JP2013131467A - Incandescent lamp, and filament - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an incandescent lamp including a filament which converts power into visible light with high efficiency.SOLUTION: The incandescent lamp has a translucent airtight container, a filament arranged in the translucent airtight container, and a lead wire for supplying a current to the filament. The filament includes a substrate composed of a first metal material, and a metal film composed of a second metal material and covering at least a part of the substrate. The second metal material composing a metal film has a melting point lower than that of the first metal material composing the substrate. Since light of large energy (visible light) can be radiated by bremsstrahlung of a metal film having a melting point lower than that of the substrate, an incandescent lamp having a high visible light luminous flux efficiency can be obtained.

Description

  The present invention relates to a light source filament with improved energy utilization efficiency, and more particularly to an incandescent lamp and a thermionic emission source using the filament.

  Incandescent light bulbs are widely used in which a current is passed through a tungsten filament or the like to heat the filament to form a light bulb. An incandescent bulb has a radiation spectrum with excellent color rendering properties close to that of sunlight, and the conversion efficiency from the power of the incandescent bulb to light is 80% or more, but the wavelength component of the emitted light is as shown in FIG. The infrared radiation component is 90% or more (in the case of 3000K in FIG. 1). For this reason, the conversion efficiency from the electric power of the incandescent light bulb to visible light is as low as about 15 lm / W. On the other hand, the fluorescent lamp has a conversion efficiency from electric power to visible light of about 90 lm / W, which is larger than the incandescent lamp. For this reason, incandescent bulbs are excellent in color rendering, but have a problem of a large environmental load.

  Various proposals have been made as attempts to increase the efficiency, brightness, and life of incandescent bulbs. For example, Patent Documents 1 and 2 have a configuration in which an inert gas or a halogen gas is sealed inside a light bulb, whereby the evaporated filament material is halogenated and returned to the filament (halogen cycle) to increase the filament temperature. Proposed. These are generally called halogen lamps. Thereby, the effect of the increase in the power conversion efficiency to visible light and the extension of a filament lifetime is acquired. In this configuration, it is important to control the components of the sealed gas and the pressure in order to increase the efficiency and extend the life.

  Patent Documents 3 to 5 disclose a configuration in which an infrared light reflection coating is applied to the surface of a bulb glass so that infrared light emitted from the filament is reflected, returned to the filament, and absorbed. As a result, infrared light is used for reheating the filament to increase efficiency.

  Patent Documents 6-9 propose a configuration in which a fine structure is produced in the filament itself, and infrared radiation is suppressed and the proportion of visible light radiation is increased by the physical effect of the fine structure.

JP-A-60-253146 Japanese Patent Laid-Open No. 62-10854 JP 59-58752 A JP-T 62-501109 JP 2000-123795 A JP 2001-519079 JP-A-6-5263 JP-A-6-2167 JP 2006-205332 A

F. Kusunoki et al., Jpn. J. Appl. Phys. 43, 8A, 5253 (2004).

  However, techniques using a halogen cycle as in Patent Documents 1 and 2 can achieve a life extension effect, but it is difficult to greatly improve the conversion efficiency.

  In addition, as in Patent Documents 3-5, the technique of reflecting infrared radiation with an infrared reflecting coat and reabsorbing the filament to the filament has a high reflectivity of 70% for infrared light, so reabsorption is efficient. It does n’t happen well. Further, the infrared light reflected by the infrared reflective coating is absorbed by other parts other than the filament, such as the filament holding part and the base, and is not used for heating the filament. For this reason, it is difficult to greatly improve the conversion efficiency by this technology.

  The technology which aims at the suppression effect of infrared radiation by fine structure like patent documents 6-9 is a report which shows the radiation enhancement and suppression effect with respect to the wavelength of the extreme part of an infrared radiation spectrum like nonpatent literature 1. However, it is very difficult to suppress infrared radiation over a wide range of infrared light. This is because when one wavelength is suppressed, another wavelength is enhanced. For this reason, it is considered difficult to achieve significant efficiency improvements using this technology. In addition, since a fine structure such as electron beam lithography is used for manufacturing a fine structure, a light source using this is very expensive. Further, there is a problem that even if a fine structure is formed on a W substrate which is a high temperature heat-resistant member, the fine structure portion is melted and destroyed at a heating temperature of about 1000 ° C.

  An object of the present invention is to provide an incandescent lamp including a filament with high efficiency for converting electric power into visible light.

  In order to achieve the above object, according to the present invention, an incandescent bulb having a translucent airtight container, a filament disposed in the translucent airtight container, and a lead wire for supplying a current to the filament. Is provided. The filament includes a base made of a first metal material and a metal film made of a second metal material and covering at least a part of the base. The melting point of the second metal material constituting the metal film is lower than the melting point of the first metal material constituting the substrate.

  According to the present invention, light of a large energy (visible light) can be emitted by bremsstrahlung of a metal film having a melting point lower than that of the substrate, so that an incandescent bulb with high visible light luminous efficiency can be obtained.

The graph which shows the wavelength dependence of the radiation energy of the conventional tungsten filament. Explanatory drawing which shows the energy radiated | emitted by (a) and (b) bremsstrahlung. Explanatory drawing which shows the bremsstrahlung by the metal film of the filament of this invention. The graph which shows the relationship between the input energy and brightness | luminance of the filament (W base material + Mo film | membrane) of specific embodiment. The cutout sectional view of the incandescent lamp of an embodiment.

  The incandescent lamp of the present invention has a light-transmitting airtight container, a filament disposed in the light-transmitting airtight container, and a lead wire for supplying a current to the filament. In the present invention, the filament includes a base made of the first metal material and a metal film made of the second metal material and covering at least a part of the base. As the second metal material constituting the metal film, a material having a melting point lower than that of the first metal material constituting the substrate is used. Thereby, the visible light radiation efficiency of a filament can be improved using the principle of bremsstrahlung mentioned below.

  It is desirable that the melting point of the second metal material constituting the metal film is higher than the temperature at which the substrate emits visible light when current is supplied from the lead wire.

  That is, it is desirable that the melting point of the second metal material constituting the metal film is higher than the lead wire temperature (for example, 2300 K) at which the lead wire, which is the first metal material, is energized and heated and used as a steady state.

  The second metal material forming the metal film is preferably softened at a temperature at which the substrate emits light upon receiving a current supplied from the lead wire.

  That is, it is desirable that the melting point of the second metal material constituting the metal film is softened at a lead wire temperature (for example, 2300 K) that is used as a steady state by energizing and heating the lead wire that is the first metal material.

  More specifically, as the first metal material constituting the substrate, for example, a material that reaches a temperature of 2300K or more when the substrate heated by energization by receiving a current from a lead wire can be used. As the second metal material constituting the metal film, for example, a material having a melting point of 2500 K or more can be used.

  The principle of the present invention will be described with reference to FIGS. The present invention utilizes the principle of bremsstrahlung (electron Compton scattering) to improve visible light radiation efficiency. As shown in FIG. 2A, in bremsstrahlung, the momentum change that occurs when electrons are scattered by lattice vibration of atoms due to heat is emitted as light. When the momentum of electrons before being scattered by the lattice vibration of atoms is P, and the momentum of electrons after scattering is P ′, the energy of (P′−P) is the light radiation energy. Thus, the greater the momentum of the scattered electrons, the greater the light radiation energy. In the case of the same metal material, as shown in FIG. 2B, the lattice vibration increases at a high temperature, so that the momentum P ′ of electrons after scattering increases and the light radiation energy also increases. That is, as the temperature of the filament is higher, a larger lattice vibration is generated, so that high energy, that is, light having a short wavelength in the visible wavelength region is emitted.

  In the present invention, by covering the substrate with a metal film made of a metal material having a lower melting point than the substrate, the metal film having a low melting point is close to a softened state (molten state or liquid state) at the same temperature as the substrate. Put it in a state. In this state, the atoms of the metal film can move greatly out of the position of the crystal lattice as shown in FIG. The velocity of the atoms that have escaped from the lattice is very slow compared to the velocity of the electrons, but since the mass is 10,000 times or more that of the electrons, the change in momentum given to the electrons becomes very large. Therefore, higher energy light can be emitted from the metal film having a temperature closer to the melting point than that of the substrate, rather than the radiation emitted from the filament in the solid state. Thereby, light of high energy (visible light component) can be emitted with high efficiency.

  In addition, the atoms of the metal film closer to the melting point than the substrate cause more erratic movement than the atoms present in the solid crystal position, so that the number of electron scattering increases. Thereby, the emitted light quantity increases.

