JP4158976B2 - Assembly for luminous vessel and high-pressure discharge lamp - Google Patents

Description

The present invention relates to a luminous container and an assembly for a high pressure discharge lamp.

  High pressure discharge lamps using quartz discharge tubes have been widely used as automotive headlights due to their brightness and high luminous efficiency. In such a discharge lamp using a quartz tube, since the discharge tube is transparent, the light emitting part by the luminescent gas in the discharge tube can be directly used as a point light source of the discharge lamp.

The present applicant disclosed in Patent Document 1 that a molybdenum pipe is inserted into the opening of both ends of a discharge tube made of translucent translucent alumina, and the pipe and the discharge tube are joined.
JP 2001-76677 A

The discharge lamp of Patent Document 1 is used as a pseudo point light source for automobile headlamps, for example. However, in the field of automobile headlamps and projector lamps, there is also a demand for discharge lamps using transparent discharge tubes.
Patent Documents 2 and 3 disclose a method of monolithically sealing a sapphire arc tube and a polycrystalline alumina end cap.
JP-T-2001-519969 JP 2003-157798 A

  In the method described in Patent Document 2, a sapphire arc tube and a polycrystalline alumina end cap are joined by a solid-phase reaction. However, when this inventor examined this conjugate | zygote, it turned out that there exist the following problems. That is, in this method, polycrystalline alumina tends to grow on the contact surface between sapphire and polycrystalline alumina. If this polycrystalline alumina does not grow until it becomes a complete single crystal (sapphire) and grain growth stops before that, coarse alumina particles remain along the bonding interface. As a result, it has been found that the bonding interface is destroyed by the thermal stress in the region that can be endured.

  An object of the present invention is to provide durability and reliability against thermal stress in a joined body of a first member having at least a joining surface made of sapphire and a second member having at least a joining surface made of a polycrystalline alumina sintered body. It is to improve.

The present invention is a luminous container comprising a discharge tube having an opening at an end thereof, and a sealing member fixed to the end of the discharge tube,
Wherein at least the bonding surface of the discharge tube is Ri Do sapphire, the Ri least bonding surfaces of the sealing member Do polycrystalline alumina sintered body, contact the bonding surface of the discharge tube and the joint surface of the sealing member is directly The sealing member has an average particle size in the vicinity of the joint surface of 1 to 8 μm, and the polycrystalline alumina sintered body has a total light transmittance of 80% or more.

  In the prior arts described in Patent Documents 2 and 3, when the discharge tube is made of sapphire and the end cap is made of a sintered polycrystalline alumina, the polycrystalline alumina is sintered and bonded to sapphire. At this time, it is indispensable to improve the bonding strength that the polycrystalline alumina grows in the vicinity of the interface with sapphire, and it has been considered that the average grain size of the polycrystalline alumina is preferably larger. However, as a result of investigation by the present inventors, when the polycrystalline alumina sintered body does not grow until it becomes a complete single crystal (sapphire) and grain growth stops before that, coarse alumina particles follow the bonding interface. It was discovered that the joints were easily destroyed by thermal shock.

  Based on these discoveries, while maintaining the translucency of the polycrystalline alumina sintered body, it suppresses the grain growth in the vicinity of the joint surface with sapphire, thereby improving the durability and reliability of the joint portion against thermal shock. And the present invention has been reached.

  According to the knowledge of Patent Documents 2 and 3, the interfacial reaction is inferior in that the average particle size in the vicinity of the joint surface of the polycrystalline alumina sintered body with sapphire is small, that is, 8 μm or less as in the present invention. It should be sufficient and the joint strength and durability against thermal shock at the joint should be low, but the fact was reversed.

The entire discharge tube is preferably made of sapphire, but it is sufficient that sapphire is exposed at least on the joint surface. Moreover, it is preferable that the whole sealing member is made of a polycrystalline alumina sintered body, but it is sufficient that the polycrystalline alumina sintered body is exposed at least on the joining surface.

The average particle size in the vicinity of the joint surface of the sealing member is 1 μm or more and 8 μm or less. This average particle size is measured by the intercept method. Further, the vicinity of the bonding surface refers to the range of 50 μm from the bonding surface. From the viewpoint of the present invention, the average particle size in the vicinity of the joint surface of the sealing member is more preferably 6 μm or less. On the other hand, if the average particle size is less than 1 μm, the translucency is lowered and the reliability of the bonded portion tends to be lowered. Therefore, the average particle size is set to 1 μm or more. In the present invention, the total light transmittance of the polycrystalline alumina sintered body is 80% or more.

The joining temperature between the discharge tube and the sealing member is preferably set to 1730 ° C. or lower, which can suppress cracks at the joining interface and increase the joining strength. From this viewpoint, the bonding temperature is more preferably 1700 ° C. or lower.

