Zinc sulfide ultra-wideband dual-band antireflection protective film and preparation method thereof

Abstract

The application belongs to the technical field of infrared coating and discloses a zinc sulfide ultra-wideband double-waveband antireflection protective film, which comprises film system structures symmetrically arranged on two sides of a zinc sulfide substrate, wherein the film system structures are sequentially arranged from the inside to the outside of the zinc sulfide substrate as YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer and LaF3 layer. The arrangement of the film system structures can improve the average transmittance of the optical lens in the 0.4-1.1 μm and 8-12 μm wavebands, and the durability of the film system structures can be improved through the cooperation of the film layers. In addition, the application also discloses a preparation method of the zinc sulfide ultra-wideband double-waveband antireflection protective film, and the durability and transmittance of the film system structures can be improved through the adjustment of the preparation process and various process parameters.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of infrared coating, and particularly relates to the preparation of an antireflection film, in particular to a zinc sulfide ultra-wideband double-waveband antireflection protective film and a preparation method thereof. BACKGROUND

[0002] Zinc sulfide is a material widely used in the optical field, and has excellent optical performance and mechanical strength. With the development of science and technology, the application range of infrared optical elements is more and more extensive, and the requirements are higher and higher. There is a demand for coating from visible light to far infrared.

[0003] However, the transmittance of zinc sulfide in some wavebands is not ideal, especially in the 0.4-1.1 micron and 8-12 micron wavebands, which limits its application in optical systems. SUMMARY

[0004] In view of the defects and deficiencies of the prior art, the first aspect of the application provides a zinc sulfide ultra-wideband double-waveband antireflection protective film, and the second aspect of the application provides a preparation method of the zinc sulfide ultra-wideband double-waveband antireflection protective film.

[0005] To achieve the above-mentioned purpose, the application provides the following technical solutions.

[0006] The first aspect of the application provides a zinc sulfide ultra-wideband double-waveband antireflection protective film, which comprises a film system structure symmetrically arranged on both sides of a zinc sulfide substrate. The film system structure comprises, from the inside to the outside of the zinc sulfide substrate, a YF3 layer, a ZnS layer, a YF3 layer, a ZnS layer, a YF3 layer, a ZnS layer, a YF3 layer, a ZnS layer and a LaF3 layer.

[0007] Preferably, the thickness of each film layer of the film system structure from the inside to the outside of the zinc sulfide substrate is as follows: the YF3 layer is 15.93 nm, the ZnS layer is 404 nm, the YF3 layer is 30.7 nm, the ZnS layer is 26.56 nm, the YF3 layer is 1168.1 nm, the ZnS layer is 23.35 nm, the YF3 layer is 20.25 nm, the ZnS layer is 106.15 nm, and the LaF3 layer is 106.30 nm.

[0008] The second aspect of the application provides a preparation method of the zinc sulfide ultra-wideband double-waveband antireflection protective film, comprising the following steps.

[0009] Step one: cleaning the surface of the zinc sulfide substrate and adding film material;

[0010] Step two: heating the zinc sulfide substrate and pre-melting the film material;

[0011] Step three: ion cleaning the zinc sulfide substrate;

[0012] Step four: one side of the zinc sulfide substrate is coated with YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, LaF3 layer in turn under vacuum atmosphere;

[0013] Step five: cooling and taking out;

[0014] Step six: repeating the above steps one to five to coat the film system structure on the other side of the zinc sulfide substrate.

[0015] Preferably, in step one, the zinc sulfide substrate is cleaned by ultrasonic wave.

[0016] Preferably, in step two, the zinc sulfide substrate is heated at 140-160℃ for 15 min.

[0017] Preferably, in step two, when the film material is pre-melted, the vacuum degree is 3.0×10 -3 ~5.0×10 -3 Pa.

[0018] Preferably, in step three, when the zinc sulfide substrate is cleaned, the vacuum degree is 1.0×10 -3 ~2.0×10 -3 Pa; the cleaning time is 250-350 s; the Hall ion source parameters are: neutralization current 0.6 A, neutralization gas flow 8 sccm, anode voltage 220 V, anode current 2 A, argon flow 100%.

[0019] Preferably, in step four, the ZnS layer, YF3 layer and LaF3 layer are evaporated by resistance heating.

[0020] Preferably, in step four, the evaporation rate of ZnS is 6 Å / s; the evaporation rate of YF3 is 5 Å / s, and the evaporation rate of LaF3 is 6 Å / s.

