Abstract:
A backlight module and a liquid crystal display (LCD) apparatus using the same are disclosed. The backlight module includes a bottom plate and multiple lamps disposed separately over the bottom plate. The bottom plate has multiple lower-reflectivity areas underneath the lamps and multiple higher-reflectivity areas between neighboring lower-reflectivity areas. The LCD apparatus includes such a backlight module and a LCD panel disposed over the lamps.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a structure of a flat-panel display. More particularly, the present invention relates to a backlight module and a liquid crystal display (LCD) apparatus using the same.  
         [0003]     2. Description of the Related Art  
         [0004]     The backlight modules for providing backlight to LCD monitors or LCD-TV can be roughly classified into direct-type modules or side-edge modules. A side-edge module includes one or two side lamps as well as a light guide plate (LGP) for evenly spreading the light from the lamp onto the LCD panel disposed in front of the LGP.  
         [0005]      FIG. 1  is a top view of a LCD apparatus having a conventional direct-type backlight module. As shown in  FIG. 1 , the direct-type backlight module includes several lamps  110  disposed underneath the LCD panel  120  of the LCD apparatus  100 . Because multiple lamps are used instead of a light guide plate (LGP), the brightness uniformity of the LCD panel can be improved more easily. Hence, the direct-type backlight module is particularly suitable for a large-sized LCD apparatus.  
         [0006]     However, the direct-type backlight module still has two major disadvantages, namely, lower brightness uniformity and larger thickness. As shown in  FIG. 1 , each area  120   a  of the LCD panel  120  directly above a lamp  110  is closest to the lamp  110 , so that the direct light in the area  120   a  is stronger and the brightness there is higher. However, each area  120   b  of the LCD panel  120  is located further away from the lamp  110  and the brightness there is lower. Even when a diffusion plate is inserted between the lamps  110  and the LCD panel  120 , alternating bright and dark bands can still be seen on the LCD panel  120  adversely affecting the display quality of the LCD panel  120 . To reduce the brightness variation across the LCD panel  120 , the distance between the LCD panel  120  and the lamps  110  is often increased so that the ratio of the distance between the LCD panel  120  and the lamps  110  to the distance between two lamps  110  is greater than 0.7. Unfortunately, this method will increase the overall thickness of the LCD apparatus.  
       SUMMARY OF THE INVENTION  
       [0007]     Accordingly, one object of this invention is to provide a direct-type backlight module that makes the LCD panel better in brightness uniformity, or allows the distance between the lamps and the LCD panel to be reduced.  
         [0008]     This invention also provides a LCD apparatus that uses the direct-type backlight module of this invention to be better in brightness uniformity of LCD panel, or to be smaller in thickness due to reduction of the distance between the lamps and LCD panel.  
         [0009]     To achieve these and other advantages and in accordance with the purposes of this invention, as embodied and broadly described herein, the invention provides a backlight module. The backlight module includes a bottom plate and multiple lamps disposed separately over the bottom plate. The bottom plate has multiple first areas with lower reflectivity underneath the lamps and multiple second areas with higher reflectivity, wherein each second area is between two first areas with lower reflectivity.  
         [0010]     On the other hand, the LCD apparatus of this invention includes the above backlight module and a LCD panel disposed over the lamps.  
         [0011]     In the backlight module and the LCD apparatus of the present invention, the bottom plate has lower reflectivity in each area underneath a lamp, so that the light reflected from such an area onto the area of the LCD panel directly above the lamp is weaker. Since the weaker reflective light on the panel area directly above the lamp can compensate for the stronger direct light on the same panel area, the brightness uniformity of the LCD panel is better and the display quality of the LCD panel is improved.  
         [0012]     In other words, since an intensity variation of reflective light across the LCD panel is caused by the bottom plate to compensate for the intensity variation of direct light, a larger intensity variation of direct light across the LCD panel is tolerable as compared with the prior art. That is, the distance between the lamps and the LCD panel can be further reduced without sacrificing the brightness uniformity and display quality. Consequently, the thickness of the LCD apparatus can be further reduced.  
         [0013]     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a top view of a LCD apparatus having a conventional direct-type backlight module.  
         [0015]      FIG. 2  is a schematic cross-sectional view showing a LCD apparatus according to a first embodiment of the present invention.  
         [0016]      FIG. 3  is a schematic cross-sectional view showing a LCD apparatus according to a second embodiment of the present invention.  
         [0017]      FIG. 4  is a schematic cross-sectional view showing a LCD apparatus according to a third embodiment of the present invention.  
         [0018]      FIG. 5  is a locally magnified view of the LCD apparatus shown in  FIG. 2 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.  
