Agricultural heat-shielding film

Abstract

This agricultural heat-shielding film comprises: an intermediate layer 2 that contains first resin; an outer layer 3 that contains second resin and is provided on one surface of the intermediate layer 2; and an inner layer 4 that contains third resin and is provided on the other surface of the intermediate layer 2. Endothermic material 5 containing a tungsten-containing compound is dispersed in the outer layer 3 and the inner layer 4.

Description

Agricultural heat-insulating film

[0001] The present invention relates to an agricultural heat-insulating film.

[0002] As a covering material for a greenhouse (an agricultural greenhouse. Hereinafter, it may be referred to as a "house") used in protected horticulture, an agricultural film is known. In some cases, the agricultural film is required to have transparency so that light in the wavelength range necessary for photosynthesis can sufficiently pass through. On the other hand, if the temperature inside the house rises too much, it may lead to deterioration of the growing environment of crops and the working environment of workers. Therefore, in some cases, it is required to suppress excessive heat intrusion into the house while being transparent. Thus, a film having a heat-insulating function (hereinafter referred to as an "agricultural heat-insulating film") may be used as the agricultural film.

[0003] In relation to the above, Patent Document 1 (Japanese Patent Application Laid-Open No. 2019-83749) discloses an agricultural heat-insulating film in which a base film, a heat-insulating layer provided on one surface of the base film, and a hydrophilic layer provided on the other surface of the base film are laminated, and the heat-insulating layer contains cesium tungstate and a synthetic resin. According to the invention of Patent Document 1, excessive heat intrusion into the house can be suppressed by the heat-insulating layer provided on the agricultural heat-insulating film.

[0004] When the heat-insulating property of the agricultural heat-insulating film is enhanced, the amount of heat incident inside the house decreases, so it becomes difficult for the internal temperature of the house to rise.

[0005] On the other hand, when the temperature inside the house drops too much during low-temperature times such as at night or in winter, it may cause a decrease in the quality of crops. Therefore, in addition to heat-insulating properties, the agricultural heat-insulating film may also be required to have a certain degree of heat-preserving property.

[0006] Therefore, an object of the present invention is to provide an agricultural heat-insulating film having excellent heat-insulating and heat-preserving properties.

[0007] An agricultural heat-shielding film according to one aspect of the present invention comprises an intermediate layer containing a first resin, an outer layer containing a second resin and provided on one surface of the intermediate layer, and an inner layer containing a third resin and provided on the other surface of the intermediate layer. A heat-absorbing material containing a tungsten-containing compound is dispersed in the outer layer and the inner layer.

[0008] According to the present invention, an agricultural heat-shielding film with excellent heat-shielding and heat-retaining properties is provided.

[0009] Figure 1 is a schematic cross-sectional view illustrating the agricultural heat-shielding film according to this embodiment. Figure 2 is a graph showing the measurement results of the visible and near-infrared transmittance of Example 1 and Comparative Example 1.

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] Figure 1 is a schematic cross-sectional view illustrating the agricultural heat-shielding film 1 according to this embodiment. As shown in Figure 1, the agricultural heat-shielding film 1 comprises an intermediate layer 2, an outer layer 3 provided on one surface of the intermediate layer 2, and an inner layer 4 provided on the other surface of the intermediate layer 2. The agricultural heat-shielding film 1 according to this embodiment is used as a covering material for greenhouses used in facility horticulture. When the agricultural heat-shielding film 1 is stretched over a greenhouse, the layer facing outwards from the greenhouse is the outer layer 3, and the layer facing inwards from the greenhouse is the inner layer 4.

[0012] The intermediate layer 2, outer layer 3, and inner layer 4 are each formed from a resin composition. The intermediate layer 2 contains a first resin, the outer layer 3 contains a second resin, and the inner layer 4 contains a third resin. Of these, the outer layer 3 and inner layer 4 contain a heat-absorbing material 5 containing a tungsten-containing compound.

[0013] The heat-absorbing material 5 containing a tungsten compound readily transmits light in the wavelength range necessary for photosynthesis, while being less permeable to light in the near-infrared wavelength range, which causes temperature rise. Therefore, by using such a heat-absorbing material 5, it is possible to prevent excessive temperature rise while maintaining high transparency.

