Abstract:
An exemplary backlight module ( 200 ) includes a light guide plate ( 50 ) and a frame ( 80 ). The light guide plate includes a plurality of surfaces, and at least one of the surfaces each defines at least one groove ( 502 ) thereat. The frame includes a plurality of sidewalls, and at least two of the sidewalls each have at least one protrusion ( 802 ). The protrusions are engaged in the grooves fixing the light guide plate in the frame. In addition, an exemplary liquid crystal display is also provided.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to backlight modules, and liquid crystal display devices that use backlight modules.  
       GENERAL BACKGROUND  
       [0002]     Due to the non-self-emitting characteristic of liquid crystals of a liquid crystal display (LCD), a backlight module is commonly included in an LCD to provide an adequate and uniform flat light source to enable the LCD to display images.  
         [0003]     A backlight module mainly includes a light source, a light guide plate (LGP) and a frame. The light source is positioned at the light entrance surface in relation to the LGP. The LGP directs the linear or point light emitted from the light source and transforms into a uniform flat light so as to display images. The frame is provided as a fixed support for the other components (e.g. diffusers, brightness enhancing films, and reflection sheets, etc.) of the backlight module. In conventional art, the frame and the LGP are connected by the protrusion of the LGP and the groove of the frame.  
         [0004]     Referring to  FIG. 10 , an exploded view of a conventional backlight module  10  is illustrated. The backlight module includes a light guide plate (LGP)  11 , a frame  12  for mounting the LGP  11 , a reflection sheet  15 , a printed circuit board (PCB)  14 , and a plurality of light emitting elements  13  mounted at the PCB  14 .  
         [0005]     The LGP  11  includes a light exit surface  111 , a light entrance surface  112  intersecting the light exit surface  111 , a bottom surface  113  which is opposite to the light exit surface  111 , and two opposing lateral surfaces  115  which are adjacent to the light entrance surface  112 . The lateral surfaces  115  have six protrusions  114 . A group of three protrusions  114  is located at each of the opposing lateral surfaces  115  and distributed symmetrically, and the thickness of the protrusion  114  is smaller than the thickness of the lateral surface  115 . The four protrusions  114  located on both ends of each lateral surfaces  115  are at the same level to the light exit surface  111  and the intermediate two protrusions  114  are at the same level of the bottom surface  113 . The frame  12  includes a plurality of openings  122  for embedding the light emitting elements  13  and six grooves  123 . Those grooves  123  are set opposing to the protrusions  114  so that in connection with the grooves  123  and the protrusions  114  the LGP  11  can be fixed at the frame  12 .  
         [0006]     The backlight module  10  can be assembled by the following method. Firstly, the LGP  11  is mounted at the frame  12  so as to inset the protrusions  114  of the LGP  11  to the grooves  123  of the frame  12 . Subsequently, the PCB  14  is set into the frame  12  so as to mount the light emitting elements  13  to the openings  122  of the frame  12 . Finally, the reflection sheet  15  is set at the bottom surface  13  of the LGP  11 .  
         [0007]     The frame  12  is usually made of plastic, and the light emitting element  13  is usually a light emitting diode (LED).  
         [0008]     However, the disadvantage of the thinner LGP  11  is that the thinner protrusions which might be difficult to be formed in the injection molding process. In particular, residual stress differentials may result in warpage and/or weakness of the LGP  11  and/or the protrusions.  
         [0009]     Accordingly, what is needed is a backlight module configured to be able to be formed easily in the injection molding process.  
       SUMMARY  
       [0010]     An exemplary backlight module includes a light guide plate and a frame. The light guide plate includes a plurality of surfaces, and at least one of the surfaces each defines at least one groove thereat. The frame includes a plurality of sidewalls, and at least two of the sidewalls each have at least one protrusion. The protrusions are engaged in the grooves fixing the light guide plate in the frame.  
         [0011]     The at least one protrusion is rectangular or trapezoidal in shape.  
