阅读说明：本技术 用于对预层压和后层压的组件中的涂层进行激光烧蚀/划线的技术、和/或相关方法 (Techniques for laser ablation/scribing coatings in pre-laminated and post-laminated assemblies, and/or related methods ) 是由 维贾延·S·维拉萨米 于 2018-07-06 设计创作，主要内容包括：本发明的某些示例性实施方案涉及用于对预层压或后层压组件、预组装或后组装绝缘玻璃单元和/或其他产品中的玻璃或其他基底上的涂层(例如,低辐射率、镜或其他涂层)的周边边缘进行激光烧蚀/划线,以便减缓或防止涂层的腐蚀的技术。例如,1064nm或其他波长的激光可用于将线刻划到低辐射率的金属和/或类金属层中,或设置在已经层压或已经组装的绝缘玻璃单元或其他产品中的其他涂层中,例如围绕其周边。划线降低了从涂层的中心到环境的电子移动性,并且从而减缓并且有时甚至防止电化学腐蚀的发生。本文还设想了与其相关的相关产品、方法和套件。(Certain exemplary embodiments of the present invention relate to techniques for laser ablation/scribing the peripheral edge of a coating (e.g., a low emissivity, mirror or other coating) on glass or other substrates in pre-laminated or post-laminated assemblies, pre-assembled or post-assembled insulated glass units, and/or other products, in order to slow or prevent corrosion of the coating. For example, a 1064nm or other wavelength laser may be used to scribe a wire into a low-e metal and/or metal-like layer, or other coating provided in an already laminated or already assembled insulating glass unit or other product, for example around its periphery. Scribing reduces electron mobility from the center of the coating to the environment and thereby slows down and sometimes even prevents the occurrence of galvanic corrosion. Related products, methods, and kits related thereto are also contemplated herein.)

1. A method of making a laminated product, the method comprising:

obtaining an intermediate product comprising first and second substantially parallel glass substrates laminated together with a laminate, the first glass substrate having formed thereon a multi-layer thin film coating comprising at least one metal-containing layer and susceptible to corrosion; and

laser scribing lines in the coating by exposing the intermediate product to a laser source while preparing the laminated product, the lines forming barriers to electron transport between opposite sides thereof.

2. The method of claim 1, wherein the laminate is PVB, the glass substrate is a transparent glass substrate, and the laser source is a 1064nm laser source.

3. The method of claim 1, wherein the laser source is a 1064nm laser source.

4. The method of any preceding claim, further comprising operating the laser source at a wavelength at which the second substrate and the laminate are each at least 90% transmissive.

5. The method of any preceding claim, wherein the coating is a low emissivity coating comprising a layer comprising Ag.

6. The method of claim 5, wherein the coating comprises at least one layer comprising Ni, Cr, and/or Ti formed on and in physical contact with the layer comprising Ag.

7. The method of claim 5, wherein the layer comprising Ag is sandwiched between and in direct physical contact with first and second layers comprising Ni, Cr, and/or Ti.

8. The method according to any one of claims 5 to 6, wherein the layer comprising Ag is formed on and in direct physical contact with the layer comprising zinc oxide.

9. The method of any preceding claim, further comprising performing the laser scribing to completely dissolve the coating adjacent the line.

10. The method of claim 9, wherein material from the dissolved coating is at least partially dissolved in the laminate.

11. The method of any preceding claim, wherein the coating comprises a bottom dielectric layer directly over the first glass substrate, and the method further comprises:

performing the laser scribing to dissolve a portion of the coating layer that includes the at least one metal-containing layer but not the bottom dielectric layer.

12. The method of any preceding claim, wherein the dissolved portion of the coating is at least partially dissolved in the laminate and/or the bottom dielectric layer.

13. The method of any preceding claim, further comprising controlling the heat generated by laser scribing to avoid damaging the surface of the substrate on which the coating is formed and to avoid unwanted damage to the laminate.

14. The method of claim 13, further comprising interrupting the laser scoring and cooling the intermediate product and/or allowing the intermediate product to cool during the interruption to help control the heat generated.

15. The method of any of claims 13 to 14, further comprising controlling a duty cycle and/or operating power of the laser source so as to assist in controlling the heat generated.

