Abstract:
A solar control coating is applied to a first glass pane interior surface and a low-E coating is applied to a second glass pane exterior surface. A safety film is applied over the coating on the interior surface of the first glass pane. The second glass pane has a low-E coating facing the interior of a room. A safety film is applied to the reverse side of the glass. The two glass panes are separated by a spacer and structural silicone is backfilled from each outboard end of the spacer to the coated inside surfaces of the first and second glass panes to form a two-glass pane composite.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to making insulated glass units used in residential, architectural and vehicle applications. More specifically, it refers to the manufacture of insulated glass (IG) units having coatings applied exhibiting solar control, low-E, and impact resistant properties. 
     2. Description of the Prior Art 
     Insulated glass windows or door units have been known for many years to reduce the heat transfer between the interior house and the environment. To further improve the insulating properties, the art taught making solar control coated and low-emissivity (low-E) coated glass or film. 
     Solar control is a term describing the property of regulating the amount of solar heat energy, which is allowed to pass through a glass article into an enclosed space such as a building or an automobile interior. Low emissivity is a term describing the property of an article&#39;s surface wherein the absorption and emission of mid-range infrared radiation is suppressed, making the surface a mid-range infrared reflector and thereby reducing heat flux through the article by attenuating the radiant component of heat transfer to and from the low emissivity surface. By suppressing solar heat gain, building and automobile interiors are kept cooler, allowing a reduction in air conditioning requirements and costs. Efficient low emissivity coatings improve comfort during both summer and winter by increasing the thermal insulating performance of a window. 
     Two typical coating methods to make solar control and low-E coatings are “in-line” and “off-line” coatings. The in-line method uses a chemical deposition method involving doping with different chemicals to make an infrared absorbing layer and low-E layer as described in U.S. Pat. Nos. 5,750,265, 5,897,957, and 6,218,018. The off-line method uses sputtering deposition to make both coatings. 
     Impact resistant glass is described in detail in the Florida Building Code. Basically, it specifies a testing protocol for a window glass to withstand up to nine pounds of force from a 2×4 board shot at the glass up to 50 feet/second. Withstanding both shots with one in the center and one in the corner without penetration, is considered as a pass. 
     U.S. Pat. Nos. 4,799,745 and 5,071,206 describe a multi-layered sputtering polyethyleneterephthalate (PET) window film construction, which gives both solar control and low-E properties. The coating-contains silver metal layers and indium-tin oxide layers in an alternate construction. The film has a high visible light transmission, above 70%, and a low visible light reflection, about 8%. The total solar heat rejection is about 56%. The color of the coating is light green. It has a very good solar control and low-E performances. However, corrosion is a major concern. To make an IG unit, it needs edge deletion and filling with inert gas in the IG unit to prevent the coating from corroding. The multi-layered coating has to be exposed within the IG unit to achieve both low-E and solar control functions. As a result, the manufacturing process becomes expensive. 
     U.S. Pat. Nos. 5,332,888 and 6,558,800 disclose a multi-layered sputtering window glass construction (off-line method), which also achieves both solar control and low-E properties. The former patent contains a silver metal layer sandwiched by zinc oxide layers and the latter contains a silver metal layer sandwiched by nickel chrome and silica nitrite layers. Similar to sputtered PET film, they also face corrosion, chemical resistant and scratch resistant concerns. 
     U.S. Pat. No. 6,546,692 assigned to Film Technologies International, Inc. discloses a method of laminating a safety film on the inside surfaces in an IG unit to build an impact resistant window. The safety feature is very important for window glass to withstand hurricane, earthquake, and terrorism. However, the low-E property would be destroyed or significantly weakened once a safety film is laminated over the low-E coating surface. 
     Besides solar control, low-E, and impact resistance, other desirable properties include an economic process, durability, maintenance, light transmission, visibility, color, clarity and reflection. These are important features during a window manufacturing process. 
     To meet the Government (Department of Energy) Energy Star Qualification Criteria for Windows, Doors and Skylights and Florida Building Code for impact resistant windows, a new window/door design is required for the window/door industry. 
     SUMMARY OF THE INVENTION 
     The present invention meets the Department of Energy criteria for windows, and has the important manufacturing features. First and second window panes are spaced apart by a spacer contacting an inside surface of each window pane. An inside surface of a first window pane is coated with a solar control and low-E coating, over which a safety film is laminated. An inside surface of a second window pane is laminated with a safety film. An outside surface of the second window pane is coated with a low-E coating (or both solar and low-E coating). This surface faces an interior of a room. It is preferred that this low-E coating be coated by the chemical vapor deposition method. Structural silicone is backfilled from each outboard end of the spacer to the coated inside surface of the first and second window pane to form a two window composite for use in window frames or door frames. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
