Patent Publication Number: US-2013234943-A1

Title: Keyboard Apparatus Having a Backlight Function

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a keyboard apparatus having a backlight function, more particular to a keyboard apparatus including first and second light guide plates for guiding light from a light emitter toward different keys, respectively. 
     2. Description of the Related Art 
       FIG. 1  illustrates a conventional keyboard apparatus including a keyboard module  11  having a plurality of keys  112 , and a backlight module  12  assembled with the keyboard module  11 . The backlight module  12  includes a light emitter  121 , a light guide plate  122  disposed under the keyboard module  11 , and a plurality of reflective elements  123  provided on a bottom surface of the light guide plate  122  for reflecting light toward the keys  112 . The light from the light emitter  121  enters a light incident surface  1221  of the light guide plate  122 , propagates in the light guide plate  122  along the length of the light guide plate  122 , and is reflected by the reflective elements  123  toward the corresponding keys  112 , thereby permitting the user to allocate the keys  112  to be operated in a dark environment. Since the light guide plate  122  is well known in the art and is commonly used in the backlight modules for applications, such as displays and illuminating keyboards, further details of the same will not be described herein for the sake of brevity. The aforesaid conventional keyboard apparatus is disadvantageous in that since the keys  112  are spaced apart from the light incident surface  1221  of the light guide plate  122  at different distances, a non-uniform optical visual condition that the light reflected by the reflective element  123  adjacent to the light incident surface  1221  will have a higher intensity than that of the light reflected by the reflective element  123  distal from the light incident surface  1221  occurs. Hence, the characters or symbols on the corresponding keys  112  will not have a uniform brightness and the character or symbol on the key  112  distal from the light incident surface  1221  may not have a sufficient brightness when the light emitter  121  is actuated. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide a keyboard apparatus that can overcome the aforesaid drawback associated with the prior art. 
     According to the present invention, there is provided a keyboard apparatus that comprises a keyboard module having a plurality of keys spaced apart from each other, and a backlight module assembled with the keyboard module and disposed under the keys. The backlight module includes a light emitter for emitting light, a first light guide plate disposed adjacent to the light emitter for guiding the light from the light emitter and provided with a first reflective member that is aligned with one of the keys in a vertical direction for reflecting the light toward said one of the keys, and a second light guide plate disposed adjacent to the light emitter for guiding the light from the light emitter, provided with a second reflective member that is aligned with another one of the keys in the vertical direction for reflecting the light toward said another one of the keys, and disposed under the first light guide plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In drawings which illustrate an embodiment of the invention, 
         FIG. 1  is a partly sectional view of a conventional keyboard apparatus; and 
         FIG. 2  is a partly sectional view of the preferred embodiment of a keyboard apparatus according to this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 2  illustrates the preferred embodiment of a keyboard apparatus according to the present invention. The keyboard apparatus includes: a keyboard module  2  having a plurality of keys  21 A,  21 B (for the sake of brevity, only two keys  21 A,  21 B are shown in  FIG. 2 ) spaced apart from each other; and a backlight module  3  assembled with the keyboard module  2  and disposed under the keys  21 A,  21 B. 
     The backlight module  3  includes: a flexible circuit board  34  adapted to be connected to a power source (not shown); a light emitter  31  connected to the flexible circuit board  34  for emitting light; a first light guide plate  32 A disposed adjacent to the light emitter  31  for guiding the light from the light emitter  31  and provided with a first reflective member  33 A that is aligned with one of the keys  21 A in a vertical direction for reflecting the light toward said one of the keys  21 A; a second light guide plate  32 B disposed adjacent to the light emitter  31  for guiding the light from the light emitter  31 , provided with a second reflective member  33 B that is aligned with another one of the keys  21 B in the vertical direction for reflecting the light toward said another one of the keys  21 B, and disposed under the first light guide plate  32 A; and a reflective plate  35  disposed under  20  the second light guide plate  32 B for reflecting the light from the first and second light guide plates  32 A,  32 B. 
     The first light guide plate  32 A has a bottom surface  321 , and has an end portion formed with a first through-hole  361 . The first reflective member  33 A is made from a reflective ink printed on the bottom surface  321  of the first light guide plate  32 A. The second light guide plate  32 B has a bottom surface  322 , and has an end portion formed with a second through-hole  362 . The second reflective member  33 B is made from the reflective ink printed on the bottom surface  322  of the second light guide plate  32 B. The light emitter  31  extends through the reflective plate  35  and into the first and second through-holes  361 ,  362  for emitting light in a sidewise direction into the first and second light guide plates  32 A,  32 B. The first and second light guide plates  32 A,  32 B overlap and are parallel to each other, are aligned with each other in the vertical direction, and are spaced apart from each other by a gap. 
     The keyboard module  2  further has a top wall  22  made from a plastic material, a base wall  24  disposed under the top wall  22 , and a membrane circuit board  23  sandwiched between the top wall  22  and the base wall  24 . The keyboard module  2  is formed with a plurality of key-mounting holes  25  extending through the top wall  22 , the base wall  24 , and the membrane circuit board  23 . The keys  21 A,  21 B are mounted to the top wall  22 , and extend into the key-mounting holes  25 , respectively. 
     Each of the keys  21 A,  21 B includes a keycap  211 , a scissors-shaped frame  212  mounted on the top wall  22  for supporting the keycap  211  thereon, and an urging element  213  urging the scissors-shaped frame  212  for restoring the keycap  211  and the scissors-shaped frame  212  to their original positions. The keycap  211  has a character or a symbol (not shown) formed thereon. The character or the symbol is made from a light transmissive material so as to provide an optical visual effect when the keys  21 A,  21 B are pressed. Since the design of the keys  21 A,  21 B, the top wall  22 , the base wall  24  and the membrane circuit board  23  is well known in the art, further details of the same will not be described herein for the sake of brevity. 
     Preferably, the light emitter  31  is a light emitting diode package that has at least one light emitting diode die. 
     With the inclusion of the first and second light  15  guide plates  32 A,  32 B and the first and second reflective members  33 A,  33 B in the keyboard apparatus of this invention, the aforesaid drawback associated with the prior art can be eliminated. 
     With the invention thus explained, it is apparent that various modifications and variations can be made without departing from the spirit of the present invention.