Abstract:
A coating apparatus includes non-orthogonal coater geometry to improve coatings on a glass ribbon, and to improve yields of such coatings. The apparatus includes a first arrangement to move the ribbon along a first imaginary straight line through a coating zone provided in a glass forming chamber. The coater has a coating nozzle and an exhaust slot, each have a longitudinal axis. The coating nozzle directs coating vapors toward the coating zone, and the exhaust slot removes vapors from the coating zone. A second arrangement mounts the coater in spaced relation to the path with the coating nozzle and the exhaust slot facing the coating zone. A second imaginary straight line is normal to the longitudinal axis of the coating nozzle, and the first imaginary line and the second imaginary line subtend an angle in the range of greater than zero degrees to 90 degrees.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a coating apparatus having a non-orthogonal coater geometry to improve coatings on a substrate, and more particularly, to position coating nozzles of a chemical vapor deposition (“CVD”) coater relative to the surface of a glass ribbon such that the direction of flow of coating vapors from the coating nozzles and the direction of movement of the glass ribbon subtend an angle measured in either a clockwise or counter-clockwise direction relative to the flow of the coating vapors or the direction of movement of the glass ribbon that is greater than zero degrees and less than ninety degrees. 
     2. Discussion of the Technology 
     Environmental coating layers are applied to a glass surface to selectively control the transmission of ultraviolet radiation, visible light, and/or infrared energy through the glass. One of the coating processes for depositing the environmental coating layers is known in the art as chemical vapor deposition (“CVD”) coating process. The CVD coater apparatus in general includes a pair of spaced gas curtain inlet slots or nozzles having one or more coating areas between the gas curtain slots and facilities to exhaust the coating area. Each of the coating areas includes a coating nozzle or slot between a pair of spaced exhaust slots or nozzles. CVD coaters having two or more coating areas usually have an exhaust slot between and distanced from adjacent coating nozzles to provide an exhaust slot on both sides of the coating nozzles. The coating nozzles and exhaust slots each have an elongated shaped outlet opening across the width of the coater. 
     A continuous glass ribbon moves under the coating nozzles and exhaust slots of the CVD coater as the coating vapors move through the coating nozzles and over the surface of the glass ribbon toward and into the exhaust slots. The coater can be mounted in a glass forming chamber, e.g. but not limiting to the discussion, as taught in U.S. Pat. Nos. 4,853,257 and 5,356,718, in which instance the glass ribbon is moved along a path in a downstream direction toward the exit end of the glass forming chamber, or the coater can be mounted between the exit end of a glass forming chamber and the entrance end of a glass annealing lehr, e.g. but not limiting to the discussion as taught in U.S. Pat. Nos. 4,584,206 and 4,900,110, in which instance the glass ribbon is moved along a path in a downstream direction toward the entrance end of the glass annealing lehr. U.S. Pat. Nos. 4,584,206; 4,853,257; 4,900,110, and 5,356,718 are hereby incorporated by reference. 
     Although the presently available CVD coaters and coating processes are commercially acceptable, there are limitations. More particularly and as discussed in more detail in the DETAILED DISCUSSION OF THE INVENTION presented below, particles of debris accumulate on the edges of the inlet slot opening of the coating nozzle and/or the edges of the opening of the exhaust slots. The debris reduces the width of the outlet opening of the coating nozzle and/or exhaust slot, which results in a disruption of flow due to the Bernoulli Effect either reducing or accelerating the flow of the coating vapors through the opening of the coating nozzle and/or exhaust slot. This disruption or reduction in the flow of coating vapors results in a coated layer or film having a coating streak. The options available when coating streaks are observed in the coating include, but are not limited to, removing the debris from the outlet opening of the coating nozzle and/or exhaust slot, and/or salvaging the coated glass on each side of the coating streak and discarding the glass with the coating streak. 
     As is appreciated by those skilled in the art, stopping the coating operation to clean the debris from the opening of the coating nozzle and/or the exhaust slot, and/or discarding glass with the color streaks, are costly expedients to solving the problem. It would be advantageous, therefore, to continue the operation of the coating process while eliminating or minimizing the impact of the debris on the outlet opening of the coating nozzle and/or the exhaust slot on the coating applied to the glass ribbon. 
     SUMMARY OF THE INVENTION 
     This invention relates to a vapor deposition coating apparatus including, among other things, a first arrangement to move a substrate along a path in a first direction through a coating zone, wherein the path through the coating zone is represented by a first imaginary straight line; a coater comprising a coating nozzle for directing coating vapors toward the coating zone, and an exhaust slot for removing vapors from the coating zone, wherein the coating nozzle and the exhaust slot are spaced from one another and each have a longitudinal axis, and a second arrangement to mount the coater in spaced relation to the path with the coating nozzle and the exhaust slot facing the coating zone, wherein a second imaginary straight line normal to the longitudinal axis of the coating nozzle and/or exhaust slot and the first imaginary line subtend an angle in the range of greater than zero degrees to 90 degrees. 
