JPH11337912A - Contrast control method for liquid crystal display module and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify circuit constitution and to improve flexibility in design changes by controlling display contrast adjustment of a liquid crystal display module with a display-off signal. SOLUTION: A display-off signal generation circuit 22 is provided in an output part of a contrast adjustment signal generation circuit 25. When a prescribed contrast value is instructed by a transparent touch panel 23, an MPU 26 specifies the number of pulses of a clock signal. The display-off signal generation circuit 22 generates the display-off signal becoming an L level only for a time according to the number of pulses. The display-off signal is superimposed on respective scanning line signals of a liquid crystal display panel 21a through COM drivers 21c. When the display-off signal is an L level, since a liquid crystal cell is turned off, by controlling this off time, the contrast is adjusted by using only a digital signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contrast control method for a liquid crystal display module and a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, portable terminals (PDAs) have been required to input and output more data smoothly and easily. Many of such mobile terminals are configured to achieve both functions of a display device and an input device by combining a liquid crystal display module and a transparent touch panel (TTP).

[0003] In a liquid crystal display module as a display device, the problem of power consumption has been given top priority with the demand for low power consumption and high image quality. For this reason, a so-called monochrome positive reflection display type liquid crystal display module without a backlight is often used. The TTP as an input device is disposed on the upper surface of the liquid crystal display module, and can easily input data and operate the PDA by touching the surface.

In a liquid crystal display module used for a PDA having such a configuration, a voltage applied to a liquid crystal cell has been conventionally adjusted in order to adjust a display contrast. In such voltage adjustment, an external variable resistor is provided, and a voltage obtained by the variable resistor is supplied to a liquid crystal display module. In another example, a soft key for adjusting display contrast is set in TTP, and a voltage corresponding to the display contrast data is supplied to the liquid crystal display module by DA-converting a read signal of TTP. Recently, examples of adopting the latter control method are increasing.

[0005] The reason is that when a variable resistor is provided in a PDA, it is necessary to protrude the variable resistor beyond the outer shape of the PDA from the viewpoint of operability. For this reason, the outer shape of the PDA becomes large, and a reliability problem due to a defective contact of the variable resistor occurs. Since a variable resistor generally has a sliding portion, and noise from the sliding portion increases with long-term use, it can be said that the electronic component has poor reliability. Also, the existence of the variable resistor itself was a factor that hindered cost reduction.

Here, a method of adjusting the contrast of the liquid crystal display module by applying a voltage corresponding to the display contrast data to the liquid crystal cell will be described.
FIG. 5 is a block diagram showing a configuration of a liquid crystal display device which is a main part of a PDA including a conventional contrast control circuit. The PDA includes a liquid crystal display module 11, a DA conversion circuit 12, a transparent touch panel (TTP) 13, a pen position reading circuit 14, a contrast adjustment signal output circuit 15, and L
It is configured to include a CD controller 16, an MPU 17, and a VRAM 18. In the liquid crystal display module 11, a signal electrode driving circuit (SEG) is provided on the liquid crystal display panel 11a.
Driver 11b and a scanning electrode drive circuit (COM driver) 11c. These drive circuits are supplied with an AC signal from an AC signal generation circuit 11e and a power voltage from a power circuit 11d.

When a soft key for adjusting display contrast is displayed on the liquid crystal display module 11, the pen 13a indicates a specific data position on the transparent touch panel 13. Then, the pen position is read by the pen position reading circuit 14, and the position data is digitally output. This position data is output from the contrast adjustment signal output circuit 1
5 is output to the MPU 17. When the MPU 17 determines that the position data is a signal that increases (darkens) the display contrast, for example, it gives an instruction to the contrast adjustment signal output circuit 15, and the digital data that makes the applied voltage higher than the current display contrast value is converted into a DA conversion circuit. 12
Is output to The DA conversion circuit 12 converts the data into an analog value and supplies the analog value to the power supply circuit 11d. Power supply circuit 11
d generates an applied voltage corresponding to the analog value,
It is supplied to the driver 11b and the COM driver 11c.
Thus, the display contrast of the liquid crystal display module 11 is controlled.

