Abstract:
A backlight module having a truss type structure comprises a plurality of truss type members, a reflector and at least a light source. The truss members and the light source positioned on the truss type structure. In a liquid crystal display (LCD) panel, the truss type structure disclosed in this invention is used as a main structure of such backlight module. Compared to those of the prior art, backlight modules that utilize the truss type structure of this invention have the advantages of reduced weight and better bending strength.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a backlight module, particularly one with a truss type structure.  
         [0003]     2. Description of the Related Art  
         [0004]     Liquid crystal display (LCD) TV has long become the mainstream of the market, and as a result, the sizes thereof are being made larger and larger.  FIG. 1  shows a conventional backlight module used in an LCD panel. The backlight module  10  comprises a back cover  11 , a reflector  12 , a plurality of light sources  13 , a plurality of optical films  16 , a diffuser plate  14 , and a front cover  15 . The back cover  11 , which provides most mechanical strength for the backlight module  10 , is made of a metal such as aluminum or zinc-plated sheet steel (SECC). As the LCD panels are made larger, the back cover  11  and tooling therefor also have to be made larger and cost therefor is absolutely increased. In this case, the current manufacturing and equipment capability may not necessarily deal well with the newly introduced requirements. In addition, the increased dimension of the back cover  11  also means that the LCD panel (not shown) will become more weighted and the back cover  11  will suffer from the problem of insufficient bending strength.  
         [0005]     In this regard, a reinforcing rib or a reinforcing plate (not shown) is generally suggested to increase the insufficient bending strength. However, mold cost is in this case further increased and such mold is in fact not easy to be fabricated. Moreover, the more weighted of such backlight module also imposes difficulties on transportation thereof and assembly therefor. In this case, further equipment has to be furnished and a further cost is required. Moreover, the weighty backlight module has to be charged with a pricy shipment cost.  
         [0006]     Therefore, how to reduce the weight of an LCD backlight module without sacrificing its bending strength is an important issue for all LCD manufacturers.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to provide an LCD backlight module with reduced weight and better bending strength.  
         [0008]     The LCD backlight module with a truss type structure, designed in line with the spirit of the present invention, comprises a plurality of truss members, a reflector and at least a light source disposed on the truss type structure, respectively. As compared to the prior art, the truss type structure is used as a main structure of the backlight module so that the weight thereof is reduced while at the same time the bending strength thereof is enhanced.  
         [0009]     With the backlight module according to the present invention, the following advantages may be achieved: (1) only one-second of weight is required for the truss type structure as compared to the prior truss structure of same size. (2) No additional mold has to be furnished and thus mold cost and mold development time for the truss type structure may be saved. (3) The manufacturing of the truss type structure may be conducted by means of the current equipment on the current production line. (4) The material cost and development cost for the truss type structure itself are inexpensive. (5) Inventory cost and shipment expenses are reduced owing to the slighter truss type structure. (6) Only a lower assembly cost is required since the assembly for the truss type structure is simple. (7) The bending strength is efficiently enhanced as compared to a prior truss type structure of same size and the warpage is well improved. (8) The truss type structure is easy to be fastened and assembled and thus no additional support or supporting means is required. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The invention can be more fully understood from the detailed description given below, the drawings and embodiments are not limitative of the right scope of the present invention, and wherein:  
         [0011]      FIG. 1  shows a conventional backlight module used in an LCD;  
         [0012]      FIG. 2  shows a backlight module having a truss type structure according to the first embodiment of the present invention;  
         [0013]      FIG. 3  shows the backlight module having the truss type structure according to the second embodiment of the present invention;  
         [0014]      FIG. 3A  is a partial view of the truss type structure equipped backlight module;  
         [0015]      FIGS. 4A  to  4 D are detailed diagrams of the truss type structures of the present invention;  
         [0016]      FIGS. 5A  to  5 C are detailed diagrams of the connectors of the truss type structures of the present invention; and  
         [0017]      FIGS. 6A  to  6 H are cross section views of the truss members of the embodiments of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]     Referring to  FIG. 2 , a backlight module  20  having a truss type structure according to the first embodiment of the present invention. The backlight module  20  comprises a truss type structure  21 , a reflector  71  and a plurality of light sources  22 . In the backlight module  20 , the truss type structure  21  comprises a plurality of truss members, which are used to provide required mechanical strength for the backlight module  20 . A first truss member  72  and a second truss member  73  of the truss type structure  21  can be jointed with each other through welding, interlocking, screwing, bonding, or any other means considered suitable.  
         [0019]     Preferably, the first truss member  72  and the second truss member  73  are jointed by a connector  24 . In other words, the connectors connect the adjacent truss members. The reflector  71  is disposed on the truss type strcuture  21  and used to reflect a light emitted from the light sources  22 . In this embodiment, the reflector  71  can be made of polycarbonate (PC) or polyethylene terephthalate (PET).  
         [0020]     The light sources  22  are positioned on the truss strcuture  21 , and may be a point light source, a linear light source or a flat light source. In this embodiment, a plurality of cold cathode fluorescent lamps (CCFLs) are evenly (i.e., with equal space in between) distributed on the truss type structure  21  and the light sources  22  are secured on the truss type structure  21 . In this embodiment, a plate  74  may be further provided between the reflector  71  and a first side  75  of the truss type structure  21  for leveling or supporting the reflector  71 .  
         [0021]     The diffuser plate  27  is provided to diffuse evenly the light emitting from the light sources  22 . A plurality of optical films  28  (e.g., a polarizing film or a prism film) are each provided with a plurality of protrusions  28   a.  Such protrusions  28   a  can also be provided on the diffuser plate  27 . The backlihgt module  20  further comprises a plurality of side walls  29 . The side walls  29  are disposed on the first side  75  of the truss type structure and have a plurality of light source holders  76  for securing the light source  22  on the first side  75  of the truss type structure  21 .  
