JP7176121B2 - Cathode parts for discharge lamps and discharge lamps - Google Patents

Description

Embodiments relate to cathode components for discharge lamps and discharge lamps.

Discharge lamps are broadly classified into two types: low-pressure discharge lamps and high-pressure discharge lamps. Low pressure discharge lamps include various arc discharge type discharge lamps such as general lighting, special lighting used for roads and tunnels, paint curing equipment, ultraviolet (UV) curing equipment, sterilization equipment, light cleaning equipment for semiconductors, etc. . High-pressure discharge lamps are used for water and sewage treatment equipment, general lighting, outdoor lighting for stadiums, etc., UV curing equipment, exposure equipment for semiconductors and printed circuit boards, wafer inspection equipment, high-pressure mercury lamps, metal halide lamps, ultra-high pressure lamps for projectors, etc. A mercury lamp, a xenon lamp, a sodium lamp, etc. are mentioned. Thus, discharge lamps are used in various devices such as lighting devices, image projection devices, and manufacturing devices.

One example of a discharge lamp cathode component (also referred to as a cathode component) controls the size of tungsten grains in lateral and circumferential cross-sections of the discharge lamp cathode component. As a durability test, a voltage is applied while the cathode component is energized and heated, and the emission current density (mA/mm ² ) after 10 hours and the emission current density (mA/mm ² ) after 100 hours are measured. do. The cathode component with the controlled grain size exhibits excellent properties in the durability test.

One example of the cathode component contains thorium oxide (ThO ₂ ) as emitter material. An example of the cathode component described above includes a cylindrical body and a pointed tip. An example of the cathode component is made of a tungsten alloy uniformly containing an emitter material. The emitter material at the tip of the example cathode component contributes to the emission characteristics, but the emitter material at the body may not contribute to the emission characteristics.

An emitter material that does not contribute to emission characteristics causes an increase in cost. Another example of the cathode component includes a dense tungsten sinter forging and a porous tungsten layer. Another example of the above cathode component can reduce the amount of emitter material used, reduce the weight, and save tungsten resources.

Other examples of the cathode component described above can be made lighter, but the life of the cathode component for a discharge lamp may be insufficient. The use of discharge lamps raises the temperature at the tip of the cathode component to around 2000°C. Therefore, the lifetime can be extended by improving the heat dissipation of the cathode component. Merely providing a porous tungsten layer is not necessarily sufficient to improve heat dissipation.

Japanese Patent No. 5800922 JP 2018-77945 A

A cathode component for a discharge lamp comprises a first portion containing tungsten and an emitter material and a second portion containing a metal different from the emitter material. When the average crystal grain size of the tungsten phase in the first portion is A μm and the average crystal grain size of the metal phase in the second portion is B μm, A and B are numbers that satisfy the formula: B>A. be.

FIG. 2 is a schematic diagram showing a lengthwise cross-section of an example cathode component for a discharge lamp having an integrated tip structure; 2 is a schematic diagram showing a cross section of the cathode component 1 shown in FIG. 1 in the direction of wire diameter D. FIG. 1 is an external view of a cathode component 1 having a fin structure; FIG. 1 is a schematic diagram showing a lengthwise cross-section of an example cathode component for a discharge lamp having a one-piece perimeter construction; FIG. 1 is a schematic diagram showing an example of a cathode component 1 having holes; FIG. FIG. 2 is a schematic diagram showing an example of a cathode component 1 having support rods integrally molded with a high-melting-point metal portion 3; It is a figure which shows the structural example of a discharge lamp.

Hereinafter, embodiments will be described with reference to the drawings. The relationship between the thickness and plane dimension of each component shown in the drawings, the ratio of the thickness of each component, and the like may differ from the actual product. In the embodiments, substantially the same components are denoted by the same reference numerals, and descriptions thereof are omitted as appropriate.

FIG. 1 is a schematic diagram showing a lengthwise cross-section of an example of a cathode component for a discharge lamp having an integrated tip structure. FIG. 1 shows a cathode component 1, a tungsten portion 2 (first portion), a refractory metal portion 3 (second portion), a central portion 4-1 in the radial direction of the cathode component, and a bonding interface 5. , the length T1 of the tungsten portion 2, the length T2 of the refractory metal portion 3, and the wire diameter D of the refractory metal portion 3 are shown. FIG. 2 is a schematic diagram showing a cross section of the cathode component 1 shown in FIG. 1 in the direction of the wire diameter D. As shown in FIG. Cathode component 1 comprises a tungsten portion 2 and a refractory metal portion 3 .

As shown in FIG. 1, the longitudinal section of the tungsten portion 2 has a tapered shape with a sharp tip. The taper angle is preferably 40 degrees or more and 120 degrees or less.

Tungsten portion 2 contains tungsten (W) and an emitter material. The tungsten portion 2 is made of, for example, a tungsten alloy containing an emitter material. The emitter material is a material having a work function of 4.0 eV or less, and has emission properties when a voltage is applied to the cathode component 1 .

The emitter material preferably contains at least one element selected from the group consisting of thorium (Th) and hafnium (Hf), for example. Thorium may be contained in the form of thorium oxide (ThO ₂ ), and the concentration of thorium can be calculated by ThO ₂ conversion. Hafnium may be contained in the form of hafnium carbide (HfC), and the concentration of hafnium can be calculated by HfC conversion.

The concentration of the emitter material of the tungsten portion 2 is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.5% by mass or more and 3% by mass or less. If the concentration of the emitter material is less than 0.1% by mass, the emission characteristics are degraded. When the concentration of the emitter material exceeds 5% by mass, the emission characteristics become saturated, which causes cost increase. More preferably, the concentration of thorium is 0.5% by mass or more and 3% by mass or less. Since thorium and hafnium have high emission properties, performance can be obtained at the above concentrations.

The high melting point metal portion 3 is provided below the tungsten portion 2 as shown in FIG. 1, for example. The refractory metal portion 3 contains a metal different from the emitter material. The high-melting-point metal part 3 contains, for example, a high-melting-point metal as a main component. The main component is an element contained in the largest amount among the constituent elements, and the main component element is contained in, for example, 50 atomic % or more of the whole. The high-melting-point metal portion 3 may contain no emitter material, or may contain an emitter material.

The melting point of the refractory metal is, for example, 2300° C. or higher. The temperature of cathode components for discharge lamps can rise to around 2000° C. during use. Therefore, it is preferable to use a high melting point metal.

Refractory metals include, for example, tungsten or molybdenum (Mo). The melting point of tungsten is 3422°C and the melting point of molybdenum is 2623°C. Due to their high melting points, tungsten and molybdenum are durable even at the operating temperatures of cathode components for discharge lamps. Therefore, the metal contained in high melting point metal portion 3 preferably contains at least one metal element selected from the group consisting of tungsten and molybdenum.

