Ultraviolet absorption type acrylate pressure sensitive adhesive, and preparation method and application thereof

Abstract

The application relates to the technical field of high-molecular functional materials, and particularly discloses a UV-absorbing acrylate pressure-sensitive adhesive as well as a preparation method and application thereof. The UV-absorbing acrylate pressure-sensitive adhesive comprises acrylate resin, a UV absorber and nanofibers; the acrylate resin is prepared through free radical copolymerization of a functionalized macromonomer, an alkyl acrylate and a benzyl acrylate; and the functionalized macromonomer is prepared through reaction of hydroxyethyl acrylate with an isocyanate group-containing chain monomer and a fluorine-containing aromatic dianhydride compound in sequence. The resin network fixed through a chemical bond and the nanometer network physically blocked provide a double locking mechanism for UV-327, realize persistent blocking of ultraviolet rays, overcome the problem that the optical performance of a traditional additive optical pressure-sensitive adhesive is deteriorated due to migration and precipitation of the UV absorber, and the UV-absorbing acrylate pressure-sensitive adhesive has high light transmittance, low color deviation and excellent anti-aging property, and perfectly matches the optical and durability requirements of a high-reliability display module.

Description

Technical Field

[0001] This invention relates to the field of polymer functional materials technology, and in particular to a UV-absorbing acrylate pressure-sensitive adhesive, its preparation method, and its application. Background Technology

[0002] With the widespread adoption of smartphones, tablets, and other electronic devices, screen display technology has advanced rapidly. OLED (Organic Light Emitting Diode) screens are widely used due to their advantages such as self-illumination, high contrast, and flexibility. However, the organic light-emitting materials in OLED screens are extremely sensitive to ultraviolet light. Prolonged exposure to ultraviolet light accelerates their aging and degradation, leading to problems such as brightness decay, color shift, and image retention, severely impacting display quality and device lifespan. To protect the screen, a layer of pressure-sensitive adhesive (PSA) is typically used beneath the outermost glass cover to bond the cover to the display module. This requires the PSA layer to not only possess excellent adhesion, high light transmittance, and weather resistance, but also to effectively block ultraviolet light.

[0003] Existing technologies typically add ultraviolet absorbers (UVA) to the optical pressure-sensitive adhesive layer of a screen to achieve ultraviolet protection. However, this approach faces the following prominent challenges in practical applications: (1) Common small-molecule UV absorbers have limited compatibility with the acrylic resin matrix in acrylate pressure-sensitive adhesives, especially in high-temperature and high-humidity environments where they are prone to migration and precipitation, leading to fogging and reduced light transmittance on the adhesive layer surface, directly affecting display clarity. (2) Some UV absorbers undergo photodegradation and become ineffective after long-term absorption of high-energy ultraviolet light, failing to provide lasting protection. Their decomposition products may also cause yellowing of the adhesive layer and even accelerate resin aging. (3) Physically mixing UV absorbers and other additives may interfere with the precise cross-linked network structure of the pressure-sensitive adhesive matrix, damaging its original cohesive strength and temperature resistance. In harsh environmental tests, this manifests as blistering, warping, or delamination of the adhesive layer, thus creating an irreconcilable contradiction between achieving ultraviolet protection and maintaining the reliability of the pressure-sensitive adhesive base.

[0004] Therefore, there is an urgent need in this field to develop a heat-resistant and migration-resistant UV-absorbing optical pressure-sensitive adhesive that can provide the pressure-sensitive adhesive with efficient and long-lasting UV blocking capabilities while ensuring its excellent optical performance, mechanical strength and long-term environmental stability. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a UV-absorbing acrylate pressure-sensitive adhesive, its preparation method, and its applications. Through a resin network fixed by chemical bonds and a physically blocking nano-network, a dual locking mechanism is provided for the UV absorber (UV-327). This not only achieves a durable blocking rate of over 99% for ultraviolet light in the 300nm~400nm band, but also fundamentally overcomes the problem of optical performance degradation caused by the migration and precipitation of UV absorbers in traditional additive optical pressure-sensitive adhesives. Furthermore, it possesses high light transmittance, low color shift, and excellent anti-aging properties, perfectly matching the optical and durability requirements of high-reliability display modules.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a UV-absorbing acrylate pressure-sensitive adhesive, comprising the following raw materials: acrylate resin, UV absorber and nanofibers; The acrylate resin is prepared by free radical copolymerization of functionalized macromonomers, alkyl acrylates, and benzyl acrylates; the functionalized macromonomer is prepared by reacting hydroxyethyl acrylate with isocyanate-containing chain monomers and fluorinated aromatic dianhydrides in sequence. The ultraviolet absorber includes UV-327.

