KR20050062273A - Liquid crystal display and driving method thereof - Google Patents

Abstract

The present invention relates to a liquid crystal display and a driving method thereof, wherein the red, green, and blue light beams irradiated to the liquid crystal display panel are varied according to the temperature of the environment in which the time-division type liquid crystal display is driven. To compensate for the change.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display and a driving method thereof, and more particularly, to a liquid crystal display and a driving thereof, which are suitable for compensating for color changes due to temperature changes of a field-sequential liquid crystal display panel. It is about a method.

In general, cathode ray tube (CRT), one of the widely used display devices, is mainly used for monitors such as televisions, measuring instruments, information terminal devices, etc. Could not respond actively to the demand for miniaturization and weight reduction.

Accordingly, liquid crystal displays having advantages of small size, light weight, and low power consumption have been actively developed in order to replace the cathode ray tube, and recently, the liquid crystal display has been developed enough to perform a role as a flat panel display, and the demand continues to increase. It is becoming.

The driving principle of the liquid crystal display device uses the optical anisotropy and polarization of the liquid crystal. In this case, since the liquid crystal has a long axis and a short axis in the shape of a round bar, the liquid crystal has directivity in the molecular arrangement, and the direction of the molecular array can be controlled by artificially applying an electric field to the liquid crystal.

Accordingly, when the molecular alignment direction of the liquid crystal is arbitrarily adjusted, light supplied from the back-light provided on the rear surface of the liquid crystal display panel is selectively transmitted or blocked according to the molecular arrangement direction of the liquid crystal. It is possible to implement the image by applying the. Such a liquid crystal display will be described in detail with reference to the accompanying drawings.

1 is an exemplary view showing a schematic cross-sectional configuration of a general liquid crystal display.

Referring to FIG. 1, the liquid crystal display device 10 may include a first substrate 20 and a second substrate 40 bonded to each other so as to have a predetermined distance from each other; A liquid crystal layer 30 formed at a distance between the first substrate 20 and the second substrate 40; The back-light is disposed on the rear surface of the second substrate 40 and supplies light to the liquid crystal display panel 15 including the first substrate 20, the second substrate 40, and the liquid crystal layer 30. backlight, 50).

The lower surface of the transparent substrate 21 of the first substrate 20 is provided with a black matrix 22 formed of a material that blocks light in the form of a net along the outer edges of the pixels in order to partition pixels through which light passes. On the bottom surface of the transparent substrate 21 on which the matrix 22 is formed, red, green, and blue color filters 23 are provided so that light transmitted from the pixels may have red, green, and blue colors.

A lower portion of the color filter 23 is provided with a transparent common electrode 24, which is one electrode that applies an electric field to the liquid crystal layer 30.

On the other hand, a thin film transistor (TFT) to the switching role on the transparent substrate 41 of the second substrate 40; A transparent pixel electrode 42 is provided to receive a signal from the thin film transistor TFT and apply an electric field to the liquid crystal layer 30 together with the transparent common electrode 24.

In addition, a plurality of gate lines are arranged laterally spaced apart on the transparent substrate 41 of the second substrate 40; A plurality of data lines arranged vertically apart and vertically intersect, pixels are defined and arranged in a matrix in a rectangular area where the gate lines and the data lines intersect, and the pixel electrode 42 is individually arranged in the pixels. It is provided with.

The thin film transistor TFT may include a gate electrode in electrical contact with the gate lines; A source electrode in electrical contact with the data lines; A drain electrode in electrical contact with the pixel electrode 42 is provided.

However, the general liquid crystal display as described above has the following problems.

First, since the transmittance of light transmitted through the color filter 23 is about 33% at maximum, the loss of light is large. Therefore, in order to improve the brightness of the liquid crystal display, the light generated from the back light 50 must be brightened, and thus the power consumption is very large.

In addition, since the color filter 23 is very expensive compared to other materials, the color filter 23 increases the manufacturing cost of the liquid crystal display.

