EVALUATION METHOD OF DOUBLE-STRENGTH GLASS

摘要

PROBLEM TO BE SOLVED: To provide an evaluation method capable of removing double-strength glass which has a fear of producing a large broken piece by eliminating a problem wherein there is a possibility of producing the large broken piece called an island in a part of double-strength glass even when it is a JIS accepted product. SOLUTION: Double-strength glass is evaluated by a stress evaluating step for confirming that the surface compressive stress of the double-strength glass is within a range prescribed by JIS R 3222, a stress difference evaluating step for confirming that the difference between the maximum and minimum values of surface compressive stress measured over the whole surface of the double-strength glass is not higher than a predetermined value and a stress balance ratio evaluating step for investigating the balanced part and unbalanced part of compressive stress and tensile stress in the thickness direction of the double-strength glass to confirm that the ratio of the balanced part occupied in a measuring frame is not higher than the predetermined value. By making the evaluation of the double-strength glass severe as mentioned above, the double-strength glass having possibility to produce a large broken piece can be preliminarily removed to more enhance safety. COPYRIGHT: (C)2005,JPO&NCIPI