The refractory metal part 3 may contain at least one selected from the group consisting of, for example, a doped tungsten alloy, a lanthanum oxide-containing tungsten alloy, a tungsten molybdenum alloy, pure tungsten, and pure molybdenum. All of these materials have high melting points of 2300° C. or higher.

The doped tungsten alloy contains at least one dopant selected from, for example, the group consisting of potassium (K), silicon (Si), and aluminum (Al). The concentration of the dopant is, for example, 500 mass ppm or less. A dopant material does not correspond to an emitter material.

The lanthanum oxide-containing tungsten alloy is a tungsten alloy containing 1% by mass or more and 2% by mass or less of lanthanum oxide in terms of La ₂ O ₃ . The tungsten-molybdenum alloy contains molybdenum in an amount of 1% by mass or more and 50% by mass or less.

Pure tungsten contains 99.9% by mass or more of tungsten. Pure molybdenum contains 99.9% by weight or more of molybdenum.

FIG. 3 is an external view of a cathode component for a discharge lamp having a fin structure. FIG. 3 illustrates cathode component 1 , tungsten portion 2 , refractory metal portion 3 and fin structure 6 . For other descriptions of the tungsten portion 2 and the high-melting-point metal portion 3, the description of the tungsten portion 2 and the high-melting-point metal portion 3 shown in FIG. 1 can be used as appropriate.

The fin structure 6 is preferably provided on part or all of the outer peripheral surface of the high-melting-point metal portion 3 . The fin structure 6 has fins. The fin structure 6 is formed by providing at least one selected from the group consisting of protrusions and recesses on the outer peripheral surface of the high-melting-point metal portion 3, and the surface area can be increased. Since the inside of the discharge lamp is kept in a vacuum, a radiation effect can be obtained by increasing the surface area. The shape of the fin structure 6 includes various shapes such as a screw groove, a V-shaped cross section, a U-shaped cross section, an S-shaped surface, a protrusion type, a roughened surface, a low-density shape, a linear shape, and a wavy shape.

The fin diameter of the fin structure 6 is the maximum diameter of the portion in contact with the high-melting-point metal portion 3 . The height of the fin is the maximum height from the root of the fin (the contact portion with the high-melting-point metal portion 3). The vertex spacing of adjacent fins is the spacing (pitch) between the vertices of the closest fins. It is preferable that the distance between the apexes of adjacent fins is 1 mm or more. When providing a plurality of fins, the diameter, height and spacing may all be the same or may be different. If the above preferable range is satisfied, the cooling efficiency can be improved. Adjacent fins may have gaps or may have a continuous shape.

The height of the fins is preferably 10 μm or more. When the fin is a convex portion, the height of the convex portion with respect to the surface of the high melting point metal portion 3 is the height of the fin. When the fin is a recess, the depth of the recess with respect to the surface of the high-melting-point metal portion 3 is the height of the fin. If the fin height is less than 10 μm, the effect of increasing the surface area may be insufficient. Although the upper limit of the fin height is not particularly limited, it is preferably 5 mm or less. If it exceeds 5 mm, the strength of the high-melting-point metal portion 3 may be lowered, or the size may become unnecessarily large. Therefore, the height of the fins is preferably 10 μm or more and 5 mm or less, 0.1 mm or more and 3 mm or less, or 0.3 mm or more and 3 mm or less.

The diameter or minimum width of the fins is preferably 1 mm or more. The fin diameter is the maximum diameter of the convex fin when viewed from above. For example, when the high-melting-point metal portion 3 is provided with conical fins, the root of the cone has the maximum diameter. The minimum width of the fins is the minimum width of the concave fins. For example, when providing a groove extending along the outer periphery of the high-melting-point metal portion 3, the width of the groove is the minimum width.

It is preferable that the apex interval (pitch) between adjacent fins is 1 mm or more. It is preferable to provide a plurality of fins. By providing a plurality of them, the surface area can be further increased. If the pitch of the fins is less than 1 mm, the strength of the gaps between the fins may decrease.

The width of the fin shape is preferably in the range of 0.5 mm or more and 3 mm or less. In the case of grooves, the minimum width is the width of the fin shape. In the case of a projection, it is the maximum diameter when the projection is viewed from above. When providing a plurality of fins, the pitch is preferably in the range of 1 mm or more and 5 mm or less.

FIG. 4 is a schematic diagram showing a lengthwise cross-section of an example of a cathode component for a discharge lamp having a one-piece structure. FIG. 4 shows the cathode component 1, the tungsten portion 2, the refractory metal portion 3, the central portion 4-2 in the longitudinal direction of the cathode component 1, the joint interface 5, and the wire diameter D1 of the refractory metal portion 3. , and the wire diameter D2 of the tungsten portion 2 are shown.

Cathode component 1 comprises a tungsten portion 2 and a refractory metal portion 3 . Refractory metal portion 3 is provided so as to surround tungsten portion 2 in a cross section of cathode component 1 in the wire radial direction. For other descriptions of the tungsten portion 2 and the high-melting-point metal portion 3, the description of the tungsten portion 2 and the high-melting-point metal portion 3 shown in FIG. 1 can be used as appropriate.

As shown in FIG. 4, the longitudinal section of the tungsten portion 2 has a tapered shape with a sharp tip. In FIG. 4, the refractory metal portion 3 also has a tapered shape matching the tapered shape of the tungsten portion 2, but only the tungsten portion 2 may be tapered. Although the lower surface of the tungsten portion 2 and the lower surface of the refractory metal portion 3 are flush in FIG. 3, either one may be lower than the other. In particular, by lowering the end face of the tungsten portion 2, a hole for attaching the electrode support rod may be formed.

When the average crystal grain size of the tungsten phase of the tungsten portion 2 is A μm, and the average crystal grain size of the metal phase of the high melting point metal portion 3 is B μm, A and B are numbers that satisfy the formula: B>A. be. In other words, the average crystal grain size of the metal phase of the refractory metal portion 3 is larger than the average crystal grain size of the tungsten phase of the tungsten portion 2 .

A vacuum is maintained in the discharge lamp using the cathode component 1 . The temperature of tungsten portion 2 may rise to a temperature of about 2000.degree. Therefore, it is preferable to conduct heat from the tungsten portion 2 to the high-melting-point metal portion 3 to escape.

A polycrystalline body has grain boundaries between crystals. Grain boundaries are impediments to heat transfer. On the other hand, the number of grain boundaries can be reduced by increasing the average crystal grain size of the metal phase of the high-melting-point metal portion 3 . Thereby, the heat generated in the tungsten portion 2 can be easily released from the high-melting-point metal portion 3 . As a result, the temperature rise of the electrode of the cathode component can be suppressed, and the life of the discharge lamp can be improved.

