JPH10232651A - Driving method of active matrix type liquid crystal display device - Google Patents

Abstract

An object of the present invention is to provide a driving method of an active matrix type liquid crystal display device capable of executing sufficient preliminary charging and main charging for a pixel electrode. A driving method of an active matrix type liquid crystal display device according to the present invention is driven by row electrodes G (m) to G (l) driven by a row electrode driving circuit and a column electrode driving circuit. Column electrodes S (n) to S (n-1) are provided, and pulse signals VG (m) to V (m) applied from row electrodes G (m) to G (l) are provided.
Precharge and full charge of the pixel electrode 10 with data signals VS (n) to VS (n-1) applied from the column electrodes S (n) to S (n-1) in synchronization with G (l). Is a driving method in which
At this time, the charge start timing of the main charge to the picture element electrode 10 is adjusted in consideration of the signal delay time in the column electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an active matrix type liquid crystal display device, and more particularly, to a technique for adjusting a timing of starting a main charge of a pixel electrode.

[0002]

2. Description of the Related Art A liquid crystal panel of an active matrix type liquid crystal display device is shown in FIG.
Row electrodes (scanning electrodes) G (m) to G arranged in a grid
(l) and column electrodes (signal electrodes) S (n) to S (n-1),
In addition, a switching transistor 11 such as a TFT is disposed between the pixel electrode 10 formed in a region surrounded by these two electrodes and the row electrode and the column electrode. 11 has a gate terminal 12 connected to a row electrode, while its source terminal 1
3 is a column electrode, and the drain terminal 14 is a pixel electrode 10
And are connected respectively. Although not shown, a counter electrode is disposed at a position facing the picture element electrode 10 via a liquid crystal layer as a display medium, and a potential change between the picture element electrode 10 and the counter electrode is prevented. Accordingly, gradation expression based on the change in the optical characteristics of the liquid crystal layer is performed.

Further, a pulse signal is applied from the row electrode driving circuit 15 to the row electrodes G (m) to G (l) when the liquid crystal panel is driven, and the column electrodes S (n) to S (n) are driven. (n-1)
, A data signal indicated by a voltage is to be periodically applied from the column electrode driving circuit 16. For example, to display the pixels in the m-th row, it is necessary to display the data in the m-th row. The necessary data signal is sent from the column electrode driving circuit 16 to the column electrode S.
(n) to S (n-1), and the switching transistor 11 is turned on by a pulse signal applied from the row electrode drive circuit 15 to the row electrode G (m), thereby turning on the column electrode. From S (n) to S (n-1), a voltage is applied to the pixel electrode 10 to perform charging. That is, in this case, the row electrode drive circuit 15 supplies the row electrodes G (m) to
G (l) is sequentially scanned with a pulse signal applied thereto, and the column electrodes S (n) to S (n) are synchronized with the scanning timing.
An image is displayed on a liquid crystal panel by changing a data signal applied to (n-1).

In recent years, it has been necessary to prevent the liquid crystal layer from deteriorating due to the application of a DC voltage.
Invert the polarity of the data signal applied to the liquid crystal layer from the column electrodes S (n-1) to S (n) through the pixel electrodes 10 every V (one vertical cycle), and improve the display quality. Therefore, a method is adopted in which the polarity of the pulse signal applied to the switching transistor 11 through each of the row electrodes G (m) to G (l) is inverted every 1H (one horizontal cycle). However, when such a method is adopted, the time of 1H, that is, the gate-on time of the switching transistor 11 becomes shorter as the resolution of the liquid crystal panel becomes higher, and therefore, for example, SVGA (800 dots × 6)
00 dot) liquid crystal panel, 1H time is about 27μ
For a liquid crystal panel of s, XGA (1024 dots × 768 dots), it takes about 21 μs.

If the time of 1H becomes short, the charging time ends before the liquid crystal layer is sufficiently charged through the picture element electrode 10, and as shown in the signal waveform diagram of FIG. Although the VG (m) pulse signal is applied from the row electrode G (m) and the VS (n) data signal is applied from the column electrode S (n), the pixel electrode 10 The charge level VLC (m, n) indicating the potential change between the electrodes will not be saturated. That is, if the time of 1H is long enough, the charge level VLC (m, n) is reduced to the original charge level (target voltage) indicated by the broken line in FIG. However, if the time of 1H is short, the voltage does not reach the target voltage, but becomes an unsaturated state of reaching a low charge level as shown by a solid line. As a result, in the liquid crystal panel in such a state, display is performed at a gray scale different from the gray scale to be originally displayed, and the display quality is deteriorated.

