Patent Publication Number: US-8536775-B2

Title: Field emission lamp with mesh cathode

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefits of the Taiwan Patent Application Serial Number 100100505, filed on Jan. 6, 2011, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a field emission lamp and, more particularly, to a field emission lamp capable of increasing the uniformity and the intensity of the light output therefrom by installing a mesh cathode portion to increasing the number of electron emitting points thereof, and of forming an anode portion on a portion of the inner surface of the outer shell thereof. 
     2. Description of Related Art 
     A conventional field emission lamp comprises: a transparent outer shell, an anode portion, a cathode portion, and a phosphor layer. The anode portion and the phosphor layer are formed on an inner surface of the transparent outer shell in sequence. The cathode portion is installed on a central position inside the transparent outer shell. Besides, the operation mechanism of the conventional field emission lamp is: electrons is emitted from the cathode portion, being accelerated by the high potential of the anode portion, then being collided with the phosphor layer formed on the anode portion. At this time, the light generated by the phosphor layer, due to the bombardment of the electrons, must passes through the phosphor layer, the anode portion, and the transparent outer shell, before being output to the exterior of the conventional field emission lamp, for the purpose of illumination. 
     Moreover, in the conventional field emission lamp, the surface of the cathode portion is a continuous flat surface, such as a flat curving surface of a clavate-shaped cathode portion. When the number of the anode electron emitting points needs to be increase, the area of the field emission surface of the cathode portion (i.e. the surface are of the cathode portion) is required to rise, or, increasing the density of the cathode portion to emit electrons without increasing the surface area of the cathode portion. In the prior art, as the cathode portion is formed by solid metal material, the increasing of the surface area of the cathode portion results in the increasing in the weight of the cathode portion. Thus, the conventional field emission lamp is easily over-weighted, making the supporting pillar thereof be easily broken. 
     Therefore, a field emission lamp capable of increasing the uniformity and the intensity of the light output therefrom by installing a mesh cathode portion to increasing the number of electron emitting points thereof, and of forming an anode portion on a portion of the inner surface of the outer shell thereof is required by the industry. 
     SUMMARY OF THE INVENTION 
     It is one object of the present invention to provide a field emission lamp capable of increasing the uniformity and the intensity of the light output therefrom by installing a mesh cathode portion to increasing the number of electron emitting points thereof. It is another object of the present invention to provide a field emission lamp by forming an anode portion on a portion of the inner surface of the outer shell thereof. 
     To achieve the object, the field emission lamp of the present invention comprises: an outer shell having an inner surface; a mesh cathode portion surrounded by the outer shell; an anode portion formed on a portion of the inner surface of the outer shell; and a phosphor layer formed on a portion of the anode portion; wherein the light generated by the phosphor layer, due to the bombardment of the electrons, outputs from the field emission lamp through the inner surface of the outer shell where none of the anode portion is formed thereon. 
     Therefore, since the electron is emitted from the mesh cathode portion of the field emission lamp of the present invention, toward the anode portion thereof, until being collided with the phosphor layer. Then, the phosphor layer generates light due to the bombardment of the electrons. The light outputs from the field emission lamp of the present invention through the inner surface of the outer shell where none of the anode portion is formed thereon. As a result, the light does not need to pass any anode portion or any phosphor layer until the light leaves the field emission lamp of the present invention, and the loss caused by the passage of light through the anode portion or the phosphor layer can be avoided. Thus, the light emitting efficiency of the field emission lamp of the present invention can be increased significantly. Moreover, since the mesh cathode portion can increase the number of electron emitting points, both of the uniformity and the intensity of the light output from the field emission lamp of the present invention can increase. 
     In addition, the form of the mesh cathode portion is not limited, the shape thereof can be clavate, or has a curving structure, spherical structure or a bowl-like structure. Besides, the material of the phosphor layer is not limited, it can be any conventional fluorescent powder, or any conventional phosphor powder suitable for application. Moreover, for different purpose or responding to different requirement, the phosphor layer can be made by mixing one or more kinds of fluorescent powder, or phosphor powder, for emitting UV light, infrared light, white light, or light of other colors. In addition, the mesh cathode portion can be manufactured in accordance with the curvature of the outer shell, such as a glass tube, and of any size suitable. Besides, as the surface area of the mesh cathode portion is much larger than that of a conventional flat cathode portion, the number of electron emitting points is increased significantly. 
     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of the field emission lamp according to first embodiment of the present invention. 
         FIG. 1B  is a cross-section view taken along the line AA′ of  FIG. 1A . 
         FIG. 2  is a perspective view of the field emission lamp according to second embodiment of the present invention. 