[0014] In this embodiment, since the outer layer 3 and inner layer 4 contain a heat-absorbing material 5, a film is realized that is excellent in both heat shielding and heat retention. Specifically, because the outer layer 3 and inner layer 4 contain a heat-absorbing material 5, the incidence of near-infrared components from the outside to the inside of the greenhouse is suppressed, and the amount of heat entering is reduced. This results in high heat shielding performance. In addition, because the inner layer 4 has a heat-absorbing material 5, the release of heat from the inside to the outside of the greenhouse is blocked by the inner layer 4. This results in high heat retention performance.

[0015] Furthermore, according to this embodiment, foaming during film manufacturing can be prevented. More specifically, in this embodiment, the heat-absorbing material 5 is distributed between the outer layer 3 and the inner layer 4. Therefore, the amount (concentration) of the heat-absorbing material 5 in each layer required to obtain the desired heat-shielding properties can be reduced. As will be described in detail later, when manufacturing agricultural heat-shielding films, compositions that serve as raw materials for forming each layer are prepared. If the amount of heat-absorbing material 5 in this composition is too large, foaming is likely to occur during the preparation of the composition. Foaming causes the film to become cloudy, incident light to be scattered, and the transmittance of wavelengths necessary for photosynthesis decreases. In contrast, according to this embodiment, since the heat-absorbing material 5 is distributed between the outer layer 3 and the inner layer 4, the concentration of the heat-absorbing material 5 in each layer can be reduced to a concentration where foaming is not a problem. Therefore, problems related to foaming can be resolved.

[0016] The above is an overview of this embodiment. Next, the detailed configurations of the intermediate layer 2, the outer layer 3, and the inner layer 4 will be described.

[0017] <Intermediate Layer> The intermediate layer 2 is the base layer of the agricultural heat-shielding film 1. The intermediate layer 2 is formed from a resin composition and contains the first resin.

[0018] (First Resin) The first resin is not particularly limited. Examples of the first resin include polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), and polymethylpentene (TPX) polyolefin resins. Examples of polyethylene (PE) include linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE). The first resin may be a single type of resin or a mixture of several types of resins.

[0019] In particular, from the viewpoint of ensuring the flexibility of the agricultural heat-shielding film 1, it is preferable to use ethylene-vinyl acetate copolymer (EVA) as the first resin. The agricultural heat-shielding film 1 is used by being stretched over a greenhouse. From the viewpoint of workability during stretching, it is preferable that the agricultural heat-shielding film 1 has a certain degree of flexibility. If EVA is included in the intermediate layer 2, suitable flexibility can be obtained from the viewpoint of workability during stretching.

[0020] The content of the resin component (i.e., the first resin) in the intermediate layer 2 is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more.

[0021] Furthermore, the thickness of the intermediate layer 2 is, for example, 10 to 150 μm, preferably 30 to 100 μm.

[0022] Furthermore, the content of the intermediate layer 2 in the agricultural heat-shielding film 1 is, for example, 30 to 70% by mass, preferably 40 to 60% by mass, based on the total mass of the intermediate layer 2, the outer layer 3, and the inner layer 4.

[0023] The intermediate layer 2 can contain various additives as needed, such as heat-retaining agents, weather-resistant agents, plasticizers, film-forming aids, thickeners, and heat stabilizers.

[0024] (Heat-retaining agent) Preferably, as shown in Figure 1, the intermediate layer 2 contains a heat-retaining agent 6. The heat-retaining agent 6 is dispersed in the first resin. The inclusion of the heat-retaining agent 6 in the intermediate layer 2 further enhances the heat retention of the agricultural heat-shielding film 1. Examples of the heat-retaining agent 6 include particles containing magnesium oxide, calcium oxide, aluminum oxide, silicon oxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, magnesium carbonate, calcium carbonate, calcium sulfate, magnesium sulfate, aluminum sulfate, lithium phosphate, calcium phosphate, magnesium silicate, calcium silicate, aluminum silicate, calcium aluminate, magnesium aluminosilicate, sodium aluminosilicate, potassium aluminosilicate, calcium aluminosilicate, kaolin, clay, talc, mica, zeolite, and hydrotalcite. In particular, from the viewpoint of ensuring both the heat retention and transparency of the intermediate layer 2, it is preferable to use particles containing hydrotalcite having flat particles.

[0025] The content of the heat-retaining agent 6 in the intermediate layer 2 is, for example, 1% by mass or more and 20% by mass or less. Preferably, from the viewpoint of ensuring sufficient heat retention and transparency of the intermediate layer 2, the content of the heat-retaining agent 6 is 3% by mass or more and 15% by mass or less.

