열 스트레스에 의한 착색 렌즈 코팅막의 특성 변화

Purpose: In the present study, the characteristic change of tinted lenses with different coatings was investigated when exposed to thermal stress. Methods: The clear and tinted lenses made of allyl-diglycol-carbonate material with no coating, hard coating, multi-layered coating, mirror coating were exposed once to the temperatures of 25, 50, 75, and 100oC for 4 hours, and then their adhesion grade, hardness, visible light and ultraviolet transmittances were measured. Results: Only hard coated clear lenses showed reduced adhesion grade at a temperature of 75oC, while clear and tinted lenses with other coatings showed similar decrease of adhesion grade at 50oC. However, it was revealed that greater coating damage was shown in the tinted lenses even in the same adhesion grade by detailed surface examination, and the greatest damage was in mirror coated one. The hardness of tinted lenses was reduced by up to 32.9%p depending on the coating type at 100oC, whereas clear lenses showed a decrease of hardness larger than 10%p in hard coating at 100oC, in multi-layered coating and mirror coating at 75oC. The visible light transmittance was not significantly changed however, a relatively large change was shown in tinted lenses compared with clear lenses depending on the degree of thermal stress. The ultraviolet transmittance was not changed in all lenses. Conclusions: The characteristics of coating films on tinted lenses by thermal stress was changed larger than clear lenses, and a significant change of the coatings was observed even in a single thermal stress. Therefore, it suggests the necessity about the further study on the degree of damage of the coating film on tinted lenses caused by long-term wear and repeat thermal stress that may occur in daily life, and the establishment of standards for acceptable range of coating film damage.