Patent GB-1266049-A (GB)
IPC: C08J9/28
Filed: 1969-07-28
Abstract: 1,266,049. Coated films. INTERNATIONAL BUSINESS MACHINES CORP. 28 July, 1969 [5 Aug., 1968 (2)], No. 37766/69. Heading B2E. [Also in Division D2] A polymer film containing an ink is produced by incorporating a volatile poreforming agent in the film, heating to cause the pore-forming agent to vaporize to produce an open-pored surface layer and providing an ink in the open-pored surface layer. The films can be produced by coating the surface of the film with a layer of a normally transparent fusible polymer, incorporating in the polymer layer a pore-forming agent and heating to cause the pore-forming agent to vapourize. Ink may then be imaged on the porous surface, e.g. using a typewriter and the printed polymer layer then subjected to either heat, pressure and/or solvent vapours which cause the polymer layer to fuse and become transparent in the non-imaged areas while the ink image retains its original sharpness and intensity. The base film may be glass, polyethylene, polystyrene, cellulose, polypropylene, polyurethane, polyamide, polyethylene glycol terephthalate and polyvinyl chloride. The polymer layer may comprise polyvinyl acetate, cellulose acetate butyrate, polyurethane, polyethylene and mixtures thereof and may be applied from a dispersion or solution in water or organic solvents. The pore-forming agent can be incorporated in the polymer layer by mixing it with the polymer before it is applied to the base layer, or it can be embedded into the polymer layer after the polymer layer has been applied to the base film by coating the polymer layer with the pore-forming agent contained in a liquid which is a solvent for the polymer. Suitable pore-forming agents can be either solids or liquids, e.g. ammonium carbonate and bicarbonate, d-1 camphor, pine oil or turpentine. Mixtures of polymers can be employed to form the porous layer, the polymers being chosen so that they are mutually insoluble at room temperature. One polymer is first coated on to the base film and the other polymer is then coated on to the surface of the first polymer as a pore-forming dispersant in a volatile liquid which is at least a partial solvent of the first polymer. The solvent action causes particles of the second polymer to become mixed with the first polymer layer and upon heating to volatilise the liquid an open-pore system is formed. In another embodiment a porous ink transfer medium is produced by impregnating the surface of the polymer film with a dispersion or solution of the pore-forming agent in a volatile solvent that is at least a partial solvent for the polymer, evaporating the solvent and then subsequently vapourizing the pore-forming agent and then filling the capillaries of the resulting porous surface layer with a marking material or ink composition. Alternatively the ink and pore-forming agent in a solvent may be first mixed then coated on to the polymer film together so that the pore-formation and ink containing capillaries are produced in one step. Suitable films may comprise polyamide, polyurethane, polyester, polycarbonate, polybutylene or ethylene-vinyl acetate copolymer. The film can be supported on a temporary substrate, e.g. glassine paper, polyethylene glycol terephthalate, polypropylene, polyethylene, release papers. Suitable pore-forming agents include alkali and alkaline earth carbonates and bicarbonates, aluminium sulphate, camphor, pine oil, turpentine or butylacetate. Suitable inks comprise colouring material, e.g. organic and inorganic dyes, pigments such as dye treated carbon black, nigrosine oleate and organic dyestuff such as methyl violet base in an oily ink vehicle, e.g mineral oil, fatty acids and fatty alcohols. The ink is mixed with a suitable volatile solvent to reduce its viscosity. Uses mentioned are: as a transparency suitable for use as a master in a copying process or as a slide for projection on a screen; typewriter ribbons or carbon paper.