JP2003295158A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a display unevenness arising from temperature difference in the vertical direction of a liquid crystal panel using an edge light system. <P>SOLUTION: The liquid crystal display device is arranged so a to modulate a gamma correction voltage or a compensation potential difference Vepp in capacitance coupling driving by a vertical cycle control voltage generated according to the temperature of at least one point in the liquid crystal device and the expected temperature distribution in the vertical direction of the liquid crystal panel. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix liquid crystal display device in which switching elements such as thin film transistors (hereinafter referred to as TFTs) are arranged for each pixel electrode.

[0002]

2. Description of the Related Art In recent years, TFT liquid crystal display devices have become larger,
As the image quality has been improved, it has come to be used not only in display monitors for PCs but also in large-sized televisions for home use. Generally, in a liquid crystal display panel, the transmittance characteristic of a liquid crystal material with respect to an applied voltage has temperature dependence. Figure 2
3 is a graph showing temperature dependence of applied voltage-transmittance characteristic of liquid crystal. For example, in a normally white mode liquid crystal display panel, as shown in FIG. 2, the transmittance decreases as the temperature rises. A display device having a temperature compensating means has been proposed in order to suppress the influence of the temperature characteristic of the liquid crystal material and to cope with a case where higher display quality is required.
For example, JP-A-7-295518 and JP-A-2000-89.
In 192, a temperature sensor is attached near the panel, and its output controls the driving conditions of the liquid crystal display device.

[0003]

However, in the prior art, since the temperature of a part of the liquid crystal display device is detected, when the temperature distribution exists in the liquid crystal display panel, it is suitable for the entire display screen. Driving conditions are not given. For example, in a TFT liquid crystal display device using an edge light type backlight, a cold cathode ray tube, which is a main cause of heat generation, is arranged at either the upper part or the lower part of the panel, or at both upper and lower ends. Differences in temperature occur at the center and bottom. FIG. 3 shows a cross-sectional view of a panel module of a liquid crystal display device adopting the edge light method and a temperature distribution on the surface of the liquid crystal panel. The light emitted from the cold cathode ray tubes 31 arranged two by two above and below is evenly applied to the TFT liquid crystal panel by the light guide plate 32. In the TFT liquid crystal display panel 33, the transmittance changes depending on the voltage applied to each pixel, and the brightness of each pixel is determined. Here, since light emission of the cold cathode ray tube is accompanied by heat generation, the temperature of the liquid crystal display panel becomes higher as it approaches the cold cathode ray tube. For example, in a 15-inch liquid crystal panel, a temperature difference of about 5 ° C. occurs between the upper part and the lower part with respect to the temperature at the center of the screen. In recent years, in particular, as the screen size and brightness have been increased, the temperature difference in the vertical direction of the liquid crystal panel tends to increase in the edge light type liquid crystal display device.

This means that in the conventional temperature compensation, the transmittance characteristics change depending on the vertical position of the liquid crystal display device, and the uniformity of the screen cannot be obtained.

The influence of this temperature distribution tends to be noticeable particularly in a portion having low luminance due to human visual characteristics. FIG. 4 shows the relationship between the applied voltage to the liquid crystal for minimizing the transmittance, that is, the optimum applied voltage for displaying black and the temperature. From the graph of FIG. 4, for example, when displaying black on the entire surface of the display device, by controlling the voltage applied to the liquid crystal with a temperature sensor attached to the upper end of the liquid crystal panel or the like, black that is almost ideal at the top of the screen is displayed. Although it can be displayed, black floating occurs at the center of the screen where the temperature is low.

In view of the above problems, it is an object of the present invention to provide a liquid crystal display device in which the influence of the temperature difference in the vertical direction on the screen is suppressed.

[0007]

In order to solve this problem, a first aspect of the present invention has pixel electrodes arranged in a matrix, and a switching element electrically connected to a video signal line and a scanning signal line has a pixel electrode. Connected to the liquid crystal display panel, a scanning wiring driving means for driving the scanning signal wiring of the liquid crystal panel, and a digital-analog converter for converting a digital video signal into a video signal wiring driving voltage using a gamma correction voltage as a reference voltage. A liquid crystal display device comprising a video signal wiring driving means comprising: a liquid crystal display device according to a temperature of at least one portion in the liquid crystal display device and a temperature distribution in a vertical direction of a liquid crystal display panel which is predicted in advance. The gamma correction voltage is changed. As a result, the voltage applied to the liquid crystal material is temperature-compensated for each scanning line, and a liquid crystal display panel in which a temperature difference occurs in the vertical direction of the screen enables uniform display over the entire screen and high-quality display.

