EP0618608A1 - Fluoreszentzlampe - Google Patents

Fluoreszentzlampe Download PDF

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Publication number
EP0618608A1
EP0618608A1 EP94302234A EP94302234A EP0618608A1 EP 0618608 A1 EP0618608 A1 EP 0618608A1 EP 94302234 A EP94302234 A EP 94302234A EP 94302234 A EP94302234 A EP 94302234A EP 0618608 A1 EP0618608 A1 EP 0618608A1
Authority
EP
European Patent Office
Prior art keywords
fluorescent
protection layer
bulb
fluorescent lamp
layer
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.)
Withdrawn
Application number
EP94302234A
Other languages
English (en)
French (fr)
Inventor
Akira Taya
Keiji Hatakeyama
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toshiba Lighting and Technology Corp
Original Assignee
Toshiba Lighting and Technology Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Toshiba Lighting and Technology Corp filed Critical Toshiba Lighting and Technology Corp
Publication of EP0618608A1 publication Critical patent/EP0618608A1/de
Withdrawn legal-status Critical Current

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    • 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
    • H01J61/40—Devices for influencing the colour or wavelength of the light by light filters; by coloured coatings in or on the envelope
    • 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
    • H01J61/35—Vessels; Containers provided with coatings on the walls thereof; Selection of materials for the coatings

