Design method and preparation method of germanium substrate 2-13 mu m far infrared antireflection film

Abstract

Provided are a design method and a preparation method of a germanium substrate 2-13 mu m middle far infrared antireflection film. The design method of the germanium substrate 2-13 mu m middle far infrared antireflection film comprises: selecting 6.5 mu m as a reference wavelength of optical film design 1 / 4 wavelength film thickness, using a film stack formula: Sub / 0.04L / 0.3H / 0.1L / 0.3H / 0.2L / 0.2H / 0.3L / 0.1H / 0.5L / 0.03M / 0.2L / 0.2M / 0.15L / 0.6M / 0.02Q / AIR, wherein Sub is a germanium substrate, AIR represents air, H represents 1 / 4 wavelength film thickness of Ge, L represents 1 / 4 wavelength film thickness of ZnS, M represents 1 / 4 wavelength film thickness of YF3, and Q represents 1 / 4 wavelength film thickness of Y2O3; a software is used to optimize the film thickness, and the best film thickness is obtained; the transmittance of the optimized germanium substrate in a 2-13 mu m wave band meets the requirements; and the optimized film thickness is input into a control computer of a coating machine. The preparation method of the germanium substrate 2-13 mu m middle far infrared antireflection film comprises the following steps: S1, cleaning before coating and film material preparation; S2, film system process parameter configuration; S3, vacuum baking and film material pre-melting constant temperature; S4, ion source cleaning; S5, film layer coating and monitoring; S6, constant temperature keeping after coating; S7, cooling and taking out; and S8, repeating steps S1 to S7 to coat the second surface.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of infrared coating, and more particularly to a design method and a preparation method of a germanium substrate 2-13 mu m mid-far infrared antireflection film. BACKGROUND

[0002] Infrared thermometry instruments and thermal imaging instruments need to use mid-far infrared filter lenses. The working wavelength range of infrared thermometry instruments and thermal imaging instruments is generally 2-13 mu m, and germanium has good light transmittance in the mid-far infrared range and is not transparent in the visible light range. Due to the very high refractive index of germanium, the refractive index is slightly greater than 4 (dimensionless), and the reflectivity can reach 36%. The material itself also has a certain light absorption, resulting in insufficient transmittance in a specific wavelength range, and the transmittance is less than 47%. This greatly limits its application in some high-precision optical systems, especially in the 2-13 mu m mid-far infrared super wide wavelength range.

[0003] How to coat a reliable optical film on the germanium substrate to improve the transmittance in the 2-13 mu m wavelength range, and how to design the film system and the film layer preparation have become technical problems to be solved in the field of optical thin films. SUMMARY

[0004] In view of the problems in the background art, an object of the present disclosure is to provide a design method and a preparation method of a germanium substrate 2-13 mu m mid-far infrared antireflection film, which can make the transmittance of the germanium substrate 2-13 mu m mid-far infrared wavelength range meet the requirements.

[0005] Another object of the present disclosure is to provide a design method and a preparation method of a germanium substrate 2-13 mu m mid-far infrared antireflection film, which can improve the moisture resistance and corrosion resistance of the film system structure.

[0006] Thus, a design method of a germanium substrate 2-13 μm mid-far infrared antireflection thin film comprises the steps of: Sa, selecting 6.5 μm as a reference wavelength of a 1 / 4 wavelength film thickness for optical thin film design, using a film stack formula: Sub / 0.04L / 0.3H / 0.1L / 0.3H / 0.2L / 0.2H / 0.3L / 0.1H / 0.5L / 0.03M / 0.2L / 0.2M / 0.15L / 0.6M / 0.02Q / AIR, wherein Sub is a germanium substrate, AIR represents air, H represents a 1 / 4 wavelength film thickness of a high refractive index material Ge (germanium), L represents a 1 / 4 wavelength film thickness of an intermediate refractive index material ZnS (zinc sulfide), M represents a 1 / 4 wavelength film thickness of a low refractive index material YF3 (yttrium fluoride), and Q represents a 1 / 4 wavelength film thickness of a material Y2O3 (yttrium oxide) as an outermost layer of the film layer; Sb, calculating and optimizing the film thickness of the film layer by a design software to obtain an optimal film thickness of the film layer, and the transmittance of the optimized germanium substrate in the 2-13 μm mid-far infrared band meets the requirements; Sc, inputting the optimized film thickness of the film layer into a control computer of a coating machine.

[0007] A preparation method of a germanium substrate 2-13 μm mid-far infrared antireflection thin film comprises the steps of: S1, cleaning the accompanying plated pieces and products of the germanium substrate as lenses and preparing four kinds of film materials Ge, ZnS, YF3 and Y2O3 before plating; S2, configuring film system process parameters, the film system process parameters including an optimal film thickness of the film layer, a film material evaporation mode, a film material deposition rate, and use of ion source assisted deposition, and the thickness of the film layer in the film system process parameters is based on the optimal film thickness of the film layer stored in the control computer of the coating machine; S3, placing the cleaned lenses into a tool clamp, hanging the tool clamp with the lenses into a cavity of the coating machine, and performing vacuum baking, film material pre-melting, degassing and impurity removal, and constant temperature; S4, cleaning the lenses by an ion source; S5, coating and monitoring the film layer, coating the film layer on a first surface of the lenses according to the film system parameter process configuration of step S2; S6, maintaining constant temperature after coating; S7, cooling and taking out the lenses; and S8, repeating steps S1 to S7 to coat the film layer on a second surface of the lenses.

