MGF2 OPTICAL THIN FILM INCLUDING AMORPHOUS SILICON OXIDE BINDER, OPTICAL ELEMENT PROVIDED WITH THE SAME, AND METHOD FOR PRODUCING MGF2 OPTICAL THIN FILM
An MgF 2 optical thin film is formed on an optical surface of a base material. The MgF 2 optical thin film includes MgF 2 particles and an amorphous silicon oxide-based binder which exists on the surfaces of the MgF 2 particles and between the MgF 2 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.
1 .- 40 . (canceled)
41 . An MgF 2 optical thin film comprising:
MgF 2 minute particles; and
an amorphous silicon oxide-based binder which exists between the MgF 2 minute particles,
wherein the MgF 2 minute particles are connected by the amorphous silicon oxide-based binder, and the amorphous silicon oxide-based binder, disposed on surfaces of MgF 2 minute particles, among the MgF 2 minute particles which exist at an outermost portion of the MgF 2 optical thin film, has a thickness which is not more than 5% of a wavelength of light to be radiated,
wherein the MgF 2 minute particles have an average particle diameter of 1 nm to 100 nm, and
wherein the amorphous silicon oxide-based binder is formed of amorphous silica.
42 . The MgF 2 optical thin film according to claim 41 , wherein a refractive index of the MgF 2 optical thin film is 1.20 to 1.41.
43 . A multilayered optical thin film comprising a plurality of stacked optical thin films, wherein the MgF 2 optical thin film as defined in claim 41 is stacked as an outermost layer of the stacked optical thin films.
44 . The multilayered optical thin film according to claim 43 , wherein a plurality of MgF 2 optical thin films are disposed adjacently to each other; and a difference in refractive index between the adjacent MgF 2 optical thin films is 0.02 to 0.23.
45 . A multilayered optical thin film comprising a plurality of stacked optical thin films, wherein a plurality of MgF 2 optical thin films, each of the films being as defined in claim 41 , are included in the multilayered optical thin film.
46 . The multilayered optical thin film according to claim 45 , wherein a plurality of MgF 2 optical thin films are disposed adjacently to each other; and a difference in refractive index between the adjacent MgF 2 optical thin films is 0.02 to 0.23.
47 . A multilayered optical thin film comprising a plurality of stacked optical thin films which includes the MgF 2 optical thin film as defined in claim 41 and an optical thin film formed by a dry process.