JP3122373U - Discharge tube - Google Patents

Abstract

Disclosed is a discharge tube capable of generating a discharge stably even at a low applied voltage.
A sealed space 12 is formed inside a dielectric tube 11 having a substantially cylindrical shape, and a predetermined discharge gas 13 is sealed in the sealed space 12. Of the pair of electrodes 15, 17 that generate an electric discharge by applying an alternating voltage to the discharge gas 13, one first electrode 15 is disposed on the outer wall of the dielectric tube 11, and the other second electrode 17 is sealed. It is arranged in the space 12.
[Selection] Figure 1

Description

  The present invention relates to a discharge tube suitable for use in, for example, a backlight of a liquid crystal display device.

  Conventionally, as this type of discharge tube, a tube using a fluorescent lamp or a dielectric barrier discharge tube is known. Dielectric barrier discharge tubes are superior to fluorescent lamps in terms of environmental considerations due to mercury-free operation and longer life due to the electrode being placed outside the discharge space. It is attracting attention as an alternative.

  Conventionally, as such a dielectric barrier discharge tube, two types of configurations, a flat discharge tube and a cylindrical discharge tube, are known. As a flat type discharge tube, there exists a structure as disclosed by patent document 1, for example. Moreover, as a cylindrical discharge tube, there exists a structure as shown, for example in FIG.6 and FIG.7.

  FIGS. 6A to 6C are cylindrical discharge tubes showing a first conventional example. The cylindrical discharge tube 50 is formed by coaxially arranging two cylindrical glass tubes (dielectric tubes) 51 and 52 having different diameters, and an inner wall of a glass tube (hereinafter referred to as an outer tube) 51 having a large diameter. And an outer wall of a glass tube (hereinafter referred to as an inner tube) 52 having a small diameter, a sealed space 53 is formed.

  At one end of the outer tube 51 in the longitudinal direction, the gas inside the tube is replaced with air by a discharge gas 54 such as xenon or a mixed gas containing xenon at the stage of manufacturing the discharge tube 50, and then sealed for sealing. A stop tube 55 is attached. As a result, the discharge gas 54 is sealed in the sealed space 53.

  A phosphor 56 is applied to the inner wall of the outer tube 51, and an outer electrode 57 and an inner electrode 58 are disposed on the outer wall of the outer tube 51 and the inner wall of the inner tube 52, respectively. The external electrode 57 is formed of a transparent electrode (such as indium tin oxide (ITO)) that can extract light out of the tube, and the internal electrode 58 is a metal electrode (aluminum or silver) that reflects light. Etc.).

  That is, the outer electrode 57 and the inner electrode 58 are arranged so that two dielectric layers of the outer tube 51 and the inner tube 52 are interposed on both sides of the sealed space 53 with a predetermined discharge distance. For convenience, the cylindrical discharge tube 50 of the type shown in FIG. 6 is hereinafter referred to as a coaxial barrier discharge tube 50.

  In the coaxial barrier discharge tube 50 configured as described above, when a predetermined voltage is applied between the electrodes 57 and 58 from a power supply device (not shown) to provide an AC electric field, the discharge gas 54 sealed in the sealed space 53 is provided. Is ionized to form plasma (discharge), and the phosphor 56 is excited to emit light by ultraviolet rays generated by the discharge.

  FIGS. 7A to 7C are cylindrical discharge tubes showing a second conventional example. The cylindrical discharge tube 60 is composed of a single glass tube (dielectric tube) 61 having a cylindrical shape, and the outer wall of the glass tube 61 is symmetrical with respect to the axis of the glass tube 61. A pair of strip-like first and second electrodes 62 and 63 are arranged on the top. The first and second electrodes 62 and 63 are formed of metal electrodes (such as aluminum and silver) that reflect light. That is, the pair of first and second electrodes 62 and 63 are arranged so that a dielectric layer (two layers) forming a peripheral wall of the glass tube 61 is interposed on both sides of the sealed space 64 having a predetermined discharge distance. ing.

  A discharge gas 65 is sealed in a sealed space 64 inside the glass tube 61 by a sealing tube 66 in the same manner as the discharge tube 50 of FIG. Further, on the inner wall of the glass tube 61, except for a light extraction window formed as an aperture portion 67 (shown by a broken line in FIG. 7C) at a position between the electrodes 62 and 63 in the circumferential direction of the tube. A phosphor 68 is applied. For convenience, the cylindrical discharge tube 60 of the type shown in FIG. 7 will be referred to as both barrier discharge tubes 60 hereinafter.