[0008] The beneficial effects of the present disclosure are as follows.

[0009] In the design method and preparation method of the germanium substrate 2-13 pm mid-far infrared antireflection film according to the present disclosure, by using Ge, ZnS, YF3, Y2O3 four kinds of film materials, Ge, ZnS as high and medium refractive index materials, YF3 as low refractive index material, combined with the germanium substrate, ZnS is selected as the bottom layer material, the outermost layer protection layer is formed by using YF3 and Y2O3 to reinforce the combination, ZnS and Ge form the first layer to the eighth layer alternately, and ZnS and YF3 form the ninth layer to the fourteenth layer alternately, so that the designed germanium substrate 2-13 pm mid-far infrared band transmittance meets the requirements.

[0010] In the design method and preparation method of the germanium substrate 2-13 pm mid-far infrared antireflection film according to the present disclosure, by using YF3 and Y2O3 to reinforce the combination to form the outermost layer protection layer, in the case that the four kinds of film materials Ge, ZnS, YF3, Y2O3 and the germanium substrate meet the requirements of the transmittance of the 2-13 pm mid-far infrared band, the outermost layer protection layer plays a role in improving hardness, enhancing mechanical friction resistance and corrosion resistance in the designed film system structure, especially the moisture corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is a schematic structural diagram of the film stack design optimization diagram of the design method of the germanium substrate 2-13 pm mid-far infrared antireflection film according to the present disclosure.

[0012] Figure 2 It is a transmittance curve diagram of the film stack design optimization diagram of the design method of the germanium substrate 2-13 pm mid-far infrared antireflection film according to the present disclosure of Example 1.

[0013] Figure 3 It is a curve diagram of the transmittance in the 2-13 pm band of the 2-13 pm mid-far infrared antireflection film plated on both sides of the accompanying plated sheet of Example 1. DETAILED DESCRIPTION

[0014] It will be understood that the disclosed embodiments are merely examples of the present disclosure, which can be implemented in various forms, therefore, the specific details disclosed herein should not be interpreted as limiting, but only as a basis for the claims and as a representative basis for teaching those skilled in the art to implement the present disclosure in various ways.

[0015] [Design method of germanium substrate 2-13 pm mid-far infrared antireflection film]

[0016] The design method of the germanium substrate 2-13 pm mid-far infrared antireflection film according to the present disclosure includes the steps of:

[0017] Sa, 6.5 pm is selected as the reference wavelength of the optical thin film design 1 / 4 wavelength film thickness, using the film stack formula:

[0018] Sub / 0.04L / 0.3H / 0.1L / 0.3H / 0.2L / 0.2H / 0.3L / 0.1H / 0.5L / 0.03M / 0.2L / 0.2M / 0.15L / 0.6M / 0.02Q / AIR,

[0019] Wherein, Sub is a germanium substrate, AIR represents air, H represents 1 / 4 wavelength film thickness of high refractive index material Ge (germanium), L represents 1 / 4 wavelength film thickness of intermediate refractive index material ZnS (zinc sulfide), M represents 1 / 4 wavelength film thickness of low refractive index material YF3 (yttrium fluoride), Q represents 1 / 4 wavelength film thickness of the outermost layer of the film layer material Y2O3 (yttrium oxide);

[0020] Sb, the film thickness of the optimized film layer is calculated by the design software, and the best film thickness of the film layer is obtained, and the transmittance of the optimized germanium substrate in the 2-13 pm mid-infrared wave band meets the requirements;

[0021] Sc, the film thickness of the optimized film layer is input into the control computer of the film coating machine.

[0022] In the design method of the germanium substrate 2-13 pm mid-infrared antireflection thin film according to the present disclosure, by using Ge, ZnS, YF3, Y2O3 four kinds of film materials, Ge, ZnS as high and intermediate refractive index materials, YF3 as low refractive index material, ZnS as bottom layer material combined with germanium substrate, YF3 and Y2O3 are used to form the outermost protective layer, ZnS and Ge form the first layer to the eighth layer alternately, and ZnS and YF3 form the ninth layer to the fourteenth layer alternately, so that the transmittance of the designed germanium substrate in the 2-13 pm mid-infrared wave band meets the requirements.

[0023] In the design method of the germanium substrate 2-13 pm mid-infrared antireflection thin film according to the present disclosure, by using YF3 and Y2O3 to form the outermost protective layer, in the case that the transmittance of the germanium substrate in the 2-13 pm mid-infrared wave band meets the requirements, the outermost protective layer plays a role in improving hardness, enhancing mechanical friction resistance and moisture resistance corrosion resistance in the designed film structure, especially the moisture resistance corrosion resistance.

