JP4640199B2 - Foil seal lamp - Google Patents

Description

  The present invention relates to a foil seal lamp in which a metal foil made of molybdenum and an external lead made of molybdenum are embedded in a seal portion.

  Conventionally, a foil-sealed lamp that uses a metal foil such as molybdenum for the power supply part of a discharge lamp or incandescent lamp to maintain the airtightness between the inside of the lamp and the outside of the lamp and to supply power to the internal electrodes and filaments. Is generally known. This will be described in detail below with reference to the drawings. FIG. 5 is an explanatory drawing showing a cross section along the tube axis of a DC lighting type discharge lamp, and FIG. 6 is an explanatory drawing showing an enlarged seal portion in FIG.

  This discharge lamp has an elliptical spherical arc tube portion 11 and a seal portion 12 continuously provided so as to extend outward from both ends of the arc tube portion 11. In the arc tube portion 11 in the discharge vessel 10, an anode 151 and a cathode 152 are arranged in close proximity with an arc gap. The anode 151 and the cathode 152 are made of tungsten, and both are fixed to the electrode rod 131 and the electrode rod 132, respectively. In one seal portion 12, an electrode rod 131 extends along the tube axis and one end thereof extends to the seal portion 12, and an electrical introduction body made of molybdenum hermetically sealed in the seal portion 12 It welds to the inner edge part of the metal foil 14 which becomes. This metal foil is a metal foil made of molybdenum, and the outer end portion of the metal foil is welded to the inner end portion of the external lead rod 15 protruding outward. The seal portion 12 related to the electrode rod 132 is constituted by a metal foil 14 made of molybdenum, like the one seal portion 12.

As an example of the above dimensions, the arc tube 11 has an outer diameter of 9 to 13 mm, an inner diameter of 4.0 to 5.0 mm, an arc gap of 0.9 mm to 1.3 mm, and the length of the discharge vessel 10 in the tube axis direction. The outer diameter of the seal portion 12 is 5.8 to 7.4 mm, and the inner volume of the arc tube portion 11 is 50 to 100 mm ³ . The electrode rods 131 and 132 have an outer diameter of 0.4 to 1.0 mm, preferably 0.5 to 0.8 mm. The metal foil 14 made of molybdenum has a thickness of 20 to 30 μm, preferably 25 μm, a length in the tube axis direction of 11 mm, and a width of 1.0 to 3.0 mm, preferably 1.5 mm. It is.

  In the seal portion 12 of the discharge lamp 10, as shown in an enlarged view in FIG. 6, a minute gap G from the outer end surface 3 </ b> A of the seal portion 12 to the molybdenum foil 14 exists around the external lead 15. To do. FIG. 6A is an explanatory view showing an enlarged view of the seal portion 12. FIG. 6B is a cross-sectional view showing the shape of the gap G in the case of a shrink seal, and the gap G on the metal foil (left in the drawing) is a cross section taken along the line MM in FIG. The gap G (right side of the drawing) of the lead bar and the glass only shows the LL cross section of FIG. Furthermore, in the case of a pinch seal, FIG. The gap formed on the metal foil has the same shape. However, in the case of a pinch seal, the lead bar 15 and the glass only portion are not formed around the lead bar 15 like a shrink seal, but are pinched. It becomes the shape which spreads in the direction orthogonal to the direction done.

  The reason why the gap G is formed will be described. When the seal portion 12 is formed by shrink seal, the metal foil 14 is sufficiently thin so that a large tensile stress is not generated on the glass and the metal foil 14 and the glass are in close contact with each other. Due to the high viscosity, the external lead 15 having a relatively large shape does not sufficiently flow along the shape of the external lead 15 and the difference in thermal expansion coefficient between the external lead 15 and the glass is large. 15 and glass are not completely adhered to each other, and a gap G is formed. In practice, it is impossible to completely eliminate the gap G.

In such a foil seal lamp, when the temperature of the seal portion 12 rises during lighting and the temperature of the metal foil 14 and the external lead 15 reaches 350 ° C. or more, the metal foil 14 and the external lead are introduced by the air entering the gap G. 15 is rapidly oxidized, MoO ₂ or MoO ₃ is formed on the surface thereof, and the volume of the metal foil 14 embedded in the seal portion 12 and the external lead 15 expands, and the seal portion 12 is cracked. The lamp was destroyed at the end.

  Although the lamp having the shrink seal structure has been described, the same applies to the pinch seal type incandescent lamp shown in FIG. As shown in FIG. 6-c), the gap G is formed between the metal foil 14 made of molybdenum embedded in the seal portion 12, the external lead 15 made of molybdenum, and the glass, and the above-described problem occurs. This is a common problem in foil seal lamps.

  Various techniques have been developed to suppress the oxidation of the molybdenum metal foil and the molybdenum external lead in the seal portion. In the past, U.S. Pat. No. 3,420,944 discloses that a half end of a metal foil made of molybdenum is coated with thin chrome. However, according to the technique disclosed in the publication, although the problem of oxidation of the metal foil is solved to some extent, another problem of lowering the adhesion strength with glass has occurred.

  Therefore, a new attempt is made in US Pat. No. 3,793,615. The chrome plating layer has a wedge shape or a taper shape, and the chrome layer is relatively thick at the outer end near the weld point of the external lead, and the metal foil that forms the hermetic seal is thin, so it is in close contact with the glass. The nature is also improved. With such a structure, oxidation of the metal foil made of molybdenum could be suppressed considerably.

