2022 年 7 巻 p. 71-76
In order to use diamond-like carbon (DLC) as a protective film, adhesion to the substrate is crucial. However, an effective nondestructive testing method for evaluation has not been established yet. Therefore, this study proposes reflective laser photoelasticity to measure the residual stress in DLC films. Through this method, the principal stress and its direction in DLC films can be measured nondestructively from the optical retardation, and the adhesion of DLC films can be evaluated indirectly from the stress states. The effectiveness of the reflective measurements is examined by comparison with the transmissive measurements of the same specimen. The value obtained by reflective measurements was 3.42 % smaller than that obtained by transmissive measurements. This error is partly caused by the reflection of laser light from the specimen surface, and a practical correction method is presented to show that the error is not a major problem. The results of this study will facilitate the non-destructive and non-contact measurement of residual stress in DLC, which can be used to determine the optimal deposition conditions with low residual stress and high adhesion.
