Intermediate infrared substrate protective film and preparation method and application thereof

Abstract

The invention provides an intermediate infrared substrate protective film and a preparation method and application thereof, the intermediate infrared substrate protective film is formed by overlapping a Ta2O5 film layer and a SiO2 film layer, and the intermediate infrared substrate protective film is arranged on the surface of an intermediate infrared substrate. The intermediate infrared substrate protective film is a hard protective film layer, the film layer is compact, the transmittance of the intermediate infrared substrate can be improved, the chemical stability and corrosion resistance of the intermediate infrared substrate are enhanced, and the adaptability of the intermediate infrared substrate to complex service environments such as moisture and salt mist is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of protective films, and in particular to a mid-infrared substrate protective film and a preparation method and application thereof. Background Art

[0002] Mid-infrared glass is a special glass material with infrared transmittance. It not only has excellent infrared transmittance, but also has the advantages of good optical uniformity, low manufacturing cost, and easy processing into large-sized or complex-shaped products. It has always been the focus of infrared material research and application. Currently, the mid-infrared glass that has been put into practical use includes aluminate glass, gallate glass, heavy metal fluoride glass, etc.

[0003] With the rapid development of science and technology, the demand for optical imaging systems is increasing, especially for mid-infrared window materials, which require a wider range of application environments, which requires window materials to have higher stability. However, the overall stability of mid-wave infrared glass systems is often poor. In actual application environments, its surface is prone to deliquesce and mold, which affects its transmission performance and performance as a window material.

[0004] In order to meet the demand for highly stable mid-infrared window materials in the field of new-generation infrared optoelectronic systems, it is of great significance to improve the stability of mid-wave infrared glass. Summary of the invention

[0005] The main purpose of the present invention is to provide a mid-infrared substrate protective film and a preparation method and application thereof. The technical problem to be solved is how to provide a mid-infrared substrate protective film which, after being arranged on the surface of the mid-infrared substrate, can improve the chemical stability and corrosion resistance of the mid-infrared substrate, and improve the adaptability of the mid-infrared substrate to complex service environments such as humidity, salt spray, etc., so as to be more suitable for practical use.

[0006] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions. According to a mid-infrared substrate protective film proposed by the present invention, the aforementioned mid-infrared substrate protective film is composed of a Ta2O5 film layer and a SiO2 film layer overlapped, and the aforementioned mid-infrared substrate protective film is arranged on the surface of the mid-infrared substrate.

[0007] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0008] In some embodiments, in the aforementioned mid-infrared base protection film, the thickness of the aforementioned mid-infrared base protection film is 900 to 1100 nm.

[0009] In some embodiments, in the aforementioned mid-infrared substrate protective film, the total thickness of the Ta2O5 film layer is 150 to 250 nm, and the total thickness of the SiO2 film layer is 750 to 850 nm.

[0010] In some embodiments, in the aforementioned mid-infrared base protective film, the aforementioned mid-infrared base protective film is stacked in the following manner:

[0011] Air / SiO2 / Ta2O5 / SiO2 / Ta2O5 / SiO2 / Ta2O5 / SiO2 / Ta2O5 / the aforementioned mid-infrared substrate.

[0012] In some embodiments, in the aforementioned mid-infrared base protective film, the thickness of each film layer of the aforementioned mid-infrared base protective film is:

[0013] Air / 237-238nm / 21-22nm / 392-394nm / 18-19nm / 146-147nm / 73-74nm / 55-56nm / 88-89nm / the mid-infrared substrate.

[0014] In some embodiments, in the aforementioned mid-infrared substrate protective film, the aforementioned mid-infrared substrate is gallate glass.

[0015] In some embodiments, in the aforementioned mid-infrared substrate protective film, the aforementioned mid-infrared substrate comprises, by weight percentage of oxides, 29% to 33% gallium oxide; 43% to 46% calcium oxide; 5% to 7% barium oxide; 3.5% to 6% aluminum oxide; 2% to 10% yttrium oxide, and the sum of alkali metal oxides and alkaline earth metal oxides other than barium oxide is 8% to 11%.

[0016] The purpose of the present invention and the solution of its technical problems are also achieved by the following technical solutions. According to a method for preparing a mid-infrared substrate protective film proposed by the present invention, the steps include: according to the film system design scheme, Ta2O5 film layers and SiO2 film layers are layered and overlapped on the mid-infrared substrate to obtain the aforementioned mid-infrared substrate protective film.

[0017] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0018] In some embodiments, in the aforementioned method for preparing the mid-infrared substrate protective film, the aforementioned mid-infrared substrate protective film is prepared by ion beam sputtering, and the working conditions are as follows: sputtering power is 100-1500W, auxiliary source power is 100-300W; temperature is 120-200°C; coating speed is 5-15rpm; oxygen and argon mixture flow rate is 20-40sccm, oxygen and argon mixture ratio is 8-10:1; target substrate distance is 10-20cm; working vacuum degree is 1-6×10 -4 Pa.

[0019] The purpose of the present invention and the technical problem solved are also achieved by the following technical solutions: The present invention proposes the application of any of the aforementioned mid-infrared substrate protective films in the field of infrared optoelectronic systems.

[0020] Through the above technical solution, the mid-infrared substrate protective film and its preparation method and application of the present invention have at least the following advantages:

[0021] The present invention provides a mid-infrared substrate protective film, which is arranged on the surface of the mid-infrared substrate and is composed of a Ta2O5 film layer and a SiO2 film layer overlapped. The mid-infrared substrate protective film is a hard protective film layer, the film layer is dense, and is arranged on the surface of the mid-infrared substrate. The single-sided anti-reflection can increase the transmittance of the mid-infrared substrate at 3.7μm to 4.8μm by more than 9%, and increase the transmittance of the mid-infrared substrate at 900 to 1700nm by more than 9%, improve the adaptability of the mid-infrared substrate to complex service environments, and pass the assessment and evaluation of moisture and salt spray in the national military standard GJB150-2009.

[0022] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the mid-infrared substrate protective film disclosed in an embodiment of the present invention.

[0024] Description of reference numerals:

[0025] 1. Mid-infrared substrate; 2. Ta2O5 film layer; 3. SiO2 film layer. DETAILED DESCRIPTION

[0026] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of a mid-infrared substrate protective film and its preparation method and its specific implementation method, structure, characteristics and effects of the application proposed by the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0027] The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the specification. The present invention provides these embodiments to make the present invention thorough and complete, and to fully express the scope of the present invention to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the parts and steps, the composition of the materials, the numerical expressions and the numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary, and not as limiting.

[0028] The present invention proposes a mid-infrared substrate protective film, such as Figure 1 As shown, the aforementioned mid-infrared substrate protective film is composed of a Ta2O5 film layer 2 and a SiO2 film layer 3 overlapping each other, and the aforementioned mid-infrared substrate protective film is arranged on the surface of the mid-infrared substrate 1.

[0029] Specifically, the mid-infrared substrate 1 is a material with infrared transmittance, such as mid-infrared glass, including aluminate glass, gallate glass, heavy metal fluoride glass, and the like.

[0030] The Ta2O5 film layer 2 has the characteristics of low impurity content, high refractive index and high transmittance. Ta2O5 is the final product of tantalum burning in air. The Ta2O5 film layer 2 has a low impurity content, which can reduce the scattering and absorption during the transmission of light, thereby improving the efficiency and clarity of the optical system, which is crucial to ensure the performance stability of optical devices. The Ta2O5 film layer 2 has a high refractive index, which can effectively concentrate light, improve the focusing ability and imaging quality of optical devices, and is conducive to the manufacture of high-performance lenses, prisms and other optical components. The Ta2O5 film layer 2 has a high transmittance, which can ensure that the loss of light is very small when passing through the film layer. At the same time, the Ta2O5 film layer 2 also has high density, which can improve the hardness and wear resistance of the mid-infrared substrate 1, and enhance the chemical stability and corrosion resistance of the mid-infrared substrate 1.

[0031] SiO2 film layer 3 is a common medium material in optical film system, Ta2O5 is a high refractive index material, and SiO2 is a low refractive index material. By using different stacking sequences and film thickness combinations of high and low refractive index materials, the surface reflectivity of substrate materials such as glass and transparent resin can be adjusted to reduce reflectivity and increase transmittance.

[0032] The mid-infrared substrate protective film proposed by the present invention can improve the transmittance of the mid-infrared substrate 1, enhance the chemical stability and corrosion resistance of the mid-infrared substrate 1, and improve the adaptability of the mid-infrared substrate 1 to complex service environments such as humidity and salt spray.