  Thus, by covering the substrate with a metal film having a melting point lower than that of the substrate, it is possible to provide a filament that emits a lot of high energy (visible light component) light as compared to the case of the substrate alone.

  The filament base itself is not composed of a low melting point metal material, and a metal film having a melting point lower than that of the base is arranged on the base. The filament base itself is composed of a low melting point metal material. Then, the softening of the metal material constituting the substrate starts at a temperature 200-300K lower than the melting point, and the filament itself becomes difficult to stand before reaching a temperature at which a sufficient amount of radiation can be obtained (for example, 2300K). Because it begins. In the present invention, by coating the substrate with a metal film having a lower melting point, the substrate can be heated to a temperature at which a sufficient amount of light can be obtained, and the lattice vibration of the metal film on the surface is increased to make it visible. A configuration capable of improving the light emission efficiency is realized.

  Examples of the base material include HfC (melting point 4160K), TaC (melting point 4150K), ZrC (melting point 3810K), C (melting point 3800K), W (melting point 3680K), Re (melting point 3453K), Os (melting point 3327K), Ta. (Melting point 3269K), Mo (melting point 2890K), Nb (melting point 2741K), Ir (melting point 2683K), Ru (melting point 2583K), Rh (melting point 2239K), V (melting point 2160K), Cr (melting point 2130K), and Zr (Melting point 2125K), or an alloy containing at least one of them, and a metal material having a melting point of 2500K or more can be used.

  As a material constituting the metal film, any of the metals listed as the material constituting the base material, or an alloy containing at least one of these, than the base material Those having a low melting point can be used.

  For example, when W, which is generally used as a filament material, is used as a base material, the metal film is any one of Re, Os, Ta, Mo, Nb, Ir, Ru, Rh, V, Cr, and Zr. Can be configured. For example, when the substrate is made of Re, the metal film can be made of any of Os, Ta, Mo, Nb, Ir, Ru, Rh, V, Cr, and Zr.

  The material of the metal film is desirable because the lower the melting point, the more the visible light luminance and the efficiency tend to increase even in a low temperature range, but the substrate was heated to a temperature necessary to obtain a sufficient amount of light as an incandescent bulb. Even in this case, it is desirable that the metal film material does not cause evaporation or sublimation in the atmosphere in the incandescent bulb.

  As an incandescent light bulb, in order to obtain an illuminating light beam (light quantity) that can be put into practical use, it is desirable to heat the base material to a high temperature of 2300K or higher. Considering evaporation and sublimation in the inner atmosphere, it is preferable that both the substrate and the metal film have a melting point of 2500 K or more.

  The thickness of the metal film is designed so that the required life of the filament can be obtained considering that the metal film and the base material are both metal and the thermal conductivity is not substantially changed. For example, the thickness of the metal film is determined in consideration of the degree of vacuum in the incandescent bulb and the reactivity of the enclosed gas species.

  As a method for forming a metal film, any method can be used as long as a metal film that covers at least a part of a substrate can be formed. Vapor phase epitaxy (evaporation or sputtering), plating (including electrolytic deposition), For example, a method in which a paste in which metal particles are dispersed in a binder is applied and heated can be used.

  Further, the shape of the filament may be a shape that rises to a necessary temperature when supplied with current. For example, it can be made into a shape such as a wire, a shape in which the wire is wound, and a plate shape.

<Specific Embodiment>
An embodiment of a filament in which a W base material is coated with a Mo metal film will be described.

  A substrate made of W with a wire shape of 200 μm in thickness was prepared, and a Mo film was formed as a metal film on the surface by a thickness of 1-10 μm by vapor deposition to produce a filament. When the radiance when the filament was supplied with power and heated was experimentally obtained, the result shown in FIG. 4 was obtained. As a comparative example, FIG. 4 shows the radiance of a W filament having a thickness of 200 μm when the power is similarly supplied and heated.

  As shown in FIG. 4, it can be seen that the W base filament coated with the Mo film of the present embodiment has a visible light luminance approximately twice that of the thermal radiation generated from the filament of W alone. More specifically, at 500 W input, both the present embodiment and the comparative filament are 2300 K, and the visible light luminous efficiency of the comparative W filament at this temperature is 10 lm / W. The visible light luminous efficiency of the filament of the W base coated with the Mo film of the embodiment was 20 lm / W.

