RU178878U1 - Lamp for plants - Google Patents

Abstract

Plant luminaire based on filament light sources, including a transparent ceramic or leucosapphire substrate, on the front surface of which there is a line of blue LEDs emitting light in the range 445-470 nm, as well as a layer of broadband red nitride phosphor dispersed in a transparent curable material, or a layer composed of a mixture of red nitride phosphors, or a mixture of red nitride phosphors and yellow-orange oxide phosphors, with a garnet structure deposited after mon LEDs on both surfaces of the carrier, as a result of which the blue light of the LEDs passing through the phosphor coating layer is partially transformed into red-orange radiation, the maximum in the emission spectrum of which is in the range of 615-670 nm, while the width of the spectrum is half the height of the ordinate of the maximum varies depending on the composition of the phosphor composition in the range 95-165 nm, and the ratio of the ordinates of the maxima in the emission spectrum of the lamp in the blue (445-470) and red (615-670 nm) regions of the spectrum varies from 1.5: 1 to 1: 10.

Description

The utility model relates to the field of agriculture and, in particular, to systems of artificial LED lighting of plants in greenhouses, as well as illumination of planting material at home.

Currently, it has been reliably established that the phyto-active effect is possessed not by the entire spectrum of visible radiation, but by its individual sections corresponding to the bands of photosynthetically active radiation (PAR) [Raven R.N., Evert R.F., Eichorn S.E. Handbook of plant science., J. Wiley, 2007]. In FIG. 1 shows three spectral curves characterizing the absorption of visible light by green plants. Curve "a" refers to the absorption of light, which is spent on the synthesis of chlorophyll (and carotenoids), curves "b" and "c" correspond to the processes of photosynthesis and photomorphogenesis.

In the case of green plants, the absorption bands in the violet-blue region, covering the wavelength range from 420 to 500 nm, are referred to as PAR bands. Absorption in the region of 600–700 nm (bands with maxima at 612, 642, 660, and 700 nm) has a stronger substrate and regulatory effect than bands in the short-wavelength region of the spectrum. Finally, in the region of 700–750 nm, light has a pronounced regulatory and weak substrate effect.

The optimum in the distribution of PAR along wavelengths depends on the type of plant, but in the case of green plants, the dominant role is played by radiation in the red region.

Light in the wavelength range of 500-600 nm does not have a significant phytoactive effect. Some authors attribute it to the category of wasted energy, while others believe that auxiliary pigments present in the leaves can transfer energy from one spectral region to another.

The development of artificial lighting and illumination systems for plants went through the stage of using conventional incandescent lamps, which were replaced by mercury, gas-discharge fluorescent, metal-halogen and sodium lamps, which are widely used today. However, the emission spectra of these lamps are poorly consistent with the absorption bands of green plants.

After developing industrial production technology for LED monochromatic light sources (blue, green and red), they began to be used to create new artificial lighting systems for plants that provided targeted light pumping in those spectral regions that corresponded to absorption bands of green plants. So, for example, in the patent US 5278432 a light source with blue (400-450 nm) and red (620 and 680 nm) LEDs was proposed.

According to the data given in the patent US 6921182, the ratio of light intensities in the blue and red regions of the spectrum under artificial lighting should be for green plants (0.06-0.08): 1. At the same time, the composition composed of blue, orange-red (612 nm) and red (660 nm) LEDs had the best characteristics. The authors recommended using 12 red LEDs (660 nm), 6 orange (612 nm) and only one blue LED in the plant lighting source.

Currently, the world's leading companies Osram, Philips, Hortilux mainly produce sources with 4 LEDs. Luminaires with 5 or more LEDs (430, 450, 470, 610, 660 and 740 nm) are also known [Iethai Lighting Guangzhou China].

Despite the seemingly obvious advantages of LED lighting due to the targeted delivery of red and blue radiation to the absorption centers in the plant, one cannot ignore the fact that under normal conditions the plant comes into contact with sunlight, whose spectrum in the visible region is quite wide and continuous. Therefore, radiation is affected not only by the wavelength that corresponds to the maximum radiation of the LED, but also by the entire set of wavelengths adjacent to the spectral maximum.

