Patent Application
20130170059
Certain example embodiments of this invention relate to second surface mirrors, and/or methods of making the same. More particularly, certain example embodiments relate to sputtered aluminum second surface mirrors with permanent protective coatings optionally provided thereto, and/or methods of making the same. In certain example instances, such mirrors may be used in interior residential, commercial, appliance, and/or other applications, e.g., with very high visible glass side reflectance and very low production-related costs.
Mirrors have been in existence for years and have been used in interior building applications such as, for example, in bathrooms, as decorations, etc.; for exterior applications such as, for example, in concentrating solar power (CSP) and concentrating photovoltaic (CPV) applications, as well as in secondary reflector panels (SRPs); as well as handheld vanity and a host of other products. Mirrors generally are either (a) first surface mirrors, where the mirror coating is provided between the viewer and the supporting glass substrate, or (b) second surface mirrors, where the supporting glass substrate is interposed between the viewer and the mirror coating. See, for example, U.S. Pat. Nos. 7,276,289 and 7,678,459; U.S. Publication Nos. 2006/0077580; 2007/0178316; 2008/0073203; 2008/0164173; 2010/0229853; 2011/0176212; and 2011/0176236; as well as U.S. application Ser. No. 12/923,836, filed on Oct. 8, 2010. The entire contents of each of these patent documents is hereby incorporated herein by reference.
Many second surface mirrors include silver-based reflecting layers. Silver is highly reflective in the visible and infrared ranges, therefore making it a good choice from a total reflectance perspective.
Unfortunately, however, silver is quite expensive. It also is not particularly durable and, for example, is subject to corrosion when exposed to even building interior environments. Durability problems can be overcome with silver-inclusive mirrors, however, by applying one or more layers of protective paint. Yet these paints are sometimes expensive and, at a minimum, inject time delays in the process because they need to be coated and dried and sometimes re-coated and re-dried. Wet coating techniques also are “messy” and potentially hazardous to humans.
Thus, it will be appreciated that there is a need in the art for improved mirrors and/or methods of making the same.
In certain example embodiments of this invention, a mirror is provided. A multilayer thin film coating is supported by a substrate. The multilayer thin film coating comprises, in order moving away from the substrate: a first silicon-inclusive layer, a metallic or substantially metallic layer comprising aluminum, a 5-150 angstrom thick layer comprising Ni and/or Cr in direct contact with the metallic or substantially metallic layer comprising aluminum, and a second silicon-inclusive layer in direct contact with the layer comprising Ni and/or Cr. A protective film is disposed directly over and contacting an outermost layer of the multilayer thin film coating, with the protective film having a peel strength of 200-500 cN/20 mm wide strip. The protective film is adapted to survive seven day exposure to an 85 degree C. temperature at 85% relative humidity, as well as seven day exposure to a 49 degree C. temperature at 100% relative humidity.
In certain example embodiments of this invention, there is provided a coated article comprising a substrate and a multilayer thin film coating supported by the substrate. The multilayer thin film coating comprises a metallic or substantially metallic layer comprising aluminum sandwiched between inner and outer silicon-inclusive layers. A protective film is disposed directly over and contacting an outermost layer of the multilayer thin film coating.
In certain example embodiments of this invention, a method of making a coated article is provided. A coating comprising at least the following layers are sputter-deposited on a glass substrate in the following order: a first silicon-inclusive layer, a metallic or substantially metallic layer comprising aluminum, and a second silicon-inclusive layer. A protective film is applied directly over and contacting an outermost layer of the coating, with the protective film having a peel strength of 200-500 cN/20 mm wide strip.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.
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 drawings, of which:
a and 1b show schematic cross-sectional views of second surface mirror coatings in accordance with certain example embodiments of this invention;
Certain example embodiments of this invention relate to high performance sputtered aluminum second surface mirrors with permanent protective adhesive films optionally provided thereto, and/or methods of making the same. In certain example instances, such mirrors may be used in interior residential, commercial, appliance, and/or other applications, e.g., where it is desirable to provide very high visible glass side reflectance while keeping associated production costs low.
In certain example embodiments, a coated article is provided. The coated article may comprise a substrate supporting a multi-layer, thin film coating including at least the following layers, in order, moving away from a second surface of the substrate: a first silicon-based layer (e.g., an oxide and/or nitride of silicon), a metallic or substantially metallic reflective layer comprising aluminum, optionally in direct contact with the first silicon-based layer; and a second silicon-based layer (e.g., an oxide and/or nitride of silicon) that serves as a protective layer. The first and second silicon-based layers may consist essentially of the same composition and/or may have substantially the same stoichiometries in certain example embodiments. Optionally, a protective barrier layer comprising Ni and/or Cr may be interposed between the reflective layer and the second silicon-based layer. A permanent protective film (PPF) may be applied to the film side of this layer stack for added overall durability. The PPF may be applied in solid form in certain example embodiments.
