| 摘要 |
PURPOSE:To make a copied substance indistinct to such an extent that it can be read without hindrance by providing one or more layers which are constituted of transparent layers having different refractive indexes and reflect a visible light beam between an absorption layer and the surface of a paper. CONSTITUTION:One or more layers which are constituted of the transparent layers having different refractive indexes and reflect the visible light beam are provided on at least one absorption layer between the absorption layer and the surface of the paper. Supposing that the refractive index of the layer which is close to the surface is n1 and the refractive index of the layer which is close to the absorption layer is n2, most of the light is transmitted when an incident angle theta is smaller than theta1, which is expressed by sintheta1=n2/n1, and the light is totally reflected on the reflection layer when theta is larger than theta1. In the case that ordinary transparent resin such as polymethyl methacrylate or polystyrene is used as the layer close to the surface and air is used as the layer close to the absorption layer respectively, the light made incident at the incident angle >=50.3 deg. is totally reflected. By forming such a reflection film, the copied substance is made indistinct to such an extent that a document and a printed matter can be read without hindrance. |
