JPH11119193A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of applying common inversion drive even when dot inversion drive excellent in picture quality is adopted. SOLUTION: In a liquid crystal panel using dot inversion drive, a counter electrode 20 is formed in each pixel, each pixel is connected to a pixel of an adjacent row on an adjacent column about each signal line Y, respective pixels of every other columns are connected in common to divide electrodes 20 into two systems and common voltage VCOM1, VCOM2 having mutually inverted phases and capable of inverting their polarity in each field period are respectively applied to the two systems of electrodes 20 to attain common inversion. In this case, CS lines 19 also are connected every other columns to form two CS line systems 19a, 19b and CS electrodes of pixels 14 on adjacent columns in adjacent rows are connected to a CS line of a certain column to impress the common voltage VCOM1, VCOM2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (L).
CD: Liquid Crystal Display, and in particular, a thin film transistor (TFT; Thin Film T) as a switching element
The present invention relates to an active matrix type liquid crystal display device using a ransistor.

[0002]

2. Description of the Related Art Typical driving methods of an active matrix type liquid crystal display device include 1H inversion (scan line inversion) and dot inversion (scan line & column line inversion). Here, 1H inversion is a driving method in which the polarity of the video signal applied to each pixel is inverted every 1H (H is a horizontal period) with respect to the common voltage. The dot inversion is a driving method for alternately inverting the polarity of a video signal applied to adjacent pixels.

[0003] These driving methods can be properly used depending on the application. In a small liquid crystal display device, 1H inversion driving is mainly used. By the combination of the 1H inversion and the common inversion, the voltage of the source driver as the horizontal drive circuit is reduced. Here, the common inversion is a driving method of inverting a common voltage applied to a common electrode of a liquid crystal cell of each pixel every 1H.

FIG. 4 shows an example of a configuration of a liquid crystal display device using a combination of 1H inversion and common inversion as a driving method. In the figure, a pixel 101 is provided at the intersection of each of a plurality of scanning lines X and a plurality of signal lines Y. The pixel 101 includes a thin film transistor TFT having a gate electrode connected to a scan line X and a source electrode connected to a signal line Y; a liquid crystal cell LC having a pixel electrode connected to a drain electrode of the thin film transistor TFT; The storage capacitor CS has one electrode connected to the electrode.

[0005] The counter electrode of the liquid crystal cell LC is
Are connected in common. Similarly, the other electrode of the auxiliary capacitance CS is commonly connected between the pixels 101 via the CS line 105. Then, as shown in FIG. 6B, a common voltage VC whose polarity is inverted every 1H is applied to each counter electrode of the liquid crystal cell LC and each other electrode of the storage capacitor CS.
OM is applied from voltage source 102.

Scan driver 10 as a vertical drive circuit
3 sequentially scans the scan line X every one vertical period (one field period) to select the pixels 101 in units of rows. On the other hand, the source driver 104, which is a horizontal drive circuit, sequentially samples an input video signal every one horizontal period (1H), and writes the video signal to the pixels 101 in the row selected by the scan driver 103. Note that the video signal input to the source drive 104 is as shown in FIG.
As shown in (A), the common voltage VCOM is 1H.
The polarity is inverted every time.

As described above, by using 1H inversion, the liquid crystal cell L
When AC is driven by AC, the polarity of the voltage applied to the liquid crystal cell LC of each pixel 101 is inverted for each line as shown in FIG. 5, so that the deterioration of the liquid crystal cell LC can be prevented. In the case of the 1H inversion drive, since the polarity of the video signal is inverted every 1H, as is clear from the waveform diagram of FIG. 6A, when the voltage necessary for gradation control of the liquid crystal cell LC is Vp. , The source driver 104 has at least 2
A power supply of Vp is required.

By using the common inversion drive together with the 1H inversion drive, the common voltage VCOM is also inverted every 1H as is clear from the waveform diagram of FIG. Is at least Vp
Therefore, the advantage of the 1H inversion driving can be utilized as it is, and the voltage of the source driver 104 can be reduced.

However, when the 1H inversion drive is applied to a large-sized liquid crystal display device, the counter electrode and the C
Due to the current concentration on the S line 105 (indicated by the arrow in the figure), as shown in FIG. 7, the crosstalk in the horizontal direction becomes remarkable, and the image quality is greatly impaired. That is,
In FIG. 7, assuming that the portion indicated by the black region is the image 111 to be actually displayed, a false image (portion indicated by a dotted region) in the horizontal direction of the real image 111 due to horizontal crosstalk.
112 occurs.

