1. A light conversion coating capable of promoting plant growth, which is characterized in that: the light conversion film is prepared by mixing and drying fluorescent powder with a Pnma structure and a polymer with a refractive index of 1.4-1.6 according to a mass ratio of 1: 9-2: 3, wherein the fluorescent powder with the Pnma structure is Rb_0.2K_1.8CaPO₄F:Eu。

2. The light conversion film according to claim 1, wherein the light conversion film is selected from the group consisting of: the phosphor is formed by doping Rb with Eu with Pnma structure_0.2K_1.8CaPO₄F, preparing the product.

3. The light conversion film according to claim 1, wherein the light conversion film is selected from the group consisting of: the polymer is PDMS or polycarbonate.

4. The method for preparing a light conversion film according to claim 1, comprising the steps of:

1) according to Rb_0.2K_1.8Ca_0.98PO₄The following raw materials are respectively weighed according to the stoichiometric ratio of each chemical composition in the chemical expression of F:0.02 Eu:

rubidium compound: adopting rubidium carbonate, hydroxide containing rubidium, nitrate containing rubidium, carbonate containing rubidium, sulfate containing rubidium or phosphate containing rubidium;

potassium compound: adopting potassium carbonate, hydroxide containing potassium, nitrate containing potassium, sulfate containing potassium or phosphate containing potassium;

calcium compound: calcium carbonate, calcium hydroxide, calcium nitrate, calcium sulfate or calcium phosphate is adopted;

phosphorus compound: adopting ammonium dihydrogen phosphate or hydroxide containing phosphorus;

fluorine compound (b): adopting potassium fluoride, hydroxide containing fluorine, nitrate containing chromium, carbonate containing chromium, sulfate containing chromium or phosphate containing chromium;

europium compound: europium oxide, hydroxide containing europium, nitrate containing europium, carbonate containing europium, sulfate containing europium or phosphate containing europium are adopted;

mixing and grinding the weighed raw material components to micron level to prepare mixed raw material powder;

2) calcining the mixed raw material powder obtained in the step 1) in a reducing atmosphere at the temperature of 850 ℃ for 4 hours; cooling the calcined raw material powder to room temperature along with the furnace to obtain Eu-containing²⁺The Pnma structure of (1);

3) mixing the polymer and the curing agent according to the mass ratio of 1:9, mixing the fluorescent powder obtained in the step 2) and the mixed polymer according to the mass ratio of 1: 9-2: 3, stirring the mixed fluorescent powder and the polymer in a vacuum defoaming machine for 2.5 minutes, placing the mixture into an oven for drying after uniform stirring, and preparing the light conversion film according to the existing film preparation process.

5. The method of claim 4, wherein: the reducing atmosphere in the step 2) adopts the following gases: the ammonia gas, or a mixed gas composed of 5-25% by volume of hydrogen gas and 95-75% by volume of nitrogen gas, or a mixed gas composed of 5-25% by volume of carbon monoxide and 95-75% by volume of nitrogen gas.

6. Use of a light conversion film according to claim 1 for promoting the growth of a crop.

Background

Plants require light to provide energy during growth and fruit ripening, and thus light regulation is one of the important means for regulating plant growth. The absorption of light by plants is mainly carried out by chlorophyll and phytochrome, the light absorbed by chlorophyll is mainly light in a blue light region (400 nm-500 nm) and a red light region (600 nm-700 nm), and the phytochrome absorbs light in red light and deep red (650 nm-750 nm) regions and respectively corresponds to the light tropism, photosynthesis and light morphology of the plants. Of these, light in the red region is most important for plant growth because red light significantly accelerates plant development, promotes dry matter accumulation, bulb, root tuber, leaf bulb and other plant organs formation, causes early flowering and fruit set of plants, plays a dominant role in plant hyperchromia, while light outside this range is less absorbed and contributes little to plant photosynthesis. Therefore, the utilization rate of sunlight is low in the growth process of the plants, so that the growth speed and the yield of the plants can be greatly improved by trying to improve the light energy utilization rate of the plants.

In order to better promote the growth of economic crops, an LED plant lamp taking an LED as a luminous body is produced. However, LED plant lights have a number of disadvantages: the difference between the emission spectrum curve of the LED plant lamp on the market at present and the spectrum curve absorbed by plant photosynthesis is large, and the energy utilization rate of a light source is not high; in addition, the price of the LED chip is high, a large amount of power resources are consumed in the using process, and the planting cost is increased. Therefore, although the LED plant growth lamp can improve the crop yield, the LED plant growth lamp is not suitable for cultivating low-economic crops and has low applicability.

