DE1035822B - Method for producing an ultraviolet luminous silicate - Google Patents

Description

The invention relates to a method for producing a silicate which, under the action of the in A gas and / or vapor discharge tube generated radiation emits short-wave ultraviolet radiation.

Rays with a wavelength between 2900 and 3000 Å are known to have a beneficial effect on Humans and animals. This radiation is often referred to as erythema radiation. It will therefore Radiation sources built that emit this radiation with sufficient intensity. A well-known radiation source of this type consists of the combination of a gas and / or vapor discharge tube, in particular one Cjucury vapor discharge tube, and a screen with phosphors, which are excited by the rays generated during the discharge, and then the erythema radiation send out. The number of phosphors that can be used for this purpose is not particularly large, especially since if the requirement is also to be met that the conversion takes place with good efficiency.

Compounds activated with cerium are known which are affected by radiation with a wavelength of less than 2900 Å can be excited and emit erythema radiation, but they have the disadvantage that when they are installed in a discharge tube, this conversion is only sufficient for a short time carry out good efficiency.

One of the most suitable materials for the above-mentioned purpose is a thallium activated orthophosphate of calcium and tin. Another relatively well-suited substance for the same purpose is a with Thallium activated orthophosphate of calcium and magnesium.

A method for producing another substance has also already been proposed which is particularly suitable for converting short-wave ultraviolet rays into erythema radiation. This substance is a lead-activated barium-zinc-silicate, which is produced by the fact that a mixture of compounds of barium, zinc, silicon and lead, which forms a lead-activated barium-zinc-silicate when heated, is left in for a few hours is heated to a temperature between 900 and HOO ⁰ C in a non-reducing atmosphere. It is assumed that the amounts of the compounds of the above-mentioned elements are such that the proportions in atoms in the mixture are such that the following conditions are met:

Method of manufacture
of an ultraviolet-conducting silicate

Applicant:

NV Philips' Gloeilampenfabrieken,
Eindhoven (Netherlands)

Representative: Dr. rer. nat. P. Roßbach, patent attorney,
Hamburg 1, Mönckebergstr. 7th

Claimed priority:
Netherlands 3 October 1955

Age Hylke Hoekstra, Eindhoven (Netherlands),
has been named as the inventor

Si

Ba + Zn + Si

Pb
Ba + Zn + Si

is between 0.40 and 0.80,

is between 5 × 10 ^-2 and 10 ^s.

Ba

The substances produced in this way can be used in combination with a low-pressure mercury vapor discharge tube Find use, because the discharge of such a tube very much rays with one wavelength of 2537 Å which are converted into erythema radiation with good efficiency.

The phosphors produced in this way have, compared to the known phosphors activated with thallium, the Emitting erythema radiation has the advantage of being easy to manufacture, since the activator lead is less volatile and is also less poisonous than thallium.

It has been suggested as a preferred composition in manufacture that

Ba

between 0.10 and 0.17,

between 0.30 and 0.45,

between 0.42 and 0.60 and

Ba + Zn + Si

Zn
Ba + Zn H-Si

is between 0.05 and 0.25,

is between 0.15 and 0.45,

Ba + Zn- f-Si Zn Ba + Zn- f- Si Si Ba + ZnH hSi Pb

between 5 ΊΟ- ² and 10- ^e . Ba + Zn + Si

From extensive investigation after this already proposed method achieved phosphors

809 580/523

it has now been found that, in addition to the above also mentioned good properties for mass production according to those common nowadays Method of radiation sources consisting of a gas and / or vapor discharge tube and one on its inner wall applied layer of such a phosphor exist, have unpleasant property.

As is known, it is customary to use the phosphor in the manufacture of such a radiation source to apply the wall of the discharge vessel that it is in an amount of liquid containing a binding agent suspended and the suspension is introduced into the discharge vessel, for example by placing it in the tube lets rise. The suspension is then allowed to run out of the discharge vessel again, one on the Wall-adhering layer of the phosphor remains with the binder. Then the discharge tube dried and the binder, for which nitrocellulose is often chosen, by heating in an oven evaporated and / or burned. The phosphor remains on the wall as a result of the Van der Waals forces be liable.

