JP2001343942A - Driving method for liquid crystal display device and portable equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the driving method of a liquid crystal display device capable of reducing power consumption. SOLUTION: In this driving method of a liquid crystal display device, a data signal is outputted from a source driver during one pixel selecting period of one of pixels having capacitive load characteristics. Both of a source driver- output period T3 and source-driver non-output periods T1, T2 exist in the one pixel selecting period.

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 which outputs a data signal from a source driver during a one-pixel selection period to any pixel having a capacitive load characteristic, and a portable device using the method. It concerns equipment.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices capable of color display have been actively developed due to low power consumption and convenience of portability.

In general, in a liquid crystal display device, a backlight consumes a large amount of power in a system, and a source driver consumes a large amount of power in a module.

[0004] As for the former, a reflective type color liquid crystal without a back light has been introduced to reduce power consumption.

On the other hand, in the latter case, the power supply is saved by setting the source driver to a high impedance state outside the selection period of the liquid crystal pixels to reduce the amount of current.

For example, in the liquid crystal display driving device disclosed in Japanese Patent Application Laid-Open No. Hei 2-210492, power consumption is reduced by setting the power supply for driving the liquid crystal to a high impedance state, that is, a standby state.

The above-mentioned liquid crystal driving power supply is, for example, a driver for driving a signal line. The output is set to a high impedance to make the driver and the liquid crystal panel electrically insulated, thereby reducing power consumption. It is intended.

[0008]

However, in the driving method of the above-mentioned conventional liquid crystal display device, in order to reduce power consumption, the source driver is set to a high impedance state outside the actual signal writing time in the liquid crystal pixels to reduce the amount of current. There is a problem that measures to reduce it are not enough.

[0009] This applies to mobile phones, PDAs (Personal).
Digital Assistants) and devices such as laptops
Since the usable time is limited even after charging once, the use of the battery may be interrupted due to running out of battery or charging.
There is a demand for further lower power consumption.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to reduce the power consumption of a liquid crystal or to secure the display quality to reduce the power consumption. It is an object of the present invention to provide a display device driving method and a portable device using the method.

[0011]

In order to solve the above-mentioned problems, a method of driving a liquid crystal display device according to the present invention includes a step of selecting a pixel having a capacitive load characteristic from a source driver during one pixel selection period. In a method for driving a liquid crystal display device that outputs a signal, a period in which a data signal is output from a source driver and a period in which a data signal is not output exist during the one pixel selection period.

According to the above invention, a data signal is output from the source driver during one pixel selection period for any pixel having a capacitive load characteristic.

In one pixel selection period, there are both a period in which the data signal is output from the source driver and a period in which the data signal is not output.

For this reason, by setting the source driver to high impedance for a part of the one pixel selection period, the total operation time of the source driver is reduced, and the power consumption of the source driver is reduced. Can be.

Therefore, it is possible to provide a method for driving a liquid crystal display device which can achieve low power consumption.

In order to solve the above-mentioned problems, a method of driving a liquid crystal display device according to the present invention is characterized in that, in the method of driving a liquid crystal display device described above, a data signal output from a source driver is provided at least in a latter half of one pixel selection period. It is characterized by being output.

According to the above invention, the data signal output from the source driver is output at least in the latter half of one pixel selection period.

For this reason, the non-output period of the source driver after the output of the data signal from the source driver can be shortened, so that the voltage applied to the pixel can be prevented from lowering and the display quality can be ensured.

In order to solve the above-mentioned problems, a method of driving a liquid crystal display device according to the present invention is the method of driving a liquid crystal display device described above, wherein an end point of data signal output from a source driver and an end point of one pixel selection period. Is greater than 0% and 20% or less in one pixel selection period.

According to the above invention, the time difference between the end point of the data signal output from the source driver and the end point of the one-pixel selection period is larger than 0% of the one-pixel selection period and equal to or less than 20%.

As a result, display quality can be ensured and low power consumption can be achieved.

In order to solve the above-mentioned problems, a method for driving a liquid crystal display device according to the present invention is characterized in that, in the method for driving a liquid crystal display device described above, the data signal from the source driver is 1
It is characterized in that it is divided into at least two parts and output during the pixel selection period.

According to the above invention, the data signal from the source driver is divided into at least two and output during one pixel selection period.

As a result, the first source driver output period has the effect of precharging, so that charging of the pixels can be assisted and high-speed response can be achieved.

In order to solve the above-mentioned problems, the driving method of the liquid crystal display device according to the present invention is the same as the driving method of the liquid crystal display device described above, wherein the data signal from the source driver during one pixel selection period is the first data signal. While the first data signal output period is divided into at least two periods of one data signal output period and the last second data signal output period, the first data signal output period exists in the first half of the one pixel selection period, The second data signal output period is present in the latter half of the one-pixel selection period.

According to the above invention, the data signal from the source driver during one pixel selection period is the first data signal.
Is divided into at least two periods of a data signal output period and a last second data signal output period, while the first data signal output period is present in the first half of one pixel selection period, The second data signal output period exists in the latter half of the one pixel selection period.

That is, the non-output period of the source driver between the start point of the first data signal output period and the start point of the one-pixel selection period needs to be written to the pixel as soon as possible. In this regard, the necessity can be satisfied by the fact that the first data signal output period exists in the first half of the one pixel selection period.

The non-output period of the source driver between the end point of the second data signal output period and the end point of the one-pixel selection period is as small as possible because the voltage applied to the pixel decreases as described above. Is better. In this regard, since the second data signal output period exists in the latter half of the one-pixel selection period, this need can be satisfied, and display quality can be ensured.

In order to solve the above-mentioned problems, the driving method of the liquid crystal display device according to the present invention is the same as the driving method of the liquid crystal display device described above, except that the starting point of the first first data signal output period and the one pixel selection period Is within 20% of one pixel selection period, and the time difference between the end point of the last second data signal output period and the end point of one pixel selection period is 20% of one pixel selection period. It is characterized by being within.

According to the above-described invention, the time difference between the start point of the first first data signal output period and the start point of the one-pixel selection period is within 20% of the one-pixel selection period, and the last second one is selected. The time difference between the end point of the data signal output period and the end point of the one-pixel selection period is within 20% of the one-pixel selection period.

As a result, it is possible to reliably ensure display quality and reduce power consumption.

In order to solve the above-mentioned problems, a driving method of a liquid crystal display device according to the present invention is the same as the driving method of the liquid crystal display device described above, wherein a gate bus to which a scanning signal indicating one pixel selection period is supplied is supplied. It is characterized in that the capacitance formed between the line and the counter electrode of the pixel and the source bus line is at least 20 times the capacitance formed between one pixel and the counter electrode.

According to the above invention, the capacitance formed between the source bus line and the gate bus line to which the scanning signal indicating the one pixel selection period is supplied and the source bus line is one pixel. Is 20 times or more the electric capacitance formed between the electrode and the counter electrode.

As a result, the electric charge discharged during the non-output period of the source driver can be compensated, and the display quality can be ensured and the power consumption can be reduced.

In order to solve the above-mentioned problems, the driving method of the liquid crystal display device according to the present invention is the same as the driving method of the liquid crystal display device described above, wherein the output of the data signal from the source driver is output to the pixel via the active element. It is characterized by being done.

According to the above invention, the output of the data signal from the source driver is output to the pixel via the active element.

Therefore, lower power consumption can be achieved for a liquid crystal display device employing an active element.

In order to solve the above-mentioned problems, a method of driving a liquid crystal display device according to the present invention is characterized in that, in the method of driving a liquid crystal display device described above, the active element is a thin film transistor.

According to the above invention, the active element is a thin film transistor.

For this reason, when the active element is a thin film transistor, power consumption can be reduced in a driving method of a liquid crystal display device having high versatility.

In order to solve the above-mentioned problems, a portable device according to the present invention uses the driving method of a liquid crystal display device according to any one of the first to ninth aspects.

According to the invention, a portable device such as a portable telephone uses the driving method of the liquid crystal display device according to any one of the first to ninth aspects.

Therefore, it is possible to provide a portable device such as a portable telephone capable of reducing power consumption or securing display quality and reducing power consumption.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] An embodiment of the present invention will be described with reference to FIGS.
It is as follows. Note that the active matrix liquid crystal display device of this embodiment is, for example, a mobile phone, a PD, or the like.
A (Personal Digital Assistants) and portable devices such as notebook computers are suitably used.

As shown in FIG. 2, the active matrix type liquid crystal display device of the present embodiment has a source driver 3 as a data signal driver for inputting a data signal to the liquid crystal panel 1 and a pixel selection period. , A gate driver 4 as a scanning signal driver for inputting a scanning signal, and the source driver 3 and the gate driver 4
And a controller 5 for controlling the

The liquid crystal panel 1 has a glass substrate 11,
Provided on the glass substrate 11 are source bus lines 6 for supplying data signals arranged in a grid and gate bus lines 7 for supplying scanning signals, and thin film transistors as switching elements provided for each lattice point. (Hereinafter, referred to as “TFT: Thin Film Transistor”)
2 and the pixel electrodes 13 connected to the source bus lines 6 via the TFTs 12 as shown in FIG.
And a liquid crystal layer 18 described later with respect to the pixel electrodes 13.
A common electrode 8 is provided so as to be opposed to the other.

The pixel electrode 13 is, as shown in FIG.
In the present embodiment, the interlayer insulating film 1 provided on the gate bus line 7 and the source bus line 6 and the TFT 12
4 and the pixel electrode 13 and T
FT12 means that the pixel electrode 13 has a contact hole 13a.
Are connected by contacting with a connection electrode 15 which is a drain electrode of the TFT 12.

Below the contact hole 13a, the charge storage capacitor 14 is formed by an overlapping region of the connection electrode 15 and a charge storage capacitor electrode (hereinafter, referred to as "Cs electrode") 16. The sandwiched gate insulating film 17 has a structure that functions as a dielectric layer of the charge storage capacitor 14.

The sources and drains of the TFTs 12 are connected to the source bus lines 6 and the connection electrodes 15, respectively.

Further, a liquid crystal layer 18 is provided above the pixel electrode 13, and a glass substrate 19 is provided thereover via the common electrode 8.

A driving method in the above liquid crystal display will be described.

In the above liquid crystal display device, as shown in FIG. 2, signals output from the source drivers 3 and the gate drivers 4 are input to the TFTs 12 through the source bus lines 6 and the gate bus lines 7. You.

For one pixel selection period selected by the scanning signal from the gate driver 4, the TFT 12
.. Are turned ON.
Are applied to the liquid crystal layers 18. Also, a counter voltage is applied to the liquid crystal layers 18 from the common electrodes 8 as counter electrodes.

In the liquid crystal display device having the above configuration, the source driver 3 equipped with the power save mode
Source driver IC (Integrated C
The output of the output circuit is set to high impedance, and the source bus lines 6 are set to a floating state. As described above, when the output of the output circuit is set to the high impedance, the current consumption in the output circuit portion is reduced, and low power consumption can be achieved.

As a result, as shown in FIG. 1A, the voltage change of the gate bus lines 7 becomes a high voltage state for a certain period so that a data signal can be inputted to an arbitrary pixel during a pixel selection period. I have.

During the one pixel selection period, as shown in FIG. 1B, a data signal output from the source driver 3 is input to the liquid crystal layer 18 via the TFTs 12.

In this embodiment, the output of the data signal from the source driver 3 is the source driver output period during which the data signal is output from the source driver 3 during one pixel selection period. T3 and a source driver non-output period T1 during which no output is made
-Both T2 and T2 are present.

By the way, if the output period from the source driver 3 is shortened in this way during one pixel selection period, there is a possibility that the charging of the drain electrode becomes worse.

On the other hand, as shown in FIG. 1C, it was confirmed that the change in the voltage of the source bus lines 6 could secure the target voltage of 10 V for charging the pixels.

Further, the display quality of the liquid crystal display device under the above conditions was experimentally examined as shown in the embodiment described later. As a result, the output period of the source driver 3 was 60% or more during one pixel selection period. In this case, it was found that the brightness and the contrast were good.

As a result, the output of the source driver 3 becomes about 4
The power consumption can be reduced by 0%.

Further, in the present embodiment, the first embodiment is used.
As a result, if the time difference between the end point of the data signal output from the source driver 3 and the end point of the one-pixel selection period is larger than 0% and equal to or less than 20% of the one-pixel selection period, the brightness and the contrast are good. It was confirmed that power consumption was reduced.

That is, as shown in FIGS. 1A, 1B, and 1C, for example, the first one in a pixel selection period of 70 μsec.
4 μsec (source driver non-output period T1) and last 14
During the period of μ seconds (source driver non-output period T2), the output of the source driver 3 is set to a high impedance state,
The signal output from the source driver 3 is not performed.

The period (source driver output period T3) between the first 14 μs (source driver non-output period T1) and the last 14 μs (source driver non-output period T2) in the pixel selection period 70 μs. ), The output from the source driver 3 is performed, and the data signal is input to the pixel.

As a result, it was confirmed that the brightness and the contrast were good and low power consumption was achieved.

In this method, the frequency corresponding to the cycle of the driving gate driver output signal is set to 60
It has been confirmed that it is effective to change the frequency without sticking to hertz.

Even if the liquid crystal panel 1 is made finer and the number of lines is increased, there is no problem in use.

In this embodiment, only the liquid crystal display device having the TFTs 12 has been described. However, the present invention is not limited to this and can be applied to other active elements.

Further, similar low power consumption can be achieved in simple matrix driving without active elements.

As described above, in the liquid crystal display device of the present embodiment, the data signal is output from the source driver 3 during one pixel selection period for any pixel having a capacitive load characteristic.

In one pixel selection period, there are both a period in which the data signal is output from the source driver 3 and a period in which the data signal is not output.

For this reason, by setting the source driver 3 to high impedance for a part of one pixel selection period, the total source driver operation time is reduced, and the power consumption of the source driver 3 is reduced. can do.

Therefore, it is possible to provide a driving method of a liquid crystal display device which can achieve low power consumption.

In the liquid crystal display device driving method of the present embodiment, the time difference between the end point of the data signal output from the source driver 3 and the end point of the one-pixel selection period is larger than 0% of the one-pixel selection period. And 20% or less.

As a result, it is possible to ensure display quality and reduce power consumption.

In the method of driving the liquid crystal display device according to the present embodiment, the output of the data signal from the source driver 3 is output to the pixel via the active element.

Therefore, lower power consumption can be achieved for a liquid crystal display device employing an active element.

In the driving method of the liquid crystal display device of the present embodiment, the active elements are the TFTs 12.

For this reason, the active elements are TFT12 ...
Accordingly, low power consumption can be achieved in a method for driving a liquid crystal display device having high versatility.

Further, a portable device such as a mobile phone according to the present embodiment uses the above-described driving method of the liquid crystal display device and the driving method of the liquid crystal display device described in the second to fourth embodiments described later.

Therefore, it is possible to provide a portable device such as a portable telephone which can achieve low power consumption or can secure display quality and achieve low power consumption.

In the present embodiment, as described above, during one pixel selection period, the source driver 3
Although there are both a period during which the data signal is output from and a period during which the data signal is not output, the concept of the actual one-pixel selection period is as follows.

That is, in the matrix type liquid crystal display device, the output signal of the gate driver 4 is represented by the waveform on the gate bus lines 7 on the gate driver 4 side (left end side in FIG. 2) and the gate driver in FIG. 4 is different from the waveform on the gate bus lines 7... On the opposite side (the right end side in the figure). This is because the gate bus lines 7 have resistance and capacitance components in a distributed constant manner.

Therefore, the output signal of the gate driver 4 has the waveform shown in FIG. 1 on the left end side of the gate bus lines 7 shown in FIG. The waveform of the output signal of the gate driver 4 is dull due to the influence of the resistance and capacitance components. Therefore, one pixel selection period is delayed on the right end side more than on the left end side.

For this reason, if the source driver output is controlled at a timing that matches only the output signal of the gate driver 4 at the left end shown in FIG. 2, a desired display quality may not be obtained at the right end shown in FIG. .

