WO2022114673A1 - Radiative cooling multilayer films - Google Patents

Abstract

Disclosed is a radiative cooling film that includes a transparent-type radiative cooling multilayer film and a reflective-type radiative cooling film and is structured to allow for the substantial implementation of radiative cooling performance on an object and the mass production. The present invention provides a radiative cooling multilayer film comprising: a first infrared radiation layer containing a first polymer in which dielectric particles with an average particle diameter of 0.01 to 30 μm are dispersed in a content of 0.1 to 25 wt%, and selectively radiatively cooling an object, from which heat is to be removed, at an average emissivity of 0.5 to 1 with respect to radiation in a wavelength range of 8-13 μm; a second infrared radiation layer disposed above the first infrared radiation layer and emitting the heat resulting from the selective radiative cooling to the outside by comprising a second polymer; and a metal reflective layer disposed below the first infrared radiation layer to reflect solar light and having a thickness of 20 to 600 nm.

Description

Radiation Cooling Multilayer Film

The present invention relates to multilayer films, and more particularly to radiation cooled multilayer films.

This application claims priority and interest to Korean Patent Application Nos. 10-2020-0158945 and 10-2020-0158954 filed on November 24, 2020, which are incorporated herein by reference in their entirety do.

Radiative cooling is a natural phenomenon in which the temperature of an object decreases when the amount of radiation emitted from the object exceeds the absorbed energy. The amount of radiant energy emitted is quantified by the Stefan-Boltzmann Law, and can be expressed as in Equation 1 below.

[Equation 1]

P = εσT ⁴

(P is the radiant energy emitted per unit area (W/m2) with respect to the absolute temperature (T) of the atmosphere, ε is the emission rate, σ = 5.67 × 10 ^-8 W/m2T ⁴ )

The surface of the Earth always emits a certain amount of radiant energy. During the daytime, it absorbs radiant energy from the sun, and the absorbed radiant energy is greater than the emitted radiant energy, so radiative cooling does not occur. That is, the radiative cooling effect may theoretically be greater at night, but in places with a lot of clouds and humidity, radiant energy emitted from the earth's surface and objects is re-radiated, so radiative cooling may be insignificant or may not occur. Due to these characteristics, the radiative cooling effect is mainly maximized on clear and dry days with short days, low humidity, and no clouds. In the case of Korea, this phenomenon is related to the cause of the extreme diurnal temperature difference between spring and autumn.

The engineering use of this natural phenomenon is called 'radiative cooling technology'. This is also called zero energy cooling or passive cooling technology in that it can implement cooling without external energy input, and is attracting attention in terms of carbon and energy reduction effects. The atmosphere that exists between the earth's surface and space is a mixture of numerous gases such as oxygen and nitrogen, which acts as a translucent medium for radiative cooling. 298 K) to space (0 K). However, the atmosphere is very transparent to thermal radiation in the 8 to 13 μm wavelength range, called the atmospheric window, allowing heat to be released into space without heating the atmosphere. Atmospheric window transmittance is affected by various environmental factors such as geographic location, cloudiness, and humidity conditions. In general, air window transmittance is high when it is clear and dry.

Chinese Patent Laid-Open Patent No. 109070695 discloses a selective heat dissipation cooling structure having an average emissivity of 0.5 to 1.0 for radiation in a wavelength region of 7 to 14 μm using a selective radiation layer including a polymer and a plurality of dielectric particles dispersed in the polymer. A method for realizing cooling from the subject (object to remove heat) by expressing the surface cooling effect caused by It can be difficult to implement effective radiative cooling only with this method, and the actual effect on radiative cooling from the subject is not presented.

The present invention is to provide a transparent radiation-cooled multilayer film and a reflective radiation-cooled multilayer film having a structure that can substantially implement radiation cooling performance for a subject in a radiation-cooled multilayer film and can be mass-produced. .

In order to solve the above problems, the present invention includes a first polymer in which dielectric particles having an average particle diameter of 0.01 to 30 μm are dispersed in an amount of 0.1 to 25% by weight, and an object from which heat is to be removed in a wavelength range of 8 to 13 μm. a first infrared radiation layer selectively radiatively cooled to an average emissivity of 0.5 to 1 with respect to radiation; a second infrared radiation layer disposed on the first infrared radiation layer and including a second polymer for emitting the selectively radiatively cooled heat to the outside; and a metal reflective layer having a thickness of 20 to 150 nm that is located under the first infrared emitting layer and reflects sunlight.

In addition, the film has a radiative cooling power of 50 to 150 W/m 2 under an operating temperature of -100 to 300° C., a visible light transmittance of 15 to 70%, and a solar reflectance of 20 to 50%, and , It provides a transparent radiation-cooled multilayer film, characterized in that the haze (Haze) is 10% or less.

