Optical conductive thin film for folding screen and preparation method of optical conductive thin film

Abstract

The invention belongs to the technical field of folding screens, and discloses an optical conductive film for a folding screen and a preparation method thereof.The optical conductive film for the folding screen comprises a composite base material, an interface transition layer, a gradient refractive index optical adjustment layer, a hybrid conductive layer and a scratch-resistant wear-resistant layer which are sequentially stacked from bottom to top; the composite base material is a blending modification layer of polyimide and transparent polyamide, the hybrid conductive layer is formed by compounding silver nanowires, a graphene sheet layer and PEDOT: PSS according to a preset proportion, and the refractive index of the gradient refractive index optical adjustment layer is gradually reduced in the direction away from the composite base material. And the difference value between the refractive index of the gradient refractive index optical adjustment layer and the refractive index of the hybrid conductive layer is not greater than 0.05. The mechanical stability, the light transmission efficiency, the conductive stability, the scratch resistance and the wear resistance of the film are improved, the performance is stable after folding circulation, the use requirements of a folding screen are met, and application in different scenes can be met.

Description

Technical Field

[0001] This invention relates to the field of foldable screen technology, and more specifically to an optical conductive thin film for foldable screens and its preparation method. Background Technology

[0002] With the rapid development of foldable screen technology, stringent requirements have been placed on the overall performance of optical conductive films. Traditional optical conductive films often employ a single substrate and a single conductive component design. In practical applications, they frequently suffer from problems such as a mismatch between mechanical flexibility and structural strength, weak interlayer bonding leading to easy peeling, difficulty in balancing optical transmittance and conductivity, significant performance degradation after folding cycles, and insufficient surface scratch and abrasion resistance. These issues prevent the films from stably adapting to the repeated folding scenarios of foldable screens, affecting the display clarity, touch sensitivity, and lifespan of the foldable screen.

[0003] In the prior art, Chinese invention patent CN119650143A discloses a homogeneous composite transparent conductive film, its preparation method, and its application. Its IPC classification numbers are H01B5 / 14 and H01B13 / 00. This scheme uses a polyimide substrate and a silver nanowire-copper nanowire composite conductive layer to form a homogeneous composite structure, which is then coated and hot-pressed to obtain the conductive film. Although this scheme improves conductivity through dual nanowire composites, it still has significant technical shortcomings: it uses a single substrate structure without an interface transition structure or a gradient refractive index adjustment structure; the interlayer bonding relies solely on physical adhesion through hot-pressing, making it prone to delamination after long-term folding; it does not optimize for reflection loss during light propagation, resulting in limited balance between light transmittance and conductivity, thus limiting the improvement in display clarity; furthermore, the surface lacks a dedicated scratch-resistant and wear-resistant structure, making it prone to surface damage after long-term use, and its conductivity decays significantly after folding cycles, making it unsuitable for the long-term stable use requirements of foldable screens.

[0004] To address the technical pain points of the aforementioned traditional technologies and existing comparative patents, there is an urgent need for a multi-layer structure with synergistic optimization and balanced performance indicators for foldable screens, along with its preparation method. Through targeted layer structure design and process optimization, a comprehensive improvement in mechanical strength, optical transmittance, conductivity, and protective performance can be achieved to meet the practical application needs of foldable screen products.

[0005] To this end, an optical conductive thin film for foldable screens and its preparation method are proposed. Summary of the Invention

[0006] The present invention aims to solve the problems mentioned in the background art by providing an optical conductive film for foldable screens and a method for preparing the same.

[0007] The specific technical solution is as follows: An optical conductive film for foldable screens includes a composite substrate, an interface transition layer, a gradient refractive index optical adjustment layer, a hybrid conductive layer, and a scratch-resistant and wear-resistant layer, which are stacked sequentially from bottom to top. The composite substrate is a blended modified layer of polyimide and transparent polyamide. The hybrid conductive layer is formed by combining silver nanowires, graphene sheets, and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) in a preset ratio. The refractive index of the gradient refractive index optical adjustment layer gradually decreases along the direction away from the composite substrate, and the difference between the refractive index of the gradient refractive index optical adjustment layer and the refractive index of the hybrid conductive layer is not greater than 0.05.

[0008] The aforementioned optical conductive film for foldable screens, wherein the composite substrate has a thickness of 25–50 μm, a tensile strength of not less than 200 MPa, an elongation at break of not less than 30%, and a glass transition temperature of not less than 280°C.

[0009] In the aforementioned optical conductive thin film for foldable screens, the interface transition layer is a mixed coating of aluminum oxide and silicon oxide, wherein the mass fraction of aluminum oxide is 60% to 80%, and the refractive index of the interface transition layer is 1.65 to 1.75.

[0010] In the aforementioned optical conductive film for foldable screens, the gradient refractive index optical adjustment layer is formed by a gradient composite of niobium oxide and silicon oxide, with a refractive index of 1.9 to 2.1 near the interface transition layer and a refractive index of 1.5 to 1.6 near the hybrid conductive layer, and the transmittance of the gradient refractive index optical adjustment layer is not less than 95%.

[0011] In the aforementioned optical conductive film for foldable screens, the diameter of the silver nanowires is 20–50 nm and the length is 10–20 μm; the graphene sheets are single-layer or few-layer graphene with no more than 5 layers; the thickness of the hybrid conductive layer is 80–120 nm, the surface sheet resistance is no greater than 8 Ω / □, and the visible light transmittance is no less than 92%.

[0012] The aforementioned optical conductive film for foldable screens has a thickness of 2-5 μm, a hardness of not less than 4H, a coefficient of friction of not more than 0.2, and after 100,000 folding cycles with a radius of 0.3 mm, a surface sheet resistance change rate of not more than 5% and a light transmittance attenuation of not more than 2%.

