JP2005267908A - External electrode type discharge lamp and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent perforation from occurring in a part just below an external electrode on the inside surface of a glass vessel even when an external electrode type discharge lamp is lit with a voltage equal to that of a conventional one. <P>SOLUTION: For this external electrode type discharge lamp including the sealed glass vessel, a gas 4 of a discharge medium and the external electrodes 2A and 2B formed on the outside surface of the glass vessel for generating dielectric barrier discharge in the glass vessel 1, magnesium oxide films 5A and 5B are formed on parts of the inside surface of the glass vessel 1 including at least parts corresponding to the external electrodes 2A and 2B. The magnesium oxide films 5A and 5B are obtained from a solution containing one or more kinds of magnesium acetate and magnesium nitrate by means of baking. Since the magnesium film formed by this method has a continuous structure and denser than a film of metal oxide powder, its spatter prevention capability against ions of the gas 4 of a discharge medium is high in a part just below the electrode of the glass vessel. It is particularly effective when the gas 4 of the discharge medium contains mercury gas having large mass. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  Discharge lamps are used for lighting and other purposes by enclosing gas in a transparent hollow sealed container, using this as a discharge medium to cause discharge in the container, and extracting the light emitted by the discharge outside the container. It is. An external electrode type discharge lamp is one of the types in which the discharge lamp is classified from the viewpoint of the location where the electrode is provided.

  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. It is advantageous for downsizing, because there is no damage to the electrode due to electron impact at the time of lighting or contamination inside the discharge vessel due to sputtering of the electrode, so the degree of shortening the life when repeated blinking and lighting is small Since it has many advantages, it is often used for applications such as backlight light sources for liquid crystal display devices, light sources for irradiating documents in various office automation equipment such as copiers, facsimile machines, and image scanners. Yes.

  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. Some of them are arranged in the longitudinal direction with a gap (for the sake of convenience, referred to as a ring shape). Alternatively, there is a so-called aperture type in which two long strip-shaped electrodes along the longitudinal direction of the glass container are arranged with a slit along the circumference of the glass container. Furthermore, the thing which spirally wound two parallel elongate electrodes around the cylindrical glass container (same, spiral shape) etc. is also considered.

  FIG. 2 shows a perspective view and a cross-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-shaped external electrodes 2 </ b> A and 2 </ b> B that surround the glass container along its circumference are provided on the outer surfaces in the vicinity of 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 gas 4, for example, 2 × 10 ³ to 15 × 10 ^3. It is sealed at a pressure of about Pa (15 to 113 Torr). A phosphor film 3 is formed on the inner surface 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 a 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. Apply high voltage AC voltage. Then, in the glass container 1 that is a dielectric, dielectric polarization occurs in the glass immediately below the external electrodes 2A and 2B, and the inner surface 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. Due to this dielectric barrier discharge, mercury in the gas 4 of the discharge medium emits ultraviolet rays. The phosphor film 3 is excited by ultraviolet rays emitted from the mercury, and emits light having a wavelength different from that of the excitation ultraviolet light such as visible light. Then, the wavelength-converted light emitted from the phosphor film 3 is radiated to the outside through the transparent glass container 1. For example, when the ultraviolet ray of mercury emission line is used as it is like a germicidal lamp, the ultraviolet light emitted by mercury is taken out through the glass container 1 without providing the phosphor film 3.

  Thus, although the external electrode type discharge lamp is the same discharge lamp, the location of the electrodes is simply different from the so-called cold cathode lamp or hot cathode lamp in which electrodes are provided near both ends inside the lamp vessel. In addition, in particular, the role that the glass container plays is greatly different in that the portion immediately below the external electrodes 2A and 2B on the inner surface 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.

  Therefore, an object of the present invention is to prevent a hole from being generated in a portion of a glass container immediately below an external electrode even when the external electrode type discharge lamp is lit at the same voltage as the conventional one.

  An external comprising a hollow hermetically sealed glass container, a gas of a discharge medium enclosed in the glass container, and an external electrode provided on the outer surface of the glass container for generating a dielectric barrier discharge in the glass container An electrode type discharge lamp is characterized in that a magnesium oxide film having a continuous structure is provided on a portion including at least a portion corresponding to an external electrode on the inner surface of the glass container.

  According to the present invention, in an external electrode type discharge lamp, it is possible to prevent perforation from occurring in a portion immediately below the external electrode of the glass container even when the discharge lamp is lit at the same voltage as the conventional one.

  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)). Further, the gas components and pressure in the glass container, the composition of the phosphor film, and the like are the same. However, as shown in FIG. 1, the difference is that magnesium oxide (MgO) films 5A and 5B are formed on the inner surface of the glass container 1 immediately below the external electrodes 2A and 2B. The magnesium oxide films 5A and 5B are obtained by firing magnesium acetate, magnesium nitrate or a mixed solution thereof, and are provided in a ring shape on the inner surface of the glass container 1.

  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 with both ends open is prepared, and ring-shaped external electrodes 2A and 2B are formed on the outer surfaces of both ends by a conventionally known method.

  Next, a solution in which magnesium acetate is dissolved in a suitable solvent is applied to the portion of the inner surface of the glass container 1 that contacts the external electrodes 2A and 2B, and heat is applied to volatilize the solvent. As the solvent, an alcohol solvent such as butanol, ethanol or propyl alcohol, or an aqueous solvent such as pure water is used. Thereafter, the magnesium oxide films 5A and 5B are obtained by baking at a temperature of about 500 to 600 ° C. in an air atmosphere. The magnesium oxide films 5A and 5B are dense continuous films having a structure in which the constituent materials of the film are continuous.

  Thereafter, the phosphor film 3 is formed on the inner surface of the glass container 1 by a conventionally known method, and after the inside of the glass container is evacuated, a xenon gas containing mercury gas as the gas 4 of the discharge medium is sealed. Thus, the external electrode type mercury fluorescent lamp according to this 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 surface 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 magnesium oxide films 5A and 5B were formed by firing magnesium nitrate. In this embodiment, the magnesium oxide films 5A and 5B are formed as follows. That is, magnesium nitrate is dissolved in a suitable solvent, and this is applied to the portion of the inner surface of the glass container 1 that corresponds to the external electrodes 2A and 2B. Then, heat was applied to volatilize the solvent, and further, the magnesium oxide films 5A and 5B were obtained by firing at a temperature of about 500 to 600 ° C. in an air atmosphere. The magnesium oxide films 5A and 5B are dense continuous films having a structure in which the constituent materials of the film are continuous.

  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 and high voltage between the two external electrodes 2A and 2B, as in the conventional mercury fluorescent lamp. Discharge by applying an alternating voltage. However, in either embodiment, no hole was generated in the portion of the glass container 1 immediately below the external electrodes 2A and 2B. Conventionally, from about 3000 hours after the start of discharge, a thing that cannot be turned on instantaneously due to the perforation of the glass container starts to occur, whereas in Examples 1 and 2, the glass container 1 is used in this degree of time. There was no change that could be visually confirmed on the inner surface. 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 surface of the glass container 1 acts as an electrode during discharge. Therefore, during lighting, mercury ions are accelerated and strongly implanted into the inner surface 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 surface of the glass container 1 is exposed, or when the phosphor film 3 is formed directly on the inner surface, mercury ions scrape the glass by sputtering and penetrate into the interior. When the sputtering and penetration of mercury ions are repeated, the glass thickness decreases and at the same time the temperature rises and the withstand voltage decreases, so the discharge current increases locally. Thereafter, thermal runaway suddenly occurs due to positive feedback such as a decrease in withstand voltage and an increase in discharge current, and finally a hole is opened in the glass. Magnesium oxide films 5A and 5B used as protective films in Example 1 and Example 2 prevent acceleration mercury ions from being sputtered onto the glass container.

  Here, it is important that the magnesium oxide films 5A and 5B have a dense continuous structure. That is, the present inventors have attempted to use a film made of metal oxide powder as a protective film for some metal oxides. For example, a metal oxide powder is dispersed in a solvent in the same manner as when forming a phosphor film, and a slurry is formed by adding a binder and the slurry is applied to the inner surface of the glass container 1 and dried. Thus, a protective film is formed. However, in the case of a protective film made of a powder film, mercury is adsorbed in the gaps between the particles of the film, and the amount of mercury in the gas 4 of the discharge medium decreases as the discharge time elapses. The side effect of shortening the lifespan appeared. In addition, an undesirable phenomenon was observed in which mercury adsorbed in the gaps between the particles reacted with the alkali component of the glass container 1 to cause glass erosion.

  On the other hand, in Examples 1 and 2, mercury reduction and glass container erosion did not occur. This is considered to be because the magnesium oxide films 5A and 5B in Examples 1 and 2 are dense continuous structures. Further, from the viewpoint of the stopping ability against accelerated mercury ions, it is predicted that the blocking film having a continuous structure has a higher stopping ability than the protective film using powder having a large space between particles. Also from this point, it can be said that the continuous film is suitable for the protective film.

  In the external electrode type discharge lamp, the sputtering of the discharge medium gas ions to the inner surface portion of the glass container 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.

  The present inventors used a solution in which magnesium acetate and magnesium nitrate were both dissolved in a solvent, and applied, dried and fired to the inner surface of the glass container to form the magnesium oxide films 5A and 5B (implementation). Example 3). As a result of investigating the perforation of the glass container for the external electrode type mercury fluorescent lamp of Example 3, it was confirmed that the effect of preventing perforation of the glass container was observed as in Example 1 and Example 2. The difference of the effect by the mixing ratio of magnesium acetate and magnesium nitrate was not recognized.

  The protective film (magnesium acetate, or magnesium nitrate, or a magnesium oxide film obtained by firing a mixed solution of magnesium acetate and magnesium nitrate) is formed on the inner surface of the glass container 1 immediately below at least the external electrodes 2A and 2B. Although the object of the present invention can be achieved, the protective film is translucent and may be formed over the entire inner surface of the lamp vessel 1. In this case, when applying magnesium acetate, magnesium nitrate, or a mixed solution thereof to the inner surface of the glass container 1 in the protective film forming step, it is not necessary to mask other than the portion that contacts the external electrodes 2A, 2B. Perhaps the protective film forming process is simplified and simplified, and the manufacturing cost can be reduced.

  In addition, the present invention can be applied to a discharge lamp that does not use a phosphor, but 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 electrodes, the case where two ring-shaped electrodes 2A and 2B are formed is illustrated, but the number of electrodes is not limited to two. Any number of geometric 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. Further, the glass container is not limited to a cylindrical one, and may be a flat discharge lamp using a flat rectangular glass container.

  INDUSTRIAL APPLICABILITY The present invention is particularly effective when used for an external electrode type mercury discharge lamp in which mercury gas is contained in the discharge medium 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 Magnesium oxide film

Claims (9)

An external comprising a hollow hermetically sealed glass container, a gas of a discharge medium enclosed in the glass container, and an external electrode provided on the outer surface of the glass container for generating a dielectric barrier discharge in the glass container In electrode-type discharge lamps,
An external electrode type discharge lamp, wherein a magnesium oxide film having a continuous structure is provided on a portion including at least a portion corresponding to an external electrode on an inner surface of the glass container.   2. The external electrode discharge lamp according to claim 1, wherein the magnesium oxide film is formed by baking from a solution containing at least one of magnesium acetate and magnesium nitrate.   The external electrode discharge lamp according to claim 1 or 2, wherein the gas of the discharge medium contains mercury gas.   The external electrode type discharge lamp according to any one of claims 1 to 3, wherein the magnesium oxide film is provided on the entire inner surface of the glass container.   The external electrode system discharge according to any one of claims 1 to 4, wherein a phosphor film is provided on the magnesium oxide film and on an inner surface of a glass container exposed from the magnesium oxide film. lamp.   6. The external electrode discharge lamp according to claim 5, wherein the phosphor film is formed on 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;
A magnesium oxide film having a continuous structure provided in a portion including at least a portion corresponding to an external electrode on the inner surface of the glass container;
A phosphor film provided on the magnesium oxide film and on the inner surface of the glass container exposed from the magnesium oxide, the phosphor film formed on a portion excluding a portion corresponding to the external electrode. External electrode type discharge lamp.   The external electrode discharge lamp according to claim 7, wherein the magnesium oxide film is formed by baking from a solution containing at least one of magnesium acetate and magnesium nitrate. A method of manufacturing an external electrode type discharge lamp according to claim 8,
Forming a pair of ring-shaped external electrodes on the outer surface of a cylindrical glass container open at both ends;
Applying a solution containing at least one of magnesium acetate and magnesium nitrate to a portion including at least a portion corresponding to the external electrode on the inner surface of the glass container;
Baking the solution to obtain the magnesium 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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