Liquid crystal display

Disclosed herein is a liquid crystal display, including: a first substrate; a first sub-pixel electrode positioned on the first substrate including a first sub-region and a second sub-region; a second sub-pixel electrode positioned on the first substrate including a third sub-region and a fourth sub-region; and an insulating layer positioned between the first sub-region of the first sub-pixel electrode and the second sub-pixel electrode, wherein liquid crystal molecules corresponding to a first region in which the second sub-region of the first sub-pixel electrode is positioned, a second region in which the first sub-region of the first sub-pixel electrode and the third sub-region of the second sub-pixel electrode overlap each other, and a third region in which the fourth sub-region of the second sub-pixel electrode is positioned are configured to have different pretilts.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0010584 filed in the Korean Intellectual Property Office on Jan. 22, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present application relates to a liquid crystal display.

(b) Description of the Related Art

A liquid crystal display is one of the flat panel displays which have been most widely used currently and includes two sheets of a display panel in which field generating electrodes, such as a pixel electrode and a common electrode, are formed and a liquid crystal layer interposed therebetween.

The field generating electrodes are applied with a voltage to generate an electric field in the liquid crystal layer and an alignment of liquid crystal molecules of the liquid crystal layer is determined and polarization of incident light is controlled based on the generated electric field to display an image.

The liquid crystal display further includes switching elements connected to each of the pixel electrodes and a plurality of signal lines, such as gate lines and data lines, which control the switching elements to apply a voltage to the pixel electrodes.

Among the liquid crystal displays, a liquid crystal display in a vertically aligned mode in which major axes of the liquid crystal molecules are aligned to be vertical to the display panel has a large contrast ratio and a wide reference viewing angle, and therefore has received much attention. Herein, a reference viewing angle means a viewing angle in which a contrast ratio is 1:10 or an inter-gray luminance inversion critical angle.

Meanwhile, in the case of the liquid crystal display according to the scheme, to make side visibility approximate front visibility, a method for making transmittance different by dividing one pixel into two sub-pixels and applying different voltages to the two sub-pixels has been suggested.

However, in the case of making side visibility approximate front visibility by dividing one pixel into two sub-pixels and making transmittance different, luminance is increased at a low gray or a high gray to make it difficult to implement gray expression at the side, thereby causing the problem that an image quality deteriorates.

Further, in the case of dividing one pixel only into a plurality of physical areas, a freedom of design is reduced to make it difficult to improve additional characteristics. Therefore, a method for improving additional characteristics by controlling a pretilt angle without changing a separate design is desired.

SUMMARY

Embodiments have been made in an effort to provide a liquid crystal display capable of making side visibility approximate front visibility and implementing an accurate color at a side.

An exemplary embodiment provides a liquid crystal display, including: a first substrate; a first sub-pixel electrode positioned on the first substrate, configured to be applied with a first voltage, and including a first sub-region and a second sub-region; a second sub-pixel electrode positioned on the first substrate, configured to be applied with a second voltage, and including a third sub-region and a fourth sub-region; an insulating layer positioned between the first sub-region of the first sub-pixel electrode and the second sub-pixel electrode; a second substrate facing the first substrate; a common electrode positioned on the second substrate and configured to be applied with a common voltage; and a liquid crystal layer positioned between the first substrate and the second substrate, wherein liquid crystal molecules corresponding to a first region in which the second sub-region of the first sub-pixel electrode is positioned, a second region in which the first sub-region of the first sub-pixel electrode and the third sub-region of the second sub-pixel electrode overlap each other, and a third region in which the fourth sub-region of the second sub-pixel electrode is positioned are configured to have different pretilts.

The pretilt of the liquid crystal molecules corresponding to the first region may have an angle larger than the pretilt of the liquid crystal molecules corresponding to the second region and the pretilt of the liquid crystal molecules corresponding to the third region.

The pretilt of the liquid crystal molecules corresponding to the second region may have an angle larger than the pretilt of the liquid crystal molecules corresponding to the third region.

