JPH04104624U - Control device for liquid crystal display device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the display contrast of a liquid crystal display device from deteriorating due to temperature changes in the liquid crystal. [Structure] A control device 20 for a liquid crystal display device includes a reference voltage setting circuit 30 that sets a reference bias voltage that is the amplitude value of a rectangular wave voltage applied to a common electrode and a segment electrode of a liquid crystal display device 10, L to match or shift the phase of the rectangular wave voltage used as the amplitude value between each electrode
It consists of a CD drive circuit 40. The resistance value of the positive temperature coefficient thermistor 32 of the reference voltage setting circuit 30 increases as the temperature of the liquid crystal increases, and the amplitude value of the rectangular wave voltage applied to the displayed segment decreases. Further, the resistance value of the positive temperature coefficient thermistor 32 decreases as the temperature of the liquid crystal decreases, and the amplitude value of the rectangular wave voltage applied to the non-displayed segment increases.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention applies voltage to the electrodes of a liquid crystal display device to display numbers and characters on the liquid crystal display. The present invention relates to a control device for a liquid crystal display device that displays characters, etc.

0002

[Conventional technology]

Conventionally, liquid crystal display devices have used liquid crystal display devices in which segments are formed by segment electrodes. Crystal display devices are widely known. A liquid crystal display device with this segment electrode configuration is equipped with The common electrode is provided over the entire surface of the device, and the shape of the letters, numbers, etc. that you want to display is shaped. A plurality of segment electrodes are arranged to face each other with the liquid crystal in between. Set up Then, a rectangular wave voltage whose amplitude is the reference bias voltage is applied to the common electrode. In this state, the voltage applied to the common electrode is applied to the segment electrode of the segment to be displayed. Apply a rectangular wave voltage with a phase shift of 180 degrees from the rectangular wave voltage, and do not display it. A rectangle that is in phase with the rectangular wave voltage applied to the common electrode on the segment electrode of the segment. Apply wave voltage. This allows only the LCD of the segment to be displayed to be driven, and the text to be displayed. Display letters, numbers, etc. In conventional liquid crystal display devices, the reference bias voltage is fixed, so At this time, a rectangular wave voltage with a constant amplitude is applied between each electrode.

0003

[Problem that the idea aims to solve]

This reference bias voltage is always approximately constant (i.e., a rectangular wave applied to each electrode). (with constant amplitude), when the temperature of the liquid crystal decreases, the density of the displayed segment increases. There was a problem that the visibility decreased, making it difficult to see, and the display contrast decreased. . Additionally, when the temperature of the liquid crystal rises, the density of segments that are not displayed increases, causing There was a problem in that the display contrast was lowered. This invention prevents the display contrast of liquid crystal display devices from decreasing due to temperature changes in the liquid crystal. The object of this invention is to obtain a control device for a liquid crystal display device that can be stopped.

0004

[Means to solve the problem]

The drive control device for a liquid crystal display device according to the present invention controls the voltage applied to the liquid crystal display device. A control device that increases the applied voltage as the temperature of the liquid crystal increases, and The invention is characterized in that it is equipped with a voltage control means that lowers the applied voltage as the temperature of the liquid crystal decreases. It is a sign.

[0005]

【Example】

The present invention will be explained below with reference to the illustrated embodiments. The liquid crystal display device (hereinafter referred to as LCD) 10, as shown in FIGS. 2 and 3, Seven segment electrodes 11, one flat common electrode 12, and these segment electrodes A liquid crystal layer 13 is formed between a common electrode 11 and a common electrode 12. these The segment electrode 11, the common electrode 12, and the liquid crystal layer 13 each form one set. A total of seven sets of segments 14 are formed. Segment electrode 11 and common electrode 12 is driven by a static drive method. That is, the sections that should be displayed Each electrode 11, 12 of the component 14 is connected to an LCD drive circuit of a drive control device 20, which will be described later. 40, each individually and simultaneously.

[0006] A drive control device (hereinafter simply referred to as a drive control device) 20 for a liquid crystal display device is shown in FIG. As shown in FIG. A reference voltage setting circuit 30 that sets a bias voltage and a reference bias voltage to be applied. A rectangular wave voltage with amplitude value is generated, and the phase of this rectangular wave voltage is matched between each electrode. and an LCD drive circuit 40 for moving or shifting the LCD.

[0007] The reference voltage setting circuit 30 includes a positive characteristic thermistor 32 connected to a constant voltage power supply 31. and a fixed resistor 33 connected in series to a positive characteristic thermistor 32. . The resistance value of the positive characteristic thermistor 32 increases as the temperature of the liquid crystal increases. and the resistance value decreases as the temperature of the liquid crystal decreases. Ru.

[0008] The LCD drive circuit 40 is connected to the reference voltage setting circuit 30, and the LCD drive circuit 40 is connected to the reference voltage setting circuit 30. An LCD 10 is connected to the output side of 0. The LCD drive circuit 40 has a reference bias The phase of the rectangular wave voltage whose amplitude value is the voltage is set between each electrode 11 and 12 of each segment 14. A reference bias voltage is applied to each electrode 11, 12 in a matched or shifted state. Apply.

