Low-e matchable coated articles, and methods

#This invention relates to low-E coated articles that have approximately the same color characteristics as viewed by the naked eye both before and after heat treatment (e.g., thermal tempering), and corresponding methods. Such articles may in certain embodiments combine: (1) high visible transmission characteristics, (2) good durability before and/or after heat treatment, and/or (3) a low ΔE* value which is indicative of color stability upon heat treatment (HT). Such coated articles may be used monolithically, in insulating glass (IG) units, laminated window units, vehicle windshields, and/or other vehicle or architectural applications.

#Low-emissivity (low-E) coating systems are known in the art. For example, commonly owned U.S. Pat. No. 5,376,455 discloses: glass/Si3N4/NiCr/Ag/NiCr/Si3N4. Unfortunately, the low-E coating system of the '455 patent is not sufficiently color matchable after heat treatment (HT) with its non-heat treated counterpart.

#The need for substantial matchability (before heat treatment vs. after heat treatment) is known. Glass substrates are often produced in large quantities and cut to size in order to fulfill the needs of a particular situation such as a new multi-window and door office building, vehicle window needs, etc. It is often desirable in such applications that some of the windows and/or doors be heat treated (i.e., tempered, heat strengthened or heat-bent) while others need not be. Office buildings often employ IG units and/or laminates for safety and/or thermal control. It is desirable that the units and/or laminates which are heat treated (HT) substantially match their non-heat treated counterparts (e.g., with regard to color, reflectance, and/or the like, at least on the glass side) for architectural and/or aesthetic purposes. Moreover, in certain example but non-limiting situations, good durability after HT (e.g., scratch resistance and/or chemical durability) may reduce the need for edge deletion so as to reduce window fabrication costs.

#FIG. 1 is a partial side cross sectional view of an embodiment of a layer system according to this invention.

#FIG. 2 is a partial cross-sectional view of an IG unit as contemplated by this invention, in which the layer system of FIG. 1 may be used.

#FIG. 3 is a graph plotting nitrogen gas flow for the undercoat (i.e., lower) barrier layer versus glass side color stability upon HT (i.e., ΔE* (glass side)), illustrating that color stability with HT degrades by causing ΔE* to increase (i.e., get worse) as nitrogen flow increases.

#Certain embodiments of this invention provide a coating or layer system that may be used in applications such as IG or monolithic window units, architectural windows, vehicle windows (e.g., windshields, backlites, etc.), and/or other suitable applications. Certain embodiments of this invention provide a layer system that combines high visible transmission, good durability (mechanical and/or chemical) before and/or after HT, and good color stability upon heat treatment. It will be shown herein how certain layers stacks surprisingly enable this unique combination.

#With regard to color stability, certain embodiments of this invention have excellent color stability (i.e., a low value of ΔE* and/or a low value of Δa*; where Δ is indicative of change in view of heat treatment) with heat treatment (e.g., thermal tempering, bending, or thermal heat strengthening) monolithically and/or in the context of dual pane environments such as IG units or windshields. Such heat treatments (HTs) often necessitate heating the coated substrate to temperatures of at least about 1100° F. (593° C.) and up to 1450° F. (788° C.) [more preferably from about 1100 to 1200 degrees F., and most preferably from 1150-1200 degrees F.] for a sufficient period of time to insure the end result (e.g., tempering, bending, and/or heat strengthening). Certain embodiments of this invention combine (i) color stability with heat treatment, and (ii) the use of a silver inclusive layer for selective IR reflection. Certain embodiments of this invention combine (i) and (ii), along with (iii) high visible transmission, (iv) good durability, and/or (v) color in the blue-green quadrant (i.e., third quadrant) of the CIE LAB color chart when applied to a clear and/or green glass substrate, although this invention may certainly be used in the context of other colors. Certain embodiments of this invention combine (i) through (v), along with (iv) low-emissivity characteristics.

#FIG. 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, grey, blue, or blue-green glass substrate from about 1.0 to 12.0 mm thick), first dielectric layer 3 (e.g., of or including silicon nitride (e.g., Si3N4), titanium dioxide, tantalum pentaoxide, zirconium oxide, silicon zirconium nitride, tin oxide, silicon oxide, silicon dioxide, or silicon oxynitride), first metal inclusive partially nitrided barrier layer 5 (e.g., of or including NiCrNx and/or CrNx), IR reflecting layer 7 (e.g., of or including Ag, Au or the like), second or overlying metal inclusive barrier layer 9 which may optionally also be at least partially nitrided (e.g., of or including Ni, NiCr, Cr, NiCrNx and/or CrNx), and second or overcoat dielectric layer 11 (e.g., of or including silicon nitride (e.g., Si3N4), titanium dioxide, tantalum pentaoxide, silicon zirconium nitride, zirconium oxide, tin oxide, silicon oxide, silicon dioxide, or silicon oxynitride). Other layer(s) below or above the illustrated coating system may also be provided. Thus, while the coating or layer system is “on” or “supported by” substrate 1 (directly or indirectly), other layer(s) may be provided therebetween. Thus, for example, the layer system of FIG. 1 may be considered “on” the substrate 1 even though other layer(s) are provided therebetween (e.g., a TiO2 layer may be provided between substrate 1 and dielectric layer 3 when layer 3 comprises silicon nitride). Additionally, those skilled in the art will recognize that the coating or layer system 3-11 of FIG. 1 may be provided as illustrated, or alternatively may be repeated on top of itself one or more times so as to form a double or triple silver layer stack.