According to the second aspect of the invention, the pixel electrodes connected to the scanning signal lines via capacitors are arranged in a matrix, and the switching elements electrically connected to the video signal lines and the scanning signal lines are pixel electrodes. The video signal voltage is transmitted to the pixel electrode during the ON period of the switching element, the modulation signal Ve (+) is applied to the scanning signal line during the OFF period of the switching element in the odd field, and the OFF period of the switching element in the even field is connected. Modulation signal V on the scanning signal wiring
A liquid crystal display device for applying a voltage to a display material by changing the electric potential of the pixel electrode by applying e (-), and superimposing the change of the electric potential of the pixel electrode and the video signal voltage on each other. Amplitude Vepp = | Ve (+) − Ve (−)
Is defined as |, the Vep in each scanning signal wiring is determined according to the temperature of at least one portion in the liquid crystal display device and the temperature distribution in the vertical direction of the liquid crystal panel which is predicted in advance.
It was made to change p.

As a result, the voltage applied to the liquid crystal material is temperature-compensated for each scanning line, and in the liquid crystal display panel in which a difference in temperature occurs in the vertical direction of the screen, it is possible to perform uniform display on the entire screen and high quality display.

Further, the pixel electrodes connected to the auxiliary capacitance wiring via the capacitance are arranged in a matrix, and the switching elements electrically connected to the video signal wiring and the scanning signal wiring are connected to the pixel electrodes, The video signal voltage is transmitted to the pixel electrode during the ON period, and the modulation signal Ve is supplied to the auxiliary capacitance line during the ON period of the switching element in the odd field.
(+) Is applied, and the modulation signal Ve (-) is applied to the auxiliary capacitance line during the ON period of the switching element in the even field, thereby changing the potential of the pixel electrode, and changing the potential of the pixel electrode and the video signal voltage. A liquid crystal display device for applying a voltage to a display material by superposing them on each other, wherein a modulation signal amplitude V
When defining as epp = | Ve (+) − Ve (−) |
Vepp in each scanning signal wiring is changed in accordance with the temperature of at least one portion in the liquid crystal display device and the expected temperature distribution in the vertical direction of the liquid crystal panel.

As a result, the voltage applied to the liquid crystal material is temperature-compensated for each scanning line, and a liquid crystal display panel in which a temperature difference occurs in the vertical direction of the screen enables uniform display on the entire screen and high-quality display.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention has pixel electrodes in a matrix, and a switching element electrically connected to a video signal line and a scanning signal line is connected to the pixel electrode. A liquid crystal display panel, a scanning wiring driving means for driving the scanning signal wiring of the liquid crystal panel, and a digital-analog converter for converting a digital video signal into a video signal wiring driving voltage using a gamma correction voltage as a reference voltage. A liquid crystal display device equipped with a video signal wiring driving means, wherein a gamma correction voltage is applied in accordance with a temperature of at least one portion in the liquid crystal display device and a predicted temperature distribution in the vertical direction of the liquid crystal display panel. Is a liquid crystal display device.

According to a second aspect of the present invention, there is provided a matrix of pixel electrodes connected to the scanning signal wirings via capacitors, and the switching is electrically connected to the video signal wirings and the scanning signal wirings. The element is connected to the pixel electrode, the video signal voltage is transmitted to the pixel electrode during the ON period of the switching element, the modulation signal Ve (+) is applied to the scanning signal line during the OFF period of the switching element in the odd field, and the even field switching is performed. By applying the modulation signal Ve (−) to the scanning signal wiring during the off period of the element, the potential of the pixel electrode is changed, and the change of the potential of the pixel electrode and the video signal voltage are superimposed on each other to apply a voltage to the display material. A liquid crystal display device for applying a modulation signal amplitude Vepp = | Ve (+) − Ve
When defined as (−) |, changing Vepp in each scanning signal wiring in accordance with the temperature of at least one portion in the liquid crystal display device and the expected temperature distribution in the vertical direction of the liquid crystal panel. Is a liquid crystal display device.

