Ultraviolet broadband low-reflection film and preparation method thereof

Abstract

The invention belongs to the technical field of optical thin films, and particularly relates to an ultraviolet broadband low-reflection thin film and a preparation method thereof. The ultraviolet broadband low-reflection film provided by the invention comprises a low-refractive-index material and a high-refractive-index material which are alternately stacked, the low-refractive-index material comprises one or two of SiO2, Al2O3 and MgF2, and the high-refractive-index material is HfO2. According to the preparation method, proper low-refractive-index materials and high-refractive-index materials are selected, then film system design is carried out on the ultraviolet broadband low-reflection film through film system design software, plating is carried out on the substrate according to the film system design result, and the ultraviolet broadband low-reflection film with the ultraviolet band being 10-400 nm and the average reflectivity being smaller than 0.5% is successfully prepared. And the preparation method is simple and easy to implement, the generation probability of impurities and defects of the film is reduced, and then the mechanical property and the laser damage resistance of the film are improved.

Description

Technical Field

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

[0002] Optical thin films are widely used. For example, in common electronic products in life, such as mobile phones, watches, drones, etc. There are applications. The types of optical thin films include antireflection films (or low-reflection thin films), beam splitting films, high-reflection films, filter films, etc. Among them, although the low-reflection thin film is relatively basic, it has the widest application and the largest number of applied products. For example, the lenses of drones and mobile phone cameras are basically coated with low-reflection thin films in the visible light band. Therefore, there are many studies on low-reflection thin films, especially on low-reflection thin films in the visible light band.

[0003] However, with the development of technology, people's research on low-reflection thin films is not limited to the visible light band (400~700nm). Many products require a lower reflectivity in the ultraviolet light band. At present, the low-reflection thin films in the ultraviolet light band are all single-point wavelengths, such as 193nm, 266nm, 355nm, etc., which affects the wide application of low-reflection thin films in the ultraviolet light band. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultraviolet wide-band low-reflection thin film and a preparation method thereof. The preparation method provided by the present invention can obtain an ultraviolet wide-band low-reflection thin film with an ultraviolet band of 10~400nm and an average reflectivity <0.5%. Moreover, the preparation method is simple and easy to operate, reduces the probability of generating film impurities and defects, and further improves the mechanical properties and laser damage resistance of the thin film, meeting the environmental adaptability requirement standard of "GBT 26332.3-2015 Optics and Photonics - Optical Thin Films".

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions: The present invention provides a preparation method of an ultraviolet wide-band low-reflection thin film. The ultraviolet wide-band low-reflection thin film includes alternately stacked low-refractive-index materials and high-refractive-index materials. The low-refractive-index materials include 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 thin film is 10~400nm, and the average reflectivity <0.5%; It includes the following steps: According to the film layer materials, ultraviolet wavelength band, and average reflectivity of the ultraviolet broadband low-reflection film, film system design software is used for film system design to obtain the film system design result of the ultraviolet broadband low-reflection film. The film system design result includes the single-layer thickness of the high-refractive-index material, the single-layer 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. Coat on the bottom surface of the substrate according to the film system design result to obtain the ultraviolet broadband low-reflection film on the bottom surface of the substrate.

[0006] Preferably, the ultraviolet broadband low-reflection film includes alternately stacked SiO2 film layers and HfO2 film layers. The number of film layers of the SiO2 film layer is the same as that of the HfO2 film layer, and one HfO2 film layer is in contact with the bottom surface of the substrate.

[0007] Preferably, the ultraviolet broadband low-reflection film includes successively stacked Al2O3 film layer, HfO2 film layer, and MgF2 film layer, and the Al2O3 film layer is in contact with the bottom surface of the substrate.

[0008] Preferably, the material of the substrate is ultraviolet fused silica; The thickness of the substrate is 0.6 - 6 mm.

[0009] Preferably, the film system design software includes TFCalc optical thin film design software or Essential Macleod optical thin film design software.

[0010] Preferably, the coating conditions include: initial vacuum degree ≤ 9×10 -4 Pa; substrate heating temperature is 180 - 300 °C; the film formation rate of the high-refractive-index material is 0.1 - 0.25 nm / s, and the film formation rate of the low-refractive-index material is 0.2 - 0.7 nm / s.

