Patent GB-1015926-A (GB)
Title: Thermographic process and materials
IPC: B41M5/04
Filed: 1962-07-16
Abstract: 1,015,926. Thermographic materials and processes. EASTMAN KODAK CO. July 16, 1962 [July 14, 1961; June 27, 1962], No. 23939/65. Divided out of 1, 015, 925. Heading G2C. A heat-sensitive material comprises a support coated with a layer comprising either (a) a crystalline polymer having a tackifying point between 50 and 200C and remaining tacky and transferable below its tackifying point or (b) a mixture of an amorphous polymer and a non-polymeric crystalline substance miscible with the polymer and melting between 50 and 200C., the mixture remaining tacky below its tackifying point and transferable under pressure, the material being provided with integral means which regulates the transfer of the tacky material. The specified means are either solid inert particles such as glass beads incorporated in the heat-sensitive layer and having an average diameter greater than the thickness of the layer or an overcoat with is porous to the tacky material such as polyvinyl alcohol containing a pre-forming agent e.g. a metal salt or a surfactant. Other porous overcoats are woven webs, perforated metals, gelted webs or porous polyesters, polycarbonates or cellulose esters. After imagewise exposing the material to infra-red radiation to produce a tacky image which remains tacky below the tackifying point, the material is pressed against a receptor sheet to transfer at least part of the image and further copies may be obtained by using further receptor sheets. Specified crystallised polymers are polybutene, polypentene, poly (tetra- or pentamethylene) carbonate, polyethylene succinate, poly (2, 2 dimethyl trimethylene succinate, poly (1, 4 cyclohexanedimethylene adipate or succinate), polyethylene glycol, polypentamethylene terephthalate, polyethylene 1, 4 cyclohexane dicarboxylate and cyclohexanedimethylene adipate/azelate copolymers. Other polymers can be found among polyvinyls, polyacrylics, polyesters, polyamides, polyesteramides, polycarbonates, polyethers, polyurethanes and polyureas. Non-crystalline polymers are atactic polystyrene, polyvinyl acetate, butadiene/styrene copolymer, polyalkyl acrylates and methacrylates, polyterpenes, polyvinyl butyral, cellulose butyral, cellulose butyrate or acetate butyrate, polyethylene terephthalate, vinyl chloride/ vinyl acetate copolymer and phenol/formaldehyde resins. Cystalline non-polymeric substances specified are benzoates, of 4 biphenylyl, eugenol, 4-cyclohexylphenyl, and pentachlorophenyl; camphor; bensoin acetate; pentaerythritol tetro-isobutyrate 2, 6 di-t-butyl-4-methyl phenol; triphenyl or thoformates; N-pentyl-1, 8-naphthalimide; bis(o-methoxy-phenyl) carbonate; 2, 5, 5-triphenyl- 1, 3-dioxolan-4-one;bis/herzyloxy diphenylmethane and anthraquinone-2-carboxyethyl. The heat-sensitive layer may include dyes or substances to decrease the amount of polymer and modify the layer such as clay, glass beads, quartz, polymethylmethacrylate beads, titanium dioxide, zinc oxide, alkyl phthalates or fumarates,tricresyl phosphate, menthol, eugenol or isoeugenol. A polymeric overcoat such as polyvinyl alcohol or carboxymethylcellulose which is not porous to the tacky material may be applied to the heat-sensitive layer and removed before transfer. The heat-sensitive material may be "annealed" before exposure, i.e. heating the material to a temperature between the glass-transition temperature and the tackifying temperature to improve its crystallinity. Used materials may also be reclaimed by such annealing. The final copies may be used as hectographic or lithographic masters.