U.S. patent application number 09/808345 was filed with the patent office on 2001-08-16 for highly tetrahedral amorphous carbon coating on glass.
This patent application is currently assigned to Guardian Industries Corporation. Invention is credited to Veerasamy, Vijayen S..
Application Number | 20010014398 09/808345 |
Document ID | / |
Family ID | 23172614 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014398 |
Kind Code |
A1 |
Veerasamy, Vijayen S. |
August 16, 2001 |
Highly tetrahedral amorphous carbon coating on glass
Abstract
A soda inclusive glass substrate is coated with a highly
tetrahedral amorphous carbon inclusive layer that is a form of
diamond-like carbon (DLC). In certain embodiments, the amorphous
carbon layer includes at least about 35% sp.sup.3 carbon-carbon
bonds, more preferably at least about 70%, and most preferably at
least about 80% of the sp.sup.3 carbon-carbon bonds. The high
density (e.g. greater than or equal to about 2.4 gm/cm.sup.3) of
the amorphous carbon layer prevents soda from exiting the glass and
reacting with water at surface(s) of the glass, thereby minimizing
visible stains (or corrosion) on the glass. The high density
amorphous carbon layer also may repel water. In some embodiments,
the highly tetrahedral amorphous carbon layer is part of a larger
DLC coating, while in other embodiments the highly tetrahedral
layer forms the entirety of a DLC coating on the substrate.
Inventors: |
Veerasamy, Vijayen S.;
(Farmington Hills, MI) |
Correspondence
Address: |
Nixon & Vanderhye P.C.
8th Floor
1100 N. Glebe Rd.
Arlington
VA
22201
US
|
Assignee: |
Guardian Industries
Corporation
|
Family ID: |
23172614 |
Appl. No.: |
09/808345 |
Filed: |
March 15, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09808345 |
Mar 15, 2001 |
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09303548 |
May 3, 1999 |
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Current U.S.
Class: |
428/408 ;
427/450; 427/569; 428/426 |
Current CPC
Class: |
C03C 2217/78 20130101;
C03C 2218/31 20130101; C03C 17/3644 20130101; B08B 17/065 20130101;
B32B 17/10174 20130101; C23C 26/00 20130101; B05D 5/083 20130101;
B32B 17/1033 20130101; B32B 17/10036 20130101; C03C 17/347
20130101; Y10T 428/30 20150115; B60S 1/54 20130101; B08B 17/06
20130101; C03C 17/3634 20130101; C03C 17/3441 20130101; B60S 1/58
20130101; C03C 17/36 20130101; C03C 2218/151 20130101; C03C 17/366
20130101; C03C 3/076 20130101; C03C 17/22 20130101; C03C 17/42
20130101; C23C 16/26 20130101; C03C 2217/282 20130101; C03C 17/3652
20130101; Y10T 428/265 20150115; C03C 2217/76 20130101; C03C
2218/112 20130101; C03C 23/0075 20130101; Y10T 428/268
20150115 |
Class at
Publication: |
428/408 ;
428/426; 427/569; 427/450 |
International
Class: |
B32B 017/06; C23C
004/10 |
Claims
I claim:
1. A coated glass comprising: a soda inclusive glass substrate
comprising, on a weight basis: SiO.sub.2 from about 60-80%,
Na.sub.2O from about 10-20%, CaO from about 0-16%, K.sub.2O from
about 0-10%, MgO from about 0-10%, Al.sub.2O.sub.3 from about 0-5%;
and a non-crystalline diamond-like carbon (DLC) coating provided on
said glass substrate, wherein said DLC coating includes at least a
first highly tetrahedral amorphous carbon layer having at least
about 35% sp.sup.3 carbon-carbon bonds and an average density of at
least about 2.4 gm/cm.sup.3.
2. The coated glass of claim 1, wherein said DLC coating further
includes a second layer therein of amorphous carbon that is in
direct contact with said substrate so that said second layer is
disposed between said substrate and said first highly tetrahedral
amorphous carbon layer, and wherein said first highly tetrahedral
amorphous carbon layer has a greater density and a greater
percentage of sp.sup.3 carbon-carbon bonds than said second layer
of amorphous carbon.
3. The coated glass of claim 1, wherein said first highly
tetrahedral amorphous carbon layer has at least about 70% sp.sup.3
carbon-carbon bonds, and wherein said glass substrate is a soda
lime silica glass substrate including from about 66-75% SiO.sub.2,
from about 10-20% Na.sub.2O, from about 5-15% CaO, from about 0-5%
MgO, from about 0-5% Al.sub.2O.sub.3, and from about 0-5%
K.sub.2O.
4. The coated glass of claim 3, wherein said highly tetrahedral
amorphous carbon layer has at least about 80% sp.sup.3
carbon-carbon bonds.
5. The coated glass of claim 3, wherein said DLC coating has an
average hardness of at least about 40 Gpa, and an average density
of at least about 2.4 gm/cm.sup.3.
6. The coated glass of claim 1, wherein said DLC coating has a
thickness of from about 30 to 3,000 .ANG..
7. The coated glass of claim 6, wherein said DLC coating has a
thickness of from about 50 to 300 .ANG..
8. The coated glass of claim 1, wherein said DLC coating has a
bandgap of from about 1.8 to 2.2 eV.
9. The coated glass of claim 1, wherein the coated glass comprises
the following characteristics: visible transmittance (Ill. A):
>60% UV transmittance: <38% IR transmittance: <35%.
10. The coated glass of claim 1, wherein said DLC coating includes
at least about 70% sp.sup.3 carbon-carbon bonds.
11. The coated glass of claim 1, wherein said DLC coating includes
at least about 80% sp.sup.3 carbon-carbon bonds.
12. The coated glass of claim 1, wherein said DLC coating is from
about 30 to 3,000 .ANG. thick, and wherein said first highly
tetrahedral amorphous carbon layer of said DLC coating is from
about 30 to 2,900 .ANG. thick.
13. The coated glass of claim 1, wherein said DLC coating includes
sp.sup.3 carbon-carbon bonds subimplanted in a surface of said
glass substrate so as to strongly bond said DLC coating to said
glass substrate.
14. The coated glass of claim 1, further comprising a low-E coating
system having at least one layer provided between said glass
substrate and said DLC layer.