To avoid this, dot inversion driving is used. FIG. 8 shows an example of the configuration of a liquid crystal display device using this dot inversion drive. In the figure, a pixel 201 including a liquid crystal cell LC, an auxiliary capacitor CS, and a thin film transistor TFT is provided at an intersection of each of a plurality of scanning lines X and a plurality of columns of signal lines Y. The counter electrodes of the liquid crystal cells LC are commonly connected between the pixels 201. Similarly, the other electrode of the auxiliary capacitance CS is also C
The pixels 201 are commonly connected via the S line 205. A fixed common voltage VCO is applied to each counter electrode of the liquid crystal cell LC and each other electrode of the storage capacitor CS.
M is applied from a voltage source 202.

The scan driver 203 sequentially scans the scan line X every vertical period to select the pixels 201 on a row basis. On the other hand, the source driver 204 sequentially samples the video signal input in a state where the polarity is inverted every 1H with respect to the common voltage VCOM every 1H, and also, one signal line (one column line) with respect to the common voltage VCOM. The video signal is written to each pixel 201 by inverting the polarity every time.

As described above, by combining the polarity inversion for each signal line and the polarity inversion for each 1H,
As shown in FIG. 9, dot inversion (checkerboard inversion) driving for alternately inverting the polarities of video signals applied to adjacent pixels can be realized. In this dot inversion drive, FIG.
As shown by an arrow in FIG.
1, the current is canceled, and no current is concentrated on the counter electrode of the liquid crystal cell LC and the CS line 205.
Deterioration of image quality due to horizontal crosstalk can be avoided.

[0013]

However, in the conventional liquid crystal display device using the dot inversion drive, it is necessary to invert the polarity of the video signal with respect to the common voltage VCOM for each signal line. Cannot be inverted every 1H, and the common inversion drive effective for lowering the voltage of the source driver 204 cannot be used together. Therefore, the voltage of the source driver 204 cannot be reduced, which is an obstacle to the reduction in power consumption of the entire liquid crystal display device at present.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to make it possible to apply the common inversion drive even when adopting dot inversion drive which is excellent in image quality. It is to provide a liquid crystal display device.

[0015]

According to the present invention, there is provided a pixel electrode two-dimensionally arranged at the intersection of each of a plurality of scanning lines and a plurality of signal lines, and a connection between the pixel electrode and the signal line. A liquid crystal display device in which a liquid crystal material is sealed between an element substrate on which a switching element whose control electrode is connected to a scanning line is formed and a counter electrode on which a counter electrode facing the pixel electrode is formed. , A counter electrode is formed in pixel units, and one signal line is connected between pixels in adjacent columns every one row.
The common electrodes are connected every other column and provided in two systems, and voltages of opposite phases, whose polarities are inverted every one field period, are applied to the two systems of the counter electrodes.

In the liquid crystal display device having the above-described structure, the scanning lines are sequentially scanned every vertical period to select the pixels row by row, while the video signal input in a state where the polarity is inverted every horizontal period is one. Sampling is sequentially performed every horizontal period, and a video signal is written to pixels of one line in a selected row, thereby realizing dot inversion driving excellent in image quality. In this dot inversion drive, two lines of common electrodes are connected to pixels in adjacent columns for each signal line and commonly connected to every other column with respect to one signal line. By applying voltages of opposite phases whose polarity is inverted every one field period, column inversion driving effective for lowering the voltage of the source driver is realized.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an active matrix type liquid crystal display device to which the present invention is applied.

In FIG. 1, the present liquid crystal display device comprises a decoder / driver 11, a timing generator 12,
An active matrix type liquid crystal panel 13 is provided. The decoder / driver 11 decodes the input composite video signal to generate R (red), G (green), and B (blue) video signals, and separates the synchronization signal SYNC from the composite video signal. And the timing generator 12
, And the polarity of the original video signal is inverted at a predetermined cycle, and the resulting signal is supplied to the liquid crystal panel 13 as an AC-converted video signal.

The timing generator 12 synchronizes with a synchronization signal SYNC supplied from the decoder / driver 11 to generate a horizontal start signal HST, two-phase horizontal clock signals HCK1 and HCK2, a vertical start signal VST, and a two-phase vertical clock signal VCK1. , VCK2, etc., and supplies these timing signals to the liquid crystal panel 13.

