JPH064045A - Driving method for liquid crystal display device - Google Patents

Abstract

PURPOSE:To make flickering hardly recognizable and to improve image quality by dispersing the timing for changing the brightness and darkness of the photoresponse of the pixel electrodes connected to row wirings in proximity. CONSTITUTION:The polarity of an image signal Vsig when the potential Vc of a counter electrode is regarded as a potential reference is inverted >=3 and <=(Ldivided by 2) times per time Tf for writing the image signal Vsig for one sheet corresponding to all the picture elements of the liquid crystal display device having L pieces of the row wirings. In Fig., 960 pieces of the row wirings are attached with numbers from 1 up to 960 successively from the top end of the screen and are divided to five wiring groups by the remainder obtd. after two numbers are divided by 5. Namely, the pulses are successively impressed to one group 192 pieces of the row wirings and the polarity of the Vsig is inverted every time the row wiring group changes. The timing of the brightness and darkness of the photoresponse of the pixel electrodes connected to the row wirings in proximity shifts by about 0.5XTf even at the Worst and the flickering is hardly recognizable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a liquid crystal display device used in laptop computers and the like.

[0002]

2. Description of the Related Art In recent years, an active matrix type liquid crystal display device (hereinafter abbreviated as AM-LCD) using a thin film transistor (hereinafter abbreviated as TFT) or the like has been used in a small television receiver, a laptop computer or the like.

A conventional method of driving a liquid crystal display device will be described below. FIG. 2 is a circuit diagram of a main part of an AM-LCD using a TFT. In FIG. 2, 1 is a pixel and 2 is a TF
T, 3 is a storage capacitor, 4 is a pixel electrode, 5 is a counter electrode, 6 is a liquid crystal, 7 is a row wiring (horizontal wiring), 8 is a column wiring (vertical wiring), 9 is a common wiring 10, 11, Reference numeral 12 is a drive circuit. In a conventional AM-LCD, a large number of pixels 1 are repeatedly arranged in a matrix in a display area surrounded by a dotted line ABCD. Each pixel 1 has a TFT 2 built in,
The gate electrode of the TFT 2 is connected to the row wiring (horizontal wiring) 7, the source electrode is connected to the column wiring (vertical wiring) 8, and the drain electrode is connected to the storage capacitor 3 for holding pixel signals and the pixel electrode 4. ing. The other end of the storage capacitor 3 is connected to the common wiring 9. The liquid crystal 6 is driven by being sandwiched between the counter electrode 5 and the pixel electrode 4. Of the constituent elements of the pixel 1, the counter electrode 5 and the liquid crystal 6 are formed on the active matrix array substrate. The counter electrode 5 is composed of one wide electrode over the entire display portion and is formed on the counter substrate. In addition, although the number of wires is small in FIG.
In the case of displaying, the number of row wirings 7 and column wirings 8 exceeds several hundreds. A portion surrounded by a dotted line EFGH is a display panel whose main constituent elements are an active matrix array substrate, a counter substrate and a liquid crystal. A liquid crystal display device is formed by connecting drive circuits 10, 11 and 12 to each wiring of this display panel. Is configured.

Next, a method of driving the liquid crystal display device shown in FIG. 2 will be described. FIG. 3A is a drive waveform diagram for explaining a driving method of a conventional liquid crystal display device, and FIG. 3B is a diagram for explaining optical response of pixels in the liquid crystal display device. These figures show the case where there are 960 row wirings (horizontal wirings) 7. First, regarding the drive waveform, FIG.
Will be described with reference to. To simplify the explanation,
The case where a uniform image signal is given to the screen is shown. Vs
y is a signal applied to any one (y-th) column wiring (vertical wiring) 8, and Vc is the potential of the counter electrode 5. Vg1 to Vg960 are signals sequentially applied to the row wiring 7, and the TFT 2 is turned on at the timing when the pulse is applied.
Then, the signal Vsy is written in the pixel electrode 4, and the liquid crystal 6 is driven by the potential difference between the pixel electrode 4 and the counter electrode 5. 9
Let Tf be the time required to write all the image signals of one screen corresponding to all the pixels 1 of the liquid crystal display device to all the pixel electrodes 4 when all the 60 row wirings 7 are selected (pulses are applied). The image signal when the counter electrode 5 is regarded as the potential reference is Vsig, and the polarity is inverted every time Tf, and the liquid crystal 6 is AC driven. FIG. 3B shows the y-th column wiring 8 at this time.
47 is an example of the optical response of a part of the pixels 1 connected to (in a normally black display mode in TN mode), 47
The optical response from the pixel electrode 4 connected to the ninth row wiring 7 to the pixel electrode 4 connected to the 483th row wiring 7 is L
479 to L483. The brightness of the optical response changes in two cycles of Tf and 2 × Tf. That is, since the maximum value differs depending on the polarity of Vsig (MAX1 and MAX2), Tf
A bright / dark change component with a cycle twice that of

[0005]

However, in the above-mentioned conventional structure, as shown in FIG. 3B, the pixels connected to the adjacent row wirings change the brightness of the optical response at almost the same timing, and the Tf changes. However, there was a problem that this light and darkness was recognized as flicker depending on the setting of the panel and the panel performance (see Flat Panel Display 1990, Nikkei BP, November 1, 1989, p. 109). In particular, flicker appears remarkably when the NTSC TV signal is used for display as it is. In order to reduce this flicker, the image signal Vsig when the counter electrode is regarded as the potential reference
For each row wiring (MAX1 and M in FIG. 3)
A method of reducing the difference of AX2 to reduce the flicker of 2 × Tf cycle) is also known, but the flicker of the Tf cycle becomes conspicuous when Tf becomes long.

The present invention solves the above-mentioned conventional problems, and provides a driving method of a liquid crystal display device which makes it difficult to visually recognize flicker.

[0007]

In order to achieve this object, a method of driving a liquid crystal display device according to the present invention includes a method for driving all image signals corresponding to all pixels of a liquid crystal display device having L row wirings. The configuration is such that the polarity of the image signal when the potential of the counter electrode is regarded as the potential reference is inverted 3 times or more (L / 2) or less (M times) per time Tf of writing to the pixel electrode.

Further, the row wirings of the liquid crystal display device are sequentially numbered from one end of the screen to the other end using the integer n, and the remainder when the integer n is divided by the number M is k. Then, a plurality of row wirings having a common k are connected to one group.
Group (row wiring group G (k)), the image signal is continuously written to the pixels connected to an arbitrary row wiring group G (k1), and then the polarity of the image signal is inverted, and the difference between k1 and the value is (M ÷ 2) ±
The image signal is written in the pixels connected to the row wiring group G (k2) having different k2 in the range of 1.

[0009]

With this configuration, the timing of the change in the brightness of the light response of the pixel electrodes connected to the adjacent row wirings is dispersed (at worst, the timing is shifted by about 0.5 × Tf),
Flicker is less likely to be recognized, and image quality is improved.
In addition, if M is set to an odd number of times, it becomes easy to reverse the polarity of the image signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of driving a liquid crystal display device according to an embodiment of the present invention will be described below with reference to the drawings. Figure 1
FIG. 1A is a drive waveform diagram illustrating a driving method of a liquid crystal display device according to an embodiment of the present invention, and FIG. 1B is a diagram illustrating a photoresponse of a pixel in the liquid crystal display device. Figure 1
Both (a) and (b) show the case where the liquid crystal display device having the configuration of FIG. 2 has 960 row wirings (horizontal wirings) 7 as in the conventional example. Is given a uniform image signal. Vsy is a signal applied to an arbitrary (y-th) one of the column wirings 8,
Vc is the potential of the counter electrode 5. Vg1 to Vg960 are signals sequentially applied to the row wiring 7. The TFT 2 is turned on at the timing when the pulse is applied, the signal Vsy is written in the pixel electrode 4, and the liquid crystal 6 is generated by the potential difference between the pixel electrode 4 and the counter electrode 5. Driven. All 960 row wirings 7 are selected (pulses are applied) and all pixels 1 of the liquid crystal display device are selected.
The time for writing the image signal for one sheet corresponding to the above to all the pixel electrodes 4 is Tf, and the image signal when the counter electrode 5 is regarded as the potential reference is Vsig. In this embodiment, 960 row wirings 7 are numbered from 1 to 960 in order from the upper end of the screen, and the number is divided by 5 to divide into 5 wiring groups. Connect each wiring group to G (1), G (2), G
If you name them (3), G (4), and G (5), G (1) → G (4) →
Pulses are applied in the order of the wiring group G (2) → G (0) → G (3) (the order in which the value of k in G (k) is sequentially changed within the range of (5 ÷ 2) ± 1). Then, the image signal is written. Ie V
After a pulse is applied to 192 row wirings 7 belonging to G (1) in the order of g1 → Vg6 → ・ ・ → Vg481 → ・ ・ → Vg956, G
A pulse is applied to the 192 row wirings 7 belonging to (4). At this time, the polarity of Vsig is inverted every time the row wiring group changes.

