KR20080056887A - Liquid crystal display device and driving method thereof - Google Patents

Abstract

An LCD device and a driving method thereof are provided to adjust easily the transmittance ratio of ECB(Electrically Controlled Birefringence) sub-pixels by reducing the difference of ranges and magnitudes between driving voltages of ECB and RGB sub-pixels. An LCD(Liquid Crystal Display) device includes an LCD panel(210) and a timing controller(260). The LCD panel includes plural data and gate lines and quad typed pixels having R,G,B sub-pixels, which display images based on a first turning point of a transmittance in a front viewing angle, and sub-pixels for viewing angle control with a second turning point of the transmittance at a side viewing angle. The timing controller, which includes plural digital data for viewing angle control corresponding to transmittance based on the first and second turning points, compares an average luminance value of digital video data to be displayed in the R,G,B sub-pixels with a reference value, and selects the digital data for viewing angle control according to the comparison result. The first transmittance of the second turning point is mapped on the second transmittance of the first turning point. A third transmittance of the second turning point is mapped on a fourth transmittance of the first turning point. The first and fourth transmittances are higher than the third and second transmittances, respectively.

Description

Liquid Crystal Display Device and Driving Method Thereof}

1 illustrates a quad type pixel structure.

2 is a view for explaining a principle of implementing a narrow viewing angle using an ECB subpixel.

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

FIG. 4 is a plan view illustrating a quad type pixel structure of the liquid crystal display panel 210 of FIG. 3.

5A and 5B are cross-sectional views taken along the line II ′ of FIG. 4 to illustrate the wide viewing angle mode.

6A and 6B are graphs showing transmission characteristics in the wide viewing angle mode.

7A and 7B are cross-sectional views taken along the line II ′ of FIG. 4 to illustrate the narrow viewing angle mode;

8A and 8B are graphs showing transmission characteristics in the narrow viewing angle mode.

FIG. 9 is a diagram illustrating in detail the timing controller of FIG. 3 for adjusting ECB data down / up according to an average luminance value of RGB data in a narrow viewing angle mode; FIG.

10 is a configuration diagram of a data sorter in FIG. 9.

11 shows TV curves at the front viewing angle of an RGB subpixel and the side viewing angle of an ECB subpixel (40-50 degrees).

12 shows grayscale curves and gray mapping of RGB subpixels and ECB subpixels at the side viewing angle (40-50 degrees).

13 is a flowchart illustrating a method of driving a liquid crystal display according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

111: lower substrate 112: gate line

115: data line 117: pixel electrode

119a, 119b, 519a: Contact hole 121: Upper board

122: black matrix 123: color filter pattern

124: common electrode 125: common line

129: overcoat layer 131: liquid crystal layer

132: liquid crystal molecules 161: first polarizing plate

162: second polarizing plate 210: liquid crystal display panel

220: data driver 230: gate driver

240: gamma reference voltage generator 250: common voltage generator

260: timing controller 262: luminance detector

264: average value calculation unit 266: mapping unit

268: Data Sorter 268-2: Mixer

268-4: Data Sorter 270: User Interface

517: ECB pixel electrode 524: ECB common electrode

525: ECB common line

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display and a driving method thereof, and in particular, by extending the driving voltage range of the ECB subpixel for controlling the viewing angle and increasing the driving voltage size. The present invention relates to a liquid crystal display device and a driving method thereof capable of achieving desired luminance for viewing angle control by eliminating optical interference.

In general, a liquid crystal display device displays an image by injecting a liquid crystal between two substrates, and applying an electric field to the liquid crystal through an electrode formed on the substrate surface to adjust the light transmittance of the liquid crystal.

Such liquid crystal displays are roughly classified into a vertical electric field application type and a horizontal electric field application type according to the direction of the electric field for driving the liquid crystal.

First, the vertical field application type liquid crystal display device drives the liquid crystal by a vertical electric field formed between the pixel electrode and the common electrode disposed to face the upper and lower substrates. To this end, the vertical field-applied liquid crystal display includes a thin film transistor array substrate (bottom plate) and a color filter array substrate (top plate) bonded to each other, a spacer for maintaining a constant cell gap between the two substrates, and the cell gap. The liquid crystal layer filled in is provided. The thin film transistor array substrate includes a gate line and a data line for defining a pixel unit, a thin film transistor formed at an intersection of the gate line and the data line, a pixel electrode formed for each pixel unit, and an alignment layer coated thereon for liquid crystal alignment. It consists of. The color filter array substrate includes a common electrode forming a vertical electric field with the pixel electrode, a color filter for color implementation, a black matrix for preventing light leakage, and an alignment layer coated thereon for liquid crystal alignment.

Next, the horizontal field application type liquid crystal display drives the liquid crystal by a horizontal electric field between the pixel electrode and the common electrode arranged side by side on the lower substrate. To this end, a horizontal field application liquid crystal display device includes a thin film transistor array substrate (bottom plate) and a color filter array substrate (top plate) bonded together to face each other, a spacer for keeping a cell gap constant between the two substrates, and the cell. And a liquid crystal layer filled in the gap. The thin film transistor array substrate is composed of a plurality of signal lines and thin film transistors for forming a horizontal electric field in pixels, and an alignment film coated thereon for liquid crystal alignment. The color filter array substrate is composed of a color filter for color implementation and a black matrix for preventing light leakage, and an alignment film coated thereon for liquid crystal alignment. Since the horizontal field type liquid crystal display device has a small change in birefringence of the liquid crystal in the viewing angle direction, the horizontal field type liquid crystal display device has an advantage of superiority in view angle in comparison with the vertical field type liquid crystal display device described above.

On the other hand, the wide viewing angle characteristics of the horizontal field type liquid crystal display device may cause side effects such as privacy exposure and personal information leakage when using a computer or performing security tasks such as banking for personal reasons.

Recently, instead of forming the pixels formed in the liquid crystal display panel into stripe type RGB subpixels for security or privacy, one viewing angle control subpixel (hereinafter referred to as "ECB subpixel") and three RGB subpixels are described. A liquid crystal display device having a quad type including the above has been proposed. According to this liquid crystal display device, switching between the wide viewing angle mode and the narrow viewing angle mode can be arbitrarily adjusted.

