JP2000028996A - Matrix type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control driving of a liquid crystal panel in consideration of not only the temperature of the end part of this liquid crystal panel but also the room temperature with respect to a matrix type liquid crystal display device provided with the liquid crystal panel using liquid crystal having high temperature dependency. SOLUTION: A microcomputer 30 sets the detected panel end temperature of a temperature sensor 20 at the time of operation start as the room temperature and determines the panel center temperature in accordance with the detected panel end temperature of the temperature sensor 20 based on data representing the relation between the panel center temperature of a liquid crystal panel 10 and the panel end temperature with the room temperature as a parameter and corrects a driving voltage of the liquid crystal panel 10 in accordance with the panel center temperature based on data representing the relation between this driving voltage and the panel center temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix type liquid crystal display device provided with a liquid crystal panel using a liquid crystal having a large temperature dependency such as a smectic liquid crystal.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device provided with a liquid crystal panel using a nematic liquid crystal, the operating temperature range of the nematic liquid crystal has been dramatically expanded due to technological advances. However, in matrix type liquid crystal display devices equipped with a liquid crystal panel using antiferroelectric liquid crystal, the operating threshold of antiferroelectric liquid crystal has a large temperature dependence, and the current situation is that it relies on temperature control of the liquid crystal panel itself. It is.

On the other hand, a liquid crystal display device for controlling the pulse width of a driving voltage according to the temperature of a liquid crystal panel is disclosed in JP-A-4-46408. Here, in this liquid crystal display device, the average temperature of the liquid crystal panel is calculated based on the detected temperatures of a plurality of thermistors provided at the ends of the liquid crystal panel, and the average temperature and the pulse width of the drive voltage at the center of the liquid crystal panel are calculated. The pulse width of the drive voltage at the center of the liquid crystal panel is determined according to the calculated average temperature based on a table representing the relationship.

[0004]

However, in the above liquid crystal display device, when determining the pulse width of the drive voltage as described above, the temperature difference between the center of the liquid crystal panel and the end of the liquid crystal panel is equal to room temperature. It fluctuates according to. This causes an error in the determined drive voltage pulse width. As a result, the drive control of the liquid crystal panel cannot be performed well.

In other words, the drive control of the liquid crystal panel using the liquid crystal having a large temperature dependency as described above can be properly performed at a specific room temperature only by detecting the temperature at the edge of the liquid crystal panel. Even so, it cannot be performed properly at other room temperatures. As a result, there arises a problem that display unevenness due to temperature unevenness is caused on the display surface of the liquid crystal panel.

[0006] On the other hand, when the temperature environment at room temperature in which the liquid crystal display device is used is examined, the liquid crystal display device is usually used in a room where the temperature change is small for a long time. In addition, it has been found that when power is supplied to the liquid crystal display device, the temperatures at the end and the center of the liquid crystal panel are usually equal. In view of the above, the present invention provides a matrix type liquid crystal display device including a liquid crystal panel using a liquid crystal having a large temperature dependency, and controls the matrix driving of the liquid crystal panel by controlling only the temperature at the end of the liquid crystal panel. The purpose is not to take into account room temperature.

[0007]

According to the first aspect of the present invention, there is provided a liquid crystal panel (10) having a liquid crystal having a large temperature dependency, and a driving voltage and a signal voltage applied to the liquid crystal panel. (40, 50, 60) for driving the matrix according to the temperature and temperature detecting means (20) for detecting the temperature of the edge of the liquid crystal panel as the panel edge temperature.
And room temperature setting means (11) for setting the temperature of the detection panel end of the temperature detection means at the start of operation of the driving means as room temperature.
0) and a panel center for determining the steam panel center temperature according to the detected panel end temperature of the temperature detecting means based on data representing the relationship between the panel center temperature and the panel end temperature using the room temperature as a parameter. Temperature determination means (1
30) and drive voltage correction means (140) for correcting the drive voltage according to the panel center temperature based on data representing the relationship between the drive voltage and the panel center temperature. Further, there is provided a matrix type liquid crystal display device in which a liquid crystal panel is driven in a matrix in accordance with a correction drive voltage by a drive voltage correction means and the signal voltage.

As described above, data representing the relationship between the panel center temperature and the panel end temperature of the liquid crystal panel using room temperature as a parameter is employed, and the drive voltage is corrected in accordance with the panel center temperature determined based on this data. Therefore, the drive voltage is corrected according to the room temperature so as to eliminate the temperature difference between the panel center temperature and the panel end temperature of the liquid crystal panel.

