Photosynthesis promotion sheet

Abstract

The purpose of the present invention is to provide a photosynthesis promotion sheet capable of effectively enhancing the PPFD of photosynthesis-effective light by converting non-photosynthesis-effective light such as ultraviolet light into blue or red photosynthesis-effective light. This photosynthesis promotion sheet includes quantum dots, and is characterized by comprising a quantum dot sheet that has a first surface and a second surface on the opposite side from the first surface and that includes quantum dots that convert non-photosynthesis-effective light into photosynthesis-effective light, the first surface being a surface on which sunlight is irradiated, and the second surface being a surface that emits the photosynthesis-effective light, and the quantum dot sheet containing a UV scattering agent.

Description

Photosynthesis promotion sheet

[0001] The present invention relates to a photosynthesis-promoting sheet containing quantum dots.

[0002] Crops and seaweed use sunlight to perform photosynthesis, but it is known that not all wavelengths contained in sunlight are involved in photosynthesis; in fact, blue and red wavelengths are the main ones.

[0003] For example, Patent Document 1 discloses a quantum dot LED that includes a quantum dot phosphor sheet on a substrate of which is a polymer film containing red quantum dots, and that emits light to the outside that is a mixture of red light that has been wavelength-converted by absorbing part of the light emitted from an LED and blue light that has passed through the phosphor sheet.

[0004] Japanese Patent Application Laid-Open No. 2019-037243

[0005] However, a structure including quantum dots for promoting photosynthesis has not yet been established. For example, Patent Document 1 requires the use of an LED light source, which is costly to use in a large area and requires a complicated structure.

[0006] The present invention has been made in consideration of these points, and aims to provide a photosynthesis-promoting sheet that can convert non-photosynthetically active light, such as ultraviolet light, contained in sunlight into photosynthetically active light in blue or red, and in the process effectively increase the photon flux density of the photosynthetically active light.

[0007] A photosynthesis promotion sheet according to one embodiment of the present invention is a photosynthesis promotion sheet containing quantum dots, having a first surface and a second surface opposite the first surface, and comprising a quantum dot sheet that converts non-photosynthetically active light into photosynthetically active light, wherein the first surface is a surface that is irradiated with sunlight and the second surface is a surface that emits the photosynthetically active light, and the quantum dot sheet contains the quantum dots and a UV scattering agent.

[0008] A photosynthesis promotion sheet according to one embodiment of the present invention is a photosynthesis promotion sheet containing quantum dots, having a first surface and a second surface opposite the first surface, and comprising a quantum dot sheet that converts non-photosynthetically active light into photosynthetically active light, wherein the first surface is a surface that is irradiated with sunlight and the second surface is a surface that emits the photosynthetically active light, the quantum dot sheet contains at least the quantum dots, and a UV scattering layer is disposed on the first surface of the quantum dot sheet.

[0009] A photosynthesis promotion sheet according to one embodiment of the present invention is a photosynthesis promotion sheet containing quantum dots, having a first surface and a second surface opposite the first surface, and comprising a quantum dot sheet that converts non-photosynthetically active light into photosynthetically active light, wherein the first surface is a surface that is irradiated with sunlight and the second surface is a surface that emits the photosynthetically active light, the quantum dot sheet contains at least the quantum dots, and a dichroic filter layer that reflects UV light and transmits visible light is disposed on the second surface of the quantum dot sheet.

[0010] The photosynthesis promotion sheet of the present invention converts non-photosynthetically active light, such as ultraviolet light, contained in sunlight into blue or red photosynthetically active light, thereby effectively increasing the photon flux density of the photosynthetically active light.

[0011] 1 shows a conceptual diagram of the light intensity of wavelengths effective for photosynthesis and the photosynthetic rate. FIG. 1 is a cross-sectional view of a photosynthesis promotion sheet in the present embodiment. FIG. 2 is a graph of Experimental Example 1 showing conversion to photosynthetically active light (red light). FIG. 3 is a graph of Experimental Example 2 showing conversion to photosynthetically active light (blue light). FIG. 4 is a graph showing the relationship between wavelength and transmittance with and without a UV scattering layer. FIG. 5 is a schematic diagram of a spectral distribution measurement method. FIG. 6 is a spectral distribution diagram for each sample sheet immediately after the start of the experiment. FIG. 7 is a spectral distribution diagram for each sample sheet two years later. FIG. 8 is a graph showing the relationship between wavelength and light intensity ratio for each sample sheet. FIG. 9 is a graph showing the optical characteristics (transmittance) of each quantum dot sheet containing blue quantum dots at a wavelength of around 430 nm. FIG. 10 is a graph showing the optical characteristics (transmittance) of each quantum dot sheet containing blue quantum dots at wavelengths of 480 nm or more.

