JP2010113921A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp having an electrode structure, capable of maintaining power supply state, without fail, at high light-emitting efficiency. <P>SOLUTION: The discharge lamp has a rare gas, filled in an arc tube 1 and has an external electrode 3 on the outer face of the arc tube 1. An internal electrode 4, which is not electrically connected to the external electrode 3, is installed on the inner face of the arc tube 1 opposed to the external electrode 3; and the internal electrode 4 is covered with dielectric layers 5, 2 and the dielectric constant between the internal electrode 4 and the surface of the dielectric layer 2 on the discharge space side is larger than that between the external electrode 3 and the surface of the arc tube 1 on the discharge space side. Furthermore, the external electrode 3 is a pair of belt-shaped electrodes and is formed, extending in a tube axis direction on the outer face of the arc tube 1, and the internal electrode 4 is a pair of belt-shaped electrodes and is formed on the inner face of the arc tube 1 facing the external electrode 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a discharge lamp used for a light source of a general lighting device, a light source of a liquid crystal display device, and a light source of a backlight device.

  Conventionally, a light source used in a backlight device such as a liquid crystal display device is formed by enclosing a rare gas in an arc tube composed of an elongated glass tube and applying a phosphor on the inner surface, and is formed on the outer surface of the arc tube. There is known an external electrode type discharge lamp in which a voltage is applied to a pair of strip-shaped external electrodes to generate excimer discharge in an arc tube and a phosphor is excited with ultraviolet rays to obtain visible light.

FIG. 7A is a schematic view of a conventional external electrode type discharge lamp, and FIG. 7B is a cross-sectional view in a direction perpendicular to the tube axis.
The discharge lamp has a phosphor layer 2 formed on the inner surface of a straight tube arc tube 1 over the entire circumference, and has a pair of strip-shaped external electrodes 3 extending in the tube axis direction on the outer surface of the arc tube 1. Yes.
In the arc tube 1, for example, xenon is sealed as a rare gas, and by applying a high frequency high voltage between the external electrodes 3, ultraviolet rays are generated by the discharge generated in the arc tube 1, and phosphors are irradiated with ultraviolet rays. To emit visible light.
In this discharge lamp, when a high frequency high voltage is applied between the external electrodes 3, the two arc tubes 1 facing the external electrode 3 become dielectrics, and excimer discharge is generated in the arc tube.
Such a technique is described in Japanese Patent Application Laid-Open No. 2007-134059.

  As another discharge lamp, a rare gas is enclosed in an arc tube made of an elongated glass tube, a strip-shaped external electrode serving as one electrode is formed on the outer surface of the arc tube, and a strip-shaped electrode serving as the other electrode is formed on the inner surface of the arc tube. An internal electrode is formed, a phosphor is applied to the inner surface of the arc tube including the surface of the internal electrode, a high frequency high voltage is applied to the external electrode and the internal electrode, an excimer discharge is generated in the arc tube, and the phosphor is irradiated with ultraviolet rays. There is known an internal / external electrode type discharge lamp which excites the light to obtain visible light.

FIG. 8A is a cross-sectional view of a conventional internal / external electrode type discharge lamp, and FIG. 8B is a cross-sectional view in a direction perpendicular to the tube axis.
In the discharge lamp, a strip-shaped external electrode 3 extending in the tube axis direction is formed on the outer surface of the arc tube 1 that is open on one end side, and a strip-shaped internal electrode 4 extending in the tube axis direction is formed on the inner surface of the arc tube 1. Has been.
A closing body 6 is fitted in the opening of the arc tube 1, and the closing body 6 and the arc tube 1 are sealed with frit glass 7, and the inner surface of the arc tube 1 including the surface of the internal electrode 4 on the discharge space side. The phosphor layer 2 is formed on the surface.
The end of the internal electrode 4 is bent at the opening side of the arc tube 1, passes between the open end 11 of the arc tube 1 and the closing body 6, and is led out to the outside.
The arc tube 1 is filled with, for example, xenon as a rare gas. By applying a high frequency high voltage to the external electrode 3 and the internal electrode 4, ultraviolet rays are generated by the discharge generated in the arc tube 1. The phosphor is excited to emit visible light.
In this discharge lamp, when a high frequency voltage is applied to the external electrode 3 and the internal electrode 4, the arc tube facing the external electrode 3 becomes the first dielectric, and the phosphor in the portion covering the internal electrode 4 Layer 2 is the second dielectric.
Such a technique is described in JP-A-2002-208379.
JP 2007-134059 A JP 2002-208379 A

  In the external electrode type discharge lamp shown in FIG. 7, the arc tube 1 at a portion facing each external electrode 3 is a dielectric, and there are two dielectrics, and the dielectric is a glass tube constituting the arc tube 1. Therefore, in order to reduce the thickness in terms of structure, there is a limit to the withstand pressure strength, and it is necessary to generate a discharge through a dielectric composed of two glass tubes, and the light emission efficiency, which is the light emission intensity with respect to the input power, is low. It was.