15. A coated glass comprising: a glass substrate including at least
about 5% by weight Na.sub.2O; a highly tetrahedral amorphous carbon
layer, for reducing corrosion on the substrate, having a density of
at least about 2.4 gm/cm.sup.3 provided on said glass substrate in
order to reduce corrosion or stains on the coated glass, wherein
said highly tetrahedral amorphous carbon layer includes sp.sup.2
and sp.sup.3 carbon-carbon bonds; and wherein said highly
tetrahedral amorphous carbon layer has more sp.sup.3 carbon-carbon
bonds than sp.sup.2 carbon-carbon bonds.
16. The coated glass of claim 15, further comprising another
amorphous carbon layer located between said substrate and said
highly tetrahedral amorphous carbon layer, and wherein said another
amorphous carbon layer has a density less than said highly
tetrahedral amorphous carbon layer and a lesser percentage of
sp.sup.3 carbon-carbon bonds than said highly tetrahedral amorphous
carbon layer.
17. The coated glass of claim 15, wherein said highly tetrahedral
amorphous carbon layer has at least about 70% sp.sup.3
carbon-carbon bonds, and a thickness of from about 30-300
.ANG..
18. The coated glass of claim 17, wherein said highly tetrahedral
amorphous carbon layer is in direct contact with said glass
substrate.
19. A coated glass comprising: a soda inclusive glass substrate
comprising, on a weight basis: SiO.sub.2 from about 60-80%,
Na.sub.2O from about 10-20%, CaO from about 0-16%, K.sub.2O from
about 0-10%, MgO from about 0-10%, Al.sub.2O.sub.3 from about 0-5%;
a diamond-like carbon (DLC) coating provided on said glass
substrate for reducing visible corrosion, wherein said DLC coating
has an average density of at least about 2.4 gm/cm.sup.3 and a
thickness of from about 50 to 300 .ANG.; and wherein the coated
glass comprises the following characteristics: visible
transmittance: >60% UV transmittance: <38% IR transmittance:
<35%.
20. A method of making a coated glass article, the method
comprising the steps of: providing a glass substrate comprising, on
a weight basis, 60-80% SiO.sub.2, 10-20% Na.sub.2O, 0-16% CaO,
0-10% K.sub.2O, 0-10% MgO, and 0-5% Al.sub.2O.sub.3; and forming at
least one highly tetrahedral amorphous carbon layer having more
sp.sup.3 carbon-carbon bonds than sp.sup.2 carbon-carbon bonds on
the glass substrate for reducing potential for corrosion.
21. The method of claim 20, wherein said forming step includes
using a plasma ion beam and using acetylene gas to form the at
least one carbon layer on the glass substrate.
22. The method of claim 20, wherein said forming step includes
using a plasma ion beam to form the highly tetrahedral amorphous
carbon layer, and varying the ion energy from about 200 to 800 eV
during the deposition of an interfacial portion of the amorphous
carbon layer deposited immediately adjacent the substrate to a
lower level of from about 100 to 150 eV during the deposition of a
higher density portion of the carbon layer that is deposited over
the interfacial portion.
23. An automotive window comprising: a substrate transparent to at
least about 70% of visible light rays; a highly tetrahedral
amorphous carbon inclusive coating provided on said substrate,
wherein said coating has a thickness of from about 50 to 300 .ANG.
and a substantial number of sp.sup.3 carbon-carbon bonds; and
wherein the automotive window comprises the following optical
characteristics: visible transmittance: >70% UV transmittance:
<38% IR transmittance: <35%.
24. The automotive window of claim 23, wherein said substrate
includes one of soda lime silica glass, borosilicate glass, and
substantially transparent plastic, and wherein said coating has an
average density of at least about 2.4 gm/cm.sup.3.
25. The automotive window of claim 23, wherein the window is an
automotive windshield.
26. A method of coating a glass substrate to improve long-term
strength of the glass substrate, the method comprising the steps
of: providing a glass substrate having at least one crack with a
tip defined therein; depositing a layer of diamond-like carbon
directly on the glass substrate at an energy level so that carbon
atoms make their way into the crack to a location proximate the tip
of the crack; and the carbon atoms in the crack preventing some
water molecules from reaching a silicon-oxygen bond at the tip of
the crack thereby improving the long-term strength of the
glass.
27. The method of claim 26, wherein said energy level is an ion
energy level of from about 200 to 1,000 eV.
Description
[0001] This invention relates to a diamond-like carbon (DLC)
coating provided on (directly or indirectly) a glass or other
substrate. More particularly, in certain preferred embodiments,
this invention relates to a highly tetrahedral amorphous diamond
like carbon coating on a soda inclusive glass substrate (e.g. on a
soda lime silica glass substrate) for purposes of repelling water
and/or reducing corrosion on the coated article. Ion beam and
filtered carbon cathodic arc deposition are preferred methods of
deposition for the coating.
BACKGROUND OF THE INVENTION
[0002] Soda inclusive glasses are known in the art. For example,
see U.S. Pat. No. 5,214,008, which is hereby incorporated herein by
reference.
[0003] Soda lime silica glass, for example, is used for
architectural glass, automotive windshields, and the like. The
aforesaid '008 patent discloses one type of soda lime silica glass
known in the art.
[0004] Unfortunately, conventional soda inclusive glasses are
susceptible to environmental corrosion which occurs when sodium
(Na) diffuses from or leaves the glass interior. This sodium, upon
reaching the surface of the glass, may react with water to produce
visible stains or smears (e.g. stains of sodium hydroxide) on the
glass surface. Such glasses are also susceptible to retaining water
on their surfaces in many different environments, including when
used as automotive windows (e.g. backlites, side windows, and/or
windshields). These glasses are also susceptible to fogging up on
the interior surface thereof in automotive and other
environments.
[0005] In view of the above, it is apparent that there exists a
need in the art to prevent and/or minimize visible stains/corrosion
on soda inclusive coated glass surfaces. There also exists a need
in the art to provide a strong protective coating on window
substrates. Other needs in the art include the need for a coating
on glass that reduces the coated article's susceptibility to
fogging up in automotive and other environments, and the need for a
coated glass article that can repel water and/or dirt.
[0006] It is known to provide diamond like carbon (DLC) coatings on
glass. U.S. Pat. No. 5,637,353, for example, states that DLC may be
applied on glass. The '353 patent teaches that because there is a
bonding problem between glass and that type of DLC, an intermediate
layer is provided therebetween. Moreover, the '353 patent does not
disclose or mention the highly tetrahedral amorphous type of DLC
used in many embodiments set forth below. The DLC of the '353
patent would not be an efficient corrosion minimizer on glass in
many instances due to its low density (likely less than 2.0
gm/cm.sup.3). Still further, the DLC of the '353 patent is
deposited in a less than efficient manner for certain embodiments
of this invention.
