PRODUCTION OF OPTICAL MASTER DISK

摘要

PROBLEM TO BE SOLVED: To form groove pits which are stable to a fluctuation in film thicknesses and are made finer by forming a photoresist film and a color fadable film on the surface of a glass substrate and exposing pit patterns thereto. SOLUTION: The photoresist film 2 is applied on the surface of the flat glass substrate 1 polished with high accuracy and is subjected to a heat treatment. The color fadable film 3 is further applied thereon after cooling and a heat-treated. The concentrical pit patterns are then exposed thereon by an optical disk exposure device. The exposure is executed by condensing the collimating beams 5 on an Ar laser beam to a condenser lens 4 and irradiating the color fadable film 3 and the photoresist film 2 with a laser spot. The color fadable film 3 induces photoreaction only in the irradiated parts, thereby forming color fading 6 and allowing the transmission of the beams. At this time, the film thickness D of the color fadable film 3 and the photoresist film 2 is formed within the range of the equation when the wavelength of the laser beam 5 is defined asλand the numerical aperture of the condenser lens 4 as NA. The laser spot transmitted through the film forms a latent image 7 on the photoresist film 2 and forms rugged pits 8 after the development. As a result, the groove pits which are stable to the fluctuation in the film thickness and are made finer are formed.