Abstract:
A liquid crystal display (LCD) device includes a backlight module for providing backlight to the LCD device; a first liquid crystal panel disposed on a top surface of the backlight module for displaying images; and a second liquid crystal panel disposed on a bottom surface of the backlight module for displaying images. The LCD device also includes at least one driver circuit board disposed on at least one side of the backlight module for driving selected cells within the first and second liquid crystal panels in order to display a same image simultaneously.

Description:
BACKGROUND OF INVENTION 
   1. Field of the Invention 
   The present invention relates to a backlight module used in a liquid crystal display (LCD) device, and more specifically, to a double-sided LCD device that uses a single backlight module. 
   2. Description of the Prior Art 
   Please refer to  FIG. 1 .  FIG. 1  is a cross-sectional view of a liquid crystal display (LCD) device  5  according to the prior art. The LCD device  5  includes a liquid crystal panel  10 , which has two substrates and a liquid crystal inserted therebetween, and a backlight module  20  disposed under the liquid crystal panel  10  for providing backlight to the liquid crystal panel  10 . A driver circuit board  12  is usually disposed below the backlight module  20  for controlling individual cells within the liquid crystal panel  10 . The backlight module  20  is arranged to distribute light from a light source uniformly over the surface of the liquid crystal panel  10 . The backlight module  20  can be broken down into categories, including direct type and edge light type. 
   Please refer to  FIG. 2 .  FIG. 2  is a direct type backlight module  20 A according to the prior art. The direct type backlight module  20 A includes a housing  70  with a reflecting plate  60  disposed at the bottom of the housing  70 . A plurality of lamps  50 , such as a fluorescence cathode tubes, are disposed at the bottom portion of the housing  70  above the reflecting plate  60  for providing backlight, and the reflectingplate  60  reflects light from the lamps  50  upwards. A diffuser plate  40  is disposed in the housing  70  for diffusing light from the lamps  50 , and a prism film  30  is disposed on the diffuser plate  40  for improving luminance of the direct type backlight module  20 A. 
   Please refer to  FIG. 3 .  FIG. 3  is an edge light type backlight module  20 B according to the prior art. The edge light type backlight module  20 B includes a light guide plate  80  for guiding light through the light guide plate  80  and a lamp  51  disposed on at least one edge of the light guide plate  80  for providing light to the light guide plate  80 . A U-type reflector  61  surrounds the lamp  51  for directing light emitted from the lamp  51  towards the light guide plate  80 . As with the direct type backlight module  20 A, the edge light type backlight module  20 B also contains the reflecting plate  60  for reflecting light upwards, a diffusing film  42  disposed on the light guide plate  80  for diffusing light from the light guide plate  80 , and the prism film  30  disposed on the diffusing film  42  for improving luminance of the edge light type backlight module  20 B. 
   Both the direct type backlight module  20 A and the edge light type backlight module  20 B can be used in the LCD device  5 , which is a single-sided device. However, because the reflecting plate  60  does not allow light to pass through a bottom side of the backlight modules  20 A and  20 B, the backlight modules  20 A  20 B cannot be used in a double-sided LCD device. 
   SUMMARY OF INVENTION 
   It is therefore a primary objective of the claimed invention to provide a backlight module for use in a liquid crystal display (LCD) device in order to solve the above-mentioned problems. 
   According to the claimed invention, a liquid crystal display (LCD) device includes a backlight module for providing backlight to the LCD device; a first liquid crystal panel disposed on a top surface of the backlight module for displaying images; and a second liquid crystal panel disposed on a bottom surface of the backlight module for displaying images. The LCD device further comprises at least one driver circuit board disposed on at least one side of the backlight module for driving selected cells within the first and second liquid crystal panels in order to display a same image simultaneously. 
   In one embodiment of the invention, the backlight module for use in a liquid crystal display (LCD) device comprises a reflecting plate having a top surface and a bottom surface for reflecting light shining incident on the top and bottom surfaces of the reflecting plate, at least one first lamp disposed on a left side of the reflecting plate and at least one second lamp disposed on a right side of the reflecting plate for providing backlight for the LCD device, a first light guide plate disposed on the top surface of the reflecting plate for guiding light emitted from the first and second lamps, and a second light guide plate disposed on the bottom surface of the reflecting plate for guiding light emitted from the first and second lamps. 
   In another embodiment of the invention, the backlight module comprises a set of lamps for providing backlight for the LCD device; a first diffuser plate disposed above the first set of lamps for diffusing light emitted from the lamps; and a second diffuser plate disposed below the first set of lamps for diffusing light emitted from the lamps. 
   The driver circuit of the LCD device is not disposed beneath the first liquid crystal panel and the second liquid crystal panel. In addition the driver circuit board is disposed substantially perpendicular to or parallel with a lateral side of the backlight module. 
   It is an advantage of the claimed invention that the present invention backlight module can provide backlight in two directions, for using a single backlight to illuminate a double-sided LCD device. 
   These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a cross-sectional view of a liquid crystal display (LCD) device according to the prior art. 
       FIG. 2  is a direct type backlight module according to the prior art. 
       FIG. 3  is an edge light type backlight module according to the prior art. 
       FIG. 4  is a cross-sectional view of an LCD device according to the present invention. 
       FIG. 5  is a front view of the LCD device shown in  FIG. 4 . 
       FIG. 6  shows an LCD device having driver circuit boards positioned parallel with a lateral side of a backlight module. 
       FIG. 7  is a front view of the LCD device shown in  FIG. 6 . 
       FIG. 8  to  FIG. 11  are backlight modules according to the first through fourth embodiments of the present invention. 