[0011] Preferably, before the coating, the substrate is also subjected to ion source cleaning. 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.

[0012] Preferably, the ultraviolet wavelength band of the ultraviolet broadband low-reflection film is 200 - 400 nm.

[0013] Preferably, the ultraviolet wavelength band of the ultraviolet broadband low-reflection film is 245 - 400 nm or 280 - 370 nm; The thickness of the ultraviolet broadband low-reflection film is 125 - 290 nm.

[0014] The present invention provides an ultraviolet wide-band low-reflection thin film prepared by the preparation method described in the above technical solution.

[0015] The present invention provides a method for preparing an ultraviolet wide-band low-reflection thin film. The ultraviolet wide-band low-reflection thin film includes alternately stacked low-refractive-index materials and high-refractive-index materials. The low-refractive-index materials include 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 thin film is 10-400 nm, and the average reflectivity <0.5%. The method includes the following steps: According to the film layer materials, ultraviolet band, and average reflectivity of the ultraviolet wide-band low-reflection thin film, a film system design software is used for film system design to obtain the film system design result of the ultraviolet wide-band low-reflection thin 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 wide-band low-reflection thin film, and the total thickness of the ultraviolet wide-band low-reflection thin film. The film is deposited on the bottom surface of the substrate according to the film system design result to obtain the ultraviolet wide-band low-reflection thin film on the bottom surface of the substrate. By selecting suitable low-refractive-index materials and high-refractive-index materials, and then performing film system design on the ultraviolet wide-band low-reflection thin film through film system design software, and depositing on the substrate according to the film system design result, the present invention successfully prepares an ultraviolet wide-band low-reflection thin film with an ultraviolet band of 10-400 nm and an average reflectivity <0.5%. The preparation method is simple and easy to operate, reduces the probability of film impurities and defects, and further improves the mechanical properties and laser damage resistance of the thin film, meeting the environmental adaptability requirement standard of "GBT 26332.3-2015 Optics and Photonics - Optical Thin Films".

[0016] Further, when the ultraviolet band of the ultraviolet wide-band low-reflection thin film is 245-400 nm, the ultraviolet wide-band low-reflection thin film includes an Al2O3 film layer, an HfO2 film layer, and an MgF2 film layer stacked in sequence, and the Al2O3 film layer is in contact with the bottom surface of the substrate. By further optimizing the film layer structure characteristics (including materials and stacking order) of the ultraviolet wide-band low-reflection thin film with an ultraviolet band of 245-400 nm, the present invention can further reduce the total thickness of the ultraviolet wide-band low-reflection thin film and the thickness of the HfO2 film layer, further improve the uniformity of the ultraviolet wide-band low-reflection thin film, shorten the film formation time, save film materials and energy consumption, and reduce the manufacturing cost.

[0017] Further, when the ultraviolet band of the ultraviolet wide-band low-reflection thin film is 280~370nm, the ultraviolet wide-band low-reflection thin film includes alternately stacked SiO2 film layers and HfO2 film layers. 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 surface of the substrate. By further optimizing the film layer structure characteristics (including materials and stacking order) of the ultraviolet wide-band low-reflection thin film with an ultraviolet band of 280~370nm, the total thickness of the ultraviolet wide-band low-reflection thin film and the thickness of the HfO2 film layer can be further reduced, the uniformity of the ultraviolet wide-band low-reflection thin film can be further improved, the film formation time can be shortened, the film material and energy consumption can be saved, and the manufacturing cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the design curve of the 245~400nm low-reflection thin film in Example 1 of the present invention; Figure 2 It is the test curve of the 245~400nm low-reflection thin film in Example 1 of the present invention; Figure 3 It is the design curve of the 245~400nm low-reflection thin film in Example 2 of the present invention; Figure 4 It is the test curve of the 245-400nm low-reflection thin film in Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention provides a preparation method of an ultraviolet wide-band low-reflection thin film. The ultraviolet wide-band low-reflection thin film includes alternately stacked low-refractive-index materials and high-refractive-index materials. The low-refractive-index materials include 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 thin film is 10~400nm, and the average reflectivity < 0.5%; It includes the following steps: According to the film layer materials, ultraviolet band, and average reflectivity of the ultraviolet wide-band low-reflection thin film, a film system design software is used for film system design to obtain the film system design result of the ultraviolet wide-band low-reflection thin film. The film system design result includes the single-layer thickness of the high-refractive-index material, the single-layer thickness of the low-refractive-index material, the number of high-refractive-index material film layers, the number of low-refractive-index material film layers, the total number of layers of the ultraviolet wide-band low-reflection thin film, and the total thickness of the ultraviolet wide-band low-reflection thin film; Coat on the bottom surface of the substrate according to the film system design result to obtain the ultraviolet wide-band low-reflection thin film on the bottom surface of the substrate.

[0020] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well-known to those skilled in the art.

[0021] In the present invention, the ultraviolet broadband low-reflection film comprises a low-refractive-index material and a high-refractive-index material which are alternately stacked. The low-refractive-index material includes one or two of SiO2, Al2O3, and MgF2. In the embodiment, it is SiO2, or Al2O3 and MgF2. The high-refractive-index material is HfO2. The ultraviolet band of the ultraviolet broadband low-reflection film is 10-400 nm, preferably 200-400 nm, more preferably 245-400 nm or 280-370 nm. The average reflectivity of the ultraviolet broadband low-reflection film < 0.5%, or the average reflectivity of the ultraviolet broadband low-reflection film < 0.25%.

[0022] In the present invention, when the ultraviolet band is 245-400 nm, the average reflectivity of the ultraviolet broadband low-reflection film < 0.5%.

[0023] In the present invention, when the ultraviolet band is 280-370 nm, the average reflectivity of the ultraviolet broadband low-reflection film < 0.25%.

[0024] 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 at the incident angle of the incident light being 0-30° < 0.25%.

[0025] In the present invention, the thickness of the ultraviolet broadband low-reflection film is preferably 125-290 nm, more preferably 127-286 nm.

[0026] In the present invention, when the ultraviolet band of the ultraviolet broadband low-reflection film is preferably 245-400 nm, the ultraviolet broadband low-reflection film preferably comprises an Al2O3 film layer, an HfO2 film layer, and an MgF2 film layer which are sequentially stacked, and the Al2O3 film layer is 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 ultraviolet broadband low-reflection film is preferably 158-170 nm.

[0027] In the present invention, when the ultraviolet (UV) band of the UV broadband low-reflection thin film is preferably 280 - 370 nm, the UV broadband low-reflection thin film is preferably composed of alternately stacked SiO2 film layers and HfO2 film layers. The number of SiO2 film layers is preferably the same as the number of HfO2 film layers. One HfO2 film layer preferably contacts the bottom surface of the substrate. The number of SiO2 film layers is preferably 2 layers, and the number of HfO2 film layers is preferably 2 layers. The UV broadband low-reflection thin film is preferably composed of 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 UV broadband low-reflection thin film is preferably 127 - 133 nm.

[0028] Based on the film layer materials, UV band, and average reflectivity of the UV broadband low-reflection thin film, the present invention uses film system design software to design the film system of the UV broadband low-reflection thin film, and obtains the film system design result of the UV broadband low-reflection thin film. The film system design result includes the single-layer thickness of the high-refractive-index material, the single-layer 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 UV broadband low-reflection thin film, and the total thickness of the UV broadband low-reflection thin 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 can be TFCalc optical thin film design software in the examples. The present invention has no special requirements for the specific implementation process of the film system design.

[0029] After obtaining the film system design result, the present invention deposits on the bottom surface of the substrate according to the film system design result, and obtains the UV broadband low-reflection thin film on the bottom surface of the substrate.

[0030] As one or more embodiments of the present invention, the present invention deposits on the two bottom surfaces of the substrate respectively according to the film system design result, and obtains the UV broadband low-reflection thin film on the two bottom surfaces of the substrate respectively.

[0031] As one or more embodiments of the present invention, the present invention deposits on any one bottom surface of the substrate according to the film system design result, and obtains the UV broadband low-reflection thin film on any one bottom surface of the substrate.

[0032] In the present invention, the deposition is preferably carried out using a vacuum evaporation coating machine. During the deposition, the present invention preferably monitors the film layer rate and thickness by means of crystal oscillator monitoring.

[0033] In the present invention, the material of the substrate is ultraviolet fused silica (UVFS). The thickness of the substrate is preferably 0.6-6 mm, more preferably 1-5 mm. The substrate is preferably a cylinder or a prism. The shape of the two bottom surfaces (coating surfaces) of the substrate can be circular or square. In the embodiment, the substrate can be a cylindrical ultraviolet fused silica glass with a diameter of 25.4 mm.

[0034] In the present invention, before the plating, the present invention preferably further comprises ion source cleaning of the substrate. The present invention preferably places the substrate in a ring, and places the ring with the substrate on the hollow umbrella of the machine; and 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 ion source cleaning. The vacuum degree of the ion source cleaning is preferably ≤9×10 -4 Pa, the time is preferably 2 to 5 minutes, more preferably 3 minutes; the heating temperature of the substrate during the ion source cleaning is preferably 180 to 300°C, and in the embodiment it can be 180°C, 200°C, 250°C, 270°C or 300°C. The present invention can reduce the ion absorption of the substrate during the ion source cleaning process by controlling the heating temperature of the substrate to 180 to 300°C during the ion source cleaning. In the present invention, the voltage of the ion source cleaning is preferably 500 to 550V; the current is preferably 500 to 550mA. The gas used for the ion source cleaning is preferably oxygen and argon, and the flow ratio of the oxygen and argon is preferably 40:8. The flow rate of the 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 0sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8sccm.

[0035] In the present invention, the plating is performed after the ion source is cleaned.

[0036] 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).

[0037] 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 the examples, 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 the examples, 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 the examples, it can be 0.4 nm / s or 0.2 nm / s.

[0038] In the present invention, the ion source for depositing the HfO2 film layer is preferably HfO2; the voltage is preferably 500 - 550 V; the current is preferably 500 - 550 mA; the gases used are preferably oxygen and argon, and the flow rate ratio of oxygen to argon is preferably 40:16; the flow rate of oxygen is preferably 40 sccm. The argon includes first argon and second argon. The flow rate of the first argon (ion source argon) is preferably 8 sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8 sccm.

[0039] In the present invention, the ion source for depositing the low refractive index material film layer is preferably the low refractive index material. The ion source for depositing the SiO2 film layer is preferably SiO2; the ion source for depositing the Al2O3 film layer is preferably Al2O3; the ion source for depositing the MgF2 film layer is preferably MgF2. The voltage for depositing the low refractive index material film layer is preferably 500 - 550 V; the current is preferably 500 - 550 mA. The gases used for depositing the SiO2 film or Al2O3 film layer are preferably oxygen and argon, and the flow rate ratio of oxygen to argon is preferably 40:8. The flow rate of oxygen is preferably 40 sccm. The argon includes first argon and 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.

[0040] The gases used for depositing the MgF2 film layer are preferably argon. The argon includes first argon and 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.

[0041] In the present invention, when the ultraviolet wide - band low - reflection thin film preferably includes SiO2 film layers and HfO2 film layers alternately stacked, the deposition preferably includes: depositing HfO2 film layer, SiO2 film layer, HfO2 film layer, SiO2 film layer,..., HfO2 film layer, SiO2 film layer on the surface of the substrate in sequence.

[0042] In the present invention, when the ultraviolet broadband low-reflection film preferably includes an Al2O3 film layer, an HfO2 film layer, and an MgF2 film layer that are sequentially stacked, the coating preferably includes: sequentially coating an Al2O3 film layer, an HfO2 film layer, and an MgF2 film layer on the surface of the substrate.

