JP2003151489A - Electrode for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for an discharge lamp attempting high longevity of the lamp by preventing heating of the electrode at the time of lighting the discharge lamp, restraining evaporation of an easy electron emission material from a cathode head end part and preventing devitrification, clouding, etc., of the lamp due to evaporation of the easy electron emission material. SOLUTION: This electrode for the discharge lamp is constituted of a base body metal 2 made of a high melting point metal of a mass body and a plurality of easy electron emission material parts 3 extended roughly in parallel with the electrifying direction as an electrode of the base body metal 2 in the base body metal 2 and a head end surface 31 exposed and provided in an electric discharge space, and each of the head end surfaces 31 of a plurality of the easy electron emission material parts 3 constitutes its characteristic feature of being arranged with a specified distance on an head end surface 21 of the base body metal 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode structure of a discharge lamp, and more specifically, to an electrode for a discharge lamp in which an electron-emissive substance is formed between refractory metals in a direction substantially the same as the current-carrying direction of the refractory metal. Regarding

[0002]

2. Description of the Related Art Conventionally, as an electrode for a discharge lamp, for example, as described in Japanese Patent Publication No. 50-14069, a metal powder and a powder of an electron-emitting substance are mixed and molded into a substantially rod shape. An electrode made of a sintered body that is sintered in a vacuum atmosphere is known. Further, in addition to the electrode made of such a sintered body, an electron-emissive substance is melted and impregnated in the pores of the porous sintered body made of a refractory metal,
An electrode in which an electron-emissive substance is formed on a porous refractory metal by a so-called impregnation method is known.

[0003]

However, with the recent demand for higher brightness and longer life of the lamp, the cathode tip is exposed to a highly heated arc more than before when the lamp is turned on. It has become. Therefore, in the electrode for a discharge lamp according to the related art as shown above, the electron-emissive substance is easily evaporated from the cathode tip portion, and as a result, the electron-emissive substance is rapidly depleted from the electrode and the lamp startability is increased. And the electron-emissive substance that has evaporated adheres to the inside of the bulb, resulting in devitrification and turbidity of the bulb, which causes a rapid decrease in the illuminance of the lamp.

In view of the above problems, an object of the present invention is to prevent the electrode from becoming highly heated when the discharge lamp is lit, and to suppress the evaporation of the electron-emissive substance from the tip of the cathode, thereby facilitating the electron-emissive substance. Prevents devitrification and white turbidity of the lamp due to evaporation of
It is an object of the present invention to provide an electrode for a discharge lamp which has a long lamp life.

[0005]

The present invention employs the following means in order to solve the above problems. A first means is to provide a base metal made of a high-melting metal in a lump form, extending in the base metal substantially parallel to the energization direction of the base metal as an electrode, and exposing the tip end surface to the discharge space. An electrode for a discharge lamp, which comprises a plurality of electron-emissive substance parts formed in such a manner that each tip surface of the plurality of electron-emissive substance parts is arranged within a predetermined distance on the tip surface of the base metal. It is characterized by being.

A second means is characterized in that, in the first means, “within the predetermined distance” is 100 μm or less.

According to a third means, in the first means or the second means, the electron-emissive substance portion is formed in a plurality of bottomed holes formed in the base metal by laser processing. Characterize.

A fourth means is the first means or the second means, wherein the electron-emissive substance portion is formed between the substantially rod-shaped members of the base metal made of a plurality of fixed substantially rod-shaped members. It is characterized in that it is formed in a plurality of gaps.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing the structure of a discharge lamp electrode according to the present invention. FIG. 1 (a) is a plan view of the discharge lamp electrode seen from the tip surface of the electrode, and FIG. 1 (b). ) Is a cross-sectional view as seen from AA in FIG. In these figures, 1 is an electrode for a discharge lamp, 2 is a base metal of an electrode for a discharge lamp 1 made of a massive refractory metal, 21 is a tip surface of a base metal 2, 3 is a discharge from the tip surface of a base metal 2. An electron-emissive substance portion in which an electron-emissive substance is formed in a plurality of bottomed holes provided substantially parallel to the energization direction of the lamp electrode 1, and 31 is an electron-emissive substance portion 3 exposed in the discharge space.
Is the tip surface of.

