JPS63144671A - Liquid crystal display driving method - Google Patents

Abstract

PURPOSE:To make flickers in the case of interlaced scanning unnoticeable by switching the voltage drive direction at the time of switching frames by combining a first kind of in which the voltage direction is not changed and a second kind of frame in which the voltage direction is changed. CONSTITUTION:The first kind of frame in which the voltage impression direction against a liquid crystal is not changed neither for odd-number fields nor even- number fields the second kind of frame in which said impression direction is changed for every field, are combined to form one cycle with four frames; said voltage impression direction is changed at the time of switching the frames. This means that, during the second field, a negative directional voltage is impressed, but in a third field where the frame is shifted from the first kind to the second kind, the voltage is impressed in the positive direction. Similarly, in a fourth field, the voltage is impressed in the negative direction, but in a fifth field where the frame shifted from the second kind to the first kind, the voltage is impressed in the positive direction. As a result, the direction of voltage impression is inverted in 45Hz field frequency out of 60Hz, and flickers accordingly come unnoticeable.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is applicable to liquid crystal displays that display one frame as an even number of fields (divided into two) for skipping operations, redundancy, or to divide the screen into fields. The present invention relates to a method for driving a liquid crystal display in a panel.

``Prior art'' In liquid crystal display panels, for example, as shown in Figure 7 (=
A liquid crystal 13 is sealed between transparent substrates 11 and 12 such as glass, and a large number of pixel electrodes 14 are arranged in rows and columns on the inner surface of one transparent substrate 11, and all pixel electrodes 14 are formed on the inner surface of the other transparent substrate 12. A liquid crystal cell 16 is constructed by forming a common base pole 15 over the entire surface. Although not shown in the figure, a row of pixel electrodes 14.

A plurality of row drive lines and a plurality of column drive lines are provided along each of the column arrays, and near each intersection position of these row drive lines and column drive lines, a thin film transistor is connected to these drive lines and one pixel electrode 14 at that position. is connected. The row drive line and the column drive line are selectively driven to pass four thin film transistors connected to both of them, and this (= connected pixel electrode 14 is charged with electric charge, and the pixel electrode 14 is connected to the pixel electrode 14). An electrode is applied to the liquid crystal 13 between the electrodes 15 and the area is controlled to be transparent or transparent for display.

To erase the display, the charge on the pixel electrode 14 is discharged.

Although video signals are displayed on liquid crystal display panels, one frame of the video input signal consists of an even field and an odd field, as shown in Figure 8A, and in the case of a so-called interlaced scanning video signal. In Figure 8B
As shown in , if the voltage applied to the liquid crystal is applied in a positive direction with respect to the common electrode 15 in even fields, and in a negative direction with respect to the common electrode 15 in odd fields,
The liquid crystal in the portion displaying even fields is always driven with a positive voltage, and the liquid crystal in the portion displaying an odd field is always driven with a negative voltage. If the driving direction for the liquid crystal is always constant in this way, the life of the liquid crystal will be shortened.

From this point of view, it is common to drive liquid crystals with alternating current. For this purpose, for example, as shown in Figure 8C,
In the frame, are both odd and even fields liquid crystal? The liquid crystal is driven with a positive direction voltage, and in the -1st and 2nd frames, both even and odd fields are driven with a negative direction voltage. The odd fields are driven with the square voltage, and the even fields of the second frame are driven with the positive direction voltage yA@1. It is conceivable that I L and odd-numbered fields are driven with a negative direction voltage.

However, in this case, for example, the liquid crystal part that is driven in an even field (if you look at the two, the positive direction voltage drive and the negative direction voltage drive are alternately reversed at 15Hz, assuming that one frame is 30Hz). .

The reversal period is long, causing flicker, which makes the display difficult to see.

"Means for Solving the Problems" According to the present invention, a liquid crystal display panel that divides one frame into an even number of fields for display.

There are two types of frames: a first type frame in which the direction of voltage applied to the liquid crystal does not change between even and odd fields, and a second type frame in which the direction of voltage applied to the liquid crystal changes between odd and even fields. When switching between the first type frame and the second type frame, the direction of voltage application to the liquid crystal is changed.

By doing this, the field wave number will be 60 H for both the even field and odd field liquid crystal parts.
In the case of z, the direction of voltage application to the liquid crystal is apparently reversed at a rate of about 45 Hz, making flicker less noticeable.

Embodiment FIG. 1 shows an example in which the liquid crystal display driving method according to the present invention is applied to interlaced scanning. Therefore, the input video fJ signal has an even field and an odd field, for example, as shown in FIG. 1A. One even field and one odd field constitute one frame, occurring alternately at 60 Hz. In contrast to such a video□Ig issue, this invention is the first
As shown in Figure B.

