Composite layered protection paste for folding screen and production process of composite layered protection paste

Abstract

The invention relates to the technical field of composite structure protection stickers, and particularly discloses a composite layered protection sticker for a folding screen and a production process of the composite layered protection sticker. The invention discloses a composite layered protection paste for a folding screen. The composite layered protection paste sequentially comprises a polymeric membrane layer, ultra-thin flexible glass, a polymeric membrane layer and a functional coating from bottom to top, the polymeric membrane layer is prepared from the following components in parts by mass: 40 to 50 parts of alicyclic epoxy resin, 20 to 30 parts of hydroxyl-terminated polyisobutene, 5 to 10 parts of hydroxyl-terminated polybutadiene, 8 to 10 parts of modified vinyl alkoxy silane, 5 to 7 parts of modified nano silicon dioxide, 30 to 40 parts of curing agent, 0.4 to 0.6 part of catalyst and 30 to 50 parts of solvent; the composite layered protective paste prepared by the invention has excellent advantages in bending resistance and impact resistance.

Description

Technical Field

[0001] The present application relates to the technical field of composite structure protection films, and more specifically, to a composite laminated protection film for a folding screen and its production process. Background Art

[0002] With the increasing demand for thinness and flexibility of electronic products in the market, ultra-thin, light-weight, and ultra-thin flexible foldable electronic products have become an important development direction in the industry. As a key basic material, ultra-thin flexible glass (UTG) stands out due to its unique advantages: First, it has an extremely high light transmittance. Based on the intrinsic optical properties of glass, the light transmittance of UTG can reach over 90%, providing a clear and bright visual effect for the display screen. Second, its durability is significantly better than that of traditional flexible materials. It is not easily damaged after bending, has strong scratch resistance, and at the same time has a good touch, effectively improving the user experience. Third, it has excellent high-temperature resistance and can maintain stable physical and chemical properties in high-temperature environments, meeting the requirements of complex usage scenarios.

[0003] However, the mechanical properties of UTG are negatively correlated with its thickness. Since its overall thickness is extremely thin (usually between 10 and 150 μm), the intrinsic strength of the material is difficult to meet industry requirements, and the inherent brittleness of tempered glass is amplified after ultra-thinning, resulting in problems such as low strength and poor impact resistance of UTG. After breaking, it is easy to form sharp fragments, posing a safety hazard. To make up for the defects, the industry generally adopts the scheme of constructing multiple composite coatings on the surface of UTG. The current typical structure is HC-CPI / PET-OCA-UTG, which improves the impact resistance and fatigue resistance through the synergistic effect of functional coatings, support layers, and OCA optical adhesives.

[0004] The patent application document with the publication number CN114571832A discloses a multi-layer material of UTG and PET hard film, including UTG(1). The front side of the UTG(1) is pasted with a first-layer PET film(3) through an OCA optical adhesive layer(2), and the back side of the UTG(1) is pasted with a second-layer PET film(4) through an OCA optical adhesive layer(2). A hardening layer(5) is provided on the side of the first-layer PET film(3) away from the UTG(1).

[0005] In this patent application document, in order to solve the problems such as low strength and poor impact resistance of UTG, multiple composite coatings are constructed on the surface of UTG. However, due to the existence of multiple low-modulus OCA adhesive layers and PET film materials on UTG, after using for a period of time, surface unevenness, serious creases, and nail marks and other appearance defects will occur, affecting the screen appearance. Summary of the Invention

[0006] In order to improve the anti-bending performance and anti-impact performance of the composite laminated protective film, the present application provides a composite laminated protective film for a folding screen and its production process.

[0007] In a first aspect, the present application provides a composite laminated protective film for a folding screen, adopting the following technical solution: A composite laminated protective film for a folding screen, sequentially including a polymer film layer, an ultra-thin flexible glass, a polymer film layer, and a functional coating from bottom to top; The preparation raw materials of the polymer film layer include the following components: 40-50 parts by mass of alicyclic epoxy resin, 20-30 parts by mass of hydroxyl-terminated polyisobutylene, 5-10 parts by mass of hydroxyl-terminated polybutadiene, 8-10 parts by mass of modified vinyl alkoxysilane, 5-7 parts by mass of modified nano-silica, 30-40 parts by mass of curing agent, 0.4-0.6 parts by mass of catalyst, and 30-50 parts by mass of solvent; The modified nano-silica is nano-silica grafted with vinyl alkoxysilane, polyether acrylate, and double-bonded epoxy compound on the surface; The modified vinyl alkoxysilane is vinyl alkoxysilane grafted with α,ω-diolefin and allyl polyoxyethylene ether on the surface.

[0008] Preferably, before using the modified vinyl alkoxysilane, it is first formulated into a hydrolysis solution.

[0009] In this solution, the alicyclic epoxy resin serves as a rigid matrix, and forms a rigid-flexible composite system through physical blending with hydroxyl-terminated polyisobutylene and hydroxyl-terminated polybutadiene, forming a rigid-flexible interpenetrating network structure. The long-chain flexible segments of hydroxyl-terminated polyisobutylene (molecular weight 5000-8000) can absorb the tensile / compressive stress in a wide temperature range during the bending process, and the short-chain elastic structure of hydroxyl-terminated polybutadiene (molecular weight 2000-3000) dissipates the local stress concentration generated by high-frequency bending through chain segment movement, enabling the polymer film layer to maintain the tensile strength while increasing the elongation at break and effectively resisting fatigue cracking. The nano-silica grafted with vinyl alkoxysilane, polyether acrylate, and double-bonded epoxy compound on the surface reduces the interfacial energy and inhibits agglomeration through the flexible grafting layer, and delays the crack propagation under stress, realizing the performance optimization of the polymer film layer between high strength and high flexibility.

[0010] The flexible chain segments grafted with modified vinylalkoxysilane form an interpenetrating network structure with the resin matrix and the elastomer. When subjected to impact, the elastic deformation of the chain segments can effectively absorb energy, relieve stress concentration, endow the film layer with excellent toughness while maintaining rigid support, and reduce the risk of brittle fracture during the bending process. The reactive silanol groups generated by the hydrolysis of the modified vinylalkoxysilane can form strong chemical covalent bonds with the hydroxyl groups on the glass surface during the hot pressing and laminating process. Meanwhile, the grafted polar groups and long-chain structures enhance the interfacial interaction through physical entanglement, constructing a composite bonding layer of "chemical anchoring-flexible buffering". This not only significantly enhances the bonding strength between the polymer film and the glass, but also resists interfacial delamination caused by environmental factors such as humidity, heat, and fatigue, achieving a stable and durable combination between the two. As a result, the polymer film layer exhibits good energy dissipation ability under impact loads, while ensuring the formation of a strong and tough interface with the UTG after hot pressing and laminating, significantly improving the comprehensive performance of the folding screen protective film.

[0011] Preferably, the alicyclic epoxy resin is selected from any one of hydrogenated bisphenol F epoxy resin and hydrogenated bisphenol A epoxy resin.

[0012] Preferably, the thickness of the ultra-thin flexible glass is 30-100 μm.

[0013] Preferably, the thickness of the ultra-thin flexible glass is 30-50 μm.

[0014] Preferably, the thickness of the polymer film layer is 10-100 μm.

[0015] Preferably, the thickness of the polymer film layer is 20-40 μm.

[0016] Preferably, the curing agent is isophorone diamine.

[0017] Preferably, the catalyst is benzyldimethylamine.

[0018] Preferably, the solvent is selected from any one of acetone and methyl ethyl ketone.

[0019] Preferably, the functional coating has at least one function of anti-fingerprint, hardening, and anti-glare.

[0020] Preferably, the thickness of the functional coating is about 5-10 μm.

[0021] Preferably, the vinylalkoxysilane is selected from any one of vinyltriethoxysilane and vinyltrimethoxysilane.

[0022] Preferably, the preparation method of the modified vinylalkoxysilane includes the following steps: Under an inert atmosphere, vinyl alkoxysilane, a part of the initiator and a solvent are mixed evenly, then α,ω-diene and an inhibitor are added, the temperature is raised to 70-90 °C, after reacting for 120-180 min, allyl polyoxyethylene ether and the remaining initiator are added, and after continuing to react for 120-180 min, it is cooled and distilled under reduced pressure to obtain the product.

[0023] Preferably, the molar ratio of the vinyl alkoxysilane, α,ω-diene and allyl polyoxyethylene ether is 1:(1.1-1.3):(0.8-1.0).

[0024] Preferably, the dosage of the initiator is 1%-2% of the total molar amount of α,ω-diene and vinyl alkoxysilane.

[0025] Preferably, the dosage of the inhibitor is 0.1%-0.2% of the molar amount of α,ω-diene.

[0026] In this solution, the modified vinyl alkoxysilane endows the polymer film layer with excellent flexibility and low bending modulus by enhancing the compatibility with epoxy resin and relying on the flexible chain segments in its molecular structure, effectively alleviating the problem of edge stress concentration during the bending of UTG; at the same time, its active groups form a "flexible anchoring interface" with the glass surface, and through the synergistic action of chemical bonding and physical entanglement, the rigidity difference between the two is bridged, avoiding interface delamination or warping caused by uneven stress, and providing stable mechanical support and interface compatibility for the folded screen composite film layer.

[0027] Preferably, the preparation method of the modified nano-silica includes the following steps: Disperse nano-silica in an ethanol solution, add vinyl alkoxysilane and mix evenly, adjust the pH to 3-5, raise the temperature to 40-60 °C, after reacting for 120-180 min, perform solid-liquid separation, after washing, add it to toluene, then add polyether acrylate and a part of the initiator and mix evenly, raise the temperature to 70-90 °C, react for 1.5-2.5 h, then add alkenyl glycidyl ether and the remaining initiator, continue to react for 1.5-2.5 h, perform solid-liquid separation, wash, and dry to obtain the product.

[0028] Preferably, the polyether acrylate is selected from any one of polyethylene glycol diacrylate and polypropylene glycol diacrylate.

[0029] Preferably, the mass ratio of the nano-silica, vinyl alkoxysilane, polyether acrylate and alkenyl glycidyl ether is 1:(0.05-0.1):(0.05-0.08):(0.03-0.05).

[0030] Preferably, the dosage of the initiator is 1%-2% of the total mass of polyether acrylate and alkenyl glycidyl ether.

[0031] Preferably, the glycidyl alkenoate is selected from any one of glycidyl acrylate and glycidyl methacrylate.

[0032] In this solution, after hydrolysis, the silane coupling agent condenses with the hydroxyl groups on the surface of nano-silica to form a chemical coating layer, effectively inhibiting particle agglomeration and ensuring the uniform dispersion of nano-fillers in the resin; the middle ether chain segment acts as a flexible spacer to build a buffer layer between the rigid nano-particles and the flexible resin, reducing stress concentration points; the epoxy groups crosslink with the resin matrix to anchor the nano-particles in the polymer network, enabling the enhancement effect of the rigid filler to be fully exerted. Through this "dispersion-buffer-bridging" mechanism, the impact toughness and the ability to resist silver streak propagation of the film layer are significantly improved, endowing the material with the ability to withstand external impacts and repeated deformations while maintaining its hardness.

[0033] Preferably, the raw materials for preparing the polymer film layer further include 3 to 5 parts by mass of methyl methacrylate-butadiene-styrene copolymer.

[0034] In a second aspect, the present application provides a production process for a composite laminated protective film for a folding screen, comprising the following steps: S1: Mix and hydrolyze the modified vinylalkoxysilane, deionized water, ethanol and acetic acid for 20 to 30 minutes to obtain a hydrolysis solution; under the condition of 50 to 70 °C, mix the alicyclic epoxy resin, hydroxyl-terminated polyisobutylene and hydroxyl-terminated polybutadiene evenly, then add the hydrolysis solution and the modified nano-silica, mix evenly, cool, and perform vacuum degassing to obtain a pretreated matrix; after mixing the curing agent, catalyst and solvent evenly, add them to the pretreated matrix, mix evenly, coat on a release film, and after pre-curing, obtain a polymer film; S2: After plasma treating the ultra-thin flexible glass for 3 to 5 minutes, stack the polymer film on both sides of the ultra-thin flexible glass in alignment, and after vacuum hot pressing, obtain a pretreated protective film; S3: Coat a functional coating on the upper layer of the pretreated protective film, cure it, and cut the outer shape to obtain a composite laminated protective film.

[0035] In this solution, first, in the pre-hydrolysis process of the modified vinylalkoxysilane in step S1, through a controllable hydrolysis reaction under acidic conditions, highly reactive silanol groups are generated, significantly enhancing its interfacial chemical bonding force with organic components such as alicyclic epoxy resin and hydroxyl-terminated polyisobutylene, as well as modified nano-silica. At the same time, the dispersion of nano-particles is improved, endowing the polymer film layer with excellent flexibility and mechanical strength. The vacuum degassing process effectively removes the bubbles in the system, ensuring that the film layer is uniform and dense. In step S2, the vacuum hot pressing and lamination of the polymer film and UTG realizes the tight chemical anchoring and physical lamination of the film layer and UTG, reducing the risk of interfacial defects and delamination. In step S3, the coating and curing of the functional coating form a protective layer with functions such as anti-fingerprint, hardening, and anti-glare on the surface of the pre-treated protective film, ensuring the structural stability of the material under high-frequency bending, and at the same time realizing the optimization of optical performance and appearance quality. The finally prepared composite laminated protective film has excellent durability, impact resistance, and function integration, meeting the stringent requirements of folding screen devices for flexible protective materials.

[0036] Preferably, the size of the polymer film is 5-7 mm larger than the outer shape of the ultra-thin flexible glass.

[0037] Preferably, the mass ratio of the modified vinylalkoxysilane, deionized water, ethanol, and acetic acid is (8-10):(0.8-1.2):(4-5):(0.02-0.04).

[0038] Preferably, the pre-curing is gradient temperature curing, which specifically includes the following steps: After being coated on the release film, first heat up to 50-70 °C, keep warm for 1-2 h, then continue to heat up to 110-130 °C, keep warm for 1-3 h, cool to room temperature, and then place for 24-30 h to obtain the polymer film.

[0039] In this solution, in the low-temperature stage, the resin system fully flows in a low-viscosity state, promoting the uniform dispersion of components such as modified silane and nano-silica, and at the same time slowly initiating the cross-linking reaction, reducing the generation of internal stress and defects; then in the high-temperature stage, the cross-linking reaction is accelerated to improve the three-dimensional network structure and enhance the mechanical properties such as the hardness and tensile strength of the film layer. This process avoids the problem of thermal stress concentration caused by direct high-temperature curing, ensuring that the film layer is flat and without warping, and the interface is tightly bonded when laminating with the release film and subsequent UTG.

[0040] In summary, this application has the following beneficial effects: 1. This application uses an alicyclic epoxy resin compounded with hydroxyl-terminated polyisobutylene and hydroxyl-terminated polybutadiene to form a matrix with both rigidity and flexibility. Combining with a modified vinyl alkoxysilane, a chemical bridging interface is constructed between the UTG and the organic film layer to improve the bonding strength and effectively avoid the separation of the UTG and the film layer during the bending process. The modified nano-silica is uniformly dispersed in the resin matrix to form an "inorganic-organic" interpenetrating network, which inhibits crack propagation and enhances the mechanical properties of the film layer, thereby enhancing the anti-bending performance.

[0041] 2. In this application, a methyl methacrylate-butadiene-styrene copolymer is preferably used. Its polar groups can enhance interfacial adsorption, and the elastic segments improve the toughness of the film layer, significantly enhancing the impact resistance. At the same time, it can also optimize the dispersion of nano-particles and reduce defects. Specific Embodiments

[0042] The following further elaborates on this application with reference to embodiments.

[0043] The raw materials of the embodiments and comparative examples of this application are all ordinary commercially available products unless otherwise specified.

[0044] The molecular weight distribution of hydroxyl-terminated polybutadiene is 2000 - 3000; the molecular weight distribution of hydroxyl-terminated polyisobutylene is 5000 - 8000.

[0045] Preparation Examples 1 - 3 Modified Vinyl Alkoxysilane Preparation Example 1 The preparation method of the modified vinyl alkoxysilane in this preparation example includes the following steps: Under a nitrogen atmosphere, 0.1 mol of vinyltrimethoxysilane, 0.002 mol of benzoyl peroxide, and 300 mL of toluene are added to a reaction vessel, stirred and mixed evenly. Then, the reaction vessel is placed in an ice-water bath, and 0.11 mol of 1,7-octadiene and 0.00022 mol of hydroquinone are slowly added dropwise. After the addition is complete, the ice-water bath is slowly removed, and the temperature is slowly raised to 70 °C, followed by stirring and reacting for 180 min. Then, 0.08 mol of allyl polyoxyethylene ether and 0.0022 mol of benzoyl peroxide are slowly added dropwise, and the mixture is stirred and reacted for 180 min. After the reaction ends, it is cooled to room temperature, and the reaction product is transferred to a vacuum distillation device. The pressure is adjusted to 10 kPa, and the temperature is slowly raised to 80 °C for vacuum distillation until a constant weight is obtained, yielding the modified vinyl alkoxysilane.

[0046] Preparation Example 2 The preparation method of the modified vinyl alkoxysilane in this preparation example includes the following steps: Under a nitrogen atmosphere, 0.1 mol of vinyltrimethoxysilane, 0.001 mol of benzoyl peroxide and 300 mL of toluene were added to a reaction vessel, stirred and mixed evenly. Then the reaction vessel was placed in an ice-water bath, and 0.13 mol of 1,9-decadiene and 0.00013 mol of hydroquinone were slowly added dropwise. After the addition was completed, the ice-water bath was slowly removed, and the temperature was slowly raised to 90 °C, and the reaction was stirred for 120 min. Then 0.1 mol of allyl polyoxyethylene ether and 0.0013 mol of benzoyl peroxide were slowly added dropwise, and the reaction was stirred for 120 min. After the reaction was completed, it was cooled to room temperature, and the reaction product was transferred to a vacuum distillation device. The pressure was adjusted to 10 kPa, and the temperature was slowly raised to 80 °C, and vacuum distillation was carried out until a constant weight was obtained to obtain modified vinylalkoxysilane.

[0047] Preparation Example 3 The preparation method of the modified vinylalkoxysilane of this preparation example includes the following steps: Under a nitrogen atmosphere, 0.1 mol of vinyltriethoxysilane, 0.0015 mol of benzoyl peroxide and 300 mL of toluene were added to a reaction vessel, stirred and mixed evenly. Then the reaction vessel was placed in an ice-water bath, and 0.12 mol of 1,9-decadiene and 0.00018 mol of hydroquinone were slowly added dropwise. After the addition was completed, the ice-water bath was slowly removed, and the temperature was slowly raised to 80 °C, and the reaction was stirred for 150 min. Then 0.09 mol of allyl polyoxyethylene ether and 0.0018 mol of benzoyl peroxide were slowly added dropwise, and the reaction was stirred for 150 min. After the reaction was completed, it was cooled to room temperature, and the reaction product was transferred to a vacuum distillation device. The pressure was adjusted to 10 kPa, and the temperature was slowly raised to 80 °C, and vacuum distillation was carried out until a constant weight was obtained to obtain modified vinylalkoxysilane.

[0048] Modified nano-silica of Preparation Examples 4-6 Preparation Example 4 The preparation method of the modified nano-silica of this preparation example includes the following steps: 100 g of nano-silica was added to 500 mL of an ethanol solution, and then placed in an ultrasonic device. The ultrasonic power was set to 120 W and the frequency was 30 kHz. After ultrasonic dispersion for 30 min, 5 g of vinyltrimethoxysilane was added, stirred and mixed evenly. Then the pH was adjusted to 5 with 10% acetic acid by mass fraction, and the temperature was raised to 40 °C, and the reaction was stirred for 180 min. After the reaction was completed, centrifugal separation was carried out, and it was washed 3 times with ethanol to obtain silanized nano-silica; Add the silylated nano-silica into 300 mL of toluene, stir and mix evenly, then add 5 g of polypropylene glycol (400) diacrylate and 0.1 g of benzoyl peroxide and mix evenly. Heat up to 70 °C, after reacting for 2.5 h, add 3 g of glycidyl acrylate and 0.06 g of benzoyl peroxide, and continue to react for 2.5 h. After the reaction is completed, perform centrifugal separation, wash with toluene 3 times, and then transfer to a vacuum oven at 80 °C to dry to constant weight to obtain the product.

[0049] Among them, the particle size distribution of the nano-silica is 1 - 50 nm.

[0050] The ethanol solution is formed by mixing ethanol and deionized water with a volume ratio of 2:1.

[0051] Preparation Example 5 The preparation method of the modified nano-silica in this preparation example includes the following steps: Add 100 g of nano-silica into 500 mL of ethanol solution, then place it in an ultrasonic device, set the ultrasonic power to 120 W and the frequency to 30 kHz. After ultrasonic dispersion for 30 min, add 10 g of vinyltriethoxysilane, stir and mix evenly, then adjust the pH to 3 with 10% acetic acid by mass fraction, heat up to 60 °C, and stir and react for 120 min. After the reaction is completed, perform centrifugal separation, wash with ethanol 3 times to obtain silylated nano-silica; Add the silylated nano-silica into 300 mL of toluene, stir and mix evenly, then add 8 g of polyethylene glycol (400) diacrylate and 0.08 g of benzoyl peroxide and mix evenly. Heat up to 90 °C, after reacting for 1.5 h, add 5 g of glycidyl methacrylate and 0.05 g of benzoyl peroxide, and continue to react for 1.5 h. After the reaction is completed, perform centrifugal separation, wash with toluene 3 times, and then transfer to a vacuum oven at 80 °C to dry to constant weight to obtain the product.

[0052] Among them, the particle size distribution of the nano-silica is 1 - 50 nm.

[0053] The ethanol solution is formed by mixing ethanol and deionized water with a volume ratio of 4:1.

[0054] Preparation Example 6 The preparation method of the modified nano-silica in this preparation example includes the following steps: 100 g of nano-silica was added to 500 mL of ethanol solution, and then placed in an ultrasonic device. The ultrasonic power was set to 120 W and the frequency to 30 kHz. After ultrasonic dispersion for 30 min, 8 g of vinyltrimethoxysilane was added and stirred until evenly mixed. Then, acetic acid with a mass fraction of 10% was used to adjust the pH to 4, and the temperature was raised to 50 °C, followed by stirring and reacting for 150 min. After the reaction, centrifugal separation was carried out, and it was washed 3 times with ethanol to obtain silanized nano-silica; The silanized nano-silica was added to 300 mL of toluene, stirred until evenly mixed, then 7 g of polyethylene glycol (400) diacrylate and 0.1 g of benzoyl peroxide were added and mixed evenly. The temperature was raised to 90 °C, and after reacting for 2 h, 4 g of glycidyl methacrylate and 0.06 g of benzoyl peroxide were added, and the reaction continued for 2 h. After the reaction, centrifugal separation was carried out, and it was washed 3 times with toluene, and then transferred to a vacuum oven at 80 °C and dried to constant weight to obtain the product.

[0055] Among them, the particle size distribution of the nano-silica is 1 - 50 nm.

[0056] The ethanol solution was prepared by mixing ethanol and deionized water with a volume ratio of 3:1.

[0057] Example 1 The production process of the composite laminated protective film for the folding screen in this example includes the following steps: S1: 80 g of modified vinylalkoxysilane was placed in a container, 8 g of deionized water, 40 g of ethanol and 0.2 g of acetic acid were added, and they were stirred and mixed at a speed of 400 r / min for 20 min to obtain a hydrolysis solution; In a reaction kettle, 400 g of hydrogenated bisphenol A epoxy resin was added, and the temperature was raised to 50 °C. 200 g of hydroxyl-terminated polyisobutylene and 50 g of hydroxyl-terminated polybutadiene were added in sequence, and they were stirred and mixed at a speed of 800 r / min for 30 min. Then, the hydrolysis solution and 50 g of modified nano-silica were added, the stirring speed was adjusted to 400 r / min, and they were stirred and mixed for 30 min. After cooling to room temperature, the reaction kettle was evacuated to -0.1 MPa and maintained for 15 min to obtain a pretreated matrix; 300 g of isophorone diamine, 4 g of benzyldimethylamine and 300 g of acetone were mixed evenly and slowly dropped into the pretreated matrix, while stirring and mixing at a speed of 200 r / min for 30 min to obtain a mixed solution; The mixed solution was coated on a PET release film, and the wet grinding thickness was controlled to be 44 μm. It was immediately transferred to an oven at 60 °C, kept warm for 1.5 h, then the temperature was raised to 120 °C, and kept warm for 2 h. After curing, the film layer was cooled to room temperature with the oven. After taking out, it was placed in an environment at 25 °C and a relative humidity of 50% for 30 h to obtain a semi-cured polymer film (with a thickness of about 40 μm); S2: Select ultra-thin flexible glass with a thickness of 50 μm, and ultrasonically clean it successively with ethanol and deionized water for 10 minutes each time. Then, after drying with nitrogen, put it into a plasma treatment device. The device evacuates to 10 -2 Pa, introduce argon gas with a gas flow rate of 30 sccm, set the radio frequency power supply power to 50 W, and the treatment time to 5 minutes. After plasma treatment, cut the semi-cured polymer film to the size of the ultra-thin flexible glass + 5 mm margin, symmetrically align it on both sides of the ultra-thin flexible glass, and put it into a vacuum hot press. The vacuum degree is 10 Pa, the pressure is 0.8 MPa, the temperature is 90 °C, and keep the pressure for 15 minutes to obtain a pre-treated protective sticker; S3: Use a slot coater to coat Shin-Etsu KY-1950 on one side of the pre-treated protective sticker, control the wet film thickness to 8 μm (dry film thickness is about 5 μm). After coating, bake it at 120 °C for 15 minutes for curing. After curing is completed, cool it to room temperature to obtain a composite laminated protective sticker.

[0058] The modified vinyl alkoxysilane is from Preparation Example 1; the modified nano-silica is from Preparation Example 4.

[0059] Example 2 The production process of the composite laminated protective sticker for a folding screen in this example includes the following steps: S1: Place 100 g of modified vinyl alkoxysilane in a container, add 12 g of deionized water, 50 g of ethanol, and 0.4 g of acetic acid, and stir and mix at a speed of 400 r / min for 30 minutes to obtain a hydrolysis solution; In a reaction kettle, add 500 g of hydrogenated bisphenol A epoxy resin, heat it up to 70 °C, and successively add 300 g of hydroxyl-terminated polyisobutylene and 100 g of hydroxyl-terminated polybutadiene. Stir and mix at a speed of 800 r / min for 50 minutes, then add the hydrolysis solution and 70 g of modified nano-silica, adjust the stirring speed to 400 r / min, stir and mix for 50 minutes, cool it to room temperature, evacuate the reaction kettle to -0.1 MPa, and keep it for 25 minutes to obtain a pre-treated matrix; Mix 400 g of isophorone diamine, 6 g of benzyl dimethylamine, and 500 g of butanone evenly, and slowly drop it into the pre-treated matrix while stirring and mixing at a speed of 200 r / min for 50 minutes to obtain a mixed solution; Coat the mixed solution on a PET release film, control the wet film thickness to 42 μm, immediately transfer it to an oven at 60 °C, keep it warm for 1.5 h, then heat it up to 120 °C and keep it warm for 2 h. After curing is completed, the film layer cools to room temperature with the oven. After taking it out, place it in an environment at 25 °C and a relative humidity of 50% for 30 h to obtain a semi-cured polymer film (thickness is about 40 μm); S2: Select ultra-thin flexible glass with a thickness of 50 μm, and ultrasonically clean it successively with ethanol and deionized water for 10 minutes each time. Then, after drying with nitrogen, put it into a plasma treatment device. The device evacuates to 10 -2 Pa, introduce argon gas with a gas flow rate of 30 sccm, set the radio frequency power supply power to 50 W, and the treatment time to 5 minutes. After plasma treatment, cut the semi-cured polymer film to the size of the ultra-thin flexible glass + 5 mm margin, symmetrically align it on both sides of the ultra-thin flexible glass, and put it into a vacuum hot press. The vacuum degree is 10 Pa, the pressure is 0.8 MPa, the temperature is 90 °C, and the pressure is maintained for 25 minutes to obtain a pre-treated protective sticker; S3: Use a slot coater to coat Shin-Etsu KY-1950 on one side of the pre-treated protective sticker, control the wet film thickness to 8 μm (the dry film thickness is about 5 μm). After coating, bake it at 120 °C for 15 minutes for curing. After curing is completed, cool it to room temperature to obtain a composite laminated protective sticker.

[0060] The modified vinylalkoxysilane is from Preparation Example 2; the modified nano-silica is from Preparation Example 5.

[0061] Example 3 The production process of the composite laminated protective sticker for a folding screen in this example includes the following steps: S1: Place 90 g of modified vinylalkoxysilane in a container, add 10 g of deionized water, 45 g of ethanol, and 0.3 g of acetic acid, and stir and mix at a speed of 400 r / min for 25 minutes to obtain a hydrolysis solution; In a reaction kettle, add 450 g of hydrogenated bisphenol F-type epoxy resin, heat it up to 60 °C, successively add 260 g of hydroxyl-terminated polyisobutylene and 70 g of hydroxyl-terminated polybutadiene, stir and mix at a speed of 800 r / min for 40 minutes, then add the hydrolysis solution and 60 g of modified nano-silica, adjust the stirring speed to 400 r / min, stir and mix for 40 minutes, cool it to room temperature, evacuate the reaction kettle to -0.1 MPa, and keep it for 20 minutes to obtain a pre-treated matrix; Mix 360 g of isophorone diamine, 5 g of benzyldimethylamine, and 400 g of acetone evenly, and slowly drip it into the pre-treated matrix while stirring and mixing at a speed of 200 r / min for 40 minutes to obtain a mixed solution; Coat the mixed solution on a PET release film, control the wet film thickness to 43 μm, immediately transfer it to an oven at 60 °C, keep it warm for 1.5 h, then heat it up to 120 °C, keep it warm for 2 h. After curing is completed, the film layer cools to room temperature with the oven. After taking it out, place it in an environment at 25 °C and a relative humidity of 50% for 30 h to obtain a semi-cured polymer film (thickness about 40 μm); S2: Select an ultra-thin flexible glass with a thickness of 50 μm, and ultrasonically clean it successively with ethanol and deionized water for 10 minutes each time. Then, dry it with nitrogen gas and place it in a plasma treatment device. The device is evacuated to 10 -2 Pa, introduce argon gas with a gas flow rate of 30 sccm, set the radio frequency power supply power to 50 W, and the treatment time to 5 minutes. After plasma treatment, cut the semi-cured polymer film to the size of the ultra-thin flexible glass + a 5-mm margin, symmetrically align it on both sides of the ultra-thin flexible glass, and place it in a vacuum hot press. The vacuum degree is 10 Pa, the pressure is applied at 0.8 MPa, the temperature is 90 °C, and the pressure is maintained for 20 minutes to obtain a pre-treated protective sticker; S3: Use a slot coater to coat Shin-Etsu KY-1950 on one side of the pre-treated protective sticker, control the wet film thickness to 8 μm (dry film thickness is about 5 μm). After coating, bake it at 120 °C for 15 minutes for curing. After curing is completed, cool it to room temperature to obtain a composite layered protective sticker.

[0062] The modified vinylalkoxysilane is from Preparation Example 3; the modified nano-silica is from Preparation Example 6.

[0063] Example 4 The difference between this example and Example 3 is as follows: In step S1, coat the mixed solution on the PET release film, control the wet film thickness to 23 μm, immediately transfer it to an oven at 50 °C, keep it warm for 2 hours, then raise the temperature to 100 °C, keep it warm for 3 hours. After curing is completed, the film layer cools to room temperature with the oven. After taking it out, place it in an environment at 25 °C and a relative humidity of 50% for 24 hours to obtain a semi-cured polymer film (thickness is about 20 μm); In step S2, select an ultra-thin flexible glass with a thickness of 30 μm, and ultrasonically clean it successively with ethanol and deionized water for 10 minutes each time. Then, dry it with nitrogen gas and place it in a plasma treatment device. The device is evacuated to 10 - 2 Pa, introduce argon gas with a gas flow rate of 20 sccm, set the radio frequency power supply power to 100 W, and the treatment time to 3 minutes. After plasma treatment, cut the semi-cured polymer film to the size of the ultra-thin flexible glass + a 5-mm margin, symmetrically align it on both sides of the ultra-thin flexible glass, and place it in a vacuum hot press. The vacuum degree is 10 Pa, the pressure is applied at 0.6 MPa, the temperature is 100 °C, and the pressure is maintained for 20 minutes to obtain a pre-treated protective sticker; S3: Use a slot coater to coat Shin-Etsu KY-1950 on one side of the pre-treated protective sticker, control the wet film thickness to 10 μm (dry film thickness is about 7 μm). After coating, bake it at 110 °C for 25 minutes for curing. After curing is completed, cool it to room temperature to obtain a composite layered protective sticker.

[0064] Others are the same as in Example 3.

[0065] Example 5 The difference between this example and Example 3 is as follows: In step S1, the mixed solution was coated on a PET release film with a thickness of 33 μm, immediately transferred into an oven at 70 °C, after holding for 1 h, the temperature was raised to 130 °C, and after holding for 1 h, after the curing was completed, the film layer was cooled to room temperature with the oven, taken out, and placed in an environment at 25 °C and a relative humidity of 50% for 27 h to obtain a semi-cured polymer film (with a thickness of about 30 μm); In step S2, an ultra-thin flexible glass with a thickness of 40 μm was selected, and it was successively ultrasonically cleaned with ethanol and deionized water, with each cleaning time being 10 min. Then, after drying with nitrogen, it was placed in a plasma treatment device. The device was evacuated to 10 - 3 Pa, argon was introduced, the gas flow rate was 25 sccm, the radio frequency power supply power was set to 70 W, and the treatment time was 4 min. After plasma treatment, the semi-cured polymer film was cut into the size of the ultra-thin flexible glass + a 7-mm margin, symmetrically aligned on both sides of the ultra-thin flexible glass, placed in a vacuum hot press, the vacuum degree was 10 Pa, the pressure was applied at 0.8 MPa, the temperature was 100 °C, and the pressure was held for 25 min to obtain a pre-treated protective sticker; S3: A Shin-Etsu KY-1950 was coated on one side of the pre-treated protective sticker using a slot coater, controlling the wet film thickness to be 10 μm (the dry film thickness was about 7 μm). After coating, it was baked at 100 °C for 30 min for curing. After curing was completed, it was cooled to room temperature to obtain a composite laminated protective sticker.

[0066] Others are the same as in Example 3.

[0067] Example 6 The difference between this example and Example 5 is as follows: In step S1, in a reaction kettle, 450 g of hydrogenated bisphenol A epoxy resin was added, the temperature was raised to 70 °C, 260 g of hydroxyl-terminated polyisobutylene, 80 g of hydroxyl-terminated polybutadiene, and 30 g of methyl methacrylate-butadiene-styrene copolymer were successively added, and they were stirred and mixed at a speed of 800 r / min for 40 min. Then, a hydrolysis solution and 60 g of modified nano-silica were added, the stirring speed was adjusted to 400 r / min, and they were stirred and mixed for 40 min. The reaction kettle was evacuated to -0.1 MPa and maintained for 20 min to obtain a pre-treated matrix; Others are the same as in Example 5.

[0068] Example 7 The difference between this example and Example 6 is as follows: The dosage of the methyl methacrylate-butadiene-styrene copolymer was 50 g.

[0069] In step S3, PPG AG203 is coated on one side of the pretreated protective sticker by a slot coater, controlling the wet film thickness to be 8 μm (dry film thickness is about 5 μm), baking at 120 °C for 15 min, then coating Shin-Etsu KY-1950, controlling the wet film thickness to be 8 μm (dry film thickness is about 5 μm). After coating, bake at 120 °C for 15 min for curing. After curing is completed, cool to room temperature to obtain a composite layered protective sticker.

[0070] Others are the same as in Example 6.

[0071] Comparative Example 1 The difference between this comparative example and Example 1 lies in: The preparation method of the modified nano-silica includes the following steps: Add 100 g of nano-silica into 500 mL of ethanol solution, then place it in an ultrasonic device, set the ultrasonic power to 120 W and the frequency to 30 kHz. After ultrasonic dispersion for 30 min, add 5 g of vinyltrimethoxysilane, stir and mix evenly, then adjust the pH to 5 with 10% acetic acid by mass fraction, heat up to 40 °C, stir and react for 180 min. After the reaction ends, perform centrifugal separation, wash with ethanol 3 times, and then transfer it to a vacuum oven at 80 °C to dry to constant weight to obtain it.

[0072] Others are the same as in Example 1.

[0073] Comparative Example 2 The difference between this comparative example and Example 1 lies in: In step S1, place 80 g of vinyltrimethoxysilane in a container, add 8 g of deionized water, 40 g of ethanol, and 0.2 g of acetic acid, stir and mix at a speed of 400 r / min for 20 min to obtain a hydrolysis solution; Others are the same as in Example 1.

[0074] Comparative Example 3 The difference between this comparative example and Example 1 lies in: In step S1, in a reaction kettle, add 400 g of hydrogenated bisphenol A type epoxy resin, heat up to 50 °C, add 250 g of hydroxyl-terminated polybutadiene, stir and mix at a speed of 800 r / min for 30 min, then add the hydrolysis solution and 50 g of modified nano-silica, adjust the stirring speed to 400 r / min, stir and mix for 30 min, evacuate the reaction kettle to -0.1 MPa, and keep it for 15 min to obtain a pretreated matrix; Others are the same as in Example 1.

[0075] Performance detection The composite laminated protective stickers in Examples 1 to 7 and Comparative Examples 1 to 3 were respectively intercepted for sample testing. The sample specifications were 100 mm × 50 mm, marked in sequence, and reserved for use.

[0076] 1. Bending property test The intercepted samples were successively fixed to the fixture of the testing machine to ensure that the ultra-thin flexible glass was bent outward. The parameters were set as follows: R1.5 mm, the number of bending times was 200,000 times, the ambient temperature was 25°C ± 2°C, and the humidity was 50% ± 5%; stop and check every 50,000 times: observe whether there are microcracks on the surface of the ultra-thin flexible glass, whether the polymer film is delaminated from the ultra-thin flexible glass, and whether the functional coating is cracked. The test results are shown in Table 1.

[0077] 2. Ball drop impact test The intercepted samples were horizontally fixed to a rigid substrate respectively, with the functional coating facing up. A 100 g steel ball was freely dropped from a height of 100 mm, and the impact point was located at the center of the sample. The test was repeated 5 times. After each impact, observe whether the ultra-thin flexible glass is broken. The test results are shown in Table 1.

[0078] 3. Transmittance test The transmittance in the wavelength range of 400 - 700 nm was measured using an ultraviolet-visible spectrophotometer. The test results are shown in Table 1.

[0079] 4. Adhesion strength test The adhesion between the polymer film and the ultra-thin flexible glass was tested by the 180° peeling method, and the fixture speed was 100 mm / min. The test results are shown in Table 1.

[0080] Table 1 Performance test data of the composite laminated protective stickers in Examples 1 to 7 and Comparative Examples 1 to 3

[0081] Analysis of the performance test data in Table 1 shows that: The composite laminated protective stickers in Examples 1 to 7 are significantly superior to the comparative examples in terms of bending property, ball drop impact, transmittance, and adhesion strength through the synergistic effect of the modified silane coupling agent and the modified nano-silica. In the examples, the modified silane coupling agent grafted long-chain groups such as α,ω-diolefins and allyl polyoxyethylene ethers, improving the flexibility of the polymer film and the interfacial compatibility with UTG, and reducing the stress concentration during bending; the modified nano-silica was surface-grafted with vinyl alkoxysilane, polyether acrylate, and double-bond-containing epoxy compounds, achieving uniform dispersion in the resin matrix and enhancing the mechanical and optical properties of the film layer. After 200,000 times of R1.5 bending test, there were no obvious cracks and delamination, the UTG did not break in the ball drop impact test, the transmittance reached more than 93%, and the adhesion strength exceeded 6 N / mm.

[0082] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A composite layered protective film for a folding screen, characterized in that: From bottom to top, it includes polymer film layer, ultra-thin flexible glass, polymer film layer and functional coating; The raw materials for preparing the polymer film layer include the following components: 40-50 parts by mass of alicyclic epoxy resin, 20-30 parts by mass of terminal hydroxyl polyisobutylene, 5-10 parts by mass of terminal hydroxyl polybutadiene, 8-10 parts by mass of modified vinyl alkoxy silane, 5-7 parts by mass of modified nano silicon dioxide, 30-40 parts by mass of curing agent, 0.4-0.6 parts by mass of catalyst and 30-50 parts by mass of solvent; The modified nano-silica is nano-silica with vinyl alkoxysilane, polyether acrylate and double-bond epoxy compound grafted on the surface; The modified vinyl alkoxysilane is a vinyl alkoxysilane with α,ω-dienes and allyl polyoxyethylene ether grafted on the surface.

2. The composite layered protective sticker for a folding screen according to claim 1, characterized in that: The modified vinyl alkoxysilane is first prepared into a hydrolyzate before use.

3. The composite layered protective sticker for a folding screen according to claim 1, characterized in that: The preparation method of the modified vinyl alkoxysilane comprises the following steps: Under an inert atmosphere, vinyl alkoxysilane, part of the initiator and the solvent are mixed evenly, and then α, ω-diolefin and the polymerization inhibitor are added. The temperature is raised to 70-90°C, and after reacting for 120-180 minutes, allyl polyoxyethylene ether and the remaining initiator are added, and the reaction is continued for 120-180 minutes. Then, the product is cooled and distilled under reduced pressure to obtain the product.

4. The composite layered protective sticker for a folding screen according to claim 3, characterized in that: The molar ratio of the vinyl alkoxysilane, α,ω-dienes and allyl polyoxyethylene ether is 1:(1.1-1.3):(0.8-1.0).

5. The composite layered protective sticker for a folding screen according to claim 1, characterized in that: The preparation method of the modified nano-silicon dioxide comprises the following steps: Disperse nano-silica in ethanol solution, add vinyl alkoxysilane and mix evenly, adjust the pH to 3-5, heat to 40-60°C, react for 120-180 minutes, separate the solid and liquid, wash, add toluene, then add polyether acrylate and part of the initiator and mix evenly, heat to 70-90°C, react for 1.5-2.5 hours, then add vinyl glycidyl ester and the remaining initiator, continue to react for 1.5-2.5 hours, separate the solid and liquid, wash, and dry to obtain the product.

6. The composite layered protective sticker for a folding screen according to claim 5, characterized in that: The mass ratio of the nano-silica, vinyl alkoxysilane, polyether acrylate and vinyl glycidyl ester is 1: (0.05-0.1): (0.05-0.08): (0.03-0.05).

7. The composite layered protective sticker for a folding screen according to claim 1, characterized in that: The raw materials for preparing the polymer film layer also include 3 to 5 parts by weight of methyl methacrylate-butadiene-styrene copolymer.

8. A process for preparing the composite layered protective film for a folding screen as claimed in any one of claims 1 to 7, characterized in that: The steps include: S1: Mix modified vinyl alkoxy silane, deionized water, ethanol and acetic acid and hydrolyze for 20-30 minutes to obtain a hydrolyzate; at 50-70°C, mix alicyclic epoxy resin, terminal hydroxyl polyisobutylene and terminal hydroxyl polybutadiene, then add the hydrolyzate and modified nano-silica, mix evenly, cool, and vacuum degas to obtain a pre-treated matrix; mix a curing agent, a catalyst and a solvent evenly, add them to the pre-treated matrix, mix evenly, apply them on a release film, and pre-cure to obtain a polymer film; S2: After the ultra-thin flexible glass is plasma treated for 3-5 minutes, the polymer film is aligned and stacked on both sides of the ultra-thin flexible glass, and vacuum hot pressing is performed to obtain a pre-treated protective film; S3: coating a functional coating on the upper layer of the pre-treated protective film, curing, and cutting the shape to obtain a composite layered protective film.

9. The process for preparing the composite layered protective film for a folding screen according to claim 8, characterized in that: The mass ratio of the modified vinyl alkoxysilane, deionized water, ethanol and acetic acid is (8-10): (0.8-1.2): (4-5): (0.02-0.04).

10. The production process of the composite layered protective film for folding screen according to claim 8, characterized in that: The pre-curing is a gradient temperature curing, which specifically includes the following steps: After coating on the release film, the temperature is first raised to 50-70° C., kept warm for 1-2 hours, then continued to be raised to 110-130° C., kept warm for 1-3 hours, cooled to room temperature, and placed for 24-30 hours to obtain a polymer film.

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