| 摘要 |
PROBLEM TO BE SOLVED: To obtain a magnesium fluoride optical thin film having a dense crystalline structure, low refractive index, excellent scratch resistance and mechanical strength by controlling the Knoop hardness of the film to almost the same value. as that of fused quartz. SOLUTION: The Knoop hardness of the magnesium fluoride optical thin film is controlled to almost same as that of fused quartz. To improve stability of the optical characteristics of this optical thin film with time, the Is concn. in the org. compd. is preferably controlled to 3 to 10 wt.%. The obtd. optical thin film has low refractive index. In this optical thin film, since the molecular refraction is decreased (the bond angle is decrease) as a method to decrease the refractive index, changes in the molecular volume due to oxygen ion during sputtering can be suppressed. This means increase in the refractive index in a film produced by IAD method can be avoided (because, when oxygen ion is trapped to increase the molecular volume, the refractive index increases). Thereby, an almost same refractive index as that of MgF2 vapor deposition film can be obtd. |
