Resin composition for forming prism structure and optical film

Abstract

This application relates to a resin composition and optical film for forming a prism structure. The resin composition, by weight, comprises: 20-40 parts of urethane (meth)acrylate prepolymer as a modified acrylic resin, providing flexibility and adhesion; 10-30 parts of high-refractive-index acrylate monomer, which has a high refractive index and improves the overall refractive index of the adhesive; 2-10 parts of a first functional monomer containing a heterocyclic structure, used to reduce curing shrinkage and provide self-lubricating properties; 2-10 parts of a second functional monomer with trifunctionality or higher, used to increase crosslinking density; 20-50 parts of a modified nano-inorganic powder dispersion; 3-7 parts of a photoinitiator; and 0.1-0.5 parts of additives. The prism structure formed by UV curing of this resin composition has a refractive index of 1.58-1.60, a cross-cut adhesion of 5B at room temperature and in water, and a wear resistance of ≥3 times under a 3kg load, achieving both high refractive index and wear resistance without increasing the prism's rounded corners.

Description

Technical Field

[0001] This application relates to the field of optical technology, and in particular to a resin composition and optical film for forming prism structures. Background Technology

[0002] Optical films are thin-film materials used to control the optical properties of light, such as propagation, reflection, refraction, polarization, or brightness. Brightness enhancement films (also known as prism sheets or BEF) are optical films used in LCD backlight modules. Their surface has a microprism array structure, which concentrates scattered light towards the normal direction through refraction, reflection, and light accumulation effects, thereby increasing axial brightness. A single film can increase brightness by 40% to 60%. In recent years, technological breakthroughs have been achieved in areas such as reflective polarizing brightness enhancement films and composite brightness enhancement films. Meanwhile, with MiniLED, 5G, and 8K technologies entering a period of rapid growth, the display industry is placing higher demands on brightness enhancement films, and products are developing towards thinner, more multifunctional, and more composite designs. Emerging application scenarios such as automotive displays are placing higher demands on the durability and weather resistance of brightness enhancement films.

[0003] In the practical application and assembly of brightness enhancement films, the wear resistance of the prism microstructure is a crucial factor affecting product yield. Prism structures are prone to scratches during transportation, assembly, or contact with display panels and other films, thus affecting optical performance. To address this issue, the industry typically employs two technical approaches: one is to replace the sharp corners of the prism structure with rounded corners (increasing the radius of curvature), and the other is to use soft, resilient materials to fabricate the prism microstructure. However, the former causes the prism tip to lose optical effectiveness; the larger the radius of curvature of the dome, the worse the optical effect, and the more severe the adhesion to the upper optical film. The latter, while requiring a high refractive index, has a higher cost for the elastic material, and suitable resilient resins are scarce when the refractive index is higher than 1.58. Therefore, how to improve the wear resistance of the prism layer while maintaining a high refractive index to preserve optical gain is a pressing technical problem in this field. Summary of the Invention

[0004] The purpose of this application is to provide a resin composition and a brightness enhancement film for forming a prism structure, thereby solving the technical problem that existing brightness enhancement films cannot simultaneously ensure high refractive index (i.e., optical gain) and the wear resistance of the prism structure. This improves the wear resistance and adhesion of the prism layer and avoids brightness loss and adsorption risks caused by increasing the rounded corners at the top of the prism. This objective is achieved through the following technical solution: the resin composition for forming the prism structure comprises the following components in parts by weight: Modified acrylic resin 20-40 High-refractive acrylate monomer 10-30 First functional unit 2-10 Second functional unit 2-10 Nano-inorganic powder dispersion 20-50 Photoinitiator 3-7 Additives 0.1-0.5 Wherein, the modified acrylic resin is a urethane (meth) acrylate prepolymer, the high-refractive-index acrylate monomer is a monofunctional acrylate monomer and / or a difunctional acrylate monomer, the first functional monomer is an acrylate including a heterocyclic structure, and the second functional monomer is an acrylate monomer containing trifunctionality or higher.

[0005] In one embodiment, the urethane (meth)acrylate prepolymer has an average (meth)acrylate functionality of 2 to 6, a refractive index in the range of 1.5 to 1.6, a viscosity at 25°C in the range of 8000-50000 mPa·s, and a number-average molecular weight in the range of 1000-5000 g / mol.

[0006] In one embodiment, the color of the urethane (meth)acrylate prepolymer is less than 50.

[0007] In one embodiment, the first functional monomer includes one or more of tetrahydrofuran acrylate, tetrahydrofuran methacrylate, cyclotrimethylolpropane methyl acetal acrylate, cyclotrimethylolpropane methyl acetal methacrylate, and pyrrole acrylate.

[0008] In one embodiment, the second functional monomer includes one or more of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

[0009] In one embodiment, the weight ratio of the first functional monomer to the second functional monomer is in the range of 10:1 to 1:1.