A and B are more preferably numbers that satisfy the formula: B≧1.5A. In other words, it is preferable that the average crystal grain size of the metal phase of the high melting point metal portion 3 is 1.5 times or more the average crystal grain size of the tungsten phase of the tungsten portion 2 . Thereby, the heat dissipation effect can be improved.

The average crystal grain size of the tungsten phase of the tungsten portion 2 is preferably 5 μm or more and 15 μm or less. The emitter material is dispersed at grain boundaries of the tungsten phase. If the average crystal grain size is less than 5 μm or more than 15 μm, uniform dispersion of the emitter material may become difficult. Therefore, the average crystal grain size is preferably 5 μm or more and 15 μm or less, more preferably 7 μm or more and 12 μm or less.

The average crystal grain size of the metal phase of the high-melting-point metal portion 3 is preferably 18 μm or more and 40 μm or less. If the average crystal grain size is less than 18 μm, the heat dissipation effect is small. If the average crystal grain size exceeds 40 μm, the heat radiation effect is improved, but the strength of the high-melting-point metal portion 3 may be lowered. Further, when manufacturing a cathode component by attaching an electrode support rod to the high-melting-point metal portion 3, if the strength of the high-melting-point metal portion 3 decreases, it may cause breakage during attachment of the electrode support rod. Similarly, there is a possibility of breakage during processing when providing the fin structure. Therefore, the average grain size is preferably 18 μm or more and 40 μm or less, more preferably 20 μm or more and 36 μm or less.

Located within 1 mm from the central portion 4-1 or the central portion 4-2 in the cross section along the length direction of the tungsten portion 2 passing through the central portion 4-1 or the central portion 4-2 of the tungsten portion 2 and 90 μm × When performing electron beam backscatter diffraction (EBSD) analysis of a region having a unit area of 90 μm, the orientation difference with respect to the <111> orientation in the longitudinal direction of the inverse pole figure (IPF) map is −15 degrees or more. The area ratio of the tungsten phase having a crystal orientation of 15 degrees or less is preferably 15% or more and 50% or less.

Also, within 1 mm from the central portion 4-1 or the central portion 4-2 in the cross section passing through the central portion 4-1 or the central portion 4-2 of the high melting point metal portion 3 and along the length direction of the high melting point metal portion 3 When performing electron beam backscatter diffraction analysis of a region located in and having a unit area of 90 μm × 90 μm, in the inverse pole figure map in the direction perpendicular to the cross section, the misorientation with respect to the <111> orientation is −15 degrees or more and 15 degrees Preferably, the area ratio of the metal phase having the following crystal orientation is lower than the area ratio of the tungsten phase. Thereby, the heat of the high-melting-point metal portion 3 can be easily transferred to the electrode supporting rod.

The central portion 4-1 of the high-melting-point metal portion 3 is the central portion in the case of the cathode component 1 having a tip-integrated structure. The central portion 4-2 of the high-melting-point metal portion 3 is the central portion in the case of the cathode component 1 integrated with the periphery. The center portion 4-1 and the center portion 4-2 may be collectively referred to as the center portion 4 in some cases.

The average grain size of the tungsten phase and the average grain size of the metal phase are obtained from the grain map obtained by EBSD. The measurement points are as follows.

In the case of the tip-integrated structure, a longitudinal section of the cathode component 1 passing through the central portion 4-1 is prepared. A place within 1 mm from the central part 4-1 of the cross section shall be the measurement point. Measurement points are selected from the tungsten portion 2 and the high-melting-point metal portion 3, respectively. The measurement surface of the measurement sample is polished until the surface roughness Ra becomes 0.8 μm or less.

In the case of the peripheral integrated structure, the measurement point of the tungsten portion 2 is selected in the same manner as in the case of the tip integrated structure. In the case of the integral-periphery structure, a cross-section along the length of the cathode component 1 and passing through the central portion 4-2 is prepared. A point within 1 mm from a point passing through the central portion 4-2 in the high-melting-point metal portion 3 is taken as a measurement point.

The EBSD crystal grain map is a diagram in which two or more consecutive measurement points within a crystal orientation angle difference of 5 degrees in a unit area of 90 μm×90 μm are identified as the same crystal grain and displayed. The average crystal grain size is calculated from the area of identified crystal grains in a unit area of 90 μm×90 μm. The particle diameter is equivalent circle diameter.

As for grains protruding from the unit area of 90 μm×90 μm, the boundaries of the unit area of 90 μm×90 μm are calculated as grain boundaries. The average grain size obtained is the median size (average grain size D ₅₀ ). That is, it becomes the cumulative particle size.

EBSD irradiates a crystal sample with an electron beam. The electrons are diffracted and emitted from the sample as backscattered electrons. This diffraction pattern can be projected and the crystal orientation measured from the projected pattern. X-ray diffraction (XRD) is a method of measuring the average crystal orientation in multiple crystals. In contrast, EBSD can measure the crystallographic orientation of individual crystals. A method of analysis similar to EBSD is sometimes referred to as electron beam backscatter pattern (EBSP) analysis.

The EBSD analysis was performed using a thermal field emission scanning electron microscope (TFE-SEM) JSM-6500F manufactured by JEOL Ltd., a DigiView IV slow scan CCD camera manufactured by TSL Solution Co., Ltd., and OIM Data Collection ver. 7.3x, OIM Analysis ver. 8.0.

The measurement conditions for the EBSD analysis were an electron beam acceleration voltage of 20 kV, an irradiation current of 12 nA, a sample tilt angle of 70 degrees, a unit area of the measurement region of 90 μm × 90 μm, a measurement position within 1 mm from the center 4, and a measurement interval of 0.3 μm/ Including steps. The cross section is a measurement surface, and a diffraction pattern is obtained by irradiating the cross section with an electron beam. The measurement surface of the measurement sample is polished until the surface roughness Ra becomes 0.8 μm or less.

Crystal orientation indicates direction using fundamental vectors. A notation consisting of a combination of square brackets ([ ]) and numbers between square brackets indicates only a specific crystal orientation. A notation consisting of angle brackets (< >) and a combination of numbers between the angle brackets indicates a specific crystal orientation and its equivalent direction. For example, the <111> orientation includes directions equivalent to [111].

An IPF map is a crystal orientation map. With the IPF map, the ratio of regions deviating from a predetermined crystal orientation can be obtained by an area ratio. The IPF map can be obtained according to the EBSD measurement method described above. Color mapping makes it easier to determine the area ratio by image analysis.

<111> in the cross section passing through the central portion 4 of the tungsten portion 2 indicates the orientation in the direction perpendicular to the cross section passing through the central portion 4 . The <111> orientation of the tungsten portion 2 makes it easier for heat to escape to the outside. Thereby, the heat dissipation property of the cathode component 1 can be improved.

