Release characteristics of a high-hardness DLC coating on an aspherical glass lens mold

Abstract

In this paper, we investigated the changes in the shape precision of a diamond-like carbon (DLC)-coated surface of an aspherical glass lens mold. The press molding process of the experiment involved placing a bulk material made of glass in an ultra-precision mold and applying cylinder pressure at a high temperature. Thermally stable tungsten carbide was used as the mold material. DTM grinding with a resolution of 0.1 [Formula: see text]m was performed to precisely process the tungsten carbide aspherical lens mold. HiPIMS–DLC and ta-C DLC coatings having excellent anti-stiction and hardness were applied on the polished mold. The hardness of the thin film was measured using nanoindentation. For the composition of the DLC, the [Formula: see text]/[Formula: see text] peak values were detected through Raman spectroscopy. Furthermore, the friction coefficient of the DLC thin film was measured using a tribology tester, and the friction coefficients of HiPIMS–DLC and ta-C were 0.018 and 0.014. Using FTS measurements, we confirmed that the precision of the aspherical lens shape (Peak to Valley) of the aspherical lens was 1.5 [Formula: see text]m and 0.5 [Formula: see text]m, respectively.