Abstract:
An exemplary a light guide plate ( 11 ) includes a top surface ( 112 ), a bottom surface ( 113 ) opposite to the top surface, and a side surface ( 114 ) between the top surface and the bottom surface. A protrusion ( 116 ) extends from the side surface. A thickness of at least part of the protrusion decreases with increasing distance away from the side surface. A backlight module ( 10 ) and a liquid crystal display device ( 1 ) employing such a light guide plate are also provided.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to light guide plates, and more particularly to a light guide plate configured to be stably and compactly retained in a frame of a backlight module of a liquid crystal display (LCD) device.  
       GENERAL 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 are also very thin. The liquid crystal molecules in a liquid crystal display do not emit any light themselves. The liquid crystal molecules have to be lit by a light source so as to clearly and sharply display text and images. Thus, a backlight module for a liquid crystal display is generally needed.  
         [0003]     A typical backlight module generally includes a plastic frame and a light guide plate (LGP). The light guide plate can be positioned in the plastic frame by way of a plurality of rectangular protrusions at a side surface of the light guide plate engaging in a plurality of corresponding grooves of the plastic frame. On the one hand, to make the backlight module stable, the protrusions can be made to have a same thickness as that of the light guide plate, and the plastic frame can be made to be a little thicker than the protrusions. However, this configuration means that the backlight module has an increased thickness. On the one hand, to make the backlight module thin, the protrusions can be made to be thinner than the light guide plate. However, with this configuration, it is difficult to manufacture the protrusions, and the strength of the protrusions is reduced. If one or more of the protrusions fractures or breaks, the backlight module may become unstable.  
         [0004]     What is needed, therefore, is a light guide plate that can overcome the above-described deficiencies. What are also needed are a backlight module and a liquid crystal display device employing such a light guide plate.  
       SUMMARY  
       [0005]     In a preferred embodiment, a light guide plate includes a top surface, a bottom surface opposite to the top surface, and a side surface between the top surface and the bottom surface. A protrusion extends from the side surface. A thickness of at least part of the protrusion decreases with increasing distance away from the side surface. A backlight module and a liquid crystal display device employing such a light guide plate are also provided.  
         [0006]     Other advantages and novel features 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  
       [0007]      FIG. 1  is an exploded, side view of a liquid crystal display device employing a backlight module according to a first embodiment of the present invention.  
         [0008]      FIG. 2  is an exploded, isometric view of the backlight module of  FIG. 1 , the backlight module employing a light guide plate according to a first embodiment of the present invention.  
         [0009]      FIG. 3  is an enlarged view of a circled portion III of  FIG. 2 .  
         [0010]      FIG. 4  is similar to  FIG. 3 , but showing a corresponding view in the case of a light guide plate according to a second embodiment of the present invention.  
         [0011]      FIG. 5  is similar to  FIG. 3 , but showing a corresponding view in the case of a light guide plate according to a third embodiment of the present invention.  
         [0012]      FIG. 6  is similar to  FIG. 3 , but showing a corresponding view in the case of a light guide plate according to a fourth embodiment of the present invention.  
         [0013]      FIG. 7  is similar to  FIG. 3 , but showing a corresponding view in the case of a light guide plate according to a fifth embodiment of the present invention.  
         [0014]      FIG. 8  is similar to  FIG. 3 , but showing a corresponding view in the case of a light guide plate according to a sixth embodiment of the present invention.  
         [0015]      FIG. 9  is similar to  FIG. 3 , but showing a corresponding view in the case of a light guide plate according to a seventh embodiment of the present invention.  
         [0016]      FIG. 10  is similar to  FIG. 3 , but showing a corresponding view in the case of a light guide plate according to an eighth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]     Reference will now be made to the drawings to describe the preferred embodiments in detail.  
         [0018]     Referring to  FIG. 1 , a liquid crystal display device  1  includes a backlight module  10 , and a liquid crystal panel  13  positioned adjacent to the backlight module  10 . Referring to  FIG. 2 , the backlight module  10  includes a light guide plate  11 , and a plastic frame  12  for positioning the light guide plate  11  therein. The light guide plate  11  includes a light incident surface  110 , a top surface  112  adjacent the light incident surface  110 , a bottom surface  113  opposite to the top surface  112 , and two opposite side surfaces  114  each adjacent to the light incident surface  110 . Each side surface  114  has two first protrusions  115  and a second protrusion  116  each integrally extending therefrom. The first protrusions  115  are arranged near two ends of the side surface  114  respectively, and the second protrusion  116  is arranged between the first protrusions  115 . Each of the first and second protrusions  115 ,  116  has a same sized triangular cross-sectional configuration. However, the first protrusions  115  have a same orientation, and the second protrusion  116  has an orientation which is inverted relative to the orientation of the first protrusions  115 . The plastic frame  12  includes a plurality of grooves  120  respectively corresponding to the first protrusions  115  and the second protrusion  116  of the light guide plate  11 .  
         [0019]     Referring also to  FIG. 3 , the second protrusion  116  has a right-angled triangle profile. The second protrusion  116  defines a two-dimensional inmost extremity  1160  where it integrally extends from the side surface  114  of the light guide plate  11 , a lower surface  1164  perpendicularly adjoining the inmost extremity  1160 , and an upper surface  1166  adjoining the inmost extremity  1160  and the lower surface  1164 . A height of the inmost extremity  1160  is the same as that of the side surface  114 . A thickness of the second protrusion  116  decreases from an inmost end thereof at the side surface  114  to an outmost end thereof. That is, the second protrusion  116  is wedge-shaped, with the lower surface  1164  being coplanar with the bottom surface  113  of the light guide plate  11 , and the upper surface  1166  adjoining the top surface  112  of the light guide plate  11 . The first protrusions  115  and the second protrusion  116  can be manufactured by an injection molding method together with the light guide plate  11 .  
         [0020]     The height of the inmost extremity  1160  of each second protrusion  116  is the same as that of the side surface  114 , which enables the second protrusion  116  to have good mechanical strength even when the light guide plate  11  is very thin. Similarly, each first protrusion  115  can have good mechanical strength even when the light guide plate  11  is very thin. Moreover, the corresponding groove  120  of the plastic frame  12  is wedge-shaped in a configuration complementary to the wedge shape of the second protrusion  116 . That is, a height of the groove  120  progressively decreases from an inmost end thereof to an outmost end thereof. Correspondingly, a height of the plastic frame  12  at the groove  120  progressively increases from the inmost end of the groove  120  to the outmost end of the groove  120 . This enables a portion of the plastic frame  12  at the groove  120  to have relatively high mechanical strength. Similarly, portions of the plastic frame  12  at the grooves  120  corresponding to the first protrusions  115  also can have relatively high mechanical strength. Thus the plastic frame  12  overall has good mechanical strength. For all these reasons, the backlight module  10  can have good mechanical strength even if the light guide plate  11  is very thin.  
         [0021]     Referring to  FIG. 4 , a light guide plate  21  according to a second embodiment of the present invention is similar to the light guide plate  11  of the first embodiment. However, in the light guide plate  21 , each of protrusions  216  at two side surfaces  214  has an isosceles triangle profile. Each protrusion  216  defines a two-dimensional inmost extremity  2168  where it integrally extends from the side surface  214 , a lower surface  2166  obliquely adjoining the inmost extremity  2168 , and an upper surface  2164  obliquely adjoining the inmost extremity  2168  and adjoining the lower surface  2166 . That is, the protrusion  216  is wedge-shaped, with the lower surface  2166  and the upper surface  2164  having a same size and adjoining the inmost extremity surface  2168  at a same oblique angle.  
         [0022]     Referring to  FIG. 5 , a light guide plate  31  according to a third embodiment of the present invention is similar to the light guide plate  11  of the first embodiment. However, in the light guide plate  31 , each of protrusions  316  at two side surfaces  314  has a trapezoidal profile. Each protrusion  316  defines a two-dimensional inmost extremity  3162  where it integrally extends from the side surface  314 , an upper surface  3164  perpendicularly adjoining the inmost extremity  3162 , a lower surface  3166  perpendicularly adjoining the inmost extremity  3162 , and a lateral surface  3168  obliquely adjoining the upper surface  3164  and the lower surface  3166 . That is, the protrusion  316  is generally wedge-shaped, with the upper surface  3164  being coplanar with a top surface (not labeled) of the light guide plate  31 , and the lower surface  3166  being coplanar with a bottom surface (not labeled) of the light guide plate  31  and having a size greater than that of the upper surface  3164 .  
         [0023]     Referring to  FIG. 6 , a light guide plate  41  according to a fourth embodiment of the present invention is similar to the light guide plate  11  of the first embodiment. However, in the light guide plate  41 , each of protrusions  416  at two side surfaces  414  has a trapezoidal profile. Each protrusion  416  defines a two-dimensional inmost extremity  4162  where it integrally extends from the side surface  414 , an upper surface  4164  obliquely adjoining the inmost extremity  4162 , a lower surface  4166  perpendicularly adjoining the inmost extremity  4162 , and a lateral surface  4168  obliquely adjoining the upper surface  4164  and perpendicularly adjoining the lower surface  4166 . That is, the protrusion  416  is generally wedge-shaped, with the lower surface  4166  being coplanar with a bottom surface (not labeled) of the light guide plate  41 , and the lateral surface  4168  being parallel to the side surface  414 .  
