KR100820843B1 - Liquid crystal display, method for detecting an inner temperature thereof and method for compensating a quality of image thereof - Google Patents

Abstract

Disclosed are a liquid crystal display, an internal temperature sensing method thereof, and an image quality compensation method for compensating for a change in image quality by sensing an internal temperature of the liquid crystal display. The lower substrate includes a gate electrode, a gate insulating film coated on the gate electrode, and a source-drain electrode coated on the gate insulating film, and incorporates a liquid crystal layer through the coalescence of the upper substrate. An AC wave is applied to the gate electrode of the lower substrate, an AC wave is detected from the source electrode, and the temperature of the liquid crystal layer is sensed based on the applied AC wave and the sensed AC wave. Accordingly, by applying an AC wave to the gate electrode and sensing the AC wave reflecting the temperature, the temperature can be calculated through the liquid crystal dielectric constant, thereby compensating for the image quality due to the temperature increase.

Liquid crystal. Temperature, sensing, image quality, compensation, OCB, AC

Description

Liquid crystal display, its internal temperature sensing method and image quality compensation method {LIQUID CRYSTAL DISPLAY, METHOD FOR DETECTING AN INNER TEMPERATURE THEREOF AND METHOD FOR COMPENSATING A QUALITY OF IMAGE THEREOF}

1 is a graph showing a change in the vertical dielectric constant (ε _⊥ ) of a specific liquid crystal with temperature.

2A is a diagram for describing a liquid crystal display device having a temperature sensing function according to an exemplary embodiment of the present invention, and FIG. 2B is a diagram for explaining an equivalent circuit of the liquid crystal display device described above.

3 is another diagram for describing a liquid crystal display device having a temperature sensing function according to the present invention.

4 shows the output voltage dVout when the liquid crystal capacitance C _LC changes with temperature. Here, it is assumed that the input voltage dVin is 2V.

5 is a flowchart illustrating an internal temperature sensing method of a liquid crystal display according to the present invention and an image quality compensation method using the same.

6 is a view for explaining a first embodiment of a liquid crystal display device having a temperature sensing function according to the present invention.                 

7 is a view for explaining the operation of the general OCB mode.

8 is a diagram for explaining an on / off cycle of the OCB mode.

9 is a graph for explaining a VT curve of a liquid crystal display device employing an OCB mode liquid crystal.

10A to 10B are diagrams for describing a gray voltage generator according to a first embodiment of the present invention.

11 is a view for explaining a second embodiment of a liquid crystal display device having a temperature sensing function according to the present invention.

12 is a view for explaining a third embodiment of a liquid crystal display device having a temperature sensing function according to the present invention.

13 is a view for explaining a fourth embodiment of a liquid crystal display device having a temperature sensing function according to the present invention.

14 is a view for explaining a fifth embodiment of a liquid crystal display device having a temperature sensing function according to the present invention.

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

10: temperature sensing unit 20: lower substrate

30 liquid crystal layer 40 upper substrate

22 signal electrode 24 dielectric layer

26 sensor electrode 100 timing control unit

200: driving voltage generator 300: common voltage generator                 

400: gray voltage generator 500: gate driver

600: data driver 700: liquid crystal display panel

800: backlight

The present invention relates to a liquid crystal display, a method for sensing an internal temperature thereof, and a method for compensating for image quality. More particularly, the present invention relates to a liquid crystal display, a method for sensing an internal temperature thereof, and a method for sensing an internal temperature thereof. It is about a compensation method.

In general, liquid crystal displays are much thinner, much lighter, and consume less power than cathode ray tubes, which are currently the mainstream of image display devices, and are already used as screen display devices of portable information devices such as mobile phones and laptop computers. It is widely used and emits less electromagnetic waves, so it is expected to be the mainstream in tabletop display devices in the future.

In the liquid crystal (Liquid Crystal) that is essentially provided in such a liquid crystal display device, each dielectric constant value varies according to temperature. That is, when the liquid crystal molecules are arranged in a direction parallel to the substrate, that is, when the liquid crystal molecules are arranged in a direction perpendicular to the direction of light, the parallel dielectric constant (ε _∥ ) or the liquid crystal molecules are arranged in a direction perpendicular to the substrate. In other words, when the liquid crystal molecules are arranged in a direction parallel to the direction of light, the vertical dielectric constant ε _⊥ and the difference dielectric constant Δε between the parallel dielectric constant and the vertical dielectric constant all change with temperature. This is because the order parameter of the liquid crystal changes.

Figure 1 illustrates in a schematic graph in accordance with the vertical dielectric constant (ε _⊥) of a specific liquid crystal to the temperature, in particular the changes in ε _⊥ value as a function of temperature for a particular liquid crystal of the VA liquid crystal.

Referring to FIG. 1, it can be seen that the vertical dielectric constant (ε _⊥ ) is severely changed according to the temperature change. The dielectric constant that changes according to the temperature change causes a problem of displaying a distorted screen rather than displaying a normal screen.

In particular, in the case of the liquid crystal display panel adopting the OCB mode, the optimum black voltage varies greatly depending on the temperature, so that the temperature increases with time after driving the environment or the product, resulting in a contrast ratio (CR). This severely changing problem occurs.

