Liquid crystal display device

A liquid crystal display device includes an insulating substrate, a data line disposed on the insulating substrate and extended in a first direction, a plurality of pixel electrodes which is disposed on the insulating substrate and in which a slit pattern is defined, a common electrode facing the pixel electrodes, and a liquid crystal layer interposed between the pixel electrodes and the common electrode, where each of the pixel electrodes includes an edge electrode portion and a plurality of branch electrode portions protruding in a direction toward a central portion of the pixel electrode from the edge electrode portion, and at least a portion of the edge electrode portion overlaps the data line.

This application claims priority to Korean Patent Application No. 10-2015-0118935, filed on Aug. 24, 2015, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of 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”), one of flat panel displays that are currently the most widely used, may generally include two substrates provided with electric field generating electrodes such as a pixel electrode, a common electrode, and the like, and a liquid crystal layer disposed between the substrates.

An LCD may apply voltage to a field generating electrode to generate an electric field in a liquid crystal layer and accordingly, determine a direction of alignment of liquid crystals of the liquid crystal layer to control the polarization of incident light, thereby displaying an image.

Among the LCDs, a vertically aligned mode LCD in which a long axis of the liquid crystal molecules are arranged to be vertical to a display panel in the state in which an electric field is not applied, has been in the limelight due to a high contrast ratio and a wide reference viewing angle thereof. In the vertically aligned mode LCD, a method of implementing a wide viewing angle is to form a plurality of domains in which alignment directions of liquid crystal molecules are different, in a single pixel region.

As a means of forming a plurality of domains, there is a method of forming a cut portion such as a slit or the like, in a field generating electrode. Liquid crystal molecules are rearranged by fringe field generated between field generating electrode portions facing an edge of the cut portion, whereby a plurality of domains may be defined.

As a result of forming the cut portion, the field generating electrode has a uniform pattern. For example, the field generating electrode may have a cross-shaped stem electrode portion and fine branch portions extended from the cross-shaped stem electrode portion. The cut portion may be disposed between the fine branch portions.

SUMMARY

However, an electrode pattern having a cross-shaped stem electrode portion and fine branch portions as described above is limited in improving transmittance and side visibility.

Accordingly, an exemplary embodiment of the invention may provide an electrode pattern capable of further improving transmittance and side visibility.

In addition, another exemplary embodiment of the invention may provide a liquid crystal display (“LCD”) device having more improved display quality.

However, exemplary embodiments of the invention are not restricted to the one 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 an LCD device. The LCD device includes an insulating substrate, a data line disposed on the insulating substrate and extended in a first direction, a plurality of pixel electrodes which is disposed on the insulating substrate and in which a slit pattern is defined, a common electrode facing the pixel electrodes, and a liquid crystal layer interposed between the pixel electrodes and the common electrode, where each of the pixel electrodes includes an edge electrode portion and a plurality of branch electrode portions protruding in a direction toward a central portion of the pixel electrode from the edge electrode portion, and at least a portion of the edge electrode portion overlaps the data line.

In an exemplary embodiment, the pixel electrodes may include a first pixel electrode and a second pixel electrode disposed to be adjacent to the first pixel electrode in a second direction, and a distance between the first electrode and the second electrode may be equal to or greater than about 5 micrometers (“μm”) and equal to or less than about 10 μm, the second direction intersecting the first direction.

In an exemplary embodiment, a region overlapping the pixel electrode defines a pixel region, the pixel region may include a plurality of different domains in which directivities of the plurality of branch electrode portions are different from one another, and the plurality of domains include a first domain, a second domain adjacent to the first domain in the first direction, and a third domain adjacent to the first domain in a second direction intersecting the first direction.

In an exemplary embodiment, a minimum distance between an end portion of a branch electrode portion overlapping the first domain and protruding toward the second domain among the plurality of branch electrode portions and an end portion of a branch electrode portion overlapping the second domain and protruding toward the first domain among the plurality of branch electrode portions may be smaller than a minimum distance between an end portion of a branch electrode portion overlapping the first domain and protruding toward the third domain among the plurality of branch electrode portions and an end portion of a branch electrode portion overlapping the third domain and protruding toward the first domain among the plurality of branch electrode portions.

In an exemplary embodiment, the minimum distance between the end portion of the branch electrode portion overlapping the first domain and protruding toward the second domain and the end portion of the branch electrode portion overlapping the second domain and protruding toward the first domain may be equal to or greater than about 2.5 μm and equal to or less than about 3.5 μm.

In an exemplary embodiment, the minimum distance between the end portion of the branch electrode portion overlapping the first domain and protruding toward the third domain and the end portion of the branch electrode portion overlapping the third domain and protruding toward the first domain may be equal to or greater than about 4.5 μm and equal to or less than about 5.5 μm.

In an exemplary embodiment, the LCD device may further include a sustain electrode line disposed between the insulating substrate and the pixel electrode and including at least a portion thereof overlapping the edge electrode portion of the pixel electrode.

In an exemplary embodiment, the at least a portion of the sustain electrode line may overlap the data line.

In an exemplary embodiment, the LCD device may further include a light shielding member disposed in a region overlapping at least a portion of the data line and the at least a portion of the edge electrode portion of the pixel electrode.

In an exemplary embodiment, the LCD device may further include a first alignment layer disposed between the pixel electrode and the liquid crystal layer, a second alignment layer disposed between the common electrode and the liquid crystal layer, a first photo-curing layer disposed between the first alignment layer and the liquid crystal layer, and a second photo-curing layer disposed between the second alignment layer and the liquid crystal layer, where the first photo-curing layer and the second photo-curing layer may be provided through polymerization of reactive mesogen.