Therefore, in an actual design, the source driver output period T3 exceeds the end point of the one pixel selection period on the left end side, and
It is designed to extend to some extent (a value in consideration of the time constant of the gate bus lines 7). That is, the source driver 3 may output the signal beyond the end point of one pixel selection period.

As described above, the concept of one pixel selection period is as follows.
At any point of the gate bus lines 7, the pixel is actually selected, and the pixel is slightly shifted on the gate bus lines 7.

[Second Embodiment] The following will describe another embodiment of the present invention with reference to FIG. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Further, it is assumed that various features of the first embodiment can be applied in combination with the present embodiment.

In the first embodiment, during one pixel selection period, a source driver output period T3 during which a data signal is output from the source driver 3, and a source driver non-output period T1 · T during which no data signal is output.
It has been explained that both 2 and 2 may be present.

In the present embodiment, based on the result of the first embodiment, the source driver output period T3
Describes how to apply voltage during one pixel selection period.

In conclusion, in the present embodiment, FIG.
As shown in (a), (b), and (c), the source driver output period T3 is at least the latter half of one pixel selection period.

That is, as shown in FIG. 5B, in the source driver non-output period T2 after the source driver output period T3, the drain voltage decreases as shown in FIG. 5C. Therefore, it is better that the period during which the drain voltage falls is as short as possible.

From this, it can be understood that it is theoretically better that the source driver output of the source driver 3 is located on the rear side as much as possible during one pixel selection period.

The reason why the drain voltage is reduced is that the pixel charge is discharged between the end of the source driver output and the end of one pixel selection period. It indicates that you depend on your ability.

As described above, in the present embodiment, the source driver output of the source driver 3 is output at least in the latter half during one pixel selection period.

In order to confirm this, as shown in Example 2 to be described later, an experimental study was made on the relationship between the time difference between the source driver output end point and the end point of one pixel selection period and the contrast. As a result, it was found that the end point side within one pixel selection period may be set as the non-output period, and the above was confirmed.

As described above, in the driving method of the liquid crystal display device according to the present embodiment, the data signal output from the source driver 3 is output at least in the latter half of one pixel selection period.

For this reason, the source driver non-output period T2 after the elapse of the source driver output period T3 can be shortened, so that the voltage applied to the pixel can be prevented from lowering and the display quality can be ensured.

[Embodiment 3] The following will describe another embodiment of the present invention with reference to FIGS. For convenience of explanation, members having the same functions as those shown in the drawings of the first and second embodiments are denoted by the same reference numerals, and description thereof is omitted. The various features of the first and second embodiments can be applied in combination with the present embodiment.

In the first and second embodiments, data input is performed only for one period during one pixel selection period. However, in the present embodiment, it is considered that data input is divided into a plurality of periods. did.

That is, in the present embodiment, FIG.
(A) As shown in (b) and (c), during one pixel selection period, the source driver output is divided into two and input.

In the above description, the source driver output is divided into two. However, the present invention is not limited to this. It is also possible to divide the output into a larger number.

Specifically, as shown in FIG.
The data signal from the source driver 3 during the pixel selection period is divided into at least two periods: a first first data signal output period t1 and a last second data signal output period t2. Further, the first data signal output period t
1 exists in the first half of the one pixel selection period, while the second data signal output period t2 exists in the second half of the one pixel selection period.

The source driver output applied in each of the first data signal output period t1 and the second data signal output period t2 has the same voltage.

As described above, the data is written into the liquid crystal layer 18 at the last timing in the latter half of the one-pixel selection period, and then written at the timing in the first half of the one-pixel selection period, whereby the interval until the next writing is completed. Is effective because it can be minimized.

In the first data signal output period t1, a precharge effect is provided for the pixel, so that charging of the pixel can be assisted and high-speed response can be achieved.

That is, the first data signal output period t1
, The liquid crystal capacitance is changed by the electric charge, and then the pixel including the liquid crystal layer 18 whose liquid crystal capacitance is changed is recharged in the second data signal output period t2, thereby obtaining the first data. The same response speed can be obtained as when the signal is applied during the entire signal output period t1 + source driver non-output period t3 + second data signal output period t2. As a result, even in the method of driving the liquid crystal display device according to the present embodiment in which no voltage is applied to the pixels during the source driver non-output period t3, a response speed equivalent to that of a normal operation can be obtained.

Also, simply, the first data signal output period t
If the source driver non-output period t3 is provided, the liquid crystal layer 18 changes during that period, and the second data signal output period again after the change, as compared to the case where 1 + second data signal output period t2 continues. The response speed is increased by applying the voltage at t2.

Here, the source driver non-output period t5 between the end point of the second data signal output period t2 and the end point of one pixel selection period shown in FIG. For the reasons stated, it is better to be a little short.

On the other hand, in the source driver non-output period t4 between the start point of the first data signal output period t1 and the start point of the one-pixel selection period shown in FIG. It is better to be as small as possible.

In this embodiment, in order to confirm this, an experimental study shown in Example 3 described later was performed. That is, in the experiment in Example 3, the contrast evaluation was performed while changing the timing of the data signal output time from the source driver 3 during one pixel selection period.

As a result, the first data signal output period t1
It has been found that is better when the second data signal output period t2 is closer to the start point during the one-pixel selection period and closer to the end point during the one-pixel selection period.

More specifically, the time difference between the start point of the first first data signal output period t1 and the start point of the one-pixel selection period is within 20% of the one-pixel selection period, and 2 and the end point of the data signal output period t2 and 1
The time difference from the end point of the pixel selection period is 2 in one pixel selection period.
It was confirmed that the content should be within 0%.

As a result, it was confirmed that the brightness and the contrast were good and low power consumption could be achieved.

As an example, for example, FIGS. 7A and 7B
As shown in (c), only during the first 15 μsec (first data signal output period t1) and the last 15 μsec (second data signal output period t2) of the 70 μsec one pixel selection period, A signal is output from the driver 3 and a data signal is input to the pixel via the TFT 12.

Note that the first data signal output period t1 and the second data signal output period t2 in one pixel selection period
During the non-output period t3 of the source driver, the output of the source driver 3 is set to the high impedance state, and the signal output from the source driver 3 and the input of the data signal to the pixel are not performed.

In the above example, particularly, the signal output from the source driver 3 is performed at the beginning from the start point of the one-pixel selection period and at the end until the end point of the one-pixel selection period. By writing data to the liquid crystal layer 18 at the last timing during one pixel selection period, and then writing at the first timing during one pixel selection period,
This is more effective because the interval until the next writing can be minimized.

As a result, brightness and contrast are good, and low power consumption can be achieved.

In this method, the frequency corresponding to the cycle of the driving gate driver output signal is set to 60 in the case of the TV signal.
It has been confirmed that it is effective to change the frequency without sticking to hertz.

Further, even if the liquid crystal panel 1 is made finer and the number of lines is increased, there is no problem in use.

In this embodiment, only the liquid crystal display device having the TFTs 12 has been described. However, the present invention is not limited to this, and can be applied to other active elements.

Further, similar low power consumption can be achieved in simple matrix driving without active elements.

As described above, in the liquid crystal display device of the present embodiment, the data signal from the source driver 3 is divided into at least two signals during one pixel selection period, and is output.

The divided source driver 3
Are applied voltages of the same magnitude. Therefore, in the present embodiment, unlike the precharge or discharge in which the maximum or minimum output voltage of the source driver 3 is applied, the increase in the current consumption at the timing is low.

The first first data signal output period t
Since 1 has the effect of precharging, it is possible to assist charging of the pixel and to achieve high-speed response.

In the method of driving the liquid crystal display device of the present embodiment, the source driver 3 during one pixel selection period
Is divided into at least two periods of a first first data signal output period t1 and a last second data signal output period t2, while the first data signal output period t1 is 1 The second data signal output period t2 exists in the first half of the pixel selection period, while the second data signal output period t2 exists in the second half of the one pixel selection period.

That is, the first data signal output period t1
Since the source driver output period t4 between the start point of (1) and the start point of the one-pixel selection period needs to be written to the pixel as soon as possible, it is better to be as small as possible. In this regard, the first
This data signal output period t1 can satisfy this need by being present in the first half of the one-pixel selection period.

In the source driver non-output period t5 between the end point of the second data signal output period and the end point of the one-pixel selection period, as described above, the voltage applied to the pixel is reduced. Smaller is better. In this regard, since the second data signal output period t2 exists in the latter half of the one-pixel selection period, this necessity can be satisfied, and the display quality can be ensured.

In the liquid crystal display device driving method of the present embodiment, the time difference between the start point of the first first data signal output period t1 and the start point of the one pixel selection period is 20% of the one pixel selection period. And the time difference between the end point of the last second data signal output period t2 and the end point of the one-pixel selection period is within 20% of the one-pixel selection period.

As a result, it is possible to reliably ensure display quality and reduce power consumption.

[Fourth Embodiment] The following will describe another embodiment of the present invention with reference to FIG. For convenience of explanation, members having the same functions as those shown in the drawings of the first to third embodiments will be described.
The same reference numerals are given and the description is omitted. Further, the various features of the first to third embodiments can be applied in combination with the present embodiment.

In the present embodiment, as shown in FIG. 8, a source bus line 6 has a first capacitance (CSC) formed between the gate bus line 7 and a common electrode 8 as a counter electrode. ) 41 and a second capacitance (CLC) formed between one pixel and a common electrode 8 which is a counter electrode.
(+ CS) An experimental study shown in Example 4 was conducted to find out the relationship with 42.

As a result, it was found that the display quality deteriorated due to the decrease in contrast when the capacitance ratio was less than 20 times.

Thus, when the capacity ratio exceeds 20 times, 1
It has been found that the display can be performed with good contrast and display quality even when both a period in which the data signal is output from the source bus lines 6 and a period in which the data signal is not output exist within the pixel selection period.

That is, in the source driver output period T3 and the first data signal output period t1 and the second data signal output period t2, not only the second capacitance (CLC + CS) 42 but also the first Capacity (CS
C) Since 41 is also charged at the same time, the source driver non-output periods T1 and T2 and the source driver non-output periods t3 and t
At 4 · t5, the first capacitance (CSC) 41 serves to supplement the charge discharged from the second capacitance (CLC + CS) 42, and when this capacitance ratio falls below 20 times, This is because the above effects cannot be expected.

However, in this case, in particular, the source driver output period T3 and the first data signal output period t1
The ratio during the one-pixel selection period in the second data signal output period t2 does not matter.

In this embodiment, this method is effective even if the frequency corresponding to the cycle of the driving gate driver output signal is changed without being limited to 60 Hz in the case of the TV signal. Has been confirmed.

In addition, even if the liquid crystal panel 1 is made finer and the number of lines is increased, there is no problem in use.

Further, in this embodiment, the TFTs 12.
Although only the liquid crystal display device provided with is described, the present invention is not necessarily limited to this and can be applied to other active elements.