In addition, the film has a radiative cooling power of 50 to 150 W/m 2 under an operating temperature of -100 to 300° C., and provides a radiation-cooled multilayer film, characterized in that the solar reflectance is 80 to 95%. do.

In addition, the dielectric particles are silica (SiO ₂ ), alumina (Al ₂ O ₃ ), aluminum silicate (Al ₂ SiO ₅ ), zeolite (Na ₂ Al ₂ Si ₃ O-2H ₂ O), calcium carbonate (CaCO ₃ ), Silicon carbide (SiC), zinc oxide (ZnO), zinc sulfate (ZnSO ₄ ), titanium dioxide (TiO ₂ ), barium sulfate (BaSO ₄ ), cerium oxide (Ce ₂ O ₃ ), zirconia (ZrO ₂ ) and kaolin oxide (Al ₂ Si ₂ O ₅ (OH) ₄ ) It provides a transparent radiation-cooled multilayer film, characterized in that at least one selected from the group consisting of.

In addition, the first polymer and the second polymer are each PET (Polyethylene terephthalate), PETG (Glycol-modified polyethylene terephthalate), PEN (Polyethylene naphthalate), PVDF (Polyvinylidene fluoride), PTFE (Polytetrafluoroethylene), PFA (Perfluoroalkoxyalkane), PCTFE ( Polychlorotrifluoroethylene), ECTFE (Ethylene chlorotrifluoroethylene), ETFE (Ethylene Tetra fluoro Ethylene), FEP (Fluorinated ethylene propylene), THV (Terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride), PVC (Polyvinyl chloride), PVDC (Polyvinylidene chloride), PU (Polyvinylidene chloride) Polyurethane), PC (Polycarbonate), PE (Polyethylene), and PP (Polypropylene) It provides a transparent type radiation cooling multilayer film, characterized in that one selected from the group consisting of or a mixture of two or more.

In addition, the first infrared emitting layer and the second infrared emitting layer have an average thickness of 10 μm to 3 mm, respectively. It provides a transparent radiation-cooled multilayer film.

In addition, it is located under the metal reflective layer, the metal oxidation prevention layer for preventing oxidation of the metal reflective layer component including a third polymer; And it provides a transparent radiation-cooled multilayer film, characterized in that it further comprises a; and a pressure-sensitive adhesive layer that is located under the metal antioxidant layer is attached to the object.

In addition, the metal reflective layer is formed of silver (Ag) or aluminum (Al) to a thickness of 20 to 150 nm, the third polymer has an oxygen transmittance of 0.1 to 1,000 cc/m 2 ·day · atm, and a moisture transmittance of 1 to 100 g It provides a transparent radiation-cooled multilayer film, characterized in that /m 2 ·day · atm.

In addition, the metal reflective layer is formed of silver (Ag) or aluminum (Al) to a thickness of 20 to 600 nm, the third polymer has an oxygen transmittance of 0.1 to 5 cc/m 2 ·day · atm, and a moisture transmittance of 1 to 20 g It provides a radiation-cooled multilayer film, characterized in that /m 2 ·day · atm.

The present invention is a radiation cooling film including a first infrared radiation layer including dielectric particles and a second infrared radiation layer located on the outermost side (upper side). It is possible to provide a transparent radiation-cooled multilayer film and a reflective radiation-cooled multilayer film capable of realizing a substantial radiation cooling effect by effectively emitting the second infrared radiation layer to the outside.

In addition, it is possible to prevent a decrease in the daytime cooling effect due to heating due to sunlight by providing a metal reflective layer and a metal oxidation prevention layer.

In addition, it has an adhesive layer attached to the object and can be easily attached to the surface of the object to be cooled, thereby reducing the thermal conduction resistance between the film and the main body, thereby further improving the radiation cooling efficiency.

In addition, in the case of the existing inorganic laminated radiation cooling technology, mass production is difficult due to the vacuum deposition process, etc., but the multilayer film according to the present invention is extrusion-molded by selecting a polymer-based material and has ease of processing, so mass production is possible and economical and It has excellent performance, can be efficiently applied to detailed applications, and has technical significance in terms of commercialization.

1 is a cross-sectional view illustrating a radiation-cooled multilayer film according to the present invention.

2 is a schematic diagram illustrating a process of realizing cooling from a main body of a radiation-cooled multilayer film according to the present invention.

3 is a graph showing the results of a comparative test in Test Example 2 of the present invention.

4 is a graph showing a comparative test result in Test Example 3 of the present invention.

5 is a graph showing the results of a comparative test in Test Example 6 of the present invention.

6 is a graph showing a comparative test result in Test Example 7 of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. Throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

1 is a cross-sectional view illustratively showing a radiation-cooled multilayer film according to the present invention, and FIG. 2 is a schematic diagram illustrating a cooling realization process from the main body of the radiation-cooled multilayer film according to the present invention.

