EP1011126A2 - Metal halogen lamp - Google Patents

Abstract

Mercury-free metal halide lamp has a filling containing hafnium and/or zirconium halide for voltage gradient formation and tungsten cycle promotion. A mercury-free metal halide lamp has a filling comprising a noble gas as buffer gas, a compound (HZH) of a halogen (X) and Hf and/or Zr (HZM) for voltage gradient formation and cycle promotion, a light generating metal halide and a further easily evaporated metal halide as a voltage gradient former, the HZH content being ≥ 3 mu mol/cm<3> and the ratio (X + Y)/HZM being 5-15.

Description

Technical field

The invention relates to a metal halide lamp according to the preamble of Claim 1. These are mercury-free metal halide lamps, preferably with a ceramic discharge vessel.

State of the art

The use of the halides of hafnium and / or zircon for metal halide lamps together with mercury as a buffer gas has long been known. From EP-B 627 759 a metal halide lamp with high luminous efficacy is known which uses mercury as the buffer gas. An exemplary embodiment therein also shows a mercury-free filling for daylight use with a color temperature of 5350 K using HfBr ₄ as the metal halide and addition of elemental tin. The xenon (cold filling pressure 1 bar) takes on the role of the buffer gas. However, these lamps have enormous re-ignition peaks of around 600 V and can therefore only be operated with complex circuitry. In addition, the life of the lamps described there are between a few hours and at best 2100 hours. These lamps are therefore not suitable for general lighting.

Presentation of the invention

It is an object of the present invention to provide a metal halide lamp according to the Provide the preamble of claim 1, which is mercury-free and still can achieve a long lifespan of more than 5000 hours.

This object is achieved by the characterizing features of claim 1. Particularly advantageous configurations can be found in the dependent claims.

For the first time, the invention realizes mercury-free metal halide lamps, in particular with ceramic discharge vessel, with properties that have previously been found in metal halide lamps known with a discharge vessel made of quartz glass and Hg-containing filling are, namely a high luminous efficacy of at least 70 lm / W, and one high color rendering index Ra of at least 80, preferred for low performance up to 250 W. The service life is at least 5000 hours in the range from warm white to daylight white. The operation is advantageously carried out on one electronic ballast.

HZM") als Halogenide ( HZH") bei Einhaltung bestimmter Konzentrationsverhältnisse die Effektivität des Kreisprozesses entscheidend verbessert und somit lange Lebensdauern auch bei Hg-freien Füllungen ermöglicht.For the first time it has now been possible to achieve excellent maintenance of the luminous flux. Blackening of the wall of the discharge vessel is largely avoided. This is done by optimizing the tungsten cycle, which, as is generally known, is no longer controlled exclusively via the halogens of the filling, which are usually present as metal halides. It has surprisingly been found that the addition of the metals Hf and / or Zr (

HZM ") as halides ( HZH ") if certain concentration ratios are adhered to, the effectiveness of the cycle process is decisively improved and thus enables long lifetimes even with mercury-free fillings.

The discharge vessel can be a quartz glass bulb. A ceramic is preferred Discharge vessel, which can be tubular or bulged.

The prerequisite for a particularly efficient cycle process is a specific minimum concentration of metals that are effective in the cycle ( HZM "), primarily Hf and Zr. They are in the form of their halides, abbreviated as halides of hafnium and / or zircon ( HZH "). Bromine, chlorine and iodine can be used as halogen X. The specific amount of HZH in the discharge vessel must be at least 3 µmol / cm ³ : HZH ≥ 3 µmol / cm 3rd .

It is fortunate that these two metals are pronounced at the same time Have properties related to the formation of a voltage gradient, so that they can partially replace mercury in this regard. However, it is necessary that at least one other metal halide of the filling as a tension generator is added in order to adapt to the voltage gradient as well as possible of mercury.

Easily evaporable metal halides MYn are suitable for this, where Y is a halogen is selected from bromine, chlorine and iodine. These easily vaporizable metal halides are generally completely evaporated because they have a boiling point or have a sublimation point of at most 1100 ° C. That temperature is achieved primarily when ceramic discharge vessels are in operation on the vessel wall. In addition, elemental metals are suitable as additives to the cycle to be designed particularly effectively and thereby a long service life of ensure more than 6000 hours. Suitable elemental metals N are those which together with free halogens at typical wall temperatures around 1000 easily evaporable metal halides or metal halide complexes up to 1100 ° C can form. The following metals are suitable for this elementary or as a metal halide: Al, Bi, In, Mg, Sc, Sn, Tl, Zn, Sb, Ga.

The sum of the amount of halogen X bound in the Hf / Zr halides and the amount of halogen Y bound in the easily evaporable metal halides MY _n (each in µmol) must be based on the amount of metal bound in the Hf / Zr portion (HZM) Adhere to the range of values to ensure an effective cycle process: 5 ≤ (X + Y) / HZM ≤ 15.

A value between 8 and 13 is preferred without the addition of additional metal halides to the metals HZM (i.e. when using elementary metals such as in the prior art) the value of this ratio would be 4.

In particular, a longer service life can be achieved with careful measurement of the entire molar metal content G "of all voltage gradient formers (incl. Hf and Zr, i.e. HZM) in the filling in relation to the molar proportion of the metals Hf and Zr ( HZM ") alone. The metals G (ie the sum of M, N and HZM) are present in the filling as almost completely evaporated metal halides and elemental metals or metals which, with free halogens, can form metal halides and metal halide complexes which at temperatures almost completely evaporated on the vessel wall of typically 1050 ° C. The G / HZM ratio should not exceed 12, ie: G / HZM ≥ 12.

The natural lower limit is as defined G / HZM = 1 .

This upper limit in the ratio between all of them as voltage gradient formers added metals G and the metals also acting on the cyclic process Hf and Zr (HZM) result because the upper limit is exceeded in comparison to the metals HZM effective in the cyclical process, too high Concentrations of competing metals (M and N) in the vicinity of the Electrodes appear. This affects the tungsten transport process and leads eventually a significant deterioration in maintenance.

Another metal that promotes the cyclic process is titanium. It is therefore an encore Hf or Zr are suitable, but should only contain up to 50 mol% of the total HZM turn off.

In a particularly preferred embodiment, there is an excess of the total molar halogen fraction X + Y (normally bound in the easily evaporable halide compounds). The value of X + Y is at least 1.4 times the molar total metal fraction G bonded together in the easily evaporable compounds MY _n and metals N, that is: (X + Y) / G ≥ 1.4.

The setting of this ratio is particularly due to the high value the HZH (their value is usually four) favors.

In compliance with all of the above An optimal cyclic process is achieved under conditions Lifespans over 6000 hours.

The main operating mode is rectangular current injection with a high slope (i.e. a time period of the voltage change during a polarity change between two rectangular pulses of different polarity), preferred less than 30 µs, in question. Operation with constant power is favorable.

In the case of mercury-free metal halide lamps, the voltage gradient is used in the discharge arc and to adjust the thermal properties of the Lamps metal halides with high vapor pressure used in the setting wall temperatures in the discharge vessel either completely or predominantly go into the vapor phase. Typical examples of voltage gradient formers in durable systems that are suitable as an addition to Hf and Zr Halides of In, Zn, Al, Mg. There are also admixtures of the metal halides of Bi, Sc, Sn, Tl, Sb and Ga in question. These are called G (total metals the voltage gradient generator).

However, the voltage gradient formers, especially the HZM, are for light formation less suitable. For this reason, it is necessary as a light designer Add at least one other metal halide to the filling, i.e. a compound the at least one intense line in the visible spectral range between 380 and 780 nm. Typical examples of these light formers are halides the alkali metals (Na) and the lanthanides. They have a significantly higher boiling point than the voltage gradient formers and accordingly a much smaller one Vapor pressure.