According to a third aspect of the present invention, the switching is electrically connected to the video signal line and the scanning signal line by having the pixel electrodes connected to the auxiliary capacitance line via the capacitance in a matrix form. The element is connected to the pixel electrode, the video signal voltage is transmitted to the pixel electrode during the ON period of the switching element, the modulation signal Ve (+) is applied to the auxiliary capacitance line during the ON period of the switching element in the odd field, and the even field switching is performed. By applying the modulation signal Ve (−) to the auxiliary capacitance line during the ON period of the element, the potential of the pixel electrode is changed, and the change in the potential of the pixel electrode and the video signal voltage are superimposed on each other to apply a voltage to the display material. A liquid crystal display device for applying a modulation signal amplitude Vepp = | Ve (+) − Ve
When defined as (−) |, changing Vepp in each scanning signal wiring in accordance with the temperature of at least one portion in the liquid crystal display device and the expected temperature distribution in the vertical direction of the liquid crystal panel. Is a liquid crystal display device.

(Embodiment 1) Hereinafter, an embodiment of the invention described in claim 1 of the present invention will be described with reference to FIGS. 1, 4, 5, 6, and 7.

FIG. 5A is a block diagram of a liquid crystal display device. The display device of FIG. 5A includes a liquid crystal display panel 51, a video signal wiring driving means 52, a scanning wiring driving means 53, a gamma correction voltage generating means 54, a vertical cycle control signal generating means 11, and a temperature detecting means 12. To be done. The liquid crystal display panel 51 includes scanning lines (X1 to XN) and video signal lines (Y1).
To YN) are arranged in a matrix, and N × M TFTs are arranged with the intersections as pixels. Figure 5 (b)
Represents the equivalent means of one pixel, the gate of the TFT 4 is connected to the scanning wiring 1, the source is connected to the video signal wiring 3, and the drain is connected to the pixel electrode. A liquid crystal is filled between the pixel electrode and the second common electrode (also referred to as a counter electrode) 9 to form a liquid crystal capacitor Clc7. An auxiliary capacitance (also called a storage capacitance) is provided between the pixel electrode and the first common electrode 10.
Cs8 is formed.

The scanning wiring driving means 53 drives the scanning wiring 1 to turn ON / OFF the gate of the TFT. The video signal wiring driving means 52 includes a digital-analog converter that converts an input digital video signal into a video signal wiring driving voltage using the gamma correction voltage as a reference voltage, and drives the video signal wiring 3. A drive voltage corresponding to the input digital video signal is applied during the ON period of the TFT.

FIG. 6 shows a gamma correction voltage generating means.
A plurality of resistors are connected in series between the first reference voltage and the second reference voltage, and a plurality of voltages between the two reference voltages are taken out by a resistance ratio.

FIG. 7 shows the input / output characteristics of the video signal wiring driving means. As shown in FIG. 7A, the video signal wiring driving unit 52 converts the input gamma correction voltage into an analog voltage and drives the video signal wiring.

By adjusting the resistance value of the gamma correction voltage generating means, the gamma characteristic of the liquid crystal display device can be changed.

Since the liquid crystal needs to be driven by an alternating current so that the electric field of the DC component is not constantly applied, FIG.
The video signal wiring drive voltage shown by and the video signal wiring drive voltage referring to the inversion side gamma correction voltage as shown in FIG. 7B are alternately applied for each frame. In the description of the above form, the operation on the inversion side will not be touched because it is complicated.

Here, in the case of compensating for the black level fluctuation due to the change of the liquid crystal transmittance due to the temperature, it is obvious that the first reference voltage corresponding to the black side reference voltage in FIG. 6 may be changed according to the temperature. . At this time, as shown in FIG. 4, when the temperature is low, the applied voltage to the liquid crystal may be increased, and the applied voltage ΔV to be changed with respect to the temperature change ΔT due to the temperature distribution of the panel is also low when the temperature is low. It becomes bigger.

FIG. 1 is a block diagram showing the structure of vertical period control voltage generating means in the first and second embodiments of the present invention. FIG. 1 shows the vertical cycle control voltage generating means 11 and the temperature detecting means 12. The vertical cycle control voltage generating means 11 is a gain adjusting means 14 for adjusting the gain of the waveform obtained from the vertical cycle waveform generating means 3 by the outputs of the vertical cycle generating means 13 and the temperature detecting means 12, and also the output of the temperature detecting means 12, It is composed of a level shifter 15 that shifts the DC level of the gain-controlled waveform and outputs it as a control voltage. The temperature detecting means 12 is a temperature sensor attached near the upper end of the liquid crystal display panel. Here, the vertical cycle generating means 13 outputs a waveform similar to the vertical temperature distribution of the panel predicted in advance. Since the number of scanning wirings is fixed for each display panel and does not generate an arbitrary waveform, it is formed by a simple logic means operating with horizontal pulse and a digital-analog converter. The gain adjusting means 14 controls the amplitude of the voltage to be modulated according to the vertical temperature change of the panel by the output of the temperature detecting means 12. That is, ΔV in FIG. 4 is adjusted, and when the temperature is high, the waveform amplitude is suppressed. The level shifter 15 detects the temperature of the upper part of the panel of the temperature detecting means 12 and, as the temperature rises, a DC waveform is generated.
It operates in the direction of lowering the level and outputs it as a vertical cycle control voltage.