The width of the bands in the absorption spectra of plants, as a rule, is much wider than the emission bands of LEDs (20-30 nm), so there is no reason to believe that monochromatic pumping is a comfortable effect for the plant. Perhaps that is why the replacement of metal-halogen and sodium high-pressure lamps with LED sources does not lead to a multiple increase in the efficiency of light exposure.

An alternative direction in phyto-lighting technology is fixtures with blue LEDs and light-transforming yellow-orange phosphors deposited on their surface [Application of LED lamps for lighting greenhouses: reality and prospects / Modern automation technology. 2010, No. 2, p. 76-82]. The emission spectrum of such sources includes a narrow blue band of residual primary radiation with a wavelength of 445-470 nm and a wide yellow-orange band covering the interval (500-680 nm) and arising upon excitation of the phosphor with primary blue light.

Despite the high light efficiency of such sources, the proportion of phyto-active, i.e. useful for plants, radiation in the red region of the spectrum does not exceed 15-20% of the total light flux. To compensate for the deficit of red light, narrow-band red LEDs have also been proposed along with blue LEDs. This decision complicated the design of the lamp and led to an increase in its cost. It is also significant that in this case it is not possible to fully compensate for the deficit of red light due to the small bandwidth emitted by the red LED.

Closest to the proposed utility model is the technical solution given in the patent [RU 153425]. The authors proposed two versions of luminaires for greenhouses, in which blue LEDs were used, combined with a broadband red phosphor. In the first constructive embodiment, the lamp included a housing, the inner walls and the bottom of which were made of a material with a high reflection coefficient. The lamp cover served as a diffuser of light emitted by chains of blue LEDs, each of which was covered with a layer of broadband red phosphor. The emitted blue light with a wavelength of 445-470 nm passed through a layer of red phosphor and excited red luminescence with a maximum in the emission spectrum at 630-670 nm and a spectral width at half height equal to 90-110 nm.

The second version of the luminaire design was characterized in that the red nitride phosphor was spatially separated from the blue-emitting LED and applied as a thin layer (4) on the inner surface of the light diffuser or dispersed in the bulk of the diffuser material.

The technical solution proposed in the patent [RU 153425] was chosen by us as a prototype. The main advantage of the previously proposed luminaire was that the primary blue radiation that passed through the red phosphor layer formed, together with the red-orange glow, a luminous flux consistent with the absorption bands of green plants.

The main disadvantage of the prototype is that the proposed lamp for greenhouses has a relatively low efficiency, which does not exceed 25 Lumen / Watt. This is due to the fact that the semiconductor chip, which is the source of the primary blue light, is located on a flat, opaque carrier (chip on board “SOV”), due to which, regardless of the modification of the lamp, all the blue light emitted by the LED towards the opaque carrier is scattered in the form heat.

It is possible to overcome this drawback when placing blue chips (LEDs) on a transparent medium (chip-on-glass “COG”). In this case, blue light is emitted in the direction of the full solid angle (4π steradian), as a result of which the efficiency of the LED light source at the same input power should increase significantly, which is an important technical result for practice.

Light sources with LEDs deposited on transparent media have found practical application in the new generation of comfortable white light lamps with a color temperature of 2700-2900K, a color rendering index of more than 80 at an efficiency of 90-110 Lm / W [USPatent Application: 20090184618, 20140362586, USPatent: 9491813, 8894252, 9502622,]. These lamps, most often performed in the configuration of traditional incandescent lamps or related forms, were called LED filament lamps for the reason that the light sources in them imitated luminous filaments in incandescent lamps. A typical construction of such lamps is shown in FIG. 2, where the arrow indicates one of the four filament radiation sources.

A filament is a combination of:

- a transparent carrier made of leucosapphire or transparent ceramic;

- a system of blue chips [US 9491813], placed along the length on the front surface of the carrier, together with the corresponding electrical wiring;

- a phosphor coating deposited from a suspension of the phosphor in a transparent polymer material (silicone or epoxy resin) over chips with electrical wiring on the front surface of the carrier, as well as a coating deposited on the lower surface of the carrier.

Thus, the filament is a radiating element of the lamp (phosphor - a carrier with chips and electrical wiring - phosphor), the axial section of which has a lenticular shape.

