Composite glass protective film for flexible folding screen and preparation method thereof

Abstract

The present application relates to the technical field of protective films, and specifically discloses a composite glass protective film for flexible folding screens and a preparation method thereof. The composite glass protective film for flexible folding screens comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer; the preparation method of the OCA adhesive layer comprises the following steps: activating the nano-silica particles to obtain modified particles with cations on the surface; reacting the modified particles with molten hydroxy acrylic resin under ultrasonic action and extruding and granulating to obtain elastic acrylic masterbatch; uniformly mixing the elastic acrylic masterbatch with a cross-linking agent and a photoinitiator to obtain an acrylic OCA optical adhesive; coating the OCA optical adhesive on one side of the release film, and curing with ultraviolet light to obtain the OCA adhesive layer. The composite glass protective film for flexible folding screens prepared by the present application improves the bending resistance of the protective film.

Description

Technical Field

[0001] The present application relates to the field of protective film technology, and more specifically, to a composite glass protective film for a flexible folding screen and a preparation method thereof. Background Art

[0002] With the advancement of science and technology, the use of foldable screens is continuously increasing, and the demand for corresponding protective films is also gradually increasing. Currently, ultra-thin glass (UTG) is widely used as a flexible protective film in the field of foldable display devices. When the thickness of UTG is reduced to below 50μm, it exhibits excellent bending performance, and the bending radius can be reduced to less than 1mm, meeting the stringent curvature radius requirements of flexible screens. However, the mechanical properties of UTG are negatively correlated with its thickness: as the thickness decreases, its impact resistance decreases significantly. As a result, in pen drop tests (simulating drops or collisions in daily use), the critical failure height is often less than 10mm, posing a very high risk of crack propagation. (For foldable tablets and foldable computers, UTG thickness is below 150μm. While increasing thickness improves strength, pen drop performance still does not significantly improve.) These reliability limitations have severely restricted the large-scale application of UTG in scenarios such as mobile terminals. To improve the impact resistance of UTG, existing technologies often use multi-layer composite structures for reinforcement.

[0003] Patent application number CN118580797A discloses a foldable screen resistant protective film, its preparation method, and application. The foldable screen resistant protective film comprises a release isolation layer, an OCA optical adhesive layer, a flexible bending layer, a silicone layer, and a protective film layer. Although this flexible foldable protective film improves the impact resistance of the protective film to a certain extent, due to the presence of the OCA adhesive layer, the OCA optical adhesive has a low elastic modulus and is difficult to fully release the applied stress. These residual stresses can cause stress corrosion, delamination, cracking, and fatigue defects in the protective film, ultimately reducing the protective film's foldability. Summary of the Invention

[0004] In order to improve the bending resistance of the protective film, the present application provides a composite glass protective film for a flexible folding screen and a preparation method thereof.

[0005] In the first aspect, the present application provides a composite glass protective film for a flexible folding screen, which adopts the following technical solution:

[0006] A composite glass protective film for a flexible folding screen, comprising, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film, and an OCA adhesive layer;

[0007] The preparation method of the OCA adhesive layer comprises the following steps:

[0008] Activating the nano-silica particles to obtain modified particles with cations on the surface;

[0009] The modified particles with a mass ratio of 1:1-3 are reacted with melted hydroxy acrylic resin under the action of 600-1000W ultrasound and extruded into granules to obtain elastic acrylic masterbatch;

[0010] The elastic acrylic masterbatch is mixed with a cross-linking agent and a photoinitiator to obtain an acrylic OCA optical adhesive;

[0011] Coat OCA optical adhesive on one side of the release film and cure it with ultraviolet light to obtain an OCA adhesive layer.

[0012] By adopting the above technical solution, the present application has developed a new UTG protective film structure, that is, a layer of thermosetting resin film is compounded on both sides of the UTG, one side is treated with a functional coating, and the other side is compounded with OCA optical glue to facilitate the screen body to fit the overall composite protective film with good bending resistance and a long service life; wherein, the thermosetting resin is insoluble and infusible after curing, has high hardness, high specific rigidity, high temperature resistance, and can form a stable, irreversible highly cross-linked network structure after curing, and has excellent dimensional stability, good corrosion resistance, high temperature resistance, wear resistance and excellent mechanical properties, which can improve the scratch resistance and wear resistance of the protective film; the functional base film has anti-fingerprint, hardening, low reflection or anti-glare functions.

[0013] In particular, the OCA adhesive layer of the present application utilizes ultrasonic cavitation to form a large number of bubbles. The nano-silica wrapped in these bubbles and the molten hydroxy acrylic resin form a core-shell structure with nano-silica as the core and hydroxy acrylic resin as the shell. At the same time, the nano-silica with cations on the surface and the hydroxy acrylic resin promote the generation of this core-shell structure through electrostatic action, thereby achieving uniform dispersion of nano-silica particles and acrylic resin polymer, which can improve the elasticity of acrylic OCA optical adhesive, avoid the defects of stress corrosion, delamination, cracking and fatigue of the protective film, and improve the bending resistance of the protective film.

[0014] Preferably, the first thermosetting polymer film and the second thermosetting polymer film are both epoxy resin films.

[0015] By adopting the above technical solution, the epoxy resin film exhibits excellent "wet" adhesion to the substrate, low shrinkage (excellent dimensional stability), chemical resistance, and excellent electrical insulation. Coatings formulated with epoxy resin exhibit excellent leveling and wettability, can be applied at room temperature or lower, and exhibit excellent protective performance after cross-linking and curing into a film. The epoxy performance molecule contains highly polar, non-hydrolyzable ether aliphatic hydroxyl groups, and the main bond has alternating rigid phenyl and flexible hydrocarbon groups. This ether bond structure imparts excellent flexibility and resilience to the product. Its long-chain structure also overcomes the steric hindrance of oligomer functional groups, allowing for better bonding to the base film during curing. This improves the adhesion stability between layers and prevents delamination or cracking of the protective film during use.

[0016] Preferably, the modified particles are prepared by adding nano-silica particles to an aqueous solution of a cationic surfactant and stirring, performing solid-liquid separation, washing the obtained solid phase, and drying to obtain the modified particles;

[0017] The mass ratio of the nano-silica particles to the cationic surfactant is 1:1-3;

[0018] The cationic surfactant is one or more of hydroxyethyl lauryl dimethyl ammonium chloride, dimethyl diallyl ammonium chloride, stearamidopropyl dimethylamine, benzyl triethyl ammonium chloride, hexadecyl trimethyl ammonium bromide and octadecyl dimethyl benzyl ammonium chloride.

[0019] By adopting the above technical solution, the cationic surfactant combines with the negative charge on the surface of the nano-silica and the surface of the modified nano-silica carries a positive charge, which can form a coating structure with the hydroxy acrylic resin through electrostatic interaction.

[0020] Preferably, the hydroxy acrylic resin is a linear hydroxy acrylic resin, and the synthesis method of the linear acrylic resin is:

[0021] Calculated by mass, the reaction monomers include 15-25 parts of methyl methacrylate, 15-25 parts of butyl acrylate, 20-35 parts of hydroxyethyl (meth)acrylate and / or hydroxypropyl (meth)acrylate, and 8-12 parts of isooctyl acrylate; the reaction monomers and the initiator are stirred and mixed until completely dissolved to obtain a premixed solution A, and the solution A is dropwise added into an organic solvent at 85-95° C., and a polymerization reaction is carried out at a temperature of 90-120° C., and the temperature is kept for 2-4 hours, and then the temperature is lowered to below 70° C. to obtain the linear hydroxy acrylic resin.

[0022] By adopting the above technical solution, the linear hydroxy acrylic resin prepared has the characteristics of high viscoelasticity, which can further improve the elasticity of the acrylic resin.

[0023] Preferably, the hydroxy acrylic resin is a reticular hydroxy acrylic resin, and the synthesis method of the reticular hydroxy acrylic resin is: adding the linear hydroxy acrylic resin to an organic solvent, adding an isocyanate crosslinking agent, and performing a crosslinking reaction at a temperature of 30-80° C. to obtain a reticular hydroxy acrylic resin;

[0024] The isocyanate cross-linking agent is one or more of toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, TDI trimer, and HDI trimer.

[0025] By adopting the above technical solution, multiple hydroxyl groups in the hydroxy acrylic resin react with the isocyanate groups in the isocyanate cross-linker to form a hydroxy acrylic resin with a spatial network structure. Due to the effect of the spatial network structure system, the prepared acrylic resin has a larger "viscoelastic effect", which further improves the viscosity and elasticity of the acrylic OCA optical adhesive.

[0026] Preferably, the epoxy resin film is made of the following raw materials in parts by weight: 60-70 parts of epoxy resin, 15-35 parts of toughening agent and 5-15 parts of curing agent, wherein the toughening agent is a core-shell particle with organic montmorillonite as the core, rubber as the secondary outer layer and polymer as the shell.

[0027] By adopting the above technical solution, the toughening agent of the present application is a type of toughening agent with rubber-coated montmorillonite as the core and polymer as the shell. On the one hand, the rubber-coated inorganic nanoparticles effectively combine the rubber and montmorillonite. When the montmorillonite undergoes plastic deformation, it can effectively inhibit the expansion of cracks in the matrix resin and absorb part of the energy, thereby playing a toughening role; at the same time, the rubber particles act as stress concentrators, which can induce silver streaks and shear bands to absorb energy and terminate silver streaks. The rubber elastic particles can also debond from the interface, release elastic strain energy, and improve the toughening and bonding strength of the material; not only can the toughening effect of 1+1>2 of the two be exerted, but the flexibility of the nanoparticles can also be improved; on the other hand, the polymer shell can achieve good compatibility with the epoxy resin. When used, the core-shell ions only need to be blended with the epoxy resin. There is no process of mutual dissolution and curing phase separation between the two. When well dispersed, the toughness of the system can be greatly improved. Since no rubber is dissolved in the resin, the addition of core-shell particles has little effect on the thermal properties of the epoxy resin.

[0028] Preferably, the preparation method of the toughening agent comprises the following steps:

[0029] (1) 1-3 parts by weight of organic montmorillonite is stirred in 100 parts by weight of deionized water at 40-50° C. for 30-60 minutes to obtain a suspension;

[0030] (2) emulsifying 20 parts by weight of an organosilicon monomer, 1-5 parts by weight of an emulsifier, 1-8 parts by weight of a silane coupling agent, 1-8 parts by weight of a vinyl silane coupling agent, and 10-20 parts by weight of deionized water for 5-10 minutes to obtain an organosilicon pre-emulsion; mixing 1-3 parts by weight of an acid catalyst and 20-25 parts by weight of deionized water to obtain an organosilicon catalyst; adding 10-40% of the organosilicon pre-emulsion and 15-25% of the organosilicon catalyst to the suspension, stirring and heating the suspension to react, and then adding the remaining organosilicon emulsion and the organosilicon catalyst to react to obtain a core layer emulsion;

[0031] (3) emulsifying 1-5 parts by weight of a double bond-containing monomer, 0.1-0.5 parts by weight of an emulsifier, and 1-3 parts by weight of deionized water to obtain a double bond-containing pre-emulsion; mixing 0.1-0.5 parts of an initiator and 1-20 parts of deionized water to obtain an initiating solution;

[0032] (4) adding the initiating liquid into the core layer emulsion, and then adding the double bond-containing pre-emulsified liquid to react to obtain a composite emulsion, and demulsifying the composite emulsion to obtain the toughening agent.

[0033] By adopting the above technical solution, the present application adopts an in-situ emulsion reaction to introduce organic montmorillonite into the polymer to form a core-shell structure, which not only has a toughening effect on the epoxy resin, but also achieves good compatibility with the epoxy resin. Evenly dispersing it in the epoxy resin can greatly improve the toughness of the system.

[0034] Preferably, in step (1), the organic montmorillonite is obtained by modifying montmorillonite with organic cations.

[0035] By adopting the above technical solution, the strong hydrophilicity of the montmorillonite surface hinders its dispersion in and wetting by the organic phase. By organically modifying the montmorillonite, the surface becomes hydrophobic. Through particle exchange with organic cations, the cations between the montmorillonite layers are replaced by organic cations. Simultaneously, since the lamellae are covered with organic groups, the surface properties of the montmorillonite are altered, changing the hydrophilicity of the raw material to a lipophilicity on both the inner and outer surfaces, thereby improving compatibility with polymers.

[0036] Preferably, in step (2), the silicon monomer is one of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and low molecular weight hydroxy silicone oil; the silane coupling agent is one or more of methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltrimethoxysilane, and tetraethyl silicate; the vinyl silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane; the acid catalyst is one or more of benzenesulfonic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, hydrochloric acid, and sulfuric acid;

[0037] The emulsifier in steps (2) and (3) is one or more of sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, dodecylbenzenesulfonic acid, sodium didodecylphenyl ether disulfonate, isomeric tridecyl alcohol ether and sorbitan monolaurate;

[0038] In step (3), the double bond-containing monomer is one or more of styrene, methyl methacrylate, butyl acrylate, isooctyl acrylate, acrylic acid, and lauryl methacrylate; and the initiator is one of potassium persulfate, ammonium persulfate, and sodium persulfate.

[0039] Preferably, the epoxy resin is one of bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol F epoxy resin, ester ring epoxy resin, multifunctional glycidyl ester, linear phenolic epoxy resin, and brominated epoxy resin.

[0040] Preferably, the preparation method of the epoxy resin film is: adding epoxy resin and curing agent into acetone solution according to a ratio to obtain a blended solution, adding toughening agent into the blended solution to obtain a dispersion; and coating the dispersion on a release film to obtain the epoxy resin film.

[0041] Preferably, the epoxy resin film has a thickness of 10-100 μm;

[0042] The thickness of the functional base film is 25-75 μm;

[0043] The thickness of the UTG ultra-thin glass layer is 30-150 μm;

[0044] The thickness of the OCA adhesive layer is 10-100 μm.

[0045] In a second aspect, the present application provides a method for preparing a composite glass protective film for a flexible folding screen, which adopts the following technical solution:

[0046] A method for preparing a composite glass protective film for a flexible folding screen comprises the following steps:

[0047] The functional base film, the first thermosetting polymer film, the UTG ultra-thin glass and the second thermosetting polymer film are stacked in sequence from top to bottom, and the film layers are pressed together by hot pressing to form a composite layer;

[0048] The OCA adhesive layer is laminated to the second thermosetting polymer film in the composite layer to form a composite glass protective film.

[0049] In summary, this application has the following beneficial effects:

[0050] 1. In the OCA adhesive layer of the present application, a large number of bubbles can be formed by ultrasonic cavitation. The nano-silica wrapped in these bubbles and the molten hydroxy acrylic resin form a core-shell structure with nano-silica as the core and hydroxy acrylic resin as the shell. At the same time, the nano-silica with cations on the surface and the hydroxy acrylic resin promote the formation of this core-shell structure through electrostatic interaction, thereby achieving uniform dispersion of nano-silica particles and acrylic resin polymer, which can improve the elasticity of acrylic OCA optical adhesive, avoid the defects of stress corrosion, delamination, cracking and fatigue of the protective film, and improve the bending resistance of the protective film.

[0051] 2. The linear hydroxy acrylic resin prepared in this application has high viscoelasticity, which can further improve the elasticity of acrylic resin.

[0052] 3. The network hydroxy acrylic resin prepared in this application has a large "viscoelastic effect" due to the effect of the spatial network structure system, which further improves the viscosity and elasticity of the acrylic OCA optical adhesive.

[0053] 4. The toughening agent of the present application is a core-shell particle with organic montmorillonite as the core, rubber as the secondary outer layer, and polymer as the shell. The organic montmorillonite and rubber as the core layer can not only exert the toughening effect of 1+1>2 of the two, but also improve the flexibility of the nanoparticles; on the other hand, the polymer shell can achieve good compatibility with epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is the infrared spectrum of the hydroxy acrylic resin prepared in Preparation Example 1. DETAILED DESCRIPTION

[0055] The present application is further described in detail below with reference to the embodiments.

[0056] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0057] Preparation Example 1-7 Hydroxyacrylate Resin

[0058] Preparation Example 1

[0059] 25 g of methyl methacrylate, 25 g of butyl acrylate, 15 g of hydroxyethyl acrylate, 15 g of hydroxypropyl acrylate, 10 g of isooctyl acrylate and 1 g of azobisisobutyronitrile were stirred and mixed until completely dissolved to obtain a premixed solution A, and the mixed solution A was added dropwise to 30 g of 90° C. tetrahydrofuran, and a polymerization reaction was carried out at 105° C. and kept warm for 3 hours, and then cooled to below 70° C. to obtain a linear hydroxy acrylic resin.

[0060] Preparation Example 2

[0061] 25 g of methyl methacrylate, 25 g of butyl acrylate, 15 g of hydroxyethyl acrylate, 15 g of hydroxypropyl acrylate, 10 g of isooctyl acrylate and 1 g of azobisisobutyronitrile were stirred and mixed until completely dissolved to obtain a premixed solution A, and the mixed solution A was dropwise added to 30 g of 90° C. tetrahydrofuran, and a polymerization reaction was carried out at 105° C. and kept warm for 3 hours, and then cooled to below 70° C. to obtain a linear hydroxy acrylic resin; 0.1 mol of the linear hydroxy acrylic resin was added to 300 ml of propylene glycol methyl ether acetate, and 0.04 mol of isophorone isocyanate crosslinking agent was added to carry out crosslinking at a temperature of 50° C. to obtain a reticulated hydroxy acrylic resin.

[0062] Preparation Example 3

[0063] 15 g of methyl methacrylate, 15 g of butyl acrylate, 35 g of hydroxyethyl acrylate, 8 g of isooctyl acrylate and 1 g of azobisisobutyronitrile were stirred and mixed until completely dissolved to obtain a premixed solution A. The mixed solution A was added dropwise to 30 g of 90° C. tetrahydrofuran, and a polymerization reaction was carried out at 105° C. and kept warm for 3 hours, and then cooled to below 70° C. to obtain a linear hydroxy acrylic resin.

[0064] Preparation Example 4

[0065] 15 g of methyl methacrylate, 15 g of butyl acrylate, 35 g of hydroxypropyl acrylate, 8 g of isooctyl acrylate and 1 g of azobisisobutyronitrile were stirred and mixed until completely dissolved to obtain a premixed solution A. The mixed solution A was added dropwise to 30 g of 90° C. tetrahydrofuran, and a polymerization reaction was carried out at 105° C. and kept warm for 3 hours, and then cooled to below 70° C. to obtain a linear hydroxy acrylic resin.

[0066] Preparation Example 5

[0067] 35 g of methyl methacrylate, 35 g of butyl acrylate, 10 g of hydroxyethyl acrylate, 10 g of hydroxypropyl acrylate, 10 g of isooctyl acrylate and 1 g of azobisisobutyronitrile were stirred and mixed until completely dissolved to obtain a premixed solution A, and the mixed solution A was added dropwise to 30 g of 90° C. tetrahydrofuran, and a polymerization reaction was carried out at 105° C. and kept warm for 3 hours, and then cooled to below 70° C. to obtain a linear hydroxy acrylic resin.

[0068] Preparation Example 6

[0069] 25 g of methyl methacrylate, 25 g of butyl acrylate, 15 g of hydroxyethyl acrylate, 15 g of hydroxypropyl acrylate, 10 g of isooctyl acrylate and 1 g of azobisisobutyronitrile were stirred and mixed until completely dissolved to obtain a premixed solution A, and the mixed solution A was added dropwise to 30 g of 85° C. tetrahydrofuran, and a polymerization reaction was carried out at 90° C. and kept warm for 4 hours, and then cooled to below 70° C. to obtain a linear hydroxy acrylic resin.

[0070] Preparation Example 7

[0071] 25 g of methyl methacrylate, 25 g of butyl acrylate, 15 g of hydroxyethyl acrylate, 15 g of hydroxypropyl acrylate, 10 g of isooctyl acrylate and 1 g of azobisisobutyronitrile were stirred and mixed until completely dissolved to obtain a premixed solution A, and the mixed solution A was added dropwise to 30 g of 95° C. tetrahydrofuran, and a polymerization reaction was carried out at 120° C. and kept warm for 2 hours, and then cooled to below 70° C. to obtain a linear hydroxy acrylic resin.

[0072] The elasticity test of the hydroxy acrylic resins of Preparation Examples 1-7 was performed with reference to GB / T 1040, and the specific data are recorded in Table 1.

[0073] Table 1 Performance test data of hydroxy acrylic resins of Preparation Examples 1-7

[0074]

[0075] Referring to Table 1, it can be seen that the hydroxyl content of the hydroxy acrylate in Preparation Examples 3 and 4 is higher than that in Preparation Example 1, while the hydroxyl content in Preparation Example 5 is lower than that in Preparation Example 1. An appropriate amount of hydroxyl groups (provided by hydroxyethyl acrylate and hydroxypropyl acrylate) serve as active sites for cross-linking reactions and can form a medium-density three-dimensional network (cross-linking degree 75%-80%) with the cross-linking agent, which not only avoids the sudden increase in resin viscosity and brittle defects caused by high hydroxyl content, but also prevents insufficient cross-linking and decreased adhesion caused by low hydroxyl content. At the same time, the hydroxyl groups and the silicon hydroxyl groups on the surface of the nano-silica form chemical anchors through hydrogen bonds or covalent bonds, and the ultrasonic cavitation effect promotes the "hard core" -Soft shell" core-shell structure is uniformly dispersed. By adjusting the content and reaction parameters between acrylic monomers, acrylic resins with different elasticities can be obtained. By comparison, it was found that 25g of methyl methacrylate, 25g of butyl acrylate, 15g of hydroxyethyl acrylate, 15g of hydroxypropyl acrylate, 10g of isooctyl acrylate and 1g of azobisisobutyronitrile were stirred and mixed until completely dissolved to obtain a premixed solution A, and the mixed solution A was added dropwise to 30g of 90°C tetrahydrofuran. The polymerization reaction was carried out at 105°C and kept warm for 3h, and then cooled to below 70°C. The linear hydroxy acrylic resin obtained had the highest elastic modulus and the highest elasticity. At the same time, the infrared spectrum of the hydroxy acrylic resin of Preparation Example 1 is shown as follows: Figure 1 shown.

[0076] Preparation Example 8-12 OCA adhesive layer

[0077] Preparation Example 8

[0078] S1: 5 g of nano-silica particles were added to 24 L of deionized water and stirred and dispersed using a magnetic stirrer at 600 rpm to obtain a dispersion; 5 g of octadecyldimethylbenzyl ammonium chloride was added and stirred for 2 h, followed by solid-liquid separation. The resulting solid phase was repeatedly washed with deionized water and ethanol, and dried to obtain modified particles; the modified particles were tested for potential using a zeta potential meter, and the surface of the modified nano-silica was found to have a positive charge;

[0079] S2: 5 g of hydroxylated acrylic resin was added from the main feed port of a twin-screw extruder, and 5 g of modified particles were added from the side feed port. An ultrasonic generator was introduced close to the side feed port. Under the condition of an ultrasonic power of 600 W, elastic acrylic masterbatch was obtained by extrusion granulation.

[0080] S3: 9.5 g of elastic acrylic masterbatch, 0.15 g of ethylene glycol diacrylate and 0.35 g of photoinitiator 1173 were mixed to obtain acrylic OCA optical adhesive for later use;

[0081] S4: an automatic coating device is used to apply acrylic OCA optical adhesive on one side of the release film, and an OCA adhesive layer with a thickness of 50 μm is obtained after UV curing.

[0082] Preparation Example 9

[0083] S1: 0.5 g of nano-silica particles were added to 2.4 L of deionized water and stirred and dispersed using a magnetic stirrer at 600 rpm to obtain a dispersion; 1 g of hexadecyltrimethylammonium bromide was added and stirred for 2 h. The solid-liquid separation was performed and the resulting solid phase was repeatedly washed with deionized water and ethanol and dried to obtain modified particles; the modified particles were tested for potential using a zeta potential meter, and it was found that the surface of the modified nano-silica had a positive charge;

[0084] S2: 10 g of hydroxylated acrylic resin was added from the main feed port of a twin-screw extruder, and 5 g of modified particles were added from the side feed port. An ultrasonic generator was introduced close to the side feed port. Under an ultrasonic power of 800 W, elastic acrylic masterbatch was obtained by extrusion granulation.

[0085] S3: 9.5 g of elastic acrylic masterbatch, 0.15 g of ethylene glycol diacrylate and 0.35 g of photoinitiator 1173 were mixed to obtain acrylic OCA optical adhesive for later use;

[0086] S4: an automatic coating device is used to apply acrylic OCA optical adhesive on one side of the release film, and an OCA adhesive layer with a thickness of 50 μm is obtained after UV curing.

[0087] Preparation Example 10

[0088] S1: 0.5 g of nano-silica particles were added to 2.4 L of deionized water and stirred and dispersed at 600 rpm using a magnetic stirrer to obtain a dispersion; 1.5 g of dimethyldiallylammonium chloride was added and stirred for 2 h, followed by solid-liquid separation. The resulting solid phase was repeatedly washed with deionized water and ethanol, and dried to obtain modified particles; the modified particles were tested for potential using a zeta potential meter, and it was found that the surface of the modified nano-silica had a positive charge;

[0089] S2: 15 g of hydroxylated acrylic resin was added from the main feed port of a twin-screw extruder, and 5 g of modified particles were added from the side feed port. An ultrasonic generator was introduced close to the side feed port. Under an ultrasonic power of 1000 W, elastic acrylic masterbatch was obtained by extrusion granulation.

[0090] S3: 9.5 g of elastic acrylic masterbatch, 0.15 g of ethylene glycol diacrylate and 0.35 g of photoinitiator 1173 were mixed to obtain acrylic OCA optical adhesive for later use;

[0091] S4: an automatic coating device is used to apply acrylic OCA optical adhesive on one side of the release film, and an OCA adhesive layer with a thickness of 50 μm is obtained after UV curing.

[0092] Preparation Example 11

[0093] S1: 0.5 g of nano-silica particles were added to 2.4 L of deionized water and stirred and dispersed using a magnetic stirrer at 600 rpm to obtain a dispersion; 1 g of hexadecyltrimethylammonium bromide was added and stirred for 2 h. The solid-liquid separation was performed and the resulting solid phase was repeatedly washed with deionized water and ethanol and dried to obtain modified particles; the modified particles were tested for potential using a zeta potential meter, and it was found that the surface of the modified nano-silica had a positive charge;

[0094] S2: 10 g of linear hydroxyl acrylic resin was added from the main feed port of a twin-screw extruder, and 5 g of modified particles were added from the side feed port. An ultrasonic generator was introduced close to the side feed port. Under an ultrasonic power of 600 W, elastic acrylic masterbatch was obtained by extrusion granulation; wherein the linear hydroxyl acrylic resin was obtained from Preparation Example 1;

[0095] S3: 9.5 g of elastic acrylic masterbatch, 0.15 g of ethylene glycol diacrylate and 0.35 g of photoinitiator 1173 were mixed to obtain acrylic OCA optical adhesive for later use;

[0096] S4: an automatic coating device is used to apply acrylic OCA optical adhesive on one side of the release film, and an OCA adhesive layer with a thickness of 50 μm is obtained after UV curing.

[0097] Preparation Example 12

[0098] S1: 0.5 g of nano-silica particles were added to 2.4 L of deionized water and stirred and dispersed using a magnetic stirrer at 600 rpm to obtain a dispersion; 1 g of hexadecyltrimethylammonium bromide was added and stirred for 2 h. The solid-liquid separation was performed and the resulting solid phase was repeatedly washed with deionized water and ethanol and dried to obtain modified particles; the modified particles were tested for potential using a zeta potential meter, and it was found that the surface of the modified nano-silica had a positive charge;

[0099] S2: 10 g of reticulated hydroxyl acrylic resin was added from the main feed port of a twin-screw extruder, and 5 g of modified particles were added from the side feed port. An ultrasonic generator was introduced close to the side feed port. Under an ultrasonic power of 600 W, elastic acrylic masterbatch was obtained by extrusion and granulation. The reticulated hydroxyl acrylic resin was obtained from Preparation Example 2.

[0100] S3: 9.5 g of elastic acrylic masterbatch, 0.15 g of ethylene glycol diacrylate and 0.35 g of photoinitiator 1173 were mixed to obtain acrylic OCA optical adhesive for later use;

[0101] S4: an automatic coating device is used to apply acrylic OCA optical adhesive on one side of the release film, and an OCA adhesive layer with a thickness of 50 μm is obtained after UV curing.

[0102] Preparation Examples 13-18 Epoxy Resin Film

[0103] Preparation Example 13

[0104] (1) Add 5 g of montmorillonite to 20 L of deionized water, stir and disperse it at a speed of 500 rpm using a magnetic stirrer to obtain a suspension, let it stand for 24 h, take the upper suspension and centrifuge it, dry it to obtain purified montmorillonite; weigh 3 g of purified montmorillonite and add it to 100 ml of deionized water to prepare a dispersion, stir it evenly and then add 2 mol / L hydrochloric acid solution dropwise to adjust the pH of the dispersion to 5, dissolve 0.6 g of hexadecyltrimethylammonium bromide in 50 ml of water, heat it slightly to completely dissolve it, then add it dropwise to the dispersion, heat it to 80 ° C and keep it at a constant temperature of 800 rpm for 3 h, cool, filter, wash, dry, grind, and pass through a 200 mesh sieve to obtain organic montmorillonite; stir 1 g of organic montmorillonite in 100 g of deionized water at 40 ° C for 30 min to obtain a suspension;

[0105] 20g hexamethylcyclotrisiloxane, 1g sodium dodecylbenzenesulfonate, 1g methyltrimethoxysilane, 1g γ-methacryloyloxypropyltrimethoxysilane and 10g deionized water were emulsified for 5 minutes to obtain an organosilicon pre-emulsion; 1g benzenesulfonic acid was mixed with 20g deionized water to obtain an organosilicon catalyst; 10% of the above organosilicon pre-emulsion and 15% of the organosilicon catalyst were added to the above suspension, stirred and heated to 75°C for 1h, and then the remaining organosilicon pre-emulsion and organosilicon catalyst were added and heated to 80°C for 3h to adjust the pH. to 9 to obtain a core layer emulsion; emulsify 1g of styrene, 0.1g of sodium dodecylbenzenesulfonate and 1g of deionized water to obtain a double bond pre-emulsion; mix 0.1g of potassium persulfate and 1g of deionized water to obtain an initiator; add the above initiator to the core layer emulsion, then add the above double bond emulsion and react at 80°C for 1.5h, then cool to 25°C to obtain a composite emulsion; add 35g of a 5wt% potassium chloride aqueous solution to the composite emulsion for demulsification, wash the precipitate with water to remove residual monomers and emulsifier, and dry to obtain a toughening agent;

[0106] (2) Mix 60g of bisphenol A epoxy resin and 5g of 4,4 ， -diaminodiphenylmethane were mixed and added to acetone solvent to obtain a blended solution after complete dissolution. 35 g of toughening agent was added to the blended solution and dispersed for 15 minutes to obtain a dispersed solution. The dispersed solution was coated on a release film to control the thickness of the epoxy resin film to be 30 μm.

[0107] Preparation Example 14

[0108] (1) Add 5 g of montmorillonite to 20 L of deionized water, stir and disperse it at a speed of 500 rpm using a magnetic stirrer to obtain a suspension, let it stand for 24 h, take the upper suspension and centrifuge it, dry it to obtain purified montmorillonite; weigh 3 g of purified montmorillonite and add it to 100 ml of deionized water to prepare a dispersion, stir it evenly and then add 2 mol / L hydrochloric acid solution dropwise to adjust the pH of the dispersion to 5, dissolve 0.6 g of hexadecyltrimethylammonium bromide in 50 ml of water, heat it slightly to completely dissolve it, then add it dropwise to the dispersion, heat it to 80 ° C and keep it at a constant temperature of 800 rpm for 3 h, cool, filter, wash, dry, grind, and pass through a 200 mesh sieve to obtain organic montmorillonite; stir 2 g of organic montmorillonite in 100 g of deionized water at 45 ° C for 45 min to obtain a suspension;

[0109] 20g of octamethylcyclotetrasiloxane, 3g of sodium dodecylsulfonate, 5g of methyltriethoxysilane, 5g of vinyltrimethoxysilane and 15g of deionized water were emulsified for 8min to obtain an organosilicon pre-emulsion; 2g of p-toluenesulfonic acid and 22g of deionized water were mixed to obtain an organosilicon catalyst; 25% of the above-mentioned organosilicon pre-emulsion and 20% of the organosilicon catalyst were added to the above-mentioned suspension, stirred and heated to 75°C for reaction for 1h, and then the remaining organosilicon pre-emulsion and organosilicon catalyst were added, heated to 80°C and kept at this temperature for reaction for 3h, and the pH was adjusted to 9 to obtain a core layer emulsion; emulsifying 3g of methyl methacrylate, 0.3g of sodium dodecylsulfonate and 2g of deionized water to obtain a pre-emulsion containing double bonds; mixing 0.3g of sodium persulfate and 10g of deionized water to obtain an initiator; adding the above initiator to the core layer emulsion, and then adding the above emulsion containing double bonds to react at 80°C for 1.5h, cooling to 25°C to obtain a composite emulsion; adding 35g of a 5wt% potassium chloride aqueous solution to the composite emulsion for demulsification, washing the precipitate with water to remove residual monomers and emulsifier, and drying to obtain a toughening agent;

[0110] (2) Mix 65g hydrogenated bisphenol A epoxy resin and 10g 4,4 ， -diaminodiphenylmethane were mixed and added to acetone solvent to obtain a blended solution after complete dissolution. 25 g of toughening agent was added to the blended solution and dispersed for 15 minutes to obtain a dispersed solution. The dispersed solution was coated on a release film to control the thickness of the epoxy resin film to be 30 μm.

[0111] Preparation Example 15

[0112] (1) Add 5 g of montmorillonite to 20 L of deionized water, stir and disperse it at a speed of 500 rpm using a magnetic stirrer to obtain a suspension, let it stand for 24 h, take the upper suspension and centrifuge it, dry it to obtain purified montmorillonite; weigh 3 g of purified montmorillonite and add it to 100 ml of deionized water to prepare a dispersion, stir it evenly and then add 2 mol / L hydrochloric acid solution dropwise to adjust the pH of the dispersion to 5, dissolve 0.6 g of hexadecyltrimethylammonium bromide in 50 ml of water, heat it slightly to completely dissolve it, then add it dropwise to the dispersion, heat it to 80 ° C and keep it at a constant temperature of 800 rpm for 3 h, cool, filter, wash, dry, grind, and pass through a 200 mesh sieve to obtain organic montmorillonite; stir 3 g of organic montmorillonite in 100 g of deionized water at 50 ° C for 60 min to obtain a suspension;

[0113] 20g of low molecular weight hydroxy silicone oil (CAS: 70131-67-8), 5g of dodecylbenzenesulfonic acid, 8g of phenyltrimethoxysilane, 8g of vinyltriethoxysilane and 20g of deionized water were emulsified for 8 minutes to obtain an organosilicon pre-emulsion; 3g of dodecylbenzenesulfonic acid and 25g of deionized water were mixed to obtain an organosilicon catalyst; 25% of the above organosilicon pre-emulsion and 20% of the organosilicon catalyst were added to the above suspension, stirred and heated to 75°C for reaction for 1 hour, and then the remaining organosilicon pre-emulsion and organosilicon catalyst were added and heated to 80°C for constant temperature reaction for 3 hours. Adjusting the pH to 9 to obtain a core layer emulsion; emulsifying 5 g of butyl acrylate, 0.5 g of dodecylbenzenesulfonic acid, and 3 g of deionized water to obtain a double bond pre-emulsion; mixing 0.5 g of ammonium persulfate and 20 g of deionized water to obtain an initiator; adding the initiator to the core layer emulsion, then adding the double bond emulsion to the mixture, and reacting at 80° C. for 1.5 hours, then cooling to 25° C. to obtain a composite emulsion; adding 35 g of a 5 wt % potassium chloride aqueous solution to the composite emulsion for demulsification, washing the precipitate with water to remove residual monomers and emulsifier, and drying to obtain a toughening agent;

[0114] (2) Mix 70g of bisphenol F epoxy resin and 15g of 4,4 ， -diaminodiphenylmethane were mixed and added to acetone solvent to obtain a blended solution after complete dissolution. 15 g of toughening agent was added to the blended solution and dispersed for 15 minutes to obtain a dispersed solution. The dispersed solution was coated on a release film to control the thickness of the epoxy resin film to be 30 μm.

[0115] Preparation Example 16

[0116] (1) Add 5 g of montmorillonite to 20 L of deionized water, stir and disperse it with a magnetic stirrer at a speed of 500 rpm to obtain a suspension, let it stand for 24 h, take the upper suspension and centrifuge it, and dry it to obtain purified montmorillonite; weigh 3 g of purified montmorillonite and add it to 100 ml of deionized water to prepare a dispersion, stir it evenly and then add 2 mol / L hydrochloric acid solution dropwise to adjust the pH of the dispersion to 5, dissolve 0.6 g of hexadecyltrimethylammonium bromide in 50 ml of water, heat it slightly to completely dissolve it, then add it dropwise to the dispersion, heat it to 80 ° C and react at a constant temperature of 800 rpm for 3 h, cool, filter, wash, dry, grind, and pass through a 200 mesh sieve to obtain organic montmorillonite;

[0117] (2) 65 g of hydrogenated bisphenol A epoxy resin and 10 g of 4,4-diaminodiphenylmethane were mixed and added to acetone solvent to obtain a blend solution after complete dissolution. 25 g of organic montmorillonite (toughening agent) was added to the blend solution and dispersed for 15 minutes to obtain a dispersed solution. The dispersed solution was coated on a release film to control the thickness of the epoxy resin film to be 30 μm.

[0118] Preparation Example 17

[0119] (1) 20g of octamethylcyclotetrasiloxane, 3g of sodium dodecylsulfonate, 5g of methyltriethoxysilane, 5g of vinyltrimethoxysilane and 15g of deionized water were emulsified for 8min to obtain an organosilicon pre-emulsion; 2g of p-toluenesulfonic acid was mixed with 22g of deionized water to obtain an organosilicon catalyst; 1g of sodium dodecylbenzenesulfonate was stirred with 10g of deionized water and heated to 55°C, and then 25% of the above-mentioned organosilicon pre-emulsion and 20% of the organosilicon catalyst were added to the above-mentioned suspension, stirred and heated to 80°C for 1h, and then the remaining organosilicon pre-emulsion and organosilicon catalyst were added and kept at a constant temperature for 3h to obtain an organosilicon catalyst. to the core layer emulsion; emulsifying 3g of methyl methacrylate, 0.3g of sodium dodecylsulfonate and 2g of deionized water to obtain a pre-emulsion containing double bonds; mixing 0.3g of sodium persulfate and 10g of deionized water to obtain an initiator; stirring the above 10g of the core layer emulsion and 1g of sodium dodecylbenzenesulfonate and heating to 80°C, and adding the above initiator and the emulsion containing double bonds to react at a constant temperature for 1.5h, and then cooling to 25°C to obtain a composite emulsion; adding 35g of a 5wt% potassium chloride aqueous solution to the composite emulsion for demulsification, washing the precipitate with water to remove residual monomers and emulsifier, and drying to obtain a nano silicone rubber core-shell polymer;

[0120] (2) Mix 65g hydrogenated bisphenol A epoxy resin and 10g 4,4 ， -diaminodiphenylmethane were mixed and added to acetone solvent to obtain a blend solution after complete dissolution. 25 g of nano silicone rubber core-shell polymer (toughening agent) was added to the blend solution and dispersed for 15 minutes to obtain a dispersed solution. The dispersed solution was coated on a release film to control the thickness of the epoxy resin film to be 30 μm.

[0121] Preparation Example 18

[0122] (1) Add 5 g of montmorillonite to 20 L of deionized water, stir and disperse it with a magnetic stirrer at a speed of 500 rpm to obtain a suspension, let it stand for 24 h, take the upper suspension and centrifuge it, and dry it to obtain purified montmorillonite; weigh 3 g of purified montmorillonite and add it to 100 ml of deionized water to prepare a dispersion, stir it evenly and then add 2 mol / L hydrochloric acid solution dropwise to adjust the pH of the dispersion to 5, dissolve 0.6 g of hexadecyltrimethylammonium bromide in 50 ml of water, heat it slightly to completely dissolve it, then add it dropwise to the dispersion, heat it to 80 ° C and react at a constant temperature of 800 rpm for 3 h, cool, filter, wash, dry, grind, and pass through a 200 mesh sieve to obtain organic montmorillonite;

[0123] (2) 20g of octamethylcyclotetrasiloxane, 3g of sodium dodecylsulfonate, 5g of methyltriethoxysilane, 5g of vinyltrimethoxysilane and 15g of deionized water were emulsified for 8min to obtain an organosilicon pre-emulsion; 2g of p-toluenesulfonic acid was mixed with 22g of deionized water to obtain an organosilicon catalyst; 1g of sodium dodecylbenzenesulfonate was stirred with 10g of deionized water and heated to 55°C, and then the above 25% organosilicon pre-emulsion and 20% organosilicon catalyst were added to the above suspension, stirred and heated to 80°C for 1h, and then the remaining organosilicon pre-emulsion and organosilicon catalyst were added and kept at a constant temperature for 3h to obtain an organosilicon catalyst. to the core layer emulsion; emulsifying 3g of methyl methacrylate, 0.3g of sodium dodecylsulfonate and 2g of deionized water to obtain a pre-emulsion containing double bonds; mixing 0.3g of sodium persulfate and 10g of deionized water to obtain an initiator; stirring the above 10g of the core layer emulsion and 1g of sodium dodecylbenzenesulfonate and heating to 80°C, and adding the above initiator and the emulsion containing double bonds to react at a constant temperature for 1.5h, and then cooling to 25°C to obtain a composite emulsion; adding 35g of a 5wt% potassium chloride aqueous solution to the composite emulsion for demulsification, washing the precipitate with water to remove residual monomers and emulsifier, and drying to obtain a nano silicone rubber core-shell polymer;

[0124] (3) Mix 65g hydrogenated bisphenol A epoxy resin and 10g 4,4 ， -diaminodiphenylmethane were mixed and added to acetone solvent to obtain a blend solution after complete dissolution. 5g of organic montmorillonite and 25g of nano silicone rubber core-shell polymer (toughening agent) were added to the blend solution and dispersed for 15 minutes to obtain a dispersed solution. The dispersed solution was coated on a release film to control the thickness of the epoxy resin film to be 30μm.

[0125] Example 1

[0126] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0127] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0128] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size of the film is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 16. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0129] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the outer shape is cut by laser to make a protective film, wherein the OCA adhesive layer comes from Preparation Example 8, and its outer size is 2mm larger than the outer size of the UTG ultra-thin glass.

[0130] Example 2

[0131] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0132] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0133] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size of the film is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 16. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0134] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the protective film is made by laser cutting the shape, wherein the OCA adhesive layer comes from Preparation Example 9, and its outer dimensions are 2 mm larger than the outer dimensions of the UTG ultra-thin glass.

[0135] Example 3

[0136] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0137] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0138] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size of the film is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 16. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0139] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the outer shape is cut by laser to make a protective film, wherein the OCA adhesive layer comes from Preparation Example 10, and its outer size is 2mm larger than the outer size of the UTG ultra-thin glass.

[0140] Example 4

[0141] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0142] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0143] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size of the film is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 16. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0144] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the protective film is made by laser cutting the shape, wherein the OCA adhesive layer comes from Preparation Example 11, and its outer dimensions are 2 mm larger than the outer dimensions of the UTG ultra-thin glass.

[0145] Example 5

[0146] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0147] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0148] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size of the film is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 16. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0149] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the protective film is made by laser cutting the shape, wherein the OCA adhesive layer comes from Preparation Example 12, and its outer dimensions are 2 mm larger than the outer dimensions of the UTG ultra-thin glass.

[0150] Example 6

[0151] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0152] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0153] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 17. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG strengthening process.

[0154] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the protective film is made by laser cutting the shape, wherein the OCA adhesive layer comes from Preparation Example 12, and its outer dimensions are 2 mm larger than the outer dimensions of the UTG ultra-thin glass.

[0155] Example 7

[0156] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0157] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0158] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size of the film is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 18. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0159] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the protective film is made by laser cutting the shape, wherein the OCA adhesive layer comes from Preparation Example 12, and its outer dimensions are 2 mm larger than the outer dimensions of the UTG ultra-thin glass.

[0160] Example 8

[0161] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0162] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0163] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size of the film is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 15. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0164] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the protective film is made by laser cutting the shape, wherein the OCA adhesive layer comes from Preparation Example 12, and its outer dimensions are 2 mm larger than the outer dimensions of the UTG ultra-thin glass.

[0165] Example 9

[0166] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0167] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0168] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 14. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0169] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the protective film is made by laser cutting the shape, wherein the OCA adhesive layer comes from Preparation Example 12, and its outer dimensions are 2 mm larger than the outer dimensions of the UTG ultra-thin glass.

[0170] Example 10

[0171] This embodiment provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0172] This embodiment also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0173] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 13. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0174] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the protective film is made by laser cutting the shape, wherein the OCA adhesive layer comes from Preparation Example 12, and its outer dimensions are 2 mm larger than the outer dimensions of the UTG ultra-thin glass.

[0175] Comparative Example 1

[0176] This comparative example provides a composite glass protective film for a flexible folding screen, which comprises, from top to bottom, a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film and an OCA adhesive layer.

[0177] This comparative example also provides a method for preparing the composite glass protective film for the flexible folding screen, comprising the following steps:

[0178] From top to bottom, the functional base film, the first thermosetting polymer film, the UTG ultra-thin glass layer, and the second thermosetting polymer film are sequentially pressed together by vacuum hot pressing to form a composite layer, wherein the temperature during vacuum hot pressing is 150° C. The size of the thermosetting polymer film is 5 mm larger than the outer shape of the UTG ultra-thin glass. The functional base film is a polydimethylsiloxane film etched by femtosecond laser so that the film has an anti-fingerprint effect. The size of the film is 5 mm larger than the outer shape of the UTG ultra-thin glass and the thickness is 25 μm. The first thermosetting polymer film and the second thermosetting polymer film are both from Preparation Example 16. The UTG ultra-thin glass layer is a 30 μm glass obtained by UTG using a strengthening process.

[0179] The OCA adhesive layer is bonded to the second thermosetting polymer layer in the composite layer using a bonding device, and then the shape is cut by laser to make a protective film. The preparation method of the OCA adhesive layer is as follows: 9.5g of elastic acrylic masterbatch, 0.15g of ethylene glycol diacrylate and 0.35g of photoinitiator 1173 are mixed evenly to obtain acrylic OCA optical adhesive for standby use; an automatic coating device is used to coat the acrylic OCA optical adhesive on one side of the release film, and after ultraviolet light curing, an OCA adhesive layer with a thickness of 50μm is obtained, and its outer dimensions are 2mm larger than the outer dimensions of the UTG ultra-thin glass.

[0180] Performance testing

[0181] Testing standards:

[0182] Bending resistance test: The OCA adhesive layer in the composite glass protective film prepared in Examples 1-10 and Comparative Example 1 was attached to a 0.1mm flexible tempered film, which was fixed on a folding screen test prop, and a bendability test was performed using an LW-102W folding screen bending life tester. The test temperature was 25°C, the bending radius R=2.0mm, and the bending angle was 180°. The folding screen bending-resistant protective film was applied in both unfolded and folded states, and bending tests were performed 200,000 times and 250,000 times respectively. When the test reached 200,000 times, the experiment was stopped, and the protective film was observed to see if bubbles, cracks, falls off, folds, etc. appeared. If so, the number of times was recorded as 200,000 times. If no such phenomena occurred, the test was continued. When it was folded to 250,000 times, the experiment was stopped, and the protective film was observed to see if bubbles, cracks, falls off, folds, etc. appeared. If so, the number of times was recorded as 250,000 times. If no such phenomena occurred, the number of times was recorded as >250,000 times.

[0183] Impact resistance testing: The composite glass screen protectors prepared in Examples 1-10 and Comparative Example 1 were tested using an MK-2M-DX directional drop tester in accordance with GB / T 2423.8-1995. The screen protectors adhered to the 3D mobile phone flatly, tightly, and without bubbles or wrinkles. The 3D mobile phone was placed with the display facing downward on a surface at a height of 1.0 m and dropped onto concrete for 50 drops. The percentage of glass breakage area was observed.

[0184] Table 2 Performance test data of the composite glass protective film for flexible folding screen in Examples 1-10 and Comparative Example 1

[0185]

[0186] Referring to Table 2, in combination with Example 1 and Comparative Example 1, it can be seen that the OCA adhesive layer of the present application can form a large number of bubbles by utilizing ultrasonic cavitation. The nano-silica wrapped in these bubbles and the molten hydroxy acrylic resin form a core-shell structure with nano-silica as the core and hydroxy acrylic resin as the shell. At the same time, the nano-silica with cations on the surface and the hydroxy acrylic resin promote the generation of this core-shell structure through electrostatic action, thereby achieving uniform dispersion of nano-silica particles in the acrylic resin polymer, thereby improving the elasticity of the acrylic OCA optical adhesive, avoiding stress corrosion, delamination, cracking and fatigue defects in the folding screen, and improving the service life of the protective film.

[0187] Referring to Table 2, in combination with Examples 2, 4 and 5, it can be seen that the protective film formed by the self-made linear hydroxy acrylic resin and the reticulated hydroxy acrylic resin in the present application has better bending resistance than the protective film formed by the commercially available hydroxy acrylic resin, thereby improving the service life of the protective film; this is because the prepared linear hydroxy acrylic resin has high viscoelastic properties, which can further improve the elasticity of the acrylic resin; and the reticulated hydroxy acrylic resin obtained on the basis of the linear hydroxy acrylic resin, due to the effect of the spatial network structure system, makes the prepared acrylic resin have a greater "viscoelastic effect", further improving the viscosity and elasticity of the acrylic OCA optical adhesive.

[0188] Referring to Table 2, combined with Examples 5-7 and 9, it can be seen that the toughening agent in the epoxy resin film of the present application is a core-shell particle with organic montmorillonite as the core, rubber as the secondary outer layer, and a polymer as the shell. Compared with the toughening agent with organic montmorillonite, rubber, or core-shell particles with rubber as the core layer and a polymer as the shell, it has a better toughening effect on the epoxy resin, improves the impact resistance of the epoxy resin film, and thus improves the impact resistance of the entire protective film. The toughening agent has rubber-coated montmorillonite as the core and polymer as the shell. On the one hand, the rubber-coated inorganic nanoparticles effectively combine the rubber and montmorillonite. When the montmorillonite undergoes plastic deformation, it can effectively inhibit the expansion of cracks in the matrix resin and absorb part of the energy, thereby playing a toughening role. At the same time, the rubber particles, as stress concentrators, can induce silver streaks and shear bands to absorb energy and terminate silver streaks. The rubber elastic particles can also debond from the interface, release elastic strain energy, and improve the toughening and bonding strength of the material. It can not only exert the toughening effect of 1+1>2 of the two, but also improve the flexibility of the montmorillonite. On the other hand, the polymer shell can achieve good compatibility with the epoxy resin, thereby improving the toughening effect on the epoxy resin.

[0189] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A composite glass protective film for a flexible folding screen, characterized in that: From top to bottom, it includes a functional base film, a first thermosetting polymer film, a UTG ultra-thin glass layer, a second thermosetting polymer film, and an OCA adhesive layer; The preparation method of the OCA adhesive layer comprises the following steps: Activating the nano-silica particles to obtain modified particles with cations on the surface; The modified particles with a mass ratio of 1:1-3 are reacted with melted hydroxy acrylic resin under the action of 600-1000W ultrasound and extruded into granules to obtain elastic acrylic masterbatch; The elastic acrylic masterbatch is mixed with a cross-linking agent and a photoinitiator to obtain an acrylic OCA optical adhesive; Apply OCA optical adhesive on one side of the release film and cure it with UV light to obtain an OCA adhesive layer; The first thermosetting polymer film and the second thermosetting polymer film are both epoxy resin films; The hydroxy acrylic resin is a linear hydroxy acrylic resin. The synthesis method of the linear hydroxy acrylic resin is as follows: 25g of methyl methacrylate, 25g of butyl acrylate, 15g of hydroxyethyl acrylate, 15g of hydroxypropyl acrylate, 10g of isooctyl acrylate and 1g of azobisisobutyronitrile are stirred and mixed until completely dissolved to obtain a premixed solution A, the mixed solution A is dropwise added to 30g of 90°C tetrahydrofuran, a polymerization reaction is carried out at 105°C and kept warm for 3h, and then the temperature is lowered to below 70°C to obtain a linear hydroxy acrylic resin.

2. The composite glass protective film for a flexible foldable screen according to claim 1, characterized in that: The modified particles are prepared by adding nano-silica particles to a cationic surfactant aqueous solution, stirring, separating the solid and the liquid, washing the obtained solid phase, and drying to obtain the modified particles. The mass ratio of the nano-silicon dioxide particles to the cationic surfactant is 1:1-3.

3. The composite glass protective film for a flexible foldable screen according to claim 1, characterized in that: The hydroxy acrylic resin is a reticular hydroxy acrylic resin. The synthesis method of the reticular hydroxy acrylic resin is as follows: adding the linear hydroxy acrylic resin to an organic solvent, adding an isocyanate crosslinking agent, and performing a crosslinking reaction at a temperature of 30-80° C. to obtain the reticular hydroxy acrylic resin.

4. The composite glass protective film for a flexible foldable screen according to claim 1, characterized in that: The epoxy resin film is made of the following raw materials in parts by weight: 60-70 parts of epoxy resin, 15-35 parts of toughening agent and 5-15 parts of curing agent. The toughening agent is a core-shell particle with organic montmorillonite as the core, rubber as the secondary outer layer and polymer as the shell.

5. The composite glass protective film for a flexible foldable screen according to claim 4, characterized in that: The preparation method of the toughening agent comprises the following steps: (1) 1-3 parts by weight of organic montmorillonite is stirred in 100 parts by weight of deionized water at 40-50°C for 30-60 minutes to obtain a suspension; (2) Emulsifying 20 parts by weight of an organosilicon monomer, 1-5 parts by weight of an emulsifier, 1-8 parts by weight of a silane coupling agent, 1-8 parts by weight of a vinyl silane coupling agent, and 10-20 parts by weight of deionized water for 5-10 minutes to obtain an organosilicon pre-emulsion; mixing 1-3 parts by weight of an acid catalyst and 20-25 parts by weight of deionized water to obtain an organosilicon catalyst; adding 10-40% of the organosilicon pre-emulsion and 15-25% of the organosilicon catalyst to the suspension, stirring and heating to react, and then adding the remaining organosilicon emulsion and the organosilicon catalyst to react to obtain a core layer emulsion; (3) emulsifying 1-5 parts by weight of a double bond-containing monomer, 0.1-0.5 parts by weight of an emulsifier and 1-3 parts by weight of deionized water to obtain a double bond-containing pre-emulsion; mixing 0.1-0.5 parts of an initiator and 1-20 parts of deionized water to obtain an initiating solution; (4) adding the initiating liquid into the core layer emulsion, and then adding the double bond-containing pre-emulsified liquid to react to obtain a composite emulsion, and demulsifying the composite emulsion to obtain the toughening agent.

6. The composite glass protective film for a flexible foldable screen according to claim 5, characterized in that: In step (1), the organic montmorillonite is obtained by modifying montmorillonite with organic cations.

7. The composite glass protective film for a flexible foldable screen according to claim 4, characterized in that: The preparation method of the epoxy resin film comprises: adding epoxy resin and curing agent into acetone solution according to a ratio and mixing to obtain a blended solution; adding a toughening agent into the blended solution and mixing to obtain a dispersion; and coating the dispersion on a release film to obtain the epoxy resin film.

8. A method for preparing a composite glass protective film for a flexible foldable screen according to any one of claims 1 to 7, characterized in that: The steps include: The functional base film, the first thermosetting polymer film, the UTG ultra-thin glass, and the second thermosetting polymer film are stacked in sequence from top to bottom, and the film layers are pressed together by heat pressing to form a composite layer; The OCA adhesive layer is laminated to the second thermosetting polymer film in the composite layer to form a composite glass protective film.

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