Patent Publication Number: US-2007103623-A1

Title: Transflective display device

Description:
BACKGROUD OF THE PRESENT INVENTION  
      1. Field of the Invention  
      The present invention relates to a transflective display device and, particularly, to a transflective flat panel display (FPD) device.  
      2. Discussion of the Related Art  
      Conventional FPD devices are generally classified into reflective devices and transmissive devices. A transmissive FPD device displays an image by using lights from a backlight source arranged on the rear side of the FPD panel, and a reflective FPD displays an image by using an ambient light.  
      A transmissive FPD device, which displays an image by using light from the backlight, is capable of producing a bright image with a high contrast ratio without being substantially influenced by the brightness of the environment, but consumes a lot of power due to the backlight. Moreover, a transmissive FPD device has a poor visibility under very bright environments (e.g., when used outdoor under a clear sky).  
      On the other hand, a reflective FPD device, which does not have a backlight, consumes little power, but the brightness and the contrast ratio thereof are substantially influenced by the conditions under which it is used, e.g., the brightness of the environment. Particularly, the visibility lowers significantly under dark environments.  
      In order to overcome these problems, transflective FPD devices, which are capable of operating both in a reflection mode and in a transmission mode, have been proposed in the art.  
      A conventional transflective FPD devices typically employs a transflective layer having a typical so-called multi-gap structure. The multi-gap structure is composed of a plurality of reflective means distributed separately, each two of which defines a transmissive gap thereby. The reflective means are configured for taking advantages of ambient lights, while the gaps are configured for allowing a backlight pass through thereby. However, since parts of the transflective layer are transmissive and the others are not, a conventional transflective FPD usually has no way to give better attention to its transmission ability and its reflection ability. Furthermore, the above-mentioned multi-gap structure is disposed above a liquid crystal layer and a color filter layer, in that an FPD device using such does not perform a satisfactory color saturation.  
      Therefore, what is needed in the art is to provide a transflective FPD device giving better attention to its transmission ability and its reflection ability and having a satisfactory color saturation.  
     SUMMARY  
      According to the present display, a transflective FPD device having a transflective layer and a color filter layer is provided. The transflective layer comprises a plurality of reflective domains, and a plurality of transmissive domains, the reflective domains and the transmissive domains being alternately distributed. The reflective domains are configured for reflecting ambient light toward the color filter layer, each of the reflective domains having a plurality of reflective nano-particles associated therewith. The transmissive domains are configured allowing backlight to pass therethrough toward the color filter layer.  
      An advantage of the FPD device is that such a device has better reflection efficient, thus less reflection area is needed and more transmission area can be used for transmitting the backlight.  
      Another advantage of the FPD device is that when the FPD device displays mainly relying on ambient light, the ambient light travels twice through the color filter layer, and therefore the FPD device can perform a better color saturation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above-mentioned and other features and advantages of the present transflective flat panel display device, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of its embodiments taken in conjunction with the accompanying drawings.  
       FIG. 1  is a schematic, cross-sectional view of an FPD device, according to an embodiment; and  
       FIG. 2  is a schematic, cross-sectional view of preferred structure of a combination between a transflective layer and a color filter layer formed thereon, according to an embodiment of the FPD device; and  
       FIG. 3  preferred structure of a transflective layer  220  and a color filter layer, according to another embodiment of the FPD device. 
    
