U.S. patent application number 09/753862 was filed with the patent office on 2001-06-14 for heat treatable coated glass.
Invention is credited to Demiryont, Hulya.
Application Number | 20010003628 09/753862 |
Document ID | / |
Family ID | 23371809 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003628 |
Kind Code |
A1 |
Demiryont, Hulya |
June 14, 2001 |
Heat treatable coated glass
Abstract
A heat-treatable coated glass article comprises a substantially
transparent substrate with a substantially transparent
dual-function coating on a surface of the substrate. The coating
provides low emissivity and high anti-solar performance properties.
It comprises a first anti-reflection layer of dielectric material,
preferably tungsten oxide. An infra-red reflective layer of silver
metal and/or copper metal overlies the anti-reflection dielectric
layer. A buffer layer, such as a chromium buffer layer, is
positioned between the anti-reflection layer and the infra-red
reflective layer. Also, optionally, a color control layer may be
used, preferably being positioned between the anti-reflection layer
and the substrate. A second buffer layer directly overlies the
infra-red reflective layer. A second anti-reflection layer overlies
the second buffer layer. In accordance with a method of
manufacturing the coated article, each of the layers of the coating
is deposited in turn by D.C. magnetron sputtering in a
multi-station sputtering chamber. Passing the transparent substrate
through the sputtering chamber a second time to produce a
double-layer coating structure is found to provide especially high
quality performance characteristics.
Inventors: |
Demiryont, Hulya;
(Philadelphia, PA) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
28 STATE STREET
28th FLOOR
BOSTON
MA
02109
US
|
Family ID: |
23371809 |
Appl. No.: |
09/753862 |
Filed: |
January 3, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09753862 |
Jan 3, 2001 |
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09349305 |
Jul 7, 1999 |
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6190776 |
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Current U.S.
Class: |
428/630 ;
204/192.27; 428/433; 428/434; 428/623 |
Current CPC
Class: |
Y10T 428/12549 20150115;
C23C 14/185 20130101; Y10T 428/12597 20150115; C03C 2217/78
20130101; C23C 14/086 20130101; C03C 17/3681 20130101; C03C 17/3652
20130101; C03C 17/36 20130101; C03C 17/3644 20130101; C03C 17/3618
20130101; Y10T 428/265 20150115; C03C 17/366 20130101; Y10T
428/24975 20150115 |
Class at
Publication: |
428/630 ;
428/623; 428/433; 428/434; 204/192.27 |
International
Class: |
B32B 017/06; C03C
017/09; C03C 017/36 |
Claims
What is claimed is:
1. A heat-treatable coated glass article comprising a substantially
transparent glass substrate with a substantially transparent
coating on a surface of the glass substrate, the substantially
transparent coating comprising: a first anti-reflection layer of
dielectric material overlying the glass substrate, a first chromium
buffer layer overlying the first anti-reflection layer, an
infra-red reflective layer of metal selected from silver metal,
copper metal and a mixture of both, directly overlying the first
buffer layer, a second chromium buffer layer directly overlying the
infra-red reflective layer, and a second anti-reflection layer of
dielectric material overlying the second buffer layer.
2. The coated article of manufacture according to claim 1 wherein
the infra-red reflective layer is silver metal and the first and
second anti-reflection layers each is SnO.sub.2.
3. The heat-treatable coated glass article according to claim 2
wherein the thickness of each chromium buffer layer is 10% to 30%
of the thickness of the infra-red reflective layer of silver
metal.
4. The heat-treatable coated glass article according to claim 2
wherein the thickness of each chromium buffer layer is 1 nm to 5 nm
and the thickness of the infra-red reflective layer of silver metal
is 6 nm to 13 nm.
5. The heat-treatable coated glass article according to claim 4
wherein the first and second anti-reflection layers of SnO.sub.2
each has a substantially uniform thickness from 20 nm to 50 nm.
6. The heat-treatable coated glass article according to claim 1
wherein said glass is not heat-treated and, when the glass has a
thickness of about 2.2 mm to 6 mm, has the following
characteristics: grey-blue color and substantially free of haze;
visible transmittance of 40% to 70%; and sheet resistance of not
more than 7 ohms/sq.
7. The heat-treatable coated glass article according to claim 1
wherein said glass is heat-treated clear glass and, when the glass
has a thickness of about 2.5 mm to 6 mm, has the following
characteristics after heat-treatment: substantially free of haze;
visible transmittance of 50% to 80%; and sheet resistance of not
more than 5 ohms/sq.
8. The heat-treatable coated glass article according to claim 1
wherein the first anti-reflection layer lies directly on the
surface of the glass.
9. The heat-treatable coated glass article according to claim 8
wherein the first chromium buffer layer lies directly on the first
anti-reflection layer.
10. The heat-treatable coated glass article according to claim 9
wherein the infra-red reflective layer directly overlies the first
chromium buffer layer.
11. The heat-treatable coated glass article according to claim 10
wherein the second chromium buffer layer directly overlies the
infra-red reflective layer.
12. The heat-treatable coated glass article according to claim 11
wherein the second anti-reflection layer directly overlies the
second buffer layer.
13. The heat-treatable coated glass article according to claim 1
wherein the substantially transparent glass substrate is
soda-lime-silica glass.
14. A motor vehicle windshield comprising a polymer sheet
sandwiched between a first heat-treated glass substrate bent to a
curved shape, a second heat-treated glass substrate bent to a
matching curved shape, and a substantially transparent coating on a
surface of at least one of the heat-treated glass substrates, the
substantially transparent coating comprising: a first
anti-reflection layer of SnO.sub.2 overlying the glass substrate
and having a thickness of about 39 nm; a first chromium buffer
layer overlying the first anti-reflection layer and having a
thickness of about 2 nm; an infra-red reflective layer of silver
metal directly overlying the first buffer layer and having a
thickness of about 95 nm; a second chromium buffer layer directly
overlying the infra-red reflective layer and having a thickness of
about 2.5 nm; and a second anti-reflection layer of SnO.sub.2
overlying the second buffer layer and having a thickness of about
39 nm; wherein, when the first heat-treated glass substrate and the
second heat-treated glass substrate each is substantially clear
soda-lime-silica glass having a thickness of about 2.2 mm, the
windshield has the following spectral properties: visible light
transmittance greater than 75%; total solar energy transmittance
less than 50%; and total solar reflectance (IR region) of at least
25%.
15. A heat-treatable coated glass article comprising a
substantially transparent glass substrate with a substantially
transparent coating on a surface of the glass substrate, the
substantially transparent coating comprising: a first
anti-reflection layer of dielectric material overlying the glass
substrate, a first buffer layer overlying the first anti-reflection
layer, a first infra-red reflective layer of silver metal directly
overlying the first buffer layer, a second buffer layer directly
overlying the infra-red reflective layer, a second anti-reflection
layer of dielectric material overlying the second buffer layer, a
third buffer layer overlying the second anti-reflection layer, a
second infra-red reflective layer of silver metal directly
overlying the third buffer layer, a fourth buffer layer overlying
the second infra-red reflective layer of silver metal, and a third
anti-reflection layer of dielectric material overlying the fourth
buffer layer.
16. The heat-treatable coated glass article of claim 15 wherein
each of the anti-reflection layers is SnO.sub.2 and the buffer
layers each is a chromium buffer layer.
17. A motor vehicle windshield having low reflectance of visible
light and high transmittance of visible light, comprising a polymer
sheet sandwiched between a first heat-treated glass substrate bent
to a curved shape, a second heat-treated glass substrate bent to a
matching curved shape, and a substantially transparent coating on a
surface of at least one of the heat-treated glass substrates, the
substantially transparent coating comprising: a first
anti-reflection layer of dielectric material overlying the glass
substrate, a first buffer layer overlying the first anti-reflection
layer, a first infra-red reflective layer of silver metal directly
overlying the first buffer layer, a second buffer layer directly
overlying the infra-red reflective layer, a second anti-reflection
layer of dielectric material overlying the second buffer layer, a
third buffer layer overlying the second anti-reflection layer, a
second infra-red reflective layer of silver metal directly
overlying the third buffer layer, a fourth buffer layer overlying
the second infra-red reflective layer of silver metal, and a third
anti-reflection layer of dielectric material overlying the fourth
buffer layer.