As described above, according to the driving method of the liquid crystal display device of the present embodiment, the gate bus lines 7 to which the scanning signal indicating one pixel selection period is supplied, the common electrodes 8 of the pixels, and the source bus lines 6 and the first
Is a second capacitance (CLC + CS) 4 formed between one pixel and the common electrode 8.
20 or more times 2.

This makes it possible to supplement the electric charge discharged during the non-output period of the source driver, thereby ensuring display quality and reducing power consumption.

[0142]

Embodiment 1 In Embodiment 1, how long the data signal of the source driver 3 should be output during one pixel selection period, in other words, 1
An experimental study was conducted on how long the output of the data signal of the source driver 3 may be turned off during the pixel selection period.

In the experiment, specifically, the display quality was observed while changing the timing of inputting the data signal from the source driver 3.

As the display quality, brightness and contrast were evaluated.

As shown in FIG. 9, the method of measuring the brightness and the contrast is such that light is incident on the liquid crystal panel 1 at an angle of 30 degrees from the vertical direction by the incident light lens 21 and the light is provided in the vertical direction. The measurement was performed by receiving light through the lens 22 and measuring the brightness. The measurement was performed with reference to a white plate made of magnesium oxide.

Further, the contrast was calculated by the following equation after measuring the brightness in both the bright and dark states and then: contrast = (bright brightness) / (dark brightness).

On the other hand, the timing of inputting the data signal from the source driver 3 is 35 μsec from the start so that the non-output time is the same between the start point side and the end point side within the pixel selection period of 70 μsec. The time was changed back and forth as the center.

As a result, as shown in FIG. 10, the relationship between the output time from the source driver 3 and the contrast is that the contrast is about 10 or less when the output time from the source driver 3 is about 40 μs. When the output time from the source driver 3 becomes about 40 μsec or more, the contrast linearly increases to about 55 μsec for the output time from the source driver 3, and the output time from the source driver 3 becomes about 55 μsec.
From μsec to 70 μsec, it was found that the contrast was in a steady state of about 30.

A practical value for contrast is
It is about 16 or more. As a result, it was found that it is preferable that the output time from the source driver 3 be about 42 μs or more.

Therefore, it was confirmed that the output period of the data signal of the source driver 3 during one pixel selection period should be 60% or more of the one pixel selection period.

According to this experiment, when the input and output of the data signal to the pixel were performed within 20% each including the start point and the end point within one pixel selection period, the brightness and the contrast were good. I understood.

[Embodiment 2] In the present embodiment 2, an experimental study was performed to determine which of the start point side and the end point side in one pixel selection period should be the non-output period.

That is, in the experiment, the contrast was measured while changing the timing of the source driver output for 20 μs within one pixel selection period of 70 μs.

It should be noted that the value of 20 μs is
The power consumption does not reach μs / 70 μs × 100 秒 30%. The reason for this is that the elements that constitute the power consumption include, for example, the source driver 3, the gate driver 4, the common electrode 8, the controller 5, and the like, and the power consumption is determined by a combination of these.

As a result of the above experiment, as shown in FIG.
It was found that the closer the end point of the data signal output from the source driver 3 to the end point of one pixel selection period, the better the contrast. That is, as shown in FIG. 11, when the time difference between the end point of the data signal output from the source driver 3 and the end point of one pixel selection period is within 14 μsec, the contrast is about 23 or more, and the contrast is good. Value.

From this, it was found that setting the end point side within one pixel selection period to the non-output period is good.

[Third Embodiment] In the third embodiment, when a source driver output is divided into two and inputted during one pixel selection period, a data signal from the source driver 3 during one pixel selection period is input. The contrast was evaluated by changing the timing of the output time.

In the experiment, the signal output from the source driver 3 was set to 15 μsec in each of the first data signal output period t1 and the second data signal output period t2 in 70 μsec during one pixel selection period.

First, as shown in FIG. 7B,
The timing of the start point of the first data signal output period t1 and the timing of the output 0N of the gate driver 4 are matched, and
Although not shown in FIG. 7, the contrast was evaluated by changing the time difference between the end point of the second data signal output period t2 and the output OFF of the gate driver 4.

As a result, as shown in FIG. 12, it was found that the closer to the end point of the one-pixel selection period, the better the output of the second data signal output period t2 was.

Next, while increasing the time difference between the start point of the first data signal output period t1 and the output 0N of the gate driver 4, as shown in FIG. 7B, the second data signal output period t2 And the output O of the gate driver 4
The contrast was evaluated in accordance with FF.

As a result, the same result as that of FIG. 12 was obtained. That is, it has been found that the closer the output of the first data signal output period t1 is to the start point of the one-pixel selection period, the better the contrast is.

Further, the time difference between the start point of the first first data signal output period t1 and the start point of one pixel selection period is one.
Within 20% of the pixel selection period and the second
It was confirmed that the time difference between the end point of the data signal output period t2 and the end point of the one pixel selection period should be within 20% of the one pixel selection period.

As a result, it was confirmed that the brightness and the contrast were good and low power consumption could be achieved.

[Embodiment 4] In the present embodiment 4, the source bus lines 6 are connected to the gate bus lines 7 and the common electrode 8 which is a counter electrode, and the first capacitance (CSC) is formed between them. 41 and a second capacitance (CLC +) formed between one pixel and the common electrode 8 as a counter electrode.
An experiment was performed to find out the relationship with CS) 42.

