| 摘要 |
1,253,697. Infra-red transmissive glass elements. MINNESOTA MINING MFG. CO. 27 Feb., 1969 [28 Feb., 1968], No. 10522/69. Heading C1M. Infra-red transmissive, black glass elements of thickness not exceeding 2 mm. comprise a clear uncoloured base glass component of refractive index at least 1À6, and light filtering components dissolved in the base glass, the light filtering components comprising (in weight per cent):- these percentages being relative to the total glass composition, and the light filtering components constituting 1À2-20% by weight of the total composition. The base glass may consist of, again in weight per cent of the total glass composition :- The compatible metal oxides may be oxides of Zn, Cd, Ge or alkaline earth metals. The glass elements have a reflective intensity not more than 25 candlepower per foot candle per square foot and an integrated retroreflectance ratio of infra-red light (7600-11,000 Š) to total light (4000-11,000 Š) of at least 0À65. The elements may be in the form of beads, fibres or flakes and are particularly useful for marking objects for identification systems, the elements not being visible to the naked eye. |
