Abstract:
The present invention discloses a pixel electrode of a liquid crystal display (LCD) panel. The pixel electrode has a specific layout. The pixel electrode contains a peripheral portion, slits, and a central part which reserves an opening. When a voltage is applied to the pixel electrode, LC molecules are slanted starting inward moving outward, preventing the central domain of the pixel electrode from being squeezed. Accordingly, the central domain without the pixel electrode can be designed to be smaller, bringing about a decrease in the non-opening domain of the LCD panel and further, a larger aperture rate of the LCD panel.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a pixel electrode and its associated liquid crystal display (LCD) panel, and more particularly to a pixel electrode having a peripheral portion and slits capable of improving an aperture rate of an LCD panel and its associated LCD panel. 
         [0003]    2. Description of Prior Art 
         [0004]    A monitor with multiple functions is a key element for use in current consumer electronic products. The demand for the novelty and colorful monitors with high resolution, e.g., liquid crystal displays (LCDs), are indispensable components used in various electronic products such as monitors for notebook computers, personal digital assistants (PDAs), digital cameras, and projectors. 
         [0005]    An LCD panel comprises a backlight module and an LCD panel. A traditional LCD panel comprises two substrates and a liquid crystal (LC) layer sandwiched by the two substrates. In general, an alignment film is formed on both of the substrates during the LCD panel manufacturing process, so that liquid crystal (LC) molecules can be arranged in a specific direction. In a traditional method of forming alignment films, an alignment material is coated and then the alignment material undergoes an alignment process. 
         [0006]    Currently, a technology called polymer stabilized vertical alignment (PSVA) has been developed by the industry. The PSVA technology is that LC material is mixed with monomers having an appropriate concentration, and then the mixed LC material is shaken evenly. Next, the mixed LC material is placed on a heater and heated until it achieves isotropy. When the mixed LC material reaches room temperature, it tends to go back to a nematic state. Subsequently, the mixed LC material is injected into an LC cell, and a voltage is applied to the LC cell. The voltage makes the LC molecules be arranged stably in the cell. Then, the mixed LC material is polymerized by exposing under ultraviolet (UV) light or by heating in order to form a polymer layer. In this way, alignment stability can be achieved. 
         [0007]    In general, for a pixel structure for use in a PSVA LCD panel, there are alignment slits formed on a pixel electrode to make the LC molecules be aligned in a specific direction. Refer to  FIG. 1 , which is an enlarged diagram of a pixel in a conventional PSVA LCD panel. The PSVA LCD comprises a data line DL, a scan line SL, a thin-film transistor (TFT)  114 , and a pixel electrode  110  as  FIG. 1  shows. The pixel electrode  110 , disposed within the pixel domain, is a snowflake-like pattern. The pixel electrode  110  comprises a vertical main trunk  111  positioned at the center, a horizontal main trunk  112  positioned at the center, and slits  113  slanted away from the X axis by ±45 degrees and ±135 degrees. The vertical main trunk  111  and the horizontal main trunk  112  divide a pixel into four equal domains. The slits  113  slanted at a 45-degree angle are paved inside the four domains. 
         [0008]    Therefore, an electrode pattern which illustrates upper-lower and left-right mirror-image symmetry like a snowflake is completed. 
         [0009]    In this electrode pattern, part of the slits  113  is electrically connected to the TFT  114  for transmitting the voltage from the scan line SL to the pixel electrode  110 . 
         [0010]    Refer to  FIG. 2 , which illustrates an alignment of the LC molecules when a constant voltage (e.g., 4 volts) is applied to the pixel electrode  110  in  FIG. 1 . As  FIG. 2  shows, when the voltage is applied to the snowflake-like pixel electrode  110 , the LC molecules become slanted gradually toward the inside of the pixel electrode  110  from the outside of the pixel electrode  110 . The slanted angle of the LC molecules in each domain extends in a direction in which the slits  113  of the same domain extend. The slanted angle of LC molecules in each of the four domains is ±45 and ±135 degrees, respectively. All of the slanted LC molecules in the four domains are directed toward the center of the pixel domain. For a detailed explanation, as  FIG. 2  shows, the included angle between the direction of the inverted LC molecules in each domain and the X axis (the scan line) is: −135 degrees in the first quadrant, −45 degrees in the second quadrant, 45 degrees in the third quadrant, and 135 degrees in the forth quadrant. 
