| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a diffraction structure that can be used for a forgery preventive medium to be used for preventing forgery of marketable securities and cash vouchers such as banknotes, bonds, merchandise coupons, lotteries, credit cards, and gift cards.SOLUTION: The diffraction structure has a saw-tooth shape in an elevated sectional view. A long side portion and a short side portion forming the saw-tooth shape are alternately and regularly arranged with given angles. On the long side portion, a fine rugged structure where fine projections and recesses are regularly arranged is formed on a surface thereof. The long side portion of the diffraction structure functions as a light-entering face. By arranging the fine rugged structure as a diffraction structure to develop optical changes on the long side portion of the saw-tooth shape that models a blazed diffraction grating, incident light to the fine rugged structure and reflected light or diffracted light developed by the fine rugged structure are varied by the angle of the saw-tooth shape inclined from a horizontal plane.</p> |
