Patent Publication Number: US-2007103618-A1

Title: Polarizer plate and liquid crystal panel using the same

Description:
FIELD OF THE INVENTION  
      The present invention relates to a polarizer plate for a liquid crystal panel.  
     GENERAL BACKGROUND  
      Because liquid crystal display devices have the merits of being thin, light in weight, and drivable by a low voltage, they are extensively employed in various electronic devices. A typical LCD device  100  as shown in  FIG. 5  includes a first substrate  120 , a second substrate  140 , and a liquid crystal layer  130  interposed between the first and second substrates  120 ,  140 . A first and a second polarizer plates  110 ,  150  are provided at two outsides of the first and second substrates  120 ,  130 . The first and the second polarizer plates  110 ,  150  have same structure.  
      As shown in  FIG. 6 , The first polarizer plate  110  includes a first protection film  111 , a polarization main body  112 , a wide view film  113 , an adhesive layer  114 , and a release layer  115 , in that order from top to bottom. The first protection film  111  is highly transparent and waterproof, which enable them to support and protect the polarization main body  112 . The release layer  115  is used to keep the adhesive layer  114  clean and sticky. In use, the release layer  115  is peeled off, and the polarizer plate  110  is attached to one or more other elements of a liquid crystal panel by the adhesive layer  114 . The p polarization main body  112  has an absorption axis  1120 , which maintains a 45 degrees angle relative to a longer side of the polarization main body  112 , being parallel to an alignment direction of the first substrate  120 . The wide view film  113  has a second protective film  1130 , an alignment layer  1131  and a discotic liquid crystal molecular layer  1132 . An alignment direction  1133  of the plurality of liquid crystal moleculars of the discotic liquid crystal molecular layer  1132  is parallel to the absorption axis  1120 . The second polarizer plate  150  has a similar structure to that of the first polarizer plate  110 , except an absorption axis of the second polarizer plate  150  being perpendicular to the absorption axis  1120  of the first second polarizer plate  110 .  
      Referring to  FIG. 7 , the optical compensation theory of the wide view film  113  is shown. Liquid crystal molecular  1301  of the liquid crystal layer  130  has three refractive indices of N X , N Y , and N Z  in three direction of X axis, Y axis, and Z axis, which have the relationship of N Z &lt;N X =N Y . The discotic liquid crystal molecular  1134  of the wide view film  113  also has three refractive indices of n X , n Y , and n Z  in three direction of X axis, Y axis, and Z axis. The three refractive indices of the liquid crystal molecular  1301  and the three refractive indices of the discotic liquid crystal molecular  1134  of the wide view film  113  satisfy the aftermentioned formula: N Z +n Z =N X +n X =N Y +n Y . Therefore, the wide view film  113  can efficiently compensate the different light beams retardation brought by the irregularly alignment of the liquid crystal molecular  1301  and resolve the lower viewing angle.  
      However, the LCD device  100  generally realizes high contrast ratio through adjusting the voltages for dark or white display in a predetermined range. When the liquid crystal layer  130  is provided a voltage larger than a threshold voltage, a phenomena of gray level inversion is produced and the LCD device has a lower viewing angle, because the alignment direction  1133  of the discotic liquid crystal molecular  1134  is parallel to the absorption axis  1120 .  
      What is needed, therefore, is a polarizer plate that overcomes the above-described deficiencies.  
     SUMMARY  
      In a preferred embodiment, a polarizer plate in order has a protection film; a polarization main body, having an absorption axis; and a wide view film, having a discotic liquid crystal layer. The discotic liquid crystal layer has a plurality of discotic liquid crystal moleculars, which are aligned in a direction maintaining an angle relative to the absorption axis.  
      In another preferred embodiment, a liquid crystal panel has a first substrate; a second substrate; a liquid crystal layer disposed between the substrates; and a first polarizer plate arranged at an outer surface of the first substrate. The first polarizer plate has a protection film; a polarization main body, having an absorption axis; and a wide view film, having a discotic liquid crystal layer. The discotic liquid crystal layer has a plurality of discotic liquid crystal moleculars, which are aligned in a direction maintaining an angle relative to the absorption axis.  
      Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic view of a liquid crystal panel according to a first embodiment of the present invention, which has a first polarizer plate.  
       FIG. 2  is a schematic view of the first polarizer plate of  FIG. 1 .  
       FIG. 3  is a schematic view of another liquid crystal panel according to a second embodiment of the present invention, which has a second polarizer plate.  
       FIG. 4  is a schematic view of the second polarizer plate of  FIG. 1 .  
       FIG. 5  is a schematic view of a conventional liquid crystal panel, which has a first polarizer plate and a wide view film.  
       FIG. 6  is a schematic view of the first polarizer plate of  FIG. 5 .  