Here, the refractory metal 2 of the lump is, for example, a purity of 99.96% or more and a theoretical density of 18.8.
Pure tungsten of g / cm ³ or more is used, and such a bar of tungsten is formed into a substantially cylindrical rod shape having an outer diameter of 1 to 6 mm and a total length of about 3 to 6 mm.
, Diameter φ _e = about 40-50 μ, depth d = 1-10 m
m, pitch P = 50 to 100 μm, and a plurality of bottomed holes are formed. This bottomed hole is in the axial direction of the refractory metal 2,
That is, the refractory metal 2 is formed substantially parallel to the energization direction as the discharge lamp electrode. These bottomed holes are formed by laser processing, and by laser processing 100 μm
The following bottomed holes can be formed by controlling the depth of several mm and the pitch of the holes on the order of several tens of μm.

Incidentally, the refractory metal consisting of the above-mentioned agglomerates is different from the one consisting of the porous sintered body used in the so-called impregnation method described in the prior art, and has such pores. It means a refractory metal that has not been added.

For example, a powdery electron-emissive substance is pressed into the bottomed hole of the refractory metal 2 or a mixture of the electron-emissive substance and a binder is impregnated, followed by firing or sintering. To form the electron-emissive material part 3,
The tip end surface of the electrode is polished and first-outed to form a final shape as the discharge lamp electrode 1 such as a flash discharge lamp electrode.

Discharge lamp electrode 1 formed into a final shape
The electron-emissive substance of the electron-emissive substance part 2 formed in each bottomed hole is exposed at the tip end face of the, and the distance L between the tip faces 31 of each exposed electron-emissive substance is 100 μm.
It is formed below.

By constructing the discharge lamp electrode 1 in this way, the electron-emissive substance diffused from the tip surface 31 of the electron-emissive substance portion 3 on the tip surface 21 of the refractory metal 2 when the lamp is lit. The electrons are easily diffused to easily emit electrons, and good electron emission characteristics are obtained. The arc discharge is a base metal 2 made of a refractory metal.
Since the heat is generated on the tip surface 21, the heat generated is efficiently transmitted from the tip surface 21 through the base metal 2 along the energization direction, so that it is possible to prevent the heat generation of the discharge lamp electrode.

Although the electron-emissive substance and its content in the electron-emissive substance part 3 are determined by the type of the lamp and the input power, when it is used as an electrode for a flash discharge lamp, the electron-emissive substance is emitted. A so-called barium aluminate using barium oxide and aluminum oxide as a substance is filled in the bottomed hole, for example, 170
The one that is baked at 0 ° C. for about 20 minutes is used.

Here, the reason why the distance between the electron-emissive substance portions 3 exposed on the tip surface 31 is set to 100 μm or less with the tip surface 21 of the base metal 2 set is described with reference to FIG. .

FIG. 2 is a sectional view schematically enlarging and showing a part of the vicinity of the tip surface of the discharge lamp electrode according to the present embodiment.

In the figure, tungsten is used as the base metal 2.
The case where BaO is used as the electron-emissive substance in the electron-emissive substance part 3 is shown. The Ba atom supplied from the electron-emissive substance part 3 and diffused on the tip surface 21 of the base metal 2 contributes to the discharge, Tip surface 31 of electron emissive material part 3
It is shown that the Ba atoms remaining above do not easily contribute to the discharge.

