Flexible infrared radiation / reflection regulation and control material and preparation method thereof

Abstract

The invention relates to the field of infrared radiation materials, in particular to a flexible infrared radiation / reflection regulation and control material and a preparation method thereof. The MgF2 transition layer is additionally arranged between the polyimide PI flexible rough substrate and the infrared radiation multilayer film, so that the problem that the bonding force between layers of an existing flexible infrared radiation / reflection regulation and control material is poor due to the rough surface of the flexible substrate is solved; and the graphical morphology of the flexible rough substrate is further designed, so that the infrared low-specular reflection effect is better, and the overall material performance is better. According to the flexible infrared radiation / reflection regulation and control material, the low emissivity of a medium-wave infrared detection wave band of 3-5 microns and a long-wave infrared detection wave band of 8-14 microns and the radiation heat dissipation effect of a non-atmospheric window of 5-8 microns are achieved, and the flexible infrared radiation / reflection regulation and control material has the better low specular reflection characteristic; and the structure is simple, the process is simple, industrial production is easy, the flexibility is good, and the diversity of application scenes can be effectively considered.

Description

Technical Field

[0001] The present invention relates to the field of infrared radiation materials, and in particular to a flexible infrared radiation / reflection regulating material and a preparation method thereof. Background Art

[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 throughout the entire spectrum, but in the temperature range encountered in industry, the thermal radiation with a wavelength between 0.38 and 1000 μm is of practical significance, and most of it is in the infrared (also known as heat ray) range of 0.76 to 20 μm. In recent years, the regulation of infrared radiation and reflection has been widely used in the scenarios of radiation cooling and avoiding infrared detectors.

[0003] Considering that most of the current infrared detectors are passive detection, that is, receiving the energy radiated by the object. According to Kirchhoff's law of thermal radiation, the energy radiated by the object is proportional to the surface emissivity of the object and the fourth power of the temperature. Therefore, to achieve infrared radiation regulation, it is necessary to reduce the infrared emissivity while radiating the energy in the frequency band that the infrared detector cannot detect. Combined with the infrared atmospheric transmission spectrum, it can be seen that electromagnetic waves in the 5-8μm frequency band will be absorbed by the atmosphere, so in order to achieve selective emission with high emission in the 5-8μm frequency band and low emission in other frequency bands, this performance can be achieved through a multi-layer film structure.

[0004] Considering that if there are other heat sources around the object, the infrared rays emitted by these heat sources will be reflected on the surface of the object, which will also expose the object to the infrared detector. Therefore, we need to reduce the reflectivity of the infrared mirror at the same time and try to scatter the thermal radiation generated by the external heat source into the entire hemispherical space. A commonly used method for infrared reflection control is to use a rough surface. However, the poor bonding force of the rough surface makes the film layer easy to fall off. Combining the multilayer film for infrared radiation control with the rough surface for infrared reflection control to achieve simultaneous control of radiation and reflection brings challenges to the actual preparation process.

[0005] In addition, in actual situations, the surface of objects is not regular and flat. In order to expand the application scenarios, the structure must develop towards flexibility, that is, the use of a flexible rough substrate is a must.

[0006] In summary, existing materials cannot well balance the regulation of infrared radiation and infrared reflection. Therefore, whether it is possible to combine the selective emission multilayer film and the flexible rough substrate through process optimization is a challenging problem. At the same time, the flexible structure is of great significance for expanding its application scenarios. Summary of the invention

[0007] In view of the above-mentioned problems or shortcomings, and in order to solve the problem of poor interlayer bonding strength of existing flexible infrared radiation / reflection regulation materials, the present invention provides a flexible infrared radiation / reflection regulation material and a preparation method thereof, so that a multilayer film (infrared radiation layer) with selective emission characteristics and a rough flexible substrate (flexible reflection regulation layer) with low mirror reflection characteristics are compounded together with a higher bonding strength to be suitable for more application scenarios.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A flexible infrared radiation / reflection regulating 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 comprises, from bottom to top, a first metal layer, a first dielectric layer, a second metal layer and a second dielectric layer. The first metal layer serves as a high reflection layer, the second metal layer serves as an infrared radiation layer, the first dielectric layer and the first metal layer and the second metal layer form an FP resonant cavity, the second dielectric layer localizes electromagnetic waves in the second metal layer and serves as a protective layer for the entire infrared radiation multilayer film; the entire infrared radiation multilayer film structure realizes the regulation of infrared radiation.

[0011] The transition layer is MgF 2 , thickness 20~35nm.

[0012] The flexible rough substrate is a patterned polyimide PI, which can achieve the regulation of infrared reflection, and its patterned side is highly bonded to the first metal layer of the infrared radiation multilayer film through a transition layer; so as to improve the problem that the existing flexible rough substrate is easy to fall off due to the poor bonding strength between the rough morphology and the infrared radiation multilayer film.

