JPS58158854A - Metal halide arc discharge lamp of long life and warm color - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention combats metal halide arc discharge lamps and specifically relates to lamps of this type which produce a warm color temperature close to that of incandescent lamps.
Arc discharge lamps contain mercury and several metal halides, usually e.g. sodium and scandium,
and an arc tube containing a lighting gas such as argon. These lamps are well known and have a long life (
1aO00 to 2ao00 hours depending on wattage)
Because of its high efficacy, it is often used in commercial equipment. Lamp efficacy is usually measured in lumens/wattage, and metal honeycomb arc lamps have efficiencies closer to 80-125 lumens/watt, depending on the wattage. Despite the many desirable properties of these lamps, their use is sometimes contraindicated when good color rendition is required. This is due to the relatively high color temperature of this type of lamp, which is 4400°. Changing the color temperature to a lower value requires increasing the ratio of red to blue radiation without a substantial change in green radiation.

Attempts to improve the color of visible radiation, which have not been entirely successful, have included adding other metals to the arc stream, such as lithium iodide, and adding phosphorescence to the inner surface of the envelope that surrounds the arc tube. There are some that are covered with the body. The latter attempt was often employed in high-pressure mercury discharge lamps (
For example, U.S. Pat. Nos. 4,824,792 and 4,241.
Reference No. 274 N). Phosphor coated metal halide lamps are also available, but their color temperature is only 40oO°.

Other recent attempts to reduce this type of color temperature include increasing the load on the arc tube. This increases the temperature of the arc tube wall, which increases the pressure in the gas phase, especially the sodium and mercury gas phases. The effect on discharge is twofold. The first is that the core temperature is reduced and therefore the production of atomic mercury radiation is reduced, resulting in a lower color temperature of the lamp. Second, the color temperature is further reduced because the sodium is expanded further into the red band under pressure. However, if the arc tube becomes too highly loaded, there will be repercussions. For example, a conventional metal halide lamp would have a load of 114 W 15", whereas this type of lamp would have a load of 2α7 W/am". High loads obviously require removal of the lamp starting pump from the arc tube. This requires an expensive external lighting circuit that employs a prong near the arc tube. This condition can cause electrolysis of sodium through the arc tube wall. Additionally, increased wall temperature accelerates life-limiting reactions between the additive and the arc tube wall. Such a reaction can result in catastrophic destruction within 4000 hours. This is an unacceptable situation.

The aim of the invention is therefore to avoid this drawback of conventional oak.

Another object of the invention is to improve metal halide arc discharge lamps.

A particular object of the invention is to provide a metal halide arc discharge lamp with low color temperature and long life.

According to one aspect of the invention, these objects of the invention are accomplished by providing a metal halide arc discharge lamp that includes an arc tube mounted within an envelope. The introversion of the envelope selectively obscures some of the arc tube's blue and ultraviolet radiation and re-radiates this absorbed energy in the red region of the spectrum, increasing the color temperature from approximately 4600'K to 3200'K.
coated with a phosphor mixture that shifts to ~3300°K. This useful shift in color temperature is accomplished according to the invention without any changes to the standard arc tube, its filling or its loading, avoiding the problems encountered with the prior art.

These and other objects and advantages of the invention will become apparent from the following description taken in conjunction with the drawings.

Referring to the drawings, the metal halide arc discharge lamp of FIG. 1 includes a mercury-containing arc tube 1 within a glass envelope 2. The arc tube 1 contains an inert lighting gas, such as argon gas, and at least disodium and scandium chlorides. Generally, halides are iodides.

The arc tube 1 is supported by a conventional mount 3 and a conventional electrical connection to the pace 4. It has liIM.

The dotted spectrum at 12fij represents the light output of the arc tube 1 during operation. As can be seen from the diagram, the spectrum has a strong peak in the blue region, but is relatively lacking in the red region. The spectrum does not show the strong UV peak (565, scream) resulting from the mercury discharge. This type of arc tube has a light output of about 58410 lumens, a color temperature of about 4465° and a color rendering index (CRI) of 6LO when operated at 400W in a clear glass BT57 jacket.

The lamp of the invention is formed by applying a phosphor coating 5 to the inner surface of the jacket 2.

The phosphor coating 5 comprises a first phosphor that absorbs radiation in the blue region and emits radiation in the red region, and a second phosphor that absorbs radiation in the ultraviolet region and emits radiation also in the red region. Contains a mixture of phosphors. The mixture contains 40% to 60% by weight of the first phosphor, the remainder being the second phosphor.
It is a phosphor.

A preferred range is 50% of each phosphor.

In a preferred embodiment, the Ill phosphor is manganese activated magnesium germanate (M
ta(F)G・0l:M1&)(Sylvanya Type 2
36 or 2161), and the second phosphor is yttrium orthovanadate (
yvoa:gw) (Sylvanya type 2590 or 2!591). A preferred mixture contains t 5 gr of each phosphor.

The spectrum of the lamp employing the phosphor coating 5 is
The mystery is shown in the figure. The difference between both spectra is clearly different, with the red region (approximately 620 nm and 658 a
An additional radiation peak is shown in m), at the same time the blue radiation is suppressed.

The overall result is a lamp color temperature of approximately 3266°;
A significant improvement in color rendering properties of CIL174.9 was demonstrated. The lumens dropped somewhat acceptably to about 56,820.

Thus, a metallurgical F-arter discharge lamp has been provided which has a low color temperature of disconnection and a high CRI. This result was obtained without disturbing the complex and proven chemistry of conventional metal pallite arc tubes, and also maintained the typical lifetime of this type of lamp.

Although the present invention has been described above with reference to preferred embodiments, those skilled in the art can make various changes and changes without departing from the technical idea of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional schematic diagram of a lamp adopting the present invention;
FIG. 2 is a spectral distribution curve illustrating the spectra of a conventional uncoated lamp and a coated lamp of the present invention. 1: Arc tube 2: Sheath 3: Mount 4: Base 5: Phosphor coating

Claims (1)

Claims: (1) an arc tube containing an inert gas, mercury, and at least a halide of sodium, which, when operated, contains radiation in the ultraviolet and blue regions of the optical spectrum; producing a light output with a spectralless dance substantially lacking in the red region, the light output of the arc tube having a color temperature of 4400°, and the arc tube having a phosphor coating on its inner wall; a first phosphor disposed within a jacket comprising a first phosphor, the phosphor coating absorbing radiation in the blue region of the spectrum and emitting radiation in the red region; It consists of a mixture with a second phosphor that absorbs radiation and emits radiation in the red region, and the emitted light is @S 200-~! ! High pressure cametal pallite arc discharge lamp with a color temperature of 500°. (2. In the lamp according to claim 1,
An arc discharge lamp wherein said first phosphor comprises a keyed phosphor weighing from about 40 to about 60 wt., the remainder comprising said second phosphor. (5) An arc discharge lamp according to claim 2, wherein said first phosphor comprises said phosphor weighing approximately 50% by weight. (4) In the lamp according to claim 2 or 3, the first phosphor is manganese-activated (tjgermanate!gnesium), and the second phosphor is aerobium-activated An arc discharge lamp comprising yttrium orthovanadate. (5) The lamp according to claim I, paragraph 1, paragraph 2, or paragraph 3, wherein the arc tube contains a scandium halogenide. lamp.