JP2009200037A - Outer face electrode discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an outer face electrode discharge lamp capable of stably obtaining good dark starting characteristics. <P>SOLUTION: The outer face electrode discharge lamp includes a discharge container 1 having a discharge space 11 formed thereinside, a discharge medium sealed in the discharge space 11, a phosphor layer 2 formed on the inner surface of the discharge container 1, and outer surface electrodes 3a and 3b formed on the outer surface of the discharge container 1. A conductive layer 4 is formed in the discharge container 1, so that at least part of the layer comes into contact with the discharge space 11 and straddles the boundary 3' of the outer surface electrode 3a on the center side of the discharge container 1. As a conductive layer 4, metal selected from zinc Zn, indium In, tin Sn, copper Cu, zirconium Zr, carbon C, or a compound of them can be used. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an outer surface electrode discharge lamp used as a light source of a backlight of a liquid crystal television, a notebook personal computer or the like.

  At present, as a light source used for a backlight of a liquid crystal display, an external electrode discharge lamp is becoming mainstream instead of a cold cathode fluorescent lamp. This outer surface electrode discharge lamp has a lamp configuration in which outer surface electrodes are formed at both outer ends of a cylindrical discharge vessel as described in JP-A-2007-53117 (Patent Document 1). When a high frequency voltage is applied to the lamp, a discharge occurs in the lamp and light is emitted.

  In this external electrode discharge lamp, there is a problem that the dark start-up characteristic, that is, the start-up characteristic of a lamp left in a dark space such as the inside of a backlight housing where no external light is incident is not good. In this way, if the dark start characteristic is poor, no discharge occurs and no light is emitted and no image is displayed, and if the discharge is not performed for several seconds, the circuit safety device operates and turns off.

  To solve this problem of dark start characteristics, the inventions of Japanese Patent Application Laid-Open No. 2004-95378 (Patent Document 2), Japanese Patent Application Laid-Open No. 2004-253245 (Patent Document 3), and Japanese Patent Application Laid-Open No. 2007-73481 (Patent Document 4) are disclosed. Proposed. Patent Document 2 discloses means for dispersing and mixing alumina fine particles in the phosphor layer, Patent Document 3 discloses means for forming a cesium oxide layer as a discharge delay preventing metal oxide on the phosphor layer surface, and Patent Document 4 discloses Discloses a means for forming an oxide layer in which zinc oxide and yttrium oxide are mixed over a wide area of the inner wall of the arc tube.

JP 2007-53117 A JP 2004-95378 A JP 2004-253245 A JP 2007-73481 A

  The inventions of these Patent Documents 2 to 4 are common in that the initial electrons are generated in the discharge space before lighting, thereby improving the dark start characteristics, and the outer surface actually provided with such means. Electrode discharge lamps are being realized. However, there is a need for further improved characteristics regarding the dark start characteristics, and further improvements are required.

  Therefore, the inventor tried to improve the dark start characteristics by a method different from the conventional method. As a result, the inventors have found an invention capable of starting discharge with a high probability even in a state where there are few initial electrons present in the discharge space.

  An object of the present invention is to provide an outer electrode discharge lamp capable of stably obtaining good dark start characteristics.

  In order to achieve the above object, an outer surface electrode discharge lamp of the present invention includes a discharge vessel in which a discharge space is formed, a discharge medium sealed in the discharge space, and a phosphor formed on the inner surface of the discharge vessel. A layer and an outer electrode formed on the outer surface of the discharge vessel, and at least a part of the inner surface of the discharge vessel is in contact with the discharge space and straddles the boundary of the outer electrode on the center side of the discharge vessel A conductive layer is formed as described above.

  According to the present invention, good dark start characteristics can be stably obtained.

(First embodiment)
Hereinafter, an outer surface electrode discharge lamp according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall view for explaining an outer surface electrode discharge lamp according to a first embodiment of the present invention.

