JP2007012508A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp free from scattering and capable of obtaining the high durability of airtightness at an airtight sealing part and a long use life, in a process of forming the airtight sealing part in a coating film having a barrier function of restraining the diffusion of an alkaline ion existing in quartz glass in metal foil formed on the metal foil during its manufacturing process. <P>SOLUTION: The discharge lamp 10 is provided with a discharge vessel having a light-emitting tube 12 made of quartz glass with a pair of electrodes arranged inside, and a sealing part 13 fitted at the end of the light-emitting tube with metal foil made of molybdenum forming an electricity guide-in body buried at the sealing part of the discharge vessel. A coating film is made of a specific rare-earth metal molybdenum oxide is formed on at least one face of the metal foil. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge lamp having a structure in which a metal foil made of molybdenum is embedded in a sealing portion of a discharge vessel, such as an ultrahigh pressure mercury lamp that is used as a light source of a projector and operates at an extremely high mercury vapor pressure. It relates to a discharge lamp.

  As a light source lamp for a projection-type liquid crystal projector or the like, a discharge vessel having an elliptical spherical arc tube portion made of, for example, quartz glass and sealing portions connected to both ends of the arc tube portion is provided. A pair of electrodes are arranged opposite to each other in the portion, and an electrode rod related to these electrodes is a metal foil made of molybdenum (hereinafter also simply referred to as “molybdenum foil”) that forms an electric introduction body embedded in the sealing portion. An external lead bar is connected to the other end of the molybdenum foil, and an airtight seal is formed by fused and fused quartz glass forming a sealing portion on the surface of the molybdenum foil. A discharge lamp is used.

In recent years, as a discharge lamp used as a light source lamp of a liquid crystal projector or the like, in order to increase the light output per solid angle, for example, 0.16 mg / mm ³ or more of mercury is sealed in an arc tube portion, and during operation, An ultra-high pressure mercury lamp having an internal pressure of 1 × 10 ⁷ Pa or higher is used. In such an ultra-high pressure mercury lamp, a halogen such as bromine in an amount of 2 × 10 ^{−4 to} 7 × 10 ⁻³ μmol / mm ³ is usually enclosed in the arc tube portion in order to reduce electrode wear. Yes.

  However, in such an ultra-high pressure mercury lamp, the outer surface temperature of the arc tube portion of the discharge vessel reaches 1000 ° C. during its operation, so that the sealing portion is overheated and the molybdenum foil is sealed. The so-called “foil float” occurs in a state of being peeled off from the quartz glass forming the portion, and further, the quartz glass forming the sealing portion is cracked from the interface with the molybdenum foil, resulting in an airtight sealability. There was a problem of being lost.

In a discharge lamp having a structure in which molybdenum foil is embedded in the sealing portion of such a discharge vessel, the molybdenum foil is prevented from being oxidized by being overheated, and quartz that forms the sealing portion with the molybdenum foil is formed. In order to improve the adhesion to glass, it has been proposed to form a coating film on the surface of the molybdenum foil to increase its oxidation resistance and hermetic sealing properties.
Specifically, for example, a film made of silica having a thickness of 3 to 20 μm is formed as a coating film (see Patent Document 1), silica 60 to 70% by mass, alumina 3 to 20% by mass, oxidation It has been proposed to form a film made of high silicate glass containing 12 to 18% by mass of potassium (see Patent Document 2), and the molybdenum foil on which such a coating film is formed emits light. When used in a discharge lamp in which halogen is enclosed in the tube and the internal pressure during operation is extremely high, sufficient adhesion to the glass forming the sealing part required for the molybdenum foil is obtained. Furthermore, it has been found that there is a problem that the service life is extremely short because cracks occur in the glass of the sealing portion due to factors other than oxidation of the molybdenum foil. Thus, as the coating film, a film made of silica having a thickness of 80 to 2500 μm (see Patent Document 3), a film made of a specific metal such as niobium (Nb) and tantalum (Ta), A multilayer film is formed by laminating a film made of the oxide of the specific metal on this film (see Patent Document 4), simple oxides such as titanium oxide and lanthanum oxide, or zirconium oxide and yttrium oxide And the like (see Patent Document 5) have been proposed.

Here, according to the discharge lamp according to Patent Document 3, high oxidation resistance is obtained in the molybdenum foil, and the glass that forms the sealing portion with the molybdenum foil under the lamp operation, which is one of the causes of cracks, Since it can prevent that the interface of this is attacked by a halogen, generation | occurrence | production of the crack in a sealing part can be suppressed.
Further, in the discharge lamps as shown in Patent Document 4 and Patent Document 5, high oxidation resistance is obtained for the molybdenum foil, and alkali ions move from the glass forming the sealing portion or from the glass surface. Therefore, it is possible to prevent the molybdenum foil from being peeled off from the glass due to the accumulation in the vicinity of the molybdenum foil.

By using the molybdenum foil having such a coating film, the arc tube portion is small and the internal pressure during operation is as high as 1.2 × 10 ⁷ Pa or more. Although the lifetime can be obtained, these coating films are formed by a vapor deposition method such as sputtering, electron cyclotron resonance (ECR), chemical vapor deposition (CVD), or physical deposition. For this reason, there are problems that the manufacturing cost related to the formation of the coating film is increased and scattering occurs in the process of forming the hermetic seal portion on the coating film.

Here, the scattering of the coating film generated in the process of forming the hermetic seal portion is not caused by the boiling point or vapor pressure, which are physical properties of the coating film itself, and the adhesion of the coating film to the molybdenum foil is small. It is guessed that this is due to this. In other words, the coating film formed by the physical deposition method is not chemically bonded to the molybdenum foil, but is bonded by a small binding energy such as the Van der Waals force, which is also physically called dispersion force. It is presumed that the adhesion to the molybdenum foil is small, and this van der Waals force is generally also present between the thin film and the substrate, and its energy is generally In addition, it is about 1/100 smaller than the cohesive energy of a substance at about several kJ / mol (Masao Kotani et al., “Chemical Physics I”, Kyoritsu Shuppan, Showa 33, p20). This is because when a titanium carbide (TiC) layer is formed on the surface of a steel substrate by a sputtering method in order to improve wear resistance, oxygen is actively introduced and the formula: TiC _X O _1-X (Wherein x is an integer of 2 or more) is also suggested by an example in which the adhesion to the substrate is reduced to 1/5 compared to the case where a layer made of the compound represented by (A. Pan and JE Greene; Thin Solid Films, 97 (1982) 73-89.).
In fact, the inventors formed an airtight seal even when a coating film made of a compound such as magnesium oxide having a boiling point of 3600 ° C. or higher was formed on a molybdenum foil by sputtering. It is experienced that scattering occurs in the coating film during the process.