         FIG. 3  is a perspective view of the field emission lamp according to third embodiment of the present invention. 
         FIG. 4  is a perspective view of the field emission lamp according to fourth embodiment of the present invention. 
         FIG. 5  is a perspective view of the field emission lamp according to fifth embodiment of the present invention. 
         FIG. 6  is a perspective view of the field emission lamp according to sixth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to  FIG. 1A  and  FIG. 1B , wherein  FIG. 1A  is a perspective view of the field emission lamp according to first embodiment of the present invention, while  FIG. 1B  is a cross-section view taken along the line AA′ of  FIG. 1A . As shown in  FIG. 1A  and  FIG. 1B , the field emission lamp according to first embodiment of the present invention comprises: an outer shell  11 , a mesh cathode portion  12 , an anode portion  13 , and a phosphor layer  14 . Wherein, the outer shell  11  can be formed by a transparent material, for example, a soda-lime glass. Besides, the material of the outer shell  11  can also be soda glass, boron-glass, flint glass, quartz glass, or alkali-free glass. In addition, the outer shell  11  has an inner surface  111 , and the light generated by the phosphor layer  14 , due to the bombardment of the electrons, outputs from the field emission lamp according to first embodiment of the present invention through the inner surface  111  of the outer shell  11  where none of the anode portion  13  is formed thereon. 
     Moreover, the shape of the outer shell  11  is tubular, and the mesh cathode portion  12  is surrounded by the outer shell  11 . It should be noticed that, the position of the mesh cathode portion  12  is not limited, except for being positioned at the interior of the outer shell  11 , and not being directly contacted to the phosphor layer  14 , or the outer shell  11 . On the other hand, the shape of the mesh cathode portion  12  is clavate in the present embodiment, and the material thereof is metal. The anode portion  13  is formed on half of the inner surface  111  of the outer shell  11 , as shown in  FIG. 1A . That is, central angle included by the portion where the anode portion  13  is formed thereon is 180 degrees. However, in other application circumstances, the central angle included by the portion where the anode portion  13  is formed thereon maybe other degrees, for example, between 30 degrees and 210 degrees. In addition, the anode portion  13  is a metallic film, for example, aluminum film, nickel film, gold film, silver film, or tin film. At final, the phosphor layer  14  is formed on portions of the surface of the anode portion  13  by spin-coating, for receiving the bombardment of electrons to generate light. 
     Please refer to  FIG. 1A  again, after a power source  15  is connected with the anode portion  13  and mesh cathode portion  12  of the field emission lamp according to first embodiment of the present invention, electrons (not shown in the figure) emits from the mesh cathode portion  12  and collides with the phosphor layer  14  formed on portions of the surface of the anode portion  13  for generating light. In addition, as the anode portion  13  is made of metal, the light generated is reflected by the anode portion  13 . Then, the reflected light outputs from the field emission lamp according to first embodiment of the present invention through the inner surface  111  of the outer shell  11  where none of the anode portion  13  is formed thereon (as indicated by the arrows of  FIG. 1A ). 
     As described above, since the mesh cathode portion can increase the number of electron emitting points, both of the uniformity and the intensity of the light output from the field emission lamp according to first embodiment of the present invention can thus increase. Moreover, since the light generated by the phosphor layer  14  due to the bombardment of electrons can output from the field emission lamp according to first embodiment of the present invention without the need to pass any anode portion or any phosphor layer, the loss caused by the passage of light through the anode portion or the phosphor layer can be avoided. Thus, the light emitting efficiency of the field emission lamp according to first embodiment of the present invention can be increased significantly. 
     With reference to  FIG. 2 , wherein  FIG. 2  is a perspective view of the field emission lamp according to second embodiment of the present invention. As shown in  FIG. 2 , the field emission lamp according to second embodiment of the present invention comprises: an outer shell  21 , a mesh cathode portion  22 , an anode portion  23 , and a phosphor layer  24 . Wherein, the outer shell  21  can be formed by a transparent material, for example, a soda-lime glass. Besides, the material of the outer shell  21  can also be soda glass, boron-glass, flint glass, quartz glass, or alkali-free glass. In addition, the outer shell  21  has an inner surface  211 , and the light generated by the phosphor layer  24 , due to the bombardment of the electrons, outputs from the field emission lamp according to second embodiment of the present invention through the inner surface  211  of the outer shell  21  where none of the anode portion  23  is formed thereon. 
