WO2006038148A1 - Quartz glass lamp with a defined ratio of aluminium and europium - Google Patents

Quartz glass lamp with a defined ratio of aluminium and europium Download PDF

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Publication number
WO2006038148A1
WO2006038148A1 PCT/IB2005/053167 IB2005053167W WO2006038148A1 WO 2006038148 A1 WO2006038148 A1 WO 2006038148A1 IB 2005053167 W IB2005053167 W IB 2005053167W WO 2006038148 A1 WO2006038148 A1 WO 2006038148A1
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WO
WIPO (PCT)
Prior art keywords
preferred
atom
quartz glass
value
colour point
Prior art date
Application number
PCT/IB2005/053167
Other languages
French (fr)
Inventor
Holger Christian Weinert
Paul Hellwig
Heinz Jansen
Simon Flink
Willem Wage
Original Assignee
Philips Intellectual Property & Standards Gmbh
Koninklijke Philips Electronics N. V.
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Application filed by Philips Intellectual Property & Standards Gmbh, Koninklijke Philips Electronics N. V. filed Critical Philips Intellectual Property & Standards Gmbh
Publication of WO2006038148A1 publication Critical patent/WO2006038148A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C4/00—Compositions for glass with special properties
    • C03C4/08—Compositions for glass with special properties for glass selectively absorbing radiation of specified wave lengths
    • C03C4/085—Compositions for glass with special properties for glass selectively absorbing radiation of specified wave lengths for ultraviolet absorbing glass
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/30—Vessels; Containers
    • H01J61/302—Vessels; Containers characterised by the material of the vessel
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01K—ELECTRIC INCANDESCENT LAMPS
    • H01K1/00—Details
    • H01K1/28—Envelopes; Vessels
    • H01K1/32—Envelopes; Vessels provided with coatings on the walls; Vessels or coatings thereon characterised by the material thereof
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/30—Doped silica-based glasses containing metals
    • C03C2201/34—Doped silica-based glasses containing metals containing rare earth metals
    • C03C2201/3423—Cerium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/30—Doped silica-based glasses containing metals
    • C03C2201/34—Doped silica-based glasses containing metals containing rare earth metals
    • C03C2201/3447—Europium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/30—Doped silica-based glasses containing metals
    • C03C2201/34—Doped silica-based glasses containing metals containing rare earth metals
    • C03C2201/36—Doped silica-based glasses containing metals containing rare earth metals containing rare earth metals and aluminium, e.g. Er-Al co-doped

Definitions

  • the invention relates to an electric lamp provided with a light- transmitting lamp vessel and a light source in said light-transmitting lamp which is closed in a vacuum-tight manner, wherein the light source has an envelope of light- transmitting, UV-absorbing quartz glass which contains aluminium in oxidic form and at least one metal in oxidic form selected from the group comprising cerium and europium as well as applications thereof.
  • EP-Al 0 658 920 discloses an electric lamp which has an envelope which is at least substantially transparent to visible radiation and which is at least substantially impervious to UV radiation. This is achieved by the composition of the quartz glass envelope, which comprises silicon, cerium, titanium, europium, and aluminium in oxidic form, whereby silicon is present as 99.01 weight-% SiO 2 , cerium as 0.54 weight-% CeAlO 3 , titanium as 0.03 weight-% TiO 2 , europium as 0.09 weight-% Eu 2 O 3 and aluminium as 0.33 weight-% Al 2 O 3 .
  • This doped quartz glass suffers from the disadvantage that if certain processing parameters are not met, the glass may at least partially begin to crystallise. A higher crystallinity of the glass may result in, amongst others, opacity of the glass, which could decrease the light efficiency of the total lamp system and lead to rejection of the product by the customer.
  • Another disadvantage is that in the quartz glass of the kind mentioned above, at least some components may not completely dissolve in the quartz matrix during processing. Furthermore, a lamp of this kind may exhibit a less than satisfying colour point stability after some time of operation, for example after 2500 hours.
  • the transmission of visible light through the quartz glass is not optimised. Typically, the transmission of the lamp disclosed in EP-B 0 658 920 in the visible portion of the spectrum is only approximately 92%. All in all this results in a decreased efficiency of the electric lamp system according to EP-Al 0 658 920.
  • the object of the present invention is achieved in that the quartz glass of the envelope of an electric lamp comprises silicon, cerium, europium and aluminium in oxidic form, while the atomic ratio aluminium/europium is in the range of 2:1 to 16:1 and whereby the titanium content of said quartz glass is at most > 0 atom-% to ⁇ 0.001 atom-%, based on said quartz glass.
  • the atomic ratio of two components is to be understood as the ratio of the respective amounts of the components, also conveniently expressed as their molar ratios.