JP-A-11-111240 Japanese Patent Laid-Open No. Sho 62-147650 JP 2002-358931 A JP 2003-317659 A JP 2003-86135 A

  The present invention has been made on the basis of the circumstances as described above, and its purpose is to diffuse alkali ions present in the quartz glass formed on the metal foil in the manufacturing process to the metal foil. Disclosed is a discharge lamp that does not cause scattering in the step of forming a hermetic seal portion on a coating film having a barrier function that suppresses this, and has a high durability and a long service life in the hermetic seal portion. It is in.

The discharge lamp of the present invention comprises a discharge vessel comprising an arc tube portion made of quartz glass and having a pair of electrodes disposed therein, and a sealing portion provided at an end of the arc tube portion, In a discharge lamp in which a metal foil made of molybdenum forming an electric introduction body is embedded in a sealing portion of a discharge vessel,
A coating film made of an oxide represented by the following general formula (1) or an oxide represented by the following general formula (2) is formed on at least one surface of the metal foil.

[Wherein, Ln represents a rare earth metal element selected from scandium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. ]

[Wherein, Ln represents a rare earth metal element selected from scandium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. ]

  In the discharge lamp of the present invention, a layer made of a silicate represented by the following general formula (3) is formed on the surface layer portion including the interface in close contact with the quartz glass constituting the discharge vessel in the coating film formed on the metal foil. Preferably it is formed.

[Wherein, Ln represents a rare earth metal element selected from scandium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. ]

According to the discharge lamp of the present invention, since at least one surface of the metal foil made of molybdenum forming the electrical introduction body in the hermetic seal portion is covered with the coating film, the metal foil is prevented from being oxidized by overheating. The coating film is formed of rare earth metal molybdenum oxide, which is a compound generated by chemically reacting with molybdenum constituting the metal foil, and is chemically bonded to the metal foil. As a result, high adhesion to the metal foil is obtained, so that no scattering occurs in the process of forming the hermetic seal portion, and this coating film is chemically coupled with quartz glass forming the sealing portion. Since the hermetic seal part is formed by connecting them together, high adhesion to quartz glass can be obtained. Even when the airtightness and the stability of the airtight state are obtained, and alkali ions such as alkali metal ions present as impurities in the quartz glass constituting the discharge vessel move and accumulate in the vicinity of the metal foil, Since the action of the barrier function of the coating film prevents the alkali ions from diffusing to the interface on the metal foil side, the metal foil does not peel from the quartz glass due to the influence of the alkali ions.
Therefore, according to the discharge lamp of the present invention, the coating film formed on the metal foil is not scattered in the manufacturing process, and the airtight seal portion is formed even in a state where the internal pressure of the arc tube portion is high. High airtight durability is obtained, and a long service life is obtained.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory cross-sectional view showing an example of the configuration of a discharge lamp according to the present invention in a cross-section along the tube axis, and FIG. 2 is an explanatory cross-sectional view showing an enlarged hermetic seal portion in FIG. is there.

The discharge lamp 10 is a direct current lighting type discharge lamp, and includes an elliptic spherical arc tube portion 12 and sealing portions 13 that are continuously provided so as to extend outward from both ends of the arc tube portion 12. The discharge vessel 11 made of quartz glass is provided, and a metal foil (molybdenum foil) 14 made of molybdenum forming an electric introducing body is hermetically embedded in the sealing portion 13 so that an airtight seal portion 15 is formed. Is formed. In this discharge vessel 11, the base end is electrically connected to the inner end portion of one (left side in FIG. 1) molybdenum foil 14 by welding, and protrudes and extends inward in the tube axis direction, for example, made of tungsten. The anode 18 formed at the tip of the electrode rod 16 and the inner end of the other (right side in FIG. 1) molybdenum foil 14 are electrically connected by welding to protrude inward in the tube axis direction. A cathode 17 formed at the tip of an electrode rod 16 made of, for example, tungsten, which is extended, faces each other in the internal space surrounded by the arc tube portion 12 and is in a close proximity state.
In this figure, 19 is an external lead bar which is electrically connected to the outer end of the molybdenum foil 14 by welding and a part thereof extends into the sealing part 13. The external lead bar 19 and the molybdenum foil 14 An anode mount is formed by the electrode rod 16 on which the anode 18 is formed, and a cathode mount is formed by the electrode rod 16 on which the external lead rod 19, the molybdenum foil 14 and the cathode 17 are formed.

Taking the dimension example of the discharge lamp 10 as described above, the maximum outer diameter of the arc tube portion 12 is 9 to 13 mm, the maximum inner diameter of the arc tube portion 12 is 4.0 to 5.0 mm, and the distance between the electrodes is 0.9 to 1. .3 mm, the total length of the internal space of the discharge vessel 11 (length in the tube axis direction) is 9.0 to 11.0 mm, the length of the sealing portion 13 is 16 to 50 mm, and the outer diameter of the sealing portion 13 is 5. 0 to 7.4 mm, and the volume of the internal space is 50 to 100 mm ³ .

The electrode rod 16 has a maximum outer diameter of 0.4 to 1.0 mm, preferably 0.5 to 0.8 mm, for example.
Moreover, the molybdenum foil 14 is a thin strip-shaped thing, for example, the thickness is 20-30 micrometers, Preferably it is 25 micrometers, The length of the pipe-axis direction is 7.0-15.0 mm, Preferably it is 11 mm. And the width is 1.0 to 3.0 mm, preferably 1.5 mm.

