JP2016115644A - Short arc type discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a short arc type discharge lamp including an electrode having a structure where a heat transfer body can be sealed in an electrode by a relatively simple method and a manufacturing method by which the electrode can be manufactured easily, in a short arc type discharge lamp having a pair of electrodes at the inside of a light emitting tube and including a heat transfer body sealed in an enclosed space of at least one electrode and a manufacturing method of the short arc type discharge lamp.SOLUTION: An electrode 4 comprises a tubular container member 6 with a bottom and a lid member 7. An upper end face of a tubular side wall of the container member 6 and a lower end face of the lid member 7 are diffusively bonded together, an enclosed space 8 is formed by the container member 6 and the lid member 7 having been bonded, and a heat transfer body M is sealed in the enclosed space 8.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a short arc type discharge lamp, and more particularly to a short arc type discharge lamp having an electrode in which a heat transfer body is sealed in a sealed space of an electrode body.

  Conventionally, in a short arc type discharge lamp used as an ultraviolet irradiation light source of an exposure apparatus that exposes a semiconductor substrate, a liquid crystal substrate for a liquid crystal display, a printed circuit board, etc., the output of the short arc type discharge lamp is increasing, and the rated power consumption is large. Has come to be used.

As an electrode used for such a lamp having a large rated power consumption, an electrode has been developed which has a good heat transfer coefficient and suppresses temperature rise at the electrode tip to suppress melting and evaporation of the electrode tip. For example, as disclosed in Japanese Patent Application Laid-Open No. 2012-28168 (Patent Document 1), a short arc type discharge lamp having an electrode structure in which a molten heat transfer body is enclosed inside a main body has been proposed.
In this short arc type discharge lamp, an electrode in which a heat transfer coefficient higher than that of an electrode material and which melts when the lamp is lit is enclosed in a sealed internal space formed in the electrode body.

This prior art will be described below with reference to FIGS.
FIG. 5 shows a short arc discharge lamp 1 having a pair of electrodes 3, 4 arranged opposite to each other in the arc tube 2, and at least one of the electrodes (in this example, an anode) 4. As shown in FIG. 6, the electrode main body 41 includes a container member 42 and a lid member 43, and a sealed space 44 is formed therein.
The sealed space 44 encloses a heat transfer body M made of a material that has a higher thermal conductivity than the material constituting the electrode 4, such as tungsten, and melts when the lamp is turned on, such as gold or silver. .
The heat transfer body M melts when the lamp is turned on, convects in the sealed space 44, and transfers the heat at the front end of the electrode main body 41 to the rear end side, thereby generating a temperature gradient in the axial direction of the electrode main body 41. As a result, the temperature of the tip can be lowered, and this is expected to suppress the melting and evaporation of the tip of the electrode.

By the way, in this kind of electrode 4, in order to enclose the heat transfer body M such as silver in the sealed space 44 inside, the electrode body 41 is divided into the container member 42 and the lid member 43, and before these are joined. The heat transfer body M is enclosed in the sealed space 44.
After the heat transfer body M is sealed, the lid member 43 is fitted into the container member 42, and the welding protrusions 42a and 43a formed in advance are welded to seal the electrode internal space 44.
As shown in FIG. 6, the electrode includes protrusions 42 a and 43 a that protrude in the radial direction on the outer peripheral surfaces of the container member 42 and the lid member 43. One of the projections 42a and 43a is a flat surface, and when the upper end surface of the container member 42 and the lower end surface of the lid member 43 are brought into contact with each other, the projections 42a and 43a have a mountain shape so that the tips of the projections 42a and 43a are substantially aligned. The tip has a sharp shape.
The reason why the protrusions are formed in this way is that the portions of the protrusions 42a and 43a that are abutted have a small heat capacity, so that welding is easy.

  However, forming a welding projection for welding as an electrode sealing means complicates the manufacturing process and increases the cost and is economically disadvantageous. In particular, the protrusion on the container member side has a problem that its structure is complicated and cutting is quite difficult. Furthermore, the projection itself is fragile, and there is also a problem that the tip portion is lost even in a slight collision.

JP 2012-28168 A

  In view of the above-described problems of the prior art, the present invention provides a relatively simple method in a short arc type discharge lamp in which a heat transfer body is sealed in an electrode sealed space and a method of manufacturing the discharge lamp electrode. The present invention provides a short arc type discharge lamp having an electrode having a structure capable of enclosing a heat transfer body inside the electrode, and a manufacturing method capable of easily manufacturing the electrode.

In order to solve the above-described problems, in the present invention, the electrode includes a bottomed cylindrical container member and a lid member, and an upper end surface of the cylindrical side wall of the container member, a lower end surface of the lid member, Are sealed by diffusion, a sealed space is formed by the joined container member and the lid member, and a heat transfer body is sealed in the sealed space.
The container member and the lid member are made of tungsten, and the container member is cylindrical, and an inner radius r and an outer radius R of the cylindrical side wall of the container member are
r / R ≦ 0.80, provided that 14 (mm) ≦ R ≦ 25 (mm)
It is characterized by having the relationship.

  Further, in a method for manufacturing an electrode for a discharge lamp in which a heat transfer body is sealed in an internal sealed space of the electrode, a step of forming a planar joining surface on a bottomed cylindrical container material and a lid material; A step of inserting a heat transfer body inside, a joining surface of the container material, and a joining surface of the lid material are brought into contact with each other, and pressure is applied from a direction perpendicular to the joining surface, so that the container material and the lid material It is characterized by comprising: a step of diffusion bonding the two by heating and a step of cutting the diffusion-bonded container material and the lid material into an electrode shape.

According to the present invention, since the cylindrical container member constituting the electrode and the lid member are diffusion-bonded, the formation of the welding projection on the container member and the lid member required in the case of conventional welding joint This eliminates the need for such a complicated work and simply diffuses and joins the flat surfaces to improve work efficiency.
Further, since the container member and the lid member are cut and processed into an electrode shape after diffusion bonding, it is only necessary to process one integrated member, and the container member and the lid member are processed separately as in the past. The effort is greatly simplified.
Further, the concern that the welding projection is fragile and the tip portion is easily chipped is also eliminated.

Sectional drawing of the electrode for discharge lamps concerning this invention. The manufacturing process diagram. Shape explanation sectional drawing before and behind joining of an electrode. The experimental result which calculates | requires the optimal shape of a container member. Sectional drawing of the conventional short arc type discharge lamp. Sectional drawing which shows the conventional electrode structure.

FIG. 1 is a sectional view showing an electrode structure for a discharge lamp according to the present invention.
In FIG. 1, an electrode 4 has an electrode body 5 composed of a bottomed cylindrical container member 6 and a lid member 7 both made of a high melting point material such as tungsten, and a sealed space 8 is formed in the electrode body 5. Is formed. And in this sealed space 8, the heat transfer body M whose heat conductivity is higher than electrode materials, such as tungsten, is enclosed. The heat transfer body M is made of metal such as gold or silver, has a melting point lower than that of the electrode material, and melts in the sealed space 8 when the lamp is turned on. Preferably, the container member 6 has a cylindrical shape, and the lid member 7 has a disk shape.
The container member 6 and the lid member 7 constituting the electrode body 5 are joined by diffusion bonding at the upper end surface of the container member 6 and the lower end surface of the lid member 7.
An electrode core wire 9 is inserted and fixed on the top of the lid member 7.

A method for manufacturing this electrode will be described with reference to FIG.
As shown in FIG. 2A, the opening upper end surface 6a of the bottomed cylindrical container material 6x made of tungsten or the like is polished to form a joining surface, and the disk-like lid material 7x made of tungsten or the like is similarly used. The lower end surface 7a is polished to form a joint surface. By polishing the bonding surface, a strong bonding strength can be obtained.
The container material 6x is formed with a cylindrical gap 8 opened at the upper end, and forms a sealed space when the container material 6x and the lid material 7x are joined.
Next, as shown in FIG. 2B, a heat transfer body M such as solid silver is inserted into the gap 8 of the container material 6.

Next, as shown in FIG. 2 (C), the lid material 7x is overlapped on the opening upper end surface of the container material 6x, and the container material 6x is closed. Then, the upper and lower sides of the container material 6x and the lid material 7x are sandwiched between the pressure electrodes 12 and 12 with the carbon blocks 11 and 11 interposed therebetween. This is energized and heated in a vacuum atmosphere with a predetermined pressure applied by the upper and lower pressure electrodes 12, 12. The pressure in this diffusion bonding treatment is, for example, 20 to 50 MPa, the heating temperature is 1400 to 2200 ° C., and the treatment time is 1 to 20 minutes.
Thereby, the upper end surface of the container material 6x and the lower end surface of the lid material 7x are diffusion-bonded.

Next, as shown in FIG. 2D, the diffusion-bonded container material 6x and lid material 7x are each cut along a predetermined cutting line S to obtain a final electrode shape. Thereby, the electrode main body 5 in which the heat transfer body M is enclosed in the internal sealed space 8 as shown in FIG. 1 is formed.
The advantage of electrodes formed by diffusion bonding is that, in the case of conventional welding bonding, bonding can be performed only in a shallow range from the outer peripheral surface of the electrode body in the radial direction, whereas in diffusion bonding, flat bonding is performed. Since bonding can be performed over the entire radial direction of the surface, the bonding area is increased and the bonding strength is improved.
Further, since it is not necessary to form a pointed tip shape as in the case of welding joint, there is no inconvenience that the tip portion is lost due to impact or collision.

Further preferred embodiments of the present invention are described below.
In the diffusion bonding step shown in FIG. 2 (C) described above, the container member 6x is loaded with pressure from above and below, and depending on the size and shape, undesirable deformation may occur in the shape of the container material 6 after diffusion bonding. There is.
This will be described with reference to FIG.
Since diffusion bonding is heated while applying pressure, some deformation may occur before and after bonding. In this figure, the outlines of the container material 6x and the lid material 7x before diffusion bonding are indicated by solid lines, and the outlines after diffusion bonding are indicated by broken lines.
That is, it was found that after joining, the amount was slightly reduced (smaller) in the axial direction and slightly thicker (larger) in the radial direction. In particular, it was found that the amount of deformation in the radial direction was larger than that in the axial direction.
Such deformation can be tolerated to some extent, but exceeding a certain amount affects the reliability of the strength of the electrode. That is, the deformation amount directly represents strain, and undesired stress is generated on the container side wall.
Therefore, the present inventors examined the shape of the container material 6x that can reduce strain.

As shown in FIG. 3, for the container material 6x and the lid material 7x, the test container in which the inner radius r is changed, that is, the wall thickness is changed, with the joining condition and the outer radius R of the cylindrical side wall of the container material 6x being constant. A plurality of materials 6x and a lid material 7x were prepared, subjected to diffusion bonding treatment, and each deformation amount ΔR was measured.
Here, the amount of deformation is defined as the amount of deformation ΔR, which is the amount by which the outer surface of the cylindrical container sidewall of the container material 6x protrudes in the radial direction. However, it experimented in the range of 14 (mm) <= R <= 25 (mm). If the outer radius R is within this range, the joining conditions are basically constant.
FIG. 4 is an experimental result table and graph showing the relationship between r / R and strain ΔR / R. In this experiment, since the outer radius R is constant, the strain ΔR / R and the deformation amount ΔR mean the same thing.

As the deformation amount ΔR, that is, the strain ΔR / R increases, the stress applied to the container also increases. In particular, when the yield stress is greater than that of tungsten, which is a container material, further plastic deformation occurs.
Therefore, the deformation amount ΔR must be kept as small as possible.
The stress that can be tolerated by tungsten has a certain upper limit, and the preferable upper limit of the deformation amount ΔR within a range not exceeding this upper limit is 0.19 mm, and the strain ΔR / R at that time is 0.011. From the experimental results described later, it can be seen that the strain increases exponentially when it exceeds 0.011.
According to this experimental result, when r / R exceeds 0.80, the deformation amount ΔR exceeds 0.19 (mm), and the strain ΔR / R exceeds 0.011.
Therefore, it can be said that r / R is preferably 0.80 or less. However, since this experiment is performed under the condition that R is 14 to 25 mm, preferable r / R is
0 <r / R ≦ 0.80, provided that 14 (mm) ≦ R ≦ 25 (mm)
It is.
Furthermore, from this experimental result, in the range of 0.51 ≦ r / R ≦ 0.74, the strain ΔR / R is stable at a low value of 0.0103 to 0.0105, which can be said to be a more preferable range.

As described above, according to the present invention, in a short arc type discharge lamp having an electrode in which a heat transfer body is sealed in a sealed space of an electrode body, the electrode is composed of a bottomed cylindrical container member and a lid member. In addition, since the upper end surface of the cylindrical side wall of the container member and the lower end surface of the lid member are diffusion-bonded, it is possible to obtain a larger bonding strength than that obtained by the conventional welding operation and to provide a projection for welding. There is no need for formation, and resistance to impact is improved.
In addition, since the cutting work for the electrode structure can be performed after the container member and the lid member are joined, the work is simplified.

DESCRIPTION OF SYMBOLS 1 Short arc type discharge lamp 2 Arc tube 3, 4 Electrode 5 Electrode main body 6 Container member 6x Container material 6a Upper end surface (joint surface)
7 Lid member 7x Lid material 7a Lower end surface (joint surface)
8 Sealed space 9 Electrode core wire 11 Carbon block 12 Pressurized electrode M Heat transfer body

Claims (3)

In a short arc type discharge lamp having a pair of electrodes inside the arc tube, and a heat transfer body sealed in a sealed space of at least one of the electrodes,
The electrode is composed of a bottomed cylindrical container member and a lid member,
A short arc type discharge lamp, wherein an upper end surface of a cylindrical side wall of the container member and a lower end surface of the lid member are diffusion bonded. The container member and the lid member are made of tungsten, and the container member is cylindrical, and an inner radius r and an outer radius R of the cylindrical side wall of the container member are
r / R ≦ 0.80, provided that 14 (mm) ≦ R ≦ 25 (mm)
The short arc type discharge lamp according to claim 1, wherein: In the manufacturing method of the electrode for the discharge lamp in which the heat transfer body is enclosed in the internal sealed space of the electrode,
Forming a flat joint surface on the bottomed cylindrical container material and the lid material;
Inserting a heat transfer body into the container material;
The container material joint surface and the lid material joint surface are brought into contact with each other, pressure is applied in a direction perpendicular to the joint surface, and the container material and the lid material are heated, whereby both are diffusion-bonded. Process,
Cutting the diffusion-bonded container material and the lid material into an electrode shape; and
A method for producing an electrode for a discharge lamp, comprising:

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