[0012] Hereinafter, one embodiment of the present invention (hereinafter abbreviated as "embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the gist. In this specification, light intensity and photon flux density refer to PPFD (Photosynthetic Photon Flux Density).

[0013] The photosynthesis promotion sheet of this embodiment is a thin sheet that converts the wavelength of non-photosynthetically active light, such as ultraviolet light, contained in sunlight into photosynthetically active light, such as blue or red light, and can effectively promote photosynthesis in photosynthetic subjects, such as agricultural crops and seaweed. A "sheet" generally refers to a structure in which the thickness is small relative to its length and width. "Sheet" can also be read as "film." The photosynthesis promotion sheet of this embodiment is preferably flexible. This allows the shape of the photosynthesis promotion sheet to be changed in various ways to suit the application.

[0014] As shown in Figure 1, light involved in photosynthesis is red light and blue light, but sunlight contains photosynthetically active wavelengths as well as non-photosynthetically active light such as ultraviolet light that is outside the photosynthetically active wavelengths. Therefore, if the light energy of the non-photosynthetically active wavelengths can be absorbed and converted to blue or red light wavelengths, and the light intensity of the photosynthetically active wavelengths can be increased, the photosynthetic rate can be increased and photosynthesis can be promoted. This will promote the growth of agricultural crops, seaweed, etc., and improve their quality.

[0015] Therefore, the inventors have developed a photosynthesis promotion sheet that uses sunlight as it is, without using an LED light source or the like, to convert non-photosynthetically active light into photosynthetically active light, thereby delivering light that is optimal for the growth of photosynthetic organisms.

[0016] FIG. 2( a) shows a photosynthesis promotion sheet 1 according to a first embodiment. As shown in FIG. 2( a), the photosynthesis promotion sheet 1 has a first surface 1a and a second surface 1b, with the first surface 1a and the second surface 1b facing each other in the thickness direction. Both the first surface 1a and the second surface 1b are preferably flat, but may also be curved depending on the application. Here, the first surface 1a is the surface that is irradiated with sunlight L, and the second surface 1b is the surface that faces the target of photosynthesis and emits photosynthetically active light toward the target of photosynthesis. In this way, in this embodiment, sunlight L is irradiated onto the photosynthesis promotion sheet 1, so that non-photosynthetically active light contained in the sunlight L can be converted into photosynthetically active wavelengths. In addition, sunlight L may be directed directly onto the first surface 1a of the photosynthesis promotion sheet 1, or sunlight L may be directed by utilizing reflection, or a member that adjusts the light energy of sunlight L may be placed in front of the first surface 1a of the photosynthesis promotion sheet 1, and sunlight L may be directed through that member.

[0017] The photosynthesis-promoting sheet 1 contains quantum dots 2 and a UV (ultraviolet) scattering agent 3 in a resin 4. The quantum dots 2 have fluorescent properties due to band-edge emission, and exhibit a quantum size effect due to their particle size.

[0018] Quantum dots refer to nanoparticles with a particle size of several nm to several tens of nm. For example, quantum dots include CdS, CdSe, ZnS, ZnSe, ZnSeS, ZnTe, ZnTeS, InP, and AgInS. ２ , CuInS ２ The quantum dots are preferably formed of quantum dots having a structure in which the quantum dots are cores and covered with a shell. Because the use of Cd is restricted in various countries due to its toxicity, it is preferable that the quantum dots do not contain Cd.

[0019] It is preferable that a large number of organic ligands are coordinated to the surface of the quantum dots 2. This makes it possible to suppress aggregation of the quantum dots 2 and to achieve the desired optical properties. There are no particular limitations on the ligands that can be used in the reaction, but the following ligands are representative examples:

[0020] Aliphatic primary amine, oleylamine: C １８ H ３５ NH ２ , stearyl(octadecyl)amine: C １８ H ３７ NH ２ , dodecyl(lauryl)amine: C １２ H ２５ NH ２ , decylamine: C １０ H ２１ NH ２ , octylamine: C ８ H １７ NH ２ Fatty acids, oleic acid: C １７ H ３３ COOH, stearic acid: C １７ H ３５ COOH, palmitic acid: C １５ H ３１ COOH, myristic acid: C １３ H ２７ COOH, lauryl (dodecanoic) acid: C １１ H ２３ COOH, decanoic acid: C ９ H １９ COOH, octanoic acid: C ７ H １５ COOH thiol, octadecanethiol: C １８ H ３７ SH, hexanedecanethiol: C １６ H ３３ SH, tetradecanethiol: C １４ H ２９ SH, dodecanethiol: C １２ H ２５ SH, decanethiol: C １０ H ２１ SH, octanethiol: C ８ H １７ SH phosphine system, trioctylphosphine: (C ８ H １７ ) ３ P, triphenylphosphine: (C ６ H ５ ) ３ P, tributylphosphine: (C ４ H ９ ) ３P Phosphine oxide series, trioctylphosphine oxide: (C ８ H １７ ) ３ P═O, triphenylphosphine oxide: (C ６ H ５ ) ３ P═O, tributylphosphine oxide: (C ４ H ９ ) ３ P=O