         FIG. 1  is a side elevational view of an insulated glass window of this invention mounted in a window frame. 
         FIG. 2  is a transmission spectrum of a glass pane on which is applied a solar control layer and a low-E layer on one surface. 
         FIG. 3  is a transmission spectrum of a glass pane on which is applied an alternate antimony based solar control and low-E coating. 
         FIG. 4  is a transmission spectrum of a glass pane on which is applied a low-E coating. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Throughout the following detailed description the same reference numbers refer to the same elements in all figures. 
     To meet solar control criteria, it would be ideal to coat a solar reflective coating on the exterior surface of a window pane. However, because of environmental aging, chemical reaction, corrosion or scratching caused by cleaning the window, the coating cannot be placed on the exterior surface. 
     Referring to  FIG. 1 , a solar control coating  12  is coated on the inside surface  2  of the first glass pane  14 . The coating can be made either by sputtering deposition or chemical deposition method. A sputtered coating, as used in  FIG. 2 , has silver or other IR reflective metal layers sandwiched by metal oxide layers. This coating reflects more infrared rays than it absorbs. The metal composite provides the window glass with high visible light transmission and low visible light reflection as well as low-E properties. As a result, it is an ideal heat mirror product. The chemical vapor deposition coating has better chemical and scratch resistance than the sputtering coated product. It will absorb solar energy instead of reflect it. As a result, it builds a heat stress over the glass pane and could cause glass breakage. Another disadvantage is that it has a lower visible light transmission than sputtering coated glass to achieve the similar solar performance. The transmission spectra for the preferred solar control coatings are shown in  FIG. 2  and  FIG. 3 . The most preferred solar control coating sold by Pittsburg Plate Glass Co. is shown in  FIG. 2 . A safety film  16  is laminated over the sputtered coating  12  on surface  2  to re-enforce the glass and also protect the metal from corrosion and other chemical reactions during aging. However, once laminated with a safety film, it destroys or significantly reduces the low-E property. 
     A safety film  16  is constructed with three layers of clear PET film laminated to each other with a pressure sensitive adhesive. The safety film has a thickness of 0.004 to 0.025 inches. The preferred thickness is 0.008 to 0.018 inches and most preferred is a film thickness of 0.015 inches. The adhesive is an acrylic based pressure sensitive type. The coat weight of the mounting adhesive, which bonds the safety film to the glass, is between 12-17 lb/ream. The multi-layered construction is better than a single layer PET film because it improves the film&#39;s impact resistance. More layers are better for impact resistance but the multi-layered laminating construction can cause distortion problem. 
     To meet the low-E requirement, a low-E coated glass film  18  has to be used. The function of the low-E coating  18  is to reflect the mid-range infrared rays and reduce the heat flux through the window glass. The coating faces the inside of the room on glass surface  4  as shown in  FIG. 1 . The preferred low-E coating is chemical deposited over the glass. The E value is 0.03-0.25. The preferred E value is 0.08-0.20. The most preferred E value is 0.17 or lower. The visible light transmission (VLT) of the low-E glass is 35-90%. The preferred VLT is 60-85%. The most preferred VLT is 80%. The preferred color is neutral or light green. A safety film  20  is laminated on the interior surface  3  of glass  22  to re-enforce the interior glass. 
     The coated window glass  14  or  22  can be any type, such as annealed, heat strengthened or tempered. 
     EXAMPLE 1  
     The exterior glass pane  14  uses PPG&#39;s SB60 CL-3 sputtered solar control low-E glass. The dimension is 2.5″×5″×⅛″. The glass has a visible light transmission (VLT) of 75.9%. The VLT is measured with a Densitometer made by Gretag Macbeth Company. The emissivity reading (E value) is 0.05. The data is obtained through an Emissometer manufactured by Devices &amp; Service Company. The color is light yellow green with a reading of a*=−2.19, b*=2.04, and L=90.79. Where a* is CIELAB 
     color space coordinate defining the red/green axis; b* is CIELAB color space coordinate defining the yellow/blue axis; and L is CIELAB color space coordinate defining the lightness axis. The color numbers are measured with a Spectrogard made by BYK Gardner Company. The transmission spectrum of the coated glass is measured by Lambda 900 UV/VIS/NIR spectrometer manufactured by Perkin Elmer Company. The spectrum is shown in  FIG. 2 . 
     The interior glass pane  22  uses Pilkington North America, Inc., Energy Advantage Low-E glass. It is coated on surface  4  through a chemical vapor deposition method. The dimension is the same as the exterior glass pane. The glass has a VLT reading of 79%. The emissivity reading is 0.18. The color is light neutral and yellow, a*=−0.91, b*=1.83, and L=92.50. The transmission spectrum of the low-E glass is shown in  FIG. 4 . 
     A 15 mil safety film is constructed with three layers of 5 mil clear PET film laminated to each other with an acrylic pressure sensitive adhesive. The coat weight for the laminating adhesive is 11 lb/ream. A mounting adhesive is used to bond the 15 mil safety film and glass together. The mounting adhesive chooses the same adhesive as the laminating adhesive but has a higher coat weight. It is about 16 lb/ream. A UV absorber is added into the adhesive formulation to eliminate UV spectrum from the sun. 
