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Krasko, Z. K. & Brates, N. April 22 1997. patent EP 0 806 791 B1. 
Added by: Sarina (20 Feb 2020 09:46:30 UTC)   
Resource type: Patent
BibTeX citation key: Krasko1997
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Categories: Englisch = English
Keywords: Halogenmetalldampflampe = Metal Halide Lamp, Spektrum = Spectrum
Creators: Brates, Krasko
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Spektrum einer Metallhalogeniddampflampe mit 

Quecksilber, Natrium, Scandium, Lithium, Dysprosium, Thallium, Jod

Added by: Sarina  
Metal halide lamps of intermediate to high wattage, i.e., 175 to 1500 watts, were introduced in the U.S. in the early 1960's. They provided high efficacy, a CCT of about 4000 K and a CRI of about 65, numbers which meet most commercial needs. These lamps employed, typically, a sodium iodide, scandium iodide fill (occasionally also employing cesium) at a reasonably high power loading of 12 W/cm2 of inner arc tube surface.

As the market need for lower lamp wattages developed, 50, 70, 100 and 150 watt sizes having a warm color temperature of about 3000 K and a CRI of about 75 were introduced. These results were achieved by the addition of lithium iodide to the sodium-scandium-mercury-inert gas fill of the prior art. See, for example, U.S. Patent No. 5,057,743, which is assigned to the assignee of this invention. While these lamps function well, the output radiation has a purplish tint which is reflected in a shift of color chromaticity coordinates from the black body at 3200 K (x=0.420, y=0.395) down to x=0.420, y=0.380. This color shift has occasionally been found to be objectionable. Moreover, the specific color rendering index No. 9 (deep red) has a low negative value of -65

US-A 3 852 630 is related to a metal halide lamp with a fill which avoids the use of lithium iodide. The lamp comprises sodium halide, thallium, calcium halide and one or more of the elements scandium, yttrium, lanthanum and dysprosium or neodymium. Its relatively high color temperatures range from 4200 K to more than 5000 K.



1. A highly efficient discharge lamp having a colour rendering index of about 85, a lumen per watt rating of about 90, a correlated colour temperature of about 3000 K, a wall loading of about 21 W/cm2, comprising:

an outer glass envelope (12) and a pair of electrical conductors (26,28) extending into the interior of the glass envelope;

a quartz discharge tube (14) disposed within the outer envelope (12) and including a pair of spaced electrodes which are electrically connected to the electrical conductors for creating an electrical discharge during operation of the lamp, the discharge tube having an arc chamber;

a fill gas selected from argon and xenon and a given quantity of mercury to achieve a desired lamp voltage;

characterized in an arc generating and sustaining medium within the arc chamber comprising the halides of sodium, scandium, lithium, dysprosium, and thallium, wherein the molar ratios are as follows:

ratio sodium: scandium is (24 to 44) : 1;

ratio scandium: lithium is about 1:9,5;

ratio scandium: dysprosium is 1:(3 to 4);

said thallium is present in an amount from more than 0.35 to less than 0.45 mg/cm3 of arc tube volume.

2. The lamp of claim 1 wherein the halides are iodides.

3. The lamp of claim 1, wherein the arc chamber has a volume of about 1,2 cm3, an arc length of about 1,0 cm; and said fill contains 15 mg of mercury.

4. The lamp of claim 1, wherein the mole ratio sodium:scandium is 44:1.


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