Liquid crystal display device comprising a plurality of pixel electrodes each having first, second, and third stem electrodes

A liquid crystal display device includes pixels, each including a pixel electrode including first and second stem electrodes, which extend in a first direction and are spaced apart from each other, a third stem electrode, which extends in a second direction perpendicular to the first direction and intersects the first and second stem electrodes, a first edge electrode, which extends in the second direction and intersects first ends of the first and second stem electrodes, a second edge electrode, which extends in the second direction and intersects second ends of the first and second stem electrodes, and branch electrodes, which extend from the first, second, and third stem electrodes in a direction which is different from the first and second directions where a boundary line is defined between the first and second stem electrode.

This application claims priority to Korean Patent Application No. 10-2016-0043234 filed on Apr. 8, 2016, and all the benefits accruing therefrom under 35 U.S.C. §119, the content f which in its entirety is herein incorporated by reference.

BACKGROUND

Exemplary embodiments of the invention relate to a liquid crystal display (“LCD”) device.

2. Description of the Related Art

A liquid crystal display (“LCD”) device, which is one of the most widely-used flat panel displays, generally includes two substrates on which field-generating electrodes such as pixel electrodes and a common electrode are formed and a liquid crystal layer which is inserted is between the two substrates. The LCD device generates an electric field in the liquid crystal layer by applying a voltage to the field-generating electrodes, and displays an image by determining an orientation of liquid crystal molecules in the liquid crystal layer and controlling a polarization of an incident light using the electric field.

A vertical alignment (“VA”)-mode LCD device in which liquid crystal molecules are aligned so as for their long axes to be perpendicular to upper and lower substrates in an absence of an electric field has been developed.

To realize a wide viewing angle in the VA-mode LCD device, a plurality of domains that differ from one another in the alignment direction of liquid crystal molecules may be formed in each pixel.

Various methods such as defining cutouts such as slits on field-generating electrodes such as pixel electrodes and forming protrusions on the field-generating electrodes are used to define a plurality of domains in each pixel of an LCD device.

In the meantime, a regional luminance of a VA-mode LCD device may differ from when the VA-mode LCD device is viewed from the front to when the VA-mode LCD device is viewed from a side. That is, a visibility of the VA-mode LCD device may decrease. To address such a problem, each pixel may be divided into two sub-pixels, and different voltages may be respectively applied to the two sub-pixels.

SUMMARY

A configuration for applying two different voltages respectively to the two sub-pixels of each pixel needs more components than a configuration for applying a single voltage to each pixel and may thus a lower the transmittance of an LCD device.

Exemplary embodiments of the invention provide a liquid crystal display (“LCD”) device capable of improving visibility and minimizing a decrease in transmittance.

However, exemplary embodiments of the invention are not restricted to those set forth herein. The above and other exemplary embodiments of the invention will become more apparent to one of ordinary skill in the art to which the invention pertains by referencing the detailed description of the invention given below.

According to an exemplary embodiment of the invention, there is provided a liquid crystal display device. The liquid crystal display device includes a plurality of pixels, each including a pixel electrode, where each of the pixel electrodes includes first and second stem electrodes, which extend in a first direction and are spaced apart from each other, a third stem electrode, which extends in a second direction that is perpendicular to the first direction and is disposed to intersect the first and second stem electrodes, a first edge electrode, which extends in the second direction and is disposed to intersect first ends of the first and second stem electrodes, a second edge electrode, which extends in the second direction and is disposed to intersect second ends of the first and second stem electrodes, and a plurality of branch electrodes, which extend from at least one of the first, second, and third stem electrodes in a direction different from the first and second directions, a border line, which is defined by the ends of at least two of the branch electrodes facing each other, is defined between the first and second stem electrode, and the first stem electrode, the border line, and the second stem electrode divide a pixel region in which the corresponding pixel electrode is disposed into a first edge area, a first central area, a second central area, and a second edge area, which are sequentially arranged along the second direction.

According to another exemplary embodiment of the invention, there is provided a liquid crystal display device. The liquid crystal display device includes a substrate including a plurality of pixels, which are arranged in a matrix form, and a plurality of pixel electrodes disposed on the substrate and provided in the pixels, respectively, where each of the pixel electrodes includes first and second stem electrodes, which extend in a first direction and are spaced apart from each other, a third stem electrode, which extends in a second direction that is perpendicular to the first direction and is disposed to intersect the first and second stem electrodes, a first edge electrode, which extends in the second direction and is disposed to intersect first ends of the first and second stem electrodes, a second edge electrode, which extends in the second direction and is disposed to intersect second ends of the first and second stem electrodes, and a plurality of branch electrodes, which extend from at least one of the first, second, and third stem electrodes in a direction which is different from the first and second directions, and a pixel region in which the corresponding pixel electrode is disposed is divided into a central area, which is surrounded by the first and second stem electrodes and the first and second edge electrodes, and first and second edge areas, which are defined in first and second sides, respectively, of the central area in the second direction.

According to the exemplary embodiments, an LCD device which improves visibility and minimizes a decrease in transmittance may be provided.

Other features and exemplary embodiments will be apparent from the following detailed description, the drawings, and the claims.

DETAILED DESCRIPTION

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 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'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. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated90degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

FIG. 1is a plan view of a pixel of a liquid crystal display (“LCD”) device according to an exemplary embodiment of the invention,FIG. 2is a cross-sectional view taken along line I-I′ of

FIG. 1, andFIG. 3is an enlarged plan view of a pixel electrode ofFIG. 1.

Referring toFIGS. 1 through 3, the LCD device according to the illustrated exemplary embodiment may include a first display substrate100, a second display substrate300, and a liquid crystal layer200.