[0008]

However, in the above-described conventional display contrast control method, since the data from the TTP 13 is converted into an analog voltage via the DA conversion circuit 12, the configuration of the contrast control circuit is complicated. There were drawbacks. Further, when it is desired to change the variable width of the analog voltage output by correcting the bit configuration of the digital input relating to the contrast adjustment, a significant circuit change is required. For this reason, it has been difficult to substantially change the display contrast adjustment width of the liquid crystal display module 11.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and has a fixed power supply voltage output from a power supply circuit, and controls an effective voltage applied to a liquid crystal cell using only digital data. Accordingly, it is an object of the present invention to adjust the display contrast of the liquid crystal display module. It is a further object of the present invention to simplify the circuit configuration relating to contrast adjustment and to realize a liquid crystal display device capable of easily changing the display contrast adjustment width of the liquid crystal display module.

[0010]

In order to solve such a problem, the invention of claim 1 of the present application is directed to a case where a signal for turning off the display of a liquid crystal display module including a plurality of liquid crystal cells is used as a display off signal. By inserting the display-off signal in a period shorter than the selection period of the liquid crystal cell according to the contrast of the image display during the period of applying the scanning signal to each scanning electrode of the liquid crystal display module, the contrast of the liquid crystal display module is improved. Is controlled.

According to a second aspect of the present invention, in the contrast control method for a liquid crystal display module according to the first aspect, the display-off signal is a signal for changing a pulse width for turning off the display in accordance with the contrast of the image display. It is characterized by having.

According to a third aspect of the present invention, in the contrast control method for a liquid crystal display module according to the first aspect, the display-off signal is a signal for changing the number of pulses for turning off the display in accordance with the contrast of the image display. It is characterized by having.

According to a fourth aspect of the present invention, in the contrast control method for a liquid crystal display module according to the first aspect, the display-off signal is a signal for changing a frequency of a pulse for turning off the display in accordance with the contrast of the image display. It is characterized by being.

According to a fifth aspect of the present invention, there is provided a liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes. A scan electrode drive circuit for applying a drive voltage to the scan electrode, a signal electrode drive circuit for applying a drive voltage in accordance with display data to the signal electrode, and a scan synchronization signal to the scan electrode drive circuit. An LCD controller for providing display data to the signal electrode drive circuit in synchronization with the display electrode, and a signal for turning off the display of the liquid crystal display panel being a display off signal, which is shorter than a selection period of the liquid crystal cell by the scan electrode drive circuit. A display off signal generating circuit for generating the display off signal according to the contrast of the image display at a time; When, it is characterized in that it comprises a contrast adjustment signal output circuit for providing a contrast control signal to the display OFF signal generating circuit.

According to a sixth aspect of the present invention, there is provided a liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes. A scan electrode drive circuit for applying a drive voltage to the scan electrode, a signal electrode drive circuit for applying a drive voltage in accordance with display data to the signal electrode, and a display off signal for turning off a display on the liquid crystal display panel. A scan synchronization signal is supplied to the scan electrode drive circuit, display data is supplied to the signal electrode drive circuit in synchronization with the scan synchronization signal, and a time period shorter than a selection period of the liquid crystal cell by the scan electrode drive circuit is provided. An LCD controller that superimposes the display off signal according to the contrast of image display on a selection signal of the liquid crystal cell. Is shall.

According to a seventh aspect of the present invention, there is provided a liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes. When a signal for turning off the display of the liquid crystal display panel is used as a display off signal, a drive voltage is applied to the scan electrode, and the scan electrode is controlled in accordance with the contrast of image display in a time shorter than a selection period of a liquid crystal cell. A scan electrode drive circuit for superimposing the display-off signal on the drive voltage, a signal electrode drive circuit for applying a drive voltage to the signal electrode, and a scan electrode drive circuit for applying a scan synchronization signal to the scan electrode drive circuit. And an LCD controller for providing display data in synchronization with the scanning synchronization signal.