[0007] It is known that many glass substrates have small cracks
defined in their surface. The stress needed to crack glass
typically decreases with increasing exposure to water. When water
enters such a crack, it causes interatomic bonds at the tip of the
crack to rupture. This weakens glass. Water can accelerate the rate
of crack growth more than a thousand times by attacking the
structure of the glass at the root or tip of the crack. Strength of
glass is in part controlled by the growth of cracks that penetrate
the glass. Water, in these cracks, reacts with glass and causes it
to crack more easily as described in "The Fracturing of Glass," by
T. A. Michalske and Bruce C. Bunker, hereby incorporated herein by
reference. Water molecules cause a concerted chemical reaction in
which a silicon-oxygen bond (of the glass) at the crack tip and on
oxygen-hydrogen bond in the water molecule are both cleaved,
producing two silanol groups. The length of the crack thus
increases by one bond rupture, thereby weakening the glass.
Reaction with water lowers the energy needed to break the
silicon-oxygen bonds by a factor of about 20, and so the
bond-rupture allows glass cracks to grow faster.
[0008] Thus, there also exists a need in the art for preventing
water from reaching silicon-oxygen bonds at tips of cracks in a
glass substrate, so as to strengthen the glass.
[0009] It is a purpose of different embodiments of this invention
to fulfill any or all of the above described needs in the art,
and/or other needs which will become apparent to the skilled
artisan once given the following disclosure.
SUMMARY OF THE INVENTION
[0010] An object of this invention is to provide a coated article
that can shed water (e.g. automotive windshield, automotive
backlite, automotive side window, architectural window, etc.).
[0011] Another object of this invention is to provide a system or
means for reducing or minimizing corrosion on soda inclusive coated
glass articles.
[0012] Another object of this invention is to provide a coated
glass article wherein a DLC coating protects the glass from acids
such as HF, nitric, and sodium hydroxide (the coating may be
chemically inert).
[0013] Another object of this invention is to provide a coated
glass article that is not readily susceptible to fogging up.
[0014] Another object is to provide a barrier layer with no pin
holes on a glass substrate.
[0015] Another object of this invention is to provide a coated
glass article that is abrasion resistant, and/or can repel dirt and
the like.
[0016] Another object of this invention is to provide a glass
substrate with a DLC coating inclusive of a highly tetrahedral
dense amorphous carbon layer, either in direct or indirect contact
with the substrate.
[0017] Another object of this invention is to provide a DLC coating
on a substrate, wherein the coating includes different portions or
layers with different densities and different sp.sup.3
carbon-carbon bond percentages. The ratio of sp.sup.3 to sp.sup.2
carbon-carbon bonds may be different in different layers or
portions of the coating. Such a coating with varying compositions
therein may be continuously formed by varying the ion energy used
in the deposition process so that stresses in the coating are
reduced in the interfacial portion/layer of the DLC coating
immediately adjacent the underlying substrate. Thus, a DLC coating
may have therein an interfacial layer with a given density and
sp.sup.3 carbon-carbon bond percentage, and another layer with a
higher density and higher sp.sup.3 carbon-carbon bond
percentage.
[0018] Generally speaking, this invention fulfills certain of the
above described needs/objects in the art by providing a coated
glass comprising:
[0019] a glass substrate including at least about 5% by weight
soda/Na.sub.2O;
[0020] an amorphous carbon layer provided on the glass substrate in
order to reduce corrosion or stains on the coated glass, wherein
said amorphous carbon layer includes sp.sup.2 and sp.sup.3
carbon-carbon bonds; and
[0021] wherein the amorphous carbon layer has more sp.sup.3
carbon-carbon bonds than sp.sup.2 carbon-carbon bonds.
[0022] In other embodiments, this invention fulfills certain of the
above described needs in the art by providing a coated glass
comprising:
[0023] a soda inclusive glass substrate comprising, on a weight
basis, from about 60-80% SiO.sub.2, from about 10-20% Na.sub.2O,
from about 0-16% CaO, from about 0-10% K.sub.20, from about 0-10%
MgO, and from about 0-5% Al.sub.2O.sub.3; and
[0024] a non-crystalline diamond-like carbon (DLC) coating provided
on the glass substrate, wherein the DLC coating includes at least
one highly tetrahedral amorphous carbon layer having at least about
35% sp.sup.3 carbon-carbon bonds.
[0025] In certain embodiments, the glass substrate is a soda lime
silica float glass substrate.
[0026] In preferred embodiments, the entire DLC coating or
alternatively only a layer within the DLC coating, has a density of
from about 2.4 to 3.4 gm/cm.sup.3, most preferably from about 2.7
to 3.0 gm/cm.sup.3.
[0027] In certain embodiments, the tetrahedral amorphous carbon
layer has the aforesaid density range and includes at least about
70% sp.sup.3 carbon-carbon bonds, and most preferably at least
about 80% sp.sup.3 carbon-carbon bonds.
[0028] In certain embodiments, the DLC coating includes a top layer
(e.g. from about 2 to 8 atomic layers, or less than about 20 A)
that is less dense than other portions of the DLC coating, thereby
providing a solid lubricant portion at the top surface of the DLC
coating. Layered graphene connected carbon atoms are provided in
this thin layer portion. The coefficient of friction is less than
about 0.1 for this thin layer portion.
[0029] Another advantage of this invention is that the temperature
of the glass substrate is less than about 2000 C., preferably less
than about 150.degree. C., most preferably from about 60-80.degree.
C., during the deposition of DLC material. This is to minimize
graphitization during the deposition process.
[0030] This invention further fulfills the above described needs in
the art by providing a window having a substrate and a highly
tetrahedral amorphous carbon layer thereon, wherein the substrate
is or includes at least one of borosilicate glass, soda lime silica
glass, and plastic.
[0031] This invention will now be described with respect to certain
embodiments thereof, along with reference to the accompanying
illustrations.
IN THE DRAWINGS
[0032] FIG. 1 is a side cross sectional view of a coated article
according to an embodiment of this invention, wherein a substrate
is provided with a DLC coating including at least two layers
therein.
[0033] FIG. 2 is a side cross sectional view of a coated article
according to another embodiment of this invention, wherein a highly
tetrahedral amorphous carbon DLC coating is provided on and in
contact with a substrate.
[0034] FIG. 3 is a side cross sectional view of a coated article
according to yet another embodiment of this invention wherein a
low-E or other coating is provided on a substrate, with the DLC
coating of either of the FIG. 1 or FIG. 2 embodiments also on the
substrate but over top of the intermediate low-E or other
coating.
