U.S. patent application number 11/636758 was filed with the patent office on 2007-08-23 for durable sputtered metal oxide coating.
Invention is credited to Mehran Arbab, James J. Finley.
Application Number | 20070196695 11/636758 |
Document ID | / |
Family ID | 22537855 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070196695 |
Kind Code |
A1 |
Finley; James J. ; et
al. |
August 23, 2007 |
Durable sputtered metal oxide coating
Abstract
A method and resultant product are disclosed wherein a metal
film is deposited by sputtering a metal cathode target in an
essentially nonreactive atmosphere comprising inert gas and a
reactive gas, wherein the concentration of reactive gas is
sufficiently low that the sputtering is accomplished in the
metallic mode, i.e. the film is deposited as metal. The metal film
of the present invention is harder than a metal film sputtered in
an atmosphere consisting of only inert gas. The method and
resultant product may further comprise thermal oxidation of the
metal film, which proceeds more efficiently than oxidation of a
metal film sputtered in an atmosphere consisting of only inert
gas.
Inventors: |
Finley; James J.;
(Pittsburgh, PA) ; Arbab; Mehran; (Pittsburgh,
PA) |
Correspondence
Address: |
PPG INDUSTRIES INC;INTELLECTUAL PROPERTY DEPT
ONE PPG PLACE
PITTSBURGH
PA
15272
US
|
Family ID: |
22537855 |
Appl. No.: |
11/636758 |
Filed: |
December 11, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10075021 |
Feb 12, 2002 |
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11636758 |
Dec 11, 2006 |
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08508408 |
Jul 28, 1995 |
6346174 |
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10075021 |
Feb 12, 2002 |
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08151229 |
Nov 12, 1993 |
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08508408 |
Jul 28, 1995 |
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Current U.S.
Class: |
428/702 ;
428/426; 428/432; 428/689; 428/699; 428/701 |
Current CPC
Class: |
C23C 14/185 20130101;
C03C 2218/155 20130101; C23C 14/0089 20130101; C03C 17/2456
20130101; Y10T 428/12576 20150115; Y10T 428/12667 20150115; C23C
14/5853 20130101; C23C 14/083 20130101; C03C 17/3417 20130101; Y10T
428/12611 20150115; C03C 2217/212 20130101; C03C 17/27 20130101;
C03C 2218/154 20130101; C23C 14/58 20130101; C23C 14/0036 20130101;
C23C 14/5806 20130101; C03C 2218/322 20130101; C03C 17/245
20130101 |
Class at
Publication: |
428/702 ;
428/426; 428/432; 428/689; 428/699; 428/701 |
International
Class: |
B32B 15/04 20060101
B32B015/04; B32B 17/06 20060101 B32B017/06; B32B 9/04 20060101
B32B009/04 |
Claims
1-20. (canceled)
21. A coated article made by the process of: placing a substrate in
an evacuated chamber having an atmosphere comprising an inert gas
and a reactive gas; sputtering a metal cathode target below its
switch point in the chamber, wherein the atmosphere is sufficiently
inert that the metals sputtered to deposit a metal film and
sufficiently reactive that the metal film deposited is
substantially amorphous; and oxidizing the metal film after the
sputtering step.
22. The article according to claim 21, wherein the metal of the
metal cathode target comprises at least one metal selected from the
group consisting of titanium, zirconium, tantalum, hafnium,
niobium, vanadium and mixtures thereof.
23. The article according to claim 21, wherein the reactive gas is
selected from the group consisting of oxygen, nitrogen and mixtures
thereof.
24. The article according to claim 21, wherein the inert gas is
argon.
25. The article according to claim 21, wherein the atmosphere
comprises argon and up to 30 percent oxygen.
26. The article according to claim 21, further including a metal
oxide layer deposited over the amorphous metal film prior to the
oxidizing step, wherein the amorphous metal film is thermally
oxidized.
27. A coated product comprising: a substrate; a film sputtered from
a metal cathode target in an atmosphere comprising inert gas and
reactive gas, the metal in the metal cathode target having a
reactive gas switch point, wherein the concentration of the
reactive gas during sputtering is below the reactive gas switch
point such that the metal target is sputtered in a metallic mode to
deposit a metal film having an amorphous structure defined as an
amorphous metal film; and a second metal oxide film over the
amorphous metal film, wherein the amorphous metal film is oxidized
to form a first metal oxide film in the coated product.
28. The article in accordance with claim 27, wherein the metal of
the metal cathode target comprises at least one metal selected from
the group consisting of titanium, zirconium, tantalum, hafnium,
niobium, vanadium and mixtures thereof.
29. The article in accordance with claim 27, wherein the deposited
amorphous metal film has a thickness ranging from 200 .ANG. to 1500
.ANG..
30. The article in accordance with claim 27, wherein the reactive
gas is selected from oxygen, nitrogen and mixtures thereof.
31. The article in accordance with claim 27, wherein the inert gas
is argon.
32. The article in accordance with claim 31, wherein the substrate
is glass and the metal in the metal film is titanium.
33. A coated article, comprising: a substrate; and a crystalline
metal oxide film from oxidation of an essentially amorphous metal
film sputtered from a metal cathode target in an atmosphere
comprising inert gas and reactive gas, the metal in the metal
cathode target having a reactive gas switch point, wherein the
concentration of the reactive gas during sputtering is below the
reactive gas switch point such that the metal target is sputtered
in a metallic mode to deposit a metal film having an amorphous
structure.
34. The article according to claim 33, further comprising another
metal oxide film directly over the crystalline metal oxide film,
where the other metal oxide film is deposited by reactive
sputtering of amorphous metal oxide.
35. The article according to claim 33, wherein: the crystalline
metal film has a predetermined property value and the amorphous
reacted metal film has a predetermined property value different
than the predetermined property value of the crystalline metal
film; the predetermined property value of the crystalline metal
film defines a first limit and the predetermined property value of
the amorphous reacted metal film defines a second limit wherein the
first limit and second limit define a predetermined value range,
and the crystalline metal film has a predetermined property value
different than the predetermined property value of at least one of
the crystalline metal films and the amorphous metal reacted
film.
36. The article according to claim 35, wherein the predetermined
property value of the amorphous metal film is different than the
predetermined property value of the crystalline metal film and of
the amorphous reacted metal film and within the predetermined value
range.
37. The article according to claim 35, wherein the predetermined
property is hardness and the amorphous metal film is harder than
crystalline metal film and softer than the amorphous reacted metal
films.
38. The article according to claim 35, wherein the predetermined
property is visible light transmittance and the crystalline metal
film has a percent transmission lower than the percent transmission
of the amorphous reacted metal film and the amorphous metal film
has a percent transmission greater than the percent transmission of
the crystalline metal film and less than the percent transmission
of the amorphous reacted metal film wherein the thickness of the
crystalline metal film, amorphous reacted metal film and amorphous
metal film being substantially equal.
39. The article according to claim 38, wherein the difference
between the percent transmission of the crystalline metal film and
the amorphous metal film is less than the difference between the
percent transmission of the amorphous metal film and the amorphous
reacted metal film.
40. The article according to claim 35, wherein the predetermined
property is selected from the group consisting of electrical
conductivity, percent reflectance, and density.
Description
BACKGROUND
[0001] The present invention relates generally to the art of
sputtered films and more particularly to the art of durable metal
oxide films produced by magnetron sputtering.
[0002] Sputtered metal oxide films are well known in the art. Tin
oxide, zinc oxide, titanium oxide and many other metal oxides are
known to be deposited by sputtering the respective metals in an
oxidizing atmosphere such as air or a mixture of oxygen and inert
gas such as argon. It is also known that a metal film can be
deposited by sputtering a metal in an inert atmosphere such as
argon, and the metal film subsequently oxidized thermally by
heating in an oxidizing atmosphere such as air.
[0003] Various metals can be deposited either as metallic films or
metal oxide films depending on whether the metal cathode target is
sputtered in an inert atmosphere or an oxidizing atmosphere.
Generally, sputtering in an inert atmosphere, i.e. in the metallic
mode, is faster and more efficient. The resulting coating is a
metal film having metallic properties, i.e. generally low
transmittance, high reflectance and electrically conductive. Such
films are generally not very hard or durable, and are easily
damaged in handling. Dielectric metal oxide films are typically
high transmittance, lower reflectance and electrically insulating.