         [0012]     A detailed description of embodiments of the present invention is given below with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     Embodiments of the invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings. In the drawings, all the views are schematic.  
         [0014]      FIG. 1  is an exploded view of a backlight module in accordance with a first embodiment of the present invention.  
         [0015]      FIG. 2  is an assembled view of part of the backlight module shown in  FIG. 1 .  
         [0016]      FIG. 3  is an enlarged side view of part of the backlight module taken along line III-III of  FIG. 2 .  
         [0017]      FIG. 4  is an enlarged side view of part of the backlight module taken along line III-III of  FIG. 2  assembled with a frame, a light guide plate, a reflect sheet, a diffuser and a brightness enhance film.  
         [0018]      FIG. 5  is an enlarged side view of a backlight module in accordance with a second embodiment of the present invention.  
         [0019]      FIG. 6  is an exploded view of a backlight module in accordance with a third embodiment of the present invention.  
         [0020]      FIG. 7  is an exploded view of a backlight module in accordance with a fourth embodiment of the present invention.  
         [0021]      FIG. 8  is an exploded view of a backlight module in accordance with a fifth embodiment of the present invention.  
         [0022]      FIG. 9  is an exploded view of a liquid crystal display of the present invention.  
         [0023]      FIG. 10  is an exploded view of a conventional backlight module. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0024]     Referring to  FIG. 1 , illustrated an exploded view of a backlight module  200  in accordance with a first embodiment of the present invention. The backlight module  200  includes a brightness enhance film  20 , a diffuser  40 , a light guide plate (LGP)  50 , a printed circuit board (PCB)  60 , a plurality of light emitting elements  70  mounted at the PCB  60 , a frame  80  for holding the LGP  50 , and a reflection sheet  90 .  
         [0025]     The LGP  50  includes a light exit surface  501 , a bottom surface  503  which is opposite to the light exit surface  501 , two opposite lateral surfaces  504 , and six grooves  502 . Three of grooves  502  are located at the edge of light exit surface  501 , also known as “the upper side” and the other three grooves  502  are located on the edge of bottom surface  503 , also known as “the lower side”. The upper and the lower side grooves  502  are offset relative to each other.  
         [0026]     The frame  80  includes a first sidewall  804 , a second sidewall  805 , a third sidewall  806  and a fourth sidewall  807 . The sidewalls  804 ,  805 ,  806 ,  807  are used to hold the LGP  50 . The first sidewall  804  has a plurality of openings  803  for embedding the light emitting elements  70  thereat. There are six protrusions  802  rectangular in shape on the second sidewall  805  and the fourth sidewall  807 . The positions of the six protrusions  802  are corresponding to the grooves  502  on the LGP  50 , such that by connection of the protrusions  802  in the grooves  502 , the LGP  50  can be fixed into the frame  80 .  
         [0027]     In the preferred embodiment, the foregoing PCB  60  can be a flexible printed circuit (also known as FPC). The light emitting element  70  can be a light emitting diode (LED), and the frame  80  can be made of plastic.  
         [0028]     The protrusions  802  are set on the frame  80 . Generally, the frame  80  is injected from a pin-point gate which has several runners. In comparison with conventional techniques, to set protrusions  802  on the frame  80  according to the present invention is easier for injection molding.  
         [0029]     Referring to  FIGS. 2 and 3 , the thickness D 2  of protrusion  802  is greater than the thickness D 1  of groove  502 . In the preferred embodiment, the thickness D 1  is 0.1 mm (or thinner) and the thickness D 2  is 0.3 mm. In fabrication, the groove  502  is connected with the protrusion  802  that the LGP can be fixed into the frame  80 . Subsequently, the reflection sheet  90  is set at the bottom surface  503  of the LGP  50 . While combining the reflection sheet  90  to the LGP  50 , the surface of the reflection sheet  90  can be substantial at the same level with the protrusion  802 .  