  In the both barrier discharge tubes 60 configured as described above, when a predetermined voltage is applied between the electrodes 62 and 63 from a power supply device (not shown) to provide an AC electric field, the discharge gas 65 sealed in the sealed space 64 is provided. Is ionized to form plasma (discharge), and the phosphor 68 emits excitation light by ultraviolet rays generated by the discharge.

JP 2003-31182 A

  Incidentally, in the coaxial barrier discharge tube 50 of FIG. 6 and the both barrier discharge tubes 60 of FIG. 7 as described above, a pair of electrodes for applying an AC electric field to the discharge gas sandwich the discharge gas through two dielectric layers. Be placed. That is, as shown in FIG. 6C, in the coaxial barrier discharge tube 50, the path of the electric field for generating discharge is “external electrode 57-dielectric layer (outer tube 51) -discharge gas 54-dielectric layer ( Inner tube 52) -internal electrode 58 ". Further, as shown in FIG. 7C, the path of the electric field in both barrier discharge tubes 60 is “first electrode 62−dielectric layer (glass tube 61) −discharge gas 65−dielectric layer (glass tube 61). -The second electrode 63 ".

In these configurations, two dielectric layers (glass tubes) interposed between both electrodes excessively function as a dielectric barrier, and a large dielectric loss occurs. The glass tube also serves to isolate the discharge gas inside the sealed space (gas pressure much lower than atmospheric pressure) from the outside air, so even if you try to reduce the thickness of the glass tube to reduce dielectric loss, It cannot be made smaller than a certain level due to strength. For this reason, there was a limit in shortening the distance between both electrodes.

  Therefore, a high voltage must be applied between both electrodes in order to give the electric field strength (V / m) necessary for starting discharge to the discharge gas, and a high voltage must be applied to the power source that supplies the applied voltage. There is a problem that an expensive material that can be generated and has excellent insulating properties is required.

  By the way, in a discharge tube (for example, a cold cathode discharge tube) in which both electrodes of a pair of discharge tubes are placed in a sealed space filled with a discharge gas, the positive column (plasma) generated by the discharge generates undulation. There is a problem that stable light cannot be obtained.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a discharge tube capable of generating a discharge stably even at a low applied voltage.

  In order to achieve the above object, according to the first aspect of the present invention, a sealed space is formed inside a cylindrical dielectric tube, and an alternating voltage is applied to the discharge gas sealed in the sealed space from a pair of electrodes. In the discharge tube for generating discharge, one of the pair of electrodes is arranged such that one first electrode is arranged on an outer wall of the dielectric tube, and the other second electrode is arranged in the sealed space. .

  The invention according to claim 2 is the gist of the invention according to claim 1, in which the inner wall of the dielectric tube is coated with a phosphor that converts ultraviolet light emitted by the discharge gas into visible light during discharge. And

  The gist of the invention described in claim 3 is that, in the invention described in claim 1 or 2, the first electrode and the second electrode are arranged in parallel along the longitudinal direction of the dielectric tube.

  The device according to claim 4 is the device according to any one of claims 1 to 3, wherein the second electrode is configured such that a distance between the first electrode and the second electrode is substantially equal. Is arranged at the center of the sealed space.

  The device according to claim 5 is the device according to any one of claims 1 to 3, wherein the second electrode is brought closer to the inner wall side of the dielectric tube with respect to the first electrode. The gist of this is

  A device according to claim 6 is the device according to any one of claims 1 to 5, wherein the first electrode is a transparent electrode made of a transparent conductor and extends over the entire circumference of the dielectric tube. The gist is that it is formed.

  A device according to a seventh aspect is the device according to any one of the first to fifth aspects, wherein the first electrode is a mirror-like metal electrode made of a metal conductor, and the periphery of the dielectric tube. The gist is that the dielectric tube is formed over the entire circumference except for the light extraction portion formed in a part of the direction.

  The gist of claim 8 is the gist of the invention according to any one of claims 1 to 7, wherein the second electrode is formed in a linear shape.

  The device according to claim 9 is the device according to any one of claims 1 to 8, wherein the first electrode excludes a portion where the second electrode is taken out of the dielectric tube from the sealed space. The main point is that they are arranged.

