JP2012178329A - Negative electrode for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode for a discharge lamp which can apply long use lifetime to the discharge lamp even when a negative electrode using a rare-earth compound or barium compound as an emitter substance material is used in a high-load short arc type discharge lamp.SOLUTION: The negative electrode for the discharge lamp is a negative electrode included in the discharge lamp and the negative electrode includes a negative electrode body composed of a high melting metal and an emitter substance supply source. A storage chamber for storing the emitter substance supply source and an emitter substance supply path formed by a hole extended from the storage chamber to the tip part of the negative electrode are formed in the negative electrode body, and an emitter substance supply suppression member is arranged in the emitter substance supply path.

Description

  The present invention relates to a discharge lamp cathode provided in a discharge lamp.

In general, an emitter material for facilitating electron emission is used for a cathode of a short arc type discharge lamp having a high load of 500 W or more as input power (see, for example, Patent Document 1).
However, thorium used as an emitter material, for example, is a radioactive material, so that sufficient consideration is required for management and handling.

Therefore, a cathode for a short arc type discharge lamp is known that uses rare earth elements or barium as the emitter material instead of thorium (see, for example, Patent Documents 2 and 3).
However, when a cathode in which a rare earth compound or barium compound is used as an emitter material is used in a high-load discharge lamp having a high heat load on the cathode, some of the rare earth compounds have vapor at the same temperature as thorium oxide. Some barium oxides produced by the reaction of barium compounds with refractory metals such as tungsten have a higher vapor pressure at the same temperature than thorium oxide. Due to the early evaporation of the system compound, the emitter material is depleted at an early stage. As a result, there is a problem in that the discharge lamp cannot have a long service life. Further, the early evaporation of the rare earth compound or barium compound promotes the progress of blackening of the arc tube, and as a result, there is a problem that a long service life cannot be obtained in the discharge lamp.

Japanese Patent Application Laid-Open No. 11-96965 Japanese Utility Model Publication No. 63-9762 JP-A-11-154488

  The present invention has been made based on the above circumstances, and even when a cathode using a rare earth compound or barium compound as an emitter material is used in a high-load short arc type discharge lamp. An object of the present invention is to provide a cathode for a discharge lamp that can provide a long service life for the discharge lamp.

The cathode for a discharge lamp of the present invention is a cathode provided in a discharge lamp,
The cathode comprises a cathode body made of a refractory metal and an emitter material supply source,
Inside the cathode body, there are formed a storage chamber for storing the emitter material supply source, and an emitter material supply path formed by a hole extending from the storage chamber toward the tip of the cathode,
The emitter material supply path is provided with an emitter material supply suppressing member.

  In the cathode for a discharge lamp of the present invention, the emitter substance supply suppressing member may be composed of a porous sintered body of a refractory metal powder.

  In the cathode for a discharge lamp of the present invention, the emitter substance supply suppressing member may be composed of a porous body made of a plurality of wires made of a refractory metal.

  In the cathode for a discharge lamp of the present invention, the emitter substance supply source preferably contains at least one emitter substance material selected from a rare earth compound and a barium compound.

In the cathode for a discharge lamp of the present invention, the emitter material supply source is lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, gadolinium oxide, barium-calcium-aluminate (Ba-Ca-Al-O). Preferably, it contains at least one emitter material selected from barium tungstate (Ba ₃ WO ₆ ) and barium-strontium-calcium-tungstate (Ba—Sr—Ca—W—O).

  In the cathode for a discharge lamp of the present invention, it is preferable that the emitter substance supply source contains an emitter substance material whose vapor pressure at a predetermined temperature is higher than that of thorium oxide.

  According to the cathode for a discharge lamp of the present invention (hereinafter also simply referred to as “cathode”), the supply of the emitter material is suppressed in the emitter material supply path extending from the storage chamber provided inside the cathode body to the tip of the cathode. By providing the member, the supply amount of the emitter material is limited, and the emitter material is gradually supplied to the tip of the cathode, so that the early decrease or depletion of the emitter material is suppressed, and light emission Early progression of tube blackening is suppressed, resulting in a long service life for the discharge lamp. Therefore, according to the cathode of the present invention, even when a cathode using a rare earth compound or barium compound as the emitter material is used for a high-load short arc type discharge lamp, the discharge lamp has a long service life. can get.

It is sectional drawing for description which shows the structure in an example of the discharge lamp provided with the cathode of this invention. It is sectional drawing for description which shows the structure in an example of the cathode of this invention. It is sectional drawing for description which shows the structure in the other example of the cathode of this invention. It is sectional drawing for description which shows the structure in the further another example of the cathode of this invention. It is sectional drawing for description which shows the structure in the further another example of the cathode of this invention. It is sectional drawing for description which shows the structure in the further another example of the cathode of this invention.

  Hereinafter, the present invention will be described in detail.

  The cathode of the present invention can be provided in a high-load short arc type discharge lamp having an input power of, for example, 500 W or more.

FIG. 1 is an explanatory cross-sectional view showing the configuration of an example of a discharge lamp provided with the cathode of the present invention, and FIG. 2 is an explanatory cross-sectional view showing the configuration of an example of the cathode of the present invention.
The discharge lamp 10 is a high-load short arc type xenon lamp, and includes an arc tube 11 made of, for example, quartz glass.

The arc tube 11 includes an elliptical spherical light emitting portion 12 and tubular sealing portions 13 at both ends of the light emitting portion 12. In the light emitting portion 12 of the arc tube 11, a cathode 14 and an anode 15 are disposed so as to face each other while being separated from each other. Each of the cathode 14 and the anode 15 is supported by lead rods 17 and 18 made of, for example, tungsten. These lead rods 17 and 18 extend along the tube axis direction from the inside of the light emitting portion 12, pass through the inside of the sealing portion 13 in an airtight manner, and protrude outward from the outer end portion of the sealing portion 13. Has been placed. The lead rods 17 and 18 are penetrated and held by a holding cylinder 16 made of, for example, quartz glass, which is fixedly disposed in the sealing portion 13, and the outer end portion of the sealing portion 13. It is sealed to the sealing portion 13 by the stepped portion 13a formed in the above.
A xenon gas is sealed in the light emitting portion 12 of the arc tube 11 at a sealing pressure of 0.66 MPa, for example.

An example of the configuration of the discharge lamp 10 is as follows. The maximum outer diameter of the arc tube 11 (the maximum outer diameter of the light emitting portion 12) is 55.0 mm, the thickness of the arc tube 11 is 3.0 mm, the cathode 14 and the anode 15 Is a separation distance of 6.0 mm, and the inner volume of the light emitting part 12 is 47 cm ³ .
The discharge lamp 10 is horizontally lit at a rated current of 80 A and a rated voltage of 25 V, the distance between electrodes during steady lighting is 5.3 mm, the tube wall load is 18.2 W / cm ² , and the xenon pressure is 2.6 MPa. To reach.

  The anode 15 includes an anode body 15A made of tungsten, for example. The anode body 15A has a truncated cone-shaped tapered portion 151 having a flat tip at the tip and a smaller diameter toward the tip. It is comprised by the cylindrical trunk | drum 152 formed integrally continuously.

  An example of the configuration of the anode 15 is as follows. The total length is 27 mm, the length of the body 152 is 18.5 mm, the diameter of the body 152 is 15 mm, the length of the taper 151 is 5 mm, The diameter of the flat surface is 5 mm, and the inclination angle of the outer surface with respect to the central axis in the tapered portion 151 is 45 °.

The cathode 14 includes a cathode body 14A made of a refractory metal, and an emitter material supply source E inside the cathode body 14A.
As shown in FIG. 2, the cathode body 14 </ b> A has a tip P that is a flat surface, and a truncated cone-shaped tapered portion 141 that decreases in diameter toward the tip P, and is formed integrally with the tapered portion 141. It is comprised by the column-shaped trunk | drum 142 made.
Examples of the refractory metal constituting the cathode body 14A include tungsten and molybdenum.
Reference numeral 143 denotes a recess formed for convenience when the cathode 14 is manufactured.

  Inside the cathode main body 14A, for example, a cylindrical emitter substance supply source E is stored, for example, a storage chamber 20 forming a cylindrical space, and an emitter formed by a hole extending from the storage chamber 20 toward the tip P. A substance supply path 21 is formed along the central axis X of the cathode body 14A.

