Ultraviolet broadband low-reflection film and preparation method thereof

Abstract

The present invention belongs to the field of optical film technology, and specifically relates to an ultraviolet broadband low-reflection film and a preparation method thereof. The ultraviolet broadband low-reflection film provided by the present invention comprises a low-refractive index material and a high-refractive index material alternately stacked, the low-refractive index material comprising one or two of SiO2, Al2O3 and MgF2, and the high-refractive index material being HfO2. The present invention selects suitable low-refractive index materials and high-refractive index materials, then designs a film system for the ultraviolet broadband low-reflection film using film system design software, and then coats the film on a substrate based on the film system design results, successfully preparing an ultraviolet broadband low-reflection film with an ultraviolet band of 10 to 400 nm and an average reflectivity of less than 0.5%. The preparation method is simple and easy, reduces the probability of impurities and defects in the film, and thereby improves the mechanical properties and resistance to laser damage of the film.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical films, and in particular relates to an ultraviolet broadband low-reflection film and a preparation method thereof. Background Art

[0002] Optical thin films have a wide range of applications, including in common electronic products like mobile phones, watches, and drones. Optical thin films include antireflection coatings (or low-reflection coatings), spectroscopic coatings, high-reflection coatings, and filter coatings. While relatively basic, low-reflection coatings are the most widely used and are used in the largest number of products. For example, drone lenses and mobile phone camera lenses are typically coated with low-reflection coatings for visible light. Consequently, extensive research has been conducted on low-reflection films, particularly those for the visible light range.

[0003] However, with the advancement of technology, research on low-reflection films is no longer limited to the visible light band (400-700nm). Many products require lower reflectivity in the ultraviolet band. Currently, low-reflection films for the ultraviolet band are all single-point wavelengths, such as 193nm, 266nm, and 355nm, which affects the widespread application of low-reflection films in the ultraviolet band. Summary of the Invention

[0004] The present invention aims to provide a broadband ultraviolet low-reflection film and a preparation method thereof. The preparation method provided by the present invention can produce a broadband ultraviolet low-reflection film with an ultraviolet band of 10 to 400 nm and an average reflectivity of less than 0.5%. The preparation method is simple and easy to implement, reduces the probability of impurities and defects in the film, and thus improves the mechanical properties and resistance to laser damage of the film, meeting the environmental adaptability requirements of "GBT 26332.3-2015 Optical Films for Optics and Photonics".

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a wide-band ultraviolet low-reflection film, wherein the wide-band ultraviolet low-reflection film comprises a low-refractive index material and a high-refractive index material alternately stacked, wherein the low-refractive index material comprises one or two of SiO2, Al2O3, and MgF2, and the high-refractive index material is HfO2. The wide-band ultraviolet low-reflection film has an ultraviolet band of 10 to 400 nm and an average reflectivity of less than 0.5%.

[0007] The following steps are involved:

[0008] According to the film layer material, ultraviolet band and average reflectivity of the ultraviolet broadband low-reflection film, a film system design software is used to design a film system to obtain a film system design result of the ultraviolet broadband low-reflection film, wherein the film system design result includes a single-layer film thickness of a high-refractive-index material, a single-layer film thickness of a low-refractive-index material, the number of film layers of the high-refractive-index material, the number of film layers of the low-refractive-index material, the total number of layers of the ultraviolet broadband low-reflection film, and the total thickness of the ultraviolet broadband low-reflection film;

[0009] The bottom surface of the substrate is plated according to the film system design result to obtain the ultraviolet wide-band low-reflection film on the bottom surface of the substrate.

[0010] Preferably, the ultraviolet broadband low-reflection film includes SiO2 film layers and HfO2 film layers alternately stacked, the number of SiO2 film layers is the same as the number of HfO2 film layers, and one HfO2 film layer is in contact with the bottom surface of the substrate.

[0011] Preferably, the ultraviolet broadband low-reflection film comprises an Al2O3 film layer, an HfO2 film layer and a MgF2 film layer stacked in sequence, and the Al2O3 film layer is in contact with the bottom surface of the substrate.

[0012] Preferably, the material of the substrate is UV fused quartz;

[0013] The thickness of the substrate is 0.6-6 mm.

[0014] Preferably, the film system design software includes TFCalc optical thin film design software or Essential Macleod optical thin film design software.

[0015] Preferably, the plating conditions include: initial vacuum degree ≤ 9×10 -4 Pa; the substrate heating temperature is 180~300℃; the film forming rate of the high refractive index material is 0.1~0.25nm / s, and the film forming rate of the low refractive index material is 0.2~0.7nm / s.

[0016] Preferably, before the plating, the substrate is further subjected to ion source cleaning, and the vacuum degree of the ion source cleaning is ≤9×10 -4 Pa, the time is 2-5 min, and the heating temperature of the substrate during the ion source cleaning is 180-300°C.

[0017] Preferably, the ultraviolet band of the ultraviolet broadband low-reflection film is 200-400 nm.

[0018] Preferably, the ultraviolet band of the ultraviolet broadband low-reflection film is 245-400 nm or 280-370 nm;

[0019] The thickness of the ultraviolet broadband low-reflection film is 125-290 nm.

[0020] The present invention provides an ultraviolet broadband low-reflection film prepared by the preparation method described in the above technical solution.

[0021] The present invention provides a method for preparing an ultraviolet wide-band low-reflection film, wherein the ultraviolet wide-band low-reflection film comprises a low-refractive index material and a high-refractive index material alternately stacked, wherein the low-refractive index material comprises one or two of SiO2, Al2O3 and MgF2, and the high-refractive index material is HfO2. The ultraviolet band of the ultraviolet wide-band low-reflection film is 10-400nm, and the average reflectivity is less than 0.5%. The method comprises the following steps: preparing the ultraviolet wide-band low-reflection film according to the film material, ultraviolet band and the average reflectivity of the film. The film system design software is used to design the film system to obtain the film system design results of the ultraviolet wide-band low-reflection film, the film system design results include the single-layer film thickness of the high-refractive index material, the single-layer film thickness of the low-refractive index material, the number of film layers of the high-refractive index material, the number of film layers of the low-refractive index material, the total number of layers of the ultraviolet wide-band low-reflection film and the total thickness of the ultraviolet wide-band low-reflection film; the bottom surface of the substrate is plated according to the film system design results to obtain the ultraviolet wide-band low-reflection film on the bottom surface of the substrate. The present invention selects suitable low-refractive index materials and high-refractive index materials, then designs a film system for the ultraviolet broadband low-reflection film using film system design software, and deposits the film on a substrate based on the film system design results. The ultraviolet broadband low-reflection film with an ultraviolet band of 10 to 400 nm and an average reflectivity of less than 0.5% is successfully prepared. The preparation method is simple and easy, reduces the probability of impurities and defects in the film, and thus improves the mechanical properties and resistance to laser damage of the film, meeting the environmental adaptability requirements of "GBT 26332.3-2015 Optical Films for Optics and Photonics".

[0022] Furthermore, when the ultraviolet broadband low-reflection film has an ultraviolet band of 245-400 nm, the film comprises an Al2O3 film layer, an HfO2 film layer, and a MgF2 film layer stacked in sequence, with the Al2O3 film layer contacting the bottom surface of the substrate. By further optimizing the film layer structural features (including materials and stacking sequence) of the ultraviolet broadband low-reflection film with an ultraviolet band of 245-400 nm, the present invention can further reduce the total thickness of the ultraviolet broadband low-reflection film and the thickness of the HfO2 film layer, thereby further improving the uniformity of the ultraviolet broadband low-reflection film. This also shortens film formation time, saves film material and energy consumption, and reduces manufacturing costs.

[0023] Furthermore, when the ultraviolet broadband low-reflection film has an ultraviolet band of 280-370 nm, the film comprises alternating SiO2 layers and HfO2 layers, the number of SiO2 layers being the same as the number of HfO2 layers, and one HfO2 layer being in contact with the substrate surface. By further optimizing the film layer structural features (including materials and layering sequence) of the ultraviolet broadband low-reflection film having an ultraviolet band of 280-370 nm, the present invention can further reduce the total thickness of the ultraviolet broadband low-reflection film and the thickness of the HfO2 layer, thereby further improving the uniformity of the ultraviolet broadband low-reflection film. This also shortens film formation time, saves film material and energy consumption, and reduces manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the design curve of the 245-400nm low-reflection film in Example 1 of the present invention;

[0025] Figure 2 This is the test curve of the 245-400nm low-reflection film in Example 1 of the present invention;

[0026] Figure 3 This is the design curve of the 245-400nm low-reflection film in Example 2 of the present invention;

[0027] Figure 4 This is the test curve of the 245-400nm low-reflection film in Example 2 of the present invention. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a wide-band ultraviolet low-reflection film, wherein the wide-band ultraviolet low-reflection film comprises a low-refractive index material and a high-refractive index material alternately stacked, wherein the low-refractive index material comprises one or two of SiO2, Al2O3, and MgF2, and the high-refractive index material is HfO2. The wide-band ultraviolet low-reflection film has an ultraviolet band of 10 to 400 nm and an average reflectivity of less than 0.5%.

