KR20060131367A - Liquid crystal display and driving method thereof - Google Patents

Abstract

An LCD and a driving method thereof are provided to allow a driving circuit to normally operate even at a low temperature by providing a thermal wire and a temperature detector. A liquid crystal panel assembly(300) includes an upper display substrate and a lower display substrate. A thermal line(TL) is disposed along an edge of the liquid crystal display panel assembly. A temperature detector(700) detects an ambient temperature. A thermal line controller(710) controls the thermal line according to temperature information from the temperature detector. One or more supports receive and support the liquid crystal display panel assembly. The thermal line is disposed at one of the supports.

Description

Liquid crystal display and driving method thereof {LIQUID CRYSTAL DISPLAY AND DRIVING METHOD THEREOF}

With reference to the accompanying drawings will be described in detail the embodiments of the present invention to make the present invention clear.

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.

FIG. 3 is an exploded perspective view of the liquid crystal display shown in FIG. 1.

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

<Description of Drawing>

3: liquid crystal layer 100: lower display panel

190: pixel electrode 200: upper display panel

230: color filter 270: common electrode

300: liquid crystal panel assembly 330: display unit

350: liquid crystal module 361: front chassis

362: rear chassis 364: mold frame

400: gate driver 500: data driver

510: data driving IC 600: signal control unit

540: data TCP 550: data PCB

700: temperature sensing unit 710: hot wire control unit

800: gray voltage generator 900: lighting unit

901: optical sheet 903: lamp

905: LGP 907: Reflector

909: cover 910: light source unit

TL: heating wire

R, G, B: Input image data DE: Data enable signal

MCLK: Main Clock Hsync: Horizontal Sync Signal

Vsync: Vertical Sync Signal CONT1: Gate Control Signal

CONT2: data control signal DAT2: digital video signal

C _LC : Liquid Crystal Capacitor C _ST : Holding Capacitor

Q: switching device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display having a heating wire and a driving method thereof so as to operate normally at low temperatures.

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 that forms 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.

The application range of such a liquid crystal display device is very diverse, and is widely applied to small display devices such as mobile phones and large display devices such as TVs. In particular, notebooks and small and medium sized display devices are easy to carry, contributing to achieving ubiquitous.

On the other hand, the liquid crystal display includes a display panel including a pixel including a switching element, a display signal line, and a gate driver to turn on / off a switching element of a pixel by sending a gate signal to a gate line among the display signal lines, and a data line among display signal lines. A data driver for applying a data voltage to the signal driver;

In this case, the driving circuit such as the gate driver may be integrated in the same process as the switching element of the pixel and integrated in the display panel.

In particular, the switching elements are made of a semiconductor such as amorphous silicon, and these semiconductor elements have a property of increasing resistance when the temperature decreases. As a result, the gate driver may not operate properly in a low temperature environment of minus 15 to 20 ° C. In the case of a portable display device such as a laptop as described above, this may be especially true in the external environment.

Accordingly, an object of the present invention is to provide a liquid crystal display and a driving method thereof capable of operating normally at low temperature.

According to an embodiment of the present invention, a liquid crystal display device includes a liquid crystal panel assembly including an upper panel and a lower panel, a heating wire disposed along an edge of the liquid crystal panel assembly, and a temperature for sensing an ambient temperature. And a sensing unit, and a heating unit controlling a heating line in accordance with temperature information from the temperature sensing unit.

The display device may further include at least one support for receiving and supporting the liquid crystal panel assembly, wherein the heating wire is disposed on one of the supports.

In detail, the support may include a front and rear chassis and a mold frame, the heating wire may be disposed in the rear chassis, and the rear chassis may have a stepped cross section.

The liquid crystal display may further include a signal line and a gate driver configured to apply a gate signal to the signal line, and the gate driver may be integrated in the lower panel.

According to an exemplary embodiment of the present invention, a method of driving a liquid crystal display device including a liquid crystal panel assembly and a heating wire disposed along an edge of the liquid crystal panel assembly may include: operating the liquid crystal display device; Sensing a temperature, determining whether the ambient temperature is below a reference temperature, and operating the hot wire according to the determination result.

The liquid crystal panel assembly may include a signal line and a gate driver configured to apply a gate signal to the signal line.

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 portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right on" 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.

First, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3.

1 is a block diagram of a liquid crystal display according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of a liquid crystal display according to an embodiment of the present invention, and FIG. 3 is a liquid crystal according to an embodiment of the present invention. It is an equivalent circuit diagram of one pixel of a display device.

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 500, a backlight unit 900 for providing light to the liquid crystal panel assembly 300, a signal controller 600 for controlling them, and a head of the liquid crystal panel assembly 300. The heating wire TL disposed along the seat, the heating wire control unit 710 for controlling the temperature and the temperature sensing unit 700 for sensing the ambient temperature.

