CA2130424A1 - Use of silver to control iodine level in electrodeless high intensity discharge lamps - Google Patents
Use of silver to control iodine level in electrodeless high intensity discharge lampsInfo
- Publication number
- CA2130424A1 CA2130424A1 CA 2130424 CA2130424A CA2130424A1 CA 2130424 A1 CA2130424 A1 CA 2130424A1 CA 2130424 CA2130424 CA 2130424 CA 2130424 A CA2130424 A CA 2130424A CA 2130424 A1 CA2130424 A1 CA 2130424A1
- Authority
- CA
- Canada
- Prior art keywords
- iodide
- silver
- iodine
- high intensity
- fill
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J65/00—Lamps without any electrode inside the vessel; Lamps with at least one main electrode outside the vessel
- H01J65/04—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels
- H01J65/042—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels by an external electromagnetic field
- H01J65/048—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels by an external electromagnetic field the field being produced by using an excitation coil
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/12—Selection of substances for gas fillings; Specified operating pressure or temperature
- H01J61/125—Selection of substances for gas fillings; Specified operating pressure or temperature having an halogenide as principal component
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/24—Means for obtaining or maintaining the desired pressure within the vessel
- H01J61/26—Means for absorbing or adsorbing gas, e.g. by gettering; Means for preventing blackening of the envelope
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/82—Lamps with high-pressure unconstricted discharge having a cold pressure > 400 Torr
- H01J61/827—Metal halide arc lamps
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Discharge Lamp (AREA)
- Discharge Lamps And Accessories Thereof (AREA)
- Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
Abstract
USE OF SILVER TO CONTROL IODINE
LEVEL IN ELECTRODELESS HIGH
INTENSITY DISCHARGE LAMPS
Abstract Silver is added to the fill of an electrodeless high intensity metal halide discharge lamp, which includes at least one metal iodide as a fill ingredient, for controlling the iodine vapor level therein. In operation, silver reacts with free iodine, forming silver iodide (AgI), which has a relatively high boiling point and a relatively low vapor pressure. The iodine level is thus controlled below an arc instability threshold to promote and maintain arc stability. In addition, silver does not attack the quartz arc tube wall because silica (SiO2) is much more stable than silver oxide (Ag2O).
Moreover, the addition of silver to the arc tube does not accelerate the decomposition of iodides in the fill, such as sodium iodide (NaI), cerium iodide (CeI3), lanthanum iodide (LaI3), neodymium iodide (NdI3), and praeseodymium iodide (PrI3), which would otherwise enhance devitrification and etching of the quartz wall. Lamp performance and life are thus substantially improved using silver as an iodine getter.
LEVEL IN ELECTRODELESS HIGH
INTENSITY DISCHARGE LAMPS
Abstract Silver is added to the fill of an electrodeless high intensity metal halide discharge lamp, which includes at least one metal iodide as a fill ingredient, for controlling the iodine vapor level therein. In operation, silver reacts with free iodine, forming silver iodide (AgI), which has a relatively high boiling point and a relatively low vapor pressure. The iodine level is thus controlled below an arc instability threshold to promote and maintain arc stability. In addition, silver does not attack the quartz arc tube wall because silica (SiO2) is much more stable than silver oxide (Ag2O).
Moreover, the addition of silver to the arc tube does not accelerate the decomposition of iodides in the fill, such as sodium iodide (NaI), cerium iodide (CeI3), lanthanum iodide (LaI3), neodymium iodide (NdI3), and praeseodymium iodide (PrI3), which would otherwise enhance devitrification and etching of the quartz wall. Lamp performance and life are thus substantially improved using silver as an iodine getter.
Description
L~ ~
USE OF SILVER TO C~ONTRQL LODINE
Fi~ld o~ _th~ Invention The present invention relates generally to high intensity metal halide discharge lamps and, more particularly, to the use of silver in metal halide discharge lamps for controlling the iodine level therein and thereby promoting arc stability and improving lamp performance.
~ack~rQI~ of the I~ven~ion In operation of a high intensity metal halide discharge lamp, visible radiation is emitted by the metal portion of the metal halide fill at relatively high pressure upon excitation typically caused by passage of current therethrough. One class of high intensity metal halide lamps comprises electrodeless lamps which generate an arc discharge by e~tablishing a solenoidal electric field in the high-pressure gaseous lamp fill comprising the combinationo~ one or more metal halides and an inert buffer gas.
