US3720855A

US3720855A - Electric discharge lamp

Info

Publication number: US3720855A
Application number: US00229933A
Authority: US
Inventors: P Gardner; A Heller; H Silver; S Ahmed
Original assignee: GTE Laboratories Inc
Current assignee: Verizon Laboratories Inc
Priority date: 1972-02-28
Filing date: 1972-02-28
Publication date: 1973-03-13
Anticipated expiration: 1990-03-13

Abstract

An electric discharge lamp comprising a sealed lighttransmissive envelope and a fill within the envelope; the fill including, as the primary light-emitting material, at least one oxytrihalide of a Group VB element, such as vanadium, niobium, and tantalum. The partial pressure of the oxytrihalide is in the range of from about 0.001 torr to about 200 torr.

Description

United States Patent 1 91 Gardner et al.

1 1March 13, 1973 ELECTRIC DISCHARGE LAMP Inventors: Phillip J. Gardner, Bayside; H. Graham Silver, Kings Point; Samir A. Ahmed, New York, all of N.Y.; Adam Heller, Sharon, Mass.

GTE Laboratories Bayside, N.Y.

Assignee: Incorporated,

Filed: Feb. 28, 1972 Appl. No.: 229,933

u. s.c1. ..313/229,313/184,313/1s5, 313/186, 313/187, 313/225, 313/227,

1111. c1 ..l-l0lj 17/20 Field 01 Search ..313/225, 227, 228, 229

[50] References Cited UNITED STATES PATENTS 3,331,982 7/1967 Waymouth et al. ..313/229 Primary Examiner-Roy Lake Assistant Examiner-Darwin R. Hostetter Attorneylrving M. Kriegsman [57] ABSTRACT An electric discharge lamp comprising a sealed lighttransmissive envelope and a fill within the envelope; the fill including, as the primary light-emitting material, at least one oxytrihalide of a Group VB element, such as vanadium, niobium, and tantalum. The partial pressure of the oxytrihalide is in the range of from about 0.001 torr to about 200 torr.

23 Claims, 2 Drawing Figures ELECTRIC DISCHARGE LAMP BACKGROUND OF THE INVENTION alone. When a potential is imposed across the spaced 1 electrodes in such a lamp, the mercury is excited and emits its characteristic spectral lines principally in the ultraviolet and blue-green region of the spectrum. It has recently been discovered that these lamps could be modified in their spectral emission by the inclusion of elements and compounds other than mercury, whereby the light produced is the combined emission of mercury and the included metals. Blending of emissions in this manner can produce wide variations in colors and, most importantly, an essentially white spectrum can be attained. Included metals which have been suggested have been the rare earth metals, added either in the form of the metal per se or as its halide.

Many of the rare earth metals, when dissociated from the halogen in the arc of a discharge lamp, emit a dense line spectrum predominantly in the visible region, thus producing a good color source. However, a sufficiently high vapor pressure must be obtained in order to achieve such emission. It has been found that the temperature of the coolest part of the envelope must be maintained near 900C if such vapor pressures are to be attained.

Heretofore, the use of such rare earth additives in an arc discharge lamp, although known, was rarely considered because of the problem of maintaining the envelope at the high temperature required to generate sufficient additive vapor pressure. Such temperatures would most probably cause softening of the quartz envelope, particularly at the glass-to-metal seal, in high pressure mercury lamps. However, the use of such rare earth additives has been accomplished in certain, lowpressure cases by mounting the discharge envelope and It is a further object of the present invention to provide an electric discharge lamp which includes a fill whose primary component is a volatile oxytrihalide of a Group VB element.

These and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed disclosure.

BRIEF SUMMARY OF THE INVENTION These and still further objects of the present invention are achieved in accordance therewith, by providing an electric discharge lamp having a sealed lighttransmissive envelope, and a fill within the envelope, the fill including as the primary light-emitting component at least one volatile oxytrihalide of a Group VB element (i.e. vanadium, niobium, and tantalum). The pressure or partial pressure of the oxytrihalide can extend from about 0.001 torr to about 200 torr.

When the oxytrihalide is used as the sole component of the fill, the light-emitting discharge is similar to those in fluorescent lamps, with the exception that the discharge does not saturate with increasing power density. This is because the emitters are not primarily resonant emitters as is the case with the mercury fill of fluorescent lamps.

a heating element within an outer glass envelope, the

space between the inner and outer glass walls either being evacuated or filled with nitrogen or an inert gas to a pressure which meets the requirement of proper discharge envelope warm-up. Such a lamp is shown, for example, in Thouret et al. U.S. Pat. No. 3,445,719. The need for this external heating element increases the complexity of the lamp, thus raising the cost of its production and, additionally, increasing the chance for its earlier failure during operation.