1 and 2, the radiation-cooled multilayer film 100 according to the present invention includes a first infrared emission layer 110, a second infrared emission layer 130, and a metal reflection layer 150, and metal oxide. It may further include a barrier layer 160 , an adhesive layer 170 , and an adhesive layer 180 .

In the present invention, the term 'film' may also be understood as 'sheet' according to its relative thickness, and therefore, 'multilayer film' in the present invention should be understood as a concept including 'multilayer sheet'.

Radiative cooling multilayer film 100 according to the present invention shows a level of 100 W/m 2 at room temperature, daytime or nighttime, radiative cooling power. Specifically, in the present invention, the transparent radiation-cooled multilayer film 100 may exhibit a radiative cooling power of 50 to 150 W/m 2 under an operating temperature of -100 to 300° C., and a visible light transmittance of 15 to 70%, and , the solar reflectance may be 20 to 50%, and the haze may be 10% or less. In addition, the reflective radiation cooling multilayer film 100 may exhibit a radiative cooling power of 50 to 150 W/m 2 under an operating temperature of -100 to 300° C., and may have a solar reflectance of 80 to 95%.

The first infrared radiation layer 110 is an object to remove heat, that is, a layer that absorbs heat radiatedly cooled from the main body, and contains dielectric particles 120 having an average particle diameter of 0.01 to 30 μm in an amount of 0.1 to 25% by weight. The dispersed first polymer 140 is included. At this time, the main body is selectively radiatively cooled to an average emissivity of 0.5 to 1 for radiation in a wavelength range of 8 to 13 μm. Here, emissivity means that an object receives light energy and reflects, transmits, or absorbs light energy. When the sum of reflectance, transmittance, and absorptivity is '1', the ratio of absorbed energy can be defined as emissivity, which means that the emissivity is It is premised on the same as the absorption rate, and this premise means a case in which the kinetic state remains the same over time (eg, a state in which the temperature does not change). On the other hand, the average emissivity defines the average emissivity when the calculation range is set to a wavelength of 8 to 13 μm.

The first polymer 140 is a material that transmits solar radiation and emits infrared radiation, and for example, absorbs sunlight in a wavelength range of 300 to 5,000 nm at a low rate of less than 20%, preferably less than 5%, and , an infrared absorption rate (emission rate) in the wavelength range of 5 to 50 μm may be 0.6 or more, preferably 0.9 or more. As such a first polymer material, for example, PET (Polyethylene terephthalate), PETG (Glycol-modified polyethylene terephthalate), PEN (Polyethylene naphthalate), PVDF (Polyvinylidene fluoride), PTFE (Polytetrafluoroethylene), PFA (Perfluoroalkoxyalkane), PCTFE (Polychlorotrifluoroethylene), ECTFE (Ethylene chlorotrifluoroethylene), ETFE (Ethylene Tetra fluoro Ethylene), FEP (Fluorinated ethylene propylene), THV (Terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride), PVC (Polyvinyl chloride), PVDC (Polyvinylidene chloride), PU (Polyurethane) PC (Polycarbonate), PE (Polyethylene), PP (Polypropylene), etc. may be mentioned, and a transparent material is applied in the present invention.

The average thickness of the first infrared emitting layer 110 may be 10 μm to 3 mm, respectively, and preferably 20 to 1,000 μm. When the thickness of the first infrared radiation layer 110 is too thin, radiation cooling heat absorption performance may be reduced, and if excessive, heat emission performance through the second infrared radiation layer 130 may be reduced.

The dielectric particles 120 are dispersed on the matrix of the first polymer 140 so that the selective radiation performance of the first infrared radiation layer 110 is implemented, and a high average emissivity for radiation in a wavelength range of 8 to 13 μm is obtained. Considering that, the dielectric particles 120 having an average particle diameter of 0.01 to 30 μm are dispersed in an amount of 0.1 to 25% by weight, and preferably, the dielectric particles 120 having an average particle diameter of 1 to 10 μm are dispersed in an amount of 1 to 5% by weight. may have been The dielectric particles 120 include, for example, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), aluminum silicate (Al ₂ SiO ₅ ), zeolite (Na ₂ Al ₂ Si ₃ O-2H ₂ O), calcium carbonate ( CaCO ₃ ), silicon carbide (SiC), zinc oxide (ZnO), zinc sulfate (ZnSO ₄ ), titanium dioxide (TiO ₂ ), barium sulfate (BaSO ₄ ), cerium oxide (Ce ₂ O ₃ ), zirconia (ZrO ₂ ) ), kaolin oxide (Al ₂ Si ₂ O ₅ (OH) ₄ ), and the like.