     An insulating glass unit  10  (IG unit) as shown in  FIG. 1  is constructed in the way described as follows. A safety film  16  is laminated to the solar control coated surface  12  of the exterior glass  14  through a laminator. A clean room environment is required. A second safety film  20  is laminated to the non-coated surface of the interior glass  22 . A spacer  24  is positioned to the four edges of the first glass pane  14  over the safety film  16 . The second glass pane  22  is over lapped to the first pane with safety film  20  facing the safety film  16  on the inside surface of the first glass  14 . The four edges are sealed with an appropriate sealant such as buytal or silicone sealants. The IG unit is filled with argon gas  26  to improve insulation. The final construction as shown in  FIG. 1  is that solar control coating  12  is on the inside surface  2  of the exterior glass  14  and the low-E coating  18  is on the exterior surface  4  of glass  22  facing the inside of a room. The safety films  16  and  20  are on the inside surfaces  2  and  3  respectively, of glass  14  and  22 . The insulating performance data is calculated as follows: 
     Both the exterior solar control glass pane  12  and interior low-E glass pane  22  are laminated with a 15 mil safety film on surfaces  2  and  3  respectively, and tested with a Perkin Elmer&#39;s Lambda 900 uv/vis/nir spectrometer. The emissivity number is measured with a digital voltmeter. The data are input into a Window 5.0 program for analyzing window thermal performance. The software is developed by Lawrence Berkeley National Laboratory. The results are listed in table 1. The U-value is the amount of conductive heat energy transferred through one square foot of a specific glazing system for each 1° F. temperature difference between the indoor and outdoor air. The lower the U-value, the better insulating qualities of the glazing system. Solar Heat Gain Coefficient (SHGC) is measurement of the percentage of solar energy that is either directly transmitted or absorbed and then re-radiated into a building. The lower the coefficient, the better the window is able to reduce solar heat. 
     A scratch resistance test is conducted with Taber 5130 Abraser. The test follows the ASTM D 1003 method. After 100 cycle abrasion, the delta haze for the low-E coating on the Pilkington North America, Inc., Energy Advantage low-E glass is 0.34%. The haze is measured with BYK Gardner&#39;s Haze Gard Plus meter. 
     EXAMPLE 2  
     Exterior glass pane  14  uses Pilkington North America, Inc., Solar E glass. The dimension is 2.5″×5″×⅛″. The glass has a visible light transmission of 60.3%. The emissivity reading is 0.20. The color is blue, a*=−2.18, b*=−2.58, L=82.40. The glass has a transmission spectrum shown in  FIG. 3 . 
     The interior glass  22  uses Pilkington North America, Inc., Energy Advantage Low-E glass. Following the same process as set forth for Example 1, an IG unit is made and tested. The U-value and SHGC reading are listed in table 1. 
     EXAMPLE 3  
     Exterior glass pane  14  uses PPG&#39;s SB60 CL-3 sputtered solar control low-E glass. The interior glass  22  uses Pilkington&#39;s Solar E glass. Following the same process as set forth for Example 1, an IG unit is made and tested. The U-value and SHGC reading are listed in Table 1. 
     A scratch resistance test is conducted in the same manner as described in Example 1. After 100 cycles of abrasion testing, the solar control low-E coating is removed. The glass is clear and has less haze. The delta haze is −0.60%. 
     EXAMPLE 4  
     Both exterior  14  and interior  22  glass panes are clear glass. The dimension is the same as described in Example 1. 
     A 17 mil safety and solar control low-E film is constructed in a way that a 2-mil sputtering coated solar control low-E film is laminated onto the 15 mil safety film with metal surface exposed. The laminating adhesive is the same acrylic pressure sensitive adhesive as previously described. 
     An IG unit is constructed in the same way as described in Example 1. The only difference is that the 17 mil safety and solar control low-E film is laminated on the inside surface of glass  14 , and the 15 mil safety film is laminated on the inside of glass  22 . Both exterior  14  and interior  22  glass panes are clear glass. The U-value and SHGC are described in Table 1. 
     EXAMPLE 5  
     Both exterior  14  and interior  22  glass panes use PPG&#39;s SB60CL-3 solar control low-E glass. An impact resistance IG unit is built the same way as described in Example 1. The only difference is that the interior glass  22  has the sputtering coated solar control and low-E coating. The U-value and SHGC are measured in Table 1. The energy performance is very good but corrosion has been found in the lab sample on a surface. 
     EXAMPLE 6  
     Exterior glass  14  uses PPG&#39;s SB60CL-3 and interior  22  glass uses a clear glass. A safety film is laminated on the inside surfaces of glass  14  and  22 . The U-value and SHGC are measured and listed in Table 1. The data shows that the glass&#39;s E value is significantly weakened. 
     EXAMPLE 7  
     Weathering Test 
     A safety film is laminated over PPG&#39;s SB60CL-3 coating. The glass pane is tested in a QUV chamber for accelerated weathering. The glass side faces the UV lamp. The testing follows ASTM G154 methods. After 5,500 hours of exposure no corrosion or chemical reaction between the adhesive and sputtered metal is found. The glass VLT and E-value has not changed. However, the corrosion was found in the uncovered area of the low-E glass. The mounting adhesive is found slightly yellow after UV exposure. 
     Corrosion Test 
     Both Energy Advantage Low-E and Solar E glass panes are placed in a bucket filled with a little water. The bucket is placed in a 135° F. hot room for 14 days. No corrosion is found. Both the glasses have very good corrosion and chemical resistance. They are made through a chemical vapor deposition process. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 IG unit energy performance data in the center of the glass: 
               