In order to solve the above problems, a time-division liquid crystal display device capable of realizing full color without applying the color filter 23 has been proposed.

In general, the back-light of the liquid crystal display is a method of supplying white light when the liquid crystal display is driven while the liquid crystal display is driven. However, the time-division type liquid crystal display is red, for one frame of an image. The red, green, and blue light sources are turned on at regular time intervals through green and blue light back-lights to display color images.

The time-division type liquid crystal display is distinguished from a general liquid crystal display by not requiring a color filter, and red, green, and blue back-lights are applied because they individually light the red, green, and blue light sources. will be.

The time-division liquid crystal display overcomes the problem of deterioration in brightness of a general liquid crystal display to which a color filter is applied, and implements full-color by applying a back light having red, green, and blue light sources. Therefore, by providing a liquid crystal display panel having high luminance and contrast characteristics and reduced manufacturing cost, it has an advantage that it can be very effectively applied to fabrication of a large area liquid crystal display device.

The red, green and blue back light includes a red light emitting diode (LED), a green LED and a blue LED.

The red LED, green LED, and blue LED are flashed by the inverter for 60 times per second, each of red, green, and blue light 180 times, so that the red, green, and blue light are mixed through the afterimage effect. By expressing color.

The red LED, the green LED, and the blue LED blink 180 times per second, but the actual human view recognizes that the red LED, the green LED, and the blue LED are all turned on.

For example, if the red LED is turned on first and the blue LED is turned on within a short time, the phenomenon that appears purple due to the afterimage effect of time is applied.

2 is a graph showing luminance characteristics according to temperatures of the red LED, the green LED, and the blue LED.

Referring to FIG. 2, the blue LED (B-LED) has a low luminance change at low temperature, room temperature, and high temperature, but the green LED (G-LED) has a higher luminance at low temperature than the blue LED (B-LED), and has a high temperature. The luminance is lowered at, and the red LED (R-LED) has a higher brightness at low temperature and a lower luminance at high temperature than the green LED (G-LED).

As described above, the red LED (R-LED), the green LED (G-LED), and the blue LED (B-LED), which have different luminance changes according to the temperature change, are applied to the back-light, thereby providing time-division liquid crystal display. The screen of the device appears red at low temperatures and blue at high temperatures.

Therefore, in the time-division type liquid crystal display device in which the red LED, the green LED, and the blue LED are applied as the back light, the color of the image changes with temperature. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device and a driving method thereof capable of compensating for color changes due to temperature changes of a time-division type liquid crystal display panel. have.

According to an aspect of the present invention, there is provided a liquid crystal display including: a control unit for time-dividing one frame of an image into a plurality of subframes and applying image information to the liquid crystal display panel; A backlight for illuminating the liquid crystal display panel with at least three lights according to the subframes; A sensor for sensing a temperature of an environment in which the liquid crystal display panel is driven; And a back-light control unit configured to control the back-light so that the irradiation periods of the three lights are different from each other according to the control signal of the controller and the control signal of the sensor.

According to an aspect of the present invention, there is provided a method of driving a liquid crystal display, the method comprising: dividing a frame of an image into a plurality of subframes and applying image information to the liquid crystal display panel to time-divisionally drive the liquid crystal display panel Wow; And sequentially applying at least three lights having different irradiation intervals to the time-division driven liquid crystal display panel according to a temperature of an environment in which the liquid crystal display panel is driven.

3 is an exemplary view showing a schematic cross-sectional configuration of a time-division liquid crystal display.

Referring to FIG. 3, the time-division type liquid crystal display device 60 includes a first substrate 70 and a second substrate 90 joined to face each other to have a predetermined spacing interval; A liquid crystal layer 80 formed at a distance between the first substrate 70 and the second substrate 90; Red, green, and blue light is emitted to the liquid crystal display panel 65 disposed on the rear surface of the second substrate 90 and composed of the first substrate 70, the second substrate 90, and the liquid crystal layer 80. It is composed of red (R), green (G), blue (B) back-light 100 to supply.