The liquid crystal panel 13 has a plurality of scanning lines X
And the pixels 14 arranged two-dimensionally at the intersections of each of the signal lines Y in a plurality of columns, and a scan driver 15 as a vertical drive circuit and a source driver 16 as a horizontal drive circuit are integrated on the same substrate. It is a configuration prepared for. The liquid crystal panel 13 has a common voltage V of opposite phases, the polarity of which is inverted every field period.
COM 1 and VCOM 2 are supplied from voltage sources 17 and 18.

In the liquid crystal panel 13, the scan driver 15 sequentially scans the scan line X every field period to select the pixels 14 on a row basis. On the other hand, the source driver 16 sequentially samples the video signal input in a state where the polarity is inverted every 1H, every 1H, and outputs the video signal to the pixels 14 of one line of the row selected by the scan driver 15. Write.

That is, the active matrix type liquid crystal panel 13 according to the present invention employs dot inversion driving which is excellent in image quality as a driving method of the liquid crystal cell 14. In the liquid crystal panel 13 using the dot inversion driving method, the present invention is characterized by a specific configuration in each pixel portion. FIG. 2 shows an example of a specific configuration of the liquid crystal panel 13 according to the present invention.

In FIG. 2, a plurality of scanning lines X as X electrodes and a plurality of signal lines Y as Y electrodes are formed on the same glass substrate (not shown). The unit pixels 14 are two-dimensionally arranged at the intersections of the signal lines Y of the plural columns. These unit pixels 1
Reference numeral 4 denotes a liquid crystal cell LC, a thin film transistor TFT as a switching element, and an auxiliary capacitor CS for increasing the tolerance of the thin film transistor TFT against leakage.

Specifically, in each of the unit pixels 14, the gate electrode of the thin film transistor TFT is connected to the scanning line X, the source electrode is connected to the signal line Y, and the drain electrode is connected to the transparent pixel electrode of the liquid crystal cell LC. .
Further, for example, an electrode having a predetermined area is opposed to a part of the transparent pixel electrode of the liquid crystal cell LC via an insulating layer, so that a storage capacitor CS is formed between the two electrodes. Hereinafter, the glass substrate on which the thin film transistors TFT and the like are formed is referred to as a TFT substrate.

On this TFT substrate, a storage capacitor CS
CS which is arranged opposite to a part of the transparent pixel electrode to form
The electrodes are connected to the CS line 19. Here, this CS line 19 is wired along the signal line Y, as shown in FIG.
As is clear from FIG.
S lines 19a and 19b are provided. Then, a CS electrode of a pixel 14 in an adjacent column is connected to a CS line 19a / 19b in a certain column for each row.
In other words, the CS electrodes are connected in a so-called staggered relationship with respect to one CS line.

On the other hand, on a counter substrate (not shown) arranged to face the TFT substrate, a counter electrode 20 in which a liquid crystal material is sealed between the TFT substrate and a transparent pixel electrode is formed in a pattern for each pixel. Then, similarly to the CS electrode, one signal line Y is connected to the opposing electrode 20 of an adjacent column for each row via the auxiliary pattern 21, and two connection patterns 22a, 22b to provide two systems.

With respect to each of the counter electrodes 20 divided into two systems, mutually opposite common voltages VCOM1 and VCOM2 whose polarity is inverted every field period are supplied to the voltage sources 17 and
18 through two connection patterns 22a and 22b. Also, for the two CS lines 19a and 19b, the common voltages VCOM1 and VCOM2 are supplied from the voltage sources 17 and 18 in the same manner as in the case of the common electrode 20, for example, in the opposite phase, in which the polarity is inverted every field period. Given.

In a field period in which a dot (pixel) corresponding to the common voltage VCOM1 writes "+" of the video signal, as shown in the waveform diagram of FIG.
COM1 is set to low level. At this time, since the dot corresponding to the common voltage VCOM2 writes the video signal “−”, the common voltage VCOM2 is set to a high level. In the next field period, the common voltages VCOM1 and VCOM2 are set to the opposite potentials, respectively. That is, the dot corresponding to the common voltage VCOM1 writes the video signal “−”, so that the common voltage VCOM1 is set to the high level. The dot corresponding to the common voltage VCOM2 writes the video signal “+”, so the common voltage VCOM2 is set to the low level. Set to each.

As described above, in the active matrix type liquid crystal panel 13 employing the dot inversion drive as a driving method of the liquid crystal cell 14, the common electrode 20 is grouped by the same polarity of the write signal at the time of the dot inversion drive. Apply voltages VCOM1 and VCOM2, and
The lines 19 are also grouped by the same polarity of the write signal at the time of the dot inversion drive, and the CS lines 19a, 19b
In contrast, common voltages VCOM1 and VCOM2 having phases opposite to each other whose polarity is inverted every one field period
, The common inversion drive can be used in the dot inversion drive.

As described above, since the common inversion drive can be used together with the dot inversion drive, the voltage of the source driver 16 can be reduced, and accordingly, the power consumption of the entire liquid crystal display device can be reduced. In particular, in the configuration of the present invention, the polarity of the common voltages VCOM1 and VCOM2 only needs to be inverted every field period, and therefore, compared to the conventional liquid crystal display device in which the polarity of the common voltage is inverted every 1H.
The number of times of inverting the voltage can be greatly reduced, and the power consumption can be further reduced.

In the above embodiment, each of the counter electrodes 20 provided in two systems and the two CS lines 1 are provided.
9a, 19b, the same common voltage VCOM1, VCOM
Although COM2 is provided, the present invention is not limited to this. For example, the amplitude of signal swing and the counter electrode 2
In the case of making the amplitude different from 0, different voltages can be supplied from different voltage sources.

Further, in the above embodiment, the case where the driving system such as the scan driver 15 and the source driver 16 is applied to the liquid crystal display device integrated with the liquid crystal panel 13 has been described as an example. Since the specific configuration of the pixel portion is characteristic, the present invention can be similarly applied to a liquid crystal display device in which the driving system is separate from the liquid crystal cell 13.

[0033]

As described above, according to the present invention,
In a liquid crystal panel using the dot inversion drive, a counter electrode is formed in pixel units, and one signal line is connected to pixels in adjacent columns every other row and commonly connected every other column. The system is divided into two systems, and two opposite electrodes are applied with opposite phase voltages whose polarity is inverted every one field period, so that column inversion can be performed even in dot inversion driving which is excellent in image quality. Since driving is possible, the voltage of the source driver can be reduced, and the power consumption of the entire device can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an active matrix liquid crystal display device to which the present invention is applied.

FIG. 2 is a schematic configuration diagram showing one embodiment of a liquid crystal panel according to the present invention.

FIG. 3 is a waveform diagram showing a relationship between a common voltage and a polarity of a video signal.

FIG. 4 is a schematic configuration diagram showing a conventional example using a combination of 1H inversion driving and common inversion driving.

FIG. 5 is a diagram illustrating signal polarity of each line in 1H inversion.

FIG. 6 is a waveform diagram of 1H inversion (A) and common inversion (B).

FIG. 7 is a diagram showing horizontal crosstalk due to current concentration.

FIG. 8 is a schematic configuration diagram showing a conventional example using dot inversion driving.

FIG. 9 is a diagram illustrating signal polarity of each line in dot inversion.

[Explanation of symbols]

11 decoder / driver, 12 timing generator, 13 liquid crystal panel, 14 pixel, 15 scan driver (vertical drive circuit), 16 source driver (horizontal drive circuit), 17, 18 voltage source, 19, 19a , 1
9b: CS line, 20: counter electrode

Claims (2)

[Claims] 1. A pixel electrode two-dimensionally arranged at an intersection of each of a plurality of scanning lines and a plurality of signal lines, and a control electrode connected between the pixel electrode and the signal line and having a control electrode connected to the pixel electrode. In a liquid crystal display device in which a liquid crystal material is sealed between an element substrate on which a switching element connected to a scan line is formed, and a counter substrate on which a counter electrode facing the pixel electrode is formed, It is formed in pixel units and connected to pixels in adjacent columns for each signal line with respect to each signal line, and is connected in common every other column and provided in two systems. In contrast, a liquid crystal display device is provided in which voltages having opposite phases whose polarity is inverted every one field period are applied. 2. The liquid crystal display device according to claim 1, wherein
A unit pixel having an auxiliary capacitance for increasing tolerance to the leakage of the switching element; forming a dedicated line for the auxiliary capacitance along the signal line; The electrodes of the auxiliary capacitors of the pixels are connected and commonly connected to every other column and provided in two systems. A liquid crystal display device to which a voltage is applied.