Abstract:
An exemplary liquid crystal display device ( 10 ) includes a liquid crystal display panel ( 11 ), and a backlight module ( 12 ) having two sets of light sources ( 18, 19 ) for illuminating the liquid crystal display panel. One set of light sources is a multicolor mixed light source, and the other set of light sources is white light source.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a backlight module having a switchable light source and a liquid crystal display employee the backlight module.  
       BACKGROUND  
       [0002]     Because LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.  
         [0003]     In a conventional LCD device, red, green, and blue LEDs (light emitting diodes) are used as a multicolor mixed light source to ensure the LCD device employing them having a high color saturation. However, an irradiation efficiency of LEDs is greatly less than the cold cathode fluorescent lamp (CCFL). Therefore, a large number of LEDs are needed to arrange in the LCD device for ensuring the LCD device has a high brightness, which makes the LCD device unduly weighty and bulky.  
         [0004]     It is desired to provide an LCD device which can overcome the above-described deficiencies.  
       SUMMARY  
       [0005]     An exemplary backlight module includes two sets of light sources. One set of light sources is a multicolor mixed light source, and the other set of light sources is white light source.  
         [0006]     An exemplary liquid crystal display device includes a liquid crystal display panel, and a backlight module having two sets of light sources for illuminating the liquid crystal display panel. One set of light sources is a multicolor mixed light source, and the other set of light sources is white light source.  
         [0007]     Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic, side view of an LCD device according to a first embodiment of the present invention.  
         [0009]      FIG. 2  is a schematic, side view of an LCD device according to a second embodiment of the present invention.  
         [0010]      FIG. 3  is schematic, side view of an LCD device according to a third embodiment of the present invention.  
         [0011]      FIG. 4  is a schematic, top view of light sources and a reflective plate of the LCD device of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0012]     Referring to  FIG. 1 , a schematic, side view of an LCD device according to a first embodiment of the present invention. The LCD device  10  includes an LCD panel  11 , and a backlight module  12  disposed at a rear side of the LCD panel  11 .  
         [0013]     The backlight module  12  includes a prism sheet  13 , a diffusion sheet  14 , a first light guide plate  15 , a second light guide plate  16 , a reflective plate  17 , a first light source  18 , and a second light source  19 . The prism sheet  13 , the diffusion sheet  14 , the first light guide plate  15 , the second light guide plate  16 , and the reflective plate  17  are disposed form top to bottom in that order. The first light source  18  is arranged adjacent to a side of the first light guide plate  15 , and the second light source  19  is arranged adjacent to a side of the second light guide plate  16 .  
         [0014]     The first light guide plate  15  and the first light source  18  cooperate with each other to form the first set of light source. The light guide plate  15  includes a light incident surface  151  and a light output surface  152 , and the first light source  18  is disposed adjacent to the light incident surface  151 . When the first light source  18  is turned on, light beams emitted from the first light source  18  directly propagate within the light guide plate  15 . Part of the light beams emits from the light output surface  152  directly, and another part of the light beams are transmitted to the reflective plate  17  via the second light guide plate  16 , and then reflected by the light reflective plate  17 , and are emitted out of the light output surface  152  via the second and the first light guide plates  16  and  15 . After that, almost all the light beams emitted from the first light source  18  are refracted and concentrated by the diffusion sheet  14  and the prism sheet  13  before illuminating the LCD panel  11 .  
         [0015]     The first light source  18  is a CCFL (cold cathode fluorescent lamp), which is a normal white light source. The white light beams emitted by the CCFL are generated via exciting the fluorescent powder by electrons. This technology is mature, and an irradiation efficiency of the CCFL is greatly larger than the multicolor mixed light source.  
         [0016]     The second light guide plate  16  and the second light source  19  cooperate with each other to form the second set of light source. The light guide plate  16  includes a light incident surface  161  and a light output surface  162 , and the second light source  19  is disposed adjacent to the light incident surface  161 . When the second light source  19  is turned on, light beams emitted from the second light source  19  directly propagate within the light guide plate  16 . Part of the light beams emits from the light output surface  162  directly, and another part of the light beams are reflected by the light reflective plate  17  before emitting out of the light output surface  162 . After that, almost all the light beams emitted from the first light source  19  passes the first light guide plate  15 , and are refracted and concentrated by the diffusion sheet  14  and the prism sheet  13  before illuminating the LCD panel  11 .  
         [0017]     The second light source  19  includes a plurality of multicolor mixed light sources, each of which includes four LEDs encapsulated in a housing. The four LEDs are a red LED, two green LEDs, and a blue LED. Each multicolor mixed light source emits white light beams mixed by the colored light beams emitted by the red, green, blue LEDs. This kind of white light beams has high color saturation.  
         [0018]     The first and second sets of light sources can individually or cooperatively illuminate the LCD panel  11 . When the LCD device  10  is in a text processing mode, it can only turn on the first light source  18  to illuminate the LCD panel  11 . The first light source  18  has high irradiation efficiency, and only turning on the first light source  18  can lower the power consumption of the LCD device  10 . When the LCD device  10  is in a multimedia processing mode, it can turn off the first light source  18  and turn on the second light source  19 , so as to illuminate the LCD panel  11 . The second light source  19  has a high color saturation, which can ensure the LCD device  10  meet with the requirement of display multimedia images. When the LCD device is in a multimedia processing mode and needs high brightness, the first and second light sources  18  and  19  are both turned on to illuminate the LCD panel  11 . This illuminating mode is adapted to use in indoor environment having power supply.  
         [0019]     With these configuration, the backlight module  12  includes two sets of light sources, which are switchable according to different operation modes. Various modifications and alterations are possible within the ambit of the invention herein. The LEDs of the second light source  19  are not limited to four LEDs encapsulated, it can be three LEDs encapsulated, or six LEDs encapsulated. The second light source  19  may be a plurality of lamps emitting color light beams.  
         [0020]     Referring to  FIG. 2 , a schematic, side view of an LCD device according to a second embodiment of the present invention is shown. The LCD device  20  has a structure similar to that of the LCD device  10 . However, The LCD device  20  includes only a light guide plate  25  having two opposite light incident surfaces  251  and  253 . The first light source  28  is disposed adjacent to the light incident surface  251 , and the second light source  29  is disposed adjacent to the light incident surface  253 . The first light source  28  includes a plurality of white LEDs, and the second light source  29  includes a plurality of lamps emitting colored light beams so as to form a multicolor mixed light source. The first and second light sources  28  and  29  are switchable.  
         [0021]     Referring to  FIG. 3 , a schematic, side view of an LCD device according to a third embodiment of the present invention is shown. The LCD device  30  has a structure similar to that of the LCD device  10 . However, The LCD device  30  includes a direct type backlight module  32 . The backlight module  32  includes a prism sheet  33 , a diffusion sheet  34 , a first light source  38 , a second light source  39 , and a reflective plate  37  disposed from top to bottom in that order.  
         [0022]     The first light source  38  includes a plurality of CCFLs parallel disposed, which are white light sources. The second light source  39  includes a plurality of LEDs arranged in an array type (shown in  FIG. 4 ). Each of the LEDs is four LED encapsulated. The first and second light sources  28  and  29  are alternatively disposed between the reflective plate  37  and the diffusion sheet  34 .  
         [0023]     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.