各種商用ガラスの紫外線照射による応力発生 : 紫外線照射によるガラス中の応力発生第3報

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Stress build-up in a borosilicate and a 96% silica glass by ultra-violet irradiation was reported by the authors (J. Ceram. Assoc. Japan, 72 [11-1] 193-97 (1964)). As a preliminary study to throw light upon the mechanism of stress build-up, effect of ultra-violet irradiation on various commercial glasses was examined. After irradiation by 400W mercury discharge lamp for 500 and 1000 hours, glass test pieces were checked up photo-elastically, and if existed, stress at surfaces and depth of stressed layers were measured. Stress release by heat treatment was also investigated. Results were as follows:1. Stress build-up was observed only in borosilicate glasses. 2. In borosilicate glasses containing PbO or ZnO, stress was very small or unrecognized. 3. Stress increased with irradiation time. 4. When heated, stress began to release at about 250°C, faded away perfectly at 470°C and did not reappear on cooling. 5. In glasses containing no boron, stress did not come out by irradiation.From the results described above, stress build-up seemed to originate from special behaviour of boron atom (change of coordination number and of compactness of network structure of glass) under the action of ultraviolet ray. Obstruction effects of PhO or ZnO is a problem to be studied further.
1965-07-01