     This invention further relates to a chemical vapor deposition coater including, among other things, a housing having a major surface; a first wall and an opposite second wall, and a center line extending from the first wall to the second wall; slit opening of a coating nozzle at the major surface of the housing, slit opening of a first exhaust slot at the major surface of the housing between the first wall of the housing and the opening of the coating nozzle, and slit opening of a second exhaust slot at the major surface of the housing between the second wall of the housing and the opening of the coating nozzle, wherein the slit opening of the coating nozzle, the slit opening of the first exhaust and the slit opening of the second exhaust slot each have a longitudinal axis, and the longitudinal axis of the opening of the coating nozzle and the center line of the housing subtends an angle that is greater than zero degrees and less than 90 degrees, and an arrangement for providing a vaporized coating mixture in gaseous form and moving the vapors through the housing and through the opening of the coating nozzle. 
     This invention still further relates to a method of depositing a coating on a substrate moving along a path through a coating zone by, among other things, moving a substrate through the coating zone in a first straight direction, and directing coating vapors toward the surface of the substrate as it moves through the coating zone, wherein lines of flow of the coating vapors over the surface of the substrate are in a second direction, wherein the first direction and the second direction subtend an angle in the range of greater than zero and less than 90 degrees. 
     This invention also relates to a coated article made by the practice of the method of this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross sectional side view of a glass forming chamber having chemical vapor deposition equipment that can be used in the practice of the invention. 
         FIGS. 2-4  are side elevated partial views of coated glasses that can be made using the chemical vapor deposition equipment shown in  FIG. 1  in accordance to the teachings of the invention. 
         FIG. 5  is a plan view of a surface of a coater that can be used in the practice of the invention;  FIG. 5  shows the position of the coating nozzles, the exhaust slots and the gas curtain nozzles of the coater. 
         FIG. 6  is a plan view of coating nozzles, gas curtain nozzles and exhaust slots positioned above a glass ribbon as disclosed in the prior art. 
         FIG. 7  is a plan view showing the flow of coating vapors from a coating nozzle to an exhaust slot using the arrangement shown in  FIG. 6 . 
         FIG. 8  is a side schematic view of the relationship of the coating nozzle, the exhaust slot, the path of the glass ribbon and the direction of the flow the coating vapors shown in  FIG. 7 . 
         FIG. 9  is a bottom view of a coating nozzle showing debris on the wall of the nozzle opening. 
         FIG. 10  is a view similar to the view of  FIG. 7  showing a coating streak or defect in the coating applied to a surface of a glass ribbon. 
         FIG. 11  is a view similar to view of  FIG. 7  showing the coating nozzle, exhaust slot and the glass ribbon positioned relative to one another according to the teachings of the invention. 
         FIG. 12  is a view similar to the view of  FIG. 2  showing a defect in the surface of the coating of a coated article made using the coating arrangement shown in  FIG. 6 . 
         FIG. 13  is a view similar to the view of  FIG. 2  showing a defect in the surface of the coating of a coated article made using the coating arrangement of the invention, e.g. but not limited to, the coating arrangement shown in  FIG. 11 . The defect shown in  FIG. 13  is significantly smaller than the defect shown in  FIG. 12 . 
         FIGS. 14 and 15  are plan views of coaters positioned relative to a glass ribbon according to non-limiting embodiments of the invention. 
         FIGS. 16 and 17  are side views of a coater and glass sheet mounted for movement relative to one another in accordance to the teachings of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, spatial or directional terms, such as “inner”, “outer”, “left”, “right”, “up”, “down”, “horizontal”, “vertical”, and the like, relate to the invention as it is shown in the drawing figures. However, it is to be understood that the invention can assume various alternative orientations and, accordingly, such terms are not to be considered as limiting. Further, all numbers expressing dimensions, physical characteristics, and so forth, used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical values set forth in the following specification and claims can vary depending upon the property desired and/or sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1 to 10” should be considered to include any and all subranges between and inclusive of the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less, e.g., 1 to 6.7, or 3.2 to 8.1, or 5.5 to 10. Also, as used herein, the term “moved over”, and “positioned over” means moved and positioned on but not necessarily in surface contact with. For example, one surface, article, film or component “moved over” and “positioned over” another surface, article, film or component of an article does not preclude the presence of materials between the surfaces of the articles, or between components of the article, respectively. 
     Before discussing several non-limiting embodiments of the invention, it is understood that the invention is not limited in its application to the details of the particular non-limiting embodiments shown and discussed herein since the invention is capable of other embodiments. Further, the terminology used herein to discuss the invention is for the purpose of description and is not of limitation. Still further, unless indicated otherwise, in the following discussion like numbers refer to like elements. 