    
      Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Reference will now be made to the drawings to describe the preferred embodiments of the present FPD device in detail.  
      Referring now to the drawings, and more particularly to  FIG. 1 , there is shown a transflective FPD device  100 . The transflective FPD device  100  includes an upper substrate  102 , a lower substrate  104 , a liquid crystal layer  110 , a transflective layer  120 , a thin film transistor (TFT) layer  130 , a color filter layer  140 , an upper polarizer  162  and a lower polarizer  164 . The liquid crystal layer  110  is interposed between the upper substrate  102  and the lower substrate  104 , and includes a plurality of liquid crystal molecules. The liquid crystal layer  110  further includes an upper alignment film  112  disposed thereon, and a lower alignment film  114  disposed thereunder. The upper alignment film  112  and the lower alignment film  114  are configured for aligning the liquid crystal molecules to control lights passed thereby. The transflective layer  120  and the color filter layer  140  are combined as a whole and are interposed between the liquid crystal layer  110  and the lower substrate  104 . The transflective layer  120  is close to the lower substrate  104  and the color filter layer  140  is close to the liquid crystal layer  130 , in that the color filter layer  140  is located on the transflective layer  120 . The transflective layer  120  is configured for allowing a backlight transmit therethrough to the liquid crystal layer  110  and allowing a light of environment be reflected back to the liquid crystal layer  110 . The TFT layer  130  is interposed between the upper substrate  102  and the liquid crystal layer  110 , for driving the FPD device to display. The upper polarizer  162  and the lower polarizer  164  are respectively configured for providing polarized light source for displaying.  
      According to an aspect of the embodiment of the FPD device, the transflective FPD device  100  further includes an upper ½ wave plate  152 , an upper ¼ wave plate  154 , a lower ¼ wave plate  156 , a lower ½ wave plate  158 . The upper ½ wave plate  152  and the upper ¼ wave plate  154  are interposed between the upper substrate  102  and the upper polarizer  162 , while the lower ¼ wave plate  156  and the lower ½ wave plate  158  are interposed between the lower substrate  104  and the lower polarizer  164 . The positions of the upper ½ wave plate  152  and the upper ¼ wave plate  154  are exchangeable, and the positions of the lower ¼ wave plate  156  and the lower ½ wave plate  158  are also exchangeable. The wave plates  152 ,  154 ,  156  and  158  are configured for complementing a phase delay of the tranflective FPD device  100 . It is to be noted that other phase complementary components can also be employed to perform such a function.  
      Furthermore, according to another aspect of the embodiment of the FPD device, the transflective FPD device  100  may further include an anti-glare coating layer  170  and a anti-reflection coating layer  180 . The anti-glare coating layer  170  is disposed on the upper polarizer  162  for eliminating uncomfortableness caused by excessive strong ambient light light. The anti-reflection coating layer  180  is disposed on the anti-glare coating layer  170  for allowing more lights in a given wavelength band pass through.  
      Referring now to  FIG. 2 , it illustrates a preferred structure of a combination between a transflective layer  220  and a color filter layer  240  formed thereon, according to an embodiment of the FPD device. The transflective layer  220  includes a plurality of reflective domains  224  for reflecting an ambient light for displaying, and a plurality of transmissive domains  222  for transmitting a backlight for displaying. The reflective domains  224  and the transmissive domains  222  are alternately distributed. Each of the reflective domains  224  further includes a plurality of reflective nano-particles distributed thereon for enhancing the reflecting ability thereof. Sizes of the nano-particles for example are in the approximate range of 2 nm to 100 nm and preferably in the approximate range of 5 nm to 20 nm.  
      In general, the transflective layer  220  is made of a material selected from a group consisting of Ag, Al, Ti, Cr and Al—Ag alloy. To configure such a transflective layer  220 , a layer of one of the foregoing materials is deposited at first, and a plurality of nano-particles are disposed thereby or thereafter. And then, a lithographic process is performed to form a certain pattern on the deposited layer. Finally, an etching process is performed to remove unneeded parts of the deposited layer, thus configuring the transflective layer  120  having a given pattern.  
      Accordingly, the transflective layer  220  has a plurality of reflective domains  224  comprised of deposited reflective materials and a plurality of transmissive domains  222  defined as spaces by the reflective domanins. In this embodiment, the reflective domains are preferably formed in a pattern comprised of a plurality of parallel straight strips, which define the transmissive domains as a plurality of straight gaps parallel to each other.  
      Again referring to  FIG. 2 , the color filter layer  240  is formed on the transflective layer  220 . The color filter layer  240  includes a plurality of reflective filter units  244  corresponding to the reflective domains  224  of the transflective layer  220 , and a plurality of transmissive filter units  242  corresponding to the transmissive domains  222  of the transflective layer  220 . The reflective filter units  244  are configured for twice filtering an ambient light to provide respectively red, green and blue lights to the liquid crystal layer  110  for displaying. The transmissive filter units  242  are configured for filtering a backlight to provide respectively red, green and blue lights to the liquid crystal layer  110  for displaying. Each of the transmissive filter units  244  has a part filled in a corresponding transmissive domain. Therefore, the transmissive filter units  244  are thicker than the reflective filter units  242 , the thickness ratio between the reflective filter units  242  and the transmissive filter units  244  being in the range of 40% to 60% (preferably 45% to 55%). Furthermore, the area ratio between the reflective filter units  242  and the transmissive filter units  244  is in the range of 40% to 60% (preferably 45% to 55%).  
      With respect to the foregoing color filter layer  240 , a thicker transmissive filter unit  242  provides better color saturation to a backlight transmitted therethrough for displaying. Similarly, a structure of a reflective filter unit  244  on a reflective domain  224  has an ambient light transmitted twice therethrough thus also providing a better color saturation to the ambient light for displaying.  
      Referring now to  FIG. 3 , it illustrates a preferred structure of a transflective layer  320  according to an embodiment of the FPD device. The transflective layer  320  includes a plurality of transmissive domains  322  and a plurality of reflective domains  324 . Each of the reflective domains  324  further includes a plurality of sub-reflective domains  326 . Each of the sub-reflective domains  326  further includes a plurality of reflective nano-particles distributed thereon for enhancing the reflecting ability thereof. Sizes of the nano-particles for example are in the approximate range of 2 nm to 100 nm and preferably in the approximate range of 5 nm to 20 nm. The sub-reflective domains  326  for example can be a plurality of reflective strips parallel to each other.  
      Moreover, the transmissive domains  322  for example can be formed by an process similar to that of  FIG. 2 . Thus a color filter layer like  FIG. 2  shown can be mounted on the transflective layer  320 . The color filter layer includes a plurality of thicker transmission filter units corresponding to the transmissive domains  322  for allowing backlights pass therethrough, and a plurality of thinner reflection filter units corresponding to the reflective domains  324  for allowing ambient lights twice reflected and pass therethrough.  
      While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.