[0024] In an example, in step Sb, for each of the two sides of the germanium substrate, the film thickness of the optimal film layer is: the film thickness of the first layer of ZnS film layer is 26.25±3nm, the film thickness of the second layer of Ge film layer is 103.16±3nm, the film thickness of the third layer of ZnS film layer is 71.92±3nm, the film thickness of the fourth layer of Ge film layer is 102.24±3nm, the film thickness of the fifth layer of ZnS film layer is 120.86±3nm, the film thickness of the sixth layer of Ge film layer is 70.99±3nm, the film thickness of the seventh layer of ZnS film layer is 185.15±3nm, the film thickness of the eighth layer of Ge film layer is 33.83±3nm, the film thickness of the ninth layer of ZnS film layer is 337.30±3nm, the film thickness of the tenth layer of YF3 film layer is 29.96±3nm, the film thickness of the eleventh layer of ZnS film layer is 157.82±3nm, the film thickness of the twelfth layer of YF3 film layer is 204.99±3nm, the film thickness of the thirteenth layer of ZnS film layer is 95.64±3nm, the film thickness of the fourteenth layer of YF3 film layer is 602.18±3nm, and the film thickness of the fifteenth layer of Y2O3 film layer is 20±5nm, as shown in Figure 1 The overall thickness of the film system structure formed by the fifteen layers of film layers is 2162.29±47nm for each of the two sides of the germanium substrate.

[0025] Correspondingly, in an example, in step Sb, the optimized transmittance of the germanium substrate 2-13μm in the far infrared band is greater than 95% on average, as shown in Figure 2

[0026] In step Sb, the design software can be, but is not limited to, TFCalc, Essential Macleod, OptiLayer, Filmstar, Filmaster, Autofilm, etc.

[0027] [Preparation method of germanium substrate 2-13μm far infrared antireflection thin film]

[0028] The preparation method of germanium substrate 2-13μm far infrared antireflection thin film according to the present disclosure comprises the steps of:

[0029] S1, before plating, the accompanying plating piece and the product of the germanium substrate as the lens are cleaned and Ge, ZnS, YF3, Y2O3 four kinds of film materials are prepared;

[0030] S2, film system process parameter configuration, the film system process parameter configuration includes the film thickness of the optimal film layer, the evaporation mode of the film material, the deposition rate of the film material, the use of ion source assisted deposition, and the thickness of the film layer in the film system process parameter is based on the optimal film thickness of the film layer stored in the control computer of the film plating machine;

[0031] ​S3, the cleaned lens is placed in a fixture, the fixture with the lens is hung in the cavity of the coating machine, vacuum baking and film pre-melting are performed, and the constant temperature is maintained;

[0032] S4, the ion source cleans the lens;

[0033] S5, film layer coating and monitoring, according to the film system parameter process configuration of step S2, the first surface of the lens is coated with a film layer;

[0034] S6, constant temperature maintenance after coating;

[0035] S7, cooling and taking out;

[0036] S8, repeat steps S1 to S7, and coat the second surface of the lens with a film layer.

[0037] In the preparation method of the germanium substrate 2-13 μm mid-far infrared antireflection film according to the present disclosure, the thickness of the film layer in the film system process parameters of steps S1 to S8 and step S2 is based on the optimal film thickness of the film layer stored in the control computer of the coating machine according to the design method of the germanium substrate 2-13 μm mid-far infrared antireflection film according to the present disclosure, so that the transmittance of the prepared germanium substrate 2-13 μm mid-far infrared waveband meets the requirements.

[0038] Similarly, in the preparation method of the germanium substrate 2-13 μm mid-far infrared antireflection film according to the present disclosure, the outermost protective layer is formed by using YF3 and Y2O3 reinforcement combination, and in the case that Ge, ZnS, YF3, Y2O3 four film materials and germanium substrate meet the requirements of 2-13 μm mid-far infrared waveband transmittance, the outermost protective layer plays a role in improving hardness, enhancing anti-mechanical friction and moisture resistance corrosion resistance in the designed film system structure, especially can improve the moisture resistance corrosion resistance.

[0039] The cleaning of step S1 is beneficial to improve the surface state of the first surface and the second surface of the lens, and helps to improve the combination performance of the film system structure on each surface and the corresponding surface of the lens. For example, the surface of the lens is cleaned by ultrasonic or hand rubbing. For example, the thickness of the accompanying coating piece is 1.0 mm.

[0040] In an example, in step S2, the thickness of the film layer in the film system process parameters is based on the optimal film thickness of the film layer stored in the control computer of the coating machine as mentioned above, that is, for each of the two sides of the germanium substrate, the optimal film thickness of the film layer is: the film thickness of the first layer of ZnS film layer is 26.25±3nm, the film thickness of the second layer of Ge film layer is 103.16±3nm, the film thickness of the third layer of ZnS film layer is 71.92±3nm, the film thickness of the fourth layer of Ge film layer is 102.24±3nm, the film thickness of the fifth layer of ZnS film layer is 120.86±3nm, the film thickness of the sixth layer of Ge film layer is 70.99±3nm, the film thickness of the seventh layer of ZnS film layer is 185.15±3nm, the film thickness of the eighth layer of Ge film layer is 33.83±3nm, the film thickness of the ninth layer of ZnS film layer is 337.30±3nm, the film thickness of the tenth layer of YF3 film layer is 29.96±3nm, the film thickness of the eleventh layer of ZnS film layer is 157.82±3nm, the film thickness of the twelfth layer of YF3 film layer is 204.99±3nm, the film thickness of the thirteenth layer of ZnS film layer is 95.64±3nm, the film thickness of the fourteenth layer of YF3 film layer is 602.18±3nm, and the film thickness of the fifteenth layer of Y2O3 film layer is 20±5nm; the evaporation mode of the film material is that Ge and Y2O3 use electron beam heating evaporation, and ZnS and YF3 use resistance heating evaporation; the deposition rate of the film material is that the deposition rate of the Ge film layer is 3-4Å / s, the deposition rate of the Y2O3 film layer is 2-3Å / s, the deposition rate of the ZnS film layer is 6-8Å / s, and the deposition rate of the YF3 film layer is 5-7Å / s; the use of ion source assisted deposition is that ion source assisted deposition is adopted when coating the first layer of ZnS film layer, the tenth layer of YF3 film layer, the twelfth layer of YF3 film layer, the fourteenth layer of YF3 film layer, and the fifteenth layer of Y2O3 film layer, and ion source assisted deposition is not adopted for the remaining layers. The use of ion source assisted deposition can make the corresponding film layer more dense and more uniform.

[0041] Further, in an example, the ion source parameters when coating the first layer of ZnS film layer are that the neutralization current is 0.5A, the neutralization gas flow is 8sccm, the anode voltage is 120V, the anode current is 1.2A, the flow rate of argon in the neutralization gas is 100%; the ion source parameters when coating the tenth layer of YF3 film layer, the twelfth layer of YF3 film layer, and the fourteenth layer of YF3 film layer are that the neutralization current is 0.5A, the neutralization gas flow is 8sccm, the anode voltage is 100V, the anode current is 1A, the flow rate of argon in the neutralization gas is 100%; the ion source parameters when coating the fifteenth layer of Y2O3 film are that the neutralization current is 0.5A, the neutralization gas flow is 8sccm, the anode voltage is 180V, the anode current is 1.8A, the flow rate of argon in the neutralization gas is 20%, and the flow rate of oxygen in the neutralization gas is 80%.

[0042] The baking in step S3 is to prepare the temperature for the pre-melting of the film material, which can release the gas in the film material and remove the impurities in the film material, so as to ensure the purity of the film material and reduce the adverse factors affecting the quality of the film layer in the film layer plating process in step S5. In addition, the baking also heats the lens. Specifically, in an example, the temperature of the cavity of the film plating machine is set to be heated to 150°C in step S3; the film material is pre-melted when the vacuum extraction reaches (4.0-6.0) × 10 -3 Pa, and after the pre-melting of the film material is completed, the temperature of the cavity of the film plating machine reaches 150°C, and the temperature is kept constant for 10 min.

[0043] The ion source cleaning in step S4 uses ion bombardment to clean the surface microstructure of the lens, which can eliminate the oxidation layer on the surface of the lens and make the surface of the lens cleaner, which is beneficial to the firm adhesion and growth of the film layer. Specifically, in an example, when the vacuum degree reaches (0.9-1.0) × 10 -3 Pa in step S4, the ion source of the vacuum film plating machine is started, and the ion cleaning parameters of the ion source are set as follows: neutralization current 0.8-1.0 A, neutralization gas flow rate 8-10 sccm, anode voltage 200-220 V, anode current 2-2.5 A, argon flow rate in the neutralization gas 100%, and cleaning time 5-8 min.

[0044] In an example, in step S5, argon is introduced and vacuum extraction is performed to maintain a flowing constant vacuum when plating each film layer, and the constant vacuum degree is set to be not less than 5.0 × 10 -3 Pa; the first layer to the fourteenth layer are completed at a temperature of 150°C in the cavity of the film plating machine, and the fifteenth layer of Y2O3 film is completed at a temperature of 180°C in the cavity of the film plating machine. By evaporating the first layer to the fourteenth layer at 150°C and evaporating the fifteenth layer at 180°C, the corresponding film layer is beneficial to the growth. In an example, the crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillator of a plurality of crystal oscillators of a crystal controller, the new crystal oscillator of the plurality of crystal oscillators is controlled to work by the crystal controller after the ion source cleaning, and the crystal oscillator frequency is not less than 5.7 MHz.

[0045] In an example, in step S6, the cavity is kept at 180°C for 5 min after plating to release the internal stress of the film system structure.

[0046] In an example, in step S7, the door is opened to take out the lens when the temperature drops to below 90°C.