[0026] <Outer and Inner Layers> The outer layer 3 and inner layer 4 each contain a second resin and a third resin, respectively. The heat-absorbing material 5 is dispersed in the second and third resins.

[0027] (Second and Third Resins) The second and third resins can be any resins that can disperse the heat-absorbing material 5 inside them. Examples of the second and third resins include polyolefin resins such as polyethylene (PE), polypropylene (PP), and polymethylpentene (TPX). Examples of polyethylene (PE) include linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE).

[0028] When the first resin contained in the intermediate layer 2 is EVA, the second and third resins are preferably polyethylene (PE) or polypropylene (PP), and more preferably polyethylene (PE). As previously mentioned, EVA has good flexibility from the viewpoint of workability during stretching. On the other hand, if EVA is exposed, blocking may occur. In contrast, PE and PP have excellent blocking resistance. If PE and PP as described above are used as the second and third resins, the surface of the intermediate layer 2 containing EVA will be covered with a material that is less prone to blocking, thus preventing the occurrence of blocking.

[0029] The second and third resins may be the same type of resin or different types of resins. In a preferred embodiment, the third resin comprises a mixture of LLDPE and LDPE, and the second resin comprises LLDPE.

[0030] The content of resin components (i.e., second resin and third resin) in the outer layer 3 and the inner layer 4 is, for example, 30% by mass or more, preferably 35% by mass or more, and more preferably 45% by mass or more.

[0031] (Heat-absorbing material) The heat-absorbing material 5 is a particle that has heat-absorbing properties. By using the heat-absorbing material 5, heat-shielding properties can be imparted to the film.

[0032] The heat-absorbing material 5 only needs to contain a tungsten-containing compound. Examples of tungsten-containing compounds include tungsten oxide.

[0033] Tungsten oxide may be a simple tungsten oxide, or it may be a composite oxide containing metals other than tungsten. Examples of metals other than tungsten include potassium, rubidium, cesium, and thallium. In particular, cesium tungsten oxide is preferred because it has extremely high heat-shielding properties and low visible light absorption.

[0034] Furthermore, the average particle size of the tungsten-containing compound is preferably 1 to 100 nm, and more preferably 10 to 50 nm.

[0035] The content of the heat-absorbing material 5 in the outer layer 3 and inner layer 4 is, for example, 0.50% by mass or less, preferably 0.01% by mass or more and 0.50% by mass or less, and more preferably 0.05% by mass or more and 0.2% by mass or less, based on the element tungsten. With such an amount, sufficient heat shielding and heat retention can be obtained without impairing transparency. The content of the heat-absorbing material 5 based on the element tungsten (i.e., tungsten content) can be determined, for example, by fluorescent X-ray analysis.

[0036] In addition, if the content of the heat-absorbing material 5 is 0.50% by mass or less based on tungsten element, foaming during manufacturing can be reduced. When manufacturing an agricultural heat-shielding film, a composition for forming the outer layer and inner layer is prepared, and the prepared composition is molded into a film. This composition includes the second resin and third resin described above, and the heat-absorbing material 5. As previously stated, if the content of the tungsten-containing compound in the composition is too high, the composition will foam, making it difficult to obtain an agricultural heat-shielding film with the desired properties. On the other hand, if the content of the heat-absorbing material 5 is within the above range, the problem of foaming is less likely to occur.

[0037] Furthermore, the outer layer 3 and inner layer 4 may contain other additives as needed. Examples of other additives include the heat-retaining agents mentioned above, as well as weather-resistant agents, antiblocking agents, plasticizers, film-forming aids, thickeners, and heat stabilizers described later.

[0038] In a preferred embodiment, the outer layer 3 and inner layer 4 also contain a heat-retaining agent. However, it is more preferable that the heat-retaining agent content (mass%) in the intermediate layer 2 is greater than the heat-retaining agent content (mass%) in the outer layer 3 and inner layer 4.

[0039] The thickness of the outer layer 3 and the inner layer 4 is, for example, 10 to 50 μm, preferably 15 to 40 μm, from the viewpoint of ensuring sufficient heat shielding, transparency, and heat retention of the agricultural heat shielding film 1.

[0040] Furthermore, the content of the outer layer 3 and inner layer 4 in the agricultural heat-shielding film 1 is, for example, 15 to 35% by mass, preferably 20 to 30% by mass, based on the total mass of the intermediate layer 2, outer layer 3, and inner layer 4.