[0035] FIG. 4 illustrates an exemplar sp.sup.3 carbon atom
hybridization bond.
[0036] FIG. 5 illustrates an exemplar sp.sup.2 carbon atom
hybridization bond.
[0037] FIG. 6 illustrates exemplar sp hybridizations of a carbon
atom.
[0038] FIG. 7 is a side cross sectional view of carbon ions
penetrating the substrate or DLC surface so as to strongly bond a
DLC layer according to any embodiment herein.
[0039] FIG. 8 is a side cross sectional view of a coated glass
substrate according to an embodiment of this invention,
illustrating DLC bonds penetrating cracks in the surface of a glass
substrate.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THIS INVENTION
[0040] Referring now more particularly to the accompanying drawings
in which like reference numerals indicate like elements throughout
the accompanying views.
[0041] FIG. 1 is a side cross sectional view of a coated glass
article according to an embodiment of this invention, wherein at
least one diamond-like carbon (DLC) protective coating(s) 3 is
provided directly on soda-inclusive glass substrate 1. DLC coating
3 in the FIG. 1 embodiment includes at least one highly tetrahedral
amorphous carbon (ta-C) layer 7 that has a high density (e.g.
greater than about 2.4 grams per cubic centimeter) and functions to
repel water and seal soda within the soda inclusive glass
substrate. Coating 3 further includes at least one interfacing
layer 8 directly adjacent substrate 1, where layer 8 has a lesser
density and a lesser percentage of sp.sup.3 carbon-carbon bonds
than ta-C layer 7. Even though layer 8 differs from layer 7 in
these manner(s), interfacing layer 8 may or may not qualify as ta-C
with a density of at least about 2.4 gm/cm.sup.3, as described
below. It is noted that in certain embodiments, coating 3 may
include multiple ta-C layers 7 and/or multiple layers 8. Layers 7
and 8 of the coating may be formed in a continuous or
non-continuous deposition process in different embodiments of this
invention.
[0042] FIG. 2 is a side cross sectional view of a coated glass
article according to another embodiment of this invention, wherein
at least one DLC coating(s) 3 is provided on glass substrate 1. In
the FIG. 2 embodiment, substantially the entire DLC coating 3 is
made up of highly tetrahedral amorphous carbon (ta-C), similar to
layer 7, having a density of at least about 2.4 grams per cubic
centimeter and a high percentage (e.g. at least about 35%, more
preferably at least about 70%, and most preferably at least about
80%) of sp.sup.3 carbon-carbon bonds. In other words, ta-C layer 7
from the FIG. 1 embodiment forms the entirety of DLC coating 3 in
the FIG. 2 embodiment. DLC coating 3 in the FIG. 2 embodiment may
or may not have equal densities and/or the same percentages of
sp.sup.3 carbon-carbon bonds throughout the thickness of coating 3,
as these parameters may be varied throughout layers 3, 7 and 8 in
the FIGS. 1 and 2 embodiments by changing the ion energy used
during the deposition process of coating 3.
[0043] In the FIG. 3 embodiment, a low-E or other coating 5 is
provided between substrate 1 and DLC coating 3 (i.e. the DLC
coating of either the FIG. 1 or FIG. 2 embodiment). However, DLC
coating 3 is still on substrate 1 in the FIG. 3 embodiment, along
with a ta-C portion 7 of coating 3. Thus, the term "on" herein
means that substrate 1 supports DLC coating 3 or any layer (e.g. 7,
8) thereof, regardless of whether or not other layer(s) 5 are
provided therebetween. Thus, protective coating 3 may be provided
directly on substrate 1 as shown in FIGS. 1-2, or may be provided
on substrate 1 with a low-E or other coating(s) 5 therebetween as
shown in FIG. 3. Coating 5, instead of its illustrated position in
FIG. 3, may also be provided on top of DLC coating 3 so that
coating 3 (of either the FIG. 1 or FIG. 2 embodiment) is located
between coating(s) 5 and substrate 1. In still other embodiments, a
DLC coating 3 may be provided on both sides of a low-E coating
5.
[0044] Exemplar coatings (in full or any portion of these coatings)
that may be used as low-E or other coating(s) 5, either on top of
or below DLC coating 3, are shown and/or described in any of U.S.
Pat. Nos. 5,837,108, 5,800,933, 5,770,321, 5,557,462, 5,514,476,
5,425,861, 5,344,718, 5,376,455, 5,298,048, 5,242,560, 5,229,194,
5,188,887 and 4,960,645, which are all hereby incorporated herein
by reference. Simple silicon oxide and/or silicon nitride
coating(s) may also be used as coating(s) 5.
[0045] As will be discussed in more detail below, highly
tetrahedral amorphous carbon (ta-C) layer(s) 7 is a special form of
diamond-like carbon (DLC), and includes at least about 35% sp.sup.3
carbon-carbon bonds (i.e. it is highly tetrahedral). In certain
embodiments of this invention, ta-C layer(s) 7 has at least about
35% sp.sup.3 carbon-carbon bonds of the total sp bonds in the
layer, more preferably at least about 70%, and most preferably at
least about 80% sp.sup.3 S carbon-carbon bonds so as to increase
the density of layer 7 and its bonding strength. The amounts of
sp.sup.3 bonds may be measured using Raman finger-printing and/or
electron energy loss spectroscopy. The high amount of sp.sup.3
bonds increases the density of layer thereby allowing it to prevent
soda diffusion to the surface of the coated article.
[0046] Ta-C layer 7 forms the entirety of DLC coating 3 in the FIG.
2 embodiment, and ta-C layer 7 forms only a portion of DLC coating
3 in the FIG. 1 embodiment. This is because interfacial amorphous
carbon layer 8 in the FIG. 1 is embodiment sometimes has a density
less than about 2.4 grams per cubic centimeter and/or less than
about 35% sp.sup.3 carbon-carbon bonds. However, it is noted that
DLC coating 3 has an interfacial layer immediately adjacent
substrate 1 in each of the FIG. 1 and FIG. 2 embodiments, with the
difference being that the interfacial layer in the FIG. 2
embodiment has a density of at least about 2.4 grams per cubic
centimeter and at least about 35% sp.sup.3 (more preferably at
least about 70%, and most preferably at least about 80%)
carbon-carbon bonds. Thus, layer 7 herein refers to both layer 7 as
illustrated in the FIG. 1 embodiment as well as DLC coating 3 in
the FIG. 2 embodiment.