The lower surface of the transparent substrate 71 of the first substrate 70 is provided with a black matrix 72 formed of a material that blocks the light of the net shape along the outer edge of the pixels in order to partition the pixels through which the light is transmitted.

The lower surface of the transparent substrate 71 on which the black matrix 72 is formed is provided with a transparent common electrode 73 which is one electrode that applies an electric field to the liquid crystal layer 80.

A thin film transistor (TFT) having a switching role on the transparent substrate 91 of the second substrate 90; A transparent pixel electrode 92 is provided to receive a signal from the thin film transistor TFT and apply an electric field to the liquid crystal layer 80 together with the transparent common electrode 73.

As described above, when the common electrode 73 is provided on the first substrate 70, and the pixel electrode 92 is provided on the second substrate 90, the liquid crystal molecules of the liquid crystal layer 80 may be formed. It is driven by the vertical electric field between the common electrode 73 and the pixel electrode 92.

Meanwhile, the common electrode 73 and the pixel electrode 92 may be provided on the second substrate 90, and the liquid crystal molecules of the liquid crystal layer 80 may be the common electrode 73 and the pixel electrode 92. Driven by a horizontal electric field between.

As described above, the pixel electrode 92 and the common electrode 73 are provided on the second substrate 90 to drive the liquid crystal molecules of the liquid crystal layer 80 by a horizontal electric field. plane switching: IPS type) Liquid crystal display.

A plurality of gate lines horizontally spaced apart from the upper portion of the transparent substrate 91 of the second substrate 90; A plurality of data lines that are vertically spaced apart and vertically intersect, pixels are defined and arranged in a matrix in a rectangular region where the gate lines and the data lines intersect, and the pixel electrode 92 is individually arranged in the pixels. It is provided with.

The thin film transistor TFT may include a gate electrode in electrical contact with the gate lines; A source electrode in electrical contact with the data lines; A drain electrode in electrical contact with the pixel electrode 92 is provided.

As described above, the time-division type liquid crystal display device 60 is distinguished from a general liquid crystal display device because a color filter is not required, and red, green, and blue light sources are individually turned on. Green (G) and blue (B) back-lights 100 are applied. At this time, the red (R), green (G), blue (B) back-light 100 is composed of a red LED, a green LED and a blue LED.

The red LED, the green LED and the blue LED are flashed by the inverter (not shown in the figure) by red, green and blue light 60 times per second, for a total of 180 times, thereby providing a red color through visual afterimage effects. , Green and blue light is mixed to express the color.

The red LED, the green LED, and the blue LED blink 180 times per second, but the actual human view recognizes that the red LED, the green LED, and the blue LED are all turned on.

For example, if the red LED is turned on first and the blue LED is turned on within a short time, the phenomenon that appears purple due to the afterimage effect of time is applied.

A liquid crystal display and a driving method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

4 is an exemplary view showing a time-division type liquid crystal display device according to the present invention.

Referring to FIG. 4, a control unit time-divides one frame of an image into first to third subframes, and applies the image information DATA [R, G, B] to the liquid crystal display panel 210. 230; A backlight unit 220 illuminating the liquid crystal display panel 210 with red, green, and blue light according to the subframes; A sensor 240 for sensing a temperature of an environment in which the liquid crystal display panel 210 is driven; A bag controlling the back-light 220 so that the irradiation sections of the red, green, and blue light are different from each other according to the control signal CS1 of the controller 230 and the control signal SS1 of the sensor 240. A light control unit 250.

The controller 230 time-divides one frame of an image into first to third subframes, and applies the image information DATA [R, G, B] to the liquid crystal display panel 210 to perform liquid crystal display. The display panel 210 is time-division driven.

