Patent Publication Number: US-7710011-B2

Title: Flat light source

Description:
BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The present invention relates to a flat light source and fabricating method thereof. More particularly, the present invention relates to a flat light source having high brightness and fabricating method thereof. 
   2. Description of Related Art 
   In recent years, the Liquid Crystal Display panel (LCD panel) plays a predominant role in the display screen. However, since the LCD panel itself is incapable of emitting light, a back light module must be disposed below the LCD panel to provide a light source, thus achieving a display function. The light source of the back light module is usually provided by the lamp. After passing through the optical film of the back light module and then being scattered, the light emitted by the lamp forms a surface light source suitable for irradiating the LCD panel. 
   But if the flat light source can be used directly, the light application efficiency and the uniformity of surface light source may be improved. Moreover, the flat light source can be used in other various fields, besides in the back light source of the LCD panel. Therefore, the flat light source has the advantages in development. 
   Generally, the flat light source is a plasma light-emitting device, mainly applying a high voltage difference between the electrode pair to produce the energetic electrons, and then to form the so-called plasma by the energetic electrons bombarding the inert gas. And then, the excited atoms in the plasma will release energy by way of radiating UV light, while the UV light radiated will further excites the phosphor of the flat light source to emit the visible light. 
   It has become one key of the active development for the existing flat light source, that how to enhance the brightness, and improve the uniformity of light emitting. 
   SUMMARY OF THE INVENTION 
   Accordingly, an objective of the present invention is to provide a flat light source, which has high brightness and high light emitting uniformity. 
   Another object of the present invention is to provide a method for fabricating the flat light source, and the fabricated flat light source has high brightness and high light emitting uniformity. 
   The present invention provides a flat light source, which includes a first substrate, a second substrate, a sealant, several sets of dielectric pattern and a phosphor layer. The first substrate has electrodes thereon. The sealant is disposed between the first and second substrates to form a space between the first and second substrates and the sealant. These sets of dielectric pattern are formed in the space between the first and second substrates. Each set of dielectric pattern has at least two dielectric strips, and each dielectric strip covers one of the electrodes correspondingly. Each dielectric strip has a top surface and two side surfaces, and the top surface has an uneven contour. The phosphor layer is disposed between the dielectric strips of each set of dielectric pattern, and the phosphor layer is further disposed on the top surface of the dielectric strips. 
   In one embodiment of the present invention, the phosphor layer described above is further disposed between the two adjacent sets of dielectric pattern. 
   In one embodiment of the present invention, the flat light source further comprises several spacers disposed in the space between the first and second substrates. In one embodiment, the phosphor layer is further coated onto the surfaces of the spacers. In another embodiment, the height of the dielectric strips is the same as that of the spacers. In yet another embodiment, the height of the dielectric strips is less than that of the spacers. 
   In one embodiment of the present invention, the height of the dielectric strips is the same as the gap between the first and second substrates. 
   In one embodiment of the present invention, the flat light source further comprises a reflective layer disposed on the surface of the first substrate. 
   In one embodiment of the present invention, the flat light source further comprises another phosphor layer disposed on the second substrate. 
   The present invention further provides a method for fabricating a flat light source. In this method, a first substrate is provided. Then, several electrodes are formed on the first substrate. And then several sets of dielectric pattern are formed on the first substrate. Each set of dielectric pattern has at least two dielectric strips, and each dielectric strip covers one of the electrodes correspondingly, wherein each of the formed dielectric strips has a top surface and two side surfaces, and the top surface has an uneven contour. Subsequently, a phosphor layer is formed between the dielectric strips of each set of dielectric pattern and on the top surface of the dielectric strips. A second substrate is provided, and a sealant is formed between the first and second substrates to bond the first and second substrates together. 
   In one embodiment of the present invention, the method for forming the dielectric strips comprise a screen-printing process, an etching process or a sandblasting process. 
   In one embodiment of the present invention, the step of forming the phosphor layer further comprises coating the phosphor layer between the adjacent sets of the dielectric pattern. 
   In one embodiment of the present invention, the method further comprises forming several spacers between the first and second substrates before bonding the first and second substrates. In one embodiment, the phosphor layer is further coated onto the surfaces of the spacers. In another embodiment, the height of the dielectric strips is the same as that of the spacers. In yet another embodiment, the height of the dielectric strips is less than that of the spacers. 
   In one embodiment of the present invention, the height of the above mentioned dielectric strips is the same as the gap between the first and second substrates. 
   In one embodiment of the present invention, the method further comprises forming a reflective layer on the first substrate, before forming the electrodes on the first substrate. 
   In one embodiment of the present invention, the method further comprises forming another phosphor layer on the second substrate. 
   Since the top surface of each dielectric strip is designed to be an uneven contour, the coating area of the phosphor layer may be increased, thus improving the brightness of the flat light source. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIGS. 1A to 1C  are schematic sectional views of the flat light source according to several embodiments of the present invention. 
