GB702000A - Multi-layer glass sheet having an interlayer reversibly changing its light transparency when subjected to changes in temperature - Google Patents

Abstract

702,000. Temperature indicators. KUHL, G. W. May 31, 1951 [Feb. 4, 1949], No. 12995/51. Class 97(3) [Also in Group VIII] In a multi-layer glass sheet having an interlayer which reversibly changes its transparency to light when subjected to changes of temperature, the interlayer contains polymers such as methyl polyvinyl ethers, and/or methyl cellulose and/or polyglycol ethers and/or alkaline earth compounds of polyacrylic acids, such substances changing from the sol to the gel state when a predetermined temperature is exceeded and reverting to the sol state on again falling below that temperature. For changing the conversion point there may be added to the interlayer substances favouring the sol state or substances impeding the sol state. Examples of the former are univalent alcohols such as methyl alcohol, ethyl alcohol, polyvinyl alcohol, or ketones such as acetone; examples of the latter are polyvalent alcohols such as glycerine or glycols, and/or ammonium hyroxide. One or more protective colloids may be added to the interlayer. The interlayer may be in liquid form or may be a solid film; it may contain a substance which readily absorbs light by conversion into heat. The interlayer may contain a mixture of colouring agents one or more of which may be precipitated on conversion of the coagulating substance or substances to the gel state; a mixture of rufigallic acid and methyl blue changes from green to blue at the conversion temperature. The multi-layer sheets may be used as windows of greenhouses, hot-beds and the like. The change of state of the interlayer may be produced at will by heating by hot air or by alternating current passed through filaments or between electrodes therein.