[0021] Preferably, in step four, ion-assisted deposition is used when the film system structure is coated.

[0022] Preferably, in step four, the ion source parameters for ion-assisted evaporation of ZnS material are: neutralization current 0.5 A, neutralization gas flow 8 sccm, anode voltage 100 V, anode current 1 A, argon flow 100%.

[0023] Preferably, the ion source parameters for ion-assisted evaporation of YF3 and LaF3 materials are: neutralization current 0.6 A, neutralization gas flow 8 sccm, anode voltage 130 V, anode current 1.3 A, argon flow 30%, oxygen flow 70%.

[0024] Preferably, in step four, the vacuum degree for film coating is 4.5×10 -3 ~5.5×10 -3Pa; the coating temperature is 140-160℃.

[0025] Preferably, in the fourth step, the film thickness control uses quartz crystal control, and the crystal frequency is 6MHz.

[0026] Preferably, after the fourth step, a heat preservation stage is further included, and after the coating of the film system structure is completed, heat preservation is performed for 5-15min, and the product is taken out after the temperature is reduced to 100℃.

[0027] Compared with the prior art, the present application has the following obvious beneficial effects:

[0028] (1) By arranging the film system structure on the zinc sulfide substrate, the average transmittance of the optical lens in the 0.4-1.1μm and 8-12μm wave bands can be improved, and the average transmittance in the 0.4-1.1μm and 8-12μm wave bands can reach more than 94%, and the durability of the film system structure is improved through the cooperation of each film layer.

[0029] (2) Through the cooperation of the film system structure and the preparation process of the film system structure, the environmental adaptability and durability of the optical lens are improved. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A schematic diagram of the film system structure prepared for the embodiment 1 of the present application is shown in the figure;

[0031] Figure 2 A transmittance curve diagram of the optical lens prepared for the embodiment 1 of the present application in the 0.4-1.1μm wave band is shown in the figure;

[0032] Figure 3 A transmittance curve diagram of the optical lens prepared for the embodiment 1 of the present application in the 8-12μm wave band is shown in the figure; DETAILED DESCRIPTION

[0033] The present application provides the following specific technical solutions.

[0034] In a first aspect, a zinc sulfide ultra-wideband dual-waveband antireflection protective film includes film system structures symmetrically arranged on both sides of a zinc sulfide substrate, and the film system structure is sequentially arranged from the inside to the outside of the zinc sulfide substrate as YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, and LaF3 layer.

[0035] In the specific embodiments of the present application, the inventors select zinc sulfide (ZnS), yttrium fluoride (YF3), lanthanum fluoride (LaF3) as the film material, which can improve the transmittance and stability of the anti-reflective protective film. The inventors have found that the film structure of YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, LaF3 layer can further improve the transmittance of the anti-reflective film, and in combination with the zinc sulfide substrate, the transmittance of the optical lens in the wavelength range of 0.4 μm to 1.1 μm and 8 μm to 12 μm can be further improved, so as to meet the market demand.

[0036] Preferably, the thickness of each film layer of the film structure from the inside to the outside of the zinc sulfide substrate is: YF3 layer 15.93 nm, ZnS layer 404 nm, YF3 layer 30.7 nm, ZnS layer 26.56 nm, YF3 layer 1168.1 nm, ZnS layer 23.35 nm, YF3 layer 20.25 nm, ZnS layer 106.15 nm, LaF3 layer 106.30 nm.

[0037] The inventors have further found that when the thickness of each film layer in the film structure is as described above, the average transmittance of the optical lens in the wavelength range of 0.4 μm to 1.1 μm and 8 μm to 12 μm can be improved.

[0038] In a second aspect, the present application provides a preparation method of the above-mentioned zinc sulfide ultra-wideband dual-band anti-reflective protective film, comprising the following steps:

[0039] Step one: cleaning the surface of the zinc sulfide substrate and adding the film material;

[0040] Step two: pre-melting the film material;

[0041] Step three: ion cleaning the zinc sulfide substrate;

[0042] Step four: coating YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, LaF3 layer on one side of the zinc sulfide substrate in a vacuum atmosphere;

[0043] Step five: cooling and taking out the product;

[0044] Step six, repeating the above steps one to five to coat the film structure on the other side of the zinc sulfide substrate.

[0045] Preferably, in step one, the zinc sulfide substrate is cleaned by ultrasonic cleaning.

