Abstract:
The present invention relates to a light emitting diode comprising a blue die and a fluorescent material layer. The blue die is used for generating blue light when being activated. The fluorescent material layer is used for generating yellow light when being activated. The light emitting diode further comprises a red die that is used for generating red light when being activated, so as to increase the red color component of the output light of the light emitting diode. The present invention also relates to a backlight module having light emitting diode, which has a well-balanced color when being used for a light source of a liquid crystal display or a liquid crystal display television.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the invention  
         [0002]     The present invention relates to a light emitting diode and backlight module having light emitting diode, particularly to a light emitting diode and backlight module that has an output light of well-balanced color.  
         [0003]     2. Description of the Related Art  
         [0004]      FIG. 1  shows a perspective view of a conventional backlight module. The conventional backlight module  1  comprises a plurality of lamps  11 , a diffusion plate  12 , a reflective plate  13  and a housing  14 . The backlight module  1  is disposed under a liquid crystal plate in a liquid crystal display device (not shown in the figure). The lamps  11  are used for providing light beams. The reflective plate  13  is disposed under the lamps  11  and is used for reflecting light beams generated by the lamps  11  to the diffusion plate  12 . The diffusion plate  12  is disposed above the lamps  11  and is used for diffusing the light beams generated by the lamps  11  and reflected by the reflective plate  13  so that the liquid crystal plate has an even distribution of light beams. The housing  14  is a square frame, which accommodates the lamps  11 , the diffusion plate  12 , and the reflective plate  13 . The lamps  11  of the conventional backlight module  1  are cold cathode fluorescent lamps (CCFL), which has a shortcoming of deficient intensity in the green region of the visible light spectrum. When the conventional backlight module  1  is applied in a liquid crystal display device, the green color is weakly displayed on the liquid crystal display device, which causes poor color rendition. Therefore, when being selected to be the light source of the conventional backlight module  1 , the cold cathode fluorescent lamps are gradually replaced by light emitting diodes.  
         [0005]      FIG. 2  is a diagram of a conventional light emitting diode. The conventional light emitting diode  2  comprises a blue die  21 , a reflector cup lead frame  22 , two leads  23  and  24 , a fluorescent material layer  25  and an encapsulant  26 . The blue die  21  is a Gallium Nitride (GaN) die and is used for generating blue light when being activated. The reflector cup lead frame  22  is used for receiving the blue die  21  and the fluorescent material layer  25 . The blue die  21  is electrically coupled to the leads  23  and  24  that are electrically connected to an outer power source, which provides electrical power to the blue die  21 . The fluorescent material layer  25  comprises Yttrium Aluminum Garnet (YAG) phosphor and covers the blue die  21 . The fluorescent material layer  25  is used for generating yellow light when being activated. The blue die  21  and the fluorescent material layer  25  are encapsulated by the encapsulant  26  which is a transparent epoxy. The output light of the conventional light emitting diode  2  is white light and has a shortcoming of deficient intensity in the red region of the visible light spectrum, which causes unbalanced color distribution.  
         [0006]     Referring to  FIG. 3 , a spectral distribution of the white light generated by the conventional light emitting diode  2  is shown, wherein the blue die  21  is applied by a direct current of 400 mA. The spectral distribution of the conventional light emitting diode  2  includes two peaks  31  and  32 , wherein the peak  31  is primarily caused by the blue die  21 , and the peak  32  is primarily caused by the fluorescent material layer  25 . As shown in the figure, the spectral distribution of the conventional light emitting diode  2  is deficient in the red region of the visible light spectrum (the range of 610 to 680 nm). When being used as a light source of a backlight for a liquid crystal display device, the red deficiency in the output light causes poor color rendition of the liquid crystal display device.  
         [0007]     In order to overcome the above-mentioned shortcoming, U.S. Pat. No. 6,351,069 B1 discloses a red-deficiency-compensating phosphor LED characterized in that a supplementary phosphor is added to a fluorescent material layer thereof so as to increase the red color component of its output light and compensate the red deficiency in the output light. However, such way will cause loss in brightness of the light emitting diode. Therefore, when being used as a light source of backlight module, it will reduce the brightness of the display device.  