  • the envelope of light-transmitting, UV-absorbing quartz glass according to the present invention can have a crystallisation visible to the naked eye of > 0% and ⁇ 10%, preferably ⁇ 1% and most preferred 0% due to the reduced tendency to crystallise. This is beneficial with respect to the opacity of the glass, which could decrease the light efficiency of the total lamp system and can lead to rejection of the product by the customer.
  • quartz glass in which said elements are present in oxidic form in the silicon dioxide matrix and in the given quantities and ratios is at least substantially transparent to visible radiation and at least substantially impervious to UV radiation.
  • the quartz glass which will also be referred to as doped quartz glass hereinafter, can owe these properties to all its components in their stated quantities in conjunction.
  • the elements cerium and europium each can absorb a spectral portion of the UV radiation, which portions supplement one another and may partly overlap one another.
  • the bivalent form will arise during melting in a reducing atmosphere, for example, of helium and hydrogen.
  • the batch may comprise the oxides of the cationogenous elements of the doped quartz glass or alternatively mixed oxides of such elements.
  • aluminium keeps the europium essentially in its bivalent form dissolved in the matrix.
  • a favourable influence of aluminium is furthermore that it counteracts the rheological changes of the quartz glass caused by the presence of bivalent europium.
  • the amount of cerium, europium and aluminium should be selected insofar that: the amount of cerium is from 0.05 atom-% to 0.3 atom-%, preferred from 0.10 atom-% to 0.25 atom-%, more preferred from 0.15 atom-% to 0.2 atom-%; and/or the amount of europium is from 0.01 atom-% to 0.1 atom-%, preferred from 0.02 atom-% to 0.07 atom-%, more preferred from 0.035 atom-% to 0.05 atom-%; and/or - the amount of aluminium is from 0.05 atom-% to 0.8 atom-%, preferred 0.2 atom-% to 0.7 atom-%, more preferred 0.36 atom-% to 0.52 atom-% of the quartz glass.
  • the quartz glass of the envelope comprises cerium in form Of CeAlO 3 .
  • the Cerium source can also be CeO 2 , Ce 2 Si 2 O 7 , (NH 4 ) 2 Ce(NO 3 ) 6 , CeCl 3 , Ce(NO 3 ) 3 and/or Ce(SO 4 ) 2 .
  • the amount of CeAlO 3 in the quartz glass is from > 0 weight- % to 0.9 weight-%, more preferred from 0.4 weight-% to 0.8 weight-% and most preferred from 0.5 weight-% to 0.7 weight-%; based on the total weight of the quartz glass.
  • the doped quartz glass comprises 0.16 atom-% ⁇ 0.1% cerium and/or 0.04 atom-% ⁇ 0.1% europium or quantities of these elements which may be up to ⁇ 0.1% greater or smaller per element.
  • the UV absorption by europium can be beneficially increased, as well as the transmission of light. Therefore it can be preferred that the atomic ratio of aluminium/europium is from 9:1 to 15:1, preferred from 13:1 to 14: 1, and in particular the atomic ratio of aluminium/europium is 13.7:1. However, it can be suitable that the atomic ratio of aluminium/europium is >8: 1.
  • the components of the ionisable filling are selected from the group comprising NaI, ScI 3 , ZnI 2 and/or Hg.
  • Electric lamps can contain mercury as a component of the ionisable filling.
  • the ionisable filling of the electric lamp according to the present invention does not contain mercury, since electric lamps free from mercury are beneficial to the environment and to the consumer, especially in the event of a breaking of the lamp.
  • the components of the ionisable filling can be selected in an amount of:
  • the invention is not restricted to a certain ionisable filling. Furthermore, any ionisable filling can be used which seems to be suitable to use with a lamp according to the present invention.
  • the ionisable filling can be 50 weight-% NaI, 30 weight-% ScI 3 and 20 weight-% ZnI 2 .
  • the ionisable filling can be 25 weight-% NaI, 10 weight-% ScI 3 and 65 weight-% Hg.
  • the interior pressure inside the light source containing the ionisable filling at room temperature can be from 4 bar to 14 bar, preferred from 8 bar to 14 bar and more preferred from 8 bar to 12 bar.
  • a lamp according to the present invention can be improved in that the colour of the emitted light remains constant during many hours of operation. For instance, it is desired that the colour point of said lamp does not shift to an undesired extent during operation time.
  • the colour point shift could be improved beneficially.
  • the relative shift of the colour point coordinates between 500 hours of operation and 2500 hours of operation can be ⁇ 0.025 for the x- value of the colour point coordinate and/or ⁇ 0.035 for the y-value of the colour point coordinate, preferred ⁇ 0.020 for the x-value of the colour point coordinate and/or ⁇ 0.025 for the y-value of the colour point coordinate and most preferred ⁇ 0.013 for the x-value of the colour point coordinate and/or ⁇ 0.019 for the y-value of the colour point coordinate.