  On the other hand, in the internal / external electrode type discharge lamp shown in FIG. 8, the first dielectric is the glass tube constituting the same arc tube 1 as the external electrode type discharge lamp shown in FIG. The dielectric is the portion of the phosphor layer 2 that covers the internal electrode 4, and this second phosphor layer 2 is much thinner than the thickness of the glass tube that is the first dielectric, so that the luminous efficiency is increased. Can do.

  However, in the internal / external electrode type discharge lamp shown in FIG. 7, the internal electrode 4 must be led out of the arc tube 1, and the end of the internal electrode 4 is bent at the open end 11 of the arc tube 1. In other words, it is a structure that is led out through the opening end 11 of the arc tube 1 and the closing body 6, and the internal electrode 4 may be cut off from the place where the internal electrode 4 is bent, which is a problem in the electrode structure. There was a discharge lamp.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a discharge lamp having an electrode structure that has high luminous efficiency and can reliably maintain a power supply state. .

  The discharge lamp according to claim 1 is a discharge lamp in which a rare gas is sealed in an arc tube, and an external electrode is provided on the outer surface of the arc tube, and an external electrode and an electric electrode are formed on the inner surface of the arc tube facing the external electrode. Internal electrodes that are not connected to each other are provided, the internal electrodes are covered with a dielectric layer, and the dielectric constant between the internal electrodes and the surface of the dielectric layer on the discharge space side is The dielectric constant between the external electrode and the surface of the arc tube on the discharge space side is larger.

  A discharge lamp according to a second aspect is the discharge lamp according to the first aspect, and in particular, the external electrodes are a pair of strip-shaped electrodes, and extend in the tube axis direction on the outer surface of the arc tube. The internal electrode is a pair of strip-shaped electrodes, and is formed on the inner surface of the arc tube facing the external electrode.

  The discharge lamp according to claim 3 is the discharge lamp according to claim 1, in particular, the external electrode is a pair of electrodes formed at both ends of the arc tube, and each external electrode is It is formed in the circumferential direction of the arc tube, and the internal electrode is a pair of strip-shaped electrodes, and is formed on the inner surface of the arc tube so as to extend in the tube axis direction, and one end of one internal electrode The side is located on the inner surface of the arc tube facing the one external electrode, and the one end side of the other internal electrode is located on the inner surface of the arc tube facing the other external electrode. .

  In the discharge lamp of the present invention, an inner electrode that is not electrically connected to the outer electrode is provided on the inner surface of the arc tube facing the outer electrode, and the inner electrode has a thinner dielectric layer than the arc tube. Therefore, the loss in the dielectric layer is reduced and the light emission efficiency is increased.

  Further, the internal electrode is present only inside the arc tube, and is not led out of the arc tube, and the internal electrode is fed by an arc tube that is a dielectric by applying a high frequency high voltage. Since the internal electrode has a structure that is not subjected to external stress or load, the electrode structure can reliably maintain the power supply state. is there.

Hereinafter, the discharge lamp of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view of a discharge lamp according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA of the discharge lamp shown in FIG.
In FIG. 1, the dielectric 5 described later is not actually visible, but is shown by a broken line for convenience.

  The arc tube 1 of the discharge lamp is made of translucent glass having an outer diameter of 9.8 mm and a wall thickness of 0.4 mm. Examples of the material include soda lime glass, aluminosilicate glass, borosilicate glass, and barium glass. be able to. A pair of strip-shaped external electrodes 3 are arranged on the outer surface of the arc tube 1 so as to extend in the tube axis direction of the arc tube 1. These external electrodes 3 are arranged so as to face each other in a cross-sectional view perpendicular to the tube axis shown in FIG.

The external electrode 3 is not particularly limited as long as it is a conductive material. For example, gold, silver, nickel, carbon, gold palladium, silver palladium, platinum, or the like can be suitably used. This is realized by sticking a tape-like metal to the outer surface of the tube 1 or screen-printing and baking a silver conductive paste.
The external electrode 3 has, for example, a width of 0.8 mm and a length of 1150 mm.

An inner electrode 4 that is not electrically connected to the outer electrode 3 is provided on the inner surface of the arc tube 1 facing the outer electrode 3.
The arc tube 1 is sealed at both ends, and the internal electrode 4 is completely isolated from the outside of the arc tube 1.
The internal electrode 4 is a pair of strip-shaped electrodes, and is formed on the inner surface of the arc tube 1 facing the external electrode 3.
The internal electrode 4 has a width of 0.5 mm and a length of 1150 mm, and is opposed to the external electrode 3 in the entire length direction, and the material thereof is the same as that of the external electrode 3.

  The internal electrode 4 is covered with a dielectric layer 5 formed by baking a glass paste so as not to be exposed to the discharge space in the arc tube 1. The material of the glass paste used here is mainly composed of bismuth oxide-boron oxide or zinc oxide-boron oxide as the main component, and has a higher dielectric constant than the glass material of the arc tube. Is preferably used.

On the inner surface of the arc tube 1 including the surface of the dielectric layer 5, the phosphor layer 2 is formed over the entire circumference. As for the phosphor, a red phosphor is a europium activated yttrium oxide phosphor (Y ₂ O ₃ : Eu) or (Y, Gd) BO ₃ : Eu, and a green phosphor is a cerium terbium activated lanthanum phosphate phosphor (LaPO). ₄ : Ce, Tb), and the blue phosphor is a europium-activated barium magnesium aluminate phosphor (BaMgAl ₁₀ O ₁₇ : Eu).

  The discharge space inside the arc tube 1 is filled with 160 Torr of a rare gas, xenon gas.

Although the dielectric layer 5 is formed so as to cover the internal electrode 4, the dielectric layer 5 that covers one of the internal electrodes 4 is omitted, and the phosphor layer 2 directly covers the internal electrode 4. May be.
In this case, the phosphor layer 2 becomes a dielectric layer.

  In this discharge lamp, when a high frequency voltage is applied to the external electrode 3 from a lighting power source (not shown), ultraviolet light having a wavelength of 172 nm is generated in the arc tube 1, and this ultraviolet light irradiates the phosphor in the phosphor layer 2. Excites and emits visible light.

Next, the discharge phenomenon of the discharge lamp of the present invention shown in FIG. 1 will be described.
An internal electrode 4 is provided on the inner surface of the arc tube 1 facing the external electrode 3. Although this internal electrode 4 is not electrically connected to the external electrode 3, when a high frequency voltage is applied to the external electrode 3 and the polarity of one of the external electrodes 3 becomes negative, the internal electrode 4 faces this external electrode 3. The polarity of the internal electrode 4 also becomes negative, and charges accumulate on the surface of the dielectric layer 5 covering the internal electrode 4. Since this discharge lamp has the phosphor layer 2, the electric charge actually accumulates on the surface of the phosphor layer 2 on the discharge space side covering the dielectric layer 5.
Then, when the polarity of the one external electrode 3 is switched to the plus side, charges accumulated on the surface of the dielectric layer 5 covering the internal electrode 4 are released. Since this discharge lamp has the phosphor layer 2, the charge accumulated on the surface of the phosphor layer 2 on the discharge space side that covers the dielectric layer 5 is actually released.
This discharged electric charge causes excimer discharge in the arc tube 1 to generate ultraviolet rays.

In such a discharge, the dielectric constant between the surface of the phosphor layer 2 on the discharge space side that covers the dielectric layer 5 that is a surface from which charges are discharged and the internal electrode 4 is the external electrode when the internal electrode 4 is not present. 3 and the inner surface of the arc tube 1 on the discharge space side, the electric permittivity is larger than that of the phosphor layer 2 covering the dielectric layer 5 which is a surface for discharging electric charges. .
In this embodiment, the loss of energy when the electric charge is generated in the dielectric composed of the dielectric layer 5 and the phosphor layer 2 is the dielectric composed of the arc tube 1 when the internal electrode 4 is not present. As a result, the emission efficiency is increased in the present invention.

  Further, the discharge lamp of the present invention shown in FIG. 1 has a structure in which the internal electrode 4 exists entirely inside the arc tube 1 and is not led out of the arc tube 1. Power feeding is performed from the external electrode 3 outside the arc tube 1 through the arc tube 1, and the internal electrode 4 has a structure that is not subjected to external stress or load. The state can be maintained.

3 is a plan view of a discharge lamp according to another embodiment of the present invention, FIG. 4 is a cross-sectional view taken along the line AA of the discharge lamp shown in FIG. 3, and FIG. 5 is a cross-sectional view taken along the line BB of the discharge lamp shown in FIG. 6 and 6 are CC cross-sectional views of the discharge lamp shown in FIG.
In FIG. 3, the internal electrodes 4 (4a, 4b) and the dielectric 5 which will be described later are actually not visible, but are shown by broken lines for convenience.
In this discharge lamp, a pair of external electrodes 3 (3a, 3b) are formed at both ends of the arc tube, and each external electrode 3a, 3b has a width of 20 mm in the tube axis direction of the arc tube. It is formed on the entire circumference of the tube 1 in the circumferential direction.

The internal electrodes 4 (4a, 4b) are a pair of strip-shaped electrodes having a width of 0.5 mm and a length of 1100 mm, and are formed on the inner surface of the arc tube 1 so as to extend in the tube axis direction.
One end side 4a1 of one internal electrode 4a is located on the inner surface of the arc tube 1 facing the one external electrode 3a and on the entire circumference of the arc tube 1, and the other end of the internal electrode 4a. The side does not extend to the inner surface of the arc tube 1 facing the other external electrode 3b.
One end side 4b1 of the other internal electrode 4b is the inner surface of the arc tube 1 facing the other external electrode 3b and is located on the entire circumference of the arc tube 1, and the other end side of the internal electrode 4b is It does not extend to the inner surface of the arc tube 1 facing the other external electrode 3a.

The internal electrode 4 is covered with a dielectric layer 5 formed by baking glass paste so as not to be exposed to the discharge space in the arc tube 1.
A phosphor layer 2 is formed on the inner surface of the arc tube 1 including the surface of the dielectric layer 5.

Although the dielectric layer 5 is formed so as to cover the internal electrode 4, the structure may be such that either one of the dielectric layers 5 is omitted and the phosphor layer 2 directly covers the internal electrode 4. In this case, the phosphor layer 2 also serves as a dielectric layer.
In this case, the phosphor layer 2 becomes a dielectric layer.

  In this discharge lamp, the shape and material of the arc tube 1, the material of the external electrode 3, the material of the internal electrode 4, the material of the phosphor layer 2, the rare gas and the pressure enclosed in the arc tube 1 are shown in FIG. Same as each of the discharge lamps.

  In this discharge lamp, when a high frequency high voltage is applied to the external electrode 3 from a lighting power source (not shown), ultraviolet light having a wavelength of 172 nm is generated in the arc tube 1, and this ultraviolet light irradiates the phosphor in the phosphor layer 2. Excited, and visible light is emitted.

Next, the discharge phenomenon of the discharge lamp of the present invention shown in FIG. 3 will be described.
An internal electrode 4 is provided on the inner surface of the arc tube 1 facing the external electrode 3. The internal electrode 4 is not electrically connected to the external electrode 3, and only one end 4a1 of one internal electrode 4a is located on the inner surface of the arc tube 1 facing the one external electrode 3a, and the other Only one end side 4b1 of the internal electrode 4b is located on the inner surface of the arc tube 1 facing the other external electrode 3b, and each internal electrode 4a, 4b has a portion other than the one end side 4a1, 4b1 except for the external electrode 3 It is in a state not facing.
When a high frequency high voltage is applied to the external electrode 3 and the polarity of one of the external electrodes 3a is negative, the polarity of the one end side 4a1 of the internal electrode 4a facing this one of the external electrodes 3a is also negative. The entire internal electrode 4a is also on the negative side. Then, charges accumulate on the surface of the dielectric layer 5 covering the internal electrode 4a. Since this discharge lamp has the phosphor layer 2, the electric charge actually accumulates on the surface of the phosphor layer 2 on the discharge space side covering the dielectric layer 5.
Then, when the polarity of the one external electrode 3a is switched to the plus side, charges accumulated on the entire surface of the dielectric layer 5 covering the internal electrode 4a are released. Since this discharge lamp has the phosphor layer 2, actually, charges accumulated on the entire surface of the phosphor layer 2 on the discharge space side covering the dielectric layer 5 are released.
This discharged electric charge causes excimer discharge in the arc tube 1 to generate ultraviolet rays.

In such a discharge, the dielectric constant between the surface of the phosphor layer 2 on the discharge space side that covers the dielectric layer 5 that is a surface from which charges are discharged and the internal electrode 4 is the external electrode when the internal electrode 4 is not present. 3 and the inner surface of the arc tube 1 on the discharge space side, the electric permittivity is larger than that of the phosphor layer 2 covering the dielectric layer 5 which is a surface for discharging electric charges. .
In this embodiment, the loss of energy when the electric charge is generated in the dielectric composed of the dielectric layer 5 and the phosphor layer 2 is the dielectric composed of the arc tube 1 when the internal electrode 4 is not present. As a result, the emission efficiency is increased in the present invention.

  Further, the discharge lamp of the present invention shown in FIG. 3 has a structure in which the internal electrode 4 exists entirely only inside the arc tube 1 and is not led out of the arc tube 1. Power feeding is performed from the external electrode 3 outside the arc tube 1 through the arc tube 1, and the internal electrode 4 has a structure that is not subjected to external stress or load. The state can be maintained.

Next, an experiment was conducted to examine the light emission efficiency, which is the light emission intensity with respect to the input power.
The discharge lamp of the present invention used in this experiment is a discharge lamp having the structure shown in FIGS. 1 and 3. The discharge lamp having the structure shown in FIG. 8 was used as a comparative lamp.
The comparison lamp is the same as the discharge lamp of the present invention shown in FIG. 1 in terms of the arc tube shape material excluding the blocking body, the external electrode material, the internal electrode material, the phosphor material shape, the type and pressure of the enclosed gas. The difference is that one electrode is an external electrode and the other electrode is an internal electrode. The width and length of each external electrode are the width of the external electrode of the discharge lamp of the present invention shown in FIG. And the length is the same.
This experiment is a result when the input power is constant at 25 W in each lamp.
The results are shown in Table 1 below.
The luminous efficiency shown in Table 1 is a relative value when the luminous efficiency of the comparative lamp is 100.

As can be seen from the results in Table 1, it can be seen that the discharge lamp of the present invention has an improvement in luminous efficiency of 1% or more compared to the comparative lamp.
Further, unlike the comparative lamp shown in FIG. 8, the lamp of the present invention does not have a closing body, so that the airtightness of the arc tube can be reliably maintained.

It is a top view of the discharge lamp of this invention. FIG. 1 is a cross-sectional view taken along line AA of the discharge lamp. It is a top view of the discharge lamp of this invention. FIG. 3 is a cross-sectional view taken along line AA of the discharge lamp. FIG. 3 is a cross-sectional view taken along the line BB of the discharge lamp. FIG. 3 is a cross-sectional view taken along the line C-C of the discharge lamp. It is the schematic perspective view and sectional drawing of the conventional discharge lamp. It is sectional drawing of the conventional discharge lamp.

Explanation of symbols

1 arc tube 2 phosphor layer 3 external electrode 4 internal electrode 5 dielectric

Claims (3)

In a discharge lamp in which a rare gas is enclosed in the discharge space in the arc tube and has an external electrode on the outer surface of the arc tube,
An inner electrode that is not electrically connected to the outer electrode is provided on the inner surface of the arc tube facing the outer electrode,
The internal electrode is covered by a dielectric layer;
A discharge lamp characterized in that a dielectric constant between the internal electrode and the surface of the dielectric layer on the discharge space side is larger than a dielectric constant between the external electrode and the surface of the arc tube on the discharge space side. . The external electrodes are a pair of strip electrodes, and are formed on the outer surface of the arc tube so as to extend in the tube axis direction,
2. The discharge lamp according to claim 1, wherein the internal electrodes are a pair of strip-shaped electrodes, and are formed on an inner surface of the arc tube facing the external electrodes. The external electrodes are a pair of electrodes formed at both ends of the arc tube, and each external electrode is formed in the circumferential direction of the arc tube,
The internal electrodes are a pair of strip-shaped electrodes, and are formed on the inner surface of the arc tube so as to extend in the tube axis direction,
One end of one internal electrode is located on the inner surface of the arc tube facing the one external electrode, and one end of the other internal electrode is located on the inner surface of the arc tube facing the other external electrode The discharge lamp according to claim 1, wherein:

Images