JPH0258021A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve the temperature dependency of linearity characteristics by varying the ratios of differences between a common signal select level and two nonselect level values to the ON/OFF level difference of a data signal with environmental temperature. CONSTITUTION:The ratio (represented in percentage as a bias) of the difference of one nonselect level value which is far away from a select level between two nonselect level values to the ON/OFF level difference of the data signal is reduced within a range of >=50%, and then linearity characteristics which are close to a binary table where a black-side black and white state is saturated are obtained. When the ratio is increased, linearity characteristics which decreases in difference in brightness between half-tones and have good gradation display performance are obtained. The characteristics are used to set the bias to 55 - 75% at high environmental temperature or to 80 - 95% at low temperature, thereby improving the temperature dependency of the linearity characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a liquid crystal display device, particularly a liquid crystal display in which a two-terminal element with nonlinear voltage-current characteristics is formed in each pixel electrically in series with a liquid crystal layer. This invention relates to a method for driving a device.

[Summary of the Invention] The present invention uses a nonlinear two-terminal element to generate a data signal consisting of two sets of voltage levels corresponding to polarity and ONOFF level, one set of selection level and two sets of non-selection level corresponding to the polarity. In a liquid crystal display device, the potential difference between the levels of the bell is equal to 1/2 of the potential difference between the data signal ONOFF level and the data signal ONOFF level difference.

The ratio of the difference between the common signal selection level and the binary non-selection level is varied in response to the environmental temperature, thereby realizing a high-quality liquid crystal display device that maintains the linearity of the image display at all times with respect to the environmental temperature. It is.

[Prior art 1 As a liquid crystal display device using a nonlinear element, MIM (
Japanese Patent Laid-Open No. 1983 (1982), which uses a Meta I-1 nsu ]ator-Metal) element and improves its characteristics by a driving method.
There is a technique called -036616.

In high-duty drive such as -119, the non-selection level is made up of a set of voltage levels corresponding to the polarity.
2) t7WK at the voltage level of Jl, and set these non-selection levels to the middle of the ONOFF level of the corresponding data signal to improve the retention characteristics, improve the contrast ratio, lower the driving voltage, and lower the temperature. The purpose was to improve the characteristics.

[Problems to be Solved by the Invention] According to the above-mentioned conventional technology, the contrast ratio and drive voltage characteristics are improved, but the change characteristics from the black level to the white level of the image display in response to changes in the environmental degree, that is, the linearity characteristics changes to 1, for example 25. If the conversion characteristics of the A/D converter are set so that the linearity characteristics are the best at temperatures around 90 degrees Celsius, at 50 degrees Celsius, the linearity characteristics will be such that the luminance difference between halftones is reduced and there is no sense of contrast; At 0°C, the linearity characteristic becomes black (original white) or saturated.

When aiming to improve the image quality of a liquid crystal display device, the temperature dependence of the linearity characteristic is a problem that cannot be overlooked, and an object of the present invention is to solve this problem and realize a liquid crystal display device with high image quality.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides a data signal ON/OFF
The ratio of the difference between the common signal selection level and the binary non-selection level to the level difference is varied in accordance with the environmental temperature.

[Function 1: Ratio of the difference in the non-selection level of one value far from the selection level among the non-selection levels of the binary values of the y-selected bell to the ONOFF level difference of the data signal (hereinafter referred to as bias, not expressed as a percentage) If you reduce by more than 50%,
The linearity characteristic is close to that of a binary display in which black measurement black and white is saturated, and when it is increased, the linearity characteristic with good gradation display performance is obtained in which the luminance difference between halftones is reduced.

The present invention makes use of the above characteristics, and at high temperatures, the bias is set to 55~55.
The temperature dependence of the linearity characteristic is improved by setting it to about 70% and setting it to 80 to 95% at low temperatures.

[Example] The present invention will be explained below based on examples.

FIG. 1 shows a common signal Sc and a pig signal S according to an embodiment of the present invention.

, and the signal 5c-8I applied to a certain pixel corresponding to the data signal of the selected common line, at 0°C, 25°C, 5
31 quality conditions at 0°C are illustrated.