18. The motor vehicle windshield in accordance with claim 17
wherein the polymer sheet is sandwiched between the concave side of
the first heat-treated glass substrate and the convex side of the
second heat-treated glass substrate, the substantially transparent
coating being on the concave side of the first heat-treated glass
substrate.
19. The motor vehicle windshield in accordance with claim 17
wherein the first and second anti-reflection layers are SnO.sub.2,
the buffer layers are chromium buffer layers, the thickness of each
chromium buffer layer is 1 nm to 4 nm and the thickness of the
infra-red reflective layer of silver metal is 6 nm to 13 nm, and
wherein the windshield, when the glass is clear soda-lime-silica
glass having a thickness of 2.2 mm to 3.5 mm, has the following
spectral characteristics: visible light transmittance greater than
75%; total solar energy transmittance less than 50%; and total
solar reflectance (IR region) of at least 25%.
20. The motor vehicle windshield in accordance with claim 19
wherein the first buffer and the second buffer have the same
thickness.
21. The motor vehicle windshield in accordance with claim 19
wherein the first buffer layer has a thickness less than that of
the second buffer layer.
22. The motor vehicle windshield in accordance with claim 19
wherein each of the buffer layers is a chromium buffer layer.
23. The motor vehicle windshield in accordance with claim 19
wherein the first buffer layer is at least 1.5 nm thick.
24. A method of manufacturing a heat-treatable coated glass article
comprising a substantially transparent glass substrate with a
substantially transparent coating on a surface of the glass
substrate, comprising the steps of: providing a substantially
transparent glass substrate; and forming a substantially
transparent coating on a surface of the substrate by: A) depositing
a first anti-reflection layer of dielectric material, B)
subsequently depositing a first chromium buffer layer overlying the
first anti-reflection layer; C) subsequently depositing silver
metal or copper metal over the first chromium buffer layer to form
a first infra-red reflection layer, D) subsequently depositing a
second chromium buffer layer directly onto the infra-red reflective
layer, and E) subsequently depositing a second anti-reflection
layer of dielectric material over the second buffer layer to form a
second anti-reflection layer.
25. The method of manufacturing a heat-treatable coated glass
article according to claim 24 wherein the first anti-reflection
layer is deposited directly onto the surface of the glass
substrate.
26. The method of manufacturing a heat-treatable coated glass
article according to claim 24 wherein the layers of steps (A)
through (E) are deposited in that order by magnetron sputtering at
a corresponding series of stations within a sputtering chamber as
the glass substrate moves continuously from station to station
within the sputtering station.
27. The method of manufacturing a heat-treatable coated glass
article according to claim 25 wherein the substantially transparent
glass substrate is soda-lime-silica glass and the method further
comprises, subsequent to step (E), bending the glass substrate in
tandem with a second glass substrate.
Description
INTRODUCTION
[0001] The present invention is directed to transparent substrates
having multi-layer coatings for thermal insulation properties, as
well as to methods of manufacturing such multi-layer coated
articles. The invention relates, in particular, to coated,
transparent glass substrates which are heat treatable. Certain
preferred embodiments are suitable especially for automotive and
architectural applications, exhibiting high visible light
transmittance and high infra-red (IR) energy reflectance.
BACKGROUND
[0002] Coated glazing products having anti-solar properties, that
is, low transmittance of wavelengths in the infra-red range, are
known to those skilled in the art. Coatings for glazing products
are disclosed, for example, in European patent application 0 646
551 A1 entitled Heat-Treatment Convertible Coated Glass and Method
of Converting Same. That document discloses silver coatings
comprising a layer of Si.sub.3N.sub.4 over a layer of nickel or
nichrome, over a layer of silver, over a second layer of nickel or
nichrome, over a second layer of Si.sub.3N.sub.4. Sputtering is
disclosed for producing such coating. Sputtered deposition of a
multi-layer coating is described, for example, in European Patent
Application 0,418,435 to Nalepka. The multi-layer coating of
Hayward et al. is said to comprise a layer of sputtered zinc, tin,
titanium, indium/tin or bismuth oxide, next a layer of sputtered
silver or silver alloy, then a layer sputtered titanium or
stainless steel and finally a layer of zinc, tin, titanium,
indium/tin or bismuth oxide. Such multi-layer film is said to have
excellent visible light transmission while controlling both near
infra-red solar energy and far infra-red reflected energy. A
temperable coated article is suggested in U.S. Pat. No. 5,552,180
to Finley et al. The coated article of Finley et al. employs a
metal-containing film such as titanium nitride which ordinarily
oxidizes at the high temperatures encountered during glass
tempering, along with an overcoating of a protective layer of a
silicon compound and an undercoating with a stabilizing
metal-containing layer. In U.S. Pat. No. 3,990,784 to Gelber a
multi-layer coating for architectural glass is suggested,
comprising first and second metal layers with a dielectric layer
disposed between them. Gelber suggests that the transmission
properties of the coating can be changed independent of its
reflection properties, by varying the thickness of the metal layers
while maintaining the ratio of their thicknesses constant.
[0003] Similar coatings are disclosed in European Patent
Application 97104710.5 published as EP0796 825 A2, wherein a low
emissivity sputtered coating employs controlled index of refraction
of an undercoat layer of an appropriate dielectric material below a
first Si.sub.3N.sub.4 layer. Also a layer of silver is used,
sandwiched between layers of nichrome. The term "nichrome" is used
to designate a layer which includes some combination of nickel and
chromium, at least some of which is in its metallic state, although
same may be oxidized. In a similar way, the term "silver" means
that the layer consists essentially of metallic silver, but may
include some other elements in small concentrations that do not
adversely affect the performance characteristics of the silver in
the system as a whole. Bent or toughened silver coated glass is
taught in European Patent Application 87300601.9 published as No.
0233 003. An additional layer of aluminum, titanium, zinc, tantalum
or zirconium is used over the silver layer, or both over and under
the silver layer. In recent years, the popularity of coated glasses
has occasioned numerous attempts to achieve a coated glass article
which, prior to heat-treatment, can be coated, and which
thereafter, can be heat-treated without adversely changing the
characteristics of the coating or the glass itself (i.e., the
resulting glass article). One of the reasons for this is, for
example, that it can be extremely difficult to achieve a uniform
coating on an already bent piece of glass. It is well-known that if
a flat glass surface can be coated and thereafter bent, much
simpler techniques can be used to get a uniform coating than if the
glass has been previously bent. This is true for architectural,
automotive, and residential glasses.
[0004] Various difficulties have been encountered by those skilled
in the art in developing commercially suitable coatings for
architectural and automotive glazing. In particular, it has proved
difficult to achieve coatings which provide good attenuation of
direct solar radiation, that is, good anti-solar properties. There
has long been need in the glazing industry for coating systems
which can be uniformly deposited, especially by sputtering onto
large surface areas with fast deposition rates, low deposition
power density, good film quality, including high film durability,
bulk or near bulk density, and long shelf life. As used here, large
area deposition refers to deposition onto transparent substrates
suitable in size for architectural and automotive glazing
applications.
[0005] It is an object of the present invention to provide coated
articles meeting some or all of these industry needs. In
particular, it is an object of at least certain preferred
embodiments of the invention to provide heat-treatable coated glass
articles comprising a substantially transparent glass substrate
with a substantially transparent coating on the surface of the
substrate, which coating has good transmittance of visible light as
well as good anti-solar performance characteristics. In accordance
with certain preferred embodiments, it is a further object to
provide glazing units incorporating such coated glass. It is an
object of at least certain preferred embodiments of the invention
to provide heat-treatable coated glass articles comprising a
substantially transparent glass substrate with a substantially
transparent coating on the surface of the substrate, which coating
has medium level of transmittance of visible light as well as
extremely high anti-solar performance characteristics. Such coated
articles can be used for architectural purposes and automotive
applications, e.g., windshields with heat shielding properties, or
windshields with defrosting and anti-fogging properties.
