Preparation method of modified cycloolefin copolymer and application of modified cycloolefin copolymer in curved screen

Abstract

The invention belongs to the technical field of high-molecular compounds, and particularly relates to a preparation method of a modified cycloolefin copolymer and application of the modified cycloolefin copolymer in a curved screen. The preparation method comprises the following steps: respectively pretreating a cycloolefin copolymer, nano calcium carbonate and NHS-PEG-NHS to sequentially obtain a pretreated cycloolefin copolymer, a nano calcium carbonate suspension and a binder solution; adding the pretreated cycloolefin copolymer into a binder solution, and dipping; and then adding into a nano calcium carbonate suspension, and adding a template agent for deposition to obtain the modified cycloolefin copolymer. According to the application, the modified cycloolefin copolymer is preheated and subjected to hot press molding, and the curved screen base material is prepared. The cycloolefin copolymer is modified, so that the problems that when the existing cycloolefin copolymer is used for manufacturing the curved screen, the surface of the manufactured curved screen is easy to scratch, thermal deformation is easy to occur in a high-temperature processing environment, and light scattering exists are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer compounds, and in particular relates to a preparation method of a modified cycloolefin copolymer and an application thereof in a curved screen. Background Art

[0002] Cyclic olefin copolymer (COC) is an amorphous, transparent material produced by the copolymerization of cyclic olefin monomers (primarily norbornene and its derivatives) with linear olefins (primarily ethylene). COC contains only non-polar, saturated covalent bonds such as carbon-hydrogen and carbon-carbon, and lacks polar or chromophore groups. It forms a dense, rigid, and low-swelling amorphous network. These microscopic molecular properties endow COC with excellent optical properties, a low dielectric constant, low water absorption, and high heat and chemical resistance. These properties make COC valuable for applications in optical lenses, AR / VR lenses, curved head-up displays (HUDs), and medical packaging. For example, COC's lightweight and high-precision processing make it an ideal material for curved displays in the era of intelligent driving.

[0003] However, since conventional COC is a linear polymer and lacks a covalent cross-linking network, the molecular chains will undergo relative displacement under the action of external forces, resulting in scratches on the surface of the curved screen when COC is used for a long time. Thermal deformation is also prone to occur in high-temperature environments. For example, during the processing (hot bending) of the curved screen, the difference in the degree of orientation in different areas leads to material anisotropy. The refractive index of light in different orientation areas is different, which causes light scattering, affecting the viewing effect at different angles.

[0004] Chinese patent CN108602928A discloses a method for preparing a branched cycloolefin copolymer, which comprises combining a catalyst precursor and an activator with a feed containing ethylene and at least one cycloolefin at a temperature in the range of 60 to 140°C; wherein the catalyst precursor is selected from a Cs-symmetric Group 4 metallocene comprising any two ligands selected from a cyclopentadienyl group and a ligand isolobal to the cyclopentadienyl group.

[0005] According to the specification, the crystallinity range of the branched cyclic olefin copolymer (bCOC) in this patent is 20~38%, and it is known that the refractive index difference between the crystalline region and the amorphous region may lead to birefringence. Amorphous COC is more in line with the requirements because it has no crystalline region; the glass transition temperature of the branched cyclic olefin copolymer (bCOC) is -20~20℃, and the dimensional stability in high temperature environment is insufficient; and the highly branched structure will have an adverse effect on the dimensional stability during extrusion / injection molding, that is, the branching point will induce flow orientation, resulting in orange peel on the surface or uneven thickness. Summary of the Invention

[0006] The present invention aims to provide a method for preparing a modified cycloolefin copolymer to address the problems of surface scratches, thermal deformation in high-temperature processing environments, and light scattering in the production of curved screens using cycloolefin copolymers. The present invention also provides specific applications of the modified cycloolefin copolymer in curved screens.