In carrying out this usual overdraft procedure, it was found that with the The above-mentioned earlier proposal recommended materials only achieve an inadequate coating can. When the binder burns away, a relatively large part of the phosphor powder applied dissolves away. When the electrodes are then installed, at least part of the tube is raised again is heated, in turn part of the luminous powder is detached. It can thus be seen that these phosphors in spite of their advantageous photometric properties, great difficulties in the manufacture of radiation sources prepare.

The purpose of the invention is now to produce a phosphor which has the favorable photometric properties of the substances produced according to the previously proposed method, but in the Manufacture of a discharge tube in which it is attached, does not peel off.

According to the method of the present invention for preparing a silica which, under the action of the radiation generated in a gas and / or vapor discharge tube emits short-wave ultraviolet rays, becomes a mixture of compounds of barium, zinc, magnesium, silicon and lead that when heated forms a lead-activated barium-magnesium-zinc-silicate, in which mixture the proportions of the above elements mentioned in atoms are such that the conditions

Ba

Ba + Zn + Mg + Si
Zn + Mg

- is between 0.05 and 0.25,

Ba + Zn + Mg + Si
Zn
Mg "

- is between 0.15 and 0.45,

is between 33 and 3,

55

60

Si

Ba + Zn + Mg + Si
Pb

_T is between 0.40 and 0.80,

- is between 5 x 10- ² and 10- ^β

Ba + Zn + Mg + Si

are satisfied for a few hours in a non-reducing atmosphere at a temperature between 900 and 1100 ° C heated.

Substances produced in this way have all the good photometric properties of the Already proposed methods produced substances, but do not dissolve from the wall of a discharge vessel if they are attached in this in the usual way and freed from the binder by heating.

To illustrate this phenomenon, a number of connections, both with and without Magnesium, a differential thermal analysis carried out. The curves obtained in this way turned out to be found that there is a transition point near 273 ° C for preparations without magnesium.

With gradually increasing magnesium content, while the molecular sum of zinc and magnesium is kept constant, the transition point is first moved to higher temperatures and is finally no longer achievable at normal annealing temperatures. From research into the manufacture of discharge tubes it has been found that the improvement in the adhesion of the displacement and the disappearance of the Corresponds to the transition point.

The best products are obtained when the proportions in atoms in the manufacture according to the invention be chosen so that

between 0.15 and 0.20,
between 0.30 and 0.42,
between 33 and 3,
between 0.42 and 0.60 and

- is ⁶ - between 5 x 10 - ² and 10 degrees. Ba + Zn + Mg + Si

In addition to the substantial improvement in adhesion, replacing part of the zinc with magnesium provides a few more advantages. When 3 to 8 mole percent zinc is replaced by magnesium, it turns out found that the quantum efficiency increases by about 3 to 6%. If more than 8 mole percent zinc through Magnesium are replaced, the quantum efficiency slowly decreases again and decreases when replacing more than about 12 mole percent even slightly below the quantum efficiency of those not containing magnesium Links. Instead of improving the quantum efficiency, however, there is a slight shift towards shorter wavelengths. The maximum value of the emission, which is initially between 3000 and 3100 Å for the lower lead contents and between 3000 and 3500 Å for the higher lead contents This moves in the direction of the maximum value of the erythema sensitivity curve, which is known to be around 2970 Ä lies.

Compounds which can be used as a starting point in the process according to the invention are very suitable Oxides, nitrates and carbonates of barium, zinc, magnesium and lead. The silicon is preferably used as Oxide added. Mixtures of these types of compounds are also very useful. The lead and / or the barium can also be added very well as fluoride, some of which also acts as a flux. This can lower the production temperature and promote crystallization.

Ba- Mg Mg Ba- MgH Ba- MgH f-Zn + hSi Zn + r-Zn + hSi Zn Mg Si 1-Zn + r Si Pb

Below are some embodiments of the In the positioning procedure, referring to the drawing, which shows some curves that appear in arbitrary units the relationship between the wavelengths of the emitted rays and their intensity indicate. All curves are measured when excited by beams with a wavelength of 2537 Å.

Example I.

