Composite flexible film based on VO2 phase change material and preparation method and application thereof

Abstract

The composite flexible thin film based on the VO2 phase change material comprises a transparent flexible substrate layer, a low-radiation layer, a gap layer and a light regulation and control layer which are sequentially laminated from bottom to top, the light regulation and control layer comprises a plurality of light regulation and control strips arranged in a linear array, the cross section of each light regulation and control strip is triangular, and the bottom surface of each triangle is attached to the top surface of the gap layer; and a flexible transparent protective layer is coated on the light control strip. The composite flexible thin film based on the VO2 phase change material not only has good flexibility so as to adapt to various curved surfaces or dynamically changed surfaces, but also has good weather resistance and dimming effect.

Description

Technical Field

[0001] The present invention relates to the field of inorganic functional materials, and in particular to a VO-based 2 Composite flexible film of phase change material and preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] With the continuous progress of industrialization, urbanization and modernization, global energy consumption has increased, and people are paying more and more attention to energy conservation and emission reduction. Building energy consumption accounts for 40% of the world's total energy consumption. Traditional windows are limited to the lack of effective regulation of solar heat and black body thermal radiation around the building, which has become the main way to increase building energy consumption. The main forms of heat exchange between indoor and building surroundings include heat conduction, heat convection and heat radiation. Energy-saving windows can reduce heating and cooling consumption by blocking one or more of these pathways, which has become the focus of current scientific researchers. In addition, cars also account for a large proportion of energy consumption, especially the front windshield, side windows and roof glass. Although tempered glass can meet the structural mechanical properties of glass, its infrared heat insulation effect is poor, which increases air-conditioning energy consumption; and the "Automobile Window Glass Sunshade Film" (GA / T744-2013) industry standard clearly requires that the visible light transmittance of the car windshield and glass other than the windshield should be greater than or equal to 70%, in order to ensure the eligibility of the car film applied by the car owner and to ensure the most basic driving safety for drivers, which makes most infrared light-controlled film materials daunting.

[0004] Vanadium dioxide (VO 2 ) is a metal oxide with phase change characteristics. It undergoes a reversible phase change from low-temperature monoclinic phase (M phase) to high-temperature rutile (R) phase at 68 °C. During this phase change process, its physical properties such as light transmittance and conductivity change dramatically, making it potentially applicable in intelligent temperature-controlled glass. At present, it has been reported that vanadium dioxide is prepared into a thin film for application. Although the coating of vanadium dioxide thin film on the surface of ordinary glass can have an infrared light regulation effect, due to the high intrinsic optical refractive index of vanadium dioxide in the visible band and the instability of tetravalent vanadium, the visible light transmittance and dimming ability of the film in the environment are still poor, and the film is easy to deteriorate or even fall off and fail, and has poor weather resistance, which is difficult to meet actual needs. At the same time, the flexibility of vanadium dioxide thin films is poor, and it is difficult to better adapt to various curved surfaces or dynamically changing surfaces. Therefore, the preparation of vanadium dioxide-based films with high visible light transmittance, good flexibility and good dimming performance has become a research hotspot in this field. Summary of the invention

[0005] To overcome the above problems, the present invention provides a composite flexible thin film based on VO 2 phase change material, and its preparation method and application.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions: In the first aspect of the present invention, there is provided a composite flexible thin film based on VO 2 phase change material, which includes a transparent flexible base layer, a low-emissivity layer, a void layer, and a light control layer stacked in sequence from bottom to top; The light control layer includes a plurality of light control strips arranged in a linear array, and the light control strips are composed of a plurality of three-dimensional pyramid-shaped VO 2 gratings, and the bottom surface of the pyramid-shaped VO 2 gratings is in contact with the top surface of the void layer; The light control strips are coated with a flexible transparent protective layer.

[0007] In the second aspect of the present invention, there is provided a preparation method of the composite flexible thin film based on VO 2 phase change material described in the first aspect, which includes the following steps: Perform plasma treatment on the upper surface of the transparent flexible base layer; Sequentially arrange a low-emissivity layer, a void layer, and a light control layer on the upper surface of the treated transparent flexible base layer; Coat a flexible transparent protective layer on the surface of the light control layer.

[0008] In the third aspect of the present invention, there is provided an application of the composite flexible thin film based on VO 2 phase change material described in the first aspect as a building energy-saving coating.

[0009] In the fourth aspect of the present invention, there is provided an application of the composite flexible thin film based on VO 2 phase change material described in the first aspect as an energy-saving window coating.

[0010] In the fifth aspect of the present invention, there is provided an application of the composite flexible thin film based on VO 2 phase change material described in the first aspect as an automobile window coating.

[0011] The beneficial effects of the present invention are as follows: (1) The composite flexible thin film based on VO 2 phase change material provided by the present invention includes a transparent flexible base layer, a low-emissivity layer, a void layer, and a light control layer stacked in sequence from bottom to top; the light control layer includes a plurality of light control strips arranged in a linear array, and the light control strips are composed of a plurality of three-dimensional pyramid-shaped VO 2 gratings, and the pyramid-shaped VO 2The bottom surface of the grating is in contact with the top surface of the void layer; the light control strip is coated with a flexible transparent protective layer. The composite flexible film based on VO 2 phase change material not only has good flexibility, so as to meet the adaptation to various curved surfaces or dynamically changing surfaces, but also has good weather resistance and light control effect.

[0012] (2) The transparent flexible base layer with high light transmittance and the flexible transparent protective layer can not only protect the VO 2 nanoparticles that make up the light control strip from falling off, but also improve the flexibility, mechanical strength and weather resistance of the overall film, and extend the service life. The low-emissivity layer can further improve the infrared reflectivity. At high temperatures, it can prevent heat from passing through the wall or glass into the room; at low temperatures, it can prevent heat from passing through the wall or glass to the outside; thus reducing the energy consumption in the room or in the car at high and low temperatures. The light control strip with a defined structure can not only improve the visibility of the light control layer, but also be antireflective, enhance the transmission in a wide wavelength band, and thus enhance the light control effect. The void layer can reduce light scattering and improve the light transmittance.

[0013] (3) The preparation process of the composite flexible film based on VO 2 phase change material adopts the doctor blade coating method and roll-to-roll imprinting molding, which is suitable for the large-scale production of large-area flexible intelligent energy-saving films and has broad application prospects in the fields of building energy conservation, automotive energy conservation, etc. Brief Description of the Drawings

[0014] The accompanying drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments and descriptions thereof of the invention are used to explain the invention and do not constitute an improper limitation of the invention.

[0015] Figure 1 It is a schematic structural diagram of a composite flexible film based on VO 2 phase change material, wherein, 1 - transparent flexible base layer, 2 - low-emissivity layer, 3 - void layer, 4 - light control strip, 5 - flexible transparent protective layer. Detailed Description of the Invention

[0016] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0017] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0018] The first typical embodiment of the present invention provides a composite flexible film based on VO 2 phase change material, comprising a transparent flexible base layer, a low-emissivity layer, a void layer, and a light regulation layer stacked in sequence from bottom to top; The light regulation layer includes a plurality of light regulation bars arranged in a linear array, and the light regulation bars are composed of a plurality of three-dimensional pyramid-shaped VO 2 gratings, and the bottom surface of the pyramid-shaped VO 2 grating is attached to the top surface of the void layer; The light regulation bars are coated with a flexible transparent protective layer.

[0019] In one or more embodiments, the thickness of the composite flexible film is 15-20 μm.

[0020] In one or more embodiments, the material of the transparent flexible base layer is a transparent polymer, and the transparent polymer is selected from one or more of polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), or polyimide (PI).

[0021] In one or more embodiments, the thickness of the transparent flexible base layer is 8-12 μm, preferably 10 μm.

[0022] In one or more embodiments, the low-emissivity layer is a transparent oxide layer, and the transparent oxide is selected from one or more of indium oxide (ITO) and zinc oxide (AZO), preferably indium oxide (ITO).

[0023] In one or more embodiments, the thickness of the low-emissivity layer is 40-60 nm, preferably 50 nm.

[0024] In one or more embodiments, the void layer is a transparent dielectric layer, and the material of the transparent dielectric is selected from PMMA (polymethyl methacrylate).

[0025] In one or more embodiments, the thickness of the void layer is 1-4 μm, preferably 2 μm.

[0026] In one or more embodiments, the material of the light regulation bar is VO 2Nanoparticles, the VO 2 The size of the nanoparticles is 30 - 50 nm, preferably 40 nm.

[0027] In one or more embodiments, the period of the pyramid-shaped grating is 500 - 800 nm, and the height is 80 - 120 nm.

[0028] In one or more embodiments, the flexible transparent protective layer is a transparent polymer, and the transparent polymer is selected from one or more of polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), or polyimide (PI), preferably polydimethylsiloxane (PDMS).

[0029] In one or more embodiments, the thickness of the flexible transparent protective layer is 4 - 6 μm, preferably 5 μm.

