| 摘要 |
<p>Thermally tempered flat glass the whole surface of which is thermally tempered, and a method of finishing edge portions of the same. In order to set conventional thermally tempered flat glass usable as a fire door and a fire window, it is necessary to practically subject the flat glass to a thermal tempering temperature, i.e., heating the flat glass at a temperature in the range (about 760 °C) considerably exceeding a softening point of the glass, and blowing cooling air at a continuous portion to be air-cooled with a back pressure of as high as 950 mmAq. Consequently, the flatness of the glass surface is lost or flexure occurs thereon, so that a reflected image is spoiled. An end surface portion (3a) of flat glass (3) is formed flat and finished so that a maximum surface unevenness is not more than 0.05 mm, and a boundary portion (3c) between the end surface portion (3a) and flat surface portions (3b) at front and rear sides of the flat glass (3) is finished so that a maximum surface unevenness is not more than 0.007 mm. Therefore, even when this flat glass is subjected to a simpler-than-before thermal tempering treatment, the fire resisting performance thereof can be retained. This enables the quality of flat glass to be improved, the cost of operating the thermal tempering equipment to be reduced, and the stress occurring in the flat glass due to the weight of itself during the installation thereof to be lessened.</p> |