[0009] A predetermined reference bias is applied to the LCD drive circuit 40 by the reference voltage setting circuit 30. A voltage is applied. Based on this voltage, this LCD driving circuit 40 is shown in FIG. , generates rectangular wave voltages (symbols A, B, C) whose amplitude is the reference bias voltage. let A rectangular wave voltage of waveform A is constantly applied to the common electrode 12 . here, When a rectangular wave voltage of waveform B having the same phase as waveform A is applied to the segment electrode 11, No voltage is applied to the liquid crystal layer 13 of the segment 14, and as a result, Riko's segment 14 is not displayed. On the other hand, the waveform on the segment electrode 11 When a rectangular wave voltage of waveform C that is out of phase with A is applied, this segment 14 A rectangular wave voltage of waveform D is relatively applied to the liquid crystal layer 13, and this segment ment 14 is displayed.

0010 When the temperature of the liquid crystal decreases, the resistance of the positive temperature coefficient thermistor 32 of the reference voltage setting circuit 30 decreases. The resistance becomes smaller and the set reference bias voltage increases. Therefore, LCD The amplitude of the rectangular wave voltage applied to each of the 10 electrodes 11 and 12 increases, and the displayed This prevents the density of the segment 14 from decreasing. This ensures good display contrast This will bring out the best in you.

[0011] Furthermore, when the temperature of the liquid crystal rises, the positive characteristic thermistor 3 of the reference voltage setting circuit 30 2 becomes larger, and the set reference bias voltage drops. therefore, The amplitude of the rectangular wave voltage applied to each electrode 11, 12 of the LCD 10 becomes smaller, and the Density increases in segments 14, which are not shown, are prevented. This provides good display quality. Trust is demonstrated.

0012 FIG. 5 shows a drive control device 50 according to another embodiment of the present invention. This drive control device The reference voltage setting circuit 60 of the device 50 includes four fixed resistors 63, 6 connected in series. 4, 65, 66 and three switches electrically interposed between the respective fixed resistors. The channels 67, 68, and 69 are installed near the LCD 10 to detect the temperature of the liquid crystal and generate electricity. Based on the temperature detection circuit 61 to be converted into a signal and the signal from the temperature detection circuit 61, Consists of a microcomputer 62 that controls switches 67, 68, and 69 on and off. .

[0013] The switch 67 is provided between the constant voltage power supply 31 and the fixed resistors 63 and 64. Ru. The switch 68 is connected between the constant voltage power supply 31 and the fixed resistors 64 and 65. The switch 69 is provided between the constant voltage power supply 31 and the fixed resistors 65 and 66. .

[0014] The microcomputer 62 switches switches 67 and 68 based on the signal from the temperature detection circuit 61. , 69 is configured to control on/off. In other words, if the temperature of the liquid crystal is high, In this case, switches 67, 68, and 69 are all turned off to lower the temperature of the liquid crystal. Accordingly, one of the switches 67, 68, and 69 is turned on.

[0015] This drive control device 50 receives a signal from the temperature detection circuit 61 when the temperature of the liquid crystal is high. Based on the above, the microcomputer 62 turns off switches 67, 68, and 69. Ru. As a result, the voltage from the constant voltage power supply 31 is applied to the four voltages of the reference voltage setting circuit 60. It is applied to the LCD drive circuit 40 via fixed resistors 63, 64, 65, and 66. That is, the reference bias voltage set by the reference voltage setting circuit 60 is It is the minimum value in the state.

[0016] Then, when the temperature of the liquid crystal becomes a little lower, it is detected based on the signal from the temperature detection circuit 61. , the microcomputer 62 turns on only the switch 67. This allows constant voltage power supply The voltage from 31 is applied through three fixed resistors 64, 65, 66 of reference voltage circuit 60. and is applied to the LCD drive circuit 40. That is, the reference voltage setting circuit 60 sets The reference bias voltage to be set is set by turning off switches 67, 68, and 69. Compared to the previous case, the increase is slightly higher.

[0017] When the temperature of the liquid crystal further decreases, the micro The controller 62 turns on either the switch 68 or 69. This is it The voltage from the constant voltage power supply 31 is applied to two fixed resistors 65 of the reference voltage circuit 60; 66 or one fixed resistor 66 to the LCD drive circuit 40 . That is, the reference bias voltage set by the reference voltage setting circuit 60 further increases. do.

[0018] In each of the above embodiments, a liquid crystal display device to which the drive control device of the present invention is applied is described. We used a device in which each electrode was driven by a static drive method, but each A liquid crystal display device in which the electrodes are driven by a multiplex driving method may also be used. . In this case, the effect of applying the drive control device of the present invention becomes more significant.

[Effect of the idea]

As described above, according to the present invention, the display control of the liquid crystal display device due to the temperature change of the liquid crystal A control device for a liquid crystal display device that prevents deterioration of trust can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a control device for a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view showing an electrode configuration of a liquid crystal display device.

FIG. 3 is a partial cross-sectional view of the liquid crystal display device of FIG. 2;

FIG. 4 is a diagram showing the waveform of a rectangular wave voltage applied to each electrode of a liquid crystal display device and the waveform of a voltage actually applied to a liquid crystal layer.

FIG. 5 is a circuit diagram of a control device for a liquid crystal display device according to another embodiment of the present invention.

[Explanation of symbols]

10 Liquid crystal display device 11 Segment electrode (electrode) 12 Common electrode (electrode) 20 Drive control device (control device for liquid crystal display device) 30 Reference voltage setting circuit (voltage control means) 60 Reference voltage setting circuit (voltage control means)

Claims (1)

[Scope of utility model registration request] 1. A device for controlling a voltage applied to a liquid crystal display device, comprising voltage control means that increases the applied voltage as the temperature of the liquid crystal increases and decreases the applied voltage as the temperature of the liquid crystal decreases. A control device for a liquid crystal display device, comprising: