Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2176891
ARTICLE HAVING A COATING
SIMULATING BRASS
Field of the Invention
This invention relates to substrates, in particular brass
substrates, coated with a decorative and protective coating
simulating brass.
Background of the Invention
It is currently the practice with various brass articles such
as lamps, trivets, candlesticks, door knobs, door handles, door
escutcheons and the like to first buff and polish the surface of
the article to a high gloss and to then apply a protective organic
coating, such as one comprised of acrylics, urethanes, epoxies, and
the like, onto this polished surface. While' this system is
generally quite satisfactory it has the drawback that the buffing
and polishing operation, particularly if the article is of a
complex shape, is labor intensive. Also, the known organic
coatings are not always as durable as desired, particularly in
outdoor applications where the articles are exposed to the elements
and ultraviolet radiation. It would, therefore, be quite
advantageous if brass articles, or indeed other metallic articles,
could be provided with a coating which gave the article the
appearance of polished brass and also provided wear resistance and
corrosion protection. The present invention provides such a
coating.
CA 02176891 1999-10-18
Summary of the Invention
The present invention is directed to a substrate
having a multi-layer coating disposed or deposited on its surface.
More particularly, it is direcaed to a metallic substrate,
particularly brass, having depcsited on its surface multiple
superposed metallic layers of certain specific types of metals or
metal compounds. The coating is decorative and also provides wear
and abrasion resistance. The coating provides the appearance of
polished brass. Thus, an article surface having the coating
thereon simulates a polished brass surface.
A first layer deposited directly on the surface of the
substrate is camprised of a tin-nickel alloy. Over the tin-nickel
alloy layer is a layer comprised o:f a non-precious refractory metal
such as zirconium, titanium, hafnium or tantalum, preferably
zirconium or titanium. A top layer comprised of a nonprecious
refractory metal compound, preferably a zirconium compound,
titanium compound, hafnium compound or tantalum compound, more
preferably a titanium compound or a zirconium compound such as
zirconium nitride, is disposed over the refractory metal layer,
preferably zirconium layer.
The tin-nickel alloy layer is applied by electroplating. The
refractory metal such as zirconium and refractory metal compound
such as zirconium compound layers are applied by vapor deposition
such as sputter ion deposition and reactive sputter ion deposition.
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68432-280
Brief Description of the Drawings
FIG. 1 is a cross-sectional view of a portion of the
substrate having the multi-layer coating deposited on its
surface .
Description of the Preferred Embodiment
The substrate 12 can be any platable substrate such
as platable metal or metallic alloy substrate such as copper,
steel, brass, tungsten, nickel alloys, and the like. In a
preferred embodiment the substrate is brass.
Disposed on the surface of the substrate 12 is a
layer 20 comprised of tin-nickel alloy. More specifically,
layer 20 is comprised of an alloy of nickel and tin. Layer 20
is deposited on the substrate surface by conventional and well
known tin-nickel electroplating processes. These processes and
plating baths are conventional and well known and are
disclosed, inter alia, in U.S. Patents Nos. 4,033,835;
4,049,508; 3,887,444; 3,772,168 and 3,940,319.
The tin-nickel alloy layer is preferably comprised of
about 60-60 weight percent tin and about 30-40 weight percent
nickel, more preferably about 65% tin and 35% nickel
representing the atomic composition SnNi. The plating bath
contains sufficient amounts of nickel and tin to provide a tin-
nickel alloy of the afore-described composition.
A commercially available tin-nickel plating process
is the NiColloyTM process available from ATOTECH, and described
in their Technical Information Sheet No: NiColloy, 10-30-94.
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CA 02176891 1999-10-18.,
The thickness of the tin-nickel alloy layer 20 is generally at
least about ZO milliont.'~s (0.00001) of an inch, preferably at least
about 20 millionths (0.00002) of an :inch, and more preferably at
least about 50 millionths (0.00005) of an inch. The upper
thickness range is not critical anct is generally dependent on
economic considerations. Generally, a thickness of about 2,000
millionths (0.002) of an inch, preferably about 1,000 millionths
(0.001), and more preferably about 500 millionths (0.0005) of an
inch should not be exceeded.
