| 摘要 |
1,225,941. Laminated glass. CORNING GLASS WORKS. 4 Feb., 1969 [5 Feb., 1968], No. 5874/69. Heading B5N. [Also in Division C1] A laminated glass windshield includes an outer glass ply, an inner glass ply spaced therefrom and a plastics interlayer, e.g. of polyvinyl butyral between the glass plies adherently bonded to at least one of the glass plies, the inner ply being provided with a compressively stressed surface layer 13, 15 so that said inner ply has a greater resistance to fracture by a blunt object than the outer ply, greater flexibility than the outer ply and the ability when fractured to dice rather than forming large pieces of glass as does the outer ply and wherein the inner ply has at least one stress control zone 11 in the surface portion adjacent the plastics interlayer of such magnitude that the inner ply fractures after a predetermined stress level has been exceeded. A stress control zone is defined as a zone at the surface of a compressively stressed ply that has a level or degree of compressive stress that is lower than the level elsewhere over the surface of the ply. The inner ply is preferably an alkali metal aluminosilicate glass stressed by contact with a source of alkali metal ions having a larger ionic radius than the primary alkali metal ions in the glass, said contact being effected at an elevated temperature below the stress point of the glass, the stress control zone being formed preferably at the periphery of the ply by the application of an abrasive air blast to cut a depression in the sheet, or by scratching the glass with diamond. |