1 illustrates a quad type pixel structure.

As shown in FIG. 1, the quad type pixel includes R subpixels, G subpixels, B subpixels, and ECB subpixels, and R and G subpixels are horizontally formed on the upper side, and ECB and B The subpixels are formed horizontally below.

Vertically located R and ECB subpixels and horizontally and vertically positioned G and B subpixels are connected to two different data lines DL, each having an upper R subpixel and a lower vertical line. The commonly located ECB subpixels are commonly connected to one data line DL, and the upper G subpixel and the B subpixels vertically located below are commonly connected to the other data line DL.

The horizontally located R and G subpixels and the G and B subpixels vertically and horizontally positioned to each other are connected to two different gate lines GL, and the R and G subpixels horizontally positioned on the upper side are horizontally positioned. The pixels are commonly connected to one gate line GL, and the ECB subpixels and the B subpixels located horizontally below are commonly connected to the other gate line GL.

The ECB subpixels included in the quad type pixels are turned off when driven in the wide viewing angle mode and turned on when driven in the narrow viewing angle mode. When driving in the narrow viewing angle mode, the ECB subpixel expresses luminance only in the lateral viewing angle direction, not in the omnidirectional direction, thereby reducing the contrast ratio in the lateral viewing angle direction.

2 is a view for explaining a principle of implementing a narrow viewing angle using an ECB subpixel.

The principle of implementing the narrow viewing angle is to detect the luminance of the R, G, and B subpixels, and to compensate for the luminance deviation between the quad type pixels by adjusting the luminance of the ECB subpixels. It is to make the luminance of? For example, as shown in FIG. 2, when the detected luminance values of the R, G, and B subpixels are smaller than a predetermined reference value, the luminance of the ECB subpixels is increased to increase the overall luminance of the quad type pixels to the reference value. (A). On the other hand, when the detected luminance values of the R, G, and B subpixels are larger than the predetermined reference value, the luminance of the ECB subpixels is lowered to reduce the overall luminance of the quad type pixels to the reference value (B).

However, in order to make the brightness between all quad type pixels similar in the lateral viewing angle direction by adjusting the brightness of the ECB subpixels, the ECB subpixel voltage is accurately implemented to a predetermined value according to the luminance values of the R, G, and B subpixels. Should be. The ECB subpixel voltage used for the conventional viewing angle control has a very narrow voltage range of 0 V < Vsubpxl-Vcom < In contrast, adjacent R, G, and B subpixels have a very wide voltage range of 0 V < Vsubpxl-Vcom | < 7.5 V, and the absolute size is much larger than the ECB subpixel voltage. For this reason, ECB subpixels are insensitive to voltage variations of adjacent R, G, and B subpixels, and thus receive crosstalk due to high voltage variations of adjacent R, G, and B subpixels.

As a result, ECB subpixels used for conventional viewing angle control have a very narrow driving voltage range and a small absolute size, and thus easily affect voltage variations of adjacent R, G, and B subpixels having a relatively large driving voltage range and a large absolute size. By receiving optical interference, there is a problem in that the desired luminance for the viewing angle control is not achieved.

Accordingly, an object of the present invention is to extend the driving voltage range of an ECB subpixel for viewing angle control and to increase the driving voltage size to exclude the optical interference caused by the voltage variation of adjacent R, G, and B subpixels, thereby controlling the viewing angle. The present invention provides a liquid crystal display and a driving method thereof capable of achieving desired luminance.

In order to achieve the above object, a liquid crystal display according to an exemplary embodiment of the present invention includes R, G, and B subs which display images by crossing a plurality of data lines and a plurality of gate lines and having a first inflection point of transmittance at a front viewing angle. A liquid crystal display panel having a quad type pixel including a pixel and a viewing angle control subpixel having a second inflection point of transmittance at a side viewing angle different from the front viewing angle; And a plurality of pieces of digital viewing angle control data corresponding to transmittances present in the downward inclination section of the second inflection point mapped to transmittances of the R, G, and B subpixels in the upward inclination section of the first inflection point. A timing controller for selecting the digital viewing angle control data according to a comparison result of an average luminance value of the digital video data to be displayed on the R, G, and B subpixels with a predetermined reference value; The first transmittance of the downward slope of the second inflection point is mapped to the second transmittance of the upward slope of the first inflection point, and the second transmittance of the downward slope of the second inflection point is the upward slope of the first inflection point Mapped to a fourth transmittance of the first transmittance is higher than the third transmittance and the fourth transmittance is higher than the second transmittance, the average luminance value of the digital video data and the luminance value of the selected digital viewing angle control data And a difference between the sum and the reference value is equal to or less than a preset threshold.

The timing controller analyzes the gray level of the digital video data to be displayed on the R, G, and B subpixels for each pixel, and then uses the analyzed gray level to display the digital video data to be displayed on the R, G, and B subpixels. A brightness detector for detecting the brightness values of the light source; An average value calculator configured to calculate an average luminance value of digital video data to be displayed on the R, G, and B subpixels using the detected luminance values; And a mapping unit for mapping the calculated average luminance values of the digital video data to be displayed on the R, G, and B subpixels with any one of the listed plurality of digital viewing angle control data by comparing with the reference value.

The mapping unit may be implemented as a lookup table.

The timing controller may further include a data aligner for mixing and rearranging the digital viewing angle control data selected through the mapping and the digital video data to be displayed on the R, G, and B subpixels.

The data sorter may include: a mixer for mixing the digital viewing angle control data selected through the mapping and digital video data to be displayed in the R, G, and B subpixels; And a data alignment unit for rearranging the mixed digital data according to the quad type pixel structure.

A data driver converting the digital viewing angle control data and the digital video data selected by the timing controller into data voltages and supplying the data voltages to the data lines; And a gate driver supplying scan pulses synchronized with the data voltage to the gate lines.

