JPH07130477A - Back light device - Google Patents

Abstract

PURPOSE:To provide a back light device which maintains the whole fluorescent to give lamp at a temp. to give highest light emission efficiency and enables back illuminating with a high brightness even in the coldness. CONSTITUTION:When a fluorescent lamp 1 is lighted up, the temp. of its central part is sensed by a thermistor 5 while the temp, of the end part is sensed by another thermistor 6. A heater control circuit 10 controls the temps. of the central part and end part of the lamp 1 so that they are maintained at the temps. which give the highest light emission efficiently on the basis of the data from the sensing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device used as a backlight for a head-up display device for automobiles, a liquid crystal display device and the like.

[0002]

2. Description of the Related Art In recent years, hot cathode fluorescent lamps capable of high-luminance emission have been used as backlight devices used for backlights of automobile head-up display devices, liquid crystal display devices, etc., as compared with cold cathode fluorescent lamps. Has been done.

[0003]

However, as shown in FIG. 6, the brightness of the hot-cathode fluorescent lamp is very sensitive to the temperature, and particularly when the temperature of the hot-cathode fluorescent lamp drops to around zero degrees. , Its brightness is extremely reduced.

Therefore, in a backlight device used for a head-up display device or a liquid crystal display device for automobiles, when those devices are started from a low temperature state in a cold region, the hot cathode fluorescent lamp emits light at a low temperature. Since the efficiency is low, the brightness is very low, and there is a problem that the display performance is deteriorated.

Therefore, it has been considered to heat the periphery of the hot cathode fluorescent lamp with a heater at a low temperature. However, when the hot cathode fluorescent lamp is turned on, a considerable temperature difference occurs between the electrode portions at both ends and the central portion. When heated with a single heater, there is a problem that it is difficult to maintain the temperature of the entire fluorescent lamp at the highest luminous efficiency.

The present invention has been made in view of the above points, and provides a backlight device which maintains the temperature of the entire fluorescent lamp at the highest luminous efficiency and enables back lighting with high brightness even in cold weather. The purpose is to do.

[0007]

In order to achieve the above object, the backlight device of the present invention has the following configuration.

That is, the backlight device according to claim 1 is a hot cathode type fluorescent lamp that emits display light from the back side of the liquid crystal display, and a central heater disposed in the outer central portion of the fluorescent lamp. An end heater disposed at both outer ends of the fluorescent lamp, a central temperature detecting element for detecting the temperature of the outer central part of the fluorescent lamp, and an end temperature for detecting the temperature of the outer end of the fluorescent lamp. Based on the temperature detection signals from the detection element, the center temperature detection element and the end temperature detection element, the central heater and the end heater are energized so that the center portion and both end portions of the fluorescent lamp are maintained at a predetermined temperature. Temperature control means for independently controlling Here, the central portion of the fluorescent lamp is a portion excluding the end portions on both sides thereof.

The backlight device according to claim 2 further includes a fan for blowing air to the fluorescent lamp and the fan when the temperature of the central portion or both ends of the fluorescent lamp exceeds a preset temperature higher than a predetermined temperature. And a fan control unit for driving.

[0010]

In the backlight device according to claim 1, when the fluorescent lamp is turned on, the temperature of the central portion is detected by the central temperature detecting element and the temperature of the end portion is detected by the end temperature detecting element. To be done. And the temperature control means
The center heater is controlled based on the detected temperature of the center, the end heater is controlled based on the detected temperature of the end, and the temperatures of the center and the end of the fluorescent lamp are respectively the highest. The temperature is maintained at a temperature at which luminous efficiency is obtained (for example, 50 to 60 ° C.).

Therefore, even in the case of a hot cathode fluorescent lamp, which tends to have a difference in temperature between the central portion and both end portions of the fluorescent lamp at the beginning of lighting in cold weather, the entire fluorescent lamp is controlled to have the highest luminous efficiency. Therefore, it is possible to always radiate light having sufficient brightness to the liquid crystal display.

In the backlight device according to claim 2,
When the temperature exceeds the predetermined temperature, the fluorescent lamp is cooled by the fan, so that it is possible to prevent a decrease in brightness due to an excessive rise in temperature.

[0013]

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

FIG. 1 is a circuit diagram of a backlight device used in a head-up display device for an automobile. Reference numeral 1 denotes a rod-shaped fluorescent lamp (hot cathode fluorescent lamp) having electrode portions at both ends, which is installed on the back side of the liquid crystal display 2 and is connected to a lighting circuit (not shown) to be lit and directed toward the liquid crystal display 2. Back lighting.

A central heater 3 and an end heater 4 are independently provided on the outer peripheral rear surface side of the fluorescent lamp 1, and the central heater 3 is attached so as to cover the substantially central rear surface of the fluorescent lamp 1. The end heaters 4 are attached so as to cover the back surfaces of both ends (portions where the electrodes are located).

Further, in order to detect the temperature of the central portion of the fluorescent lamp 1, a thermistor 5 is attached to the approximate center of the tube, and in order to detect the temperature of the end portion of the fluorescent lamp 1, the thermistor 6 is provided. Mounted near the edge. In FIG. 1, the thermistor 5 is attached to the outside of the central heater 3, and the thermistor 6 is attached to the outside of the end heater 4. Good.

Reference numeral 10 denotes a heater control circuit, which independently controls the currents supplied to the central heater 3 and the end heater 4 based on the detection signals from the thermistors 5 and 6 so as to control the central portion of the fluorescent lamp 1. The whole structure including the end portion is configured to be maintained at a temperature (for example, 50 to 60 ° C.) having the highest luminous efficiency.

That is, the heater control circuit 10 is composed of a central heater control unit 10a and an end heater control unit 10b. The thermistor 5 is connected to the inverting input side of the comparator 11 of the central heater control unit 10a. A power supply (constant voltage power supply) is connected via a resistor 14, a power supply is connected to the non-inverting input side of the comparator 11 via a resistor 15, and a resistor 1
6 is connected to the ground. The output side of the comparator 11 is connected to the base of the transistor 12, and the power source is connected thereto via the resistor 18. Between the output side and the inverting input side of the comparator 11, a resistor 17 for hysteresis operation is provided.
Are connected. Further, the collector of the transistor 12 is connected to the base of the transistor 13, and the power source is connected thereto via the resistor 19.

Further, the central heater 3 is connected to the collector of the transistor 13 and the emitters of the transistors 12 and 13 are connected to the ground to form a Darlington circuit.

Similarly to the end heater control section 10b, the thermistor 6 is connected to the inverting input side of the comparator 21 as well as the power source (constant voltage power source) via the resistor 24, so that the comparator is connected. A power supply is connected to the non-inverting input side of 21 via a resistor 25, and a resistor 26 is connected to the ground. The output side of the comparator 21 is a transistor 22
To the base of which the power supply is connected via a resistor 28. A resistor 27 for hysteresis operation is connected between the output side and the inverting input side of the comparator 21.

Further, the collector of the transistor 22 is connected to the base of the transistor 23, and the power source is connected thereto via the resistor 29. Further, the end heater 4 is connected to the collector of the transistor 23, and the emitters of the transistors 22 and 23 are connected to the ground, forming a Darlington circuit.

Next, the operation of the backlight device having the above structure will be described.

In the backlight device, the fluorescent lamp 1 is turned on by the operation of a lighting circuit (not shown) and emits light toward the liquid crystal display 2. At the same time, the heater control circuit 1
0 operates, and the center heater 3 and the end heater 4 are used in cold weather.
Then, the fluorescent lamp 1 is controlled so that the entire fluorescent lamp 1 is maintained at a temperature (for example, 50 to 60 ° C.) having the highest luminous efficiency.

For example, the fluorescent lamp 1 detected by the thermistors 5 and 6 when the backlight device is used in cold weather.
If the temperature is lower than a predetermined temperature (for example, 50 ° C.), the resistance value of the thermistor 5 rises in the central heater control unit 10a, and the voltage applied to the inverting input side of the comparator 11 becomes higher than that of the non-inverting input side. When the voltage rises above the voltage, a low level signal is output from the comparator 11, the transistor 12 is turned off, the transistor 13 is turned on, and a current flows through the central heater 3.
The central heater 3 heats the fluorescent lamp 1,
Is heated to a predetermined temperature.

At the same time, in the end heater controller 10b, when the resistance value of the thermistor 6 rises and the voltage applied to the inverting input side of the comparator 21 rises above the voltage on the non-inverting input side, the comparator 21 Outputs a low level signal, the transistor 22 is turned off, the transistor 23 is turned on, and current flows through the end heaters 4 on both sides. The end heaters 4 heat the fluorescent lamp 1 to bring the fluorescent lamp 1 to a predetermined temperature. Raise the temperature.

When the temperature of the fluorescent lamp 1 rises to a predetermined temperature, the resistance values of the thermistors 5 and 6 decrease,
When the voltage applied to the inverting input side of the comparators 11 and 21 falls below the voltage on the non-inverting input side, the outputs of the comparators 11 and 21 change to high level, the transistors 12 and 22 turn on, and the central heater 3 The power supply to the end heater 4 is stopped.