[0043] The present invention provides an ultraviolet broadband low-reflection film prepared by the preparation method described in the above technical solution. The ultraviolet band of the ultraviolet broadband low-reflection film is 10-400 nm, preferably 200-400 nm, the average reflectivity <0.5%, or the average reflectivity <0.25%. In a specific embodiment of the present invention, the average reflectivity of the ultraviolet broadband low-reflection film is <0.5%, or <0.25% when the incident angle of the incident light is 0-30°.

[0044] In the present invention, the ultraviolet band of the ultraviolet broadband low-reflection film is further preferably 245-400 nm or 280-370 nm.

[0045] In the present invention, when the ultraviolet band of the ultraviolet broadband low-reflection film is 245-400 nm, the ultraviolet broadband low-reflection film is preferably an Al2O3 film layer, an HfO2 film layer, and an MgF2 film layer that are sequentially stacked, and the Al2O3 film layer preferably contacts 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. The thickness of the MgF2 film layer is preferably 50-54 nm. The total thickness of the ultraviolet broadband low-reflection film is preferably 158-170 nm.

[0046] 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 SiO2 film layer and an HfO2 film layer that are alternately stacked, and the number of film layers of the SiO2 film layer and the number of film layers of the HfO2 film layer are preferably the same. One HfO2 film layer preferably contacts the substrate. The number of film layers of the SiO2 film layer is preferably 2 layers, and the number of film layers of the HfO2 film layer is preferably 2 layers. 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 that are sequentially stacked. 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.

[0047] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0048] Embodiment 1: 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 following steps are included: 1. The coating material is selected from low refractive index material silicon dioxide (SiO2) and high refractive index material hafnium oxide (HfO2), because hafnium oxide has stable chemical properties in the transparent area of ​​226~12000nm. The substrate material is selected from ultraviolet fused quartz (UVFS), the transparent area of ​​the substrate is about 185~2100nm, and the performance is stable.

[0049] 2. This embodiment uses TFC film system design software to design, and the film structure is as shown in Table 1, with a total of 10 layers and 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 10th layer: silicon dioxide. The design curve is as follows 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, Rave=0.3426%.

[0050] Table 1 Designed membrane structure data for Example 1

[0051] 3. A vacuum evaporation coating machine manufactured by a domestic vacuum equipment factory is 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: First, place the clean substrate (here, a cylindrical UV fused quartz glass with a diameter of 25.4 mm and a height of 5 mm) in the prepared ring, and place the ring on the hollow umbrella of the machine to prepare for coating. In this embodiment, the two bottom surfaces of the cylinder need to be coated, and the side surfaces 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 is carried out at [[Pa]], the heating temperature of the substrate is 270 °C, set for 3 min, and the detailed ion source parameters are shown in Table 2. After cleaning is completed, film formation begins. The film formation rate: the coating rate of hafnium oxide is 0.2 nm / s, and the coating rate of silicon dioxide is 0.4 nm / s. The layer in direct contact with the substrate is the first layer in the design, namely hafnium oxide (HfO2); then the second layer is deposited, namely silicon dioxide (SiO2); then the third layer is deposited, namely hafnium oxide (HfO2); then the fourth layer is deposited, namely silicon dioxide (SiO2); and so on, repeating the overlapping deposition until all the film layers are deposited, that is, the coating of the first bottom surface is completed.

[0052] Next, the preparation of the second bottom surface film is completed, that is, the substrate with the first bottom surface already coated is turned over, the chamber door is closed and evacuated. When the vacuum reaches the set ≤ 9.0×10 -4 Pa, ion source cleaning is carried out. The heating temperature of the substrate is 270 °C, set for 3 min, and the detailed ion source parameters are as shown in Table 2 below. After cleaning is completed, film formation begins. The steps and parameters are the same as those for coating the first bottom surface until the end, that is, the preparation of the ultraviolet broadband low-reflection film in this embodiment is completed. During the film preparation process, this embodiment uses heating + full-process ion source-assisted coating, where the heating is at 270 °C, the film formation rate of SiO2 is 0.4 nm / s, and the film formation rate of HfO2 is 0.2 nm / s. The detailed coating parameters are shown in Table 3.