[0046] The inventors have found that, by cleaning the surface of the ZnS substrate before processing, the plating effect can be improved and the interference of impurities can be reduced. In practical applications, the cleaning process can use ultrasonic cleaning, steam cleaning, high-pressure cleaning, and other processes to process the ZnS substrate.

[0047] Preferably, in step two, the ZnS substrate is heated at 150°C for 15 min.

[0048] By heating and baking the ZnS substrate, in the first aspect, the water vapor, oil vapor, and other volatile impurities on the surface of the ZnS substrate can be volatilized, avoiding affecting the adhesion of the film layer and improving the firmness between the film system structure and the ZnS substrate. In the second aspect, the temperature of the ZnS substrate affects the subsequent plating process. By controlling the substrate temperature and matching the subsequent plating temperature, the crystal structure, surface morphology, stoichiometry, and electronic properties of the film system structure can be optimized, thereby improving the overall quality of the film system structure.

[0049] Preferably, in step two, when the film material is pre-melted, the vacuum degree is 3.0×10 -3 ~5.0×10 -3 Pa.

[0050] In practical applications, when the film material is pre-melted, the power of the evaporation source is adjusted according to the melting point of the film material.

[0051] Preferably, in step three, when the ZnS substrate is cleaned, the vacuum degree is 1.0×10 -3 ~2.0×10 -3 Pa; the cleaning time is 250-350 s; the Hall ion source parameters are: neutralization current 0.6 A, neutralization gas flow 8 sccm, anode voltage 220 V, anode current 2 A, and argon gas flow 100%.

[0052] Using the Hall ion source to clean the surface microstructure of the ZnS substrate can eliminate impurities such as surface oxidation layers and organic matter, making the surface cleaner and avoiding the influence of the oxidation layer on the transmittance of the optical lens and improving the adhesion conditions of the film layer.

[0053] Preferably, in step four, the ZnS layer, YF3 layer, and LaF3 layer are evaporated using resistance heating.

[0054] Preferably, in step four, the evaporation rate of ZnS is 6 Å / s; the evaporation rate of YF3 is 5 Å / s, and the evaporation rate of LaF3 is 6 Å / s.

[0055] Preferably, in step four, when the film system structure is plated, ion-assisted deposition is used.

[0056] Preferably, in step four, the ion source parameters for ion-assisted evaporation of the ZnS material are: neutralization current 0.5 A, neutralization gas flow 8 sccm, anode voltage 100 V, anode current 1 A, argon flow 100%.

[0057] Preferably, the ion source parameters for ion-assisted evaporation of the YF3 and LaF3 materials are: neutralization current 0.6 A, neutralization gas flow 8 sccm, anode voltage 130 V, anode current 1.3 A, argon flow 30%, oxygen flow 70%.

[0058] Preferably, in step four, the vacuum degree during film plating is 4.5x10 -3 ~5.5x10 -3 Pa, and the film plating temperature is 140-160°C.

[0059] The inventors have found that baking the zinc sulfide substrate and plating the film at the same temperature is beneficial to improving the film quality.

[0060] Preferably, in step four, the film thickness is controlled using a quartz crystal control, and the crystal frequency is 6 MHz.

[0061] Preferably, after step four, a heat preservation stage is further included, in which the film system structure is preserved at 150°C for 5-15 min after plating, and the sample is taken out after the temperature drops to 100°C.

[0062] To make the technical problems, technical solutions and technical advantages of the present application clearer, specific examples will be described in detail below, but the protection scope of the present application is not limited to the following specific examples.

[0063] Unless otherwise defined, all the professional terms used below have the same meaning as commonly understood by those skilled in the art. The professional terms used in this document are only for the purpose of describing specific examples and are not intended to limit the protection scope of the present application.

[0064] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0065] Example 1:

[0066] A preparation method of a zinc sulfide dual-band antireflection film includes the following steps:

[0067] Step one, select a zinc sulfide substrate with a smooth surface and no defects, clean the plating piece and the zinc sulfide substrate using an ultrasonic cleaner, place the plating piece and the zinc sulfide substrate in a tool clamp, and then hang the tool clamp in the cavity of a vacuum plating machine.

[0068] Step two, start the vacuum coating machine to extract the gas in the cavity, heat the zinc sulfide substrate to 150℃ for 15min, and when the vacuum degree is 4.0*10 -3 Pa, start to pre-melt the film material.

