WO2007034997A2 - Fluorescent lamp - Google Patents

Abstract

A fluorescent lamp and a process for the production thereof are provided whereby the consumption of mercury is prevented, sealed-in mercury is drastically reduced, and the lamp has high retention of luminous flux and achieves an expanded lifespan. The fluorescent lamp includes an arc tube and a protective layer on an inner surface of the arc tube, the protective layer including connected particles having a volume-average particle diameter of 10 to 300 nm, the connected particles being composed of an oxide of a metal not forming an amalgam with mercury. The fluorescent lamp includes: an arc tube; and on an inner surface of the arc tube and in the order named: at least one of a UV absorbing layer and a UV reflecting layer; a protective layer including connected particles having a volume-average particle diameter of 10 to 300 nm, the connected particles being composed of an oxide of a metal not forming an amalgam with mercury; and a fluorescent layer.

Description

^{' ■} , ^■ DESCRIPTION

FLUORESCENT LAMP ; ^' ,

^■• FIELD OF THE INVENTION • ^■ ■

The present invention relates to a fluorescent lamp and a. process for producing the same. ^*

v .. . ^{■ ■} BACKGROUND ^'OF THE INVENTION ". . ,^' Common fluorescent lamps have a protective layer of a metal oxide on a fluorescent layer on the inne,r surface of a

^■glass tube,, orbetween the glass tube an'd'the phosphor layer.

_.The protective layer is generally produced by mixing fine metal

^■ oxide particles s'uch as aluminum oxide in an organic solvent ■ ' ^'such- as^' butyl acetate, and applying the solution such that the layer will have a predetermined thickness, followed by, ^• " heat-treatment¹ (Patent Document 1) . • • ^{' ■ ■■}

However, the protective layer produced as described ^{' ■} above is not dense and does not achieve an intended function as protective layer, often causing reduced luminous flux. This is probably because mercury sealed in the glass tube penetrates the protective layer and reacts with sodium in the glass tube, forming mercury compounds such as amalgams that do not contribute to light production. .

I ' ^{* '} . ^{' •"} . ;

The conventional fluorescent lamps prevent this problem by including' far more mercury than required for fluorescing in the glass tube to prevent the reduction of luminous flux 'by consumption ofmercury^ However, sealing large amounts of harmful mercury Is not. environmentally good, and reduction of mercury use is a .big assignment.. - . ^{■ • •'} ' \ ^{' ■}

To address the above problem, Patent Document 2 disclqses-,; that a layer of fine- metal -oxide particles is formed on^' a fluorescent^' layer. : However, the layer is not sufficiently continuous and is incapable of preventing , the reduction of ^'< luminous flux adequately. - Specifically, the /metal oxide ^■ particles^' don' t have sufficiently small^' diameters to cause .voids, in the layer, and the, particles .in the coating solution ^■, aggregate ^' to cause uneven application, resulting in_. ' 'insufficiently continuous layers. . . ^•

Nonpatent Document 1 discloses conventional lamps ^• having a non-continύous^' layer. These ;lamps have reduced, aggregation in the^' protective layer and achieved an increased^{' ■} lifespan, but_. improvements in life expansion and void prevention in the protective layers are still insufficient. Patent Document 1: JP-A-S62-229752 Patent Document 2: JP-A-2000-294193 Nonpatent Document 1: Press Release of Matsushita Electric Industrial Co., Ltd., August 17, 2005 (featuring ^■•PA-LOOK PREMIER, extended-life straight-tube 20_. W fluorescent ^{• '■} lamps available in three ^•. light colors), ^{' ' •}

^{•'' ■ • ■} ■ DISCLOSURE QF THE ^'INVENTION - 5 ^{■ '} PROBLEMS TO BE SOLVED BY- THE INVENTION ^{' '}■^'.

It is an Object of■ the present ^• invention to provide -a fluorescent lamp and a process for the production thereof . whereby the consumption of. mercury is --prevented, sealed÷in mercury is drastically reduced, and the, lamp has high retention 10 of luminous flux and achieves an .expanded lifespan.

^{■ '} ; ¹J .^'. . MEANS^' FOR SOLVING THE_1. PROBLEMS - ^'. . ^': The present^' inventors diligently studied to solve -the -,problems in the conventional art, and have found that a 15^{j '}fluorescent lamp that has a continuous layer.of a_.specific oxide solves the problems. The present invention is completed based on the finding: . , _, ^' • • - - . . . The present invention is concerned with the following.^' [1] A fluorescent lamp comprising an arc tube and a 20 protective layer on an inner surface of the arc tube, the protective layer comprising connected particles having a volume-average particle diameter of 10 to 300 nm, the connected particles comprising an oxide of a metal not forming an amalgam with mercury. [2] The fluorescent lamp as described in [ϊ] , comprising: ^{■ '■} an arc tube; and on -an inner surface of the arc tube and in the order named: ^{' ■} •:

^{■' ■ ■} at least one of a'-UV absorbing layer and-a.UV reflecting 5 layer; ^•; . . ^' . • ^{■ "} ■^'.

^■ a protective layer comprising connected particles having a volume-average particle diameter of 10 to 300 run, the. •

^{■ •} connected particles comprising an oxide- of- a metai not forming v ^' an amalgam with mercury;- and . • , . , ^• • ' ' ^' ;

10- a fluorescentflayer. ■ • i

[3] The fluorescent'lamp as described in [1], comprising: I an arc tube; and on an inner surface of the arc tube and ' ,iή the order named: . , , ^• . ■'_. ^{• •} • at least one of a UV -absorbing layer and a- UV reflecting -. 15^{1 '}layer; ^{" '} . ^■' . ^' . a • fluorescent layer; and - ^{■ • '} a protective layer. comprising connected particles . - having a. volume-average particle diameter of 10 to 300 nm, the^{' ■} connected particles comprising an oxide of a metal not forming 20 an amalgam with mercury.

[4] A fluorescent lamp comprising an arc tube, and a UV absorbing layer and/or a UV reflecting layer on an inner surface of the arc tube, the UV absorbing layer and/or the UV reflecting layer comprising connected particles having a volume-average •particle diameter of 10 tσ 300- nm, the connected particles ^{■ '} comprising an oxide of a -metal not forming an^'-amalgam with mercury. . ' ^' , . '

' ^■ [5] The fluorescent lamp' as described in any one of [1] 5¹ to [4], wherein -the oxide of a- metal^' not forming an^'ama_.lgam ^'.with mercury is based on _tat least one of yttria,_. cer,ia and silica. ^{' ' ■} . ^{' ■ •}; ^{■ '} ■'_. ^' > [6] .The fluorescent lamp- as described in any, -one of _;[2] _.to [5] , wherein the^' UiV absorbing layer and/or- the UV reflecting 10 layer comprises at least one of alumina, zinc oxide^' and titanium , oxide . ^{' ■} ■ .

^{1 ■ '} [7] /The. fluorescent lamp as described in [6], wherein .the at least one of alumina, zinc oxide and titanium ox^'ide is ^•. ,in the form o,f fine- metal oxide particles having .a ■ . ^{' ■} 15- -^'volume-average particle- diameter of 10 to 300 .rim.

[8] The fluorescent lamp as described in [7], wherein^', the ^'fine metal oxide particles ^'forming the UV absorbing layer or the UV reflecting layer are coated with silica.

[9] A -process for producing the fluorescent lamp as 20 described in [1] or [4] ,. comprising: applying a slurry of fine metal oxide particles in a dispersion medium to an inner surface of an arc tube, the fine metal oxide particles comprising an oxide of a metal not forming an amalgam with mercury, the dispersed fine metal oxide ■particles having a volume-ayerage particle diameter of 10 to 300 nm; -. . - ^{■ •}. ,^{• • •} drying the slurry; -and _. .■ heat treating the resultant layer to form, a protective ^' layer, or a UV absorbing layer and/or a UV reflecting layer.

. _. [10] The process as, described, in [9], wherein the ■ dispersion medium is a polyhydric alcohol derivative.

'^'. / [11] The process as described in- [iO], wherein the polyhydric alcohol derivative is a l-alkqxy-2₇alkyl_. alcohol . [12] The process as described in. [10]-, wherein the , , polyhydric alcohol derivative is at least one of ¹ l-methoxy-2-propanol and l-ethoxy-2-ethanol . ,.

^• . , [13] The process, as-described. in [9] , wherein the slurry '

-of the fine metal ^'oxide particles includes a β-diketone metal ... ' 'complex^'- as a binder. ■ ^■'■ . ■ '

[14] The process as described in [,9] , wherein the slurry^' of the fine metal oxide, particles is a dispersion of fine . particles of an oxide of a metal in a dispersion medium, the-

oxide being produced by gas-phase oxidation of a β-diketone metal complex, the metal not forming an amalgam with mercury.

[15] A fluorescent lamp produced by the process as described in any one of [9] to [14] .

[16] A luminaire comprising the fluorescent lamp as described in any one of [1] to [8] and [15] . [17] ¹A display device comprising the fluorescent lamp as described in any one of [1] to [8] .and [15]-;

^{■'' ■} ' ^• EFFECTS OF THE INVENTION , • ^• .

5 ^' The protective layer in the invention .is compos.ed of

^' uniform> dense^' and strongly connected metal oxide parti-cles.

According to the invention, such protective layer is easily_. , produced-.. The protective layer increases the lifespan of v. ^' ' ■ fluorescent lamps. iA UV -absorbing or. reflecting layer may be 0 formed in combination with the protective layer. In that case,, , the protective layer, .and- the UV absorbing or reflecting layer ^■have high^' adhesion,^' ancl therefore thes'e- layers achieve a .reduced thickness. Fluorescent lamps having,these layers' are ' , drastically improved in prevention of mercury consumption in._. 5' -^'spi_.te of the reduced thickness of these layers-.^'

The invention enables substantial cost reduction in the production of protective, layers. The -fluorescent lamps according to the invention have small reduction in luminous- ^■ flux after long use. Such high-quality products may be 0 produced with efficiency. The invention does not require much mercury and is safe.

Dispersants and binders may be added to the metal oxide slurry for the production of protective layers. In that case, heat treatment of the slurry containing such additives results ■ in a more dense protective^' layer, and fluorescent lamps with ^■ the protective .layer are. capable of increased effects in preventing mercury consumption over the conventional lamps..

5 BRPEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic^' view of. an apparatus for producing fine metal oxide particles in the present invention; and ¹ > Fig. 2 shows luminous -flux retention in .Examples 7 ^'and-

* ^■ 8 and Comparative Example 3. ^• ,

10 . ^' . ^', ^{" ' ■}

_; ^* PREFERRED. EMBODIMENTS ^• OF THE INVENTION The ^'present invention will be i described in^' detail .,-hereinbelow. . , • . , . '

As used herein,, the fluorescent lamps are general 15' ^{' '}discharge lamps with phosphors and they include hot cathode fluorescent lamps, 'cold cathode fluorescent lamps and external electrode discharge lamps. The lamps may be straight tubes,- circular or balls ^'in shape. ^■ Protective layer^'

20 In the invention, a protective layer is formed on an inner surface of an arc tube to extend the life of the fluorescent lamp. The protective layer is composed by connected particles of an oxide of a metal not forming an amalgam with mercury. The particles have a volume-average particle diameter of 10 . to 300 nm. ' ^{' '}

Preferably, the particles ^■ have a volume-average particle diameter of 10 to 100 nm. As used herein, the ^' 'connected particles are fine particles that are_.very strongly attached together by a physical force such as the van der Waals' ^'.force, or that are chemically bonded.together (sintered). The protective layer is very dense and each particles are connected together- uniformly.; So there are no continuous ^' flaws that penetrate the layer to the underlying base.. ' Consequently, the layer with a^' small thickness achieves a .sufficient protecting performance. ^'•• .

^■ _. The protective layer is generally composed .of the metal oxide, and may contain a dispersant and a binder as required ^■, ,in amounts not more than 40% by mass relative to the metal oxάde . ^{' '} .^'' The oxide of a metal not-forming an amalgam with mercury ^' is based on at least one of yttria, ceria and silica. These oxides may form a complex oxide. ■

The protective layer is preferably from 0.05 to 1 μm in ^• thickness, more preferably from 0.05 to 0.3 μm in thickness. When the thickness is small, mercury will penetrate the layer and the fluorescent lamp often has a shorter lifespan than expected. When the thickness is large, the layer does not allow sufficient permeation of visible light or ultraviolet light. .^{' " ■}' .^' "^{•' "} : ^• 10 ^' . ' ' -^{■ ■} .. ^' .^{' •} .. . ^{• "}

To prevent the contact between mercury and the glass ^■ ' ^■ tube, the protective layer' may be formed on or under the flu orescent layer. . ' ,

UV absorbing layer and UV reflecting layer ,

.5 ^' It is general practice to form- ^'a UV absorbing layer or ^' a UV reflecting layer on the inner surface of the arc tube to • prevent UV light from escaping,from the arc tube . These layers .

^■ maybe composed of a.general UV absorbing or reflecting material, and may be preferably based on at. least one kind of fine metal

10 oxide particles selected from.alumina, zinc oxide ^'and titanium , ^' . oxide. ^■■

As with .the protective layer, the UV absorbing layer and .the UV reflecting layer -are formed of continuous fine ^'metal ^{■ •}.oxide particles having a volume-average particle diameter of. 15' '^'1O to 300 nm, more preferably- 10 to 100 nm. ^' . '

The fine metal oxide particles that are a main component^' of the UV absorbing and UV reflecting -layers, are preferably- coated with silica. ^' Coated with silica, the particles show

^■ improved dispersibility in the coating solution. The coating 20 is preferably 0.5 to 100 nm, preferably 0.5 to 25 nm in thickness from the surface of the fine metal oxide particles.

Silica coating may be performed before or after the fine metal oxide particles are dispersed in the dispersion medium. The coating method may be conventional. The coating prior- to ■ the dispersing step may be ^'carried put by a^' method disclosed ^{■ •} in JP-A-2004-210586, and, the coating subsequent ^' to ^' the dispersing step may be performed as described in , . ' ^{' ■ •}JP-A-20-04-124069/ ^' '^{■ " '} . ^' . " _. . . 5 In the.present invention, the ^'UV absorbing- layer .and the ^'.UV reflecting layer may άή^'clude fine particles of the _soxide of a metal not forming an- amalgam with mercury, whereby the ' ^■ UV absorbing layer and the. UV reflecting, layer liave another function as a protective layer for increasing,the lifespan -of 10 the fluorescent lamp. In this case, the separate protective layer is- not necessary, and the steps in the fluorescent lamp ^■production may be reduced. . , . ' ^■ , ■

The UV absorbing layer and the UV reflecting layer- may ^■...consist solely of the fine particles of the oxide of a metal 15 ' not forming an amalgam with mercury, or may be ^'desirably composed of a mixture of such fine particles and at ieast one kind of fine metal oxide.particles selected from-alumina, zinc oxide and titanium oxide. ^{' •}

Desirably, the above mixture includes (a) the fine 20 particles of the oxide of a metal not forming an amalgam with mercury, and (b) the at least one kind of fine metal oxide particles selected from alumina, zinc oxide and titanium oxide, in a mass ratio (a) : (b) of 10:1 to 1:5, preferably 5:1 to 1:1. When the mass ratio is in this range, the layer shows excellent UV absorbing properties and UV reflecting properties as well as high protective properties. When-two_. or more kinds of fine metal oxide particles^'are used, 'these particles are .connected ^{■ '} ' together to form continuous _p fine metal oxide particles . 5 ^' When the UV absorbing layer and ^'the UV reflecting layer have another function as .a protective layer, the metal oxide particles for the UV .absorbing and UV reflecting layers are , preferably coated with silica as described above to prevent adsorption of mercury. \ ^' . ^' ■ ■ 0 The- UV absorbing layer and the UV. reflecting layer are , preferably from 0.1 to 1 'μm. in thickness. When the thickness ^■ is small,, the layer cannot prevent UV_tlight from- escaping from .the arc tube sufficiently._, When the thickness ^'is large, -the ' ^■.layer does not allow ' sufficient permeation of .visible light 5' ^{' '}through the arc tube. - ., -^{'■ '} ■ ^•

The protective layer, the UV absorbing layer and the. UV^' reflecting layer (hereinafter, collectively -referred to as layers) are free from continuous flaws that penetrate the ^{■ ■} layers to the underlying base. ^'Consequently, the layers

0 having a thickness of 200 nm to 50 μm achieve a sufficient protecting performance. The layers may contain a dispersant and a binder as required.

The layers are composed of the connected particles having a volume-average particle diameter of 10 to 300 nm. Particles . (more than' 100 in- number) are_. measured for diameter using an ^{■ ■} electron photomicrograph,- and a particle size distribution is obtained and a volume-average particle diameter is calculated. 'When the particle diameter is large, the layer produced-in small 5 thickness will have pinholes and will not produce sufficient .effects.- ^' . , ^' ■ , ^■ : , _s

Layer production ^■

'_. ^' , -The protective. layer, the UV absorbing layer and^' the UV reflecting layer do not produce sufficient effects unless they 10 are continuous and ^'dense. Accordingly, these layers are preferably produced as^' follows. ^■ _t ^'

The¹ protective layer. is compos,ed -of the .fine particles ._.of the oxide of a metal not forming an amalgam -with mercury. ..The UV absorbing and UV reflecting layers are composed of the 15 ^'fine metal oxide particles. as described above.^{' l} These fine metal oxide particles are producible by similar methods, and . the ^' layers may be formed by similar methods. .Accordingly,.- these metal oxide particles will be referred to collectively ^■ as fine metal oxide particles.

20 The layers may be produced by applying a slurry of the relevant metal oxide to a base (or a next layer below) , followed by drying and heat treatment to sinter the metal oxide particles . The fine metal oxide particles easily aggregate, and it is generally difficult that they give a satisfactory slurry. - , I ' ' .' ' ^f " • ' *^{* ' ' ■"}■When the particles are applied, the space between the particles ^{■ •} in the layer is critical .- ^■ Optimizing the.^' types and^" amounts of dispersion medium, dispersaht and binder, the slurry^{' •}concentration and^'heat 'treatment conditions enables dense and 5¹ firm layers without cracks and pinholes.

^'. ■ ^■ The steps in the production of, layers will be described below. . ^{■' •} .

^' Preparation of metal- oxide. -slurry - ^{" ' •}

The layers are! produced from a slurry of .the metal oxide

10 particles having a volume-average particle diameter of 10 to 300- nm. -The particle diameter of dispersed particles is a

^■ volume-average particle diameter of (the particles dispersed , in the slurry- (or diluted with a' dispersion medium) . ^' it-may

^■ be determined by ' the laser Doppler technique.■ ^• ■ ■ ^' . 15 ' ^' The particle diameter ,of^'the fine metal oxide particles dispersed in the slurry is more preferably from 10 to 200 nm, optimally from 10 to I¹OO .nm. The metal, oxide particles having diameters of the_. order of nm will be referred to as nano metal' ^■ oxide particles. When the particle diameter in the dispersion 20 exceeds 300 nm, heat treatment at low temperatures can result in insufficient aggregation of the particles, and the heat treatment temperature should be raised, making it difficult to use a less heat resistant base (such as glass tube) . Heat treatment at low temperatures does not induce aggregation of the nano particles. Consequently, the layer has greater flaws and should be increased in thickness to achieve ^'desired properties. ^• ,_: . ^{' λ ■} When the dispersed particles have diameters smaller than 5 required, dispersing such particles.^'consumes enormous^' energy. •For the production of the, metal ox-i.de particles,, gas.-phase , ^' processes (JP-A-2004-168641) .'and neutralization crystallization processes ( JP-A-H08-12-7773) may^' _.be selected \ appropriately.¹ i • ^{• '} '• ^{' '} •. • ^■

10 The metal oxide particles may be_. dispersed in the dispersion medium by means of ultrasonic waves, ₍ball mills and ^■ bead mills .. T.he bead mills may use yt1;ria-stabilized zirconia

.beads. 5 μm. to' 1 mm in, diameter. , ^{• '} • ^{' '}-.

-. Dispersion medium of metal oxide slurry ^'. ^• 15; '^' . ^' The dispersion medium of the metal oxide, slurry is ' desirably a polyhydric alcohol derivative. The nano metal oxide particles have' very, strong interaction and easily aggregate. ^■ The dispersion. medium permits the nano metal oxide- ^■ particles to be dispersed substantially without aggregation. 20 Dispersing properties are deferent depending on the types of the dispersion media. From the viewpoints of dipole moment and viscosity, polyhydric alcohol derivatives are suitable.

Preferred examples of the polyhydric alcohol derivatives include monoethers, diethers, monoesters and ^■■diesters of po.lyhydric alcohols. Examples of the polyhydric ^{• '•} alcohol derivatives include dihydric alcohol derivatives such as l-methoxy-2-propanol, ^■l-ethoxy-2-prppanol, ^' . ' l-butoxy-2-propanol, d-iethylene glycol ethyl methyl- ether, 5' diethylene glycol diethyl ether, diethylene .glycol dibutyl ^' ether, diethylene. glycol .dimethyl e.ther, diethylene glycol monόethyl ether, diethylene glycol monoethyl ether ^'acetate,

' .^• diethylene ^'glycol monobύtyl- ether, diethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether,

10 ethylene glycol diacetate, ethylene glycol diethyl ether, ethylene-glycol dibutyl ether, ethylene glycol dimethyl ether, ^■ ethylene .glycol monbacetate, ethylene glycol . monoisopropyl ether, ethylene glycol monoethyl .ether, ethylene glycol ^■.monoethyl ether acetate, ethylene glycol monobutyl ether,.

15' 'ethylene glycol monobutyl ether acetate, ^' ethylene glycol' monohexyl ether, ethylene glycol monomethyl ether, ^'ethylene glycol monomethyl ether acetate and ethylene glycol monomethoxy methyl ether; arid polyhydric alcohol derivatives- ^• with three or more hydroxyl groups such as glyceryl monoa^'cetate,

20 glyceryl diacetate, glyceryl triacetate, glyceryl dialkyl ethers (for example, 1,2-dimethyl glycerol, 1,3-dimethyl glycerol and 1,3-diethyl glycerol). Of these, l-methoxy-2-propanol and l-ethoxy-2-ethanol are particularly preferable. ^■• Dispersant' for slurry ^{• ■} .

^{■ '} . The-.metal_ι oxide slurry may contain a^' dispersant . In the

invention, β-diketones are suitable as dispersants .

Examples of the "β-diketones ^' include . - , 5 2,2, 6, 6-tetramethylheptane-3,5-dione (DPM-H),- -

2, 6-dimethyl-3, 5-heptanedione (DMHD -H) and 2, 4-pentanedione

(acac-H) . The dispersants further include β-ketoesters such. aύ methyl-3-oxopentanoate, e,thyl-3-oxopentanoate, methyl-4-methyl-3~oxopentanoate-, , . . • 10 ethyl-4-methyl~3-oxopentanoate, methyl-4, 4-dimethyl-3-oX'θpentanόate and ,^{' ■} ethyl-4ι, 4-dimethyl-3-oxopentanoate.₁ . ' ^■ •■^■ . ^' _. ._,,^{' ■} The use of the dispersants^' reduces the particle diameter

^•. ,of the dispersed particles, reduces the dispersing time_/ and . 15' 'prevents the dispersed particles from aggregating. The

β-diketones are volatile and are evaporated during the .heat ^• treatment, and' consequently they do not remain -in the layers

produced. The amount of the β-diketones is- 1 to 10 parts by ^■ mass, preferably 5 to 10 parts by mass based on 100 parts by 20 mass of the fine metal oxide particles.

Nonionic surfactants may be added as dispersants in

combination with the β-diketones. Examples of the nonionic surfactants include ethers such as polyoxyethylene alkyl ethers, polyoxyethylene secondary alcohol ethers, . polyoxyethylene alkyl phenyl ethers, polyoxyethylene, ^'• polyoxypropylene block copolymers and ■polyoxyethylene polyoxypropylene alkyl ethers; and ester ethers such as "polyoxyethylene glyceryl fatty acid esters, -polyoxyethylene 5 castor oils, polyoxyethylene hydrogenated castor oils and ^'..polyoxyethylene sorbitan fatty acid esters. The amount Of the ^■ nonionic surfactants is 1 to 10 parts by mass_/ ^■ preferably 5-.; to.10 parts by mass based on 10,0 parts byma-ss of the fine metal oxide particles-. ,' ^• , . . • • ^' . ^' 0 Too much dispersants remain as impurities in the layer ' after the heat treatment/ 'and pinholes which..mai?ks evaporation . of_. the dispersants are generated im the ^' layer^'. 'Too_. little ._.dispersants do not produce, satisfactory dispersing effects-.^{' •}, Binders_. ^{" '} • .

5' ^•' The metal oxide slurry may contain -β.-diketone metal ^• complexes as binders which are free from alkali metals avoided in fluorescent ^■ lamps . . ; ^■ ' , ^{■ ■}

By using the binders, the heat treatment of the metal ^• oxide particles may be performed at low temperatures, the nano 0 particles show high cohesion in the layer, and the layer has high adhesion.

The metal in the complexes is preferably yttrium.

Examples of the β-diketone metal complexes include Yttrium complexes with 2, 2, 6, 6~tetrarαethylheptane-3, 5-dione •. (DPM-H), 2,β-dimethyl-3,5-heptanedione (DMHD-H) and ^{' ■ '}• 2, 4-pentanedione (acac-H)-. ^■ Specific examples- include Y (DPM) ₃, Y(DMHD)₃ and Y(acac)₃. The complexes further include ^• '

β-ketoester metal complexes such a's metal complexes Of 5' methyl-3-oxopentanoate, ethyl-3-oxopentanoate, ■ .

^'.methyl-4-methyl-3-oxopenta"noate, ■ , ^' , _s ethyl-4-methyl-3-oxopentanoate, • me^'thyl-4, 4-dimethyl-3-oxopentanoate and ^'. _. •^{' "} ' ^{■ •} ethyl-4, 4-dimethyl-3—oxopentahoate . .

10 The amount of ^he β-diketone metal complexes is preferably 1 to 10 parts by mass, more preferably 5 to 10 parts ^■ by mass > based, on 100 parts, by mass of the fine metal oxide .particles .. Too much binders remain as impurities in the layer,^{' •}.and evaporation of the binders leaves pinholes. in the layer. 15' ''When the binders are.too little, the layer is not sufficiently dense. ' Production of fine metal, oxide particles • < . .

The fine metal oxide particles may be produced, for

^■ example by gas-phase oxidation of β-diketone metal complexes 20 (the metal in the complex is selected depending on the oxide of the layer), specifically as follows. A solution of the

β-diketone metal complex is vaporized. The vapor containing the gaseous β-diketone metal complex is mixed with an oxygen-containing gas or oxygen. The mixture is ^••quantitatively supplied to a heating apparatus such as tubular

' ^" electric furnace, and the -β-.diketone^' metal complex is. cracked and oxidized to produce fine metal oxide particles . • The metal

'oxide particles may be'-also produced by known processes such

5' as neutralization crystallization arid sol-gel processes.

The fine metal oxide particles- obtained by gas^-phase

. oxidation of β-diketoήe metal complexes generally contain ^{■ ■} several %^'of carbon residues as, impurities . • _.When the particles contain much carbon

such impurities remain in the 10 layer and elimination of carbon leaves pinholes in the layer. To prevent this problem,- the particles are preferably • ^■ subjected¹ to heat treatment in an air atmosphere at 100 to ,1000⁰C for-1 to 12 hours to, reduce the carbon residue content .to less than 0.5% by mass. ' ^'

15' ^•' ^{'■ ' '} The fine metal oxide particles synthesized- as described above are aggregates. Accordingly, they should be crushed by^' an appropriate method into fine particles so that the particles are finely dispersed to¹ give a stable slurry. A number of ^{' ■} methods such as bead mills, jet mills and ball mills may be 20 used to finely disperse the fine metal oxide particles, with bead mills being preferred. The smaller the beads used, the higher the dispersing rate and the smaller the particle diameter. Preferably, the diameter of the beads is from 5 to

200 μm, particularly from 10 to 100 μm. Yttria-stabilized ^■. zirconia beadS_j having high abrasion resistance are preferable ^{■ '} from the viewpoint of minimizing the^' contamination of slurry. To produce a metal oxide slurry using a bead-.mili, the 'fine metal oxide particles, , organic dispersion medium, 5 dispersant, binder and beads are added to a vessel, followed ^'by stirring. The packing ■ density of the beads in the' vessel is preferably from 85 to 95%.. ■ The fine metal Qxide particles _. ^{• ■} preferably account fo 'r- .1 to 50%^• by mass- of .thte total (100% by mass) of the fine metal oxide particles,, organic^', dispersion 10 medium,_, dispersant and binder. The stirring time may be ■ ' determined depending on a desired particle diameter, and is ^•generally from about 10 minutes to 12. hours. 'The slurry obtained contains the. fine, metal oxide particles having'the above-described particle diameter. ^•

15' ^•' . In the production, of a slurry with a bead mill_/ the ■_. particles maybe pretreated by applying ultrasonic wave or with a planetary mixer, whereby the particles are- appropriately dispersed. . ^• _.

^■ Application -of metal oxide slurry

20 The slurry has a metal oxide concentration of 0.1 to 40% by mass, more preferably 0.5 to 10% by mass. Too high a concentration can result in cracks in the layer. Too low a concentration reduces the productivity.

The slurry may be applied by known methods such as air .spraying and flow coating, depending on the size and shape of ^{■ ■} the base on which the slurry is applied.^{• ■} ■ ^{' '' ■} ■ Heat treatment of metal oxide ' ^' .• '

¹ ■ After the slurry- is applied,- it is heat treated. The 5^p heat treatment temperature is preferably from 100 to.600⁰C, more preferably from 300.to 550⁰C. ..Temperatures above _S600°C are unsuitable in view of heat resistance of the glass arc tube . Top , low a. heat treatment temperature doe^'s not induce the sintering, and the layer obtained has many flaws and low 10 strength, and the dispersant and binder remain as impurities in the layer. The heat treatment time is preferably from 10 ^■minutesi to 5 hours, more preferably from- 30 minute,s to 1 hour; ..Whether ^"the heat treatment time is long or short produces, the ^■, same results as whether the heat treatment temperature is high 15 Or low. ^{' ■}. . ^{' '} _ ^■ .'^{" 1}

To produce the protective layer,, the fine metal oxide^'

particles obtained by' gas-phase oxidation of β-diketone metal complexes wherein 'the metal does not form an amalgam with ^{• •} mercury are dispersed in the dispersion medium, and the^'slurry 20 of the fine particles is applied and heat treated. To produce the UV absorbing or reflecting layer, the fine metal oxide

particles obtained by gas-phase oxidation of β-diketone metal complexes are dispersed in the dispersion medium, and the slurry of the fine particles is applied and heat treated. To produce the UV absorbing or reflecting layer with a function as a protective layer, the fine metal oxide particles wherein the metal does not form an amalgam with mercury are

^{■ '} ' dispersed in the dispersion medium, 'and the slurry of the fine

5 particles is applied .and heat treated. Alternatively, the

■slurry is mixed with a slurry of fine metal oxide particles as required wherein the^' fine metal oxide particles are^'obtained

by.- gas-phase oxidation of β-diketone metal complexes and are dispersed in the dispersion medium; and the mixture is applied 0 and heat treated. ^{' '} _t . ^{' ■ '}

A laminate of these layers may be produced by sequentially applying t-he^' slurries and' heat treating.

The fluorescent lamp according to the present invention ^■ is manufactured as described above. The lamp is suitably used 5' ''in luminaires and display devices.

^{• ■ " '} . " . EXAMPLES

The present invention will be describedby examples below ^■ without limiting the scope of the invention. 0 <Production Example 1>

Nano Y₂O₃ particles were produced using an apparatus shown in Fig. 1.

The apparatus shown in Fig. 1 was designed such that a

vapor containing a gaseous β-diketone metal complex that had ^•been obtained by vaporizing a solution of the β-diketone metal complex was mixed with an oxygen-containing gas or Oxygen; the mixture was quantitatively supplied to a heating apparatus

^{• "} /such as tubular electric furnace; ^' and the . β-*diketone metal 5' complex was thermally cracked and. oxidized to produce fine^' ■metal oxide particles. ■ ,^' • , .- , •> ^■

A mixture solution of 300 g and 700 g of yttrium tr.idipivaloylmethane- and methanol, respectively,. ^' was^'

.^' ' . ^{■ '} v . ^' . introduced at 4 ml/min to a vaporizer . (6) heated at 200⁰C, and 0 was vaporized therein. Air (1) was fed at 40 1/rαin to a , , preheater (5) and was heated to 200⁰C.- The gaseous yttrium ^■ tridipivaloylmethan^'e and methanol,, and' air were .supplied to ^■

..^■a^"coaxial nozzle at an inlet of a tubular electric furnace (7) ^:. '

^■ The combustion temperature in the tubular electric furnace was ._. 5^{' ''}950⁰C, and the yttrium tridipivaloylmethane and methanol were oxidized into Y2O3. Nano^' Y2O3 particles were^' collected in a • collector (8) with -a¹ yield of^'not less than -95%. , .

The nano Y₂O₃ particles contained a few % of carbon residues as -impurities . To remove the impurities, the 0 particles were heat treated in an air atmosphere at 500⁰C for 8 hours. Thermogravimetric measurement with a thermobalance (TG/DTA 6200 manufactured by Seiko Instruments inc. ) resulted in less than 0.5% by mass of carbon residues. A field emission scanning electron microscope (S-900 manufactured by Hitachi, ^{' •}' ^{" ' • ' • " ' '} 2 5 . ^{■ ■ •} . . - . . ^• - ^■ ' •

' ^" . ^• . ; ' ' ' '

•.Ltd. ) determined the primary particle diameter of the nano Y₂O₃ ^{■ '■} particles to be approximately 20 nm. • ^''•

<Productibn Example 2> '

^■ ■ To 400 ml of a 1 τnol/1 yttrium nitrate solution heated 5' to 80⁰C, 1.651 of 0.4 mol/1 ammonium oxalate solution-was added ^'.dropwise with stirring over a period of 1 hour, followed by stirring at 80⁰C for ^' 1 hour. The mixture was cooled to. room , temperature and was ^• filtered ,to separate ^'.precipitates . The , precipitates were washed by filtration with 21 of water. The 10 precipitates were vacuum dried at 80⁰C to_.give yttrium oxalate. , The dried product was placed in a porcelain crucible and was ■heat treated .in an air^" atmosphere at 700⁰C for 3 hours, .producing Y₂O₃.. The,yield of the nano Y₂O3 particles was .not ^• .less than 99%. An electron microscope determined the primary 15' ^'particle diameter of the nano Y₂O₃ particles to be approximately , 20 nm. ^{• ' '}. . ^■' . . : ^■

[Example 1] . , ^' • ■ •

^{• '} 15 g of the ^'nano Y₂O₃ particles produced in Production- ^■ Example 1 were mixed with 352 g of l-methoxy-2-propanol . To 20 the mixture were added 1.5 g of acetylacetone as dispersant 1, 1.5 g of hardly water-soluble triol dispersant (ADEKA CARPOL GL-100 manufactured by ADEKA CORPORATION) as dispersant 2, and 5 g of yttrium triacetyl acetone as binder. The mixture was subjected to ultrasonic wave for 1 hour, resulting in a uniform ■ ^{' •}' . ^{' ' " '} 2 6 ^' . . ^{' •} . ^• . ^■•. - ^{• '}.

slurry. The slurry was treated in a bead mill ^' (UAM-015 ^{• '■} manufactured by KOIOBUKI ^• ENGINEERING &. MANUFACTURING^' CO.,-

LTD.) containing 400 g of 50 μm zirconium oxide beads for 6 hours. Consequently, a slurryof 4% by mass Y₂O_3.was obtained. 5 The slurry was measured for particle¹ size distribution with ^'■a. particle size analyzer . (,Nanotrac U.PA-EX150 manufactured by NIKKISO CO., LTD.), resulting' in a volume-average particle_, diameter-^'of 18 nm and a_. maximum particle diameter of 102 nm. _,[Example 2] J ^• •

10 A slurry of 4% by mass Y₂O₃ was obtained in the same manner as in Example 1, except that 15 g of the nano_;Y₂0₃ particles ^■ produced . in Production^" Example 2 was used.. The, slurry was .measured fqr^'particle size distribution with theparticl^'e size analyzer, ^'resulting-in similar results to those of Example 1, . 15' ^{' '}with a volume-average particle diameter of 20 nm -and a maximum , particle diameter of 102 nm. The results are shown in Table

[Comparative Example I]' .

15 g of a commercially available Y₂O₃ reagent (average

20 particle diameter: 15 μm, manufactured by KANTO CHEMICAL CO., INC.) was mixed with 360 g of water, followed by ultrasonic wave treatment for 1 hour. Consequently, a uniform slurry was obtained. The slurry was treated with a bead mill as described in Example 1, resulting in a slurry of 4% by mass Y₂O₃. The ^•■slurry was measured for particle size distribution with the particle size- analyzer, resulting in. bad dispersion compared to Examples 1 and 2, with a volume-average particle- diameter of 890 nm and a maximum particle diameter of 3270 nm. The results are shown in Table 1. ' . ^{■ '}.

^■ Table 1

-

Drain: minimum particle diameter

Dav: volume-average particle diameter

K)

Dmax: maximum particle diameter 00

<Production Example 3> ^■

^{■ '•} . The -procedures of Production Example 1 were repeated, except that 300 g of yttrium tridipivaloylmethane was replaced by300 g of zinc tridipivaloylmethane. Consequently, nano ZnO

5^' particles were collected in the collector (8) ,with a yield of not less than 95%. . ,^' • , ^{•' ■} ,■ , _s ^■.

The nano ZnO particles . contained a few- % of carbon residues.¹ as impurities. ^' To remove the impurities, the _. ^■ particles were- heat treated in an air atmpsphere at 500⁰C for 10 8 hours. Thermogravimetric measurement with a thermobalance ^■ , (TG/DTA 6200 manufactured by Seiko Instruments ,inc . ) resulted in less than 0.5% by mass of carbon residues . A.field emission ._.scanning electron microscope (S-900 manufactured by Hitachi, ^■ , Ltd. ) determined the primary particle diameter of the nano ZnO , 15' 'particles to be approximately- 15 nm. ^' -^{' '}

[Example 3] ^■ . ^' . ^{' '} .

The procedures 'of Example 1 were .repeated, except that

15 g of the nano Y₂O₃ particles were replaced by 15 g of the

^■ nano ZnO particles obtained in Production Example 3, and that

20 5 g of yttrium triacetyl acetone as binder was replaced by 5 g of zinc triacetyl acetone. Consequently, a slurry of 4% by mass ZnO was obtained. The slurry was measured for particle size distribution with the particle size analyzer, resulting in a volume-average particle diameter of 16 nm and a maximum "■ particle_] diameter of 102 run. ■ ■.

[Comparative Example 2] ^'■ ..

The procedures of Comparative Example 1 were repeated, ^{' '} 'except that 15 g^' of the YgO₃ reagent was replaced by 15 g of 5 a commercially 'available ZnO reagent (average^' particle

^■diameter:^' 18 μm, manufactured by KANTO. CHEMICAL CQ^''.,^' INC.) .

Consequently, a slurry of 4%' by mass ZnO was^' obtained. 'The slurry was measured for particle size 'distribution with the particle size ^"analyzer, resulting in bad< dispersion compared 0 to Example.3, with a volume-average particle diameter of 920

■ nm and a maximum particle -diameter qf 3970 nm. The results are shown in -Table 2. , ^l •^{' '}

Table 2

Dmin: minimum particle diameter

Dav: volume-average particle diameter

Dmax: maximum particle diameter . ^■

•^{" '}32 . ^' _. ^■ . . .. ^■ . ^' - .._ ' ^'

^•.[Example 4} ^• .^'

^{■ '■} . The procedures of Example 1 were repeated, e'xcept that

15 g of the nano Y2O₃ particles were replaced by ^'15 g of nano

TiO₂ particles (SUPER TITANIA F-I , average particle diameter:

5- 10 nm, manufactured by ^'SHOWA TITANIUM 'CORPORATION) , and that

Vthe binder was not added. , Consequently/ a slurry of 4% byjnass

TiO₂ was obtained. The slurry, was measured for particle size

^■ distribution with the particle size analyzer, resulting in a v_. ^' ' « - volume-average- particle diameter of 22 nm 'and a ^' maximum

10 particle diameter of 102 nm. [Example- 5]

The procedures 0if^" Example 1 wei;e. repeated, except that _.15 g of the nano Y₂O₃ particles were replaced by 15 g ^'of, ^• silica-coated, nano TiO₂ particles (SUPER TITANIA F-6S10, - 15^p 'average particle diameter: 15^' nm, manufactured by SHQWA , TITANIUM ■ CORPORATION) ,' and that the^' binder was_. not ^'added.^' Consequently, a slurry of 4% by mass TiO₂ was .obtained. The. slurry was measured for' particle size distribution with the ^{■ ■} particle size analyzer, resulting in a volume-average particle 20 diameter of 26 nm and a maximum particle diameter of 123 nm. [Example 6]

25 g of the slurry of the nano TiO₂ particles produced in Example 5 was mixed with 75 g of the slurry of the nano Y₂O₃ particles produced in Example 1, followed by stirring for 3 •.minutes. The slurry mixture was measured for particle size distribution with the particle size analyzer, ^' but ho, aggregate^'s ^' were observed-. ' _p .•

¹ [Example 7] ^• -• / ^{• ■} , ^{" • ■} 5 A straight tube fluorescent lamp with a .rated output of ^'.30 W was manufactured as .follows. One opening of an ,-arCs.tube made of soda glass was brought into contact with the surface

. of the ZnO ^' dispersion produced in Example 3, ariςi the^' .other opening was connected -with a pressure reducing device. The 0 ZnO dispersion was^' suctioned by reducing, the pressure, and the inner surface of the. tube .was flow-coated with t,he dispersion.

^■ -The coating was dried at^~40°C and was he.at treateddn, an electric

.furnace at.500⁰C for, 10 minutes to. give a UV absorbing layer :•

¹A fluorescent 'layer, was formed by similar 'flow-coating -5 ^■' in a ^' common manner. The Y₂O₃ dispersion produced in Example

1 was applied by flow-coating. The coating was dried at 40⁰C and was heat treated' in an electric furnace at '500⁰C for 10. minutes. to give. a^' life-expanding protective layer.

The arc tube was degassed. Immediately before the 0 degassing completed, mercury for light production was fed, followed by sealing of an argon gas as emission medium. Tip-off covers were fitted, and a fluorescent lamp was manufactured . [Comparative Example 3] A 30 W straight tube 'fluorescent lamp was manufactured ^{■ '■} as described in Example 7_/ except that . the ZnO- dispersion produced in Comparative Example 2 and the Y₂O₃ dispersion produced in Comparative Example 1 'were used.. 5 [Example 8] •^• . ^{' • '} .^' • ^' •

• A- straight tube fluorescent lamp with a rated output of _. ^■ 30 W was manufactured as follows. One- opening- of an arc tube

^■ ' ^■ ma^'de of soda glass was brought into con-tact with-^' the surface. v . of the Tiθ₂/^'Y₂θ₃ mixed' dispersion .produced in .Example 6, and^'

10 the other opening was connected with a pressure reducing device . The Tiθ₂/Y₂θ₃ mixed dispersion was • suctioned by reducing the ^■ pressure,, and. the inner surface of the_, 'tube was flow-coated^' , with the dispersion., ,The coating was dried at 40⁰C and was- ^•.heat treated in an electric furnace at 500⁰C fo'r 10 minutes 15' ^' 'to give a UV, absorbing layer.-^'■ . ^■

A fluorescent layer was formed by similar flow-coating in a common manner. • • , _. ^■ . ^• ' , ■

The arc tube" was degassed. Immediately before the ¹ degassing completed, mercury for light production was fed, 20 followed by sealing of an argon gas as emission medium. Tip-off covers were fitted, and a fluorescent lamp was manufactured.

The 30 W straight tube fluorescent lamps manufactured in Examples 7 and 8 and Comparative Example 3 were tested to ^{' •}' ^' ; ■ ^{' ■} - 35 . ' . ^' . . .. ^{' ' ■•}. ^• * ^'.

■- study the relation between the lighting time and luminous flux retention . (luminous flux retention properties) . The results are shown in Fig. 2. ^" • ' • . ^■ '

The fluorescent lamp of Example 7 retained 91% luminous flux after 10000 hours of lighting, while the conventional ^■ .fluorescent lamp^' of Comparative Example 3 retained • 80%_v luminous flux. In the fluorescent lamps according ^'to the present .invention, the layers^' were dense^', and co^'ntinuous ;to i block mercury and UV light. Consequently, blackening of the arc tube was prevented.^' tn contrast,, the conventional layers . were insufficiently deris-e _.and continuous because the metal ^•■'oxide particles aggregated in the coating liquids. .Consequently, much mercury and UV light contacted with^'the .arc •. _/tube glass, and mercury reacted with the alkali metal of the arc tube glass, whereby the a'rc tube was blackened and the luminous flux retention was reduced. The fluorescent lamp .of Example 8 showed impr'oved luminous flux retention properties, because the Tiθ2/Y2θ3 mixed layer had sufficient properties, to ^{• •} prevent blackening of the arc tube.

Claims

■ ' ' CLAIMS

1. A fluorescent' lamp comprising an arc tube and a_, ■^' ' protective layer -on an- inner ^'surface of. the .arc tube, the .5' protective layer comprising connected particles having a ^'.volume-average particle diameter of 10 to 300 nm, the connected particles comprising an oxide of a metal not forming an 'amalgam with mercury. • ^{• •} .. . ■ , •^{' " • • ■}

0 2. The fluorescent lamp according to claim 1, comprising: _. ^'•■ . ^{' •} ₍ an arc tube; and on an inner surface¹ of the arc tube and in the order named: , ^■ . ^' _. ^{• ' '} at least one of a^' UV •absorbing layer and a.UV reflecting 5' ^'layer; ^' ' ^{' '} _ ^' ■ ' a protective layer comprising connected particles^ having a volume-average particle diameter of 10 to 300 run, the connected particle^'s comprising an oxide of a metal not forming ^{• •} an amalgam with mercury; ^' and 0 a fluorescent layer.

3. The fluorescent lamp according to claim 1, comprising: an arc tube; and on an inner surface of the arc tube and

.in the order named: • ^'■ • at least one of a UV absorbing layer and a UV ^'reflecting layer; ^' • ^' . '

•^{' •} ' a fluorescent layer; and ^■ , 5 a protective layer comprising connected particles

^'.having a volume-average particle diameter of 10 to 300 run,, the connected particles comprising- an oxide of a metal not forming an amalgam with mercury.^" . , •^"",^{• ■}

10 4. . A fluorescent ■ lamp comprising an arc^' tube, and 'a , ■ . UV absorbing layer and/or a UV reflecting layer on an inner ^■ surfaceiof the arc tube^'; the UV absorbing layer..and/or the UV _, reflecting, layer comprising connected particles having a -. yolume-average particle diameter^'of 10 to 300 run,. the connected

15 particles comprising an oxide of a metal not forming an amalgam with mercury:- ' ^'

5. • The fluorescent lamp according to claim 1, wherein- ^■ the oxide of a metal not forming an amalgam with mercury is

20 based on at least one of yttria, ceria and silica.

6. The fluorescent lamp according to claim 4, wherein the UV absorbing layer and/or the UV reflecting layer comprises at least one of alumina, zinc oxide and titanium oxide.

7.^■ The fluorescent lamp according-to claim' 6, wherein the at least one of alumina, zinc oxide and titanium oxide is in the form of fine metal oxide particles haying a . ■

5¹ volume-average particle diameter of 10 to 300 run. - ^',^■

8. The fluorescent lamp according to claim 7,' wherein

^■ the ,fine metal oxide particles forming the ^'UV absorbing layer v . '

^', or the UV reflecting layer ^' are coated with¹, silica. ■

0 ^{' ' • '■} . .

,. ■ 9.. A process for producing the fluorescent lamp ^■ claimed, in claim 1 or 4, comprising:, - ■ . applying. a slurry of fine metal oxide particles ' in a , dispersion medium to- an inner surface of an arc tube, the fine 5' 'metal oxide particles comprising an oxide of a metaTnot forming an amalgam with mercury, the dispersed fine metal oxide . ■ ' particles having a volume-average particle diameter of 10 to_.

300 nm; ^{' "}. ^{' ' ■} • ^{' ■} ■ drying the slurry; and 0 heat treating the resultant layer to form a protective layer, or a UV absorbing layer and/or a UV reflecting layer.

10. The process according to claim 9, wherein the dispersion medium is a polyhydric alcohol derivative.

11.., The process according to claim 10, -.wherein the. polyhydric alcohol derivative is a l-alkoxy-2-alkyl. alcohol.

12. The .process according to ^■ claim 10, wherein the

^'.polyhydric alcohol derivative is a.t_ least one of _,• , _N l₇inethoxy-2-propanol and l-ethoxy-2-ethanol .

13. The process according to claim 9^',_ wherein, the-

slurry of the fine metal oxide particles includes a β-diketone . metal complex as a binder._,

^".

14. The process ^■ according, to . claim 9, wherein ' the ^{' ■} ,slurry of the fine metal .oxide particles is. a .dispersion of ' -' fine particles of an oxide of a metal in a dispersion medium,

the oxide being produced by gas-phase oxidation of a β-diketone metal complex, the metal^' not forming an,amalgam with mercury._.

15. -A fluorescent lamp produced by theprocess claimed in claim 9.

16. A luminaire comprising the fluorescent lamp claimed in any one of claims 1 and 15.

17. ^■ A display device comprising the fluorescent lamp claimed in any one of claims 1 and 15. ' ^{' '} _.