According to another exemplary embodiment of the invention, there is provided an LCD device. The LCD device includes an insulating substrate, a plurality of pixel electrodes which is disposed on the insulating substrate and in which a slit pattern is defined, a common electrode facing the pixel electrodes, and a liquid crystal layer interposed between the pixel electrodes and the common electrode and including liquid crystal molecules, where a central slit portion including a horizontal slit portion and a vertical slit portion and a plurality of fine slit portions extended in a direction inclined from the central slit portion are defined in each of the pixel electrodes, a width of the horizontal slit portion is narrower than that of the vertical slit portion, a region overlapping the pixel electrode defines the pixel region, the pixel region includes a plurality of different domains in which directivities of the liquid crystal molecules are different from one another, and in a state in which an electric field is generated between the pixel electrode and the common electrode, the liquid crystal molecules within one of the plurality of domains are disposed in parallel with an extension direction of the fine slit portion and are aligned in a direction toward a central portion of the pixel electrode from a circumferential portion thereof.

In an exemplary embodiment, the width of the horizontal slit portion may be equal to or greater than about 2.5 μm and equal to or less than about 3.5 μm.

In an exemplary embodiment, the width of the vertical slit portion may be equal to or greater than about 4.5 μm and equal to or less than about 5.5 μm.

In an exemplary embodiment, the pixel electrode may further include an edge electrode portion disposed in the circumferential portion of the pixel electrode along an edge of the pixel electrode.

In an exemplary embodiment, the plurality of pixel electrodes may include a first pixel electrode and a second pixel electrode disposed to be adjacent to the first pixel electrode in a first direction, and a distance between the first electrode and the second electrode may be equal to or greater than about 5 μm and equal to or less than about 10 μm.

In an exemplary embodiment, the LCD device may further include a data line disposed on the insulating substrate and extended in a second direction, and at least a portion of the edge electrode portion overlaps the data line.

In an exemplary embodiment, the LCD device may further include a sustain electrode line disposed between the insulating substrate and the pixel electrode and including at least a portion thereof overlapping the edge electrode portion of the pixel electrode.

In an exemplary embodiment, the at least a portion of the sustain electrode line may overlap the data line.

In an exemplary embodiment, the LCD device may further include a light shielding member disposed in a region overlapping at least a portion of the data line and the at least a portion of the edge electrode portion of the pixel electrode.

In an exemplary embodiment, the LCD device may further include a first alignment layer disposed between the pixel electrode and the liquid crystal layer, a second alignment layer disposed between the common electrode and the liquid crystal layer, a first photo-curing layer disposed between the first alignment layer and the liquid crystal layer, and a second photo-curing layer disposed between the second alignment layer and the liquid crystal layer, where the first photo-curing layer and the second photo-curing layer may be provided through polymerization of reactive mesogen.

DETAILED DESCRIPTION

Features of the invention and methods of accomplishing the same may be understood more readily by reference to the following detailed description of preferred embodiments and the accompanying drawings.

The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art, and the invention will only be defined by the appended claims.

Hereinafter, exemplary embodiments of the invention will be described with reference to the attached drawings.

FIG. 1is an exploded perspective view of a liquid crystal display (“LCD”) device according to an exemplary embodiment of the invention.

Referring toFIG. 1, an LCD device according to an exemplary embodiment of the invention may include a first substrate100, a second substrate200spaced apart from and facing the first substrate100, and a liquid crystal layer300interposed between the first substrate100and the second substrate200. The first substrate100may be a lower substrate and the second substrate200may be an upper substrate.

Each of the first substrate100and the second substrate200may include a display area DA and a non-display area NA. The display area DA may be an image-visible region, and the non-display area NA may be an image-invisible region. An edge of the display area DA may be surrounded by the non-display area NA.

The display area DA may include a plurality of data lines DL extended in a first direction X1(e.g., a row direction), a plurality of gate lines GL extended in a second direction X2(e.g., a column direction), and a plurality of pixels PX disposed in intersections of the data lines DL and the gate lines GL. However, the invention is not limited thereto, and the plurality of data lines DL may extend in a column direction, and a plurality of gate lines GL may extend in a row direction. The plurality of pixels PX may be disposed in the first direction X1and the second direction X2and may have a substantially matrix shape.

Each of the pixels PX may inherently display one color among primary colors in order to implement a color display. In an exemplary embodiment, the primary colors may be, for example, red, green, and blue. However, the invention is not limited thereto, and the primary colors may include various other colors.

The non-display area NA may be a light-shielding region. In the non-display area NA of the first substrate100, a driver (not shown) providing a gate driving signal, a data driving signal, and the like to the respective pixels PX may be disposed. The gate lines GL and the data lines DL may be extended from the display area DA to the non-display area NA and may be electrically connected to the driver (not shown).

The liquid crystal layer300may be interposed between the first substrate100and the second substrate200. The liquid crystal layer300may include liquid crystal molecules LC having negative dielectric constant anisotropy but is not limited thereto. The liquid crystal layer300may also include liquid crystal molecules LC having positive dielectric constant anisotropy.

Hereinafter, pixels of the LCD device according to an exemplary embodiment of the invention will be described in detail.

FIG. 2is a plan view illustrating optional pixels of the LCD device ofFIG. 1.FIG. 3is a cross-sectional view, taken along line of III-III′FIG. 2.

Referring toFIGS. 2 and 3, the first substrate100may include a first base substrate101, a plurality of thin film transistors (“TFTs”), a color filter170, pixel electrodes150and160, and the like.

In an exemplary embodiment, the first base substrate101, a transparent insulating substrate, may include a material having superior transmittance, heat-resistant, and chemically-resistant properties. In an exemplary embodiment, the first base substrate101may be a silicon substrate, a glass substrate, a plastic substrate or the like, for example.

Gate wirings may be disposed on the first base substrate101. The gate wirings may include a gate line GLi, a first gate electrode111, a second gate electrode121, a third gate electrode131, and a voltage dividing reference line140.