In order to achieve the above object, a liquid crystal display according to an exemplary embodiment of the present invention includes a first subpixel displaying an image by having a first inflection point of transmittance at a front viewing angle; A second subpixel having a second inflection point of transmittance at the side viewing angle different from the front viewing angle; And the second subpixel based on a mapping relationship between transmittances of the second subpixels in the downward slope period of the second inflection point and transmittances of the first subpixels in the upward slope period of the first inflection point. A viewing angle control data generating circuit for generating data to be displayed; The first transmittance of the downward slope of the second inflection point is mapped to the second transmittance of the upward slope of the first inflection point, and the second transmittance of the downward slope of the second inflection point is the upward slope of the first inflection point Is mapped to a fourth transmittance, wherein the first transmittance is higher than the third transmittance and the fourth transmittance is higher than the second transmittance.

The first subpixel is an R, G, and B subpixel, and the second subpixel is a subpixel for viewing angle control.

In order to achieve the above object, according to an embodiment of the present invention, a plurality of data lines and a plurality of gate lines are intersected, and a first inflection point of transmittance is present at a front viewing angle to display an image. A driving method of a liquid crystal display device having a liquid crystal display panel in which a quad type pixel including a viewing angle control subpixel having a transmittance second inflection point at a viewing angle different from the viewing angle is formed is present in an upward inclination section of the first inflection point. Listing a plurality of digital viewing angle control data corresponding to a transmittance present in a downward slope of the second inflection point mapped to transmittances of the R, G, and B subpixels in a lookup table; And selecting the digital viewing angle control data according to a result of comparing the average luminance value of the digital video data to be displayed on the R, G, and B subpixels with a predetermined reference value; The first transmittance of the downward slope of the second inflection point is mapped to the second transmittance of the upward slope of the first inflection point, and the second transmittance of the downward slope of the second inflection point is the upward slope of the first inflection point Mapped to a fourth transmittance of the first transmittance is higher than the third transmittance and the fourth transmittance is higher than the second transmittance, the average luminance value of the digital video data and the luminance value of the selected digital viewing angle control data And a difference between the sum and the reference value is equal to or less than a preset threshold.

In order to achieve the above object, a first subpixel displaying an image by displaying a first inflection point of transmittance at a front viewing angle and a second inflection point of transmittance at a side viewing angle different from the front viewing angle according to an embodiment of the present invention. A driving method of a liquid crystal display having two subpixels may include a transmittance of the second subpixel in a downward slope period of the second inflection point and a transmittance of the first subpixel in an upward slope period of the first inflection point. Mapping of; And generating data to be displayed on the second subpixel based on the mapping relationship; The first transmittance of the downward slope of the second inflection point is mapped to the second transmittance of the upward slope of the first inflection point, and the second transmittance of the downward slope of the second inflection point is the upward slope of the first inflection point Is mapped to a fourth transmittance, wherein the first transmittance is higher than the third transmittance and the fourth transmittance is higher than the second transmittance.

Other objects and advantages of the present invention in addition to the above object will be apparent from the description of the preferred embodiment of the present invention with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 3 to 13.

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

Referring to FIG. 3, in the liquid crystal display of the present invention, the data lines DL1 through DL2m and the gate lines GL1 through GL2n cross each other, and subpixels Pr, Pg, Pb, and Pv are disposed at the intersections thereof. A liquid crystal display panel 210 having a thin film transistor (TFT) for driving, a data driver 220 for supplying data to data lines DL1 to DL2m of the liquid crystal display panel 210; A gate driver 230 for supplying scan pulses to the gate lines GL1 to GL2n of the liquid crystal display panel 210 and a gamma reference voltage for generating and supplying a gamma reference voltage GMA to the data driver 220. The generator 240, the common voltage generator 250 for generating the common voltage Vcom and supplying the common electrode to the common electrode of the subpixel of the liquid crystal display panel 210, and average luminance values of the R, G, and B data. The ECB data is adjusted downward / upward accordingly and the data driver 220 and the gate driver 230 are driven. A timing controller 260 for controlling timing and a user interface 270 for inputting a viewing angle selection signal Cmode for selecting a wide viewing angle mode or a narrow viewing angle mode are provided.

In the liquid crystal display panel 210, the data lines DL1 to DL2m and the gate lines GL1 to GL2n are orthogonally formed at regular intervals, and the data lines DL1 to DL2m and the gate lines GL1 to GL2n are orthogonal to each other. R, G, and B subpixels Pr, Pg, and Pb and ECB subpixel Pv are formed in the intersecting regions where? A thin film transistor TFT is formed in each of the subpixels Pr, Pg, Pb, and Pv thus formed. The thin film transistor TFT is turned on by a scan pulse supplied to the gate terminals through the gate lines GL1 through GL2n, and R, G, and B data voltages supplied through the data lines DL1 through DL2m are respectively supplied. It is applied to the pixel electrodes of the R, G, and B subpixels Pr, Pg, and Pb. In addition, the thin film transistor TFT is turned on by a scan pulse supplied to the gate terminals through the gate lines GL1 through GL2n, so that the ECB data voltage supplied through the data lines DL1 through DL2m is an ECB subpixel. It is applied to the pixel electrode of (Pv). To this end, the gate electrodes of the TFTs are connected to the gate lines GL1 to GL2n, the source electrodes are connected to the data lines DL1 to DL2m, and the drain electrodes are connected to the respective subpixels Pr, Pg, It is connected to the pixel electrodes of Pb and Pv. The liquid crystal display panel 210 will be described in detail with reference to FIGS. 4 to 8B.

The data driver 220 samples and latches the digital RGB data supplied from the timing controller 260 in the wide viewing angle mode / narrow viewing angle mode in response to the data control signal DDC, and then supplies the data from the gamma reference voltage generator 240. Based on the gamma reference voltage, the R, G, and B subpixels Pr, Pg, and Pb of the liquid crystal display panel 210 are converted into data voltages representing gray levels, and are supplied to the data lines DL1 through DL2m. do. In addition, the data driver 220 samples and latches the ECB disable data supplied from the timing controller 260 in the wide viewing angle mode in response to the data control signal DDC, and then supplies the data from the gamma reference voltage generator 240. The gamma reference voltage is converted into the same disable data voltage as the common voltage and supplied to the odd-numbered data lines DL1, DL3, DL, and DL2m-1. In addition, the data driver 220 samples and latches ECB data supplied from the timing controller 260 in response to the data driving control signal DDC in the narrow viewing angle mode, and then gamma supplied from the gamma reference voltage generator 240. Based on the reference voltage, the ECB subpixel Pv of the liquid crystal display panel 210 is converted into an ECB data voltage capable of expressing gray scales, and the odd-numbered data lines DL1, DL3, ... connected to the ECB subpixel Pv. , DL (2m-1)). The ECB data supplied from the timing controller 260 is adjusted up / down according to the average luminance value of the RGB data.

