Silicon or silica substrate with a modified surface, process for

Details Silicon or silica substrate with a modified surface, process for Silicon or silica substrate with a modified surface, process for

1994-05-19

1998-01-20

Diamond, Alan

Bleaching and dyeing; fluid treatment and chemical modification

Chemical modification of textiles or fibers or products thereof

8120, 428404, 428405, 428543, 428446, 428406, 428409, 428365, 428428, 428429, 4273898, 4273855, 4273897, 427386, 427331, 4273899, 427299, 568595, 549560, C03C 1728, C04B 4146, C07C 6954

Patent

active

057097151

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/CH93/00173 filed Jul. 6, 1993.
The invention refers to a silicon or silicon dioxide substrate with a modified surface and to processes for producing the same, as well as to new orthoesters and methods for preparing the same.
The modification of surfaces of silicon and silicon dioxide substrates in particular in connection with the development of adhesives or adhesion promotors for such substrates, particularly for glass, so far was generally based on the idea that the silicon and silicon dioxide surfaces, respectively, are covered by silanol groups and water. Thus, so far, in the majority of cases such compounds as chloro silanes or alkoxy silanes were used for modifying silicon and silicon dioxide surfaces, respectively, inasmuch that it was thought that they do react with the silanol groups and do form covalent bonds therewith. Accordingly, this method was called "silanization".
Now, the basis of the present invention is the finding that the hydroxyl groups present on the surface of such a substrate, e.g. on a glass surface, at least partially form part of water which is molecularly bonded to the silicon dioxide surface.
Thus, it is the object of the present invention to provide silicon and silicon dioxide substrates, which are modified in a novel manner with organic compounds, have novel properties, and are particularly useful as a basis for anchoring of organic polymers.
Now, said novel silicon and silicon dioxide substrates, having a modified surface, are characterized in that their surface is occupied by an alcohol or a silylether.
Such a modified surface shows an essentially increased boundary or contact angle for water, as compared with corresponding non-modified surfaces. Thus, the wettability for water is reduced, whereas the wettability for many organic compounds is increased.
In the method for preparing such modified substrates according to the present invention the surfaces to be modified are treated with an orthoester.
As is generally known, the term "orthoester" stands for the aliphatic and aromatic esters of the corresponding orthocarbonic acids, which are not known to exist in free form, thus compounds of the type R.sup.1
According to the actual status of knowledge it is assumed that, on treating the surface of silicon or silicon dioxide substrate, an alcohol is formed from the orthoester. Thereby, the water is eliminated by hydrolysis from said surface, and the alcohol or silylether formed thereafter take the place of the eliminated water.
Schematically this may be represented as follows: ##STR1##
Examples of the manifold field of applications of the new technology are summarized in Table 1 hereafter.
Among the applications listed there, the method according to the present invention is particularly useful for modifying the surfaces of glass, quartz, silicon or silicon covered with silicon dioxide. Preferred applications are e.g. the modification of pyrogenic silicic acid, glass panes, wafers and oxidized wafers.
By such a treatment, e.g., the adherence of many plastics on the substrate can be essentially improved in an inexpensive manner. In particular, it allows to directly polymerize onto the substrate adhesives and coating materials, and polymeric interlayers for a later chemical reaction with adhesives and coating materials.


TABLE 1 ______________________________________ Product group/products Applications Utilities ______________________________________ 1 Silicate fillers 11 Pyrogenic silicic acid Hydrophobizing Adhesives Surface coating Sealants Plastics Coatings Lacquers Colors Molding compounds 12 Precipitated silicic Hydrophobizing Adhesives acid Surface coating Sealants Plastics Coatings Lacquers Colors Molding compounds 13 Silica gels Hydrophobizing Catalysts Surface coating Siccatives chromatographic substrates 14 Quartz powder Hydrophobizing Adhesives Surface coating Sealants Plastics Coatings Lacquers Colors Molding compounds 15 Glass powder Hydrophobizing D

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