| 摘要 |
A security design 2, such as a guilloche or latent image, is formed by printing or embossing on a substrate 1 using an ink or other material which includes a light collecting dye. When light from a source 3 is incident on the design 2 it is absorbed by the light collecting dye which then fluoresces so as to emit light at a (visible) wavelength. This is internally reflected within the material 4 until it emerges from the edges 5,6. Little fluorescent light is emitted through major surface 7. Thus the design 2 is only faintly visible when viewed normally. It becomes more visible when viewed at a shallow angle 8. The effect may be enhanced by creating multiple upstanding edges (25, figure 5) through which light emission is concentrated resulting in a broad image when viewed at the shallow angle. |