The gate line GLi may be extended in approximately the second direction X2. The first gate electrode to the third gate electrode111,121and131may be provided to protrude from the gate line GLi. Specifically, the first gate electrode111and the second gate electrode121may protrude downwardly from the gate line GLi and may be unitary with each other, without a physical boundary therebetween. The third gate electrode131may be positioned on the right side, than the first and second gate electrodes111and121. The first to third gate electrodes111,121, and131may be physically connected to the gate line GLi, and thus, the same gate signal may be applied to the first to third gate electrodes111,121, and131.

The voltage dividing reference line140and the gate line GLi may be disposed on the same layer, and the voltage dividing reference line140may be extended to be substantially parallel to the gate line GLi. A reference voltage may be applied to the voltage dividing reference line140. The reference voltage will be described to be later.

The voltage dividing reference line140may include a voltage dividing electrode141, a sustain electrode142, and a sustain electrode line143. The voltage dividing electrode141may protrude downwardly from the voltage dividing reference line140and have a wide surface to thereby provide a space allowing for stable contact with a drain electrode134. The sustain electrode142may be disposed in the neighborhood of the voltage dividing electrode141. The sustain electrode142may also protrude downwardly from the voltage dividing reference line140and have a wide surface. The sustain electrode142, together with a first drain electrode114disposed on the sustain electrode142to overlap therewith and a plurality of protective layers disposed therebetween, may form a sustain electric condenser.FIG. 2illustrates a case in which the voltage dividing electrode141and the sustain electrode142are not continuous and a width of the voltage dividing reference line140between the voltage dividing electrode141and the sustain electrode142is slightly reduced. However, the invention is not limited thereto, and the voltage dividing electrode141and the sustain electrode142may be continuously provided while a boundary therebetween may not be discernible. The voltage dividing reference line140between the voltage dividing electrode141and the sustain electrode142may have the same width as that of the voltage dividing electrode141and/or the sustain electrode142.

The sustain electrode line143may have a shape in which it protrudes from the voltage dividing reference line140, overlaps at least one portion of an edge electrode portion151of the first sub-pixel electrode150while not overlapping a data line DLj, and is disposed along an edge of the first sub-pixel electrode150. The sustain electrode line143may overlap at least one portion of the edge electrode portion151to shield a liquid crystal collision region to be described later, but is not limited thereto. In exemplary embodiments, the sustain electrode and/or the sustain electrode line may be omitted, and a shape and a disposition thereof may be variously modified.

On the gate line GLi and the voltage dividing reference line140, a gate insulating layer181may be disposed over the entire surface of the first base substrate101. The gate insulating layer181may include an insulating material and may electrically insulate an upper layer positioned above the gate insulating layer181and a lower layer positioned below the gate insulating layer181from each other. In an exemplary embodiment, the gate insulating layer181may include a material such as a silicon nitride (SiNx), a silicon oxide (SiOx), a silicon nitride oxide (SiNxOy), a silicon oxynitride (SiOxNy) or the like and may also have a multilayer structure including at least two insulating layers having different physical properties.

On the gate insulating layer181, a semiconductor layer including first to third semiconductor layers112,122and132may be disposed.

The first to third semiconductor layers112,122and132may be disposed in regions overlapping the first to third gate electrodes111,121and131, respectively. The respective semiconductor layers may serve channels of the TFTs. The semiconductor layers may include a semiconductor material such as amorphous silicon, polycrystalline silicon, an oxide semiconductor or the like and may turn-on or -off the channels according levels of voltage supplied to the gate electrodes.

Data wirings may be disposed on the semiconductor layers. The data wirings may include data lines DLj and DLj+1, first to third source electrodes113,123, and133, and first to third drain electrodes114,124and134.

The data line DLj may be extended in approximately the first direction X1and may intersect with the gate line GLi. A data signal may be applied to the data line DLj. Pixel regions may be defined in an intersection of the data line DLj and the gate line GLi. However, the invention is not limited thereto, and Pixel regions may not be defined in an intersection of the data line DLj and the gate line GLi. The plurality of respective pixel regions may be independently operated by the plurality of TFTs connected to the gate line GLi and data line DLj corresponding thereto.

The first to third source electrodes113,123, and133and the first to third drain electrodes114,124and134may be disposed on the first to third semiconductor layers112,122and132. The first source electrode113and the second source electrode123connected to each other without a physical boundary therebetween may protrude from the data line DLj in a direction of the first and second gate electrodes111and121and may be disposed on the first semiconductor layer112and the second semiconductor layer122, respectively. The first and second source electrodes113and123may be respectively provided to surround at least a portion of the first and second drain electrodes114and124. In an exemplary embodiment, each of the first and second source electrodes113and123may have a shape such as a C-shape, a U-shape, a reverse C-shape, a reverse U-shape or the like. The third source electrode133will be described to be later.

The first drain electrode114may be disposed on the first semiconductor layer112to be spaced apart from the first source electrode113. In a similar manner, the second drain electrode124may be disposed on the second semiconductor layer122to be spaced apart from the second source electrode123. The first and second drain electrodes114and124may be electrically connected to the first and second sub-pixel electrodes150and160through first and second contact holes115and125, respectively, to be described later.

The third source electrode133may be disposed on the third semiconductor layer132. The third source electrode133may be physically connected to the second drain electrode124. The third drain electrode134may be disposed on the third semiconductor layer132to be spaced apart from the third source electrode133. In addition, the third drain electrode134may be electrically connected to the voltage dividing electrode141through a third contact hole135and a contact electrode159.

The first to third gate electrodes111,121and131, the first to third semiconductor layers112,122and132, the first to third source electrodes113,123, and133, and the first to third drain electrodes114,124and134may configure TFTs, three-terminal devices.