The LCD device according to the illustrated exemplary embodiment further includes a pixel10, which is arranged in a matrix form with other pixels. The pixel10may be a basic unit for displaying a color with a particular gray level. The first display substrate100includes a pixel electrode182, which is disposed in the pixel10, and a thin-film transistor (“TFT”)167, which is a switching device for providing a data voltage to the pixel electrode182. The second display substrate300may face the first display substrate100. The liquid crystal layer200is a space in which liquid crystal molecules210injected between the first and second display substrates100and300reside.

The first display substrate100will hereinafter be described.

The first display substrate100includes a first base substrate110. The first base substrate110may be a transparent insulating substrate. In an exemplary embodiment, the first base substrate110may be provided as a glass substrate, a quartz substrate, or a transparent resin substrate, for example. The first base substrate110may be a flat substrate, or may be curved along one direction.

A gate line122, a gate electrode124, and a sustain line125may be disposed on the first base substrate110.

The gate line122transmits a gate signal, which controls the TFT167. The gate line122may extend in a first direction D1. The first direction D1may be a direction parallel to one side of the first base substrate110, and may be defined as a direction indicated by an arbitrary straight line extending from the left to the right ofFIG. 2. However, the first direction D1is not particularly limited to the direction parallel to one side of the first base substrate110, but may be a direction indicated by a straight line extending across the first base substrate100in any particular direction.

The gate signal may be a signal having a variable voltage, provided by an external source. The turning on or off of the TFT167may be controlled by the voltage of the gate signal.

The gate electrode124is connected to the gate line122. The gate electrode124may protrude from the gate line122, and serve as a control electrode of the TFT167. The gate line122may be connected to a plurality of gate electrodes124.

The sustain line125may be disposed between the gate line122and another gate line next to the gate line122and may extend substantially in the first direction D1. The sustain line125may be adjacent to the pixel electrode182or partially overlapped by the pixel electrode182. The sustain line125has a predetermined capacitance with the pixel electrode182and maintains the voltage that the pixel electrode182is charged with. In another exemplary embodiment, the sustain line125may not be provided when a voltage drop in the pixel electrode182is expected to be relatively insignificant in the absence of the sustain line125.

The shape in which the sustain line125is overlapped by the pixel electrode182will be described later.

In an exemplary embodiment, the gate line122, the gate electrode124, and the sustain line125may include aluminum (Al), an Al-based metal such as an Al alloy, silver (Ag), a Ag-based metal such as a Ag alloy, copper (Cu), a Cu-based metal such as a Cu alloy, molybdenum (Mo), a Mo-based metal such as a Mo alloy, chromium (Cr), tantalum (Ta), titanium (Ti), or any combinations thereof. The gate line122, the gate electrode124, and the sustain line125may have a single-layer structure or may have a multilayer structure including two conductive films having different physical properties.

A gate insulating layer130is disposed on the gate line122, the gate electrode124, and the sustain line125. The gate insulating layer130may include an insulating material. In an exemplary embodiment, the gate insulating layer130may include silicon nitride or silicon oxide, for example. The gate insulating layer130may have a single-layer structure or may have a multilayer structure including two insulating films having different physical properties.

A semiconductor layer140is disposed on the gate insulating layer130. The semiconductor layer140may at least partially overlap the gate electrode124. In an exemplary embodiment, the semiconductor layer140may include amorphous silicon, polycrystalline silicon, or an oxide semiconductor, for example.

The semiconductor layer140may not only overlap the gate electrode124, but also overlap, at least partially or entirely, a data line162, a source electrode165, and a drain electrode166.

Although not illustrated inFIGS. 1 through 3, in exemplary embodiments, ohmic contact members may be additionally provided on the semiconductor layer140. In an exemplary embodiment, the ohmic contact members may include n+ hydrogenated amorphous silicon doped with a high concentration of n-type impurities, or silicide, for example. The ohmic contact members may be disposed on the semiconductor layer140in a pair. The ohmic contact members, which are disposed among the source electrode165, the drain electrode166, and the semiconductor layer140, may enable the source electrode165, the drain electrode166, and the semiconductor layer140to have ohmic contact properties.

The data line162, the source electrode165, and the drain electrode166are disposed on the semiconductor layer140and the gate insulating layer130.

The data line162may extend in a second direction D2and may intersect the gate line122.

The second direction D2may be a direction that crosses the first direction D1at a right angle, for example, a direction indicated by an arbitrary straight line extending from the top to the bottom ofFIG. 1, but the invention is not limited thereto. That is, the angle that the second direction D2defines with the first direction D1may not necessarily be a right angle, and the second direction D2may be a direction indicated by an arbitrary straight line not extending in parallel to the first direction D1.

The data line162may be insulated from the gate line122, the gate electrode124, and the sustain line125by the gate insulating layer130.

The data line162may provide a data signal to the source electrode165. The data signal may be a signal having a variable voltage, provided by an external source. The gray level of the pixel10may be controlled by the data signal.

The source electrode165may be branched off from the data line162and may at least partially overlap the gate electrode124.

The drain electrode166may be spaced apart from the source electrode165, in a plan view, over the semiconductor layer140and may partially overlap the gate electrode124. As illustrated inFIG. 1, the source electrode165may be provided in a “U” shape, for example, to surround the drain electrode166with a predetermined gap provided therebetween, but the invention is not limited thereto. That is, in another exemplary embodiment, the source electrode165may extend in a bar shape to be in parallel to the drain electrode166and may be spaced apart from the drain electrode166by a uniform gap therebetween.

