KR20070021839A - Liquid crystal display - Google Patents

Abstract

A liquid crystal display device capable of maintaining stable luminance is provided. According to an exemplary embodiment of the present invention, a liquid crystal display device includes a liquid crystal display panel including a plurality of unit pixels two-dimensionally arranged in an area where a plurality of gate lines and a plurality of data lines intersect, and light is applied to the liquid crystal display panel. A backlight unit configured to provide a gate signal to a plurality of gate lines, a data driver to provide a data signal to a plurality of data lines in synchronization with the gate signal, and a driving voltage to provide a driving voltage AVDD to the data driver. And a driving voltage controller configured to vary the driving voltage so as to correspond to an operating time of the negative and liquid crystal display panels and / or the backlight unit.

LCD, luminance, driving voltage controller, inverter controller, temperature sensor

Description

Liquid crystal display

FIG. 1A is a graph illustrating a change in luminance over time of a liquid crystal display, and FIG. 1B is a graph illustrating a change in luminance according to a driving voltage of the liquid crystal display.

2A and 2B schematically illustrate a liquid crystal display according to an exemplary embodiment of the present invention and a modified embodiment thereof.

3A and 3B are schematic diagrams illustrating a liquid crystal display device according to another embodiment of the present invention and a modified embodiment thereof.

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

210: liquid crystal display panel 220: data driver

230: gate driver 240: signal controller

250: driving voltage generator 260: driving voltage controller

270 temperature sensor 280 backlight unit

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of maintaining more stable luminance.

In recent years, liquid crystal displays have been spotlighted as display means.

The liquid crystal display performs display functions using the electrical and optical properties of the liquid crystal injected into the panel, and is widely applied to various fields such as computer monitors and mobile communication terminals due to the advantages of small size, light weight, and low power consumption. There is a trend.

The liquid crystal display device has an active matrix display method using a switching element and a twisted nematic liquid crystal and a passive matrix display method using a super-twisted nematic liquid crystal according to a difference in driving method. It can be divided into

The biggest difference between the two display methods is that the active matrix display method uses a thin film transistor (TFT) as a switch to drive the LCD, whereas the passive matrix display method does not use a transistor, and thus requires a complicated circuit. It is not to be. However, the liquid crystal display of the active matrix display method, which is technically superior in terms of image quality, is widely used.

Since the liquid crystal display device is not a self-luminous display device but a light receiving type display device, a separate light source such as a back light unit equipped with a lamp is required. That is, by selectively transmitting the light applied from the backlight unit through the liquid crystal display panel, desired image information can be displayed.

However, such a liquid crystal display device has a problem in that the brightness of the lamp and the transmittance of the liquid crystal display panel are changed due to the temperature rise as the operation time elapses, and thus the brightness of the screen felt by the user is changed.

The technical problem to be achieved by the present invention is to provide a liquid crystal display device that can maintain a more stable brightness.

The technical problem of the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a liquid crystal display device including: a liquid crystal display panel including a plurality of unit pixels two-dimensionally arranged in an area where a plurality of gate lines and a plurality of data lines cross each other; A backlight unit for applying light to the liquid crystal display panel, a gate driver for applying a gate signal to the plurality of gate lines, a data driver for providing data signals to the plurality of data lines in synchronization with the gate signal, and a driving voltage (AVDD) to the data driver. And a driving voltage controller for varying the driving voltage so as to correspond to an operating time of the liquid crystal display panel and / or the backlight unit.

In this case, the driving voltage controller may increase the driving voltage after a predetermined reference time elapses after the operation of the liquid crystal display panel and / or the backlight unit starts.

In addition, a liquid crystal display device according to a second embodiment of the present invention includes a liquid crystal display panel having a plurality of unit pixels two-dimensionally arranged in a region where a plurality of gate lines and a plurality of data lines intersect, A backlight unit for applying a gate signal, a gate driver for applying a gate signal to a plurality of gate lines, a data driver for providing a data signal to a plurality of data lines in synchronization with the gate signal, and a driving voltage generator for providing a driving voltage to the data driver. The apparatus may include a temperature sensor sensing a temperature of the liquid crystal display panel and / or the backlight unit, and a driving voltage controller configured to vary the driving voltage to correspond to the temperature of the liquid crystal display panel and / or the backlight unit sensed by the temperature sensor.

The driving voltage controller may be operated when the temperature of the liquid crystal display panel and / or the backlight unit sensed by the temperature sensor exceeds a predetermined reference temperature.

