Ruthenium alloy heater

Abstract

To provide a heater using a long-life ruthenium alloy heat generator (a heat generation material) with a high electric resistance and a low temperature independence.SOLUTION: A ruthenium alloy heat generation material is formed of an alloy of ruthenium and at least one of dissimilar metal element, and the ruthenium alloy heat generation material includes the largest ratio of ruthenium.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ruthenium alloy heating element (heating element) with high resistance, little temperature dependency, and long life, and also to a heater using a ruthenium alloy heating element (heating element) with high resistance, little temperature dependency, and long life. [Background technology]

[0002] Transition metal elements, refractory metal elements, and alloys thereof have recently been used in, for example, organic and inorganic electroluminescence (EL) vapor deposition cells. An example of such a vapor deposition cell is described in, for example, Japanese Patent Application Laid-Open No. 2005-32464 (Patent Document 1). The vapor deposition cell described in Patent Document 1 comprises a container and a heating means. The container can be a cylindrical container made of a refractory oxide such as titanium (Ti), alumina (Al2O3), or beryllia (BeO), or a refractory metal such as tantalum (Ta), molybdenum (Mo), tungsten (W), stainless steel (SUS), or titanium (Ti), or an oxide, nitride, or alloy thereof. The heating means can be a high-frequency heating method in which a filament or heating coil made of a refractory metal such as tantalum, molybdenum, or tungsten is wound directly or indirectly around the periphery of the cell and current is applied; a resistance heating method; a laser heating method; an electron beam heating method; or the like. Furthermore, for example, when producing organic EL, vacuum deposition is often used to form thin films, and tantalum is generally used as the deposition cell for this purpose.

[0003] In recent years, platinum or platinum alloys, which have a high melting point and chemical stability, have become known as metal wires used in high-temperature applications such as spark plug electrodes (center electrodes, ground electrodes), various sensor electrodes, and temperature measurement. Furthermore, advances in processing technology have led to the use of iridium or iridium alloy wires, which have a higher melting point than platinum and high oxidation resistance, as the metal wires used in the aforementioned spark plugs, various sensors, and temperature measurement. An example of an iridium alloy wire used in such electrodes is disclosed in Japanese Patent Laid-Open Publication No. 2015-90012 (Patent Document 2). The iridium alloy wire described in Patent Document 2 has improved properties such as oxidation resistance and mechanical properties in high-temperature environments. By adding a transition metal element or a high-melting point metal, such as platinum, ruthenium, rhodium, or nickel, to iridium and using the micro-pulling down method (μ-PD method), the shape of the crystal grains is controlled, and a wire with a small number of crystal grains equivalent to a single crystal is produced.

[0004] However, in Patent Document 2, when controlling the shape of crystal grains, it is limited to the preparation of inorganic material samples using a noble metal crucible, and has not been successful with metallic materials such as alloys due to reasons such as the reaction between the noble metal crucible and the molten metal. Here, a method for producing an iridium alloy using an improved crucible for the micro-pulling-down method is disclosed in JP 2017-200867 A (Patent Document 3). The method described in Patent Document 3 uses a crucible made of ceramics that has a wetting angle of 60° or more with the molten metal material, and the temperature of the bottom part of the crucible, which has an opening, is lowered while being kept below the freezing point of the metallic material that constitutes the metallic component. This makes it possible to produce components of desired shapes from metallic materials such as alloys using the micro-pulling-down method. Furthermore, based on the method described in Patent Document 3, ruthenium or ruthenium alloy wire or plate containing the maximum proportion of ruthenium is disclosed, for example, in International Patent Publication No. 2019 / 004273 (Patent Document 4).

[0005] The ruthenium alloy wire described in Patent Document 4 is a wire that not only has excellent high temperature resistance and oxidation resistance like alloy wires of iridium, platinum, ruthenium, and rhodium, but also has excellent ductility (e.g., the property of being easily bendable). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-32464 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-90012 [Patent Document 3] Japanese Patent Application Publication No. 2017-200867 [Patent Document 4] International Patent Publication No. 2019 / 004273 [Patent Document 5] Patent Publication No. 2021-18890 Summary of the Invention [Problem to be solved by the invention]

[0007] However, for example, in the case of the deposition cell disclosed in Patent Document 1 or a deposition cell using tantalum, although they have excellent high-temperature resistance, there are concerns about low electrical resistivity and a resulting decrease in temperature controllability due to an increase in current-carrying capacity, as well as a shortened lifespan due to evaporation during use and denaturation of the surface structure.