[0021] The quantum dot 2 may also have a core-shell structure. That is, a structure in which a core is located at the center and the core is surrounded by a shell. In a core-shell structure, a large number of organic ligands can be coordinated to the surface of the shell. The core is formed of, for example, one of the materials listed above, and the shell may be made of any material, such as zinc sulfide (ZnS). Like the core, the shell preferably does not contain cadmium (Cd).

[0022] The wavelength conversion range can be adjusted by changing the particle size of the quantum dots 2, even if they are made of the same material. Therefore, in order to obtain the optimal photosynthetic wavelength for each photosynthetic target, the particle size of the quantum dots 2 can be adjusted to convert to the optimal wavelength.

[0023] In this embodiment, the quantum dots 2 preferably include at least red quantum dots that emit red light. This allows non-photosynthetically active light to be appropriately converted into red light. Red light has a wavelength of approximately 640 nm to 770 nm, and quantum dots 2 that can cover a wavelength range of approximately 670 nm can be selected.

[0024] It is more preferable that the quantum dots 2 include both red quantum dots that emit red light and blue quantum dots that emit blue light. This allows non-photosynthetically active light to be appropriately converted into both red light and blue light. Blue light has a wavelength of approximately 380 nm to 500 nm, and quantum dots 2 that can cover a wavelength range of, for example, around 430 nm can be selected.

[0025] The quantum dots 2 are preferably contained in an amount of 1% by mass to 10% by mass, and more preferably 2% by mass to 8% by mass, in the photosynthesis-promoting sheet 1. Furthermore, as will be described later, when the photosynthesis-promoting sheet has a multi-layer structure, the content can be determined by the content in the quantum dot sheet containing the quantum dots.

[0026] The UV scattering agent 3 is a component that has the property of scattering ultraviolet light. UV scattering agents that can be used in this embodiment include nanoparticles of titanium oxide, zirconia oxide, zinc oxide, cerium oxide, silica, etc., and one or more of these can be used, or two or more of them can be used in combination. It is particularly preferable to use nanoparticles of titanium oxide (titania) or zirconium oxide (zirconia).

[0027] Thus, one of the features of the photosynthesis promotion sheet 1 of this embodiment is that it contains a UV scattering agent 3 that scatters ultraviolet light, which is non-photosynthetically active light. That is, in this embodiment, sunlight L is irradiated onto the photosynthesis promotion sheet 1, so that ultraviolet light, which is non-photosynthetically active light contained in sunlight L, is also captured by the photosynthesis promotion sheet 1. However, by including a UV scattering agent 3 in the photosynthesis promotion sheet 1, scattering of ultraviolet light within the photosynthesis promotion sheet 1 can be enhanced, and the ultraviolet light can be effectively absorbed by the quantum dots 2 and converted into red or blue photosynthetically active light.

[0028] As shown in Fig. 2(a), the quantum dots 2 and the UV scattering agent 3 are dispersed throughout the resin 4. It is preferable to use an amorphous resin as the resin 4. The amorphous resin is not particularly limited, but a resin with high transparency is used. Generally, a resin with a total light transmittance of 85% or more is preferable, but this is not particularly limited. Examples of amorphous resins include cyclic polyolefin polymer (COP), cyclic polyolefin copolymer (COC), polystyrene (PS), acrylic resin, polycarbonate (PC), modified polyphenylene ether (PPE), polyethylene terephthalate (PET), ethylene vinyl alcohol (EVAL), and polymethylpentene (PMP). Examples of highly transparent semi-crystalline resins include polyethylene (PE) and polypropylene (PMP). A melt-extrudable resin such as PP or poly(vinylidene fluoride) (PVDF) can be used.

[0029] Furthermore, as the amorphous resin constituting the resin molding in which the quantum dots 2 are dispersed, from the viewpoint of the dispersibility of the quantum dots 2 in the resin 4 and the fluorescence intensity after dispersion, acrylic resin, homopolymer (COP) or copolymer (COC) of cyclic olefin resin, polyethylene terephthalate (PET), or polycarbonate (PC) from the viewpoint of heat resistance is preferred.