The central heater control section 10a and the end heater control section 10b repeat the above-mentioned operation to control the temperature of the fluorescent lamp 1 to be kept at a predetermined temperature. Usually, the temperature of the central portion of the fluorescent lamp 1 is more likely to rise than that of the end portions thereof, and the temperature of each portion of the fluorescent lamp is not uniform, but as described above, the central heater control unit 10a and the end heater control are performed. Since the portion 10b independently controls the temperature, the central portion and the end portions of the fluorescent lamp 1 are similarly maintained at a predetermined temperature (for example, 50 ° C.), and the fluorescent lamp 1 has high luminous efficiency as shown in FIG. Works with.

FIG. 2 shows another embodiment in which, in addition to the central heater 3, the end heater 4, and the heater control circuit 10 having the above-described structure, cooling is performed when the temperature of the fluorescent lamp 1 rises too much. The electric fan 7 for controlling the electric fan 7 is provided, and the electric fan 7 is controlled by the fan control circuit 30.

The fan control circuit 30 is also used as the thermistor 5 for detecting the temperature of the central part of the fluorescent lamp 1.
Connect the thermistor 5 to the inverting input side of the comparator 31,
A transistor 32 is connected to the output side of the comparator 31, and further connected to a power source via a resistor 37, a coil of a relay 33 is connected to the collector of the transistor 32, and a motor of the electric fan 7 is connected to a contact of the relay 33. Consists of Further, a power supply (constant voltage power supply) is connected to the inverting input side of the comparator 31 via a resistor 36, and a non-inverting input side of the comparator 31 is connected to the middle point of the resistors 34 and 35, and the resistor 34. Is connected to the power supply, and the resistor 35 is connected to the ground.

In the backlight device constructed as described above, as in the above-described embodiment, the central heater 3 is used during cold weather.
Then, the end heater 4 is energized to heat the fluorescent lamp 1, and the temperature is detected by the thermistors 5 and 6, and the heater control is performed so as to maintain the temperature at which the highest luminous efficiency is obtained.

At the same time, if the temperature of the fluorescent lamp 1 has risen abnormally excessively, the fan control circuit 30 activates the electric fan 7 to operate to cool the fluorescent lamp 1 to a predetermined temperature. For example, when the temperature of the central portion of the fluorescent lamp 1 rises to 60 ° C. or higher, the resistance value of the thermistor 5 decreases, and the voltage applied to the inverting input side of the comparator 31 becomes lower than the voltage on the non-inverting input side. Therefore, the comparator 31
A high level signal is generated on the output side of the transistor and the transistor 32 becomes conductive.

As a result, the relay 33 is energized, its contact is turned on, the electric fan 7 is activated, and air is blown,
The fluorescent lamp 1 is air-cooled. Then, for example, when the temperature drops to 50 ° C., by stopping the electric fan 7,
The temperature of the fluorescent lamp 1 can be maintained at a temperature at which the highest luminous efficiency can be obtained.

In the above two embodiments, one fluorescent lamp is used. However, when a plurality of fluorescent lamps are used, a heater is attached to each fluorescent lamp and the thermistor is attached. The temperature of each fluorescent lamp may be controlled to an optimum temperature by controlling each heater while detecting the temperatures thereof.

FIGS. 3 to 5 show a backlight device for a head-up display device having a bright line spectrum lamp (hot cathode fluorescent lamp) which emits a plurality of different colored lights.

In this backlight device, three pairs of bright line spectrum lamps 42a, 42b, 42c and dichroic mirrors 45, 46 are used, and the color difference of the display color becomes the largest with respect to the background color detected by the colorimeter. Thus, the bright line spectrum lamps 42a, 42b, 42c are switched and controlled.

The bright line spectrum lamp includes a red bright line spectrum lamp 42a for emitting red monochromatic light, a green bright line spectrum lamp 42b for emitting green monochromatic light, and a blue bright line spectrum lamp 42 for emitting blue monochromatic light.
each of the emission line spectrum lamps 42a, 42b,
The heaters 40a, 40b, 4 are provided on the rear surface side of the outer peripheral portion of 42c.
0c is attached, and temperature sensors 41a, 41b, 41c such as a thermistor are attached on them.

Reference numeral 44 denotes a display device arranged in front of the backlight device, which is composed of, for example, a monochrome liquid crystal display, and displays information such as vehicle speed by digital values, codes, figures and the like. Behind the display device 44, dichroic mirrors 45 and 46 are arranged so as to cross each other in a cross shape. The dichroic mirror 45 reflects only red light, the dichroic mirror 46 reflects only blue light, and other light is reflected. Make it transparent.

Then, those dichroic mirrors 4
5, the red line spectrum lamp 42a is arranged in the upper part where the openings of 5, 46 are arranged, the blue line spectrum lamp 42c is arranged in the lower part thereof, and the green line spectrum lamp 42b is arranged behind it. The display light of each of the three primary colors emitted from the bright line spectrum lamps 42a, 42b, 42c is emitted with a more uniform distribution. Further, a diffusion plate 43 is arranged in front of each bright line spectrum lamp.