Although not shown in FIG. 1, when inverting the polarity of the image signal when the counter electrode 5 is regarded as a potential reference, the potential of the counter electrode 5 is changed in a direction in which the potential change of the image signal is promoted. We are also doing. Further, by setting the number M of times of inverting the polarity to an odd number, the timing of switching the polarity of the image signal is equalized and the uniformity of the image is increased.

Next, in the driving method shown in FIG.
The optical response (in normally-black display mode) of some of the pixels 1 connected to the column wiring 8 will be described with reference to FIG. In FIG. 1 (b), 4
The pixel electrodes 4 to 483 connected to the 79th row wiring 7
The light response of the pixel electrode 4 connected to the first row wiring 7 is L47.
It is shown from 9 to L483. As shown in FIG. 1B, the lightness and darkness of the optical response of the closest pixel 1 changes with a timing shift of (2/5) × Tf. Further, the light and dark timings of the light response of the pixels 1 connected to the adjacent five row wirings 7 are shifted by (1/5) × Tf, which makes the flicker very difficult to visually recognize. That is, the flicker of the period of Tf becomes inconspicuous. On the contrary, Tf can be set longer by that amount, the writing of the image signal is facilitated, and the circuit design and the LCD panel design are facilitated. In this respect, it is more advantageous when used for OA equipment than a television receiver. Further, when the potential of the counter electrode 5 is changed in a direction in which the potential change of the image signal is promoted, the width of the output dynamic range of Vsy can be narrowed, so that the power consumption can be reduced.

In the above embodiment, the polarity was inverted when M = 5, but when expressed using M, M adjacent row wirings 7
The timing of light and dark of the optical response of the pixel 1 connected to is (1
÷ M) × Tf, and the flicker becomes very hard to see.

[0014]

As described above, according to the present invention, the counter electrode is used as the potential reference per time Tf for writing one image signal corresponding to all pixels of the liquid crystal display device having L row wirings to all pixel electrodes. The polarity of the image signal when considered is 3 or more (L ÷
2) It has a configuration of inverting the number of times (M times) or less, and the timings of changes in brightness and darkness of the photoresponse of pixel electrodes connected to adjacent row wirings are dispersed (at worst, the timings are shifted by about 0.5 × Tf). ), Flicker is less likely to be recognized, and a driving method of a liquid crystal display device capable of improving image quality can be realized. Further, by setting the number M of times of inverting the polarity of the image signal to an odd number, it becomes easier to invert the polarity of the image signal.

[Brief description of drawings]

FIG. 1A is a drive waveform diagram illustrating a driving method of a liquid crystal display device according to an embodiment of the present invention, and FIG. 1B is a diagram illustrating a photoresponse of a pixel in the liquid crystal display device.

FIG. 2 is a circuit diagram of a main part of an AM-LCD using a TFT.

FIG. 3A is a drive waveform diagram illustrating a driving method of a conventional liquid crystal display device, and FIG. 3B is a diagram illustrating optical response of pixels in the liquid crystal display device.

[Explanation of symbols]

 1 pixel 4 pixel electrode 5 counter electrode 7 row wiring Vc potential of counter electrode Vsig image signal

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroshi Sano 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Mamoru Furuta 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. In a liquid crystal display device having L row wirings (horizontal wirings), the potential of the counter electrode is referred to as a potential per time Tf for writing an image signal for one screen corresponding to all pixels to all pixel electrodes. The polarity of the image signal when
A method for driving a liquid crystal display device, which comprises inverting the number of times (L ÷ 2) or less (M times). 2. The method of driving a liquid crystal display device according to claim 1, wherein the number M of times of inverting the polarity of the image signal is odd. 3. The potential of the counter electrode is changed in a direction of promoting the potential change of the image signal when inverting the polarity of the image signal when the counter electrode is regarded as the potential reference. Driving method of the liquid crystal display device. 4. The row wirings of the liquid crystal display device are sequentially numbered from one end of the screen to the other end using an integer n, and the remainder when the integer n is divided by the number M is k. Then, a plurality of row wirings having a common k are treated as one group (row wiring group G (k)), and image signals are continuously supplied to pixels connected to the same row wiring group G (k). 2. The method for driving a liquid crystal display device according to claim 1, wherein writing is performed and the polarity of the image signal is inverted for each row wiring group G (k). 5. An image signal is continuously written to a pixel connected to an arbitrary row wiring group G (k1), and then the polarity of the image signal is inverted to form an image on a pixel connected to the row wiring group G (k2). When writing a signal, the difference between the values of k1 and k2 is (M / 2) -1
5. The method for driving a liquid crystal display device according to claim 4, wherein the driving force is in the range of (M ÷ 2) +1.