[0047] At least some carbon atoms of DLC coating 3, and/or some
sp.sup.2 and/or sp.sup.3 carbon-carbon bonds, are provided in
fissures or cracks in a surface (e.g. top surface) of the glass
substrate, or may penetrate the glass surface of substrate 1 itself
or the surface of growing DLC, so as to strongly bond coating 3 to
substrate 1. Subimplantation of carbon atoms into the surface of
substrate 1 enables coating 3 to be strongly bonded to substrate
1.
[0048] For purposes of simplicity, FIG. 4 illustrates an exemplar
sp.sup.3 carbon-carbon or C--C bond (i.e. carbon to carbon diamond
like bond) in coating 3, FIG. 4 an exemplar sp.sup.2 C--C bond in
coating 3, and FIG. 5 an exemplar sp.
[0049] The provision of dense (density of at least about 2.4
gm/cm.sup.3) ta-C layer 7 on soda inclusive glass substrate 1
reduces the amount of soda which can exit the substrate or reach
the surface of the substrate or coated article (i.e. ta-C limits
sodium diffusion from the substrate). Thus, less soda is allowed to
react with water or other material(s) on the surface of the
article. The end result is that the provision of ta-C layer 7 on
the substrate reduces stains and/or corrosion on the glass article
which can form over time. The large number of sp.sup.3
carbon-carbon bonds increases the density of layer 7 and allows the
layer to repel water and minimize soda diffusion from soda
inclusive glass.
[0050] Coating(s) 3, and layer(s) 7, 8, also strengthen the glass
article, reduce stress at the bonding surfaces between coating 3
and substrate 1, and provide a solid lubricant surface on the
article when coating 3 is located at a surface of the article.
Coating(s) 3 and/or layer 7 may includes a top layer portion (e.g.
the top 3 to 15 .ANG.) that is less dense than central areas of
coating 3, thereby providing a solid lubricant at the top surface
of coating 3 furthest from the substrate so that the article is
resistant to scratching. Ta-C layer 7 also provides resistance to
water/moisture entering or coming into substrate 1. Coating 3, and
thus ta-C layer 7, are preferably formed/deposited continuously
across glass substrate 1, absent any pinholes or apertures.
[0051] In certain embodiments, layer 7 and/or 8 adjacent the glass
substrate is deposited at an ion energy that allows significant
numbers of carbon atoms to penetrate cracks in the glass surface as
shown in FIG. 8. The small size of carbon atoms and the ion energy
utilized prevent substantial water from reaching the tip of the
crack(s). This strengthens the glass in the long term by slowing
down and/or stopping the rupture of silicon-oxygen bonds at crack
tips caused by water exposure.
[0052] Advantages associated with certain embodiments of this
invention include: (i) coated window articles that can shed water
in different environments (e.g. automotive windows such as
backlites and windshields, or commercial and residential windows);
(ii) anti-fog coated articles that are resistant to fogging up;
(iii) strengthened coated windows; (iv) abrasion resistant coated
windows; (v) coated articles that can repel dirt; and (vi) coated
glass articles less susceptible to visible corrosion on surfaces
thereof. For example, in automotive window embodiments, the outer
surface of substrate 1 exposed to the environment is coated with
coating 3 in accordance with any of the FIGS. 1-3 embodiments. In
anti-fog automotive embodiments, the inner surface of automotive
window substrates 1 may be coated with coating 3 in accordance with
any of the FIGS. 1-3 embodiments.
[0053] In certain embodiments, coating 3 is at least about 70%
transparent to or transmissive of visible light rays, preferably at
least about 80%, and most preferably at least about 90% transparent
to visible light rays.
[0054] In certain embodiments, DLC coating 3 (and thus layer 7 in
the FIG. 2 embodiment) may be from about 30 to 3,000 .ANG. thick,
most preferably from about 50 to 300 .ANG. thick. As for glass
substrate 1, it may be from about 1.5 to 5.0 mm thick, preferably
from about 2.3 to 4.8 mm thick, and most preferably from about 3.7
to 4.8 mm thick. Ta-C layer 7, in certain embodiments, has a
density of at least about 2.4 grams per cubic centimeter, more
preferably from about 2.4 to 3.4 gm/cm.sup.3, and most preferably
from about 2.7 to 3.0 gm/cm.sup.3.
[0055] Substrate 1 includes soda or Na.sub.2O in certain
embodiments of this invention. Thus, ta-C layer(s) 7 minimize the
amount of soda that can reach the surface of the coated article and
cause stains/corrosion. In certain embodiments, substrate 1
includes, on a weight basis, from about 60-80% SiO.sub.2, from
about 10-20% Na.sub.2O, from about 0-16% CaO, from about 0-10%
K.sub.2O, from about 0-10% MgO, and from about 0-5%
Al.sub.2O.sub.3. In certain other embodiments, substrate 1 may be
soda lime silica glass including, on a weight basis, from about
66-75% SiO.sub.2, from about 10-20% Na.sub.2O, from about 5-15%
CaO, from about 0-5% MgO, from about 0-5% Al.sub.2O.sub.3, and from
about 0-5% K.sub.2O. Most preferably, substrate 1 is soda lime
silica glass including, by weight, from about 70-74% SiO.sub.2,
from about 12-16% Na.sub.2O, from about 7-12% CaO, from about 3.5
to 4.5% MgO, from about 0 to 2.0% Al.sub.2O.sub.3, from about 0-5%
K.sub.2O, and from about 0.08 to 0.15% iron oxide. Soda lime silica
glass according to any of the above embodiments may have a density
of from about 150 to 160 pounds per cubic foot (preferably about
156), an average short term bending strength of from about 6,500 to
7,500 psi (preferably about 7,000 psi), a specific heat (0-100
degrees C) of about 0.20 Btu/lbF, a softening point of from about
1330 to 1345 degrees F, a thermal conductivity of from about 0.52
to 0.57 Btu/hrftF, and a coefficient of linear expansion (room
temperature to 350 degrees C) of from about 4.7 to
5.0.times.10.sup.-6 degrees F. In certain embodiments, any glass
disclosed in U.S. Pat. No. 5,214,008 or Pat. No. 5,877,103, each
incorporated herein by reference, may be used as substrate 1. Also,
soda lime silica float glass available from Guardian Industries
Corp., Auburn Hills, Michigan, may be used as substrate 1.
[0056] Any such aforesaid glass substrate 1 may be, for example,
green, blue or grey in color when appropriate colorant(s) are
provided in the glass.
