Abstract:
A method and apparatus for depositing a homogeneous pyrolytic coating on substrates. These coatings would include insulator, metal and semiconductor films on a glass substrate. The apparatus controls the size and distribution of the spray droplets to improve the uniformity of the coatings.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to using liquid spray pyrolysis for the coating of substrates, such as glass plates, for architectural, appliance and electronic applications.  
       DESCRIPTION OF THE RELATED ARTS  
       [0002]     It is known that substrates, such as glass plates, can be coated with films by using an atomized liquid precursor and delivering it to the surface of the substrate to form a coating.  
         [0003]     U.S. Pat. No. 6,332,923 to Richard Crawley et al discloses a liquid spray system for depositing coatings on glass. The spray pattern delivered to the substrate would be oval in shape. This would necessarily deposit a non-uniform coating with the coating being thick at the center and thinner at the edge of the pattern. Large substrates would require the uses of multiple spray guns.  
         [0004]     U.S. Pat. No. 5,882,368 to Ciro Flacony-Guajardo et al discloses a method and apparatus for coating a hot glass substrate with a mist of fine droplets from a solution of a chemical precursor, by nebulizing a solution with ultrasonic vibration to form a mist of fine droplets; conducting the mist to the hot glass substrate; and depositing the mist on the hot glass substrate to form a coating. The size of the droplet is controlled by the nebulizer.  
         [0005]     There is no means of controlling the droplet size after atomization or the homogeneity of the mist deposited on the substrate, in either of the above mentioned patents.  
       SUMMARY OF THE INVENTION  
       [0006]     It is the main objective of the invention to provide an improved pyrolytic spray apparatus for depositing a uniform coating on substrates.  
         [0007]     It is also the main objective of the invention to provide an apparatus for depositing a uniform coating on substrates by generating a homogenous mist of liquid droplets by the combined features of the mixing chamber and restriction.  
         [0008]     It is also the main objective of the invention for depositing a uniform coating on substrates by regulating the size of the atomized liquid droplet once it leaves the spray gun by regulating the flow of the mist in the mixing chamber.  
         [0009]     Still further advantages will become apparent from the study of the following description and accompanying drawings. 
     
    
     DRAWINGS  
       [0010]      FIG. 1  Vertical cross-sectional view of coating apparatus for coating the top surface of a horizontal substrate:  
         [0011]      FIG. 2  Cross-section view taken along line A-A in  FIG. 1 ;  
         [0012]      FIG. 3  Cross-section view taken along line B-B in  FIG. 1 ;  
         [0013]      FIG. 4  Horizontal cross-sectional view of coating apparatus for coating the surface of a vertical substrate;  
         [0014]      FIG. 5  Vertical cross-section view taken along line C-C in  FIG. 4 ;  
         [0015]      FIG. 6  Vertical cross-sectional view of coating apparatus for coating the bottom surface of a horizontal substrate; and  
         [0016]      FIG. 7  Vertical cross-section view taken along line D-D in  FIG. 6 .  
         [0017]      FIG. 8  Close up of screening gas ports in  FIG. 1 .  
         [0018]      FIG. 9  Close up of screening gas ports in  FIG. 4 .  
         [0019]      FIG. 10  Close up of screening gas ports in  FIG. 6 . 
     
