JP5243153B2 - Luminescent container for high-intensity discharge lamp - Google Patents

Abstract

An object of the present invention is to improve the color temperature stability of light emission and maintain durability when repeating light-on and light-off, while narrowing light emission from the light-emitting vessel. A light-emitting container 1 for a high intensity discharge lamp includes: a light-emitting vessel 7 of a translucent polycrystalline ceramics having a substantially constant linear transmittance in a visible light region and having a central light-emitting portion 7e, thick portions 7d provided on both sides of the central light-emitting portion 7e and thicker than the central light-emitting portion 7e, respectively, and side end portions 7c provided on outer sides of the thick portions 7d, respectively; tubular portions 3 protruded from the side end portions, respectively; electrodes 5 provided in the inner space of the light-emitting vessel; electrode holding members 2 inserted through the tubular portions and holding the electrodes, respectively; a sealing material 4 sealing a space between the tubular portion and electrode holding member; and light-shielding films 11 for coating the outer surface 7b of the thick portions over full-circumference around a tube axis of the light-emitting vessel. The outer surfaces of the central light-emitting portion 7e, the side end portions 7c and the tubular portions 3 are not coated with the light-shielding film.

Description

  The present invention relates to a luminous vessel for a high-intensity discharge lamp.

  Since the light-transmitting ceramic transmits visible light, it has been used as a light-emitting container for high-intensity discharge lamps. In particular, translucent alumina ceramics are used as a light-emitting container for high-intensity discharge lamps.

In order to improve the stability of the color temperature of the ceramic metal halide lamp, it is necessary to increase the vapor pressure of the metal halide in the plasma arc. Disclosed is to improve the metal halide vapor pressure by increasing the temperature inside the arc tube by coating part of the ceramic tube with zirconium oxide and reflecting the infrared radiation emitted from the plasma arc inside the arc tube. (Patent Documents 1 and 2). In Patent Document 1: 2, both end faces (end plugs) of an arc tube and the surface of an elongated tubular portion (leg) attached to the arc tube are covered with a zirconium oxide film, thereby filling a metal halide. Prevents liquefaction and low temperature of the product, ensuring good color rendering.
European patent EP 0 869 540 A1 JP 10-335059 A

Further, it is disclosed that a heat reflective coating is applied to both ends of the arc tube so that the color temperature and luminous efficiency of a metal halide lamp with an inner volume of the arc tube of less than 1 cc and 150 W or less do not change depending on the lighting direction (patent) Reference 3).
US Patent 5,708,328

Further, in a high-pressure discharge lamp for an automotive headlamp in which a light emitting portion having an average linear light transmittance of 15% or more and a plug end portion having a mean linear transmittance of less than 15% are produced by shrink fitting, a light shielding film is further formed on the surface of the arc tube. It is described in Patent Document 4 (0054) that light emission in an undesired direction is shielded by forming.
JP 2006-93045 A

Further, in Patent Document 5, in a high-pressure discharge lamp for an automobile headlamp, the central portion of the arc tube is made thin so that a luminance center is arranged at the central portion, thereby improving the light collection efficiency to the focal point of the projection beam. It is described.
JP2004-6198

  In a high-intensity discharge lamp, first, a discharge is generated between electrodes in a starting gas such as mercury vapor or argon gas, and the heat energy generated by the discharge energy is used to evaporate sodium or metal iodide, which is a luminescent material, to gas. Further, the light emitting material is excited by the energy of electrons discharged between the electrodes, and light generated when the electrons of the light emitting material return from the excited state to the ground state is used as a light source.

  For this reason, the higher the vapor pressure of the luminescent material, the higher the probability of collision between the discharged electrons and the luminescent material, and the luminescent material is more easily excited, resulting in higher luminous efficiency. In order to increase the vapor pressure of the luminescent material, it is necessary to increase the temperature of the luminescent material. For this purpose, it is important to keep the gas temperature inside the arc tube high.