Although there is no particular lower limit of the joining temperature between the discharge tube and the sealing member, it is usually preferably 1300 ° C. or higher, and more preferably 1400 ° C. or higher. Thereby, the reactivity of the interface of the joint portion can be ensured.

In order to control the average particle size of the polycrystalline alumina sintered body in the vicinity of the joint surface of the sealing member to 8 μm or less and to make the total light transmittance 80% or more, the particle size is larger than that of ordinary translucent alumina. It is necessary to use a raw material that suppresses growth.

  As such a raw material, for example, a raw material in which an auxiliary of 150 to 1000 ppm is added to high-purity alumina powder having a purity of 99.9% or more (preferably 99.95% or more) is preferable. The primary particle diameter of the high purity alumina powder is preferably 1.0 μm or less, and more preferably 0.5 μm or less.

  As such high-purity alumina powder, high-purity alumina powder “Tymicron TM-D”, “Tymicron TM-DR”, “Tymicron TM-DA”, “Tymicron TM-DAR” manufactured by Daimei Chemical Co., Ltd. “Tymicron TM-5D” can be exemplified.

As the above-mentioned auxiliary agent, magnesium oxide is preferable, but ZrO2, Y2O3, La2O3,
Sc2O3 can also be exemplified. The amount of auxiliary agent added is more preferably 500 ppm or less.

  For example, in the case of ordinary translucent alumina, the average particle diameter becomes 15 μm by heat treatment at 1730 ° C. × 2 hours, and the average particle diameter becomes about 30 μm by heat treatment at 1880 ° C. × 2 hours. On the other hand, when a raw material in which 250 ppm of magnesium oxide is added to the high-purity alumina powder as described above is used, the average particle diameter is 2 μm by heat treatment at 1600 ° C., the average particle diameter is 4 μm by heat treatment at 1700 ° C., and 1750 ° C. With this heat treatment, the average particle diameter becomes about 6 μm, and the grain growth is suppressed while maintaining the translucency.

  FIG. 1 is a longitudinal sectional view schematically showing a high-pressure discharge lamp 11 and a luminous vessel 20B according to an embodiment of the present invention. The arc tube 2A includes a pair of opening portions 2a and a light emitting portion 2f sandwiched between the pair of opening portions 2a. The end sealing member 14 of this example includes a flat plate portion 14a, an annular flange portion 14b protruding from the edge of the flat plate portion 14a, and an electrode holding portion 14e protruding from the center of the flat plate portion 14a. Yes. An electrode member 16 is inserted into a through hole 14a inside the electrode holding portion 14e, and an electrode 16a is provided at the tip thereof. The joint surface 14c of the flat plate portion 14a of the sealing member 14 is in contact with the end surface 2d of the discharge tube 2A. Further, the joint surface 14d of the flange portion 14b of the sealing member 14 is in direct contact with and joined to the outer end surface (joint surface) 2e of the discharge tube 2A.

  An ionized luminescent substance and a starting gas are sealed in the inner space 3 of the arc tube 2. In the case of a metal halide high pressure discharge lamp, an inert gas such as argon or xenon and a metal halide are sealed in the internal space of the discharge tube, and mercury or metal zinc is sealed as necessary.

  In the discharge lamp 21 and the luminous container 20C of FIG. 2, the discharge tube 2A and the end sealing member 24 are joined. An annular groove 24b is formed in the flat plate portion 24a of the end sealing member 24 of this example, and an electrode holding portion 24c protrudes on the opposite side. The electrode member 16 is inserted into the through hole 24f inside the electrode holding portion 24c, and the electrode 16a is provided at the tip thereof.

  The end 2a of the discharge tube 2A is inserted into the groove 24b. The outer surface (joint surface) 2e of the discharge tube 2A is in direct contact with and joined to the inner wall surface (joint surface) 24c of the groove 24b of the sealing member 24.

  When joining the discharge tube and the end sealing member, it is preferable to perform so-called shrink fitting. That is, the end sealing member molded body is placed on the outside of the discharge tube and sintered, thereby generating a crimping force from the end sealing member toward the outer surface of the discharge tube.

  In this embodiment, in the firing step, the outer diameter of the discharge tube is larger than the inner diameter of the sintered body (the diameter of the facing surface facing the discharge tube) when the end sealing member molded body is fired alone. Make it bigger. Thereby, a crimping force is applied in the radial direction from the end sealing member to the outer surface of the discharge tube at the time of firing, and adhesion and airtightness are improved.

  From this point of view, the ratio (RO / RI) of the inner diameter RO of the discharge tube to the inner diameter (diameter of the facing surface facing the discharge tube) RI when the end sealing member is fired alone is 1.01. It is preferable that it is above, and it is especially preferable that it is 1.03 or more.

