KR20060016924A - Liquid crystal display - Google Patents

Abstract

The present invention relates to a liquid crystal display device, which includes a plurality of pixels, a gray voltage generator for generating a plurality of gray voltages, a DC driving voltage from outside and a gray voltage from a gray voltage generator according to a selection signal from the outside. A driving voltage selector for selecting and outputting any one of voltages, and a data driver for applying a data voltage based on the selected voltage from the driving voltage selector to the pixel. As described above, since the driving method of the liquid crystal display device can be selected from the inversion driving method and the DC driving method according to an external selection signal, the afterimage of the liquid crystal due to the DC driving can be easily confirmed.

LCD, afterimage, DC drive, data driver, gray voltage, pixel voltage

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 an example of a circuit diagram of a driving voltage selector of a liquid crystal display according to an exemplary embodiment of the present invention.

The present invention relates to a liquid crystal display device.

A typical liquid crystal display (LCD) includes two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors (TFTs) to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the display panel and receives a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor, and the liquid crystal capacitor becomes a basic unit forming a pixel together with a switching element connected thereto.

In such a liquid crystal display, a voltage is applied to two electrodes to generate an electric field in the liquid crystal layer, and the intensity of the electric field is adjusted to adjust the transmittance of light passing through the liquid crystal layer to obtain a desired image. At this time, in order to prevent deterioration caused by the application of an electric field in one direction for a long time, the polarity of the data voltage with respect to the common voltage is inverted frame by frame, row by pixel, or pixel by pixel.

On the other hand, it is necessary to check the afterimage caused by the ion impurity of the liquid crystal in the manufacturing step of the liquid crystal display device and to extract the panel in which the afterimage problem occurs. Such an afterimage can be easily confirmed by driving the liquid crystal to the DC driving voltage. However, since the liquid crystal display needs to be turned on for a long time in order to check the residual image of the liquid crystal while inverting the driving, it is difficult to check such an afterimage in the conventional liquid crystal display which employs the inversion driving method to prevent the degradation of the liquid crystal. In addition, it is difficult to replace the driving unit of the liquid crystal display device, which is already fixed in the inversion driving method, by the DC driving method.

Accordingly, an object of the present invention is to provide a liquid crystal display device which can easily check an afterimage.

According to an embodiment of the present invention, a liquid crystal display device includes a plurality of pixels, a gray voltage generator for generating a plurality of gray voltages, a DC driving voltage from an external source according to a selection signal from the outside, and And a driving voltage selector for selecting and outputting any one of the gray voltages from the gray voltage generator, and a data driver for applying a data voltage based on the selected voltage from the driving voltage selector to the pixel.

The driving voltage selector may include a first switching device receiving the gray voltage and outputting the gray level voltage according to the selection signal, and a second switching device receiving the DC driving voltage and outputting the gray level voltage according to the selection signal.

The driving voltage selector may further include a NOT gate connected to one of the control terminals of the first and second switching devices.

When the selection signal is at a high level, the first switching device may be turned off, and the second switching device may be turned on.

The data driver includes an integrated circuit chip and may include the driving voltage selector.

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 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.

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 gray voltage generator connected thereto. The unit 800 includes a driving voltage selector 550 and a signal controller 600 for controlling them.

The liquid crystal panel assembly 300 includes a plurality of display signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels connected to the plurality of display signal lines G ₁ -G _n , D ₁ -D _m , and arranged in a substantially matrix form. .

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

Each pixel includes a switching element Q connected to a display signal line G ₁ -G _n , D ₁ -D _m , and a liquid crystal capacitor C _LC and a storage capacitor C _ST connected thereto. It includes. The holding capacitor C _ST can be omitted as necessary.

The switching element Q, such as a thin film transistor, is provided in the lower panel 100, and the control terminal and the input terminal are three-terminal elements, respectively, with gate lines G ₁ -G _n and data lines D ₁ -D _m . The output terminal is connected to a liquid crystal capacitor (C _LC ) and a holding capacitor (C _ST ).

The liquid crystal capacitor C _LC has two terminals, the pixel electrode 190 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 190 and 270. It functions as a dielectric. The pixel electrode 190 is connected to the switching element Q, and the common electrode 270 is formed on the front surface of the upper panel 200 and receives a common voltage V _com . 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 190 and 270 may be linear or rod-shaped.

The storage capacitor C _ST , which serves as an auxiliary part of the liquid crystal capacitor C _LC , is formed by overlapping a separate signal line (not shown) and the pixel electrode 190 provided on the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage V _com is applied to this separate signal line. However, the storage capacitor C _ST may be formed such that the pixel electrode 190 overlaps the front end gate line directly above the insulator.