[0006] It is a further object of the invention to provide methods
of manufacturing the aforesaid coated articles. In accordance with
preferred embodiments, such manufacturing includes applying a
coating in accordance with the invention. Optionally, the methods
disclosed here further include the steps of applying an
electrically conductive bus bar, if desired, and performing heat
treatment of the coated article, e.g., bending or tempering, and
also optionally conducting laminating processes.
[0007] Additional objects and advantages of the present invention
will be readily understood by those skilled in the art given the
benefit of the following disclosure of the invention and detailed
description of preferred embodiments.
SUMMARY
[0008] In accordance with a first aspect of the invention, a
heat-treatable, coated glass article of manufacture comprises a
substantially transparent substrate with a substantially
transparent multi-layer coating on a surface of the glass
substrate. The substantially transparent coating comprises a first
anti-reflection layer of dielectric material overlying the surface
of the substrate. Preferably, the anti-reflection layer is directly
on the surface of the substrate. As used here and in the appended
claims, any particular layer of the substantially transparent,
multi-layer coating is said to be "directly" on or to "directly"
overlie the substrate or another layer of the coating if no other
layer of the coating is positioned between them. In this regard,
any particular layer of the coating may be said to lie directly on
another layer of the coating notwithstanding that there may be a
slight transition zone between the two layers involving migration
of the material of one layer into the other and/or interlayer
reaction products different from the primary composition of the
layers. A first buffer layer, most preferably a chromium buffer
layer, overlies the first anti-reflection layer. Preferably it lies
directly on the anti-reflection layer. A chromium buffer layer, as
that term is used here, means a layer which is essentially metallic
chromium, such as a layer deposited by sputtering from a chromium
metal target in an inert atmosphere. It may be in part oxidized,
especially in preferred embodiments wherein the chromium buffer
layer scavanges oxygen from an adjacent silver or copper metal or
silver-copper mixed metal IR reflective layer and/or from
anti-reflection layers during a heat treatment step, as further
discussed below. An infrared reflective layer of silver metal or
copper metal or silver-copper mixed metal directly overlies the
first chromium buffer layer. A second chromium buffer layer
directly overlies the infrared reflective layer. Finally, a second
anti-reflection layer of dielectric material overlies the second
buffer layer. Preferably, it directly overlies the second buffer
layer. Preferably, the first and second anti-reflection layers of
dielectric material are SnO.sub.2, in view of the good D.C.
magnetron sputter deposition properties of SnO.sub.2 and its
compatibility with other preferred materials of the film stack
coating disclosed here. Other suitable anti-reflective materials
for use in the coating include other oxide and nitrade materials,
such as, for example, WO.sub.3, TiO.sub.2, ZnO, BiOx and
Si.sub.3N.sub.4. Additional suitable anti-reflection layer
materials will be apparent to those skilled in the art given the
benefit of this disclosure. Similarly, the use of copper,
copper-silver, or most preferably silver in the IR reflective
layer, especially with the chromium buffer layers sandwiching it,
provides highly durable coatings which are heat-treatable and, in
fact, even yield improved spectral properties upon undergoing
heat-treatment. That is, especially in preferred embodiments, heat
treatment of the system with or without the IR reflective layers
shows several significant effects. First, optical transmittance of
the coated article improves upon heat treatment. There is a
temperature threshold to start transparency improvement, around
400.degree. C., to start the oxidation of the buffer layers.
Second, electrical resistance reduces upon heat treatment e.g.,
sheet resistance of 6 Ohm may be reduced to 3 Ohm after heat
treatment. This improvement in sheet resistance is believed due to
the diminishing of interface scattering at the abrupt Ag--Cr. The
degree of interface by forming an extended interface of Ag--CrOx
upon heat treatment. Crystalinity degree of the Ag film may also
improve upon heat treatment, producing increased conductivity. This
effect is achieved at least in preferred embodiments without
noticeable degradation in the IR properties of the system. This
excellent electrical conductance of the system allows the
electrical heating of the coated glass in certain preferred
embodiments by conducting an electrical current through the Ag
layer. Third, optical transmittance of the system with
anti-reflecting oxide layers improves, as does durability as
compared with buffer-silver-buffer three-layer system.
[0009] Unless the individual instance of usage clearly indicates
otherwise, reference herein to heat-treatable glass should be
understood to mean glass with a coating according to the present
invention, which has not been heat-treated (but which can undergo
heat treatment successfully in accordance with the principles
disclosed here) or which has not been heat-treated. The term
heat-treated is used to mean glass which has been subjected to a
heat-treating process, such as tempering, annealing and/or bending,
etc.
[0010] It is one advantage of the present invention that the
heat-treatable, coated glass articles disclosed here exhibit
certain improvements or changes in spectral properties upon
undergoing heat-treating (e.g., at temperatures of about
600.degree. C.). Visible light transmittance increases and sheet
resistance decreases, and both mechanical stability and
environmental stability improve with heat-treating. In a typical
embodiment employing a multi-layer coating deposited by D.C.
magnetron sputtering on clear soda-lime-silica glass having a glass
thickness from 2.2 mm thick for an automotive windshield
application to 6 mm thick for common architectural applications,
using SnO.sub.2 layers about 20 nm to 60 nm thick for the
anti-reflection layers, chromium buffer layers about 1 to 4 nm
thick, and a silver metal IR reflectance layer 6 nm to 17 nm thick,
emissivity may improve, typically, from a value of 0.15 to 0.01,
visible transmittance may increase or may reduce, e.g., from a
value of about 85% to about 70%, and sheet resistance will improve
from about 13 Ohm/sq. to only about 1.5 Ohm/sq., with no haze
occurring. Thus, the coated glass disclosed here can be used as
different products. Before heat treatment, coated glass in
accordance with an embodiment of the invention may have grey-blue
color and Tvis of 50% to 70%. After heat-treating, the same glass
may have Tvis of about 70% to 85% and be colorless.
[0011] In accordance with certain preferred embodiments, such
heat-treatable, coated glass is especially well-suited for use in
motor vehicle windshield applications with high transmittance, low
visible light reflectance and high energy reflectance, wherein a
polyvinyl butyryl or other suitable polymer sheet is sandwiched
between one coated glass sheet as disclosed here and an uncoated
sheet. Certain especially preferred embodiments employing a coating
having the above five layer coating structure, wherein the first
buffer layer is a chromium buffer layer of 2 nm and the second
buffer is a chromium buffer layer of 2.5 nm, and the infrared
reflective layer is a silver metal layer 10 nm thick, when the
glass of the windshield (in total for both glass sheets) is about
2.2 mm thick soda-lime-silica glass, have visible light
transmittance greater than 76%, solar energy transmittance less
than 50%, and solar reflectance (IR region) of at least 25%. In
such especially preferred windshield embodiments, and in other
preferred embodiments of the invention disclosed here, the infrared
reflector layer is silver and each of the chromium buffer layers
has a thickness which is about 10% to 30% of the thickness of the
silver layer after heat treatment. In such especially preferred
windshield embodiments, and in other preferred embodiments of the
invention disclosed here, the first buffer layer is about 20%
thinner than the second buffer layer.
[0012] In accordance with certain preferred embodiments, such
heat-treatable ,bendable, coated glass is especially well-suited
for use in architectural applications, especially for round
buildings or buildings with cylindrical outside elevators. Certain
especially preferred embodiments employing a coating having the
above five layer coating structure, wherein the buffer layers are
chromium buffer layers of 4 nm for first buffer and 4 nm for the
second buffer the infrared reflective layer is silver metal 14 nm
thick, and the glass of about 6 mm thick soda-lime-silica glass,
have the ratio of visible light transmittance/total solar energy
transmittance of about 50/27. This assumes, for example, a 6 mm-12
mm-6 mm two pane configuration, with the coating at the surface No.
2. Such terminology, when used herein, means that a first 6 mm pane
in spaced 12 mm from the second 6 mm No. 1; its inside surface is
surface No. 2; etc.