         [0024]     Referring to  FIG. 7 , a light guide plate  51  according to a fifth embodiment of the present invention is similar to the light guide plate  41  of the fourth embodiment. However, in the light guide plate  51 , each of protrusions  516  at two side surfaces  514  has another kind of trapezoidal profile. Each protrusion  516  defines a two-dimensional inmost extremity  5162  where it integrally extends from the side surface  514 , an upper surface  5164  obliquely adjoining the inmost extremity  5162 , a lower surface  5166  obliquely adjoining the inmost extremity  5162 , and a lateral surface  5168  obliquely adjoining the upper surface  5164  and the lower surface  5166 . That is, the protrusion  516  is generally wedge-shaped, with the upper surface  5164  and the lower surface  5166  having a same size and adjoining the inmost extremity  5162  at a same oblique angle, and the lateral surface  5168  being parallel to the side surface  514 .  
         [0025]     Referring to  FIG. 8 , a light guide plate  61  according to a sixth embodiment of the present invention is similar to the light guide plate  11  of the first embodiment. However, in the light guide plate  61 , each of protrusions  616  at two side surfaces  614  has a pentagonal profile. Each protrusion  616  defines a two-dimensional inmost extremity  6162  where it integrally extends from the side surface  614 , an upper surface  6164  perpendicularly adjoining the inmost extremity  6162 , a lower surface  6166  perpendicularly adjoining the inmost extremity  6162 , a first lateral surface  6167  perpendicularly adjoining the lower surface  6166 , and a second lateral surface  6168  obliquely adjoining the upper surface  6164  and the first lateral surface  6167 . That is, the protrusion  616  is generally wedge-shaped, with the upper surface  6164  being coplanar with a top surface (not labeled) of the light guide plate  61 , the lower surface  6166  being coplanar with a bottom surface (not labeled) of the light guide plate  61 , and the second lateral surface  6168  being parallel to the side surface  614 .  
         [0026]     Referring to  FIG. 9 , a light guide plate  71  according to a seventh embodiment of the present invention is similar to the light guide plate  11  of the first embodiment. However, in the light guide plate  71 , each of protrusions  716  at two side surfaces  714  has a pentagonal profile. Each protrusion  716  defines a two-dimensional inmost extremity  7162  where it integrally extends from the side surface  714 , a top surface  7164  perpendicularly adjoining the inmost extremity  7162 , an upper surface  7166  perpendicularly adjoining the inmost extremity  7162 , a first lateral surface  7167  obliquely adjoining the upper surface  7164 , and a second lateral surface  7168  obliquely adjoining the upper surface  7166  and adjoining the first lateral surface  7167 . That is, the protrusion  716  is generally wedge-shaped, with the upper surface  7164  being coplanar with a top surface (not labeled) of the light guide plate  71 , the lower surface  7166  being coplanar with a bottom surface (not labeled) of the light guide plate  71 , and the first lateral surface  7167  and the second lateral surface  7168  having a same size and respectively adjoining the upper surface  7164  and the lower surface  7166  at a same oblique angle.  
         [0027]     Referring to  FIG. 10 , a light guide plate  81  according to an eighth embodiment of the present invention is similar to the light guide plate  71  of the seventh embodiment. However, in the light guide plate  81 , each of protrusions  816  at two side surfaces  814  has a hexagonal profile. Each protrusion  816  defines a two-dimensional inmost extremity  8162  where it integrally extends from the side surface  814 , an upper surface  8164  perpendicularly adjoining the inmost extremity  8162 , a lower surface  8166  perpendicularly adjoining the inmost extremity  8162 , a first lateral surface  8168  obliquely adjoining the upper surface  8164 , a second lateral surface  8169  obliquely adjoining the lower surface  8166 , and a third lateral surface  8167  obliquely adjoining the first lateral surface  8168  and the second lateral surface  8169 . That is, the protrusion  816  is generally wedge-shaped, with the upper surface  8164  being coplanar with a top surface (not labeled) of the light guide plate  81 , the lower surface  8166  being coplanar with a bottom surface (not labeled) of the light guide plate  81 , the first lateral surface  8168  and the second lateral surface  8169  having a same size and respectively adjoining the upper surface  8164  and the lower surface  8166  at a same oblique angle, and the third lateral surface  8167  being parallel to the side surface  814 .  
         [0028]     Further or alternative embodiments may include the following. There can be only one first protrusion and one second protrusion positioned at each of one or more side surfaces of the light guide plate. There can be only one first protrusion positioned at each of one or more side surfaces of the light guide plate. There can be only one second protrusion positioned at each of one or more side surfaces of the light guide plate.  
         [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.