JPH0992210A - Double tube type low pressure mercury vapor electric discharge lamp and lamp device and lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the rising of light flux in the case of starting a low pressure mercury vapor electric discharge lamp under low temp. atmosphere and prevent excessive rising of temp. in an arc tube during stable operation causing decrease in the luminance. SOLUTION: In a light transmissive outer tube 20 having an air-tight space therein an arc tube 10 in which mercury and rare gas are sealed is contained. Between the two 10, 20 a heat transmission member such as silicone rubber 25 for connecting the two 10, 20 to each other in a heat transmissible manner is disposed. Thereby when the thus constructed lamp starts under the low temp. atmosphere the temp. increase in the arc tube 10 is facilitated with the heat insulation action in the heat insulating space in the outer tube 20. Even when the temp. in the tube 10 tends to rise the heat in the tube 10 escapes through the silicone rubber. Accordingly fluctuation in the luminance caused by the temp. change of the circumference can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-tube low-pressure mercury vapor discharge lamp typified by a double-tube fluorescent lamp, a lamp device therefor, and a lighting device using this lamp.

[0002]

2. Description of the Related Art Recently, a fluorescent lamp with low power consumption is used as a backlight of a liquid crystal display device, and a cold cathode fluorescent lamp is also used in a small liquid crystal display device. However, such a fluorescent lamp has a problem that the temperature of the arc tube is easily affected by the ambient temperature because the amount of heat generated during lighting is small. That is, for example, when the fluorescent lamp is started below freezing, it takes a long time until the vapor pressure rises because the enclosed mercury is difficult to evaporate, and it is necessary to wait a few minutes until the brightness reaches a predetermined level. Therefore, there is a problem that the rising characteristic is not good in a low temperature condition.

As a means for improving such a problem,
Various measures have been taken such as providing a heater for low temperature compensation around the fluorescent lamp. However, since such a structure requires a heater, a temperature fuse for controlling the heater, a thermistor, and the like, the number of parts increases, and there is a problem that these parts block light.

On the other hand, Japanese Utility Model Publication No. 4-53293 discloses that
It has been proposed that the arc tube be housed in an airtight outer tube to have a double tube structure. When the arc tube is housed in an outer tube and has a double tube structure, the surroundings of the arc tube are surrounded by a heat insulating space, so when the lamp is started, the heat emitted from the arc tube is prevented from escaping, and the temperature of the arc tube is reduced. It prompts the rise and the rise of the luminous flux becomes quick.

[0005]

However, in the case of the double-tube fluorescent lamp constructed as described above, the fluorescent lamp is lit in a low temperature atmosphere for a long time, or a large lamp power is supplied to obtain a large brightness. Or, particularly when the ambient temperature is high for a long time, the temperature of the arc tube may rise excessively due to the heat insulating function of the heat insulating space in the outer tube. When the temperature rises excessively in this way, the vapor pressure of mercury exceeds an optimum value, and self-absorption of mercury occurs, conversely causing a decrease in brightness.

The present invention has been made in view of the above circumstances, and an object thereof is to promote the rise of a luminous flux in a low temperature atmosphere and prevent an excessive temperature rise of an arc tube during stable lighting. The present invention aims to provide a double-tube low-pressure mercury vapor discharge lamp, a lamp device and a lighting device for the double-tube low-pressure mercury vapor discharge lamp.

[0007]

[Means for Solving the Problems]

[Structure] The invention according to claim 1 is a translucent outer tube having an airtight space; an arc tube which is housed in the outer tube, in which an electrode is sealed in the discharge space, and mercury and a rare gas are sealed. A double-tube low-pressure mercury vapor discharge, comprising: a heat conductive member provided between the light emitting tube and the outer tube and connecting the light emitting tube and the outer tube so as to be able to conduct heat. It is a lamp.

The invention of claim 2 is characterized in that the heat conducting member is a heat conductor having one end in contact with the arc tube and the other end in contact with the outer tube. It is a tube type low pressure mercury vapor discharge lamp.

According to a third aspect of the present invention, the heat-conducting member is a thermal responsive element that is bridged between the light emitting tube and the outer tube, and the light emitting tube and the outer tube are thermally coupled when the temperature exceeds a predetermined temperature. The double-tube low-pressure mercury vapor discharge lamp according to claim 1, wherein

According to a fourth aspect of the present invention, the heat conducting member is filled between the light emitting tube and the outer tube, evaporates when the temperature exceeds a predetermined temperature, and thermally connects the light emitting tube and the outer tube. The double-tube low-pressure mercury vapor discharge lamp according to claim 1, wherein

A fifth aspect of the present invention includes the double-tube low-pressure mercury vapor discharge lamp according to any one of the first to fourth aspects, and a high-frequency lighting circuit for lighting the low-pressure mercury vapor discharge lamp. A double-tube low-pressure mercury vapor discharge lamp device characterized in that it is provided.