In detail, the first gate electrode111, e.g., a control terminal of a first TFT110, may be physically connected to the gate line GLi. The first source electrode113, e.g., an input terminal of the first TFT110, may be physically connected to the data line DLj. The first drain electrode114, e.g., an output terminal of the first TFT110, may be electrically connected to the first sub-pixel electrode150.

The second gate electrode121, e.g., a control terminal of a second TFT120, may be physically connected to the gate line GLi. The second source electrode123, e.g., an input terminal of the second TFT120, may be physically connected to the data line DLj. The second drain electrode124, e.g., an output terminal of the second TFT120, may be electrically connected to the second sub-pixel electrode160.

The third gate electrode131, e.g., a control terminal of a third TFT130, may be physically connected to the gate line GLi. The third source electrode133, e.g., an input terminal of the third TFT130, may be physically connected to the second drain electrode124. The third drain electrode134, e.g., an output terminal of the third TFT130, may be electrically connected to the voltage dividing electrode141.

Although not illustrated, an ohmic-contact layer (not shown) may be disposed between the semiconductor layers and the data wirings. In an exemplary embodiment, the ohmic-contact layer may include n+ amorphous silicon hydride or may include a silicide, for example.

A protective layer including a first protective film182, the color filter170, and a second protective film183may be disposed over the entire surface of the first to third TFTs110,120and130and the data line DLj. The protective layer may include an organic layer and/or an inorganic layer and may have a single layer or multilayer structure.

In an exemplary embodiment, the first protective film182may include an inorganic insulating material such as a silicon nitride, a silicon oxide or the like. The first protective film182may prevent the wirings and electrodes disposed therebelow from being in direct contact with an organic material. The color filter170may be disposed between the plurality of neighboring data lines. The color filter170may allow for selective transmission of light in a specific wavelength band and, for example, color filters having different colors and allowing for transmission of light in different wavelength bands may be disposed in respective pixel regions adjacent to each other. The exemplary embodiment illustrates a case in which the color filter170has a color filter on array (“COA”) structure disposed above the TFT, but the color filter may have an array on color filter (“AOC”) structure disposed below the TFT or alternatively, the color filter may be disposed on the second substrate. In addition, a planarization layer (not shown) may be disposed on the color filter170. The planarization layer may uniformize heights of a plurality of components stacked on the first base substrate101.

The second protective film183may be disposed on the color filter170. The second protective film183may prevent the lifting of the color filter170and inhibit contamination of the liquid crystal layer300due to an organic material such as a solvent introduced from the color filter170to prevent a defect such as an afterimage from being caused at the time of driving a screen.

The first protective film182, the color filter170, the planarization layer (not shown) and contact holes may be defined in the second protective film183to partially expose the first to third drain electrodes114,124and134and the voltage dividing electrode141. The first drain electrode114may be electrically connected to the first sub-pixel electrode150through the first contact hole115, the second drain electrode124may be electrically connected to the second sub-pixel electrode160through the second contact hole125, and the third drain electrode134may be electrically connected to the voltage dividing electrode141through the third contact hole135and the contact electrode159.

On a portion of the second protective film183and regions exposed through the first to third contact holes115,125and135, the pixel electrodes including the first sub-pixel electrode150and the second sub-pixel electrode160and the contact electrode159may be disposed. The contact electrode159may serve to electrically connect the third drain electrode134and the voltage dividing electrode141exposed through the third contact hole135to each other. The contact electrode159may include the same material as that of the first and second sub-pixel electrodes150and160and provided through an integral process with first and second sub-pixel electrodes150and160to be described later.

The pixel electrodes may be disposed to correspond to the plurality of respective pixel regions and may form an electric field, together with a common electrode250disposed on the second substrate201to control an alignment direction of liquid crystal molecules LC of the liquid crystal layer300interposed therebetween. The pixel electrodes may be transparent electrodes. The transparent electrodes may include an indium tin oxide, an indium zinc oxide or the like, but are limited thereto. The pixel electrodes may include the first sub-pixel electrode150and the second sub-pixel electrode160spaced apart from each other in the first direction X1. As described above, the first sub-pixel electrode150may be electrically connected to the first drain electrode114and the second sub-pixel electrode160may be electrically connected to the second drain electrode124.

The first sub-pixel electrode150may include a first edge electrode portion151having a substantially quadrangular shape, a plurality of first branch electrode portions152, a plurality of first fine slit portions153, a first central slit portion154, and a first protrusion electrode portion155protruding downwardly.

In detail, the first edge electrode portion151may be disposed in the circumference of the first sub-pixel electrode150along an edge of the first sub-pixel electrode150and may connect end portions of the plurality of first branch electrode portions152to each other. The first branch electrode portions152may protrude and extend toward a central portion of the first pixel electrode150in directions inclined from respective sides of the first edge electrode portion151having a quadrangular shape, for example, in directions of approximately 45°. The first central slit portion154may be positioned in the central portion of the first sub-pixel electrode150to have a substantially cross (+) shape, and the first fine slit portions153may be defined and extended in a radial manner in directions inclined from the first central slit portion154having the cross (+) shape, for example, in directions of approximately 45°. Consequently, the first sub-pixel electrode150may have four regions divided by the first central slit portion154and having different directivities of the first branch electrode portions152and the first fine slit portions153. The respective regions may serve as directors of the liquid crystal molecules LC and may form domains making different alignment directions of the liquid crystal molecules at the time of the driving thereof. In the specification, the domains may be referred to as first to fourth domains D1, D2, D3and D4from a left upper domain in a clockwise direction, whereby liquid crystal control force may be increased to allow for an increase in viewing angle and a decrease in texture and further, transmittance and a response speed may be improved. A concrete principle of forming the domains will be described with reference toFIGS. 4 and 5. The first protrusion electrode portion155may protrude downwardly of the first edge electrode portion151and may be electrically connected to the first drain electrode114through the first contact hole115, as described above.

