Heat-sensitive copying method for preparation of printing stencils

Method for producing a printing stencil comprising

• (a) positioning a stencil sheet which includes a thin stretched thermoplastic resin film supported on an ink pervious porous substrate, on an original with an imaged side of said original in close contact with said resin film, said original image comprising a substance which absorbs light of a wavelength in the near infra-red range of and above 0.7 micron and which releases heat of absorption at said wavelengths, and
• (b) irradiating the resulting assembly formed in (a) with high intensity light having a high radiation intensity for wavelengths of 0.7 micron or more concentrated at 60% or more in terms of quantity of light within the wavelength range of from 0.7 to 1.2 microns, said radiation being effected for a time interval only of from about 10.sup.-4 to about 10.sup.-3 second, said radiation being absorbed by said original image to generate absorptive heat thereat, and
• (c) producing openings by said absorptive heat in corresponding portions of said resin film which are opposed to said original image.