JP2003329999A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of efficiently performing temperature control or heating control. <P>SOLUTION: A temperature sensor 33 is arranged between a thin film transistor substrate 20 and a counter substrate 21. On the basis of the temperature detected by the sensor 33, it is controlled whether or not voltage for heating is to be supplied to wiring 51 for pixel signals connecting the counter electrodes 32 arranged on the counter substrate 21 or each pixel electrode 31. <P>COPYRIGHT: (C)2004,JPO

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, and more particularly to a liquid crystal display device having a function of adjusting the temperature of liquid crystal.

[0002]

2. Description of the Related Art Display devices using liquid crystals (such as liquid crystal displays) are used in various places as display devices for personal computers, car navigation systems and the like.

It is known that the characteristics of the liquid crystal used in the liquid crystal display device change depending on the temperature. Then, in general, when the temperature of the liquid crystal is low, good operation may not be obtained as a display device. Therefore, some liquid crystal display devices are known that have a function of increasing the temperature of the liquid crystal portion. Then, in the liquid crystal display device having such a function, the display operation is started after the temperature of the liquid crystal element is raised to a predetermined value or more by heating the entire device or the entire substrate sandwiching the liquid crystal. It has become so.

[0004]

However, in the prior art,
The temperature sensor for detecting the temperature of the liquid crystal display device, for example, in the case of the liquid crystal display device included in the car navigation system, detects the temperature inside the vehicle. That is, the temperature sensor for detecting the temperature of the liquid crystal element,
It was provided at a position away from the liquid crystal element.

However, if the temperature sensor is provided at a position distant from the liquid crystal element, the temperature of the liquid crystal portion cannot be measured accurately. For example, when the temperature of the position where the temperature sensor is provided is lower than the temperature of the liquid crystal element, the temperature of the liquid crystal element is raised more than necessary, resulting in deterioration of the display performance of the device and further failure due to excessive heating. It was also the cause of

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a liquid crystal display device capable of efficiently controlling temperature in order to solve such a problem.

[0007]

In order to solve the above problems, the present invention employs the following configurations. That is, the liquid crystal display device of the present invention is formed so as to be sandwiched between the first substrate on which the pixel electrode is formed, the second substrate on which the counter electrode is formed, and the above first and second substrates. A liquid crystal display device that includes a liquid crystal layer and displays an image by applying a predetermined display driving voltage to the pixel electrode and the counter electrode, the liquid crystal display device being provided between the first substrate and the second substrate. And a control means for controlling the temperature of the liquid crystal layer according to the temperature detected by the detection means.

As described above, by disposing the detecting means for detecting the temperature between the first and second substrates, it is possible to accurately respond to the temperature change of the liquid crystal layer, so that the temperature control is performed efficiently. It becomes possible. Further, by efficiently controlling the temperature in this manner, it is possible to suppress unnecessary heat from being applied to the liquid crystal display device, so that it is possible to improve the durability of the device and save power. Become.

Further, the liquid crystal display device may be arranged such that the detection means is formed on the surface of the first substrate. As a result, since it is possible to accurately respond to the temperature change of the liquid crystal layer, it becomes possible to efficiently control the temperature, which improves the durability of the device and saves power.

In the liquid crystal display device of the present invention, the first substrate on which the pixel electrode is formed and the second substrate on which the counter electrode is formed are provided.
And a liquid crystal layer formed so as to be sandwiched between the first and second substrates, and a liquid crystal for displaying an image by applying a predetermined display driving voltage to the pixel electrode and the counter electrode. In the display device, a heating voltage is applied to the wiring for transmitting the display driving voltage to the pixel electrode.

As a result, the temperature of the liquid crystal layer can be efficiently raised. As described above, by efficiently performing the heating control, it is possible to shorten the waiting time from the start of the apparatus to the switching to the display drive. Also,
A liquid crystal display device of the present invention includes: a first substrate on which a pixel electrode is formed; a second substrate on which a counter electrode is formed;
And a liquid crystal layer formed so as to be sandwiched between the second substrate and a liquid crystal display device for displaying an image by applying a predetermined display driving voltage to the pixel electrode and the counter electrode. It is characterized in that a heating voltage is applied to.

As a result, the temperature of the liquid crystal layer can be efficiently raised. By efficiently performing the heating control in this way, it is possible to shorten the waiting time from the start of the apparatus to the switching to the display drive. In addition, the liquid crystal display device of the present invention is formed so as to be sandwiched between the first substrate on which the pixel electrode is formed, the second substrate on which the counter electrode is formed, and the first and second substrates. In a liquid crystal display device that includes a liquid crystal layer and displays an image by applying a predetermined display driving voltage to the pixel electrode and the counter electrode, the temperature of the liquid crystal layer is arranged inside the liquid crystal display device. Detecting means for detecting, and control means for controlling the temperature of the liquid crystal layer according to the temperature detected by the detecting means.

As a result, the temperature change of the liquid crystal layer can be accurately accommodated, so that the temperature can be controlled efficiently. Then, by efficiently controlling the temperature in this way, it is possible to suppress unnecessary heat from being applied to the liquid crystal display device, improve the durability of the device, and save power. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a schematic side view of a liquid crystal display device according to an embodiment of the present invention when viewed from the side.

In FIG. 1A, the liquid crystal display device 11 is
The liquid crystal unit 12 includes a liquid crystal unit 12 and a light source unit 13. The liquid crystal unit 12 receives light from the light source unit 13 from below, and thus the liquid crystal unit 1
A predetermined image is displayed on the upper surface of 2. The light source unit 13
Is an inverter board 14, a light source 15, and a light guide plate 16.
And a reflection sheet 17 and a lens sheet 18, and the light emitted from the inverter substrate 14 and the light source 15 is reflected upward by the reflection sheet 17 via the light guide plate 16 and transmitted to the liquid crystal section 12 through the lens sheet 18. There is.

The liquid crystal section 12 is composed of a plurality of layers, and comprises a polarizing plate 19, a thin film transistor substrate 20, a counter substrate 21 and a polarizing plate 22 in order from the bottom. The thin film transistor substrate 20 and the counter substrate 21 are insulative substrates. FIG. 1B is an enlarged cross-sectional view of the thin film transistor substrate 20 and the counter substrate 21.

As shown in FIG. 1B, a liquid crystal layer 23 is provided between the thin film transistor substrate 20 and the counter substrate 21. For example, each of the thin film transistor substrate 20 and the counter substrate 21 has a thickness of 700 μm, and the liquid crystal layer 2
The thickness of 3 is 3 to 4 μm. Conventionally, as described above, since the liquid crystal layer 23 is heated from the outside of the substrate having such a thickness, a large amount of heat is required.

FIG. 2 is a diagram showing a characteristic part of the liquid crystal display device according to the embodiment of the present invention, and is a diagram schematically showing the liquid crystal portion 12. As shown in FIG. 2, one dot (one pixel) is formed on the upper surface of the thin film transistor substrate 20.
Pixel electrodes 31 are provided in a matrix, and each pixel electrode 31 is connected to a wiring of a metal thin film. Further, a counter electrode 32 of a metal thin film is provided on one surface of the lower surface of the counter substrate 21 so as to face the pixel electrode 31. The liquid crystal display device 11 displays a predetermined image by applying a predetermined voltage to the pixel electrode 31 and the counter electrode 32.
A temperature sensor 33 for detecting the temperature is arranged on the upper surface (front surface) of the thin film transistor substrate 20. That is, the temperature sensor 33 is arranged between the thin film transistor substrate 20 and the counter substrate 21 shown in FIG.

By thus disposing the temperature sensor 33 at a position sandwiched between the thin film transistor substrate 20 and the counter substrate 21, the liquid crystal layer 23 is close to the liquid crystal layer 23 as shown in FIG. 1B. Can detect the temperature of
It is possible to accurately measure the temperature of the liquid crystal layer 23.
Further, since the temperature of the liquid crystal layer 23 can be accurately measured in this way, the temperature can be controlled efficiently. In addition, since efficient temperature control can prevent unnecessary heat from being applied to the liquid crystal display device in this way, it is possible to improve the durability of the device and save power. Become.

Another characteristic of the liquid crystal display device of this embodiment is that a heating voltage is applied to the counter electrode 32 formed on substantially the entire surface of the counter substrate 21, and the voltage is applied. This is the point of warming the liquid crystal layer 23 by utilizing the heat generated. In this way, by applying the heat generation voltage to the counter electrode 32 and using the counter electrode 32 as a heat generating resistor, the liquid crystal layer 23 can be heated at a position close to the liquid crystal layer 23, and thus, as in the conventional case. As compared with heating from the outside of the substrate, it is possible to efficiently raise the temperature to a desired temperature in a shorter time. By efficiently performing the heating control in this way, it is possible to shorten the waiting time from the startup of the liquid crystal display device to the display drive.

