JPH0996796A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element capable of displaying an image of high definition even under a low temperature environment. SOLUTION: An AC power source 29 is connected to an auxiliary capacitance electrode 25 connected to an auxiliary capacitance CS. An AC having the current value corresponding to a detection signal from a temperature sensor 30 and indicating the temperature of the liquid crystal is supplied to the auxiliary capacitance electrode 25 by the AC power source 29 at a frequency of about 1 to 2MHz capable of avoiding the response of the liquid crystal. Joule heat is generated by the auxiliary capacitance electrode 25, then, the temperature of the liquid crystal is increased, and the response of the liquid crystal speeds up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device capable of displaying a high quality image.

[0002]

2. Description of the Related Art Liquid crystal display devices are used in various environments. However, when the liquid crystal display element is used in a low temperature environment, the temperature of the liquid crystal decreases and the viscosity increases, so the response speed of the liquid crystal molecules slows down. The device has a problem that the display quality is degraded.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal display device capable of displaying a high-quality image even in a low temperature environment.

[0004]

In order to achieve the above object, a liquid crystal display element according to the present invention is an active matrix liquid crystal display in which liquid crystal capacitors and auxiliary capacitors and switching elements connected thereto are arranged in a matrix. The element is characterized by including a heating means for heating the liquid crystal by supplying an alternating current to the auxiliary capacitance electrode forming the auxiliary capacitance to generate heat.

According to the liquid crystal display element having the above structure, by supplying an alternating current from the heating means to the auxiliary capacitance electrode,
Joule heat is generated in the auxiliary capacitance electrode. This Joule heat raises the temperature of the liquid crystal, which in turn accelerates the response speed of the liquid crystal. Therefore, even if the response speed of the liquid crystal is low in a low temperature environment, the liquid crystal can be heated to increase the response speed and display an image with high display quality.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, one embodiment of the present invention will be described.
A TFT liquid crystal display element will be described as an example with reference to the drawings. T
The FT liquid crystal display device has a pair of transparent substrates 11 and 12, a liquid crystal 13 sealed between the pair of transparent substrates 11 and 12, and an outside of the pair of transparent substrates 11 and 12, as shown in a cross section in FIG. It is composed of a pair of polarizing plates 19 and 20 arranged in the.

One of the pair of transparent substrates (TFT
The substrate 11 has a TFT 14 as a switching element.
And pixel electrodes 15 connected to the TFTs 14 are arranged in a matrix. An alignment film 16 is arranged on the entire surface of each TFT 14 and the pixel electrode 15. Further, on the other substrate (counter substrate) 12, one counter electrode 17 facing each pixel electrode 15 is arranged. Counter electrode 1
An alignment film 18 is disposed on the entire surface of the alignment film 7.

The gate electrode of each TFT 14 has a gate line GL arranged in the row direction, as shown in the circuit diagram of FIG.
, The drain electrode is connected to the data line DL arranged in the column direction, and the source electrode is connected to the liquid crystal capacitance CLC and the auxiliary capacitance CS formed between the drain electrode and the counter electrode 17. The other end of the auxiliary capacitance CS has a plurality of pixel electrodes 1
5 are formed so as to face each other through the gate insulating film of the TFT 14 and are connected to the auxiliary capacitance electrodes 25 arranged in the row direction.

Each auxiliary capacitance electrode 25 is made of metal or the like, and is connected to each other. Further, one end of the auxiliary capacitance electrode 25 is grounded via a DC cut capacitor 27. Further, the other end of the auxiliary capacitance electrode 25 is provided with a DC cut capacitor 26 and an AC ammeter 28.
Is connected to the grounded AC power source 29 via the. The DC cutting capacitors 26 and 27 block the DC component of the current supplied from the AC power supply 29 to the auxiliary capacitance electrode 25. The AC power supply 29 supplies an AC current for raising the temperature of the liquid crystal 13 to the auxiliary capacitance electrode 25. The AC ammeter 28 detects the value of the AC current and supplies a detection signal to the AC power supply 29.

A temperature sensor 30 for measuring the temperature of the liquid crystal 13 is arranged in the display section 21 of the liquid crystal display element. The detection signal of the temperature sensor 30 is the AC power supply 22.
Is supplied to.