  The container of the outer electrode discharge lamp is composed of a discharge container 1 made of hard glass, for example. The discharge vessel 1 has an elongated cylindrical shape whose both ends are sealed by sealing, and a discharge space 11 is formed in the inside thereof. The discharge space 11 is filled with a discharge medium made of mercury Hg and a rare gas. As the rare gas, a mixed gas of neon Ne and argon Ar is suitable, and adjustment such as improving the startability of the lamp can be performed by increasing the ratio of argon Ar. A phosphor layer 2 is formed on the inner surface of the discharge vessel 1. The phosphor layer 2 is a single wavelength phosphor emitting R (red), G (green), and B (blue), a three wavelength phosphor mixed with RGB, and a four wavelength fluorescence mixed with a deep red phosphor. The body can be used according to the intended purpose. In addition, the formation range of the phosphor layer 2 only needs to cover the light emission region of the lamp.

  Outer electrodes 3a and 3b are formed at both ends of the discharge vessel 1 along the outer surface thereof. The outer surface electrodes 3a and 3b can be formed, for example, by ultrasonic solder dipping a metal material mainly composed of tin Sn, zinc Zn, and antimony Sb. The outer electrodes 3a and 3b can be replaced with a metallic cap or an electrode layer formed by solder dipping after covering a tube end with a metal plate formed in a cylindrical shape.

  A conductive layer 4 is formed on the inner surface of the discharge vessel 1. The conductive layer 4 will be described in detail with reference to FIGS. FIG. 2 is a view for explaining the range of X shown in FIG. 1, and FIG. 3 is a view for explaining the Y-Y 'cross section shown in FIG.

  As can be seen from these drawings, the conductive layer 4 is formed in a cylindrical shape on the inner surface of the phosphor layer 2 so as to straddle the boundary 3 ′ of the outer electrode 3 a on the center side of the discharge vessel 1. Such a conductive layer 4 can be formed by, for example, a so-called sucking method in which a slurryed conductive material is sucked and applied from the opening side of the discharge vessel 1 in the same manner as the application of the phosphor layer 2. The formation range L in the tube axis direction of the conductive layer 4 is preferably 1.0 mm or more and 20 mm or less, and more preferably 2.0 mm or more and 10 mm or less. Within this range, it is possible to obtain a stable dark starting characteristic and to reduce the change in light emission in the axial direction. The film thickness T of the conductive layer 4 is preferably 0.2 μm or more and 25 μm or less, more preferably 1.0 μm or more and 10 μm or less from the viewpoints of conductivity, ease of film formation, and light shielding.

  Here, as is clear from FIG. 3, the inner peripheral surface of the conductive layer 4 is in contact with the discharge space 11. However, the entire conductive layer 4 does not need to be in contact with the discharge space 11, and it is sufficient that at least a part thereof is in contact. The “part” is not particularly limited in place, size, and the like. That is, as long as at least a part of the conductive layer 4 is in contact with the discharge space 11, a structure in which a film is further formed on the conductive layer 4 is allowed.

The material of the conductive layer 4 will be described. The conductive layer 4 was selected from materials having excellent electrical conductivity having an electric conductivity of 10 ⁻¹⁰ Ω / cm or more, such as zinc Zn, indium In, tin Sn, copper Cu, zirconium Zr, and carbon C. A layer containing a simple metal, an oxide, or a compound can be used. In the present invention, zinc oxide ZnO is particularly suitable. Further, a mixed layer containing a simple substance, oxide or compound of cesium Cs is more desirable. In order to improve the effect of the present invention, it is desirable that the particles constituting the conductive layer 4 have an average particle size of about 1.0 μm or less. Incidentally, the average particle size and the like can be measured by a laser diffraction / scattering method using a particle size analyzer.

  An example of the outer surface electrode discharge lamp of the present embodiment is shown below. The tests described below are based on this specification unless otherwise specified.

(Example)
Discharge vessel 1; made of borosilicate glass, total length = 733 mm, outer diameter = 3.0 mm, inner diameter = 2.0 mm,
Discharge medium; mercury Hg, mixed gas of neon Ne and argon Ar = 60 torr,
Phosphor layer 2; RGB three-wavelength phosphor,
Electrodes 3a, 3b; electrode length = 25 mm,
Conductive layer 4; zinc oxide ZnO, average particle size = 0.920 μm (center particle size = 0.848 μm), axial length L = 4.0 mm (boundary 3 ′ is at the center), film thickness T = 2.0 μm Cylindrical shape.

  FIG. 4 is a diagram for explaining the dark start-up characteristics in the early stage of lighting of the conventional lamp in which the conductive layer is not formed with the lamp of the above embodiment. The dark start characteristic is measured by applying a voltage at which the discharge is stabilized, for example, a voltage of about 2000 Vrms, after leaving the lamp in the dark space for 48 hours.

  As can be seen from the results, in the example, the discharge started at 1 msec or less and stable dark discharge characteristics were obtained, whereas in the conventional example, the discharge start time was slow and the variation was large. . Thus, in the present invention, good dark start characteristics could be stably obtained because the conductive layer 4 acted to reliably start the initial electrons present in the discharge space 11. That is, by forming the conductive layer 4 so as to straddle the boundary 3 ′ of the outer surface electrode 3a where the electric field is most concentrated, creeping discharge occurs at the end of the conductive layer 4 in the tube axis direction, and this assists the generation of the avalanche. Therefore, it is considered that the dark start characteristics are improved.

  In addition, since the formation range of the conductive layer 4 of the present invention in the tube axis direction is sufficiently small with respect to the entire length of the lamp, it was also confirmed that there was almost no change in light emission in the axial direction. In addition to the zinc oxide ZnO, the effects as described above are not only a zinc Zn compound, but also a simple substance, oxide or compound of a metal selected from other compounds such as zinc Zn, indium In, tin Sn, copper Cu, zirconium Zr, and carbon C. Even if it exists, it has been confirmed that it can be obtained.

  Therefore, in the first embodiment, the inner surface of the discharge vessel 1 is made of zinc oxide ZnO so that at least a part thereof is in contact with the discharge space 11 and straddles the boundary 3 ′ of the outer surface electrode 3 a on the discharge vessel 1 center side. Since the conductive layer 4 is formed, the initial electrons existing in the discharge space 11 by the creeping discharge can be started with a high probability, so that favorable dark start characteristics can be stably obtained.

  In addition, since the formation range L in the tube axis direction of the conductive layer 4 is 1.0 mm or more and 20 mm or less, it is possible to obtain a stable dark start characteristic and to reduce a change in light emission in the axial direction.

  Furthermore, since the film thickness T of the conductive layer 4 is not less than 0.2 μm and not more than 25 μm, it is easy to ensure conductivity, it is easy to form a film, and the influence of light emission characteristics due to light shielding can be reduced.

(Second Embodiment)
In the present embodiment, a mixed layer having a thickness of 2.0 μm in which zinc oxide ZnO and cesium sulfate Cs ₂ SO ₄ are mixed at a ratio of 2: 5 is used as the conductive layer 4. As a result of confirming the dark start-up characteristics of the lamp formed with this mixed layer, it was confirmed that the discharge start time at the beginning of lighting was as early as about 1 msec as in FIG. In addition, as shown in FIG. 5, in the dark start characteristics after lighting for 3000 hours, in the lamp of the conventional example in which the conductive layer is not formed, the discharge start time is much slower than the initial lighting time. As with the discharge start time at the beginning of lighting, it was confirmed to be as fast as about 1 msec.