  The device according to claim 10 is the device according to any one of claims 1 to 8, wherein a power supply line for supplying power to the second electrode is connected to both ends of the second electrode. The second electrode is supported by the dielectric tube by the feeder line.

  The device according to claim 11 is the device according to any one of claims 1 to 8, wherein the length of the first electrode relative to the longitudinal direction of the dielectric tube is larger than the length of the second electrode. The gist is short.

(Function)
According to the first aspect of the present invention, the second electrode paired with the first electrode disposed on the outer wall of the cylindrical dielectric tube is in the sealed space formed inside the dielectric tube. Be placed. In this configuration, since the path of the electric field for generating discharge in the discharge gas by the pair of electrodes is the first electrode-dielectric tube-discharge gas-second electrode, the distance between both electrodes can be shortened. . Thereby, even if the voltage applied between both electrodes is a low voltage, it is possible to give the electric field strength necessary for starting discharge to the discharge gas. In this configuration, a stable discharge state can be obtained by arranging only the second electrode in the sealed space in which the discharge gas is sealed.

According to the second aspect of the present invention, in addition to the function of the first aspect of the invention, the inner wall of the dielectric tube is coated with a phosphor so that ultraviolet rays emitted from the discharge gas at the time of discharge can be obtained. Is converted into visible light by the phosphor and becomes illumination light.

  According to the invention described in claim 3, in addition to the operation of the invention described in claim 1 or 2, the first electrode and the second electrode are arranged in parallel along the longitudinal direction of the dielectric tube. Thus, a uniform light emission state can be obtained by generating a discharge uniformly over the entire discharge tube.

  According to the device described in claim 4, in addition to the operation of the device described in any one of claims 1 to 3, the second electrode is a distance between the first electrode and the second electrode. Are arranged in the center of the sealed space so that the distances are substantially equal, the discharge distance during discharge can be made uniform and a good light emission state can be obtained.

  According to the device described in claim 5, in addition to the operation of the device described in any one of claims 1 to 3, the second electrode has a peripheral wall of the dielectric tube with respect to the first electrode. Since it is arranged close to the inner wall side that is separated, the distance between the two electrodes can be further shortened to further reduce the voltage required for starting discharge and the voltage required for continuing discharge.

  According to the device described in claim 6, in addition to the operation of the device described in any one of claims 1 to 5, the first electrode is a transparent electrode made of a transparent conductor, and the dielectric It is formed over the entire circumference of the tube. Thereby, a discharge tube from which light is extracted over the entire circumference of the dielectric tube is created.

  According to the invention described in claim 7, in addition to the operation of the invention described in any one of claims 1 to 5, the first electrode is a mirror-like metal electrode made of a metal conductor. It is formed over the entire circumference of the dielectric tube except for the light extraction portion formed in a part in the circumferential direction of the dielectric tube. As a result, a discharge tube from which light is extracted from a portion in the circumferential direction of the dielectric tube is created.

  According to the invention described in claim 8, in addition to the operation of the invention described in any one of claims 1 to 7, the second electrode is formed in a linear shape. With this configuration, it is possible to suppress the occurrence of sputtering during discharge.

  According to the ninth aspect of the present invention, in addition to the operation of the first aspect of the present invention, the first electrode connects the second electrode from the sealed space to the dielectric tube. Arranged except for the part to be taken out. In this configuration, the creeping distance between the first electrode and the second electrode outlet can be secured to prevent the occurrence of creeping discharge.

  According to the device of claim 10, in addition to the operation of the device of any one of claims 1 to 8, a power supply for supplying power to the second electrode is provided at both ends of the second electrode. An electric wire is connected, and the second electrode is supported by the dielectric tube by the feeder line. In this configuration, the supply voltage from the power source is applied to the second electrode via the feeder line.

  According to the eleventh aspect of the present invention, in addition to the function of the first aspect of the present invention, the length of the first electrode with respect to the longitudinal direction of the dielectric tube is the second electrode. Short compared to the length of. With this configuration, it is possible to reduce the occurrence of discharge in a space other than between the first electrode and the second electrode.

  As described above, according to the present invention, it is possible to provide a discharge tube capable of generating a discharge stably even at a low applied voltage.

