Abstract:
A method and a system is provided to form deletion windows on a glass substrate. The method includes the steps of applying a provisional masking substance of the glass substrate for masking preestablished regions of said glass substrate. The method also includes applying a reflective material on the glass substrate including the provisional masking substance. The method further includes applying heat to the glass substrate for removing the provisional masking substance of the glass substrate forming the deletion windows.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a method and system to form deletion windows on any coated glass substrate using an enamel paint to temporary cover such areas during the reflective coating application, and then remove it by burning such enamel leaving exposed the desired opening areas on the glass (deletion windows). 
         [0003]    2. Description of the Related Art 
         [0004]    On the current automotive glass market has being an increasing need for glasses that prevent the solar radiation to penetrate into the automobile cabin causing undesired heat, causing additional fuel consumption to operate the air conditioning system for longer periods trying to cool it down. A solution well known by the automotive glass manufacturers are the reflective coated glasses that uses a multilayer metallic coat applied using a coater as described on U.S. Pat. No. 4,166,018 from Airco, to reflect a big portion of the Infra Red spectrum of the solar light (700 to 2500 nanometers wavelength). The reflective property is given by one or several layers of silver nano particles applied in between other specialized metallic coats like described on the U.S. Pat. No. 6,445,503 from Guardian, U.S. Pat. No. 7,807,248 from Cardinal or U.S. Pat. No. 7,037,588 from Glayerbel. 
         [0005]    Typical glass coating compositions for a triple silver layer system including: glass; TiO 2  (layer1); ZnO (layer 2); Ag (layer 3); NiCr (layer 4); SnO 2  (layer 5); ZnO (layer 6); Ag (layer 7); NiCr (layer 8); SnO 2  (layer 9); ZnO (layer 10); Ag (layer 11); NiCr (layer 12); SnO 2  (layer 13); and Si 3 N 4  (layer 14). 
         [0006]    The problem with this solution is that all those metallic coats acts also as a barrier for the Electro Magnetic Fields commonly used in the transmission of signals (Radio, GPS, Garage door openers, TV, Toll Road Cards, etc) another problem is the corrosion caused when the coat is in direct contact to the atmospheric elements (humidity, acid rain, cleaning agents, etc). A simple solution for this problem has being the addition of areas where the metallic coat is removed, either strategically located or minimum all around the edge of the glass; these areas are commonly named “deletion windows” and act as access ports for all those electromagnetic signals and in case of the edge deletion they seal the reflective coat from the effect of the atmospheric elements. 
         [0007]    Currently there are different methods and systems to generate opening areas on coated glass consisting mainly on methods to attack the coating by: abrasion, laser, plasma or chemicals. The actual coat removal methods and systems are associated to high operation cost mainly due to the high defective rate coming from the coat damage due to handling and the need for specialized production processes to avoid any contact with the coat that is extremely fragile. 
         [0008]    For example the U.S. Pat. No. 5,449,312 of Peter Lisec, describes a device for cutting a glass sheet with the help of a cutting tool, which can be rotated around an axis perpendicular to a supporting surface for the glass sheet to be machined, and for removing a coating, applied on the glass sheet, with the help of a grinding tool, which removes the coating from the glass sheet in strips lying on both sides of the scratch lines, running parallel to the grinding tool, with a beam, which is guided movably over the supporting surface on its edges, and with a cutting tool as well as a grinding tool, which are guided movably on the beam along the same. Those mechanisms allow the grinding wheel to be moved through the areas where the coat is to be removed. 
         [0009]    However, this method requires special attention to the grinding wheel condition and the cleanliness of the working area, a worn out wheel can cause permanent damage to the glass or an uneven coat removal. The method and system is limited in precision and can not handle tight radius or narrow-small size areas very well, due to the fact that the grinding wheel contact area, applied pressure and form are changing with the use. 
         [0010]    An alternative method which in fact is a derivation of the grinding wheel method is the one developed by Saint Gobain (US patent application US2007/0090092 A1) where the grinding wheel is replaced by plasma heads that depending on the size and form a system will move such heads around the glass surface turning on and off the plasma according to the deletion windows design. 
         [0011]    Advantages of this innovative system are cleanliness and precision of the removed area form. This application suggests high operational cost. Also under this scenario the coated glass needs to be handled with extra care to avoid handling damages. However, the production equipment capable to handle coated glass with minimal damage is really expensive and requires of costly maintenance routines, as well. 
