Optical articles and sol-gel process for their manufacture

Abstract

An optical article, having an almost complete isotropy and dimensions equal to or lower than 500 μm, is prepared in which the sol-gel procedure comprises a preliminar step wherein the mould is cool filled with a sol containing the interesting oxide precursors, the sol gelation, the gel drying, the removal of gel from the mould and the final miniaturization of the dried gel. The optical article can be used for optic telecommunications.

1 - 7 . (canceled) 
     
     
         8 . Process for the preparation of a mould for the manufacture of an optical article of final miniaturized dimensions formed of pure silicon dioxide, optionally modified by the addition of one or more oxides of elements other than silicon, having essentially complete isotropy and wherein dimensions of said article are equal to or lower than 500 μm,
 the process comprising the following steps:
 a) preparation of an original high precision mould; 
 b) reproducing, in a silicon rubber one or more imprints, having the same size and a reversed symmetry with respect to said mould; 
 c) preparation, by the employment of a mould obtained in step a) or imprint obtained in step b), of a first optical article having reduced dimensions and reversed symmetry with respect to the starting mould or imprint according to a sol-gel procedure in which the sol-gel procedure comprises 
   a preliminary step of filling the mould which is cool with a sol containing a pure silica precursor, gelling the sol to form a gelled sol, drying the gelled sol to form a dried gel, removing the dried gel from the mould, whereby a miniaturized first optical article is obtained;
 d) repeating the preparation of optical articles by the sol-gel procedure according to step c) and/or by an imprint according to step b), until the desired dimension is achieved. 
   
     
     
         9 . Process for the preparation of a mould according to claim  1  in which the mould of item a) is produced from a nickel/phosphorus alloy on an aluminum carrier or an aluminum alloy. 
     
     
         10 . Process for the preparation of the optical article of final miniaturized dimensions formed of pure silicon dioxide, optionally modified by the addition of one or more oxides of elements other than silicon, having essentially complete isotropy and wherein dimensions of said article are equal to or lower than 500 μm
 said process 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) preparing at least one original high precision mould having an average roughness lower than 20 nm; 
 b) reproducing, in a silicone rubber, one or more imprints, having the same size and a reversed symmetry with respect to said mould; 
 c) preparing, by the employment of the original mould obtained in step a) or an imprint obtained in step b), of a first optical article having reduced dimensions and reversed symmetry with respect to the original high precision mould or imprint according to a sol-gel procedure; 
 d) preparing, inside the so obtained optical article, of a further optical article again having reduced sizes and reversed symmetry, or of an imprint according to the preceding step b); 
 e) repeating the preparation of further optical articles by the sol-gel procedure and/or imprints according to b), until desired miniaturized 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 optical article obtained, 
 in which the sol-gel procedure comprises a preliminary step wherein the mould is cooled and filled with a sol containing a pure silicon oxide precursor, the sol is gelled, the gel is dried, the gel is removed from the mould and the dried gel is miniaturized. 
   
     
     
         11 . Process for the preparation of an optical article according to claim  3  in which the mould is previously submitted to surface treatments by means of appropriate antiadhesive agents. 
     
     
         12 . Process for the preparation of a mould for manufacture of a miniaturized pure silica optical article, of final miniaturized dimensions formed of pure silicon dioxide, optionally modified by the addition of one or more oxides of elements other than silicon, having essentially complete isotropy and wherein dimensions of said article are equal to or lower than 500 μm,
 comprising the following steps:   a) preparing an original high precision mould having an average roughness lower than 20 nm;   b) reproducing, in a silicone rubber, one or more initial imprints, having the same size and reversed symmetry with respect to said original mould;   c) preparing, by the employment of the original mould obtained in step a) or an imprint obtained in step b), a pure silica optical article having reduced dimensions and reversed symmetry with respect to the original mould or initial imprint according to a sol-gel procedure in which the sol-gel procedure comprises   a preliminary step of filling said mould in a cool state with a sol containing pure silicon oxide precursors, gelling the sol, drying the sol to form a dried gel, removing the dried gel from the mould and miniaturizing the dried gel to obtain a pure silica optical article,   d) preparing a further pure silica optical article again having reduced sizes and reversed symmetry with respect to the pure silica optical article produced in step c), or of an imprint according to the preceding step b);   e) repeating the preparation of pure silica optical articles by sol-gel procedure and/or imprints according to step b) to obtain pure silica optical article of successively reduced dimensions, until the desired miniaturized dimensions is achieved; and   f) separating the imprint of a mould with the desired miniaturized dimensions.   
     
     
         13 . Process for the preparation of a mould according to claim  5  in which the mould of item a) is produced from a nickel/phosphorus alloy on an aluminum carrier or aluminum alloy. 
     
     
         14 . Process for the preparation of a pure silica optical article of miniaturized dimensions comprising:
 a) preparing at least one original high precision mould;   b) reproducing, in a silicone rubber, one or more imprints, having the same size and a reversed symmetry with respect to said original mould;   c) preparing, by the employment of one or more of the original mould or imprints from step b), of a pure silica optical article having reduced dimensions and reversed symmetry with respect to the original mould or one or more of said imprints; according to a sol-gel procedure in which the sol-gel procedure comprises   a preliminary step of filling an original mould which is cool with a sol containing pure silica and hydrolyzied TEOS at a pH of 4, gelling the sol to form a gelled sol within 60 minutes, drying the gelled sol with aerogel in an autoclave to form a dried gel, removing the dried gel from the mould to obtain an optical article,   d) preparing, using the so obtained optical article, a further optical article again having reduced size and reversed symmetry with respect to the article produced in step c), or of imprints according to the preceding step b);   e) repeating the preparation of pure silica optical articles by the sol-gel procedure and/or imprints according to b), of reduced dimensions with respect to the article produced in step d), until the desired miniaturized dimensions or, the lowest dimensions on the ground of the physical limitation of the process is achieved;   f) separating of the imprint and/or the optical article obtained in step e).   
     
     
         15 . Process for the preparation of an optical article according to claim  7  in which the original mould is previously submitted to surface treatments by means of appropriate antiadhesive agents.