U.S. patent application number 10/832600 was filed with the patent office on 2005-10-27 for hybrid coating stack.
Invention is credited to Thiel, James P..
Application Number | 20050238923 10/832600 |
Document ID | / |
Family ID | 34993321 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050238923 |
Kind Code |
A1 |
Thiel, James P. |
October 27, 2005 |
Hybrid coating stack
Abstract
A coating includes a functional coating, such as a solar control
coating having at least one metal layer. A topcoat is formed over
at least a portion of the functional coating. The topcoat includes
a first topcoat layer having a thickness in the range of 0.5 QWOT
to 1.5 QWOT with respect to a reference wavelength of 550 nm and a
first refractive index, and a second topcoat layer having a
thickness in the range of 0.5 QWOT to 1.5 QWOT with respect to a
reference wavelength of 550 nm and a second refractive index
different from the first refractive index.
Inventors: |
Thiel, James P.;
(Pittsburgh, PA) |
Correspondence
Address: |
PPG INDUSTRIES, INC.
Intellectual Property Dept.
One PPG Place
Pittsburgh
PA
15272
US
|
Family ID: |
34993321 |
Appl. No.: |
10/832600 |
Filed: |
April 27, 2004 |
Current U.S.
Class: |
428/701 ;
428/702 |
Current CPC
Class: |
C03C 17/3681 20130101;
C03C 2217/734 20130101; C03C 17/366 20130101; B32B 17/10174
20130101; B32B 17/10761 20130101; C03C 17/36 20130101; B32B
17/10005 20210101; B32B 2367/00 20130101 |
Class at
Publication: |
428/701 ;
428/702 |
International
Class: |
B32B 009/00 |
Claims
What is claimed is:
1. A coating, comprising: a functional coating comprising at least
one metal layer; and a topcoat formed over at least a portion of
the functional coating, the topcoat comprising: a first topcoat
layer having a thickness in the range of 0.5 QWOT to 1.5 QWOT with
respect to a wavelength of 550 nm and a first refractive index; and
a second topcoat layer having a thickness in the range of 0.5 QWOT
to 1.5 QWOT with respect to a wavelength of 550 nm and having a
second refractive index different from the first refractive
index.
2. The coating of claim 1, wherein the metal layer includes at
least one of gold, copper, silver, or mixtures, alloys, or
combinations including at least one thereof.
3. The coating of claim 1, wherein the functional coating comprises
a first metal oxide layer and a second metal oxide layer, with the
metal layer positioned between the metal oxide layers.
4. The coating of claim 1, wherein the first topcoat layer has a
low refractive index and the second topcoat layer has a high
refractive index.
5. The coating of claim 1, wherein the first topcoat layer has a
high refractive index and the second topcoat layer has a low
refractive index.
6. The coating of claim 1, wherein the refractive index of the
first topcoat layer differs from the refractive index of the second
topcoat layer by a value in the range of 0.2 to 1.0.
7. The coating of claim 1, wherein the first topcoat layer has a
refractive index of 2 or less and the second topcoat layer has a
refractive index greater than 2.
8. The coating of claim 1, wherein the first topcoat layer has a
refractive index of greater than 2 and the second topcoat layer has
a refractive index of 2 or less.
9. The coating of claim 1, wherein the first topcoat layer
comprises at least one metal oxide selected, from oxides of
aluminum, silicon, yttrium, tin, and mixtures thereof.
10. The coating of claim 1, wherein the second topcoat layer
comprises at least one metal oxide selected from oxides of
titanium, zirconium, niobium, bismuth, tungsten, zinc, tin, and
mixtures thereof.
11. The coating of claim 3, wherein the first metal oxide layer
comprises at least one oxide of zinc, tin, or alloys or mixtures
thereof, the second metal oxide layer comprises at least one oxide
of zinc, tin, or alloys or mixtures thereof, the metal layer
comprises silver, one of the first topcoat layer or the second
topcoat layer comprises at least one metal oxide selected from
oxides of aluminum, silicon, yttrium, tin, and mixtures thereof,
and the other of the first topcoat layer or second topcoat layer
comprises at least one metal oxide selected from oxides of
titanium, zirconium, niobium, bismuth, tungsten, zinc, tin, and
mixtures thereof.
12. The coating of claim 1, wherein the topcoat further comprises a
third topcoat layer having a thickness in the range of 0.5 QWOT to
1 QWOT with respect to a reference wavelength of 550 nm and a
refractive index different from the second refractive index.
13. The coating of claim 12, wherein the third topcoat layer
comprises a low refractive index material.
14. The coating of claim 12, wherein the third topcoat layer
comprises a high refractive index material.
15. The coating of claim 12, wherein the third topcoat layer
comprises silicon dioxide.
16. A coating, comprising: a functional coating comprising at least
one infrared reflective metal layer; and a topcoat formed over at
least a portion of the functional coating, wherein the topcoat
comprises: a first topcoat layer having a first refractive index
deposited over at least a portion of the functional coating; and a
second topcoat layer having a second refractive index deposited
over at least a portion of the first dielectric layer, wherein the
difference between the first refractive index and the second
refractive index is in the range of 0.2 to 1.
17. The coating of claim 16, wherein the refractive index
difference is in the range of 0.2 to 0.6.
18. The coating of claim 16, wherein the first topcoat layer has a
low refractive index and the second topcoat layer has a high
refractive index.
19. The coating of claim 16, wherein the first topcoat layer has a
high refractive index and the second topcoat layer has a low
refractive index.
