JPH05232903A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To suppress flickering in a wide temperature range by detecting temperature on the surface of a liquid crystal panel and adjusting the center potential of AC driving voltage impressed to an electrode formed on a glass base. CONSTITUTION:Two glass bases on which plural electrodes are formed are opposed to each other, liquid crystal is held between both the bases and AC voltage is impressed at least to one of the glass base electrodes to drive it. Flickering on a display screen can be removed by adjusting a voltage difference between the electrodes at the positive frame of AC driving and that of its negative frame. Thereby the temperature of the electrode parts of the glass bases can be detected by a thermistor 2 and the center voltage of AC driving voltage can be adjusted by means of an operational amplifier 3. Consequently flickering on a liquid crytal panel can be reduced over a wide range.

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,
In particular, at least one of the glass electrodes will be
The present invention relates to a liquid crystal display device driven by alternating current.

[0002]

2. Description of the Related Art In a conventional liquid crystal display device, when the center potential of the AC drive of the electrodes of the glass substrate holding the liquid crystal is determined, it is adjusted so that the flicker of the display surface is minimized at a certain temperature. , It was fixed at that value and was not adjusted by temperature. At this time, if you make adjustments at room temperature and immediately after lighting, as time passes after lighting,
Since the temperature rises due to the radiant heat of the light source, and the flicker increases, the method of adjusting after lighting for one hour in an atmosphere of 30 to 40 ° or at room temperature has been adopted.

[0003]

In this conventional liquid crystal display device, flickering on the display surface occurs when the temperature of the electrode of the glass substrate changes due to a change in the outside air temperature and a temperature rise due to the radiation heat of the light source of the liquid crystal display device. There was a growing problem.
Further, as shown in the related art, there is a problem that even if the flicker is adjusted to minimize the flicker after the temperature is raised to a certain temperature, the flicker immediately after the lighting and the flicker in a place where the outside temperature changes drastically cannot be suppressed. .

[0004]

The liquid crystal display device of the present invention detects the temperature of the liquid crystal panel surface and uses the signal to detect the central potential of the electrode of one glass substrate relative to the potential of the electrode of the other glass substrate. I am adjusting.

[0005]

The flicker on the display surface can be eliminated by adjusting the voltage difference between the electrodes by adjusting the voltage difference between the positive frame and the negative frame of AC driving. By adjusting the center potential of the AC drive voltage, it is possible to suppress the flicker on the display surface by adjusting the voltage difference between the positive frame and the negative frame.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of the first embodiment of the present invention. In the present embodiment, the thermistor 2 detects the temperature of the electrode portion of the glass substrate, and the operational amplifier 3 is used to adjust the center potential of AC driving. Generally, in a liquid crystal panel, as the temperature rises, the center voltage of Vout at which flicker is minimized increases as shown in FIG. Further, in the case where the resistance value change due to the temperature of the thermistor 2 has the characteristics shown in FIG. 3, how to reduce the flicker of the liquid crystal panel in a wide temperature range will be described below.

For example, when a square wave of 0 V and 5 V as shown in FIG. 4 which is synchronized with the scanning period for one pixel is input as Vin, the center potential of Vout is represented by the equation (1) 30 × ( R ₂ + R _x ) / (R ₁ + R ₂ + R _x ) -2.5 (V) (1) Here, when the electrode temperature of the glass substrate is 0 ° C., R _x = 10K
From the optimum value of Ω and Vout of 5.0 V, the formula (1) is as follows: 30 × (R ₂ +10) / (R ₁ + R ₂ +10) −2.5 = 5 (2) Further, the electrode temperature of the glass substrate is 60. R _X = 40 at ℃
From the optimum value of KΩ and Vout of 10.0 V, the equation (1) becomes 30 × (R ₂ +40) / (R ₁ + R ₂ +40) −2.5 = 10.0 ... (3). From equations (2) and (3), R1 is 78.9 (K
Ω), R2 16.3 (KΩ) If you choose 0 ℃ 6
Flicker can be reduced in the range of 0 ° C.

As a second embodiment of the present invention, an example of a circuit when a thermocouple is used as the temperature detecting means is shown in FIG. In this case, the voltage generated by the thermocouple 6 is 0.5 V when the temperature is 0 °,
If the voltage is 1 V when the temperature is 60 ° C., the voltage of the constant voltage source 1 is 16.7 V, the voltage of the constant voltage source 7 is 15 V, and R5 is 10 V, for example.
If KΩ and R6 are 90 KΩ, the same effect as in the first embodiment can be obtained.

If a temperature measuring means such as a thermistor or a thermocouple cannot be installed directly on the electrode part of the glass substrate,
You may install in the position which reflects the temperature of the electrode part of the vicinity.

[0010]

As described above, according to the present invention, the temperature of the liquid crystal panel surface is detected and the central potential of the AC drive voltage of the electrodes of the glass substrate is adjusted by the signal, so that the flicker can be prevented over a wide temperature range. Can be suppressed. For example, conventional 0-6
In the atmosphere of 0 ° C., the flicker level was about −70 dB to −20 dB as measured by the FFT analyzer, but 0 to 60 in the liquid crystal display device of the present invention.
Even in an atmosphere of ° C, the flicker can be suppressed to -70 dB to -50 dB, which is almost invisible to the human eye.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the electrode temperature of the glass substrate and the center potential of the output voltage to the glass electrode that minimizes panel flicker.

FIG. 3 is a graph showing temperature characteristics of the thermistor used in the example shown in FIG.

FIG. 4 is a timing chart of output and input of the embodiment shown in FIG.

FIG. 5 is a circuit diagram of a second embodiment of the present invention.

[Explanation of symbols] 1,7 constant voltage source 2 thermistor 3 operational amplifier 4 input terminal 5 output terminal to electrode of glass substrate 6 thermocouple

Claims (1)

[Claims] 1. A liquid crystal display device in which two glass substrates having a plurality of electrodes are opposed to each other, a liquid crystal is sandwiched therebetween, and an AC voltage is applied to at least one of the glass substrate electrodes to drive the liquid crystal display device. A liquid crystal display device comprising: a glass substrate electrode portion or its vicinity, and a circuit for adjusting a central potential of an electrode of one glass substrate with respect to a potential of an electrode of one glass substrate by a signal thereof.