In addition, in most TFT LCD modes such as PVA, TN, and OCB, when the temperature is changed, the dielectric anisotropy of the liquid crystal changes, so the kickback voltage is changed, and thus the flicker level is changed. Occurs.

In addition, in the STN or the like, when the temperature is severe, the retardation value is severely changed and the image and the color itself may change.

In addition, in all liquid crystal display devices, when the temperature rises above the threshold, the liquid crystal original characteristics are lost, and an image cannot be represented.

Accordingly, the technical and problem of the present invention are to solve such a conventional problem, and an object of the present invention is to sense a temperature of a liquid crystal display panel to minimize the effect on the image quality or quality of the liquid crystal display device depending on the temperature. It is to provide a liquid crystal display device having a function.

Another object of the present invention is to provide an internal temperature sensing method of a liquid crystal display having the above-described temperature sensing function.

In addition, another object of the present invention is to provide a method for compensating image quality of a liquid crystal display device having the above-described temperature sensing function.

According to an aspect of the present invention, there is provided a liquid crystal display device comprising: an upper substrate; A lower substrate facing the upper substrate, the lower substrate including a first signal electrode, a dielectric layer applied over the first signal electrode, and a second signal electrode applied over the dielectric layer; A liquid crystal layer filled in a predetermined gap between the lower substrate and the upper substrate and having a liquid crystal capacitance varying in response to a constant electric field and a temperature change provided from the lower substrate; And applying a first AC wave having a constant amplitude to the first signal electrode to indirectly detect a change in the liquid crystal capacitance, and a second AC wave interlocked with the capacitance of the dielectric layer and the liquid crystal capacitance from the second signal electrode. Including a temperature sensing unit for receiving the temperature of the liquid crystal layer received.                     

According to another aspect of the present invention, a liquid crystal display device includes a gate electrode, a gate insulating film coated on the gate electrode, and a source-drain electrode coated on the gate insulating film. Liquid crystal display having a lower substrate facing the upper substrate, an upper substrate facing the lower substrate, and a liquid crystal layer filled in a predetermined gap between the lower substrate and the upper substrate and having a liquid crystal capacitance varying with temperature change. panel; A timing controller for outputting an image signal, a first control signal for controlling the output of the image signal, and a second control signal for selecting the output of the image signal; A source driver configured to output a data signal to the source electrode based on the image signal and the first control signal; A gate driver configured to output a scan signal to the gate electrode based on the second control signal; And applying an AC wave to one side of the lower substrate, receiving an AC wave reflecting a temperature from the other side of the lower substrate, sensing an internal temperature of the liquid crystal display panel, and compensating for image quality when the internal temperature is higher than a threshold temperature. It comprises a temperature sensor for outputting a signal.

In addition, an internal temperature sensing method of a liquid crystal display according to an aspect for realizing the object of the present invention, a gate electrode, a gate insulating film coated on the gate electrode, a source-drain electrode coated on the gate insulating film A temperature sensing method of a liquid crystal display device for displaying an image by embedding a liquid crystal layer through incorporation of the array substrate and the array substrate, the method comprising: (a) the temperature of the liquid crystal layer according to the start-up of the liquid crystal display device; Applying a first AC wave for sensing to the gate electrode; (b) sensing a second AC wave output in response to the first AC wave from the source-drain electrode; (c) calculating a liquid crystal capacitance of the liquid crystal layer based on the first AC wave and the second AC wave; (d) calculating a liquid crystal dielectric constant based on the calculated liquid crystal capacitance; (e) extracting a temperature based on the liquid crystal dielectric constant from a temperature table storing a temperature corresponding to the liquid crystal dielectric constant; (f) checking whether the temperature extracted in step (e) exceeds a threshold temperature; (g) feeding back to step (a) if the extracted temperature is checked to be below the threshold temperature in step (f); And (h) if it is checked that the extracted temperature is greater than the threshold temperature in step (f), determining that the liquid crystal display is at a high temperature and compensating for the image quality change.

According to one aspect of the present invention, there is provided a method of compensating for an image quality of a liquid crystal display, comprising a gate electrode, a gate insulating film coated on the gate electrode, and a source-drain electrode coated on the gate insulating film. A temperature sensing method of a liquid crystal display device displaying an image by embedding a liquid crystal layer through a combination of an array substrate and the array substrate, the method comprising: (a) sensing the temperature of the liquid crystal layer as the liquid crystal display is activated; Applying a first AC wave for the gate electrode; (b) sensing a second AC wave output in response to the first AC wave from the source-drain electrode; (c) calculating a liquid crystal capacitance of the liquid crystal layer based on the first AC wave and the second AC wave; (d) calculating a liquid crystal dielectric constant based on the calculated liquid crystal capacitance; (e) extracting a temperature based on the liquid crystal dielectric constant from a temperature table storing a temperature corresponding to the liquid crystal dielectric constant; (f) checking whether the temperature extracted in step (e) exceeds a threshold temperature; (g) feeding back to step (a) if the extracted temperature is checked to be below the threshold temperature in step (f); And (h) if it is checked that the extracted temperature is greater than the threshold temperature in step (f), determining that the liquid crystal display is at a high temperature and compensating for the image quality change.