On the other hand, in order to implement color display, each pixel uniquely displays one of the three primary colors (spatial division) or each pixel alternately displays the three primary colors according to time (time division) so that the desired color can be spatially and temporally combined with the three primary colors. To be recognized. 2 shows that each pixel includes a red, green, or blue color filter 230 in a region corresponding to the pixel electrode 190 as an example of spatial division. Unlike FIG. 2, the color filter 230 may be formed above or below the pixel electrode 190 of the lower panel 100.

A polarizer (not shown) for polarizing light is attached to an outer surface of at least one of the two display panels 100 and 200 of the liquid crystal panel assembly 300.

The gray voltage generator 800 generates two sets of gray voltages related to the transmittance of the pixel. One of the two sets has a positive value for the common voltage (V _com ) and the other set has a negative value.

The driving voltage selector 550 selects and outputs any one of a DC driving voltage V _DC from the outside and a gray voltage from the gray voltage generator 800 according to the selection signal SC from the outside.

The gate driver 400 is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300 to receive a gate signal formed by a combination of a gate on voltage V _on and a gate off voltage V _off from the outside. It is applied to the gate lines G ₁ -G _n and may be formed of a plurality of integrated circuits.

The data driver 500 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300 to receive one of the gray voltage from the driving voltage selector 550 and the DC driving voltage V _DC . It is applied to the pixel as a signal and may be composed of a plurality of integrated circuits.

The plurality of gate driving integrated circuits or data driving integrated circuits may be mounted in a chip carrier package (TCP) (not shown) in the form of a chip to attach the TCP to the liquid crystal panel assembly 300, or may not use TCP. These integrated circuit chips may be directly attached onto a glass substrate (chip on glass, COG mounting method), and these integrated circuits may be directly formed on the liquid crystal panel assembly 300 together with the thin film transistors of the pixel.

The signal controller 600 controls operations of the gate driver 400 and the data driver 500.

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

The signal controller 600 may control the input image signals R, G, and B and their display from an external graphic controller (not shown), for example, a vertical sync signal V _sync and a horizontal sync signal. (H _sync ), a main clock (MCLK), a data enable signal (DE) is provided. The signal controller 600 properly processes the image signals R, G, and B according to the 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 control signal. After generating the 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 gate-on voltage vertical synchronization start signal (STV) for instructing the start of output of the (V _on), the gate-on voltage gated clock signal that controls the output timing of the (V _on) (CPV) and the gate-on An output enable signal OE or the like that defines the duration of the voltage V _on .

The data control signal CONT2 includes a horizontal synchronization start signal STH indicating the start of input of the image data DAT, a load signal LOAD for applying a corresponding data voltage to the data lines D ₁ -D _m , and a common voltage. The inversion signal RVS and the data clock signal HCLK for inverting the polarity of the data voltage with respect to (V _com ) (hereinafter referred to as the "polarity of the data voltage by reducing the polarity of the data voltage with respect to the common voltage"). Include.

The data driver 500 sequentially receives image data DAT for one row of pixels according to the data control signal CONT2 from the signal controller 600. In addition, when the driving voltage selector 550 selects the gray voltage from the gray voltage generator 800 as the driving voltage, the data driver 500 stores the image data of the gray voltages from the driving voltage selector 550. By selecting the gray scale voltage corresponding to the DAT, the image data DAT is converted into the corresponding data voltage and then applied to the corresponding data lines D ₁ -D _m . On the other hand, when the driving voltage selector 550 selects the DC driving voltage V _DC as the driving voltage, the data driver 500 sets the DC driving voltage V _DC as the data voltage for each image data DAT. It is applied to the data lines D ₁ -D _m . As a result, the liquid crystal display may be driven by DC to check an afterimage caused by liquid crystal impurities.

The gate driver 400 applies the gate-on voltage V _on 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 lines G ₁ -G _n. ) Turns on the switching element Q connected thereto, so that the data voltage applied to the data lines D ₁ -D _m is applied to the corresponding pixel through the turned-on switching element Q.

The difference between the data voltage applied to the pixel and the common voltage V _com is shown as the charging voltage of the liquid crystal capacitor C _LC , that is, the pixel voltage. The arrangement of the liquid crystal molecules varies according to the magnitude of the pixel voltage, thereby changing the polarization of light passing through the liquid crystal layer 3. The change in polarization is represented by a change in transmittance of light by a polarizer (not shown) attached to the display panels 100 and 200.