The second sub-pixel electrode160may include a second edge electrode portion161having a substantially quadrangular shape, a plurality of second branch electrode portions162, a plurality of second fine slit portions163, a second central slit portion164, and a second protrusion electrode portion165protruding upwardly. The second sub-pixel electrode160may generally have a shape and a configuration substantially identical to those of the first sub-pixel electrode150. However, the second sub-pixel electrode160may have a rectangular shape in which a distance thereof in a vertical direction is greater than a distance thereof in a horizontal direction. In an exemplary embodiment, a planar area ratio of pixel regions overlapping the first sub-pixel electrode150(hereinafter, high pixel regions) to pixel regions overlapping the second sub-pixel electrode160(hereinafter, low pixel regions) may be equal to or more than approximately 1:1.6 and may be equal to or less than approximately 1:2.4, for example.

Describing operations of pixels in a single frame interval, when a gate signal may be applied to the gate line GLi and thus, the first TFT110is turned on, a data voltage provided from the data line DLj may be applied to the first sub-pixel electrode150. In this case, the amount of voltage equal to a difference between the data voltage and the common voltage may be charged between the first sub-pixel electrode150and the common electrode250, and the pixel regions overlapping the first sub-pixel electrode150(high pixel regions) may be charged with a voltage having a voltage level relatively high than that of the pixel regions overlapping the second sub-pixel electrode160, to be described later, to thereby control liquid crystals. At the same time, the second and third TFTs120and130may be electrically connect the data line DLj and the voltage dividing reference line140to each other and due to a voltage drop, a predetermined voltage having a value between a value of the data voltage and a voltage of a reference voltage lower than the data voltage may be applied to the second sub-pixel electrode160. Thus, the pixel regions overlapping the second sub-pixel electrode160(low pixel regions) may be charged with a voltage having a voltage level relatively lower than that in the pixel regions overlapping the first sub-pixel electrode150to thereby control the liquid crystals. In the case of the high pixel regions charged with a relatively high voltage, side visibility may be low in a low grayscale section in which the liquid crystals are vertically aligned. In the case of the low pixel regions charged with a relatively low voltage, side visibility may be low in intermediate and high grayscale sections in which the liquid crystals are almost vertically aligned. That is, charging voltages of high and low pixels may be represented as different gamma curves and a gamma curve for a single pixel voltage, recognized by a viewer, may be provided by synthesizing these different gamma curves. The synthesized gamma curve in a front view is provided to coincide with a reference gamma curve in the front view determined to be most appropriate to the LCD device, and the synthesized gamma curve in a side view is provided to be closest to the reference gamma curve in the front view. In this manner, image data may be converted to improve side visibility. Effects of improving side visibility according to an exemplary embodiment of the invention will be described with reference toFIGS. 6 through 8.

The shapes and dispositions of the first and second sub-pixel electrodes150and160are merely provided by way of example, and in exemplary embodiments, the first and second sub-pixel electrodes150and160may be provided to be bent from the gate lines and the data lines, and may be modified to have branch electrode portions and slit portions having various shapes.

A first alignment layer190may be disposed over the entire surface of the first and second sub-pixel electrodes150and160, the contact electrode159, and the second protective film183. The first alignment layer190may allow the liquid crystal molecules LC included in the liquid crystal layer300to be aligned in a specific direction on a plane. The first alignment layer190may be a photo-alignment layer including a first alignment layer (not shown) and a first photo-curing layer (not shown) disposed on the first alignment layer. In an exemplary embodiment, the first alignment layer190may be a vertically aligned mode alignment layer including a polyimide in which an imide group is included in a repeating unit of a main chain thereof, and at least one vertical alignment group among an alkyl group, a hydrocarbon derivative having an end substituted with the alkyl group, a hydrocarbon derivative having an end substituted with a cycloalkyl group, and a hydrocarbon derivative having an end substituted with an aromatic hydrocarbon is introduced to a side chain thereof. In an exemplary embodiment, the first photo-curing layer may be a polymer combination in which single molecules including the vertical alignment group and a photo-curing agent are chemically combined with each other. The photo-curing agent may be reactive mesogen. The reactive mesogen refers to a photo-crosslinkable low molecular or high molecular copolymer including a mesogen group having liquid crystal properties and absorbs light of a specific wavelength to generate a polymerization reaction. In an exemplary embodiment, the reactive mesogen may be, for example, acrylate, methacrylate, epoxy, oxetane, vinyl-ether, styrene, a thiolene group or the like. The first alignment layer190including the first alignment layer and the first photo-curing layer may maintain a pre-tilt even in a case in which an electric field is not provided by a light irradiation process and consequently, a response speed of the LCD device may be improved. In exemplary embodiments, the first alignment layer may be a rubbing alignment layer, not a photo-alignment layer.

Then, describing the second substrate200, the second substrate200may be an upper substrate facing the first substrate100. The second substrate200may include a second base substrate201, a light shielding member210, an overcoating layer230, and the common electrode250. The second base substrate201may be configured to include the same material as that of the first base substrate101.

The light shielding member210and the overcoating layer230may be disposed on the second base substrate201. The light shielding member210may be a black matrix. The light shielding member210may be disposed in a boundary between a plurality of the color filters to prevent light leakage defects. In detail, the light shielding member210may be disposed in a region overlapping components configuring the first to third TFTs as well as in a region overlapping the plurality data lines DLj and DLj+1, at least a portion of the sustain electrode line143, and at least a portion of the first and second edge electrode portions151and161. Unlike the case illustrated in the embodiment, the light shielding member may be disposed on the first substrate or may be omitted.

The overcoating layer230may be disposed on the light shielding member210. The overcoating layer230may prevent the light shielding member210from being separated therefrom and may uniformize heights of components stacked on the second base substrate201.