Definitions

  • This invention relates to a fluorescent lamp with a fluorescent layer of a rare earth metal fluorescent substance, and a protection layer, both of which layers are coated on an inner surface of a bulb of the fluorescent lamp.
  • a fluorescent lamp with a protection layer is disclosed in JP-A-55-161352, in which the protection layer is composed of crystalline titanium oxide, which is coated on an inner surface of a glass bulb.
  • a fluorescent layer is then formed on an inner surface of the protection layer and is made of a conventional halophosphor activated by Mn2+ and Sb2+.
  • the purpose of the protection layer is to prevent impurities contained in the glass bulb from diffusing into the fluorescent layer, as the impurities decrease the operating efficiency of the fluorescent layer.
  • a fluorescent lamp using soda-lime glass for the glass bulb is well-known and disclosed, for example, in JP-A-58-19850.
  • Soda-lime glass contains little or no lead oxide (PbO) (which is an expensive material) and therefore the use of soda-lime glass reduces the manufacturing costs and also prevents environmental pollution caused by the scrapping of bulbs.
  • soda-lime glass contains about 15-17% by weight of sodium (Na), which is three times the amount of sodium contained in lead glass, which is also used for making fluorescent lamps.
  • Na sodium
  • the sodium (Na) contained in soda-lime glass diffuses into the fluorescent layer formed on the inner surface of the bulb when the bulb is heated during its manufacture and its operation.
  • This diffused sodium reacts which elements of the fluorescent layer and reduces the luminous efficiency of the fluorescent layer.
  • This sodium (Na) becomes an amalgam owing to the reaction with mercury (Hg) in the discharge space of the lamp, and the resulting amalgam constitutes coloured portions of the inner surface of the bulb. The coloured portions consequently increase the loss of transmission of light.
  • the diffusion of sodium (Na) as described above is increased by ultraviolet irradiation from the bulb, in addition to heating. Furthermore, the thickness of the fluorescent layer using a rare earth metal fluorescent substance is thin in comparison with other fluorescent layers using a halophosphate phosphor activated by Mn2+ and Sb2+.
  • mercury diffuses through the fluorescent layer and reacts with sodium which has diffused to the inner surface of the bulb.
  • the amalgam resulting from this reaction also creates coloured portions on the bulb which reduce light transmission. Consequently, in bulbs in which the fluorescent layer is composed of a rare earth metal, the light emission of the fluorescent lamp decreases in proportion to its amount of use.
  • a fluorescent lamp having a protection layer absorbing ultraviolet rays for preventing the diffusion of sodium (Na) is described in JP-A-50-12885.
  • this fluorescent lamp uses a halophosphate phosphor activated by Mn2+ and Sb2+ which is conventional and the protection layer is made by special methods including a baking step and is, therefore, extremely thin.
  • this technique cannot be easily applied to the fluorescent lamp using a rare earth metal fluorescent substance and the protection layer cannot be made by such special methods.
  • US-A-5051650 and US-A-5227693 disclose other types of fluorescent lamp using a protection layer for preventing ultraviolet rays from emitting from the lamp.
  • the protection layer comprises a mixture of particles of titanium oxide (TiO2) and zinc oxide (ZnO).
  • the fluorescent substance of the lamp comprises a rare earth metal fluorescent substance.
  • the lamp is supposed to use a lead glass, for easily bending or connecting the glass.
  • the protection layer is very thick as the protection layer is intended to prevent more than 90% of ultraviolet rays from emitting from the lamp. The efficiency of this lamp is lower than that of a fluorescent lamp without the protection layer because of the thick protection layer absorbing visible light.
  • a fluorescent lamp comprising: a bulb formed of glass containing at least 15% by weight of sodium; mercury vapour and a rare gas sealed in the bulb; a fluorescent layer formed inside an inner surface of the bulb, the fluorescent layer comprising a fluorescent material including a rare earth metal fluorescent material; and a protection layer formed between the inner surface of the bulb and the fluorescent layer; characterized by the protection layer having a thickness of from 0.2 ⁇ m to 1.5 ⁇ m and comprising fine grains of a metal oxide which absorbs ultraviolet rays.
  • the present invention can thus provide a fluorescent lamp in which reduction of luminous efficiency, due to interaction between mercury (Hg) and sodium (Na), is prevented or reduced.
  • a preferred example of the metal oxide is at least one oxide selected from zinc oxide and titanium oxide.
  • the metal oxide of the protection layer is preferably a mixture of zinc oxide and titanium oxide in which the zinc oxide is more than 50% by weight.
  • the fluorescent layer can include cerium.
  • the fluorescent material contains a rare earth metal fluorescent material preferably capable of emitting three kinds of visible light corresponding to blue, green and red.
  • a rare earth metal fluorescent material preferably capable of emitting three kinds of visible light corresponding to blue, green and red.
  • Preferably more than 90% by weight of fluorescent layer is constituted by the rare earth metal fluorescent material.
  • the protection layer is constituted by the fine grains of metal oxide.
  • Figs. 1(a) and 1(b) show an embodiment of the present invention in which a fluorescent layer is formed inside an inner surface of a bulb 1 composed of soda lime glass comprising about 15-17% by weight of sodium (Na).
  • Bulb 1 is formed as a straight tube.
  • a flarestem 2 is inserted to form an air-tight seal at both ends of the bulb 1.
  • a pair of lead wires 3 penetrates through the flarestem 2 at both ends of the bulb 1 without disruption of the air-tight seal.
  • a respective filament electrode 4 is connected to and supported by the pair of lead wires 3 at each end of the bulb 1.
  • Each filament electrode 4 is made of tungsten (W) or any conventional composition used for filament electrodes.
  • An electron emitter substrate such as BaO, SrO or CaO, is added to the filament electrode 4.
  • Two metal caps 5 are attached at the opposite ends of the bulb 1.
  • a pair of pins 6 passes through each metal cap 5 and is insulated therefrom, and the pins 6 are electrically connected to each pair of lead wires 3.
  • a protection layer 11 is formed on the inner surface of the bulb 1, and comprises fine metal oxide grains which absorb ultraviolet rays.
  • a fluorescent layer 12 is formed on the protection layer 11, and comprises a rare earth metal fluorescent substance.
  • the protection layer 11 comprises fine metal oxide grains of zinc oxide (ZnO), titanium oxide (TiO2) or a mixture of these metal oxide.
  • the average particle size of fine metal oxide grains is less than 0.1 ⁇ m.
  • the zinc oxide (ZnO) grains are highly absorptive of ultraviolet rays, but have very low absorption of visible light.
  • the zinc oxide (ZnO) is the preferred materia for the structure of the protection layer 11 in this embodiment.
  • Metal oxide materials for the protection layer 11 other than zinc oxide (ZnO) or titanium oxide (TiO2) cause a larger absorption of visible radiation.
  • the protection layer 11 has a thickness of less than 0.5 ⁇ m.
  • the fine metal oxide grains are dispersed in a disperse medium such as water to form a mixture.
  • a disperse medium such as water
  • the mixture is coated on the inner surface of the bulb 1 and the coated layer is dried thereafter.
  • only fine grains remain in the protection layer 11 and are accumulated to form the protection layer 11.
  • the fine grains of protection layer 11 adhere to the inner surface of the bulb 1 by the effect of van der Waals' force.
  • the fluorescent layer 12 includes three kinds of rare earth metal phosphors for emitting red light, green light and blue light during lamp operation.
  • the phosphor for emitting red light is yttrium oxide (Y2O3) or yttrium oxide activated by europium (Y2O3:Eu).
  • the phosphor for emitting blue light is an alkaline earth halophosphate phosphor activated by divalent europium (which phosphor is disclosed in US-A-4038204) or an alkaline earth aluminate phosphor activated by divalent europium (BaMg2Al16O27:Eu) (which phosphor is disclosed in US-A-4216408).
  • the phosphor for emitting green light is represented by the chemical formula (La, Ce, Tb) . (P,Si)O4. The fine grains of these three kinds of phosphors are mixed.
  • the protection layer 11 having an absorptive property of ultraviolet rays is formed between the inner surface of the bulb 1 and the fluorescent layer 12; therefore, protection layer 11 prevents direct contact between the inner surface of the bulb 1 and the fluorescent layer 12, and absorbs ultraviolet rays which would otherwise reach the inner surface of bulb 1 through the fluorescent layer 12. Consequently, the diffusion of sodium (Na) from the bulb 1 made of soda-lime glass, which would be caused by ultraviolet rays, is reduced. Protection layer 11 blocks direct contact between mercury (Hg) and diffused sodium (Na) and, therefore, the occurrence of coloured or blackened portions on the inner surface of the bulb 1 is reduced or prevented, and a maintenance ratio of light output is maintained high.
  • Hg mercury
  • Na diffused sodium
  • Protection layer 11 comprises substantially no binder and thus is different from the disclosure in US-A-5051650, so that there are substantially no diffused impurities of the binder on an inner surface of the bulb 1.
  • the protection layer 11 does not include a binder, it is possible to employ no heating or only low temperature heating during formation of protection layer 11 and, therefore, diffusion of sodium (Na) from bulb 1, which would otherwise result from such high temperature heating like a baking step, is avoided.
  • the protection layer 11 is substantially composed of only fine grains, and impurities are scarcely present in the protection layer 11. Therefore, the likelihood of blackening or short life of the lamp is low as compared with a fluorescent lamp with a protection layer including a binder such as that of US-A-5051650 and a fluorescent lamp with a protection layer formed by a special method including a baking step for baking an organometallic compound.
  • the term "substantially” means that protection layer 11 contains more than 90% by weight of the fine grains of the metal oxide.
  • the fluorescent layer 12 comprising the rare earth metal phosphors can be formed thinner than previously used conventional fluorescent layers such as a halophosphate phosphor activated by manganese and antimonide.
  • the fluorescent layer 12 can be formed thinner (for example 10-25 ⁇ m) because the particle size (3-5 ⁇ m) of the fine grains of the rare earth metal phosphors is smaller than the grains (particle size: 7-10 ⁇ m) of conventional fluorescent layers (having a thickness of 30-70 ⁇ m).
  • the probability of mercury (Hg) passing through the fluorescent 12 comprising rare earth metal phosphors becomes larger as fluorescent layer 12 is formed thinner, but nevertheless the reaction between mercury (Hg) in bulb 1 and sodium (Na) diffused from the bulb is reduced in view of the presence of the protection layer 11.
  • Protection layer 11 comprising fine grains of zinc oxide (ZnO) or titanium oxide (TiO2), or a mixture of both, has a high absorptive property of ultraviolet rays and substantially no absorption of visible light, and enables provision of a fluorescent lamp having a high lighting efficiency.
  • Protection layer 11 comprising a mixture of fine grains of zinc oxide (ZnO) and titanium oxide (TiO2) has a fine structure and high strength, due to the fine grains of the zinc and titanium oxides. Furthermore, protection layer 11 does not cause an undesirable interference fringe because the fine grains of the zinc oxide (ZnO) and titanium oxide (TiO2) have respectively different average particle sizes.
  • the average particle size of fine grains of the zinc oxide is about 0.04 ⁇ m and that of titanium oxide is about 0.1 ⁇ m. The particle size is measured by photography with an electron microscope.
  • the protection layer 11 provides high transmission of effective visible radiation owing to absorption of ultraviolet rays and substantially no absorption of visible light, especially when the quantity of zinc oxide (ZnO) is more than 50% by weight of the mixture of the zinc and titanium oxides.
  • a protection layer 11 having a thickness of more than 1.5 ⁇ m causes an undesirable excessive absorption of visible light.
  • a protection layer 11 having a thickness of less than 0.2 ⁇ m permits too much ultraviolet rays to pass therethrough.
  • a more desirable thickness for the protection layer 11 is between 0.5 and 1.0 ⁇ m.
  • a conventional protection layer used in conjunction with a conventional fluorescent material to intercept ultraviolet rays including near visible light required a thickness of more than 1.5 ⁇ m. Consequently, the conventional protection layer was made thick with the consequential disadvantage of visible light absorption.
  • protection layer 11 is capable of absorbing short wavelength ultraviolet rays which makes sodium (Na) diffuse more than others. Therefore, even a thin protection layer 11 has effects which are possible to prevent diffusion of sodium (Na) and to reduce reaction with mercury (Hg).
  • Fig. 2 shows graphically the relationship between the life of four fluorescent lamps and the light output thereof; the vertical axis shows the light output (Lm), and horizontal axis shows the lifetime in hours (hr).
  • the lamp structure of type-a is an embodiment of this invention having a protection layer of less than 0.5 ⁇ m thickness, of type-b has no protection layer, of type-c has a protection layer using easily absorbed Al2O3 as fine metal oxide grains, and of type-d has a protection layer which comprises fine metal oxide grains of zinc oxide (ZnO) and titanium oxide (TiO2) such as taught by this invention, but having a thickness of 1.0 ⁇ m.
  • ZnO zinc oxide
  • TiO2 titanium oxide
  • Fig. 2 suggests that protection layer 11 having a thickness more than necessary does not have an effect of increasing the maintenance of the light output.
  • an increased thickness protection layer 11 results in reduced visible light output both initially and during the lamp life.
  • type-a is recognized as providing an increased maintenance of the light output as compared with type-c.
  • Fluorescent layer 12 comprising cerium (Ce) as a phosphor for green light is effective for practising this invention. Although cerium phosphor also radiates 300-380nm as ultraviolet rays, protection layer 11 absorbs this ultraviolet radiation.

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  • Vessels And Coating Films For Discharge Lamps (AREA)
EP94302234A 1993-03-31 1994-03-29 Fluoreszentzlampe Withdrawn EP0618608A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP7467493 1993-03-31
JP74674/93 1993-03-31

Publications (1)

Publication Number Publication Date
EP0618608A1 true EP0618608A1 (de) 1994-10-05

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ID=13554016

Family Applications (1)

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EP94302234A Withdrawn EP0618608A1 (de) 1993-03-31 1994-03-29 Fluoreszentzlampe

Country Status (2)

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EP (1) EP0618608A1 (de)
KR (1) KR940022673A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100323035B1 (ko) * 1998-04-28 2002-02-09 모리시타 요이찌 형광램프 및 그 제조방법
EP1524683A2 (de) * 2003-09-24 2005-04-20 Toshiba Lighting & Technology Corporation Leuchtstofflampe und Beleuchtungsvorrichtung unter Verwendung derselben
US6919679B2 (en) 2001-12-14 2005-07-19 Koninklijke Philips Electronics N.V. Contaminant getter on UV reflective base coat in fluorescent lamps
WO2007034997A2 (en) * 2005-09-26 2007-03-29 Showa Denko K.K. Fluorescent lamp

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3141990A (en) * 1960-04-06 1964-07-21 Sylvania Electric Prod Fluorescent lamp having a tio2 coating on the inner surface of the bulb
US3748518A (en) * 1972-06-14 1973-07-24 Westinghouse Electric Corp Fluorescent lamp having titania-doped glass envelope with transparent buffer film of titania
US4289991A (en) * 1974-11-25 1981-09-15 Gte Products Corporation Fluorescent lamp with a low reflectivity protective film of aluminum oxide
EP0449307A2 (de) * 1990-03-30 1991-10-02 Toshiba Lighting & Technology Corporation Leuchtstofflampe und ihr Herstellungsverfahren

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3141990A (en) * 1960-04-06 1964-07-21 Sylvania Electric Prod Fluorescent lamp having a tio2 coating on the inner surface of the bulb
US3748518A (en) * 1972-06-14 1973-07-24 Westinghouse Electric Corp Fluorescent lamp having titania-doped glass envelope with transparent buffer film of titania
US4289991A (en) * 1974-11-25 1981-09-15 Gte Products Corporation Fluorescent lamp with a low reflectivity protective film of aluminum oxide
EP0449307A2 (de) * 1990-03-30 1991-10-02 Toshiba Lighting & Technology Corporation Leuchtstofflampe und ihr Herstellungsverfahren

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100323035B1 (ko) * 1998-04-28 2002-02-09 모리시타 요이찌 형광램프 및 그 제조방법
US6919679B2 (en) 2001-12-14 2005-07-19 Koninklijke Philips Electronics N.V. Contaminant getter on UV reflective base coat in fluorescent lamps
EP1524683A2 (de) * 2003-09-24 2005-04-20 Toshiba Lighting & Technology Corporation Leuchtstofflampe und Beleuchtungsvorrichtung unter Verwendung derselben
EP1524683A3 (de) * 2003-09-24 2008-02-27 Toshiba Lighting & Technology Corporation Leuchtstofflampe und Beleuchtungsvorrichtung unter Verwendung derselben
WO2007034997A2 (en) * 2005-09-26 2007-03-29 Showa Denko K.K. Fluorescent lamp
WO2007034997A3 (en) * 2005-09-26 2007-08-30 Showa Denko Kk Fluorescent lamp

Also Published As

Publication number Publication date
KR940022673A (ko) 1994-10-21

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