[0030] The use of acrylic resin can also provide protection from external damage. Alternatively, polyethylene terephthalate resin (PET), ethylene vinyl alcohol (EVAL), or the like can function as a barrier layer against water and oxygen. Alternatively, the use of PET, polycarbonate (PC), cyclic polyolefin (COP), cyclic polyolefin copolymer (COC), or the like can make the sheet less likely to crack and improve the sheet's handling properties.

[0031] Various resins 4 can be selected depending on the usage environment. For example, when the material is used outdoors, it is preferable to use acrylic resin, PET, or the like, or to use a mixture of these resin components, in order to obtain barrier properties and protection from external damage.

[0032] The photosynthesis-promoting sheet 1 shown in FIG. 2( a) can be formed, for example, by extrusion molding. That is, a resin composition obtained by mixing quantum dots 2 and a UV scattering agent 3 in a resin 4 can be molded into a sheet-shaped quantum dot sheet using an extruder. The photosynthesis-promoting sheet 1 preferably contains a metal soap, which can improve mold releasability during extrusion molding. The metal soap is not limited to, but can be one or more appropriately selected from lithium stearate, magnesium stearate, calcium stearate, barium stearate, zinc stearate, calcium laurate, barium laurate, etc.

[0033] Alternatively, a resin composition in which quantum dots 2 and a UV scattering agent 3 are mixed in a resin 4 is applied to the surface of a substrate, and after curing, the substrate is removed, thereby forming a sheet-like quantum dot sheet.

[0034] The photosynthesis promotion sheet 1 of this embodiment can have a thickness t as thin as approximately 50 to 2000 μm, although this is not limited thereto. The photosynthesis promotion sheet 1 may be molded or coated. Furthermore, the length S of one side of the photosynthesis promotion sheet 1 is not limited, and the size can be varied depending on the type of use. For example, a greenhouse can be constructed using the photosynthesis promotion sheet 1 of this embodiment, and the photosynthesis promotion sheet 1 can be coated on glass, attached to glass, or installed on the ceiling. The planar shape of the photosynthesis promotion sheet 1 may be rectangular, square, polygonal, circular, elliptical, or the like. The shape can be adjusted in various ways depending on the application of the photosynthesis promotion sheet 1. In particular, in this embodiment, the photosynthesis promotion sheet 1 can be formed by extrusion molding or coating, which makes it easy to adjust the shape and size, resulting in excellent yield and high manufacturing efficiency.

[0035] The photosynthesis promotion sheet 10 shown in Figure 2(b) has a first surface 11a and a second surface 11b, and is equipped with a quantum dot sheet 11 containing quantum dots 2 that convert non-photosynthetically active light into photosynthetically active light, and a UV scattering layer 12 disposed on the first surface 11a of the quantum dot sheet 11. In Figure 2(b), the same reference numerals as in Figure 2(a) indicate the same components.

[0036] In the photosynthesis promotion sheet 10 shown in Figure 2(b), a UV scattering layer 12 is placed on the first surface 11a, which is the surface of the quantum dot sheet 11 that is irradiated with sunlight L. This causes the ultraviolet light contained in the sunlight L to be appropriately scattered before it reaches the quantum dot sheet 11. Therefore, the quantum dot sheet 11 can effectively absorb the ultraviolet light and convert it into photosynthetically active red and blue light.

[0037] 2(b), the quantum dot sheet 11 may contain a UV scattering agent 3 together with the quantum dots 2, as in FIG. 2(a), but the content may be less than that in FIG. 2(a). In addition, the amount of UV scattering agent 3 per unit volume in the UV scattering layer 12 is preferably greater than that in the quantum dot sheet 11.

[0038] The UV scattering layer 12 can be formed with a structure in which a UV scattering agent 3 is dispersed in a resin 4. The resins 4 constituting the quantum dot sheet 11 and the UV scattering layer 12 may be the same or different materials, but using the same material is preferable because it increases adhesion between the quantum dot sheet 11 and the UV scattering layer 12. Alternatively, when the type of resin 4 is changed, for example, an acrylic resin can be used as the resin 4 used for the UV scattering layer 12 on the sunlight L side to protect it from external damage, and a resin 4 with high barrier properties such as polyethylene terephthalate resin (PET) or ethylene vinyl alcohol (EVAL) can be used for the quantum dot sheet 11 to suppress deterioration due to moisture and oxygen.

[0039] In the photosynthesis-promoting sheet 10 shown in FIG. 2(b), the quantum dot sheet 11 and the UV scattering layer 12 can be integrated by co-extrusion molding. Alternatively, the quantum dot sheet 11 and the UV scattering layer 12 can be formed by coating. Alternatively, a TiO ２ and ZrO ２ The UV scattering layer 12 can also be formed by vapor deposition of inorganic materials such as:

[0040] The photosynthesis promotion sheet 20 shown in Figure 2(c) has a first surface 21a and a second surface 21b, and is equipped with a quantum dot sheet 21 containing quantum dots 2 that convert non-photosynthetically active light into photosynthetically active light, and a dichroic filter layer 22 disposed on the second surface 21b of the quantum dot sheet 21. In Figure 2(c), the same reference numerals as in Figure 2(a) indicate the same components.

[0041] The dichroic filter layer 22 has the property of reflecting ultraviolet light and transmitting visible light. The dichroic filter layer 22 may be made of, for example, TiO 2 having a high refractive index. ２ and SiO with a low refractive index ２ It is a multilayer film in which TiO ２ and SiO ２ are all transparent materials.

[0042] In the photosynthesis promotion sheet 20 shown in Figure 2(c), when sunlight L is irradiated onto the first surface 21a of the quantum dot sheet 21, the quantum dots 2 contained in the quantum dot sheet 21 convert the wavelength of non-photosynthetically active light into photosynthetically active light. At this time, a portion of the ultraviolet light that passes through the quantum dot sheet 21 is reflected by the dichroic filter layer 22. The reflected ultraviolet light is converted into red light or blue light by the quantum dots 2 of the quantum dot sheet 21. Therefore, the intensity of the ultraviolet light radiated from the second surface 21b side of the quantum dot sheet 21 to the photosynthetic target can be weakened as much as possible.

[0043] 2(c) and 2(b) can be combined to form a UV scattering layer 12 on the first surface of the quantum dot sheet and a dichroic filter layer 22 on the second surface of the quantum dot sheet, which can more effectively convert non-photosynthetically active light into photosynthetically active light.

[0044] The photosynthesis-promoting sheet 20 in FIG. 2(c) can also be formed by co-extrusion molding or coating.

[0045] The photosynthesis promoting sheet 30 shown in FIG. 2( d ) has substrates 32 and 33 disposed on a first surface 31 a and a second surface 31 b of a quantum dot sheet 31 , respectively.

[0046] 2(d), the quantum dot sheet 31 has quantum dots 2 and a UV scattering agent 3 dispersed in a resin 4. For the materials of the quantum dots 2, the UV scattering agent 3, and the resin 4, please refer to the description of FIG.

[0047] The quantum dot sheet 31 shown in FIG. 2(d) is a coated sheet, and the quantum dot sheet 31 is coated on one or both of the substrates 32 and 33. When the quantum dot sheet 31 is coated on one of the substrates 32 and 33, the remaining substrates 33 and 32 are attached to the exposed surface of the quantum dot sheet 31 to form a laminated structure. When the quantum dot sheet 31 is coated on both of the substrates 32 and 33, the quantum dot sheets 31 are attached with their inner surfaces facing inward. This allows for a laminated structure in which the substrates 32 and 33 are arranged on both sides of the quantum dot sheet 31. In FIG. 2(d), the substrates 32 and 33 may be arranged on only one side of the quantum dot sheet 31.

[0048] 2(d) can be formed by co-extrusion. In addition, the substrates 32 and 33 are made of a material with excellent barrier properties, so that the quantum dot sheet 31 can be appropriately protected from moisture and oxygen.

[0049] The base materials 32 and 33 are both made of transparent resin, and although there are no restrictions on the material, polyethylene terephthalate (PET) or polycarbonate (PC) can be selected.

[0050] The photosynthesis promotion sheet of the present embodiment has a photon flux density of 0.6 μmol m in a wavelength band of 400 nm or more and 500 nm or less. －２ s －１ It is also preferable that the photon flux density in the wavelength band of 600 nm or more and 700 nm or less is 1.0 μmol m －２ s －１ In this manner, in this embodiment, non-photosynthetically active light such as ultraviolet light contained in sunlight is converted into blue or red photosynthetically active light, thereby effectively increasing the photon flux density of the photosynthetically active light.

[0051] Furthermore, the light intensity ratio between blue and red light remains almost unchanged immediately after use of the photosynthesis-promoting sheet and after several years of use (two years in the experiment), demonstrating that the wavelength conversion function can be maintained for a long period of time.