       FIG. 7  illustrates the optical compensation theory of the wide view film of  FIG. 5 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       FIG. 1  shows a schematic view of a liquid crystal panel according to a first embodiment of the present invention. The liquid crystal panel  200  has a first polarizer plate  210 , a first substrate  220 , a liquid crystal layer  230 , a second substrate  240 , and a second polarizer plate  250 , which are sequentially disposed in that order from top to bottom.  
       FIG. 2  is a schematic view of the first polarizer plate  210  of the liquid crystal panel  200 . The polarizer plate  210  includes a first protection film  211 , a polarization main body  212 , a wide view film  213 , an adhesive layer  214 , and a release layer  25 , in that order from top to bottom. The first protection film  211  covers and protects the polarization main body  212 . The release layer  215  is to keep the adhesive layer  214  clean and sticky. In use, the polarizer plate  200  is adhered to one or more other elements of the first substrate  220  by the adhesive layer  214 . The polarization main body  213  is made from polyvinyl alcohol mixed with iodine molecules, or polyvinyl alcohol mixed with iodine molecules and potassium iodide, which has an absorption axis  2120 . The absorption axis  2120  maintains a 45-degree angle relative to a longer side of the polarization main body  212 , and which is parallel to an alignment direction of the first substrate  220 .  
      The wide view film  213  has a second protection film  2130 , an alignment layer  2131  and a discotic liquid crystal layer  2132 , which are sequentially disposed in that order from top to bottom. The discotic liquid crystal layer  2132  has a plurality of discotic liquid crystal molecular, which are oriented at an alignment direction  2133 . The alignment direction  2133  of the discotic liquid crystal molecular clockwise maintains a 2-degree angle relative to the absorption axis  2120  of the polarization main body  212 .  
      The liquid crystal panel  200  utilize the discotic liquid crystal molecular having a predetermined alignment direction of the wide view film  213  to compensate the retardation and influence the polarization state of the light beams transmitting the liquid crystal layer  230 . Therefore, the liquid crystal panel  200  can efficiently improve the contrast ratio and keep a large viewing angle.  
      In addition, the alignment direction  2133  of the discotic liquid crystal molecular may maintain an angle of 1 degree, 3 degrees, or 1 degree to 3 degrees relative to the absorption axis  2120  of the polarization main body  212 . The liquid crystal panel  200  can also efficiently improve the contrast ratio and keep a large view angle.  
       FIG. 3  shows a schematic view of a liquid crystal panel according to a second embodiment of the present invention. The liquid crystal panel  300  has a first polarizer plate  310 , a first substrate  320 , a liquid crystal layer  330 , a second substrate  340 , and a second polarizer plate  350 , which are sequentially disposed in that order from top to bottom.  
       FIG. 4  is a schematic view of the second polarizer plate  350  of the liquid crystal panel  300 . The polarizer plate  350  includes a first protection film  351 , a polarization main body  352 , a wide view film  353 , an adhesive layer  354 , and a release layer  355 , in that order from bottom to top. The first protection film  351  covers and protects the polarization main body  352 . The release layer  355  is to keep the adhesive layer  354  clean and sticky. In use, the polarizer plate  350  is adhered to the second substrate  340  by the adhesive layer  354 . The polarization main body  352  is made from polyvinyl alcohol mixed with iodine molecules, or polyvinyl alcohol mixed with iodine molecules and potassium iodide, which has an absorption axis  3520 . The absorption axis  3520  maintains 135 degrees relative to a longer side of the polarization main body  352 , and which is parallel to an alignment direction of the second substrate  340 .  
      The wide view film  353  has a second protection film  3530 , an alignment layer  3531  and a discotic liquid crystal layer  3532 , which are sequentially disposed in that order from bottom to top. The discotic liquid crystal layer  3532  has a plurality of discotic liquid crystal moleculars, which are oriented at an alignment direction  3533 . The alignment direction  3533  of the discotic liquid crystal molecular counter clockwise maintains a 2-degree angle relative to the absorption axis  3520  of the polarization main body  352 .  
      The liquid crystal panel  300  utilize the discotic liquid crystal molecular having a predetermined alignment direction of the wide view film  313  to compensate the retardation and influence the polarization state of the light beams transmitting the liquid crystal layer  330 . Therefore, the liquid crystal panel  300  can efficiently improve the contrast ratio and keep a large viewing angle.  
      In addition, the alignment direction  3533  of the discotic liquid crystal molecular may maintain an angle of 1 degree, 3 degrees, or 1 degree to 3 degrees relative to the absorption axis  3520  of the polarization main body  352 . The liquid crystal panel  300  can also efficiently improve the contrast ratio and keep a large view angle.  
      It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.