With the filling according to the invention, maintenance of more than 80% of the luminous flux can be achieved after an operating time of 5000 h, based on the 100 h value. The initial efficiency after 100 h is at least 70 lm / W. A warm white light color with T _n = 3500 K with a color locus near the Planck curve is typical. A preferred area of application is interior lighting with color temperatures between approximately 2800 and 4200 K, with small wattages between 35 W and 150 W being the main target. Good color rendering (better than 80) is particularly difficult to achieve, especially at low color temperatures. The specific behavior depends on the choice of the admixed voltage generator and the mixture of the components filled in as a light generator.

This maintenance behavior can be improved by a significantly improved W cycle with the direct participation of Hf and Zr in the gas phase. The Examination of discharge vessels regarding the condition according to the invention of the share of HZH does not show any deposits of tungsten as Solid in the discharge vessel, in accordance with a negligible Blackening of the discharge vessel over the life of the lamp.

The filling compositions according to the invention can be taken into account the reactivity of the other filling components with those used Use wall materials, both in quartz glass vessels and in ceramic vessels. Translucent polycrystalline aluminum oxide or similar translucent polycrystalline ceramic materials (such as AlON, AlN, etc.) or monocrystalline Sapphire, however, are considered to be quartz glass because of their higher thermal resistance Wall material is preferable. These materials show a significantly lower reactivity under higher operating temperatures compared to the filling components.

The invention can be used for general lighting applications as well for automotive lighting and photo optics. At These applications are highly efficient Hg-free lamps with constant Maintenance of the luminous flux and constancy of the remaining light data over the lifetime of great importance. The scope extends to Power from about 20 W to more than 250 W.

The lamp systems according to the invention are advantageous in an illumination system operated on rectangular or HF ballasts.

In addition to an inert gas that acts as a buffer gas (Ar, Kr, Xe with a typical 0.1 to 1 bar, possibly up to 10 bar cold filling pressure), the filling should contain at least Hf and / or Zr halides, for example HfX ₄ ( X = J, Br, Cl) because these substances are the basis for a functioning W cycle process with mercury-free filling.

In addition, the filling contains at least one additional tension generator, to further increase the voltage gradient and to protect against premature Remelt the electrodes. Because the electrodes are covered by the Presence of Hf or Zr due to their high solubility in tungsten. Metal halides which have a high operating steam pressure are suitable for this a typical wall temperature (approx. 900 to 1100 ° C). A typical partial pressure the voltage generator during operation is more than 0.5 bar. A similar one The effective measure is to increase the cold filling pressure of the one acting as a buffer gas Starting gas (usually xenon) to more than 1 bar, namely up to 10 bar.

The filling also contains other metal halides which are difficult to evaporate. she act as a light generator and stabilize the bow. Halides are suitable Rare earth metals (lanthanides) and / or the alkali metals, in particular Na, Pr, Nd, La, Dy, Ho, Tm.

The absolute filling quantity of the Hf / Zr-halide mixture must exceed a lower limit so that an extraordinarily stable chemical cycle can take place in the lamp: HZH ≥ 3 µmol / cm 3rd .

If this limit is undershot, there is a noticeable deterioration in maintenance behavior and the W cycle process is not effective enough. A value between 4 and 6 μmol / cm ³ is preferred. If the value exceeds 6 µmol / cm ³ , the high percentage of HZH and the high solubility of the HZM in tungsten may melt the electrode at the highly loaded tip.

At least one further metal halide is added to the HZM. This is done in the form of a light generator, i.e. at least one other easily evaporating metal halide MY _n (with Y = J, Br, Cl; and n = 1 to 5). In addition, further elemental metals N (for example, M, N = Zn, Mg, Sn, In, Tl, Al, Sb) can be added, which with free halogens at the wall temperatures typically occurring in operation (for example 1000 ° C.) with metal halides can develop high vapor pressure. Thus, the combination of the aforementioned substances together with the Hf / Zr halides HZH provides the largest proportion of the total vapor pressure in the lamp, apart from the buffer gas filled. The filling quantity of the metal portion added to HZM (incl. HZM) in relation to the metal portions HZM bound only in the Hf / Zr halides should preferably not exceed a critical value of 12. With G = M + N + HZM applies to this ratio B: B = G / HZM ≤ 12.

The ratio B is preferably between 3.3 and 7.5. Without adding additional Metal halides for the halides of the HZM would have the value 1.

