Abstract:
A frame ( 34 ) for fixing an optical sheet ( 31 ) thereon includes a frame body ( 35 ) and at least a fastener ( 36 ). The frame body includes a plurality of contiguous sidewalls ( 352, 353, 354 , and  355 ) and at least one latching portion ( 358 ) defined on the at least one of sidewalls. The fastener is mounted into the latching portion correspondingly such that the optical sheet is fixed on the top portions of sidewalls of the frame body. A backlight module using the frame is also provided, which has a lightweight, and also can be assembled easily.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a frame typically used in a backlight module, more particularly a bottom-lighting type backlight module typically used in a liquid crystal display (LCD). 
     DISCUSSION OF THE RELATED ART 
     In a liquid crystal display device, liquid crystal is manipulated to provide images for display. However, liquid crystal is a substance that does not itself illuminate light. Instead, the liquid crystal relies on light received from a light source, and thereby can display images and data. In the case of a typical liquid crystal display, a backlight module powered by electricity supplies the needed light. 
     Typically, a bottom-lighting type backlight module includes a plurality of light sources, a number of optical sheets, and a frame fixing the plurality of light sources and accommodating the optical sheets. The optical sheets can be selected from the group consisting of a diffusing plate, a prism sheet, or a brightness enhancement film. The optical sheets are used to improve the backlight module&#39;s optical uniformity. 
       FIG. 8  shows a typical backlight module  10 . The frame  10  includes a bottom frame  11 , a top frame  12 , a plurality of light sources  13 , a reflective sheet  14 , and an optical sheet  16 . The bottom frame  111  includes a base (not shown) and four sidewalls  112  extending from a periphery of the base to define a recess  116 . A plurality of screw holes  114  is defined in top portions of the sidewalls  112 . The top frame  12  has a frame body  121  defining a rectangular opening  123  therein, and a plurality of screw holes  124  disposed on the frame body  121  corresponding to the screw holes  1114  of the sidewalls  112 . The reflective sheet  14  is positioned on the base of the bottom frame  11 . The light sources  13  are aligned regularly above the reflective sheet  14  in the bottom frame  11 . The optical sheet  16  is supported on the top of the sidewalls  112  of the bottom frame  11 . The top frame  12  can be mounted onto the top of the bottom frame  111  by locking a plurality of screws (not shown) through the corresponding screw holes  114  and  124 , so as to fix the optical sheet  16  tightly on the top portions of the sidewalls  112 . 
     However, the procedure of assembling the backlight module  10  is complex and complicated, because it requires the screws to be individually locked through the screw holes  114  of the bottom frame  111  and the top frame  12 . In addition, the top frame  12  makes the backlight module  10  relatively heavy, and adds to manufacturing costs. 
     What is needed, therefore, is a frame and backlight module using the frame which can overcome the above-described shortcomings. 
     SUMMARY 
     In one aspect, a frame for fixing an optical sheet thereon according to a preferred embodiment includes a frame body and at least one fastener. The frame body includes a plurality of contiguous sidewalls and at least one latching portion defined on at least one of the sidewalls. A supporting ledge is defined at inner sides of top portions of the sidewalls for supporting the optical sheet. Each latching portion includes at least one first latching slot defined at an inner surface of the top portion of at least one of the sidewalls adjacent to the supporting ledge, and at least one first protrusion protruding out from an outer surface of the top portion of the at least one sidewall. The at least one first latching slot and the at least one first protrusion are on opposite sides of the top portion of the at least one sidewall. The at least one fastener is mounted into the at least one latching portion correspondingly such that the optical sheet is fixed on the top portions of the sidewalls. 
     In another aspect, a backlight module according to a preferred embodiment includes a plurality of light sources, at least one optical sheet and a frame. The same frame as described in the previous paragraph is employed in this embodiment. The optical sheet is fixed on the top portions of the frame body by the fastener mounted into the latching portion of the frame body. The light sources are regularly arranged in the frame body under the optical sheet. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present frame and related backlight module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is an abbreviated, schematic, exploded isometric view of a backlight module according to a first preferred embodiment of the present invention. 
         FIG. 2  is an enlarged view of a circled portion II of  FIG. 1 . 
         FIG. 3  is an enlarged view of a circled portion III of  FIG. 1 . 
         FIG. 4  is an enlarged, assembled view of the backlight module of  FIG. 1 . 
         FIG. 5  is an abbreviated, schematic, exploded isometric view of a frame according to a second preferred embodiment of the present invention. 