<111> in the cross section passing through the center portion 4-1 or the center portion 4-2 of the high melting point metal portion 3 indicates the orientation in the direction perpendicular to the cross section passing through the center portion 4. FIG.

The area ratio of the metal phase having a crystal orientation with a misorientation of −15 degrees or more and 15 degrees or less with respect to the <111> orientation of the high melting point metal portion 3 is preferably 5% or more and 90% or less. By giving an orientation different from <111>, there is an effect of suppressing grain growth of the high-melting-point metal portion 3 . By giving the high-melting-point metal portion 3 a <111> orientation, heat can easily escape to the outside.

The area ratio of the phase having a crystal orientation with a misorientation of −15 degrees or more and 15 degrees or less with respect to the <111> orientation of the tungsten portion 2 and the refractory metal portion 3 is preferably 5% or more and 40% or less. Since the tungsten portion 2 and the high-melting-point metal portion 3 have a predetermined ratio of <111>, the relationship that satisfies the formula: B>A can be maintained even after the heat treatment. The cathode component 1 may be subjected to heat treatment when mounted in a discharge lamp. This heat treatment includes recrystallization heat treatment, strain relief heat treatment, and the like. <111> indicates the orientation perpendicular to the cross section. By providing vertical orientation, abnormal grain growth accompanying heat treatment can be suppressed. As a result, the cathode component 1 according to the embodiment can satisfy the formula: B>A even after the heat treatment.

A and B satisfy the formula: B>A, even though the cathode component 1 is of a perimeter integral structure. By increasing B, the heat dissipation effect can be improved. A and B more preferably satisfy the formula: B≧1.5A.

It is preferable that at least a part of the bonding interface 5 has unevenness. By having unevenness on the bonding interface, an anchor effect between the tungsten portion 2 and the high-melting-point metal portion 3 can be generated to improve the bonding strength.

The peak-to-peak value is defined by the difference between the deepest part of the recess and the topmost part of the protrusion. The unevenness value is preferably 0.01 mm or more, more preferably 0.1 mm or more. The bonding strength can be increased to 200 MPa or more by forming the unevenness of 0.01 mm or more. When the bonding strength is improved, it is possible to suppress breakage during press-fitting of the electrode support rod, breakage during handling, and the like. Although the upper limit of the unevenness is not particularly limited, it is preferably 1 mm or less. If it exceeds 1 mm, the unevenness is too large, and there is a possibility that gaps will occur at the bonding interface. Therefore, the unevenness of the bonding interface is preferably 0.01 mm or more and 1 mm or less, more preferably 0.1 mm or more and 0.5 mm or less. Within this range, the bonding strength can be 200 MPa or more, further 400 MPa or more.

Bonding strength is measured by a peel test. Measurement of bond strength is performed by a four-point bending test. Place the test piece so that the joint interface is between the inner fulcrum and the outer fulcrum, and apply a load. The bond strength is calculated from the maximum load when the test piece breaks. The four-point bending test is performed according to JISR1631 (testing method for room temperature bending strength of fine ceramics).

The unevenness of the bonding interface 5 can be confirmed by observing the cross section with a laser microscope. If the bonding interface 5 has unevenness, unevenness will occur in the distribution state of the emitter material. The emitter material appears black in laser micrographs. It is distinguishable from tungsten or refractory metals due to its different contrast.

A laser micrograph is obtained by observing a sample at a magnification of 500 times or more and 1500 times or less and a measurement field of view of 200 μm×200 μm or more. The uneven shape can be confirmed by connecting the emitter material regions in the laser micrograph with a line.

The unevenness of the bonding interface 5 can also be confirmed by observation of a cross section with a scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDS). It is possible to distinguish between tungsten or refractory metals and emitter materials by elemental analysis. If the bonding interface 5 has unevenness, unevenness will occur in the distribution state of the emitter material. In the SEM observation, the sample is observed at a magnification of 500 times or more and 1500 times or less and a measurement field of view of 200 μm×200 μm or more. The uneven shape can be confirmed by connecting the emitter material regions identified by the elemental analysis with a line.

The wire diameter D of the cathode component 1 is preferably 2 mm or more and 35 mm or less. In the case of the integrated tip structure, the wire diameter D is the diameter of the high-melting-point metal portion 3 . In the case of the peripheral integrated structure, the wire diameter D1 of the high-melting-point metal portion 3 is the wire diameter D. As shown in FIG. If the wire diameter D is less than 2 mm, the emission characteristics may be insufficient. If the wire diameter D exceeds 35 mm, there is a possibility that no further effect will be obtained.

In the case of the integrated tip structure, the length T1 of the tungsten portion 2 and the length T2 of the refractory metal portion 3 are preferably within the range of 0.4≦T2/T1≦3. In the case of the peripheral integrated structure, the wire diameter D1 of the high-melting-point metal portion 3 and the wire diameter D2 of the tungsten portion 2 are preferably within the range of 0.2≦D2/D1≦0.8. By adjusting the ratio T2/T1 or the ratio D2/D1, deterioration of emission characteristics can be suppressed without adding an emitter material to the high-melting-point metal portion 3 . In other words, it is possible to prevent the use of emitter materials that do not contribute to emission characteristics. By suppressing the amount of emitter material used, manufacturing costs can be reduced.

FIG. 5 is a schematic diagram showing an example of a cathode component 1 having holes. The high melting point metal portion 3 may have holes 7 as shown in FIG. A hole 7 is a hole for joining an electrode supporting rod. The hole 7 is provided on the lower surface of the high-melting-point metal portion 3 (the side on which the tungsten portion 2 is not provided).

Various methods such as press-fitting and brazing can be used to join the support rods 8 . A thread groove may be provided inside the hole 7 . A structure in which a screw groove is provided in the support rod 8 and screwed in is also possible. By providing a thread groove, it is possible to suppress breakage of the high-melting-point metal portion 3 when attaching the support rod 8 .

FIG. 6 is a schematic diagram showing an example of a cathode component 1 having support rods integrally molded with a high-melting-point metal portion 3. As shown in FIG. By integrating the support rod 8 with the high-melting-point metal portion 3, the process of forming a hole and the process of joining the support rod 8 are not required. Therefore, manufacturing costs can be reduced. In addition, the length of the support rod 8 is not limited to the length shown in FIGS.

The three-point bending strength of the high melting point metal portion 3 is preferably 100 MPa or more and 600 MPa or less. For example, a three-point bending strength of 700 MPa or more can be achieved by manufacturing a cathode component using a sintered body formed by forging or rolling. This is because a dense sintered body with few voids can be formed.

A cathode component for a discharge lamp is exposed to a high temperature environment during operation of the discharge lamp. Therefore, durability at high temperatures is required. On the other hand, physical strength requirements are small. For the three-point bending strength of 100 MPa or more and 600 MPa or less, it is effective to reduce the density of the cathode component. For example, the density can be changed by using a modeling technique using a 3D printer (3D printing).

Forming pores is effective for strength control. It is preferable that the existence ratio of pores is within the range of 0% or more and 60% or less in terms of area ratio per unit area of 200 μm×200 μm or more. If the ratio of pores exceeds 60% by area ratio, the three-point bending strength may decrease to less than 100 MPa.

The area ratio of pores can be measured by observing an arbitrary cross section of the high melting point metal portion 3 with an optical microscope such as a laser microscope. Magnification shall be 100 times or more. Pores appear in black contrast in optical micrographs. Refractory metals such as tungsten appear gray. Obtain the black area ratio per unit area of 200 μm×200 μm or more. This operation is performed at arbitrary three locations, and the average value is taken as the pore area ratio.

When the high-melting-point metal portion 3 does not contain an emitter material, the oxygen concentration is preferably 0.1% by mass or less. Emitter materials may also be added with oxides such as thorium oxide. On the other hand, oxygen that is not a constituent element of the emitter material becomes impurity oxygen. If the oxygen concentration exceeds 0.1% by mass, the strength may decrease. Therefore, the oxygen concentration of the high melting point metal portion 3 is preferably 0.1% by mass or less, more preferably 0.05% by mass or less. The oxygen concentration of the high-melting-point metal portion 3 is measured, for example, by semi-quantitative analysis of SEM-EDX, or by pulverizing the high-melting-point metal portion 3 and measuring by an infrared absorption method.

Embodiment cathode components can be applied to discharge lamps. FIG. 7 is a diagram showing a structural example of a discharge lamp. A discharge lamp 20 shown in FIG. 7 includes a cathode component 1 , a support rod 8 that is a cathode electrode support rod, an anode component 9 , a support rod 10 that is an anode electrode support rod, and a glass tube 11 .

Cathode part 1 is connected to support rod 8 . Anode component 9 is connected to support rod 10 . The connection is made by press-fitting, brazing, or the like. The cathode part 1 and the anode part 9 are arranged opposite each other in a glass tube 11 and sealed together with part of the support rod 8 and part of the support rod 10 . The inside of the glass tube 11 is kept vacuum.

The cathode component 1 can be applied to both low-pressure discharge lamps and high-pressure discharge lamps. Low-pressure discharge lamps include general lighting, special lighting used for roads and tunnels, paint curing equipment, UV curing equipment, sterilization equipment, and various arc discharge type discharge lamps used for light cleaning equipment such as semiconductors. be done. High-pressure discharge lamps are used for water and sewage treatment equipment, general lighting, outdoor lighting for stadiums, etc., UV curing equipment, exposure equipment for semiconductors and printed circuit boards, wafer inspection equipment, high-pressure mercury lamps, metal halide lamps, ultra-high pressure lamps for projectors, etc. A mercury lamp, a xenon lamp, a sodium lamp, etc. are mentioned. Thus, discharge lamps are used in various devices such as lighting devices, image projection devices, and manufacturing devices.

Since the cathode component according to the embodiment has improved heat dissipation properties, it is possible to suppress temperature rise. Since the durability of the cathode component 1 can be improved, a decrease in the luminance maintenance factor of the discharge lamp can be suppressed. Therefore, it is particularly suitable for high-pressure discharge lamps.

Next, an example of a method for manufacturing the cathode component of the embodiment will be described. The method for manufacturing the cathode component of the embodiment is not particularly limited as long as it has the above configuration, but the following method can be mentioned as a method for manufacturing the cathode component with good yield.

First, a method for manufacturing the tungsten portion 2 will be described. Tungsten portion 2 contains a tungsten alloy containing an emitter material. Here, a manufacturing method using thorium as an emitter material will be described.

A tungsten alloy powder containing thorium is prepared. Methods for preparing tungsten alloy powder include, for example, a wet method and a dry method.

In the wet method, first, a step of preparing a tungsten material powder is performed. Tungsten material powders include ammonium tungstate (APT) powders, metallic tungsten powders, and tungsten oxide powders. One of these tungsten material powders may be used, or two or more thereof may be used. Ammonium tungstate powder is preferred due to its relatively low cost. The average particle size of the tungsten material powder is preferably 5 μm or less.

When ammonium tungstate powder is used, the ammonium tungstate powder is heated at a temperature of 400° C. or higher and 600° C. or lower in the atmosphere or an inert atmosphere (nitrogen, argon, etc.) to convert the ammonium tungstate powder into tungsten oxide powder. Let At a temperature of less than 400°C, the tungsten oxide powder cannot be sufficiently converted, and at a temperature of more than 600°C, the particles of the tungsten oxide powder become coarse, making it difficult to uniformly disperse it with the thorium oxide powder in the subsequent process. . This step prepares a tungsten oxide powder.

Next, a step of adding thorium material powder and tungsten oxide powder into the solution is performed. The thorium material powder includes metallic thorium powder, thorium oxide powder, and thorium nitrate powder. Among these, thorium nitrate powder is preferred. Thorium nitrate powder is easy to mix evenly in liquid. This step prepares a solution containing thorium material powder and tungsten oxide powder. It is preferable to add thorium oxide so that the final concentration is the same as or slightly higher than the target thorium oxide concentration. The average particle size of the thorium material powder is preferably 5 μm or less. Preferably, the solution is pure water.

Next, a step of evaporating the liquid component of the solution containing the thorium material powder and the tungsten oxide powder is performed. Next, a decomposition step is performed in which the thorium material powder such as thorium nitrate is heated at a temperature of 400° C. or higher and 900° C. or lower in an air atmosphere to convert the thorium material powder such as thorium nitrate into thorium oxide powder. Through this step, mixed powder containing thorium oxide powder and tungsten oxide powder can be prepared. It is preferable to measure the thorium oxide concentration of the mixed powder containing the obtained thorium oxide powder and tungsten oxide powder, and add tungsten oxide powder when the concentration is low.

Next, a step of heating the mixed powder containing the thorium oxide powder and the tungsten oxide powder at a temperature of 750° C. or more and 950° C. or less in a reducing atmosphere such as hydrogen to reduce the tungsten oxide powder to metallic tungsten powder is performed. . Through this process, a tungsten powder containing thorium oxide powder can be prepared.

A method of mixing metal tungsten powder and thorium material powder is also effective. The metallic tungsten powder is preferably formed by forming tungsten oxide powder from ammonium tungstate powder and reducing the resulting tungsten oxide. When ammonium tungstate powder is changed to tungsten oxide powder, the resulting tungsten oxide preferably has oxygen deficiency. As for the composition of tungsten oxide _, WO3 is stable. If there is an oxygen deficiency, WO _3-x , x>0. Oxygen vacancies form distortions in the crystal structure. The metal tungsten powder obtained by reduction in this state has a high effect of suppressing abnormal grain growth. The value of x is preferably in the range of 0.05≤x≤0.30.

The step of forming tungsten oxide powder from ammonium tungstate powder is preferably a step of heating in an inert atmosphere. An inert atmosphere is a nitrogen atmosphere or an argon atmosphere. In order to control the value of x, reducing the amount of oxygen in the inert atmosphere (for example, 1% by volume or less), mixing hydrogen, and the like can be mentioned. The heat treatment temperature is preferably in the range of 400° C. or higher and 600° C. or lower. If the temperature is less than 400°C, the reaction rate is slow and the mass productivity is lowered. If the temperature exceeds 600°C, excessive grain growth may occur.

The step of reducing the WO _3-x powder is preferably carried out in a hydrogen-containing atmosphere. The heat treatment temperature is preferably in the range of 600° C. or higher and 800° C. or lower. If the heat treatment temperature is less than 600° C., the rate of reduction is slow and the mass productivity is lowered. If the temperature exceeds 800°C, excessive grain growth may occur.

Next, a step of evaporating the liquid component of the solution containing the thorium material powder and the metallic tungsten powder is performed. Next, the sample is heated at a temperature of 400° C. or more and 900° C. or less in an air atmosphere to perform a decomposition step of changing thorium material powder such as thorium nitrate into thorium oxide powder. By this process, a tungsten powder containing thorium oxide powder can be prepared.

In the dry method, first, thorium oxide powder is prepared. Next, a step of pulverizing and mixing the thorium oxide powder with a ball mill is carried out. By this step, the agglomerated thorium oxide powder can be loosened and the agglomerated thorium oxide powder can be reduced. A small amount of metallic tungsten powder may be added during the mixing step.

If necessary, it is preferable to sift the pulverized and mixed thorium oxide powder to remove aggregated powder or coarse particles that have not been completely pulverized. It is preferable to remove agglomerated powder or coarse particles having a maximum diameter exceeding 10 μm by sieving.

Next, a step of mixing metallic tungsten powder is carried out. Metallic tungsten powder is added so that the final concentration of thorium oxide becomes the target. A mixed powder of thorium oxide powder and metal tungsten powder is placed in a mixing vessel, and the mixing vessel is rotated to uniformly mix the powder. At this time, the mixture can be smoothly mixed by rotating the cylindrical mixing container in the circumferential direction. Through this process, a tungsten powder containing thorium oxide powder can be prepared.

A dry method is suitable when hafnium is used as the emitter material. The emitter material is mixed so as to have a content of 0.1% by mass or more and 5% by mass or less.

Next, a compact is prepared using the obtained tungsten powder containing the emitter material. If necessary, a binder may be used when forming the compact. It is preferable that the compact has a cylindrical shape. The length of the molded body is arbitrary.

Next, a step of pre-sintering the compact is carried out. Pre-sintering is preferably performed at a temperature of 1250°C or higher and 1500°C or lower. Through this step, a pre-sintered body can be obtained.

Next, a step of electrically sintering the pre-sintered body is carried out. In the electric sintering, it is preferable to apply electric current so that the sintered body has a temperature of 2100° C. or higher and 2500° C. or lower. If the temperature is less than 2100° C., sufficient densification may not be achieved and the strength may decrease. If the temperature exceeds 2500° C., the thorium oxide particles and tungsten particles may undergo excessive grain growth and the desired crystal structure may not be obtained. Through this step, a thorium oxide-containing tungsten alloy sintered body can be obtained. If the presintered body has a cylindrical shape, the sintered body also has a cylindrical shape.

Next, the cylindrical sintered body (ingot) is subjected to a first processing step of adjusting the wire diameter by forging, rolling, extrusion, or the like. The processing rate of the first processing step is preferably in the range of 10% or more and 30% or less.

After the first processing step, the second processing step is performed. The second working step is preferably rolling with a working ratio of 30% or more and 70% or less, more preferably 40% or more and 70% or less.

The processing rate is, where C is the cross-sectional area of the cylindrical sintered body before processing and D is the cross-sectional area of the cylindrical sintered body after processing, the processing rate = [(CD) / C] × 100%. , is calculated by For example, the processing rate when processing a cylindrical sintered body with a diameter of 25 mm into a cylindrical sintered body with a diameter of 20 mm will be described. Since the cross-sectional area C of a circle with a diameter of 25 mm is 460.6 mm ² and the cross-sectional area D of a circle with a diameter of 20 mm is 314 mm ² , the processing rate is 32%=[(460.6−314)/460.6]×100%. becomes.

The processing rate of the first processing step being 10% or more and 30% or less is obtained by taking the cross-sectional area C as the cross-sectional area of the cylindrical sintered body (ingot) before the first processing step. The processing rate of the second processing step being 30% or more and 70% or less is obtained by defining the cross-sectional area C as the cross-sectional area of the cylindrical sintered body after the first processing step.

Forging is a process of applying pressure by hitting a sintered body with a hammer. Rolling is a method of working while sandwiching a sintered body between two or more rollers. Extrusion is a method of extruding from a die hole under strong pressure.

The first processing step preferably includes at least one processing selected from the group consisting of forging, rolling, and extrusion. These processing methods can reduce the wire diameter. Therefore, the number of pores in the cylindrical sintered body can be reduced. The first processing step is preferably forging or extrusion. Forging or extrusion is highly effective in reducing pores because the entire circumference of the cylindrical sintered body can be easily processed.

The processing rate of the first processing step is preferably 10% or more and 30% or less. If the processing rate is less than 10%, the effect of reducing pores is small. If the processing rate exceeds 30%, it becomes difficult to control the crystal orientation. The first processing step may be performed in multiple steps as long as the processing rate is within the range of 10% or more and 30% or less.

The second processing step is rolling. Rolling makes it easier to control the crystal orientation. Rolling is a method of reducing the cross-sectional area while sandwiching between a plurality of rollers. The crystal orientation can be controlled by rolling only.

The forging process involves hitting with a hammer, which tends to cause partial variations in crystal orientation. In extrusion processing, since stress is strong when the material is passed through a die, a difference in crystal orientation tends to occur between the central portion and the surface portion. With rolling, the stress from the rollers can be adjusted, making it easier to control the crystal orientation.

In the second working step, the rolling working rate is 30% or more and 70% or less. The processing rate is controlled by setting the cross-sectional area after the first processing step as the cross-sectional area C. As long as the processing rate is within the range of 30% or more and 70% or less, the processing may be performed once or may be divided into two or more times. If the processing rate is less than 30% or more than 70%, the intended crystal orientation cannot be obtained.

The first working step and the second working step are preferably cold working. Cold working is a method of working an object at a temperature below the recrystallization temperature. Working in a heated state above the recrystallization temperature is called hot working. Hot working recrystallizes the cylindrical sintered body. Cold working does not recrystallize. It is important to control the crystal orientation in a structure that does not recrystallize.

By cold working, it is possible to suppress an increase in the average crystal grain size of the tungsten phase of the tungsten portion 2 . By controlling the working rate of the rolling process, the area ratio of the tungsten phase having a crystal orientation with an orientation difference of −15 degrees or more and 15 degrees or less with respect to the <111> orientation of the tungsten portion 2 can also be controlled. A dense tungsten portion 2 having a relative density of 99.5% or more can be formed by combining forging and rolling.

Moreover, the process of forming the high-melting-point metal part 3 is performed. The refractory metal portion 3 has a larger average crystal grain size than the tungsten portion 2 . Methods for forming the high-melting-point metal portion 3 include, for example, a method of preparing in advance a high-melting-point metal sintered body having a large average crystal grain size, and a method of using 3D printing. It is particularly preferred to use 3D printing.

3D printing is a technology that directly forms a three-dimensional object using a three-dimensional solid model. 3D printing includes, for example, methods using laser beams or electron beams.

3D printing using a laser beam is called selective laser sintering (SLS). One type of laser sintering method is direct metal laser sintering (DMLS). SLS is a method of spreading a powder material on a modeling stage and irradiating it with a laser beam. The powder material is melted by the irradiation of the laser beam, and then cooled to be shaped. In this method, after molding, a new powder material is supplied and laser irradiation is repeated.

DMLS is a laser sintering method using high laser power. DMLS uses a Ytterbium laser. SLS uses a carbon dioxide laser.

SLS and DMLS are methods of sintering powder materials with a laser beam. Another method using a laser beam is selective laser melting (SLM). SLM is a method in which a powder material is melted by laser irradiation and shaped. There is also laser metal deposition (LMD), which is a building-up modeling method in which powder is sprayed onto a region irradiated with a laser beam and melted to form a model.

3D printing using an electron beam is called electron beam melting (EBM). An electron beam is a beam that emits electrons by heating a filament in a vacuum. Electron beams are characterized by higher output and higher speed than laser beams. EBM is a technology that melts and shapes powder materials. There is also a method of modeling using metal wires in EBM. SLM or EBM are preferred when 3D printing the aforementioned refractory metals. SLM or EBM is a method of melting metal particles. When melted, it becomes easier to obtain a high-density model.

In 3D printing using a laser beam, a process of laying metal powder and irradiating it with a laser beam to harden it is performed, and the process of laying metal powder on top of it and irradiating it with a laser beam to harden it is repeated. By using high-melting-point metal powder as the metal powder, the high-melting-point metal portion 3 can be formed. In the case of the tip-integrated structure, there is a method of forming on the lower surface (opposite side of the high-melting-point metal portion 3). In the case of the peripheral integrated type, there is a method of forming around the tungsten portion 2 by LMD.

In the case of 3D printing, it is preferable to use high melting point metal powder having an average crystal grain size larger than that of the tungsten portion 2 . This makes it easier to manufacture a cathode component that satisfies the formula: B>A and further the formula: B≧1.5A.

DMLS and SLS preferably have a laser output of 100 W or more. It is preferable that the SLM and LMD have a laser output of 100 W or more. The EBM preferably has an electron beam output of 2000 W or more.

SLS, SLM, EBM, or LMD preferably has a modeling speed of 100 mm/s or more. The build speed is the speed at which the laser or electron beam is scanned. If the shaping speed is less than 100 mm/s, the shaping speed is slow and the mass productivity decreases. Although the upper limit of the modeling speed is not particularly limited, it is preferably 5000 mm/s or less. In the case of refractory metals, if the speed is faster than 5000 mm/s, the sintered state or molten state may vary, and the density may decrease more than necessary. As the density decreases, the strength of the refractory metal portion 3 decreases.

By controlling the power of the laser beam or the electron beam and the molding speed, the average crystal grain size of the high-melting-point metal portion 3 can be increased. By irradiating the tungsten portion 2 with a laser beam or an electron beam, it is possible to form unevenness on the bonding interface 5 . When the high-melting-point metal portion 3 is viewed as a reference, the portion hit by the laser beam becomes a concave portion. By setting the output and modeling speed within the ranges described above, the unevenness value can be set to 0.1 mm or more. By controlling the irradiation diameter of the laser beam or electron beam, the width and interval of the unevenness can be controlled.

By forming the high-melting-point metal part 3 by 3D printing, the modeling method and the modeling direction can be determined. Therefore, it is possible to control the area ratio of the metal phase having a crystal orientation with a misorientation of −15 degrees or more and 15 degrees or less with respect to the <111> orientation.

By 3D printing, the holes 7 for joining the support bars 8 may be directly shaped, as shown in FIG. It is also easy to form a thread groove in the hole 7 by a direct molding method. After forming the high-melting-point metal portion 3 , processing to form the hole 7 may be performed. Since the tungsten portion 2 is formed by forging and rolling, it is a dense and difficult-to-work material. On the other hand, since the high-melting-point metal part 3 is formed by 3D printing, it is shaped by melting high-melting-point metal powder. Therefore, the workability is higher than that of the tungsten portion 2, and the holes 7 are easily formed. Further, by not rolling the refractory metal portion 3, it is possible to control the area ratio of the phase of the above metal having a crystal orientation with a misorientation of -15 degrees or more and 15 degrees or less with respect to the <111> orientation.

By using 3D printing, the high melting point metal part 3 and the support rod 8 can be integrated as shown in FIG. This reduces manufacturing costs.

By 3D printing, a fin structure 6 can be formed directly on the refractory metal part 3, as shown in FIG. The refractory metal part 3 formed by 3D printing may be processed to form the fin structure 6 . Processing includes cutting, laser beam processing, and the like.

The tungsten portion 2 may be formed by subjecting the tip of the high-melting-point metal portion 3 to sharpening. After manufacturing the tungsten portion 2, the tip may be sharpened.

(Examples 1 to 6, Comparative Example 1)
A tungsten portion 2 was formed. Tungsten powder with an average particle size of 3 μm and an emitter material with an average particle size of 2 μm were mixed in a cylindrical mixing container while being rotated in the circumferential direction of the container. After that, preliminary sintering and electrical sintering were performed. Through this process, a cylindrical sintered body (ingot) was produced. Table 1 shows the manufacturing conditions.

Next, the cylindrical sintered body was processed. Table 2 shows the processing conditions. In addition, each example was performed by cold working.

After processing the cylindrical sintered body, the tungsten portion 2 was produced by subjecting the tip to a sharpening process. The obtained tungsten portion 2 was cut along the central portion in the length direction, and the average crystal grain size of the tungsten phase was measured. In addition, the area ratio of the tungsten phase having a crystal orientation with an orientation difference of -15 degrees or more and 15 degrees or less with respect to the <111> orientation of the tungsten portion 2 was measured. Table 3 shows the measurement results.

Next, a refractory metal portion 3 was formed on the surface of the tungsten portion 2 using 3D printing. For 3D printing, the example of the tip integrated structure was formed by the SLM method, and the example of the peripheral integrated structure was formed by the LMD method.

A laser output of 100 W or more was used for the SLM method and the LMD method. The modeling speed was 100 mm/s or more and 5000 mm/s or less. In the example, a high-melting-point metal powder having an average crystal grain size larger than that of the tungsten phase of the tungsten portion 2 was used. In the comparative example, high melting point metal powder having an average crystal grain size smaller than that of the tungsten phase of the tungsten portion 2 was used. A fin structure 6 was formed on the refractory metal portion 3 of the cathode component 1 according to the example and the comparative example. The fin structure has concave fins with a height of 0.5 mm and a minimum width of 1 mm so as to encircle the outer periphery of the high-melting-point metal portion 3 . A plurality of fins were formed at a pitch of 2 mm.

In Examples 1 to 5 and Comparative Example 1, holes 7 for mounting electrode support rods were formed. In Example 6, the high melting point metal portion 3 and the support rod 8 were integrally formed by 3D printing. In Comparative Example 1, the cathode component 1 was formed by manufacturing the tungsten portion 2 by forging and rolling without using 3D printing, and forming the refractory metal portion 3 from a part of the tungsten portion 2 . That is, in the cathode component of Comparative Example 1, the tungsten portion 2 and the refractory metal portion 3 were made of a tungsten alloy containing thorium oxide.

In the cathode component 1 according to the example and the comparative example, the refractory metal portion 3 has an average crystal grain size and a crystal orientation difference of -15 degrees or more and 15 degrees or less with respect to the <111> orientation. ratio was measured. Also, the three-point bending strength of the high-melting-point metal portion 3 was measured. The measurement was performed according to JISR1631. Thus, cathode parts for discharge lamps shown in Tables 4 and 5 were produced. In addition, the three-point bending strength, average grain size, and area ratio of the metal phase having a crystal orientation of -15 degrees or more and 15 degrees or less with respect to the <111> orientation of Comparative Example 1 shown in Table 4 are high melting point It was measured at a position corresponding to the metal part 3.

Observation of the bonding interface between the tungsten portion 2 and the high-melting-point metal portion 3 revealed unevenness of 0.01 mm or more. When the oxygen concentration of the high-melting-point metal portion 3 was measured by an infrared absorption method, all of them were 0.1% by mass or less.

Next, using the obtained cathode component 1, a discharge lamp was produced. In the discharge lamp, the distance between the electrodes of the cathode part 1 and the anode part 9 was unified to 5 mm. The temperature and illuminance maintenance rate of the cathode component 1 were measured for each discharge lamp.

As for the temperature of the cathode component 1, the input power was set to 3000 W, and the temperature of the tungsten portion 2 of the cathode component 1 was measured using a thermography when lighting was continued for 3 hours.

The illuminance maintenance rate was measured by a lighting test. The lamp voltage was set to 40 V when lit, and the lamp voltage was set to 20 V when not lit. Lighting and non-lighting were repeated, and the rate of change in illuminance after a total of 10 hours and a total of 700 hours was measured. Illuminance maintenance rate (%)=[(illuminance after 10 hours−illuminance at 700 hours)/illuminance after 10 hours]×100. Illuminance was measured with an illuminometer. Table 6 shows the results.

As can be seen from the table, the cathode component 1 according to Example was excellent in the illuminance maintenance rate (%). As in Comparative Example 1, the same performance as the cathode component 1 in which the tungsten portion 2 and the high-melting-point metal portion 3 are made of one material was exhibited. This is because the control of the average crystal grain size and the existence of the fin structure improved the heat dissipation and suppressed the temperature rise of the cathode component 1 . It was also found that excellent characteristics can be obtained even if the high-melting-point metal portion 3 does not contain an emitter material. Therefore, the amount of emitter material used can be reduced.

Although some embodiments of the present invention have been illustrated above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, etc. can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof. Each of the above-described embodiments can be implemented in combination with each other.

Claims (12)

a first portion containing tungsten and an emitter material;
a second portion containing a metal different from the emitter material;
When the average crystal grain size of the tungsten phase in the first portion is A μm and the average crystal grain size of the metal phase in the second portion is B μm, A and B are represented by the formula: B>A and a number that satisfies the formula: B≧1.5A,
The average crystal grain size of the tungsten phase is 5 μm or more and 15 μm or less,
A cathode component for a discharge lamp, wherein the metal phase has an average crystal grain size of 18 μm or more and 40 μm or less . A region located within 1 mm from the center of the first portion and having a unit area of 90 μm × 90 μm in a cross section passing through the center of the first portion and along the length direction of the first portion When performing electron beam backscatter diffraction analysis, in the Inverse Pole Figure map in the direction perpendicular to the cross section, the area ratio of the tungsten phase having a crystal orientation of -15 degrees or more and 15 degrees or less with respect to the <111> orientation is 15. % or more and 50% or less. 3. The cathode component according to claim 2, wherein said area ratio of said tungsten phase is between 21% and 50%. A region located within 1 mm from the center of the second portion and having a unit area of 90 μm × 90 μm in a cross section passing through the center of the second portion and along the length direction of the second portion When performing electron beam backscatter diffraction analysis, the area ratio of the phase of the metal having a crystal orientation with a misorientation of -15 degrees or more and 15 degrees or less with respect to the <111> orientation in the inverse pole figure map in the direction perpendicular to the cross section is lower than the area ratio of the tungsten phase. 5. The cathode component according to claim 4, wherein said area ratio of said metallic phase is between 5% and 40%. 6. A cathode component according to any one of claims 1 to 5, wherein said metal comprises at least one metallic element selected from the group consisting of tungsten and molybdenum. 7. Cathode component according to any one of the preceding claims , wherein the emitter material comprises at least one element selected from the group consisting of thorium and hafnium. the first portion is joined to the second portion;
8. The cathode component according to any one of claims 1 to 7, wherein a bonding interface between said first portion and said second portion has unevenness. 9. A cathode component as claimed in any preceding claim , wherein the second portion comprises fins. 10. Cathode component according to any one of the preceding claims , wherein the second part has holes for joining support bars. 10. Cathode component according to any one of the preceding claims , wherein the second part comprises a support bar. A discharge lamp comprising the cathode component according to any one of claims 1 to 11 .

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