A flexible infrared radiation / reflection modulation material and its preparation method

Abstract

This invention relates to the field of infrared radiation materials, specifically to a flexible infrared radiation / reflection control material and its preparation method. This invention improves the poor bonding strength between layers in existing flexible infrared radiation / reflection control materials caused by the rough surface of the flexible substrate by adding a MgF2 transition layer between a flexible rough polyimide (PI) substrate and an infrared radiation multilayer film. Furthermore, the patterned morphology of the flexible rough substrate is designed to enhance the low specular reflection effect in infrared radiation, resulting in superior overall material performance. The flexible infrared radiation / reflection control material of this invention achieves low emissivity in the mid-wave infrared detection band (3-5 μm) and the long-wave infrared detection band (8-14 μm), as well as effective radiative heat dissipation in the non-atmospheric window (5-8 μm), and exhibits superior low specular reflection characteristics. It also features a simple structure, easy manufacturing process for industrial production, and good flexibility to effectively accommodate diverse application scenarios.

Description

Technical Field

[0001] This invention relates to the field of infrared radiation materials, specifically to a flexible infrared radiation / reflection modulation material and its preparation method. Background Technology

[0002] In nature, any object with a temperature above absolute zero constantly radiates energy in the form of electromagnetic waves. Theoretically, the electromagnetic waves emitted by an object are distributed across the entire spectrum. However, in industrial applications, the most practically significant temperature range is that of thermal radiation with wavelengths between 0.38 and 1000 μm, with the majority falling within the infrared (also known as thermal radiation) range of 0.76 to 20 μm. In recent years, the manipulation of infrared radiation and reflection has found widespread application in scenarios involving radiative cooling and circumventing infrared detectors.

[0003] Considering that most current infrared detectors are passive detectors, meaning they receive energy radiated by objects, and according to Kirchhoff's law of thermal radiation, the energy radiated by an object is proportional to the fourth power of its surface emissivity and temperature, achieving infrared radiation modulation requires reducing infrared emissivity while radiating energy into frequency bands undetectable by infrared detectors. Based on the infrared atmospheric transmission spectrum, electromagnetic waves in the 5-8 μm frequency band are absorbed by the atmosphere. Therefore, selective emission—high emission in the 5-8 μm band and low emission in other frequency bands—can be achieved through multilayer film structures.

[0004] Considering that if other heat sources exist around the object, the infrared radiation emitted by these sources will be reflected off the object's surface, exposing the object to the infrared detector. Therefore, we need to simultaneously reduce the infrared specular reflectivity to scatter the thermal radiation generated by external heat sources throughout the entire hemispherical space. A common method for controlling infrared reflection is to use a rough surface. However, the poor adhesion of rough surfaces makes the film layer prone to peeling off. Combining a multilayer film for infrared radiation control with a rough surface for infrared reflection control to achieve simultaneous control of radiation and reflection presents a challenge to the actual fabrication process.

[0005] In addition, in reality, the surface of an object is not regular and flat. In order to expand the application scenarios, the structure is developing towards flexibility, that is, the use of flexible rough substrate is an inevitable path.

[0006] In summary, existing materials cannot effectively control both infrared radiation and infrared reflection. Therefore, combining selective emission multilayer films with flexible, rough substrates through process optimization is a challenging problem, while flexible structures are of great significance for expanding their application scenarios. Summary of the Invention

[0007] To address the aforementioned problems or shortcomings and to solve the issue of poor interlayer bonding in existing flexible infrared radiation / reflection control materials, this invention provides a flexible infrared radiation / reflection control material and its preparation method. This allows a multilayer film with selective emission characteristics (infrared radiation layer) and a rough flexible substrate with low specular reflection characteristics (flexible reflection control layer) to be bonded together with high bonding strength, making it suitable for more application scenarios.

[0008] The specific technical solution of this invention is as follows:

[0009] A flexible infrared radiation / reflection modulation material, the structure of which is as follows: Figure 1 As shown, it includes a flexible rough substrate, a transition layer, and an infrared radiation multilayer film.