[0047] [TEST]

[0048] Example 1

[0049] First part: design method of germanium substrate 2-13 μm far-infrared antireflection thin film

[0050] The design method of the germanium substrate 2-13 μm mid-far infrared antireflection film of embodiment 1 adopts the following steps:

[0051] Sa, 6.5 μm is selected as the reference wavelength of the optical film design 1 / 4 wave film thickness, and the film stack formula is used:

[0052] Sub / 0.04L / 0.3H / 0.1L / 0.3H / 0.2L / 0.2H / 0.3L / 0.1H / 0.5L / 0.03M / 0.2L / 0.2M / 0.15L / 0.6M / 0.02Q / AIR,

[0053] Wherein, Sub is the germanium substrate, AIR represents air, H represents 1 / 4 wave film thickness of high refractive index material Ge (germanium), L represents 1 / 4 wave film thickness of intermediate refractive index material ZnS (zinc sulfide), M represents 1 / 4 wave film thickness of low refractive index material YF3 (yttrium fluoride), Q represents 1 / 4 wave film thickness of the outermost layer of the film layer material Y2O3 (yttrium oxide);

[0054] Sb, the film thickness of the film layer is calculated and optimized by the design software, and the best film thickness of the film layer is obtained, and the transmittance of the optimized germanium substrate in the 2-13 μm mid-far infrared band meets the requirements;

[0055] Sc, the optimized film thickness of the film layer is input into the control computer of the film plating machine;

[0056] Wherein, in step Sb, the best film thickness of the film layer for each of the two sides of the germanium substrate is:

[0057] The film thickness of the first layer of ZnS film layer is 26.25 nm,

[0058] The film thickness of the second layer of Ge film layer is 103.16 nm,

[0059] The film thickness of the third layer of ZnS film layer is 71.92 nm,

[0060] The film thickness of the fourth layer of Ge film layer is 102.24 nm,

[0061] The film thickness of the fifth layer of ZnS film layer is 120.86 nm,

[0062] The film thickness of the sixth layer of Ge film layer is 70.99 nm,

[0063] The film thickness of the seventh layer of ZnS film layer is 185.15 nm,

[0064] The film thickness of the eighth layer of Ge film layer is 33.83 nm,

[0065] The film thickness of the ninth layer of ZnS film layer is 337.30 nm,

[0066] The film thickness of the tenth YF3 film layer is 29.96 nm,

[0067] The film thickness of the eleventh ZnS film layer is 157.82 nm,

[0068] The film thickness of the twelfth YF3 film layer is 204.99 nm,

[0069] The film thickness of the thirteenth ZnS film layer is 95.64 nm,

[0070] The film thickness of the fourteenth YF3 film layer is 602.18 nm,

[0071] The film thickness of the fifteenth Y2O3 film layer is 20 nm;

[0072] In step Sb, the design software is TFCalc.

[0073] Figure 2 is a transmittance curve diagram of the film stack design optimization diagram of the germanium substrate 2-13 μm mid-far infrared antireflection thin film design method according to the present disclosure of embodiment 1. From Figure 2 It can be seen that the optimized transmittance of the germanium substrate 2-13 μm mid-far infrared waveband is greater than 95% on average.

[0074] Part II: Preparation method of germanium substrate 2-13 μm mid-far infrared antireflection thin film

[0075] The preparation method of the germanium substrate 2-13 μm mid-far infrared antireflection thin film of embodiment 1 adopts the following steps:

[0076] S1, before plating, the ultrasonic cleaning is used for the cleaning of the accompanying plating piece and the product of the germanium substrate as the lens, and the preparation work of four film materials Ge, ZnS, YF3 and Y2O3, wherein the thickness of the accompanying plating piece is 1.0 mm;

[0077] S2, the vacuum coating machine is a vacuum coating machine with a neutralizer Hall ion source manufactured and sold by Chengdu Xiwoker Vacuum Technology Co., Ltd., and the Hall ion source with a neutralizer is commercially available from Borton Opto-Electronics Technology Co., Ltd. The film system process parameter configuration includes the optimal film thickness of the film layer, the evaporation mode of the film material, the deposition rate of the film material, and the use of ion source assisted deposition. The thickness of the film layer in the film system process parameter is based on the optimal film thickness of the film layer stored in the control computer of the coating machine in the first part. The evaporation mode of the film material is electron beam heating evaporation for Ge and Y2O3, and resistance heating evaporation for ZnS and YF3. The deposition rate of the film material is: the deposition rate of the Ge film layer is 4Å / s, the deposition rate of the Y2O3 film layer is 2Å / s, the deposition rate of the ZnS film layer is 8Å / s, and the deposition rate of the YF3 film layer is 5Å / s. The use of ion source assisted deposition is: ion source assisted deposition is used when coating the first layer of ZnS film layer, the tenth layer of YF3 film layer, the twelfth layer of YF3 film layer, the fourteenth layer of YF3 film layer, and the fifteenth layer of Y2O3 film layer, and the rest of the layers do not use ion source assisted deposition. The ion source parameters when coating the first layer of ZnS film layer are: neutralizing current 0.5A, neutralizing gas flow 8sccm, anode voltage 120V, anode current 1.2A, and the flow rate of argon in the neutralizing gas is 100%; The ion source parameters when coating the tenth layer of YF3 film layer, the twelfth layer of YF3 film layer, and the fourteenth layer of YF3 film layer are: neutralizing current 0.5A, neutralizing gas flow 8sccm, anode voltage 100V, anode current 1A, and the flow rate of argon in the neutralizing gas is 100%; The ion source parameters when coating the fifteenth layer of Y2O3 film are: neutralizing current 0.5A, neutralizing gas flow 8sccm, anode voltage 180V, anode current 1.8A, and the flow rate of argon in the neutralizing gas is 20%, and the flow rate of oxygen in the neutralizing gas is 80%;