If the upper limit B = 12 is exceeded, the effectiveness of the W-Hf-Zr cycle is reduced noticeably hampered by competition from other types of metal. The service life decreases and the maintenance of the lamp during one operating period from 5000 h deteriorates.

The ratio D of the sums of the amount of halogen X bound in HZH (predominantly HfX ₄ and / or ZrX ₄ ) and the amount of halogen Y bound in the easily evaporable metal halide portion added, i.e. (X + Y), to the sum of all metal portions ( G = M + N + HZM ) The substances Hf / Zr-X ₄ and MY _n and N acting as stress generators should preferably reach a minimum value: D = (X + Y) / (HZM + M + N) ≥ 1.4.

This ratio is preferably above 1.46. Without adding additional Metals and metal halides to the HZM, this ratio would be four.

characters

Figur 1

eine Metallhalogenidlampe, teilweise im Schnitt;

Figur 2

eine Darstellung der Maintenance des Lichtstroms für eine bevorzugte Füllung;

Figur 3

ein weiteres Ausführungsbeispiel einer Metallhalogenidlampe.

The invention will be explained in more detail below with the aid of several exemplary embodiments. Show it:

Figure 1

a metal halide lamp, partly in section;

Figure 2

a representation of the maintenance of the luminous flux for a preferred filling;

Figure 3

another embodiment of a metal halide lamp.

Description of the drawings

A metal halide lamp with an output of 70 W is shown schematically in FIG. It consists of a cylindrical outer bulb 1 made of quartz glass which defines a lamp axis and is squeezed (2) and base (3) on two sides. The axially arranged discharge vessel 4 made of Al ₂ O ₃ ceramic is bulged in the middle 5 and has two cylindrical ends 6a and 6b. However, it can also be cylindrical with elongated capillary tubes as plugs, as is known, for example, from EP-A 587 238. The discharge vessel is held in the outer bulb 1 by means of two power supply lines 7, which are connected to the base parts 3 via foils 8. The power supply lines 7, one of which is a molybdenum band to compensate for the large expansion differences, are welded to bushings 9, 10, each of which is fitted in an end plug 11 at the end of the discharge vessel.

The bushings 9, 10 are, for example, molybdenum pins. Both executions 9, 10 are on the plug 11 on both sides and hold electrodes on the discharge side 14, consisting of an electrode shaft 15 made of tungsten and an am End pushed onto the discharge end 16. The bushing 9, 10 is each with the electrode shaft 15 and with the external power supply 7 butt welded.

The end plugs 11 essentially consist of a cermet known per se with the ceramic component Al ₂ O ₃ and the metallic component tungsten or molybdenum.

At the second end 6b there is also an axially parallel bore 12 in the plug 11 provided that for evacuating and filling the discharge vessel in a known manner Way serves. This bore 12 is made after filling by means of a pen 13, referred to in technical jargon as a stopper, or closed by means of melting ceramic.

The filling of the discharge vessel consists of an inert ignition gas / buffer gas, here argon with a cold filling pressure of 150 mbar, and various additives of metal halides. A proportion of at least 3 µmol / cm ³ HZH is essential.

The filling contains a total of up to three voltage gradient formers, one suitable selected mixture as light generator and possibly other additives. In particular TIJ has proven itself as an additional voltage gradient generator, possibly in combination with further voltage gradient formers. TIJ also makes a contribution in the visible spectral range.

Table 1 shows some fillings, with voltage gradient formers and light formers shown separately. Luminous efficiencies of between 70 and 77 lm / W (100-hour value) with good color rendering between Ra = 84 and 88 result. Not only bromine and iodine, but also chlorine are suitable as halogens. The color temperatures of these systems are between 3300 and 4000 K.

A mixture consisting of sodium as is particularly suitable as a light generator first component and at least one rare earth metal as the second component.

A lamp volume of 0.3 cm ^{3 was} used for all fillings. The electrode gap is 9 mm. The specific wall load (defined as electrical power / inner surface) varies between 15 and 50 W / cm ² . On average, it is 30 W / cm ² . The specific electrical power density varies between 100 and 500 W / cm ³ . On average, it is 235 W / cm ³ .

The lamps were each operated on an electronic ballast with rectangular current injection in a regulated power operation of 70 W with l _eff <1.8 A.

The lifespan of these lamps is more than 5000 hours. Convenient for one Fillings with halides of In or Mg have a relatively long lifespan proven.

Show particularly good maintenance behavior with regard to luminous flux Fillings containing the halides of Hf or Zr with careful consideration of an optimal Use the total amount of halogens and metals in the filling.

Figure 2 shows an example of the good maintenance of the luminous flux (in lm) over the operating time (in hours). The filling is based on HfBr ₄ (0.7 mg), with the additional tension builders InBr (0.7 mg), InBr ₃ (0.3 mg), TIJ (0.7 mg) and the additional light builders NaJ (2.4 mg), TmJ ₃ (1.5 mg), DyJ ₃ (1.4 mg), and HoJ ₃ (1.5 mg).

In a further exemplary embodiment (FIG. 3), the lamp is a metal halide lamp 18 with 70 W power, which is squeezed on one side, including the discharge vessel 19 is a quartz glass bulb pinched on one side. Otherwise match the same reference numerals for analog components as in FIG. 1. In the outer bulb 1 also accommodated a getter 17.

Very good start-up behavior is achieved with an electronic ballast (EVG) be realized that the lamp impresses a sufficiently high power ("constant wattage operation"). The TOE has the important advantage that it is the occurrence avoids reignition peaks due to a high slope.

Claims (10)

Mercury-free metal halide lamp with a luminous efficacy of at least 70 Im / W and a color rendering index of at least 80, the lamp comprising a discharge vessel into which electrodes are inserted in a vacuum-tight manner, characterized in that the filling comprises the following components: a noble gas that acts as a buffer gas, at least one compound of a halogen X with at least one of the metals hafnium and / or zirconium (hereinafter referred to as metals HZM), these halides HZMX _P hereinafter being referred to collectively as HZH, HZH simultaneously performing tasks of voltage gradient formation and promoting the cyclic process , a light former consisting of at least one further metal halide, at least one further metal M or a compound of a metal M with a halogen Y to form a metal halide MY _n which evaporates easily and which is used as a voltage gradient generator, the specific molar content of HZH being greater than or equal to 3 μmol / cm ³ , the following also applies: 5 ≤ (X + Y) / HZM ≤ 15 , which means the lamp life is more than 5000 hours. Mercury-free metal halide lamp according to Claim 1, characterized in that the specific molar content of the HZH is between 4 and 6 µmol / cm ³ . Mercury-free metal halide lamp according to claim 1, characterized in that that as HZM additionally titanium in an amount up to 50 mol .-% of the total amount HZM is used. Mercury-free metal halide lamp according to claim 1, characterized in that that at least one other elemental metal N as a voltage gradient generator is used. Mercury-free metal halide lamp according to claim 1 or 4, characterized in that that the ratio between the proportion of metals G (in µmol), where G is formed from HZM, M and possibly N, and the proportion of HZM is less than or equal to 12, and in particular the G / HZM ratio is between 3.3 and 8. Mercury-free metal halide lamp according to Claim 5, characterized in that the following applies: (X + Y) / (HZM + M + N) ≥ 1.4 . Mercury-free metal halide lamp according to Claim 1, characterized in that the following applies: 8 ≤ (X + Y) / HZM ≤ 13 . Mercury-free metal halide lamp according to claim 1, characterized in that that the discharge vessel is made of ceramic. Mercury-free metal halide lamp according to claim 1, characterized in that that as a light generator at least one of the following metals or a compound of this metal, in particular a halide thereof, is used: Na, Pr, Nd, La, Dy, Ho, Tm. Mercury-free metal halide lamp according to claim 1 or 4, characterized in that that as an additional voltage gradient generator at least one of the following Metals or a halide thereof (except fluoride) is used: Al, Bi, In, Mg, Sc, Sn, Tl, Zn, Sb, Ga.

Images