JPH05107522A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide an on-vehicle LCD device which executes display with appropriate contrast even when temperature changes. CONSTITUTION:An LCD driver 14 for supplying a driving signal DRVV from an LCD controller 13 to a liquid crystal display element 1 is provided. A temperature detecting element 23 for detecting the temperature of the element 1 is provided. Then, a control circuit 21 which controls the level of the driving signal DRVV supplied from the LCD driver 14 to the element 1 according to the detection output from the temperature detecting element 23 is provided. According to the detection output from the element 23, the control circuit 21 controls to such polarity that the level of the driving signal DRVV supplied from the LCD driver 14 to the element 1 may be low when the temperature of the element 1 is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art With the sophistication of car audio systems, that is, so-called car audio systems, it has become possible to reproduce not only radio broadcasts and tape cassettes but also CDs. In addition, not only simple graphic equalizer correction but also various sound field corrections such as hall tone effect and surround effect can be performed on the reproduced sound.

For this reason, even in the car audio system, a display device is provided on the dashboard of the car, and when a CD is being reproduced, the track number and the elapsed time are displayed, as in a general audio device. It has become necessary to display various information regarding the reproduction state, such as displaying the state of sound field correction.

Therefore, as a display device of the display device, an LCD element (liquid crystal display module) for full graphics display, for example, 64 pixels (vertical) as shown in FIG.
It is conceivable to use the LCD element 1 having a resolution of × 240 pixels (horizontal). That is, if such an LCD device 1 is used, various information such as the track number and elapsed time of the CD are displayed digitally, the volume is displayed analogly, and the state of the sound field correction is displayed in characters. it can. In addition, it is easy to change the brightness between daytime and nighttime, and it has excellent earthquake resistance.

[0005]

However, when the vehicle is parked in the hot summer of midsummer, the temperature inside the vehicle reaches 70 to 80 ° C and rises to near 95 ° C on the dashboard. Therefore, when the display device is provided on the dashboard, the temperature of the LCD element 1 of the display device similarly rises.

When the temperature of the LCD element 1 rises, the sensitivity of the polarization of the liquid crystal to the drive voltage increases, so that in the case of a low scanning ratio such as an LCD element for graphics display, the temperature rises to 60%. The contrast sharply deteriorates from around ℃ (the contrast becomes too high), and eventually the display disappears.

In this state, the contrast can be restored to an appropriate contrast by adjusting the contrast. However, when the LCD device 1 is actually used for a car audio display device, the following inconvenience occurs. I will end up.

That is, when a passenger parked in a parked car, the temperature of the car interior or the temperature of the dashboard is high as described above, and the display of the LCD element 1 cannot be seen well.
The contrast knob of the display device is adjusted so that the display is performed with the optimum contrast.

However, if the vehicle is running for a while, the temperature inside the vehicle or the dashboard temperature will decrease.
Then, in this state, the contrast with respect to the LCD element 1 is insufficient (this is because the sensitivity of the polarized light of the liquid crystal returns to the original sensitivity), and the display cannot be seen well.
Therefore, the contrast knob of the display device is readjusted so that the display is performed with the optimum contrast.

Such a contrast adjustment is performed every time the temperature inside the vehicle changes, that is, every time the passenger gets on or off the vehicle, which is inconvenient.

Of course, if a fluorescent display tube, for example, is used as the display element of the display device, it is not easily affected by the ambient temperature, so that the above-mentioned inconvenience does not occur. However, it is difficult to realize graphics display with 64 pixels x 240 pixels with a fluorescent display tube. It is also disadvantageous in terms of earthquake resistance.

The present invention is intended to solve the above problems.

[0013]

Therefore, in the present invention, when the reference numerals of the respective parts are made to correspond to the embodiments described later, the liquid crystal display element 1 and the characters and the like displayed on the liquid crystal display element 1 are displayed. An LCD controller 13 that converts the data DSPD into a drive signal DRVV, an LCD driver 14 that supplies the drive signal DRVV from the LCD controller 13 to the liquid crystal display element 1, and a temperature that detects the temperature of the display surface of the liquid crystal display element 1. Drive signal DR supplied from the detection element 23 and the LCD driver 14 to the liquid crystal display element 1
A control circuit 21 for controlling the level of VV according to the detection output of the temperature detection element 23 is provided. Then, the control circuit 21 controls the level of the drive signal DRVV supplied from the LCD driver 14 to the liquid crystal display element 1 with a polarity that decreases when the temperature of the display surface of the liquid crystal display element 1 is high. It is a thing.

[0014]

When the temperature of the liquid crystal display element 1 changes, this is detected by the temperature detecting element 23, and the level of the drive signal supplied to the liquid crystal display element 1 is controlled by this detection output, and the display contrast of the liquid crystal display element 1 is controlled. Is corrected to an appropriate value.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes an LCD element, which is for displaying graphics having the resolution described in FIG. Although not shown, the LCD device 1 is of a light transmission type,
A light source for illumination, that is, a backlight is provided on the rear surface.

Reference numeral 11 is a car audio device such as a CD player, and 12 is a control microcomputer. And the key of the microcomputer 12 (not shown)
When this is operated, this is interpreted by the microcomputer 12, and the audio device 11 is controlled by the microcomputer 12 in accordance with the result of the interpretation to reproduce the desired CD or the like. At this time, the display data DSPD for displaying the reproduction state of the audio device 11 is also output from the microcomputer 12.

Further, 13 is an LCD controller and 14
Indicates an LCD driver. And the controller 13
Displays the display data DSPD from the microcomputer 12 on the LCD device 1
Drive voltage (drive signal) DRVV, and the driver 14 drives the drive voltage DRVV on the LCD.
It supplies to the device 1 to drive the LCD device 1. In this way, the LCD device 1 displays characters and figures indicating the reproduction state of the audio device 11 according to the display data DSPD and the drive voltage DRVV. The circuits 12 to 14 are each composed of a one-chip IC.

Reference numeral 15 denotes a power supply circuit having a car battery or the like, and the output voltage of the power supply circuit 15 is supplied to the above-mentioned circuits 11 to 14 as their operating voltages.

In this case, however, the power supply circuit 15 and the LC
The control circuit 21 is provided between the power source line of the D driver 14 and the DC voltage from the power source circuit 15 is applied to the control circuit 21.
Is supplied as the operating voltage V14 to the driver 14 through the control circuit 21, and a manually operated variable resistor 22 is connected to the control circuit 21. When adjusting the variable resistor 22, the level of the operating voltage V14 supplied to the driver 14 is adjusted. Is controlled.

Further, a temperature detecting element 23 is provided in the vicinity of the LCD element 1, for example, by being thermally coupled to the display surface,
The detection output of the detection element 23 is supplied to the control circuit 21 as a control signal through the error amplifier 24, and as the temperature of the display surface of the LCD element 1 increases, the control circuit 21
The polarity of the operating voltage V14 supplied from the driver to the driver 14 is controlled so that the magnitude of the operating voltage V14 is controlled.

According to such a configuration, the variable resistor 22
Is adjusted, the control circuit 21 controls the magnitude of the operating voltage V14 supplied to the driver 14. However, when the magnitude of the operating voltage V14 changes, the driver 14 changes the LC
The level (amplitude) of the drive voltage DRVV supplied to the D element 1 changes according to the magnitude of the operating voltage V14. Then, if the level of the drive voltage DRVV supplied to the LCD element 1 changes, the display contrast of the LCD element 1 changes.

Therefore, by adjusting the variable resistor 22, the display contrast of the LCD element 1 can be manually adjusted.

Further, in this case, although the temperature of the LCD element 1 changes according to the temperature inside the vehicle, the temperature of the display surface of the LCD element 1 is detected by the detecting element 23, and the driver 14 corresponding to the detected output thereof. The operating voltage V14 changes. At this time, when the temperature of the display surface of the LCD element 1 rises, the operating voltage V14 of the driver 14 is lowered, and when the temperature of the display surface of the LCD element 1 drops, the operating voltage V14 of the driver 14 is raised. ..

Therefore, the level of the drive voltage DRVV supplied to the LCD element 1 changes according to the temperature of the LCD element 1, and the display contrast of the LCD element 1 changes accordingly. Element 1
The display of will be adjusted automatically so that it is easy to see.

Thus, according to the present invention, the temperature of the LCD element 1 is detected, and the LCD is detected according to the detected output.
Since the level of the drive voltage DRVV supplied to the element 1 is controlled, this control automatically adjusts the display contrast of the LCD element 1 to a proper value, and displays the LCD element 1 with the proper contrast regardless of the vehicle interior temperature. Is done.

By the way, the LCD element 1 consumes less power, and therefore the driver 14 also consumes less power.

FIG. 2 shows the means 21 focusing on such a point.
24 is an example of a case where the configurations of 24 are simplified. That is, the power supply voltage from the power supply circuit 15 is supplied to the series circuit of the variable resistor 31 and the thermistor 32 to be divided, and the divided voltage is supplied to the LCD driver 14 by its operating voltage V14.
Supplied as. Further, the thermistor 32 is thermally coupled to, for example, the display surface of the LCD element 1.

As an example, the power supply voltage is -12 V, the variable resistor 31 has a resistance of 4.7 kΩ, and the thermistor 32 has a resistance value of
At 25 ° C, it is 10 kΩ and B constant is 4800.

According to such a configuration, the variable resistor 31
Is adjusted, the operating voltage V14 supplied to the driver 14
Changes, the level (amplitude) of the drive voltage DRVV supplied from the driver 14 to the LCD element 1 becomes
It changes according to the magnitude of the operating voltage V14. And L
If the level of the drive voltage DRVV supplied to the CD element 1 changes, the display contrast of the LCD element 1 changes.

Therefore, by adjusting the variable resistor 31, it is possible to manually adjust the display contrast of the LCD element 1.

Further, when the temperature of the LCD element 1 is high, for example, the sensitivity of polarization to the drive voltage DRVV of the liquid crystal is high. However, in this case, the temperature of the display surface of the LCD element 1 is detected by the thermistor 32, and the LCD
When the temperature of the display surface of the element 1 is high, the thermistor 32
Of the drive voltage DRVV supplied to the LCD element 1 due to the decrease in the resistance value of the
The level of is getting smaller.

Therefore, even if the temperature inside the vehicle rises and the sensitivity of the polarization of the liquid crystal to the drive voltage DRVV of the LCD element 1 increases, the drive voltage DR supplied to the LCD element 1 is increased.
The VV level is getting smaller, so at this time the LCD
The liquid crystal of the element 1 has an appropriate polarization amount, and the display of the LCD element 1 has an appropriate contrast.

Further, when the temperature inside the vehicle is lowered, contrary to the above, the sensitivity of the polarization of the liquid crystal to the drive voltage DRVV of the LCD element 1 is low and the drive voltage DRVV supplied to the LCD element 1 is decreased. Since the level of is increased, the contrast is still appropriate.

Therefore, the contrast of the LCD element 1 is automatically adjusted to a state in which it is easy to see regardless of the temperature inside the vehicle.

According to this example, the variable resistor 31
Is an element originally required for manually adjusting the contrast, and therefore only the thermistor 32 needs to be added, and the structure is simple and the cost is low.

FIG. 3 shows the case where a positive temperature coefficient thermistor 33 is used as the temperature detecting element 23. That is, a series circuit of the variable resistor 31 and the positive temperature coefficient thermistor 33 is connected between the power supply circuit 15 and the power supply line of the LCD driver 14. The positive temperature coefficient thermistor 33 is an LC
It is arranged close to the D element 1.

According to such a configuration, the DC voltage from the power supply circuit 15 is supplied to the driver 14 through the series circuit of the elements 31 and 33. At this time, the DC voltage from the power supply circuit 15 is supplied to the element 31. , 33, and the impedance of the driver 14 (impedance as seen from the power supply line), the divided voltage is divided by the driver 1
4 as the operating voltage V14.

Then, when the temperature of the LCD element 1 is high, the resistance value of the positive temperature coefficient thermistor 33 becomes large.
The operating voltage V14 of the driver 14 becomes low, and conversely, the LCD
When the temperature of the element 1 is low, the resistance value of the positive temperature coefficient thermistor 33 becomes small, so that the operating voltage V14 of the driver 14 is reduced.
Will be higher. Therefore, also in this example, the contrast of the LCD element 1 is automatically adjusted to be in a state that is easy to see regardless of the vehicle interior temperature.

