U.S. patent application number 09/927507 was filed with the patent office on 2002-01-24 for hydrophobic coating including dlc on substrate.
This patent application is currently assigned to Guardian Industries Corporation. Invention is credited to Veerasamy, Vijayen S..
Application Number | 20020009593 09/927507 |
Document ID | / |
Family ID | 23758218 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020009593 |
Kind Code |
A1 |
Veerasamy, Vijayen S. |
January 24, 2002 |
Hydrophobic coating including DLC on substrate
Abstract
A substrate is coated with a hydrophobic coating that includes
highly tetrahedral amorphous carbon that is a form of diamond-like
carbon (DLC). In certain embodiments, the coating is deposited on
the substrate in a manner to increase its hydrophobicity (e.g. so
that the coating has an initial contact angle .theta. of at least
about 100 degrees; and/or a surface energy of no more than about
20.2 mN/m). In certain embodiments, the coating is deposited in a
manner such that it has an average hardness of at least about 10
GPa, more preferably from about 20-80 GPa.
Inventors: |
Veerasamy, Vijayen S.;
(Farmington Hills, MI) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
1100 North Glebe Road, 8th Floor
Arlington
VA
22201-4714
US
|
Assignee: |
Guardian Industries
Corporation
|
Family ID: |
23758218 |
Appl. No.: |
09/927507 |
Filed: |
August 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09927507 |
Aug 13, 2001 |
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09442805 |
Nov 18, 1999 |
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09442805 |
Nov 18, 1999 |
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09303548 |
May 3, 1999 |
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6261693 |
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Current U.S.
Class: |
428/408 ;
428/426; 428/428 |
Current CPC
Class: |
B08B 17/06 20130101;
C03C 2217/78 20130101; C03C 17/3652 20130101; B32B 17/1033
20130101; B32B 17/10577 20130101; C03C 3/076 20130101; B05D 5/083
20130101; C03C 17/3644 20130101; Y10T 428/265 20150115; C03C 17/366
20130101; C03C 17/22 20130101; B62D 35/007 20130101; C03C 17/36
20130101; B60S 1/58 20130101; B60S 1/54 20130101; C03C 2217/76
20130101; C03C 2218/151 20130101; C03C 2217/282 20130101; C03C
23/0075 20130101; C03C 17/3634 20130101; C03C 17/3441 20130101;
Y10T 428/24942 20150115; Y02T 10/82 20130101; B08B 17/065 20130101;
Y10T 428/30 20150115; B32B 17/10018 20130101; C03C 2218/31
20130101 |
Class at
Publication: |
428/408 ;
428/426; 428/428 |
International
Class: |
B32B 017/06 |
Claims
I claim:
1. A coated glass article comprising: a 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 hydrophobic
coating including diamond-like carbon (DLC) and sp.sup.3
carbon-carbon bonds provided on said glass substrate; and wherein
said hydrophobic coating has an initial contact angle .theta. with
a sessile drop of water thereon of at least about 100 degrees, and
an average hardness of at least about 10 GPa.
2. The coated glass article of claim 1, wherein said initial
contact angle is at least about 110 degrees.
3. The coated glass article of claim 2, wherein said initial
contact angle is at least about 115 degrees.
4. The coated glass article of claim 2, wherein said initial
contact angle is at least about 125 degrees.
5. The coated glass article of claim 1, wherein said coating has a
surface energy Y.sub.C of less than or equal to about 20.2
mN/m.
6. The coated glass article of claim 1, wherein said coating has a
surface energy Y.sub.C of less than or equal to about 19.5
mN/m.
7. The coated glass article of claim 1, wherein said coating has a
surface energy Y.sub.C of less than or equal to about 18.0 mN/m,
and wherein the refractive index "n" of said coating is from about
1.5 to 1.7.
8. The coated glass article of claim 1, wherein said coating is in
direct contact with said glass substrate.
9. The coated glass article of claim 1, further comprising a
DLC-inclusive layer disposed between said coating and said glass
substrate.
10. The coated glass article of claim 1, further comprising a low-E
layer disposed between said coating and said glass substrate.
11. The coated glass article of claim 1, 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.
12. The coated glass article of claim 1, wherein said hydrophobic
coating has an average hardness of at least about 20 GPa.
13. The coated glass article of claim 12, wherein said hydrophobic
coating has an average hardness of from about 20-80 GPa.
14. The coated glass of claim 1, wherein said hydrophobic coating
has a thickness of from about 100 -500 .ANG..
15. The coated glass article of claim 1, wherein the coated glass
article comprises the following characteristics:
4 visible transmittance (Ill. A): >60% UV transmittance: <38%
IR transmittance: <35%.
16. The coated glass article of claim 1, wherein said hydrophobic
coating includes sp.sup.3 carbon-carbon bonds subimplanted in a
surface of said glass substrate so as to strongly bond said coating
to said glass substrate.
17. The coated glass article of claim 1, wherein at least about 50%
of carbon-carbon bonds in said hydrophobic coating are highly
tetrahedral sp.sup.3 carbon-carbon bonds.
18. A coated article comprising: a substrate; a coating including
diamond-like carbon (DLC) provided on said substrate, said coating
including sp.sup.3 carbon-carbon bonds; and wherein said coating
has an initial contact angle .theta. with a drop of water of at
least about 100 degrees, and an average hardness of at least about
10 GPa.
19. The coated article of claim 18, wherein said initial contact
angle is at least about 110 degrees, and wherein said substrate is
substantially transparent to visible light.
20. The coated article of claim 18, wherein said substrate is one
of glass and plastic.
21. A coated glass article comprising: a glass substrate; and a
hydrophobic coating including diamond-like carbon (DLC) provided on
said glass substrate, wherein said hydrophobic coating has an
initial contact angle .theta. with a drop of water of at least
about 110 degrees, and an average hardness of at least about 10
GPa.
22. The coated glass article of claim 21, wherein said initial
contact angle is at least about 115 degrees.
23. The coated glass article of claim 22, wherein said initial
contact angle is at least about 125 degrees.
24. The coated glass article of claim 21, wherein said coating has
a surface energy Y.sub.C of less than or equal to about 20.2
mN/m.
25. The coated glass article of claim 24, wherein said coating has
a surface energy Y.sub.C of less than or equal to about 18.0
mN/m.
26. The coated glass article of claim 21, wherein said hydrophobic
coating is one of: (i) in direct contact with said glass substrate,
and (ii) on said glass substrate in a manner such that at least one
low-E layer is disposed between said substrate and said hydrophobic
coating.
27. The coated glass article of claim 21, wherein said hydrophobic
coating has an average hardness of from about 20-80 GPa.
28. The coated glass article of claim 27, wherein the coated glass
article comprises the following characteristics:
5 visible transmittance (Ill. A): >60% UV transmittance: <38%
IR transmittance: <35%.