(First embodiment)
A first embodiment in which the present invention is embodied in, for example, a cylindrical discharge tube used in a backlight of a liquid crystal display device will be described with reference to FIGS.
FIGS. 1A to 1C show a configuration of a cylindrical discharge tube 10 according to the present embodiment. The cylindrical discharge tube 10 has a substantially cylindrical hollow glass tube that functions as a dielectric (dielectric). Tube) 11. The glass tube 11 is closed at both ends in the longitudinal direction to form a sealed space 12 inside. The sealed space 12 is filled with a predetermined discharge gas 13 that emits vacuum ultraviolet rays by discharge. As the discharge gas 13, for example, xenon or a mixed gas containing xenon is used.

  The discharge gas 13 is injected from a sealing tube 14 attached to one end of the glass tube 11 in the longitudinal direction. Specifically, the gas inside the glass tube 11 is replaced with air by the discharge gas 13 at the stage of manufacturing the discharge tube 10, and then the sealing tube 14 is burned off by a burner or the like and sealed.

  On the outer wall of the glass tube 11 (the outer wall surface of the glass tube 11), an external electrode 15 as a first electrode is formed in the longitudinal direction of the tube over the entire circumference. Moreover, the phosphor 16 is applied to the inner wall of the glass tube 11 (the inner wall surface of the glass tube 11) in the longitudinal direction of the tube over the entire circumference. The external electrode 15 is formed of a transparent conductor (for example, Indium Tin Oxide (ITO) or the like) that can extract light (light from the phosphor 16) obtained by the discharge to the outside of the tube. Yes. Further, as the phosphor 16, a three-wavelength phosphor having good emission characteristics is used, and its coating thickness is adjusted to about 20 μm, for example, in order to improve the luminous efficiency.

  In the sealed space 12 of the glass tube 11, an internal electrode 17 as a second electrode is disposed so as to be parallel to the external electrode 15 along the longitudinal direction of the tube. In the present embodiment, the internal electrode 17 is formed in a linear shape using a material that can suppress the occurrence of spatter during discharge, such as a nickel alloy.

  Connected to both ends of the internal electrode 17 are zimet wires 18 as power supply lines for supplying power to the internal electrode 17. The internal electrode 17 and the jimet wire 18 are pressure-bonded by a pressure-bonding member 19 in order to ensure plasma resistance due to electric discharge, and the jimet wire 18 is taken out from both ends of the glass tube 11 to the outside of the tube.

  That is, the internal electrode 17 is supported in the sealed space 12 of the glass tube 11 while the inside of the tube is kept sealed by the jimet wires 18 connected to both ends thereof. Specifically, in the present embodiment, the internal electrode 17 is disposed in the center of the sealed space 12 so that the distance from the external electrode 15 is substantially equal over the entire circumference of the tube.

  The dimet wire 18 is formed of, for example, an alloy of copper and nickel, and absorbs the thermal extension of the internal electrode 17 during discharge in a tube connected to the internal electrode 17 as shown in FIG. In order to do so, it is provided in a wave shape.

  Incidentally, the length of the internal electrode 17 is slightly longer than the length of the external electrode 15 in the longitudinal direction of the tube in order to reduce the discharge to the jimet wire 18. In addition, the creepage distance between the outlet of the internal electrode 17 and the external electrode 15 is ensured so that the creeping discharge does not occur between the jimet wire 18 and the external electrode 15.

FIG. 2 shows an electrical connection diagram of the cylindrical discharge tube 10 of the present embodiment.
An external electrode lead wire 21 is connected to the external electrode 15 via a conductive adhesive 22. In addition, an internal electrode lead wire 23 is pressure-bonded to a dimet wire 18 connected to one end of the internal electrode 17 by a pressure-bonding member 24. Therefore, the AC voltage supplied from the power supply device 25 is applied to the external electrode 15 and the internal electrode 17 via the external electrode lead wire 21 and the internal electrode lead wire 23. The jimet wire 18 connected to the other end of the internal electrode 17 supports the internal electrode 17 in the sealed space 12 together with the jimet wire 18 (power connection side) connected to one end of the internal electrode 17. It functions as a support member.

