Toyo Ink Manufacturing Company

Makiko Hamuro

Takeshi Yoshikawa

Koji Hanada

Motohiko Kashioka

Toru Ohmura

A data-written medium in which the data is readable with a light source having a main wavelength of 600 to 700 nm, the medium comprising a substrate and an ink layer containing not more than 0.1 g/m.sup.2 of a chromatic color dyestuff having absorption substantially at 600 to 700 nm and at least one other color dyestuff as the remainder. The ink layer is formed on the substrate so as to have a form constituting the data. Also provided is a data-written medium in which the data is readable with light sources having a main wavelength of 600 to 1,500 nm, the medium comprising a substrate, a first ink layer containing not more than 0.1 g/m.sup.2 of a chromatic color dyestuff having substantial absorption at 600 to 700 nm and another dyestuff as the remainder, and a second ink layer containing a substance having substantial absorption in a near infrared region. Each of the two ink layers is formed so as to individually have a form constituting to two corresponding data.

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Tokyo, Japan

Makiko Hamuro