Abstract:
An exemplary backlight module ( 2 ) includes a light source ( 21 ) having at least two light emitting diodes ( 211 ), and a reflection layer ( 218 ). Each light emitting diode includes a top surface ( 214 ), a side surface ( 215 ) adjacent to the top surface. Each of the light emitting diodes configured to emit different colored light respectively. The reflection layer is formed on the top surface of the light emitting diode.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to backlight modules and liquid crystal displays, and more particularly to a backlight module of a liquid crystal display configured to provide a reflection layer for improving color mixing of various light emitting diodes thereat. 
       GENERAL BACKGROUND 
       [0002]    A typical liquid crystal display (LCD) generally includes a liquid crystal panel and a backlight module. The backlight module generally includes a reflection sheet, a light source, a diffuser, and a brightness enhancement film. The light source of the backlight module can be one or more cold cathode fluorescent lamps, or one or more light emitting diodes (LEDs). A backlight module using LEDs as a light source can include three different types of LEDs, which emit red, green, and blue light beams respectively. After mixing of the color light beams emitted by the red, green, and blue LEDs, a planar white light source can be provided by the backlight module. The planar white light source illuminates the liquid crystal panel. 
         [0003]    Referring to  FIG. 5 , this is a schematic, exploded, isometric view of a conventional backlight module  1 . The backlight module  1  includes a reflection sheet  14 , a plurality of light sources  11 , a diffuser  12 , and a brightness enhancement film  13 . The light sources  11  are formed on the reflection sheet  14 . Each light source  11  includes a red LED  111 , a green LED  112 , and a blue LED  113 . The diffuser  12  is formed on the light sources  11  opposite to the reflection sheet  14 . The brightness enhancement film  13  is formed on the diffuser  12 . 
         [0004]    Some of the light beams emitted by the red, green, and blue LEDs  111 ,  112 ,  113  are mixed and enter the diffuser  12  directly. Other of the light beams are mixed and reflected by the reflection sheet  14 , and then mixed again before entering the diffuser  12 . Then all the light beams are mixed and scattered by the diffuser  12  to form substantially white light, which then enters the brightness enhancement film  13 . 
         [0005]    Referring to  FIG. 6 , this is an enlarged side view of part of the backlight module  1 . Each of the red, green, and blue LEDs  111 ,  112 ,  113  has a similar structure. Taking the red LED  111  as an example, the red LED  111  includes a top surface  114  and at least two side surfaces  115 . The top surface  114  is adjacent and substantially perpendicular to the side surfaces  115 . The light beams can emit from both the top and side surfaces  114 ,  115 . A light path from the top surface  114  to the diffuser  12  is shorter than that from the side surface  115  to the diffuser  12 . That is, the light beams of the same color transmitting along different light paths will mix unevenly with other light beams of other colors. Therefore, a color shift is liable to occur within the planar white light source. This in turn impairs the display quality of the liquid crystal display using the backlight module  1 . 
         [0006]    Accordingly, what is needed is a backlight module of a liquid crystal display configured to overcome the above-described problems. 
       SUMMARY 
       [0007]    An exemplary backlight module includes a light source having at least two light emitting diodes, and a reflection layer. Each light emitting diode includes a top surface, a side surface adjacent to the top surface. Each of the light emitting diodes configured to emit different colored light respectively. The reflection layer is formed on the top surface of the light emitting diode. 
         [0008]    A detailed description of embodiments of the present invention is given below with reference to the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    In the drawings, all the views are schematic. 
           [0010]      FIG. 1  is an exploded, isometric view of a backlight module in accordance with a first embodiment of the present invention. 
           [0011]      FIG. 2  is an enlarged, side plan view of part of the backlight module of  FIG. 1 . 
           [0012]      FIG. 3  is a side plan view of part of a backlight module in accordance with a second embodiment of the present invention. 
           [0013]      FIG. 4  is a side plan view of a liquid crystal display in accordance with a third embodiment of the present invention, the liquid crystal display incorporating the backlight module of  FIG. 1 . 
           [0014]      FIG. 5  is an exploded, isometric view of a conventional backlight module. 