[0057] In certain other embodiments of this invention, substrate 1
may be of borosilicate glass, or of substantially transparent
plastic. In certain borosilicate embodiments, the substrate 1 may
include from about 75-85% SiO.sub.2, from about 0-5% Na.sub.2O,
from about 0 to 4% Al.sub.2O.sub.3, from about 0-5% K.sub.2O, from
about 8-15% B.sub.2O.sub.3, and from about 0-5% Li.sub.2O.
[0058] In still further embodiments, an automotive window (e.g.
windshield or side window) including any of the above glass
substrates laminated to a plastic substrate may combine to make up
substrate 1, with the coating 3 of any of the FIGS. 1-3 embodiments
provided on either or both sides of such a window. Other
embodiments would have substrate 1 made up of a sheet of soda lime
silica glass laminated to a plastic sheet for automotive window
purpose, with coating(s) 3 of any of the FIGS. 1-3 embodiments on
the inner side of the substrate bonded to the plastic. In other
embodiments, substrate 1 may include first and second glass sheets
of any of the above mentioned glass materials laminated to one
another, for use in window (e.g. automotive windshield, residential
window, commercial window, automotive side window, automotive
backlite or back window, etc.) and other similar environments.
[0059] In certain embodiments, coating 3 and/or ta-C layer 7 may
have an average hardness of from about 30-80 GPa (most preferably
from about 40-75 GPa), and a bandgap of from about 1.8 to 2.2 eV.
It is noted that the hardness and density of coating 3 and/or
layers 7, 8 thereof may be adjusted by varying the ion energy of
the depositing apparatus or process described below.
[0060] When substrate 1 of any of the aforesaid materials is coated
with at least DLC coating 3 according to any of the FIGS. 1-3
embodiments, the resulting coated article has the following
characteristics in certain embodiments: visible transmittance (Ill.
A) greater than about 60% (preferably greater than about 70%), UV
(ultraviolet) transmittance less than about 38%, total solar
transmittance less than about 45%, and IR (infrared) transmittance
less than about 35% (preferably less than about 25%, and most
preferably less than about 21%). Visible, "total solar", UV, and IR
transmittance measuring techniques are set forth in U.S. Pat. No.
5,800,933, as well as the '008 patent, incorporated herein by
reference.
[0061] Diamond-like carbon (DLC) and the special tetrahedral
amorphous carbon (ta-C) form 7 of DLC utilized in certain
embodiments herein will now be described in detail. All DLC 3 shown
in drawings herein is amorphous. Ta-C 7 is amorphous and yet has
substantial C--C tetrahedral (sp.sup.3-type) bonding and hence is
termed tetrahedral amorphous carbon (ta-C) [or highly ta-C] as it
has at least 35% sp.sup.3 C--C bonds, preferably at least about 70%
and most preferably at least about 80% sp.sup.3 C--C bonds.
Diamond-like bonding gives this ta-C material gross physical
properties approaching those of diamond such as high hardness, high
density and chemical inertness. However, ta-C also includes
sp.sup.2 C--C trigonal bonding and its optical and electronic
properties are largely determined by this bonding component. The
fraction of sp.sup.2 bonding, and thus the density, in a ta-C layer
depends for example on the carbon ion energy used during deposition
of coating 3 and/or layers 7 and 8. Properties of a given DLC
coating are a function of the fraction of sp.sup.3 to sp.sup.2
bonding throughout the coating and thus throughout layers 7 and
8.
[0062] It is noted that the sp.sup.3 bonds discussed herein are
sp.sup.3 carbon-carbon bonds which result in a high density coating
3 and/or 7 and are not sp.sup.3 carbon-hydrogen bonds which do not
provide as high of density.
[0063] Depending on the technique of deposition, many ta-C layers 7
herein contain amounts of H (up to about 4%) which either include
the C atom to take either a tetrahedral configuration or an
sp.sup.2 planar configuration or to be sp-hybridised within a
linear polymeric-like form. In other words C--C, C--H and H--H
correlations all contribute to the average structure of layers 7 in
some embodiments.
[0064] In the case of ta-C which is fully or at least about 90%
hydrogen-free, C--C bonding describes the local structure. Ta-C
films also have some fraction of sp.sup.2 or graphic bonding. The
spatial distribution of trigonal (sp.sup.2) and tetrahedral carbon
atoms may determine the bonding strength of layer(s) 3 to glass, as
well as the layer's density, strength, stress, etc. Tetrahedral
amorphous carbon (ta-C) and its hydrogenated form ta-C:H (which
contains no more than about 10 at % or so H) have the highest
percentage of carbon-carbon (C--C) sp.sup.3 bonding, and are used
as layer 7 in the FIG. 1 embodiment and coating 3 in the FIG. 2
embodiment, and either of these in the FIG. 3 embodiment. This
diamond-like bonding confers upon ta-C 7 properties which are
unrivaled by other forms of so called DLC which have lower
densities and/or greater proportion of graphitic sp.sup.2 and
polymeric sp C--C and C--H bonding.
[0065] Ta-C 7 has high density (at least about 2.4 grams per cubic
centimeter), hardness, Young's modulus (700-800), as well as a low
coefficient of friction (see Table 1 below).
1TABLE 1 Ta-C:H Properties c-Diamond ta-C (10% at H) Bandgap (eV)
5.45 2.0 2.2-2.5 Breakdown voltage 100 25-14 35 30 (V cm-1) 10 5
Dielectric Constant 5.5 4.5 4.7 Resistivity (ohm-cm) 10.sup.18
10.sup.11 10.sup.12 Thermal Conductivity 20 0.1 0.1
(Wcm.sup.-1K.sup.-1) Young's modulus Gpa 1000 700-800 500 Hardness
(Gpa) 100 30-80 5-80 Refractive index 2.4 2.0 1.6-1.9 Structure
crystalline amorphous amorphous Deposition high temp CVD 0.1 low
temp low temp condition/rate um/hr <200 C. 20 A/s wetability
contact angle 5 to 50 Max thickness >1 um <200 nm <200 nm
stress limited Coefficient of Friction <0.2 single crystal
<0.1 <0.1
[0066] Methods of depositing coating 3 on substrate 1 are described
below for certain embodiments of this invention.
[0067] Prior to coating 3 being formed on the glass substrate, the
top surface of substrate 1 is preferably cleaned by way of an ion
beam utilizing oxygen gas in each of the FIG. 1 and 2 embodiments.
Oxygen gas physically cleans the surface due to its atomic weight
of from about 28-40 amu, most preferably about 32. Substrate 1 may
also be cleaned by, for example, sputter cleaning the substrate
prior to actual deposition of ta-C or other DLC material. This
cleaning may utilize oxygen and/or carbon atoms, and can be at an
ion energy of from about 800 to 1200 eV, most preferably about
1,000 eV.
[0068] In plasma ion beam embodiments for depositing coatings 3, 7
and/or 8, carbon ions may be energized to form a stream from plasma
toward substrate 1 so that carbon from the ions is deposited on
substrate 1. An ion beam from gas phase produces a beam of C+, CH+,
C.sub.2H, and/or C.sub.2H.sub.2+ ions (i.e. carbon or carbon based
radicals). Preferably, acetylene feedstock gas (C.sub.2H.sub.2) is
used to prevent or minimize polymerization and to obtain an
appropriate energy to allow the ions to penetrate the substrate 1
surface and subimplant therein, thereby causing coating 3 atoms to
intermix with the surface of substrate 1 a few atom layers
thereinto. Impact energy of ions for the bulk of coating 3 (e.g.
layer 7 in the FIGS. 1 and 2 embodiments) may be from about 100 to
200 eV per carbon atom, preferably from about 100-150 eV, to cause
dense sp.sup.3 C--C bonds to form in the DLC layer. The ions impact
the substrate with this energy which promotes formation of sp.sup.3
carbon-carbon bonds. The impact energy of the energetic carbon ions
may be within a range to promote formation of the desired lattice
structure, such bonds in an interfacing portion (e.g. layer 8 in
the FIG. 1 embodiment) of coating 3 apparently being formed at
least in part by subimplantation into the substrate as shown in
FIG. 7. The stream may be optionally composed of ions having
approximately uniform weight, so that impact energy will be
approximately uniform. Effectively, the energetic ions impact on
the growing film surface and/or substrate 1 and are driven into the
growing film and/or substrate 1 to cause densification. Coating 3,
and especially layer 7, are preferably free of pinholes, to achieve
satisfactory water repulsion and suppression of soda diffusion.
[0069] Thus, the C--C sp.sup.3 bonding is preferably formed by
having a predetermined range of ion energy prior to reaching
substrate 1, or prior to reaching ta-C growing on the substrate.
The optimal ion energy window for ta-C layer 7 formation in the
FIGS. 1 and 2 embodiments is from about 100-200 eV (preferably from
about 100-150 eV, and most preferably from about 100-140 eV) per
carbon ion. At these energies, films 7 (i.e. layer 3 in the FIG. 2
embodiment) emulate diamond.
[0070] However, compressive stresses can develop in ta-C when being
deposited at 100-150 eV. Such stress can reach as high as 10 Gpa
and can potentially cause delamination from many substrates. It has
been found that these stresses can be controlled and decreased by
increasing the ion energy the deposition process to a range of from
about 200-1,000 eV. The plasma ion beam source enables ion energy
to be controlled within different ranges in an industrial process
for large area deposition utilized herein. The compressive stress
in amorphous carbon is thus decreased significantly at this higher
ion energy range of 200-1,000 eV.
[0071] High stress is undesirable in the thin interfacing portion 8
of coating 3 that directly contacts the surface of a glass
substrate 1. Thus, for example, the first 1-40% thickness
(preferably the first 1-20% and most preferably the first 5-10%
thickness) 8 of coating 3 is deposited on substrate 1 using high
anti-stress energy levels of from about 200-1,000 eV, preferably
from about 400-500 eV. Then, after this initial interfacing portion
8 of coating 3 has been grown, the ion energy in the ion deposition
process is decreased (either quickly or gradually while deposition
continues) to about 100-200 eV, preferably from about 100-150 eV,
to grow the remainder ta-C layer 7 of coating 3.
[0072] For example, assume for exemplary purposes only with
reference to FIG. 1 that DLC coating 3 is 100 .ANG. thick. The
first 10 .ANG. layer 8 of coating 3 (i.e. interfacing portion 8)
may be deposited using an ion energy of from about 400 to 500 eV so
that layer 8 of coating 3 that contacts the surface of substrate 1
has reduced compressive stresses relative to the remainder 7 of
coating 3. Interfacing portion 8 of coating 3 at least partially
subimplants into the surface of substrate 1 to allow intermixing
with the glass surface. In certain embodiments, only C ions are
used in the deposition of interfacing layer 8, with the graded
composition interface being mainly SiC. This interface 8 between
substrate 1 and coating 3 improves adhesion of coating 3 to
substrate 1 and the gradual composition change distributes strain
in the interfacial region instead of narrowly concentrating it.
Layer 8 of DLC coating 3 may or may not have a density of at least
about 2.4 grams per cubic centimeter in different embodiments, and
may or may not have at least about 35%, 70%, or 80% sp.sup.3
carbon-carbon bonds in different embodiments. After the first 10
.ANG. (i.e. layer 8) of coating 3 has been deposited, then the ion
energy is gradually or quickly decreased to 100 to 150 eV for the
remainder [may be either ta-C or ta-C:H] 7 of coating 3 so that
layer 7 has a higher density and a higher percentage of sp.sup.3
C--C bonds than layer 8.
[0073] Thus, in certain embodiments, because of the adjustment in
ion energy during the deposition process, ta-C coating 3 in FIGS.
1-3 has different densities and different percentages of sp.sup.3
C--C bonds at different areas therein. However, at least a portion
of coating 3 is a highly tetrahedral ta-C layer 7 having a density
of at least about 2.4 grams per cubic centimeter and at least about
35% sp.sup.3. The highly tetrahedral ta-C portion is the portion
furthest from substrate 1 in FIG. 1, but may optionally be at other
areas of coating 3. In a similar manner, the portion of coating 3
having a lesser percentage of sp.sup.3 C--C bonds is preferably the
portion immediately adjacent substrate 1 (e.g. interfacing layer
8).
[0074] In certain embodiments, CH.sub.4 may be used as a feedstock
gas during the deposition process instead of or in combination with
the aforesaid C.sub.2H.sub.2 gas.
[0075] Referring to FIG. 8, it is noted that the surface of a glass
substrate has tiny cracks or microcracks defined therein. These
cracks may weaken glass by orders of magnitude, especially when
water seeps therein and ruptures further bonds. Thus, another
advantage of this invention is that in certain embodiments
amorphous carbon atoms and/or networks of layer 7 or 8 fill in or
collect in these small cracks because of the small size of carbon
atoms (e.g. less than about 100 pm radius atomic, most preferably
less than about 80 pm, and most preferably about 76.7 pm) and
because of the ion energy of 200 to 1,000 eV, preferably about
400-500 eV, and momentum. This increases the mechanical strength of
the glass. The nano cracks in the glass surface shown in FIG. 8 may
sometimes be from about 0.4 nm to 1 nm is in width. The inert
nature and size of the carbon atoms in these nonocracks will
prevent water from attacking bonds at the crack tip 14 and
weakening the glass. The carbon atoms make their way to positions
adjacent the tips 14 of these cracks, due to their size and energy.
