| 摘要 |
Paper embodying for purposes of identification one or more pigments, inconspicuous in daylight but visible on inspection in darkened surroundings or after illumination at predetermined wavelength from an artificial source, wherein the pigment is in the form of granules which are of 30 to 500 microns particle size and, to secure contrast between the pigment and background in said inspection, are essentially free of finer particles. |