The gate driver 230 sequentially generates scan pulses and supplies them to the gate lines GL1 to GL2n in response to the gate control signal GDC supplied from the timing controller 260. The scan pulse is swinged between a gate high voltage for turning on the thin film transistor TFT and a gate low voltage for turning off the thin film transistor TFT.

The gamma reference voltage generator 240 receives a high potential power voltage to generate a positive gamma reference voltage and a negative gamma reference voltage to output the data to the data driver 220.

The common voltage generator 250 receives a high potential power supply voltage to generate a common voltage Vcom and supplies the common voltage Vcom to the common electrode of the liquid crystal display panel 210.

The timing controller 260 generates a data control signal DDC for controlling RGB data and / or ECB data supply by using the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, and the input clock CLK. Supply to 220. The timing controller 260 generates a gate control signal GDC for controlling the supply of the scan pulse by using the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, and the input clock CLK to the gate driver 230. Supply. The data control signal DDC includes a source shift clock SSC, a source start pulse SSP, a polarity control signal POL, a source output enable signal SOE, and the gate control signal GDC. And a gate start pulse GSP and a gate output enable signal GOE. In addition, the timing controller 260 calculates an average luminance value of the RGB data in the narrow-view angle mode and maps the calculated average luminance value to the ECB data stored in advance by experiment to determine the ECB data that can lower the contrast ratio at the side viewing angle. do. The ECB data is mixed with the input RGB data and rearranged according to the quad pixel structure to be supplied to the data driver 220. The timing controller 260 mixes the ECB disable data with the input RGB data so that the ECB subpixel Pv formed in the liquid crystal display panel 210 is not driven in the wide viewing angle mode, and then applies the quad pixel structure. The rearrangement is performed to the data driver 220.

The user interface 270 is used to input the viewing angle selection signal Cmode for selecting the wide viewing angle mode or the narrow viewing angle mode. The user interface 270 may be implemented as a keyboard, a mouse, a touch panel, an on screen display (OSD), or the like. When the viewing angle selection signal Cmode is input by the user, the user interface 270 interprets this and supplies it to the timing controller 260.

FIG. 4 is a plan view illustrating a quad type pixel structure of the liquid crystal display panel 210 of FIG. 3, and FIGS. 5A and 5B are cutaway views of FIG. 4 taken along line II ′ in order to explain the wide viewing angle mode. 6A and 6B are graphs showing transmission characteristics in the wide viewing angle mode.

4 to 6B, the lower substrate 111 of the liquid crystal display panel 210 has subpixels Pr and Pg defined as intersecting regions of the plurality of gate lines 112 and the plurality of data lines 115. , Pb, Pv) are arranged. Among them, R, G, and B subpixels Pr, Pg, and Pb are formed at the intersection of the gate line 112 and the data line 115 to switch data voltages to the respective subpixels Pr, Pg, and Pb. A plurality of common electrodes 124 connected to the thin film transistor TFT, a common line 125 parallel to the gate line 112, and branched vertically into a subpixel, and a common electrode connected to the thin film transistor TFT. A pixel electrode 117 formed in parallel with 124 is provided. A gate insulating layer 113 formed by depositing an inorganic insulating material such as silicon nitride (SiNx) or silicon oxide (SiOx) by PECVD is further formed between the gate line 112 and the data line 115. In the ECB sub-pixel Pv, a thin film transistor TFT formed at an intersection of the gate line 112 and the data line 115 to switch the data voltage, and an ECB connected to the thin film transistor TFT and formed as a plate. The pixel electrode 517 is provided.

The protective layer 116 is formed by coating an inorganic insulating material such as silicon nitride (SiNx) or silicon oxide (SiOx) or an organic insulating material such as benzocyclobutence (BCB) or acryl-based material on the front surface of the data line 115. do. The protective film 116 serves to planarize the surface and protect the pattern.

The thin film transistor TFT formed in the R, G, and B subpixels Pr, Pg, and Pb is formed on the entire surface including the gate electrode 112a branched from the gate line 112 and the gate electrode 112a. A semiconductor layer 114 formed by sequentially depositing a gate insulating film 113, an amorphous silicon (a-Si) and an amorphous silicon (n + a-Si) ion-implanted with impurities on the gate insulating film 113, and a data line Source / drain electrodes 115a and 115b branched from 115 and formed on edges of the semiconductor layer 114, respectively. The thin film transistor TFT is turned on in response to a scan signal supplied to the gate electrode 112a to supply a data voltage to the pixel electrode 117 of the R, G, and B subpixels Pr, Pg, and Pb. . The pixel electrode 117 is connected to the drain electrode 115b through the first contact hole 119a. The thin film transistor TFT formed in the ECB subpixel Pv includes a gate electrode 512a branched from the gate line 112, a gate insulating film 113 formed on the entire surface including the gate electrode 512a, and a gate. A semiconductor layer 514 formed by sequentially depositing amorphous silicon (a-Si) and amorphous silicon (n + a-Si) ion-implanted with impurities on the insulating layer 113, and a semiconductor layer branched from the data line 115. Source / drain electrodes 515a and 515b formed on the edge of 514, respectively. The thin film transistor TFT is turned on in response to a scan signal supplied to the gate electrode 512a to supply a data voltage to the pixel electrode 517 of the ECB subpixel Pv. The pixel electrode 517 is connected to the drain electrode 515b through the second contact hole 519a.

Gate line 112 and data line 115 are copper (Cu), aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), molybdenum- It may be formed of a low resistance metal such as tungsten (MoW). The common line 125 may be formed at the same time as the gate line.