[0041] (Thickness of Agricultural Heat-Insulating Film) The overall thickness of the agricultural heat-insulating film 1 is, for example, 30 to 300 μm, preferably 50 to 200 μm.

[0042] (Transparency) As described above, the agricultural heat-insulating film 1 according to the present embodiment has high transparency. For example, the visible light transmittance (average value of transmittance in the wavelength range of 400 to 700 nm) of the agricultural heat-insulating film 1 is 80% or more. In a preferred embodiment, the visible light transmittance is 86% or more. The higher the transmittance in this wavelength range, the more preferable it is for plant photosynthesis and growth.

[0043] (Heat-Insulating Property) As described above, the agricultural heat-insulating film 1 according to the present embodiment has high heat-insulating property. The near-infrared transmittance (average value of light transmittance in the wavelength range of 780 to 2500 nm) of the agricultural heat-insulating film 1 is, for example, 80% or less, and in a preferred embodiment, 77% or less. The lower the transmittance in this wavelength range, the higher the heat-insulating effect.

[0044] (Others) The intermediate layer 2, outer layer 3, and inner layer 4 may contain additives other than the above-mentioned components. Hereinafter, other typical additives will be described.

[0045] (Weathering Agent) Adding a weathering agent improves the weather resistance of each layer.

[0046] Examples of the weathering agent include ultraviolet absorbers such as benzotriazole-based, triazine-based, benzophenone-based, phenyl salicylate-based, and cyanoacrylate-based, and hindered amine-based light stabilizers.

[0047] When adding a weathering agent, the content of the weathering agent in each layer is, for example, 1 to 20% by mass, preferably 3 to 10% by mass.

[0048] Since the agricultural heat-insulating film 1 is extended in a greenhouse and used outdoors, it will be constantly exposed to outside air, sunlight, wind and rain, etc. Therefore, it is required to have good weather resistance for long-term use. In contrast, by containing 1% by mass or more of the weathering agent, the weather resistance of each layer can be sufficiently ensured.

[0049] On the other hand, if the weather-resistant agent content in the outer layer 3 and inner layer 4 is too high, it can easily cause a bleeding phenomenon where the weather-resistant agent seeps out onto the surface of each layer. When a bleeding phenomenon occurs, the surfaces of the agricultural heat-shielding film 1 stick together due to a blocking phenomenon, reducing its handling properties. In contrast, if the weather-resistant agent content is 20% by mass or less, the occurrence of the bleeding phenomenon can be suppressed, and the resulting reduction in handling properties can be prevented.

[0050] (Antiblocking agent) By adding an antiblocking agent to the outer layer 3 and the inner layer 4, the blocking resistance of each layer is improved.

[0051] Examples of antiblocking agents include synthetic silica powder, synthetic aluminosilicate powder, polymer beads, and silicone resin compounds.

[0052] (Anti-fogging agent) The agricultural heat-shielding film may also have an anti-fogging agent applied to the inner layer 4. As the anti-fogging agent, a general type of anti-fogging agent applied to agricultural films can be used. Specifically, an anti-fogging agent containing silica colloid particles and alumina colloid particles can be used.

[0053] (Method for manufacturing agricultural heat-shielding film) The method for manufacturing the agricultural heat-shielding film 1 is not particularly limited. For example, the agricultural heat-shielding film 1 having a multilayer structure can be manufactured by co-extrusion. For example, the inflation method can be used as the extrusion molding.

[0054] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the essence of the invention.

[0055] <Evaluation Method>

[0056] <Transparency and Heat Shielding 1> The spectral transmittance of the sample film and the comparison film at each wavelength from 300 to 2500 nm was measured using a UV-Vis-Near-Infrared Spectrophotometer (V-770) manufactured by JASCO. Subsequently, the average value of the spectral transmittance (visible light transmittance) at wavelengths from 400 to 700 nm was calculated to evaluate the transparency of each film. In addition, the average value of the spectral transmittance (near-infrared transmittance) at 780 to 2500 nm was calculated to evaluate the heat shielding properties of each film.

[0057] <Heat Shielding and Heat Retention> In a field greenhouse, the sample film and the comparison film were laid out as covering materials in a pipe greenhouse, and the heat shielding performance was evaluated by measuring the maximum temperature inside each greenhouse over several days during the summer. In addition, the heat retention performance was evaluated by measuring the minimum temperature inside each greenhouse over several days during the winter.