[0010] The infrared radiation multilayer film consists of a first metal layer, a first dielectric layer, a second metal layer, and a second dielectric layer from bottom to top. The first metal layer serves as a high-reflectivity layer, and the second metal layer serves as an infrared radiation layer. The first dielectric layer, the first metal layer, and the second metal layer form an FP resonant cavity. The second dielectric layer localizes electromagnetic waves within the second metal layer and serves as a protective layer for the entire infrared radiation multilayer film. The entire infrared radiation multilayer film structure enables the regulation of infrared radiation.

[0011] The transition layer is MgF2 with a thickness of 20–35 nm.

[0012] The flexible rough substrate is a patterned polyimide (PI) to control infrared reflection. Its patterned side is highly bonded to the first metal layer of the infrared radiation multilayer film through a transition layer, thereby improving the problem of easy detachment of existing flexible rough substrates due to poor adhesion between the rough morphology and the infrared radiation multilayer film.

[0013] Furthermore, the patterned morphology of the flexible rough substrate is hexagonal, and the hexagonal pattern is arranged in a disordered manner, which makes the infrared low specular reflection effect of the flexible rough substrate better.

[0014] Furthermore, the first metal layer is Ag with a thickness of 50–60 nm.

[0015] Furthermore, the first dielectric layer is Ge, with a thickness of 600-700 nm.

[0016] Furthermore, the second metal layer is Ag with a thickness of 12-18 nm.

[0017] Furthermore, the second dielectric layer is Ge, with a thickness of 300-350 nm.

[0018] The preparation method of the above-mentioned flexible infrared radiation / reflection modulation material includes the following steps:

[0019] Step 1: Pattern the polyimide (PI) flexible rough substrate.

[0020] Step 2: Deposit a 20-35 nm MgF2 transition layer on the flexible rough substrate prepared in Step 1.

[0021] Step 3: Based on Step 2, deposit a first metal layer, a first dielectric layer, a second metal layer, and a second dielectric layer of a preset thickness in sequence.

[0022] Furthermore, the polyimide (PI) flexible roughened substrate is cleaned after patterning before reuse.

[0023] Furthermore, the cleaning method is plasma cleaning.

[0024] In summary, this invention improves the poor bonding strength between layers in existing flexible infrared radiation / reflection control materials caused by the rough surface of the flexible substrate by adding a MgF2 transition layer between the flexible roughened polyimide (PI) substrate and the infrared radiation multilayer film. Furthermore, the patterned morphology of the flexible roughened substrate is designed to enhance the low specular reflection effect in infrared radiation, resulting in superior overall material performance. The flexible infrared radiation / reflection control material of this invention achieves low emissivity in the mid-wave infrared detection band (3-5 μm) and long-wave infrared detection band (8-14 μm), as well as radiative heat dissipation effect in the non-atmospheric window (5-8 μm), and exhibits superior low specular reflection characteristics. It also features a simple structure, easy manufacturing process for industrial production, and good flexibility to effectively accommodate diverse application scenarios. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of an embodiment;

[0026] Figure 2 The image shows the actual sample of the example and its optical microscope.

[0027] Figure 3 The image shows the infrared radiation test results of the sample in the example.

[0028] Figure 4 The image shows the infrared specular reflection test results of the sample at different angles in the example. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example

[0031] A flexible infrared radiation / reflection modulation material, the structure of which is as follows: Figure 1As shown; in addition to the flexible rough substrate, the flexible thin film includes: a transition layer MgF2, a high reflectivity layer Ag (first metal layer), a first dielectric layer Ge, an infrared radiation layer Ag (second metal layer), and a protective layer Ge (second dielectric layer).

[0032] All thin film layers were deposited using physical vapor deposition, specifically magnetron sputtering. The patterned flexible rough PI substrate was first cleaned with oxygen plasma. The plasma cleaning equipment was powered on (water, electricity, and gas) and the substrate was placed inside. A vacuum was then drawn until the instrument reading exceeded 85, the oxygen valve was opened, and plasma cleaning lasted for 5 minutes.

