JPH09292595A - Driving method for liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal panel driving meth capable of preventing the degrading of picture quality in other part in which a display in not performed when a duty driving is performed in the display of the whole of a liquid crystal panel and a static driving method so is at the time of performing the display of only one part. SOLUTION: In the case of performing a station driving method by selecting only commons of one part with respect top the liquid crystal panel in which a duty driving method driving the liquid crystal part 101 of the intersection of an ability segment and a selected common by successively selecting one of plural commons in time division and by applying a prescribed voltage to the arbitrary segment is used, other commons 104 (COM1∼COMn) which are not selected are made to be high impedance states by making a switch 106 open.

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 panel.

[0002]

2. Description of the Related Art A duty driving method is known as a driving method for a liquid crystal panel. This driving method is designed to reduce CO when driving a dot matrix liquid crystal as shown in FIG.
By sequentially selecting one of the commons from M0 to COMn in time division, and by applying a predetermined voltage to any segment from SEG0 to SEGm,
In this method, a liquid crystal portion at an intersection of an arbitrary segment and the selected common is brought into a light transmitting state or a light blocking state.
FIG. 4 is a time chart showing the voltage level applied to the common and the voltage level applied to the segment in the duty driving, and the point a in FIG. 3 (that is, CO
(M0, SEG0) is shown as an example. When COM0 is selected as the display line, V5 is
When a voltage of 5 is applied to the SEG0, and a voltage of GND level is applied to the SEG0, a potential difference of V5 is generated in the liquid crystal portion at the intersection, and the liquid crystal portion is in a light blocking state (hereinafter, this state is simply referred to as lighting. ), While SEG
When a voltage of V5 is applied to 0 as well, the potential difference of the liquid crystal portion at the intersection becomes 0 V, and the liquid crystal portion is in the light transmitting state (hereinafter, this state is simply turned off). Then, when COM0 is not selected, a voltage other than V5 is applied to the COM0. That is, in the duty driving method, 1/5 bias driving is performed as in the example of FIG. 4 so that the liquid crystal is not turned on at the so-called half-selected point.

A static drive system is known as a drive system for liquid crystal panels. This drive method does not require the bias drive as in the above duty drive method, and therefore has the advantage that the voltage applied to the liquid crystal can be made lower than V5 and the power consumption can be reduced. However, there is a drawback that the liquid crystal can be driven only in a small area.

By the way, for example, a liquid crystal panel used for a pager or the like is provided with a portion for displaying a specific character called a so-called icon in addition to an original information display portion. Then, in such a liquid crystal panel, for example, 1
Six commons are allocated, and one common is allocated to the icon display portion.

In order to reduce power consumption, such a liquid crystal panel has a mode for driving only the icon display portion when no information is displayed on the information display portion, that is, It is possible to switch between duty drive and static drive programmatically. In this case, since the icon display portion is a small area, it can be driven by the static drive method described above.

In the case where COM1 to COMn are used as the information display portion and COM0 is used as the icon display portion,
As shown in FIG. 5, a voltage is applied to the statically driven COM0, and a voltage is also applied to the SEG0, for example, as shown in FIG. When there is a potential difference between COM0 and SEG0, it turns on, and when there is no potential difference, it turns off. Also, COM1 to COM
Since n is turned off, it is possible to give a GND level to them. The voltage level applied to COM0 is Vc at regular intervals.
It is switched to c and GND alternately, but this is for so-called AC driving of the liquid crystal.

[0007]

However, as described above, static driving is performed on COM0, which is the icon display portion, and C, which is the information display portion, is performed.
If the GND level is applied to the OM1 to COMn, there arises a problem that the image quality deteriorates in these COM1 to COMn regions. In other words, as shown in FIG.
Repeated application of (“1”) and Low (“0”) voltage,
In SEG0 to SEG3, as shown in the figure, High
When voltage of “(1)” and Low (“0”) is applied, S
EG1, SEG3 are lit (ON), SEG0, SEG2
Is turned off (OFF), and a desired display can be performed in the COM0. However, the GND level is applied to the common (only COM1 and COM2 are shown in the figure) which is the information display portion. Therefore, the liquid crystal of these information display portions is repeatedly turned ON / OFF by the potential change in SEG0 to SEG3,
Although it seems that the light is off as a whole, flickering occurs and the image quality deteriorates.

As shown in FIG. 7, the segment (SEG)
If the voltage applied to the common (COM) can be changed in accordance with the change in the potential, the above deterioration of the image quality can be prevented, but since the voltage changes randomly in many segments, it becomes an information display portion. It is impossible to control the voltage applied to all commons according to the potential change of the segment.

In view of the above circumstances, the present invention provides a duty-driving method for displaying the entire liquid crystal, and a static driving method for displaying only a part of the liquid crystal. An object of the present invention is to provide a driving method of a liquid crystal panel capable of preventing deterioration of image quality.