[0007] To achieve the above object, the technical solution adopted by the present invention is: The method for preparing the modified cycloolefin copolymer of the present invention comprises the following steps: (1) Pre-treating cyclic olefin copolymer, nano-calcium carbonate and polyethylene glycol disubstituted N-hydroxysuccinimide ester respectively to obtain pre-treated cyclic olefin copolymer, nano-calcium carbonate suspension and binder solution in sequence; polyethylene glycol disubstituted N-hydroxysuccinimide ester is referred to as NHS-PEG-NHS; (2) The pretreated cycloolefin copolymer is added to a binder solution for impregnation; then added to a nano-calcium carbonate suspension, a template is added, and deposition is performed to obtain a modified cycloolefin copolymer.

[0008] in: In the step (1), the pretreatment process of the cycloolefin copolymer is to immerse the cycloolefin copolymer in anhydrous ethanol, and sequentially perform ultrasonic cleaning, deionized water cleaning, drying and plasma surface treatment to obtain a pretreated cycloolefin copolymer; the ratio of the added amount of the cycloolefin copolymer to the anhydrous ethanol is 800:(6300~7000), wherein the cycloolefin copolymer is measured in g and the anhydrous ethanol is measured in mL.

[0009] In the step (1), the ultrasonic power is 450-520 W, the ultrasonic time is 18-25 min; the drying temperature is 65-72 ° C, the drying pressure is 0.05-0.06 MPa, and the drying time is 2-3 h; during the plasma surface treatment, the oxygen flow rate is 30-35 sccm, the radio frequency power is 100-120 W, and the treatment time is 5-10 min.

[0010] In the step (1), the pretreatment process of nano-calcium carbonate is to add stearic acid to anhydrous ethanol to prepare a stearic acid solution; then, sodium polyacrylate and the stearic acid solution are added to water, and then nano-calcium carbonate is added in batches and mixed to prepare a nano-calcium carbonate suspension; the ratio of the added amounts of nano-calcium carbonate, sodium polyacrylate, stearic acid and water is 1000:(90~110):(420~460):(7300~7600), and the ratio of the added amounts of stearic acid to anhydrous ethanol is (420~460):(1000~1400), wherein the nano-calcium carbonate, sodium polyacrylate and stearic acid are measured in g, and the water and anhydrous ethanol are measured in mL.

[0011] In the step (1), based on 7300-7600 mL of water, each batch of nano calcium carbonate is ≤200 g when added in batches.

[0012] In the step (1), the pretreatment process of polyethylene glycol disubstituted N-hydroxysuccinimide ester is to add polyethylene glycol disubstituted N-hydroxysuccinimide ester and polydopamine to anhydrous ethanol, stir until dissolved, then add triethylamine, stir and react at room temperature to obtain a binder solution.

[0013] In the step (1), the ratio of the added amounts of polyethylene glycol disubstituted N-hydroxysuccinimide ester, polydopamine, triethylamine and anhydrous ethanol is 800:(330~360):(60~90):(2800~3000), wherein the polyethylene glycol disubstituted N-hydroxysuccinimide ester, polydopamine and triethylamine are measured in g, and the anhydrous ethanol is measured in mL.

[0014] In the step (2), during the impregnation, the mass ratio of the pretreated cyclic olefin copolymer to the binder solution is 700:(1200~1300); the impregnation temperature is 38~45°C, and the impregnation time is 35~45min; during the deposition, the mass ratio of the pretreated cyclic olefin copolymer, the nano-calcium carbonate suspension and the template is 700:4000:(85~120); ultrasonic dispersion is used during the deposition, the ultrasonic power is 120~180W, the ultrasonic temperature is 35~45°C, and the ultrasonic time is 25~35min; the template is 1-octadecyl-3-triethoxypropylsilane imidazole bromide.

[0015] Application of the modified cycloolefin copolymer of the present invention in a curved screen: Preparation of a curved screen substrate, the preparation process includes the following steps: S1. Spraying a release agent on the mold surface, wherein the release agent is prepared by mixing hydroxy silicone oil, petroleum ether, dibutyltin dilaurate, and tri-n-butylamine in a mass ratio of 1:(0.5-2):(0.1-0.2):(0.1-0.2); S2. Preheating the modified cycloolefin copolymer, then placing the modified cycloolefin copolymer in a mold, and hot-pressing the mold to obtain a curved screen substrate.

