Abstract:
A surface light source ( 50 ) includes a light source ( 53 ); an optical element ( 54 ) configured for receiving light beams from the light source, guiding and uniformizing the light beams, and outputting the light beams; an optical film ( 56 ) positioned on the optical element and configured for receiving the output light beams; and a frame ( 58 ) accommodating the light source, the optical element and the optical film. The surface light source further has at least one fastening post ( 542 ) being formed on one of the optical element and the optical film, and at least one fastening hole ( 562 ) being formed on one of the optical film and the optical element, which is corresponding to the at least one fastening post. The optical film is located at the optical element through the cooperation of the at least one fastening post and the at least one fastening hole.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to surface light sources and liquid crystal displays using the same, and more particularly to a surface light source having fastening means that interconnect an optical film with an optical element such as a light guide plate or a diffusing plate.  
         [0003]     2. General Background  
         [0004]     In general, 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. In general, an LCD needs a surface light source to provide even light for a clear display.  
         [0005]     A surface light source generally has a light source and a light guide plate. The light source may be a light-emitting diode (LED), or one or more fluorescent lamps. The light guide plate has a thin 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 linear or point light source(s) into a surface light source, for evenly illuminating a whole display screen of the LCD.  
         [0007]      FIG. 3  shows a conventional surface light source  10 , which has a frame  18 , a light guide plate  14 , a plurality of point light sources  13 , a reflector  12 , and an optical film assembly  16 . The frame  18  has a pair of notches  181  defined in each of two opposite sidewalls (not labeled) thereof. The light guide plate  14  has a pair of first ears  141  extending from each of two opposite sides thereof. The optical film assembly  16  has a pair of second ears  161  extending from each of two opposite sides thereof. The second ears  161  correspond to the first ears  141  of the light guide plate  14 . The optical film assembly  16 , the light guide plate  14  and the reflector  12  are laminated one on the other in that order from top to bottom, and this subassembly is accommodated in the frame  18 . The first and second ears  141 ,  161  of the light guide plate  14  and the optical film assembly  16  are received in the notches  181  of the frame  18 . The frame  18  also accommodates the point light sources  13  therein, with the point light sources  13  being positioned adjacent to one side of the light guide plate  14 . In use, light beams from the point light sources  13  enter the light guide plate  14  through an incident surface (not labeled) of said side of the light guide plate  14 .  
         [0008]     Each second ear  161  of the optical film assembly  16  and a corresponding first ear  141  of the light guide plate  14  are accommodated in a corresponding notch  181  of the frame  18  together, with the second ear  161  abutting the first ear  141 . In general, the second ear  161  is thinner than the first ear  141 . Further, the first ear  141  is sandwiched between the frame  18  and the second ear  161 , whereas the second ear  161  is merely located in a topmost portion of the notch  181 . Therefore if the surface light source  10  is subjected to shock, the second ear  161  is liable to shift position within the notch  181  or even slip out from the notch  181  altogether. When one or more of the second ears  161  are displaced, the optical film assembly  16  shifts slightly and may even disengage from the frame  18 . Thus in mass manufacturing of the surface light source  10 , the precision of the surface light source  10  may be unsatisfactory, and the assembly process may be retarded by the need for correction of the imprecision. In addition, the frame  18  is generally made from plastic, therefore the frame  18  generally has a low manufacturing precision. Thus even when the surface light source  10  is properly assembled, the optical film assembly  16  may not be precisely fixed in the frame  18 , and the performance of the surface light source  10  may be diminished.  
         [0009]     A new surface light source for an LCD which overcomes the above-mentioned disadvantages is desired. In particular, what is needed is a surface light source having optical components precisely positioned therein.  
       SUMMARY  
       [0010]     A surface light source includes a light source; an optical element configured for receiving light beams from the light source, guiding and uniformizing the light beams, and outputting the light beams; an optical film positioned on the optical element and configured for receiving the output light beams; and a frame accommodating the light source, the optical element and the optical film. The surface light source further has at least one fastening post being formed on one of the optical element and the optical film, and at least one fastening hole being formed on one of the optical film and the optical element, which is corresponding to the at least one fastening post. The optical film is located at the optical element through the cooperation of the at least one fastening post and the at least one fastening hole.  