On the other hand, the liquid crystal display device according to the third embodiment of the present invention includes a liquid crystal display panel, a lamp as a light source, a backlight unit for applying light to the liquid crystal display panel, an inverter for providing a lamp driving voltage to the backlight unit, and a liquid crystal display Inverter control unit for varying the lamp driving voltage to correspond to the operating time of the panel and / or the backlight unit.

In this case, the inverter controller may increase the lamp driving voltage after a predetermined time elapses after the operation of the liquid crystal display panel and / or the backlight unit is started.

In addition, a liquid crystal display device according to a fourth embodiment of the present invention includes a liquid crystal display panel, a lamp as a light source, a backlight unit for applying light to the liquid crystal display panel, an inverter for providing a lamp driving voltage to the backlight unit, and a liquid crystal display. A temperature sensor for sensing a temperature of the panel and / or the backlight unit, and an inverter controller for varying the lamp driving voltage to correspond to the temperature of the liquid crystal display panel and / or the backlight unit sensed by the temperature sensor.

The inverter controller may be operated when a temperature of the liquid crystal display panel and / or the backlight unit sensed by a temperature sensor exceeds a predetermined reference temperature.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be embodied in various forms, and the present embodiments are merely provided to make the disclosure of the present invention complete and the general knowledge in the art to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, the invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1A is a graph illustrating a change in luminance over time of a liquid crystal display, and FIG. 1B is a graph illustrating a change in luminance according to a driving voltage of the liquid crystal display.

Referring to FIG. 1A, the luminance increases for about 5 minutes after the operation of the liquid crystal display is started, and then the luminance decreases little by little. Therefore, by controlling the luminance so as to correspond to such a change in the luminance value by an artificial control signal or the like, it is possible to provide image information having more stable luminance.

To this end, in the case of FIG. 1A, the luminance is decreased or maintained for the first 5 minutes after the operation of the liquid crystal display is started, and the luminance is gradually increased in response to the luminance value decreased from the subsequent time. The method may be used. Alternatively, since a change in luminance is caused by a change in temperature of a liquid crystal display panel or the like, a method of measuring a change in temperature at a predetermined position of the liquid crystal display and controlling the luminance to correspond thereto may be used. Could be.

At this time, the change in luminance with time may vary slightly depending on the size of the liquid crystal display and various product characteristics, and thus, it will be apparent to those skilled in the art that the characteristics of the control signal should be changed to suit each product characteristic. .

For reference, the graph shown in FIG. 1A shows a luminance characteristic graph for a 40-inch normally white liquid crystal display product.

FIG. 1B is a graph showing a change in luminance according to the magnitude of the driving voltage AVDD, and it can be seen that the luminance of the LCD increases gradually in response to an increase in the driving voltage. Therefore, the compensation for the luminance change of the liquid crystal display may be possible by controlling the driving voltage.

In addition, a brightness compensation method through direct brightness control of a lamp may be used.

2A and 2B schematically illustrate a liquid crystal display according to an exemplary embodiment of the present invention and a modified embodiment thereof.

First, as shown in FIG. 2A, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal display panel 210, a data driver 220, a gate driver 230, a driving voltage generator 250, and a driving voltage. The controller 260 and the backlight unit 280 may be configured.

In the liquid crystal display panel 210, a plurality of gate lines and data lines are formed in a matrix form. The thin film transistor 215 is formed at the intersection of the plurality of gate lines and the data lines.

In general, a common electrode and a color filter are formed on an opposite substrate facing the substrate on which the thin film transistor 215 is formed, and the liquid crystal display panel 210 is formed by encapsulating liquid crystal between the two substrates.

Although not shown in detail, the thin film transistor 215 includes a gate electrode, a source electrode, a drain electrode, an active layer, an ohmic contact layer, and the like, and the drain electrode is connected to the pixel electrode to form the unit pixel P. In addition, when the gate signal is applied to the gate electrode through the gate line, the thin film transistor 215 having such a structure operates so that the data signal applied to the data line is transferred from the source electrode to the drain electrode through the ohmic contact layer and the active layer. .

That is, when a data signal is applied to the source electrode, a voltage corresponding thereto is applied to the pixel electrode connected to the source electrode, which causes a voltage difference between the pixel electrode and the common electrode. In addition, due to the voltage difference between the pixel electrode and the common electrode, the molecular arrangement of the liquid crystal interposed therebetween changes, and the light transmittance of the pixel changes due to the change in the molecular arrangement of the liquid crystal, thereby causing the data signal applied to each pixel. The color difference of the pixel is generated according to the difference.