  Then, on both surfaces of the molybdenum foil 14, as shown in FIG. 3, quartz that forms the molybdenum foil 14 and the sealing portion 13 in a region other than the connection portions of the electrode rod 16 and the external lead rod 19 on the entire surface. An oxide (hereinafter also referred to as “first specific molybdenum oxide”) represented by the above general formula (1) or an oxide represented by the above general formula (2). Hereinafter, a coating film (hereinafter also referred to as “specific coating film”) 20 made of “second specific molybdenum oxide”) is formed.

In the general formulas (1) and (2), Ln represents scandium (Sc), yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er). , A rare earth metal element selected from thulium (Tm), ytterbium (Yb), and lutetium (Lu) (hereinafter also referred to as “specific rare earth metal element”).
In general, the rare earth metal element is a group of 17 elements (hereinafter referred to as “rare earth”) obtained by adding scandium and yttrium to 15 elements from lanthanum having an atomic number of 57 to lutetium having an atomic number of 71. Also referred to as a “metal element group”), and 10 of these elements are “specific rare earth metal elements” in this specification.

The first specific molybdenum oxide is crystalline, and its melting point is required to be equal to or higher than the temperature at which the molybdenum foil 14 is exposed in the step of forming the hermetic seal portion 15. Based on the relationship between the cell volume, the ionic radius and the melting point, it is estimated that the temperature is 2000 ° C. or higher. The first specific molybdenum oxide constituting the film 20 is not in a molten state, and no cracks are generated in the hermetic seal portion 15, and vacancies existing in the crystal structure are not present in the discharge lamp 10. It is smaller than the alkali ions accumulated in the vicinity of the molybdenum foil 14.
Further, the first specific molybdenum oxide is chemically bonded by forming a compound with quartz glass forming the sealing portion 13.

On the other hand, the second specific molybdenum oxide is crystalline, and its melting point is required to be equal to or higher than the temperature at which the molybdenum foil 14 is exposed in the step of forming the hermetic seal portion 15. Is estimated to be 2200 ° C. or higher, which is higher than the melting point of the first specific molybdenum oxide, from the relationship between the unit cell volume, the ionic radius, and the melting point, whereby the temperature of the step of forming the hermetic seal portion 15 is increased. Even under a high temperature condition of 1900 ° C. or higher, the second specific molybdenum oxide constituting the specific coating film 20 is not in a molten state, and the airtight seal portion 15 is not cracked, The vacancies existing in the crystal structure are smaller than the alkali ions accumulated near the molybdenum foil 14 in the discharge lamp 10.
The second specific molybdenum oxide is chemically bonded by forming a compound with quartz glass forming the sealing portion 13.

Here, the reason why the first specific molybdenum oxide or the second specific molybdenum oxide is selected as the oxide constituting the specific coating film 20 formed on the molybdenum foil 14 will be described.
In general, the metal molybdenum oxide is generated by a powder sintering method and is represented by the formula: R _m O _n (wherein R represents a metal element that can be a cation, and m and n are integers). ) And a metal oxide represented by the formula: MoO ₃ , and compounds having stability of several crystal structures having different ratios are known. However, these melting points are increased as the ratio of the molybdenum oxide represented by the formula: MoO ₃ to the metal oxide represented by the formula: R _m O _n increases, that is, the proportion of the metal oxide increases. It tends to be higher. Based on this, as a result of investigating a metal molybdenum oxide having a high melting point that can withstand a high temperature condition in which the temperature of the hermetic seal portion in the manufacturing process of the discharge lamp is 2000 ° C., the formula: R only those R of the metal oxide represented by _m O _n is lanthanoid a trivalent rare earth metal element has been found to be appropriate. As the rare earth metal molybdenum oxide, a compound represented by the formula: Ln ′ ₂ (MoO ₄ ) ₃ , a compound represented by the formula: Ln ′ ₂ Mo ₂ O ₉ , a formula: Ln ′ ₂ Mo ₂ O ₇ A compound represented by the formula: Ln ′ ₂ MoO ₆ and a compound represented by the formula: Ln ′ ₆ MoO ₁₂ (in the above formula, Ln ′ was selected from the group of rare earth metal elements) Among them, a compound represented by the formula: Ln ′ ₂ MoO ₆ and a compound represented by the formula: Ln ′ ₆ MoO ₁₂ have a melting point of 2000 ° C. or higher. May have. Therefore, the material of the coating film on which the rare earth metal molybdenum oxide selected from these compounds represented by the formula: Ln ′ ₂ MoO ₆ and the compound represented by the formula: Ln ′ ₆ MoO ₁₂ is formed on the molybdenum foil. As a result, it has been inferred that the tightness of the hermetic seal portion in the discharge lamp having a configuration in which molybdenum foil is embedded in the sealing portion of the discharge vessel can be achieved.

