Abstract:
A backlight module ( 200 ) includes a fame ( 55 ) having a plurality of side walls ( 551, 552, 553, 554 ); a light guide plate ( 53 ) received in the frame, having a light incident surface ( 533 ); at least one spring element ( 5523 ), having a spring finger ( 5525 ) and a connecting arm ( 5524 ) connecting the spring finger and one side wall of the frame; and at least one radiation element ( 56 ) disposed between the spring finger and the light incident surface. The width of the at least one radiation element is larger than a distance between the light incident surface and the spring finger in a free state.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a backlight module and a liquid crystal display (LCD) device using the same, and more particularly to a backlight module with a spring finger. 
       GENERAL BACKGROUND 
       [0002]    Liquid crystal displays are commonly used as display devices for compact electronic apparatuses, because they not only are very thin but also provide good quality images with little power consumption. 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]      FIG. 9  shows a schematic, top view of a conventional LCD  100 . The LCD  100  includes a flexible printed circuit board (FPC)  110 , a liquid crystal display panel  120 , a plastic frame  130 , two light emitting diodes (LEDs)  140  cooperatively serving as a light source, and a light guide plate  150 . 
         [0004]    The FPC  110  connects with the liquid crystal display panel  120 , and includes a main circuit area  111  and a light source setting area  112 . The light source setting area  112  extends from the main circuit area  111 . The LEDs  140  are arranged on the light source setting area  112  of the FPC  110 . The frame  130  includes a depressed portion  131 , and the depressed portion  131  has two openings  132 . 
         [0005]    The LCD  100  can be assembled according to the following sequence: firstly, setting the light guide plate  150  inside the frame  130 ; secondly, putting the light source setting area  112  into the depressed portion  131 , and placing the LEDs  140  into the openings  132 ; thirdly, attaching the main circuit area  111  to the frame  130  and the light guide plate  150 ; and finally, attaching the liquid crystal display panel  120  to the frame  130 . 
         [0006]    However, the above-mentioned conventional liquid crystal display has the following problems. 
         [0007]    The sizes of the openings  132  may not accurately match the sizes of the LEDs  140 , due to imprecise manufacturing. When this happens, small gaps exist between the LEDs  140  and the light guide plate  150  after assembly. These gaps may diminish the emitting luminance of the light guide plate  150 . 
         [0008]      FIG. 10  is a graph showing the negative impact of the above mentioned gaps on the effective utilization of the emitting luminance. X represents the distance between the LEDs  140  and a light incident surface (not labeled) of the light guide plate  150  in millimeters (mm), and Y represents the relative emitting luminance of the light guide plate  150  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 gap, the lower the value of the relative emitting luminance. 
         [0009]    What is needed, therefore, is a backlight module and a liquid crystal display device using the same that overcome the above-described deficiencies. 
       SUMMARY 
       [0010]    In a preferred embodiment, a backlight module includes a fame having a plurality of side walls; a light guide plate received in the frame, having a light incident surface; at least one spring element, having a spring finger and a connecting arm connecting the spring finger and one side wall of the frame; and at least one radiation element disposed between the spring finger and the light incident surface. The width of the at least one radiation element is larger than, a distance between the light incident surface and the spring finger in a free state. 
         [0011]    In another preferred embodiment, a liquid crystal display device a liquid crystal display panel; and a backlight module disposed adjacent to the liquid crystal display panel. The backlight module has a fame having a plurality of side walls; a light guide plate received in the frame, having a light incident surface; at least one spring element, having a spring finger and a connecting arm connecting the spring finger and one side wall of the frame; and at least one radiation element disposed between the spring finger and the light incident surface. The width of the at least one radiation element is larger than a distance between the light incident surface and the spring finger in a free state. 
         [0012]    In a further another preferred embodiment, a backlight module includes a light guide plate, at least one spring element, and at least one radiation element. The light guide plate has a main body and at least one protruding frame, the main body having a light incident surface, the at least one protruding frame extending from the light incident surface. The at least one spring element has a spring finger and a connecting arm connecting the spring finger and a side wall of the protruding frame, facing the light incident surface. The at least one radiation element is disposed between the spring finger and the light incident surface. The width of the at least one radiation element is larger than a distance between the light incident surface and the spring finger in a free state. 
         [0013]    Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is an exploded, isometric view of an LCD device according to a preferred embodiment of the present invention, the LCD device including a printed circuit board, a frame, a light guide plate, a reflective plate, a bottom tray, and LEDs. 
           [0015]      FIG. 2  is an isometric view of the frame of  FIG. 1 , shown from top side. 
           [0016]      FIG. 3  is an isometric view of the frame of  FIG. 1 , shown from bottom side. 
           [0017]      FIG. 4  is a partially enlarged view of a circled region IV of  FIG. 3 . 
           [0018]      FIG. 5  is a top plan view of the printed circuit board, frame, light guide plate, reflective plate, bottom tray and LEDs of  FIG. 1  assembled together, with the circuit board partially cut away to show two of the LEDs. 
           [0019]      FIG. 6  is an exploded, isometric view of an LCD device according to a second preferred embodiment of the present invention, the LCD device including a printed circuit board, a frame, a light guide plate, a reflective plate, a bottom tray, and LEDs. 
           [0020]      FIG. 7  is an enlarged view of the light guide plate of  FIG. 5 . 
           [0021]      FIG. 8  is an enlarged view of the light guide plate of  FIG. 5 , viewed from another side. 
           [0022]      FIG. 9  is a partially enlarged view of a circled region IX of  FIG. 8 . 
           [0023]      FIG. 10  is a top plan view of the printed circuit board, frame, light guide plate, reflective plate, bottom tray and LEDs of  FIG. 5  assembled together, with the circuit board partially cut away to show two of the LEDs. 
           [0024]      FIG. 11  is a schematic, top plan view of a conventional LCD device prior to assembly thereof, the LCD device including a light guide plate and two LEDs, the light guide plate having a light incident surface. 
           [0025]      FIG. 12  is a graph showing relative emitting luminance (“Y”) of the light guide plate of  FIG. 6  varying as a function of a distance (“X”) between the LEDs and the light incident surface of the light guide plate. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0026]    Reference will now be made to the drawings to describe the preferred embodiments in detail. 
         [0027]      FIG. 1  is an exploded, isometric view of an LCD device according to a preferred embodiment of the present invention. The LCD device  200  includes a liquid crystal display panel  3 , and a backlight module  5 . 
         [0028]    The backlight module  5  includes a plurality of optical films  51 , a frame  55 , a light guide plate  53 , and a reflective plate  54  arranged from top to bottom in that order. The backlight module  5  further includes a plurality of radiation elements  56 , and a printed circuit board  52 . 
         [0029]    The light guide plate  53  includes a light incident surface  533 , and a light emitting surface  534  adjoining the light incident surface  533 . The optical films are provided on the light emitting surface  534 , the reflective plate  54  is provided at a bottom surface (not labeled) thereof. The plurality of radiation elements  56  fixed on the printed circuit board  52  is disposed between the frame  55  and the light guide plate  53 , facing the light incident surface  533  of the light guide plate  53 . 
         [0030]    The printed circuit board  52  includes a connection strip  521  extending from a main body (not labeled) thereof. The radiation elements  56  are attached on the printed circuit board  52 , and cooperatively serve as a light source. The radiation elements  56  are typically light emitting diodes (LEDs). Typically, the printed circuit board  52  is a flexible printed circuit. Each radiation element  56  has a side surface  561  having a groove  562  formed thereon, 
         [0031]    Referring to  FIG. 2  and  FIG. 3 , the frame  55  is shown from different viewing angles. The frame  55  is preferably made of plastic, which includes a first side wall  551 , a second side wall  552 , a third side wall  553 , a fourth side wall  554 . The first side wall  551 , the second side wall  552 , the third side wall  553 , and the fourth side wall  554  cooperatively define a space (not labeled) therebetween. 
         [0032]    The second side wall  552  defines an opening  5521  at one end thereof. A plurality of partition arms  5522  and a plurality of spring elements  5523  are alternately formed along an inside surface of the frame  55  at the second side wall  552 . The partition arms  5522  and the spring elements  5523  are disposed parallel to each other, and extend into the space. Two adjacent partition arms  5522  and one spring elements  5523  formed therebetween define a light source setting area (not labeled). The radiation elements  56  can be respectively disposed in a series of light source setting areas including areas between two adjacent partition arms  5522 , corresponding one spring element  5523 . That is, the radiation elements  556  can be arranged to abut the partition arms  5522  respectively. Each spring element  5523  protrudes toward to the fourth side wall  554 . As shown in  FIG. 4 , each spring element  5523  includes a connecting arm  5524  and a spring finger  5525 . The connecting arm  5524  is strip-shaped, having a predetermined thickness, and connecting the second side wall  552  and the spring finger  5525 . The spring finger  5525  is parallel to the second side wall  552 , spacing a predetermined interval with the second side wall  552 . Each spring finger  5525  has a contacting surface  5526 , corresponding to the radiation element  5523 . A protrusion  5527  is provided at the contacting surface  5526 , extending toward the fourth side wall  554 . which corresponds to the groove  562  of the radiation elements  56 . In assembly, a top surface of the protrusion  5527  can tightly mates with a bottom surface of the groove  562 , i.e. the top surface of the protrusion  5527  can wholly adjoins the bottom surface of the groove  562 . The spring element  5523  is made from the same material of the frame  55 , being integrated on the frame  55 . d    
         [0033]    In assembly, as shown in  FIG. 5 , the printed circuit board, frame, light guide plate, reflective plate, bottom tray and LEDs of  FIG. 1  are assembled together, with the circuit board partially cut away to show two of the LEDs. The light guide plate  53  is received in the space of the frame  55 . The reflective plate  54  is adhered to the bottom surface of the light guide plate  53 . The plurality of optical films  51  is disposed on the light emitting surface  534  of the light guide plate  53 . The printed circuit board  52  with the radiation elements  56  is received in the space adjacent to the second side wall  552 , such that the printed circuit board  52  covers the arms  5522  and the spring element  5523 . The radiation elements  56  are thus received in the series of light source setting areas including the areas between each two adjacent arms  5522 , such that the radiation elements  56  abut the incident surface  533  of the light guide plate  53 . The protrusion  5527  of each spring element  5523  tightly mates with the groove of each radiation elements  56 . Thus, the side surface  561  of the radiation element  56  adjoins the contacting surface  5526  of the spring finger  5525 . The spring finger  5525  of the spring element  5523  presses the radiation element  56  toward the incident surface  533  of light guide plate  53 , so that the light incident surface  533  of the light guide plate  53  is held very close to or against the radiation elements  56 . Thus, the printed circuit board  52  with the radiation elements  56  is also fixed in the frame  55 . The connection strip  521  of the printed circuit board  52  extends out from the opening  5521  of the second side wall  552  of the frame  55 . In addition, a liquid crystal panel  3  is provided on the backlight module  5  to form the liquid crystal display device  200 . 
         [0034]    As shown in  FIG. 4 , the liquid crystal display device  200  utilizes the spring element  5523  to realize a stable fixation of the radiation element  56 . In the assembly process, the spring finger  5525  of the spring element  5523  presses the radiation element  56  toward the incident surface  533  of light guide plate  53 , so that the light incident surface  533  of the light guide plate  53  is held very close to or against the radiation elements  56 . Thereby, distances between the radiation elements  56  and the light incident surface  533  are decreased or even eliminated. This enables the LCD device  200  to provide improved brightness and uniformity of emitting luminance and prevents the light beams from the radiation element  56  from emitting rearward. 
         [0035]    In addition, each connecting arm  5524  connecting with the frame  55  has a width same to the interval between two adjacent partition arms  5522 , and has a predetermined thickness. Thus, the connecting portion between the connecting arm  5524  and the frame  55  has a larger area, and thus the connecting portion does not easily produce rupture therebetween. In addition, the spring finger  5525  of the spring element  5523  is parallel to the second side wall  552  of the frame  552 . Thus, in the assembly process, the process of assembling the radiation elements  56  in the frame  552  just needs pressing the radiation elements  56  downward. And the spring finger  5525  is not easy to be broken off. 
         [0036]      FIG. 5  is an exploded, isometric view of an LCD device according to a second preferred embodiment of the present invention. The LCD device  300  includes a liquid crystal display panel  4 , and a backlight module  6 . 
         [0037]    The backlight module  6  includes a plurality of optical films  61 , a frame  65 , a light guide plate  63 , and a reflective plate  64  arranged from top to bottom in that order. The backlight module  6  further includes a plurality of radiation elements  66 , and a printed circuit board  62 . 
