Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-08-02
2003-05-06
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C106S287140, C106S287190, C525S478000
Reexamination Certificate
active
06558804
ABSTRACT:
This invention relates to coating compositions from which coatings having a low refractive index and a high hardness as well as water repellency, oil repellency and antifouling property can be briefly formed at low temperatures, and articles having cured coatings of the coating compositions.
BACKGROUND OF THE INVENTION
In the last decades, polymer coatings such as coatings of exterior paint, hard coatings, moisture-proof coatings, and antireflection coatings are required to have various properties such as adhesion to substrates, mar resistance, weather resistance, water repellency, antifouling and low refractive index.
Recently, fluorine-containing polymeric materials become of great interest in a variety of fields including building exterior paint because they are resistant to weathering. It is attempted to increase the proportion of fluorine atoms in such polymeric materials for the purpose of reducing the refractive index thereof.
However, the fluorine-containing polymers are characterized by a solubility parameter which largely differs from that of other organic materials and a weak intermolecular cohesive force. This imposes a limit on the type of solvent which can be used during preparation of polymeric materials. When a coating of polymeric material is formed on a substrate surface, there arise several problems including a low adhesive force to the substrate, a low hardness of the coating, and difficulty to provide sufficient transparency. To solve these problems, several techniques have been proposed.
(a) U.S. Pat. No. 4,701,508, U.S. Pat. No. 4,751,114 discloses a method for preparing a fluorinated polymer having improved adhesion by copolymerizing a fluoroolefin, a vinyl ether and a vinylalkoxysilane.
(b) JP-A 62-185740 discloses a composition comprising a fluoroolefin copolymer having amino and carboxyl groups, an epoxy functional alkoxysilane, and a silanol group-containing compound. This composition has good weather resistance and effective cure.
(c) JP-A 4-275379 discloses an overcoat paint composition for automobiles comprising a fluorinated polymer having hydroxyl and carboxyl groups and a hydrolytic condensate of a metal alkoxide. This composition has improved weather resistance, mar resistance and acid resistance.
(d) JP-A 61-40845 and U.S. Pat. No. 4,904,525, U.S. Pat. No. 4,940,602 disclose a method for preparing an antireflection part utilizing a hydrolyzate of fluorinated alkoxysilane.
(e) JP-A 2-19801 and U.S. Pat. No. 5,510,406 disclose a composition of a polymer having a fluorinated aliphatic ring structure in a solvent, which composition is used as a processing agent to provide low reflection.
(f) JP-A 10-147740 discloses a method of forming a low refractive index coating using a functional group-containing fluoropolymer and a silane compound in the presence of a metal catalyst.
(g) JP-A 2000-119634 discloses the use as an antifouling agent a mixture of hydrolyzates of a fluorinated silane compound and a fluorine-free polyfunctional organosilicon compound.
While a variety of methods as mentioned above are known, the methods disclosed in JP-A 61-258852, JP-A 62-185740 and JP-A 64-1527 suffer from low productivity because coatings as applied must be dried over a long time. Additionally, these coatings have insufficient mar resistance. The methods disclosed in JP-A 61-40845 and JP-A 4-275379 carry out drying treatment at high temperatures, which limit the type of substrate that can be used. In the method disclosed in JP-A 2-19801, the type of solvent that constitutes the composition is limited, and the resulting coating is less mar resistant. JP-A 10-147740 is a complex manufacturing process which increases the cost. The reduction of refractive index is below the expectation. JP-A 64-1527 fails to achieve a fully reduced refractive index and good antireflection effect since a trifluoropropyltrialkoxysilane is used as the fluorinated silane. JP-A 2000-119634 fails to produce a uniform coating since the compounds used are less compatible.
In the prior art, there are known no coating compositions which can effectively form cured coatings satisfying all the desired features of substrate adhesion, mar resistance, weather resistance, water repellency, antifouling, low refractive index and transparency.
SUMMARY OF THE INVENTION
An object of the invention is to provide a coating composition which can effectively form a protective coating having improved substrate adhesion, mar resistance, weather resistance, water repellency, antifouling, low refractive index and transparency.