For example, the first field and the second field apply a voltage in the negative direction to the liquid crystal (two fields), the third field applies a voltage in the positive direction to the liquid crystal, and the fourth field applies a voltage in the negative direction to the liquid crystal, In the 5th field, a voltage is applied to the liquid crystal in the positive direction, and in the 6th field, the liquid crystal (
Two pairs of positive directions C: A voltage is applied, and in the seventh field, a voltage is applied in a negative direction to the liquid crystal, and in the eighth field, a voltage is applied in a positive direction to the liquid crystal.

This is defined as one cycle. That is, the period is four frames from the first frame to the fourth frame, and as can be seen from this, for example, in the first frame, the direction of voltage application to the liquid crystal C2 is not changed in both the odd and even fields, and it is the same. The third frame is also a type 1 frame in which the voltage application direction is not changed in both the even and odd fields.On the other hand, in the second and fourth frames, the voltage applied to the liquid crystal is changed between the even and odd fields. This is a $2 type frame that changes the direction of application.

In this way, there are type 1 frames in which the direction of voltage application to the liquid crystal does not change in both odd and even fields, and type 2 frames in which the direction of voltage application to the liquid crystal changes in odd and even fields. and when switching between type 2 frames (changing the direction of voltage application to one liquid crystal). In other words, in the figure, voltage is applied to the liquid crystal in the negative direction in the second field, but when switching from type 1 frame to type 2 frame. In the switched third field, a voltage is applied in the positive direction to the liquid crystal.Similarly, in the fourth field, a voltage is applied in the negative direction (= voltage is applied to the liquid crystal, but
From the second type frame to the first type frame (= in the switched fifth field, the liquid crystal (2) in the positive direction (-voltage is applied).

In this way, the direction of application of the wake-up pressure is reversed six times in eight fields, and when the field station wave number is 60 Hz, the reversal frequency is approximately 45 Hz, and among these, even field elements ≦: those for the opposite, and those for the odd field elements. Since the direction of voltage application is reversed by half for 22
．． The voltage application to the liquid crystal is reversed at 5 Hz, which is higher than the above-mentioned 15 Hz, making flicker less noticeable.

To create a liquid crystal drive signal as shown in FIG. 1B (=), for example, the second factor (≦2 as shown in FIG. Therefore, the vertical synchronizing pulse as shown in FIG. Figure 3 B and C for even and odd fields.
As shown in Fig. 13 and 14, respectively.

These even field vertical synchronizing pulses and odd field vertical synchronizing pulses are connected to the Σ divider 15.161, respectively.
= divided into three parts, each with a third figure.

The signals shown in FIG. 3 are obtained as shown in FIG.

On the other hand, the output of the divider 16 (FIG. 3E) is further divided by the Σ frequency divider 18 (-), resulting in the signal shown in FIG. 3G. The logical sum is obtained by the circuit 19.

The result is as shown in FIG. 3H, and the drive signal shown in FIG. 1B is obtained at the output terminal 21.

Such alternating current driving for liquid crystals is not limited to interlaced scanning (i.e., it is not limited to two-pair scanning. In other words, the present invention generally drives the liquid crystal display panel by sending the same video data through different series for each field or frame. !11′
It can also be applied when f. That is, for example, as shown in FIG. 4, the pixel electrode pH of the liquid crystal display panel, p1□, B13...
・are arranged in the row direction.

Also, along with this, pixel electrode P21 + P2□, B23
. . . are arranged in the row direction (-), and pixel electrodes are similarly arranged in the following although not shown in the figure.For each row direction arrangement of each pixel electrode, the row direction drive line is AI+B1°A2
+ B2, A3, B3, . . . two each are provided. Furthermore, the same (: each column direction arrangement of pixel electrodes (=
Column drive lines S1 . B2. B3... is provided. Each pixel electrode P11 + PI□, B1
3... has thin film transistors 22 on the column drive lines on both sides.
They are connected through the drain and source of .23, respectively. The gate of one of the transistors 22 is A of the row drive line.
The gate of the other thin film transistor 23 is connected to the B side of the row drive line.

With such a configuration, for example, the A side of the row drive line and each column drive line are selectively driven, so each pixel electrode is driven from the thin film transistor 22 side, and then the B side of the first row drive line and each column drive line are driven. , and therefore, each of the same pixel electrodes is selectively driven from the thin film transistor 23 side. In this way, the same pixel electrodes are alternately driven from opposite directions, and the column drive lines S,.

With respect to the common electrode 15 (FIG. 7), B2... is set to a positive voltage or a negative voltage (-switched).

The liquid crystal facing each pixel electrode is AC driven (-).

However, if there is a break somewhere in the row drive line.

On the other hand, the pixel electrode on the side farther from the driving source than the disconnection point is driven by only one voltage, and as a result, the liquid crystal in that part is not driven by alternating current.

In this redundant case, AC drive for the liquid crystal is performed regardless of the wire breakage. When driving the liquid crystal≦2, apply a voltage in the negative direction (5 voltages are applied to all column drive lines S, S2, etc. with a negative voltage with respect to the common electrode 15), and drive the B side of the row drive line in the second field. When driving, a negative direction voltage is applied to the liquid crystal, and when driving the A side of the row drive line in the third field, a positive direction voltage is applied to the liquid crystal. In the fourth field, when driving the A side of the row drive line, a negative voltage is applied to the liquid crystal, and the same operation is performed thereafter.

Figure 4 (2) Redundant driving may be performed as shown in Figure 5. In Figure 5, the column drive lines are made redundant, and for each SIT s,, SB @... Further (
2 Sl + S2 + S's... are provided, and each row drive line has two column drive lines s for each pixel electrode on both sides thereof.
, s' are connected through thin film transistors 22 and 23, respectively. In this case as well, the present invention is applied to the first row drive line A1. Every other one of A2...A1+
A3...and every other one A2 e A4...
may be associated with the COA side and the B side in FIG. 1, respectively.

There are eight types of such AC drive signals whose phases are sequentially shifted from those shown in Fig. 1B, as shown in Fig. 6C2H1 to H8. May be used. In addition, each column yi of these drive signals with different phases
It may be used by assigning it to each AvJ line.

Furthermore, for example, when displaying red in the first field, green in the second field, and displaying a color that appears yellow as a whole, this also applies when changing the drive for color switching of this field to AC. The invention can be applied.

For example, as shown in the first diagram (= drive in the negative direction with the red field of the first field, drive in the negative direction with the green field of the second field, drive in the positive direction with the red field of the third field, and so on. It is possible to control the liquid crystal to drive the liquid crystal using AC.

"Effects of the Invention" As stated above (= this invention (-), by combining a $1 type frame that does not switch the voltage direction and a type 2 frame that switches the voltage direction, - Such a drive voltage can be easily created by a simple method of switching the voltage drive direction in 7 lines when switching between the type frame and the second type frame, and by such means, flicker in interlaced scanning can be reduced. It is possible to reduce the number of defective pixels (:
(Secondly, by temporally combining various color fields, flicker can be made inconspicuous by applying AC drive to the liquid crystal during color switching when obtaining various mixed colors.) , the lifespan of the liquid crystal can be extended accordingly.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing an example of the liquid crystal driving method according to the present invention, FIG. 2 is a logic circuit diagram showing a specific example of generating the driving signal, FIG. 3 is an operation waveform diagram of FIG. 2, and FIGS. FIG. 5 is a diagram showing an example of a redundant drive configuration, FIG. 6 is a diagram showing each ridge side of the drive signal of the present invention, FIG. 7 is a diagram schematically showing a cross section of a liquid crystal display panel, and FIG. 3 is a time chart for explaining a conventional driving method. Patent Applicant Hoshi Electric Manufacturing Co., Ltd. Representative Takuo Kusano 1 Eno 2 and a half figures 3 figures* 4 figures* 5th 5176 figure H8 Thu 7 Miyu 8 figure procedural amendment C/FJ 1988 1 January 19th, 1, Indication of the case: Japanese patent application No. 61-2922322, Title of the invention: Liquid crystal display driving method 3, Person making the amendment Relationship to the case: Patent applicant: Hoshi Denki Manufacturing Co., Ltd. 4, Agent: Shinjuku, Shinjuku-ku, Tokyo 4-chome 2 @21
No. Sagami Building 5, subject of amendment Detailed explanation of the invention in the specification column 6,
Correction details +11 Light 1Il Book 2 Page 18 Line 18 Changed “electrode” to “Voltage”
I am corrected. -15...-1 (3) In the same book, page 12, line 1, ``Each column drive line'' is corrected to ``Each column or each row drive line.''that's all〕. . ′

Claims (1)

[Claims] (1) In a liquid crystal display panel that displays a frame by dividing it into even fields, one period is four frames, and the first type does not reverse the direction of the voltage applied to the liquid crystal of the liquid crystal display panel between even and odd fields. A method for driving a liquid crystal display comprising: a frame and a second type frame which is reversed for each field, and the direction of voltage application to the liquid crystal is reversed when switching between the first type frame and the second type frame.