It would, therefore, be desirable to provide an electric discharge lamp which does not require external means to heat the fill to higher than normal operating temperatures, yet generates light of a desired and acceptable spectral quality.

OBJECTS OF THE INVENTION It is, therefore, an object of the present invention to provide a novel electric discharge lamp.

It is a further object of the present invention to provide an electric discharge lamp having a volatile active component whereby external means for increasing the temperature of the lamp are rendered unnecessary.

It is a further object of the invention to provide an electric discharge lamp having an improved fill.

The fill may also include a conventional quantity of an inert or noble gas, such as argon, to facilitate starting. In addition, mercury can be added in a conventional amount if it is desired to have a higher pressure discharge lamp with a lower operating voltage. Furthermore, other well known and conventional materials, such as thallium, sodium, or cesium halides, for example sodium iodide or thallium iodide, can be added to the fill for their known purposes, e.g. to lower operating voltages, adjust spectral output, etc.

In the higher pressure discharge lamps contemplated by this invention, the total pressure is defined, primarily by the partial pressure of the mercury vapor. Such total pressures are normally in the range of about onehalf to about 10 atmospheres, generally from about 1 to about 3 atmospheres. In these higher pressure lamps, the partial pressure of the oxytrihalide is from about 0.01 torr to about 200 torr.

In the lower pressure lamps contemplated by this invention, the total pressure is on the order of about 0.0l torr to about 30 torr, with the partial pressure of the oxyhalide being from about 0.001 torr to about 3 torr. The remainder of the total pressure created by the fill is from the other fill components, principally mercury. In these lower pressure lamps, there is a diffuse glow-type discharge where the discharge fills the entire envelope. In the higher pressure lamps, the arc tends to be more constricted.

Because of the volatility of the primary light-emitting component (i.e. the oxytrihalide of the Group VB element), the discharge lamps of the present invention do not require external wall heaters to maintain the oxyhalide in a volatile state. This is a distinct advantage which not only reduces production cost and chance of earlier operational failure, but is achieved with excellent light output having excellent spectral characteristics. For example, efficiencies on the order of about -130 lumens per watt have been attained with these lamps, while light of excellent quality was generated. Additionally, the lower pressure discharge lamps, as contemplated herein, would not require a cooling period before the lamps are reignited.

The sealed light-transmissive envelope is generally made of quartz, although other types of glass may be used, such as alumina glass or Vycor, the latter being a glass of high silica content. It is essential, of course, that the material selected for the envelope and the materials utilized in the fill not adversely react with one another, or with reaction products that might be produced during operation. The lamp further includes energizing means located either inside or outside of the envelope, depending on the type of energy applied for producing an electrical discharge inside the envelope.

Of the oxytrihalides of the Group VB elements, the chlorides and bromides are presently preferred, followed by the iodides. The fluorides can be utilized to the extent that the use thereof can be matched with envelope materials, electrode materials, seals, etc. which are non-reactive therewith.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of an electric discharge lamp constructed according to one embodiment of the invention; and

FIG. 2 is an emission spectrum of an electric discharge lamp constructed according to this invention and containing a fill of niobium oxychloride and argon.

DESCRIPTION OF SPECIFIC EMBODIMENTS Referring to FIG. 1, discharge lamp includes a sealed light-transmissive envelope 12 having

main discharge electrodes

13 and 14 at opposite ends thereof.

Electrodes

13 and 14, made of a suitable metal such as thoriated tungsten, are supported on lead-in

wires

15 and 16, respectively, and have

tungsten helixes

17 and 18, respectively, at their interior ends 8. An auxiliary starting electrode 19, generally prepared of tantalum or tungsten, is provided at one end of envelope 12 adjacent main discharge electrode 14, and comprises an inwardly projecting end of another leadin wire 20.

Each of the three current lead-in

wires

15, 16 and 20 have their ends welded to

intermediate foil sections

21, 22 and 23, respectively, of molybdenum which are hermetically sealed within pinched sealed

portions

24 and 25 of envelope 12. The foil sections are very thin, for example, approximately 0.0008 inch thick, and go into tension without rupturing or sealing off when the heated envelope cools. Molybdenum or

tantalum wires

26, 27 and 28 are welded to the outer ends of

foils

21, 22 and 23, respectively, and serve to convey current to the electrodes inside envelope 12. Inside envelope 12, there is volume 29 in which the complex herein described is volatilized, etc., during operation of the lamp.

