Abstract:
A light emitting key is disclosed. A through hole is made through piezoresistive layer; a light source is arranged under the bottom of the light emitting key. When the light source is turned on, light beams shall emit out of the top substrate. The light emitting effect of the key facilitates it to be used in a dark area such as an aircraft flying in the night sky.

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a light emitting key which can be used in a key board or a key pad. The lighting effect facilitates the key board or key pad to be operable visibly in a dark area such as an aircraft flying in the night time. 
     2. Description of Related Art 
       FIG. 1  is a prior art 
       FIG. 1  is a prior art of U.S. Pat. No. 7,068,142. It disclosed a pressure-sensitive sensor  1  which includes first and second base films  2  serving as base materials, a pair of electrodes  3  formed on the respective base films  2 , pressure-sensitive resistors  4  formed on the respective electrodes  3  and a spacer  6  for setting a predetermined gap  5  between the pressure-sensitive resistors  4 . The deficiency for the prior art is that the pressure-sensitive sensor  1  can not be seen clearly in a dark environment. The invisibility of the sensor prevents it from being operable in a dark area. A light emitting key that can be operated visibly in a dark area is desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a prior art 
         FIG. 2  shows a first embodiment of a light emitting key according to the present invention. 
         FIG. 3  shows an elevation view of the piezoresistive layers of  FIG. 2   
         FIG. 4  shows a second embodiment of a light emitting key according to the present invention 
         FIG. 5A  shows a top view of  FIG. 4   
         FIG. 5B  shows a modified pattern of the piezoresistive layers 
         FIG. 6A  shows a further modified pattern of the piezoresistive layers 
         FIG. 6B  shows a further modified pattern of the piezoresistive layers 
         FIG. 6C  shows a further modified pattern of the piezoresistive layers 
         FIG. 7  shows an exploded view for a single key 
         FIG. 8  is an assembly of  FIG. 7   
         FIG. 9  shows a third embodiment of a light emitting key according to the present invention 
         FIG. 10  shows a modified light source for  FIG. 9   
         FIG. 11  shows a modified light emitting key for  FIG. 10   
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention discloses a light emitting key. A through hole or ditch is made through the piezoresistive layer of the light emitting key. A light source, such as a light emitted diode or a light panel, is configured under the bottom of the light emitting key. The light beam emitted from the light source is able to pass the through hole or ditch to emit light beams on a top substrate of the light emitting key so that the light emitting key can be operated visibly in a dark environment. Several different structures of a single analog key is introduced in the present invention. 
       FIG. 2  shows a first embodiment of a light emitting key according to the present invention. 
       FIG. 2  shows a section view of a first embodiment for a light emitting key. A top transparent substrate  50 T is prepared. A top electrode  30 T is configured under the top substrate  50 T. A top piezo piezoresistive layer  31 T is configured on a bottom of the top electrode  30 T. A bottom piezoresistive layer  31 B is configured under the top piezoresistive layer  31 T but maintains a space  302  therebetween. A bottom electrode  30 B is configured on a bottom of the bottom piezoresistive layer  31 B. A top through hole  301 T is made through the top piezoresistive layer  31 T. A bottom through hole  301 B is made through the bottom piezoresistive layer  31 B. A pair of spacers  404  is configured between the top electrode  30 T and the bottom electrode  30 B so that the gap  302  is formed between the top piezoresistive layer  31 T and the bottom piezoresistive layer  31 B. A bottom substrate  50 B is configured on the bottom of the bottom electrode  30 B. A light source  90 , such as a light emitted diode or a light panel, is configured under the bottom substrate  50 B. 
     The top substrate  50 T and the top electrode  30 T, the bottom substrate  50 B and the bottom electrode  30 B, are all made of transparent material. A transparent flexible circuit board which has transparent electric conductive traces is good for use to play a role of either a combination of the top substrate  50 T plus the top electrode  30 T or a combination of the bottom substrate  50 B and the bottom electrode  30 B in the present invention. 
     When the light emitting key of  FIG. 2  is pressed, the two piezoresistive layer  31 T,  31 B are contacted and then compressed. The higher the pressure is, the thinner the total thickness becomes. According to the Law of Resistance (R=ρL/S). The output resistance R decreases in proportion to the compressed total thickness L of the piezoresistive layer  31 T and  31 B. That is to say, an output resistance decreases with an increase of the pressure P. A corresponding analog signal can be output through the top electrode  30 T and the bottom electrode  30 B. 
       FIG. 3  shows an elevation view of the piezoresistive layers of  FIG. 2   
     A rectangular top through hole  301 T is made through the top piezoresistive layer  31 T; and a rectangular bottom through hole  301 B aligned with the top through hole  301 T is made through the bottom piezoresistive layer  31 B. A light source  90  is then arranged under the bottom of the light emitting key so that light beams are able to pass through the through hole  301 T,  301 B and emitted on the top substrate of the light emitting key of  FIG. 2 . 