After one horizontal period (or “1H”) (one period of the horizontal sync signal H _sync , the data enable signal DE, and the gate clock CPV), the data driver 500 and the gate driver 400 are next. The same operation is repeated for the pixels in the row. In this manner, the gate-on voltages V _{on are} sequentially applied to all the gate lines G ₁ -G _n during one frame to apply data voltages to all the pixels. At the end of one frame, the next frame starts and the state of the inversion signal RVS applied to the data driver 500 is controlled so that the polarity of the data voltage applied to each pixel is opposite to that of the previous frame ("frame"reversal"). In this case, the polarity of the data voltage flowing through one data line may be changed (“line inversion”) within one frame or the polarity of the data voltage applied to one pixel row may be different according to the characteristics of the inversion signal RVS ( "Dot reversal"). However, when the driving voltage selector 550 selects the DC driving voltage V _DC as the driving voltage, the driving voltage selection unit 550 performs the DC driving instead of the inverting driving.

Next, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 3.

3 is an example of a circuit diagram of a driving voltage selector of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the driving voltage selector 550 is connected to the DC driving voltage V _DC , the selection signal SC, the gray voltage generator 800, and the data driver 500. Switching elements Q1, Q2 and r NOT gates.

For convenience of explanation, the gray voltage generator 800 generates and outputs _r gray voltages V ₁ to V _r .

The input terminals of the r switching elements Q1 are respectively connected to the gray scale voltages V ₁ to V _r , the control terminal is connected to the selection signal SC through the NOT gate NOT, and the output terminal is connected to the data. It is connected to the drive unit 500.

The input terminals of the r switching elements Q2 are connected to the DC driving voltage V _DC , the control terminal is connected to the selection signal SC, and the output terminals are connected together with the output terminals of the switching element Q1. It is connected to the drive unit 500.

The driving voltage selector 550 selects an inversion driving method or a DC driving method according to the selection signal SC. That is, the driving voltage selector 550 may include one of the gray voltages V ₁ to V _r from the gray voltage generator 800 and the DC driving voltage V _DC from the outside according to the signal level of the selection signal SC. Select one and send it to the data driver 500.

In detail, when the selection signal SC is at a high level, the DC driving method is selected. The switching element Q2 is turned on, and the switching element Q1 is turned off, so that the driving voltage selector 550 may switch to the switching element ( The DC driving voltage V _DC is sent to the data driver 500 through Q2).

When the selection signal SC is at a low level, the inversion driving method is selected. The switching element Q1 is turned on, the switching element Q2 is turned off, and the driving voltage selector 550 turns the switching element Q1 on. The gray voltages V ₁ to V _r from the gray voltage generator 800 are sent to the data driver 500.

Accordingly, the data driver 500 applies a DC driving voltage V _DC to the data lines D ₁ -D _{m when the} selection signal SC is at a high level, and image data (if the selection signal SC is at a low level). The gray voltages V ₁ to V _r corresponding to the DAT are selected and applied to the data lines D ₁ -D _m .

Meanwhile, if necessary, the NOT gate NOT may be connected to the control terminal of the switching element Q2 without being connected to the control terminal of the switching element Q1. In this way, the signal levels of the selection signals SC for selecting each driving method are changed.

The driving voltage selector 550 of the liquid crystal display according to the exemplary embodiment of the present invention may be included in the data driver 500 and implemented as an integrated circuit chip. In this case, the size of the liquid crystal display may not be increased. You do not need to add extra parts.

 As described above, since the driving method of the liquid crystal display device can be selected from the inversion driving method and the DC driving method according to an external selection signal, the afterimage of the liquid crystal due to the DC driving can be easily confirmed.

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 (5)

A plurality of pixels, A gray voltage generator for generating a plurality of gray voltages; A driving voltage selector for selecting and outputting any one of a DC driving voltage from the outside and the gray voltage from the gray voltage generator according to a selection signal from the outside; and A data driver for applying a data voltage based on the selected voltage from the driving voltage selector to the pixel Liquid crystal display comprising a. In claim 1, The driving voltage selector, A first switching device receiving the gray voltage and outputting the gray level voltage according to the selection signal, and And a second switching element receiving the DC driving voltage and outputting the DC driving voltage according to the selection signal. In claim 2, The driving voltage selector further includes a NOT gate connected to one of the control terminals of the first and second switching devices. In claim 3, And the first switching element is turned off and the second switching element is turned on when the selection signal is at a high level. In claim 3, The data driver includes an integrated circuit chip and includes the driving voltage selector.

Images