[0008] Furthermore, when considering electrical resistivity and temperature controllability in materials for EL vapor deposition cells, the use of iridium alloys according to the inventions of Patent Documents 2 and 3 is considered as the heating means for the cell, but while they are effective in terms of high temperature resistance and oxidation resistance as mentioned above, when used as a heating means such as a heater, it is unclear whether they can be used for the long term, and their workability, such as ductility, is unknown, and iridium itself is expensive. In light of these factors, it is considered to use ruthenium alloy wire or plate material as described in Patent Document 4.

[0009] Ruthenium itself is less expensive than iridium, has a high melting point like iridium, and like iridium, has high-temperature resistance and oxidation resistance, and is stable even at room temperature and atmospheric pressure. However, as a metallic solid, it is brittle. Even when used as a heater of some kind, ruthenium is used as a surface protection film rather than as a heating means, as disclosed in, for example, JP 2021-18890 A (Patent Document 5). Furthermore, due to its low solid solubility, ruthenium is difficult to form into alloys mainly composed of ruthenium, and has been used as a secondary metal to main metals such as iridium, tungsten, and nickel. As mentioned above, the ruthenium alloy wire described in Patent Document 4 is used as a heating means for, for example, evaporation cells and heaters for electroluminescence (EL) applications. However, the ruthenium alloy wire described in Patent Document 4 is described solely for improved mechanical properties such as high-temperature resistance, oxidation resistance, toughness, and ductility. The effects of workability, heat generation strength, electrical resistivity, temperature controllability, and other factors required for use as a heating means for heaters and the like are unknown.

[0010] In view of the above circumstances, the present invention provides a heater using a ruthenium alloy heating element (heat generating material) that has high electrical resistance, little temperature dependency, a long life, and excellent workability. [Means for solving the problem]

[0011] The object of the heater using the ruthenium alloy heating material according to the present invention is to: This can be achieved by providing a heater using a ruthenium alloy heating material made of an alloy of ruthenium and one or more different metal elements, wherein the ruthenium alloy heating material contains ruthenium in the maximum ratio.

[0012] The above object of the heater using the ruthenium alloy heating material according to the present invention is to This is more effectively achieved by the different metal element being tungsten, or by the ruthenium alloy heat generating material containing 50 to 70 at % ruthenium, or by the ruthenium alloy heat generating material containing 0.1 to 33 at % tungsten, or by the ruthenium alloy heat generating material further containing 0.1 to 33 at % molybdenum, or by the ruthenium alloy heat generating material being shaped like a wire, or by the ruthenium alloy heat generating material being shaped like a rod, or by the ruthenium alloy heat generating material being shaped like a plate. [Effects of the Invention]

[0013] In the present invention, a ruthenium alloy heat generating material having excellent workability and heat generating properties as well as high temperature resistance has been obtained. In particular, wire material has difficulty in maintaining its shape after bending due to springback, but it can be made to maintain its shape by applying heat treatment.

[0014] Furthermore, since the ruthenium alloy heat generating material according to the present invention has an appropriate strength, it can be processed into not only a wire but also a rod or a plate, and can be further processed by cold working. Furthermore, it is possible to produce a heater with high resistance, small temperature dependency, and long life using the heat generating material. [Brief explanation of the drawings]

[0015] [Figure 1] 10A and 10B are diagrams showing the state of a W—Mo—Ru alloy heater in Example 2 before and after heating. [Figure 2] 10 is a diagram showing the state of a tantalum heater (a comparative example to a W—Mo—Ru alloy heater) in Example 2 before and after heating. FIG. [Figure 3] 1 is an image of the surface of the heating part of a tantalum heater (comparative example) observed with a microscope. [Figure 4] 10 is a graph showing temperature changes in a durability test of Example 2. [Figure 5] 10 is a graph showing the relationship between voltage value and time in a durability test of Example 2. [Figure 6] 1A and 1B are diagrams showing a top heater and a bottom heater fabricated using a wire material related to a W—Mo—Ru based alloy heat generating material. [Figure 7] FIG. 10 is a diagram showing the current value (A) of the top heater and the current value (A) of the bottom heater of each of the heat generating material vapor deposition cell of the example and the tantalum vapor deposition cell of the comparative example in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described.

[0017] First, the ruthenium alloy heat generating material according to the present invention is basically composed of ruthenium and at least one or more different metal elements, and the heat generating material contains ruthenium at a maximum ratio. Incidentally, the "maximum ratio" as used in this specification will be described later.

[0018] The heterometal element in the ruthenium alloy heat generating material according to the present invention is a transition metal element, i.e., any of molybdenum (Mo), tantalum (Ta), tungsten (W), niobium (Nb), and rhenium. The heterometal element in the heat generating element of the present invention can be selected from the above elements, but considering the control of the electrical resistance of ruthenium (increasing resistance), temperature control, and various improvements in brittleness, tungsten (W) and / or molybdenum (Mo) are preferred. This is because these heterometal elements differ significantly from ruthenium in atomic radius and electronegativity, making them relatively easy to dissolve and sinter. Therefore, they are easily crystallized when alloyed, i.e., any crystal growth method (manufacturing method) can be used, including single crystal manufacturing processes such as the micro-pulling down method, the FZ method (floating zone method), and the zone melt method.

[0019] Here, the maximum ratio refers to a ratio such that, when considering the ratio between ruthenium and a metal other than ruthenium, i.e., the above-mentioned different metal elements, ruthenium is always greater than the above-mentioned different metal elements.

[0020] Next, in the ruthenium alloy heat generating material of the present invention, the atomic composition ratio of ruthenium (hereinafter referred to as "at %) is preferably 50 to 70 at %. If the ruthenium content is less than 50 at %, it is difficult to control the electrical resistance (to increase the resistance) and the temperature. If the ruthenium content is more than 70 at %, the heat generating material becomes brittle, and there is a concern that it will be difficult to process at high temperatures, let alone cold work, and this is not commercially viable.

[0021] Furthermore, the tungsten and molybdenum contents are preferably 0.1 to 33 at%. If the content is less than 0.1 at%, the material becomes brittle as a heat-generating material, making it difficult to process at high temperatures, let alone cold work. If the content is more than 33 at%, the maximum ratio mentioned above cannot be maintained, and it becomes difficult to control the electrical resistance (to increase the resistance) and temperature.

[0022] When ruthenium is combined with both tungsten and molybdenum, the atomic composition ratio is preferably ruthenium>tungsten≧molybdenum.

[0023] Furthermore, ruthenium may contain not only tungsten and / or molybdenum but also other different metal elements to form a quaternary or more system. In this case, the ruthenium alloy heat generating material according to the present invention preferably contains 0.1 to 20 at%. If it contains less than 0.1 at%, the heat generating material becomes brittle, making it difficult to process at high temperatures, let alone cold work. If it contains more than 20 at%, it becomes difficult to maintain the maximum ratio mentioned above, and it becomes difficult to control the electrical resistance (to increase the resistance) and temperature control.

[0024] When a new different metal element is combined with ruthenium, the atomic composition ratio is preferably ruthenium>tungsten≧molybdenum≧new different metal element.

[0025] To obtain wire with such limited hardness, it is necessary to process and manufacture it to the required wire diameter while restricting the processing conditions to prevent residual distortion; this manufacturing process will be described later. In this case, "wire" refers to a metal member in the form of a thin wire with a diameter of 0.1 mm or more and 3.0 mm or less. "Rod-shaped" refers to a cylindrical rod or stick-shaped metal member. "Plate" refers to a metal member having at least two linear regions in a cross section perpendicular to the longitudinal direction.

[0026] Next, a heater using the ruthenium alloy heating material according to the present invention will be described. However, the composition ratio of the ruthenium alloy heating material and the selection of metals for the heater are as described above. Below, the characteristics of the heater will be described in order.

[0027] The increase rate of the electrical resistance of a heater using the ruthenium alloy heating material of the present invention is 0.5% or less. If the increase rate is greater than 0.5%, it will lead to deterioration of temperature control. Here, the increase rate of the electrical resistance refers to the increase rate of the electrical resistance after heating a vapor deposition cell such as an EL.

[0028] The usable temperature of a heater using the ruthenium alloy heat generating material of the present invention is 1800° C. or less. If the usable temperature is higher than 1800° C., the heater will deteriorate.

[0029] In addition, in the case of a heater using a wire-shaped ruthenium alloy heating material, the diameter is preferably 0.5 to 1.5 mm, more preferably 0.8 to 1.2 mm. If the diameter is less than 0.5 mm, it cannot withstand high temperatures and becomes difficult to cold work. If the diameter is 1.5 mm or more, it will function well as a heater, but will not be able to cold work.

[0030] In the case of a heater using a rod-shaped ruthenium alloy heating material, the diameter is preferably 1.5 to 5.5 mm, more preferably 2.4 to 4.8 mm. If the diameter is less than 1.5 mm, it cannot withstand high temperatures. If the diameter is 5.5 mm or more, it will function well as a heater, but will not be able to be cold worked.

[0031] Furthermore, in the case of heaters using plate-shaped ruthenium alloy heating materials, the thickness is preferably 0.2 to 5.5 mm. If the thickness is less than 0.2 mm, it cannot withstand high temperatures. If the thickness is 5.5 mm or more, it will function well as a heater, but will not be able to be cold worked.

[0032] Next, a method for manufacturing a heater using the ruthenium alloy heating material of the present invention will be described using an example of manufacturing a heater having a vertical double spiral shape.

[0033] The wire of the ruthenium alloy heat generating material of the present invention, which has been prepared in advance, is folded in half, and the folded portion of the wire is fixed to a jig, which serves as the starting point for winding. At this time, the jig may be any known jig. The parameters of the wire, such as the atomic composition ratio and the rate of increase in electrical resistance, are as described above.

[0034] Next, the jig is rotated the required number of turns, that is, a spiral-shaped wire is produced.

[0035] Then, the pitch is adjusted to the required pitch using a pitch jig.

[0036] Thereafter, the jig is removed and the heater in the form of a vertical double spiral made of the wire of the ruthenium alloy heat generating material of the present invention is completed.

[0037] Before removing the jig (including the pitch jig), the wire is heat-treated while still fixed to the jig. This heat treatment is performed to reduce or eliminate springback of the heater, which is made of a spiral-shaped wire, in order to maintain the heater shape. Note that this heat treatment is performed in a vacuum (10 -2 ~10 -8 It is desirable to heat the heater at 800 to 1400°C for 1 to 3 hours under a pressure of 100 Pa. If the heat treatment is performed for less than 1 hour at a temperature below 800°C, springback will not be reduced effectively, making it difficult for the heater to maintain its shape. If the heat treatment is performed for more than 3 hours at a temperature higher than 1400°C, springback will be reduced effectively, i.e., the heater will be able to maintain its shape, but its lifespan will be shortened. The heat treatment method may be any known technique.

[0038] In the above, the method for manufacturing a heater using a ruthenium alloy heating material of the present invention has been described with reference to the example of manufacturing a heater having a longitudinal double helix shape, but when manufacturing a heater using a wire material, the heater may be manufactured not only in a helical shape but also by twisting or bundling the wire and then bending it. Note that the bending process referred to here may be any method.

[0039] In this manufacturing method, when a rod-shaped ruthenium alloy heating material is used, the heater is manufactured by bending the rod as necessary and then connecting both ends to electrodes. Note that the bending process here may be any method.

[0040] In this manufacturing method, when a plate-shaped ruthenium alloy heating material is used, the heater is manufactured by cutting it into the required shape by electric discharge machining, laser cutting, water cutting, shearing cutting, or by plastic processing, and then processing both ends to connect with electrodes. The plastic processing referred to here may be any method.

[0041] Although an embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to this embodiment, and various aspects may be adopted within the scope of the matters described in the specification, claims and / or drawings of this application. [Example]

[0042] An example of the embodiment described above will be described. Note that this example is merely an example, and the present invention is not limited to the following example, and various embodiments may be adopted within the scope of the matters described in the specification, claims, and / or drawings of the present application.

[0043] [Example 1] Preparation of heat generating material (wire) from W-Mo-Ru alloy A mass-production μ-PD furnace was used to fabricate wire from a ruthenium-tungsten-molybdenum alloy heat generating material (hereinafter referred to as "W-Mo-Ru alloy heat generating material" in this example). The ratios (at%) of ruthenium, tungsten, and molybdenum were 60 at%, 25 at%, and 15 at%, respectively. The fabricated W-Mo-Ru alloy heat generating material was a wire measuring 0.8 mm in diameter and 13.2 m in length, with a wire diameter error of less than ±20 μm measured with a micrometer. The surface exhibited a good metallic luster, with no defects such as scratches or chips. The electrical resistivity of the resulting wire was measured using the two-terminal method, and it was confirmed that the electrical resistivity within the wire was within 3%. The fabricated wire could be bent 180° at any desired bending radius, and it was also found to be durable against torsional deformation. This not only indicates that the composition is optimized, but also that the grain boundary density in the manufactured wire is low, and it has become clear that not only is it single crystal in the observed region, but it also has a single crystal or similar structure macroscopically.

[0044] [Example 2] Evaluation of heater using W-Mo-Ru alloy heating material Next, the W-Mo-Ru alloy heat generating material produced in Example 1 above was evaluated as a heater.

[0045] First, a coil-shaped heater (hereinafter referred to as a "W-Mo-Ru alloy heater" in this Example 2) was fabricated using the wire (Φ0.8 mm) fabricated in Example 1 above. As a comparative example for the W-Mo-Ru alloy heater, a coil-shaped heater (hereinafter referred to as a "tantalum heater") was fabricated using a tantalum wire similar to the W-Mo-Ru alloy heater. A durability test was conducted using a heating device (manufactured by Sunric Co., Ltd.). The appearance of the wire of the W-Mo-Ru alloy heater before heating (see FIG. 1(A)) and after 1000 hours of heating (see FIG. 1(B)) is shown in FIG. 1, and the appearance of the wire of the comparative tantalum heater before heating (see FIG. 2(A)) and after 1000 hours of heating (see FIG. 2(B)) is shown in FIG. 2. The test conditions were a temperature of 1600°C under vacuum conditions, and an applied constant current of 14.0 A (amperes). The results are shown in FIGS. 4 and 5. Figure 4 is a graph showing the temperature change during a durability test for a W-Mo-Ru alloy heater, with the vertical axis representing temperature (°C) and time (h). As can be seen from Figure 4, there was almost no change in temperature even after 3000 hours, meaning that the temperature remained constant without any drop.

[0046] The relationship between voltage and time (h) for the W-Mo-Ru alloy heater is shown in Figure 5. In Figure 5, both the maximum and minimum voltage values ​​(average value ±3σ) remained almost constant even after 3000 hours.

[0047] Furthermore, in Figure 1, although there was a slight change in the surface gloss of the W-Mo-Ru alloy heater before and after heating, there was almost no change in the surface properties (surface shape). On the other hand, in Figure 2, there was a clear change in the surface condition of the tantalum heater before and after heating. Furthermore, when the heated part surface of the tantalum heater was observed under a microscope, a bamboo structure was observed on the surface (see Figure 3). This is thought to be due to grain growth in the heated part. On the other hand, no bamboo structure was observed in the W-Mo-Ru alloy heater.

[0048] From the above, it was found that the W-Mo-Ru alloy heating material (W-Mo-Ru alloy heater) can withstand the relatively high temperature of 1600°C and has a durability of more than 1000 hours (approximately 3000 hours).

[0049] [Example 3] Preparation of an organic EL deposition cell using a heater made of a W-Mo-Ru alloy heating material and evaluation of its temperature characteristics (Part 1)

[0050] First, a top heater and a bottom heater of the same type as the evaporation source were fabricated by cold working using the wire (Φ0.8 mm) of the W-Mo-Ru-based alloy heat generating material fabricated in Example 1 above. These top heaters and bottom heaters are shown in FIG. 6. The fabricated top heater and bottom heater were incorporated into a crucible to form a vapor deposition cell (hereinafter referred to as the "example heat generating material vapor deposition cell"). On the other hand, as a comparative example, both the top heater and the bottom heater were made of tantalum (Ta), and they were incorporated into a crucible to form a vapor deposition cell (hereinafter referred to as the "comparative example tantalum vapor deposition cell").

[0051] In this Example 3, the durability of each of the prototype deposition cells was evaluated by evaluating the weight change and the surface condition by SEM / EDX under the conditions of a constant vacuum, various temperature conditions, and various time periods.

[0052] Next, the top temperature of both the example heat generating material vapor deposition cell and the comparative tantalum vapor deposition cell was increased in 11 steps (corresponding to "STEP 1 to 11" in Table 1), and the current value (A) of the top heater and the current value (A) of the bottom heater were measured for each of the example heat generating material vapor deposition cell and the comparative tantalum vapor deposition cell. FIG. 7 and Table 1 show a graph and a table of values ​​showing the changes. From FIG. 7 and Table 1, it was confirmed that the new alloy heater wire for the example heat generating material vapor deposition cell had a high resistance and could reach temperatures equivalent to those of the tantalum heater wire for the comparative tantalum vapor deposition cell, as well as that it could rise in temperature with a low applied current.

[0053] [Table 1]

[0054] Next, there was a large difference in the change in resistance value before and after the temperature rise test, and the additional effects of the new alloy were obtained. The results are shown in Table 2.

[0055] [Table 2]

[0056] In Table 2, for the comparative tantalum vapor deposition cell, the resistance increase rate before and after heating was approximately 3.3 to 3.9% for both the top and bottom heaters, whereas for the example heating material vapor deposition cell, the resistance increase rate before and after heating was approximately 0.14 to 0.33% for both the top and bottom heaters. This shows that there is a large difference in the increase or decrease in resistance value before and after heating, suggesting that the additional effects of the new alloy can be obtained.

[0057] Although the embodiments have been described above, the present invention is not limited to these embodiments, and it goes without saying that various embodiments can be adopted within the scope of the matters described in the specification, claims and / or drawings of this application. [Industrial Applicability]

[0058] The ruthenium-containing alloy of the present invention can be used to provide a heater having high electrical resistivity, and can be used not only for heaters used in evaporation cells but also for heaters related to devices used in other evaporation processes.

Claims

1. A heater using a W-Mo-Ru alloy heating material made of ruthenium, tungsten, and molybdenum, The W-Mo-Ru based alloy heat generating material contains 50 to 70 at % ruthenium, The W—Mo—Ru based alloy heat generating material contains 0.1 to 30 at % of tungsten, The W—Mo—Ru based alloy heat generating material contains 0.1 to 30 at % molybdenum, The W—Mo—Ru based alloy heat generating material contains ruthenium at a maximum ratio, The heater is characterized in that the rate of increase in electrical resistance is 0.5% or less and it can be used at temperatures of 1800°C or less.

2. 2. The heater according to claim 1, wherein the W--Mo--Ru based alloy heat generating material is wire-shaped and has a diameter of 0.5 to 1.5 mm.

3. 2. The heater according to claim 1, wherein the W--Mo--Ru based alloy heat generating material is rod-shaped and has a diameter of 1.5 to 5.5 mm.

4. 2. The heater according to claim 1, wherein the W--Mo--Ru based alloy heat generating material is in the form of a plate, and the thickness of the W--Mo--Ru based alloy heat generating material is 0.2 to 5.5 mm.

5. The heater of claim 1 , wherein the heater is for a deposition cell.

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