         [0030]     Referring to  FIG. 4 , the diffuser  40  and brightness enhance film  20  are set sequentially at the light exit surface  501  of the LGP  50 . While combining the diffuser  40  and the brightness enhance film  20  to the LGP  50 , the surface of the brightness enhance film  20  can be substantially at the same level with the protrusion  802 .  
         [0031]     It should be noted that there is no protrusion on the LGP  50  then during the mold releasing process for the LGP  50 , it is easier to release without deformation. On the other hand, the structure of the LGP  50  is simpler than the conventional technique (with protrusion on the edge of the LGP) that there is much less residual stress remaining on the LGP. Accordingly, the thinner LGP can be achieved so as to reduce the whole thickness of the backlight module. Therefore, the thickness D 1  of the groove  502  on the LGP  50  can be smaller than 0.1 mm and the optical characteristics are not affected without protrusions on the LGP. Additionally, the protrusions  802  are set on the frame  80 . Generally, the molding for the frame making is injected from pin-point gate with several runners that in compare with the conventional technique, to set protrusions on the frame, the present invention is much easier for injection molding. The thickness D 2  of protrusion  802  can be larger than 0.3 mm. Although the thickness D 2  is larger than D 1 , in connection with the frame  80  and the LGP  50  and combining with other optical films, the total thickness are not change. Consequently, the protrusion  802  can provide sufficient strength for the structure so as to fix the LGP  50  on the frame  80  effectively.  
         [0032]     Referring to  FIG. 5 , illustrated an enlarged side view of a backlight module in accordance with a second embodiment of the present invention. The difference between first embodiment and second embodiment is that the shape of the protrusion  812  of the frame  81  can be trapezoid, and shape of the LGP  51  is corresponding with thereof.  
         [0033]     Referring to  FIG. 6 , illustrated an exploded view of a backlight module  300  in accordance with a third embodiment of the present invention. The difference between first embodiment and third embodiment is that the LGP  52  includes twelve grooves  522  also known as six pairs and set correspondingly with each other. In each pair grooves, one may be set on the edge of light exit surface  521  and the other may be set on the edge of bottom surface  523  alternatively. For the four pair grooves of the two end of the LGP  52 , the position of the upper side (also known as the light exit side) grooves and the lower side (also known as the bottom side) grooves may be interlaced with each other. Furthermore, the intermediate grooves on the LGP  52  are set as opposite dual.  
         [0034]     Relatively, the frame  82  also includes twelve protrusions  822  that the protrusions  822  of the frame  82  can link up the grooves  522  on the LGP so as to fix the LGP  50  into the frame  82 .  
         [0035]     Referring to  FIG. 7 , illustrated a schematic view of backlight module according to the fourth embodiment of the present invention. The difference between first embodiment and fourth embodiment is that each opposite lateral surfaces  534  of the LGP  53  may set one groove  532  symmetrically and respectively. Each groove  532  is located between the light exit surface  531  and the bottom surface  533 . Furthermore, the thickness of the groove  532  is smaller than the thickness of the LGP  53 .  
         [0036]     Relatively, the frame  83  includes two protrusions  832 . The location of the two protrusions  832  relates to the location of the two grooves  532  on the LGP  53  that the protrusion  832  can be inserted to the groove  532  while combining the LGP  53  to the frame  83 .  
         [0037]     Referring to  FIG. 8 , an exploded view of a backlight module in accordance with a fifth embodiment of the present invention is illustrated. The difference between the fourth embodiment and the fifth embodiment is that the frame  84  here further may include a bottom plate  845 . The thickness of the groove  542  is substantially identical to the thickness of the LGP  54  that the groove  542  penetrates the lateral edge of the LGP  54 .  
         [0038]     Referring to  FIG. 9 , a liquid crystal display  3  includes the aforementioned backlight module  300  and a liquid crystal panel  310  which is set at opposite side of the backlight module  300 .  
         [0039]     While the invention has been described by way of examples and in terms of preferred embodiments, 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 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.