Coated article with low-E coating having multilayer overcoat and method of making same
A coated article is provided so as to include a low-E (low emissivity) coating having an infrared (IR) reflecting layer sandwiched between at least a pair of dielectric layers. The IR reflecting layer may be of or include a material such as silver (Ag), and is provided between a pair of contact layers. The low-E coating includes an overcoat having a substantially metallic layer (e.g., NbZr or Zr) which has been found to improve the durability of the coating without significantly sacrificing desired optical characteristics. Such coated articles may be used in the context of windows.
1. A coated article including a coating having a layer system supported by a glass substrate, the layer system comprising:
a first dielectric layer on the glass substrate;
an IR reflecting layer comprising silver on the glass substrate over at least the first dielectric layer;
a contact layer on the glass substrate over and directly contacting the IR reflecting layer;
a second dielectric layer comprising silicon nitride on the glass substrate over at least the contact layer;
a layer comprising Ni and Cr on the glass substrate over and directly contacting the second dielectric layer comprising silicon nitride;
a third dielectric layer comprising silicon nitride on the glass substrate over and directly contacting the layer comprising Ni and Cr;
a layer comprising zirconium oxide on the glass substrate over and directly contacting the third dielectric layer comprising silicon nitride, so that the layer comprising Ni and Cr is located between and directly contacting said second dielectric layer comprising silicon nitride and said third dielectric layer comprising silicon nitride;
wherein the layer comprising Ni and Cr is from 1-3 nm thick;
wherein the layer comprising zirconium oxide is from 3-8 nm thick;
wherein the layer comprising Ni and Cr is substantially thinner than each of the second and third dielectric layers comprising silicon nitride and is also substantially thinner than the IR reflecting layer comprising silver;
wherein the layer comprising zirconium oxide is substantially thinner than each of the second and third dielectric layers comprising silicon nitride; and
wherein the coating contains only one silver-based IR reflecting layer.
2. The coated article of claim 1 , wherein the first dielectric layer comprises silicon nitride.
3. The coated article of claim 1 , further comprising a contact layer under and directly contacting the IR reflecting layer.
4. The coated article of claim 1 , wherein the coated article has a visible transmission of from about 40 to 60%.
5. The coated article of claim 1 , wherein the coated article is a window.
6. The coated article of claim 1 , wherein the layer system has a sheet resistance (R s ) of less than about 20 ohms/square.
7. The coated article of claim 1 , wherein the layer comprising Ni and Cr does not contact any IR reflecting layer comprising Ag or Au.