Flexible glass protection sticker for folding screen and preparation process thereof

Abstract

The present application belongs to the technical field of flexible glass protection stickers, and particularly relates to a flexible glass protection sticker for a foldable screen and a preparation process thereof. The present application adjusts the layered structure of the protection sticker, uses modified UV glue solution to prepare a UV type acrylic polymer film layer, and matches an acrylic foldable OCA layer, thereby effectively solving the problem of poor bending resistance of the existing foldable screen protection sticker. The synergistic effect of the components enables the protection sticker to have excellent bending resistance and high optical transmittance, thereby meeting the long-term use requirements of the foldable screen.

Description

Technical Field

[0001] This invention belongs to the field of flexible glass protective film technology, specifically relating to a flexible glass protective film for foldable screens and its preparation process. Background Technology

[0002] With the rapid iteration of flexible display technology, foldable screen terminal devices, with their advantages of being foldable, highly portable, and allowing for flexible adjustment of display area, are being applied in fields such as smartphones, tablets, and wearable devices, becoming an important development direction for the display industry. Correspondingly, the performance requirements and structure of display screen protective films also need to be upgraded.

[0003] Display screen protectors have evolved from single-layer PET films to TPU films, and then to TPU / PET multilayer composite films. However, when these protective films are applied to curved screens, foldable screens, and flexible displays, they still have performance defects such as being prone to creases, having high hardness, and insufficient adhesion, which affect the user experience of electronic devices.

[0004] Chinese patent application CN117363226A discloses a high-adhesion flexible optical protective film, which enhances the adhesion of curved screens by forming a curing shrinkage gradient through two polyurethane acrylate layers with different functionalities, thus solving the problem of poor adhesion of traditional protective films. However, this solution has the following shortcomings: (1) This application mainly optimizes the adhesion problem of static curved screens and does not verify it for the long-term repeated bending scenario of flexible screens. Although its polyester substrate layer is a double-layer structure, stress concentration is easily generated between the two layers due to the difference in modulus during long-term dynamic bending, which leads to cracking or delamination of the substrate layer and cannot meet the long-term use requirements of foldable mobile devices. (2) This application adopts a process route of thermosetting as the main method, followed by multiple room temperature static placement and long-term baking in a vacuum oven. The entire preparation cycle is as long as 7 to 10 days. The process is time-consuming and energy-intensive, which is not conducive to industrial mass production.

[0005] Therefore, it is necessary to develop a flexible glass protective film for foldable screens with high light transmittance and long bending life, while the manufacturing process is efficient, controllable, and suitable for mass production. Summary of the Invention

[0006] Existing flexible glass screen protectors for foldable screens suffer from short bending lifespan. To address this issue, this invention provides a flexible glass screen protector for foldable screens and its manufacturing process.

[0007] To achieve the objectives of this invention, the following technical solution is adopted:

[0008] In a first aspect, the present invention provides a flexible glass protective film for foldable screens, comprising, from top to bottom, a base film layer, a first UV-type acrylic polymer film layer, a UTG layer, a second UV-type acrylic polymer film layer, and an acrylic-based foldable OCA layer;

[0009] Both the first UV-type acrylic polymer film and the second UV-type acrylic polymer film are formed by curing modified UV adhesive.

[0010] The preparation method of the modified UV adhesive includes the following steps:

[0011] Aliphatic polycarbonate-type polyurethane acrylate and acrylated polyrotaxane are mixed evenly at 40~50℃; the mixture is cooled to 25~30℃ and PDMS-acrylate copolymer and long-chain aliphatic acrylate are added and stirred for 30~45 min. Under light-protected conditions, 3-isocyanate-propyltrimethoxysilane and photoinitiator are added and stirred evenly. The mixture is then degassed under vacuum and filtered to obtain modified UV adhesive.

[0012] The acrylated polyrotaxane is prepared by forming an inclusion complex between amino polyethylene glycol and α-cyclodextrin, followed by sequential end-group blocking with 1-adamantane carboxylic acid, ring-opening graft polymerization with ε-caprolactone, and esterification with acryloyl chloride end groups.

[0013] By adopting the above technical solution, the special topological structure of acrylated polyrotaxane is utilized in the modified UV adhesive to introduce a pulley effect into the UV curing network. When the foldable screen is bent, the polyrotaxane can effectively dissipate stress through molecular sliding, avoiding local stress concentration, thereby giving the UV adhesive layer excellent flexibility and fatigue resistance. It will not generate permanent stress accumulation at the folding centerline, and the crease will not easily deepen after long-term bending. At the same time, the double-layer modified UV adhesive acts as a buffer layer to wrap the extremely thin UTG flexible glass, which greatly reduces the risk of UTG breakage during repeated folding.

[0014] By adopting the above technical solutions, the flexibility, bending resistance and bonding strength between layers of the screen protector can be effectively improved, while ensuring excellent optical transmittance, making it suitable for the long-term bending and use requirements of foldable screens.

[0015] Preferably, the mass ratio of the aliphatic polycarbonate polyurethane acrylate, acrylated polyrotaxane, PDMS-acrylate copolymer, long-chain aliphatic acrylate, 3-isocyanate-propyltrimethoxysilane to the photoinitiator is (40~60):(3~8):(15~25):(10~20):(2~5):(1~3).

[0016] Preferably, the long-chain aliphatic acrylate is selected from dodecyl acrylate or octadecyl acrylate.

[0017] By adopting the above technical solutions, long-chain aliphatic monomers can improve the flexibility and deformation recovery ability of the adhesive layer.

[0018] Preferably, the base film layer is a colorless transparent polyimide film or a polyethylene terephthalate film.

[0019] Preferably, the method for preparing the acrylated polyrotaxane includes the following steps:

[0020] (1) Slowly add polyethylene glycol aqueous solution to α-cyclodextrin aqueous solution, mix and stir for 24 h, centrifuge, freeze dry to obtain P1;

[0021] (2) P1, anhydrous N,N-dimethylformamide, 1-adamantane carboxylic acid, DCC and DMAP are mixed evenly and reacted under nitrogen protection for 24-26 h. After precipitation, washing and drying, P2 is obtained.

[0022] (3) Under nitrogen protection, P2, ε-caprolactone, stannous octoate and toluene were mixed evenly, heated to 110~130℃ and reacted for 12~16h, precipitated and dried to obtain P3;

[0023] (4) P3, anhydrous dichloromethane and triethylamine are mixed evenly, and a dichloromethane solution containing acryloyl chloride is slowly added dropwise under ice bath conditions of 0~5℃. The reaction is carried out at room temperature in the dark for 10~12h. After washing, drying, concentration, methanol precipitation and drying, acrylated polyrotaxane is obtained.

[0024] By adopting the above technical solutions, the formation of inclusion complexes, end-group sealing to prevent detachment, branching toughening, and introduction of polymeric active groups are achieved in sequence. This prevents the cyclodextrin molecules from detaching from the acrylated polyrotaxane, and increases the compatibility with the UV adhesive main resin by introducing flexible side chains with ε-caprolactone. Finally, the double bonds participate in photocuring, firmly anchoring it in the crosslinked network, ensuring the bending resistance and adhesion of the UV-type acrylic polymer film.

[0025] Preferably, in step (1), the polyethylene glycol aqueous solution is prepared by mixing amino polyethylene glycol and water at a mass ratio of 1:(10~12); the α-cyclodextrin aqueous solution is prepared by mixing α-cyclodextrin and water at a mass ratio of (3.5~4.5):(28~30); the mass ratio of amino polyethylene glycol to α-cyclodextrin is 1:(3.5~4.5).

[0026] By adopting the above technical solution, this ratio can ensure that α-cyclodextrin has the best penetration and inclusion rate on the polyethylene glycol segment, which not only ensures that the polyrotaxane has sufficient sliding nodes, but also avoids the increase in segment rigidity caused by excessive inclusion.

[0027] Preferably, in step (2), the mass ratio of P1, anhydrous N,N-dimethylformamide, 1-adamantane carboxylic acid, DCC and DMAP is 10:(80~100):(1~3):(1.5~4):(0.1~0.5).

[0028] By adopting the above technical solution, high conversion end-capping is achieved by utilizing sterically hindered 1-adamantane carboxylic acid. This ratio ensures that α-cyclodextrin will not slip off the axial chain during subsequent high-temperature or vigorous stirring processes.

[0029] Preferably, in step (3), the mass ratio of P2, ε-caprolactone, stannous octoate and toluene is 10:(30~50):(0.1~0.3):(50~100).

[0030] By adopting the above technical solution, the degree of ε-caprolactone ring-opening graft polymerization is controlled. The appropriate length of polycaprolactone side chain can play an internal plasticizing role in the subsequent adhesive solution, further reducing stress concentration, so that P3 has suitable flexibility and compatibility, and is suitable for subsequent end-group esterification reaction.

[0031] Preferably, in step (4), the mass ratio of P3, anhydrous dichloromethane, triethylamine, acryloyl chloride and dichloromethane is (15~20):(130~150):(2~3):(2~2.5):(15~20).

[0032] By adopting the above technical solution, an appropriate amount of double bonds are grafted to ensure that the acrylated polyrotaxane has good reactivity and can be fully compatible with other components in the modified UV adhesive.

[0033] Preferably, the acrylic-based folded OCA layer is obtained by cutting an acrylic-based folded OCA roll; the preparation method of the acrylic-based folded OCA roll includes the following steps:

[0034] 70-85 parts by weight of isooctyl acrylate, 10-20 parts by weight of acryloylmorpholine, 1-5 parts by weight of hydroxyethyl acrylate, 80-110 parts by weight of ethyl acetate, and 0.2-0.5 parts by weight of azobisisobutyronitrile are mixed evenly and reacted at 60-80℃ for 6-8 hours under nitrogen protection. After the reaction, 0.1-0.3 parts by weight of hexamethylene diisocyanate, 0.05-0.25 parts by weight of silane coupling agent KH-570, 0.05-0.1 parts by weight of antioxidant 1076, and 0.1-0.2 parts by weight of antioxidant 168 are added, stirred evenly, and vacuum degassed. The mixture is then coated onto the first release film, baked at a gradient temperature, bonded with the second release film, cured, and wound up to obtain an acrylic folded OCA roll.

[0035] By adopting the above technical solution, acryloylmorpholine is introduced into the OCA adhesive system to improve the cohesive strength of the adhesive layer and prevent overflow and creep during repeated bending. Gradient heating baking can remove solvents, prevent bubble formation, and allow the adhesive layer to slowly release internal stress during baking, giving it excellent folding durability.

[0036] The gradient heating baking includes: a first temperature zone of 60℃~70℃, a second temperature zone of 90℃~100℃, a third temperature zone of 110℃~120℃, and a total baking time of 3~8 minutes.

[0037] The curing temperature is 35℃~45℃, and the curing time is 48h~72h.

[0038] Preferably, the thickness of the base film layer is 25~75μm, the thickness of the first UV-type acrylic polymer film layer is 15~60μm, the thickness of the UTG layer is 30~100μm, the thickness of the second UV-type acrylic polymer film layer is 10~40μm, and the thickness of the acrylic folded OCA layer is 25~100μm.

[0039] By adopting the above technical solution, the thickness of each layer is reasonably configured, taking into account the flexibility, support and optical performance of the protective film.

[0040] Secondly, the present invention provides a manufacturing process for the above-mentioned flexible glass protective film for foldable screens, comprising the following steps:

[0041] S1: A modified UV adhesive is uniformly coated on the third release film, pre-cured, and a fourth release film is laminated on the other side. The film is then wound up to obtain a first UV-type acrylic polymer film roll. A modified UV adhesive is uniformly coated on the fifth release film, pre-cured, and a sixth release film is laminated on the other side. The film is then wound up to obtain a second UV-type acrylic polymer film roll.

[0042] S2: Cut the first UV-type acrylic polymer film roll, the second UV-type acrylic polymer film roll, the base film layer, and the acrylic folded OCA roll respectively: cut the first UV-type acrylic polymer film roll into the first sheet as the first UV-type acrylic polymer film layer, cut the second UV-type acrylic polymer film roll into the second sheet as the second UV-type acrylic polymer film layer, cut the base film layer into the base film layer sheet, and cut the acrylic folded OCA roll into the acrylic folded OCA sheet;

[0043] S3: Before bonding, peel off the release film on both sides of the first sheet and the second sheet respectively, and peel off the release film on one side of the acrylic folded OCA sheet at the same time; in order from top to bottom, bond the base film sheet, the first sheet, the UTG layer, the second sheet, and the acrylic folded OCA sheet in sequence, and cure it a second time; cut to obtain the flexible glass protective film for foldable screen.

[0044] By adopting the above technical solution, the preparation process is simple and suitable for large-scale production; the overall stacked layers are bonded together in sequence, and combined with the secondary curing process, the bonding strength between each layer can be improved, especially the modulus of the UV-type acrylic polymer film layer, which is suitable for the repeated bending requirements of foldable screens, avoiding problems such as delamination and edge lifting of the product, and the interlayer bonding is tight, resulting in excellent product surface flatness.

[0045] Preferably, the dimensions of each sheet should meet the following requirements: base film layer sheet > first sheet, second sheet, acrylic folded OCA sheet > UTG.

[0046] By adopting the above technical solution, the size is gradually reduced from the outer layer to the inner layer, which conforms to the principle of the outer layer protecting the inner layer and is also compatible with the cutting process in step S3. During cutting, the excess edges of the base film sheet, the first sheet, the second sheet, and the acrylic folded OCA sheet are removed according to the UTG size, and finally a finished protective film with the same UTG size is formed. This can ensure that the edges of each layer are aligned after cutting, and there is no risk of delamination or edge curling.

[0047] In summary, the beneficial effects of this invention are:

[0048] 1. This invention introduces acrylated polyrotaxane molecules into the UV adhesive and utilizes their molecular pulley mechanism to enable the cured film layer to effectively slide and release concentrated stress when subjected to folding deformation. Combined with the structure of double UV acrylic polymer film layers on the upper and lower sides of the UTG layer, it can effectively absorb and disperse external impact loads, has excellent impact resistance, avoids the problem of fatigue cracking of UTG, and is suitable for the long-term use requirements of foldable screens.

[0049] 2. The acrylic-based folding OCA layer in this invention has moderate adhesion, good bending resistance, and excellent optical properties, which can ensure a tight fit between the protective film and the folding screen, and it is not easy to delaminate after long-term use.

[0050] 3. The system of this invention introduces an acrylated polyrotaxane topology, which combines an upper and lower symmetrical double UV acrylic polymer film layer with an acrylic folded OCA layer. This can dynamically dissipate bending stress, avoid permanent stress accumulation, and result in shallow creases after long-term repeated bending, making it difficult to deepen and cure.

[0051] 4. The preparation process of this invention is simple and controllable, with a short overall preparation cycle, which facilitates industrial production and has good application prospects. Attached Figure Description

[0052] Figure 1 This is the infrared spectrum of the acrylated polyrotaxane of the present invention. Detailed Implementation

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available.

[0055] Preparation Examples 1-3: Preparation of acrylated polyrotaxane;

[0056] Preparation Example 1

[0057] The preparation method of acrylated polyrotaxane in this example includes the following specific steps:

[0058] (1) Dissolve 10g of amino polyethylene glycol (number average molecular weight Mn≈10,000) in 120mL of deionized water to obtain polyethylene glycol aqueous solution; dissolve 42g of α-cyclodextrin in 285mL of deionized water heated to 80℃ to obtain α-cyclodextrin aqueous solution; slowly add polyethylene glycol aqueous solution to α-cyclodextrin aqueous solution and mix, stir continuously at room temperature for 24h, centrifuge at 8000r / min for 15min, discard the supernatant and collect the white precipitate at the bottom; place the precipitate in a freeze dryer and freeze dry for 48h to obtain P1;

[0059] (2) Add 10g of P1 to a three-necked flask, add 80g of anhydrous N,N-dimethylformamide and stir until completely dissolved, add 3g of 1-adamantane carboxylic acid, 3.5g of DCC and 0.5g of DMAP, react at room temperature for 24h under nitrogen protection, precipitate with methanol, wash repeatedly with methanol and acetone, and dry under vacuum at 40℃ for 12h to obtain P2;

[0060] (3) Under nitrogen protection, 10g P2, 45g ε-caprolactone purified by vacuum distillation and 70g toluene were added to a three-necked flask, stirred for 10min, 0.15g stannous octoate was added, and the temperature was raised to 120℃ and reacted for 16h. After the reaction was completed, the product was cooled to room temperature, and the product was added dropwise into n-hexane and stirred to precipitate. The precipitate was collected and transferred to a vacuum drying oven and dried under vacuum at 40℃ for 12h to obtain P3.

[0061] (4) Add 18g P3 to a three-necked flask, add 140g anhydrous dichloromethane, stir for 10min, add 2.5g triethylamine, stir for 5min; place the three-necked flask in an ice bath, control the system temperature to 0℃, and slowly add 18g dichloromethane solution containing 2.2g acryloyl chloride under nitrogen protection; after the addition is complete, remove the ice bath, raise the system to room temperature, and stir the reaction in the dark for 10~12h; after the reaction is completed, wash the reaction solution with saturated sodium bicarbonate aqueous solution and saturated saline solution in sequence, and let it stand to separate the layers after each washing, and separate the organic layer; add anhydrous magnesium sulfate to the organic layer, stir and dry for 30min; filter to remove anhydrous magnesium sulfate, place the filtrate under the dark to evaporate and concentrate; precipitate with methanol, and dry under vacuum at 40℃ for 12h to obtain acrylated polyrotaxane.

[0062] Preparation Example 2

[0063] The preparation method of acrylated polyrotaxane in this example includes the following specific steps:

[0064] (1) Dissolve 10g of amino polyethylene glycol (number average molecular weight Mn≈10,000) in 110mL of deionized water to obtain polyethylene glycol aqueous solution; dissolve 40g of α-cyclodextrin in 300mL of deionized water heated to 80℃ to obtain α-cyclodextrin aqueous solution; slowly add polyethylene glycol aqueous solution to α-cyclodextrin aqueous solution and mix, stir continuously at room temperature for 24h, centrifuge at 8000r / min for 15min, discard the supernatant and collect the white precipitate at the bottom; place the precipitate in a freeze dryer and freeze dry for 48h to obtain P1;

[0065] (2) Add 10g of P1 to a three-necked flask, add 100g of anhydrous N,N-dimethylformamide and stir until completely dissolved, add 2g of 1-adamantane carboxylic acid, 2.5g of DCC and 0.4g of DMAP, react at room temperature for 24h under nitrogen protection, precipitate with methanol, wash repeatedly with methanol and acetone, and dry under vacuum at 40℃ for 12h to obtain P2;

[0066] (3) Under nitrogen protection, 10g P2, 40g ε-caprolactone purified by vacuum distillation and 80g toluene were added to a three-necked flask, stirred for 10min, 0.1g stannous octoate was added, and the temperature was raised to 115℃ and reacted for 15h. After the reaction was completed, the mixture was cooled to room temperature, and the product was added dropwise into n-hexane and stirred to precipitate. The precipitate was collected and transferred to a vacuum drying oven and dried under vacuum at 40℃ for 12h to obtain P3.

[0067] (4) Add 16g P3 to a three-necked flask, add 135g anhydrous dichloromethane, stir for 10min, add 3g triethylamine, stir for 5min; place the three-necked flask in an ice bath, control the system temperature to 0℃, and slowly add 20g dichloromethane solution containing 2g acryloyl chloride under nitrogen protection; after the addition is complete, remove the ice bath, raise the system to room temperature, and stir the reaction in the dark for 12h; after the reaction is completed, wash the reaction solution with saturated sodium bicarbonate aqueous solution and saturated saline solution in turn, and let it stand to separate the layers after each washing to separate the organic layer; add anhydrous magnesium sulfate to the organic layer, stir and dry for 30min; filter to remove anhydrous magnesium sulfate, place the filtrate under the dark to evaporate and concentrate; precipitate with methanol, and dry under vacuum at 40℃ for 12h to obtain acrylated polyrotaxane.

[0068] Preparation Example 3

[0069] The preparation method of acrylated polyrotaxane in this example includes the following specific steps:

[0070] (1) Dissolve 10g of amino polyethylene glycol (number average molecular weight Mn≈10,000) in 105mL of deionized water to obtain polyethylene glycol aqueous solution; dissolve 38g of α-cyclodextrin in 280mL of deionized water heated to 80℃ to obtain α-cyclodextrin aqueous solution; slowly add polyethylene glycol aqueous solution to α-cyclodextrin aqueous solution and mix, stir continuously at room temperature for 24h, centrifuge at 8000r / min for 15min, discard the supernatant and collect the white precipitate at the bottom; place the precipitate in a freeze dryer and freeze dry for 48h to obtain P1;

[0071] (2) Add 10g of P1 to a three-necked flask, add 85g of anhydrous N,N-dimethylformamide and stir until completely dissolved, add 2.5g of 1-adamantane carboxylic acid, 3g of DCC and 0.3g of DMAP, react at room temperature for 25h under nitrogen protection, precipitate with methanol, wash repeatedly with methanol and acetone, and dry under vacuum at 40℃ for 12h to obtain P2;

[0072] (3) Under nitrogen protection, 10g P2, 30g ε-caprolactone purified by vacuum distillation and 60g toluene were added to a three-necked flask, stirred for 10min, 0.22g stannous octoate was added, and the temperature was raised to 130℃ and reacted for 13h. After the reaction was completed, the mixture was cooled to room temperature, and the product was added dropwise into n-hexane and stirred to precipitate. The precipitate was collected and transferred to a vacuum drying oven and dried under vacuum at 40℃ for 12h to obtain P3.

[0073] (4) Add 20g P3 to a three-necked flask, add 150g anhydrous dichloromethane, stir for 10min, add 3g triethylamine, and stir for 5min; place the three-necked flask in an ice bath, control the system temperature at 5℃, and slowly add 15g dichloromethane solution containing 2.5g acryloyl chloride under nitrogen protection; after the addition is complete, remove the ice bath, raise the system to room temperature, and stir the reaction in the dark for 12h; after the reaction is complete, wash the reaction solution with saturated sodium bicarbonate aqueous solution and saturated saline solution in sequence, and let it stand to separate the layers after each washing to separate the organic layer; add anhydrous magnesium sulfate to the organic layer, stir and dry for 30min; filter to remove anhydrous magnesium sulfate, place the filtrate under the dark to evaporate and concentrate; precipitate with methanol, and dry under vacuum at 40℃ for 12h to obtain acrylated polyrotaxane.

[0074] Preparation Examples 4-7: Preparation of Modified UV Adhesive Liquid;

[0075] Preparation Example 4

[0076] The preparation method of the modified UV adhesive in this example includes the following specific steps:

[0077] 45g of UC3211 (aliphatic polycarbonate polyurethane acrylate oligomer IPDI, Zhongshan Qianyou Chemical Materials Co., Ltd.) and 4g of acrylated polyrotaxane prepared in Preparation Example 1 were added to a reaction vessel and stirred at 45°C for 30 min. The temperature was lowered to 25°C and 25g of PDMS-acrylate copolymer and 13g of dodecyl acrylate were added and stirred for 35 min. Under light-protected conditions, 5g of 3-isocyanate-propyltrimethoxysilane and 2.5g of photoinitiator TPO were added and stirred for 1 h. The mixture was then transferred to a vacuum degassing machine for vacuum degassing for 30 min and filtered through a 1μm~3μm filter membrane to obtain the modified UV adhesive.

[0078] Preparation Example 5

[0079] The preparation method of the modified UV adhesive in this example includes the following specific steps:

[0080] 48g of UC3211 and 3.5g of acrylated polyrotaxane prepared in Preparation Example 1 were added to a reaction vessel and stirred at 40°C for 30 min. The temperature was lowered to 28°C and 18g of PDMS-acrylate copolymer and 16g of octadecyl acrylate were added and stirred for 30 min. Under light-protected conditions, 3g of 3-isocyanate-propyltrimethoxysilane and 1.5g of photoinitiator TPO were added and stirred for 1 h. The mixture was then transferred to a vacuum degassing machine for vacuum degassing for 30 min and filtered through a 1μm~3μm filter membrane to obtain the modified UV adhesive.

[0081] Preparation Example 6

[0082] The preparation method of the modified UV adhesive in this example includes the following specific steps:

[0083] 55g of UC3211 and 6.5g of the acrylated polyrotaxane prepared in Preparation Example 3 were added to a reaction vessel and stirred at 48°C for 30 min. The temperature was lowered to 25°C and 22g of PDMS-acrylate copolymer and 12g of dodecyl acrylate were added and stirred for 40 min. Under light-protected conditions, 4g of 3-isocyanate-propyltrimethoxysilane and 3g of photoinitiator TPO were added and stirred for 1 h. The mixture was then transferred to a vacuum degassing machine for vacuum degassing for 30 min and filtered through a 1μm~3μm filter membrane to obtain the modified UV adhesive.

[0084] Preparation Example 7

[0085] The preparation method of the modified UV adhesive in this example includes the following specific steps:

[0086] 58g of UC3211 and 7g of the acrylated polyrotaxane prepared in Preparation Example 1 were added to a reaction vessel and stirred at 50°C for 30 min. The temperature was lowered to 30°C and 23.5g of PDMS-acrylate copolymer and 18.5g of octadecyl acrylate were added and stirred for 38 min. Under light-protected conditions, 4.5g of 3-isocyanate-propyltrimethoxysilane and 2.8g of photoinitiator TPO were added and stirred for 1 h. The mixture was then transferred to a vacuum degassing machine for vacuum degassing for 30 min and filtered through a 1μm~3μm filter membrane to obtain the modified UV adhesive.

[0087] Preparation Examples 8-11: Preparation of Acrylic Folded OCA Rolls;

[0088] Preparation Example 8

[0089] The preparation method of this example for an acrylic folded OCA roll includes the following specific steps:

[0090] 75g of isooctyl acrylate, 15g of acrylamide, 4.5g of hydroxyethyl acrylate, 108g of ethyl acetate, and 0.25g of azobisisobutyronitrile were mixed evenly and reacted at 80℃ for 6.5h under nitrogen protection. After the reaction, 0.15g of hexamethylene diisocyanate, 0.15g of silane coupling agent KH-570, 0.05g of antioxidant 1076, and 0.1g of antioxidant 168 were added, stirred evenly, and vacuum degassed. The mixture was then coated onto the first release film and baked at a gradient temperature of 65℃ in the first zone, 90℃ in the second zone, and 118℃ in the third zone, for a total baking time of 5min. After bonding with the second release film, the mixture was cured at 45℃ for 56h. Finally, the mixture was wound up to obtain an acrylic folded OCA roll.

[0091] Preparation Example 9

[0092] The preparation method of this example for an acrylic folded OCA roll includes the following specific steps:

[0093] 82g of isooctyl acrylate, 14g of acrylmorpholine, 5g of hydroxyethyl acrylate, 102g of ethyl acetate, and 0.35g of azobisisobutyronitrile were mixed evenly and reacted at 75℃ for 7h under nitrogen protection. After the reaction, 0.25g of hexamethylene diisocyanate, 0.25g of silane coupling agent KH-570, 0.08g of antioxidant 1076, and 0.18g of antioxidant 168 were added, stirred evenly, and vacuum degassed. The mixture was then coated onto the first release film and baked at a gradient temperature of 68℃ in the first zone, 95℃ in the second zone, and 120℃ in the third zone, for a total baking time of 6min. After bonding with the second release film, the mixture was cured at 35℃ for 60h. Finally, the mixture was wound up to obtain an acrylic folded OCA roll.

[0094] Preparation Example 10

[0095] The preparation method of this example for an acrylic folded OCA roll includes the following specific steps:

[0096] 72g of isooctyl acrylate, 12g of acrylamide, 2g of hydroxyethyl acrylate, 90g of ethyl acetate, and 0.4g of azobisisobutyronitrile were mixed evenly and reacted at 65℃ for 8h under nitrogen protection. After the reaction, 0.1g of hexamethylene diisocyanate, 0.23g of silane coupling agent KH-570, 0.09g of antioxidant 1076, and 0.2g of antioxidant 168 were added, stirred evenly, and vacuum degassed. The mixture was then coated onto the first release film and baked at a gradient temperature of 70℃ in the first zone, 98℃ in the second zone, and 116℃ in the third zone, for a total baking time of 4min. After bonding with the second release film, the mixture was cured at 40℃ for 50h. Finally, the mixture was wound up to obtain an acrylic folded OCA roll.

[0097] Preparation Example 11

[0098] The preparation method of this example for an acrylic folded OCA roll includes the following specific steps:

[0099] 70g of isooctyl acrylate, 18g of acrylmorpholine, 1.5g of hydroxyethyl acrylate, 85g of ethyl acetate, and 0.36g of azobisisobutyronitrile were mixed evenly and reacted at 66℃ for 7h under nitrogen protection. After the reaction, 0.21g of hexamethylene diisocyanate, 0.1g of silane coupling agent KH-570, 0.1g of antioxidant 1076, and 0.14g of antioxidant 168 were added, stirred evenly, and vacuum degassed. The mixture was then coated onto the first release film and baked at a gradient temperature of 70℃ in the first zone, 100℃ in the second zone, and 115℃ in the third zone, for a total baking time of 7min. After bonding with the second release film, the mixture was cured at 35℃ for 72h. Finally, the mixture was wound up to obtain an acrylic folded OCA roll.

[0100] Examples 1-4: Preparation of flexible glass protective film for foldable screens;

[0101] Example 1

[0102] A flexible glass protective film for foldable screens comprises, from top to bottom, a base film layer with a thickness of 55 μm, a first UV-type acrylic polymer film layer with a thickness of 30 μm, a UTG layer with a thickness of 50 μm, a second UV-type acrylic polymer film layer with a thickness of 20 μm, and an acrylic foldable OCA layer with a thickness of 50 μm prepared in Preparation Example 8.

[0103] The base film is a colorless and transparent polyimide film;

[0104] Both the first UV-type acrylic polymer film and the second UV-type acrylic polymer film were formed by curing the modified UV adhesive prepared in Preparation Example 4.

[0105] The specific steps of the manufacturing process of a flexible glass protective film for foldable screens in this embodiment are as follows:

[0106] S1: A modified UV adhesive is uniformly coated on the third release film, pre-cured, and a fourth release film is laminated on the other side. The film is then wound up to obtain a first UV-type acrylic polymer film roll. A modified UV adhesive is uniformly coated on the fifth release film, pre-cured, and a sixth release film is laminated on the other side. The film is then wound up to obtain a second UV-type acrylic polymer film roll.

[0107] S2: Cut the first UV-type acrylic polymer film roll, the second UV-type acrylic polymer film roll, the base film layer, and the acrylic folded OCA roll respectively: cut the first UV-type acrylic polymer film roll into the first sheet as the first UV-type acrylic polymer film layer, cut the second UV-type acrylic polymer film roll into the second sheet as the second UV-type acrylic polymer film layer, cut the base film layer into the base film layer sheet, and cut the acrylic folded OCA roll into the acrylic folded OCA sheet;

[0108] S3: Before bonding, peel off the release film on both sides of the first sheet and the second sheet respectively, and peel off the release film on one side of the acrylic folded OCA sheet at the same time; in order from top to bottom, bond the base film sheet, the first sheet, the UTG layer, the second sheet, and the acrylic folded OCA sheet in sequence, and cure it a second time; cut to obtain the flexible glass protective film for foldable screen.

[0109] Example 2

[0110] A flexible glass protective film for foldable screens comprises, from top to bottom, a base film layer with a thickness of 60 μm, a first UV-type acrylic polymer film layer with a thickness of 25 μm, a UTG layer with a thickness of 40 μm, a second UV-type acrylic polymer film layer with a thickness of 20 μm, and an acrylic foldable OCA layer with a thickness of 40 μm prepared in Preparation Example 8.

[0111] The base film is a colorless and transparent polyimide film;

[0112] Both the first UV-type acrylic polymer film and the second UV-type acrylic polymer film were formed by curing the modified UV adhesive prepared in Preparation Example 5.

[0113] The manufacturing process of the flexible glass protective film for foldable screens in this embodiment is the same as in Embodiment 1.

[0114] Example 3

[0115] A flexible glass protective film for foldable screens comprises, from top to bottom, a base film layer with a thickness of 35 μm, a first UV-type acrylic polymer film layer with a thickness of 25 μm, a UTG layer with a thickness of 45 μm, a second UV-type acrylic polymer film layer with a thickness of 15 μm, and an acrylic foldable OCA layer with a thickness of 60 μm prepared in Preparation Example 10.

[0116] The base film layer is a polyethylene terephthalate film;

[0117] Both the first UV-type acrylic polymer film and the second UV-type acrylic polymer film were formed by curing the modified UV adhesive prepared in Preparation Example 5.

[0118] The manufacturing process of the flexible glass protective film for foldable screens in this embodiment is the same as in Embodiment 1.

[0119] Example 4

[0120] A flexible glass protective film for foldable screens comprises, from top to bottom, a base film layer with a thickness of 45 μm, a first UV-type acrylic polymer film layer with a thickness of 50 μm, a UTG layer with a thickness of 40 μm, a second UV-type acrylic polymer film layer with a thickness of 35 μm, and an acrylic foldable OCA layer with a thickness of 80 μm prepared in Preparation Example 9.

[0121] The base film layer is a polyethylene terephthalate film;

[0122] Both the first UV-type acrylic polymer film and the second UV-type acrylic polymer film were formed by curing the modified UV adhesive prepared in Preparation Example 6.

[0123] The manufacturing process of the flexible glass protective film for foldable screens in this embodiment is the same as in Embodiment 1.

[0124] Comparative Examples 1-3: Preparation of flexible glass protective film for foldable screens;

[0125] Comparative Example 1

[0126] It is basically the same as Example 1, except that acrylated polyrotaxane is not added to the formulation of the modified UV adhesive.

[0127] Comparative Example 2

[0128] The formulation is basically the same as that in Example 1, except that acryloylmorpholine is not added in the preparation formula of the acrylic folded OCA layer.

[0129] Comparative Example 3

[0130] Similar to Example 1, this comparative example of a flexible glass protective film for a foldable screen includes, from top to bottom, a base film layer with a thickness of 55 μm, a first UV-type acrylic polymer film layer with a thickness of 30 μm, a UTG layer with a thickness of 50 μm, and an acrylic foldable OCA layer with a thickness of 50 μm prepared in Preparation Example 8.

[0131] Performance testing

[0132] The bending resistance and optical transmittance of Examples 1-4 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1.

[0133] 1. Bending Resistance Test: The foldable screen is attached to a bending tester with a flexible glass protective film. The attached surface must be flat, tight, and free of bubbles and wrinkles. The test temperature is 25℃, the bending radius R=1.5mm, and the bending angle is 180°. 200,000 bending tests are conducted. The test is stopped every 50,000 times to observe the protective film for bubbles, cracks, peeling, creases, etc. If any of these occur, the number of times is recorded. If no such phenomena occur, the test continues. When the screen is folded 200,000 times, the test is stopped. If no such phenomena occur, the number of folds is recorded as >200,000 times.

[0134] 2. Optical transmittance test: The transmittance at a wavelength of 550nm was measured using a visible light spectrophotometer.

[0135] Table 1 Test Results

[0136]

[0137] As shown in Table 1, Comparative Example 1 lacked acrylated polyrotaxane, and the UV adhesive layer was prone to stress concentration during repeated bending, resulting in cracking of the adhesive layer after approximately 100,000 repeated bending cycles.

[0138] Comparative Example 2 lacks acrylamide, resulting in poorer resistance to deformation recovery. After more than 100,000 bends, it is prone to residual glue, wrinkles, or bubbles.

[0139] In Comparative Example 3, the flexible ultrathin glass (UTG) is extremely fragile. In this example, the second UV-type acrylic polymer film layer under the UTG acts as a stress buffer. Without this layer, the UTG is easily subjected to direct stress and will break during early bending.

[0140] The changes in the above comparative ratio had little impact on the light transmittance, so the light transmittance remained basically normal and was not significantly different from the test results of the example.

[0141] The flexible glass protective film for foldable screens prepared by this invention can pass 200,000 bending tests without cracking or bubbles; it also has excellent optical transmittance.

[0142] The acrylated polyrotaxane prepared in Preparation Example 1 was subjected to infrared spectroscopy using a Fourier transform infrared spectrometer. The test results are as follows: Figure 1 As shown.

[0143] From the infrared spectrum, it can be observed that: in the range of 3300~3450 cm⁻¹ -1 An absorption peak at 2850–2950 cm⁻¹ was observed, attributed to the OH stretching vibration of α-cyclodextrin; [the peak was observed in the range of 2850–2950 cm⁻¹]. -1 A distinct CH stretching vibration peak appeared at 1734 cm⁻¹; -1 The appearance of a stretching vibration peak at 1633 cm⁻¹ confirms that ε-caprolactone successfully underwent ring-opening grafting to form a polyester side chain; furthermore, a peak was observed at 1633 cm⁻¹. -1 An absorption peak for the stretching vibration of the carbon-carbon double bond appeared at 812 cm⁻¹. -1 A corresponding out-of-plane bending vibration peak of the double bond appeared at the specified location. The appearance of the above characteristic absorption peaks indicates the successful synthesis of acrylated polyrotaxane.

[0144] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A flexible glass protective film for foldable screens, characterized in that, From top to bottom, it includes a base film layer, a first UV-type acrylic polymer film layer, a UTG layer, a second UV-type acrylic polymer film layer, and an acrylic-based folded OCA layer; both the first UV-type acrylic polymer film layer and the second UV-type acrylic polymer film layer are formed by curing modified UV adhesive; The preparation method of the modified UV adhesive includes the following steps: Aliphatic polycarbonate-type polyurethane acrylate and acrylated polyrotaxane are mixed evenly at 40~50℃; the mixture is cooled to 25~30℃ and PDMS-acrylate copolymer and long-chain aliphatic acrylate are added and stirred for 30~45 min. Under light-protected conditions, 3-isocyanate-propyltrimethoxysilane and photoinitiator are added and stirred evenly. The mixture is then degassed under vacuum and filtered to obtain modified UV adhesive. The acrylated polyrotaxane is prepared by forming an inclusion complex between amino polyethylene glycol and α-cyclodextrin, followed by sequential end-group blocking with 1-adamantane carboxylic acid, ring-opening graft polymerization with ε-caprolactone, and esterification with acryloyl chloride end groups.

2. The flexible glass protective film for foldable screens according to claim 1, characterized in that, The mass ratio of the aliphatic polycarbonate polyurethane acrylate, acrylated polyrotaxane, PDMS-acrylate copolymer, long-chain aliphatic acrylate, 3-isocyanate-propyltrimethoxysilane to the photoinitiator is (40~60):(3~8):(15~25):(10~20):(2~5):(1~3).

3. The flexible glass protective film for foldable screens according to claim 1, characterized in that, The method for preparing the acrylated polyrotaxane includes the following steps: (1) Slowly add polyethylene glycol aqueous solution to α-cyclodextrin aqueous solution, mix and stir for 24 h, centrifuge, freeze dry to obtain P1; (2) P1, anhydrous N,N-dimethylformamide, 1-adamantane carboxylic acid, DCC and DMAP are mixed evenly and reacted under nitrogen protection for 24-26 h. After precipitation, washing and drying, P2 is obtained. (3) Under nitrogen protection, P2, ε-caprolactone, stannous octoate and toluene were mixed evenly, heated to 110~130℃ and reacted for 12~16h, precipitated and dried to obtain P3; (4) P3, anhydrous dichloromethane and triethylamine are mixed evenly, and a dichloromethane solution containing acryloyl chloride is slowly added dropwise under ice bath conditions of 0~5℃. The reaction is carried out at room temperature in the dark for 10~12h. After washing, drying, concentration, methanol precipitation and drying, acrylated polyrotaxane is obtained.

4. A flexible glass protective film for foldable screens according to claim 3, characterized in that, In step (1), the polyethylene glycol aqueous solution is prepared by mixing amino polyethylene glycol and water at a mass ratio of 1:(10~12); the α-cyclodextrin aqueous solution is prepared by mixing α-cyclodextrin and water at a mass ratio of (3.5~4.5):(28~30); the mass ratio of amino polyethylene glycol to α-cyclodextrin is 1:(3.5~4.5).

5. A flexible glass protective film for foldable screens according to claim 3, characterized in that, In step (2), the mass ratio of P1, anhydrous N,N-dimethylformamide, 1-adamantane carboxylic acid, DCC and DMAP is 10:(80~100):(1~3):(1.5~4):(0.1~0.5).

6. A flexible glass protective film for foldable screens according to claim 3, characterized in that, In step (3), the mass ratio of P2, ε-caprolactone, stannous octoate and toluene is 10:(30~50):(0.1~0.3):(50~100).

7. A flexible glass protective film for foldable screens according to claim 3, characterized in that, In step (4), the mass ratio of P3, anhydrous dichloromethane, triethylamine, acryloyl chloride and dichloromethane is (15~20):(130~150):(2~3):(2~2.5):(15~20).

8. A flexible glass protective film for foldable screens according to claim 1, characterized in that, The acrylic-based folded OCA layer is obtained by cutting acrylic-based folded OCA rolls; the preparation method of the acrylic-based folded OCA rolls includes the following steps: 70-85 parts by weight of isooctyl acrylate, 10-20 parts by weight of acryloylmorpholine, 1-5 parts by weight of hydroxyethyl acrylate, 80-110 parts by weight of ethyl acetate, and 0.2-0.5 parts by weight of azobisisobutyronitrile are mixed evenly and reacted at 60-80℃ for 6-8 hours under nitrogen protection. After the reaction, 0.1-0.3 parts by weight of hexamethylene diisocyanate, 0.05-0.25 parts by weight of silane coupling agent KH-570, 0.05-0.1 parts by weight of antioxidant 1076, and 0.1-0.2 parts by weight of antioxidant 168 are added, stirred evenly, and vacuum degassed. The mixture is then coated onto the first release film, baked at a gradient temperature, bonded with the second release film, cured, and wound up to obtain an acrylic folded OCA roll.

9. A flexible glass protective film for foldable screens according to claim 1, characterized in that, The thickness of the base film layer is 25~75μm, the thickness of the first UV-type acrylic polymer film layer is 15~60μm, the thickness of the UTG layer is 30~100μm, the thickness of the second UV-type acrylic polymer film layer is 10~40μm, and the thickness of the acrylic folded OCA layer is 25~100μm.

10. The manufacturing process of a flexible glass protective film for a foldable screen according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1: A modified UV adhesive is uniformly coated on the third release film, pre-cured, and a fourth release film is laminated on the other side. The film is then wound up to obtain a first UV-type acrylic polymer film roll. A modified UV adhesive is uniformly coated on the fifth release film, pre-cured, and a sixth release film is laminated on the other side. The film is then wound up to obtain a second UV-type acrylic polymer film roll. S2: Cut the first UV-type acrylic polymer film roll, the second UV-type acrylic polymer film roll, the base film layer, and the acrylic folded OCA roll respectively: cut the first UV-type acrylic polymer film roll into the first sheet as the first UV-type acrylic polymer film layer, cut the second UV-type acrylic polymer film roll into the second sheet as the second UV-type acrylic polymer film layer, cut the base film layer into the base film layer sheet, and cut the acrylic folded OCA roll into the acrylic folded OCA sheet; S3: Before bonding, peel off the release film on both sides of the first sheet and the second sheet respectively, and peel off the release film on one side of the acrylic folded OCA sheet at the same time; bond the base film sheet, the first sheet, the UTG layer, the second sheet, and the acrylic folded OCA sheet in sequence from top to bottom, and cure them in the second step. Cut to obtain a flexible glass protective film for the foldable screen.

Images