The melting point of each of the compound represented by the formula: Ln ′ ₂ MoO ₆ and the compound represented by the formula: Ln ′ ₆ MoO ₁₂ (hereinafter collectively referred to as “specific rare earth metal molybdenum oxide”). Was estimated based on the relationship between the unit cell volume, the ionic radius, and the melting point, and an appropriate one of these specific rare earth metal molybdenum oxides was used as a compound for constituting the specific coating film 20. That is, many crystallographic studies have obtained many data on the unit cell volume of the compound represented by the formula: Ln ′ ₂ MoO ₆ and the compound represented by the formula: Ln ′ ₆ MoO ₁₂ . However, the melting point is not clear. However, it is known that Mo ⁶⁺ (molybdenum ion) has an ion radius of 0.62Å and the same ion radius as W ⁶⁺ (tungsten ion). Since it is known that there is a correlation between the same unit cell volume and the rare earth metal element, the rare earth metal tungsten oxide has the same chemical bonding force as the specific rare earth metal molybdenum oxide, and its melting point is Presumed to show a value close to the melting point of the specific rare earth metal molybdenum oxide, based on such an idea, based on the melting point of the rare earth metal tungsten oxide that has been clarified, the specific rare earth metal molybdenum that has not been clarified The estimation of the melting point of the oxide was considered.
Specifically, for each of the compound represented by the formula: Ln ′ ₂ MoO ₆ and the compound represented by the formula: Ln ′ ₂ WO ₆ , the horizontal axis in FIG. On the vertical axis, Schlusselelement: d (9)-, d (10)-, d (1). . . d (3)-, f-elemente, W.M. P. A Weiss (Landolt-Bornstein Zahlenwerte unFunktionen aus Naturewissenshaften und Technik, also referred to as "Let: 1 Fig. 5 shows a plot of unit cell volume. Fig. 5 shows the rare earth metal elements arranged in order from the smallest atomic number on the horizontal axis and the melting point (provided in the literature etc.) plotted on the vertical axis. From these figures, it is suggested that the melting point tends to increase as the unit cell volume decreases, and that the ionic radius and the value of the 1/3 power of the unit cell volume have a proportional relationship. From the above, it is suggested that the binding force between ions, which is represented simply by the size of the melting point, increases as the ionic radius decreases, that is, so-called lanthanide contraction. Such a relationship as shown in FIG. 4 and FIG. 5 is a well-known relationship in all rare earth metal element oxides (Ln ′ ₂ O ₃ ) except for the radioactive element promethium (Pm). Since the oxide (Ln ′ ₂ O ₃ ) has a relationship that the melting point increases as the atomic number increases, this relationship also holds for the compound represented by the formula: Ln ′ ₂ MoO _6. I guessed. As a result, among the compounds represented by the formula: Ln ′ ₂ MoO ₆ , the unit cell volume is 119Å ³ or less, Ln ′ is scandium (Sc), yttrium (Y), gadolinium (Gd), terbium (Tb), It was estimated that dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) or lutetium (Lu) would have a melting point of 2000 ° C. or higher.
For each of the compound represented by the formula: Ln ′ ₆ MoO ₁₂ and the compound represented by the formula: Ln ′ ₆ WO ₁₂ , the horizontal axis in FIG. FIG. 7 shows a plot of the unit cell volume calculated from the lattice constant described in Reference 1, and FIG. 7 shows the rare earth metal elements arranged in order from the smallest atomic number on the horizontal axis and the melting point (however, the literature etc. As a result of inferring in the same manner as described above, the unit cell volume of the compound represented by the formula: Ln ′ ₆ MoO ₁₂ is 309 Å ³ or less, and Ln ′ is Scandium (Sc), yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) It estimated that it would have a melting point that is lutetium (Lu) becomes 2200 ° C. or higher.

In each of the first molybdenum oxide or the second molybdenum oxide constituting the specific coating film 20 described above, vacancies existing in the crystal structure are accumulated in the vicinity of the molybdenum foil 14 in the discharge lamp 10. The grounds for being smaller than the alkali ions will be described.
The compound represented by the formula: Ln ′ ₂ MoO ₆ has a chemical structure obtained by modifying the fluorite (CaF ₂ ) structure as a whole. Specifically, Ln ′ is a lanthanum (La) having a large ionic radius. Is a tetragonal space group I-42m, and only when Ln ′ is cerium (Ce) has a fluorite structure of cubic space group Fm3m, and Ln ′ has an intermediate ionic radius. In the case of praseodymium (Pr) and neodymium (Nd), the intermediate state becomes a cubic structure at a low temperature and a celite structure (tetragonal, space group I41 / a) at a high temperature. Is yttrium (Y) and samarium (Sm) to lutetium (Lu) having a small ionic radius, a fluorite deformed structure that forms a monoclinic space group C2 / c is obtained. In this fluorite (CaF ₂ ) deformation structure, the position of Ca is occupied by two Ln ′ and one Mo, and the position of F at the tetrahedral site is occupied by six O, The site occupancy is perfect. In addition, J.H. A. Alonso, F.M. Rivillas, M.M. J. et al. Martinez-Lope, and V.M. Pomjakushin; Solid State Chemistry, 177 (2004) 2470-2476. (Hereinafter also referred to as “Reference 2”), while coordination Ln′O ₈ has almost cubic symmetry, coordination MoO ₈ has symmetry distorted from cubic. The coordination Ln′O ₈ and the coordination MoO ₈ are connected via a common oxygen located in the corner. Therefore, it is only the octahedral site that alkali ions such as sodium ions may enter as impurities during discharge lamp materials such as ultra-high pressure mercury lamps and their manufacturing processes. It was confirmed by calculating the size of the vacancies related to the octahedral site whether or not vacancies that allow sodium ions to enter the octahedral sites surrounded by these six Ln ′. Is from dysprosium (Dy) to lutetium (Lu) and yttrium (Y) with a maximum radius of 0.761 to 0.748 Å, which corresponds to an ionic radius of sodium (Na) of 0.97 Smaller than that. Therefore, sodium ions cannot enter the pores having these sizes.
The chemical structure of the compound represented by the formula: Ln ′ ₆ MoO ₁₂ is the same as the fluorite (CaF ₂ ) structure when Ln ′ is yttrium (Y) and lanthanum (La) to holmium (Ho). When Ln ′ is erbium (Er), it transforms into a tetragonal space group R3 at low temperatures and a space group Fm3m with cubic symmetry at high temperatures. It is known that when Ln ′ is thulium (Tm) to lutetium (Lu) having a small ion radius, an ilmenite crystal structure having a tetragonal space group R3 is obtained. All of these are predicted to have defects in 1/8 of the tetrahedral sites where O enters, and when the size of vacancies made of these defects is calculated, ions of sodium (Na) Since the radius is larger than 0.97 mm, sodium ions can enter this hole. However, when the compound represented by the formula: Ln ′ ₆ MoO ₁₂ is observed by X-ray diffraction, there are many diffraction lines related to the weakly ordered state. Although it is predicted that there are no more detailed crystal structures at this time, it is not clear whether the aforementioned tetrahedral site defects actually exist. Rather, like the compound represented by the formula: Ln ′ ₂ MoO ₆ , the tetrahedral site defect disappears by the coordination of coordination Ln′O ₈ as a polyhedron with highly distorted coordination MoO _8. There is also a possibility. If it does so, the site | part in which alkali ions, such as a sodium ion, may enter | penetrate as an impurity in the materials of discharge lamps, such as an ultrahigh pressure mercury lamp, and its manufacturing process is only an octahedral site. Therefore, like the compound represented by the formula: Ln ′ ₂ MoO ₆ , the compound represented by the formula: Ln ′ ₆ MoO ₁₂ cannot contain sodium ions in its structure.

