JPH07335015A - Display device - Google Patents

Abstract

PURPOSE:To control the temperature rise or a display panel and prevent the deterioration of picture quality and the breakage of the panel by constructing a display device so that a heat, radiating means is turned off when a temperature in a reflection box is low and it is turned on when the temperature is high. CONSTITUTION:In a display device, when a temperature (a) in a reflection box 100 is lower than 40 deg.C at the peak brightness of a fluorescent tube 101, a temperature (b) in an exterior case 5 is lower than 25 deg.C. At this time, a temperature switch 400 with a shape memory alloy 41 and a constantly elastic material 42 laminated is kept in non-contact with the back of the reflection box 100 and so a heat radiating means for a heat radiating fin 6 is in an OFF state. When the temperature (a) in the reflection box 100 is not lower than 40 deg.C and the temperature (b) in the case 5 is not lower than 25 deg.C the temperature switch 400 is deformed except in the fixed center area and put in contact with the back of the reflection box 100, and so the heat radiating means for the heat radiating fin 6 is in an ON state. In this way, the temperature rise of a transmissive display panel, the deterioration of picture quality and the breakage of the panel are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display panel of a transmissive liquid crystal or the like and a display device in which a light source for illuminating the panel is a fluorescent tube in which mercury gas is sealed. The present invention relates to a display device suitable for mounting on a vehicle, an airplane or the like that requires an operating temperature range.

[0002]

2. Description of the Related Art In recent years, there have been increasing opportunities to use a display device such as a transmissive liquid crystal display panel and a fluorescent tube, which is small, lightweight, and thin and can be arranged in a narrow space, mounted on a vehicle, an airplane or the like. There is.

Since a display device mounted on a vehicle receives external light (sunlight) and is often used by being incorporated in a front box of a vehicle, heat is likely to be accumulated around the device,
It is often used in a high temperature environment (70 ° C or higher) as compared to household use. In addition, especially in the daytime when the weather is fine in summer, the external light is incident on the display image, making it difficult to see the display image. There is a need to. At that time, the amount of heat generated from the fluorescent tube increases, and the heat easily accumulates in the display device. As described above, the liquid crystal display device mounted on the vehicle often has a high temperature both inside and outside the device.
There is a problem that the luminous efficiency is lowered due to the temperature dependence of the fluorescent tube and the surface temperature of the display panel exceeds the operation guarantee temperature of the panel, which causes deterioration of image quality and destruction of the panel. Was needed.

A conventional heat radiating means is disclosed in, for example, Japanese Patent Laid-Open No. 2-8.
There is a heat dissipation means as described in Japanese Patent No. 2406. Figure 9
FIG. 1 is an exploded perspective view of the same, showing a transmissive display panel 1 such as a liquid crystal, a light diffusing plate 2, and a metal such as iron or aluminum.
A reflective box body 1 whose inner surface is a reflective surface such as a mirror surface or a white surface
00, a fluorescent tube 101 arranged on the reflection surface of the reflection box 100, and a metal cylindrical cap 102 molded so as to cover the electrode portions at both ends of the fluorescent tube 101. In FIG. 9, the tubular cap 102 is closely adhered and fixed to the surface of the electrode portion at both ends of the fluorescent tube 101 and the side surface of the reflection box body 100 by an adhesive or caulking having excellent thermal conductivity. As a result, the heat from the electrode part, which generates the most heat in the fluorescent tube 101, is collected in the cylindrical cap 102 and heated. Then, the heat of these cylindrical caps 102 is conducted to the entire surface of the reflection box body 100 and radiated to the outside air through the outer surface of the reflection box body 100. Thus, the conventional heat radiating means radiates the heat from the fluorescent tube, which is the light source, from the metallic reflection box.

[0005]

In a display device mounted on a vehicle or the like, the ambient temperature of the device during use is kept at a low temperature environment of 0 ° C. or less especially in the winter morning in cold regions (Hokkaido, Tohoku, etc.). Become. However, since the above-mentioned conventional example radiates heat even in a low temperature environment, there is a problem that the luminous efficiency at a low temperature is lowered.

FIG. 10 shows the temperature dependence of the brightness of the fluorescent tube. The fluorescent tube is a high-intensity and long-life type cold cathode fluorescent tube, and has a tube current (discharge current) of 9 mA. The brightness at an ambient temperature of 25 ° C. is 100%. As shown in FIG.
The brightness of the fluorescent tube peaks at 40 ° C,
When the temperature is lower than that, the brightness is lowered, and the brightness is drastically lowered particularly at a low temperature, and the brightness at 0 ° C. is about 50% of the brightness at 25 ° C. This is because when the temperature is low, the vapor pressure of the mercury gas sealed in the fluorescent tube decreases, and the luminous efficiency of the fluorescent tube decreases.

In the above-mentioned conventional example, even at low temperature, the heat of the fluorescent tube is radiated to some extent from the entire surface of the reflection box body by the metallic cylindrical cap covering the fluorescent tube electrode portion. At this time, due to the characteristics of the fluorescent tube shown in FIG. 10, the decrease in luminous efficiency at low temperature is further increased.

The present invention provides a display device suitable for mounting on a vehicle, an airplane or the like having a wide operating temperature range from low temperature to high temperature, with the heat dissipation means turned off at low temperature and turned on at high temperature. To aim.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention directly or directly reflects light from a fluorescent tube, which is a light source in which mercury gas is sealed, on the inner surface of a metallic reflecting box. In the display device that makes a uniform surface light by entering the light diffusing plate by illuminating the transmissive display panel such as liquid crystal to display a screen, a certain distance is provided with respect to the back surface of the reflective box body. A heat radiation part such as a heat radiation fin provided in advance,
Laminated with a shape memory alloy and a constant elastic material, a part of which is fixed to the heat dissipation part, and when the fluorescent tube is at a certain temperature or lower, it is deformed so as to be separated from the back surface of the reflection box body at a certain interval, It is characterized in that it has a temperature switch that is deformed so as to come into contact with the back surface of the reflection box body in a wide range when the temperature of the fluorescent tube exceeds a certain temperature.

[0010]

In the present invention, at a low temperature, the temperature switch, which is formed by laminating the shape memory alloy and the constant elastic material, makes the reflection box body and the heat radiation portion non-contact with each other, so that the heat radiation effect can be improved. Since the heat from the fluorescent tube is easily retained in the display device, the decrease in luminous efficiency of the fluorescent tube can be suppressed. On the contrary, when the temperature is high, the reflection box body and the heat radiation portion are brought into contact with each other by the temperature switch, and the heat from the fluorescent tube is radiated to the outside air through the reflection box body and the heat radiation portion. The temperature rise can be prevented, and the deterioration of image quality and the destruction of the panel can be prevented.

[0011]

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

1 and 2 are cross-sectional views of the display device of the present invention at a low temperature and a high temperature according to the first embodiment. In FIGS. 1 and 2, a face plate 3 made of transparent plastic or the like for protecting the transmissive display panel 1, an outer case 5, a shape memory alloy 41 whose shape is stored at a predetermined temperature, and a constant temperature change. The constant elastic material 42 is a material having spring elasticity. The shape memory alloy 41 and the constant elastic material 42 are bonded together, and the central portion thereof is fixed to the heat radiation fin 6 which is a heat radiation portion by screwing or the like to form the temperature switch 400. Internal temperature a of the reflection box,
The case internal temperature b indicates the ambient temperature of the fluorescent tube 101 and the ambient temperature of the temperature switch 400, respectively.

FIG. 1 shows an example of a low temperature state in which heat radiation is not required, and is a case where the internal temperature a of the reflection box is lower than the peak temperature 40 ° C. of the brightness of the fluorescent tube as shown in FIG. a <40 ° C.), and the temperature b in the case at that time is 25 ° C., which is 15 ° C. lower than the internal temperature a of the reflection box by 15 ° C. from the actual measurement result.
Therefore, b <25 ° C. At that time, the temperature switch 400 maintains a non-contact separated relationship with the back surface of the reflection box body 100, and the heat dissipation means by the heat dissipation fins 6 is in an off state. FIG. 2 shows an example of a high temperature state that requires heat dissipation. The internal temperature of the reflection box is a ≧ 40 ° C. and the internal temperature of the case is b ≧ 25 ° C. Temperature switch 400 at that time
Is a modified reflective box body 10 with the fixed central portion left.
0 is in contact with the back surface, and the heat dissipation means is in the on state.

The temperature switch 400, which is deformed when the temperature b in the case is 25 ° C., is 25 ° C. so that the rear surface of the reflection box body 100 is contacted in a wide range as shown in FIG.
1 in which the shape-memory alloy 41 that has been shape-memorized in FIG. 1 and the shape-memory alloy 41 at 25 ° C. or below do not work, maintain a constant distance (shape) from the back surface of the reflection box body 100. And the shape memory alloy 41 is formed on the rear side of the reflection box 100,
The constant elastic material 42 is disposed on the heat radiation fin side. As a result, in the movement of the temperature switch 400 as a whole, the elastic force of the constant elastic material 42 is superior at a temperature not requiring heat dissipation or less,
The shape memory alloy 41 is maintained at a temperature higher than that required to radiate heat while keeping the state away from the back surface of the reflection box body 100 as shown in FIG.
Since the shape returns to the memorized shape, the state is in close contact with the back surface of the reflection box body 100 as shown in FIG.

With such a temperature switch 400, the fluorescent tube 1 can be operated in the low temperature state in FIG.
The heat generated from 01 is not transferred from the reflection box body 100 to the heat radiation fins 6 and is almost kept in the apparatus, and it is possible to reduce a decrease in luminous efficiency of the fluorescent tube due to a low temperature. On the contrary, in the high temperature state of FIG. 2 where heat radiation is required, the heat generated from the fluorescent tube 101 is radiated to the outside through the radiation fins 6, and the temperature rise of the liquid crystal panel 1 can be suppressed, so that the image quality is deteriorated and the panel is deteriorated. Can prevent destruction,
It is possible to provide a display device suitable for mounting on a vehicle, an airplane or the like having a wide operating temperature range from low temperature to high temperature.

FIGS. 3 and 4 are sectional views showing a second embodiment of the display device of the present invention. In the second embodiment, the heat is not dissipated by the heat dissipating fins as in the first embodiment, but is dissipated from the entire surface of the metallic outer case.

3 and 4, a metal outer case 7, a shape memory alloy 43 and a constant elastic material 44 are attached to each other, and one end portion is fixed to the outer case 7 with a screw or the like. 401 is shown. FIG. 3 shows a temperature switch 40 at that time in a low temperature state that does not require heat dissipation.
No. 1 maintains a non-contact separated relationship with the back surface of the reflection box body 100, and heat generated from the fluorescent tube 101 is not transferred from the reflection box body 100 to the outer case 7, and almost no heat is kept inside the device. Therefore, it is possible to reduce the decrease in the luminous efficiency of the fluorescent tube due to the low temperature. FIG. 4 shows a high temperature state that requires heat radiation, and the temperature switch 401 at that time is deformed and is in contact with the back surface of the reflection box body 100, and the heat generated from the fluorescent tube 101 is radiated to the outside from the entire outer case. As a result, the temperature rise of the liquid crystal panel 1 can be reduced, so that the deterioration of the image quality and the panel destruction can be prevented. As described above, the second embodiment can provide a display device suitable for mounting on a vehicle, an airplane or the like having a wide operating temperature range from low temperature to high temperature, like the first embodiment.

FIGS. 5 and 6 are sectional views of a third embodiment of the display device of the present invention. The third embodiment uses a resin-based material such as ABS or PBT instead of a metal for the reflection box body, and uses a fan instead of a radiation fin or a metal outer case for the heat radiation means to keep the temperature around the fluorescent tube at low temperature. And the structure that enhances the heat dissipation effect at high temperature.

In FIGS. 5 and 6, the opening is the light diffusion plate 2.
Resin-based material reflection box 200, shape memory alloy 45 and constant elastic material 4 which are arranged at a predetermined distance from the back surface of
6 are bonded to each other to form a temperature switch 402 whose one end is fixed to the opening of the reflection box body 200. Further, a fan control circuit 10 and a fan 13 for controlling a temperature detection element 8 such as a diode and a thermistor, a temperature detection circuit 9, and a switch means 11 for turning on and off a fan power source 12 are shown. 5 and 6, in the fan control system, the temperature detection element 8 and the temperature detection circuit 9 detect the temperature in the case 5 and transmit the temperature information to the fan control circuit 10. The fan control circuit 10 turns off the switch means 11 to turn off the fan when the temperature in the case 5 is equal to or lower than a predetermined temperature. When the temperature inside the case 5 is equal to or higher than the predetermined temperature, the switch means 11 is turned on to turn on the fan.

FIG. 5 shows a low temperature condition that does not require heat dissipation.
The temperature switch 402 is shaped so as to fill the space between the opening of the reflection box body 200 and the back surface of the light diffusion plate 2, and the fluorescent tube 101 surrounding the reflection box body 200, the light diffusion plate 2, and the temperature switch. It is in a sealed state by 402. Further, the fan 13 for heat dissipation is in the off state. At this time,
The ambient temperature of the fluorescent tube 101 in the reflection box body 200 is
The reflection box body 2 is different from that of the metal reflection box body of the second embodiment.
Since the material of No. 00 is a resin system, the thermal conductivity is poor, so that the heat from the fluorescent tube 101 is easily retained in the reflection box body 200, the ambient temperature of the fluorescent tube 101 is increased, and the light emission efficiency is improved. FIG. 6 shows that the temperature switch 402 bends to the outside of the reflection box body 200 so as to open a gap between the opening of the reflection box body 200 and the back surface of the light diffusion plate 2 in a high temperature state requiring heat dissipation, The box 200, the light diffusion plate 2, and the temperature switch 402 are not sealed. As a result, the heat from the fluorescent tube 101 is not kept in the reflective box body 200 but is directly transferred into the case 5 and dissipated in the entire case 5. At that time, the fan 13 is turned on (exhaust) to radiate the heat in the case 5 to the outside. The heat from the fluorescent tube 101 is passed through the fan 13 without passing through the heat radiation fins or the metal outer case.
Since the heat is directly radiated to the outside, the heat radiation effect is better than that of the first and second embodiments.

As described above, the third embodiment further improves the effects of the present invention as compared with the first and second embodiments.

FIG. 7 shows a sectional view of a fourth embodiment of the display device of the present invention. In the fourth embodiment, the heater control means, which is a general low-temperature brightness compensating means, which turns on the heater mounted on the surface of the fluorescent tube at a low temperature to heat the fluorescent tube and prevent a decrease in luminous efficiency, is the first embodiment. It is characterized by being applied to the embodiment.

In FIG. 7, a temperature detecting element 15 such as a diode or thermistor mounted on the surface of the fluorescent tube 101.
And a heater 1 made of a material such as Ni-Cr or Cu-Ni
6, the temperature detection circuit 17, and the heater control circuit 18 for controlling the switch means 19 for turning on / off the heater power source 20. In the heater control system, the temperature detection element 15 and the temperature detection circuit 17 detect the temperature of the fluorescent tube 101 and transmit the temperature information to the heater control circuit 18. The heater control circuit 18
When the temperature of the fluorescent tube 101 is below a predetermined temperature,
The switch means 19 is turned on, electric power is supplied from the heater power source 20 to the heater 16 to heat the heater 16, and the fluorescent tube 1
01 is prevented to prevent a decrease in luminous efficiency. In addition, the fluorescent tube 101
If the temperature is higher than a predetermined temperature, the switch means 19
Is turned off, power supply to the heater 16 is stopped, and heating of the fluorescent tube 101 is stopped.

In FIG. 7, the heater 16 is turned on to turn on the fluorescent tube 10.
In the low temperature state in which 1 is heated, the temperature switch 400 composed of the shape memory alloy 41 and the constant elastic material 42 is the same as that shown in FIG.
Similarly, the non-contact separated relationship is maintained on the back surface of the reflection box body 100, and the heat dissipation means by the heat dissipation fins 6 is in the off state. As a result, the heater 16 is connected to the fluorescent tube 101.
The heater 16 efficiently heats the fluorescent tube 101 without radiating heat to the outside, and the heater 16 efficiently heats the fluorescent tube 101.
The brightness compensation effect of 1 can be improved. Further, in a high temperature state that requires heat radiation, although not shown, the heater is in an off state and the temperature switch is similar to that shown in FIG.
With the central portion fixed to the radiating fins remaining, it is deformed and comes into contact with the back surface of the reflection box body, and the heat radiating means is in an on state, so that the heat inside the device is radiated to the outside.

As described above, in the fourth embodiment, the effect of brightness compensation by the heater can be improved when the temperature is low, and the heat radiation effect similar to that of the first embodiment can be obtained when the temperature is high.

FIG. 8 shows a sectional view of a fifth embodiment of the display device of the present invention. In the fifth embodiment, the tube current control means which is a low temperature brightness compensating means for controlling the tube current (discharge current) of the fluorescent tube at a low temperature to prevent a decrease in the luminous efficiency of the fluorescent tube due to a low temperature is provided in the first embodiment. It is characterized by being applied to.

FIG. 8 shows an inverter control circuit 22 for controlling the tube current of the fluorescent tube 101 by controlling the power supply voltage and the dimming ratio of the temperature detection circuit 21 and the inverter 23 that lights the fluorescent tube 101. In the tube current control system, the temperature detection element 15 and the temperature detection circuit 21 detect the temperature of the fluorescent tube 101 and transmit the temperature information to the inverter control circuit 22. When the temperature of the fluorescent tube 101 is lower than a predetermined temperature, the inverter control circuit 22 controls the power supply voltage of the inverter 23, the dimming ratio, etc. to make the tube current of the fluorescent tube 101 larger than that at room temperature. Then, when the temperature is low, the amount of heat generated by the fluorescent tube 101 itself is increased to warm the fluorescent tube 101 and prevent a decrease in luminous efficiency.

FIG. 8 shows a temperature switch 400 composed of the shape memory alloy 41 and the constant elastic material 42 in a low temperature state in which the tube current is made a large current to perform brightness compensation. The non-contact and distant relationship is maintained on the back surface of the heat radiating fin 6, and the heat radiating means by the heat radiating fins 6 is in the off state. As a result, a large amount of heat from the fluorescent tube is kept inside the device without being radiated to the outside, and the effect of brightness compensation by controlling the tube current can be improved. In addition, in a high temperature state that requires heat radiation, although not shown, the tube current of the fluorescent tube is in a state of normal temperature, and the temperature switch leaves the central portion fixed to the heat radiation fin as in FIG. It deforms and comes into contact with the back surface of the reflection box body, and the heat radiating means is in the ON state, so that the heat inside the device is radiated to the outside.

As described above, in the fifth embodiment, the effect of brightness compensation by controlling the tube current can be improved at low temperature, and the heat radiation effect similar to that of the first embodiment can be obtained at high temperature.

The present invention is not limited to the above-mentioned embodiment, and, for example, the second embodiment shown in FIGS.
The low temperature brightness compensating means by the heater control shown in FIG. 7 and the low temperature brightness compensating means by the tube current control shown in FIG. 8 may be added to the third embodiment shown in FIGS.

[0031]

As described above, according to the present invention,
At a low temperature, the temperature switch formed by laminating the shape memory alloy and the constant elastic material makes the reflection box and the heat radiating section non-contact with each other, so that the heat radiating effect is lost, and the heat from the fluorescent tube is stored in the display device. It becomes easier to keep the temperature, and it is possible to reduce the decrease in luminous efficiency of the fluorescent tube. On the contrary, when the temperature is high, the temperature switch causes the reflection box body and the heat radiation section to come into contact with each other, and the heat from the fluorescent tube is dissipated to the outside through the reflection box body and the heat radiation section. It is possible to provide a display device suitable for mounting on a vehicle, an airplane or the like having a wide operating temperature range from low temperature to high temperature, since it is possible to prevent the temperature rise of the device, prevent the deterioration of the image quality and the destruction of the panel. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first embodiment of a display device of the present invention at low temperature.

FIG. 2 is a cross-sectional view of the first embodiment of the display device of the present invention at high temperature.

FIG. 3 is a cross-sectional view of a second embodiment of the display device of the present invention at a low temperature.

FIG. 4 is a cross-sectional view of a second embodiment of the display device of the present invention at high temperature.

FIG. 5 is a sectional view of a third embodiment of the display device of the present invention at a low temperature.

FIG. 6 is a cross-sectional view of a third embodiment of the display device of the present invention at high temperature.

FIG. 7 is a cross-sectional view of a fourth embodiment of the display device of the present invention at low temperature.

FIG. 8 is a sectional view of a fifth embodiment of the display device of the present invention at low temperature.

FIG. 9 is an exploded perspective view of a conventional example.

FIG. 10 is a graph showing ambient temperature and fluorescent tube surface temperature-luminance characteristic of the fluorescent tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transmissive display panel, 2 ... Light diffusion plate, 3 ... Face plate, 5, 7 ... Exterior case, 6 ... Radiating fins, 8, 15 ... Temperature detector, 9, 17, 21 ... Temperature detection circuit, 10 ... Fan control circuit, 11, 19 ... Switch means, 12 ... Fan power supply, 13 ... Fan, 16 ... Heater, 18 ... Heater control circuit, 20 ... Heater power supply, 22 ... Inverter control circuit, 23 ... Inverter, 41, 43 , 45 ... Shape memory alloy, 42, 44, 46 ... Constant elastic material, 100, 200 ... Reflecting box body, 101 ... Fluorescent tube, 400, 401, 402 ... Temperature switch, a ... Reflecting box inside temperature, b ... Case Inner temperature.

Claims (4)

[Claims] 1. A fluorescent tube as a light source, a light diffusing plate for uniform surface light, a display panel such as a transmissive liquid crystal, a reflective box body having an inner surface as a reflecting surface, a heat radiating portion for radiating heat inside the device, and a temperature depending on temperature. In a display device including a temperature switch whose shape changes, the reflection box body is made of metal, and the heat dissipation portion is provided at a certain distance from the back surface of the reflection box body, and the temperature switch has a shape memory. It is laminated with an alloy and a constant elastic material, and is partially fixed to the heat radiating part. When the temperature inside the device is below a certain temperature, it deforms so as to be separated from the back surface of the reflection box by a certain distance, and the temperature inside the device changes. When the temperature is higher than a certain temperature, the display device is deformed so as to come into contact with the back surface of the reflection box body in a wide range. 2. The display device according to claim 1, wherein the heat dissipation portion is a heat dissipation fin arranged on the back surface of the reflection box body. 3. The display device according to claim 1, wherein the heat dissipation portion is a metallic outer case that covers the entire display device. 4. A fluorescent tube as a light source, a light diffusing plate for uniform surface light, a display panel such as a transmissive liquid crystal, a reflective box body having an inner surface as a reflecting surface, and a device temperature detected by a temperature detecting means. In a display device including a heat radiating means by a fan for controlling on or off and a temperature switch whose shape changes depending on temperature, the reflection box body is made of a resin material, and the opening is formed on the back surface of the light diffusion plate. When the temperature switch is arranged with a predetermined distance, the temperature switch is laminated with a shape memory alloy and a constant elastic material, and one end of the temperature switch is fixed to the opening of the reflection box body. Fills the space between the opening of the reflection box and the back surface of the light diffusing plate and transforms it into a shape that seals the inside of the reflection box. There is a gap between the opening of the reflection box and the back surface of the light diffusion plate. As becomes available, the display apparatus characterized by deformed as bends.