The vertical cycle control voltage controlled as described above is used as the first reference voltage which is the black side reference voltage of the gamma correction voltage generating means shown in FIG. 6, or the vertical cycle control voltage is the first reference voltage. By modulating the reference voltage of, the temperature compensation for the fluctuation of the black level of the liquid crystal display device can be realized in consideration of the temperature distribution of the panel.

The temperature detecting means 12 may use a thermistor or the like, and the vertical cycle control voltage generating means 11 may also be constituted by digital means up to the functions of gain adjustment and level shift. Further, the place where the temperature is detected does not need to directly measure the temperature of any part of the panel, but naturally there is no problem as long as the temperature can be correlated with the temperature of any part of the panel.

(Embodiment 2) Next, claim 2 of the present invention
An embodiment of the invention described in 1. will be described with reference to FIG.

FIG. 8A is a block diagram of a liquid crystal display device. Although the configuration is almost the same as that of the first embodiment, it has a Vep adjusting means 81 due to the difference in the driving method.
Two signal modulation voltages of (+) and V (-) are generated and given to the scanning wiring driving means 53.

FIG. 8 (b) shows an electrical equivalent means seen at the pixel level of the liquid crystal display device. nth scanning signal wiring 1, n-1th scanning signal wiring 2, video signal wiring 3, T
The TFT 4 has an FT 4 and has a gate-drain capacitance Cgd 5 and a source-drain capacitance Csd 6 which are parasitic capacitances. Further, as the capacitances intentionally formed, there are a liquid crystal capacitance Clc * 7 and a storage capacitance Cs8.

A driving voltage is externally applied to each of these element electrodes, and a scanning signal Vg is applied to the n-th scanning signal wiring 1.
(N) is the scanning signal V on the (n-1) th scanning signal wiring 2.
g (n-1) is applied to the image signal wiring 3 by the image signal voltage Vsig
A constant voltage is applied to the counter electrode of the liquid crystal capacitance Clc *. The influence of the driving voltage appears on the pixel electrode (point A in the same figure) through each of the above capacitors. FIG. 9 is a diagram showing drive waveforms of the liquid crystal display device according to the second embodiment of the present invention. Figure 9
When Vg, Ve (+), Ve (-), Vt, and Vsig shown in FIG. 2 are applied to the respective points in FIG. 2, the potential change ΔV * of the pixel electrode due to capacitive coupling is expressed by equation (1) in each of the even and odd fields. ), (2).

[0030]

[Equation 1]

[0031]

[Equation 2]

[0032]

[Equation 3]

The first term in equations (1) and (2) is the potential change due to the modulation signal. The second term is a potential change induced in the pixel electrode by the scanning signal Vg through the parasitic capacitance Cgd of the TFT 4. The third term shows a potential change that the pixel signal voltage induces in the pixel electrode through the parasitic capacitance. Clc * is the signal voltage (Vsi
As the liquid crystal orientation changes depending on the size of g),
It is the capacitance of the liquid crystal that changes under the influence of its dielectric anisotropy. Therefore, Clc * and ΔV * are large liquid crystal capacitances (Clc
(H)) Corresponds to small (Clc (l)). If the potential changes ΔV * + and ΔV * − in the even and odd fields are equal, a symmetrical AC drive can be performed without applying a DC voltage to the liquid crystal. That is, the following formula should be satisfied.

[0034]

[Equation 4]

Since Vsig gives a signal which is inverted in each field, the effect of the third term CsdVsig is canceled in each field. Therefore, equation (3) is

[0036]

[Equation 5]

It is simplified as follows.