According to a sixth aspect of the present invention, there is provided a double-tube low-pressure mercury vapor discharge lamp according to any one of the first to fourth aspects, and a lighting fixture body to which the lamp is attached. It is a characteristic lighting device.

[Operation] According to the invention of claim 1, when starting in an atmosphere with a low ambient temperature, the circumference of the arc tube is surrounded by the airtight heat insulating space formed in the outer tube, so that the heat emitted from the arc tube is generated. The escape is suppressed, and the temperature rise of the arc tube is promoted. When the temperature of the arc tube rises excessively, the heat of the arc tube is released to the outer tube through the heat conductive member that connects the arc tube and the outer tube so that heat can be conducted, and is radiated from the surface of the outer tube. It Therefore, it is possible to improve the start-up characteristics at the time of low temperature start, suppress the excessive temperature rise of the arc tube at the time of high temperature and maintain the optimum temperature, and suppress the fluctuation of the brightness due to the ambient temperature change.

According to the second aspect of the invention, the heat conducting member is a heat conductor whose one end is in contact with the arc tube and the other end is in contact with the outer tube. Therefore, the heat conduction between the arc tube and the outer tube is prevented. Prompt,
Moreover, the structure is simple and the mounting is easy.

According to the third aspect of the present invention, since the heat conducting member is a heat responsive element that is bridged between the arc tube and the outer tube, if the temperature is lower than a predetermined temperature, the arc tube and the outer tube are heated. Therefore, the heat of the arc tube, which does not increase its temperature at the time of starting, is not transmitted to the outer tube, so that the temperature rise of the arc tube is promoted. However, if the temperature of the arc tube exceeds a predetermined temperature, the thermoresponsive element When activated, the arc tube and the outer tube are thermally connected to each other, and the heat of the arc tube is transferred to the outer tube and radiated from the outer tube. Therefore, it is possible to improve the start-up characteristics at the time of low-temperature start, and to suppress the excessive temperature rise of the arc tube at the time of high temperature to maintain the optimum temperature.

According to the invention of claim 4, the heat conducting member comprises:
Since it is the evaporative heat medium filled between the arc tube and the outer tube, if the arc tube is below a predetermined temperature, the evaporation amount of the evaporative heat medium in the outer tube is small, so that the heat conducting function as a heat medium. It is small and the temperature rise of the arc tube becomes faster. However, when the temperature inside the outer tube exceeds a predetermined temperature, the amount of evaporation of the evaporative heat medium increases, the heat conduction effect increases, and the rate at which the heat of the arc tube is transferred to the outer tube increases, so the temperature rise of the arc tube is suppressed.

According to the invention of claim 5, the double-tube low-pressure mercury vapor discharge lamp according to any one of claims 1 to 4 is lit at a high frequency by using a high-frequency lighting circuit. Also, the cathode drop voltage is lowered, and the lamp voltage can be lowered, thus improving the luminous efficiency of the lamp.

In the illuminating device according to the sixth aspect, since the double-tube low-pressure mercury vapor discharge lamp used as the light source is excellent in low-temperature startability, the rise of the luminance is good, and the variation of the luminance is caused even when the temperature changes. There is little change in the brightness of the screen.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the first embodiment shown in FIGS. FIG. 1 is a diagram showing the configuration of a double-tube cold cathode fluorescent lamp 1 and its lighting circuit.

Double-tube cold cathode fluorescent lamp 1 shown in FIG.
Has a double tube structure including an arc tube 10 serving as an inner tube and an outer tube 20 accommodating the arc tube 10. Arc tube 10
Has a straight tube type valve 11 made of lead glass having an outer diameter D of, for example, 3 mm and a total length of 230 mm.
The inner surface of the phosphor is a phosphor that emits visible light when excited by ultraviolet rays having a wavelength of 254 nm emitted from mercury, for example, a color temperature of 65
Phosphor layer 1 made of a three-wavelength light-emitting phosphor emitting 00K
2 is formed.

Cold cathodes 13, 13 are sealed at both longitudinal ends of the bulb 11. Each of the cold cathodes 13 and 13 is configured by joining a rod-shaped or cylindrical electrode main body 13a to an electrode shaft 13b also serving as a lead wire, and the electrode main body 13a is formed of nickel Ni. The electrode shaft 13b is connected to a sealing wire 14 made of a metal having a coefficient of thermal expansion similar to that of glass, for example, a large diameter Dumet wire, and the sealing wire 14 is sealed to a sealing portion 15 at the end of the valve 11. Has been done. Each of the sealing wires 14 is connected to an external lead wire 16.