The liquid crystal display panel 210 is time-divided and driven by the first to third subframes under the control of the controller 230, and red and green from the back light 220 in the first to third subframes. And the blue light to display the color image according to the image information DATA [R, G, B]. In this case, the liquid crystal display panel 210 includes a first substrate and a second substrate bonded together to maintain a constant cell-gap, and a liquid crystal layer formed between the first substrate and the second substrate. do.

The liquid crystal layer may be a ferroelectric liquid crystal, an optical compensated birefringent (OCB), twisted nematic (TN), or the like having high-speed response characteristics.

The back light 220 includes a light guide plate corresponding to the entire rear surface of the liquid crystal display panel 210 and a light source unit generating red, green, and blue light provided on one side or both sides of the light guide plate. As such, the back light 220 provided on one side or both sides of the light guide plate to generate red, green, and blue light is referred to as a wave guide type.

Meanwhile, the back light 220 includes a light source unit for generating red, green, and blue light corresponding to the entire rear surface of the liquid crystal display panel 210, and between the light source unit and the liquid crystal display panel 210. A scattering plate may be provided so that a direct type for directly supplying red, green, and blue light to the front surface of the liquid crystal display panel 210 may be applied. Such a direct backlight 220 is mainly applied to a liquid crystal display in which luminance is emphasized.

In addition, the back-light controller 250 emits red, green, and blue light to the liquid crystal display panel 210 that is time-divisionally driven according to the control signal CS1 applied from the controller 230. -Control the light 220.

As described above, the blue LED of the back-light 220 does not have a large change in brightness at low temperature, room temperature, and high temperature, but the green LED has a high brightness at low temperature, low brightness at high temperature, and red at low temperature, compared to a blue LED. LEDs have higher brightness at lower temperatures and lower brightness at higher temperatures than green LEDs.

Accordingly, in the time-division type liquid crystal display according to the present invention, the control signal SS1 is applied by the back-light controller 250 from the sensor 240 that senses the temperature of the environment in which the liquid crystal display panel 210 is driven. The back-light 220 is controlled such that the irradiation sections of the red, green, and blue light are different from each other. In this case, the sensor 240 may apply a thermistor whose resistance is sensitive to temperature changes.

The back-light control unit 250 performs pulse width modulation (PWM) by the control signal SS1 applied from the sensor 240 so that the irradiation sections of the red, green, and blue light are different from each other. The back light 220 is controlled.

That is, when the time-division liquid crystal display according to the present invention is driven at a low temperature, the back-light control unit 250 may control the red LED, the green LED, and the red LED by the control signal SS1 applied from the sensor 240. By controlling the back light 220 so that the irradiation period of the blue LED is gradually increased, the luminance of the red LED may be reduced to prevent the screen of the time-division liquid crystal display from appearing red at low temperature.

In addition, when the time-division liquid crystal display according to the present invention is driven at a high temperature, the back-light control unit 250 may control the red LED, the green LED, and the light by the control signal SS1 applied from the sensor 240. By controlling the back light 220 to shorten the irradiation period of the blue LED, the luminance of the blue LED may be reduced to prevent the screen of the time-division liquid crystal display from appearing blue at a high temperature.

On the other hand, when the time-division liquid crystal display according to the present invention is driven at room temperature, the back-light control unit 250 controls the red LED, green LED, and the like by the control signal SS1 applied from the sensor 240. The back-light 220 is controlled to have the same irradiation period of the blue LED.

5 to 7 are exemplary views showing irradiation sections of a red LED, a green LED, and a blue LED when the time-division type liquid crystal display panel according to the present invention is driven at room temperature, low temperature, and high temperature. The driving of the time-divisional liquid crystal display panel according to the present invention will be described in detail with reference to the exemplary diagram of FIG. 7.

4 and 5, the time-division type liquid crystal display according to the present invention will be described in detail as follows.

First, the controller 230 time-divides one frame FRAME1 of an image into first to third subframes SUB-FRAME1 to SUB-FRAME3, and accordingly image information DATA [R, G, B ] Is applied to the liquid crystal display panel 210 to time-division drive the liquid crystal display panel 210.