Here, if the equation (4) is rewritten,

[0039]

[Equation 6]

It becomes

The potential ΔV * induced in the pixel electrode is even,
In each odd field, the positive and negative can be made equal to the counter electrode regardless of the liquid crystal capacitance. Therefore, positive and negative polarities are equally applied to the liquid crystal, and flicker is essentially reduced. In addition, since Clc * does not appear in equations (3) and (4), the influence of the dielectric anisotropy of the liquid crystal disappears when driving under the condition that equations (3) and (4) are satisfied, and Clc * appears. Due D
The C voltage is not generated inside the display device. Furthermore, equation (3),
Under the driving condition satisfying (4), the DC potential induced between the image signal wiring and the display electrode by the scanning signal Vg through the parasitic capacitance Cgd can be canceled to be zero. In the driving method of this embodiment, since signals of positive and negative reverse polarities are applied to the potential of the counter electrode for each field, a DC electric field is generated between the potentials of the pixel electrode, the signal electrode and the counter electrode when viewing two fields. Therefore, no DC voltage is applied to the liquid crystal.

The conditional expressions (3) and (4) are two voltage parameters Ve (+) and Ve which can be arbitrarily set on the display device side.
It has (-). Therefore, Ve (+) and Ve (-)
Can be set to an arbitrary magnitude by controlling in accordance with equations (3) and (4), and by changing this ΔV *, that is, Vepp, the liquid crystal material can be changed. The voltage applied to can be varied.

FIG. 10 shows Vepp adjusting means. The output V (+) and V (-) are output by the scanning wiring driving means 53 shown in FIG.
Ve (+), Ve in the scanning wiring drive signal shown in
It is used as a reference potential when (-) is output. V
In (+), the voltage input to the Vepp adjusting terminal is directly output by the voltage follower, and V (-) is a voltage symmetrical to V (+) with respect to the separately determined central potential (Vcenter).

As described above, controlling Vepp is equivalent to controlling the voltage applied to the liquid crystal material, and therefore V (+) corresponds to the vertical period control voltage shown in the first embodiment. ) Is generated, in other words, Vepp
Is modulated by the vertical cycle control voltage, it is possible to apply an appropriate applied voltage according to the temperature distribution of the liquid crystal display panel.

As described above, according to the present invention, it is possible to provide a high-quality liquid crystal display device in which the black level is appropriately temperature-compensated in the entire screen even when there is a temperature difference in the vertical direction of the screen. realizable.

(Embodiment 3) Next, claim 3 of the present invention
An embodiment of the invention described in 1. will be described with reference to FIG.

Although the present embodiment has the same operation as that shown in the second embodiment, the configuration is slightly different due to the difference in the driving method of the liquid crystal display panel, and only different parts will be described.

FIG. 11 is a block diagram of a liquid crystal display device according to the third embodiment of the present invention. In FIG. 11A, the liquid crystal display panel 56 includes the auxiliary capacitance line C1 in addition to the scanning lines X1 to XN.
To CN, which are driven by the storage capacitor drive means 55. However, there may be N + 1 auxiliary capacitance lines depending on the AC drive method.

In FIG. 11B, the auxiliary capacitance Cs8 is connected to the auxiliary capacitance line 16. In FIG. 8, the auxiliary capacitance is connected to the scanning wiring in the preceding stage of the scanning wiring to which the gate of the TFT 4 is connected, and the pixel electrode of the self-stage according to Ve (+) and Ve (−) given to the scanning wiring in the preceding stage. Is modulated, but in the liquid crystal display device in FIG.
It has an auxiliary capacitance line for supplying e (+) and Ve (-) independently of the scanning line.

FIG. 12 shows an example of the drive waveform of the liquid crystal display device according to the third embodiment of the present invention. Since the amplitude of the drive waveform can be suppressed as compared with FIG. 9, the display device shown in FIG. By comparison, the driving means can be configured in a process having a low breakdown voltage.

Since Ve (+) and V (-) apply the modulation to the pixel electrode via the auxiliary capacitance Cs8, they are the same.
Also in this configuration, even when a temperature difference is generated in the vertical direction of the screen by controlling Vepp as in the second embodiment, a high-quality liquid crystal display in which the black level is appropriately temperature-compensated in the entire screen is displayed. The device can be realized.

As described above, according to the first aspect of the invention, the temperature of at least one part in the liquid crystal display device and the temperature distribution in the vertical direction of the liquid crystal display panel to be predicted in advance are set in accordance with
Since the voltage for gamma correction and Vepp in each scanning signal wiring are changed, the voltage applied to the liquid crystal material is temperature-compensated for each scanning line, so that a temperature difference occurs in the vertical direction of the screen of the liquid crystal panel. A uniform and high-quality display is possible on all screens.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of vertical period control voltage generating means according to first and second embodiments of the present invention.

FIG. 2 is a graph showing temperature dependence of applied voltage-transmittance characteristic of liquid crystal.

FIG. 3 is a diagram showing an example of vertical temperature distribution of a liquid crystal panel.