[0069] Step three, adjust the vacuum degree to 1.3*10 -3 Pa again, start the Hall ion source to clean the zinc sulfide substrate for 300 seconds, and the Hall ion source parameters during cleaning are: neutralizing current 0.6A, neutralizing gas flow 8sccm, anode voltage 220V, anode current 2A, argon flow 100%.

[0070] Step four, maintain a constant vacuum degree of 5.0*10 -3 Pa and a temperature of 150℃ to deposit each film layer on one side of the zinc sulfide substrate in turn, and the thickness of each film layer is: YF3 layer 15.93nm, ZnS layer 404nm, YF3 layer 30.7nm, ZnS layer 26.56nm, YF3 layer 1168.1nm, ZnS layer 23.35nm, YF3 layer 20.25nm, ZnS layer 106.15nm, LaF3 layer 106.30nm.

[0071] Among them, when depositing the ZnS layer, the evaporation rate of ZnS is 6Å / s, and the ion source parameters are: neutralizing current 0.5A, neutralizing gas flow 8sccm, anode voltage 100V, anode current 1A, argon flow 100%.

[0072] When depositing the YF3 layer, the evaporation rate of YF3 is 5Å / s; when depositing the LaF3 layer, the evaporation rate of LaF3 is 6Å / s. When depositing the YF3 layer and the LaF3 layer, the ion source parameters are: neutralizing current 0.6A, neutralizing gas flow 8sccm, anode voltage 130V, anode current 1.3A, argon flow 30%, oxygen flow 70%.

[0073] Step five, after 150℃ for 10min, reduce to below 100℃ and take out.

[0074] Step six, repeat steps one to five to deposit the film system structure on the other side of the zinc sulfide substrate, and obtain the optical lens.

[0075] Example 2:

[0076] A method for preparing a zinc sulfide dual-band antireflection film, comprising the following steps:

[0077] Step one, select a zinc sulfide substrate with a smooth surface and no defects, clean the plating piece and the zinc sulfide substrate with an ultrasonic cleaner, put the plating piece and the zinc sulfide substrate into a tool clamp, and then hang the tool clamp into the cavity of the vacuum coating machine.

[0078] Step two, start the vacuum coating machine to extract the gas in the cavity, heat to 150℃ for 15min to heat the zinc sulfide substrate, when the vacuum degree is 3.0*10 -3 Pa, start to pre-melt the film material.

[0079] Step three, adjust the vacuum degree to 1.0*10 -3 Pa again, start the Hall ion source to clean the zinc sulfide substrate for 250 seconds, and the Hall ion source parameters during cleaning are: neutralizing current 0.6A, neutralizing gas flow 8sccm, anode voltage 220V, anode current 2A, argon flow 100%.

[0080] Step four, maintain a constant vacuum degree of 4.5*10 -3 Pa, temperature 140℃, and the thickness of each film layer plated on one side of the zinc sulfide substrate is: YF3 layer 15.93nm, ZnS layer 404nm, YF3 layer 30.7nm, ZnS layer 26.56nm, YF3 layer 1168.1nm, ZnS layer 23.35nm, YF3 layer 20.25nm, ZnS layer 106.15nm, LaF3 layer 106.30nm.

[0081] Among them, when plating ZnS layer, the evaporation rate of ZnS is 6Å / s, and the ion source parameters are: neutralizing current 0.5A, neutralizing gas flow 8sccm, anode voltage 100V, anode current 1A, argon flow 100%.

[0082] When plating YF3 layer, the evaporation rate of YF3 is 5Å / s; when plating LaF3 layer, the evaporation rate of LaF3 is 6Å / s. The ion source parameters when plating YF3 layer and LaF3 layer are: neutralizing current 0.6A, neutralizing gas flow 8sccm, anode voltage 130V, anode current 1.3A, argon flow 30%, oxygen flow 70%.

[0083] Step five, after 140℃ for 5min, reduce to below 100℃ and take out.

[0084] Step six, repeat steps one to five to plate the film system structure on the other side of the zinc sulfide substrate, that is, obtain the optical lens.

[0085] Example 3:

[0086] A preparation method of a zinc sulfide dual-band antireflection film, comprising the following steps:

[0087] Step one, select a zinc sulfide substrate with a smooth surface and no defects, clean the plating piece and the zinc sulfide substrate with an ultrasonic cleaner, put the plating piece and the zinc sulfide substrate into a tool clamp, and then hang the tool clamp into the cavity of the vacuum coating machine.