[0010] In one embodiment, the photoinitiator includes one or two of the following: α-hydroxy ketone photoinitiators, α-aminobenzophenone photoinitiators, acylphosphine photoinitiators, α-oxyacyloxime ester photoinitiators, acylgermanium or tin photoinitiators, hexaaryldiimidazole photoinitiators, benzophenones, thioxanthones, quinones and their derivatives.

[0011] In one embodiment, the additives include one or more of dispersants, leveling agents, and defoamers.

[0012] In one embodiment, the solvent of the nano-inorganic powder dispersion is 3-phenoxybenzyl acrylate, which includes modified nano-zirconia or modified nano-titanium oxide.

[0013] In addition, this application also provides an optical film comprising a prism formed from the aforementioned resin composition for forming a prism structure.

[0014] Compared with the prior art, this application has the following beneficial effects: The resin composition and brightness enhancement film for forming a prism structure provided in this application, through the use of specific weight parts of modified acrylic resin (urethane (meth)acrylate prepolymer), high-refractive-index acrylate monomers (monofunctional and / or bifunctional), a first functional monomer containing a heterocyclic structure, a second functional monomer with trifunctionality or higher, a modified nano-inorganic powder dispersion, a photoinitiator, and additives, enable the resin composition to form a prism structure with high refractive index and dense cross-linking after UV curing. This ensures both appropriate cross-linking density and structural compactness while avoiding increased brittleness due to excessive cross-linking, thereby improving wear resistance while maintaining good flexibility and adhesion. Furthermore, since the improvement in wear resistance does not rely on increasing the radius of the prism top, it avoids the resulting brightness loss and assembly adsorption risks. While maintaining a high refractive index (1.58~1.60) to preserve optical gain, it effectively solves the technical problem of insufficient wear resistance in existing brightness enhancement film prism layers, improves assembly yield, and meets the display industry's requirements for thinner and more weather-resistant brightness enhancement films. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the optical film in one embodiment of this application.

[0016] Explanation of reference numerals in the attached figures: 100, substrate layer; 200, prism layer; 300, prism structure. Detailed Implementation

[0017] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0018] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0019] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0020] As described in the background section, existing brightness enhancement films are prone to wear and tear on their prism microstructures due to scratches during assembly and use, reducing assembly yield. Improving wear resistance by increasing the prism's top radius or using soft, resilient materials can lead to a decrease in optical gain or failure to simultaneously meet the high refractive index requirement. To address these technical problems, this application provides a resin composition and optical film for forming prisms. This resin composition is formulated by compounding specific weight parts of modified acrylic resin, high-refractive-index acrylate monomer, a first functional monomer containing a heterocyclic structure, a second functional monomer with trifunctionality or higher, a modified nano-inorganic powder dispersion, a photoinitiator, and additives. After UV curing, it forms a prism structure with a high refractive index and dense cross-linking, thereby improving the wear resistance and adhesion of the prism layer while maintaining optical gain. Detailed descriptions are provided below through specific embodiments.

[0021] The resin composition for forming a prism structure according to this application comprises the following components: modified acrylic resin, high-refractive-index acrylate monomer, first functional monomer, second functional monomer, nano-inorganic powder dispersion, photoinitiator, and additives. The modified acrylic resin is a urethane (meth)acrylate prepolymer, the high-refractive-index acrylate monomer is a monofunctional acrylate monomer and / or a difunctional acrylate monomer, the first functional monomer is an acrylate comprising a heterocyclic structure, and the second functional monomer is an acrylate monomer containing trifunctionality or higher.

[0022] Based on the functional synergy of each component and the comprehensive performance optimization of the prism structure after curing, the weight range of each component is determined. In the resin composition provided in this application, the weight of modified acrylic resin is 20 to 40 parts. If its content is less than 20 parts, the prepolymer in the composition as the main film-forming substance is insufficient, the stability of the prism structure formed after curing is poor, and the adhesion decreases. If it is more than 40 parts, the viscosity of the composition is too high, which is not conducive to coating and molding, and the relative proportion of high-refractive acrylate monomer and functional monomer is compressed, making it difficult to achieve the required crosslinking density and refractive index.

[0023] The high-refractive-index acrylate monomer comprises 10 to 30 parts by weight. This monomer acts as a refractive index adjusting component. If the amount is too low, it will not contribute sufficiently to the overall high refractive index; if the amount is too high, the relative content of the prepolymer will decrease, affecting the mechanical properties and abrasion resistance of the cured film. The first functional monomer comprises 2 to 10 parts by weight, and the second functional monomer comprises 2 to 10 parts by weight. Both are functional monomers, but their functions are different. The first functional monomer provides low shrinkage, self-lubrication, and improved adhesion, while the second functional monomer provides high crosslinking density to enhance abrasion resistance. If the first functional monomer is less than 2 parts by weight, the low shrinkage and self-lubrication effects brought by the heterocyclic structure are insufficient, the prism forming accuracy is easily affected by curing shrinkage, and the decrease in the coefficient of friction is not significant. If the first functional monomer is more than 10 parts by weight, the proportion of low crosslinking structure is too high, and the crosslinking density after curing is insufficient. Similarly, when the second functional monomer is less than 2 parts, the crosslinking density is insufficient; when it is more than 10 parts, brittleness increases. The two monomers should be combined within an independent range of 2 to 10 parts, with a preferred weight ratio of 10:1 to 1:1, to ensure adequate density and flexibility of the crosslinked network. The term "high-refractive-index acrylate monomer" used in this application is a designation used to distinguish it from other acrylic monomers used in this application. It refers to a monomer with a higher refractive index than other acrylic monomers used in this application. "High-refractive-index" does not imply a limitation on a specific refractive index value.

[0024] The nano-inorganic powder dispersion comprises 20 to 50 parts by weight. The main function of the nano-zirconia or titanium dioxide dispersion is to improve the refractive index of the cured composition. If the addition amount is too low, the refractive index improvement is limited and cannot reach the level of 1.58 to 1.60. If the addition amount is too high, the inorganic powder is prone to agglomeration, affecting the dispersion uniformity and light transmittance, and the viscosity of the composition will increase excessively, resulting in a decrease in coating process performance. The photoinitiator comprises 3 to 7 parts by weight. If it is less than 3 parts, the curing is insufficient, the prism structure surface becomes sticky, the crosslinking density is insufficient, and the wear resistance cannot be achieved. If it is more than 7 parts, the excess initiator remains in the cured product, which may cause yellowing or degradation, affecting optical transparency and weather resistance. The additives comprise 0.1 to 0.5 parts by weight. Very small amounts of additives can improve dispersion, leveling, and defoaming. Exceeding this range may lead to surface defects or the risk of incompatibility with other components. Within the above weight range, the cured resin composition achieves a balance between refractive index, adhesion, wear resistance, and scratch resistance.

[0025] The modified acrylic resin used in this application is a urethane (meth)acrylate prepolymer. This prepolymer contains both urethane bonds and (meth)acrylate groups in its molecular structure. The urethane bonds endow the prepolymer with the properties of polyurethane-like materials, including high flexibility, good adhesion, and wetting ability on various substrates; while the acrylate groups provide the reactivity for UV curing. Furthermore, this prepolymer has an average (meth)acrylate functionality of 2 to 6. The functionality directly affects the crosslinking density during UV curing. If the functionality is too low, the crosslinking network formed after curing is not dense enough, making it difficult to provide sufficient mechanical strength and abrasion resistance; if the functionality is too high, the crosslinking density is too large, which may increase the brittleness of the cured product, negatively impacting the impact resistance of the prism structure. Controlling the functionality within the range of 2 to 6 allows the prepolymer to form a network structure with appropriate crosslinking density after curing while maintaining good flexibility. The refractive index of the prepolymer is controlled within the range of 1.5 to 1.6, the viscosity at 25°C is 8000 to 50000 mPa·s, the number-average molecular weight is 1000 to 5000 g / mol, and the chromaticity is less than 50. Through the above-mentioned further optimized scheme, the prepolymer is ensured to have moderate fluidity in the composition system, facilitating uniform mixing with each component, while maintaining the overall optical transparency and high refractive index of the composition. Specifically, it can be one of Sartoma's CU208NS, CU612NS, PRO33016, PRO33025, or RAHN AG's GENOMER4205, GENOMER4277, GENOMER4297, GENOMER4365.

[0026] The high-refractive-index acrylate monomers used in this application are selected from monofunctional and / or difunctional acrylate monomers. Their function is twofold: firstly, to adjust the refractive index of the adhesive; and secondly, to participate in the polymerization reaction during UV curing, influencing the mechanical properties of the cured product. Specifically, monofunctional acrylate monomers such as o-phenylphenoxyethyl acrylate (OPPEA) have a refractive index of approximately 1.575 to 1.576, contain a biphenyl group, and the high molar refractive index of the benzene ring structure in the molecule endows this monomer with a high refractive index. Simultaneously, the linear segments formed after polymerization by its monofunctional structure provide a certain degree of flexibility. Specifically, the monofunctional acrylate monomers include, but are not limited to, any one or more of o-phenylphenol acrylate (OPPA), o-phenylphenoxyethyl acrylate (OPPEA), 2(ethoxy)-o-phenylphenoxyethyl acrylate (OPP(EO)2A), 3-phenoxybenzyl acrylate (PBA), and biphenylmethanol acrylate (BPMA).