Disposed over the tin-nickel aJ.loy layer 20 is a Layer 22
comprised of a non-precious ref=act,ory metal such as hafnium,
tantalum, zirconium or titanium, preferably zirconium or titanium,
and more preferably zirconium.
Layer 22 serves, inter alia, to improve or enhance the
adhesion of layer 24 to layer 20. Layer 22 is deposited on layer
20 by conventional and well known techniques such as vacuum
coating, physical vapor deposition such as ion sputtering, and the
like. Ion sputtering techniques and e.cuipment are disclosed, inter
alia, in T. Van Vorous, 'Planar riagnetron Sputtering; A New
Industrial Coating Technique', Solid State Technology, Dec. 1976,
pp 62-66; U. Kapacz and S. Schulz, 'Industrial Application of
Decorative Coatings - Principle and Advantages of the Sputter Ion
Plating Process", Soc. Vac. Coat., Proc. 34th Arn. Techn. Conf.,
Philadelphia, U.S.A., 1991, 48-51; and U.S. patent Nos. 4,162,954,
and 4,591,418.
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Briefly, in the sputter ion deposition process the refractory
metal such as titanium or zirconium target, which is the cathode,
and the substrate are placed in a vacuum chamber. Tie air in the
chamber is evacuated to produce vacuum conditions in the chamber.
An inert gas, such as Argon, is introduced into the chamber. The
gas particles are ionized and are accelerated to the target to
dislodge titanium or zirconium atoms. The dislodged target
material is then typically deposited as a coating film on the
substrate.
Layer 22 has a thickness which is at least effective to
improve the adhesion of layer 24 to layer 20. Generally, this
thickness is~ at least about 0.25 millionths (0.00000025) of an
inch, preferably at least about 0.5 millionths (0.0000005) of an
inch, and more preferably at least about one millionth (0.000001)
of an inch. The upper thickness range is not critical and is
generally dependent upon considerations such as cost. Generally,
however, layer 22 should not be thicker than about 50 millionths
(0.00005) of an inch, preferably about 15 millionths (0.000015) of
an inch, and more preferably about 10 millionths (0.000010) of an
inch.
In a preferred embodiment of the present invention layer 22 is
comprised of titanium or zirconium, preferably zirconium, and is
deposited by sputter ion plating.
Layer 24 is preferably deposited on layer 22 by reactive ion
sputter deposition. Reactive ion sputter deposition is generally
similar to ion sputter deposition except that a reactive gas which
X116891
reacts with the dislodged target material is introduced into the
chamber. Thus, in the case where zirconium nitride is the top
layer 24, the target is comprised of zirconium and nitrogen gas is
the reactive gas introduced into the chamber. By controlling the
amount of nitrogen available to react with the zirconium, the color
of the zirconium nitride can be made to be similar to that of brass
of various hues.
Layer 24 is comprised of a hafnium compound, a tantalum
compound, a titanium compound or a zirconium compound, preferably
a titanium compound or a zirconium compound, and more preferably a
zirconium compound. The titanium compound is selected from
titanium nitride, titanium carbide, and titanium carbonitride, with
titanium nitride being preferred. The zirconium compound is
selected from zirconium nitride, zirconium carbonitride, -and
zirconium carbide, with zirconium nitride being preferred.
Layer 24 provides wear and abrasion resistance and the desired
color or appearance, such as for example, polished brass. Layer 24
is deposited on layer 22 by any of the well known and conventional
plating or deposition processes such as vacuum coating, reactive
sputter ion plating, and the like. The preferred method is
reactive ion sputter plating.
