Method for producing optical element having multi-layered film

#The present invention relates to a method for producing an optical element, in which a multi-layered film is provided on a substrate, having a resistance against lights in a wavelength range of 300 nm to 450 nm. In particular, the present invention relates to a method for producing an optical element with a multi-layered film which can be used in a short-wavelength, high-power (30 mW/mm2 or more) blue laser.

#A short-wavelength, high-power blue laser is expected to be more widely used in an optical pickup or the like. In general, plastic is easily damaged by a laser. Therefore, some optical parts of devices using a short-wavelength, high-power blue laser consist of glass instead of plastic to avoid damage by a laser. For this reason, the prices of devices are relatively high. The relatively high prices are a hurdle to be overcome to enlarge the market of the devices.

#At present, plastic materials which can cope with a relatively-low-power blue laser are supplied from various material manufacturers. However, there is no plastic material which can withstand a high-power blue laser.

#FIG. 1 is a diagram showing a configuration of an optical element having a laser damage suppression film according to a first embodiment of the present invention;

#FIG. 2 is a graph showing a result obtained by measuring a rate of change of light intensity of an optical element after a blue laser is irradiated on the optical element for 1000 hours;

#FIG. 3 is a graph showing results obtained by measuring total wavefront aberrations (RMS) of the optical element before and after the blue laser is irradiated on the optical element for 1000 hours;

#FIG. 1 is a diagram showing a configuration of an optical element having a laser damage suppression film according to a first embodiment of the present invention. In FIG. 1, a layer 103 consisting of silicon monoxide (SiO) is formed on a substrate 101 consisting of a blue-laser-coping plastic material. The layer 103 consisting of silicon monoxide functions to improve adhesiveness between the substrate 101 consisting of a plastic material and a layer formed thereon. On the layer 103 consisting of silicon monoxide, layers 105 consisting of a low-refractive-index material and layers 107 consisting of a high-refractive-index material are alternately formed. In the embodiment, three layers 105 consisting of low-refractive-index material and two layers 107 consisting of high-refractive-index material are formed.

#In this case, the blue-laser-coping plastic material is an olefin-based material. More specifically, the material is a thermoplastic transparent resin cycloolefin polymer having an antioxidant function.

#The layer 103 consisting of silicon monoxide is formed on the substrate 101 by a vacuum deposition method. In the vacuum deposition method, a material (in this case, silicon monoxide) to be formed as a thin film, is heated by a resistance wire or by electron beam irradiation to evaporate the material. The evaporated material is caused to attach to (deposited on) the substrate to form a thin film. The thickness of the layer 103 consisting of silicon monoxide is about several hundred nanometers.