However, because they are insulating, they do not deposit as
efficiently by sputtering. To produce very thick metal oxide films
by sputtering is inefficient, costly and may not result in a
durable film. To produce very thick metal oxide films by thermally
oxidizing metal films efficiently sputtered in an inert atmosphere
is inherently rate-limited because oxygen may not readily penetrate
beyond the initially formed surface layer of metal oxide.
SUMMARY OF THE INVENTION
[0004] The present invention involves a method of sputtering a
metal target in an atmosphere sufficiently inert that sputtering is
performed in the metallic mode and the film deposited is in an
essentially metallic state. However, sufficient reactive gas is
added to the atmosphere so that the metal film is amorphous rather
than crystalline. The amorphous sputtered metal film is harder and
more durable than a metal film sputtered in an atmosphere
consisting of only inert gas. The amorphous sputtered metal film
may be thermally oxidized more efficiently than a metal film
deposited in an atmosphere consisting of only inert gas, resulting
in a crystalline metal oxide film which is substantially more
chemically durable than an amorphous metal oxide film deposited by
sputtering metal in an oxidizing atmosphere.
DESCRIPTION OF THE DRAWING
[0005] FIG. 1 illustrates the maximum percentage of oxygen in inert
gas which allows sputtering of titanium in the metallic mode using
an AIRCO ILS-1600 laboratory scale coater as a function of power
level in kilowatts (kw).
[0006] FIG. 2 illustrates the maximum percentage of oxygen in inert
gas which allows sputtering of zirconium in the metallic mode using
an AIRCO ILS-1600 laboratory scale coater as a function of power
level in kw.
[0007] FIG. 3 illustrates the voltage as a function of percent
oxygen in inert gas for the sputtering of titanium at power levels
of 1, 2, 3 and 4 kilowatts using an AIRCO ILS-1600 laboratory scale
coater. The peak on each curve is the switching point where the
amount of oxygen causes the sputtering mode to change from the
metal mode to the oxide mode.
DESCRIPTION OF PREFERRED EMBODIMENT
[0008] Metals such as titanium, zirconium, tantalum, hafnium,
niobium, vanadium and mixtures thereof, preferably titanium and
zirconium, may be deposited in a substantially amorphous metallic
state in accordance with the present invention by sputtering the
metal in a nonreactive atmosphere substantially comprising inert
gas, but also comprising a small amount of reactive gas, such as
oxygen and/or nitrogen, preferably oxygen. The amount of oxygen is
sufficient to effect the deposition of the metal in a substantially
amorphous rather than crystalline state, but insufficient to effect
the transition of sputtering from the metallic mode to the oxide
mode. The appropriate amount of oxygen in the inert gas for
purposes of the present invention is related to the cathode
operating parameters, particularly the power, and the size of the
target.
[0009] FIGS. 1 and 2 illustrate the maximum oxygen concentration in
argon at various levels of power for titanium and zirconium targets
respectively operated in an AIRCO ILS-1600 laboratory scale coater.
At higher oxygen concentrations, the sputtering mode will switch
from metallic to oxide, resulting in the slow deposition of
amorphous metal oxide. Therefore, the oxygen concentration is kept
sufficiently low to avoid depositing metal oxide. However, it has
been discovered that the higher the oxygen concentration, below the
switching point, the harder the amorphous metal deposited in the
metal sputtering mode.
[0010] FIG. 3 illustrates the voltage as a function of oxygen
concentration for titanium films deposited at power levels of from
1 to 4 kilowatts in an AIRCO ILS-1600 laboratory scale coater. The
voltage peak for each curve illustrates the switching point between
metallic and oxide sputtering modes, and indicates the maximum
oxygen concentration for the specified power level using this
coating apparatus. It is preferred to operate near the peak, i.e.
at a relatively higher concentration of oxygen, for maximum metal
hardness, but without switching from the metallic sputtering mode
to the oxide sputtering mode.
[0011] The amorphous metal film sputtered in an oxygen-containing
but substantially nonreactive atmosphere is only slightly higher in
transmission than a metal film sputtered in pure argon; and the
sputtering rate is approximately the same. However, the amorphous
metal coating sputtered in an oxygen-containing but substantially
nonreactive atmosphere is significantly harder and less dense than
a crystalline metal film sputtered in pure argon.