FIG. 4 shows a block diagram of the heater of the backlight device and the control device for controlling the switching of the bright line spectrum lamp. Reference numeral 48 denotes a controller composed of a CPU and the like, which includes a chromaticity meter 47 for detecting the chromaticity of the background color, the bright line spectrum lamps 42a, 42b, 42c, the heaters 40a, 40b, 40c, and the temperature sensors 41.
a, 41b, 41c are connected thereto.

The controller 48 controls the temperature sensors 41a, 41 regardless of whether the bright line spectrum lamp is on or off.
b, 41c based on the detected temperature, heaters 40a, 4a
0b, 40c to control the bright line spectrum lamp 42a,
It operates to keep the temperatures of 42b and 42c within a predetermined range. Further, based on the detection signal of the background color from the chromaticity meter 47, the color difference between the background color and the display color is maximized,
The bright line spectrum lamps 42a, 42b, 42c are switched and controlled.

That is, as shown in the flow chart of FIG. 5, the controller 48 first determines in step 100 whether or not the heater 40a is in the ON state. If the heater 40a is in the OFF state, then in step 110, Temperature sensor 41
It is determined whether the detected temperature of a is 30 ° C. or lower, and if the temperature is 30 ° C. or lower, the heater 40 a is turned on in step 130. If the temperature exceeds 30 ° C., the heater 40a is not turned on and the process proceeds to the next step 150.

On the other hand, if it is determined in step 100 that the heater 40a is in the on state, then the process proceeds to step 120, in which it is determined whether the temperature detected by the temperature sensor 41a is 35 ° C. or higher, and the temperature is 35 ° C. or higher. If so, step 140
Then, the heater 40a is turned off. Also, the temperature is 35
If the temperature is less than 0 ° C., the heater 40a is not turned off and the process proceeds to the next step 150.

In step 150, the other heaters 40b,
40c is processed in the same manner as in steps 100 to 140, and when the heaters 40b and 40c are off and the detected temperature of each lamp is 30 ° C. or lower, the heaters 40b and 4
0c is in the ON state and the heaters 40b and 40c are in the ON state and the detected temperature of each lamp is 35 ° C. or higher, the heater 4
Control is performed so that 0b and 40c are turned off.

Next, in step 160, it is judged whether or not the display color is changed, and if the color difference between the background color and the display color detected by the chromaticity meter 47 is small, the step for changing the display color is performed. At 170, the display color is determined, and on / off control of each of the emission line spectrum lamps 42a, 42b, 42c of the three primary colors is performed or the brightness thereof is adjusted so that the backlight device emits the display color.

Thus, the heater 4 provided on the lamp
0a, 40b, 40c to the temperature sensors 41a, 41b,
The temperature of each of the bright line spectrum lamps 42a, 42b, 42c is controlled by controlling the detection signal from 41c.
Regardless of whether it is turned on or off, it will always be at a predetermined temperature (30-3
5 ° C.), and especially when changing the display color, the bright line spectrum lamps 42a, 42b,
Since the lamp is always heated to an appropriate temperature when the on / off control of 42c is performed, it is possible to emit the display light having sufficient brightness from the initial stage of lighting. Therefore, even in cold weather, display light of an appropriate color can be emitted to the display device without causing a color shift in the display color.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a backlight device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a backlight device showing another embodiment.

FIG. 3 is a perspective view of a backlight device according to another embodiment.

FIG. 4 is a block diagram of the backlight device.

FIG. 5 is a flowchart showing the operation of the same device.

FIG. 6 is a graph showing a change in brightness with temperature of a fluorescent lamp.

[Explanation of symbols]

 1-Fluorescent lamp, 2-Liquid crystal display, 3-Center heater, 4-End heater, 5,6-Thermistor, 10-Heater control circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G09G 3/18

Claims (2)

[Claims] 1. A hot-cathode fluorescent lamp that emits display light from the back side of a liquid crystal display, a central heater disposed in the outer central portion of the fluorescent lamp, and outer end portions of the fluorescent lamp. An arranged end heater, a central temperature detecting element for detecting a temperature of an outer central portion of the fluorescent lamp, an end temperature detecting element for detecting a temperature of an outer end of the fluorescent lamp, and the central portion Based on the temperature detection signals from the temperature detection element and the end temperature detection element, the central heater and the end heater are independently energized so that the central portion and both end portions of the fluorescent lamp are maintained at a predetermined temperature. A backlight device comprising: 2. A fan for blowing air to the fluorescent lamp, and fan control means for driving the fan when the temperature of the central portion or both end portions of the fluorescent lamp exceeds a preset temperature higher than the predetermined temperature. The backlight device according to claim 1, wherein: