Ultralow-reflection coated nano-coating for optical lens and preparation method of ultralow-reflection coated nano-coating

Abstract

The invention discloses an ultralow-reflection coated nano coating for an optical lens and a preparation method of the ultralow-reflection coated nano coating, and relates to the technical field of optical thin films. The prepared ultralow-reflection coating nano coating for the optical lens is of a multi-layer structure, the outer layer is a six-layer anti-reflection film formed by overlapping MgF2 and SiOxNy prepared through a vapor deposition method, meanwhile, the three SiOxNy film layers present a gradient anti-reflection effect, the innermost layer is a TiO2 and SiO2 blended film prepared through an evaporation method, secondary annealing treatment is conducted on a product obtained after film coating is completed, and the prepared ultralow-reflection coating nano coating has a good anti-reflection effect. The formed film has higher flatness, and the light transmittance of the film is improved. According to the prepared ultra-low-reflection coated nano coating for the optical lens, the ultra-low reflectivity of the coated nano coating is achieved, and meanwhile the light transmittance, the adhesion and the hardness of a film are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of optical thin films, and in particular to an ultra-low reflection film-plated nano coating for an optical lens and a preparation method thereof. Background Art

[0002] Optical lens coatings are widely used in camera lenses, telescopes, microscopes, projectors, and car headlights, and are essential to improving imaging quality and efficiency. For example, in camera lenses, coatings can make the captured images purer and clearer; in telescopes, coatings can improve the clarity and color reproduction of observations; in microscopes, coatings can make the details of observed samples clearer; in projectors, coatings can improve the brightness and clarity of projected images; in car headlights, coatings can improve the transmittance and lighting effects of light. Optical lens coatings can reduce the reflected light on the lens surface, thereby improving the brightness, clarity, contrast, and color saturation of the image. By coating one or more layers of thin film on the lens surface, the interference and reflection of the film on light are used to adjust the light entering the lens, thereby controlling the reflection and transmission of light of various wavelengths. The environment requirements for the use of optical lenses are high, and the coatings are required to have high transmittance and low refractive index. Some use conditions will cause greater wear on the lens. With the development of technology, the requirements for the film are getting higher and higher. Therefore, it is urgent to prepare a coating for optical lenses to meet the requirements of the above-mentioned use conditions. Summary of the invention

[0003] The object of the present invention is to provide an ultra-low reflection coating nano coating for an optical lens and a preparation method thereof, so as to solve the problems existing in the prior art.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: an ultra-low reflection coating nano coating for an optical lens, the ultra-low reflection coating nano coating for an optical lens comprises MgF2 and SiO x N y The innermost layer is formed by co-evaporation of six overlapping anti-reflection films and a mixture of TiO2 and SiO2.

[0005] Furthermore, the MgF2 and SiO x N y The six layers of anti-reflection film formed by overlapping are MgF2, SiO x N y 、MgF2、SiO x N y 、MgF2、SiO x N y , three-layer SiO x N y The oxygen content in the film gradually decreases.

[0006] Furthermore, the innermost layer is made of a mixture of TiO2 and SiO2 in a mass ratio of 6:7.

[0007] Furthermore, the thickness of the innermost layer ranges from 65 to 85 nm.

[0008] Furthermore, the total thickness of the ultra-low reflection coating nano-coating for the optical lens is between 500 and 550 nm.

[0009] Furthermore, a method for preparing an ultra-low reflection coating nano-coating for an optical lens comprises the following preparation steps:

[0010] (1) Preparation of the innermost film: Remove dirt and dust from the surface of K9 glass, place it in ether solution, and perform ultrasonic cleaning at 20kHz for 30-50min. After cleaning, dry the surface and place it in a coating machine. Take titanium dioxide and silicon dioxide in a mass ratio of 6:7, add ether to mix into an emulsion, apply it on the resistance wire, and evacuate to 2×10 -2 Pa, instantaneously heated until titanium dioxide and silicon dioxide evaporate, and after evaporation, a mixed coating is deposited on a high-speed rotating substrate, the bias voltage is 150V, the bombardment time is 40 to 60 seconds, and the thickness is 60 to 80nm;

[0011] (2) Preparation of six-layer anti-reflection film: Adjust the RF power to 200-250W, set the working pressure to 20-25Pa, and turn off the vacuum gauge power at 200-250℃. Pass SiH4, N2O, and NH3 reaction gases into the vacuum chamber in a certain proportion, set the parameters, and deposit the first layer of SiO x N y After the film and gas reaction are completed, close the air inlet valve and the heating device, extract the residual gas in the vacuum chamber, and maintain the vacuum degree at 6×10 -3 ~10×10 -3 Pa, the first layer of MgF2 coating was carried out, with magnesium as the target, the target temperature was 200 ° C, the sputtering current was 10-13A, and a mixed gas of SiF4, water vapor, and argon was introduced at a flow rate of 200-400sccm. The gas was mixed in a volume ratio of 1:5:50, and the deposition rate was 10-15nm / min. Then the first layer of SiO was deposited. x N y Thin film method, changing the ratio of SiH4, N2O, NH3, depositing the second layer of SiO x N y The second layer of MgF2 film is deposited according to the method of MgF2 film deposition, and the first layer of SiO x N y Thin film method, changing the ratio of SiH4, N2O, NH3, depositing the third layer of SiO x Ny The film is then deposited according to the MgF2 coating method, and after completion, the temperature is lowered to room temperature and the experimental sample is taken out;

[0012] (3) Secondary annealing: the experimental sample is heated to 600-650°C, kept at this temperature for 1-3 h, cooled to 300-350°C at a rate of 10-20°C / min, kept at this temperature for 1-3 h, cooled to room temperature at a rate of 10-20°C / min, and the lens is taken out;

[0013] (4) The lens is cleaned with an organic solvent of acetone and methanol in a mass ratio of 5:4, and then vacuum packed. x N y When forming thin films, the volume flow ratio of SiH4, N2O and NH3 is 60:8:50-60:10:55, the film thickness is 30-50nm, and the deposition rate is 11-15nm / min.

[0014] Furthermore, in step (2), a second layer of SiO x N y When forming thin films, the volume flow ratio of SiH4, N2O and NH3 is 60:18:40-60:20:45, the film thickness is 70-90nm, and the deposition rate is 11-15nm / min.

[0015] Furthermore, in step (2), a third layer of SiO x N y When forming thin films, the volume flow ratio of SiH4, N2O and NH3 is 60:40:5-60:45:10, the film thickness is 30-50nm, and the deposition rate is 11-15nm / min.

[0016] Furthermore, in step (2), the thickness of each layer of MgF2 is 80 to 90 nm.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0018] The present invention provides a method for preparing an ultra-low reflection film-plated nano coating for an optical lens, which achieves ultra-low reflectivity of the film-plated nano coating while enhancing the light transmittance, adhesion and hardness of the film.

[0019] The present invention is a multi-layer nano-film coating, the outer layer of which is MgF2 and SiO x N yThe innermost layer of the anti-reflection film formed by overlapping is obtained by co-evaporation of a mixture of TiO2 and SiO2. The mixture of TiO2 and SiO2 improves the adhesion and hardness between the film and the substrate, making the application of the film on the substrate more stable and reliable. The refractive index of the composite film is maintained at about 1.61 in the wavelength range of 400-750nm, which is similar to that of glass, effectively reducing light reflection caused by a large refractive index difference. x N y The overlapping anti-reflection film not only reduces the overall reflectivity of the composite film, but also optimizes the hardness and adhesion of the film, and improves the mechanical properties of the film. Secondly, the coated product is subjected to a secondary annealing treatment to provide sufficient energy for the growth of crystal nuclei in each layer of the film, so that the stress at the junction of the layers can be released, and the connection strength between the films can be enhanced. At the same time, the gaps formed in the evaporation process of the coating can be effectively filled, so that the formed film has higher flatness and the light transmittance of the film is improved. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the various index testing methods of the ultra-low reflection coating nano coating for optical lenses prepared in the following examples are as follows:

[0022] Light transmittance: The light transmittance and reflectivity of the ultra-low reflection coating nano coating for optical lenses prepared in Examples 1-3 and Comparative Examples 1-10 were tested using a spectrophotometer in accordance with GB / T 7962.17-2010 "Test Methods for Colorless Optical Glass Part 17: Ultraviolet and Infrared Refractive Index";

[0023] Adhesion: According to the method of GB / T 5210-2006 / IDT "Adhesion test of paint and varnish by pull-off method", the adhesion of the ultra-low reflection coating nano coating for optical lens prepared in Examples 1-3 and Comparative Examples 1-10 was tested.

[0024] Example 1

[0025] (1) Preparation of the innermost film: Remove dirt and dust from the surface of K9 glass, place it in ether solution, and perform ultrasonic cleaning at 20kHz for 40min. After cleaning, dry the surface and place it in a coating machine. Take titanium dioxide and silicon dioxide in a mass ratio of 6:7, add ether to mix into an emulsion, apply it on the resistance wire, and evacuate to 2×10-2 Pa, instantaneously heated until titanium dioxide and silicon dioxide evaporated, and after evaporation, a mixed coating was deposited on a high-speed rotating substrate, with a bias voltage of 150V, a bombardment time of 50s, and a thickness of 80nm;

[0026] (2) Preparation of six-layer anti-reflection film: Regulate the RF power to 220W, set the working pressure to 20Pa, and at 200°C, turn off the vacuum gauge power supply, and introduce SiH4, N2O, and NH3 reaction gases into the vacuum chamber in a volume ratio of 60:8:50. The film thickness is 50nm and the deposition rate is 11nm / min. Deposit the first layer of SiO x N y After the gas reaction is completed, close the gas inlet valve and the heating device, extract the residual gas in the vacuum chamber, and maintain the vacuum degree at 8×10 -3 Pa, the first layer of MgF2 coating was carried out, with magnesium as the target, the target temperature was 200℃, the sputtering current was 10A, and a mixed gas of SiF4, water vapor, and argon was introduced at a flow rate of 300sccm. The gas was mixed in a volume ratio of 1:5:50, the deposition rate was 10nm / min, and the film thickness was 90nm. Then the first layer of SiO x N y The thin film method was used to set the volume ratio of SiH4, N2O, and NH3 reaction gases to 60:18:40, the film thickness to 90nm, and the deposition rate to 11nm / min. The second layer of SiO x N y The second layer of MgF2 film was deposited according to the MgF2 film deposition method, with a deposition rate of 10nm / min and a film thickness of 90nm. The first layer of SiO x N y The thin film method was used to set the volume ratio of SiH4, N2O, and NH3 reaction gases to 60:40:5, the film thickness to 50nm, and the deposition rate to 11nm / min. The third layer of SiO x N y The third layer of MgF2 coating is deposited according to the MgF2 coating method, with a deposition rate of 10nm / min and a film thickness of 90nm. After completion, the temperature is lowered to room temperature and the experimental sample is taken out;

[0027] (3) Secondary annealing: The experimental sample was heated to 620°C, kept at this temperature for 3 h, cooled to 300°C at a rate of 20°C / min, kept at this temperature for 2 h, cooled to room temperature at a rate of 10°C / min, and the lens was taken out;

[0028] (4) The lenses are cleaned with an organic solvent consisting of acetone and methanol in a mass ratio of 5:4, and then vacuum packed.

[0029] Example 2

[0030] (1) Preparation of the innermost film: Remove dirt and dust from the surface of K9 glass, place it in ether solution, and perform ultrasonic cleaning at 20kHz for 40min. After cleaning, dry the surface and place it in a coating machine. Take titanium dioxide and silicon dioxide in a mass ratio of 6:7, add ether to mix into an emulsion, apply it on the resistance wire, and evacuate to 2×10 -2 Pa, instantaneously heated until titanium dioxide and silicon dioxide evaporated, and after evaporation, a mixed coating was deposited on a high-speed rotating substrate, with a bias voltage of 150V, a bombardment time of 50s, and a thickness of 80nm;

[0031] (2) Preparation of six-layer anti-reflection film: Regulate the RF power to 220W, set the working pressure to 20Pa, and at 200℃, turn off the vacuum gauge power supply, and introduce SiH4, N2O, and NH3 reaction gases into the vacuum chamber in a volume ratio of 60:9:53. The film thickness is 50nm, and the deposition rate is 11nm / min. The first layer of SiO x N y After the gas reaction is completed, close the gas inlet valve and the heating device, extract the residual gas in the vacuum chamber, and maintain the vacuum degree at 8×10 -3 Pa, the first layer of MgF2 coating was carried out, with magnesium as the target, the target temperature was 200℃, the sputtering current was 10A, and a mixed gas of SiF4, water vapor, and argon was introduced at a flow rate of 300sccm. The gas was mixed in a volume ratio of 1:5:50, the deposition rate was 10nm / min, and the film thickness was 90nm. Then the first layer of SiO x N y The thin film method was used to set the volume ratio of SiH4, N2O, and NH3 reaction gases to 60:19:43, the film thickness to 90nm, and the deposition rate to 11nm / min. The second layer of SiO x N y The second layer of MgF2 film was deposited according to the MgF2 film deposition method, with a deposition rate of 10nm / min and a film thickness of 90nm. The first layer of SiO x N y The thin film method was used to set the volume ratio of SiH4, N2O, and NH3 reaction gases to 60:43:8, the film thickness to 50nm, and the deposition rate to 11nm / min. The third layer of SiO x N y The third layer of MgF2 coating is deposited according to the MgF2 coating method, with a deposition rate of 10nm / min and a film thickness of 90nm. After completion, the temperature is lowered to room temperature and the experimental sample is taken out;

[0032] (3) Secondary annealing: The experimental sample was heated to 620°C, kept at this temperature for 3 h, cooled to 300°C at a rate of 20°C / min, kept at this temperature for 2 h, cooled to room temperature at a rate of 10°C / min, and the lens was taken out;

[0033] (4) The lenses are cleaned with an organic solvent consisting of acetone and methanol in a mass ratio of 5:4, and then vacuum packed.

[0034] Example 3

[0035] (1) Preparation of the innermost film: Remove dirt and dust from the surface of K9 glass, place it in ether solution, and perform ultrasonic cleaning at 20kHz for 40min. After cleaning, dry the surface and place it in a coating machine. Take titanium dioxide and silicon dioxide in a mass ratio of 6:7, add ether to mix into an emulsion, apply it on the resistance wire, and evacuate to 2×10 -2 Pa, instantaneously heated until titanium dioxide and silicon dioxide evaporated, and after evaporation, a mixed coating was deposited on a high-speed rotating substrate, with a bias voltage of 150V, a bombardment time of 50s, and a thickness of 80nm;

[0036] (2) Preparation of six-layer anti-reflection film: Regulate the RF power to 220W, set the working pressure to 20Pa, and at 200℃, turn off the vacuum gauge power supply, and introduce SiH4, N2O, and NH3 reaction gases into the vacuum chamber in a volume ratio of 60:10:55. The film thickness is 50nm, and the deposition rate is 11nm / min. The first layer of SiO x N y After the gas reaction is completed, close the gas inlet valve and the heating device, extract the residual gas in the vacuum chamber, and maintain the vacuum degree at 8×10 -3 Pa, the first layer of MgF2 coating was carried out, with magnesium as the target, the target temperature was 200℃, the sputtering current was 10A, and a mixed gas of SiF4, water vapor, and argon was introduced at a flow rate of 300sccm. The gas was mixed in a volume ratio of 1:5:50, the deposition rate was 10nm / min, and the film thickness was 90nm. Then the first layer of SiO x N y The thin film method was used to set the volume ratio of SiH4, N2O, and NH3 reaction gases to 60:20:45, the film thickness was 90nm, the deposition rate was 11nm / min, and the second layer of SiO x N y The second layer of MgF2 film was deposited according to the MgF2 film deposition method, with a deposition rate of 10nm / min and a film thickness of 90nm. The first layer of SiO x N yThe thin film method was used to set the volume ratio of SiH4, N2O, and NH3 reaction gases to 60:45:10, the film thickness to 50nm, and the deposition rate to 11nm / min. The third layer of SiO x N y The third layer of MgF2 coating is deposited according to the MgF2 coating method, with a deposition rate of 10nm / min and a film thickness of 90nm. After completion, the temperature is lowered to room temperature and the experimental sample is taken out;

[0037] (3) Secondary annealing: The experimental sample was heated to 620°C, kept at this temperature for 3 h, cooled to 300°C at a rate of 20°C / min, kept at this temperature for 2 h, cooled to room temperature at a rate of 10°C / min, and the lens was taken out;

[0038] (4) The lenses are cleaned with an organic solvent consisting of acetone and methanol in a mass ratio of 5:4, and then vacuum packed.

[0039] Comparative Example 1

[0040] The difference between Comparative Example 1 and Example 2 is that in step (1), only silicon dioxide is added to ether to be blended into an emulsion, and the remaining steps are the same as in Example 2.

[0041] Comparative Example 2

[0042] The difference between Comparative Example 2 and Example 2 is that in step (1), only titanium dioxide is added to ether to be blended into an emulsion, and the remaining steps are the same as Example 2.

[0043] Comparative Example 3

[0044] The difference between Comparative Example 3 and Example 2 is that SiO x N y When forming the thin film, the volume ratio of SiH4, N2O and NH3 reaction gases is 60:43:8, and the remaining steps are the same as those in Example 2.

[0045] Comparative Example 4

[0046] The difference between Comparative Example 4 and Example 2 is that SiO x N y When forming the thin film, the volume ratio of SiH4, N2O and NH3 reaction gases is 60:9:53, and the remaining steps are the same as those in Example 2.

[0047] Comparative Example 5

[0048] The difference between Comparative Example 5 and Example 2 is that SiO x N y When forming the thin film, the volume ratio of SiH4, N2O and NH3 reaction gases is 60:19:43, and the remaining steps are the same as those in Example 2.

[0049] Comparative Example 6

[0050] The difference between Comparative Example 6 and Example 2 is that each layer of MgF2 coating is 80nm, and the remaining steps are the same as Example 2.

[0051] Comparative Example 7

[0052] The difference between Comparative Example 7 and Example 2 is that each layer of MgF2 coating is 70nm, and the remaining steps are the same as Example 2.

[0053] Comparative Example 8

[0054] The difference between Comparative Example 8 and Example 2 is that each layer of MgF2 coating is 100 nm, and the remaining steps are the same as Example 2.

[0055] Comparative Example 9

[0056] The difference between Comparative Example 9 and Example 2 is that in step (3), the temperature of the experimental sample is raised to 650° C., and the remaining steps are the same as Example 2.

[0057] Comparative Example 10

[0058] The difference between Comparative Example 10 and Example 2 is that step (3) is different. Step (3) is changed to: heating the experimental sample to 300°C, keeping it warm for 2 hours, cooling it to room temperature at a rate of 10°C / min, taking out the lens, and the remaining steps are the same as Example 2.

[0059] Effect example

[0060] Table 1 below shows the performance test results of the ultra-low reflection coating nano-coating for optical lenses using Examples 1 to 3 of the present invention and Comparative Examples 1 to 10.

[0061] Table 1 Performance of ultra-low reflection coating nano coating for optical lens of Examples 1 to 3 and Comparative Examples 1 to 10

[0062] Single-side reflectivity (%) Double-sided light transmittance (%) Shedding situation (%) Example 1 0.045 ≥99.6 0 Example 2 0.033 ≥99.6 0 Example 3 0.037 ≥99.6 0 Comparative Example 1 0.767 ≥94.3 13 Comparative Example 2 0.734 ≥93.2 16 Comparative Example 3 0.467 ≥96.5 3 Comparative Example 4 0.731 ≥95.1 5 Comparative Example 5 0.627 ≥95.8 4 Comparative Example 6 0.035 ≥99.3 1 Comparative Example 7 0.034 ≥99.5 2 Comparative Example 8 0.036 ≥99.4 0 Comparative Example 9 0.797 ≥93.5 20 Comparative Example 10 1.351 ≥92.7 18

[0063] From the results of Example 2 and Comparative Examples 1-2 in Table 1, it is found that the mixture of TiO2 and SiO2 improves the adhesion between the film and the substrate, making the application of the film on the substrate more stable and reliable. From the results of Example 2 and Comparative Examples 3-8, it is found that the mixture of MgF2 and SiO2 improves the adhesion between the film and the substrate, making the application of the film on the substrate more stable and reliable. x N y The overlapping anti-reflection film not only reduces the overall reflectivity of the composite film, but also optimizes the hardness and adhesion of the film, and improves the mechanical properties of the film. At the same time, the reduction in film thickness has a small effect on the reflectivity and projection rate of the film. x N yWhen the oxygen element forms a gradient change, the reflectivity and transmission rate of the film can be optimized. From the results of Example 2 and Comparative Examples 9-10, it is found that the secondary annealing treatment of the coated product provides sufficient energy for the growth of crystal nuclei in each layer of the film, releases the stress at the junction of the layers, and enhances the connection strength between the films. At the same time, the gaps formed in the coating during the evaporation process can be effectively filled. However, when the annealing temperature is too high, it will easily cause burning to the film and damage the quality of the film.

[0064] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. An ultra-low reflection coating nano coating for an optical lens, characterized in that: The ultra-low reflection coating nano coating for optical lens comprises MgF2 and SiO x N y The innermost layer is formed by co-evaporation of six overlapping anti-reflection films and a mixture of TiO2 and SiO2.

2. The ultra-low reflection coating nano coating for optical lens according to claim 1, characterized in that: The MgF2 and SiO x N y The six overlapping anti-reflection films are MgF2, SiO x N y 、MgF2、SiO x N y 、MgF2、SiO x N y , three-layer SiO x N y The oxygen content in the film gradually decreases.

3. The ultra-low reflection coating nano coating for optical lens according to claim 1, characterized in that: The innermost layer is made of a mixture of TiO2 and SiO2 in a mass ratio of 6:

7.

4. The ultra-low reflection coating nano coating for optical lens according to claim 1, characterized in that: The thickness of the innermost layer ranges from 65 to 85 nm.

5. The ultra-low reflection coating nano coating for optical lens according to claim 1, characterized in that: The total thickness of the ultra-low reflection coating nano-coating for the optical lens is between 500 and 550 nm.

6. A method for preparing an ultra-low reflection coating nano coating for an optical lens, characterized in that: The method comprises the following preparation steps: (1) Preparation of the innermost film: Remove dirt and dust from the surface of K9 glass, place it in ether solution, and perform ultrasonic cleaning at 20kHz for 30-50min. After cleaning, dry the surface and place it in a coating machine. Take titanium dioxide and silicon dioxide in a mass ratio of 6:7, add ether to mix into an emulsion, apply it on the resistance wire, and evacuate to 2×10 -2 Pa, instantaneously heated until titanium dioxide and silicon dioxide evaporate, and after evaporation, a mixed coating is deposited on a high-speed rotating substrate, the bias voltage is 150V, the bombardment time is 40~60s, and the thickness is 60~80nm; (2) Preparation of six-layer anti-reflection film: Adjust the RF power to 200-250 W, set the working pressure to 20-25 Pa, and turn off the vacuum gauge power at 200-250 °C. Pass SiH4, N2O, and NH3 reaction gases into the vacuum chamber in a certain proportion, set the parameters, and deposit the first layer of SiO x N y After the film and gas reaction are completed, close the air inlet valve and the heating device, extract the residual gas in the vacuum chamber, and maintain the vacuum degree at 6×10 -3 ~10×10 -3 Pa, the first layer of MgF2 coating was carried out, with magnesium as the target, the target temperature was 200℃, the sputtering current was 10~13A, and a mixed gas of SiF4, water vapor, and argon was introduced at a flow rate of 200~400sccm. The gas was mixed in a volume ratio of 1:5:50, and the deposition rate was 10~15nm / min. Then the first layer of SiO was deposited. x N y Thin film method, changing the ratio of SiH4, N2O, NH3, depositing the second layer of SiO x N y The second layer of MgF2 film is deposited according to the method of MgF2 film deposition, and the first layer of SiO x N y Thin film method, changing the ratio of SiH4, N2O, NH3, depositing the third layer of SiO x N y The film is then deposited according to the MgF2 coating method, and after completion, the temperature is lowered to room temperature and the experimental sample is taken out; (3) Secondary annealing: heat the experimental sample to 600-650°C, keep it at this temperature for 1-3 hours, cool it down to 300-350°C at a rate of 10-20°C / min, keep it at this temperature for 1-3 hours, cool it down to room temperature at a rate of 10-20°C / min, and take out the lens; (4) The lenses are cleaned with an organic solvent consisting of acetone and methanol in a mass ratio of 5:4 and then vacuum packed.

7. The method for preparing an ultra-low reflection coating nano-coating for an optical lens according to claim 6, characterized in that: In the step (2), a first layer of SiO x N y When forming thin films, the volume flow ratio of SiH4, N2O and NH3 is 60:8:50~60:10:55, the film thickness is 30~50nm, and the deposition rate is 11~15nm / min.

8. The method for preparing an ultra-low reflection coating nano-coating for an optical lens according to claim 6, characterized in that: In the step (2), a second layer of SiO x N y When forming thin films, the volume flow ratio of SiH4, N2O and NH3 is 60:18:40~60:20:45, the film thickness is 70~90nm, and the deposition rate is 11~15nm / min.

9. The method for preparing an ultra-low reflection coating nano-coating for an optical lens according to claim 6, characterized in that: In the step (2), a third layer of SiO x N y When forming thin films, the volume flow ratio of SiH4, N2O and NH3 is 60:40:5~60:45:10, the film thickness is 30~50nm, and the deposition rate is 11~15nm / min.

10. The method for preparing an ultra-low reflection coating nano-coating for an optical lens according to claim 6, characterized in that: The thickness of each layer of MgF2 in step (2) is 80-90 nm.