Abstract:
An exemplary liquid crystal display includes two substrates ( 21, 22 ) opposite to each other and spaced apart a predetermined distance, each of the substrates having an alignment layer ( 211, 221 ); a liquid crystal layer ( 23 ) between the two substrates, and having a plurality of liquid crystal molecules; and a plurality of gate lines ( 241 ) formed between one alignment layer and one substrate. The two alignment layers have two orthogonal aligning directions, one aligning direction of the two alignment layers being parallel to an extending direction of the gate lines.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to liquid crystal displays (LCDs), and particularly to an LCD having a good display characteristics and a method for manufacturing the LCD. 
         [0003]    2. General Background 
         [0004]    In general, an LCD has two main advantages in comparison with cathode ray tubes (CRTs): LCDs are thin and have low power consumption. It has been said that LCDs might one day completely replace CRT display devices, and LCDs have aroused great interest in many industries in recent times. 
         [0005]    However, LCDs generally provide a narrower viewing angle compared with CRT display devices. Various means have been devised in endeavoring to widen the viewing angle of LCDs.  FIG. 5  is a viewing angle versus luminance plot illustrating the gray characteristics of a typical LCD. The various curves represent driving voltages from 0.4V to 4.0V applied thereon. Gray level performance of an LCD is very important.  FIG. 5  shows the typical LCD having an undersirable display characteristic because of the inversion hump present in the area of the viewing angle larger than about 50 degrees. The term “inversion hump” means that the luminance aspect of the curves monotonically decreases as the driving voltage increases. For example, 0.4 and 2.0 volts increase, the luminance of radiation emitted from a pixel decreases accordingly in the viewing angle range larger than about 50 degrees. 
         [0006]      FIG. 6  is a contrast ratio curve graph for the typical LCD of  FIG. 5 . The Circumference line represents a polar angle of the LCD. Four concentric circles sequentially illustrate directions inclined at angles of 20.0 degrees, 40.0 degrees, 60.0 degrees, and 28.0 degrees with respect to the normal of a display of the LCD from the center toward the outside. Curve line  10  illustrates a region where the value of the contrast ratio is 10:1, and curve line  100  illustrates a region where the value of the contrast ratio is 100:1. At the region of polar angle 270 degrees, the viewing angle is less than 80 degrees. 
         [0007]    Thus, what is needed is an LCD and a method for manufacturing the LCD that can overcome the above-mentioned disadvantages is desired. 
       SUMMARY OF THE INVENTION 
       [0008]    An exemplary liquid crystal display includes two substrates opposite to each other and spaced apart a predetermined distance, each of the substrates having an alignment layer; a liquid crystal layer between the two substrates, and having a plurality of liquid crystal molecules; and a plurality of gate lines formed between one alignment layer and one substrate. The two alignment layers have two orthogonal aligning directions, one aligning direction of the two alignment layers being parallel to an extending direction of the gate lines. 
         [0009]    An exemplary method for manufacturing an LCD comprises the following steps: providing two substrates; forming two alignment films on the two substrates, respectively; forming a plurality of gate lines of one of the substrate; aligning the two alignment films; adhering the two substrates, making the two alignment films facing to each other, and the aligning directions of the two alignment films orthogonal to each other, and one of the aligning direction of the two alignment films being perpendicular to the extending direction of the gate lines; filling liquid crystal moleculars between an space defined by the adhered two substrates. 
         [0010]    Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic, cross-sectional view of part of an LCD in accordance with a preferred embodiment of the present invention, which has a second substrate; 
           [0012]      FIG. 2  is a schematic top view of the second substrate of  FIG. 1 ; 
           [0013]      FIG. 3  is a viewing angle versus luminance plot illustrating the gray level characteristics of the LCD of  FIG. 1 ; 
           [0014]      FIG. 4  is a contrast ratio curve graph showing viewing characteristics of the LCD of  FIG. 1 ; 
           [0015]      FIG. 5  is a viewing angle versus luminance plot illustrating the gray level characteristics of a conventional LCD; 
           [0016]      FIG. 6  is a contrast ratio curve graph showing viewing characteristics of the LCD of  FIG. 5 ; 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Hereinafter, preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. 
         [0018]    As shown in  FIGS. 1 and 2 , an LCD according to a preferred embodiment of the present invention includes a first substrate  21 , a second substrate  22  disposed parallel to and spaced apart from the first substrate  21 , and a liquid crystal layer  23  having liquid crystal molecules (not labeled) sandwiched between the two substrates  22  and  21 . The liquid crystal layer  23  is positive or negative liquid crystal material. 