16. The method of any preceding claim, wherein the lines have a width of at least 100 to 800 um.

17. The method of any preceding claim, wherein the line is formed around a perimeter of an intermediate article, the barrier being defined around the perimeter of the intermediate article.

18. A method according to any preceding claim, wherein the laser scribing is carried out in conjunction with multiple overlapping scans of the laser source.

19. The method of any preceding claim, wherein the laser scribing is performed to produce a sub-10 pico A electrically isolating barrier.

20. A method according to any preceding claim, wherein during the laser scribing the second substrate is oriented closer to the laser source than the first substrate.

21. A method of making a laminated product, the method comprising:

forming a multilayer thin film coating on a first glass substrate, the coating comprising at least one metal-containing layer and being susceptible to corrosion;

laminating the first glass substrate to a second glass substrate using a laminating material such that the coating is oriented between the first substrate and the second substrate and such that the first substrate and the second substrate are substantially parallel to each other; and

laser scribing a border line around a perimeter of the coating layer after the laminating, the laser scribing at least partially dissolving the coating layer adjacent the border line and increasing the electrochemical corrosion resistance of the coating layer inside the border line by electrically isolating the coating layer inside the border line when the laminated product is manufactured,

wherein at least the at least one metal-containing layer is dissolved by means of the laser scribing such that the associated ablated material (a) reforms in a non-conductive manner, and/or (b) dissolves and/or diffuses into the first substrate, the laminate, and/or at least one other layer of the multilayer thin film coating.

22. A laminated product, comprising:

a first glass substrate supporting a multilayer thin film coating, the coating comprising at least one metal-containing layer and being susceptible to corrosion;

a second glass substrate laminated to the first glass substrate using a laminating material such that the coating is oriented between the first substrate and the second substrate and such that the first substrate and the second substrate are substantially parallel to each other; and

a laser-scribed boundary around a perimeter of the coating formed after the first and second substrates have been laminated together,

wherein at least the at least one metal-containing layer of the coating adjacent to the boundary is dissolved by means of the laser scribing,

wherein dissolved material from the coating is (a) incorporated into the first substrate, laminate and/or cushion layer of the coating and/or (b) ablated and/or vaporized to reform in a non-conductive manner, and by means of the laser scribing, and

wherein the boundary has a width and a depth sufficient to electrically isolate a region inside the boundary from a region outside the boundary to a degree sufficient to at least delay electrochemical corrosion in the region inside the boundary.

23. The product of claim 22, wherein:

the glass substrate is a transparent glass substrate and the laminate is PVB, and

the coating is a low E coating comprising at least one layer comprising Ag.

24. A kit for preparing a laminated product, the kit comprising:

a laser source; and

an intermediate product comprising first and second substantially parallel glass substrates laminated together with a laminate, the first glass substrate having formed thereon a multi-layer thin film coating comprising at least one metal-containing layer and susceptible to corrosion;

wherein the laser source is controllable to laser scribe lines in the coating layer by exposing the intermediate product to the laser source as the laminated product is being produced, the lines forming barriers to electron transport between opposite sides thereof.

25. The kit of claim 24, wherein the laser source is portable.

26. A method of making a laminated product, the method comprising:

obtaining an intermediate product comprising first and second substantially parallel glass substrates laminated together with a laminating material, the first glass substrate having formed thereon a multi-layer thin film coating comprising at least one metal-containing layer; and

coupling energy into the coating by exposing the intermediate product to laser light from a laser source when preparing the laminated product, the laser source operates at a wavelength at which the second glass substrate and the laminate are substantially transmissive, the energy is coupled into the coating and the laser source is controlled so as to selectively cause at least a portion of the coating to dissolve in the first substrate, the laminate and/or a cushion layer of the coating in a desired pattern (a), and/or (b) vaporize and reform in a non-conductive manner, the desired pattern defining at least a first region and a second region, and is shaped to a width and depth sufficient to electrically isolate the first and second regions from each other, the electrical isolation is at a level sufficient to at least substantially delay galvanic corrosion in the first region.

