Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-10-18
2004-03-23
Peng, Kuo-Liang (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C427S387000, C427S508000, C428S429000, C428S421000, C428S451000, C428S688000, C428S500000, C428S447000, C528S032000, C528S039000, C528S041000
Reexamination Certificate
active
06709755
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for priming inorganic substrates, e.g., silicon wafers, to enhance polymer adhesion thereon and improve shelf life and also to layered structures utilizing the same.
BACKGROUND OF THE INVENTION
A polymeric coating applied to an inorganic substrate, without some kind of pre-treatment, often exhibits coating failure in the form of cracking or peeling. Previous methods for preparing a substrate for application of a coating film include subjecting the surface of the inorganic substrate to a chemical composition which contains, for example, phosphoric acid, sulfuric acid, chromic acid, oxalic acid, or other substances known for treating surfaces to improve adhesion; or subjecting the inorganic substrate to surface roughening by sand blasting, shot blasting, grit blasting, honing, paper scratching, wire scratching, hair line finishing, and the like. For purposes of having a clear surface pattern on the substrate, the surface may be subjected to coloring, printing, etching, and the like. All of these methods, however, do not ensure that the film will adequately bind to the surface of the substrate.
Primer compositions are compositions which promote the adhesion of an overcoating to a substrate. A primer layer is a thin layer between a substrate and a coating that serves to bind the two strongly. Many primer compositions are known in the art. Primer compositions are particularly useful for ensuring the formation of strong bonds between an organic substance and an inorganic substrate. The bonds between the organic layer and the priming composition enhance the ability of the inorganic substrate to be coated with a polymeric substance. However, there still remain problems with polymer films adhering sufficiently to the surface of the substrate for long periods of time, and problems with peeling and cracking once the film has been applied.
It is well known in the prior art that organosilanes are useful for promoting the adhesion of organic coatings. For example, Hamada, in European Patent Application EP 82-301396, discloses adhesive primers for bonding silicone rubber to substrates by applying a solution of an organosilane, organic hydroperoxide, and an organic solvent. However, adhesion of the silicone rubber is only achieved by thermocompression.
Lange et al., U.S. Pat. No. 4,356,233, discloses a primer composition for adhering overcoatings derived from in situ polymerization of uncured monomers onto inorganic substrates. However, the primer composition of Lange et al. includes a non-amino or non-amido containing silane and requires the presence of a metal ester.
Holmes-Farley et al., U.S. Pat. No. 5,139,601, is directed to a method for bonding a metal substrate to a similar or dissimilar substrate wherein a primer coating is first applied to the metal substrate surface and the metal substrate is then bonded to the similar or dissimilar substrate with a bonding adhesive. The primer coating used by Holmes-Farley is formed in situ by immersing the substrate in a solution containing 0.0001 to 30 parts by volume of hydrolyzable metal alkoxide, 20-95 parts by weight of solvent and 0.01 to 3 parts by weight of a base and optionally containing a coupling agent. It is noted that suitable adhesion occurs only when both the tetraalkoxysilane and aminosilane are present in the priming composition.
There remains a need for a method for priming inorganic substrates wherein the applied primer film has good shelf life and promotes adhesion of subsequently applied layers of fluorinated materials. In addition, there remains a need for a coated substrate that has improved shelf-life which can be stored and transported without loss of its adhesion-promoting characteristics.
SUMMARY OF THE INVENTION
The present invention is directed to a primer composition comprising: a diluent silane compound of formula (I):
R
d
Si(OR
1
)(OR
2
)(OR
3
) (I)
wherein R
d
comprises a non-polymerizable moiety;and R
1
, R
2
, and R
3
are independently selected from the group consisting of H, halogen, C
1
to C
10
alkyl, C
6
to C
14
aryl, and a silicate network;
and a free radical-polymerizable silane compound of formula (II):
R
e
Si(OR
4
)(OR
5
)(OR
6
) (II)
wherein R
e
comprises a free radical-polymerizable moiety,
R
4
, R
5
and R
6
are independently selected from the group consisting of H, halogen, C
1
to C
10
alkyl, C
6
to C
14
aryl, and a silicate network;
wherein the mole ratio of diluent silane to free radical polymerizable silane is between 1:9 and 9:1, preferably 1:3 and 3:1, or most preferably 1:2 and 2:1, and the composition optionally comprises a solvent.
In one embodiment of the invention, R
d
is selected from the group consisting of hydroxide, halide, C
1
to C
10
alkoxy, C
1
to C
10
aryloxy, and a silicate network. In another embodiment of the invention, R
d
is selected from the group consisting of alkyl, aryl, alkaryl, cycloalkyl, heteroaryl, fluoroalkyl, fluoroaryl, alkoxy, nitro, halo, amide, and ester. In another embodiment of the invention, R
d
comprises a moiety selected from the group consisting of amino, alkylamino, dialkylamino and trialkylamino.
Another aspect of the invention is directed to a process for priming an inorganic substrate comprising the steps of applying to the surface of the substrate a thin film of a primer composition comprising a diluent silane compound of formula (I):
R
d
Si(OR
1
)(OR
2
)(OR
3
) (I)
wherein R
d
comprises an organic non-polymerizable moiety, and R
1
, R
2
, and R
3
are independently selected from the group consisting of H, halogen, C
1
to C
10
alkyl, C
6
to C
14
aryl, and a silicate network; and a free radical-polymerizable silane compound of formula (II)
R
e
Si(OR
4
)(OR
5
)(OR
6
) (II)
wherein R
e
comprises a free radical-polymerizable moiety,
R
4
, R
5
and R
6
are independently selected from the group consisting of H, halogen, C
1
to C
10
alkyl, C
6
to C
14
aryl, and a silicate network; wherein the mole ratio of diluent silane to free radical polymerizable silane is between 1:9 and 9:1, preferably 1:3 and 3:1, or most preferably 1:2 and 2:1; and at least partially condensing the silanes to form a silicate network, thereby forming a primed substrate having a condensed primer layer covalently bonded to the substrate. The condensed primer layer has reactive polymerizable moieties available for copolymerization with a subsequently applied material. The composition can be applied by many methods, for example, by spin-coating, immersing, drenching, spraying and precipitating. Partial condensation of the silanes can occur by baking the thin film of the composition. In a preferred aspect of the process for priming the inorganic substrate, the silanes of the primer composition have been at least partially condensed to form a sol.
In one embodiment of the invention, the inorganic substrate is a silicon wafer. One aspect of this embodiment relates to a silicon wafer that comprises a layer of silicon dioxide, to which the thin film of the primer composition is applied. Application of the primer composition results in a primer layer having a thickness of about 30 Å to about 2 &mgr;m, and is preferably between about 30 Å and about 300 Å.
Another embodiment of the invention relates to a process for forming a polymer layer on an inorganic substrate which includes applying to the surface of the substrate a thin film of a primer composition which includes a diluent silane compound of formula (I):
R
d
Si(OR
1
)(OR
2
)(OR
3
) (I)
wherein R
d
comprises an organic non-polymerizable moiety, and R
1
, R
2
, and R
3
are independently selected from the group consisting of H, halogen, C
1
to C
10
alkyl, C
6
to C
14
aryl, and a silicate network;
and a free radical-polymerizable silane compound of formula (II):
R
e
Si(OR
4
)(OR
5
)(OR
6
) (II)
wherein R
e
comprises a free radical-polymerizable moiety; R
4
, R
5
and R
6
are independently selected from the group consisting of H, halogen, C
1
to C
10
alk
Ferm Paul M.
Hancock, Jr. Robert R.
Lewis Mark A.
E. I. du Pont de Nemours and Company
Peng Kuo-Liang
LandOfFree
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