A predetermined amount of mercury is contained in the bulb 11.
A mixed rare gas composed of argon Ar and neon Ne at a predetermined pressure is enclosed. Filling pressure of mixed rare gas is about 100
It is Torr.

The arc tube 10 is housed in the outer tube 20. The outer tube 20 has an outer diameter of, for example, 4 mm and a total length of 25.
It is made of lead glass with a size of 5 mm, and both ends are closed. The closed ends 21 and 21 are made of a metal having a coefficient of thermal expansion similar to that of glass, for example, a conductor 2 made of a large diameter Dumet wire.
2 and 22 are hermetically sealed, and the conductors 22 and 22
The outer lead wires 16, 16 of the arc tube 10 are attached to the inner end surface of the
, And other external lead wires 23, 23 are connected to the outer end face.

The inside of the outer tube 20 is airtight, and the inside of the outer tube 20 is filled with a vacuum or a rare gas at a low pressure. In this embodiment, the outer tube is evacuated.
Further, between the arc tube 10 and the outer tube 20, heat conducting members 25 ... Are provided at one place or a plurality of places. The heat conducting members 25 may be made of metal, a heat conducting adhesive or the like, but in this embodiment, silicone rubber having excellent heat conductivity is used. The silicon rubbers 25 are arranged at one or more locations, for example, three locations along the axial direction of the arc tube 10. At each location, three silicone rubbers 25 are disposed in the radial direction as shown in FIG. 1 (B). Has been done. These silicone rubbers 25 ... Are joined in a state where their inner ends are in close contact with the outer surface of the arc tube 10 and are in a state where their outer ends are in contact with the inner surface of the outer tube 20. Therefore, the arc tube 10 and the outer tube 20 are mechanically and thermally connected via the silicone rubber 25.

Double tube type cold cathode fluorescent lamp 1 as described above
Are connected to the high frequency lighting circuit 2 shown in FIG. The high frequency lighting circuit 2 supplies high frequency power having a frequency of about 50 kHz to the fluorescent lamp 1, so that the fluorescent lamp 1 is lit at a high frequency. In this case, the lamp current is set to 5 mA.

The operation of the double-tube cold cathode fluorescent lamp 1 having such a configuration will be described. Frequency 50kHz, voltage 1200V from the high frequency lighting circuit 2 to the cold cathode fluorescent lamp 1.
When a high frequency voltage of about (rms) is supplied, the cold cathodes 13 provided at both ends of the arc tube 10 in the cold cathode fluorescent lamp 1,
The high-frequency voltage is applied to the cold cathode 13 so that discharge is started between the cold cathodes 13 and 13. Due to this discharge, a lamp current of about 5 mA flows, the mercury sealed in the arc tube 10 is evaporated, ionized and excited, and this mercury emits ultraviolet rays. This ultraviolet ray is converted into visible light by the phosphor layer 12 formed on the inner surface of the arc tube 10, and this visible light is transmitted to the outside through the bulb 11 and the outer tube 20 of the arc tube 10.

When the double-tube cold-cathode fluorescent lamp 1 having the above structure is started in a low temperature atmosphere, the arc tube 10 is surrounded by the outer tube 20, and the inside of the outer tube 20 is a vacuum space. The arc tube 10 is surrounded by a heat insulating space. Therefore, the heat of the arc tube 10 is prevented from escaping to the outside at the time of start-up, and the temperature of the arc tube 10 rises quickly due to the so-called heat retaining effect of the vacuum space. Therefore, the arc tube 10
The evaporation of mercury in the inside is promoted, the rise of the luminous flux becomes faster,
Cold startability is improved.

Then, when the stable lighting time becomes long and the temperature of the arc tube 10 tries to rise excessively, the heat of the arc tube 10 is transferred to the outer tube 20 through the silicone rubber 25 which is in contact with the outer surface of the arc tube 10. It is directly transmitted and discharged from the surface of the outer tube 20. Therefore, the excessive temperature rise of the arc tube 10 can be prevented, and the vapor pressure of mercury can be suppressed,
It is possible to suppress self-absorption of mercury and prevent a decrease in luminous flux.