[0088] Step two, start the vacuum coating machine to extract the gas in the cavity, heat the zinc sulfide substrate to 150℃ for 15 minutes, and when the vacuum degree rises to 5.0x10 -3 Pa, start pre-melting the film material.

[0089] Step three, adjust the vacuum degree to 2.0x10 -3 Pa again, start the Hall ion source to clean the zinc sulfide substrate for 350 seconds, and the Hall ion source parameters during cleaning are: neutralizing current 0.6A, neutralizing gas flow 8sccm, anode voltage 220V, anode current 2A, argon flow 100%.

[0090] Step four, maintain a constant vacuum degree of 5.5x10 -3 Pa, temperature of 160℃ on one side of the zinc sulfide substrate to coat each film layer in turn with thickness: YF3 layer 15.93nm, ZnS layer 404nm, YF3 layer 30.7nm, ZnS layer 26.56nm, YF3 layer 1168.1nm, ZnS layer 23.35nm, YF3 layer 20.25nm, ZnS layer 106.15nm, LaF3 layer 106.30nm.

[0091] Among them, when coating the ZnS layer, the evaporation rate of ZnS is 6Å / s, and the ion source parameters are: neutralizing current 0.5A, neutralizing gas flow 8sccm, anode voltage 100V, anode current 1A, argon flow 100%.

[0092] When coating the YF3 layer, the evaporation rate of YF3 is 5Å / s; when coating the LaF3 layer, the evaporation rate of LaF3 is 6Å / s. When coating the YF3 layer and the LaF3 layer, the ion source parameters are: neutralizing current 0.6A, neutralizing gas flow 8sccm, anode voltage 130V, anode current 1.3A, argon flow 30%, oxygen flow 70%.

[0093] Step five, after 15 minutes of 160℃, reduce to below 100℃ and take out.

[0094] Step six, repeat steps one to five to coat the film system structure on the other side of the zinc sulfide substrate, i.e. to obtain an optical lens.

[0095] Comparative Example 1:

[0096] The difference from Example 1 is that in step four, the YF3 layer, the ZnS layer, the YF3 layer, the ZnS layer, the YF3 layer, the ZnS layer, the YF3 layer, and the ZnS layer are coated on one side of the zinc sulfide substrate in turn.

[0097] Comparative Example 2:

[0098] The difference between Example 1 is that in step four, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, LaF3 layer are successively plated on one side of the zinc sulfide substrate at 180℃.

[0099] In Examples 1-3 and Comparative Examples 1-2, the plating auxiliary sheet used is zinc sulfide.

[0100] The optical lens prepared in Examples 1-3 and Comparative Examples 1-2 is tested by a spectrometer, and the results are shown in Table 1. Figure 2 Figure 3 It can be seen that the transmittance of the optical lens prepared in Example 1 is 94% in the wavelength range of 0.4 μm-1.1 μm, and the average transmittance is 94.6% in the wavelength range of 8 μm-12 μm, which can meet the market demand.

[0101] The stability of the film system structure of Examples 1-3 and Comparative Examples 1-2 is tested by the following test methods:

[0102] Bubble test: the optical lens is subjected to a bubble test in tap water for 24 h.

[0103] Adhesion test: after the bubble and salt spray tests in tap water are completed, 3M adhesive tape is attached to each surface of the lens by hand, and the tape is pulled in the opposite direction of the attached end.

[0104] Cold and hot impact test: cold and hot impact test is performed in a high and low temperature chamber at-40℃ to 85℃ for 24 h.

[0105] Constant temperature and humidity test: constant temperature and humidity test is performed in a constant temperature and humidity chamber at 50℃ and 95% relative humidity for 48 h.

[0106] Salt spray test: neutral salt spray test is performed for 48 h.

[0107] Low temperature test: low temperature test is performed in a low temperature chamber at-40℃ for 48 h.

[0108] High temperature test: high temperature test is performed in a high temperature chamber at 85℃ for 48 h.

[0109] Moderate friction test: the lens is subjected to friction by a rubber friction head wrapped with a degreasing cloth under a pressure of 4.9 N for 50 times (25 times back and forth), and whether there are scratches or other damage marks is observed. If there are no such marks, it is qualified; if there are such marks, it is unqualified.

[0110] Table 1- Stability test results of the film system structure prepared in Examples 1-3 and Comparative Examples 1-2

[0111]

[0112] ​The film system structure prepared by the preparation method provided in the application has good stability and wear resistance.