[0030] The second typical embodiment of the present invention provides the preparation method of the composite flexible film based on the VO 2 phase change material as described in the first aspect, including the following steps: Perform plasma treatment on the upper surface of the transparent flexible substrate layer; Sequentially arrange a low-emissivity layer, a void layer, and a light control layer on the upper surface of the treated transparent flexible substrate layer; Coat a flexible transparent protective layer on the surface of the light control layer.

[0031] The third typical embodiment of the present invention provides the application of the composite flexible film based on the VO 2 phase change material as described in the first aspect as a building energy-saving coating.

[0032] The fourth typical embodiment of the present invention provides the application of the composite flexible film based on the VO 2 phase change material as described in the first aspect as an energy-saving window coating.

[0033] The fifth typical embodiment of the present invention provides the application of the composite flexible film based on the VO 2 phase change material as described in the first aspect as an automotive window coating.

[0034] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0035] Example 1 Figure 1 It is a schematic structural diagram of the composite flexible film based on the VO 2 phase change material. Refer to Figure 1 , a kind of VO-based 2Composite flexible film of phase change material, comprising a transparent flexible base layer 1, a low-emissivity layer 2, a void layer 3 and a light regulation layer stacked in sequence from bottom to top; The light regulation layer includes a plurality of light regulation bars 4 arranged in a linear array, and the light regulation bars are composed of a plurality of three-dimensional pyramid-shaped VO 2 gratings, and the bottom surface of the pyramid-shaped VO 2 gratings is attached to the top surface of the void layer; The light regulation bar 4 is coated with a flexible transparent protective layer 5.

[0036] The material of the transparent flexible base layer 1 is one or several of polydimethylsiloxane (PDMS), polyethylene terephthalate (PET) or polyimide (PI), and the thickness is 10 μm; The material of the low-emissivity layer 2 is indium oxide, and the thickness is 50 nm; The void layer 3 is a transparent dielectric layer, the material of the transparent dielectric is PMMA, and the thickness of the void layer is 2 μm.

[0037] Pyramid-shaped VO 2 The period of the gratings is 500 nm, and the height is 100 nm.

[0038] The material of the pyramid-shaped gratings is VO 2 nanoparticles, and the size of the VO 2 nanoparticles is 40 nm.

[0039] The material of the flexible transparent protective layer 5 is polydimethylsiloxane (PDMS), and the thickness is 5 μm.

[0040] The thickness of the overall composite flexible film is 15 - 20 μm.

[0041] Example 2 Preparation method of composite flexible film based on VO 2 phase change material: (1) Preparation of transparent flexible base layer The base layer is prepared on a flexible substrate (PET or PI film) by the doctor blade coating method. The polymer solution (polyimide precursor) is uniformly coated through the doctor blade, and the speed and pressure of the doctor blade are controlled to form a transparent flexible base layer with a thickness of 10 μm. After coating, it is dried at 80 - 100 °C for 10 minutes, and then cured at high temperature (350 - 400 °C, 1 hour) to form a dense flexible film.

[0042] II. Preparation of low-emissivity layer Deposit a metal oxide nanoparticle dispersion (ITO) on the surface of a transparent flexible substrate layer by the doctor blade coating method. Adjust the solid content of the dispersion (10 - 15 wt%) and the doctor blade gap to form a low-emissivity layer with a thickness of 50 nm. After coating, dry it at 150 °C for 30 minutes, and enhance the film density and infrared reflection performance by heat treatment (300 °C, 2 hours).

[0043] III. Void layer construction Coat a polymer precursor solution (PMMA solution) on the low-emissivity layer by the doctor blade coating method. By controlling the solution concentration (5 - 8 wt%) and the doctor blade speed, form a wet film with a thickness of 2 - 4 μm. After solvent evaporation (standing at room temperature for 30 minutes), conduct thermal crosslinking at 120 °C for 2 hours to form a void layer with a thickness of 2 μm.

[0044] IV. Preparation of the light control layer: Prepare VO 2 nanoparticles by the hydrothermal method: Add 30 mmol of ammonium metavanadate and 40 mmol of oxalic acid to 16 mL of deionized water to prepare a mixed solution. Transfer the mixed solution to a polytetrafluoroethylene reaction kettle and react at 200 °C for 24 hours. After cooling, centrifugal separation, and washing, conduct low-temperature drying to synthesize VO 2 nanoparticles, obtaining monoclinic VO 2 particles with a size of 40 nm. Disperse the VO 2 particles in an organic solvent acrylic resin containing a surfactant to prepare a dispersion with a solid content of 20 wt%.

[0045] Roll-to-roll nanoimprinting Use a roll-to-roll nanoimprinting device to coat the VO 2 dispersion on the surface of the mold roll by a doctor blade. The surface of the mold roll is etched with a periodic pyramid grating structure (period 500 nm, height 100 nm). In the imprinting stage, apply a positive pressure of 1 MPa to the imprinting roll, and the mold roll synchronously evacuates (-0.08 MPa) to promote filling, and assist the UV curing module (365 nm, 500 mJ / cm²) for rapid crosslinking. When demolding, the mold roll switches to a positive pressure (0.2 MPa), and the demolding roll adsorbs with negative pressure to achieve damage-free separation.

[0046] V. Finally, scrape a layer of silicone PDMS on the surface of the top structure. Adjust the doctor blade gap to 80 μm and the coating speed to 3 m / min to form a protective layer with a thickness of about 5 μm. Cure the coated sample at room temperature for 24 hours to form a surface protective layer with both flexibility and wear resistance.

[0047] VI. Laminating integration process Stack the functional layers in sequence according to the order of the base layer → low-emissivity layer → void layer → light control layer, and use a hot pressing process (100 °C, 0.1 MPa) to enhance the interlayer adhesion. Finally, a flexible composite film with a thickness of 15 - 20 μm is formed, with a visible light transmittance ≥ 60%, an infrared modulation rate ΔTIR ≥ 25%, and the phase change temperature is reduced to 45 - 55 °C through doping modification.

[0048] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite flexible film based on VO2 phase change material, characterized in that: It includes a transparent flexible substrate layer, a low-emissivity layer, a gap layer and a light regulation layer stacked in sequence from bottom to top; The light regulation layer includes a plurality of light regulation strips arranged in a linear array, the light regulation strips are composed of a plurality of three-dimensional pyramid-shaped VO2 gratings, and the bottom surface of the pyramid-shaped VO2 grating is in contact with the top surface of the gap layer; The light regulating strip is covered with a flexible transparent protective layer.

2. The composite flexible film based on VO2 phase change material according to claim 1, characterized in that: The thickness of the composite flexible film is 15-20 μm.

3. The composite flexible film based on VO2 phase change material according to claim 1, characterized in that: The material of the transparent flexible substrate layer is a transparent polymer, and the transparent polymer is selected from one or more of polydimethylsiloxane, polyethylene terephthalate or polyimide; Or, the thickness of the transparent flexible substrate layer is 8-12 μm, preferably 10 μm; Or, the low-emissivity layer is a transparent oxide layer, and the transparent oxide is selected from one or more of indium oxide and zinc oxide, preferably indium oxide; Alternatively, the thickness of the low-emissivity layer is 40-60 nm, preferably 50 nm.

4. The composite flexible film based on VO2 phase change material according to claim 1, characterized in that: The gap layer is a transparent medium layer, and the material of the transparent medium is selected from polymethyl methacrylate; Alternatively, the thickness of the void layer is 1-4 μm, preferably 2 μm.

5. The composite flexible film based on VO2 phase change material according to claim 1, characterized in that: The light regulating strip is made of VO2 nanoparticles, and the size of the VO2 nanoparticles is 30-50 nm, preferably 40 nm; Or, the pyramid grating period is 500~800 nm and the height is 80~120 nm.

6. The composite flexible film based on VO2 phase change material according to claim 1, characterized in that: The flexible transparent protective layer is a transparent polymer, and the transparent polymer is selected from one or more of polydimethylsiloxane, polyethylene terephthalate or polyimide, preferably polydimethylsiloxane; Alternatively, the thickness of the flexible transparent protective layer is 4-6 μm, preferably 5 μm.

7. The method for preparing a composite flexible film based on VO2 phase change material according to any one of claims 1 to 6, characterized in that: The steps include: Plasma treatment is performed on the upper surface of the transparent flexible substrate layer; A low-emissivity layer, a gap layer and a light regulation layer are sequentially arranged on the upper surface of the processed transparent flexible substrate layer; A flexible transparent protective layer is coated on the surface of the light regulating layer.

8. Use of the composite flexible film based on VO2 phase change material as described in any one of claims 1 to 6 as a building energy-saving coating.

9. Use of the composite flexible film based on VO2 phase change material as claimed in any one of claims 1 to 6 as energy-saving window coating.

10. Use of the composite flexible film based on VO2 phase change material according to any one of claims 1 to 6 as a coating for automobile windows.

Images