The aluminum-inclusive second surface mirrors of certain example embodiments may be advantageous over conventional silver-based second surface mirrors. For example, the lower material cost for aluminum may result in a reduced cost to coat as compared to a silver-based mirror. Aluminum also is known to have superior chemical, mechanical, and environmental durability as compared to silver. Certain example embodiments also may offer superior adhesion of the reflective metal to a broader range of underlying layers and/or substrates as compared to conventional mirrors. For instance, aluminum adheres well to silicon-based thin film layers, whereas silver growth is known to benefit from the presence of seed layers (e.g., of or including zinc oxide and/or an optionally oxidized Ni and/or Cr inclusive layer) in terms of both adhesion and uniformity. Aluminum also better adheres to bare glass than silver. The reflective optical properties for aluminum are also very similar to silver, even though aluminum is advantageous in the above-described and/or other ways.
Some current second surface mirrors incorporate a protective paint on the film side of the coated article. The protective paint is intended to increase chemical, mechanical, and environmental durability. This protective paint can be particularly important where silver-based sputter deposited second surface mirrors are concerned, as the silver can be damaged very easily, e.g., via scratching or marring, via oxidation through normal environmental exposure or inadvertent chemical attack, etc. By contrast, certain example embodiments replace the typically used protective paint with a permanent protective film. The removal of the paint and replacement with a permanent protective film can actually lower the cost of the final product while also conferring a number of other advantages. For example, costly paint application hardware and drying systems can be replaced with lower-cost roll application of the permanent protective plastic film. This, in turn, may impart a substantial increase in throughput speed as compared to protective paints, e.g., because application may be simplified and drying/curing steps may be removed. There also is an opportunity to substantially reduce environmentally hazardous waste, thereby possibly also reducing clean room, maintenance, and disposal costs. The roll application technique also may reduce labor and utility costs, while also offering savings in safety related fabrication costs. For instance, protective paints oftentimes necessitate risk management procedures associated with, for example, chemical storage, application, training, personal protective equipment (PPE), etc.
The protective film may also help enhance the safety of the final product as compared to existing mirrors with standard protective paints. For instance, plastic protective films tend to better trap and/or contain material that may flake or otherwise come off This also applies to glass shards that may result if the mirror is broken. The paints also may be hazardous when ingested or exposed to the skin, whereas plastic protective films may be harmful only in much larger doses.
a and 1b show schematic cross-sectional views of second surface mirror coatings in accordance with certain example embodiments of this invention. As shown in
The layer stack design shown in
The
In
Although the coatings described above in connection with
For example, where the SunGuard Low-E layer stack has a first silicon nitride inclusive undercoat layer in contact with the glass that has a thickness greater than about 100 angstroms, the aluminum mirror layer stack of certain example embodiments includes a first silicon nitride inclusive undercoat layer in contact with the glass of less than 100, with an example thickness of 40 angstroms. It has been determined that a thickness of 40 angstroms also would be sufficient for certain example embodiments. The use of the silicon nitride inclusive undercoat in SunGuard layer stacks has been shown to improve the chemical, environmental, and mechanical durability of the full stack compared to an otherwise identical layer stack that does not employ such an undercoat layer. The same has been shown in experiments for the aluminum mirror layer stack of certain example embodiments. That is, while aluminum generally adheres poorly to float glass, the addition of a very thin layer including silicon nitride between the aluminum layer and the float glass improves adhesion dramatically. However, maintaining the silicon nitride inclusive undercoat thickness at less than 40 angstrom reduces the loss of visible reflectance of the overall layer stack while also maintaining the improvements in durability mentioned above. Thus, the inventors have determined that a thickness of less than 100 angstroms, and sometimes even less than 40 angstroms, is desirable both for good adhesion and high reflectivity. In certain example embodiments, the first layer including silicon nitride 104 is preferably less than 100 angstroms thick, more preferably less than 75 angstroms thick, and still more preferably less than 50 angstroms thick.