In such a mixed layer, a good dark start-up characteristic can be obtained by the effect as a conductive material by zinc oxide ZnO and the initial electron emission effect by cesium sulfate Cs ₂ SO _{4 at the} beginning of lighting. On the other hand, during the lifetime, cesium sulfate Cs ₂ SO ₄ having a high mercury affinity attracts mercury Hg, whereby a mercury layer is formed on the surface of the mixed layer. Since the mixed layer in which the mercury layer is formed functions as a conductive material in the same manner as zinc oxide ZnO or the like, good dark start-up characteristics can be obtained during the lifetime. Therefore, in the present embodiment, it is considered that stable dark starting characteristics could be obtained over the initial lighting period to the lifetime. Note that the same effect can be obtained with a combination of another conductive substance and a substance having high mercury affinity, but a combination of a mixed conductive layer of zinc oxide ZnO and cesium sulfate Cs ₂ SO ₄ is optimal.

Next, the discharge start time after lighting for 3000 hours when the compounding ratio of zinc oxide ZnO and cesium sulfate Cs ₂ SO ₄ was changed was tested. The result is shown in FIG. Here, the blending ratio can be measured by an electron beam microanalyzer (EPMA).

As can be seen from FIG. 6, the discharge start time is delayed when the proportion of cesium sulfate Cs ₂ SO ₄ is too low or too high, and there is an appropriate blending ratio to make the discharge start time faster. Recognize. That is, when the ratio of cesium sulfate Cs ₂ SO ₄ is 20%, 40%, and 100%, the discharge start time tends to be slow, but when it is 60% and 80%, the discharge start time is early. Therefore, the mixing ratio of cesium sulfate Cs ₂ SO ₄ is preferably 60 to 80%. In addition, there was a tendency that the same effect was obtained even when a conductive substance other than zinc oxide ZnO and cesium sulfate Cs ₂ SO ₄ was combined with a substance having a high mercury affinity, or even when a small amount of other substances were mixed. It is considered that the mixing ratio of the substance with high mercury affinity should be 60 to 80%.

(Third embodiment)
FIG. 7 is a diagram for explaining an outer surface electrode discharge lamp according to a third embodiment of the present invention. About each part of embodiment after this, the same part as each part of the outer surface electrode discharge lamp of 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  In the present embodiment, a slit 51 is formed in the conductive layer 4 in the tube axis direction from the boundary 3 ′ of the outer electrode 3 a, and the conductive layer 4 is divided into a first conductive layer 41 and a second conductive layer 42. . By adopting such a structure, the second conductive layer 42 has a potential close to ground, so that creeping discharge is likely to occur between the first conductive layer 41 and the second conductive layer 42, and A stable dark starting characteristic can be obtained. Note that such a conductive layer 4 can be formed by scraping a desired portion, and the slit 51 is preferably 1.0 mm or less from the viewpoint of easy occurrence of creeping discharge.

  Therefore, in the third embodiment, creeping discharge is likely to occur, and more stable dark starting characteristics can be obtained.

(Fourth embodiment)
FIG. 8 is a diagram for explaining an outer electrode discharge lamp according to a fourth embodiment of the present invention.

  In the present embodiment, in addition to the conductive layer 4 (first conductive layer 41) of the first embodiment, a third conductive layer 43 is formed in a portion where the phosphor layer 2 is not formed on the end portion side of the lamp. is doing. The third conductive layer 43 is formed in anticipation of a getter action of an impure gas that mainly causes a voltage rise or a snake phenomenon with the passage of lighting time. Note that the getter action is more effective as the average particle size of the material constituting the third conductive layer 43 is smaller and the formation range is wider.

  Therefore, in the fourth embodiment, it is possible to obtain a good dark start characteristic and to prevent a voltage increase or a snake phenomenon that occurs with the passage of lighting time.

(Fifth embodiment)
FIG. 9 is a diagram for explaining an outer electrode discharge lamp according to a fifth embodiment of the present invention.