         [0038]    As shown in  FIG. 6  and  FIG. 7  and  FIG. 8 , the light guide plate  63  includes a main body  631  and a plurality of protruding frames  632 . The min body  631  has a light incident surface  633 , and a light emitting surface  634  adjoining the light incident surface  633 , a bottom surface  635  opposite to the light emitting surface  634 . Each protruding frame  632  has a first side wall  6321 , a second side wall  6322 , a third side wall  6323  connecting the first and the second side walls  6321 ,  6322 , and a spring element  636 . The first and the second side walls  6321 ,  6322  vertically connect to the incident surface  633  of the main body  631 , which have a thickness same to that of the main body  631 . Thus, the third side wall  6323  is parallel to the incident surface  633 . The spring element  636  is disposed on the third side wall  6323 , protruding toward the incident surface  633 . The spring element  636  has a structure same to that of the spring element  5523  of the first embodiment. The spring element  636  includes a connecting arm  6361  and a spring finger  6362 . The connecting arm  6361  is strip-shaped, connecting the third side wall  6323  and the spring finger  6362 . The spring finger  6362  is parallel to the third side wall  6323 , spacing a predetermined interval with the third side wall  6323 . Each spring finger  6362  has a contacting surface  6363 . A protrusion  6364  is provided at the contacting surface  6363 , extending from the contacting surface  6363  toward the incident surface  633 . The spring element  636  is made from the same material of the light guide plate  63 , being integrated on the light guide plate  63 . 
         [0039]    The printed circuit board  62  includes a connection strip  621  extending from a main body (not labeled) thereof. The radiation elements  66  are attached on the printed circuit board  62 , and cooperatively serve as a light source. The radiation elements  66  are typically light emitting diodes (LEDs). Typically, the printed circuit board  62  is a flexible printed circuit. Each radiation element  66  has a side surface  661  having a groove  662  formed thereon, which the groove  662  corresponds to the protrusion  6364  of the spring finger  6362 . In assembly, a top surface of the protrusion  6364  can tightly mates with a bottom surface of the groove  662 , i.e. the top surface of the protrusion  6364  can wholly touches the bottom surface of the groove  662 . 
         [0040]    The frame  65  is preferably made of plastic. The frame  65  includes a first side wall  651 , a second side wall  652 , a third side wall  653 , a fourth side wall  654 . The first side wall  651 , the second side wall  652 , the third side wall  653 , and the fourth side wall  654  cooperatively define a space (not labeled) therebetween. The second side wall  652  defines an opening  6521  at one end thereof. A plurality of partition arms  6522  and a plurality of spring elements  6523  are formed along an inside surface of the frame  65  at the second side wall  652 . The partition arms  6522  and the spring elements  6523  are disposed parallel to each other, and extend into the space. The plurality of protruding frames  632  can be respectively disposed in a series of spaces including spaces between two adjacent partition arms  65223 . 
         [0041]    In assembly, the light guide plate  63  is received in the space of the frame  65 . The plurality of protruding frame  632  is adjacent to the second side wall  652 , respectively disposed in a series of spaces including spaces between two adjacent partition arms  65223 . The reflective plate  64  is adhered to the bottom surface of the light guide plate  63 . The plurality of optical films  61  is disposed on the light emitting surface  634  of the light guide plate  63 . The printed circuit board  62  with the radiation elements  66  is received in the space adjacent the second side wall  652 , such that the printed circuit board  62  covers the arms  6522  and the radiation elements  66  are respectively received in the spaces defined by the plurality of protruding frames  632 , such that the radiation elements  66  abut the incident surface  633  of the light guide plate  63 . The top surface of the protrusion  6364  wholly touches the bottom surface of the groove  662 . Thus, the side surface  661  of the radiation element  66  contacts with the contacting surface  6363  of the spring finger  6362 . The spring finger  6362  of the spring element  633  presses the radiation element  66  toward the incident surface  633  of light guide plate  63 , so that the light incident surface  633  of the light guide plate  63  is held very close to or against the radiation elements  66 . Thus, the printed circuit board  62  with the radiation elements  66  is also fixed at the frame  65 . The connection strip  621  of the printed circuit board  62  extends out from the opening  6521  of the second side wall  652  of the frame  65 . In addition, a liquid crystal panel  4  is provided on the backlight module  6  to form the liquid crystal display device  300 . 
         [0042]    The liquid crystal display device  300  utilizes the spring element  636  to realize a stable fixation of the radiation element  66 . In the assembly process, the spring finger  6362  of the spring element  636  presses the radiation element  66  toward the incident surface  633  of light guide plate  63 , so that the light incident surface  633  of the light guide plate  63  is held very close to or against the radiation elements  66 . Thereby, distances between the radiation elements  66  and the light incident surface  633  are decreased or even eliminated. This enables the LCD device  300  to provide improved brightness and uniformity of emitting luminance and prevents the light beams from the radiation element  66  from emitting rearward. 
         [0043]    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.