The semiconductor layer140may be disposed even in an area between the source electrode165and the drain electrode166, which are spaced apart from each other. That is, the source electrode165and the drain electrode166may partially overlap or contact the semiconductor layer140and may face each other with the semiconductor layer140interposed therebetween.

In an exemplary embodiment, the data line162, the source electrode165, and the drain electrode166may include Al, Cu, Ag, Mo, Cr, Ti, Ta or any alloys thereof, for example. The data line162, the source electrode165, and the drain electrode166may have a multilayer structure including a lower film including a refractory metal and a low-resistance upper film disposed on the lower film, but the invention is not limited thereto.

The gate electrode124, the semiconductor layer140, the source electrode165, and the drain electrode166may form the TFT167. The TFT167may electrically connect the source electrode165and the drain electrode166according to the voltage of the gate signal provided to the gate electrode124. More specifically, when the voltage of the gate signal provided to the gate electrode124is a voltage for turning off the TFT167, the source electrode165and the drain electrode166may be electrically disconnected. When the voltage of the gate signal provided to the gate electrode124is a voltage for turning on the TFT167, the source electrode165and the drain electrode166may be electrically connected via a channel defined in the semiconductor layer140.

A channel is defined mainly in a part of the semiconductor layer140in the area between the source electrode165and the drain electrode166. That is, in a case in which the TFT167is in an on state, a channel is defined mainly in the part of the semiconductor layer140in the area between the source electrode165and the drain electrode166, and thus, the voltage of the source electrode165may be transmitted to the drain electrode166via the channel. The data signal transmitted to the drain electrode166may also be transmitted to the pixel electrode182.

A passivation layer171is disposed on the gate insulating layer130and the TFT167. The passivation layer171may include an inorganic insulating material and may cover the TFT167. The passivation layer171may protect the TFT167from elements disposed on the TFT167.

A planarization layer172is disposed on the passivation layer171. The planarization layer172may have a function of planarizing a surface. The planarization layer172may include an organic material. In exemplary embodiments, the planarization layer172may include a photosensitive organic composition, for example. In other exemplary embodiments, the planarization layer172may include a material including a pigment for realizing a color, or a photosensitive organic composition layer including the pigment may be additionally provided below the planarization layer172, for example. Since the pigment can perform the functions of a color filter, a color filter layer330of the second display substrate300that will be described later may not be provided.

In another exemplary embodiment, one of the passivation layer171and the planarization layer172may not be provided.

A contact hole181, which exposes a part of the TFT167, particularly, a part of the drain electrode166, may be defined in the passivation layer171and the planarization layer172.

The contact hole181may be defined to vertically penetrate the planarization layer172and the passivation layer171. The contact hole181may be defined to expose and overlap a part of the drain electrode166.

The pixel electrode182is disposed on the planarization layer172. The pixel electrode182may be physically connected to the drain electrode166via the contact hole181and may thus be provided with a voltage by the drain electrode166.

In an exemplary embodiment, the pixel electrode182may include a transparent conductive material such as indium tin oxide (“ITO”), indium zinc oxide (“IZO”), indium tin zinc oxide (“ITZO”), or Al-doped zinc oxide (“AZO”).

Openings in which no conductive material is provided may be defined in the pixel electrode182. Due to the openings, a pattern may be provided on the pixel electrode182, and a direction in which the liquid crystal molecules210are tilted over the pixel electrode182may be controlled by the shape and pattern of the pixel electrode182.

The shape of the pixel electrode182will hereinafter be described.

The pixel electrode182includes first, second, and third stem electrodes401,402, and403, a plurality of branch electrodes406, and first and second edge electrodes404and405.

The first and second stem electrodes401and402may extend in the first direction D1and may be spaced apart from each other. A boundary line407, which extends in the first direction D1, may be defined between the first and second stem electrodes401and402. Here, the term “boundary line” may be any types of a line-shaped area including an incision line, for example. The first stem electrode401, the boundary line407, and the second stem electrode402may be sequentially arranged along the second direction D2, and as a result, a region in which the pixel electrode182is disposed, i.e., a pixel region11, may be divided into a first edge area413, a first central area411, a second central area412, and a second edge area414.

The boundary line407may be defined along the boundary between the first and second central areas411and412. Some of the branch electrodes406extending in different directions may end at the boundary line407. In an exemplary embodiment, a width Wi of the boundary line407may be about 2 micrometers (μm) to about 10 μm, for example.

The third stem electrode403may extend in the second direction D2and may intersect the first and second stem electrodes401and402. The third stem electrode403may intersect the first stem electrode401in the shape of a cross (+), and may also interest the second stem electrode402in the shape of a cross (+). Accordingly, the third stem electrode403may connect the first and second stem electrodes401and402.

The branch electrodes406may extend from the first, second, and third stem electrodes401,402, and403in a diagonal direction not in parallel to the first direction D1or the second direction D2.

The first and second edge electrodes404and405may both extend in the second direction D2.

The first edge electrode404may intersect a first end (for example, the left end) of the first stem electrode401and a first end (for example, the left end) of the second stem electrode402. Accordingly, the first edge electrode404may connect the first and second stem electrodes401and402.

The second edge electrode405may intersect a second end (for example, the right end) of the first stem electrode401and a second end (for example, the right end) of the second stem electrode402. Accordingly, the second edge electrode405, like the first edge electrode404, may connect the first and second stem electrodes401and402.

The first and second edge electrodes404and405may extend to have the same length in the second direction D2as that of the third stem electrode403. The first and second central areas411and412and the first and second edge areas413and414may all be defined between the first and second edge electrodes404and405. As a result, the first and second central areas411and412may be surrounded by the first and second stem electrodes401and402and the first and second edge electrodes404and405.