The common electrode 124 and the pixel electrodes 117 and 517 are transparent conductive metals having excellent light transmittance, such as indium tin-oxide (ITO) or indium zinc-oxide (IZO). Can be formed at the same time. Meanwhile, the common electrode 124 may be branched when the common line 125 is formed to form a low resistance metal layer. That is, the common electrode 124 may be formed on the same layer as the pixel electrodes 117 and 517 as ITO or IZO, which is a transparent conductive film that transmits light, or may be formed on the same layer as the gate line 112. The common electrode 124 is electrically connected to the common line 125 through the third contact hole 119b to receive a common voltage from the common line 125. The common electrode 124 and the pixel electrode 117 are alternately formed in parallel to each other, and may be formed in a straight line shape or a zigzag shape.

The upper substrate 121 of the liquid crystal display panel 210 includes a black matrix 122, a color filter pattern 123, an overcoat layer 129, an ECB common electrode 524, and an ECB common line 525. The color filter pattern 123 is formed on the R, G, and B subpixels Pr, Pg, and Pb, and the ECB common electrode 524 and the ECB common line 525 are formed on the ECB subpixel Pv. .

The black matrix 122 is formed of a metal such as chromium oxide (CrOx) or chromium (Cr) having a light density of 3.5 or more, or an organic material of carbon system. The black matrix 122 has light leakage generated in an area where the thin film transistor TFT of the lower substrate 111 is formed, an area where the gate line 112 and the data line 115 are formed, and an area around the black matrix 122. It serves to block.

The color filter pattern 123 includes a red layer formed on the R subpixel Pr, a green layer formed on the G subpixel Pg, and a blue layer formed on the B subpixel Pb.

The overcoat layer 129 is formed on the black matrix 122 and the color filter pattern 123. The overcoat layer 129 serves to planarize the step of the inner surface due to the formation of the black matrix 122 and the color filter pattern 123.

The ECB common electrode 524 is formed of a transparent electrode material on the overcoat layer 129 formed on the ECB subpixel Pv. As the transparent electrode material, a transparent conductive metal having excellent light transmittance, such as indium tin-oxide (ITO) or indium zinc-oxide (IZO), is used.

The ECB common line 525 is formed on the black matrix 122, and serves to supply the common voltage applied to the ECB common electrode 524. The ECB common line 525 may be formed of a transparent conductive metal having excellent light transmittance, such as indium tin oxide (ITO) or indium zinc oxide (IZO). (Cu), aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), molybdenum-tungsten (MoW), and may be formed of low resistance metals have.

The upper and lower substrates 111 and 121 are bonded to each other by a seal material that is printed on the edge of the substrate and serves as an adhesive, and the liquid crystal layer 131 is injected between the substrates 111 and 121. First and second polarizing plates 161 and 162 are attached to the outer circumferential surfaces of both substrates 111 and 121 such that transmission axes are perpendicular to each other. The rubbing direction of the alignment layer formed on the lower substrate 111 is parallel to the transmission axis of any one polarizing plate to realize a normally black mode.

When the wide viewing angle mode is selected, the ECB subpixel Pv is turned off because the liquid crystal molecules 132 are kept in the initial state due to the application of the disable data voltage equal to the common voltage as shown in FIGS. 5A and 5B. Off State). That is, as shown in FIG. 6B, the ECB subpixel Pv has a transmittance close to 0% and always remains black. On the other hand, the R, G, and B subpixels Pr, Pg, and Pb are in an off state as the liquid crystal molecules 132 are arranged as shown in FIG. 5A when no voltage is applied, but when the voltage is applied, FIG. 5B. As described above, the liquid crystal molecules 132 are arranged side by side in the electric field to be in an on state. That is, as shown in FIG. 6A, the R, G, and B subpixels Pr, Pg, and Pb implement white to black at a wide viewing angle according to an appropriate voltage applied thereto.

7A and 7B are cross-sectional views taken along the line II ′ of FIG. 4 to explain the narrow viewing angle mode, and FIGS. 8A and 8B are graphs showing transmission characteristics in the narrow viewing angle mode.

When the narrow viewing angle mode is selected, an appropriate voltage is applied to the ECB subpixel Pv for controlling the side viewing angle.

As shown in FIGS. 7A and 8A, a horizontal electric field is formed between the common electrode 124 and the pixel electrode 117 of the R, G, and B subpixels Pr, Pg, and Pb in the voltage off state. Since not formed, the liquid crystal molecules 132 oriented between the common electrode 124 and the pixel electrode 117 are maintained in an initial arrangement. Since the liquid crystal molecules 132 are maintained in an initial arrangement state, the R, G, and B subpixels Pr, Pg, and Pb display a black state in a voltage off state. As shown in FIGS. 7A and 8B, since the ECB subpixel Pv is turned on, a vertical electric field is formed between the ECB pixel electrode 517 and the ECB common electrode 524 so that the liquid crystal molecules oriented therebetween ( 132) stand upright. The ECB subpixel Pv becomes black when the appropriate voltage is applied, ideally approaching 0% at the front viewing angle, and white at the side viewing angle. Accordingly, the phase difference of the liquid crystal molecules 132 does not occur at the front viewing angle, thereby forming a black state. However, at the left and right side viewing angles, the retardation is performed by the liquid crystal molecules 132 rising at the ECB subpixel Pv. This occurs largely, resulting in a low contrast ratio, resulting in a narrow viewing angle.