[0016] in: The thickness of the mold surface release agent is 5-10 μm, the preheating temperature is 165-180° C., and the preheating time is 5-10 min; the hot pressing temperature is 150-160° C., the hot pressing pressure is 20-30 MPa, and the hot pressing time is 10-20 min.

[0017] The beneficial effects of the present invention are as follows: (1) Polydopamine has multiple functions, one of which is to form a polydopamine network through oxidative cross-linking: under the action of triethylamine base catalyst and oxygen, the catechol group of polydopamine is oxidized to quinone group, cross-linked with NHS-PEG-NHS, and then condensed with COC and the surface polar groups of nano-calcium carbonate to form a dopamine cross-linked network. This network has both high adhesion (catechol group) and mechanical toughness (stress conduction synergy formed by flexible polyethylene glycol segments and rigid polydopamine segments). Finally, by bonding with nano-calcium carbonate, nano-calcium carbonate fills the molecular gaps of COC. Since the thermal decomposition temperature of nano-calcium carbonate is much higher than the glass transition temperature of COC, it acts as a rigid anchor to inhibit the thermal motion of the COC molecular chain.

[0018] During COC pretreatment, plasma surface treatment is utilized to introduce polar groups such as hydroxyl groups onto the COC surface through reactive O2 plasma. Under the action of the template agent 1-octadecyl-3-triethoxypropylsilane imidazolium bromide, the oxygen-containing dopamine cross-linked network hydrolyzes the silane groups (-Si(OEt)) in the template agent to generate silanol groups (-SiOH), which can condense with the hydroxyl groups on the surface of the pretreated COC and the hydroxyl groups on the surface of calcium carbonate, thereby enhancing the anchoring effect of nano-calcium carbonate in COC. At this time, the long-chain alkyl group (octadecyl) of the template agent forms an amphiphilic structure with the imidazolium cation, which can self-assemble in aqueous solution to form a lamellar liquid crystal structure, serving as a template for nano-calcium carbonate deposition, guiding the deposition of nano-calcium carbonate particles on the COC surface, and enhancing the hardness of COC.

[0019] Nano-calcium carbonate is arranged without agglomeration on the COC, and its inherent high hardness effectively resists scratches. Furthermore, the stress-conduction synergistic mechanism of the dopamine cross-linked network provides a buffer for the COC. When the surface is impacted by external forces, the flexible PEG segments can orderly transmit internal stress along the rigid structure, which absorbs the internal stress and prevents it from being directly transferred to the COC matrix. This prevents scratches from remaining and reduces their propagation.

[0020] (2) Dispersing and stabilizing function of sodium polyacrylate (PAAS): As a polymer electrolyte, the carboxylate ionized by PAAS wraps around the nano-calcium carbonate particles through electrostatic repulsion, inhibiting their aggregation; at the same time, the hydrophilic chain of PAAS forms hydrogen bonds with water molecules, forming a hydration layer on the surface of the particles, further improving the stability of the suspension. 2+ Forming ionic bonds, forming an organic coating on the surface of calcium carbonate, improving the inorganic-organic compatibility. Surface modification effect of stearic acid: The long-chain alkyl group of stearic acid is coated on the surface of calcium carbonate through physical adsorption or melting, neutralizing its surface polarity, reducing the surface energy, and changing it from hydrophilic to weakly lipophilic, making it easier to form van der Waals forces with organic groups in the binder (such as the alkyl chain of polydopamine); the carboxyl group of stearic acid cooperates with the carboxylate radical of PAAS to form an ionic bond with CaCO3. 2+The synergistic dispersion of PAAS and stearic acid makes the calcium carbonate particles monodisperse in the composite layer without orientation differences, thus avoiding light scattering caused by filler agglomeration. DETAILED DESCRIPTION

[0021] The present invention is described and illustrated in detail below with reference to the embodiments.

