KR20080110025A - Liquid crystal display - Google Patents

Abstract

A liquid crystal display is provided to prevent the texture generation of the liquid crystal molecule, and secure the wide viewing angle. A pixel electrode(191) has a plurality of cut-outs. A first direction control electrode(176) is electrically separated from the pixel electrode. A second direction control electrode(196) is formed on the different layer from the first electrode direction. A first thin film transistor(Qa) is connected to the pixel electrode. A second thin film transistor(Qb) is connected with the second direction control electrode.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY}

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of one pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a layout view of a liquid crystal panel assembly according to an exemplary embodiment of the present invention.

4 is a layout view illustrating a first direction control electrode of the liquid crystal panel assembly illustrated in FIG. 3.

FIG. 5 is a layout view illustrating pixel electrodes of the liquid crystal panel assembly illustrated in FIG. 3. FIG.

FIG. 6 is a layout view illustrating a second direction control electrode of the liquid crystal panel assembly illustrated in FIG. 3.

FIG. 7 is a layout view illustrating the pixel electrode of FIG. 5 and the second direction control electrode of FIG. 6 together.

8, 9, and 10 are cross-sectional views of the liquid crystal panel assembly shown in FIG. 3 taken along the lines VII-VII, VII-VII and VII-VII, respectively.

FIG. 11 is a diagram illustrating a motion of liquid crystal molecules of a liquid crystal display according to an exemplary embodiment of the present invention. FIG.

The present invention relates to a liquid crystal display device.

The liquid crystal display is one of the flat panel display devices most widely used. The liquid crystal display includes two display panels on which field generating electrodes, such as a pixel electrode and a common electrode, are formed, and a liquid crystal layer interposed therebetween. Is applied to generate an electric field in the liquid crystal layer, thereby determining the orientation of the liquid crystal molecules of the liquid crystal layer and controlling the polarization of incident light to display an image.

Among them, the vertical alignment mode liquid crystal display in which the long axis of the liquid crystal molecules are arranged perpendicular to the upper and lower display panels without an electric field is applied, and thus a high contrast ratio and a wide reference viewing angle can be easily realized. Here, the reference viewing angle refers to a viewing angle having a contrast ratio of 1:10 or a luminance inversion limit angle between gray levels.

Means for implementing a wide viewing angle in a vertical alignment liquid crystal display include a method of forming a cutout in the field generating electrode and a method of forming a protrusion on the field generating electrode. Since the incision or protrusion determines the direction in which the liquid crystal molecules are inclined, the reference viewing angle may be widened by disposing the variously arranged and dispersing the inclination directions of the liquid crystal molecules in various directions.

However, the method of forming cutouts in both the pixel electrode and the common electrode requires a separate mask to pattern the common electrode, and to prevent the pigment of the color filter from exiting through the cutout of the common electrode and contaminating the liquid crystal layer. An overcoat must be formed on the color filter. In addition, the method of forming the protrusion also complicates the manufacturing method of the liquid crystal display device because a separate process for forming the protrusion or a conventional process must be modified. In addition, the vertically aligned liquid crystal display device having protrusions or cutouts strongly controls the liquid crystal molecules around the protrusions or cutouts, but the response speed of the display device decreases because the influence of the liquid crystal molecules far from the projections is weak.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a vertically aligned liquid crystal display device having a wide viewing angle without forming cutouts or protrusions on a common electrode.

In addition, the technical problem to be achieved by the present invention is to secure a wide viewing angle without the generation of texture (texture).

A liquid crystal display according to an exemplary embodiment of the present invention may include a pixel electrode having a plurality of cutouts, a first direction control electrode overlapping at least one cutout of the plurality of cutouts, and electrically separated from the pixel electrode; A second direction control electrode overlapping the first direction control electrode and formed on a different layer from the first direction control electrode, a first thin film transistor connected to the pixel electrode, and the first direction control electrode or the And a second thin film transistor connected to the second direction control electrode.

