Radiative cooling film

Abstract

Provided in the present application is a radiative cooling film, comprising a base film layer, wherein the base film layer comprises a resin matrix, and a plurality of isolated cells, a plurality of separate first particles and a plurality of cell-enveloped second particles, which are all dispersed in the resin matrix. In the radiative cooling film using the technical solution of the present application, air in the cells in the base film layer is a substance with a low refractive index, the first particles and the second particles are each a substance with a high refractive index, and there are differences between the refractive index of the air in the cells and the refractive indices of the first particles and the second particles, thereby improving the reflectivity of the base film layer; by controlling the differences between the refractive index of the air in the cells and the refractive indices of the first particles and the second particles, high reflectivity is achieved; moreover, since the radiative cooling film of the present application does not contain a metal coating, signal shielding can be avoided, which is beneficial to the wide application of the radiative cooling film.

Description

Radiation refrigeration film TECHNICAL FIELD

[0001] The present application relates to the technical field of radiation refrigeration, in particular to a radiation refrigeration film. BACKGROUND

[0002] In recent years, with the introduction of the national "energy saving and emission reduction" policy, radiation refrigeration technology has developed rapidly. Radiation refrigeration is a technology that converts heat into electromagnetic waves of "8 μm~13 μm", and then dissipates the electromagnetic waves to outer space through the "8 μm~13 μm" window of the atmosphere to achieve the effect of cooling and refrigeration. The radiation refrigeration film is a thin film based on radiation refrigeration technology and has refrigeration function. TECHNICAL PROBLEM

[0003] At present, the radiation refrigeration film is mainly prepared by combining high-reflective coating (such as silver, aluminum, indium, etc.) with high-emissivity particles. However, these high-reflective coatings have shielding effect on signals, so that the radiation refrigeration film cannot be used in some devices with internal signal emission sources. TECHNICAL SOLUTION

[0004] The purpose of the present application is to provide a radiation refrigeration film which can solve the problem of signal shielding.

[0005] The present application provides a radiation refrigeration film, which comprises a base film layer, and the base film layer comprises a resin matrix and a plurality of independent cells, a plurality of independent first particles and a plurality of second particles wrapped by the cells dispersed in the resin matrix.

[0006] In a feasible implementation mode, the ratio of the total volume of the plurality of independent cells, the plurality of independent first particles and the plurality of second particles wrapped by the cells to the volume of the resin matrix is (0.15-0.5):1.

[0007] In a feasible implementation mode, the diameter of the cell is 0.5 μm~2 μm;

[0008] The resin matrix is a polyethylene matrix, a polypropylene matrix, a polymethyl methacrylate matrix, a polyethylene terephthalate matrix, a polyvinyl chloride matrix or a polyvinyl fluoride matrix;

[0009] The thickness of the base film layer is 30 μm~200 μm.

[0010] In a feasible implementation mode, the first particles and the second particles are both silica, titanium dioxide, barium sulfate, aluminum oxide or calcium carbonate;

[0011] The particle size of the first particles and the second particles is 200 nm~800 nm.

[0012] In an implementable implementation, the radiative cooling film further comprises a self-cleaning layer, an adhesive layer and a release layer, the self-cleaning layer is located on one side of the base film layer, the adhesive layer is located on the other side of the base film layer, and the release layer is located on the side of the adhesive layer away from the base film layer.

[0013] In an implementable implementation, the self-cleaning layer is a polymer layer containing silicon or fluorine; or the surface of the self-cleaning layer away from the base film layer has a micro-nano structure, and the micro-nano structure comprises alternating convex portions and concave portions.

[0014] The thickness of the self-cleaning layer is 200 nm to 500 nm.

[0015] In an implementable implementation, the adhesive layer is an acrylic adhesive.

[0016] The thickness of the adhesive layer is 20 μm to 100 μm.

[0017] In an implementable implementation, the release layer is a release film or a release paper.

[0018] The release film is a PET release film or a CPP release film.

[0019] In an implementable implementation, the radiative cooling film further comprises a thermal radiation layer, and the thermal radiation layer is located between the base film layer and the self-cleaning layer or between the base film layer and the adhesive layer.

[0020] In an implementable implementation, the thermal radiation layer comprises a coating matrix and cooling particles dispersed in the coating matrix.

[0021] The coating matrix is an acrylic coating matrix, an epoxy coating matrix or a polyester coating matrix.

[0022] The cooling particles in the thermal radiation layer are silicon dioxide, titanium dioxide, barium sulfate, aluminum oxide or calcium carbonate.