In addition, US Pat. No. 5,217,711 discloses a method by ion implantation, a method of coating Al, Cr—Al, SIC, Si ₃ N ₄ in addition to Cr on a metal foil, and German Patent No. 3006846, sputtering, CVD, ion A method of coating metal foil with Cr, Ta, Nb, La, Sc, Hf, etc. in addition to Cr by a method such as injection is disclosed. However, these methods have a problem that the manufacturing cost is high because the coating is performed in advance before sealing.

  As described above, in the method of coating chromium on the metal foil or the external lead, the metal foil or external lead is coated with chromium, and then the sealing is performed, which makes the manufacturing process complicated and increases the manufacturing cost. there were. Furthermore, as environmental problems have recently become more serious, substances with a high environmental load have a tendency to be regulated, and chromium is no exception. Metal chromium itself is unlikely to be converted to hexavalent chromium, but mist containing hexavalent chromium generated from the electrolyzer in the plating process is thought to cause lung cancer. That is, the environmental impact of the manufacturing process also becomes a problem. Furthermore, the chromate film which decomposes chromic acid and chromium chloride as in US Pat. No. 3,420,944 has a problem of environmental impact due to the formation of hexavalent chromium.

On the other hand, in recent years, a method not using chromium is also disclosed. For example, Japanese Patent Application Laid-Open No. 9-12335 discloses a gap formed in a sealing portion with a fusion-sealed glass containing 55 to 85% Sb ₂ O ₃ , 5 to 30% B ₂ O ₃ and 1 to 18% Tl ₂ O _3. A method of closing is disclosed. However, Tl ₂ O ₃ used in the present technology has a problem of influence on the environment, and Sb ₂ O ₃ is also a substance having a relatively high environmental load.

  As a method for adding a sealing substance in the form of an aqueous solution from the gap after sealing, US Pat. No. 4,918,353 discloses a method for adding an alkali metal silicate into the gap. Furthermore, Japanese Patent Publication No. 6-54657 also discloses a method of generating a sealing substance mainly composed of lead or lead oxide in the gap after sealing. However, even in these methods, the influence on the environment has become a problem because lead oxide is used.

  In these methods, since the sealing material is formed after sealing, the manufacturing cost is relatively low compared with the aforementioned US Pat. No. 3,420,944, US Pat. No. 3,793,615, US Pat. No. 5,217,711, and German Patent 3006846. There are advantages.

Among such attempts, there is, for example, Japanese Patent Application Laid-Open No. 2004-139959 as a technique for improving the oxidation resistance at high temperatures. The gazette is a method of forming a protective film made of molybdate on a molybdenum foil and a molybdenum external lead after sealing, which can prevent oxidation reliably, has a low manufacturing cost, and uses a substance with high environmental impact. It's not an excellent way to solve the problems so far. However, the disclosed coating material reliably prevents oxidation of the molybdenum metal foil and the molybdenum external lead exposed in the gap of the seal part in an environment where the temperature of the seal part exceeds about 500 ° C. I couldn't. In order to solve this, the next disclosed technique is Japanese Patent Application Laid-Open No. 2005-228665, in which a second protective film made of alkali silicate is formed on a first protective film made of crystalline molybdate. This was a technology that significantly extended the life of the seal. According to the present invention, it has become possible to provide a foil-sealed lamp that reliably suppresses the oxidation of molybdenum foil and external leads even at a high temperature exceeding 500 ° C., and provides a long service life. However, this method has a problem in that the production process is complicated and the production takes time. Furthermore, as a demand from the market, a product that has a longer life and does not oxidize even at a high seal temperature has come to be demanded.
U.S. Pat.No. 3,420,944 U.S. Pat. No. 3,793,615 US Pat. No. 5,021,711 German Patent No. 3006846 U.S. Pat. No. 4,918,353 No. 6-54657 JP 2004-139959 A JP 2005-228665 A

  In view of the circumstances as described above, an object of the present invention is a foil seal that is a simple production method and that can realize a long-life lamp as a lamp without oxidizing the seal portion for a long time even at a higher temperature. To provide a lamp. In particular, even when the temperature is higher than 500 ° C., it is possible to reliably prevent oxidation of the molybdenum metal foil embedded in the seal portion and the external lead, to ensure a long life, and a simple method for manufacturing the protective film. A foil seal lamp is provided.

  The foil-sealed lamp according to the present invention has a sealing portion at the end of a glass envelope, a molybdenum metal foil embedded in the sealing portion, one end connected to the metal foil, and the other end In a foil seal lamp comprising an external lead made of molybdenum extending outside the envelope, on the surface of the metal foil embedded in the seal portion and the external lead, a molybdate double salt made of magnesium and sodium, and A protective film made of at least one of molybdate double salt made of magnesium and potassium is formed.

  The foil seal lamp of the present invention fills the gap formed between the glass of the seal portion, the metal foil made of molybdenum, and the external lead made of molybdenum with a protective film constituent sealing agent that serves as a protective film. By reacting the film constituent sealing agent with the metal foil and molybdenum constituting the external lead, the molybdenum surface constituting the metal foil and the external lead has a molybdate double salt composed of magnesium and sodium, or magnesium. Since the molybdic acid double salt composed of potassium and a protective film composed of a plurality of them are formed, it is ensured that the metal foil and the external lead are oxidized even when the temperature of the seal portion reaches 500 ° C. or higher. There is an advantage that a long-life foil seal lamp can be provided without being cracked in the seal portion. Furthermore, there is an advantage that the manufacturing method of the protective film is simplified.