The first direction control electrode and the second direction control electrode may be electrically connected.

The display device may further include a first gate line and a data line connected to the first thin film transistor and intersecting with each other, and a second gate line connected to the second thin film transistor and intersecting the data line.

The first direction control electrode may be formed on the same layer of the same material as the data line.

The cutout may include an oblique line forming an oblique angle with the data line.

The oblique angle may be 45 degrees.

Each of the first and second direction control electrodes may include an oblique portion overlapping with an oblique portion of the cutout.

The ratio of the distance between the oblique portion of the cutout portion and the oblique portion of the second direction control electrode, the diagonal portion width of the second direction control electrode, and the diagonal portion width of the first direction control electrode is 3: 4: 12 days Can be.

The ratio of the distance between the oblique portion of the cutout portion and the oblique portion of the second direction control electrode, the diagonal portion width of the second direction control electrode, and the diagonal portion width of the first direction control electrode is 2: 2: 7 days Can be.

The second direction control electrode may be formed on the same layer as the same material as the pixel electrode.

The display device may further include an insulating layer formed between the first direction control electrode and the second direction control electrode.

The voltage of the first and second direction control electrodes may be greater than the voltage of the pixel electrode with respect to a predetermined voltage.

The display device may further include a common electrode facing the pixel electrode and the first and second direction control electrodes and having a continuous surface.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A liquid crystal display according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, and a data driver 500. ), A gray voltage generator 800, and a signal controller 600.

Referring to FIG. 1, the liquid crystal panel assembly 300, when viewed in an equivalent circuit, includes a plurality of signal lines (not shown) and a plurality of pixels PX connected thereto and arranged in a substantially matrix form. ). On the other hand, in the structure shown in FIG. 2, the liquid crystal panel assembly 300 includes lower and upper panels 100 and 200 facing each other and a liquid crystal layer 3 interposed therebetween.

The liquid crystal panel assembly 300 includes a plurality of signal lines and a plurality of pixels PX connected to the signal lines and arranged in a substantially matrix form when viewed in an equivalent circuit. On the other hand, in the structure shown in FIG. 2, the liquid crystal panel assembly 300 includes lower and upper panels 100 and 200 facing each other and a liquid crystal layer 3 interposed therebetween.

Referring to FIG. 2, the signal line includes a plurality of gate lines G _i-1 , which transfer gate signals (also referred to as “scan signals”). G _i ) and a plurality of data lines D _j and D _{j + 1} for transmitting a data signal. Gate line (G _i-1 , G _i ) extend substantially in the row direction and are substantially parallel to each other, and the data lines D _j and D _{j + 1} extend substantially in the column direction and are substantially parallel to each other.

Each pixel PX, for example, the pixel PX connected to the gate lines G _i and G _i-1 and the data lines D _j and D _{j + 1} , may include the first and second switching elements Qa and Qb. ), A first liquid crystal capacitor Clca, a second liquid crystal capacitor Clcb, and a direction control capacitor Cdce.

The first and second switching elements Qa and Qb are three-terminal elements such as thin film transistors provided in the lower panel 100.

The control terminal of the first switching element Qa is connected to the front gate line G _i-1 , the input terminal is connected to the left data line D _j , and the output terminal is connected to the direction control electrode 176. It is connected.

The control terminal of the second switching element Qb is connected to the rear gate line G _i , the input terminal is connected to the right data line D _{j + 1} , and the output terminal is connected to the pixel electrode 191. It is.

The first and second liquid crystal capacitors Clca and Clcb have direction control electrodes 176 / pixel electrodes 191 of the lower panel 100 and a common electrode 270 of the upper panel 200 as two terminals, and control the direction. The liquid crystal layer 3 between the electrode 176 / pixel electrode 191 and the common electrode 270 functions as a dielectric. The common electrode 270 is formed on the entire surface of the upper panel 200 and receives a common voltage Vcom.

The liquid crystal layer 3 has negative dielectric anisotropy, and the liquid crystal molecules of the liquid crystal layer 3 may be aligned such that their major axes are perpendicular to the surfaces of the two display panels in the absence of an electric field. Unlike in FIG. 2, the common electrode 270 may be provided in the lower panel 100. In this case, at least one of the two electrodes 191 and 270 may be formed in a linear or bar shape.

The direction control capacitor Cdce is formed by overlapping the pixel electrode 191 and the direction control electrode 176 of the lower panel 100 with an insulator interposed therebetween.

On the other hand, in order to implement color display, each pixel PX uniquely displays one of the primary colors (spatial division) or each pixel PX alternately displays the primary colors over time (time division). The desired color is recognized by the spatial and temporal sum of these primary colors. Examples of the primary colors include three primary colors such as red, green, and blue. 2 illustrates that each pixel PX includes a color filter CF representing one of the primary colors in an area of the upper panel 200 as an example of spatial division. Unlike FIG. 2, the color filter CF may be formed above or below the subpixel electrodes PEa and PEb of the lower panel 100.

At least one polarizer (not shown) for polarizing light is attached to an outer surface of the liquid crystal panel assembly 300.

Next, the liquid crystal panel assembly 300 will be described in detail with reference to FIGS. 3 to 10.

3 is a layout view of a liquid crystal panel assembly according to an exemplary embodiment of the present invention, FIG. 4 is a layout view showing a first direction control electrode of the liquid crystal panel assembly illustrated in FIG. 3, and FIG. 5 is a liquid crystal shown in FIG. 3. FIG. 6 is a layout view illustrating a pixel electrode of the display panel assembly, and FIG. 6 is a layout view illustrating a second direction control electrode of the liquid crystal panel assembly illustrated in FIG. 3, and FIG. 7 is a pixel electrode of FIG. 5 and a second direction control of FIG. 6. 8, 9, and 10 are cross-sectional views of the liquid crystal panel assembly shown in FIG. 3 taken along the line VII-VII, VII-VII, and VII-VII, respectively.

3 to 10, the liquid crystal panel assembly according to the exemplary embodiment of the present invention includes a lower panel 100, an upper panel 200, a liquid crystal layer 3, and polarizers 12 and 22.

First, the lower panel 100 will be described in detail.

A plurality of gate lines 121p and 121c and a plurality of storage electrode lines 131 are formed on an insulating substrate 110 made of transparent glass or plastic.

The gate lines 121p and 121c mainly extend in the horizontal direction. Each gate line 121p and 121c includes a plurality of first and second gate electrodes 124p and 124c and wide end portions 129p and 129c for connection with another layer or gate driver 400. do.

The storage electrode line 131 extends substantially in parallel with the gate line 121 and includes a storage electrode 137 extending up and down. However, the shape and arrangement of the storage electrode line 131 may be modified in various ways.

A gate insulating layer 140 made of silicon nitride (SiNx) or silicon oxide (SiOx) is formed on the gate lines 121p and 121c and the storage electrode line 131.

First and second island semiconductors 154p and 154c made of hydrogenated amorphous silicon (amorphous silicon is abbreviated a-Si) or polysilicon are formed on the gate insulating layer 140. .

First island-type ohmic contacts (not shown) and second island-type ohmic contacts 163 and 165c are formed on the first and second island-like semiconductors 154p and 154c. The ohmic contacts 163 and 165c may be made of a material such as n + hydrogenated amorphous silicon in which n-type impurities such as phosphorus are heavily doped, or may be made of silicide.

A plurality of data lines 171a and 171b and a plurality of first and second drain electrodes 175p and 175c are formed on the ohmic contacts 163 and 165c and the gate insulating layer 140. have.

The data lines 171a and 171b mainly extend in the vertical direction and intersect the gate lines 121p and 121c. Each data line 171a and 171b includes a plurality of source electrodes 173 extending toward the first and second gate electrodes 124p and 124. The data lines 171a and 171b also include wide end portions 179a and 179b for connection with other layers or the data driver 400.

The first and second drain electrodes 175p and 175c are separated from each other and also separated from the data lines 171a and 171b.

The source electrode 173 and the first drain electrode 175p of the left data line 171a are positioned on the first island semiconductor 154p, and the first drain electrode 175p is a source electrode of the left data line 171a. And a first end control electrode 176 connected to the rod-shaped end facing the 173.

The source electrode 173 and the second drain electrode 175c of the right data line 171b are positioned on the second island-type semiconductor 154c, and the second drain electrode 175c is a source electrode of the right data line 171b. 173) and the wide end located opposite the rod-shaped end.

The first gate electrode 124p, the source electrode 173 of the left data line 171a, and the first drain electrode 175p together with the first island semiconductor 154p include one first thin film transistor (TFT). (Qa), a channel of the thin film transistor is formed in the first island-shaped semiconductor 154p between the source electrode 173 and the first drain electrode 175p of the left data line 171a. In addition, the second gate electrode 124c, the source electrode 173 and the second drain electrode 175c of the right data line 171b together with the second island semiconductor 154c may include one second thin film transistor, A channel (Qb) of the thin film transistor is formed in the second island-like semiconductor 154c between the source electrode 173 and the second drain electrode 175c of the right data line 171b.

The ohmic contacts 163 and 165c exist only between the semiconductors 154p and 154c below and the data lines 171 and the drain electrodes 175p and 175c thereunder and lower the contact resistance therebetween. The semiconductors 154p and 154c have portions exposed between the source electrodes 173 and the drain electrodes 175p and 175c and not covered by the data lines 171a and 171b and the drain electrodes 175p and 175c.

A passivation layer 180 is formed on the data lines 171a and 171b, the drain electrodes 175p and 175c, and the exposed semiconductors 154p and 154c. The passivation layer 180 may be made of an organic insulator, and may have a flat surface. The organic insulator may have photosensitivity and its dielectric conctant is preferably about 4.0 or less. However, the passivation layer 180 may have a double layer structure of the lower inorganic layer and the upper organic layer so as not to damage the exposed portions of the semiconductors 154p and 154c while maintaining excellent insulating properties of the inorganic insulator or the organic layer.

The passivation layer 180 is formed with a plurality of contact holes 182a and 182b exposing end portions 179a and 179b of the data line 171. In the protective film, a plurality of contact holes 185 and 187 exposing the second drain electrode 175c and the first direction control electrode 176 are formed. In addition, a plurality of contact holes 181p and 181c exposing end portions 129 of the gate lines 121p and 121c are formed in the passivation layer 180 and the gate insulating layer 140.

A plurality of pixel electrodes 191, a second direction control electrode 196, and a plurality of contact assistants 81p, 81c, and 82 are formed on the passivation layer 180. They may be made of a transparent conductive material such as ITO or IZO or a reflective metal such as aluminum, silver, chromium or an alloy thereof.

The first direction control electrode 176 is connected to the first drain electrode 175p to receive a data voltage from the first drain electrode 175p.

The second direction control electrode 196 is physically and electrically connected to the first direction control electrode 176 through the contact hole 187 to receive a data voltage from the first direction control electrode 176. The first and second direction control electrodes 176 and 196 to which the data voltage is applied generate an electric field together with the common electrode 270 of the common electrode display panel 200 to which the common voltage is applied. By this, the direction of the liquid crystal molecules of the liquid crystal layer 3 between the two electrodes is determined. The polarization of light passing through the liquid crystal layer varies according to the direction of the liquid crystal molecules determined as described above. The first and second direction control electrodes 176 and 196 and the common electrode 270 form a first liquid crystal capacitor Clca to maintain an applied voltage even after the thin film transistor is turned off.

