Abstract:
A cholesteric liquid crystal display device and a manufacturing method for the same are proposed. A micro-capsule uses a coating process to manufacture a color cholesteric liquid crystal display device. The present invention coats cholesteric liquid crystal having tunable chiral on a substrate with an electrode layer.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention is related to a color cholesteric liquid crystal display device and a manufacturing method for the same, and more particularly to a color cholesteric liquid crystals having a tunable chiral that is coated on a bottom substrate with an electrode layer. The display is made of a cholesteric liquid crystal material via a micro-capsule and a coating process.  
         [0003]     2. Description of Related Art  
         [0004]     In recent years, polymer dispersed liquid crystal has been used in the form of droplets with a diameter of about 1 to 10 microns. From the application point of the view, PDLCs have unique optical properties: opaque in a field-OFF condition and transparent in a field-ON condition. They do not require polarizes and have very high transmittance in the ON-state. PDLCs may be used for switchable windows, direct-viewing displays and projection displays.  
         [0005]     Starting from a uniform mixture of liquid crystal and polymer, phase separation can be induced via temperature change (Temperature Induced Phase Separation or TIPS), solvent evaporation (Solvent Induced Phase Separation or SIPS), and polymerization of the polymer precursor in the mixture (Polymerization Induced Phase Separation or PIPS). The size of the droplets can be controlled by the phase separation conditions.  
         [0006]     U.S. Pat. No. 6,203,723B1 discloses a micro-capsule comprising liquid crystal material encapsulated in 1) polyurethanelpolyurea or polyurea polymer wall and 2) melamine-formaldehyde or a urea-formaldehyde polymer wall. The liquid crystal material is aligned in a polydomain configuration via a polymerization process. The liquid crystal that is to be microencapsulated, may be either nematic, cholesteric, smetic A, or ferroelectric. Reference is made to  FIG. 1 , which is an illustration of a polydomain configuration of a liquid crystal director induced by a polymer network in a liquid crystal capsule of the prior art. The discrete liquid crystal microcapsules  10  consist of the liquid crystal droplets  100  microcapsulated by the capsule wall  102 . The polydomain configuration of liquid crystal director is induced by a polymer network (web-like structure) in a liquid crystal capsule. The polymer network  104  is performed via polymerization.  
         [0007]     U.S. Pat. No. 6,061,107, “Bistable polymer dispersed cholesteric liquid crystal displays” uses a cholesteric liquid crystal having a color display effect. The cholesteric liquid crystals are confined in droplets or a domain. The size of the droplets or domain is controlled by the cell thickness and the process condition. The cholesteric liquid crystals focus on a plane spiral structure or a vertical spiral structure. At a zero field condition, the plane spiral structure or the vertical spiral structure are stable. The cell appears color reflective when the cholesteric liquid crystal has the plane spiral structure. The cell appears black (such as the black substrate appears to be coated with a black material) when the cholesteric liquid crystal has the vertical spiral structure. Between the liquid crystals are solid polymer walls.  
         [0008]     A multicolor display prepared by the use of a photo tunable chiral material which is added to the cholesteric liquid crystal mixture. Different pitch lengths are achieved by irradiation with different levels of UV light.  
       SUMMARY OF THE INVENTION  
       [0009]     An object of the present invention is to form an UV-curable coating on a substrate having an electrode via a coating process. The UV curable coating is made of a mixture of cholesteric liquid crystal material, tunable chiral material and UV-curable resin. The present invention uses masking and ultraviolet light exposure processes to provide a color cholesteric liquid crystal display device.  
         [0010]     For reaching the object above, the present invention provides a method for manufacturing a color cholesteric liquid crystal display device. It includes: providing a bottom substrate; making an electrode layer on the bottom substrate; forming a UV curable coating on the electrode layer; executing a curing process on the UV curable coating; and forming a color cholesteric liquid crystal display device.  
         [0011]     The present invention provides a color cholesteric liquid crystal display device. It includes a bottom substrate; an electrode layer formed on the bottom substrate; UV curable coating on the electrode layer; and an exposed area formed on the UV curable coating, the exposed area concentrates a plurality of exposed sub-areas that give a plurality of exposure relative for forming the color cholesteric liquid crystal display.  
         [0012]     The manufacturing method of the present invention uses the simple coat process to provide the color cholesteric liquid crystal display having a micro-capsule cholesteric liquid crystal feature on the substrate having electrodes.  
