Patent Publication Number: US-2012039090-A1

Title: Surface light source device and display apparatus using the same

Description:
FIELD OF THE INVENTION 
     The invention relates to a surface light source device, and more particularly to a surface light source device having a light guide plate and to a display apparatus using the surface light source device. 
     BACKGROUND OF THE INVENTION 
     Backlight modules are applied in liquid crystal display devices to provide display light to the liquid crystal display panels. Backlight modules include bottom lighting backlight modules and edge lighting backlight modules. Technologies about the edge lighting backlight modules are disclosed in many patents, such as Taiwan patents No. I315015, M270369, and M303389, Taiwan published applications No. 200809318, 200727040, 200815870, and 200813592, U.S. Pat. No. 7,545,461, and United States published applications No. 20070029915, 20050253980, 20090256987 and so on. 
     Referring to  FIG. 1 , a conventional edge lighting backlight module  100  includes a light guide plate  110  and a light source assembly  120 . The light guide plate  110  has a light incident surface  112  and a light emitting surface  114  adjacent to the light incident surface  112 . The light source assembly  120  is disposed beside the light incident surface  112 . Moreover, the light source assembly  120  includes a circuit board  122  and a plurality of light emitting diodes  124  disposed on the circuit board  122 . The light emitting diodes  124  are capable of providing light for the light guide plate  110 . After the light enters the light guide plate  110  via the light incident surface  112 , the light guide plate  110  converts the light into a surface light source, and the surface light source is emitted from the light emitting surface  114 . The surface light source may be used as display light source for the liquid crystal display panel. 
     In the conventional technology, the light emitting diodes  124  generate heat when the light emitting diodes  124  are lightened, thereby resulting in heat expansion of the light guide plate  110 . When the expanded light guide plate  110  jostles the light emitting diodes  124 , the light emitting diodes  124  may be damaged. In order to prevent the expanded light guide plate  110  from jostling the light emitting diodes  124 , a sufficient gap G between the light guide plate  110  and the light emitting diodes  124  should be kept. However, light utilization efficiency of the backlight module  100  may be reduced. 
     SUMMARY OF THE INVENTION 
     The invention provides a surface light source to promote light utilization efficiency. 
     The invention also provides a display apparatus to promote light utilization efficiency. 
     In order to achieve one or a portion of or all of the objects or other objects, an embodiment of the invention provides a surface light source device. The surface light source device includes a light guide plate, a light source assembly, and at least one protecting frame. The light guide plate has a light incident surface. The light source assembly includes a substrate and a plurality of point light sources disposed on the substrate. A light emitting surface of each of the point light sources faces the light incident surface of the light guide plate. The protecting frame is disposed on the substrate and surrounds at least a part of the point light sources. A distance between a top surface of the protecting frame facing the light incident surface and the substrate is larger than a distance between the light emitting surface of each point light source and the substrate. 
     In one embodiment of the invention, the top surface of the protecting frame abuts the light guide plate. 
     In one embodiment of the invention, the surface light source device includes a plurality of the protecting frames, each of the protecting frames surrounds one of the point light sources, and a number of the protecting frames is equal to a number of the point light sources. 
     In one embodiment of the invention, the surface light source device includes a plurality of the protecting frames, each of the protecting frames surrounds one of the point light sources, and a number of the protecting frames is smaller than a number of the point light sources. 
     In one embodiment of the invention, the surface light source device includes a plurality of the protecting frames, and each protecting frame surrounds at least one of the point light sources. 
     In one embodiment of the invention, a material of the protecting frame includes a flexible material. 
     In one embodiment of the invention, the flexible material includes a rubber or a plastic. 
     In one embodiment of the invention, the protecting frame further has a bottom surface abutting the substrate, and a caliber of the protecting frame is gradually decreased from the top surface to the bottom surface. 
     In one embodiment of the invention, an inner surface of the protecting frame is a reflecting surface. 
     In one embodiment of the invention, a color of the protecting frame is white. 
     In one embodiment of the invention, the surface light source device further includes a reflecting layer disposed on an inner surface of each protecting frame. 
     In one embodiment of the invention, a color of the reflecting layer is white. 
     The invention also provides a display apparatus. The display apparatus includes a display panel and the above-mentioned surface light source device. The surface light source device is disposed beside the display panel. 
     In summary, the embodiment or embodiments of the invention may have at least one of the following advantages. In the surface light source device according to embodiments of the invention, since the at least one protecting frame disposed on the substrate is used to prevent the expanded light guide plate from jostling the point light sources, a gap between the light guide plate and the point light sources may be as small as possible, so as to promote the light utilization efficiency. Furthermore, the display apparatus according to embodiments of the invention uses the surface light source device. Thus, the display apparatus has better light utilization efficiency. 
     Other objectives, features and advantages of the invention will be further understood from the further technological features disclosed by the embodiments of the 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 above objects and advantages of the invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
         FIG. 1  is a schematic view of a conventional edge lighting backlight module. 
         FIG. 2  is a schematic, top view of a surface light source device according to an embodiment of the invention. 
         FIG. 3  is a schematic, three-dimensional view of a light source assembly and protecting frames of  FIG. 2 . 
         FIG. 4  is a schematic, three-dimensional view of a light source assembly and protecting frames according to another embodiment of the invention. 
         FIG. 5  is a schematic, three-dimensional view of a light source assembly and protecting frames according to another embodiment of the invention. 
         FIG. 6  is a schematic, three-dimensional view of a protecting frame according to another embodiment of the invention. 
         FIG. 7  is a schematic view of a display apparatus according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED 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 invention may 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 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 “adjacent to” and variations thereof herein are used broadly and encompass directly and indirectly “adjacent 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 “adjacent to” “B” component herein may contain the situations that “A” component is directly “adjacent 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. 2  and  FIG. 3 , a surface light source device  200  of the embodiment includes a light guide plate  210 , a light source assembly  220 , and at least one protecting frame  230  (a plurality of the protecting frames  230  are taken as an example in the embodiment). The light guide plate  210  has a light incident surface  212 . The light source assembly  220  includes a substrate  222  and a plurality of point light sources  224  disposed on the substrate  222 . The point light sources  224  may be light emitting diodes or other suitable point light sources. A light emitting surface  225  of each of the point light sources  224  faces to the light incident surface  212  of the light guide plate  210 . The protecting frames  230  are disposed on the substrate  222 , and each of the protecting frames  230  surrounds at least a part of the point light sources  224 . In the embodiment, each protecting frame  230 , for example, surrounds a point light source  224 . A number of the protecting frames  230  is equal to a number of the point light sources  224 , that is, each of the point light sources  224  is surrounded by one protecting frame  230 . In addition, a distance D 1  between a top surface  232  of the protecting frame  230  facing the light incident surface  212  and the substrate  222  is larger than a distance D 2  between the light emitting surface  225  of each of the point light sources  224  and the substrate  222 . 
     In the embodiment, the above-mentioned top surface  232  of the protecting frame  230  abuts the light guide plate  210 . However, in other embodiments, the top surface  232  of the protecting frame  230  may be kept a gap from the light incident surface  212  of the light guide plate  210 . Additionally, a material of the protecting frame  230  may be a flexible material, such as a rubber or a plastic and so on. Moreover, the protecting frames  230  of the embodiment are, for example, rectangle frames. However, the protecting frames  230  may also be circular frames or oval-shaped frames, and the invention does not limit the shape of the protecting frames. 
     In the surface light source device  200 , light provided by the point light sources  224  enters the light guide plate  210  via the light incident surface  212  of the light guide plate  210 . The light guide plate  210  converts the light into a surface light source, and the surface light source is emitted from a light emitting surface  214  of the light guide plate  210 . The point light sources  224  generate heat when the point light sources  224  are lightened, thereby resulting in heat expansion of the light guide plate  210 . Therefore, in the embodiment, the protecting frames  230  are disposed on the substrate  222 , and the distance D 1  between the top surface  232  of the protecting frames  230  and the substrate  222  is larger than the distance D 2  between the light emitting surface  225  of each of the point light source  224  and the substrate  222 . When the heat generated by the point light source  224  cause the light guide plate  210  to be expanded, the light guide plate  210  may jostle the protecting frames  230  but not the point light sources  224 . In such way, not only the point light sources  224  are prevented from damage caused by jostle of the light guide plate  210 , but also a gap between the point light sources  224  and the light guide plate  210  may be as small as possible, so as to promote light utilization efficiency of the surface light source device  200 . 
     Furthermore, since the protecting frames  230  may be made of flexible material, the protecting frames  230  may be deformed under the jostle of the light guide plate  210 , and thereby the light guide plate  210  may expand towards the point light sources  224 . If the light guide plate  210  does not expand towards the point light sources  224 , a bump of the light guide plate  210  may be formed. However, in the embodiment, the bump may not be formed because the light guide plate  210  may expand towards the point light sources  224 . In addition, in the embodiment, the material of the protecting frames  230  may has high reflectivity so that an inner surface  234  of each protecting frame  230  may be used as a reflective surface to promote the light utilization efficiency. In order to prevent the color of the light reflected by the protecting frames  230  from being changed, a color of the protecting frames  230  may be corresponded with the color of the light emitted by the point light sources  224 . For example, when the point light sources  224  are white point light sources, the color of the protecting frames  230  may be white. 
     Although in the embodiment, the protecting frames  230  are, for example, made of the material with the high reflectivity, in another embodiment, a reflecting layer (not shown) may be directly disposed on the inner surface  234  of each protecting frame  230 . The reflecting layer is configured to reflect light. In addition, a color of the reflecting layer may be corresponded with the color of the light emitted by the point light sources  224 . For example, the colors of the reflecting layer and the color of the light emitted by the point light sources  224  may be white. 
     In the invention, a protecting frame  230  is not limited to only surrounds a point light source  224 , that is, the protecting frame  230  may surrounds at least one of the point light sources  224 . Referring to  FIG. 4 ,  FIG. 5 , and  FIG. 6 , as shown in  FIG. 4 , each protecting frame  230  may surround two point light sources  224 . Moreover, the invention does not limit that each of the point light sources  224  should be surrounded by the protecting frame  230 . For example, as shown in  FIG. 5 , each of the protecting frames  230  surrounds one of the point light sources  224 , and a number of the protecting frames  230  is smaller than a number of the point light sources  224 . In addition, as shown in  FIG. 6 , in another embodiment, a caliber of a protecting frame  230 ′ is gradually decreased from the top surface  232  to a bottom surface  236  abutting the substrate (not shown) of the light source assembly, and thereby the light utilization efficiency may be promoted. 
     The surface light source device  200  may be applied in a display apparatus to provide a display light to a display panel of the display apparatus. However, the invention does not limit the applications of the surface light source device  200 . 
     Referring to  FIG. 7 , a display apparatus  300  of the embodiment includes a display panel  310  and the above-mentioned surface light source device  200 , and the surface light source device  200  provides display light  202  to the display panel  310 . The display panel  310  may be, but not limited to, a liquid crystal display panel. Since the light utilization efficiency of the surface light source device  200  applied in the display apparatus  300  is high, light utilization efficiency of the display apparatus  300  of the embodiment may be promoted. 
     In summary, the surface light source device and the display apparatus using the same according to embodiments of the invention at least have one of the following advantages: 
     1. In the surface light source device according to embodiments of the invention, the at least one protecting frame disposed on the substrate is used to prevent the expanded light guide plate from jostling the point light sources disposed on the substrate. Therefore, the gap between the light guide plate and the point light sources may be as small as possible, so as to promote the light utilization efficiency. 
     2. The at least one protecting frame of the surface light source device according to embodiments of the invention may be made of the flexible material. In such way, when the expanded light guide plate jostles the protecting frame, the protecting frame is deformed, and thereby the light guide plate may expand towards the point light sources and the bump of the light guide plate may be avoided. 
     3. The display apparatus according to embodiments of the invention uses the surface light source having high light utilization efficiency. Thus, the light utilization efficiency of the display apparatus is high. 
     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. Moreover, these claims may refer to use “first”, “second”, etc. following with noun or element. Such terms should be understood as a nomenclature and should not be construed as giving the limitation on the number of the elements modified by such nomenclature unless specific number has been given. 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 invention as defined by the following claims. Moreover, no element and component in the disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.