[0053] Table 2 Ion source cleaning parameter table in Example 1

[0054] Table 3 Coating parameter table in Example 1

[0055] In this embodiment, the reflectivity of the coated substrate is tested to confirm whether it meets the specifications. This embodiment uses a Nanjing Shigu ultraviolet low-reflection tester for testing, and the test curve is as Figure 2 , after calculation, in the range of 240 - 410 nm, Rave = 0.3857%, so in the range of 245 - 400 nm, it meets the specification requirements and the optics is OK.

[0056] In this embodiment, reliability tests are carried out on the prepared film products, such as adhesion, chemical stability, thermal shock, high temperature and high humidity, etc. The environmental adaptability requirements standard of "GBT 26332.3 - 2015 Optics and Photonics - Optical Thin Films" is adopted, and the results are all OK, indicating that the film preparation method provided in this embodiment can withstand the test of environmental tests, as shown in Table 4 in detail.

[0057] Table 4 Reliability results of Example 1

[0058] Example 2: This embodiment provides a method for preparing an ultraviolet broadband low-reflection film. The specification requirements for the ultraviolet broadband low-reflection film provided in this embodiment are as follows: in the ultraviolet band of 245 - 400 nm, the average reflectivity Rave < 0.5%. In Example 1, by alternately stacking two materials, HfO2 and SiO2, the specification requirements were met. However, the total thickness of HfO2 was close to 125 nm. Since the material HfO2 is expensive, with a price per kilogram approximately 50 times that of titanium trioxide (Ti3O5). In view of this, this embodiment optimizes the preparation method provided in Example 1. The specific preparation method provided in this embodiment includes: 1. Select low-refractive-index materials Al2O3 and MgF2, and high-refractive-index material hafnium oxide (HfO2) as the coating materials. Select ultraviolet fused silica (UVFS) as the substrate material. The transparent region range of the substrate is approximately 185 - 2100 nm, and its performance is stable.

[0059] The coating materials used in this embodiment are Al2O3, HfO2, and MgF2. Compared with SiO2, the specific data is shown in Table 5.

[0060] Table 5 Data table of film layer materials in Example 1 and Example 2

[0061] 2. This embodiment uses TFC film system design software for design and obtains a stack structure with only 3 layers. The order is: substrate, Al2O3, HfO2, MgF2. The thicknesses are Al2O3: 43.69 nm, HfO2: 69.79 nm, MgF2: 52.93 nm, and the total thickness is approximately 166.4 nm. Among them, HfO2 is 69.79 nm, which is less than 125 nm in Example 1.

[0062] The design curve is as Figure 3 . In the range of 240 - 410 nm, Rave = 0.1999% < 0.5% (specification requirements), and the design meets the requirements.

[0063] 3. Use the same coating machine and coating steps as in Example 1 for coating. Except for the coating parameters shown in Table 6, other parameters remain the same as in Example 1. The order is still to take out the sample after coating the first bottom surface, turn it over and coat the second bottom surface until the entire film layer coating is completed. The deposition rate of Al2O3 is 0.2 nm / s, and the deposition rate of MgF2 is 0.4 nm / s. The coating parameters are shown in Table 6.

[0064] Table 6 Coating parameter table in Example 2

[0065] 4. The reflectivity of the coated substrate is tested to confirm whether it meets the specifications. In this embodiment, the Nanjing Shigu ultraviolet low-reflectivity tester is also used for testing, and the test curve is as Figure 4 , after calculation, in the range of 240 - 410 nm, Rave = 0.20777%, so in the range of 245 - 400 nm, it meets the specification requirements and the optics is OK.

[0066] 5. In this embodiment, the reliability test is also carried out on the prepared thin film products. The test items are the same as those in Embodiment 1, and the results are all OK, indicating that the solutions of the three materials can also withstand the environmental test. See Table 7 for details.