Technical Field

Certain exemplary embodiments of the present invention relate to techniques for laser ablation/scribing coatings in pre-laminated and post-laminated assemblies, pre-assembled and post-assembled insulated glass units, and/or other products, and related methods. More particularly, certain exemplary embodiments of the present invention relate to techniques for laser ablation/scribing the peripheral edge of a coating (e.g., a low emissivity, mirror or other coating) on glass or other substrates in pre-laminated or post-laminated assemblies, pre-assembled or post-assembled insulated glass units, and/or other products, in order to slow or prevent corrosion of the coating and/or related products.

Background and summary of the invention

Laminated products have been used in a variety of applications including, for example, low emissivity (low E), mirrors, and other applications. Fig. 1 is a cross-sectional view of an exemplary laminate product 100. The exemplary laminate product 100 of fig. 1 includes substantially parallel spaced apart first and second substrates 102a and 102b (e.g., glass substrates), also sometimes referred to as interlayers, laminated together with a laminate material 104. Typical laminates include, for example, PVB, EVA, PET, PU, and the like. Depending on the application, the laminate 104 may be optically "transparent," i.e., it may have a high visible light transmittance. One or more coatings may be formed on one or more major surfaces of the first substrate 102a and/or the second substrate 102. For example, it is not uncommon to include a low E, mirror, anti-reflective (AR) or other coating on the second or third surface of the laminate product. In some cases, a coating may be provided to each of the second and third surfaces. For ease of understanding, fig. 1 includes an exemplary coating 106 on surface 3. An optional additional edge seal 108 may be disposed around the perimeter of the article 100, and the edge seal 108 may be intended to protect the side edges of the article 100, laminate 104, coating 106, etc., from mechanical, environmental, and/or other types of damage.

One problem with laminated products is that laminated metal layer-containing films and laminated metal layer-containing films (such as those typically used in mirrors and low E coatings) can generally corrode gradually from the edge to the center of the device, e.g., when exposed to gradients of temperature, humidity, etc., corrosion occurs in the presence or intrusion of ionized water. Edge defects and lack of edge removal during lamination can also trigger corrosion. While edge sealants may be used to reduce the likelihood of corrosion front advancement, such techniques may not be practical because these sealants may also crack over time.

Edge removal typically involves removing a portion of the coating around the peripheral edge of the underlying substrate, and edge removal tables are known. See, for example, U.S. patent 4,716,686; 5,713,986, respectively; 5,934,982, respectively; 6,971,948, respectively; 6,988,938, respectively; 7,125,462, respectively; 7,140,953, respectively; and 8,449,348, each of which is hereby incorporated by reference in its entirety. Generally, in such tables, a series of casters are provided to the table to allow the glass to move smoothly across the surface of the table. Grinding wheels of various widths may be used in conjunction with the shroud to help reduce the splattering of debris and for safety purposes. Passing the glass substantially uniformly under the removal head can effectively "remove" the coating from the glass so that it can be used, for example, in conjunction with the above and/or other articles. Wider or narrower grinding wheels may be used to remove more or less coating from the glass surface.

Although edge removal tables can be used in a variety of applications, they unfortunately have their limitations, particularly when they are subject to corrosion prevention. For example, edge removal tables are typically large and require additional machinery in the converting line. Adding process steps can increase processing time and cost. Edge removal tables, by their nature, can also form debris that requires disposal. Thus, although edge removal can sometimes remove edge defects, it can also cause them due to the generation of additional debris.

Furthermore, while edge removal tables are generally suitable for edge removal, as the name suggests, they are generally limited in their ability to remove coatings from interior areas. This may become increasingly problematic as the area to be removed becomes smaller, as there are practical limitations to the size reduction possible with grinding wheels and the like. And because the edge removal tables function on exposed surfaces, they cannot do anything to "repair" an already assembled product and must be used in the converting line at an early and potentially adverse time.

Certain example embodiments address these and/or other issues. For example, certain exemplary embodiments relate to techniques for stopping or at least slowing the progression of a corrosion or delamination edge front relative to a coating in a laminated product.

Certain exemplary embodiments are based on the recognition from research on soft low-E coatings that electrochemical corrosion driven by stress and ionized moisture intrusion is the primary thermodynamic force behind this phenomenon. Based on this recognition, certain exemplary embodiments attempt to electrically isolate the coating from the edge while shunting the layers and de-stressing the stack. In this regard, certain exemplary embodiments include laser scribing the edges of the metal-containing layer coating or the metal-containing layer coating on the overlaminate. As one example, the coating may be laser scribed through the laminate using a diode fiber laser operating at 1064 nm. By optimizing or at least adjusting the width and position of the score line relative to the glass edge, film corrosion can be stopped or delayed. The feasibility of laser scribing techniques is related to the fact that: glass substrates and many laminates (including very commonly used PVB) are transparent to 1064nm laser radiation and therefore cannot be directly etched (or at least cannot be readily directly etched by certain lasers, including, for example, 1064nm lasers).

In certain exemplary embodiments, a method of making a laminated product is provided. An intermediate product includes first and second substantially parallel glass substrates laminated together with a laminate, wherein the first glass substrate has a multi-layer thin film coating formed thereon, and wherein the coating includes at least one metal-containing layer and is susceptible to corrosion. In the preparation of the laminated product, lines are laser scribed in the coating by exposing the intermediate product to a laser source, wherein the lines form barriers to electron transport between opposite sides thereof.

In certain exemplary embodiments, a method of making a laminated product is provided. A multi-layer thin film coating is formed on the first glass substrate, wherein the coating includes at least one metal-containing layer and is susceptible to corrosion. Laminating a first glass substrate to a second glass substrate using a laminating material such that the coating is oriented between the first substrate and the second substrate and such that the first substrate and the second substrate are substantially parallel to each other. After lamination, and while preparing the laminated product, a boundary line is laser scribed around the periphery of the coating. Laser scribing at least partially dissolves the coating adjacent the boundary line and increases the resistance of the coating inside the boundary line to electrochemical corrosion by electrically isolating the coating inside the boundary line. By means of the laser scribing, dissolved material from the coating is (a) incorporated into the first substrate, laminate and/or cushion layer of the coating, and/or (b) ablated and/or vaporized so as to reform in a non-conductive manner.

In certain exemplary embodiments, a laminated product is provided. The first glass substrate supports the multilayer thin film coating. The coating includes at least one metal-containing layer and is susceptible to corrosion. Laminating a second glass substrate to the first glass substrate using a laminating material such that the coating is oriented between the first substrate and the second substrate and such that the first substrate and the second substrate are substantially parallel to each other. Forming a laser scribed boundary around a perimeter of the coating after the first and second substrates have been laminated together. At least the at least one metal-containing layer of the coating adjacent to the boundary is dissolved by means of the laser scribing. By means of the laser scribing, dissolved material from the coating is (a) incorporated into the first substrate, laminate and/or cushion layer of the coating, and/or (b) ablated and/or vaporized so as to reform in a non-conductive manner. The boundary has a width and a depth sufficient to electrically isolate a region inside the boundary from a region outside the boundary to a degree sufficient to at least delay electrochemical corrosion in the region inside the boundary.

In certain exemplary embodiments, a kit for making a laminated product is provided. The kit includes a laser source and an intermediate product comprising first and second substantially parallel glass substrates laminated together with a laminate, wherein the first glass substrate has a multi-layer thin film coating formed thereon, and wherein the coating includes at least one metal-containing layer and is susceptible to corrosion. The laser source is controllable to laser scribe lines in the coating by exposing the intermediate product to the laser source when preparing the laminated product, wherein the lines form barriers to electron transport between opposite sides thereof.

In certain exemplary embodiments, a method of making a laminated product comprises: obtaining an intermediate product comprising first and second substantially parallel glass substrates laminated together with a laminating material, the first glass substrate having formed thereon a multi-layer thin film coating comprising at least one metal-containing layer; and coupling energy into the coating by exposing the intermediate product to laser light from a laser source when preparing the laminated product, the laser source operates at a wavelength at which the second glass substrate and the laminate are substantially transmissive, the energy is coupled into the coating and the laser source is controlled so as to selectively cause at least a portion of the coating to dissolve in the first substrate, the laminate and/or a cushion layer of the coating in a desired pattern (a), and/or (b) vaporize and reform in a non-conductive manner, the desired pattern defining at least a first region and a second region, and is shaped to a width and depth sufficient to electrically isolate the first and second regions from each other, the electrical isolation is at a level sufficient to at least substantially delay galvanic corrosion in the first substrate.