20. The coating of claim 16, wherein the first topcoat layer
comprises at least one metal oxide selected from the group
consisting of oxides of aluminum, silicon, yttrium, tin, and
mixtures thereof.
21. The coating of claim 16, wherein the second topcoat layer
comprises at least one metal oxide selected from the group
consisting of oxides of titanium, zirconium, niobium, bismuth,
tungsten, zinc, tin, and mixtures thereof.
22. The coating of claim 16, wherein the infrared reflective metal
layer comprises silver, one of the first topcoat layer or the
second topcoat layer comprises at least one metal oxide selected
from oxides of aluminum, silicon, yttrium, tin, and mixtures
thereof, and the other of the first topcoat layer or second topcoat
layer comprises at least one metal oxide selected from oxides of
titanium, zirconium, niobium, bismuth, tungsten, zinc, tin, and
mixtures thereof.
23. The coating of claim 16, wherein the topcoat further comprises
a third topcoat layer deposited over the second topcoat layer, the
third topcoat having a third refractive index different from the
second refractive index.
24. A coated article, comprising: a substrate; and a coating as
defined in claim 1 deposited over at least a portion of the
substrate.
25. A coated article, comprising: a substrate; and a coating
deposited over at least a portion of the substrate, the coating
comprising: a functional coating comprising a first metal oxide
layer, a second metal oxide layer, and an infrared reflective metal
layer positioned between the first and second metal oxide layers;
and a topcoat comprising a first topcoat layer and a second topcoat
layer, wherein the first topcoat layer has a thickness in the range
of 0.5 QWOT to 1.5 QWOT with respect to a reference wavelength of
550 nm and a first refractive index of (i) less than or equal to 2,
or (ii) greater than 2, and wherein the second topcoat layer has a
thickness in the range of 0.5 QWOT to 1.5 QWOT with respect to a
wavelength of 550 nm and a second refractive index of (i) greater
than 2 when the first refractive index is less than or equal to 2,
and (ii) less than or equal to 2 when the first refractive index is
greater than 2.
26. The coated article of claim 25, wherein the first metal oxide
layer comprises at least one oxide of zinc, tin or alloys or
mixtures thereof and having a thickness in the range of 0.25 QWOT
to 1 QWOT, the metal layer comprises silver, and the second metal
oxide layer comprises at least one oxide of zinc, tin or alloys or
mixtures thereof and having a thickness in the range of 0.1 QWOT to
0.9 QWOT.
27. The coated article of claim 25, further comprising a second
substrate laminated to the first substrate.
28. The coated article of claim 25, wherein one of the first
topcoat layer or the second topcoat layer comprises at least one
metal oxide selected from oxides of aluminum, silicon, yttrium,
tin, and mixtures thereof, and the other of the first topcoat layer
or second topcoat layer comprises at least one metal oxide selected
from oxides of titanium, zirconium, niobium, bismuth, tungsten,
zinc, tin, and mixtures thereof.
29. The coated article of claim 25, wherein the topcoat further
comprises a third topcoat layer having a thickness in the range of
0.5 QWOT to 1 QWOT and a third refractive index of (i) less than or
equal to 2 when the second refractive index is greater than 2, and
(ii) greater than 2 when the second refractive index is less than
or equal to 2.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to coatings and coated
articles and, more particularly, to coatings having a solar control
coating with a durability-enhancing topcoat and to articles coated
therewith.
[0003] 2. Description of the Currently Available Technology
[0004] Solar control coatings are known for controlling the amount
of solar radiation passing into buildings, vehicles, and other
structures. These solar control coatings can block or reflect
selected electromagnetic wavelengths and can help reduce the costs
of heating and/or cooling.
[0005] Conventional solar control coatings typically include an
infrared reflecting metal layer positioned between two dielectric
layers. Conventional dielectric layers typically include metal
oxides. A thin protective overcoat, such as titania, is deposited
over the outermost dielectric layer to help protect the underlying
layers from chemical and mechanical damage. Examples of known solar
control coatings are disclosed in U.S. Pat. Nos. 4,610,771;
4,716,086; and 4,898,789.
[0006] Coated substrates, such as glass substrates coated with
solar control coatings, can be utilized in laminated or
non-laminated articles. An example of a laminated article is a
conventional automotive windshield. An example of a non-laminated
article is a conventional architectural window. Known solar control
coatings are well suited for their intended purpose of modifying
the solar control properties of the coated article.
[0007] However, conventional solar control coatings can be
susceptible to mechanical or chemical damage during handling even
with a conventional protective overcoat. While it would be possible
to increase the mechanical and/or chemical durability of a
conventional solar control coating stack by increasing the
thickness of the outer protective overcoat, such an increase in
thickness would also impact other parameters of the coated article,
such as the reflectance, transmittance, or emissivity of the
article and could significantly change the transmission
characteristics, solar performance properties, and aesthetics of
the coated article. This would be disadvantageous, particularly for
coated glass articles destined for use in the automotive field
where solar control properties, such as transmittance and/or
reflectance, are controlled to meet government regulations.
Additionally, increasing the thickness of the protective overcoat
could also adversely impact upon the processing parameters of the
coated article, such as adversely impacting the bending, annealing,
tempering, or laminating processes.
