KR20080099426A - Display device - Google Patents

Abstract

A display device is provided to widening a viewing angle without forming a protrusion on a common electrode. A display device comprises a gate line, a first and second data line, a first and second switching device, a liquid crystal capacitor, and a control capacitor. A first data line intersects with the gate line. The first data line is parallel with the second data line. A first switching device is connected with the gate line, the first data line, and a pixel electrode. A second switching device is connected with the gate line, the second data line, and the pixel electrode. The liquid crystal capacitor contains the pixel electrode, and the common electrode. The direction control capacitor contains the pixel electrode, and the control electrode.

Description

Display device {DISPLAY DEVICE}

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

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

3 is a schematic diagram of one pixel in a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a signal waveform diagram illustrating an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

The present invention relates to a display device.

The liquid crystal display generally includes an upper display panel on which a common electrode, a color filter, and the like are formed, a lower display panel on which a thin film transistor and a pixel electrode are formed, and a liquid crystal layer interposed between the two display panels. When a potential difference is applied to the pixel electrode and the common electrode, an electric field is generated in the liquid crystal layer, and the direction is determined by the electric field. Since the transmittance of incident light is determined according to the alignment direction of the liquid crystal molecules, a desired image may be displayed by adjusting a potential difference between two electrodes.

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 the incision requires a separate mask to pattern the common electrode, and an overcoat is formed on the color filter to prevent the pigment of the color filter from escaping through the incision of the common electrode and contaminating the liquid crystal layer. do. In addition, the method of forming the protrusions also complicates the manufacturing method of the display device since a separate process for forming the protrusions or a modification of the existing process is required. 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.

The present invention has been made in an effort to provide a vertical alignment liquid crystal display device having a wide viewing angle without forming cutouts or protrusions on a common electrode.

According to an exemplary embodiment of the present invention, a display device includes a gate line, a first data line crossing the gate line, a second data line parallel to the first data line, the gate line, and the first data. A first switching element connected to a line and a pixel electrode, a second switching element connected to the gate line, the second data line and the pixel electrode, a liquid crystal capacitor including the pixel electrode and a common electrode, and the pixel And a direction control capacitor including an electrode and a direction control electrode, wherein the voltage of the second data line is higher than the voltage of the first data line.

The voltage of the second data line may be set based on the voltage of the first data line.

The voltage difference between the voltage of the first data line and the second data line may be constant.

The pixel electrode may include a plurality of cutouts.

The direction control electrode may be exposed by the cutout of the pixel electrode.

A storage capacitor may be further included to maintain the voltage of the pixel electrode.

DETAILED DESCRIPTION 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.

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, which is one example of a display device, will now be described in detail with reference to FIGS. 1 and 2.

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

As shown in 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, a data driver 500, and a data driver 500 connected thereto. The gray voltage generator 800 connected to the signal generator 500 and a signal controller 600 for controlling the gray voltage generator 800 are included.

The liquid crystal panel assembly 300 includes a plurality of signal lines G ₁ -G _n , D ₁ -D _2m and a plurality of pixels PX connected to the plurality of signal lines G ₁ -G _n , D ₁ -D _2m and arranged in a substantially matrix form. Include. In contrast, in the structure shown in FIG. 3, the liquid crystal panel assembly 300 includes lower and upper panel 100 and 200 facing each other and a liquid crystal layer 3 interposed therebetween.

The signal lines G ₁ -G _n and D ₁ -D _2m are a plurality of gate lines G ₁ -G _n for transmitting a gate signal (also called a “scan signal”) and a plurality of data lines for transmitting a data voltage ( D ₁ -D _2m ). The gate lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _2m extend substantially in the column direction and are substantially parallel to each other.

Each pixel PX, for example, the i-th (i = 1, 2, ..., n) gate line G _i and the j-th and j + 1th (j = 1, 2, ..., m) data lines ( The pixel PX connected to D _j and D _{j + 1} includes a first switching element Qa connected to the signal lines G _i and D _j , a liquid crystal capacitor Clc, and a storage capacitor connected thereto. The capacitor Cst includes a second switching element Qb connected to the signal lines G _i and D _{j + 1} and a direction control capacitor Cdce connected thereto. Holding capacitor Cst can be omitted as needed.

The first and second switching elements Qa and Qb are three-terminal elements, such as thin film transistors, provided in the lower panel 100, and the control terminal of the first switching element Qa is connected to the gate line Gi. The input terminal is connected to the data line Dj and the output terminal is connected to the pixel electrode 191.

In addition, the control terminal of the second switching element Qb is connected to the gate line G _i , the input terminal is connected to the data line D _{j + 1} , and the output terminal is connected to the direction control electrode 176. It is. The thin film transistor may include polycrystalline silicon or amorphous silicon.