  In the cylindrical discharge tube 10 configured as described above, when an AC voltage necessary for starting discharge is applied between the external electrode 15 and the internal electrode 17 from the power supply device 25, it is enclosed in the sealed space 12 inside the glass tube 11. The discharged discharge gas 13 is ionized to form (discharge) plasma. Here, for example, when xenon is used as the discharge gas 13, the xenon emits ultraviolet rays of 147 nm and 172 nm by discharge. These ultraviolet rays are converted into visible light by the phosphor 16 applied to the inner wall of the glass tube 11 to become illumination light. At this time, since the external electrode 15 and the internal electrode 17 are arranged along the longitudinal direction of the glass tube 11, a discharge is generated over the entire tube, and uniform light emission can be obtained.

  Further, in such a cylindrical discharge tube 10, the path of the electric field formed between the external electrode 15 and the internal electrode 17 is “external electrode 15 -glass tube 11 ( Dielectric layer) −discharge gas 13−internal electrode 17 ”. That is, in the present embodiment, since only one dielectric layer is sandwiched between the pair of electrodes 15 and 17, the distance between the electrodes 15 and 17 can be shortened. As a result, a high electric field strength (V / m) can be obtained even with a low supply voltage, the voltage (starting voltage) required for starting discharge can be lowered, and the voltage (sustaining voltage) required for continuing discharge. Can be lowered.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The external electrode 15 of the cylindrical discharge tube 10 is disposed on the outer wall of the glass tube 11, and the internal electrode 17 is disposed in the sealed space 12 in which the discharge gas 13 is enclosed. Thereby, since the distance between the external electrode 15 and the internal electrode 17 can be shortened, the starting voltage required for the start of discharge and the sustain voltage required for the discharge continuation can be kept low. This also contributes to keeping the cost of the power supply device 25 low.

(2) Since there is only one dielectric layer interposed between the external electrode 15 and the internal electrode 17, the dielectric loss during discharge can be reduced. Thereby, the distance between the electrodes 15 and 17 can be shortened while ensuring a strong glass thickness that can sufficiently withstand the pressure difference between the outside air (atmospheric pressure) and the gas pressure in the tube. Therefore, it is possible to give the electric field strength necessary for starting discharge even with a low applied voltage.

(3) Since the starting voltage and sustaining voltage for discharging can be kept low, the discharge tube 10 realizing low power consumption can be manufactured.

(4) The external electrode 15 and the internal electrode 17 are arranged so as to be parallel to each other along the longitudinal direction of the glass tube 11. Thereby, it is possible to manufacture a discharge tube lamp capable of uniformly generating discharge over the entire tube and obtaining uniform light emission.

(5) In the present embodiment, since the internal electrode 17 is disposed in the sealed space 12 inside the glass tube 11, the discharge tube has a structure as compared with the structure of the coaxial barrier discharge tube 50 (first conventional example) in FIG. 6. Miniaturization can be achieved.

(6) In the present embodiment, the internal electrode 17 is arranged in the center of the sealed space 12 so that the distance between the internal electrode 17 and the external electrode 15 is substantially equal, so that the discharge distance during discharge is uniform. Thus, a better light emitting state can be obtained.

(7) In the present embodiment, since the internal electrode 17 is a linear electrode formed using, for example, a nickel alloy, it is possible to suppress the occurrence of sputtering during discharge.

(Second embodiment)
Hereinafter, a second embodiment in which the present invention is embodied in, for example, a cylindrical discharge tube used in a backlight of a liquid crystal display device will be described with reference to FIG. 3 with a focus on differences from the first embodiment. . In addition, the same code | symbol is attached | subjected and demonstrated about the component similar to 1st embodiment.

  As shown in FIGS. 3A to 3C, the cylindrical discharge tube 30 according to the second embodiment includes an inner peripheral surface (with the glass wall separated from the outer electrode 15 by the inner electrode 17). The arrangement in the vicinity of the inner wall side (specifically, in the vicinity of the phosphor 16) is different from the first embodiment. The other configuration is the same as that of the discharge tube 10 of FIG. The creepage distance between the outlet of the internal electrode 17 and the external electrode 15 is a sufficient distance so that no creeping discharge occurs between the jimet wire 18 and the external electrode 15 as in the first embodiment. Is secured.

  Incidentally, in the present embodiment, the shortest distance d1 (see FIG. 3C) between the internal electrode 17 and the external electrode 15 is not particularly defined. That is, the distance between the external electrode 15 and the internal electrode 17 is preferably as short as possible to obtain a sufficient electric field strength (V / m) for starting discharge even at a low supply voltage. You may arrange | position so that the inner wall surface (phosphor 16) of the glass tube 11 may be contacted. In this case, although light emission is hindered on the surface where the internal electrode 17 comes into contact, the influence can be almost eliminated by forming the internal electrode 17 in a linear shape.