According to the liquid crystal display, its internal temperature sensing method, and the image quality compensation method, an AC wave is applied to a gate electrode, and a temperature can be calculated through a liquid crystal dielectric constant by sensing an AC wave reflecting a temperature. Can compensate.

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

2A is a diagram for describing a liquid crystal display device having a temperature sensing function according to an exemplary embodiment of the present invention, and FIG. 2B is a diagram for explaining an equivalent circuit of the liquid crystal display device described above.

Referring to FIG. 2A, a liquid crystal display having a temperature sensing function according to an exemplary embodiment of the present invention includes a temperature sensing unit 10, a lower substrate 20, a liquid crystal layer 30, and an upper substrate 40.

The temperature sensing unit 10 includes an AC wave applying unit 12 for applying AC waves to one side of the lower substrate 20 and an AC wave sensing unit 14 for detecting AC waves output from the other side of the lower substrate 20. The internal temperature of the liquid crystal layer 30 is sensed based on the applied AC wave and the extracted AC wave. In this case, the AC wave applying unit 12 preferably inputs an AC voltage such as a square wave or a sin wave having a constant up and down peak value, and the intensity of the corresponding voltage is the voltage at which the change in the liquid crystal properties is most severe depending on the temperature. It is more preferable to select. This is obviously applied differently depending on whether the liquid crystal mode is OCB, TN, or STN.

The lower substrate 20, which is called an array substrate, includes a signal electrode 22, a dielectric layer 24, and a sensor electrode 26, and exchanges AC waves from the AC wave applying unit 12 of the temperature sensing unit 10 through one side. Is provided, and provides the AC wave in which the temperature information is reflected through the other side to the AC wave detector 14 of the temperature detector 10.

Here, it is preferable that the signal electrode 22 is a gate electrode formed on a transparent substrate, and the dielectric layer 24 is preferably a gate insulating film coated on the gate electrode.

In addition, the sensor electrode 26 may be implemented through a source-drain electrode coated on the gate insulating layer, or may be implemented through an ITO electrode which is a transparent electrode.

As such, the signal electrode, the dielectric layer, and the sensor electrode use a widely used gate electrode, a gate insulating film, a source-drain electrode, an ITO electrode, and the like to sense the internal temperature of the liquid crystal display panel. It will be easy to apply the temperature sensing function accordingly.

The liquid crystal layer 30 fills a predetermined gap between the lower substrate 20 and the upper substrate 40, and changes the liquid crystal capacitance C _LC that changes in response to a predetermined electric field provided from the lower substrate 20. Have That is, when the liquid crystal capacitance C _LC varies, the dielectric constant ε also changes in proportion to the liquid crystal capacitance C _LC , so that the internal temperature of the liquid crystal display panel may be calculated from the graph shown in FIG. 1.

The upper substrate 40, called a color filter substrate, incorporates the liquid crystal layer 30 through incorporation with the lower substrate 20, and displays an image in response to light passing through the liquid crystal layer 30.

As shown in FIG. 2B, when the voltage Vin applied to the signal electrode 22 changes, the voltage Vout of the sensor electrode 26 also changes. At this time, the rate of change is shown in Equation 1 below.

Where C _LC is the liquid crystal capacitance, Cd is the capacitance of the dielectric layer, ΔVin is the amplitude of the input voltage Vin, and ΔVout is the amplitude of the output voltage Vout.

Therefore, when the input voltage Vin is constant, the change in the liquid crystal capacitance C _LC may be sensed by reading the output voltage Vout.

That is, the liquid crystal capacitance C _LC calculated from Equation 1 can be easily detected by Equation 2 below.

Referring to Equation 2, since the capacitance Cd of the dielectric layer is a fixed value, the liquid crystal capacitance C _LC of the liquid crystal layer may be calculated based on the input alternating wave and the output alternating wave. The liquid crystal capacitance C _LC calculated as described above may be easily calculated based on Equation 3 below.

Here, A is the surface area of the liquid crystal layer, preferably the area of the effective display area formed between the array substrate and the color filter substrate, and d is the thickness of the liquid crystal layer, preferably the gap between the array substrate and the color filter substrate.

In the above description, an AC wave having a constant amplitude is applied to the first signal electrode of the array substrate provided in the liquid crystal display panel, and an AC wave interlocking with the capacitance of the dielectric layer and the liquid crystal capacitance is inputted from the second signal electrode. An example of sensing an internal temperature of the liquid crystal display panel by indirectly detecting the above is described. However, the present invention may be applied to a device such as a thermometer separately without being applied to the liquid crystal display device.                     

3 is another diagram for describing a liquid crystal display device having a temperature sensing function according to the present invention.

Referring to FIG. 3, a gate line formed on an array substrate and a data line formed orthogonal to the gate line define one pixel region, and for operation of the pixel region, The gate terminal and the source terminal of the TFT switching element are connected to the gate line and the data line, respectively.

A liquid crystal layer (not shown) is built in the upper portion of the formed pixel region, and according to the on / off operation of the gate terminal, a data voltage input to the source terminal is applied to the drain terminal to form a constant electric field. The liquid crystal capacitance (C _LC ) of is changed. Of course, a storage capacitor Cst is formed between adjacent gate lines to compensate for the loss of liquid crystal capacitance during one frame.

In the drawings, the detection of the AC wave according to the temperature change is performed through the source terminal, but may be performed through the drain terminal or through the transparent ITO electrode.

In addition, as described above, a structure in which an AC wave is applied to one pixel area and the AC wave is detected according to a temperature change from the pixel area may be implemented in one pixel area of a plurality of pixel areas constituting the liquid crystal display panel. It may be implemented in a plurality of pixel areas.

On the other hand, when considering the sensitivity of the output voltage (dVout) change with respect to the change amount of the liquid crystal capacitance (C _LC ) in the above equation 1, it is preferable to satisfy the condition of Cd <C _LC . For example, the case where Cd = 0.5C _LC is shown in FIG.

4 shows the output voltage dVout when the liquid crystal capacitance C _LC changes with temperature. Here, it is assumed that the input voltage dVin is 2V.

Referring to FIG. 4, when the liquid crystal capacitance C _LC changes with temperature, the output voltage dVout also changes accordingly, thereby detecting the internal temperature of the liquid crystal display panel by detecting the output voltage dVout.

5 is a flowchart illustrating an internal temperature sensing method of a liquid crystal display according to the present invention and an image quality compensation method using the same.

Referring to FIG. 5, first, it is checked whether the liquid crystal display is activated (step S110), and when the liquid crystal display is checked to be activated, the first AC wave is applied to the signal electrode of the array substrate, that is, the gate electrode line. (Step S120).

Subsequently, a second AC wave is detected from a source electrode, a drain electrode, or an ITO electrode of the array substrate (step S130), and a liquid crystal capacitance C _LC is calculated based on the detected second AC wave (step S140). The liquid crystal dielectric constant is calculated based on the liquid crystal capacitance (step S150).

Then, the temperature corresponding to the liquid crystal dielectric constant is extracted from the temperature table (step S160). Here, the temperature table stores a temperature corresponding to the liquid crystal dielectric constant. That is, it is obvious that the liquid crystal has a separate temperature table according to the liquid crystal constituting the liquid crystal layer because the liquid crystal dielectric constant is different according to the temperature change according to TN, STN, VA, PVA, OCB.

In the above, the temperature sensing method of the liquid crystal display device having the temperature sensing function has been described.

In addition, as shown in the drawing, when the liquid crystal display rises to a high temperature, it may be possible to compensate for a change in image quality deteriorated with the high temperature. That is, it is checked whether the extracted temperature exceeds a predetermined threshold temperature (step S170), and if it is checked that the extracted temperature is less than the predetermined threshold temperature, it is fed back to step S120, but the extracted temperature is checked to be below the predetermined threshold temperature. If it is determined that the internal temperature of the liquid crystal display device, preferably the liquid crystal display panel is high, compensate for the change in image quality or notify the user that the internal temperature is high (step S180).

In particular, since the above-described step S180 can be variously applied, a detailed description thereof will be described with reference to the following drawings.

FIG. 6 is a view for explaining a first embodiment of a liquid crystal display having a temperature sensing function according to the present invention. In particular, an embodiment of compensating for image quality by changing a gray voltage is described.

Referring to FIG. 6, a liquid crystal display having a temperature sensing function according to a first embodiment of the present invention may include a temperature sensing unit 10, a timing controller 100, a driving voltage generator 200, and a common voltage generator ( 300, a gray voltage generator 400, a gate driver 500, a data driver 600, a liquid crystal display panel 700, and a backlight unit 800.                     

As described above with reference to FIG. 2, the temperature sensing unit 10 applies an AC wave Vin for temperature sensing to one side of the liquid crystal display panel 700, preferably, a gate electrode of a TFT, and according to a response thereof. It detects an AC wave Vout provided from the other side of the liquid crystal display panel 600, preferably, a source electrode of the TFT, and displays the corresponding liquid crystal display based on the applied AC wave and the detected AC wave Vout. The internal temperature of the panel 600 is calculated.

In addition, the temperature sensor 10 outputs the gray voltage control signal 10a to the gray voltage generator 400 when it is determined that the temperature is high by comparing the calculated internal temperature with a threshold temperature as a reference for high temperature determination. do.

The timing controller 100 is an R, G, B data signals R [0: N], G [0: N], B [0: N], and frame discrimination signals from an external graphic controller (not shown). Provides vertical sync signal (Vsync), horizontal sync signal (Hsync), which is a line discrimination signal, and high level signal (DE) and main clock signal (MCLK) only during the data output period to indicate the area where data enters. In response, the data driver 600 and the gate driver 500 are converted into digital signals for driving and output to the corresponding driver.

In more detail, the timing controller 100 receives the digital data signals R [0: N], G [0: N], and B [0: N] from the graphic controller (not shown). The data driver receives a signal Hstart for input start, a signal LOAD for applying data to the LCD panel 700, and a clock signal HCLK for shifting data in the data driver 600. Output to 600.

In addition, the timing controller 100 may include a vertical line start signal STV that commands the start of the gate on signal, and a gate clock signal Gate clk for sequentially performing the gate on signal on each gate line. ) That is, a digital signal for driving the gate driver 500 and the data driver 600 is generated and output to the corresponding drivers 500 and 600.

The driving voltage generator 200 generates a voltage Von for making the gate on signal and a voltage Voff for making the gate off signal, and provides the generated voltage to the gate driver 500, and generates a voltage 201 for generating a common voltage. ) Is provided to the common voltage generator 300, the voltage 203 for generating the gray voltage is provided to the gray voltage generator 400, and the power for backlight generation is provided to the backlight 800. .

The common voltage generator 300 receives the voltage 201 for generating the common voltage provided from the driving voltage generator 200 and provides the common voltage Vcom to the common electrode line of the liquid crystal display panel 700. In the present invention, the driving voltage generator and the common voltage generator are separately described, but may be configured integrally.

The gray voltage generator 400 is configured to supply digital code values according to the number of bits of RGB data R [0: N], G [0: N], and B [0: N] provided from a graphic controller (not shown). Appropriate gray voltages (V0, V1, V2, ..., V3n) are generated and provided to the data driver 500, respectively. For example, if R data is applied with 6 bits (R [0: 5]), 2 ⁶ = 64 gradations are produced and R of 64 gradations is represented. Here, the gray voltage generator 400 extracts a voltage corresponding to a gray level of the negative side and the positive side VT (voltage vs. transmittance curve) from the built-in resistance string, and applies the gray level voltage adapted to each gray level to the data driver 600. ) In particular, the gray voltage generator 400 includes a negative fixed resistance string, a negative variable resistance string, a positive variable resistance string, and a positive fixed resistance string, and the gray voltage control signal from the temperature sensing unit 10 ( When 10a) is applied, the gradation voltage corresponding to the black color is varied and output.

In more detail, the negative fixed resistance string outputs one or more fixed negative gray level voltages, and the negative variable resistance string is connected in series with the negative fixed resistance string to vary in response to the image quality compensation signal. A gray level voltage, a positive variable resistance row connected in series to the negative variable resistance row, and outputting one or more positive gray level voltages that vary in response to the image quality compensation signal, and the positive fixed resistance row is the positive polarity The image quality is compensated by changing the black gray voltage through a method of outputting one or more fixed gray scale voltages connected in series to the variable resistance string. For example, in the case of a liquid crystal display panel employing an OCB type liquid crystal, the gradation voltage corresponding to the black color is changed. This will be described in detail with reference to FIGS. 7 to 10B to be described later.

The gate driver 500 may include a shift register, a level shifter, a buffer, and the like, and receive a gate clock signal Gate clk and a vertical line start signal Vstart from the timing controller 100, and the driving voltage generator 200. The gate on / off control voltages Von and Voff are received from the gate voltage and the common voltage Vcom is supplied from the common voltage generator 300 to display the gate voltages G1, G2, G3,. The panel 700 may be provided to the panel 700 to open the path so that the voltage value of each pixel on the liquid crystal display panel 700 is transferred to the pixel.

The data driver 600 receives and stores R, G, and B digital data (R [0: N], G [0: N], and B [0: N]) from the timing controller 100 and stores the liquid crystal display. When the load signal LOAD for commanding the panel 700 is applied, the voltage corresponding to each data is selected in cooperation with the gray voltage provided from the gray voltage generator 400 to the liquid crystal display panel 700. It carries data voltages D1, D2, D3, ..., Dm.

In addition, the data driver 500 outputs data voltages D1, D2, D3,..., And Dm so that the polarities of the pixels arranged on the liquid crystal display panel 700 are inverted differently for each predetermined frame. In this case, the inversion of the pixels so that the polarities are different every predetermined frame is due to the general characteristics of the liquid crystal, as is already known.

The liquid crystal display panel 700 is formed in m data lines, n gate lines arranged orthogonal to the data lines, and a predetermined region lattice arranged between the data lines and the gate lines, one end of which is disposed on the gate line. A pixel electrode having a switching element (TFT) connected to the other end and connected to the data line, and the gate voltages G1, G2,..., Gn provided from the gate driver 500 are applied to the pixel. As a result, the corresponding pixel electrode is driven in response to the data voltages D1, D2,..., And Dm provided from the data driver 600. In particular, the gate terminal of the TFT receives an AC wave input from the temperature sensing unit 10, and the source terminal outputs the AC wave reflecting the temperature to the temperature sensing unit 10. As such, the number of TFTs connected to the temperature sensing unit 10 may be one, or may be plural.                     

The backlight unit 800 may include an inverter 810 and a lamp 820, and may emit light whose brightness is adjusted based on the lamp control signal 205 provided from the driving voltage generator 200. To provide.

As described in the first embodiment, the example in which the image quality is compensated by controlling the gray voltage generator when the liquid crystal display is high temperature is preferably applied to the liquid crystal display adopting the OCB mode liquid crystal. In general, in the case of OCB (Optical Compensated Birefringency) mode, research is being actively conducted because of the fast response speed of the liquid crystal and the characteristics of the wide viewing angle. Next, a brief description will be given with reference to FIGS. 7 and 8 to which the above-described operation of the OCB mode is attached.

7 is a view for explaining the operation of the general OCB mode, Figure 8 is a view for explaining the on / off cycle of the OCB mode.

Referring to FIG. 7, the initial alignment state of the liquid crystal positioned between the upper electrode and the lower electrode is a homogenous state (H), and when a predetermined voltage is applied to the upper and lower electrodes, a transient splay is performed. T) and Asymmetric splay (hereinafter referred to as A) are converted to bend state (hereinafter referred to as B) and operate in OCB mode.

As shown in FIG. 7, in general, the OCB liquid crystal cell has a pretilt angle of about 10 to 20 °, a thickness of the liquid crystal cell of 1.5 to 2.5 μm, and rubbing the alignment film in the same direction. Since the arrangement of liquid crystal molecules in the center of the liquid crystal layer is symmetrical, the inclination angle is 0 ° below a certain voltage, and the inclination angle is 90 ° above a specific voltage, and a large voltage is initially applied to the center of the liquid crystal layer. The inclination angle of the liquid crystal molecules is set to 90 °, and the applied voltage is changed to modulate the polarization of the light passing through the liquid crystal layer by a tilt change of the remaining liquid crystal molecules except for the liquid crystal molecules in the center of the alignment layer and the liquid crystal layer.

The inclination angle of the liquid crystal molecules in the center is usually several seconds to arrange from 0 ° to 90 °, the cell thickness is thin, the elastic modulus of the bending deformation is large, the reaction time is characterized by very fast as about 10㎳.

As shown in FIG. 8, the conversion from 'T' to 'A' is fast and the conversion from 'T' to 'B' is relatively fast while the general OCB mode is on, but the conversion from 'A' to 'B' is slow. In addition, the conversion from 'B' to 'H' is slow in the off state of the general OCB mode, but the conversion from 'T' to 'H' or 'A' to 'H' is fast.

Although the OCB mode liquid crystal has a fast response speed, the transmittance curve, ie, the VT curve, which is optimally set for each voltage is shifted according to temperature changes, thereby adversely affecting display quality. In particular, the shift phenomenon of the VT curve has a problem of causing abnormal black color characteristics because the shift degree of the voltage set to the black color is severe.

FIG. 9 is a graph for explaining a VT curve (transmission characteristic curve versus voltage) of a liquid crystal display device employing an OCB mode liquid crystal.

Referring to FIG. 9, in the case of an OCB type liquid crystal display having a normally white mode driving method, a voltage range of 0 to V1 is regarded as an invalid display area that is not suitable for use in a display operation and is excluded. Consider the area as an effective display area and use it for display operation.

However, as the temperature is changed, the liquid crystal characteristics are changed, so that the voltage V2 set to the optimum black color is shifted to V3, which adversely affects the image quality characteristics.

With this in mind, in the first embodiment of the present invention, the black voltage is changed based on the sensed internal temperature of the liquid crystal display panel, thereby maintaining the optimum black voltage state to prevent adverse effects of the image quality characteristics.

The change of the black voltage to maintain such an optimum black voltage state is provided in the gray voltage generator, and as shown in FIGS. 10A to 10B, it is variable in a resistor string for outputting a plurality of gray voltages according to an external gamma voltage. This can be done by adding a resistor.

10A to 10B are diagrams for describing a gray voltage generator according to a first embodiment of the present invention.

FIG. 10A is a diagram for describing a resistor string and a VT curve corresponding to a gray voltage generator used in a liquid crystal display having a normally black mode driving method, and FIG. 10B is a liquid crystal display with a normally white mode driving method. It is a figure for demonstrating the resistance string of the gradation voltage generation part employ | adopted in an apparatus, and the corresponding VT curve.

As described above, the variable resistance may be adjusted according to the change in the internal temperature of the liquid crystal display by replacing the fixed resistor corresponding to the optimal black voltage set among the fixed resistors provided in the gray voltage generator with a variable resistor. The optimal black voltage can be maintained in the OCB type liquid crystal without shifting the optimally set black voltage like a dashed curve.

On the other hand, in a liquid crystal display device employing a PVA mode liquid crystal, the kickback voltage increases as the internal temperature increases, causing adverse effects on image quality. A description will be given with reference to FIG. 11 to which an embodiment for preventing such adverse effects of image quality is attached.

FIG. 11 is a view for explaining a second embodiment of a liquid crystal display device having a temperature sensing function according to the present invention. In particular, an embodiment of compensating for image quality by changing a common electrode voltage will be described.

Referring to FIG. 11, in the liquid crystal display according to the second exemplary embodiment, the temperature detector 10, the timing controller 100, the driving voltage generator 200, the common voltage generator 300, and the gray voltage are described. The generator 400, the gate driver 500, the data driver 600, the liquid crystal display panel 700, and the backlight unit 800 may be included, and the same components may be the same as those of FIG. 6. Reference numerals are given, and detailed description thereof is omitted.

That is, when the temperature change of the liquid crystal display panel is detected and checked as a high temperature, the temperature detector 10 requests the common voltage generator 300 to change the common electrode voltage via the driving voltage generator 200. The common voltage generator 300 outputs the changed common electrode voltage to the common electrode line provided in the liquid crystal display panel 700.

According to the second embodiment of the present invention, the flicker generation can be minimized and the afterimage can be minimized by varying the common electrode voltage to block the increase of the kickback voltage as the temperature increases.                     

On the other hand, in general, as the internal temperature increases, the liquid crystal display device may not only adversely affect the image quality, but also cause the worst situation in which the liquid crystal characteristics are lost by causing a phase change of the liquid crystal. An example for preventing this worst case will be described with reference to FIG. 12.