In the liquid crystal display device having such a circuit structure, the AC power supply 29 is 1 to 2 MHz at which the liquid crystal 13 does not respond.
An alternating current having a frequency of about 10 is supplied to the auxiliary capacitance electrode 25,
The auxiliary capacitance electrode 25 generates Joule heat. This Joule heat raises the temperature of the liquid crystal 13. The temperature of the liquid crystal 13 is measured by the temperature sensor 30, and the detection signal is supplied to the AC power supply 29. The AC power supply 29 supplies a current for maintaining the temperature of the liquid crystal 13 to a target temperature (operating temperature) to the auxiliary capacitance electrode 25 while monitoring it with an AC ammeter 28 according to the detection signal.

As an AC current control method, any known method such as P (proportional) control, PI (proportional integral) control, PID (proportional integral derivative) control or the like can be used. Also,
In order to increase the amount of heat generation, the auxiliary capacitance electrode 25 may be made of a conductor having a resistance higher than that of metal, such as ITO. In this case, since the auxiliary capacitance electrode 25 is transparent, even if it overlaps with the pixel electrode 15, the aperture ratio does not decrease and high-definition display is possible.

When the temperature of the liquid crystal 13 rises, the viscosity of the liquid crystal 13 decreases and the response speed increases. Therefore, in a low temperature environment, an alternating current is supplied to the auxiliary capacitance electrode 25 to raise the temperature of the liquid crystal 13 to a target temperature and maintain the temperature constant, thereby maintaining a constant drivable response speed. , High-quality images can be displayed. Further, the alternating current has a frequency at which the liquid crystal molecules do not respond, and the image is not deteriorated by the alternating current for heating.

The present invention is not limited to the above embodiment, and can be modified and applied. For example, the temperature of the liquid crystal 13 may be measured without using the temperature sensor 30. The resistance value of the auxiliary capacitance electrode 25 changes with temperature, and the resistance value of the auxiliary capacitance electrode 25 can be obtained from the current value measured by the AC ammeter 28 and the voltage value of the AC power supply 29. Therefore, the temperature of the auxiliary capacitance electrode 25 is indirectly obtained from this resistance value, and the current supplied from the AC power supply 29 is adjusted so that the temperature of the auxiliary capacitance electrode 25 matches the target operating temperature of the liquid crystal 13. Is also possible.

It is also possible to automatically start the AC power supply 29 when the temperature of the liquid crystal 13 falls below a reference value. For example, the detection signal from the temperature sensor 30 is compared with a reference value by a comparator, and when the level of the detection signal becomes smaller than the reference value, a flip-flop is set and the relay is turned on by the output signal of this flip-flop. Then, the relay may supply power to the AC power supply 29.

In the above embodiment, the liquid crystal display element using the TFT as a switching element has been described as an example.
The present invention can also be applied to a liquid crystal display element using MIM as a switching element.

[0017]

As described above, according to the present invention, it is possible to provide a liquid crystal display device capable of displaying a high quality image even in a low temperature environment.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a TFT liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a TFT substrate of the TFT liquid crystal display element according to the embodiment of the present invention.

[Explanation of symbols]

11 ... TFT substrate, 12 ... counter substrate, 13 ... liquid crystal,
14 ... TFT, 15 ... Pixel electrode, 16 ... Alignment film, 1
7 ... Counter electrode, 18 ... Alignment film, 19 ... Polarizing plate, 20 ...
..Polarizing plate, 21 ... Display unit, 25 ... Auxiliary capacitance electrode, 26
27 ... DC cut capacitor, 28 ... AC ammeter, 29 ... AC power supply, 30 ... Temperature sensor, GL ... Gate line, DL ... Data line, CLC ... Liquid crystal capacity,
CS: auxiliary capacity

Claims (4)

[Claims] 1. An active matrix liquid crystal display device in which a liquid crystal capacitor and an auxiliary capacitor and switching elements connected to them are arranged in a matrix, and an alternating current is supplied to an auxiliary capacitor electrode forming the auxiliary capacitor to generate heat. A liquid crystal display device comprising a heating means for heating the liquid crystal. 2. The liquid crystal display device comprises a temperature sensor for measuring the temperature of liquid crystal, and the heating means supplies an alternating current corresponding to the temperature measured by the temperature sensor to the auxiliary capacitance electrode. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. 3. The heating means obtains a resistance value of the auxiliary capacitance electrode from a current and a voltage supplied to the auxiliary capacitance electrode, and supplies an alternating current corresponding to the resistance value to the auxiliary capacitance electrode. The liquid crystal display element according to claim 1, wherein 4. The liquid crystal display element according to claim 1, wherein the alternating current has a frequency at which liquid crystal molecules do not respond.