Tips 14 of these cracks are, typically, from about 0.5 to 50 nm
below the glass substrate surface. The top surface of layers 7
and/or 8 remains smooth and/or approximately flat within about less
than 1.0 nm even above the cracks.
[0076] Carbon is now described generally, in many of its forms, to
aid in the understanding of this invention.
[0077] Carbon has the ability to form structures based on directed
covalent bonds in all three spatial dimensions. Two out of the six
electrons of a carbon atom lie in the 1s core and hence do not
participate in bonding, while the four remaining 2s and 2p
electrons take part in chemical bonding to neighboring atoms. The
carbon atom's one 2s and three 2p electron orbitals can hybridise
in three different ways. This enables carbon to exist as several
allotropes. In nature, three allotropic crystalline phase exists,
namely diamond, graphite and the fullerenes and a plethora of
non-crystalline forms.
[0078] For the diamond crystalline allotrope, in tetrahedral or
sp.sup.3 bonding all the four bonding electrons form .sigma. bonds.
The space lattice in diamond is shown in FIG. 4 where each carbon
atom is tetrahedrally bonded to four other carbon atoms by .sigma.
bonds of length 0 154 nm and bond angle of 109.degree. 53". The
strength of such a bond coupled with the fact that diamond is a
macromolecule (with entirely covalent bonds) give diamond unique
physical properties: high atomic density, transparency, extreme
hardness, exceptionally high thermal conductivity and extremely
high electrical resistivity (10.sup.16 .OMEGA.-cm)
[0079] The properties of graphite are governed by its trigonal
bonding. The outer 2s, 2p.sub.x and 2p.sub.y orbitals hybridise in
a manner to give three co-planar sp.sup.2 orbitals which form a
bonds and a p-type n orbital 2p.sub.z perpendicular to the sp.sup.2
orbital plane, as shown in FIG. 5. Graphite consists of hexagonal
layers separated from each other by a distance of 0.34 nm. Each
carbon atom is bonded to three others by 0.142 nm long .sigma.
bonds within an hexagonal plane. These planes are held together by
weak van der Waals bonding which explains why graphite is soft
along the sp.sup.2 plane.
[0080] As for fullerenes, it is known that C.sub.60 and C.sub.70
are the most accessible members of the family of closed-cage
molecules called fullerenes, formed entirely of carbon in the
sp.sup.2 hybridised state. Each fullerenes C.sub.n consists of 12
pentagonal rings and m hexagonal rings such that m=(n-20)/2
(satisfying Euler's Theorem). The .sigma. bonds are wrapped such
that the fullerene has a highly strained structure and the molecule
is rigid.
[0081] As for amorphous carbon, there exists a class of carbon in
the metastable state without any long range order. Material
properties change when using different deposition techniques or
even by varying the deposition parameters within a single
technique. In this category of materials on one extreme we have
ta-C (e.g. layer 7) which is the most diamond-like with up to 90%
C--C sp.sup.3 bonding in certain preferred embodiments and on the
other a-C (amorphous carbon), produced by thermal evaporation of
carbon, in which more than 95% graphitic bonds are prevalent. In
this respect, these two materials reflect the intrinsic diversity
of non-crystalline forms of carbon.
[0082] Amorphous materials, such as layer(s) 3, 7 and 8, are
metastable solids. In an amorphous solid there exists a set of
equilibrium positions about which atoms oscillate. The atoms in an
amorphous material are often extended into a three dimensional
network with the absence of order beyond the second nearest
neighbor distance.
[0083] Referring again to ta-C layer 7, the sp.sup.3/sp.sup.2 C--C
bonded fraction or percentage (%), e.g. in a vacuum arc deposition
technique or techniques used in the '477 patent or deposition
techniques discussed above, can be controlled by changing the
energy of the incident C.sup.+ ions. The films deposited being
metastable in nature are under high compressive stress. The
sp.sup.2 hybridised carbon atoms are clustered and embedded within
a sp.sup.3 matrix. The extent of the latter bonding confers onto
ta-C its diamond-like physical properties. The fraction of the
sp.sup.2 hybridised atoms determines the extent of clustering. The
degree of clustering, which is seen as a strain relief mechanism,
implies that the .pi. and .pi.* states become delocalised to such
an extent that they control the electronic and optical properties
of the films. At high density of states, the .pi. bands merge with
the .sigma. states to form the conduction and valence mobility
band-edges. Their lower density tail states are localised giving a
pseudo-gap. The term "tetrahedral amorphous carbon (ta-C)" is thus
used to distinguish this highly tetrahedral material from other
"diamond-like carbon" which have C--C correlations mostly of the
sp.sup.2 type.
[0084] The sp.sup.3 bonding in coatings 3 is believed to arise from
a densification process under energetic ion bombardment conditions.
Hybridisation of the carbon atom is expected to adjust to the local
density, becoming more sp.sup.3 if the density is high and more
sp.sup.2 if low. This can occur if an incident ion penetrates the
first atomic layer and then enters an interstitial subsurface
position. The local bonding then reforms around this atom and its
neighbours to adopt the most appropriate hybridisation. High energy
ions in principle can penetrate the surface layer of the substrate
or growing DLC, increase the density of deeper layers which then
forces sp.sup.3 bonding. Ions of lower energy than the penetration
threshold only append to the surface forming sp.sup.2 bonded
a-C.
[0085] Coated articles according to any of the aforesaid
embodiments may be used, for example, in the context of automotive
windshields, automotive back windows, automotive side windows,
architectural glass, IG glass units, is residential or commercial
windows, and the like.
[0086] In any of the aforesaid embodiments, a layer of non-porous
tungsten disulfide (WS.sub.2) 12 may be provided on top of layer 7
to prevent the DLC from burning off upon exposure to air if taken
to high temperatures after the coating deposition. Layer 12 (e.g.
see FIG. 8) may be applied by plasma spraying to a thickness of
from about 300 to 10,000 .ANG.. WS.sub.2 layer 12 is removeable in
certain embodiments. Other suitable materials may instead be used
for layer 12.
[0087] Once given the above disclosure, many other features,
modifications, and improvements will become apparent to the skilled
artisan. Such other features, modifications, and improvements are,
therefore, considered to be a part of this invention, the scope of
which is to be determined by the following claims.
* * * * *