[0033] In some embodiments, the thickness of the aforementioned mid-infrared substrate protective film is 900-1100 nm.

[0034] Specifically, if the thickness of the mid-infrared substrate protective film is less than 900nm, the film layer is too thin and the protection performance for the mid-infrared substrate is poor; if the thickness of the mid-infrared substrate protective film is greater than 1100nm, the film layer is too thick, affecting the preparation efficiency; therefore, the thickness of the mid-infrared substrate protective film is controlled at 900-1100nm.

[0035] In some embodiments, in the aforementioned mid-infrared substrate protective film, the total thickness of the Ta2O5 film layer 2 is 150-250 nm, and the total thickness of the SiO2 film layer 3 is 750-850 nm.

[0036] Specifically, the refractive index of the Ta2O5 film layer 2 and the SiO2 film layer 3 are different, and they are overlapped. By adjusting the thickness of each film layer, the transmittance of the mid-infrared substrate 1 can be increased. Therefore, the total thickness of the Ta2O5 film layer 2 is controlled to be 150-250nm, and the total thickness of the SiO2 film layer 3 is controlled to be 750-850nm.

[0037] In some embodiments, the aforementioned mid-infrared base protective film is stacked in the following manner:

[0038] Air / SiO2-4 / Ta2O5-4 / SiO2-3 / Ta2O5-3 / SiO2-2 / Ta2O5-2 / SiO2-1 / Ta2O5-1 / mid-infrared substrate 1.

[0039] In some embodiments, the thickness of each film layer of the aforementioned mid-infrared base protective film is:

[0040] Air / 237-238nm / 21-22nm / 392-394nm / 18-19nm / 146-147nm / 73-74nm / 55-56nm / 88-89nm / the mid-infrared substrate 1.

[0041] Specifically, Ta2O5-1 is the Ta2O5 film layer 2, which is the first film layer adjacent to the mid-infrared substrate 1. Preferably, its thickness is 237-238 nm, and more preferably, its thickness is 237.46 nm.

[0042] SiO2-1 is the SiO2 film layer 3, which is the second film layer adjacent to Ta2O5-1. Preferably, its thickness is 21 to 22 nm, and more preferably, its thickness is 21.54 nm.

[0043] Ta2O5-2 is Ta2O5 film layer 2, which is the third film layer adjacent to SiO2-1. Preferably, its thickness is 392-394 nm, and more preferably, its thickness is 393 nm.

[0044] SiO2-2 is SiO2 film layer 3, which is the fourth film layer adjacent to Ta2O5-2. Preferably, its thickness is 18 to 19 nm, and more preferably, its thickness is 18.19 nm.

[0045] Ta2O5-3 is Ta2O5 film layer 2, which is the fifth film layer adjacent to SiO2-2. Preferably, its thickness is 146 to 147 nm, and more preferably, its thickness is 146.66 nm.

[0046] SiO2-3 is SiO2 film layer 3, which is the sixth film layer adjacent to Ta2O5-3. Preferably, its thickness is 73-74 nm, and more preferably, its thickness is 73.37 nm.

[0047] Ta2O5-4 is Ta2O5 film layer 2, which is the seventh film layer adjacent to SiO2-3. Preferably, its thickness is 55 to 56 nm, and more preferably, its thickness is 55.38 nm.

[0048] SiO2-4 is SiO2 film layer 3, which is the eighth film layer adjacent to Ta2O5-4. Preferably, its thickness is 88-89 nm, and more preferably, its thickness is 88.06 nm.

[0049] The reason for selecting the above-mentioned film structure and film thickness is that the film system is designed using optical film design software, and the optimal film thickness combination is selected to achieve a high transmittance effect.

[0050] In some embodiments, the aforementioned mid-infrared substrate 1 is gallate glass.

[0051] Specifically, the mid-infrared glasses that have been put into practical use include aluminate glass, gallate glass, heavy metal fluoride glass and other systems. Gallate glass is a kind of mid-wave infrared glass with gallium oxide, aluminum oxide, calcium oxide and other components as the main components. It has excellent multi-spectral transmittance, and has good transmittance from visible to mid-infrared. Compared with aluminate glass, the transmittance of gallate glass system can be improved by more than 20% at around 5.0μm; compared with heavy metal fluoride glass, it has higher environmental adaptability and low production cost.

[0052] In some embodiments, in the aforementioned mid-infrared substrate protective film, the aforementioned mid-infrared substrate 1 comprises, by weight percentage of oxides, 29% to 33% gallium oxide; 43% to 46% calcium oxide; 5% to 7% barium oxide; 3.5% to 6% aluminum oxide; 2% to 10% yttrium oxide, and the sum of alkali metal oxides and alkaline earth metal oxides other than barium oxide is 8% to 11%.

[0053] Specifically, the mid-infrared substrate 1 composed of the above components has high transmittance, good mechanical properties, high stability, and strong adaptability to complex environments. Ga2O3 is an important network former of mid-infrared gallate glass, which can improve the glass-forming ability and chemical stability of glass. The mass fraction of this component is controlled between 29% and 33% in the present invention. Within this range, the glass has good glass-forming ability, good elastic modulus, and good chemical stability. CaO is a necessary component for mid-infrared gallate glass to have good elastic modulus and chemical stability. The mass fraction of this component is controlled between 43% and 46%. Within this range, the glass structure is dense and the glass has high acid resistance and stability. Al2O3 can form a network structure with SiO2, making the glass structure tend to be compact, improving the mechanical properties and stability of the glass, and the mass fraction of this component is controlled between 3.5% and 6%. If the Al2O3 content is lower than 3.1%, the internal network structure of the glass is small, and the strength, transmittance and other properties are low, and the network gap is small; if the content is higher than 6.5%, the temperature required for melting is too high, which is easy to cause defects such as stones. Y2O3 is a network outer body of glass, which is used to reduce the melting temperature of glass and facilitate the discharge of bubbles during the melting process. The mass fraction of this component is controlled between 2% and 10%. If the mass fraction of this component is less than 2%, the melting temperature of the glass is high, the viscosity increases, and the bubbles are not easy to discharge; if the mass fraction of this component is higher than 10%, the elastic modulus and chemical stability of the glass deteriorate. BaO is a divalent network outer body oxide, which can increase the refractive index, density, gloss and chemical stability of the glass. A small amount of BaO can accelerate the melting of glass, but too much content will cause secondary bubbles to appear during clarification. The mass fraction of this component is controlled between 5% and 7%. If the BaO content is less than 5%, its effect of accelerating the melting of glass is not obvious; when the BaO content is greater than 7%, it will increase the crystallization temperature of the glass, increase the crystallization tendency of the glass, and react with oxygen, making it difficult to clarify the melt. Alkali metal oxides include Na2O and / or K2O, and alkaline earth metal oxides other than barium oxide include SrO and / or MgO. Alkaline earth metal oxides are glass intermediates used to improve the glass forming properties. Na2O and K2O are network outer oxides of the basic glass network, which can improve the chemical stability and surface tension of the glass, have the function of high temperature fluxing, accelerate glass melting, reduce the high temperature viscosity of the glass, and are also conducive to the clarification of the glass. Preferably, the mass fraction of alkali metal oxides is controlled between 1% and 5%.

[0054] The present invention proposes a method for preparing a mid-infrared substrate protective film, the steps of which include: according to the film system design scheme, layer by layer Ta2O5 film layer 2 and SiO2 film layer 3 are overlapped on the mid-infrared substrate 1 to obtain the aforementioned mid-infrared substrate protective film.

[0055] Specifically, the coating method of the film layer can adopt existing technology, for example, physical vapor deposition, chemical vapor deposition, solid powder spraying or ion beam sputtering, etc., which are not limited here. Physical vapor deposition (PVD) technology refers to the technology of using physical methods to vaporize the surface of the material source into gaseous atoms or molecules, or partially ionize into ions under vacuum conditions, and deposit a thin film with certain special functions on the surface of the substrate through a low-pressure gas (or plasma) process. PVD coating technology is mainly divided into three categories: vacuum evaporation coating, vacuum sputtering coating and vacuum ion coating. Chemical vapor deposition (CVD) is a process technology that supplies one or several compounds or single gases containing thin film elements to the substrate, and uses gas phase reaction to deposit the desired solid film on the surface of the substrate. It continuously deposits compound films during the production process of float glass and is currently the most advanced coating technology in the world. The solid powder spraying method is to spray one or more components of organic metal salt powder onto the surface of hot glass through a special spray gun with the help of a compressed gas carrier, and use the high-temperature thermal decomposition of the organic metal salt to form a layer of metal oxide film on the glass surface.