[0012] The relative hardness of such metal films is determined by
abrasion of the film followed by visual examination and rating on
the basis of film damage. A method of judging the hardness of metal
films comprises repeated strokes of an abrasive pad
(Scotch-Brite.RTM. 98 Light Duty Cleaning Pad from 3M) followed by
visual examination on a light board and rating the film damage on a
scale of 1 to 9, with 1 being insignificant damage and 9 being
substantial removal of the metal film.
[0013] The density of amorphous titanium metal film sputtered in an
essentially nonreactive atmosphere comprising inert gas and 10
percent oxygen is 4.0 grams per cubic centimeter (g/cm.sup.3),
compared with a density of 4.5 g/cm.sup.3 for a titanium metal film
sputtered in pure argon. The lower density of the amorphous
titanium metal film enhances its rate of oxidation, so that the
amorphous titanium metal film may be thoroughly oxidized at lower
temperatures and/or in shorter times than required for oxidation of
crystalline titanium metal film.
[0014] The hard, dense, amorphous metal coating of the present
invention, preferably in a thickness range of about 100 to 1500
Angstroms, more preferably about 200 to 1000 Angstroms for
titanium, is sufficiently durable to withstand handling, shipping
and processing, such as heat strengthening, tempering and bending.
It is preferred to further process the amorphous metal film of the
present invention by thermally oxidizing the metal to metal oxide.
The hard amorphous metal film of the present invention may be
thermally oxidized to metal oxide by heating to produce a
haze-free, dense, substantially crystalline metal oxide coating
which is sufficiently chemically and physically durable to be
coated on the exposed surface of a glass substrate. The amorphous
metal film is preferably heated to a temperature of at least
400.degree. C., preferably 500 to 700.degree. C., in air in order
to effect complete oxidation in a reasonable time, e.g. a few
minutes. The method of the present invention of heating an
amorphous sputtered metal film to produce a crystalline metal oxide
film is a more efficient method to produce thick metal oxide films
than reactively sputtering such films. Moreover, the crystalline
thermally oxidized metal oxide films are more chemically durable
than the substantially amorphous reactively sputtered metal oxide
films. Such crystalline thermally oxidized metal oxide films may be
produced over a wide range of thicknesses having a wide range of
desirable reflected colors produced by interference effects.
[0015] The density of the titanium oxide coatings is determined
using the measured thickness of the coating and the weight percent
titanium in fully oxidized titanium oxide. The thickness was
measured using a Tencor P-1 Long Scan Profiler; the weight percent
titanium was measured using x-ray fluorescence. The density of the
crystalline thermally oxidized titanium coating is greater than the
density of amorphous reactively sputtered titanium dioxide coating;
the crystalline thermally oxidized titanium oxide coating has a
density of 4.0 grams per cubic centimeter (g/cm.sup.3) while the
amorphous sputtered titanium oxide has a density of 3.4 g/cm.sup.3.
The density of crystalline thermally oxidized titanium oxide
coatings approaches the bulk density of 4.26 g/cm.sup.3 for the
rutile phase of TiO.sub.2.
[0016] The refractive index at 600 nanometers of an amorphous
reactively sputtered titanium oxide film is 2.3, whereas the
refractive index at 600 nanometers of a crystalline titanium oxide
film thermally oxidized from an amorphous titanium metal film
sputtered in an essentially nonreactive atmosphere comprising argon
and 10 percent oxygen is 2.5, which is nearly the refractive index
of the rutile phase of bulk crystalline TiO.sub.2.
[0017] In a preferred embodiment of the present invention, coatings
are produced on a large-scale magnetron sputtering device capable
of coating glass up to 100.times.144 inches (2.54.times.3.66
meters). Using a commercial production scale coater, the acceptable
amount of reactive gas may be considerably higher without switching
from the metal mode compared with a small-scale coater,
particularly if multiple cathodes are sputtered simultaneously
within a chamber at higher power density.
[0018] In the following examples, the coatings are deposited on a
smaller scale, using planar magnetron cathodes having 5.times.17
inch (12.7.times.43.2 centimeters) targets. Base pressure is in the
10.sup.-6 Torr range. The coatings are made by first admitting the
sputtering gas to a pressure of 4 microns and then setting the
cathode power. In each example, glass substrates pass under the
target on a conveyor roll at a speed of 120 inches (3.05 meters)
per minute. The transmittance is monitored every other pass during
the sputtering process at a wavelength of 550 nanometers using a
Dyn-Optics 580D optical monitor. After the coating is deposited,
the transmittance and reflectance from both the glass and coated
surfaces are measured in the wavelength range from 380 to 720
nanometers using Pacific Scientific Spectrogard Color System
spectrophotometer.