The transparent chip carrier is typically rod-shaped [US Patent Application 20140369036] with dimensions of length (5 mm - 200 mm), width (0.5 mm - 10 mm) and thickness (0.1 mm - 5.0 mm). Currently, carriers are most often used with a length of 38-39 mm, a width of 1.5 mm and a thickness of less than 1 mm, along the length of which there are 28 (or another number) chips of low power (for example, 0.02-0.04 Watt). As a rule, all chips in the filament emit blue light [USPatent 9491813, US Patent Application 20140362586], the spectral range of which may vary from 420 to 480 nm depending on the ratio between indium and gallium nitrides in the chip material. In commercial products, this range narrows to 445-460 nm.

Currently, filaments have become the subject of sale as a structural element of lamps of various configurations. The cost of a standard filament based on a sapphire-based carrier is only 0.14 US $ per piece for the purchase of 5000 pieces (Epistar chips sapphire Led Filament, model EGL-L01LN28AN-A).

The main and so far the only sphere of practical application of filament LED lamps are highly efficient sources of comfortable white light. In the manufacture of them, as in the case of conventional LED lamps with blue chips on an opaque carrier, a mixture of green and yellow YAG: Ce phosphors [(Y ₃ Al _5-x Ga _x O ₁₂ ): Ce, Lu ₃ Al is used to convert blue light ₅ O ₁₂ (Y ₃ Al ₅ O ₁₂ ): Ce] with one of the known types of red nitride phosphor, for example, composition Ca _1-x Sr _x AlSiN ₃ : Eu or composition (Ca _1-x Sr _x ) ₂ Si ₅ N ₈ : Eu [USP 9491813, US20140362586].

The technical result of the proposed utility model is the creation of a new functional device - namely, a lamp for plants, which has increased efficiency and has a radiation spectrum that is consistent with the absorption spectrum of plants. This technical result is achieved by using LEDs located on the surface of the transparent carrier, as well as by changing the composition of the phosphor applied to the surface of the carrier of blue chips. The conversion of blue light in the proposed lamp for plants is carried out using broadband red nitride phosphors or mixed compositions based on red nitride and yellow-orange oxide phosphors with a garnet structure.

Thus, the task is achieved by creating a lamp for plants based on filament light sources, including a transparent ceramic or leucosapphire substrate, on the front surface of which there is a line of blue LEDs emitting light in the range 445-470 nm, as well as a layer of broadband red nitride phosphor, dispersed in a transparent curable material, or a layer composed of a mixture of red nitride phosphors, or a mixture of red nitride phosphor and yellow-orange x oxide phosphors, with a garnet structure, deposited after mounting the LEDs on both surfaces of the carrier, as a result of which the blue light of the LEDs passing through the phosphor coating layer is partially transformed into red-orange radiation, the maximum of which is in the range of 615-670 nm, the width of the spectrum at half the height of the ordinate of the maximum varies depending on the composition of the phosphor composition in the range of 95-165 nm, and the ratio of the ordinates of the maxima in the emission spectrum of the lamp in blue (445-470) and red (615-670 nm) areas of the spectrum can vary from 1.5: 1 to 1:10.

Practical examples

Example No. 1

For the preparation of a filament light source were taken, manufactured by Shenzhen Lianshang Optical Co., Ltd. leucosapphire substrates with a line of deposited blue LEDs and mounted electrical wiring, but not containing a phosphor coating. LEDs emitted light with a wavelength of 455 nm. A suspension of broadband red phosphor (Sr ₄₉₃ Ca _0.493 Eu _0.014 ) AlSiN ₃ in silicone was deposited on the surface of the substrate, coated with chips, as well as on a surface free of chips. Similarly, for the phosphor of this composition, 3 more filaments were made, which, after curing the silicone, were mounted in a lamp having the configuration of ordinary incandescent lamps and including 4 filaments (see Fig. 2).

The results of measuring the spectral characteristics of the obtained lamp are shown in FIG. 3-a and in table No. 1. As can be seen, the maximum radiation in the red region was located at 650 nm, the width of the spectrum at half the height of the ordinate at the maximum radiation was 121 nm. The ratio of the peaks of the blue and red bands of the lamp was 1: 1.34.

Example No. 2

In this case, in contrast to Example No. 1, a mixture of broadband red nitride phosphor (Sr ₄₉₃ Ca _0.493 Eu _0.014 ) AlSiN ₃ with a yellow-orange phosphor of the composition (Y-Gd) ₃ Al ₅ O ₁₂ : Ce was taken as a phosphor in the preparation of filaments with a mass ratio of components equal to 1: 1

As in example No. 1, a lamp was manufactured having the configuration of conventional incandescent lamps and including 4 filaments. For this composition (see Fig. 3-b and Table 1), the emission maximum in the red region of the spectrum was located at 631 nm, the half-width of the spectrum was 111 nm, and the ratio of the band peaks in the blue and red spectral regions was 1: 5.9 .

Example No. 3

The mixture of phosphors taken for the preparation of filaments in example No. 3 contained the same components as in example No. 2, but the ratio between them was 1: 3. In this case (see Fig. 3-c and Table 1), the maximum emission of the red region of the spectrum was located at 631 nm, the half-width of the spectrum was 119 nm, and the ratio of the peak peaks in the blue and red regions of the spectrum was 1: 2.

Example No. 4

This example differs from sample No. 3 in the composition of the phosphor mixture, which in this case corresponded to a component ratio of 1: 6. As in the previous examples, the installation of filaments was carried out in the lamp configuration of conventional incandescent lamps. In this case (see Fig. 3-d and Table 1), the radiation maximum in the red region of the spectrum was located at 625 nm, the half-width of the spectrum was 130 nm, and the ratio of the peak peaks in the blue and red spectral regions was 1: 1.05.

Example No. 5

In this example, a mixture of a red nitride phosphor with a yellow garnet phosphor of the composition (Y _0.95 Ce _0.05 ) ₃ Al ₅ O _{12 was used} . In this case, the glow had a warm white light with a color temperature of 2750K. Compared to samples nos. 1-4, the emission spectrum of the luminaire had the largest width of 165 nm, while the maximum in the red region of the spectrum (616 nm) was most strongly shifted to the short-wavelength region. However, this did not lead to a decrease in the radiation intensity at a wavelength of 700 nm.

A summary of the information obtained in the illustrative examples is given in table. No. 1.

As can be seen from the above data, the spectrum of the LED lamp for plants always contains a band of primary blue exciting radiation and a wide band in the red region, which covers all phyto-active radiation bands in the wavelength range of 560-780 nm.

The ratio of the bands in the blue and red regions of the spectrum depends on the thickness of the applied layer and the concentration of the phosphor in the suspension with silicone, which is applied to the surface of the blue LED. In this case, the position of the maximum in the red region (from 616 to 670 nm) and the width of the spectral curve are determined by the composition of the red phosphor and its mixtures with yellow-orange phosphors.

The light emitted by the lamp in examples No. 1-4 had a purple color with gradations of fuchsia (# FF00FF), magenta (# FF008F), purple (# C400AV) depending on the ratio of the blue and red components in the spectrum.

Mixing the red phosphor with yellow-orange leads to a shift of the long-wavelength branch of the spectral curve to the short-wavelength region, but the luminescence intensity at a wavelength of 700 nm always remained at the level of 50% of the maximum. At the same time, the luminous flux of fixtures made using mixtures of phosphors was almost 1.5-2 times higher than that of fixtures with a red phosphor. As a result, it was possible to increase the efficiency of the LED filament fixtures obtained by more than 70% in comparison with the efficiency of the prototype while reducing the cost of the fixtures. The latter was achieved by reducing mixtures of red and yellow-orange phosphors instead of the expensive red phosphor.

Claims (1)

A plant luminaire based on filament light sources, including a transparent ceramic or leucosapphire substrate, on the front surface of which there is a line of blue LEDs emitting light in the range 445-470 nm, as well as a layer of a mixture of red nitride phosphor powders deposited after mounting the LEDs on both surfaces of the carrier and yellow-orange oxide phosphors with a garnet structure dispersed in a transparent curable material, resulting in blue light of the LEDs passing through the layer phosphor coating, partially transformed into red-orange radiation, the maximum in the emission spectrum of which is in the range of 615-670 nm, while the width of the spectrum at half the height of the ordinate of the maximum varies depending on the composition of the phosphor composition in the range of 95-165 nm, and the ordinate ratio the maximums in the emission spectrum of the lamp in the blue (445-470) and red (615-670 nm) regions of the spectrum varies from 1.5: 1 to 1:10.

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