[0013] Furthermore, the graphic morphology of the flexible rough substrate is hexagonal, and the hexagonal pattern is arranged in a disordered manner, so that the infrared low mirror reflection effect of the flexible rough substrate is 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 method for preparing the above-mentioned flexible infrared radiation / reflection regulating material comprises the following steps:

[0019] Step 1: Patterning the polyimide PI flexible rough substrate.

[0020] Step 2: Deposit 20-35 nm of MgF on the flexible rough substrate treated in step 1. 2 Transition layer.

[0021] Step 3: Based on step 2, a first metal layer, a first dielectric layer, a second metal layer and a second dielectric layer with preset thicknesses are deposited in sequence.

[0022] Furthermore, the polyimide PI flexible rough substrate can be used after cleaning after patterning.

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

[0024] In summary, the present invention adds MgF 2 A transition layer is used to improve the problem of poor bonding between layers of existing flexible infrared radiation / reflection regulating materials due to the rough surface of the flexible substrate; and the graphical morphology of the flexible rough substrate is further designed to make the infrared low specular reflection effect better, thereby improving the overall material performance. The flexible infrared radiation / reflection regulating material of the present invention achieves low emissivity in the medium-wave infrared detection band of 3-5μm and the long-wave infrared detection band of 8-14μm, as well as the radiation heat dissipation effect of 5-8μm in the non-atmospheric window, and has better low specular reflection characteristics; and has a simple structure, simple process, and is easy to industrialize, and has good flexibility to effectively take into account the diversity of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of an embodiment;

[0026] Figure 2 The figure is a physical picture of the sample of the embodiment and its optical microscope;

[0027] Figure 3 This is a graph showing the infrared radiation test results of the samples of the embodiment;

[0028] Figure 4 The infrared mirror reflection test results of the example samples at different angles are shown. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0030] Example

[0031] A flexible infrared radiation / reflection regulating material, the structure of which is as follows Figure 1 As shown; in addition to the flexible rough substrate, the flexible film includes: a transition layer MgF2 , a high reflective 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] The deposition method of each layer of thin film is physical vapor deposition, and the specific method is magnetron sputtering. The patterned flexible rough substrate PI is first cleaned with oxygen plasma. The plasma cleaning equipment is turned on with water, electricity, and gas, and then the substrate to be treated is placed in it. Then the vacuum is evacuated until the instrument reading is greater than 85, and the oxygen valve is opened. The plasma cleaning is carried out for 5 minutes.

[0033] The cleaned substrate is placed in the magnetron sputtering equipment, and the water, electricity, and gas are turned on and the vacuum is evacuated to 3×10^-4Pa. Open the argon valve, set the flow rate to 200, use the constant pressure valve to adjust the pressure in the chamber to 1Pa, set the bias power supply to 300V, set the filament current to 3A, and the filament voltage to 50V, and treat the substrate for 5min. Set the argon flow rate to 100, use the constant pressure valve to adjust the pressure in the chamber to 0.1Pa, set the ion source to 1000V, and treat the substrate for 5min. Set the argon flow rate to 200, use the constant pressure valve to adjust the pressure in the chamber to 0.5Pa, set the RF power supply to 1.8KW, the sample stage speed to 2 revolutions per minute, pre-sputter the target for 3 minutes, then open the baffle, and sputter at a deposition rate of 0.97nm / min for 19 minutes and 25 seconds to obtain a 20nm thick MgF 2 film.

[0034] The argon flow rate was maintained at 200, the pressure in the chamber was maintained at 0.5 Pa using a constant pressure valve, the DC power supply was set to 2 kW, the sample stage speed was set to 2 rpm, the target was pre-sputtered for 3 minutes, and then the baffle was opened. A 56 nm thick Ag film was obtained by sputtering for 3 minutes and 30 seconds at a deposition rate of 15.94 nm / min.

[0035] The argon flow rate was maintained at 200, the pressure in the chamber was maintained at 0.5 Pa using a constant pressure valve, the RF power was set to 2 kW, the sample stage speed was set to 2 rpm, the target was pre-sputtered for 3 minutes, the baffle was opened, and a 660 nm thick Ge film was obtained by sputtering at a deposition rate of 5.20 nm / min for 127 minutes.

[0036] The argon flow rate was maintained at 200, the pressure in the chamber was maintained at 0.5 Pa using a constant pressure valve, the DC power supply was set to 2 kW, the sample stage speed was set to 1.77 rpm, the target was pre-sputtered for 3 minutes, the baffle was opened, and a 18 nm thick Ag film was obtained by sputtering for 1 minute at a deposition rate of 18.01 nm / min.

[0037] The argon flow rate was maintained at 200, the pressure in the chamber was maintained at 0.5 Pa using a constant pressure valve, the DC power supply was set to 2KW, the sample stage speed was set to 2 rpm, the target was pre-sputtered for 3 minutes, the shutter was opened, and a 333 nm thick Ge film was obtained by sputtering at a deposition rate of 5.20 nm / min for 64 minutes. The final sample structure is shown in the figure below: Figure 1 As shown, the actual Figure 2 shown.

