Patent Publication Number: US-2011069509-A1

Title: Backlight module

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial No. 98131781, filed on Sep. 21, 2009. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a light source module, and more particularly, to a backlight module adapted to a liquid crystal display (LCD). 
     2. Description of Related Art 
     A liquid crystal display (LCD) mainly includes an LCD panel and a backlight module, wherein the backlight module is a planar light source disposed behind the LCD panel. The backlight modules may be grouped into direct type backlight modules and edge lighting backlight modules according to different configurations of lamps of the backlight modules. 
     Taking the edge lighting backlight module as an example, a principle of the edge lighting backlight module is to dispose a light source at a side of a light guiding plate, so that a light beam may be incident from a side surface of the light guiding plate, and emitted out from a front surface of the light guiding plate. U.S. Pat. No. 7,359,614 discloses an edge lighting backlight module, wherein at least one pillar is provided to associate with an arc angle on the light guiding plate, so that the light guiding plate and the pillar are maintained to a planar contact state, so as to avoid a light gathering phenomenon of the light guiding plate, and accordingly avoid light-leakage. Moreover, the pillar may position the light guiding plate, so that the light guiding plate is not slid during a movement, and the pillar may further provide a support, so that the structure strength of the backlight module is increased. 
     However, when the backlight module is impacted or in a vibration state, the pillar is liable to scrape the light guiding plate. Based on a structural consideration, a material of the pillar is preferably metal, so that the light guiding plate may generate scrapings, or even be seriously damaged (such as cracked, etc.). 
     SUMMARY OF THE INVENTION 
     The invention is directed to a backlight module having a good durability. 
     Additional aspects and advantages of the invention will be set forth in the description of the techniques disclosed in the invention. 
     To achieve at least one of the advantages, one embodiment of the invention provides a backlight module including a back plate, a plurality of position limiting elements, a light guiding plate, and a light source. The position limiting elements are disposed on the back plate, and each of the position limiting elements includes a pillar and a cushion sheath covering the pillar. The light guiding plate is disposed on the back plate, and has a plurality of first position limiting portions. The first position limiting portions respectively contact the position limiting elements to position the light guiding plate on the back plate. The light source is disposed at a side of the light guiding plate. 
     According to the above description, by covering the cushion sheath on the pillar, the light guiding plate may be positioned on the back plate, and the cushion sheath is located between the pillar and the light guiding plate, so as to protect the pillar and the light guiding plate. When the backlight module is vibrated or impacted, the cushion sheath may absorb a vibration force or an impact force, so as to avoid a direct scraping between the pillar and the light guiding plate. Therefore, the backlight module has a good durability. 
     Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is an exploded view of a backlight module according to an embodiment of the invention. 
         FIG. 2  is a schematic view illustrating some of members of a backlight module of  FIG. 1  after being assembled. 
         FIG. 3  is a top view of some of members of a backlight module of  FIG. 2 . 
         FIG. 4  is a cross-sectional view of a backlight module of  FIG. 3  taken along line A-A. 
         FIG. 5  is a partial enlarged view of a backlight module according to another embodiment of the invention. 
         FIG. 6  is a partial enlarged view of a backlight module according to another embodiment of the invention. 
         FIG. 7  is a partial enlarged view of a backlight module according to another embodiment of the invention. 
         FIG. 8  is a partial enlarged view of a backlight module according to another embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” etc., is used with reference to the orientation of the Figure(s) being described. The components of the present invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Similarly, the terms “facing,” “faces” and variations thereof herein are used broadly and encompass direct and indirect facing, and “adjacently to” and variations thereof herein are used broadly and encompass directly and indirectly “adjacently to”. Therefore, the description of “A” component facing “B” component herein may contain the situations that “A” component directly faces “B” component or one or more additional components are between “A” component and “B” component. Also, the description of “A” component “adjacently to” “B” component herein may contain the situations that “A” component is directly “adjacently to” “B” component or one or more additional components are between “A” component and “B” component. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
     Referring to  FIG. 1  and  FIG. 2 , the backlight muddle  100  includes a back plate  110 , a plurality of position limiting elements  120 , a light guiding plate  130 , and a light source  140 . In the embodiment, a shape of the back plate  110  is substantially a rectangle, and the back plate  110  includes a bottom portion  112  and four side portions  114  extended from four sides of the bottom portion  112  and perpendicular to the bottom portion  112 . The light source  140  is, for example, a plurality of light emitting diodes (LEDs) respectively disposed between the side portions  114  and the light guiding plate  130 . However, implementation of the light source  140  is not limited by the embodiment, and in another embodiment, the light source  140  may also be one or a plurality of cold cathode fluorescent lamps (CCFLs). 
