JP3092407B2 - Method of manufacturing electrode for lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device for general lighting,
The present invention relates to a method for manufacturing an electrode of a discharge lamp used as a light source device for a projector and a photoresist exposure device.

[0002]

2. Description of the Related Art Conventionally, tungsten containing about 1 to 10% by weight of thorium oxide has been used in order to improve the starting performance of a discharge lamp or to reduce the electrode drop consumed as heat at the electrodes and improve the luminous efficiency. Is used as an electrode. For example, an electrode made of a tungsten rod containing 1 to 3% by weight of thorium oxide is used for an electrode of a discharge lamp which is turned on by an AC power supply or a cathode which is turned on by a DC electrode, or 6 to 10% by weight. For example, an electrode is used in which a tungsten sintered tip containing% thorium oxide is pressed into the tip of a tungsten or molybdenum rod. In these conventional electrodes, in the former, it is difficult to increase the content of thorium oxide due to various processing operations such as drawing and swaging, and the production of tungsten containing 4% by weight at most is the limit. It is said. As a result, an electrode with a high content of thorium oxide is manufactured as the latter electrode. This electrode is manufactured by sintering a sintered chip by powder pressing and sintering the chip. The contact between the two is poor, so the heat transfer is poor and the temperature of the sintered chip rises remarkably, so that the thorium oxide is scattered quickly, that is, the rate at which the electrode has a short life is reduced. high.

[0003] As a result, lighting failure or difficult lighting may occur during a short usage time of the lamp.
This is because thorium oxide does not exist at the tip of the electrode and the diffusion of thorium oxide at the tip deteriorates due to coarsening of tungsten single crystal due to high temperature at the tip, thereby reducing electron emission. ,
It is considered that the starting voltage increases and lighting failure occurs.

[0004]

SUMMARY OF THE INVENTION In order to solve this problem,
Although there is a method of increasing the absolute concentration of thorium oxide, there is a problem in the production of the electrode material as in the previous period, and it is difficult with the conventional electrode production method and its technology. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a new method of manufacturing an electrode for a discharge lamp that stably lights for a long time and does not increase a starting voltage. It is.

[0005]

The new method for manufacturing a lamp electrode according to the present invention is as follows. The first step of press-molding a mixed powder of tungsten powder and thorium oxide powder, or a mixed powder of tungsten powder, tantalum powder and thorium oxide powder, press-molding a high melting point metal powder so that a concave structure is formed at one end. The second step, the third step of inserting the molded body of the first step into the recess of the molded body of the second step and press-molding the two together, the fourth step of sintering the molded body of the third step, the fourth step A step of compressing the sintered body in the step in a state of being heated by arc discharge in a rare gas.

[0006]

[Function] It is possible to improve the adhesion between the tip portion of the electrode tip containing thorium oxide and the electrode base portion made of a high melting point metal, and it is possible to incorporate high-concentration thorium oxide into the chip in the previous period. Since the density of the part is sufficiently increased (for example, 17 g / cc), when the electrode obtained by this method is used for a discharge lamp, the lamp is stably operated even after a long use, and the starting voltage is also increased. Will not do. In particular, a lamp electrode containing up to 15% by weight of thorium oxide can be obtained, and it is difficult to single crystallize even if the tip of the electrode (arc discharge portion) becomes high temperature. it can.

[0007]

FIG. 1 is an explanatory view of a cathode of a xenon short arc lamp used in a movie theater. The lamp has a rated power consumption of 2 kW, a voltage of 30 V, and a current of 70 A, and has a service life of 1,500 hours at which the initial light amount can be maintained at 70%.
More than time is required. In the figure, 1
Is a molded part formed by the first step, and is generally called a “chip”. Reference numeral 2 denotes a molded body portion formed in the second step, which is generally called an “electrode substrate”. 3 is a hole for inserting the internal lead rod. Since the first step and the second step are steps for forming separate electrode portions, either of them may be called the first step.

Next, a process for obtaining the above-mentioned electrodes will be described with reference to FIGS. FIG. 2 shows a cylindrical tip made of tungsten powder containing 10% by weight of thorium oxide at a molding pressure of 2 ton / cm ² . Length l is 6 mm, diameter d is 2
mm. Incidentally, the amount of tungsten may be slightly replaced with tantalum. FIG. 3 shows a cylindrical electrode substrate formed by molding a tungsten powder so as to form a recess for receiving the chip. The length 1 is 18 mm and the diameter D is 7 mm. Because of the post-process of pressing these two together, L
And l, and D and d, from various experimental results, d is
A range smaller than one-half of D and larger than one-tenth is preferable, and a range of 1 is smaller than one-third of L and larger than one-fifteenth. The relation between the diameter d 'of the concave portion and d is preferably d + 0.5>d'> d + 0.3 in mm units.
FIG. 4 shows a columnar member formed by assembling a chip and an electrode substrate and pressing them at a molding pressure of 5 ton / cm ² . The molding pressure in the third step is larger than the molding pressure in the first or second step, and is a "main press" -type molding. The molding in the first or second step is a "temporary press" -type step. It is. It is a "temporary press" that only needs to have the strength to withstand transport and handling. The “main press” is required to obtain a material having a strength enough to withstand sintering and machining at a later stage. The average density of the columnar member thus obtained is about 12.5 g / cc, but when this is sintered at 2400 ° C. for 1 hour, it shrinks and rises to about 16.4 g / cc.

FIG. 5 is an explanatory diagram of the fifth step. In the drawing, reference numeral 100 denotes a columnar member that has undergone a fourth step, and is discharged by facing the electrode 101 for arc discharge in an argon atmosphere.
After the temperature is raised to about 00 ° C., the portion where the chip is located is pressed from the periphery by the pressing punch 102. This pressurization can increase the density of a tungsten chip containing 10% by weight of thorium oxide to a density of 17 grams / cc. FIG. 6 shows the columnar member that has passed through the fifth step.
It is explanatory drawing of the cathode machined into the electrode shape for lamps.

[0010]

According to the electrode manufacturing method of the present invention, a high-density electrode can be obtained while the tip of the electrode is a high-concentration thorium oxide-containing chip, so that a lamp having good starting characteristics and a long life can be obtained. Can be In particular, conventionally, a 15% by weight tungsten chip containing thorium oxide and a density of 17.0 g / cc could not be obtained, but the present invention has made it possible. Therefore, the single crystal coarsening of the chip is reduced, and the diffusion of thorium to the tip of the chip becomes stable over a long period of time.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a cathode of a xenon short arc lamp.

FIG. 2 is an explanatory diagram of a first step in the present invention.

FIG. 3 is an explanatory view of a second step in the present invention.

FIG. 4 is an explanatory view of a third step and a fourth step in the present invention.

FIG. 5 is an explanatory view of a fifth step in the present invention.

FIG. 6 is an explanatory view of machining of a cathode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chip 2 Metal substrate 3 Hole for internal lead rod

Claims (2)

(57) [Claims] 1. A first step of press-molding a mixed powder of a tungsten powder and a thorium oxide powder or a mixed powder of a tungsten powder, a tantalum powder and a thorium oxide powder, wherein a concave structure is formed at one end of the high melting metal powder. The second step of press-molding, the third step of inserting the molded body of the first step into the recess of the molded body of the second step and press-molding the two together, and sintering the molded body of the third step Four steps,
And a fifth step of compressing the sintered body of the fourth step in a state of being heated by arc discharge in a rare gas. 2. The method according to claim 1, wherein the amount of thorium oxide in the first step is 1 to 3.
The method according to claim 1, wherein the amount is 15% by weight.