The second infrared radiation layer 130 is a layer for effectively radiating heat absorbed by radiation cooling in the first infrared radiation layer 110 to the outside. It is formed of a polymer material that gives long-term durability and weather resistance characteristics according to exposure, and in the present invention, a substantial radiative cooling effect is realized through the second infrared radiation layer 130 . That is, since the second infrared radiation layer 130 is provided, the radiation cooling heat does not stay in the first infrared radiation layer 110 and can be rapidly emitted to the outside.

In the present invention, since the dielectric particles 120 included in the first infrared radiation layer 110 are not included in the second infrared radiation layer 130 , the heat absorbed by radiative cooling in the first infrared radiation layer 110 is removed. It was confirmed that it can be effectively radiated to the outside.

The material of the second infrared emitting layer 130 is PET (Polyethylene terephthalate), PETG (Glycol-modified polyethylene terephthalate), PEN (Polyethylene naphthalate), PVDF (Polyvinylidene fluoride), PTFE (Polyethylene terephthalate), like the first infrared emitting layer 110 . Polytetrafluoroethylene), PFA (Perfluoroalkoxyalkane), PCTFE (Polychlorotrifluoroethylene), ECTFE (Ethylene chlorotrifluoroethylene), ETFE (Ethylene Tetra fluoro Ethylene), FEP (Fluorinated ethylene propylene), THV (Terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride), PVC (Polyvinyl chloride) ), PVDC (Polyvinylidene chloride), PU (Polyurethane) and PC (Polycarbonate), PE (Polyethylene), PP (Polypropylene) can be applied using one or a mixture of two or more polymers. , a transparent material is applied in the present invention.

The average thickness of the second infrared emission layer 130 may be 10 μm to 3 mm, respectively, and preferably, 20 to 1,000 μm. When the thickness of the second infrared radiation layer 130 is excessive, heat dissipation performance may be deteriorated due to the thickness of the second infrared radiation layer 130 itself. Here, if the polymer has a thickness of 50 μm or more, or 100 μm or more, it acts as a broadband emitter (BE) and includes wavelengths other than the atmospheric window (8 to 13 μm wavelength) for 4 to 20 μm wavelength. It emits radiation and shows relatively high cooling power compared to a selective emitter (SE). However, a polymer having a thickness of less than 50 μm can act as a selective emitter depending on the material and selectively radiate to the atmospheric window wavelength region, thereby increasing the cooling temperature compared to a broadband emitter. It is advantageous in terms of heat dissipation performance because selective radiation is possible when it is thin.

On the other hand, the first infrared emitting layer 110 and the second infrared emitting layer 130 may be used by blending additives such as UV stabilizers, flame retardants, antioxidants, neutralizers, and processing aids in the range of 0.1 to 5% by weight, respectively. .

In the present invention, a metal reflective layer 150 and a metal oxidation prevention layer 160 may be further provided in order to prevent a decrease in the daytime cooling effect due to heating due to sunlight. That is, the present invention is provided with a metal reflective layer 150 having a thickness of 20 to 150 nm that is located under the first infrared emitting layer 110 to reflect sunlight, and is also located under the metal reflective layer 150, and the second 3 A metal anti-oxidation layer 160 for preventing oxidation of the metal reflective layer 150 component including a polymer may be provided.

Here, the thickness of the metal reflective layer 150 is preferably 20 to 150 nm in the case of the transparent radiation-cooled multilayer film 100, and 20 to 600 nm in the case of the reflective radiation-cooled multilayer film 100, preferably It may be 200 to 400 nm.

The metal reflective layer 150 is positioned under the first infrared emitting layer 110 to reflect solar radiation, and in the present invention, the transparent radiation cooling multilayer by adjusting the thickness of the metal reflective layer 150 within the above range. In the case of the film 100, the solar reflectance is set in the range of 20 to 50% to partially transmit sunlight for securing a view, and in the case of the reflective radiation-cooled multilayer film 100, 80 to 95% of It can be made to have sunlight reflectance.

The material constituting the metal reflective layer 150 is a solar reflective metal material, and silver (Ag) or aluminum (Al) may be preferably applied.

In addition, in the case of the transparent radiation-cooled multilayer film 100 in the present invention, the visible light transmittance may be 15 to 70%, which is by adjusting the metal deposition thickness of the metal reflective layer 150 in the range of 20 to 150 nm as described above. can be achieved.

In the present invention, in order to prevent the metal component constituting the metal reflection layer 150 from being easily oxidized due to moisture or the like depending on the purpose of application of the film, thereby reducing the sunlight reflection performance, a third polymer is included in the lower portion of the metal reflection layer 150. A metal oxidation prevention layer 160 may be provided.

For this, a material having low oxygen and moisture permeability may be selected for the third polymer, and specifically, the oxygen permeability is 0.1 to 1,000 cc/m 2 ·day · atm, and the water transmittance is 1 to 100 g/m 2 dayatm, preferably A polymer having an oxygen permeability of 0.1 to 100 cc/m 2 ·day·atm and a water permeability of 1 to 50 g/m2·day·atm may be selected. In the case of the reflective radiation-cooled multilayer film 100, more preferably, a polymer having an oxygen transmittance of 0.1 to 5 cc/m2·day·atm and a water transmittance of 1 to 20 g/m2·day·atm may be selected.

The third polymer material is not particularly limited as long as it satisfies the oxygen and moisture permeability, but preferably PET (Polyethylene terephthalate), PVDC (Polyvinylidene chloride) or EvOH (Ethylene vinyl alcohol) may be used, and more Preferably, PET (Polyethylene terephthalate) may be used.

In addition, in the present invention, as a means to further improve the radiation cooling efficiency by reducing the thermal conduction resistance between the multilayer film 100 and the main body, the adhesive layer 170 is located below the metal oxidation prevention layer 160 and is attached to the object. ) may be further provided.

The material constituting the adhesive layer 170 is not particularly limited as long as it provides adhesive performance between the metal oxidation prevention layer 160 and the object and does not reduce the radiation cooling performance according to the present invention, for example, a silicone-based resin. , an acrylic resin, etc. may be used.

In addition, in the present invention, an adhesive layer 180 connecting between the first infrared emitting layer 110 and the second infrared emitting layer 130 and between the metal reflective layer 150 and the metal oxidation prevention layer 160 is further provided. can be

The material constituting the adhesive layer 180 is not particularly limited as long as it imparts adhesive performance to the adhesive layer and does not reduce the radiation cooling performance according to the present invention, for example, silicone-based resin, acrylic resin, urethane-based resin A resin, an epoxy-based resin, or the like may be used.

All of the layers constituting the multilayer film 100 according to the present invention can be extrusion-molded except for the metal reflective layer 150 . That is, the multilayer film 100 according to the present invention can be manufactured by known methods such as extrusion lamination or co-extrusion by using the pellet-like raw material constituting each layer, and thus, in the case of the conventional inorganic material lamination type radiation cooling technology, vacuum There was a problem that mass production was difficult due to the deposition process, etc., but since the multilayer film 100 according to the present invention is extruded and has ease of processing, it has the advantage of easy mass production. In this case, in the case of the first infrared radiation layer 110 , the dielectric particles 120 are uniformly dispersed in the polymer resin itself, pelletized, and then manufactured through extrusion molding.

Subjects subject to selective radiative cooling using the multilayer film 100 according to the present invention include, for example, solar panels, automobile exterior materials or windows, roofs or windows of buildings, curtains and blinds, agricultural protective films and plastic houses, and flexible It can be applied to a wide variety of objects that require radiant cooling, such as transparent electrodes and large outdoor display surfaces.

In addition, in the case of the reflective radiation cooling film in the present invention, it can be used to achieve cooling by circulating an internal fluid such as air, water, and antifreeze in connection with a passive or active system. Through the above system, it can be applied to air-cooling/water-cooled air conditioning equipment using the radiative cooling effect and used for the purpose of reducing house cooling costs. Here, in order to implement the system, the following contents are included. That is, all device configurations in the plurality of systems are in thermal connection with the cooling fluid, and the plurality of selective radiative cooling structures are placed in contact between the surfaces of one of the plurality of thermal cooling collecting devices to allow heat exchange, each The selective radiative cooling structure includes the selective radiative cooling layer.

The process of selective radiative cooling using the multilayer film 100 according to the present invention is as follows.

First, the film or sheet 100 having a selective radiation cooling structure is attached in close contact with the surface of the main body (target) to be cooled by directing the adhesive layer 170 to the main body. At this time, it can be attached in close contact with all surfaces (top and side) except for the bottom of the main body.

Next, the surface of the film or sheet 100 having a selective radiation cooling structure is cooled by infrared radiation (Surface cool), and the temperature of the subject (target) in a relatively high temperature state compared to the film or sheet 100 is relatively As a result, heat is transferred to the film or sheet 100 in a low temperature state (Space cool).

Next, cooling corresponding to the radiative cooling force generated by the selective radiative cooling structure is provided to the subject (target).

As such, the transparent radiation cooling multilayer film 100 according to the present invention provides a selective radiation cooling film structure that performs selective infrared radiation and solar light reflection functions, thereby lowering the temperature of the subject (target) without separate energy. have. By providing such a zero-energy cooling composite material, it can contribute to real-life applicability and, as a result, can significantly contribute to energy reduction and carbon reduction effects.

Hereinafter, specific examples according to the present invention will be described.

Example 1

PETG (a portion corresponding to 30 mol% of ethylene units constituting polyethylene terephthalate (PET) is replaced with 1,4-cyclohexanedimethylene units) and silica (SiO ₂ ) having an average particle diameter of 2 to 5 μm by 0.1 weight % content was introduced into a single screw extruder, melt-kneaded and solidified by cooling to prepare pellets, and then extrusion-molded to prepare a first infrared radiation layer having a thickness of 25 μm. Thereafter, silver (Ag) was heated and vaporized by an electron beam heating method to deposit a metal reflective layer having a thickness of 100 nm.

In addition, PVDF was extruded in the same manner to prepare a second infrared emitting layer having a thickness of 25 μm.

In addition, PET having an oxygen permeability of 40 cc/m 2 dayatm and a moisture permeability of 20 g/m 2 dayatm was extruded in the same manner to prepare a metal antioxidant layer.

Using a multi-layer film forming machine, an adhesive layer is formed and adhered between the first infrared emitting layer and the second infrared emitting layer and between the metal reflective layer and the metal antioxidant layer with an acrylic resin, and an acrylic adhesive layer on the back surface of the metal antioxidant layer was formed to prepare a transparent radiation-cooled multilayer film.

Test Example 1

Visible light transmittance, solar reflectance, and haze were measured for the prepared transparent radiation-cooled multilayer film according to the following method, and the results are shown in Table 1 below.

[How to measure]

(1) Visible light transmittance and solar reflectance

It was measured according to ASTM E424 method.

(3) Haze

It was measured according to ASTM D1003 method.

division	Visible light transmittance (%)	Solar Reflectance (%)	Haze (%)
Example 1	65	25	5

Test Example 2

A comparative test was conducted under the following conditions on the transparent window to which the prepared transparent radiation-cooling multilayer film was applied (Example 1) and the general transparent window to which it was not applied (Comparative Example 1), and the results are shown in FIG. 3 .

[Exam conditions]

- Subject (target) material: transparent acrylic material

- Temperature measurement location: inside air (Space cool)

- Climatic conditions: (Daytime) Humidity 20 ~ 40%, Clouds 2 ~ 30% / (Night) Humidity 40 ~ 90%, Clouds 0 ~ 100%

Referring to FIG. 3 , the air temperature of the transparent window applied with the transparent radiation cooling multilayer film was lower by up to about 3° C. compared to the air temperature of the general transparent window (no film attached to the surface). The section in which the temperature reduction effect of Example 1 compared to Comparative Example 1 was exhibited was from about 7:00 am to about 7:00 pm. This is limited to the case of space cool temperature measurement.

Test Example 3

The transparent window to which the above-prepared transparent radiation cooling multilayer film is applied, a transparent window not applied (not attached), a transparent window to which a commercial tinting film is applied, and a transparent window to which a commercial Low-Emissivity (Low-Emissivity) film is applied, under the following conditions A comparative test was conducted, and the results are shown in FIG. 4 . For reference, the commercial tinting film and the commercial Low-E film are a type of thermal barrier film, and commercially available products are used. Both films transmit visible light, but the tinting film blocks both ultraviolet and infrared rays, and the Low-E film is different in that it is characterized by low emissivity.

[Exam conditions]

- Subject (target) material: iron

- Temperature measurement location: internal liquid (water) (Space cool)

- Climatic conditions: (Day) Humidity 20 ~ 45%, Clouds 0 ~ 70% / (Night) Humidity 40 ~ 90%, Clouds 0 ~ 70%

4, the transparent radiation-cooled multilayer film (Example 1), the film not attached to the surface, the tinting film, and the Low-E film all correspond to visible light transmitting films, and in Test Example 3, infrared rays are reflected and blocked. From the point of view of irradiating or radiating, we tried to verify the effect by comparing films applied to similar fields in real life. Referring to FIG. 4 , when the transparent radiation-cooling multilayer film was applied, the maximum temperature reduction effect was 4°C compared to the non-attached case, 5°C compared to the case where the tinting film was applied, and 2°C compared to the case where the Low-E film was applied. In particular, in the case where the tinting film was applied, the temperature rose to a maximum of 7° C. during the day compared to the case where the tinting film was applied, and in the case of Example 1, the temperature was mostly kept low compared to the comparative examples. Applicability to real life can be checked.

Test Example 4

In order to confirm the effect of the adhesive layer in the transparent radiation-cooled multilayer film according to the present invention, the same radiation-cooled film as in Example 1 was prepared (Comparative Example 2), except that there was no adhesive layer in Example 1, and the test A comparative test was performed under the same conditions as the test conditions in Example 2. After the test, the surface temperature of the subject was measured, and the results are shown in Table 2 below.

division	Example 1	Comparative Example 2
Surface temperature (℃)	9.1	11.3

Referring to Table 2, according to the present invention, it is confirmed that the radiation cooling efficiency can be further improved by reducing the thermal conduction resistance between the film and the main body by further including an adhesive layer attached to the main body and located under the metal antioxidant layer according to the present invention. .

Example 2

PETG (a portion corresponding to 30 mol% of ethylene units constituting polyethylene terephthalate (PET) is replaced with 1,4-cyclohexanedimethylene units) silica (SiO ₂ ) having an average particle diameter of 2 to 5 μm 3 wt% The content was put into a single-screw extruder, melt-kneaded and solidified by cooling to prepare pellets, and then extrusion-molded to prepare a first infrared radiation layer having a thickness of 65 μm. Thereafter, silver (Ag) was heated and vaporized by an electron beam heating method to deposit a metal reflective layer having a thickness of 500 nm.

In addition, PVDF was extruded in the same manner to prepare a second infrared emitting layer having a thickness of 25 μm.

In addition, a metal antioxidant layer was prepared by extrusion molding PET having an oxygen permeability of 40 cc/m 2 dayatm and a water permeability of 20 g/m 2 ·day·atm in the same manner.

Using a multi-layer film forming machine, an adhesive layer is formed and adhered between the first infrared emitting layer and the second infrared emitting layer and between the metal reflective layer and the metal antioxidant layer with an acrylic resin, and an acrylic adhesive layer on the back surface of the metal antioxidant layer was formed to prepare a reflective radiation-cooled multilayer film.

Test Example 5

The solar reflectance of the prepared reflective radiation-cooled multilayer film was measured according to the following method, and the results are shown in Table 3 below.

[Method for measuring solar reflectance]

It was measured according to ASTM E424 method.

division	Solar Reflectance (%)
Example	93

Referring to Table 3, it can be seen that the reflective radiation-cooled multilayer film including the first infrared emitting layer and the second infrared emitting layer including dielectric particles according to the present invention has very excellent solar reflection performance.

Test Example 6

A comparative test was conducted under the following conditions on the container to which the prepared reflective radiation-cooling multilayer film was applied (Example 2) and the container to which it was not applied (Comparative Example 3, Reference), and the results are shown in FIG. 5 .

[Exam conditions]

- Subject (target) material: acrylic

- Temperature measurement location: inside air (Space cool)

- Climatic conditions: (Daytime) Humidity 20 ~ 40%, Clouds 2 ~ 30% / (Night) Humidity 40 ~ 90%, Clouds 0 ~ 100%

Referring to FIG. 5 , the temperature of the inner temperature of the multilayer film attachment of Example 2 was lower by about 8° C. at most compared to the inner temperature of Comparative Example 3 (no film attached to the surface), and compared to Comparative Example 3 in the results of all the days carried out The temperature reduction effect of Example 2 was shown. These results demonstrate that the selective wavelength heat radiation of the reflective radiative cooling film has a significant effect of taking heat away from the air in the space inside the box.

The above effects are applicable to the field of the air conditioner outdoor unit cover or housing. The outdoor unit of the air conditioner discharges the high-temperature circulating air used to cool the room to the outside. Therefore, in the summer season when the amount of air conditioner usage increases, the internal temperature can be lowered by attaching the radiation cooling film of the present invention to the surface of the outdoor unit, thereby improving the indoor cooling effect and reducing power consumption.

Test Example 7

In Test Example 6, a comparative test was performed by changing the subject material and the temperature measurement position as follows, and the results are shown in FIG. 6 .

[Exam conditions]

- Main (target) material: iron (Fe)

- Temperature measurement location: internal liquid (water) (Space cool)

- Climate conditions: (Daytime) Humidity 20 ~ 45%, Clouds 0 ~ 70% / (Night) Humidity 40 ~ 90%, Clouds 0 ~ 70%

Referring to FIG. 6 , the internal water temperature of the multilayer film attachment of Example 2 compared to the internal temperature of Comparative Example 3 (no film attached to the surface, Reference) was reduced by more than 7°C during the day and 3°C at night. These results show that the selective wavelength thermal radiation at the surface of the reflective radiation cooling film exhibits an effect capable of cooling the temperature of the internal liquid (including water).

The above effects may be applied to detailed fields such as storage tanks and oil tankers. In the case of tankers, they are exposed to the outdoors for a long time in the process of transporting oil or oil gas. At this time, the surface and internal temperature rises rapidly with a large amount of sunlight irradiation, and the evaporation of the oil product is accelerated. In particular, in the case of an oil gas storage tank, a gas valve must be opened periodically due to such an increase in internal pressure of the tank, and in the case of a transport tanker, there is a risk of an explosion accident due to excessive internal pressure. To prevent oil vapor generation, the surface is cooled by spraying water periodically in summer, or an additional power-driven air conditioning system using cooling circulating water is used. Therefore, through the cooling effect of the reflective radiation cooling multilayer film according to the present invention, it is possible to secure the advantages of water saving or power saving.

