Photochemical Bonding of Fluorocarbon and Fused Silica Glass for Ultraviolet Ray Transmitting

Abstract

ABSTRACTFluorocarbon was photo-chemically combined to a fused silica glass with the silicon oil used as a bonding agent. Balsam, unsaturated polyester resins and UV hardening adhesives have been generally used for joining two optical glasses together. They, however, have a strong absorption band in the UV region. Therefore, a new bonding method was developed for optical materials to allow UV rays to pass through using silicone oil and excimer- lamp. This new method requires the fluorocarbon-polishing pad employed in our PCP (Photo-Chemical Polishing) method in hydrofluoric acid ambience, which is bonded with the silica glass. The silicone oil was put between the fused silica glass and the fluorocarbon (FEP), and an excimer- lamp was irradiated. When the excimer lamplight was irradiated vertically, the silicon oil ((-O-Si(CH3)-O-)n) was photo-dissociated and reacted with the oxygen adsorbed on the silica glass surface to produce a SiO2. On the other hand, the H atoms photo-dissociated from the silicon oil pulled out the F atoms of the FEP. As a result, the FEP and the silica glass were combined. The tensile strength of the sample bonded by the photo-chemical reaction was evaluated. The tensile strength of 5.4 [kgf/cm2] was obtained, whereas that of the non-treatment sample was nil. Moreover, the transmittance of the vitrified silicone oil was measured at the 193 nm of ArF laser wavelength. It increased by 90.6% from 29.2% without the UV photon irradiation. The results showed that the silicon oil changed to silica glass by the excited oxygen, which improved the UV rays under 200nm transmittance.