  As described above, in the high-intensity discharge lamp, light emission occurs by using electron discharge between the electrodes, the temperature of the light emitting portion is the highest, and the temperature at the base of the electrode and the rear portion of the electrode is lowered. The lowest part of this temperature is called the coldest point, but the vapor pressure of the luminescent material in the lamp is governed by this coldest point, so raising the temperature of the coldest point increases the vapor pressure of the luminescent material. Is important to.

  In order to increase the temperature of the coldest spot, it is effective to provide a light shielding film on the surface of the end plug of the electrode base or the annular portion (leg portion) as in the prior art (Patent Documents 1, 2, 3). ). As a result, the temperature of the metal halide vapor is improved, the vapor pressure of luminescent materials such as metal halide is improved, the luminous efficiency (lm / W) is improved, and at the same time, the arc tube for high-intensity discharge lamp lamps with good color temperature stability is provided. It becomes possible to do.

  In addition, ceramic arc tubes are generally translucent but not transparent, so the entire arc tube emits light generated and emitted by the plasma arc, so the size of the light source is the same as the size of the arc tube. . For this reason, it is difficult to control the light emitting part according to the performance of the lighting fixture used in combination with the arc tube. For lamps that allow a relatively large light source size, such as a lamp for general lighting, the large light source size is not a problem for lighting fixtures, but ceramic light emission is used as a headlamp for automobiles or a lamp for projectors. The tube has a large light source size and is difficult to combine with a lighting fixture.

  It is also known that the light collection efficiency by the projection beam is enhanced by emitting light from a narrow region at the center of the arc tube (Patent Documents 4 and 5). As described in these documents, increasing the thickness of both ends of the arc tube or forming a light-shielding film on both ends is also effective in raising the temperature at the coldest spot.

  However, the present inventor has made a large number of high-pressure discharge lamps of the above-mentioned idea and examined them. As a result, unlike conventional common sense, the color temperature stability, durability when repeated lighting, etc. On the other hand, I discovered that there was an inconvenience.

  That is, by covering the end plug and the tubular portion of the arc tube with a light-shielding film and making the central light emitting portion of the arc tube thin, the luminance center can be arranged in the central light emitting portion. In addition, the end plug from both sides of the central light emitting part, and light and heat radiation from the tubular part should be suppressed to prevent gas stagnation and liquefaction at the coldest point and improve color temperature stability. .

  However, it has been found that when such an arc tube is actually manufactured, the color temperature stability is deteriorated and the durability when the light-on / off is repeated is lowered.

  An object of the present invention is to improve the color temperature stability of light emission while reducing the light emission from the arc tube, and to maintain the durability when lighting-off is repeated.

A luminous container for a high-intensity discharge lamp according to the present invention,
A light-emitting tube made of translucent polycrystalline ceramics, provided on the central light-emitting part, on both sides of the central light-emitting part, thicker than the central light-emitting part, and on the outside of each thick-walled part are respectively provided, arc tube provided with a plate-like side edge portions for closing the ends of the arc tube,
Tubular portions projecting from the respective side end portions,
Electrodes provided in the inner space of the arc tube,
An electrode holding member that is inserted through each tubular portion and holds the electrode;
A sealing material that seals between the tubular portion and the electrode holding member, and a light shielding film that covers the entire outer surface of the thick portion around the tube axis of the arc tube,
The central light emitting part is recessed from the outer surface of the thick part to form a concave part, the ratio of the length of the central light emitting part to the total length of the arc tube is 90% to 5%, and the thickness of the central light emitting part is 0.3 mm to 1.5 mm, the thickness of the thick part is 0.5 mm to 5.0 mm, and the thickness of the thick part is 1.1 to 10 times the thickness of the central light emitting part The outer surface of the central light emitting part, the side end part, and the tubular part is not covered with a light shielding film.

  According to the present invention, the central light-emitting portion of the arc tube is relatively thin and the luminance center is arranged, so that the light collection efficiency to the projection beam can be increased. At this time, the light emission can be concentrated on the central light emitting portion by providing a light shielding film that covers the outer surfaces of the thick portions on both sides of the central light emitting portion over the entire circumference around the tube axis of the arc tube.