That is, in the first sub frame SUB-FRAME1, gate pulse voltages are sequentially scanned on the gate lines of the liquid crystal display panel 210 during the thin film transistor scan period TFT-SCAN1, and red light is applied to the red lines through the data lines. Image information DATA [R] is supplied.

Therefore, the liquid crystal molecules of the liquid crystal display panel 210 supplied with the image information DATA [R] for red in the thin film transistor scan period TFT-SCAN1 are rearranged during the liquid crystal response period LC-RESPONSE1.

When the liquid crystal molecules are rearranged during the liquid crystal response section LC-RESPONSE1, the control unit 230 applies a control signal CS1 to the back-light control unit 250, and accordingly the back-light control unit 250. By controlling the back light 220 to turn on the red LED, the red color is displayed during the red flashing section R-FLASHING1 in the liquid crystal display panel 210, and the first sub-frame SUB-FRAME1 is terminated.

After the first sub frame SUB-FRAME1 ends, a gate pulse voltage is sequentially applied to the gate lines of the liquid crystal display panel 210 during the thin film transistor scan period TFT-SCAN1 in the second sub frame SUB-FRAME2. Is scanned and image information DATA [G] for green is supplied through the data lines.

Accordingly, the liquid crystal molecules of the liquid crystal display panel 210 supplied with the green image information DATA [G] in the thin film transistor scan period TFT-SCAN1 are rearranged during the liquid crystal response period LC-RESPONSE1.

When the liquid crystal molecules are rearranged during the liquid crystal response section LC-RESPONSE1, the control unit 230 applies a control signal CS1 to the back-light control unit 250, and accordingly the back-light control unit 250. By controlling the back light 220 to turn on the green LED, green is displayed during the green flashing period G-FLASHING1 in the liquid crystal display panel 210, and the second sub-frame SUB-FRAME2 ends.

In addition, after the second sub frame SUB-FRAME2 ends, the third sub frame SUB-FRAME3 sequentially gates the gate lines of the liquid crystal display panel 210 during the thin film transistor scan period TFT-SCAN1. The pulse voltage is scanned, and image information DATA [B] for blue is supplied through the data lines.

Accordingly, the liquid crystal molecules of the liquid crystal display panel 210 supplied with the blue image information DATA [B] in the thin film transistor scan period TFT-SCAN1 are rearranged during the liquid crystal response period LC-RESPONSE1.

When the liquid crystal molecules are rearranged during the liquid crystal response section LC-RESPONSE1, the control unit 230 applies a control signal CS1 to the back-light control unit 250, and accordingly the back-light control unit 250. By controlling the back light 220 to light the blue LED, the blue color is displayed during the blue flashing period B-FLASHING1 in the liquid crystal display panel 210, and the third sub-frame SUB-FRAME3 is terminated.

The sensor 240 applies the control signal SS1 to the back-light control unit 250 when the time-division liquid crystal display is driven at room temperature, thereby applying the red flashing section R-FLASHING1, The back-light 220 is controlled such that the green flashing section G-FLASHING1 and the blue flashing section B-FLASHING1 are the same.

On the other hand, when the time-division type liquid crystal display according to the present invention is driven at a low temperature, the sensor 240 applies a control signal SS1 to the back-light controller 250 as shown in FIG. 6. By controlling the back-light 220 so that the red flashing section R-FLASHING11, the green flashing section G-FLASHING11, and the blue flashing section B-FLASHING11 are gradually longer, the luminance of red is reduced to time-division The screen of the liquid crystal display is prevented from appearing red at low temperatures.

In addition, when the time-division type liquid crystal display according to the present invention is driven at a high temperature, the sensor 240 applies a control signal SS1 to the back-light controller 250 as shown in FIG. 7. By controlling the back-light 220 so that the red flashing section R-FLASHING22, the green flashing section G-FLASHING22, and the blue flashing section B-FLASHING22 are gradually shortened, the luminance of blue is reduced to time-division This prevents the screen of the liquid crystal display from appearing blue at a high temperature.