As shown in FIGS. 7B and 8A, a horizontal electric field is formed between the common electrode 124 and the pixel electrode 117 of the R, G, and B subpixels Pr, Pg, and Pb in the voltage applied state. Since the long axes of the liquid crystal molecules 132 oriented between the common electrode 124 and the pixel electrode 117 are arranged side by side in the electric field. If the dielectric anisotropy of the liquid crystal is negative, the short axis of the liquid crystal molecules 132 is arranged side by side in the electric field. Since the liquid crystal molecules 132 are arranged side by side in the electric field, the R, G, and B subpixels Pr, Pg, and Pb indicate a white state in a voltage applied state. As shown in FIGS. 7B and 8B, since the ECB subpixel Pv is turned on, a vertical electric field is formed between the ECB pixel electrode 517 and the ECB common electrode 524 so that the liquid crystal molecules oriented therebetween ( 132) stand upright. The ECB subpixel Pv becomes black when the appropriate voltage is applied, ideally approaching 0% at the front viewing angle, and white at the side viewing angle. Accordingly, the phase difference of the liquid crystal molecules 132 does not occur at the front viewing angle, thereby forming a white state. However, at the left and right side viewing angles, retardation is performed by the liquid crystal molecules 132 rising at the ECB subpixel Pv. This occurs largely, resulting in a low contrast ratio, resulting in a narrow viewing angle.

FIG. 9 illustrates the timing controller 260 of FIG. 3 for adjusting the downlink / uplink ECB data according to the average luminance value of the RGB data in the narrow viewing angle mode.

Referring to FIG. 9, the timing controller 260 includes a luminance detector 262, an average value calculator 264, a mapper 266, and a data sorter 268.

When the viewing angle selection signal Cmode indicating the narrow viewing angle mode is input, the luminance detector 262 analyzes the gray level of the RGB data of the current frame input from the system for each quad type pixel, and then analyzes the gray level of the analyzed RGB data. The RGB luminance values Ry, Gy, and By of the quad type pixels are detected by using the same. When the luminance value is detected, the luminance detector 262 supplies the RGB luminance values Ry, Gy, and By of the quad type pixels to the average value calculator 264.

The average value calculator 264 adds RGB luminance values Ry, Gy, and By for each quad type pixel detected by the luminance detector 262, divides the addition value by three, and then averages the RGB average luminance for each quad type pixel. The value Avi (Ry, Gy, By) is calculated. When the average luminance value Avi (Ry, Gy, By) is calculated in this manner, the average value calculator 264 converts the average luminance value Avi (Ry, Gy, By) of each quad type pixel to the mapping unit 266. Supply.

The mapping unit 266 compares the RGB average luminance value Avi (Ry, Gy, By) of each quad type pixel calculated by the average value calculating unit 264 with a predetermined reference value Ty, and looks up according to the comparison result. Measurements are mapped to the table (LUT) with ECB data pre-registered. The mapping unit 266, when the detected average luminance value Avi (Ry, Gy, By) of the R, G, B data is smaller than the predetermined reference luminance value Ty, the overall luminance of the quad type pixel is the reference luminance value. Map ECB data having a relatively high luminance value to increase up to (Ty). On the other hand, when the detected average luminance value Avi (Ry, Gy, By) of the R, G, and B data is larger than the predetermined reference luminance value Ty, the mapping unit 266 may reference the entire luminance of the quad type pixel. ECB data having a relatively low luminance value is mapped so as to decrease to the luminance value Ty. This mapping process will be described in detail with reference to FIGS. 11 and 12. When the ECB data is mapped according to the average luminance values Avi (Ry, Gy, By) of the R, G, and B data, the mapping unit 266 supplies the ECB data selected through the mapping to the data sorter 268. do.

The data sorter 188 mixes the RGB data input with the ECB data selected through the mapping unit 266 in the narrow viewing angle mode, and then rearranges the mixed RGB data and the ECB data according to the quad type pixel structure. 220).

Although not shown in the drawing, when the viewing angle selection signal Cmode indicating the wide viewing angle mode is input, the ECB disable data storage unit (not shown) may set the preset ECB disable data to the data sorter 268. To supply. The data aligner 268 aligns the ECB disable data from the ECB disable data storage unit (not shown) and the input RGB data to the quad type pixel structure in the wide viewing angle mode to the data driver 220. Output

The detailed configuration and operation of the data sorter 268 having this function will be described in detail with reference to FIG. 10. However, the operation of the data sorter 188 in the narrow viewing angle mode in which the present invention is disclosed will be described.

FIG. 10 is a configuration diagram of the data sorter in FIG. 9.

Referring to FIG. 10, the data sorter 268 includes a mixer 268-1 and a data sorter 268-2.

The mixer 268-1 mixes RGB data and ECB data mixed in a stripe form by mixing RGB data input in parallel from a scaler (not shown) of the system and ECB data selected by the mapping unit 266. 268-2).

The data aligning unit 268-2 rearranges the RGB data and the ECB data mixed in the stripe form by the mixer 268-1 to match the quad type pixel structure and outputs the RGB data and the ECB data to the data driver 220.

11 and 12 are diagrams for describing a mapping process in the mapping unit 266 of FIG. 9. FIG. 11 shows TV curves at the front viewing angle of the RGB subpixels and the side viewing angles (40-50 degrees) of the ECB subpixels, and FIG. 12 shows the RGB subpixels and ECB subs at the side viewing angles (40-50 degrees). A diagram showing gray level curves and gray mapping of pixels. In FIG. 11, the horizontal axis represents driving voltage, the vertical axis represents transmittance, the horizontal axis represents gray scale, and the vertical axis represents transmittance.

Unlike the related art, in the present invention, the (B) area of the TV curve of the ECB subpixel of FIG. 11 is used as the mapping area. Accordingly, the ECB subpixel voltage used for the viewing angle control is increased in the voltage range of 2.5 V < Vsubpxl-Vcom < 7.5 V and the absolute size is also increased. Adjacent R, G, and B subpixels have a voltage range of 0 V <| Vsubpxl-Vcom | <7.5 V, which significantly reduces the difference between the driving voltage range and size of ECB subpixels and R, G, and B subpixels. . By reducing the difference in driving voltage range and size, the ECB subpixel is prevented from being greatly influenced by the voltage variation of the adjacent R, G, and B subpixels, thereby greatly reducing crosstalk.