In particular, the lamp fill, or discharge plasma, is excited by radio frequency (RF) current in an excitation coiL surrounding an arc tube which contains th~ fill. The arc tube and excitation coil assembly acts essentially as a transformer which couples RF
energy to the plasma. That is, the excitation coil acts as a primary coil, and the plasma functions as a single-turn secondary. RF current in the excitation coil produces a time-varying magnetic field, in turn creating an electric field in the plasma which closes 2~3~J~L~ :
completely upon itself, i.e., a solenoidal electric field. Current flows as a result of this electric field, producing a toroidal arc discharge in the arc tube.
Typical electrodeless metal halide -discharge lamps use metal halides for generating white color lamp emission for general lighting applications.
Disadvantageously, however~ free iodine formation and devitrification of the arc tube wall occur in electrodeless high intensity metal halide discharge lamps after exposure to the plasma arc discharge. The amount of ~ree iodine in the arc tube increases with time. This accumulating iodine, beyond a certain threshold, causes arc instability and eventual arc extinction.
Accordingly, it is desirable to provide an iodine getter for controlling the iodine level in electrodeless high intensity metal halide discharge lamps and thereby promote arc stability. To be practicable, such an iodine getter should extend the useful life of the lamp and hence not enhance devitrification and etching of the arc tube wall.
$ummaI~ of the Inven~iQn Silver is added to the fill of an electrodeless high intensity metal halide discharge lamp, which includes at least one metal iodide as a fill ingredient, for controlling the iodine vapor level ~herein. In operation, silver reacts with free iodine, forming silver iodide (AgI), which has a relatively high boiling point and a relatively low vapor pressure. The iodine level is thus controlled below an arc instability threshold to promote and 2~ ~L~ ~
maintain arc stability. In addition, silver does not attack the quartz arc tube wall because silica (si2) is much more stable than silver oxide (Ay2O).
~oreover, the addition of silver to the arc tube does not accelerate the decomposition of iodides in the fill, such as sodium iodide (NaI), cerium iodide (CeI3), lanthanum iodide (LaI3) and neodymium iodide (NdI3), which would otherwise enhance devitrification and etching of the quartz wall. Lamp performance and life are thus substantially improved using silver as an iodine getter.
The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which:
Figure 1 is a partially schematic and partially cross sectional illustration of a typical electrodeless high intensity metal halide discharge 20 lamp; ~- ;
Figure 2 graphically compares the efficacy of a group A of electrodeless high intensity metal halide discharge lamps using silver as an iodine getter with corresponding control lamps not using the getter;
Figures 3 and 4 graphically compare the iodlne absorbance of groups A and B, respectively, of electrodeless high intensity metal hallde discharge lamps u~ing silver as an iodine getter with corresponding control lamps not using the getter;
Figure 5 graphically compares the color temperature for silver-gettered and control lamps of group A; and Figure 6 graphically compares color rendition index values for silver-gettered and control lamps of group A.
Detailed ~escriptlon of_the Figure 1 illustrates a typical electrodeless high intensity metal halide discharge lamp 10. As shown, lamp 10 includes an arc tube 14 formed of a high temperature glass, such as fused silica. ~y way of example, arc tube 19 is shown as having a substantially ellipsoid shape. However, arc tubes of other shapes may be desirable, de~ending upon the application. For example, arc tube 14 may be spherical or may have the shape of a short cylinder, or "pillbox", having rounded edges, if desired.
Arc tube 19 contains a metal halide fill, including at least one metal iodide, in which a solenoidal arc discharge is excited during lamp operation. A suitable fill comprises at least one rare earth metal halide (e~g., cerium iodide ~CeI3), lanthanum iodide (LaI3), neodymium iodide (NdI3), praeqeodymium iodide (PrI3)3 and at least one alkali metal halide (e.g., sodium iodldei (NaI), cesium iodide (CCiI) and lithium iodide ~LiI). One exemplary fill comprises sodium iodide, cerium iodide and xenon combined in weight proportions to generate visible radiation exhibiting high efficacy and good color rendering capability at white color ~emperatures.
j,s;,~ ~, : .,: .:: . ~:: ' 2 ~
Such a fill is described in commonly assigned U.S.
Pat. No. 4,810,938 of P.D. Johnson, J.T. Dakin and J.M. Anderson, issued on Mar. 7, 1989 and incorporated by reference herein. Another exemplary fill comprises S a combination of lanthanum iodide, sodium iodide, cerium iodide, and xenon, as described in commonly assigned U.S. Pat. No. 4,972,120 of H.L. Witting, issued Nov. 20, 1990 and incorporated by reference herein.
Electrical power is applied to lamp 10 by an excitation coil 16 disposed about arc tube 14 which is driven by an RF signal via a ballast 18. A
suitable excitation coil 16 may comprise, for example, a two-turn coil having a configuration such as that described in commonly assigned U.S. Pat. No. 5,039,903 of G.A. Farrall, issued Aug. 13, 1991 and incorporated by reference herein. Such a coil configuration results in very high efficiency and causes only minimal blockage of light from the lamp. The overall shape of the excitation coil of the Farrall patent is generally tha~ of a surface formed by rotating a bilaterally symmetrical trapezoid about a coil center line situated in the same plane as the ~xapezoid, but which line does not intexsect the trapezoid. However, other suitable coil configurations may be used, such as that described in commonly assigned U.S. Pat. No.
9,812,702 of J.M. Anderson, issued Mar. 14, 1989 and incorporated by reference herein. In particular, the Anderson patent describes a coil having six turns which are arranged to have a substantially V-shaped cross section on each side of a coil center line.
Still another suitable excitation coil may be of solenoidal shape, for exampie.
~3~2~
In operation, RF current in coil 16 results in a time-varying magnetic field which produces within arc tube 14 an electric field that completely closes upon itself. Current flows through the fill within arc tube 14 as a result of this solenoidal electric field, producing a toroidal arc discharge 20 in arc tube 14. The operation of an exemplary electrodeless high intensity discharge lamp is described in Johnson et al. U.S. Pat. No. 4,810,938, cited hereinabove.
In accordance with the present invention, silver is added to the metal iodide fill of an electrodeless high intensity discharge lamp in order to control the level o~ iodine vapor therein, thereby promoting arc stability. In operation, silver reacts lS with free iodine that has been released due to metal loss in the arc tube wall, forming silver iodide (AgI).
Under lamp operating conditions, some of the silver iodide vaporizes and some remains in the liquid phase. The vapor pressure of the silver iodide ls determined by its liquid temperature which, in turn, is controlled by the power applied to the syqtem. The iodine that i5 bound to silver in the liquid phase is not released to the vapor phase because silver iodide has a relatively high boiling point tl506 C) and a relatively low vapor pressure.
Hence, the total iodine concentration in the vapor phase is regulated by the liquid temperature only, and an excessive iodine buildup i5 avoided. Hence, with the iodine vapor pressure controlled below an arc instability threshold, arc stabllity is promoted and maintained.
, 2 ~ 2 j~
The quantity of silver employed as an iodine getter according to the present invention in order to control iodine vapor pressure below an arc instability threshold is dependent upon such factors as type and quantity of fill ingredients, size and shape of the arc tube, excitation power and operating temperature. An exemplary quantity is in the range, for example, from approximately 0.4 to 4 milligrams.
Advantageously, silver does not attack (or i reduce) the quartz arc tube wall because silica (si2) is much more stable than silver oxide (Ag2O).
Moreover, silver is less stable than the iodides of ~ -the lamp fill such as, for example, sodium iodide (NaI), cerium iodide (CeI3), lanthanum iodide (LaI3), neodymium iodide (NdI3), and praeseodymium iodide (PrI3), so that the addition of silver to the arc tube doss not accelerate the decomposition of the iodides of the fill which would otherwise enhance ~ `
devitrification and etching of the quartz wall. Lamp performance and life are thus substantially improved using silver as an iodine getter. `
The performance of two groups A and B of lamps were compared, each group consisting of lamps which did employ silver as an iodi.ne getter and corresponding control lamps which did not employ an iodine getter. The lamps of groups A and B are ellipsoid wlth dimensio~s l9mm x 26mm. Each lamp of group A (and its corresponding control group) conta~ned 8 mg of a ~ill mixture comprising sodium iodide (NaI) and neodymium iodide (NdI3) in a 5:1 -molar ratio. Each lamp of group B (and its 2 ~ 3 ~ ~ 2 ~
corresponding control group) contained 10 mg of a fill mixture comprising sodium iodide (NaI) and neodymium iodide (NdI3) in a 7:1 molar ratio. The lamps of group A were dosed with 1 mg of silver, and the lamps of group B were dosed with 0.49 mg of silver. The lamps of group A were operated with excitation coils of 31 mm inner diameter (I.D.), and the lamps of group B were operated with excitation coils of 34 mm I.D., each group being tested at a power level of 300 coil Watts. Each lamp of groups A and B had a quartz outer jacket filled with nitrogen gas surrounding the arc tube, thé group A jackets having an outer diameter ~O.D.) of 30 mm and the group B jackets having an O.D.
of 33 mm.
Photometric data were taken for the lamps of group A at burn times of 100, 500, 1000 and 2000 hours. The graph of Figure 2 compares the efficacy of the lamps of group A using silver as an iodine getter and the corresponding control lamps. Lamp efficacy was higher for the lamps of group A using silver as an iodine getter than for the control lamps. In addition, the lumen loss over the first 2000 hours of operation was much lower for the lamps of group A
t2.5%) than ~or the control lamps (15%).
Free iodine formed in the arc tubes was measured by absorption spectroscopy at a wavelength of 515 nm. The results for group A and B and their corresponding control groups are illustrated graphically in Figures 3 and 4, respectively. Iodine accumulated rapidly in the ungettered control lamps.
Advantageously, however, the level of fr~e iodine in the lamps using silver as an iodine getter ~as very low. As iLlustrated in Figure ~, arc instability was 9 2~3~ -7 2~
observed in a lamp of control group B at 2642 hours at an iodine absorbance of 0.36, equivalent to 0.56 mg of I2 formed in the lamp. At the same burn time, the arc was stable and the iodine absorbance was near zero in a corresponding silver-gettered lamp.
Advantageously, the addition of silver as a fill ingredient also improved the color temperature ;
and color consistency of the lamps of groups A and B.
Figure 5 shows color temperature as a function of lamp operating time for group A silver-gettered lamps and group A control lamps. The color temperature increased by 400 C in the control lamps at 2000 hours, while a constant color temperature was observed in the silver-gettered lamps.
Figure 6 compares the color rendition index (CRI) values measured for the silver-gettered and control lamps of group A. The CRI values measured at 100 hours were very similar in both the silver- ~
gettered and control lamps. As lamp operation time ~-increased, the CRI value of the control lamps increased, while the CRI of the silver-gettered lamps remained almost constant. Hence, color consistency is improved with the addition of silver to the fill.
For the lamps of groups A and B, it was also observed that the additions of silver to the lamps did not enhance deterioration of the arc tube walls.
~ hile the preferred embodiments of the present invention have been ~hown and described herein, it will be obvious that such ~mbodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to ~hose of skill - 10 - 2~3~.12i.~
in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
.
`'
USE OF SILVER TO C~ONTRQL LODINE
Fi~ld o~ _th~ Invention The present invention relates generally to high intensity metal halide discharge lamps and, more particularly, to the use of silver in metal halide discharge lamps for controlling the iodine level therein and thereby promoting arc stability and improving lamp performance.
~ack~rQI~ of the I~ven~ion In operation of a high intensity metal halide discharge lamp, visible radiation is emitted by the metal portion of the metal halide fill at relatively high pressure upon excitation typically caused by passage of current therethrough. One class of high intensity metal halide lamps comprises electrodeless lamps which generate an arc discharge by e~tablishing a solenoidal electric field in the high-pressure gaseous lamp fill comprising the combinationo~ one or more metal halides and an inert buffer gas.
In particular, the lamp fill, or discharge plasma, is excited by radio frequency (RF) current in an excitation coiL surrounding an arc tube which contains th~ fill. The arc tube and excitation coil assembly acts essentially as a transformer which couples RF
energy to the plasma. That is, the excitation coil acts as a primary coil, and the plasma functions as a single-turn secondary. RF current in the excitation coil produces a time-varying magnetic field, in turn creating an electric field in the plasma which closes 2~3~J~L~ :
completely upon itself, i.e., a solenoidal electric field. Current flows as a result of this electric field, producing a toroidal arc discharge in the arc tube.
Typical electrodeless metal halide -discharge lamps use metal halides for generating white color lamp emission for general lighting applications.
Disadvantageously, however~ free iodine formation and devitrification of the arc tube wall occur in electrodeless high intensity metal halide discharge lamps after exposure to the plasma arc discharge. The amount of ~ree iodine in the arc tube increases with time. This accumulating iodine, beyond a certain threshold, causes arc instability and eventual arc extinction.
Accordingly, it is desirable to provide an iodine getter for controlling the iodine level in electrodeless high intensity metal halide discharge lamps and thereby promote arc stability. To be practicable, such an iodine getter should extend the useful life of the lamp and hence not enhance devitrification and etching of the arc tube wall.
$ummaI~ of the Inven~iQn Silver is added to the fill of an electrodeless high intensity metal halide discharge lamp, which includes at least one metal iodide as a fill ingredient, for controlling the iodine vapor level ~herein. In operation, silver reacts with free iodine, forming silver iodide (AgI), which has a relatively high boiling point and a relatively low vapor pressure. The iodine level is thus controlled below an arc instability threshold to promote and 2~ ~L~ ~
maintain arc stability. In addition, silver does not attack the quartz arc tube wall because silica (si2) is much more stable than silver oxide (Ay2O).
~oreover, the addition of silver to the arc tube does not accelerate the decomposition of iodides in the fill, such as sodium iodide (NaI), cerium iodide (CeI3), lanthanum iodide (LaI3) and neodymium iodide (NdI3), which would otherwise enhance devitrification and etching of the quartz wall. Lamp performance and life are thus substantially improved using silver as an iodine getter.
The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which:
Figure 1 is a partially schematic and partially cross sectional illustration of a typical electrodeless high intensity metal halide discharge 20 lamp; ~- ;
Figure 2 graphically compares the efficacy of a group A of electrodeless high intensity metal halide discharge lamps using silver as an iodine getter with corresponding control lamps not using the getter;
Figures 3 and 4 graphically compare the iodlne absorbance of groups A and B, respectively, of electrodeless high intensity metal hallde discharge lamps u~ing silver as an iodine getter with corresponding control lamps not using the getter;
Figure 5 graphically compares the color temperature for silver-gettered and control lamps of group A; and Figure 6 graphically compares color rendition index values for silver-gettered and control lamps of group A.
Detailed ~escriptlon of_the Figure 1 illustrates a typical electrodeless high intensity metal halide discharge lamp 10. As shown, lamp 10 includes an arc tube 14 formed of a high temperature glass, such as fused silica. ~y way of example, arc tube 19 is shown as having a substantially ellipsoid shape. However, arc tubes of other shapes may be desirable, de~ending upon the application. For example, arc tube 14 may be spherical or may have the shape of a short cylinder, or "pillbox", having rounded edges, if desired.
Arc tube 19 contains a metal halide fill, including at least one metal iodide, in which a solenoidal arc discharge is excited during lamp operation. A suitable fill comprises at least one rare earth metal halide (e~g., cerium iodide ~CeI3), lanthanum iodide (LaI3), neodymium iodide (NdI3), praeqeodymium iodide (PrI3)3 and at least one alkali metal halide (e.g., sodium iodldei (NaI), cesium iodide (CCiI) and lithium iodide ~LiI). One exemplary fill comprises sodium iodide, cerium iodide and xenon combined in weight proportions to generate visible radiation exhibiting high efficacy and good color rendering capability at white color ~emperatures.
j,s;,~ ~, : .,: .:: . ~:: ' 2 ~
Such a fill is described in commonly assigned U.S.
Pat. No. 4,810,938 of P.D. Johnson, J.T. Dakin and J.M. Anderson, issued on Mar. 7, 1989 and incorporated by reference herein. Another exemplary fill comprises S a combination of lanthanum iodide, sodium iodide, cerium iodide, and xenon, as described in commonly assigned U.S. Pat. No. 4,972,120 of H.L. Witting, issued Nov. 20, 1990 and incorporated by reference herein.
Electrical power is applied to lamp 10 by an excitation coil 16 disposed about arc tube 14 which is driven by an RF signal via a ballast 18. A
suitable excitation coil 16 may comprise, for example, a two-turn coil having a configuration such as that described in commonly assigned U.S. Pat. No. 5,039,903 of G.A. Farrall, issued Aug. 13, 1991 and incorporated by reference herein. Such a coil configuration results in very high efficiency and causes only minimal blockage of light from the lamp. The overall shape of the excitation coil of the Farrall patent is generally tha~ of a surface formed by rotating a bilaterally symmetrical trapezoid about a coil center line situated in the same plane as the ~xapezoid, but which line does not intexsect the trapezoid. However, other suitable coil configurations may be used, such as that described in commonly assigned U.S. Pat. No.
9,812,702 of J.M. Anderson, issued Mar. 14, 1989 and incorporated by reference herein. In particular, the Anderson patent describes a coil having six turns which are arranged to have a substantially V-shaped cross section on each side of a coil center line.
Still another suitable excitation coil may be of solenoidal shape, for exampie.
~3~2~
In operation, RF current in coil 16 results in a time-varying magnetic field which produces within arc tube 14 an electric field that completely closes upon itself. Current flows through the fill within arc tube 14 as a result of this solenoidal electric field, producing a toroidal arc discharge 20 in arc tube 14. The operation of an exemplary electrodeless high intensity discharge lamp is described in Johnson et al. U.S. Pat. No. 4,810,938, cited hereinabove.
In accordance with the present invention, silver is added to the metal iodide fill of an electrodeless high intensity discharge lamp in order to control the level o~ iodine vapor therein, thereby promoting arc stability. In operation, silver reacts lS with free iodine that has been released due to metal loss in the arc tube wall, forming silver iodide (AgI).
Under lamp operating conditions, some of the silver iodide vaporizes and some remains in the liquid phase. The vapor pressure of the silver iodide ls determined by its liquid temperature which, in turn, is controlled by the power applied to the syqtem. The iodine that i5 bound to silver in the liquid phase is not released to the vapor phase because silver iodide has a relatively high boiling point tl506 C) and a relatively low vapor pressure.
Hence, the total iodine concentration in the vapor phase is regulated by the liquid temperature only, and an excessive iodine buildup i5 avoided. Hence, with the iodine vapor pressure controlled below an arc instability threshold, arc stabllity is promoted and maintained.
, 2 ~ 2 j~
The quantity of silver employed as an iodine getter according to the present invention in order to control iodine vapor pressure below an arc instability threshold is dependent upon such factors as type and quantity of fill ingredients, size and shape of the arc tube, excitation power and operating temperature. An exemplary quantity is in the range, for example, from approximately 0.4 to 4 milligrams.
Advantageously, silver does not attack (or i reduce) the quartz arc tube wall because silica (si2) is much more stable than silver oxide (Ag2O).
Moreover, silver is less stable than the iodides of ~ -the lamp fill such as, for example, sodium iodide (NaI), cerium iodide (CeI3), lanthanum iodide (LaI3), neodymium iodide (NdI3), and praeseodymium iodide (PrI3), so that the addition of silver to the arc tube doss not accelerate the decomposition of the iodides of the fill which would otherwise enhance ~ `
devitrification and etching of the quartz wall. Lamp performance and life are thus substantially improved using silver as an iodine getter. `
The performance of two groups A and B of lamps were compared, each group consisting of lamps which did employ silver as an iodi.ne getter and corresponding control lamps which did not employ an iodine getter. The lamps of groups A and B are ellipsoid wlth dimensio~s l9mm x 26mm. Each lamp of group A (and its corresponding control group) conta~ned 8 mg of a ~ill mixture comprising sodium iodide (NaI) and neodymium iodide (NdI3) in a 5:1 -molar ratio. Each lamp of group B (and its 2 ~ 3 ~ ~ 2 ~
corresponding control group) contained 10 mg of a fill mixture comprising sodium iodide (NaI) and neodymium iodide (NdI3) in a 7:1 molar ratio. The lamps of group A were dosed with 1 mg of silver, and the lamps of group B were dosed with 0.49 mg of silver. The lamps of group A were operated with excitation coils of 31 mm inner diameter (I.D.), and the lamps of group B were operated with excitation coils of 34 mm I.D., each group being tested at a power level of 300 coil Watts. Each lamp of groups A and B had a quartz outer jacket filled with nitrogen gas surrounding the arc tube, thé group A jackets having an outer diameter ~O.D.) of 30 mm and the group B jackets having an O.D.
of 33 mm.
Photometric data were taken for the lamps of group A at burn times of 100, 500, 1000 and 2000 hours. The graph of Figure 2 compares the efficacy of the lamps of group A using silver as an iodine getter and the corresponding control lamps. Lamp efficacy was higher for the lamps of group A using silver as an iodine getter than for the control lamps. In addition, the lumen loss over the first 2000 hours of operation was much lower for the lamps of group A
t2.5%) than ~or the control lamps (15%).
Free iodine formed in the arc tubes was measured by absorption spectroscopy at a wavelength of 515 nm. The results for group A and B and their corresponding control groups are illustrated graphically in Figures 3 and 4, respectively. Iodine accumulated rapidly in the ungettered control lamps.
Advantageously, however, the level of fr~e iodine in the lamps using silver as an iodine getter ~as very low. As iLlustrated in Figure ~, arc instability was 9 2~3~ -7 2~
observed in a lamp of control group B at 2642 hours at an iodine absorbance of 0.36, equivalent to 0.56 mg of I2 formed in the lamp. At the same burn time, the arc was stable and the iodine absorbance was near zero in a corresponding silver-gettered lamp.
Advantageously, the addition of silver as a fill ingredient also improved the color temperature ;
and color consistency of the lamps of groups A and B.
Figure 5 shows color temperature as a function of lamp operating time for group A silver-gettered lamps and group A control lamps. The color temperature increased by 400 C in the control lamps at 2000 hours, while a constant color temperature was observed in the silver-gettered lamps.
Figure 6 compares the color rendition index (CRI) values measured for the silver-gettered and control lamps of group A. The CRI values measured at 100 hours were very similar in both the silver- ~
gettered and control lamps. As lamp operation time ~-increased, the CRI value of the control lamps increased, while the CRI of the silver-gettered lamps remained almost constant. Hence, color consistency is improved with the addition of silver to the fill.
For the lamps of groups A and B, it was also observed that the additions of silver to the lamps did not enhance deterioration of the arc tube walls.
~ hile the preferred embodiments of the present invention have been ~hown and described herein, it will be obvious that such ~mbodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to ~hose of skill - 10 - 2~3~.12i.~
in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
.
`'
Claims (6)
1. An electrodeless high intensity discharge lamp, comprising:
a light-transmissive arc tube for containing a plasma arc discharge;
a fill disposed in said arc tube, said fill including at least one metal iodide;
an excitation coil situated about said arc tube for exciting said arc discharge in said fill; and an iodine getter comprising silver added to said fill in a predetermined quantity for controlling the iodine vapor level during lamp operation to promote arc stability.
a light-transmissive arc tube for containing a plasma arc discharge;
a fill disposed in said arc tube, said fill including at least one metal iodide;
an excitation coil situated about said arc tube for exciting said arc discharge in said fill; and an iodine getter comprising silver added to said fill in a predetermined quantity for controlling the iodine vapor level during lamp operation to promote arc stability.
2. The electrodeless high intensity discharge lamp of claim 1 wherein said at least one metal iodide is selected from a group of rare earth metal iodides consisting of: cerium iodide (CeI3), lanthanum iodide (LaI3), neodymium iodide (NdI3), praeseodymium iodide (PrI3), and any combination thereof.
3. The electrodeless high intensity discharge lamp of claim 1 wherein said at least one metal iodide is selected from a group of alkali metal iodides consisting of: sodium iodide (NaI), cesium iodide (CsI) and lithium iodide (LiI), and any combination thereof.
4. The electrodeless high intensity discharge lamp of claim 1 wherein said fill comprises at least one rare earth metal halide and at least one alkali metal halide.
5. The electrodeless high intensity discharge lamp of claim 4 wherein said at least one rare earth metal halide comprises neodymium iodide (NdI3) and said at least one alkali metal iodide comprises sodium iodide (NaI).
6. The electrodeless high intensity discharge lamp of claim 1 wherein said predetermined quantity is in a range from approximately 0.4 to 4 milligrams.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12538893A | 1993-09-23 | 1993-09-23 | |
| US08/125,388 | 1993-09-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2130424A1 true CA2130424A1 (en) | 1995-03-24 |
Family
ID=22419485
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2130424 Abandoned CA2130424A1 (en) | 1993-09-23 | 1994-08-18 | Use of silver to control iodine level in electrodeless high intensity discharge lamps |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0645799A1 (en) |
| JP (1) | JPH07153371A (en) |
| CA (1) | CA2130424A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5866981A (en) * | 1995-08-11 | 1999-02-02 | Matsushita Electric Works, Ltd. | Electrodeless discharge lamp with rare earth metal halides and halogen cycle promoting substance |
| TW343348B (en) * | 1996-12-04 | 1998-10-21 | Philips Electronics Nv | Metal halide lamp |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4360756A (en) * | 1979-11-13 | 1982-11-23 | General Electric Company | Metal halide lamp containing ThI4 with added elemental cadmium or zinc |
| JPS5914246A (en) * | 1982-07-15 | 1984-01-25 | Toshiba Corp | Metal halide lamp |
| US4810938A (en) * | 1987-10-01 | 1989-03-07 | General Electric Company | High efficacy electrodeless high intensity discharge lamp |
| US4929869A (en) * | 1987-11-12 | 1990-05-29 | Kabushiki Kaisha Toshiba | High intensity discharge lamp containing iron and silver in the arc tube filling |
| US4972120A (en) * | 1989-05-08 | 1990-11-20 | General Electric Company | High efficacy electrodeless high intensity discharge lamp |
| DE4013039A1 (en) * | 1990-04-24 | 1991-10-31 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | HIGH PRESSURE DISCHARGE LAMP |
-
1994
- 1994-08-18 CA CA 2130424 patent/CA2130424A1/en not_active Abandoned
- 1994-09-02 EP EP94306479A patent/EP0645799A1/en not_active Withdrawn
- 1994-09-19 JP JP22230794A patent/JPH07153371A/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07153371A (en) | 1995-06-16 |
| EP0645799A1 (en) | 1995-03-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0399288B1 (en) | Discharge lamp using acoustic resonant oscillations to ensure high efficiency | |
| US4810938A (en) | High efficacy electrodeless high intensity discharge lamp | |
| EP0207333B1 (en) | Electrodeless high pressure sodium iodide arc lamp | |
| US4890042A (en) | High efficacy electrodeless high intensity discharge lamp exhibiting easy starting | |
| US5864210A (en) | Electrodeless hid lamp and electrodeless hid lamp system using the same | |
| US4117378A (en) | Reflective coating for external core electrodeless fluorescent lamp | |
| JP2740200B2 (en) | High-pressure discharge lamp and lighting equipment equipped with this lamp | |
| US5479072A (en) | Low mercury arc discharge lamp containing neodymium | |
| US5438235A (en) | Electrostatic shield to reduce wall damage in an electrodeless high intensity discharge lamp | |
| EP0397421A2 (en) | High efficacy electrodeless high intensity discharge lamp | |
| US5270615A (en) | Multi-layer oxide coating for high intensity metal halide discharge lamps | |
| US7245075B2 (en) | Dimmable metal halide HID lamp with good color consistency | |
| US6501220B1 (en) | Thallium free—metal halide lamp with magnesium and cerium halide filling for improved dimming properties | |
| US5363015A (en) | Low mercury arc discharge lamp containing praseodymium | |
| JP2003249196A (en) | Microwave electrodeless discharge lamp lighting device | |
| CA2130424A1 (en) | Use of silver to control iodine level in electrodeless high intensity discharge lamps | |
| US5438244A (en) | Use of silver and nickel silicide to control iodine level in electrodeless high intensity discharge lamps | |
| US5343118A (en) | Iodine getter for a high intensity metal halide discharge lamp | |
| JPH0231458B2 (en) | ||
| US5136214A (en) | Use of silicon to extend useful life of metal halide discharge lamps | |
| JP3196647B2 (en) | Electrodeless high pressure discharge lamp | |
| JP3241611B2 (en) | Metal halide lamp | |
| JP3107269B2 (en) | Electrodeless lamp | |
| CA2000521A1 (en) | High efficacy electrodeless high intensity discharge lamp exhibiting easy starting | |
| JPH04289654A (en) | Metal halide lamp |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |