Abstract:
An exemplary liquid crystal display ( 2 ) has a liquid crystal panel ( 50 ) and a backlight module ( 20 ) being disposed under the liquid crystal panel, the backlight module has a light guide plate ( 21 ), and a light source having at least one point light source ( 23 ), at least one light guide bar ( 22 ) transmitting light beams from the at least one point light source, and a reflector ( 24 ) reflecting light beams from the at least one light guide bar into the light guide plate.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to backlight modules and the liquid crystal displays, and especially to backlight modules and the liquid crystal displays having a light guide bar.  
       BACKGROUND  
       [0002]     Liquid crystal displays are commonly used as display devices for compact electronic apparatuses, because they not only provide good quality images with little power but also are very thin. The liquid crystals in a liquid crystal display do not emit any light themselves. The liquid crystals have to be lit by a light source so as to clearly and sharply display text and images. Thus, a backlight module for an LCD is generally needed.  
         [0003]     Referring to  FIG. 4 , a related backlight module  10  includes a light guide plate (LGP)  11  and a light source  12 . The light source  12  is an L-shaped light source, which has a bent region  121  connecting two linear regions (not labeled). The LGP  11  is in a shape of rectangle, which has two light incident surfaces  111 , a light emitting surface  112  connecting with the two light incident surfaces  111 , and a bottom surface  113  opposite to the light emitting surface  112 , and a corner  114  at the intersection of the two light incident surfaces  111 . The light source  12  is disposed adjacent to the two adjacent incident surfaces  111 , and the bent region  121  is opposite the corner of the LGP  11 . Light beams from the light source  12  are directed into the LGP  11  through the two incident surfaces  111 . In assembly, the bent region  121  faces the corner  114 . Because the corner  114  has a point, the operator needs special carefulness in the process of assembling the light source  12  to the LGP  11  for preventing the point of the corner  121  from destroying the bent region  114  of the light source  12 . In addition, a gap between the light source  12  and the two incident surfaces  111  is larger because the corner. Thus, the backlight module  10  has a larger size.  
         [0004]     What is needed, therefore, is a safe backlight module and liquid crystal display having a high reliability.  
       SUMMARY  
       [0005]     In an exemplary example, a backlight module is provided. The backlight module a light guide plate, and a light source having at least one point light source, at least one light guide bar transmitting light beams from the at least one point light source, and a reflector reflecting light beams from the at least one light guide bar into the light guide plate.  
         [0006]     In another exemplary example, a liquid crystal display is provided. The exemplary liquid crystal display has a liquid crystal panel and a backlight module being disposed under the liquid crystal panel, the backlight module has a light guide plate, and a light source having at least one point light source, at least one light guide bar transmitting light beams from the at least one point light source, and a reflector reflecting light beams from the at least one light guide bar into the light guide plate.  
         [0007]     Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which:  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic view of a liquid crystal display, which has a backlight module and a liquid crystal panel provided on the backlight module;  
         [0009]      FIG. 2  is an exploded, isometric view showing the backlight module in  FIG. 1 ;  
         [0010]      FIG. 3  is an exploded, isometric view showing a backlight module of a liquid crystal display according to a second embodiment of the present invention; and  
         [0011]      FIG. 4  is a schematic, isometric view of a conventional backlight module. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0012]     Reference will now be made to the drawings to describe the preferred embodiments in detail.  
         [0013]     Referring to  FIG. 1 , a liquid crystal display  2  according to a first embodiment of the present invention has a backlight module  20  and a liquid crystal panel  50  provided on the backlight module  20 .  
         [0014]     Referring to  FIG. 2 , the backlight module  20  has a light guide plate (LGP)  21  and a strip-shaped light source (not labeled). The strip-shaped light source has a light guide bar  22 , two point light sources  23  and a reflector  24 .  
         [0015]     The LGP  21  includes a bottom surface  213 , a light emitting surface  212  opposite to the bottom surface  213 , a light incident surface  211  orthogonal connected with the bottom surface  213  and the light emitting surface  212 . The LGP  300  is in a shape of rectangular.  
         [0016]     The light guide bar  22  is in a shape of rectangular, which has two light incident surfaces  221 , opposite to each other, and a light emitting surface  222  orthogonal connected with the two light incident surfaces  221 .  
         [0017]     In assembly, the two point light sources  23  are respectively provided adjacent to the two light incident surfaces  221  of the light guide bar  22 . The light guide bar  22  is disposed adjacent to the light incident surface  211  of the light guide plate  21 , the light emitting surface  222  of the light guide bar  22  facing the light incident surface  211  of the light guide plate  21 . The reflector  24  surrounds three sides of the light guide bar  22 , which reflects light beams leaking from the light guide bar  22  into the light guide bar  22  again.  
