JP2001249643A - Driving method for liquid crystal display device and liquid crystal display device using the same method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the driving method of a liquid crystal display device capable of dissolving discharge shortage by the high definition of the liquid crystal display device and, at the same time, capable of improving flicker and crosstalk. SOLUTION: In the driving method of the liquid crystal display device in which plural gate wirings and plural source wirings intersecting these gate wirings are formed on a substrate and common electrodes are formed on the different substrate opposed to the substrate, this method is a dot inversion driving method in which respective gate wirings are successively selected by impressing a first gate signal on them and polarities of voltages of the source signal impressed on the source wirings are inverted for every source wiring with respect to voltages of the common electrodes in this selection period and, also, the polarities are inverted for every gate wiring group of adjacent two lines or more and a second gate signal is impressed on the respective gate wirings with intervals being roughly double of a period when the gate wiring group is selected.

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 a liquid crystal display device, which is characterized by combining 1 × 2 dot inversion driving and double gate signal driving, and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art First, the structure of an active matrix type liquid crystal display device will be described with reference to FIG.

A gate wiring 10 is provided on a glass substrate 104.
1, a source wiring 102, a thin film transistor (TFT) 103 formed near an intersection of these wirings,
03 is provided with a pixel electrode 109 electrically connected thereto.
Further, a common electrode 105 for applying a reference voltage is provided on another glass substrate 106 facing the glass substrate 104. These glass substrates 104 and 106 are opposed to each other with a gap of about 5 μm therebetween, and a liquid crystal material (not shown) is injected between the gaps.

Next, a driving method of the liquid crystal display device will be described with reference to FIG.

The switching property of the TFT 103 is controlled by supplying a gate signal from the gate driver circuit 107 to the gate wiring 101. When the TFT 103 is on, a data signal is applied to the pixel electrode 109 from the source driver circuit 108 via the source wiring 102 and the TFT 103, and when the TFT 103 is off, the voltage of the pixel electrode 109 is held. Then, the electric field between the pixel electrode 109 and the common electrode 105 changes the molecular alignment state of the liquid crystal material to control the display characteristics of the liquid crystal display device. That is, the pixel charging (voltage application) of the source signal voltage is started in synchronization with the rise time of the start pulse for controlling the output timing of the gate driver circuit 107. The width of the gate signal is called one horizontal period 1H. During this period, all the TFTs 103 of each gate wiring 101 are in a conductive (selected) state. Gate wiring 10 on glass substrate 104
Reference numerals 1 are sequentially selected one by one from the end of the substrate by a gate signal, and when the selection of all the gate wirings 101 is completed, the process shifts to the next frame. A period in which all the gate wirings 101 are selected is called one frame period.

A source signal of a liquid crystal display device is normally inverted for the purpose of preventing flicker (screen flicker) and the like. Line inversion driving and dot inversion driving are employed as signal inversion driving methods. The dot inversion means that the voltage polarity of the source signal is inverted with respect to the reference voltage of the common electrode 105 for each of the gate wiring 101 and each of the source wirings 102.
It means that the voltage polarity of the source signal is inverted with respect to the voltage of the common electrode 105 only every 01.

In recent years, in response to a demand for higher image quality of multimedia equipment, adoption of dot inversion drive has been advanced in order to improve horizontal line (gate wiring direction) flicker (screen flicker). Since the light transmittance changes for each pixel due to a slight shift of the voltage applied to each pixel during the AC driving, flicker occurs. Therefore, by inverting the voltage polarity of the source signal for each of the gate wiring 101 and each of the source wirings 102 by the dot inversion drive, it is expected that the applied voltage deviations of the pixels can be canceled more reliably. Further, in the line inversion driving method, since the polarity is inverted for each line, a display defect called horizontal crosstalk occurs. For example, when a black image is displayed on a white background, there is a phenomenon in which the black image trails right and left, and this phenomenon is called a horizontal crosstalk phenomenon. This phenomenon is caused by charge leakage during the non-selection period when the off characteristic of the TFT 103 is insufficient. In the line inversion drive, since the source signal outputs of the whole horizontal period have the same polarity, the influence of the coupling between the source line and the common electrode is large, and the charge leakage is promoted. Since the polarity of the source signal output is inverted for each pixel, the influence of coupling is small, and charge leakage can be canceled.

FIG. 7 shows an example of a source voltage polarity pattern for dot inversion driving. If the source voltage is high with respect to the voltage of the common electrode 105, it is called positive polarity (marked by A in the figure), and if it is low, it is called negative polarity (marked by B in the figure). The voltage polarity of the source signal of each pixel is inverted with respect to that of the adjacent pixels in the direction of the gate wiring 101 and the direction of the source wiring 102. Such dot inversion is called 1 × 1 dot inversion. The voltage polarity of the source signal is inverted every frame in order to prevent polarization of the liquid crystal molecules, and the voltage polarity patterns shown in FIGS. 7A and 7B alternately appear every frame. .

[0009]

However, the driving method of the liquid crystal display device according to the prior art has the following problems.

(1) Insufficient pixel charging One horizontal period has been shortened with the increase in the definition of the liquid crystal display device, and therefore a sufficient charging period cannot be secured. To solve this problem, for example, Japanese Patent Application Laid-Open No. 4-67122 introduces a double gate driving method in which a gate signal is divided into a spare gate-on signal and a normal gate-on signal. However, since the driving method described in this publication is a line inversion driving method, the problems of the horizontal line flicker and the horizontal crosstalk cannot be solved.

(2) Occurrence of Flicker in Checkered Pattern In the checkerboard display, occurrence of flicker was confirmed in 1 × 1 dot inversion driving. Since the polarity pattern of the 1 × 1 dot inversion drive is the same as the checkerboard pattern, it is considered that flicker visibility is enhanced in the checkerboard display by the 1 × 1 dot inversion drive.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method of driving a liquid crystal display device which eliminates insufficient charging due to high definition of the liquid crystal display device and at the same time improves flicker and crosstalk.

[0013]

According to a first aspect of the present invention, there is provided a method of driving a liquid crystal display device, wherein a gate line is sequentially selected by applying a gate signal to the gate line. A dot inversion driving method in which the voltage polarity of the source signal applied to the source wiring 102 is inverted for each source wiring 102 with respect to the voltage of the common electrode, and also for each of two or more adjacent gate wiring groups. And a double gate driving method in which another gate signal is applied to the gate wiring at intervals of about twice as long as the selected period of the gate wiring group.

According to a third aspect of the present invention, there is provided a liquid crystal display device comprising: a first substrate on which a plurality of gate lines and a plurality of source lines intersecting the first line are formed; In the formed second substrate, the voltage polarity of the source signal applied to the source wiring is inverted with respect to the voltage of the common electrode for each of the source wirings during the application period of the gate signal. A source driver circuit for applying a source signal, which is controlled so as to be inverted also for each of the above-mentioned gate line groups, and another gate signal is provided with a period interval substantially twice as long as a selected period of the gate line group. It has a gate driver circuit for applying a gate signal to each gate wiring.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 will be described below with reference to the drawings.

FIG. 1 is a block diagram of a driving circuit of a liquid crystal display (LCD), FIG. 2 is a diagram showing a polarity pattern of a source signal voltage of 1 × 2 dot inversion driving, and FIGS. 3 and 4 are gates of this driving system. FIG. 3 is an explanatory diagram of signal and source signal waveforms. The features of this drive system are double gate signal and 1 × 2
This is in combination with dot inversion driving. Here,
The basic configuration of the liquid crystal display device is the same as that shown in FIG. 6, and a description thereof will be omitted.

The control circuit 1 includes the gradation data DATA and the LCD
This is a controller that supplies a control signal to the LCD panel 7. The LCD control signals input to the source driver circuit 3 include a polarity inversion control signal POL, a source signal start pulse STH, and a source clock signal CLKH. The LCD control signals input to the gate driver circuit 2 include a gate signal start pulse STV and a gate clock signal. CLK
There is V.

The 1 × 2 dot inversion driving is to invert the voltage polarity of the source signal for each source line 5 corresponding to the output of the source driver circuit 3 as shown in FIG.
This refers to driving in which inversion is performed also for each wiring group of the adjacent two-line gate wiring 4 corresponding to the output of the gate driver circuit 2. If the source voltage is higher than the voltage of the common electrode, it is called positive polarity (marked by A in the figure). Conversely, if the source voltage is low, it is negative polarity (marked by B in the figure).
Mark). The source signal is AC-driven to the positive polarity side and the negative polarity side around the voltage of the common electrode.

The polarity inversion is also performed for each frame (screen) switched at 60 Hz for the purpose of avoiding polarization of the liquid crystal molecules and preventing image sticking such as display burn-in. FIG. 2B illustrates a frame 1 and a frame 2 representing the next screen, respectively.

With the 1 × 2 dot inversion drive, it is possible to improve the checkered flicker which has been a problem in the 1 × 1 dot inversion drive. At the same time, by inverting the polarity for each pixel, the horizontal crosstalk which has been a problem in the line inversion drive can be improved.

The correlation between the gate signal waveform and the source signal waveform will be described with reference to FIGS. Here, the signal waveform of the pixel selected by the gate wiring 40 of the Nth line and the source wiring 50 of the Mth line, and the signal waveform of the pixel selected by the gate wiring 41 of the (N + 1) th line and the source wiring 50 of the Mth line. The signal waveform will be described.

The gate wiring 40 of the Nth line and (N + 1)
The two lines of the gate wiring 41 of the line form a pair and form a group of gate wirings.

In the gate wiring 40 of the N-th line, at time t1
, The gate signal application is started. The period during which this voltage is applied is one horizontal period 1H. Then, after the elapse of the 4H period, another gate signal application is started to the gate wiring 40 of the Nth line, and the voltage application period is 1H. Also, (N
In the (+1) th line of the gate wiring 41, the application of the gate signal starts at time t2, and after the elapse of the 4H period, the application of another gate signal starts at time t4. That is, two gate signals are applied to the gate wiring 4 at a 4H horizontal period interval.

On the other hand, the voltage polarity of the source signal on the M-th line is changed to the period (2
H), the voltage polarity of the source signal at time t1 is the same as that of the source signal at time t3. As a result, after the voltage is precharged to the pixel at time t1, a normal voltage is applied to the pixel at time t3. As described above, since the gate signal is applied to the TFT twice at the timing when the voltage polarities of the source signal are equal (double gate driving), insufficient charging of the pixel electrode with the voltage of the source signal can be solved. In particular, one horizontal period is shortened by the high definition of the liquid crystal display device, and the importance of the double gate driving is increasing.

Embodiment 2 Hereinafter, Embodiment 2 will be described with reference to the drawings.

FIG. 5 shows a voltage polarity pattern diagram of 1 × N dot inversion driving.

The 1 × N dot inversion drive is a drive in which the polarity of the voltage of the source signal is inverted for each source line 5 and also for each group of adjacent N-line gate lines 4 as shown in FIG. Say.

With respect to the waveforms of the gate signal and the source signal in this driving method, two gate signals are applied to the gate wiring 4 with a 2N horizontal period interval using double gate driving as in the first embodiment. .

[0029]

According to the present invention, the gate lines are sequentially selected by applying a gate signal to the gate lines,
Dot inversion driving in which the voltage polarity of the source signal applied to the source line during this selection period is inverted for each source line with respect to the voltage of the common electrode, and also for each of two or more adjacent lines of gate lines. By combining this method with a double gate drive method in which another gate signal is applied to the gate wiring at intervals of about twice as long as the selected period of the gate wiring group, insufficient charging due to higher definition is eliminated. In addition, it is possible to obtain a liquid crystal display driving method which improves flicker and crosstalk, and a liquid crystal display using the same.

[Brief description of the drawings]

FIG. 1 is a block diagram of a driving circuit of a liquid crystal display device.

FIG. 2 is a diagram showing a source signal voltage polarity pattern of 1 × 2 dot inversion driving.

FIG. 3 is a diagram showing a relationship between a pixel and a gate line and a source line.

FIG. 4 is an explanatory diagram of waveforms of a gate signal and a source signal.

FIG. 5 is a diagram showing a source signal polarity pattern of 1 × N dot inversion driving.

FIG. 6 is a diagram illustrating a basic configuration of an active matrix liquid crystal display device.

FIG. 7 is a diagram showing a source signal polarity pattern of 1 × 1 dot inversion driving.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control circuit 2 Gate driver circuit 3 Source driver circuit 4, 101 Gate wiring 5, 102 Source wiring 7 LCD panel

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 622 G09G 3/20 622D H04N 5/66 102 H04N 5/66 102B F-term (Reference) 2H093 NA32 NA34 NA43 NC34 ND10 ND15 5C006 AC26 AF44 BB16 BC03 BC12 FA11 FA23 FA36 5C058 AA09 BA01 BA02 BA09 BA10 BB01 BB09 BB12 5C080 AA10 BB05 DD06 DD07 DD10 FF11 JJ02 JJ04 JJ05

Claims (4)

[Claims] In a driving method of a liquid crystal display device, a plurality of gate wirings and a plurality of source wirings intersecting the gate wirings are formed on a substrate, and a common electrode is formed on another substrate facing the substrate. Each of the gate lines is sequentially selected by applying a first gate signal, and the voltage polarity of the source signal applied to the source line during the selection period is different from the voltage of the common electrode for each source line. This is a dot inversion driving method that inverts and also inverts for every two or more adjacent lines of gate lines. The second line is driven at intervals of approximately twice the selected period of the gate lines.
A method for driving a liquid crystal display device, wherein the gate signal is applied to each of the gate lines. 2. The method according to claim 1, wherein the number of wirings in the group of gate wirings is three or more. 3. A first substrate on which a plurality of gate wirings and a plurality of source wirings intersecting therewith are formed, a second substrate is disposed opposite to the first substrate and has a common electrode, and a gate signal is provided. During the application period, the voltage polarity of the source signal applied to the source line is inverted for each of the source lines with respect to the voltage of the common electrode, and also for each of two or more adjacent lines of gate lines. Source driver circuit for applying a source signal controlled as described above, a gate for applying another gate signal to each gate line at a time interval substantially twice as long as a selected period of the gate line group with respect to the gate signal A liquid crystal display device including a driver circuit. 4. The liquid crystal display device according to claim 3, wherein the number of wirings in the group of gate wirings is three or more.