In operation, the oxyhalides of the present invention break down, due to the electric discharge between the discharge electrodes and the high temperatures created thereby, to yield an oxide molecule of the Group VB metal or the Group VB metal atom itself. At the same time, free halogen and oxygen are also formed. No metallic oxide deposits are found on the cooler portions of the envelope wall since the metallic oxide (or the metal atom) reacts with the free halogen and oxygen to regenerate the oxyhalide compounds. Unfortunately, at the same time the spaced electrodes are slowly transported due to the atmosphere containing both oxygen and halogen atoms. Thus, the lamps of the present invention can be operated on the order of up to about I00 hours prior to electrode failure, and accordingly, are limited in the uses to which they may be put. During their lifetime, however, these lamps are exceptionally fine light generators, producing light of excellent quality at high efficiencies.

In other embodiments of the lamp (not shown) the

pair ofinternal electrodes

13 and 14 are eliminated and replaced by radio frequency or microwave discharge activators or energizers. This eliminates the electrode failure problem. With such energizers, the electrode transport problem is eliminated, whereby the discharge lamp can be operated for greater periods of time.

The following Examples are given to enable those skilled in the art to more fully understand and practice the present invention. They should not be considered as a limitation upon the scope of the invention but merely as being illustrative and representative thereof.

In Examples I XI the envelope utilized is a 400 watt quartz envelope having a diameter of about 2.3 cm, a length of about 6.0 cm, a length between tungsten electrode tips of about 5.3 cm, and a volume of about 14.0

EXAMPLE I A 400 watt quartz envelope is filled with 3.1 mg NbOCl and 100 torr argon. After the lamp is turned on, light output rises to a maximum and then decreases slightly. At the maximum light output, power is 260 watts, lamp current is 2 amps, and the efficiency is .2 lumens per watt (lm/w). After the light output decreased slightly, power is 237 watts, lamp current is 2 amps, and the efficiency is 83.4 lm/w. The discharge assumed an exceptionally brilliant white color with a slight reddish-pink tinge.

A typical spectrum attained with such a lamp is shown in FIG. 2 where molecular (Nb-0) band emission is seeri at the bottom of the Figure. Upon this emission there is superimposed substantial atomic line emission, both of these emissions contributing to the warm" white discharge attained with lamps of the present invention.

EXAMPLE II A 400 watt quartz envelope is filled with 5.4 mg NbOCl a small amount of l-Igl and torr argon. When operated at 1.5 amps and 330-360 watts, the lamp has an efficiency of 83.4-89.8 lm/w. The discharge is an exceptionally brilliant white with a slight reddish-pink tinge.

EXAMPLE III A 400 watt quartz envelope is filled with 7.5 mg NboBr 12.6 mg l-Igl, and 100 torr argon. When operated at 1.5 amps and 310 watts, the lamp has an efficiency of 81.7 lm/w. When operated at 1.5 amps and 235 watts, the lamp has an efficiency of 73.0 lm/w. In each case, the discharge is an exceptionally brilliant white with a slight reddish-pink tinge.

EXAMPLElV A 400 watt quartz envelope is filled with 3.9 mg NbOBr; 16.8 mg Hg l and torr argon. When operated at 1.5 amps and about 230 watts, the lamp has efficiencies of about 92.5 101.9 lm/w. The discharge is a brilliant white color with a slight reddish-pink tinge.

EXAMPLE V A 400 watt envelope is filled with 5.62 mg Nbl 4.14 mg HgO, 5.24 mg Hgl,, 5 torr Hg and 23 torr argon. When operated at 2 amps and 220 watts, the lamp has an efficiency of 80 lm/w. The discharge is an exceptionally brilliant white with a slight reddish-pink tinge.

EXAMPLE VI A 400 watt quartz envelope is filled with 2.54 mg NbOCl 5.07 mg I-lgl 1.69 mg Hg and 50 torr argon. When operated at 2 amps A.C. and 200 watts, the lamp has an efficiency of 68 lm/w. When operated at 2 amps D.C. and 200 watts, the lamp has an efficiency of 97 lm/w. The discharge is white with a slight reddish-pink tinge.

EXAMPLE VII A 400 watt quartz envelope is filled with 15.4 mg Nbl 4.6 mg I-IgO and 100 torr argon. When operated at 2 amps and 300 watts, the lamp has an efficiency of 88 lm/w.

