Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/36—Seals between parts of vessels; Seals for leading-in conductors; Leading-in conductors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/36—Seals between parts of vessels; Seals for leading-in conductors; Leading-in conductors
  • H01J61/361—Seals between parts of vessel
  • H01J61/363—End-disc seals or plug seals
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/30—Vessels; Containers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/82—Lamps with high-pressure unconstricted discharge having a cold pressure > 400 Torr
  • H01J61/827—Metal halide arc lamps
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/84—Lamps with discharge constricted by high pressure

Definitions

• the invention relates to a high-pressure discharge lamp comprising a ceramic discharge vessel having a first and a second end, with a first edge at the first end; a first metal closing member closing off the vessel at the first edge, the first metal closing member comprising a current feedthrough; an intermediate layer between the first edge of the ceramic discharge vessel's first end and the first closing member, with a coefficient of thermal expansion in between those of the ceramic discharge vessel and the first metal closing member.
• High-pressure discharge lamps include high-pressure mercury vapor lamps, metal halide lamps, and high-pressure sodium vapor lamps. These well-known lamp types have found a widespread application, for instance, in illuminating lamps for factories, light sources for overhead projectors and color liquid crystal projectors, lamps for automobiles and public lighting.
• a high-pressure lamp having a light-transmissive ceramic discharge vessel generally comprises ceramic closing members and metal current feedthroughs. Because of the different thermal expansion coefficients of the ceramic vessel and the metal feedthrough, quite some developments have been directed to providing a gas-tight seal for such high- pressure lamps.
• a sealing ceramic was used, as described in U.S. patent 4,011,480. Sealing ceramic is also known in the art as sealing glass. However, the known sealing ceramic is particularly susceptible to metal halide fills. In spite of great efforts, it has hitherto been impossible to develop a sealing glass that is capable of resisting corrosion.
• the greatest drawback of the end construction with a sealing ceramic is a crevice which remains or arises between the feedthrough and the ceramic plug. Salt can creep into this crevice.
• strongly demixing salts such as NaCe iodide to obtain a high luminous efficacy
• the color point of the light emitted by the burner will be influenced negatively, which results in a large color point spread and/or an unstable color-corrected temperature (CCT) and color point. This is caused by transport of different amounts of the different salt components from the vessel into the crevice during burning, for instance, when more Na iodide than Ce iodide deposits into the crevice.
• CCT color-corrected temperature
• the lamp has a ceramic discharge vessel with ceramic plugs closing off the ends of the lamp, each provided with a molybdenum current feedthrough of circular cross-section. At least a main or first member of the current feedthrough is tubular and has a coefficient of thermal expansion which is smaller than that of the ceramic plug.
• the current feedthrough is sintered in a gas-tight manner into the plug without using a sealing glass.
• the ceramic discharge vessel consists essentially of alumina and the non-conductive plug has alumina at least as a main component thereof. The direct sintering of the metal current feedthrough into the plug permits elimination of use of a sealing glass, which is subject to attack by the fill in the lamp.
• the current feedthrough is sintered in a gas-tight manner into the plug without using a sealing material.
• the vessel and the plug-shaped bodies are pre-fired, the feedthroughs are fitted into the axial hole of the pre-fired plug body, together with electrodes and connecting elements, and the sub-assembly is positioned in the axial hole of the pre-fired plug body.
• This sub-assembly with the plug body is positioned in the pre-fired edges of the vessel body, and the final assembly of feedthrough, plug body and vessel body are then sintered together.
• sintering three parts together in one operation increases the risk of leakage, and a tubular feedthrough is difficult to make.
• Another disadvantage is that this construction makes it very difficult to seal lamps with very small dimensions and or high buffer gas pressures. During the sealing process, the lamp content is heated, leading to effusion of gas and mercury.
• Nagayama in U.S. patent 5,742,123 has proposed another solution for a gas- tight feedthrough.
• This patent describes a high-pressure discharge lamp comprising a ceramic discharge vessel with two edges and two closing members closing off the vessel, which closing members comprise a metal current feedthrough and several intermediate layers between the ceramic discharge vessel and the closing members, with gradually increasing coefficients of thermal expansion obtained by increasing amounts of metal in the respective intermediate layers.
• a high-pressure discharge lamp comprises a ceramic discharge vessel having a first and a second end, with a first edge at the first end; a first metal closing member closing off the vessel at the first edge, the first metal closing member comprising a current feedthrough; an intermediate layer between the first edge of the ceramic discharge vessel's first end and the first closing member, with a coefficient of thermal expansion in between those of the ceramic discharge vessel and the first metal closing member, and is characterized in that the first edge is profiled.
• the advantage of a simple closure of the discharge vessel of the lamp can be profitably used at both sides, thus leading to a lamp of the invention, with a further intermediate layer between a second profiled edge at the second end and a second closing member.
• a simple, inexpensive sealing structure is used which provides a stable-stable lamp and allows filling with high gas pressures in metal halide lamps.
• the lamp of the invention comprises a ceramic discharge vessel.
• ceramic is understood to mean a translucent refractory material such as a monocrystalline metal oxide (e.g. sapphire), polycrystalline metal oxide (e.g. polycrystalline densely sintered aluminum oxide and yttrium oxide), and polycrystalline non-oxide material (e.g. aluminum nitride). Such materials allow wall temperatures of 1500-1700 K and resist chemical attacks by halides and Na.
• polycrystalline aluminum oxide (PCA) has been found to be most suitable.
• the ceramic discharge vessel may be a tube, but may alternatively have a barrel shape.
• the lamp of the invention preferably comprises at least two intermediate layers between the first edge of the ceramic discharge vessel's first end and the first metal closing member, with coefficients of thermal expansion gradually increasing from the vessel to the closing member.
• the ceramic vessel including the intermediate layer or layers may be made, for example, by co-molding (powder injection molding) or insert molding.
• the last intermediate layer, adjacent to the metal closing member as well as the closing member itself substantially consists of a similar metal. This allows the metal closing member including the feedthrough to be welded or brazed onto the metallized discharge vessel.
• edges of the vessel's ends in the lamp of the invention are profiled.
• the profiled edges strongly promote avoidance of crack initiation, delamination and or cracking at the interface.
• the shape of this profile may vary, but it is preferably formed by a beveled outer side of the edge of the vessel's end.
• the inner side of the edge is also beveled. Beveling the inner and outer sides of the edges of the vessel's end is a very simple way of realizing a profiled edge and results in a good adhesion between the vessel and a first intermediate layer, without forming detachments at the interlace of the alumina vessel and the first intermediate layer, which easily cause formation of cracks and leakages.
• Profiling the edge of the discharge vessel, for instance, by beveling has the important advantage that the edge has a surface which incorporates only obtuse or at most rectangular angles. Exclusion of acute angles, particularly at the outer and inner sides of the edge is very advantageous for reducing stresses in the closing construction of the discharge vessel formed by its end, the intermediate layers and the metal closing member.
• the intermediate layers between the first end of the ceramic discharge vessel and the first metal closing member have coefficients of thermal expansion gradually increasing from the end of the vessel to the closing member. This can be preferably obtained by intermediate layers that comprise an increasing amount of metal, such that the last layer, being the layer closest to the metal closing member, substantially consists of metal only.
• the metal used in the last intermediate layer and the metal closing member is preferably a metal having a high corrosion resistance and a coefficient of thermal expansion close to that of the closing member.
• the metal is preferably molybdenum.
• An additional advantage of the lamp of the invention is that the last intermediate layer and the metal closing member can easily be sealed by laser welding or brazing, thereby realizing a simple construction without any crevices.
• This way of sealing has the further advantage that the internal pressure in the lamp can be higher, whereas the lamp can have smaller dimensions.
• Fig. 1 shows a part of a lamp of the invention
• Figs. 2 and 3 show SEM pictures of a detail of the discharge vessel closure with the closing member in the lamp of the invention
• Fig. 4 shows a SEM picture of a detail of a seal between a vessel and a closing member in a lamp according to the state of the art.
• Fig. 1 schematically shows an example of a part of a lamp according to the invention at a first end 11 of a ceramic discharge vessel 1 having a first edge 100, wherein the alumina vessel is closed off with a molybdenum closing member 2 by a laser seal 6 on a molybdenum intermediate layer 4.
• a first intermediate cermet layer 3 for instance, consisting of a 1 : 1 mixture of alumina and molybdenum, which is co-molded with the alumina vessel 1.
• a molybdenum feedthrough 5 and a tungsten electrode 7 are welded to the closing member 2.
• Fig. 2 shows a SEM picture of a closure of the discharge vessel 1 in the lamp according to the invention as described with reference to Fig. 1.
• the beveled outer side 9 of the first edge 100 of the vessel 1 is connected in a gas-tight manner to the first intermediate cermet layer 3, comprising a 25:75 weight percentage ratio (w/w) mixture of molybdenum and alumina.
• a second cermet intermediate layer 10 comprises a 50/50 w/w mixture of molybdenum and alumina.
• the last intermediate layer 4 is made of molybdenum and welded to the molybdenum closing member (not shown).
• Fig.3 shows a SEM picture of a further closure of the discharge vessel 1 in the lamp according to the invention.
• the beveled sides 9, 8 of the first edge 100 of the vessel's first end 11 is connected in a gas-tight manner to the first intermediate cermet layer 3, comprising a 50/50 w/w mixture of molybdenum and alumina.
• the last intermediate layer 4 is made of molybdenum and welded to the molybdenum closing member (not shown).
• Fig. 4 shows a state-of-the-art seal between a vessel 21 and a closing member (not shown) with intermediate layers 23, 210 having a composition which is similar to that of layers 3 and 10 shown in Fig. 2.
• the edge sides of the vessel 21 are not beveled.
• a detachment 22 is shown at the interface of the alumina vessel and the first intermediate layer.

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• Vessels And Coating Films For Discharge Lamps (AREA)

Priority Applications (1)

Applications Claiming Priority (3)

Publications (1)

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• 2005
  • 2005-11-15 JP JP2007542403A patent/JP2008521191A/ja active Pending
  • 2005-11-15 KR KR1020077013843A patent/KR20070086407A/ko not_active Application Discontinuation
  • 2005-11-15 CN CNA2005800397087A patent/CN101258578A/zh active Pending
  • 2005-11-15 EP EP05804146A patent/EP1817940A2/en not_active Withdrawn
  • 2005-11-15 WO PCT/IB2005/053758 patent/WO2006054237A2/en active Application Filing
  • 2005-11-16 TW TW094140270A patent/TW200644042A/zh unknown

Non-Patent Citations (1)

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