Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
  • C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
  • C09K11/7772—Halogenides
  • C09K11/7773—Halogenides with alkali or alkaline earth metal
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
  • C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
  • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
  • H01J29/18—Luminescent screens
  • H01J29/20—Luminescent screens characterised by the luminescent material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/38—Devices for influencing the colour or wavelength of the light
  • H01J61/42—Devices for influencing the colour or wavelength of the light by transforming the wavelength of the light by luminescence
  • H01J61/44—Devices characterised by the luminescent material

Definitions

• the invention relates to a luminescent material having a fundamental lattice consisting of an inorganic crystalline compound, which material comprises at least 1 mol% of gadolinium, at least 0.1 mol% of an activator chosen from the group of transition metals and rare earths, and at least 0.1 mol% of a sensitizer.
• a luminescent material of this type is known from Netherlands patent application 186707.
• the sensitizer is chosen from the group of lead, antimony and bismuth
• the activator is chosen from the group of manganese, terbium and dysprosium.
• the inorganic crystalline compound and the concentrations of sensitizer and gadolinium are chosen to be such that, if no activator is present in the material but comprises only a sensitizer and gadolinium, the material has the characteristic line emission of gadolinium in the range of 310 nm to 315 nm upon excitation by UV radiation at a wavelength of approximately 254 nm. In other words, upon excitation of the material, an energy transfer from the sensitizer to gadolinium takes place.
• the material comprises an activator in addition to a sensitizer and gadolinium
• an efficient transfer of energy also takes place from gadolinium to the activator, even at a relatively low concentration of the activator.
• Such a low concentration of the activator renders the luminescent material relatively inexpensive.
• there is little concentration quenching so that a high luminous flux can be obtained.
• a drawback of the known luminescent material is, however, that the quantum efficiency is limited in that only one visible photon is generated for each exciting UN photon.
• a luminescent material as described in the opening paragraph is therefore characterized in that the sensitizer is erbium and in that the material, if not activated but only sensitized, has the characteristic line emission of gadolinium in the range of 310 nm to 315 nm upon excitation by UN radiation at a wavelength in the wavelength range of 100 nm to 195 nm.
• the presence of the characteristic line emission of gadolinium, if the material does not comprise any activator but only sensitizer and gadolinium means that energy transfer takes place from erbium to gadolinium upon excitation.
• the concentrations of sensitizer and activator can be chosen to be such that the sensitizer ions are spatially separated from the activator ions so that quenching due to cross- relaxation in sensitizer-activator pairs is prevented and the quantum efficiency is relatively high.
• the activator comprises one or more of the elements from the group of manganese, samarium, europium, gadolinium, terbium, dysprosium, holmium and thulium.
• the concentration of erbium is in the range of 0.1 mol% to 5 mol% and the concentration of the activator is in the range of 0.1 mol% to 1 mol%.
• luminescent materials according to the invention which, in addition to erbium, gadolinium and the activator(s), also comprise at least one element chosen from the group of yttrium, scandium and lanthanum.
• These three elements are relatively inexpensive so that the luminescent material may be relatively inexpensive by making use of one or more of these elements. It has also been found that the location of the maximum of the absorption band of the luminescent material is influenced by these elements, so that addition of one or more of these elements renders it possible to obtain a good overlap of the absorption band of the luminescent material with the emission band of the excitation source. It has further been found that the presence of fluorine influences the location of the 4f 10 5d level of the Er 3+ ion in such a way that a favorable absorption behavior of the luminescent material is obtained.
• luminescent materials according to the invention in which the fundamental lattice is constituted by LiGdF in which gadolinium may be partly replaced by at least one element chosen from the group of yttrium, scandium and lanthanum.
• Luminescent materials according to the invention are very suitable for use in the luminescent screen of a discharge lamp, more particularly a discharge lamp provided with a gastight lamp vessel comprising xenon. A xenon discharge produces relatively much UV radiation in a wavelength range which is very suitable for exciting a luminescent material according to the invention.
• the wavelength of the emitted light is plotted in nm on the horizontal axis.
• the radiation intensity is plotted in arbitrary units on the vertical axis.
• the Er 3+ ion is excited from the 4f n state to the 4f 10 5d 1 state.
• the emission spectrum of the powder has a number of lines in the blue spectrum, which are ascribed to emissions from the 5 D 3 level of the Tb 3+ ion.
• the emission spectrum in the green range shows a number of lines corresponding to emissions from the 5 D 4 level to the Tb 3+ ion. A number of lines are also visible in the emission spectrum originating from Er + emission from the S 3/2 level.
• the 4f 10 5d level of the Er 3+ ion is not excited.
• the Gd 3+ ion is excited from the 4f 7 ( 8 S 7 2 ) to the 4f 7 ( 6 I j) state.
• the energy is subsequently transferred to Tb and also a little bit to Er.
• the emission spectrum has the same lines as upon excitation by means of radiation at a wavelength of 145 nm.
• the measured intensity ratios of the different Er and Tb emissions in this spectrum represent the ratios in the case where the 4f 10 5d level of the Er 3+ ion is not excited and no energy transfer takes place from Er to Tb, as in the case of excitation by means of radiation at a wavelength of 145 nm. It can be calculated from the increase of the Er( 4 S 3/ ) emission at 145 nm excitation with respect to 273 nm excitation which percentage of the Er ions at 145 nm excitation transfers only a part of the energy to Gd so that it drops back to the 4 S 3/2 level or a level directly above it. This appears to be approximately 30% for the LiGdF 4 lattice used.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Luminescent Compositions (AREA)
• Vessels And Coating Films For Discharge Lamps (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (6)

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Citations (3)

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• 1999
  • 1999-09-20 CN CN99801844.9A patent/CN1129950C/zh not_active Expired - Fee Related
  • 1999-09-20 WO PCT/EP1999/007021 patent/WO2000024028A1/en not_active Ceased
  • 1999-09-20 EP EP99970782A patent/EP1048049B1/en not_active Expired - Lifetime
  • 1999-09-20 DE DE69934667T patent/DE69934667T2/de not_active Expired - Fee Related
  • 1999-09-20 JP JP2000577690A patent/JP2002528563A/ja not_active Abandoned
  • 1999-10-18 US US09/421,358 patent/US6251304B1/en not_active Expired - Fee Related

Patent Citations (3)

Non-Patent Citations (1)

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