12 is a view for explaining a third embodiment of a liquid crystal display device having a temperature sensing function according to the present invention. In particular, an embodiment for notifying a user of a high temperature of the liquid crystal will be described.

Referring to FIG. 12, the liquid crystal display according to the third exemplary embodiment of the present invention may include a temperature sensor 10, a timing controller 100, a driving voltage generator 200, a common voltage generator 300, and a gray voltage. It includes a generator 400, a gate driver 500, a data driver 600, a liquid crystal display panel 700, a backlight unit 800, and an alarm unit 900, and when compared with FIG. 6 described above. The same reference numerals are assigned to the same components, and detailed description thereof will be omitted.

The timing controller 100 requests the alarm unit 900 to output an alarm signal as the high temperature message of the liquid crystal display panel is input from the temperature sensor 10, and the alarm unit 900 is in a state where the current temperature is too high. This provides the user with a message that the environment needs adjustment. Of course, in the drawings, although the temperature sensing unit requests an output of the alarm signal through the timing controller, the alarm unit may directly request the output of the alarm signal. The user side provided with such an alarm message may avoid the worst case in which the liquid crystal characteristics are lost by turning off the power of the liquid crystal display device or reducing the temperature of the surrounding environment in which the liquid crystal display device is driven.

On the other hand, the liquid crystal display may display a specific luminance or color such as sRGB (Standard R, G, B) mode, and even when the LCD temperature rises, the luminance may decrease. In this case, compensation according to the temperature rise may be performed as shown in FIG. 13 or FIG. 14.

FIG. 13 is a view for explaining a fourth embodiment of a liquid crystal display device having a temperature sensing function according to the present invention. In particular, an embodiment of compensating for image quality through RGB color data for image quality compensation will be described.

Referring to FIG. 13, the liquid crystal display according to the fourth exemplary embodiment of the present invention may include a temperature sensor 10, a timing controller 100, a driving voltage generator 200, a common voltage generator 300, and a gray voltage. The generator 400, the gate driver 500, the data driver 600, the liquid crystal display panel 700, and the backlight unit 800 may be included, and the same components may be the same as those of FIG. 6. Reference numerals are given, and detailed description thereof is omitted.

When the timing controller 100 receives the image quality compensation signal 10d from the temperature sensor 10, the data of each of R, G, and B provided from an external graphic controller (not shown) is transferred to a high temperature liquid crystal display panel. The R, G, and B data (RC, GC, BC) are changed and output to the data driver 600 to maintain a normal color.

According to this method, even if the liquid crystal display becomes high temperature, by outputting the RGB data modified by reflecting the temperature, it is possible to express normal and accurate colors.

FIG. 14 is a view for explaining a fifth embodiment of a liquid crystal display device having a temperature sensing function according to the present invention. In particular, an embodiment of compensating for image quality by adjusting backlight brightness will be described.

Referring to FIG. 14, the liquid crystal display according to the fifth exemplary embodiment of the present invention may include a temperature sensor 10, a timing controller 100, a driving voltage generator 200, a common voltage generator 300, and a gray voltage. The generator 400, the gate driver 500, the data driver 600, the liquid crystal display panel 700, and the backlight unit 800 may be included, and the same components may be the same as those of FIG. 6. Reference numerals are given, and detailed description thereof is omitted.

When the driving voltage generator 200 receives the image quality compensation signal 10e from the temperature sensor 10, the driving voltage generator 200 outputs the changed lamp control signal 205 to the backlight unit 800.

In this way, even if the temperature of the liquid crystal display rises, it is possible to express the correct brightness by compensating for the inappropriate brightness caused by the temperature rise.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

As described above, according to the present invention, an AC wave is applied to a pixel region of a liquid crystal display panel, and an AC wave according to a temperature change is detected from the pixel region to detect an internal temperature of the liquid crystal layer. The temperature can be varied.

For example, the image quality deterioration caused by an increase in the temperature of the liquid crystal display panel may be prevented by changing the gray scale voltage or the common electrode voltage based on the sensed internal temperature.

In addition, the light output level of the backlight may be adjusted based on the sensed internal temperature to prevent deterioration of image quality, and the RGB color data may be compensated and output as the temperature rises to display normal RGB colors. The user may be notified by outputting an alarm message indicating that the temperature rises.

Claims (19)