       FIG. 2  is a schematic sectional view of the flat light source according to another embodiment of the present invention. 
       FIG. 3  is a schematic sectional view of the flat light source according to yet another embodiment of the present invention. 
       FIG. 4  is a three-dimensional schematic view of the dielectric pattern of the flat light source according to a preferred embodiment of the present invention. 
       FIG. 5  is a sectional view of one of the dielectric strips of the flat light source along its extending direction according to a preferred embodiment of the present invention. 
   

   DESCRIPTION OF EMBODIMENTS 
     FIG. 1A  is a schematic sectional view of the flat light source according to a preferred embodiment of the present invention. Referring to  FIG. 1A , the flat light source of the present invention includes a first substrate  100 , a second substrate  120 , a sealant  104 , several electrodes  102 , several sets of dielectric pattern  108  and a phosphor layer  110 . 
   The electrodes  102  are disposed on the first substrate  100 . Each of the electrodes  102  is in a strip shape and these electrodes  102  are disposed on the first substrate  100  parallel to each other. The sealant  104  is disposed between the first and second substrates  100 ,  120  to form a space  106  between the first and second substrates  100 ,  120  and the sealant  104 . The sealant  104  is used to bond the first and second substrates  100 , 120  together, and leave a gap between the two substrates  100 ,  120 . The dielectric pattern  108  is disposed on the first substrate  100  and in the space  106 . Each set of dielectric pattern  108  has at least two dielectric strips  108   a ,  108   b , and each of the dielectric strips  108   a ,  108   b  covers one of the electrodes  102  correspondingly. Therefore, the two electrodes  102  covered by the two dielectric strips  108   a ,  108   b  of a set of dielectric pattern  108  are an electrode pair. 
   Particularly, the dielectric strips  108   a ,  108   b  of the present invention have special contours. Referring to  FIG. 4 , it depicts a three-dimensional schematic view of several sets of dielectric pattern  108  on the first substrate  100 . Each of the dielectric strips  108   a ,  108   b  has a top surface  202  and two side surfaces  204 ,  206 , and the top surface  202  has an uneven contour. In other words, each of the dielectric strips  108   a ,  108   b  has a protruding portion and a recessing portion, thus forming an uneven structure or a stepped structure. 
   Moreover, referring to  FIG. 1A , the phosphor layer  110  is disposed between the two dielectric strips  108   a ,  108   b  of each set of dielectric pattern  108 , and the phosphor layer  110  is further disposed on the top surface  202  of the dielectric strips  108   a ,  108   b , in which the top surface  202  is uneven contour. As shown in  FIG. 5 , it is a sectional view of the dielectric strips  108   a  or  108   b  along its extending direction. The phosphor layer  110  is further coated onto the top surface  202  of the dielectric strip  108   a  or  108   b.    
   According to another embodiment of the present invention, a reflective layer  112  is further disposed on the first substrate  100 . The reflective layer  112  may be disposed on the top surface of the first substrate  100 , and the electrodes  102  are disposed on the reflective layer  112 . The reflective layer  112  may also be disposed under the bottom surface of the first substrate  100  (not shown). No matter the reflective layer  112  is disposed on the top surface of the first substrate  100  or under the bottom surface of the first substrate  100 , the reflective layer  112  can be made of nonconductive material. 
   According to one embodiment of the present invention, a phosphor layer  114  can be further disposed on the second substrate  120 . Thus, the area coated by the phosphor layer in the flat light source may be further increased. 
   The phosphor layer  110  in the flat light source of the present invention is not only coated between the two dielectric strips  108   a  and  108   b , but also coated to the top surface  202  of the dielectric strips  108   a , 108   b , in which the top surface  202  has an uneven contour. Therefore, compared with the conventional flat light source, the area coated by the phosphor layer in the flat light source of the present invention is larger, and the cross-talking phenomenon may occur at the recessing portion of the dielectric strips  108   a ,  108   b , so that the portion incapable of emitting light before may emit light because of cross-taking phenomenon. Thus, the brightness of the flat light source may be improved. 
   According to a preferred embodiment of the present invention, as shown in  FIG. 1A , the flat light source may further comprises several spacers  116  disposed in the space  106  between the first and second substrates  100 ,  120  for maintaining the height of the gap between the first and second substrates  100 ,  120 . In another preferred embodiment of the present invention, the phosphor layer  110  described above is further coated onto the surfaces of the spacers  116 , as shown in  FIG. 1B . Thus, the area coated by the phosphor layer is further increased, and thereby the brightness and light emitting uniformity of the flat light source may be improved. 
   If spacers  116  (as shown in  FIGS. 1A and 1B ) are included in the flat light source, the height of the dielectric pattern  108  may be less than that of the spacers  116 . Definitely, the height of the dielectric pattern  108  can also be the same as that of the spacers  116 , as shown in  FIG. 1C . Thus, the spacers  116  and the dielectric pattern  108  may support the two substrates  100 , 120  to maintain the height of the gap between the two substrates  100 ,  120 . 