  At the same time, it has been found that gas liquefaction and temperature drop at the coldest point of the arc tube can be appropriately controlled by making both sides of the central light emitting portion thick and providing a light shielding film. At this time, if the outer surface of the side end portion and the tubular portion is covered with a light shielding film, the temperature of the sealing material is increased, so that the sealing material is deteriorated. As a result, the color temperature stability is lowered, and the lighting / lighting is repeated. Durability decreased. This is presumably because the gas temperature at the end plug is higher than expected, and corrosive gas flows into the tubular portion and the sealing portion is easily eroded.

  Therefore, in the present invention, the outer surfaces of the side end portions and the tubular portion are not covered with a light shielding film. As a result, the color temperature stability was remarkably improved, and the durability during repeated lighting and extinguishing was improved. In the prior art, the object of the invention is to obtain color temperature stability by covering the surface of the side surface portion and the tubular portion with a light shielding film.

  FIG. 1 is a schematic cross-sectional view of a luminous container 1 for a high-intensity discharge lamp used for a metal halide lamp, and FIG. 2 is a front view showing the appearance of the container 1.

  The arc tube 7 of the luminous container 1 includes a central light emitting portion 7e, thick portions 7d on both sides of the central light emitting portion 7e, and side end portions 7c outside the thick portions 7d. In this example, the central light emitting portion 7e is recessed from the outside with respect to the thick portion 7d, and the inner surface of the central light emitting portion and the inner surface of the thick portion are smoothly continuous.

  Tubular portions (leg portions) 3 are attached to the outer sides of the respective side end portions. An electrode holding member 2 is inserted into the inner space 3 a of the tubular portion 3, and an electrode 5 is attached to the inner end of the electrode holding member 2. The outer end portion of the electrode holding member 2 is sealed with respect to the inner wall surface of the tubular portion 3 by the sealing material 4, and is further sealed with respect to the outer end surface of the tubular portion 3 by the sealing material 12. The pair of electrodes 5 is located in the inner space of the arc tube 7 and is designed so as to be able to discharge between the electrodes 5.

  The thick part means having a thickness larger than the thickness of the central light emitting part, and in the present invention, it is formed on both sides of the central light emitting part. The thickness t of the central light emitting portion 7e is smaller than the thickness T of the thick portion 7d.

  In the embodiment of FIG. 1, the outer surface 7f of the central light emitting portion 7e is recessed from the outer surface 7b of the thick portion 7d, thereby making the thickness of the central light emitting portion relatively small. The inner wall surface of the central light emitting portion 7e and the inner wall surface of the thick portion 7d are smoothly continuous and have no step. However, the inner wall surface of the central light emitting portion 7e can be recessed from the inner wall surface of the thick portion 7d.

  The outer surface 7b of each thick portion 7d is covered with a light shielding film 11. The light shielding film 11 covers the thick portion outer surface 7b so as to go around the arc tube around the tube axis O of the arc tube. The surface of the step side surface 7g between each thick portion 7d and the central light emitting portion may also be covered with the light shielding film 11. The outer surface 7f of the central light emitting portion 7e, the outer surface 7a of the side end portion 7c, and the outer surface 3b of the tubular portion 3 are not covered with a light shielding film.

  The central light-emitting portion 7e is thinned and no light-shielding film is provided, and the thick-walled portions 7d on both sides thereof are covered with the light-shielding film 11, so that the light projection range from the plasma arc light-emitting region 6 is within the range of the projection angle θ. Be regulated within. This projection range is smaller than the total length L of the arc tube 7.

  Since the ceramic arc tube is translucent but not transparent, the entire arc tube emits light by the light generated and emitted by the plasma arc, so the size of the light source is the same as the size of the arc tube. For this reason, it is difficult to make the light source size suitable for the performance of the lighting fixture in the headlamp for automobiles and the light source lamp of the projector that require a small light source size. However, in the present invention, it is possible to provide a lamp that matches the performance of the lighting fixture by limiting the light source size to a predetermined size.

  For example, in a light-emitting tube for automobiles, the light-transmitting portion can be made small so that the light source size is 2 mmφ × 4 mm, which is equivalent to the size of the filament of the halogen lamp. Furthermore, for application to a light source for a projector, the light source size can be made to be 1 mm or less in diameter.

