Surface coating process for optical component products

Abstract

The present invention relates to the field of coating, and specifically to a surface coating process for an optical component product, comprising the following steps: step 1, cleaning and drying a zinc selenide substrate to obtain a pre-treated zinc selenide substrate; step 2, preparing a coating material, the coating material comprising iridium indium selenide, zinc selenide, and yttrium fluoride, grinding and screening; step 3, placing the pre-treated zinc selenide substrate in a coating device, then adding the coating material, and coating layer by layer to obtain a coated optical component product. The process of the present invention is not only simple to operate, but also has a high quality of the obtained coating, and the coating has the advantages of being uniform and dense, having good adhesion, and being resistant to moisture and heat.

Description

Technical Field

[0001] The invention relates to the field of film coating, and in particular to a surface coating process for an optical element product. Background Art

[0002] Optical coating technology is to coat one or more layers of thin film on the surface of optical components to change or optimize the optical performance of the components. This layer of film can enhance the light transmittance of the components, reduce reflection, improve color reproduction, etc., making our visual experience clearer and more realistic.

[0003] The common method of optical coating technology is to coat a thin film on a glass substrate by vacuum sputtering, which is generally used to control the reflectivity and transmittance of the substrate to the incident light beam to meet different needs. In order to eliminate the reflection loss on the surface of optical parts and improve the imaging quality, one or more layers of transparent dielectric film are coated, which is called an anti-reflection film or an anti-reflection film. With the development of laser technology, higher requirements are placed on the reflectivity and transmittance of the film layer. The vacuum sputtering coating method has the defects of low sputtering rate, uneven deposition flow distribution, and difficulty in controlling gas composition, which limits industrial applications with high production requirements and increases the complexity and cost of the sputtering system.

[0004] Lenses or prisms are both optical elements and are widely used in carbon dioxide lasers. Their main functions include focusing the laser beam, changing the direction of the laser beam, and protecting the laser. Zinc selenide is a commonly used material for manufacturing lenses or prisms. When zinc selenide lenses or prisms are used in optical systems, they usually need to be coated with an anti-reflection film to reduce their surface optical reflection losses and improve optical transmittance. The anti-reflection film of a zinc selenide lens or prism is generally composed of two or more materials such as sulfides, selenides or fluorides. However, when the anti-reflection film composed of the above-mentioned material combinations is used on zinc selenide substrates, there are usually defects such as poor adhesion, insufficient moisture and heat resistance, and uneven deposition, especially low transmittance, which affects its performance in certain optical systems. Therefore, it is necessary to select a more suitable surface anti-reflection film to protect the zinc selenide components and obtain a higher transmittance at the same time. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a surface coating process for optical element products.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A surface coating process for an optical component product comprises the following steps:

[0008] Step 1, cleaning and drying the zinc selenide substrate to obtain a pre-treated zinc selenide substrate;

[0009] Step 2, preparing coating materials, the coating materials including iridium indium selenide, zinc selenide, and yttrium fluoride, grinding and screening;

[0010] Step 3, placing the pre-treated zinc selenide substrate in a coating device, then adding a coating material, and performing a layer-by-layer coating process to obtain a coated optical element product.

[0011] Preferably, in step 1, the purity of the zinc selenide substrate is ≥99.99% and the thickness is 0.5-5 mm.

[0012] Preferably, in step 1, the cleaning method includes any one of wiping cleaning, ultrasonic cleaning, steam cleaning, and ion beam cleaning.

[0013] More preferably, in step 1, the cleaning is carried out by a combination of wiping cleaning and ultrasonic cleaning. Specifically, the zinc selenide substrate is first cleaned with a cleaning agent to remove surface grease, then cleaned with distilled water for 3-5 times, and then cleaned with acetone or ethanol in an ultrasonic cleaning machine. The cleaning frequency is 20-80kHz, the cleaning temperature is 20-60°C, and the cleaning time is 5-20min.

[0014] Preferably, in step 1, the drying is vacuum drying or nitrogen blowing drying.

