Mgf2 optical thin film including amorphous silicon oxide binder, optical element provided with the same, and method for producing mgf2 optical thin film

Abstract

An MgF2 optical thin film is formed on an optical surface of a base material. The MgF2 optical thin film includes MgF2 particles and an amorphous silicon oxide-based binder which exists on the surfaces of the MgF2 particles and between the MgF2 particles. Owing to this amorphous silicon oxide-based binder, the optical thin film can have high mechanical strength and high adhesion to the base material, while having excellent environment resistance and a lower refractive index.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a division of U.S. patent application Ser. No. 11 / 662,892 filed Mar. 15, 2007, which is a 371 of International Patent Application No. PCT / JP2005 / 017015 filed Sep. 15, 2005.TECHNICAL FIELD[0002]The present invention relates to a singlelayered or multilayered optical thin film formed of MgF2, a method for producing the same, an optical element having the MgF2 optical thin film, and an optical system for optical instruments such as cameras, microscopes, binoculars, and exposure apparatuses which is provided with the optical element.BACKGROUND ART[0003]Surfaces of individual lenses, which construct an optical system such as a camera lens and an objective lens of a microscope, are coated with an antireflection film in order to reduce the reflection. In general, the optical thin film such as the antireflection film is produced by the dry method (dry process), in which the vacuum vapor deposition method, the sputtering method,...

AI Technical Summary

Benefits of technology

The solution enhances mechanical strength, adhesive force, and environmental resistance while achieving low reflectance across a wide spectral range, suitable for complex optical systems, including cameras and microscopes, with improved durability and optical performance.

Problems solved by technology

However, in the case of the film using MgF2 as described in International Publication No. 02 / 18982A1, the film strength and the adhesive force with respect to the base material are insufficient, although the refractive index of the optical thin film can be lowered to be not more than 1.30.

In the case of the films in which the film strength and the adhesive force with respect to the base material can be secured as described in Japanese Patent No. 3272111, Japanese Patent Application Laid-open No. 11-6902, Japanese Patent Application Laid-open No. 7-48527, Japanese Patent Application Laid-open No. 8-122501 and Japanese Patent Application Laid-open No. 2000-169133, the problem arises such that the refractive index of the film cannot be lowered sufficiently, and the environment resistance is insufficient.

There has been the problem such that it is not possible to obtain any optical thin film which is capable of sufficiently decreasing the refractive index and of securing the mechanical strength of the film, the adhesive force with respect to the base material, and the environment resistance.

However, in the case of the wet process, it is difficult to perform the multilayered coating.

On the contrary, if it is intended to lower the refractive index by providing a porous property to a film which is dense and which has a high refractive index, there is such a high possibility that the film itself may be collapsed (destroyed).

Therefore, such a procedure is extremely difficult to be executed.

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