On the other hand, as shown in Figure 2, in the structural view of the liquid crystal display device according to an embodiment of the present invention, the liquid crystal module 350 and the liquid crystal module 350 including the display unit 330 and the illumination unit 900 Front and rear chassis 361 and 362 for receiving and fixing, and a mold frame 364.

The display unit 330 includes a liquid crystal panel assembly 300, a data tape carrier packet (TCP) 540 attached thereto, and a data printed circuit board (PCB) 550 attached thereto. do. The gate driver 400 is integrated in the lower panel 100.

The liquid crystal panel assembly 300 includes a lower panel 100, an upper panel 200, and a liquid crystal layer 3 interposed therebetween, as shown in FIGS. 2 and 3. And a plurality of signal lines G ₁ -G _n , D ₁ -D _m , connected thereto, and arranged in a substantially matrix form, as shown in FIG. 3, in an equivalent circuit. It includes.

The 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 plurality of data lines for transmitting a data signal ( D 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 PX, for example, the pixel PX connected to the i-th (i = 1, 2,, n) gate line G _i and the j-th (j = 1, 2,, m) data line Dj. ) Includes a switching element Q connected to the signal line G _i D _j , a liquid crystal capacitor C _LC , and a storage capacitor C _ST connected thereto. The holding capacitor C _ST can be omitted as necessary.

The switching element Q is a three-terminal element of a thin film transistor or the like provided in the lower panel 100, the control terminal of which is connected to the gate line G _i , and the input terminal of which is connected to the data line D _j . The output terminal is connected to the liquid crystal capacitor C _LC and the storage capacitor C _ST .

The liquid crystal capacitor C _LC has two terminals, a pixel electrode 191 of the lower panel 100 and a common electrode 270 of the upper panel 200, and a liquid crystal layer 3 between the two electrodes 191 and 270. It functions as a dielectric. The pixel electrode 191 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 the common voltage Vcom. 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 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 191 provided on the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage Vcom is applied to this separate signal line. However, the storage capacitor C _ST may be formed such that the pixel electrode 191 overlaps the front gate line directly above the insulator.

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 FIG. 2, the color filter 230 may be formed above or below the pixel electrode 191 of the lower panel 100.

In FIG. 2, the lighting unit 900 accommodated and fixed on the rear chassis 32 includes a light source unit 910, an optical sheet 901, and a reflector plate 907, and the light source unit 910 of the liquid crystal panel assembly 300. A plurality of lamps 903 mounted at an edge, a light guide plate 905 for guiding light from the lamp 903 to the liquid crystal panel assembly 300, and a lamp cover 909 for wrapping and protecting the lamp 903. It includes. The reflector plate 907 is positioned under the light guide plate 905 to reflect light from the lamp 903, and the optical sheet 901 secures luminance characteristics of the light from the lamp 903 to the liquid crystal panel assembly 300. to provide. The lamp 903 uses a cold cathode fluorescent lamp (CCFL), but may use an external electrode fluorescent lamp (EEFL), a light emitting diode (LED), or the like.

In addition, the lighting unit 900 illustrated in FIG. 2 is an edge type in which the lamp 903 is disposed at the edge of the liquid crystal panel assembly 300, but the lamp is disposed on the side surface of the liquid crystal panel assembly 300 and the light guide plate 905. It may also be a direct type in which the diffusion plate is disposed instead.

In addition, as shown in the enlarged circle, the rear chassis 362 has a stepped cross section, and the heating wire TL located at the second staircase is disposed along the inner edge of the rear chassis 362 as a whole. When the ambient temperature decreases, the heating wire TL operates to transfer heat to the gate driver 400 and the like to allow the gate driver 400 to operate normally.

At least one polarizer (not shown) is attached to outer surfaces of the two display panels 100 and 200 of the liquid crystal panel assembly 300 to polarize light emitted from the lamp 903.

Referring again to FIGS. 1 and 2, the gray voltage generator 800 is provided in the data PCB 550 and includes two sets of gray voltage sets (or reference gray voltage sets) related to transmittance of the pixel PX. Create One of the two sets has a positive value for the common voltage Vcom and the other set has a negative value.

As described above, the gate driver 400 is formed and integrated on the lower panel 100 by the same process as the switching element Q of the pixel, and is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300. Thus, a gate signal formed of a combination of the gate-on voltage Von and the gate-off voltage Voff is applied to the gate lines G ₁ -G _n .

The data driver 500 is mounted on each data TCP 540 in the form of an IC chip, is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300, and the gray voltage generator 800 is provided. The gray voltage from is selected and applied to the data lines D ₁ -D _m as data signals. However, when the gray voltage generator 800 provides only a predetermined number of reference gray voltages instead of providing all of the voltages for all grays, the data driver 500 divides the reference gray voltages to divide the gray voltages for all grays. Generate and select the data signal from it.

