DE2053200A1 - Fluorescent - Google Patents

Description

hW '- ■■;: -. .!. V. I · '-. ■ i ■ - LLUDU-VHcNFABRiEKEN PHN. hh OQ

^Alcie: PHi- 4400

Registration from: 28.0ct _o 1970 Va / WG

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The invention relates to a luminescent screen having a luminescent bivalent europium contains activated silicate, and on a low-pressure mercury vapor discharge lamp, which is provided with such a screen. The invention also relates to.

activated on a luminescent with bivalent europium Silicate.

The use of the element europium as an activating agent for phosphors has been the subject of the last few years been many investigations; these investigations have shown a large number of useful phosphors. It has been found that europium is in trivalent form when incorporated into various basic lattices in both Excitation with ultraviolet radiation as well as with excitation

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with Klektromm a “red” and / or an orange first line emission caused. The bivalent Kuropium causes fine, narrow band emission in blue, green or yellow Part of the spectrum, with the location of the maximum of the emitted Radiant energy, as it turned out, depends on the basic grid used.

Suitable basic lattices for activation with bivalent europium include certain silicates. For example, alkaline earth metal silicates activated with divalent curopium are known from British patent specification 5kk.] 6O. This patent also describes some ternary silicates whose basic lattice can be represented by the formula Me'0.Me "O.pSiO", in which formula Me 'and Me "represent the alkaline earth metals calcium, strontium and barium, while ρ represents the value 1, 2 or 3 can have. The Dutch patent applications 671 ^ 517 and 671 ^ 518 describe ternary silicates of the type Me_MgSi_0 ₇ and Me.MgSi O ", where Me represents calcium, strontium or barium. These silicates are also activated with bivalent europium and have ο ine holif quantum yield when excited with ultraviolet radiation, whereby they have an emission in the wavelength range of about 50 to 550 mm. It is also known to activate barium disilicate, in which the barium can be partially replaced by strontium, with divalent europium (see Dutch patent application 6717185). The barium disilicate has a particularly broad stimulation spectrum and can even be used with deep blue

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visible radiation. The maximum of the The emission is around 500 nm.

KIn lampshade according to the invention contains a luminescent activated with bivalent europium Silicate and is characterized in that the silicate

of the formula Ha ₁ Sr Eu ⁺ ZrSi „O _r . corresponds, in which 1-xp x ρ 3 9 ^H '

Formula 0 ί = χ - ^ 0, 2 and 0.002- ^ p ^ 0.10.

A phosphor of the formula mentioned above, which corresponds to the conditions mentioned, can both with short-wave as well as long-wave ultraviolet radiation and even blue visible radiation good be stimulated. Even when excited with electrons, a phosphor according to the invention exhibits a satisfactory one Degree of conversion. IHe emitted radiation consists of a narrow band with all substances according to the invention a maximum at about ^ 475 nm.

The formula shows that the phosphor according to the invention consists of a barium zirconium silicate activated with divalent europium, in which the barium toibveisp can be replaced by strontium. If χ in the formula takes on the value 0, the pure barium zirconium silicate is obtained, which is activated with divalent europium. From the Russian article in Izv. Vyssh. Ucheb. Zaved., Fiz _K) (7), p. 122 (1967) it is known _{to activate this BaZrSi “O q} basic lattice with trivalent europium. In connection with the great differences between the chemical and physical properties

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of the divalent and trivalent europium ions It is not to be expected that the activation of this basic lattice with divalent europium would be a very effective phosphor would result. It is also well known that not all silicates * when activated with bivalent Europium form phosphors, so that a prediction with regard to any luminescent properties is not possible

m_ is possible. The aforementioned Russian article also mentions, for example, the activation of the Ba ₂ Zr ₂ Si ^ O .. "basic lattice with trivalent europium. It has been found, however, that this basic lattice has practically no luminescence when activated with bivalent buropium.

Investigations have shown that a partial replacement of the Barixms by strontium in a phosphor after the Invention affects the luminescent properties of the substance only to a small extent. So it turns out that both the excitation spectrum and the emission spectrum are always the same. However, if the strontium content χ is greater than 0.2, it turns out that the luminous efficiency of the phosphor is considerably lower than that of the substances containing no strontium.

The value of ρ can be changed within the above-mentioned limits. For ρ ^ L 0.002, the absorption of the stimulating radiation is so low that no substances which can be used in practice are obtained, while for ρ '_> 0.10 the light yield due to concentration quenching is low. Values of ρ between 0.005 and 0.05 are preferred.

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Kin LeuchLschi rni according to the invention is suitable especially due to the high luminous efficacy of the fluorescent material good for use in low pressure mercury vapor discharge lamps. The light output of the barium zirconium silicates activated with bivalent europium according to the invention is about equal to the light output of the known with antimony activated strontium halophosphate that is in the same part of the spectrum emitted.

Another advantage of the phosphors after the Invention is that they are better with short-wave visible blue radiation than the aforementioned Let the known barium disilicate be stimulated. This is special favorable when using the substance in low-pressure mercury vapor discharge lamps with good color rendering, the so-called "de luxe" lamps and in particular in such lamps with a low color temperature.

As is well known, the intensity of the blue radiation in these lamps must be suppressed as far as possible. Until now this was mostly achieved by using a blue-absorbing pigment, mostly in the form of a separate layer. Of course, this leads to a reduction in the degree of efficiency. A phosphor can also be used find that can be excited with blue radiation; for this purpose only the one activated with Nfangan has so far been activated Magnesium arsenate used in practice. The emission of this Substance is in the red part of the spectrum. This can be in those cases where there is a certain amount of red Radiation is desirable to have a beneficial effect; the lumen

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but is equivalent to the radiation of the MagnesLumarsenate small amount. The barium zirconium silicate according to the invention is absorbed however, the unwanted blue radiation and converts it into blue-green radiation with a high lumen equivalent around. When lamps with a high red content are required, the choice is now greater than when using them of the mentioned arsenates. E.g. a connection like the yttrium vanadate activated with trivalent europium used that compared to the magnesium arsenate Radiation with a considerably higher lumen equivalent emitted.

Dif · Emission of barium (Strontium) zirconium silicate according to the invention, the wavelength is shorter than that of the known barium diSilicate. This is the case when using the Fluorescent material in low-pressure mercury-vapor discharge lamps with good color rendering is advantageous because the emission lines of the mercury vapor discharge are now green and blue part of the spectrum just next to the area of the maximum emission of the phosphor.

The phosphors according to the invention also have the advantage that they are resistant to oxidation. In the It is the manufacture of mercury vapor discharge lamps required that the fluorescent screen, e.g. for removal a temporary midway point, to a higher temperature is brought. It is important that the luniinesZlerendon Properties not due to possible oxidation get lost.

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The invention is subsequently based on a Table, nines llerstolluiigsbeispiel and a drawing explained in more detail.

Tabel

I.
Example formula rin % q in f> r. L. A H 1 B ^a O.995 ^Eu O, OO ₅ ^ZrSi 3 ° 9 60 ho 16 5 2 ^{Ba O.99 Eu} O, O1 ZrSi 3 ° 9 4o hO 2h H 3 ^Ha O, 98 ^Eu O, O2 ^ZrSi 3 ° 9 30th 35 24.5 3 4th ^Ba O, 95 ^Eu O, O5 ^ZrSi 3 ° 9 20th 23 18.5 4th 5 ^Ba O, 79 ^Sr O, 2 ^Eu O, O1 ^ZrSi 3 ° 9 30th 26th 18th 4th ; ο
I. ^Ba O, 89 ^Sr O, 1 ^Eu O, O1 ^ZrSl 3 ° 9 30th 30th 21st

Manufacture; i spi eJ ;

To produce a phosphor according to Example 1 of the above table, the following are mixed: 1.870 g BaCo ₃ ,

0.087 g BaF ₂ .

