Patent GB-866076-A (GB)
Title: Heat-sensitive copying paper
IPC: B41M5/30
Filed: 1957-06-28
Abstract: 866,076. Photographic processes. MINNESOTA MINING & MANUFACTURING CO. June 28, 1957 [June 28, 1956], No. 20589/57. Drawings to Specification. Class 98(2) [Also in Group XVI] A heat-sensitive copy-sheet for reproducing graphic originals by application of a corresponding heat-pattern is visibly stable under normal storage conditions and includes a visibly heat-sensitive layer containing, in intimate association, an oxidising reagent and a reducing agent which are rapidly mutually inter-reactive in an oxidation-reduction type electron transfer reaction involving a valence change with formation of at least one visibly distinct reaction product when briefly heated together at a temperature insufficient to cause independent decomposition of either reagent or to damage either the copy-sheet or the original, while being sufficient to promote the reaction. The oxidising and reducing agents may be uniformly dispersed in a water-resistant binder film. A transparent protective layer may be applied over the heat-sensitive layer. The oxidising agent may be an organic acid salt of a reducible metal and the reducing agent an aromatic organic compound. Examples of oxidising agents are Silver benehate and behenic acid, silver acid phthalate, mercuric benehate, ferric stearate, gold stearate, cerium stearate, cupric stearate, tetradecyl amine molybdate, silver stearate, and silver salts of oleic, lauric, hvdroxystearic, acetic, phthalic, terephthalic, butyric, m-nitrobenzoic, salicylic, phenylacetic, pyromellitic, p-phenylbenzoic, undecylenic, camphoric, furoic, acetamidobenzoic and O- aminobenzoic acids. Examples of reducing agents are protocatechuic acid, methyl gallate, 2,3-dihydroxybenzoic acid, phthalic anhydride, 4-methoxy, 1-hydroxy-dihydronaphthalene, 2,5- dihydroxybenzoic acid, hydroquinone, propyl gallate, pyrogallol, 4-azeloyl-bis-pyrogallol, 4- stearoyl pyrogallol, galloacetophenone, di-tertiary-butyl pyrogallol, gallic acide anilide, ethyl gallate, normal and iso-propyl gallate, butyl gallate, dodecyl gallate, gallic acid, ammonium gallate, ethyl protocatechuate, cetyl protocatechuate, 1-hydroxy-2-naphthoic acid, 2- hydroxy-3-naphthoic acid, phloroglucinol, catechol, 2,3-naphthalene diol, 4-lauroyl catechol, sodium gallate, protocatechualdehyde, 4-methyl esculetin, 3, 4-hydroxybenzoic acid, 4, 41-dihydroxy biphenyl, 3,4-dihydroxyphenylacetic acid, 4 (3<SP>1</SP>,4<SP>1</SP>-dihydroxyphenylazo) benzoic acid, 2,21-methylene bis-3,4,5-trihydroxybenzoic acid, benzidine, ortho- and para-phenylene diamine, tetramethyl benzidine 4,41,411-diethylamino triphenylmethane, O-, m- and p-amino - benzoic acids, alpha and beta naphthols, 4- methoxy, 1-hydroxy-dihydronaphthalene, and tetrahydroquinoline. Examples of binder are polystyrene resin, ethyl acetate and diphenyl phthalate; polystyrene resin, heptane and acetone; ethyl cellulose. Plasticisers for the binders may be used, e.g. phosphates and phthalates. An example of a protective coating is a mixture of styrene-isobutylene copolymer hexane, zinc oxide and silica gel; zinc oxide, Parapol resin, "Santocel" (Registered Trade Mark) filler, phthalic anhydride and heptane. In conjunction with the protective coating there may be used pigments and fillers such as zinc sulphide, titanium dioxide and diatomaceous earth, metal powders and carbon black. The paper base may be map overlay tracing paper, Monarco paper or the substance known under the Registered Trade Mark "Cellophane". The sheet is placed under or on a graphic original and the assembly exposed to infra-red radiation, which generates heat in the dark design areas.