[0056] In some embodiments, the aforementioned mid-infrared substrate protective film is prepared by ion beam sputtering, and the working conditions are as follows: sputtering power is 100-1500 W, auxiliary source power is 100-300 W; temperature is 120-200 ° C; coating speed is 5-15 rpm; oxygen and argon mixture flow rate is 20-40 sccm, oxygen and argon mixture ratio is 8-10:1; target substrate distance is 10-20 cm; working vacuum degree is 1×10 -4 ~6×10 -4 Pa.

[0057] Specifically, the ion beam sputtering method is to generate positive gas ions by glow discharge in a partially vacuum sputtering chamber. Under the accelerating effect of the voltage between the cathode (target) and the anode (sample), the positively charged ions bombard the cathode surface, atomizing the cathode surface material. The formed neutral atoms are sputtered from all directions and fall on the surface of the sample, thus forming a uniform thin film on the surface of the sample. The advantages of this method are: uniform coating, high coating rate; high film density and strong adhesion.

[0058] The present invention proposes the application of the aforementioned mid-infrared substrate protective film in the field of infrared optoelectronic systems. For example, it can be applied to infrared detectors, infrared aircraft, fairings or hoods, etc.

[0059] The present invention will be further described below in conjunction with specific embodiments, but this should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by technicians in this field based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0060] Unless otherwise specified, the materials, reagents, etc. involved below are all commercially available products well known to those skilled in the art; unless otherwise specified, the methods described are all methods well known in the art. Unless otherwise defined, the technical terms or scientific terms used should have the common meanings understood by ordinary technicians in the field to which the present invention belongs.

[0061] Example 1

[0062] This embodiment provides a mid-infrared substrate protective film and a preparation method and application thereof.

[0063] The mid-infrared substrate 1 with a thickness of 2 mm after surface grinding and polishing is cleaned.

[0064] The gallate glass used in the mid-infrared substrate 1 of this embodiment includes, by oxide mass percentage, the following components: Ga2O3: 32.19%; CaO: 43.21%; Al2O3: 5.53%; Y2O3: 3.1%; BaO: 6.08%; MgO: 6.99%; Na2O: 1.36%; K2O: 0.51%; TeO2: 1%; and Sb2O3: 0.03%. The preparation method is as follows: grind the raw materials into powder and mix them evenly, melt them at 1460°C for 12 hours, cool them, and obtain a primary melting clinker. Melt the primary melting clinker in a vacuum environment with a vacuum degree of 2.5×10 -2 Pa, the melting temperature is 1470℃, the melting time is 8h, and after complete melting, it is clarified, formed, annealed and cooled to obtain gallate glass.

[0065] By adopting the ion beam sputtering method and according to the film system design plan, Ta2O5 film layer 2 and SiO2 film layer 3 are alternately deposited layer by layer on the mid-infrared substrate 1 to obtain the mid-infrared substrate protective film.

[0066] The specific method is as follows: pure tantalum and pure silicon target materials are selected, and a mixed gas of oxygen and argon is used as the working gas. The specific process parameters during the sputtering process are as follows: sputtering power 500W, auxiliary source power 200W; deposition temperature 180℃; coating speed 10rpm; oxygen and argon mixture flow rate 35sccm, oxygen and argon mixture ratio 9:1; target substrate distance 15cm; working vacuum 4×10 -4 Pa.

[0067] The membrane system design is as follows:

[0068] Air / SiO2 / Ta2O5 / SiO2 / Ta2O5 / SiO2 / Ta2O5 / SiO2 / Ta2O5 / mid-infrared substrate 1.

[0069] The thickness parameters of each film layer corresponding to the film system design are:

[0070] Air / 237.46nm / 21.54nm / 393nm / 18.19nm / 46.66nm / 73.37nm / 55.38nm /

[0071] 88.06nm / Mid-infrared substrate 1.

[0072] The transmittance and environmental stability of the above-mentioned mid-infrared substrate 1 and the above-mentioned mid-infrared substrate 1 coated with a mid-infrared substrate protective film were tested. The transmittance test method is to use an infrared light transmittance spectrum to test the infrared light transmittance of the sample in the infrared band range of 0 to 8 μm; the moisture resistance of the sample is tested according to the inspection standard GB / T6582-1997; the acid resistance of the sample is tested according to the inspection standard GB / T6581-2007.

[0073] The average transmittance of the mid-infrared substrate 1 under infrared light with a wavelength of 3.7 to 4.8 μm is 82%, and the average transmittance under infrared light with a wavelength of 900 to 1700 nm is 84%. After evaluation according to the moisture and salt spray assessment plan in the national military standard GJB150-2009, there are erosion patches on the sample surface.

[0074] The average transmittance of the mid-infrared substrate 1 coated with the mid-infrared substrate protective film is 91.2% under infrared light with a wavelength of 3.7 to 4.8 μm, and the average transmittance under infrared light with a wavelength of 900 to 1700 nm is 93.4%. After evaluation according to the moisture and salt spray assessment plan in the national military standard GJB150-2009, the surface of the sample has not changed.

[0075] It can be seen from Example 1 that the mid-infrared substrate protective film provided by the present invention can improve the transmittance of the mid-infrared substrate 1, enhance the chemical stability and corrosion resistance of the mid-infrared substrate 1, improve the adaptability of the mid-infrared substrate 1 to complex service environments such as moisture, salt spray, etc., and pass the moisture and salt spray assessment evaluation in the national military standard GJB150-2009.

[0076] The technical features in the claims and / or the specification of the present invention may be combined, and the combination is not limited to the combination obtained by reference in the claims. The technical solution obtained by combining the technical features in the claims and / or the specification is also within the protection scope of the present invention.

[0077] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A mid-infrared substrate protective film, characterized in that: The mid-infrared substrate protective film is composed of a Ta2O5 film layer and a SiO2 film layer overlapped, and the mid-infrared substrate protective film is arranged on the surface of the mid-infrared substrate.

2. The mid-infrared base protective film according to claim 1, characterized in that: The thickness of the mid-infrared substrate protective film is 900-1100 nm.

3. The mid-infrared substrate protective film according to claim 2, characterized in that: In the mid-infrared substrate protective film, the total thickness of the Ta2O5 film layer is 150-250nm, and the total thickness of the SiO2 film layer is 750-850nm.

4. The mid-infrared base protective film according to claim 2, characterized in that: The stacking method of the mid-infrared base protective film is: Air / SiO2 / Ta2O5 / SiO2 / Ta2O5 / SiO2 / Ta2O5 / SiO2 / Ta2O5 / the mid-infrared substrate.

5. The mid-infrared base protective film according to claim 4, characterized in that: The thickness of each film layer of the mid-infrared base protective film is: Air / 237-238nm / 21-22nm / 392-394nm / 18-19nm / 146-147nm / 73-74nm / 55-56nm / 88-89nm / the mid-infrared substrate.

6. The mid-infrared substrate protective film according to claim 1, characterized in that: The mid-infrared substrate is gallate glass.

7. The mid-infrared base protective film according to claim 6, characterized in that: The mid-infrared substrate comprises, by oxide mass percentage, 29% to 33% gallium oxide, 43% to 46% calcium oxide, 5% to 7% barium oxide, 3.5% to 6% aluminum oxide, 2% to 10% yttrium oxide, and 8% to 11% of the sum of alkali metal oxides and alkaline earth metal oxides other than barium oxide.

8. A method for preparing a mid-infrared substrate protective film, characterized in that: The steps include: according to the film system design plan, Ta2O5 film layers and SiO2 film layers are overlapped and deposited on the mid-infrared substrate layer by layer to obtain the mid-infrared substrate protective film.

9. The preparation method according to claim 8, characterized in that: The mid-infrared substrate protective film is prepared by ion beam sputtering, and the working conditions are as follows: sputtering power is 100-1500W, auxiliary source power is 100-300W; temperature is 120-200°C; coating speed is 5-15rpm; oxygen and argon mixture flow rate is 20-40sccm, oxygen and argon mixture ratio is 8-10:1; target substrate distance is 10-20cm; working vacuum degree is 1×10 -4 ~6×10 -4 Pa.

10. Application of the mid-infrared substrate protective film according to any one of claims 1 to 7 in the field of infrared optoelectronic systems.

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