0.009 g Eu ₂ O ₃ ,

1.230 g of ^Zr0 2 ^and 2.220 g of SiO ₂ .nH ₂ 0.

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(The used silica containing about 89.7 wt. ° h S ₂ The mixture obtained in dinse manner is heated for about k hours at a temperature of about 125O ° C. After cooling, the product obtained is ground and heated again for 2 hours at a Temperature of about 1320 C. Heating takes place in both cases in a reducing atmosphere, for example in nitrogen with ^ 5 vol. $> Hydrogen. After cooling after the second heat treatment, the reaction product obtained is ground and, if necessary, sieved. It is then ready for use .

In the example above is 5 wt.% Added to the mixture of the required barium in the form of barium fluoride. It has been found that the barium fluoride acts like a melting salt and promotes the reaction. Furthermore, an excess of 10% by weight of the silica is used to promote a smooth reaction.

The other lights specified in the table

P substances can already refer to the example above described manner. If the substance contains strontium, this element can be in the form of strontium carbonate can be added to the heating mixture.

The table shows the results of measurements on various phosphors according to the invention. The column r indicates the reflection in $ of the exciting radiation with a wavelength of 25 ** nm. In the column q is the quantum yield given by excitation with radiation with a wavelength of 25 ^ nm. A measure for that The luminous efficacy of the phosphors is determined by the relative

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Luminous efficiency (rLA) is given, which is calculated according to rLA = q.—. Here, the absorption factor is represented. Finally, in the table in the column / £ _CR, the degree of energy conversion of the phosphors when excited with electrons with an energy of 20 kV is given in $. It show in the drawing:

1 schematically shows a low-pressure mercury vapor discharge lamp with a luminescent screen according to the invention,

Fig. 2 is a graph of the radiation intensity of a phosphor according to the invention as Function of wavelength, and

3 shows the excitation spectrum of a light material according to the invention.

In Fig. 1, 1 designates the wall of a low-pressure mercury vapor discharge lamp. At the ends of the lamp there are electrodes 2 and 3. The wall 1, for example made of glass, has a Luminous layer 4 coated, which contains a phosphor according to the invention. The phosphor is due to one of the usual method attached to the wall 1.

In the graph according to FIG. 2, the abscissa is the wavelength Λ. plotted in nm. The radiation intensity E is plotted in arbitrary units as the ordinate. The curve shows the spectral distribution of the emission of the substance according to Example 2 from the table when excited with radiation with a wavelength of 25 ^ nm.

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The graph of Fig. 3 shows this Excitation spectrum of the phosphor according to Example 2 from Tabel. (Curve 6) The relative luminous efficacy (r.L.A.) as a function of the wavelength ^ (in nm) of the exciting Radiation applied with the maximum excitation set to 100. It is clear that the Phosphors according to the invention are well excited with both short-wave and long-wave ultraviolet radiation

w can be. The excitation with deep blue visible radiation is considerably better than when using the known barium disilicate, the excitation spectrum of which is shown by the dashed curve 7.

Finally, it should be noted that the phosphors according to the invention can also be used in conjunction mifc discharge lamps that emit both short-wave and long-wave ultraviolet radiation, e.g. High pressure mercury vapor discharge lamps.

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Claims (3)

Claim j_e_ 1. fluorescent with a luminescent with divalent .iuropiun activated silicate, characterized in that that this silicate of the formula ^Ba 1-xp ^Sr _X ^Eu P ^{+ ZrSi} 3 ° 9 corresponds to, in which formula O ^ χ «^ 0.2 and 0.002 «S ρ ^ 0.10 1st. 2. phosphor according to claim 1, characterized in that U, 005 ^ ρ < Is 0.05. 3. Use of a phosphor according to claims 1 and 2 in ane ^ i Le-uchtschirni a low-pressure mercury vapor discharge ur.gsampe. 09821/20 ^ 7 Al ■ Blank page