  If (RO / RI) is too large, cracks are likely to occur at the joint. From this viewpoint, (RO / RI) is preferably 1.19 or less.

  The electrode member 16 includes a support portion and a coiled electrode 16a provided at the tip of the support portion. In addition, although the coil 16a was provided in the front-end | tip of the electrode member 16 in this example, the coil 16a is not necessarily required.

  In this example, the angle formed by the c-axis (arrow C) of sapphire constituting the discharge tube 2A and the tube axis L of the discharge tube 2 is 10 ° or less. Thus, by aligning the c-axis of the discharge tube made of sapphire in substantially the same direction as the tube axis (center axis) of the discharge tube, the discharge tube and the end sealing member fixed to the end of the discharge tube In the vicinity of the interface with sapphire, the crack generation rate of sapphire can be significantly reduced. From this viewpoint, it is more preferable that the angle formed by the c-axis of sapphire constituting the discharge tube and the tube axis of the discharge tube be 5 ° or less.

  In any example, an ionized luminescent substance and a starting gas are sealed in the inner space 3 of the arc tube. In the case of a metal halide high pressure discharge lamp, an inert gas such as argon or xenon and a metal halide are sealed in the internal space of the discharge tube, and mercury or metal zinc is sealed as necessary.

  The material of the discharge electrode is not limited, but a pure metal selected from the group consisting of tungsten, molybdenum, niobium, rhenium and tantalum is preferable, or two types selected from the group consisting of tungsten, molybdenum, niobium, rhenium and tantalum Alloys of the above metals are preferred. A composite material of these pure metals or alloys and ceramics is preferable.

  In the present invention, a sealant can be used in combination. The sealing material can be used for sealing the electrode member 16, for example. In this case, the type of the sealing material is not particularly limited. In a preferred embodiment, the sealing material is made of an oxide or oxynitride containing a rare earth element, aluminum, and silicon. Here, the sealing material may be an oxide substantially made of a rare earth element, aluminum, and silicon. Alternatively, it may further contain a nitrogen atom.

  Specifically, the raw material of the sealing material contains a rare earth oxide, alumina and a silicon compound, and may further contain a nitride.

The rare earth oxide is one or more elements selected from the group consisting of samarium, scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. It is an oxide. Particularly preferred is Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ or Tm ₂ O ₃ .

  Examples of the silicon compound include silicon oxide, silicon nitride, and sialon (SiAlON). Examples of the nitride include silicon nitride, sialon, aluminum nitride, and boron nitride.

In a preferred embodiment, the sealing material is a mixture having the following raw material composition.
Composition (A)
Rare earth oxide: 15 mol% or more and 70 mol% or less (particularly preferably 20 mol% or more or 60 mol% or less)
Silicon oxide: 3 mol% or more and 10 mol% or less (particularly preferably 4 mol% or more or 8 mol% or less)
Alumina: 10 mol% or more and 65 mol% or less (particularly preferably 15 mol% or more or 60 mol% or less)
Raw material composition (B)
Rare earth oxide: 10 mol% or more and 35 mol% or less (particularly preferably 15 mol% or more or 30 mol% or less)
Silicon oxide: 3 mol% or more and 10 mol% or less (particularly preferably 4 mol% or more or 9 mol% or less)
Alumina: 7 mol% or more and 40 mol% or less Nitride (including silicon nitride): 8 mol% or more and 65 mol% or less

The raw materials of the following composition system are particularly preferable.
_{Dy 2 O 3 -Si 2 O 3} -Al 2 O 3, Sc 2 O 3 -SiO 2 -Al 2 O 3, Y 2 O 3 -SiO 2 -Al 2 O 3, Dy2O3-Al2O3, Dy2O3-Al2O3-Sc2O3
_{Dy 2 O 3 -Si 2 O 3} -Al 2 O 3 -Si 3 N 4, Sc 2 O 3 -SiO 2 -Al 2 O 3 -Si 3 N 4, Y 2 O 3 -SiO 2 -Al 2 O 3 -Si ₃ N _{4,
Dy 2 O 3 -Si 2 O 3} -Al 2 O 3 -AlN, Sc 2 O 3 -SiO 2 -Al 2 O 3 -AlN, Y 2 O 3 -SiO 2 -Al 2 O 3 -AlN,
Y2O3-Al2O3-AlN-Si3N4
Dy2O3-Al2O3-AlN-Si3N4

The high-pressure discharge lamp of the present invention can be applied to various lighting devices.

For example, there are automobile headlamps, OHP (overhead projector), and liquid crystal projectors.

