| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-layered sheet produced by forming invisible images on a nonwoven fabric with a plurality of different transparent materials and then using the sheet as a middle layer to make the sheet, and to provide a method for determining whether the multi-layered sheet is genuine or not on the basis of transmission imaging by infrared spectroscopy. SOLUTION: This multi-layered sheet produced by applying invisible information to at least one side of a nonwoven fabric with at least two or more kinds of different transparent materials, nipping the invisible information-applied nonwoven fabric between an upper layer paper material and a lower layer paper material on a paper-making machine to form a multi-layered sheet having the upper layer paper material layer, the nonwoven fabric layer and the lower paper material layer, and then drying the formed multi-layered sheet in the drying section of the paper-making machine. And, the method for determining whether the multi-layered sheet is genuine or not includes determining the multi-layered sheet on the basis of transmission imaging by infrared spectroscopy. COPYRIGHT: (C)2008,JPO&INPIT
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