JP3645897B2 - External electrode type discharge lamp and manufacturing method thereof - Google Patents

Description

  The present invention relates to an external electrode type discharge lamp, and more particularly, to a technique effective in preventing drilling of a glass container directly under an external electrode.

  A discharge lamp encloses a gas in a transparent sealed container, uses this as a discharge medium to cause a discharge in the container, takes out light emitted by the discharge outside the container, and uses it for lighting or the like. One of the types in the case of classification from the viewpoint of the location where the electrodes are provided is an external electrode type discharge lamp.

  An external electrode type discharge lamp has a structural feature in that an electrode is provided outside the container, and is also referred to as an electrodeless discharge lamp because it does not have an electrode in the container. Compared to a lamp with a structure in which an electrode is provided in the container, it is not necessary to seal the lead that leads from the outside of the container to the electrode in the container, and therefore it is easy to manufacture. Many advantages such as miniaturization, no damage to the electrode due to electron impact during lighting, no contamination inside the discharge vessel due to electrode sputtering, and a small degree of shortening the lifetime when repeated flashing Therefore, it is often used for applications such as a light source for a backlight of a liquid crystal display device, a light source for irradiating a document in various OA devices such as a copying machine, a facsimile machine, and an image scanner. .

  Most of the discharge vessels are made of glass and cylindrical. There are various types of electrodes. For example, as exemplified in Patent Document 1, a pair of ring-shaped electrodes that surround the outer circumference of a cylindrical glass container along the circumference thereof are provided on the glass container. Arranged with a gap in the longitudinal direction (for the sake of convenience, described as a ring shape) and two long strip-shaped electrodes along the longitudinal direction of the glass container, with a slit along the circumference of the glass container The so-called aperture shape, and two parallel elongated electrodes wound in a spiral shape on a glass container (same spiral shape) are considered.

  FIG. 2 is a perspective view and a sectional view of a conventional external electrode type discharge lamp, taking a ring-shaped discharge lamp as an example. Referring to FIG. 2, two ring electrodes 2 </ b> A and 2 </ b> B that surround the glass container along its circumference are provided on the outer wall near both ends of the sealed cylindrical glass container 1. In general, a metal is often used as the material of the electrode. However, a transparent conductive material such as ITO may be used, or a metal may be used in combination.

In the space inside the glass container 1, a mixed gas of a rare gas such as xenon (Xe) or argon (Ar) and mercury gas is used as the discharge medium 4, for example, 2 × 10 ³ to 15 × 10 ³ Pa ( 15 to 113 Torr), and the phosphor film 3 is formed on the inner wall of the glass container 1 as necessary. In addition, only the rare gas which does not contain mercury may be used for the gas 4 of the said discharge medium. It is a well-known rare gas discharge lamp.

  In this external electrode type discharge lamp, as shown in FIG. 2B, a high frequency such as a sine wave or a pulse wave with a frequency of about 25 kHz and a voltage of about 2500 V is provided between the two external electrodes 2A and 2B. When a high-voltage AC voltage is applied, dielectric polarization occurs in the glass immediately below the external electrodes 2A and 2B in the glass container 1 that is a dielectric, and the inner wall of that portion acts as an electrode. As a result, a high voltage is introduced into the glass container 1, and dielectric barrier discharge is generated in the container. The mercury in the discharge medium 4 emits ultraviolet rays by this dielectric barrier discharge, and the phosphor film 3 is excited by the ultraviolet rays emitted by the mercury, and light having a wavelength different from that of the excited ultraviolet light, such as visible light, for example. The wavelength-converted light emitted from the phosphor 3 is emitted to the outside through the transparent glass container 1. For example, when the ultraviolet rays of mercury emission lines are used as they are like a germicidal lamp, the ultraviolet rays emitted by mercury are taken out through the glass container 1 as they are without providing the phosphor film 3.

  As described above, the discharge lamp of the external electrode type is the same discharge lamp, but the so-called cold cathode lamp and hot cathode lamp in which electrodes are provided in the vicinity of both ends inside the lamp vessel simply have an electrode arrangement place. In addition to being different, in particular, the glass container plays a very different role in that the portion directly below the external electrodes 2A and 2B on the inner wall of the glass container acts as an electrode.