[0023] The particle size of the cooling particles in the thermal radiation layer is 1 μm to 10 μm.

[0024] The thickness of the thermal radiation layer is 10 μm to 50 μm. Advantages

[0025] The radiation cooling film provided by the present application has air in the pores of the base film layer as a low refractive index material, and the first particles and the second particles as high refractive index materials. The air in the pores and the first particles and the second particles have a refractive index difference, so that the reflectivity of the base film layer is improved. The radiation cooling film of the present application has a high reflectivity by controlling the refractive index between the air in the pores and the first particles and the second particles. In addition, the radiation cooling film of the present application does not contain a metal plating layer, so that signal shielding can be avoided, and the radiation cooling film can be widely applied. BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a schematic view of the radiation cooling film according to the first embodiment of the present application.

[0027] FIG. 2 is a schematic view of the base film layer of the radiation cooling film according to the first embodiment of the present application.

[0028] FIG. 3 is a schematic view of the radiation cooling film according to the second embodiment of the present application.

[0029] FIG. 4 is a schematic view of the radiation cooling film according to the third embodiment of the present application. EMBODIMENTS OF THE INVENTION

[0030] In order to make the above objects, features and advantages of the present application more clear and easily understood, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a number of ways other than those specifically described herein, and the present application is not limited to the embodiments described below. It can be easily understood by those skilled in the art that the present application can be implemented in other specific forms without changing the technical concept or essential characteristics of the present application. Accordingly, it should be understood that the embodiments described herein are illustrative only and not restrictive ones.

[0031] It should be noted that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can also be present. The terms "vertical", "horizontal", "left", "right" and similar expressions as used herein are for the purpose of illustration only.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0033] Please refer to FIG. 1 and FIG. 2, the radiant cooling film 100 of the first embodiment of the present application comprises a base film layer 110. The base film layer 110 comprises a resin matrix 111 and a plurality of independent cells 112, a plurality of independent first particles 113 and a plurality of second particles 114 wrapped by the cells 112.

[0034] The material of the resin matrix 111 can comprise polymethyl methacrylate (PMMA) and the like, and can further comprise some additives, such as ultraviolet aging agent and the like.

[0035] The "plurality" means indefinite quantity, which can be one, two or more than two.

[0036] The base film layer 110 is a porous film, the independent cells 112 refer to the cells without wrapping particles, and the independent first particles 113 refer to the particles without being wrapped by the cells 112. The first particles 113 and the second particles 114 play a reflecting role. Further, the first particles 113 and the second particles 114 are both opaque inorganic particles.

[0037] In the radiant cooling film 100 of the embodiment, the air in the cells 112 in the base film layer 110 is a low refractive index material, the first particles 113 and the second particles 114 are high refractive index materials, and the air in the cells 112 and the first particles 113 and the second particles 114 have refractive index difference, so that the reflectivity of the base film layer 110 is improved. Therefore, the radiant cooling film 100 of the embodiment realizes high reflectivity by controlling the refractive index between the air in the cells 112 and the first particles 113 and the second particles 114. Since the radiant cooling film 100 of the embodiment does not contain a metal plating layer, signal shielding can be avoided, which is conducive to the wide application of the radiant cooling film 100. Further, the radiant cooling film 100 of the embodiment also has high weather resistance and aging resistance, and the decay rate is slowed down when used outdoors.

[0038] On the basis of the foregoing embodiment, the ratio of the total volume of the plurality of independent cells 112, the plurality of independent first particles 113 and the plurality of second particles 114 wrapped by the cells 112 to the volume of the resin matrix 111 is (0.15-0.5):1. Further, the ratio of the total volume of the plurality of independent cells 112, the plurality of independent first particles 113 and the plurality of second particles 114 wrapped by the cells 112 to the volume of the resin matrix 111 can be but is not limited to 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1 or 0.5:1. The present application can obtain the best reflectivity by controlling the number and size of the first particles 113, the second particles 114 and the cells 112.

[0039] On the basis of the foregoing embodiment, the diameter of the cell 112 is 0.5 μm to 2 μm. Further, the diameter of the cell 112 can be, but is not limited to, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, or 2 μm. Still further, the diameter of the cell 112 is preferably 1 μm to 1.5 μm.

[0040] On the basis of the foregoing embodiment, the resin matrix 110 is a polyethylene matrix, a polypropylene matrix, a polymethyl methacrylate matrix, a polyethylene terephthalate matrix, a polyvinyl chloride matrix, or a polyvinyl fluoride matrix.