  The high-pressure discharge lamp of the present invention can be applied to other illumination devices to which a pseudo point light source can be applied, such as an automotive headlamp, an overhead projector (OHP), and a liquid crystal projector.

  In the present invention, the central light emitting portion means a portion having a relatively small thickness sandwiched between thick portions on both sides of the arc tube 7. The thick part is a part between the central light emitting part and the side end part. Specifically, as shown in FIG. 1, a portion from the inner wall surface 13 of the side end portion 7 b to the step 14 with respect to the central light emitting portion is a thick portion. Further, the side end portion means a plate-like portion that closes both ends of the arc tube.

In the discharge lamp of the present invention, ratio of the length p of the central light-emitting portion of the total length L of the arc tube 7, from the viewpoint of obtaining suitable size of the light source, Ri 90% to 5% der 60% More preferably, it is 10%.

Further, the ratio of the light shielding film to the surfaces 7b and 7g of each thick part is preferably 30% or more, and more preferably 50% or more, from the viewpoint of the present invention. A light shielding film may cover the entire outer surface of each thick portion.
The light shielding film preferably covers 20% or more and 95% or less of the surface area of the outer surface of the arc tube.

The thickness t of the central light emitting portion is set to 1.5 mm or less and more preferably 1.0 mm or less from the viewpoint of increasing the light emission amount. Further, the thickness t of the central light-emitting portion, from the viewpoint of mechanical strength, and 0.3mm or more.

The thickness T of the thick portion is set to 0.5 mm or more, and more preferably 1.0 mm or more from the viewpoint of color temperature stability. However, when the thickness T of the thick portion exceeds 5mm, since reliability of the light emitting tube is reduced thermal stresses during lighting is increased, and 5mm or less.

From the viewpoint of the present invention, the ratio of the thickness T of the thick portion when the thickness t of the central light emitting portion is 1, is 1.1 or more, and more preferably 1.5 or more. Further, the ratio of the thickness T of the thick portion when the thickness t of the central light emitting portion is 1, is 10 or less, and more preferably 5 or less, from the viewpoint of avoiding stress concentration on the stepped portion.

  In order to partially increase the thickness of the arc tube, the inner and outer mold shapes are devised to form a thickness difference, or the portion corresponding to the translucent part is processed from the outside to reduce the thickness. By doing so, it becomes possible to make the thick part thicker than the translucent part. Processing to reduce the wall thickness is easier when the green body is processed after sintering (white processing: Green Machining).

  The light shielding film may have a linear transmittance of 3% or less, but more preferably 1% or less. Further, the material of the light shielding film is preferably a black coating material that absorbs light. Further, since the temperature of the arc tube may be about 1,000 ° C. during use, it is desirable that the arc tube be a material having excellent heat resistance. Furthermore, the material needs to be close to the thermal expansion coefficient of the arc tube. As a material satisfying such characteristics, a cermet material made of a refractory metal such as tungsten or molybdenum and a ceramic material such as alumina is suitable as a coating material for the thick portion.

  The thickness of the coating material is preferably 3 microns or more in order to ensure sufficient light shielding performance. On the other hand, when the thickness exceeds 10 microns, it becomes too thick due to mismatch of thermal expansion and is easily peeled off from the arc tube. The cermet material is made into a paste and applied to the outer surface of the arc tube after calcining at a predetermined position and thickness by a method such as screen printing, and after drying, a coating film is formed on the arc tube surface by firing in a hydrogen atmosphere be able to.

Examples of the translucent translucent ceramic constituting the arc tube include the following.
Polycrystalline Al ₂ O ₃ , AlN, AlON. Alternatively, single crystal Al ₂ O ₃ , YAG, Y ₂ O _{3 having a} surface roughness Ra ≧ 1.0 μm.

Semi-transparent means the following light transmittance.
Total light transmittance of 85% or more and linear transmittance of 45% or less

  The luminance center means a portion having the highest luminance in the light emitting unit. The luminance center need not be a single point, and may extend in the direction of the longitudinal section.

What is a high-intensity discharge lamp?
A mercury lamp using mercury as a luminescent material, a high pressure sodium lamp using sodium as a luminescent material, and a metal halide lamp using metal iodide as a luminescent material.

  Polycrystalline ceramics are molded by a molding method such as extrusion molding, dry molding, etc. suitable for a desired shape, casting molding, injection molding, gel casting molding or the like.

Example 1
Using the raw material powder for translucent alumina, a molded body of a luminous container for a high-intensity discharge lamp for a metal halide lamp shown in FIGS. 1 and 2 was prepared by a gel cast molding method. In the molded body, the diameter of the central light emitting portion 7e was 3.9 mm, the thickness was 0.7 mm, and the thickness of each thick portion 7d was 1.7 mm. The thickness of the tubular part 3 was 0.5 mm, and the thickness of the side end part was 1.3 mm.

  At the time of molding, an outer mold and an intermediate mold were prepared, respectively, and a gel cast molding slurry was poured into a gap formed between the outer mold and the intermediate mold, and the mold was released after curing. The surface roughness of the mold was uniformly Ra 0.1 microns. In a state where the obtained male molded body and female molded body are fitted together, the portion corresponding to the thick part of the integrated calcined body is fired at 1300 ° C. in the atmosphere and integrated by removing the binder and calcining. Further, a paste made of tungsten powder and alumina powder was applied by screen printing and dried. This alumina pre-sintered body was fired at 1,800 ° C. for 3 hours in a hydrogen atmosphere to produce a luminous container 1 made of a translucent polycrystalline alumina ceramic.

  The average particle diameter of the crystals of the luminous container 1 after sintering is 25 microns. The wall thickness of the tubular part 3 is 0.4 mm. The total length L of the arc tube 7 is 10 mm, the diameter of the central light emitting portion 7e is 3 mm, the length p is 4 mm, and the wall thickness t is 0.5 mm. The thickness n of the thick part 7b is 2 mm, and the thickness T is 1.3 mm. A light shielding film 11 having a thickness of 5 microns made of tungsten-alumina cermet was formed on the surface of the thick portion. The light transmittance of the light shielding film 11 is 2% or less. The light shielding film 11 covers 100% of the stepped surface 7g between the outer surface 7b of the thick portion 7d and the central light emitting portion.

  An electrode holding member 2 in which an electrode 5 having a coil portion made of tungsten and an introduction conductor portion made of niobium are joined via molybdenum is inserted into one tubular portion 3 of the luminous container 1. The position of the joint between the lead-in conductor and molybdenum is temporarily fixed with a jig so that the lead-in conductor comes out of the capillary near the capillary end, and a ring-shaped sealing frit material is inserted from the lead-in conductor into the end of the capillary. After being placed on the part, the part was heated and melted to a predetermined temperature and hermetically sealed.

  Furthermore, inside a glove box in an argon atmosphere, this one end is hermetically sealed in a composite luminous container. From the other unsealed capillary side, mercury and iodides of Na, Tl, and Dy as luminous metals As in the previous step, a metal part in which an electrode part having a coil part made of tungsten and an introduction conductor part made of niobium are joined via molybdenum is inserted, and the position of the joint part of the introduction conductor part and molybdenum is Temporarily fix it with a jig so that the introduction conductor comes out of the capillary near the end of the capillary, insert a ring-shaped sealing frit material from the introduction conductor, and place it on the end of the capillary. The mixture was heated and melted until hermetically sealed.

  FIG. 1 shows a cross-sectional view of the arc tube during lighting. With this arc tube, it is possible to realize an arc tube size smaller than that of a conventional ceramic arc tube.

The following tests were conducted on the obtained discharge lamp. Test methods and results are shown.
A lead wire for supplying current is welded to the electrode holding member of the discharge lamp, inserted into a glass outer bulb to form a lamp, and a current is supplied by using a predetermined ballast power supply, thereby lighting as a metal halide high pressure discharge lamp. I was able to.
(Color stability)
The color stability of the lamp was evaluated by evaluating the time dependence of the color rendering properties. The lamp exhibited a color rendering index Ra85 in the initial state, and a substantially equivalent color rendering index 83 even after a 1,000-hour lighting test. The lamp luminous efficiency evaluated at the same time was 90 lm / W in the initial state, and the lamp luminous efficiency of 88 lm / W was almost the same after the 1,000-hour lighting test.

(Durability of lighting-extinguishing)
The durability of the lamp was evaluated by repeating the turning on and off and confirming the change in the luminous efficiency of the lamp. With respect to the initial lamp luminous efficiency of 90 lm / W, the lamp luminous efficiency after the 1,000-cycle lighting-off test was 85 lm / W, and substantially the same lamp luminous efficiency was maintained after the lighting-off test.

(Comparative Example 1)
In Example 1, the light-shielding film 11 covered the outer surface 7a of the side end 7c and the outer surface 3b of the tubular portion 3 in addition to the outer surface 7b of the thick portion 7d. The test results are shown below.

(Color stability)
The color stability of the lamp was evaluated by evaluating the time dependency of the color rendering properties in the same manner as in the examples. The lamp showed a color rendering index Ra85 in the initial state, and after 400 hours, the color rendering index dropped to 60, and the lamp was not turned on after 500 hours.

(Durability of lighting-extinguishing)
The durability of the lamp was evaluated by repeating turning on and off in the same manner as in the example and confirming the change in the luminous efficiency of the lamp. With respect to the initial lamp luminous efficiency of 90 lm / W, the lamp luminous efficiency after the 300-cycle lighting-off test was deteriorated to 50 lm / W, and it was not lit at 350th cycle.

It is sectional drawing which shows typically the luminous container 1 which concerns on embodiment of this invention. It is a front view which shows the external appearance of the container 1 of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Light emitting container 2 Electrode holding member 3 Tubular part 3a Inner side surface 3b of the tubular part 3 Outer side surface of the tubular part 3, 4, 12 Sealing material 5 Electrode 6 Light emitting region 7 Light emitting tube 7a Outer surface of side end 7c Thick part 7d outer surface 7c side edge 7d thick part 7e central light emitting part 7f outer surface of central light emitting part 7g outer surface of step difference between thick part 7d and central light emitting part 7e 8 concave part 11 light shielding film 13 inner side of side end part 7b Wall 14 Step between the thick portion 7d and the central light emitting portion t Thickness of the central light emitting portion T Thickness of the thick portion A Light emission O Tube axis θ Projection angle

Claims (3)

A light-emitting tube made of translucent polycrystalline ceramics, provided on each side of the central light-emitting portion, the central light-emitting portion, and a thicker portion thicker than the central light-emitting portion, and each thick-walled portion are respectively provided on the outer side, the light-emitting tube has a plate-like side edge portions for closing the ends of the arc tube,
Tubular portions protruding from the respective side end portions,
An electrode provided in an inner space of the arc tube,
An electrode holding member that is inserted through each tubular portion and holds the electrode;
A sealing material that seals between the tubular portion and the electrode holding member; and a light-shielding film that covers the outer surface of the thick portion over the entire circumference around the tube axis of the arc tube,
The central light-emitting portion is recessed from the outer surface of the thick-walled portion to form a recess, the ratio of the length of the central light-emitting portion to the total length of the arc tube is 90% to 5%, and the central light emission The thickness of the thick part is 0.3 mm to 1.5 mm, the thickness of the thick part is 0.5 mm to 5.0 mm, and the thickness of the thick part is 1 of the thickness of the central light emitting part. A luminous container for a high-intensity discharge lamp, characterized in that the outer surface of the central light emitting part, the side end part and the tubular part is not covered with a light shielding film.   The light-emitting container for a high-intensity discharge lamp according to claim 1, wherein the light-shielding film is made of cermet of refractory metal and ceramics, and the thickness of the light-shielding film is 3 to 10 µm. The light-shielding film has a surface area of 20% or more and 95% or less of the total surface area of the outer surface of the central light emitting part, the outer surface of the thick part, and the stepped surface between the central light emitting part and the thick part. The light-emitting container for a high-intensity discharge lamp according to claim 1 or 2 , characterized in that it is coated.

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