[0015] Preferably, in step 2, the particle size range of the coating material is controlled to be 100-200 μm.

[0016] Preferably, in step 2, the preparation process of iridium indium selenide includes:

[0017] S1. Weigh sodium chloroiridate and indium acetate, add them to deionized water, then add selenium powder, mix and dissolve them thoroughly, then add a dispersant and a reducing agent to obtain a mixed reaction solution;

[0018] S2, pouring the mixed reaction liquid into a reaction kettle, and heat-treating it at a temperature of 160-200° C. for 10-20 hours. After the reaction is completed, filtering out the solid, washing it with pure water at least three times, and vacuum drying it to obtain a precursor;

[0019] S3. Place the precursor in a high-temperature graphite furnace, raise the temperature to 400-500° C. under the protection of an inert gas, and keep the temperature for 1-3 hours. After cooling in the furnace, iridium indium selenide is obtained.

[0020] Preferably, in S1, the mass volume ratio of sodium chloroiridate, indium acetate, selenium powder and deionized water is (0.28-0.56) g: (0.36-0.72) g: (0.48-0.96) g: (10-30) mL.

[0021] Preferably, in S1, the dispersant is hydroxyethyl cellulose, and the added amount is 10%-20% of the mass of the selenium powder; the reducing agent is ethylenediamine, and the added amount is 2.5-6.5 times the mass of the selenium powder.

[0022] Preferably, in step 3, the layer-by-layer coating treatment is to coat both the upper and lower surfaces of the pre-treated zinc selenide substrate, and the coatings on the upper and lower surfaces of the pre-treated zinc selenide substrate are completely symmetrical; that is, the coating on the upper surface of the pre-treated zinc selenide substrate includes a first iridium indium selenide layer, a zinc selenide layer, a yttrium fluoride layer, and a second iridium indium selenide layer arranged in sequence from bottom to top; the coating on the lower surface of the pre-treated zinc selenide substrate includes a first iridium indium selenide layer, a zinc selenide layer, a yttrium fluoride layer, and a second iridium indium selenide layer arranged in sequence from top to bottom.

[0023] Preferably, in step 3, the thickness of the first iridium indium selenide layer is 214-348 nm, the thickness of the zinc selenide layer is 176-228 nm, the thickness of the yttrium fluoride layer is 125-173 nm, and the thickness of the second iridium indium selenide layer is 152-197 nm.

[0024] Preferably, in step 3, the coating equipment is a six-source evaporation coating equipment, model NTE-4000(A).

[0025] Preferably, in step 3, during the vacuum coating process, the vacuum degree of the coating equipment during operation is (5-8)×10 -4 Pa.

[0026] Preferably, in step 3, during the vacuum coating process, the rotation speed of the sample carrier is 15-25 rpm.

[0027] Preferably, in step 3, during the vacuum coating process, the evaporation source area is heated to evaporate the coating material particles, the heating rate is controlled to be 300-500°C / min, and the evaporation rate is controlled to be 0.3-1Å / s.

[0028] Preferably, in step 3, a cooling treatment is performed after the coating is completed, and the cooling rate is 100-200° C. / min until natural cooling.

[0029] The beneficial effects of the present invention are:

[0030] 1. The present invention discloses a surface coating process for an optical element product, which includes the steps of surface cleaning, drying and coating. The process of the present invention is not only simple to operate, but also has high quality of the obtained coating, and the coating has the advantages of uniformity and density, good adhesion, and resistance to moisture and heat. In practical application, for the wavelength band commonly used by carbon dioxide lasers, especially at a wavelength of 0.8-10.6μm, the transmittance is excellent, and a good surface anti-reflection effect can be achieved.

[0031] 2. The coating process of the present invention adopts vacuum evaporation, and uses iridium indium selenide, zinc selenide, and yttrium fluoride as coating materials to form a film on the surface of a zinc selenide substrate. Compared with traditional coating technology, the coating obtained by the present invention not only has high continuity and good adhesion, but also has high light transmittance and good anti-reflection effect.

[0032] 3. The surface coating material, coating thickness and coating sequence of the zinc selenide substrate of the present invention are specially selected after experiments. Among them, zinc selenide has a high tolerance to thermal shock; yttrium fluoride has good optical properties and chemical stability; and iridium indium selenide not only has strong adhesion and good resistance to moisture and heat, but also can better increase transmitted light and reduce reflected light, thereby improving the imaging quality of optical components. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to limit the scope of the present invention. The change or adjustment of the relative relationship thereof shall also be regarded as the scope of the present invention without substantially changing the technical content.

[0034] In order to better understand the above technical scheme, the exemplary embodiments of the present invention are described in more detail below. Although exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0035] The present invention will be further described below in conjunction with the following examples.

[0036] Example 1

[0037] A surface coating process for an optical component product comprises the following steps:

[0038] Step 1, wipe and clean the zinc selenide substrate with a purity of ≥99.99%, a diameter of 25.4 mm, and a thickness of 1.5 mm in turn, first clean the zinc selenide substrate with a cleaning agent to remove surface grease, then clean it with distilled water for 4 times, and then clean it with acetone or ethanol in an ultrasonic cleaning machine, the cleaning frequency is 50 kHz, the cleaning temperature is 40° C., and the cleaning time is 15 min. After cleaning, vacuum drying or nitrogen blowing drying is completed to obtain a pre-treated zinc selenide substrate;

[0039] Step 2, preparing the coating material, the coating material includes iridium indium selenide, zinc selenide, and yttrium fluoride, grinding and sieving, and the particle size range is controlled to be 100-200 μm; wherein the preparation process of iridium indium selenide includes:

[0040] S1. Weigh 0.42 g of sodium chloroiridate (Na2IrCl6) and 0.54 g of indium acetate (In(C2H3O2)3) and add them to 20 mL of deionized water, then add 0.72 g of selenium powder, mix and dissolve thoroughly, then add 15% of the mass of the selenium powder as a dispersant, hydroxyethyl cellulose, and 4.5 times the mass of the selenium powder as a reducing agent, ethylenediamine, to obtain a mixed reaction solution;

[0041] S2, pouring the mixed reaction liquid into a reaction kettle, and heat-treating it at 180° C. for 15 hours. After the reaction is completed, filtering out the solid, washing it with pure water for at least three times, and vacuum drying it to obtain a precursor;

[0042] S3. Place the precursor in a high-temperature graphite furnace, raise the temperature to 450°C under the protection of an inert gas, and keep the temperature for 2 hours. After cooling in the furnace, iridium indium selenide is obtained.

[0043] Step 3: Place the pre-treated ZnSe substrate on the sample carrier of the NTE-4000(A) six-source evaporation coating equipment chamber, then add the coating material as the evaporation source and place it in the evaporation source area. Evacuate the coating chamber to a vacuum degree of 6×10 -4 After Pa, the rotation speed of the sample stage is 20rpm, and then the evaporation source area is heated until the coating material particles evaporate. The previously treated zinc selenide substrate is used as the basis for layer-by-layer coating treatment:

[0044] First, the first iridium indium selenide layer is evaporated on the upper surface of the pre-treated zinc selenide substrate, the heating rate is controlled to be 365°C / min, the evaporation rate is controlled to be 0.8Å / s, and the evaporation thickness is 287nm; then the zinc selenide layer is evaporated, the heating rate is controlled to be 325°C / min, the evaporation rate is controlled to be 0.5Å / s, and the evaporation thickness is 206nm; then the yttrium fluoride layer is evaporated, the heating rate is controlled to be 350°C / min, the evaporation rate is controlled to be 0.4Å / s, and the evaporation thickness is 158nm; finally, the second iridium indium selenide layer is evaporated, the heating rate is controlled to be 420°C / min, the evaporation rate is controlled to be 0.5Å / s, and the evaporation thickness is 173nm, after the upper surface coating is completed, the temperature is lowered at a cooling rate of 150°C / min until it is naturally cooled, and then the lower surface of the pre-treated zinc selenide substrate is coated, and the coating process is the same as that of the upper surface, and finally an optical element product with both sides coated is obtained.

[0045] Example 2

[0046] A surface coating process for an optical component product comprises the following steps:

[0047] Step 1, wipe and clean the zinc selenide substrate with a purity of ≥99.99%, a diameter of 12.5 mm, and a thickness of 0.5 mm in turn, first clean the zinc selenide substrate with a cleaning agent to remove surface grease, then clean it with distilled water for 3 times, and then clean it with acetone or ethanol in an ultrasonic cleaning machine, the cleaning frequency is 20 kHz, the cleaning temperature is 20° C., and the cleaning time is 20 min. After cleaning, vacuum drying or nitrogen blowing drying is completed to obtain a pre-treated zinc selenide substrate;

[0048] Step 2, preparing the coating material, the coating material includes iridium indium selenide, zinc selenide, and yttrium fluoride, grinding and sieving, and the particle size range is controlled to be 100-200 μm; wherein the preparation process of iridium indium selenide includes:

[0049] S1. Weigh 0.28 g of sodium chloroiridate (Na2IrCl6) and 0.36 g of indium acetate (In(C2H3O2)3) and add them to 10 mL of deionized water, then add 0.48 g of selenium powder, mix and dissolve thoroughly, then add 10% of the mass of the selenium powder as a dispersant, hydroxyethyl cellulose, and 2.5 times the mass of the selenium powder as a reducing agent, ethylenediamine, to obtain a mixed reaction solution;

[0050] S2, pouring the mixed reaction liquid into a reaction kettle, and heat-treating it at 160° C. for 20 hours. After the reaction is completed, filtering out the solid, washing it with pure water for at least three times, and vacuum drying it to obtain a precursor;

[0051] S3. Place the precursor in a high-temperature graphite furnace, raise the temperature to 400°C under the protection of an inert gas, and keep the temperature for 3 hours. After cooling in the furnace, iridium indium selenide is obtained.

[0052] Step 3: Place the pre-treated ZnSe substrate on the sample carrier of the NTE-4000(A) six-source evaporation coating equipment chamber, then add the coating material as the evaporation source and place it in the evaporation source area. Evacuate the coating chamber to a vacuum degree of 5×10 -4 After Pa, the rotation speed of the sample stage is 15rpm, and then the evaporation source area is heated until the coating material particles evaporate. The previously treated zinc selenide substrate is used as the basis for layer-by-layer coating:

[0053] First, the first iridium indium selenide layer is evaporated, the heating rate is controlled to be 310℃ / min, the evaporation rate is controlled to be 0.6Å / s, and the evaporation thickness is 214nm; then the zinc selenide layer is evaporated, the heating rate is controlled to be 400℃ / min, the evaporation rate is controlled to be 0.4Å / s, and the evaporation thickness is 228nm; then the yttrium fluoride layer is evaporated, the heating rate is controlled to be 375℃ / min, the evaporation rate is controlled to be 0.3Å / s, and the evaporation thickness is 125nm; finally, the second iridium indium selenide layer is evaporated, the heating rate is controlled to be 450℃ / min, the evaporation rate is controlled to be 0.6Å / s, and the evaporation thickness is 197nm. After the coating is completed, the temperature is lowered at a rate of 100℃ / min until it is naturally cooled, and then the lower surface of the pre-treated zinc selenide substrate is coated, and the coating process is the same as that of the upper surface, and finally an optical element product with both sides coated is obtained.

[0054] Example 3

[0055] A surface coating process for an optical component product comprises the following steps:

[0056] Step 1, wipe and clean the zinc selenide substrate with a purity of ≥99.99%, a diameter of 38.6 mm, and a thickness of 5 mm in turn, first clean the zinc selenide substrate with a cleaning agent to remove surface grease, then clean it with distilled water for 5 times, and then clean it with acetone or ethanol in an ultrasonic cleaning machine, the cleaning frequency is 80 kHz, the cleaning temperature is 60° C., and the cleaning time is 5 min. After cleaning, vacuum drying or nitrogen blowing drying is completed to obtain a pre-treated zinc selenide substrate;

[0057] Step 2, preparing the coating material, the coating material includes iridium indium selenide, zinc selenide, and yttrium fluoride, grinding and sieving, and the particle size range is controlled to be 100-200 μm; wherein the preparation process of iridium indium selenide includes:

[0058] S1. Weigh 0.56 g of sodium chloroiridate (Na2IrCl6) and 0.72 g of indium acetate (In(C2H3O2)3) and add them to 30 mL of deionized water, then add 0.96 g of selenium powder, mix and dissolve thoroughly, then add 20% of the mass of the selenium powder as a dispersant, hydroxyethyl cellulose, and 6.5 times the mass of the selenium powder as a reducing agent, ethylenediamine, to obtain a mixed reaction solution;

[0059] S2, pouring the mixed reaction liquid into a reaction kettle, and heat-treating it at a temperature of 200° C. for 10 hours. After the reaction is completed, filtering out the solid, washing it with pure water for at least three times, and vacuum drying it to obtain a precursor;

[0060] S3. Place the precursor in a high-temperature graphite furnace, raise the temperature to 500°C under the protection of an inert gas, and keep the temperature for 1 hour. After cooling in the furnace, iridium indium selenide is obtained.

[0061] Step 3: Place the pre-treated ZnSe substrate on the sample carrier of the NTE-4000(A) six-source evaporation coating equipment chamber, then add the coating material as the evaporation source and place it in the evaporation source area. Evacuate the coating chamber to a vacuum degree of 8×10 -4 After Pa, the rotation speed of the sample stage is 25rpm, and then the evaporation source area is heated until the coating material particles evaporate. The previously treated zinc selenide substrate is used as the basis for layer-by-layer coating:

[0062] First, the first iridium indium selenide layer is evaporated, the heating rate is controlled to be 350℃ / min, the evaporation rate is controlled to be 0.7Å / s, and the evaporation thickness is 348nm; then the zinc selenide layer is evaporated, the heating rate is controlled to be 325℃ / min, the evaporation rate is controlled to be 0.5Å / s, and the evaporation thickness is 176nm; then the yttrium fluoride layer is evaporated, the heating rate is controlled to be 400℃ / min, the evaporation rate is controlled to be 0.5Å / s, and the evaporation thickness is 173nm; finally, the second iridium indium selenide layer is evaporated, the heating rate is controlled to be 425℃ / min, the evaporation rate is controlled to be 0.6Å / s, and the evaporation thickness is 152nm. After the coating is completed, the temperature is lowered at a rate of 200℃ / min until it is naturally cooled, and then the lower surface of the pre-treated zinc selenide substrate is coated, and the coating process is the same as that of the upper surface, and finally an optical component product with both sides coated is obtained.

[0063] Comparative Example 1

[0064] A surface coating process for an optical element product, which differs from Example 1 in that the coating material only includes zinc selenide and yttrium fluoride, wherein the coating sequence is based on a zinc selenide substrate, and from bottom to top is a first zinc selenide layer of 287 nm, a first yttrium fluoride layer of 206 nm, a second zinc selenide layer of 158 nm, and a second yttrium fluoride layer of 173 nm.

[0065] Comparative Example 2

[0066] A surface coating process for an optical element product, which differs from Example 1 in that the coating material includes indium selenide, zinc selenide and yttrium fluoride, wherein the coating sequence is based on a zinc selenide substrate, and from bottom to top is a first indium selenide layer of 287 nm, a zinc selenide layer of 206 nm, a yttrium fluoride layer of 158 nm and a second indium selenide layer of 173 nm.

[0067] The preparation process of indium selenide includes:

[0068] S1. Weigh 0.54 g of indium acetate (In(C2H3O2)3) and add it to 20 mL of deionized water, then add 0.58 g of selenium powder, mix and dissolve thoroughly, then add 15% of the mass of the selenium powder as a dispersant, hydroxyethyl cellulose, and 4.5 times the mass of the selenium powder as a reducing agent, ethylenediamine, to obtain a mixed reaction solution;

[0069] S2, pouring the mixed reaction liquid into a reaction kettle, and heat-treating it at 180° C. for 15 hours. After the reaction is completed, filtering out the solid, washing it with pure water for at least three times, and vacuum drying it to obtain a precursor;

[0070] S3. Place the precursor in a high-temperature graphite furnace, raise the temperature to 450°C under the protection of an inert gas, and keep the temperature for 2 hours. After cooling in the furnace, indium selenide is obtained.

[0071] Comparative Example 3

[0072] A surface coating process for an optical element product, which differs from Example 1 in that the coating material includes iridium selenide, zinc selenide and yttrium fluoride, wherein the coating sequence is based on a zinc selenide substrate, and from bottom to top is a first iridium selenide layer of 287 nm, a zinc selenide layer of 206 nm, a yttrium fluoride layer of 158 nm and a second iridium selenide layer of 173 nm.

[0073] The preparation process of iridium selenide includes:

[0074] S1. Weigh 0.42 g of sodium chloroiridate (Na2IrCl6) and add it to 20 mL of deionized water, then add 0.14 g of selenium powder, mix and dissolve thoroughly, then add 15% of the mass of the selenium powder as a dispersant, hydroxyethyl cellulose, and 4.5 times the mass of the selenium powder as a reducing agent, ethylenediamine, to obtain a mixed reaction solution;

[0075] S2, pouring the mixed reaction liquid into a reaction kettle, and heat-treating it at 180° C. for 15 hours. After the reaction is completed, filtering out the solid, washing it with pure water for at least three times, and vacuum drying it to obtain a precursor;

[0076] S3. Place the precursor in a high-temperature graphite furnace, raise the temperature to 450°C under the protection of an inert gas, and keep the temperature for 2 hours. After cooling in the furnace, iridium selenide is obtained.

[0077] The performance of the optical element products obtained by the coating process of Example 1 and Comparative Examples 1-3 is compared. First, the transmittance performance is detected, including the transmittance of multiple wavelengths in the 600nm-16μm band (the incident angle is 0-15°); secondly, the physical properties of the product are detected, and the adhesion and moisture and heat detection reference standard "GJB 2485-1995 General Specification for Optical Film Layers" is used. Among them, adhesion test: use 2cm wide tape with a peeling strength of not less than 2.74N / cm to firmly stick it on the surface of the film layer, pull it up vertically and quickly, and observe whether it is demolded; moisture and heat detection: keep it at a temperature of 50±2℃ and a relative humidity of 95%-100% for 48h, and observe whether the film layer has defects such as demolding, cracks, and blistering. The results are shown in Table 1 and Table 2:

[0078] Table 1 Transmittance performance of different products

[0079]

[0080] It can be seen from Table 1 that the optical element product obtained by the coating process of Example 1 of the present invention can achieve very excellent transmittance at wavelengths of 808nm, 880nm, 915nm, 3.7-4.8μm and 10.6μm, especially the laser transmittance at wavelengths of 3.7-4.8μm and 10.6μm can reach more than 99%.

[0081] Table 2 Physical properties of different products

[0082]

[0083] It can be seen from Table 2 that the optical element product obtained by the coating process of Example 1 of the present invention has excellent adhesion and moisture and heat resistance and can meet certain moisture and heat environment requirements, which is very important for its use in optoelectronic devices and other applications requiring moisture and heat resistance.

[0084] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily being directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0085] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A surface coating process for an optical component product, characterized in that: The following steps are involved: Step 1, cleaning and drying the zinc selenide substrate to obtain a pre-treated zinc selenide substrate; Step 2, preparing coating materials, the coating materials including iridium indium selenide, zinc selenide, and yttrium fluoride, grinding and screening; Step 3, placing the pre-treated zinc selenide substrate in a coating device, then adding a coating material, and performing a layer-by-layer coating process to obtain a coated optical element product; The coating process adopts vacuum evaporation; In step 3, the layer-by-layer coating treatment is to coat both the upper and lower surfaces of the pre-treated zinc selenide substrate, and the coatings on the upper and lower surfaces of the pre-treated zinc selenide substrate are completely symmetrical; that is, the coating on the upper surface of the pre-treated zinc selenide substrate includes a first iridium indium selenide layer, a zinc selenide layer, a yttrium fluoride layer, and a second iridium indium selenide layer arranged in sequence from bottom to top; the coating on the lower surface of the pre-treated zinc selenide substrate includes a first iridium indium selenide layer, a zinc selenide layer, a yttrium fluoride layer, and a second iridium indium selenide layer arranged in sequence from top to bottom; In the step 3, the thickness of the first iridium indium selenide layer is 214-348 nm, the thickness of the zinc selenide layer is 176-228 nm, the thickness of the yttrium fluoride layer is 125-173 nm, and the thickness of the second iridium indium selenide layer is 152-197 nm.

2. The surface coating process of an optical element product according to claim 1, characterized in that: In step 1, the cleaning method includes any one of wiping cleaning, ultrasonic cleaning, steam cleaning, and ion beam cleaning.

3. The surface coating process of an optical element product according to claim 2, characterized in that: In the step 1, the cleaning is carried out by combining wiping cleaning and ultrasonic cleaning. Specifically, the zinc selenide substrate is first cleaned with a cleaning agent to remove surface grease, then cleaned with distilled water for 3-5 times, and then cleaned with acetone or ethanol in an ultrasonic cleaning machine. The cleaning frequency is 20-80kHz, the cleaning temperature is 20-60°C, and the cleaning time is 5-20min.

4. The surface coating process of an optical element product according to claim 1, characterized in that: In the step 2, the particle size range of the coating material is controlled to be 100-200 μm.

5. The surface coating process of an optical element product according to claim 1, characterized in that: In the step 2, the preparation process of iridium indium selenide includes: S1. Weigh sodium chloroiridate and indium acetate, add them to deionized water, then add selenium powder, mix and dissolve them thoroughly, then add a dispersant and a reducing agent to obtain a mixed reaction solution; S2, pouring the mixed reaction liquid into a reaction kettle, and heat-treating it at a temperature of 160-200° C. for 10-20 hours. After the reaction is completed, filtering out the solid, washing it with pure water at least three times, and vacuum drying it to obtain a precursor; S3. Place the precursor in a high-temperature graphite furnace, raise the temperature to 400-500° C. under the protection of an inert gas, and keep the temperature for 1-3 hours. After cooling in the furnace, iridium indium selenide is obtained.

6. The surface coating process of an optical element product according to claim 5, characterized in that: In the preparation process of the iridium indium selenide, the mass volume ratio of sodium chloroiridate, indium acetate, selenium powder and deionized water is (0.28-0.56) g: (0.36-0.72) g: (0.48-0.96) g: (10-30) mL; the dispersant is hydroxyethyl cellulose, and the added amount is 10%-20% of the mass of the selenium powder; the reducing agent is ethylenediamine, and the added amount is 2.5-6.5 times the mass of the selenium powder.

7. The surface coating process of an optical element product according to claim 1, characterized in that: In the step 3, during the vacuum coating process, the vacuum degree of the coating equipment during operation is (5-8)×10 -4 Pa; the rotation speed of the sample stage is 15-25rpm; the evaporation source area is heated to evaporate the coating material particles, the heating rate is controlled to be 300-500℃ / min, and the evaporation rate is controlled to be 0.3-1Å / s.

8. The surface coating process of an optical element product according to claim 1, characterized in that: In the step 3, after the coating is completed, a cooling treatment is performed, and the cooling rate is 100-200° C. / min until natural cooling.

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