JPH02238438A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To assure good visibility even in a place of extremely cold weather by providing a heating element in the liquid crystal display device and controlling the current supplied to the heating element in such a manner that the temp. of the liquid crystal display device is maintained in a prescribed temp. range. CONSTITUTION:The liquid crystal display device 1 is heated by the heat generated by the heating element 2. The output voltage of a temp. sensor 3 rises above a 2nd prescribed voltage Vr2 or above when the temp. of the liquid crystal display device 1 rises above the 2nd prescribed temp. higher than the 1st prescribed temp. The output level of a comparator 6 attains a low level and a driving circuit 7 stops supplying the current to the heating element 2, thereby stopping the heat generation of the heating element 2. The output level of the comparator 6 inverts to a high level and the liquid crystal display device 1 is heated by the heat generated by the heating element 2 when the temp. of the liquid crystal display device 1 falls again down to the 1st prescribed or below. Such actions are repeated and the temp. of the liquid crystal display device 1 is controlled nearly between the 1st prescribed temp. and the 2nd prescribed temp. The good visibility is assured even in the place of extremely cold weather.

Description

[Detailed description of the invention] The present invention relates to a cold-resistant liquid crystal display device.

Background Art When a liquid crystal display device is used as a display device installed in a car, etc., the response speed of the liquid crystal becomes slower as the temperature drops below room temperature. A problem occurs when you want to make a change. Particularly when it is desired to display a display that changes continuously, visibility deteriorates.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a liquid crystal display device that can ensure good visibility even in cold regions.

The liquid crystal display device of the present invention includes a heating element that is provided in the liquid crystal display and generates heat according to the supplied current, a detection means that detects the temperature of the liquid crystal display, and a temperature detected by the detection means that is set to a predetermined value. The heating element is characterized by having a driving means for supplying current to the heating element so that the temperature is within the range.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a liquid crystal display device according to the invention. In this liquid crystal display device, the liquid crystal display 1 is, for example, of a dot matrix type, and the liquid crystal display 1 is provided with a plate-shaped heating element 2 as a heating element. Further, a temperature sensor 3 for detecting the temperature of the liquid crystal display 1 is provided.

The temperature sensor 3 includes a thermistor 4, and this thermistor 4
A predetermined voltage Vcc is applied to a series circuit of the resistor 5 and the resistor 5, and the voltage across the resistor 5 is used as the output voltage. The output voltage of the temperature sensor 3 is supplied to a converter 6.

The comparator 6 has a hysteresis function, and the output voltage of the temperature sensor 3 and the first and second predetermined voltages Vrl, V
Compare r2. A heater drive circuit 7 is connected to the output of the comparator 6, and the drive circuit 7 supplies current to the heating element 2 according to the comparison result of the comparator 6.

FIG. 2 shows the structure of the liquid crystal display 1. As shown in FIG. In this liquid crystal display 1, a liquid crystal assembly 12 is provided within a case member 11 fixed to a circuit board 10. The liquid crystal assembly 12 has a liquid crystal layer 15 sandwiched between glass substrates 13 and 14 each provided with transparent electrodes (not shown), and is further provided with polarizing plates 16 and 17 on its front and rear surfaces, respectively. The liquid crystal assembly 12 has a case member 1 on the top.
1 opening (not shown) is located. A rubber connector 18 is also connected to the end of the liquid crystal assembly 12 for electrical connection to the liquid crystal assembly 12. The heating element 2 is inserted at a position outside the opening between the polarizing beam 16 and the case member 11.

Further, the thermistor 4 is provided at a position not shown in the case member 11.

A display drive circuit 21 is connected to the liquid crystal display 1 .

The display drive circuit 21 has, for example, a memory (not shown) having a memory location corresponding to each dot of the liquid crystal display 1,
The contents of the memory are updated in accordance with the video data signal output from the video data signal generating means (not shown), and the on/off of each dot on the liquid crystal display 1, that is, the brightness and darkness, is determined according to the contents of the memory. ing.

In this configuration, the temperature of the liquid crystal display 1 is detected by the temperature sensor 3. As the temperature rises, the output voltage of the temperature sensor 3 rises.

When the temperature of the liquid crystal display 1 is below the first predetermined temperature, the output voltage of the temperature sensor 3 becomes below the first predetermined voltage Vr1, and the output level of the comparator 6 becomes a high level. In response to this high level, the drive circuit 7 supplies current to the heating element 2 to
generates heat. Since the liquid crystal display 1 is heated by the heat generated by the heating element 2, the temperature of the liquid crystal display 1 increases. When the temperature of the liquid crystal display 1 rises above a second predetermined temperature that is higher than the first predetermined temperature, the output voltage of the temperature sensor 3 increases to the second predetermined voltage Vr.
2 or more, the output level of the comparator 6 becomes a low level. In response to this low level, the drive circuit 7 stops supplying current to the heating element 2 to stop the heating element 2 from generating heat. By stopping the heating element 2 from generating heat, excessive heating of the liquid crystal display 1 is prevented. Further, when the temperature of the liquid crystal display 1 decreases again to be below the first predetermined temperature, the output level of the comparator 6 is reversed to a high level, and the liquid crystal display 1 is heated by the heat generated by the heating element 2. By repeating this operation, the temperature of the liquid crystal display 1 is controlled approximately between the first predetermined temperature and the second predetermined temperature.

In the embodiment described above, a current is supplied to the heating element 2 until the temperature of the liquid crystal display 1 decreases below the first predetermined temperature and rises to the second predetermined temperature. The current supply to the heating element 2 is stopped from when the temperature reaches the second predetermined temperature until it drops to or below the first predetermined temperature, but the present invention is not limited to this.

For example, duty ratio control may be performed to supply current to the heating element 2 at predetermined time intervals with a time width depending on the temperature. Alternatively, the current value supplied to the heating element 2 may be lowered in accordance with the rise in temperature to control the heat generation temperature of the heating element 2 and maintain it within a predetermined temperature.

Furthermore, the heating element 2 is not limited to being provided inside the case member 11 in the liquid crystal display 1 as described above, but may be provided on the side surface of the case member 11 as shown in FIG.

Effects of the Invention As described above, in the liquid crystal display device of the present invention, a heating element is provided in the liquid crystal display and the current supplied to the heating element is controlled to heat the liquid crystal display so that the temperature of the liquid crystal display reaches a predetermined temperature. I try to keep it within the range. Therefore, when the air temperature is lower than room temperature, the temperature of the liquid crystal display can be maintained at room temperature, which prevents the liquid crystal from slowing down in its response speed to commands that change the displayed content, resulting in good visibility even in cold regions. can be ensured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing the configuration of a liquid crystal display equipped with the heating element shown in FIG. 1, respectively. Explanation of symbols of main parts 1...Liquid crystal display 2...Heating element 3...Temperature sensor 6...Comparators 7, 21...
Drive circuit 12...Liquid crystal assembly Figure 1

Claims (2)

[Claims] (1) A liquid crystal display, a heating element that is provided in the liquid crystal display and generates heat according to the current supplied, a detection means for detecting the temperature of the liquid crystal display, and a temperature detected by the detection means. a driving means for supplying current to the heating element so that the temperature is within a predetermined temperature range. (2) The driving means supplies current to the heating element when the temperature detected by the detecting means falls below a first predetermined temperature, and the detected temperature increases to a second predetermined temperature or higher that is higher than the first predetermined temperature. 2. The liquid crystal display device according to claim 1, wherein the current supply to the heating element is stopped when the temperature rises.