[0078] S3, the cleaned lens is placed in the tool clamp, the lens tool clamp is hung in the cavity of the coating machine, vacuum baking and film material pre-melting are performed, and the temperature of the cavity of the coating machine is set to 150°C. When the vacuum is extracted to 4.0×10 -3 Pa, the film material is pre-melted. After the film material is pre-melted, the temperature of the cavity of the coating machine reaches 150°C, and the temperature is kept constant for 10 minutes;

[0079] S4, the ion source cleans the lens. When the vacuum degree reaches 1.0×10 -3 Pa, the ion source of the vacuum coating machine is started, the ion cleaning parameters of the ion source are set as follows: neutralizing current 1.0A, neutralizing gas flow 10sccm, anode voltage 220V, anode current 2A, the flow rate of argon in the neutralizing gas is 100%, and the cleaning time is 8 minutes;

[0080] S5, film layer plating and monitoring, according to the film system parameter process configuration of step S2, the first surface of the lens is plated with film layers, argon is introduced and vacuum is extracted to maintain a flowing constant vacuum when plating each film layer, the constant vacuum degree is set to 5.0x10 -3 Pa, the first layer film layer to the fourteenth layer film layer is completed at a temperature of 150°C in the cavity temperature of the film plating machine, the fifteenth layer Y2O3 film layer is completed at a temperature of 180°C in the cavity temperature of the film plating machine, the crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillator pieces of the crystal controller, the new crystal oscillator pieces in the multiple crystal oscillator pieces are controlled to work by the crystal controller after the ion source is cleaned, and the crystal oscillator frequency is 6MHz;

[0081] S6, after plating is completed, the cavity is kept at 180°C for 5min;

[0082] S7, after the temperature is reduced to below 90°C, the door is opened to take out the piece;

[0083] S8, repeating steps S1 to S7, film layer plating is performed on the second surface of the lens.

[0084] Comparative Example 1

[0085] Except that the outermost Y2O3 layer (i.e. the fifteenth layer film layer) and the plating of the outermost Y2O3 layer are omitted in the first part and the second part, the rest is the same as example 1.

[0086] Comparative Example 2

[0087] Except that the fifteenth layer Y2O3 film layer in step S5 of the second part is completed at a temperature of 150°C in the cavity temperature of the film plating machine, the rest is the same as example 1.

[0088] Figure 3 is a curve graph of the transmittance in the 2-13μm mid-far infrared band of the two surfaces of the accompanying plating piece plated with 2-13μm mid-far infrared antireflection thin films in example 1. From Figure 3 It can be seen that the transmittance of the prepared germanium substrate in the 2-13μm mid-far infrared band is greater than 95% on average.

[0089] According to GJB2485A-2019, the two surfaces of the accompanying plating piece plated in example 1, comparative example 1 and comparative example 2 are tested as follows.

[0090] Water bubble test: tap water is taken for water bubble test for 2h, whether the film layer on each surface falls off from the accompanying plating piece is observed, and whether the film layer on each surface is cracked is observed.

[0091] Salt spray test: neutral salt spray test for 48h, whether the film layer on each surface of the accompanying plating piece falls off is observed, and whether the film layer on each surface of the accompanying plating piece is cracked is observed.

[0092] Adhesion test: 3M tape was adhered to each side of the plated sample by hand, and the tape was pulled in the direction opposite to the adhered end to observe whether the film layer was pulled up.

[0093] Cold and hot shock test: The cold and hot shock test was performed in a high and low temperature chamber at -40°C to 85°C for 24h, and the film layer on each side of the plated sample was observed for peeling and cracking.

[0094] Constant temperature and humidity test: The constant temperature and humidity test was performed in a constant temperature and humidity chamber at 50°C and 95% relative humidity for 48h, and the film layer on each side of the plated sample was observed for peeling and cracking.

[0095] Friction resistance test (moderate friction test): The rubber friction head of a friction tester was wrapped with a piece of absorbent cloth, and the film layer of the plated sample was rubbed for 50 times (25 times back and forth) with a pressure of 4.9N, and the film layer surface was observed for scratch damage.

[0096] Low temperature test: The low temperature test was performed in a low temperature chamber at -40°C for 48h, and the film layer on each side of the plated sample was observed for peeling and cracking.

[0097] High temperature test: The high temperature test was performed in a high temperature chamber at 85°C for 48h, and the film layer on each side of the plated sample was observed for peeling and cracking.

[0098] Table 1 shows the transmittance and the results of various tests of Example 1 and Comparative Examples 1-2.

[0099] Table 1 shows the transmittance and the results of various tests of Example 1 and Comparative Examples 1-2.