[0113] The above-described embodiments are merely preferred specific embodiments of the application, but the protection scope of the application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes to the technical solutions and concepts of the application within the technical scope of the application, which should be covered within the protection scope of the application.

Claims

1. A zinc sulfide ultrawideband dual-band antireflective protective film, characterized in that, The system includes a film structure symmetrically arranged on both sides of a zinc sulfide substrate, wherein the film structure consists of a YF3 layer, a ZnS layer, a YF3 layer, a ZnS layer, a YF3 layer, a ZnS layer, a YF3 layer, a ZnS layer, a YF3 layer, a ZnS layer, and a LaF3 layer, arranged sequentially from the inside to the outside of the zinc sulfide substrate. The thicknesses of each film layer in the membrane structure from the inside to the outside of the zinc sulfide substrate are as follows: YF3 layer 15.93 nm, ZnS layer 404 nm, YF3 layer 30.7 nm, ZnS layer 26.56 nm, YF3 layer 1168.1 nm, ZnS layer 23.35 nm, YF3 layer 20.25 nm, ZnS layer 106.15 nm, and LaF3 layer 106.30 nm. The antireflective protective film can achieve an average transmittance of over 94% in the 0.4μm~1.1μm and 8μm~12μm wavelength bands.

2. The method for preparing the zinc sulfide ultrawideband dual-band antireflective protective film as described in claim 1, characterized in that, Includes the following steps: Step 1: Cleaning the zinc sulfide substrate surface and adding the film material; Step 2: Heating and baking, and pre-melting of the film material; Step 3: Ion cleaning of the zinc sulfide substrate; Step 4: On one side of the zinc sulfide substrate, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, YF3 layer, ZnS layer, and LaF3 layer are sequentially deposited under a vacuum atmosphere; Step 5: Cool and remove the part; Step six: Repeat steps one through five above to deposit a film structure on the other side of the zinc sulfide substrate.

3. The method for preparing the zinc sulfide ultrawideband dual-band antireflective protective film as described in claim 2, characterized in that, In step two, the zinc sulfide substrate is heated at 140~160℃ for 15 minutes.

4. The method for preparing the zinc sulfide ultrawideband dual-band antireflective protective film as described in claim 2 or 3, characterized in that, In step two, during the pre-melting of the film material, the vacuum degree is 3.0 × 10⁻⁶. -3 ~5.0×10 -3 Pa.

5. The method for preparing the zinc sulfide ultrawideband dual-band antireflective protective film as described in claim 3, characterized in that, In step three, the vacuum level is 1.0 × 10⁻⁶ when cleaning the zinc sulfide substrate. -3 ~2.0×10 -3 Pa; cleaning time is 250-350s; Hall ion source parameters are: neutralization current 0.6A, neutralization gas flow rate 8sccm, anode voltage 220V, anode current 2A, argon flow rate 100%.

6. The method for preparing the zinc sulfide ultrawideband dual-band antireflective protective film as described in claim 2, characterized in that, In step four, the ZnS layer, YF3 layer, and LaF3 layer are evaporated using resistance heating; the evaporation rate of ZnS is 6 Å / s; the evaporation rate of YF3 is 5 Å / s; and the evaporation rate of LaF3 is 6 Å / s.

7. The method for preparing the zinc sulfide ultrawideband dual-band antireflective protective film as described in claim 2 or 6, characterized in that, In step four, ion-assisted deposition is used when depositing the film structure. The ion source parameters for ion-assisted deposition of ZnS material are: neutralization current 0.5A, neutralization gas flow rate 8sccm, anode voltage 100V, anode current 1A, and argon flow rate 100%. The ion source parameters for ion-assisted deposition of YF3 and LaF3 materials are: neutralization current 0.6A, neutralization gas flow rate 8sccm, anode voltage 130V, anode current 1.3A, argon flow rate 30%, and oxygen flow rate 70%.

8. The method for preparing the zinc sulfide ultrawideband dual-band antireflective protective film as described in claim 2, characterized in that, In step four, the coating vacuum degree is 4.5 × 10⁻⁶. -3 ~5.5×10 -3 Pa; coating temperature is 140~160℃; film thickness is controlled by a quartz crystal controller with a crystal oscillator frequency of 6MHz.

9. The method for preparing the zinc sulfide ultrawideband dual-band antireflective protective film as described in claim 2, characterized in that, Step four is followed by a heat preservation stage. After the film structure is deposited, the heat preservation stage is maintained for 5 to 15 minutes. The part is removed after the temperature drops to 100°C.

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