9 and 12 to describe the mapping process, the mapping unit 266 may determine the RGB average luminance values Avi (Ry, Gy, By) of each quad type pixel calculated by the average value calculating unit 264. Is compared with a predetermined reference value Ty and mapped to the ECB data previously listed through measurement in the lookup table LUT according to the comparison result. To this end, a plurality of ECB data corresponding to transmittances existing in the down slope of the inflection point TP1 in the grayscale curve of the ECB subpixel is registered in the lookup table. These listed ECB data are mapped to be complementary to the average transmittance of the RGB data present in the up gradient of the inflection point TP2 in the grayscale curve of the RGB subpixel as a value preset by the measurement. The ECB data selected through this mapping serves to similarize the luminance between all quad type pixels in the lateral viewing angle direction by compensating for the luminance deviation between quad type pixels. That is, ECB data corresponding to high transmittance is mapped to RGB data corresponding to low average transmittance, and ECB data corresponding to low transmittance is mapped to RGB data corresponding to high average transmittance. For example, as shown in FIG. 12, when the RGB average transmittance is the lowest near 0%, the mapping unit maps the ECB data having the highest transmittance near 70% to be selected, and when the RGB average transmittance is the highest near 50%, the mapping unit Map so that ECB data with transmittance close to 20% is selected. Through this mapping process, the difference between the overall luminance value of the quad type pixel and the predetermined reference luminance value is equal to or less than a preset threshold. Here, the threshold is the maximum value of the luminance difference between the quad type pixels to make the luminance similar among all the quad type pixels at the side viewing angle.

13 is a flowchart for explaining a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

When the viewing angle selection signal indicating the narrow viewing angle mode is input (S200), the luminance detector analyzes the gray level of the RGB data of the current frame input from the system for each quad type pixel and then uses the gray level of the analyzed RGB data. RGB luminance values Ry, Gy and By of the quad type pixel are detected (S202).

The average value calculator adds the RGB luminance values Ry, Gy and By for each quad type pixel detected by the luminance detector, divides the addition value by three, and then calculates the RGB average luminance values Avi for each quad type pixel (Avi (Ry, Gy). (By)) is calculated (S204).

The mapping unit compares the calculated average luminance values Avi (Ry, Gy, By) of the R, G, and B data with a predetermined reference luminance value Ty (S206).

As a result of the comparison, when the average luminance value Avi (Ry, Gy, By) of the R, G, and B data is larger than the predetermined reference luminance value Ty, the mapping unit has the overall luminance of the quad type pixel as the reference luminance value Ty ECB data having a relatively low luminance value is mapped so as to be reduced to (S208). For mapping, the down-slope section of the inflection point of the TV curve of the ECB subpixel is used as the mapping area. This is to extend the driving voltage range of the ECB subpixel for viewing angle control and to increase the driving voltage to exclude optical interference due to the voltage variation of adjacent R, G, and B subpixels.

On the other hand, when the average luminance value Avi (Ry, Gy, By) of the R, G, and B data is smaller than the predetermined reference luminance value Ty, the mapping unit has the overall luminance of the quad type pixel as the reference luminance value Ty. ECB data having a relatively high luminance value is mapped to increase until step S210. For mapping, the down-slope section of the inflection point of the TV curve of the ECB subpixel is used as the mapping area. This is to extend the driving voltage range of the ECB subpixel for viewing angle control and to increase the driving voltage to exclude optical interference due to the voltage variation of adjacent R, G, and B subpixels.

As described above, the liquid crystal display and the driving method thereof according to the embodiment of the present invention extend the driving voltage range of the ECB subpixel by using the downward slope of the inflection point of the TV curve of the ECB subpixel as the mapping region. The voltage magnitude can be increased. As a result, the difference between the driving voltage range and the size of the ECB subpixels and the R, G, and B subpixels is greatly reduced, and the transmittance of the ECB subpixels is affected by the voltage variation of the R, G, and B subpixels. ), The transmittance of the ECB subpixel for viewing angle control can be easily controlled.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (22)