[0058] (Example 1) An intermediate layer composition, an inner layer composition, and an outer layer composition were prepared. The prepared compositions were molded using a co-extrusion extrusion molding method (inflation method) to obtain an agricultural heat-shielding film according to Example 1. No significant foaming was observed during the preparation of each composition.

[0059] Table 1 shows the composition and thickness of each layer. The content of the intermediate layer relative to the total mass of the agricultural heat-shielding film was 50% by mass, while the content of the outer layer and inner layer was 25% by mass each. Each of the inner and outer layers contained 28% by mass of heat-absorbing material. The heat-absorbing material used was a material containing tungsten cesium oxide in LLDPE. The tungsten content in the heat-absorbing material was 0.39% by mass, as determined by X-ray fluorescence analysis. Therefore, the tungsten content of the heat-absorbing material in each of the inner and outer layers, based on elemental tungsten, was approximately 0.11% (≒0.28 × 0.0039 × 100). In addition, particles containing hydrotalcite were used as the heat-insulating agent.

[0060]

[0061] (Comparative Example 1) As Comparative Example 1, an agricultural heat-shielding film (thickness 150 μm) related to commercially available product A was prepared. Commercial product A has an intermediate layer, an outer layer, and an inner layer, but the heat-absorbing material is contained only in the intermediate layer.

[0062] (Comparative Example 2) As Comparative Example 2, a commercially available transparent agricultural film (thickness 100 μm) related to product B was prepared. Commercial product B had an intermediate layer, an outer layer, and an inner layer, but none of the layers contained a heat-absorbing material.

[0063] Transparency and heat shielding properties 1 were measured for Example 1 and Comparative Example 1 using the method described above. Heat shielding properties 2 and heat retention properties were also measured for Example 1 and Comparative Example 2 using the method described above. The evaluation results are shown in Figure 2 and Table 2.

[0064]

[0065] Figure 2 is a graph showing the measurement results of visible and near-infrared transmittance for Example 1 and Comparative Example 1.

[0066] As shown in Figure 2, Example 1 showed a slight increase in visible light transmittance in the 400-700 nm wavelength range, which is necessary for crop growth, compared to Comparative Example 1. On the other hand, Example 1 showed a decrease in infrared transmittance in the 780-2500 nm wavelength range compared to Comparative Example 1.

[0067] Furthermore, comparing Example 1 with Comparative Example 2, which lacked a heat-absorbing material, Example 1 showed a heat shielding performance of nearly 3°C lower, while there was almost no difference in heat retention. In other words, Example 1 was superior to Comparative Example 2 in terms of heat shielding performance, while its heat retention performance was equivalent to that of Comparative Example 2. As previously mentioned, it is generally expected that increasing heat shielding performance will reduce the amount of heat entering the greenhouse, thus lowering heat retention performance. However, contrary to this expectation, Example 1 shows that heat shielding performance is improved without compromising heat retention performance.

[0068] (Investigation of foaming properties) To investigate foaming properties, inner and outer layer compositions were prepared for samples 1 to 4, each with a different heat-shielding material content, as described below. Although the content of components other than the heat-shielding material in these compositions differed slightly from that of Example 1, the differences were kept within a range that did not affect foaming properties. The prepared inner and outer layer compositions were used for the inner and outer layers, and a film having a three-layer structure was formed in the same manner as in Example 1, and the presence or absence of foaming during molding was observed.

[0069] (Sample 1) A composition containing 14% by mass of a heat-shielding material with a tungsten content of 4.79% by mass (the tungsten content of the heat-shielding material in the composition is approximately 0.67% by mass) (Sample 2) A composition containing 7.0% by mass of a heat-shielding material with a tungsten content of 4.79% by mass (the tungsten content of the heat-shielding material in the composition is approximately 0.34% by mass) (Sample 3) A composition containing 10% by mass of a heat-shielding material with a tungsten content of 4.79% by mass (the tungsten content of the heat-shielding material in the composition is approximately 0.48% by mass) (Sample 4) A composition containing 40% by mass of a heat-shielding material with a tungsten content of 0.39% by mass (the same as the one used in Example 1) (the tungsten content of the heat-shielding material in the composition is approximately 0.16% by mass)

[0070] Of samples 1 to 4, foaming was observed in sample 1. On the other hand, foaming was not observed in samples 2 to 4. Furthermore, as previously mentioned, foaming was not observed during molding in Example 1 (the content of the heat-absorbing material based on tungsten element in the inner and outer layers was approximately 0.11 mass%). From this, it was found that foaming can be suppressed if the content of the heat-absorbing material is 0.48 mass% or less based on tungsten element.

[0071] (Investigation of the location of the heat-absorbing material) As Comparative Example 3, a film was prepared in which the total amount of heat-absorbing material contained in the film was the same as in Example 1, but the heat-absorbing material was contained in the intermediate layer instead of the inner and outer layers.

[0072] For Comparative Example 3, transparency and heat shielding properties 1 were evaluated using the method described above.

[0073] Furthermore, the heat transfer coefficient was measured for Example 1 and Comparative Example 3 to evaluate their heat retention (heat retention 2). The heat transfer coefficient is a known parameter used to evaluate heat retention, and a smaller value indicates higher heat retention. Specifically, the heat transfer coefficient was measured at -15°C to 25°C using an ESPECMIC constant temperature chamber.

[0074] In addition, the heat retention index was measured for Example 1 and Comparative Example 3 to evaluate their heat retention (heat retention 3). The heat retention index is a well-known parameter used to evaluate heat retention, and a higher value indicates better heat retention. Specifically, the heat retention index was measured using a heat retention meter (FT / IR4600) manufactured by JASCO.

[0075]

[0076] As a result, as shown in Table 3, it was found that Example 1 has the same level of transparency and heat shielding properties as Comparative Example 3.

[0077] On the other hand, the heat transfer coefficient for Comparative Example 3 was 8.96 ± 0.07 W / m². ２ In contrast to the previous example, Example 1 showed 8.29 ± 0.07 W / m². ２ The value was / K. In other words, Example 1 showed a smaller value. Furthermore, in terms of heat retention index, Example 1 showed a larger value than Comparative Example 3. From this, it can be understood that Example 1 is superior to Comparative Example 3 in terms of heat retention. In other words, it can be seen that including heat-absorbing material in both the outer and inner layers results in higher heat retention compared to the case where heat-absorbing material is included only in the intermediate layer.

[0078] [Note] The main embodiments and their effects included in the present invention are summarized below as a note.

[0079] (Note 1) An agricultural heat-shielding film comprising an intermediate layer 2 containing a first resin, an outer layer 3 containing a second resin and provided on one surface of the intermediate layer 2, and an inner layer 4 containing a third resin and provided on the other surface of the intermediate layer 2, wherein a heat-absorbing material 5 containing a tungsten-containing compound is dispersed in the outer layer 3 and the inner layer 4.

[0080] (Note 2) An agricultural heat-shielding film as described in Note 1, wherein the second resin and the third resin are polyethylene.

[0081] (Note 3) An agricultural heat-shielding film as described in Note 1 or 2, wherein the first resin is EVA (ethylene-vinyl acetate copolymer).

[0082] (Note 4) An agricultural heat-shielding film as described in any one of Notes 1 to 3, wherein the content of the heat-absorbing material 5 in the outer layer 3 and inner layer 4 is 0.50% by mass or less, based on the element tungsten.

[0083] (Note 5) An agricultural heat-shielding film as described in any one of Notes 1 to 4, wherein a heat-insulating agent 6 is dispersed in the intermediate layer 2.

[0084] 1: Agricultural heat-shielding film, 2: Intermediate layer, 3: Outer layer, 4: Inner layer, 5: Heat-absorbing material, 6: Heat-retaining agent

Claims

1. An agricultural heat-shielding film comprising: an intermediate layer containing a first resin; an outer layer containing a second resin and provided on one surface of the intermediate layer; and an inner layer containing a third resin and provided on the other surface of the intermediate layer, wherein a heat-absorbing material containing a tungsten-containing compound is dispersed in the outer layer and the inner layer.

2. An agricultural heat-shielding film according to claim 1, wherein the second resin and the third resin are polyethylene.

3. An agricultural heat-shielding film according to claim 1, wherein the first resin is EVA (ethylene-vinyl acetate copolymer).

4. An agricultural heat-shielding film according to claim 1 or 2, wherein the content of the heat-absorbing material in the outer layer and the inner layer is 0.50% by mass or less based on the element tungsten.

5. An agricultural heat-shielding film according to claim 1 or 3, wherein a heat-retaining agent is dispersed in the intermediate layer.

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