GB1079835A - Improvements in or relating to the printing of plastics articles - Google Patents

Abstract

1,079,835. Laminates. THOMAS DE LA RUE & CO. Ltd. Oct. 6, 1964 [Oct. 11, 1963], No. 40291/63. Heading B5N. [Also in Divisions B6 and G4] A decorative laminate such as a coin or token is formed by printing a design, for example in accurately registered colours, on an unimpregnated or partially impregnated fibrous sheet (e.g. impregnated from one side only) applying resin-impregnated fibrous core sheets to the under side of the printed sheet and a resinimpregnated fibrous overlay to the printed side, and pressing the assembly in a mould having a relief surface. The fibrous material may be paper, non-woven material such as textryl, woven textile, cellulosic material, or at least in part of asbestos, glass or metal fibres (usable for magnetic or electric detection or for giving recognizable combustion residues). The transparent overlay sheet may be alpha cellulose impregnated with melamine formaldehyde resin, and preferably sprinkled with powdered resin before pressing, or a film capable of polarizing light comprising optically active vinyl polymers, polyacrylonitrile, polymethacrylic acid, polymethacrylate, polymethacrylic acid anhydride and polyvinyl alcohol. Impregnating resins specified are phenol-melamine- and ureaformaldehyde, polyester resins or epoxy resins. The resins may be coloured. Impregnation may be assisted by ultra-sonic vibrations. A printed sheet and overlay may be provided on both sides of a coin or token, and the two designs may be made to register accurately, or to be in pre-chosen relation, with each other, or to be accurately spaced from the edge of the coin, or token. The edge may extend above the embossments. The embossing may include lenticular surfaces over parts of the design, or a line screen producing different views from different angles may be included in the covering. For further security the coin or token may include radioactive tracers, a magnetic characteristic, ink having a particular electric conductivity, or a particular colour, refractive index, electroluminescence or fluorescence or radio wave absorption, X-ray diffraction or light polarizing properties, of the materials used. Coins according to the invention, being of light weight, may be made for higher valve denominations. Pressing and embossing apparatus, Fig. 2, comprises steam platens 10, 11, dies 14, 12, pressure pads 15, 13, and a central component 16 containing a blanking cavity 17 and a temperature-controlling thermocouple 18, all moving parts being spring-pressed and furnished with stops such as 19. To avoid tearing of the print sheet or sheets the press is closed slowly, permitting the sheets to warm up and stretch.