The liquid crystal capacitor Clc has two terminals, the pixel electrode 191 of the lower panel 100 and the common electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 191 and 270 is a dielectric material. Function as. The pixel electrode 191 is connected to the first switching element Qa, and the common electrode 270 is formed on the entire surface of the upper panel 200 and receives the common voltage Vcom.

The pixel electrode 191 determines the direction of the liquid crystal molecules of the liquid crystal layer 3 between the two electrodes by generating an electric field together with the common electrode 270. The polarization of light passing through the liquid crystal layer varies according to the direction of the liquid crystal molecules determined as described above.

Each pixel electrode 191 is chamfered with a right corner and a left side center, and includes a plurality of cutouts (not shown).

A cutout (not shown) of the pixel electrode 191 completely exposes the direction control electrode 176.

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 storage capacitor Cst, which serves as an auxiliary part of the liquid crystal capacitor Clc, is formed by overlapping the storage signal line SL and the pixel electrode 191 provided on the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage Vcom is applied to the. However, the storage capacitor Cst may be formed such that the pixel electrode 191 overlaps the front gate line directly above the insulator.

The direction control capacitor Cdce overlaps the pixel electrode 191 and the direction control electrode 176 of the lower panel 100 with the insulator interposed therebetween. The direction control electrode 176 receives the direction control voltage from the second switching element Qb. The direction control electrode 176 to which the direction control voltage is applied generates two electric fields near the direction control electrode 176 by generating an electric field together with the common electrode 270 of the common electrode display panel 200 to which the common voltage Vcom is applied. The inclination direction of the liquid crystal molecules of the liquid crystal layer 3 between the 176 and 270 is determined. The reference viewing angle of the liquid crystal display device may be increased according to the inclination direction of the liquid crystal molecules determined as described above.

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. FIG. 3 illustrates that each pixel PX includes a color filter 230 representing one of the primary colors in an area of the upper panel 200 corresponding to the pixel electrode 191 as an example of spatial division. Unlike in FIG. 3, the color filter 230 may be disposed above or below the pixel electrode 191 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.

Referring back to FIG. 1, the gray voltage generator 800 generates two sets of gray voltages related to transmittance of the pixel PX. One of the two sets has a positive value for the common voltage Vcom and the other set has a negative value. The number of gray voltages included in the set of gray voltages generated by the gray voltage generator 800 may be the same as the number of grays that the liquid crystal display can display.

A gate driver 400, a gate line (G ₁ -G _n) and is connected to the gate turn-on voltage (Von), and a gate signal consisting of a combination of a gate-off voltage (Voff), a gate line (G ₁ of the liquid crystal panel assembly 300 -G _n ).

Data driver 500 is connected with the data lines (D ₁ -D _2m) of the liquid crystal panel assembly 300, select a gray voltage from the gray voltage generator 800 and the data lines do this as a data voltage (D ₁ -D _2m ).

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

Each of the driving devices 400, 500, 600, and 800 may be integrated in the liquid crystal panel assembly 300 together with signal lines G ₁ -G _n , D ₁ -D _2m , and switching elements Qa and Qb. . Alternatively, these driving devices 400, 500, 600, 800 may be mounted directly on the liquid crystal panel assembly 300 in the form of at least one integrated circuit chip, or may be a flexible printed circuit film (not shown). It may be mounted on the liquid crystal panel assembly 300 in the form of a tape carrier package (TCP), or may be mounted on a separate printed circuit board (not shown). In addition, the driving devices 400, 500, 600, and 800 may be integrated into a single chip, in which case at least one of them or at least one circuit element constituting them may be outside the single chip.

Next, an operation of the liquid crystal display will be described in detail with reference to FIG. 4.

4 is a signal waveform diagram illustrating an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

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 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. Export to).

The gate control signal CONT1 includes a scan start signal STV indicating a scan start and at least one clock signal controlling an output period of the gate-on voltage Von. The gate control signal CONT1 may also further include an output enable signal OE that defines the duration of the gate-on voltage Von.

The data control signal CONT2 applies an analog data voltage to the horizontal synchronizing start signal STH and the data lines D ₁ -D _2m indicating the start of transmission of the digital image signal DAT for one row of pixels PX. Includes a load signal LOAD and a data clock signal HCLK. The data control signal CONT2 is also an inverted signal that inverts the voltage polarity of the analog data voltage relative to the common voltage Vcom (hereinafter referred to as " polarity of the data voltage " RVS) may be further included.

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. The digital image signal DAT is converted into an analog data voltage by selecting a gray voltage to be applied to the data lines D ₁ -D _2m .

In this case, the data driver 500 supplies the data voltage Vd _j of the pixel PX to the data line Dj connected to the first switching element Qa, and supplies the second switching element Qb to the data line Dj. The direction control voltage Vd _{j + 1} is supplied to the connected data line D _{j + 1} . The direction control voltage Vd _{j + 1} is higher than the data voltage Vd _j of the pixel PX, and the direction control voltage Vd _{j + 1} and the data voltage Vd _{j for} all the pixels PX. ), The difference (?? V) remains constant.

