GB1376611A - Thermographic sheet - Google Patents

Abstract

1376611 Temperature indicating J TRICOIRE 19 Oct 1971 [20 Oct 1970] 48585/71 Heading G1D [Also in Divisions H3-5] A thermographic sheet comprises a layer 12 including temperature sensitive cholesteric liquid crystal material and a parallel layer 11 formed to have a higher thermal conductivity in the direction of arrows 15 than laterally in the layer, so that the resolution of thermal images provided e.g. at a support layer 10 is not decreased by thermal diffusion. The layer 11 is produced from a latex, e.g. of a styrene-butadiene copolymer, either by heat reticulation of a single layer thereof, or by sequential deposition of a plurality of latex paint layers less than 50Á thick, for example by spraying. The layer 12 may comprise gelatine encapsulated liquid crystal material dispersed in a latex. The support layer 10, preferably a good heat conductor, may be of polyethylene glycol terephthalate, inter alia, and may be disposed between layers 11 and 12, Fig.2 (not shown). Alternatively the layers 10 and 11 may be identical and/or the liquid crystal material may be dispersed in a combined heat sensitive and heat guiding layer 11. The thermographic sheet may be mounted in a rigid or flexible frame, which itself may have provision for being mounted at one end of an arm, a camera being adjustably mounted at the other end of the arm for recording purposes, Fig.5 (not shown). In a further embodiment, Fig.7 (not shown) the sheet is flexible and is secured at its edge to a rigid transparent plate so that by inflation the sheet may be applied to shaped surfaces and observed through the rigid plate. In other variants, the sheet may be mounted on various types of medical instruments, and layers 12 including different cholesteric materials may be laterally juxtaposed ona common layer 11, to cover a wider temperature measuring range.