29. The coated glass article of claim 21, wherein at least about
50% of carbon-carbon bonds in said hydrophobic coating are highly
tetrahedral sp.sup.3 carbon-carbon bonds.
30. The coated glass article of claim 21, wherein the outermost
10.ANG. layer portion of coating 3 includes in atomic percentage:
from about 5-60% carbon (C), from about 0-40% oxygen (O) , from
about 0-40% silicon (Si) , from about 10-95% hydrogen (H), and from
about 0-10% fluorine (F).
31. The coated glass article of claim 21, wherein at least one
10.ANG. thick layer portion of the coating includes in atomic
percentage: from about 15-80% carbon (C), from about 5-45% oxygen
(O), from about 5-45% silicon (Si), from about 0-30% hydrogen (H),
and from about 0-10% fluorine (F).
32. The coated glass article of claim 21, wherein a ratio of carbon
(C) to silicon (Si) in said coating is from about 1:1 to 4:1.
33. The coated glass article of claim 21, wherein the outermost
5.ANG. layer portion of said coating includes in atomic percentage
at least about 25% H.
34. A coated glass article comprising: a glass substrate; and a
coating including diamond-like carbon (DLC) provided on said glass
substrate, wherein the outermost 5.ANG. of said coating includes in
atomic percentage at least about 50% H.
35. The coated glass article of claim 34, wherein said coating has
an initial contact angle .theta. of at least about 110 degrees, and
an average hardness of at least about 10 GPa.
36. The coated glass article of claim 34, wherein said coating has
a surface energy Y.sub.C of less than or equal to about 18.0
mN/m.
37. A method of making a coated article, the method comprising the
steps of: providing a substrate; and depositing a highly
tetrahedral amorphous carbon (ta-C) inclusive coating having more
sp.sup.3 carbon-carbon bonds than sp.sup.2 carbon-carbon bonds on
the substrate in a manner such that the ta-C inclusive coating has
an initial contact angle .theta. of at least about 100 degrees.
38. The method of claim 36, further comprising depositing the ta-C
inclusive coating in a manner such that the ta-C inclusive coating
has an initial contact angle .theta. of at least about 115
degrees.
39. The method of claim 37, further comprising plasma treating an
outmost surface of the coating in order to provide at least H atoms
in the coating proximate the outermost surface thereof, so as to
reduce surface energy of the coating.
40. The method of claim 37, wherein said depositing step is carried
out using at least plasma ion beam deposition.
41. The method of claim 40, wherein said depositing step includes
using at least one of H.sub.2 and acetylene feedstock gas.
42. The method of claim 40, wherein said depositing step includes
varying ion energy within a range of from about 100 to 800 eV
during said depositing so that the coating has different layer
portions having different densities.
43. 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 1,000
.ANG. and a substantial number of sp.sup.3 carbon-carbon bonds;
wherein the automotive window comprises the following optical
characteristics:
6 visible transmittance: >70% UV transmittance: <38% IR
transmittance: <35%;
wherein said coating has an initial contact angle of at least about
100 degrees.
44. The automotive window of claim 43, 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.
45. A coated glass article comprising: a glass substrate; at least
one hydrophobic coating including diamond-like carbon (DLC)
provided on said substrate; and wherein at least one 10.ANG. thick
layer portion of said hydrophobic coating includes, in atomic
percentage, from about 15-80% carbon (C), from about 5-45% oxygen
(O), from about 5-45% silicon (Si), from about 0-30% hydrogen (H),
and from about 0-10% fluorine (F).
46. The coated glass article of claim 45, wherein a ratio of carbon
(C) to silicon (Si) in at least one portion of said coating is
approximately 1:1.
47. A coated article comprising: a glass substrate; a coating
including diamond-like carbon (DLC) provided on said glass
substrate, said coating including sp.sup.3 carbon-carbon bonds; and
wherein said coating is doped so as to have an index of refraction
"n" of no greater than about 1.75.
48. The coated article of claim 47, wherein said coating includes
C, Si, and F atoms, and wherein an atomic ratio of C to Si in said
coating may be from about 1:1 to 4:1.
49. A method of cleaning a glass substrate comprising the steps of:
providing a linear ion beam source; directing an ion beam from the
source toward the glass substrate in a manner so that impurities on
a surface of the glass substrate are removed by the ion beam; and
said directing step being performed in a manner so as to create
free radicals on the surface of the substrate.
Description
[0001] This is a continuation-in-part (CIP) of U.S. patent
application Ser. No. 09/303,548, filed May 3, 1999, the disclosure
of which is hereby incorporated herein by reference.
[0002] This invention relates to a hydrophobic coating including
diamond-like carbon (DLC) provided on (directly or indirectly) a
substrate of glass, plastic, or the like, and a method of making
the same. The coating may be deposited on the substrate utilizing
plasma ion beam deposition in certain embodiments.
BACKGROUND OF THE INVENTION
[0003] Conventional soda inclusive glasses are susceptible to
environmental corrosion which occurs when sodium (Na) diffuses from
or leaves the glass interior, as well as to retaining water on
their surfaces in many different environments, including when used
as automotive windows (e.g. backlites, side windows, and/or
windshields). When water is retained or collects on automotive
windows, the water may freeze (i.e. forming ice) in certain
environments. Additionally, the more water retained on a
windshield, the higher power wiper motor(s) and/or wiper blade(s)
required.
[0004] In view of the above, it is apparent that there exists a
need in the art for (i) a coated article (e.g. coated glass or
plastic substrate) that can repel water and/or dirt, and a method
of making the same, (ii) a coated soda inclusive glass where the
coating(s) reduces the likelihood of visible stains/corrosion
forming; and/or (iii) a protective hydrophobic coating for window,
glass, or plastic substrates that is somewhat resistant to
scratching, damage, or the like.
[0005] 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. Unfortunately, the DLC of the '353 patent would
not be-an efficient hydrophobic coating and/or would not be an
efficient corrosion minimizer on glass in many instances.
[0006] U.S. Pat. No. 5,900,342 to Visser et al. discloses a
fluorinated DLC layer on an electrophotographic element. From about
25-65% fluorine content by atomic percentage is provided at an
outermost surface, to provide for low surface energy in an attempt
to make removal of xerographic toner easier. Unfortunately, this
DLC inclusive layer of the '342 patent would be too soft for use on
a glass substrate in automotive applications and the like. Its
apparent lack of SP C--C bonds and/or lack of Si--O bonds
contribute to its softness. It is also believed that continuous
exposure to sun, rain, humidity, dust, windshield wipers, and/or
the environment in general would cause the '342 DLC layer to break
down or degrade rather quickly over time.
[0007] Thus, there also exists a need in the art for a DLC
inclusive layer that has sufficient hardness and durability to
withstand the environment while still exhibiting satisfactory
hydrophobic qualities.
[0008] 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
[0009] An object of this invention is to provide a durable coated
article that can shed or repel water (e.g. automotive windshield,
automotive backlite, automotive side window, architectural window,
etc.).
[0010] Another object of this invention is to provide a coated
substrate, wherein a coating includes sp.sup.3 carbon-carbon bonds
and has a wettability W with regard to water of less than or equal
to about 23 mN/m, more preferably less than or equal to about 21
mN/m, and most preferably less than or equal to about 20 mN/m, and
in most preferred embodiments less than or equal to about 19
mN/meter. This can also be explained or measured in Joules per unit
area (mJ/m.sup.2)
[0011] Another object of this invention is to provide a coated
substrate, wherein a coating includes sp.sup.3 carbon-carbon bonds
and has a surface energy Y.sub.C of less than or equal to about
20.2 mN/m, more preferably less than or equal to about 19.5 mN/m,
and most preferably less than or equal to about 18 mN/m.
[0012] Another object of this invention is to provide a coated
substrate, wherein a DLC inclusive coating has an initial (i.e.
prior to being exposed to environmental tests, rubbing tests, acid
tests, UV tests, or the like) water contact angle .theta. of at
least about 100 degrees, more preferably of at least about 110
degrees, even more preferably of at least about 115 degrees, and
most preferably of at least about 125 degrees.
[0013] Another object of this invention is to provide a coating for
a substrate, wherein at least about 15% (more preferably at least
about 25%, and most preferably at least about 30%) of the bonds in
the coating are sp.sup.3 carbon-carbon (C--C) bonds; and wherein
the coating includes by atomic percentage at least about 5% silicon
(Si) atoms (more preferably at least about 15%, and most preferably
at least about 20% Si), at least about 5% oxygen (O) atoms (more
preferably at least about 15% and most preferably at least about
20%), at least about 5% hydrogen (H) atoms (more preferably at
least about 10% and most preferably at least about 15%) taking into
consideration either the coating's entire thickness or only a thin
layer portion thereof. In certain embodiments, an increased
percentage of H atoms may be provided near the coating's outermost
surface. In certain embodiments, the coating has approximately the
same amount of C and Si atoms.
[0014] Another object of this invention is to provide a coating for
a glass substrate, wherein the coating includes a greater number of
Sp.sup.3 carbon-carbon (C--C) bonds than sp.sup.2 carbon-carbon
(C--C) bonds. In certain of these embodiments, the coating need not
include any sp.sup.2 carbon-carbon (C--C) bonds.
[0015] 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
substantially chemically inert).
[0016] Another object of this invention is to provide a coated
glass article that is abrasion resistant.
[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 portion
proximate a mid-section of the coating having a higher density of
Sp.sup.3 carbon-carbon (C--C) bonds. The outermost layer portion at
the surface of the coating may be doped (e.g. addition of Si, O
and/or F) so that this surface portion of the coating is less dense
which increases contact angle and decreases the dispersive
component of surface energy so as to improve hydrophobic
characteristics of the coating.
[0018] Another object of this invention is to manufacture a coating
having hydrophobic qualities wherein the temperature of an
underlying glass substrate may be less than about 200.degree. C.,
preferably less than about 150.degree. C., most preferably less
than about 80.degree. C., during the deposition of a DLC inclusive
coating. This reduces graphitization during the deposition process,
as well as reduces detempering and/or damage to low-E coatings
already on the substrate in certain embodiments.
[0019] Generally speaking, this invention fulfills any or all of
the above described needs or objects by providing a coated article
comprising:
[0020] a substrate (e.g. glass or plastic);
[0021] a coating including diamond-like carbon (DLC) provided on
said substrate, said coating including sp.sup.3 carbon-carbon
bonds; and
[0022] wherein said coating has an initial contact angle .theta.
with a drop of water of at least about 100 degrees, and an average
hardness of at least about 10 GPa.
[0023] This invention further fulfills any or all of the above
described needs and/or objects by providing a coated glass article
comprising:
[0024] a glass substrate; and
[0025] a coating including diamond-like carbon (DLC) provided on
said glass substrate, wherein the outermost 5.ANG. of said coating
includes in atomic percentage at least about 50% H.
[0026] This invention further fulfills any or all of the above
described needs and/or objects by providing a coated glass article
comprising:
[0027] a glass substrate comprising, on a weight basis:
[0028] SiO.sub.2 from about 60-80%,
[0029] Na.sub.2O from about 10-20%,
[0030] CaO from about 0-16%,
[0031] K.sub.2O from about 0-10%,
[0032] Mgo from about 0-10%,
[0033] Al.sub.2O.sub.3 from about 0-5%;
[0034] a hydrophobic coating including diamond-like carbon (DLC)
and sp.sup.3 carbon-carbon bonds provided on said glass substrate;
and
[0035] wherein said hydrophobic coating has an initial contact
angle .theta. with a sessile drop of water of at least about 100
degrees, and an average hardness of at least about 10 GPa.
[0036] This invention further fulfills any or all of the above
described needs and/or objects by providing a method of making a
coated article, the method comprising the steps of:
[0037] providing a substrate; and
[0038] depositing a highly tetrahedral amorphous carbon (ta--C)
inclusive coating having more sp.sup.3 carbon-carbon bonds than sp2
carbon-carbon bonds on the substrate in a manner such that the
ta--C inclusive coating has an initial contact angle .theta. of at
least about 100 degrees.
[0039] In certain embodiments, the method includes plasma treating
an outmost surface of the coating in order to provide at least H
atoms in the coating proximate the outermost surface thereof so as
to reduce surface energy of the coating.
[0040] This invention will now be described with respect to certain
embodiments thereof, along with reference to the accompanying
illustrations.
IN THE DRAWINGS
[0041] FIG. 1 is a side cross sectional view of a coated article
according to an embodiment of this invention, wherein a glass or
plastic substrate is provided with a DLC inclusive coating thereon
having hydrophobic qualities.
[0042] FIG. 2 is a side cross sectional view of a coated article
according to another embodiment of this invention, wherein first
and second DLC inclusive coatings are provided on a substrate of
glass or plastic.
[0043] 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
hydrophobic DLC inclusive coating(s) 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.
[0044] FIG. 4 illustrates exemplar sp.sup.3 orbitals of carbon in a
tetrahedral state.
[0045] FIG. 5 illustrates exemplar orbitals of carbon in a sp.sup.2
state (i.e. graphitic).
[0046] FIG. 6 illustrates exemplar sp hybridizations of a carbon
atom.
[0047] FIG. 7 is a side cross sectional view of carbon ions
penetrating the substrate or growing DLC coating surface so as to
strongly bond a DLC layer to an underlying DLC layer or other
substrate according to any embodiment herein.
[0048] FIG. 8 is a side cross sectional view of a coated glass
substrate according to an embodiment of this invention,
illustrating at least DLC bonds of the coating penetrating cracks
in the surface of a glass substrate.