         [0008]     Consequently, there is an existing need for a novel and improved light emitting diode and backlight module to solve the above-mentioned problem.  
       SUMMARY OF THE INVENTION  
       [0009]     One objective of the present invention is to improve the color saturation of a liquid crystal display television (LCD TV) or a liquid crystal display device.  
         [0010]     Another objective of the present invention is to provide a light emitting diode that has a blue die and a red die so as to compensate the red deficiency in the output light. When the light emitting diode is used as a light source of a backlight module, it can increase the color saturation.  
         [0011]     Another objective of the present invention is to provide a backlight module that has cold cathode fluorescent lamps and green light emitting diodes so as to compensate the green deficiency in the output light. When the backlight module is used as a light source of a liquid crystal display television or a liquid crystal display device, it can increase the color saturation.  
         [0012]     Another objective of the present invention is to provide a backlight module that has white light emitting diodes and red light emitting diodes so as to compensate the red deficiency in the output light. When the backlight module is used as a light source of a liquid crystal display television or a liquid crystal display device, it can increase the color saturation.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  shows a perspective view of a conventional backlight module;  
         [0014]      FIG. 2  is a diagram of a conventional light emitting diode;  
         [0015]      FIG. 3  shows a spectral distribution of the white light generated by the conventional light emitting diode of  FIG. 2 ;  
         [0016]      FIG. 4  shows a perspective view of a backlight module according to the present invention, wherein the light emitting diodes adapted in the backlight module are conventional;  
         [0017]      FIG. 5  is a diagram of a light emitting diode according to the present invention;  
         [0018]      FIG. 6  shows a spectral distribution of the white light generated by the light emitting diode of  FIG. 5 ;  
         [0019]      FIG. 7  shows a perspective view of a backlight module according to the present invention, wherein the light emitting diodes of  FIG. 5  are adapted in the backlight module; and  
         [0020]      FIG. 8  shows a perspective view of another type of backlight module according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]      FIG. 4  shows a perspective view of a backlight module according to the present invention, wherein the light emitting diodes adapted in the backlight module are conventional. The backlight module  4  comprises a plurality of lamps  41 , a diffusion plate  42 , a reflective plate  43 , a housing  44  and a plurality of green light emitting diodes  45 .  
         [0022]     The backlight module  4  is disposed under a liquid crystal plate in a liquid crystal display device (not shown in the figure). The lamps  41  are cold cathode fluorescent lamps and are used for providing light beams. The reflective plate  43  is disposed under the lamps  41  and is used for reflecting light beams generated by the lamps  41  to the diffusion plate  42 . The diffusion plate  42  is disposed above the lamps  41  and is used for diffusing the light beams generated by the lamps  41  and the green light emitting diodes  45  and reflected by the reflective plate  43  so that the liquid crystal plate has an even distribution of light beams. The housing  44  is a square frame, which accommodates the lamps  41 , the diffusion plate  42 , and the reflective plate  43 . The green light emitting diodes  45  are conventional green light emitting diodes and are used for compensating green deficiency in the output light of the lamps  41 . As a result, when the backlight module  4  is used as a light source of a liquid crystal display television or a liquid crystal display device, it can increase the color saturation of the liquid crystal display television or the liquid crystal display device.  
         [0023]     In this embodiment, each of the green light emitting diodes  45  is in a configuration of grain. Alternatively, each of the green light emitting diodes  45  may be in a configuration of strip or other types. In this embodiment, the green light emitting diodes  45  and the lamps  41  are arrayed alternatively by column. Alternatively, all of the lamps  41  may be surrounded by the green light emitting diodes  45 .  
         [0024]      FIG. 5  is a diagram of a light emitting diode according to the present invention. The light emitting diode  5  comprises a blue die  51 , a reflector cup lead frame  52 , two blue die leads  53  and  54 , a fluorescent material layer  55 , an encapsulant  56 , a red die  57  and two red die leads  58  and  59 .  