The invention according to claim 8 of the present application is directed to a liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes. A transparent touch panel integrated with the liquid crystal display panel, a scan electrode drive circuit for applying a drive voltage to the scan electrodes, a signal electrode drive circuit for applying a drive voltage to the signal electrodes in accordance with display data, and the liquid crystal. When a signal for turning off the display of the display panel is a display-off signal, a display-off signal for generating the display-off signal in accordance with the contrast of image display in a time shorter than a selection period of the liquid crystal cell by the scan electrode driving circuit. When a predetermined contrast value is designated by the generation circuit and the transparent touch panel, a contrast control signal is transmitted to the display panel. It is characterized in that it comprises a contrast adjustment signal output circuit for applying a play-off signal generating circuit.

According to a ninth aspect of the present invention, there is provided a liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes. A transparent touch panel integrated with the liquid crystal display panel, a scan electrode drive circuit for applying a drive voltage to the scan electrodes, a signal electrode drive circuit for applying a drive voltage to the signal electrodes in accordance with display data, and the liquid crystal. When a signal for turning off the display of the display panel is a display-off signal, a scan synchronization signal is given to the scan electrode drive circuit, and display data is given to the signal electrode drive circuit in synchronization with the scan synchronization signal. In a time period shorter than the liquid crystal cell selection period by the scan electrode drive circuit, the digital display according to the contrast of the image display instructed by the transparent touch panel is performed. A play-off signal, is characterized in that it comprises a and a LCD controller to be superimposed on the selection signal of the liquid crystal cell.

According to a tenth aspect of the present invention, there is provided a liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes. A transparent touch panel integrally attached to the liquid crystal display panel, and when a signal for turning off the display of the liquid crystal display panel is a display off signal,
A drive voltage is applied to the scan electrode, and the display-off signal according to the contrast of the image display instructed by the transparent touch panel is superimposed on the drive voltage for a time shorter than a selection period of the liquid crystal cell by the scan electrode. A scan electrode drive circuit, a signal electrode drive circuit that applies a drive voltage according to display data to the signal electrode, a scan synchronization signal to the scan electrode drive circuit, and the signal electrode drive circuit synchronizes with the scan synchronization signal. And an LCD controller for providing display data.

[0020]

(Embodiment 1) A contrast control method and a contrast control circuit of a liquid crystal display module according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a main part including a contrast control circuit of the liquid crystal display device of the present embodiment. This liquid crystal display device includes a liquid crystal display module 21, an LCD controller 22, a transparent touch panel (TTP) 23, a pen position reading circuit 24, a contrast adjustment signal output circuit 25, an MPU
26, and a VRAM 27. The liquid crystal display module 21 includes a liquid crystal display panel 21a, a signal electrode drive circuit (SEG driver) 21b, a scan electrode drive circuit (COM driver) 21c, and an AC signal generation circuit 21e.
Is similar to the conventional example of FIG.
The SEG driver 21b is a circuit that applies a drive voltage to a signal electrode according to display data. The COM driver 21c is a circuit that applies a drive voltage to sequentially select a plurality of scan electrodes.

Unlike the conventional example, the liquid crystal display module 21
Are provided with a power supply circuit 21d for generating a fixed power supply voltage and a display-off signal generation circuit 21f. The display-off signal generating circuit 21f is a circuit that controls on / off of the display of the liquid crystal display panel 21a, and a portion that also exhibits this function in the conventional liquid crystal display device is any one of the circuit units constituting the liquid crystal display device. It was provided in. Here, the display-off signal generation circuit 21f is used for controlling the contrast of the liquid crystal display panel 21a.

FIG. 2 shows a display off signal generation circuit 21.
6 is a time chart showing a relationship between a display-off signal output by f and a signal output from another circuit. FIG.
The display-off signal shown in (c) is an active-low signal that goes low when the display of the liquid crystal display module is turned off (off) and goes high when the display is performed (on).