Another method for promoting plant growth by converting sunlight into red light, which is commonly used at present, is to cover plants with an organic red light emitting material such as a vinyl film containing heterocyclic compounds, like a conventional plant vinyl house. However, ultraviolet light exists in sunlight and is harmful to the film, so that the film is yellowed and disintegrated; and the stability of the organic red luminescent material under the sun is low, the emitted red light can be attenuated within 3 months, and the growth requirement of plants cannot be met. Therefore, designing a novel light conversion film which is low in price and can improve the utilization rate of solar radiation energy of plants is of great significance in the aspects of improving the growth speed and yield of the plants.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for utilizing Rb_0.2K_1.8CaPO₄The preparation method of the light conversion film by taking Eu fluorescent powder and PDMS as raw materials has the advantages of simple technology, no harmful substances, environmental protection and obvious reduction of production cost, and meanwhile, the light conversion film prepared by the method has strong light supplementing capability and high efficiency, is more beneficial to promoting the growth and development of plants and has good economic benefit.

In order to achieve the purpose, the invention adopts the technical scheme that:

a light conversion film capable of promoting plant growth is prepared by mixing and drying fluorescent powder with a Pnma structure and a polymer with a refractive index of 1.4-1.6 according to a mass ratio of 1: 9-2: 3, wherein the fluorescent powder with the Pnma structure is Rb_0.2K_1.8CaPO₄F:Eu。

The phosphor is formed by doping Rb with Eu with Pnma structure_0.2K_1.8CaPO₄F, preparing the product.

The polymer is PDMS or polycarbonate.

The preparation method of the light conversion film comprises the preparation of fluorescent powder and the preparation of the fluorescent powder light conversion film, and specifically comprises the following steps:

1) according to Rb_0.2K_1.8Ca_0.98PO₄The following raw materials are respectively weighed according to the stoichiometric ratio of each chemical composition in the chemical expression of F:0.02 Eu:

rubidium compound: using rubidium carbonate (Rb)₂CO₃) A rubidium-containing hydroxide, a rubidium-containing nitrate, a rubidium-containing carbonate, a rubidium-containing sulfate, or a rubidium-containing phosphate;

potassium compound: using potassium carbonate (K)₂CO₃) Potassium-containing hydroxides, potassium-containing nitrates, potassium-containing sulfates or potassium-containing phosphates;

calcium compound: using calcium carbonate (CaCO)₃) A calcium hydroxide, a calcium nitrate, a calcium sulfate or a calcium phosphate;

phosphorus compound: using ammonium dihydrogen phosphate (NH)₄H₂PO₄) Or a phosphorus-containing hydroxide;

fluorine compound (b): adopting potassium fluoride (KF), fluorine-containing hydroxide, chromium-containing nitrate, chromium-containing carbonate, chromium-containing sulfate or chromium-containing phosphate;

europium compound: using europium oxide (Eu)₂O₃) Europium-containing hydroxide, europium-containing nitrate, europium-containing carbonate, europium-containing sulfate, or europium-containing phosphate;

mixing and grinding the raw material components to micron level to obtain mixed raw material powder;

2) calcining the mixed raw material powder obtained in the step 1) in a reducing atmosphere at the temperature of 850 ℃ for 4 hours; cooling the calcined raw material powder to room temperature along with the furnace to obtain Eu-containing²⁺The Pnma structure of (1);

3) mixing the polymer and the curing agent according to the mass ratio of 1:9, mixing the fluorescent powder obtained in the step 2) and the mixed polymer according to the mass ratio of 1: 9-2: 3, stirring the mixed fluorescent powder and the polymer in a vacuum defoaming machine for 2.5 minutes, placing the mixture into an oven for drying after uniform stirring, and preparing the light conversion film according to the existing film preparation process.

The reducing atmosphere in the step 2) adopts the following gases: ammonia gas (NH)₃) Or 5-25% by volume of hydrogen (H)₂) And 95-75% nitrogen (N)₂) The mixed gas is composed of 5-25% of carbon monoxide (CO) and 95-75% of nitrogen (N) according to volume percentage₂) The composition of the mixed gas.

The application of the light conversion film in promoting the growth process of crops.

Compared with the prior art, the invention has the following beneficial effects:

1) the process method has simple technology, the obtained film has uniform fluorescent powder distribution, the equipment operation is simple, no harmful substance is generated, the process method is green and environment-friendly, and the production cost is obviously reduced;

2) the light conversion film prepared by the method has the advantages of strong light supplementing capability, high efficiency, emission spectrum range of 400-850 nm, wide spectrum coverage area, contribution to promoting the growth and development of plants and good economic benefit.

Drawings

FIG. 1 is Rb prepared in example 1_0.2K_1.8CaPO₄Xrd diagram of Eu phosphor and comparison diagram of standard card.

FIG. 2 is Rb as obtained in example 1_0.2K_1.8CaPO₄F, excitation and emission spectrograms of the Eu fluorescent powder.

FIG. 3 is Rb prepared in example 2_0.2K_1.8CaPO₄F, comparing the emission spectra of the light conversion film made of the Eu fluorescent powder and the PDMS with the emission spectra of the fluorescent powder.

FIG. 4 is Rb prepared in example 3_0.2K_1.8CaPO₄F, comparing the emission spectra of the light conversion film made of the Eu fluorescent powder and the PDMS with the emission spectra of the fluorescent powder.

FIG. 5 is a block diagramRb from example 4_0.2K_1.8CaPO₄F, comparing the emission spectra of the light conversion film made of the Eu fluorescent powder and the PDMS with the emission spectra of the fluorescent powder.

FIG. 6 is Rb obtained in example 5_0.2K_1.8CaPO₄F, comparing the emission spectra of the light conversion film made of the Eu fluorescent powder and the PDMS with the emission spectra of the fluorescent powder.

FIG. 7 is a schematic view of the arrangement of a light conversion film using the positional relationship of a plant and the sun.

Detailed Description

The present invention will now be described in detail with reference to the following detailed description and accompanying drawings, wherein the present invention will be described by way of illustration and description, but not by way of limitation.

For a better understanding of the substance of the invention, the following description is made:

the invention relates to a fluorescent powder light conversion film for converting sunlight into red light, which consists of a polymer and fluorescent powder dispersed in the polymer. To date, nitrides such as CaAlSiN₃Eu has been used for plant growth. When the silicon nitride fluorescent powder absorbs solar rays to generate red light, the red light cannot be easily separated from the surface of the powder, because the red light enters air from the inside of the powder and is totally reflected. In the case of nitride phosphors, light in excess of 1/3 cannot enter the outside of the particle. Through our research, a polymer with excellent optical performance, such as PDMS glue and Rb, is invented_0.2K_1.8CaPO₄F is a combination of Eu phosphors, when Rb is_0.2K_1.8CaPO₄When Eu (n 1.47) is dispersed in PDMS (n 1.41), the refractive indices n of these two substances are almost not different. So that after mixing, total reflection occurs comparatively little.

Rb prepared by doping Eu with Pnma structure in phosphate_0.2K_1.8CaPO₄The Eu fluorescent powder can convert sunlight into bright red light, wherein the emission spectrum range is (400-850 nm).

As shown in figure 7, the position relation between the plants and the sun is used for arranging films or flat plates on two sides of the plants, so that the problem that when the plants are covered by the films from the upper part of the plants, the films emit red light and reflection loss occurs is solved. In contrast, the thin film or the flat plate is disposed on both sides of the plant, so that almost all of the deep red light emitted from both sides of the flat plate can be emitted toward the plant, thereby accelerating the growth of the plant.

The invention provides a light conversion film capable of promoting plant growth, which is prepared from PDMS (polydimethylsiloxane) glue and Rb_0.2K_1.8CaPO₄F, Eu fluorescent powder synthesis.

The Rb is_0.2K_1.8CaPO₄And F, synthesizing Eu fluorescent powder according to a chemical expression, wherein the content of PDMS glue in the process of synthesizing the light conversion film is respectively 90%, 80%, 70% and 60%.

The PDMS gums may be replaced with polycarbonate polymers.

The preparation method of the light conversion film is specifically carried out according to the following steps:

step 1, press Rb_0.2K_1.8CaPO₄The stoichiometric ratio of each chemical composition in the Eu chemical expression is respectively called a compound of each element in the chemical formula, wherein the raw materials are as follows: rb₂CO₃，K₂CO₃，CaCO₃，NH₄H₂PO₄，KF，Eu₂O₃；

Fully grinding the raw materials weighed according to the metering ratio, calcining the ground raw materials in a reducing atmosphere at the temperature of 850 ℃ for 4 hours, cooling the calcined raw materials to room temperature along with a furnace to obtain a calcined product, and grinding the calcined product to obtain Eu-containing Eu²⁺Rb of Pnma structure of_0.2K_1.8CaPO₄F is Eu powder;

step 2: mixing PDMS glue and a curing agent in a mass ratio of 1:9, mixing the fluorescent powder synthesized in the step 1 with PDMS glue in different proportions to obtain a mixture;

and step 3: and putting the mixture into a vacuum defoaming machine for vacuumizing stirring (the stirring time is different according to different amounts so as to ensure that the fluorescent powder is uniformly dispersed in the glue without segregation), then putting the mixture into an oven for drying for 4-8 hours, and preparing the light conversion film according to the conventional film preparation process after drying.

Example 1

According to Rb_0.2K_1.8Ca_0.98PO₄F:0.02Eu in the formula, 0.6928g of Rb are weighed₂CO₃1.656g of K₂CO₃2.97g of CaCO₃3.45g of NH₄H₂PO₄1.745g of KF and 0.0528g of Eu₂O₃Fully grinding and uniformly mixing the weighed raw materials, putting the mixture into an alumina crucible, putting the alumina crucible into a tubular furnace, calcining for 4 hours (the temperature rise speed is 5 ℃/min) at the temperature of 850 ℃ (5% H2 and 95% N2 atmosphere), and cooling to room temperature along with the furnace to obtain a calcined substance; and grinding the obtained calcined substance to obtain the fluorescent powder. The XRD pattern of the phosphor is shown in figure 1, wherein the peak shape and the peak position of each peak correspond to PDF card one by one, and the phase of the prepared powder is proved to be single phase.

Then measuring excitation and emission spectra of the sample, as shown in FIG. 2, wherein the excitation spectra show that a relatively wide absorption spectrum (300-450 nm) exists, and excitation peak values are respectively positioned at 380 nm; the emission spectrum showed a broad emission peak with a peak at 650 nm. From the spectrogram we can find that Rb is_0.2K_1.8CaPO₄Eu absorbs in the ultraviolet light area of 300-380 nm, so that yellowing and disintegration of the film caused by sunlight are avoided.

Example 2

Based on example 1, a light conversion film was prepared by mixing phosphor and glue at a ratio of 1: 9. The method specifically comprises the following steps: weighing 1.215g of PDMS adhesive, adding 0.15g of the fluorescent powder prepared in the example 1, and then adding 0.135g of the curing agent; then the mixture is placed into a vacuum defoaming machine for vacuum stirring (the stirring time is 2min and is 30 s). And (4) putting the uniformly stirred mixture into an oven for drying. After 6h, the dried light conversion film 1 was taken out, and its emission spectrum under excitation at 380nm was measured, as shown in FIG. 3.

Example 3

Based on example 1, a light conversion film was prepared by mixing phosphor and glue at a ratio of 2: 8. The method specifically comprises the following steps: weighing 1.08g of PDMS adhesive, adding 0.3g of the fluorescent powder prepared in the example 1, and then adding 0.12g of the curing agent; putting the mixture into a vacuum defoaming machine and stirring the mixture evenly. And (4) putting the uniformly stirred mixture into an oven for drying. After 6h, the dried light conversion film 2 was taken out, and its emission spectrum under excitation at 380nm was measured, as shown in FIG. 4.

Example 4

Based on example 1, a light conversion film was prepared by mixing the phosphor and the glue at a ratio of 3: 7. The method specifically comprises the following steps: weighing 0.945 parts of PDMS adhesive, adding 0.45g of the fluorescent powder prepared in the example 1, and then adding 0.105g of the curing agent; putting the mixture into a vacuum defoaming machine for vacuumizing and stirring. And (4) putting the uniformly stirred mixture into an oven for drying. After 6h, the dried light conversion film 3 was taken out, and its emission spectrum under excitation at 380nm was measured, as shown in FIG. 5.

Example 5

Based on example 1, a light conversion film was prepared by mixing the phosphor and the glue at a ratio of 4: 6. The method specifically comprises the following steps: weighing 0.81 g of PDMS (polydimethylsiloxane) adhesive, adding 0.6g of the fluorescent powder prepared in the example 1, and then adding 0.09g of the curing agent; putting the mixture into a vacuum defoaming machine for vacuumizing and stirring. And (4) putting the uniformly stirred mixture into an oven for drying. After 6h, the dried light conversion film 4 was taken out, and its emission spectrum under excitation at 380nm was measured, as shown in FIG. 6.

And (4) conclusion: the emission intensity of the phosphor prepared in example 1 and the light conversion film prepared in examples 2 to 5 excited at 380nm were compared. From fig. 3, we can see that the luminous intensity of the light conversion film 1 prepared in example 2 is 27.7% of that of the phosphor; from fig. 4, it can be seen that the luminous intensity of the light conversion film 2 prepared in example 3 is 46.4% of that of the phosphor; from fig. 5, it can be seen that the luminescence intensity of the light conversion film 3 prepared in example 4 is 51.9% of that of the phosphor; from fig. 6, it can be seen that the luminous intensity of the light conversion film 4 prepared in example 5 is 56.8% of that of the phosphor. From the results obtained above, it is obvious that the light emitting intensity of the light conversion film continuously increases with the increase of the doping ratio of the fluorescent powder, and when the ratio of the fluorescent powder in the light conversion film is more than 30%, the light emitting intensity of the light conversion film exceeds 50% of the light emitting intensity of the fluorescent powder, so that the expected effect is achieved, and the light conversion film prepared by the method can provide strong red light for plants, thereby promoting the growth of the plants.

The technical solutions provided by the embodiments of the present invention are described in detail above, and the principles and embodiments of the present invention are explained in the present document by using specific examples, and the descriptions of the embodiments are only used to help understanding the principles of the embodiments of the present invention.