FIG. 4 is a graph showing temperature dependence of an applied voltage to a liquid crystal having a minimum transmittance.

FIG. 5 is a configuration diagram of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 6 is a diagram showing gamma correction voltage generating means.

FIG. 7 is a diagram showing input / output characteristics of video signal wiring driving means.

FIG. 8 is a configuration diagram of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing drive waveforms of the liquid crystal display device according to the second embodiment of the present invention.

FIG. 10 is a diagram showing an example of Vepp adjusting means according to the second embodiment of the present invention.

FIG. 11 is a configuration diagram of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 12 is a diagram showing drive waveforms of the liquid crystal display device according to the third embodiment of the present invention.

[Explanation of symbols]

1 nth scan signal wiring 2n + 1st scan signal wiring 3 video signal wiring 4 TFT 5 Gate-drain capacitance 6 Source-drain capacitance 7 Liquid crystal capacity 8 auxiliary capacity 9 Second common electrode 10 First common electrode 11 Vertical cycle control voltage generating means 12 Temperature detection means 13 Vertical period waveform generating means 14 Gain adjustment means 15 level shifter 16 nth auxiliary capacitance wiring 31 Example Cathode ray tube 32 light guide plate 33, 51, 56 Liquid crystal display panel 52 signal wiring driving means 53 Scanning wiring driving means 54 Gamma correction voltage generation means 55 Capacitance wiring driving means 81 Veppe adjustment means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 G09G 3/20 642P 3/36 3/36 F term (reference) 2H093 NA16 NA31 NA41 NC47 NC57 ND10 ND44 ND60 5C006 AC22 AF42 AF44 AF46 AF51 AF54 AF62 AF82 BB16 BC03 BF25 BF38 BF43 BF46 FA19 FA22 5C080 AA10 BB05 DD05 EE28 FF11 JJ02 JJ03 JJ04 JJ05

Claims (3)

[Claims] 1. A liquid crystal display panel having pixel electrodes in a matrix, wherein switching elements electrically connected to video signal wirings and scanning signal wirings are connected to the pixel electrodes.
A scanning wiring driving means for driving the scanning signal wiring of the liquid crystal panel, and a digital-converting digital video signal into a video signal wiring driving voltage by using a gamma correction voltage as a reference voltage.
A liquid crystal display device having a video signal wiring driving means having an analog converter, wherein the temperature of at least one portion in the liquid crystal display device and the expected temperature distribution in the vertical direction of the liquid crystal display panel are calculated. A liquid crystal display device, characterized in that the gamma correction voltage is changed in accordance therewith. 2. A pixel electrode connected to a scanning signal line through a capacitor is arranged in a matrix, and a switching element electrically connected to a video signal line and the scanning signal line is connected to the pixel electrode, A video signal voltage is transmitted to a pixel electrode during an ON period of the switching element, a modulation signal Ve (+) is applied to the scan signal line during an OFF period of the switching element in an odd field, and an OFF period of the switching element in an even field. By applying a modulation signal Ve (-) to the scanning signal wiring, the potential of the pixel electrode is changed, and the change in the potential of the pixel electrode and the video signal voltage are superimposed on each other to apply a voltage to the display material. A liquid crystal display device for applying a modulation signal amplitude Vepp = | Ve
When defined as (+) − Ve (−) |, in each scan signal wiring, the temperature of at least one portion in the liquid crystal display device and the expected temperature distribution in the vertical direction of the liquid crystal panel are determined. A liquid crystal display device, characterized in that Vepp is changed. 3. A pixel electrode connected to an auxiliary capacitance line via a capacitance in a matrix form, and a switching element electrically connected to a video signal line and the scanning signal line is connected to the pixel electrode, The video signal voltage is transmitted to the pixel electrode during the ON period of the switching element, the modulation signal Ve (+) is applied to the auxiliary capacitance line during the ON period of the switching element in the odd field, and the ON period of the switching element in the even field is applied. By applying a modulation signal Ve (-) to the auxiliary capacitance line, the potential of the pixel electrode is changed, and the change in the potential of the pixel electrode and the video signal voltage are superimposed on each other to apply a voltage to the display material. A liquid crystal display device for applying a modulation signal amplitude Vepp = | Ve
When defined as (+) − Ve (−) |, in each scan signal wiring, the temperature of at least one portion in the liquid crystal display device and the expected temperature distribution in the vertical direction of the liquid crystal panel are determined. A liquid crystal display device, characterized in that Vepp is changed.