    
     DESCRIPTION  
       [0020]      FIGS. 1 through 3  and  FIG. 8  show a coating apparatus  10  for coating the top surface of a horizontal substrate G. The apparatus  10  contains one or more atomizing spray guns  20 , a mixing chamber  21 , a restriction  22  in the duct  23  and a diffuser  24  that forms the discharge and is directed downward to the substrate G surface. The opening area of the restriction  22  is smaller than that of the mixing chamber  21  or duct  23 . The opening area of the restriction  22  is adjustable. The screening gas ports  27  are connected to the screening gas outlets.  28 . The duct  23  and diffuser  24  are rectangular in cross-section. The cross-section area of the diffuser  24  is larger at the discharge end as compared to the end connected to the duct  23 . The restriction  22 , duct  23 , mixing chamber  21  and diffuser  24  are lined with a cooling jacket  15 . The exhaust duct  16  is rectangular in cross-section. The discharge of the diffuser  24  has a rounded profile  25  on the side nearest the exhaust duct  16 . The exhaust has a blower  18 . The apparatus is covered with insulation  19 . The mixing chamber has an outlet  26 . The coating apparatus  10  is mounted above but in close proximity to the substrate G. The substrate G is supported on rollers R.  
         [0021]      FIGS. 4, 5  and  9  show a coating apparatus  30  for coating the surface of a vertical substrate G. The apparatus  30  contains one or more atomizing spray guns  40 , a mixing chamber  41 , a restriction  42  and a diffuser  44  that forms the discharge and is directed horizontally to the substrate G surface. The opening area of the restriction  42  is smaller than that of the mixing chamber  41 . The opening area of the restriction  42  is adjustable. The screening gas ports  47  are connected to the screening gas outlets.  48 . The diffuser  44  is rectangular in cross-section. The cross-section area of the diffuser  44  is larger at the discharge end as compared to the end connected to the mixing chamber  41 . The restriction  42 , mixing chamber  41  and diffuser  44  are lined with a cooling jacket  36 . The exhaust duct  37  is rectangular in cross-section. The discharge of the diffuser  44  has a rounded profile  45  on the side nearest the exhaust duct  37 . The exhaust has a blower  39 . The apparatus is covered with insulation  39 . The mixing chamber has an outlet  35 . The coating apparatus  30  is mounted in close proximity to the substrate G. The substrate G is supported by suitable means such as tongs (not shown).  
         [0022]      FIGS. 6 and 7  show a coating apparatus  10  for coating the bottom surface of a horizontal substrate G. The apparatus  60  contains one or more atomizing spray guns  70 , a mixing chamber  71 , a restriction  72  and a diffuser  74  that forms the discharge and is directed upward to the substrate G surface. The opening area of the restriction  72  is smaller than that of the mixing chamber  21 . The opening area of the restriction  72  is adjustable. The screening gas ports  77  are connected to the screening gas outlets.  78 . The diffuser  24  is rectangular in cross-section. The cross-section area of the diffuser  74  is larger at the discharge end as compared to the end connected to the mixing chamber  71 . The restriction  72 , mixing chamber  71  and diffuser  74  are lined with a cooling jacket  65 . The exhaust duct  66  is rectangular in cross-section. The discharge of the diffuser  74  has a rounded profile  75  on the side nearest the exhaust duct  66 . The exhaust has a blower  68 . The apparatus is covered with insulation  69 . The mixing chamber  71  has an outlet  77 . The coating apparatus  60  is mounted above but in close proximity to the substrate G. The substrate G is supported on rollers R.  
       Reference Numbers  
       [0023]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                   
               
             
             
               
                   
                 10, 30, 60 
                 coating apparatus 
               
               
                   
                 20, 40, 70 
                 atomizing spray gun 
               
               
                   
                 21, 41, 71 
                 mixing chamber 
               
               
                   
                 22, 42, 72 
                 restriction 
               
               
                   
                 27, 47, 77 
                 screening gas port 
               
               
                   
                 28, 48, 78 
                 screening gas outlet 
               
               
                   
                 23 
                 duct 
               
               
                   
                 24, 44, 74 
                 diffuser 
               
               
                   
                 15, 36, 65 
                 cooling jacket 
               
               
                   
                 16, 37, 66 
                 exhaust duct 
               
               
                   
                 25, 45, 75 
                 rounded profile 
               
               
                   
                 26, 35, 77 
                 outlet 
               
               
                   
                 18, 39, 68 
                 exhaust blower 
               
               
                   
                 19, 39, 69 
                 insulation 
               
               
                   
                 R 
                 roller 
               
               
                   
                 G 
                 substrate 
               
               
                   
                   
               
             
          
         
       
     
       Operation of Invention  
       [0024]     Referring to  FIGS. 1 through 3  and  8 , the apparatus  10  is mounted above the substrate G and is used for the coating of the top surface of a horizontal substrate. In operation a precursor liquid is delivered to the atomizing spray gun(s)  20  contained in the coating apparatus  10 . The atomizing spray gun can be of electrostatic, airless, pneumatic, piezoelectric or any other suitable design. The atomized spray enters the mixing chamber  21 . The restriction  22  causes a back pressure to be formed in the mixing chamber  21  and uniformly distributes the atomized spray within the mixing chamber  21 . The section area of the mixing chamber  21  is large compared to the opening in the restriction  22 . The restriction  22  is adjustable to vary the opening. A smaller opening causes more back pressure in the mixing chamber  21 . The result is a slower flow velocity of atomized liquid in the mixing chamber  21 . The atomized liquid consists of droplets of varying size. As the atomized liquid flows upward towards the restriction  22 , the larger droplets fall out of the flow from gravitation forces and are collected in the outlet  26  at the bottom of the mixing chamber  21  to be re-sprayed. The result is a homogeneous atomized liquid with more uniformly sized droplets than otherwise possible. The atomized liquid passes through the restriction  22 . At this point there is a pressure drop and an increase in flow velocity. A screening gas is supplied through the screening gas port  27  and flows out the screening gas outlet  28 . The screening gas provides a shield to prevent the atomized liquid from depositing upon the duct  23  or diffuser  24 . The atomized spray is transported through the duct  23  until it reaches the diffuse  24  where the pressure increases and the flow velocity decreases. This aids in further increasing the uniform distribution of the droplets. The wider opening at the discharge end of the diffuser  24  also aids in preventing the build up of material from decreasing the flow. The atomized liquid is discharged from the diffuser  24  and impinges upon the substrate G forming a coating. The size of the diffuser  24  and duct  23  can be of sufficient size to coat large substrates G. Unused material flows towards the exhaust duct  16  with the aid of the exhaust blower  18 . The rounded profile  25  assists in the uniform flow of unused material to the exhaust duct  16 . The coating apparatus  10  is protected from heat by a covering of insulation  19 . The temperature of the atomized liquid is controlled as it passes through the mixing chamber  21 , restriction  22 , duct  23  and diffuser  24  by means of the cooling jacket  15 . This prevents pre-reaction of the precursor before it is discharge from the diffuser  24 . The temperature can also be controlled to prevent the atomized liquid from condensing upon the walls of the cooling jacket  15 . In this example, the substrate G is transported past the discharge of the diffuser  24  on rollers R, although, any suitable mode of transport could be used.  
         [0025]     Referring to  FIGS. 4, 5  and  9 , the apparatus  30  is mounted in close proximity to the substrate G and is used for the coating the vertical surface of a substrate. In operation a precursor liquid is delivered to the atomizing spray gun(s)  40  contained in the coating apparatus  30 . The atomizing spray gun can be of electrostatic, airless, pneumatic, piezoelectric or any other suitable design. The atomized spray enters the mixing chamber  41 . The restriction  42  causes a back pressure to be formed in the mixing chamber  41  and uniformly distributes the atomized spray within the mixing chamber  41 . The section area of the mixing chamber  41  is large compared to the opening in the restriction  42 . The restriction  42  is adjustable to vary the opening. A smaller opening causes more back pressure in the mixing chamber  41 . The result is a slower flow velocity of atomized liquid in the mixing chamber  41 . The atomized liquid consists of droplets of varying size. As the atomized liquid flows laterally towards the restriction  42 , the larger droplets fall out of the flow from gravitation forces and are collected in the outlet  35  at the bottom of the mixing chamber  41  to be re-sprayed. The result is a homogeneous atomized liquid with more uniformly sized droplets than otherwise possible. The atomized