Generally, the requirements for the cathode are that an electron-emissive substance that lowers the work function is present on the electrode surface, and that the electron-emissive substance is uniformly coated on the substrate metal surface. is there. In particular, the latter condition
The distance that the electron-emissive substance diffuses onto the surface of the base metal is involved, and if the distance that has to diffuse increases, the electron-emissive substance is consumed by evaporation during the diffusion.

More specifically, the electrode, especially the cathode, is made of a high melting point metal such as W, Ta, Mo having a melting point of 2000 ° C. or more, which is generally referred to as a base metal. It has a structure containing an electron emitting substance, a metal called Ba, Th, La, Cs or a compound thereof, which is called an emitter.

Here, as shown in the figure, when BaO is used as the electron-emissive substance, BaO exists in the base metal 2 in the BaO state even when the lamp is lit, and BaO as an oxide is high. The current is more difficult to flow than the melting point metal. On the other hand, on the electrode surface, BaO and Ba atoms and O
O atoms and Ba atoms are adsorbed on the base metal 1 in this order, but it is the Ba atom on the refractory metal, which is the base metal 2, that contributes to the discharge more than the Ba atom directly on BaO.
Is an atom. By supplying Ba atoms so as to be sufficiently coated on the refractory metal, arc discharge is stably performed, and stable starting and lighting can be performed.

Therefore, in order to efficiently coat the tip surface 21 of the base metal 2 made of a refractory metal with the electron-emissive material, the distance over which the electron-emissive material diffuses on the tip surface 21 of the base metal 2 is taken into consideration. However, it is important to control the distance appropriately.

The diffusion distance of the electron-emissive substance varies depending on conditions such as the type of electron-emissive substance and the operating temperature.
Generally, it is in the range of several tens of μm to hundreds of tens of μm. If the region between the electron-emitting substance and the refractory metal can be structurally controlled within such a range, the surface of the refractory metal can be efficiently coated with the electron-emitting substance.

In the invention of this embodiment, in order to uniformly diffuse and coat the tip surface 21 of the base metal 2 with the electron-emissive substance that contributes to discharge, the electron-emissive substance portion 3 for supplying the electron-emissive substance is provided. The distance between the surfaces is set to 100 μm or less.

As described above, according to the invention of this embodiment, since the conventional discharge lamp electrode is manufactured by the powder metallurgy technique, the positions of the electron-emissive substance and the base metal are accidentally determined. On the other hand, a plurality of the electron-emissive substance portions 3 are extended in the base metal 2 made of a solid refractory metal in a lump form substantially parallel to the energization direction as the discharge lamp electrode, and Since the tip surface 31 of the radioactive substance portion 3 is provided so as to be exposed in the discharge space, and the tip surfaces 31 of the plurality of electron-emissive material portions 3 are arranged on the tip surface 21 of the base metal 2 with a predetermined distance therebetween. Since the heat generated by the arc discharge on the tip surface of the electrode can be efficiently transmitted to the rear end portion of the base metal 2 through the base metal 2 without being hindered by the electron-emissive substance portion 3, Smooth heat Performed, the heat can be prevented evaporation of unwanted emit electrons material caused by heat is stored.

FIG. 3 (a) is a plan view showing the structure of the discharge lamp electrode according to the second embodiment of the invention as seen from the electrode tip surface, and FIG. 3 (b) is the same as FIG. 3 (a). It is the top view which expanded and showed the electrode structure 5 of 1.

In the figure, 4 is the base metal of the discharge lamp electrode 1 made of a high melting point metal having a substantially rod-like shape, 41 is the front end surface of the base metal 4, and 5 is the base metal 4 in the conduction direction. A plurality of first electrode structures, which are arranged substantially parallel to each other, are temporarily fixed, 6 is a second electrode structure to which a plurality of first electrode structures 5 are temporarily fixed, and 7 is a plurality of second electrode structures A third electrode structure 6 is temporarily fixed, and an electron-emissive substance 8 is inserted in a plurality of gaps formed between a plurality of base metal layers 4 so that the tip surface is exposed to the discharge space. The electron emissive material portion 81 is the tip surface of the electron emissive material portion 8.

The production of this discharge lamp electrode 1 is as follows.
As shown in FIGS. 3 (a) and 3 (b), a plurality of, for example, 7 base metals 4 made of a refractory metal in a lump form are combined, and the periphery thereof is temporarily fixed by a metal wire (not shown). To form the first electrode structure 5. Next, as shown in FIG. 3A, a plurality of these first electrode structures 5 are formed, for example, 7
The second electrode assembly 6 is formed by combining the bodies and temporarily fixing the periphery thereof with a metal wire (not shown), and further combining a plurality of these second electrode assemblies 6, for example, 7 bodies,
The third electrode structure 7 is formed by temporarily fixing the periphery thereof with a metal wire (not shown). Next, a voltage is applied to the temporarily fixed third electrode structure 7 to energize it for heating. When the base metal 4 made of a refractory metal forming the third electrode assembly 7 is energized, each base metal 4 is heated to about 2000 ° C. and a part of the contact surface between the base metals 4 is melted. Is fixed. As a result, a plurality of integrated base metal bodies 4 are obtained. Next, the integrated base metal 4 is cut into a predetermined length and shaped into a substantially columnar shape, and is further filled in a gap formed between the plurality of base metal 4 by an impregnation method or the like. A radioactive substance is inserted to form the electron-emissive substance portion 8. Here, as the base metal 4 of the substantially rod-shaped member made of the high melting point metal of the lump, φ70 made of pure tungsten is used.
Using a rod of μm, the final shape is 1.05m in outer diameter
A discharge lamp electrode 1 having a length of m and a length of about 10 mm was obtained.

Also in the invention of this embodiment, when the lamp is turned on, the electron-emissive substance is transferred from the tip end surface 81 of the electron-emissive substance portion 8 formed in the gap of the substrate metal 4 onto the base metal 4 made of a refractory metal. It is supplied so as to be sufficiently covered so that arc discharge can be stably performed. Further, the heat generated by the arc discharge is such that the base metal 4 made of a high melting point metal in the form of an agglomerate formed of a substantially rod-shaped member is formed continuously from the front end face 41 to the rear end portion. It is possible to quickly transfer the heat in 41 toward the rear end portion, and as a result, it is possible to prevent the electrode tip surfaces 41, 81 from overheating and prevent evaporation of the electron-emissive substance. .

FIG. 4 is a plan view showing the structure of the discharge lamp electrode according to the invention of the third embodiment as seen from the electrode tip surface.

In the figure, 9 is the base metal of the discharge lamp electrode 1 in which a plurality of massive refractory metals formed in the shape of rods having different wire diameters are arranged substantially parallel to the energization direction, and 91 is the base metal. The tip surfaces of 9 are a plurality of electron-emissive material portions, in which the electron-emissive substance is inserted into a plurality of gaps formed between the base metal 9, and the tip surfaces are exposed to the discharge space. It is the front end surface of the radioactive substance portion 10.
Note that the other configurations correspond to the configurations of the same reference numerals shown in FIG.

The discharge lamp electrode of the present embodiment is used for the discharge lamp of the second embodiment in that a plurality of substantially rod-shaped lumps of refractory metals having different wire diameters are used as the base metal 9 in combination. Different from the electrode.

The production of this discharge lamp electrode 1 is as follows.
As shown in FIG. 4, a plurality of base metal 9 having a large wire diameter is arranged, and further, a plurality of base metal 9 having a small wire diameter is provided in a gap formed between the plurality of base metal 9 having a large wire diameter. Is inserted, and the entire base metal 9 is temporarily fixed by a metal wire (not shown). Next, a voltage is applied to the temporarily fixed bundle of the base metal 9 to heat the bundle. The base metal 9 made of high melting point metal having different wire diameters is heated to about 2000 ° C.
Part of the contact surface of the base metal 9 is melted and fixed by being heated to, whereby a plurality of base metals 9 having different wire diameters are formed.
Are integrated. Next, the integrated base metal 9 is cut into a predetermined length and shaped into a substantially columnar shape, and is further easily filled in a gap formed between the substantially bar-shaped base metal 9 by an impregnation method or the like. An electron-emissive substance is inserted to form the electron-emissive substance portion 10.

Here, as the base metal 9 made of a solid refractory metal, φ20 μm made of pure tungsten is used.
A rod having a diameter of 100 μm was used.

Also in the invention of this embodiment, when the lamp is turned on, the electron-emissive substance is formed on the base metal 9 made of a refractory metal from the tip surface 101 of the electron-emissive substance part 10 formed in the gap of the base metal 9. Since it is supplied so as to be sufficiently covered, the arc discharge can be stably performed.
Further, the heat generated by the arc discharge is formed because the base metal 9 made of a high melting point metal in the form of an agglomerate formed of a substantially rod-shaped member is continuously formed from the front end surface 91 to the rear end thereof. It becomes possible to quickly transfer the heat at the front end surfaces 91 and 101 toward the rear end portion, and as a result,
Prevent the electrode tip surfaces 91, 101 from overheating,
It is possible to prevent evaporation of the electron-emissive substance.

In the invention of this embodiment, the base metal 9
Since it is possible to change the formation location and size of the gap formed in the above, it is possible to form the formation location and size of the electron-emissive material portion 10 in a desired state. Furthermore, the invention of this embodiment is excellent in workability because the shape deviation when temporarily fixing the substantially rod-shaped base metal 9 does not easily occur.

Although the discharge lamp electrode of each of the above-described embodiments is applied to the flash discharge lamp electrode, the high intensity discharge lamp (high intensity) is described.
It goes without saying that the present invention can be applied to the electrodes for discharge lamps of the "type discharge lamp".

The discharge lamp electrode shown in FIG. 5 is a high-intensity discharge lamp electrode 11 manufactured by the same method as the discharge lamp electrode 1 shown in FIG. Reference numeral 11 denotes a base metal 12 made of a refractory metal in a lump form, and a plurality of bottomed holes are provided from the tip surface 121 thereof by laser processing substantially parallel to the energization direction of the electrode 11, and the plurality of bottomed holes are formed in the bottomed holes. It is manufactured by providing the electron-emissive substance portion 13 whose tip 131 is exposed to the discharge space.

The discharge lamp electrode shown in FIG. 6 is a high-intensity discharge lamp electrode 11 manufactured by the same method as the discharge lamp electrode 1 shown in FIGS. Is a base metal 12 made of a high-melting-point metal in the form of a block, and provided with a bottomed cylindrical hole 122 from the tip surface thereof substantially parallel to the energization direction of the electrode 11.
3A, for example, a base metal 14 corresponding to a plurality of base metals 4 formed by integrating the third electrode structure 7 shown in FIG. It is manufactured by inserting an electron-emissive substance by a method such as an impregnation method into the gap formed between the metals 14 and providing the electron-emissive substance portion 13 whose tip 131 is exposed to the discharge space.

The present invention is not limited to the invention of each of the above-described embodiments. For example, in the first embodiment, the bottomed holes formed by laser processing are
In addition to the dot shape, it may be formed in a linear shape or a grid shape, and the substantially rod-shaped member made of the high melting point metal used in the second and third embodiments has a circular cross-sectional shape. The shape is not limited, and one formed in another shape such as a polygon may be used.

