Abstract:
An exemplary backlight module ( 23 ) used in a liquid crystal display ( 2 ) includes light emitting units ( 29 ), a light guide plate ( 26 ), and a frame ( 25 ) for receiving the light guide plate. The light guide plate includes a light incident surface ( 261 ) and protrusions ( 267 ) extending from the light incident surface. The protrusions together with corresponding portions of the light incident surface cooperatively define receptacles ( 260 ). Each of the receptacles has one of the light emitting units fittingly received therein.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to light guide plates such as those used in liquid crystal displays (LCDs); and more particularly to a light guide plate having light emitting unit receptacles, a backlight module using the light guide plate, as well as a liquid crystal display using the backlight module. 
       GENERAL BACKGROUND 
       [0002]    The liquid crystal of an LCD does not itself emit light. Rather, the liquid crystal needs to be illuminated by a light source such as ambient light or an accompanying backlight. Thus a typical LCD has a backlight module installed therewith. The backlight module provides a uniform flat light source to enable the LCD to display images. 
         [0003]      FIG. 7  is a schematic, top view of a conventional LCD prior to it being assembled. The LCD  1  includes a printed circuit board (PCB)  11 , a liquid crystal panel  12  mechanically and electrically connected with one end of the PCB  11 , two light emitting diodes (LEDs)  14  cooperatively serving as a light source, an LGP  15 , and a frame  13  for receiving the PCB  11 , the LEDs  14 , and the LGP  15 . 
         [0004]    The PCB  11  includes a main area  110 , and a subarea  112  extending from one end of the main area  110 . The LEDs  14  are arranged on the subarea  112  of the PCB  11 . The LGP  15  includes a light incident surface  151  adjacent to the LEDs  14 , a top light emission surface  152  perpendicularly connecting with the light incident surface  151 , and a bottom surface (not labeled) perpendicularly connecting with the light incident surface  151 . The frame  13  includes a side wall  130  generally adjacent to the light incident surface  151  of the LGP  15 . Two openings  131  are defined at an inner surface (not labeled) of the side wall  130 . The openings  131  generally face toward the light incident surface  151 , and are for receiving the LEDs  14 . 
         [0005]    The LCD  1  is assembled by the following steps. Firstly, the LGP  15  is received in the frame  13 , with the light incident surface  151  located generally adjacent to the side wall  130 . The light emission surface  152  of the LGP  15  is oriented face up. Secondly, the subarea  112  of the PCB  11  is disposed on the side wall  130  of the frame  13 . Thus, the LEDs  14  disposed on the subarea  112  are received in the openings  131  and are located adjacent to the light incident surface  151  of the LGP  15 . The main area  110  of the PCB  11  is folded down and around to a location adjacent to the bottom surface of the LGP  15 . Then the liquid crystal panel  12  is folded up and around to a location adjacent to the light emission surface  152  of the LGP  15 . Thereby, the subarea  112  of the PCB  11  is sandwiched generally between the side wall  130  of the frame  13  and the liquid crystal panel  12 . 
         [0006]    The LEDs  14  are thus positioned in the openings  131 , and located adjacent to the light incident surface  151  of the LGP  15 . However, due to imprecision in the manufacture of the LCD  1 , the size of the frame  13  may not precisely match the size of the LGP  15 . In such case, gaps may exist between the frame  13  and the LGP  15 . Then when the LCD  1  is transported or utilized by an end user, the LCD  1  may be subjected to vibration or shock. When this happens, the light incident surface  151  of the LGP  15  is liable to deviate from the side wall  130  of the frame  13 . As a result, the distance from the LEDs  14  to the light incident surface  151  is increased. Then in use, some of the light beams emitted from the LEDs  14  may not enter the incident surface  151  of the LGP  15 . Thus, the emitting luminance of the LGP  15  is diminished. 
         [0007]      FIG. 8  is a graph showing a relationship between the relative emitting luminance of the LGP  15  and the distance from each of the LEDs  14  to the light incident surface  151 . The X abscissa represents the distance from each of the LEDs  14  to the light incident surface  151  in millimeters (mm). The Y ordinate represents the relative emitting luminance of the LGP  15  as a function of X. It can be seen that the greater the value of X, the lower the value of Y. That is, the greater the distance from the LEDs  14  to the light incident surface  151 , the lower the value of the relative emitting luminance of the LGP  15 . 
         [0008]    What is needed, therefore, is a light guide plate and a backlight module and liquid crystal display employing such a light guide plate that can overcome the above-described deficiencies. 
       SUMMARY 
       [0009]    A backlight module includes a plurality of light emitting units, a light guide plate, and a frame for receiving the light guide plate. The light guide plate includes a light incident surface and a plurality of protrusions extending from the light incident surface. The protrusions together with corresponding portions of the light incident surface cooperatively define a plurality of receptacles. Each of the receptacles has one of the light emitting units fittingly received therein. 
         [0010]    A liquid crystal display includes a liquid crystal panel, and a backlight module opposite to the liquid crystal panel. The backlight module includes a plurality of light emitting units and a light guide plate. The light guide plate includes a light incident surface and a plurality of protrusions extending from the light incident surface. The protrusions together with corresponding portions of the light incident surface cooperatively define a plurality of receptacles, and each of the receptacles has one of the light emitting units fittingly received therein. 