The temperature detector 700 detects an ambient temperature and transmits the detected temperature to the hot wire controller 710, and the hot wire controller 710 controls the operation of the hot wire TL based on the temperature information from the temperature detector 700.

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

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

The signal controller 600 receives input image signals R, G, and B and an input control signal for controlling the display thereof from an external graphic controller (not shown). 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 is a load for applying a data signal to the horizontal synchronization start signal STH and the data lines D ₁ -D _m indicating the start of image data transmission for the pixels PX in one row [bundling]. Signal LOAD and data clock signal HCLK. The data control signal CONT2 is also an inverted signal that inverts the voltage polarity of the data signal relative to the common voltage Vcom (hereinafter referred to as " polarity of the data signal " by reducing the " voltage polarity of the data signal for the common voltage &quot;) 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 gradation voltage is selected to convert the digital image signal DAT into an analog data signal and then apply it to the data lines D ₁ -D _m .

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 lines G ₁ -G _n . Turn on the switching element (Q) connected to. Then, the data signal applied to the data lines D ₁ -D _m is applied to the pixel PX through the turned-on switching element Q.

The difference between the voltage of the data signal applied to the pixel PX and the common voltage Vcom is represented 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 size of the pixel voltage, and thus the polarization of light emitted from the light source 910 through the liquid crystal layer 3 is changed. The change in polarization is represented by a change in transmittance of light by a polarizer attached to the display panel assembly 300.

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 gate lines G ₁ -G _n ), The gate-on voltage Von is sequentially applied to the data signal to all the pixels PX, thereby displaying 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 signal applied to each pixel PX is opposite to the polarity of the previous frame. "Invert frame"). In this case, the polarity of the data signal flowing through one data line is changed (eg, row inversion and point inversion) or the polarity of the data signal applied to one pixel row is different depending on the characteristics of the inversion signal RVS within one frame. (E.g. column inversion, point inversion).

Next, the operation of the heating wire TL described above will be described in detail with reference to FIG. 4.

4 is an example of a flowchart illustrating an operation of a liquid crystal display including a hot wire according to an exemplary embodiment of the present invention.

Referring to FIG. 4, when the liquid crystal display device operates (S41), the temperature detector 700 detects an ambient temperature. As is known, the temperature sensing unit 700 may have a Wheatstone bridge structure including a transistor and a resistor connected thereto.

Subsequently, the hot wire controller 710 determines whether the ambient temperature is lower than or equal to the reference temperature based on the temperature information from the temperature detector 700 (S43), and operates the hot wire TL when it is lower than or equal to the reference temperature (S44). Otherwise, the operation is not performed (S45). The hot wire controller 710 may be a proportional integral (PI) controller or a proportional integral differential (PID) controller.

In this case, the reference temperature may be a temperature at which a semiconductor such as amorphous silicon forming the switching element Q of the pixel PX and the gate driver 400 is not properly operated, for example, about 15 ° C. to about 20 ° C. or less. .

Next, it is checked whether the liquid crystal display device is operating (S46). If not, the operation of the heating wire TL is stopped (S47).

Meanwhile, in the exemplary embodiment of the present invention, the gate driver 400 is integrated as an example, but the same may be applied to the data driver 500, and the present invention may be applied to a case in which not only amorphous silicon but also polycrystalline silicon are used. Can be.

In this way, the heating wire and the temperature sensing unit for controlling the same can ensure a reliable operating characteristics even at low temperatures.

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 (7)

A liquid crystal panel assembly comprising an upper panel and a lower panel; A heating wire disposed along an edge of the liquid crystal panel assembly A temperature sensor for detecting ambient temperature, and Hot wire control unit for controlling the hot wire in accordance with the temperature information from the temperature sensing unit Liquid crystal display comprising a. In claim 1, Further comprising at least one support for receiving and supporting the liquid crystal panel assembly, The heating wire is disposed on one of the supports Liquid crystal display. In claim 2, The support includes a front and rear chassis and a mold frame, The heating wire is disposed in the rear chassis. Liquid crystal display. In claim 3, The rear chassis has a cross-section in the shape of a staircase. In claim 4, A gate driver for applying a gate signal to the signal line and the signal line; The gate driver is integrated in the lower panel. Liquid crystal display. A driving method of a liquid crystal display device comprising a liquid crystal panel assembly and a heating wire disposed along an edge of the liquid crystal panel assembly. Operating the liquid crystal display device; Detecting an ambient temperature of the liquid crystal display device; Determining whether the ambient temperature is below a reference temperature, and Operating the hot wire according to the determination result. Method of driving a liquid crystal display comprising a. In claim 6, And a gate driver for applying a gate signal to the signal line.

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