[0013] In accordance with another aspect, a heat-treatable coated
glass article is provided, having a substantially transparent
coating, preferably deposited on soda-lime-silica glass by D.C.
magnetron sputtering, wherein the coating comprises:
[0014] a first anti-reflection layer of dielectric material
overlying the glass substrate
[0015] a first buffer layer overlying the first anti-reflection
layer
[0016] a first infra-red reflective layer of silver metal directly
overlying the first buffer layer
[0017] a second buffer layer directly overlying the infra-red
reflective layer
[0018] a second anti-reflection layer of dielectric material
overlying the second buffer layer
[0019] a third buffer layer overlying the second anti-reflection
layer
[0020] a second infra-red reflective layer of silver metal directly
overlying the third buffer layer
[0021] a fourth buffer layer directly overlying the second
infra-red reflective layer
[0022] a top anti-reflection layer of dielectric material overlying
the fourth buffer layer.
[0023] In accordance with certain preferred embodiments, such
heat-treatable, coated glass is especially well-suited for use in
motor vehicle windshield applications, wherein a polyvinyl butyral
(PVB) or other suitable polymer sheet is sandwiched between one
coated glass sheet as disclosed here and an uncoated sheet. Such
preferred embodiments have very low reflectance of visible light
and high transmittance of visible light, as well as low total solar
energy transmittance and high solar reflectance (IR region).
Certain especially preferred embodiments employing a coating having
the above nine layer film stack, wherein the buffer layers are
chromium buffer layers of 1 nm to 4 nm thickness, the infrared
reflective layer is silver metal around 50 nm to 60 nm thick, when
the glass of the windshield (in total for both glass sheets
laminated with PVB) is about 5.5 mm thick soda-lime-silica glass,
have visible light transmittance greater than 75%; total solar
energy transmittance less than 50%; and solar reflectance (IR
region) of at least 25%. In such especially preferred windshield
embodiments, and in other preferred embodiments of the invention
disclosed here, each infrared reflector layer is silver and each of
the chromium buffer layers has a thickness which is about 10% to
30%, the thickness of the silver layer after heat treatment.
[0024] The chromium buffer layers are found to perform a crucial
role in rendering the coated glass articles disclosed here durable
and effective. Without wishing to be bound by theory, it is
currently understood that the chromium buffer layers, although
deposited as chromium metal, oxidize to some degree, especially
during heat-treatment of the coated glass. The buffer layers
oxidize by taking oxygen from adjacent layers, such as SnO.sub.2 or
other oxide material of an adjacent anti-reflection layer. There is
a resulting increase in volume of the chromium buffer layer and
corresponding increase in buffer layer density without cracking of
the buffer layer. This is highly advantageous, since the buffer
layer should be crack-free and void-free following heat treatment
to prevent oxygen diffusion through the buffer layer to the silver
metal IR reflection layer. Also, the high-density of the buffer
layers reduces or eliminates the adverse affects of migration of
silver into the buffer layers. Thus, long term durability and
performance are achieved in the multi-layer coated, heat-treatable
glass articles disclosed here. In preferred motor vehicle
windshield embodiments of the present invention, the multi-layer
heat-treatable coating is provided on one of the two glass panes
which sandwiched between them a PVB sheet. Preferably, the coating
is provided on the inside glass pane (i.e., the one facing the
exterior pane vehicle passenger compartment rather than the
exterior pane), most preferably on the so-called surface No. 2 of
the windshield, i.e., on the outside surface of the inside pane
(i.e., adjacent the PVB sheet). The two glass panes, one coated and
one uncoated, typically are paired and bent together. In accordance
with preferred embodiments, special powder to prevent the glass
panes sticking together are usually used between the matched panes
during such bending process can be eliminated. The multi-layer
coating serves to prevent sticking. Moreover, the multi-layer
coating in accordance with preferred embodiments is sufficiently
durable and though, that it can be placed into contact with the
second glass pane during the bending process without causing
unacceptable scratching or other degradation of the coating.
[0025] In accordance with another aspect of the invention, methods
are provided for making the coated article disclosed above. Such
methods comprise providing a substantially transparent substrate,
typically with appropriate surface preparation steps being
performed on the surface to be coated. The multi-layer, anti-solar
coating is then formed on the surface of the substrate. The first
anti-reflection layer of dielectric material is deposited, followed
by the first chromium buffer layer, followed by the silver metal
infra-red reflective layer, followed by the second chromium buffer
layer, followed by the second anti-reflection layer. In accordance
with preferred embodiments, each of the layers of the substantially
transparent coating is deposited by sputtering in a series of
sputter stations arranged sequentially in a single sputtering
chamber through which the transparent substrate passes at constant
travel speed. Suitable partitions, such as curtains or the like,
separate one sputter station from the next within the sputtering
chamber, such that different deposition atmospheres can be employed
at different stations. A reactive atmosphere comprising nitrogen or
oxygen or both can be used, for example, at a first station to
deposit an anti-reflection layer, followed by a non-reactive
atmosphere consisting essentially of argon or other suitable inert
gas at a subsequent station for depositing the silver metal IR
reflection layer.
[0026] In accordance with certain highly preferred embodiments of
the manufacturing method disclosed here, the substantially
transparent coating is deposited by multiple passes, preferably two
passes through such multi-station sputtering chamber. If the
multi-station sputtering chamber has a sufficient number of
cathodes, e.g., at least nine cathode materials mentioned above,
this method is especially suitable, for example, for depositing the
nine layer coating disclosed above in a single pass. Alternatively,
during each of the passes through the sputtering chamber, a
multi-layer coating is deposited comprising the aforesaid first
anti-reflection layer, first chromium buffer layer, silver metal
layer, second buffer layer and second anti-reflection layer.
Coatings formed in accordance with such multi-pass methods of the
invention are found to have substantially improved coating
properties, including especially colour spectral uniformity.
[0027] It will be apparent to those skilled in the art in view of
the present disclosure, that the present invention is a significant
technological advance. Preferred embodiments of the substantially
transparent coatings disclosed here have excellent spectral
performance characteristics, including excellent transmittance of
visible light and advantageously high anti-solar properties, that
is, high attenuation levels of direct solar radiation. Employing
the above disclosed silver metal infra-red reflective layer,
sandwiched between chromium buffer layers, together with the
anti-reflection layers results in novel multi-layer coatings which
are highly suitable for large area deposition by planar DC
magnetron sputtering. Fast deposition rates can be obtained, even
employing advantageously low deposition power densities. The
resulting coating has high durability, bulk or near bulk density
and long shelf life.
[0028] Additional features and advantages of the various
embodiments of the present invention will be further understood in
view of the following detailed description of certain preferred
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Various preferred embodiments of the coated article of
manufacture and method of manufacture disclosed above are discussed
below with reference to the appended drawing in which:
[0030] FIG. 1 is a schematic cross-sectional view of a coated
article of manufacture according to a first preferred
embodiment;
[0031] FIG. 2 is a schematic cross-sectional view of a second
preferred embodiment;
[0032] FIG. 3 is a schematic illustration of a motor vehicle
windshield (partially broken away) in accordance with a preferred
embodiment, having the coating of FIG. 2 on surface No. 2 of the
glazing panes; and
[0033] FIGS. 4-7 are graphical representations of the spectral
properties of various preferred embodiments described in Examples
1-3, respectively;
[0034] It should be understood that the schematic illustrations in
FIGS. 1-3 are not necessarily to scale. In particular, the
thickness of the various individual layers forming the
substantially transparent multi-function coating are increased
relative the thickness of the substrate for the purpose of clarity
and ease of illustration.
DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS
[0035] The coatings disclosed here are thermostable in that, when
subjected to thermal stress, they are resistant, against
degradation, most notably in their capacity to block or transmit
light. In addition, the term "thermostable" refers to a coating or
coated article of manufacture which substantially retains its
characteristic mechanical properties, such as body integrity,
surface continuity, tensile strength and adhesiveness (e.g.,
between coating and substrate). The term "thermal stress" is herein
taken to mean the stresses encountered upon exposure to high
temperatures used for heat treatment, e.g., for tempering or
bending the glazing substrate. Typically, such temperatures are in
the range of 590.degree. C. to 650.degree. C. The solar coatings of
the invention are thermostable at the tempering temperature of the
glazing substrate and/or at its bending temperature.
