Water-added evaporation process for making thin plastic lettering webs

For use as thin flexible signage-lettering material adapted for computerized cutting, the process of making a pigmented display layer, comprising the steps of:

• mixing water-based polymers of polyurethane or acrylic composition, or mixtures thereof, with water-soluble or water-dispersible pigment and functional additives in a predetermined quantity to form a substantially non-flowing mixture, together with such amount of water as renders the resultant mixture substantially fluid and such amount of viscosity-increasing agent as makes it machine-spreadable,
• then machine-spreading such resultant mixture on a transparent release sheet or preliminary foundation sheet at such spread depth as will, on subsequent drying, shrink, coalesce and harden to a chosen film thickness, such machine spread depth being determined according to the equation ##EQU2## and evaporating all water therefrom,
• whereby to shrink and coalesce the mixture into a thin, pigmented polymer display layer on such foundation sheet or release sheet, and by such coalesce, to cause preliminary adherence to a sheet, all without substantially exceeding the evaporation temperature of water.