A very thin Ni and/or Cr inclusive layer optionally may be deposited after the Al-inclusive metal layer to further improve overall durability. The thickness of this optional layer, when provided, preferably is between 1-150 angstroms, more preferably 1-50 angstroms, and still more preferably 5-20 angstroms. In general, a thickness of even 5-10 angstroms has been found to increase overall durability. The layer comprising Ni and/or Cr also may help reduce the visible transmission to nearly 0%, possibly also improving visible reflectivity and also helping to adhere the Al-based layer to the protective overcoat layer comprising silicon nitride. The ratio of Ni-to-Cr may be 80/20, or any other suitable ratio. It is noted that a layer comprising NiCr layer may add complexity and expense, and may not always be necessary as the aluminum-based mirror layer stack can in some implementations be adequately protected by a permanent protective plastic film. Thus, certain example embodiments may omit a layer comprising Ni and/or Cr, e.g., when a PPF is provided, although these material are not necessarily mutually exclusive alternatives in all embodiments. It is noted that the layer comprising Ni and/or Cr may serve as an “environmentally protective layer” but also may help increase overall coating thickness in a manner that helps reduce light transmission (e.g., preferably below 3%, more preferably below 2%, and still more preferably below 1-1.5%, and possibly all the way to 0%). This may be advantageous because it may reduce the need to increase the thickness of the layer comprising aluminum and/or to provide an opaque PPF, e.g., in order to accomplish suitable visible light transmission reductions.
The second layer including silicon nitride 106 is preferably 10-1000 angstroms thick, more preferably 50-500 angstroms thick, and still more preferably 70-200 angstroms thick. This layer may help provide mechanical, chemical, and environmental durability. It also may be much thicker than the silicon nitride inclusive undercoat layer, as its thickness will have little to no practical impact on glass side reflectivity. In practice, a thickness of about 80 angstroms has been found to be sufficient to provide adequate overall durability at reasonable cost. It is noted that the thickness may be increased in the absence of PPF or decreased when PPF is present, although this need not always be the case, e.g., where further durability is desirable.
Certain example embodiments may incorporate a permanent protective film (PPF) with very high adhesion levels, very good chemical resistance, and/or excellent environmental durability. The protective film may be resistant to delamination from moisture penetration and/or the use of asphalitic based adhesives applied to the exterior surface of the protective film. Adhesive strengths of the protective films are greater than or equal to 150 cN/20 mm wide strip, more preferably 275 cN/20 mm wide strip, as measured in the tape removal test. For instance, certain example embodiments may have an adhesive strength of 200-500 cN/20 mm wide strip, more preferably 200-300 cN/20 mm wide strip. Certain example embodiments may even have an adhesive peel strength of greater than or equal to about 320-430 cN/20 mm wide strip. The peel strength test used may be the peel strength test defined in EN 1939. Good abrasion resistance also is desirable, e.g., such that the there is no change in visible appearance when viewed from the glass side after the post-PPF coated article is wiped with a rubber material at a force of 250-250 g, back and forth 20 times. In certain example embodiments, the PPF may be thin, e.g., having a thickness of <200 microns, and sometimes about 40-100 microns in thickness. Peel strength may be increased through the incorporation of additional cross-linking polymers in certain example embodiments.
The protective film may also be relatively low in cost. To aid in manufacturing ease of setup, it would be desirable to use a permanent protective film that may be applied using the same equipment that is used to apply standard temporary protective films. Typical protective films from Nitto-Denko include: SPV-9310, SPV-9320, SPV-30800, SPV 5057 A5, and SPV 5057 A7. Other manufacturers of similar preferred protective films include Permacel, Tessa Tapes, B&K Films, and Novacell. These plastic films come in a wide variety of opacities and colors.
The PPFs of certain example embodiments preferably will pass environmental tests including, for example, high temperature-high humidity testing (e.g., at 49 degrees C. with 100% relative humidity), thermal cycling testing, and 85/85 testing (e.g., 85 degrees C. with 85% relative humidity). Standard ASTM tests may be performed to test for compliance, e.g., using 7 days exposure cycles. Salt fog exposure (e.g., to simulate oversees shipment) also may be tested for a 24-hour period. Permanent plastic films that do not blister or lose adhesion to the coated surface are preferred. Resistance to cutting oils and Windex also may be tested by soaking in such materials over 24 hour periods. These tests may be performed after the PPF is applied. PPFs that survive these tests are preferred because of their apparent durability and ability to withstand environmental conditions. In a similar vein, the thin film coating preferably does not delaminate after 3M 610 Scotch tape is applied thereto and removed therefrom.
It has been found that the addition of the permanent plastic protective films significantly enhances the safety of the final product. For example, as alluded to above, when a mirror is broken, pieces and shards of glass sometimes adhere very strongly to the protective film. The few remaining smaller pieces of the broken mirror that do not adhere to the protective film are far less likely to cause injury to anyone in the vicinity of the mirror when the mirror is broken.