[0036] It will be apparent to those skilled in the art, given the
above disclosure and the following detailed description, that the
coated articles disclosed here, comprising a substantially
transparent glass substrate carrying a substantially transparent
coating have numerous commercially significant applications. For
ease of discussion, the following detailed description of certain
preferred embodiments will focus primarily on articles suitable for
automotive or architectural glazing applications. It will be within
the ability of those skilled in the art, given the above disclosure
and this detailed description, to employ the invention in
alternative applications.
[0037] Referring now to FIG. 1, a coated article 10 is seen to
comprise a substantially transparent substrate 12 having a main
surface 14 carrying substantially transparent, multi-layer coating
16. In preferred embodiments, the substantially transparent
substrate is a flat or curvo-planer pane of glass or glass ceramic.
It is highly preferred that the substantially transparent substrate
be a panel of glass selected from the group consisting of
soda-lime-silica glass, borosilicate glass, aluminosilicate glass,
vycor, fused silica and vitreous silica. It is particularly
preferred that the glass be soda-lime-silica glass. Coating 16
provides thermal insulation or anti-solar performance
characteristics for the coated article. Coating 16 includes a first
anti-reflection layer 18 directly on the surface 14. Numerous
suitable materials for anti-reflection layer 18 are disclosed above
and will be apparent to those skilled in the art given the benefit
of this disclosure. Most preferably anti-reflection layer 18 is
formed of S.sub.nO.sub.2. It should be understood that all
references here and in the appended claims to an oxide, unless
otherwise clear the context of any particular instance of its use,
are intended to include variations in the degree of oxidation.
Chromium buffer layer 19 lies directly on anti-reflection layer 18.
Silver metal layer 20 lies directly on buffer layer 19. Second
buffer layer 22 directly overlies silver metal layer 20. The
overlying anti-reflection film 24 is exposed to the atmosphere. It
will be within the ability of those skilled in the art, given the
benefit of this disclosure, to determine suitable thickness for the
individual layers of coating 16, given the benefit of the
disclosure, including suitable thickness for silver metal layer 20
adapted to the intended application of the coated article. Silver
metal layers of greater thickness will provide enhanced infra-red
reflectivity, while thinner silver metal layers will provide
increased transmittance of light in the visible wavelength range.
In accordance with certain preferred embodiments, the silver metal
layer has a thickness between 6 nm and 18 mm, more preferably
between 8 nm and 12 nm for automotive applications and between 8 nm
and 16 nm for architectural applications.
[0038] It will be within the ability of those skilled in the art,
given the benefit of this disclosure, to employ additional coatings
or additional coating layers with the multi-layer, heat-treatable,
thermal insulation coatings disclosed here. For example,
transparent oxide or nitrite over-layers may be used at the surface
of the coating exposed to the atmosphere. Also, colour control
layer(s) can be used, preferably at the interface of the coating
with the glass substrate or on a different surface of the glass
substrate. One or more other additional coatings may be used, e.g.,
an all-dielectric anti-reflecting coating system on a different
surface of the glass substrate, preferably on the number 4 surface
of a double pane (interior side). Such AR coating improves the
visible transmittance of the overall coated article. Also, adhesion
enhancing layer(s) can be used, e.g., at the interface of the
coating with the glass substrate or on a different surface of the
glass substrate.
[0039] The adhesion increasing layer or colour forming layer
preferably has a thickness less than 50 .ANG. and is formed
preferably of silicon or tungsten metal. It will be within the
ability of those skilled in the art, given the benefit of this
disclosure, to select a suitable material and thickness for the
colour control layer to achieve both enhanced uniformity and
desired hue or colour of the coated article. Reference here to
uniformity of colour refers to reduction in blotchiness or the like
which may otherwise appear in a coated article
[0040] An alternative preferred embodiment of the coated articles
disclosed here is illustrated in FIG. 2, having a substantially
transparent soda-lime-silica glass substrate 32. A substantially
transparent, heat-treatable coating 36 is carried on surface 34 of
substrate 32. In coating 36, first anti-reflection layer 38
directly over the surface 34 of substrate 32.
[0041] The anti-reflection layer 38 in coating 36 of coated article
30 is comparable to anti-reflection layer 18 in the embodiment of
FIG. 1. Directly overlying anti-reflection layer 38 is a first
buffer layer 40, preferably a chromium buffer layer, for the
reasons discussed above. Silver metal layer 42 in the embodiment of
FIG. 2 corresponds generally to silver metal layer 20 in the
embodiment of FIG. 1. Similarly, second buffer layer 44 corresponds
generally to buffer layer 22 in the embodiment of FIG. 1. It will
be within the ability of those skilled in the art to select a
suitable thickness for buffer layer 40, in conjunction with
selection of the thickness of buffer layer 44, to provide good
protection for the silver metal layer 42 and the other layers of
coating 36 within the constraints of meeting spectral performance
requirements in the finished article. Oxide layer 46 directly
overlies record buffer layer 44, and may be deposited in two parts.
Specifically, if a double pass sputtering deposition is carried out
as disclosed above, a first portion of oxide layer 46 may be
deposited at the last deposition station during the first pass of
the glass substrate through the sputtering chamber. The second
portion would then be deposited at the first deposition station
during the final pass. Third buffer layer 48 directly overlies
oxide layer 46. Second IR reflection layer 50 directly overlies
third buffer layer 48. Fourth buffer layer 52 directly overlies
silver metal layer 50. Outer anti-reflective layer 54 directly
overlies fourth buffer layer 52, and is exposed to the atmosphere
or to the space between pane 32 and a second, coated or uncoated
pane used with pane 32 to form a double-glazed unit. Such space
between two panes can be a vacuum or filled with inert gas. The
coated surface also can be positioned to lie against a PVB
laminating sheet in a windshield construction or the like.
Anti-reflection film 54 in the embodiment of FIG. 2 corresponds
generally to tin oxide or other oxide anti-reflection layer 24 in
the embodiment of FIG. 1. The thickness of the outer
anti-reflection layer, that is, anti-reflection layer 24 in FIG. 1
and 44 in FIG. 2, is selected to provide, in conjunction with the
other layers of the coating, suitably low reflectance of visible
light, with reflectance color preferably being neutral or grey-blue
in the unheat-treated condition.
[0042] In accordance with certain preferred embodiments, the coated
article 30 is subjected to a tempering step subsequent to
deposition of the coating 36. Coating 36 survives exposure to the
high temperatures required for tempering a glass substrate, such as
a soda-lime-silica glass substrate intended for architectural or
automotive applications.
[0043] FIG. 3 illustrates a motor vehicle windshield partially
broken away, in accordance with a preferred embodiment. A first
pane 62 is laminated to a record sheet 64 by PVC sheet 66 between
them. The inside pane 62, i.e., the one toward the motor vehicle
passenger compartment, was bent in tandem with outer pane 64 and
then separated for laminating. A heat-treatable, multi-layer
coating 70, in accordance with the present disclosure is on surface
No. 2 of the windshield, i.e., inside surface 68 of outside pane
64. Preferably coating 70 is in accordance with the coating shown
in FIG. 1 or FIG. 2. Above figure showing two panes of glass
window, withe the temperable multi functioning coating on the No. 2
surface is necessary here.
[0044] The heating temperature/time profile of the bending furnace
or lehr used for bending a heat-treatable coated glazing of the
present invention is important. Suitable lehrs include, for
example, a Tamglass bending furnace for simultaneous shaping of the
two panes of an automobile windshield by gravity sag forming. The
top pane preferably is coating free and the inside of the lower
pane comprises the coating. Such bending furnace has five thermal
zones. A first heating zone is from room temperature to 350.degree.