[0019] In a most preferred embodiment of the present invention, the
amorphous metal film sputtered in an essentially nonreactive
atmosphere comprising sufficient reactive gas to effect the
deposition of a harder, less dense, amorphous, rather than
crystalline, metal film, but insufficient to effect the transition
of the sputtering process from the metallic to the oxide mode, is
overcoated with a thin layer of reactively sputtered amorphous
metal oxide. This layer of reactively sputtered amorphous metal
oxide increases the thermal stability of the amorphous metal film
sputtered in an essentially nonreactive atmosphere comprising inert
gas and sufficient reactive gas to effect the deposition of an
amorphous metal film but insufficient to effect the transition of
the sputtering mode from metallic to oxide, during thermal
oxidation. The amorphous sputtered metal oxide layer preferably
comprises the same metal as the underlying amorphous metal layer.
The thickness of the amorphous metal oxide layer is preferably in
the range of 40 to 120 Angstroms.
[0020] The thickness of the underlying amorphous metal layer is
preferably in the range of 200 to 1000 Angstroms prior to thermal
oxidation, for production of a wide range of chromas in the metal
oxide films. The amount of reactive gas in the essentially
nonreactive atmosphere may vary widely depending on the metal to be
sputtered, size and geometry of targets, number and power level of
cathodes, and so on. The upper limit in any case is below the point
at which sputtering switches from the metallic to the oxide mode.
For optimum hardness of the amorphous metal film, it is preferred
to operate near this upper limit consistent with maintaining
sputtering in the metal mode. A range of 2 to 30 percent oxygen,
preferably 5 to 25 percent may be preferred when sputtering
titanium.
[0021] The present invention will be further understood from the
descriptions of specific examples which follow.
EXAMPLE 1
[0022] A clear glass substrate six millimeters thick was coated
with titanium as follows. A titanium cathode target was sputtered
in an atmosphere of argon containing 2.5 percent oxygen. The base
pressure was 2.times.10.sup.-6 Torr, operating pressure 4.0
microns. Power was set at 3.0 kilowatts (kw), voltage was 381 volts
(V), current was 7.8 amps and line speed 120 inches (3.05 meters),
per minute. After 1 pass, the transmittance was 19.1 percent, after
three passes 2.0 percent, and zero after four passes. The
resistance of the titanium film was 41.9 ohms per square. The
coated surface was wiped with an abrasive pad (Scotch-Brite from
3M), and the coated substrate placed on a light board for visual
examination. It was rated 7 in transmittance and 5 in
reflectance.
EXAMPLE 2
[0023] A glass substrate was coated as in Example 1 except that the
atmosphere was argon with 5 percent oxygen, the voltage was 385V
and the current 7.7 amps. The transmittance after one pass was 21.0
percent, after three passes 2.6 percent, and less than one percent
after four passes. The resistance of the titanium film was 48 ohms
per square. The coated surface was rated 5 in transmittance and 4
in reflectance after abrasion.
EXAMPLE 3
[0024] A glass substrate was coated as in Examples 1 and 2 except
that the atmosphere was argon with 10 percent oxygen, the voltage
was 393V and the current 7.6 amps. The transmittance after one pass
was 26.4 percent, after three passes 6.0 percent, and 2.0 percent
after four passes. The resistance of the titanium film was 82 ohms
per square. The coated surface was rated 2 in both transmittance
and reflectance after abrasion.
EXAMPLE 4
[0025] A glass substrate was coated as in the previous examples
except that the atmosphere contained 15 percent oxygen, the voltage
was 432V and the current 6.9 amps. The transmittance after one pass
was 57.0 percent, after three passes 21.0 percent, and 13.6 percent
after four passes. The resistance of the titanium film was 330 ohms
per square. The coated surface was rated 1 in both transmittance
and reflectance after abrasion. The increasing transmittance and
resistance indicate that the oxygen concentration is approaching
the maximum for sputtering in the metal mode, although the film is
still metallic, since the resistance is still very low in
comparison with the resistance of titanium oxide, which is
infinite, i.e. titanium oxide is an insulating material.