[0067] Table 7 Reliability results of the ultraviolet wide-band low-reflection thin film prepared in Embodiment 2

[0068] 6. By comparing the preparation methods provided in Embodiment 2 and Embodiment 1, it can be seen that the characteristics of the ultraviolet wide-band low-reflection thin films prepared in Embodiment 1 and Embodiment 2 are similar, and the performance of the ultraviolet wide-band low-reflection thin films is all OK. In addition, the total thickness of the ultraviolet wide-band low-reflection thin film prepared in Embodiment 2 is close to 170 nm, which is about 110 nm thinner than the total thickness of 280 nm of the ultraviolet wide-band low-reflection thin film prepared in Embodiment 1, shortening the film-forming time and saving film materials and energy consumption. Especially in terms of hafnium oxide, the thickness of the HfO2 film layer in the ultraviolet wide-band low-reflection thin film prepared in Embodiment 2 is only about 70 nm, and the total thickness of the HfO2 film layer in Embodiment 1 is 125 nm. For each furnace (ultraviolet wide-band low-reflection thin film on one bottom surface of the substrate) of the ultraviolet wide-band low-reflection thin film prepared in Embodiment 2, about 55 nm thickness is saved, accounting for about 44% (= 55 / 125×100%). Considering mass industrial production, this is a quite large saving. Moreover, the reduction of the film layer thickness can avoid the risk of film cracking caused by excessive film layer stress.

[0069] Embodiment 3: This embodiment provides a method for preparing an ultraviolet wide-band low-reflection thin film. The specification requirements of the ultraviolet wide-band low-reflection thin film provided in this embodiment are: in the ultraviolet band of 280 - 370 nm, when the incident light angle is 0 - 35°, the average reflectivity Rave < 0.25%. The specific steps are as follows: 1. The coating materials are selected as the low-refractive-index material silicon dioxide (SiO2) and the high-refractive-index material hafnium oxide (HfO2). The substrate material is selected as ultraviolet fused silica (UVFS), and the transparent region range of the substrate is approximately 185 - 2100 nm, with stable performance.

[0070] 2. This embodiment uses TFC film system design software to design, and the film structure is shown in Table 8, with a total of 4 layers and a total thickness of 130.56nm (of which the total thickness of hafnium oxide is about 58.8nm). The first layer in contact with the bottom surface of 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 fourth layer: silicon dioxide. After calculation, Rave = 0.2133%.

[0071] Table 8 Designed membrane structure data for Example 3

[0072] 3. A vacuum evaporation coating machine manufactured by a domestic vacuum equipment factory was used to coat the film system in Table 8. This embodiment uses a crystal oscillator to monitor the film rate and thickness. The coating steps and parameters are the same as those in Example 1.

[0073] This embodiment tests the reflectivity of the plated substrate to confirm whether it meets the specifications. This embodiment uses Nanjing Shibuya UV low reflection tester for testing, and the optical results are OK.

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

[0075] Embodiment 4: 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, when the incident light angle is 0~35°, the average reflectivity Rave is less than 0.25%. Specifically, the following steps are included: 1. The coating material is selected from low refractive index materials Al2O3 and MgF2, and high refractive index material hafnium oxide (HfO2). The substrate material is selected from ultraviolet fused quartz (UVFS), the transparent area of ​​the substrate is about 185~2100nm, and the performance is stable.

[0076] 2. This embodiment uses TFC film system design software to design, and the film structure is shown in Table 9, with a total of 3 layers and a total thickness of 191.32nm (of which the total thickness of hafnium oxide is about 79.81nm). The first layer in contact with the substrate is Al2O3, followed by the second layer: HfO2, and then the third layer: MgF2, and finally ends with the third layer: MgF2. After calculation, Rave = 0.2084%.

[0077] Table 9 Design data of the film layer structure in Example 4

[0078] 3. The film system in Table 8 was deposited using a vacuum evaporation coating machine manufactured by a domestic vacuum equipment factory. In this example, the film layer rate and thickness were monitored by means of crystal oscillator monitoring. The deposition steps were the same as those in Example 1.

[0079] In this example, the reflectivity of the deposited substrate was tested to confirm whether it meets the specifications. In this example, a Nanjing Shigu ultraviolet low-reflection tester was used for testing, and the optics was OK.

[0080] In this example, the prepared thin film products were subjected to reliability tests, such as adhesion, chemical stability, thermal shock, high temperature and high humidity, etc. The environmental adaptability requirements standard of "GBT 26332.3-2015 Optics and Photonics - Optical Thin Films" was adopted, and the results were all OK, indicating that the thin film preparation method provided in this example can withstand the test of environmental tests.

[0081] It can be seen from Example 3 and Example 4 that when preparing an ultraviolet broadband low-reflection thin film with an ultraviolet wavelength range of 280~370nm, an incident light angle of 0~35°, and an average reflectivity Rave < 0.25%, by comparing the two preparation methods provided in Example 3 and Example 4, it was found that the design of the two film layer materials in Example 3 was better. The comparison data is shown in Table 10. The reliability and optics after actual coating in Example 3 and Example 4 both meet the requirements.

[0082] Table 10 Comparison of film layer materials and thicknesses of the reflective thin films prepared in Example 3 and Example 4

[0083] It can be seen from the above examples that the present invention provides a method for preparing an ultraviolet broadband low-reflection thin film. The ultraviolet wavelength range is 10~400nm, preferably in the near-ultraviolet (200~400nm) region. The preparation method provided by the present invention reduces the film thickness through the combination of film layer materials, saving the film material and time costs to a certain extent; at the same time, the reduction of the film thickness reduces the probability of the generation of film impurities and defects, thereby improving the mechanical properties and the ability of the thin film to resist laser damage.

[0084] Although the above examples have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can also be obtained based on this example without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an ultraviolet wide-band low-reflection thin film, characterized in that, The ultraviolet wide-band low-reflection thin film comprises a low-refractive-index material and a high-refractive-index material which are alternately stacked. 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 thin film is 10-400 nm, and the average reflectivity < 0.5%; It includes the following steps: According to the film layer materials, ultraviolet band and average reflectivity of the ultraviolet wide-band low-reflection thin film, film system design software is used for film system design to obtain the film system design result of the ultraviolet wide-band low-reflection thin film. The film system design result includes the single-layer thickness of the high-refractive-index material, the single-layer 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 thin film and the total thickness of the ultraviolet wide-band low-reflection thin film; Coat on the bottom surface of the substrate according to the film system design result to obtain the ultraviolet wide-band low-reflection thin film on the bottom surface of the substrate.

2. The preparation method according to claim 1, characterized in that, The ultraviolet wide-band low-reflection thin film comprises alternately stacked SiO2 film layers and HfO2 film layers. The number of film layers of the SiO2 film layer is the same as that of the HfO2 film layer, and 1 HfO2 film layer is in contact with the bottom surface of the substrate.

3. The preparation method according to claim 1, characterized in that, The ultraviolet wide-band low-reflection thin film comprises successively stacked Al2O3 film layer, HfO2 film layer and MgF2 film layer, and the Al2O3 film layer is in contact with the bottom surface of the substrate.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The material of the substrate is ultraviolet fused quartz; The thickness of the substrate is 0.6-6 mm.

5. The preparation method according to claim 1, characterized in that, The film system design software includes TFCalc optical thin film design software or Essential Macleod optical thin film design software.

6. The preparation method according to claim 1, characterized in that, The plating conditions include: an initial vacuum degree ≤ 9×10 -4 Pa; the substrate heating temperature is 180 - 300°C; the film formation rate of the high refractive index material is 0.1 - 0.25 nm / s, and the film formation rate of the low refractive index material is 0.2 - 0.7 nm / s.

7. The preparation method according to claim 1 or 6, characterized in that, Before the coating, it also includes ion source cleaning of the substrate, and the vacuum degree of the ion source cleaning is ≤ 9×10 -4 Pa, the time is 2 to 5 minutes, and the heating temperature of the substrate during the ion source cleaning is 180 to 300 °C.

8. The preparation method according to claim 1, characterized in that, The ultraviolet band of the ultraviolet wide-band low-reflection thin film is 200-400 nm.

9. The preparation method according to claim 1 or 8, characterized in that, The ultraviolet band of the ultraviolet wide-band low-reflection thin film is 245-400 nm or 280-370 nm; The thickness of the ultraviolet wide-band low-reflection thin film is 125-290 nm.

10. The ultraviolet wide-band low-reflection thin film prepared by the preparation method according to any one of claims 1-9.

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