Patent GB-1139891-A (GB)
Title: Heat and pressure-sensitive recording and information-recording processes
Inventor: VRANCKEN MARCEL NICOLAS
IPC: G03C5/18
Filed: 1963-12-05
Abstract: 1,139,891. Thermographic materials. GEVAERT PHOTO-PRODUCTEN N. V. Jan. 5, 1965 [ Dec. 5, 1963] No.48128/63. Headings G2C and G2M. [Also in Divisions B2 and D2] A heat-sensitive material comprises a waterpermeable layer containing a hydrophilic binder in which are dispersed hydrophobic particles of polyethylene, polyvinylidene chloride, polyethylmethacrylate, polyacrylonitrile or polyvinylcarbazole; the ratio of particles to binder being more than 1:1 and the layer being formed by dispersing the particles in aqueous medium containing the binder and the layer capable of being rendered less water-permeable on heating. The invention also relates to a thermographic process in which the above material (except that any hydrophilic polymer may be used as the particulate dispersion) is imagewise exposed and becomes less water-permeable or water-impermeable in the heated areas. The exposed material may be developed by (1) treatment with an aqueous solution of a dye, a catalyst for initiating a colour reaction between components present in the material, a colour forming component with the other component present in the material, a bleaching agent for a dye or silver present in the layer or an etching agent for etching silver or a metal support; the aqueous solution permeating the water-permeable areas, (2) diffusion of a water-soluble dye, catalyst, colour-forming component or a complexed silver salt on to a receptor sheet which (if necessary) contains the requisite reactants (3) removing the water-permeable areas by washing out to produce a water-permeable membrane which can be used in electrolytic printing, a printing plate after etching the metal support, a dye image if a dye is present in the material or if the support is electrically conductive, charging the developed material and either powder developing the heated, water-impermeable areas or transferring the charge to a receptor sheet, or, if the support is a woven material, produce a screen printing master and (4) by transferring the water-permeable areas to a receptor sheet or by transferring portions of a dye sheet to the water-permeable areas to produce a hectographic master. The heat-sensitive material may be self-supporting or be carried by a support which may be coated with waterpermeable hydrophilic or hydrophobic layers depending on the result desired after exposure and development and may contain a dye or pigment in the heat-sensitive or in another layer. In the examples, a heat-sensitive layer of an aqueous dispersion of polymethyl methacrylate, polystyrene, vinyl chloride/diethyl maleate copolymer, or polyethylene particles and an aqueous solution of gelatine or polyvinyl alcohol, are coated on a support of paper, cellulose triacetate or polyester carrying an intermediate gelatine layer are imagewise exposed to heat and developed by (i) applying a gum arabic/carboxy-methylcellulose solution to render water-permeable areas hydrophilic and then optionally applying a colophony resin to render remaining areas oleophilic to produce a planographic printing plate (ii) applying an aqueous dye solution to produce a dye master (iii) contacting with an art paper which removes the waterpermeable areas or (iv) contacting with a carbon paper which is transferred to the water-permeable areas to produce a spirit-duplicating master. Alternatively, the gelatine layer may contain infrared absorbent carbon black or silver Specification 1,139, 894 or Congo Red and these materials may be developed as above or by bleaching out the . silver or by applying hydrogen chloride gas which turns the Congo Red blue. The gelatine layer may otherwise be a print-out or heat-developable silver halide emulsion layer Specification 1,139, 896 so that it may be imagewise exposed to light and uniformly heated to produce water-impermeable layers. A stencil master may be produced by directly coating a heat-sensitive layer on to Japan paper, imagewise exposed and developed with Javel water to remove the water-permeable areas.