Layer 24 has a thickness at least effective to provide
abrasion resistance. Generally, this thickness is at least 2
millionths (0.000002) of an inch, preferably at least 4 millionths
(0.000004) of an inch, and more preferably at least 6 millionths
(0.000006) of an inch. The upper thickness range is generally not
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2176891
critical and is dependent upon considerations such as cost.
Generally a thickness of about 30 millionths (0.00003) of an inch,
preferably about 25 millionths (0.000025) of an inch, and mare
preferably about 20 millionths (0.000020) of an inch should not be
exceeded.
Zirconium nitride is the preferred coating material as it most
closely provides the appearance of polished brass.
In order that the invention may be more readily understood the
following example is provided. The example is illustrative and
does not limit the invention thereto.
EXAMPLE 1
Brass door escutcheons are placed in a conventional soak
cleaner bath containing the standard and well known soaps,
detergents, defloculants and the like which is maintained at a pH
of 8.9 - 9.2 and a temperature of 180 - 200oF for 30 minutes. The
brass escutcheons are then placed for six minutes in a conventional
ultrasonic alkaline cleaner bath. The ultrasonic cleaner bath has
a pH of 8.9 - 9.2, is maintained at a temperature of about 160 -
180~F, and contains the conventional and well known soaps,
detergents, defloculants and the like. After the ultrasonic
cleaning the escutcheons are rinsed and placed in a conventional
alkaline electro cleaner bath for about two minutes. The electro
cleaner bath contains an insoluble submerged steel anode, is
maintained at a temperature of about 140 - 180oF, a pH of about
10.5 - 11.5, and contains standard and conventional detergents.
The escutcheons are then rinsed twice and placed in a conventional
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2116891
~'' acid activator bath for about one minute. The acid activator bath
has a pH of about 2.0 - 3.0, is at an ambient temperature, and
contains a sodium fluoride based acid salt.
The escutcheons are rinsed twice and placed in a tin-nickel
plating bath for about 7 1/2 minutes. The bath is maintained at a
temperature of about 1200-140~F and a pH of about 4.5-5Ø The
bath contains stannous chloride, nickel chloride, ammonium
bif luoride, and other well known and conventional complexing and
wetting agents. A tin-nickel layer of an average thickness of
about 200 millionths of an inch (0.0002) is deposited on the
surface of the escutcheons.
The tin-nickel alloy plated escutcheons are placed in a
sputter ion plating vessel. This vessel is a stainless steel
vacuum vessel marketed by Leybold A.G. of Germany. The vessel is
generally a cylindrical enclosure containing a vacuum chamber which
is adapted to be evacuated by means of pumps. A source of argon
gas is connected to the chamber by an adjustable valve for varying
the rate of flow of argon into the chamber. In addition, two
sources of nitrogen gas are connected to the chamber by an
adjustable valve for varying the rate of flow of nitrogen into the
chamber.
Two pairs of magnetron-type target assemblies are mounted in
a spaced apart relationship in the chamber and connected to
negative outputs of variable D.C. power supplies. The targets
constitute cathodes and the chamber wall is an anode common to the
target cathodes. The target material comprises zirconium.
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2176891
A substrate carrier which carries the substrates, i.e.,
escutcheons, is provided, e.g., it may be suspended from the top of
the chamber, and is rotated by a variable speed motor to carry the
substrates between each pair of magnetron target assemblies. The
carrier is conductive and is electrically connected to the negative
output of a variable D.C. power supply.
The plated escutcheons are mounted onto the substrate carrier
in the sputter ion plating vessel. The vacuum chamber is evacuated
to a pressure of about 5x10'3 millibar and.is heated to about 400oC
via a radiative electric resistance heater. The target material is
sputter cleaned to remove contaminants from its surface. Sputter
cleaning is carried out for about one half minute by applying power
to the cathodes sufficient to achieve a current flow of about 18
amps and introducing argon gas at the rate of about 200 standard
cubic centimeters per minute. A pressure of about 3x10'3 millibars
is maintained during sputter cleaning.
The escutcheons are then cleaned by a low pressure etch
process. The low pressure etch process is carried on for about
five minutes and involves applying a negative D.C. potential which
increases over a one minute period from about 1200 to about 1400
volts to the escutcheons and applying D.C. power to the cathodes to
achieve a current flow of about 3.6 amps. Argon gas is introduced
at a rate which increases over a one minute period from about 800
to about 1000 standard cubic centimeters per minute, and the
pressure is maintained at about 1.1x10'Z millibars. The escutcheons
are rotated between the magnetron target assemblies at a rate of
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~~T6891
one revolution per minute. The escutcheons are then subjected to
a high pressure etch cleaning process for about 15 minutes. In the
high pressure etch process argon gas is introduced into the vacuum
chamber at a rate which increases over a 10 minute period from
about 500 to 650 standard cubic centimeters per minute (i.e., at
the beginning the flow rate is 500 scan and after ten minutes the
flow rate is 650 scan and remains 650 scan during the remainder of
the high pressure etch process), the pressure is maintained at
about 2x10- millibars, and a negative potential which increases
over a ten minute period from about 1400 to 2000 volts is applied
to the escutcheons. The escutcheons are rotated between the
magnetron target assemblies at about one revolution per minute.
The pressure in the vessel is maintained at about 2x10- millibar.
The escutcheons are then subjected to another low pressure
etch cleaning process for about five minutes. During this low
pressure etch cleaning process a negative potential of about 1400
volts is applied to the escutcheons, D.C. power is applied to the
cathodes to achieve a current flow of about 2.6 amps, and argon gas
is introduced into the vacuum chamber at a rate Which increases
over a five minute period from about 800 sccm (standard cubic
centimeters per minute) to about 1000 sccm. The pressure is
maintained at about 1.1x10-2 millibar and the escutcheons are
rotated at about one rpm.
The target material is again sputter cleaned for about one
minute by applying power to the cathodes sufficient to achieve a
current flow of about 18 amps, introducing argon gas at a rate of
2176891
''"' about 150 sccm, and maintaining a pressure of about 3x10'3
millibars.
During the cleaning process shields ate interposed between the
escutcheons and the magnetron target assemblies to prevent
deposition of the target material onto the escutcheons.
The shields are removed and a layer of zirconium having an
average thickness of about 3 millionths (0.000003) of an inch is
deposited on the tin-nickel layer during a four minute period.
This sputter deposition process comprises applying D.C. power to
the cathodes to achieve a current flow of about 18 amps,
introducing argon gas into the vessel at about 450 sccm,
maintaining the pressure in the vessel at about 6x10'3 millibar, and
rotating the escutcheons at about 0.7 revolutions per minute.
After the zirconium layer is deposited a zirconium nitride
layer having an average thickness of about 14 millionths (0.000014)
of an inch is deposited on the zirconium layer by reactive ion
sputtering over a 14 minute period. A negative potential of about
200 volts D.C. is applied to the escutcheons while D.C. power is
applied to the cathodes to achieve a current flow of about 18 amps.
Argon gas is introduced at a flow rate of about 500 scan. Nitrogen
gas is introduced into the vessel from two sources. One source
introduces nitrogen at a generally steady flow rate of about 40
scan. The other source is variable and is regulated so as to
maintain a partial ion current of 6.3x10'~~ amps, with the variable
flow of nitrogen being increased or decreased as necessary to
maintain the partial ion current at this predetermined value.
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~i?689i
' The pressure in the vessel is maintained at about 7.5x10'3
millibar.
The zirconium-nitride coated escutcheons are then subjected to
low pressure cool down, where the heating is discontinued, pressure
is increased from about 1.1x10'2 millibar to about 2x10' millibar,
and argon gas is introduced at a rate of 950 scan.
This invention may be further developed within the scope of
the following claims. Accordingly, the above specification is to
be interpreted as illustrative of only a single 'operative
embodiment of the present invention, rather than in a strictly
limited sense.
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