| 摘要 |
<p>PURPOSE:To obtain a new IR absorber and an ink which absorb light only in an IR region and do not absorb visible light. CONSTITUTION:The absorber comprises YbPO4 crystallites having diameters of 5-200nm. This absorber is mixed with an ink vehicle to obtain an ink. By using this ink, an invisible non-information pattern having intense absorption in the range of 900-1,000nm, e.g. a detection mark or a code pattern, can be formed. The code pattern formed from this ink cannot be recognized with the naked eye and has excellent IR absorption. An optical detection mark formed from the ink on a clear sheet, e.g. OHP, is transparent and can be detected with IR rays.</p> |