(Experiment 1)
A joined body 17 as shown in FIG. However, the cylinder 6 was formed of sapphire. The outer diameter RO of the cylinder 11 is 5 mm. On the other hand, for a high-purity alumina powder having a purity of 99.99% or more, a primary particle diameter of 0.10 μm, a BET surface area of 13.5 m ² / g, a tap density of 0.9 g / cm ³ , and a sintered density of 3.95 g / cm ³ 200 ppm of magnesium oxide powder was added.

  A binder was added to this raw material powder to obtain a molded body 12 shown in FIG. The end of the cylinder 11 was inserted into the recess 12 b of the molded body 12, and the inner wall surface 12 a of the recess 12 b was brought into contact with the outer wall surface 11 a of the cylinder 11. RO / RI was 1.04, where RI was the inner diameter when the compact 12 was fired alone.

  The assembly shown in FIG. 3A is fired at 1700 ° C. in a 100% dry hydrogen gas atmosphere for 1 hour, and an end sealing member 13 made of translucent alumina as shown in FIG. Obtained. The end of the cylinder 6 is inserted into the recess 13 b of the end sealing member 13, and a crimping force is applied from the inner wall surface 13 a of the recess 13 b to the outer wall surface 6 a of the cylinder 6.

  In the bonded body 17 thus obtained, the average particle diameter in the vicinity of the bonding surface 13a of the end sealing member was measured, and the results are shown in Table 1.

(Experiments 2-5)
A joined body 17 was produced in the same manner as in Experiment 1. However, the average particle diameter in the vicinity of the joint surface 13a of the end sealing member was changed by changing the purity and primary particle diameter of the alumina raw material powder, the amount of magnesium oxide, the baking temperature, and the baking time.

(Measurement)
About the joined body of each example, the presence or absence of leakage of the joined body was measured by a helium leak test, and the results are shown in Table 1. A sample having a leak amount of less than 10 ⁻¹⁰ atm · cc · sec was regarded as acceptable. Five samples were prepared for each example, and the acceptance rate (%) is shown in Table 1.
In addition, a spalling test was performed and the results are shown in Table 1. That is, each sample is heated to a predetermined temperature in the atmosphere, and then the sample is dropped into water. Under the present circumstances, (heating temperature under air | atmosphere)-water temperature is set to (DELTA) T (degreeC). Table 1 shows the minimum ΔT at which a crack occurred in the joint after dropping in water.

  As can be seen from the results, it has been found that, according to the present invention, not only the leakage from the joint portion is suppressed, but also the thermal shock resistance in the spalling test is remarkably improved.

  FIG. 4 is a scanning photomicrograph showing the cross section of the sample of Example 3 (average grain size of polycrystalline alumina in the vicinity of the joining surface is 3 μm). It can be seen that in the vicinity of the bonding interface, the grain growth of the polycrystalline alumina particles is suppressed and refined.

It is sectional drawing which shows roughly the edge part of the luminous container 20B and the assembly 11 for high pressure discharge lamps concerning one Embodiment of this invention. It is sectional drawing which shows roughly the edge part of 20 C of light emission containers and the assembly 21 for high pressure discharge lamps concerning one Embodiment of this invention. (A) is sectional drawing which shows the state which fixed the molded part 12 for edge part sealing members to the cylinder 6 made from sapphire, (b) is the joined body 17 formed by shrink fitting. It is sectional drawing shown roughly. It is a scanning microscope picture which shows the cross section of the sample of Example 3 (average particle diameter of the polycrystalline alumina in the joint surface vicinity 3 micrometers).

Explanation of symbols

2A discharge tube 2e, 6a, 13a, 14d joint surface 43 discharge space 6 cylinder 11, 21 high pressure discharge lamp assembly 13, 14, 24 sealing member 17 joint 20B, 20C luminous vessel

Claims (4)

A light emitting container comprising a discharge tube having an opening at an end, and a sealing member fixed to an end of the discharge tube,
Wherein at least the bonding surface of the discharge tube is Ri Do sapphire, the Ri least bonding surfaces of the sealing member Do polycrystalline alumina sintered body, contact the bonding surface of the discharge tube and the joint surface of the sealing member is directly and has an average particle diameter of the joint surface near the sealing member is 1μm or more and 8μm or less, wherein the total light transmittance of the polycrystalline alumina sintered body is 80% or more, the light emitting Container . The luminous container according to claim 1, wherein the polycrystalline alumina sintered body is produced from a high-purity alumina raw material containing 150 to 1000 ppm of magnesium oxide. The luminous vessel according to claim 1 or 2 , wherein an angle formed by a c-axis of sapphire constituting the discharge tube and a tube axis of the discharge tube is 10 ° or less. A light emitting container according to any one of claims 1 to 3, an electrode provided in an internal space of the discharge tube, and a conductor provided in the sealing member. An assembly for a high-pressure discharge lamp.

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