[0008] Coating stacks for non-solar control purposes are known. For
example, conventional camera lenses typically include an
anti-reflective coating made up of a series of layers of high and
low refractive index materials. These layers reduce visible light
reflection when taking photographs. While these anti-reflective
lens coatings are adequate for their intended purpose of reducing
visible light reflection, they do not have infrared reflective
metal layers and, thus, provide little or no solar control
properties. While one might consider adding a conventional lens
coating to a conventional solar control coating stack, such a
combination would not be feasible since the resultant coating stack
would not meet the optical and/or solar reflecting characteristics
typically required for solar control articles, such as automotive
transparencies and architectural transparencies.
[0009] Therefore, it would be advantageous to provide a coating
stack having solar control properties as well as enhanced
durability but without adversely impacting upon the solar control
and/or aesthetic properties of the coating stack.
SUMMARY OF THE INVENTION
[0010] A coating comprises a functional coating, such as a solar
control coating comprising at least one metal layer. A topcoat is
formed over at least a portion of the functional coating. The
topcoat comprises a first topcoat layer having a thickness in the
range of 0.5 Quarter Wave Optical Thickness (QWOT) to 1.5 QWOT with
respect to a reference wavelength of 550 nm and a first refractive
index, and a second topcoat layer having a thickness in the range
of 0.5 QWOT to 1.5 QWOT with respect to a reference wavelength of
550 nm and a second refractive index different from the first
refractive index. In one non-limiting embodiment, one of the first
topcoat layer or the second topcoat layer comprises at least one
metal oxide selected from oxides of aluminum, silicon, yttrium,
tin, and mixtures thereof, and the other of the first topcoat layer
or second topcoat layer comprises at least one metal oxide selected
from oxides of titanium, zirconium, niobium, bismuth, tungsten,
zinc, tin, and mixtures thereof. The topcoat can further include a
third topcoat layer having a thickness in the range of 0.5 QWOT to
1.5 QWOT. In one non-limiting embodiment, the third topcoat layer
comprises silica.
[0011] Another coating comprises a functional coating, such as a
solar control coating comprising at least one infrared reflective
metal layer. A topcoat is formed over at least a portion of the
functional coating. The topcoat comprises a first topcoat layer
deposited over at least a portion of the functional coating and a
second topcoat layer deposited over at least a portion of the first
topcoat layer. The refractive index of the first topcoat layer can
differ from the refractive index of the second topcoat layer by a
value in the range of 0.2 to 1.
[0012] A coated article comprises a substrate and a coating as
defined above deposited over at least a portion of the
substrate.
[0013] Another coated article comprises a substrate and a coating
deposited over at least a portion of the substrate. The coating
comprises: (a) a functional coating comprising a first metal oxide
layer, a second metal oxide layer, and an infrared reflective metal
layer positioned between the first and second metal oxide layers,
and (b) a topcoat formed over the functional coating and comprising
a first topcoat layer and a second topcoat layer, wherein the first
topcoat layer has a thickness in the range of 0.5 QWOT to 1.5 QWOT
with respect to a reference wavelength of 550 nm and a first
refractive index of either (i) less than or equal to 2 or (ii)
greater than 2, and the second topcoat layer has a thickness in the
range of 0.5 QWOT to 1.5 QWOT with respect to a wavelength of 550
nm and a second refractive index of (i) greater than 2 when the
first refractive index is less than or equal 2 or (ii) less than or
equal to 2 when the first refractive index is greater than 2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a cross-sectional view (not to scale) of a
monolithic article having a hybrid coating incorporating features
of the invention;
[0015] FIG. 2 is a cross-sectional view (not to scale) of a
laminated article having a hybrid coating incorporating features of
the invention;
[0016] FIG. 3 is a graph of percent reflectance versus wavelength
(nanometers) comparing a single silver layer coating having a
topcoat of the invention with a similar single silver layer coating
without the topcoat of the invention; and
[0017] FIG. 4 is a graph of percent reflectance versus wavelength
(nanometers) comparing a double silver layer coating having a
topcoat of the invention with a similar double silver layer coating
without the topcoat of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] As used herein, spatial or directional terms, such as
"inner", "outer", "above", "below", and the like, relate to the
invention as it is shown in the drawing figures. However, it is to
be understood that the invention can assume various alternative
orientations and, accordingly, such terms are not to be considered
as limiting. Further, all numbers expressing dimensions, physical
characteristics, and so forth, used in the specification and claims
are to be understood as being modified in all instances by the term
"about". Accordingly, unless indicated to the contrary, the
numerical values set forth in the following specification and
claims can vary, depending upon the desired properties sought to be
obtained by the present invention. At the very least, and not as an
attempt to limit the application of the doctrine of equivalents to
the scope of the claims, each numerical parameter should at least
be construed in light of the number of reported significant digits
and by applying ordinary rounding techniques. Moreover, all ranges
disclosed herein are to be understood to encompass any and all
subranges subsumed therein. For example, a stated range of "1 to
10" should be considered to include any and all subranges between
(and inclusive of) the minimum value of 1 and the maximum value of
10; that is, all subranges beginning with a minimum value of 1 or
more and ending with a maximum value of 10 or less, e.g., 1 to 3.7,
5.5 to 10, or 6.5 to 9.5, just to name a few. As used herein, the
terms "deposited over", "applied over", or "formed over" mean
deposited, applied, or formed on but not necessarily in contact
with the surface. For example, a material "deposited over" a
substrate does not preclude the presence of one or more other
materials of the same or different composition located between the
deposited material and the substrate. Additionally, all references
referred to herein are to be understood as being incorporated by
reference in their entirety. The terms "visible region" or "visible
light" refer to electromagnetic radiation having a wavelength in
the range of 400 nm to 700 nm. The terms "infrared region" or
"infrared radiation" refer to electromagnetic radiation having a
wavelength in the range of greater than 700 nm to 100,000 nm. The
terms "ultraviolet region" or "ultraviolet radiation" mean
electromagnetic energy having a wavelength in the range of 300 nm
to less than 400 nm. The term "film" refers to a region of a
coating having a desired or selected composition. A "layer"
comprises one or more "films". A "coating" or "coating stack" is
comprised of one or more "layers". All quarter wave optical
thicknesses values herein are defined relative to a reference
wavelength of 550 nm.