liquid passes through the restriction  42 . At this point there is a pressure drop and an increase in flow velocity. A screening gas is supplied through the screening gas port  47  and flows out the screening gas outlet  48 . The screening gas provides a shield to prevent the atomized liquid from depositing upon the diffuser  44 . The atomized spray is transported through the diffuser  44  where the pressure increases and the flow velocity decreases. This aids in further increasing the uniform distribution of the droplets. The wider opening at the discharge end of the diffuser  44  also aids in preventing the build up of material from decreasing the flow. The atomized liquid is discharged from the diffuser  44  and impinges upon the substrate G forming a coating. The size of the diffuser  44  can be of sufficient size to coat large substrates G. Unused material flows towards the exhaust duct  37  with the aid of the exhaust blower  38 . The rounded profile  45  assists in the uniform flow of unused material to the exhaust duct  37 . The coating apparatus  30  is protected from heat by a covering of insulation  39 . The temperature of the atomized liquid is controlled as it passes through the mixing chamber  41 , restriction  42  and diffuser  44  by means of the cooling jacket  36 . This prevents pre-reaction of the precursor before it is discharge from the diffuser  44 . The temperature can also be controlled to prevent the atomized liquid from condensing upon the walls of the cooling jacket  36 . The substrate G is transported vertically past the discharge of the diffuser  44  by any suitable mode of transport.  
         [0026]     Referring to  FIGS. 6, 7  and  10 , the apparatus  60  is mounted in close proximity to the substrate G and is used for the coating the bottom surface of a horizontal substrate. In operation a precursor liquid is delivered to the atomizing spray gun(s)  70  contained in the coating apparatus  60 . The atomizing spray gun can be of electrostatic, airless, pneumatic, piezoelectric or any other suitable design. The atomized spray enters the mixing chamber  71 . The restriction  72  causes a back pressure to be formed in the mixing chamber  71  and uniformly distributes the atomized spray within the mixing chamber  71 . The section area of the mixing chamber  71  is large compared to the opening in the restriction  72 . The restriction  72  is adjustable to vary the opening. A smaller opening causes more back pressure in the mixing chamber  71 . The result is a slower flow velocity of atomized liquid in the mixing chamber  71 . The atomized liquid consists of droplets of varying size. As the atomized liquid flows upward towards the restriction  72 , the larger droplets fall out of the flow from gravitation forces and are collected in the outlet  77  at the bottom of the mixing chamber  71  to be re-sprayed. The result is a homogeneous atomized liquid with more uniformly sized droplets than otherwise possible. The atomized liquid passes through the restriction  72 . At this point there is a pressure drop and an increase in flow velocity. A screening gas is supplied through the screening gas port  77  and flows out the screening gas outlet  78 . The screening gas provides a shield to prevent the atomized liquid from depositing upon the diffuser  74 . The atomized spray is transported through the diffuser  74  where the pressure increases and the flow velocity decreases. This aids in further increasing the uniform distribution of the droplets. The wider opening at the discharge end of the diffuser  74  also aids in preventing the build up of material from decreasing the flow. The atomized liquid is discharged from the diffuser  74  and impinges upon the substrate G forming a coating. The size of the diffuser  74  can be of sufficient size to coat large substrates G. Unused material flows towards the exhaust duct  66  with the aid of the exhaust blower  68 . The rounded profile  75  assists in the uniform flow of unused material to the exhaust duct  66 . The coating apparatus  60  is protected from heat by a covering of insulation  69 . The temperature of the atomized liquid is controlled as it passes through the mixing chamber  71 , restriction  72  and diffuser  74  by means of the cooling jacket  65 . This prevents pre-reaction of the precursor before it is discharge from the diffuser  74 . The temperature can also be controlled to prevent the atomized liquid from condensing upon the walls of the cooling jacket  65 . The substrate G is transported horizontally past the discharge of the diffuser  44  by any suitable mode of transport such as rollers R.