In order to avoid such inconvenience, the applicant of the present invention precharges the pixel electrode 10 with a data signal having the same polarity as that applied to the pixel electrode 10. In addition, the main charge to the picture element electrode 10 is continuously performed, that is, the column electrodes S (n) to S (n-1)
, A data signal is applied periodically from the column electrode drive circuit 16 and two pulse signals are applied from the row electrode drive circuit 15 to the row electrode G (m), thereby The technology of performing preliminary charging and main charging of the electrode 10
This is proposed in Japanese Patent Application Laid-Open No. 60-134293, which has already become publicly known.

When this technology is adopted, 1H
The data signals of the same polarity are applied to the column electrodes S (n) to S (n-1) in a 2H cycle in each inversion method, and the total charging time for the pixel electrodes 10 is 1H or more. As a result, as shown in the signal waveform diagram of FIG. 6, the charge level VLC (m, n) between the pixel electrode 10 and the counter electrode reaches the original charge level (target voltage). After that, it can be saturated. Note that for other row electrodes when displaying the pixels in the m-th row, for example, the row electrode G (l) at a position far from the column electrode drive circuit 16,
As exemplified in FIG. 6, the pulse signal from the row electrode drive circuit 15 is of course not applied.

[0008]

However, when the technique disclosed in Japanese Patent Application Laid-Open No. 60-134293 is adopted, the following inconveniences are caused. That is, FIG.
The signal waveforms indicated by are row electrode G (m) to row electrode G (m) to the time constant of charge and discharge of the pixel electrode 10 and the on-resistance of the switching transistor 11 determined based on the capacitance of the liquid crystal layer
This is an example where the signal delay of G (l) and the column electrodes S (n-1) to S (n) can be neglected. As the size and definition of the liquid crystal panel increase, the pixel electrode 10 Charge time for 1H
Despite the above, as shown in FIG. 7, the row electrode G (l) and the column electrode S
The charge level VLC (l, n) between the pixel electrode 10 and the counter electrode surrounded by (n) to S (n-1) does not saturate, and does not reach the target voltage. In this case, the potential of the column electrodes S (n) to S (n-1) at the time of the main charging may not reach the potential of the pre-charged pixel electrode 10. If the potential at the time of main charging performed through the column electrodes S (n) to S (n-1) has not reached the potential of the precharged pixel electrode 10, the pixel electrode 10 has been charged. A part of the charged electric charge is discharged on the contrary, so that the original purpose of the precharge cannot be achieved.

However, such inconvenience occurs because the column electrodes S are increased with the size and definition of the liquid crystal panel.
The line widths of (n) to S (n-1) are reduced, and each column electrode S (n) to S (n-
1), the electric resistance of the column electrodes S (n) to S (n-
1) The coupling capacitance between them becomes large, that is, the time constants of these column electrodes S (n) to S (n-1) become large, and as a result, the column electrodes S (n) to S (n-1) It is considered that signal delay occurs at each input terminal and each output terminal. That is, in this case, as illustrated in FIG. 7, the data signal VS (n) applied from the column electrode S (n) is applied to the column electrode S (n).
And the waveform of the data signal VS (n) has a substantially trapezoidal shape with rising and falling edges. As a result, the pixel electrode 10 is not sufficiently charged. . The row electrode G here
(m) to G (l) have a smaller time constant because there are fewer layout constraints on the row electrodes G (m) to G (l) than the column electrodes S (n) to S (n-1). And the row electrode driving circuit 1
It is also easy to dispose them at both ends of the row electrodes G (m) to G (l) after dividing the signal lines 5, so that the signal delay of the row electrodes G (m) to G (l) becomes a serious problem. There is no fact.

The present invention has been made in view of these disadvantages, and provides a driving method of an active matrix type liquid crystal display device capable of executing sufficient pre-charging and main charging of a pixel electrode. What you want to do.

[0011]

According to a first aspect of the present invention, there is provided a method of driving an active matrix type liquid crystal display device, comprising: a row electrode driven by a row electrode driving circuit; and a column electrode driven by a column electrode driving circuit. And a driving method in which pre-charging and main charging of the pixel electrodes are executed by a data signal applied from the column electrode in synchronization with a pulse signal applied to the row electrode. Is characterized in that the charge start timing of the main charge for the picture element electrode is adjusted in consideration of the signal delay time in the column electrode.

