JPH11142815A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device capable of using a common inversion drive together even in the case of adopting a dot inversion drive excellent in picture quality. SOLUTION: In a liquid crystal panel using a dot inversion drive, counter electrodes in each column unit are formed like a stripe in a row direction, every other counter electrode columns are connected in common to form two systems of stripe-like electrodes 20, 21 and common voltages VCOM1, VCOM2 having mutually reversed phases of which polarity is inverted in each one horizontal period are impressed to the two systems of stripe-like electrodes 20, 21 to attain common inversion. In CS lines 19 also, every other columns are connected to form two systems of CS lines 19a, 19b and the common voltages VCOM1, VCOM2 are impressed also to these CS lines 19a, 19b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (L).
For CD (Liquid Crystal Display), in particular, scanning lines (X) arranged in a matrix on the same transparent insulating substrate
A switching element, for example, a thin film transistor (TFT), is provided at the intersection of the electrode and the signal line (Y electrode).
An active matrix type liquid crystal display device provided with an anistor.

[0002]

2. Description of the Related Art As typical driving methods of an active matrix type liquid crystal display device, there are a 1H inversion method (scan line inversion method) and a dot inversion method (scan line & column line inversion method). Here, the 1H inversion method means that the polarity of the video signal applied to each pixel is 1H with respect to the common voltage.
(H is a horizontal period). Further, the dot inversion method is a driving method in which the polarities of video signals applied to pixels adjacent to each other are alternately inverted.

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

FIG. 5 shows an example of a configuration of a liquid crystal display device using a combination of a 1H inversion method and a common inversion method as a driving method. In the figure, a pixel 101 is located at the intersection of each of a plurality of scanning lines X and a plurality of signal lines Y.
Is provided. 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.

The opposite electrodes of the liquid crystal cell LC are commonly connected between the pixels 101. Similarly, the other electrode of the storage capacitor CS is commonly connected between the pixels 101 via the CS line 105. Then, each counter electrode of the liquid crystal cell LC and each other electrode of the storage capacitor CS are provided with the electrodes shown in FIG.
, The common voltage V whose polarity is inverted every 1H
COM is applied from the 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 driver 104 is
As shown in (A), the common voltage VCOM is 1H.
The polarity is inverted every time.

As described above, when the liquid crystal cell LC is AC-driven using the 1H inversion method, the polarity of the voltage applied to the liquid crystal cell LC of each pixel 101 becomes 1 as shown in FIG.
Since the inversion is performed for each line, the deterioration of the liquid crystal cell LC can be prevented. In the case of the 1H inversion method, since the polarity of the video signal is inverted every 1H, as is apparent from the waveform diagram of FIG. , 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 apparent 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 an arrow in the figure), as shown in FIG. 8, crosstalk in the horizontal direction becomes remarkable, and the image quality is greatly impaired. That is,
In FIG. 8, assuming that the portion indicated by the black region is the actual image 111 to be actually displayed, a false image (portion indicated by a dotted region) 112 is generated in the horizontal direction of the real image 111 due to horizontal crosstalk.

In order to avoid this image quality deterioration, the above-described dot inversion driving is used. FIG. 9 shows an example of the configuration of a liquid crystal display device using this dot inversion drive.
In the figure, at the intersection of each of a plurality of scanning lines X and a plurality of signal lines Y, a pixel 2 composed of a liquid crystal cell LC, an auxiliary capacitor CS and a thin film transistor TFT is provided.
01 is provided. The counter electrode of the liquid crystal cell LC is commonly connected between the pixels 201. Similarly, the other electrode of the storage capacitor CS is connected to each pixel 2 via the CS line 205.
01 are commonly connected. And the liquid crystal cell LC
And the other electrode of the storage capacitor CS,
A fixed common voltage VCOM is applied from the 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. 10, it is possible to realize dot inversion (checkerboard inversion) driving in which the polarities of video signals applied to adjacent pixels are alternately inverted. 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.