[0019] An exemplary coated article 10 incorporating features of the
invention is shown in FIG. 1. The article 10 includes a substrate
12 which can have at least one major surface. A hybrid coating 14
of the invention can be formed over at least a portion of the
substrate 12. In the embodiment illustrated in FIG. 1, the hybrid
coating 14 comprises at least one functional coating 16 formed over
at least a portion of the substrate 12, e.g., over at least a
portion of a major surface, and an anti-reflective topcoat 18 of
the invention formed over at least a portion of the functional
coating 16. The article 10 can be a monolithic article, as shown in
FIG. 1. By "monolithic" is meant having a single structural
substrate or primary ply. By "primary ply" is meant a primary
support or structural member. Or, as will be described with respect
to FIG. 2, the invention can be practiced to form a laminated
article.
[0020] In the broad practice of the invention, the substrate 12 can
be of any desired dimensions, e.g., length, width, shape, or
thickness, and can be of any desired material having any desired
characteristics, such as opaque, translucent, or transparent to
visible light. By "transparent" is meant having a transmittance of
visible light through the substrate of greater than 0% up to 100%.
By "translucent" is meant allowing electromagnetic energy (e.g.,
visible light) to pass through the substrate but diffusing this
energy such that objects on the side of the substrate opposite to
the viewer are not clearly visible. By "opaque" is meant having a
visible light transmittance of less than 0.001%. Examples of
suitable substrates include, but are not limited to, plastic
substrates (such as acrylic polymers, such as polyacrylates;
polyalkylmethacrylates, such as polymethylmethacrylates,
polyethylmethacrylates, polypropylmethacrylates, and the like;
polyurethanes; polycarbonates; polyalkylterephthalates, such as
polyethyleneterephthalate (PET), polypropyleneterephthalates,
polybutyleneterephthalates, and the like; polysiloxane-containing
polymers; or copolymers of any monomers for preparing these, or any
mixtures thereof); metal substrates, such as but not limited to
galvanized steel, stainless steel, and aluminum; ceramic
substrates; tile substrates; glass substrates; fiberglass
substrates; or mixtures or combinations of any of the above. For
example, the substrate can be conventional untinted
soda-lime-silica glass, i.e., "clear glass", or can be tinted or
otherwise colored glass, borosilicate glass, leaded glass,
tempered, untempered, annealed, or heat-strengthened glass. The
glass can be of any type, such as conventional float glass or flat
glass, and can be of any composition having any optical properties,
e.g., any value of visible radiation transmission, ultraviolet
radiation transmission, infrared radiation transmission, and/or
total solar energy transmission. Typical automotive-type glasses
can have such colors as blue, green, bronze, gray, and
non-exclusive examples of these glasses include glasses
commercially available from PPG Industries, Inc. of Pittsburgh,
Pa., under the names Solex.RTM. glass, Solargreen.RTM. glass,
Solextra.RTM. glass, and VistaGray.TM. glass. The glass can be
untempered, heat treated, or heat strengthened glass. As used
herein, the term "heat treated" means heated to a temperature
sufficient to bend or anneal or temper the glass. The term "heat
strengthened" means annealed, tempered, or at least partially
tempered. Although not limiting to the invention, examples of glass
suitable for the practice of the invention are described in U.S.
Pat. Nos. 4,746,347; 4,792,536; 5,240,886; 5,385,872; and
5,393,593.
[0021] In one particular practice of the invention, the substrate
12 is or comprises glass, such as but not limited to a glass sheet,
such as a sheet of flat glass or window glass. For conventional
automotive transparencies, a glass substrate can typically be up to
10 mm thick, e.g., in the range of 1 mm to 10 mm thick, e.g., less
than 10 mm thick, e.g., 1 mm to 5 mm thick, e.g., 1.5 mm to 2.5 mm,
e.g., 1.6 mm to 2.3 mm. The substrate 12 can be a flat substrate or
can be shaped, bent, or curved. By the term "flat substrate" is
meant a substrate lying primarily in a single geometric plane,
e.g., such as a piece of flat glass produced by a conventional
float glass process. By "shaped" or "bent" is meant a substrate
that is not flat.
[0022] As described above, a functional coating 16 can be formed
over at least a portion of the substrate 12. By "functional
coating" is meant a coating that modifies one or more physical or
optical properties of the substrate on which it is deposited, e.g.,
optical, thermal, chemical or mechanical properties, and is not
intended to be entirely removed from the substrate during
subsequent processing. The functional coating 16 can have one or
more functional coating films or layers of the same or different
composition or functionality.
[0023] The functional coating 16 can be, for example, an
electrically conductive coating used to make heatable windows, such
as is disclosed in U.S. Pat. Nos. 5,653,903 and 5,028,759, or a
single-film or multi-film coating used as an antenna. Likewise, the
functional coating 16 can be a solar control coating. As used
herein, the terms "solar control coating" and/or "low emissivity
coating" refer to a coating comprised of one or more layers or
films that affect the solar properties of the coated article, such
as but not limited to the shading coefficient and/or the amount of
solar radiation, for example, visible, infrared (IR), or
ultraviolet (UV) radiation, reflected from and/or passing through
the coated article 10. A solar control coating can block, absorb or
filter selected portions of the solar spectrum, such as but not
limited to the IR, UV, and/or visible spectrums. Examples of solar
control coatings that can be used in the practice of the invention
are found in, but are not limited to, U.S. Pat. Nos. 4,898,789;
5,821,001; 4,716,086; 4,610,771; 4,902,580; 4,716,086; 4,806,220;
4,898,790; 4,834,857; 4,948,677; 5,059,295; and 5,028,759, and also
in U.S. patent application Ser. Nos. 09/058,440 and 60/355,912.
[0024] As will be appreciated by those skilled in the art, the
functional coating 16 can affect the emissivity of the coated
article, i.e., can be a low emissivity coating. A low emissivity
coating allows short wavelength energy, e.g., visible or
ultraviolet energy to be transmitted through the coating but
reflects longer wavelength energy, such as infrared energy. By "low
emissivity" is meant emissivity less than 0.4, such as less than
0.3, such as less than 0.2, such as less than 0.1, such as less
than or equal to 0.05. The lower the emissivity, the more infrared
wavelength energy is reflected. Non-limiting examples of low
emissivity coatings are found in U.S. Pat. Nos. 4,952,423 and
4,504,109 and British reference GB 2,302,102.
[0025] The functional coating 16 can include one or more
anti-reflective coating films comprising dielectric or
anti-reflective materials, such as metal oxides, oxides of metal
alloys, or doped metal oxides and/or doped metal alloys that are
transparent to visible light. The functional coating 16 can also
include one or more infrared reflective films comprising a
reflective metal, e.g., a noble metal such as gold, copper or
silver, or combinations or alloys thereof, and can further comprise
one or more primer films or barrier films, such as titanium,
nickel, chrome, nickel-chrome alloy, niobium, zirconium, or other
primers known in the art, located over and/or under the metal
reflective layer(s). Examples of suitable functional coatings 16
for use with the invention are commercially available from PPG
Industries, Inc. of Pittsburgh, Pa. under the SUNGATE.RTM. and
SOLARBAN.RTM. families of coatings.
[0026] In one practice, the functional coating 16 can include one
or more coating units 26 as shown in FIG. 1. The coating unit(s) 26
can comprise a first dielectric layer 28, an infrared reflective
metal layer 30, a primer layer 32, and a second dielectric layer
34. The first and/or second dielectric layers 28, 34 and the
reflective metal layer 30 can be of any of the general materials
described above and can be of any desired thickness. The functional
coating 16 can include one coating unit 26 or can include a
plurality of coating units 26 formed over the substrate 12.
[0027] The functional coating 16 can be deposited over the
substrate 12 by any conventional method, such as conventional
physical vapor deposition (PVD) or chemical vapor deposition (CVD)
processes. Suitable deposition processes include, but are not
limited to, spray pyrolysis, sol-gel, electron beam evaporation, or
vacuum sputtering such as magnetron sputter vapor deposition
(MSVD). In one embodiment, the functional coating 16 can be
deposited by MSVD. Examples of MSVD coating devices and methods
will be well understood by one of ordinary skill in the art and are
described, for example, in U.S. Pat. Nos. 4,379,040; 4,861,669;
4,898,789; 4,898,790; 4,900,633; 4,920,006; 4,938,857; 5,328,768;
and 5,492,750.
[0028] In one specific embodiment, one or both of the dielectric
layers 28 and/or 34 can comprise one or more films of
anti-reflective materials and/or dielectric materials, such as but
not limited to metal oxides, oxides of metal alloys, nitrides,
oxynitrides, or mixtures thereof. The dielectric layers can be
transparent to visible light. Examples of suitable metal oxides
include, but are not limited to, oxides of titanium, hafnium,
zirconium, niobium, zinc, bismuth, lead, indium, tin, and mixtures
thereof. These metal oxides can have small amounts of other
materials (e.g., dopants), such as manganese in bismuth oxide,
indium-tin oxide, etc. Additionally, oxides of metal alloys or
metal mixtures can be used, such as oxides containing zinc and tin
(e.g., zinc stannate), oxides of indium-tin alloys, silicon
nitrides, silicon aluminum nitrides, oxynitrides, or aluminum
nitrides. Further, doped metal oxides or doped metal alloy oxides,
such as but not limited to antimony or indium doped tin oxides or
nickel or boron doped silicon oxides or tin doped zinc oxides, can
be used. The dielectric layers 28, 34 can be substantially single
phase films, such as a metal alloy oxide film, e.g., zinc stannate,
or can be a mixture of phases composed of zinc and tin oxides, or
can be composed of a plurality of metal oxide films, such as but
not limited to those disclosed in U.S. Pat. Nos. 5,821,001;
4,898,789; and 4,898,790, or can be doped metal oxide films or
doped metal alloy oxides films.
[0029] In one embodiment, the first dielectric layer 28 can have a
total thickness of less than or equal to 500 .ANG., e.g., less than
or equal to 400 .ANG., e.g., less than or equal to 280 .ANG.. For
example, the metal alloy oxide film 28 can have a thickness in the
range of 100 .ANG. to 500 .ANG., such as 150 .ANG. to 400 .ANG.,
e.g., 200 .ANG., to 400 .ANG.. The reflective layer 30 be an IR
reflective metal, such as but not limited to gold, copper, silver,
or mixtures, alloys, or combinations thereof, and can have a
thickness in the range of 50 .ANG. to 200 .ANG., such as 75 .ANG.
to 150 .ANG., e.g., 100 .ANG.. In one particular embodiment of the
invention, the IR reflective layer 30 comprises silver. The metal
alloy oxide films 28, 34 can each include a zinc/tin alloy oxide.
The zinc/tin alloy can comprise zinc and tin in proportions of 10
wt. % to 90 wt. % zinc and 90 wt. % to 10 wt. % tin. One suitable
metal alloy oxide for use in the invention is zinc stannate. By
"zinc stannate" is meant a composition of
Zn.sub.xSn.sub.1-xO.sub.2-x (Formula 1), where x varies in the
range of greater than 0 to less than 1. For instance the number x
can be greater than 0 and can be any fraction or decimal between
greater than 0 up to the number 1. For example, where x=2/3,
Formula 1 is Zn.sub.2/3Sn.sub.1/3O.sub.4/3, which is more commonly
described as "Zn.sub.2SnO.sub.4". A zinc stannate containing film
has one or more of the forms of Formula 1 in a predominant amount
in the film. The metal oxide film can include a zinc-containing
film, such as zinc oxide. The zinc oxide film can include other
materials to improve the sputtering characteristics of the
associated cathode, e.g., the zinc oxide can contain 0 to 20 wt. %
tin, e.g., 0 to 15 wt. % tin, e.g., 0 to 10 wt. % tin.
[0030] The primer film 32 can be an oxygen capturing material, such
as titanium, that can be sacrificial during the deposition process
to prevent degradation or oxidation of the reflective layer 30
during a sputtering process. The oxygen capturing material can be
chosen to oxidize before the material of the reflective layer
30.
[0031] The hybrid coating 14 further includes a protective coating
or topcoat 18 to assist in providing protection against mechanical
and chemical attack. For the monolithic article 10 shown in FIG. 1,
the topcoat 18 includes a first topcoat layer 40, a second topcoat
layer 42, and a third topcoat layer 44. Thus, unlike conventional
protective overcoats that are typically a thin, single component
film, the topcoat 18 of the invention is a multi-layer structure.
However, unlike conventional lens coatings, the topcoat 18 has much
fewer layers.
[0032] In one embodiment, the first topcoat layer 40 can have a low
refractive index, the second topcoat layer 42 can have a high
refractive index, and the third topcoat layer 44 can have a low
refractive index. By "low refractive index" is meant a material
having a refractive index less than that of the "high refractive
index" material. That is, the terms "low" and "high" can be
relative terms with respect to the materials chosen for the topcoat
layers. For example, but not to be considered as limiting, the "low
refractive index" material can have a refractive index of 2 or
less. Examples of some suitable materials include, but are not
limited to, oxides comprising aluminum, silicon, yttrium, tin, or
mixtures or combinations thereof. The "high refractive index"
material has a refractive index greater than that of the low
refractive index material. For example, the high refractive index
material can have a refractive index of greater than 2. Examples of
some suitable materials include, but are not limited to, oxides
comprising titanium, zirconium, niobium, bismuth, tungsten, zinc,
tin, or mixtures or combinations thereof. In one non-limiting
embodiment, the first topcoat layer 40 comprises silica, the second
topcoat layer 42 comprises zinc oxide, and the third topcoat layer
44 comprises silica. As described above, some of the topcoat layers
can include small amounts of other materials, e.g., dopants, for
example provided to increase the conductivity of the cathode from
which they are deposited. These other materials can include one or
more of aluminum, silicon, and/or tin, just to name a few. The
adjacent low and high index materials can have a refractive index
difference of at least 0.2. By "refractive index difference" is
meant the difference between the refractive indices of two adjacent
topcoat layers. For example, the refractive index difference can be
in the range of 0.2 to 1, such as 0.2 to 0.6, such as 0.4.
Alternatively, the first topcoat layer 40 can comprise a high
refractive index material, the second topcoat 42 can comprise a low
refractive index material, and the optional third topcoat layer 44
can comprise a high refractive index material.
[0033] One or more of the topcoat layers can include a dopant to
increase the conductivity of the cathode from which they are
deposited. For example, one or more of the topcoat layers can
comprise silica doped with aluminum, e.g., 0.1 wt. % to 25 wt. %
aluminum, such as 5 wt. % to 20 wt. % aluminum, such as 10 wt. % to
20 wt. % aluminum, such as 10 wt. % aluminum. As a further
non-limiting example, one or more of the topcoat layers can
comprise zinc oxide doped with tin, e.g., 1 wt. % to 15 wt. % tin,
such as 2 wt. % to 10 wt. % tin, such as 5 wt. % tin.
[0034] The topcoat layers 40, 42, and 44 can be of any desired
thickness. However, in one particular embodiment, the first topcoat
layer 40 and second topcoat layer 42 can have a thickness of about
1 quarter wave optical thickness (i.e., 1 QWOT) with respect to a
reference wavelength of 550 nanometers and the third topcoat layer
44 can have a QWOT less than 1. As will be appreciated by one
skilled in the art and as used herein, the "optical thickness" of a
material is defined as the thickness of the material divided by the
refractive index of the material. Thus, 1 quarter wave optical
thickness (QWOT) of a material having a refractive index of 2 with
respect to a reference wavelength of 550 nm would be
0.25.times.(550 nm.div.2), which equals 68.75 nm. As another
example, 0.33 QWOT of a material having a refractive index of 1.75
with respect to a reference wavelength of 550 nm would be
equivalent to 0.33.times.[0.25.times.(550 nm.div.1.75)] or 25.93
nm. Conversely, a material with an index of refraction of 2.2 and a
thickness of 50 nm would be equivalent to [(50 nm.div.550
nm).times.2.2].div.0.25 or 0.8 QWOT based on a wavelength of 550
nm. As will be appreciated, although the quarter wave optical
thickness of two materials may be the same, the actual physical
thickness of the layers may be different due to the differing
refractive indices of the materials. In the following discussion,
the QWOT values are those defined with respect to a reference
wavelength of 550 nm.
[0035] In another embodiment, the first topcoat layer 40 can have a
QWOT in the range of 0.1 to 1, such as 0.5 to 0.6. The second
topcoat layer 42 can have a QWOT in the range of 0.5 to 1.5, such
as 1 to 1.5, such as 1.2 to 1.4. The third topcoat layer 44 can
have a QWOT in the range of 0.5 to 1, such as 0.6 to 0.8.
[0036] In one particular embodiment, the hybrid coating 14 can
include a functional coating 16 having a first dielectric layer 28
comprising a first film comprising a zinc and tin alloy, e.g., zinc
stannate, having a QWOT in the range of 0.1 to 1, such as 0.2 to
0.7. The first dielectric layer 28 can also include a second film
formed over the first film. In one embodiment, the second film
comprises zinc oxide. Although not required, the zinc-oxide second
film can be doped with another material, such as 1 wt. % to 10 wt.
% tin, such as 2 wt. % to 7 wt. % tin, such as 5 wt. % tin. The
second film can have a QWOT in the range of 0.01 to 1, such as 0.05
to 0.5, such as 0.1 to 0.15. The IR reflective layer 30 comprises
silver and can have a thickness in the range of 0.005 QWOT to 0.1
QWOT, such as 0.007 QWOT to 0.03 QWOT, such as 0.01 QWOT to 0.015
QWOT, such as 0.0125 QWOT. The primer 32 can be titania and can
have a thickness in the range of 0.01 QWOT to 0.06 QWOT, such as
0.02 QWOT to 0.04 QWOT, such as 0.03 QWOT. The second dielectric
layer 34 can include a first film comprising zinc oxide doped with
tin, such as 1 wt. % to 10 wt. % tin, such as 2 wt. % to 7 wt. %
tin, such as 5 wt. % tin. The first film can have a thickness in
the range of 0.05 QWOT to 0.5 QWOT, such as 0.1 QWOT to 0.15 QWOT.
A second dielectric film can be formed over the first film. The
second film can comprise a zinc-tin alloy, such as zinc stannate,
and can have a thickness in the range of 0.1 to 1.5 QWOT, such as
0.2 to 1 QWOT.
[0037] The exemplary hybrid coating 14 further includes a topcoat
18 having a first topcoat layer comprising silica having a
thickness in the range of 0.5 QWOT to 1.5 QWOT, such as 0.8 QWOT to
1.3 QWOT, such as 0.9 QWOT to 1.2 QWOT, such as 1 QWOT. The second
topcoat layer 42 can comprise tin oxide and can have a thickness in
the range of 0.05 QWOT to 1.5 QWOT, such as 0.08 QWOT to 1.3 QWOT,
such as 0.09 QWOT to 1.2 QWOT, such as 1 QWOT. The third topcoat
layer 44 can comprise silica and can have a thickness in the range
of 0.1 QWOT to 1 QWOT, such as 0.2 QWOT to 0.9 QWOT, such as 0.3
QWOT to 0.8 QWOT, such as 0.4 QWOT to 0.8 QWOT, such as 0.5 QWOT to
0.8 QWOT, such as 0.6 QWOT to 0.8 QWOT, such as 0.7 QWOT.
[0038] A laminated article 50 is shown in FIG. 2. In the laminated
article 50, the coated substrate 12 can be laminated to another
substrate 52 by a conventional adhesive layer 54. The substrate 52
can be of any of the materials described above with respect to
substrate 12 and can be the same or different than substrate 12.
The adhesive layer 54 can include one or more plastic or polymeric
materials, such as polyvinyl butyral, plasticized polyvinyl
chloride, or multi-layered thermoplastic materials including
polyethylene terephthalate. Suitable adhesive materials are
described in U.S. Pat. Nos. 4,287,107 and 3,762,988. For automotive
purposes, the adhesive layer 54 is typically polyvinyl butyral
having a thickness in the range of 0.5 mm to 1 mm. The functional
coating 16 can be the same as described above. However, the
outermost topcoat layer 44 (shown in FIG. 1) can be eliminated for
the laminated article 50.
[0039] Illustrating the invention are the following Examples, which
are not to be considered as limiting the invention to the
specifically disclosed details.
EXAMPLE 1
[0040] This Example illustrates the solar reflectivity of a single
silver layer solar control coating with a topcoat of the invention
and without a topcoat of the invention.
[0041] Table 1 shows the layer structure of a solar control coating
having a single silver infrared reflective layer. The first
dielectric layer comprises two dielectric films (1 and 2). The
first dielectric film (film 1) comprises zinc stannate while the
second dielectric film (film 2) comprises a tin doped zinc oxide.
The tin is due to the fact that the sputtering cathode from which
the layer is deposited includes some time to improve the sputtering
characteristics of the zinc cathode. Thus, while the second
dielectric film is primarily zinc oxide, some tin from the cathode
can also be present, such as incorporated into the zinc oxide
structure or as tin oxide. The second dielectric layer comprises
two dielectric films (5 and 6). The first dielectric film (film 5)
comprises a tin doped zinc oxide while the second dielectric film
(film 6) comprises zinc stannate.
