Abstract:
A back light apparatus comprises a base having a container, a lamp module, a diffuser, and at least one elastic device. The inside surface of the base are coated a reflection layers. The lamp module consists of CCFLs disposed in the container. One end of the elastic element is fixed on the bottom surface of the container; the other end supports the diffuser. The elastic device reduces the deformation of the diffuser to avoid forming the uneven surface on the diffuser. That is, it can provide the high and even brightness for a liquid crystal display panel.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a liquid crystal display, and more particularly to a back light apparatus for use in a liquid crystal display.  
           [0003]    2. Description of the Prior Art  
           [0004]    A back light module is the key component for liquid crystal display (LCD). By means of the brightness and uniform light source being provided by the backlight module, the LCD panel can display images.  
           [0005]    The backlight module can divide into a sidelight mode and a direct light mode according to the position of the light source. The sidelight mode places lamps of the light source on the side edge of a LCD panel and, then, uses a guiding-panel to control light path so that light beams project to a diffuser below the panel and provide uniform light beams. Because of the position of the light source, it suits being used in a light, thin, and power saving display equipment, e.g. a monitor of a notebook. But for big size display and brightness occasions, e.g. TV and desk PC. The sidelight mode cant provide enough brightness. Hence, it needs the direct light mode to directly place the light source below the display panel. The contain space for the light source is bigger, and has a capacity for over two lamps to increase the brightness of the light source and satisfy what&#39;s need.  
           [0006]    Referring to FIG. 1 and FIG. 2, a direct light back light module  10  comprises a rectangular frame  11  having a container  111 , a light source module  12 , a diffuser  13 , and a supporting rod  14 . The surface of the container  111  has a reflection layer  112  to reflect the light beam provided by the light source module  12  to the diffuser  13 . The light source module  12  comprises a plurality of light tubes  121  side by side inside the container  111 . The two ends of the diffuser  13  fix on a top surface  113  of the rectangular frame  11  and, then, the supporting rod  14  properly is placed on the bottom of the rectangular frame  11 , which has one end holding the diffuser  13  to support the diffuser  13 .  
           [0007]    Due to the supporting rod  14  directly contacting the diffuser  13 , the contact part hinders the light from passing. For avoiding the diffuser  13  forming bigger dark area, the supporting rod  14  generally uses a cone having a smaller cross-section on top point and, thus, the top of the supporting rod  14  directly contacts the diffuser  13  with a pointed tip. As the size of the back light module  10  increasing or the inside temperature of the frame  11  raising that causes by the light source module  12 , the deformation of the diffuser  13  is increasing and makes downward indentation. Meanwhile, the pointed tip of the supporting rod  14  easily protrudes the diffuser  13  so the diffuser  13  forms a uneven surface or even causes the unequal interval between the diffuser  13  and the light source module  12  such that the diffuser  13  has uneven brightness. The LCD panel display images have light and shade phenomenon. In addition, the supporting rod  14  is placed inside the container  111 . As the light source providing light beams impinging onto the surface of the supporting rod  14 , the light beams cant effectively reflect or transmissive and, hence, cant project to the surface of the diffuser  13 , which easily causes illumination light source loss.  
         SUMMARY OF INVENTION  
         [0008]    An object of the present invention is to provide a back light apparatus. By means of the elastic device, the diffuser has the supporting buffer to reduce the deformation of the diffuser.  
           [0009]    Another object of the present invention is to provide a back light apparatus. By means of the buffer provided by the elastic device, the diffuser can avoid damage to provide high brightness and even lightness light source.  
           [0010]    Still another object of the present invention is to provide a back light apparatus. The diffuser is supported by the elastic device to keep the same space for providing high brightness and even lightness.  
           [0011]    Further another object of the present invention is to provide a back light apparatus to reduce the illumination loss by means of the reflection layer.  
           [0012]    To achieve the above and other objects, the back light apparatus of the present invention comprises a frame having a container, a light source module, a diffuser, and at least one elastic device. The inner surface of the container has a reflection layer, and the light source module has a plurality of cold cathode fluorescent lamps side by side placed inside the container. The diffuser is placed upon the top of the frame. The elastic device has one end fixed on the bottom of the container and has the other end pressed to the diffuser. The top of the elastic device has a protrusion which could be transparent materials or high reflection materials to avoid the spots. In addition, the bottom of the container could have a fixing base or a cavity for containing the elastic device. Further, the fixing base could have a reflection layer to raise the reflection area of the light beam. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]    The above and other objects, advantages, and features of the present invention will be understood from the following detailed description of the invention when considered in connection with the accompanying drawings below.  
         [0014]    [0014]FIG. 1 is an explored view showing a back light apparatus of a direct light mode of the prior art.  
         [0015]    [0015]FIG. 2 is a sectional view showing a back light apparatus of a direct light mode of the prior art.  
         [0016]    [0016]FIG. 3 is an explored view showing the first embodiment of a back light apparatus of the present invention.  
         [0017]    [0017]FIG. 4 is a sectional view showing the first embodiment of a back light apparatus of the present invention.  
         [0018]    [0018]FIGS. 5A, 5B and  5 C are active schematic views showing the first embodiment of a back light apparatus of the present invention.  
         [0019]    [0019]FIG. 6 is a sectional view showing the elastic device for a back light apparatus of a first embodiment of the present invention.  
         [0020]    [0020]FIG. 7, FIG. 8, FIG. 9, and FIG. 10 are schematic views showing a back light apparatus having a cavity of the second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
     The First Embodiment  
       [0021]    Referring to FIG. 3, a back light apparatus  20  of the present invention comprises a rectangular frame  21 , a light source module  22 , a diffuser  23 , at least one elastic device  24 , and a cover  25 .  
         [0022]    The rectangular frame  21  has a container  211  and a top  212 , a bottom surface  2111  and an inner surface  2112  of the container  211  have a reflection layer to reflect light beams provided by the light source  22  onto the diffuser  23 . The light source module  22  is placed inside the container  211 , which comprises a plurality of cold cathode fluorescent lamp  221  (CCFL). The lamps  221  have properly interval and horizontally placed inside the container  211 , which has two ends respectively extending to the inner surface  2112  of the frame  21  for fasten. The diffuser  23  is placed upon the top  212  of the rectangular frame  21 . The surface of the diffuser  23  facing to the lamps  221  is as a diffuser layer so the light beams through the diffuser layer causes the diffusion that makes the light beams even. The diffuser  23  is made by plastic material. The elastic device  24  is erected and placed inside the container  211 , which has one end fixed on the bottom  2111  of the container  211  and the other end forming a space D with the diffuser  23  (as shown in FIG. 5A). The elastic device  24  can be a transparent or high reflection-material spring, elastic piece or plastic element to reduce the effect upon reflection light passing through the diffuser  23 . As shown in FIG. 4, the cover  25  is covered on the top  212  of the frame  21 , which has a winder  251  smaller than the area of the diffuser  23 . Side edges of the cover  25  have a plurality of fixing openings  252  for screwing devices  253  to the top  212  of the frame  21  that clips the two ends of the diffuser  23  for fixing.  
         [0023]    The back light apparatus of the present invention is placed behind the LCD panel (not shown in drawing). Part of the light beams provided by the lamps  221  directly project to the diffuser  23 , and part of the light beams reflected by the reflection layer of the inner of the container  211  project to the diffuser  23 . Then, the light beams pass through the diffuser  23  causes the diffusion to provide high and even brightness for LCD panel to display images.  
         [0024]    As shown in FIG. 5A, the diffuser  23  of the back light apparatus  20  of the present invention has a space D with the elastic device  24  that can avoid effecting the light beam passing through the diffuser  23  and forming dark points. As the light source module  22  using for a period, the temperature raises so the plastic diffuser  23  is heated and caused downward deformation. Referring to FIG. 5B, as contacting with the elastic device  24 , the diffuser  23  is supported by the elastic device  24  to reduce the deformation of the diffuser  23  and keep the same space for providing high and even brightness. As the deformation of the diffuser  23  increasing to press the elastic device  24 , referring to FIG. 5C, the elastic device  24  can compress the elastic device  24  for buffer. Hence, the elastic device  24  doesn&#39;t protrude the diffuser  23  to avoid damaging the diffuser  23  to form an uneven surface. Furthermore, the elastic device  24  gradually provides more support to further prevent the diffuser  23  increasing deformation so the diffuser  23  has a better flat providing high and even brightness for LCD panel.  
         [0025]    Referring to FIG. 6, for the size of the monitor becomes bigger; the size of the diffuser  23  is bigger. The plastic diffuser  23  only fixes upon around the rectangular frame  21 , and the central part of the diffuser  23  is easier to form downward deformation. Hence, one end of the elastic device  24  of the present invention is fixed to the bottom  2111  of the container  211 , and the other end directly holds the diffuser  23  to stably support the diffuser  23 . Thus, the deformation of the diffuser  23  can be reduced so that the diffuser  23  has a better flat to provide high and even brightness for LCD panel.  
       The Second Embodiment  
       [0026]    Referring to FIG. 7, the same or similar devices of the present embodiment uses the same marks as the above-mentioned first embodiment. The difference between the present embodiment and the above-mentioned embodiment is that the elastic device  24  could use a spring of metal. The elastic device  24  can collocate a protrusion  241  upon the elastic device  24  to replace the transparent or high reflection optical material spring to lower the cost. The protrusion  241  can be transparent or high reflection material. The present embodiment uses the cone and transparent-material as the protrusion  241 , so the contacting area between the protrusion  241  and the diffuser  23  is decreased not to hinder the light beams and to avoid the diffuser  23  forming dark points. In addition, the protrusion  241  could be elastic material to prevent directly protruding the diffuser  23  to damage the diffuser  23  forming an indent. Besides, because the protrusion  241  placed inside the container  211 , for avoiding the illumination loss, the protrusion  241  could have reflection layer on the surface.  
         [0027]    Referring to FIG. 8, the bottom  2111  of the container  211  has a cavity  213  for placing the elastic device  24 . The protrusion  241  fixes upon the elastic device  24 , which protrudes out of the top of the cavity  213  and keeps a space D 1  with the diffuser  23  or presses to the diffuser  23 . The spring  24 A having bad reflection is hidden inside the cavity  213  to reduce hindering the light beams. Hence, the light beams provided by the lamps  221  can be reflected by the protrusion  241  and projected onto the diffuser  23  to reduce the illumination loss and shadow.  
         [0028]    In addition, referring to FIG. 9, the bottom  2111  of the container  211  has the cavity  213  to place the elastic device  24  inside the cavity  213 . An opening  2131  of the cavity  213  is smaller than the than the diameter of the elastic device  24 . The bottom of the protrusion  241  has a flange  2411 . The flange  2411  is mounted in the cavity  213  to limit only the protrusion  241  out of the cavity  213 . The protrusion  241  keeps a space D 2  with the diffuser  23  or presses to the diffuser  23 . The light beams provided by the lamps  221  could be reflected by the protrusion  241  to the diffuser  23  as being used. In addition, according the size of the diffuser  23 , properly set original elasticity of the elastic device  24  so that could reduce the illumination loss and shadow caused by the deformation of the diffuser  23 .  
         [0029]    Referring to FIG. 10, a fixing base  214  is arranged on the bottom  2111  of the container  211 . The fixing base  214  could contain the elastic device  24  so the volume of the back light apparatus  20  wont increase to shrink the product volume. The size of an opening  2141  of the fixing base  214  is smaller than the diameter of the elastic device  24  and the surface of the fixing base  214  has a reflection layer. The bottom of the protrusion  241  has a flange  2411 . The flange  2411  is mounted in the fixing base  214  to limit only the protrusion  241  out of the fixing base  214 . The protrusion  241  keeps a space D 3  with the diffuser  23  or presses to the diffuser  23 . The light beams provided by the lamps  221  could be reflected by the protrusion  241  and the reflection layer of the fixing base  214  to the diffuser  23  to reduce the illumination loss and shadow caused by the deformation of the elastic device  24 .  
         [0030]    It will be apparent to those skilled in the art that in light of the forgoing disclosure, many alternations and modifications are possible in the practice of this invention without departing from the spirit or scoop thereof. Accordingly, the scoop of the invention is to be considered in accordance with the substance defined in the following claims.