Further, the above-mentioned structure is a structure in which the arc tube 10 is mechanically held in the outer tube 20 through the silicone rubber 25, so that the silicone rubber is not affected by external vibration or shock. Since 25 ... Are elastically deformed and have an absorbing action, vibration and impact are prevented from being transmitted to the arc tube 10, the arc tube 10 is protected, and stress can be prevented from being concentrated on the external lead wires 16, 16. . Furthermore, even if the outer tube 20 is cracked due to impact or the like, the arc tube 1
If 0 is safe, it works as a lamp.

The heat releasing action of the silicone rubbers 25 ... Can be selected by appropriately selecting the number of silicone rubbers 25 ... FIG.
4 to 4 are measurement diagrams of the light output rising characteristics at ambient temperatures of -30 [deg.] C., 25 [deg.] C., and 85 [deg.] C., respectively, and as shown in FIG.
When the lamp is started in an atmosphere with an ambient temperature of −30 ° C. without an outer tube, the increase in the brightness is slow and the lighting 1
Even after 0 minutes, the brightness is 3000 cd / m ² . On the other hand, when the arc tube 10 is housed in the outer tube 20,
In the case of the double-tube fluorescent lamp 1 of the present invention in which the inside is evacuated and the silicon rubber 25 is installed between the arc tube 10 and the outer tube 20, when the lamp current is 5 mA and the lamp is started in an atmosphere of −30 ° C., As shown by the characteristic B in FIG.
A brightness of 2000 cd / m ² is obtained, and the low temperature starting characteristic is improved.

In the double-tube cold cathode fluorescent lamp, if the silicone rubber 25 is not installed between the arc tube 10 and the outer tube 20, the lamp current is 5 mA and the lamp is started in an atmosphere of -30 ° C. As shown by the characteristic C in FIG. 2, the low temperature starting characteristic becomes good.

Similarly, when the arc tube 10 without an outer tube is started in an atmosphere with an ambient temperature of 25 ° C., the brightness rises quickly as shown by the characteristic A in FIG.
A brightness of cd / m ² was obtained.

Further, the above-mentioned arc tube 10 is housed in an outer tube 20, the inside of the outer tube 20 is evacuated, and silicone rubber 25 is installed between the arc tube 10 and the outer tube 20. In the case of the lamp 1, when it is started in an atmosphere of 25 ° C. with a lamp current of 5 mA, the brightness increases rapidly as shown by the characteristic B of FIG. 3, and then the brightness gradually increases with the temperature rise of the arc tube 10. Although it decreases, the brightness is 2400 after 2 minutes of lighting.
It settled down to 0 cd / m ² .

In the double-tube cold-cathode fluorescent lamp, if the silicone rubber 25 is not installed between the arc tube 10 and the outer tube 20, the lamp current is 5 mA and the lamp is started at 25 ° C. As shown by the characteristic C, the luminance rises sharply, but there is a tendency that the luminance gradually decreases after stable lighting.

Further, when the arc tube 10 without the outer tube is started in an atmosphere having an ambient temperature of 85 ° C., the brightness after 2 minutes of lighting is 25000 cd / m ² , as shown by the characteristic A in FIG. There was no significant decrease in brightness.

Further, the arc tube 10 is housed in the outer tube 20, the inside of the outer tube 20 is evacuated, and the silicone rubber 25 is installed between the arc tube 10 and the outer tube 20. In the case of No. 1, when it is started in an atmosphere of 85 ° C. with a lamp current of 5 mA, the brightness after 2 minutes of lighting is 24000 cd / m ² , as shown by the characteristic B in FIG. There was no

However, in the double-tube cold cathode fluorescent lamp, if the silicone rubber 25 is not installed between the arc tube 10 and the outer tube 20, the lamp current is 5 mA and the lamp is started in an atmosphere of 85 ° C. As shown by the characteristic C of No. 4, the luminance is 175 when the arc tube 10 overheats and is stably lit.
There was a tendency for the value to drop to around 00 cd / m ² .

From the above, the arc tube 10 is replaced by the outer tube 2
In the case of the double tube fluorescent lamp 1 of the present invention in which the outer tube 20 is vacuumized and the silicon rubber 25 is installed between the arc tube 10 and the outer tube 20, the luminous flux rises in a low temperature atmosphere. The characteristics are improved, the heat of the arc tube 10 is released to the outside even in a high temperature atmosphere, an excessive temperature rise is prevented, and the mercury vapor pressure is maintained at an appropriate level, so that a change in brightness can be suppressed.

5 and 6 show an example in which the double-tube cold cathode discharge lamp 1 and its lighting device shown in FIG. 1 are used as a light source device of a liquid crystal display device as an illuminating device. That is, in FIGS. 5 and 6, reference numeral 30 denotes a backlight and 40 denotes a liquid crystal display panel.

