Ricoh Company, Ltd.

Isao Shiojima

Shigeru Kusakata

Hiroshi Gotoh

Aimi Suzuki

Leuco dyes of the formula (I) are disclosed, ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 each represent an alkyl group having 1 to 10 carbon atoms; X represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a halogen; and Y represents R.sub.5 --Z--SO.sub.2 NH--, R.sub.6 --Z--CONH--, or ##STR2## in which Z represents ##STR3## R.sub.5 and R.sub.6 each represent hydrogen, an alkyl group having 1 to 10 carbon atoms, or a halogen; and R.sub.7 and R.sub.8 each represent hydrogen, a cyano group, or --COR.sub.9, in which R.sub.9 represents a lower alkyl group, a lower alkoxyl group, a phenyl group which may be substituted by an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, or a halogen; a naphthyl group which may be substituted by an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms or a halogen with the proviso that R.sub.7 and R.sub.8 are not both hydrogen. Further a recording material comprising any of the above-mentioned leuco dyes and a particular phenolic compound as a color developer capable of inducing color formation in the leuco dye is disclosed.

Leuco dyes and recording material employing the same

A leuco dye of the formula (I): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, and R.sup.8 each represent a lower alkyl group; A represents ##STR2## in which R.sup.9 and R.sup.10 each represent hydrogen, provided that both R.sup.9 and R.sup.10 may not be hydrogen, --CN or --COR.sup.14 in which R.sup.14 represents a phenyl group which is unsubstituted or is substituted by an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, or a halogen, a naphthyl group which is unsubstituted or is substituted by an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms or a halogen, or a lower alkoxyl group, ##STR3## in which ##STR4## represents a phenyl group or a naphthyl group, R.sup.11 represents hydrogen, a lower alkyl group, a halogen, an amino group, which is unsubstituted or is substituted by an alkyl group having 1 to 4 carbon atoms, or a nitro group, or ##STR5## in which R.sup.12 represents a lower alkyl group, or ##STR6## in which R.sup.13 represents hydrogen, a lower alkyl group, a halogen, a hydroxyl group, a trifluoromethyl group, a nitro group, an amino group which is unsubstituted or is substituted by an alkyl group having 1 to 4 carbon atoms, or amide group. These dyes absorb in the near-infrared region and yields colored images with a color developer therefor with excellent preservability.

Leuco dyes of the formula (I) are disclosed, ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 each represent an alkyl group having 1 to 10 carbon atoms; X represents hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms or a halogen; and Y represents R.sub.5 --Z--SO.sub.2 NH--, R.sub.6 --Z--CONH--, or ##STR2## in which Z represents ##STR3## R.sub.5 and R.sub.6 each represent hydrogen, an alkyl group having 1 to 10 carbon atoms, or a halogen; and R.sub.7 and R.sub.8 each represent hydrogen, provided that both R.sub.7 and R.sub.8 may not be hydrogen, a cyano group, or --COR.sub.9, in which R.sub.9 represents a lower alkyl group, a lower alkoxyl group, a phenyl group which may be substituted by an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, or a halogen; a naphthyl group which may be substituted by an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms or a halogen. Further a recording material comprising any of the above-mentioned leuco dyes and a particular phenolic compound as a color developer capable of inducing color formation in the leuco dye is disclosed.

A cyanine dye having formula (I): ##STR1## wherein R.sup.1 represents Cl, Br or hydrogen; R.sup.2 represents Cl, Br, hydrogen, or a nitro group; R.sup.3 and R.sup.4 each represent a methyl group, an ethyl group, a propyl group or --(CH.sub.2).sub.n OR.sup.5 (in which n is an integer of 2 or 3, and R.sup.5 represents hydrogen or an acetyl group), and X.sup..crclbar. represents an acid anion, provided that the case where R.sup.3 and R.sup.4 are both an identical alkyl group, and R.sup.1 and R.sup.2 are an identical group, is excluded; and

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Mishima, Japan

Isao Shiojima