EP4125112A1 - Mercury free cold cathode lamp internally coated with a luminescent down shifting layer - Google Patents

Mercury free cold cathode lamp internally coated with a luminescent down shifting layer Download PDF

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Publication number
EP4125112A1
EP4125112A1 EP22187122.1A EP22187122A EP4125112A1 EP 4125112 A1 EP4125112 A1 EP 4125112A1 EP 22187122 A EP22187122 A EP 22187122A EP 4125112 A1 EP4125112 A1 EP 4125112A1
Authority
EP
European Patent Office
Prior art keywords
cold cathode
cathode lamp
lds
shifting
luminescent down
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.)
Pending
Application number
EP22187122.1A
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German (de)
French (fr)
Inventor
Raimondo Piaia
Martin Fausto
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Individual
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Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP4125112A1 publication Critical patent/EP4125112A1/en
Pending legal-status Critical Current

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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00Gas-discharge or vapour-discharge lamps
    • H01J61/02Details
    • H01J61/12Selection of substances for gas fillings; Specified operating pressure or temperature
    • H01J61/16Selection of substances for gas fillings; Specified operating pressure or temperature having helium, argon, neon, krypton, or xenon as the principle constituent
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00Gas-discharge or vapour-discharge lamps
    • H01J61/02Details
    • H01J61/38Devices for influencing the colour or wavelength of the light
    • H01J61/40Devices for influencing the colour or wavelength of the light by light filters; by coloured coatings in or on the envelope
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00Gas-discharge or vapour-discharge lamps
    • H01J61/02Details
    • H01J61/38Devices for influencing the colour or wavelength of the light
    • H01J61/42Devices for influencing the colour or wavelength of the light by transforming the wavelength of the light by luminescence
    • H01J61/44Devices characterised by the luminescent material

Definitions

  • the subject of the present invention is a cold cathode gas discharge lamp using mercury free noble gases as a source of ultraviolet rays that excite a luminescent down-shifting (LDS) layer for generating visible light.
  • LDS luminescent down-shifting
  • a technical problem solved by this invention is how to provide a cold cathode discharge gas lamp using mercury free gases as a source for generating ultraviolet rays which can substitute existing cold cathode discharge gas lamps such as mercury vapour discharge lamp, generally known as neon tubes, banned by EU Directives and Regulations.
  • a noble gas such as Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr) or Xenon (Xe) or a mixture of the same and a certain amount of mercury (few hundreds milligrams) are sealed within a glass tube, the inner surfaces of which have been coated with fluorescent material (phosphors).
  • the application of a high electric field (high voltage) across electrodes - provided at the two ends of the glass tube - produces a discharge in the mercury vapour and the gas mixture.
  • the mercury that has been excited by the discharge emits ultraviolet rays upon transitioning to the normal state and the fluorescent material is excited by the emitted ultraviolet rays and gives off visible light.
  • mercury in low-pressure discharges for advertising and lighting applications has been standard technology for several decades.
  • Mercury as a source of UV is favoured because of its low ionisation potential (10.4 eV) and its high vapour pressure.
  • Phosphors coating on the inside of the lamp walls convert the resonant radiation (mainly 253.4 nm) into visible radiation, which combines with the mercury visible emissions at the blue and green part of the spectrum (404.7 nm, 435.8 nm and 546.1 nm) to produce the desired white light and/or other colours.
  • Phosphors are Rare Earths based components (due to lesser concentration in the earth's crust and consequently traded at higher prices), i.e. a group of 17 elements with similar characteristics. They comprise the group of Lanthanides plus the elements Scandium and Yttrium. While the trade dispute between the US and China has reached a point where export restrictions on Rare Earths have become a possible means for sanction, cold cathode industry could be affected as well and should be prepared to mitigate supply disruptions or shortage in Rare Earths trade.
  • NPs Nanoparticles
  • tiny materials having size from 1 to 100 nm. They can be classified into different classes based on their properties, shapes or sizes. NPs possess unique physical and chemical properties due to their high surface area and nanoscale size. Their optical properties are reported to be dependent on the size, not on the material, which imparts different colours due to absorption of the exciting UV radiation.
  • the mercury free cold cathode lamp of the present invention is a cold cathode lamp in which at least Xenon gas - preferably in a percentage not exceeding 10% - and another noble gas (i.e. Neon) or a mixture of other gases are enclosed and includes a sealed glass tube internally coated with a layer of luminescent down-shifting (LDS) material, with a thickness ranging from 10 to 50 ⁇ m approximately.
  • LDS luminescent down-shifting
  • NPs as a component of the luminescent down-shifting (LDS) layer can be used as alone or in addiction to standard phosphors or other chemical optically inert components; while better results can be achieved with a coating made of pure NPs layer, nowadays a good compromise in terms of light efficacy and raw material cost recommends a mixture of both components.
  • LDS luminescent down-shifting
  • the luminescent down-shifting (LDS) layer absorbs photons, typically in the 200 ⁇ 500 nm range, and re-emits them at a longer wavelength, in the visible spectrum.
  • the energy conversion efficiency of NPs is generally higher compared with traditional Rare Earths based Phosphors, assuring a better energy efficacy than prior art mercury discharge lamps.
  • FIG. 1 a schematic sectional view showing an embodiment of the cold cathode lamp
  • a cold cathode lamp is made of a sealed glass tube 1 with two electrodes 2, 2' arranged on each tube ends.
  • the inner surface of the glass tube 1 is coated with a layer 3 of luminescent down-shifting (LDS) material, with a thickness ranging from 10 to 50 ⁇ m approximately.
  • LDS luminescent down-shifting
  • Such a luminescent down-shifting (LDS) layer 3 can be used as alone or in addiction to standard phosphors or other inert components.
  • the filling pressure of the gas mixture shall not exceed 6.600 Pa approximately.
  • Cold cathode lamps can be shaped in any form, i.e. linear, bended, circular, etc.