The branch electrodes406may not be directly connected to the first and second edge electrodes404and405. Accordingly, the ends of the branch electrodes406may be spaced apart from the first and second edge electrodes404and405by a predetermined gap.

The branch electrodes406extend in different directions in the first and second central areas411and412, and thus, the liquid crystal molecules210may be tilted in different directions on both sides of the boundary line407.

The angle that the branch electrodes406define with the first direction D1may be uniform throughout the first and second central areas411and412and the first and second edge areas413and414. In an exemplary embodiment, the branch electrodes406may extend to define an angle of about 45 degrees (°) with the first direction D1, for example. However, the invention is not limited to this. That is, the direction in which the branch electrodes406may differ from one part to another part of the pixel electrode182.

The angle that the branch electrodes406define with the first direction D1may indicate the angle that the branch electrodes406define with an arbitrary straight line extending in the first direction D1, and when the branch electrodes406define both an acute angle and an obtuse angle with the first direction D1, the acute angle may be determined as the angle that the branch electrodes406define with the first direction D1.

More specifically, the branch electrodes406may extend in an upper left direction from the third stem electrode403in the left half of the first edge area413. The branch electrodes406may extend in an upper right direction from the third stem electrode403in the right half of the first edge area413.

The branch electrodes406may extend in a lower left direction from the third stem electrode403in the left half of the first central area411, and may extend in a lower right direction from the third stem electrode403in the right half of the first central area411.

The branch electrodes406may extend in the upper left direction from the third stem electrode403in the left half of the second central area412, and may extend in the upper right direction from the third stem electrode403in the right half of the second central area412.

The branch electrodes406may extend in the lower left direction from the third stem electrode403in the left half of the second edge area414, and may extend in the lower right direction from the third stem electrode403in the right half of the second edge area414.

Since the branch electrodes406extend in different directions in different parts of the pixel region11, the liquid crystal molecules210may be tilted in various directions over the branch electrodes406. Thus, the viewing angle of the LCD device according to the exemplary embodiment may be improved.

Due to the arrangement of the first, second, and third stem electrodes401,402, and403and the first and second edge electrodes404and405, the visibility of the LCD device according to the exemplary embodiment may be improved.

As mentioned above, the first and second central areas411and412may be surrounded by the first and second stem electrodes401and402and the first and second edge electrodes404and405. Thus, the first and second stem electrodes401and402and the first and second edge electrodes404and405may minimize the influence of an electric field generated outside the first and second central areas411and412on the liquid crystal molecules210in the first and second central areas411and412.

Openings in which no transparent conductive material is provided may be defined between the first and second central areas411and412to define the boundary line407, which extends in the first direction D1. The boundary line407, unlike the first and second stem electrodes401and402and the first and second edge electrodes404and405, does not block an electric field. Thus, an electric field generated in the first central area411and an electric field generated in the second central area412may affect each other. As a result, the control over the liquid crystal molecules210may be weakened in the first and second central areas411and412, between which the boundary line407is defined and which control the liquid crystal molecules210in different directions.

The liquid crystal molecules210may be tilted in the upper right direction in the left half of the first central area411and may be tilted in the lower right direction in the left half of the second central area412. That is, the liquid crystal molecule210may have the tendency to be tilted rightward in general, but in particular, in opposite directions, i.e., in upper and lower directions, in the left halves of the first and second central areas411and412, respectively. Thus, the force to tilt the liquid crystal molecules210upward may be weakened in the left half of the first central area411, and the force to tilt the liquid crystal molecules210downward may be weakened in the left half of the second central area412. This principle may directly apply to the liquid crystal molecules210in the right halves of the first and second central areas411and412.

Accordingly, the angle that the liquid crystal molecules210define with the first direction D1in the first and second central areas411and412may be minimized, and thus, the visibility of the LCD device according to the exemplary embodiment may be improved. This will hereinafter be described in further detail with reference toFIGS. 4 and 5.

In an exemplary embodiment, the first central area411may include a first sub-central area411_1and a second sub-central area411_2, the second central area412may include a third ub-central area412_1and a fourth sub-central area412_2, the first edge area413may include a first sub-edge area413_1and a second sub-edge area413_2, and the second edge area414may include a third sub-edge area414_1and a fourth sub-edge area414_2. In the exemplary embodiment, first sub-branch electrodes defining the first sub-central area411_1, third sub-branch electrodes defining the third sub-central area412_1, fifth sub-branch electrodes defining the first sub-edge area413_1and seventh sub-branch electrodes defining the sub-edge area414_1may be symmetrical to second sub-branch electrodes defining the second sub-central area411_2, fourth sub-branch electrodes defining the fourth sub-central area412_2, sixth sub-branch electrodes defining the second sub-edge area413_2and eighth sub-branch electrodes defining the fourth sub-edge area414_2, respectively, with reference to the third stem electrode403.

FIG. 4is an enlarged plan view of an area A ofFIG. 3at a low gray level with a relatively low voltage provided to the pixel electrode182, andFIG. 5is an enlarged plan view of the area A ofFIG. 3at a high gray level with a relatively high voltage provided to the pixel electrode182.

FIGS. 4 and 5both illustrate the same part of the pixel electrode182, and thus, the pixel electrode182ofFIG. 4has the same structure as the pixel electrode182ofFIG. 5. However, sinceFIGS. 4 and 5illustrate different cases in terms of the level of the voltage applied to the pixel electrode182, the pixel electrode182ofFIG. 4may differ from the pixel electrode182ofFIG. 5in terms of the pattern of the alignment of the liquid crystal molecules210.