Test Example 8

In order to confirm the effect of the adhesive layer in the reflective radiation-cooled multilayer film according to the present invention, the same radiation-cooled film as in Example 2 was prepared (Comparative Example 4) except that there was no adhesive layer in the above example, and the test A comparative test was performed under the same conditions as the test conditions in Example 6. After the test, the surface temperature of the subject was measured, and the results are shown in Table 2 below.

division	Example 2	Comparative Example 4
Surface temperature (℃)	7.1	8.4

Referring to Table 4, according to the present invention, it is confirmed that the radiation cooling efficiency can be further improved by reducing the thermal conduction resistance between the film and the main body by further including an adhesive layer attached to the main body and located under the metal antioxidant layer according to the present invention. .

The preferred embodiment of the present invention has been described in detail above. The description of the present invention is for illustration, and those of ordinary skill in the art to which the present invention pertains will understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention.

Accordingly, the scope of the present invention is indicated by the claims described later rather than the detailed description, and all changes or modifications derived from the meaning, scope, and equivalent concept of the claims are included in the scope of the present invention. should be interpreted

* Explanation of symbols

100: transparent radiation-cooled multilayer film 110: first infrared radiation layer

120: dielectric particles 130: second infrared radiation layer

140: first polymer 150: metal reflective layer

160: metal oxidation prevention layer 170: adhesive layer

180: adhesive layer

Claims (9)

1. An object from which heat is to be removed is selected with an average emissivity of 0.5 to 1 for radiation in a wavelength range of 8 to 13 μm, comprising a first polymer in which dielectric particles having an average particle diameter of 0.01 to 30 μm are dispersed in an amount of 0.1 to 25 wt% a first infrared emitting layer for radiative cooling;

   a second infrared radiation layer disposed on the first infrared radiation layer and including a second polymer to emit the selectively radiatively cooled heat to the outside; and

   a metal reflective layer having a thickness of 20 to 600 nm that is positioned under the first infrared emitting layer and reflects sunlight;

   Radiation cooling multilayer film comprising a.
2. According to claim 1,

   The film has a radiative cooling power of 50 to 150 W / m 2 under an operating temperature of -100 to 300 ° C, a visible light transmittance of 15 to 70%, and a solar reflectance of 20 to 50%, Radiation cooled multilayer film, characterized in that the haze (Haze) is 10% or less.
3. According to claim 1,

   The film has a radiative cooling power of 50 to 150 W/m 2 under an operating temperature of -100 to 300° C., and a solar reflectance of 80 to 95%.
4. According to claim 1,

   The dielectric particles are silica (SiO ₂ ), alumina (Al ₂ O ₃ ), aluminum silicate (Al ₂ SiO ₅ ), zeolite (Na ₂ Al ₂ Si ₃ O-2H ₂ O), calcium carbonate (CaCO ₃ ), carbide Silicon (SiC), zinc oxide (ZnO), zinc sulfate (ZnSO ₄ ), titanium dioxide (TiO ₂ ), barium sulfate (BaSO ₄ ), cerium oxide (Ce ₂ O ₃ ), zirconia (ZrO ₂ ) and kaolin oxide ( Al ₂ Si ₂ O ₅ (OH) ₄ ) Radiation-cooled multilayer film, characterized in that at least one selected from the group consisting of.
5. According to claim 1,

   The first polymer and the second polymer are polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), polyethylene naphthalate (PEN), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), polychlorotrifluoroethylene (PCTFE), respectively. ), ECTFE (Ethylene chlorotrifluoroethylene), ETFE (Ethylene Tetra fluoro Ethylene), FEP (Fluorinated ethylene propylene), THV (Terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride), PVC (Polyvinyl chloride), PVDC (Polyvinylidene chloride), PU (Polyurethane) ), PC (Polycarbonate), PE (Polyethylene) and PP (Polypropylene) radiation-cooled multilayer film, characterized in that one selected from the group consisting of or a mixture of two or more.
6. According to claim 1,

   The radiation-cooled multilayer film, characterized in that the average thickness of the first infrared emitting layer and the second infrared emitting layer is 10 μm to 3 mm, respectively.
7. According to claim 1,

   a metal anti-oxidation layer positioned under the metal reflective layer and including a third polymer to prevent oxidation of the metal reflective layer component; and

   an adhesive layer positioned under the metal oxidation prevention layer and attached to the object;

   Radiation cooling multilayer film, characterized in that it further comprises.
8. 8. The method of claim 7,

   The metal reflective layer is formed of silver (Ag) or aluminum (Al) with a thickness of 20 to 150 nm,

   The third polymer has an oxygen transmittance of 0.1 to 1,000 cc/m2·day·atm, and a moisture transmittance of 1 to 100 g/m2·day·atm.
9. 8. The method of claim 7,

   The metal reflective layer is formed of silver (Ag) or aluminum (Al) with a thickness of 20 to 600 nm,

   The third polymer has an oxygen transmittance of 0.1 to 5 cc/m2·day·atm, and a moisture transmittance of 1 to 20 g/m2·day·atm.

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