Also as alluded to above, one advantage of plastic protective films compared to commercially available protective paints is the speed of application. In many current sputter coating facilities, for example, the typical roll applicator is able to apply the protective films at line speeds of 8.0 m/min. or greater. This is much faster than the typical process speed of 5.5 m/min. used to dry the paint in the painted mirror product. As was also previously mentioned, there is a reduced set of chemical safety issues related to the application of the protective film as compared to chemical paints.
A number of layer stacks in addition or as alternatives to the examples shown in
Example 1: glass/Si3N4 (40 angstroms)/Al (400 angstroms)/NiCr (50 angstroms)/Si3N4 (80 angstroms). RgY (C/2): 82.32%.
Example 2: glass/Si3N4 (40 angstroms)/Al (400 angstroms)/Cr (50 angstroms)/Si3N4 (80 angstroms). RgY (C/2): 81.83%. It will be appreciated that the presence of Ni together with Cr in the layer “behind” the Al improves reflectivity.
Example 3: glass/Si3N4 (40 angstroms)/NiCr (5 angstroms)/Al (400 angstroms)/NiCr (50 angstroms)/Si3N4 (80 angstroms). RgY (C/2): 78.87%. While the presence of a layer comprising Ni and/or Cr interposed between the Al and the glass substrate may help with adhesion, it nonetheless may reduce reflectance, possibly because of increased absorption on the part of the front layer comprising Ni and/or Cr.
Example 4: glass/Si3N4 (40 angstroms)/NiCr (5 angstroms)/Al (400 angstroms)/Cr (50 angstroms)/Si3N4 (80 angstroms). RgY (C/2): 78.83%.
Example 5: glass/Si3N4 (40 angstroms)/Al (400 angstroms)/NiCr (50 angstroms)/Si3N4 (80 angstroms)/PPF (Nitto-Denko SPV-9310). RgY (C/2): 82.32%.
Example 6: glass/Si3N4 (40 angstroms)/Al (400 angstroms)/Cr (50 angstroms)/Si3N4 (80 angstroms)/PPF (Nitto-Denko SPV-9310). RgY (C/2): 81.83%.
Example 7: glass/Si3N4 (40 angstroms)/NiCr (5 angstroms)/Al (400 angstroms)/NiCr (50 angstroms)/Si3N4 (80 angstroms)/PPF (Nitto-Denko SPV-9310). RgY (C/2): 78.87%.
Example 8: glass/Si3N4 (40 angstroms) NiCr (5 angstroms)/Al (400 angstroms)/Cr (50 angstroms)/Si3N4 (80 angstroms)/PPF (Nitto-Denko SPV-9310). RgY (C/2): 78.83%.
Example 9: glass/Al (450 angstroms)/Si3N4 (80 angstroms). RgY (C/2): 84.06%. Although reflectivity was very high, adherence to the substrate is potentially compromised because the Al is in direct contact with the glass. Sodium migration from the underlying substrate may also negatively impact the quality of the Al over time.
Example 10: glass/Si3N4 (40 angstroms)/Al (450 angstroms)/Si3N4 (80 angstroms). RgY (C/2): 82.03%.
Example 11: glass/Si3N4 (40 angstroms)/Al (450 angstroms)/NiCr (5-10 angstroms)/Si3N4 (80 angstroms). RgY (C/2): 82.04%.
Example 12: glass/Al (450 angstroms)/Si3N4 (80 angstroms)/PPF (Nitto-Denko SPV-9310). RgY (C/2): 84.06%.
Example 13: glass/Si3N4 (40 angstroms)/Al (450 angstroms)/Si3N4 (80 angstroms)/PPF (Nitto-Denko SPV-9310). RgY (C/2): 82.03%.
Example 14: glass/Si3N4 (40 angstroms)/Al (450 angstroms)/NiCr (5-10 angstroms)/Si3N4 (80 angstroms)/PPF (Nitto-Denko SPV-9310). RgY (C/2): 82.04%.
It is noted that aluminum may be added to the silicon inclusive layers and/or the layers comprising Ni and/or Cr to help improve sputtering performance. Also, although certain example embodiments have been described as including sputter-deposited layers, it will be appreciated that some or all layers may be deposited by an alternate thin film deposition technique in different embodiments of this invention.