[0029] The following steps are involved:

[0030] According to the film layer material, ultraviolet band and average reflectivity of the ultraviolet broadband low-reflection film, a film system design software is used to design a film system to obtain a film system design result of the ultraviolet broadband low-reflection film, wherein the film system design result includes a single-layer film thickness of a high-refractive-index material, a single-layer film thickness of a low-refractive-index material, the number of film layers of the high-refractive-index material, the number of film layers of the low-refractive-index material, the total number of layers of the ultraviolet broadband low-reflection film, and the total thickness of the ultraviolet broadband low-reflection film;

[0031] The bottom surface of the substrate is plated according to the film system design result to obtain the ultraviolet wide-band low-reflection film on the bottom surface of the substrate.

[0032] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0033] In the present invention, the ultraviolet broadband low-reflection film comprises alternating layers of low-refractive-index materials and high-refractive-index materials. The low-refractive-index material comprises one or two of SiO2, Al2O3, and MgF2, with SiO2 being used in the embodiments, or Al2O3 and MgF2 being used. The high-refractive-index material is HfO2. The ultraviolet broadband low-reflection film has an ultraviolet wavelength of 10 to 400 nm, preferably 200 to 400 nm, and more preferably 245 to 400 nm or 280 to 370 nm. The average reflectivity of the ultraviolet broadband low-reflection film is less than 0.5%, or the average reflectivity of the ultraviolet broadband low-reflection film is less than 0.25%.

[0034] In the present invention, when the ultraviolet band is 245-400 nm, the average reflectivity of the ultraviolet wide-band low-reflection film is less than 0.5%.

[0035] In the present invention, when the ultraviolet band is 280-370 nm, the average reflectivity of the ultraviolet wide-band low-reflection film is less than 0.25%.

[0036] In a specific embodiment of the present invention, when the ultraviolet band is 280-370 nm, the average reflectivity of the ultraviolet broadband low-reflection film is less than 0.25% when the incident angle of the incident light is 0-30°.

[0037] In the present invention, the thickness of the ultraviolet broadband low-reflection film is preferably 125-290 nm, more preferably 127-286 nm.

[0038] In the present invention, when the ultraviolet wavelength of the broadband low-reflection film is preferably 245-400 nm, the broadband low-reflection film is preferably composed of an Al2O3 film layer, an HfO2 film layer, and a MgF2 film layer stacked in sequence, with the Al2O3 film layer in contact with the bottom surface of the substrate. The thickness of the Al2O3 film layer is preferably 40-45 nm, the thickness of the HfO2 film layer is preferably 68-71 nm, and the thickness of the MgF2 film layer is preferably 50-54 nm. The total thickness of the broadband low-reflection film is preferably 158-170 nm.

[0039] In the present invention, when the ultraviolet band of the ultraviolet broadband low-reflection film is preferably 280-370 nm, the ultraviolet broadband low-reflection film is preferably an alternating stack of SiO2 film layers and HfO2 film layers. The number of SiO2 film layers and the number of HfO2 film layers are preferably the same, and one HfO2 film layer is preferably in contact with the bottom surface of the substrate. The number of SiO2 film layers is preferably two, and the number of HfO2 film layers is preferably two. The ultraviolet broadband low-reflection film is preferably a first HfO2 film layer, a first SiO2 film layer, a second HfO2 film layer, and a second SiO2 film layer stacked in sequence. The thickness of the first HfO2 film layer is preferably 12-15 nm, the thickness of the first SiO2 film layer is preferably 16-17 nm, the thickness of the second HfO2 film layer is preferably 44-45 nm, and the thickness of the second SiO2 film layer is preferably 55-56 nm. The total thickness of the ultraviolet broadband low-reflection film is preferably 127-133 nm.

[0040] The present invention uses film system design software to design a film system for the ultraviolet broadband low-reflection film based on the film layer material, ultraviolet band, and average reflectivity of the ultraviolet broadband low-reflection film, and obtains a film system design result for the ultraviolet broadband low-reflection film. The film system design result includes the single-layer film thickness of the high-refractive index material, the single-layer film thickness of the low-refractive index material, the number of film layers of the high-refractive index material, the number of film layers of the low-refractive index material, the total number of layers of the ultraviolet broadband low-reflection film, and the total thickness of the ultraviolet broadband low-reflection film. In the present invention, the film system design software preferably includes TFCalc optical thin film design software or Essential Macleod optical thin film design software, and in an embodiment, it can be TFCalc optical thin film design software. The present invention has no special requirements for the specific implementation process of the film system design.

[0041] After obtaining the film system design result, the present invention performs plating on the bottom surface of the substrate according to the film system design result, and obtains the ultraviolet wide-band low-reflection film on the bottom surface of the substrate.

[0042] As one or more embodiments of the present invention, the present invention respectively coats the two bottom surfaces of the substrate according to the film system design results, and obtains the ultraviolet wide-band low-reflection film on the two bottom surfaces of the substrate.

[0043] As one or more embodiments of the present invention, the present invention performs coating on any bottom surface of the substrate according to the film system design result, and obtains the ultraviolet broadband low-reflection film on any bottom surface of the substrate.

[0044] In the present invention, the coating is preferably performed using a vacuum evaporation coating machine. During the coating, the present invention preferably uses a crystal oscillator to monitor the film rate and thickness.

[0045] In the present invention, the substrate is made of ultraviolet fused silica (UVFS). The substrate thickness is preferably 0.6 to 6 mm, more preferably 1 to 5 mm. The substrate is preferably cylindrical or prism-shaped. The two bottom surfaces (coated surfaces) of the substrate can be circular or square. In one embodiment, the substrate can be a cylindrical UV fused silica glass with a diameter of 25.4 mm.

[0046] In the present invention, before the plating, the present invention preferably further comprises performing ion source cleaning on the substrate. The present invention preferably places the substrate in a collar, and places the collar with the substrate on a hollow umbrella of the machine; then performs ion source cleaning. The present invention preferably improves the adhesion of the ultraviolet broadband low-reflection film on the bottom surface of the substrate by performing the ion source cleaning. The vacuum degree of the ion source cleaning is preferably ≤9×10 -4 Pa, the time is preferably 2-5 minutes, more preferably 3 minutes; the substrate heating temperature during ion source cleaning is preferably 180-300°C, and in embodiments, it can be 180°C, 200°C, 250°C, 270°C, or 300°C. By controlling the substrate heating temperature during ion source cleaning to 180-300°C, the present invention can reduce ion absorption by the substrate during the ion source cleaning process. In the present invention, the voltage for ion source cleaning is preferably 500-550V, and the current is preferably 500-550mA. The gases used for ion source cleaning are preferably oxygen and argon, with the flow ratio of oxygen to argon preferably being 40:8. The flow rate of oxygen is preferably 40 sccm. The argon gas comprises a first argon gas and a second argon gas. The flow rate of the first argon gas (ion source argon gas) is preferably 0 sccm, and the flow rate of the second argon gas (neutralizer argon gas) is preferably 8 sccm.

[0047] In the present invention, the plating is performed after the ion source is cleaned.

[0048] In the present invention, when the coating is preferably performed separately on the two bottom surfaces of the substrate according to the film system design results, the coating preferably includes first coating the ultraviolet wide-band low-reflection film on one bottom surface of the substrate (i.e., the first bottom surface); and then coating the ultraviolet wide-band low-reflection film on the other bottom surface of the substrate (i.e., the second bottom surface).

[0049] In the present invention, during the plating, the present invention preferably places the substrate in the ring, and places the ring with the substrate on the hollow umbrella of the machine. The plating conditions preferably include: the initial vacuum degree is preferably ≤9×10 -4Pa; the substrate heating temperature is preferably 180-300°C, and in embodiments, it can be 180°C, 200°C, 250°C, 270°C, or 300°C. The film formation rate of the high refractive index material is preferably 0.1-0.25 nm / s, and in embodiments, it can be 0.2 nm / s. The film formation rate of the low refractive index material is preferably 0.2-0.7 nm / s, and in embodiments, it can be 0.4 nm / s or 0.2 nm / s.

[0050] In the present invention, the ion source for coating the HfO2 film layer is preferably HfO2; the voltage is preferably 500~550V; the current is preferably 500~550mA; the gases used are preferably oxygen and argon, and the flow ratio of oxygen and argon is preferably 40:16; the flow rate of oxygen is preferably 40sccm, and the argon includes a first argon and a second argon, the flow rate of the first argon (ion source argon) is preferably 8sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8sccm.

[0051] In the present invention, the ion source for coating the low-refractive-index material film layer is preferably a low-refractive-index material. The ion source for coating the SiO2 film layer is preferably SiO2; the ion source for coating the Al2O3 film layer is preferably Al2O3; and the ion source for coating the MgF2 film layer is preferably MgF2. The voltage for coating the low-refractive-index material film layer is preferably 500-550V; and the current is preferably 500-550mA. The gases used for coating the SiO2 or Al2O3 film layer are preferably oxygen and argon, with the flow ratio of oxygen to argon preferably being 40:8. The flow rate of oxygen is preferably 40 sccm. The argon gas comprises a first argon gas and a second argon gas. The flow rate of the first argon gas (ion source argon) is preferably 0 sccm, and the flow rate of the second argon gas (neutralizer argon) is preferably 8 sccm.

[0052] The gas used for coating the MgF2 film is preferably argon, which includes a first argon and a second argon. The flow rate of the first argon (ion source argon) is preferably 0 sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8 sccm.

[0053] In the present invention, when the ultraviolet wide-band low-reflection film preferably includes SiO2 film layers and HfO2 film layers alternately stacked, the coating preferably includes: coating the surface of the substrate with HfO2 film layers, SiO2 film layers, HfO2 film layers, SiO2 film layers, ..., HfO2 film layers, and SiO2 film layers in sequence.

[0054] In the present invention, when the ultraviolet broadband low-reflection film preferably includes an Al2O3 film layer, an HfO2 film layer and a MgF2 film layer stacked in sequence, the coating preferably includes: coating an Al2O3 film layer, an HfO2 film layer and a MgF2 film layer in sequence on the surface of the substrate.

[0055] The present invention provides a broadband ultraviolet low-reflection film produced by the preparation method described in the above technical solution. The broadband ultraviolet low-reflection film has an ultraviolet wavelength range of 10 to 400 nm, preferably 200 to 400 nm, and an average reflectivity of less than 0.5%, or an average reflectivity of less than 0.25%. In a specific embodiment of the present invention, the broadband ultraviolet low-reflection film has an average reflectivity of less than 0.5%, or less than 0.25%, when the incident light angle is 0 to 30 degrees.

[0056] In the present invention, the ultraviolet band of the ultraviolet broadband low-reflection film is further preferably 245-400 nm or 280-370 nm.

[0057] In the present invention, when the ultraviolet wavelength of the broadband low-reflection film is preferably 245-400 nm, the broadband low-reflection film is preferably composed of an Al2O3 film layer, an HfO2 film layer, and a MgF2 film layer stacked in sequence, with the Al2O3 film layer preferably in contact with the substrate. The thickness of the Al2O3 film layer is preferably 40-45 nm, the thickness of the HfO2 film layer is preferably 68-71 nm, and the thickness of the MgF2 film layer is preferably 50-54 nm. The total thickness of the broadband low-reflection film is preferably 158-170 nm.

[0058] In the present invention, when the ultraviolet band of the ultraviolet broadband low-reflection film is 280-370 nm, the ultraviolet broadband low-reflection film is preferably an alternating stack of SiO2 film layers and HfO2 film layers, the number of SiO2 film layers and the number of HfO2 film layers are preferably the same, and one HfO2 film layer is preferably in contact with the substrate. The number of SiO2 film layers is preferably two, and the number of HfO2 film layers is preferably two. The ultraviolet broadband low-reflection film is preferably a first HfO2 film layer, a first SiO2 film layer, a second HfO2 film layer, and a second SiO2 film layer stacked in sequence. The thickness of the first HfO2 film layer is preferably 12-15 nm, the thickness of the first SiO2 film layer is preferably 16-17 nm, the thickness of the second HfO2 film layer is preferably 44-45 nm, and the thickness of the second SiO2 film layer is preferably 55-56 nm. The total thickness of the ultraviolet broadband low-reflection film is preferably 127-133 nm.

[0059] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1:

[0061] This embodiment provides a method for preparing a wide-band ultraviolet low-reflection film. The specification requirements of the wide-band ultraviolet low-reflection film provided in this embodiment are: ultraviolet band 245-400nm, average reflectivity Rave <0.5%. Specifically, the method includes the following steps:

[0062] 1. The coating materials are silicon dioxide (SiO2), a low-refractive-index material, and hafnium oxide (HfO2), a high-refractive-index material, because hafnium oxide has stable chemical properties within its transparent range of 226 to 12,000 nm. The substrate material is ultraviolet fused silica (UVFS), which has a stable performance with a transparent range of approximately 185 to 2,100 nm.

[0063] 2. This embodiment uses TFC membrane design software to design the membrane structure as shown in Table 1. There are 10 layers in total with a total thickness of about 285nm (of which the total thickness of hafnium oxide is about 124.9nm and the total thickness of silicon oxide is about 160.5nm). The first layer in contact with the substrate is hafnium oxide, followed by the second layer: silicon dioxide, then the third layer: hafnium oxide, followed by the fourth layer: silicon dioxide, ..., hafnium oxide and silicon dioxide are repeated alternately, and finally end with the tenth layer: silicon dioxide. The design curve is shown in Figure 1 .observe Figure 1 The design curve shown, within 245~400nm, R max <0.5%, so Rave<0.5% meets the requirement. After calculation, we get Rave=0.3426%.

[0064] Table 1 Designed membrane structure data for Example 1

[0065]

[0066] 3. A vacuum evaporation coating machine manufactured by a domestic vacuum equipment manufacturer was used to coat the film system in Table 1. This embodiment uses a crystal oscillator to monitor the film rate and thickness. The coating steps are as follows:

[0067] First, place the clean substrate (here, a cylindrical UV fused silica glass with a diameter of 25.4 mm and a height of 5 mm) in the prepared ring. Place the ring on the hollow umbrella of the machine and prepare for coating. In this example, the two bottom surfaces of the cylinder need to be coated, and the sides do not need to be coated. Close the chamber door and evacuate. When the vacuum reaches the set value of ≤9.0×10 -4Ion source cleaning was performed at Pa, with the substrate heating temperature set at 270°C for 3 minutes. Detailed ion source parameters are shown in Table 2. After cleaning, film deposition began at a rate of 0.2 nm / s for hafnium oxide and 0.4 nm / s for silicon dioxide. The first layer in direct contact with the substrate, hafnium oxide (HfO2), was deposited immediately. This was followed by the second layer of silicon dioxide (SiO2), followed by the third layer of hafnium oxide (HfO2), and the fourth layer of silicon dioxide (SiO2). This process was repeated in an overlapping fashion until all layers were deposited, completing the first bottom surface coating.

[0068] Next, the second bottom film is prepared, that is, the substrate coated with the first bottom surface is turned over, the chamber door is closed and vacuum is drawn. When the vacuum reaches the set value of ≤9.0×10 -4 Ion source cleaning was performed at 100 Pa, with the substrate heated to 270°C for 3 minutes. Detailed ion source parameters are shown in Table 2. After cleaning, film formation began, using the same steps and parameters as for the first bottom surface coating. This process completed the preparation of the ultraviolet broadband low-reflection film in this embodiment. During film preparation, this embodiment employed heating combined with full ion source-assisted coating, with heating at 270°C and a film formation rate of 0.4 nm / s for SiO2 and 0.2 nm / s for HfO2. Detailed coating parameters are shown in Table 3.

[0069] Table 2 Ion source cleaning parameters in Example 1

[0070]

[0071] Table 3 Coating parameters in Example 1

[0072]

[0073] This embodiment tests the reflectivity of the substrate after plating to confirm whether it meets the specifications. This embodiment uses Nanjing Shibuya UV low reflection tester for testing, and the test curve is as follows: Figure 2 ,After calculation, 240~410nm, Rave=0.3857%, so 245~400nm meets the specification requirements and is optically OK.

[0074] The film products prepared in this embodiment were subjected to reliability tests such as adhesion, chemical stability, thermal shock, high temperature and high humidity, etc., using the environmental adaptability requirements of the "GBT 26332.3-2015 Optical and Photonics Optical Films" standard. The results were all OK, indicating that the film preparation method provided in this embodiment can withstand the test of environmental tests. See Table 4 for details.

[0075] Table 4 Reliability results of Example 1

[0076]

[0077] Example 2:

[0078] The present embodiment provides a method for preparing a wide-band ultraviolet low-reflection film. The specification requirements of the wide-band ultraviolet low-reflection film provided in this embodiment are: ultraviolet band 245~400nm, average reflectivity Rave<0.5%. Example 1 meets the specification requirements by alternately stacking two materials, HfO2 and SiO2. However, the total thickness of HfO2 is close to 125nm. Because the HfO2 material is expensive, the price per kilogram is about 50 times that of titanium pentoxide (Ti3O5). In view of this, this embodiment optimizes the preparation method provided in Example 1. The preparation method provided in this embodiment specifically includes:

[0079] 1. The coating materials used are low-refractive-index materials Al2O3 and MgF2, and high-refractive-index material hafnium oxide (HfO2). The substrate material is ultraviolet fused silica (UVFS), with a transparent range of approximately 185-2100nm and stable performance.

[0080] The coating materials used in this embodiment are Al2O3, HfO2, and MgF2. Compared with SiO2, the specific data are shown in Table 5.

[0081] Table 5 Data of membrane materials in Example 1 and Example 2

[0082]

[0083] 2. This embodiment is designed using TFC film system design software, resulting in a stacked structure with only three layers, in the following order: substrate, Al2O3, HfO2, and MgF2. The thicknesses are respectively Al2O3: 43.69nm, HfO2: 69.79nm, and MgF2: 52.93nm. The total thickness is approximately 166.4nm, of which HfO2 is 69.79nm, which is less than the 125nm in Example 1.

[0084] Design curve as Figure 3 . 240~410nm, Rave=0.1999%<0.5% (specification requirement), the design meets the requirements.

[0085] 3. Coating was performed using the same coating machine and steps as in Example 1. Except for the coating parameters shown in Table 6, all other parameters remained the same as in Example 1. The sequence remained the same: after coating the first bottom surface, remove the substrate, flip it over, and coat the second bottom surface until the entire film layer was coated. The Al2O3 coating rate was 0.2 nm / s, and the MgF2 coating rate was 0.4 nm / s. The coating parameters are shown in Table 6.

[0086] Table 6 Coating parameters in Example 2

[0087]

[0088] 4. Test the reflectivity of the plated substrate to confirm whether it meets the specifications. This embodiment also uses the Nanjing Shibuya UV low reflection tester for testing. The test curve is as follows: Figure 4 ,After calculation, 240~410nm, Rave=0.20777%, so 245-400nm meets the specification requirements and is optically OK.

[0089] 5. This embodiment also conducted a reliability test on the prepared film products. The test items were consistent with those in Example 1, and the results were all OK, indicating that the three material solutions can also withstand the test of environmental testing. See Table 7 for details.

[0090] Table 7 Reliability results of the ultraviolet broadband low-reflection film prepared in Example 2

[0091]

[0092] 6. Comparing the preparation methods provided in Example 2 with those in Example 1 reveals that the properties of the UV broadband low-reflection films prepared in Examples 1 and 2 are similar, with both films exhibiting acceptable performance. Furthermore, the total thickness of the UV broadband low-reflection film prepared in Example 2 is approximately 170 nm, approximately 110 nm thinner than the 280 nm total thickness of the UV broadband low-reflection film prepared in Example 1. This shortens film formation time, saves film material, and reduces energy consumption. Specifically, with regard to hafnium oxide, the HfO2 film layer in the UV broadband low-reflection film prepared in Example 2 is only approximately 70 nm thick, compared to 125 nm in Example 1. This represents a savings of approximately 55 nm per batch (for the UV broadband low-reflection film on one bottom surface of the substrate), representing approximately 44% (55 / 125 × 100%). Considering industrial mass production, this represents a significant saving. Furthermore, the film thickness is reduced, which can avoid the risk of film cracking due to excessive stress in the film.

[0093] Example 3:

[0094] This embodiment provides a method for preparing a wide-band ultraviolet low-reflection film. The specification requirements of the wide-band ultraviolet low-reflection film provided in this embodiment are: ultraviolet band 280-370nm, incident light angle 0-35°, average reflectivity Rave <0.25%. The method specifically includes the following steps:

[0095] 1. The coating materials are low-refractive-index silicon dioxide (SiO2) and high-refractive-index hafnium oxide (HfO2). The substrate material is ultraviolet fused silica (UVFS), with a transparent range of approximately 185-2100nm and stable performance.

[0096] 2. This example was designed using TFC membrane design software, resulting in the membrane structure shown in Table 8. The membrane structure consists of four layers with a total thickness of 130.56 nm (of which the total thickness of hafnium oxide is approximately 58.8 nm). The first layer in contact with the substrate is hafnium oxide, followed by the second layer of silicon dioxide, the third layer of hafnium oxide, and the fourth layer of silicon dioxide. The hafnium oxide and silicon dioxide layers alternate repeatedly, ultimately ending with the fourth layer of silicon dioxide. Calculated Rave = 0.2133%.

[0097] Table 8 Designed membrane structure data for Example 3

[0098]

[0099] 3. A vacuum evaporation coating machine manufactured by a domestic vacuum equipment manufacturer was used to coat the films in Table 8. This embodiment used a crystal oscillator to monitor the film rate and thickness. The coating steps and parameters were the same as those in Example 1.

[0100] This embodiment tests the reflectivity of the plated substrate to confirm whether it meets the specifications. This embodiment uses a Nanjing Shibuya UV low reflectivity tester to test, and the results are optically OK.

[0101] The thin film products prepared in this embodiment were subjected to reliability tests such as adhesion, chemical stability, thermal shock, high temperature and high humidity, etc., using the environmental adaptability requirements of the "GBT 26332.3-2015 Optical and Photonics Optical Films" standard. The results were all OK, indicating that the thin film preparation method provided in this embodiment can withstand the test of environmental tests.

[0102] Example 4:

[0103] This embodiment provides a method for preparing a wide-band ultraviolet low-reflection film. The specification requirements of the wide-band ultraviolet low-reflection film provided in this embodiment are: ultraviolet band 280-370nm, incident light angle 0-35°, average reflectivity Rave <0.25%. The method specifically includes the following steps:

[0104] 1. The coating materials used are low-refractive-index materials Al2O3 and MgF2, and high-refractive-index material hafnium oxide (HfO2). The substrate material is ultraviolet fused silica (UVFS), with a transparent range of approximately 185-2100nm and stable performance.

[0105] 2. This example was designed using TFC membrane design software, resulting in a membrane structure as shown in Table 9. The membrane consists of three layers with a total thickness of 191.32 nm (of which the total thickness of hafnium oxide is approximately 79.81 nm). The first layer in contact with the substrate is Al2O3, followed by the second layer: HfO2, and then the third layer: MgF2, ultimately ending with the third layer: MgF2. Calculated Rave = 0.2084%.

[0106] Table 9 Designed membrane structure data for Example 4

[0107]

[0108] 3. A vacuum evaporation coating machine manufactured by a domestic vacuum equipment manufacturer was used to coat the films in Table 8. This embodiment uses a crystal oscillator to monitor the film rate and thickness. The coating steps are the same as those in Example 1.

[0109] This embodiment tests the reflectivity of the plated substrate to confirm whether it meets the specifications. This embodiment uses a Nanjing Shibuya UV low reflectivity tester to test, and the results are optically OK.

[0110] The thin film products prepared in this embodiment were subjected to reliability tests such as adhesion, chemical stability, thermal shock, high temperature and high humidity, etc., using the environmental adaptability requirements of the "GBT 26332.3-2015 Optical and Photonics Optical Films" standard. The results were all OK, indicating that the thin film preparation method provided in this embodiment can withstand the test of environmental tests.

[0111] As can be seen from Examples 3 and 4, when preparing a low-reflection ultraviolet broadband film with an ultraviolet wavelength range of 280-370 nm, an incident light angle of 0-35°, and an average reflectivity Rave of less than 0.25%, a comparison of the two preparation methods provided in Examples 3 and 4 reveals that the two film layer material designs of Example 3 are superior. The comparative data are shown in Table 10. The reliability and optical properties of the actual films after coating in Examples 3 and 4 both meet the requirements.

[0112] Table 10 Comparison of film materials and thicknesses of reflective films prepared in Example 3 and Example 4

[0113]

[0114] As can be seen from the above examples, the present invention provides a method for preparing a broadband ultraviolet (UV) low-reflection film. The UV wavelength range is 10-400 nm, preferably in the near-UV region (200-400 nm). The preparation method provided by the present invention reduces the film thickness by combining the film layer materials, saving film material and time costs to a certain extent. Furthermore, the reduced film thickness reduces the probability of impurities and defects in the film, thereby improving the film's mechanical properties and resistance to laser damage.

[0115] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A wide-band ultraviolet low-reflection film, characterized in that: The ultraviolet band of the ultraviolet broadband low-reflection film is 240-400nm, and when the average reflectivity is less than 0.5%, the ultraviolet broadband low-reflection film is an Al2O3 film layer, a HfO2 film layer, and a MgF2 film layer stacked in sequence, wherein the Al2O3 film layer contacts the bottom surface of the substrate, and the thicknesses of Al2O3, HfO2, and MgF2 are respectively 43.69nm, 69.79nm, and 52.93nm; Or the ultraviolet band of the ultraviolet wide-band low-reflection film is 280~370nm, when the incident light angle is 0~35° and the average reflectivity is less than 0.25%, the ultraviolet wide-band low-reflection film is a first hafnium oxide layer stacked in sequence with a thickness of 14.42nm, the first hafnium oxide layer contacts the bottom surface of the substrate, the second silicon dioxide layer has a thickness of 16.21nm, the third hafnium oxide layer has a thickness of 44.37nm, and the fourth silicon dioxide layer has a thickness of 55.56nm.

2. The method for preparing the ultraviolet broadband low-reflection film according to claim 1, comprising the following steps: The bottom surface of the substrate is plated according to the structure of the ultraviolet broadband low-reflection film, so that the ultraviolet broadband low-reflection film is obtained on the bottom surface of the substrate.

3. The preparation method according to claim 2, characterized in that The material of the substrate is ultraviolet fused quartz; The thickness of the substrate is 0.6-6 mm.

4. The preparation method according to claim 2, characterized in that The plating conditions include: initial vacuum degree ≤ 9×10 -4 Pa; substrate heating temperature is 180~300℃.

5. The preparation method according to claim 2 or 4, characterized in that Before the plating, the substrate is further subjected to ion source cleaning, wherein the vacuum degree of the ion source cleaning is ≤9×10 -4 Pa, the time is 2-5 min, and the heating temperature of the substrate during the ion source cleaning is 180-300°C.

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