         [0022]     In this embodiment, ends  25  of the light sources  22  are secured by the light source holders  76 . The protrusions  28   a  can fit on recesses  29   a  of the side walls  29  in such a manner that the optical film  28  and the diffuser  27  can be provided at the side walls  29 . The side walls  29  is made of a metal or plastic and may be fixed to the truss type structure  21  by interlocking or screwing.  
         [0023]     A plurality of second printed circuit boards (PCBs)  26  can include a control system board, an inverter board, or a power supply board. The second PCBs  26  are fixed on the truss type structure  21  and can alternatively be disposed on an external side or a second side  77  of the back light module  20 .  
         [0024]      FIG. 3 , illustrates a second preferred embodiment of the backlight module  30  having the truss type structure according to the spirit of the present invention. The backlight module  30  comprises a truss type structure  31 , a first printed circuit board (PCB)  32  and a plurality of light sources  33 .  
         [0025]     The truss type structure  31  comprises a plurality of truss members  34  jointed through a plurality of connectors  35 ; and used to provide mechanical strength for the backlight module  30 . Furthermore, the first PCB  32  may have a relecitve material coated on a surface as a reflector to reflect light like that functioned by a conventional reflector. The light sources  33  are electrically mounted on the first PCB  32  and disposed on the refelctor surface. A diffuser plate  37  is provided to diffuse the lgiht emitted from the light sources  33 .  
         [0026]     A plurality of optical films  38  (e.g., a polarizing film or a prism film) is provided with a plurality of protrusions  38   a.  Such protrusions  38   a  can also be provided on the diffuser plate  37 . The backlihgt module  30  further comprises a plurality of side walls  39 . The protrusions  38   a  can fit on recesses  39   a  of the side walls  39  in such a manner that the optical film  38  and the diffuser plate  37  may be provided in the backlgiht module  39 . The side walls  39  is made of a metal or plastic and can be fixed to the truss type structure  31  by interlocking or screwing.  
         [0027]     Referring to  FIG. 3A , a partial view of the truss type structure equipped backlight module. As shown, the light sources  33  are disposed on the first PCB  32  and can be a point light source, such as a white light-emitting diode (LED). The diffuser plate  37  can diffuse the light emitted from the light sources  33  and thus form an evenly distributed flat light source.  
         [0028]     In this embodiment, the first PCB  32  can be a reflector made of PC or PET. The light sources  33 , which can comprises a plurality of LEDs, are positioned on the reflector.  
         [0029]     A plurality of second PCBs  36  can include a control system board, an inverter board, or a power supply board. The second PCBs  36  are fixed on the truss type structure  31 .  
         [0030]      FIG. 4A  through  FIG. 4D  are detailed diagrams of the truss type structures of the present invention in which the first, second, third and fourth fundamental type truss strcutures are shown respectively. As shown in these figures, each of the truss type structures  41 ,  42 ,  43 ,  44  is obtained by connecting a plurality of truss members through a plurality of connectors. With backlight modules having a diagonal dimension of 30 to 50 inches, the first and fourth type truss strcutures  41 ,  44  are preferred. On the other hand, with backlight modules having a diagonal dimension greater than 50 inches, the second and third type truss strcutures  42 ,  43  are preferred.  
         [0031]      FIG. 5A through 5C  are detailed diagrams of the connectors used in the truss type structures of the present invention. As shown in these figures, an L-shaped two way connector  51  is used to connect the first truss member  52  and the second truss member  53 . The angle between the first truss member  52  and the second truss member  53  is 90 degree. An T-shaped three-way conenctor  54  and an multi-way connector  55  are used to connect three and eight truss members respectively, wherein the angle between the third truss member  56  and the fourth truss member  57  is 180 degree and the angle between the fifth truss member  58  and the sixth truss member  59  is 30 degree. The angle between two adjacent truss members is from 30 degrees to 180 degrees. The shape of connectors is based on that of the truss members. The truss members and the connectors can be made of plastic, SECC, Al, Mg and Ti and the truss members can be alternatively made of paper.  
         [0032]      FIG. 6A  to  FIG. 6F  show cross sectional views of the truss members of the truss type structures according to the present invention. The truss members can be solid truss members or hollow truss members of three-dimensional structure. In the case of the truss members, lines or wires required for the backlight module can run through them. The hollow truss members can be a square shape  61 , a rectangular shape  62 , a circular shape  63 , an L shape  64 , an I shape  65 , a T shape  66 , a B shape  67 , a C shape  68  or other alphabet letter shape cross section structure, wherein from the L shape  64  to C shape  68  and the alphabet letters shaped are called letter-shaped cross section structure. As an example, with a 50-inch backlight module, zinc-plated steel sheet (SECC) will be chosen as the material of the truss members and the connectors, while the first type truss strcuture with truss members having square-shaped cross sections will be chosen to go with the module. Compared with that of conventional back coverd modules, the weight of a the truss-structured backlight module is up to at least 50% lighter, while its bending strength is more than doubled.  
         [0033]     Also contemplated in the present invention, sectional structure of the truss members may vary with the strength requirements of the backlight module. Further, area and type of the sectional structure of the truss members can be different in the truss type structure. For instance, the truss members further comprise a plurality of main truss members and a plurality of secondary truss member. The main truss member can have a sectional shape having a greater moment of inertia while the secondary truss member may have a sectional shape having a smaller moment of inertia so as to reduce the weight of the truss type structure.  
         [0034]     As is understood by a person skilled in the art, the foregoing preferred embodiment of the present invention is an illustration, rather than a limiting description, of the present invention. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.