   However, the present invention is not limited to that the spacers must be disposed in the flat light source. In another embodiment of the present invention, the spacers are not included in the flat light source, as shown in  FIG. 2 . Since the spacers are not included in the flat light source, the height of the set of dielectric pattern  108  is preferably the same as that of the spacers  116  so as to maintain the height of the gap between the two substrates  100 ,  120 . While in the embodiment of  FIG. 2 , the phosphor layer  110  is not only coated between the two dielectric strips  108   a  and  108   b  of each set of dielectric pattern  108  and on the uneven contoured top surface of the dielectric strips  108   a ,  108   b , but also coated between the two adjacent sets of dielectric pattern  108 . Thus, the area coated by the phosphor layer is further increased, and thereby the brightness of the flat light source is enhanced. 
   In the embodiments of  FIGS. 1A to 1C  and  FIG. 2  described above, each set of dielectric pattern  108  has two dielectric strips  108   a ,  108   b  (an electrode pair), but the present invention is not limited to this. The flat light source structure of the present invention can also be that each set of dielectric pattern  108  has three or more dielectric strips  108   a ,  108   b  and  108   c  (and three electrodes  102 ), as shown in  FIG. 3 . In particularly, the contour of the top surface of the dielectric strips  108   a ,  108   b  and  108   c  is uneven, and the phosphor layer  110  does not only cover between the dielectric strips  108   a ,  108   b  and  108   c , but also cover the top surface of the dielectric strips  108   a ,  108   b  and  108   c . While if the spacer  106  is further included in the flat light source, the phosphor layer  110  further covers on the surfaces of the spacers  116 . 
   The method for fabricating the flat light source described above is illustrated as follows. First, referring to  FIG. 1A ,  1 B or  1 C, a first substrate  100  is provided. And then several electrodes  102  are formed on the first substrate  100  by known methods, such as deposition and etching process or screen-printing process. In one embodiment, the method further comprises forming a reflective layer  112  on the first substrate  100 . 
   Subsequently, several sets of dielectric pattern  108  are formed on the first substrate, wherein each set of dielectric pattern  108  has at least two dielectric strips  108   a  and  108   b , and each of the dielectric strips  108   a ,  108   b  covers one of the electrodes  102  correspondingly. Particularly, each of the formed dielectric strips  108   a ,  108   b  has a top surface  202  and two side surfaces  204 ,  206 , and the top surface  202  has an uneven contour, as shown in  FIG. 4 . The methods for forming the dielectric strips  108   a ,  108   b  comprise a screen-printing process, an etching process or a sandblasting process. 
   After that, a phosphor layer  110  is formed between the dielectric strips  108   a  and  108   b  of each set of dielectric pattern  108 , and the phosphor layer  110  is further coated on the top surface  202  of the dielectric strips  108   a ,  108   b  (as shown in  FIG. 5 ). And then, a second substrate  120  is provided. In a preferred embodiment, another phosphor layer  114  is further formed on the second substrate  120 . A sealant  104  is formed between the first and second substrates  100  and  120 , and the first and second substrates  100 ,  120  are bonded together to form a space  106  between the first and second substrates  100 ,  120  and the sealant  104 . Afterward, the inert gas is filled into the space  106 . When the power supply is on, the energetic electrons produced between the electrodes  102  may bombard the inert gas, thus forming the plasma. 
   According to the preferred embodiment, before bonding the substrates  100  and  120 , and more particularly, before coating the phosphor layer  110 , the method further comprises forming the spacers  116  on the first substrate  100  or the second substrate  120 . If the spacers  116  are formed in the flat light source, and more preferably, the phosphor layer  110  is further coated onto the surfaces of the spacers  116  during the process of coating the phosphor layer  110 . If the spacers are not formed in the flat light source, the phosphor layer  110  is further coated between the two adjacent sets of the dielectric pattern  108  during the process of coating the phosphor layer  110 , as shown in  FIG. 2 . 
   In view of the above, in the flat light source and fabricating method thereof of the present invention, since the formed dielectric strips have a top surface with an uneven contour, and the phosphor layer is not only coated between the two dielectric strips, but also coated on the uneven contoured top surface of the dielectric strips. Therefore, compared with the conventional flat light source, the area coated by the phosphor layer in the flat light source of the present invention is larger, and the cross-talking phenomenon may occur at the recessing portion of the dielectric strips, so that this portion incapable of emitting light before may emit light because of cross-talking phenomenon. Thus, the brightness of the flat light source may be improved. 
   Additionally, the phosphor layer is coated on other locations which are not coated with phosphor layer in the prior art, such as the surfaces of the spacers or between the two adjacent sets of dielectric pattern. Thus, the area coated by the phosphor layer may be increased, and thereby the brightness of the flat light source may be enhanced. Furthermore, the overall light emitting uniformity of the flat light source will be improved. 
   The present invention has been disclosed above in the preferred embodiments, but is not limited to those. It is known to persons skilled in the art that some modifications and innovations may be made without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be defined by the following claims.