FIGS. 4 and 5illustrate the liquid crystal molecules210as viewed in a plan view. Thus, the longer the long axes of the liquid crystal molecules210appear to be inFIGS. 4 and 5, the more tilted the liquid crystal molecules210are, and the direction in which the long axes of the liquid crystal molecules210extend may refer to the direction in which the liquid crystal molecules210are tilted.

Referring toFIG. 4, in a case in which a relatively weak electric field is generated in the right half of the first central area411, which corresponds to the area A, the liquid crystal molecules210may be tilted to form a first angle θ1with the first direction D1. As mentioned above, an electric field generated in the first central area411and an electric field generated in the second central area412affect each other, and thus, the control over the liquid crystal io molecules210may be weakened in the first and second central areas411and412. Accordingly, the first angle θ1may be smaller than a second angle θ2that the direction in which the branch electrodes406extend defines with the first direction D1.

Referring toFIG. 5, in a case in which a relatively strong electric field is generated in the right half of the first central area411, which corresponds to the area A, the liquid crystal molecules210may be tilted to form a third angle θ3with the first direction D1. Since a relatively high voltage is provided to the pixel electrode182, the liquid crystal molecules210are affected considerably by the pixel electrode182. Thus, the third angle θ3may be greater than the first angle θ1and may be similar to the second angle θ2.

Due to the liquid crystal molecules210being tilted in different directions at a low gray level and a high gray level, the visibility of the LCD device according to the exemplary embodiment may be improved, and this effect may be further achieved by arrangement of an upper polarizer (not illustrated) and a lower polarizer (not illustrated).

More specifically, the LCD device according to the exemplary embodiment may further include the lower polarizer, which is disposed on the outside of the first display substrate100, and the upper polarizer, which is disposed on the outside of the second display substrate300.

The transmittance of light may be determined by the direction of the polarization axis of the lower polarizer, the direction of the polarization axis of the upper polarizer, and the direction in which the liquid crystal molecules210are tilted. In an exemplary embodiment, in a case in which the polarization axis of the lower polarizer is parallel to the first direction D1and the polarization axis of the upper polarizer is parallel to the second direction D2, the closer the angle that the liquid crystal molecules210define with the first direction D1is to about 45° , the higher the transmittance of light becomes, for example. The closer the angle that the liquid crystal molecules210define with the first direction D1is to about 0° or about 90° , the lower the transmittance of light becomes. A decrease in the transmittance of light may be more evident when the LCD device according to the exemplary embodiment is viewed from a side (i.e., the left or right side) than when the LCD device according to the exemplary embodiment is viewed from the front.

As mentioned above, at a low gray level, the liquid crystal molecules210are generally tilted to define an angle close to about 0° with the first direction D1in the first central area411. Thus, the transmittance of light may decrease when the LCD device according to the exemplary embodiment is viewed from a side. Due to this pattern of alignment of the liquid crystal molecules210in the first central area411, a phenomenon in which the LCD device according to the exemplary embodiment appears brighter than necessary at a low gray level may be alleviated, and thus, the visibility of the LCD device according to the exemplary embodiment may be improved.

At a high gray level, the liquid crystal molecules210are generally tilted to define an angle close to about 45° with the first direction D1in the first central area411. Thus, a decrease in the transmittance of light may be minimized when the LCD device according to the exemplary embodiment is viewed from a side. In short, at a low gray level, the visibility of the LCD device according to the exemplary embodiment may be improved, and at a high gray level, a decrease in the transmittance of the LCD device according to the exemplary embodiment may be minimized.

The pattern of alignment of the liquid crystal molecules210in the first central area411, described above with reference toFIGS. 4 and 5, may directly apply to the second central area412, except that the direction in which the liquid crystal molecules210are tilted in the second central area412is opposite to the direction in which the liquid crystal molecules210are tilted in the first central area411.

In an exemplary embodiment, the ratio of the sum of the areas of the first and second central areas411and412to the sum of the areas of the first and second edge areas413and414may be controlled to be within the range of about 1:1 to about 1:3, for example. The ratio of the sum of the areas of the first and second central areas411and412to the sum of the areas of the first and second edge areas413and414may be determined according to the degree to which the visibility of the LCD device according to the exemplary embodiment should be improved.

A part of the sustain line125may be overlapped by the third stem electrode403. As mentioned above, the sustain line125includes an opaque metal and thus does not transmit light therethrough. Thus, light leakage that may be caused by a misalignment of the liquid crystal molecules210in an area where the third stem electrode403is disposed may be prevented.

The elements disposed on the pixel electrode182will hereinafter be described with reference toFIGS. 1 through 3.

A first alignment layer190may be disposed on the pixel electrode182. The first alignment layer190may control the initial alignment angle of the liquid crystal molecules210, which are injected into the liquid crystal layer200. In another exemplary embodiment, the first alignment layer190may not be provided.

The second display substrate300will hereinafter be described.

The second display substrate300may include a second base substrate310, a light-shielding member320, a color filter layer330, a common electrode380, an overcoat layer340, and a second alignment layer390.

The second base substrate310may face the first base substrate110. The second base substrate310may be durable enough to withstand an external shock. The second base substrate310may be a transparent insulating substrate. In an exemplary embodiment, the second base substrate310may be a glass substrate, a quartz substrate, a transparent resin substrate, or the like, for example. The second base substrate310may be in the shape of a flat plate, or may be curved in a particular direction.

The light-shielding member320is disposed on the second base substrate310(e.g., below the second base substrate310inFIG. 2). The light-shielding member320may overlap the gate line122, the sustain line125, the data line162, the TFT167, and the contact hole181, i.e., a region other than the pixel region11, and may block the transmission of light in the region other than the pixel region11.