           [0015]      FIG. 6  is an enlarged, side plan view of part of the backlight module of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0016]    Referring to  FIG. 1 , this is a schematic, exploded, isometric view of a backlight module  2  in accordance with a first embodiment of the present invention. The backlight module  2  includes a plurality of light sources  21 , a diffuser  22 , a brightness enhancement film  23 , and a reflection sheet  24 . The light sources  21  are formed on the reflection sheet  24 . Each light source  21  includes a red LED  211 , a green LED  212 , and a blue LED  213 . The diffuser  22  is formed on the light source  21  opposite to the reflection sheet  24 . The brightness enhancement film  23  is formed on the diffuser  22 . 
         [0017]    Referring to  FIG. 2 , this is an enlarged, side plan view of part of the backlight module  2 . Each of the red, green, and blue LEDs  211 ,  212 ,  213  has a similar structure. Taking the red LED  211  as an example, the red LED  211  includes a top surface  214  and at least two side surfaces  215 . The top surface  214  is adjacent and substantially perpendicular to the side surfaces  215 . The light beams can emit from both the top and side surfaces  214 ,  215 . A reflection layer  218  is formed on the top surface  214  of the red LED  211 . The reflection layer  218  can be formed by coating or adhering a reflective material on the top surface  214 . The reflective material can for example be a silver layer. 
         [0018]    Some of the light beams emitted by the red, green, and blue LEDs  211 ,  212 ,  213  emit from the side surface  215 , are mixed and enter the diffuser  22  directly or are mixed and reflected by the reflection sheet  24 , and then enter the diffuser  22 . Other of the light beams are reflected by the reflection layer  218  on the top surface  214 , emit from the side surface  215 , are mixed and enter the diffuser  22  directly or are mixed and reflected by the reflection sheet  24 , and then enter the diffuser  22 . Then all the light beams are mixed and scattered by the diffuser  22  to become substantially white light, which then enters the brightness enhancement film  23 . 
         [0019]    The light beams can emit out from the red LED  211  through the top and the side surfaces  214 ,  215 . However, the light beams emitted toward the top surface  214  are reflected by the reflection layer  218 , and then the reflected light is guided toward and emitted out from the red LED  211  from the side surfaces  215 . 
         [0020]    All the light are emitted out from the red LED  211  through the side surfaces  215 . Therefore, there are as few as only two different light paths for transmitting the light beams to the diffuser  22 . Accordingly, a color difference caused by different color mixing between various light paths can be reduced, and the planar light source yielded is more uniformly white. 
         [0021]    Referring to  FIG. 3 , this is an enlarged, side view of part of a backlight module in accordance with a second embodiment of present invention. The backlight module  3  includes a reflection sheet  34 , and a plurality of LEDs  311 . The reflection sheet  34  has a reflection surface  341 . The LEDs  311  are formed on the reflection surface  341  of the reflection sheet  34 , which has a structure similar to that of the red LED  211  as shown in  FIG. 2 . 
         [0022]    A plurality of light-scattered structures  349  are formed on the reflection surface  341 . The light-scattered structures  349  are formed of light reflecting material such as silver, can have convex structures, and can be arranged randomly or in a matrix. The light-scattered structure  349  can provide reflection and diffusion of light beams and increase the amount of color mixing. This helps ensure the backlight module  3  provides a uniformly white planar light source. 
         [0023]    In alternative embodiments, the light-scattered structures  349  can be concave structures, which are also formed on the reflection surface  341 . The light sources  311  can be arranged in a line forming at a side of the reflection sheet  34 , known as a side-lighting backlight module. 
         [0024]    Referring to  FIG. 4 , this is a schematic, side view of a liquid crystal display in accordance with a third embodiment of the present invention. The liquid crystal display  100  includes the backlight module  2  and a liquid crystal panel  9 . The liquid crystal panel  9  is positioned adjacent the backlight module  2 . Planar white light emitted from the backlight module  2  enters and illuminates the liquid crystal panel  9 . 
         [0025]    While preferred and exemplary embodiments have been described above, it is to be understood that the invention is not limited thereto. To the contrary, the above description is intended to cover various modifications and similar arrangements including as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.