HEAT TREATABLE LOW-E COATED ARTICLES AND METHODS OF MAKING SAME
This invention relates to heat treatable (low-E) coated articles, and methods of
making the same. Such coated articles may be used in the context of vehicle windshields,
insulating glass (IG) units, and other suitable applications.
BACKGROUND OF THE INVENTION
Layer coatings provided for solar management purposes are known in the art. Such
coatings often seek to reflect infrared (IR) radiation while at the same time enabling a high
amount of visible light transmittance. In the automobile industry, for example, vehicle
windshields often must have a visible light transmittance of at least 70% in the United
States, and at least 75% in Europe, even when laminated with a polyvinyl butyral (PVB)
layer provided between opposing glass substrates. This need for high visible transmittance
often conflicts with the need for good IR reflection, and it is difficult to obtain both
simultaneously. Making low-E coating designs more difficult is the need for a
mechanically and/or chemically durable coating, as well as the need for a coating with low
visible reflectance (glass side) that does not suffer radical color change when viewed at
different viewing angles. It is also desirable for such coatings to be heat treatable, so that
they may be used in vehicle windshields where heat bending is required, tempered IG
units, and the like.
U. S. Patent No. 5,584,902 (commonly owned herewith) discloses a low-E coating
system including, from the glass substrate outward, a stack of:
Unfortunately, while this coating is heat treatable and low-E in nature, it is characterized
by rather high emissivity and/or sheet resistance values which lead to rather low Rsoiar
(total solar energy reflectance) values around 22-24 %. For example, one coating reported
in the '902 patent had a sheet resistance (Rs) of 14.4 ohms/square and a normal emissivity
(En) of 0.15 before heat treatment; and a Rs of 10.5 ohms/square and a En of 0.11 after heat
treatment.
U. S. Patent No. 5,557,462 (commonly owned herewith) discloses a dual silver low-
E coating including from the glass outwardly a stack of:
Si3N4/NiCr/Ag/NiCr/Si3N4/NiCr/Ag/NiCr/Si3N4. The coating system of the '462 patent is
characterized by good emissivity values and good Rsolar values. Unfortunately, the coating
systems described in the '462 patent are not heat treatable (e.g., upon heat treatment Rs
goes way up, such as from about 3-5 to well over 10, and haze tends to set in). Because
the coatings described in the '462 patent are not heat treatable, as a practical matter they
cannot be used in applications such as vehicle windshields (where heat bending is
required) or other applications requiring heat treatment (HT) such as tempering, heat
strengthening, or bending.
Certain other dual-silver coatings are described in the background section of the
aforesaid provisional application. See also U. S. Patent No. 6,060,178. Unfortunately,
these coating systems are plagued by poor durability before and/or after heat treatment.
SUMMARY OF THE INVENTION
An object of certain exemplary embodiments of this invention is to provide a heat
treatable low-E coating (or layer system) which is mechanically and/or chemically durable
before and after heat treatment, the coating system having a visible transmittance of at
least about 70%.
Another object of certain exemplary embodiments of this invention is to provide a
dual silver low-E coating which is heat treatable and is mechanically and chemically
durable.
Another object of certain exemplary embodiments of this invention is to provide a
dual-silver low-E coating including at least one oxidation graded contact layer which
contacts an IR reflecting layer, where the degree of oxidation in the contact layer is graded
or changes throughout the thickness of the layer. Graded contact layer(s) can help enable
the coating to have high visible transmittance coupled with heat treatability.
Another object of certain exemplary embodiments of this invention is to provide a
coating including a Ni or NiCr inclusive contact layer(s) (e.g., NiCrOx layer) which is
oxidation graded in thickness so that one portion of the layer is more oxidized than another
portion of the layer. Again, it is believed that graded contact layer(s) can help enable the
coating to have high visible transmittance coupled with heat treatability.
Another object of certain exemplary embodiments of this invention is to utilize a
silicon nitride layer in a layer stack in order to reduce haze experienced upon heat
treatment. This silicon nitride layer may be Si-rich in certain embodiments.
Another object of certain exemplary embodiments of this invention is to provide a
heat treatable dual-silver coating/layer system designed to: a) be mechanically durable, b)
have a visible transmittance of at least about 70%, more preferably of at least about 75%,
and c) have a Rsolar value of at least about 26%, more preferably of at least about 28%, and
most preferably of at least about 29%.
Another object of certain exemplary embodiments of this invention is to provide a
coating according to one or more of the above-listed objects which may be used in the
context of an IG window unit and/or a vehicle windshield.
Another object of certain exemplary embodiments of this invention is to provide a
heat treatable low-E coating having high visible transmittance combined with a normal
emissivity (En) of no greater than 0.08 (more preferably no greater than 0.06) before heat
treatment, and/or an En of no greater than 0.07 (more preferably no greater than 0.05) after
heat treatment (HT).
Another object of certain exemplary embodiments of this invention is to provide a
heat treatable low-E coating having high visible transmittance combined with a sheet
resistance (Rs) of no greater than 10.0 ohms/sq. (more preferably no greater than 8.0
ohms/sq., and most preferably no greater than about 5.0 ohms/sq.) before heat treatment;
and/or a Rs of no greater than 8.0 ohms/sq. (more preferably no greater than 6.0 ohms/sq.,
and most preferably no greater than about 4.0 ohms/sq.) after heat treatment.
Another object of certain exemplary embodiments of this invention is to provide a
heat treatable low-E coating which is characterized by substantial reflective color stability
with shifts in viewing angle (VA). For example, in certain exemplary embodiments,
coated articles of this invention may experience a glass side reflective color coordinate a*
shift (i.e., Δa*) of no more than 4.0, more preferably no more than 3.0, and most preferably
no more than 2.0, given a VA shift of about 60 degrees.
Another object of certain exemplary embodiments of this invention is to provide a
heat treatable low-E dual silver coating with a glass side reflective color coordinate a*
value within the range of from -2.0 to 2.0 before and/or after a 60 degree VA shift from
normal, so as to minimize or reduce color change detectable by the human naked eye.
Another object of certain exemplary embodiments of this invention is to provide a
heat treatable low-E dual silver coating having a haze value after heat treatment of no
greater than 0.40, more preferably no greater than 0.30 (monolithic and/or in the context of
a laminate such as a windshield).
Another object of certain exemplary embodiments of this invention is to provide a
heat treated laminated article having a dual silver low-E coating, with a glass side visible
reflectance (RgY) (111. C, 2 degree) of no greater than 11%, more preferably no greater than
about 9.0%, and most preferably no greater than 8.5%.
Another object of this invention is to fulfill one or more of the above-listed objects.
Generally speaking, certain example embodiments of this invention fulfill one or
more of the above-listed objects by providing a coated article including a coating
supported by a glass substrate, the coating comprising:
an infrared (IR) reflecting layer contacting and sandwiched between first and
second layers, said second layer comprising NiCrOx; and
wherein at least said second layer comprising NiCrOx is oxidation graded so that a
first portion of said second layer close to said infrared (IR) reflecting layer is less oxidized
than a second portion of said second layer that is further from said infrared (IR) reflecting
layer.
