Abstract:
A flexible transflective LCD device having a dual-polarizer structure is manufactured by means of coating the thin-film polarizer therein. The object of the present invention is to solve a drawback of the conventional LCD incapable of being flexible. Multiple supporting microstructures and an external flexible light source collocated with the flexible components and the means of coating method are incorporated to form the flexible transflective LCD device with dual polarizers.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention is related to a flexible transflective liquid-crystal-display (LCD) device and a manufacturing method thereof, and more particularly, to a flexible transflective LCD device made according to a single-cell-gap design. The flexible transflective LCD device is formed with multiple supporting microstructures and a dual-polarizer structure made according to the technologies of producing flexible components and coating thin film polarizer.  
         [0003]     2. Description of Related Art  
         [0004]     In general, when a transmissive display is placed outdoors or under intense light, the contrast of images shown thereon is lowered due to the influence of environmental light. Comparatively, since a reflective display relies on an external light source to display images, it has better performance or higher contrast outdoors or under intense light. In addition, the reflective display reduces the power consumption because back light is not required. Thus, the reflective display is very suitable for use in portable products. However, when the environmental light is insufficient, the contrast and brightness of the reflective display are degraded greatly. Hence, a transflective display that modulates light from an external source by reflection and from another source by transmission through a transmission region could have the advantages of the reflective display and the transmissive display at the same time. The transflective display can be driven passively, and furthermore, the transflective display can also be driven actively by thin film transistors (TFTs).  
         [0005]     A related art, such as a TN-mode TFT-LCD with in-cell polarizers proposed by Sony Company, Optiva Company, and Nakan Company in the Society for Information Display, in 2004, is shown in  FIGS. 1   a - b.  Thin crystal films (TCFs) are coated in-cell to provide the functionality of polarization. The built-in reflector is coated with a TCF to overcome the parallax problem caused by the thick polarizing sheet conventionally used. Furthermore, images are not inverted thereby. Thus, this technique fulfills the requirements for making a transflective LCD device with a dual-polarizer structure under a single-cell-gap architecture. In the structure shown in  FIG. 1   a,  thin crystal films  10  are coated directly on conductive layers  12  and the conductive layers  12  are coated on a color filter  14  and on an organic layer  16 . The difference between the structures shown in  FIG. 1   a  and  FIG. 1   b  is that the thin crystal films  10  of the structure shown in  FIG. 1   b  are respectively formed below the color filter  14  and between the organic layer  16  and a specific layer  18  for deployment of signal lines. However, this related art is applied on a glass substrate and its structure does not fulfill the requirements of next generation technology for a flexible display.  
       SUMMARY OF THE INVENTION  
       [0006]     An objective of the present invention is to provide a flexible transflective LCD device. The present invention uses technologies of producing flexible components and coating TCFs together to produce the flexible transflective LCD device with a dual-polarizer structure under a design with single-cell-gap architecture. The present invention has a simple manufacturing procedure and a flexible feature that can be used to extend the applicable area of LCD devices.  
         [0007]     For reaching the objective above, the present invention provides a flexible transflective LCD device and its manufacturing method. The flexible transflective LCD device includes a first flexible substrate, a second flexible substrate and a liquid crystal layer sandwiched by the first and second substrates. A reflective plate is formed on an internal surface of the second flexible substrate to define the reflective area. The transmissive area is the region located above the second flexible substrate that doesn&#39;t have the reflective plate. A polarization layer is provided on the first flexible substrate and on the internal surface of the second flexible substrate in the reflective and transmissive areas. A conductive layer is provided on the internal surface of the first flexible substrate and on the second flexible substrate in the reflective and transmissive areas; multiple supporting microstructures are formed between the first flexible substrate and the second flexible substrate. A flexible light source is attached on an external surface of the second flexible substrate.  
         [0008]     The manufacturing method of the present invention includes the following steps. A first flexible substrate and a second flexible substrate are provided. A color filter is provided on the first flexible substrate. The first flexible substrate is coated with a first polarization layer. A conductive layer is provided on the first polarization layer. A reflective plate is provided on the second flexible substrate. The reflective plate is located in a reflective area. A conductive layer is provided on the second flexible substrate. The second flexible substrate is coated with second polarization layer. Multiple supporting microstructures are provided between the first flexible substrate and the second flexible substrate. A plurality of liquid crystal is filled between the first flexible substrate and the second flexible substrate to form a liquid crystal layer. Finally, a flexible light source is attached on an external surface of the second flexible substrate.  
         [0009]     Numerous additional features, benefits and details of the present invention are described in the detailed description, which follows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The foregoing aspects and many of the attendant advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0011]      FIG. 1   a  is a schematic diagram of the prior art, formed with thin crystal films (TCFs) to provide the functionality of polarization;  
         [0012]      FIG. 1   b  is schematic diagram of the prior art formed with TCFs to provide the functionality of polarization;  
         [0013]      FIG. 2  is a schematic diagram of a preferred embodiment in accordance with the present invention;  
         [0014]      FIG. 3  is a manufacturing procedure of the device in accordance with the present invention;  
         [0015]      FIG. 4  shows the flexible transflective LCD device of the present invention when it is in a bright status; and  
         [0016]      FIG. 5  shows the flexible transflective LCD device of the present invention when it is in a dark status. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]     The present invention uses the current developing technologies of flexible components and coating polarizer and provides multiple supporting microstructures inside the flexible substrates. The transflective LCD device can be made with a flexible feature and thus the field of application is extended. Furthermore, the manufacturing procedure can also be simplified to lower the cost.  
         [0018]     The present invention employs the current developing technologies of flexible components and coating polarizer to produce a flexible transflective LCD device. A structure of a preferred embodiment in accordance with the present invention is shown in  FIG. 2 . The structure forms a flexible transflective LCD device that mainly includes a first flexible substrate  30 , a second flexible substrate  40 , multiple supporting microstructures  52  and a liquid crystal layer. As shown in the figure, a cell is formed between the first flexible substrate  30  and the second flexible substrate  40 . The cell includes reflective areas  48  and transmissive areas  50 . The first flexible substrate  30  and the second flexible substrate  40  are flexible transparent substrates, such as Polyesterurethane (PET), Polyethersulfone (PES) and Metallocene-based Cyclic Olefin Copolymer (MCOC).  
         [0019]     The structure of the flexible transflective LCD device further has a color filter  32  formed on an internal surface of the first flexible substrate  30  to form a flexible color LCD. A reflective plate  42  disposed on an internal surface of the second flexible substrate  40 . The region above the second flexible substrate  40  having the reflective plate  42  forms the first region (reflection region), and another region above the second flexible substrate  40  that doesn&#39;t have the reflective plate  42  forms the second region (transmission region). A conductive layer  44  is formed on the first and second regions. A polarization layer  34  is provided on the color filter  32  of the first flexible substrate and on the conductive layer  44  of the second flexible substrate  40 . Alignment layers (not shown in the figure) are disposed on the inner surfaces of the flexible substrates and they are contiguous with the liquid crystal layer. The polarization layer  34  could be made of disk-like Lyotropic Dichroic dyes or rod-like Lyotropic Dichroic dyes. Multiple supporting microstructures  52  are formed. These supporting microstructures  52  can have a closed type or a non-closed type. They can be formed with any geometrical shape, such as a straight line, a cross, a trident, a rectangle, a circular shape and a honeycomb shape. The liquid crystal layer is formed between the first flexible substrate  30  and the second flexible substrate  40 . Finally, a flexible light source  54  is disposed at an external surface of the second flexible substrate  40 . The backlight module  54  could be a side-edged type backlight module or a direct  20  type backlight module. A flexible direct type backlight module or a side-edged type backlight with a flexible light guide should be used and located on the external side of the lower substrate in order to form a flexible transflective liquid crystal display. The flexible direct type backlight could be a light source, such as organic light emitting diodes (OLED), polymer light emitting diodes (PLED), an electroluminescent source and a microdischarge source, fabricated on a flexible substrate.  
         [0020]      FIG. 3  shows a manufacturing procedure of the flexible transflective display. The first step provides a first flexible substrate  30  and a second flexible substrate  40  (step S 301 ). Then, a color filter  32  is provided on the first flexible substrate  30  (step S 303 ). After that, a first polarization layer  34  is formed on the color filter  32  and then a conductive layer  44 ′ is further provided on the first polarization layer  34 . The location of the first polarization layer  34  on the first flexible substrate  30  is not limited (step S 305 ). The first polarization layer  34  can also be disposed on an external surface of the first flexible substrate  30 .  
         [0021]     A reflective plate  42  is disposed on an internal surface of the second flexible substrate  40  (step S 307 ). The region above the reflective plate  42  forms the first region of this structure. The other region above the second flexible substrate  40  that doesn&#39;t have the reflective plate  42  forms the second region, which is optically transmissive.  
         [0022]     Subsequently, a conductive layer  44  is provided on the reflective plate  42  and the second region (step S 309 ). A second polarization layer  46  is provided on the conductive layer  44  (step S 311 ). Multiple supporting microstructures  52  are provided between the first flexible substrate  30  and the second flexible substrate  40  (step S 313 ). The supporting microstructures  52  can be made via a process, such as photolithography, molding, embossing, casting, flexography, printing, coating and photo-induced phase separation process. Then, a plurality of liquid crystal is filled to form a liquid crystal layer (step S 314 ). Finally, a flexible light source  54  is attached to one side of the LCD structure, and is located at an external surface of the second flexible substrate  40  (step S 315 ).  
         [0023]     The foresaid first region, i.e. the region above the second flexible substrate  40  having the reflective plate  42 , is the reflective region  48  of this structure. The second region above the second flexible substrate  40  with the conductive layer formed thereon without the reflective plate  42  is the transmissive region  50 . The conductive layer  44  is a transparent electrode, which can be made of transparent conducting material, such as indium tin oxide (ITO), Poly-3,4-Ethylenedioxythiophene (PEDOT) or Carbon Nanotubes. The reflective plate can be made via a manufacture process, such as sputtering, printing and molding. The material of the reflective plate can be a metal, such as aluminum, or a diffusive material, such as barium sulfate and titanium dioxide.  
         [0024]     It is noted that the flexible transflective LCD device of the present invention can be operated in an active mode or a passive mode. In the active mode, the thin film transistors (TFT) can be fabricated under the reflective plate to increase the aperture ratio.  
         [0025]     A flexible transflective LCD device of the present invention operated in a bright state is shown in  FIG. 4 . This figure shows that, when no voltage is provided (i.e. in a voltage-off state), only P-polarized light of the external light enters the reflective area  48  of the liquid crystal layer after the external light passes through the first polarization layer  34  (assume that the first polarization layer  34  absorbs the S-polarized light). Then, the liquid crystal layer makes the incoming P-polarized light to rotate and become a S-polarized light so as to make the incoming light to pass the second polarization layer  46  (assume that the second polarization layer  46  absorbs the P-polarized light). Subsequently, the light is reflected back to the liquid crystal layer by the reflective plate  42 . Then, the liquid crystal layer makes the reflected S-polarized light to rotate and become a P-polarized light to pass the first polarization layer  34 . Thus, the reflective area  48  is in a bright state.  
         [0026]     On the other hand, in the transmissive area  50 , when the light emitted from the flexible light source passes through the second polarization layer  46 , only S-polarized light enters the liquid crystal layer. Then, after rotation by the liquid crystal layer to form P-polarized light, the light is able to pass through the first polarization layer  34 . Thus, the transmissive area  50  is also in a bright state.  
         [0027]     When voltage is provided (i.e. in a voltage-on state), the liquid crystal layer doesn&#39;t perform the polarization function. Thus, both the reflective area and the transmissive area are in a dark state as shown in  FIG. 5 .  
         [0028]     Based on the operation principle of this device, the first polarization layer  34  doesn&#39;t need to be located between the color filter  32  and the conductive layer  44 ′. It can be placed on any side of the first flexible substrate  30  or at any layer. The second polarization layer  46  needs to be located above the reflective plate  42  but it could be disposed either above or below the conductive layer  44 .  
         [0029]     As description above, the present invention uses the flexible components and coating polarization layer to fulfill the requirements of the technology for making a flexible transflective display with a single cell gap. The present invention further uses multiple supporting microstructures to keep a constant cell gap of the display when the display is bent. Furthermore, the manufacturing procedure is roll-to-roll compatible. Thus, the present invention can be used in mass production and for lowering the cost. In addition, the flexible feature of the present invention can be used to extend the field of application for products.  
         [0030]     Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are embraced within the scope of the invention as defined in the appended claims.