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 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.