The invention provides a coating composition comprising a silicone resin having at least two types of fluorinated organic substituent groups, represented by the following average compositional formula (1).
R
1
m
R
2
n
R
3
p
SiX
q
O
(4−m−n−p−q)/2
(1)
Herein R
1
and R
2
are different monovalent fluorinated organic groups of 3 to 30 carbon atoms, R
3
is hydrogen or a monovalent organic group of 1 to 10 carbon atoms, X is OH or a monovalent hydrolyzable group, m, n, p and q are numbers satisfying 0<m<1, 0<n<1, 0≦p<1, 0<q<1.8, 0<m+n≦1, and 0<m+n+p+q≦3. On brief curing at low temperature, the composition forms a uniform transparent coating having a high fluorine content, a low refractive index and a high hardness. The coating has excellent water repellency, oil repellency, and antifouling property. It is possible to reduce the refractive index of the coating to or below 1.42. Stacking the coating on a high refractive index layer having a refractive index of at least 1.65 results in an antireflection article having an improved reflectance.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The coating composition of the invention contains a silicone resin having at least two types of fluorinated organic substituent groups. The silicone resin is represented by the following average compositional formula (1):
R
1
m
R
2
n
R
3
p
SiX
q
O
(4−m−n−p−q)/2
(1)
wherein R
1
and R
2
are different monovalent fluorinated organic groups of 3 to 30 carbon atoms, R
3
is hydrogen or a monovalent organic group of 1 to 10 carbon atoms, X is OH or a monovalent hydrolyzable group, m, n, p and q are numbers satisfying 0<m<1, 0<n<1, 0≦p<1, 0<q<1.8, 0<m+n≦1, and 0<m+n+p+q≦3.
The silicone resin is obtained by hydrolysis or hydrolysis and partial condensation of a mixture of components (1) to (3):
(1) 100 parts by weight of a fluorinated silane compound of the following formula (1a):
R
1
R
3
a
SiY
3−a
(1a)
or a (partial) hydrolyzate or condensate thereof,
(2) 1 to 1,000 parts by weight of a fluorinated silane compound of the following formula (1b):
R
2
R
3
b
SiY
3−b
(1b)
or a (partial) hydrolyzate or condensate thereof, and
(3) 0 to 1,000 parts by weight of a fluorine-free silane compound of the following formula (1c):
R
3
c
SiY
4−c
(1c)
or a (partial) hydrolyzate or condensate thereof. In the formulae, R
1
, R
2
and R
3
are as defined above, Y is OH or a monovalent hydrolyzable group, “a” is a number from 0 to 2, “b” is a number from 0 to 2, and “c” is a number from 0 to 3.
The monovalent fluorinated organic groups of 3 to 30 carbon atoms represented by R
1
and R
2
typically have the following formula.
Rf(CH
2
)
r
Z(CH
2
)
s
—
Herein Rf is C
x
F
2x+1
or a polyfluoroalkyl group which may contain at least one ether bond, represented by the formula:
wherein x is an integer of 1 to 20, and y is an integer of at least 1, preferably 1 to 20, and more preferably 1 to 10. Z is one or more linking groups selected from among —CH
2
—, —CH
2
O—, —NR—, —COO—, —CONR—, —S—, —SO
3
— or —SO
2
NR—, wherein R is hydrogen or an alkyl group of 1 to 8 carbon atoms. The letter r is an integer of 0 to 3 and s is an integer of 1 to 3.
R
1
differs from R
2
. It is preferred that R
1
be 3,3,3-trifluoropropyl and R
2
be a different fluorinated organic group.
R
3
is hydrogen or a monovalent organic gro
Asai Mitsuo
Matsumura Kazuyuki
Sato Kazuharu
Yamaya Masaaki
Birch & Stewart Kolasch & Birch, LLP
Dawson Robert
Keehan Christopher M.
Shin-Etsu Chemical Co. , Ltd.
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