  From this, it was found that high luminance and high efficiency can be obtained by the filament having the substrate coated with the low melting point metal film of the present embodiment.

<Embodiment of incandescent bulb>
The incandescent lamp using the filament of the above embodiment will be described.

FIG. 5 shows a cut-away cross-sectional view of an incandescent bulb using the filament of this embodiment. The incandescent lamp 1 includes a translucent airtight container 2, a filament 3 disposed inside the translucent airtight container 2, and a pair of lead wires that are electrically connected to both ends of the filament 3 and support the filament 3. 4 and 5. The translucent airtight container 2 is constituted by a glass bulb, for example. The inside of the translucent airtight container 2 is in a high vacuum state of 10 ⁻¹ to 10 ⁻⁶ Pa. In addition, by introducing 10 ⁵ to 10 ⁻¹ Pa of O ₂ , H ₂ , a halogen gas, an inert gas, and a mixed gas thereof into the inside of the light-transmitting hermetic vessel 2, the same as in the conventional halogen lamp. , It is possible to suppress the sublimation and deterioration of the metal film formed on the filament, and to expect the effect of extending the life.

  A base 9 is joined to the sealing portion of the translucent airtight container 2. The base 9 includes a side electrode 6, a center electrode 7, and an insulating portion 8 that insulates the side electrode 6 from the center electrode 7. The end portion of the lead wire 4 is electrically connected to the side electrode 6, and the end portion of the lead wire 5 is electrically connected to the center electrode 7.

  The filament 3 is a filament of the present invention, and here has a structure in which a wire-shaped filament is spirally wound.

  As described in the above embodiment, the filament 3 has a simple configuration in which at least a part of the surface of the base is covered with a metal film having a melting point lower than that of the base, but has high visible light radiation efficiency. Therefore, in the present invention, an inexpensive and efficient energy-saving lighting bulb can be provided.

  In this embodiment, it has been described that the filament of the present invention is used as a filament of an incandescent bulb, but it is also possible to use it other than an incandescent bulb. For example, it can be employed as a heater wire, a welding wire, a thermionic emission electron source (such as an X-ray tube or an electron microscope), and the like.

DESCRIPTION OF SYMBOLS 1 ... Incandescent light bulb, 2 ... Translucent airtight container, 3 ... Filament, 4 ... Lead wire, 5 ... Lead wire, 6 ... Side electrode, 7 ... Center electrode, 8 ... Insulation part, 9 ... Base

Claims (8)

An incandescent bulb having a translucent airtight container, a filament disposed in the translucent airtight container, and a lead wire for supplying a current to the filament,
The filament includes a base made of a first metal material and a metal film made of a second metal material and covering at least a part of the base.
An incandescent lamp characterized in that the melting point of the second metal material constituting the metal film is lower than the melting point of the first metal material constituting the substrate.   2. The incandescent lamp according to claim 1, wherein a melting point of the second metal material constituting the metal film is higher than a temperature at which the substrate emits visible light upon receiving a current supplied from the lead wire. An incandescent light bulb.   3. The incandescent lamp according to claim 1, wherein the second metal material constituting the metal film is softened at a temperature at which the base body emits light upon receiving a current supplied from the lead wire. Incandescent light bulb.   The incandescent lamp according to claim 2 or 3, wherein a temperature at which the base body emits light upon receiving a current from the lead wire is 2300K or more.   The incandescent lamp according to any one of claims 1 to 4, wherein the melting point of the second metal material constituting the metal film is 2500K or more.   The incandescent lamp according to claim 1, wherein the second metal material constituting the metal film is any one of TaC, ZrC, C, W, Re, Os, Ta, Mo, Nb, Ir, and Ru. An incandescent bulb characterized by containing the above.   The incandescent lamp according to claim 1, wherein the first metal material constituting the substrate is selected from the group consisting of HfC, TaC, ZrC, C, W, Re, Os, Ta, Mo, Nb, Ir, and Ru. An incandescent bulb characterized by containing either. A base composed of a first metal material; and a metal film composed of a second metal material and covering at least a part of the base;
The filament characterized in that the melting point of the second metal material constituting the metal film is lower than the melting point of the first metal material constituting the substrate.

Images