EXAMPLE VIII A 400 watt quartz envelope is filled with 9.58 mg V1 5.62 mg 1,, 4.8 mg HgO and 100 torr argon. The lamp has an efficiency of 40 lm/w, and the discharge is white with a slight reddish-pink tinge.

EXAMPLE IX A 400 watt quartz envelope is filled with 24.65 mg V1 13.35 mg HgO and 100 torr argon. When operated at 2.5 amps and 350 watts, the lamp has an efficiency of 70 lm/w, and the discharge is white with a slight reddish-pink tinge.

EXAMPLE X A 400 watt quartz envelope is filled with a minor quantity of TaOCl and 100 torr argon. When operated at 300 watts, the discharge is principally infra-red emission.

EXAMPLE XI A 400 watt quartz envelope is filled with a minor quantity of VOCl and 100 torr argon. During operation at 300 watts, the discharge is white with a slight reddish pink tinge.

The use of HgO in combination with NbI, or V1,, as in Examples V, VII, VIII, and IX, is believed to form NbOI or V01 under the conditions which exist in the respective lamps during operation thereof.

In Examples XII XIX, light emission is promoted by the microwave activation of the components of the fill within the sealed light-transmissive envelope.

The envelope is made of quartz, is about 2.5 inches long, and about 0.75 inch in diameter. The ends are flat with one end having a side arm closely adjacent thereto. The other end (i.e. the end without the adjacent side arm) is inserted into the waveguide. Approximately l.3 inches of the length of the envelope is within the waveguide. Temperature adjustments and the control of the amount of the active component in the fill is by heating or cooling that portion of the envelope which extends out of the waveguide. Excess oxytrihalide material is present, but definitive weight or concentration measurements of the fill are not taken.

EXAMPLE XII The envelope is filled with NbOCl and 50 torr argon. When operated at temperatures from about 240C to about 320C, and microwave input power (at 2.45 G Hz) from about 145 to about 319 watts, the discharge is white with a reddish-pink tinge. Efficiencies range from 50 to 79 lm/w.

EXAMPLE XIII The envelope 'is filled with NbOCl and torr argon. When operated at temperatures from about 240C to about 295C, and input power from about 146 watts to about 258 watts at a frequency of 2.45 G Hz, the discharge is white with a reddish-pink tinge. Efficiencies range from 46 to 59 lm/w.

EXAMPLE XIV The envelope is filled with NbOCl and'150 torr argon. When operated at temperatures from about 240C to about 350C, and input power from about 150 watts to about 419 watts at a frequency of 2.45 G Hz, the discharge is white with a reddish-pink tinge. Efficiencies range from 47 to 78 lm/w.

EXAMPLE XV The envelope is filled with NbOCl TlCl and 150 torr argon. When operated at temperatures from about C to about 340C, and input power from about 225 watts to about 416 watts at a frequency of 2.45 G Hz, the discharge is white with a reddish-pink tinge. Efficiencies range from 62 to 141 lm/w.

EXAMPLE XVI The envelope is filled with NbOCl TlCl and torr argon. When operated at temperatures from about 250C to about 310C, and input power from about 144 watts to about 327 watts at a frequency of 2.45 G Hz, the discharge is white with a reddish-pink tinge. Efficiencies range from 78 to 127'lm/w.

EXAMPLE XVII The envelope is filled with TaOCl and 150 torr argon. When operated at about 230C, input power of approximately 100 watts at an excitation frequency of 2.45 G Hz, the discharge is a bright white.

EXAMPLE XVIII The envelope is filled with 3.42 mg NbOBr and 75 torr argon. When operated at 280C, input power of approximately 150 watts and an excitation frequency of 2.45 G Hz, the discharge is bright white with a pink tinge. I

EXAMPLE XIX The envelope is filled with VOBr and 150 torr argon. When operated at about 100C, input power of about 56 watts at excitation frequency of 2.45 G Hz, the discharge is white with a golden tinge.

EXAMPLE xx A 1 1% inches 1.D. quartz tube is formed into a closed square loop which is inches on a side. The envelope is filled with 5 torr of argon and VOCl in equilibrium with an extended stem at C. The closed loop is inductively coupled to a power source operating at a frequency of 3.0 M Hz. With 2 kilowatts of input power the light intensity at the surface of the envelope is 600 ft-candles. When operated with 3.5 kilowatts of input power, the light intensity is 1,500 ft-candles. in both cases the discharge is white with a reddish-pink tinge.

While the present invention has been described with reference to specific embodiments thereof, it will be understood by those skilled in this art that various changes may be made without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, apparatus, process or then present objective to the spirit of this invention without departing from its essential teachings.

What is claimed is:

1. An electric discharge lamp comprising a sealed light-transmissive envelope, a fill within said envelope, said fill including, as a primary light-emitting component, at least one oxytrihalide of a Group VB element, and energizing means for producing an electric discharge within said envelope.

2. The electric discharge lamp of claim 1 said oxytrihalide is vanadium oxytrihalide.

3. The electric discharge lamp of claim 1 said oxytrihalide is niobium oxytrihalide.

4. The electric discharge lamp of claim 1 said oxytrihalide is tantalum oxytrihalide.

5. The electric discharge lamp of claim 1 said oxytrihalide is an oxytrichloride.

6. The electric discharge lamp of claim 1 said oxytrihalide is an oxytribromide.

7. The electric discharge lamp of claim 1 said oxytrihalide is an oxytriiodide.

8. The electric discharge lamp of claim 1 wherein said oxytrihalide is an oxytrifluoride, said sealed envelope being of materials which are substantially inert with respect to said oxytrifluoride.

9. The electric discharge lamp of claim 1 wherein the wherein wherein wherein wherein wherein wherein total operating pressure within said envelope is from about k to about 10 atmospheres, the partial pressure of said oxytrihalide being from about 0.01 torr to about 200 torr.

10. The electric discharge lamp of claim 1 wherein the total pressure within said envelope is from about 0.01 torr to about 30 torr, the partial pressure of said oxytrihalide being from about 0.001 torr to about 3 torr.

11. The electric discharge lamp of claim 1 wherein said oxytrihalide is present in a partial pressure from about 0.001 torr to about 200 torr.

12. The electric discharge lamp of claim 1 and further including a pair of electrodes spaced apart within said envelope.

13. The electric discharge lamp of of claim 1 wherein said fill further includes a small quantity of an inert or noble gas to facilitate starting.

14. The electric discharge lamp of claim 1 wherein said fill further includes a quantity of mercury.

15. The electric discharge lamp of claim 14 wherein said mercury is present in a quantity sufficient to generate a pressure during operation of about one-half to about 10 atmospheres.

16. The electric discharge lamp of claim 14 wherein said mercury is present in a quantity sufficient to generate a pressure during operation of about 1 to about 3 atmospheres.

17. The electric discharge lamp of claim 1 wherein said fill further includes mercury in a quantity sufficient to generate a pressure during operation of about onehalf to about 10 atmospheres, and a minor quantity of an inert or noble gas.

18. The electric discharge lamp of claim 1 wherein said fill further includes a materialselected from the group consisting of the halides of sodium, thallium and cesium.-

19. An electric discharge lamp comprising a sealed light-transmissive envelope; and a fill within said envelope, said fill including at least one material which will, during operation of said lamp, yield the molecular emission of an oxide of a Group VB element.

20. The electric discharge lamp of claim 19 wherein said emission is that of Nb-O.

21. The electric discharge lamp of claim 19 wherein said emission is that of Ta-O.

22. The electric discharge lamp of claim 19 wherein said emission is that of V-O.

23. The electric discharge lamp of claim 19 and further including a pair of electrodes spaced apart within said envelope.

Claims

2. The electric discharge lamp of claim 1 wherein said oxytrihalide is vanadium oxytrihalide.

3. The electric discharge lamp of claim 1 wherein said oxytrihalide is niobium oxytrihalide.

4. The electric discharge lamp of claim 1 wherein said oxytrihalide is tantalum oxytrihalide.

5. The electric discharge lamp of claim 1 wherein said oxytrihalide is an oxytrichloride.

6. The electric discharge lamp of claim 1 wherein said oxytrihalide is an oxytribromide.

7. The electric discharge lamp of claim 1 wherein said oxytrihalide is an oxytriiodide.

9. The electric discharge lamp of claim 1 wherein the total operating pressure within said envelope is from about 1/2 to about 10 atmospheres, the partial pressure of said oxytrihalide being from about 0.01 torr to about 200 torr.

17. The electric discharge lamp of claim 1 wherein said fill further includes mercury in a quantity sufficient to generate a pressure during operation of about one-half to about 10 atmospheres, and a minor quantity of an inert or noble gas.

18. The electric discharge lamp of claim 1 wherein said fill further includes a material selected from the group consisting of the halides of sodium, thallium and cesium.