[0041] On the basis of the foregoing embodiment, the thickness of the base film layer 110 is 30 μm to 200 μm. Further, the thickness of the base film layer 110 can be, but is not limited to, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, or 200 μm.

[0042] On the basis of the foregoing embodiment, both the first particles 113 and the second particles 114 in the base film layer 110 are silica, titanium dioxide, barium sulfate, aluminum oxide, or calcium carbonate.

[0043] On the basis of the foregoing embodiment, the particle size of both the first particles 113 and the second particles 114 in the base film layer 110 is 200 nm to 800 nm. Further, the particle size of the first particles 113 and the second particles 114 can be, but is not limited to, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, or 800 nm. Still further, the particle size of the first particles 113 and the second particles 114 is preferably 400 nm to 600 nm.

[0044] The base film layer 110 of the present embodiment is prepared by melt-extruding a plastic master batch, inorganic particles, and a foaming agent, and then stretching the extrudate in two directions. The melt-extruding process foams the extrudate to form the round cells 112, and the stretching process stretches the cells 112 from round to oval. Further, the foaming agent is an azo compound, a sulfonhydrazide compound, polymethyl pentene, a nitroso compound, or a cyclic olefin copolymer resin, and the azo compound can be azodicarbonamide. Further, the mass ratio of the inorganic particles to the foaming agent is 1: (0.3 to 0.8), and is preferably 1:0.5.

[0045] On the basis of the foregoing embodiment, the radiative cooling film 100 further comprises a self-cleaning layer 120, an adhesive layer 130 and a release layer 140, the self-cleaning layer 120 is located on one side of the base film layer 110, the adhesive layer 130 is located on the other side of the base film layer 110, and the release layer 140 is located on the side of the adhesive layer 130 away from the base film layer 110.

[0046] On the basis of the foregoing embodiment, the self-cleaning layer 120 is a polymer layer containing silicon or fluorine to achieve the self-cleaning function. Specifically, the polymer layer containing silicon or fluorine can be one or a combination of more than one of silicone resin, fluorocarbon resin and fluorocarbon modified particles. The thickness of the self-cleaning layer 120 is 200 nm to 500 nm. Further, the thickness of the self-cleaning layer 120 can be but is not limited to 200 nm, 300 nm, 400 nm or 500 nm.

[0047] On the basis of the foregoing embodiment, the adhesive layer 130 is an acrylic adhesive, and the thickness of the adhesive layer 130 is 20 μm to 100 μm. Further, the thickness of the adhesive layer 130 can be but is not limited to 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm.

[0048] On the basis of the foregoing embodiment, the release layer 140 is a release film or a release paper. Further, the release film is a PET release film or a CPP release film.

[0049] On the basis of the foregoing embodiment, the radiative cooling film 100 further comprises a thermal radiation layer 150, which is located between the base film layer 110 and the self-cleaning layer 120. The thermal radiation layer 150 is used to emit heat in the form of infrared radiation through the "atmospheric window".

[0050] On the basis of the foregoing embodiment, the thermal radiation layer 150 comprises a coating matrix 151 and cooling particles 152 dispersed in the coating matrix. The cooling particles 152 have high emissivity in the 8 μm to 13 μm wave band, so that the thermal radiation layer 150 can emit heat in the form of infrared radiation through the "atmospheric window". Further, the cooling particles 152 are inorganic particles.

[0051] Further, the coating base 151 is an acrylic coating base, an epoxy coating base, or a polyester coating base. Further, the refrigeration particles 152 in the heat radiation layer 150 are silicon dioxide, titanium dioxide, barium sulfate, aluminum oxide, or calcium carbonate. Further, the particle size of the refrigeration particles 152 in the heat radiation layer 150 is 1 μm to 10 μm. Further, the particle size of the refrigeration particles 152 in the heat radiation layer 150 can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. Further, the thickness of the heat radiation layer 150 is 10 μm to 50 μm. Further, the thickness of the heat radiation layer 150 can be, but is not limited to, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm.

[0052] The heat radiation layer 150 of the present embodiment is a transparent coating layer prepared by mixing a coating material with the refrigeration particles 152, and the mass ratio of the coating material to the refrigeration particles 152 is 10: (0.1 to 2). Further, the mass ratio of the coating material to the refrigeration particles 152 is preferably 10: (0.3 to 0.5).

[0053] It should be further noted that the structure of the self-cleaning layer in the radiation refrigeration film of the present application is not limited to the first embodiment described above, but can also be other structures.