The brightness of the image is V. This is done by varying the duty ratio of NVOFF, and as shown in the conceptual diagram of drive waveforms and liquid crystal layer applied voltage for data signals fully ON and fully OFF in Figure 2, the resistance value of the nonlinear element (here MIM element) is changed at the time of selection. By lowering, a sufficient voltage is applied to the liquid crystal layer, and when it is not selected, the resistance value increases and is maintained, which is expressed by the difference in effective voltage shown in the shaded area in FIG.

In the example, a bias of 0°C (V ON V N2/
V oNVorr ) 90%, 25°C is 80%, 5
70% is used for 0°C, which means that the holding capacity at low temperatures is high.

Drive voltage V under each temperature condition at this time, (=2VoH
) against. The transmittance characteristics from the data signal completely OFF black to the fully ON white are shown in FIG. 3(a).

The linearity characteristic at the optimum point where (2) is varied by adjusting the brightness of the screen, indicated by a straight line in the figure, becomes almost constant as shown in FIG. 3(b).

Figure 4(a) shows the drive voltage Vp and transmittance characteristics under each temperature condition when the bias is constant using the conventional technology, and Figure 4(b) shows the linearity characteristics with respect to the optimum drive voltage.
It is clear that according to the present invention, the slope of the transmittance change characteristic with respect to the VP change becomes almost constant regardless of temperature conditions, and as a result, the dependence of the linearity characteristic on one temperature is improved.

Figure 5 shows an example of a liquid crystal display device. I'J] This is a power supply circuit diagram in which a temperature compensation thermistor satisfies the relationship between temperature conditions and bias.

FIG. 6 is an example of a conventional liquid crystal display drive power supply circuit diagram.

[Effects of the Invention] As described above, according to the present invention, a nonlinear two-terminal element is used to generate a data signal composed of two sets of voltage levels corresponding to polarity and ONOFF level, and one set corresponding to polarity. In a liquid crystal display device driven by a common signal consisting of a selection level and two sets of non-selection levels, the ratio of the difference between the common signal selection level and the binary non-selection level to the data signal ONOFF level difference is calculated based on the environment. By varying the temperature in response to changes in temperature, it is possible to realize a high-quality liquid crystal display device that always maintains constant linearity characteristics of image display with respect to environmental temperature.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(c) are drive waveform diagrams for temperature conditions in an embodiment of the present invention. Figure 2(a) shows the data signal all ON, Figure 2(b) shows the data signal all 0.
A conceptual diagram of driving waveforms for FF and voltage applied to the liquid crystal layer. Figures 3 (a) to (c) are driving voltage transmittance characteristic diagrams under the actual side number (blackness condition). Figures 4 (a) to (C) are linearity characteristic diagrams under the actual side number temperature condition. (a) to (C) are drive voltage transmittance characteristic diagrams for each conventional wave t+IIi (blackness condition). Figures 6 (a) to (c) are linearity characteristic diagrams for each conventional wave (hotel temperature condition). Fig. 7 is a power supply circuit diagram for driving a liquid crystal display device according to an embodiment. Fig. 8 is an original circuit diagram of a conventional liquid crystal display device driving type. 66 ・ ・ Common signal data signal image 2) S applied signal thermistor buffer circuit buffer circuit (of) Above

Claims (1)

[Claims] a) A plurality of row electrodes and column electrodes, a liquid crystal display layer disposed between the two electrodes, and an element with nonlinear voltage-current characteristics disposed between the liquid crystal display layer and the row electrode or column electrode. A liquid crystal display section in which pixels are arranged in a matrix. b) A common consisting of several types of selection voltages that increase the voltage applied between the row and column electrodes when selected, and several types of non-selection voltages that decrease the voltage applied between the row and column electrodes when not selected. A common line side drive circuit that generates signals and selects common lines in sequence. c) Depending on the ONOFF data of the image, several types of ON
A data line side drive circuit that generates a data signal consisting of an OFF voltage to the column electrode. d) The data signal is composed of two sets of voltage levels corresponding to the polarity and ON/OFF, whose polarity is inverted every common scan, e) The common signal is composed of one set of selection levels corresponding to the polarity of the data signal, and two sets of voltage levels corresponding to the polarity of the data signal. f) The potential difference between the average value of the binary non-select levels of each polarity of the common signal and the selected level is the data signal ONOF.
In a liquid crystal display device whose potential difference is equal to 1/2 of the F level potential difference, g) The ratio of the difference between the common signal selection level and the binary non-selection level to the data signal ONOFF level difference is varied in accordance with the environmental temperature. Characteristic liquid crystal display device.