An upper substrate; A lower substrate facing the upper substrate, the lower substrate including a first signal electrode, a dielectric layer applied over the first signal electrode, and a second signal electrode applied over the dielectric layer; A liquid crystal layer filled in a predetermined gap between the lower substrate and the upper substrate and having a liquid crystal capacitance varying in response to a constant electric field and a temperature change provided from the lower substrate; And In order to indirectly detect a change in the liquid crystal capacitance, a first AC wave having a constant amplitude is applied to the first signal electrode, and a second AC wave interlocked with the capacitance of the dielectric layer and the liquid crystal capacitance is input from the second signal electrode. And a temperature sensing unit configured to detect the temperature of the liquid crystal layer. 2. The voltage distribution of claim 1, wherein the second AC wave includes a liquid crystal capacitor having one end connected to a predetermined voltage terminal, one end connected to the liquid crystal capacitor in series, and the other end connected to a capacitor of a dielectric layer connected to the first AC wave. And output to the temperature sensing unit through the other end of the liquid crystal capacitor. The liquid crystal display of claim 1, wherein the first signal electrode is a gate electrode. The liquid crystal display of claim 1, wherein the second signal electrode is a source electrode. The liquid crystal display of claim 1, wherein the second signal electrode is a drain electrode. The liquid crystal display of claim 1, wherein the second signal electrode is an ITO electrode. A lower substrate facing the upper substrate, a lower substrate facing the upper substrate, having a gate electrode, a gate insulating film coated on the gate electrode, and a source-drain electrode applied on the gate insulating film; A liquid crystal display panel having a liquid crystal layer filled in a predetermined gap between the lower substrate and the upper substrate and having a liquid crystal capacitance varying with temperature change; A timing controller for outputting an image signal, a first control signal for controlling the output of the image signal, and a second control signal for selecting the output of the image signal; A source driver configured to output a data signal to the source electrode based on the image signal and the first control signal; A gate driver configured to output a scan signal to the gate electrode based on the second control signal; And Applying an AC wave to one side of the lower substrate, receiving an AC wave reflecting a temperature from the other side of the lower substrate, sensing the internal temperature of the liquid crystal display panel, and if the internal temperature is higher than a threshold temperature, an image quality compensation signal Liquid crystal display comprising a temperature sensor for outputting. The liquid crystal display device according to claim 7, A negative fixed resistance string outputting one or more fixed negative gray voltages; A negative variable resistance column connected in series with the negative fixed resistance column and outputting one or more negative gray voltages that vary in response to the image quality compensation signal; A positive variable resistance row connected in series with the negative variable resistance row and outputting one or more positive gray level voltages that vary in response to the image quality compensation signal; And And a gray voltage generator connected in series with the positive variable resistance row and having a fixed fixed row of positive polarity voltages to adjust the black gray voltage. The liquid crystal display device according to claim 8, wherein the liquid crystal layer is an OCB mode liquid crystal. The liquid crystal display device according to claim 7, A driving voltage generator configured to output a driving voltage in response to the image quality compensation signal; And And a common voltage generator configured to output a common electrode voltage varying in response to the driving voltage to the liquid crystal display panel. The liquid crystal display device according to claim 7, A driving voltage generator configured to output a driving voltage in response to the image quality compensation signal; And And a backlight unit comprising one or more lamps and an inverter for supplying power to the lamps, the backlight unit configured to output light having an output level converted in response to the driving voltage to the liquid crystal display panel. . The liquid crystal display device according to claim 7, And an alarm unit for alarming an increase in the internal temperature of the liquid crystal layer, and providing a signal for controlling the operation of the alarm unit to the timing controller in response to the image quality compensation signal. An array substrate having a gate electrode, a gate insulating film coated on the gate electrode, a source-drain electrode applied on the gate insulating film, and a liquid crystal display incorporating a liquid crystal layer through the combination of the array substrate to display an image In the temperature sensing method of the device, (a) applying a first AC wave for sensing the temperature of the liquid crystal layer to the gate electrode according to the activation of the liquid crystal display; (b) sensing a second AC wave output in response to the first AC wave from the source-drain electrode; (c) calculating a liquid crystal capacitance of the liquid crystal layer based on the first AC wave and the second AC wave; (d) calculating a liquid crystal dielectric constant based on the calculated liquid crystal capacitance; And (e) extracting a temperature based on the liquid crystal dielectric constant from a temperature table storing a temperature corresponding to the liquid crystal dielectric constant. The method of claim 13, wherein the amount of change in liquid crystal capacitance is

Wherein C _LC is the liquid crystal capacitance, Cd is the capacitance of the gate insulating film, ΔVin is the amplitude of the first AC wave, and ΔVout is the amplitude of the second AC wave. Temperature detection method. An array substrate having a gate electrode, a gate insulating film coated on the gate electrode, a source-drain electrode applied on the gate insulating film, and a liquid crystal display incorporating a liquid crystal layer through the combination of the array substrate to display an image In the temperature sensing method of the device, (a) applying a first AC wave for sensing the temperature of the liquid crystal layer to the gate electrode according to the activation of the liquid crystal display; (b) sensing a second AC wave output in response to the first AC wave from the source-drain electrode; (c) calculating a liquid crystal capacitance of the liquid crystal layer based on the first AC wave and the second AC wave; (d) calculating a liquid crystal dielectric constant based on the calculated liquid crystal capacitance; (e) extracting a temperature based on the liquid crystal dielectric constant from a temperature table storing a temperature corresponding to the liquid crystal dielectric constant; (f) checking whether the temperature extracted in step (e) exceeds a threshold temperature; (g) feeding back to step (a) if the extracted temperature is checked to be below the threshold temperature in step (f); And (h) if the extracted temperature is checked to be above the threshold temperature in step (f), determining that the liquid crystal display is at a high temperature and compensating for a change in image quality. The method of claim 15, wherein step (h) is And varying a gray voltage corresponding to a black color. The method of claim 15, wherein step (h) is Comprising the step of varying the common electrode voltage, the image quality compensation method of the liquid crystal display device. The method of claim 15, wherein step (h) is And varying an output level of the backlight output to the liquid crystal layer. The method of claim 15, wherein step (h) is Compensating for the color of any one of the R, G, B applied to the source electrode.

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