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 use the common inversion drive in combination with the 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. , The counter electrodes are formed in stripes in the row direction in column units and connected in common every other column to be provided in two systems, and the polarities of the two system counter electrodes are inverted every horizontal period. Apply voltages of opposite phases to each other.

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 in each 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 opposite electrodes, which are formed by connecting the opposite electrodes formed in stripes in column units in common every other column, have opposite phases whose polarity is inverted every horizontal period. By applying a voltage, common 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 obtain R (red), G (green), B
In addition to generating the three video signals (blue), the synchronizing signal SYNC is separated from the composite video signal and supplied to the timing generator 12, and the original video signal is subjected to polarity inversion processing at a predetermined cycle to be converted to AC. The video signal is supplied to the liquid crystal panel 13.

The timing generator 12 synchronizes with a synchronizing signal SYNC supplied from the decoder / driver 11 to drive a horizontal start signal HST for driving a source driver 16 in the liquid crystal panel 13 and a two-phase horizontal clock signal HCK1, HCK1. HCK2 and scan driver 15
, A timing signal such as a vertical start signal VST, two-phase vertical clock signals VCK1 and VCK2, and the like, 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. Then, the liquid crystal panel 13 has a common voltage VCOM of opposite phase, the polarity of which is inverted every horizontal period.
1 and VCOM2 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 rows of scanning lines X serving as X electrodes and a plurality of columns of signal lines Y serving as Y electrodes are formed in a matrix on the same glass substrate (not shown). The unit pixels 14 are two-dimensionally arranged at the intersections of each of the Xs and the signal lines Y of a plurality of columns. Each of these unit pixels 14 is composed of a liquid crystal cell LC, a thin film transistor TFT as a switching element, and an auxiliary capacitor CS for increasing tolerance to leakage of the thin film transistor TFT.

Specifically, in each of the unit pixels 14, the gate electrode (control electrode) of the thin film transistor TFT
Are 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 auxiliary capacitor CS is formed between the two electrodes by arranging a CS electrode of a predetermined area to face a part of the transparent pixel electrode of the liquid crystal cell LC via an insulating layer. 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. The CS lines 19a and 19b are connected to the CS electrodes of the storage capacitors CS in each of the unit pixels 14 in column units.

On the other hand, on a counter substrate (not shown) disposed opposite to the TFT substrate, a counter electrode in which liquid crystal is sealed between the TFT substrate and a transparent pixel electrode (a portion indicated by a dotted area in the drawing).
Are formed as stripe-shaped electrodes 20 and 21 having a horizontal width of one pixel (one dot) in the row direction in column units at a repetition of a horizontal dot pitch. As in the case of the CS electrode, the A and B two-system striped electrodes are connected every other row, for example, to two connection patterns 22a and 22b arranged in the column direction above and below the pixel portion, respectively. 20, 21. FIG. 3 shows patterns of the A and B stripe electrodes 20 and 21.

With respect to the A and B stripe electrodes 20 and 21 divided into two systems, common voltages VCOM1 and VCOM2 having phases opposite to each other, whose polarity is inverted every horizontal period.
Are two connection patterns 22a, 2 from the voltage sources 17, 18.
2b. In addition, two CS lines 1
Also for 9a and 19b, voltages of opposite phases whose polarity is inverted every horizontal period, for example, stripe-shaped electrodes 20,
The same common voltages VCOM1 and VCOM2 as 21 are supplied from the voltage sources 17 and 18.

In a horizontal period in which a dot (pixel) on the A-striped electrode 20 to which the common voltage VCOM1 is applied writes "+" of the video signal, the common voltage VCO1 is applied.
M1 becomes low level, and at this time, the common voltage VCO
Since the dot on the B-stripe electrode 21 to which M2 is applied writes "-" of the video signal, the common voltage VCOM
2 is at a high level so that the common voltages VCOM1,
Set the phase relationship of VCOM2. FIG. 4 shows the waveforms of the common voltages VCOM1 and VCOM2 having opposite phases.

In the next horizontal period, the common voltages VCOM1 and VCOM2 are set to the opposite potentials. 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 adopting the dot inversion driving method as the driving method of the liquid crystal cell 14, the opposing electrodes are formed in stripes in the row direction on a column basis, and are shared every other column. And divided into A and B two-system striped electrodes 20 and 21,
The common voltages VCOM having opposite phases to each other in which the polarity is inverted for each of the stripe-shaped electrodes 20 and 21 every horizontal period.
1, VCOM2, and the CS lines 19 are also connected in common every other column to provide CS lines 19a, 1
9b, and by applying common voltages VCOM1 and VCOM2 to these CS lines 19a and 19b,
Also in the dot inversion drive, the common inversion drive can be used together.

As described above, since the common inversion driving method can be used in combination with the dot inversion driving method having an advantage that image quality deterioration due to horizontal crosstalk can be avoided, the feature of the dot inversion driving method which is excellent in image quality is obtained. The voltage of the source driver 16 for applying the voltage Vp required for the gradation control of the liquid crystal cell LC can be reduced while utilizing the above, and accordingly, the power consumption of the entire liquid crystal display device can be reduced.

In the above embodiment, the same common voltage V is applied to the striped electrodes 20 and 21 and the CS lines 19a and 19b provided in two systems.
Although COM1 and VCOM2 are provided, the present invention is not limited to this. For example, when the amplitude of oscillating a signal and the amplitude of oscillating the stripe-shaped electrodes 20 and 21 are made different, different voltage sources are used. It is also possible to provide different values of voltage.

In the above-described embodiment, the present invention is applied to a drive circuit integrated type liquid crystal display device in which drive circuits such as the scan driver 15 and the source driver 16 are formed and integrated on the same substrate as the liquid crystal panel 13. However, since the present invention is characterized by the specific configuration of the pixel portion, the present invention can be similarly applied to a liquid crystal display device in which the driving circuit is a separate type from the liquid crystal cell 13. It is.

[0034]

As described above, according to the present invention,
In a liquid crystal panel using dot inversion driving, opposing electrodes are formed in stripes in the row direction on a column basis and connected in common every other column to be provided in two systems. By applying voltages of opposite phases, the polarity of which is inverted every horizontal period, common inversion driving is possible even in dot inversion driving, which is excellent in image quality, so that the voltage of the source driver can be reduced. Thus, 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 pattern diagram of A and B stripe electrodes.

FIG. 4 is a waveform diagram showing a relationship between a common voltage and a polarity of a video signal.

FIG. 5 is a schematic configuration diagram showing a conventional example using a combination of 1H inversion driving and common inversion driving.

FIG. 6 is a diagram illustrating signal polarity of each line in 1H inversion.

FIG. 7 is a waveform diagram of 1H inversion (A) and common inversion (B).

FIG. 8 is a diagram showing horizontal crosstalk due to current concentration.

FIG. 9 is a schematic configuration diagram showing a conventional example using dot inversion driving.

FIG. 10 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 unit pixel, 15 scan driver (vertical drive circuit), 16 source driver (horizontal drive circuit), 17, 18 voltage source, 19, 19
a, 19b: CS line, 20, 21: Striped electrode (counter electrode)

Claims (4)

[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 stripes in the row direction in column units and connected in common every other column to be divided into two systems. The opposite electrodes of the two systems have opposite phases in which the polarity is inverted every horizontal period. A liquid crystal display device to which a voltage is applied. 2. The liquid crystal display device according to claim 1, wherein
The unit pixel has an auxiliary capacitance for increasing the tolerance to the leakage of the switching element. An electrode line for the auxiliary capacitance is formed along the signal line and commonly connected every other column to form two systems. A liquid crystal display device, wherein the liquid crystal display device is provided with two separate electrode lines, in which voltages having opposite phases whose polarities are inverted every horizontal period are applied to the two electrode lines. 3. The liquid crystal display device according to claim 2, wherein the voltage applied to the two electrode lines is supplied from the same voltage source as the voltage applied to the two counter electrodes. 4. The liquid crystal display device according to claim 2, wherein the voltage applied to the two electrode lines is supplied from a voltage source different from the voltage applied to the two counter electrodes.