[0049] FIG. 9 is a perspective view of a linear ion beam source
which may be used in any embodiment of this invention for
depositing a DLC inclusive coating.
[0050] FIG. 10 is a cross sectional view of the linear ion beam
source of FIG. 9.
[0051] FIG. 11 is a side cross sectional partially schematic view
illustrating a low contact angle .theta. of a drop on a glass
substrate.
[0052] FIG. 12 is a side cross sectional partially schematic view
illustrating-the coated article of the FIG. 1 embodiment and the
contact angle .theta. of a water drop thereon.
[0053] FIG. 13 is a schematic diagram of an assembly for
manufacturing a coated article according to an embodiment of this
invention.
[0054] FIG. 14 is a binding energy (eV) versus counts graph of a
coated article according to an embodiment of this invention, taken
by x-ray photo electron spectroscopy (XPS).
[0055] FIG. 15 is a binding energy (eV) versus counts graph of the
coated article of FIG. 14 in another eV region, taken by XPS.
[0056] FIG. 16 is a wavelength (nm) versus index of refraction (n)
and extinction coefficient (k) according to an embodiment of this
invention.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THIS INVENTION
[0057] Referring now more particularly to the accompanying drawings
in which like reference numerals indicate like elements throughout
the accompanying views.
[0058] FIG. 1 is a side cross sectional view of a coated article
according to an embodiment of this invention, wherein at least one
diamond-like carbon (DLC) inclusive protective coating(s) 3 is
provided directly on substrate 1. Substrate 1 may be of glass,
plastic, or the like. DLC inclusive coating 3 in the FIG. 1
embodiment includes at least one layer including highly tetrahedral
amorphous carbon (ta--C). Coating 3 functions in a hydrophobic
manner (i.e. it is characterized by high water contact angles
.theta. and/or low surface energies as described below). In certain
embodiments, coating 3 may be from about 50-1,000.ANG. thick, more
preferably from about 100-500.ANG. thick, and most preferably from
about 150-200.ANG. thick.
[0059] In certain embodiments, hydrophobic coating 3 may have an
approximately uniform distribution of sp.sup.3 carbon-carbon bonds
throughout a large portion of its thickness, so that much of the
coating has approximately the same density. In other more preferred
embodiments, hydrophobic coating 3 may include a lesser percentage
of sp.sup.3 carbon-carbon bonds near the interface with substrate
1, with the percentage or ratio of sp.sup.3 carbon-carbon bonds
increasing throughout the thickness of the coating toward the
outermost surface. Thus, coating 3 may include at least one
interfacing layer directly adjacent substrate 1, this interfacing
layer having a lesser density and a lesser percentage of sp.sup.3
carbon-carbon bonds than the middle portion of DLC inclusive
coating 3. In general, the network of sp.sup.3 carbon-carbon bonds
functions to hold the other atoms (e.g. Si, O, F, and/or H atoms)
around it in the coating. In certain embodiments, it is desired to
keep number of sp.sup.2 carbon-carbon bonds throughout the entire
thickness of the coating to no greater than about 25%, more
preferably no greater than about 10%, and most preferably from
about 0-5%, as these type bonds are hydrophillic in nature and
attract water and the like. Thus, in preferred embodiments, at
least about 50% (more preferably at least about 75%, and most
preferably at least about 90%) or the carbon-carbon bonds in
coating 3 are of the sp.sup.3 carbon-carbon type.
[0060] The presence of sp.sup.3 carbon-carbon bonds in coating 3
increases the density and hardness of the coating, thereby enabling
it to satisfactorily function in automotive environments. In
certain embodiments, taking only a thin layer portion of, or
alternatively the entire thickness of, coating 3 into
consideration, at least about 15% (more preferably at least about
25%, and most preferably at least about 30%) of the bonds in the
coating or coating layer portion are sp.sup.3 carbon-carbon (C--C)
bonds (as opposed to sp.sup.2 carbon-carbon bonds). Coating may or
may not include sp.sup.2 carbon-carbon bonds in different
embodiments (if so, most sp.sup.2 carbon-carbon bonds may be
provided at the portion of the coating interfacing with the
underlying substrate).
[0061] In order to improve the hydrophobic nature of coating 3,
atoms other than carbon (C) are provided in the coating in
different amounts in different embodiments. For example, in certain
embodiments of this invention coating 3 (taking the entire coating
thickness, or only a thin 10.ANG. thick layer portion thereof into
consideration) may include in addition to the carbon atoms of the
sp.sup.3 carbon-carbon bonds, by atomic percentage, at least about
5% silicon (Si) atoms (more preferably at least about 15%, and most
preferably at least about 20% Si), at least about 5% oxygen (O)
atoms (more preferably at least about 15% and most preferably at
least about 20% O), at least about 5% hydrogen (H) atoms (more
preferably at least about 10% and most preferably at least about
15% H). In certain preferred embodiments, the atomic percentage of
C and Si atoms in coating 3 are approximately equal. Optionally,
coating 3 may include and from about 0-10% (atomic percentage)
fluorine (F) (more preferably from about 0-5% F) in order to
further enhance hydrophobic characteristics of the coating.
[0062] In certain embodiments, the outermost thin layer portion of
hydrophobic coating 3 may also include a larger percentage of H
atoms deposited via plasma ion beam treatment relative to the rest
of the coating in order to reduce the number of polar bonds at the
coating's surface, thereby improving the coating's hydrophobic
properties by reducing the polar component of the surface energy.
For example, in certain embodiments the outermost 5.ANG. layer
portion of coating 3 may include at least about 10% H atoms, more
preferably at least about 25% H atoms, and most preferably at least
about 50% H atoms. This higher concentration or percentage of H
atoms near the surface of coating 3 is illustrated in FIGS. 1-3 by
the dots which become more concentrated near the coating's surface.
The deposition of these H atoms near the coating's surface results
in a more passive or non-polar coating surface. It is noted that
deposition of the H atoms near the coating's surface may tend to
etch away any sp.sup.2 or graphite C--C bonds in that area. This
increase in H near the coating's surface also decreases the
coating's density at this outermost 5.ANG. layer portion.
[0063] Accordingly, in certain preferred embodiments of this
invention, coating 3 as a whole or any 10.ANG. thick layer portion
thereof (e.g. a 10.ANG. thick portion near the middle of the
coating) may include in atomic percentage: from about 15-80% carbon
(C) (mostly via sp.sup.3 bonds), from about 5-45% oxygen (O), from
about 5-45% silicon (Si), from about 0-30% hydrogen (H), and from
about 0-10% fluorine (F). The outermost 5.ANG. layer portion of
coating 3 may include in atomic percentage: from about 5-60% carbon
(C) (mostly via sp.sup.3 bonds), from about 0-40% oxygen (O), from
about 0-40% silicon (Si), from about 10-60% hydrogen (H), and from
about 0-10% fluorine (F). As discussed above, additional H may be
provided at the outermost portion of layer 3, largely at the
expense of C, in order to reduce surface energy. An example of a
10.ANG. thick layer portion near the middle of coating 3 is as
follows, by atomic percentage: 35% C, 30% Si, 15% H, and 20% O. An
example of the outermost 5.ANG. thick layer portion of coating 3 is
as follows, by atomic percentage: 20% C, 15% Si, 50% H, and 15% O.
Optionally, in certain preferred embodiments, from about 0-5% F may
also be provided in this outermost 5.ANG. thick layer portion. It
is noted that many of the Si, H, O, and F atoms in the coating are
connected to many carbon atoms via sp.sup.3 bonds. A substantial
number of Si-O, C--C Si-C sp.sup.3, and C-H sp.sup.3 bonds are thus
present. In certain embodiments, the Si-O bonds tend to cancel out
some of the charge due to the carbon thereby reducing surface
energy. The presence of the O also reduces density and permits the
dispersive component of surface energy to be reduced. These
examples are for purposes of example only, and are not intended to
be limiting in any way.
[0064] In certain preferred embodiments, coating 3 has an average
hardness of at least about 10 GPa, more preferably at least about
20 GPa, and most preferably from about 20-50 GPa. Such hardness
renders coating 3 resistant to scratching, solvents, and the like.
It is noted that the hardness and density of coating 3 and/or layer
5 may be adjusted by varying the ion energy of the depositing
apparatus or process described below.
[0065] FIG. 2 is a side cross sectional view of a coated article
according to another embodiment of this invention, including
substrate 1 (e.g. glass), hydrophobic DLC inclusive coating 3 as
described above with regard to the FIG. 1 embodiment, and
intermediate DLC inclusive layer 5 sandwiched therebetween. In
certain embodiments, at least about 35% of the bonds in layer 5 may
be of the sp.sup.3 C--C type, more preferably at least about 70%,
and most preferably at least about 80%. Any of the DLC inclusive
layers described in Ser. No. 09/303,548 (incorporated herein by
reference) may be used as layer 5. In effect, layer 5 may function
in certain embodiments to reduce corrosion of the coated article
(e.g. when the substrate includes Na, or is soda-lime-silica
glass), while overlying coating 3 provides a hydrophobic
function.
[0066] In the FIG. 3 embodiment, a low-E or other coating 7 is
provided between substrate 1 and hydrophobic DLC inclusive coating
3. However, coating 3 is still on substrate 1 in the FIG. 3
embodiment. The term "on" herein means that substrate 1 supports
DLC coating 3 or any layer portion thereof, regardless of whether
or not other layer(s) (e.g. 5, 7) are provided therebetween. Thus,
protective coating 3 may be provided directly on substrate 1 as
shown in FIG. 1, or may be provided on substrate 1 with a low-E or
other coating(s) 5 therebetween as shown in FIGS. 2-3. In still
other embodiments, a low-E coating(s) 7 may be provided between
hydrophobic coating 3 and DLC layer 5 of the FIG. 2
embodiment).
[0067] Exemplar coatings (in full or any portion of these coatings)
that may be used as low-E or other coating(s) 7 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. Silicon oxide and/or silicon
nitride coating(s) may also be used as coating(s) 7.
[0068] As will be discussed in more detail below, highly
tetrahedral amorphous carbon (ta--C) forms sp.sup.3 carbon-carbon
bonds, and is a special form of diamond-like carbon (DLC). The
amounts of sp.sup.3 bonds may be measured using Raman
finger-printing and/or electron energy loss spectroscopy. A high
amount of sp.sup.3 bonds increases the density of a layer, thereby
making it stronger and allowing it to reduce soda diffusion to the
surface of the coated article. However, in certain embodiments,
there is a lesser percentage of such bonds at the outmost layer
portion of coating 3 than at middle areas of the coating, so that H
atoms may be provided in order to improve the coating's hydrophobic
characteristics.
[0069] For purposes of simplicity, FIG. 4 illustrates orbitals of a
C atom in a tetrahedral or sp.sup.3 state (i.e. capable of forming
carbon to carbon sp.sup.3 diamond like bonds) in coating 3 or layer
5. FIG. 5 is an example of Sp.sup.2 C orbitals, and FIG. 6 an
example of sp hybridization of a carbon atom. It would be
recognized by those of skill in the art that the angles shown in
FIGS. 4-5 are for purposes of example only, are not limiting, and
may be changed in different embodiments of this invention. Thus,
regarding FIG. 4 for example, in certain embodiments of this
invention orbitals in C--C sp.sup.3 bonds may be from about 100-120
degrees apart. The angles of FIG. 5 may vary in a similar
manner.
[0070] In certain embodiments, coating 3 is at least about 75%
transparent to or transmissive of visible light rays, preferably at
least about 85%, and most preferably at least about 95%.
[0071] When substrate 1 is of glass, 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. Thus, ta--C inclusive
coating 3 and/or layer 5 reduce 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 percubic 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, Mich., may be used as
substrate 1.
[0072] 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 in certain embodiments.
[0073] 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.
[0074] 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 the outside surface of such a window. 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 architectural window, automotive side window,
vacuum IG window, automotive backlight or back window, etc.) and
other similar environments.
[0075] 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%, and
most preferably greater than about 80%), 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 Pat. No. 5,800,933, as well
as the '008 patent, incorporated herein by reference.
[0076] Hydrophobic performance of coating 3 in any of the above
embodiments is a function of contact angle .theta., surface energy
y, and wettability or adhesion energy W. The surface energy y of
coating 3 may be calculated by measuring its contact angle .theta.
(contact angle .theta. is illustrated in FIGS. 11-12). A sessile
drop 31 of a liquid such as water is placed on the coating as shown
in FIG. 12. A contact angle .theta. between the drop 31 and
underlying coating 31 appears, defining an angle depending upon the
interface tension between the three phases in the point of contact.
Generally, the surface energy Y.sub.C of coating 3 can be
determined by the addition of a polar and a dispersive component,
as follows: Y.sub.C=Y.sub.CP+Y.sub.CD, where Y.sub.CP is the
coating's polar component and Y.sub.CD the coating's dispersive
component. The polar component of the surface energy represents the
interactions of the surface which is mainly based on dipoles, while
the dispersive component represents, for example, van der Waals
forces, based upon electronic interactions. Generally speaking, the
lower the surface energy Y.sub.C of coating 3, the more hydrophobic
the coating and the higher the contact angle .theta..
