JPS62242920A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE:To reduce a flicker by inverting the polarity of one group, among three signal electrode groups. CONSTITUTION:As for a color switching circuit 8, in case of a zigzag type color filter arrangement, (a), (b), and (c) become switching of R and G, G and G, and B and R, respectively. A polarity inverting circuit 9 inverts the polarity of only (b) and (c). Also, only (a) is applied to a polarity inverting circuit 11 which is operated by an opposite phase to the circuit 9, and the polarity is inverted. Subsequently, it is applied to a sample holding circuit 10. Therefore, the polarities of signals applied to a signal electrode of the group (a) and signal electrodes of the groups (b), (c) become the opposite phase. In this way, a picture element of an area in which a waveform of a transmission light is 1/3 of the whole is cancelled against other 2/3 to some extent, and comes not to be sensed as a flicker.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color liquid crystal display device using an active matrix method in which R, G, and B micro color filters and switching elements are provided in each display picture element.

(Prior Art) In recent years, in order to display color images using liquid crystals, the so-called active matrix method, in which a switching element (generally a thin film transistor formed on a transparent substrate) is used for each picture element to statically drive the liquid crystal, has been developed. (
It has been put into practical use in combination with R), Green (G), and Blue (B) micro color filters.

An example of this is shown in FIG. In FIG. 3, reference numeral 1 indicates an array of active matrix type thin film transistors. The array 1 is composed of scanning electrodes 2, signal electrodes 3, and picture elements 4. The number of scanning electrodes 2 is the same as the number of effective scanning lines included in the video signal, and NTSC
With this method, there are approximately 240 lines (non-interlace display) or approximately 480 lines (interlace display). Next, the internal equivalent circuit of picture element 4 is shown in FIG. In Figure 4, 2
3 is a scanning electrode as in FIG. 3, and 3 is a signal electrode. and,
4 is a thin film transistor which is a switching element, 5 is a liquid crystal cell, and 6 is a common electrode provided on the substrate on the opposite side of the substrate on which the array is provided and the liquid crystal. Generally, R2O, B are placed on the substrate on this common electrode side. micro color filters are provided.

Regarding the operations of the thin film transistor 4 and the liquid crystal 5, detailed explanation will be omitted since the technology has already been implemented.

In FIG. 3, reference numeral 7 denotes a scanning electrode driving circuit, which has a structure of a shift register that sequentially applies driving pulses having a width of a horizontal scanning period to the scanning electrodes from top to bottom. Reference numeral 8 in FIG. 3 is a color switching circuit, which switches the color-decoded three primary color video signals every horizontal scanning period according to the arrangement of the micro color filters.

FIG. 5 shows an example of the arrangement of micro color filters.

This is an example of a staggered arrangement, in which a certain signal electrode (a on the left end of FIG. 5) is R, G.

Switch between R and G. Similarly, the signal electrode indicated by b is G.

By switching the signal electrode shown by B and changing the signal electrode shown by C to B and R, it corresponds to the arrangement of the color filter.

The signals divided into three groups a, b, and c by this color switching circuit 8 are sent to a common electrode every vertical scanning period by a polarity reversing circuit shown at 9 in FIG. 3 in order to AC drive the liquid crystal. The polarity is reversed. Then, it is converted into a line-sequential drive signal by the sample-and-hold circuit 10, and the signal electrode 3
to drive.

(Problems to be Solved by the Invention) Next, the waveforms of various parts of the conventional example shown in FIG. 3 are shown in FIGS.
Shown in (d). FIG. 6(a) shows the signal electrode waveform when displaying a uniform white signal, and as described above, the polarity is reversed every vertical period. FIG. 6(b) shows a waveform applied to a certain scanning electrode. During the period when a positive pulse is applied, the thin film transistor is conductive, and the liquid crystal cell is charged or discharged to the potential of the signal electrode. During other periods, the liquid crystal cell is in a cut-off state and retains the charge stored in the liquid crystal cell. However, the hold period is not completely cut off, and a certain amount of leakage current flows, and the waveform applied to the liquid crystal cell becomes a waveform slightly deviated from a rectangular wave, as shown in FIG. 6(c). This leakage current varies to some extent depending on the thin film transistor, and also changes slightly depending on the polarity of the signal electrode waveform. On top of that,
The voltage applied to the liquid crystal does not have a perfect AC voltage waveform due to leakage of the driving pulse of the scanning electrode through the internal capacitance of the thin film transistor. Therefore, the fluctuation of the transmitted light passing through the liquid crystal cell generates a component whose cycle is two vertical scanning periods.0 For a normal NTSC signal, it is 1/16.6ms
2 = 30I (z component, this frequency flickers even with a slight variation, resulting in so-called flicker, resulting in an unpleasant image. (d) is the transmitted light waveform.

The present invention aims to eliminate such drawbacks of the prior art and reduce flicker in color liquid crystal displays.

(Means for Solving the Problems) The present invention attempts to reduce flicker by inverting the phase of the waveform applied to one group among the three groups of signal electrodes with respect to the other two groups. be.

That is, in the present invention, in a color liquid crystal display device, a liquid crystal is sandwiched between two substrates, a scanning electrode is provided on the first substrate, and three
A switching element is provided near the signal electrodes divided into groups, the scanning electrodes and the signal electrodes, and R2O and B micro color filters corresponding to the three groups of signal electrodes are provided, and among the signal electrodes of the three groups, a switching element is provided. , is characterized in that means is provided for making the polarity of the signal applied to the signal electrodes of one group different from the polarity of the signals applied to the signal electrodes of the other two groups.

(Function) By reversing the polarity of one of the three signal electrode groups, the waveform of transmitted light is
A pixel with an area of 3 cancels to some extent with the other 2/3,
It no longer feels like flicker. This takes advantage of the fact that flicker is not perceived as the flickering of light from individual picture elements, but as the average light over a fairly wide area.

(Embodiment) FIG. 1 shows an embodiment of the present invention. Components that operate in the same way as in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted. In FIG. 1, the color switching circuit 8 switches between R and G for A, G and B for the mouth, and B and R for C when the color filter arrangement is as shown in FIG. The polarity inversion circuit 9 inverts the polarity of only the opening and the C, as in the conventional case. Then, in addition to the polarity inversion circuit 11 which operates in the opposite phase to the polarity inversion circuit 9, the polarity is inverted. Then, it is applied to the sample and hold circuit 10 as in the conventional case.

For this reason, the polarities of the signals applied to the signal electrodes in group A and the signal electrodes in groups mouth and C are in opposite phase6.
Next, FIG. 2 shows the waveforms of each part.

(,) is an example of the liquid crystal applied voltage waveform of the groups 1 and 2, and the waveform is the same as the conventional one. (b) is the liquid crystal applied voltage waveform of group A with reversed polarity. however,(
The picture element on the same scanning electrode as in a) is shown. and(
C) is the transmitted light waveform of the mouth of (a) and the group of C, (d)
is the transmitted light waveform of group A in (b), and in (c) and (d), the 30 Hz component is generated as described above, but its phase is opposite. Therefore, the average transmitted light perceived by the eye is only 601(z) as shown in (e), and flicker is no longer perceived.

In the example explained above, since the group a of R and G is inverted, half of the pixels of G, which is the most sensitive to the eye in terms of luminance, and R, which is the next most sensitive, are inverted. .

In the remaining B, the 307 component remains, but the visibility is low and it is dark, so the flicker is not noticeable. Therefore, even though this combination only inverts the entire 173, it can almost completely cancel out the visibility and is the most effective.

Next, a case where the present invention is applied to a diagonal striped color filter arrangement as shown in FIG. 7 will be described. In this case, since each group is a repetition of R, G, and B, there is no difference in effect no matter which group is inverted. The configuration is the same as that in FIG. 1, and only the operation of the one-color switching circuit 8 differs. In this example, since 1/3 is canceled, the remaining 1/3 is 30
The seven components remain, and although the effect is weaker in white uniform signals and the like compared to the previous embodiment, the effect is clearly recognized as compared to the conventional example. Another advantage is that it works equally well on all colors.

(Effects of the Invention) According to the present invention, 3
It is possible to prevent the 0 Hz flicker component with a simple configuration. With the arrangement of the staggered color filters shown in FIG. 5, except for the case of only one color B (even in that case, it is hardly noticeable under normal brightness), it can be almost completely prevented, and has high practical value. In the diagonal striped color filter arrangement shown in FIG. 7, it is possible to reduce the 30 Hz frizz force component for any color.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a color display device according to an embodiment of the present invention. FIG. 2 is a waveform diagram of each part of the present invention, FIG. 3 is a configuration diagram showing a conventional display device, FIG. 4 is an internal equivalent circuit diagram of a picture element, FIG. 5 is a staggered color filter arrangement diagram, and FIG. Figure 6 is a waveform diagram of each part of the conventional example. FIG. 7 is a diagram illustrating the arrangement of diagonal striped color filters. DESCRIPTION OF SYMBOLS 1...Transistor array, 2...Scanning electrode, 3
...Signal electrode, 4.Picture element, 7.Scanning electrode drive circuit, 8.Color switching circuit, 9.Polarity inversion circuit, 10.Sample/hold circuit, 11.
...Polarity inversion circuit (operates in opposite phase to 9). Patent author Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 5 Figure 7 Figure 6 Diagram 1! ! Asaaki

Claims (3)

[Claims] (1) sandwiching a liquid crystal between two substrates, providing a scanning electrode on the first substrate, a signal electrode divided into three groups, and a switching element near the scanning electrode and the signal electrode;
R, G, and B micro color filters corresponding to the three groups of signal electrodes are provided, and the polarity of the signal applied to one group of signal electrodes among the three groups of signal electrodes is the same as that of the other two. 1. A color liquid crystal display device comprising means for making the polarity of a signal different from that of a signal applied to a group of signal electrodes. (2) The arrangement of micro color filters is staggered,
The three groups of signal electrodes are R and G, G and B, and B and R groups, and the polarity of the signal electrodes of the R and G groups is different from that of the other groups.
1) The color liquid crystal display device described in item 1). (3) A patent claim characterized in that the micro color filter is arranged in a diagonal stripe state, and a signal electrode applied to one group of signal electrodes among the three groups of signal electrodes is different from that of the other groups. range first (1
) The color liquid crystal display device described in item 2.