Process of printing by impact and for marking areas where impact or pressure is applied

Claim 1

Process for printing by impact, or for marking the precise areas to which low to moderate impact or pressure is applied, comprising: (1) Producing on a substrate, a surface responsive - by color change - to low to moderate impact or pressure, by the sequence of steps consisting essentially of: (a) depositing on the substrate--in a crystalline form which becomes colored and partially polymerized upon heating below the melting point for a period of time or exposing to high energy radiation--a crystalline solid consisting essentially of at least one monomeric acetylene compound having at least two triple bonds in the molecule, of which bonds at least two are conjugated, said acetylene compound being doubly terminally substituted by a chain consisting of from one to four methylene diradicals terminated by a radical selected from para-bromophenyl urethane, n-butoxycar- bonylmethylene urethane, phenyl urethane, meta-tolyl urethane, ana hydroxy; and (b) partially polymerizing said monomeric acetylene compound to form a composition consisting essentially of 0.1 to 50 weight percent of polymer, the balance of this composition being predominantly the parent acetylene monomer or monomers; said composition irreversibly changing color when subjected to low to moderate impact or pressure, at the precise areas where such impact or pressure is applied; and (2) Applying by impact or pressure, to selected areas of the resulting surface, a force sufficient to produce a color change in those areas and not greater than can be developed, by hand, tnrougn the tip of a sharp pointed rod.