In the experiment, first, a voltage of 5 V was applied as the source voltage of the source driver 3 for 50% of one pixel selection period, and thereafter, the source driver 3 was set to a high impedance state so that no signal was output. The voltage of the second capacitance, that is, the drain voltage,
(Hereinafter referred to as “capacity ratio”)
Was discussed.

As a result, it was found that the drain voltage changes as shown in FIG. 13 depending on the capacitance ratio.

That is, it can be seen that when the capacitance ratio is less than 20 times, the drain voltage decreases and the contrast lowers.

Next, in the equivalent circuit shown in FIG.
A rectangular wave of ± 5 V was applied to change the capacitance ratio.

As a result, as shown in FIG. 14, it is found that the contrast gradually decreases as the capacitance ratio is reduced. In particular, when the capacitance ratio falls below 20 times, the contrast decreases. .

At this time, actual visual evaluation was performed. As a result, as shown in FIG. 15, the result of visual evaluation was poor when the capacitance ratio was 15 or less, but the visual evaluation was not performed when the capacitance ratio was 20 or more. The results were found to be good.

As a result, when the capacity ratio exceeds 20 times, 1
It has been found that the display can be performed with good contrast and display quality even when both a period during which the data signal is output from the source driver 3 and a period during which the data signal is not output during the pixel selection period.

[0173]

As described above, the driving method of the liquid crystal display device according to the present invention includes both a period in which the data signal is output from the source driver and a period in which the data signal is not output during one pixel selection period. There is a way.

Therefore, by setting the source driver to high impedance for a part of one pixel selection period, the total source driver operation time is reduced, and the power consumption of the source driver is reduced. Can be.

Therefore, there is an effect that a driving method of a liquid crystal display device which can achieve low power consumption can be provided.

As described above, in the method of driving a liquid crystal display device according to the present invention, in the method of driving a liquid crystal display device described above, the data signal output from the source driver is output at least in the latter half of one pixel selection period. Is the way.

Therefore, the non-output period of the source driver after the output of the data signal from the source driver can be shortened, so that the voltage applied to the pixel can be prevented from lowering and the display quality can be ensured. To play.

As described above, the driving method of the liquid crystal display device of the present invention is the same as the driving method of the liquid crystal display device described above, except that the time difference between the end point of the data signal output from the source driver and the end point of one pixel selection period. Is 0% of one pixel selection period
The method is larger than 20% or less.

Therefore, there is an effect that the display quality can be reliably ensured and the power consumption can be reduced.

As described above, in the method for driving a liquid crystal display device according to the present invention, in the method for driving a liquid crystal display device described above, the data signal from the source driver is divided into at least two or more during one pixel selection period. This is the method that is output.

Therefore, since the first source driver output period has the effect of precharging, it is possible to assist the charging of the pixel and to achieve the high-speed response.

As described above, in the method for driving a liquid crystal display device according to the present invention, the data signal from the source driver during one pixel selection period is the first data signal in the liquid crystal display device described above. The signal is divided into at least two periods of a signal output period and a final second data signal output period, while the first data signal output period is 1
While present in the first half during the pixel selection period, the second
Is a method that exists in the latter half of one pixel selection period.

Therefore, the non-output period of the source driver between the start point of the first data signal output period and the start point of the one-pixel selection period needs to be written to the pixel as soon as possible. . In this regard, the necessity can be satisfied by the fact that the first data signal output period exists in the first half of the one pixel selection period.

As described above, the source driver non-output period between the end point of the second data signal output period and the end point of one pixel selection period is as small as possible because the voltage applied to the pixel decreases. Is better. In this regard, since the second data signal output period exists in the latter half of the one-pixel selection period, this necessity can be satisfied and the display quality can be ensured.

As described above, the driving method of the liquid crystal display device according to the present invention is the same as the driving method of the liquid crystal display device described above, except that the start point of the first first data signal output period and the start point of one pixel selection period. Is 20% of 1 pixel selection period
And the time difference between the end point of the last second data signal output period and the end point of one pixel selection period is within 20% of one pixel selection period.

Therefore, there is an effect that the display quality can be reliably ensured and the power consumption can be reduced.

As described above, the driving method of the liquid crystal display device according to the present invention is the same as the driving method of the liquid crystal display device described above, except that the gate bus line and the pixel to which the scanning signal indicating one pixel selection period is supplied are supplied. In this method, the electric capacitance formed between the common electrode and the source bus line is 20 times or more the electric capacitance formed between one pixel and the common electrode.

Therefore, the electric charge discharged during the non-output period of the source driver can be compensated for, and the effect that the display quality can be ensured and the power consumption can be reduced can be achieved.

As described above, in the method for driving a liquid crystal display device according to the present invention, in the method for driving a liquid crystal display device described above, a method in which an output of a data signal from a source driver is output to a pixel via an active element. It is.

Therefore, it is possible to reduce the power consumption of a liquid crystal display device employing an active element.

As described above, the method for driving a liquid crystal display device of the present invention is a method in which the active element is a thin film transistor in the method for driving a liquid crystal display device described above.

Therefore, when the active element is a thin film transistor, an effect of reducing power consumption can be achieved in a highly versatile driving method of a liquid crystal display device.

As described above, the portable device of the present invention uses the above-described method for driving a liquid crystal display device.

[0194] Therefore, it is possible to provide a portable device capable of reducing power consumption or securing display quality and reducing power consumption.