[0052] A method for producing the photosynthesis-promoting sheet will now be described. As an example, a quantum dot solution, a UV scattering agent solution, and resin pellets are mixed and dried to obtain resin pellets coated with the quantum dots and UV scattering agent on their surfaces.

[0053] The resin pellets are then kneaded using, for example, a twin-screw extruder, and the resulting strands are cut using a pelletizer to obtain resin pellets in which the quantum dots and UV dispersant are dispersed. The resin pellets are then melted and extruded through a T-die using an extrusion molding machine to obtain a sheet-like photosynthesis-promoting sheet 1.

[0054] 2(b), resin pellets in which quantum dots are dispersed and resin pellets in which a UV dispersant is dispersed are fed into separate raw material inlets of a molding machine, and then melted and extruded through a T-die by a co-extrusion molding machine, thereby obtaining a photosynthesis promotion sheet 10 in which a quantum dot sheet 11 and a UV scattering layer 12 are laminated. The photosynthesis promotion sheet 20 in FIG. 2(c) can also be formed by co-extrusion molding or the like. Alternatively, the quantum dot sheet 21 and the dichroic filter layer 22 may be molded separately and then bonded together.

[0055] 2(d), a photosynthesis-promoting sheet 30 is obtained by applying a resin composition containing quantum dots, a UV accelerator, and a resin component to the surface of a substrate 33 and curing the composition to obtain a quantum dot sheet 31. Then, another substrate 32 is attached to the surface of the quantum dot sheet 31, thereby forming a laminated structure in which the substrates 32 and 33 are arranged on both sides of the quantum dot sheet 31.

[0056] The photosynthesis promotion sheet of this embodiment has a simple structure, yet can efficiently convert non-photosynthetically active light from sunlight into photosynthetically active light. The photosynthesis promotion sheet is thin and flexible, and is suitable for use in sunlight, making it suitable for large facilities, farms, etc.

[0057] The effects of the present invention will be explained below by way of examples of the present invention, but the embodiments of the present invention are not limited to the following examples.

[0058] [Experimental Example 1] The following sample sheet was prepared. (Sample Sheet 1) Sample sheet 1 was a photosynthesis-promoting sheet having a laminated structure of a quantum dot sheet 11 shown in FIG. 2(b) and a UV scattering layer 12 disposed on the first surface 11a of the quantum dot sheet 11. The quantum dots 2 contained in the quantum dot sheet 11 were red light-emitting quantum dots (CdSe / ZnS (average particle size: 10-15 nm)). The UV scattering layer 12 contained titanium oxide (approximately spherical with a particle size of approximately 100-300 nm). The quantum dots were contained in the quantum dot sheet 11 at approximately 0.1-0.5% by mass, and the UV scattering agent 3 was contained in the UV scattering layer 12 at approximately 0.5-2% by mass.

[0059] (Sample Sheet 2) A non-wavelength conversion film was used as Sample Sheet 2. Sample Sheet 2 has a configuration in which the quantum dots have been removed from Sample Sheet 1. As shown in FIG. 3 , Sample Sheet 1 was found to be able to effectively increase the photon flux density of red light (wavelength of approximately 630 nm) compared to sunlight while sufficiently reducing the photon flux density (PPFD) of non-photosynthetically active light such as ultraviolet light compared to sunlight. On the other hand, Sample Sheet 2 had a lower photon flux density across the entire wavelength range compared to sunlight, but its photon flux density for ultraviolet light was higher than Sample Sheet 1, and its photon flux density for red light was also lower than sunlight. Based on these experimental results, Sample Sheet 1 was designated as an example, and Sample Sheet 2 was designated as a comparative example.

[0060] [Experimental Example 2] The following sample sheets were produced. (Sample Sheets 3 to 5) Sample sheets 3 to 5 were photosynthesis-promoting sheets having a laminated structure of a quantum dot sheet 11 shown in FIG. 2(b) and a UV scattering layer 12 disposed on the first surface 11a of the quantum dot sheet 11. The quantum dots 2 contained in the quantum dot sheet 11 were blue light quantum dots (ZnSe / ZnSeS / ZnS (average particle size: approximately 10 to 15 nm)) that emit blue light. The UV scattering layer 12 also contained titanium oxide.

[0061] The sheet thickness of sample sheet 3 was 125 μm, the sheet thickness of sample sheet 4 was 187.5 μm, and the sheet thickness of sample sheet 5 was 250 μm.

[0062] (Sample Sheet 6) As Sample Sheet 6, a transparent resin sheet was prepared by removing the quantum dots from Sample Sheet 3.

[0063] 4, it was found that sample sheets 3 to 5 were able to effectively increase the photon flux density of blue light (wavelength of about 470 nm) compared to sunlight, while sufficiently reducing the photon flux density of non-photosynthetically active light such as ultraviolet light compared to sunlight. On the other hand, sample sheet 6 had a lower photon flux density across the entire wavelength range compared to sunlight, but its photon flux density for ultraviolet light was higher than that of sample sheets 3 to 5, and its photon flux density for blue light was also lower than that of sunlight.

[0064] Based on the results of this experiment, sample sheets 3 to 5 were designated as examples, and sample sheet 6 was designated as a comparative example.

[0065] Furthermore, as shown in Samples 3 to 5, it was found that the thicker the sheet, the lower the photon flux density of ultraviolet light and the higher the photon flux density of blue light.

[0066] [Experimental Example 3] The following sample sheet was prepared. (Sample Sheet 7) Sample sheet 7 was a photosynthesis-promoting sheet having a laminated structure of a quantum dot sheet 11 shown in Figure 2(b) and a UV scattering layer 12 disposed on the first surface 11a of the quantum dot sheet 11. The UV scattering layer 12 contained titanium oxide.

[0067] (Sample Sheet 8) The UV scattering layer was removed from Sample 7. Thus, Sample Sheet 8 has a single-layer structure of the quantum dot sheet 11.

[0068] The graph in Figure 5 shows the transmittance (the straightness of light rays) measured by a haze meter with and without a UV scattering layer. As shown in Figure 5, Sample 7 exhibited a sharp drop in transmittance at ultraviolet wavelengths, whereas Sample 8 maintained a flat transmittance even in the ultraviolet wavelength range.

[0069] This indicates that the transmittance of ultraviolet light can be sufficiently reduced by providing a UV scattering layer. Based on the experimental results, Sample 7 was designated as an example, and Sample 8 was designated as a comparative example.

[0070] [Experiment 4] Fig. 6 is a schematic diagram of the spectral distribution measurement method. Reference numeral 40 in Fig. 6 denotes an artificial solar lighting device (light source), reference numeral 42 denotes a spectroradiometer, and a photosynthesis promotion sheet 41 was placed between the artificial solar lighting device 40 and the spectroradiometer 42.

[0071] The photosynthesis promotion sheets 41 used were a sheet containing blue quantum dots with a peak wavelength of 420 nm, a sheet containing red quantum dots with a peak wavelength of 630 nm, and a transparent sheet containing no quantum dots. The quantum dots used were the same as those used in the above experiment.

[0072] In addition, zirconia (with an aspect ratio of approximately 1.5 to 6, a roughly rectangular cross section, and a long side of approximately 15 to 30 nm) was attached to the quantum dot-containing sheet as a UV scattering agent. A SOLAX XC-100BF was used as the artificial sunlight lighting device 40. A HIDAMARI mini s-2440C was used as the spectroradiometer 42.

[0073] In the experiment, the spectral distribution of each sample sheet was measured at the start of the experiment (initial stage) and after it had been used in the cultivation experiment for two years.

[0074] FIG. 7 shows the spectral distribution of each sample sheet immediately after the start of the experiment, and FIG. 8 shows the spectral distribution two years later. The spectral distribution of sample sheet 10 shown in FIG. 7 is the photon flux density of the transparent sheet. The spectral distribution of sample sheet 11 shown in FIG. 7 is the photon flux density of the blue quantum dot sheet. The spectral distribution of sample sheet 12 shown in FIG. 7 is the photon flux density of the red quantum dots. The spectral distribution of sample sheet 13 shown in FIG. 8 is the photon flux density of the transparent sheet. The spectral distribution of sample sheet 14 shown in FIG. 8 is the photon flux density of the blue quantum dot sheet. The spectral distribution of sample sheet 15 shown in FIG. 8 is the photon flux density of the red quantum dots.

[0075] 7 and 8, it was found that sample sheets 11 and 14 can effectively increase the photon flux density of blue light (wavelength: about 470 nm) while sufficiently reducing the photon flux density of non-photosynthetically active light such as ultraviolet light compared to the light source. Also, as shown in Figures 7 and 8, it was found that sample sheets 12 and 15 can effectively increase the photon flux density of red light (wavelength: about 630 nm) compared to sunlight while sufficiently reducing the photon flux density of non-photosynthetically active light such as ultraviolet light compared to the light source.

[0076] FIG. 9 is a graph showing the relationship between wavelength and light intensity ratio for each sample sheet. The light intensity ratio was calculated as the ratio of light intensity to the light source. As shown in sample sheets 11 and 14 in FIG. 9, the light intensity ratio of blue light (wavelength approximately 470 nm) remained almost unchanged immediately after the start of the experiment and two years later. As shown in sample sheets 12 and 15 in FIG. 9, the light intensity ratio of red light (wavelength approximately 630 nm) remained almost unchanged immediately after the start of the experiment and two years later. In other words, it was found that the wavelength conversion function can be maintained even after two years of continuous use.

[0077] [Experiment 5] An experiment on optical properties was conducted using a blue quantum dot sheet. Sample sheet 16 was a blue quantum dot sheet containing 2.5% by mass of blue quantum dots but no scattering agent. Sample sheet 17 was a blue quantum dot sheet containing 5.0% by mass of blue quantum dots but no scattering agent. Sample sheet 18 was a blue quantum dot sheet containing 2.5% by mass of blue quantum dots and a scattering agent. The UV scattering agent used was zirconia (a roughly rectangular cross section with an aspect ratio of approximately 1.5 to 6 and a long side of approximately 15 to 30 nm). Sample sheet 19 was a blue quantum dot sheet containing 2.5% by mass of blue quantum dots and a scattering agent. The UV scattering agent used was titanium oxide (approximately spherical with a particle size of approximately 100 to 300 nm). The scattering agent contained in sample sheet 19 was 0.01% by mass. In sample sheet 18, the amount of scattering agent was diluted 100 times more than in sample sheet 19.

[0078] 10 and 11 are graphs showing the optical characteristics (transmittance) of each quantum dot sheet containing blue quantum dots at wavelengths of around 430 nm and 480 nm, respectively.

[0079] It was found that increasing the content of quantum dots increases the peak intensity near a wavelength of 430 nm, as shown in Figure 10. Furthermore, as shown in Figure 11, the transmittance can be increased overall even at wavelengths other than 430 nm.

[0080] It was also found that increasing the dilution ratio of the scattering agent increased the overall transmittance. The content of the scattering agent is preferably 0.00001% by mass or more and 0.001% by mass or less, and more preferably 0.00005% by mass or more and 0.0005% by mass or less.

[0081] The photosynthesis-promoting sheet of the present invention can efficiently convert non-photosynthetically active light contained in sunlight into photosynthetically active light, thereby promoting the photosynthesis and growth of, for example, agricultural crops and seaweed, thereby improving their quality.

[0082] This application is based on Japanese Patent Application No. 2023-211606, filed December 15, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A photosynthesis promotion sheet containing quantum dots, comprising a quantum dot sheet having a first surface and a second surface opposite to the first surface, the quantum dot sheet converting non-photosynthetically active light into photosynthetically active light, the first surface being a surface that is irradiated with sunlight, the second surface being a surface that emits the photosynthetically active light, and the quantum dot sheet containing the quantum dots and a UV scattering agent.

2. A photosynthesis promotion sheet containing quantum dots, comprising a quantum dot sheet having a first surface and a second surface opposite to the first surface, which converts non-photosynthetically active light into photosynthetically active light, wherein the first surface is a surface that is irradiated with sunlight, and the second surface is a surface that emits the photosynthetically active light, the quantum dot sheet contains at least the quantum dots, and a UV scattering layer is disposed on the first surface of the quantum dot sheet.

3. A photosynthesis promotion sheet containing quantum dots, comprising a quantum dot sheet having a first surface and a second surface opposite to the first surface, which converts non-photosynthetically active light into photosynthetically active light, wherein the first surface is a surface that is irradiated with sunlight, and the second surface is a surface that emits the photosynthetically active light, the quantum dot sheet contains at least the quantum dots, and a dichroic filter layer that reflects UV light and transmits visible light is disposed on the second surface of the quantum dot sheet.

4. The photosynthesis-promoting sheet according to claim 1, characterized in that the quantum dot sheet is an extrusion molded sheet or a coated sheet.

5. The photosynthesis promotion sheet according to claim 1, characterized in that the quantum dots include at least red-emitting quantum dots, or include red-emitting quantum dots and blue-emitting quantum dots.

6. The photon flux density in the wavelength range of 400 nm to 500 nm is 0.6 μmol m －２ s －１ The photosynthesis promoting sheet according to any one of claims 1 to 3, characterized in that:

7. The photon flux density in the wavelength band of 600 nm to 700 nm is 1.0 μmol m －２ s －１ The photosynthesis promoting sheet according to any one of claims 1 to 3, characterized in that:

8. The photosynthesis promotion sheet according to claim 2, characterized in that the content of the quantum dots contained in the quantum dot sheet is 1% by mass or more and 10% by mass or less.

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