A description will be given of a display contrast control method in the liquid crystal display module configured as described above.
When adjusting the display contrast, the liquid crystal display module 21 is used.
When the soft key for adjusting the display contrast is displayed on the touch panel 23, the user touches the transparent touch panel 23 using the pen 23a.
Point to the data location above. Then, the position data is read by the pen position reading circuit 24, and the position data is digitally output. This position data is output to the MPU 26 via the contrast adjustment signal output circuit 25. When the MPU 26 determines that the position data is a signal for controlling the display contrast, it gives an instruction to the contrast adjustment signal output circuit 25 to output a contrast control signal for controlling the display contrast value to the display-off signal generation circuit 21f.

When the MPU 26 determines that the position data is to increase the display contrast, the MPU 26 increments the digital data so that the display data is darker than the current display contrast value, and outputs the data to the contrast adjustment signal output circuit 25. Contrast adjustment signal output circuit 2
5 outputs a contrast control signal to the display-off signal generation circuit 21f according to the data. The contrast control signal may be any type of signal as long as it controls the pulse width, the number of pulses, the frequency of the pulses, and the like. In the signal shown in FIG. 2C, the pulse width is controlled.

More specifically, a monochrome positive reflective display type liquid crystal display module 2 commonly used in PDAs
1 is usually 320 × 240 dots. As shown in FIG. 2A, the frequency of a frame signal (also referred to as a frame pulse or a scan synchronization signal) is generally about 70 Hz, and is output from the LCD controller 22 at a cycle of about 14 m. Since 240 scanning line electrodes are driven during this 14 ms, a display-off signal is incorporated in synchronization with each scanning line signal. The display-off signal is inserted in a shorter time than the liquid crystal cell selection period according to the contrast of the image display during the application period of the scanning signal to each scanning electrode of the liquid crystal display module 21, that is, during the liquid crystal cell selection period.

Since the liquid crystal cell responds to the effective value of the drive voltage, the display contrast becomes thinner as the pulse width of the display-off signal is increased. Specifically, the liquid crystal driving voltage output from the power supply circuit 21d is fixed at 22V,
The pulse width of the display-off signal is varied from 0 μS to 6 μS. Thus, it was confirmed that the display contrast could be adjusted well. In the experiment, in order to generate a display-off output signal synchronized with the frame signal, a display-off signal was generated using a one-shot multivibrator, an external capacitor of 10 pF, and a variable resistor of 500 kΩ.

As shown in FIG. 2B, a contrast control circuit mounted on a liquid crystal display device uses a shift clock signal generated in synchronization with a frame signal. That is, the number of pulses of the shift clock signal is counted from the time of generation of each scanning line signal, and the count value is controlled according to the contrast, so that the display-off signal becomes L level for a predetermined time as shown in FIG. Output. Thus, the display contrast can be adjusted with the liquid crystal drive voltage kept constant.

In this embodiment, the count value of the shift clock signal can be easily changed by changing the software of the MPU 26 or the like. Since the hardware change of the DA conversion circuit is not involved as in the related art, it is possible to easily cope with a change in the drive voltage due to a change in the liquid crystal material. In addition, it is possible to easily cope with a drive voltage variation due to a cell gap variation of the liquid crystal display panel.

To finely change the variable width of the display-off signal, a high-frequency clock signal may be used. In this example, in order to simplify the circuit, L
The shift clock signal output from the CD controller 22 was used. The frequency of this shift clock signal is 32
In a 0 × 240 dot liquid crystal display module, the frame frequency is about 1.5 MHz in the case of a 70 Hz frame and a 4-bit data bus. However, since the operating frequency of recent MPUs is even higher, the clock may be used.

Since the display contrast can be adjusted only by the digital value, it is easy to incorporate the output function of the display-off signal into the LCD controller or driver. This method means that the number of LSIs to be used can be reduced, which can lead to cost reduction and improvement in reliability of the liquid crystal display module. FIG. 3 shows an example in which the LCD controller incorporates a contrast control function.

The liquid crystal display device shown in FIG. 3 includes a liquid crystal display module 41, an LCD controller 42, a transparent touch panel (TTP) 43, a pen position reading circuit 44, an MPU 4
5, including the VRAM 46. Also, the liquid crystal display module 41 is provided with a liquid crystal display panel 41a, a signal electrode drive circuit (SEG driver) 41b, a scan electrode drive circuit (COM driver) 41c, a power supply circuit 41d, and an AC signal generation circuit 41e. , And FIG.

The LCD controller 42 is a circuit for generating a frame signal and a display-off signal, and its output is supplied to an AC signal generation circuit 41e. In this example,
There is no need to provide a contrast control circuit independently.
The PU 45 controls the number of output pulses in accordance with the contrast value, and outputs the pulses to the LCD controller 42. Also in this case, the LCD controller 42
From the display-off signal shown in FIG.
It is output to the EG driver 41b and the COM driver 41c.

FIG. 4 shows an example in which the contrast control function is incorporated in the driver. As shown in the figure, the COM driver 52 in the liquid crystal display module has both the function of the COM driver shown in FIG. 1 or 3 and the function of generating a display-off signal. LCD controller 51
Generates a latch signal, a frame signal, and a shift clock signal under the control of the MPU 53. The MPU 53 identifies a contrast value from the position data obtained from the pen position reading circuit 53 and outputs a clock number setting signal corresponding to the contrast value to the COM driver 52. COM
The driver 52 outputs a frame signal and an LCD
The shift clock signal output from the controller 51 is counted, and a display-off signal as shown in FIG. 2C is generated.

Also in this example, since the clock number setting signal is directly output from the MPU 53, a contrast adjustment signal output circuit and a DA conversion circuit are not required as compared with the case of FIG. Therefore, the cost of the liquid crystal display module can be reduced, and the reliability can be improved.

[0035]

As described above, according to the present invention, the display contrast can be adjusted by applying the pulse of the display-off signal to the liquid crystal display module. Therefore, it is possible to realize a liquid crystal display module with excellent flexibility that can easily change the contrast adjustment range without using a variable resistor or a power supply circuit of an applied voltage. Further, since the output voltage of the power supply circuit can be fixed, the configuration of the contrast control circuit can be simplified. Further, since the signal related to the contrast control is a digital signal, the change of the contrast control range can be easily changed by the MPU software.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a liquid crystal display device (part 1) according to an embodiment of the present invention.

FIG. 2 is a timing chart of signals showing a contrast control method according to the embodiment.

FIG. 3 is a liquid crystal display device (part 2) according to the present embodiment.
FIG.

FIG. 4 is a liquid crystal display device according to the present embodiment (part 3).
FIG.

FIG. 5 is a configuration diagram of a conventional liquid crystal display device.

[Explanation of symbols]

 21, 41 Liquid crystal display module 21a, 41a Liquid crystal display panel 21b, 41b Segment driver 21c, 41c, 52 Common driver 21d, 41d Power supply circuit 21e, 41e Alternating signal generation circuit 21f Display off signal generation circuit 22, 42, 51 LCD controller 23, 43 Transparent touch panel (TTP) 23a, 43a Pen 24, 44, 54 Pen position reading circuit 25 Contrast adjustment signal generation circuit 26, 45, 53 MPU 27, 46 VRAM

Claims (10)