  In the present embodiment, the formation range is the same as that of the conductive layer 4 of the first embodiment, but is formed directly on the inner surface of the discharge vessel 1 rather than on the phosphor layer 2. In this configuration, the conductive layer 4 is difficult to peel off, and a stable layer can be obtained. In addition, since the conductive layer 4 such as zinc oxide ZnO has an ultraviolet blocking function, ultraviolet rays are not emitted to the outside through the portion, but in the case of the conductive layer 4 of zinc oxide ZnO, a lamp is used. When turned on, the part emits green light. However, when the lamp is incorporated in the backlight, the green light emission does not appear on the light emitting surface, and can be ignored in practice. In this embodiment, the conductive layer 4 on the end portion side of the lamp may be extended as in the fourth embodiment.

  Therefore, in the fifth embodiment, good dark start characteristics can be obtained, and a stable conductive layer 4 can be obtained.

(Sixth embodiment)
FIGS. 10A and 10B are views for explaining an outer surface electrode discharge lamp according to a sixth embodiment of the present invention. FIG. 10A is an axial sectional view, and FIG. 10B is a circumferential sectional view.

  In this embodiment, the slit 52 is formed in the axial direction of the conductive layer 4 so that the conductive layer 4 is divided into a plurality of sections in the cross section. Specifically, the conductive layer 4 is divided into six by the slits 52, and the peripheral length of each conductive layer 4 is 0.5 mm. As a matter of course, the six conductive layers 4 straddle the boundary 3 ′ of the outer surface electrode 3 a in the axial direction. In this way, by electrically dividing the conductive layer 4 across the boundary 3 ′ of the outer electrode 3a into a plurality of parts, the probability of discharge is further increased by the proximity conductor effect, and good dark start characteristics can be obtained. It becomes.

  Therefore, in the sixth embodiment, a more stable dark starting characteristic can be obtained by the proximity conductor effect.

(Seventh embodiment)
FIG. 11 is a diagram for explaining an outer surface electrode discharge lamp according to a seventh embodiment of the present invention.

  In the present embodiment, the slit 31 is formed at the center side end of the discharge vessel 1 of the outer surface electrode 3a to form the boundary 31 ′ and the boundary 32 ′ in the outer surface electrode 3a, and the boundary 31 ′ and the boundary 32 ′. It is comprised so that the conductive layer 4 may straddle between. As a result, as in the sixth embodiment, the probability of discharge is further increased, and good dark start characteristics can be obtained.

  Therefore, in the seventh embodiment, a more stable dark start characteristic can be obtained.

  The embodiment of the present invention is not limited to the above, and may be modified as follows, for example.

  The present invention can be applied not only to the straight tube type outer surface electrode discharge lamp but also to lamps of U-shape, L-shape, and various other shapes.

Alumina Al ₂ O ₃ may be mixed into the phosphor layer 2 to improve the emission of initial electrons into the discharge space 11. At that time, when using large alumina Al ₂ O ₃ having a particle ratio of 10% or less as measured by a scanning electron microscope (SEM), the initial lighting period to the lifetime Further, it is more preferable since the initial electron emission of alumina can be maintained.

  The boundary 3 ′ of the outer surface electrodes 3 a and 3 b is not limited to a linear shape as in the first embodiment and an uneven shape as in the seventh embodiment, but may be a shape such as an oblique shape. At this time, the positional relationship with the conductive layer 4 does not need to straddle the entire boundary 3 ′, and it is sufficient that at least a part thereof straddles.

  It is allowed to add other materials to the conductive layer 4 as long as the conductivity is not lost. For example, 30% by weight of alumina may be added with respect to the weight of zinc oxide ZnO. In this case, the effect of supplementing the initial electrons is increased, so that the dark start-up characteristics particularly in the initial lighting are improved and the zinc oxide is improved. It is possible to reduce the green emission color due to ZnO. Further, if 15% by weight of a phosphor is added to the weight of zinc oxide ZnO, the light emission color around the conductive layer 4 can be made close to white. Moreover, if low melting glass is added to zinc oxide ZnO, peeling of the conductive layer can be prevented and durability against discharge can be increased.

  The conductive layer 4 is not limited to being formed in a cylindrical shape, but may be formed only in a part of the small region so as to straddle the boundary 3 ′ of the external electrodes 3 a and 3 b as shown in FIG. 12. Even in this configuration, it is possible to stably obtain a better dark start-up characteristic than in the prior art. In addition, such a conductive layer 4 can be easily formed by dropping and drying a slurry-like conductive material at a desired location.

  The conductive layer 4 does not need to be formed on both of the outer surface electrodes 3a and 3b. It is sufficient if the conductive layer 4 is formed on one of the outer surface electrodes. However, a high voltage is applied to one outer surface electrode and a lower pressure is applied to the other outer surface electrode. Alternatively, in the case of grounding, it is desirable to form the conductive layer 4 on the high voltage side.

  Since the discharge start mechanism in the dark of the present invention also affects the probability of secondary electron emission, electric field strength, gas pressure, and interelectrode distance, more appropriate dark start characteristics can be achieved by suitably adjusting these conditions. Can be obtained.

The figure for demonstrating the outer surface electrode discharge lamp of the 1st Embodiment of this invention. The figure for demonstrating the range of X shown by FIG. The figure for demonstrating the Y-Y 'cross section shown by FIG. The figure for demonstrating the dark start-up characteristic in the lighting initial stage of the lamp | ramp of the prior art example which does not form the lamp | ramp of an Example and a conductive layer. The figure for demonstrating the dark starting characteristic after 3000 hours lighting of the lamp | ramp in the 2nd Embodiment of this invention and the lamp | ramp of a prior art example. Diagram for explaining dark starting characteristic of 3,000 hours after lighting when changing the mixing ratio of zinc oxide ZnO and cesium sulfate _Cs 2 SO _4. The figure for demonstrating the outer surface electrode discharge lamp of the 3rd Embodiment of this invention. The figure for demonstrating the outer surface electrode discharge lamp of the 4th Embodiment of this invention. The figure for demonstrating the outer surface electrode discharge lamp of the 5th Embodiment of this invention. The figure for demonstrating the outer surface electrode discharge lamp of the 6th Embodiment of this invention. The figure for demonstrating the outer surface electrode discharge lamp of the 7th Embodiment of this invention. The figure for demonstrating the other form of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge container 11 Discharge space 2 Phosphor layer 3a, 3b Outer surface electrode 3 'Boundary 4 Conductive layer

Claims (6)

A discharge vessel in which a discharge space is formed; a discharge medium enclosed in the discharge space; a phosphor layer formed on the inner surface of the discharge vessel; and an outer surface electrode formed on the outer surface of the discharge vessel. ,
An outer electrode discharge lamp characterized in that a conductive layer is formed on the inner surface of the discharge vessel so that at least a part thereof is in contact with the discharge space and straddles the boundary of the outer electrode on the center side of the discharge vessel. .   The said conductive layer is a layer containing the simple substance, oxide, or compound of the metal selected from zinc Zn, indium In, tin Sn, copper Cu, zirconium Zr, and carbon C, The Claim 1 characterized by the above-mentioned. External electrode discharge lamp.   The outer electrode discharge lamp according to claim 2, wherein the conductive layer contains a simple substance, oxide or compound of cesium Cs. The conductive layer is composed of zinc oxide ZnO and cesium sulfate Cs ₂ SO _4, and cesium sulfate Cs ₂ SO ₄ is mixed in a ratio of 60 to 80%. External electrode discharge lamp.   The external electrode discharge lamp according to any one of claims 1 to 4, wherein a formation range L in the tube axis direction of the conductive layer is 1.0 mm or more and 20 mm or less.   6. The outer electrode discharge lamp according to claim 1, wherein a thickness T of the conductive layer is 0.2 μm or more and 25 μm or less.

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