       FIG. 4  shows a second embodiment of a light emitting key according to the present invention 
       FIG. 4  shows a light emitting key having a cruciform ditch  401  made through the top electrode  40 T, the top piezoresistive layer  41 T, the bottom piezoresistive layer  41 B, and the bottom electrode  40 B. In this embodiment, four top stacks and four bottom stacks occupy the outer four corners of the cruciform ditch  401 . The four top electrodes  40 T of the four top stacks are electrically coupled to a first electrode  701 , say, a positive electrode. The four bottom electrodes  40 B of the four bottom stacks are electrically coupled to a second electrode  702 , say, a negative electrode. A light source  90  is then configured under the bottom to make the whole structure a single light emitting key. 
       FIG. 5A  shows a top view of  FIG. 4   
       FIG. 5A  shows that a cruciform ditch  401  is made for light emitting. Four stacks occupy the outer four corners of the cruciform ditch  401 . Each block includes a top electrode  40 T, top piezoresistive layer  41 T, bottom piezoresistive layer  41 B, and the bottom electrode  40 B as shown in  FIG. 4 . 
       FIG. 5B  shows a modified pattern of the piezoresistive layers 
       FIG. 5B  shows the through ditch is made fan blade  401 B for light emitting. Three fan stacks occupy the outer of the fan blade  401 B. Each top electrode  405 T of the three stacks is shown in the top view. 
       FIG. 6A  shows a further modified pattern of the piezoresistive layers 
       FIG. 6A  shows the through ditch is made starburst  401 C for light emitting. The remaining blocks are also starburst patterned. The top electrode  406 T of the remaining blocks is shown in the top view. 
       FIG. 6B  shows a further modified pattern of the piezoresistive layers 
       FIG. 6B  shows a through hole  401 D and four through cuts  401 E are made for light emitting. The top electrode  407 T of the remaining single stack is shown in the top view. 
       FIG. 6C  shows a further modified pattern of the piezoresistive layers 
       FIG. 6C  shows a modified cruciform  401 F is made for light emitting. The top electrode  408 T is shown in this pattern. The remaining stacks are four columns patterned. 
       FIG. 7  shows an exploded view for a single key 
     A flexible top substrate  50 T is prepared; a top electrode  40 T is made on a bottom side of the flexible top substrate  50 T. A top piezoresistive layer  41 T is made on a bottom side of the top piezoresistive layer  41 T. A gap  402  is reserved under the top piezoresistive layer  41 T. A bottom piezoresistive layer  41 B is made under the gap  402 . A bottom electrode  40 B is made on a bottom side of the bottom piezoresistive layer  41 B. A bottom flexible substrate  50 B is made on a bottom side of the bottom electrode  40 B. A light panel  901  is configured under the bottom substrate  50 B. A light source  90 , such as a light emitted diode, configured on a lateral side of the light panel  901 . The light source  90  emits light beams to the light panel  901 , the light panel  901  guides the light beams upward passing through the through ditch  401  to give off light beams and emits out of the top substrate  50 T for the light emitting key. A pair of spacers  404  is configured between the top substrate  50 T and the bottom substrate  50 B for maintaining a space  402  between the top piezoresistive layer  41 T and the bottom piezoresistive layer  41 B. 
       FIG. 8  is an assembly of  FIG. 7   
       FIG. 8  shows when the light source  90  is turned on, light beams shall emit from area  501  of the top substrate  50 T for an illumination of the key. 
       FIG. 9  shows a third embodiment of a light emitting key according to the present invention 
       FIG. 9  shows single piezoresistive layer  31  is used. The basic principle is the same as described above. A top substrate  50 T is prepared. A top electrode  30 T is made on a bottom of the top substrate  50 T. A piezoresistor layer  31  is made on a bottom of the top electrode  30 T. A gap  402  is reserved under the piezoresistive layer  31 . A bottom electrode  30 B is made under the gap  302 . A bottom substrate  50 B is made on a bottom of the bottom electrode  30 B. A spacer  404  is configured between the top substrate  50 T and the bottom substrate  50 B. A light source  90 , such as a light emitted diode (LED), is arranged under the bottom substrate  50 B. A rectangular through hole is made through the piezoresistive layer  31 . When the light emitted diode  90  is turned on, light beams shall emit from area  601  on the top substrate  50 T. 
     The space  302  is made between the piezoresistive layer  31  and the bottom electrode  30 B, this is for example only. Similarly, the space  302  can be made between the piezoresistive layer  31  and the top electrode  30 T. 
       FIG. 10  shows a modified light source for  FIG. 9   
       FIG. 10  shows that a light panel  901  is configured under the bottom substrate  50 B. A light source  90 , such as a light emitted diode, is arranged in a lateral side of the light panel  901 . The light panel guides the light beams of the light source  90  upward, so that when the light source  90  is turned on, light beams emit from area  601  on the top substrate  50 T. 
       FIG. 11  shows a modified light emitting key for  FIG. 10   
       FIG. 11  is a structure similar to  FIG. 10 , the only difference is that the position of the gap  302 B is different.  FIG. 11  shows that the gap  302 B is configured between the top electrode  30 T and the piezoresistive layer  31 . 
     While several embodiments have been described by way of example, it will be apparent to those skilled in the art that various modifications may be configured without departing from the spirit of the present invention. Such modifications are all within the scope of the present invention, as defined by the appended claims.