R, G, and B subpixels that display images by intersecting a plurality of data lines and a plurality of gate lines and having a first inflection point of transmission at a front viewing angle, and a second inflection point of transmission at a side viewing angle different from the front viewing angle A liquid crystal display panel in which a quad type pixel including a sub-pixel for viewing angle control is formed; And A plurality of digital viewing angle control data corresponding to the transmittance present in the downward inclination section of the second inflection point mapped to the transmittance of the R, G, and B subpixels present in the upward inclination section of the first inflection point are listed. A timing control section for selecting the digital viewing angle control data according to a result of comparing the average luminance value of the digital video data to be displayed on the R, G, and B subpixels with a predetermined reference value; The first transmittance of the downward slope of the second inflection point is mapped to the second transmittance of the upward slope of the first inflection point, and the second transmittance of the downward slope of the second inflection point is the upward slope of the first inflection point Mapped to a fourth transmittance of wherein the first transmittance is higher than the third transmittance and the fourth transmittance is higher than the second transmittance, And a difference between the sum of the average luminance value of the digital video data and the luminance value of the selected digital viewing angle control data and the reference value is equal to or less than a preset threshold. The method of claim 1, The timing controller, After analyzing the gray level of the digital video data to be displayed on the R, G, and B subpixels for each pixel, the luminance values of the digital video data to be displayed on the R, G, and B subpixels are detected using the analyzed gray level. Luminance detector An average value calculator for calculating average luminance values of digital video data to be displayed on the R, G, and B subpixels using the detected luminance values; And a mapping unit configured to compare the average luminance values of the digital video data to be displayed on the R, G, and B subpixels with one of the listed plurality of digital viewing angle control data by comparing with the reference value. Liquid crystal display device. The method of claim 2, And the mapping unit is implemented as a lookup table. The method of claim 2, The timing controller, And a data aligner for mixing and rearranging the digital viewing angle control data selected through the mapping and the digital video data to be displayed on the R, G, and B subpixels. The method of claim 4, wherein The data sorter, A mixer for mixing the digital viewing angle control data selected through the mapping with the digital video data to be displayed in the R, G, and B subpixels; And And a data alignment unit for rearranging the mixed digital data according to the quad type pixel structure. The method of claim 1, A data driver converting the digital viewing angle control data and the digital video data selected by the timing controller into data voltages and supplying the data voltages to the data lines; And And a gate driver for supplying scan pulses synchronized with the data voltages to the gate lines. A first subpixel for displaying an image by having a first inflection point of transmittance at a front viewing angle; A second subpixel having a second inflection point of transmittance at the side viewing angle different from the front viewing angle; And The second subpixel is based on a mapping relationship between the transmittance of the second subpixel in the downward slope period of the second inflection point and the transmittance of the first subpixel in the upward slope period of the first inflection point. A data generation circuit for viewing angle control for generating data to be displayed; The first transmittance of the downward slope of the second inflection point is mapped to the second transmittance of the upward slope of the first inflection point, and the second transmittance of the downward slope of the second inflection point is the upward slope of the first inflection point And a first transmittance higher than the third transmittance and a fourth transmittance higher than the second transmittance. The method of claim 7, wherein Wherein the first subpixel is an R, G, and B subpixel, and the second subpixel is a viewing angle control subpixel. The method of claim 7, wherein The viewing angle control data generation circuit, After analyzing the gray level of the digital video data to be displayed on the R, G, and B subpixels for each pixel, the luminance values of the digital video data to be displayed on the R, G, and B subpixels are detected using the analyzed gray level. A luminance detector; An average value calculator configured to calculate an average luminance value of digital video data to be displayed on the R, G, and B subpixels using the detected luminance values; And a mapping unit configured to compare the average luminance value of the digital video data to be displayed on the R, G, and B subpixels with a predetermined reference value and to map any one of the data to be displayed on the viewing angle control subpixel. A liquid crystal display device. The method of claim 9, And the mapping unit is implemented as a look-up table in which a plurality of digital viewing angle control data are registered through measurement. The method of claim 9, The viewing angle control data generation circuit, And a data aligner for mixing and rearranging the digital viewing angle control data selected through the mapping and the digital video data to be displayed on the R, G, and B subpixels. The method of claim 11, The data sorter, A mixer for mixing the digital viewing angle control data selected through the mapping with the digital video data to be displayed in the R, G, and B subpixels; And And a data alignment unit for rearranging the mixed digital data in accordance with a quad type pixel structure composed of the subpixels. The method of claim 10, And a difference between the sum of the average luminance values of the R, G, and B digital video data and the luminance value of the digital viewing angle control data selected from the lookup table and the reference value is equal to or less than a preset threshold. R, G, and B subpixels that display images by intersecting a plurality of data lines and a plurality of gate lines and having a first inflection point of transmission at a front viewing angle, and a second inflection point of transmission at a side viewing angle different from the front viewing angle In the driving method of a liquid crystal display device having a liquid crystal display panel in which a quad type pixel including a sub-pixel for viewing angle control is formed. The plurality of digital viewing angle control data corresponding to the transmittance in the downward inclination section of the second inflection point mapped to the transmittance of the R, G, and B subpixels in the upward inclination section of the first inflection point are registered in the lookup table. Making; And Selecting the digital viewing angle control data according to a result of comparing the average luminance value of the digital video data to be displayed on the R, G, and B subpixels with a predetermined reference value; The first transmittance of the downward slope of the second inflection point is mapped to the second transmittance of the upward slope of the first inflection point, and the second transmittance of the downward slope of the second inflection point is the upward slope of the first inflection point Mapped to a fourth transmittance of wherein the first transmittance is higher than the third transmittance and the fourth transmittance is higher than the second transmittance, And a difference between the sum of the average luminance value of the digital video data and the luminance value of the selected digital viewing angle control data and the reference value is equal to or less than a preset threshold. The method of claim 14, Selecting the digital viewing angle control data, After analyzing the gray level of the digital video data to be displayed on the R, G, and B subpixels for each pixel, the luminance values of the digital video data to be displayed on the R, G, and B subpixels are detected using the analyzed gray level. Making; Calculating average luminance values of digital video data to be displayed in the R, G, and B subpixels using the detected luminance values; And And comparing the average luminance value of the digital video data to be displayed on the R, G, and B subpixels with the reference value and mapping with any one of the listed plurality of digital viewing angle control data. A method of driving a liquid crystal display device. The method of claim 15, And rearranging the digital viewing angle control data selected through the mapping and the digital video data to be displayed on the R, G, and B subpixels and then rearranging the mixed data. The method of claim 14, Converting the selected digital viewing angle control data and the digital video data into data voltages and supplying the data voltages to the data lines; And And supplying a scan pulse synchronized with the data voltage to the gate lines. A driving method of a liquid crystal display device having a first subpixel displaying an image by having a first inflection point of transmittance at a front viewing angle and a second subpixel having a second inflection point of transmittance at a side viewing angle different from the front viewing angle. , Mapping a transmittance of the second subpixel in the downward slope of the second inflection point and a transmittance of the first subpixel in the upward slope of the first inflection point; And Generating data to be displayed in the second subpixel based on the mapping relationship; The first transmittance of the downward slope of the second inflection point is mapped to the second transmittance of the upward slope of the first inflection point, and the second transmittance of the downward slope of the second inflection point is the upward slope of the first inflection point And a first transmittance higher than the third transmittance and a fourth transmittance higher than the second transmittance. The method of claim 18, Wherein the first subpixel is an R, G, and B subpixel, and the second subpixel is a viewing angle control subpixel. The method of claim 19, The generating of the data to be displayed in the second subpixel may include: After analyzing the gray level of the digital video data to be displayed on the R, G, and B subpixels for each pixel, the luminance values of the digital video data to be displayed on the R, G, and B subpixels are detected using the analyzed gray level. Making; Calculating average luminance values of digital video data to be displayed in the R, G, and B subpixels using the detected luminance values; And comparing the average luminance value of the digital video data to be displayed on the R, G, and B subpixels with a predetermined reference value and mapping it with any one of data to be displayed on the viewing angle control subpixel. A method of driving a liquid crystal display device. The method of claim 20, The generating of the data to be displayed in the second subpixel may include: And rearranging the digital viewing angle control data selected through the mapping and the digital video data to be displayed on the R, G, and B subpixels and then rearranging the mixed data. The method of claim 20, And a difference between the sum of the average luminance values of the R, G, and B digital video data and the luminance values of the digital viewing angle control data generated through the mapping and the reference value is equal to or less than a preset threshold.

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