Abstract:
An exemplary backlight module ( 20 ) includes a light guide plate ( 21 ) having an incident surface ( 211 ) and a side surface ( 714 ) between an emission surface ( 212 ) and a bottom surface ( 213 ), the bottom surface being opposite to the emission surface, the side surface being substantially perpendicular to the incident surface; a light source ( 22 ) opposite to the incident surface; and a light source cover ( 23 ) for reflecting light beams from the light source into the light guide plate. The light source cover is engaged with the light guide plate through a fastening mechanism. The light source cover surrounds one end of the light guide plate at the incident surface, thereby forming a space in cooperation with the end of the light guide plate, and the light source is received in the space.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to backlight modules typically used in liquid crystal displays, and more particularly to a backlight module which includes fastening means that interconnect a light guide plate and a light source cover thereof.  
         [0003]     2. General Background  
         [0004]     In general, liquid crystal displays (LCDs) have two main advantages in comparison with cathode ray tubes (CRTs): LCDs are thin, and have low power consumption. It has been said that LCDs might one day completely replace CRT display devices, and LCDs have aroused great interest in many industries in recent times. Because liquid crystal used in an LCD is not self-illuminating, ambient light or an accompanying backlight module is needed to illuminate the liquid crystal. Thus one kind of LCD includes a backlight module, which provides even light for a clear display.  
         [0005]     A typical backlight module has a light source and a light guide plate. The light source may be one or more point light sources such as light-emitting diodes (LEDs), or a linear light source such as an elongate fluorescent lamp. The light guide plate has a low-profile end face through which light is introduced, and two opposite major faces one of which functions as an emission face.  
         [0006]     The light guide plate functions to change a direction of propagation of light beams emitted from the light source and introduced into the light guide plate, from a direction roughly parallel to the emission face of the light guide plate to a direction perpendicular to the emission face. That is, the light guide plate effectively changes the point light source(s) or linear light source into a surface light source, for evenly illuminating a whole display screen of the LCD.  
         [0007]      FIG. 11  shows a conventional backlight module  10 , which includes a frame  14 , a light guide plate  11 , a linear light source  12  (such as an elongate fluorescent lamp), and a light source cover  13 . The frame  14  receives the light guide plate  11 , the linear light source  12 , and the light source cover  13  therein. The light guide plate  11  has an incident surface  111 , and a side surface  113  opposite to the incident surface  111 . The linear light source  12  is disposed adjacent to the incident surface  111 . The light source cover  13  resiliently clips end portions of four sides of the light guide plate  11  which surround the incident surface  111 . The light source cover  13  and the incident surface  111  thereby cooperatively define a space therebetween. The linear light source  12  is accommodated in the space. Accordingly, light beams emitted from the linear light source  12  are prevented from leaking out from the backlight module  10  and being wasted.  
         [0008]     However, a top part of the light source cover  13  covers only a small part of a top side of the light guide plate  11 , because the top side functions as a light emission surface and must be kept as free from obstruction as possible. If the backlight module  10  is subjected to impact, dropping, shock, or vibration, the top part of the light source cover  13  is liable to slide off from the top side of the light guide plate  11 . When this happens, a gap is created between the light source cover  13  and the light guide plate  11 , and light leakage occurs.  
         [0009]     A new backlight module for an LCD which overcomes the above-mentioned disadvantages is desired. In particular, what is needed is a backlight module having optical components precisely and securely positioned therein.  
       SUMMARY  
       [0010]     A backlight module includes: a light guide plate having an incident surface and a side surface between an emission surface and a bottom surface, the bottom surface being opposite to the emission surface, the side surface being substantially perpendicular to the incident surface; a light source opposite to the incident surface; and a light source cover for reflecting light beams from the light source into the light guide plate. The light source cover is engaged with the light guide plate through a fastening mechanism. The light source cover surrounds one end of the light guide plate at the incident surface, thereby forming a space in cooperation with the end of the light guide plate. The light source is received in the space.  
         [0011]     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  
       [0012]      FIG. 1  is a side cross-sectional view of a backlight module according to a first embodiment of the invention.  
         [0013]      FIG. 2  is an exploded view of the backlight module shown in  FIG. 1 .  
         [0014]      FIG. 3  is a side cross-sectional view of a backlight module according to a second embodiment of the invention.  
         [0015]      FIG. 4  is an enlarged view of a circled portion IV of  FIG. 3 .  
         [0016]      FIG. 5  is a side cross-sectional view of a backlight module according to a third embodiment of the invention.  
         [0017]      FIG. 6  is an enlarged view of a circled portion VI of  FIG. 5 .  
         [0018]      FIG. 7  is a side cross-sectional view of a backlight module according to a fourth embodiment of the invention.  
         [0019]      FIG. 8  is a side cross-sectional view of a backlight module according to a fifth embodiment of the invention.  
         [0020]      FIG. 9  is an enlarged view of a circled portion IX of  FIG. 8 .  
         [0021]      FIG. 10  is a side view of a backlight module according to a sixth embodiment of the invention.  
         [0022]      FIG. 11  is a side cross-sectional view of a conventional backlight module. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.  
         [0024]     Referring to  FIG. 1  and  FIG. 2 , a backlight module  20  according to a first embodiment of the present invention includes a light guide plate  21 , a light source  22 , and a light source cover  23 . The light guide plate  21  includes an incident surface  211 , an emission surface  212  perpendicularly connecting with the incident surface  211 , and a bottom surface  213  opposite to the emission surface  212 . The light source  22  can be a linear source such as an elongate fluorescent lamp, or one or more point sources such as light-emitting diodes. The light source cover  23  resiliently clips end portions of the emission surface  212 , bottom surface  213 , and two side surfaces (not shown) which surround the incident surface  211 . The light source cover  23  and the incident surface  211  thereby cooperatively define a space therebetween. The light source  22  is accommodated in the space, opposite to the incident surface  211 . The light source cover  23  is used to reflect light beams emitted from the light source  22  back to the incident surface  211  of the light guide plate  21 .  
         [0025]     The light source cover  23  includes a top holding plate  231 , and a bottom holding plate  232  opposite to the top holding plate  231 . The top holding plate  231  clips an end portion of the emission surface  212  of the light guide plate  21 , and the bottom holding plate  232  clips an end portion of the bottom surface  213  of the light guide plate  21 . In addition, the top holding plate  231  defines a through hole  242 , and the light guide plate  21  at the emission surface  212  defines an aperture  241  corresponding to the through hole  242 .  
         [0026]     In assembly, the light source  22  is positioned adjacent to the incident surface  211  of the light guide plate  21 . The light source cover  23  is positioned to surround substantially three sides of the light source  22 , with the light source cover  23  resiliently clipping the end portions of the light guide plate  21  that surround the incident surface  211 . In addition, a fastening pin  243  is provided. The fastening pin  243  extends through the through hole  242  of the light source cover  23  and is threadedly engaged in the aperture  241  of the light guide plate  21 . Thereby, the fastening pin  243  helps secure the light source cover  23  to the light guide plate  21 . In alternative embodiments, the fastening pin  243  may instead be interferingly engaged in the aperture  241 , and/or may be adhered in the aperture  241 .  
         [0027]     In summary, the backlight module  20  has an integrated structure whereby the light source cover  23  is securely attached to the light guide plate  21 . This is achieved by the extension of the fastening pin  243  through the through hole  242  of the light source cover  23  and engagement of the fastening pin  243  in the aperture  241  of the light source cover  23 . Thus, the backlight module  20  has a firm structure. If the backlight module  20  is subjected to impact, dropping, shock, or vibration, the light source cover  23  resists detachment from the light guide plate  21 , and no gaps are created. Therefore leakage of light beams is avoided, and the light beams emitted from the light source  22  can continue to be efficiently guided into the light guide plate  21 .  
         [0028]      FIG. 3  and  FIG. 4  show a backlight module  30  according to a second embodiment of the present invention. The backlight module  30  has a structure similar to that of the backlight module  20 . However, in the backlight module  30 , a light guide plate  31  has a fastening pin  343  extending vertically upwardly from an emission surface  312  thereof. The fastening pin  343  corresponds to a through hole  342  defined in a light source cover  33 . The fastening pin  343  is engaged in the through hole  342 . Thereby, the light source cover  33  and the light guide plate  31  are securely fastened together. In particular, the fastening pin  343  may be interferingly engaged in the through hole  342 , and/or may be adhered in the through hole  342 .  
         [0029]      FIG. 5  and  FIG. 6  show a backlight module  40  according to a third embodiment of the present invention. The backlight module  40  has a structure similar to that of the backlight module  20 . However, in the backlight module  40 , a light source cover  43  has a U-shaped protuberance  442  corresponding to an aperture  441  defined in a light guide plate  41  at an emission surface  412  thereof. The U-shaped protuberance  442  is engaged in the aperture  441 . Thereby, the light source cover  43  and the light guide plate  41  are securely fastened together. In particular, the U-shaped protuberance  442  may be interferingly engaged in the aperture  441 , and/or may be adhered in the aperture  441 .  
         [0030]      FIG. 7  shows a backlight module  50  according to a fourth embodiment of the present invention. The backlight module  50  has a structure similar to that of the backlight module  20 . However, in the backlight module  50 , a light guide plate  51  has a recessed portion  541  at an emission surface  512  thereof adjacent to an incident surface  511  thereof. In particular, the recessed portion  541  slants down from the incident surface  511 . Thus the recessed portion  541  defines a recess having a triangular-shaped cross-section. A vertical surface of the recessed portion  541  distal from the incident surface  511  substantially perpendicularly connects with the emission surface  512 . A light source cover  53  includes a top elastic holding plate  542  opposite to a bottom holding plate  532 . The elastic holding plate  542  resiliently engages with the recessed portion  541 , and the bottom holding plate  532  resiliently clips a bottom surface  513  of the light guide plate  51 . Prior to assembly of the backlight module  50 , a distance between the elastic holding plate  542  and the bottom holding plate  532  is less than a corresponding distance between the recessed portion  541  and the bottom surface  513  of the light guide plate  51 . Thus, once the backlight module  50  is assembled, the elastic holding plate  542  and the bottom holding plate  532  resiliently clip an end of the light guide plate  51  at the incident surface  511 .  
         [0031]      FIG. 8  and  FIG. 9  show a backlight module  60  according to a fifth embodiment of the present invention. The backlight module  60  has a structure similar to that of the backlight module  20 . However, the backlight module  60  further includes a reflector  65  disposed under a bottom surface  613  of a light guide plate  61 , and a frame  66 . The frame  66  receives the light guide plate  61 , a light source  62 , a light source cover  63 , and a fastening pin  644  therein. The light source cover  63  surrounds one end of the light guide plate  61 . The light source cover  63 , a portion of the reflector  65 , and an incident surface (not labeled) of the light guide plate  61  cooperatively define a space therebetween. The light source  62  is accommodated in the space. The light source cover  63  defines a through hole  642  in a bottom holding plate  632  thereof. The reflector  65  defines a through hole  643  corresponding to the through hole  642 . The light guide plate  61  defines an aperture  641  at the bottom surface  613 . In assembly, the reflector  65  is adhered to the bottom surface  613  of the light guide plate  61 . The light source cover  63  resiliently clips one end of the combined light guide plate  61  and reflector  65 , and surrounds substantially three sides of the light source  62 . The fastening pin  644  extends through the two through holes  642 ,  643  and is threadedly engaged in the aperture  641  of the light guide plate  61 . Thereby, the fastening pin  644  helps secure the light source cover  63  to the light guide plate  61 . In alternative embodiments, the fastening pin  644  may instead be interferingly engaged in the aperture  641 , and/or may be adhered in the aperture  641 .  
         [0032]      FIG. 10  shows a backlight module  70  according to a fifth embodiment of the present invention. The backlight module  70  has a structure similar to that of the backlight module  60 . However, in the backlight module  70 , an aperture (not visible) is defined at a side surface  714  of a light guide plate  71 . The aperture is located at an end of the side surface  714  near an incident surface (not visible) of the light guide plate  71 , between an emission surface  712  and a bottom surface  713  of the light guide plate  71 . A through hole  742  is defined in a side wall (not labeled) of a light source cover  73 , between a top holding plate  731  and a bottom holding plate  732  of the light source cover  73 . A reflector  75  is adhered to the bottom surface  713  of the light guide plate  71 , but there is no frame. The light source cover  73  resiliently clips one end of the combined light guide plate  71  and reflector  75 , and surrounds substantially three sides of a light source (not visible). A fastening pin  743  extends through the through hole  742  and is threadedly engaged in the aperture of the light guide plate  71 . Thereby, the fastening pin  743  helps secure the light source cover  73  to the light guide plate  71 . In alternative embodiments, the fastening pin  743  may instead be interferingly engaged in the aperture of the light guide plate  71 , and/or may be adhered in the aperture of the light guide plate  71 .  
         [0033]     It is to be further understood that even though numerous characteristics and advantages of various embodiments have been set forth 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.