             
          
           
               
                   
                   
                 Total 
                   
                   
               
               
                 No. 
                 IG unit construction 
                 VLT % 
                 U-value 
                 SHGC 
               
               
                   
               
             
          
           
               
                 Government 
                 Energy Star Criteria 
                   
                 ≦0.35 
                 ≦0.40 
               
               
                 requirements 
               
               
                 Example 1 
                 Glass/sb60cl-3/SG15 mil/ 
                 50.1 
                 0.34 
                 0.32 
               
               
                   
                 Ar/SG15 mil/glass/EA-low E 
               
               
                 Example 2 
                 Glass/solar E/SG15 mil/ 
                 41.7 
                 0.34 
                 0.40 
               
               
                   
                 Ar/SG15 mil/glass/EA-low E 
               
               
                 Example 3 
                 Glass/sb60cl-3/SG15 mil/ 
                 37.2 
                 0.35 
                 0.28 
               
               
                   
                 Ar/SG15 mil/glass/solar E 
               
               
                 Example 4 
                 Glass/17 mil solar E/Ar/ 
                 58.9 
                 0.26 
                 0.35 
               
               
                   
                 SG 15 mil/glass 
               
               
                 Example 5 
                 SB60cl-3 glass/SG15 Mil/ 
                 56.5 
                 0.31 
                 0.30 
               
               
                   
                 Ar/SG15 mil/sb60cl-3 Glass 
               
               
                 Example 6 
                 SB60cl-3 glass/SG15 Mil/ 
                 62.9 
                 0.46 
                 0.35 
               
               
                   
                 Ar/SG15 mil/glass 
               
               
                   
               
             
          
         
       
     
     The above description has described specific steps and materials to form an insulated high impact resistant composite mounted in a window frame. However, it will be within the knowledge of one having ordinary skill in the art to make modifications without departing from the way and scope of the underlying inventive steps to obtain the same results. The inventive function for the steps employed are not limited to the materials employed but include modifications and equivalent materials as would normally be employed.