The storage chamber 20 stores an emitter substance supply source E containing an emitter substance material made of a rare earth compound, specifically, lanthanum oxide (La ₂ O ₃ ).
In the emitter substance supply source E, when discharge of the discharge lamp 10 is started, the temperature of the emitter substance supply source E rises due to the temperature rise of the cathode main body 14A, and the oxidation contained in the emitter substance supply source E. By reducing lanthanum (La ₂ O ₃ ), a metal atom (La) as an emitter material is extracted. This emitter material (La) acts as an emitter by being radiated and diffused to the tip of the cathode 14.

The emitter material supply source is not particularly limited as long as it can supply an emitter material (metal atom) acting as an emitter.
Examples of the emitter material contained in the emitter material supply source include rare earth compounds such as lanthanum oxide (La ₂ O ₃ ) and lanthanum hexaboride (LaB ₆ ), barium-calcium-aluminate (Ba-Ca-). And barium-based compounds such as Al-O).

In the present invention, the emitter substance supply source preferably contains at least one emitter substance material selected from rare earth compounds and barium compounds.
Examples of rare earth compounds include oxides or borides of rare earth elements made of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), or gadolinium (Gd). Specifically, lanthanum oxide (La ₂ O ₃ ), cerium oxide (CeO ₂ ), praseodymium oxide (Pr ₆ O ₁₁ ), neodymium oxide (Nd ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ), gadolinium oxide ( Rare earth oxides of Gd ₂ O ₃ ); lanthanum boride (LaB ₆ ), cerium boride (CeB ₆ ), praseodymium boride (PrB ₆ ), neodymium boride (NdB ₆ ), samarium boride (SmB ₆ ), An example is a rare earth boride of gadolinium boride (GdB ₆ ).
Examples of barium-based compounds include barium-calcium-aluminate (Ba-Ca-Al-O), barium-tungstate (Ba ₃ WO ₆ ), and barium-strontium-calcium-tungstate (Ba-Sr-Ca-W). -O) and the like.

In particular, the emitter material supply source is lanthanum oxide (La ₂ O ₃ ), cerium oxide (CeO ₂ ), praseodymium oxide (Pr ₆ O ₁₁ ), neodymium oxide (Nd ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ). , Rare earth oxides of gadolinium oxide (Gd ₂ O ₃ ), barium-calcium-aluminate (Ba—Ca—Al—O), barium tungstate (Ba ₃ WO ₆ ) and barium-strontium-calcium-tungstate (Ba) It is preferable to contain at least one emitter material selected from —Sr—Ca—W—O).

In the present invention, the emitter substance supply source preferably contains an emitter substance material whose vapor pressure at a predetermined temperature is higher than that of thorium oxide (ThO ₂ ).
Specifically, for example, since the vapor pressure of thorium oxide (ThO ₂ ) at 3000 K is 9.4 × 10 [Pa], the emitter material supply source has a vapor pressure of 9.4 × 10 [Pa] at 3000 K. It is preferable to contain the above emitter substance materials.
Emitter materials whose vapor pressure at 3000 K is 9.4 × 10 [Pa] or higher include lanthanum oxide (1.7 × 10 ³ [Pa]), cerium oxide (5.7 × 10 ⁴ [Pa]), oxidation Praseodymium (1.5 × 10 ³ [Pa]), neodymium oxide (1.3 × 10 ³ [Pa]), samarium oxide (5.0 × 10 ² [Pa]), gadolinium oxide (2.1 × 10 ²⁾ [Pa]) and barium oxide (3.4 × 10 ⁴ [Pa]). The value shown in parentheses is the vapor pressure at 3000K.
Barium oxide produced by the reaction of these rare earth oxides and barium compounds with a refractory metal such as tungsten has a higher vapor pressure than thorium oxide (ThO ₂ ). Even when the cathode 14 using such an emitter substance material is used in the discharge lamp 10 of a high load short arc type, the emitter substance supply restraining member 22 described later is provided, so that the emitter substance can be made early. It is particularly effective because it is not reduced or prematurely depleted.

In the present invention, the above-mentioned lanthanum boride (LaB ₆ ), cerium boride (CeB ₆ ), praseodymium boride (PrB ₆ ), neodymium boride (NdB ₆ ), samarium boride are used as the emitter substance supply source. In the case of including an emitter material made of a rare earth boride of (SmB ₆ ) and gadolinium boride (GdB ₆ ), a storage for storing the emitter material supply source E because these rare earth borides have a low melting point. The chamber 20 is preferably formed in the cathode main body 14A at a position below the melting point of the rare earth boride.

The emitter substance supply source is more preferably a sintered body in which the emitter substance material is supported by porous tungsten.
Such an emitter material supply source can be manufactured, for example, as follows.
Powdered emitter substance material and powdered tungsten having an average particle diameter of 3 to 5 μm are mixed at a mass ratio (emitter substance material / tungsten) of 2/10, and 2 masses of stearic acid is added to this mixture. %, And heated to 100 to 200 ° C. to form a coating film made of stearic acid on the particle surface of the mixture. Next, the mixture on which the coating film is formed is pressed under pressure to form a pressed body made of a mixture of the emitter material and tungsten. And it pre-bakes at 1000-1200 degreeC in a hydrogen atmosphere, and it obtains by performing main baking at 1400-1600 degreeC in a vacuum or a reducing atmosphere.
The mixing mass ratio (emitter material / tungsten) of the powdered emitter substance material and the powdered tungsten is preferably 1/10 to 3/10.
In such an emitter substance supply source E, when the cathode 14 is manufactured, the press body is disposed in the storage chamber 20 in the preliminary firing stage, and the lead bar 17 is inserted into the recess 143 in the cathode body 14A. And may be obtained by performing high-temperature heat treatment.

A hole forming the emitter material supply path 21 is formed by a first hole 21a that is continuous with the storage chamber 20 and forms a cylindrical space having the same inner diameter as the storage chamber 20, and an inner diameter of the first hole 21a. A second hole 21b forming a cylindrical space having a small inner diameter is continuously formed along the central axis X of the cathode body 14A.
For example, a columnar emitter substance supply suppressing member 22 is disposed in the first hole 21 a forming the emitter substance supply path 21. In addition, an opening 23 for supplying the emitter material to the tip P is provided at one end of the second hole 21 b forming the emitter material supply path 21.

  In the cathode main body 14A in this example, the first hole 21a, the second hole 21b, the storage chamber 20, and the recess 143 are formed in communication.

The shape of the hole forming the emitter material supply path 21 is not particularly limited as long as the emitter material is supplied to the tip of the cathode 14, and the configuration of the cathode body 14A and the emitter material are not limited. Depending on the configuration of the supply suppressing member 22, it can be changed as appropriate.
Specifically, the length L of the first hole 21a is, for example, 2 to 20 mm, the inner diameter D of the first hole 21a is, for example, 1 to 5 mm, and the length l of the second hole 21b is, for example, 1 to 1. The inner diameter d of the second hole 21b (opening 23) is 10 mm, for example, 0.1 to 1.0 mm.

The emitter material supply suppressing member 22 provided in the emitter material supply path 21 has a function of limiting the supply amount of the emitter material and gradually supplying the emitter material to the tip of the cathode 14.
The emitter material supply suppressing member 22 is configured such that an emitter material acting as an emitter is supplied from the emitter material supply source E stored in the storage chamber 20 to the tip of the cathode 14 via the emitter material supply suppressing member 22. As long as the material supply path 21 is provided, the shape, size, arrangement position, and the like are not particularly limited, and can be changed as appropriate.

The emitter material supply suppressing member 22 in this example is configured by a porous sintered body of a refractory metal powder. Since the emitter material supply suppressing member 22 is a porous sintered body of a refractory metal powder, a supply path of the emitter material is secured while a movement path of the emitter material is secured by the voids of the porous sintered body. And the emitter material is gradually supplied to the tip of the cathode 14, so that the early decrease or depletion of the emitter material is suppressed.
Examples of the refractory metal powder include tungsten and tantalum, and the average particle size is preferably 2 to 5 μm. The porosity of the porous sintered body is preferably 20 to 50%, more preferably 30 to 40%.

  An example of the configuration of the cathode 14 is as follows. The overall length is 15.5 mm, the length of the barrel 142 in the axial direction is 10 mm, the diameter of the barrel 142 is 8 mm, and the length of the taper 141 in the axial direction is 5.5 mm. The diameter of the flat surface of the tip P is 0.6 mm, the inclination angle of the outer surface with respect to the central axis X in the taper portion 141 is 40 °, the length L of the first hole 21a in the emitter material supply path 21 is 5 mm, The inner diameter D of the hole 21a is 3 mm, the length l of the second hole 21b is 5 mm, and the inner diameter d of the second hole 21b (opening 23) is 0.2 mm.

  In such a discharge lamp 10, when discharge is started, in the cathode 14, an emitter material (La) acting as an emitter from the emitter material supply source E stored in the storage chamber 20 is generated in the emitter material supply path 21. While the movement path is secured by the gap of the emitter substance supply suppressing member 22 disposed in the first hole 21a, the supply amount is limited, and the cathode main body is opened from the opening 23 via the second hole 21b. It is gradually supplied to the tip P of 14A. Then, the emitter substance (La) acts as an emitter by radiating and diffusing to the tip P of the cathode body 14A and its peripheral part.

  According to the cathode 14 as described above, the emitter material supply suppressing member 22 is provided in the emitter material supply path 21 extending from the storage chamber 20 provided in the cathode body 14A toward the tip P of the cathode body 14A. As a result, the supply amount of the emitter material is limited, and the emitter material is gradually supplied to the tip of the cathode 14, so that the early decrease or depletion of the emitter material is suppressed, and the arc tube 11 Early progression of blackening is suppressed, resulting in a long service life for the discharge lamp.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be added.

  For example, the emitter material supply suppressing member 22 may have any function as long as it has a function of limiting the supply amount of the emitter material and gradually supplying the emitter material to the tip portion of the cathode 14. It can be set as the porous body which consists of a several wire which consists of. In the case where the emitter substance supply suppressing member 22 is a porous body made of a plurality of wires made of a refractory metal, as shown in FIG. 3, the wires are extended along the emitter substance supply path 21 in the extending direction of the wires. It can be set as the structure to arrange. With such a configuration, while the movement path of the emitter material is secured by the gap between the wire materials, the supply amount of the emitter material is limited, and the emitter material is gradually supplied to the tip of the cathode 14, Early reduction or early depletion of emitter material is suppressed.

  Further, for example, the emitter material supply path 21 formed by the holes may be provided so that the emitter material is supplied to the tip portion of the cathode 14, and as shown in FIG. A first hole 21a in which the emitter substance supply suppressing member 22 is arranged, a plurality of (in this example, two) second holes 21b, and a third hole 21c, are formed. Each may be provided so as to extend from the first hole 21a toward the tapered portion 141 of the cathode body 14A.

  Further, for example, the emitter material supply suppressing member 22 may be provided in the emitter material supply path 21 so that the emitter material is supplied to the tip of the cathode 14 through the emitter material supply suppressing member 22. As shown, the emitter substance supply suppressing member 22 may be provided so as to contain the storage chamber 20.

  Further, for example, the storage chamber 20 for storing the emitter material supply source E is provided so that the emitter material in the emitter material supply source E is supplied to the tip of the cathode 14 via the emitter material supply suppressing member 22. As shown in FIG. 6, the storage chamber 20 may be provided at a position deviated on the side surface side (lower side in FIG. 6) of the body portion 142 in the cathode body 14 </ b> A. Reference numeral 30 denotes a lid that closes the storage chamber 20, and 31 denotes a screw member that fixes the lid.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

[Example 1]
According to the structure shown in FIG. 2, a cathode [1] having the following specifications was produced.
Cathode body (14A): made of tungsten, axial length of the barrel portion (142): 5.5 mm, diameter of the barrel portion (142): 8 mm, axial length of the tapered portion (141): 10 mm, Diameter of flat surface of tip (P): 0.6 mm, inclination angle of outer surface with respect to central axis (X) at taper portion (141): 40 °
Emitter material supply source (E): sintered body of lanthanum oxide (La ₂ O ₃ ) and porous tungsten Emitter material supply path (21): length (L) of the first hole (21a): 2 mm, Inner diameter (D) of the first hole (21a): 2 mm, length (l) of the second hole (21b): 1.5 mm, inner diameter (d) of the second hole (21b): 0.2 mm
Emitter substance supply suppression member (22): Porous sintered body of tungsten powder (average particle size 5 μm, porosity 30%)
And the discharge lamp [1] of the following specification provided with this cathode [1] was produced.
Arc tube (11): made of quartz glass, maximum outer diameter of light emitting part (12): 55.0 mm, wall thickness of light emitting part (12): 3.0 mm, internal volume of light emitting part (12): 47 cm ³
-Anode body (15A): made of tungsten, length in the axial direction of the trunk portion (152): 18.5 mm, diameter of the trunk portion (152): 15 mm, length in the axial direction of the tapered portion (151): 5 mm, Diameter of flat surface at the tip: 5 mm, angle of inclination of the outer surface with respect to the central axis at the taper portion (151): 45 °
-Distance between the cathode (14) and the anode (15): 6.0 mm
Lead rod (17, 18): made of tungsten, total length: 120 mm, outer diameter: 4 mm
・ Rated current: 80A
・ Rated voltage: 25V
-Xenon sealing pressure: 0.66 MPa

