Optical articles and sol-gel for their manufacture

Abstract

An optical article, having an almost complete isotropy and dimensions equal to or lower than 500 μm, is prepared by a sol-gel procedure comprising a preliminary step wherein the mould is filled cold with a sol containing the desired oxide precursors, sol gelation, gel drying, removal of the gel from the mould and the subsequent miniaturization of the dried gel. The optical article can be used for optic telecommunications.

1 . An optical article of final or nearly final dimensions, comprising silicon oxide, optionally modified by the addition of one or more oxides of elements other than silicon, having an almost complete isotropy and dimensions equal to or lower than 500 μm.  
   
   
       2 . Process for the preparation of a mould suitable to manufacture an optical article, according to  claim 1 , comprising one or more of the following operations that, all together, can be continuously carried out as a cascade and/or stopped at the desired or suitable step: 
 a) preparation of an original high precision mould;    b) reproducing, in a siliconic rubber or other suitable compound, one or more imprints, having the same sizes and a reversed symmetry with respect to said mould;    c) preparation, by the employment of one or more of the products obtained in the preceding steps, of the optical article having reduced dimensions and reversed symmetry with respect to the starting mould/imprint; according to a sol-gel procedure;    d) preparation, inside the so obtained optical article, of a further article again having reduced sizes and reversed symmetry, or of imprints according to the preceding item b);    e) repeating the preparation of optical articles by sol-gel procedures and/or imprints according to b), until the desired dimensions or, the lowest dimensions on the ground of the physical limitation of the process is achieved;    f) separation, in relation with any step, of the imprint and/or the article obtained in the very step.    
   
   
       3 . Process for the preparation of a mould according to  claim 2  in which the mould of item a) is produced from nickel/phosphorus alloys on aluminum carriers and aluminum alloys.  
   
   
       4 . Process for the preparation of the optical article according to  claim 2  in which the sol-gel procedure comprises a preliminary step wherein the mould is cool filled with a sol containing the oxide precursors, the sol is gelled, the gel is dried, the of gel is removed from the mould and the dried gel is miniaturized.  
   
   
       5 . Process for the preparation of an optical article according to  claim 4  in which the mould is previously submitted to surface treatments by means of appropriate antiadhesive agents.  
   
   
       6 . Process for the preparation of an optical article according to  claim 4  in which the mould is previously filled by a silicon oxide precursor.  
   
   
       7 . Process for the preparation of an optical article according to  claim 6  in which the mould is filled also by a precursor of at least an oxide of titanium, germanium, lanthanides and rare earths.