[0100] 2-13 μm average transmittance Blister test Salt spray test Adhesion test Cold and hot impact test Constant temperature and humidity test Rub resistance test Low temperature test High temperature test Example 1 95.3% The film layer was not peeled off and cracked The film layer was not peeled off and cracked The film layer was not pulled up The film layer was not peeled off and cracked The film layer was not peeled off and cracked Moderate rub resistance The film layer was not peeled off and cracked The film layer was not peeled off and cracked Comparative Example 1 95.2% The film layer was not peeled off and cracked The film layer was not pulled up The film layer was not peeled off and cracked Moderate rub resistance The film layer was not peeled off and cracked The film layer was not peeled off and cracked Comparative Example 2 95.3% The film layer was peeled off and cracked The film layer was not pulled up The film layer was not peeled off and cracked The film layer was not peeled off and cracked Moderate rub resistance The film layer was not peeled off and cracked The film layer was not peeled off and cracked

[0101] As can be seen from Comparative Example 1 and Example 1, in Comparative Example 1, the outermost layer of the film system structure is a YF3 film layer, although the film system structure has good firmness and friction resistance performance in the environmental adaptability test, it fails in the salt spray test and the constant temperature and humidity test, and the film layer is prone to moisture absorption and corrosion in a humid and hot environment for a long time, resulting in a decrease in the durability of the film layer, and therefore, the moisture resistance and corrosion resistance of the YF3 film layer need to be considered. In Example 1, a Y2O3 film layer is added as the outermost layer of the film system structure based on Comparative Example 1, which can improve the moisture resistance and corrosion resistance.

[0102] Further, as can be seen from Comparative Example 2 and Example 1, the temperature during the plating of the Y2O3 film layer of Comparative Example 2 is lower than that of Example 1, and the salt spray test fails. The temperature increase (under ion source assisted deposition) of Example 1 can effectively optimize the growth conditions of the Y2O3 film layer, making the Y2O3 film layer more dense, thereby achieving the effect of moisture resistance and corrosion resistance.

[0103] A number of example embodiments are described above with the understanding that the foregoing description is intended to encompass and guide the forming of additional combinations by those who are skilled in the art in view of the entire disclosure, and no limitations of such combinations are intended unless otherwise indicated.

Claims

1. A method for designing a 2-13μm mid-far-infrared antireflection thin film on a germanium substrate, characterized in that, Including the following steps: Sa, 6.5 μm is selected as the reference wavelength for 1 / 4 wavelength film thickness in optical thin film design, using the film stack formula: Sub / 0.04L / 0.3H / 0.1L / 0.3H / 0.2L / 0.2H / 0.3L / 0.1H / 0.5L / 0.03M / 0.2L / 0.2M / 0.15L / 0.6M / 0.02Q / AIR, Wherein, Sub represents germanium substrate, AIR represents air, H represents Ge (germanium), a high refractive index material with a film thickness of 1 / 4 wavelength, L represents ZnS (zinc sulfide), an intermediate refractive index material with a film thickness of 1 / 4 wavelength, M represents YF3 (yttrium fluoride), a low refractive index material with a film thickness of 1 / 4 wavelength, and Q represents Y2O3 (yttrium oxide), the outermost material of the film layer with a film thickness of 1 / 4 wavelength. Sb, by using design software to calculate and optimize the film thickness, the optimal film thickness was obtained. The transmittance of the optimized germanium substrate in the 2-13μm mid-far infrared band meets the requirements. Sc inputs the optimized film thickness into the control computer of the coating machine; In step Sb, for each of the two sides of the germanium substrate, the optimal film thickness is: The thickness of the first ZnS film is 26.25 ± 3 nm. The thickness of the second Ge film is 103.16 ± 3 nm. The thickness of the third ZnS film is 71.92 ± 3 nm. The thickness of the fourth Ge film is 102.24 ± 3 nm. The thickness of the fifth ZnS film is 120.86 ± 3 nm. The thickness of the sixth Ge film is 70.99±3 nm. The thickness of the seventh ZnS film is 185.15 ± 3 nm. The thickness of the eighth Ge film is 33.83 ± 3 nm. The thickness of the ninth ZnS film is 337.30 ± 3 nm. The thickness of the tenth YF3 film is 29.96±3 nm. The thickness of the eleventh ZnS film is 157.82 ± 3 nm. The thickness of the twelfth YF3 film is 204.99±3 nm. The thickness of the thirteenth ZnS film is 95.64 ± 3 nm. The thickness of the fourteenth YF3 film is 602.18±3 nm. The thickness of the fifteenth Y2O3 film is 20±5nm; In step Sb, the average transmittance of the far-infrared band in the 2-13μm region of the optimized germanium substrate is greater than 95%.

2. The design method for a 2-13 μm far-infrared antireflection film on a germanium substrate according to claim 1, characterized in that, In step Sb, the design software is TFCalc, Essential Macleod, OptiLayer, Filmstar, Filmaster, and Autofilm.

3. A method for preparing a 2-13 μm mid-far-infrared antireflection film on a germanium substrate, characterized in that, Including the following steps: S1. Before plating, the co-plating sheet and product used as the germanium substrate for the lens are cleaned and four types of film materials, namely Ge, ZnS, YF3 and Y2O3, are prepared. S2, membrane system process parameter configuration, the membrane system process parameter configuration includes the optimal membrane thickness, the vapor deposition mode of the membrane material, the deposition rate of the membrane material, and the use of ion source assisted deposition. The membrane thickness in the membrane system process parameters is based on the optimal membrane thickness stored in the control computer of the coating machine according to the design method of the far-infrared anti-reflection film of 2-13μm in germanium substrate according to any one of claims 1-2. S3, the cleaned lens is placed into the tooling fixture, the tooling fixture with the lens is hung into the cavity of the coating machine, vacuum baking, pre-melting of the film material, degassing, impurity removal and constant temperature. S4, Ion source cleaning of lenses; S5, Coating and monitoring: Coating is performed on the first surface of the lens according to the coating system parameters and process configuration in step S2. S6, constant temperature maintenance after plating; S7, cool down before picking up the part; S8. Repeat steps S1 to S7 to apply a coating to the second surface of the lens.

4. The method for preparing a 2-13 μm far-infrared antireflection film on a germanium substrate according to claim 3, characterized in that, In step S1, Cleaning is performed using ultrasonic cleaning and manual wiping. The thickness of the plating sheet is 1.0 mm.

5. The method for preparing a 2-13 μm far-infrared antireflection film on a germanium substrate according to claim 3, characterized in that, In step S2, The thickness of the film layer in the film system process parameters is based on the optimal film thickness stored in the control computer of the coating machine according to the design method of the far-infrared anti-reflection film of 2-13μm in germanium substrate as described in claim 1. The evaporation mode of the film material is as follows: Ge and Y2O3 are evaporated by electron beam heating, while ZnS and YF3 are evaporated by resistance heating. The deposition rates of the film materials are as follows: the deposition rate of Ge film is 3-4 Å / s, the deposition rate of Y2O3 film is 2-3 Å / s, the deposition rate of ZnS film is 6-8 Å / s, and the deposition rate of YF3 film is 5-7 Å / s. Ion source-assisted deposition was used for depositing the first ZnS film, the tenth YF3 film, the twelfth YF3 film, the fourteenth YF3 film, and the fifteenth Y2O3 film. Ion source-assisted deposition was not used for the remaining layers.

6. The method for preparing a 2-13 μm far-infrared antireflection film on a germanium substrate according to claim 5, characterized in that, The ion source parameters for depositing the first ZnS film were: neutralization current 0.5A, neutralization gas flow rate 8sccm, anode voltage 120V, anode current 1.2A, and argon gas flow rate in the neutralization gas 100%. The ion source parameters for depositing the tenth, twelfth, and fourteenth YF3 film layers were: neutralization current 0.5A, neutralization gas flow rate 8sccm, anode voltage 100V, anode current 1A, and argon gas flow rate in the neutralization gas 100%. The ion source parameters for depositing the fifteenth Y2O3 film were: neutralization current 0.5A, neutralization gas flow rate 8sccm, anode voltage 180V, anode current 1.8A, argon flow rate in the neutralization gas 20%, and oxygen flow rate in the neutralization gas 80%.

7. The method for preparing a 2-13 μm far-infrared antireflection film on a germanium substrate according to claim 3, characterized in that, In step S3, The temperature of the coating machine's cavity is set to 150°C; When the vacuum reaches (4.0-6.0)×10 -3 The film material is pre-melted at Pa. After the film material is pre-melted, the temperature of the cavity of the coating machine reaches 150°C and is kept constant for 10 minutes.

8. The method for preparing a 2-13 μm far-infrared antireflection film on a germanium substrate according to claim 3, characterized in that, In step S4, When the vacuum degree reaches (0.9-1.0)×10 -3 At Pa, the ion source of the vacuum coating machine is started. The ion cleaning parameters for the ion source are set as follows: neutralization current 0.8-1.0A, neutralization gas flow rate 8-10sccm, anode voltage 200-220V, anode current 2-2.5A, argon gas flow rate in the neutralization gas is 100%, and cleaning time is 5-8min.

9. The method for preparing a 2-13 μm far-infrared antireflection film on a germanium substrate according to claim 3, characterized in that, In step S5, Argon gas is introduced and a vacuum is drawn during the deposition of each film layer to maintain a constant vacuum in a flow-through manner. The constant vacuum level is set to be no less than 5.0 × 10⁻⁶. -3 Pa; The first to fourteenth film layers were deposited by vapor deposition at a chamber temperature of 150°C in the coating machine, and the fifteenth Y2O3 film layer was deposited by vapor deposition at a chamber temperature of 180°C in the coating machine. The crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillators of multiple crystal oscillators in the crystal controller. After cleaning with the ion source, the crystal controller controls the new crystal oscillator in the multiple crystal oscillators to work accordingly, and the crystal oscillator frequency is not less than 5.7MHz.

10. The method for preparing a 2-13 μm far-infrared antireflection film on a germanium substrate according to claim 3, characterized in that, In step S6, after the plating is completed, the cavity is kept at a constant temperature of 180°C for 5 minutes; In step S7, the door is opened and the item is retrieved once the temperature drops below 90°C.

Images