Therefore, even if the liquid crystal of the liquid crystal panel is a liquid crystal having a large temperature dependency (for example, a smectic liquid crystal),
Matrix drive control of the liquid crystal panel can be performed substantially in the same manner as when there is no change in room temperature. As a result, it is possible to favorably prevent display unevenness due to temperature in the liquid crystal panel.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
4 through FIG. FIG. 1 shows an overall schematic configuration of a matrix type liquid crystal display device according to the present invention. This liquid crystal display device is placed indoors. The liquid crystal display device includes a liquid crystal panel 10.
Reference numeral 0 denotes a configuration in which a smectic liquid crystal such as an antiferroelectric liquid crystal or a ferroelectric liquid crystal is sealed between the two electrode substrates 11 (only the electrode substrate on the display surface side is shown in FIG. 1).

Here, one of the two electrode substrates 11 has a plurality of scanning electrodes, and the other electrode substrate 11 has a plurality of signal electrodes. In addition, a plurality of signal electrodes
The plurality of scanning electrodes are arranged so as to intersect with each other, and a plurality of matrix-shaped pixels are formed together with each of the scanning electrodes and the smectic liquid crystal. Further, the liquid crystal display device,
It includes a temperature sensor 20, a microcomputer 30, a drive voltage power supply 40, a scan side drive circuit 50, and a signal side drive circuit 60.

The temperature sensor 20 is composed of a thermistor. The temperature sensor 20 is provided at an end of the surface of the electrode substrate 11 of the liquid crystal panel 10. The temperature sensor 20 detects the temperature at the end of the liquid crystal panel 10 as the panel end temperature. The microcomputer 30
The computer program is executed according to the flowchart shown in FIG.
The processing required for drive control of the drive voltage power supply 40 is performed on the basis of the detected output. The computer program is stored in the ROM of the microcomputer 30 in advance. Further, the microcomputer 30 is supplied with electric power by turning on the power supply, enters an operating state, and starts executing the computer program.

A drive voltage power supply 40 outputs a write voltage, a refresh voltage, and a holding voltage to the scan side drive circuit 50 as drive voltages under the control of the microcomputer 30, and supplies a signal voltage to the signal side drive circuit 60. Is output. The scanning side driving circuit 50 applies the driving voltage from the driving voltage power supply 40 to one of the plurality of scanning electrodes of the two electrode substrates 11 by line sequential scanning, while the signal side driving circuit 60 applies the driving voltage from the driving voltage power supply 40. Is applied to a plurality of signal electrodes on the other electrode substrate 11 in synchronization with the line sequential scanning. As a result, the liquid crystal panel 10 is driven in a matrix, and performs a matrix display on its display surface.

In this embodiment configured as described above,
When the microcomputer 30 is activated by turning on its power, the execution of the computer program is
The microcomputer 30 starts the processing according to the flowchart of FIG. Then, in step 100, various internal elements of the microcomputer 10 are initialized. Next, in step 110, the temperature of the detection panel end of the temperature sensor 20 is set to the microcomputer 3
0, and the room temperature at the current stage (hereinafter, referred to as
Room temperature).

This means that the detection panel end temperature of the temperature sensor 20 is set to room temperature every time the microcomputer 30 is turned on. Here, the temperature sensor 2
The reason why the detection panel end temperature of 0 is set to room temperature is that the panel end temperature of the liquid crystal panel 10 is usually equal to the room temperature when the microcomputer 30 is turned on.

When the processing in step 110 is completed, the temperature of the detection panel end of the temperature sensor 20 is input to the microcomputer 30 in the next step 120. Next, in step 130, the liquid crystal panel 10
3 (hereinafter referred to as the panel center temperature)
Is determined according to the panel end temperature in step 120 based on data specifying the relationship between the panel center temperature and the panel end temperature (hereinafter, referred to as panel center temperature−panel end temperature data).

In the present embodiment, the panel center temperature-panel end temperature data is created as follows. That is, as described above, the temperature difference between the center and the end of the liquid crystal panel varies according to the room temperature. Further, since the temperature dependence of the smectic liquid crystal is large, the matrix drive control of the liquid crystal panel 10 using such a smectic liquid crystal has a large influence of room temperature. It cannot be done properly.

An examination was made of how the panel end temperature and the panel center temperature of the liquid crystal panel 10 were affected by room temperature. At a certain room temperature, the panel center temperature as indicated by L in FIG. A curve representing the relationship between the temperature and the panel end temperature was obtained as data. here,
In the curve L, as shown in FIG. 3, the panel center temperature increases and saturates as the panel end temperature increases.

When the room temperature was changed, the curve L
Move in the direction of the arrow P shown in FIG. For this reason, panel center temperature-panel end temperature data was created as data representing the relationship between panel center temperature and panel end temperature using room temperature as a parameter. The panel center temperature-panel end temperature data is stored in the ROM of the microcomputer 30 in advance.