         [0012]    Other alternative to remove the glass coating is showed in the U.S. Pat. No. 5,986,234 of Matthews, et al, which describes a compact laser system that removes surface coatings (such as paint, dirt, etc.) at a removal rate as high as 1000 ft2/hr or more without damaging the surface. A high repetition rate laser with multiple amplification passes propagating through at least one optical amplifier is used, along with a delivery system consisting of a telescoping and articulating tube which also contains an evacuation system for simultaneously sweeping up the debris produced in the process. The amplified beam can be converted to an output beam by passively switching the polarization of at least one amplified beam. The system also has a personal safety system which protects against accidental exposures. 
         [0013]    However, one problem with this method is that the time taken by the laser to remove the material is too long, making it not suitable for large areas like the ones expected on the automotive products. Maintenance and operational cost of the laser generator is also very expensive. 
         [0014]    On other industries like the fiber optic production and installation, they have adopted a method where special chemicals that dissolve the external coat are applied on the fiber to expose the fiber only on the specific area that is required. 
         [0015]    For example, a method for removing a coating from a portion of optical fiber is described in U.S. Pat. No. 6,582,527 of Marazzi, et al. This method consist on immerse on a special acid the coated fiber; the acid will dissolve only the coating material exposing the fiber without causing any damage. 
         [0016]    The method described in U.S. Pat. No. 6,582,527, even when interesting is extremely risky to be used with large pieces like automotive windshield. During the process the portion of the coat that needs to remain on the glass shall be covered-protected from the acid to avoid damages in case of spills. This makes this process extremely complicated and none suitable for our purposes. 
         [0017]    Other problem associated with processing coated glass is the fragility of the coat itself. The coat is an over posed composition of ultra thin layers of metallic components like oxides that can be easily damaged by corrosion and or abrasion. This coat increases it chemical and mechanical resistance once is heated above 620° C. (after bending), where it can be handled similar but not equal to the standard methods due to the properties of the coat. 
         [0018]    Based on the above the purpose of this invention is to accomplish the processing of automotive (reflective laminated sidelites or windshields) or architectural glass (energy efficient windows) that can contain, as part of their design, deletion windows of a controlled form and size and or edge deletion areas. 
         [0019]    In accordance with the above, the present invention considers the application of the coating to a precut and pre masked deletion areas on the glass using a special enamel, instead to cut to form and then remove the coat starting from a glass bracket with the coat already on its surface. 
         [0020]    With the proposed method, the glass with no coat will be handled on regular production lines with no risk to damage the coat because it is not on the glass yet, eliminating the need of big investments on specialized production lines. To generate the deletion windows, the proposal is to use an organic enamel, which can be applied with the current serigraphic painting machines, widely used on the automotive glass fabrication process, then to dry this paint using a regular IR oven, this will provide enough mechanical resistance to the enamel for the handling, packing, shipping and washing prior to the glass coater. Another characteristic of this proposed enamel is that it will not release any component into the coater atmosphere avoiding any kind of contamination. 
         [0021]    It is important to note that under this proposed method and system, there is no limitation of the glass forms and deletion windows design, all is needed is a new printing screen with the desired window form and size and paint this pattern over the glass to be coated. 
         [0022]    Another important benefit is that the glass can be stored under regular conditions not like the coated glass that demands special temperature and humidity (≦50%) control to avoid the metallic coat to get oxidized. 
       OBJECTIVES OF THE INVENTION 
       [0023]    Therefore, it is a main objective of the present invention to provide a method and system to form deletion windows on a reflective coated glass substrate, for removing the masking enamel once the coat is applied and just before the pair of glasses are placed into the furnace to produce a windshield or reflective laminated sidelites. 
         [0024]    It is another objective of the present invention to provide a method and system to form deletion windows on a reflective coated glass substrate, wherein the enamel is an organic based paint selected of the group of epoxy resins, titanium dioxides, organo-functional silanes or mixtures of the same, that will burn out at temperature range such as 280° C. to 500° C., which when exposed for a time in a range of 5 min to 15 min it will be carbonized eliminating the original mechanical bonding of the paint and therefore the bonding of the coat with the enamel. Those ashes product of the enamel carbonization can be easily removed by the regular after bending washing process (Assembly) existing on all windshield manufacturing processes, leaving a well define deletion window where originally the paint was printed. 
         [0025]    It is other objective of the present invention to provide a method and system to form deletion windows on a reflective coated glass substrate, to process coated glass with or without deletion areas, with out the need for special processing equipment and with very low to cero coat damage due to handling, by changing the process sequence of applying the coat once the glass is cut and edge finished where the deletion areas are covered by an especial enamel that will be carbonized and removed together with the coating sections in said deletion areas. 
