Heat treatable low-E coated articles and methods of making same

Details Heat treatable low-E coated articles and methods of making same Heat treatable low-E coated articles and methods of making same

2001-02-28

2003-06-10

Jones, Deborah (Department: 1775)

Stock material or miscellaneous articles

All metal or with adjacent metals

Having composition, density, or hardness gradient

C428S426000, C428S428000, C428S432000, C428S446000, C428S448000, C428S450000, C428S469000, C428S472000, C428S666000, C428S673000, C428S680000, C428S697000, C428S698000, C428S699000, C428S702000, C428S701000

Reexamination Certificate

active

06576349

ABSTRACT:

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. Pat. No. 5,584,902 (commonly owned herewith) discloses a low-E coating system including, from the glass substrate outward, a stack of: Si
3
N
4
/NiCr/Ag/NiCr/Si
3
N
4
. 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 R
solar
(total solar energy reflectance) values around 22-24%. For example, one coating reported in the '902 patent had a sheet resistance (R
s
) of 14.4 ohms/square and a normal emissivity (E
n
) of 0.15 before heat treatment; and a R
s
of 10.5 ohms/square and a E
n
of 0.11 after heat treatment.
U.S. Pat. No. 5,557,462 (commonly owned herewith) discloses a dual silver low-E coating including from the glass outwardly a stack of:
Si
3
N
4
/NiCr/Ag/NiCr/Si
3
N
4
/NiCr/Ag/NiCr/Si
3
N
4
. The coating system of the '462 patent is characterized by good emissivity values and good R
solar
values. Unfortunately, the coating systems described in the '462 patent are not heat treatable (e.g., upon heat treatment R
s
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. Pat. 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., NiCrO
x
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 R
solar
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 (E
n
) of no greater than 0.08 (more preferably no greater than 0.06) before heat treatment, and/or an E
n
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 (R
s
) 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 R
s
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., &Dgr;a*) 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 (R
g
Y) (Ill. 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 NiCrO
x
; and
wherein at least said second layer comprising NiCr

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