[0077] Adhesion energy (or wettability) W can be understood as an
interaction between polar with polar, and dispersive with
dispersive forces, between coating 3 and a liquid thereon such as
water. Y.sup.P is the product of the polar aspects of liquid
tension and coating/substrate tension; while Y.sup.P is the product
of the dispersive forces of liquid tension and coating/substrate
tension. In other words, y.sup.P=Y.sub.LP*Y.sub.CP; and
Y.sup.D=Y.sub.LD*Y.sub.CD; where Y.sub.LP is the polar aspect of
the liquid (e.g. water), Y.sub.CP is the polar aspect of coating 3;
Y.sub.LD is the dispersive aspect of liquid (e.g. water), and
Y.sub.CD is the dispersive aspect of coating 3. It is noted that
adhesion energy (or effective interactive energy) W, using the
extended Fowkes equation, may be determined by:
[0078]
W=[Y.sub.LP*Y.sub.CP].sup.1/2+[Y.sub.LD*Y.sub.CD].sup.1/2=Y.sub.1
(1+cos.theta.), where Y.sub.1 is liquid tension and .theta. is the
contact angle. W of two materials (e.g. coating 3 and water
thereon) is a measure of wettability indicative of how hydrophobic
the coating is.
[0079] When analyzing the degree of hydrophobicity of coating 3
with regard to water, it is noted that for water Y.sub.LP is 51
mN/m and Y.sub.LD is 22 mN/m. In certain embodiments of this
invention, the polar aspect Y.sub.CP of surface energy of coating 3
is from about 0 to 0.2 (more preferably variable or tunable between
0 and 0.1) and the dispersive aspect Y.sub.CD of the surface energy
of coating 3 is from about 16-22 mN/m (more preferably from about
16-20 mN/m).
[0080] Using the above-listed numbers, according to certain
embodiments of this invention, the surface energy Y.sub.C of
coating 3 is less than or equal to about 20.2 mN/m, more preferably
less than or equal to about 19.5 mN/m, and most preferably less
than or equal to about 18.0 mN/m; and the adhesion energy W between
water and coating 3 is less than about 25 mN/m, more preferably
less than about 23 mN/m, even more preferably less than about 20
mN/m, and most preferably less than about 19 mN/m. These low values
of adhesion energy W and coating 3 surface energy Y.sub.C, and the
high initial contact angles .theta. achievable, illustrate the
improved hydrophobic nature of coatings 3 according to different
embodiments of this invention.
[0081] The initial contact angle .theta. of a conventional glass
substrate 1 with sessile water drop 31 thereon is typically from
about 22-24 degrees, as illustrated in FIG. 11. Thus, conventional
glass substrates are not particularly hydrophobic in nature. The
provision of coating(s) 3 on substrate 1 causes the contact angle
.theta. to increase to the angles discussed above, as shown in FIG.
12 for example, thereby improving the hydrophobic nature of the
article. As discussed in Table 1 of 09/303,548, the contact angle
.theta. of a ta--C DLC layer is typically from about 5 to 50
degrees. However, the makeup of DLC-inclusive coating 3 described
herein enables the initial contact angle .theta. between coating 3
and a water drop (i.e. sessile drop 31 of water) to be increased in
certain embodiments to at least about 100 degrees, more preferably
at least about 110 degrees, even more preferably at least about 115
degrees, and most preferably at least about 125 degrees, thereby
improving the hydrophobic characteristics of the DLC-inclusive
material. An "initial" contact angle .theta. means prior to
exposure to environmental conditions such as sun, rain, humidity,
etc.
[0082] Referring to FIG. 8, it is noted that the surface of a glass
substrate 1 often 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. Another
advantage of certain embodiments of this invention is that
amorphous carbon atoms and/or networks of DLC inclusive coating 3
(or DLC inclusive layer 5) 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 1. The nanocracks in the glass
surface shown in FIG. 8 may sometimes be from about 0.4 nm to 1 nm
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.
[0083] FIGS. 9-10 illustrate an exemplary linear or direct ion beam
source 25 which may be used to deposit coating 3, layer 5, clean a
substrate, or surface plasma treat a DLC inclusive coating
according to different embodiments of this invention. Ion beam
source 25 includes gas/power inlet 26, anode 27, grounded cathode
magnet portion 28, magnet poles 29, and insulators 30. A 3kV DC
power supply may be used for source 25 in some embodiments. Linear
source ion deposition allows for substantially uniform deposition
of coating 3 as to thickness and stoichiometry.
[0084] Ion beam source 25 is based upon a known gridless ion source
design. The linear source is composed of a linear shell (which is
the cathode and grounded) inside of which lies a concentric anode
(which is at a positive potential). This geometry of cathode-anode
and magnetic field 33 gives rise to a close drift condition. The
magnetic field configuration further gives rise to an anode layer
that allows the linear ion beam source to work absent any electron
emitter. The anode layer ion source can also work in a reactive
mode (e.g. with oxygen and nitrogen). The source includes a metal
housing with a slit in a shape of a race track as shown in FIGS.
9-10. The hollow housing is at ground potential. The anode
electrode is situated within the cathode body (though electrically
insulated) and is positioned just below the slit. The anode can be
connected to a positive potential as high was 3,000 volts. Both
electrodes may be water cooled in certain embodiments. Feedstock
gases are fed through the cavity between the anode and cathode. The
linear ion source also contains a labyrinth system that distributes
the precursor gas (e.g. gaseous mixture of TMS (i.e.
(CH.sub.3).sub.4Si or tetramethyl silane) and O.sub.2; or mixture
of 3MS (i.e. (CH.sub.3).sub.3Si--H) and O.sub.2) evenly along its
length and which allows it to supersonically expand between the
anode-cathode space internally. TMS and 3MS are commercial
available from Dow Chemical. The electrical energy then cracks the
gas to produce a plasma within the source. The ions are expelled
out at energies in the order of eVc-a/2 when the voltage is Vc-a.
The ion beam emanating from the slit is approximately uniform in
the longitudinal direction and has a gaussian profile in the
transverse direction. Exemplary ions 34 are shown in FIG. 10. A
source as long as one meter may be made, although sources of
different lengths are anticipated in different embodiments of this
invention. Finally, electron layer 35 is shown in FIG. 10 completes
the circuit thereby enabling the ion beam source to function
properly.
[0085] FIG. 13 illustrates an assembly for manufacturing a coated
article according to any of the FIG. 1-2 embodiments of this
invention; the assembly including first, second, and third linear
ion beam sources 61, 62 and 63, respectively. These three ion beam
sources may be of the type shown in FIGS. 9-10, or alternatively
may be other types of ion beam sources (e.g. filtered arc type on
beam sources). Conveyor 64 functions to move substrates through the
assembly, from one source to the next.
[0086] Referring to FIGS. 1, 9, 10; 12 and 13, an exemplary method
of depositing a coating 3 on substrate 1 will now be described.
This method is for purposes of example only.
[0087] Prior to coating 3 being formed on glass substrate 1, the
top surface of substrate 1 is preferably cleaned by way of first
linear or direct ion beam source 61. For example, a glow discharge
in argon (Ar) gas or mixtures of Ar/O.sub.2 (alternatively CF.sub.4
plasma) may be used to remove any impurities on the substrate
surface, by source 61. Such interactions are physio-chemical in
nature. This cleaning creates free radicals on the substrate
surface that subsequently can be reacted with other monomers
yielding substrate surfaces with specialized properties. The power
used may be from about 100-300 Watts. Substrate 1 may also be
cleaned by, for example, sputter cleaning the substrate prior to
actual deposition of coating 3; using oxygen and/or carbon atoms at
an ion energy of from about 800 to 1200 eV, most preferably about
1,000 eV.
[0088] After cleaning, the deposition process begins using a linear
ion beam deposition technique via second ion beam source 62; with
conveyor 64 having moved the cleaned substrate 1 from first source
61 to a position under second source 62 as shown in FIG. 13. Ion
beam source 62 functions to deposit a ta--C/SiO (or ta--C/SiO:F in
alternative embodiments) coating 3 onto substrate 1, as follows. In
preferred embodiments; the ratio of C to Si in coating 3 is
approximately 1:1 (i.e. 1:1 plus/minus about 20%). However, in
other preferred embodiments (e.g. see XPS analyzed Sample Nos. 1-3
below), the ratio of C to Si in coating 3 may be from about 1:1 to
4:1. The dopant gas may be produced by bubbling a carrier gas (e.g.
C.sub.2H.sub.2) through the precursor monomer (e.g. TMS or 3MS)
held at about 70 degrees C (well below the flashing point).
Acetylene feedstock gas (C.sub.2H.sub.2) is used in certain
embodiments to prevent or minimize/reduce polymerization and to
obtain an appropriate energy to allow the ions to penetrate the
substrate 1 or other surface and subimplant therein, thereby
causing coating 3 atoms to intermix with the surface of substrate 1
(or the surface of the growing coating) a few atom layers
thereinto. In alternative embodiments, the dopant gas may be
produced by heating or warming the monomer (e.g. to about 25-30
degrees C.) so that vapor therefrom proceeds through a mass flow
controller to the ion beam source; so that C.sub.2H.sub.2 is not
needed. The actual gas flow may be controlled by a mass flow
controller (MFC) which may be heated to about 70 degrees C. Oxygen
(O.sub.2) gas is independently flowed through an MFC. In certain
embodiments, a target consisting essentially of approximately equal
molar percentages of C and Si may be isostatically compressed at
about 20 MPa. The temperature of substrate 1 may be room
temperature; an arc power of about 1000 W may be used; precursor
gas flow may be about 25 sccm; the base pressure may be about
10.sup.-6 Torr, and a Hoescht type carbon electrode may be used.
Coating 3 is preferably free of pinholes to achieve satisfactory
water repulsion and/or suppression of soda diffusion.
[0089] The C--C sp.sup.3 bonding in coating 3 is preferably formed
by having a predetermined range of ion energy prior to reaching
substrate 1, or prior to reaching a coating or layer growing on the
substrate. The optimal ion energy window for the majority of
coating 3 is from about 100-200 eV (preferably from about 100-150
eV) per carbon ion. At these energies, the carbon in coating 3 (and
layer 5) emulates diamond, and sp.sup.3 C--C bonds form in coating
3. 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 during 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.
[0090] High stress is undesirable in the thin interfacing portion
of coating 3 that directly contacts the surface of a glass
substrate 1 in the FIG. 1 embodiment (and the thin interfacing
layer portion of layer 5 in the FIG. 2 embodiment). Thus, for
example, the first 1-40% thickness (preferably the first 1-20% and
most preferably the first 5-10% thickness) of coating 3 (or layer
5) 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 layer portion 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
of coating 3 (or layer 5). Thus, in certain embodiments, because of
the adjustment in ion energy during the deposition process, DLC
inclusive coating 3 in FIGS. 1-3 has different densities and
different percentages of sp.sup.3 C--C bonds at different layer
portions thereof (the lower the ion energy, the more sp.sup.3 C--C
bonds and the higher the density).
[0091] While direct ion beam deposition techniques are preferred in
certain embodiments, other methods of deposition may also be used
in different embodiments. For example, filtered cathodic vacuum arc
ion beam techniques may be used to deposit coating 3 and/or layer
5. Also, 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. Alternatively,
any of the deposition methods disclosed in U.S. Pat. No. 5,858,477
may be used to deposit coating 3 and/or layer 5, the disclosure of
Pat. No. 5,858,477 hereby being incorporated herein by
reference.
[0092] In certain alternative embodiments of this invention, second
source 62 may deposit a ta-C:SiO:F coating 3 on substrate 1 instead
of a ta-C:SiO coating. The n, k and Tauc optical bandgap may be
tailored by doping the bulk of coating 3 with F and/or H; where "n"
is refractive index and "k" is extinction coefficient. As the
refractive index n of glass is approximately 1.5, it is desirable
in certain embodiments for the refractive index n of coating 3 to
be close to that of the underlying glass substrate 1 in order to
achieve good transmission and minimal reflection of the coated
article. It is also desirable in certain embodiments for the "k"
value to be low in order to achieve good transmission. In certain
embodiments, the refractive index of coating 3 is from about 1.4 to
2.0, more preferably no greater than about 1.75, and most
preferably from about 1.5 to 1.7. The refractive index n of the
coating can also be altered using CF.sub.4 or CF.sub.6 as the
doping gas. Fluorination of no more than about 5% atomic is
preferred. The table below shows variation of n & k with atomic
F content:
1 F % n @ 543 nm k @ 43 nm Eg(eV) 0 2.2 0.02 2.0 1.5 1.75 0.007 2.9
3.0 1.65 0.0001 3.7
[0093] Thus, fluorination provides a way in which to independently
tune the n & k to match desired optical properties of the
substrate 1 in order to improve transmission and the like.
Fluorination may also scavenge a graphitic sp.sup.2 fraction within
the carbon matrix thus leaving mostly sp.sup.3 enriched carbon
matrix.
[0094] Third ion beam source 63 is optional. In certain embodiments
of this invention, the hydrophobicity of coating 3 can be further
enhanced using a plasma treatment by another source 63 or grafting
procedure after the main portion of DLC-inclusive coating 3 has
been deposited. This technique using third source 63 removes
certain polar functional groups at the outermost surface, thereby
altering the surface chemical reactivity (i.e. lowering surface
energy) while the bulk of coating 3 remains the same or
substantially unaffected. After conveyor has moved the DLC-coated
substrate from the second source 62 station to a position under
third source 63, the plasma treatment by source 63 introduces
hydrogen (H) atoms into the outermost surface of coating 3, thereby
making the coating's surface substantially non-polar and less dense
than the rest of the coating 3. These H atoms are introduced,
because H.sub.2 or ArH.sub.2 feedstock gas is used by source 63
instead of the C.sub.2H.sub.2 gas. Thus, third source 63 does not
deposit any significant amounts of C atoms or Si atoms; but instead
treats the outermost surface of the ta-C:SiO coating by adding H
atoms thereto in order to improve its hydrophobic characteristics.