[0013] This invention also provides a method for preparing an optically conductive thin film for a foldable screen, comprising the following steps: Step (1), preparation of composite substrate: add polyimide monomer and transparent polyamide monomer to solvent at a mass ratio of 3:1 to 5:1, and polymerize by stirring, cast into film, and heat imidize to obtain composite substrate; Step (2), Deposit interface transition layer: An interface transition layer with a thickness of 1 to 3 nm is deposited on the surface of the composite substrate using plasma-enhanced chemical vapor deposition. Step (3), prepare gradient refractive index optical adjustment layer: use electron beam evaporation method to prepare a gradient refractive index optical adjustment layer with a thickness of 50-100nm on the surface of the interface transition layer by gradually adjusting the component ratio of the evaporation material; Step (4), preparation of hybrid conductive layer: silver nanowire dispersion, graphene dispersion and PEDOT:PSS solution are mixed evenly in volume ratio of 2:1:1 to 4:1:1, and coated on the surface of gradient refractive index optical adjustment layer by micro-concave coating method. After drying and laser densification treatment, hybrid conductive layer is obtained. Step (5), prepare the scratch-resistant and wear-resistant layer: coat the surface of the hybrid conductive layer with UV-curable resin, and then cure it with UV to obtain the optical conductive film for foldable screen.

[0014] The above-mentioned method for preparing optical conductive films for foldable screens, wherein the solvent in step (1) is N,N-dimethylacetamide, the stirring polymerization temperature is 25-35℃, and the stirring polymerization time is 4-6h; the thermal imidization treatment adopts a three-stage heating process, the first stage is heated to 120℃ and held for 1h, the second stage is heated to 200℃ and held for 1h, and the third stage is heated to 300℃ and held for 2h.

[0015] In the above-mentioned method for preparing optical conductive thin films for foldable screens, the reaction gas in step (2) of plasma-enhanced chemical vapor deposition is a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 9:1 to 10:1, a deposition power of 80 to 120 W, and a deposition pressure of 0.5 to 1 Pa.

[0016] The above-mentioned method for preparing optical conductive thin films for foldable screens includes the following steps: In step (4), the laser densification process uses a femtosecond laser with a wavelength of 532 nm, a laser power of 50–80 mW, and a scanning speed of 40–60 mm / s; the drying temperature is 80–100 °C, and the drying time is 30–60 min.

[0017] The present invention has the following beneficial effects: Through blending modification and process optimization of the composite substrate, the mechanical strength and flexibility of the substrate are effectively improved, ensuring that the film is not easily damaged during repeated folding. It also possesses good high-temperature resistance, adapting to the fabrication process requirements of subsequent functional layers and providing stable support for the overall structure. The design of the interface transition layer eliminates abrupt changes in refractive index between adjacent layers, reducing optical loss and significantly enhancing interlayer bonding strength, improving the overall structural stability of the film and avoiding the risk of interlayer delamination. The gradient refractive index optical adjustment layer's component gradient design effectively reduces light reflection loss between layers, improving overall light transmittance and ensuring the clarity of the foldable screen display. The multi-component composite and densification process of the hybrid conductive layer achieves a balance between high conductivity and high light transmittance. The resulting conductive network is stable and not prone to performance fluctuations due to folding, ensuring touch sensitivity. The scratch-resistant and abrasion-resistant layer enhances the film surface's resistance to damage, reducing scratches and wear during daily use and extending the film's lifespan.

[0018] Overall, through structural adaptation and performance synergy of each functional layer, the film achieves a balanced performance in terms of mechanical, optical, conductive, and protective properties, which can stably meet the usage requirements of foldable screens, taking into account display clarity, touch conductivity, and anti-folding durability. At the same time, some embodiments have achieved lightweight or high-performance enhanced designs through parameter optimization, which can respectively meet the requirements of low-cost mass production or the stringent usage requirements of high-end foldable screens, effectively solving various technical pain points of traditional optical conductive films in foldable screen applications. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation method of an optically conductive thin film for a foldable screen according to an embodiment of the present invention. Figure 2 This is a graph showing the relationship between the thickness of the composite substrate and its tensile strength. Figure 3 These are comparison images of the surface sheet resistance of the hybrid conductive layers in Examples 1-3; Figure 4 This is a comparison chart of visible light transmittance in Examples 1-3; Figure 5 The graph shows the performance changes of the optical conductive films in Examples 1-3 after 100,000 folds. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0022] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0023] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] This specific embodiment provides an optical conductive film for foldable screens, comprising a composite substrate, an interface transition layer, a gradient refractive index optical adjustment layer, a hybrid conductive layer, and a scratch-resistant and wear-resistant layer, stacked sequentially from bottom to top. The composite substrate is a blended modified layer of polyimide and transparent polyamide. The hybrid conductive layer is formed by combining silver nanowires, graphene sheets, and PEDOT:PSS in a preset ratio. The refractive index of the gradient refractive index optical adjustment layer gradually decreases along the direction away from the composite substrate, and the difference between the refractive index of the gradient refractive index optical adjustment layer and the refractive index of the hybrid conductive layer is no greater than 0.05. In this solution, through a specific layered structure design, the blended modification of the composite substrate can improve flexibility and structural stability; the multi-component composite of the hybrid conductive layer can optimize conductivity; and the gradient refractive index design of the gradient refractive index optical adjustment layer can reduce interlayer light reflection. With the synergistic effect of each layer, both optical transmittance and conductivity are balanced, while also adapting to the flexible usage requirements of foldable screens and improving interlayer structural compatibility.

[0025] The composite substrate has a thickness of 25–50 μm, a tensile strength of not less than 200 MPa, an elongation at break of not less than 30%, and a glass transition temperature of not less than 280°C. This solution enhances the mechanical strength and deformation resistance of the composite substrate through targeted modification and parameter control, ensuring it is not easily damaged during repeated folding. Simultaneously, it strengthens the substrate's high-temperature resistance, preventing structural failure due to temperature changes during subsequent processing or use, and providing a stable substrate for the adhesion of subsequent functional layers.

[0026] The interface transition layer is a mixed coating of alumina and silicon oxide, wherein the mass fraction of alumina is 60%–80%, and the refractive index of the interface transition layer is 1.65–1.75. This design employs a mixed coating of specific components for the interface transition layer, which enhances the bonding strength between the composite substrate and the gradient refractive index optical adjustment layer, reduces the risk of interlayer delamination, and allows for a smooth transition of refractive index between adjacent layers, reducing interfacial optical loss and ensuring the consistency of overall optical performance.

[0027] The gradient refractive index optical adjustment layer is formed by a gradient composite of niobium oxide and silicon oxide. The refractive index near the interface transition layer is 1.9–2.1, and the refractive index near the hybrid conductive layer is 1.5–1.6. The transmittance of the gradient refractive index optical adjustment layer is not less than 95%. This design employs a gradient composite composition for the gradient refractive index optical adjustment layer. By gradually adjusting the refractive index, it effectively reduces reflection loss during light propagation between layers, improves overall light transmission efficiency, and ensures smoother light transmission. Simultaneously, it adapts to the refractive index characteristics of adjacent layers, further optimizing overall optical compatibility.

[0028] The silver nanowires have a diameter of 20–50 nm and a length of 10–20 μm; the graphene sheets are single-layer or few-layer graphene with no more than 5 layers; the hybrid conductive layer has a thickness of 80–120 nm, a surface sheet resistance of no more than 8 Ω / □, and a visible light transmittance of no less than 92%. In this design, the hybrid conductive layer is a composite of silver nanowires, graphene sheets, and PEDOT:PSS with a specific structure. The silver nanowires and graphene form a continuous conductive path, improving conductivity. The introduction of PEDOT:PSS optimizes the uniformity and adhesion of the conductive layer. Through the synergistic effect of these three components, stable conductivity is achieved while ensuring good light transmittance, thus meeting the performance requirements of foldable screen touch and display.

[0029] The scratch-resistant and wear-resistant layer has a thickness of 2–5 μm, a hardness of not less than 4H, a coefficient of friction of not more than 0.2, and after 100,000 folding cycles with a radius of 0.3 mm, the change rate of surface sheet resistance is not more than 5%, and the decrease in light transmittance is not more than 2%. This design of the scratch-resistant and wear-resistant layer enhances the scratch resistance and wear resistance of the film surface, reduces surface damage during daily use, and maintains performance stability during folding cycles. It also prevents significant attenuation of conductivity and light transmittance due to repeated folding, thus extending the service life of the film.

[0030] This specific embodiment also provides a method for preparing an optically conductive thin film for a foldable screen, comprising the following steps: Step (1), preparation of composite substrate: add polyimide monomer and transparent polyamide monomer to solvent at a mass ratio of 3:1 to 5:1, and polymerize by stirring, cast into film, and heat imidize to obtain composite substrate; Step (2), Deposit interface transition layer: An interface transition layer with a thickness of 1 to 3 nm is deposited on the surface of the composite substrate using plasma-enhanced chemical vapor deposition. Step (3), prepare gradient refractive index optical adjustment layer: use electron beam evaporation method to prepare a gradient refractive index optical adjustment layer with a thickness of 50-100nm on the surface of the interface transition layer by gradually adjusting the component ratio of the evaporation material; Step (4), preparation of hybrid conductive layer: silver nanowire dispersion, graphene dispersion and PEDOT:PSS solution are mixed evenly in volume ratio of 2:1:1 to 4:1:1, and coated on the surface of gradient refractive index optical adjustment layer by micro-concave coating method. After drying and laser densification treatment, hybrid conductive layer is obtained. Step (5), prepare the scratch-resistant and wear-resistant layer: coat the surface of the hybrid conductive layer with UV-curable resin, and then cure it with UV to obtain the optical conductive film for foldable screen.

[0031] The preparation method in this scheme uses a step-by-step and orderly process design to precisely control the preparation process of each functional layer, ensuring that the structure of each layer is intact and tightly bonded, achieving synergistic compliance of various performance indicators, and the process flow is coherent and controllable. It can stably prepare optical conductive films that meet the requirements of foldable screens and adapt to the needs of large-scale production.

[0032] In step (1), the solvent is N,N-dimethylacetamide, the polymerization temperature is 25–35°C, and the polymerization time is 4–6 h. The thermal imidization treatment uses a three-stage heating process: the first stage heats to 120°C and holds for 1 h, the second stage heats to 200°C and holds for 1 h, and the third stage heats to 300°C and holds for 2 h. In this scheme, the selection of a specific solvent and the staged heating thermal imidization process during the preparation of the composite substrate can ensure sufficient monomer polymerization, improve the structural density of the substrate, reduce internal defects, and enhance the mechanical properties and thermal stability of the substrate, providing a high-quality substrate for subsequent layer deposition.

[0033] In step (2), the reaction gas in plasma-enhanced chemical vapor deposition is a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 9:1 to 10:1, a deposition power of 80 to 120 W, and a deposition pressure of 0.5 to 1 Pa. This scheme employs specific reaction gas ratios and process parameters for the deposition of the interface transition layer, ensuring uniform deposition, improving the strength of interlayer bonding, and precisely controlling the optical properties of the transition layer to ensure its refractive index matches adjacent layers, reducing interfacial optical loss, and guaranteeing overall optical performance.