[Comparative Example 1]
In Example 1, instead of providing an emitter material supply suppressing member and an emitter material supply path, lanthanum oxide (La ₂ O ₃ ) is formed on the discharge surface in a state doped with tungsten in the same form as that of triated tungsten. A discharge lamp [2] was produced in the same manner except that the exposed storage chamber was provided on the cathode.

[Comparative Example 2]
In Example 1, instead of providing the emitter material supply suppressing member and the emitter material supply path, lanthanum oxide (La ₂ O ₃ ) is stored in a state doped with tungsten in the same form as that of triated tungsten. The storage chamber (20) is disposed inside the cathode body (14A), and a hole (length: 1.5 mm, inner diameter: 0.2 mm) extending from the storage chamber toward the tip of the cathode is provided. A discharge lamp [3] was produced in the same manner.

  The discharge lamps [1] to [3] were lit at 2 kW for 2 hours and then turned off for 30 minutes. The lighting / extinguishing cycle was repeated, and the following evaluation was performed. The results are shown in Table 1.

[Evaluation 1: Arc tube blackening rate]
According to the following formula (1), the blackening rate η of the arc tube was calculated and evaluated according to the following evaluation criteria.
Formula (1): η (%) = (transmittance of arc tube central part at end of life) / (transmittance of arc tube central part at initial stage) × 100
-Evaluation criteria-
A: 90% or more B: 80% or more and less than 90% C: less than 80%

[Evaluation 2: Retraction distance of bright spot position]
The backward distance Δd of the bright spot position was calculated according to the following formula (2) and evaluated according to the following evaluation criteria.
Formula (2): Δd (mm) = (initial bright spot position) − (bright spot position at the end of life or when non-lighting occurs)
-Evaluation criteria-
A: 0 mm or more and less than 2 mm B: 2 mm or more and less than 4 mm C: 4 mm or more

DESCRIPTION OF SYMBOLS 10 Discharge lamp 11 Light-emitting tube 12 Light-emitting part 13 Sealing part 13a Step joint part 14 Cathode 14A Cathode main body 141 Tapered part 142 Body part 143 Recessed part 15 Anode 15A Anode body 151 Tapered part 152 Body part 16 Holding cylinders 17 and 18 Lead Rod 20 Storage chamber 21 Emitter material supply paths 21a, 21b, 21c Hole 22 Emitter material supply restraining member 23 Opening 30 Lid 31 Screw member E Emitter material supply source P Tip X Central axis of cathode body

Claims (6)

A cathode provided in a discharge lamp,
The cathode comprises a cathode body made of a refractory metal and an emitter material supply source,
Inside the cathode body, there are formed a storage chamber for storing the emitter material supply source, and an emitter material supply path formed by a hole extending from the storage chamber toward the tip of the cathode,
An emitter material supply path is provided with an emitter material supply suppressing member.   2. The cathode for a discharge lamp according to claim 1, wherein the emitter substance supply suppressing member is made of a porous sintered body of a refractory metal powder.   2. The cathode for a discharge lamp according to claim 1, wherein the emitter substance supply suppressing member is a porous body made of a plurality of wires made of a refractory metal.   The discharge lamp cathode according to any one of claims 1 to 3, wherein the emitter substance supply source contains at least one emitter substance material selected from a rare earth compound and a barium compound. The emitter material supply source is lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, gadolinium oxide, barium-calcium-aluminate (Ba-Ca-Al-O), barium tungstate (Ba ₃ WO ₆ ). And at least one emitter material selected from barium-strontium-calcium-tungstate (Ba-Sr-Ca-W-O). Cathode for discharge lamps.   4. The discharge lamp cathode according to claim 1, wherein the emitter substance supply source contains an emitter substance material having a vapor pressure higher than that of thorium oxide.