FIG. 4 and FIG. 5 show examples of arrangement of the temperature detecting element 23, in which the printed circuit board 4 is provided on the rear surface of the LCD element 1.
1 is mounted, and the temperature detecting element 23 is provided on the printed circuit board 41 close to the LCD element 1.

Therefore, the temperature of the LCD element 1 can be detected by the detection element 23, and as a result, the contrast of the LCD element 1 can be automatically controlled to the optimum state regardless of the temperature as described above. it can.

6 and 7 show an example of assembling the LCD element 1, its backlight, the temperature detecting element 23 and the like.
That is, reference numeral 51 denotes a horn. The horn 51 is formed of a tin plate or a white plastic material so that the opening has a rectangular shape, and the LCD element 1 is provided at the front opening of the horn 51. A sub-printed circuit board 52 is provided in the section.

Then, the horn 51 of the printed circuit board 52
A backlight 53 such as a lamp and the temperature detection element 23 are provided in an area surrounded by the rear opening of the. Further, the end portion of the printed board 52 and the contact end portion of the LCD element 1 are fixed and connected to the mother printed board 54.

With this structure, the LCD device 1 is illuminated by the light from the backlight 53, and
At this time, the light from the backlight 53 is efficiently supplied to the LCD element 1 by the reflection of the horn 51. Also,
The detection element 23 can detect the temperature inside the horn 51, that is, the temperature of the LCD element 1.

In the above description, the LCD driver 14
Drive voltage supplied from this driver 14 to the LCD element 1 instead of controlling the operating voltage V14 supplied to
By supplying DRVV to the series circuit of the variable resistor 31 and the thermistor 32, for example, the level of the drive signal DRVV supplied to the LCD element 1 can be controlled to obtain an appropriate contrast.

[0045]

According to the present invention, the temperature of the LCD element 1 is detected and the level of the drive voltage DRVV supplied to the LCD element 1 is controlled according to the detected output, so that the LCD element is controlled by this control. The contrast of the display of 1 is automatically adjusted to an appropriate value, and the display of the LCD element 1 is performed with an appropriate contrast regardless of the vehicle interior temperature.

Moreover, the structure therefor is simple and low in cost.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of the present invention.

FIG. 2 is a connection diagram showing another example of the present invention.

FIG. 3 is a connection diagram showing still another example of the present invention.

FIG. 4 is a plan view showing an example of a main part of the present invention.

FIG. 5 is a front view corresponding to FIG.

FIG. 6 is a cross-sectional view showing another example of the main part of the present invention.

FIG. 7 is an exploded perspective view corresponding to FIG.

FIG. 8 is a front view showing an example of an LCD device.

[Explanation of symbols]

 1 LCD Element 11 Car Audio Device 12 Microcomputer 13 LCD Controller 14 LCD Driver 15 Power Supply Circuit 21 Control Circuit 22 Variable Resistor 23 Temperature Detection Element 31 Variable Resistor 32 Thermistor 33 Positive Characteristic Thermistor 41, 52, 54 Printed Circuit Board 51 Horn 53 Backlight

Claims (2)

[Claims] 1. A liquid crystal display device, an LCD controller for converting display data such as characters displayed on the liquid crystal display device into a drive signal, and an LCD for supplying the drive signal from the LCD controller to the liquid crystal display device. A driver, a temperature detection element that detects the temperature of the display surface of the liquid crystal display element, and the level of the drive signal supplied from the LCD driver to the liquid crystal display element according to the detection output of the temperature detection element. And a control circuit for controlling the level of the drive signal supplied from the LCD driver to the liquid crystal display element by the control circuit when the temperature of the display surface of the liquid crystal display element is high. A liquid crystal display device that is controlled. 2. A liquid crystal display device, an LCD controller for converting display data such as characters displayed on the liquid crystal display device into a drive signal, and an LCD for supplying the drive signal from the LCD controller to the liquid crystal display device. A driver, a thermistor for detecting the temperature of the display surface of the liquid crystal display element, and a variable resistor connected in series with the thermistor are provided, and a power supply voltage is applied to a series circuit of the thermistor and the variable resistor. The divided voltage that is supplied and divided and that is obtained across the thermistor is the LC
A liquid crystal display device adapted to be supplied to the D driver as its operating voltage.