Nippon Paper Industries Co., Ltd.

Yukiko Ryu

Reiji Ohashi

Tomoaki Nagai

Hidetoshi Yoshioka

Takashi Date

Thermally sensitive recording medium

A phenanthridine derivative metal complex of formula 1 having a large absorption in the near-infrared range and a reduced absorption in the visible range, which phenanthridine derivative metal complex is used in a transparent recording medium: ##STR1## where M is a metal atom, and X is a negative ion.

Phenanthridine derivatives and metal complexes thereof used for

An acridine derivative metal complex of formula 2 having a large absorption in the near-infrared range and a reduced absorption in the visible range, which acridine derivative metal complex is used in a transparent recording medium: ##STR1## where M is a metal atom, and X is a negative ion.

Acridine derivative metal complexes used for transparent recording

An acridine derivative metal complex of formula 1 or formula 2 having a large absorption in the near-infrared range and a reduced absorption in the visible range, which acridine derivative metal complex is used in a transparent recording medium: ##STR1## where M is a metal atom, and X is a negative ion.

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Tokyo, Japan

Yukiko Ryu