By using the light applied from the backlight unit 280 located at the rear of the liquid crystal display panel 210, it is possible to display the image information according to the color difference.

The data signal applied to the source electrode is provided from the data driver 220, and the gate signal applied to the gate electrode is provided from the gate driver 230.

The gate driver 230 sequentially provides a gate signal to a plurality of gate lines to activate or deactivate the gate electrode. Then, the data driver 220 provides the gray voltage corresponding to the data signal to the plurality of data lines in accordance with the timing at which the gate signal is applied. Timing synchronization between the data driver 220 and the gate driver 230 is performed by the signal controller 240 or the like.

The driving voltage generator 250 receives the voltage VIN from the outside to generate the driving voltage AVDD and provides the driving voltage AVDD to the data driver 220.

In this case, the driving voltage generated by the driving voltage generator 250 may vary according to a control signal input from the driving voltage controller 260. That is, as described with reference to FIG. 1B, it is possible to compensate for the luminance value of the liquid crystal display device that varies with time by changing the luminance through the control of the driving voltage.

In other words, the driving voltage controller 260 increases or decreases the driving voltage generated from the driving voltage generator 250 by generating a control signal corresponding to the operation time of the liquid crystal display panel 210 and / or the backlight unit 280. You can.

Since the LCD has a constant luminance change pattern with time, the luminance value can be compensated by changing the driving voltage by a control signal having a constant change corresponding to time, as described above with reference to FIG. 1A. . In this case, since the luminance change pattern of the liquid crystal display device may vary depending on the size of the liquid crystal display device and various product characteristics, the control signal value according to time should be set differently to suit each liquid crystal display device. Of course it will.

Next, FIG. 2B is a configuration diagram illustrating a liquid crystal display according to another exemplary embodiment of the present invention, and illustrates a modification of the liquid crystal display according to the exemplary embodiment of the present invention illustrated in FIG. 2A. That is, referring to FIG. 2B, it can be seen that the temperature sensor 270 is additionally provided in the liquid crystal display according to the exemplary embodiment of the present invention illustrated in FIG. 2A.

In other words, since the luminance change of the liquid crystal display device with time is caused by the temperature change of the liquid crystal display panel 210 and the backlight unit 280, the liquid crystal display panel 210 and / or the backlight unit 280 By grasping the change in the luminance value according to the temperature at a predetermined position of and setting the control value corresponding thereto, the luminance is changed by changing the driving voltage by a control signal which is changed in accordance with the change of the real-time temperature grasped by the temperature sensor 270. The value can be compensated.

Accordingly, the generation of the control signal according to the temperature is only a control signal over time in that the control signal corresponding to the temperature of the liquid crystal display panel 210 and / or the backlight unit 280 that changes every moment should be generated. Compared to the method of generating the present invention, there is a difficulty in configuration, but it is possible to immediately reflect the unpredictable changing conditions such as the external temperature, thereby providing a relatively more uniform luminance.

Description of the configuration and operation of other unexplained reference numerals will be replaced by the description of FIG. 2A.

3A and 3B are schematic diagrams illustrating a liquid crystal display according to another exemplary embodiment of the present invention and a modification thereof.

First, as shown in FIG. 3A, a liquid crystal display according to another exemplary embodiment of the present invention includes a liquid crystal display panel 310, a backlight unit 320, an inverter 330, and an inverter controller 340. do.

The liquid crystal display panel 310 is composed of an upper substrate 312 such as a color filter substrate, a lower substrate 314 such as a thin film transistor substrate, and liquid crystal (not shown) injected therebetween.

The backlight unit 320 applies light to the liquid crystal display panel 310, and includes a lamp 325, which is a light source, and a reflector and a diffusion plate (not shown).

The inverter 330 operates the backlight unit 320 by supplying the lamp 325 which has changed the voltage applied from the outside to be suitable for driving the lamp 325 to the lamp 325.

In this case, the lamp driving voltage generated by the inverter 330 is changed according to a control signal input from the inverter controller 340, and the inverter controller 340 is the liquid crystal display panel 310 and / or the backlight unit 320. Generate a control signal to correspond to the operating time of the.