[Brief description of the drawings]

FIGS. 1A and 1B show an embodiment of a driving method of a liquid crystal display device according to the present invention, in which FIG. 1A is a timing chart showing a gate driver output, FIG. 1B is a timing chart showing a source driver output, and FIG. () Is a timing chart showing the drain voltage.

FIG. 2 is a schematic configuration diagram showing the liquid crystal display device.

FIG. 3 is a plan view showing one pixel of the liquid crystal panel.

FIG. 4 is a sectional view showing a configuration of the liquid crystal panel.

5A and 5B show another embodiment of the method of driving the liquid crystal display device according to the present invention, wherein FIG. 5A is a timing chart showing a gate driver output, FIG. 5B is a timing chart showing a source driver output, and FIG. c) is a timing chart showing the drain voltage.

6A and 6B show still another embodiment of the driving method of the liquid crystal display device according to the present invention, wherein FIG. 6A is a timing chart showing a gate driver output, FIG. 6B is a timing chart showing a source driver output, (C) is a timing chart showing the drain voltage.

7A and 7B show a modified example of the driving method of the liquid crystal display device, wherein FIG. 7A is a timing chart showing a gate driver output, FIG. 7B is a timing chart showing a source driver output, and FIG. FIG.

FIG. 8 shows still another embodiment of the driving method of the liquid crystal display device according to the present invention, in which a source bus line has a first capacitance formed between a gate bus line and a counter electrode; FIG. 9 is an equivalent circuit diagram illustrating a second capacitor formed between one pixel and a counter electrode.

FIG. 9 is an explanatory diagram showing a method for measuring brightness and contrast in a method for driving a liquid crystal display device.

FIG. 10 is an explanatory diagram showing a relationship between output time from a source driver and contrast in a method of driving a liquid crystal display device.

FIG. 11 illustrates a time difference between an output end point of a source driver and an end point of one pixel selection period in a driving method of a liquid crystal display device;
FIG. 4 is an explanatory diagram showing a relationship with contrast.

FIG. 12 is an explanatory diagram showing a measurement result of a relationship between a time difference between an end point of a second output and an end point of one pixel selection period and contrast in a method of driving the liquid crystal display device.

FIG. 13 is an explanatory diagram showing measurement results in a relationship between a capacitance ratio and a drain voltage in a method for driving a liquid crystal display device.

FIG. 14 is an explanatory diagram showing measurement results in a relationship between a capacitance ratio and a contrast in a driving method of a liquid crystal display device.

FIG. 15 is an explanatory diagram showing a result of a visual evaluation with respect to a capacitance ratio in a driving method of a liquid crystal display device.

[Explanation of symbols]

Reference Signs List 1 liquid crystal panel 3 source driver 4 gate driver 6 source bus line 7 gate bus line 8 common electrode (counter electrode) 12 TFT (thin film transistor, active element) 13 pixel electrode 18 liquid crystal layer 41 first capacitance [CSC] (gate bus 42 The second capacitance [CLC + CS] (the capacitance formed between one pixel and the common electrode) T1 Source driver non-output period T2 Source Driver non-output period T3 Source driver output period t1 First data signal output period t2 Second data signal output period t3 Source driver non-output period t4 Source driver non-output period t5 Source driver non-output period

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H04M 1/73 H04M 1/73 F term (Reference) 2H093 NB10 NC12 NC16 NC34 ND04 ND34 ND39 NE02 5C006 AC02 AC21 AF64 AF69 AF71 BB16 BC06 BC13 EC13 FA47 GA03 5C080 AA10 BB05 DD26 FF09 JJ02 JJ04 JJ05 KK07 5K027 AA11 BB17 FF00 FF22 MM17

Claims (10)

[Claims] 1. A method of driving a liquid crystal display device, wherein a data signal is output from a source driver during one pixel selection period to any pixel having a capacitive load characteristic, the method comprising the steps of: A period during which the data signal is output and a period during which the data signal is not output. 2. A data signal output from a source driver is:
2. The driving method for a liquid crystal display device according to claim 1, wherein the signal is output at least in the latter half of one pixel selection period. 3. The time difference between the end point of the data signal output from the source driver and the end point of the one-pixel selection period is larger than 0% of the one-pixel selection period and equal to or less than 20%. The driving method of the liquid crystal display device according to the above. 4. The method according to claim 1, wherein the data signal from the source driver is divided into at least two parts during one pixel selection period and output. 5. A data signal from a source driver during one pixel selection period includes at least two of a first first data signal output period and a last second data signal output period.
While the first data signal output period is present in the first half of the one-pixel selection period, while the second data signal output period is present in the second half of the one-pixel selection period. 5. The method for driving a liquid crystal display device according to claim 4, wherein: 6. The time difference between the start point of the first first data signal output period and the start point of the one pixel selection period is within 20% of the one pixel selection period, and the last second data signal output period. 6. The driving method for a liquid crystal display device according to claim 4, wherein a time difference between the end point of the pixel selection period and the end point of the one pixel selection period is within 20% of the one pixel selection period. 7. An electric capacitance formed between a gate bus line to which a scanning signal indicating a one-pixel selection period is supplied and a counter electrode of a pixel and a source bus line is equal to the capacitance between one pixel and the counter electrode. 2. The driving method for a liquid crystal display device according to claim 1, wherein the capacitance is at least 20 times as large as the capacitance formed between them. 8. A data signal output from a source driver is:
2. The method according to claim 1, wherein the signal is output to a pixel via an active element. 9. The method according to claim 8, wherein the active element is a thin film transistor. 10. A portable device using the method for driving a liquid crystal display device according to claim 1.