[0042]

According to the invention as set forth in claim 1, a base metal made of a high melting point metal in a lump form, and extending in the base metal substantially parallel to the direction of electricity flow of the base metal as an electrode, An electrode for a discharge lamp comprising a plurality of electron-emissive substance portions whose tip faces are exposed to the discharge space, wherein each tip face of the plurality of electron-emissive substance portions is a tip face of the base metal. Since they are arranged within a predetermined distance above, the heat generated by the arc discharge of the electrode tip surface can be efficiently transferred to the rear end portion of the base metal without being blocked by the electron-emissive substance portion through the base metal. Since the heat can be transferred, the heat is smoothly discharged from the electrodes, and unnecessary evaporation of the electron-emissive substance caused by the accumulated heat can be prevented.

According to the second aspect of the present invention, by setting the predetermined distance to 100 μm or less, the region between the electron-emissive substance and the refractory metal is structurally controlled within this range. Therefore, when the lamp is turned on, the surface of the refractory metal can be efficiently covered with the electron-emissive substance.

According to the third aspect of the present invention, the electron-emissive substance portion is formed in the plurality of bottomed holes formed in the base metal by laser processing. The part can be easily formed.

According to the invention of claim 4, the electron-emissive substance portion is formed in a plurality of gaps formed between the substantially rod-shaped members of the base metal made of a plurality of fixed substantially rod-shaped members. Therefore, the electron-emissive substance portion can be easily formed on the base metal without using laser processing.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a discharge lamp electrode according to a first embodiment of the invention.

FIG. 2 is a sectional view schematically enlarging and showing a part of a discharge lamp electrode near a tip surface.

FIG. 3 is a plan view showing the configuration of a discharge lamp electrode according to the second embodiment of the invention as seen from the electrode tip surface.

FIG. 4 is a plan view showing the structure of a discharge lamp electrode according to the invention of a third embodiment as seen from the electrode tip surface.

5 is a cross-sectional view showing a structure of a high-intensity discharge lamp electrode manufactured by the same method as the method for manufacturing the discharge lamp electrode shown in FIG.

FIG. 6 is a perspective view showing a structure of a high-intensity discharge lamp electrode manufactured by the same method as the discharge lamp electrode shown in FIGS. 3 to 4;

[Explanation of symbols]

1 Discharge lamp electrode 2 Base metal 21 Front end surface of base metal 2 3 Easy Electron Radioactive Material Department 31 Tip surface of the electron-emitting material part 3 4 Base metal 41 tip surface of base metal 4 5 First electrode structure 6 Second electrode structure 7 Third electrode structure 8 Easy Electron Radioactive Material Department 81 Tip surface of the electron-emissive material part 8 9 Base metal 91 tip surface of base metal 9 10 Easy Electron Radioactive Material Department 101 Tip surface of the electron-emitting material part 10 11 High-intensity discharge lamp electrodes 12 Base metal 121 tip surface of base metal 12 122 Bottomed cylindrical hole of base metal 12 13 Easy Electron Radioactive Material Department 131 Tip Surface of Electron Emissive Material Part 13 14 Base metal

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshitaka Sugioka             1194 Sado, Bessho Town, Himeji City, Hyogo Prefecture Usio             Electric Co., Ltd. F-term (reference) 5C015 AA03 AA05 BB02 CC04 CC15                       CC18

Claims (4)

[Claims] 1. A base metal made of a high melting point metal in the form of a lump, and extending in the base metal substantially parallel to the energization direction of the base metal as an electrode, the front end surface being exposed to the discharge space. And a plurality of electron-emissive substance portions, wherein the tip surfaces of the plurality of electron-emissive substance portions are arranged at predetermined distances on the tip face of the base metal. An electrode for a discharge lamp, which is characterized in that 2. The electrode for a discharge lamp according to claim 1, wherein the predetermined distance is 100 μm or less. 3. The electron-emissive substance portion is formed in a plurality of bottomed holes formed in the base metal by laser processing.
The electrode for a discharge lamp according to. 4. The electron-emissive substance portion is formed in a plurality of gaps formed between the substantially rod-shaped members of the base metal composed of a plurality of fixed substantially rod-shaped members. The electrode for a discharge lamp according to claim 1 or 2.