JP 2002-216704 A (FIGS. 1 to 10)

  In the conventional external electrode type discharge lamp, the inventors started to open a hole from the inside in the portion immediately below the external electrodes 2A and 2B of the glass container 1 as the lighting time passed, and finally proceeded to the outer surface. And found a phenomenon that the airtightness of the glass container is not maintained. This perforation phenomenon was remarkable especially when the gas 4 of the discharge medium contained mercury gas, and it appeared early and the traveling speed was high.

  It has been found that this phenomenon can be reduced by reducing the voltage of the high-frequency AC voltage applied between the external electrodes 2A and 2B. However, although the life characteristics are slightly improved, the lamp brightness is reduced accordingly.

  Accordingly, an object of the present invention is to prevent a hole-drilling phenomenon in a portion immediately below an external electrode of a glass container under the same lighting conditions as in a conventional discharge lamp of an external electrode system.

The external electrode type discharge lamp of the present invention includes a sealed glass container, a gas of a discharge medium sealed in the glass container, and an outer wall of the glass container for generating a dielectric barrier discharge in the glass container. In an external electrode type discharge lamp including an external electrode provided, at least one of yttrium octylate and yttrium propionate is included in at least a portion corresponding to the external electrode on the inner wall of the glass container. It has a yttrium oxide film formed by baking from a solution.

  According to the present invention, in an external electrode type discharge lamp, it is possible to prevent a punching phenomenon in a portion immediately below an external electrode of a glass container under the same lighting conditions as before.

Next, embodiments of the present invention will be described with reference to the drawings. Referring to FIG. 1 showing a sectional view of a ring-type external electrode type mercury fluorescent lamp according to an embodiment of the present invention, the appearance of the mercury fluorescent lamp shown in this figure is the same as that of a conventional mercury fluorescent lamp. (See FIG. 2 (a)). However, as shown in FIG. 1, the difference is that yttrium oxide (Y ₂ O ₃ ) films 5A and 5B are formed on the inner surface side of the glass container 1 immediately below the external electrodes 2A and 2B. The yttrium oxide films 5A and 5B are obtained by firing yttrium octylate, yttrium propionate, or a mixed solution thereof, and are provided in a ring shape at portions corresponding to the external electrodes 2A and 2B.

  The inventors manufactured the first example (Example 1) of the external electrode type mercury fluorescent lamp shown in FIG. 1 as follows. First, a cylindrical glass container having both ends open is prepared, and ring-shaped external electrodes 2A and 2B are formed on the outer walls on both ends by a conventionally known method.

  Next, a solution in which yttrium octylate is dissolved in a suitable solvent to adjust the viscosity is applied to the portion of the inner wall of the glass container 1 that contacts the external electrodes 2A and 2B, and heat is applied to volatilize the solvent. Further, dense yttrium oxide films 5A and 5B are formed by firing at a temperature of about 500 to 600 ° C. in an air atmosphere.

  Thereafter, the phosphor film 3 is formed on the inner wall of the glass container 1 by a conventionally known method, and the inside of the glass container is once evacuated, and then the xenon gas containing mercury gas as the discharge medium 4 is sealed in this embodiment. An external electrode type mercury fluorescent lamp according to the example is completed.

  The external electrodes 2A and 2B are formed first in the above-described example, for example, because they are formed by firing a conductive paste. Depending on the phosphor film 3 to be used, the property may be changed by heating. Therefore, when adopting a method that requires heating to form the external electrode, the external electrode is formed prior to the formation of the phosphor film 3. Is preferably formed. If, for example, an aluminum foil is used for the external electrodes 2A and 2B and is fixed to the outer wall of the glass container 1 by a method such as adhesion, the external electrode can be formed after the phosphor film 3 is formed. That is, after the phosphor film 3 is formed, the external electrode is formed before the discharge medium gas 4 is sealed, or the discharge electrode gas 4 is sealed first and the external electrode is formed last. May be.