         [0011]    Refer to  FIG. 3 , which illustrates an alignment of the LC molecules corresponding to a cross section view along a dotted line from point A to point B to point C in  FIG. 1 . As  FIG. 3  shows the cross section view along the dotted line (perpendicular to the cross section of the sheet surface) in  FIG. 1 , the LC molecules are slanted toward the inside of the pixel electrode  110  from the outside of the pixel electrode  110 . The slanted LC molecules are directed toward the inside of the pixel. 
         [0012]    It is notified that, the pixel electrode  110  highly relies on the vertical main trunk  111  and the horizontal main trunk  112  at the center according to the prior art. Basically, the vertical main trunk  111  and the horizontal main trunk  112  are opaque domains. It is because the inverted LC molecules inside the vertical main trunk  111  and the horizontal main trunk  112  are directed toward the main trunks. The included angle between the inverted LC molecules of the vertical main trunk  111  and the X axis is zero degree; the included angle between the inverted LC molecules of the horizontal main trunk  112  and the X axis is 90 degrees. The included angle between a upper polarizer film and the X axis is fixed as zero degree; the included angle between a lower polarizer film and the X axis is fixed as 90 degrees. Therefore, a transmissive rate of the vertical main trunk  111  and of the horizontal main trunk  112  is zero based on a formula for transmissive rate. On the other hand, both of the vertical main trunk  111  and the horizontal main trunk  112  have a very large area, resulting in a decrease in an aperture rate of the LCD panel. 
         [0013]    As a result, the industry needs to develop a pixel electrode pattern having a larger aperture rate. 
       SUMMARY OF THE INVENTION 
       [0014]    An object of the present invention is to provide a pixel electrode pattern with its associated LCD panel. The pixel electrode pattern can increase an aperture rate of the LCD panel, and further, the pixel electrode pattern can solve problems occurring in the prior art. 
         [0015]    According to the present invention, a pixel electrode of a liquid crystal display (LCD) panel is provided. The LCD panel comprises a scan line, a switch unit, and a pixel domain. One terminal of the switch unit is electrically connected to the scan line. The pixel electrode is disposed in the pixel domain. The pixel electrode comprises a peripheral portion and a plurality of slits. The peripheral portion is electrically connected to another terminal of the switch unit. The plurality of slits are surrounded by the peripheral portion and connected to the peripheral portion. An opening is located in a center of the plurality of slits, and divides the plurality of slits into at least two domains. 
         [0016]    According to the present invention, a liquid crystal display (LCD) panel comprises a scan line, a switch unit, a pixel electrode, and a pixel domain. One terminal of the switch unit is electrically connected to the scan line. The pixel electrode is disposed in the pixel domain. The pixel electrode comprises a peripheral portion and a plurality of slits. The peripheral portion is electrically connected to another terminal of the switch unit. The plurality of slits are surrounded by the peripheral portion and connected to the peripheral portion. An opening is located in a center of the plurality of slits, and divides the plurality of slits into at least two domains. 
         [0017]    In contrast to the prior art, the pixel electrode and its associated LCD panel of the present invention comprises a peripheral portion and slits. The present invention reduces the domain of the central main trunk of the prior art, so an opaque domain is reduced greatly. As a result, an aperture rate of the LCD panel is successfully improved. 
         [0018]    These and other features, aspects and advantages of the present disclosure will become understood with reference to the following description, appended claims and accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an enlarged diagram of a pixel in a conventional PSVA LCD panel. 
           [0020]      FIG. 2  illustrates an alignment of the LC molecules when a constant voltage is applied to the pixel electrode in  FIG. 1 . 
           [0021]      FIG. 3  illustrates an alignment of the LC molecules corresponding to a cross section view along a dotted line from point A to point B to point C in  FIG. 1 . 
           [0022]      FIG. 4  is an enlarged diagram of a pixel in an LCD panel according to a preferred embodiment of the present invention. 
           [0023]      FIG. 5  illustrates an alignment of the LC molecules when a voltage is applied to the pixel electrode in  FIG. 4 . 
           [0024]      FIG. 6  illustrates an alignment of the LC molecules corresponding to a cross section view along a dotted line from point A to point B to point C in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. 
         [0026]    Refer to  FIG. 4 , which is an enlarged diagram of a pixel in an LCD panel according to a preferred embodiment of the present invention. According to the present embodiment, the LCD panel  400  uses a PSVA LCD pane. The LCD panel  400  comprises a data line DL, a scan line SL, a switch unit  414 , and a pixel electrode  410 . Preferably, the switch unit  414  is a TFT or any other switch unit having a similar switch function. As  FIG. 4  shows, the pixel electrode  410  is disposed within the pixel domain. The pattern of the pixel electrode  410  is different from that of the aforementioned pixel electrode  110 . The pixel electrode  410  comprises a square-shaped peripheral portion  411  and slits  413  surrounded by the peripheral portion  411 . An opening  412  is located in a center of the slits  413 . The opening  412  divides the pixel electrode into four roughly equal domains. The slits  413  slanted at a 45-degree angle are paved within the four domains. 