In a similar respect, certain exemplary embodiments relate to IG units made in the same or similar manner. For example, in certain exemplary embodiments, a method of making an IG unit is provided. The intermediate product includes first and second substantially parallel spaced apart glass substrates joined together with a peripheral edge pad. A gap is defined between the first substrate and the second substrate. The first glass substrate has a multilayer thin film coating formed thereon. The coating includes at least one metal-containing layer and is susceptible to corrosion. Laser scribing lines in the coating by exposing the intermediate product to a laser source while preparing the IG unit, wherein the lines form a barrier to electron transport between opposite sides thereof.

In certain exemplary embodiments, a method of making an IG unit is provided. On a first glass substrate, a multilayer thin film coating is formed, wherein the coating comprises at least one metal-containing layer and is susceptible to corrosion. Joining a first glass substrate to a second glass substrate, the second glass substrate joined with a peripheral edge gasket such that the coating is oriented between the first substrate and the second substrate and such that the first substrate and the second substrate are substantially parallel and spaced apart from each other. After joining, a boundary line is laser scribed around the perimeter of the coating when making the IG unit. Laser scribing at least partially dissolves the coating adjacent the boundary line and increases the resistance of the coating inside the boundary line to electrochemical corrosion by electrically isolating the coating inside the boundary line. Dissolving at least the at least one metal-containing layer by means of the laser scribing such that the associated ablated material (a) reforms in a non-conductive manner, and/or (b) dissolves and/or diffuses into the first substrate and/or at least one other layer of the multilayer thin film coating.

In certain exemplary embodiments, an IG unit is provided. The first glass substrate supports a multilayer thin film coating, wherein the coating comprises at least one metal-containing layer and is susceptible to corrosion. A second glass substrate is substantially parallel to and spaced apart from the first glass substrate, wherein the coating is oriented between the first substrate and the second substrate. Including edge seals. Forming a laser-scribed boundary around a perimeter of the coating after the first and second substrates have been joined together. At least the at least one metal-containing layer of the coating adjacent to the boundary is dissolved by means of the laser scribing. By means of laser scribing, dissolved material from the coating is (a) incorporated into the first substrate and/or into the cushion layer of the coating, and/or (b) ablated and/or vaporized to reform in a non-conductive manner. The boundary has a width and a depth sufficient to electrically isolate a region inside the boundary from a region outside the boundary to a degree sufficient to at least delay electrochemical corrosion in the region inside the boundary.

In certain exemplary embodiments, a kit for preparing an IG unit is provided. The kit includes a laser source and an intermediate product. The intermediate product includes substantially parallel spaced apart first and second glass substrates joined together with a peripheral edge gasket, a gap defined between the first and second substrates, the first glass substrate having a multi-layer thin film coating formed thereon, the coating including at least one metal-containing layer and being susceptible to corrosion. The laser source is controllable to laser scribe lines in the coating by exposing the intermediate product to the laser source when preparing the IG unit, wherein the lines form a barrier to electron transport between opposite sides thereof.

In certain exemplary embodiments, a method of making an IG unit is provided, wherein the method comprises: obtaining an intermediate product comprising first and second substantially parallel spaced apart glass substrates connected together with a peripheral edge pad, a gap being defined between the first and second substrates, the first glass substrate having a multilayer thin film coating formed thereon, the coating comprising at least one metal-containing layer; and coupling energy into the coating by exposing the intermediate product to laser light from a laser source operating at a wavelength at which the second glass substrate is substantially transmissive when the IG unit is manufactured, the energy being coupled into the coating and the laser source being controlled so as to selectively cause at least a portion of the coating to (a) dissolve in the first substrate and/or a cushion layer of the coating, and/or (b) vaporize and reform in a non-conductive manner, in a desired pattern that defines at least first and second regions and is shaped to a width and depth sufficient to electrically isolate the first and second regions from each other, the electrical isolation being at a degree sufficient to at least substantially delay electrochemical corrosion in the first region.

In a similar regard, certain exemplary embodiments relate to coated articles comprising a substrate supporting a multilayer thin film coating and/or methods of making the same. Laser scribing a thin film coating to form at least a first region and a second region, the first region and the second region being electrically isolated from each other by means of the laser scribing. Laser scribing can be performed while the coating of the coated article is in a closed or open geometry relative to the coated article and/or any object in which it may be built.

Features, aspects, advantages, and example embodiments described herein may be combined to realize another embodiment.

Drawings

These and other features and advantages may be better and more completely understood by reference to the following detailed description of exemplary illustrative embodiments in conjunction with the accompanying drawings, of which:

FIG. 1 is a cross-sectional view of an exemplary laminate product;

FIG. 2 schematically illustrates an exemplary corrosion mechanism;

FIG. 3 is a schematic cross-sectional view of an exemplary low-emissivity coating that sometimes suffers from corrosion problems;

FIG. 4 is a schematic view of a laser scoring apparatus that may be used in connection with certain exemplary embodiments;

FIG. 5 illustrates scribe lines obtained with a 1064nm nanosecond pulsed laser, which may be used in connection with certain exemplary embodiments;

fig. 6 is a first exemplary apparatus illustrating how a laminate may be laser scribed according to certain exemplary embodiments;

fig. 7 is a second exemplary apparatus illustrating how a laminate may be laser scribed according to certain exemplary embodiments;

fig. 8 is a flow diagram illustrating an exemplary method for laser scribing a laminate in accordance with certain exemplary embodiments;

FIG. 9 is a cross-sectional view of an exemplary insulated glass unit (IG unit or IGU) that may have a coating laser ablated in accordance with certain exemplary embodiments; and

fig. 10 is a flowchart illustrating an exemplary method for laser scribing an IG unit according to certain exemplary embodiments.

Detailed Description

Certain exemplary embodiments relate to techniques for laser ablating/scribing the peripheral edge of a metal-containing or metal-like layer-containing coating (e.g., low-e, mirror, or other coating) on glass or other substrates in pre-laminated or post-laminated assemblies, insulated glass units (IG units or IGUs), or other products, in order to slow or prevent corrosion of the coating and/or related products. Certain exemplary embodiments may be used in conjunction with products having coatings that have started to erode, for example, even after such products have been installed (e.g., in buildings, vehicles, etc.).

Corrosion can be considered as degradation of the material by chemical processes. One subset is electrochemical corrosion of metals, where the oxidation process M → M⁺+e^-Facilitated by the presence of a suitable electron acceptor. At the electron acceptor site, a series resistance called a polarization resistance is formed. The magnitude of this resistance affects the corrosion rate. One feature of most corrosion processes is that the oxidation and reduction steps occur at separate locations on the metal. This is possible because the metal is conductive and therefore electrons can flow through the metal from the anode to the cathode region. The presence of water helps transport ions to and from the metal, but a thin film that adsorbs moisture may be sufficient to effect corrosion.

Thus, it should be understood that the corrosion system can be considered as a short circuit electrochemical cell, which includes anode and cathode steps that follow a general pattern. For example, the anodic process may be similar to the following:

M(s)→M^x+(aq)+xe^-

the cathodic process may be any of the following:

O₂+2H₂O+4e^-→4OH^-

H⁺+e^-→¹/₂H₂(g)

M1^x++xe^-→M1(s)

where M1 is another metal.

Many currently available low E coatings include a layer comprising Ag directly above and contacting a layer comprising ZnO, and directly below or contacting a layer comprising Ni (e.g., a layer comprising NiCr, NiTi, or an oxide thereof). In such systems, layers with electrochemical potentials lower than that of Ag will "preferentially" corrode from a simple thermodynamic modeling perspective. For example, a layer comprising Ni will start to corrode very quickly relative to a layer comprising Ag, and in such a system the entire interface between the two may be compromised. On the other hand, when considering a layer containing ZnO and a layer containing Ag, the situation is reversed, since the layer containing Ag will corrode faster (with and without light). A layer containing NiO would also be "superior" to a layer containing Ag. Of course, the model assumes the integrity of the circuit and H₂The role of O is to provide H in the presence of an electrolyte (e.g. a salt)⁺Ions.

