Abstract:
A transflective layer is inserted in between a light modulator and a specific-color reflector to allow partial transmission and partial reflection of the light transmitted through the light modulator. The specific-color reflector is arranged to reflect a light component of a designated color of the transmitted light.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is based on, and claims priority from, Taiwan Application Serial Number 097132646, filed Aug. 27, 2008, the disclosure of which is hereby incorporated by reference herein in its entirety. 
       BACKGROUND 
       [0002]    This disclosure relates to a color pixel, a color display apparatus and a displaying method. 
         [0003]      FIG. 1  shows a schematic side view of a known black and white pixel, as seen from top to bottom. The pixel includes: a combination of a top plate  20 , a transparent electrode  21 , a light modulator  30 , a transparent pixel electrode  11 , a bottom plate  10 , and an ambient light reflector  12 . 
         [0004]    When the light modulator  30  turns on, most of the ambient light “A” passes through the light modulator  30  and reaches the ambient light reflector  12 . Reflective light “B” from ambient light reflector  12  reaches the top of the system, i.e., a bright state can be observed by an observer on top of the display. On the other hand, when the light modulator  30  turns off, most of the ambient light “A” is prevented from passing through the light modulator  30  and no reflective light “B” can reach the top of the display, i.e., a dark state will be observed by an observer on top of the display. When the ambient light is natural white or colorless, the bright state appears white and the dark state appears black, and therefore the known configuration is called “black-white” pixel or display apparatus. Nowadays, a black-white pixel/display apparatus is no longer satisfactory to users; a color pixel/display apparatus is desired. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    One or more embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout. 
           [0006]      FIG. 1  is a schematic side view of a known black and white pixel. 
           [0007]      FIG. 2 . is a schematic view showing a principle of an embodiment of the present invention 
           [0008]      FIG. 3 . is a schematic side view of an embodiment of the present invention. 
           [0009]      FIG. 4 . is a schematic side view of another embodiment of the present invention. 
           [0010]      FIG. 5 . is a schematic side view of still another embodiment of the present invention. 
           [0011]      FIG. 6 . is a schematic side view of still another embodiment of the present invention. 
           [0012]      FIG. 7 . is a schematic side view of still another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0013]    An embodiment of the present invention provides a mechanism for “a color pixel” to provide a color display apparatus that changes its color softly with a transflective layer inserted in between a modulator and a reflector. The color display apparatus is composed of one or more color pixels arranged, e.g., in an array. 
         [0014]    The right side of  FIG. 2  shows a state when a light modulator  30  turns on and the left side of  FIG. 2  shows a state when the light modulator  30  turns off. From top to bottom, the color pixel comprises: the light modulator  30 , a transflective layer  13 , and a specific-color light reflector  14 . An observer on top of the display should be able to see a minimum amount of light brightness when the light modulator  30  turns off as shown on the left side of  FIG. 2 . On the other hand, the observer should be able to see a maximum amount of light brightness when the light modulator  30  turns on as shown on the right side of  FIG. 2 . 
         [0015]    Either Polymer-dispersed liquid crystal (PDLC) or Polymer-network liquid crystal (PNLC) can be used in an embodiment for the light modulator  30 . Either PDLC or PNLC scatters, rather than blocking, light while the liquid crystal molecules are random, and allows light to pass through while the liquid crystal molecules are aligned. In the latter case, the ambient light passes through the modulator  30  due to the aligned liquid crystal molecules. Other types of liquid crystal having properties similar to PDLC or PNLC, such as twisted-nematic liquid-crystal, can be used for the light modulator  30 . The light modulator  30  can be turned on/off through appropriately controlling a voltage across a top electrode and a bottom electrode (not shown). 
         [0016]    On the right side of  FIG. 2 , where the state when the light modulator  30  turns on is shown, most of the ambient light “W” should be able to pass through the light modulator  30 . W 2 , a portion of W, passes through the light modulator  30  and reaches the transflective layer  13 . W 22 , a portion of W 2 , further passes through the transflective layer  13  and reaches the specific-color light reflector  14 . T 2 , a portion of the light W 22 , is reflected from the specific-color light reflector  14 . T 22 , a portion of the light T 2 , passes through the transflective layer  13  and reaches the light modulator  30 . R 2 , a portion of light W 2 , is reflected by the transflective layer  13  towards the light modulator  30 . Finally, a portion of R 2  plus a portion of T 22  pass through the light modulator  30  and reach the observer on top of the system, as indicated by the hatched arrow R 2 T 22 . 
         [0017]    On the left side of  FIG. 2 , where the state when the light modulator  30  turns off is shown, most of the ambient light “W” should be scattered within the light modulator  30 . Due to the scattering effect, only W 1 , a small portion of W, passes through the light modulator  30  and reaches the transflective layer  13 . W 12 , a portion of W 1 , further passes through the transflective layer  13  and reaches the specific-color light reflector  14 . T 1 , a portion of the light W 12 , is reflected from the specific-color light reflector  14 . T 12 , a portion of the light T 1 , passes through the transflective layer  13  and reaches the light modulator  30 . R 1 , a portion of light W 1 , is reflected by the transflective layer  13  towards the light modulator  30 . Finally, a portion of R 1  plus a portion of T 12  pass through the light modulator  30  and reach the observer on top of the system, as indicated by the hatched arrow R 1 T 12 . The light amount of R 1 T 12  is relatively small compared to the light amount of R 2 T 22 . Therefore, the pixel in the state “Off” on the left appears darker than in the state “On” on the right. 