  The specific coating film 20 preferably has a thickness of 50 to 500 nm.

In addition, the surface layer portion including the interface of the specific coating film 20 that is fused and adhered to the quartz glass constituting the discharge vessel 11 is a layer made of a rare earth metal molybdenum silicate represented by the above general formula (3) (hereinafter, Also referred to as “silicate layer”) 21 is preferably formed.
The rare earth metal molybdenum silicate represented by the general formula (3) constituting the silicate layer 21 is crystalline, and the alkali in which the vacancies existing in the crystal structure are accumulated in the vicinity of the molybdenum foil 14 in the discharge lamp 10. It is smaller than ions.

Here, the grounds that the silicate layer 21 has pores existing in the crystal structure smaller than the alkali ions accumulated in the vicinity of the molybdenum foil 14 in the discharge lamp 10 will be described.
According to Reference 2, the crystal structure of the rare earth metal molybdenum silicate represented by the formula: Ln ′ ₂ SiMoO ₈ (wherein Ln ′ represents an element selected from the group of rare earth metal elements) is Ln ′. Is yttrium (Y), it has a zircon structure (tetragonal, space group I41 / amd), and when Ln ′ is other than yttrium (Y), it has a β ferrugsonite structure (single It is said that it transforms into a celite type structure (tetragonal, space group I41 / a) at high temperatures, and the short-range structures of these three structures are very similar to each other. is doing. That is, the laminated state of the SiO ₄ tetrahedron, the MoO ₄ tetrahedron and the coordination Ln ′ (Si, Mo) _{8 in} the C-axis direction is the same as that of the celite type structure. Therefore, when Ln ′ is yttrium (Y), the structure is a zircon structure, and when Ln ′ is lanthanum (La) to lutetium (Lu), the structure is a celite structure in consideration of the actual temperature used. It was confirmed by calculating the size of the vacancies related to the octahedral site whether or not there are vacancies into which sodium ions can enter. , The maximum radius is 0.89 to 0.91 A, which is smaller than the ionic radius 0.97 of sodium (Na). Therefore, sodium ions cannot enter the pores having these sizes.

  In general, the thickness of the silicate layer 21 in the specific coating film 20 is preferably about 50 nm.

  The specific coating film 20 has a high solubility in water on the surface of the molybdenum foil 14, and a coating solution (hereinafter, also referred to as “specific salt”) containing an aqueous solution containing a specific rare earth metal element in its configuration ( Hereinafter, a coating film baking step of forming a coating film by applying “a coating film forming aqueous solution”), applying a drying process to the coating film, and then baking the coating film from the first specific molybdenum oxide is performed. The coating film (hereinafter also referred to as “first specific coating film”) is a coating film made of the second specific molybdenum oxide (hereinafter also referred to as “second specific coating film”). .) Can be suitably formed by a method of repeating three times.

Here, the reason why the above method is suitable as a method for forming the specific coating film 20 will be described.
When the specific coating film 20 made of the first specific molybdenum oxide or the second specific molybdenum oxide is to be formed on the molybdenum foil 14 at the lowest cost, the molybdenum foil 14 is chemically reacted. Although a method is recommended, such a method is not known. Conventionally, molybdenum is obtained from a raw material made of rare earth metal oxide (Ln ₂ O ₃ ) and molybdenum oxide (MoO ₃ ) by a powder sintering method. Obtaining oxides was only known in many literatures. Thus, the inventors have made the rare earth metal molybdenum oxide Ln ₂ (MoO ₄ ) ₃ composed of rare earth metal oxide (Ln ₂ O ₃ ) and molybdenum oxide (MoO ₃ ) with the smallest ratio. Produced by direct reaction with molybdenum foil under low temperature conditions, and with it, rare earth metal molybdenum oxide Ln ₂ (MoO ₄ ) ₃ reacts with rare earth metal oxide (Ln ₂ O ₃ ) As a result of examining the above, the aqueous solution containing rare earth metal is used as a raw material by a two-step reaction, and this is directly reacted with the molybdenum foil, and the oxidation represented by the general formula (1) on the molybdenum foil. It was found that a product (first specific molybdenum oxide) can be produced. Further, focusing on the reaction between the first specific molybdenum oxide and the rare earth metal oxide (Ln ₂ O ₃ ) on the phase diagram, this first specific molybdenum oxide and the rare earth metal oxide (Ln ₂ O). ₃ ) is reacted at a temperature higher than the temperature related to the reaction for obtaining the first specific molybdenum oxide, whereby the oxide represented by the general formula (2) (second specific molybdenum) is formed on the molybdenum foil. It has been found that (oxide) can be produced. The method as described above has a high solubility in water such as rare earth metal nitrate as an aqueous solution used as a material, and an aqueous solution having a concentration of 55 to 70% by mass can be selected. This method is preferable from the viewpoint of manufacturing cost.