         [0026]    An additional objective of the present invention is to provide a method and system to form deletion windows on a reflective coated glass substrate, which can coat the glass on the current regular production lines eliminating the need for large investments, and to load a coater with precut glass forms that can be or not of the same model or color. 
         [0027]    Other objective of the present invention is to provide a method and system to form deletion windows on a reflective coated glass substrate, wherein the enamel from the family of the organic Inks, is applied to the glass surface using the serigraphic method and, after drying the paint using a regular IR or UV curing oven. 
         [0028]    An additional objective of the present invention is to provide a method and system to form deletion windows on a reflective coated glass substrate, wherein the enamel is burned before the bending process in a glass sheet is carried out. The enamel is burned out by means of a complementary IR furnace that works at a temperature range between 280° C. and 500° C. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a schematic diagram detailing the system steps to produce “deletion windows” on coated glass substrate on a regular production process; 
           [0030]      FIG. 2  is a schematic diagram of the method steps in relation with the system for processing a coated glass substrate with or without deletion windows, in accordance with preferred embodiment of the present invention; 
           [0031]      FIG. 3  is a top view of a glass sheet showing examples of the mostly commonly used deletion windows on coated glass substrate; 
           [0032]      FIG. 4  shows a side view of a none coated glass substrate with an enamel applied over the deletion windows areas of said none coated glass substrate. 
           [0033]      FIG. 5  shows a schematic elevation view showing the enamel and coating steps to form deletion windows on any coated glass substrate. 
           [0034]      FIG. 6  is a schematic elevation view, according to the present invention, showing the step of applying infrared energy to carbonize the enamel to form deletion windows on any coated glass substrate. 
           [0035]      FIG. 7  is a schematic elevation view showing the washing step to clean the carbonized enamel from the glass substrate to form deletion windows on any coated glass in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    In accordance with the previous art, the Figure shows 1 a schematic diagram, describing a traditional production of a coating windshields with edge deletion or deletion windows. 
         [0037]    In the schematic diagram of  FIG. 1 , a set of coated glass sheets (step A), are cut in different sizes (short and long sheets) (step B). After, coating is removed of the long sheets, in areas previously selected or edge deletion areas (step C), to permit the transmission of electro magnetic fields commonly used in the transmission of signals (Radio, GPS, Garage door openers, TV, Toll Road Cards, etc), these areas are commonly named “deletion windows” which act as access ports for all those electromagnetic signals and in case of the edge deletion they seal the reflective coat from the effect of the atmospheric elements. Problems when removing of the coating from a glass sheet to form the “deletion windows” have been widely described in the prior art. 
         [0038]    In step D, the edge of the glass sheets are finished (seaming or grinding) according to the product specifications. In step E, the cut and edge finished glasses are washed on a regular production washer machine. 
         [0039]    After, the short and long sheets are separated and the short sheet (step F) is decorated in some areas, with a ceramic frit layer, for example, to protect the adhesive that bonds the glass to the vehicle from the ultraviolet rays of the sun, to hide electrical wires and other hardware behind the glass, and also to provide a filter for the amount of sunlight allowed into the vehicle such as “half tones” on the moon roof and certain backlites. Meanwhile, in step G, a release or departing agent (i.e. a separating power) is applied to the long sheet to provide a temporary protection for a surface, as well as an interleaving material for protection and separation of adjacent surfaces. 
         [0040]    In the step H, the short and long sheets are formed in pairs. In step I, the glass sheets are subjected to a bending process to provide a curvature for use, e.g., in an automobile window. 
         [0041]    In step J, the glass sheets are washed before the assembly. In step K, two pieces of glass with a layer of polyvinyl butyral (PVB) which is provided of step L, are encased between to form a windshield. In this step K, a vacuum process is applied to hold the PVB layer in place between the glass sheets to remove air bubbles. After, the glass sheets are put into an oven called an autoclave (step M) which heats the assembled windshield. The entire setup reaches 135° C. to 145° C., thereby melting the PVB, making it transparent, and fusing the three layers into one. The quality of lamination, or adhesiveness between the PVB and the glass sheets, are dependent on the temperature within the autoclave and the effectiveness of the pressure on the glass sheets and PVB. 
         [0042]    Once the product has been assembled, the glass product is shipped to a customer location (step N) for sale. 
         [0043]    Making now reference to  FIGS. 2 to 7 , the method and system to produce coated automotive glass with “deletion windows” in accordance with the present invention will now be described. 
         [0044]    Referring now to  FIG. 2 , the schematic diagram of the method steps in relation with the system for the processing coated glass substrate with edge deletion or deletion windows or both comprises of the following steps: 
         [0045]    A set of none coated glass sheets (step  10 ) are cut in different sizes (short and long sheets) (step  12 ). 
         [0046]    In step  14 , the edge of the short and long glass sheets are finished (seaming or grinding) according to the product specifications. In step  16 , the cut and edge finished glasses are washed on a regular production washer machine. 
         [0047]    After, the short and long sheets are separated, the short sheet (step  18 ) is decorated in some areas, with a ceramic frit layer, for example, to protect the adhesive that bonds the glass to the vehicle from the ultraviolet rays of the sun, to hide electrical wires and other hardware behind the glass, and also to provide a filter for the amount of sunlight allowed into the vehicle such as “half tones” on the moon roof and certain backlites. Similar to step F in  FIG. 1 . 
         [0048]    Meanwhile, in step  20 , the long sheet (b) is printed with an enamel, to print “the deletion windows” over the long glass sheet (b). The enamel is applied by means of a screen printing device to apply the enamel on preestablished regions to said glass sheet or substrate. The printing device applies the enamel using a serigraphic method and, after drying the paint using a regular IR or UV curing oven. 
         [0049]    The painted area (a) in  FIG. 4 , is identical as the deletion edge or “deletion windows” and can be easily modified using a new printing screen. The most commonly used “deletion windows” in a windshield GS ( FIG. 3 ) are the traffic control VICS device (I); rain sensor, line departure camera, garage door opener (II); toll gate prepaid card (III); GPS, satellite radio (IV); and edge deletion to avoid metallic coat oxidation (V). 
         [0050]    In the step  22 , the glass sheet (b) with the painted area (a) passes now through a regular production equipment like infrared, convective or ultraviolet drying oven, to dry out all the enamel solvents, normally using a temperature in a range of 150° C. to 250° C. for a resident time such as 10 to 20 minutes. 
         [0051]    After, the long sheet (b) with the painted area (a) will be pre-washed and loaded into a coating line (coater) CO, which is schematic showed in  FIG. 5 , to apply a multi layer metallic coating film (c) over on side of the glass that creates the reflective properties. 
         [0052]    The coated glass (b) will be now heated in an infrared oven (IR) or convective oven to a temperature in a range from 280° C. to 550° C. over enough time, most of the time being between 5 to 15 minutes to carbonize the applied enamel; this action allows to remove the enamel (step  24  in  FIG. 2 ) to glass bonding preparing it for a later removal. 
         [0053]    In step  26 , a release or departing agent (i.e. a separating power) is applied to the long glass sheet (b) to provide a temporary protection for a surface, as well as an interleaving material for protection and separation of adjacent surfaces. 
         [0054]    In the step  28 , the short and long sheets are formed in pairs. In step  30 , the glass sheets are subjected to a bending process to provide a curvature for use, e.g., in an automobile window. 
         [0055]    In step  32 , the short and long glass sheets are loaded onto a glass washer equipment WM ( FIG. 7 ) where by means of the high pressure water nozzles and the use of some auxiliary mechanical cleaning device like for instance brushes, the carbonized enamel (a), now in form of ashes (d) will be cleaned from the glass surface (b) together with the coat deposit (c) applied over said enamel (a). 
         [0056]    The action of removing the enamel ashes and the inherent coating, will leave as a consequence “none coated areas” on the glass surface identical in form and size as the desired “deletion windows”. 
         [0057]    The control of the form and size of the deletion window is dependant on the customer design which is translated on to a printing screen which is used on the printing machine to print the image on the glass. 
         [0058]    Finally, the bending and washed glass sheets are now being assembled in pairs, including a layer of polyvinyl butyral (PVB)  36  between the same to form a windshield (step  34 ). After, the glass sheets are put inside an oven called an autoclave (step  38 ) which heats the vacuumed windshield, as was previously described. 
         [0059]    Once the product has been assembled, the glass product is shipped to a customer location (step  40 ) for sale. 
         [0060]    The present invention has been described in an illustrative manner. It is to be understood, that the terminology that has been used, is intended to be in the nature of words of description rather than of limitation. 
         [0061]    Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, the present invention may be practiced other than as specifically described.