METHOD FOR PREPARING SECURITY SHEET

摘要

PURPOSE: A method for preparing a security sheet which prevents the generation of irregularities on sheet and can be applied to plastic sheets is provided, to obtain a security sheet having various shapes and good visual identification effect. CONSTITUTION: A method for preparing a security sheet(10) comprising a hidden line comprises calcifying a predetermined part of the hidden line by means of a laser to expose the part. The sheet is made of paper, synthetic fibers, natural fibers or plastics. The hidden line comprises a plastic film coated with a metal thin film or metal.