Thermosensitive opaque copying sheets - including a layer of styrene or methyl methacrylate copolymer with a plasticising monomer

摘要

Thermosensitive registration material comprise a support carrying an opaque thermosensitive layer contg. 0.1-1 mu m particles of a copolymer of (a) a first monomer (I) which gives homopolymers with a refractive index of >1.48 at 20 degrees C and (b) >=1 plasticizing monomer (II), the ratio (I): (II) being chosen to give a copolymer wit (i) a refractive index of >=1.48 at 20 degrees C, (ii) a min. film forming temp. of 50 degrees C 90 degrees C and (iii) a light transmission of >=0.4 after casting and =0.12 in the zones of reduced transparency after heating for 2 seconds at 90 degrees C. The support may be e.g. of paper or polyethylene terephthalate film, and is opt. coloured. Monomer (I) is pref. styrene or methylmethacrylate and the monomer (II) is e.g. methyl acrylate or n-butyl acrylate. The materials are useful in the prodn. of opaque thermosensitive copying sheets which become transparent on heating, e.g. using a hot stylus or by exposure to i. r. radiation while in contact with an original which absorbs i. r. in imagewise fashion.