[0038] Use a Fourier transform infrared microspectrometer to measure the 3-14μm infrared integrating sphere reflectivity of the sample and calculate the 3-14μm infrared emissivity of the sample. Connect the integrating sphere accessory, open the test software, and switch the test light path to the integrating sphere reflection accessory on the right. Determine the state of the integrating sphere, which is in the Reference gear, click Monitor to view the energy value, open the black hole above the integrating sphere, insert the funnel, and slowly add liquid nitrogen until the energy increases to 3000. At the same time, the integrating sphere indicator light turns green. Click Halt to turn off the energy measurement and cover the liquid nitrogen hole. Select the test mode as reflection mode, set the scanning range (4000cm -1 ~400cm -1 ), scanning speed, after setting, adjust the integrating sphere to Sample gear, place the gold mirror at the measuring port, and click Background to scan the background. After the background scan is completed, place the sample with the sample facing inwards, making sure to cover the sample hole, and click Scan to scan. Figure 3 This is a diagram of the infrared radiation test results of this embodiment.

[0039] Use a Fourier transform infrared microspectrometer to measure the specular reflectivity of the sample at different angles from 3 to 14 μm. Connect the specular reflectance accessory, open the test software, adjust the specular reflectance accessory to select the measurement angle, set the scanning range (4000 cm -1 ~400cm -1 ), scanning speed, after setting, place the gold mirror at the measuring port, click Background to scan the background. After the background scan is completed, place the sample with the sample facing inward, making sure to cover the sample hole, and click Scan to scan. After the scan is completed, change the measurement angle by rotating the knob on the mirror reflection accessory, and repeat the above steps. Figure 4 These are infrared mirror reflection test result diagrams at different angles (30°, 40°, 50°, 60°, 70°, 80°) of the embodiments.

[0040] It can be seen from the above embodiments that the present invention cleans the flexible substrate and then sputters the transition layer MgF 2, effectively improving the bonding force between the film layer and the substrate. Through the high-reflection layer Ag, the intermediate dielectric layer Ge, the infrared radiation layer Ag and the protective layer Ge, low emissivity in the medium-wave infrared and long-wave infrared detection bands (the average absorption rate of 3-5μm and 8-14μm is less than 20%), and the radiation heat dissipation effect of the non-atmospheric window 5-8μm (the absorption peak position is near 6μm, the maximum absorption rate is greater than 80%, and the half-peak width is greater than 1.5μm) are achieved. Low specular reflection in a large angle range (the specular reflectivity of 30-80° is less than 30%) is achieved through the rough surface, which can effectively scatter infrared waves emitted by nearby heat sources. The present invention has a simple structure, realizes large-area (20×20cm) preparation, and has good flexibility, which can effectively take into account the diversity of application scenarios.

Claims

1. A flexible infrared radiation / reflection regulating material, characterized in that: It includes a flexible rough substrate, a transition layer and an infrared radiation multilayer film; The infrared radiation multilayer film comprises, from bottom to top, a first metal layer, a first dielectric layer, a second metal layer and a second dielectric layer, wherein the first metal layer serves as a high reflection layer, the second metal layer serves as an infrared radiation layer, the first dielectric layer and the first metal layer and the second metal layer form an FP resonant cavity, the second dielectric layer localizes electromagnetic waves in the second metal layer and serves as a protective layer for the entire infrared radiation multilayer film; the entire infrared radiation multilayer film structure realizes the regulation of infrared radiation; The transition layer is MgF2 with a thickness of 20 to 35 nm; The flexible rough substrate is a patterned polyimide PI, which realizes the regulation of infrared reflection, and its patterned side is highly combined with the first metal layer of the infrared radiation multilayer film through a transition layer.

2. The flexible infrared radiation / reflection regulating material according to claim 1, characterized in that: The graphic morphology of the flexible rough substrate is hexagonal, and the hexagonal pattern is arranged in a disordered manner.

3. The flexible infrared radiation / reflection regulating material according to claim 1, characterized in that: The first metal layer is Ag, and has a thickness of 50-60 nm.

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

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

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

7. The method for preparing the flexible infrared radiation / reflection regulating material according to claim 1, characterized in that: The following steps are involved: Step 1, patterning the polyimide PI flexible rough substrate; Step 2, depositing a 20-35 nm MgF2 transition layer on the flexible rough substrate processed in step 1; Step 3: Based on step 2, a first metal layer, a first dielectric layer, a second metal layer and a second dielectric layer with preset thicknesses are deposited in sequence.

8. The method for preparing the flexible infrared radiation / reflection regulating material according to claim 7, characterized in that: The polyimide PI flexible rough substrate is used after being cleaned after patterning.

9. The method for preparing the flexible infrared radiation / reflection regulating material according to claim 8, characterized in that: The cleaning method is plasma cleaning.

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