The color filter layer330is disposed on the second base substrate310and the light-shielding member320(e.g., below the second base substrate310and the light-shielding member320inFIG. 2). The color filter layer330may render light incident from the outside of the first base substrate110and emitted to the outside of the second base substrate310to appear in a particular color.

The color filter layer330may include a photosensitive organic composition including a pigment for realizing a color. In an exemplary embodiment, the color filter layer330may include one of a red pigment, a green pigment, and a blue pigment, for example. However, the invention is not limited thereto, and the color filter layer330may include various other color pigments.

The arrangement of the color filter layer330is not particularly limited. That is, as mentioned above, the color filter layer330may be disposed on the first base substrate110, instead of on the second base substrate310.

The overcoat layer340is disposed on the light-shielding member320and the color filter layer330(e.g., below the light-shielding member320and the color filter layer330inFIG. 2). The overcoat layer340may reduce any height differences generated by the light-shielding member320and the color filter layer330. In exemplary embodiments, the overcoat layer340may not be provided.

The common electrode380is disposed on the overcoat layer340(e.g., below the overcoat layer340inFIG. 2). In a case in which the overcoat layer340is not provided, the common electrode380may be disposed on the light-shielding member320and the color filter layer330. In an exemplary embodiment, the common electrode380may include a transparent conductive material such as ITO, IZO, ITZO, or AZO. The common electrode380may be disposed on the entire surface of the second base substrate310. A common signal provided by an external source is applied to the common electrode380, and the common electrode380may generate an electric field together with the pixel electrode182.

The second alignment layer390is disposed on the common electrode380(e.g., below the common electrode380inFIG. 2). The second alignment layer390performs similar functions to those of the first alignment layer190. That is, the second alignment layer390controls the initial alignment of the liquid crystal molecules210in the liquid crystal layer200.

The liquid crystal layer200will hereinafter be described.

The liquid crystal layer200includes the liquid crystal molecules210, which have dielectric anisotropy and refractive anisotropy. In an exemplary embodiment, the liquid crystal molecules210may be of a vertical alignment (“VA”) mode, for example. That is, the liquid crystal molecules210may be vertically aligned between two substrates, i.e., the first and second display substrates100and300. In response to an electric field being applied between the first and second display substrates100and300, the liquid crystal molecules210may rotate in a particular direction, or may be tilted, between the first and second display substrates100and300, thereby changing the polarization of light.

FIG. 6is a plan view of a pixel electrode of an LCD device according to another exemplary embodiment of the invention.

In the exemplary embodiments ofFIGS. 1 and 6, like reference numerals indicate like elements, and thus, descriptions thereof will be omitted or at least simplified. The exemplary embodiment ofFIG. 6will hereinafter be described, focusing mainly on differences from the exemplary embodiment ofFIG. 1.

Referring toFIG. 6, a pixel electrode500, unlike the pixel electrode182ofFIG. 3, may further include fourth and fifth stem electrodes508and509.

The fourth stem electrode508may extend in a first direction D1and may be connected to a first end (for example, the upper end) of a third stem electrode503. The fifth stem electrode509may extend in the first direction D1and may be connected to a second end (for example, the lower end) of the third stem electrode503. The fourth and fifth stem electrodes508and509may be connected to the ends of some of a plurality of branch electrodes506. A boundary line507, which extends in the first direction D1, may be defined between the first and second stem electrodes501and502.

A first edge area513may be surrounded by a first stem electrode501, the fourth stem electrode508, a first edge electrode504, and a second edge electrode505, and the influence from the outside of the first edge area513on liquid crystal molecules210(refer toFIGS. 2, 4 and 5) in the first edge area513may be minimized.

Liquid crystal molecules210may be tilted toward the pixel electrode500on the outside of the pixel electrode500. The liquid crystal molecules210are not aligned independently of one another, but are tilted in series, affecting one another. Thus, the liquid crystal molecules210may be tilted downward on the outside of the fourth stem electrode508, and the liquid crystal molecules210on the outside of the first edge area513may be affected by the force to tilt the liquid crystal molecules210downward on the outside of the fourth stem electrode508. However, the fourth stem electrode508may minimize the force applied to tilt the liquid crystal molecules210in the first edge area513downward. Thus, the angle that the direction in which the liquid crystal molecules210are tilted in the first edge area513defines with the first direction D1may be minimized. This effect may be evident at a low gray level, as mentioned above, and the visibility of the LCD device according to the exemplary embodiment may be improved.

The improvement of the visibility of the LCD device according to the exemplary embodiment ofFIG. 6will hereinafter be described with reference toFIGS. 7 and 8.

FIG. 7is a graph showing measurements of the direction in which the liquid crystal molecules210(refer toFIGS. 2, 4 and 5) are tilted, obtained from locations along line B-B′ ofFIG. 6, in a case in which a relatively low voltage is provided to the pixel electrode500, andFIG. 8is a graph showing measurements of the direction in which the liquid crystal molecules210are tilted, obtained from locations along line B-B′ ofFIG. 6, in a case in which a relatively high voltage is provided to the pixel electrode500.

InFIGS. 7 and 8, the X-axis represents the locations along line B-B′ ofFIG. 6, and the Y-axis represents the direction in which the liquid crystal molecules210are tilted. More specifically, the Y-axis shows the angle at which the liquid crystal molecules210are tilted, measured clockwise from the opposite direction to the first direction D1(i.e., a leftward direction).

Since line B-B′ ofFIG. 6is located in the left half of a pixel region11, the closer the angle at which the liquid crystal molecules210are tilted is to about 180°, the darker the LCD device according to the exemplary embodiment ofFIG. 6appears.