The backlight 30 includes a light guide plate 31, a pair of the double-tube cold-cathode fluorescent lamps 1 and 1 and a reflection corresponding to the main body of the luminaire surrounding the double-tube cold-cathode fluorescent lamps 1 and 1. The light guide plate 31 includes the bodies 32 and 32.
Is made of a transparent or milky white light-transmissive material such as acrylic resin, and is formed in a rectangular flat plate shape. The double-tube cold cathode fluorescent lamps 1, 1 are arranged at both ends of the light guide plate 31 so as to face the end faces of the light guide plate 31. The double-tube cold-cathode fluorescent lamps 1 and 1 have the structure shown in FIG. 1, and are connected to the high-frequency lighting circuit 2 not shown in FIGS. 5 and 6 as shown in FIG. .

Each double-tube cold cathode fluorescent lamp 1, 1 is covered with a reflector 32, 32, respectively. These reflectors 32, 32 are made of metal, resin, or the like, and have a semicircular or quadratic cross section, and have a substantially gutter shape extending along the tube axis direction of the fluorescent lamps 1, 1. Reflective surfaces 33, 33 are formed on the inner surfaces of the reflectors 32, 32 so as to reflect the light emitted from the fluorescent lamps 1, 1 toward the end surface of the light guide plate 41.

A reflection plate 35 or a reflection sheet is provided on the lower surface of the light guide plate 31, that is, the back surface, and the reflection plate 35 reflects the light introduced into the light guide plate 31 and is directed to the upper surface (front surface) side. Tell A light diffusing plate 36 or a light diffusing sheet having a milky white color made of acrylic resin or the like is provided on the upper surface of the light guiding plate 31, and the light diffusing plate 36 diffuses the light emitted from the upper surface of the light guiding plate 31. Control is performed so that a uniform brightness distribution is obtained, and thereby uneven brightness is eliminated.

The backlight 30 is constructed with such a configuration, and the liquid crystal display panel 40 is installed on the front surface of the light diffusion plate 36 of the backlight 30. Therefore, the backlight 30 and the liquid crystal display panel 40 constitute a liquid crystal display device.

In the liquid crystal display device having such a structure, when the double-tube cold cathode fluorescent lamps 1, 1 as the light source are lit at high frequency, the light emitted from the fluorescent lamps 1, 1 directly and by the reflector 32. , 32 toward the end face of the light guide plate 31 after being reflected by the reflection faces 33, 33 of the light guide plate 32, and enters the inside of the light guide plate 31 from this end face. Inside the light guide plate 31, light travels while repeating total reflection on each surface, and is reflected by the reflection plate 35 provided on the back surface, so that the light is eventually emitted toward the front surface. In this way, the light traveling toward the front surface of the light guide plate 31 is
The diffused light is diffused by the light diffusing plate 36, and the diffused light illuminates the back surface of the liquid crystal display panel 40. Therefore, the liquid crystal display panel 4
0 is illuminated by the light from the backlight 30, and a predetermined display can be displayed on the front surface.

In such a backlight 30, since the low-temperature startability of the lamp 1 used as a light source is good, the brightness of the screen of the liquid crystal display panel 40 rises well, and the lamp 1 has a brightness which varies due to a change in ambient temperature. Since the change is small, the change in the brightness of the screen of the liquid crystal display panel 40 is small.

The present invention is not limited to the above-mentioned first embodiment. That is, in the first embodiment, as a heat conducting member that thermally connects the arc tube 10 and the outer tube 20,
Although the case where the silicon rubber 25 ... Joined across the arc tube 10 and the outer tube 20 is used has been described, the present invention is not limited to this, and as in the second embodiment shown in FIG. A heat-actuated heat conducting member, such as a bimetal piece 40, may be used. In the case of this embodiment, a plurality of supporting strips 41 are wound around the outer surface of the arc tube 10, and one end of the bimetal piece 40 is joined to these strips 41 by welding or the like. The bimetal pieces 40 are deformed by a temperature difference, and when the temperature of the arc tube 10 side exceeds the temperature of the outer tube 20 by a predetermined temperature or more, the tip is thermally deformed as shown by an imaginary line. It extends so that its tip comes into contact with the inner surface of the outer tube 20.

When the heat-actuated heat conduction member having such a structure, that is, the bimetal piece 40 ... Is used, the lamp 1 is started when the ambient temperature is low and both the arc tube 10 and the outer tube 20 are in a low temperature state. Then, since the circumference of the arc tube 10 is surrounded by the vacuum space, the vacuum space performs a heat insulating action, thereby promoting the temperature rise of the arc tube 10. At this time,
Since the tip of the bimetal piece 40 ... Does not contact the outer tube 20, the heat of the arc tube 10 does not escape through the bimetal piece 40.

Therefore, the luminous flux rises quickly at low temperature startup, and the brightness rises in a short time. On the other hand, when the temperature of the arc tube 10 rises due to continuous stable lighting, even if the ambient temperature is as low as around 0 ° C., for example, the arc tube temperature is 50
When the temperature is higher than or equal to ℃, the bimetal piece 40 is thermally deformed by the heat of the arc tube 10, and the tip portion contacts the inner surface of the outer tube 20.
Therefore, the heat of the arc tube 10 is transferred to the outer tube 20 through the bimetal piece 40 and is radiated from the surface of the outer tube 20. Therefore, the temperature rise of the arc tube 10 is suppressed, and the mercury vapor pressure is prevented from rising excessively.

Since the bimetal piece 40 is thermally deformed when the temperature difference between the temperature of the arc tube 10 and the ambient temperature reaches a predetermined value, for example, when the ambient temperature of the outside is 80 ° C. or higher, the temperature of the arc tube 10 becomes higher. If the temperature is below the above temperature difference,
Does not contact the outer tube 20 without thermal deformation. Therefore, high external heat is not picked up and transmitted to the arc tube 10, and it is possible to avoid problems such as excessive rise of the arc tube temperature when the ambient temperature is extremely high.

Further, in the present invention, an evaporative heat medium may be used as the heat conducting member as in the third embodiment shown in FIG. The double-tube cold-cathode fluorescent lamp of FIG. 8 is basically the same in structure as the conventional one, but the evaporative heat medium, for example, mercury is enclosed in the outer tube 20. Mercury is an outer tube 20
The amount of evaporation changes according to the internal temperature. The mercury vapor acts as a heat medium to transfer heat between the arc tube 10 and the outer tube 20.

Therefore, in the case of such a structure, when the lamp 1 is started in a state where the ambient temperature is low, the amount of mercury vaporized in the outer tube 20 is small, so that the outer tube 20 is close to a vacuum state, and thus the vacuum space is reduced. Has an adiabatic effect, which promotes a rise in temperature of the arc tube 10. Therefore, the rising of the luminous flux at the time of low temperature start is promoted, and the brightness is increased in a short time.

On the other hand, when the temperature of the arc tube 10 rises, the temperature in the outer tube 20 also rises, the evaporation of mercury enclosed in the outer tube 20 is promoted, and the mercury vapor in the outer tube 20 increases. Since this mercury vapor acts as a heat medium, the heat of the arc tube 10 is transferred to the outer tube 20 through the mercury vapor in the outer tube, and thus the outer tube 20.
To be released from the surface of. For this reason, the temperature rise of the arc tube 10 is suppressed, and the mercury vapor pressure in the arc tube 20 is suppressed from being excessively increased.

In the case of the third embodiment shown in FIG. 8, an example has been described in which mercury is enclosed as the evaporative heat medium in the outer tube 20, but the mercury enclosed in the outer tube is used only as the heat medium. Since it is wasteful to do so, it may be performed as in the fourth embodiment shown in FIG. That is, in the fourth embodiment of FIG. 9, the outer tube 20 is filled with a rare gas such as mercury and argon / neon, and the fluorescent layer 24 is formed on the inner surface of the outer tube 20. The outer tube electrodes 25, 25 are sealed at the ends of the. These external electrodes 25, 25 are also the high frequency circuit 2
Connected to

According to this structure, when the lamp 1 is started, the electrodes 13, 13 of the arc tube 10 and the outer tube electrode 25,
High-frequency power is applied to 25 at the same time, and each arc tube 1
A discharge is generated in the 0 and the outer tube 20. When the ambient temperature is low, the temperature rise in the outer tube 20 is delayed, but the arc tube 1
Since 0 is kept warm in the airtight space of the outer tube 20, the temperature rise is promoted, and thus the luminous flux rise of the arc tube 10 is improved.

After that, when the temperature of the arc tube 10 rises, the heat of the arc tube 10 is transferred to the mercury and the rare gas in the outer tube 20, and at the same time, the temperature of the inner space of the outer tube 20 also rises due to the discharge in the outer tube 20. Mercury is also ionized and excited in the outer tube 20 and emits ultraviolet rays, so that it is converted into visible light by the phosphor layer 24.

Therefore, when the stable lighting state is reached, the outer tube 20 discharges light in addition to the discharge light emission of the arc tube 10, so that theoretically, the light output more than twice as much as the discharge light emission of only the arc tube. can get.