[0022] Example 1 First, the raw materials were pretreated. 800g of COC (provided by Liaoning Luhua Hongjin New Materials Technology Co., Ltd.) was immersed in 6600mL of anhydrous ethanol and ultrasonicated at 490W for 20 minutes. After removal, the COC was rinsed three times with deionized water and dried at 68°C and 0.06MPa for 2.5 hours. Subsequently, the COC was plasma treated at an oxygen flow rate of 30sccm and a radio frequency power of 100W for 10 minutes to obtain the pretreated COC. The COC was then sealed and stored for future use.

[0023] Weigh 420g of stearic acid and add it to 1000mL of anhydrous ethanol to prepare a stearic acid solution. Weigh 110g of sodium polyacrylate, add the sodium polyacrylate and stearic acid solution to 7300mL of deionized water and stir evenly. Maintain stirring, add 1000g of nano-calcium carbonate in batches, 200g per batch, and continue stirring for 15 minutes after the addition is complete to obtain a nano-calcium carbonate suspension for standby use. Weigh 800g of NHS-PEG-NHS and 340g of polydopamine and add them to 2900mL of anhydrous ethanol, stir until dissolved, then add 80g of triethylamine dropwise, and react at 65°C with stirring until the solution turns light brown and does not change color when left standing to obtain a binder solution for standby use.

[0024] First, 700 g of pretreated COC was immersed in 1200 g of binder solution, kept at a constant temperature of 38°C for 35 min, taken out, rinsed with deionized water for 3 min, and dried until the weight did not change.

[0025] Then, the mixture was added to 4000 g of nano-calcium carbonate suspension, and 85 g of 1-octadecyl-3-triethoxypropylsilane imidazole bromide was added. After ultrasonication at 160 W and 35 ° C for 25 min, the mixture was taken out, rinsed with deionized water for 3 min, and dried until the weight did not change to obtain a modified cycloolefin copolymer.

[0026] Example 2 First, the raw materials were pretreated. 800 g of COC (provided by Liaoning Luhua Hongjin New Materials Technology Co., Ltd.) was immersed in 6800 mL of anhydrous ethanol and ultrasonicated at 500 W for 22 minutes. After removal, the COC was rinsed three times with deionized water and dried at 70°C and 0.05 MPa for 2.2 hours. Subsequently, the COC was plasma treated at an oxygen flow rate of 33 sccm and a radio frequency power of 115 W for 9 minutes to obtain the pretreated COC. The COC was then sealed and stored for future use.

[0027] Weigh 430g of stearic acid and add it to 1100mL of anhydrous ethanol to prepare a stearic acid solution. Weigh 100g of sodium polyacrylate, add the sodium polyacrylate and stearic acid solution to 7400mL of deionized water and stir evenly. Maintain stirring, add 1000g of nano-calcium carbonate in batches, 200g per batch, and continue stirring for 15 minutes after the addition is complete to obtain a nano-calcium carbonate suspension for later use. Weigh 800g of NHS-PEG-NHS and 342g of polydopamine and add them to 2850mL of anhydrous ethanol, stir until dissolved, then add 75g of triethylamine dropwise, and react at 68°C with stirring until the solution turns light brown and does not change color when left standing to obtain a binder solution for later use.

[0028] First, 800 g of pretreated COC was immersed in 1250 g of binder solution, kept at a constant temperature of 41°C for 42 min, taken out, rinsed with deionized water for 3 min, and dried until the weight did not change.

[0029] Then, the mixture was added to 4000 g of nano-calcium carbonate suspension, and 98 g of 1-octadecyl-3-triethoxypropylsilane imidazole bromide was added. After ultrasonication at 155 W and 40° C. for 30 min, the mixture was taken out, rinsed with deionized water for 3 min, and dried until the weight did not change to obtain a modified cycloolefin copolymer.

[0030] Example 3 First, the raw materials were pretreated. 800g of COC (provided by Liaoning Luhua Hongjin New Materials Technology Co., Ltd.) was immersed in 7000mL of anhydrous ethanol and ultrasonicated at 450W for 25 minutes. After removal, the COC was rinsed three times with deionized water and dried at 72°C and 0.06MPa for 2 hours. Subsequently, the COC was plasma treated at an oxygen flow rate of 35sccm and a radio frequency power of 110W for 5 minutes to obtain the pretreated COC. The COC was then sealed and stored for future use.

[0031] Weigh 420g of stearic acid and add it to 1200mL of anhydrous ethanol to prepare a stearic acid solution. Weigh 90g of sodium polyacrylate, add the sodium polyacrylate and stearic acid solution to 7500mL of deionized water and stir evenly. Maintain stirring, add 1000g of nano-calcium carbonate in batches, 200g per batch, and continue stirring for 15min after the addition is complete to obtain a nano-calcium carbonate suspension for standby use. Weigh 800g of NHS-PEG-NHS and 330g of polydopamine and add them to 2800mL of anhydrous ethanol, stir until dissolved, then add 60g of triethylamine dropwise, and stir the reaction at 75°C until the solution turns light brown and does not change color when left standing to obtain a binder solution for standby use.

[0032] First, 800 g of pretreated COC was immersed in 1300 g of binder solution, kept at a constant temperature of 45°C for 40 min, taken out, rinsed with deionized water for 3 min, and dried until the weight did not change.

[0033] Then, the mixture was added to 4000 g of nano-calcium carbonate suspension, and 120 g of 1-octadecyl-3-triethoxypropylsilane imidazole bromide was added. After ultrasonication at 180 W and 35 ° C for 35 minutes, the mixture was taken out, rinsed with deionized water for 3 minutes, and dried until the weight did not change to obtain a modified cycloolefin copolymer.

[0034] Example 4 First, the raw materials were pretreated. 800g of COC (provided by Liaoning Luhua Hongjin New Materials Technology Co., Ltd.) was immersed in 6300mL of anhydrous ethanol and ultrasonicated at 520W for 18 minutes. After removal, the COC was rinsed three times with deionized water and dried at 65°C and 0.06MPa for 3 hours. Subsequently, the COC was plasma treated at an oxygen flow rate of 30sccm and a radio frequency power of 120W for 10 minutes to obtain the pretreated COC. The COC was then sealed and stored for future use.

[0035] Weigh 460g of stearic acid and add it to 1400mL of anhydrous ethanol to prepare a stearic acid solution. Weigh 110g of sodium polyacrylate, add the sodium polyacrylate and stearic acid solution to 7600mL of deionized water and stir evenly. Maintain stirring, add 1000g of nano-calcium carbonate in batches, 200g per batch, and continue stirring for 15min after the addition is complete to obtain a nano-calcium carbonate suspension for standby use. Weigh 800g of NHS-PEG-NHS and 360g of polydopamine and add them to 3000mL of anhydrous ethanol, stir until dissolved, then add 90g of triethylamine dropwise, and react at 65°C with stirring until the solution turns light brown and does not change color when left standing to obtain a binder solution for standby use.

[0036] First, 800 g of pretreated COC was immersed in 1200 g of binder solution, kept at a constant temperature of 43° C. for 45 min, taken out, rinsed with deionized water for 3 min, and dried until the weight did not change.

[0037] Then, the mixture was added to 4000 g of nano-calcium carbonate suspension, and 90 g of 1-octadecyl-3-triethoxypropylsilane imidazole bromide was added. After ultrasonication at 120 W and 45 ° C for 25 min, the mixture was taken out, rinsed with deionized water for 3 min, and dried until the weight did not change to obtain a modified cycloolefin copolymer.

[0038] Example 5 Wipe the mold with anhydrous ethanol and let it dry. Then, evenly spray the mold surface with a release agent (the release agent is prepared by hydroxy silicone oil, petroleum ether, dibutyltin dilaurate, and tri-n-butylamine in a mass ratio of 1:2:0.2:0.2). The thickness is controlled at 5 μm and dried at 80 °C for 8 min.

[0039] The modified cycloolefin copolymer prepared in Example 1 was placed on the preheating platform of a hot press, set to a preheating temperature of 165°C for 10 minutes. The preheated modified cycloolefin copolymer was quickly transferred to the mold cavity, and a pressure of 20 MPa was applied, maintaining the temperature at 160°C for 20 minutes. The mold's water cooling system was then activated, maintaining the water temperature at 30°C. When the temperature dropped below 50°C, the pressure was released, the mold was opened, and the mold was cooled to room temperature to produce the curved screen substrate.

[0040] Example 6 Wipe the mold with anhydrous ethanol and let it dry. Then, evenly spray the mold surface with a release agent (the release agent is prepared by hydroxy silicone oil, petroleum ether, dibutyltin dilaurate, and tri-n-butylamine in a mass ratio of 1:1.5:0.13:0.18). The thickness is controlled at 10 μm and dried at 100 °C for 5 min.

[0041] The modified cycloolefin copolymer prepared in Example 2 was placed on the preheating platform of a hot press, set to a preheating temperature of 172°C for 9 minutes. The preheated modified cycloolefin copolymer was quickly transferred to the mold cavity, where a pressure of 25 MPa was applied, maintaining the temperature at 155°C for 18 minutes. The mold's water cooling system was then activated, maintaining the water temperature at 25°C. When the temperature dropped below 50°C, the pressure was released, the mold was opened, and the mold was cooled to room temperature to produce the curved screen substrate.

[0042] Example 7 Wipe the mold with anhydrous ethanol and let it dry. Then, evenly spray the mold surface with a release agent (the release agent is prepared by hydroxy silicone oil, petroleum ether, dibutyltin dilaurate, and tri-n-butylamine in a mass ratio of 1:0.5:0.1:0.1). The thickness is controlled at 8 μm and dried at 85 °C for 10 min.

[0043] The modified cycloolefin copolymer prepared in Example 3 was placed on the preheating platform of a hot press, set to 180°C for 5 minutes. The preheated modified cycloolefin copolymer was quickly transferred to the mold cavity, where a pressure of 23 MPa was applied, maintaining the temperature at 150°C for 10 minutes. The mold's water cooling system was then activated, maintaining the water temperature at 20°C. When the temperature dropped below 50°C, the pressure was released, the mold was opened, and the mold was cooled to room temperature to produce the curved screen substrate.

[0044] Example 8 Wipe the mold with anhydrous ethanol and let it dry. Then, evenly spray the mold surface with a release agent (the release agent is prepared by hydroxy silicone oil, petroleum ether, dibutyltin dilaurate, and tri-n-butylamine in a mass ratio of 1:1.2:0.15:0.15) with a thickness of 10 μm. Dry at 95 °C for 5 min.

[0045] The modified cycloolefin copolymer prepared in Example 4 was placed on the preheating platform of a hot press, set to 170°C for 8 minutes. The preheated modified cycloolefin copolymer was quickly transferred to the mold cavity, where a pressure of 22 MPa was applied, maintaining the temperature at 155°C for 16 minutes. The mold's water cooling system was then activated, maintaining the water temperature at 28°C. When the temperature dropped below 50°C, the pressure was released, the mold was opened, and the mold was cooled to room temperature to produce the curved screen substrate.

[0046] Comparative Example 1 The template 1-octadecyl-3-triethoxypropylsilane imidazolium bromide was not added, and the remaining steps and raw materials were the same as those in Example 1 and Example 5.

[0047] Comparative Example 2 Without adding sodium polyacrylate and stearic acid, the remaining steps and raw materials were the same as those in Example 1 and Example 5 to prepare a curved screen substrate.