COMPARATIVE EXAMPLE A
[0026] A glass substrate was coated as in the previous examples
except that the atmosphere was pure argon, the voltage was 378V and
the current 7.85 amps. The transmittance after one pass was 18.0
percent, after three passes 1.8 percent, and zero after four
passes. The resistance of the titanium film was 24 ohms per square.
The coated surface was rated 9 in both transmittance and
reflectance after abrasion.
EXAMPLE 5
[0027] A tinted glass (SOLEX.RTM. glass from PPG Industries, Inc.)
substrate 4.0 millimeters thick was coated with titanium and
titanium dioxide as follows. The first layer of coating is prepared
by sputtering a planar titanium cathode in an atmosphere of argon
containing 10 percent oxygen. The base pressure was
7.0.times.10.sup.-6 Torr, operating pressure 4.0 microns, power set
at 3.4 kilowatts, voltage was 399 volts, current 8.42 amps and line
speed 120 inches (3.05 meters) per minute. After 4 passes, the
transmittance was 1.4 percent. The titanium layer thickness was 599
Angstroms. This layer deposition was followed by reactively
sputtering titanium in a 50/50 argon/oxygen gas mixture. Power was
set at 5.0 kilowatts, voltage was 470 volts, current 10.57 amps and
the line speed 120 inches (3.05 meters) per minute. After 6 passes,
the final transmittance was 2.0 percent. The coating thickness for
the reactively sputtered titanium oxide layer was 76 Angstroms. The
two layer coating was then heated for 4 minutes to a temperature of
650.degree. C., producing a single homogeneous layer of titanium
oxide coating with thickness of 1062 Angstroms. The optical
properties of the coated article were analyzed and are shown in the
Table following the Examples.
EXAMPLE 6
[0028] A clear glass substrate 6.0 millimeters thick was coated
with titanium as follows. A coating was prepared by sputtering a
planar titanium cathode in an atmosphere of argon containing 10
percent oxygen. The base pressure was 5.9.times.10.sup.-6 Torr,
operating pressure 4.0 microns, power set at 3.4 kilowatts, voltage
was 398 volts, current 8.45 amps and line speed 120 inches (3.05
meters) per minute. After 6 passes the transmittance was zero. The
coating thickness was 893 Angstroms. The coating was then heated
for 6.5 minutes to a temperature of 637.degree. C. producing an
oxide coating with a thickness of 1469 Angstroms. The optical
properties are shown in the Table following the Examples.
EXAMPLE 7
[0029] A clear glass substrate 6.0 millimeters thick was coated
with titanium as follows. A coating was prepared by sputtering a
planar titanium cathode in an atmosphere of argon containing 10
percent oxygen. The base pressure was 5.0.times.10.sup.-6 Torr,
operating pressure 4.0 microns, power set at 3.4 kilowatts, voltage
was 398 volts, current 8.45 amps and line speed 120 inches (3.05
meters) per minute. After 5 passes the transmittance was 0.5
percent. The coating thickness was 742 Angstroms. The coating was
then heated for 6.5 minutes to a temperature of 637.degree. C.,
producing an oxide coating with a thickness of 1220 Angstroms. The
optical properties are shown in the Table following the
Examples.
EXAMPLE 8
[0030] A clear glass substrate 6.0 millimeters thick was coated
with titanium as follows. A coating was prepared by sputtering a
planar titanium cathode in an atmosphere of argon containing 10
percent oxygen. The base pressure was 3.9.times.10.sup.-6 Torr,
operating pressure 4.0 microns, power was set at 3.4 kilowatts,
voltage was 398 volts, current 8.45 amps and line speed 120 inches
(3.05 meters) per minute. After 4 passes the transmittance was 1.6
percent. The coating thickness was 599 Angstroms. The coating was
then heated for 6.5 minutes to a temperature of 637.degree. C.,
producing an oxide coating with a thickness of 986 Angstroms. The
optical properties are shown in the Table following the
Examples.
EXAMPLE 9
[0031] A clear glass substrate 6.0 millimeters thick was coated
with titanium as follows. A coating was prepared by sputtering a
planar titanium cathode in an atmosphere of argon containing 10
percent oxygen. The base pressure was 5.9.times.10.sup.-6 Torr,
operating pressure 4.0 microns, power was set at 3.4 kilowatts,
voltage was 398 volts, current 8.45 amps and line speed 120 inches
(3.05 meters) per minute. After 3 passes the transmittance was 3.9
percent. The coating thickness was 447 Angstroms. The coating was
then heated for 6.5 minutes to a temperature of 637.degree. C.,
producing an oxide coating with a thickness of 735 Angstroms. The
optical properties are shown in the Table following the
Examples.
EXAMPLE 10
[0032] A clear glass substrate 6.0 millimeters thick was coated
with titanium as follows. A coating was prepared by sputtering a
planar titanium cathode in an atmosphere of argon containing 10
percent oxygen. The base pressure was 5.2.times.10.sup.-6 Torr,
operating pressure 4.0 microns, power was set at 3.4 kilowatts,
voltage was 398 volts, current 8.45 amps and line speed 120 inches
(3.05 meters) per minute. After 2 passes the transmittance was 8.9
percent. The coating thickness was 301 Angstroms. The coating was
then heated for 6.5 minutes to a temperature of 637.degree. C.,
producing an oxide coating with thickness of 495 Angstroms. The
optical properties are shown in the Table following the
Examples.
EXAMPLE 11
[0033] A tinted glass (SOLEX.RTM. glass from PPG Industries, Inc.)
substrate 4.0 millimeters thick was coated with titanium as
follows. A coating was prepared by sputtering a planar titanium
cathode in an atmosphere of argon containing 10 percent oxygen. The
base pressure was 7.0.times.10.sup.-6 Torr, operating pressure 4.0
microns, power was set at 3.4 kilowatts, voltage was 400 volts,
current 8.4 amps and line speed 120 inches (3.05 meters) per
minute. After 4 passes the transmittance was 1.5 percent. The
coating thickness was 599 Angstroms. The coating was then heated
for 4 minutes to a temperature of 650.degree. C., producing an
oxide coating with thickness of 986 Angstroms. The optical
properties are shown in the Table following the Examples.
TABLE-US-00001 TABLE Reflectance* Exam- Transmittance* Film Side
Glass Side ple # Y x y Y x y Y x y 5 74.46 .3102 .3646 12.25 .3038
.2152 10.34 .3032 .2286 6 65.71 .3444 .3373 30.43 .2418 .3182 28.94
.2412 .3209 7 82.90 .3451 .3792 13.23 .2056 .1833 12.82 .2074 .1884
8 79.31 .2968 .3374 17.33 .3733 .3072 16.37 .3679 .3105 9 60.37
.2897 .3022 36.54 .3574 .3914 34.31 .3502 .3922 10 56.63 .3205
.3374 40.09 .2985 .3205 37.76 .2940 .3224 11 72.15 .2925 .3398
17.51 .3794 .3165 14.73 .3652 .3264 *C.I.E. Chromaticity
Coordinates (1931 2 degree observer, Illuminant D-65)
[0034] The above examples are offered to illustrate the present
invention. Other metals such as zirconium, tantalum, vanadium,
hafium and niobium may be sputtered in an atmosphere which contains
a reactive gas but which remains essentially nonreactive. Other
reactive gases such as nitrogen may be used instead of or in
addition to oxygen. The amount of reactive gas is kept sufficiently
low so that the sputtering mode is essentially metallic, and the
film deposited is essentially metallic. To optimize the hardness of
the metal film, the amount of reactive gas in the inert gas is
preferably as high as is consistent with maintaining an essentially
nonreactive atmosphere, i.e. sputtering in the metallic mode. When
the reactive gas is oxygen, the minimum amount is sufficient to
effect deposition of amorphous metal, generally at least about 2
percent, and higher amounts, at least about 10 percent, are
preferred in order to thermally oxidize at an efficient rate.
Thermal oxidation of the metallic film may be performed throughout
a range of temperatures sufficient to oxidize the metal without
deteriorating the integrity of the film. Typically, a temperature
of at least 400.degree. C. is selected to thoroughly oxidize the
metal film in a reasonable time, e.g. a few minutes. Film
thicknesses may vary over a wide range to obtain desirable
properties, particularly interference color effects in reflectance.
The scope of the invention is defined by the following claims.
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