Certain other example embodiments of this invention fulfill one or more of the
above-listed objects or needs by providing a coated article including a coating supported
by a substrate, the coating comprising:
a metallic infrared (IR) reflecting layer contacting and sandwiched between first
and second contact layers; and
wherein said second contact layer is oxidation graded and becomes progressively
more oxidized through its thickness proceeding further from said infrared (IR) reflecting
layer.
Certain other example embodiments of this invention fulfill one or more of the
above-listed needs or objects by providing a coated article comprising:
a coating provided on a glass substrate, said coating comprising from the glass
substrate outwardly:
a) at least one dielectric layer;
b) a first contact layer that is at least partially oxidized;
c) a first IR reflecting layer comprising Ag;
d) a second contact layer that is at least partially oxidized, said first IR
reflecting layer contacting each of said first and second contact layers;
e) at least one additional dielectric layer;
f) a third contact layer that is at least partially oxidized;
g) a second IR reflecting layer comprising Ag;
h) a fourth contact layer that is at least partially oxidized, said second IR
reflecting layer contacting each of said third and fourth contact layers;
i) at least one additional dielectric layer;
wherein after being heat treated (HT) and laminated said coated article has a visible
transmittance of at least about 70%, a Tsoiar no greater than about 50%, an Rsoiar of at least
26%, and a sheet resistance (Rs) of no greater than 8.0 ohms/sq; and
wherein at least two of said first, second, third and fourth contact layers comprise at
least Ni or a Ni alloy.
Certain other example embodiments of this invention fulfill one or more of the
above listed needs or objects by providing a coated article comprising:
a coating provided on a glass substrate, said coating comprising from the glass
substrate outwardly:
a) at least one dielectric layer comprising silicon nitride;
b) a first contact layer comprising Ni or a Ni alloy at least partially oxidized;
c) a first IR reflecting layer comprising Ag;
d) a second contact layer comprising Ni or a Ni alloy at least partially oxidized;
e) at least one additional dielectric layer;
f) a third contact layer comprising Ni or a Ni alloy at least partially oxidized;
g) a second IR reflecting layer comprising Ag;
h) a fourth contact layer comprising Ni or a Ni alloy at least partially oxidized;
i) at least one additional dielectric layer;
wherein after being heat treated (HT) said coated article has a visible transmittance
of at least 70%, a Tsoiar no greater than 50%, an Rsoiar of at least 26%, and a sheet resistance
(Rs) of no greater than 8.0 ohms/sq.
Certain other example embodiments of this invention fulfill one of more of the
above-listed needs or objects by providing a method of sputtering an oxidation graded
layer, the method comprising:
providing a substrate;
providing a sputtering apparatus including at least one target;
directing a first gas portion proximate a first side of the target and a second gas
portion proximate a second side of the target, the first gas portion including more oxygen
than the second gas portion so that as the substrate passes below the target an oxidation
graded layer is formed on an IR reflecting layer, the oxidation graded layer being more
oxidized at one portion thereof than at another portion thereof.
Certain other embodiments of this invention fulfill one or more of the above listed
objects by providing a coated article comprising:
a layer system supported by a glass substrate, the layer system comprising from the
substrate outwardly:
a Si-rich silicon nitride SixNy layer where x/y is from 0.76 to 1.5 in at least
part of the layer;
a first contact layer; and
an IR reflecting layer.
In different embodiments of this invention, part of all of Si-rich silicon nitride
layers may be Si-rich.
This invention will now be described with respect to certain example embodiments
thereof as illustrated in the following drawings, wherein:
IN THE DRAWINGS
Figure 1 is a side cross sectional view of a coated article according to an
embodiment of this invention.
Figure 2 is a schematic partial cross sectional view of a laminated vehicle
windshield according to an embodiment of this invention, in which coatings according to
any embodiment of this invention may be used.
Figure 3(a) is cross sectional view of a portion of a coating according to an
embodiment of this invention illustrating a pair of oxidation graded contact layers (e.g.,
NiCrOx layers) surrounding an IR reflecting layer (e.g., Ag).
Figure 3(b) is cross sectional view of a portion of a coating according to another
embodiment of this invention illustrating an IR reflecting layer (e.g., Ag) surrounded by a
pair of contact layers (e.g., NiCrOx layers), only one of which is oxidation graded.
Figure 4 is a schematic and partial cross sectional view illustrating how a graded
contact layer (e.g., NiCrOx layer) is deposited via sputtering in accordance with an
embodiment of this invention.
Figure 5 is a cross sectional view of the layer stack of coatings of Examples 1-3.
Figure 6 is a cross sectional view of a coated article according to another
embodiment of this invention.
DETAILED DESCRIPTION OF CERTAIN EXEMPLARY EMBODIMENTS
OF THE INVENTION
Referring now more particularly to the accompanying drawings in which like
reference numerals indicate like parts or layers throughout the several views.
Certain embodiments of this invention provide a low-E coating or layer system that
may be used in applications such as vehicle windshields, other vehicle windows, skylights,
glass doors, IG units, and the like. Coatings according to certain embodiments of this
invention preferably have low-E characteristics as well as high visible transmittance, and
are heat treatable. Preferably, coatings of certain embodiments herein are mechanically
durable before and/or after heat treatment (HT), and HT does not cause a significant jump
in sheet resistance (Rs) and/or haze. As is known in the art, such HT often necessitates
heating the coated substrate to temperatures of from 1100° F (593° C) to 1450° F (788° C)
for a sufficient period of time to attain the desired result (e.g., tempering, bending, and/or
heat strengthening).
Figure 1 is a side cross sectional view of a coated article according to an
embodiment of this invention. The coated article includes substrate 1 (e.g., clear, green,
bronze, or blue-green glass substrate from about 1.0 to 10.0 mm thick, more preferably
from about 1.8 mm to 4 mm thick), first dielectric anti-reflection layer 3, second dielectric
haze-reducing layer 5, first lower contact layer 7 (which contacts layer 9), first conductive
metallic infrared (IR) reflecting layer 9, first upper contact layer 11 (which contacts layer
9), third dielectric layer 13 (which may be deposited in one or multiple steps in different
embodiments of this invention), fourth dielectric layer 15, second lower contact layer 17
(which contacts layer 19), second conductive metallic IR reflecting layer 19, second upper
contact layer 21 (which contacts layer 19), fifth dielectric layer 23, and finally sixth
protective dielectric layer 25. The "contact" layers each contact at least one IR reflecting
layer. The aforesaid layers 3-25 make up heat treatable low-E (i.e., low emissivity)
coating 27 which is provided on glass or plastic substrate 1.
In certain embodiments of this invention, first dielectric layer 3 may be of or
include titanium dioxide (TiOx where x is from 1.7 to 2.3, most preferably 2.0), silicon
nitride (SixNy where x/y may be about 0.75 (i.e., Si3N4), or alternatively x/y may be from
about 0.76 to 1.5 in Si-rich embodiments), silicon dioxide (SiOx where x is from 1.7 to 2.3,
most preferably about 2.0), niobium oxide (e.g., Nb205), SiZrN, tin oxide, zinc oxide,
silicon oxynitride, or any other suitable dielectric material. First dielectric layer 3
functions as an antireflection layer in certain embodiments of this invention.
