JPH0772771B2 - Liquid crystal display - Google Patents

Description

The present invention relates to a configuration of a time-division matrix driven liquid crystal display device.

[Conventional technology]

Conventionally, various studies have been made to suppress a crosstalk voltage and realize a high contrast in a liquid crystal display device having a matrix pixel array. As one of the methods, the present inventor has proposed a liquid crystal display device using a liquid crystal driving method with a quiescent phase in JP-A-59-121391. The liquid crystal driving with resting phase is a driving method in which a liquid crystal display device is applied with a voltage of a driving phase corresponding to a plurality of pixel regions and the applied voltage is suppressed to zero in the non-driving phase of each pixel region.

Hereinafter, a liquid crystal driving method with a rest phase will be described with reference to the drawings.

FIG. 2 shows a drive voltage waveform when there is no conventional idle phase. As is clear from the waveform, it can be seen that the moving average for calculating the effective value has no time and time dependency.

FIG. 3 shows a waveform of a voltage applied to a pixel of a conventional liquid crystal display device driven with a rest phase. The period of the drive voltage waveform is (t9−
t0), and the idle phase interval of the drive waveforms VA1 to VAn is t5 to t9.
Is. In the drive waveforms VBn + 1 to VB2n, t0 to t5 are idle phases. Of the voltage application phases, the phase with the highest peak value is the digit selection phase. In the drive waveform VB2n, the phase from t8 to t9 is the digit selection phase.

[Problems to be Solved by the Invention]

However, in the driving method with the rest phase, uneven brightness may occur at the boundary of the pixel area.

It is an object of the present invention to provide a liquid crystal display device that suppresses the uneven brightness by improving the driving method, assuming that the cause of the uneven brightness is the transient response of the liquid crystal.

[Means for solving problems]

In a matrix driven liquid crystal display device, it is based on the fact that the optical response corresponds to the effective value of the applied voltage. However, considering the principle of RMS response, it is clear that the integrated average of the square value of the voltage should be a continuous moving average on the time axis, and the average time should be the response time of the liquid crystal. Is. In the case of an LCD TV, the screen change takes about 30 milliseconds, and the drive voltage waveform period also becomes about 30 milliseconds.
The electro-optical characteristics of the liquid crystal display device have a non-linear response with a threshold value. In matrix driving, the threshold voltage is covered by the crosstalk voltage, and the slight voltage in the digit selection phase is used. Optical modulation is performed by the modulation. Therefore, when a time-division matrix drive with a quiescent phase is adopted for contrast enhancement, and when a liquid crystal with a fast response of about 30 milliseconds or less is used, digit selection is performed according to the phase difference between the digit selection phase and the quiescent phase. It is considered that the influence of voltage is different.

In order to reduce this effect as much as possible, the present invention provides a liquid crystal display device that drives a pixel region by providing a preliminary drive phase immediately before selection when the pixel region to be selected next is driven by providing a rest phase. And

〔Example〕

 A detailed description will be given below with reference to the drawings.

In FIG. 1, the pre-driving phase is provided in the latter half of the rest phase. 1 shows an example of the present invention. By performing pre-driving during the rest phase, the contrast is slightly reduced,
The influence of the position of the digit drive phase is reduced, and the uneven brightness at the pixel area boundary can be suppressed. Incidentally, the drive voltage waveform and the rest phase are mostly the same as those of the conventional configuration shown in FIG.

FIG. 4 shows voltage waveforms when pre-driving is performed after the idle phase. The influence / effect of the pre-driving is the same as in the case of the waveform in FIG.

FIG. 5 is an enlarged view for explaining the details of the drive waveforms shown in FIG. In FIG. 5, t0 to t4 are voltage application phases p2, and t4 to t8 are rest phases p3. Of the voltage application phases t0 to t4, t0 to t1 is the pre-driving phase p0, and t1 to
t2 is the digit selection phase p1, and the peak value in this digit selection phase p1 can be modulated as a1.V0 and a2.V0 in FIG. The minimum value of the effective value voltage for pixel driving is when a1 · V0 is selected, and the maximum value is when a2 · V0 is selected. To drive the liquid crystal with gradation, it is achieved by dividing the digit selection phase P1 and allocating the voltage to a1.V0 and a2.V0.

FIG. 6 shows an example of an electrode structure of a liquid crystal display device having a matrix pixel array applied to the driving system of the present invention. In FIG. 6, reference numeral 602 is a timing substrate, which is formed by partially removing by etching an insulating substrate such as a glass plate on which a transparent electrode such as an indium oxide thin film is formed. 612 and 614 are display electrodes,
Reference numeral 632 is a timing drive circuit. The timing drive waveform is a voltage waveform defined by a function of time without depending on display pixel information. A data board 604 has a structure similar to that of the timing board. 604 is a transparent insulating substrate, 622
Reference numeral 624 is a data electrode, and 634 and 636 are data driving circuits.
The waveform of the data drive voltage changes according to the display information. Reference numeral 606 exemplifies a liquid crystal display element having a structure in which liquid crystal is sandwiched by making the electrode surfaces of both substrates face each other. The data electrode is, for example, 2
The voltage is applied in different phases. The display pixel is defined by the combination of the timing electrode and the data electrode, and is arranged as shown in S11 to S85 of the figure.

FIG. 7 shows the drive voltage waveform dependence of the liquid crystal response. In Fig. 7, when the digit selection phase of the drive voltage is VA1, VAn-3, and VAn located at the leading edge, middle portion, and trailing edge of the voltage application phase, the optical responses are BA1, BAn-3, and BAn, respectively. It becomes like this. Luminance is greatly raised in the digit selection phase, is maintained at almost the level in the other bias voltage application phases, and is slightly lowered in the rest phase. This is because the deformation of the liquid crystal is slightly relaxed during the rest phase, and the advantage of the pulse voltage kick in the digit selection phase decreases after the rest. Although a liquid crystal with a response time of about several tens of milliseconds is suitable for displaying a television image, the cumulative response including the pause phase is as shown in FIG. 7 when the liquid crystal is driven with 30 screens / second.

Figures 8A and 8B show 2 on the upper half and the lower half of the TV display screen.
It shows the relationship of the brightness unevenness at the boundary when the divided pixel area is driven with a rest phase. The brightness BA becomes a function of the position of the horizontal line, and the brightness of the shaded area decreases as in BA1 and BA2, and a streak appears in the center of the screen. Here, when pre-driving is performed after the rest, the function after the brightness is raised can be used, and the streak disappears.

FIG. 9 shows the electro-optical response of the liquid crystal, and shows that the luminance can be modulated by applying a voltage above the threshold value.

FIG. 10 shows an example of the timing drive waveform and the data drive waveform in the time division drive of the liquid crystal. The difference voltage between the two is applied to the liquid crystal pixel. Therefore, it is possible to freely add an arbitrary voltage waveform to both, so that an appropriate voltage is applied to adjust the drive waveform and the convenience of IC design is often drawn. Although there are various drive waveforms, subtracting the above components results in the waveform shown in Fig. 10. The brightness of an arbitrary pixel can be modulated by switching the polarity of the data drive voltage in FIG. 10 in an arbitrary phase to positive or negative.

〔The invention's effect〕

As described above, the pre-driving of the present invention realizes a matrix-driving liquid crystal display device having high contrast and no brightness unevenness, and the advantage of the driving with pause is fully utilized.

[Brief description of drawings]

FIG. 1 is a drive voltage waveform diagram with a pause phase showing an embodiment of the present invention, FIG. 2 is a normal matrix drive voltage waveform diagram, and FIG.
FIG. 4 is a conventional drive voltage waveform diagram with pause phase, FIG. 4 is another waveform diagram of the present invention, FIG. 5 is a pause phase drive voltage waveform diagram with gradation of the present invention, and FIG. 6 is a matrix liquid crystal display device. FIG. 7 is an electrode configuration diagram, FIG. 7 is an optical response characteristic diagram of drive with rest phase, and FIG.
FIG. 9 is a luminance distribution chart showing the effect of pre-driving of the present invention, FIG. 9 is a characteristic diagram of liquid crystal electro-optical effect, and FIG. is there. 602 ... Timing board, 612/614 ... Timing electrode, 604 ... Data board, 622/624 ... Data electrode, 632
...... Timing drive circuit, 634 …… Data drive circuit.

Claims (3)

[Claims] 1. A pixel region of a time division matrix liquid crystal display device is divided into a plurality of regions, each pixel region is sequentially selected, a selected pixel region is set to a drive phase, and at least one pixel region that is not selected is a pause. In a liquid crystal display device that drives by providing a phase, when a pixel region to be selected next is driven by providing a pause phase, a preliminary drive phase is provided immediately before selection to drive the pixel region. Liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein a bias waveform is applied to the corresponding pixel in the pre-driving phase. 3. The liquid crystal display device according to claim 1, wherein a waveform different from the bias waveform is applied to the corresponding pixel in the pre-driving phase.