Composite optical film with intrinsic hydrophobicity and preparation method thereof

Abstract

The invention discloses a composite optical thin film with intrinsic hydrophobicity and a preparation method thereof. The composite optical thin film comprises a substrate and an optical film system arranged on the substrate, wherein the optical film system comprises an organic-inorganic hybrid hydrophobic film layer. The organic-inorganic hybrid hydrophobic membrane layer is composed of an inorganic porous skeleton and an organic nano dispersed phase dispersed in the inorganic porous skeleton, and the inorganic porous skeleton has micro porosity gradually increased from the inner side surface to the outer side surface. The micro pores are filled with the organic nano dispersed phase in situ to form a space embedded structure with gradually increased distribution concentration gradient. According to the invention, covalent bonding and spatial embedding of organic components and an inorganic framework are utilized, so that the mechanical wear resistance and the hydrophobic antifouling life of the film layer are remarkably improved. According to the preparation method, double-source co-deposition is combined with a pulse type ion beam technology, and precise construction of a gradient distribution structure is achieved by dynamically modulating a deposition rate ratio and a pulse energy phase.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, and in particular to a composite optical thin film with intrinsic hydrophobicity and its preparation method. Background Technology

[0002] With the rapid development of touch displays, wearable devices, and automotive optical systems, composite optical films, while providing optical properties such as anti-reflection and anti-reflection, typically also need to possess good hydrophobic and antifouling properties. Existing hydrophobic and antifouling treatments mostly involve attaching an additional layer of fluorine- or silicon-containing organic low-surface-energy coating to the outer surface of the inorganic optical film through processes such as evaporation, spraying, or lamination. However, this additional surface coating is usually thin and mainly relies on physical adsorption or limited interfacial chemical bonds to bond with the underlying film system. Under long-term daily wiping or external mechanical friction, this surface coating is prone to peeling and dissipation, causing the hydrophobic and antifouling function of the optical film to quickly fail.

[0003] To improve wear resistance, the industry has attempted to use conventional physical blending or continuous co-deposition of organic hydrophobic materials with inorganic optical materials. However, conventional co-deposition processes tend to cause irregular aggregation of organic matter in the inorganic medium. This not only induces Rayleigh scattering, reducing the light transmittance of the film, but also significantly weakens the overall mechanical hardness of the film due to its loose internal microstructure. It is difficult to achieve both long-term antifouling life and stable optical transmittance in harsh operating environments. Summary of the Invention

[0004] In view of the technical defects of existing optical thin film surface hydrophobic and antifouling coatings being easily worn off under mechanical friction, leading to rapid functional failure, and conventional organic-inorganic co-deposition processes easily resulting in loose internal structure and poor overall mechanical strength of the film, this invention provides a composite optical thin film with intrinsic hydrophobicity and its preparation method.

[0005] The present invention provides a composite optical thin film with intrinsic hydrophobicity, comprising a substrate and an optical film system disposed on the substrate, wherein the optical film system comprises at least one organic-inorganic hybrid hydrophobic film layer; The organic-inorganic hybrid hydrophobic membrane layer includes an inorganic porous framework and multiple organic segments dispersed in the inorganic porous framework. The organic segment has reactive functional groups that crosslink with the inorganic porous framework and hydrophobic end groups that are away from the inorganic porous framework. The reactive functional groups are covalently bonded to the inorganic porous framework. Multiple organic segments aggregate in the inorganic porous framework to form an organic nano-dispersed phase; The inorganic porous framework has micropores formed within it, and the inorganic porous framework has a microporosity that gradually increases from the inner surface near the substrate to the outer surface away from the substrate. In the thickness direction of the organic-inorganic hybrid hydrophobic film layer, the organic nano-dispersed phase is in situ filled in the micropores of the inorganic porous framework, forming a spatial interlocking structure in which the concentration distribution increases in a gradient from the inner surface to the outer surface.

[0006] Preferably, the inorganic porous framework defines an opening that serves as a local bottleneck for the micropores and an internal cavity communicating with the opening, wherein the aperture of the opening is smaller than the maximum inner diameter of the internal cavity. Within the organic nano-dispersed phase filling the micropores, the hydrophobic end groups of multiple organic chain segments become entangled with each other in the internal cavity, forming a molecular interlocking structure with an overall three-dimensional size larger than the opening pore size. The organic nano-dispersed phase is doubly anchored in the inorganic porous framework through the covalent bonding of the reactive functional groups and the physical confinement of the molecular locking structure.

[0007] Preferably, the organic segment further comprises secondary crosslinkable groups; Within the same organic nano-dispersion phase, adjacent organic segments cross-link with each other through the secondary cross-linkable groups, forming a flexible organic subnetwork contained within the micropores. The flexible organic subnetwork and the inorganic porous framework interpenetrate within the organic-inorganic hybrid hydrophobic membrane layer to form a composite cross-linked framework.

[0008] Preferably, the inorganic porous framework is a silicon dioxide network; The organic segment is a fluoropolymer segment with siloxane groups, and the siloxane groups, as the reactive functional groups, are bonded to the silica network through silicon-oxygen-silicon covalent bonds.

[0009] Preferably, the optical film system is an antireflection film system composed of alternating layers of high refractive index medium layer and low refractive index medium layer from the substrate in a direction away from the substrate; The organic-inorganic hybrid hydrophobic film layer is disposed on the outermost side of the antireflective film system away from the substrate, and constitutes the outermost low refractive index dielectric layer of the antireflective film system.

[0010] Preferably, the maximum three-dimensional size of the organic nanodispersed phase is 1 nanometer to 100 nanometers to suppress Rayleigh scattering of visible light by the organic-inorganic hybrid hydrophobic film.

[0011] Preferably, the physical thickness of the organic-inorganic hybrid hydrophobic film layer is 10 nanometers to 150 nanometers, so as to retain the visible light transmittance of the composite optical film while providing mechanical abrasion resistance.

[0012] Preferably, the intrinsic refractive index of the inorganic porous framework is greater than the intrinsic refractive index of the organic chain segment; Because the concentration of the organic nano-dispersed phase increases in a gradient from the inner surface to the outer surface, the equivalent refractive index of the organic-inorganic hybrid hydrophobic film layer continuously decreases in the thickness direction of the organic-inorganic hybrid hydrophobic film layer.

[0013] The present invention also provides a method for preparing the above-mentioned composite optical thin film, characterized by comprising the following steps: Provide the substrate and place it in a vacuum deposition environment; A first vapor deposition source is activated to release the first deposited material that forms the inorganic porous framework, and a second vapor deposition source is activated simultaneously to release the second deposited material that forms the organic segments, and co-deposition is performed on the substrate; During the co-deposition process, the deposition rate ratio between the first vapor deposition source and the second vapor deposition source is dynamically modulated to form a gradient distribution of the first deposited material and the second deposited material along the thickness direction away from the substrate; Simultaneously, during the co-deposition process, a pulsed ion beam with alternating high and low energy fields is applied to the substrate; During the high-energy bombardment phase of the pulsed ion beam, the high-energy ions drive the first deposited material to form the inorganic porous framework with the micropores. During the low-energy deposition phase of the pulsed ion beam, the second deposited material enters the micropores in situ and, while retaining the activity of the hydrophobic end groups, covalently bonds with the inorganic porous framework through the reactive functional groups, thereby self-assembling to form the organic nano-dispersed phase with an increasing concentration gradient.

[0014] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention overcomes the structural limitations of traditional surface-coated antifouling layers. By constructing a nanoscale organic dispersed phase in situ within an inorganic porous framework, and ensuring its concentration increases in a gradient from the inner to the outer surface, the optical film acquires excellent intrinsic hydrophobicity. Since the hydrophobic organic segments are firmly bonded to the inorganic porous framework via covalent bonds, this means that even if the outer surface of the film suffers external mechanical wear, the exposed internal network still contains the intercalated organic nanoscale dispersed phase to continuously exert its hydrophobic and antifouling effect, thereby significantly extending the overall antifouling lifespan of the film.

[0015] Furthermore, this invention utilizes the gradual increase in microporosity of the inorganic porous framework and the in-situ filling mechanism of the organic nano-dispersed phase to construct a unique spatial interlocking structure, achieving an effective synergy between film hardness and toughness. The highly dense inorganic porous framework near the substrate interface ensures that the film possesses good underlying support hardness; while the outwardly extending micropores and the flexible organic segments filling them act as nanoscale stress buffer micro-regions. When the outer surface is subjected to frictional shear stress, this spatial interlocking structure can effectively absorb mechanical deformation energy, inhibit the generation and inward propagation of microcracks, thereby significantly improving the overall scratch resistance yield limit of the film.

[0016] Furthermore, the preparation method of this invention employs a pulsed ion beam-assisted co-deposition technique with alternating high and low energy fields, effectively overcoming the process contradiction between the compactness of the inorganic framework and the activity of organic groups in the film formation. The high-energy bombardment phase compacts the inorganic deposited material to construct a robust dielectric network with specific micropores, while the low-energy deposition phase provides a mild deposition window for the organic material, promoting in-situ covalent bonding of reactive functional groups within the pores while ensuring the hydrophobic end-group activity of organic molecules is not compromised. This method offers precise process control, facilitating the large-scale preparation of high-performance composite optical thin films with complex spatial interlocking structures. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the macroscopic cross-sectional structure of the composite optical thin film provided in an embodiment of the present invention. Explanation of reference numerals in the attached figures: 10, substrate; 20, optical film system; 21, organic-inorganic hybrid hydrophobic film layer; 211, inner surface; 212, outer surface. Detailed Implementation

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] like Figure 1 As shown, this embodiment of the invention provides a composite optical thin film with intrinsic hydrophobicity. The thin film mainly includes a substrate 10 and an optical film system 20 disposed on the substrate 10 in terms of macroscopic structure. The optical film system 20 includes at least one organic-inorganic hybrid hydrophobic film layer 21 located at a specific position.

[0021] In practical applications, the specific material of the substrate 10 can be flexibly selected according to the application scenario of the optical component. For example, in scenarios requiring high rigidity support, such as automotive central control screens or smartphone cover plates, the substrate 10 can be made of inorganic rigid materials such as soda-lime glass, aluminosilicate glass, or sapphire glass; while in wearable devices or flexible display scenarios, the substrate 10 can be replaced with flexible polymer materials such as polyethylene terephthalate (PET), polycarbonate (PC), or polyimide (PI). The wide applicability of the substrate 10 enables the optical film of the present invention to be easily integrated into various mainstream consumer electronics and optical instruments.

[0022] The optical film system 20 disposed on the substrate 10 is typically composed of alternating layers of high-refractive-index and low-refractive-index dielectric layers to achieve specific anti-reflection or anti-reflection optical effects. To further improve the weather resistance and interface compatibility of the film, the high-refractive-index dielectric layer is preferably titanium dioxide, tantalum pentoxide, or niobium pentoxide, while the low-refractive-index dielectric layer is preferably silicon dioxide or magnesium fluoride. The core organic-inorganic hybrid hydrophobic film layer 21 of this invention is preferably disposed on the outermost side of the optical film system 20 away from the substrate 10, and directly serves as the outermost low-refractive-index dielectric layer of the optical film system 20, thereby endowing the outermost surface of the film system with excellent optical and anti-fouling dual functions without adding additional coating processes.

[0023] In-depth analysis of the microstructure reveals that the organic-inorganic hybrid hydrophobic film 21 is not a traditional homogeneous coating, but rather a spatial composite system constructed from an inorganic porous framework and multiple organic segments dispersed within it. The inorganic porous framework, serving as the main structural support, is typically made of silica, a material with low intrinsic refractive index and extremely high mechanical hardness. This inorganic porous framework exhibits a gradually increasing microporosity along its thickness from the inner surface 211 near the substrate 10 to the outer surface 212 away from the substrate 10. This gradient structure is ingeniously designed; the dense framework near the inner surface 211 ensures strong interfacial adhesion and compressive yield strength between the hybrid film and the underlying film system, while the loose pores extending towards the outer surface 212 act as nanoscale stress buffer micro-regions, effectively absorbing and dissipating shear deformation energy from external mechanical friction.

[0024] To achieve a durable intrinsic hydrophobic effect, flexible organic segments with hydrophobic end groups and reactive functional groups aggregate within an inorganic porous framework to form an organic nano-dispersion phase, which fills the aforementioned micropores in situ. This organic segment is preferably a fluoropolymer segment with siloxane alkyl groups, such as perfluoropolyether silanes or fluoroalkyl silanes. The siloxane alkyl group, as a reactive functional group, can undergo a condensation reaction with the hydroxyl groups on the surface of the inorganic porous framework, firmly anchoring the organic phase within the inorganic framework through stable siloxane-silicon covalent bonds. Meanwhile, the perfluoroalkyl or perfluoropolyether long chains, which are deviated from the framework, act as hydrophobic end groups, imparting extremely low surface free energy to the film layer. Due to the increasing gradient of microporosity, the organic nano-dispersion phase filling it also exhibits a spatially interlocked structure with an increasing distribution concentration gradient along the thickness direction of the organic-inorganic hybrid hydrophobic film. This means that even if the outer surface 212 of the film suffers severe mechanical wear and causes the surface material to peel off, the exposed subsurface skeleton still contains a high concentration of organic hydrophobic microdomains, which can continuously provide antifouling performance to the outside, fundamentally overcoming the technical bottleneck that traditional single-layer antifouling coatings on the surface fail once worn.

[0025] More uniquely, the micropores defined by the inorganic porous framework are not simple cylindrical through-holes, but rather localized bottleneck structures with specific physical morphologies. Specifically, these micropores include an opening serving as a localized bottleneck and an internal cavity connected to the opening, with the opening's diameter strictly smaller than the maximum inner diameter of the internal cavity. During preparation and film formation, the hydrophobic end groups of multiple organic chain segments become physically entangled within the large internal cavity, forming a molecularly locked structure with an overall three-dimensional maximum size significantly larger than the opening's diameter. This unique geometrically confined state, combined with the aforementioned covalent bonding, enables the organic nano-dispersed phase to achieve dual chemical and physical anchoring within the inorganic porous framework. Even under prolonged high-intensity steel wool friction or ultrasonic cleaning conditions, the organic hydrophobic components are unlikely to escape or detach from the micropores of the inorganic framework.

[0026] In a preferred alternative embodiment, the organic segments may further include secondary crosslinkable groups such as double bonds or epoxy groups. Within the same organic nanodispersion phase, adjacent organic segments can undergo secondary crosslinking through these secondary crosslinkable groups, thereby forming a flexible organic subnetwork within the micropores. This flexible organic subnetwork interpenetrates with the rigid inorganic porous framework, constructing a composite crosslinked framework that combines rigidity and flexibility. This not only further locks in the organic components but also greatly improves the macroscopic fracture toughness of the hybrid film.

[0027] To prepare the aforementioned composite optical thin film possessing both complex spatial microstructure and excellent macroscopic properties, this invention also provides a unique preparation method. This method employs dual-source co-deposition combined with pulsed ion beam modulation technology. The substrate is placed in a deposition chamber under vacuum, while a first gas-phase deposition source releasing inorganic materials and a second gas-phase deposition source releasing organic materials are simultaneously activated. By dynamically modulating the deposition rate ratio of the two sources, the material concentration gradient along the thickness direction can be precisely controlled. Crucially, a pulsed ion beam with alternating high and low energy fields is introduced simultaneously during the co-deposition process. In the high-energy bombardment phase of the pulse, high-energy argon or oxygen ions strongly compact the deposited inorganic materials, forming a dense inorganic porous framework with microcavities at the top. In the low-energy deposition phase of the pulse, the ion beam energy is significantly reduced, providing a mild thermodynamic window for the organic materials. This allows long-chain organic molecules to in-situ penetrate and fill the micropores, successfully completing interfacial coupling of covalent bonds and spontaneous entanglement within the pores without damaging their fragile hydrophobic end groups, ultimately achieving efficient film formation in a single step.

Claims

1. A composite optical thin film with intrinsic hydrophobicity, characterized in that, The invention includes a substrate and an optical film system disposed on the substrate, wherein the optical film system includes at least one organic-inorganic hybrid hydrophobic film layer. The organic-inorganic hybrid hydrophobic membrane layer includes an inorganic porous framework and multiple organic segments dispersed in the inorganic porous framework. The organic segment has reactive functional groups that crosslink with the inorganic porous framework and hydrophobic end groups that are away from the inorganic porous framework. The reactive functional groups are covalently bonded to the inorganic porous framework. Multiple organic segments aggregate in the inorganic porous framework to form an organic nano-dispersed phase; The inorganic porous framework has micropores formed within it, and the inorganic porous framework has a microporosity that gradually increases from the inner surface near the substrate to the outer surface away from the substrate. In the thickness direction of the organic-inorganic hybrid hydrophobic film layer, the organic nano-dispersed phase is in situ filled in the micropores of the inorganic porous framework, forming a spatial interlocking structure in which the concentration distribution increases in a gradient from the inner surface to the outer surface.

2. The composite optical thin film according to claim 1, characterized in that, The inorganic porous framework defines an opening that serves as a local bottleneck for the micropores and an internal cavity communicating with the opening, wherein the diameter of the opening is smaller than the maximum inner diameter of the internal cavity. Within the organic nano-dispersed phase filling the micropores, the hydrophobic end groups of multiple organic chain segments become entangled with each other in the internal cavity, forming a molecular interlocking structure with an overall three-dimensional size larger than the opening pore size. The organic nano-dispersed phase is doubly anchored in the inorganic porous framework through the covalent bonding of the reactive functional groups and the physical confinement of the molecular locking structure.

3. The composite optical thin film according to claim 1, characterized in that, The organic segment also contains secondary crosslinkable groups; Within the same organic nano-dispersion phase, adjacent organic segments cross-link with each other through the secondary cross-linkable groups, forming a flexible organic subnetwork contained within the micropores. The flexible organic subnetwork and the inorganic porous framework interpenetrate within the organic-inorganic hybrid hydrophobic membrane layer to form a composite cross-linked framework.

4. The composite optical thin film according to claim 1, characterized in that, The inorganic porous framework is a silicon dioxide network; The organic segment is a fluoropolymer segment with siloxane groups, and the siloxane groups, as the reactive functional groups, are bonded to the silica network through silicon-oxygen-silicon covalent bonds.

5. The composite optical thin film according to claim 1, characterized in that, The optical film system is an anti-reflection film system composed of alternating layers of high refractive index medium layer and low refractive index medium layer from the substrate in a direction away from the substrate; The organic-inorganic hybrid hydrophobic film layer is disposed on the outermost side of the antireflective film system away from the substrate, and constitutes the outermost low refractive index dielectric layer of the antireflective film system.

6. The composite optical thin film according to claim 1, characterized in that, The maximum three-dimensional size of the organic nanodispersed phase is 1 nanometer to 100 nanometers to suppress Rayleigh scattering of visible light by the organic-inorganic hybrid hydrophobic film.

7. The composite optical thin film according to claim 1, characterized in that, The physical thickness of the organic-inorganic hybrid hydrophobic film is 10 nanometers to 150 nanometers to retain the visible light transmittance of the composite optical film while providing mechanical abrasion resistance.

8. The composite optical thin film according to claim 1, characterized in that, The intrinsic refractive index of the inorganic porous framework is greater than that of the organic chain segment; Because the concentration of the organic nano-dispersed phase increases in a gradient from the inner surface to the outer surface, the equivalent refractive index of the organic-inorganic hybrid hydrophobic film layer continuously decreases in the thickness direction of the organic-inorganic hybrid hydrophobic film layer.

9. A method for preparing a composite optical thin film as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Provide the substrate and place it in a vacuum deposition environment; A first vapor deposition source is activated to release the first deposited material that forms the inorganic porous framework, and a second vapor deposition source is activated simultaneously to release the second deposited material that forms the organic segments, and co-deposition is performed on the substrate; During the co-deposition process, the deposition rate ratio between the first vapor deposition source and the second vapor deposition source is dynamically modulated to form a gradient distribution of the first deposited material and the second deposited material along the thickness direction away from the substrate; Simultaneously, during the co-deposition process, a pulsed ion beam with alternating high and low energy fields is applied to the substrate; During the high-energy bombardment phase of the pulsed ion beam, the high-energy ions drive the first deposited material to form the inorganic porous framework with the micropores. During the low-energy deposition phase of the pulsed ion beam, the second deposited material enters the micropores in situ and, while retaining the activity of the hydrophobic end groups, covalently bonds with the inorganic porous framework through the reactive functional groups, thereby self-assembling to form the organic nano-dispersed phase with an increasing concentration gradient.

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