         [0011]     A liquid crystal display includes a liquid crystal panel, a surface light source providing surface light beams to the liquid crystal panel, and a frame for accommodating the liquid crystal panel and the surface light source. The surface light source has a light source; an optical element configured for receiving light beams from the light source, guiding and uniformizing the light beams, and outputting the light beams; an optical film positioned on the optical element and configured for receiving the output light beams. The liquid crystal display further has at least one fastening post being formed on one of the optical element and the optical film, and at least one fastening hole being formed on one of the optical film and the optical element, which is corresponding to the at least one fastening post. The optical film is located at the optical element through the cooperation of the at least one fastening post and the at least one fastening hole.  
         [0012]     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  
       [0013]      FIG. 1  is an exploded, isometric view of an LCD according to a first embodiment of the invention.  
         [0014]      FIG. 2  is an exploded, isometric view of an LCD according to a second embodiment of the invention.  
         [0015]      FIG. 3  is an exploded, isometric view of a conventional surface light source, which is typically used in an LCD. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.  
         [0017]     Referring to  FIG. 1 , a liquid crystal display  20  according to a first embodiment of the present invention includes a top bezel  30 , a liquid crystal panel  40 , and a surface light source  50 , disposed in that order from top to bottom. The surface light source  50  includes an optical film  56 , a light guide plate  54 , a reflector  52 , and a frame  58 , disposed generally in that order from top to bottom. The frame  58  receives the liquid crystal panel  40 , the optical film  56 , the light guide plate  54 , and the reflector  52  therein. In addition, the liquid crystal display  20  further includes a plurality of light sources  53  disposed adjacent one side of the light guide plate  54 .  
         [0018]     The top bezel  30  includes a top wall  301 , and two opposite first side walls  302  integrally connecting with the top wall  301 . The top wall  301  defines a rectangular first opening (not labeled), corresponding to a display area (not labeled) of the liquid crystal panel  40 . The first side walls  302  perpendicularly extend down from opposite long sides (not labeled) of the top wall  301  respectively. Each first side wall  302  defines two hatches  303  therein. The top bezel  30  can be made from iron, aluminum, magnesium, or any other suitable metal or alloy.  
         [0019]     The light guide plate  54  has two opposite side surfaces  543 , a first top surface  544  perpendicularly adjoining the side surfaces  543 , and a first bottom surface  545  opposite to the first top surface  544 . Two rectangular first ears  541  integrally extend from each side surface  543 . Each first ear  541  has a fastening post  542  formed thereon. The light guide plate  54  is used to introduce light beams from the light sources  53  into the light guide plate  54 , from a direction roughly parallel to the first top surface  544  of the light guide plate  54  to a direction perpendicular to the first top surface  544 . That is, the light guide plate  54  effectively changes the light sources  53  into a surface light source, for guiding and uniformizing the light beams over the whole first top surface  544 , and outputting the light beams to the liquid crystal panel  40 .  
         [0020]     The optical film  56  has two opposite side surfaces  563 , and two rectangular second ears  561  integrally extending from each side surface  563 . A fastening through-hole  562  is defined in each second ear  561 .  
         [0021]     The frame  58  includes a bottom wall  582 , and two second side walls  583  integrally connecting with the bottom wall  582 . The bottom wall  582  is generally frame-shaped. Each second side wall  583  has a generally asymmetrical U-shape. The second side walls  583  extend perpendicularly up from two opposite sides (not labeled) of the bottom wall  582  respectively, and are symmetrically opposite each other. Outmost vertical faces of the bottom wall  582  are coplanar with corresponding outmost vertical faces of the second side walls  583 . Each second side wall  583  includes two first protrusions  584  integrally extending perpendicularly outward from the outmost vertical face thereof that is at a corresponding long side (not labeled) of the frame  58 .  
         [0022]     In addition, the frame  58  further defines two pairs of first notches  581 , positioned at two opposite inner long sides (not labeled) of the bottom wall  582  respectively. Each first notch  581  is located opposite to one respective first protrusion  584 .  
         [0023]     When the liquid crystal display  20  is assembled, the top bezel  30  and the frame  58  cooperatively accommodate the liquid crystal panel  40  and the surface light source  50  therebetween. The hatches  303  engagingly receive the first protrusions  584  therein, thereby locking the top bezel  30  and the frame  58  together. Each first notch  581  of the frame  58  receives a corresponding first ear  541  of the light guide plate  54  and a corresponding second ear  561  of the optical film  56  therein, and the fastening post  542  of the first ear  541  engages in the fastening through-hole  562  of the second ear  561 . Thus, the above-described configuration can help to precisely position the second ears  561  in the first notches  581 . In particular, the optical film  56  is precisely positioned relative to the light guide plate  54 . Further, the second ears  561  are more securely retained in the first notches  581  by reason of the attachment of the second ears  561  to the first ears  541 . Thus, the optical film  56  can be precisely and securely fixed in the frame  58 , and the liquid crystal display  20  can provide good quality, reliable display images. In addition, the fastening posts  542  and the fastening through-holes  562  help an operator to assemble the liquid crystal display  20  more easily. In particular, once the fastening through-holes  562  of the optical film  56  engagingly receive the fastening posts  542  of the light guide plate  54 , there is no need for the operator to further correct or adjust the location of the optical film  56 .  
         [0024]      FIG. 2  shows a liquid crystal display  21  according to a second embodiment of the present invention. The liquid crystal display  21  has a structure similar to that of the liquid crystal display  20 , except that the liquid crystal display  21  includes a surface light source  60 . The surface light source  60  includes an optical film  66 , a diffusing plate  64 , a plurality of light sources  63 , a reflector  62 , and a frame  68 , disposed generally in that order from top to bottom. The light sources  63  are linear light sources such as cold cathode fluorescent lamps (CCFLs), and are arranged parallel to each other.  
         [0025]     The diffusing plate  64  has two opposite side surfaces  643 . Two rectangular first ears  641  integrally extend from each side surface  643 . Each first ear  641  has a fastening post  642  formed thereon. The diffusing plate  64  is used to diffusing and uniformizing the light beams from down-disposed the light sources  63  over the whole top surface, and outputting the light beams to the liquid crystal panel.  
         [0026]     The optical film  66  has two opposite side surfaces  663 , and two rectangular second ears  661  integrally extending from each side surface  663 . A fastening through-hole  662  is defined in each second ear  661 .  
         [0027]     In assembly, the optical film  66 , the diffusing plate  64 , the light sources  63 , and the reflector  62  are accommodated in the frame  68  in that order from top to bottom. Each first notch  681  of the frame  68  receives a corresponding first ear  641  of the diffusing plate  64  and a corresponding second ear  661  of the optical film  66  therein, and the fastening post  642  of the first ear  641  engages in the fastening through-hole  662  of the second ear  661 . Thus, the above-described configuration can help to precisely position the second ears  661  in the first notches  681 . In particular, the optical film  66  is precisely positioned relative to the diffusing plate  64 . Further, the second ears  661  are more securely retained in the first notches  681  by reason of the attachment of the second ears  661  to the first ears  641 . Thus, the optical film  66  can be precisely and securely fixed in the frame  68 , and the liquid crystal display  21  can provide good quality, reliable display images. In addition, the fastening posts  642  and the fastening through-holes  662  help an operator to assemble the liquid crystal display  21  more easily. In particular, once the fastening through-holes  662  of the optical film  66  engagingly receive the fastening posts  642  of the diffusing plate  64 , there is no need for the operator to further correct or adjust the location of the optical film  56 .  
         [0028]     In alternative embodiments of the present invention, each of the fastening posts  542 ,  642  can be in the form of a triangular, square, rectangular or multifaceted prism, and the fastening through-hole  562 ,  662  can be correspondingly triangular, square, rectangular or polygonal in cross-section. In another alternative embodiments, there is only one hatch in total, or only one hatch at each of the two opposite sides of the top bezel, or only three hatches in total, or five or more hatches in total (and there is a corresponding number of first protrusions each time). In addition, there is only one first ear in total, or only one first ear at each of the two opposite sides of the light guide plate, or only three first ears in total, or five or more first ears in total (and there is a corresponding number of second ears and first notches each time). Moreover, two or more first ears are at any selected one or more of the four sides of the light guide plate including said two opposite sides (and there is corresponding positioning of the second ears and first notches each time). Furthermore, the post can be formed on the second ears, and the fastening through-holes can be formed on the first ears.  
         [0029]     It is to be understood, however, 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.