Next, the discharge principle of the cylindrical discharge tube 30 configured as described above will be described.
When an AC voltage is applied between the pair of external electrodes 15 and the internal electrodes 17 in the same manner as in the first embodiment, first, in the vicinity near the electrode indicated by the shortest distance d1 in FIG. The discharge gas 13 is ionized to form plasma (discharge). Then, the plasma that is ionized to become a conductor immediately diffuses throughout the tube, and the plasma that has become the conductor promotes the discharge of the entire tube regardless of the position of the internal electrode 17. As in the first embodiment, the ultraviolet rays emitted by the discharge are converted into visible light by the phosphor 16 and become illumination light.

As described above, according to the present embodiment, in addition to the same effects as (1) to (5) and (7) of the first embodiment, the following effects are further achieved.
(1) By arranging the internal electrode 17 in the vicinity of the inner wall side with the glass wall separated from the external electrode 15, a voltage (starting voltage) required for starting discharge and continuation of discharge compared to the first embodiment The voltage (sustain voltage) required for the above can be further reduced.

(Third embodiment)
Hereinafter, a third embodiment in which the present invention is embodied in, for example, a cylindrical discharge tube used for a backlight of a liquid crystal display device will be described with reference to FIG. 4 focusing on differences from the first and second embodiments. It explains according to. In addition, the same code | symbol is attached | subjected and demonstrated about the component similar to 1st and 2nd embodiment.

  As shown in FIGS. 4A to 4C, the cylindrical discharge tube 40 of the third embodiment includes an external electrode 15 and a phosphor 16 formed on the glass tube 11 in FIG. It is arranged over the entire circumference excluding the light extraction portion 41 indicated by the broken line (the window portion for extracting the light obtained from the discharge (light from the phosphor 16) to the outside of the tube).

  In this embodiment, the external electrode 15 is formed in a mirror shape with a highly conductive metal conductor in order to reflect light efficiently. Moreover, the internal electrode 17 is arrange | positioned in the vicinity of the inner wall side which separated the glass wall with respect to the external electrode 15 like 2nd Embodiment in the side facing the optical extraction part 41. FIG. Further, the phosphor 16 is applied thicker than the discharge tubes 10 and 30 in the first and second embodiments, and the amount of emitted light is increased. Other configurations are the same as those of the discharge tubes 10 and 30 of FIGS. The creepage distance between the outlet of the internal electrode 17 and the external electrode 15 is such that no creeping discharge occurs between the jimet wire 18 and the external electrode 15 as in the first and second embodiments. Sufficient distance is secured.

  In the cylindrical discharge tube 40 configured as described above, the illumination light emitted from the phosphor 16 by the discharge is guided to the light extraction portion 41 at the position of the cut of the external electrode 15 while reflecting the inner surface of the tube. It is taken out from the take-out portion 41 outside the pipe.

  As described above, according to the present embodiment, in addition to the same effects as (1) to (4), (7) of the first embodiment and (1) of the second embodiment. Furthermore, the following effects are produced.

(1) In the present embodiment, the external electrode 15 is formed in a mirror shape with a highly conductive metal conductor, and the external electrode 15 and the phosphor 16 are formed over the entire circumference excluding the light extraction portion 41. Is done. According to this configuration, by applying the configurations of the first and second embodiments, it is possible to manufacture a discharge tube 40 that takes out light from only a part of the glass tube 11 in the circumferential direction.

(Measured values of starting voltage and sustaining voltage in each embodiment)
FIG. 5A is a characteristic diagram showing the relationship between the applied voltage (KV) and the light emission luminance (cd / m 2) in the discharge tube (lamp). As shown in the figure, the voltage for starting discharge (start-up voltage) needs to be higher than the voltage for continuing discharge (sustain voltage).

  FIG. 5B is an explanatory diagram showing measured values of the starting voltage and the sustaining voltage of the cylindrical discharge tubes 10, 30, 40 of the above embodiments. For convenience, in FIG. 5B, the cylindrical discharge tube 10 of the first embodiment is shown as a one-barrier discharge tube (center electrode), and the cylindrical discharge tube 30 of the second and third embodiments. , 40 are shown as single barrier discharge tubes (edge electrodes). For reference, actual measured values of the starting voltage and the sustaining voltage in the coaxial barrier discharge tube 50 of FIG. 6 and the barrier discharge tubes 60 of FIG. 7 are shown.

  As shown in FIG. 5B, in the one-barrier discharge tube (center electrode) in the first embodiment, the starting voltage is about 1.0 KV and the sustain voltage is about 0.5 KV. Therefore, compared with the coaxial barrier discharge tube 50 in the first conventional example, the starting voltage can be lowered by about 0.5 KV and the sustain voltage can be lowered by about 0.3 KV.

  In the single barrier discharge tube (edge electrode) in the second and third embodiments, the starting voltage is about 0.6 KV and the sustain voltage is about 0.5 KV. Therefore, compared with the coaxial barrier discharge tube 50 in the first conventional example, the starting voltage can be lowered by about 0.9 KV and the sustain voltage can be lowered by about 0.3 KV.

(Another example)
Note that the present invention is not limited to the above-described embodiments, and may be modified as follows.
In each embodiment, the example in which the cylindrical discharge tubes 10, 30, and 40 are used for the backlight of the liquid crystal display device has been described. However, each of these discharge tubes 10, 30, and 40 is used as an illumination device, for example. Also good.

In each embodiment, the glass tube 11 has a substantially cylindrical shape, but is not necessarily limited to this shape, and may have a polygonal cylindrical shape.

In each embodiment, the phosphor 16 is applied to the inner wall of the glass tube 11 in order to obtain visible light from the ultraviolet rays emitted by the discharge, but the phosphor is not applied when using ultraviolet rays is used. Shall. In this case, the glass tube 11 is preferably formed of quartz glass that transmits ultraviolet light.

-In each embodiment, although the internal electrode 17 was linear, it is not restricted to this shape. For example, the internal electrode 17 may have a planar shape (a rectangular shape extending along the longitudinal direction of the tube).

As another configuration example of the internal electrode 17, the internal electrode 17 is formed in a linear shape, and a plurality of planar (for example, disc-shaped) electrodes are equally spaced on the linear electrode. It is good also as a structure provided so that it may become respectively parallel to the perpendicular | vertical direction or axial direction. Further, the internal electrode 17 may be formed in a planar shape, and the side along the longitudinal direction of the planar electrode may be formed in a saw shape. Further, the internal electrode 17 may be formed in a linear shape, and the linear electrode may be formed in a spiral shape. The internal electrode 17 may be composed of a plurality of linear electrodes, and the plurality of linear electrodes may be twisted together. In these configurations, the discharge can be generated more uniformly in the tube.

In each embodiment, the number of internal electrodes 17 provided in the sealed space 12 inside the glass tube 11 is not limited to one and may be two or more. However, in this case, it is necessary to set the potentials of a plurality of internal electrodes provided in the sealed space 12 to the same potential.

In each embodiment, the internal electrode 17 is not limited to being formed using a nickel alloy, but may be any other material as long as it can suppress the occurrence of spatter during discharge.

In each embodiment, the material of the dimet wire 18 is not limited to a material made of an alloy of copper and nickel, and any other material can be used as long as it can suppress the occurrence of spatter during discharge. Also good.

In each embodiment, the discharge gas 13 is not limited to xenon or a mixed gas containing xenon, but may be a gas having another gas or composition.
In the first and second embodiments, indium tin oxide (ITO) is used as the transparent conductor that forms the external electrode 15, but is not limited thereto.

In the third embodiment, the position of the internal electrode 17 is not necessarily arranged near the inner wall side across the glass wall, but is arranged in the center of the sealed space 12 as in the first embodiment. It may be done.

Below, the technical idea which can be grasped | ascertained from said each embodiment is described.
(A) In the discharge tube according to any one of claims 1 to 8,
The discharge tube according to claim 1, wherein the first electrode is disposed excluding a portion where the second electrode is taken out from the sealed space to the outside of the dielectric tube. In this configuration, the creeping distance between the first electrode and the second electrode outlet can be secured to prevent the occurrence of creeping discharge.

(B) In the discharge tube according to any one of claims 1 to 8,
A power supply line for supplying power to the second electrode is connected to both ends of the second electrode, and the second electrode is supported by the dielectric tube by the power supply line. Discharge tube. In this configuration, the supply voltage from the power source is applied to the second electrode via the feeder line.