The following table gives several standard electrode potentials in volts relative to a standard hydrogen electrode:

other commonly used low-E coatings involve a layer comprising Ag sandwiched between and in direct contact with a layer comprising NiCr. (specific exemplary coatings of this type will be discussed in more detail below). Based on the electrochemical potential, in such coatings, corrosion of metallic Ni present in the NiCr-containing barrier layer surrounding the Ag will lead to "binder release" and subsequent agglomeration of the silver, which is one of the characteristics of electrochemical corrosion. An electrolyte containing water in electrical contact with both metals will exacerbate the "preferential" corrosion of Ni and ultimately lead to corrosion of Ag.

Fig. 2 schematically illustrates this corrosion mechanism. As shown in fig. 2, the layer comprising Ag 202 is sandwiched between first and second layers comprising NiCr204a and 204 b. The electrolyte 206 (in water) is in contact with these layers. The electrons will migrate into the layer comprising Ag 202 while preferentially leaching Ni2+ from one or both layers comprising NiCr204 a/204b into the electrolyte 206. The overall mechanism results in "preferential" dissolution and redeposition of (corroded) Ni, along with agglomeration or "coagulation" of Ag.

Other commonly used low E coatings relate to a layer comprising zinc oxide (e.g., a layer comprising zinc oxide, which may include aluminum, tin, etc.), a layer comprising Ag formed over (optionally directly over or in direct physical contact with) the layer comprising zinc oxide, and a layer comprising Ni, Cr, and/or Ti, or oxides thereof (e.g., NiCr, NiCrOx, NiTi, NiTiOx, etc.) formed over (optionally directly over or in direct physical contact with) the layer comprising Ag. In a ZnOx/Ag/NiCrOx containing stack, the presence of relatively small and oxidized Ni indicates a different mechanism of Ag corrosion, which nominally has no interfacial release, which is visually significantly less undesirable as demonstrated by testing and analysis.

When placed in an electrolyte (e.g., salt plus H)₂O), a separate Ag layer stack (e.g., when using the same metallic structural material but spatially separated from the electroactive dielectric) may develop a potential difference as a result of biaxial stress becoming interfacial stress; a metal particle composition; defects, scratches, threads, etc.; electrolyte gradients in dielectrics, laminated PVB or other materials, and the like; and so on.

In so-called double silver low E products, one of the two silver layers may start to corrode preferentially over the other, which is mediated by the electrolyte gradient in the electroactive dielectric acting as a polarizing layer. This is similar to the battery establishing a voltage difference due to chemical potential imbalance. One of the Ag layers becomes anodic with respect to the rest of the stack and the other Ag layer will corrode preferentially. Here, however, this behavior occurs in the event that the dielectric integrity is compromised and water vapor can enter the layer. Therefore, the Water Vapor Transmission Rate (WVTR) can become an important parameter. The electrochemical model predicts that the corrosion front should not move if there is no intrusion of ionized moisture.

In a related aspect, the electrochemical model of corrosion makes some other predictions that may be used in future designs, i.e., the thickness ratio of Ag to NiCr also affects the corrosion propensity. Surprisingly, the modeling also predicts that the ionic conductivity/polarization of the glass can help reduce corrosion. Therefore, thinner cushions or ionic cushions should help reduce corrosion.

To aid in evaluating the model, consider fig. 3, which is a cross-sectional view of an exemplary low E layer stack arrangement. As shown in fig. 3, the substrate 300 supports a first silicon-containing layer 302a (e.g., a layer comprising silicon and oxides and/or nitrides thereof); a first layer 304a comprising Ni, Cr, and/or Ti (which may or may not be oxidized); a layer 306 comprising silver; a second layer 304b (which may or may not be oxidized) comprising Ni, Cr, and/or Ti; and a second silicon-containing layer 302b (e.g., a layer comprising silicon and oxides and/or nitrides thereof). The following three exemplary layer thicknesses correspond to layers having different visual appearances and/or low-E, among other properties: