Elastic film for glass protective sheet and manufacturing method thereof

Abstract

The present invention relates to an elastic film for a glass protective sheet, and more specifically, to an elastic film for a glass protective sheet that can simultaneously secure excellent impact resistance and recovery power while having excellent transparency and visibility, and a method for manufacturing the same. To this end, the elastic film for a glass protective sheet comprises: an elastic film layer; and protective film layers located on each side of the elastic film layer; wherein the elastic film layer is characterized by being manufactured by an elastic film composition comprising a urethane acrylate-based reactive resin represented by the following chemical formula 1, an acrylic monomer, a photoinitiator, and a stabilizer.

Description

Technology Field

[0001] The present invention relates to an elastic film for a glass protective sheet, and more specifically, to an elastic film for a glass protective sheet that can simultaneously secure excellent impact resistance and recovery power while having excellent transparency and visibility, and a method for manufacturing the same. Background Technology

[0002] A vehicle's windshield is subjected to repeated impacts from flying debris, such as gravel, sand, and metal fragments, while driving. These impacts can cause fine scratches, pitting, or microcracks on the glass surface. Although micro-damage may be difficult to identify with the naked eye initially, it can reduce visibility by increasing optical scattering. In particular, during nighttime driving, glare and visual distortion can increase when reflections from headlights or streetlights overlap.

[0003] In addition, windshields are repeatedly exposed to environments with significant temperature fluctuations. Thermal cycles between high summer temperatures and low winter temperatures can increase the risk of microcrack growth and fatigue failure. Repetitive contact, such as wiper operation, car wash brushes, and dust friction, also contributes to the accumulation of surface defects.

[0004] For this reason, protective films or sheets attached to windshields are widely used. Protective sheets improve safety and durability by mitigating shattering impacts and suppressing damage to the glass surface. However, the performance of protective sheets can vary significantly depending on the material composition and lamination structure.

[0005] In conventional technology, the application of a hard coating layer has been primarily used to increase surface hardness. The hard coating layer has the advantage of improving scratch resistance.

[0006] However, if hardening is excessive, stress concentration may occur upon impact, leading to cracking or delamination.

[0007] Furthermore, if the protective sheet lacks flexibility, it may fail to absorb energy from localized impacts, potentially leading to perforation or fracture. Conversely, while the excessive application of elastic materials may be advantageous for shock absorption, it can increase surface damage and residual deformation. In particular, if the elastic layer does not fully recover after an impact, indentations, wrinkles, or optical distortions may remain. Such residual deformation degrades the driver's visibility, posing safety issues.

[0008] In addition, elastic materials may experience increased haze and decreased transmittance depending on their composition. If fillers or rubber-based dispersed phases coarsen or are poorly dispersed, light scattering increases, leading to deteriorated visibility.

[0009] As automotive windshields are components requiring high light transmittance and low distortion, their optical requirements are very stringent. Therefore, protective sheets and their constituent films must reliably maintain high transparency and low haze characteristics. Furthermore, prolonged outdoor exposure may lead to yellowing caused by ultraviolet rays, degradation of physical properties, and deterioration of the adhesive layer.

[0010] In addition, resistance to humid and hot environments and chemicals (cleaners, washer fluid, etc.) must also be ensured. In particular, windshield-mounted products are exposed to a complex degradation environment where temperature, humidity, and ultraviolet rays act simultaneously. As a result, it is difficult to design a composition that maintains optical properties while enhancing impact resistance and elastic recovery.

[0011] Conventional elastic films tend to exhibit increased haze as the amount of elastic component is increased to enhance impact resistance. Conversely, prioritizing transparency may result in limitations in securing shock absorption and resilience. Additionally, optical quality deteriorates if bubbles, striations, or dispersion defects occur depending on the mixing and molding conditions during the production process.

[0012] Therefore, there is a continuously increasing technical demand for elastic films suitable for automotive windshield protective sheets that simultaneously secure impact resistance and resilience (elasticity) while possessing excellent transparency and visibility.

[0013] Meanwhile, the aforementioned background technology is technical information that the inventor possessed for the derivation of the present invention or acquired during the process of deriving the present invention, and it cannot necessarily be considered publicly known technology disclosed to the general public prior to the filing of the present invention. Prior art literature

[0014] Republic of Korea Registered Patent No. 10-2346586 The problem to be solved

[0015] The present invention aims to solve the aforementioned problems, and the objective of the present invention is to provide an elastic film for a glass protective sheet that can simultaneously secure excellent impact resistance and resilience, while also possessing excellent transparency and visibility, and a method for manufacturing the same.

[0016] The above and other objects and advantages of the present invention will become apparent from the following description describing preferred embodiments. means of solving the problem

[0017] The above objective can be achieved by an elastic film for a glass protective sheet, comprising: an elastic film layer; and protective film layers respectively located on both sides of the elastic film layer; wherein the elastic film layer is manufactured by a composition for an elastic film comprising a urethane acrylate-based reactive resin, an acrylic monomer, a photoinitiator, and a stabilizer:

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[0022] The above acrylic monomer is characterized by comprising one or more selected from isobornyl (meth)acrylate, trimethylcyclohexylformal (meth)acrylate, pentaerythritol triacrylate, and 2-hydroxyethyl methacrylate.

[0023] The above stabilizer is characterized by being one or more light and / or oxidation stabilizers selected from the group consisting of butyrated hydroxytoluene, pentaerythritol tetrakis 3,5-di-tertiary-butyl-4-hydroxyphenyl propionate, octadecyl 3,5-di-tertiary-butyl-4-hydroxyphenyl propionate, benzotriazole-based, triazine-based, benzophenone-based, and bis-octadecyl hydroxyamine, and interfering amine-based light stabilizers (HALS).

[0024] The above urethane acrylate-based reactive resin is characterized by being mixed with 40 to 75 parts by weight of the acrylic monomer, 0.25 to 4 parts by weight of the photoinitiator, and 0.5 to 5 parts by weight of the stabilizer, for every 50 parts by weight of the above urethane acrylate-based reactive resin. Effects of the invention

[0025] According to the present invention, an elastic film prepared by photocuring a composition containing a urethane acrylate-based reactive resin has simultaneously improved impact resistance and recovery power due to an elastic modulus adjusted to a suitable range, is resistant to external light and heat, has improved transparency and visibility, and can exhibit excellent adhesion and adhesion stability with upper and lower coating layers added thereafter.

[0026] However, the effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below. Brief explanation of the drawing

[0027] FIG. 1 is a schematic diagram showing an elastic film according to one embodiment of the present invention. Specific details for implementing the invention

[0028] The present invention will be described in detail below with reference to the embodiments and drawings. These embodiments are presented merely as examples to explain the invention more specifically, and it will be obvious to those skilled in the art that the scope of the invention is not limited by these embodiments.

[0029] Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains, and in the event of a conflict, the description in this specification, including the definitions, shall prevail.

[0030] To clearly explain the proposed invention in the drawings, parts unrelated to the description have been omitted, and similar parts throughout the specification have been given similar reference numerals. Furthermore, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Additionally, the term "part" as described in the specification refers to a single unit or block that performs a specific function.

[0031] In each step, identification codes (1st, 2nd, etc.) are used for convenience of explanation and do not describe the order of the steps; the steps may be performed differently from the specified order unless a specific order is clearly indicated in the context. That is, the steps may be performed in the same order as specified, substantially simultaneously, or in the reverse order.

[0033] FIG. 1 is a schematic diagram showing an elastic film for a glass protective sheet according to one embodiment of the present invention.

[0034] Referring to FIG. 1, an elastic film for a glass protective sheet according to one embodiment of the present invention may have a structure in which a first protective film layer (110), an elastic film layer (100), and a second protective film layer (90) are laminated in sequence.

[0035] The first protective film layer (110) and the second protective film layer (90) can serve as a supporting substrate, carrier, or liner that applies an elastic film composition, controls the thickness, flattens, and prevents the composition from spreading or contaminating during curing in order to form the elastic film layer (100).

[0036] Specifically, the first protective film layer (110) and the second protective film layer (90) may use a non-treatment PET film. When a non-treatment PET film is used, the surface of the elastic film can be protected from contamination or scratches during manufacturing, winding, transportation, and lamination processes, and handling properties can be improved. In addition, since non-treatment PET has low surface energy, it has good peelability as a temporary protective film, allowing the protective film to be easily removed immediately before final application.

[0037] For example, the thickness of each of the first protective film layer (110) and the second protective film layer (90) can be formed to be 50 to 125 μm independently of each other.

[0039] The above elastic film layer (100) can serve as a buffer layer that absorbs and disperses impact energy through deformation upon external impact, thereby suppressing cracks, perforations, and breakage of the glass surface. Additionally, by inducing shape recovery after impact through elastic restoring force, it can reduce residual indentation, marks, and optical distortion, and can exhibit the effect of improving the durability and long-term visibility of the entire protective sheet.

[0040] The above elastic film layer (100) can be manufactured in the form of a sheet by applying an elastic film composition containing a urethane acrylate-based reactive resin between the protective film layers (110, 90) and then photocuring.

[0041] The above composition for the elastic film may include the above urethane acrylate-based reactive resin, acrylic monomer, photoinitiator, and stabilizer.

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[0056] The above acrylic monomer can further improve physical properties such as adhesion, elasticity, impact resistance, transparency, and recovery by linearly extending the polymer chains formed by polymerization between urethane acrylate-based reactive resins.

[0057] The above acrylic monomers are methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexylformal (meth)acrylate, o-phenylphenol (meth)acrylate, phenol (EO) (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, phenylthioethyl (meth)acrylate, cumylphenoxyethyl (meth)acrylate, (Met)acrylic acid, 2-carboxyethyl acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth), caprolactone (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylamide, glycidyl (meth)acrylate and N-vinylpyrrolidone, 1,6-hexanediol di(meth)acrylate 1.6-Hexanediol(EO)n di(meth)acrylate, Hydroxylpivalsan neopentylglycol di(meth)acrylate, Neopentylglycol(PO)n di(meth)acrylate, Tripropylene glycol di(meth)acrylate, Dipropylene glycol di(meth)acrylate, Triethylene glycol di(meth)acrylate, 1,4-Butanediol di(meth)acrylate, Bisphenol A(EO)n di(meth)acrylate, Tricyclodecane dimethanol di(meth)acrylate, Tetraethylene glycol di(meth)acrylate, (Polyethylene glycol) di(meth)acrylate, Bisphenol F(EO)n di(meth)acrylate, (Polypropylene glycol) di(meth)acrylate, Tris(2-hydroxyethyl)isocyanurate di(meth)acrylate, Trimethylolpropane It may include one or more selected from the group consisting of tri(meth)acrylate, trimethylolpropane(EO)n tri(meth)acrylate, pentaethritol tri(meth)acrylate, trimethylolpropane(PO) tri(meth)acrylate, glycerin (PO)n tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0058] The above acrylic monomer can be mixed in an amount of 10 to 250 parts by weight, specifically 40 to 75 parts by weight, more specifically 45 to 55 parts by weight, with respect to 50 parts by weight of the above reactive resin.

[0059] If the content of the acrylic monomer is below the aforementioned range, the viscosity of the elastic film composition is high, making it difficult to achieve an accurate thickness and potentially worsening workability; if it exceeds the aforementioned range, the viscosity of the elastic film composition is low, making it difficult to achieve an accurate thickness and potentially resulting in insufficient elasticity and strength.

[0060] Meanwhile, in addition to the above acrylic monomer, one or more additional monomers selected from polytetramethylene glycol, polycarbonate diol monomer, polypropylene glycol monomer, and polyester monomer may be further included.

[0061] The weight ratio of the acrylic monomer and the additional monomer may be 1:5 to 5:1.

[0063] The above photoinitiator generates active radicals (or cations) upon UV irradiation to initiate the polymerization and crosslinking reactions of the resin, and can rapidly cure the composition to ensure film strength and durability.

[0064] The above photoinitiator is, for example, benzyl dimethyl ketal, hydroxycyclohexyl phenyl ketone, methyl benzoyl formate, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl)]-2-(4-morpholinyl)-1-propanone, oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester, 2-isopropylthioxantone, It may include one or more selected from the group consisting of 2-(2-chlorophenyl)-1-[2-(2-chlorophenyl)-4,5-diphenyl-2-imidazole-2-yl]-4,5-diphenyl-1-imidazole, phenyl bis(2,4,6-trimethylbenzoyl), diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide, and bis(eta 5-2,4-cyclopentadiene-1-yl)bis[2,6-difluoro-3-(1-pyrrole-1-yl)phenyl]titanium.

[0065] The above photoinitiator may be mixed in an amount of 0.25 to 4 parts by weight, specifically 0.5 to 2.5 parts by weight, more specifically 0.5 to 1.5 parts by weight, with respect to 50 parts by weight of the above reactive resin.

[0066] If the content of the photoinitiator is less than the aforementioned range, the degree of curing of the elastic film composition may be reduced, and film molding may be insufficient, and if it exceeds the aforementioned range, the strength of the elastic film composition may be insufficient.

[0068] The above stabilizer refers to a light and / or oxidation stabilizer, and inhibits radicals and degradation reactions generated by ultraviolet rays, heat, and oxygen to prevent yellowing, cracking, and deterioration of physical properties, and to maintain long-term durability and visibility.

[0069] The above stabilizer may include, for example, one or more light and / or oxidation stabilizers selected from the group consisting of butyrated hydroxytoluene, pentaerythritol tetrakis 3,5-di-tert-butyl-4-hydroxyphenyl propionate, octadecyl 3,5-di-tert-butyl-4-hydroxyphenyl propionate, benzotriazole-based, triazine-based, benzophenone-based and bis-octadecyl hydroxyamine, and interfering amine-based light stabilizers (HALS).

[0070] The above stabilizer may be mixed in an amount of 0.5 to 5 parts by weight, specifically 0.5 to 4 parts by weight, more specifically 0.5 to 3.5 parts by weight, with respect to 50 parts by weight of the above reactive resin.

[0071] If the content of the above-mentioned stabilizer is less than the aforementioned range, it may be difficult to prevent deformation such as aging caused by external exposure of the composition, and if it exceeds the aforementioned range, the degree of curing of the composition for the elastic film may be reduced, thereby lowering elasticity and strength.

[0073] Meanwhile, the above composition may further include additives such as, for example, dispersants, wetting agents, coupling agents, adhesion promoters, rheology modifiers, viscosity modifiers, leveling agents, flow modifiers, defoaming agents, degassing agents, slip agents, lubricants, friction reducing agents, anti-blocking agents, impact modifiers, antifouling agents, anti-contamination agents, anti-problem agents, hardness aids, and wear-resistant aids.

[0074] The above adhesion promoter may be included to strengthen the interfacial bonding between the glass (silica) surface and the elastic film.

[0075] The above adhesion promoter may include, for example, one or more selected from poly(dopamine), tannic acid, caffeic acid, and ferulic acid.

[0076] The above components can increase initial adhesion and peel strength by improving polar interaction and wettability with the resin matrix, and can significantly contribute to suppressing migration and degradation of adhesion even during long-term use.

[0077] The above impact modifier may be included to improve the impact resistance and toughness of the film.

[0078] The above impact modifier may include, for example, one or more of cellulose nanofiber (CNF), chitin nanofiber (CNF), poly(glycerol sebacate), lignin nanoparticles (LNP), and acrylated epoxidized soybean oil (AESO).

[0079] The above impact modifier can significantly improve durability under repeated impact and fatigue conditions. In particular, when lignin nanoparticles are uniformly dispersed at the level of tens of nanometers, they can suppress light scattering to provide mechanical reinforcement effects while maintaining transparency and low haze; additionally, when used in combination with poly(glycerol sebacate) (PGS), they impart flexible energy dissipation pathways to the elastic matrix, thereby mitigating stress concentration during impact and significantly improving toughness (impact resistance) and recovery behavior.

[0080] In addition to the aforementioned components, the above additive may further include, without limitation, known components commonly used in the field.

[0081] The above additive may be mixed in an amount of 0.1 to 5 parts by weight, specifically 0.5 to 2 parts by weight, with respect to 50 parts by weight of the reactive resin.

[0083] The method of applying the above elastic film composition may be performed, for example, by slot die coating or knife (doctor blade) coating, but is not limited thereto.

[0084] After applying the composition, an elastic film can be formed by irradiating with a UV lamp of 200 to 400 nm, for example, to promote polymerization and crosslinking by a photoinitiator. If necessary, for example, a low-temperature heat treatment of 50 to 95°C can be performed in parallel as post-curing to reduce residual reactions and improve physical property stability.

[0086] Thus, an elastic film for a glass protective sheet comprising an elastic film layer can be manufactured. However, the method for manufacturing the elastic film for a glass protective sheet is not limited thereto, and may follow known techniques commonly used in the field or apply known techniques by modifying the design as much as possible.

[0087] The thickness of the above elastic film layer may be, for example, 30 to 350 μm.

[0088] For the above elastic film, durability against the protected object and strength of the elastic film itself are important against deformation caused by external impact, light, and heat, and this can be controlled by the elastic modulus and storage loss elastic modulus of the film. This can be verified by measuring the mechanical properties of the film using a DMA (Dynamic Mechanical Analyzer).

[0089] For example, the above elastic film may have a Tg of 40 to 60°C. At a Tg of less than 40°C, the storage modulus may be 100 MPa or more and the elastic modulus may be 0.75 or less. In the Tg value range, the storage modulus may be 10 to 100 MPa and the elastic modulus may be 0.75 or more. In the Tg range exceeding 60°C, the storage modulus may be 10 MPa or less and the elastic modulus may be 0.75 or less.

[0090] When the Tg is below 40℃, the strength may decrease, and in the range above 60℃, the film may be too stiff, making installation difficult. Additionally, if the elastic modulus is 0.75 or higher at temperatures below 40℃ or 0.75 or higher in the range above 60℃, the impact resistance of the film may decrease.

[0092] An elastic film for a glass protective sheet manufactured according to one embodiment of the present invention can, specifically, be applied as a core cushioning layer of an automobile windshield protective sheet. By doing so, it can absorb and disperse energy upon impact with flying debris (gravel, etc.) and suppress cracking or breakage. Furthermore, when combined with an adhesive layer in the laminated structure of the windshield protective sheet, it can alleviate stress concentration between the glass and the protective layer and improve long-term durability.

[0093] Furthermore, the elastic film for glass protection sheets can be applied in the same way to protection sheets for vehicle glass parts such as sunroofs and quarter glass. In addition, if necessary, it can be laminated with a surface functional layer (such as anti-fouling and anti-scratch properties) to simultaneously improve visibility and maintainability.

[0094] However, the application examples of the elastic film for the glass protective sheet described above are not limited thereto.

[0096] Hereinafter, the structure of the present invention and the resulting effects are to be explained in more detail through specific embodiments and comparative examples. However, these embodiments are intended to explain the present invention more specifically, and the scope of the present invention is not limited to these embodiments.

[0098] [Preparation Example]

[0099] An elastic film composition comprising a urethane acrylate-based reactive resin, an acrylic monomer, a photoinitiator, and a stabilizer was slot-die coated between two 100㎛ PET films for release liners, and then cured to produce an elastic film layer with a thickness of 160㎛.

[0101] [Examples 1 to 10]

[0102] An elastic film layer was prepared in the same manner as the aforementioned manufacturing example, but the elastic film layers of Examples 1 to 10 were prepared according to the component composition and content (parts by weight) of Tables 1 and 2 below.

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[0106] [Comparative Examples 1 to 5]

[0107] An elastic film layer was prepared using the same method as the aforementioned manufacturing example, but the elastic film layers of Comparative Examples 1 to 5 were each prepared according to the component composition and content (parts by weight) of Table 3 below.

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[0110] <Experimental Example 1: Evaluation of Physical Properties>

[0111] For each elastic film prepared according to the aforementioned Examples 1 to 13 and Comparative Examples 1 to 5, physical properties were measured according to known techniques, including UV blocking rate (%) (UV transmittance meter), Shore hardness (SH A) (Shore Hardness Tester-A), constant temperature and humidity (visual) (8585 evaluation 200hr), initial tensile strength (MPa) (tensile strength tester), tensile strength (MPa) (tensile strength tester), elongation (%) (tensile strength tester), self-healing ability (visual) (degree of recovery within 20 minutes), and elastic modulus at different temperatures (25℃, 50℃, 85℃). The results are shown in Tables 4 to 6 below.

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[0115] As shown in Tables 4 to 6 above, the elastic films manufactured according to the embodiments of the present invention exhibited significantly superior physical property evaluation results in all items, including UV blocking rate, hardness, constant temperature and humidity, tensile strength, elongation, self-healing ability, and elastic modulus at different temperatures, compared to the comparative examples. However, it is determined that Examples 6 and 8 have high Shore hardness and tensile load, making the film too stiff and potentially causing lifting during construction, while Examples 5 and 7 are too soft, resulting in weak strength and potentially causing tearing. That is, among the examples, the elastic films of Examples 1 and 9 to 13 demonstrate that they can exhibit the best physical properties by satisfying all optimal conditions, such as a UV blocking rate of at least 5%, Shore hardness of 50 to 60, constant temperature and humidity of within 5%, initial tensile strength of 8 to 15 MPa, tensile strength of 21 to 30 MPa, elongation of 150 to 250%, self-healing ability (recovery within 20 minutes), and elastic modulus of 0.2 to 0.6 at 25°C, 0.6 to 1 at 50°C, and 0.02 to 0.2 at 85°C.

[0117] In this specification, only a few examples among the various embodiments performed by the inventors are described; however, the technical concept of the present invention is not limited or restricted thereto, and it is obvious that it can be modified and implemented in various ways by those skilled in the art. Explanation of the symbols

[0118] 100: Elastic film layer 110, 90: Protective film layer

Claims

Claim 1 An elastic film layer; and protective film layers respectively located on both sides of the elastic film layer; Glass Elastic film for protective sheets. Claim 2 delete Claim 3 delete Claim 4 An elastic film for a glass protective sheet according to claim 1, wherein the stabilizer is one or more light and / or oxidation stabilizers selected from the group consisting of butyrated hydroxytoluene, pentaerythritol tetrakis 3,5-di-tertiary-butyl-4-hydroxyphenyl propionate, octadecyl 3,5-di-tertiary-butyl-4-hydroxyphenyl propionate, benzotriazole-based, triazine-based, benzophenone-based, and bis-octadecyl hydroxyamine, and interfering amine-based light stabilizers (HALS). Claim 5 delete

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