For example, when the difference (?? V) voltage between the direction control voltage Vd _{j + 1} and the data voltage Vd _j is set to 5V, the data driver 500 may store the data voltage (V) of the pixel PX. Vd _j ) is boosted by 5V and supplied to the data line D _{j + 1} connected to the second switching element Qb.

As shown in FIG. 4, the gate driver 400 applies the gate-on voltage Von to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600, thereby applying the gate line G _1. -Turn on the first and second switching elements (Qa, Qb) connected to -G _n ) at the same time. Then, the voltage applied to the data lines D _j and D _{j + 1} is applied to the pixel PX through the turned on first and second switching elements Qa and Qb.

The difference between the data voltage Vd _j and the common voltage Vcom applied to the pixel electrode 191 is represented as the charging voltage of the liquid crystal capacitor Clc, that is, the main pixel electrode voltage Vpx _ij .

In addition, the difference between the direction control voltage Vd _{j + 1} and the common voltage Vcom applied to the direction control electrode 176 is represented by the negative pixel electrode voltage Vdce _ij .

The liquid crystal molecules vary in arrangement depending on the magnitude of the main and sub pixel electrode voltages Vpx _ij and Vdce _ij , and thus the polarization of light passing through the liquid crystal layer 3 changes. The change in polarization is represented by a change in transmittance of light by a polarizer attached to the display panel assembly 300.

When the first and second switching elements Qa and Qb are turned off, the pixel electrode 191 and the direction control electrode 176 are in a floating state, and the direction control capacitor Cdce and the liquid crystal capacitor Clc are turned off. And the storage capacitor Cst maintains the charging voltage so that the voltage of the direction control electrode 176 with respect to the common voltage Vcom is maintained higher than the voltage of the pixel electrode 191 with respect to the common voltage Vcom.

When a voltage difference occurs between the common electrode 270, the pixel electrode 191, and the direction control electrode 176, a main electric field (electric field) that is 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. From now on, the pixel electrode 191 and the common electrode 271 will be referred to as an electric field generating electrode.

A cutout (not shown) of the pixel electrode 191 distorts the electric field to create a horizontal component that determines the inclination direction of the liquid crystal molecules. The horizontal component of the main electric field is substantially perpendicular to the cutout (not shown) and is directed inside or outside the pixel electrode 191 depending on 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 direction control electrode 176 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 voltage of the direction control electrode 176 is 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, and its intensity is also stronger than that of the main electric field. Therefore, the net horizontal component of the electric field at the cutout (not shown) with the direction control electrode 176 is in the same direction as the horizontal component at the side of the pixel electrode 191 adjacent thereto.

A cutout (not shown) divides the pixel electrode 191 into a plurality of regions, and each region has two major edges parallel to each other. Since the liquid crystal molecules on each region are mostly perpendicular to the periphery and are subjected to the force of the electric field horizontal component in the above-described direction, the liquid crystal molecules may have various directions in which the liquid crystal molecules are inclined.

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), thereby all the gate lines G ₁ -G _n. ), The gate-on voltage Von is sequentially applied, and the data voltage is applied to all the pixels PX to display an image of one frame.

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 voltage applied to each pixel PX is opposite to the polarity of the previous frame. "Invert frame"). In this case, the polarities of the data voltages flowing through one data line may be changed (eg, row inversion and point inversion), or polarities of data voltages applied to one pixel row may be different depending on the characteristics of the inversion signal RVS within one frame. (E.g. column inversion, point inversion).

As described above, according to the present invention, the absolute value of the direction control electrode voltage is maintained to be greater than the absolute value of the pixel electrode voltage, so that the liquid crystal molecules are pretilt by the electric field of the direction control electrode. Therefore, a wide viewing angle can be secured without forming cutouts or protrusions in the common electrode.

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.

Claims (6)

Gate Line, A first data line crossing the gate line; A second data line parallel to the first data line, A first switching element connected to the gate line, the first data line and the pixel electrode; A second switching element connected to the gate line, the second data line, and the pixel electrode; A liquid crystal capacitor including the pixel electrode and a common electrode, and A direction control capacitor comprising the pixel electrode and a direction control electrode Including; The voltage of the second data line is higher than the voltage of the first data line. Display device. In claim 1, And a voltage of the second data line is set based on the voltage of the first data line. In claim 2, And a voltage difference between the voltage of the first data line and the voltage of the second data line is constant. In claim 3, The pixel electrode includes a plurality of cutouts. In claim 4, The direction control electrode is exposed by the cutout of the pixel electrode. In claim 5, The display device And a storage capacitor for maintaining the voltage of the pixel electrode.

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