When the temperature of the arc tube 10 becomes high,
The mercury vapor in the inner space of the outer tube serves as a heat medium to transfer the heat of the arc tube to the outer tube 20, so that the heat is radiated from the surface of the outer tube 20 and the excessive temperature rise of the arc tube 10 is prevented.

In the case of the double-tube fluorescent lamp structure as shown in FIG. 9, the external lead wire and the sealing wire are shared, and the respective electrodes 13 and 25 may be branched in parallel from the sealing wire. Well, or electrodes 13 and 25 may be connected in series.

Further, when the discharge light emission of the outer tube 20 reaches a stable state, the discharge light emission of the arc tube 10 may be stopped so that only the outer tube 10 emits light. Further, the present invention is not limited to the straight tube fluorescent lamp, may be a bent fluorescent lamp, and the electrode is not limited to being a cold cathode,
It may be a hot cathode, or may be an electrodeless fluorescent discharge lamp like the fifth embodiment shown in FIG. In the electrodeless fluorescent discharge lamp shown in FIG. 10, a rare gas such as mercury and argon is sealed inside a substantially spherical inner tube 70, and a phosphor layer 71 is provided on the inner surface of the inner tube 70.
A high frequency excitation coil 72 is wound around the outer circumference of the inner tube 70. The high frequency excitation coil 72 is connected to the high frequency lighting circuit 73.

The inner pipe 70 is housed in the outer pipe 75. The outer tube 75 is filled with a vacuum or a rare gas at a low pressure. Reference numeral 76 is a lamp holder. The double-tube type electrodeless fluorescent discharge lamp having such a structure has a high-frequency circuit 7
When high-frequency electric power is supplied to the high-frequency excitation coil 72 through 3, a high-frequency electric field is formed in the inner tube 70, which causes high-frequency discharge. Therefore, mercury is ionized and excited, so that it emits ultraviolet rays, and this ultraviolet ray emits ultraviolet rays.
At 1, it is converted to visible light. The visible light passes through the inner tube 70 and the outer tube 75 and is emitted to the outside.

Although not shown in FIG. 10, between the inner tube 70 and the outer tube 75, a silicon rubber 25 as shown in FIG. 1 is used as a heat conducting member, or a bimetal piece 40 as shown in FIG. If an evaporative heat medium such as mercury is interposed, the temperature of the inner tube 70 is increased by the heat retaining effect of the space inside the outer tube 75 at the time of low temperature startup, and thus the mercury vapor pressure is rapidly increased to increase the brightness. Starts up quickly. Further, when the temperature of the inner pipe 70 rises, the heat of the inner pipe 70 is transferred from the silicone rubber 25 or the like through the heat conducting member or the bimetal piece 40 or the evaporative heat medium such as mercury.
5 and is radiated from the surface of the outer tube 75.

Therefore, even in the double-tube type electrodeless fluorescent discharge lamp having such a structure, it is possible to improve the starting characteristics at low temperature and suppress the change in luminance due to the change in ambient temperature. The cross-sectional shape of the arc tube 10 may be any of a circular shape, an elliptical shape, and an oval shape.

[0063]

As described above, according to the invention of claim 1, when the engine is started in an atmosphere with a low ambient temperature, the heat generated by the arc tube is prevented from escaping due to the heat retaining function of the heat insulating space formed in the outer tube. , The temperature rise of the arc tube is promoted.
Further, if the temperature of the arc tube rises excessively, the heat of the arc tube is released to the outer tube through the heat conductive member and is radiated from the surface of the outer tube. Therefore, the start-up characteristic at the time of cold start is improved, the excessive temperature rise of the arc tube is suppressed, and the fluctuation of the brightness due to the ambient temperature change can be suppressed.

According to the invention of claim 2, since the heat conducting member is a heat conductor having one end in contact with the arc tube and the other end in contact with the outer tube, heat conduction between the arc tube and the outer tube is prevented. Prompt,
Moreover, the structure is simple and the mounting is easy.

According to the third aspect of the present invention, since the heat conducting member is the heat responsive element that is bridged between the arc tube and the outer tube, if the temperature is lower than the predetermined temperature, the arc tube and the outer tube are heated. Therefore, the heat of the arc tube, which does not increase its temperature at the time of starting, is not transmitted to the outer tube, so that the temperature rise of the arc tube is promoted. However, if the temperature of the arc tube exceeds a predetermined temperature, the thermoresponsive element When activated, the arc tube and the outer tube are thermally connected to each other, and the heat of the arc tube is transferred to the outer tube and radiated from the outer tube. Therefore, it is possible to improve the start-up characteristics at the time of low-temperature start, and to suppress the excessive temperature rise of the arc tube at the time of high temperature to maintain the optimum temperature.