1 TABLE 1 Film Material Thickness (nm) QWOT 1 Zn.sub.2SnO.sub.4
41.67 0.62341 2 Sn:ZnO.sub.4 8.00 0.11514 3 Ag 9.42 0.00792 4
TiO.sub.2 2.00 0.03577 5 Sn:ZnO.sub.4 8.00 0.11514 6
Zn.sub.2SnO.sub.4 26.79 0.4008
[0042] Table 2 shows the structure of a similar coating but also
incorporates a topcoat (films 7, 8 and 9) of the invention. The
topcoat comprises a first topcoat layer of silica that also
includes a small portion of alumina. The alumina is present due to
the presence of aluminum in the silicon sputtering target. The
second topcoat layer comprises zinc oxide with a small portion of
tin. The third topcoat layer comprises silica with a small portion
of alumina.
2 TABLE 2 Film Material Thickness (nm) QWOT 1 Zn.sub.2SnO.sub.4
41.67 0.62341 2 Sn:ZnO.sub.4 8.00 0.11514 3 Ag 9.42 0.00792 4
TiO.sub.2 2.00 0.03577 5 Sn:ZnO.sub.4 8.00 0.11514 6
Zn.sub.2SnO.sub.4 26.79 0.4008 7 Si.sub.0.85Al.sub.0.15O.sub.1.9-
25 89.92 0.97174 8 Sn:ZnO.sub.4 91.13 1.36336 9
Si.sub.0.85Al.sub.0.15O.sub.1.925 63.65 0.68785
[0043] FIG. 3 shows the percent reflectance versus wavelength for
the coating of Table 1 (curve 80) and of Table 2 (curve 82). The
reflectance values shown in FIG. 3 were calculated using FilmStar
DESIGN software commercially available from FTG Software Associates
of Princeton, N.J. As shown in FIG. 3, the hybrid coating of curve
82 has substantially better solar reflectance in the near infrared
region of the spectrum than the coating of curve 80 without the
topcoat of the invention. The hybrid coating provides a region of
enhanced solar infrared reflectance in the near solar infrared
region adjacent the visible region of the electromagnetic spectrum.
Such an enhanced infrared reflective region would not be expected
simply from the addition of a multi-layer topcoat. Therefore, the
utilization of a topcoat having low and high refractive index
materials in accordance with the present invention appears to
improve the solar control performance compared to a similar
functional coating without the topcoat. Additionally, it is to be
expected that the topcoat of the invention will provide improved
mechanical and/or chemical durability compared to conventional
thinner titania coatings of the known art.
EXAMPLE 2
[0044] This Example illustrates the effects of a topcoat on the
invention of a functional coating having two silver infrared
reflective metal layers.
[0045] A coating stack having two infrared reflective silver layers
is set forth in Table 3.
3 TABLE 3 Film Material Thickness (nm) QWOT 1 Zn.sub.2SnO.sub.4
31.79 0.4756 2 Sn:ZnO.sub.4 8.00 0.11514 3 Ag 8.91 0.00749 4
TiO.sub.2 2.00 0.03577 5 Sn:ZnO.sub.4 8.00 0.11514 6
Zn.sub.2SnO.sub.4 60.85 0.91036 7 Zn.sub.0.95Sn.sub.0.05O.sub.1.0-
5 8.00 0.11514 8 Ag 10.95 0.00921 9 TiO.sub.2 2.00 0.03577 10
Sn:ZnO.sub.4 8.00 0.11514 11 Zn.sub.2SnO.sub.4 32.55 0.48697
[0046] A similar coating having a topcoat of the invention is shown
in Table 4.
4 TABLE 4 Film Material Thickness (nm) QWOT 1 Zn.sub.2SnO.sub.4
18.04 0.26989 2 Sn:ZnO.sub.4 8.00 0.11514 3 Ag 8.91 0.00749 4
TiO.sub.2 2.00 0.03577 5 Sn:ZnO.sub.4 8.00 0.11514 6
Zn.sub.2SnO.sub.4 54.22 0.81117 7 Sn:ZnO.sub.4 8.00 0.11514 8 Ag
10.95 0.00921 9 TiO.sub.2 2.00 0.03577 10 Sn:ZnO.sub.4 8.00 0.11514
11 Zn.sub.2SnO.sub.4 26.61 0.3981 12
Si.sub.0.85Al.sub.0.15O.sub.1.925 51.85 0.56033 13 Sn:ZnO.sub.4
89.22 1.33479 14 Si.sub.0.85Al.sub.0.15O.sub.1.925 69.68
0.75301
[0047] In both coatings, the thickness of the dielectric layers has
been adjusted to produce a film having a reflected color of
L*=25.85, a*=-1.00, and b=-2.00.
[0048] The solar reflectivity of the coatings shown in Tables 3 and
4 is depicted in FIG. 4. As can been seen from the figure, the
coating with the topcoat of the invention (curve 84) shows improved
solar reflectivity in the near infrared region compared to the
coating without the topcoat of the invention (curve 86).
[0049] It will be readily appreciated by those skilled in the art
modifications may be made to the invention without departing from
the concepts disclosed in the foregoing description. Accordingly,
the particular embodiments described in detail herein are
illustrative only and are not limiting to the scope of the
invention, which is to be given the full breadth of the appended
claims and any and all equivalents thereof.
* * * * *