As described above with reference to FIG. 1A, the liquid crystal display has a constant luminance change pattern with time, so that the brightness of the lamp 325 is changed by changing the lamp driving voltage by a control signal having a constant change corresponding thereto with time. The luminance value can be compensated by varying.

Since the luminance variation pattern of the liquid crystal display device may vary depending on the size of the liquid crystal display device and various product characteristics, the control signal value according to time should be set differently to suit each liquid crystal display device. same.

Next, FIG. 3B is a configuration diagram illustrating a liquid crystal display device according to still another embodiment of the present invention, and illustrates a modification of the liquid crystal display device according to another embodiment of the present invention shown in FIG. 3A. That is, referring to FIG. 3B, it can be seen that the temperature sensor 350 is additionally provided in the liquid crystal display according to another exemplary embodiment of the present invention illustrated in FIG. 3A.

In other words, since the luminance change of the liquid crystal display device with time is caused by the temperature change of the liquid crystal display panel 310 and the backlight unit 320, the liquid crystal display panel 310 and / or the backlight unit 320 is changed. By grasping the change in the luminance value according to the temperature at a predetermined position and setting a control value corresponding thereto, the luminance value can be compensated by changing the lamp driving voltage by a control signal which varies according to the change in real-time temperature.

Although generation of control signals according to temperature is more difficult than configuration of generation of control signals over time, there is an advantage in that it is possible to immediately reflect changing conditions such as external temperature, thereby providing higher quality image information. As described above.

Description of the configuration and operation of other non-described reference numerals will be replaced by the description of FIG. 3A.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, the embodiments described above are to be understood in all respects as illustrative and not restrictive.

According to the liquid crystal display device according to the embodiments of the present invention as described above, there is an advantage that it is possible to provide a liquid crystal display device capable of providing image information having a more stable brightness.

Claims (8)

A liquid crystal display panel including a plurality of unit pixels two-dimensionally arranged in an area where a plurality of gate lines and a plurality of data lines cross each other; A backlight unit applying light to the liquid crystal display panel; A gate driver configured to apply gate signals to the plurality of gate lines; A data driver configured to provide a data signal to the plurality of data lines in synchronization with the gate signal; A driving voltage generator configured to provide a driving voltage AVDD to the data driver; And And a driving voltage controller configured to vary the driving voltage to correspond to an operating time of the liquid crystal display panel and / or the backlight unit. The method of claim 1, And the driving voltage controller increases the driving voltage after a predetermined reference time has elapsed after the operation of the liquid crystal display panel and / or the backlight unit is started. A liquid crystal display panel including a plurality of unit pixels two-dimensionally arranged in an area where a plurality of gate lines and a plurality of data lines cross each other; A backlight unit applying light to the liquid crystal display panel; A gate driver configured to apply gate signals to the plurality of gate lines; A data driver configured to provide a data signal to the plurality of data lines in synchronization with the gate signal; A driving voltage generator configured to provide a driving voltage AVDD to the data driver; A temperature sensor configured to sense a temperature of the liquid crystal display panel and / or the backlight unit; And And a driving voltage controller configured to vary the driving voltage so as to correspond to a temperature of the liquid crystal display panel and / or the backlight unit sensed by the temperature sensor. The method of claim 3, wherein And the driving voltage controller is operated when a temperature of the liquid crystal display panel and / or the backlight unit sensed by the temperature sensor exceeds a predetermined reference temperature. A liquid crystal display panel; A backlight unit having a lamp as a light source and applying light to the liquid crystal display panel; An inverter providing a lamp driving voltage to the backlight unit; And And an inverter controller configured to vary the lamp driving voltage to correspond to an operation time of the liquid crystal display panel and / or the backlight unit. The method of claim 5, wherein And the inverter controller increases the lamp driving voltage after a predetermined time has passed since the operation of the liquid crystal display panel and / or the backlight unit. A liquid crystal display panel; A backlight unit having a lamp as a light source and applying light to the liquid crystal display panel; An inverter providing a lamp driving voltage to the backlight unit; A temperature sensor configured to sense a temperature of the liquid crystal display panel and / or the backlight unit; And And an inverter controller configured to vary the lamp driving voltage to correspond to a temperature of the liquid crystal display panel and / or the backlight unit sensed by the temperature sensor. The method of claim 7, wherein And the inverter controller is operated when a temperature of the liquid crystal display panel and / or the backlight unit sensed by the temperature sensor exceeds a predetermined reference temperature.

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