This plasma treatment may also function to roughen the otherwise
smooth surface. It is noted that H.sub.2 feedstock gas is preferred
in ion beam source 63 when it is not desired to roughen the surface
of coating 3, while ArH.sub.2 feedstock gas is preferred in surface
roughing embodiments. Additionally, a CF.sub.4 RF induced plasma
may be used to provide a striation process with RMS roughness of at
least about 100.ANG..
[0095] Contact angle .theta. of coating 3 with water increases with
surface roughness as shown below, via certain examples performed in
accordance with certain embodiments of this invention:
2 Sample No. Roughness RMS (.ANG.) Contact Angle .theta. 1 5
101.degree. 2 30 109.degree. 3 120 117.degree.
[0096] In certain alternative embodiments of this invention, third
source 63 may be used to introduce F atoms to the outermost 5.ANG.
layer portion of coating 3 (in addition to or instead of the H
atoms) in order to reduce surface energy. Flourination of no more
than about 5% (atomic percent) is preferred.
[0097] Coatings 3 according to different embodiments of this
invention may have the following characteristics: coefficient of
friction of from about 0.02 to 0.15; good abrasion resistance; an
average density of from about 2.5 to 3.0 g/cm.sup.2; permeability
barrier to gases and ions; surface roughness less than about 0.5
nm; inert reactivity to acids, alkalis, solvents, salts and water;
corrosion resistance; variable or tunable surface tension; tunable
optical bandgap of from about 2.0 to 3.7 eV; IR transmission @ 10
.mu.m of at least about 85%; UV transmission @ 350 nm of no greater
than about 30%; tunable refractive index @ 550 nm [n=1.6 to 2.3;
k=0.0001 to 0.1], permittivity @ GHz 4.5; an undoped electrical
resistivity of at least about 10.sup.10 .OMEGA./cm; dielectric
constant of about 11 @ 10 kHz and 4 @ 100 MHZ; an electrical
breakdown strength (V cm.sup.-1) of about 10.sup.6; thermal
coefficient of expansion of about 9.times.10.sup.-6/C; and thermal
conductivity of about 0.1 Wcm K.
[0098] Referring to FIG. 13, in certain preferred embodiments of
this invention, three separate ion beam sources 61-63 are used to
make coated articles according to either of the FIG. 1-2
embodiments. However, in alternative embodiments, it is recognized
that a single ion beam source (linear, curved, or the like) may be
used to perform each of the cleaning step, the deposition step of
DLC-inclusive coating 3, and the plasma surface treatment for
introducing H and/or F atoms into the outermost surface area of the
coating. In such embodiments, the feedstock gas may be changed
between each such process.
ADDITIONAL EXAMPLE SAMPLE NOS. 1-3
[0099] Three additional example coated articles were manufactured
and tested according to different embodiments of this invention as
follows. They are additional Sample Nos. 1-3, each including a
coating 3 according to an embodiment of this invention deposited on
glass using tetramethyl-silane (TMS) and O.sub.2 gas introduced
within the linear ion beam. All sample coatings 3 were of
approximately the same thickness of about 750.ANG.. A low energy
electron flood gun was used to sharpen the spectral analysis
conducted by x-ray photo electron spectroscopy (XPS) for chemical
analysis. In XPS analysis of a coating 3, high energy x-ray photons
(monochromatic) impinge on the surface of coating 3. Electrons from
the surface are ejected and their energy and number (count)
measured. With these measurements, one can deduce the electron
binding energy. From the binding energy, one can determine three
things: elemental fingerprinting, relative quantity of elements,
and the chemical state of the elements (i.e. how they are bonding).
Components used in the XPS analysis (e.g. see FIGS. 14-15) include
the monochromatic x-ray source, an electron energy analyzer, and
electron flood gun to prevent samples from charging up; and an ion
source used to clean and depth profile. Photoelectrons are
collected from the entire XPS field simultaneously, and using a
combination of lenses before and after the energy analyzer are
energy filtered and brought to a channel plate. The result is
parallel imaging in real time images. Sample Nos. 1-3 were made and
analyzed using XPS, which indicated that the samples included the
following chemical elements by atomic percentage (H was excluded
from the chart below).
3 Sample No. C O Si F 1 54.6% 23.7% 20.5% 1.2% 2. 45.7% 21.7% 32.7%
0% 3. 59.5% 22.7% 17.8% 0%
[0100] H was excluded from the XPS analysis because of its
difficulty to measure. Thus, H atoms present in the coating Sample
Nos. 1-3 were not taken into consideration for these results. For
example, if Sample No. 1 included 9% H by atomic percentage, then
the atomic percentages of each of the above-listed elements C, O,
Si and F would be reduced by an amount so that all five atomic
percentages totaled 100%.
[0101] FIGS. 14-15 illustrate actual XPS analysis of Sample No. 1.
The large hump in the FIG. 14 graph at approximately the 530-535 eV
binding energy indicates that most of the Si--O and C--O bonds
proximate the surface of coating 3 are of the tetrahedral or
sp.sup.3 type (i.e. tetrahedral bonds of these elements are at that
particular binding energy). The large hump 70 in the FIG. 15 graph
at approximately the 282-288 eV binding energy indicates that the
C--C and C--H bonds proximate the surface of coating 3 are of the
tetrahedral or sp.sup.3 type (i.e. tetrahedral bonds of these
elements C and H are at that particular binding energy). Smaller
hump 71 in FIG. 15 is illustrative of C--F and O--C.dbd.O bonds in
coating 3. Hump 72 in FIG. 15 is illustrative of C.dbd.O bonds in
coating 3. Hump 73 is illustrative of C--O bonds in coating 3. It
is noted that large hump 70 indicates that coating 3 may include
bonds where a C atom is bonded to at least three other C atoms as
well as to a H atom via tetrahedral or sp.sup.3 type bonding.
[0102] Certain aspects of carbon (C) are now described generally,
to aid in the understanding of this invention.
[0103] 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 phases exist,
namely diamond, graphite and the fullerenes and a plethora of
non-crystalline forms.
[0104] 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).
[0105] 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
.sigma. bonds and a p-type .pi. 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.
[0106] 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. inclusive in coating 3 and layer 5) 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.
[0107] 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, residential or commercial
windows, and the like.
[0108] In certain embodiments of this invention, coating 3 has a
contact angle of at least about 70.degree., more preferably at
least about 80.degree., and even more preferably at least about
100.degree. after a taber abrasion resistance test has been
performed pursuant to ANSI Z26.1. The test utilizes 1,000 rubbing
cycles of coating 3, with a load a specified in Z26.1 on the
wheel(s). Another purpose of this abrasion resistance test is to
determine whether the coated article is resistive to abrasion (e.g.
whether hazing is less than 4% afterwards). ANSI Z26.1 is hereby
incorporated into this application by reference.
[0109] 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.
* * * * *