  • the absolute shift of the colour point coordinates after 500 hours of operation can be: - from 0.382 to 0.374 for the x-value of the colour point coordinate; and/or from 0.386 to 0.378 for the y-value of the colour point coordinate; preferred: - from 0.380 to 0.376 for the x-value of the colour point coordinate; and/or from 0.384 to 0.380 for the y-value of the colour point coordinate; most preferred: from 0.378 to 0.377 for the x-value of the colour point coordinate; and/or - from 0.382 to 0.381 for the y-value of the colour point coordinate; and/or wherein the absolute shift of the colour point coordinates after 2500 hours of operation can be: from 0.369 to 0.361 for the x-value of the colour point coordinate; and/or from 0.368 to 0.360 for the y-value of the colour point coordinate; preferred: from 0.367 to 0.363 for the x-value of the colour point coordinate; and/or from 0.366 to 0.362
  • lamps according to the present invention possess a high light efficiency.
  • the light efficiency of lamps according to the present invention can be from 70 Lumen/Watt to 100 Lumen/Watt, preferred from 75 Lumen/Watt to 95 Lumen/Watt and more preferred from 80 Lumen/Watt to 90 Lumen/Watt.
  • the quartz glass envelope of the light source will have a suitable thickness. It is preferred that the wall thickness of the quartz glass envelope between the inner surface wall and the outer surface wall is from 0.5 mm to 1.5 mm, preferred from 0.7 mm to 1.3 mm and more preferred from 0.9 mm to 1.1 mm.
  • the minimum quantities of the additives for the glass are based on this. Smaller quantities would render the glass insufficiently impervious to UV radiation.
  • the doped quartz glass will still comprise approximately 99% by weight silicon dioxide and will still have the properties of molten silicon dioxide to a high degree, apart from the optical properties.
  • the doped quartz glass may contain impurities introduced by its components.
  • the light source may be an incandescent body, for example made of tungsten, for example arranged in an inert gas comprising halogen.
  • the light source may be a pair of electrodes in an ionisable medium, between which electrodes a, for example high-pressure, discharge arc is maintained during operation.
  • the ionisable medium may comprise a rare gas, possibly with mercury, possibly with metal halide.
  • the distance of the electrode tips in the light source of a lamp may also have an influence on, amongst others, its light efficiency.
  • the distance of the electrode tips can be from 3.0 mm to 4.5 mm, preferably from 3.5 mm to 4.0 mm and more preferred from 3.7 mm to 3.9 mm.
  • the lamp vessel and the envelope of doped quartz glass may be integral, in which case the lamp vessel, for example, consists entirely of the doped quartz glass.
  • the envelope may be a separate body, for example, a body surrounding the lamp vessel.
  • the envelope may then be an outer bulb which is closed in a vacuum- tight manner, but alternatively it may be a body between the lamp vessel and an outer bulb, for example a tubular body which may or may not be closed at one end or both ends.
  • the envelope is important in all those cases in which the light source generates not only visible radiation but also UV radiation, and the lamp is to be used on account of the visible radiation generated. It is then prevented that the UV radiation causes injury or damage to living beings or goods.
  • the envelope may also be important for bringing the light source to a higher temperature than it would have in the absence of the envelope. This generally benefits the luminous efficacy of the lamp.
  • the envelope in the form of a tube in an outer bulb or of an outer bulb may also contribute to the safety of the lamp if there is a risk of the lamp vessel exploding and fragments thereof causing damage to the surroundings of the lamp in the absence of the envelope.
  • Fig. 1 is a lamp according to the present invention
  • Fig. 2 is a graph of the transmission curve of a doped quartz glass according to the present invention and of a transmission curve of a prior art doped quartz glass
  • the electric lamp is provided with a light source 1 in a transparent quartz glass lamp vessel 2 which is closed in a vacuum-tight manner.
  • the light source in this Figure is a pair of electrodes in an ionisable gas, for example, rare gas, mercury and metal halides.
  • the light source has an envelope 3 of light- transmitting, UV- absorbing quartz glass which contains aluminium in oxidic form and a metal chosen from a group to which cerium belongs in oxidic form.
  • the envelope of doped quartz glass is fused to the lamp vessel at the ends of the latter.
  • the lamp has a lamp cap 4 from which cables 5 issue to the exterior for connection to a supply source.
  • the lamp may be used, for example, as a motorcar headlamp.