         FIG. 6  is an abbreviated, schematic, exploded isometric view of a frame according to a third preferred embodiment of the present invention. 
         FIG. 7  is an abbreviated, schematic, exploded isometric view of a frame according to a fourth preferred embodiment of the present invention. 
         FIG. 8  is an abbreviated, schematic, exploded isometric view of a conventional backlight module. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made to the drawings to describe preferred embodiments of the present frame and backlight module, in detail. 
     Referring to  FIGS. 1 and 2 , a backlight module  30  in accordance with a first preferred embodiment is shown. The backlight module  30  includes an optical sheet  31 , a plurality of light sources  32 , a reflective sheet  33 , and a frame  34 . The frame  34  includes a frame body  35  and two fasteners  36 . The frame body  35  includes a rectangular base  351  and four sidewalls  352 ,  353 ,  354 , and  355  formed at a periphery of the base  351 , thereby cooperatively defining a recess  356 . The sidewall  353  defines two latching portions  358  at a top area thereof. The reflective sheet  33  is disposed on the base  351 . The optical sheet  31  is fixed on top of the frame body  35  by mounting the two fasteners  36  into the two latching portions  358  of the frame body  35 . The light sources  32  are regularly arranged within the frame body  35  between the optical sheet  31  and the reflective sheet  33 . The light sources  32  are configured for emitting light to the optical sheet  31 . The reflective sheet  33  is configured for reflecting light to the optical sheet  31 , so as to increase a light energy utilization rate of the backlight module  30 . The light is refracted and diffused in the optical sheet  31 , so that substantially planar light is outputted from the optical sheet  31 . In this embodiment, the optical sheet  31  is a light diffusion sheet. 
     A supporting ledge  359  is defined along an inner side of top areas of the four sidewalls  352 ,  353 ,  354 , and  355 . That is, the supporting ledge  359  is configured to be a continuous recessed shelf at top surface portions of the four sidewalls  352 ,  353 ,  354 , and  355 . A size of the optical sheet  31  is configured to conform with a size defined by inner boundaries of the sidewalls  352 ,  353 ,  354 , and  355  that surround the supporting ledge  359 . Thus the optical sheet  31  can be fittingly received between the sidewalls  352 ,  353 ,  354 , and  355  and supported on the supporting ledge  359  of the frame body  35 . 
     The two latching portions  358  are separate from each other but aligned with each other at the top area of the sidewall  353 . Each latching portion  358  includes two latching slots  3582  and two protrusions  3584 . The two latching slots  3582  are separate from each other, and are defined in an inner surface portion of the top area of the sidewall  353  that bounds the supporting ledge  359 . The two protrusions  3584  protrude out from an outer surface of the top area of the sidewall  353  between the two latching slots  3582 . 
     Each fastener  36  includes a mounting plate  361 , and a retaining plate  362  that extends perpendicularly from a side of the mounting plate  361 . The mounting plate  361  defines two openings  3612  therein corresponding to the two protrusions  3584 . The retaining plate  362  defines two hooked tabs  3622  at two ends thereof corresponding to the two latching slots  3582 . Each hooked tab  3622  runs parallel to the mounting plate  361 . A size of the hooked tab  3622  is configured for mating in the corresponding latching slot  3582 , and a size of the opening  3612  is configured for receiving the corresponding protrusion  3584 . A width of the retaining plate  362  is configured to be approximately equal to or larger than a transverse width of the sidewall  353 . When each of the fasteners  36  is mounted onto the corresponding latching portion  358 , the two protrusions  3584  are inserted into the two openings  3612  for restricting the mounting plate  361  of the fasteners  36  to slide along an outer surface of the sidewall  353 , and the two hooked tabs  3622  are held in the two latching slots  3582  to keep an inner surface of the mounting plate  361  tightly held on the outer surface of the sidewall  353 . Accordingly, the retaining plate  362  can press the optical sheet  31  tightly. 
     Also referring to  FIG. 3 , the sidewall  355  defines a plurality of protruding rims  357  at an inner surface of a top area thereof that bounds the supporting ledge  359 . The protruding rims  357  and the supporting ledge  359  cooperatively defines a receiving channel  360  for receiving the optical sheet  31 . In addition, a rubber film may be formed on a bottom surface of each protruding rim  357  that faces the supporting ledge  359 . The rubber film improves friction between the protruding rim  357  and the optical sheet  31  in Thereby, the optical sheet  31  is restricted from moving along a direction parallel to the sidewall  355  in the event that the frame  34  sustains shock or vibration. 