  Here, the protective film-forming sealing agent here is typically a sealing agent of a nitrate aqueous solution. As a method for forming this protective film, a metal foil made of molybdenum in the seal portion is formed even when the temperature of the seal portion is as high as about 500 ° C. The external lead made of molybdenum does not oxidize and a good hermetic seal can be obtained, so that the foil seal lamp has a very long seal life. The protective film of the present invention is a molybdate double salt with a divalent metal (such as magnesium) containing a monovalent alkali element (such as potassium). In addition, the raw material consisting of mixed alkali element and magnesium, or magnesium nitrate and alkali silicate at the time of manufacture is reacted directly with molybdenum metal foil and external leads after coating and drying, and then molybdic acid consisting of magnesium and alkali. It is a double salt.

  The foil seal lamp of the present invention has a protective film made of a double salt of molybdate formed by adding sodium or potassium as an alkali to magnesium-based molybdate and a metal foil embedded in the seal portion of the foil seal lamp and the outside. It is formed on an extending external lead rod. In the present invention, potassium or sodium is selected as the monovalent alkali element, and magnesium is particularly selected as the divalent metal. The reason is described in each item below.

<Thermal expansion coefficient of the protective film on the molybdenum surface>
The protective film is preferably a crystalline molybdate having a thermal expansion coefficient similar to that of molybdenum constituting the metal foil or external lead. Specifically, the thermal expansion coefficient of the crystalline molybdate that is the protective film is close to 5.2 × 10 ⁻⁶ (250 ° C.) that is the thermal expansion coefficient of molybdenum constituting the metal foil or the external lead. good. When the crystalline molybdate is formed on the surface of molybdenum constituting the metal foil or the external lead, in the heat treatment process of the crystalline molybdate, no stress is applied. When returning, a stress is generated between the molybdate and the molybdenum. If the thermal expansion coefficient of the crystalline molybdate is greater than 5.2 × 10 ⁻⁶ (250 ° C.) which is the thermal expansion coefficient of molybdenum constituting the metal foil or the external lead, the crystalline molybdate is pulled against the metal foil or the external lead. If stress is applied and it is smaller than 5.2 × 10 ⁻⁶ (250 ° C.), compressive stress is applied. In addition, there are lamps in which the protective film is formed which are used to repeatedly blink in a relatively short time depending on use conditions. In this way, in a lamp that repeatedly blinks in a short time, a crack occurs in the crystalline molybdate that is a protective film, oxidation of molybdenum constituting the metal foil and the external lead proceeds, and stress is applied to the glass of the seal part. It occurs and the frequency that leads to glass breakage of the seal portion increases.

<Crystal structure of protective film on molybdenum surface>
As a result of searching for crystalline molybdate and searching for candidates based on the idea of matching the thermal expansion coefficient as described above, the molybdate has an iron manganese barite type structure and a celite type structure. And a substance group having a value close to the thermal expansion coefficient of Mo constituting the external lead. Here, in the crystalline molybdate AMoO ₄ , A is not limited to a divalent ion, but may be a double salt in which A is monovalent and trivalent 1: 1, or 4 instead of Mo. It may be a double salt in which 1: 1 is replaced with valent Ti and hexavalent Mo, and A is a trivalent rare earth metal.

In order to actually measure the thermal expansion coefficient of these crystalline molybdates, the inventors made elongated rectangular parallelepipeds of these crystalline molybdate crystals by the sintering method, and measured the thermal expansion coefficient. CoMoO ₄ , MnMoO ₄ , NiMoO _4, and MgMoO ₄ each have a coefficient of thermal expansion close to that of molybdenum of 5.2 × 10 ⁻⁶ (250 ° C.), which is a promising material. It was.

From the X-ray diffraction of a sample in which molybdate is formed on a molybdenum foil, all of the above films are molybdates with an iron manganese barite structure (Wolframite structure monoclinic space group C2 / m). I found out. A small amount of other compounds were also identified by the ASTM (American Society for Testing Materials) card and matched MoO ₃ and Mn ₂ O ₃ . Taking the ratio of the strongest peak intensities of the respective compounds, for example, MnMoO ₄ : Mn ₂ O ₃ : MoO ₃ = 75: 15: 10 in the case of manganese, and MgMoO ₄ : MgO: MoO in the case of magnesium. ₃ = 80: 15: 5. Since MoO ₃ is the sum of the substance formed as a reaction product and Mo of the metal foil oxidized in the air and heat treatment, it is not preferable from the viewpoint of an oxidation resistant coating. From this, it was found that the main products MnMoO ₄ and MgMoO ₄ are preferable films for oxidation resistance.

Furthermore, a lamp in which these substances were formed in the gap between the seal portion and the external lead was put in an electric furnace in an air atmosphere, and the life test of the protective film was performed. As a result, when a protective film reacted under a heat treatment condition with a large production rate of MnMoO ₄ or MgMoO ₄ is formed, a foil floating state in which a rainbow shape can be seen due to Newton rings, which is one index for evaluating the life of the lamp seal portion. It was found that the time to exit was the longest.

<Crystal transformation of protective film on molybdenum surface>
In addition, it is necessary that the crystalline molybdate does not have a crystal transformation below the service temperature of the seal portion. This is because when a crystal transformation exists, the volume changes greatly above and below the transformation point, and a large stress is applied to the crystalline molybdate, which leads to glass breakage of the seal portion. Considering this, molybdate was investigated experimentally and theoretically.

In celite type AMoO ₄ , when A = Sr, Ca, Ba, the thermal expansion coefficient often exceeds 10 × 10 ⁻⁶ . On the other hand, in AMoO ₄ having an iron manganese barite structure (Wolframite structure monoclinic space group C2 / m), A = Mg, Mn, Co, and Ni have 4 to 6.2 × 10 ^−6. This was confirmed by performing the thermal expansion coefficient measurement of the bar obtained by the sintering method using the literature and the actual oxide raw material. That is, a crystalline molybdate that is practically close to the thermal expansion coefficient of molybdenum constituting the metal foil or the external lead could be obtained.

It is pointed out that the values of these thermal expansion coefficients are smaller than the A = Sr, Ca, Ba molybdates of the celite type structure having the same AMoO ₄ . It is expected that there is a positive correlation between the lattice constant and the thermal expansion coefficient.

However, AMoO _4, A = Co, the crystalline molybdate Ni confirmed from the presence of crystal modification is the thermal analysis, the 400 ° C. in CoMoO _4, in NiMoO ₄ present in the 680 ° C.. At this time, volume change occurs above and below the transformation point, so CoMoO ₄ cannot be used for the protective film of the present invention. However, it is pointed out that it can be used at a temperature of 550 ° C. or lower by using a pseudo binary system such as (Co _0.4 Ni _0.6 ) MoO ₄ and increasing the transformation temperature.
On the other hand, if AMoO ₄ , A = Mn, and Mg, the thermal expansion coefficient is practically close to that of molybdenum constituting the metal foil and the external lead, and there is no crystal transformation. It becomes a protective film.

<Oxygen permeability>
Furthermore, when various studies were made on the reaction generation rate and oxygen permeability of crystalline molybdate, a better material was found. Among these molybdates, the MgMoO ₄ system showed particularly high temperature oxidation resistance. The reason for this is that the thermal expansion coefficient is close to that of the metal foil and the molybdenum that constitutes the external leads, and that the crystal structure is not affected by temperature, humidity, etc., and a stable film is formed. The reason is that MgMoO ₄ hardly transmits oxygen.

Under these protective films, there is molybdenum that constitutes metal foils and external leads, so if the film has a high rate of permeation of oxygen, the molybdenum under the film is oxidized faster and MoO ₂ and MoO ₃ are formed. It is thought that early destruction of the coating occurs.
Accordingly, a crystalline molybdate having a low oxygen permeability of the coating is preferable. Mn, Co, and Ni are transition metals, and the electronic structure can be changed depending on the crystal structure or atomic coordination, so that it becomes divalent or trivalent. The oxygen permeability of the crystalline molybdate that selects such a metal as the counterpart element tends to be large. That is, when oxygen permeates, the cation can change its valence according to the amount of oxygen that is the surrounding anion. Conversely, alkaline earth metals and Zn, Cd, and rare earth metals can only be divalent or trivalent, so the electronic state cannot be changed by the amount of oxygen ions around the cation, so the structure around the cation is It cannot be free. Therefore, the oxygen diffusion rate is slow. Alternatively, the structure of the crystalline molybdate is so stable that the valence cannot be changed flexibly according to the amount of surrounding oxygen.

It was proved in fact in the X-ray diffraction pattern. Peaks appear at diffraction angles 2θ = 58.60 ° and 73.68 °, which are diffraction lines from the molybdenum foil under the coating. The intensity of this peak depends not only on the thickness of the molybdate that is the film adhering to the top, but also strongly influenced by the degree of oxidation of the molybdate. It has been found that even if the thickness of the crystalline molybdate is constant, a decrease in this peak intensity as molybdenum oxidation proceeds is a good measure correlated with the degree of oxidation. In fact, in the case of transition metal Mn, Co, and Ni-based crystalline molybdates, the Mo diffraction peak decreases considerably quickly when the substrate on which the film is formed is placed at a high temperature, whereas the MgMoO ₄ film In such a case, the peak intensity does not decrease at a very long time at a high temperature.

That is, Mn, Co, and Ni are polyvalent metals, which is a cause of a high oxygen diffusion rate of a crystalline molybdate containing the metal, and a high oxygen permeability. As a result, it is expected that the coating film, which is a protective film of crystalline molybdate containing magnesium, has excellent oxidation resistance at high temperatures. That is, the reason why the MgMoO ₄ system exhibits particularly excellent high-temperature oxidation resistance is that the thermal expansion coefficient is close to that of molybdenum constituting a metal foil or an external lead, and that the crystal structure is stable without being affected by temperature or humidity. The reason is that MgMoO ₄ is difficult to transmit oxygen as described above.

However, the lifetime is short at a high temperature exceeding 500 ° C. due to a phenomenon called pasting. Furthermore, in order to develop a long-life protective film, Japanese Patent Application Laid-Open No. 2005-228665 disclosed a technique for suppressing pesting. In this technique, MgMoO ₄ is formed as the most effective crystalline molybdate as the first protective film. However, MgMoO ₄ is oxidized at an accelerated rate only by exceeding 500 ° C. by 50 ° C. It is a catastrophic oxidation called pasting. The starting point of oxidation is pores, cracks and grain boundaries. That is, the cause of pesting is that MgMoO ₄ originally has a very low oxygen solid solution rate and low oxygen permeability, but once oxygen permeates, the underlying molybdenum metal foil or external lead Mo Oxidation produces MoO _{3 in a} wedge shape and causes a volume expansion of 250%. The subsequent adsorption of oxygen at the pores and cracks lowers the surface energy and accelerates crack growth by plague-like oxidation. Furthermore, the volatilization of MoO ₃ additionally promotes crack growth at the defects. That is, the weight where the MoO ₃ occurs is only a small part of the original, but the destruction propagates to the surrounding protective film one after another, and finally leads to the complete collapse of the protective film. This is pasting. JP 2005-228665 A MoO ₃ formed in the wedge-shaped, made of a high temperature of the second 500 ° C. during lighting from the protective film, MgMoO ₄ coating by making the _Na 2 MoO ₄ was reacted Na ₂ O is immediately It is a technology that repairs the destruction of the material and prevents plague oxidation.

However, in addition to the double coating film disclosed in Japanese Patent Application Laid-Open No. 2005-228665, various molybdates were tested for a method for suppressing pesting, but their performance was not sufficient. That is, in addition to the crystalline molybdate disclosed in JP-A-2004-139959, a molybdate containing an alkali molybdate not directly disclosed in the art was tested. A ₂ MoO ₄ composed of a monovalent element such as alkali, MMoO ₄ composed of a divalent element such as alkali, or R ₂ (MoO) ₃ composed of a rare earth metal in R was tested. The life of the seal part was not sufficient with salt.

Therefore, in the present invention, a molybdate double salt made of magnesium and alkali was considered in place of the magnesium-based MgMoO ₄ molybdate having the best performance among the divalent elements. This is because, when alkali is added to the molybdate, a uniform film is formed in a consistent manner on the metal foil and the molybdenum substrate of the external lead, and it is expected that the oxygen permeability is small. In addition, it was examined which double salt with alkali element had good performance by fixing magnesium.

  The general remarks about molybdates are monovalent alkali metal molybdates, alkaline earth metal molybdates composed of divalent metals, and trivalent rare earth metal molybdates. , By itself, the crystal structure cannot be cubic. The crystal systems of the structures found in many of the above simple molybdates are hexagonal, trigonal, tetragonal, orthorhombic or monoclinic, but when they are formed as a stacked coating layer, they are non-cubic. Then it is disadvantageous. That is, if other lifetime factors are ignored, the stack of cubic crystal structures has a smaller gap, so that the coating layer is expected to be less likely to be oxidized and stable. By the way, the combination which takes a cubic crystal is known in the monovalent and the bivalent mixed crystal. FIG. 1 shows an example of the crystal structure of a molybdate double salt made of monovalent (eg, metal such as Li, K, Na, Rb) and divalent (eg, metal such as Mg, Fe, Co, Ni).

When the divalent molybdate MMoO ₄ and Li ₂ MoO ₄ interact, the composite molybdate Li ₂ M ₂ (MoO ₄ ) ₃ is obtained. However, with the divalent molybdate MMoO ₄ having a celite structure, a composite molybdate is not formed, and it becomes eutectic without exception. The interaction between the divalent element molybdate and Na ₂ MoO ₄ proceeds in a more complicated form as compared to the Li-based element. When it becomes a K, Rb, Cs system, it becomes a simple interaction again, and 1: 1 complex molybdate A ₂ M ₂ (MoO ₄ ) ₃ is stably formed. Cubic crystals also appear in the crystal structure. That is, the existence of 1: 1 is not known in Na, and the composition close to this is only the non-stoichiometric composition. This crystal system is monoclinic. On the other hand, it is known that when the alkali element is K, Rb, Cs and the ion radius is increased, a cubic salt known as languineite is formed by a double salt with a divalent element. In K, cubic crystals are formed only when Mg or Mn is combined, but as Rb and Cs and the ionic radius of alkali increase, the combinations of Co, Ni and cubic crystals expand in addition to Mg and Mn.

In addition to the crystal system, the difference in ionic radius is also related to the properties of the molybdate double salt. The ionic radius of Li ^{+ 1} (0.67A) is closest to the ionic radius of Mg ^{+ 2} (0.66A). ^{Na +1 (0.97A), K +1} (1.33A), increases in the order of Rb ⁺¹ (1.47A), ionic radius of Cs ⁺¹ (1.66A) is the largest, the Mg ⁺² The difference with the ion radius is widened. When molybdate double salt is made, the filling degree in the crystal structure is the highest in the Mg / Li system, and the crystal is considered to be stable. However, as a result, it is considered that the crystal system became non-cubic even when the degree of filling increased.

In view of the above, when an alkali is added instead of a magnesium-based MgMoO ₄ molybdate, a uniform film is formed consistently on the metal foil and the molybdenum substrate of the external lead, and the oxygen permeability is low. The test was conducted with various specifications of the molybdate double salt composed of magnesium and alkali. As a result, the protective film of the molybdate double salt consisting of magnesium and sodium and the molybdate double salt consisting of magnesium and potassium showed excellent test results.

As an example of this excellent molybdate, a reaction material of a mixed aqueous solution of magnesium nitrate and potassium nitrate and Mo foil was confirmed by X-ray diffraction. As a result, a diffraction pattern that closely matched K ₂ Mg ₂ (MoO ₄ ) _{3 of} JCPDS Powder Diffraction File was obtained. In addition, small amounts of K ₂ Mo ₂ O ₇ and Mg ₂ Mo ₃ O ₁₁ appeared. This small amount of material tended to increase with time in the atmosphere at 500 ° C.

The foil seal lamp of the present invention can be used in various lamps such as a discharge lamp for shrink-sealing a metal foil made of molybdenum and a halogen lamp for pinch-sealing. A first embodiment of the present invention will be described using a single-ended halogen lamp.
FIG. 3A is a schematic explanatory view showing a single-ended halogen lamp 20 in the present invention. In the single-ended halogen lamp 20, a filament 25 made of tungsten is disposed inside a sealing body 21 made of quartz glass, and is connected to a metal foil 22 made of molybdenum by an internal lead 26. In addition, a rare gas such as argon and a halogen gas such as bromine are sealed in the sealed body 21 as a buffer gas. These gases are sealed by a seal portion 23 in which one end of the sealing body 21 is sealed with a pinch seal. The metal foil 22 is embedded in the seal portion 23, and external leads 24 are connected to the metal foil 22. One end of the external lead 24 protrudes from the seal portion 23 to the outside.

  FIG. 3B is an enlarged explanatory view of the seal portion 23 in the single-ended halogen lamp 20, and is an enlarged view of a circle A portion indicated by a one-dot chain line in FIG. Between the external lead 24 made of molybdenum welded to one end (outer end portion 29) of the metal foil 22 embedded in the seal portion 23, and a fine gap between the quartz glass of the seal portion 23 27 is formed. A protective film constituting sealing material 28 is injected into the gap portion 27 so as to fill the gap portion 27. The protective film constituting sealing material 28 penetrates into the gap portion 27 by dropping an aqueous sealing agent solution from the gap portion end 27a opened in the outer end surface 23a of the seal portion 23, and It reaches the outer end 29 of the metal foil 22 made of molybdenum.

  Thus, the protective film constituting sealing material 28 reaching the outer end 29 of the metal foil 22 was naturally dried for 5 hours, then dried in a dryer at 130 ° C. for 15 minutes, and subsequently 510 ° C. The metal foil made of molybdenum and the external lead made of molybdenum protruding outside were coated by reacting with the Mo member in the lamp for 10 minutes in an electric furnace. In the electric furnace, the reaction was performed in an air atmosphere.

  In this way, a lamp for a life test was produced. Samples for comparative tests were prepared in the same manner. In the life test of various samples, the method of lighting the lamp is not adopted, the lamp is placed in an electric furnace, and the elapsed time until a crack occurs across both metal foils in the seal part is observed. did. In addition, the foil floating phenomenon was always seen before the cracks in the quartz glass, so this was also used as a reference for the judgment. It should be noted that such a life test that does not light the lamp does not match the actual lamp light life test, but it is known that it corresponds relatively well and is a simple and reliable determination method. (In an actual lamp lighting test, current flows through the metal foil and external leads, and self-heating is applied, so that the temperature load applied to the seal portion becomes more severe). In particular, it is useful for determining the lifetime of the protective film when the material specification of the protective film is changed or when the formation conditions are changed.

  FIG. 2 shows the specifications of the coating materials of various samples used for the life test and the expected molybdate of the coating material. These coating agents are for forming magnesium or alkali alone molybdate and magnesium / alkali molybdic acid double salt as a coating layer. Each sample is described below.

No. 1 is a magnesium nitrate to which sodium (Na) is added as an alkali. This is a 1: 1 mixture of an aqueous solution of magnesium nitrate and sodium nitrate (NaNO ₃ ). This mixed aqueous solution is applied to and dried on the external lead of the lamp and its gap, and then fired in an electric furnace at 510 ° C. for 10 minutes to react with the Mo member in the lamp, so that magnesium / sodium / molybdate (Na ₂ Mg ₂ (MoO ₄ ) ₃ ) is formed.

No. 2 is a case where sodium silicate (NaO · 2.91SiO ₂ ) added with sodium (Na) as an alkali and magnesium nitrate are used in combination. When an aqueous solution of sodium silicate and an aqueous solution of magnesium nitrate are mixed, a precipitate is formed and the mixture cannot be used as an aqueous solution. Then, it was made to react with molybdenum as follows. Magnesium nitrate (Mg (NO ₃ ) ₂ · 6H ₂ O) was poured into the gap, dried and applied to the molybdenum member, and then a sodium silicate aqueous solution was poured into the gap from the top and dried, followed by 510 ° C. Reacted with molybdenum parts in an electric furnace in the atmosphere. In any drying, after natural drying, it was dried in a drying furnace at 130 ° C. for 15 minutes. Here, the raw material is coated in two layers, but the reaction product with the molybdenum member at 510 ° C. is a single layer of molybdate. No. is generated. 1 is the same magnesium / sodium / molybdate (Na ₂ Mg ₂ (MoO ₄ ) ₃ ).

No. 3 is a magnesium nitrate to which potassium (K) is added as an alkali. This is a 1: 1 mixture of an aqueous solution of magnesium nitrate and potassium nitrate (KNO ₃ ). This mixed aqueous solution is applied to and dried on the external lead of the lamp and its gap, and then fired in an electric furnace at 510 ° C. for 10 minutes to react with the Mo member in the lamp, thereby producing magnesium, potassium, molybdate. (K ₂ Mg ₂ (MoO ₄ ) ₃ ) is formed.

No. 4 is a case where potassium silicate (K ₂ O · 4SiO ₂ ) added with potassium (K) as an alkali and magnesium nitrate are used in combination. When an aqueous solution of potassium silicate and an aqueous solution of magnesium nitrate were mixed, As in the case of 2, a precipitate is formed and the mixture cannot be used as an aqueous solution. Then, it was made to react with molybdenum as follows. Magnesium nitrate (Mg (NO ₃ ) ₂ · 6H ₂ O) was poured into the gap, dried and applied to the molybdenum member, and then an aqueous potassium silicate solution was poured into the gap from the top and dried, followed by 510 ° C. Reacted with molybdenum parts in an electric furnace in the atmosphere. In any drying, after natural drying, it was dried in a drying furnace at 130 ° C. for 15 minutes. Here, the raw material is coated in two layers, but the reaction product with the molybdenum member at 510 ° C. is a single layer of molybdate. No. is generated. 3 is the same magnesium, potassium and molybdate (K ₂ Mg ₂ (MoO ₄ ) ₃ ).

No. 5 is a magnesium nitrate to which rubidium (Rb) is added as an alkali. This is a 1: 1 mixture of an aqueous solution of magnesium nitrate and rubidium nitrate (RbNO ₃ ). This mixed aqueous solution is applied to and dried on the external lead of the lamp and its gap, and then fired in an electric furnace at 510 ° C. for 10 minutes to react with the Mo member in the lamp, thereby causing magnesium, rubidium, molybdate. (Rb ₂ Mg ₂ (MoO ₄ ) ₃ ) is formed.

No. 6 is a magnesium nitrate to which lithium (Li) is added as an alkali. This is a 1: 1 mixture of an aqueous solution of magnesium nitrate and lithium nitrate (LiNO ₃ ). This mixed aqueous solution is applied to and dried on the external lead of the lamp and its gap, and then fired in an electric furnace at 510 ° C. for 10 minutes to react with the Mo member in the lamp, and thereby magnesium, lithium molybdate. (Li ₂ Mg ₂ (MoO ₄ ) ₃ ) is formed.

No. 7 is a rubidium nitrate (RbNO ₃ ) as a comparative sample. This aqueous solution is applied to and dried on the external lead of the lamp and its gap, and then fired in an electric furnace at 510 ° C. for 10 minutes to react with the Mo member in the lamp, and molybdate (Rb ₂ MoO ₄ Or Rb ₂ Mo ₂ O ₇ ).

No. 8 is a potassium silicate as a comparative sample _{(K 2 O · 4SiO 2 ·} 45.5H 2 O). This aqueous solution is applied to and dried on the external leads of the lamp and the gaps, and then fired in an electric furnace at 510 ° C. for 10 minutes to react with the Mo member in the lamp and molybdate (K ₂ MoO ₄ Or K ₂ Mo ₂ O ₇ ).

No. 9 is sodium nitrate (Na (NO ₃ )) as a comparative sample. This aqueous solution is applied to and dried on the external leads of the lamp and the gaps, and then fired for 10 minutes in an electric furnace at 510 ° C. to react with the Mo member in the lamp, and molybdate (Na ₂ MoO ₄ Or Na ₂ Mo ₂ O ₇ ).

No. No. 10 described above 6 is an aqueous solution of lithium nitrate (LiNO ₃ ). This aqueous solution is applied to and dried on the external leads of the lamp and the gaps, and then fired for 10 minutes in an electric furnace at 510 ° C. to react with the Mo member in the lamp, thereby causing lithium molybdate (Li ₂ MoO ₄ or Li ₂ Mo ₂ O ₇ ) is formed.

No. 11 is a magnesium nitrate (Mg (NO ₃ ) 2 .6H ₂ O) as a comparative sample. This aqueous solution is applied to and dried on the external lead of the lamp and its gap, and then fired in an electric furnace at 510 ° C. for 10 minutes to react with the Mo member in the lamp and molybdate (MgMoO ₄ ) is formed. It is formed.

  To summarize each of the above samples, no. 1, no. 2, no. 3, no. 4, no. 5 and No. 6 is a molybdate double salt composed of magnesium and alkali produced from a mixed aqueous solution. No. 1, no. 2, no. 3, no. 4, no. 5, no. In each of Nos. 6 and 6, a mixed aqueous solution obtained by mixing an aqueous solution of magnesium nitrate and an aqueous solution of alkali nitrate at a ratio of 1: 1 is coated on molybdenum metal, dried, and fired to produce a molybdate double salt. In each sample, magnesium nitrate 1.2 mol / L and alkali nitrate 1.2 mol / L were dissolved to prepare a mixed aqueous solution.

No. 2 and No. No. 4 is a specification using alkali silicate as an alkali element, and when each aqueous solution is mixed, a precipitate is formed and does not become a mixed aqueous solution. Therefore, as described above, magnesium nitrate (Mg (NO ₃ ) ₂ · 6H ₂ O) is poured into the gap, dried and applied to the molybdenum member, and then an alkali silicate aqueous solution is poured into the gap and dried. Then, it was reacted with the molybdenum member in an electric furnace in the air at 510 ° C.

  Using these samples, a seal portion life test was performed. The result is shown in FIG. No. 1, no. 2, no. 3, no. 4, no. 5 and no. 6 is the seal part life test result of the molybdate double salt composed of magnesium and alkali. Of these, No. 2 and No. 4 is the result of sodium silicate or potassium silicate applied following magnesium nitrate. Other, No. 7, no. 8, no. 9, no. 10 and no. 11 is a life test result of a simple molybdate for comparison with the result of molybdate double salt.

  As a result of the test, the coating results of magnesium / sodium-based molybdate double salt (No. 1, No. 2) and magnesium / potassium-based molybdate double salt (No. 3, No. 4) were found to be simple molybdate (No. 1). No. 7, No. 8, No. 9, No. 10, and No. 11). On the other hand, the coating results of magnesium / rubidium molybdate double salt (No. 5) and magnesium / lithium molybdate double salt (No. 6) were obtained as simple molybdate (No. 7, No. 8, No. 9, No. 6). 10 and No. 11). Therefore, the protective film recommended as an effective sealing film-forming sealing material in the present invention is No. 1 and no. No. 2 magnesium / sodium molybdate double salt and No. 2 3. And No. 4 is a magnesium / potassium-based molybdic acid double salt.

  Although the composite molybdate is a coating having an intermediate composition of elemental molybdate, it does not take an intermediate life between them and is longer than any of the elemental molybdates (Mg / Na, Mg / K composite molybdenum) Acid salt), shorter than any of the simple substance (Mg / Li, Mg / Rb composite molybdate). This fact is not the result of mere mixing of Mg molybdate and alkali molybdate, but is evidence that a complex molybdate having a special structure and chemical bond was produced and performed.

  Considering the reason, when Mg / Li molybdate double salt is made, the filling degree in the crystal structure is the highest in the Mg / Li system, and the crystal is stable with the elements having the closest cation radius. it is conceivable that. However, as a result, the crystal system becomes a non-cubic system even when the degree of filling is high, and there is a large discrepancy in coating deposition and a large number of gaps. On the other hand, when the Mg / Rb molybdate double salt with the largest difference in cation radii is made, the crystal system becomes cubic and the coating deposition contradiction is the lowest, but conversely the atomic filling degree is the lowest. I think the oxygen transmission rate has also increased. Also, when the intermediate Mg / Na molybdate double salt and Mg / K molybdate double salt are made, there is not much difference in the cation radius in the former, and even if the crystal system is non-cubic, the filling degree Is relatively large, and even in the latter case, the difference in cation radius is large, but it is not so much cubic and the degree of packing is relatively large. Therefore, it is considered that a Mg / Na molybdic acid double salt and an Mg / K molybdic acid double salt intermediate in the alkali ion radius formed a film quality coating with good crystallinity and filling degree and low oxygen permeability.

As described above, with the Mg / K molybdate _double salt coating, an X-ray diffraction pattern well matched with K ₂ Mg ₂ (MoO ₄ ) ₃ was obtained, but in addition, a small amount of K ₂ Mo ₂ O ₇ and Mg ₂ Mo ₃ O ₁₁ appeared. This small amount of material tended to increase with time in the atmosphere at 500 ° C. This is considered that the reaction of K ₂ Mo ₂ O ₇ and Mg ₂ Mo ₃ O ₁₁ becomes rate-limiting rather than the underlying Mo is directly oxidized. That is, it means that the coating film is decomposed into K ₂ Mo ₂ O ₇ and Mg ₂ Mo ₃ O ₁₁ before it is broken and the base becomes MoO ₃ . K ₂ Mo ₂ O ₇ is a molybdate having the lowest melting point in the K ₂ O—MoO ₃ system, and the molybdate having the lowest melting point in both Mg ₂ Mo ₃ O ₁₁ and Mg—MoO _3. Therefore, it is expected from the reaction law side that it is divided into these two. Furthermore, since K ₂ Mo ₂ O ₇ has a melting point of 490 ° C., it becomes a fluid at the lamp seal temperature around 500 ° C., so that during the lamp life test, Mo will not flow directly over the surface of the Mo member. Maybe it's convenient to do. When considered in this way, it is natural that the coating of the molybdate double salt recited in the claims is a substance having a mechanism for protecting the underlying Mo foil and Mo external leads from oxidation.

The table | surface which shows the example of the crystal structure of the molybdate double salt made from monovalent and bivalent. The table | surface which shows the specification of the coating material used for the seal part life test of molybdate coating. Explanatory drawing of the foil seal lamp of the one-end sealing incandescent lamp type used as an Example. It is a seal part life test result of molybdate coating. Explanatory drawing which shows an example of a structure of the discharge lamp with a foil seal part in the cross section along a tube axis. The enlarged view which shows the space | gap of the sealing part of the foil seal lamp of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge lamp 10 Discharge vessel 11 Arc tube part 12 Sealing part 13 Electrode bar 131 Electrode bar 132 Electrode bar 14 Metal foil 15 External lead bar 151 Anode 152 Cathode G Cavity L Protective film 20 Single-ended halogen lamp 21 Enclosure 22 Metal foil 23 Seal part 23a Outer end face 24 External lead 25 Filament 26 Internal lead 27 Gap part 27a Gap part end 28 Sealing material for protective film construction 29 Outer end part

Claims (1)

A metal foil made of molybdenum having a seal portion at the end of the glass envelope, one end connected to the metal foil, and the other end extending to the outside of the envelope. In foil seal lamps with external leads,
A protective film made of at least one of a molybdate double salt made of magnesium and sodium and a molybdate double salt made of magnesium and potassium is formed on the surface of the metal foil embedded in the seal portion and the external lead. Foil seal lamp characterized by that.

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