Nippon Paper Industries Co., Ltd.

Yoshitomi Pharmaceutical Industries, Ltd.

Ryuzo Minakami

Tomoaki Nagai

Toshiaki Minami

Kaoru Hamada

Akio Sekine

Ryoichi Kinishi

A thermal recording sheet wherein a compound of Formula (I) or (II) is contained in a thermal color developing layer including a basic colorless dye and an organic color developer as main ingredients: ##STR1## (wherein A denotes hydrogen atom, an alkyl group of C.sub.1 to C.sub.4, an alkoxy group of C.sub.1 to C.sub.4, hydroxy group, or nitro group. R.sub.1, R.sub.2, and R.sub.3 are hydrogen atom, an alkyl group of C.sub.1 to C.sub.4, an alkoxy group of C.sub.1 to C.sub.4, hydroxy group, or nitro group. R.sub.1 and R.sub.2 may combine with each other to form an aromatic ring. Y is sulfur or oxygen atom.), ##STR2## (wherein B denotes hydrogen atom, an alkyl group of C.sub.1 to C.sub.4, an alkoxy group of C.sub.1 to C.sub.4, hydroxy group, or nitro group. R.sub.1, R.sub.2, and R.sub.3 are hydrogen atom, an alkyl group of C.sub.1 to C.sub.4, an alkoxy group of C.sub.1 to C.sub.4, hydroxy group, or nitro group. R.sub.1 and R.sub.2 may combine with each other to form an aromatic ring. Y is sulfur or oxygen atom.). The thermal recording sheet has a high sensitivity and high image stability.

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Fukuoka-ken, Japan

Ryuzo Minakami