[0034] In step (4), the laser densification process uses a femtosecond laser with a wavelength of 532 nm, a laser power of 50–80 mW, and a scanning speed of 40–60 mm / s; the drying temperature is 80–100 °C, and the drying time is 30–60 min. The drying and laser densification processes in this hybrid conductive layer preparation method can improve the structural density of the conductive layer, enhance the stability of the conductive pathway, reduce fluctuations in conductivity, and simultaneously ensure the bonding strength between the conductive layer and adjacent layers, ensuring long-term stable conductivity during subsequent use and folding.

[0035] In addition, refer to Figures 1-5 This specific implementation also provides the following three embodiments, wherein Figure 1 The fabrication process of optical conductive thin films for foldable screens was demonstrated; Figure 2 The positive correlation between substrate thickness (25-50 μm) and tensile strength (200-260 MPa) is shown in Examples 1-3, with the 50 μm thickness in Example 3 corresponding to the highest strength of 260 MPa. Figure 3 Example 3 shows that it uses 5 layers of graphene + high proportion of silver nanowires to achieve the lowest sheet resistance of 4Ω / □, which is about 33% higher than Example 1 (6Ω / □). Figure 4 Example 2 shows that the highest transmittance of 94% was achieved through optimization of single-layer graphene, which is 2 percentage points higher than that of Example 3 (92%), verifying the effect of few-layer graphene on improving transmittance; Figure 5The results show that Example 3 exhibits only a 2% change in sheet resistance and a 0.8% decrease in light transmittance after folding tests, verifying its excellent folding stability, which is superior to other examples.

[0036] Example 1 I. Technical Solution The optical conductive film for foldable screens in this embodiment comprises, from bottom to top, a composite substrate, an interface transition layer, a gradient refractive index optical adjustment layer, a hybrid conductive layer, and a scratch-resistant and wear-resistant layer. The specific configuration and fabrication process of each layer are as follows: 1. Composite substrate: It is made by blending and modifying polyimide and transparent polyamide. Polyimide monomer and transparent polyamide monomer are added to N,N-dimethylacetamide solvent at a mass ratio of 4:1. The solid content of the monomer in the solvent is 25wt%. The total mass of the solvent added is 3 times the total mass of the monomer. The mixture is stirred and polymerized at 30℃ for 5h. After film formation by casting with a doctor blade gap of 50μm and a casting speed of 1.2m / min, it is treated by a three-stage thermal imidization process of holding at 120℃ for 1h, 200℃ for 1h, and 300℃ for 2h to obtain a composite substrate with a thickness of 35μm.

[0037] 2. Interface transition layer: Deposited on the surface of the composite substrate using plasma-enhanced chemical vapor deposition, with argon and oxygen as the reaction gases in a volume ratio of 9.5:1, a deposition power of 100W, a deposition pressure of 0.8Pa, and a deposition thickness of 2nm. This transition layer is a mixed coating of alumina and silicon oxide, with alumina content of 70%.

[0038] 3. Gradient refractive index optical adjustment layer: Prepared on the surface of the interface transition layer by electron beam evaporation. The composition ratio of niobium oxide and silicon oxide is gradually adjusted, with a higher proportion of niobium oxide near the interface transition layer and a higher proportion of silicon oxide near the hybrid conductive layer, forming a gradient composite layer with a thickness of 80 nm. The refractive index is 2.0 near the interface transition layer and 1.55 near the hybrid conductive layer.

[0039] 4. Hybrid conductive layer: A silver nanowire dispersion with a concentration of 10 mg / mL, a graphene dispersion with a concentration of 5 mg / mL, and a PEDOT:PSS solution with a solid content of 1.5 wt% were mixed uniformly at a volume ratio of 3:1:1. The mixture was then encapsulated using a micro-grooving roller with a screen count of 200 lines / inch and a cell volume of 5 cm³. 3 / m 2The coating was applied to the surface of the gradient refractive index optical adjustment layer using a micro-grooving method with a coating speed of 3 m / min and a micro-grooving roller speed ratio of 1.1:1. After drying at 90℃ for 45 min, a densification process was performed using a femtosecond laser with a wavelength of 532 nm, a power of 65 mW, and a scanning speed of 50 mm / s to obtain a hybrid conductive layer with a thickness of 100 nm. The silver nanowires have a diameter of 35 nm and a length of 15 μm, and the graphene sheets are 3 layers of few-layer graphene.

[0040] 5. Scratch-resistant and wear-resistant layer: UV-curable resin is coated on the surface of the hybrid conductive layer, and after UV curing, a scratch-resistant and wear-resistant layer with a thickness of 3.5μm is formed.

[0041] II. Working Principle The composite substrate is modified by blending polyimide and transparent polyamide. The molecular chains of the two components intertwine, retaining the high temperature resistance and high mechanical strength of polyimide while enhancing the flexibility of the substrate with transparent polyamide, providing a stable and fold-resistant base support for the overall film. The alumina and silicon oxide mixture in the interface transition layer has a refractive index between the composite substrate and the gradient refractive index optical adjustment layer, which can eliminate the abrupt change in refractive index between the two layers and enhance interlayer adhesion to prevent delamination. The gradient refractive index optical adjustment layer achieves a smooth transition from high to low refractive index through the gradual change in the composition of niobium oxide and silicon oxide, reducing reflection loss of light during interlayer propagation and improving light transmission efficiency. In the hybrid conductive layer, silver nanowires and graphene sheets overlap to form a continuous conductive network, ensuring high conductivity. PEDOT:PSS fills the gaps in the network, improving the uniformity and adhesion stability of the conductive layer. The three work together to achieve a balance between conductivity and light transmission. The scratch-resistant and wear-resistant layer covers the surface, resisting external friction and scratches, and also acts as a buffer during folding to maintain overall performance stability. Through structural adaptation and performance synergy, each layer achieves comprehensive compliance with the optical, conductive, and mechanical properties of the thin film in folded scenarios.

[0042] III. Experimental Data The optically conductive thin film prepared in this embodiment was subjected to performance tests, and the test results are as follows: The composite substrate was tested according to GB / T1040.3-2006 standard at a tensile speed of 50 mm / min, with a tensile strength of 230 MPa and an elongation at break of 35%. According to GB / T19466.2-2004 standard, the glass transition temperature was 300℃. The peel strength between the interface transition layer and the composite substrate, and the gradient refractive index optical adjustment layer, was tested according to GB / T2790-1995 standard using a 180° peel test at a tensile speed of 3... Measured at 00 mm / min, all values ​​are greater than 1.5 N / mm; the transmittance of the gradient refractive index optical adjustment layer is 96%; the surface sheet resistance of the hybrid conductive layer is 6 Ω / □, and the visible light transmittance is 93%; the hardness of the scratch-resistant and wear-resistant layer is 4.5H according to GB / T6739-2024 standard, tested with a pencil hardness tester under a load of 1 kg, and the coefficient of friction is 0.15 according to GB / T3960-2016 standard; after 100,000 folding cycles (folding radius 0.3 mm), the surface sheet resistance change rate is 3%, and the transmittance decreases by 1.2%.

[0043] IV. Technical Effects Through blending modification and optimization processes of the composite substrate, the mechanical strength and flexibility of the substrate are improved, ensuring that the film is not easily damaged during repeated folding. Its high-temperature resistance can adapt to the preparation process requirements of subsequent layers. The design of the interface transition layer eliminates the abrupt change in refractive index between layers, reduces optical loss, and enhances the interlayer bonding strength, thereby improving the overall structural stability of the film. The gradient component design of the gradient refractive index optical adjustment layer effectively reduces light reflection loss, improves overall light transmission efficiency, and makes light transmission smoother. The multi-component composite and laser densification treatment of the hybrid conductive layer achieves a balance between high conductivity and high light transmission performance. The conductive network is stable and not prone to performance fluctuations due to folding. The addition of the scratch-resistant and wear-resistant layer improves the damage resistance of the film surface and extends its service life. With the synergistic effect of each layer, the film can stably adapt to the usage requirements of foldable screens, taking into account optical clarity, touch conductivity, and anti-folding durability.

[0044] Example 2 I. Technical Solution The optical conductive film for foldable screens in this embodiment comprises, from bottom to top, a composite substrate, an interface transition layer, a gradient refractive index optical adjustment layer, a hybrid conductive layer, and a scratch-resistant and wear-resistant layer. The specific configuration and fabrication process of each layer are as follows: 1. Composite substrate: It is made by blending and modifying polyimide and transparent polyamide. The polyimide monomer and the transparent polyamide monomer are added to N,N-dimethylacetamide solvent at a mass ratio of 3:1 and stirred and polymerized at 25°C for 6 hours. After casting into a film, it is treated with a three-stage heating thermal imidization process, namely, holding at 120°C for 1 hour, holding at 200°C for 1 hour, and holding at 300°C for 2 hours to obtain a composite substrate with a thickness of 25μm.

[0045] 2. Interface transition layer: Deposited on the surface of the composite substrate using plasma-enhanced chemical vapor deposition, with argon and oxygen as the reaction gases, in a volume ratio of 9:1. The deposition power is 80W, the deposition pressure is 0.5Pa, and the deposition thickness is 1nm. This transition layer is a mixed coating of alumina and silicon oxide, with alumina accounting for 60% by mass.

[0046] 3. Gradient refractive index optical adjustment layer: Prepared on the surface of the interface transition layer by electron beam evaporation. The composition ratio of niobium oxide and silicon oxide is gradually adjusted, with a higher proportion of niobium oxide near the interface transition layer and a higher proportion of silicon oxide near the hybrid conductive layer, forming a gradient composite layer with a thickness of 50 nm. The refractive index is 1.9 near the interface transition layer and 1.5 near the hybrid conductive layer.

[0047] 4. Hybrid conductive layer: Silver nanowire dispersion, graphene dispersion and PEDOT:PSS solution were mixed uniformly at a volume ratio of 2:1:1 and coated onto the surface of the gradient refractive index optical adjustment layer using a micro-concave coating method. After drying at 80℃ for 60 min, densification was performed using a femtosecond laser with a wavelength of 532 nm, a power of 50 mW and a scanning speed of 40 mm / s, resulting in a hybrid conductive layer with a thickness of 80 nm. The silver nanowires had a diameter of 20 nm and a length of 10 μm, and the graphene sheet was a single layer of graphene.

[0048] 5. Scratch-resistant and wear-resistant layer: UV-curable resin is coated on the surface of the hybrid conductive layer, and after UV curing, a scratch-resistant and wear-resistant layer with a thickness of 2μm is formed.

[0049] II. Working Principle The composite substrate uses a low proportion of transparent polyamide and polyimide blends to ensure substrate flexibility while focusing on improving structural density. Its thinner thickness is suitable for the requirements of lightweight foldable screens. The interface transition layer employs a low alumina ratio and a thinner design to achieve refractive index transition and interlayer adhesion while minimizing the impact on overall optical performance. The gradient refractive index optical adjustment layer simplifies the fabrication process and reduces light reflection through its thinner thickness and lower refractive index difference. The hybrid conductive layer uses a low proportion of silver nanowires and monolayer graphene composites. The high light transmittance of monolayer graphene and the high conductivity of silver nanowires achieve an efficient balance between light transmission and conductivity. Lower laser power and scanning speed prevent damage to the conductive layer components. The scratch-resistant and abrasion-resistant layer is also thin, ensuring basic scratch resistance while improving the overall flexibility of the film. Through parameter optimization, each layer simplifies the process, reduces thickness, and ensures that core performance standards are met.

[0050] III. Experimental Data The optical conductive film prepared in this embodiment was subjected to performance tests, and the test results are as follows: the tensile strength of the composite substrate is 200 MPa, the elongation at break is 30%, and the glass transition temperature is 280℃; the peel strength between the interface transition layer and the composite substrate and the gradient refractive index optical adjustment layer is greater than 1.2 N / mm; the transmittance of the gradient refractive index optical adjustment layer is 95%; the surface sheet resistance of the hybrid conductive layer is 8 Ω / □, and the visible light transmittance is 94%; the hardness of the scratch-resistant and wear-resistant layer is 4H, and the coefficient of friction is 0.2; after 100,000 folding cycles with a fold radius of 0.3 mm, the surface sheet resistance change rate is 5%, and the transmittance decreases by 2%.

[0051] IV. Technical Effects Through optimized monomer ratios and preparation processes, the composite substrate achieves a balance between basic mechanical strength and flexibility at a relatively thin thickness, meeting the requirements for thinner and lighter foldable screens. Its high-temperature resistance ensures structural stability during subsequent processing. Although the interface transition layer is thin, it still effectively achieves refractive index transition between adjacent layers, enhancing interlayer adhesion and preventing interlayer delamination, without significantly increasing the overall film thickness. The simplified design of the gradient refractive index optical adjustment layer effectively reduces light reflection loss and ensures that light transmittance meets standards. The hybrid conductive layer uses a low-proportion silver nanowire and monolayer graphene composite, which further improves light transmittance while ensuring conductivity meets touch requirements. Optimization of laser densification process parameters avoids damage to conductive layer components and improves conductivity stability. The scratch-resistant and abrasion-resistant layer achieves basic scratch-resistant and abrasion-resistant performance at a relatively thin thickness, while ensuring the overall flexibility of the film, and controlling performance degradation within a reasonable range after folding. The overall solution achieves synergistic compliance of optical, conductive, and mechanical properties while simplifying the process and reducing thickness, meeting the needs of low-cost mass production.

[0052] Example 3 I. Technical Solution The optical conductive film for foldable screens in this embodiment comprises, from bottom to top, a composite substrate, an interface transition layer, a gradient refractive index optical adjustment layer, a hybrid conductive layer, and a scratch-resistant and wear-resistant layer. The specific configuration and fabrication process of each layer are as follows: 1. Composite substrate: It is made by blending and modifying polyimide and transparent polyamide. The polyimide monomer and the transparent polyamide monomer are added to N,N-dimethylacetamide solvent at a mass ratio of 5:1 and stirred and polymerized at 35°C for 4 hours. After casting into a film, it is treated with a three-stage heating thermal imidization process, namely, holding at 120°C for 1 hour, holding at 200°C for 1 hour, and holding at 300°C for 2 hours to obtain a composite substrate with a thickness of 50μm.

[0053] 2. Interface transition layer: Deposited on the surface of the composite substrate using plasma-enhanced chemical vapor deposition. The reaction gases are argon and oxygen, with a volume ratio of 10:1. The deposition power is 120W, the deposition pressure is 1Pa, and the deposition thickness is 3nm. This transition layer is a mixed coating of alumina and silicon oxide, with alumina mass fraction of 80%.

[0054] 3. Gradient refractive index optical adjustment layer: Prepared on the surface of the interface transition layer by electron beam evaporation. The composition ratio of niobium oxide and silicon oxide is gradually adjusted, with a higher proportion of niobium oxide near the interface transition layer and a higher proportion of silicon oxide near the hybrid conductive layer, forming a gradient composite layer with a thickness of 100 nm. The refractive index is 2.1 near the interface transition layer and 1.6 near the hybrid conductive layer.

[0055] 4. Hybrid conductive layer: Silver nanowire dispersion, graphene dispersion and PEDOT:PSS solution were mixed uniformly at a volume ratio of 4:1:1 and coated onto the surface of the gradient refractive index optical adjustment layer using a micro-concave coating method. After drying at 100℃ for 30 min, densification was performed using a femtosecond laser with a wavelength of 532 nm, a power of 80 mW and a scanning speed of 60 mm / s to obtain a hybrid conductive layer with a thickness of 120 nm. The silver nanowires had a diameter of 50 nm and a length of 20 μm, and the graphene sheets were 5 layers of few-layer graphene.

[0056] 5. Scratch-resistant and wear-resistant layer: UV-curable resin is coated on the surface of the hybrid conductive layer, and after UV curing, a scratch-resistant and wear-resistant layer with a thickness of 5μm is formed.

[0057] II. Working Principle The composite substrate is made of a high proportion of polyimide and transparent polyamide blend. The high proportion of polyimide significantly improves the mechanical strength and high-temperature resistance of the substrate, while the thicker thickness further enhances the load-bearing capacity of the substrate, providing a more stable adhesion base for each functional layer. The interface transition layer adopts a high alumina ratio and a thicker design, with its refractive index closer to the high refractive index side of the gradient refractive index optical adjustment layer, enabling a smoother refractive index transition. At the same time, higher deposition power and pressure ensure the structural compactness of the transition layer, further enhancing the interlayer bonding strength. The gradient refractive index optical adjustment layer adopts a thicker design and a larger refractive index difference. Through more precise component gradient, it can minimize light reflection loss and improve light transmission efficiency. The hybrid conductive layer adopts a high proportion of silver nanowires and multilayer graphene composite, which can form a denser conductive network and improve conductivity. Higher laser power and scanning speed can enhance the densification of the conductive layer, improve conductivity stability and interlayer adhesion. The scratch-resistant and wear-resistant layer adopts a thicker design, which can significantly improve the surface scratch resistance and wear resistance, and better protect the internal functional layers during long-term use and repeated folding. Each layer is reinforced to achieve high-performance and stable output of the film under harsh usage scenarios.

[0058] III. Experimental Data The optical conductive film prepared in this embodiment was subjected to performance tests, and the test results are as follows: the tensile strength of the composite substrate is 260 MPa, the elongation at break is 32%, and the glass transition temperature is 320℃; the peel strength between the interface transition layer and the composite substrate and the gradient refractive index optical adjustment layer is greater than 1.8 N / mm; the transmittance of the gradient refractive index optical adjustment layer is 97%; the surface sheet resistance of the hybrid conductive layer is 4 Ω / □, and the visible light transmittance is 92%; the hardness of the scratch-resistant and wear-resistant layer is 5H, and the coefficient of friction is 0.12; after 100,000 folding cycles with a fold radius of 0.3 mm, the surface sheet resistance change rate is 2%, and the transmittance decreases by 0.8%.

[0059] IV. Technical Effects The composite substrate, through the introduction of a high proportion of polyimide and a thicker design, significantly improves mechanical strength and high-temperature resistance, enabling it to withstand more severe folding impacts and processing temperatures, providing stable and reliable substrate support for the internal functional layers. The reinforced design of the interface transition layer achieves precise matching of refractive indices between adjacent layers, minimizing optical loss while significantly enhancing interlayer bonding strength, completely avoiding the risk of interlayer delamination, and improving the overall structural durability of the film. The thick film design and precise compositional gradient of the gradient refractive index optical adjustment layer further reduce light reflection loss, achieving a higher level of light transmission efficiency and ensuring... The foldable screen boasts superior display clarity. A high proportion of silver nanowires in the hybrid conductive layer, combined with multilayer graphene, forms a dense and stable conductive network, significantly enhancing conductivity. Laser densification further strengthens the structural stability and interlayer adhesion of the conductive layer, resulting in minimal fluctuations in conductivity after folding. The thick-film design of the scratch-resistant and abrasion-resistant layer significantly improves surface scratch and abrasion resistance, effectively resisting external damage during long-term use and extending the film's lifespan. The overall solution, through the reinforced design of each layer, achieves higher performance indicators and superior stability, meeting the stringent requirements of high-end foldable screens.

[0060] In summary, the working principle of this invention is as follows: This foldable screen uses a layered synergistic design for its optical conductive film. Through structural adaptation and performance complementarity of each functional layer, it achieves balanced overall performance. The core working logic revolves around the synergistic function of each layer: the composite substrate serves as the base, achieving a balance between mechanical strength and flexibility through the blending and modification of two polymer materials, providing a stable adhesion foundation for subsequent functional layers; the interface transition layer, located between the composite substrate and the gradient refractive index optical adjustment layer, achieves a smooth transition of refractive indices between adjacent layers through specific component design, while enhancing interlayer bonding and preventing delamination; the gradient refractive index optical adjustment layer, through a component gradient design, reduces reflection loss during light propagation between layers, improving overall light transmission efficiency and ensuring smooth light transmission; the hybrid conductive layer employs a multi-component composite design, with each conductive component overlapping to form a continuous conductive path, while the filler component optimizes the uniformity and adhesion stability of the conductive layer, achieving a balance between light transmission and conductivity; the scratch-resistant and abrasion-resistant layer covers the outermost layer, resisting external friction and scratch damage, while also acting as a buffer during folding, maintaining the performance stability of the internal functional layers. Through the coordinated efforts of material selection, structural design, and process optimization, each layer ensures that the film continues to provide stable optical, conductive, and mechanical protection in folded scenarios.

[0061] Instructions for use: The use of this optical conductive film for foldable screens needs to be adapted to the assembly process of the foldable screen. The specific usage method is as follows: First, according to the size and assembly requirements of the foldable screen, cut the prepared optical conductive film to ensure that the size is accurately matched with the display area and touch area of ​​the foldable screen; then, use a special bonding process to bond and fix the composite substrate side of the film to the base plate of the foldable screen. During the bonding process, ensure that there are no air bubbles or misalignment between the layers to ensure a firm bond; after bonding, place the scratch-resistant and wear-resistant layer side of the film outward as the surface protection and touch conduction interface of the foldable screen; after assembly and integration, the film can be repeatedly folded and used with the foldable screen without additional maintenance. Relying on the synergistic effect of its various functional layers, it continuously provides stable optical transmission, touch conductivity and surface protection functions for the foldable screen, adapting to the needs of various scenarios in the daily use of foldable screens.

[0062] In summary, the optical conductive film for foldable screens provided in this embodiment has the following advantages: Through blending modification and process optimization of the composite substrate, the mechanical strength and flexibility of the substrate are effectively improved, ensuring that the film is not easily damaged during repeated folding. It also possesses good high-temperature resistance, adapting to the fabrication process requirements of subsequent functional layers and providing stable support for the overall structure. The design of the interface transition layer eliminates abrupt changes in refractive index between adjacent layers, reducing optical loss and significantly enhancing interlayer bonding strength, improving the overall structural stability of the film and avoiding the risk of interlayer delamination. The gradient refractive index optical adjustment layer's component gradient design effectively reduces light reflection loss between layers, improving overall light transmittance and ensuring the clarity of the foldable screen display. The multi-component composite and densification process of the hybrid conductive layer achieves a balance between high conductivity and high light transmittance. The resulting conductive network is stable and not prone to performance fluctuations due to folding, ensuring touch sensitivity. The scratch-resistant and abrasion-resistant layer enhances the film surface's resistance to damage, reducing scratches and wear during daily use and extending the film's lifespan.

[0063] Overall, through structural adaptation and performance synergy of each functional layer, the film achieves a balanced performance in terms of mechanical, optical, conductive, and protective properties, which can stably meet the usage requirements of foldable screens, taking into account display clarity, touch conductivity, and anti-folding durability. At the same time, some embodiments have achieved lightweight or high-performance enhanced designs through parameter optimization, which can respectively meet the requirements of low-cost mass production or the stringent usage requirements of high-end foldable screens, effectively solving various technical pain points of traditional optical conductive films in foldable screen applications.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. An optically conductive thin film for foldable screens, characterized in that, The material comprises, from bottom to top, a composite substrate, an interface transition layer, a gradient refractive index optical adjustment layer, a hybrid conductive layer, and a scratch-resistant and wear-resistant layer, which are stacked sequentially. The composite substrate is a blended modified layer of polyimide and transparent polyamide. The hybrid conductive layer is formed by combining silver nanowires, graphene sheets, and PEDOT:PSS in a preset ratio. The refractive index of the gradient refractive index optical adjustment layer gradually decreases along the direction away from the composite substrate, and the difference between the refractive index of the gradient refractive index optical adjustment layer and the refractive index of the hybrid conductive layer is not greater than 0.

05.

2. The optical conductive film for foldable screens according to claim 1, characterized in that, The composite substrate has a thickness of 25–50 μm, a tensile strength of not less than 200 MPa, an elongation at break of not less than 30%, and a glass transition temperature of not less than 280 °C.

3. The optical conductive film for foldable screens according to claim 1, characterized in that, The interface transition layer is a mixed coating of alumina and silicon oxide, wherein the mass fraction of alumina is 60% to 80%, and the refractive index of the interface transition layer is 1.65 to 1.

75.

4. The optical conductive film for foldable screens according to claim 1, characterized in that, The gradient refractive index optical adjustment layer is formed by a gradient composite of niobium oxide and silicon oxide. The refractive index is 1.9 to 2.1 on the side near the interface transition layer and 1.5 to 1.6 on the side near the hybrid conductive layer. The transmittance of the gradient refractive index optical adjustment layer is not less than 95%.

5. The optical conductive film for foldable screens according to claim 1, characterized in that, The silver nanowires have a diameter of 20–50 nm and a length of 10–20 μm; the graphene sheets are single-layer or few-layer graphene with no more than 5 layers; the hybrid conductive layer has a thickness of 80–120 nm, a surface sheet resistance of no more than 8 Ω / □, and a visible light transmittance of no less than 92%.

6. The optical conductive film for foldable screens according to claim 1, characterized in that, The thickness of the scratch-resistant and wear-resistant layer is 2-5 μm, the hardness is not less than 4H, the coefficient of friction is not greater than 0.2, and after 100,000 folding cycles with a radius of 0.3 mm, the surface sheet resistance change rate is not greater than 5%, and the light transmittance decreases by not more than 2%.

7. A method for preparing an optically conductive thin film for a foldable screen as described in any one of claims 1-6, characterized in that, Includes the following steps: Step (1), preparation of composite substrate: add polyimide monomer and transparent polyamide monomer to solvent at a mass ratio of 3:1 to 5:1, and polymerize by stirring, cast into film, and heat imidize to obtain composite substrate; Step (2), Deposit interface transition layer: An interface transition layer with a thickness of 1 to 3 nm is deposited on the surface of the composite substrate using plasma-enhanced chemical vapor deposition. Step (3), prepare gradient refractive index optical adjustment layer: use electron beam evaporation method to prepare a gradient refractive index optical adjustment layer with a thickness of 50-100nm on the surface of the interface transition layer by gradually adjusting the component ratio of the evaporation material; Step (4), preparation of hybrid conductive layer: silver nanowire dispersion, graphene dispersion and PEDOT:PSS solution are mixed evenly in volume ratio of 2:1:1 to 4:1:1, and coated on the surface of gradient refractive index optical adjustment layer by micro-concave coating method. After drying and laser densification treatment, hybrid conductive layer is obtained. Step (5), prepare the scratch-resistant and wear-resistant layer: coat the surface of the hybrid conductive layer with UV-curable resin, and then cure it with UV to obtain the optical conductive film for foldable screen.

8. The method for preparing an optically conductive thin film for a foldable screen according to claim 7, characterized in that, In step (1), the solvent is N,N-dimethylacetamide, the stirring polymerization temperature is 25-35℃, and the stirring polymerization time is 4-6h; the thermal imidization treatment adopts a three-stage heating process, the first stage is heated to 120℃ and held for 1h, the second stage is heated to 200℃ and held for 1h, and the third stage is heated to 300℃ and held for 2h.

9. The method for preparing an optically conductive thin film for a foldable screen according to claim 7, characterized in that, In step (2), the reaction gas of plasma-enhanced chemical vapor deposition is a mixture of argon and oxygen, with a volume ratio of argon to oxygen of 9:1 to 10:1, a deposition power of 80 to 120 W, and a deposition pressure of 0.5 to 1 Pa.

10. The method for preparing an optically conductive thin film for a foldable screen according to claim 7, characterized in that, In step (4), the laser densification process uses a femtosecond laser with a wavelength of 532nm, a laser power of 50-80mW, and a scanning speed of 40-60mm / s; the drying temperature is 80-100℃ and the drying time is 30-60min.

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