[Claims] When a signal for turning off a display of a liquid crystal display module including a plurality of liquid crystal cells is used as a display off signal, a contrast of image display is increased during a period of application of a scan signal to each scan electrode of the liquid crystal display module. A contrast control method for a liquid crystal display module, wherein the contrast of the liquid crystal display module is controlled by inserting the display off signal in a time shorter than a selection period of a liquid crystal cell in accordance with the following. 2. The contrast control method for a liquid crystal display module according to claim 1, wherein the display off signal is a signal for changing a pulse width for turning off a display in accordance with a contrast of an image display. 3. The contrast control method for a liquid crystal display module according to claim 1, wherein the display off signal is a signal for changing the number of pulses for turning off the display in accordance with the contrast of the image display. 4. The contrast control method for a liquid crystal display module according to claim 1, wherein the display off signal is a signal for changing a frequency of a pulse for turning off a display in accordance with a contrast of an image display. 5. A liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes, and a driving voltage applied to the scanning electrodes. A scan electrode drive circuit that applies a drive voltage according to display data to the signal electrode; a scan synchronization signal that is applied to the scan electrode drive circuit; and display data that is synchronized with the scan synchronization signal. An LCD controller to be provided to the signal electrode driving circuit; and a display off signal for turning off the display of the liquid crystal display panel. A display-off signal generating circuit for generating the display-off signal according to a predetermined contrast value; The liquid crystal display device characterized by comprising a contrast adjustment signal output circuit that provides a list control signal to the display-off signal generating circuit. 6. A liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes, and a driving voltage applied to the scanning electrodes. A scan electrode drive circuit that applies a drive voltage corresponding to display data to the signal electrode; and a scan off signal when a signal for turning off the display of the liquid crystal display panel is a display off signal. A scan synchronization signal is applied to the circuit, and display data is applied to the signal electrode drive circuit in synchronization with the scan synchronization signal, and in a time shorter than a selection period of the liquid crystal cell by the scan electrode drive circuit,
A liquid crystal display device comprising: an LCD controller that superimposes the display off signal according to the contrast of image display on a selection signal of the liquid crystal cell. 7. A liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes, and a display on the liquid crystal display panel. When the signal to turn off the display off signal, while applying a drive voltage to the scan electrode, in a time shorter than the selection period of the liquid crystal cell by the scan electrode, the display off signal according to the contrast of image display, A scan electrode drive circuit that superimposes the drive voltage, a signal electrode drive circuit that applies a drive voltage to the signal electrode, a scan synchronization signal to the scan electrode drive circuit, and a signal electrode drive circuit that synchronizes with the scan synchronization signal. And a LCD controller for providing display data. 8. A liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes, and a liquid crystal display panel integrated with the liquid crystal display panel. A transparent touch panel attached to a scan electrode, a scan electrode drive circuit for applying a drive voltage to the scan electrode, a signal electrode drive circuit for applying a drive voltage according to display data to the signal electrode, and turning off the display of the liquid crystal display panel. A display-off signal generating circuit for generating the display-off signal in accordance with the contrast of image display in a time shorter than a selection period of the liquid crystal cell by the scan electrode driving circuit, When a predetermined contrast value is indicated by the display control signal, a display control signal is generated by the display off signal. The liquid crystal display device characterized by comprising a contrast adjustment signal output circuit for giving the road, the. 9. A liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes, and an integral part of the liquid crystal display panel. A transparent touch panel attached to a scan electrode, a scan electrode drive circuit for applying a drive voltage to the scan electrode, a signal electrode drive circuit for applying a drive voltage according to display data to the signal electrode, and turning off the display of the liquid crystal display panel. When a signal to be turned off is a display-off signal, a scan synchronization signal is supplied to the scan electrode drive circuit, display data is supplied to the signal electrode drive circuit in synchronization with the scan synchronization signal, and a liquid crystal cell by the scan electrode drive circuit is provided. In a time shorter than the selection period of,
A liquid crystal display device comprising: an LCD controller that superimposes the display off signal according to the contrast of image display instructed by the transparent touch panel on a selection signal of the liquid crystal cell. 10. A liquid crystal display panel having a plurality of scanning electrodes and a plurality of signal electrodes, and displaying an image by applying a voltage to a liquid crystal cell sandwiched between the two electrodes, and an integral part of the liquid crystal display panel. When a signal for turning off the display of the liquid crystal display panel is used as a display-off signal, a drive voltage is applied to the scan electrode, and a time shorter than a selection period of the liquid crystal cell by the scan electrode is used. A scan electrode drive circuit that superimposes the display off signal according to the contrast of image display instructed by the transparent touch panel on the drive voltage, and a signal electrode drive circuit that applies a drive voltage to the signal electrode according to display data Providing a scan synchronization signal to the scan electrode drive circuit, and displaying the scan electrode drive circuit in synchronization with the scan synchronization signal. The liquid crystal display device, characterized by comprising: a LCD controller providing a data.