C. A second heating zone is from 350.degree. C. to 620.degree. C. A
third heating zone is the bending zone and the last two zones are
the cooling regions where glass cool downs slowly at first and then
faster. The total time of the bending process is typically about 30
minutes: 15 min. for heating & bending and 15 min. for cooling.
The best results of bending in the third zone occur for typical
automotive soda-lime-silica glass, at about 615.degree. C. over 45
to 60 seconds. It will be within the ability of those scheduled in
the art to determine alternative suitable temperature/time profiles
given the benefit of the present disclosure.
[0045] Preferred embodiments of the coated articles disclosed here
can be prepared in accordance with various suitable techniques
employing commercially available equipment and materials.
Preferably, the substantially transparent dual-function coating is
formed on the surface of the substantially transparent substrate by
cathodic sputtering. In accordance with certain preferred
embodiments, a coated article is manufactured by depositing each of
the layers of the coating in sequence. Preferably, each of the
layers is deposited in turn as the substrate travels continuously
through a multi-station sputtering chamber. Thus, in manufacturing
the embodiment of FIG. 1, for example, as the substrate passes
through a first sputtering station within such multi-station
chamber, the first anti-reflection layer of dielectric material is
deposited by DC magnetron sputtering onto the surface of the
substrate. Depending on the substrate travel speed, deposition
parameters, and the thickness of the anti-reflection layer, one,
two or more sputtering stations can be used to deposit the same
coating material. In this way, one can achieve shorter deposition
cycle time. After having deposited the first anti-reflection layer
onto the glass surface, the buffer layer and infrared reflective
layer are then deposited by sputtering as the substrate passes
through a subsequent station of the multi-station chamber. The
second buffer layer is deposited at a subsequent station within the
chamber, and then the second anti-reflection layer is deposited on
a subsequent station. Preferably, the substrate moves continuously
through the chamber, such that the individual layers are deposited
onto the substrate as it is traveling. The individual stations are
sufficiently isolated by curtains or other suitable partition
means, such that the reactive atmosphere employed at a first
sputtering station does not contaminate the non-reactive atmosphere
employed at an adjacent station. In this regard, where less than
all stations of a multi-station deposition chamber are to be
employed, for example, where an eight-station chamber is to be used
to deposit a four-layer coating, a station can be left unused
between one employing a reactive atmosphere and another employing a
non-reactive atmosphere to achieve better isolation. Suitable
multi-station sputter deposition chambers are commercially
available, including pilot plant size coaters, for example, Model
Z600 from Balzers Process System GmbH, D-63755, Alzenau, Germany,
and full commercial scale coaters, for example, Interpane 1993
model Coater available from Interpane Glass Industrie AG, Sohnr
Eystasse 2137697 Lauenforde, Germany. Table A gives the typical
process parameters for Model Z600 pilot plant coater and for an
Interpane 1993 Model production coater.
1 Parameters Z600 Interpane Maximum Substrate 40 .times. 50 600
.times. 300 Dimensions, cm Background Pressure, 5 5 mbar
(10.sup.-5) Power Density (Watt/cm.sup.2) 0.2-5 0.2-5 Working
Pressure, 1.5-4 2-7 mbar (10.sup.-3) Argon, sccm sputter sputter
Oxygen, sccm reactive reactive Nitrogen, sccm reactive reactive
[0046] Advantageously, such preferred multi-station sputtering
chambers employ sputter targets which are wider than the glass
substrates being coated and are mounted in a direction extending
perpendicular to the travel direction of the substrate. It will be
within the ability of those skilled in the art to select suitable
deposition conditions and parameters for magnetron DC sputtering of
the various layers disclosed above for the transparent coated
articles of the present invention. The following deposition
parameters are suitable for a typical deposition process to produce
a heat-treatable, multi-layer coating in accordance with the
embodiment of FIG. 1 coating on a soda-lime-silica glass substrate
40 cm wide by 50 cm long traveling at a rate of 2 meters per minute
through the sputtering chamber.
[0047] 1. The sputtering chamber is initially evacuated to about
5.times.10.sup.-5 millibar and then raised to an operating pressure
of approximately 3.times.10.sup.-3 millibar by the injection of
operating gases at the various sputtering stations.
[0048] 2. Tin oxide anti-reflection layers are deposited by
sputtering from a pure tin target in an operating atmosphere of
3.2.times.10.sup.-3 millibar with an Argon/Oxygen flow rate ratio
of 45/82, at a power level of about 4 to 5.5 Watts/cm.sup.2. The
throw distance from the tin target to the substrate is typically
about 5 to 15 cm.
[0049] 3. The silver infra-red reflective layer is deposited from a
pure silver target in a non-reactive atmosphere, for example, a
substantially pure argon atmosphere, in an operating atmosphere of
2.0.times.10.sup.-3 millibar at a power level of about 0.4 to 2.6
Watts/cm.sup.2. The throw distance from the silver target to the
substrate is typically about 5 to 15 cm.
[0050] 4. The chromium buffer layers are deposited from a chromium
target in a non-reactive atmosphere, for example, a substantially
pure argon atmosphere, in an operating atmosphere of
11.times.10.sup.-4 millibar at a power level of about 0.4 to 1.0
Watts/cm.sup.2. The throw distance from the silicon target to the
substrate is typically about 5 to 15 cm.
[0051] In accordance with certain preferred embodiments, a
substantially transparent, heat treatable coating in accordance
with the structure of the embodiment of FIG. 2 described above is
formed by passing the substrate through the multi-station
sputtering chamber a first time, followed by passing it through the
sputtering chamber a second time. Preferably the deposition
characteristics and process parameters are maintained the same
before the two passes, such that substantially identical sets of
layers are deposited during each pass. Optionally, a slightly
thicker final oxide layer is deposited for enhanced performance
characteristics. In general, it would be understood that the
thickness of the deposited layers will be determined largely by the
deposition power level, working gas conditions, and the exposure
time. The exposure time is determined primarily by the speed at
which the substrate is traveling through the sputtering chamber,
although additional thickness can be achieved by employing multiple
targets for a deposited layer. Throw distance is also a significant
factor in determining layer thickness. In preferred embodiments
employing sputtering targets wider than the substrate,
advantageously small throw distances can be used without
sacrificing uniformity of deposition thickness.
[0052] It has been found that, generally, multi-pane glazing
systems employing the heat-treatable coating of the present
invention provide best results when the coating is placed at the
second surface as illustrated in FIG. 3.
[0053] The present invention is further disclosed by the following
examples, which are intended for purposes of illustration and not
limitation.
EXAMPLES
[0054] The following examples illustrate coated articles according
to the invention, and their manufacture. In each of the following
examples, a soda-lime-silica glass panel 30 cm wide by 30 cm long
by 6mm thick is passed through a multi-station sputtering chamber,
Model Z600 available from Balzers Process System. At the same time,
for visual inspection, measurement and characterizations, test
pieces also were coated in the system. That is, same, a 5 cm wide
by 5 cm long by 2.2 mm thick glass was used for windshield
applications and the same size test pieces of 6 mm thick samples
for architectural applications. The glass panel traveled in each
case through the sputtering chamber at a travel speed of 2 meters
per minute. Immediately prior to entering the sputtering chamber,
the glass panel surface to be coated was washed with demineralized
water (max 5 microsiemens) and substantially dried by pressurized
air. For each of the examples, the sputtering conditions are
provided for each layer of the dual-function coating. In those of
the examples involving a double-layer structure, as disclosed
above, the deposition conditions and parameters were identical for
the first and second passes unless otherwise stated.
[0055] The spectral properties were measured for the resultant
coated article of each example. Perkin Elmer Model Lambda 900 UV
Vis NIR spectrophotometer was used to measure the optical
performance of each sample, e.g., transmittance, T %, reflectance
from film side, R %, and reflectance from glass side, R' %, with
all spectra being measured over the 350 nm-2100 nm spectral region.