         [0011]    A light guide plate includes a light incident surface and a plurality of protrusions extending from the light incident surface. The protrusions together with corresponding portions of the light incident surface cooperatively define a plurality of receptacles, and each of the receptacles has one of the light emitting units fittingly received therein. 
         [0012]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all the views are schematic. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is an exploded, isometric view of an LCD according to a first embodiment of the present invention, the LCD including a backlight module. 
           [0014]      FIG. 2  is an enlarged view of a circled portion, labeled II, of  FIG. 1 . 
           [0015]      FIG. 3  is an assembled view of the backlight module of  FIG. 1 . 
           [0016]      FIG. 4  is an assembled view of the LCD of  FIG. 1 . 
           [0017]      FIG. 5  is an isometric view of a part of an LGP of a backlight module according to a second embodiment of the present invention. 
           [0018]      FIG. 6  is an isometric view of a part of an LGP of a backlight module according to a third embodiment of the present invention. 
           [0019]      FIG. 7  is a schematic, top view of a conventional LCD prior to it being assembled, the LCD including an LGP and a plurality of LEDs. 
           [0020]      FIG. 8  is a graph relating to performance of the LCD of  FIG. 7  once it has been assembled and is in use, the graph showing a relationship between relative emitting luminance of the LGP and a distance from each of the LEDs to a light incident surface of the LGP. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0021]    Reference will now be made to the drawings to describe the preferred embodiments in detail. 
         [0022]      FIG. 1  is an exploded, isometric view of an LCD according to a first embodiment of the present invention. The LCD  2  mainly includes a top cover  21 , a liquid crystal panel  22  for displaying images, a backlight module  23  for providing light beams to the liquid crystal panel  22 , and a bottom cover  24 . The top cover  21  and the bottom cover  24  are coupled together to cooperatively accommodate the liquid crystal panel  22  and the backlight module  23  therein. The top cover  21  and the bottom cover  24  may be made of iron or another suitable metal. 
         [0023]    The backlight module  23  includes an LGP  26 , a reflector  27 , a flexible printed circuit board (FPCB)  28 , a plurality of light emitting units  29 , and a frame  25  for receiving the LGP  26 , the reflector  27 , the FPCB  28 , and the light emitting units  29 . In the illustrated embodiment, there are four light emitting units  29 . The light emitting units  29  can for example be light emitting diodes (LEDs). 
         [0024]    The FPCB  28  includes an attaching area  281 , and a connection strip  283  extending from the attaching area  281 . The LEDs  29  are disposed on an underside of the attaching area  281  of the FPCB  28 . 
         [0025]    The frame  25  includes a first side wall  251 , a second side wall  253 , a third side wall  255 , and a fourth side wall  257 . The first, second, third, and fourth side walls  251 ,  253 ,  255 ,  257  cooperatively form a four-sided closed space (not labeled) therebetween, for receiving the LGP  26 , the reflector  27 , and the LEDs  29 . The side walls  251 ,  253 ,  255 ,  257  include a plurality of locking lugs (not labeled) respectively disposed at outer surfaces thereof. 
         [0026]    The first side wall  251  includes a gap  259 . The connection strip  283  extends out of the frame  25  through the gap  259 . The first side wall  251  further includes a plurality of protrusions  252  that are parallel with each other. The protrusions  252  extend from an inner surface (not labeled) of the first side wall  251 , and thereby define a plurality of notches  250  therebetween. 
         [0027]    The LGP  26  includes a light incident surface  261  adjacent to the first side wall  251  of the frame  25 , a top light emission surface  263  perpendicularly connecting with the light incident surface  261 , a bottom surface  265  perpendicularly connecting with the light incident surface  261 , and a plurality of L-shaped protrusions  267  extending from the light incident surface  261 . In the illustrated embodiment, there are eight L-shaped protrusions  267 , arranged as four pairs. In each pair, the two adjacent L-shaped protrusions  267  are symmetrically opposite each other. The two L-shaped protrusions  267  together with a corresponding portion of the light incident surface  261  cooperatively define a receptacle  260 , the receptacle  260  having an open side where free ends of the L-shaped protrusions  267  oppose each other. The receptacle  260  is for receiving a corresponding LED  29 . The LGP  26  can for example be made of polymethyl methacrylate (PMMA) or polycarbonate (PC). Thus the L-shaped protrusions  267  are elastically deformable to a certain degree. 
         [0028]    Also referring to  FIG. 2 , the L-shaped protrusions  267  are integrally formed with a main body of the LGP  26 . The L-shaped protrusions  267  have a same thickness as the main body of the LGP  26 , and are substantially coplanar with the main body of the LGP  26 . A first arm of each L-shaped protrusion  267  perpendicularly extends from the light incident surface  261 , and a second arm of the L-shaped protrusion  267  extends from the first arm and is parallel to the light incident surface  261 . That is, the two arms of the L-shaped protrusion  267  form a right angle. A chamfer  262  is formed on both arms of the L-shaped protrusion  267 , between an inner surface  264  and a top surface  266  of the L-shaped protrusion  267 . 