  • Fig. 2 shows a first transmission curve (full line) of a quartz glass according to the present invention, wherein the quartz glass contains 99.16 weight-% SiO 2 , 0.16 weight-% Al 2 O 3 , 0.57 weight-% CeAlO 3 and 0.11 weight-% Eu 2 O 3 as shown in Table 1 for Example 1 (Ex 1) as well as a second transmission curve (broken line) of the same quartz glass as mentioned above with the exception that the quartz glass contains 99.01 weight-% SiO 2 , 0.33 weight-% Al 2 O 3 , 0.03 weight-% TiO 2 , 0.54 weight- % CeAlO 3 and 0.09 weight-% Eu 2 O 3 as shown in Table 1 for comparative Example 2 (Ex 2).
  • the quartz glass according to Example 1 has an improved transparency for visible radiation and an improved imperviousness for UV radiation.
  • the quartz glass obtained according to comparative Example 2 has a reduced transparency for visible radiation and a reduced imperviousness for UV radiation. It is noted that the transmission in the visible portion of the spectrum is approximately > 93% for Example 1 and only 92% for the comparative Example 2.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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Abstract

An electric lamp provided with a light-transmitting lamp vessel (2) and a ligh source(l) in said light-transmitting lamp vessel(2) which is closed in a vacuum tight manner, wherein the light source has an envelope(3) of light-transmitting UV-absorbing quartz glass which contains aluminium in oxidic form and at least one metal in oxidic form selected from the group comprising cerium and europium wherein the quartz glass of the envelope(3) comprises silicon, cerium, europium and aluminium in oxidic form, while the atomic ratio aluminium/europium is in he range of 2:1 to 16:1 and whereby the titanium content of said quartz glass is at most >= 0 to An electric lamp provided with a light-transmitting lamp vessel and a light source in said light-transmitting lamp vessel which is closed in a vacuum-tight manner, wherein the light source has an envelope of light-transmiting, UV-absorbing quartz glass which contains aluminium in oxidic form and at least one metal in oxidic form selected from the group comprising cerium and europium, wherein the quartz glass of the envelope comprises silicon, cerium, europium and aluminium in oxidic form, while the atomic ratio aluminium/europium is in the range of 2:1 to 16:1 and whereby the titanium content of said quartz glass is at most >= 0 to <An electric lamp provided with a light-transmitting lamp vessel and a light source in said light-transmitting lamp vessel which is closed it a vacuum-tight manner, wherein the light source has an envelope of light-transmitting, UV-absorbing quartz glass which contains aluminium in oxidic form and at least one metal in oxidic form selected from the group comprising cerium and europium, wherein the quartz glass of the envelope comprises silicon, cerium, europium and aluminium in oxidic form, while the atomic ratio aluminium/europium is in the range of 2:1 to 16:1 and whereby the titanium content of said quartz glass is at most >= 0 to <= 0.001 atom-%, based on said quartz glass.

Description

Quartz glass lamp with a defined ratio of aluminium and europium
The invention relates to an electric lamp provided with a light- transmitting lamp vessel and a light source in said light-transmitting lamp which is closed in a vacuum-tight manner, wherein the light source has an envelope of light- transmitting, UV-absorbing quartz glass which contains aluminium in oxidic form and at least one metal in oxidic form selected from the group comprising cerium and europium as well as applications thereof.
Electric lamps with envelopes comprising doped quartz glass of a more general basis are known in prior art. EP-Al 0 658 920 discloses an electric lamp which has an envelope which is at least substantially transparent to visible radiation and which is at least substantially impervious to UV radiation. This is achieved by the composition of the quartz glass envelope, which comprises silicon, cerium, titanium, europium, and aluminium in oxidic form, whereby silicon is present as 99.01 weight-% SiO2, cerium as 0.54 weight-% CeAlO3, titanium as 0.03 weight-% TiO2, europium as 0.09 weight-% Eu2O3 and aluminium as 0.33 weight-% Al2O3. This doped quartz glass suffers from the disadvantage that if certain processing parameters are not met, the glass may at least partially begin to crystallise. A higher crystallinity of the glass may result in, amongst others, opacity of the glass, which could decrease the light efficiency of the total lamp system and lead to rejection of the product by the customer. Another disadvantage is that in the quartz glass of the kind mentioned above, at least some components may not completely dissolve in the quartz matrix during processing. Furthermore, a lamp of this kind may exhibit a less than satisfying colour point stability after some time of operation, for example after 2500 hours. In addition, the transmission of visible light through the quartz glass is not optimised. Typically, the transmission of the lamp disclosed in EP-B 0 658 920 in the visible portion of the spectrum is only approximately 92%. All in all this results in a decreased efficiency of the electric lamp system according to EP-Al 0 658 920.
It is an object of the present invention to provide an electric lamp of the kind mentioned in the opening paragraph which has an envelope which is transparent to visible radiation and at least substantially impervious to UV radiation while at the same time overcoming at least one of the drawbacks mentioned above, such as crystallisation of the glass of the envelope, colour point stability, inefficient transmission and/or homogeneity of the components throughout the quartz glass matrix. The object of the present invention is achieved in that the quartz glass of the envelope of an electric lamp comprises silicon, cerium, europium and aluminium in oxidic form, while the atomic ratio aluminium/europium is in the range of 2:1 to 16:1 and whereby the titanium content of said quartz glass is at most > 0 atom-% to < 0.001 atom-%, based on said quartz glass. The atomic ratio of two components is to be understood as the ratio of the respective amounts of the components, also conveniently expressed as their molar ratios.
It has been surprisingly found that the components and their respective ratios according to the invention allow for a good miscibility in the quartz glass, by which the presence or formation of seed crystals may be reduced substantially or even may be prevented.
The envelope of light-transmitting, UV-absorbing quartz glass according to the present invention can have a crystallisation visible to the naked eye of > 0% and < 10%, preferably < 1% and most preferred 0% due to the reduced tendency to crystallise. This is beneficial with respect to the opacity of the glass, which could decrease the light efficiency of the total lamp system and can lead to rejection of the product by the customer.
It was found that quartz glass in which said elements are present in oxidic form in the silicon dioxide matrix and in the given quantities and ratios is at least substantially transparent to visible radiation and at least substantially impervious to UV radiation. The quartz glass, which will also be referred to as doped quartz glass hereinafter, can owe these properties to all its components in their stated quantities in conjunction. The elements cerium and europium each can absorb a spectral portion of the UV radiation, which portions supplement one another and may partly overlap one another.
Also, if europium is present in the trivalent oxidic form in the batch from which the quartz glass is obtained, the bivalent form will arise during melting in a reducing atmosphere, for example, of helium and hydrogen. The batch may comprise the oxides of the cationogenous elements of the doped quartz glass or alternatively mixed oxides of such elements.
It is believed that the oxidic aluminium keeps the europium essentially in its bivalent form dissolved in the matrix. A favourable influence of aluminium is furthermore that it counteracts the rheological changes of the quartz glass caused by the presence of bivalent europium.
It was found that a maximum value for the aluminium content can be important because the doped quartz glass starts showing a tendency to crystallise at aluminium quantities above 0.8 atom-%.
Thus, in order to further improve the properties of the quartz glass according to the present invention the amount of cerium, europium and aluminium should be selected insofar that: the amount of cerium is from 0.05 atom-% to 0.3 atom-%, preferred from 0.10 atom-% to 0.25 atom-%, more preferred from 0.15 atom-% to 0.2 atom-%; and/or the amount of europium is from 0.01 atom-% to 0.1 atom-%, preferred from 0.02 atom-% to 0.07 atom-%, more preferred from 0.035 atom-% to 0.05 atom-%; and/or - the amount of aluminium is from 0.05 atom-% to 0.8 atom-%, preferred 0.2 atom-% to 0.7 atom-%, more preferred 0.36 atom-% to 0.52 atom-% of the quartz glass.
Further, it can be favourable that the quartz glass of the envelope comprises cerium in form Of CeAlO3. However, the Cerium source can also be CeO2, Ce2Si2O7, (NH4)2Ce(NO3)6, CeCl3, Ce(NO3)3 and/or Ce(SO4)2.
Preferably the amount of CeAlO3 in the quartz glass is from > 0 weight- % to 0.9 weight-%, more preferred from 0.4 weight-% to 0.8 weight-% and most preferred from 0.5 weight-% to 0.7 weight-%; based on the total weight of the quartz glass.
In a preferred embodiment according to the present invention the doped quartz glass comprises 0.16 atom-% ±0.1% cerium and/or 0.04 atom-% ±0.1% europium or quantities of these elements which may be up to ±0.1% greater or smaller per element.
It has been found that at an atomic ratio Al/Eu of 4 or higher, the UV absorption by europium can be beneficially increased, as well as the transmission of light. Therefore it can be preferred that the atomic ratio of aluminium/europium is from 9:1 to 15:1, preferred from 13:1 to 14: 1, and in particular the atomic ratio of aluminium/europium is 13.7:1. However, it can be suitable that the atomic ratio of aluminium/europium is >8: 1.
For efficient operation of the electric lamp according to the present invention, it may be advantageous that the components of the ionisable filling are selected from the group comprising NaI, ScI3, ZnI2 and/or Hg.
Electric lamps can contain mercury as a component of the ionisable filling. However, it can be preferred that the ionisable filling of the electric lamp according to the present invention does not contain mercury, since electric lamps free from mercury are beneficial to the environment and to the consumer, especially in the event of a breaking of the lamp.
According to a preferred embodiment of the present invention, the components of the ionisable filling can be selected in an amount of:
20 weight-% to 60 weight-%, preferred 30 weight-% to 55 weight-%, more preferred 45 weight-% to 52 weight-% NaI; and/or - 10 weight-% to 35 weight-%, preferred 20 weight-% to 32 weight-%, more preferred 25 weight-% to 30 weight-% ScI3; and/or
0 weight-% to 25 weight-%, preferred 10 weight-% to 22 weight- %, more preferred 15 weight-% to 20 weight-% ZnI2; and/or
< 70 weight-%, preferred <10 weight-%, more preferred <1 weight-% Hg.
It should be noted at this point that the invention is not restricted to a certain ionisable filling. Furthermore, any ionisable filling can be used which seems to be suitable to use with a lamp according to the present invention.
According to a first preferred embodiment of the present invention the ionisable filling can be 50 weight-% NaI, 30 weight-% ScI3 and 20 weight-% ZnI2.
According to a second preferred embodiment of the present invention the ionisable filling can be 25 weight-% NaI, 10 weight-% ScI3 and 65 weight-% Hg.
The interior pressure inside the light source containing the ionisable filling at room temperature can be from 4 bar to 14 bar, preferred from 8 bar to 14 bar and more preferred from 8 bar to 12 bar.
A lamp according to the present invention can be improved in that the colour of the emitted light remains constant during many hours of operation. For instance, it is desired that the colour point of said lamp does not shift to an undesired extent during operation time.
Due to the defined ratios and mixture of the dopants of the quartz glass and the selected filling of the present invention the colour point shift could be improved beneficially.
For example, the relative shift of the colour point coordinates between 500 hours of operation and 2500 hours of operation can be < 0.025 for the x- value of the colour point coordinate and/or < 0.035 for the y-value of the colour point coordinate, preferred < 0.020 for the x-value of the colour point coordinate and/or < 0.025 for the y-value of the colour point coordinate and most preferred < 0.013 for the x-value of the colour point coordinate and/or < 0.019 for the y-value of the colour point coordinate.
Additionally, the absolute shift of the colour point coordinates after 500 hours of operation can be: - from 0.382 to 0.374 for the x-value of the colour point coordinate; and/or from 0.386 to 0.378 for the y-value of the colour point coordinate; preferred: - from 0.380 to 0.376 for the x-value of the colour point coordinate; and/or from 0.384 to 0.380 for the y-value of the colour point coordinate; most preferred: from 0.378 to 0.377 for the x-value of the colour point coordinate; and/or - from 0.382 to 0.381 for the y-value of the colour point coordinate; and/or wherein the absolute shift of the colour point coordinates after 2500 hours of operation can be: from 0.369 to 0.361 for the x-value of the colour point coordinate; and/or from 0.368 to 0.360 for the y-value of the colour point coordinate; preferred: from 0.367 to 0.363 for the x-value of the colour point coordinate; and/or from 0.366 to 0.362 for the y-value of the colour point coordinate; most preferred: from 0.365 to 0.364 for the x-value of the colour point coordinate; and/or from 0.364 to 0.363 for the y-value of the colour point coordinate.
Further, lamps according to the present invention possess a high light efficiency. The light efficiency of lamps according to the present invention can be from 70 Lumen/Watt to 100 Lumen/Watt, preferred from 75 Lumen/Watt to 95 Lumen/Watt and more preferred from 80 Lumen/Watt to 90 Lumen/Watt.
In general, the quartz glass envelope of the light source will have a suitable thickness. It is preferred that the wall thickness of the quartz glass envelope between the inner surface wall and the outer surface wall is from 0.5 mm to 1.5 mm, preferred from 0.7 mm to 1.3 mm and more preferred from 0.9 mm to 1.1 mm.
The minimum quantities of the additives for the glass are based on this. Smaller quantities would render the glass insufficiently impervious to UV radiation. Given the maximum quantities of additives, the doped quartz glass will still comprise approximately 99% by weight silicon dioxide and will still have the properties of molten silicon dioxide to a high degree, apart from the optical properties. The doped quartz glass may contain impurities introduced by its components. The light source may be an incandescent body, for example made of tungsten, for example arranged in an inert gas comprising halogen. Alternatively, the light source may be a pair of electrodes in an ionisable medium, between which electrodes a, for example high-pressure, discharge arc is maintained during operation. The ionisable medium may comprise a rare gas, possibly with mercury, possibly with metal halide.
The distance of the electrode tips in the light source of a lamp may also have an influence on, amongst others, its light efficiency. In the lamp according to the present invention the distance of the electrode tips can be from 3.0 mm to 4.5 mm, preferably from 3.5 mm to 4.0 mm and more preferred from 3.7 mm to 3.9 mm. The lamp vessel and the envelope of doped quartz glass may be integral, in which case the lamp vessel, for example, consists entirely of the doped quartz glass. Alternatively, the envelope may be a separate body, for example, a body surrounding the lamp vessel. The envelope may then be an outer bulb which is closed in a vacuum- tight manner, but alternatively it may be a body between the lamp vessel and an outer bulb, for example a tubular body which may or may not be closed at one end or both ends.
The envelope is important in all those cases in which the light source generates not only visible radiation but also UV radiation, and the lamp is to be used on account of the visible radiation generated. It is then prevented that the UV radiation causes injury or damage to living beings or goods. The envelope may also be important for bringing the light source to a higher temperature than it would have in the absence of the envelope. This generally benefits the luminous efficacy of the lamp. The envelope in the form of a tube in an outer bulb or of an outer bulb may also contribute to the safety of the lamp if there is a risk of the lamp vessel exploding and fragments thereof causing damage to the surroundings of the lamp in the absence of the envelope.
The present invention is further illustrated in Figures 1 and 2 and by comparative example I. Fig. 1 is a lamp according to the present invention Fig. 2 is a graph of the transmission curve of a doped quartz glass according to the present invention and of a transmission curve of a prior art doped quartz glass
In Fig. 1 the electric lamp is provided with a light source 1 in a transparent quartz glass lamp vessel 2 which is closed in a vacuum-tight manner. The light source in this Figure is a pair of electrodes in an ionisable gas, for example, rare gas, mercury and metal halides. The light source has an envelope 3 of light- transmitting, UV- absorbing quartz glass which contains aluminium in oxidic form and a metal chosen from a group to which cerium belongs in oxidic form. The envelope of doped quartz glass is fused to the lamp vessel at the ends of the latter. The lamp has a lamp cap 4 from which cables 5 issue to the exterior for connection to a supply source. The lamp may be used, for example, as a motorcar headlamp.
Fig. 2 shows a first transmission curve (full line) of a quartz glass according to the present invention, wherein the quartz glass contains 99.16 weight-% SiO2, 0.16 weight-% Al2O3, 0.57 weight-% CeAlO3 and 0.11 weight-% Eu2O3 as shown in Table 1 for Example 1 (Ex 1) as well as a second transmission curve (broken line) of the same quartz glass as mentioned above with the exception that the quartz glass contains 99.01 weight-% SiO2, 0.33 weight-% Al2O3, 0.03 weight-% TiO2, 0.54 weight- % CeAlO3 and 0.09 weight-% Eu2O3 as shown in Table 1 for comparative Example 2 (Ex 2).
Figure imgf000011_0001
Table 1
Legend: a: comparative example as disclosed in EP 0 658 920 Bl b: of the cationogenous element c: exclusive of Al in CeAlO3
It can be seen that the quartz glass according to Example 1 has an improved transparency for visible radiation and an improved imperviousness for UV radiation. In comparison, the quartz glass obtained according to comparative Example 2 has a reduced transparency for visible radiation and a reduced imperviousness for UV radiation. It is noted that the transmission in the visible portion of the spectrum is approximately > 93% for Example 1 and only 92% for the comparative Example 2.

Claims

CLAIMS:
1. An electric lamp provided with a light-transmitting lamp vessel (2) and a light source (1) in said light-transmitting lamp vessel (2) which is closed in a vacuum- tight manner, wherein the light source has an envelope (3) of light-transmitting, UV- absorbing quartz glass which contains aluminium in oxidic form and at least one metal in oxidic form selected from the group comprising cerium and europium, characterised in that the quartz glass of the envelope (3) comprises silicon, cerium, europium and aluminium in oxidic form, while the atomic ratio aluminium/europium is in the range of 2:1 to 16: 1 and whereby the titanium content of said quartz glass is at most > 0 to < 0.001 atom-%, based on said quartz glass.
2. The electric lamp according to claim 1, wherein the metal oxide as constituent of the quartz glass is/are selected in an amount of:
- 0.05 atom-% to 0.3 atom-%, preferred 0.10 atom-% to 0.25 atom-%, more preferred 0.15 atom-% to 0.2 atom-% cerium; and/or - 0.01 atom-% to 0.1 atom-%, preferred 0.02 atom-% to 0.07 atom-%, more preferred 0.035 atom-% to 0.05 atom-% europium; and/or
- 0.05 atom-% to 0.8 atom-%, preferred 0.2 atom-% to 0.7 atom-%, more preferred 0.36 atom-% to 0.52 atom-% aluminium; based on the quartz glass.
3. The electric lamp according to claims 1 to 2, wherein the atomic ratio aluminium/europium is in the range of 9:1 to 15:1 and preferably 13:1 to 14:1.
4. The electric lamp according to claims 1 to 3, wherein the envelope (3) of light-transmitting, UV-absorbing quartz glass has a crystallisation visible to the naked eye of > 0% and < 10%, preferably < 1 % and most preferred 0%.
5. The electric lamp according to claims 1 to 4, wherein at least one component of the ionisable filling is selected from the group comprising sodium halogenides, scandium halogenides and/or mercury, whereby it is preferred that the ionisable filling is free of mercury.
6. The electric lamp according to claims 1 to 5, wherein the relative shift of the colour point coordinates between 500 hours of operation and 2500 hours of operation is:
< 0.025 for the x- value of the colour point coordinate; and/or
< 0.035 for the y- value of the colour point coordinate; preferred:
< 0.020 for the x- value of the colour point coordinate; and/or
< 0.025 for the y- value of the colour point coordinate; most preferred:
< 0.013 for the x- value of the colour point coordinate; and/or - < 0.019 for the y- value of the colour point coordinate.
7. The electric lamp according to claims 1 to 6, wherein the absolute shift of the colour point coordinates after 500 hours of operation is:
0.382 to 0.374 for the x-value of the colour point coordinate; and/or - 0.386 to 0.378 for the y- value of the colour point coordinate; preferred:
0.380 to 0.376 for the x-value of the colour point coordinate; and/or
0.384 to 0.380 for the y-value of the colour point coordinate; most preferred: - 0.378 to 0.377 for the x-value of the colour point coordinate; and/or
0.382 to 0.381 for the y-value of the colour point coordinate; and/or wherein the absolute shift of the colour point coordinates after 2500 hours of operation is:
0.369 to 0.361 for the x-value of the colour point coordinate; and/or - 0.368 to 0.360 for the y-value of the colour point coordinate; preferred: 0.367 to 0.363 for the x-value of the colour point coordinate; and/or 0.366 to 0.362 for the y-value of the colour point coordinate; most preferred:
0.365 to 0.364 for the x-value of the colour point coordinate; and/or - 0.364 to 0.363 for the y-value of the colour point coordinate.
8. The electric lamp according to claims 1 to 7, wherein
- the wall thickness of the quartz glass envelope (3) between the inner surface wall and the outer surface wall is from 0.5 mm to 1.5 mm, preferred from 0.7 mm to 1.3 mm and more preferred from 0.9 mm to 1.1 mm.
9. The electric lamp according to claims 1 to 8, wherein the quartz glass of the envelope has a transmission from 250 nm to 300 nm of > 0% to 4%, preferred from > 0% to 3%, more preferred from > 0 % to 1.5 %; and/or from 450 nm to 600 nm of 89% to 99%, preferred from 90% to 96%, more preferred from 93% to 94%, most preferred from 93.0% to 93.9%
10. A system containing at least one lamp according to any of the claims 1 to 9 and being used in one or more of the following applications: shop lighting, home lighting, head lamps accent lighting, - spot lighting, theatre lighting, office lighting illumination of workplaces automotive front lighting - automotive auxiliary lighting automotive interior lighting consumer TV applications, fibre-optics applications, and projection systems.
PCT/IB2005/053167 2004-10-04 2005-09-26 Quartz glass lamp with a defined ratio of aluminium and europium WO2006038148A1 (en)

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EP04104846 2004-10-04

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU391074A1 (en) * 1971-12-09 1973-07-25
EP0478059A1 (en) * 1990-09-27 1992-04-01 Koninklijke Philips Electronics N.V. Body of cerium-doped quartz glass
EP0574158A1 (en) * 1992-06-01 1993-12-15 General Electric Company UV absorbing fused quartz and its use for lamp envelopes
EP0658920A1 (en) * 1993-12-14 1995-06-21 Koninklijke Philips Electronics N.V. Electric lamp
EP0964431A2 (en) * 1998-06-12 1999-12-15 Matsushita Electronics Corporation Discharge lamp

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU391074A1 (en) * 1971-12-09 1973-07-25
EP0478059A1 (en) * 1990-09-27 1992-04-01 Koninklijke Philips Electronics N.V. Body of cerium-doped quartz glass
EP0574158A1 (en) * 1992-06-01 1993-12-15 General Electric Company UV absorbing fused quartz and its use for lamp envelopes
EP0658920A1 (en) * 1993-12-14 1995-06-21 Koninklijke Philips Electronics N.V. Electric lamp
EP0964431A2 (en) * 1998-06-12 1999-12-15 Matsushita Electronics Corporation Discharge lamp

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Section Ch Week 197414, Derwent World Patents Index; Class L01, AN 1974-26570V, XP002357790, "Ultraviolet light absorbing glass - caesium oxide and cerium oxide added to glass based on silica, alumina, and europium oxide to improve luminescence and solarization resp" *

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