Second dielectric layer 5 may function to reduce haze in certain embodiments of
this invention, and is preferably of or includes silicon nitride (e.g., Si3N4, or alternatively
silicon-rich silicon nitride SixNy where x/y is from 0.76 to 1.5, more preferably from 0.85
to 1.2). When sputtering silicon nitride layer(s) herein, a Si target may be used, or
alternative a target including Si admixed with up to 3-20% by weight aluminum and/or
stainless steel (e.g. SS#316) may be used, with about this amount of aluminum and/or steel
then appearing in the layer(s) so formed. Other materials may also be used for haze
reducing layer 5, including but not limited to SiZrN.
While Si3N4 may be used for layer 5 (and/or layer 15) in certain embodiments, it
has been found that a silicon rich type of silicon nitride as layer 5 is better at reducing haze
and/or improving mechanical durability in certain embodiments of this invention. Absent
this layer 5 (and/or 15), haze tends to be at least 0.45; whereas with this layer(s) it is
reduced to no greater than 0.4 as discussed herein. In Si-rich silicon nitride embodiments,
layer 5 (and/or layer 15) is of or includes SixNy where x/y is from 0.76 to 1.5, more
preferably from about 0.85 to 1.2. Si3N4 has an index of refraction "n" of about 2.04, and
an extinction coefficient "k" of about 0. However, Si-rich silicon nitride according to
certain embodiments of this invention may have an index of refraction of at least about
2.05, more preferably of at least about 2.07, and may be 2.08 (at 632 nm) in exemplary
embodiments. Also, Si-rich silicon nitride according to certain embodiments of this
invention may have an extinction coefficient "k" of at least about 0.001, and more
preferably of at least about 0.003. In a first monolithic example after HT of a Si-rich
nitride layer 5 (and/or 15), "n" was 2.099 and "k" was 0.0034; while in a second
monolithic example after HT "n" was 2.168 and "k" was 0.014. Si-rich silicon nitride, in
addition to being better at reducing haze than Si3N4, has also been found to adhere better to
the titanium oxide of layer 3 in example embodiments. Surprisingly, it has also been
found that Si-rich silicon nitride under the NiCrOx and Ag layers in Figs. 1, 5 and 6
provides a lower sheet resistance (Rs).
Infrared (IR) reflecting layers 9 and 19 are preferably metallic and conductive, and
may be made of or include silver (Ag), gold, or any other suitable IR reflecting material.
However, metallic Ag is the material of choice for the IR reflecting layers 9 and 19 in
certain example embodiments of this invention. These IR reflecting layers help enable
coating 27 to have low-E characteristics.
Contact layers 7, 11, 17, and 21 are of or include nickel (Ni) oxide, or a nickel alloy
oxide such as nickel chrome oxide (NiCrOx), in preferred embodiments of this invention.
NiCrOx layers 7, 11, 17, and/or 21 may be fully oxidized in certain embodiments of this
invention (i.e., fully stochiometric), or may be at least about 75% oxidized in other
embodiments of this invention. While NiCrOx is a preferred material for layers 7, 11, 17
and or 21, those skilled in the art will recognized that other materials may instead be used
(e.g., oxides of Ni, oxides of Ni alloys, oxides of Cr, oxides of Cr alloys, NiCrOxNy, or any
other suitable material) for one or more of these layers. It is noted that contact layers 7,
11, 17 and/or 21 may or may not be continuous in different embodiments of this invention.
When layers 7, 11, 17 and/or 21 comprise NiCrOx in certain embodiments, the Ni
and Cr may be provided in different amounts, such as in the form of nichrome by weight
about 80-90% Ni and 10-20% Cr. An exemplary sputtering target for depositing these
layers includes not only SS-316 which consists essentially of 10% Ni and 90% other
ingredients, mainly Fe and Cr, but Haynes 214 alloy as well, which by weight consists
essentially of (as a nominal composition) the following materials which may also show up
in these layers:
Element Weight %
Ni 75.45
Fe 4.00
Cr 16.00
C .04
Al 4.50
Y .01
One or more of contact layers 7, 11, 17, and/or 21 (e.g., of or including NiCrOx)
is/are preferably oxidation graded in certain embodiments of this invention so that the
degree of oxidation in the layer(s) changes throughout the thickness of the layer(s). For
example, one or more of contact layers (7, 11, 17 and/or 21) may be graded so as to be less
oxidized at the contact interface with the immediately adjacent IR reflecting layer (9 or 19)
than at a portion of the contact layer(s) further or more/most distant from the immediately
adjacent IR reflecting layer. It is believed that oxidation grading of one or more of contact
layer(s) 7, 11, 17 and/or 21 enables the low-E coating 27 to achieve the combination of
heat treatability and high visible transmission (which was not previously achievable using
NiCrOx contact layers in a dual silver low-E coating system; e.g., see the aforesaid '462
patent). This will be explained in more detail below with reference to Figs. 3(a) and 3(b).
Turning back to Figure 1, third dielectric layer 13 acts as a coupling layer between
the two halves of the coating 27, and is of or includes tin oxide in certain embodiments of
this invention. However, other dielectric materials may instead be used for layer 13,
including but not limited to silicon nitride, titanium dioxide, niobium oxide, silicon
oxynitride, zinc oxide, or the like. Fourth dielectric layer 15 functions as a haze reducer in
certain embodiments of this invention, and is preferably of or includes silicon nitride (e.g.,
Si3N4, or alternatively silicon-rich silicon nitride discussed above). However, in
alternative embodiments of this invention, other materials (e.g., SiZrN) may instead be
used for dielectric layer 15.
Fifth dielectric layer 23 may be of or include tin oxide in certain embodiments of
this invention. However, other dielectric materials may instead be used for layer 23,
including but not limited to silicon nitride, titanium dioxide, niobium oxide, silicon
oxynitride, zinc oxide, or the like. Protective overcoat dielectric layer 25 is provided at
least for durability purposes, and may be of or include silicon nitride (e.g., Si3N4) in certain
embodiments of this invention. However, other dielectric materials may instead be used
for layer 25, including but not limited to titanium dioxide, silicon oxynitride, tin oxide,
zinc oxide, niobium oxide, SiZrN, or the like.
Other layer(s) below or above the illustrated coating 27 may also be provided. Thus,
while the layer system or coating 27 is "on" or "supported by" substrate 1 (directly or
indirectly), other layer(s) may be provided therebetween. Thus, for example, coating 27 of
Fig. 1 may be considered "on" and "supported by" the substrate 1 even if other layer(s) are
provided between layer 3 and substrate 1. Moreover, certain layers of coating 27 may be
removed in certain embodiments, while others may be added in other embodiments of this
invention without departing from the overall spirit of certain embodiments of this
invention.
Figure 2 illustrates a laminate (e.g., vehicle windshield) according to an
embodiment of this invention, including coating 27 of Fig. 1. As shown in Fig. 2, the
laminate (e.g., windshield) includes first glass substrate 1 on which coating 27 is provided,
and second glass substrate 31. PVB layer 33 is provided between the substrates in a
known manner, so as to contact coating 27 on one side thereof. In the Fig. 2 embodiment,
coating 27 is provided at/on the second (or #2) surface 37 of the laminate. The first surface
35 is at the exterior of the laminate exposed to the outside of the vehicle, second surface 37
is on the interior or inside of outer substrate 1, third surface 39 is on the inside of the
interior substrate 31, and fourth surface 41 is at the interior of the vehicle. Coatings 27
herein are preferably provided on either the second 37 or third 39 surface(s) of such
laminates (the same is also true with regard to IG units).
Turning back to Fig. 1, while various thicknesses may be used consistent with one
or more of the objects discussed herein, exemplary preferred thicknesses and example
materials for the respective layers on the glass substrate 1 in the Fig. 1 embodiment are as
follows:
Table 1 (Example Materials/Thicknesses: Fig. 1 Embodiment)
Layer Preferred Range (A) More Preferred (A) Example (A)
Ti02 (layer 3) 0-400 A 50-250 A 100 A
SixNy (layer 5) 0-400 A 50-250 A 170 A
NiCrOx (layer 7) 5-100 A 10-50 A 18 A
Ag (layer 9) 50-250 A 80-120 A 105 A
NiCrOx (layer 11) 5-100 A 10-50 A 16 A
Sn02 (layer 13) 0-800 A 500-850 A 650 A
SixNy (layer 15) 0-800 A 50-250 A 170 A
NiCrOx (layer 17) 5-100 A 10-50 A 18 A
Ag (layer 19) 50-250 A 80-120 A 105 A
NiCrOx (layer 21) 5-100 A 10-50 A 16 A
Sn02 (layer 23) 0-500 A 100-300 A 150 A
Si3N4 (layer 25) 0-500 A 100-300 A 250 A
Figure 6 illustrates a low-E heat treatable coating 27 according to another
embodiment of this invention. The Fig. 6 coating 27 is the same as the Fig. 1 coating
described above, except that either (i) dielectric layer 3 is removed, or (ii) layers 3 and 5
are replaced with a single silicon nitride layer 40. Silicon nitride layer 40 may be of or
include Si3N4 in certain embodiments of this invention. In other embodiments, silicon
nitride layer 40 may be of or include SixNy where x/y may be from about 0.65 to 0.80, or
alternatively from about 0.76 to 1.5 in silicon rich embodiments. In another embodiment
of the particular Fig. 6 embodiment, layer 40 may be of or include SiZrN. Nitride layer 40
is advantageous because if functions to reduce haze, and is preferably from about 10 to 500
A thick, more preferably from about 200-400 A thick. In this embodiment, upper IR
reflecting layer 19 may also be thickened by about 0 to 10 A, and/or the top dielectric 25
may be thickened by about 0-10%. In another aspect of the Fig. 6 embodiment, silicon
nitride may be used for layer 40 but in a manner such that the lower portion of the layer is
of or includes Si3N , while the upper portion is of the silicon rich type silicon nitride
discussed above. As with all embodiments herein, Si-rich silicon nitride has improved
performance in reducing haze compared to Si3N4. The Fig. 6 embodiment tends to have
reduced visible transmission (but still at least 70%) relative to the Fig. 1 embodiment, but
may be more durable under certain circumstances, and
may be higher than in the Fig.
1 embodiment which is of course beneficial.
In certain exemplary embodiments of this invention, coating/layer systems 27
according to all embodiments above have the following low-E characteristics before/after
heat treatment (HT) when in monolithic form, as set forth in Table 2:
Table 2: Monolithic Before/After Heat Treatment (HT)
Characteristic General More Preferred Most Preferred
Rs (ohms/sq.)(before HT): <= 10.0 <= 8.0 <= 5.0
Rs (ohms/sq.)(after HT) : <= 8.0 <= 6.0 <= 4.0
En (before HT): <= 0.08 <= 0.06 n/a
EQ (after HT): <= 0.07 <= 0.05 n/a
Haze (after HT): <= 0.40 <= 0.30 <= 0.28
Coatings 27 according to certain exemplary embodiments of this invention (e.g,
Figs. 1-6) have the following color/transmission/reflection/haze characteristics (e.g.,
preferred greyish color can be seen below) when on a clear soda lime silica glass substrate
(e.g., 2.1 mm thick) in laminated form with another similar clear soda lime silica glass
substrate (e.g., in the form of a vehicle windshield with PVB or index oil between the two
substrates) as shown in Fig. 2 (i.e., on the #2 surface of the laminate), as set forth in Table
3. In Table 3 below, RσY is visible reflection from the exterior of the vehicle as shown in
Fig. 2, and RfY is visible reflection from the other side of the laminate such as from the
vehicle interior in Fig. 2, and the a*, b* values under these respective reflection parameters
also correspond to glass (g) side (e.g., outside vehicle in Fig. 2) and film (f) side (e.g.,
vehicle interior in Fig. 2), respectively.
Table 3: Color/Transmission After HT: Laminated Form
Characteristic General More Preferred
Tvis (111. A, 2 deg.): >= 70% >= 75% (Fig. 1 only)
Tvis (111. C, 2 deg.): >= 70% >= 75% (Fig. 1 only)
RgY (111. A, C; 2 deg.): <= 11% <= 9%
a*g (111. A, C; 2°): -2.0 to +2.0 -1.0 to +1.0
b*g (111. A, C; 2°): -10.0 to +1.0 -8.0 to -2.0
RfY (111. A, C; 2 deg.): <= 11% <= 9%
a*f (111. A, C; 2°): -3.0 to +1.0 -2.0 to 0.0
b*f (111. A, C; 2°): -5.0 to 0.0 -4.0 to -1.0
Rsoiar: >= 26% >= 28%
Haze: <= 0.4 <= 0.3
Tsoiar: <= 50 % <= 48 %
Surprisingly, it has been found that layer stacks according to certain embodiments of this
invention are characterized by rather low visible color shifts due to viewing angle
(VA) change when viewed from the glass side of the article (e.g., from the exterior of the
vehicle in Fig. 2). For example, Table 4 below illustrates the low Δa*g values associated
with laminated coated articles of certain embodiments of this invention when viewed from
a normal viewing angle (i.e., straight on) vs. a 60 degree off axis viewing angle. In other
words, Table 4 below illustrates that according to certain embodiments of this invention
Δa*g can be kept rather low even given a viewing angle (VA) shift of 60 degrees
so that coated articles do not appear to change color to the naked eye when viewed
at different angles. It is noted that Δb* values are not deemed as important as Δa*
values, because a* changes are typically more noticeable to the naked human eye
than are corresponding b* changes. In certain exemplary embodiments, a*g is within
the range of -2.0 to + 2.0 both before and after the 60 degree viewing angle (VA) shift, so
that a*g remains proximate the b* axis (i.e., the b* axis is vertical blue(-)/yellow(+), while
the a* axis is horizontal green(-)/red(+)) even through this radical change in viewing angle
thereby minimizing the appearance of color change.
Table 4: Color Change with 60° Viewing Angle (VA) Change
Characteristic General More Preferred Best
RgY (normal VA): <= 11% <= 9% <= 8%
a*g (normal VA): -2.0 to +2.0 -1.0 to +1.0 -1.0 to 0.0
RgY (60° VA): <= 18% <= 16% <= 15%
a*σ (60° VA): -2.0 to +4.0 0.0 to +4.0 0.0 to 2.0
Δa* (60° VA change): <= 3.0 <= 2.0 n/a
It was mentioned above that the dual silver low-E coating system of U. S. Patent
No. 5,557,462 (i.e., glass/Si3N4/NiCr/Ag/NiCr/Si3N4/NiCr/Ag/NiCr/Si3N4) is not heat
treatable at least because upon heat treatment Rs goes way up, e.g., from about 3-5 to well
over 10, and haze tends to set in. It is currently believed that if one were to significantly
increase the thickness of the NiCr layers of the '462 patent in an attempt to achieve heat
treatability, this would unfortunately result in visible transmittance going down well below
70% which would of course render the coated articles non-useable in vehicle windshield
applications.
However, it has surprisingly been found that by oxidation grading one or more of
the non-crystalline contact layers 7, 11, 17, and/or 21, the resulting coated article can
maintain high visible transmission, low-E characteristics including low Rs, and good
durability upon heat treatment (e.g., tempering* heat bending, etc.). Reference is made to
Figs. 3(a) and 3(b) in this regard.
As shown in Fig. 3(a), both contact layers 7 and 11 (and/or 17 and 21) on either side
of the applicable IR reflecting layer 9 (and/or 19) are oxidation graded so that they are less
oxidized (including not oxidized at all in some optional embodiments) at the IR reflecting
layer (e.g., Ag) interface. In other words, the two contact layers on either side of the Ag
layer 9 are progressively less oxidized through their respective thicknesses as they near Ag
layer 9. Accordingly, in certain embodiments of this invention, the portions (e.g., 5 A
thick portions) of layers 7 and 11 (or 17 and 21) closest to layer 9 (or 19) are from about 0
to 40% oxidized, more preferably from about 0 to 20% oxidized, and most preferably from
about 0 to 10% oxidized. Meanwhile, the portions (e.g., 5 A thick portions) of layer 7 and
11 (or 17 and 21) furthest from layer 9 (or 19) are at least about 50% oxidized, more
preferably at least about 60% oxidized, even more preferably at least about 75% oxidized,
and most preferably at least about 85% oxidized.
Thus, the contact layers become progressively less oxidized through their respective
thicknesses as they approach the IR reflecting layer 9, 19. In certain embodiments, this
causes the contact layers 7 and 11 (or 17 and 21) to be conductive or at least semi-
conductive at the interface with the IR reflecting layer 9 (or 19), and substantially non-
conductive at other parts of the layers 7 and 11 (or 17 and 21) such as in the 5 A thick
portion furthest from layer 9 (or 19). Thus, when the contact layers are of or include
graded NiCrOx, the x value progressively decreases through the thickness of the layer
toward the IR reflecting layer 9, 19. This value x may even approach or equal zero near
the immediately adjacent IR reflecting layer in certain instances.
It is believed that the less oxidized portions of the contact layers 7 and 11 (and/or 17
and 21) near the IR reflecting layer 9 (or 19) interface enable the coating 27 to withstand
heat treatment (HT) and provide good adhesion to layer 9, 19. However, these less (or no)
oxidized portions of the contact layers are also less transparent to visible light than are the
more oxidized portions of the contact layers. Thus, when oxidation graded: (a) the highly
oxidized portions of graded contact layers 7 and 11 (and/or 17 and 21) are more
transparent to visible light and enable the coating 27 to maintain its high visible
transmission characteristics, while (b) the less oxidized portions of the graded contact
layers better support the IR reflecting layer(s) 9, 19 during HT and provide good adhesion
thereto, and enable the coating to withstand the same.
The Figure 3(b) embodiment of this invention is similar to the Fig. 3(a)
embodiment, except that only one of the contact layers contacting an IR reflecting layer is
graded. In this particular embodiment, the upper contact layer(s) 11, 21 is oxidation
graded as discussed above, while the lower one is not and is substantially oxidized, or at
least about 50% oxidized. In certain embodiments of this invention, all four non-
crystalline contact layers 7, 11, 17 and 21 may be oxidation graded in such a manner,
while in other embodiments only the upper contact layers 11 and 21 may be graded. In
still further embodiments of this invention, three of the contact layers may be graded, or
alternatively only one of the contact layers may be oxidation graded. While NiCrOx is a
preferred material for graded contact layers herein, it will be appreciated by those skilled
in the art that other materials may instead be used (e.g., including but not limited to
NiCrOxNy, nickel oxide, chromium oxide, nickel-alloy oxide, etc.), and may be oxidation
graded to enable a dual silver coating system to maintain high transmission and good low-
E characteristics even in view of HT.
Figure 4 illustrates how an oxidation graded contact layer 7, 17 may be deposited
on a substrate as part of a coating according to an exemplary embodiment of this invention,
using an asymmetric introduction of oxygen gas at a target area. Substrate 1 with part of a
layer system thereon proceeds in direction D through the sputter coater. Sputtering
cathode target 51 within shield 53 may comprise NiCr or any of the Ni inclusive targets
discussed above when the contact layer (e.g., layer 7) is to be of or include NiCrOx. Other
metallic or ceramic targets may be used when other materials are to be used as contact
layer(s). When the substrate 1 is moving in direction D beneath target 51, gas is
introduced around the target on two sides 57 and 59 thereof. On one side 57 of target 51,
at least oxygen (e.g., 02) gas (e.g., oxygen flow of about 30-60 mL/min. at 4.1 kW), and
optionally a mixture of oxygen and an inert gas such as argon (Ar), is fed into the coating
zone beneath and/or proximate the target. However, on the other side 59 of target 51, less
oxygen gas is used and more of another gas such as Ar is introduced into the coating zone
beneath and/or proximate the target. For purposes of example, on side 57 of the target the
gas flow may comprise any of (a) 100% oxygen, (b) a 70/30 mixture of oxygen/argon, (c)
a 50/50 mixture of oxygen/argon, (d) a 30/70 mixture of oxygen/argon, or (e) a 50/25/25
mixture of oxygen/argon nitrogen; while on the other side 59 of the target the gas flow
may comprise any of (a) 100% argon or some other inert gas, (b) a 50/50 mixture of
argon/nitrogen, or (c) a 90/10 mixture of argon/oxygen. Thus, there is more oxygen gas
flow on side 57 of the target than on the other side 59. Thus, as the substrate 1 passes
under the target 51, the first portion of layer 7 to be deposited is highly oxidized because of
the presence of the oxygen gas on side 57 of the target, but the latter portion of layer 7 to
be deposited is much less oxidized because of the lack of oxygen gas at the exit side 59 of
the target. Thus, proximate target 51, the substrate first passes through an oxygen gas
enriched sputter coating area and thereafter passes through an oxygen gas depleted sputter
coating area having less oxygen gas. After layer 7 has been deposited in Fig. 4, the
substrate moves on so that target 60 can be used to sputter coat layer 9 onto the substrate
over the already deposited layers.
The amounts of oxygen and or other gas(es) can of course be adjusted to oxidation
grade contact layers in any desired manner. When it is desired to grade the contact
layer(s) 11, 21 on the upper side of the IR reflecting layer 9, 19, the gas flow shown in Fig.
4 and described above is inverted so that the higher oxygen inclusive flow is at the exit
side 59 of the target and the lower/no oxygen gas flow is at the entry side 57 of the target.