(C) In the discharge tube according to any one of claims 1 to 8,
The discharge tube according to claim 1, wherein a length of the first electrode with respect to a longitudinal direction of the dielectric tube is shorter than a length of the second electrode. With this configuration, it is possible to reduce the occurrence of discharge in a space other than between the first electrode and the second electrode.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cylindrical discharge tube which shows 1st embodiment, (a) is a partial cross section perspective view which shows schematic structure, (b) is sectional drawing which cut | disconnected the tube to the longitudinal direction, (c) is the center of a tube Sectional drawing which cut | disconnected the vicinity in radial direction is shown. It is an electrical connection diagram of the cylindrical discharge tube of the same embodiment. It is the cylindrical discharge tube which shows 2nd embodiment, (a) is a partial cross section perspective view which shows schematic structure, (b) is sectional drawing which cut | disconnected the tube to the longitudinal direction, (c) is the center of a tube Sectional drawing which cut | disconnected the vicinity in radial direction is shown. It is the cylindrical discharge tube which shows 3rd embodiment, (a) is a partial cross section perspective view which shows schematic structure, (b) is sectional drawing which cut | disconnected the tube to the longitudinal direction, (c) is the center of a tube Sectional drawing which cut | disconnected the vicinity in radial direction is shown. (A) is a characteristic diagram which shows the relationship between the applied voltage and light emission luminance in a discharge tube (lamp), (b) is explanatory drawing which shows the actual value of the starting voltage and sustain voltage in each embodiment. It is a cylindrical discharge tube showing a first conventional example, (a) is a partially sectional perspective view showing a schematic configuration, (b) is a sectional view of the tube cut in the longitudinal direction, (c) is near the center of the tube Sectional drawing which cut | disconnected this to radial direction is shown. It is a cylindrical discharge tube which shows a 2nd prior art example, (a) is a partial cross section perspective view which shows schematic structure, (b) is sectional drawing which cut | disconnected the tube to the longitudinal direction, (c) is the center vicinity of a tube Sectional drawing which cut | disconnected this to radial direction is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 30, 40 ... Discharge tube, 11 ... Glass tube as dielectric tube, 12 ... Sealed space, 13 ... Discharge gas, 15 ... External electrode as 1st electrode, 16 ... Phosphor, 17 ... As 2nd electrode Internal electrodes, 41...

Claims (11)

In a discharge tube that forms a sealed space inside a cylindrical dielectric tube and generates an electric discharge by applying an alternating voltage from a pair of electrodes to a discharge gas sealed in the sealed space,
One discharge electrode of the pair of electrodes is disposed on an outer wall of the dielectric tube, and the other second electrode is disposed in the sealed space. The discharge tube according to claim 1, wherein a fluorescent material that converts ultraviolet rays generated by the discharge gas during discharge into visible light is applied to an inner wall of the dielectric tube. The discharge tube according to claim 1 or 2, wherein the first electrode and the second electrode are arranged in parallel along a longitudinal direction of the dielectric tube. The second electrode is disposed at the center of the sealed space so that the distance between the first electrode and the second electrode is substantially equal. 4. The discharge tube as described. 4. The discharge tube according to claim 1, wherein the second electrode is disposed adjacent to the inner wall side of the dielectric tube with respect to the first electrode. 5. The discharge tube according to any one of claims 1 to 5, wherein the first electrode is a transparent electrode made of a transparent conductor and is formed over the entire circumference of the dielectric tube. The first electrode is a mirror-like metal electrode made of a metal conductor, and is formed over the entire circumference of the dielectric tube except for a light extraction portion formed in a part in the circumferential direction of the dielectric tube. The discharge tube according to any one of claims 1 to 5, wherein the discharge tube is provided. The discharge tube according to claim 1, wherein the second electrode is formed in a linear shape. The discharge tube according to any one of claims 1 to 8, wherein the first electrode is arranged except for a portion where the second electrode is taken out of the dielectric tube from the sealed space. A power supply line for supplying power to the second electrode is connected to both ends of the second electrode, and the second electrode is supported by the dielectric tube by the power supply line. The discharge tube according to any one of claims 1 to 8. The discharge tube according to claim 1, wherein a length of the first electrode with respect to a longitudinal direction of the dielectric tube is shorter than a length of the second electrode.

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