     The position limiting elements  120  are disposed on the back plate  110 , and each of the position limiting elements  120  includes a pillar  122  and a cushion sheath  124  covering the pillar  122 . In the embodiment, the pillar  122  is a metal pillar (for example, a copper pillar) having a structure independent to the back plate  110 , and the pillar  122  is externally assembled to the back plate  110 . However, in other embodiments, the pillar  122  may also be directly formed by a small portion of the back plate  110 . A material of the cushion sheath  124  is silicone, rubber or foam, and the cushion sheath  124  is used for cushioning an impact effect, though the embodiment is not limited to the materials. 
     The light guiding plate  130  has a plurality of first position limiting portions  132 . The first position limiting portions  132  include a plurality of grooves. The first position limiting portions  132  respectively contact the position limiting elements  120  to position the light guiding plate  130  on the back plate  110 , and the cushion sheaths  124  may cushion impacts between the pillars  122  and the light guiding plate  130 . In detail, by using the first position limiting portions  132  of the light guiding plate  130  and the position limiting elements  120 , two degrees of freedom of the light guiding plate  130  being shifted on a geometric plane substantially parallel to the bottom portion  112  of the back plate  110  are limited. 
     Moreover, the light source  140  disposed at the side portion  114  is adjacent to a side surface  134  of the light guiding plate  130 , so that a light beam generated by the light source  140  may be incident to the light guiding plate  130  from the side surface  134  of the light guiding plate  130 , and may be emitted out from a light emitting surface  136  of the light guiding plate  130 . Here, the position and the quantity of the light sources  140  are not limited. As long as the light sources  140  are disposed at the side portions  114 , and the light beams generated by the light sources  140  may be incident to the light guiding plate  130  from the side surface  134  of the light guiding plate  130 , and in the embodiment, the light sources  140  may be disposed at one, two, three or all of the side portions  114 . 
     Referring to  FIG. 1  and  FIG. 2 , in the embodiment, the backlight module  100  further includes one or a plurality of optical films  150 , and the optical films  150  are, for example, diffuser films, brightness enhancement films, or other optical films. The optical films  150  are sequentially stacked on the light emitting surface  136  of the light guiding plate  130 , and each of the optical films  150  has a plurality of second position limiting portions  152 . Similar to the first position limiting portions  132  of the light guiding plate  130 , the second position limiting portions  152  also include a plurality of grooves, and the second position limiting portions  152  respectively contact the position limiting elements  120  to position the optical films  150  on the light guiding plate  130 . 
     Referring to  FIG. 1  again, in the embodiment, the backlight module  100  further includes a light reflecting layer  160 , and the light reflecting layer  160  is disposed between the back plate  110  and the light guiding plate  130  for reflecting the light beam of the light source  140 , and the light beam of the source  140  is incident to the light guiding plate  130  and is emitted out from a bottom surface of the light guiding plate  130  to the light emitting surface  136  of the light guiding plate  130 , so that the light beam may be effectively used, and a brightness of the light beam provided by the backlight module  100  may be increased. In the embodiment, the light reflecting layer  160  is, for example, a coating layer coated on the bottom surface of the light guiding plate  130 . However, in other embodiments, the light reflecting layer  160  may also be a light reflecting sheet disposed between the back plate  110  and the light guiding plate  130 . 
     Referring to  FIG. 1  again, in the embodiment, the backlight module  100  further includes a frame  170 , and the frame  170  is assembled to the back plate  110  to avoid the light guiding plate  130  and the optical films  150  falling off the back plate  110 . Moreover, the frame  170  further has a window  172 , so that the light beam emitted out from the light emitting surface  136  of the light guiding plate  130  may pass through the window  172 . 
     Referring to  FIG. 3  and  FIG. 4 , the position limiting elements  120  are symmetrically disposed around the back plate  110 . In the embodiment, the position limiting elements  120  are respectively located at four corners of the back plate  110  to avoid a light incident path of the light source  140 , so that the light beam may be incident to the light guiding plate  130  from the side surface  134  of the light guiding plate  130  without being blocked, and the light beam output from the backlight module  100  may have a relatively high brightness. In another embodiment, the position limiting elements  120  are also disposed at two corners of any diagonal of the back plate  110 . 