         [0029]    The top cover  21  includes two side walls (not labeled) opposite to each other. The side walls of the top cover  21  include a plurality of locking holes (not labeled), corresponding to the locking lugs of the first and third side walls  251 ,  255  of the frame  25 . The bottom cover  24  includes three side walls (not labeled). Two opposite of the side walls of the bottom cover  24  include a plurality of locking holes (not labeled), corresponding to the locking lugs of the second and fourth side walls  253 ,  257  of the frame  25 . 
         [0030]    Also referring to  FIG. 3 , this is an assembled view of the backlight module  23 . The backlight module  23  is assembled by the following steps. Firstly, the reflector  27  is disposed in the frame  25 . Secondly, the LGP  26  is disposed on the reflector  27 , with the bottom surface  265  abutting the reflector  27 . Each pair of L-shaped protrusions  267  is located in a corresponding notch  250  of the first side wall  251  of the frame  25 . Thirdly, the FPCB  28  is placed on the first side wall  251 . In this process, the LEDs  29  are fittingly received in the receptacles  260  of the LGP  26 . The connection strip  283  extends out of the frame  25  through the gap  259  of the first side wall  251 . A free end portion of the connection strip  283  is folded down and around to an underside of the reflector  27 . 
         [0031]    Also referring to  FIG. 4 , an assembled view of the LCD  2  is shown. After the backlight module  23  is assembled, the LCD  2  can be further assembled by the following steps. Firstly, the liquid crystal panel  22  is placed above the LGP  26  so that the liquid crystal panel  22  is adjacent to the light incident surface  261  of the LGP  26 . Thereby, the FPCB  28  is sandwiched between the liquid crystal panel  22  and the first side wall  251 . Subsequently, the locking lugs of the second and fourth side walls  253 ,  257  are engaged in the locking holes of the bottom cover  24 , so as to fix the bottom cover  24  to the frame  25 . Finally, the locking lugs of the first and third side walls  251 ,  255  are engaged in the locking holes of the top cover  21 , so as to fix the top cover  21  to the frame  25 . 
         [0032]    With the L-shaped protrusions  267 , the LGP  26  forms a plurality of receptacles  260  at the light incident surface  261 . The L-shaped protrusions  267  are integrated with the main body of the LGP  26 , and are elastically deformable. Thereby, the LEDs  29  can be firmly engaged in the receptacles  260 . Accordingly, even if there are gaps between the frame  25  and the LGP  26 , a constant distance between each LED  29  and the corresponding portion of the light incident surface  261  is maintained. Preferably, each LED  29  abuts against the corresponding portion of the light incident surface  261 . As a result, most or even all of the light beams emitted from the LEDs  29  enter the LGP  26  via the light incident surface  261 . Thereby, the emitting luminance of the LGP  26  is increased. 
         [0033]    Furthermore, at each L-shaped protrusion  267 , the chamfer  262  is provided between the top surface  266  and the inner surface  264 . Therefore, at each pair of L-shaped protrusions  267 , the corresponding LED  29  can be easily inserted into and engaged in the receptacle  260  of the LGP  26 . This makes assembly of the LCD  2  convenient. 
         [0034]      FIG. 5  is an isometric view of a part of an LGP  36  of a backlight module according to a second embodiment of the present invention. The LGP  36  has a structure similar to that of the LGP  26 . However, a first arm of each of L-shaped protrusions  367  perpendicularly extends from a light incident surface  361  of the LGP  36 , and a second arm of the L-shaped protrusion  367  extends oblique from the first arm slightly toward the light incident surface  361 . That is, the two arms of the L-shaped protrusion  367  form an acute angle. Each pair of L-shaped protrusions  367  together with a corresponding portion of the light incident surface  361  of the LGP  36  define a receptacle  360 , the receptacle  360  having an open side where free ends of the L-shaped protrusions  367  oppose each other. The receptacle  360  is for receiving a corresponding LED (not shown). 
         [0035]      FIG. 6  is an isometric view of a part of an LGP  46  of a backlight module according to a third embodiment of the present invention. The LGP  46  has a structure similar to that of the LGP  26 . However, a light incident surface  461  of the LGP  46  has a plurality of generally U-shaped protrusions  467  extending therefrom. Each of the U-shaped protrusions  467  includes a main body (not labeled) parallel with the light incident surface  461 , and two arms perpendicularly extending from the light incident surface  461 . The main body of each U-shaped protrusion  467  includes an arc-shaped bulge  4670  at an inner surface thereof. The arc-shaped bulge  4670  protrudes slightly from a main portion of the main body toward the light incident surface  461 . Each of the U-shaped protrusions  467  together with a corresponding portion of the light incident surface  461  defines a receptacle  460  for receiving a corresponding LED (not shown). 
         [0036]    Various modifications and alterations are possible within the ambit of the invention herein. For example, in the first embodiment, the chamfer  262  formed between the inner surface  264  and the top surface  266  of each L-shaped protrusion  267  can instead be a curved or rounded fillet. 
         [0037]    It is to be further understood 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.