         [0018]     When voltage is provided to the two light sources  23 , light beams from the two light sources  23  enter into the light guide bar  22 . Light beams transmit in the light guide bar  22  and are reflected by the reflector  24  into the light guide plate  21  from the light emitting surface  222  of the light guide bar  22  to the light incident surface  211  of the light guide plate  21 . The light guide bar  22  uniforms light beam before it transmits into the light guide plate  21  through the light incident surface  211 . After the light beams transmit into the light guide plate  21 , the light guide plate  21  functions to change a direction of propagation of light beams emitted from the light guide bar  22  and introduced into the light guide plate  21 , from a direction roughly parallel to the emission face  212  of the light guide plate  21  to a direction perpendicular to the emission face  212  by the diffusion of the dot patterns (not labeled) on the bottom surface  213 . That is, the light guide plate  21  effectively changes the linear light source(s) into a surface light source, for evenly illuminating a whole display screen of the LCD panel  50 .  
         [0019]     The light guide plate  21  and the light guide bar  22  can be made from Polymethyl Methacrylate (PMMA) or Polycarbonate (PC) by the injection molding method. The two point light sources  23  also can be replaced by one point light source, which are light emitting diodes (LEDs).  
         [0020]     The LCD  2  utilizes the point light sources  23  cooperating with the light guide bar  22  to replace conventional cold cathode fluorescent lamp (CCFL). Because the light emitting diodes have the advantages of long usage life time, high response time, high reliability and safe, comparing to the cold cathode fluorescent lamp (CCFL), the LCD  2  can attain long life time, high response time, high reliability and safe backlight module  20 .  
         [0021]     Referring to  FIG. 3 , a backlight module  30  of a liquid crystal display according to a second embodiment is shown. The backlight module  30  has a light guide plate (LGP)  31  and an L-shaped light source (not labeled). The L-shaped light source has two light guide bars  32 , two point light sources  33  and a reflector  34 .  
         [0022]     The LGP  31  includes a bottom surface  313 , a light emitting surface  312  opposite to the bottom surface  313 , two light incident surfaces  311  orthogonal connecting with the bottom surface  313  and the light emitting surface  312 . The LGP  300  is in a shape of rectangular. The two light incident surfaces  311  connect at one end, are configured in an L shape.  
         [0023]     The two light guide bars  32  each are in a shape of rectangular. Each has a light incident surface  321 , and a light emitting surface  322  orthogonal connected with the light incident surface  321 .  
         [0024]     In assembly, the two point light sources  33  are respectively provided adjacent to the two light incident surfaces  321  of the two light guide bar  32 . The two light guide bar  22  are respective disposed adjacent to the two light incident surfaces  311  of the light guide plate  31 , light emitting surfaces  322  of the two light guide bars  32  respectively facing the light incident surface  311  of the light guide plate  31 . The reflector  34  being L-shaped surrounds three sides of the two light guide bars  32 , which reflects light beams leaking from the light guide bar  32  into the light guide bar  32  again.  
         [0025]     When voltage is provided to the two light sources  33 , light beams from the two light sources  33  respectively enter into the two light guide bars  322  from two light incident surfaces  321 . Light beams transmit in the light guide bars  32  and are reflected by the reflector  34  into the light guide plate  31 . The two light guide bars  32  uniform light beams before they transmit into the light guide plate  31  through the light incident surfaces  311 . After the light beams transmit into the light guide plate  31 , the light guide plate  31  functions to change a direction of propagation of light beams emitted from the light guide bars  32  and introduced into the light guide plate  31 , from a direction roughly parallel to the emission face  312  of the light guide plate  31  to a direction perpendicular to the emission face  312  by the diffusion of the dot patterns (not labeled) on the bottom surface  313 . That is, the light guide plate  31  effectively changes the linear light source(s) into a surface light source, for evenly illuminating a whole display screen of the LCD.  
         [0026]     The light guide plate  31  and the light guide bar  32  can be made from Polymethyl Methacrylate (PMMA) or Polycarbonate (PC) by the injection molding method. The two point light sources  33  also can be replaced by one point light source, which are light emitting diodes (LEDs).  
         [0027]     The backlight module  30  utilize two point light sources  33  cooperating with two light guide bars  32  to replace conventional L-shaped cold cathode fluorescent lamp (CCFL). Because the light emitting diodes have the advantages of long usage life time, high response time, high reliability and safe, comparing to the cold cathode fluorescent lamp (CCFL), the backlight module  30  can attain long life time, high response time, high reliability and safe characteristics.  
         [0028]     In alternative changes, the L-shaped light source can be a U-shaped light source, which has three light sources and three light guide bars connecting, each light source being disposed at one end of the light guide bar.  
         [0029]     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.