| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an information recording medium which is easily manufactured and is expressed by diffraction structures which are hardly forged or duplicated. SOLUTION: Among three layers 3, 4 and 5 having a refractive index n3, n4 and n5, the layer 4 forms undulating structures 7 only by partially covering the layer 3. Diffraction structures 6a and 6b are formed on a surface of the layer 3. The layers 4 and 5 are transparent, and a difference|n4-n3|and|n5-n3|in a refractive index is larger than 0.2 in a great part of a visible area, and diffraction by the diffraction structure 6a can be visually observed. A difference between n4 and n5 is almost equal to each other in the visible area, and the undulating structures 7 are not seen, on the one hand, it is not less than 0.1 in a spectral area of a reading light beam by a mchine. The undulating structures 7 are hardly discriminated by the naked eye, and since they can be discriminated only by the reading light beam, an information recording medium which is hardly forged or duplicated can be obtained.</p> |