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  • Vessels And Coating Films For Discharge Lamps (AREA)
  • Luminescent Compositions (AREA)

Abstract

A mercury free cold cathode discharge lamp generally known as neon tube using mercury free gases as a source of ultraviolet rays that excites a luminescent down-shifting (LDS) layer for generating visible light. Luminescent down-shifting (LDS) material absorbs UV radiation, with higher efficiency than phosphors, and re-emits light at a longer wavelength, in the visible spectrum.

Description

    Subject of Invention
  • The subject of the present invention is a cold cathode gas discharge lamp using mercury free noble gases as a source of ultraviolet rays that excite a luminescent down-shifting (LDS) layer for generating visible light.
  • Technical Problem
  • A technical problem solved by this invention is how to provide a cold cathode discharge gas lamp using mercury free gases as a source for generating ultraviolet rays which can substitute existing cold cathode discharge gas lamps such as mercury vapour discharge lamp, generally known as neon tubes, banned by EU Directives and Regulations.
  • Prior Art
  • In related discharge lamps, a noble gas such as Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr) or Xenon (Xe) or a mixture of the same and a certain amount of mercury (few hundreds milligrams) are sealed within a glass tube, the inner surfaces of which have been coated with fluorescent material (phosphors). The application of a high electric field (high voltage) across electrodes - provided at the two ends of the glass tube - produces a discharge in the mercury vapour and the gas mixture. The mercury that has been excited by the discharge emits ultraviolet rays upon transitioning to the normal state and the fluorescent material is excited by the emitted ultraviolet rays and gives off visible light.
  • The use of mercury in low-pressure discharges for advertising and lighting applications has been standard technology for several decades. Mercury as a source of UV is favoured because of its low ionisation potential (10.4 eV) and its high vapour pressure. Phosphors coating on the inside of the lamp walls convert the resonant radiation (mainly 253.4 nm) into visible radiation, which combines with the mercury visible emissions at the blue and green part of the spectrum (404.7 nm, 435.8 nm and 546.1 nm) to produce the desired white light and/or other colours.
  • With the adoption of the Regulation of the European Parliament 852/2017/EU on the banning of exports and the safe storage of metallic Mercury - which took effect since 31/12/2018 - Mercury cold cathode lamps became forbidden. In the same time the Minamata Convention on Mercury (a global treaty to protect human health and the environment from the adverse effects of mercury) was adopted at a Conference held in the Japanese City, with the same goals and is already in force since Jan. 1st 2021.
  • In the past years there have been attempts to use Xenon instead of Mercury on phosphor coated tubes as an ultraviolet source; Xenon discharge lamps did show low luminous efficacy and a proneness to discharge contraction.
  • Phosphors are Rare Earths based components (due to lesser concentration in the earth's crust and consequently traded at higher prices), i.e. a group of 17 elements with similar characteristics. They comprise the group of Lanthanides plus the elements Scandium and Yttrium. While the trade dispute between the US and China has reached a point where export restrictions on Rare Earths have become a possible means for sanction, cold cathode industry could be affected as well and should be prepared to mitigate supply disruptions or shortage in Rare Earths trade.
