| abstract |
(57) [Summary] [Purpose] To provide a new infrared absorbing material and ink which have absorption characteristics only in the infrared region and do not absorb in the visible light region. [Constitution] Ytterbium and acid salt (provided that YbPO Infrared absorbing material consisting of (except 4 ). For example, ytterbium sulfate and ytterbium acetate. An ink containing the infrared absorbing material and an ink vehicle. By using this ink, it is possible to form an invisible non-information pattern having strong absorption around 975 nm, such as a detection mark, or an invisible non-information pattern, such as a code pattern. A code pattern formed using this ink is invisible to the naked eye and has excellent infrared absorption characteristics. Furthermore, the optical detection mark of a transparent sheet such as OHP formed using this ink is transparent and can be detected by infrared rays. |