         [0025]     The blue die  51  is a Gallium Nitride (GaN) die and is used for generating blue light when being activated. The red die  57  is used for generating red light having a wavelength between 615 nm and 640 nm when being activated. The material of the red die  57  includes but is not limited to Indium Gallium Aluminium Phosphide (InGaAlP). The reflector cup lead frame  52  is used for receiving the blue die  51 , the red die  57  and the fluorescent material layer  55 . The blue die  51  is electrically coupled to the blue die leads  53  and  54  that are electrically connected to an outer power source, which provides electrical power to the blue die  51 . The red die  57  is electrically coupled to the red die leads  58  and  59  that are electrically connected to an outer power source, which provides electrical power to the red die  57 . The fluorescent material layer  55  comprises Yttrium Aluminum Garnet (YAG) phosphor and covers the blue die  51  and red die  57 . The fluorescent material layer  55  is used for generating yellow light when being activated. The blue die  51 , the red die  57  and the fluorescent material layer  55  are encapsulated by the encapsulant  56  that is a transparent epoxy.  
         [0026]     Referring to  FIG. 6 , a spectral distribution of the white light generated by the light emitting diode  5  of  FIG. 5  is shown, wherein the blue die  51  is applied by a direct current of 400 mA, the red die  57  is applied by a direct current of 100 mA. The spectral distribution of the light emitting diode  5  includes three peaks  61 ,  62  and  63 , wherein the peak  61  is primarily caused by the blue die  51  and the peak  62  is primarily caused by the fluorescent material layer  55 . Compared with the spectral distribution of  FIG. 3 , the difference is that the spectral distribution of  FIG. 6  has an extra peak  63  which corresponds to the wavelength of 640 nm and is in the red region of the visible spectrum. Therefore, the light emitting diode  5  can compensate red deficiency in the output light of conventional light emitting diode.  
         [0027]      FIG. 7  shows a perspective view of a backlight module according to the present invention, wherein the light emitting diodes  5  of  FIG. 5  are adapted in the backlight module  7 . The backlight module  7  comprises a plurality of light emitting diodes  5 , a diffusion plate  72 , a reflective plate  73  and a housing  74 . The backlight module  7  is disposed under a liquid crystal plate in a liquid crystal display device (not shown in the figure). The light emitting diodes  5  are same as the light emitting diodes  5  of  FIG. 5  and are used for providing light beams. The diffusion plate  72 , reflective plate  73  and housing  74  are same as the diffusion plate  12 , reflective plate  13  and housing  14  of the conventional light emitting diodes  1  as shown in  FIG. 1 . Because the light emitting diodes  5  can compensate the red deficiency in the output light, when the backlight module  7  is applied in a liquid crystal display television or a liquid crystal display device, they can increase the color saturation of the liquid crystal display television or the liquid crystal display device.  
         [0028]      FIG. 8  shows a perspective view of another type of backlight module according to the present invention. The backlight module  8  comprises a plurality of white light emitting diodes  81 , a diffusion plate  82 , a reflective plate  83 , a housing  84  and a plurality of red light emitting diodes  85 . The backlight module  8  is disposed under a liquid crystal plate in a liquid crystal display device (not shown in the figure). The white light emitting diodes  81  are conventional white light emitting diodes and are used for providing main light beams. The red light emitting diodes  85  are conventional red light emitting diodes and are used for compensating the red deficiency in the output white light of the conventional white light emitting diodes  81 . The diffusion plate  82 , reflective plate  83  and housing  84  are same as the diffusion plate  12 , reflective plate  13  and housing  14  of the conventional light emitting diodes  1  as shown in  FIG. 1 . In this embodiment, the red light emitting diodes  85  are added for compensating the red deficiency in the output light; therefore, when the backlight module  8  is applied in a liquid crystal display television or a liquid crystal display device, they can increase the color saturation of the liquid crystal display television or the liquid crystal display device. In this embodiment, the red light emitting diodes  85  and the white light emitting diodes  81  are arrayed alternatively by column. However, in other application, all of the white light emitting diodes  81  are surrounded by the red light emitting diodes  85 , or they are arrayed alternatively.  
         [0029]     While several embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention may not be limited to the particular forms as illustrated, and that all modifications which maintain the spirit and scope of the present invention are within the scope as defined in the appended claims.