EXAMPLES 1-3
The following three Example coated articles were made in accordance with certain
embodiments of this invention. For each of the three Examples, the coating/layer system
27 shown in Fig. 5 was sputtered onto a clear 2.1 mm thick large soda lime silica float
glass substrate 1, and then cut into at least a 3" x 3" sample. A Leybold Terra-G six-
chamber sputter coating apparatus was used to sputter the coatings 27 onto the substrates
1. Five cathodes were in each chamber, so there were a total of 30 cathode targets in the
sputter coater. Cathode numbering utilizes the first digit to refer to the coater chamber,
and the second digit to refer to the cathode position in that chamber. For example, cathode
# 32 was the second cathode (second digit) in the third (first digit) sputter chamber.
Cathode #s C13, C14, C23, C62, C31, C32, C62, C64 and C65 were Twin Mag II type
cathodes; cathode # C42 was a dual C-Mag type cathode; and cathode #s C44, C51, and
C53 were planar cathodes. As will be appreciated by those skilled in the art, the first half
of a coating 27 may be deposited in a sputter coater, and then the article may be again run
through the coater to sputter the second half of the coating onto the substrate. In the
sputter coater, layers 7-11 and 17-21 were sputtered onto the substrate using DC power
sputtering, while the other layers were sputtered onto the substrate using a mid-frequency
AC type system. Below, "*" means Al content of approximately 10%. The line speed for
each Example was 2.6 meters per minute (m/min.). The coater/process setups for the three
Examples are in Table 5. All gas flows (e.g., oxygen, argon, nitrogen) are presented in
units of mL/minute. In the below examples, though not shown in the charts, the oxygen
flow was turned off at the sides of the NiCr targets discussed above in order to oxidation
grade the contact layers 11 and 21 as shown in Fig. 3(b) (i.e., only the two contact layers
11 and 21 above the respective silver layers were oxidation graded in these Examples).
Volts refers to cathode volts, and amps (A) refers to cathode amps. "Tr" stands for trim;
and trim (Tr) console, trim (Tr) Mid, and trim (Tr) pump are all measured in mL/minute.
Pressure is measured in mbar x 10"J. Trim gas refers to individually adjusted gas flows
along the cathode length to make corrections regarding layer thickness uniformity. The
NiCr targets were approximately 80/20 NiCr. The process for each Example is broken into
three separate charts (i.e., Part #s 1-3) because so much information is presented; only the
cathode and target data is provided for all three charts in each example for ease of
reference. Both silicon nitride layers 5 and 15 were Si-rich through their entire
thickness(es); as can be seen by the fact that much more inert argon (Ar) gas than nitrogen
gas was used in sputtering these silicon nitride layers.
Table 5: Coater Setup/Processes for Examples 1-3
EXAMPLE 1
EXAMPLE #1 (Part #1)
Cathode Target Volts (V) Power (kW) Ar Flow (mL/min O Flow (rnL/min) N Flow
#13 Ti 743 73 200 25 80
#14 Ti 703 64 200 35 50
#23 Ti 738 63.5 200 35 50
#42 Si* 456 29.7 225 0 165
#51 Ag 7.4 0 0 Ar
#53 NiCr 10.5 0 0 Ar
#62 Sn 42 208 25.1 02
#64 Si* 93.5 264 26.4 N2
#65 Si* 93.5 273 26.2 N
EXAMPLE #1 (Part #3 continued from Parts #1-2 abovercathode/target in commonl)
Cathode Target Tr Console Tr Mid Tr Pump Pressure Lambda Lambda active
#13 Ti 7.5 15 7.5 2.79E"03 252 True
#14 Ti 12.5 25 12.5 3.03E"03 252 True
#23 Ti 7.5 35 7.5 4.83E"03 252 True
#42 Si* 50 5 45 2.18E"03 0 False
#44 NiCr 15 70 15 2.26E"03 0 False
#51 Ag 15 70 15 1.37E"03 0 False
#53 NiCr 15 70 15 2.16E"03 0 False
#62 Sn 15 70 15 2.12E-03 220 True
#31 Sn 15 70 15 2.97E"03 220 True
#32 Sn 15 70 15 3.19E"03 220 True
#42 Si* 50 5 45 2.52E"03 0 False
#44 NiCr 15 70 15 2.30E"03 0 False
#51 Ag 15 70 15 1.44E"03 0 False
#53 NiCr 15 70 15 2.38E-03 0 False
#62 Sn 15 70 15 2.24E"03 220 True
#64 Si* 20 60 20 2.88E"03 0 False
#65 Si* 20 60 20 3.6 IE"03 0 False
EXAMPLE 2
#44 NiCr 11.4 0 0 Ar
#51 Ag 7.3 0 0 Ar
#53 NiCr 10.3 0 0 Ar
#62 Sn 45.5 203 25.03 o2
#31 Sn 62 225 25.6 o2
#32 Sn 61 226 25.64 o2
#42 Si* n/a 230 26.18 N2
#44 NiCr 11.6 0 0 Ar
#51 Ag 7.4 0 0 Ar
#53 NiCr 10.5 0 0 Ar
#62 Sn 44 206 25.1 o2
#64 Si* 93.5 264 26.4 N2
#65 Si* 93.5 273 26.2 N
EXAMPLE #2 (Part #3 continued from Parts #1-2 abovercathode/target in commonl)
Cathode Target Tr Console Tr Mid Tr Pump Pressure Lambda Lambda active
#13 Ti 7.5 15 7.5 2.79E"03 252 True
#14 Ti 12.5 25 12.5 3.03E-03 252 True
#23 Ti 7.5 35 7.5 4.83 03 252 True
#42 Si* 50 5 45 2.13E"03 0 False
#44 NiCr 15 70 15 2.26E"03 0 False
#51 Ag 15 70 15 1.35F03 0 False
#53 NiCr 15 70 15 2.14F03 0 False
#62 Sn 15 70 15 2.13E"03 220 True
#31 Sn 15 70 15 3.22E"03 220 True
#32 Sn 15 70 15 3.25E"03 220 True
#42 Si* 50 5 45 2.2 IE"03 0 False
#44 NiCr 15 70 15 2.26E"03 0 False
θ> 45-
UA UA
4. UA
UA O
4p5.
to to
UA 0 0
σ o
EXAMPLE #3 (Part #2 continued from Part #1 abovercathode/target in commonl)
Cathode Target Amps (A) Tank Voltage (V) Freq. (kHz) Trim Gas
#14 Ti 125 346 26.7 o2
#23 Ti 110 344 26.5 o2
#42 Si* n a 230 26.18 N2
#44 NiCr 11.4 0 0 Ar
#51 Ag 7.4 0 0 Ar
#53 NiCr 10.7 0 0 Ar
#44 NiCr 11.4 0 0 Ar
#51 Aσ 7.5 0 0 Ar
#53 NiCr 10.5 0 0 Ar
#62 Sn 45.4 212 25.1 Oo
#64 Si* 94 264 26.4 No
#65 Si* 93.5 273 26.2 N2
EXAMPLE #3 (Part #3 continued from Parts #1-2 abovercathode/target in commonl)
Cathode Target Tr Console Tr Mid Tr Pump Pressure Lambda Lambda active
#13 Ti 7.5 15 7.5 2.79E"03 252 True
#14 Ti 12.5 25 12.5 3.03E"03 252 True
#23 Ti 7.5 35 7.5 4.83E"03 252 True
#42 Si* 50 5 45 2.18E"03 0 - False
#44 NiCr 15 70 15 2.26E-03 0 False
#51 Ag 15 70 15 1.37E"03 0 False
#53 NiCr 15 70 15 2.16E'03 0 False
#62 Sn 15 70 15 2.12F03 220 True
#31 Sn 15 70 15 3.01F03 220 True
#32 Sn 15 70 15 3.24F03 220 True
#42 Si* 50 5 45 2.58F03 0 False
#44 NiCr 15 70 15 2.27F03 0 False
#51 Ag 15 70 15 1.4 IE"03 0 False
#53 NiCr 15 70 15 2.37F03 0 False
#62 Sn 15 70 15 2.26F03 220 True
#64 Si* 20 60 20 2.90F03 0 False
#65 Si* 20 60 20 3.69F03 0 False
After coatings 27 of Examples 1-3 were sputtered onto respective substrates 1 in
accordance with the above, they were tested/measured as follows in Table 6 (i.e., in a
monolithic state). Heat treatment was performed by placing the coated articles into a
furnace heated to about 625 degrees C for about five (5) minutes.
