| 摘要 |
PROBLEM TO BE SOLVED: To provide a nondestructive and simple authenticity determination method for preventing paper money, valuable paper and the like from being counterfeited.SOLUTION: The paper has at least part composed of a sheet containing fine fibers having an average fiber width of 2 to 1,000 nm and is used for producing a printed matter whose authenticity can be determined by measuring an ultrasonic wave propagation speed of the at least part. In the paper, the fine fiber may have a substituent having electrostatic and/or three-dimensional functionality introduced thereinto. Additionally, the fine fiber is a cellulose fiber and has at least one kind of substituent selected from a group derived from phosphoric acid, a group derived from carboxylic acid and a group derived from sulfuric acid introduced thereinto in which the introduction amount of the substituent is 0.01 to 3.0 mmol/g.SELECTED DRAWING: None |