     Non-limiting embodiments of the invention will be discussed using a chemical vapor deposition (“CVD”) coating process to deposit a doped or an un-doped tin oxide film or layer over or on a surface of a substrate. As is appreciated, the invention is not limited to the coating process, the substrate, the coating layer and/or the coated product. More particularly, the coating process can be any coating process that applies a coating film or layer from a flow of coating vapor or gas moving over a surface of a substrate, e.g. but not limited to the coating process disclosed in U.S. Pat. No. 5,356,718, and the substrate can be made of any material, e.g. but not limited to clear or colored glass, plastic, metal and wood. The coating layer can be, but is not limited to, a tin oxide film over a glass substrate; a tin oxide film over an anti-iridescence, or color suppression film, or layer over or on a glass substrate; a doped tin oxide film over or on a glass substrate, e.g. but not limited to Sungate® 300 coated glass sold by PPG Industries, Inc., which includes a fluorine doped tin oxide film on a surface of a glass substrate, and a doped tin oxide film over an underlying film over or on a glass substrate e.g. but not limited to Sungate® 500 coated glass sold by PPG Industries, Inc., which includes a fluorine doped tin oxide film on an anti-iridescence film on a surface of a glass substrate. The products that can be made with the coated glass include, but are not limited to coated transparencies, coated bottles, coated glass for low-emissivity windows, thin film photovoltaic applications, electrical touch panels, and electrically heated glass for anti-fog commercial refrigerator doors and for aircraft transparencies. 
     With reference to  FIG. 1 , one non-limiting embodiment of the CVD coating apparatus and process of the invention includes surface  20  of a continuous glass ribbon  22  floating on a pool of molten metal  24  and moving in the direction of arrow  23 . The pool of molten metal is contained in a glass forming chamber  26 , e.g. but not limited to the type disclosed in U.S. Pat. Nos. 3,333,936 and 4,402,722; the disclosures of the patents are hereby incorporated by reference. As the glass ribbon  22  moves under CVD coater  28 , e.g. first CVD coater, an anti-iridescence or color suppression film  30  is applied to surface  32  of the glass ribbon  22  (see also  FIG. 2 ). Continued movement of the glass ribbon  22  in the direction of arrow  23  moves the glass ribbon  22  under CVD coater  34 , e.g. second CVD coater to apply a fluorine-doped tin oxide film  36  (see  FIG. 2 ) onto surface  38  of the anti-iridescence film  30 . 
     In the preferred practice of the invention, the anti-iridescence or color suppression film  30  is a gradient layer of tin oxide and silicon oxide, and is of the type disclosed in U.S. Pat. Nos. 5,356,718 and 5,863,337, which patents are hereby incorporated by reference. The percent of silicon oxide in the anti-iridescence or color suppression film  30  decreases as the distance from the surface  32  of the glass ribbon  22  increases to provide a gradient anti-iridescence or color suppression film  30  having 100% silicon oxide at the surface  32  of the glass ribbon and 100% tin oxide at the surface  38  of the anti-iridescence or color suppression film  30  (see  FIG. 2 ). For a detailed discussion of the chemistry and application of the anti-iridescence or color suppression film  30  references can be made to U.S. Pat. Nos. 5,356,718 and 5,863,337. 
     As is appreciated, the invention is not limited to a gradient anti-iridescence or color suppression film, and the invention contemplates an anti-iridescence or color suppression layer having a plurality of homogeneous silicon oxide and tin oxide films. More particularly and not limiting to the invention, shown in  FIG. 3  is an anti-iridescence or color suppression layer  42  having tin oxide films  44  and  46  alternating with silicon oxide films  50  and  51 . For a detailed discussion of anti-iridescence or color suppression layers having a plurality of homogeneous silicon oxide and tin oxide films reference can be made to U.S. patent application Ser. No. 09/434,823 filed Nov. 5, 1999, which patent application is hereby incorporated by reference. Optionally the anti-iridescence or color suppression film  30  and the layer  42  can be omitted, and the tin oxide or fluorine doped tin oxide film  36  can be applied directly to the surface  32  of the glass ribbon  22  as shown in  FIG. 4 . 
     With reference to  FIG. 5 , the CVD coating apparatus  28  for applying the anti-iridescence or color suppression film  30  (see  FIG. 2 ), or layer  42  (see  FIG. 3 ) in relationship to the direction of glass flow  26  (see  FIG. 1 ) has an elongated exhaust slot, upstream and downstream of each elongated coating nozzle, e.g. and not limiting to the invention, exhaust slot  54  is upstream of coating nozzle  56 ; exhaust slot  58  is downstream of the coating nozzle  56  and upstream of the coating nozzle  60 ; exhaust slot  62  is downstream of the coating nozzle  60  and upstream of the coating nozzle  64 , and exhaust slot  66  is downstream of the coating nozzle  64 . The effluent streams from the exhaust slots  54 ,  58 ,  62  and  66  are moved through conduits  67 - 70 , respectively, to a disposal area and processed in accordance with local, state and federal environmental regulations. The coating apparatus  28  further includes a gas curtain nozzle  72  upstream of outermost upstream exhaust slot, e.g. the exhaust slot  54 , and a gas curtain nozzle  74  downstream of outermost downstream exhaust slot, e.g. the exhaust slot  66 . An inert gas, e.g. nitrogen is moved through the gas curtain nozzles  72  and  74  to provide an inert gas barrier or curtain to prevent or limit the movement of the coating vapors or gases from the coating nozzles  56 ,  60  and  64  into the atmosphere of the glass forming chamber  26 , and to prevent or limit movement of the atmosphere of the glass forming chamber into the space between the coater and the surface  32  of the glass ribbon  22 . As discussed in more detail below, the gas curtain nozzles  72  and  74 , the exhaust slots  54 ,  58 ,  62 , and  66 , and the coating nozzles  56 ,  60 , and  64 , each have a slit outlet opening, or an elongated outlet opening  102 . 
     With reference to  FIG. 1 , the CVD coating apparatus  34  for applying the fluorine doped tin oxide film  36  (see  FIGS. 2-4 ) has an exhaust slot  78  upstream of a coating nozzle  80 , and an exhaust slot  82  downstream of the coating nozzle  80 . The effluent streams moving through the exhaust nozzles  78  and  82  are moved through conduits  84  and  86 , respectively, and properly disposed of, e.g. as disclosed in U.S. patent application Ser. No. 12/414,818 filed on Mar. 31, 2009. The coating apparatus  34  also includes a gas curtain nozzle  72  upstream of outermost upstream exhaust slot  78 , and a gas curtain nozzle  74  downstream of outermost downstream exhaust slot  82  (see  FIG. 6 ). 
     For purposes of clarity, the width of the slit or opening  102  of the coating nozzles  56 ,  60  and  64 ; exhaust slots  54 ,  58 ,  62  and  66 , and gas curtain nozzles  72  and  74 , of the coater  28  (see  FIGS. 1 and 5 ) and the coating nozzle  80 , the exhaust slots  78  and  82 , and gas curtain nozzles  72  and  74  of the coater  34  (see  FIGS. 1 and 6 ) are designated as “WN.” The length of the slit or elongated opening  102  of the coating nozzles  56 ,  60  and  64 ; exhaust slots  54 ,  58 ,  62  and  66 , and gas curtain nozzles  72  and  74 , of the coater  28  and the coating nozzle  80 , exhaust slots  78  and  82 , and gas curtain nozzles  72  and  74  of the coater  34  are designated as “LN.” The designations “WN” and “LN” are shown only for the coating nozzle  56  and shown only in  FIGS. 5 and 9 . The width of the coater  28  (see  FIG. 5 ) and the coater  34  (see  FIG. 1 ) are designated as “WC”, and the length of the coater  28  (see  FIG. 5 ) and of the coater  34  (see  FIG. 1 ) are designated as “LC.” The designations “WC” and “LC” are shown only in  FIG. 5  and shown only for the coater  28 . As can now be appreciated, the coating nozzles, the exhaust slots and the gas curtain nozzles of the coaters  28  and  34  are nozzles having elongated outlet openings and slots having elongated outlet openings across the width (WC) of their respective coater. 
     The invention is not limited to the length and width of the outlet opening  102  of the nozzles and the slots, and the width of the outlet openings  102  of the nozzles and slots. The length of the openings of the nozzles and slots can be equal to one another or different from one another. In one non-limiting embodiment of the invention, the width of the opening of the coating nozzles  56 ,  60  and  64  are equal; the length of the opening of the coating nozzles are equal; the width of the opening of the exhaust slots  54 ,  58 ,  62  and  66  are equal; the length of the opening of the exhaust slots are equal; the width of the opening of the gas curtain nozzles  72  and  74  are equal, and the length of the opening of the gas curtain nozzles are equal. In another non-limiting embodiment of the invention, the length of the opening of the gas curtain nozzles  72  and  74  are equal to one another and greater than the length of the opening of the exhaust slots  54 ,  58 ,  62  and  66 ; the length of the opening of exhaust slots are equal to one another and greater than the length of the opening of coating nozzles  56 ,  60  and  64 , and the width of the opening of the gas curtain nozzles, the coating nozzles and the exhaust slots are equal to one another. 
     The invention is not limited to the number of coating nozzles and exhaust slots for each of the coaters  28  and  34 . In the preferred non-limited embodiment of the invention, the coater  28 , and the coater  34  can have one or more coating nozzles. More particularly, for making coated glass of the type similar to Sungate® 500 coated glass, the prior art CVD coater used to deposit a gradient anti-iridescent or color suppression film  32  has three coating nozzles and four exhaust slots between gas curtain slots (see  FIG. 5 ), and the prior art CVD coater used to deposit a fluorine doped tin oxide film has seven coating nozzles and eight exhaust slots between gas curtain slots (see  FIG. 15 ). 
     With continued reference to  FIG. 5 , in one non-limiting embodiment of the invention, the exhaust slot upstream of a coating nozzle is spaced a greater distance from the coating nozzle than the exhaust slot downstream of the coating nozzle, e.g. and not limiting to the discussion, the exhaust slot  54  upstream of the coating nozzle  56  is spaced a greater distance from the coating nozzle  56  than the exhaust slot  58  downstream of the coating nozzle  56  is spaced from the coating nozzle  56 . The invention, however, is not limited to the spacing between the coaters  28  and  34 , the coating nozzles, the exhaust slots, and/or the gas curtain nozzles, and those skilled in the art have the knowledge to select the spacing to optimize their coating practice. Further, the invention is not limited to the dimensions of the openings of the coating nozzles, the exhaust slots, and/or the gas curtain nozzles, and those skilled in the art have the knowledge to select the size of the slot and nozzle openings to optimize their coating practice. Still further, the invention is not limited to the coating precursors used in the practice of the invention, nor the resultant composition of the coating. In one non-limiting embodiment of the invention, the coating precursors of the type disclosed in U.S. Pat. Nos. 5,356,718 and 5,599,387, and in U.S. patent application Ser. No. 09/434,823 are used in the practice of the invention. 
     In one non-limiting embodiment of the invention, as the glass ribbon  22  moves under the coater  28 , the coating precursors to apply the anti-iridescence or color suppression film  30  or layer  42  (see  FIGS. 2 and 3 ) over the surface  32  of the glass ribbon  22  (see  FIG. 4 ) are vaporized. The vaporized coating precursors are moved into the coater  28 , and then through two or more of the coating nozzles  56 ,  60  and  64  toward the surface  32  of the glass ribbon  22  to apply the anti-iridescence or color suppression film  30  or layer  42  (see  FIGS. 2 and 3 ) over the surface  32  of the glass ribbon  22  (see  FIG. 4 ). The coating vapors, the reaction vapors and gases are removed from the coating area of the coating nozzles by the exhaust slots  54 ,  58 ,  62  and  66 . The glass ribbon  22  continues to move along the path  23  and moves under the coater  34 . The coating precursors to apply a fluorine doped tin oxide film  36  over the anti-iridescence film  32  or layer  42  are vaporized. The vaporized coating precursors are moved into the coater  34 , and then through the coating nozzle  80  toward the film  30  or layer  42  to apply a fluorine doped tin oxide film  36  over the anti-iridescence or color suppression film  32  or layer  42  (see  FIGS. 2 and 3 ). The coating vapors, the reaction vapors and gases are removed from the coating area of the coating nozzle  80  by the exhaust slots  78  and  82 . In one non-limiting embodiment of the invention, the length of the coating nozzles and exhaust slots of the coaters  28  and  34  are sized such that the coating nozzles and exhaust slots of the coaters  28  and  34  do not extend beyond the edge  132  (shown in  FIG. 14 ) of the glass ribbon  22  so that the coating vapors are not directed onto the pool of molten metal  24  (see  FIG. 1 ). 
     The discussion is now directed to the flow path of the vapors or gases moving out of the coating nozzles of the coaters and over the glass ribbon surface  32  (see  FIG. 1 ) and into the exhaust slots on each side of the coating nozzle. In the following discussion, coating zone of the coating nozzle  80  of the coater  34  is discussed with the understanding that the discussion is applicable to the coating zone of the coating nozzles  56 ,  60  and  64  of the coater  28 , and additional coating zones of the coater  34  when present, unless indicated otherwise. The term “coating zone” as used herein means the zone defined by the exhaust slot immediately upstream of a coating nozzle, and the exhaust slot immediately downstream of the coating nozzle. With reference to  FIG. 6 , the coating zone of the coating nozzle  80  is identified by the number  88  and is between the upstream exhaust slot  78  and the downstream exhaust slot  82 . For ease of discussion, the coating zone, e.g. the coating zone  88  has an upstream portion  90  between the coating nozzle  80  and the exhaust slot  78 , and a downstream portion  92  between the coating nozzle  80  and the exhaust slot  82 . For a better appreciation of the invention, the coating activity of the downstream portion  92  of the coating zone  88  is discussed with the understanding that the discussion is applicable to the upstream portion  90  unless indicated otherwise. As can be appreciated, when considering the upstream portion  90  of the coating zone  88 , the coating nozzle  80  is included as shown in  FIG. 6 , and when considering the downstream portion  92  of the coating zone  88 , the coating nozzle  80  is included as shown in  FIG. 7 . 
     The discussion is now directed to the drawback of the present practice of coating a glass ribbon with a CVD coating apparatus. With reference to  FIGS. 7 and 8 , the flow of the coating vapors in the downstream portion  92  of the coating zone  88  move from the coating nozzle  80  in a direction, e.g. a downstream direction, designated by the arrowed lines  94  to the exhaust slot  82 . As is appreciated by those skilled in the art, the flow of the coating vapors is shown by the arrowed lines  94  to designate direction; however, the coating vapors move as a gaseous vapor over the surface  32  of the glass ribbon  20  in the direction of the arrowed lines. The flow of the coating vapors from the coating nozzle  80  to the downstream exhaust slot  82 , i.e. passing through the downstream portion  92  of the coating zone  88  (see  FIG. 7 ) is either a laminar flow or a turbulent flow. With specific reference to  FIG. 8 , there is shown a plane  96  passing through the longitudinal axis  97  of the coating nozzle  80 , and a plane  98  passing through the longitudinal axis  97  of the exhaust slot  82  (longitudinal axis  97  shown only for the coating nozzle  80 , and only shown in  FIG. 9 ). The planes  96  and  98  are parallel to one another. The direction of the ribbon designated by the arrow  23  and the direction of the flow of the gaseous coating, or the line of coating in the downstream portion  92  of the coating zone  88  designated by the arrowed lines  94  (only one shown in  FIG. 8 ) are normal to the planes  96  and  98 . 
     The drawback with this arrangement is that any reduction in the width of the opening  102  of the coating nozzles due to collection of debris on the coating nozzles reduces the width of the opening  102  of the coating nozzle and results in streaks in the coating. More particularly, the width “WN” of the opening  102  of the coating nozzles (see  FIG. 9 ), of the gas curtain nozzles and of the exhaust slots of the coaters  28  and  34  is measured between inner side surfaces  99  of the nozzles and slots, and the length “LN” of the opening  102  of the coating nozzles, of the gas curtain nozzles and of the exhaust slots of the coaters  28  and  34  is measured between inner end surfaces  100  of the nozzles and slots. The inner side surfaces  99  and the inner end surfaces  100  of the coating nozzle are numbered only in  FIG. 9  and are numbered only for the coating nozzle  80 . 
     Shown in  FIG. 10  is a section of the coated glass ribbon  22 , having coating streak  103  in the fluorine doped tin oxide film  36 . After a study of the coating process, it was concluded that coating streaks, e.g., the coating streak  103  is caused by the collection of debris, e.g., coating debris  104  (see also  FIG. 9 ) on the inner surface of the nozzle opening  102 , e.g. but not limiting to the discussion, on the inner side surfaces  99  of the nozzle opening  102 . The coating debris  104  decreases the width “WN” of the opening  102  of the coating nozzle  80 . With the current geometry of the coating nozzles and exhaust slots (see  FIGS. 8 and 9 ), the longitudinal axis  97  of the coating nozzles and the exhaust slots are aligned perpendicular to the direction  23  of glass travel. It has been observed that across most (about 90%-95%) of the middle portion of the coating nozzle opening  102 , the lines  94  of the coating vapors are oriented perpendicular to the longitudinal axis of the coating nozzle and the exhaust slot. At end portions  95  (identified only in  FIG. 7 ) which are each 2.5-5% of the length of the opening of the exhaust slot the flow of the gaseous coating is not expected to be normal to the longitudinal axis of the exhaust slot. Further, the direction of the lines  94  of the coating vapors are generally parallel to the direction  23  of glass travel. This means that the total coating material deposited at a particular location on the glass ribbon is the integral of the deposition rate along the line  94  of the coating vapors at that location. If the chemical supplied to the line  94  of coating vapors is decreased by the debris, e.g. by 10%, then the thickness of the coating film in that location is also reduced by a like amount. Optical modeling and compositional profiling with secondary ion-mass spectroscopy (commonly known as “SIMS”) has shown that a 4% reduction in coating thickness will induce a change in the color of the coating by 4 Delta E units as measured using the Hunter 1948 L, a, b color space thus making the defect visible to the unaided eye of a person not skilled in the art. As is appreciated by those skilled in the art, Delta-E is a single number that represents the “distance” in color space that numerically expresses a color difference. In the matter under discussion, the color of the coating streak  103  (see  FIG. 10 ) is one color, and the color of the coating surrounding the streak is another color. The practice of the invention provides a difference between the color of the streak  103  and the color of the coating surrounding the streak of Delta-E less than 4. As is appreciated by those skilled in the art, a Delta-E of less than 4 is not visible to the unaided eye of a person not skilled in the art. 
     It was further concluded from the study of the coating that the direction of the lines  94  of coating vapors is primarily driven by the pressure differential between the coating nozzle and the exhaust slot of the coating zone. Therefore by orienting the upstream portion  92  of the coating zone  88  such that the direction of the lines  94  of coating vapor is at an angle to the direction  23  of glass travel, e.g. the lines  94  of the coating vapors and the direction  23  of glass travel are not each normal to the longitudinal axis  97  of the coating nozzle and exhaust slot at a particular location on the glass ribbon, the coating defect  103  will cross multiple lines  94  of coating vapor as shown in  FIG. 11 . In this case, the total thickness at a particular location on the glass ribbon  20  is the integral of the deposition rates of the lines  94  of coating vapor that the location crosses. Thus the impact on coating thickness due to a decrease in the flow along a single or group of lines  94  of coating vapor will be reduced, i.e. an averaging effect will be realized. More particularly, as shown in  FIG. 11 , the greater the angle A of the lines  94  of coating vapor relative to the direction  23  of the glass ribbon travel, the greater this averaging effect will be on local coating thickness variations and the greater the improvement in color difference. 
     As can now be appreciated when rotating the lines  94  of coating vapor and the direction  23  of glass travel relative to one another, the openings of the coating nozzles and the exhaust slots are preferably sized such that they do not extend beyond the edge  132  of the glass ribbon. Further as can now be appreciated, the rotation of the lines  94  of coating vapor and the direction  23  of glass travel relative to one another can be in a clockwise direction or in a counter-clockwise direction. 
     With continued reference to  FIG. 11  there is shown the coating nozzle  80  and the exhaust slot  82  mounted relative to the glass ribbon  22  in accordance to the teachings of the invention. The direction  23  of travel of the glass ribbon  20  and the direction of the lines  94  of coating vapors subtend an angle A that is greater than 0 degrees, or 10 degrees or 30 degrees e.g. and not limiting to the invention in one or more ranges selected from the group of greater than 0 and less than 90 degrees, 5 to 70 degrees, greater than 0 to 45 degrees, greater than 0 to 30 degree, 5-30 degrees, and 10-30 degrees. The direction  23  of travel of the glass ribbon  20  and the direction of the lines  94  of coating vapors can be rotated in a clockwise or counter-clockwise direction relative to one another to subtend the angle A 
     As can now be appreciated, increasing the angle A, increases the number of lines  94  of coating vapor that the coating defect  103  will pass through. Further increasing the angle A decreases the depth of the defect  103 , e.g. decreases the value of Delta E. More particularly,  FIG. 12  shows a coated glass sheet  120  of the prior art having the anti-iridescence or color suppression film or layer  30  deposited on the glass ribbon  22  and the fluorine doped tin oxide layer  36  over the anti-iridescence film  30 . The fluorine doped tin oxide film  30  has a coating defect  126  in the surface  127  of the layer  36  caused by debris on the opening of a coating nozzle, e.g. the debris  104  on the opening  102  of the coating nozzle  80  (see  FIG. 9 ). The depth of the defect  126  measured from the surface  127  is at least 4% of the thickness of the fluorine doped tin oxide film  36  and is visible to the unaided eye of a person not skilled in the art.  FIG. 13  shows a coated glass sheet  128  of the present invention having the anti-iridescence or color suppression film or layer  30  deposited on the glass ribbon  22  and a fluorine doped tin oxide layer  36  over the film  30 . The direction  23  of the glass ribbon and the lines  94  of coating vapor are set at an angle A of 10 degrees (see  FIG. 11 ). The fluorine doped tin oxide film  36  has a coating defect  129  caused by debris on the opening of a coating nozzle, e.g. the debris  104  of the opening  102  of the coating nozzle  80  (see  FIG. 9 ). The depth of the defect  129  measured from the surface  127  of the coated glass sheet  128  is at less than 4% of the thickness of the fluorine doped tin oxide film  36  and is not visible to the unaided eye of a person not skilled in the art. As used herein the term “unaided eye” means a person having 20-20 eyesight viewing the object without any vision enhancing equipment between the eyes and the object viewed. As can be appreciated, the percent of thickness change is also determined by dividing the thickness of the film, e.g., the thickness of the film  36  into the thickness of the film  36  at the coating defect. 
     As can now be appreciated, the invention is not limited to the manner in which the lines  94  of coating vapor are positioned at an angle A to the direction  23  of the glass ribbon  22 . For example and not limiting to the invention, in the instance when the longitudinal axis  97  (see  FIG. 9 ) of the nozzles and slots are normal to longitudinal axis  130  of the coater  34  and the lines  94  of coating vapor (see  FIG. 14 ), the coater  34  is angled relative to the direction  23  of the glass ribbon such that the longitudinal axis  130  of the coater  34  and the lines  94  of the coating vapor each subtend the angle A with the direction  23  of the glass ribbon as shown in  FIG. 14 . In the event, rotation of a coater, e.g. the coater  34  shown in  FIG. 14  results in a wide coating edge, i.e. the distance between edge  132  of the ribbon  22  and edge  134  of the film  36 , the length of the opening  102  of the coating nozzle can be increased in any convenient manner, e.g. but not limited to adjusting the end plugs in each mixing chamber to reduce the wide coating edge. 
     In the instance when the longitudinal axis  97  of the nozzles and slots are parallel to one another and at an angle to the longitudinal axis of the coater, the coater can be positioned relative to the glass ribbon such that the longitudinal axis  130  of the coater is parallel with the direction  23  of glass travel. More particularly, shown in  FIG. 15  is a coater  140  having seven coating nozzles designated  80 ,  142 ,  143 ,  144 ,  145 ,  146  and  147 , and eight exhaust slots designated  78 ,  82 ,  150 ,  151 ,  152 ,  153 ,  154  and  155  between gas curtain nozzles  72  and  74 . Longitudinal axis  160  of the coater  140  is parallel to the direction  23  of glass travel, and the longitudinal axis  160  of the coater and the direction  23  of glass travel are each at the angle A with the lines  94  of coating vapor. 
     The invention contemplates angling the nozzles and slots of the coater  28  in a similar manner as the nozzles and slots of the coater  34  and/or  140  were angled relative to the direction of the glass ribbon as discussed above. In this manner defects caused by debris on the openings of the nozzles and slots of the coater  28  are minimized or eliminated as discussed above for the coater  34 . Further, the invention contemplates having the longitudinal axis of the gas curtain slots  72  and  74  parallel to the longitudinal axis  94  of the coating nozzle and/or exhaust slots (see  FIG. 5 ) or having the longitudinal axis of the gas curtain slots  72  and  74  at an angle to the longitudinal axis of the coating nozzles and/or coating exhaust slots (see  FIG. 15 ). Still further, the invention contemplates having the flow of the gaseous coating of one coating zone of a coater angled relative to the direction of glass travel, e.g. at an angle greater than 0 and less than 90 degrees, and having the flow of the gaseous coating of another coating zone of the coater parallel to the direction of glass travel, e.g. at an angle of 0 degrees. 
     In addition to reducing the Delta E, the practice of the invention provides additional benefits. As discussed above, the total thickness of the coating film is the integral of the deposition rate along or across the lines  94  of coating vapor. If the path of the lines of coating vapor are made longer e.g. by increasing the angle A (see  FIG. 11 ), the thickness of the coating film, e.g. the film  36  (see  FIG. 2 ) will be increased for the same amount of chemical flow. As can now be appreciated, the invention provides for, but is not limited to (1) an increase in chemical utilization, e.g. but not limited to the invention a 1% improvement with a 10 degree increase in the angle A and (2) a reduction in the environmental impact and associated disposal costs of the chemicals of the coating process resulting from by an increase in chemical utilization. 
     As can now be appreciated by those skilled in the art, the embodiments of the invention are not limited to the embodiments discussed above. More particularly, the longitudinal axis of the nozzles and slots are shown in  FIGS. 14 and 15  to be rotated in a clockwise direction relative to the direction  23  of the glass ribbon  22  as viewed in  FIGS. 14 and 15  to provide the angle A. The invention is not limited thereto, and the longitudinal axis of the nozzles and slots can be rotated in counterclockwise direction relative to the path of the glass ribbon as viewed in  FIGS. 14 and 15 . Further, the coater can also be located at the exit end of any furnace, e.g. but not limited to a roller hearth or an oscillating hearth, that heats glass for tempering or heat strengthening. Still further, with reference to  FIG. 16 , the invention contemplates coating a glass sheet  160  secured on a stationary table  162  in any convenient manner, and the coater, e.g. but not limiting to the discussion the coater  30 ,  34  or  140  moved over the sheet  162 . With reference to  FIG. 17 , the invention contemplates securing the coater  30 ,  34  or  140  in position and moving the sheet  160  along conveyor rolls  166  under the coaters. The invention also contemplates simultaneously moving the coater and the glass sheet. Systems for moving glass sheets and/or coaters, and for maintaining coaters and/or glass sheets stationary are will known in the art and no further discussion regarding such systems is deemed necessary. 
     It will be readily appreciated by those skilled in the art that modifications can be made to the non-limiting embodiments of the invention without departing from the concepts disclosed in the foregoing description. Accordingly, the particular non-limiting embodiments of the invention described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.