When the panel center temperature is determined as described above, in the next step 140, the driving voltage power supply 4
The drive voltage of 0 is determined based on data (hereinafter, referred to as drive voltage-panel center temperature data) specifying the relationship between the drive voltage and the panel center temperature as shown in FIG.
The correction is made according to the panel center temperature at 30. However, as shown in FIG. 4, the drive voltage-panel center temperature data includes a characteristic curve M1 indicating the relationship between the write voltage and the panel center temperature, a characteristic curve M2 indicating the relationship between the refresh voltage and the panel center temperature, and It comprises a characteristic curve M3 indicating the relationship between the holding voltage and the panel center temperature.

Here, the drive voltage-panel center temperature data is prepared as shown in FIG. 4 in consideration of the panel center temperature-panel end temperature data of FIG. That is,
In each of the characteristic curves M1 to M3, the drive voltage hardly changes in a region where the panel center temperature of the liquid crystal panel 10 is high, and increases as the panel center temperature of the liquid crystal panel 10 decreases. I have.

When the driving voltage of the driving voltage power supply 40 is corrected as described above, the writing voltage, the refresh voltage, and the holding voltage to be applied to the scanning side driving circuit 50 are between the panel center temperature and the panel end temperature. This value matches the condition in which the room temperature is added to the temperature difference. Then, in step 150, the write voltage, refresh voltage, and holding voltage corrected in step 140 are applied to the scanning drive circuit 50, and the signal voltage is applied to the signal drive circuit 60.

For this reason, the scanning drive circuit 50 applies the write voltage, the refresh voltage and the holding voltage corrected as described above to the one electrode substrate 1 under the line sequential scanning.
1 to each scanning electrode, while the signal side driving circuit 60
Applies a signal voltage to a plurality of signal electrodes on the other electrode substrate 11 in synchronization with the line sequential scanning. Thus, the liquid crystal panel 10 is driven in a matrix.

As described above, in the present embodiment, the panel center temperature and the panel end temperature data of FIG. 3 and the drive voltage-panel center temperature data of FIG. The drive voltage to be applied to the liquid crystal panel 10 is corrected according to the room temperature so as to eliminate the temperature difference from the panel end temperature. Therefore, even if the liquid crystal of the liquid crystal panel 10 is a smectic liquid crystal having a large temperature dependency, the matrix drive control of the liquid crystal panel 10 can be performed substantially in the same manner as when there is no change in room temperature.
As a result, the liquid crystal panel 10 can display satisfactorily on its display surface without display unevenness caused by temperature unevenness due to a change in room temperature.

In implementing the present invention, a table representing the relationship between the panel center temperature and the panel end temperature using room temperature as a parameter is employed instead of the panel center temperature-panel end temperature data shown in FIG. Is also good. In this case, when the panel center temperature cannot be directly obtained from the table, the panel center temperature is obtained by linear interpolation.

In practicing the present invention, the liquid crystal of the liquid crystal panel 10 is not limited to a smectic liquid crystal, but may be a liquid crystal having a large temperature dependency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a matrix type liquid crystal display device according to the present invention.

FIG. 2 is a flowchart showing the operation of the microcomputer of FIG.

3 is a graph showing the relationship between the panel center temperature and the panel end temperature of the liquid crystal panel of FIG. 1 using room temperature as a parameter.

FIG. 4 shows a driving voltage (writing voltage,
6 is a graph showing a relationship between a refresh voltage and a holding voltage) and a panel center temperature.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal panel, 20 ... Temperature sensor, 30 ... Microcomputer, 40 ... Drive voltage power supply, 50 ... Scanning side drive circuit, 60 ... Signal side drive circuit.

Claims (1)

[Claims] 1. A liquid crystal panel (10) having a liquid crystal having a large temperature dependency, driving means (40, 50, 60) for driving the liquid crystal panel in a matrix according to a driving voltage and a signal voltage; Temperature detection means (20) for detecting an end temperature as a panel end temperature; room temperature setting means (110) for setting a detection panel end temperature of the temperature detection means at the start of operation of the driving means as room temperature; Panel center temperature determining means for determining the panel center temperature according to the detected panel end temperature of the temperature detecting means based on data representing the relationship between the panel center temperature and the panel end temperature of the liquid crystal panel using room temperature as a parameter (1
30); and a drive voltage correction means (140) for correcting the drive voltage according to the panel center temperature based on data representing a relationship between the drive voltage and the panel center temperature; Is a matrix type liquid crystal display device in which the liquid crystal panel is driven in a matrix in accordance with the correction driving voltage by the driving voltage correction means and the signal voltage.