[0027] Bifunctional acrylate monomers, such as (ethoxy)bisphenol fluorene diacrylate, contain two acrylate groups and a fluorene backbone in their molecules. The fluorene backbone has a high molar refractive index, allowing the refractive index of this type of monomer to reach above 1.622. The introduction of bifunctional monomers can form crosslinking points during polymerization, increasing the crosslinking density and thus improving the mechanical strength of the cured product. Specifically, the bifunctional acrylate monomers include, but are not limited to, 2(ethoxy)bisphenol A diacrylate (BPA(EO)2DA), 3(ethoxy)bisphenol A diacrylate (BPA(EO)3DA), 4(ethoxy)bisphenol A diacrylate (BPA(EO)4DA), 4(ethoxy)bisphenol fluorene diacrylate (BPF(EO)4DA), 6(ethoxy)bisphenol fluorene diacrylate (BPF(EO)6DA), 8(ethoxy)bisphenol fluorene diacrylate (BPF(EO)8DA), 10(ethoxy)bisphenol fluorene diacrylate (BPF(EO)10DA), 2( The ethoxybisphenol A dimethacrylate (BPA(EO)2DMA), 3(ethoxy)bisphenol A dimethacrylate (BPA(EO)3DMA), 4(ethoxy)bisphenol A dimethacrylate (BPA(EO)4DMA), 4(ethoxy)bisphenol fluorene dimethacrylate (BPF(EO)4DMA), 6(ethoxy)bisphenol fluorene dimethacrylate (BPF(EO)6DMA), 8(ethoxy)bisphenol fluorene dimethacrylate (BPF(EO)8DMA), and 10(ethoxy)bisphenol fluorene dimethacrylate (BPF(EO)10DMA) are any one or more of the following:

[0028] This application classifies functional monomers into two categories: first functional monomers and second functional monomers. These two types play different technical roles in the composition and achieve synergistic performance through specific ratios. The first functional monomer is an acrylate containing a heterocyclic structure, specifically selected from one or more of tetrahydrofuran acrylate (THFA), tetrahydrofuran methacrylate (THFMA), cyclotrimethylolpropane methyl acetal acrylate (CTFA), cyclotrimethylolpropane methyl acetal methacrylate (CTFMA), and pyrrole acrylate (PYRA). Taking CTFA as an example, its molecule contains a cyclic acetal structure. This unique heterocyclic structure endows the monomer with extremely low volume shrinkage during UV curing. For example, CTFA monomer has properties such as low shrinkage, excellent wear resistance, and excellent flexibility. The low shrinkage characteristic is crucial for the molding accuracy of the prism structure. Excessive curing shrinkage will cause deformation or warping of the sharp corners of the prism structure, leading to a decrease in optical gain. Simultaneously, polymers containing heterocyclic structures have self-lubricating properties and a low coefficient of friction, helping to reduce friction and wear on the prism surface during assembly and use. In addition, CTFA has good adhesion to plastics and metals, which can improve the adhesion between the prism layer and the substrate.

[0029] The second functional monomer is an acrylate monomer with trifunctionality or higher, specifically selected from one or more of trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA). Taking TMPTA as an example, its molecule contains three acrylate groups, which can form a high-density cross-linked network through free radical polymerization during UV curing. Compared with low-functionality monomers, it can more efficiently increase the cross-linking density of the cured product while reducing dependence on photoinitiators. The increased cross-linking density makes the molecular structure more compact, and the cured prism structure can better resist external wear damage, thereby improving wear resistance.

[0030] The weight ratio of the first functional monomer and the second functional monomer is limited to the range of 10:1 to 1:1. If the proportion of the first functional monomer is too high (i.e., the weight ratio is greater than 10:1), there will be too many components with low crosslinking density in the composition, resulting in poor reactivity and insufficient crosslinking density after curing, leading to a decrease in the strength and adhesion of the prism structure. If the proportion of the second functional monomer is too high (i.e., the weight ratio is less than 1:1), the crosslinking density will be too high, the curing reaction will be too fast, the brittleness of the adhesive layer will increase, and the flexibility and wear resistance will weaken. This application limits the compounding of the two within a specific ratio range, so that the first functional monomer with low shrinkage and high adhesion complements the second functional monomer with high crosslinking density, taking into account curing accuracy, crosslinking density, and flexibility. More preferably, the weight ratio between the first functional monomer and the second functional monomer is 8:1 to 2:1.

[0031] The modified nano-inorganic powder dispersion in this application is a dispersion of modified nano-zirconia (55% to 65% by mass) or modified nano-titanium oxide (35% to 45% by mass) dispersed in 3-phenoxybenzyl acrylate. The refractive indices of the two dispersions are 1.69 and 1.89, respectively. Most photocurable resins have relatively low refractive indices, typically in the range of 1.4 to 1.55, requiring the addition of inorganic nanoparticles to increase the refractive index. This application utilizes the high refractive index of the inorganic nanoparticles themselves to increase the refractive index of the entire resin composition after curing by adding nano-zirconia or nano-titanium oxide dispersions to the composition, thereby ensuring that the prism structure has high light refraction and reflection efficiency and maintaining optical gain. Simultaneously, the above dispersion uses 3-phenoxybenzyl acrylate as the dispersion medium, which is itself a high-refractive-index acrylate monomer with relatively low viscosity. This maintains the compatibility and low viscosity of the dispersion system without introducing low-refractive-index components that would affect the overall refractive index. The proportion of modified nano-zirconia in 3-phenoxybenzyl acrylate is within a range. When the proportion is 55%, the refractive index of the system is 1.67; when the proportion is 60%, the refractive index of the system is 1.69; and when the proportion is 65%, the refractive index of the system is 1.7. The zirconia dispersions used are purchased from the market, including but not limited to KCtech P67 and P69, and Guoci DPZ-6721 and DPZ-6989. Similarly, the modified nano-titanium oxide dispersions are also purchased from the market, including but not limited to Guoci DPAT-1.

[0032] Photoinitiators are components in the resin composition of this application that enable UV curing. The photoinitiators used in this application include one or two of the following: α-hydroxy ketone photoinitiators, α-aminobenzophenone photoinitiators, acylphosphine photoinitiators, α-oxyacyloxime ester photoinitiators, acylgermanium or tin photoinitiators, hexaaryl diimidazole photoinitiators, benzophenone (BP) derivatives, thioxanthone derivatives, quinones and their derivatives, specifically including but not limited to: 2-hydroxy-2-methylphenylacetone (1173), 1-hydroxy... Cyclohexylphenyl ketone (184), 2,4,6-trimethylbenzoyl (TPO), 2-methyl-1-[4-(methylthio)benzene]-2-morpholinopropanone (907), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (369), 2-(4-methylbenzyl)-2-dimethylamino-1-(4-morpholinophenyl)butanone (379), 2-isopropylthioxanthone (ITX), 2,4-diethylthiazolinone (DETX), and benzophenone (BP). Different types of photoinitiators have different absorption wavelengths and initiation efficiencies. Using them in combination can broaden the response range of photocuring to the UV band (280nm to 420nm), improving curing efficiency and curing depth. The amount of photoinitiator should be controlled between 3 and 7 parts by weight to ensure sufficient curing reaction while avoiding side reactions or residues that may affect optical transparency due to excessive initiator.

[0033] The additives in this application include one or more of dispersants, leveling agents, and defoamers. Dispersants are used to improve the uniformity of dispersion of nano-inorganic powders in the resin composition, preventing agglomeration of nanoparticles that leads to decreased light transmittance or uneven local performance. Leveling agents are used to reduce the surface tension of the resin composition, improving the wettability and leveling of the composition on the substrate surface during coating, ensuring the forming accuracy and surface smoothness of the prism structure. Defoamers are used to eliminate bubbles generated during mixing and coating, preventing bubbles from forming defects after curing that affect optical performance. The dispersant is one of BYK-9076, BYK-9077, BYK-W940, BYK-W966, BYK-111, BYK-180, and BYK-2009R; the leveling agent is surface additives BYK-3500, BYK-3511, BYK-3518, BYK-3535, BYK-3505, BYK-3575, BYK-357, TEGO RAD2500, TEGORAD2700, TEGO RAD2200N, and TEGO Glide. ZG400, preferably one of the reactive surface additives BYK-3535, BYK-3505, BYK-3575, and BYK-3576, and one of the defoamers BYK-1811, BYK-1815, BYK-1816, BYK-1818, BYK-1799, BYK-329, BYK-141, and TEGO Airex920.

[0034] Please see Figure 1 This application also provides an optical film comprising a substrate layer 100 and a prism layer 200 formed on the substrate layer. The prism layer 200 includes a prism structure 300, which is formed by UV curing of the aforementioned resin composition used to form the prism structure. The substrate layer 100 is made of PET, PP, or PC, with a thickness of 25 to 125 μm; the prism structure 300 has a height of 20 to 70 μm and an angle of 0° to 90°. The prism structure 300 can be transferred to the substrate surface using a soft film or hard roller molding process, and then cured by UV light. The curing wavelength is 280 nm to 420 nm, and the curing energy is 400 to 800 mJ / cm², ultimately obtaining an optical film containing the prism structure 300. The above-mentioned optical film can be used as a brightness enhancement film in a liquid crystal display backlight module, utilizing the refraction and total internal reflection of the prism structure 300 to concentrate scattered light towards the normal direction, thereby improving the axial brightness. Specific Implementation The following will further introduce some specific implementation methods to provide a more detailed explanation of the technical solution of this application.

[0036] Example 1: Modified acrylic resin: 30 parts by weight of urethane (meth)acrylate prepolymer, specifically Sartoma's CU208 NS, high refractive index monomers: 5 parts by weight of o-phenylphenoxyethyl acrylate (OPPEA); 10 parts by weight of 4-(ethoxy)bisphenol fluorene diacrylate (BPA(EO)4DA); 5 parts by weight of 2-(ethoxy)o-phenylphenoxyethyl acrylate (OPP(EO)2A). Functional monomers: First functional monomer: 8 parts by weight of cyclotrimethylolpropane methyl acetal acrylate (CTFA); Second functional monomer: 2 parts by weight of trimethylolpropane triacrylate (TMPTA); Modified nano-inorganic powder dispersion: 40 parts by weight of modified nano-zirconia dispersed in 3-phenoxybenzyl acrylate (modified nano-zirconia accounts for 55~65% by mass), specifically DPZ-6721 from Guoci; Photoinitiator: 2 parts by weight of photoinitiator 1173 and 1 part by weight of photoinitiator TPO; Additives: 0.2 parts by weight of dispersant BYK180, 0.3 parts by weight of leveling agent BYK3505, and 0.1 parts by weight of defoamer BYK1799. According to the above weight proportions, first add the modified acrylic resin to the mixing tank, heat to 60℃ and stir for 10 minutes in the dark, then add BYK180 and stir at high speed for 20 minutes. Then add OPPEA, BPA(EO)4DA, OPP(EO)2A, CTFA, TMPTA, modified nano-inorganic powder dispersion, 1173, TOP, BYK3505, and BYK1799 in sequence, and continue stirring for 2 hours. After standing to defoam, a UV-type acrylic adhesive is obtained. Then, the obtained UV-type acrylic adhesive is coated and molded onto a 38μm chemically pre-coated PET substrate using a 20μm height isosceles right-angle prism and a 5° hard wheel mold, and cured by UV light at a curing energy of 500mJ / cm to obtain an optical film product containing a prism structure.

[0037] Example 2: The difference from Example 1 is: The functional monomers are: first functional monomer: 8 parts by weight of THFA; second functional monomer: 2 parts by weight of TMPTA.

[0038] Example 3: The difference from Example 1 is: The functional monomers are: first functional monomer: 7.5 parts by weight of CTFA; second functional monomer: 2.5 parts by weight of TMPTA.

[0039] Example 4: The difference from Example 1 is: The photoinitiator consists of 2 parts by weight of photoinitiator 184 and 1 part by weight of photoinitiator TPO.

[0040] Example 5: The difference from Example 1 is: The photoinitiator consists of 3 parts by weight of photoinitiator 184 and 1 part by weight of photoinitiator TPO.

[0041] Example 6: The difference from Example 1 is: The additives include: 0.3 parts by weight of leveling agent TEGO RAD2200N and 0.1 parts by weight of defoamer TEGOAirex920. Example 7: The difference from Example 1 is: The high refractive index monomer; 10 parts by weight of 3-phenoxybenzyl acrylate (PBA); 10 parts by weight of 10(ethoxy)bisphenol fluorene diacrylate (BPF(EO)10DA).

[0042] Example 8: The difference from Example 1 is: The modified acrylic resin is 40 parts by weight of urethane (meth) acrylate prepolymer, specifically Sartoma's CU208 NS. The modified nano-inorganic powder dispersion is 30 parts by weight of modified nano-titanium oxide dispersed in 3-phenoxybenzyl acrylate (modified nano-titanium oxide accounts for 35~45% by mass), specifically Guoci DPAT-1.

[0043] Example 9: The difference from Example 1 is: The high refractive index monomer consists of 20 parts by weight of 4(ethoxy)bisphenol fluorene diacrylate (BPF(EO)4DA) and 10 parts by weight of 2(ethoxy)o-phenylphenoxyethyl acrylate (OPP(EO)2A). The modified nano-inorganic powder dispersion consists of 30 parts by weight of modified nano-titanium oxide dispersed in 3-phenoxybenzyl acrylate (modified nano-titanium oxide accounts for 35~45% by mass), specifically Guoci DPAT-1.

[0044] Example 10: The difference from Example 1 is that: The high refractive index monomers are: 10 parts by weight of 2(ethoxy)o-phenylphenoxyethyl acrylate (OPP(EO)2A); and 10 parts by weight of 10(ethoxy)bisphenol fluorene diacrylate (BPF(EO)10DA). The functional monomers are: first functional monomer: 16 parts by weight of cyclotrimethylolpropane methyl acetal acrylate (CTFA), and second functional monomer: 4 parts by weight of trimethylolpropane triacrylate (TMPTA). The modified nano-inorganic powder dispersion consists of 30 parts by weight of modified nano-titanium oxide dispersed in 3-phenoxybenzyl acrylate (modified nano-titanium oxide accounts for 35~45% by mass), specifically Guoci DPAT-1.

[0045] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that: The functional monomers are: first functional monomer: 4 parts by weight of CTFA; second functional monomer: 6 parts by weight of TMPTA.

[0046] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that: The functional monomers are: first functional monomer: 10 parts by weight of CTFA; no second functional monomers.

[0047] Comparative Example 3: The difference between it and Example 1 is that: The functional monomer: Second functional monomer: 10 parts by weight of TMPTA; No first functional monomer.

[0048] Viscosity test: The viscosity of the abrasion-resistant prism adhesive at 25°C was tested using a Bollefeld DV1 cone / plate viscometer. Refractive index test: The refractive index of the wear-resistant prism adhesive at 25℃ was tested using a Jiahang fully automatic refractometer, and the value was read directly.

[0049] Adhesion test: At 1.25℃, the industry-standard cross-cut adhesion test is used. The cross-cut adhesion tester draws 100 small squares on the prism surface of the prism sheet by drawing mutually perpendicular parallel lines. Then, the coating in the squares is peeled off with 3M 600 tape, and the proportion of the area of ​​coating that has fallen off is observed to determine the strength of the adhesion.

[0050] 2. Place the prism sheet in a 100℃ water bath and boil for 0.5 hours. After removing and drying, use the industry-standard cross-cut tester to draw 100 small squares on the prism surface of the prism sheet. Then, peel off the coating in the squares with 3M 600 tape and observe the proportion of the area where the coating is peeled off to determine the strength of the adhesion.

[0051] Abrasion resistance test: Use Qingbo abrasion resistance tester with a load of 3kg. The test head runs perpendicular to the prism of the prism sheet. The friction surface is back coated with 2%. After friction, observe the wear of the prism sheet. Scratch resistance test: Using the Chingbo scratch resistance tester, the prism sheet is sandwiched between PET and the friction pad. The contact surface between the friction pad and the prism sheet is 2% back-coated, and the other side is PET. A 1kg weight is pressed on the PET surface, and the prism sheet layer is pulled at a constant speed along a certain straight trajectory. The wear condition of the prism sheet is then observed.

[0052] The test results for each implementation method are shown in Table 1.

[0053] Table 1 Summary of test results for each embodiment The test results show that the prism structures formed by the cured resin compositions prepared in Examples 1 to 10 exhibit excellent comprehensive performance in terms of refractive index, adhesion, abrasion resistance, and scratch resistance. Specifically, all examples achieved a 5B result in both the room temperature cross-cut adhesion test and the boiling cross-cut adhesion test, indicating that the prism layer maintains high adhesion to the substrate under both room temperature and humid heat aging conditions. In the abrasion resistance test (3kg load), Examples 1 to 7 and Examples 9 to 10 withstood 3 abrasions without scratching, while Example 8 withstood 5 abrasions without scratching. In the scratch resistance test (1kg load), all examples withstood 1 scratch without scratching. These results demonstrate that within the component and ratio range defined in this application, the cured resin composition can achieve a balance between high refractive index (1.58~1.60) and good abrasion resistance, scratch resistance, and adhesion.

[0054] The main difference between Comparative Examples 1 to 3 and Example 1 lies in the ratio or type of functional monomers. In Comparative Example 1, the weight ratio of the first functional monomer to the second functional monomer is 4:6 (i.e., 4 parts of the first functional monomer and 6 parts of the second functional monomer), which exceeds the preferred range of 10:1 to 1:1 in this application (Example 1 is 8:2, i.e., 4:1, which is within the range). Test results show that the cross-linking density of Comparative Example 1 drops to 4B at room temperature and to 2B after boiling, with only one pass of abrasion resistance test. This indicates that when the first functional monomer is relatively insufficient and the second functional monomer is relatively excessive, the excessive cross-linking density leads to increased brittleness, while the low shrinkage and adhesion-enhancing effects brought by the heterocyclic structure are weakened, resulting in decreased adhesion and abrasion resistance.

[0055] Comparative Example 2, which does not contain the second functional monomer (only 10 parts of the first functional monomer), showed a cross-linking density of only 2B at room temperature and 0B after boiling, and only passed the abrasion test once (OK). This indicates that without the cross-linking network provided by high-functionality monomers, the cross-linking density of the cured product is too low, the molecular structure is not dense enough, the bonding force between the prism layer and the substrate is poor, and it cannot effectively resist frictional damage.

[0056] Comparative Example 3, which did not contain the first functional monomer (only 10 parts of the second functional monomer), showed a 3B cross-cut adhesion test result at room temperature and an 0B cross-cut adhesion test result after boiling. The abrasion resistance test result was NG (not passed) once, and the scratch resistance test result was also NG. This indicates that in the absence of the first functional monomer containing heterocyclic structures, the curing shrinkage rate is large, the molding accuracy and adhesion of the prism structure are reduced, and the self-lubricating properties are lacking, resulting in a higher coefficient of friction and thus deterioration in abrasion and scratch resistance.

[0057] In summary, the advantages of this application's technical solution lie in the following: by compounding modified acrylic resin, high-refractive-index acrylate monomer, first functional monomer containing heterocyclic structure, second functional monomer with trifunctionality or higher, and modified nano-inorganic powder dispersion according to a defined weight range and proportion, the resin composition, after curing, can simultaneously achieve a high refractive index of 1.58~1.60, 5B-level adhesion (at room temperature and after boiling in water), abrasion resistance with at least three scratch-free rubs under a 3kg load, and scratch resistance with one scratch-free rub under a 1kg load. Comparative Examples 1 to 3, deviating from the functional monomer ratio or type requirements of this application, all showed deterioration in different performance indicators, further confirming the necessity of the synergistic effect among the components of this application, especially the first and second functional monomers, for improving the overall performance of the prism layer.

[0058] As described above, this application addresses the technical problem that existing brightness enhancement film prism structures cannot simultaneously satisfy high refractive index and wear resistance by providing a resin composition and optical film for forming prism structures. The resin composition comprises 20-40 parts by weight of modified acrylic resin (urethane (meth)acrylate prepolymer), 10-30 parts by weight of high-refractive-index acrylate monomer (monofunctional and / or difunctional), 2-10 parts by weight of a first functional monomer containing a heterocyclic structure, 2-10 parts by weight of a second functional monomer with trifunctionality or higher, 20-50 parts by weight of modified nano-inorganic powder dispersion, 3-7 parts by weight of a photoinitiator, and 0.1-0.5 parts by weight of additives. This application achieves a balance between high refractive index and good wear resistance and adhesion without increasing the rounded corners of the prism top, avoiding brightness loss and assembly adsorption risks, and is suitable for brightness enhancement films in liquid crystal display backlight modules.

[0059] The above is only one specific implementation of this application, and any other improvements made based on the concept of this application shall be considered within the scope of protection of this application.

Claims

1. A resin composition for forming a prism structure, characterized in that, It includes the following components in parts by weight: Modified acrylic resin 20-40 High-refractive acrylate monomer 10-30 First functional unit 2-10 Second functional unit 2-10 Nano-inorganic powder dispersion 20-50 Photoinitiator 3-7 Additives 0.1-0.5 Wherein, the modified acrylic resin is a urethane (meth) acrylate prepolymer, the high-refractive-index acrylate monomer is a monofunctional acrylate monomer and / or a difunctional acrylate monomer, the first functional monomer is an acrylate including a heterocyclic structure, and the second functional monomer is an acrylate monomer containing trifunctionality or higher.

2. The resin composition for forming a prism structure according to claim 1, characterized in that, The urethane (meth)acrylate prepolymer has an average (meth)acrylate functionality of 2 to 6, a refractive index in the range of 1.5 to 1.6, a viscosity at 25°C in the range of 8000-50000 mPa·s, and a number-average molecular weight in the range of 1000-5000 g / mol.

3. The resin composition for forming a prism structure according to claim 2, characterized in that, The color of the urethane (meth)acrylate prepolymer is less than 50.

4. The resin composition for forming a prism structure according to claim 1, characterized in that, The first functional monomer includes one or more of tetrahydrofuran acrylate, tetrahydrofuran methacrylate, cyclotrimethylolpropane methyl acetal acrylate, cyclotrimethylolpropane methyl acetal methacrylate, and pyrrole acrylate.

5. The resin composition for forming a prism structure according to claim 1, characterized in that, The second functional monomer includes one or more of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

6. The resin composition for forming a prism structure according to claim 1, characterized in that, The weight ratio of the first functional monomer to the second functional monomer is in the range of 10:1 to 1:

1.

7. The resin composition for forming a prism structure according to claim 1, characterized in that, The photoinitiator includes one or two of the following: α-hydroxy ketone photoinitiators, α-aminobenzophenone photoinitiators, acylphosphine photoinitiators, α-oxyacyloxime ester photoinitiators, acylgermanium or tin photoinitiators, hexaaryldiimidazole photoinitiators, benzophenones, thioxanthones, quinones and their derivatives.

8. The resin composition for forming a prism structure according to claim 1, characterized in that, The additives include one or more of dispersants, leveling agents, and defoamers.

9. The resin composition for forming a prism structure according to claim 1, characterized in that, The solvent for the nano-inorganic powder dispersion is 3-phenoxybenzyl acrylate, which includes modified nano-zirconia or modified nano-titanium oxide.

10. An optical film, characterized in that, This includes prisms formed from the resin composition for forming prism structures as described in any one of claims 1-9.

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