[0010]

In order to solve the above-mentioned problems, the liquid crystal panel driving method of the present invention sequentially selects one of a plurality of commons in a time division manner, and applies a predetermined voltage to an arbitrary segment. When a static drive is performed by selecting only a part of commons for a liquid crystal panel that uses a duty driving method for driving a liquid crystal part at an intersection of an arbitrary segment and the selected common by giving It is characterized in that the unselected common is brought to a high impedance state.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a common signal supply portion for driving the liquid crystal element portions 101 ... In the liquid crystal drive circuit according to this embodiment. In this drive circuit, in addition to the highest potential power source and the lowest potential power source, four voltage levels (intermediate voltage levels) between these potentials are prepared.
Two resistors 102 are provided, and the intermediate voltage level is obtained by dividing the voltage of the resistors 102. Then, each power supply voltage value divided by each resistor 102 is applied to a voltage follower 103 configured by applying negative feedback to an operational amplifier, and this voltage follower 103 is used as a liquid crystal drive power supply, and an appropriate value according to display data is obtained. Different voltage levels are applied to the common terminal 104 connected to each liquid crystal element portion 101 of the liquid crystal display panel.

Then, each of the above voltage followers 10
One end side of the switch 105 is connected to each output terminal of No. 3, the maximum potential power source, and the output terminal of the minimum potential power source, and the other end sides of these switches 105 are connected to each other. A switch 106 for switching the common terminal 104 between a high impedance state and a voltage application state is provided between a connection point between the other ends of these switches 105 and the common terminal 104. There is. At the time of duty driving, the switch 106 is turned on, and one of the switches 105 which is turned on is turned on.
The electric potential from is applied to the common terminal 104, but the switch 106 is turned off during static drive.
By opening (opening), the common terminal 104
To a high impedance state.

The above-mentioned duty driving has been described in the section of the conventional example, but there are a plurality of commons (COM0 to COMn).
One of the above is sequentially selected by time division, and a predetermined voltage is applied to any segment (SEG0 to SEGm) to drive the liquid crystal portion at the intersection of the any segment and the selected common. The drive is a drive system in which, for example, only COM0 is selected and, as shown in FIG. 6, COM0 and SEG0 to SEGm are alternately supplied with a High potential and a Low potential. Different, other COM than COM0
For 1 to COMn, the switches 106 are opened to bring COM1 to COMn into a high impedance state.

Since the liquid crystal panel has electrodes on the front side and electrodes on the back side so as to sandwich the liquid crystal layer, a parasitic capacitance is generated in the liquid crystal element portion 101 as shown in FIG. . Then, as a property of the capacitance, there is a so-called coupling effect in which when one electrode is kept in a high impedance state, a potential corresponding to the potential applied to the other electrode is generated in the one electrode. Therefore, during static drive, even if the segment potential changes due to AC drive because the common is placed in a high-impedance state as described above, the potential corresponding to the change is applied to the other unselected common side. Will occur on the electrode.

That is, as shown in FIG. 2, for example,
When a voltage displacement of ΔV occurs due to AC driving in the electrodes on the SEG1 side, COM1 to C in high impedance state
A voltage of ΔV ′ corresponding to the above voltage ΔV is generated at the electrode on the OMm (only COM1 is shown in the figure) side. Since the voltages ΔV and ΔV ′ are substantially equal to each other, there is no potential difference in the liquid crystal element portion 101, and the liquid crystal does not light up. Further, even if there is a predetermined potential difference between the voltages ΔV and ΔV ′, this potential difference is held constant, so that if the potential difference does not exceed the threshold value of the liquid crystal, the image quality is not deteriorated. Not noticeable.

As described above, according to the liquid crystal panel driving method of the present invention, by switching between duty driving and static driving, an appropriate driving method can be selected according to the display mode, and the static driving can be performed. Even when is used, it is possible to prevent the deterioration of the image quality in the portion where the display is not performed.

In the above embodiment, the switch 1
By providing 06, the common that is not displayed is placed in a high-impedance state. However, by performing control to set all the switches 105 to high impedance, the common that is not displayed is set to high impedance. It can also be in an impedance state.

[0019]

According to the present invention, by switching between duty driving and static driving, an appropriate driving method can be selected according to the display mode to achieve low power consumption and use of the static driving. Even when I was there
This has an effect of preventing deterioration of image quality in a portion where no display is performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a liquid crystal drive circuit used in a liquid crystal panel drive method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a coupling effect.

FIG. 3 is an explanatory diagram showing a duty drive type liquid crystal panel.

FIG. 4 is a timing chart showing changes in applied voltage during duty driving.

FIG. 5 is a timing chart showing changes in applied voltage during static driving.

FIG. 6 is an explanatory diagram for explaining lighting / extinguishing states of liquid crystal during static driving.

FIG. 7 is a timing chart showing a principle for turning off an unnecessary portion of liquid crystal during static driving.

[Explanation of symbols]

 101 liquid crystal element section 103 voltage follower 104 common terminal 105 switch 106 switch

Claims (1)

[Claims] 1. A duty driving for driving a liquid crystal portion at an intersection of an arbitrary segment and the selected common by sequentially selecting one of a plurality of commons in a time division manner and applying a predetermined voltage to the arbitrary segment. A method for driving a liquid crystal panel, characterized in that when only a part of commons is selected and statically driven, the other unselected commons are set to a high impedance state in the liquid crystal panel in which the method is used.