         [0027]    The peripheral portion  411  is electrically connected to one terminal of the switch unit  414 . The other terminal of the switch unit  414  is electrically connected to the scan line SL. So the voltage applied to the scan line SL can be transmitted to the pixel electrode  410  by means of the conduction of the switch unit  414  and the peripheral portion. 
         [0028]    The slits  413  of each of the four domains have their individual direction. The included angle between each of the slits  413  in the four domains and the X axis (the scan line SL) is ±45 degrees and ±135 degrees, respectively. According to a preferred embodiment of the present invention, all of the slits  413  of the domains are directed toward the center of the pixel domain. That is, as  FIG. 4  shows, the included angle between the slits  413  in the first quadrant and the scan line SL is −135 degrees; the included angle between the slits  413  in the second quadrant and the scan line SL is −45 degrees; the included angle between the slits  413  in the third quadrant and the scan line SL is 45 degrees; the included angle between the slits  413  in the fourth quadrant and the scan line SL is 135 degrees. It should be notified that, however, the included angle between each of the slits  413  of the four domains and the scan line SL only applies to the embodiment of the present invention. These included angles are not intended to limit the present invention. Designers can design other included angles depending on their demands. Such corresponding changes also belong to the scope of the present invention. 
         [0029]    Moreover, it is notified that, although the peripheral portion  411  is shaped as a square according to the present embodiment, it can be shaped as a circle, a regular hexagon, a regular octagon, or any other shapes in practical applications. In other words, the peripheral portion  411  is not restricted to being a square. It is also notified that, although the opening  412  is cruciform according to the present embodiment, it not restricted to a cruciform pattern; instead, the opening  412  can show a straight-line-shaped pattern or a snowflake-like pattern. As long as an opening can divide the slits  413  into upper and lower parts or left and right parts displaying upper-lower or left-right minor-image symmetry, it is within the scope of the present invention. 
         [0030]    Refer to  FIG. 5 , which illustrates an alignment of the LC molecules when a voltage is applied to the pixel electrode  410  in  FIG. 4 . As  FIG. 5  shows, when the voltage is applied to the pixel electrode  410 , the LC molecules become slanted gradually toward the outside of the pixel electrode  410  from the inside of the pixel electrode  410 . The slanted angle of the LC molecules in each domain extends in the direction of the slits  413  of the same domain. The slanted LC molecules in the four domains have a direction of ±45 and ±135 degrees, respectively. The directions of the slanted LC molecules indicate four corners of the pixel domain from the center of the pixel domain. 
         [0031]    Refer to  FIG. 6 , which illustrates an alignment of the LC molecules corresponding to a cross section view along a dotted line from point A to point B to point C in  FIG. 4 . As  FIG. 6  shows the cross section along the dotted line (perpendicular to the cross section of the sheet surface) in  FIG. 4 , the LC molecules are slanted toward the outside of the pixel electrode  410  from the inside of the pixel electrode  410 . The slanted LC molecules indicate four corners of the pixel. In other words, the LC molecules are slanted inward to outward when the voltage is applied to the pixel electrode  410 . So the central domain of the pixel electrode  410  can be prevented from being squeezed. Thus, in a preferred embodiment of the present invention, designers can reduce the domain of the central opening  412  (the domain without ITO) as much as possible. In this way, the non-opening domain is greatly reduced and the aperture rate becomes relatively larger. 
         [0032]    It is notified that, the pattern of the pixel electrode  410  is not difficult for the one skilled in this art; that is, no specific process is required to form the pattern of the pixel electrode  410 . The pattern of the pixel electrode  410  of the present invention can directly substitute for the pixel electrode  110  of the prior art. The one skilled in this art should fully understand the descriptions, so no details for the process are provided. 
         [0033]    In contrast to the prior art, the LCD panel of the present invention comprises a pixel electrode having a specific pattern. The pixel electrode comprises a peripheral portion and slits, removing an opaque main trunk of the pixel electrode in the prior art. Thus, the pixel electrode of the present invention has a larger transmittable domain, providing the LCD panel of the present invention with a larger aperture rate. 
         [0034]    The pixel electrode of the present invention is qualified to be applied to a PSVA LCD panel, a twisted nematic (TN) LCD panel, a pattern vertical alignment (PVA) LCD panel, and so on. 
         [0035]    Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.