     Moreover, the shape of the outer shell  21  is tubular, and the mesh cathode portion  22  is surrounded by the outer shell  21 . It should be noticed that, the position of the mesh cathode portion  22  is not limited, except for being positioned at the interior of the outer shell  21 , and not being directly contacted to the phosphor layer  24 , or the outer shell  21 . On the other hand, the shape of the mesh cathode portion  22  has a curving structure and the curving structure faces the anode portion  23 , as shown in  FIG. 2 . That is, the central angle included by the curving structure is 180 degrees. However, in other application circumstances, the central angle included by the curving structure maybe other degrees, for example, between 30 degrees and 210 degrees. 
     In the present embodiment, the anode portion  23  is formed on half of the inner surface  211  of the outer shell  21 , as shown in  FIG. 2 . That is, the central angle included by the portion where the anode portion  23  is formed thereon is 180 degrees. However, in other application circumstances, the central angle included by the portion where the anode portion  23  is formed thereon maybe other degrees, for example, between 30 degrees and 210 degrees. In addition, in the present embodiment, the anode portion  23  can also be used as a reflective layer, which is a metallic film, for example, aluminum film, nickel film, gold film, silver film, or tin film. At final, the phosphor layer  24  is formed on portions of the surface of the anode portion  23  by film-coating, for receiving the bombardment of electrons to generate light. 
     Please refer to  FIG. 2  again, after a power source  25  is connected with the anode portion  23  and mesh cathode portion  22  of the field emission lamp according to second embodiment of the present invention, electrons (not shown in the figure) emits from the mesh cathode portion  22  and collides with the phosphor layer  24  formed on portions of the surface of the anode portion  23  for generating light. In addition, as the anode portion  23  is made of metal, the light generated is further reflected by the anode portion  23 . Then, the reflected light outputs from the field emission lamp according to second embodiment of the present invention through the inner surface  211  of the outer shell  21  where none of the anode portion  23  is formed thereon. 
     With reference to  FIG. 3 , the field emission lamp according to third embodiment of the present invention comprises: an outer shell  31 , a mesh cathode portion  32 , an anode portion  33 , and a phosphor layer  34 . Wherein, the outer shell  31  can be formed by a transparent material, for example, a soda-lime glass. Besides, the material of the outer shell  31  can also be soda glass, boron-glass, flint glass, quartz glass, or alkali-free glass. In addition, the outer shell  31  has an inner surface  311 , and the light generated by the phosphor layer  34 , due to the bombardment of the electrons, outputs from the field emission lamp according to third embodiment of the present invention through the inner surface  311  of the outer shell  31  where none of the anode portion  33  is formed thereon. 
     Moreover, the outer shell  31  is a bulb-like shell, and the mesh cathode portion  32  is surrounded by the outer shell  31  and the shape thereof is sphere. Besides, the mesh cathode portion  32  and the anode portion  33  are both made of metal, such as stainless steel, aluminum alloy or nickel alloy. At final, the phosphor layer  34  is formed on portions of the surface of the anode portion  33  by film-coating, for receiving the bombardment of electrons to generate light. 
     As the structure of the field emission lamp according to third embodiment of the present invention is similar to that of the field emission lamp according to first embodiment of the present invention, and the only difference between them are: the shape of the outer shell (tubular vs. bulb-like shape) and the shape of the mesh cathode portion (clavate vs. spherical), the detail description regarding the operation of the field emission lamp according to third embodiment of the present invention, such as the mechanism of the generation of light, is omitted hereinafter. 
     With reference to  FIG. 4 , the field emission lamp according to fourth embodiment of the present invention comprises: an outer shell  41 , a mesh cathode portion  42 , an anode portion  43 , and a phosphor layer  44 . Wherein, the outer shell  41  can be formed by a transparent material, for example, a soda-lime glass. Besides, the material of the outer shell  41  can also be soda glass, boron-glass, flint glass, quartz glass, or alkali-free glass. In addition, the outer shell  41  has an inner surface  411 , and the light generated by the phosphor layer  44 , due to the bombardment of the electrons, outputs from the field emission lamp according to fourth embodiment of the present invention through the inner surface  411  of the outer shell  41  where none of the anode portion  43  is formed thereon. 
     Moreover, the outer shell  41  is a bulb-like shell, and the mesh cathode portion  42  is surrounded by the outer shell  41  and has a bowl-like structure. Besides, the mesh cathode portion  42  is made of metal, such as stainless steel, aluminum, nickel, gold, silver, tin or the alloy thereof. In addition, the opening of the bowl-like structure faces the inner surface  411  of the outer shell  41  where none of the anode portion  43  is formed thereon, as shown in  FIG. 4 . In the present embodiment, the anode portion  43  can also be used as a reflective layer, which is a metallic film, for example, aluminum film, nickel film, gold film, silver film, or tin film. At final, the phosphor layer  44  is formed on portions of the surface of the anode portion  43  by spin-coating, for receiving the bombardment of electrons to generate light. 