[0048] Comparative Example 3 Without adding nano calcium carbonate, the remaining steps and raw materials used were the same as those in Example 1 and Example 5 to prepare a curved screen substrate.

[0049] Comparative Example 4 Without adding NHS-PEG-NHS, the remaining steps and raw materials were the same as those in Example 1 and Example 5 to prepare a curved screen substrate.

[0050] Comparative Example 5 Without adding polydopamine, the remaining steps and raw materials used were the same as those in Example 1 and Example 5 to prepare a curved screen substrate.

[0051] Comparative Example 6 Without adding NHS-PEG-NHS and polydopamine, the remaining steps and raw materials were the same as those in Example 1 and Example 5 to prepare a curved screen substrate.

[0052] Comparative Example 7 Without adding NHS-PEG-NHS, polydopamine and nano-calcium carbonate, the remaining steps and raw materials were the same as those in Example 1 and Example 5 to prepare a curved screen substrate.

[0053] Implementation Effect Examples 5-8 and Comparative Examples 1-7 were numbered as Samples 1-11. The hardness of Samples 1-11 was measured using a Shore D durometer. Five different locations on each sample surface were tested, and the average hardness value was taken as the sample hardness. During the test, the durometer was pressed vertically against the sample surface for 5 seconds, then the reading was taken to obtain the Shore hardness reading. Specific data are shown in Table 1.

[0054] Using a heat distortion Vicat softening point tester, samples were processed into standard dimensions (80 mm long, 10 mm wide, and 4 mm thick). A specified load (3.5 kg) was applied and heated at a heating rate of 5°C / min. The temperature at which the sample deformed to a specified amount (0.30 mm) was recorded, representing the heat distortion temperature. Each sample was tested three times, and the average value was taken to determine the heat distortion temperature. Specific data are shown in Table 1.

[0055] The refractive index of different areas of each sample was measured at 25°C using an Abbe refractometer. Ten different areas of each sample were measured, and the average and standard deviation were calculated. The specific data are shown in Table 1.

[0056]

[0057] Table 1 shows that the Shore hardness and heat deformation temperature of samples 1-4 (Examples 5-8) are superior to those of samples 5-11 (Comparative Examples 1-7). Furthermore, the average refractive index of samples 1-4 is closer to the theoretical value and has a smaller standard deviation. It is known that higher hardness values ​​indicate greater scratch resistance on the surface, making the material more resistant to wear and tear, thus meeting the wear resistance requirements of curved screens. Higher heat deformation temperatures indicate less deformation in high-temperature environments, resulting in better dimensional stability and greater suitability for mass production of curved screens. A closer average refractive index value to the theoretically expected value (1.530-1.540) indicates lower interfacial reflection when used in the production of curved screens. Furthermore, a smaller standard deviation indicates greater refractive index uniformity, reduced light scattering, and a clearer display, effectively improving the viewing experience of curved screens.

Claims

1. A method for preparing a modified cycloolefin copolymer, characterized in that: The following steps are involved: (1) Pre-treating the cyclic olefin copolymer, nano-calcium carbonate and polyethylene glycol disubstituted N-hydroxysuccinimide ester respectively to obtain the pre-treated cyclic olefin copolymer, nano-calcium carbonate suspension and binder solution in sequence; (2) adding the pretreated cyclic olefin copolymer into the binder solution for impregnation; Then, the mixture is added into a nano-calcium carbonate suspension, a template is added, and deposition is performed to obtain a modified cycloolefin copolymer.

2. The method for preparing the modified cycloolefin copolymer according to claim 1, wherein In step (1), the pretreatment process of the cycloolefin copolymer is to immerse the cycloolefin copolymer in anhydrous ethanol, and sequentially perform ultrasonic cleaning, deionized water cleaning, drying and plasma surface treatment to obtain a pretreated cycloolefin copolymer; the ratio of the added amount of the cycloolefin copolymer to the anhydrous ethanol is 800:(6300~7000), wherein the cycloolefin copolymer is measured in g and the anhydrous ethanol is measured in mL.