         [0019]    A color filter  213 , a common electrode  212  and a first alignment film  211  are orderly formed on an inner surface of the first substrate  21 , from top to bottom. The first alignment film  211  has a first aligning direction. The LCD  2  further has a first retardation film  214  and a first polarizer  215 , which are orderly disposed on an outer surface of the first substrate  21 , from bottom to top. 
         [0020]    A pixel electrode array  222  and a second alignment film  221  are orderly formed on an inner surface of the first substrate  21 , from top to bottom. The second alignment film  221  has a second aligning direction, which is orthogonal to the first aligning direction of the first alignment film  211 . A second retardation film  224  and a second polarizer  225  are orderly disposed on an outer surface of the second substrate  22 , from top to bottom. 
         [0021]    In addition, the pixel electrode array  222  includes a plurality of gate lines  241  that are parallel to each other and that each extend along a first direction, and a plurality of data lines  242  that are parallel to each other and that each extend along a second direction orthogonal to the first direction. The smallest rectangular area formed by any two adjacent gate lines  241  together with any two adjacent data lines  242  defines a pixel region thereat. In each pixel region, a thin film transistor (TFT)  251  is provided in the vicinity of a respective point of intersection of one of the gate lines  241  and one of the data lines  242 . In each pixel region, a pixel electrode  243  is connected to the TFT  251 . The gate lines  241  extend along the first direction, which is parallel to any one of the first and the second aligning directions of the first and second alignment films  211 ,  221 . 
         [0022]    The common electrode  212  and the pixel electrode  243  are made of a transparent conductive material, such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO). 
         [0023]      FIG. 3  is a viewing angle versus luminance plot illustrating the gray characteristics of a typical LCD. The various curves represent driving voltages from 0.4V to 4.0V applied thereon. From the drawing, we can see no inversion hump is produced. That is, in the whole viewing angle area, no the phenomena of luminance aspect of the curves monotonically decreasing as the driving voltage increases. 
         [0024]      FIG. 4  is a contrast ratio curve graph for the typical LCD of  FIG. 3 . The Circumference line represents a polar angle of the LCD. Four concentric circles sequentially illustrate directions inclined at angles of 20.0 degrees, 40.0 degrees, 60.0 degrees, and 28.0 degrees with respect to the normal of a display of the LCD from the center toward the outside. Curve line  10  illustrates a region where the value of the contrast is 10:1, and curve line  100  illustrates a region where the value of the contrast is 100:1. At the region of polar angle 270 degrees, the viewing angle is larger than 80 degrees. 
         [0025]    The LCD can be manufactured by a following method. The method mainly includes the following steps: 
         [0026]    step a: providing the first substrate  21 ; 
         [0027]    step b: forming the color filter  213  and a conductive film on the first substrate  21 ; 
         [0028]    step c: providing the second substrate  22 ; 
         [0029]    step d: forming the plurality of parallel gate lines  241 , the plurality of parallel data lines  242  orthogonal to the gate lines  241 , and the plurality of TFTs  251  in the vicinity of a respective point of intersection of each of the gate lines  241  and each of the data lines  242 ; 
         [0030]    step e: forming a conductive film on the second substrate  22 ; 
         [0031]    step f: forming the first and the second alignment films  211 ,  221  respectively on the first and the second substrates  21 ,  22 ; 
         [0032]    step g: aligning the first and the second alignment films  211 ,  221 ; 
         [0033]    step h: adhering the first and the second substrates  21 ,  22 , wherein the alignment directions of the first and the second alignment films  211 ,  221  are orthogonal to each other, and one of the alignment direction of the first and the second alignment films  211 ,  221  are parallel to the gate lines  241 ; 
         [0034]    step i: filling liquid crystal moleculars into a space defined between the adhered first and the second substrates  21 ,  22 ; 
         [0035]    step j: providing the first and the second retardation films  214 ,  224  respectively on the outer surfaces of the first and the second substrates  21 ,  22 ; and 
         [0036]    step k: providing the first and the second polarizers  215 ,  225  respectively on the outer surfaces of the first and the second retardation films  214 ,  224 . 
         [0037]    In the step g, the first and the second alignment films  211 ,  221  can be aligned through rubbing method, lithography method, ion beam bombarding method and UV illuminating method. 
         [0038]    The LCD utilizes one of the two alignment films  211 ,  221  having an aligning direction parallel to the gate lines  241  to realize a good viewing angle characteristics as shown in  FIGS. 3 and 4 . 
         [0039]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, 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.