Table 6: Exs. 1-3, Monolithic Before/After Heat Treatment (HT)
Characteristic Example 1 Example 2 Example 3
Tvis, 111. A, 2° (before HT): >=70% >=70% >=70%
Tvis, 111. A, 2° (after HT): >=78% >=78% >=78%
Rs (ohms/sq.)(before HT): 4.43 4.37 4.27
Rs (ohms/sq.)(after HT): 3.46 3.44
Eα (before HT): <=0.06 <=0.06 <=0.06
En (after HT): <=0.05 <=0.05 <=0.05
Haze (after HT): 0.15 0.28 0.22
Thereafter, the monolithic heat treated coated articles of Examples 1-3 were each
laminated to another corresponding clear 2.1 mm thick 3 inch by 3 inch soda lime silica
float glass substrate 1, with a layer of PVB (about 0.8 mm thick) being located between the
substrates in a known manner, and coating 27 provided on the #2 surface as shown in Fig.
2. The resulting laminated coated articles (see Fig. 2) were then tested/measured and were
found to exhibit the following characteristics set forth in Table 7. In Table 7, the glass (G)
side is the same as outside the vehicle in Fig. 2, while the film (F) side is the same as the
vehicle interior in Fig. 2.
Table 7: Color of Exs. 1-3 in Laminated Form Post-HT (i.e., as in Fig. 2)
Value/Measurement Example 1 Example 2 Example 3
111. C. 2°
Transmission (TY or TVIS) %: 75.37 75.32 74.68 a*τ: -2.92 -3.17 -2.25 b*τ: 3.87 4.39 4.07
Reflectance as viewed from glass (G) side: RGY (%): 7.93 8.02 8.22 a*G: 0.53 0.93 0.29 b*G: -5.23 -7.10 -5.64
Reflectance as viewed from film/coating (F) side: RFY (%): 7.83 7.85 8.11 a*F: -1.59 -1.23 -1.68 b*F: -2.75 -3.74 -2.73
111. D65. 2°
Transmission (TY or TVis) %: 75.69 75.34 74.71 a*τ: -2.81 -3.05 -2.16 b*τ: 3.85 4.35 4.07
Reflectance as viewed from glass (G) side: RGY (%): 7.93 8.03 8.22 a*G: 0.26 0.57 -0.01 b*G: -5.17 -7.03 -5.58
Reflectance as viewed from film coating (F) side: RFY (%): 7.84 7.85 8.12 a*F: -1.79 -1.48 -1.88 b*F: -2.71 -3.69 -2.69
111. A, 2°
Transmission (TY or Tvis) %: 75.27 75.23 74.78 a*τ: -1.95 -2.05 -1.37 b*T: 3.28 3.74 3.68
111. C, 10°
Transmission (TY or Tvis) %: 75.16 75.08 74.91 a*τ: -2.39 -2.59 -2.78 b*τ: 3.93 4.45 4.02
Reflectance as viewed from glass (G) side: RGY (%): 8.01 8.14 8.31 a*G: 0.11 0.28 -0.15 b*G: -5.21 -7.03 -5.60
Reflectance as viewed from film/coating (F) side: RFY (%): 7.87 7.90 8.16 a*F: -1.54 -1.30 -1.62 b*F: -2.79 -3.78 -2.77
111. D65, 10°
Transmission (TY or Tvis) %: 75.19 75.12 74.92 a*τ: -2.29 -2.49 -2.66
b*τ: 3.92 4.45 3.99 ■
Reflectance as viewed from glass (G) side: RGY (%): 8.01 8.14 8.31 a*G: -0.09 0.01 -0.37 b*G: -5.20 -7.02 -5.58
Reflectance as viewed from film/coating (F) side: RFY (%): 7.88 7.91 8.16 a*F: -1.69 -1.49 -1.78 b*F: -2.77 -3.76 -2.75
111. A. 10°
Transmission (TY or Tvis) %: 75.20 75.15 74.85 a*τ: -1.41 -1.63 -1.75 b*τ: 3.34 3.98 4.02
Moreover, each of Examples 1-3 was found to be chemically and mechanically durable as
these terms are defined below, both before and after HT.
As can be seen above, in depositing each of the silicon nitride layers, more Ar gas
than N gas was used in the sputtering process. In the Examples the ratio Ar/N as about
225/165 (or 1.36) as can be seen above. In preferred embodiments of this invention the
ratio Ar/N is from about 1.15 to 3.0, more preferably from about 1.20 to 2.0, and most
preferably from about 1.2 to 1.5. This ratio which uses more of an inert gas (e.g., Ar) than
nitrogen in sputtering the silicon nitride layers enables the resulting silicon nitride layers to
be Si-rich as discussed above.
Table 8 below compares, for the HT laminate of Example 1, viewing characteristics
at a normal viewing angle (VA) versus at a 60° off axis VA (i.e., the 60° VA is 60 degrees
from the normal VA). As can be seen, Example 1 is characterized by substantial color
stability over this wide range of viewing angles, so that a viewer looking at the laminate of
Example 1 at both a normal VA (i.e., straight on so that the line or site is perpendicular to
the plane of the article) and a 60° VA would not notice much if any color change. This is
due to the low reflective Δa* value from the glass (G) side (i.e., Δa* means the difference
between a* at the normal VA and the 60° off-axis VA). Note: the sixty degree color is 111.
D65, 10 degree standard observer.
Table 8: Color Change with 60° Viewing Angle (VA) Change (Ex. 1)
Characteristic Ex. 1 (Normal VA) Ex. 1 (60° off-axis VA)
T 1 vi ■s •- 75.27% n/a a*τ: -2.2 n/a b*τ: 4.2 n a
J- solar- 46.75%
-K-solar- 30.15 36.11
RgY: 7.8% 14.56% σ -0.23 1.6 b U* g •. -5.59 -1.33
Δa*g (60° VA change): 1.83 same
ΔL*j ; (60° VA change): 11.4 same
As can be seen above in Table 8, Δa*g (60° VA change) reflective in accordance
with certain embodiments of this invention is preferably no greater than 3.0, and more
preferably no greater than 2.0. In Table 8, it was 1.83. Moreover, Tsoiar is preferably no
greater than 50% in certain embodiments of this invention, even more preferably no
greater than 48%, and most preferably no greater than about 47%.
Certain embodiments of this invention after heat treatment and lamination are
characterized as follows regarding glass (G) side reflective color:
Table 9
Parameter Normal VA 60° off-axis VA
a* -2.0 to +2.0 -2.0 to + 3.0
b* -1.0 to -12.0 0 to -9.0
Certain terms are prevalently used in the glass coating art, particularly when
defining the properties and solar management characteristics of coated glass. Such terms
are used herein in accordance with their well known meaning. For example, as used
herein:
Intensity of reflected visible wavelength light, i.e. "reflectance" is defined by its
percentage and is reported as RXY or Rx (i.e. the Y value cited below in ASTM E-308-85),
wherein "X" is either "G" for glass side or "F" for film side. "Glass side" (e.g. "G") means,
as viewed from the side of the glass substrate opposite that on which the coating resides,
while "film side" (i.e. "F") means, as viewed from the side of the glass substrate on which
the coating resides.
Color characteristics are measured and reported herein using the CIE LAB 1976 a*,
b* coordinates and scale (i.e. the CIE 1976 a*b* diagram, 111. CIE-C 2 degree observer),
wherein:
L* is (CIE 1976) lightness units
a* is (CIE 1976) red-green units
b* is (CIE 1976) yellow-blue units
Other similar coordinates may be equivalently used such as by the subscript "h" to
signify the conventional use of the Hunter method (or units) 111. C, 10° observer, or the CIE
LUV u*v* coordinates. These scales are defined herein according to ASTM D-2244-93
"Standard Test Method for Calculation of Color Differences From Instrumentally
Measured Color Coordinates" 9/15/93 as augmented by ASTM E-308-95, Annual Book of
ASTM Standards, Vol. 06.01 "Standard Method for Computing the Colors of Objects by
10 Using the CIE System" and/or as reported in IES LIGHTING HANDBOOK 1981
Reference Volume.
The terms "emissivity" (or emittance) and "transmittance" are well understood in
the art and are used herein according to their well known meaning. Thus, for example, the
term "transmittance" herein means solar transmittance, which is made up of visible light
transmittance (TY of TV1S), infrared energy transmittance (T^), and ultraviolet light
transmittance (T
uv). Total solar energy transmittance (TS or
can be characterized as
a weighted average of these other values. With respect to these transmittances, visible
transmittance may be characterized for architectural purposes by the standard Illuminant C,
2 degree technique; while visible transmittance may be characterized for automotive
purposes by the standard 111. A 2 degree technique (for these techniques, see for example
ASTM E-308-95, incorporated herein by reference). For purposes of emissivity a
particular infrared range (i.e. 2,500 - 40,000 nm) is employed. Various standards for
calculating/measuring any and/or all of the above parameters may be found in the
aforesaid provisional application upon which priority is claimed herein.
The term Rsoiar refers to total solar energy reflectance (glass side herein), and is a
weighted average of IR reflectance, visible reflectance, and UV reflectance. This term
may be calculated in accordance with the known DIN 410 and ISO 13837 (12/98) Table 1,
p. 22 for automotive applications, and the known ASHRAE 142 standard for architectural
applications, both of which are incorporated herein by reference.
"Haze" is defined as follows. Light diffused in many directions causes a loss in
contrast. The term "haze" is defined herein in accordance with ASTM D 1003 which
defines haze as that percentage of light which in passing through deviates from the incident
beam greater than 2.5 degrees on the average. "Haze" may be measured herein by a Byk
Gardner haze meter (all haze values herein are measured by such a haze meter and are
unitless).
"Emissivity" (or emittance) (E) is a measure, or characteristic of both absorption
and reflectance of light at given wavelengths. It is usually represented by the formula:
E = 1 - Reflectancefiim
For architectural purposes, emissivity values become quite important in the so-
called "mid-range", sometimes also called the "far range" of the infrared spectrum, i.e.
about 2,500 - 40,000 nm., for example, as specified by the WINDOW 4.1 program, LBL-
35298 (1994) by Lawrence Berkeley Laboratories, as referenced below. The term
"emissivity" as used herein, is thus used to refer to emissivity values measured in this
infrared range as specified by ASTM Standard E 1585-93 entitled "Standard Test Method
for Measuring and Calculating Emittance of Architectural Flat Glass Products Using
Radiometric Measurements". This Standard, and its provisions, are incorporated herein by
reference. In this Standard, emissivity is reported as hemispherical emissivity (Eh) and
normal emissivity (En).
The actual accumulation of data for measurement of such emissivity values is
conventional and may be done by using, for example, a Beckman Model 4260
spectrophotometer with "VW" attachment (Beckman Scientific Inst. Corp.). This
spectrophotometer measures reflectance versus wavelength, and from this, emissivity is
calculated using the aforesaid ASTM Standard 1585-93.
Another term employed herein is "sheet resistance". Sheet resistance (Rs) is a well
known term in the art and is used herein in accordance with its well known meaning. It is
here reported in ohms per square units. Generally speaking, this term refers to the
resistance in ohms for any square of a layer system on a glass substrate to an electric
current passed through the layer system. Sheet resistance is an indication of how well the
layer or layer system is reflecting infrared energy, and is thus often used along with
emissivity as a measure of this characteristic. "Sheet resistance" may for example be
conveniently measured by using a 4-point probe ohmmeter, such as a dispensable 4-point
resistivity probe with a Magnetron Instruments Corp. head, Model M-800 produced by
Signatone Corp. of Santa Clara, California.
"Chemical durability" or "chemically durable" is used herein synonymously with
the term of art "chemically resistant" or "chemical stability". Chemical durability is
determined by boiling a 2"x 5" sample of a coated glass substrate in about 500 cc of 5%
HCl for 5 minutes (i.e. at about 220°F). The sample is deemed to pass this test (and thus
the layer system is "chemically resistant" or is deemed to be "chemically durable" or to
have "chemical durability") herein if at least half of the sample's layer system remains after
the 5 minutes.
"Mechanical durabilility" as used herein is defined by the following tests. The test
uses a Pacific Scientific Abrasion Tester (or equivalent) wherein a 2" x 4" x 1" nylon brush
(e.g., as made by Wright Bernet of Franklin Park, Illinois, Model 1280 Hand & Nail
Brush) is cyclically passed over the layer system in 500 cycles employing 150 gm of
weight, applied to a 6" x 17" sample. In this test, if no substantial, noticeable scratches
appear when viewed with the naked eye under visible light, the test is deemed passed, and
the article is said to be "mechanically durable" or to have "mechanical durability".
The terms "heat treatment" and "heat treating" as used herein mean heating the
article to a temperature sufficient to enabling thermal tempering, bending, or heat
strengthening of the glass inclusive article. This definition includes, for example, heating a
coated article to a temperature of at least about 1100 degrees F (e.g., to a temperature of
from about 550 degrees C to 900 degrees C) for a sufficient period to enable tempering.
Once given the above disclosure many other features, modifications and
improvements will become apparent to the skilled artisan. For example, and without
Umitation, the aforesaid oxidation graded contact layer(s) and Si-rich silicon nitride
layer(s) can be used with single silver layer stacks, as well as the illustrated dual silver
layer stacks. Such other features, modifications and improvements are therefore
considered to be a part of this invention, the scope of which is to be determined by the
following claims: