Optical film, method of making and use thereof

Abstract

The present application relates to optical film and its preparation method and application. The optical film comprises a substrate, a dielectric film and a nanostructure surface layer arranged in sequence, the material of the nanostructure surface layer is selected from fluorine-containing resin or nano-organic silicon, and the porosity of the nanostructure surface layer is 20%-91%; wherein the surface of the nanostructure surface layer away from the substrate has a concave-convex structure, in the convex part of the concave-convex structure, the maximum width of the bottom part close to the substrate is L1, the maximum width of the top part away from the substrate is L2, the height of the convex part is H, 1.1:1≤L1 / L2≤15:1, 1.5:1≤H / L1≤20:1. The optical film has wide spectrum, low reflectivity, low scattering and high laser damage threshold, and can effectively improve the shooting definition and laser damage resistance effect when used in optical devices.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to an optical thin film, its preparation method, and its application. Background Technology

[0002] While traditional multilayer low-reflection coatings possess a nanoscale subwavelength structure, the disordered arrangement of these nanostructures results in a large specific surface area and a heterogeneous state. This leads to multiple reflections of light entering the coating, causing severe light scattering, especially as the angle of incidence increases. Consequently, lenses using multiple layers of traditional multilayer low-reflection coatings suffer from reduced image clarity and noticeable haziness, impacting image sharpness. Furthermore, with the rapid proliferation of autonomous vehicles, most self-driving cars are equipped with LiDAR, and the damage caused by the laser in LiDAR to the coatings in lens modules cannot be ignored.

[0003] Therefore, there is an urgent need to develop an optical thin film that simultaneously possesses a wide spectrum of low reflectivity, low scattering, and a high laser damage threshold. Summary of the Invention

[0004] Therefore, it is necessary to provide an optical thin film, its preparation method, and its application to address the above problems. The optical thin film simultaneously possesses wide-spectrum low reflectivity, low scattering, and a high laser damage threshold. When used in optical devices, it can effectively improve the image clarity and anti-laser damage effect of optical devices.

[0005] An optical thin film includes a substrate, a dielectric thin film, and a nanostructured surface layer stacked sequentially, wherein the material of the nanostructured surface layer is selected from fluorinated resin or nano-organic silicon, and the porosity of the nanostructured surface layer is 20%-91%.

[0006] The nanostructure surface away from the substrate has an uneven structure. The maximum width of the protrusions near the substrate is L1, the maximum width of the top away from the substrate is L2, and the height of the protrusions is H. The ratios are 1.1:1≤L1 / L2≤15:1 and 1.5:1≤H / L1≤20:1.

[0007] In one embodiment, at least one nanostructure intermediate layer is provided between the dielectric film and the nanostructure surface layer, wherein the material of the nanostructure intermediate layer includes at least a fluorinated resin or nano-organic silicon.

[0008] In one embodiment, the porosity of the surface layer of the nanostructure is greater than the porosity of the middle layer of the nanostructure;

[0009] And / or, when the intermediate layer of the nanostructure is multilayered, the porosity of the intermediate layer of the nanostructure decreases layer by layer along the direction from the surface of the nanostructure to the substrate;

[0010] And / or, the total thickness of the nanostructure surface layer and the nanostructure intermediate layer is less than 500 nm.

[0011] In one embodiment, the dielectric film has a single-layer structure;

[0012] Alternatively, the dielectric film has a 2N-layer structure, comprising alternating layers of a first dielectric film and a second dielectric film, wherein the substrate is bonded to the first dielectric film, the refractive index of the first dielectric film is greater than the refractive index of the second dielectric film, and N is a positive integer;

[0013] Alternatively, the dielectric film has a 2N+1 layer structure, comprising an alternately stacked third dielectric film and a fourth dielectric film, wherein the substrate is bonded to the third dielectric film, the refractive index of the third dielectric film is less than the refractive index of the fourth dielectric film, and N is a positive integer.

[0014] In one embodiment, the material of the dielectric film is selected from at least one of titanium pentoxide, tantalum pentoxide, lanthanum titanate H4, silicon dioxide, aluminum oxide, or a mixture of silicon and aluminum.

[0015] In one embodiment, when the material of the nanostructure surface layer is selected from nano-organosilicon, the total content of silicon and oxygen elements in the nanostructure surface layer is greater than 80%.

[0016] In one embodiment, the substrate is made of glass or optical resin, and the substrate has a refractive index of 1.35-1.9.

[0017] In one embodiment, the optical thin film has an equivalent refractive index of 1.01-1.39.

[0018] A method for preparing an optical thin film as described above includes the following steps:

[0019] Provide a substrate, and deposit a dielectric thin film on any surface of the substrate;

[0020] A first film layer is deposited on the surface of the dielectric thin film at 10 -3 Under a vacuum pressure of Pa-10Pa, the first film layer is subjected to plasma etching to form a nanostructure surface layer, thereby obtaining the optical thin film. The porosity of the first film layer is 9%-89%, and the material of the first film layer is selected from fluorinated resin or nano-organic silicon.

[0021] In one embodiment, at least one second film layer is first deposited on the surface of the dielectric thin film, followed by the deposition of the first film layer. After the deposition of the first or second film layer, at 10 -3 Under a vacuum pressure of Pa-10Pa, at least the first film layer is subjected to plasma etching to form a nanostructured surface layer and a nanostructured intermediate layer. The porosity of the second film layer is 9%-50%, and the material of the second film layer includes at least fluorinated resin or nano-organic silicon.

[0022] In one embodiment, before plasma etching, a protective layer with a thickness of less than 10 nm is prepared on the surface of the film to be etched, and the material of the protective layer is titanium oxide or silicon oxide.

[0023] An optical device comprising the optical thin film as described above.

[0024] The fluorinated resin or nano-organic silicon on the surface of the optical thin film of the present invention is arranged unidirectionally from the inside to the outside, forming a concave-convex structure with special dimensions. This gives the optical thin film a unique nanostructure surface layer. On the one hand, the heterogeneous part of the nanostructure surface layer in the optical thin film is reduced, and the refracted optical path generated when light is incident is reduced, which is beneficial to significantly reduce light reflection and scattering, thereby reducing broadband reflectivity and improving haze effect. On the other hand, based on the special interference phenomenon unique to the nanostructure surface layer, it can not only effectively reduce the reflectivity of the 905nm band of lidar, but also has a significant low reflectivity effect for special lasers in the 1550nm band, thereby increasing the laser damage threshold of the optical thin film. Therefore, when the optical thin film of the present invention is used in optical devices, it can effectively improve the imaging clarity and anti-laser damage effect of optical devices. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic cross-sectional view of the optical thin film in one embodiment of the present invention;

[0027] Figure 2 This is a schematic cross-sectional view of the optical thin film in another embodiment of the present invention;

[0028] Figure 3 The image shows a scanning electron microscope (SEM) image of the surface of the first film layer obtained in Example 1.

[0029] Figure 4The image shows a scanning electron microscope (SEM) image of the nanostructured surface layer in the optical thin film prepared in Example 1.

[0030] Figure 5 The elemental analysis spectrum of the nanostructured surface layer in the optical thin film prepared in Example 1;

[0031] Figure 6 The scanning electron microscope image of the surface of the first film layer obtained in Example 3;

[0032] Figure 7 This is a scanning electron microscope image of the nanostructured surface layer in the optical thin film prepared in Example 3;

[0033] Figure 8 The scanning electron microscope image of the surface film layer of the optical thin film prepared in Comparative Example 1;

[0034] Figure 9 The graph shows a comparison of reflectivity performance, where A is the reflectivity variation curve of the optical film prepared in Example 1, B is the reflectivity variation curve of the optical film prepared in Example 3, and C is the reflectivity variation curve of the optical film prepared in Comparative Example 1.

[0035] Figure 10 The images show a comparison of the fogging effects. In the image, A represents the fogging effect of the optical film prepared in Comparative Example 1, and B represents the fogging effect of the optical film prepared in Example 1.

[0036] Wherein: 10, substrate; 20, dielectric film; 30, nanostructure surface layer; 40, nanostructure intermediate layer. Detailed Implementation

[0037] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0039] Combination Figure 1As shown, an optical thin film provided by the present invention includes a substrate 10, a dielectric thin film 20 and a nanostructured surface layer 30 stacked sequentially. The material of the nanostructured surface layer 30 is selected from fluorinated resin or nano-organic silicon, and the porosity of the nanostructured surface layer 30 is 20%-91%.

[0040] The nanostructure surface 30 has an uneven structure on the surface away from the substrate 10. The maximum width of the protrusions in the uneven structure is L1 at the bottom near the substrate 10 and L2 at the top away from the substrate 10. The height of the protrusions is H, and 1.1:1≤L1 / L2≤15:1, 1.5:1≤H / L1≤20:1.

[0041] The fluorinated resin or nano-organic silicon on the surface of the optical thin film of the present invention are arranged unidirectionally from the inside to the outside, forming a concave-convex structure with special size, so that the optical thin film has a unique nanostructure surface layer 30. On the one hand, the heterogeneous part of the nanostructure surface layer 30 in the optical thin film is reduced, and the refracted optical path generated when light is incident is reduced, which is beneficial to significantly reduce the reflection and scattering of light, thereby reducing the broadband reflectivity and improving the haze effect.

[0042] On the other hand, based on the unique interference phenomenon of the nanostructure surface layer 30, it can not only effectively reduce the reflectivity of the 905nm lidar band, but also reduce the reflectivity of special lasers in the 1550nm band, thereby increasing the laser damage threshold of the optical thin film to as high as 10J / cm. 2 -28J / cm 2 Furthermore, by reducing the extinction coefficient to less than 0.01 at a wavelength of 550nm, the optical thin film described in this invention can be used in optical devices to effectively improve the image clarity and anti-laser damage effect of optical devices.

[0043] It is understood that the specific shape of the protruding structure can be columnar, trapezoidal, hill-shaped, or other irregular shapes; L1 / L2 includes, but is not limited to, any one or any two point values ​​from 1:1, 1.5:1, 2.2:1, 2.6:1, 3.0:1, 3.5:1, 5:1, 10:1, 15:1, preferably 1.1:1≤L1 / L2≤3.5:1; H / L1 includes, but is not limited to, any one or any two point values ​​from 1.5:1, 2.1:1, 2.4:1, 2.8:1, 3.0:1, 3.6:1, 5:1, 10:1, 15:1, 20:1, preferably 1.5:1≤H / L1≤3:1.

[0044] Preferably, in the protrusion of the concave-convex structure, the maximum width L1 at the bottom near the substrate 10 is 20nm-150nm, the maximum width L2 at the top away from the substrate 10 is 10nm-100nm, and the height H of the protrusion is 50nm-400nm.

[0045] In one embodiment, when the material of the nanostructured surface layer 30 is selected from nano-organic silicon, the total content of silicon and oxygen elements in the nanostructured surface layer 30 is greater than 80%, which is close to the level of fused silica material. This is beneficial to further improve the laser damage resistance of the optical film, so that the laser damage threshold reaches 20 J / cm. 2 above.

[0046] It should be noted that the morphology of the nano-organosilicon (nSCH) includes, but is not limited to, solid or hollow spheres, solid or hollow ellipsoids, solid or hollow columns, and solid or hollow particles, with a preferred size of 10 nm to 100 nm. When the nano-organosilicon is a hollow structure, adjusting the wall thickness of the hollow structure facilitates further control of the porosity of the nanostructure surface layer 30, allowing for flexible adjustment of the porosity.

[0047] In one embodiment, when the material of the nanostructure surface layer 30 is selected from fluorinated resin, since the water contact angle of the fluorinated resin material is greater than 100°, the optical film can have waterproof and anti-pollution effects, thereby avoiding the optical device from being contaminated by glue, volatile organic compounds, etc.

[0048] Specifically, the fluorinated resin includes, but is not limited to, polytetrafluoroethylene, preferably polytetrafluoroethylene.

[0049] Combination Figure 2 As shown, a nanostructure intermediate layer 40 can be added between the dielectric film 20 and the nanostructure surface layer 30. The material of the nanostructure intermediate layer 40 includes at least fluorinated resin or nano-organic silicon.

[0050] It is understood that the materials of the nanostructure surface layer 30 and the nanostructure intermediate layer 40 can be the same or different; the material of the nanostructure intermediate layer 40 can be fluorinated resin or nano-organosilicon, or it can be a mixture of fluorinated resin, nano-organosilicon and other materials, preferably the mass proportion of fluorinated resin or nano-organosilicon in the mixture is higher than 80%.

[0051] In one embodiment, the porosity of the nanostructure surface layer 30 is greater than that of the nanostructure intermediate layer 40. Preferably, the porosity difference between the nanostructure surface layer 30 and the nanostructure intermediate layer 40 is 10%-49%, which is beneficial to achieving an equivalent refractive index gradient change in the nanostructure. Furthermore, the nanostructure surface layer 30 has the lowest equivalent refractive index, contains subwavelength structures of 10nm-200nm, and also has a certain anti-reflectivity effect. Thus, by utilizing the combined structure of the nanostructure surface layer 30 and the nanostructure intermediate layer 40, an even lower reflectivity effect can be achieved.

[0052] In one embodiment, when the nanostructure intermediate layer 40 is multilayered, the porosity of the nanostructure intermediate layer 40 decreases layer by layer along the direction from the nanostructure surface layer 30 to the substrate 10. The combination structure of the multilayer nanostructure intermediate layer 40 is beneficial to further reduce the reflectivity.

[0053] Preferably, the intermediate layer 40 of the nanostructure has three or fewer layers.

[0054] It is understood that the surface of the nanostructure intermediate layer 40 away from the substrate can have an uneven structure or a relatively smooth surface, and the present invention does not limit this.

[0055] In one embodiment, the thickness of the nanostructure surface layer 30 is less than 500 nm, or the total thickness of the nanostructure surface layer 30 and the nanostructure intermediate layer 40 is less than 500 nm; the thickness of the nanostructure surface layer 30 and the nanostructure intermediate layer 40 are independently selected from 50 nm to 100 nm.

[0056] In one embodiment, the dielectric film 20 has a single-layer structure, and preferably the refractive index of the dielectric film 20 is 1.3-2.6.

[0057] In one embodiment, the dielectric film 20 has a 2N-layer structure, comprising alternating layers of a first dielectric film and a second dielectric film. The substrate 10 is bonded to the first dielectric film. The refractive index of the first dielectric film is greater than that of the second dielectric film. Preferably, the refractive index of the first dielectric film is 1.6-2.6, and the refractive index of the second dielectric film is 1.3-1.6. More preferably, the refractive index of the first dielectric film differs from that of the second dielectric film by 0.3-1. N is a positive integer, preferably N = 1 or 2.

[0058] It is understood that in the dielectric film 20, along the direction away from the substrate 10, the first dielectric film and the second dielectric film are stacked and alternately stacked.

[0059] In one embodiment, when the dielectric film 20 has a 2N+1 layer structure, the dielectric film 20 includes an alternately stacked third dielectric film and a fourth dielectric film. The substrate 10 is bonded to the third dielectric film. The refractive index of the third dielectric film is less than that of the fourth dielectric film. Preferably, the refractive index of the third dielectric film is 1.3-1.6, and the refractive index of the fourth dielectric film is 1.6-2.6. More preferably, the refractive index of the third dielectric film differs from that of the fourth dielectric film by 0.3-1. N is a positive integer, preferably N = 1 or 2.

[0060] It is understood that in the dielectric film 20, along the direction away from the substrate 10, the third dielectric film and the fourth dielectric film are stacked alternately in a cycle.

[0061] Preferably, when the optical thin film does not contain a nanostructured intermediate layer 40, the dielectric thin film 20 preferably adopts a three-layer structure; when the optical thin film contains a nanostructured intermediate layer 40, the dielectric thin film 20 preferably adopts a single-layer structure, a double-layer structure, or a three-layer structure.

[0062] In one embodiment, the material of the dielectric film 20 includes, but is not limited to, at least one of titanium pentoxide, tantalum pentoxide, lanthanum titanate H4, silicon dioxide, aluminum oxide, or a mixture of silicon and aluminum.

[0063] In one embodiment, the material of the substrate 10 is selected from glass or optical resin, and the refractive index of the substrate 10 is 1.35-1.9.

[0064] In one embodiment, the equivalent refractive index of the optical thin film is 1.01-1.39, preferably 1.03-1.26.

[0065] This invention provides a method for preparing the optical thin film as described above, comprising the following steps:

[0066] S1, a substrate 10 is provided, and a dielectric thin film 20 is prepared by stacking on any surface of the substrate 10;

[0067] S2, depositing a first film layer on the surface of the dielectric thin film 20, at 10 -3 Under a vacuum pressure of Pa-10Pa, the first film layer is subjected to plasma etching to form a nanostructure surface layer 30, thereby obtaining the optical thin film. The porosity of the first film layer is 9%-89%, and the material of the first film layer is selected from fluorinated resin or nano-organic silicon.

[0068] In step S1, the present invention does not limit the preparation method of the dielectric thin film 20; any existing method, such as physical vapor deposition (PVD), can be used.

[0069] Specifically, the material of the dielectric thin film 20 includes, but is not limited to, at least one of titanium pentoxide, tantalum pentoxide, lanthanum titanate, silicon dioxide, aluminum oxide, or a mixture of silicon and aluminum. The material of the substrate 10 is selected from glass or optical resin, and the refractive index of the substrate 10 is preferably 1.35-1.9.

[0070] In step S2, after depositing a fluorinated resin film or a nano-organic silicon film on the surface of the dielectric thin film 20, the vacuum pressure conditions of the plasma etching are controlled so that the film is etched in an atmosphere with a specific oxygen content. This results in the fluorinated resin or nano-organic silicon in the first film being arranged unidirectionally from the inside out, having a special-sized concave-convex structure, while controlling the film to have a specific porosity. As a result, the optical thin film simultaneously possesses a wide spectrum of low reflectivity, low scattering, and a high laser damage resistance threshold.

[0071] It should be noted that the present invention does not limit the deposition process, including but not limited to vacuum thermal evaporation deposition, plasma enhanced chemical vapor deposition (PECVD), and plasma enhanced atomic layer deposition (PEALD). Vacuum thermal evaporation deposition is preferred, as it enables the film material to propagate almost linearly from the evaporation source to the surface of the dielectric film 20, which is beneficial to further reduce the heterogeneity of the nanostructure surface layer 30. Specifically, vacuum thermal evaporation deposition includes, but is not limited to, electron beam evaporation deposition or barrier vacuum deposition.

[0072] It is understandable that the porosity of the deposited film can be further optimized and controlled by adjusting the gas flow rate in the deposition apparatus. The types of gas used in the deposition apparatus include, but are not limited to, oxygen and argon.

[0073] In one embodiment, at least one second film layer is first deposited on the surface of the dielectric thin film 20, followed by the deposition of the first film layer. After the deposition of the first or second film layer, at 10 -3 Under a vacuum pressure of Pa-10Pa, at least the first film layer is plasma etched to form a nanostructured surface layer 30 and a nanostructured intermediate layer 40, wherein the porosity of the second film layer is 9%-50%, and the material of the second film layer includes at least fluorinated resin or nano-organic silicon.

[0074] It is understood that in this invention, the first film layer and the second film layer can be plasma etched, or only the first film layer can be plasma etched. That is, the second film layer located between the first film layer and the dielectric thin film 20 can be a film layer with an uneven surface formed by plasma etching, or it can be a relatively smooth film layer that has not been etched.

[0075] Preferably, when at least one second film layer is first deposited on the surface of the dielectric film 20, and then one first film layer is deposited, at 10 -3Under a vacuum pressure of Pa-10Pa, the first film layer is subjected to plasma etching to form a nanostructured surface layer 30 and a nanostructured intermediate layer 40.

[0076] In one embodiment, before plasma etching, a protective layer is prepared on the surface of the film to be etched. The protective layer is a discontinuous film with a thickness of less than 10 nm, and the material of the protective layer is titanium oxide or silicon oxide.

[0077] The present invention also provides an optical device, including the optical thin film as described above. It is understood that the optical device includes, but is not limited to, a lens module. The optical thin film described in the present invention is particularly suitable for lens modules and can effectively improve the clarity of lens shooting and the effect of resisting laser damage.

[0078] The optical thin film, its preparation method, and its applications will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0079] Example 1

[0080] Using resin as a substrate (refractive index 1.51), a silicon dioxide dielectric film (refractive index 1.46) was prepared on any surface of the resin substrate by physical vapor deposition (PVD) vacuum deposition process.

[0081] Electron beam evaporation deposition was used to deposit a mixed material of silica and hexamethyldisiloxane (mass ratio of silica to hexamethyldisiloxane 1:2) on the surface of a silica dielectric film to form a nanostructured intermediate layer (approximately 85 nm thick, porosity approximately 30%). Hexamethyldisiloxane was then deposited as the first film layer (approximately 90 nm thick, porosity approximately 51%). The scanning electron microscope image of the first film layer is shown below. Figure 3 As shown in the figure. After depositing a thin silicon dioxide protective layer on the surface of the first film layer using PVD, plasma etching was performed under a low vacuum pressure of 1 Pa to obtain an optical thin film. The scanning electron microscope image and elemental analysis spectrum of the nanostructured film layer on the surface of the optical thin film are shown in the figure. Figure 4 , Figure 5 As shown.

[0082] Example 2

[0083] Using glass as a substrate (refractive index 1.52), a silicon dioxide dielectric film (refractive index 1.46) is prepared on any surface of the glass substrate by PVD vacuum deposition.

[0084] Two layers of hexamethyldisiloxane were deposited on the surface of a silica dielectric film using PECVD, serving as an intermediate layer (approximately 100 nm thick with a porosity of approximately 35%) and a first layer (approximately 120 nm thick with a porosity of approximately 60%). The first layer was then subjected to plasma etching under a low vacuum pressure of 0.1 Pa to obtain an optical thin film.

[0085] Example 3

[0086] Using resin as a substrate (refractive index 1.62), a three-layer silica dielectric film was prepared on any surface of the resin by PVD vacuum deposition process (the refractive indices of the three silica dielectric films are 1.46, 2.45 and 1.46 respectively along the direction away from the substrate).

[0087] Polytetrafluoroethylene (PTFE) was deposited as the first film layer (approximately 170 nm thick, with a porosity of approximately 50%) on the surface of a silica dielectric film using electron beam evaporation deposition. The scanning electron microscope (SEM) image of the first film layer surface is shown below. Figure 6 As shown. After vacuum depositing a titanium dioxide protective layer on the surface of the first film layer, at 10... -2 An optical thin film was fabricated by plasma etching under low vacuum pressure conditions. A scanning electron microscope image of the nanostructured film layer on the surface of this optical thin film is shown below. Figure 7 As shown.

[0088] Example 4

[0089] Using optical resin as a substrate (refractive index 1.51), a six-layer silicon dioxide dielectric film was prepared on any surface of the optical resin by PVD vacuum deposition process (the refractive indices of the six silicon dioxide dielectric films along the direction away from the substrate are 2.45, 1.46, 2.45, 1.46, 2.45, and 1.46 respectively).

[0090] A polytetrafluoroethylene (PTFE) film (approximately 150 nm thick, with a porosity of approximately 45%) was deposited on the surface of a silica dielectric film using an electron beam evaporation deposition process. After depositing a titanium dioxide protective layer on the first film layer, a 10-year-old PTFE film was formed. -2 Optical thin films were fabricated by plasma etching under low vacuum pressure conditions.

[0091] Comparative Example 1

[0092] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses a PVD process to directly deposit aluminum oxide on the surface of a silica dielectric film, followed by drying with ultrapure water to obtain an optical nanofilm. The scanning electron microscope image of the film surface layer of this optical film is shown below. Figure 8 As shown.

[0093] Comparative Example 2

[0094] The difference between Comparative Example 2 and Example 2 is that two layers of silicon dioxide were deposited on the surface of the silicon dioxide dielectric film using PECVD, serving as the first film layer (approximately 90 nm thick, with a porosity of approximately 5%) and the second film layer (approximately 80 nm thick, with a porosity of approximately 8%), respectively. -2 An optical thin film is prepared by plasma etching of the first film layer under a low vacuum pressure of Pa.

[0095] Comparative Example 3

[0096] The difference between Comparative Example 3 and Example 2 is that, at 5.0 × 10 -4 The first film layer was plasma etched under vacuum pressure of Pa to obtain an optical thin film.

[0097] Examples 1 to 4 and Comparative Examples 1 to 3 were tested, and the results are as follows: Figure 9 , Figure 10 As shown in Tables 1 and 2.

[0098] Table 1

[0099]

[0100] Table 2

[0101]

[0102] Combination Figure 9 , Figure 10 As shown in Tables 1 and 2, the optical thin film provided by the present invention simultaneously possesses wide-spectrum low reflectivity, low scattering, and a high laser damage threshold. When used in optical devices, it can effectively improve image clarity and resistance to laser damage.

[0103] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An optical thin film, characterized in that, The optical thin film comprises a substrate, a dielectric thin film, and a nanostructured surface layer stacked sequentially. The nanostructured surface layer is made of nano-organic silicon, has a porosity of 20%-91%, and a laser damage threshold of 20 J / cm². 2 -28J / cm 2 The extinction coefficient is less than 0.01 at a wavelength of 550 nm; The nanostructure surface away from the substrate has an uneven structure. The maximum width of the protrusions near the substrate is L1, the maximum width of the top away from the substrate is L2, and the height of the protrusions is H. The ratios are 1.1:1≤L1 / L2≤2.6:1 and 1.5:1≤H / L1≤2.4:

1.

2. The optical thin film according to claim 1, characterized in that, Between the dielectric film and the nanostructure surface layer, at least one nanostructure intermediate layer is also provided, wherein the material of the nanostructure intermediate layer includes at least fluorinated resin or nano-organic silicon.

3. The optical thin film according to claim 2, characterized in that, The porosity of the surface layer of the nanostructure is greater than that of the middle layer of the nanostructure. And / or, when the intermediate layer of the nanostructure is multilayered, the porosity of the intermediate layer of the nanostructure decreases layer by layer along the direction from the surface of the nanostructure to the substrate; And / or, the total thickness of the nanostructure surface layer and the nanostructure intermediate layer is less than 500 nm.

4. The optical thin film according to claim 1, characterized in that, The dielectric film has a single-layer structure; Alternatively, the dielectric film has a 2N-layer structure, comprising alternating layers of a first dielectric film and a second dielectric film, wherein the substrate is bonded to the first dielectric film, the refractive index of the first dielectric film is greater than the refractive index of the second dielectric film, and N is a positive integer; Alternatively, the dielectric film has a 2N+1 layer structure, comprising an alternately stacked third dielectric film and a fourth dielectric film, wherein the substrate is bonded to the third dielectric film, the refractive index of the third dielectric film is less than the refractive index of the fourth dielectric film, and N is a positive integer.

5. The optical thin film according to claim 1, characterized in that, The material of the dielectric film is selected from at least one of titanium pentoxide, tantalum pentoxide, lanthanum titanate H4, silicon dioxide, aluminum oxide, or a mixture of silicon and aluminum.

6. The optical thin film according to claim 1, characterized in that, When the material of the nanostructure surface layer is selected from nano-organic silicon, the total content of silicon and oxygen elements in the nanostructure surface layer is greater than 80%.

7. The optical thin film according to claim 1, characterized in that, The substrate is made of glass or optical resin, and the refractive index of the substrate is 1.35-1.

9.

8. The optical thin film according to any one of claims 1 to 7, characterized in that, The optical thin film has an equivalent refractive index of 1.01-1.

39.

9. A method for preparing an optical thin film as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Provide a substrate, and deposit a dielectric thin film on any surface of the substrate; A first film layer is deposited on the surface of the dielectric thin film at 10 -3 Under a vacuum pressure of Pa-10Pa, the first film layer is subjected to plasma etching to form a nanostructured surface layer, thereby obtaining the optical thin film. The porosity of the first film layer is 9%-89%, and the material of the first film layer is selected from nano-organic silicon.

10. The method for preparing an optical thin film according to claim 9, characterized in that, At least one second film layer is first deposited on the surface of the dielectric thin film, followed by the deposition of the first film layer. After the deposition of the first or second film layer, at 10 -3 Under a vacuum pressure of Pa-10Pa, at least the first film layer is subjected to plasma etching to form a nanostructured surface layer and a nanostructured intermediate layer. The porosity of the second film layer is 9%-50%, and the material of the second film layer includes at least fluorinated resin or nano-organic silicon.

11. The method for preparing an optical thin film according to claim 9 or claim 10, characterized in that, Before plasma etching, a protective layer with a thickness of less than 10 nm is prepared on the surface of the film to be etched. The material of the protective layer is selected from titanium oxide or silicon oxide.

12. An optical device, characterized in that, Includes the optical thin film as described in any one of claims 1 to 8.

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