The pixel electrode 191 is physically and electrically connected to the second drain electrode 175c through the contact hole 185 to receive a data voltage from the second drain electrode 175p. The pixel electrode 191 to which the data voltage is applied generates an electric field together with the common electrode 270 of the common electrode display panel 200 to which the common voltage is applied, thereby creating a liquid crystal layer 3 between the two electrodes. Direction of the liquid crystal molecules. The polarization of light passing through the liquid crystal layer varies according to the direction of the liquid crystal molecules determined as described above. The pixel electrode 191 and the common electrode 270 form a second liquid crystal capacitor Clcb to maintain the applied voltage even after the thin film transistor is turned off.

The first and second direction control electrodes 176 and 196 and the pixel electrode 191 form a storage capacitor that enhances the voltage holding capability of the liquid crystal capacitor and the storage electrode line 131 including the storage electrode 137.

The direction control capacitor Csts is formed by overlapping the first and second direction control electrodes 176 and 196 and the pixel electrode 191 with each other.

5 and 7, each pixel electrode 191 has four peripheral sides substantially parallel to the gate lines 121p and 121c or the data lines 171p and 171c and chamfered at the right corner. ) It is approximately square shape. The hypotenuse of the pixel electrode 191 forms an angle of about 45 ° with respect to the gate lines 121p and 121c.

The pixel electrode 191 includes a plurality of lower cutouts 91a. 92a, 93a, 94a, 95a, 96a, and 97a, a plurality of upper cutouts 91b, 92b, 93b, 94b, 95b, 96b, and 97b, and a first portion. The center cutout 98, the second center cutout 99a, and the horizontal cutout 99b are formed, and the pixel electrode 191 is divided into a plurality of regions by the cutouts 91a-99b. Divided.

The cutouts 91a-99b are almost inverted symmetric with respect to the sustain electrode line 131. The lower and upper cutouts 91a-97b extend from the left side of the pixel electrode 191 to the right and are positioned at the upper half and the lower half of the storage electrode line 131, respectively. The lower and upper cutouts 91a-97b extend perpendicular to each other at an angle of about 45 ° with respect to the gate lines 121p and 121c.

The first central cutout 98 includes a pair of oblique portions. The horizontal portion of the pair of diagonal lines extends substantially parallel to the lower and upper cutouts 91a-97b toward the left side of the pixel electrode 191 in the horizontal portion.

The second central cutout 99a extends along the storage electrode line 131 and has an inlet at the left side. The inlet of the second central cutout 99a has a pair of hypotenuses approximately parallel to the lower and upper cutouts 91a-97b, respectively.

The horizontal cutout 97b is connected to the lower and upper cutouts 91a-97b.

6 and 7, the second direction control electrode 196 includes lower diagonal portions 61a, 62a, 63a and 64a and upper diagonal portions 61b, 62b, 63b and 64b, and includes lower and upper portions. Diagonal portions 61a to 64b are connected to each other. The lower and upper oblique portions 61a-64b are inserted into portions 91a, 91b, 93a, 93b, 95a, 95b, 97a and 97b of the cutouts 91a-99b of the pixel electrode 191.

Referring to FIG. 4, the first direction control electrode 176 includes lower diagonal portions 71a, 72a, 73a, and 74a and upper diagonal portions 71b, 72b, 73b, and 74b, and includes lower and upper diagonal portions ( 71a-74b are connected to each other. The lower and upper diagonal portions 71a-74b overlap the lower and upper diagonal portions 61a-64b of the second direction control electrode 196.

Referring to FIG. 9, the width D of the lower and upper oblique portions 71a to 74b of the first direction control electrode 176 is the width C of the lower and upper cutouts 91a to 97b of the pixel electrode 191. The width C of the lower and upper cutouts 91a-97b of the pixel electrode 191 is greater than the width B of the lower and upper diagonal lines 61a-64b of the second direction control electrode 196. The distance A and the second direction control electrode 196 between the lower and upper cutouts 91a-97b of the pixel electrode 191 and the lower and upper diagonal lines 61a-64b of the second direction control electrode 196. The ratio of the width B of the lower and upper diagonal portions 61a to 64b and the width D of the lower and upper diagonal portions 71a to 74b of the first direction control electrode 176 is 3: 4: 12 or 2 May be 2: 2.

The contact auxiliary members 81p, 81c, 82a, and 82b have the end portions 129 of the gate lines 121 and the end portions of the data lines 171a and 171b through the contact holes 181p, 181c, 182a, and 182b, respectively. 179a, 179b). The contact auxiliary members 81p, 81c, 82a, and 82b adhere to the end portions 129p and 129c of the gate lines 121p and 121c and the end portions 179a and 179b of the data lines 171a and 171b and the external device. Complement and protect them.

Next, the upper panel 200 will be described.

A light blocking member 220 is formed on the substrate 210. The light blocking member 220 is also referred to as a black matrix and defines a plurality of opening regions facing the pixel electrode 191, and prevents light leakage between the pixel electrodes 191.

A plurality of color filters 230 are also formed on the substrate 210 and are arranged to almost fit into the opening region surrounded by the light blocking member 220. The color filter 230 may extend in the vertical direction along the pixel electrode 190 to form a stripe. Each color filter 230 may display one of primary colors such as three primary colors of red, green, and blue.

The common electrode 270 is formed on the color filter 230 and the light blocking member 220. Since the cutout is not required in the common electrode 270, the common electrode 270 has a continuous surface. In addition, no projection is necessary for the common electrode 270. The common electrode 270 is preferably made of a transparent conductive conductor such as ITO or IZO.

Alignment layers 11 and 21 are applied on the inner surfaces of the display panels 100 and 200, and polarizers are disposed on the outer surfaces of the display panels 100 and 200. 12, 22) are attached.

The liquid crystal display may include a polarizer 12 and 22, display panels 100 and 200, and a backlight unit (not shown) that supplies light to the liquid crystal layer 3.

The liquid crystal layer 3 has negative dielectric anisotropy, and the liquid crystal molecules of the liquid crystal layer 3 are aligned such that their major axes are perpendicular to the surfaces of the two display panels 100 and 200 in the absence of an electric field. Therefore, incident light does not pass through the quadrature polarizers 12 and 22 and is blocked.

Referring back to FIG. 1, the gray voltage generator 800 generates a total gray voltage related to the transmittance of the pixel PX or a limited number of gray voltages (hereinafter referred to as a “reference gray voltage”). The reference gray voltage may include having a positive value and a negative value with respect to the common voltage Vcom.

A gate driver 400, a gate line of the gate signal (Vg) which is a combination of a liquid crystal panel assembly 300, a gate line is connected to the (G), the gate-on voltage (Von) and the gate off voltage (Voff) of the _(i- G ₁ , G _i ).

The data driver 500 may include data lines D _j , of the liquid crystal panel assembly 300. It is connected to D _{j + 1} and selects a gray voltage from the gray voltage generator 800 and applies it to the data lines D _j and D _{j + 1} as the data voltage Vd. However, when the gray voltage generator 800 does not provide all the gray voltages but provides only a limited number of reference gray voltages, the data driver 500 divides the reference gray voltages to generate a desired data voltage.

The signal controller 600 controls the gate driver 400, the data driver 500, and the like.

Next, the operation of the liquid crystal display will be described in detail.

The signal controller 600 receives input image signals R, G, and B and an input control signal for controlling the display thereof from an external graphic controller (not shown). The input image signals R, G, and B contain luminance information of each pixel PX, and the luminance is a predetermined number, for example, 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ), or 64 (= 2 ⁶ ) It has gray. Examples of the input control signal include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock signal MCLK, and a data enable signal DE.

The signal controller 600 properly processes the input image signals R, G, and B according to operating conditions of the liquid crystal panel assembly 300 based on the input image signals R, G, and B and the input control signal, and controls the gate. After generating the signal CONT1 and the data control signal CONT2, the gate control signal CONT1 is sent to the gate driver 400, and the data control signal CONT2 and the processed image signal DAT are transmitted to the data driver 500. ) And the sustain electrode control signal CONT3 to the sustain electrode driver 700.

According to the data control signal CONT2 from the signal controller 600, the data driver 500 receives the digital image signal DAT for the pixel PX in one row and corresponds to each digital image signal DAT. By converting the digital image signal DAT into an analog data voltage by selecting the gray scale voltage, the corresponding data line D _j , D _{j + 1} ).

The gate driver 400 applies the gate-on voltage Von to the front gate line G _i-1 according to the gate control signal CONT1 from the signal controller 600 to the gate line G _i-1 . The connected first switching element Qa is turned on. Then, the data voltage applied to the left data line D _j is applied to the first and second direction control electrodes 176 and 196 through the turned-on first switching element Qa. The difference between the data voltage applied to the second direction control electrodes 176 and 196 and the common voltage Vcom is shown as the charging voltage of the first liquid crystal capacitor Clca.

Thereafter, when the first switching element Qa is turned off, the gate driver 400 applies the gate-on voltage Von to the rear gate line G _i-1 according to the gate control signal CONT1 from the signal controller 600. applied to the thus turns on the second switching element (Qb) connected to the gate line (G _i). Then, the data voltage applied to the right data line D _{j + 1} is applied to the pixel electrode 191 through the turned-on second switching element Qb. The difference between the data voltage applied to the pixel electrode 191 and the common voltage Vcom is shown as the charging voltage of the second liquid crystal capacitor Clcb.

When the first switching elements Qa, Qb, and Qd are turned off, the first and second direction control electrodes 176 and 196 are in a floating state. However, since the first and second direction control electrodes 176 and 196 form a capacitor Cdce with the pixel electrode 191, the first and second direction control electrodes 176 according to the voltage change of the pixel electrode 191. , 196) also changes. In the point inversion driving, the polarities of the data voltages applied to the first and second thin film transistors Qa and Qb facing in the diagonal direction are the same. Therefore, the charging voltage of the first liquid crystal capacitor Clca is increased to the voltage at which the second liquid crystal capacitor Clcb is dropped in accordance with the direction control capacitor Cdce. That is, the average voltage of the first and second direction control electrodes 176 and 196 with respect to the common voltage Vcom may be higher than the average voltage of the pixel electrode 191 with respect to the common voltage Vcom.

When a voltage difference is generated between the common electrode 270, the pixel electrode 191, and the direction control electrode 195, a main electric field (electric field) substantially perpendicular to the surfaces of the display panels 100 and 200 is generated. In response to the electric field, the liquid crystal molecules attempt to change their long axis to be perpendicular to the direction of the main electric field.

The cutouts 91a-99b and the sides of the pixel electrode 191 distort the electric field to produce horizontal components that determine the inclination direction of the liquid crystal molecules. The horizontal component of the main electric field is substantially perpendicular to the sides of the cutouts 91a-99b and the sides of the pixel electrode 191, and faces toward or inside the pixel electrode 191 according to the polarity of the voltage of the pixel electrode 191. For example, when the voltage of the pixel electrode 191 is greater than the common voltage Vcom, the horizontal component faces the outside of the pixel electrode 191.

Meanwhile, since there is a voltage difference between the first and second direction control electrodes 176 and 196 and the pixel electrode 191, a negative electric field is generated accordingly, and the negative electric field has a horizontal component substantially parallel to the horizontal component of the main electric field. As described above, since the voltages of the first and second direction control electrodes 176 and 196 with respect to the common voltage Vcom are higher than the voltage of the pixel electrode 191, the horizontal component of the negative electric field is opposite to the horizontal component of the main electric field. Its strength is also stronger than the horizontal component of the main electric field. Therefore, the net horizontal component of the electric field at the cutouts 91a, 91b, 93a, 93b, 95a, 95b, 97a, 97b of the pixel electrode 191 overlapping the first and second direction control electrodes 176, 196 The remaining cutouts 92a, 92b, 94a, 94b, 96a, 96b, 98, 99a adjacent thereto or the horizontal component in the side of the pixel electrode 191 are in the same direction.

As described above, the cutouts 91a-99b divide the pixel electrode 191 into a plurality of regions, and each region has two major edges parallel to each other. Most of the liquid crystal molecules on each region are perpendicular to the periphery and are subjected to the force of the electric field horizontal component in the direction as described above, so that the inclination direction is approximately four directions. As described above, when the liquid crystal molecules are inclined in various directions, the reference viewing angle of the liquid crystal display is increased.

This process is repeated in units of one horizontal period (also referred to as "1H" and equal to one period of the horizontal sync signal Hsync and the data enable signal DE), in order for all the gate lines G in order. The image signal of one frame is displayed by applying a data signal to all the pixels PX by applying the gate-on voltage Von.

When one frame ends, the state of the inversion signal RVS applied to the data driver 500 is controlled so that the next frame starts and the polarity of the data signal applied to each pixel PX is opposite to the polarity of the previous frame. "Invert frame"). At this time, even within one frame, the polarity of the data signal flowing through one data line is changed in units of rows according to the characteristics of the inversion signal RVS ("row inversion").

A motion of the liquid crystal molecules in the liquid crystal display according to the exemplary embodiment of the present invention will now be described in detail with reference to FIG. 11.

FIG. 11 is a diagram illustrating a liquid crystal molecule moving in the liquid crystal display according to the exemplary embodiment of the present invention.

Referring to FIG. 11, the second direction control electrode 196 and the first direction control electrode 176 inserted into the cutout of the pixel electrode 191 overlap each other. In the portions of the first and second direction control electrodes 176 and 196 formed in the double, the horizontal component of the negative electric field in the opposite direction to the horizontal component of the main electric field may have a stronger intensity than the horizontal component of the main electric field. . Therefore, the liquid crystal molecules are effectively controlled in this area so that no texture occurs.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the present invention, a wide viewing angle of the liquid crystal display can be secured without forming cutouts or protrusions on the common electrode, and texture of the liquid crystal molecules can be prevented.

Claims (13)

A pixel electrode having a plurality of cutouts, A first direction control electrode overlapping at least one of the plurality of cutouts and electrically separated from the pixel electrode; A second direction control electrode overlapping the first direction control electrode and formed on a different layer from the first direction control electrode; A first thin film transistor connected to the pixel electrode, and A second thin film transistor connected to the first direction control electrode or the second direction control electrode Liquid crystal display comprising a. In claim 1, And the first direction control electrode and the second direction control electrode are electrically connected to each other. In claim 2, A first gate line and a data line connected to the first thin film transistor and intersecting with each other, and And a second gate line connected to the second thin film transistor and crossing the data line. In claim 3, And the first direction control electrode is formed on the same layer of the same material as the data line. In claim 3, And the cutout portion includes an oblique portion that forms an oblique angle with the data line. In claim 5, The oblique angle is 45 ° liquid crystal display device. In claim 5, Each of the first and second direction control electrodes includes an oblique portion overlapping with an oblique portion of the cutout portion. In claim 7, The ratio of the distance between the oblique portion of the cutout portion and the oblique portion of the second direction control electrode, the diagonal width of the second direction control electrode, and the diagonal width of the first direction control electrode is 3: 4: 12. Liquid crystal display. In claim 7, The ratio of the distance between the oblique portion of the cutout portion and the oblique portion of the second direction control electrode, the diagonal portion width of the second direction control electrode, and the diagonal portion width of the first direction control electrode is 2: 2: 7 Liquid crystal display. In claim 1, And the second direction control electrode is formed on the same layer with the same material as the pixel electrode. In claim 1, And an insulating film formed between the first direction control electrode and the second direction control electrode. In claim 1, The voltage of the first and second direction control electrodes is greater than the voltage of the pixel electrode with respect to a predetermined voltage. In claim 1, And a common electrode facing the pixel electrode and the first and second direction control electrodes and having a continuous surface.

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