| 摘要 |
A method of producing photochromic multifocal spectacle lenses by fusion of a reading segment with a photochromic major lens portion. The reading segment and the main photochromic portion of the lens are fused together at a temperature which does not adversely affect the photochromic properties of the glass. In one embodiment of the invention, the parts are fused at a temperature in the tempering range but below the turbidity range of the photochromic glass, and are held at the fusing temperature for a sufficiently limited time so that turbidity does not occur. In another embodiment of the invention, the temperature of the glass is raised rather rapidly through the tempering range and through the turbidity range to a point above the turbidity range, and fusion occurs above this range, and then the glass is cooled rather rapidly down through the turbidity range and through the tempering range. It is found that if this is done sufficiently fast, the photochromic properties of the main piece of glass are not adversely affected even though the glass has passed through the temperature range which is normally considered to be the turbidity range. Various details of procedure are described.
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