  Next, as a second example, the same external electrode type mercury fluorescent lamp (Example 2) as in Example 1 was produced except that the yttrium oxide films 5A and 5B were formed by firing yttrium propionate. In this embodiment, the yttrium oxide films 5A and 5B were formed as follows. That is, yttrium propionate is dissolved in a solvent, the viscosity is adjusted, and this is applied to the portion of the inner wall of the glass container 1 that contacts the external electrodes 2A and 2B. Then, heat was applied to volatilize the solvent, and further, baking was performed at a temperature of about 500 to 600 ° C. in an air atmosphere to obtain yttrium oxide films 5A and 5B.

  Both the external electrode type mercury fluorescent lamp according to Example 1 and the external electrode type mercury fluorescent lamp according to Example 2 have a high frequency between the two external electrodes 2A and 2B, as in the conventional mercury fluorescent lamp shown in FIG. However, in either embodiment, unlike the conventional lamp, a hole is generated in the portion immediately below the external electrodes 2A and 2B of the glass container 1 in both embodiments. There was no. In the conventional external electrode type mercury fluorescent lamp, some of the lamps that cannot be turned on instantaneously due to the drilling of the glass container start to occur about 3000 hours after the start of discharge. In such a time, no change was observed that could be visually confirmed on the inner wall of the glass container. This is considered as follows.

  As described above, in the external electrode type discharge lamp, the portion immediately below the external electrodes 2A and 2B on the inner wall of the glass container 1 acts as an electrode during discharge. Therefore, during lighting, mercury ions are accelerated and strongly implanted into the inner wall portion of the glass container acting as the electrode, and sputtering occurs. When there is no protective film and the above portion of the inner wall of the glass container 1 is exposed, or when the phosphor film C is formed directly on the inner wall, mercury ions scrape the glass by sputtering and penetrate into the interior. When mercury ion sputtering and permeation are repeated, the glass thickness decreases, the temperature rises, and the withstand voltage decreases, so the discharge current increases. Thereafter, positive feedback that the withstand voltage decreases and the discharge current increases. This causes a sudden thermal runaway and eventually opens a hole in the glass.

In order to prevent the glass container from being perforated by the sputtering of mercury ions, at least the portion of the inner wall of the glass container 1 that contacts the external electrodes 2A and 2B is covered with a protective film so as to prevent direct contact between the mercury ions and the glass container However, it was not effective in the case of this example, although an attempt was made to form a metal oxide film such as aluminum oxide (Al ₂ O ₃ ) or silicon oxide (SiO ₂ ). It was. Moreover, even if it is the same yttrium oxide film, for example, using a suspension in which fine powder of yttrium oxide is dispersed in a solvent, this is applied to the portion of the inner wall of the glass container 1 that corresponds to the external electrodes 2A and 2B and dried. In the case of the protective film obtained in this way, the effect was still small.

  As described above, in the external electrode type mercury fluorescent lamp, the portion immediately below the electrode of the glass container acts as an electrode, so that mercury ions concentrate on that portion and are accelerated and collide. This is because the powdered yttrium oxide film is likely to be etched by sputtering because there is a lot of space between the particles and not dense with respect to the sputtering of mercury ions. On the other hand, the yttrium oxide films 5A and 5B used in Example 1 and Example 2 are baked yttrium octylate or yttrium propionate, and are denser than the powdered yttrium oxide film. It is thought that the ability to prevent the impact of accelerated mercury ions is high.

  Here, in the external electrode type discharge lamp, the sputtering by the gas ions of the discharge medium on the inner wall portion of the glass vessel acting as an electrode naturally occurs even in the case of only a rare gas not containing mercury. In particular, the phenomenon of glass drilling is particularly remarkable when mercury gas is included. Mercury ions are heavier than rare gases for discharge lamps typified by Xe, Kr, Ar, Ne, and the like. It is presumed that the sputtering effect is large.

  As a result of investigating the case where yttrium oxide films 5A and 5B are formed by applying, drying, and firing a liquid obtained by mixing yttrium octylate and yttrium propionate, the present inventors have found that Example 1 and Example In the same manner as in Example 2, it was confirmed that the effect of preventing the glass container from being punched was observed. There was no difference in effect depending on the mixing ratio of yttrium octylate and yttrium propionate.

