PURPOSE: To obtain an inexpensive filter having good workability and satisfactory ray transmission performance in a near IR region by compounding a specific coloring agent with a synthetic resin.
CONSTITUTION: A colorable dye expressed by the formula I as an essential additive and further a red dye and UV absorbent in order to completely shut off some transmitted light at 400W600nm are added to the synthetic resin having the ray transmittability in the near IR region ranging 700W1,600nm wavelength. In the formula, R denotes hydrogen, methyl group, ethyl group, isopropyl group, n-propyl group, phenyl group, methoxy group or ethoxy group. The amt. of the colorable dye to be added to the synthetic resin is 0.01W1.0wt% in terms of 2.0mm filter thickness.
HAMAGUCHI KUNIMASA
YAMADA HACHIRO
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