     Referring to  FIG. 4 , the process of assembling the optical sheet  31  onto the frame body  35  is simple. Firstly, one end of the optical sheet  31  is inserted into the receiving channel  360  of the sidewall  355 , so that the optical sheet  31  is supported on the supporting ledge  359  thereat; secondly, the two fasteners  36  are mounted onto the corresponding two latching portions  358  of the frame body  35 , whereby the protrusions  3584  are inserted into the openings  3612 , and the hooked tabs  3622  are held in the latching slots  3582 . Therefore, the optical sheet  31  is secured on the securing ledge  359  of the frame body  35  tightly with the cooperative help of the fasteners  36  and the protruding rims  357 . In addition, compared with the above-described conventional backlight module  10 , the present backlight module  30  has a relatively lightweight design because a top frame such as the top frame  12  is not employed. 
     The light sources  32  may be selected from the group consisting of cold cathode fluorescent lamps and light emitting diodes. It is to be understood that the present backlight module is not limited to only employing one optical sheet  31  such as the light diffusion sheet used for uniformly diffusing light emitted from the light source. Rather, any desired combination of optical sheets may be employed. For example, the optical sheets can include at least one light diffusion sheet and at least one prism sheet, or can be other suitable optical sheets for improving optical performance. 
     It is noted that the numbers and shapes of the latching portions  358  and the fasteners  36  are not limited to those as described above and illustrated in relation to the first preferred embodiment. At least one latching portion  358  and at least one fastener  36  should be considered to be within the scope of the present backlight module, as long as the applicable latching portion(s)  358  and fastener(s)  36  cooperatively fix the optical sheet  31  on the frame body  35 . Similarly, the numbers and shapes of the latching slots  3582  and the protrusions  3584  of the latching portions  358 , the numbers and shapes of the openings  3612  and the hooked tabs  3622  of the fasteners  36 , are all not limited to those as described above and illustrated in relation to the first preferred embodiment. It is to be understood that the base  351  of the frame body  35 , and the reflective sheet  33  of the backlight module  30 , can be omitted in other embodiments. 
     Referring to  FIG. 5 , a frame  40  in accordance with the second preferred embodiment is shown. The frame  40  is similar in principle to the frame  34  of the first embodiment, except that fasteners  46  and latching portions  458  of the frame  40  are different. Each latching portion  458  includes two first latching slots  4582  and two second latching slots  4584 . The two first latching slots  4582  are separate from each other, and are defined in an inner surface portion of a top area of a sidewall  453  that bounds a supporting ledge  459 . The two second latching slots  4584  are defined in an outer surface portion of the top area of the sidewall  453  between the two first latching slots  4582 . Each fastener  46  includes a mounting plate  461  and a retaining plate  462 . The mounting plate  461  includes two protrusions  4612  each protruding out from an inner surface thereof, the protrusions  4612  corresponding to the two second latching slots  4584 . The retaining plate  462  includes two hooked tabs  4622  at two ends thereof, corresponding to the two first latching slots  4582 . Each hooked tab  4622  is bent down from the retaining plate  462 , and is parallel to the mounting plate  461 . 
     When each fastener  46  is mounted into the corresponding latching portion  458 , the two protrusions  4612  are inserted into the two second latching slots  4584 , and the two hooked tabs  4622  are held in the two first latching slots  4582 . 
     Referring to  FIG. 6 , a frame  50  in accordance with a third preferred embodiment is shown. The frame  50  is similar in principle to the frame  34  of the first embodiment, except that the frame  50  includes four latching portions  558  and four fasteners  56 . The four latching portions  558  are defined on two opposite sidewalls  553  and  555  respectively. Each latching portion  558  includes two latching slots  5582  and two protrusions  5584 . The four fasteners  56  can be mounted onto the four corresponding latching portions  558 , so as to fix an optical sheet (not shown) on the frame  50 . 
     Referring to  FIG. 7 , a frame  60  in accordance with a fourth preferred embodiment is shown. The frame  60  is similar in principle to the frame  40  of the second embodiment, except that the frame  60  includes a protruding wall  654  protruding out from inner sides of top areas of sidewalls  655  of a frame body  65 . The protruding wall  654  serves as a supporting ledge  659  for supporting an optical sheet (not shown). In this embodiment, the frame  60  is lightweight because the sidewalls  655  of the frame body  65  are configured to be thin. 
     Finally, while particular embodiments have been described above, the description is illustrative of principles of the invention and is not to be construed as limiting the invention. Therefore, various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.