  The protective film (yttrium octylate, yttrium propionate, or an yttrium oxide film obtained by firing a mixed solution of yttrium octylate and yttrium propionate) is disposed on the inner wall of the glass container 1 at least directly below the external electrodes 2A and 2B. If formed, the object of the present invention can be achieved. However, since the protective film is translucent, it may be formed over the entire inner wall of the lamp vessel 1. In this way, when applying yttrium octylate to the inner wall of the glass container 1 in the protective film forming step, it is not necessary to mask other than the portions that contact the external electrodes 2A and 2B, so that the protective film forming step is simplified. Simplify and reduce manufacturing costs.

  In addition, the present invention can be applied to a discharge lamp that does not use a phosphor. In the case of a so-called mercury fluorescent lamp using a gas containing mercury gas and the phosphor film 3, the following is performed. Better. That is, the phosphor film 3 is generally made of a granular phosphor, and there are many gaps between the phosphor particles. Therefore, in the mercury fluorescent lamp, mercury aggregates in the gaps between the phosphor particles, and the vapor pressure of mercury gas in the glass container 1 decreases as the lighting time elapses, and the brightness of the lamp decreases. Therefore, it is desirable that the area of the phosphor film 3 is as small as possible. Therefore, in the case of an external electrode type mercury fluorescent lamp, it is preferable not to form a phosphor film on the portions corresponding to the external electrodes 2A and 2B.

  In addition, as for the external electrode, the case where two ring-shaped electrodes 2A and 2B are formed is illustrated, but the number of electrodes is not particularly limited to two. Any number of geometrical electrodes may be used as long as they are paired in terms of potential. The shape of the electrode is not limited to the ring shape but may be an aperture shape or a spiral shape. Furthermore, the glass container is not limited to a cylindrical one, but may be a flat discharge lamp using a flat rectangular glass container.

  The present invention is particularly effective when used in an external electrode type mercury discharge lamp in which a discharge medium contains mercury gas.

It is sectional drawing of the ring-shaped external electrode system mercury fluorescent lamp which concerns on one embodiment of this invention. It is the perspective view and sectional drawing of an example of the conventional external electrode system mercury fluorescent lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass container 2A, 2B External electrode 3 Phosphor film 4 Gas of discharge medium 5A, 5B Yttrium oxide film

Claims (7)

A hermetically sealed glass container, a discharge medium gas sealed in the glass container, and an external electrode provided on the outer wall of the glass container for generating a dielectric barrier discharge in the glass container. In an external electrode type discharge lamp,
An external electrode having an yttrium oxide film formed by firing from a solution containing at least one of yttrium octylate and yttrium propionate on at least a portion corresponding to an external electrode on the inner wall of the glass container Method discharge lamp.   The external electrode discharge lamp according to claim 1, wherein the discharge medium contains mercury gas.   The external electrode type discharge lamp according to claim 1 or 2, wherein the yttrium oxide film is provided on the entire inner wall of the glass container.   4. The external electrode type discharge lamp according to claim 1, further comprising a phosphor film on an outermost layer on an inner surface side of the glass container. 5.   5. The external electrode discharge lamp according to claim 4, wherein the phosphor film is formed in a portion excluding a portion corresponding to the external electrode. A cylindrical sealed glass container;
A pair of ring-shaped electrodes surrounding the cylindrical glass container along its circumference, and electrodes arranged side by side along the longitudinal direction of the glass container;
A discharge medium gas containing mercury gas enclosed in the glass container;
An yttrium oxide film formed by firing from a solution containing at least one of yttrium octylate and yttrium propionate , provided in a portion including at least a portion corresponding to the external electrode of the inner wall of the glass container;
An external electrode type discharge lamp comprising: a phosphor film formed on an outermost layer on the inner surface side of the glass container, the phosphor film formed on a portion excluding a portion corresponding to the external electrode. A method of manufacturing an external electrode type discharge lamp according to claim 6,
Forming the pair of ring-shaped external electrodes on the outer wall of the cylindrical glass container open at both ends;
Applying a solution containing at least one of yttrium octylate and yttrium propionate to a portion including at least a portion corresponding to the external electrode of the inner wall of the glass container;
Drying the solution and baking to obtain the yttrium oxide film;
Forming the phosphor film;
A method of manufacturing an external electrode type discharge lamp comprising at least a step of enclosing a gas of a discharge medium containing mercury gas in the glass container.

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