Reference herein to spectral properties in the IR range mean 750 nm
to 2100 nm. The weighted spectral averages of the visible region,
T.sub.vis, R.sub.vis, R'.sub.vis and other performance and color
information shown in Tables 1-6 were determined by the "Window
4.0", and Uwinter and Usummer were calculated using the "Window
4.1" calculation program both publicly available from the USA
Department of Energy. These "U" values are a measure of overall
conductance of the thermal energy in terms of Watt/m.sup.2 K,
calculated using the following table:
2 Outside Temp Inside Temp Wind Speed Wind Direct Solar T.sub.sky
Name (.degree. C.) (.degree. C.) (m/s) Direction (W/m.sup.2)
(.degree. C.) E.sub.sky Uwinter Uvalue -17.8 21.1 6.7 0 Windward
0.0 -17.8 1.00 Solar -17.8 21.1 6.7 0 Windward 0.0 -17.8 1.00
Usummer Uvalue 31.7 23.9 3.4 0 Windward 783.0 31.7 1.00 Solar 31.7
23.9 3.4 0 Windward 783.0 31.7 1.00
[0056] In addition, the R.sub.s surface resistance was measured by
a Signatron four probe, and emissivity, e was measured by an IR
spectrometer and calculated from the following equation:
e=1-(1/((1+0.0053).times.R.sub.s)).sup.2
[0057] Ref.: K. L. Chopra, S. Major, D. K. Pandya. It was found
that measured and calculated values fit well with each other for
the films having surface resistance R.sub.s less than 10 Omhs. The
shading coefficient, sc, was calculated as the performance ratio,
T.sub.vis/T.sub.solar, was used to determine the quality of the
coatings. The theoretical limit of the T.sub.vis/T.sub.total solar
ratio is 2.15.
Example 1
[0058] This example shows the properties of a bendable and
otherwise heat treatable coated glass suitable for motor vehicle
windshield applications. In Table 1 below, the coated glass of this
example is identified by reference No. 1345. The same glass
following heat treatment as described below is identified in Table
1 as Sample No. t1345. The same sample following such heat
treatment and then lamination to an uncoated but otherwise
substantially identical glass pane by means of a PVB polymer layer
sandwiched between the two glass panes is identified by reference
number LI 345. The sample of this example is a single silver/single
pass sample. That is, the glass is passed through the DC magnetron
sputtering chamber only once (hence, being referred to as a single
pass coating) wherein it is coated, in order, with an
anti-reflection layer, chromium buffer layer, silver layer, second
chromium buffer layer and finally second anti-reflection layer.
Thus, the coated glass sample of this example has only a single
layer of silver in the film stack which makes up the coating
deposited on the glass in the sputtering chamber.
[0059] The glass panel was prepared and passed through the
multi-station sputtering chamber as described above. In this
example, the heat-treatable multi-layer coating was
SnO.sub.2/Cr/Ag/Cr/SnO.sub.2 where the first SnO.sub.2 layer
(directly on the glass substrate surface) and the topmost SnO.sub.2
layer have the same thickness, but the first Cr layer is thinner
than the second Cr film. The total thickness of the coating was
around 920 .ANG..
[0060] At station 1 within the multi-station sputtering chamber, a
39 nm thick layer of SnO.sub.2 was deposited by sputtering from a
tin target at 5.1 Watts/cm.sup.2 in an atmosphere of Argon and
Oxygen gasses with the flow ratio of 45 to 82 sccm (i.e., with
Argon and Oxygen flow rates of 45 sccm and 82 sccm, respectively)
at a vacuum level of 3.2.times.10 .sup.-3 mbar.
[0061] At station 2, within the multi-station sputtering chamber, a
2 nm thick layer of Cr was deposited by sputtering from a chromium
target at 0.4 Watts/cm.sup.2 in an atmosphere of Argon gas with a
flow rate of 20 sccm at a vacuum level of 11.times.10.sup.-4
mbar.
[0062] At station 3, within the multi-station sputtering chamber, a
95 nm thick layer of Ag was deposited by sputtering from a Silver
(Ag) target at 1.3 Watts/cm.sup.2 in an atmosphere of Argon gas
with a flow rate of 50 sccm at a vacuum level of
2.0.times.10.sup.-3 mbar.
[0063] At station 4, within the multi-station sputtering chamber, a
2.5 nm thick layer of Cr was deposited by sputtering from a
chromium target at 0.4 Watts/cm.sup.2 in an atmosphere of Argon gas
with the flow rate of 30 sccm at a vacuum level of
11.times.10.sup.-4 mbar.
[0064] At station 5, within the multi-station sputtering chamber, a
39 nm thick layer of SnO.sub.2 was deposited by sputtering from a
tin target at 5.1 Watts/cm.sup.2 in an atmosphere of Argon and
Oxygen gasses with a flow rate of 45 to 82 sccm at a vacuum level
of 3.2.times.10.sup.-3 mbar.
[0065] The resultant coated glass panel, Sample No. 1345, had good
color uniformity. Its spectral properties are shown in Table 1
below, and spectral transmittance and reflection properties of the
coated panel of this Example 1 are shown in the graphs of FIG. 4,
wherein the horizontal axis shows wavelength and the vertical axis
shows level of transmittance. Specifically, FIG. 4a shows intensity
as a function of wavelength for Sample No. 1345, that is, the
coating as deposited. FIG. 4b shows corresponding spectral
properties for Sample No. t1345, that is, the coating after heat
treatment at 635.degree. C. for 1 minute. FIG. 4c shows the
spectral properties for Sample No. LI 345, that is, the laminated
glazing system incorporating the glazing pane carrying the
heat-treated coating and laminated by means of a PVB lamination
layer to a second, uncoated glazing pane. In all cases, the
spectral properties include transmittance (T %), reflection
measured from the coated side (R %), and reflection measured from
the uncoated side (R' %). As noted above, coated articles of these
examples were characterized by spectrophotometric measurements
(Perkin Elmer Lambda 900 UV/VIS/NIR Spectrometer), resistance
measurements (signatone four probes Model SYS 301 instrument
combined with Keithly Model 224 current source and Model 2000
multimeter), and thickness measurements (Tencor Alpha Step Model
500). Film thicknesses were measured by a Tencor Model Alpha step
500 thickness measuring apparatus. Mechanical properties of the
samples were determined by a Taber Abraser machine. Environmental
stability of the samples were evaluated by using a weathering cabin
controlling ambient temperature and humidity. Spectrophotometric
measurements were taken over 300 nm to 2100 nm spectral region,
including transmittance T %, reflection R % measured from the
coated side, and reflection R' % measured from the glass (uncoated)
side. As can be seen from Table 1 and the graphs of FIG. 4, the
coated panel prepared in accordance with this Example 1 has
excellent transmittance of visible light together with good
anti-solar properties. In addition, it has excellent environmental
properties and long shelf life, specifically, passing a test of at
least two weeks in the humidity chamber at 60.degree. C. and 95%
relative humidity with substantially no degradation observed
throughout the sample surface of 40 cm by 50 cm, including the
edges of the laminated product Sample No. 1345. Furthermore, the
coating process can be seen from the description here to be fast
and economical, so as to be commercially suitable for producing
automotive and architectural glazing products. In that regard, the
sputter deposition process required only approximately 2.5
minutes.
Example 2
[0066] This example illustrates a double pass/double silver layer
coating system. That is, in this example, the soda-lime silica
glass pane is passed through the DC magnetron sputtering chamber
substantially as in Example 1 above, but is then passed through the
DC magnetron sputtering chamber a second time to produce a
double-layer coating. The resultant coating system deposited onto
the glass surface has two IR reflective layers, that is, two layers
of silver in the film stack which forms the coating. It will be
appreciated from the foregoing disclosure and discussion of the
invention, that single pass, single silver layer systems are
advantageous in that they are simpler to produce, and are suitable
for both automotive and architectural applications. Double pass,
double silver layer coating systems, however, in accordance with
the invention, also provide excellent spectral properties,
environmental durability, etc. In accordance with this Example 2,
the glass panel was prepared and passed through the multi-station
sputtering chamber as described above in Example 1, except coating
was doubled, that is, a coating system of
SnO.sub.2/Cr/A.sub.g/Cr/SnO.sub.2/Cr/Ag/Cr/SnO.sub.2 system was
deposited with the respective thicknesses (measured in nanometers)
of 40/2/7/2/80/2/7/2/40. The total thickness of the resultant
coating was around 182 nm. As mentioned above, in this example the
coating was produced by passing the glass panel twice through the
coater. The same deposition parameters were maintained during the
second pass. The coated sample of this Example 2 was subjected to
heat treatment as in Example 1. The resulting heat treated sample
is identified in table 1 below by reference No. t1288. The
corresponding sample after being laminated to an uncoated but
otherwise substantially identical pane by means of a PVB laminating
layer is identified in Table 1 below by Reference No. L1288. The
spectral properties of Sample No. t1288 and Sample No. L1288 are
shown in Table 1 below. Spectral transmittance and reflectance
properties of the coated panel of Example 2 are shown in the graphs
of FIG. 5a and 5b. Specifically, FIG. 5a shows the spectral
properties T, R and R' as intensity (%) as a function of wavelength
for Sample No. t1288. FIG. 5b shows the corresponding spectral
properties for the laminated Sample No. L1288. Performance values
for Sample No. tl288 and Sample No. L1288 also are given in Table
1, below. The samples of this Example 2 were found to have
excellent environmental properties and a long shelf life comparable
to those of Example 1. More specifically, as can be seen from Table
2 and the graph of FIG. 5, the coated panel prepared in accordance
with this Example 2 has excellent transmittance of visible light
together with good anti-solar properties. In addition, it has
excellent mechanical properties, including long shelf life.
Furthermore, the coating process can be seen from the description
here to be fast and economical, so as to be commercially suitable
for producing automotive and architectural glazing products.
Example 3
[0067] Addition examples of the present invention were prepared to
show architectural applications. Specifically, sheets or panes of
soda-lime-silica glass having the same composition as in Examples 1
and 2, being 6 mm thick, were used to prepare four architectural
glass glazing products. In each case, a first 6 mm pane coated as
described below was spaced 12 mm from a second, uncoated 6 mm thick
pane. The coating was carried on surface No. 2 of the resultant
double pane architectural glazing product. In all four samples, the
coating system was deposited under the same conditions recited
above in Example 1 except as follows. In the first sample, Sample
No. t 1372 IG, the chromium and silver layers were thicker than in
Example 1. Specifically, the silver layer was 14 nm thick and the
two chromium layers, which sandwich the silver layer between them,
were each 4 nm thick. The tin oxide layers each was 22 nm thick.
The spectral properties of the resulting Sample No. 1372 (tested as
a single pane corresponding to the test of Sample 1345 shown in
FIG. 4a) carrying the coating system SnO.sub.2/Cr/Ag/Cr/SnO.sub.- 2
are shown in FIG. 6a. Specifically, spectral values T, R and R' are
shown in FIG. 6a as a function of wavelength. In FIG. 6b the
corresponding spectral properties for the same sample after heat
treatment are shown. The heat treatment was the same as that for
Example 1. Additional performance characteristics of the heat
treated Sample t1372 are shown in Table 1, below.
[0068] A series of additional samples in accordance with this
Example 3 were prepared, having the same chromium and silver film
thicknesses as for the first Sample No. 1372, above. Specifically,
each of these additional samples was prepared in accordance with
the method of Example 1, having 4 nm thick (before heat treatment)
chromium layers sandwiching between them a 14 nm thick silver
layer. The thickness of the tin oxide layers of these additional
samples was varied. More specifically, the samples were prepared,
each carrying a coating system of SnO.sub.2/Cr/Ag/Cr/SnO.sub.2 on 6
mm thick glass, wherein each of the two tin oxide layers for the
sample had the thickness given below.
3 Sample No. Thickness of SnO.sub.2 Layers t1372 22 nm t1376 35 nm
t1378 55 nm t1377 65 nm
[0069] In each case, the thickness recited above is for each of the
tin oxide layers, rather than for the two tin oxide layers
combined. FIG. 7 shows the transmission spectra for these four
samples. As seen there, as the oxide layer thicknesses increase,
the transmission maxima or color shifts from blue toward yellow.
The same color shifts are observed for reflectance. Additional
performance properties for these samples are provided in Table 1,
below. It should be noted that the transmission spectra shown in
FIG. 7 are for each of the samples following heat treatment as
described for the sample of claim 1, at 650.degree. C. As noted
above, the performance characteristics provided in Table 1 below
are for each of the samples used in a "6+12+6" double glazing
product, that is, a double glazing wherein a first 6 mm pane
carrying the respective coating for that sample is paired with a
second 6 mm, uncoated pane with a distance of 12 mm between the two
panes. Excellent mechanical properties, including long shelf life
are obtained for the heat treated samples and for the double pane
glazing products made using the coated samples of this example.
4TABLE 1 PERFORMANCE TABLE FOR MULTI-FUNCTIONAL GLAZING SYSTEM
Optical Properties Sol. Energy Visible Region Region Relat.
Reflection Reflection Therm. Prop. Shading Solar Heat Color
Coordinates System Trans. OUT IN Trans. Out In Winter Summer Coef
Factor Gain Transmittance Reflectance (Out) Descr. Tvis R1 R4 Tsol
R1 R4 U win U sum SCc SHGCc RHG TL a* b* RL a* b* AUTOMOTIVE
GLAZING 1345 0.74 0.06 0.05 0.47 0.26 0.32 6.20 5.99 0.63 0.54 445
88.8 -3.20 0.38 29.3 7.34 -9.10 1345 0.84 0.06 0.05 0.54 0.27 0.31
6.36 6.05 0.69 0.59 483 93.2 -2.20 2.64 29.6 5.23 -9.30 1345 0.76
0.12 0.12 0.48 0.29 0.26 6.24 5.98 0.63 0.54 444 90.1 -3.70 1.96
40.5 5.94 5.89 1288 0.76 0.07 0.07 0.50 0.27 0.30 6.36 6.10 0.65
0.56 458 89.8 -0.30 1.77 31.7 3.49 1.22 1288 0.75 0.07 0.07 0.44
0.29 0.26 6.20 6.00 0.60 0.51 423 89.1 -2.00 3.73 32.7 0.75 -1.10
ARCHITECTURAL GLAZING (6 + 0.50 0.33 0.34 0.23 0.45 0.46 1.63 1.65
0.31 0.27 211 76.6 -12.00 -1.60 63.2 10.30 16.10 12 + 6) t1372 IG
(6 + 0.37 0.47 0.48 0.20 0.49 0.50 1.63 1.65 0.28 0.24 188 68.6
-9.80 -16.00 73.1 2.64 31.70 12 + 6) t1372 IG (6 + 0.44 0.33 0.37
0.22 0.41 0.44 1.63 1.65 0.31 0.26 206 71.5 -4.60 14.90 64.1 1.35
-7.80 12 + 6) t1372 IG (6 + 0.49 0.33 0.32 0.23 0.44 0.45 1.63 1.65
0.33 0.29 236 75.3 -8.50 11.00 63.8 3.59 -1.00 22 + 6) t1372 IG
[0070] It will be apparent from the foregoing disclosure that
alternative embodiments are possible within the scope of the
invention, including, for example, modifications to the preferred
embodiments described above. It will be recognized by those skilled
in the art, given the benefit of the present invention, that coated
articles of manufacture in accordance with the present invention
can be prepared which are more or less colorless, depending on the
thicknesses of the various films employed to form the coating. In
particular, increasing the thickness of one or more of the
anti-reflection oxide layers and/or decreasing the thickness of the
silver infra-red reflective layer can be employed to provide a more
colorless sample. This is consistent with the discussion in Example
7, above. Correspondingly, a more color-forming article can be
prepared by decreasing the thickness of the anti-reflection layers
and increasing the silver layer thickness. Additional alternative
embodiments of the present invention, including those employing
SnO.sub.2 and the like can be employed in accordance with the
principles disclosed here to provide color-forming or colorless
coated articles within the scope of the present invention.
* * * * *