     Referring to  FIG. 5 , the backlight module  200  of the embodiment further has a plurality of fastening members  280  (for example, screws), and the pillar  222  of each of the position limiting elements  220  on the back plate  210  has a fastening hole  222   a . The fastening hole  222   a  is exposed by the cushion sheath  224 , and the frame  270  has a plurality of openings  272  corresponding to the fastening holes  222   a . Therefore, by fastening the fastening members  280  passing through the openings  272  in the fastening holes  222   a , the frame  270  is fastened to the back plate  210 . 
     Referring to  FIG. 6 , in the backlight module  300 , the light guiding plate  330  has a plurality of first position limiting planes  332 , and the first position limiting planes  332  are oblique to the side surface  334  of the light guiding plate  330 . The position limiting elements  320  are triangular pillars, and have second position limiting planes  322  corresponding to the first position limiting planes  332 . The first position limiting planes  332  respectively contact to the second position limiting planes  322 , so the light guiding plate  330  may be positioned on the back plate  310 . 
     When the backlight module  300  sustains an external impact from the right, the light guiding plate  330  sustains a force F 1  exerted by the position limiting element  320 . Due to a plane contact between the first position limiting plane  332  and the second position limiting plane  322 , the force F 1  is divided into two sub-forces F 2  and F 3 , wherein the sub-force F 2  is perpendicular to the first position limiting plane  332 , and the sub-force F 3  is parallel to the first position limiting plane  332 , and only the sub-force F 2  perpendicular to the first position limiting plane  332  is operative to the light guiding plate  330 . Therefore, the sub-force F 2  sustained by the light guiding plate  330  is less than the force F 1 , so that damage of the light guiding plate  330  due to excessive impact may be avoided. 
     Referring to  FIG. 7 , in the backlight module  400 , the position limiting element  420  is a rectangular pillar, and the first position limiting portion  432  of the light guiding plate  430  is a corresponding rectangular groove. The first position limiting portions  432  respectively contact to the position limiting elements  420 , so the light guiding plate  430  is positioned on the back plate  410 . 
     Referring to  FIG. 8 , in the backlight module  500 , the position limiting element  520  is a trapezoidal pillar, and the first position limiting portion  534  of the light guiding plate  530  is a corresponding trapezoidal groove. The first position limiting portions  534  are respectively contact to the position limiting elements  520 , so the light guiding plate  530  is positioned on the back plate  510 . Moreover, the position limiting element  520  has a second position limiting plane  522 , and the light guiding plate  530  has a first position limiting plane  532  corresponding to the second position limiting plane  522 . Therefore, as described in the embodiment of  FIG. 6 , an impact between the light guiding plate  530  and the position limiting element  520  is cushioned, so as to avoid the damage of the light guiding plate  530  due to excessive impact. 
     In the above embodiments of the invention, a shape of the position limiting element is not limited, and the shape of the position limiting element may be a column of  FIG. 3 , a triangle pillar of  FIG. 6 , a rectangular pillar of  FIG. 7  or a trapezoidal pillar of  FIG. 8 . Any types of the position limiting element covered by the cushion sheath capable of absorbing the impact between the light guiding plate and the position limiting element to avoid damage of the light guiding plate is adapted to the invention. 
     In summary, the embodiment or the embodiments of the invention may have at least one of the advantages, by the position limiting elements and the position limiting portions of the light guiding plate, the light guiding plate may be positioned on the back plate, and the cushion sheath covering the pillar is used to cushion the impact between the pillar and the light guiding plate, so as to avoid damage of the light guiding plate due to excessive impact. Moreover, since the position limiting element and the light guiding plate respectively have the corresponding position limiting planes oblique to the side surface of the light guiding plate, the impact between the light guiding plate and the position limiting elements may be cushioned due to a force differentiation, so that damage of the light guiding plate due to excessive impact may be avoided. 
     The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. Therefore, the term “the invention”, “the present invention” or the like does not necessarily limit the claim scope to a specific embodiment, and the reference to particularly preferred exemplary embodiments of the invention does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is limited only by the spirit and scope of the appended claims. The abstract of the disclosure is provided to comply with the rules requiring an abstract, which will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Any advantages and benefits described may not apply to all embodiments of the invention. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.