[0033] After cleaning, the substrate was placed in the magnetron sputtering equipment. Water, electricity, and gas were turned on, and a vacuum was evacuated to 3 × 10⁻⁴ Pa. The argon gas valve was opened, the flow rate was set to 200, and the chamber pressure was adjusted to 1 Pa using a constant pressure valve. The bias power supply was set to 300 V, the filament current to 3 A, and the filament voltage to 50 V. The substrate was treated for 5 minutes. The argon gas flow rate was set to 100, and the chamber pressure was adjusted to 0.1 Pa using a constant pressure valve. The ion source was set to 1000 V, and the substrate was treated for 5 minutes. The argon gas flow rate was set to 200, and the chamber pressure was adjusted to 0.5 Pa using a constant pressure valve. The RF power supply was set to 1.8 kW, the sample stage speed to 2 rpm, and the target was pre-sputtered for 3 minutes. After opening the baffle, a 20 nm thick MgF₂ film was obtained by sputtering at a deposition rate of 0.97 nm / min for 19 minutes and 25 seconds.

[0034] Maintain an argon flow rate of 200, use a pressure regulating valve to maintain the chamber pressure at 0.5 Pa, set the DC power supply to 2 KW, and the sample stage speed to 2 revolutions per minute. After pre-sputtering the target material for 3 minutes, open the baffle and sputter at a deposition rate of 15.94 nm / min for 3 minutes and 30 seconds to obtain a 56 nm thick Ag film.

[0035] Maintain an argon flow rate of 200, use a pressure regulating valve to maintain the chamber pressure at 0.5 Pa, set the RF power supply to 2 KW, and the sample stage speed to 2 revolutions per minute. After pre-sputtering the target material for 3 minutes, open the baffle and sputter at a deposition rate of 5.20 nm / min for 127 minutes to obtain a 660 nm thick Ge film.

[0036] Maintain an argon flow rate of 200, use a pressure regulating valve to maintain the chamber pressure at 0.5 Pa, set the DC power supply to 2 KW, and the sample stage speed to 1.77 rpm. After pre-sputtering the target material for 3 minutes, open the baffle and sputter at a deposition rate of 18.01 nm / min for 1 minute to obtain an 18 nm thick Ag film.

[0037] The argon flow rate was maintained at 200 m³ / h, and the chamber pressure was maintained at 0.5 Pa using a pressure regulating valve. A 2 kW DC power supply was set, and the sample stage rotation speed was 2 rpm. After 3 minutes of pre-sputtering of the target, the baffle was opened, and sputtering was performed at a deposition rate of 5.20 nm / min for 64 minutes to obtain a 333 nm thick Ge film. The final sample structure is shown below. Figure 1 As shown, the actual object is as follows Figure 2 As shown.

[0038] The reflectance of the 3-14 μm infrared integrating sphere of the sample was measured using a Fourier transform infrared microspectroscopy (FTIR) instrument, and the 3-14 μm infrared emissivity of the sample was calculated. The integrating sphere accessory was connected, the testing software was opened, and the test optical path was switched to the right-side integrating sphere reflection accessory. The integrating sphere was confirmed to be in Reference mode. The energy value was checked by clicking Monitor. The small black hole on top of the integrating sphere was opened, a funnel was inserted, and liquid nitrogen was slowly added until the energy increased to 3000. Simultaneously, the integrating sphere indicator light turned green. The Halt button was clicked to close the energy measurement, and the liquid nitrogen hole was closed. The test mode was selected as reflection mode, and the scan range was set to 4000 cm⁻¹. -1 ~400cm -1 After setting the scanning speed, adjust the integrating sphere to Sample mode, place the gold mirror in the measurement port, and click Background to scan the background. After the background scan is complete, place the sample with the sample side facing inward, ensuring it covers the sample well, and click Scan to begin scanning. Figure 3 This is a graph showing the infrared radiation test results of this embodiment.

[0039] The specular reflectance of the sample at different angles (3-14 μm) was measured using Fourier transform infrared microscopy. The specular reflectance attachment was connected, the testing software was opened, the specular reflectance attachment was adjusted, the measurement angle was selected, and the scanning range was set (4000 cm⁻¹). -1 ~400cm -1 After setting the scanning speed, place the gold mirror in the measurement port and click "Background" to scan the background. Once the background scan is complete, place the sample with the sample side facing inwards, ensuring it covers the sample well, and click "Scan" to scan. After scanning, change the measurement angle by rotating the knob on the mirror reflection accessory, and repeat the above steps. Figure 4 The results of infrared specular reflection tests at different angles (30°, 40°, 50°, 60°, 70°, 80°) are shown in the example.

[0040] As can be seen from the above embodiments, this invention effectively improves the adhesion between the film layer and the substrate by sputtering a transition layer of MgF2 after cleaning the flexible substrate. Through the high-reflectivity Ag layer, the intermediate dielectric layer Ge, the infrared radiation layer Ag, and the protective layer Ge, low emissivity (average absorptivity below 20% in the 3-5μm and 8-14μm bands) and radiative heat dissipation effect within the non-atmospheric window of 5-8μm are achieved (absorption peak position near 6μm, maximum absorptivity greater than 80%, and half-maximum width at half maximum greater than 1.5μm). The rough surface achieves low specular reflection over a wide angle range (specular reflectivity below 30% in the 30-80° range), effectively scattering infrared waves emitted by nearby heat sources. This invention has a simple structure, enables large-area (20×20cm) fabrication, and possesses good flexibility, effectively accommodating diverse application scenarios.

Claims

1. A flexible infrared radiation / reflection modulation material, characterized in that: Includes a flexible rough substrate, a transition layer, and an infrared radiation multilayer film; The infrared radiation multilayer film consists of a first metal layer, a first dielectric layer, a second metal layer, and a second dielectric layer from bottom to top. The first metal layer serves as a high-reflectivity layer, and the second metal layer serves as an infrared radiation layer. The first dielectric layer, the first metal layer, and the second metal layer form an FP resonant cavity. The second dielectric layer localizes electromagnetic waves within the second metal layer and serves as a protective layer for the entire infrared radiation multilayer film. The entire infrared radiation multilayer film structure enables the regulation of infrared radiation. The transition layer is MgF2 with a thickness of 20–35 nm; The flexible rough substrate is a patterned polyimide (PI) to control infrared reflection. Its patterned side is highly bonded to the first metal layer of the infrared radiation multilayer film through a transition layer.

2. The flexible infrared radiation / reflection modulation material as described in claim 1, characterized in that: The patterned morphology of the flexible rough substrate is hexagonal, and the hexagonal pattern is arranged in a disordered manner.

3. The flexible infrared radiation / reflection modulation material as described in claim 1, characterized in that: The first metal layer is Ag with a thickness of 50-60 nm.

4. The flexible infrared radiation / reflection modulation material as described in claim 1, characterized in that: The first dielectric layer is Ge, with a thickness of 600-700 nm.

5. The flexible infrared radiation / reflection modulation material as described in claim 1, characterized in that: The second metal layer is Ag, with a thickness of 12-18 nm.

6. The flexible infrared radiation / reflection modulation material as described in claim 1, characterized in that: The second dielectric layer is Ge, with a thickness of 300-350 nm.

7. The method for preparing the flexible infrared radiation / reflection modulation material as described in claim 1, characterized in that, Includes the following steps: Step 1: Pattern the polyimide (PI) flexible roughened substrate; Step 2: Deposit a 20-35 nm MgF2 transition layer on the flexible rough substrate prepared in Step 1; Step 3: Based on Step 2, deposit a first metal layer, a first dielectric layer, a second metal layer, and a second dielectric layer of a preset thickness in sequence.

8. The method for preparing the flexible infrared radiation / reflection modulation material as described in claim 7, characterized in that: The polyimide (PI) flexible rough substrate is cleaned after patterning before use.

9. The method for preparing the flexible infrared radiation / reflection modulation material as described in claim 8, characterized in that: The cleaning method is plasma cleaning.

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