Abstract:
An exemplary transmission liquid crystal display ( 100 ) includes a first glass substrate ( 110 ) and a second glass substrate ( 120 ); a liquid crystal layer ( 130 ) having liquid crystal molecules interposed between the first and second substrates, the liquid crystal molecules being bend-aligned whereby the liquid crystal display device to operate in an optically compensated bend (OCB) mode; a front polarizer ( 171 ) disposed at a front surface of the first substrate, a rear polarizer ( 172 ) disposed at a rear surface of the second substrate; a first compensation member ( 180 ) between the front polarizer and the first substrate; and a second compensation member ( 190 ) between the rear polarizer and the second substrate.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to transmission liquid crystal displays (LCDs), and more particularly to transmission LCDs that operate in OCB (optically compensated bend) mode.  
       BACKGROUND  
       [0002]     Recently, LCDs that are light and thin and have low power consumption characteristics have been widely used in office automation equipment, video units and the like.  
         [0003]     As shown in  FIG. 12 , a conventional transmission liquid crystal display  1  includes a first substrate  10 , a second substrate  20  opposite to the first substrate  10 , and a liquid crystal layer  30  interposed between the first and second substrates  10 ,  20 . A front polarizer  71  and a front retardation film  80  are disposed on an outer surface of the first glass substrate  10 , in that order from top to bottom. A front alignment film  61 , a common electrode  51 , and a color filter  40  are disposed on an inner surface of the first substrate  10 , in that order from bottom to top. A pixel electrode  52  is laminated on an inner surface of the second substrate  20 . A rear alignment film  62  is laminated on the pixel electrode  52 . A rear retardation film  90  and a rear polarizer  72  are disposed on an outer surface of the second substrate  20 , in that order from top to bottom. A backlight module (not shown) is provided under the rear polarizer  72 .  
         [0004]     The front retardation film  80  and the rear retardation film  90  are quarter-wavelength plates. The liquid crystal molecules of the liquid crystal layer  30  are homogeneously aligned. An absorption axis of the front polarizer  71  is orthogonal to that of the rear polarizer  72 . Anchoring energy exists between the alignment films  61 ,  62  and certain of the liquid crystal molecules adjacent to the alignment films  61 ,  62 . Therefore when an electrical field is applied, these liquid crystal molecules need an unduly long amount of time to become oriented according to the applied electrical field. This typically results in residual images being produced.  
         [0005]     What is needed, therefore, is a liquid crystal display device which has a fast response time.  
       SUMMARY  
       [0006]     In a preferred embodiment, a transmission LCD device includes a first glass substrate and a second glass substrate; a liquid crystal layer having liquid crystal molecules interposed between the first and second substrates, the liquid crystal molecules being bend-aligned whereby the liquid crystal display device to operate in an optically compensated bend (OCB) mode; a front polarizer disposed at a front surface of the first substrate, a rear polarizer disposed at a rear surface of the second substrate; a first compensation member between the front polarizer and the first substrate; and a second compensation member between the rear polarizer and the second substrate.  
         [0007]     Further, the transmission LCD device preferably includes a first front compensation film and a second front compensation film. Preferably, the first front compensation film is a hybrid C-compensation film.  
         [0008]     According to other embodiments, the transmission LCD device preferably includes a first rear compensation film and a second rear compensation film; and the first rear compensation film is a C-compensation film.  
         [0009]     Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic, exploded, side cross-sectional view of a transmission LCD according to a first preferred embodiment of the present invention;  
         [0011]      FIG. 2  is a schematic, exploded, side cross-sectional view of a transmission LCD according to a second preferred embodiment of the present invention;  
         [0012]      FIG. 3  is a graph illustrating contrast ratio characteristics of the transmission LCD of  FIG. 2 , when light is incident and received at a predetermined wavelength;  
         [0013]      FIG. 4  is a graph illustrating gray scale performance along a horizontal direction of the transmission LCD of  FIG. 2 , when different voltages are applied;  
         [0014]      FIG. 5  is a graph illustrating gray scale performance along a vertical direction of the transmission LCD of  FIG. 2 , when different voltages are applied;  
         [0015]      FIG. 6  is a schematic, exploded, side cross-sectional view of a transmission LCD according to a third preferred embodiment of the present invention;  
         [0016]      FIG. 7  is a schematic, exploded, side cross-sectional view of a transmission LCD according to a fourth preferred embodiment of the present invention;  
         [0017]      FIG. 8  is a schematic, exploded, side cross-sectional view of a transmission LCD according to a fifth preferred embodiment of the present invention;  
         [0018]      FIG. 9  is a graph illustrating contrast ratio characteristics of the transmission LCD of  FIG. 8 , when light is incident and received at a predetermined wavelength;  
         [0019]      FIG. 10  is a graph illustrating gray scale performance along a horizontal direction of the transmission LCD of  FIG. 8 , when different voltages are applied;  
         [0020]      FIG. 11  is a graph illustrating gray scale performance along a vertical direction of the transmission LCD of  FIG. 8 , when different voltages are applied; and  
         [0021]      FIG. 12  is a schematic, exploded, side cross-sectional view of a conventional transmission LCD. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]     In this description, unless the context indicates otherwise, a reference to a compensation member is a reference to a kind of optical compensation member.  
         [0023]      FIG. 1  is a schematic, exploded, side cross-sectional view of a transmission LCD  100  according to a first preferred embodiment of the present invention. The transmission LCD  100  includes a first substrate assembly  101 , a second substrate assembly  102  opposite to the first substrate assembly  101 , and a liquid crystal layer  130  interposed between the first and second substrate assemblies  101 ,  102 .  
         [0024]     The first substrate assembly  101  includes a front polarizer  171 , a front compensation member  180 , a first glass substrate  110 , a color filter  140 , a common electrode  151 , and a front alignment film  161 , which are laminated one on the other and disposed in that order from top to bottom. The front polarizer  171  and the front compensation member  180  are disposed on an outer surface of the first glass substrate  110 , in that order from top to bottom. The front alignment film  161 , the common electrode  151  and the color filter  140  are disposed on an inner surface of the first glass substrate  110 , in that order from bottom to top.  
         [0025]     The second substrate assembly  102  includes a rear alignment film  162 , a pixel electrode  152 , a second glass substrate  120 , a rear compensation member  190 , and a rear polarizer  172 , which are laminated one on the other and disposed in that order from top to bottom. In addition, in a typical application, a backlight module (not shown) is provided under the rear polarizer  172 .  
         [0026]     The liquid crystal layer  130 , the common electrode  151 , and the pixel electrode  152  cooperatively define a pixel region. When a voltage is applied to the transmission LCD  100 , an electric field is generated between the common electrode  151  and the pixel electrode  152 . The electric field can control the orientation of liquid crystal molecules (not labeled) in the liquid crystal layer  130  in order to display images.  
         [0027]     In assembly, the liquid crystal molecules are bend-aligned to enable the transmission LCD  100  to operate in an optically compensated bend (OCB) mode. A pretilt angle of the liquid crystal molecules adjacent to the substrate assemblies  101  and  102  is in a range of 0° to 15°. An absorption axis of the front polarizer  171  maintains an angle of 45 degrees relative to the orientation direction of the liquid crystal molecules in the liquid crystal layer  130 , and the absorption axis of the front polarizer  171  is orthogonal to an absorption axis of the rear polarizer  172 .  
         [0028]      FIG. 2  is a schematic, exploded, side cross-sectional view of a transmission LCD  200  according to a second preferred embodiment of the present invention. The transmission LCD  200  is similar to the transmission LCD  100  of  FIG. 1 . However, a front compensation member  280  of the transmission LCD  200  includes a first front compensation film  281  and a second front compensation film  282 . The first front compensation film  281  and the second front compensation film  282  are disposed on an outer surface of a first glass substrate  210 , in that order from bottom to top. A rear compensation member  290  of the transmission LCD  200  includes a first rear compensation film  291  and a second rear compensation film  292 . The first rear compensation film  291  and the second rear compensation film  292  are disposed on an outer surface of a second glass substrate  220 , in that order from top to bottom. A rear polarizer  272  is disposed on a bottom of the second rear compensation film  292 .  
         [0029]     The first front and rear compensation films  281 ,  291  are hybrid C-plate compensation films, each of which is made from a uniaxial crystal. The second front compensation film  282  is a biaxial compensation film, which is made from a biaxial material. The second rear compensation film  292  is a C-plate compensation film, which is made from a uniaxial material. A slow axis of the second front compensation film  282  is parallel to an absorption axis of the rear polarizer  272 .  
         [0030]     In each pixel region of the transmission LCD  200 , the liquid crystal molecules (not labeled) have a pre-tilt angle, which ensures that the liquid crystal molecules can more easily adjust their orientation when a voltage is applied to the transmission LCD  200  and a change in a driving electric field is effected. Thereby, the transmission LCD  200  has a fast response time. Moreover, the compensation films are used for compensating for phase delay produced by the liquid crystal molecules, so as to ensure that the transmission LCD  200  has improved contrast and viewing angle characteristics and displays good quality images.  
         [0031]      FIG. 3  is a computer simulation contrast ratio graph for the transmission LCD  200  when light having a predetermined wavelength is utilized. As shown in  FIG. 3 , a 30:1 contrast ratio curve extends horizontally along the 0° vertical viewing axis a total of more than 150°, and a 50:1 contrast ratio curve extends vertically along the 0° horizontal viewing axis a total of more than 150°, which shows that a large viewing angle is obtained.  
         [0032]      FIG. 4  and  FIG. 5  illustrate gray scale performance along a horizontal direction and a vertical direction of the transmission LCD  200 , respectively, when different voltages are applied. In  FIG. 4  and  FIG. 5 , curve V 1  represents a voltage of 1.5V applied, curve V 2  represents a voltage of 2V applied, curve V 3  represents a voltage of 3V applied, curve V 4  represents a voltage of 4V applied, and curve V 5  represents a voltage of 7V applied. As shown in  FIG. 4  and  FIG. 5 , no gray scale inversion is produced along a horizontal direction along the 0° vertical viewing axis from -80° to 80°.  
         [0033]      FIG. 6  is a schematic, exploded, side cross-sectional view of a transmission LCD  300  according to a third preferred embodiment of the present invention. The transmission LCD  300  is similar to the transmission LCD  200  of  FIG. 2 . However, a front compensation member  380  of the transmission LCD  300  includes a first front compensation film  381 , a second front compensation film  382 , and a third front compensation film  383 . The first front compensation film  381 , the second front compensation film  382 , and the third front compensation film  383  are disposed on an outer surface of a first glass substrate  310 , in that order from bottom to top. A rear compensation member  390  of the transmission LCD  300  includes a first rear compensation film  391 , a second rear compensation film  392 , and a third rear compensation film  393 . The first rear compensation film  391 , the second rear compensation film  392 , and the third rear compensation film  393  are disposed on an outer surface of a second glass substrate  320 , in that order from top to bottom. A rear polarizer  372  is disposed on a bottom of the third rear compensation film  393 .  
         [0034]     The first front and rear compensation films  381 ,  391  are hybrid C-plate compensation films. The second front and rear compensation films  382 ,  392  are C-plate compensation films. The third front and rear compensation films  383 ,  393  are A-plate compensation films, each of which is made from a uniaxial material. A slow axis of the third front compensation film  383  and a slow axis of the third rear compensation film  393  are parallel to an absorption axis of the rear polarizer  372 , respectively.  
         [0035]      FIG. 7  is a schematic, exploded, side cross-sectional view of a transmission LCD  400  according to a fourth preferred embodiment of the present invention. The transmission LCD  400  is similar to the transmission LCD  200  of  FIG. 2 . However, a front compensation member  480  of the transmission LCD  400  includes a first front compensation film  481 , a second front compensation film  482 , and a front retardation film  485 . The first front compensation film  481 , the second front compensation film  482 , and the front retardation film  485  are disposed on an outer surface of a first glass substrate  410 , in that order from bottom to top. A front polarizer  471  is disposed on top of the front retardation film  485 . A rear compensation member  490  of the transmission LCD  400  includes a first rear compensation film  491 , a second rear compensation film  492 , and a rear retardation film  495 . The first rear compensation film  491 , the second rear compensation film  492 , and the rear retardation film  495  are disposed on an outer surface of a second glass substrate  420 , in that order from top to bottom.  
         [0036]     The first front and rear compensation films  481 ,  491  are hybrid C-plate compensation films. The second front and rear compensation films  482 ,  492  are C-plate compensation films. The front and rear retardation films  485 ,  495  are quarter-wave plates. A slow axis of the front retardation film  485  maintains an angle of 45 degrees relative to an absorption axis of the front polarizer  471 , and the slow axis of the front retardation film  485  is orthogonal to a slow axis of the rear retardation film  495 .  
         [0037]      FIG. 8  is a schematic, exploded, side cross-sectional view of a transmission LCD  500  according to a fifth preferred embodiment of the present invention. The transmission LCD  500  is similar to the transmission LCD  400  of  FIG. 7 . However, a front compensation member  580  of the transmission LCD  500  further includes a third front compensation film  583  disposed between a front retardation film  585  and a front polarizer  571 . The third front compensation film  583  is an A-plate compensation film. A slow axis of the third front compensation film  583  is orthogonal to an absorption axis of the front polarizer  571 .  
         [0038]      FIG. 9  is a computer simulation contrast ratio graph for the transmission LCD  500  when light having a predetermined wavelength is utilized. As shown in  FIG. 9 , a 30:1 contrast ratio curve extends horizontally along the 0° vertical viewing axis a total of more than 150°, and a 50:1 contrast ratio curve extends vertically along the 0° horizontal viewing axis a total of more than 150°, which shows that a large viewing angle is obtained.  
         [0039]      FIG. 10  and  FIG. 11  illustrate gray scale performance along a horizontal direction and a vertical direction of the transmission LCD  500 , respectively, when different voltages are applied. In  FIG. 10  and  FIG. 11 , curve V 1  represents a voltage of 1.5V applied, curve V 2  represents a voltage of 2V applied, curve V 3  represents a voltage of 3V applied, curve V 4  represents a voltage of 4V applied, and curve V 5  represents a voltage of 7V applied. As shown in  FIG. 10  and  FIG. 11 , no gray scale inversion is produced along a horizontal direction along the 0° vertical viewing axis from -800 to 800.  
         [0040]     In each pixel region of each of the above-described transmission LCDs, the liquid crystal molecules have a pre-tilt angle, which ensures that the liquid crystal molecules can more easily adjust their orientation when a voltage is applied to the transmission LCD and a change in a driving electric field is effected. Thereby, the transmission LCDs have a fast response time. Moreover, the retardation films and the compensation films are used for compensating for color, so as to ensure that the transmission LCDs have improved contrast and viewing angle characteristics and display good quality images.  
         [0041]     It is to be understood, however, that even though numerous characteristics and advantages of various embodiments have been set forth 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 to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.