Flexible enhanced TFT alkali-free glass substrate and preparation method thereof

Abstract

The invention discloses a flexible enhanced TFT alkali-free glass substrate and a preparation method thereof, and belongs to the technical field of alkali-free glass substrates. Through the structural design of the organic-inorganic hybrid fiber reinforced layer and the gradient modulus transition layer, the bending resistance is remarkably improved while the high light transmittance is kept, and a low-temperature manufacturing process is adapted; the surface resistivity of the Al2O3 thin film prepared through atomic layer deposition is smaller than 109 omega.m, electrostatic adsorption is effectively restrained, and meanwhile the Al2O3 thin film serves as an insulating layer of the follow-up TFT manufacturing process. Therefore, the alkali-free glass substrate disclosed by the invention can meet higher requirements of the flexible display device on bendability, stability and integration.

Description

Technical Field

[0001] The present invention relates to the technical field of alkali-free glass substrates, and in particular to a flexible enhanced TFT alkali-free glass substrate and a preparation method thereof. Background Art

[0002] The rapid development of flexible display technology is placing higher demands on the flexibility, foldability, and reliability of display devices. Traditional TFT (thin-film transistor) alkali-free glass substrates, while renowned for their superior optical properties (high transmittance) and outstanding chemical stability, are insufficient for flexible display applications. The fundamental reason lies in the inherent brittleness of glass, which results in poor bending resistance. Typically, its safe bending radius exceeds 100mm, which falls far short of the demanding substrate bendability requirements of flexible display devices.

[0003] To overcome this defect of traditional glass substrates, researchers have explored a variety of enhancement technologies, mainly including surface strengthening and composite layer lamination. However, these technologies still have some difficult to solve problems in practical applications:

[0004] 1. Limitations of strengthening process:

[0005] Disadvantages of chemical tempering: While the widely used chemical tempering technology can improve glass strength to a certain extent, it has significant limitations. The chemical tempering process requires ion exchange at temperatures exceeding 400°C, which can easily cause thermal deformation of the glass substrate, affecting its dimensional accuracy and surface flatness. More importantly, chemical tempering technology struggles to achieve uniform strengthening of edge regions, leaving them relatively fragile and prone to stress concentration and fracture.

[0006] Disadvantages of edge chamfering technology: Although edge chamfering technology can reduce edge stress concentration and improve impact resistance, it has limited effect on improving overall bending resistance.

[0007] 2. Defects of composite layer bonding:

[0008] Thermal expansion coefficient mismatch problem: In order to improve the flexibility of the substrate, another common method is to composite the glass substrate with flexible materials (such as polyimide). However, there is a large difference in thermal expansion coefficient between glass and organic materials such as polyimide (usually greater than 5×10 -6 / ℃), in a temperature-changing environment, this mismatch will lead to thermal stress, which can easily cause interface peeling, blistering and other problems during long-term use, seriously affecting the stability and life of the display device.

[0009] Interface bonding strength issues: The interface bonding strength between different materials is also a challenge, which requires special adhesives and processes to ensure, which increases process complexity and cost.

[0010] 3. Deficiencies in functional integration:

[0011] Lack of integrated structural design: Existing enhancement technologies mostly focus on improving the mechanical strength of the substrate, while ignoring the special electrical performance requirements of flexible displays. For example, flexible displays require the substrate to have good electrical insulation to prevent current leakage and short circuits. However, the current lack of an integrated structural design that can simultaneously enhance flexibility and electrical insulation has limited the performance improvement and miniaturization of flexible displays.

[0012] In summary, traditional TFT alkali-free glass substrate enhancement technology is insufficient when facing the challenges of flexible display technology. To promote the further development of flexible display technology, it is urgent to develop new material systems and structural designs to meet the higher requirements of flexible display devices for bendability, stability and integration. Summary of the Invention

[0013] The technical problem to be solved by the present invention is: to overcome the shortcomings of the existing technology and provide a flexible reinforced TFT alkali-free glass substrate and a preparation method thereof. Through the design of an organic-inorganic hybrid fiber reinforcement layer and a gradient modulus transition layer structure, the bending resistance is significantly improved while maintaining high transmittance, and it is adapted to low-temperature process technology.

[0014] The technical solution of the present invention is:

[0015] In one aspect, the present invention provides a method for preparing a flexible enhanced TFT alkali-free glass substrate, comprising the following steps:

[0016] S1 has zirconia-polyimide hybrid fibers embedded in the alkali-free glass substrate;

[0017] S2 prepared a TiO2 / SiO2 gradient film on the surface of an alkali-free glass substrate by magnetron sputtering, and the TiO2 content in the TiO2 / SiO2 gradient film gradually decreased from the glass side to the air side;

[0018] S3 uses atomic layer deposition (ALD) to deposit an Al2O3 film on the TiO2 / SiO2 gradient film layer.

[0019] Preferably, in step S1, the alkali-free glass substrate comprises the following components by mass percentage: SiO2: 59-63.5%, Al2O3: 14-18%, B2O3: 9.5-12.5%, CaO: 4.5-7%, MgO: 1.3-1.8%, SrO: 0.5-2%, SnO2: 0.1-0.2%. The elastic modulus is controlled at 68-72 GPa, and the coefficient of thermal expansion (CTE) is ≤3.5×10 -6 / ℃, providing basic toughness for flexibility enhancement.

[0020] Preferably, in step S1 , the thickness of the zirconia-polyimide hybrid fiber is 10-15% of the thickness of the alkali-free glass substrate.

[0021] Preferably, step S1 includes the following steps:

[0022] S11 Preparation of Zirconia-Polyimide Hybrid Fiber

[0023] (1) Zirconium oxide core: Add a dispersant to the zirconium oxychloride solution (to avoid agglomeration), adjust the pH to 8-10 after hydrolysis, centrifuge, wash and dry to obtain zirconium oxide nanoparticles;

[0024] (2) Polyimide shell: Zirconia nanoparticles are dispersed in N,N-dimethylformamide (DMF), and pyromellitic dianhydride and 4,4'-diaminodiphenyl ether are added to react to form a fiber precursor solution with a core-shell structure;

[0025] (3) Spinning: The fiber precursor solution is electrospun to form a hybrid fiber membrane;

[0026] S12 glass substrate composite molding

[0027] 1) Melting: The alkali-free glass substrate raw material is melted at 1500-1550℃. During the glass liquid drawing process, the hybrid fiber membrane is synchronously rolled and embedded (temperature ≤ 1100℃) to avoid high temperature damage to the polyimide structure;

[0028] 2) Annealing: Annealing is performed at 650-680°C to eliminate the fiber-glass interface stress.

[0029] Zirconia core (rigid support): Zirconia nanoparticles have a high elastic modulus and provide bending rigidity as the fiber core, inhibiting crack propagation when the glass substrate is bent.

[0030] Polyimide shell (flexible connection): The polyimide shell forms a covalent bond with the glass surface (SiO2 matrix) through Si-OC chemical bonds. Its flexible chain segments can absorb bending stress while reducing the modulus difference between the fiber and the glass, avoiding interfacial stress concentration.

[0031] Preferably, in step (1), the concentration of the zirconium oxychloride solution is 0.05-0.3M; the dispersant is PEG-2000 with a concentration of 0.3-0.7wt.%; the hydrolysis temperature is 60-70°C; the centrifugal speed is 6000-10000 rpm, and the centrifugation time is 5-15 min; the drying temperature is 60-70°C, and the drying time is 8-16 h; and the particle size of the zirconium oxide nanoparticles is 45-65 nm.

[0032] Preferably, in step (2), the molar ratio of pyromellitic dianhydride to 4,4'-diaminodiphenyl ether is 1:1; the reaction temperature is 100-140°C, and the reaction time is 3-5h; the concentration of the fiber precursor solution is 0.2-0.3M; the mass ratio of zirconium oxide nanoparticles to pyromellitic dianhydride is 1:(0.05-0.15), and the thickness of the polyimide shell is 10-20nm.

[0033] Preferably, in step (3), the electrospinning voltage is 10-20 kV, the receiving distance is 10-20 cm, the flow rate is 0.3-0.7 mL / h, and the aluminum foil rotation speed of the aluminum foil receiving electrode is 40-60 rpm; the fiber diameter of the hybrid fiber membrane is 50-100 nm, and the aspect ratio is 50-100.

[0034] Aspect ratio effect: The fiber aspect ratio is 50-100, forming a "bridging effect". When the glass substrate bends, the fiber transfers the load by bridging the two sides of the crack, thereby improving fatigue resistance.

[0035] Preferably, the specific operation of step S2 is: using TiO2 and SiO2 targets, alternately depositing by magnetron sputtering and linearly changing the power ratio of TiO2 to SiO2 from 8:2 to 2:8, the argon flow rate is 40-60sccm, and the deposition rate is 0.5-1.5nm / s; the thickness of the TiO2 / SiO2 gradient film layer is 200-500nm. From the glass side to the air side, the TiO2 content gradually decreases from 80% to 20%, forming a modulus gradient that matches the substrate glass modulus (68-72GPa). The difference in modulus between traditional single-layer films (such as pure TiO2) and glass is too large, which easily forms stress concentration. The gradient structure of the gradient modulus transition layer of the present invention gradually releases stress along the thickness direction, reduces the interface shear stress, and eliminates interface stress concentration.

[0036] Preferably, the specific operation of step S3 is: using trimethylaluminum (TMA) and water vapor as precursors, depositing Al2O3 by atomic layer deposition at 100-200°C, and cycling until the thickness of the Al2O3 film is 50-100nm. The surface resistivity of the Al2O3 film is less than 10 9Ω·m, effectively suppressing electrostatic adsorption and serving as an insulating layer in subsequent TFT manufacturing processes. Furthermore, the low temperature used in the atomic layer deposition process to prepare the Al2O3 antistatic protective layer prevents high temperatures (>300°C) from damaging organic materials in TFT devices (such as insulating layers and electrodes).

[0037] On the other hand, the present invention provides a flexible enhanced TFT alkali-free glass substrate, which is prepared by the above-mentioned method for preparing the flexible enhanced TFT alkali-free glass substrate.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention adopts the design of organic-inorganic hybrid fiber reinforcement layer and gradient modulus transition layer structure to significantly improve the bending resistance while maintaining high light transmittance, and is suitable for low-temperature process technology. The alkali-free glass substrate of the present invention has significantly improved flexibility: the bending radius can be reduced to below 50mm (conventional substrate>100mm), and the bending fatigue resistance is>10 5 times (under 100mm bending radius), meeting the bending requirements of flexible display devices. Interface compatibility optimization: the zirconia core of the hybrid fiber is chemically matched with the glass matrix (CTE difference <

[0040] 1×10 -6 / ℃), the polyimide shell is bonded to the glass surface through a chemical bond (Si-OC), and the interface peel strength is >50N / cm. The Al2O3 film prepared by atomic layer deposition has a surface resistivity of <10 9 Ω·m, effectively suppressing electrostatic adsorption and serving as an insulating layer in subsequent TFT processes. Therefore, the alkali-free glass substrate of the present invention can meet the higher requirements of flexible display devices for bendability, stability, and integration. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0042] Example 1

[0043] The method for preparing the flexible enhanced TFT alkali-free glass substrate of this embodiment comprises the following steps:

[0044] S1 has zirconia-polyimide hybrid fibers embedded in the alkali-free glass substrate

[0045] S11 Preparation of Zirconia-Polyimide Hybrid Fiber

[0046] (1) Zirconia core: Prepare 500 mL of 0.1 M zirconium oxychloride solution, add 0.5 wt.% PEG-2000 dispersant, and stir in a 60°C water bath for 30 min. After hydrolysis, add ammonia water dropwise to adjust the pH to 9 to generate a white precipitate. Centrifuge at 8000 rpm for 10 min, wash three times with deionized water, and dry in a vacuum at 60°C for 12 h to obtain zirconium oxide nanoparticles with a particle size of 50 nm.

[0047] (2) Polyimide shell: 10 g of zirconium oxide nanoparticles were dispersed in 500 mL of DMF and ultrasonicated for 30 min. 0.005 mol of pyromellitic dianhydride and 0.005 mol of 4,4'-diaminodiphenyl ether were added and stirred in an oil bath at 120 °C for 4 h to react and form a core-shell structured fiber precursor solution (shell thickness 15 nm).

[0048] (3) Spinning: 0.2 M fiber precursor solution was injected into the syringe at a voltage of 15 kV, a receiving distance of 15 cm, a flow rate of 0.5 mL / h, and an aluminum foil rotation speed of 50 rpm to collect the hybrid fiber membrane (fiber diameter 80 nm, aspect ratio 80).

[0049] S12 glass substrate composite molding

[0050] 1) Melting: The alkali-free glass substrate comprises the following components by weight: SiO2: 61%, Al2O3: 18%, B2O3: 12.5%, CaO: 5.5%, MgO: 1.5%, SrO: 1.3%, and SnO2: 0.2%. The alkali-free glass substrate is melted at 1520°C. During the glass drawing process, the hybrid fiber membrane (thickness 12% of the alkali-free glass substrate) is simultaneously embedded using a roller pressing device at 1050°C.

[0051] 2) Annealing: Annealing is performed at 660°C at a cooling rate of 2°C / min to eliminate the fiber-glass interface stress.

[0052] S2 preparation of gradient modulus transition layer

[0053] TiO2 / SiO2 gradient films were prepared on the surface of alkali-free glass substrates by magnetron sputtering, and the TiO2 content in the TiO2 / SiO2 gradient films gradually decreased from the glass side to the air side.

[0054] Using TiO2 and SiO2 targets, alternating deposition was performed by magnetron sputtering, and the power ratio of TiO2 to SiO2 was adjusted from 8:2 to 2:8 at an average rate. The argon flow rate was 50 sccm and the deposition rate was 1 nm / s. The thickness of the TiO2 / SiO2 gradient film layer was 300 nm.

[0055] S3 preparation of antistatic protective layer

[0056] Al2O3 was deposited by atomic layer deposition at 150°C using TMA and water vapor as precursors until the thickness of the Al2O3 film reached 75 nm and the surface resistivity was 8×10 8 Ω·m.

[0057] The performance test of the alkali-free glass substrate prepared in this embodiment was carried out, and the test method and test results are as follows:

[0058] Bending radius: 45mm (three-point bending method, tested in accordance with ASTM C1584).

[0059] Bending fatigue resistance times: 1.2×10 5 times (100mm radius, 1Hz).

[0060] Interfacial peel strength: 60N / cm (tested according to ASTM D3330).

[0061] Thermal stability: CTE = 3.2 × 10 -6 / ℃.

[0062] Example 2

[0063] The difference from Example 1 is that: in step (1), the concentration of the zirconium oxychloride solution is 0.3M; in step (2), the amounts of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether are 0.006 mol respectively, and the shell thickness of the core-shell structure fiber precursor solution formed is 20 nm; in step (3), the flow rate is 0.6 mL / h, the concentration of the fiber precursor solution is increased to 0.3 M, and the aspect ratio of the hybrid fiber membrane is 90; in step 1), the alkali-free glass substrate includes the following components in mass percentage: SiO2: 60%, Al2O3: 18%, B2O3: 12%, CaO: 6.5%, MgO: 1.5%, SrO: 1.8%, SnO2: 0.2%, the melting temperature is 1530°C, and the hybrid fiber membrane is synchronously embedded by a rolling device at 1080°C during the glass liquid drawing process.

[0064] The performance of the alkali-free glass substrate prepared in this embodiment was tested, and the test results are as follows:

[0065] Bending radius: 42mm.

[0066] Bending fatigue resistance times: 1.3×10 5 Second-rate.

[0067] Interfacial peel strength: 65N / cm.

[0068] Thermal stability: CTE = 3.1 × 10 -6 / ℃.

[0069] Compared with Example 1, Example 2 increases the volume fraction of the hybrid fiber to 18%, so that the fiber forms a denser three-dimensional network dispersion structure in the substrate glass, thereby enhancing the load transfer efficiency. The monomer concentration in the fiber precursor solution (i.e., the total molar concentration of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether) is increased to 0.3M, and the shell thickness is increased to 20nm, further enhancing the chemical bond strength between the polyimide shell and the glass surface, thereby improving the interfacial peeling strength and bending fatigue resistance. The fiber aspect ratio of the hybrid fiber membrane is increased to 90, and the "bridging effect" is more significant, effectively inhibiting crack propagation and reducing the bending radius.

[0070] Example 3

[0071] The difference from Example 1 is that in step S2, the deposition rate is 1.2 nm / s, and the thickness of the TiO2 / SiO2 gradient film layer is controlled to be 500 nm, so that the rate of change of the power ratio is slowed down.

[0072] The performance of the alkali-free glass substrate prepared in this embodiment was tested, and the test results are as follows:

[0073] Bending radius: 40mm.

[0074] Bending fatigue resistance times: 1.4×10 5 Second-rate.

[0075] Interfacial peel strength: 62N / cm.

[0076] Thermal stability: CTE = 3.3 × 10 -6 / ℃.

[0077] Compared to Example 1, the total thickness of the gradient modulus transition layer in Example 3 was increased to 500 nm, and the rate of change in power ratio was slowed, resulting in a smoother gradient change in TiO2 content from 80% to 20% and a more uniform transition in modulus reduction. This further reduced interfacial shear stress and effectively eliminated stress concentration, thereby improving flexural fatigue resistance and bending radius. The interfacial peel strength decreased slightly, likely due to the increased thickness of the gradient modulus transition layer, which had some impact on the fiber-glass interface during the preparation process, but it still remained at a high level.

[0078] Example 4

[0079] The method for preparing the flexible enhanced TFT alkali-free glass substrate of this embodiment comprises the following steps:

[0080] S1 has zirconia-polyimide hybrid fibers embedded in the alkali-free glass substrate

[0081] S11 Preparation of Zirconia-Polyimide Hybrid Fiber

[0082] (1) Zirconium oxide core: Prepare 500 mL of 0.05 M zirconium oxychloride solution, add 0.3 wt.% PEG-2000 dispersant, and stir in a 60°C water bath for 30 min. After hydrolysis, add ammonia water dropwise to adjust the pH to 9 to generate a white precipitate. Centrifuge at 6000 rpm for 15 min, wash three times with deionized water, and dry in a vacuum at 60°C for 12 h to obtain zirconium oxide nanoparticles with a particle size of 45 nm.

[0083] (2) Polyimide shell: 10 g of zirconium oxide nanoparticles were dispersed in 500 mL of DMF and ultrasonicated for 30 min. 0.0037 mol of pyromellitic dianhydride and 0.0037 mol of 4,4'-diaminodiphenyl ether were added and stirred in an oil bath at 120 °C for 4 h to react and form a core-shell structured fiber precursor solution (shell thickness 15 nm).

[0084] (3) Spinning: 0.2 M fiber precursor solution was injected into the syringe at a voltage of 10 kV, a receiving distance of 10 cm, a flow rate of 0.3 mL / h, and an aluminum foil rotation speed of 40 rpm to collect the hybrid fiber membrane (fiber diameter 50 nm, aspect ratio 50).

[0085] S12 glass substrate composite molding

[0086] 1) Melting: The alkali-free glass substrate comprises the following components by weight: SiO2: 59%, Al2O3: 18%, B2O3: 12%, CaO: 7%, MgO: 1.8%, SrO: 2%, and SnO2: 0.2%. The alkali-free glass substrate is melted at 1520°C. During the glass drawing process, the hybrid fiber membrane (thickness 15% of the alkali-free glass substrate) is simultaneously embedded using a roller pressing device at 1050°C.

[0087] 2) Annealing: Annealing is performed at 650°C at a cooling rate of 1°C / min to eliminate the fiber-glass interface stress.

[0088] S2 preparation of gradient modulus transition layer

[0089] TiO2 / SiO2 gradient films were prepared on the surface of alkali-free glass substrates by magnetron sputtering, and the TiO2 content in the TiO2 / SiO2 gradient films gradually decreased from the glass side to the air side.

[0090] Using TiO2 and SiO2 targets, alternating deposition was performed by magnetron sputtering, and the power ratio of TiO2 to SiO2 was uniformly adjusted from 8:2 to 2:8, the argon flow rate was 50 sccm, and the deposition rate was 0.5 nm / s; the thickness of the TiO2 / SiO2 gradient film layer was 200 nm.

[0091] S3 preparation of antistatic protective layer

[0092] Al2O3 was deposited by atomic layer deposition at 100°C using TMA and water vapor as precursors, and the thickness of the Al2O3 film was 50 nm and the surface resistivity was 8×10 8 Ω·m.

[0093] The performance of the alkali-free glass substrate prepared in this embodiment was tested, and the test results are as follows:

[0094] Bending radius: 50mm.

[0095] Bending fatigue resistance times: 8×10 4 times (100mm radius, 1Hz).

[0096] Interfacial peel strength: 50N / cm.

[0097] Thermal stability: CTE = 3.5 × 10 -6 / ℃.

[0098] Example 5

[0099] The method for preparing the flexible enhanced TFT alkali-free glass substrate of this embodiment comprises the following steps:

[0100] S1 has zirconia-polyimide hybrid fibers embedded in the alkali-free glass substrate

[0101] S11 Preparation of Zirconia-Polyimide Hybrid Fiber

[0102] (1) Zirconia core: Prepare 500 mL of 0.2 M zirconium oxychloride solution, add 0.7 wt.% PEG-2000 dispersant, and stir in a 60°C water bath for 30 min. After hydrolysis, add ammonia water dropwise to adjust the pH to 9 to generate a white precipitate. Centrifuge at 10,000 rpm for 5 min, wash three times with deionized water, and dry in a vacuum at 60°C for 12 h to obtain zirconium oxide nanoparticles with a particle size of 65 nm.

[0103] (2) Polyimide shell: 10 g of zirconium oxide nanoparticles were dispersed in 500 mL of DMF and ultrasonicated for 30 min. 0.0068 mol of pyromellitic dianhydride and 0.0068 mol of 4,4'-diaminodiphenyl ether were added and stirred in an oil bath at 120 °C for 4 h to form a core-shell structured fiber precursor solution (shell thickness 20 nm).

[0104] (3) Spinning: 0.3 M fiber precursor solution was injected into a syringe at a voltage of 20 kV, a receiving distance of 20 cm, a flow rate of 0.7 mL / h, and an aluminum foil rotation speed of 60 rpm to collect the hybrid fiber membrane (fiber diameter 100 nm, aspect ratio 100).

[0105] S12 glass substrate composite molding

[0106] 1) Melting: The alkali-free glass substrate comprises the following components by weight: SiO2: 63.5%, Al2O3: 18%, B2O3: 10.5%, CaO: 4.5%, MgO: 1.4%, SrO: 2%, and SnO2: 0.1%. The alkali-free glass substrate is melted at 1550°C. During the glass drawing process, the hybrid fiber membrane (thickness 10% of the alkali-free glass substrate) is simultaneously embedded using a roller pressing device at 1000°C.

[0107] 2) Annealing: Annealing is performed at 680°C at a cooling rate of 3°C / min to eliminate the fiber-glass interface stress.

[0108] S2 preparation of gradient modulus transition layer

[0109] TiO2 / SiO2 gradient films were prepared on the surface of alkali-free glass substrates by magnetron sputtering, and the TiO2 content in the TiO2 / SiO2 gradient films gradually decreased from the glass side to the air side.

[0110] Using TiO2 and SiO2 targets, alternating deposition was performed by magnetron sputtering, and the power ratio of TiO2 to SiO2 was uniformly adjusted from 8:2 to 2:8, the argon flow rate was 50 sccm, and the deposition rate was 1.5 nm / s; the thickness of the TiO2 / SiO2 gradient film layer was 500 nm.

[0111] S3 preparation of antistatic protective layer

[0112] Al2O3 was deposited by atomic layer deposition at 200℃ using TMA and water vapor as precursors. The thickness of the Al2O3 film was 100nm and the surface resistivity was 7×10 8 Ω·m.

[0113] The performance of the alkali-free glass substrate prepared in this embodiment was tested, and the test results are as follows:

[0114] Bending radius: 38mm.

[0115] Bending fatigue resistance times: 1.5×10 5 times (100mm radius, 1Hz).

[0116] Interface peel strength: 70N / cm.

[0117] Thermal stability: CTE = 3 × 10 -6 / ℃.

[0118] Comparative Example 1

[0119] The difference from Example 1 is that the zirconia-polyimide hybrid fiber is not embedded in the alkali-free glass substrate.

[0120] The performance test of the alkali-free glass substrate prepared in Comparative Example 1 was carried out, and the test results are as follows:

[0121] Bending radius: 120mm.

[0122] Bending fatigue resistance times: 3×10 4 Second-rate.

[0123] Interfacial peel strength: 18N / cm.

[0124] Thermal stability: CTE = 3.2 × 10 -6 / ℃.

[0125] By comparing Example 1 with Comparative Example 1, it can be seen that since Comparative Example 1 does not embed zirconia-polyimide hybrid fibers inside the alkali-free glass substrate, the base glass lacks the synergistic effect of rigid support and flexible connection, and cannot effectively inhibit crack propagation and absorb bending stress, resulting in an increase in the bending radius and a significant reduction in the number of bending fatigue resistance times; at the same time, relying only on the gradient modulus transition layer and the antistatic protective layer, the interface bonding force is weak and the interface peeling strength is low.

[0126] Comparative Example 2

[0127] The difference from Example 1 is that the zirconia-polyimide hybrid fiber is not embedded in the alkali-free glass substrate, the glass is annealed and then immersed in KNO3 molten salt at 450°C for 2 hours for chemical tempering; and no gradient modulus transition layer is prepared.

[0128] The performance test of the alkali-free glass substrate prepared in Comparative Example 2 was carried out, and the test results are as follows:

[0129] Bending radius: 110mm.

[0130] Bending fatigue resistance times: 4×10 4 Second-rate.

[0131] Interfacial peel strength: 16N / cm.

[0132] Thermal stability: CTE = 3.5 × 10 -6 / ℃ (Due to high temperature treatment, the glass is slightly deformed and the thermal expansion coefficient increases slightly).

[0133] Comparative Example 2 employed traditional chemical tempering on the glass substrate. While this improved the glass's surface strength to a certain extent, the high temperature (450°C) treatment easily led to thermal deformation of the glass substrate and poor strengthening uniformity at the edges. Without the bridging effect of hybrid fibers and the stress transition of the gradient modulus transition layer, the glass substrate's brittleness and insufficient bending resistance could not be effectively addressed. The bending radius and bending fatigue resistance were significantly lower than those in Example 1. Furthermore, the lack of chemical bonding between the polyimide shell and the glass in Comparative Example 2 resulted in low interfacial peel strength.

[0134] Comparative Example 3

[0135] The difference from Example 1 is that the gradient modulus transition layer in Example 1 is replaced by a pure TiO2 film (thickness 300 nm).

[0136] The performance test of the alkali-free glass substrate prepared in Comparative Example 3 was carried out, and the test results are as follows:

[0137] Bending radius: 60mm.

[0138] Bending fatigue resistance times: 8×10 4 Second-rate.

[0139] Interface peel strength: 30N / cm.

[0140] Thermal stability: CTE = 3.2 × 10 -6 / ℃.

[0141] While the hybrid fiber provides some bending stiffness and stress absorption for the alkali-free glass substrate in Comparative Example 3, the significant difference in modulus between the single-layer TiO2 film (120 GPa) and the underlying glass (68-72 GPa) leads to stress concentration, resulting in high interfacial shear stress and thus impacting bending fatigue resistance and bending radius. While the interfacial peel strength improves compared to Comparative Examples 1-2, this is due to the chemical bonding between the hybrid fiber's polyimide shell and the glass surface. However, the lack of a gradient modulus transition layer effectively addresses the interfacial stress concentration issue, limiting performance improvements.

[0142] Comparative Example 4

[0143] The difference from Example 1 is that the Al2O3 film is not deposited on the alkali-free glass substrate.

[0144] The performance test of the alkali-free glass substrate prepared in Comparative Example 4 was carried out, and the test results are as follows:

[0145] Bending radius: 45mm.

[0146] Bending fatigue resistance times: 1.1×10 5 Second-rate.

[0147] Interface peel strength: 60N / cm.

[0148] Thermal stability: CTE = 3.2 × 10 -6 / ℃.

[0149] Comparative Example 4 did not deposit an Al2O3 film, resulting in the following performance changes: 1) Loss of electrostatic suppression ability: The surface resistivity of the Al2O3 film was less than 10 9Ω·m, which can effectively conduct away electrostatic charges, avoid dust adsorption and device interference. The absence of this layer will cause static electricity accumulation on the surface of the substrate, affecting the stability and yield of the display device. 2) Loss of insulating layer function: The Al2O3 film serves as an insulating layer in the TFT process, isolating the electrode from the glass substrate. Its absence may lead to increased leakage current and decreased device performance. 3) Weakened auxiliary effect of interface stress: Although the main function of the Al2O3 film is electrical performance, the density of atomic layer deposition may play a certain protective role for the gradient film layer. Its absence may indirectly affect the long-term stability of the overall structure. The absence of the Al2O3 film causes the substrate to lose its antistatic and insulating functions, and may also affect the structural integrity. Therefore, the performance is significantly reduced in the actual application of flexible display devices.

Claims

1. A method for preparing a flexible enhanced TFT alkali-free glass substrate, characterized in that: The following steps are involved: S1 has zirconia-polyimide hybrid fibers embedded in the alkali-free glass substrate; S2 prepared a TiO2 / SiO2 gradient film on the surface of an alkali-free glass substrate by magnetron sputtering, and the TiO2 content in the TiO2 / SiO2 gradient film gradually decreased from the glass side to the air side; S3 uses atomic layer deposition to deposit an Al2O3 film on the TiO2 / SiO2 gradient film layer.

2. The method for preparing a flexible enhanced TFT alkali-free glass substrate according to claim 1, wherein: In step S1, the alkali-free glass substrate includes the following components in mass percentage: SiO2: 59-63.5%, Al2O3: 14-18%, B2O3: 9.5-12.5%, CaO: 4.5-7%, MgO: 1.3-1.8%, SrO: 0.5-2%, and SnO2: 0.1-0.2%.

3. The method for preparing a flexible enhanced TFT alkali-free glass substrate according to claim 1, wherein: In step S1 , the thickness of the zirconia-polyimide hybrid fiber is 10-15% of the thickness of the alkali-free glass substrate.

4. The method for preparing a flexible enhanced TFT alkali-free glass substrate according to any one of claims 1 to 3, wherein: Step S1 includes the following steps: S11 Preparation of Zirconia-Polyimide Hybrid Fiber (1) Zirconium oxide core: a dispersant is added to a zirconium oxychloride solution, the solution is hydrolyzed and the pH is adjusted to 8-10, the solution is centrifuged, washed, and dried to obtain zirconium oxide nanoparticles; (2) Polyimide shell: Zirconia nanoparticles are dispersed in N,N-dimethylformamide, and pyromellitic dianhydride and 4,4'-diaminodiphenyl ether are added to react to form a fiber precursor solution with a core-shell structure; (3) Spinning: The fiber precursor solution is electrospun to form a hybrid fiber membrane; S12 glass substrate composite molding 1) Melting: The alkali-free glass substrate raw material is melted at 1500-1550°C, and the hybrid fiber membrane is synchronously rolled and embedded in the glass liquid during the glass liquid drawing process; 2) Annealing: Annealing is performed at 650-680°C.

5. The method for preparing a flexible enhanced TFT alkali-free glass substrate according to claim 4, wherein: In step (1), the concentration of the zirconium oxychloride solution is 0.05-0.3M; the dispersant is PEG-2000 with a concentration of 0.3-0.7wt.%; the hydrolysis temperature is 60-70°C; the centrifugal speed is 6000-10000 rpm, and the centrifugation time is 5-15 minutes; the drying temperature is 60-70°C, and the drying time is 8-16 hours; and the particle size of the zirconium oxide nanoparticles is 45-65 nm.

6. The method for preparing a flexible enhanced TFT alkali-free glass substrate according to claim 4, wherein: In step (2), the molar ratio of pyromellitic dianhydride to 4,4'-diaminodiphenyl ether is 1:1; the reaction temperature is 100-140°C, and the reaction time is 3-5h; the concentration of the fiber precursor solution is 0.2-0.3M; the mass ratio of zirconium oxide nanoparticles to pyromellitic dianhydride is 1:(0.05-0.15), and the thickness of the polyimide shell is 10-20nm.

7. The method for preparing a flexible enhanced TFT alkali-free glass substrate according to claim 4, wherein: In step (3), the electrospinning voltage is 10-20 kV, the receiving distance is 10-20 cm, the flow rate is 0.3-0.7 mL / h, and the aluminum foil rotation speed of the aluminum foil receiving electrode is 40-60 rpm; the fiber diameter of the hybrid fiber membrane is 50-100 nm, and the aspect ratio is 50-100.

8. The method for preparing a flexible enhanced TFT alkali-free glass substrate according to claim 1, wherein: The specific operation of step S2 is: using TiO2 and SiO2 targets, alternately depositing by magnetron sputtering, with the power ratio of TiO2 to SiO2 linearly changing from 8:2 to 2:8, the argon flow rate being 40-60 sccm, and the deposition rate being 0.5-1.5 nm / s; The thickness of the TiO2 / SiO2 gradient film layer is 200-500nm.

9. The method for preparing a flexible enhanced TFT alkali-free glass substrate according to claim 1, wherein: The specific operation of step S3 is: using trimethylaluminum and water vapor as precursors, depositing Al2O3 by atomic layer deposition at 100-200°C, and cycling until the thickness of the Al2O3 film is 50-100nm.

10. A flexible enhanced TFT alkali-free glass substrate, characterized in that: The flexible enhanced TFT alkali-free glass substrate is prepared by the preparation method of any one of claims 1 to 9.