A driving method according to a second aspect is the driving method according to the first aspect, wherein the charge start timing of the main charge for the picture element electrode is connected to the row electrode located far from the column electrode drive circuit. It is characterized in that a pixel electrode is delayed more than a pixel electrode connected to a row electrode closer to the column electrode drive circuit. Further, in the driving method according to the third aspect of the present invention, the charge start timing of the main charge for the pixel electrode described in the first aspect is such that the more the pixel electrode connected to the row electrode closer to the column electrode drive circuit. It is characterized in that it is earlier than the picture element electrode connected to the row electrode located far from the column electrode drive circuit.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a block diagram showing a drive circuit of an active matrix type liquid crystal display device according to the present embodiment, FIG. 1B is a waveform diagram thereof, and FIG. 2 is a main configuration of the drive circuit. FIG. 3 is a signal waveform diagram showing a driving method of the active matrix type liquid crystal display device according to the present embodiment. In FIGS. 1 to 3, the same components, devices and signals as those in FIGS. 4 to 7 showing the conventional embodiment are denoted by the same reference numerals. Further, the configuration of the main part of the liquid crystal panel provided in the active matrix type liquid crystal display device is basically not different from that of the conventional embodiment, so this liquid crystal panel will be described with reference to FIG.

In the active matrix type liquid crystal display device according to the present embodiment, row electrodes G (m) to G (l) and column electrodes S (n) to S (n-1) are arranged in a grid. A switching transistor 11 such as a TFT made of amorphous silicon is arranged between the pixel electrode 10 formed in a region surrounded by these two electrodes and the row electrode and the column electrode. A liquid crystal panel 17 is provided.
The column electrodes S (n) to S (n−
In each of the cases 1), a data signal is applied from the switching transistor 11 to the pixel electrode 10 during the ON operation, and then the pixel electrode 10 is charged. These column electrodes S (n)
~ S (n-1) is a column electrode drive circuit (column electrode drive) configured with a shift register, sample hold, etc.
16 are connected. In the column electrode drive circuit 16, the data signal D sent from the signal controller 18 is sampled and held in synchronization with the clock φ1, and then the column electrodes S (n) to S (n The output of the data signal D for each of -1) is executed.

On the other hand, each of the row electrodes G (m) to G (l) outputs a pulse signal to turn on the switching transistor 11, and a row electrode drive circuit (row electrode drive) 15 comprising a shift register. Connected to In the row electrode drive circuit 15, the signal control unit 1
8, the pulse signal for executing the pre-charging and the main charging, based on the basic scanning pulse signal HS and the clock φ2 output from the clock 8 and the clock φ3 for instructing the charging start timing for the main charging of the picture element electrode 10. And a series of pulse signals VG (m) to VG comprising pulse signals to be executed.
(l) is to be generated. Further, in response to the clock φ3 at this time, as shown in FIG.
(n) to S (n-1) time constants, that is, column electrodes S (n)
~ S (n-1), the adjustment time for adjusting the charging start timing of the pixel electrode 10 at the time of the main charging by a time determined in consideration of the signal delay time in each of the above.
d is to be provided by the timing generator 19, and the clock φ 3 to which the adjustment time Δd has been provided is input to the row electrode drive circuit 15. In FIG. 2, reference numerals 20 and 21 denote counters, reference numeral 22 denotes a timing table in which the adjustment time Δd is stored, and reference numeral 23 denotes a demultiplexer.

Therefore, the row electrode driving circuit 15 supplies
For each of (m) to G (l), pulse signals VG (m) to VG (l) are output at timings that take into account the adjustment time △ d for adjusting the charging start timing during main charging. It will be. That is, in the timing table 22 shown in FIG. 2, each of the row electrodes G (m) to G (l) having a correlation with the time constant of each of the column electrodes S (n) to S (n-1) is provided. The position, that is, the adjustment time △ d determined based on whether each of the row electrodes G (m) to G (l) is located far or close to the column electrode drive circuit 16 is stored in advance, and the column A clock signal φ3 that generates a pulse signal output through a row electrode G (l) located far from the electrode drive circuit 16 on the basis of a row electrode G (m) located near the electrode drive circuit 16 is applied with △ d, and The charge start timing of the main charge to the elementary electrode 10 is delayed, or the row electrode G (l) at a far position is
△ d is added to a clock φ3 that generates a pulse signal output from a row electrode G (m) located at a position close to the reference to advance the charge start timing of the main charge.