[0054] Referring to FIG. 3, the radiation refrigeration film 200 of the second embodiment of the present application comprises a self-cleaning layer 210, a heat radiation layer 220, a base film layer 230, an adhesive layer 240, and a release layer 250 which are sequentially stacked. The surface of the self-cleaning layer 210 away from the base film layer 230 has a micro-nano structure 211 comprising alternating convex portions 212 and concave portions 213 to achieve the self-cleaning function.

[0055] In addition, the position of the heat radiation layer in the radiation refrigeration film of the present application is not limited to the first embodiment described above, but can also be between the base film layer and the adhesive layer.

[0056] Referring to FIG. 4, the radiation refrigeration film 300 of the third embodiment of the present application comprises a self-cleaning layer 310, a base film layer 320, a heat radiation layer 330, an adhesive layer 340, and a release layer 350 which are sequentially stacked. The heat radiation layer 330 is located between the base film layer 320 and the adhesive layer 340.

[0057] The air in the pores in the base film layer of the radiation cooling film provided by the technical scheme of the present application is a low-refractive-index substance, and the first particles and the second particles are high-refractive-index substances, so that the refractive index difference between the air in the pores and the first particles and the second particles increases the reflectivity of the base film layer. Therefore, the radiation cooling film provided by the present application realizes high reflectivity by controlling the refractive index difference between the air in the pores and the first particles and the second particles. Since the radiation cooling film provided by the present application does not contain a metal plating layer, signal shielding can be avoided, and the radiation cooling film is conducive to wide application. Further, the radiation cooling film provided by the present application also has high weather resistance and aging resistance, and the decay rate is reduced when used outdoors. In addition, the radiation cooling film provided by the present application can also reduce costs.

[0058] With reference to the above implementation, in order to make the technical scheme of the present application more specific, clear and easy to understand, the technical scheme of the present application will be exemplified, but it should be noted that the content to be protected by the present application is not limited to the following examples.

[0059] Example 1

[0060] The present embodiment provides a radiation cooling film and a preparation method thereof, wherein the structure of the radiation cooling film is shown in FIG. 1 and FIG. 2. The preparation method is as follows:

[0061] According to Table 1, each raw material is weighed according to the mass ratio; poly (methyl methacrylate) (PMMA), titanium dioxide (particle size 500 nm), azodicarbonamide (azo compound) and 2,4-dihydroxybenzophenone (ultraviolet aging agent) are added to a trough, and then extruded into a film through a melt extruder, and the film is bidirectional stretched to obtain a porous base film, i.e. a base film layer, with a thickness of 80 μm; then a thermal radiation layer (raw materials are shown in Table 2) and a nano self-cleaning layer (specifically, a polysiloxane resin) are coated on the surface of the base film layer in sequence, with thicknesses of 20 μm and 300 nm, respectively; then an acrylic adhesive composite CPP release film is coated on the back of the base film layer, with an acrylic adhesive thickness of 50 μm and a CPP release film thickness of 23 μm.

[0062] Example 2

[0063] The present embodiment provides a radiation cooling film, which has the same structure and preparation method as the radiation cooling film of Example 1, and the only difference is that the proportion of the raw materials of the base film layer is different, which is shown in Table 1.

[0064] Example 3

[0065] The present embodiment provides a radiation cooling film, which has the same structure and preparation method as the radiation cooling film of Example 2, and the only difference is that the thickness of the base film layer is different, which is specifically 100 μm.

[0066] Example 4

[0067] The embodiment provides a radiation cooling film, which has the same structure and preparation method as the radiation cooling film in Embodiment 3, and the only difference is that the plastic master batch is polyethylene terephthalate diethyl ester.

[0068] Comparative Example 1

[0069] A UV glue is used to mold a frosted structure on the surface of a 100-micron PET base film, a thermal radiation layer with a thickness of 20 microns is coated on the back of the PET, and silver is plated, the thickness of the silver layer is 200 nm, and an acrylic adhesive composite CPP release film with a thickness of 50 microns is coated on the surface of the silver layer.

[0070] Table 1. Composition and mass of base film layer raw materials

[0071] Raw material Example 1 Example 2 Example 3 Example 4 Polymethyl methacrylate 77.5 / polyethylene terephthalate / / 7.5 Titanium dioxide 1.3 1.8 1.8 1.8 Azodicarbonamide 0.7 0.7 0.7 0.7 2,4-dihydroxybenzophenone 11 11

[0072] Table 2. Thermal radiation layer raw materials

[0073] Raw material Mass ratio Acrylic paint 9.5 Silicon dioxide 0.5

[0074] Performance test:

[0075] The film thickness, solar reflectivity, thermal radiation coefficient, hydrophobicity and aging resistance of the radiation cooling films prepared in Examples 1-4 and Comparative Example 1 are tested, and the test methods are as follows, and the test results are shown in Table 3.

[0076] Film thickness: tested by an electronic thickness tester;

[0077] Solar reflectivity: tested by an ultraviolet-visible-infrared spectrophotometer in the 0.3-micron-2.5-micron wave band;

[0078] Thermal radiation coefficient: tested by a thermal emissivity instrument in the 8-micron-13-micron wave band;

[0079] Hydrophobicity: tested by a surface water droplet contact angle tester;

[0080] Aging resistance: tested by an ultraviolet aging instrument.

[0081] Table 3. Performance test results of the radiation cooling films in Examples 1-4 and Comparative Example 1

[0082] Performance parameter Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Film thickness / μm 173 173 193 193 203 Solar reflectance 91% 93% 96% 95% 90% 8μm~13μm Emissivity 0.94 0.94 0.95 0.95 0.95 UV300Kwh Yellowing △b ≤2 ≤2 ≤2 ≤2 Silver layer yellowing and delamination UV300Kwh Solar reflectance attenuation 2.4% 2.6% 2.7% 2.8% 5.3% Water droplet angle 123° 123° 123° 123° 95°

[0083] As can be seen from Table 3, compared with the radiant cooling film of Comparative Example 1, the radiant cooling films of Examples 1-4 of the present application have higher solar reflectance, at the same time, UV300Kwh yellowing △b is all ≤2, UV300Kwh solar reflectance attenuation is smaller, indicating that the anti-aging performance of the radiant cooling films of Examples 1-4 of the present application is improved.

[0084] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, it should be considered that it is within the scope of the present disclosure.

[0085] The above-described embodiments only express several implementation manners of the present application, the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. A radiative cooling film, characterized in that, The radiation cooling film comprises a base film layer, the base film layer comprises a resin matrix and a plurality of independent cells, a plurality of first particles and a plurality of second particles wrapped by the cells are dispersed in the resin matrix.

2. The radiative cooling film of claim 1, wherein, The ratio of the total volume of the plurality of independent cells, the plurality of first particles and the plurality of second particles wrapped by the cells to the volume of the resin matrix is (0.15-0.5):

1.

3. The radiative cooling film of claim 1, wherein, The diameter of the cells is 0.5 μm-2 μm; The resin matrix is a polyethylene matrix, a polypropylene matrix, a polymethyl methacrylate matrix, a polydiethyl terephthalate matrix, a polyvinyl chloride matrix or a polyvinyl fluoride matrix; The thickness of the base film layer is 30 μm-200 μm.

4. The radiative cooling film of claim 1, wherein, The first particles and the second particles are both silica, titanium dioxide, barium sulfate, aluminum oxide or calcium carbonate; The particle size of the first particles and the second particles is 200 nm-800 nm.

5. The radiative cooling film of claim 1, wherein, The radiation cooling film further comprises a self-cleaning layer, an adhesive layer and a release layer, the self-cleaning layer is located on one side of the base film layer, the adhesive layer is located on the other side of the base film layer, and the release layer is located on the side of the adhesive layer away from the base film layer.

6. The radiative cooling film of claim 5, wherein, The self-cleaning layer is a polymer layer containing silicon or fluorine; or the surface of the self-cleaning layer away from the base film layer has a micro-nano structure, the micro-nano structure comprises alternating convex and concave parts; The thickness of the self-cleaning layer is 200 nm-500 nm.

7. The radiative cooling film of claim 5, wherein, The adhesive layer is an acrylic adhesive; The thickness of the adhesive layer is 20 μm-100 μm.

8. The radiative cooling film of claim 5, wherein, The release layer is a release film or a release paper; The release film is a PET release film or a CPP release film.

9. The radiative cooling film of claim 5, wherein, The radiation cooling film further comprises a thermal radiation layer, the thermal radiation layer is located between the base film layer and the self-cleaning layer or between the base film layer and the adhesive layer.

10. The radiative cooling film of claim 9, wherein, The thermal radiation layer comprises a coating matrix and cooling particles dispersed in the coating matrix; The coating matrix is an acrylic coating matrix, an epoxy coating matrix or a polyester coating matrix; The cooling particles in the thermal radiation layer are silica, titanium dioxide, barium sulfate, aluminum oxide or calcium carbonate; The particle size of the cooling particles in the thermal radiation layer is 1 μm-10 μm; The thickness of the thermal radiation layer is 10 μm-50 μm.

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