         [0018]    The color displayed in the color pixel is determined by the color reflected by the corresponding reflector  14 . The color selected by the specific-color light reflector  14  can be any visible color depending on design choices. A product (e.g., a color display apparatus) can then be configured to be capable of displaying multiple colors by combining a plurality of color pixels where the color reflected from the specific-color light reflector  14  of one color pixel is different from the color reflected from the specific-color light reflector  14  of another color pixel. 
         [0019]    The color selected to be reflected by the specific-color light reflector  14  include, but are not limited to the following: red, orange, yellow green, blue, cyanine, purple, and black. For example, the color pixel displays red if the corresponding specific-color light reflector  14  is made such that red light is reflected, wherein only the red component of the incident light is reflected and the remaining components of the incident light are absorbed by the reflector  14 . For another example, the color pixel displays green if the corresponding specific-color light reflector  14  is made such that green light is reflected, wherein only the green component of the incident light is reflected and the remaining components of the incident light are absorbed by the reflector  14  etc. 
         [0020]    The transflective layer  13  is inserted between the light modulator  30  and the specific-color light reflector  14  to allow a part of the incident light to pass and reflect a part of the incident light. Such arrangement diminishes the sharpness of color change so as to provide the color pixel with a capability to change its color softly between the on and off states. 
         [0021]      FIG. 3  shows a configuration of a color pixel in accordance with an embodiment. The color pixel includes, from top to bottom, a top plate  20 , a transparent electrode  21 , the light modulator  30 , a transparent pixel electrode  11 , a bottom plate  10 , the transflective layer  13  and the specific-color light reflector  14 . The transparent electrode  21  is provided on the top of the light modulator  30 . The transparent pixel electrode  11  is provided on the bottom of the light modulator  30 . The transparent electrode  21 , the light modulator  30  and the transparent pixel electrode  11  are provided between the top plate  20  and the bottom plate  10 . The transflective layer  13  is provided between the bottom plate  10  and the specific-color light reflector  14 . The principle of the color pixel in  FIG. 3  is essentially the same as that described with respect to  FIG. 2 . The transparent electrode  21  and the transparent pixel electrode  11  are used to control the light modulator  30 . The top plate  20  and the bottom plate  10  are used as a support and a protection layer to the elements provided between the top plate  20  and the bottom plate  10 . 
         [0022]    The disclosed color pixel is applicable to various color display apparatuses such as electronic digital watches, electronic digital thermometers, electronic digital timepieces, color back panels etc. One or more color pixels are used as the display components in the color display apparatus. 
         [0023]      FIG. 4  shows a configuration of a color pixel in accordance with another embodiment of the present invention. The color pixel includes, from top to bottom, a top plate  20 , a transparent electrode  21 , a light modulator  30 , a transflective pixel electrode  112 , a bottom plate  10  and a specific-color light reflector  14 . The transflective pixel electrode  112  is arranged on the bottom of the light modulator  30 . The transflective pixel electrode  112  plays a dual role of both a transflective layer and a pixel electrode. Compared with  FIG. 3 , the configuration of  FIG. 4  has omitted an independent transflective layer. The transflective pixel electrode  112  can be made of a thin film metal. The principle of the color pixel of  FIG. 4  is essentially the same as that described with respect to  FIG. 2 . 
         [0024]      FIG. 5  shows a configuration of a color pixel in accordance with still another embodiment of the present invention. The color pixel includes, from top to bottom, a top plate  20 , a transparent electrode  21 , a light modulator  30 , a transflective pixel electrode  112 , a specific-color light reflector  14  and a bottom plate  10 . The specific-color light reflector  14  is provided between the transflective pixel electrode  112  and the bottom plate  10 . The principle of the color pixel of  FIG. 5  is essentially the same as that described with respect to  FIG. 2 . 
         [0025]      FIG. 6  shows a configuration of a color pixel in accordance with still another embodiment of the present invention. The color pixel includes, from top to bottom, a top plate  20 , a transparent electrode  21 , a light modulator  30 , coplanar two transflective pixel electrodes  112 , a bottom plate  10 , and coplanar two specific-color light reflectors  14 A,  14 B. The two transflective pixel electrodes  112  are arranged separately from each other. Each of the two reflectors  14 A,  14 B is configured to be in a position downward aligned to one of the two transflective pixel electrodes  112 . The color reflected by the first specific-color light reflector  14 A is different from the color reflected by the second specific-color light reflector  14 B so as to provide a multicolor pixel. The principle of the color pixel of  FIG. 6  is essentially the same as that described with respect to  FIG. 2 . 
         [0026]      FIG. 7  shows a configuration of a color pixel in accordance with still another embodiment of the present invention. The color pixel includes, from top to bottom, a top plate  20 , a transparent electrode  21 , a light modulator  30 , coplanar two transflective pixel electrodes  112 , coplanar two specific-color light reflector  14 A,  14 B and a bottom plate  10 . The two transflective pixel electrodes  112  are arranged separately from each other. Each of the two specific-color light reflectors  14 A,  14 B is configured to be immediately below one of the two transflective pixel electrodes  112 . The principle of the color pixel of  FIG. 7  is essentially the same as that described with respect to  FIG. 2 . 
         [0027]    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 made 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.