Therefore, when the charging start timing of the main charging is delayed by applying △ d to the clock φ3 of the row electrode G (l) based on the row electrode G (m), as shown in FIG. As shown in the signal waveform diagram, the charge level between the pixel electrode 10 and the counter electrode formed in the region surrounded by the row electrode G (l) and the column electrodes S (n) to S (n-1). VLC (l, n) is sufficiently saturated by the preliminary charge and the main charge, and the pixel electrode 10 can be easily charged to the target voltage. Although not shown, the charge start timing of the main charge was advanced by applying Δd to the clock φ3 of the row electrode G (m) based on the row electrode G (l). In this case, the row electrode G (m) and the column electrode S (n)
To a pixel electrode 10 formed in a region surrounded by S (n-1).
In addition, the charge level VLC (m, n) between the counter electrodes is sufficiently saturated by the preliminary charge and the main charge, and the target voltage can be easily charged.

[0019]

As described above, in the method of driving an active matrix type liquid crystal display device according to the present invention, a picture signal is applied by a data signal applied from a column electrode in synchronization with a pulse signal applied to a row electrode. In performing the preliminary charge and the main charge for the pixel electrodes, the charge start timing of the main charge for the pixel electrodes is adjusted in consideration of the signal delay time in the column electrodes,
The original purpose of the pre-charging can be achieved without inconvenience, and the pre-charging and the main charging have an effect that the pixel electrodes can be easily charged to the target voltage. When adjusting the charging start timing of the main charge to the pixel electrode, the pixel electrode connected to the row electrode located farther from the column electrode drive circuit is connected to the row electrode located closer to the column electrode drive circuit. A pixel electrode connected to a row electrode closer to the column electrode drive circuit, or a pixel electrode connected to a row electrode farther from the column electrode drive circuit, It is conceivable to adopt a method of making the charging start timing earlier than that of the charging.

[Brief description of the drawings]

FIG. 1 is a block diagram and a waveform diagram illustrating a drive circuit of an active matrix liquid crystal display device according to an embodiment.

FIG. 2 is a block diagram illustrating a main configuration of a drive circuit.

FIG. 3 is a signal waveform diagram illustrating a method of driving the active matrix type liquid crystal display device according to the present embodiment.

FIG. 4 is a plan view showing a main configuration of a liquid crystal panel of an active matrix type liquid crystal display device according to the present embodiment and a conventional embodiment.

FIG. 5 is a signal waveform diagram showing a driving method of an active matrix type liquid crystal display device according to a conventional mode.

FIG. 6 is a signal waveform diagram showing a driving method of an active matrix type liquid crystal display device according to a conventional mode.

FIG. 7 is a signal waveform diagram showing a driving method of an active matrix type liquid crystal display device according to a conventional mode.

[Explanation of symbols]

 10 picture element electrode 15 row electrode drive circuit 16 column electrode drive circuit G (m) -G (l) row electrode S (n) -S (n-1) column electrode VG (m) -VG (l) pulse signal VS (n) to VS (n-1) Data signal

Claims (3)

[Claims] A row electrode driven by a row electrode drive circuit;
A column electrode driven by a column electrode drive circuit is provided, and a precharge and a main charge to the pixel electrode are executed by a data signal applied from the column electrode in synchronization with a pulse signal applied to the row electrode. A method for driving an active matrix type liquid crystal display device, wherein the charge start timing of the main charge to the picture element electrode is adjusted in consideration of the signal delay time at the column electrode. A method for driving a liquid crystal display device. 2. The method of driving an active matrix liquid crystal display device according to claim 1, wherein the charge start timing of the main charge to the picture element electrode is connected to a row electrode located far from the column electrode drive circuit. A method for driving an active matrix type liquid crystal display device, wherein a pixel electrode is delayed more than a pixel electrode connected to a row electrode located closer to a column electrode driving circuit. 3. The method of driving an active matrix liquid crystal display device according to claim 1, wherein the charge start timing of the main charge to the picture element electrode is connected to a row electrode close to the column electrode drive circuit. A driving method for an active matrix type liquid crystal display device, wherein a pixel electrode is earlier than a pixel electrode connected to a row electrode located farther from a column electrode driving circuit.