JP2001076678A - Ceramic discharge lamp and high-pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent oxidation of electrode parts and to enhance the sealing of current conductors and their bonding to an arc tube made of a ceramic by using platinum or a platinum coating for the easily oxidizable current conductors. SOLUTION: Current conductors 8 each provided with a discharge electrode 7 on their ends are formed by an inner conductor 8a made of cermet and by an outer conductor 8b made of platinum, and the current conductors 8, including the outer conductors 8b, are bonded to and sealed in a capillary 5 by the use of a glass solder 12. Each outer conductor (8b) has a ring-shaped porous skeleton 13 formed thereon of a sintered metallic powder body and is bonded to the capillary with the porous skeleton 13 interposed between them by the use of the glass solder 12. The glass solder 12 is impregnated into the porous skeleton 13, thereby chemically bonding platinum to the capillary 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure discharge lamp such as a sodium lamp or a metal halide lamp, and more particularly to an improvement in an electrode structure of a ceramic discharge lamp forming a light emitting portion thereof.

[0002]

2. Description of the Related Art As shown in FIG. 4, a high-pressure discharge lamp such as a sodium lamp or a metal halide lamp is made of a niobium or cermet having a transparent ceramic tube 21 provided with electrodes at one end at both ends. A ceramic discharge lamp 24 is used in which the conductor 23 is inserted and the insertion portion is hermetically sealed with a sealing material such as a glass braze. In the case of a sodium lamp, sodium, mercury, xenon gas, or the like is sealed inside the discharge lamp. The metal halide lamp is filled with mercury, metal halide, argon gas and the like. In each lamp, the current conductor 22 is made of niobium, molybdenum, tungsten, or the like, and is easily oxidized at a high temperature. Therefore, the ceramic discharge lamp 24 is incorporated into an outer tube 25 made of hard glass or quartz glass, and is inserted into the outer tube. The ceramic discharge lamp 2 is filled with an inert gas or held in a vacuum to prevent oxidation.
4 longevity.

[0003] Such a high-pressure discharge lamp has a high luminous efficiency, and thus its use as a substitute for a light source such as an incandescent lamp is expanding. However, as described above, the conventional high-pressure discharge lamp has an outer tube 2.
5, the manufacturing process is complicated, and it is difficult to reduce the size. Therefore, a high-pressure discharge lamp that does not require an outer tube has been studied and proposed. For example, Japanese Patent Application Laid-Open No. 8-273618 and Japanese Patent Application Laid-Open
There is a configuration disclosed in Japanese Patent No. 273619. In both cases, an electric conductor (current conductor) made of ceramic is inserted into both ends of an arc tube made of translucent ceramic, and both are sealed with glass braze. The other end of the introduction body is electrically connected via a platinum film formed on a side surface of the electricity introduction body.
In this way, the use of platinum, which does not oxidize even at high temperatures and exhibits stable characteristics, eliminates the use of easily oxidizable inner electrodes and current conductor materials at least in the exposed portions of the electrodes.
The ceramic discharge lamp can be turned on in the air without an outer tube.

[0004]

However, the present inventor has
As a result of studying the above-mentioned electrode structure, it was found that there were the following problems. That is, although the gap between the platinum or the electric conductor and the arc tube is sealed by the glass solder, the platinum and the glass solder have poor wettability and cannot be chemically bonded. Adhesion is weaker than the adhesion. Therefore, lighting-
If cracks occur in the glass braze during many cycles of turning off the light, the cracks easily propagate in the glass braze, and the interface between the electrointroducer and the glass braze due to the difference in thermal expansion coefficient between the two. Is generated, and the inner electrode and the current conductor, which are easily oxidized, are damaged by the atmosphere, which causes arc tube leakage.

In view of the above problems, the present invention uses platinum or a platinum coating on a current conductor which is easily oxidized to prevent oxidation of the electrode portion, and also to join or seal the current conductor and the ceramic arc tube. The task is to provide good stopping. Another object of the present invention is to provide a high-pressure discharge lamp having high reliability without an outer tube by applying such a good electrode structure to a high-pressure discharge lamp.

[0006]

According to a first aspect of the present invention, there is provided a ceramic discharge lamp in which electrodes are inserted into openings at both ends of an arc tube made of a translucent ceramic and sealed. A discharge space filled with an ionized luminescent substance and a starting gas, wherein the discharge space is formed in the arc tube, wherein the electrode portion is formed by a discharge electrode and a current conductor for supplying a current to the discharge electrode; One end of the conductor exposed to the outside of the arc tube is formed of platinum or a conductor coated with platinum, and the one end and the arc tube opening are formed of a sintered body of metal powder having an affinity for platinum between both ends. Characterized by being bonded and covered with a glass braze with a porous skeleton formed therebetween.

According to a second aspect of the present invention, in the first aspect of the present invention, the current conductor comprises an inner conductor made of a halogen-resistant material and connected to a discharge electrode, and platinum or platinum partially exposed to the outside of the arc tube. An outer conductor made of a coated conductor, a porous skeleton is arranged at a junction of the outer conductor with the arc tube opening, and the porous skeleton is impregnated with glass braze to form an outer conductor. An arc tube opening is joined to the inner conductor, and the arc tube opening is joined to the arc tube opening with a glass solder.

According to a third aspect of the present invention, in the first or second aspect, the porous skeleton is formed in a ring shape around the current conductor.

A high-pressure discharge lamp according to a fourth aspect of the present invention comprises the ceramic discharge lamp according to any one of the first to third aspects, and has no outer tube.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory sectional view of a ceramic discharge lamp according to the present invention, and FIG. 2 is an enlarged view of an electrode portion thereof. The luminous tube 2 of the ceramic discharge lamp 1 has a cylindrical body 3 made of translucent ceramic forming a luminous space, a ring-shaped closing member 4 provided at both end openings 3a, and an insertion connection at the center opening. And an electrode portion 6 is formed in the through hole 5a. The electrode portion 6 includes a current conductor 8 and a discharge electrode 7 provided at the tip of the current conductor 8. The discharge electrode 7 has a filament 10 attached to the tip of an electrode shaft 9 extending from the tip of the current conductor 8.
Is formed. The current conductor 8 is formed by joining the inner conductor 8a and the outer conductor 8b,
The outer conductor 8b is formed of platinum or a conductor coated with platinum, and has a rear end exposed to the outside to form an external lead connected to a power supply.

The inner conductor 8a and the electrode shaft 9, and the inner conductor 8a and the outer conductor 8b are joined by welding, brazing or metallization, and the inner conductor 8a and the outer conductor 8b are connected to the capillary 5. Between the glass wax 12
And the arc tube 2 is hermetically sealed. Further, the inside of the arc tube 2 is filled with an ionized luminescent substance and a starting gas. A porous skeleton 13 made of a sintered body of molybdenum powder and having open pores is formed in a ring shape around the platinum portion, which is the outer conductor 8b covered with the glass brazing material. Porous skeleton 1
3 is covered.

The luminous tube 2 composed of the cylindrical body 3, the closing member 4, and the capillary 5 is formed by forming the cylindrical body 3 with alumina, and forming the closing member and the capillary with alumina or a cermet containing alumina. From the difference in shrinkage, it can be formed integrally in the firing step, or the whole can be integrally formed of alumina and then fired.

The inner conductor 8a may be formed of a cermet. The cermet is a conductive cermet made of a composite material of ceramics and metal. For example, the cermet is formed at a mixing ratio of molybdenum and alumina of 50/50% by volume. Good. The mixing ratio of molybdenum and alumina is 70
If it is between / 30% by volume and 30/70% by volume, it can be used as a current conductor, and the thermal expansion characteristics of both alumina and glass can be balanced.

Such a cermet is prepared by weighing a predetermined amount of molybdenum powder and high-purity alumina, crushing and drying in an acetone or alcohol solvent without an alumina pot for 5 to 20 hours. Then, the dried mixed powder is mixed with, for example, ethyl cellulose or an acrylic binder and a solvent or the like suitable for the binder, for example, a triroll or the like to form an extrusion paste. At this time, granules for press molding may be formed using an appropriate binder. Next, the paste is formed by an extrusion method, cut into a required length, and dried at 30 ° C to 80 ° C. When granules for press molding are used, they are press-molded and dried. Then, the molded body is placed in a reducing atmosphere or in a vacuum at 1400 ° C. to 2000 ° C.
Baking. In this way, a current conductor made of cermet can be obtained.

The glass braze 12 is made of Al ₂ O ₃ , SiO ₂ ,
Y ₂ O _3, Dy ₂ O _3, B is preferably configured by a material selected from the group consisting of ₂ O ₃ and MoO _3, it is particularly preferable to contain Al ₂ O ₃ and SiO ₂ .
Further, from the viewpoint of wettability, it is preferable to contain a main component of ceramic or cermet. Here, the main component refers to a ceramic component occupying 70% by weight or more of the ceramic, or a ceramic component occupying 60% by weight or more of the cermet.
Then, a powder or a frit prepared to have a predetermined glass composition, for example, dysprosium oxide of 60% by weight, alumina of 15% by weight, and silica of 25% by weight is crushed, a binder such as polyvinyl alcohol is added, and granulation is performed. ,
The glass material is obtained by press molding and degreasing.

The porous skeleton 13 is a sintered body of metal powder and has open pores. Here, it is formed from a sintered body of molybdenum powder, but other materials such as tungsten, silicon, niobium, cobalt, platinum, or a metal such as kovar (an alloy of iron-nickel-cobalt) may be used as the material of the metal powder. Metals can be used. Above all, molybdenum, nickel, silicon, and cobalt are preferable because of their affinity with platinum.

The manufacturing process of the porous skeleton 13 and the electrode portion will be described with reference to FIG. First, mix the metal powder, crush,
After drying, a binder such as ethyl cellulose or an acrylic resin is added and kneaded to form a paste, thereby obtaining a porous skeleton material. The paste is applied in a ring shape (step 2) to a predetermined portion, that is, the side of the outer conductor 8b of platinum or a conductor coated with platinum (step 1) (step 2).
Dry at 0 ° C. This calcined body is subjected to a dew point of 20 ° C to 50 ° C.
Under a reducing atmosphere, an inert gas atmosphere or a vacuum
Baking at a temperature of 0 ° C. to 1700 ° C. (Step 3). By doing so, the porous skeleton 13 having open pores can be formed.

The open porosity of the porous skeleton is preferably at least 30%, more preferably at least 40%, whereby the strength of the joint region can be further increased. Further, the open porosity is preferably 80% or less, and more preferably 70% or less, whereby the glass material is appropriately impregnated into the open pores of the porous skeleton, and the stress applied to the porous skeleton is dispersed. The durability to a heat cycle can be improved. In order to appropriately generate an impregnated glass layer in which such a porous skeleton is impregnated with glass, the tap density of the metal powder, which is a raw material of the porous skeleton, must be 2.5 to 3.5 g / cc.
It is preferable that

Next, in step 4, the inner conductor 8a having the discharge electrode 7 is connected by welding or metallization bonding. In step 5, a predetermined amount of this current conductor is inserted into the capillary 5 of the arc tube 2 from the inner conductor side. A glass material is attached to the sealing portion as a glass braze 12, and the glass is heated and melted to join the current conductor 8 to the capillary 5 and seal the gap.
At this time, the glass material is preferably formed in a ring shape in advance.

The junction between the current conductor 8 and the arc tube 2 thus formed is impregnated into the open pores of the porous skeleton 13 when the attached glass material is melted, so that the porous skeleton 13 and the impregnated glass phase are impregnated. To form a main phase consisting of Therefore, poor wettability between platinum and glass solder is improved, and the porous skeleton 13
The glass solder is bonded to the platinum via. In addition, the inner conductor 8a formed of cermet and the capillary made of ceramic have good wettability and are well bonded to glass.

The amount of insertion of the current conductor 8 when joining the capillary 5 and the current conductor 8 is such that a part of the formed porous skeleton 13 is inserted as shown in FIGS. 2 (a) and 2 (b). Even when the glass material is melted, it may be joined in a state where the glass material is stopped immediately before it is inserted. When the glass material is melted, the glass material is impregnated into the tip end of the current conductor 8 and the entire porous skeleton 13 by capillary action. A glass phase is formed between the inner conductor 8a and the capillary 5 and on the surface of the porous skeleton.

By forming the joint in this manner, the tensile strength applied to the glass is dispersed by the porous skeleton, and the compressive strength applied to the porous skeleton 13 is dispersed by the glass in the open pores, and It can cope with both tensile stress and compressive stress applied. In addition, although cracks easily occur with glass alone, in this case, even if cracks occur in the glass phase, the propagation of the cracks is prevented by the porous skeleton 13, so that the fracture of the joining region can be prevented. Also, the main phase composed of the porous skeleton 13 and the impregnated glass phase adheres tightly to the platinum, and the interfacial glass layer firmly adheres to the discharge tube (capillary).

Further, since the main phase can act as a thermal expansion relaxation layer between the platinum and the capillary 5, it is strong against thermal cycling and can prevent the occurrence of leaks. Due to the formation of mechanical and scientific joints, confidentiality is high and cracks are difficult to progress. The outer conductor may be formed only of platinum, or the core may be formed of niobium, molybdenum, tungsten, cermet or Kovar, and may be covered with platinum. Although the inner conductor is formed of cermet, it may be formed of a halide-resistant material such as molybdenum or tungsten.

The ceramic discharge lamp 1 thus formed may be housed in a conventional outer tube made of hard glass or quartz to form a high-pressure discharge lamp, but the exposed portion of the electrode portion is only the platinum portion. Therefore, the current conductor is not oxidized even when exposed to the air at a high temperature, so that the current conductor is not oxidized even in a high temperature state, and cracks are not easily generated in the glass solder. Therefore, even if the lamp is turned on in the atmosphere without being housed in the outer tube, the life can be extended. Therefore, the ceramic photoelectric tube 1 can be used as it is as a high-pressure discharge lamp, whereby a small high-pressure discharge lamp can be easily produced and the manufacturing process can be simplified.

In the above embodiment, the tip portion of the current conductor provided with the discharge electrode is formed of cermet. However, it may be a composite in which ceramic is coated with cermet, or may be a halide-resistant compound such as molybdenum or tungsten. May be formed alone. The shape of the ceramic discharge tube can be generally tubular, cylindrical, barrel, or the like, and is not particularly limited.

[0026]

As described above in detail, according to the first aspect of the present invention, at least the surface of the current conductor exposed from the arc tube is formed of platinum, so that the current conductor is oxidized even at a high temperature. This prevents the sealing portion from peeling off and the glass brazing from cracking.
In addition, by joining and covering the glass with a porous skeleton having an affinity for platinum at the junction between the platinum portion of the current conductor and the opening of the arc tube, the platinum portion can be securely inserted into the arc tube opening. Can be joined.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, the portion of the current conductor formed of the anti-halide is securely joined to the arc tube opening by the glass brazing, The platinum or the platinum-coated portion is also securely joined to the arc tube opening with a glass brazing via the porous skeleton, so that both are well joined and sealed to the arc tube. Therefore, the sealing portion does not deteriorate due to the heat cycle and the internal gas does not leak.

According to the invention of claim 3, claim 1 or 2
In addition to the effects of the invention, the porous skeleton is formed in a ring shape, so that even if cracks occur in the glass brazing, the cracks do not easily spread to the entire joint, and the life of the discharge lamp can be extended. .

According to the fourth aspect of the present invention, since there is no outer tube, a small high-pressure discharge lamp can be easily produced, and the manufacturing process can be simplified.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view of a ceramic discharge lamp and a high-pressure discharge lamp showing an example of an embodiment of the present invention.

FIG. 2 is an enlarged view of an electrode unit of FIG.

FIG. 3 is a flowchart showing a sealing process of an electrode unit.

FIG. 4 is a side view of a conventional high-pressure discharge lamp.

[Explanation of symbols]

1. Ceramic discharge lamp, 2. Arc tube, 3. Cylindrical body,
4 ··· Clogging material, 5 ·· Capillary, 5a ·· Through hole, 6
..Electrode part, 7 ·· Discharge electrode, 8 ··· Current conductor, 8a ·
· Inner conductor, 8b · · · outer conductor, 9 · · electrode axis, 1
0 .. filament, 12 .. glass braze, 13 .. porous skeleton.

Claims (4)

[Claims] 1. A ceramic discharge lamp having a discharge space filled with an ionized luminous substance and a starting gas formed in said arc tube by inserting and sealing an electrode portion into both end openings of an arc tube made of a translucent ceramic. Wherein the electrode portion is formed of a discharge electrode and a current conductor for supplying a current to the discharge electrode, and one end of the current conductor exposed to the outside of the arc tube is formed of platinum or a conductor coated with platinum, A ceramic discharge lamp characterized in that the one end and the arc tube opening are joined and covered with glass brazing with a porous skeleton made of a sintered body of metal powder having an affinity for platinum interposed therebetween. . 2. A current conductor comprising an inner conductor made of a halide-resistant material and connected to a discharge electrode, and an outer conductor made of platinum or a platinum-coated conductor partially exposed to the outside of the arc tube. A porous skeleton is disposed at a joint of the outer conductor with the arc tube opening, and the porous skeleton is impregnated with glass braze to join the outer conductor with the arc tube opening, and the inner conductor is connected to the inner tube. 2. The ceramic discharge lamp according to claim 1, wherein the conductor and the arc tube opening are joined by a glass solder. 3. The ceramic discharge lamp according to claim 1, wherein the porous skeleton is formed in a ring shape around the current conductor. 4. A high-pressure discharge lamp comprising the ceramic discharge lamp according to claim 1 and having no outer tube.