         [0020]     FIGS.  2 / 3 / 4  is a cross-sectional view showing the LCD apparatus according to the first/second/third embodiment of the present invention. As shown in each of  FIGS. 2-4 , the LCD apparatus  200  includes a bottom plate  205 , a plurality of lamps  210  and a LCD panel  220 . The bottom plate  205  and the lamps  210  together form a backlight module. The lamps  210  are preferably disposed in parallel and equidistantly over the bottom plate  205  to increase the brightness uniformity. In these embodiments, the areas with lower/higher reflectivity are formed using films having lower/higher reflectivity.  
         [0021]     To increase the brightness uniformity of the LCD panel  220  and also utilize the light from the lamps  210  as completely as possible, the reflectivity of the areas with lower reflectivity is preferably 75-85%, and the reflectivity of the areas with higher reflectivity is preferably 90-99.9%. However, the more preferable combination is that the reflectivity of the areas with lower reflectivity is about 80% and the reflectivity of the areas with higher reflectivity is about 96%.  
         [0022]     In the first embodiment as shown in  FIG. 2 , multiple lower- reflectivity films  230  and higher-reflectivity films  240  are alternately disposed on the bottom plate  205 . The lower-reflectivity films  230  are positioned underneath the lamps  210  and each higher-reflectivity film  240  is disposed between two lower-reflectivity films  230 . The lower-reflectivity films  230  and the higher-reflectivity films  240  form the aforementioned lower-reflectivity areas and higher-reflectivity areas, respectively, of the bottom plate  205 . To fabricate such a bottom plate  250 , for example, multiple lower-reflectivity films  230  and higher-reflectivity films  240  each having a predetermined size are cut off from a large-sized lower-reflectivity film and a large-sized higher-reflectivity film, respectively. Thereafter, the lower-reflectivity films  230  and the higher-reflectivity films  240  are attached to the predetermined areas of the bottom plate  205 . The higher-reflectivity film can be made from 3M&#39;s ESR high-molecular polymer material, which can make a reflectivity up to 98%. The lower-reflectivity film can be a surface-treated metallic film, such as, an anodized aluminum film.  
         [0023]     In the second embodiment as shown in  FIG. 3 , a single sheet of lower-reflectivity film  330  is disposed on the bottom plate  205 , and multiple higher-reflectivity films  240  are disposed on the lower-reflectivity film  330 . The higher-reflectivity films  240  are disposed on the lower-reflectivity film  330  away from the areas underneath the lamps  210  to form the aforementioned higher-reflectivity areas on the bottom plate  205 . The lower-reflectivity areas are constituted of the exposed portions of the lower- reflectivity film  330  not covered by the high reflectivity films  240 . To fabricate such a bottom plate  250 , the single sheet of lower-reflectivity film  330  is attached to the bottom plate  250 , and then the higher-reflectivity films  240  are attached to the predetermined areas of the lower-reflectivity film  330 .  
         [0024]     In the third embodiment as shown in  FIG. 4 , a single sheet of higher-reflectivity film  440  is disposed on the bottom plate  205 , and multiple lower-reflectivity films  230  are disposed on the higher-reflectivity film  440 . The lower-reflectivity films  230  are disposed on the areas of the higher-reflectivity film  440  underneath the lamps  210  to form the aforementioned lower-reflectivity areas of the bottom plate  205 . The higher-reflectivity areas are constituted of the exposed portions of the higher-reflectivity film  440  not covered by the lower-reflectivity films  230 . To fabricate such a bottom plate  250 , the higher-reflectivity film  440  is attached to the bottom plate  250 , and then the lower-reflectivity films  230  are attached to the predetermined areas of the higher-reflectivity film  440 .  
         [0025]      FIG. 5  is a locally magnified view of the LCD apparatus shown in  FIG. 2 . In the LCD apparatus, the reflectivity of the lower-reflectivity films  230  underneath the lamps  210  is lower, so that the reflective light from such areas to the areas  220   a  of the LCD panel  220  directly above the lamps  210  is weaker. The weaker reflective light on the areas  220   a  can compensate for the stronger direct light on the same areas  220   a . On the contrary, the reflectivity of the higher-reflectivity films  240  not underneath the lamps  210  is higher, so that the reflective light from such areas to the areas  220   b  of the LCD panel  220  farther away from the lamps  210  is stronger. The stronger reflective light on the areas  220   b  can compensate for the weaker direct light on the same areas  220   b . Hence, the present invention is able to enhance the brightness uniformity of a LCD panel and improve the display quality of the same.  
         [0026]     In other words, since an intensity variation of reflective light across the LCD panel is caused by the bottom plate to compensate for the intensity variation of direct light, a larger intensity variation of direct light across the LCD panel is tolerable as compared with the prior art. Therefore, the ratio (h/w) of the lamp-to-panel distance “h” to the lamp-to-lamp distance “w” (see  FIG. 2 ) can be reduced to below 0.7 without sacrificing the brightness uniformity and the display quality of the LCD panel, and the thickness of the LCD apparatus can be further reduced accordingly.  
         [0027]     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.