         [0013]     Numerous additional features, benefits and details of the present invention are described in the detailed description, which follows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     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:  
         [0015]      FIG. 1  is an illustration of a multi-domain configuration of liquid crystal director induced by a polymer network in a liquid crystal capsule of the prior art;  
         [0016]      FIG. 2A  is a schematic diagram of a flexible substrate of the present invention;  
         [0017]      FIG. 2B  shows a schematic diagram of an electrode layer manufacturing of the present invention;  
         [0018]      FIG. 2C  shows a schematic diagram of UV curable coating of the present invention;  
         [0019]      FIG. 2D  shows a schematic diagram of an exposure process of the present invention;  
         [0020]      FIG. 2E  shows a schematic diagram of a color cholesteric liquid crystal display device in accordance with the first embodiment of the present invention; and  
         [0021]      FIG. 3  shows a schematic diagram of a color cholesteric liquid crystal display device of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]     Reference is made to FIGS.  2 A-D, which shows a schematic diagram of a color cholesteric liquid crystal display device manufactured in accordance with the present invention. In  FIG. 2A , a bottom substrate  20  is shown. The bottom substrate  20  is made of a plastic substrate. In  FIG. 2B , an electrode layer  22  is formed on the bottom substrate  20 . The electrode layer  22  can be made of an inorganic conductive material or an organic conductive material. In  FIG. 2C , a UV curable coating  24  is formed on the electrode layer  22  via a roll-to-roll process. The UV curable coating  24  is comprised of a mixture of liquid crystal material (such as nematic liquid crystals), a different ratio of a twist agent material, a tunable chiral material and UV-curable resin  
         [0023]     In  FIG. 2D , a curing process utilizes a mask  26  and an ultraviolet light  28  on the UV curable coating  24 . The ultraviolet light  28  has a wavelength of 200-400 nm. A single layer of color micro-capsule cholesteric liquid crystal display device is formed by controlling the ultraviolet light  28  exposure. For example, if a defined area of the micro-capsule cholesteric liquid crystal layer  24  is red, than the mask  26  having high transmittance is used on the defined area of UV curable coating. If the defined area of the micro-capsule cholesteric liquid crystal layer  24  is green, than the mask  26  having medium transmittance is used on the defined area of UV curable coating. If the defined area of the micro-capsule cholesteric liquid crystal layer  24  is blue, than the mask  26  having low transmittance is used on the defined area of UV curable coating. A cholesteric liquid crystal layer display device is made after curing process.  
         [0024]     Reference is made to  FIG. 2E , which shows a schematic diagram of a color cholesteric liquid crystal display device manufactured in accordance with a second embodiment of the present invention. In this embodiment, an upper substrate  32  having an electrode layer covered over the micro-capsule cholesteric liquid crystal layer  24  via a coating process to make the cholesteric liquid crystal display device. Alternatively, an electrode layer is formed on the micro-capsule cholesteric liquid crystal layer  24  via a coating process firstly. Next, the upper substrate  32  is covered over the electrode layer to make the cholesteric liquid crystal display device. The electrode layer can be made of an inorganic conductive material or an organic conductive material.  
         [0025]     Reference is made to  FIG. 3 , which shows a schematic diagram of a color cholesteric liquid crystal display device in accordance with the present invention. The color cholesteric liquid crystal display device includes a bottom substrate  20 . The bottom substrate  20  is a plastic substrate. An electrode layer  22  is made on the bottom substrate  20 . The electrode layer  22  can be made of an inorganic conductive material or an organic conductive material. UV curable coating is formed on the electrode layer  22  via a roll-to-roll process. The UV curable coating is made of a mixture of liquid crystal material (such as nematic liquid crystals), a different ratio of a twist agent material, a tunable chiral material and UV-curable resin. In the second embodiment, the micro-capsule cholesteric liquid crystal layer covers the flexible upper having an electrode layer. Alternatively, an electrode layer is formed on the UV curable coating via a coating process to form a cholesteric liquid crystal display device. The electrode layer is formed via a coating process. A plurality of different exposed areas  30  are defined on the UV curable coating. Cure processes concentrate a plurality of exposed sub-areas via a mask  26  and ultraviolet light  28  to give a plurality of exposure amounts relative for achieving the color cholesteric liquid crystal display. The ultraviolet light  28  has a wavelength of 200-400 nm.  
         [0026]     Although the present invention has been described with reference to the preferred embodiments 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 others 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.