It will be appreciated that the steps need not be performed in the order shown in
In some cases, a flat surface product may be sold. In other cases, the substrate may be bent (e.g., hot or cold bent) before or after the mirror coating and/or PPF is applied thereto.
In certain example embodiments, a mirror is provided. A multilayer thin film coating is supported by a substrate. The multilayer thin film coating comprises, in order moving away from the substrate: a first silicon-inclusive layer, a metallic or substantially metallic layer comprising aluminum, a 5-150 angstrom thick layer comprising Ni and/or Cr in direct contact with the metallic or substantially metallic layer comprising aluminum, and a second silicon-inclusive layer in direct contact with the layer comprising Ni and/or Cr. A protective film is disposed directly over and contacting an outermost layer of the multilayer thin film coating, with the protective film having a peel strength of 200-500 (e.g., 200-300 or 320-430) cN/20 mm wide strip. The protective film is adapted to survive seven day exposure to an 85 degree C. temperature at 85% relative humidity, as well as seven day exposure to a 49 degree C. temperature at 100% relative humidity.
In certain example embodiments, there is provided a coated article comprising a substrate and a multilayer thin film coating supported by the substrate. The multilayer thin film coating comprises a metallic or substantially metallic layer comprising aluminum sandwiched between inner and outer silicon-inclusive layers. A protective film is disposed directly over and contacting an outermost layer of the multilayer thin film coating.
In certain example embodiments, a method of making a coated article is provided. A coating comprising at least the following layers are sputter-deposited on a glass substrate in the following order: a first silicon-inclusive layer, a metallic or substantially metallic layer comprising aluminum, and a second silicon-inclusive layer. A protective film is applied directly over and contacting an outermost layer of the coating, with the protective film having a peel strength of 200-500 cN/20 mm wide strip.
Certain example embodiments relate to a method of making mirrors. The method may comprise, for example, receiving, at a fabricator location, a coated article made in accordance with any of the methods described herein; and cutting the coated article into pieces of one or more respective desired sizes in making the mirrors, with the pieces optionally having finished edges and/or the like.
In addition to the features of any of the previous four paragraphs, in certain example embodiments, as alluded to above, the protective film may have a peel strength of 200-500 cN/20 mm wide strip.
In addition to the features of any of the previous five paragraphs, in certain example embodiments, as alluded to above, the protective film is capable of surviving seven day exposure to an 85 degree C. temperature at 85% relative humidity, as well as seven day exposure to a 49 degree C. temperature at 100% relative humidity, e.g., with no evidence of delamination of the protective film and no evidence of deterioration of the coating.
In addition to the features of any of the previous six paragraphs, in certain example embodiments, as alluded to above, a layer comprising Ni and/or Cr may be interposed between the metallic or substantially metallic layer comprising aluminum and the outer silicon-inclusive layer. The layer optionally may be NiCr, and/or optionally may be 5-150 angstroms thick, e.g., as alluded to above. In some example cases, when the layer comprising NiCr is 5-20 angstroms thick, the protective film may be opaque. In other example cases, when the layer comprising NiCr is 50-150 angstroms thick, the protective film may be transparent (e.g., so as to lower tranmission through the substrate to less than 1-1.5%.
In addition to the features of any of the previous seven paragraphs, in certain example embodiments, the inner and outer silicon-inclusive layers may each comprise silicon nitride.
In addition to the features of any of the previous eight paragraphs, in certain example embodiments, the inner and outer silicon-inclusive layers may be less than 100 angstroms thick and 70-200 angstroms thick, respectively, and/or the metallic or substantially metallic layer comprising aluminum may be 250-650 (e.g., 400-600) angstroms thick.
In addition to the features of any of the previous nine paragraphs, in certain example embodiments, the coated article may have a glass side reflectance of at least 76%.
In addition to the features of any of the previous ten paragraphs, in certain example embodiments, the coated article may have a glass side reflectance of at least 82%.
Although certain example embodiments have been referred to as including “permanent protective films,” it will be appreciated that the word “permanent” should not be read in a strictest or literal sense. Rather, any film that is capable of surviving the above-described and/or other equivalent tests may be considered a “permanent” protective film. Similarly, any film that can survive the expected lifetime of the overall product may be considered sufficiently “permanent” to comply with the way that that word is used herein.
While a layer, layer system, coating, or the like, may be said to be “on” or “supported by” a substrate, layer, layer system, coating, or the like, other layer(s) may be provided therebetween. Thus, for example, the coatings or layers described above may be considered “on” and “supported by” the substrate and/or other coatings or layers even if other layer(s) are provided therebetween.
While the invention has been described in connection with what is presently considered to he the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
