsu

Disclosed is a heat-sensitive recording material comprising a base sheet and a heat-sensitive record layer formed over the base sheet and comprising a colorless or pale-colored basic dye and a color developing material capable of forming a color when contacted with the dye, the heat-sensitive recording material being characterized in that the heat-sensitive record layer contains as the color developing material at least one multi-valent metal salt of an indole-2-carboxylic acid derivative represented by the formula ##STR1## wherein R.sub.1 through R.sub.6 are hydrogen or other substituent. The heat-sensitive recording material is resistant to plasticizer and diazo developer, and also is suitable for high-speed recording.

Heat-sensitive recording material

An improved heat sensitive recording sheet having a wealth of high speed recording characteristics and remarkably improved resistances against plasticizers and against diazo developers which contain at least a 3,4-dihydroxydiphenyl sulfone derivative.

Heat sensitive recording sheets containing sulfone derivatives

This invention provides a heat-sensitive recording material comprising a base sheet and a heat-sensitive record layer formed over the base sheet and comprising a colorless or pale-colored basic dye and a color developing material capable of forming a color when contacted with the dye, the recording material being characterized in that the heat-sensitive record layer comprises as the color developing material at least one compound represented by the formula ##STR1## wherein X is straight- or branched-chain alkylene group having 1 to 4 carbon atoms, R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each hydrogen atom, halogen atom, alkyl group having 1 to 4 carbon atoms, alkoxy group having 1 to 4 carbon atoms, phenyl group or benzyl group, or R.sub.1 and R.sub.2 R.sub.2 and R.sub.3, and R.sub.4 and R.sub.5, when taken together, may form an aromatic ring, and when R.sub.4 and R.sub.5 taken together form an aromatic ring, the hydroxy group on the benzene ring to which R.sub.4 and R.sub.5 are attached may be substituted on the aromatic ring formed by R.sub.4 and R.sub.5.

A hydroxydiphenyl sulfone derivative represented by the formula (I) is a novel compound and a heat-sensitive recording material which comprises at least one of the derivatives as a color acceptor not only has an excellent recording sensitivity, resistances to plasticizer and diazo developer but also suits to high-speed recording, has an excellent storage stability of record images and does not decrease in whiteness of the background, ##STR1## wherein R.sup.1 and R.sup.2 are each hydrogen, halogen, lower alkyl, lower alkoxyl or hydroxyl and n is an integer of 3 or 4.

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Osaka, Japan

Fumio Hama