Patent GB-649336-A (GB)
Title: Improvements in or relating to laminated patterned plastic articles
IPC: B44F1/06
Filed: 1947-11-27
Abstract: 649,336. Compound sheet material. UNDERWOOD, G. C. L. Nov. 27, 1947, No. 31470. [Class 140] [Also in Group XX] A laminated structure which incorporates a reproduction of a pattern existing in natural materials such as tortoiseshell, marble, onyx, horn, shell, amber foliage, and in manufactured materials such as enamel, stained glass, parchment, silks, brocades, photographs, paintings, and drawings, is produced by assembling without distortion laminae of transparent or translucent plastic material, such as polymethyl methacrylate and cellulose acetate, two or more of which are of different but uniform colour and varying in thickness and having non- planar mating and interengaging contiguous surfaces so that the structure shows the pattern with gradations in the density of one shade in a groundwork of a different shade. In this manner a structure having flat, parallel outer faces is formed in which varying depths of shade in one or more colours are controlled by varying thickness of the corresponding coloured laminµ. An opaque backing or interlayer may be included so that the pattern may be viewed from one or either side by reflected light. In the manufacture of a two-layer structure representing a pattern, such as tortoiseshell, either a pattern or a groundwork layer is first produced from a relief plate which is made by hand, cast, pressed, electrotyped or produced photographically or heliographically (see Group XX) and used as a mould to preform the plastic material when it is in a granulated, powdered, or pasty condition, or to cast it when it is in a liquid or viscous condition, or as a die for pressing it out to a uniformly coloured layer. Alternatively, the plate is used to press out a mould in plastic which is filled in with the plastic material which is to form the first layer. Another method of forming a contoured layer for incorporation in the structure comprises pressing an apertured screen into a mass of plastic material in molten or plastic form to cause the material to well up through the apertures, and then solidifying or hardening the plastic, or controlling the fall of particles of plastic material in solid form and then rendering the plastic soft so as to convert the particulate mass into a coherent sheet. A sheet of plastic material, which is to form the second layer of the structure, is finally cast or pressed into the contoured face of the layer first. formed and bonded thereto. For structures involving more complex patterns, compound laminµ, each composed of a pattern layer and a groundwork layer representing for example the surface and under grain of a wood grain, may be superposed and united by a solvent or plasticizer. According to a modification, a reproduction of a three-colour print involving yellow, magenta, and peacock bluegreen is produced by uniting four superposed laminµ. The two outer laminµ represent in relief on their inner surfaces shade variation in yellow and peacock blue-green respectively. The magenta layer, laid adjacent to the yellow layer, has on its upper surface contours formed complementary to the contoured face of the yellow layer from a negative relief plate formed by deposition of metal on the electrotype from which the yellow layer was prepared ; the under face of the magenta layer is so contoured that the total thickness of that lamina varied in accordance with the depth of magenta shade in the print (see Group XX). The final lamina between the magenta and peacock bluegreen laminµ was formed by interposing a sheet of clear cellulose acetate rendered softer and more highly plasticized than the composition of the adjacent layers and consolidating the assembly under heat and pressure.