GB1219161A - Vitreous and vitro-crystalline laminates - Google Patents

Abstract

1,219,161. Laminated glass articles. GLAVERBEL. 16 Jan., 1968 [30 Aug., 1967], No. 2385/68. Heading C1M. A method of forming a vitreous or glassceramic laminate comprises uniting together two sheets of vitreous or glass-ceramic material by contacting them in facing relationship with an intervening molten or plastic layer of glass or glass-ceramic material having a coefficient of thermal expansion greater than that of the material of either of said sheets, and cooling and solidifying the molten or plastic material during which the intervening layer unites the outer bodies and places them under compression. Preferably the sheets are in a solid state at all times and have length and width dimensions very much greater than their thickness, and the formed product may be a sheet of " safety " glass The interlayer may be applied molten to the or each sheet, or by spraying or immersing the sheets with or in a molten source, or by spraying with powdered constituents or applying in discrete form and melting in situ; or it may be applied as a paste or by evaporation or cathodic volatilization under reduced pressure and melted subsequently; or the layer may have electrically conductive particles therein which causes melting when an electric current is passed through it Preferably both the sheets and the intervening layer are glass but either or both may be a glass incorporating a crystalline phase or a glass which during the heating and subsequent cooling forms within itself one or more crystalline phases. In one embodiment two sheets of glass of composition in weight per cent SiO 2 73, CaO 11, MgO 2, Na 2 O 12, K 2 O 2 and coefficient of expansion 7À65 Î 10<SP>-6</SP>/‹ C. at 20‹ C. were united together. The intervening layer was applied as a pulverent glass (between 20 and 50 microns grain size) spread over one face of one sheet, of composition SiO 2 50, Na 2 O 45, B 2 O 3 5 and coefficient of expansion 14À9 x 10<SP>-6</SP>/‹ C. at 20‹ C. After the second glass sheet had been placed in position the unit was heated at 510‹ C. for 40 minutes. This allowed only the intervening layer to become molten. A coating of 1 mm. thickness gave a final layer of 0À6 mm. When slight pressure was applied during heating the final layer thickness was 0À4 mm. Where desired, heating could take place under a reduced pressure of 0À01 atmosphere. In a further example one sheet was made from glass of composition SiO 2 73, CaO 10, Na 2 O 16, As 2 O 3 0À2, Al 3 O 3 +Fe 2 O 3 0À8 having a coefficient of expansion of 10À8 x 10<SP>-6</SP>/‹ C. at 20‹ C. One surface and the edges of this sheet were then coated with metallic titanium and then with a mixture comprising 80% by weight of an enamel of composition BeF 2 47, KF 35, AlF 3 17, SiO 2 1 of expansion coefficient 22 x 10<SP>-6</SP>/‹ C. at 20‹ C. and 20% of SnO 2 . A glassceramic sheet containing 60% by wt. of the glass of the first sheet and having a coefficient of expansion of 9À5 x 10<SP>-6</SP>/‹ C. at 20‹ C. was then laminated to the coated first sheet by passing an electric current through the intervening layer. In another embodiment two sheets of glass of composition as in the first embodiment above had placed between them a glass-ceramic enamel of composition Li 2 O 20, PbO 30, ZrO 2 4, SiO 2 36, ZnO 10 and coefficient of thermal expansion 9 x 10<SP>-6</SP>/‹ C. at 20‹ C. The assembly was then heated to melt the interlayer.