   

   DETAILED DESCRIPTION 
   Please refer to  FIG. 4 .  FIG. 4  is a cross-sectional view of an LCD device  100  according to the present invention. The LCD device  100  comprises two liquid crystal panels  102  and a backlight module  120  for providing backlight to the liquid crystal panels  102 . The LCD device  100  also contains at least one driver circuit board  104  for controlling individual cells within the liquid crystal panels  102 . In  FIG. 4 , two driver circuit boards  104  are shown, with each driver circuit board  104  being perpendicular to a lateral side  122  of the backlight module  120 . The liquid crystal panels  102  are capable of simultaneously displaying identical images or different images according to the wishes of the manufacturer and user. 
   Please refer to  FIG. 5  with reference to  FIG. 4 .  FIG. 5  is a front view of the LCD device  100  shown in  FIG. 4 . The LCD device  100  contains a housing  106  for holding the liquid crystal panels  102 . One of the liquid crystal panels  102  is visible in  FIG. 5 , with the other liquid crystal panel  102  being disposed directly behind. Since the driver circuit boards  104  are perpendicular to the lateral side  122  of the backlight module  120 , the driver circuit boards  104  are shown as being disposed on an outer perimeter of the liquid crystal panels  102 . In this case, driver circuit boards  104  are disposed on each side of the liquid crystal panels  102 . Please note that it is not required that the driver circuit boards  104  be disposed on all four sides of the liquid crystal panels  102 . Two driver circuit boards  104  could also be used, with one controlling rows of cells and the other controlling columns of cells. 
   Please refer to  FIG. 6 .  FIG. 6  shows an LCD device  200  having driver circuit boards  104  positioned parallel with the lateral side  122  of the backlight module  120 . The LCD device  200  structure shown in  FIG. 6  is preferably used when the backlight module  10  is direct type, but be used with either a direct type or an edge light type backlight module. Also, the two driver circuit boards  104  shown in  FIG. 6  can instead be combined into a single driver circuit board  104  if desired. 
   Please refer to  FIG. 7  with reference to  FIG. 6 .  FIG. 7  is a front view of the LCD device  200  shown in  FIG. 6 . The LCD device  200  contains the housing  106  for holding the liquid crystal panels  102 . Since the driver circuit boards  104  are parallel with the lateral side  122  of the backlight module  120  in the LCD device  200 , so the margin M of the LCD device  200  can be reduced. 
   Please refer to  FIG. 8 .  FIG. 8  is a backlight module  120 A according to the first embodiment of the present invention. The backlight module  120 A is an edge light type backlight module that can be used in the double-sided LCD device  100 . The backlight module  120 A contains a reflecting plate  130  for reflecting light towards each of the liquid crystal panels  102 . Lamps  140  are used for providing light to light guide plates  136  disposed in the backlight module  120 A. The lamps  140  are disposed beside the two light guide plates  136 , and the light guide plates  136  distribute the light from the lamps  140  across the backlight module  120 A. A U-type reflector  142  surrounds each lamp  140  for directing light from the lamps  140  into the light guide plates  136 . Please note that each of the lamps  140  is used to emit light into both of the light guide plates  136 . The backlight module  120 A includes diffusing films  132  disposed on the light guide plates  136  for diffusing light from the light guide plates  136 . Additionally, prism films  134  are disposed on the diffusing films  132  for improving luminance of the backlight module  120 A. As shown in  FIG. 8 , the reflecting plate  130  is substantially parallel with the light guide plates  136 . 
   Please refer to  FIG. 9 .  FIG. 9  is a backlight module  120 B according to the second embodiment of the present invention. The backlight module  120 B is another edge light type backlight module that can be used in the double-sided LCD device  100 . The main difference between the backlight module  120 B and the backlight module  120 A of  FIG. 8  is the backlight module  120 B contains lamps  140  corresponding to each of the light guide plates  136  instead of having each lamp  140  emit light to both light guide plates  136 . By placing lamps  140  directly beside each light guide plate  136 , light emitted from the lamps  140  has a direct path to the light guide plates  136 . 
   Please refer to  FIG. 10 .  FIG. 10  is a backlight module  120 C according to the third embodiment of the present invention. The backlight module  120 C is a direct type backlight module that can be used in the double-sided LCD device  100 . The backlight module  120 C contains a plurality of lamps  140  for emitting light to both of the liquid crystal panels  102 . Disposed in the backlight module  120 C on either side of the lamps  140  are diffuser plates  138  for diffusing light from the lamps  140 . In addition, prism films  134  are disposed on the diffuser plates  138  for improving luminance of the backlight module  120 C. 
   Please refer to  FIG. 11 .  FIG. 11  is a backlight module  120 D according to the fourth embodiment of the present invention. The backlight module  120 D is another direct type backlight module that can be used in the double-sided LCD device  100 . The main difference between the backlight module  120 D and the backlight module  120 C of  FIG. 10  is the backlight module  120 D contains two sets of lamps  140 , with one set of lamps  140  being disposed on either side of a reflecting plate  130 . As shown in  FIG. 11 , the reflecting plate  130  is substantially parallel with the two sets of lamps  140 . The reflecting plate  130  reflects light from each set of lamps  140 , and does not allow light to pass through the reflecting plate  130 . 
   In summary, each of the backlight modules  120 A– 120 D shown in  FIG. 8  to  FIG. 11  can be used as the backlight module  120  for the LCD device  100  shown in  FIG. 4 . The backlight module  120  can provide light to each of the liquid crystal panels  102 , so that the double-sided LCD device  100  can be built using a single backlight module  120 . Using a single backlight module  120  reduces the cost and the size of double-sided LCD devices as compared to double-sided LCD devices that use two backlight modules. 
   Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.