As described above, the liquid crystal display and the driving method thereof according to the present invention allow the irradiation sections of the red, green, and blue light to be irradiated to the liquid crystal display panel to be different depending on the temperature of the environment in which the time-division type liquid crystal display is driven. Therefore, the color change can be compensated.

Therefore, it is possible to prevent the screen of the time-division type liquid crystal display from appearing red at a low temperature and to appear blue at a high temperature, thereby improving the image quality of the time-division type liquid crystal display.

1 is an exemplary view showing a schematic cross-sectional configuration of a general liquid crystal display.

FIG. 2 is a graph showing luminance characteristics of a red LED, a green LED, and a blue LED applied to a back-light of a time-division liquid crystal display. FIG.

3 is an exemplary view showing a schematic cross-sectional configuration of a time-division liquid crystal display.

4 is an exemplary view showing a time-division type liquid crystal display device according to the present invention.

Figure 5 is an exemplary view showing the irradiation section of the red LED, green LED and blue LED when the time-division type liquid crystal display panel according to the present invention is driven at room temperature.

Figure 6 is an exemplary view showing the irradiation section of the red LED, green LED and blue LED when the time-division type liquid crystal display panel according to the present invention is driven at a low temperature.

Figure 7 is an exemplary view showing the irradiation section of the red LED, green LED and blue LED when the time-division type liquid crystal display panel according to the present invention is driven at a high temperature.

*** Explanation of symbols for main parts of drawing ***

210: liquid crystal display panel 220: back light

230: control unit 240: sensor

250: Back-light control part DATA [R, G, B]: Image information

CS1: control signal of the control unit

SS1: sensor control signal

Claims (10)

A control unit for time-dividing one frame of an image into a plurality of subframes and applying image information accordingly to the liquid crystal display panel; A backlight for illuminating the liquid crystal display panel with at least three lights according to the subframes; A sensor for sensing a temperature of an environment in which the liquid crystal display panel is driven; And a back-light controller configured to control the back-light such that the three light irradiation sections are different from each other according to a control signal of the controller and a control signal of the sensor. The liquid crystal display panel of claim 1, wherein the liquid crystal display panel comprises a first substrate and a second substrate bonded to each other to maintain a constant cell gap, and a liquid crystal layer formed on the cell gap of the first substrate and the second substrate. Liquid crystal display device characterized in that. 3. The liquid crystal display of claim 2, wherein the liquid crystal layer is formed of a ferroelectric liquid crystal, an optically compensated birefringent (OCB), a twisted nematic (TN), or the like having high-speed response speed. 2. The back light of claim 1, wherein the back light includes a wave guide type back light having a light source unit on one side or both sides of the light guide plate, or a direct type having a light source unit corresponding to the entire rear surface of the liquid crystal display panel. A liquid crystal display, characterized in that the back-light. The liquid crystal display of claim 1, wherein the back light emits red, green, and blue light to the liquid crystal display panel through red, green, and blue light emitting diodes. The liquid crystal display of claim 1, wherein the sensor is configured of a thermistor. The liquid crystal display of claim 1, wherein the back-light control unit controls the back-light so that the irradiation period of the red, green, and blue light is gradually longer or shorter in accordance with the control signal of the sensor. Dividing a frame of an image into a plurality of subframes, and applying image information to the liquid crystal display panel to time-division drive the liquid crystal display panel; And sequentially irradiating red, green, and blue light having different irradiation intervals to the time-division driven liquid crystal display panel according to the temperature of the environment in which the liquid crystal display panel is driven. Method of driving the device. The method of claim 8, wherein the red, green, and blue light irradiation sections are gradually lengthened by pulse width modulation. The method of claim 8, wherein the red, green, and blue light irradiation sections are gradually shortened by pulse width modulation.