The common electrode250may be disposed on the overcoating layer230. A common voltage may be applied to the common electrode250and thus, the common electrode250, together with the pixel electrodes of the first substrate100, may generate an electric field to thereby control alignment directions of the liquid crystal molecules LC of the liquid crystal layer300interposed therebetween. The common electrode250may be a transparent electrode such as the pixel electrode150or160and may be a patternless electrode having no slit pattern, but is not limited thereto. The common electrode250may also have a predetermined pattern. A second alignment layer290may be disposed on the common electrode250. The second alignment layer290may include a configuration substantially identical to that of the first alignment layer190and thus, a detailed description thereof will be omitted.

Hereinafter, with reference toFIGS. 4 and 5, the principle of forming the plurality of domains in the pixel region and an alignment direction of liquid crystal molecules in each domain will be described in detail.

Referring toFIGS. 2 and 4, when a common voltage is applied to the common electrode250and a data voltage is applied to the first sub-pixel electrode150, an electrical field may be generated between the common electrode250and the first sub-pixel electrode150. In this case, a long axis of the liquid crystal molecules LC having negative dielectric constant anisotropy, included in the liquid crystal layer300may be vertically inclined with respect to the electric field, and a direction thereof may be a direction toward a circumferential portion of the first sub-pixel electrode150from a central portion thereof. Control force for controlling the liquid crystal molecules LC is the highest in end portions of the first fine branch electrode portions152, and the liquid crystal molecules adjacent to each other may have the same directivity through a process of collision between the adjacent liquid crystal molecules, whereby a final alignment direction of the liquid crystal molecules within the same domain may be determined. The alignment direction may be substantially parallel to a direction in which the plurality of first fine branch electrode portions152of the first sub-pixel electrode150are extended. Thus, liquid crystal molecules of the first domain D1may be aligned in approximately a third direction X3, and liquid crystal molecules of the second domain D2may be aligned in approximately a fourth direction X4. The liquid crystal molecules of the third domain D3may be aligned in approximately a fifth direction X5, and liquid crystal molecules of the fourth domain D4may be aligned in approximately a sixth direction X6. Consequently, the plurality of domains D1, D2, D3and D4in which alignment directions of the liquid crystal molecules LC are different in the pixel region of the first sub-pixel electrode150may be implemented, and schematic alignment directions of the liquid crystal molecules within the plurality of domains may be directed toward the circumferential portion of the first sub-pixel electrode150from the central portion thereof

Referring toFIGS. 2 and 5, as described inFIG. 4, due to the alignment of the liquid crystal molecules aligned in the end portions of the first fine branch electrode portions152having a high degree of liquid crystal control force, and the collision between the liquid crystal molecules belonging to the same domain, schematic alignment directions of the liquid crystal molecules in the vicinity of the circumferential portion of the first sub-pixel electrode150, more particularly, an internal edge (a right edge in view of the drawing) of the first edge electrode portion151, may also be directed toward the circumferential portion of the first sub-pixel electrode150from the central portion thereof. In the specification, a region in which the liquid crystal molecules are controlled to have a constant directivity, in the interior of the first edge electrode portion151and the central portion of the first sub-pixel electrode150, is referred to an effective pixel region A. That is, the effective pixel region A may be a region not overlapping the light shielding member210and allowing light to be substantially transmitted therethrough.

The liquid crystal molecules in the vicinity of an external edge of the first edge electrode portion151(a left edge in view of the drawing) may be inclined toward the interior of the first sub-pixel electrode150by the electric filed generated between the common electrode250and the first edge electrode portion151. In addition, in an approximately central region of a cross-section of the first edge electrode portion151, cut in a width direction thereof, the liquid crystal molecules having different alignment directions may collide with each other, such that the liquid crystal molecules may be aligned in approximately the first direction X1. In the specification, a region in which the liquid crystal molecules are aligned in a direction different from that of the liquid crystal molecules of the effective pixel region A or the liquid crystal molecules collide with each other, in the vicinity of the external edge of the first edge electrode portion151and the approximately central region of the first edge electrode portion151, is referred to as a liquid crystal collision region B. The alignment direction of the liquid crystal molecules in the liquid crystal collision region B may be different from that of the liquid crystal molecules in the effective pixel region A, whereby improvements in luminance and side visibility may be insignificant and light leakage defects may be caused. Thus, light may be blocked by the disposition of the light shielding member210or the like.

That is, a boundary between the effective pixel region A and the liquid crystal collision region B may be disposed on the first edge electrode portion151, and in accordance with an increase in a planar area, transmittance and luminance as well as side visibility may be further improved. The properties may be controlled by a distance between the pixels adjacent to each other. A detailed description thereof will be described with reference toFIGS. 9 through 11.

FIG. 6is a graph illustrating results provided by measuring degrees of luminance according to voltage levels in a front surface and a side surface.FIG. 7ais an image of one pixel region of a high grayscale section in a front surface of an LCD device according to an exemplary embodiment of the invention,FIG. 7bis an image of one pixel region of a high grayscale section in a front surface of an LCD device (reference) having a cross-shaped stem electrode portion,FIG. 7cis an image of one pixel region of a low grayscale section in a side surface of the LCD device according to an exemplary embodiment of the invention, andFIG. 7dis an image of one pixel region of a low grayscale section in a side surface of the LCD device (reference) having a cross-shaped stem electrode portion.FIG. 8is a graph illustrating a gamma curve.

Referring toFIG. 6, in both of the front surface and the side surface, in the case of the LCD device according to an exemplary embodiment of the invention, it could be confirmed that degrees of luminance in intermediate and high grayscale sections were increased as compared to the LCD device (reference) having a cross-shaped stem electrode portion, and in particular, a degree of luminance is improved by about 6.2 percent (%) in the high grayscale section to which a voltage of about 8 volts (V) is applied. In addition, comparingFIGS. 7aand 7bwith each other, it could be confirmed that as compared toFIG. 7aaccording to the exemplary embodiment of the invention, more amount of dark portions (i.e., texture) recognized as an approximately cross (+) shape is shown in a central portion of a pixel region in the case ofFIG. 7b. In addition, inFIG. 7b, it could be confirmed that dark portions recognized as diagonal lines were shown in upper and lower ends of the pixel region. This is because that in the case of the LCD device according to an exemplary embodiment of the invention, since a cross-shaped stem electrode portion may be omitted as compared to the LCD device having a cross-shaped stem electrode portion, a collision region of liquid crystal molecules in a central portion of a pixel electrode may not be caused, such that transmission efficiency in the central portion of the pixel electrode may be increased.

Referring to the side surface, in the case of the LCD device (reference) having the cross-shaped stem electrode portion, a luminance increase curve according to an increase in voltage is not smooth and in particular, it could be confirmed that a lifting phenomenon of a side luminance curve in which a degree of luminance is hardly increased even with an increase in voltage in a low grayscale section to which a voltage of about 3V is applied occurred. It could be confirmed that in the case of the LCD device according to an exemplary embodiment of the invention, a luminance increase curve according to an increase in voltage is relatively smooth as compared to the LCD device (reference) having the cross-shaped stem electrode portion. In addition, comparingFIGS. 7cand 7dwith each other, it could be confirmed that a contrast ratio of a brightly recognized left-half region and a darkly recognized right-half region is relatively large inFIG. 7c. It could be confirmed that a contrast ratio of a brightly recognized right-half region and a darkly recognized left-half region is relatively small inFIG. 7c.

As illustrated inFIG. 8, it could be confirmed that a side gamma curve is down in the entire grayscale section in the case of the LCD device according to an exemplary embodiment of the invention, as compared to the LCD device (reference) having the cross-shaped stem electrode portion. This means that the side gamma curve is more proximate to a front gamma curve, whereby even in the case of viewing the LCD device from the side surface thereof, an image proximate to that when viewing the LCD device from the front surface thereof may be recognized.

Hereinafter, a distance between components configuring the pixel electrode will be described with reference toFIGS. 9 through 13.

FIG. 9is a cross-sectional view, taken along line IX-IX′ ofFIG. 2.FIGS. 10 and 11are graphs illustrating results provided by measuring degrees of luminance in positions within a pixel according to a distance thereof from an adjacent pixel.

Referring toFIGS. 2 and 9, at least one portion of the first edge electrode portion151of one first sub-pixel electrode150may overlap the data line DLj+1, and the one first sub-pixel electrode150and another sub-pixel electrode may be adjacent to each other in the second direction X2with the data line DLj+1 interposed therebetween. In addition, the light shielding member210may be disposed to overlap the data line DLj+1, the at least one portion of the first edge electrode portion151of the first sub-pixel electrode150, and at least one portion of the sustain electrode line143. A shape and a disposition of the adjacent sub-pixel electrode may be symmetrical with respect to the first sub-pixel electrode150based on the data line DLj+1. In this case, a space between the first edge electrode portion151of the first sub-pixel electrode150and an edge electrode portion158of the adjacent sub-pixel electrode in the second direction X2may be defined as a pixel-to-pixel distance Wa.

FIG. 10is a graph illustrating results provided by measuring luminance variations of a single domain of the first sub-pixel electrode in a diagonal direction in a high grayscale section (e.g., about 8V), from a front surface.FIG. 11is a graph illustrating results provided by measuring luminance variations of a single domain of the first sub-pixel electrode in a horizontal direction in a low grayscale section (e.g., about 3V), from a side surface. InFIGS. 10 and 11, a point in which a distance from a pixel central portion is 0 refers to a central portion of the effective pixel region A, and a point far away from the pixel central portion is close to an edge of the effective pixel region A.

As illustrated inFIG. 10, in the central portion of the effective pixel region A, specifically, in a region ranging from the central portion of the first sub-pixel electrode to approximately about 190 μm in a diagonal direction, a difference in luminance depending on the pixel-to-pixel distance Wa is hardly shown. In an edge region of the effective pixel region A distant apart from the central portion of the first sub-pixel electrode by a distance of approximately about 190 μm or more, it could be confirmed that the difference in luminance depending on the pixel-to-pixel distance Wa is generated. Specifically, in accordance with the increase in the pixel-to-pixel distance Wa, a degree of luminance in the same point is reduced. This means that due to a decrease in a planar area of the effective pixel region A, texture occurred in the vicinity of the edge of the pixel region in a high grayscale section from the front surface and a degree of transmittance is reduced in the entire pixel region.

As illustrated inFIG. 11, in the central portion of the effective pixel region A, specifically, in a region ranging from the central portion of the first sub-pixel electrode to approximately about 130 μm in a horizontal direction, a difference in luminance depending on the pixel-to-pixel distance Wa is hardly shown. In an edge region of the effective pixel region A distant apart from the central portion of the first sub-pixel electrode by a distance of approximately about 130 μm or more, it could be confirmed that the difference in luminance depending on the pixel-to-pixel distance Wa is generated. Specifically, in accordance with the increase in the pixel-to-pixel distance Wa, degree of luminance in the same point is increased. This means that light leakage defects occurred in the vicinity of the edge of the pixel region in the low grayscale section from the side surface.

Consequently, a distance between adjacent pixels, that is, the pixel-to-pixel distance Wa, of the LCD device according to an exemplary embodiment of the invention, may be equal to or greater than about 5 μm and equal to or less than about 10 μm. When the pixel-to-pixel distance Wa is about 5 μm or more, pattern defects such as a pattern short and the like during the formation of a pixel electrode pattern may be prevented. When the pixel-to-pixel distance Wa is about 10 μm or less, the occurrence of texture may be minimized and a high degree of transmittance may be secured in the high grayscale section. In the low grayscale section, light leakage defects may be effectively prevented.