Referring toFIG. 7, at a low gray level, the liquid crystal molecules210are tilted at an angle greater than about 135° in a second edge area514and a first central area511. Referring toFIG. 8, at a high gray level, the liquid crystal molecules210are tilted at an angle close to about 135° in the second edge area514and the first central area511.

Referring toFIG. 7, at a low gray level, the liquid crystal molecules210are tilted at an angle smaller than about 225° in a second edge area512and the first edge area513. Referring toFIG. 8, at a high gray level, the liquid crystal molecules210are tilted at an angle close to about 225° in the second edge area512and the first edge area513.

That is, the angle at which the liquid crystal molecules210are tilted in the first and second central areas511and512and the first and second edge areas513and514at a low gray level may be closer to about 180° than the angle at which the liquid crystal molecules210are tilted in the first and second central areas511and512and the first and second edge areas513and514at a high gray level is, and thus, an improvement in the visibility of the LCD device according to the exemplary embodiment ofFIG. 6can be achieved.

FIG. 9is a plan view of a pixel electrode of an LCD device according to another exemplary embodiment of the invention.

Referring toFIG. 9, branch electrodes606_1, which are disposed in a first central area611, extend to form a fourth angle θ4with a first direction D1. Branch electrodes606_2, which are disposed in a second central area612, extend to form a fifth angle θ5with the first direction D1. Branch electrodes606_3, which are disposed in a first edge area613, extend to form a sixth angle θ6with the first direction D1. Branch electrodes606_4, which are disposed in a second edge area614, extend to form a seventh angle θ7with the first direction D1.

The fourth and fifth angles θ4and θ5may be identical, and the sixth and seventh angles θ6and θ7may be identical. The fourth and sixth angles θ4and θ6may differ from each other. That is, the direction in which the branch electrodes of a pixel electrode600extend and the angle that the branch electrodes of the pixel electrode600define with the first direction D1may differ from one part to another part of the pixel electrode600.

Accordingly, even when the same voltage is provided throughout the pixel electrode600, the direction in which liquid crystal molecules210(refer toFIGS. 2, 4 and 5) are tilted may be controlled differently in each part of the pixel electrode600, and thus, the visibility of the LCD device according to the exemplary embodiment may be improved. Since the first and second central areas611and612can be clearly distinguished from the first edge area613by a first stem electrode601, the improvement of the visibility of the LCD device according to the exemplary embodiment may be maximized. Also, since the first and second central areas611and612can be clearly distinguished from the second edge area613due to the presence of a first stem electrode601, the improvement of the visibility of the LCD device according to the exemplary embodiment may be maximized.

The sixth and seventh angles θ6and θ7may be set to be smaller than the fourth and fifth angles θ4and θ5. More specifically, the fourth and fifth angles θ4and θ5may be set to about 40° to about 45°, and the sixth and seventh angles θ6and θ7may be set to about 33° to about 40°, in which case, the first and second edge areas613and614may be rendered to appear darker than the first and second central areas611and612, even when the same voltage is provided throughout the pixel electrode600. In a case in which relatively bright areas are provided in the middle of a pixel region11(refer toFIG. 1) and relatively dark areas are provided on the edges f the pixel region11, the visibility of the LCD device according to the exemplary embodiment may be improved, and at the same time, the pixel10(refer to FIG.1) may be clearly distinguished from its neighboring pixels.

The fourth stem electrode608may extend in a first direction D1and may be connected to a first end (for example, the upper end) of a third stem electrode603. The fifth stem electrode609may extend in the first direction D1and may be connected to a second end (for example, the lower end) of the third stem electrode603. A boundary line607, which extends in the first direction D1, may be disposed between the first and second stem electrodes601and602. A first edge area613may be surrounded by a first stem electrode601, the fourth stem electrode608, a first edge electrode604, and a second edge electrode605, and the influence from the outside of the first edge area613on liquid crystal molecules210in the first edge area613may be minimized.

FIG. 10is a plan view of a pixel electrode of an LCD device according to another exemplary embodiment of the invention.

Referring toFIG. 10, a width W1of branch electrodes706_1, which are disposed in first and second central areas711and712, may differ from a width W2of branch electrodes706_2, which are disposed in first and second edge areas713and714. Here, the width may be taken along a direction perpendicular to an extension direction of the branch electrodes706_1and706_2.

In an exemplary embodiment, the width W2of the branch electrodes706_2, which are disposed in the first and second edge areas713and714, may be greater than the width W1of the branch electrodes706_1, which are disposed in the first and second central areas711and712.

Also, a distance between adjacent branch electrodes706_1, which are disposed in the s first and second central areas711and712, may differ from a distance between adjacent branch electrodes706_2, which are disposed in the first and second edge areas713and714.

In an exemplary embodiment, the distance between adjacent branch electrodes706_2, which are disposed in the first and second edge areas713and714, may be greater than the distance between adjacent branch electrodes706_1, which are disposed in the first and second central areas711and712.

Thus, a second pitch732or a third pitch733, which is the sum of the widths of one of the branch electrodes706_2in the first and second edge areas713and714and an opening adjacent thereto, may be greater than a first pitch731, which is the sum of the widths of one of the branch electrodes706_1in the first and second central areas711and712and an opening adjacent thereto. The smaller the pitch of a pixel electrode700is, the stronger the control over liquid crystal molecules210becomes, and thus, the brighter the pixel electrode700appears. The greater the pitch of the pixel electrode700is, the weaker the control over the liquid crystal molecules210becomes, and thus, the darker the pixel electrode700appears. Thus, even when the same voltage is provided throughout the pixel electrode700, the first and second edge areas713and714may appear relatively darker than the first and second central areas711and712, and the visibility of the LCD device according to the exemplary embodiment may be improved.

The fourth stem electrode708may extend in a first direction D1and may be connected to a first end (for example, the upper end) of a third stem electrode703. The fifth stem electrode709may extend in the first direction D1and may be connected to a second end (for example, the lower end) of the third stem electrode703. A boundary line707, which extends in the first direction D1, may be defined between the first and second stem electrodes701and702. A first edge area713may be surrounded by a first stem electrode701, the fourth stem electrode708, a first edge electrode704, and a second edge electrode705, and the influence from the outside of the first edge area713on liquid crystal molecules210in the first edge area713may be minimized.

The structure of the pixel electrode700and the structure of the pixel electrode600ofFIG. 9may both be employed in a single LCD device, in which case, the improvement of the visibility of the LCD device may be further maximized.

FIG. 11is a plan view of a pixel electrode of an LCD device according to another exemplary embodiment of the invention.

Referring toFIG. 11, a third stem electrode803may be divided into first and second sub-stem electrodes803_1and803_2. The third stem electrode803differs from the third stem electrode503ofFIG. 6, which is integrally provided on the entire surface of the pixel region11and extends in the second direction D2.

That is, the third stem electrode803may be divided into two parts, i.e., the first and second sub-stem electrodes803_1and803_2, by a boundary line807.

Since the third stem electrode803is divided into the first and second sub-stem electrodes803_1and803_2, first and second central areas811and812may be clearly distinguished from each other.

Even though the third stem electrode803is divided into the first and second sub-stem electrodes803_1and803_2, the first and second sub-stem electrodes803_1and803_2may be physically connected to each other via first and second stem electrodes801and802and first and second edge electrodes803and805. Thus, the same voltage may be provided throughout a pixel electrode800.

The fourth stem electrode808may extend in a first direction D1and may be connected to a first end (for example, the upper end) of a third stem electrode803_1. The fifth stem electrode809may extend in the first direction D1and may be connected to a second end (for example, the lower end) of the third stem electrode803_2. A first edge area813may be surrounded by a first stem electrode801, the fourth stem electrode808, a first edge electrode804, and a second edge electrode805, and the influence from the outside of the first edge area813on liquid crystal molecules210in the first edge area813may be minimized. The second edge area814may be symmetrical to the first edge area813.

FIG. 12is a plan view of a pixel electrode of an LCD device according to another exemplary embodiment of the invention.

Referring toFIG. 12, a pixel electrode900, unlike the pixel electrode500ofFIG. 6, further includes third and fourth edge electrodes921and922.

The third edge electrode921may extend in a first direction D1to connect a first end (for example, the upper end) of a first edge electrode904and a first end (for example, the upper end) of a second edge electrode905. The fourth edge electrode922may extend in the first direction D1to connect a second end (for example, the lower end) of the first edge electrode904and a second end (for example, the lower end) of the second edge electrode905.

Thus, the first, second, third, and fourth edge electrodes904,905,921, and922may be connected to one another to have a rectangular shape. Accordingly, the influence of liquid crystal molecules on the outside of the first, second, third, and fourth edge electrodes904,905,921, and922on liquid crystal molecules210on the inside of the first, second, third, and fourth edge electrodes904,905,921, and922may be minimized. As a result, the improvement of the visibility of the LCD device according to the exemplary embodiment may be maximized.

The fourth stem electrode908may extend in a first direction D1and may be connected to a first end (for example, the upper end) of a third stem electrode903. The fifth stem electrode909may extend in the first direction D1and may be connected to a second end (for example, the lower end) of the third stem electrode903. A boundary line907, which extends in the first direction D1, may be defined between the first and second stem electrodes901and902. A first edge area913may be surrounded by a first stem electrode901, the fourth stem electrode908, a first edge electrode904, and a second edge electrode905, and the influence from the outside of the first edge area913on liquid crystal molecules210in the first edge area913may be minimized. The second edge area914may be symmetrical to the first edge area913.

FIG. 13is a plan view of a pixel electrode of an LCD device according to another exemplary embodiment of the invention.

Referring toFIG. 13, a distance between a first or second edge electrode1004or1005and the ends of branch electrodes1006may differ from one part to another part of a pixel region11(refer toFIG. 1). More specifically, the distance between the first or second edge electrode1004or1005and the ends of the branch electrodes1006may become smaller, closer to a first or second stem electrode1001or1002. The distance between the first or second edge electrode1004or1005and the ends of the branch electrodes1006may become greater, closer to a boundary line1007.

In an exemplary embodiment, the distance between the first or second edge electrode1004or1005and the ends of the branch electrodes1006may be set to be within the range of about 1 μm to about 7 μm, for example.

In an exemplary embodiment, a first distance1041, which is the distance between the end of an uppermost branch electrode1006in a first central area1011and the second edge electrode1005may be smaller than a second distance1042, which is the distance between the end of a lowermost branch electrode1006and the second edge electrode1005, for example.

The fourth stem electrode1008may extend in a first direction D1and may be connected to a first end (for example, the upper end) of a third stem electrode1003. The fifth stem electrode1009may extend in the first direction D1and may be connected to a second end (for example, the lower end) of the third stem electrode1003. A boundary line1007, which extends in the first direction D1, may be defined between the first and second stem electrodes1001and1002. A first edge area1013may be symmetrical to the second edge area1014, and the first central area1011may be symmetrical to the second central area1012.

Due to the aforementioned structure of the pixel electrode1000, the improvement of the visibility of the LCD device according to the exemplary embodiment may be maximized.