EP0092220A2 - Fluoresent lamp for stimulating a uniform plant growth - Google Patents

Abstract

1. A fluorescent lamp for stimulating a balanced plant growth in which the phosphor blend applied to the inner wall of the lamp envelope comprises three components, the first component used being a manganese activated magnesium fluorogermanate with an emission maximum at 660 nm and the second component used being a tin-activated strontium magnesium orthophosphate with an emission maximum at 626 nm, characterized in that the third component is a barium magnesium aluminate activated with divalent europium and having an emission maximum at 447 nm.

Description

The invention relates to a fluorescent lamp for stimulating balanced plant growth, in which the phosphor mixture applied to the inner wall of the lamp bulb contains three components, the first component being a manganese-activated magnesium fluorogermanate with an emission maximum at 660 nm and the second component being a tin-activated strontium-magnesium Orthophosphate with an emission maximum at 626 nm is used.

Various fluorescent mixtures have been proposed for fluorescent lamps for the purpose of irradiation of plants, flowers and ornamental fish, the emission of which is matched to the different absorption of the plants at the individual wavelengths, in particular of the visible spectral range. In practice, phosphor mixtures are often used for this purpose, which are composed of approximately 55% by weight of a calcium tungstate and 45% by weight of a magnesium fluorogermanate activated with manganese. However, the magnesium fluorogermanate is very expensive, which is why other fluorescent mixtures without or with a significantly reduced proportion of this expensive component have long been sought, without the spectral emission properties of the fluorescent lamp being adversely affected. For example, it is known from US Pat. No. 4,055,781 that the proportion of the magnesium fluorogermanate phosphor with its dark red emission is preferably from 10% to 30% by weight To reduce 20 wt .-%. In order to maintain the energies in the spectral ranges essential for the plant, however, it was necessary to add three further phosphor components with different emission properties to the phosphor mixture in addition to the magnesium fluorogermanate. With the help of these measures, the material price of the phosphor mixture used could be reduced to a third of the original price, but in order to achieve a defined color location of the mixture consisting of a total of four phosphors, the most exact adherence to all manufacturing tolerances is necessary. The reason is that a mixture consisting of four phosphor components is not a sufficient criterion for determining the color location. Although it is possible to set the color locale here using various mixing ratios, the radiation properties of the lamp then shift.

Another disadvantage of the phosphor mixture used in practice, consisting of calcium tungstate and magnesium fluorogermanate, is the necessity to have to coat the lamp bulbs with a suspension containing an organic binder. As binders e.g. dilute solutions of a highly viscous nitrocellulose in butyl acetate are used. In addition to an odor nuisance that occurs during the processing of phosphor suspensions prepared with these organic binders, the effort to prevent environmental damage with such solvents is also quite considerable.

The object of the invention is to provide a phosphor mixture which is suitable for plant irradiation and which is inexpensive to produce and easy to process and for which the environmentally friendly, inexpensive water sludge can be used. In addition, the effect of the characteristic wavelength ranges that are essential for plant physiology should be as close as possible to that of natural sunlight.

The fluorescent lamp for stimulating balanced plant growth with the features mentioned in the preamble of the main claim is characterized according to the invention in that the third component is a barium magnesium aluminate activated with divalent europium with an emission maximum at 447 nm. The magnesium fluorogermanate activated with manganese is only present in an amount of 10 to 25% by weight, preferably 20% by weight, of the total weight of the phosphor mixture. With more than 25% by weight, the price advantage would no longer be sufficiently attractive, while with less than 10% by weight, certain colors would be rendered inadequately. The cheap, tin-activated strontium-magnesium orthophosphate is 55 to 80% by weight, preferably 65% by weight, and the barium-magnesium aluminate activated with divalent europium is 10 to 20% by weight, preferably containing 15% by weight of the total weight of the phosphor mixture.

The phosphor mixture according to the invention is about two thirds cheaper than the mixture previously used. The new phosphor mixture is also easy to manufacture and well suited for processing in mass production. By using only three components, the target color location is a clear criterion for the phosphor composition. The standard color value share of the preferred mixture is 0.339 for x and 0.247 for y; the lamp thus emits Although in a purple hue that is common in plant lighting, in which plants and ornamental fish have a particularly attractive appearance, the color locus is shifted by approx. 30 SWE (threshold value units) towards the achromatic point. This makes it possible to use such a fluorescent lamp as room lighting in greenhouses and corresponding sales rooms.

Because the germanate component is used only to a small extent, the transition from the previously used phosphor suspension with organic binder to the cheaper, environmentally friendly water slurry is possible. With the new type of phosphor and the simultaneous use of lamp bulbs with a bulb diameter reduced to 26 mm, approximately 10% of the electrical energy costs can be saved with an approximately doubled luminous flux. In addition, the resulting material savings reduce the end costs for the phosphor to approximately a quarter of the original costs.

• Figur 1a zeigt die relative spektrale Wirkungsfunktion ^{s (λ)} sy, rel der Photosynthese.
• Figur 1b zeigt die relative spektrale Wirkungsfunktion ^{s (λ)}ch, rel der Chlorophyllsynthese.
• Figur 1c zeigt die relative spektrale Wirkungsfunktion ^{s (λ)} tr, rel des Phototropismus.
• Figur 1d zeigt die relative spektrale Wirkungsfunktion ^{s (λ)} mo, rel der Photomorphogenese.
• Figur 2 zeigt das Emissionsspektrum einer Leuchtstofflampe, die mit einer herkömmlichen Leuchtstoffmischung beschlämmt wurde.
• Figur 3 zeigt das Emissionsspektrum einer Leuchtstofflampe, die mit der erfindungsgemäßen Leuchtstoffmischung beschlämmt wurde.

The invention is explained in more detail below with reference to the figures:

• FIG. 1a shows the relative spectral function ^{s (λ)} sy, rel of photosynthesis.
• Figure 1b shows the relative spectral function ^{s (λ)} ch, rel of chlorophyll synthesis.
• Figure 1c shows the relative spectral function ^{s (λ)} tr, rel of the phototropism.
• FIG. 1d shows the relative spectral function ^{s (λ)} mo, rel of the photomorphogenesis.
• Figure 2 shows the emission spectrum of a fluorescent lamp, which was slurried with a conventional phosphor mixture.
• FIG. 3 shows the emission spectrum of a fluorescent lamp which was slurried with the phosphor mixture according to the invention.

FIGS. 1a to 1d show the different courses of the plant physiological action functions in accordance with DIN 5031. Photosynthesis. (Fig. 1a) and the chlorophyll synthesis (Fig. 1b) each show maxima at 445 nm and 660 nm. The phototropism (Fig. 1c) shows a broad curve with maxima at 440 nm and 470 nm and the photomorphogenesis (Fig. 1d) shows a narrow induction maximum (curve A) at 660 nm and a somewhat wider reversion maximum (curve B) at approx. 730 nm. In the green spectral range (510 nm to 610 nm) the plants show only a lower photosynthetic effectiveness and a weak morphogenetic activity. Radiation of wavelengths above 1000 nm, if the plant absorbs it at all, is converted into heat by the plant without disturbing the biochemical processes. A fluorescent lamp used for plant irradiation should therefore also have a maximum with its total emission, at least in the maxima specified above of the plant physiological reaction curves. In plant breeding, however, it has also been shown that certain plants thrive not only with the radiation components in the ranges from approx. 400 nm to approx. 500 nm (blue) and approx. 600 nm to approx. 700 nm (red), but also beyond also a certain proportion of daylight, in particular its green-yellow radiation component in the range of approximately 550 nm to 580 nm for the synthesis of enzymes and and other substances.

FIGS. 2 and 3 show the respective emission spectrum of a fluorescent lamp coated with a conventional and with a phosphor mixture according to the invention. The emission spectrum in FIG. 2 originates from a 40 W fluorescent lamp with a bulb diameter of 38 mm, the phosphor mixture of which is approx. 55% by weight from the blue-emitting calcium tungstate and approx. 45% by weight from the expensive red-emitting magnesium fluorogermanate activated with manganese. The phosphor mixture is dissolved in a dilute solution of a highly viscous nitrocellulose in butyl acetate. After Beschlämmung the lamp bulb is eheizt in a baking oven of ^g, wherein the organic constituents of the suspension volatilize.

The emission spectrum of FIG. 3 comes from a 36 W fluorescent lamp with a bulb diameter of 26 mm. According to the invention, the phosphor mixture contains only 20% by weight of the expensive, red-emitting, manganese-activated magnesium fluorogermanate. The resultant lack of red in the mixture was made up by adding 65% by weight of the much cheaper, red-orange emitting, tin-activated strontium-magnesium-orthophosphate phosphor. The fluorescent lamp obtains the necessary proportion of blue by adding 15% by weight of a barium-magnesium-aluminate phosphor which has been activated with divalent europium to the phosphor mixture. In addition to optimization in the blue area, the spectrum also shows the balance of the blue and red emissions. Likewise - compared to the spectrum of a conventional fluorescent lamp - the green-yellow radiation component (550 nm - 580 nm) was clear Lich raised. In addition to promoting the synthesis of enzymes, this also causes a shift in the color locus towards the achromatic point, which in turn improves color rendering and enables the use of radiation lamps in greenhouses and their sales rooms. The emission spectrum in the standard color chart according to DIN 5033 results in a color locus with the standard color value components x = 0.339 and y = 0.247. The fluorescent lamp coated with the phosphor mixture according to the invention is manufactured in a known manner like conventional fluorescent lamps, but the phosphor mixture was dissolved in the much more environmentally friendly water instead of in an organic solvent.

As Table 1 below shows, the radiation proportions of the phosphor mixture according to the invention standardized to chlorophyll synthesis are significantly more favorable compared to a mixture of a calcium tungstate and a magnesium fluorogermanate activated with manganese used in the past if the sunlight is used as a reference source. In particular, the value of the metamorphosis at 730 nm could be tripled compared to the fluorescent lamps previously used for plant irradiation and thus much closer to sunlight. The higher value of photosynthesis also causes an increased production of the biomass.

Table 2 shows what percentage of the electrical power consumed by the lamp relates to the individual radiation components available to the plant.

Claims (3)

1. Fluorescent lamp for stimulating balanced plant growth, in which the phosphor mixture applied to the inner wall of the lamp bulb contains three components, the first component being a manganese-activated magnesium fluorogermanate with an emission maximum at 660 nm and the second component being a tin-activated strontium-magnesium orthophosphate an emission maximum at 626 nm is used, characterized in that the third component is a barium magnesium aluminate activated with divalent europium with an emission maximum at 447 nm. 2. Fluorescent lamp according to claim 1, characterized in that the magnesium fluorogermanate with 10 to 25 wt .-%, the strontium-magnesium orthophosphate with 55 to 80 wt .-% and the barium-magnesium _- aluminum, minate with 10 up to 20 wt .-% of the total amount of the phosphor mixture is included. 3. Fluorescent lamp according to claim 1 and 2, characterized in that the magnesium fluorogermanate with 20 wt .-%, the strontium-magnesium orthophosphate with 65 wt .-% and the barium-magnesium aluminate with 15 wt .-% of the total amount of the phosphor mixture is included.

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