FIG. 12is a cross-sectional view, taken along line XII-XII′ ofFIG. 2.FIG. 13is a graph illustrating results provided by measuring indices of visibility and transmittance according to a width of a horizontal slit portion and a width of a vertical slit portion.

Referring toFIGS. 2 and 12, the plurality of first fine slit portions153and the first central slit portion154including a horizontal slit portion and a vertical slit portion and having a substantially cross-shape may be positioned between the plurality of first branch electrode portions152of the first sub-pixel electrode150. Through this, in the pixel region overlapping the first sub-pixel electrode150, a plurality of different domains divided by the first central slit portion154and having different directivities of the first branch electrode portions152and the first fine slit portions153may be defined. The plurality of domains may include the first domain D1in which the first branch electrode portions152protrude and extend in the fifth direction X5from the first edge electrode portion151, the second domain D2in which the first branch electrode portions152protrude and extend in the sixth direction X6from the first edge electrode portion151, and the fourth domain D4in which the first branch electrode portions152protrude and extend in the fourth direction X4from the first edge electrode portion151. In this case, a minimum distance between an end portion of the first branch electrode portion protruding and extending toward the fourth domain D4adjacent to the first domain D1in the first direction X1among the plurality of first branch electrode portions within the first domain D1and an end portion of the first branch electrode portion protruding and extending toward the first domain D1among the plurality of first branch electrode portions within the fourth domain D4may be defined by a width Wb of the horizontal slit portion. A minimum distance between an end portion of the first branch electrode portion protruded and extended toward the second domain D2adjacent to the first domain D1in the second direction X2among the plurality of first branch electrode portions within the first domain D1and an end portion of the first branch electrode portion protruding and extending toward the first domain D1among the plurality of first branch electrode portions within the second domain D2may be defined by a width Wc of the vertical slit portion.

As illustrated inFIG. 13, when the width Wb of the horizontal slit portion is about 3 μm or about 5 μm, it could be confirmed that a degree of transmittance is relatively high and a visibility index is relatively low as compared to the case in which the width Wb of the horizontal slit portion is about 7 μm. In addition, when the width Wb of the horizontal slit portion is about 3 μm, it could be confirmed that a visibility index is relatively low as compared to the case in which the width Wb of the horizontal slit portion is 5 μm. In particular, when the width Wb of the horizontal slit portion is about 3 μm and the width Wc of the vertical slit portion is about 5 μm, it could be confirmed that a degree of transmittance is relatively high and a visibility index is relatively low as compared to the case in which the width Wb of the horizontal slit portion is 3 μm and the width Wc of the vertical slit portion is about 3 μm or about 7 μm.

Consequently, the width Wb of the horizontal slit portion of the first sub-pixel electrode in the LCD device according to an exemplary embodiment of the invention may be narrower than the width Wc of the vertical slit portion thereof and in detail, the width Wb of the horizontal slit portion may be about 3 μm and the width Wc of the vertical slit portion may be about 5 μm, but the invention is not limited thereto. The widths of the horizontal slit portion and/or the vertical slit portion may be variously modified depending on desired properties of the LCD device.

Hereinafter, LCD devices according to other exemplary embodiments of the invention will be described. However, in order to clarify the substance of the invention, a description of components substantially identical to or similar to the foregoing LCD device will be omitted, and the said components could be clearly understood to a person having ordinary skill in the art from the attached drawings.

FIGS. 14 and 15are cross-sectional views of LCD devices according to other exemplary embodiment of the invention.

The embodiment ofFIG. 14is different from that ofFIG. 9in that the light shielding member211is disposed on the first substrate100. The light shielding member211according to the exemplary embodiment may be a black column spacer. The black column spacer may be disposed to overlap the data line DLj+1 and the at least a portion of the first edge electrode portion151of the first sub-pixel electrode150to prevent light leakage defects in the liquid crystal collision region B and at the same time, may allow a distance between the first substrate100and the second substrate200to be maintained.FIG. 14illustrates a case of the black column spacer in which a top portion of the light shielding member211is spaced apart from the second substrate200by a predetermined distance to provide buffering properties to the second substrate200, but in other exemplary embodiments, the top portion of the light shielding member211may substantially contact with the second substrate.

The embodiment ofFIG. 15is different from that ofFIG. 9in that a width of a sustain electrode line144in the second direction X2is greater than that of the sustain electrode line143in the embodiment ofFIG. 9. The width of the sustain electrode line144in the second direction X2, specifically, the width of the sustain electrode line144in a direction of the data line DLj+1 may be increased, such that the sustain electrode line144may overlap the data line DLj+1 and at least a portion of the semiconductor layers disposed below the data line. The sustain electrode line, an opaque electrode may overlap the data line DLj+1, an opaque electrode by increasing the width of the sustain electrode line144, whereby light leakage defects in the liquid crystal collision region B may be minimized and at the same time, the light shielding member such as a separate black matrix may be omitted to thereby result in improvements in transmittance properties.

With the LCD device according to an exemplary embodiment of the invention, directors of liquid crystal molecules in a pixel region may be arranged in a direction from a central portion of a pixel electrode to an circumferential portion thereof, whereby light leakage defects occurring in a central portion of a pixel region in a low grayscale section may be alleviated and side visibility may be improved.

In addition, in a high grayscale section, a degree of transmittance in the central portion of the pixel region may be further improved, whereby an LCD device having improved display quality may be provided.

Effects according the invention are not limited to the contents exemplified above and more various effects are involved in the specification.

While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the spirit and scope of the invention as defined by the appended claims. The exemplary embodiments should be considered in a descriptive sense only and not for purposes of limitation.