Note: Descriptions are shown in the official language in which they were submitted.
WO91/17283 PCT/US9~/0~97~
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A VACUUM DEPOSITED DARK COATING ON A SUBSTRATE
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates generally to vacuurn vapor
deposition processes and coatings for primarily glass or
plastic substrates, and more particularly, to a dark coating
which provides a decorative and/or functional border or band
on glass, plastic or other transparent article for automotive
: win(lr~w~: ~nrl winrlc:hiPlds inrlua~n9 ~1 'SS rccfs, ~ir~r~_
windows and windshields, architectural applications,rcomputer
screens, display panels, glass freezer doors, microwave oven
glass doors, home or office skylights, mirrors, marine vehicle
windows, framed glass as well as many other similar
applications.
. Dark coatings on substrates have been used for strictly
decorative, aesthetic purposes as well as for performing a
useful function. For e~ample, in automobile windshields
there has been a relatively recent advancement of
electrically heating the windshields to defrost, de-ice or
defog them. One manner of doing this has been to place bus
bars near the top and bottom of a windshield for supplying an
electrical power across a transparent conductive coating
which is applied on the vision portion of the windshield and
is in contact with the electrical conducting bus bars. To
conceal from view, the bus bars which may not be
aesthetically pleasing, a dark or near opaque coating is
. applied to a border area of the windshield. The coating is
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usually black but could be many other darker shades such as
gray, blue, magenta, bronze, brown and golden. There are
many other uses for this dark border coating such as: to
conceal electric wires, antenna conductors and other
assemblies that appear behind glass, or just for aesthetic
purposes.
U.S. Patent No. 4,684,388 to Boaz (incorporated by
reference herein) discloses a method for forming a glass
sheet with a W-base ceramic paint th~r~n C~ramir n~;nt
compositions are generally well-known in the art. These
paints usually include a mixture o metal oxides which act as
a coloring agent. Such ceramic paint compositions include a
low melting point glass frit. This frit bonds the mixture of
metal oxides to the glass sheet and insures that the mixture
remains bonded after the glass sheet has been cooled to room
temperature.
In some processes, the metal o:~ide frits and enamels are
heated to a temperature in a range up to 1300F. A zinc
metal powder is mi~ed with stannous oxide and the
aforementioned materials to form a liquid type paint which
can be silkscreen pr nted. Ceramic base paints also contain
volatiles which must be driven off. Non-reactive metal
oxides are used such as chrome, cobalt, nlckel, manganese,
iron, and copper. Such mi~tures are commonly known as blac~
oxide powders. Other mixtures of oxides may be used in order
to get different colors which is well-known in the art. :
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Boaz uses the addition o the stannous oxide powder to
the zinc metal powder to prevent sticking of the paint to a
forming die. In Boaz the forming die is what comes in
contact with the glass and paint during the application of
the paint to the glass.
There are several disadvantages to the above mentioned
ceramic paint applications. One disadvantage is that the
paint and frit use volatile solvents with coloring pigments.
Another disadvantaqe is that prior coatinas have been thick
(.00l to .003 inches). Also, high temperature firing causes
stress and weakness in the glass. Another disadvantage is
that the paint may tend to stick to another glass in contact,
with the forming die and other fixtures used in this method.
Yet another disadvantage is that previous application
processes have not been easily integrated into the window
lamination process such as for automobile and aircraft glass.
Vapor deposition processes are also well known in the art
but until now have been used primarily for applying
transparent conductive coatings for heated windshields. For
example, U.S. Patent No. ~,861,669 to Gillery (incorporated
; by reference herein) describes one such process called
sputtering. However, vapor deposition processes have not
been used for applying dark coatings for various reasons.
One reason is that it is difficult to get the dark coating to
adhere to a substrate when the coating is applied using this
process, Without adhesion the coating may peel off with
time.' The present invention discloses a way to use a vapor
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deposition process to apply dark coatings and to get the
coatings to adhere to the substrate. Other reasons may be
difficulty with, obtaining a dark color using a vapor
deposition process or, masking areas of the substrate not to
be coated for placing in a vacuum chamber.
Thus it is an object of the present invention to provide
a transparent substrate where a dark coating is applied at a
low temperature and is significantly thinner than
conventional cer~mie paints or frit5 ~urther oh~Pcts are to
provide fewer production steps (the old way requires: mix
paint, silk screen, fire at high temperature) in the
manufacture of such coated substrates and to provide an
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improvement in function and different physical
characteristics from a paint band. One of the advantages of
the present invention is its relatively low temperature
process which results in less thermal stress induced in the
substrate. -
Therefore, the present invention provides a coating or
film of ceramic carbonitrides, metal oxides, metal nitrides
or combinations thereof, deposited by using anyone of three
:
vapor deposition processes known as sputtering, cathodic arc, `
or ion plating. The coating is applied upon a selected
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substrate to the thickness necessary to control light
transmission and reflectance. Typically, an opaque coating
of 500 Angstroms to 5,000 Angstroms or more is deposited to
form an obscured band that light cannot pass through. The
coating may be continuous or segmented or even applied in a
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WO9l/17283 PC~/~S91/0297
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; particular pattern. In some applications, thinner coatings
may be desired in which partial light may be transmitted.
Oxynitride mixtures are used to change color and light
transmission. The foregoing and other objects and advantages
will become more apparent when viewed in light of the
accompanying drawings and following detailed description.
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~RIEF DESCRIPTION OF THE DRAWINGS
FIGU~E 1 is a perspective view of an alltnm~hil~
windshield having the coating of the present invention; and
FIGURE 2 is a cross-sectional view taken along the
section line 2-2 in FIGURE 1.
DESCXIPTION OF PREFERRED EMBODIMENT(S~
Referring to FIGURE 1, there is shown a typical
automobile windshield 10 comprising a glass panel 11. (It
should be noted that this is just one use for the subject
invention which could be used on glass, plastic, or
transparent substrates of many kinds in many different
applications.~ The glass panel 11 may have electrical bus
bars ~not sho~n) at a top portion 12 and bottom portion 14 of
the windshield. These bus bars may be used to transfer
electrical current across the windshield, through a
conductive coating, to heat, defrost, defog or de-ice the
windshield, To make the windshield more aesthetically
pleasing, a dark coating 16 may be applied in a band shape
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around the border or on other portions or segments of the
glass ll to conceal the bus bars or other assorted components.
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As shown in FIGURE 2, a windshield lO panel~ll may
typically contain multiple layers. Starting from outside the
automobile, there is a first surface 18 on a first outside
layer 20 of glass. Inside the first layer 20 of glass is a
second surface 22 which lies between the first layer 20 of
glass and a layer of plastic 24. Inside the layer of p`lastic
24 i~ ?~ thlrrl ~llrf~rP 26 wh~Ch 1iPS bpt~^?een- the lay~r ^r
plastic 24 and a second inner layer 28 of glass. Lastly,
there is the inside surface 30 of the glass which is inside
the automobile. The coating band 16 or border of the present
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invention is preferably applied to the second surface 22 or
the third surface 26. However, it is also feasible to apply
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~the coating to the fourth, inside surface 30 of the second
glass layer 28. In case of a single monolithic glass sheet
or window the coating band would preferably be applied to the
inner surface of the glass or window.
Because these multiple layers 20, 24, 28 of the
windshield lO are sandwiched together during the
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manufacturing of the windshield lO, it is important to keep
the thickness of any applied coatings 16 to a minimum to
avoid having undue stress imposed on the glass. Since a dark
coating 16 is usually not applied across the entire surface
of the glass ll, but typically at the edges, when the layers
20, 24, 28 are compressed together, they will tend to bow at
the edges if the coating 16 is too thick. This may induce
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critical stresses. By sputtering the coating 16 onto the
glass 11, the coating 16 can be applied in a much thinner
layer than previous ceramic type paints applied with high
temperature firing.
In order to obtain good adhesion of the coating to the
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substrate, the substrate must be washed. First it is washed
with a warm water detergent wash. Then it is rinsed with
water followed by rinsing again with deionized water. The
substrate i~ th~n ~r;ed wi th warm 2i r hlnwn oYer it. The
substrate is then placed in a vacuum chamber and heated or
glow discharge cleaned by ionic bombardment in a wet gas as
is known in the glass cleaning art. The coating is then
applied immediately.
The coating may be applied in a DC reactive vacuum
sputtering apparatus which uses an ion sputtering method with
a shield or mask to protect selected uncoated areas of the
glass. This low temperature process allows a very thin,
durable coating with no curing required. This translates
into less stress in the glass. The coating can be altered to
appear black, gray, magenta, golden, brown, bronze, and blue
as well as other darker shades. The sputtering process is
compatible with the window lamination process currently in
use by most windshield manufacturers. Because sputtering
does not require high temperatures, or silk screening the
application of the coating of the present invention can be
accomplished aster by using fewer process steps.
~ The metal rich coating of the present invention may be
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WO91/172~3 PCT/US91/0297
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comprised of a chromium o~ide-nitride or o~ynitride. Other
metal compounds may also be used, such as: oxides, nitrides,
carbides, and oxynitrides of base metals chromium, aluminum,
titanium, molybdenum, tantalum, tungsten, stainless steel,
niobium, and zirconium, and their alloys.
The dark color of the coating is obtained by regulating
reactive gases which interact with the metal and its compound
-~' in the vacuum chamber. The reactive gases are nitrogen,
oxygen! and w~ter ~n r The snuttering nr~cc ~l c~ llc~c
argon ~as which is non-reactive. Atmospheric air has the
three reactive gases which make it suitable for this
process. The relative amounts of the. reactive gases mixed
with the argon in a metal rich environment are varied to
develop different colors. Generally, as th~ percentage of
reactive gases are increased and the thickness of the coating
remains the same the color of the coating will lighten (the
light transmittance will increase).
It is thought that the improved dark coating and method
of the present invention and many of its attendant advantages
will be understood from the foregoing description and it will
be apparent that various changes may be made in the form and
construction of the components thereof without departing from
the spirit and scope of the invention or sacrificing all of
its material advantages, the form herein before described
being merely a preferred or e~emplary embodiment thereof.
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