Patent Publication Number: US-2011069269-A1

Title: Continuous domain vertical alignment liquid crystal display panel

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure generally relates to liquid crystal displays (LCDs) panels, and particularly to a continuous domain vertical alignment (CDVA) liquid crystal display panel. 
     2. Description of Related Art 
     Popular features of LCDs are that they are thin and light, consume relatively little electrical power and do not cause flickering, so they are widely used in electronic devices such as laptop personal computers, and televisions, wherein a panel is one of the main components of each LCD. 
     An LCD panel usually includes two opposing substrates and a liquid crystal unit sandwiched therebetween. Electrodes are formed on the surfaces of the two substrates. When voltages are applied to the LCD panel, electric fields are generated between the two substrates. Liquid crystal molecules of the liquid crystal unit are twisted by the electric fields to control the light beams, and display a desired image. However, inclinations of each liquid crystal molecule may differ because of effects of gravity and interactions of the liquid crystals with their surroundings. Therefore, images may appear different when observed from different angles. 
     In order to compensate for the variation in appearance of images displayed by the LCD panels, vertical alignment liquid crystal display panels have been promoted. Referring to  FIG. 6 , a typical vertical alignment liquid crystal display panel  1  includes a first substrate  11 , a second substrate  12  parallel to the first substrate  11 , and a liquid crystal layer  13  sandwiched therebetween. The first substrate  11  includes a first electrode  111  and a plurality of protrusions  112  arranged at an inner surface of the first electrode  111 . The second substrate  12  includes a second electrode  121  and a plurality of slits  122  defined in the second electrode  121 . The projection of each protrusion  112  perpendicular to the second substrate  12  is between two adjacent slits  122 . The liquid crystal layer  13  contacted to the first electrode  111 , the second electrode  121 , the protrusions  112  and the slits  122  includes a number of liquid crystal molecules  131  having negative dielectric anisotropy. The liquid crystal molecules  131  can be driven by electric fields generated by the first electrode  111  and the second electrode  112 . 
     Also referring to  FIG. 6 , when the LCD panel  1  is in an off state, and no voltage is applied to it, the liquid crystal molecules  131  adjacent to the protrusions  112  and the slits  122  are inclined relative to the protrusions  112 . Most of the light beams passing though the second substrate  12  cannot pass though the first substrate  11 , because the light beams do not change their polarization states when passing through the liquid crystal molecules  131 . As a result, the LCD panel  1  displays a black image. 
     Referring to  FIG. 7 , when the LCD panel  1  is in an on state, voltages are applied thereto, and voltage differences between the first electrode  111  and the second electrode  112  generates electric fields perpendicular to a plane of the liquid crystal unit  13 . In addition, electrical field lines adjacent to the slits  122  are generally arced. The liquid crystal molecules  131  are twisted relative perpendicular to the electric fields, and the liquid crystal molecules  131  adjacent to the protrusions  112  are further inclined relative to the protrusions  112 . Because of birefringence of the liquid crystal molecules  131  and the further incline between the protrusions  112  and the liquid crystals, the polarization states of the light beams are changed to align with the polarization direction of the first substrate  11 . Therefore, light is emitted from the first substrate  11 , and the LCD panel  1  displays an image with improved brightness. 
     Referring to  FIG. 8 , Because the liquid crystal molecules  131  are oriented in four directions X 1 , X 2 , X 3  and X 4 , color shift that would otherwise be manifest in images displayed by the LCD panel  1  is compensated for. In particular, the LCD panel  1  has a more consistent display performance along four different viewing directions corresponding to the directions X 1 , X 2 , X 3  and X 4 . That is, the LCD panel  1  attains a display having four domains. However, the four-domain configuration can only ensure desired visual performance in four directions. 
     In addition, when portions of the LCD panel  1  are in an off state to produce black colors in an image, the liquid crystal molecules  131  are inclined relative to the protrusions  112 , the polarization states of some of light beams may be changed to align with the polarization direction of the first substrate  11 . Therefore, there may be some light leaks from the first substrate  11 , and the LCD panel  1  has a lower contrast ratio. 
     Therefore, there is room for improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the CDVA liquid crystal display panels can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the CDVA liquid crystal display panels. 
         FIG. 1  is a top view of a schematic view of a CDVA liquid crystal panel, according to a first exemplary embodiment. 
         FIG. 2  is a cross-section view of the CDVA liquid crystal panel of  FIG. 1 . 
         FIG. 3  is a schematic view of a sine curve and a base line of the CDVA liquid crystal panel of  FIG. 1 . 
         FIG. 4  is a test table obtained from the CDVA liquid crystal panel of  FIG. 1 , disclosing transmittances and contrast ratio varying with angle between a protrusion of the CDVA liquid crystal panel and a baseline. 
         FIG. 5  is a top view of a schematic view of a CDVA liquid crystal panel, according to a second exemplary embodiment. 
         FIG. 6  is a cross-section view of a conventional CDVA liquid crystal panel in an off state. 
         FIG. 7  is a cross-section view of a conventional CDVA liquid crystal panel in an on state. 
         FIG. 8  is a top view of a schematic view of a conventional CDVA liquid crystal panel. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , a CDVA liquid crystal display panel  2  according to a first exemplary embodiment of the present disclosure, includes a first substrate  3 , a second substrate  4 , and a liquid crystal unit  5 . 
     The first substrate  3  includes a first electrode  31  and a plurality of protrusions  32 . The protrusions  31  are arranged on the inner surface of the first electrode  31  and spaced from each other. Each protrusion  32  is strip-shaped, and the section width of each protrusion  32  is about 10 μm. Referring to  FIG. 2  and  FIG. 3 , each protrusion  32  is substantially extended along a sine curve S. A base line  200  is defined passing through 0 degrees and 180 degrees on the sine curve S, and an angle α between the protrusion  32  and the base line  200  at 0 degrees on the sine curve S is about 15 degrees. Two ends of the protrusions  32  adjacent to a pixel region (not labeled) are converted to extend along a straight line that is designed as a protruding wing to avoid reducing the transmittance of the CDVA liquid crystal display panel  2 . 
     The second substrate  4  includes a plurality of second electrodes  41  spaced from each other. The second electrodes  41  define a plurality of slits  411 . At least one slit  411  is defined adjacent to each protrusion  32 . Each slit  411  is extended along a straight line, and the section width of each slit  411  is about 10 μm. The projection of each protrusion  32 , perpendicular to the second substrate  4 , falls between two adjacent slits  411  and opposite to an electrode  41 . 
     The liquid crystal unit  5  is sandwiched between the first substrate  3  and the second substrate  4 , and contacts the first electrodes  31 , the second electrodes  41 , the slits  411 , and the protrusions  32 . The liquid crystal unit  5  includes a number of liquid crystal molecules  51  having negative dielectric anisotropy, and can be driven by the electrical fields generated by the first and second electrodes  31 ,  41 . 
     When the CDVA liquid crystal display  2  is in an off state, and no voltage is applied to it, the liquid crystal molecules  51  adjacent to the protrusions  32  and the slits  411  are inclined relative to the protrusions  32 . The liquid crystal molecules  51  arranged along the protrusion  32  includes a plurality of orientations. Most light beams passing though the second substrate  4  cannot pass though the first substrate  3 , because the light beams do not change their polarization states when passing through the liquid crystal molecules  51 . As a result, the CDVA liquid crystal display  2  displays a black image. 
     When the CDVA liquid crystal display  2  is in an on state, voltages are applied thereto, and voltage differences between the first electrode  31  and the second electrode  41  generates electric fields perpendicular to a plane of the liquid crystal unit  51 . The liquid crystal molecules  51  are twisted relative perpendicular to the electric fields, and the liquid crystal molecules  51  adjacent to the protrusions  32  are further inclined relative to the protrusions  32 . Because of birefringence of the liquid crystal molecules  51  and the further incline between the protrusions  32  and the liquid crystals, the polarization states of light beams are changed to align with the polarization direction of the first substrate  3 . Therefore light is emitted from the first substrate  3 , and the LCD panel  2  displays an image with improved brightness relative to conventional technology. 
     Because the protrusions  32  are extended along a sine curve S and the slits  411  are extended along a straight line, the liquid crystal molecules  51  are arranged along the sine curve S of the protrusions  32  and have a plurality of inclinations. The plurality of inclinations of the liquid crystal molecules  51  decrease the leaking of light from the LCD panel  2  and raises the contrast ratio when the LCD panel  2  is in the off state, and also improves the color shift when the LCD panel  2  is in the on state. 
     Referring to  FIG. 4 , when the angle α between the protrusion  32  and the baseline  200  at 0 degrees on the sine curve is 12 degrees, the transmittance is 98.77%, and the contrast ratio is 4215; when the angle α between the protrusion  32  and the baseline  200  at 0 degrees on the sine curve is 25 degrees, the transmittance is down to 82.68, and the contrast ratio is raised to 4299. The angle α between the protrusion  32  and the baseline  200  at 0 degrees on the sine curve is from 10 degrees to 20 degrees in this exemplary embodiment, and more specifically about 15 degrees. In addition, the section width of each protrusion  32  and slit  411  may be from 8 μm to 12 μm. 
     Referring to  FIG. 5 , a CDVA liquid crystal display panel  6  according to a second exemplary embodiment of the present disclosure is substantially similar to the CDVA liquid crystal displayer panel  2 , the difference is that each protrusion  32  of the CDVA liquid crystal displayer panel  6  is extended along a straight line, and each slit  411  of the CDVA liquid crystal displayer panel  6  is extended along a sine curve S. An angle between the slit  411  of the CDVA liquid crystal displayer panel  6  extended along the sine curve S and the baseline  200  at 0 degrees of the sine curve S is smaller than 25 degrees, and is from 10 degrees to 20 degrees in this exemplary embodiment, and more specifically about 15 degrees. The section width of each protrusion  32  and slit  411  may be from 8 μm to 12 μm. 
     The design of the CDVA liquid crystal display panel  6  with the protrusions  32  extended along a straight line and the slits  411  extended along a sine curve means that the liquid crystal molecules  51  are also arranged along the sine curve of the protrusions  32  and have a plurality of inclinations. The plurality of inclinations of the liquid crystal molecules  51  decrease the leaking of light from the LCD panel  6  and raise the contrast ratio of the LCD panel  6 , and also improves the color shift of the LCD panel  6 . 
     It is believed that the exemplary embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.