     As the structure of the field emission lamp according to fourth embodiment of the present invention is similar to that of the field emission lamp according to second embodiment of the present invention, and the only difference between them are: the shape of the outer shell (tubular vs. bulb-like shape) and the shape of the mesh cathode portion (curving structure vs. bowl-like structure), the detail description regarding the operation of the field emission lamp according to fourth embodiment of the present invention, such as the mechanism of the generation of light, is omitted hereinafter. 
     With reference to  FIG. 5 , wherein  FIG. 5  is a perspective view of the field emission lamp according to fifth embodiment of the present invention. The field emission lamp according to fifth embodiment of the present invention comprises: an outer shell  51 , a mesh cathode portion  52 , an anode portion  53 , and a phosphor layer  54 . Wherein, the outer shell  51  can be formed by a transparent material, for example, a soda-lime glass. Besides, the outer shell  51  has an inner surface  511 , and the light generated by the phosphor layer  54 , due to the bombardment of the electrons, outputs from the field emission lamp according to fifth embodiment of the present invention through the inner surface  511  of the outer shell  51  where none of the anode portion  53  is formed thereon. 
     However, as shown in  FIG. 5 , the field emission lamp according to fifth embodiment of the present invention further comprises a lens unit  55 , and the lens unit  55  is formed on an outer surface  512  of the outer shell  51 . Thus, when the field emission lamp according to fifth embodiment of the present invention is operating, the light generated by the phosphor layer  54 , due to the bombardment of the electrons, outputs from the field emission lamp according to fifth embodiment of the present invention through the inner surface  511  of the outer shell  51  where none of the anode portion  53  is formed thereon, and then through the lens unit  55  to the exterior. The lens unit  55  can has a convex lens structure capable of concentrating light, such as a double convex lens or a flat-convex lens, or a concave structure capable of diffusing light, such as a double concave lens or a flat-concave lens. As a result, the field emission lamp according to fifth embodiment of the present invention can provide light suitable for different purpose. In other state of the present embodiment, the lens unit  55  is formed on the inner surface  511  of the outer shell  51  where none of the anode portion  53  is formed thereon. 
     As the structure of the field emission lamp according to fifth embodiment of the present invention is similar to that of the field emission lamp according to first embodiment of the present invention, and the only difference between them is the installation of the lens unit, the detail description regarding the operation of the field emission lamp according to fifth embodiment of the present invention, such as the mechanism of the generation of light, is omitted hereinafter. 
     With reference to  FIG. 6 , wherein  FIG. 6  is a perspective view of the field emission lamp according to sixth embodiment of the present invention. The field emission lamp according to sixth embodiment of the present invention comprises: an outer shell  61 , a mesh cathode portion  62 , an anode portion  63 , and a phosphor layer  64 . Wherein, the outer shell  61  can be formed by a transparent material, for example, a soda-lime glass. Besides, the outer shell  61  has an inner surface  611 , and the light generated by the phosphor layer  64 , due to the bombardment of the electrons, outputs from the field emission lamp according to sixth embodiment of the present invention through the inner surface  611  of the outer shell  61  where none of the anode portion  63  is formed thereon. 
     However, as shown in  FIG. 6 , the field emission lamp according to sixth embodiment of the present invention further comprises a lens unit  65 , and the lens unit  65  is formed inside the outer shell  61 . Thus, when the field emission lamp according to sixth embodiment of the present invention is operating, the light generated by the phosphor layer  64 , due to the bombardment of the electrons, passes through the lens unit  65  first, then outputs from the field emission lamp according to sixth embodiment of the present invention through the inner surface  611  of the outer shell  61  where none of the anode portion  63  is formed thereon. The lens unit  65  can has a convex lens structure capable of concentrating light, such as a double convex lens or a flat-convex lens, or a concave structure capable of diffusing light, such as a double concave lens or a flat-concave lens. As a result, the field emission lamp according to sixth embodiment of the present invention can provide light suitable for different purpose. In other state of the present embodiment, the lens unit  65  is formed on the outer surface of the outer shell  61 . 
     As the structure of the field emission lamp according to sixth embodiment of the present invention is similar to that of the field emission lamp according to first embodiment of the present invention, and the only difference between them is the installation of the lens unit, the detail description regarding the operation of the field emission lamp according to sixth embodiment of the present invention, such as the mechanism of the generation of light, is omitted hereinafter. 
     Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.