A mixture of 12.35 g BaCO ₃ , 12.73 g ZnO, 0.70 g MgO and 15.8 g SiO ₂ is suspended in 150 to 250 cm ^{3 of} alcohol and, with 25 cm ^{3 of} an aqueous solution of Pb (NO offset _{3) 2} at a concentration of 10 ^-4 gram mole Pb per cm ^3, milled for 16 hours in a ball mill. It is then evaporated dry and the dry product is ground in a mortar, after which the powder is heated in a quartz crucible for 2 hours at 700 ° C. in the open air in an oven. After the crucible and its contents have cooled down in the oven, the reaction product obtained is ground again in a mortar. The powder obtained is heated again in an oven at 1010 ° C. for 4 hours. This heating takes place in a quartz crucible with a closed lid. The crucible and its contents are then allowed to cool down to room temperature. The product obtained is ground and sieved with corn. The spectral distribution is shown by curve 1 of the drawing. The quantum efficiency of the emitted radiation is practically the same as that of a correspondingly manufactured substance in which the MgO is replaced by an equivalent amount of ZnO.

Example II

A mixture of 35.14 g BaCO ₃ , 29.30 g ZnO, 1.61 g MgO, 25.24 g SiO ₂ , 0.35 g BaF ₂ and 1.12 g PbO is dry-mixed for 3 hours in a ball mill , then heated in air to around 1000 ° C for 3 hours and then ground again. The ground product is heated again in air to 1000 ° C. for 1 hour. The phosphor thus obtained has a spectral distribution almost coinciding with that of the above example and also almost the same quantum efficiency.

Example III

A mixture of 25.14 g BaCO ₃ , 26.04 g ZnO, 3.22 g MgO, 25.24 g SiO ₂ , 0.35 g BaF ₂ and 1.12 g PbO is produced in exactly the same way as in Example I. ground and heated. The spectral distribution of the luminescent light is shown by curve 2 of the drawing. The quantum efficiency of the emitted radiation is about 3% lower than that of the corresponding substance in which the MgO is replaced by an equivalent amount of ZnO.

Example IV

The phosphors produced according to one of the preceding examples can be used in a known, customary manner be applied as a luminescent layer on the inside of the glass wall of a gas and / or vapor discharge tube. Nitrocellulose, methyl methacrylate, ammonium alginate or similar substances can be used as binders can be used, a suitable solvent, e.g. B. butyl acetate, can be used.

Claims (4)

Patent claims: 1. Process for the production of a silicate, which under the action of in a gas and / or Vapor discharge tube emits short-wave ultraviolet rays, characterized in that that a mixture of compounds of barium, zinc, magnesium, silicon and lead that when heated a lead-activated barium-magnesium-zinc-silicate forms, in which mixture the proportions in atoms of the above elements are such that the conditions 55 A mixture of 26.14 g Ba (NO ₃ ) ₂ , 22.71 g ZnO, 0.60 g MgO, 36.00 g SiO ₂ and 0.7 g PbF ₂ is ground in a mortar. The powder obtained is heated in an alumina crucible in an oven at 950 ° C. in air for 1 hour. The cold product is ground again in a mortar and heated in air in an alumina crucible in an oven at 1050 ° C for 1 hour. The crucible and its contents are then allowed to cool to room temperature in the oven. The spectral distribution is almost the same as that of a substance produced according to Example I. The quantum efficiency of the radiation is about 6% higher than that of the corresponding substance in which the MgO is replaced by an equivalent amount of ZnO. Ba Ba + Zn + Mg + Si
Zn + Mg - is between 0.05 and 0.25, Ba + Zn + Mg + Si
Zn - is between 0.15 and 0.45, is between 33 and 3, Mg Si Ba + Zn + Mg + Si
Pb - is between 0.40 and 0.80, - is between 5 × 10 ^-2 and 1O ^-6 Ba + Zn + Mg + Si are fulfilled for a few hours at a temperature between 900 and 1100 ° C in a non-reducing Atmosphere is heated. 2. The method according to claim 1, characterized in that the conditions Ba Ba + Zn - (- Mg + Si
Zn + Mg - is between 0.15 and 0.20, Ba + Zn + Mg + Si
Zn Mg
Si - is between 0.30 and 0.42, between 33 and 3, Ba + Zn + Mg + Si
Pb - is between 0.42 and 0.60, _r is between 5 ■ IQ- ² and 10- « Ba + Zn + Mg + Si are fulfilled. 3. The method according to claim 1 or 2, characterized in that at least one of the compounds of barium, zinc, magnesium, silicon and lead is used as an oxide. 4. The method according to claim 1 or 2, characterized in that the barium and / or the lead as Fluoride is added. 1 sheet of drawings ® 809 580/523 7.58