According to the invention of claim 4, the heat conducting member comprises:
Since it is the evaporative heat medium filled between the arc tube and the outer tube, if the arc tube is below a predetermined temperature, the evaporation amount of the evaporative heat medium in the outer tube is small, so that the heat conducting function as a heat medium. It is small and the temperature rise of the arc tube becomes faster. However, when the temperature inside the outer tube exceeds a predetermined temperature, the amount of evaporation of the evaporative heat medium increases, the heat conduction effect increases, and the rate at which the heat of the arc tube is transferred to the outer tube increases, so the temperature rise of the arc tube is suppressed.

According to the invention of claim 5, the double-tube low-pressure mercury vapor discharge lamp according to any one of claims 1 to 4 is lit at a high frequency by using a high-frequency lighting circuit. Also, the cathode drop voltage is lowered, and the lamp voltage can be lowered, thus improving the luminous efficiency of the lamp.

In the lighting device of the sixth aspect, since the double-tube low-pressure mercury vapor discharge lamp used as the light source is excellent in low-temperature startability, the rise of the luminance is good, and the variation of the luminance is caused even when the temperature changes. There is little change in the brightness of the screen.

[Brief description of drawings]

1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a sectional view of a double-tube cold-cathode fluorescent lamp, and FIG. 1B is a sectional view taken along line BB in FIG. 1A. .

FIG. 2 is a diagram showing light output rising characteristics of various cold cathode fluorescent lamps at an ambient temperature of −30 ° C.

FIG. 3 is a diagram showing light output rising characteristics of various cold cathode fluorescent lamps at an ambient temperature of 25 ° C.

FIG. 4 is a diagram showing light output rising characteristics of various cold cathode fluorescent lamps at an ambient temperature of 85 ° C.

5 is an exploded perspective view showing an entire liquid crystal display device using a backlight having the fluorescent lamp of FIG. 1 as a light source.

FIG. 6 is a sectional view of the liquid crystal display device.

7A and 7B show a second embodiment of the present invention, wherein FIG. 7A is a sectional view of a double-tube cold cathode fluorescent lamp, and FIG. 7B is a sectional view taken along the line BB of FIG. 7A. .

FIG. 8 is a sectional view of a double-tube cold-cathode fluorescent lamp showing a third embodiment of the present invention.

FIG. 9 is a sectional view of a double-tube cold cathode fluorescent lamp showing a fourth embodiment of the present invention.

FIG. 10 is a cross-sectional view of a double-tube type electrodeless fluorescent discharge lamp showing a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Double-tube cold cathode fluorescent lamp 2, 73 ... High frequency lighting circuit 10 ... Arc tube 11 ... Bulb 12 ... Phosphor layer 13 ... Cold cathode 20 ... Outer tube 25 ... Silicon rubber (heat conductive member) 40 ... Bimetal piece 70 ... Inner tube 72 ... High frequency excitation coil 75 ... Outer tube 31 ... Light guide plate 32 ... Reflector 36 ... Light diffusing plate 40 ... Liquid crystal display panel

Claims (6)

[Claims] 1. A light-transmitting outer tube having an airtight space; an arc tube which is housed in the outer tube, has an electrode sealed in the discharge space, and has mercury and a rare gas sealed therein; A double-tube low-pressure mercury vapor discharge lamp, characterized by comprising: a heat conductive member provided between the light emitting tube and the outer tube, the heat conductive member connecting the light emitting tube and the outer tube so that heat can be conducted. 2. The double-tube low-pressure mercury vapor according to claim 1, wherein the heat conducting member is a heat conductor having one end in contact with the arc tube and the other end in contact with the outer tube. Discharge lamp. 3. The heat-conducting member is a thermal responsive element that is bridged between the arc tube and the outer tube, and thermally connects the arc tube and the outer tube when a predetermined temperature or higher is reached. The double-tube low-pressure mercury vapor discharge lamp according to claim 1. 4. The heat conducting member is an evaporative heat medium that is filled between the arc tube and the outer tube and evaporates when the temperature exceeds a predetermined temperature to thermally connect the arc tube and the outer tube. The double-tube low-pressure mercury vapor discharge lamp according to claim 1. 5. A double-tube low-pressure mercury vapor discharge lamp according to claim 1, and a high-frequency lighting circuit for lighting the low-pressure mercury vapor discharge lamp. Double-tube low-pressure mercury vapor discharge lamp device. 6. A lighting device comprising: the double-tube low-pressure mercury vapor discharge lamp according to claim 1; and a luminaire main body to which the lamp is attached. .