Specifically, the first specific coating film can be formed by, for example, the following method.
First, a coating film is formed by applying an aqueous solution for forming a coating film on the surface of the molybdenum foil 14, and after drying the coating film, in an atmosphere containing oxygen gas, such as in the atmosphere, 500 to In the first coating film baking step in which the baking treatment is performed at a temperature condition of 550 ° C., the following general formula (generated by reacting molybdenum constituting the molybdenum foil 14 with the specific salt on the molybdenum foil 14) 4) (hereinafter, also referred to as “intermediate molybdenum oxide”) is formed (hereinafter also referred to as “intermediate film”).
Next, an aqueous solution for forming a coating film is applied onto the intermediate film formed on the molybdenum foil 14 to form a coating film, followed by a drying process, and then the intermediate film is formed, for example, in an argon gas atmosphere. The film was dried by the second coating film baking step in which the baking treatment was performed at a temperature slightly lower than the melting point of the intermediate molybdenum oxide (specifically, a temperature range of 1150 to 1490 ° C.), for example, about 1400 ° C. A rare earth metal oxide (Ln ₂ O ₃ ) produced by decomposition of a specific salt (a salt containing a specific rare earth metal element) constituting the coating film is reacted with an intermediate molybdenum oxide constituting the intermediate film. Thereby, the intermediate film is changed to form a film made of the first specific molybdenum oxide, and further, the molybdenum foil 1 on which the film made of the first specific molybdenum oxide is formed. By removing by-produced molybdenum oxide (MoO ₃₎ by performing a reduction treatment by heating at a temperature of 1000 ° C. in a hydrogen stream with respect to the first specific coating film on the surface of the molybdenum foil 14 Form.
In the first specific coating film forming method, the laminate formed by forming a coating film on the intermediate film formed on the molybdenum foil 14 during the second coating film baking step and drying it is used. By performing the baking process in a hydrogen atmosphere, the reduction process can be performed simultaneously with the baking process.

[Wherein, Ln represents a rare earth metal element selected from scandium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. ]

The second specific coating film can be formed by, for example, the following method.
First, according to the first specific coating film forming method, the first specific coating film is formed on the molybdenum foil 14 by performing the first coating film baking step and the second coating film baking step. Next, after applying a coating film forming aqueous solution on the first specific coating film formed on the molybdenum foil 14 to form a coating film and performing a drying process, for example, in an argon gas atmosphere Rare earth produced by decomposition of a specific salt (a salt containing a specific rare earth metal element) constituting the dried coating film in the third coating film baking step in which baking processing is performed at a temperature of 1500 ° C. or higher. The metal oxide (Ln ₂ O ₃ ) is reacted with the first specific molybdenum oxide constituting the first specific coating film, thereby changing the first specific coating film to change the second specific coating film. A film made of specific molybdenum oxide By, forming a second specific coating film on the surface of the molybdenum foil 14.

  As the specific salt (salt containing a specific rare earth metal element) constituting the coating film forming aqueous solution, for example, nitrate, fluoride, chloride, bromide, carbonate, acetate, and the like can be used.

The silicate layer 21 in the specific coating film 20 is formed in the process of manufacturing the discharge lamp 10.
Specifically, the inside of the quartz glass tube used as the discharge vessel 11 is in a decompressed state, and the molybdenum foil in which the mount is formed inside the quartz glass tube and the specific coating film 20 is formed on the surface thereof. 14 (hereinafter also referred to as “specific molybdenum foil”) is located in a portion where the sealing portion 13 is formed (hereinafter also referred to as “sealing portion portion”), and the electrode is the arc tube portion 12 (Hereinafter, also referred to as “the arc tube portion”), and the outer periphery of the portion located on the specific molybdenum foil of the sealing portion in the quartz glass tube in this state is heated with a burner or the like, In the step of forming the hermetic seal portion 15 by the shrink seal method that softens and reduces the diameter of the quartz glass that forms the tube wall of the quartz glass tube, the specific molybdenum foil and the specific molybdenum foil are used under a high temperature condition of 1900 ° C. or higher. Silicon dioxide constituting the quartz glass (SiO ₂₎ is diffused in the surface layer part of the specific coating film 20 in a particular molybdenum foil by British and glass melt adhesion, and the compound and silicon dioxide constituting the surface layer portion By reacting and generating the compound represented by the general formula (3), the silicate layer 21 is formed on the surface layer portion including the interface of the specific coating film 20 with the quartz glass.
In addition, G. Blasse, J. et al. Inorg. Nucl. Chem. 30 (1968) 2091. Shows that a molybdenum silicate represented by the general formula (3) is formed under the condition of being in an equilibrium state, such as a production process by a powder metallurgy / heat treatment method.

  Here, in the anode mount and the cathode mount, for example, the specific coating film 20 is formed on the entire surface of the molybdenum foil 14, and the electrode rod 16 and the external lead rod 19 in the specific coating film 20 are connected to portions to be connected. The surface of the molybdenum foil 14 is exposed by polishing the corresponding region, and the electrode rod 16 having the cathode 17 or the anode 18 formed at the tip thereof and the external lead rod 19 are connected to each other, or in advance, molybdenum. An electrode rod 16 having a cathode 17 or an anode 18 formed at the tip thereof and an external lead rod 19 are connected to the foil 14, and the electrode rod 16 and, if necessary, an external lead rod to the surface of the molybdenum foil 14. It can manufacture by forming the specific coating film 20 in the state which masked 19. When the specific coating film 20 is formed without masking the external lead bar 19, it is not necessary to perform a polishing process after the specific coating film 20 is formed, and the specific coating film 20 is not formed on the external lead bar 19. Since the covering film 20 is formed, high oxidation resistance and heat resistance can be obtained for the external lead rod 19.

In the internal space of the discharge vessel 11 of the discharge lamp 10, for example, mercury in an amount of 0.16 mg / mm ³ or more, halogen in an amount of 2 × 10 ⁻³ μmol / mm ³ , for example bromine, and An enclosed gas made of a rare gas such as argon is enclosed, and thereby the internal pressure during operation becomes 1.5 × 10 ⁷ Pa or more, and for example, a continuous spectrum of visible light having a wavelength of 380 to 780 nm can be emitted. For example, it can be suitably used as a light source for a liquid crystal projector or a DLP (Digital Light Processing) projector.

According to the discharge lamp 10 described above, since both surfaces of the molybdenum foil 14 forming the electric introduction body in the hermetic seal portion 15 are covered with the specific coating film 20, the molybdenum foil 14 is prevented from being oxidized by overheating. And the specific coating film 20 is formed of the first specific molybdenum oxide or the second specific molybdenum oxide generated by chemically reacting with molybdenum constituting the molybdenum foil 14. Since it is chemically bonded to the molybdenum foil 14, high adhesion to the molybdenum foil 14 can be obtained. Therefore, in the step of forming the hermetic seal portion 15, the temperature is 1900 ° C. or higher. The molybdenum oxide constituting the specific coating film 20 does not evaporate and scatter even if it is exposed to the water, and the specific coating film 2 Is chemically bonded by forming the silicate layer 21 in the surface layer portion including the interface with the quartz glass constituting the sealing portion 13 to form the hermetic seal portion 15. However, even if the internal pressure during operation is as high as 1.5 × 10 ⁷ Pa or more, for example, extremely high airtightness and airtight state in the airtight seal portion 15 are obtained. Stability is obtained.

Moreover, according to the discharge lamp 10, as disclosed in Japanese Patent Application Laid-Open No. 2003-317659, the discharge lamp 10 is taken in from the atmospheric atmosphere in contact with the components during the process of manufacturing the discharge lamp 10, or the discharge vessel Alkali ions such as alkali metal ions present as impurities in the quartz glass constituting the metal 11 or flowing in from the surface thereof move and accumulate particularly in the vicinity of the molybdenum foil 14 constituting the sealing portion 13 related to the cathode 17. However, the first specific molybdenum oxide or the second specific molybdenum oxide constituting the specific coating film 20 and the rare earth constituting the silicate layer 21 forming the surface layer portion of the specific coating film 20 In the metal molybdenum silicate crystal structure, the vacancies are of a size that alkali ions cannot enter. Therefore, the alkali ions do not permeate the specific coating film 20, and it is possible to prevent the alkali ions from diffusing into the molybdenum foil 14 and its interface by the action of the barrier function of the specific coating film 20. Therefore, the molybdenum foil 14 does not peel from the quartz glass due to the influence of alkali ions.
Therefore, according to the discharge lamp 10, the specific coating film 20 formed on the molybdenum foil 14 does not scatter during the manufacturing process, and the arc tube portion 12 has a high internal pressure. The hermetic seal portion 15 has very high airtight durability and a long service life.

As mentioned above, although embodiment of this invention was described, the discharge lamp of this invention is not limited to said example, A various change can be added.
For example, since a discharge lamp can obtain very high airtight durability at an airtight seal portion, it is preferable that a specific coating film is formed on both sides of the molybdenum foil. The thing of the structure currently formed in one surface of foil may be sufficient.
Further, the discharge lamp is not limited to a DC lighting type, but is an AC lighting type ultra-high pressure mercury lamp which is preferably used in that a long service life can be obtained as a light source lamp such as a rear type liquid crystal projector. There may be.

  Hereinafter, although the Example of the discharge lamp of this invention is described concretely, this invention is not restrict | limited by this.

[Example 1]
A discharge vessel made of quartz glass having an elliptical spherical arc tube portion having the configuration of FIG. 1 and sealing portions continuously provided so as to extend outward from both ends of the arc tube portion. A structure in which a molybdenum foil in which a specific coating film made of an oxide represented by the general formula (1) (first specific molybdenum oxide) is formed on both surfaces is embedded in the sealing portion of the discharge vessel The direct current lighting type discharge lamp (hereinafter also referred to as “discharge lamp (1)”) was formed by forming an airtight seal portion by a shrink seal method.
When this discharge lamp (1) was observed, no deposit was adhered to the weld surface between the quartz glasses in the vicinity of the molybdenum foil in the sealing portion. Therefore, a process for manufacturing the discharge lamp (1), specifically In the step of forming the hermetic seal portion, it was confirmed that the first specific molybdenum oxide constituting the specific coating film did not evaporate and no scattering occurred in the specific coating film.

In the discharge lamp (1), mercury 0.16 mg / mm ³ , bromine 2 × 10 ⁻³ μmol / mm ³ , and argon gas are enclosed as an enclosed gas in the internal space of the discharge vessel. The internal pressure is 1.5 × 10 ⁷ Pa or more.
The dimensions of the discharge lamp (1) are as follows: the maximum outer diameter of the arc tube portion is 10.5 mm, the maximum inner diameter of the arc tube portion is 4.5 mm, the distance between the electrodes is 1.3 mm, and the total length of the internal space of the discharge vessel ( The length in the tube axis direction) is 9 mm, the length of the sealing portion is 20 mm, the outer diameter of the sealing portion is 5.0 mm, and the volume of the internal space is 75 mm ³ .

The anode mount and cathode mount constituting this discharge lamp (1) were produced as follows.
First, two molybdenum foils having a length of 11 mm, a width of 1.5 mm, and a thickness of 25 μm were prepared, and ytterbium nitrate tetrahydrate (Yb (NO ₃ ) ₃ .4H _{2 was} applied to the entire surface of these molybdenum foils. A coating film is formed by applying an aqueous solution of O) having a concentration of 4 mol / L (hereinafter also referred to as “coating film forming aqueous solution (1)”), and the coating film is dried at a temperature of 100 ° C. After the treatment, by baking for 5 minutes at 500 ° C. in an argon gas atmosphere containing oxygen gas at a concentration of 1% using an electric furnace, A laminated body in which a film made of an oxide having Ln of Yb (ytterbium) was formed was obtained.

Next, a coating film-forming aqueous solution (1) is applied to the entire surface of the film on which the obtained laminate is formed to form a coating film, and this coating film is dried at a temperature of 150 ° C. After that, it is baked for 10 minutes under a temperature condition of 1400 ° C. in a high purity argon gas atmosphere using an electric furnace, and further heated under a temperature condition of 1000 ° C. in a hydrogen stream using an electric furnace. By removing molybdenum oxide (MoO ₃ ) by-produced by the treatment, a coating film is formed on the entire surface of the molybdenum foil (hereinafter also referred to as “coating film forming molybdenum foil (1)”). .)
The coating film formed on the molybdenum foil is formed by an X-ray diffraction method using an oxide of general formula (1) where Ln is Yb (ytterbium), specifically an oxide of the formula: Yb ₂ MoO ₆ It was confirmed that it consisted of.

  And after exposing the surface of molybdenum foil by grind | polishing the area | region corresponding to the part which should connect the electrode stick | rod and external lead stick | rod in the both ends of a coating film formation molybdenum foil (1), By welding an electrode rod made of tungsten with an outer diameter of 0.8 mm, on which an anode or a cathode is formed, and by welding an external lead rod made of tungsten with an outer diameter of 0.5 mm on the other side, an anode mount and a cathode mount Got.

When the interface of the coating film-formed molybdenum foil (1) constituting the discharge lamp (1) in the melt-adhered state with the quartz glass constituting the discharge vessel was observed by an X-ray diffraction method, the general formula (3) It was confirmed that a layer composed of a silicate in which Ln is Yb (ytterbium), specifically, a rare earth metal molybdenum silicate composed of the formula: Yb ₂ SiMoO ₈ was formed.

  A lighting test was conducted in which the discharge lamp (1) was continuously lit for a long time, and the presence or absence of peeling of the molybdenum foil from the quartz glass in the hermetic seal portion was visually confirmed. As a result, no peeling of the molybdenum foil occurred.

[Example 2]
In Example 1, instead of the molybdenum foil formed with the specific coating film made of the first specific molybdenum oxide, the oxide represented by the general formula (2) (second specific molybdenum oxide) A discharge lamp (hereinafter, also referred to as “discharge lamp (2)”) having the same configuration as in Example 1 was prepared except that the molybdenum foil formed with the specific coating film was formed.
When this discharge lamp (2) was observed, no deposit was adhered to the weld surface between the quartz glasses in the vicinity of the molybdenum foil in the sealing portion. Therefore, a process for manufacturing the discharge lamp (2), specifically In the step of forming the hermetic seal portion, it was confirmed that the second specific molybdenum oxide constituting the specific coating film did not evaporate and no scattering occurred in the specific coating film.

The anode mount and cathode mount constituting the discharge lamp (2) were obtained by the method for producing the anode mount and cathode mount according to Example 1, and Ln was Yb (ytterbium) in the general formula (1) over the entire surface. A coating film is formed by applying a coating film-forming aqueous solution (1) to the surface of a molybdenum foil (coating film forming molybdenum foil (1)) formed with a coating film made of an oxide. After forming and drying this coating film at a temperature condition of 150 ° C., it is baked for 5 minutes at a temperature condition of 1500 ° C. in a high-purity argon gas atmosphere using an electric furnace. A molybdenum foil formed with a coating film (hereinafter also referred to as “coating film forming molybdenum foil (2)”) was obtained, and the same technique as in Example 1 was applied to this coating film forming molybdenum foil (2). In It was produced by welding the electrode rod and the external lead rod I.
Here, the coating film formed on the molybdenum foil constituting the coating film forming molybdenum foil (2) is oxidized by the X-ray diffraction method in which Ln is Yb (ytterbium) in the general formula (2). It was confirmed that the product was made of an oxide comprising the formula: Yb ₆ MoO ₁₂ .

When the interface of the coating film-formed molybdenum foil (2) constituting the discharge lamp (2) in the melt-adhered state with the quartz glass constituting the discharge vessel was observed by an X-ray diffraction method, the general formula (3) It was confirmed that a layer composed of a silicate in which Ln is Yb (ytterbium), specifically, a rare earth metal molybdenum silicate composed of the formula: Yb ₂ SiMoO ₈ was formed.

  When a lighting test was performed in which the discharge lamp (2) was continuously lit for a long time, and the presence or absence of peeling of the molybdenum foil from the quartz glass in the hermetic seal portion was visually confirmed, peeling of the molybdenum foil did not occur.

It is sectional drawing for description which shows an example of a structure of the discharge lamp in this invention in the cross section along a tube axis. It is sectional drawing for description which expands and shows the airtight seal | sticker part in FIG. It is sectional drawing for description which expands and shows the area | region A in FIG. It is a graph showing the relationship between the rare earth metal element having an Ln 'in each the unit cell volume of the rare earth metal molybdenum oxide (Ln' ₂ MoO ₆₎ and rare earth metals tungsten oxide (Ln _'2 WO _6). It is a graph showing the relationship between the rare earth metal element and a melting point indicating a Ln 'in each of the rare earth metal molybdenum oxide (Ln' ₂ MoO ₆₎ and rare earth metals tungsten oxide (Ln _'2 WO _6). It is a graph showing the relationship between the rare earth metal element having an Ln 'in each the unit cell volume of the rare earth metal molybdenum oxide (Ln' ₆ MoO ₁₂₎ and rare earth metals tungsten oxide (Ln _'6 WO _12). It is a graph showing the relationship between the rare earth metal element and a melting point indicating a Ln 'in each of the rare earth metal molybdenum oxide (Ln' ₆ MoO ₁₂₎ and rare earth metals tungsten oxide (Ln _'6 WO _12).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Discharge lamp 11 Discharge vessel 12 Arc tube part 13 Sealing part 14 Metal foil 15 Airtight seal part 16 Electrode rod 17 Cathode 18 Anode 19 External lead rod 20 Coating film 21 Silicate layer

Claims (2)

A discharge vessel having a light emitting tube portion made of quartz glass and having a pair of electrodes disposed therein and a sealing portion provided at an end of the light emitting tube portion, the sealing portion of the discharge vessel In a discharge lamp in which a metal foil made of molybdenum forming an electrical introduction body is embedded,
A discharge lamp characterized in that a coating film made of an oxide represented by the following general formula (1) or an oxide represented by the following general formula (2) is formed on at least one surface of the metal foil. .

[Wherein, Ln represents a rare earth metal element selected from scandium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. ]

[Wherein, Ln represents a rare earth metal element selected from scandium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. ] A layer made of a silicate represented by the following general formula (3) is formed on a surface layer portion including an interface in close contact with quartz glass constituting a discharge vessel in a coating film formed on a metal foil. The discharge lamp according to claim 1.

[Wherein, Ln represents a rare earth metal element selected from scandium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. ]

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