  • Phosphors can be replaced by Nanoparticles (NPs), tiny materials having size from 1 to 100 nm. They can be classified into different classes based on their properties, shapes or sizes. NPs possess unique physical and chemical properties due to their high surface area and nanoscale size. Their optical properties are reported to be dependent on the size, not on the material, which imparts different colours due to absorption of the exciting UV radiation.
  • Solution to the Technical Problem
  • The above described technical problem is solved by a mercury free cold cathode lamp that can achieve a lighting emission comparable with that of a prior art mercury vapour discharge lamp.
  • The mercury free cold cathode lamp of the present invention is a cold cathode lamp in which at least Xenon gas - preferably in a percentage not exceeding 10% - and another noble gas (i.e. Neon) or a mixture of other gases are enclosed and includes a sealed glass tube internally coated with a layer of luminescent down-shifting (LDS) material, with a thickness ranging from 10 to 50 µm approximately. The filling pressure of the gas mixture shall not exceed 6.600 Pa approximately.
  • NPs as a component of the luminescent down-shifting (LDS) layer can be used as alone or in addiction to standard phosphors or other chemical optically inert components; while better results can be achieved with a coating made of pure NPs layer, nowadays a good compromise in terms of light efficacy and raw material cost recommends a mixture of both components. Once the NPs will be produced in large scale a fully NPs coating will be economically affordable by cold cathode industry.
  • The luminescent down-shifting (LDS) layer absorbs photons, typically in the 200÷500 nm range, and re-emits them at a longer wavelength, in the visible spectrum. The energy conversion efficiency of NPs is generally higher compared with traditional Rare Earths based Phosphors, assuring a better energy efficacy than prior art mercury discharge lamps.
  • In the specification, explanation regarded a case in which a mixture of Xenon gas and Neon gas is used as discharge gas, but the gas that is mixed with Xenon gas is not limited to Neon gas and a desired gas such as Helium (He), Argon (Ar), Krypton (Kr) or any mixture of the same or other gasses can also be selected. In the present example, high voltage can be applied either in high frequency (i.e. 20 kHz or above) as well as at 50/60 cycles, using standard neon power supplies.
  • The above and other objects, features and advantages of the present invention will become apparent from the following descriptions with reference to the accompanying drawing
    FIG. 1 a schematic sectional view showing an embodiment of the cold cathode lamp
  • The following description concerns the details of a standard cold cathode lamp with reference to FIG. 1 where a schematic sectional view shows its typical components: a cold cathode lamp is made of a sealed glass tube 1 with two electrodes 2, 2' arranged on each tube ends.
  • The inner surface of the glass tube 1 is coated with a layer 3 of luminescent down-shifting (LDS) material, with a thickness ranging from 10 to 50 µm approximately. Such a luminescent down-shifting (LDS) layer 3 can be used as alone or in addiction to standard phosphors or other inert components.
  • The filling pressure of the gas mixture shall not exceed 6.600 Pa approximately.
  • Although a cold cathode lamp of the internal electrode type was described as an example of an embodiment of the present invention, the invention can also be applied to a cold cathode lamp of the external electrode type, normally known as EEFL (external electrode fluorescent lamp). Cold cathode lamps can be shaped in any form, i.e. linear, bended, circular, etc.
  • While a preferred embodiment of the present invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit of scope of the claims. In the same way, the filling pressure of the gas mixture will not affect the spirit of scope of the claims.

Claims (6)

  1. A mercury free cold cathode lamp in which electrodes are arranged at the two ends of a glass tube (1) in which pure Xenon or Xenon and another gas or gasses are enclosed, characterised in that the inner surface has been coated with a layer (3) of luminescent down-shifting (LDS) materials.
  2. A mercury free cold cathode lamp in which, according to claim 1, wherein said luminescent down-shifting (LDS) materials comprise some Nanoparticles (NPs) having size ranging from 1 to 100 nm.
  3. A cold cathode lamp according to claim 2, wherein said luminescent down-shifting (LDS) materials comprise a mixture of NPs and standard phosphors in any percentage.
  4. A cold cathode lamp according to claim 3, wherein said luminescent down-shifting (LDS) materials include chemical additives.
  5. A cold cathode lamp according to claim 4, wherein said luminescent down-shifting (LDS) materials are sealed into a glass tube (1) filled with pure Xenon or Xenon and another gas or gasses.
  6. A cold cathode lamp according to claim 5, wherein said sealed glass tube (1) is provided with at least two electrodes (2, 2') at both ends.
EP22187122.1A 2021-07-30 2022-07-27 Mercury free cold cathode lamp internally coated with a luminescent down shifting layer Pending EP4125112A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SI202100149A SI26229A (en) 2021-07-30 2021-07-30 Mercury free cold cathode lamp internally coated with a luminiscent down shifting layer

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EP4125112A1 true EP4125112A1 (en) 2023-02-01

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5523655A (en) * 1994-08-31 1996-06-04 Osram Sylvania Inc. Neon fluorescent lamp and method of operating
US6259214B1 (en) * 1999-06-23 2001-07-10 Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen Mbh Method for operating a discharge lamp

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5523655A (en) * 1994-08-31 1996-06-04 Osram Sylvania Inc. Neon fluorescent lamp and method of operating
US6259214B1 (en) * 1999-06-23 2001-07-10 Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen Mbh Method for operating a discharge lamp

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
JIN Y ET AL: "Synthesis of Gd"3PO"7:Eu^3^+ nanospheres via a facile combustion method and optical properties", JOURNAL OF SOLID STATE CHEMISTRY, ORLANDO, FL, US, vol. 181, no. 4, 1 April 2008 (2008-04-01), pages 724 - 729, XP022656122, ISSN: 0022-4596, [retrieved on 20080112], DOI: 10.1016/J.JSSC.2008.01.013 *
LI QUANHONG ET AL: "Deposition of luminescence YBO3:Eu3+,Gd3+on ferromagnetic Fe@C nanoparticles", DYES AND PIGMENTS, ELSEVIER APPLIED SCIENCE PUBLISHERS BARKING, GB, vol. 107, 13 April 2014 (2014-04-13), pages 161 - 165, XP028659838, ISSN: 0143-7208, DOI: 10.1016/J.DYEPIG.2014.03.033 *
SANTA CHAWLA ET AL: "Enhanced luminescence and degradation resistance in Tb modified Yttrium Borate core-nano silica shell phosphor under UV and VUV excitation", APPLIED SURFACE SCIENCE, ELSEVIER, AMSTERDAM , NL, vol. 257, no. 16, 14 March 2011 (2011-03-14), pages 7167 - 7171, XP028200899, ISSN: 0169-4332, [retrieved on 20110321], DOI: 10.1016/J.APSUSC.2011.03.082 *
SILVER JACK . ET AL: "By Understanding How Light Emission Depends on Size, Morphology and Phase in Inorganic Phosphor Materials, Can We Deduce Properties to Design Efficient Nanostructures for Tomorrow Industrial Needs", PROCEEDINGS OF 22ND INTERNATIONAL DISPLAY WORKSHOP (IDW' 15), 1 December 2015 (2015-12-01), pages 1246 - 1249, XP093005876 *

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