[0007] Compared to existing technologies, the UV-absorbing acrylic pressure-sensitive adhesive provided by this invention involves the hydroxyl group (-OH) in hydroxyethyl acrylate (HEA) first undergoing an addition reaction with the isocyanate group (-CNO) in the monomer containing the isocyanate chain, generating an intermediate containing a urethane bond (-NH-COO-) and a polymerizable double bond. This introduces flexible linking segments into the acrylic resin, forming strong hydrogen bonds, thereby significantly improving the polymer's cohesive strength and hydrolysis resistance. The hydroxyl group in hydroxyethyl acrylate then undergoes a ring-opening reaction with the anhydride group in the fluorinated aromatic dianhydride compound, introducing a fluorinated rigid aromatic structure into the side chain of the acrylate molecule via chemical bonds, constructing a rigid molecular backbone. Fluorine, being the most electronegative element, contributes electron-withdrawing properties to the aromatic ring skeleton in fluorinated aromatic dianhydrides. This results in a more uniform electron distribution and higher bond energies, thereby endowing the polymer with chemical and thermal stability. This significantly improves the polymer's glass transition temperature (Tg), high-temperature modulus, and creep resistance, giving acrylate pressure-sensitive adhesives excellent thermal and dimensional stability. Then, through free radical copolymerization between carbon-carbon double bonds, acrylate resins with customized functional units in the side chains are obtained. This invention, through molecular structure design, utilizes the synergistic effect of flexible connecting segments and rigid structural units to form acrylate resins that simultaneously possess flexible connecting arms and rigid structural units.

[0008] This invention uses nanofibers as nanoscale space-blocking agents to form a three-dimensional nano network within the adhesive layer, physically binding small molecules such as UV absorber UV-327, effectively inhibiting their migration and precipitation under harsh environments, thereby ensuring the long-term stability of optical performance.

[0009] Preferably, the mass ratio of hydroxyethyl acrylate, isocyanate-containing chain monomer, fluorinated aromatic dianhydride compound, alkyl acrylate and benzyl acrylate in the comonomer of the acrylate resin is (1~3):(0.5~1):(0.1~1):(70~75):(24~28).

[0010] Preferably, the weight-average molecular weight of the acrylate resin is 1 million to 1.3 million.

[0011] Preferably, the structural formula of the monomer containing the isocyanate group chain is shown in Formula I: R1-NCO Formula I In Formula I, R1 represents an alkyl chain containing 3 to 10 carbon atoms with a carbon-carbon double bond, wherein one or more -CH2- can be independently replaced by -CH=CH-, -O-, -CO-, -CO-O- or -O-CO-.

[0012] More preferably, the isocyanate-containing monomer comprises isocyanate ethyl methacrylate.

[0013] Preferably, the structural formula of the fluorinated aromatic dianhydride compound is shown in Formula II:

[0014] Formula II In Formula II, R2 represents an alkyl chain with 1 to 5 carbon atoms, and one or more hydrogen atoms therein can be independently substituted by -F.

[0015] More preferably, the fluorinated aromatic dianhydride compound includes 4,4'-(hexafluoroisopropene)phthalic anhydride.

[0016] The structural formula of isocyanate methacrylate (IEM) is shown in Formula 1, and the structural formula of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) is shown in Formula 2.

[0017]

[0018] Formula 1

[0019] Formula 2 Preferably, the alkyl acrylate includes butyl acrylate.

[0020] Preferably, the nanofibers comprise cellulose nanocrystals (CNC).

[0021] More preferably, the cellulose nanocrystals have a diameter of 5nm~30nm and a length of 100nm~500nm.

[0022] Preferably, the UV-absorbing acrylate pressure-sensitive adhesive further includes the following raw materials: curing agent and coupling agent.

[0023] More preferably, the curing agent includes an isocyanate curing agent.

[0024] More preferably, the curing agent includes Bayer HLBA.

[0025] More preferably, the coupling agent includes KH560.

[0026] Preferably, the UV-absorbing acrylate pressure-sensitive adhesive comprises the following raw materials in parts by weight: 1 to 3 parts hydroxyethyl acrylate, 0.5 to 1 part isocyanate-containing monomer, 0.1 to 1 part fluorinated aromatic dianhydride compound, 70 to 75 parts alkyl acrylate, 24 to 28 parts benzyl acrylate, 0.5 to 5 parts UV absorber, 0.1 to 1 part nanofiber, 0.1 to 1 part curing agent, 0.1 to 1 part coupling agent, and 300 to 600 parts solvent.

[0027] More preferably, the UV-absorbing acrylate pressure-sensitive adhesive comprises the following raw materials in parts by weight: 1 to 3 parts hydroxyethyl acrylate, 0.5 to 1 part isocyanate-containing monomer, 0.3 to 0.8 parts fluorinated aromatic dianhydride compound, 70 to 75 parts alkyl acrylate, 25 to 28 parts benzyl acrylate, 0.02 to 0.06 parts initiator, 2 to 4 parts UV absorber, 0.2 to 0.7 parts nanofiber, 0.2 to 0.8 parts curing agent, 0.1 to 0.6 parts coupling agent, and 350 to 550 parts solvent.

[0028] More preferably, the solvent includes ethyl acetate.

[0029] More preferably, the initiator includes azobisisobutyronitrile (AIBN).

[0030] More preferably, the solid content of the UV-absorbing acrylate pressure-sensitive adhesive is 12% to 20%.

[0031] Preferably, the UV-absorbing acrylate pressure-sensitive adhesive has a UV light blocking rate of >99% in the 300nm~400nm wavelength range, a haze of <1%, a yellowness b-value of <1, and exhibits no bubbles, warping, or yellowing after aging for 500 hours at 85℃±5℃ and 85%±5% RH.

[0032] Secondly, the present invention provides a method for preparing the ultraviolet-absorbing acrylate pressure-sensitive adhesive, comprising the following steps: S1. Under an inert atmosphere, hydroxyethyl acrylate and a monomer solution containing isocyanate chains are added to a solvent to carry out an addition reaction; then, under an inert atmosphere, a fluorinated aromatic dianhydride compound is added to the resulting reaction system to carry out a ring-opening reaction, yielding a functionalized macromonomer solution. S2. Add alkyl acrylate, benzyl acrylate and initiator to the functionalized macromonomer solution to carry out free radical copolymerization reaction to obtain acrylate resin solution. S3. Add UV absorber, nanofibers, curing agent, coupling agent and solvent to the acrylate resin solution, mix evenly to obtain UV-absorbing acrylate pressure-sensitive adhesive.

[0033] The method for preparing UV-absorbing acrylate pressure-sensitive adhesive provided by this invention adopts a process route combining "sequential chemical modification" and "efficient dispersion". Through precise chemical reaction design, a molecular structure with specific functions is pre-constructed in the polymer synthesis stage, which solves the problems of compatibility and long-term stability between functional additives and matrix resins in the prior art. This lays the chemical foundation for obtaining pressure-sensitive adhesive products with high UV barrier properties, excellent heat resistance and long-term environmental reliability. Then, it is uniformly mixed with functional additives to form a stable composite system.

[0034] Preferably, the solvent includes ethyl acetate.

[0035] Preferably, in S1, the mass ratio of hydroxyethyl acrylate to solvent is (1~3):(40~60).

[0036] Preferably, in S1, the mass concentration of the isocyanate-containing monomer solution is 3% to 8%.

[0037] For example, in S1, the solvent for the isocyanate chain monomer solution is ethyl acetate.

[0038] Preferably, in S1, the addition rate of the isocyanate-containing monomer solution is 0.1 g / min to 0.15 g / min.

[0039] Preferably, in S1, the temperature of the addition reaction is 25℃~30℃, and the reaction time is 2h~5h.

[0040] Preferably, in S1, the temperature of the ring-opening reaction is 70℃~80℃, and the reaction time is 2h~4h.

[0041] Preferably, in S2, the temperature of the free radical copolymerization reaction is 65℃~70℃, and the reaction time is 6h~10h.

[0042] Thirdly, the present invention provides an optical protective film, comprising the aforementioned ultraviolet-absorbing acrylate pressure-sensitive adhesive.

[0043] Preferably, the optical protective film is made by coating, drying and curing the ultraviolet-absorbing acrylate pressure-sensitive adhesive.

[0044] Preferably, the thickness of the optical protective film is 20nm~50nm.

[0045] Fourthly, the present invention provides a screen module, including a display panel and a transparent cover plate, wherein the ultraviolet-absorbing acrylic pressure-sensitive adhesive or the optical protective film is disposed between the display panel and the transparent cover plate.

[0046] The screen module provided by this invention can be applied to optical display devices, especially mobile phone screens, tablet screens or computer screens.

[0047] The present invention has the following beneficial effects: This invention, through the specific molecular structure design of acrylate resin and its compounding with functional additives, synergistically enhances the heat resistance, creep resistance, and structural density of the pressure-sensitive adhesive matrix from both chemical and physical perspectives. This results in UV-absorbing acrylate pressure-sensitive adhesives possessing extremely high UV light blocking rate, excellent optical transparency, outstanding heat resistance stability, and long-term environmental reliability. It also prevents the functional small molecules (UV absorbers) from migrating and precipitating out, meeting industry demands for thermomechanical properties and long-term reliability under high temperature and humidity conditions.

[0048] This invention utilizes the sequential reaction of HEA with IEM and 6FDA to construct a precise structure with both rigidity and flexibility in situ on the polymer side chains. This structure significantly increases the glass transition temperature of the pressure-sensitive adhesive, exhibiting extremely high modulus retention and creep resistance at 95°C. It fundamentally eliminates failure phenomena such as bubbling and warping caused by matrix softening, and overcomes the limitation that using IEM crosslinking alone can only improve room temperature modulus but cannot guarantee high-temperature stability, achieving a breakthrough in molecular-level heat resistance and creep resistance.

[0049] This invention introduces CNC, which is designed to construct a nano-barrier network, in synergy with the aforementioned dense molecular network. This provides a dual locking mechanism for the UV absorber UV-327, effectively eliminating the long-standing problems of additive precipitation, yellowing, and haze increase in existing UV-absorbing pressure-sensitive adhesives. It ensures the long-term stability of UV blocking rate (>99%) and optical performance (haze <1%, b-value <1) after rigorous aging tests, achieving long-term anti-migration and optical stability of the pressure-sensitive adhesive.

[0050] In this invention, the rigid framework provided by the heat-resistant structural monomer 6FDA enhances the matrix's ability to bear the load of the nanofiber CNC, while the uniformly dispersed nanofiber network further consolidates the overall structure. This synergistic effect from the molecular to the nanoscale enables the pressure-sensitive adhesive to achieve higher cohesive strength and durability than conventional physical blend formulations while maintaining excellent peel performance, forming a multi-scale synergistic reinforcement system. Attached Figure Description

[0051] Figure 1 This is a comparison chart of the UV-Vis transmittance of the acrylate pressure-sensitive adhesive in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0053] In this embodiment of the invention, the diameter of the CNC is 5nm~30nm and the length is 100nm~500nm; other raw materials, unless otherwise specified in the preparation method, are all commercially available products.

[0054] To better illustrate the present invention, further examples are provided below.

[0055] Example 1 This embodiment provides a UV-absorbing acrylic pressure-sensitive adhesive, comprising the following raw materials in parts by weight: 2 parts hydroxyethyl acrylate, 0.5 parts IEM, 0.5 parts 6FDA, 72 parts butyl acrylate, 26 parts benzyl acrylate, 0.04 parts initiator (AIBN), 3 parts UV absorber (UV-327), 0.3 parts CNC, 0.5 parts curing agent (Bayer HLBA), 0.3 parts coupling agent (KH560), and solvent (ethyl acetate, the amount of solvent added is based on the final solid content).

[0056] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive includes the following steps: S1. Add 50 parts of solvent and hydroxyethyl acrylate to a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube. Start stirring and purge with nitrogen, maintaining the temperature at 25°C. Using a constant-pressure dropping funnel, add a monomer solution containing isocyanate chains (IEM dissolved in 10 parts of solvent) dropwise to the four-necked flask at a rate of 0.12 g / min to carry out the addition reaction. After the addition is complete, continue stirring for 2.5 h. Continue purging with nitrogen, maintaining the temperature at 75°C, and add 6 FDA to the resulting reaction system to carry out the ring-opening reaction for 3 h to obtain a functionalized macromonomer solution.

[0057] S2. Butyl acrylate, benzyl acrylate and initiator are added sequentially to the functionalized macromonomer solution, and a free radical copolymerization reaction is carried out at 68°C. After 8 hours, an acrylate resin solution is obtained.

[0058] Tests showed that the weight-average molecular weight of the acrylate resin was 1.16 million.

[0059] S3. Add UV absorber, CNC, curing agent, coupling agent and 150 parts solvent sequentially to an acrylic resin solution (containing about 100 parts acrylic resin). Mix and treat with a high-efficiency dispersion process for 2 hours. Add more solvent to obtain a UV-absorbing acrylic pressure-sensitive adhesive with a solid content of 15.0%.

[0060] Example 2 This embodiment provides a UV-absorbing acrylic pressure-sensitive adhesive, comprising the following raw materials in parts by weight: 1 part hydroxyethyl acrylate, 0.5 parts IEM, 0.3 parts 6FDA, 75 parts butyl acrylate, 28 parts benzyl acrylate, 0.06 parts initiator (AIBN), 4 parts UV absorber (UV-327), 0.7 parts CNC, 0.8 parts curing agent (Bayer HLBA), 0.1 parts coupling agent (KH560), and solvent (ethyl acetate, the amount of solvent added is based on the final solid content).

[0061] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive includes the following steps: S1. Add 40 parts of solvent and hydroxyethyl acrylate to a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube. Start stirring and purge with nitrogen, maintaining the temperature at 30°C. Using a constant-pressure dropping funnel, add a monomer solution containing isocyanate chains (IEM dissolved in 10 parts of solvent) dropwise to the four-necked flask at a rate of 0.15 g / min to carry out the addition reaction. After the addition is complete, continue stirring for 3 hours. Continue purging with nitrogen, maintaining the temperature at 80°C, and add 6 FDA to the resulting reaction system to carry out the ring-opening reaction for 2.2 hours to obtain a functionalized macromonomer solution.

[0062] S2. Butyl acrylate, benzyl acrylate and initiator are added sequentially to the functionalized macromonomer solution, and a free radical copolymerization reaction is carried out at 65°C. After 10 h, an acrylate resin solution is obtained.

[0063] Tests showed that the weight-average molecular weight of the acrylate resin was 1.28 million.

[0064] S3. Add UV absorber, CNC, curing agent, coupling agent and 150 parts solvent sequentially to the acrylic resin solution, mix and treat with high efficiency dispersion process for 2 hours, add solvent to obtain UV-absorbing acrylic pressure-sensitive adhesive with solid content of 17.8%.

[0065] Example 3 This embodiment provides a UV-absorbing acrylic pressure-sensitive adhesive, comprising the following raw materials in parts by weight: 3 parts hydroxyethyl acrylate, 1 part IEM, 0.8 parts 6FDA, 70 parts butyl acrylate, 24 parts benzyl acrylate, 0.02 parts initiator (AIBN), 2 parts UV absorber (UV-327), 0.2 parts CNC, 0.2 parts curing agent (Bayer HLBA), 0.6 parts coupling agent (KH560), and solvent (ethyl acetate, the amount of solvent added is based on the final solid content).

[0066] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive includes the following steps: S1. Add 60 parts of solvent and hydroxyethyl acrylate to a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube. Start stirring and purge with nitrogen, maintaining the temperature at 28°C. Using a constant-pressure dropping funnel, add a monomer solution containing isocyanate chains (IEM dissolved in 10 parts of solvent) dropwise to the four-necked flask at a rate of 0.1 g / min to carry out the addition reaction. After the addition is complete, continue stirring for 2.2 h. Continue purging with nitrogen, maintaining the temperature at 70°C, and add 6 FDA to the resulting reaction system to carry out the ring-opening reaction for 4 h to obtain a functionalized macromonomer solution.

[0067] S2. Butyl acrylate, benzyl acrylate and initiator are added sequentially to the functionalized macromonomer solution, and a free radical copolymerization reaction is carried out at 70°C. After 6.5 h, an acrylate resin solution is obtained.

[0068] Tests showed that the weight-average molecular weight of the acrylate resin was 1.02 million.

[0069] S3. Add UV absorber, CNC, curing agent, coupling agent and 150 parts solvent sequentially to the acrylic resin solution, mix and treat with high efficiency dispersion process for 2 hours, add solvent to obtain UV-absorbing acrylic pressure-sensitive adhesive with solid content of 12.5%.

[0070] Example 4 This embodiment provides a UV-absorbing acrylic pressure-sensitive adhesive, similar to Example 1, except that CNC is replaced with an equal mass of silica nanofibers (purchased from Zhejiang Zhongchuan New Material Technology Co., Ltd., model ZC-SiO2-N10). The remaining raw materials and proportions are the same as in Example 1 and will not be repeated.

[0071] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive is similar to that of Example 1, except that CNC is replaced with silica nanofibers in S3. The remaining operations and parameter settings are the same as in Example 1 and will not be repeated here.

[0072] Comparative Example 1 This comparative example provides an acrylic pressure-sensitive adhesive, similar to Example 1, except that it does not contain a UV absorber. The remaining raw materials and proportions are the same as in Example 1 and will not be repeated.

[0073] The preparation method of the above-mentioned acrylic pressure-sensitive adhesive is similar to that of Example 1, except that no ultraviolet absorber is added in step S3. The remaining operations and parameter settings are the same as in Example 1 and will not be repeated here.

[0074] Comparative Example 2 This comparative example provides a UV-absorbing acrylic pressure-sensitive adhesive, similar to Example 1, except that the UV absorber UV-327 is replaced with an equal mass of UV absorber UV-531. The remaining raw materials and proportions are the same as in Example 1 and will not be repeated.

[0075] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive, the operation and parameter settings are the same as those in Example 1, and will not be repeated here.

[0076] Comparative Example 3 This comparative example provides a UV-absorbing acrylic pressure-sensitive adhesive, similar to Example 1, except that it does not contain CNC. The remaining raw materials and proportions are the same as in Example 1 and will not be repeated.

[0077] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive is similar to that of Example 1, except that CNC is not added in S3. The remaining operations and parameter settings are the same as in Example 1, and will not be repeated here.

[0078] Comparative Example 4 This comparative example provides a UV-absorbing acrylic pressure-sensitive adhesive, similar to Example 1, except that 6FDA is not added during the synthesis of the acrylic resin, i.e., the raw materials do not contain 6FDA. The remaining raw materials and proportions are the same as in Example 1 and will not be repeated.

[0079] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive includes the following steps: S1. Add 50 parts of solvent and hydroxyethyl acrylate to a four-necked flask equipped with a stirrer, thermometer, condenser and nitrogen inlet tube. Start stirring and introduce nitrogen gas. Control the temperature at 25°C. Using a constant pressure dropping funnel, add the monomer solution containing isocyanate chain (IEM dissolved in 10 parts of solvent) dropwise to the above four-necked flask at a rate of 0.12 g / min to carry out the addition reaction. After the addition is complete, continue stirring the reaction for 2.5 h to obtain the functionalized macromonomer solution.

[0080] S2~S3 are the same as S2~S3 in Example 1, and will not be described again.

[0081] Comparative Example 5 This comparative example provides a UV-absorbing acrylic pressure-sensitive adhesive, similar to Example 1, except that IEM is not added during the synthesis of the acrylic resin, i.e., the raw materials do not contain IEM. The remaining raw materials and proportions are the same as in Example 1 and will not be repeated.

[0082] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive includes the following steps: S1. Add 50 parts of solvent and hydroxyethyl acrylate to a four-necked flask equipped with a stirrer, thermometer, condenser and nitrogen inlet tube. Start stirring and introduce nitrogen gas. Control the temperature at 75°C. Add 6 FDA to the four-necked flask and carry out the ring-opening reaction for 3 hours to obtain a functionalized macromonomer solution.

[0083] S2~S3 are the same as S2~S3 in Example 1, and will not be described again.

[0084] Comparative Example 6 This comparative example provides a UV-absorbing acrylic pressure-sensitive adhesive, with the same raw materials and proportions as in Example 1, which will not be repeated here.

[0085] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive is similar to that of Example 1, except that in the synthesis of the functionalized macromonomer, 6FDA is added first, followed by IEM. Specifically, it includes the following steps: S1. Add 50 parts of solvent and hydroxyethyl acrylate to a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube. Start stirring and purge with nitrogen, maintaining the temperature at 75°C. Add 6 FDA to the flask and allow the ring-opening reaction to proceed for 3 hours. Continue purging with nitrogen and maintain the temperature at 25°C. Using a constant-pressure dropping funnel, add a monomer solution containing isocyanate chains (IEM dissolved in 10 parts of solvent) dropwise to the reaction system at a rate of 0.12 g / min to allow the addition reaction to proceed. After the addition is complete, continue stirring for 2.5 hours to obtain a functionalized macromonomer solution.

[0086] S2~S3 are the same as S2~S3 in Example 1, and will not be described again.

[0087] Comparative Example 7 This comparative example provides a UV-absorbing acrylic pressure-sensitive adhesive, similar to Example 1, except that IEM and 6FDA are not added during the synthesis of the acrylic resin; that is, the raw materials do not contain IEM and 6FDA. The acrylic resin is prepared by free radical copolymerization of hydroxyethyl acrylate, butyl acrylate, and benzyl acrylate. The remaining raw materials and proportions are the same as in Example 1 and will not be repeated.

[0088] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive includes the following steps: S1. Add 50 parts of solvent and hydroxyethyl acrylate to a four-necked flask equipped with a stirrer, thermometer, condenser and nitrogen inlet tube, then add butyl acrylate, benzyl acrylate and initiator in sequence, and carry out free radical copolymerization reaction at 68°C. After 8 hours, acrylate resin solution is obtained.

[0089] S2 is the same as S3 in Example 1, and will not be described again.

[0090] Comparative Example 8 This comparative example provides a UV-absorbing acrylic pressure-sensitive adhesive, similar to Example 1, except that the raw materials do not contain 6FDA, and the acrylic resin is prepared by free radical copolymerization of hydroxyethyl acrylate, IEM, butyl acrylate, and benzyl acrylate. The remaining raw materials and proportions are the same as in Example 1 and will not be repeated.

[0091] The preparation method of the above-mentioned UV-absorbing acrylate pressure-sensitive adhesive includes the following steps: S1. Add 50 parts of solvent and hydroxyethyl acrylate to a four-necked flask equipped with a stirrer, thermometer, condenser and nitrogen inlet tube, then add IEM, butyl acrylate, benzyl acrylate and initiator in sequence, and carry out free radical copolymerization reaction at 68°C. After 8 hours, acrylate resin solution is obtained.

[0092] S2 is the same as S3 in Example 1, and will not be described again.

[0093] Verification test The acrylic pressure-sensitive adhesives provided in Examples 1-4 and Comparative Examples 1-8 were coated onto release films. After drying in an oven at 120°C for 2 minutes to remove most of the solvent, they were placed in a constant temperature and humidity chamber at 35°C±2°C and 35%±2% RH for 5 days to allow the curing agent to fully react and the adhesive layer to reach its final usability. Optical protective films with a thickness of 25 μm were then prepared for performance testing.

[0094] The performance of each optical protective film was tested, and the results are shown in Table 1 and 2. Figure 1 As shown.

[0095] Aging test: Each optical protective film was placed in a constant temperature and humidity test chamber and aged continuously for 500 hours at 85℃ and 85% RH.

[0096] Table 1. Performance test results of optical protective films corresponding to the acrylic pressure-sensitive adhesives in the examples and comparative examples.

[0097] As can be seen from the table above, the UV-absorbing acrylate pressure-sensitive adhesives provided in Examples 1-3 of this invention exhibit a UV light blocking rate >99% in the 300nm-400nm wavelength range, haze <1%, and yellowness b-value <1. After aging for 500 hours at 85℃±5℃ and 85%±5% RH, they show no bubbles, warping, or yellowing. These results demonstrate that this invention, through precise formulation ratios and synthetic process design, achieves optimal synergistic effects from both chemical fixation and physical locking mechanisms. By employing a sequential reaction of "IEM followed by 6FDA," a complete rigid aromatic ring covalent structure is constructed on the resin side chains, intrinsically enhancing the UV absorption function and fundamentally improving the thermal stability of the matrix. Simultaneously, a suitable amount of uniformly dispersed CNC forms a dense three-dimensional nano-barrier network, effectively locking in the migration of small molecules. This complete construction from molecular design to microstructure is the fundamental reason why the UV-absorbing acrylate pressure-sensitive adhesive achieves long-term stable protection.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A UV-absorbing acrylic pressure-sensitive adhesive, characterized in that, The raw materials include: acrylate resin, ultraviolet absorber, and nanofibers; The acrylate resin is prepared by free radical copolymerization of functionalized macromonomers, alkyl acrylates, and benzyl acrylates; the functionalized macromonomer is prepared by reacting hydroxyethyl acrylate with isocyanate-containing chain monomers and fluorinated aromatic dianhydrides in sequence. The ultraviolet absorber includes UV-327.

2. The UV-absorbing acrylic pressure-sensitive adhesive as described in claim 1, characterized in that, The mass ratio of hydroxyethyl acrylate, isocyanate-containing chain monomer, fluorinated aromatic dianhydride compound, alkyl acrylate and benzyl acrylate in the comonomer of the acrylate resin is (1~3):(0.5~1):(0.1~1):(70~75):(24~28).

3. The UV-absorbing acrylic pressure-sensitive adhesive as described in claim 1 or 2, characterized in that, The structural formula of the isocyanate-containing chain monomer is shown in Formula I: R1-NCO Formula I In Formula I, R1 represents an alkyl chain containing 3 to 10 carbon atoms with a carbon-carbon double bond, wherein one or more -CH2- can be independently replaced by -CH=CH-, -O-, -CO-, -CO-O- or -O-CO-; The structural formula of the fluorinated aromatic dianhydride compound is shown in Formula II: Formula II In Formula II, R2 represents an alkyl chain with 1 to 5 carbon atoms, and one or more hydrogen atoms therein can be independently substituted by -F.

4. The UV-absorbing acrylic pressure-sensitive adhesive as described in claim 3, characterized in that, The isocyanate-containing monomer includes isocyanate ethyl methacrylate, the fluorinated aromatic dianhydride compound includes 4,4'-(hexafluoroisopropene) diazotidine anhydride, and the alkyl acrylate includes butyl acrylate.

5. The UV-absorbing acrylic pressure-sensitive adhesive as described in claim 1 or 4, characterized in that, The weight-average molecular weight of the acrylate resin is 1 million to 1.3 million. The nanofibers include cellulose nanofibers.

6. The UV-absorbing acrylic pressure-sensitive adhesive as described in claim 1, characterized in that, The UV-absorbing acrylic pressure-sensitive adhesive comprises the following raw materials in parts by weight: 1-3 parts hydroxyethyl acrylate, 0.5-1 part isocyanate-containing monomer, 0.1-1 part fluorinated aromatic dianhydride compound, 70-75 parts alkyl acrylate, 24-28 parts benzyl acrylate, 0.5-5 parts UV absorber, 0.1-1 part nanofiber, 0.1-1 part curing agent, 0.1-1 part coupling agent, and 300-600 parts solvent.

7. The method for preparing the ultraviolet-absorbing acrylate pressure-sensitive adhesive according to claim 6, characterized in that, Includes the following steps: S1. Under an inert atmosphere, hydroxyethyl acrylate and a monomer solution containing isocyanate chains are added to a solvent to carry out an addition reaction; then, under an inert atmosphere, a fluorinated aromatic dianhydride compound is added to the resulting reaction system to carry out a ring-opening reaction, yielding a functionalized macromonomer solution. S2. Add alkyl acrylate, benzyl acrylate and initiator to the functionalized macromonomer solution to carry out free radical copolymerization reaction to obtain acrylate resin solution. S3. Add UV absorber, nanofibers, curing agent, coupling agent and solvent to the acrylate resin solution, mix evenly to obtain UV-absorbing acrylate pressure-sensitive adhesive.

8. The preparation method of the ultraviolet-absorbing acrylate pressure-sensitive adhesive as described in claim 7, characterized in that, The solvent includes ethyl acetate; In S1, the mass ratio of hydroxyethyl acrylate to solvent is (1~3):(40~60); the mass concentration of the isocyanate-containing monomer solution is 3%~8%, and the addition rate of the isocyanate-containing monomer solution is 0.1g / min~0.15g / min; In S1, the temperature of the addition reaction is 25℃~30℃, and the reaction time is 2h~5h; the temperature of the ring-opening reaction is 70℃~80℃, and the reaction time is 2h~4h. In S2, the temperature of the free radical copolymerization reaction is 65℃~70℃, and the reaction time is 6h~10h.

9. An optical protective film, characterized in that, Includes the UV-absorbing acrylate pressure-sensitive adhesive as described in any one of claims 1 to 6, or the UV-absorbing acrylate pressure-sensitive adhesive prepared by the preparation method of the UV-absorbing acrylate pressure-sensitive adhesive as described in any one of claims 7 to 8.

10. A screen module, comprising a display panel and a transparent cover plate, characterized in that, An ultraviolet-absorbing acrylic pressure-sensitive adhesive as described in any one of claims 1 to 6 or an optical protective film as described in claim 9 is disposed between the display panel and the transparent cover.

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