3. The method for preparing the modified cycloolefin copolymer according to claim 2, wherein In step (1), the ultrasonic power is 450~520W, the ultrasonic time is 18~25min; the drying temperature is 65~72℃, the drying pressure is 0.05~0.06MPa, and the drying time is 2~3h; during the plasma surface treatment, the oxygen flow rate is 30~35sccm, the radio frequency power is 100~120W, and the treatment time is 5~10min.

4. The method for preparing the modified cycloolefin copolymer according to claim 1, wherein In step (1), the pretreatment process of nano-calcium carbonate is to add stearic acid to anhydrous ethanol to prepare a stearic acid solution; then, sodium polyacrylate and the stearic acid solution are added to water, and then nano-calcium carbonate is added in batches and mixed to prepare a nano-calcium carbonate suspension; the ratio of the added amounts of nano-calcium carbonate, sodium polyacrylate, stearic acid and water is 1000:(90~110):(420~460):(7300~7600), and the ratio of the added amounts of stearic acid to anhydrous ethanol is (420~460):(1000~1400), wherein the nano-calcium carbonate, sodium polyacrylate and stearic acid are measured in g, and water and anhydrous ethanol are measured in mL.

5. The method for preparing the modified cycloolefin copolymer according to claim 4, wherein In step (1), based on 7300-7600 mL of water, each batch of nano calcium carbonate is ≤200 g when added in batches.

6. The method for preparing the modified cycloolefin copolymer according to claim 1, wherein In step (1), the pretreatment process of polyethylene glycol disubstituted N-hydroxysuccinimide ester is to add polyethylene glycol disubstituted N-hydroxysuccinimide ester and polydopamine to anhydrous ethanol, stir until dissolved, then add triethylamine, stir and react at room temperature to obtain a binder solution.

7. The method for preparing the modified cycloolefin copolymer according to claim 6, wherein In step (1), the ratio of the added amounts of polyethylene glycol disubstituted N-hydroxysuccinimide ester, polydopamine, triethylamine and anhydrous ethanol is 800:(330~360):(60~90):(2800~3000), wherein the polyethylene glycol disubstituted N-hydroxysuccinimide ester, polydopamine and triethylamine are measured in g, and the anhydrous ethanol is measured in mL.

8. The method for preparing the modified cycloolefin copolymer according to claim 1, wherein In step (2), during the impregnation, the mass ratio of the pretreated cyclic olefin copolymer to the binder solution is 700:(1200~1300); the impregnation temperature is 38~45°C, and the impregnation time is 35~45min; during the deposition, the mass ratio of the pretreated cyclic olefin copolymer, the nano-calcium carbonate suspension and the template is 700:4000:(85~120); ultrasonic dispersion is used during the deposition, the ultrasonic power is 120~180W, the ultrasonic temperature is 35~45°C, and the ultrasonic time is 25~35min; the template is 1-octadecyl-3-triethoxypropylsilane imidazole bromide.

9. Use of a modified cycloolefin copolymer obtained by the method for preparing the modified cycloolefin copolymer according to any one of claims 1 to 8 in a curved screen, characterized in that: The curved screen substrate is prepared, and the preparation process includes the following steps: S1. Spraying a release agent on the mold surface, wherein the release agent is prepared by mixing hydroxy silicone oil, petroleum ether, dibutyltin dilaurate, and tri-n-butylamine in a mass ratio of 1:(0.5-2):(0.1-0.2):(0.1-0.2); S2. Preheating the modified cycloolefin copolymer, then placing the modified cycloolefin copolymer in a mold, and hot-pressing the mold to obtain a curved screen substrate.

10. Use of the modified cycloolefin copolymer in a curved screen according to claim 9, characterized in that: The thickness of the mold release agent is 5~10μm, the preheating temperature is 165~180℃, and the preheating time is 5~10min; the hot pressing temperature is 150~160℃, the hot pressing pressure is 20~30MPa, and the hot pressing time is 10~20min.

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