DE2023772C3 - Metal halide discharge lamp - Google Patents

Description

30 if the following condition is met in the lamp will:

[M]> [Cl] (1)

The invention relates to a metal halide

charge lamp with an aluminum trichloride filling. 35 where [M] is the total concentration of metals and

The high-pressure mercury vapor lamp in [Cl] meant the total concentration of chlorine. the last few years by adding certain metal To realize this condition, can be in the lamp iodide for the main filling of mercury and noble gas with regard to excess metal, expediently 3 aluminum of color rendering and luminous efficiency. In addition, the lamp can be improved. Most were additives such as sodium filling iodides of metal, especially aluminum iodide, Thallium iodide and indium iodide are preferred, and triiodide, may be added. This will additionally used. The presence of sodium iodide negates the extent of the corrosion on the electrodes a considerable increase in the ineffectiveness.

It was also found that aluminum trichloride

constantly through its resonance lines the mercury is incompatible with the quartz bulb of the lamp,

Radiation in the blue-green and yellow area of the spec- since aluminum trichloride can react _{with SiO 2.} It

trums. Although the color rendering, which is mainly necessary to use a lamp envelope

of lines with a weak line underneath, which is not affected by aluminum chloride

Continuum exists, has been greatly improved, is being taken up. This is the case when using a

no equivalent to natural daylight. 50 pistons made of highly compressed polycrystalline aluminum

In the French patent specification 1 544 036, miniumoxide is used, since aluminum trichloride with the Al ₂ O ₃

a high-power discharge lamp with a light-unresponsive. However, if you have lamp bulbs off

described permeable flask, which wants to use under quartz glass, the quartz must go through

can also consist of aluminum oxide. Which are protected by an inner AI ₂ O _{3 coating.}
The filling contains aluminum trichloride. 55 The invention is further illustrated by the drawings

An aluminum trichloride vapor discharge illustrated.

results in an emission that is almost completely shown in FIG. 1 shows an aluminum chloride lamp with

Close to solar radiation. However, if you have a piston made of highly compressed, polycrystalline

tried a lamp of the usual type with aluminum oxide;

a bulb made of quartz or quartz glass, tungsten 60 F i g. 2 shows the spectrum of an aluminum electrode and a filling of argon, mercury chloride discharge.

and to produce aluminum trichloride, one finds that a measure of the extent of the chlorides The piston reacts very quickly with the corrosion caused by the aluminum chloride tungsten and devitrified, while the tungsten electrodes weight gas pressure of the wolfin formed in the lamp can be destroyed in a few minutes. Even during 65 ram connections. The on values of the JANAF-der short life, the lamp is not stable, tables and their supplements based on earth the tungsten used as electrode material results from thermodynamic analyzes are in the Table 1 compiled from colder to warmer regions of the electrode:

If

table

Pwci.beUQQu'K

Pwci, at 2QOQ ⁰ K

Pwci, at 3QQQ ⁰ K

Trace-free Cl, ....
Fa »= 10-» Τοπ ...

AICI _{9 only}

Paicis * 1 atm

AlCl ₃ + Al

Paici »= i atm

Pajci = 1 atm

AlCl ₉ + Al + AtI ₃ .
Paios. Faxci = 1 atm
Pah = 1 atm.

5.4 atm 10- '° atm 10- * «atm 4 · IQ-" atm

4 · IQ- ⁸ atm

10 ' ⁴ atm

2.5 ♦ 10- ⁷ atm

4 · 10- ^ls atm

0.3 atm
1.2-10- * atm

2 · 10- * atm

The first line of the table gives the equilibrium pressure of tungsten chloride which forms in the presence of 10 " ³ Torr or 1 micron chlorine in the absence of aluminum or another getter metal. The equation to be considered in this case is:

20th

1. Oxygen-containing trace impurities can in the lamp made of aluminum trichloride chlorine release according to the following formula:

AlCl ₃ · (O) - Ai_O ₃

¹ CL

(6)

W (f) I- Cl (g) -> W ₁ CIj, (g)

(2)

The second line of the table contains the results for the case that only aluminum trichloride is in the Lamp is present. The reaction then proceeds as follows:

AlCI ₃ (g) + ■ W (f)

l _tf (g) - AlCI (g) (3)

These traces of free chlorine can then start a transport cycle in which the metals of the Participate lamp. This attacks the electrodes very quickly. However, if excess Aluminum is present, either the acidic

Substance contamination or the traces of free chlorine gettered, and this prevents the transport cycle.