FIG. 3A shows a circuit diagram of the temperature sensor 33. The temperature sensor 33 includes a MOS transistor 41 having a gate and a drain connected to each other, and a constant current for supplying a constant current to the MOS transistor 41. It comprises a source 42 and a voltmeter 43 for measuring the voltage across the MOS transistor 41. Here, the temperature to be detected is the MOS transistor 4
It is obtained based on the temperature dependence of the current-voltage characteristic of No. 1.
The temperature sensor 33 has a voltage value detected by the voltmeter 43 and a predetermined voltage value (a voltage value corresponding to a desired temperature).
A comparator 44 is connected to compare with. Then, if the detected temperature is lower than a predetermined temperature, an operation mode for raising the temperature of the liquid crystal element is executed, and if the temperature becomes higher than the predetermined temperature, a mode for displaying an image is entered. In the operation mode for raising the temperature of the liquid crystal element, for example, by applying a heating voltage to the counter electrode 32, the signal line or electrode is used as a heating element (heater).

Besides the MOS transistor 41, the temperature sensor 33 may be constructed by using a diode or the like having a junction of a P-type impurity diffusion layer and an N-type impurity diffusion layer. FIG. 3B shows a temperature sensor 33 using a P-type and N-type diode 45.
It is a circuit diagram of. In this configuration, the comparator 44 compares the voltage across the diode 45 with a predetermined voltage value.

Since the temperature sensor shown in FIG. 3A or FIG. 3B is composed of transistors, diodes, etc., it is formed at the same time by using the process of forming other elements on the thin film transistor substrate 20. be able to. In this way, the temperature sensor 33 is connected to the thin film transistor substrate 20.
And the counter substrate 21, and the counter electrode 32 provided on the lower surface of the counter substrate 21 is used as a resistor for heat generation, so that only the liquid crystal layer 23 can be temperature-controlled or heat-controlled efficiently and in a short time. Is possible. By controlling the temperature of the liquid crystal layer 23 efficiently in this way, unnecessary heat is prevented from being applied to the liquid crystal display device, so that the durability of the device is improved and power saving is achieved. It will be possible. Further, by efficiently controlling the heating of the liquid crystal layer 23, it is possible to shorten the waiting time required from the start of the apparatus until the liquid crystal layer 23 reaches an appropriate temperature and drive the display.

Further, since the conventional one is used as the heating resistor, it is possible to prevent the manufacturing cost from increasing. Further, as the heating resistor, a resistor other than the signal line or the counter electrode 32 for supplying a drive signal to the pixel electrode 31 may be used. For example, a wiring for transmitting a display signal to each pixel electrode 31 may be used as a heating resistor.

FIG. 4 is a diagram for explaining the operation when the wiring connecting the pixel electrodes 31 is used as a heating resistor. The temperature sensor 33 and the comparator 44 are
Since the same operation as that of FIG. 3 is performed, the description thereof is omitted. In FIG. 4, the pixel signal wiring 51 is connected to each pixel electrode 31 (see FIG.
(Not shown) is a wiring connected to each pixel electrode 31 for applying a pixel signal voltage. Wiring 5 for each pixel signal
Both ends of 1 are connected to the source of the transistor 52 and the drain of the transistor 53. The signal output from the comparator 44 is input to the respective gates of the transistor 52 and the transistor 53.

When the detected temperature is lower than the predetermined temperature, the transistors 52 and 53 are controlled so that the heating voltage is applied to the pixel signal wiring 51. On the other hand, if the detected temperature is higher than the predetermined temperature, the transistor 52 and the transistor 5 are set so that the pixel signal voltage is applied to the pixel signal wiring 51.
3 is controlled.

FIG. 5 is a configuration including a changeover switch for applying one of the display drive voltage and the heat generation voltage to the voltage applied to the pixel signal wiring 51 in accordance with the output signal of the comparator 44 in FIG. FIG. In FIG. 5, the switch 61 is for switching to either the display drive voltage output from the display drive circuit 62 or the heat generation voltage from the power supply Vcc, and similar to FIG. The switching operation is controlled based on the signal output from the device 44.

The switch 61 is brought into the state as shown in FIG.
Is set, the heating voltage from the power source Vcc is applied to the pixel signal wiring 51, and the pixel signal wiring 5
1 warms the liquid crystal layer 23. Further, when the switch is set in a state opposite to the state shown in FIG. 5, the display drive voltage (a signal for display drive) output from the display drive circuit 62 is the pixel signal wiring. It is applied to each pixel electrode 31 (not shown) via 51 to be in a state of displaying an image. Further, the necessary amount of heat can be finely adjusted by adjusting the number of pixel signal wirings 51 to be used as heating resistors in the design stage.

[0029]

As described above, according to the liquid crystal display device of the present invention, since the detecting means for detecting the temperature is arranged between the two substrates sandwiching the liquid crystal layer, the temperature change of the liquid crystal layer can be accurately detected. Therefore, the temperature control can be efficiently performed. Further, by efficiently controlling the temperature in this way, it is possible to prevent unnecessary heat from being applied to the liquid crystal display device, so that it is possible to improve the durability of the device and save power. Become.

Further, in the liquid crystal display device of the present invention, since the heating voltage is applied to the wiring for applying the display driving voltage to the counter electrode or the pixel electrode, the temperature of the liquid crystal layer can be efficiently increased in a short time. It becomes possible to reach a desired temperature. By efficiently performing the heating control in this way, it is possible to shorten the waiting time from the startup of the liquid crystal display device to the switching to the display drive.

[Brief description of drawings]

FIG. 1A is an overall side view of a liquid crystal display device according to an embodiment of the present invention. (b) is an enlarged cross-sectional view of a thin film transistor substrate and a counter substrate.

FIG. 2 is a perspective view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 3A is a circuit diagram of a temperature sensor using a MOS transistor. (b) is a circuit diagram of a temperature sensor using a diode.

FIG. 4 is a circuit diagram of wiring for applying a signal voltage to an electrode of each pixel.

5 is a circuit diagram including a changeover switch in the circuit diagram of FIG.

[Explanation of symbols]

11 Liquid crystal display 12 Liquid crystal part 13 Light emitting part 14 Inverter board 15 light source 16 Light guide plate 17 Reflective sheet 18 lens sheet 19 Polarizer 20 Thin film transistor substrate 21 Counter substrate 22 Polarizer 23 Liquid crystal layer 31 pixel electrode 32 counter electrode 33 Temperature sensor 41 MOS transistor 42 constant current circuit 43 Voltmeter 44 Comparator 45 diode 51 Pixel signal wiring 52, 53 transistors 61 switch 62 Display drive circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideo Takeuchi             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. F term (reference) 2H092 GA63 JA24 JB13 JB31 NA25                       NA26 PA06                 2H093 NC47 NC49 NC57 NC63 NC76                       ND02 ND39 ND45 ND47 ND54                       NE03                 5C094 AA34 BA03 BA43 EA07 FB14                       FB18 HA08                 5G435 AA12 BB12 CC09 KK05 LL07                       LL08

Claims (5)

[Claims] 1. A first substrate on which a pixel electrode is formed, a second substrate on which a counter electrode is formed, and the above first and second substrates.
Including a liquid crystal layer formed so as to be sandwiched between the substrates of
A liquid crystal display device for displaying an image by applying a predetermined display driving voltage to the pixel electrode and the counter electrode, the liquid crystal display device being provided between the first substrate and the second substrate, A liquid crystal display device comprising: a detection unit that detects a temperature; and a control unit that controls the temperature of the liquid crystal layer according to the temperature detected by the detection unit. 2. The liquid crystal display device according to claim 1, wherein the detection means is formed on a surface of the first substrate. 3. A first substrate on which a pixel electrode is formed, a second substrate on which a counter electrode is formed, and the above first and second substrates.
Including a liquid crystal layer formed so as to be sandwiched between the substrates of
In a liquid crystal display device that displays an image by applying a predetermined display driving voltage to the pixel electrode and the counter electrode, a heating voltage is applied to a wiring for transmitting the display driving voltage to the pixel electrode. Characteristic liquid crystal display device. 4. A first substrate on which a pixel electrode is formed, a second substrate on which a counter electrode is formed, and the above first and second substrates.
Including a liquid crystal layer formed so as to be sandwiched between the substrates of
A liquid crystal display device for displaying an image by applying a predetermined display driving voltage to the pixel electrode and the counter electrode, wherein a heating voltage is applied to the counter electrode. 5. A first substrate on which a pixel electrode is formed, a second substrate on which a counter electrode is formed, and the above first and second substrates.
Including a liquid crystal layer formed so as to be sandwiched between the substrates of
In a liquid crystal display device that displays an image by applying a predetermined display driving voltage to the pixel electrode and the counter electrode, a detection unit that is disposed inside the liquid crystal display device and detects the temperature of the liquid crystal layer, A liquid crystal display device, comprising: a control unit that controls the temperature of the liquid crystal layer according to the temperature detected by the detection unit.