Folding screen protector and preparation process thereof

Abstract

The invention belongs to the technical field of ultra-thin glass, and particularly relates to a folding screen protector and a preparation process thereof. The folding screen protector sequentially comprises a functional base film layer, a thermosetting resin film layer, a UTG layer, a thermosetting resin film layer and an OCA adhesive film layer from top to bottom. A layer of photocureable coating added with modified silicon dioxide and methallyl polyhedral oligomeric silsesquioxane is sprayed on PET resin to serve as a functional base film, and a rigid phenyl group is introduced into a molecular structure of a thermosetting resin film; according to the invention, methyltrimethoxysilane, phenyltrimethoxysilane and 3-glycidyl ether oxypropyl trimethoxysilane are adopted as monomers for co-polymerization to obtain high-transparency polysiloxane as an OCA adhesive, so that the bending performance and the impact resistance of the folding screen protector are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-thin glass, and particularly relates to a folding screen protector and a preparation process thereof. Background Art

[0002] Compared with traditional electronic devices, foldable electronic devices can increase the screen area while maintaining portability. Therefore, foldable electronic devices have received increasing attention in the smart terminal market, which also puts forward higher technical requirements for foldable display devices.

[0003] In the field of foldable display devices, ultra-thin glass (UTG) is used as a flexible cover material. When the thickness of UTG is reduced to less than 50 μm, it exhibits excellent bending performance, and the bending radius can be reduced to less than 1 mm, meeting the stringent requirements of flexible screens for extremely small curvature radii. However, when the thickness of UTG is reduced, its impact resistance significantly decreases, resulting in the critical failure height in the ball drop test being reduced to less than 10 mm. Although increasing the thickness of UTG can improve its strength, its impact resistance is not significantly improved.

[0004] In the prior art, to improve the impact resistance of UTG, a multi-layer composite structure is usually used for reinforcement. For example, a layer of polyimide (CPI) or polyethylene terephthalate (PET) film with a hardened surface is adhered to the surface of UTG through a foldable optical adhesive (OCA) to form a laminated structure. For example, the Chinese patent application document with the application publication number CN119445980A discloses a flexible screen cover, a flexible screen, and a foldable electronic device. The flexible screen cover includes ultra-thin glass, a first buffer coating, and a second buffer coating. Among them, the ultra-thin glass has a first surface and a second surface arranged opposite to each other. The first buffer coating is provided on the first surface, and the second buffer coating is provided on the second surface. The first buffer coating and the second buffer coating can physically protect both the first surface and the second surface of the ultra-thin glass, improving the impact resistance of the ultra-thin glass. The material of the first buffer coating includes any one or several of acrylate resin, silicone resin, epoxy resin, and polyurethane resin, and the material of the second buffer coating includes any one or several of acrylate-modified polyurethane, epoxy-modified polyurethane, hyperbranched polyurethane, acrylic resin, silicone resin, and epoxy resin. However, although this flexible folding cover can improve the impact resistance of UTG to a certain extent, due to the presence of multiple layers of low-modulus foldable optical adhesives and polyethylene terephthalate films on both sides of UTG, after using for a period of time, the folding area will show phenomena such as uneven surface, delamination, serious creases, or fingernail marks, affecting the screen appearance. Therefore, developing a folding screen protector with good adhesion and functionality has become a development trend in this industry. Summary of the Invention

[0005] In order to solve the technical problems of poor bending and fitting performance and poor impact resistance of the folding screen protector in the above-mentioned prior art, the present invention provides a folding screen protector and its preparation process.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A folding screen protector sequentially includes a functional base film layer, a thermosetting resin film layer, a UTG layer, a thermosetting resin film layer, and an OCA adhesive film layer from top to bottom; The preparation method of the functional base film is: (1) fully mix modified silica and β-hydroxyethyl methacrylate to obtain a mixed solution I; (2) mix methacryloylcage silsesquioxane, acetone, and tetrahydrofuran evenly to obtain a mixed solution II; (3) add the mixed solution I, bisphenol A epoxy acrylate, and benzophenone to the mixed solution II in a light-shielded environment, and obtain a mixed solution III after ultrasonic treatment; (4) spray the mixed solution III on the surface of a washed PET film, and obtain the functional base film after curing.

[0007] Through the above technical solution, modified silica and methacryloylcage silsesquioxane are added to the photocurable coating, and a uniform nano-coating is formed on the surface of the PET film by spraying. Among them, the modified silica has the characteristics of small particle size, high hardness, and good stability. Uniformly dispersing it in the nano-coating can effectively improve the wear resistance and hardness of the functional base film; and methacryloylcage silsesquioxane is an organic / inorganic hybrid hollow closed polysiloxane with a nano size, which can be uniformly dispersed in the nano-coating and connected to the organic polymer by chemical bonds, improving the crosslinking degree of the polymer, and thus effectively enhancing the mechanical properties such as the toughness and impact resistance of the film. In addition, the surface energy of the nano-coating on the surface of the functional base film is relatively low, and it has good hydrophobicity. Sweat stains on the fingers will form droplets on the surface of the functional base film, so it has a good fingerprint-proof effect.

[0008] Further, the preparation method of the modified silica in the preparation method of the functional base film is: mix nano-silica and deionized water evenly to prepare an emulsion with a mass percentage of silica of 14%-17%, heat it to 60-70°C, then add vinyltris(β-methoxyethoxy)silane, stir and heat to 80-90°C, keep the temperature for reaction for 1-1.5 h, filter, and dry to obtain the modified silica.

[0009] Through the above technical solution, vinyltris(β-methoxyethoxy)silane is used to modify nano-silica. This not only enables the prepared modified nano-silica to be evenly dispersed in the functional base film, but also allows vinyltris(β-methoxyethoxy)silane to undergo a cross-linking reaction with the organic polymer. While increasing the cross-linking degree of the nano-coating, it can effectively fix the nano-silica, making the prepared nano-coating have good mechanical properties.

[0010] Furthermore, in the preparation method of the modified silica, the mass of vinyltris(β-methoxyethoxy)silane is 5%-8% of the mass of nano-silica.

[0011] Further, the weight parts of each component in the preparation method of the functional base film are: 8-12 parts of modified silica, 20-25 parts of β-hydroxyethyl methacrylate, 10-15 parts of methacryloylcage silsesquioxane, 30-40 parts of acetone, 30-40 parts of tetrahydrofuran, 35-40 parts of bisphenol A epoxy acrylate, and 12-15 parts of benzophenone.

[0012] Further, the preparation method of the thermosetting resin film is as follows: Heat phenyltris(dimethylsilyl)silane to 115-120 °C, add chloroplatinic acid, then add glycidyl methacrylate, keep the temperature for reaction for 3.5-4 h, cool down, add bisphenol A epoxy resin, curing agent and catalyst, stir and then defoam, and then coat it on a release film and cure to obtain the thermosetting resin film.

[0013] Through the above technical solution, phenyltris(dimethylsilyl)silane undergoes an addition reaction with glycidyl methacrylate, and then reacts with bisphenol A epoxy resin, introducing the rigid phenyl group on phenyltris(dimethylsilyl)silane into the molecule of bisphenol A epoxy resin, thereby effectively improving the impact resistance of bisphenol A epoxy resin.

[0014] Furthermore, the weight parts of each component in the preparation method of the thermosetting resin film are: 10-13 parts of phenyltris(dimethylsilyl)silane, 1-3 parts of chloroplatinic acid, 15-18 parts of glycidyl methacrylate, 100-120 parts of bisphenol A epoxy resin, 30-35 parts of curing agent, and 3-5 parts of catalyst; the curing agent is polyetheramine D230, and the catalyst is octylphenol.

[0015] Further, the OCA adhesive film layer is prepared by coating and curing OCA adhesive. The preparation method of the OCA adhesive is as follows: Add an aqueous sulfuric acid solution with a mass percentage of 75%-85% and methyltrimethoxysilane into a reaction kettle, heat up to 70-80°C, and then simultaneously add phenyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane under stirring. Keep the temperature for reaction for 4-5 hours, cool down, let it stand for layer separation, remove the aqueous phase, and wash the organic phase with deionized water until it is neutral to obtain the OCA adhesive.

[0016] In the above technical solution, methyltrimethoxysilane, phenyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane are used as monomers to copolymerize to obtain a highly transparent polysiloxane as the OCA adhesive. 3-Glycidoxypropyltrimethoxysilane can introduce a long side chain containing an epoxy group into the molecular structure of the OCA adhesive, and phenyltrimethoxysilane can introduce a phenyl side chain into the molecular structure of the OCA adhesive, enhancing the internal cohesion of the OCA adhesive to overcome various stresses on the protective film during the bending process of the foldable screen protective film, enabling the OCA adhesive to automatically repair minor damages caused by external forces, thereby effectively improving the service life of the foldable screen protective film. In addition, the above OCA adhesive has good adhesion, effectively preventing delamination caused by external forces.

[0017] Furthermore, the weight parts of each component in the preparation method of the OCA adhesive are as follows: 20-25 parts of aqueous sulfuric acid solution, 30-40 parts of methyltrimethoxysilane, 10-15 parts of phenyltrimethoxysilane, and 15-20 parts of 3-glycidoxypropyltrimethoxysilane.

[0018] Further, the thickness of the functional base film layer is 38-50μm, the thickness of the thermosetting resin film layer is 40-50μm, the thickness of the UTG layer is 30-40μm, and the thickness of the OCA layer is 35-50μm.

[0019] During the research process of the present invention, it is found that the OCA adhesive layer is a key factor affecting the bonding performance of the foldable screen protective film. When the thickness of the OCA adhesive layer is too small, the bonding performance of the foldable screen protective film is poor, and the protective film is prone to degumming and forming creases. When the thickness of the OCA adhesive layer is too large, it will cause an increase in light scattering and absorption during light passing, thereby reducing the light transmittance of the foldable screen protective film and affecting the display effect. When the OCA adhesive layer is within the range provided by the present invention, when the foldable screen protective film is bent, the force on the adhesive layer per unit length is reduced, and the strain of the adhesive layer is decreased, effectively avoiding the shedding of the adhesive layer and forming creases.

[0020] The present invention also provides a preparation process for the foldable screen protector, specifically as follows: The functional base film PET is laminated with the thermosetting resin film without the release paper, and then the UTG, the thermosetting resin film without the release paper, and the OCA adhesive film are sequentially laminated on the thermosetting resin film. Lamination and cutting are carried out by a fully automatic hot press laminator to obtain the foldable screen protector.

[0021] Through the above technical solution, the thermosetting resin film is laminated on both sides of the UTG, and then the functional base film is laminated on one side and the OCA adhesive film is laminated on the other side. The foldable screen protector is prepared by hot pressing. The hot pressing process can effectively avoid the delamination between the film layers and effectively improve the service life of the foldable screen protector.

[0022] Compared with the prior art, the foldable screen protector and its preparation process provided by the present invention have the following technical advantages: (1) In the present invention, a photocurable coating added with modified silica and methacryloylcage silsesquioxane is sprayed on the PET resin to form a uniform nano-coating, which can not only effectively improve the impact resistance of the functional base film, but also endow the functional base film with good fingerprint-proof effect; (2) In the present invention, a rigid group phenyl is introduced into the molecular structure of the thermosetting resin film, effectively improving the impact resistance of bisphenol A epoxy resin; (3) In the present invention, methyltrimethoxysilane, phenyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane are used as monomers to copolymerize to obtain a highly transparent polysiloxane as the OCA adhesive. The long side chains of epoxy groups and phenyl side chains in its molecular structure can effectively enhance the internal cohesion of the OCA adhesive, thereby avoiding the delamination phenomenon of the foldable screen protector during the bending process. Description of the Drawings

[0023] Figure 1 It is a picture of the foldable screen protector prepared in Example 3 before bending; Figure 2 It is a picture of the foldable screen protector prepared in Example 3 after bending under a microscope; Figure 3 It is an infrared spectrum diagram of the OCA adhesive prepared in Example 3. Detailed Embodiments

[0024] The following will be further described in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Those skilled in the art can make various modifications according to the basic idea of the present invention, but as long as they do not depart from the basic idea of the present invention, they are within the scope of the present invention.

[0025] The preparation process of the foldable screen protector described in this specific embodiment is as follows: Bond the functional base film PET to the thermosetting resin film with the release paper removed, and then sequentially bond UTG, the thermosetting resin film with the release paper removed, and the OCA adhesive film onto the thermosetting resin film. Perform bonding and cutting through a fully automatic hot press laminator to obtain the foldable screen protector.

[0026] In this specific embodiment, the molecular weight of the bisphenol A epoxy resin is 500 - 700, and the degree of polymerization n < 2.

[0027] Example 1 A foldable screen protector includes, from top to bottom, a functional base film layer, a thermosetting resin film layer, a UTG layer, a thermosetting resin film layer, and an OCA adhesive film layer; the thickness of the functional base film layer is 38 μm, the thickness of the thermosetting resin film layer is 40 μm, the thickness of the UTG layer is 30 μm, and the thickness of the OCA layer is 35 μm.

[0028] The preparation method of the functional base film is as follows: (1) Thoroughly mix 8 g of modified silica with 20 g of β - hydroxyethyl methacrylate to obtain mixture I; (2) Mix 10 g of methacryloylcage silsesquioxane, 30 g of acetone, and 30 g of tetrahydrofuran evenly to obtain mixture II; (3) Add mixture I, 35 g of bisphenol A epoxy acrylate, and 12 g of benzophenone to mixture II in a light - proof environment, and obtain mixture III after ultrasonic treatment; (4) Spray mixture III on the surface of a washed PET film (with a thickness of 10 μm), and obtain the functional base film after curing.

[0029] The preparation method of the modified silica is as follows: Mix nano - silica and deionized water evenly to prepare an emulsion with a mass percentage of silica of 14%. After heating to 60°C, add vinyltris(β - methoxyethoxy)silane accounting for 5% of the mass of nano - silica, stir and heat to 80°C, keep the temperature for reaction for 1 h, filter, and dry to obtain the modified silica.

[0030] The preparation method of the thermosetting resin film is as follows: Heat 10 g of phenyltris(dimethylsilyl)silane to 115°C, add 1 g of chloroplatinic acid, and then drop - wise add 15 g of glycidyl methacrylate within 1 h. After dropping, keep the temperature for reaction for 3.5 h, cool, add 100 g of bisphenol A epoxy resin, 30 g of polyetheramine D230, and 3 g of octylphenol, stir, and perform degassing in a vacuum mixer, and then coat it onto a release film and cure at 90°C for 4.5 h to obtain the thermosetting resin film.

[0031] The OCA film layer is obtained by coating and curing OCA adhesive. The preparation method of the OCA adhesive is as follows: Add 20 g of sulfuric acid aqueous solution with a mass percentage of 75% and 30 g of methyltrimethoxysilane into a reaction kettle, heat up to 70 °C, and then simultaneously add 10 g of phenyltrimethoxysilane and 15 g of 3-glycidoxypropyltrimethoxysilane under stirring. Keep the temperature for reaction for 4 h, cool down, let it stand for layering, remove the aqueous phase, and wash the organic phase with deionized water until neutral to obtain the OCA adhesive.

[0032] Example 2 A foldable screen protector, which sequentially includes a functional base film layer, a thermosetting resin film layer, a UTG layer, a thermosetting resin film layer, and an OCA film layer from top to bottom; the thickness of the functional base film layer is 50 μm, the thickness of the thermosetting resin film layer is 50 μm, the thickness of the UTG layer is 40 μm, and the thickness of the OCA layer is 50 μm.

[0033] The preparation method of the functional base film is as follows: (1) Fully mix 12 g of modified silica and 25 g of 2-hydroxyethyl methacrylate to obtain mixture I; (2) Mix 15 g of methacryloylcage silsesquioxane, 40 g of acetone, and 40 g of tetrahydrofuran evenly to obtain mixture II; (3) Add mixture I, 40 g of bisphenol A epoxy acrylate, and 15 g of benzophenone to mixture II under a light-proof environment, and obtain mixture III after ultrasonic treatment; (4) Spray mixture III on the surface of a washed PET film (with a thickness of 15 μm), and obtain the functional base film after curing.

[0034] The preparation method of the modified silica is as follows: Mix nano-silica and deionized water evenly to prepare an emulsion with a mass percentage of silica of 17%, heat up to 70 °C, add vinyltris(β-methoxyethoxy)silane accounting for 8% of the mass of nano-silica, stir and heat up to 90 °C, keep the temperature for reaction for 1.5 h, filter, and dry to obtain the modified silica.

[0035] The preparation method of the thermosetting resin film is as follows: Heat 13 g of phenyltris(dimethylsilyl)silane to 120 °C, add 3 g of chloroplatinic acid, and then dropwise add 18 g of glycidyl methacrylate within 1 h. After dropping, keep the temperature for reaction for 4 h, cool down, add 120 parts of bisphenol A epoxy resin, 35 g of polyetheramine D230, and 5 g of octylphenol, stir, and carry out defoaming in a vacuum mixer, and then coat it on a release film and cure it at 90 °C for 4.5 h to obtain the thermosetting resin film.

[0036] The OCA adhesive film layer is prepared by coating and curing the OCA adhesive. The preparation method of the OCA adhesive is as follows: add 25g of an aqueous sulfuric acid solution with a mass percentage of 85% and 40g of methyltrimethoxysilane into a reaction kettle, heat it to 80°C, and then add 15g of phenyltrimethoxysilane and 20g of 3-glycidyloxypropyltrimethoxysilane while stirring, keep the temperature for reaction for 5h, cool, stand for stratification, remove the aqueous phase, and wash the organic phase with deionized water until it is neutral to obtain the OCA adhesive.

[0037] Example 3 A folding screen protector comprises, from top to bottom, a functional base film layer, a thermosetting resin film layer, a UTG layer, a thermosetting resin film layer and an OCA adhesive film layer; the thickness of the functional base film layer is 38 μm, the thickness of the thermosetting resin film layer is 40 μm, the thickness of the UTG layer is 40 μm, and the thickness of the OCA layer is 50 μm.

[0038] The preparation method of the functional base film is as follows: (1) 10 g of modified silicon dioxide and 22 g of β-hydroxyethyl methacrylate are fully mixed to obtain a mixed solution I; (2) 12 g of methyl acryloyl cage-type silsesquioxane, 35 g of acetone and 35 g of tetrahydrofuran are evenly mixed to obtain a mixed solution II; (3) mixed solution I, 38 g of bisphenol A epoxy acrylate and 14 g of benzophenone are added to the mixed solution II under a light-proof environment, and mixed solution III is obtained after ultrasonic treatment; (4) mixed solution III is sprayed on the surface of a cleaned PET film (with a thickness of 12 μm), and the functional base film is obtained after curing.

[0039] The preparation method of the modified silica is as follows: nano silica and deionized water are uniformly mixed to prepare an emulsion with a mass percentage of silica of 15%, and then the mixture is heated to 65° C. and vinyl tri(β-methoxyethoxy)silane with a mass percentage of 7% of the mass of the nano silica is added, and the mixture is stirred and heated to 85° C., and the mixture is kept warm for reaction for 1.2 hours, filtered, and dried to obtain the modified silica.

[0040] The preparation method of the thermosetting resin film is as follows: 12g of phenyl tris (dimethylsiloxy) silane is heated to 118°C, 2g of chloroplatinic acid is added, and then 17g of glycidyl methacrylate is added dropwise, and the dripping is completed within 1 hour, and the reaction is kept warm for 3.8 hours, and then cooled, 115g of bisphenol A epoxy resin, 32g of polyetheramine D230 and 4g of octylphenol are added, and after stirring, degassing is performed in a vacuum mixer, and then coated on a release film, and cured at 90°C for 4.5 hours to obtain a thermosetting resin film.

[0041] The OCA film layer is obtained by coating and curing OCA glue. The preparation method of the OCA glue is as follows: Add 22 g of sulfuric acid aqueous solution with a mass percentage of 80% and 35 g of methyltrimethoxysilane into a reaction kettle, heat up to 75 °C, and then simultaneously add 13 g of phenyltrimethoxysilane and 18 g of 3-glycidoxypropyltrimethoxysilane under stirring, keep the temperature for reaction for 4.5 h, cool down, let it stand for layering, remove the aqueous phase, and wash the organic phase with deionized water until neutral to obtain the OCA glue.

[0042] Comparative Example 1 The foldable screen protector described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in the preparation method of the functional base film in this comparative example, an equal amount of acetone is used instead of modified silica.

[0043] Comparative Example 2 The foldable screen protector described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in the preparation method of the functional base film in this comparative example, an equal amount of acetone is used instead of methylallyl silsesquioxane.

[0044] Comparative Example 3 The foldable screen protector described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in the preparation method of the functional base film in this comparative example, an equal amount of nano-silica is used instead of modified silica.

[0045] Comparative Example 4 The foldable screen protector described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in this comparative example, the preparation method of the thermosetting resin film is as follows: After degassing bisphenol A epoxy resin, coat it on a release film and cure it to obtain the thermosetting resin film.

[0046] Comparative Example 5 The foldable screen protector described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the OCA glue in this comparative example is prepared according to the preparation method of the OCA glue disclosed in Example 3 in the patent application text with the publication number of CN118389101A.

[0047] Comparative Example 6 The foldable screen protector described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in the preparation method of the OCA glue in this comparative example, methyltrimethoxysilane is used instead of 3-glycidoxypropyltrimethoxysilane.

[0048] Comparative Example 7 The foldable screen protector described in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in the preparation method of the OCA glue in this comparative example, methyltrimethoxysilane is used instead of phenyltrimethoxysilane.

[0049] Test Example 1: Bending Performance and Impact Resistance Test Test Samples: Foldable screen protectors prepared in Examples 1 - 3 and Comparative Examples 1 - 7.

[0050] Bending Test: Attach the foldable screen protector to the bending test machine. The attachment plane should be flat, tight, without air bubbles or wrinkles (μg SA6500 mobile phone bending durability test machine). If the protective film at the bending part of the test machine shows deformation, cracking, warping, etc., the bending test stops, and the number of bending times is recorded. Among them, the pictures of the foldable screen protector prepared in Example 3 before and after bending under the microscope can be seen in Figure 1 and Figure 2 .

[0051] Impact Resistance Test: A steel ball with a diameter of 20 mm and a mass of 32.6 g is freely dropped from different heights onto the foldable screen with the foldable screen protective film attached, and the height until the appearance of broken points and bright points is recorded.

[0052] The test is carried out in accordance with ASTM D3363 - 2005 "Standard Test Method for Determining Film Hardness by Pencil Test Method". Using a YASUDA pencil hardness tester, the surface layer of the protective film is tested for pencil hardness with a load of 750 g; Peeling Force of the OCA Layer: The peeling force of the OCA layer is tested with reference to JIS Z0237 (300 mm / min, 180°).

[0053] The test results are shown in Table 1.

[0054] Table 1 Performance Test Results

[0055] As can be seen from Table 1, the number of bending times of the foldable screen protector provided by the present invention > 110,000 times, and the ball drop height ≥ 2.1 m, which fully shows that the foldable screen protector provided by the present invention has good bending and attachment performance and impact resistance.

[0056] Compared with Example 3, in the preparation method of the functional base film of Comparative Example 1, an equal amount of acetone was used to replace the modified silica, but the pencil hardness of the obtained foldable screen protector decreased. This shows that the addition of modified silica can effectively improve the hardness of the foldable screen protector; in the preparation method of the functional base film of Comparative Example 2, an equal amount of acetone was used to replace methylallyl silsesquioxane, but the ball drop height of the obtained foldable screen protector decreased. This shows that methylallyl silsesquioxane can improve the toughness and impact resistance of the foldable screen protector; in the preparation method of the functional base film of Comparative Example 3, an equal amount of nano-silica was used to replace the modified silica, but the ball drop height of the obtained foldable screen protector decreased slightly and the pencil hardness decreased. This is due to the uneven dispersion of unmodified silica in the functional base film. The uniform dispersion of silica in the functional base film can improve the impact resistance of the foldable screen protector; in Comparative Example 4, the thermosetting resin film was a bisphenol A epoxy resin film, but the ball drop height of the obtained foldable screen protector decreased significantly. This shows that the process of introducing phenyl groups into the molecular structure of bisphenol A epoxy resin in the present invention can effectively improve the impact resistance of the bisphenol A epoxy resin film; the OCA adhesive in Comparative Example 5 was the OCA adhesive disclosed in Example 3 of the patent application text with the publication number CN118389101A, but the number of bending times of the obtained foldable screen protector decreased and the OCA layer peel strength decreased; in the preparation method of the OCA adhesive of Comparative Example 6, methyltrimethoxysilane was used to replace 3-glycidoxypropyltrimethoxysilane, and in the preparation method of the OCA adhesive of Comparative Example 7, methyltrimethoxysilane was used to replace phenyltrimethoxysilane, but the number of bending times and the OCA layer peel strength of the obtained foldable screen protector decreased significantly. This shows that introducing long side chains containing epoxy groups and phenyl side chains into the molecular structure of the OCA adhesive in the present invention can effectively improve the cohesion of the OCA adhesive, thereby improving the bending performance of the foldable screen protector.

[0057] It can be seen from Figure 1 that there are no obvious creases on the foldable screen protector prepared in Example 3 of the present invention before bending. It can be seen from Figure 2 that after folding, when the protector is observed under a 50-fold microscope, no creases appear on the right side of the boundary of the foldable screen protector. This shows that the foldable screen protector provided by the present invention has good bending performance.

[0058] Test Example 2: Transmittance and Water Contact Angle Test Test samples: Foldable screen protectors prepared in Examples 1 - 3; Transmittance: The transmittance of the foldable screen protector was tested with reference to the method for the determination of light transmittance and haze of transparent plastics in "GB / T2410 - 2008".

[0059] Water contact angle test: A conventional water contact angle tester was used to test the surface layer of the protective film.

[0060] The test results are shown in Table 2.

[0061] Table 2

[0062] As can be seen from Table 2, the foldable screen protector provided by the present invention has good light transmission effect and hydrophobic effect.

[0063] Test Example 3: Infrared spectrum test The OCA adhesive prepared in Example 3 was tested using a Fourier transform infrared spectrometer (FT-IR, Nicolet 5700, Nicolet Corporation). Sample preparation method: The OCA adhesive was coated on a KBr tablet, dried, and after the cured film was dried, it was crushed and directly mixed evenly with KBr powder, and then pressed into a tablet. The test method was as follows: The resolution was 4 cm -1 , the number of scans was 32 times, and the scanning range was 4000 cm -1 -500 cm -1 , and infrared spectrum analysis was performed on the OCA adhesive. The test results are as shown in Figure 3 .

[0064] From Figure 3 it can be seen that a characteristic absorption peak of the silicon-oxygen bond Si-O-Si appeared at 1100 cm -1 , a characteristic absorption peak of Si-CH3 appeared at 1259 cm -1 , a characteristic absorption peak of Si-phenyl appeared at 1240 cm -1 , a bending vibration peak of C-O-C appeared at 842 cm -1 , a characteristic absorption peak of the epoxy group appeared at 754 cm -1 , and a stretching vibration peak of CH3 in Si-O-CH3 appeared at 2840 cm -1 . Therefore, in the preparation process of the OCA adhesive of the present invention, methyltrimethoxysilane, phenyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane achieved good polycondensation effect.

[0065] The above embodiments are only illustrative of the present invention and do not limit the present invention. Those skilled in the art shall not modify the above embodiments without departing from the spirit and scope of the present invention. All equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the technical idea of the present invention still fall within the protection scope of the present invention.

Claims

1. A foldable screen protector, characterized in that: From top to bottom, it includes a functional base film layer, a thermosetting resin film layer, a UTG layer, a thermosetting resin film layer and an OCA adhesive film layer; The preparation method of the functional base film is as follows: (1) fully mixing modified silicon dioxide and β-hydroxyethyl methacrylate to obtain a mixed solution I; (2) evenly mixing methacrylic cage-type silsesquioxane, acetone and tetrahydrofuran to obtain a mixed solution II; (3) adding mixed solution I, bisphenol A epoxy acrylate and benzophenone to the mixed solution II in a light-proof environment, and obtaining a mixed solution III after ultrasonic treatment; (4) spraying the mixed solution III on the surface of a cleaned PET film, and obtaining a functional base film after curing.

2. The folding screen protector according to claim 1, characterized in that: The preparation method of the modified silicon dioxide is as follows: nano silicon dioxide and deionized water are uniformly mixed to prepare an emulsion with a mass percentage of silicon dioxide of 14%-17%, and then vinyl tri(β-methoxyethoxy)silane is added after heating to 60-70°C, and the mixture is stirred and heated to 80-90°C, and the mixture is kept warm for reaction for 1-1.5 hours, filtered, and dried to obtain the modified silicon dioxide.

3. The folding screen protector according to claim 2, characterized in that: The mass of the vinyl tris(β-methoxyethoxy)silane is 5%-8% of the mass of the nano silicon dioxide.

4. The folding screen protector according to claim 1, characterized in that: The weight proportions of the components in the preparation method of the functional base film are: 8-12 parts of modified silicon dioxide, 20-25 parts of beta-hydroxyethyl methacrylate, 10-15 parts of methacrylic cage-type silsesquioxane, 30-40 parts of acetone, 30-40 parts of tetrahydrofuran, 35-40 parts of bisphenol A epoxy acrylate, and 12-15 parts of benzophenone.

5. The folding screen protector according to claim 1, characterized in that: The preparation method of the thermosetting resin film is as follows: heating phenyl tri (dimethylsiloxy) silane to 115-120° C., adding chloroplatinic acid and then glycidyl methacrylate, keeping the temperature for reaction for 3.5-4 hours, cooling, adding bisphenol A type epoxy resin, curing agent and catalyst, stirring and degassing, then coating on a release film, curing, and obtaining a thermosetting resin film.

6. The folding screen protector according to claim 5, characterized in that: The weight proportions of the components in the preparation method of the thermosetting resin film are: 10-13 parts of phenyl tris (dimethylsiloxy) silane, 1-3 parts of chloroplatinic acid, 15-18 parts of glycidyl methacrylate, 100-120 parts of bisphenol A type epoxy resin, 30-35 parts of curing agent, and 3-5 parts of catalyst; the curing agent is polyetheramine D230, and the catalyst is octylphenol.

7. The folding screen protector according to claim 1, characterized in that: The OCA adhesive film layer is prepared by coating and curing the OCA adhesive. The preparation method of the OCA adhesive is as follows: adding a sulfuric acid aqueous solution with a mass percentage of 75%-85% and methyltrimethoxysilane into a reaction kettle, heating to 70-80°C, and then adding phenyltrimethoxysilane and 3-glycidyloxypropyltrimethoxysilane at the same time under stirring, keeping the temperature for reaction for 4-5 hours, cooling, standing for stratification, removing the aqueous phase and washing the organic phase with deionized water until neutral, to obtain the OCA adhesive.

8. The folding screen protector according to claim 7, characterized in that: The weight proportions of the components in the preparation method of OCA glue are: 20-25 parts of sulfuric acid aqueous solution, 30-40 parts of methyltrimethoxysilane, 10-15 parts of phenyltrimethoxysilane, and 15-20 parts of 3-glycidyloxypropyltrimethoxysilane.

9. The folding screen protector according to claim 1, characterized in that: The thickness of the functional base film layer is 38-50 μm, the thickness of the thermosetting resin film layer is 40-50 μm, the thickness of the UTG layer is 30-40 μm, and the thickness of the OCA adhesive film layer is 35-50 μm.

10. The preparation process of the foldable screen protector according to any one of claims 1 to 9, characterized in that: Specifically, the functional base film PET is laminated with the thermosetting resin film without the release paper, and then UTG, the thermosetting resin film without the release paper and the OCA adhesive film are laminated on the thermosetting resin film in sequence, and laminated and cut by a fully automatic hot pressing laminating machine to obtain a folding screen protector.

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