2. At high temperatures, aluminum trichloride can be used according to the following equation

dissociate directly and release chlorine:

The third line of the table shows the results when aluminum trichloride and aluminum are in the Lamp are present. The reaction then proceeds as follows:

2 AlCI (g) + W (f) -y W ₁ CI ₁ , (g) - 2 Al (g) (4)

Finally, the last line shows the results, which are determined by the presence of aluminum trichloride, Aluminum and aluminum iodide can be obtained in the lamp. The reaction then proceeds as according to formula (4), but with the aluminum partial pressure, which results from the following dissociation forms:

AICl ₁ ^ AICI + 2Cl

50

All (g) - * Al (g) f I (g)

(5) The excess aluminum tends to react with the released chlorine, and so reduces the extent of the chlorine attack on the tungsten electrodes. If the If the lamp is switched off and cools down, the reaction (4) proceeds in the opposite direction. Excess Aluminum metal can therefore often be in the form of dendritic crystals or as a deposit can be observed as a dark film.

The beneficial effect of a further reduction triggered by the addition of aluminum triiodide to the lamp filling The attack on the electrodes is likely due to the following three factors:

The table clearly shows the reduction in corrosion caused by application excess Metal and metal iodide is achieved.

Since certain uncertainties have to be taken into account when determining the values, the information Table 1 should be understood more in a qualitative than in an absolute sense. However, they clearly show one strong effect, which is achieved according to the invention by the added metals and metal iodides.

These thermodynamic considerations apply not only to aluminum chloride but to others as well Halide systems applicable.

There is an excess for the following reasons of metal, especially aluminum, is desirable in the lattice.

1. The trace impurities contained in aluminum trichloride by oxygen (reaction 3) Released chlorine can corrode the tungsten electrodes before it becomes excess aluminum arrives and is gettered there. But if there is aluminum triiodide in the lamp filling is present, the following reaction can occur:

_^3/2 Cl ₂ + All, - AICI ₃ + ¹ V ₂ 1 "

Although some free iodine may be temporarily present as the lamp warms up, there is the attack on the tungsten electrodes far

lower, since iodine has to react weaker with tungsten. In a convenient lamp it will than chlorine. the discharge tube is not operated in air, but

Iodine can still be used to excess AIu in an evacuated outer casing (not shown) reach minium and become aluminum there. The lamp shown operates at 200 V and regenerate triiodide. The composition of 5 a current of 1.6 A for alternating current. One The lamp atmosphere therefore remains constant. Single peak voltage of 600 V when re-igniting Some of the excess aluminum was observed. To attack the electrodes consumed to further reduce oxygen-containing trace amounts, 0.1 mg of aluminum can be cleaned to getter. triiodide can be added to the filling. The Qucck-

2. The presence of aluminum triiodide in the ¹⁰ amount of silver can be reduced to the atmosphere through the air continue to AIu- Aluminiumtryodid increases caused increasing miniumkonzentration and reduces the chlorine voltage drop across the arc to kompensier ™,
concentration. This in turn reduces the corrosion of the lamp electrodes. In other ^f * ^{s "Unler} use e.nes discharge tube of words" volatilized "iodine excess' ⁵ fused silica or quartz produced when the metal and thereby reduces the amount the inside with a top pull of alumina by chlorine at the electrodes caused ^ ^erse _A ^h , ^{cn lst} . < ^der . ^d ff silicon oxide protects against corrosion attack by aluminum trichloride. A method to

Silicon dioxide with an aluminum oxide coating

3. The presence of iodides can also _be provided _ao, is the hot pipe promote a regenerative transport cycles that contribute mixture of Aluminiumtrichloriddampf and the walls of the lamp of tungsten oxidizing gas mixture to be kept free expedient verablagerungen CO _2. thin with argon, suspend. The

following reaction:

F i g. t shows an advantageous embodiment 25

a metal halide discharge lamp after the Er- AlCi ₃ \ - [O] (g) heated quartz Al ₂ O ₃ -f [Cl] (g)

finding. The lamp contains the bulb 2 made of ceramic tube, which was made of sintered, highly compressed, poly- For example, an aluminum chloride lamp crystalline aluminum oxide. The material consists of an aluminum oxide coated silicon coating More likely to be translucent than clear and made of quartz-oxide flasks that have a volume of 0.2 to to be similar. However, it has an excellent 1 ecm and with 2.2 mg of aluminum, 3.9 mg high light transmission and is therefore well filled for mercury chloride and argon of 40 torr Suitable for lamp purposes. The center piece of the lamp was. The discharge distance was about 4 mm; at has been omitted to avoid the figure. 600 watts, 5.1 A and 148 V was the efficiency shorten. The inner construction is from an average of 35 75 lumens per watt.

drawn part can be seen. For example, in the case of an alumina flask, you can

a 400 W lamp, the discharge tube is about 65 mm long, the niobium end caps are sealed directly with the jacket and have an inner diameter of 7 mm, by first fitting them as precisely as possible and having an electrode spacing of 40 mm. The tube inserted and then in a vacuum to the highest possible ends are heated by sleeve-like niobium seals or * o temperatures. When the other end caps 3 and 3 'are closed and sealed by a sealing process - sealing with a Mi-Aluminum-Oxyd-Calcium-Oxyd-Mischui! » 4 a mixture of calcium oxide and aluminum oxide - table sealed and used with the ceramic material used to attach the niobium end caps. Pipes connected. A niobium tube 5 protrudes through the sealed areas with aluminum oxide sleeve and will be coated during manufacture 45 in order to use the calcium dioxide from AIuz to evacuate the flask and then to protect against attack by minium chloride,
locked. A thermionic electrode 6 is shown in FIG. 2 of the drawing is the spectrum of the

attached to each end of the tube and is turned by the niobium-aluminum chloride discharge lamp through the curve tube 5 carried by the end cap 3. 11 reproduced. The dashed line 12 shows the

The filling of the discharge tube consists of aluminum 50 Compare the solar spectrum, while the curve 13 is minium trichloride, aluminum, mercury, argon as the sensitivity curve of the eye. You can see ignition gas and possibly aluminum triiodide. In that the spectrum is a strong continuum with one of the lamps shown, the following quantities are kept in a large number of relatively weak superimposed lines: 1 mg aluminum trichloride, 0.5 to 1 mg aluminum or bands. The amplitude is in the range minium, 5 mg mercury and argon at 20 torr. 55 of the eye sensitivity curve large, so that a high temperature of more than 600 ⁰ C, and this means, can be expected. Measurements have shown efficiencies of 70 Ludass, which protect the metal end caps from oxidation, men per watt and more.

1 sheet of drawings

Claims (5)

is transported and thereby its shape. Patent claims: changes quickly. The insufficiency is reinforced by the entry of impurities into the arc, 1. Metahhalide discharge lamp with a e.g. B. of SiCT ₄ , which is produced by the reaction between. A straight-through flask made of one material, aluminum trichloride and SiO, is also created through but not with aluminum at elevated temperatures. Change in the impermeability due to the chloride reacts, with rapid devitrification of the flask in the ends of the flask. melted tungsten electrodes and with and through changes in the vapor pressure of the K.om- a filling, the aluminum tricloride and the components, which by changing the thermal supply Facilitating the ignition contains a noble gas, 10 standing shape of the components in the lamp marked by the fact that this is gentle. . FüBung still contains aluminum. The aim of the invention is therefore an improved AIu- 2. Metal halide discharge lamp after aluminum chloride larope of longer life and spoke J, characterized in that the FOl-stable characteristic with which the above treatment also contains aluminum triiodide »5 disadvantages can be avoided. 3. MetaUhalogenidentladungslampe after arrival These objects are achieved by a ernndungsspruchl, characterized in that the folic proper MetaUbalogenidentladungsIampe with a lung addition Ahnniniumtrijodid and mercury light-transmissive envelope of a material containing silver with. elevated temperature not with aluminum 4. The metal halide discharge lamp reacts with the ends of the bulb after it has melted Claim 1, characterized in that the piston has tungsten electrodes and a filling, the aluminum high-density polycrystalline aluminum minium trichloride and to facilitate ignition oxide. contains a noble gas, which is characterized by 5. Metal halide discharge lamp as indicated is that this filling continues to be aluminum Claim 1, characterized in that the piston contains 25. consists of quartz glass, which is covered on the inside with It has been found that in aluminum chloride Discharge lamps containing a protective layer of aluminum oxide prevent the corrosion of the im is. Lamp bulb containing metals, such as. B. tungsten electrodes, can be significantly reduced,