A difference in the pretilt of the liquid crystal molecules corresponding to the first region, the pretilt of the liquid crystal molecules corresponding to the second region, or the pretilt of the liquid crystal molecules corresponding to the third region may be equal to or more than about 0.5°.

The difference in the pretilt of the liquid crystal molecules corresponding to the first region, the pretilt of the liquid crystal molecules corresponding to the second region, or the pretilt of the liquid crystal molecules corresponding to the third region may be equal to or more than about 15°.

A difference between the first voltage and the common voltage may be larger than a difference between the second voltage and the common voltage.

Luminance of the first region, the second region, and the third region may be configured to be different from one another.

The liquid crystal display may further include: a plurality of pixels, wherein the plurality of pixels includes a first sub-pixel, a second sub-pixel, and a third sub-pixel each configured to display red, blue, and green and the first sub-pixel, the second sub-pixel, and the third sub-pixel have different pretilt angles.

The first region of the second sub-pixel configured to display the blue may have the pretilt angle smaller than the pretilt angle of the liquid crystal molecules corresponding to the first region of the first sub-pixel configured to display the red.

The first region of the second sub-pixel configured to display the blue may have the pretilt angle smaller than the pretilt angle of the liquid crystal molecules corresponding to the first region of the third sub-pixel configured to display the green.

A difference in the pretilt angles of the liquid crystal molecules corresponding to the first region of the first sub-pixel, the second sub-pixel, and the third sub-pixel may be equal to or more than about 0.5° and may be equal to or less than about 1.5°.

In the first sub-pixel configured to display the red, the second sub-pixel configured to display the blue, and the third sub-pixel configured to display the green, the pretilt of the liquid crystal molecules corresponding to the first region of each sub-pixel may have an angle larger than the pretilt of the liquid crystal molecules corresponding to the second region of each sub-pixel and the pretilt of the liquid crystal molecules corresponding the third region and the pretilt of the liquid crystal molecules corresponding to the second region may have an angle larger than the pretilt of the liquid crystal molecules corresponding to the third region.

The difference in the pretilt of the liquid crystal molecules corresponding to the first region, the pretilt of the liquid crystal molecules corresponding to the second region, or the pretilt of the liquid crystal molecules corresponding to the third region may be equal to or more than about 0.5° and may be equal to or less than about 1.5°.

The first sub-region of the first sub-pixel electrode may have an integrated plate shape.

The first sub-pixel electrode and the second sub-pixel electrode may be physically and electrically separated from each other.

The second sub-region of the first sub-pixel electrode may be positioned on the some layer as the third sub-region and the fourth sub-region of the second sub-pixel electrode.

According to an exemplary embodiment, it is possible to provide the structure of the liquid crystal display capable of making the side visibility approximate the front visibility, implementing the accurate gray expression in the low gray area, preventing the display quality from deteriorating, and controlling the pretilt angle without changing the separate design to improve the additional characteristics.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Next, a liquid crystal display according to the exemplary embodiment will be described in detail with reference toFIGS. 1 to 7.FIG. 1is a layout view of a liquid crystal display according to an exemplary embodiment.FIG. 2is a cross-sectional view of the liquid crystal display device ofFIG. 1taken along the line II-II.FIG. 3is a layout view of a first portion of a first sub-pixel electrode of the liquid crystal display ofFIG. 1.FIG. 4is a layout view of a second portion of the first sub-pixel electrode and a second sub-pixel electrode of the liquid crystal display ofFIG. 1.FIG. 5is a cross-sectional view of the liquid crystal display ofFIG. 1taken along the line VI-VI.FIG. 6is a cross-sectional view of the liquid crystal display ofFIG. 1taken along the line VII-VII.FIG. 7is a cross-sectional view of the liquid crystal display ofFIG. 1taken along the line VIII-VIII.

Referring toFIGS. 1 and 2, the liquid crystal display according to the exemplary embodiment includes the lower panel100and the upper panel200facing each other and the liquid crystal layer3interposed between the two display panels100and200.

First, the lower display panel100will be described.

A gate line121, a reference voltage line131, and a sustain electrode135are formed on a first insulating substrate110which is made of transparent glass, plastic, or the like. The gate line121mainly extends in a horizontal direction to transfer a gate signal.

The gate line121includes a wide end (not illustrated) on as to be connected to a first gate electrode124aa second gate electrode124b, a third gate electrode124cand other layers or external driving circuits.

The reference voltage line131may extend in parallel with the gate line121and has an extension136which is connected to a third drain electrode175cto be described below.

The reference voltage line131includes the sustain electrode135which encloses a pixel area.

A gate insulating layer140is formed on the gate line121, the reference voltage line131, and the sustain electrode135.

A first semiconductor154a, a second semiconductor154b, and a third semiconductor154cwhich may be made of amorphous or crystalline silicon, etc., are formed on the gate insulating layer140.

A plurality of ohmic contacts163a,163b,163c,165a,165b, and165care formed on the first, second, and third semiconductors154a,154b, and154c. When the semiconductors154a,154b, and154care oxide semiconductor, the ohmic contacts may be omitted.

Data lines171which include a first source electrode173aand a second source electrode173band data conductors171,173a,173b,173c,175a,175b, and175cwhich include a first drain electrode175a, a second drain electrode175b, a third source electrode173c, and the third drain electrode175care formed on the ohmic contacts163a,163b,163c,165a,165b, and165cand the gate insulating layer140.

The second drain electrode175bis connected to the third source electrode173c.

The first gate electrode124a, the first source electrode173a, and the first drain electrode175aform a first thin film transistor Qa together with the first semiconductor154aand a channel of the first thin film transistor Qa is formed at the first semiconductor154abetween the first source electrode173aand the first drain electrode175a. Similarly, the second gate electrode124b, the second source electrode173b, and the second drain electrode175bform a second thin film transistor Qb together with the second semiconductor154b, the channel of the second thin film transistor Qb is formed at the second semiconductor154bbetween the second source electrode173band the second drain electrode175b. The third gate electrode124c, the third source electrode173c, and the third drain electrode175cform a third thin film transistor Qc together with the third semiconductor154c, and the channel of the third thin film transistor Qc is formed at the third semiconductor154cbetween the third source electrode173cand the third drain electrode175c.

A first passivation layer180awhich may be made of an insulating material such as silicon nitride and silicon oxide is formed on the data conductors171,173a,173b,173c,175a,175b, and175cand exposed portions of the semiconductors154a,154b, and154c.

A color filter230is formed on the first passivation layer180a.

A light blocking member220may be positioned in an area in which the color filter230is not positioned and on a portion of the color filter230. The light blocking member220is referred to as a black matrix and prevents light from leaking.

The capping layer80is positioned on the color filter230. The capping layer80prevents the color filter230from being lifted and suppresses pollution of the liquid crystal layer3due to organic materials such as a solvent introduced from the color filter230, thereby preventing defects such as afterimage which may occur when a screen is driven.

A first sub-region191a1of a first sub-pixel electrode191ais disposed on the capping layer80.

Referring toFIG. 3, the first sub-region191a1of the first sub-pixel electrode191ahas a plane shape which includes a horizontal connection part192and four parallelograms positioned around the horizontal connection part192to enclose the horizontal connection part192. Further, an extension193ais positioned at a central portion of the horizontal connection part192. Further, the first sub-region191a1includes a protrusion193which extends vertically from a horizontal central portion of the pixel area. As such, the first sub-region191a1of the first sub-pixel electrode191ais positioned at a portion of the pixel area.

A second passivation layer180bis formed on the capping layer80and the first sub-region191a1of the first sub-pixel electrode191a.

A second sub-region191a2of the first sub-pixel electrode191aand a second sub-pixel electrode191bare formed on the second passivation layer180b. A pixel electrode191includes the first sub-pixel electrode191aand the second sub-pixel electrode191b.

Referring toFIG. 4, the second sub-region191a2of the first sub-pixel electrode191ais positioned at a central portion of the pixel and the whole shape thereof is a rhombus. The second sub-region191a2of the first sub-pixel electrode191aincludes a cruciform stem part194having a horizontal part and a vertical part and a plurality of first branch electrodes198which extend from the cruciform stem part194. The first branch electrodes198extend in four directions.

The second sub-pixel electrode191bmay include an outer stem part196which is formed at an edge of the pixel area and a plurality of second branch electrodes197which extend from the outer stem part196.

The plurality of first branch electrodes198and the plurality of second branch electrodes197extend in parallel with each other, while facing each other.

The second sub-pixel electrode191bincludes a third sub-region191b1overlapping the first sub-region191a1of the first sub-pixel electrode191aand another fourth sub-region191b2. The third sub-region191b1of the second sub-pixel electrode191boverlaps the first sub-region191a1of the first sub-pixel electrode191a, having an insulating layer, in detail, the second passivation layer180bdisposed therebetween.

A first contact hole185awhich extends to and through which a portion of the first drain electrode175ais exposed is formed on the first passivation layer180aand the capping layer80. A second contact hole185bwhich extends to and through which a portion of the second drain electrode175bis exposed is formed on the first passivation layer180a, the capping layer80, and the second passivation layer180b. Further, a third contact hole186which extends to and through which a central portion of the first sub-region191a1of the first sub-pixel electrode191ais exposed is formed on the second passivation layer180b. The first sub-region191a1of the first sub-pixel electrode191ais physically and electrically connected to the first drain electrode175athrough the first contact hole185aand the second sub-pixel electrode191bis physically and electrically connected to the second drain electrode175bthrough the second contact hole185b. Further, the second sub-region191a2of the first sub-pixel electrode191ais connected to the first sub-region191a1of the first sub-pixel electrode191athrough the third contact hole186which is formed on the second passivation layer180b.

The first sub-pixel electrode191aand the second sub-pixel electrode191bare each applied with a data voltage from the first drain electrode175aand the second drain electrode175b, respectively, through the first contact hole185aand the second contact hole185b.

Next, the upper panel200will be described.

The light blocking member220and a common electrode270are formed on an insulating substrate210made of transparent glass, plastic, or the like.

However, in the case of the liquid crystal display device according to another exemplary embodiment, the light blocking member220may be positioned on the lower panel100and in the case of the liquid crystal display device according to another exemplary embodiment the color filter230may be positioned on the upper panel200.

The inner sides of the display panels100and200are provided with the alignment layers (not illustrated) which may be the vertical alignment layer (not illustrated).

The polarizer (not illustrated) is disposed on the outer surfaces of the two display panels100and200and the transmission axes of the two polarizers are orthogonal to each other, in which one of the transmission axes is preferably parallel with the gate line121. However, the polarizer may also be disposed only on the outer surface of any one of the two display panels100and200.

The liquid crystal layer3has a negative dielectric anisotropy and the liquid crystal molecules of the liquid crystal layer3are aligned so that the major axes thereof are vertical to the surfaces of the two display panels100and200in the state in which no electric field is present. Therefore, incident light does not pass through the crossed polarizers but is blocked, in the state in which no electric field is present.

At least one of the liquid crystal layer3and an alignment layer may include a photoreactive material, in more detail, reactive mesogen.

Next, a method for driving a liquid crystal display according to an exemplary embodiment will be briefly described.

When a gate on signal is applied to the gate line121, the gate on signal is applied to the first gate electrode124a, the second gate electrode124b, and the third gate electrode124cand thus the first switching element Qa, the second switching element Qb, and the third switch element Qc are turned on. Therefore, the data voltage applied to the data line171is applied to the first sub-pixel electrode191aand the second sub-pixel electrode191b, respectively, through the first and second switching elements Qa and Qb which are turned on. In this case, the first subpixel electrode191aand the second subpixel electrode191bare applied with the same magnitude of voltage. However, the voltage applied to the second sub-pixel electrode191bis divided through the third switching element Qc which is connected to the second switching element Qb in series. Therefore, the voltage applied to the second sub-pixel electrode191bis smaller than the voltage applied to the first sub-pixel electrode191a.

Referring again toFIG. 1, one pixel area of the liquid crystal display according to the exemplary embodiment is configured to include a first region R1in which the second sub-region191a2of the first sub-pixel electrode191a, a second region R2in which the first sub-region191a1of the first sub-pixel electrode191aand the third sub-region191b1of the second sub-pixel electrode191boverlap each other, and a third region R3in which the fourth sub-region191b2of the second sub-pixel electrode191bis positioned.

The first region R1, the second region R2, and the third region R3are configured to include each four sub-regions, by a direction in which the plurality of first branch electrodes198and the plurality of second branch electrodes197extend.

An area of the second region R2may be two times as large as that of the first area R1and an area of the third region R3may be two times as large as that of the second region R2. However, an area ratio of the first region R1, the second region R2, and the third region R3may be changed.

Next, the first region R1, the second region R2, and the third region R3including one pixel area of the liquid crystal display according to the exemplary embodiment will be described with reference toFIGS. 5 to 7.

Referring toFIG. 5, in the first region R1of one pixel area of the liquid crystal display according to the exemplary embodiment is positioned on the lower panel100and the second sub-region191a2of the first sub-pixel electrode191awhich is connected to the extension193of the first sub-region191a1of the first sub-pixel electrode191aand the common electrode270positioned on the upper panel200generate an electric field. In this case, the second sub-region191a2of the first sub-pixel electrode191aincludes the cruciform stem part124and the plurality of first branch electrodes198which extend in four different directions. The plurality of first branch electrodes198may be inclined by about 40° to about 45° with respect to the gate line121. The liquid crystal molecules of the liquid crystal layer3which is positioned in the first region R1lie in four different directions, by a fringe field generated by edges of the plurality of first branch electrodes198. In more detail, the liquid crystal molecules are inclined in a direction parallel with a length direction of the plurality of first branch electrodes198.

Referring toFIG. 6, in the second region R2of one pixel area of the liquid crystal display according to the exemplary embodiment, the third sub-region191b1of the second sub-pixel electrode191bpositioned on the lower panel100and the first sub-region191a1of the first sub-pixel electrode191aoverlap each other. The liquid crystal molecules of the liquid crystal layer3are aligned by an electric field which is formed between the first sub-region191a1of the first sub-pixel electrode191apositioned between the plurality of second branch electrodes197of the third sub-region191b1of the second sub-pixel electrode191band the common electrode270and an electric field which is formed between the third sub-region191b1of the second sub-pixel electrode191band the first sub-region191a1of the first sub-pixel electrode191a, along with the electric field which is formed between the third sub-region191b1of the second sub-pixel electrode191band the common electrode270of the upper display panel200. In this case, the liquid crystal molecules are inclined in a direction parallel with a length direction of the plurality of second branch electrodes197.

Next, referring toFIG. 7, the third region R3of one pixel area of the liquid crystal display according to the exemplary embodiment generates an electric field, along with the fourth sub-region191b2of the second sub-pixel electrode191bwhich is positioned on the lower panel100and the common electrode270which is positioned on the upper panel200. In this case, the fourth sub-region191b2of the second sub-pixel electrode191bincludes the plurality of second branch electrodes197. Therefore, the liquid crystal molecules are inclined in a direction parallel with the length direction of the plurality of second branch electrodes197.

As described above, a magnitude of second voltage applied to the second sub-pixel electrode191bis smaller than that of first voltage which is applied to the first sub-pixel electrode191a.

Therefore, a strength of the electric field applied to the liquid crystal layer which is positioned in the first region R1is largest and a strength of the electric field applied to the liquid crystal layer which is positioned in the third region R3is smallest. Since an effect of the electric field of the first sub-pixel electrode191awhich is present under the second sub-pixel electrode191bis present in the second region R2, the strength of the electric field applied to the liquid crystal layer which is positioned in the second region R2is smaller than that of the electric field applied to the liquid crystal layer positioned in the first region R1and is larger than the strength of the electric field applied to the liquid crystal layer positioned in the third region R3.

As such, in the liquid crystal display according to the exemplary embodiment, one pixel area is divided into the first region R1in which the first sub-pixel electrode191ato which a relatively higher first voltage is applied is positioned, the second region R2in which a portion of the first sub-pixel electrode191aand a portion of the second sub-pixel electrode191bto which a relatively lower second voltage is applied overlap each other, having the insulating layer180bdisposed therebetween and the third region R3in which the second sub-pixel electrode191bto which the relatively lower second voltage is applied is positioned. Therefore, the strength of the electric field applied to the liquid crystal molecules corresponding to the first region the second region R2, the third region R3is different and thus an inclined angle of the liquid crystal molecules is different, such that luminance of each region is different. As such, when one pixel area is divided into three regions R2, R3having different luminance, a change in transmittance depending on gray is smoothly controlled to prevent the transmittance from being suddenly changed depending on the change in gray even in the low gray and the high gray at the side, thereby making the side visibility approximate the front visibility and accurately express the gray even in the low gray and the high gray.

Further, inFIG. 1, in the liquid crystal display according to the exemplary embodiment, the liquid crystal molecules in each region R1, R2, and R3may have different pretilt angles. In the liquid crystal display according to the exemplary embodiment, the liquid crystal molecules corresponding to the first region R1in which the second sub-region191a2of the first sub-pixel electrode191ais positioned, the second region R2in which the first sub-region191a1of the first sub-pixel electrode191aand the third sub-region191b1of the second sub-pixel electrode191boverlap each other, and the third region R3in which the fourth sub-region191b2of the second sub-pixel electrode191bis positioned may have different pretilts.FIG. 8is a diagram illustrating a pretilt angle of liquid crystal molecules in each area of the liquid crystal display according to the exemplary embodiment.

Referring toFIG. 8, in the liquid crystal display according to the exemplary embodiment, a pretilt angle θR1of the liquid crystal molecule corresponding to the first region R1has an angle larger than a pretilt angle θR2of the liquid crystal molecule corresponding to the second region R2and a pretilt angle θR3of the liquid crystal molecule corresponding to the third region R3. Further, the pretilt angle θR2of the liquid crystal molecule corresponding to the second region R2has an angle larger than the pretilt angle θR3of the liquid crystal molecule corresponding to the third region R3. Here, a difference in the pretilt angle θR1of the liquid crystal molecule corresponding to the first region R1, the pretilt angle θR2of the liquid crystal molecule corresponding to the second region R2, and the pretilt angle θR3of the liquid crystal molecule corresponding to the third region R3may be equal to or more than about 0.5° and may be equal to or less than about 1.5°.

As described above, the liquid crystal display according to the exemplary embodiment has a structure in which two pixel layers overlap each other, having the insulating layer disposed therebetween, to form a 3 division pixel. Further, the pretilt angle of the first region R1which serves as the low gray is formed to be larger than the pretilt angles of the second region R2and the third region R3to make a curve of transmittance to voltage of a liquid crystal steep and reduce a side leakage amount, thereby additionally improving visibility characteristics.

FIGS. 9A and 9Bare diagrams illustrating a pretilt angle of a first region for each sub-pixel according to an exemplary embodiment.

Referring toFIGS. 9A and 9B, the liquid crystal display according to an exemplary embodiment includes the plurality of pixels. Further, each pixel includes sub-pixels each displaying red (R), green (G), and blue (B). Further, the first regions of each sub-pixels may have different pretilt angles.

For example, in the liquid crystal display according to the exemplary embodiment, a pretilt angle θ1 of the liquid crystal molecule of the first region of the sub-pixel displaying blue may be smaller than a pretilt angle θ2 of the liquid crystal molecule of the first region of the sub-pixel displaying green. Further, the pretilt angle of the liquid crystal molecule corresponding to the first region of the sub-pixel displaying red may be formed to be equal to or similar to the pretilt angle of the liquid crystal molecule of the first region of the sub-pixel displaying green.

Further, the difference between the pretilt angle of the liquid crystal molecule corresponding to the first region of the sub-pixel displaying blue and the pretilt angle of the liquid crystal molecule corresponding to the first region of the sub-pixels each displaying red or green may be equal to or more than about 0.5° and may be equal to or less than about 1.5°.

As described above, in the liquid crystal display according to the exemplary embodiment, different pretilt angles for each RGB sub-pixel are formed. The existing liquid crystal display has a front magentish phenomenon at the time of ACC off to adjust blue gamma based on ACC tuning, in terms of vertical alignment (VA) liquid crystal characteristics

This reduces side blue luminance in the low gray and the intermediate gray after the tuning, thereby causing side yellowish badness.

Therefore, the liquid crystal display according to the exemplary embodiment, the pretilt angle of the sub-pixel displaying blue is formed to be smaller than the sub-pixel displaying red and the sub-pixel displaying green to reduce the side light leakage and minimize the front transmittance loss, thereby improving the side yellowish badness.

As such, the liquid crystal display according to the exemplary embodiment has a structure in which the pretilt angle of the pixel electrode is controlled without changing a separate design to form the differential pretilts for each pixel electrode so as to improve intermediate gray bump, high gray wash out and color shift which occur in the vertical alignment (VA) liquid crystal structure.

FIG. 10is a graph illustrating transmittance to gray of the liquid display device according to the exemplary embodiment andFIG. 11is a graph illustrating transmittance to applied voltage of the liquid display device according to the exemplary embodiment.

Referring toFIGS. 10 and 11, the liquid crystal display according to the exemplary embodiment shows the effect that the low gray area side gamma is sunk when steepness of transmittance to voltage of the first region R1(high) is more increased than that of the third region (low) to improve a level as much as about 0.01 based on a gamma distortion index (GDI). Further, in the liquid crystal display according to the exemplary embodiment, as illustrated inFIG. 11, as the pretilt is changed from 89.5° to 87°, a curved line of transmittance to voltage moves to the left, such that a slope is increased. In the liquid crystal display according to the exemplary embodiment, the lower the low gray gamma and the higher the high gray gamma, the higher the value is calculated and a method for evaluating side visibility is improved.

FIG. 12is a graph illustrating transmittance to gray of the liquid display device according to the Inventive Example and Comparative Example andFIG. 13is a graph illustrating a pretilt angle to a condition of the liquid display device according to the Inventive Example and Comparative Example.

Referring toFIGS. 12 and 13, in the case of Comparative Example (−87°) in which the high and low pretilts are identical, the side visibility is not improved to a level of 0.302 based on the GDI. However, the liquid crystal display according to the exemplary embodiment shows an effect that when the high and low pretilts are formed differently (e.g., high is 88.4° and low is 89.2°, and therefore there is a difference of 0.8°), more excellent characteristics than a target are secured as a level of 0.192 based on the GDI.

As described above, the liquid crystal display according to the exemplary embodiment has a structure in which it is possible to implement the accurate gray expression in the low gray area while making the side visibility approximate the front visibility and prevent the display quality from deteriorating.

Further, the liquid crystal display according to the exemplary embodiment has a structure in which the pretilt angle of the pixel electrode is controlled without changing a separate design to form the differential pretilts for each pixel electrode so as to improve intermediate gray bump, high gray wash out, and color shift which occur in the vertical alignment (VA) liquid crystal structure.

The foregoing exemplary embodiments are not implemented only by an apparatus and a method and therefore, may be realized by programs realizing functions corresponding to the configuration of the exemplary embodiment or recording media on which the programs are recorded