Improvement of adhesion between plastic substrates and antireflection layers by ion-assisted reaction

Enhanced adhesion was observed between antireflection (AR) layers and polycarbonate (PC) substrates by irradiating the substrates with low-energy Ar ions in an O2 environment. The AR coating consisted of SiO2/TiO2 multi-layers that were deposited by ion-beam sputtering. Improved adhesion was evidenced by a peeling test. Ion irradiation caused the surface characteristics to become more hydrophilic as measured by the water contact angle, which decreased from 76 deg. to 18 deg. after the ion irradiation. X-ray photoelectron spectroscopy analysis showed that the concentration of hydrophilic groups such as C=O and C-O increased as a result of the ion irradiation. The changes in surface roughness and in optical transmittance were negligible. The optical reflectance of the AR/PC structure was below 1% in the visible range