Optical cement with dynamic bond exchange and gradient curing functions and preparation method thereof

Abstract

The invention discloses an optical adhesive with dynamic bond exchange and gradient curing functions and a preparation method thereof, relates to an optical adhesive, and aims to solve the problems of interface failure and light transmission attenuation which are easy to occur in the existing optical adhesive. The invention starts from the following three points: 1, two-stage dynamic covalent cross-linking: 1, UV (ultraviolet) initiates acrylate polymerization to form a main network; part of unreacted epoxy groups are retained. 2, thermally activating dynamic boric acid ester bond exchange to realize network reconstruction and stress release; 2, a dual-wavelength gradient initiation system: a 365nm UV curing surface and a 405nm LED penetrate through a curing deep layer to avoid an uncured layer caused by oxygen inhibition; 3, a nano composite anti-reflection technology: mesoporous SiO (at) TiO core-shell nanoparticles (refractive index gradient matching) improve the light transmittance to gt; the content is 99.5%.

Description

Technical Field

[0001] The present invention relates to an optical adhesive, in particular to an optical adhesive with dynamic bond exchange and gradient curing functions and a preparation method thereof. Background Art

[0002] Optical Clear Adhesive (OCA) is a specialty adhesive used in the optical field and is an optimal adhesive for touch screens. However, existing optical adhesives are prone to the following issues when subjected to repeated bending or high temperature and humidity environments: 1. Interface failure: Traditional acrylic adhesives can delaminate due to stress concentration during curing (bond strength decreases by >30% after folding a foldable screen more than 200,000 times); 2. Light transmission degradation: Nanoparticle aggregation or initiator residue can result in light transmittance less than 90% (in the visible light range). Summary of the Invention

[0003] In order to solve the above-mentioned problems, the present invention provides an optical adhesive with dynamic bond exchange and gradient curing functions and a preparation method thereof.

[0004] First, weigh the following raw materials in parts by weight: 60-70 parts of 2-EHA main monomer (isooctyl acrylate, flexibility), 10-20 parts of GMA (glycidyl methacrylate), 5-10 parts of Si-AC (silane acrylate), 1-5 parts of HDDA (1,6-hexanediol diacrylate), 1-3 parts of phenylboronic acid acrylamide (dynamic crosslinker), 1-2 parts of photoinitiator 184 (molecular formula: C13H 16 O2), TPO-L deep layer photoinitiator 1-1.5 parts, mesoporous SiO2@TiO2 nanoparticles 1-1.5 parts, BAPO (bisacylphosphine oxide) 0.1-0.5 parts; The first step (pre-polymerization stage): 1. Mix 2-EHA main monomer, GMA, Si-AC, HDDA, phenylboronic acid acrylamide, photoinitiator 184, and mesoporous SiO2@TiO2 nanoparticles, and irradiate with 365nm UV (90-110mW / cm², 3-7 minutes) under nitrogen protection, and control the conversion rate to 40-50%.

[0005] 2. Obtain a coatable prepolymer (viscosity ≈ 2500 cP, containing some unreacted epoxy groups and borate precursors).

[0006] 3. Add the remaining materials to the prepolymer: TPO-L deep photoinitiator and BAPO, and stir evenly.

[0007] Step 2 (final solidification and dynamic reconstruction): 1. Before coating, first use a 405nm LED (180-220mW / cm², 25-40 seconds) to trigger BAPO and TPO-L to complete deep curing.

[0008] 2. Heat treatment for 8-12 minutes (preferably 10 minutes) at a temperature of 75-85°C, using a gradient cycle heating treatment of 75°C → 85°C → 75°C to activate borate ester bond exchange, eliminate internal stress and improve fatigue resistance.

[0009] In the technical solution provided by the present invention: 1. Two-stage dynamic covalent cross-linking: Step 1: UV-initiated acrylate polymerization forms the main network, leaving some unreacted epoxy groups. Step 2: Thermally activated dynamic borate ester bond exchange to achieve network reconstruction and stress release. 2. Dual wavelength gradient initiation system: 365nm UV cures the surface, 405nm LED penetrates and cures deep layers, avoiding uncured layers caused by oxygen inhibition. 3. Nanocomposite anti-reflection technology: Mesoporous SiO2@TiO2 core-shell nanoparticles (refractive index gradient matching) increase the transmittance to >99.5%. DETAILED DESCRIPTION

[0010] The technology of the present invention is further explained and illustrated below in conjunction with specific implementation methods.

[0011] Example 1 First, weigh the following raw materials in parts by weight: 65 parts of 2-EHA main monomer (isooctyl acrylate, flexibility), 15 parts of GMA (glycidyl methacrylate), 7 parts of Si-AC (silane acrylate), 3 parts of HDDA (1,6-hexanediol diacrylate), 2 parts of phenylboronic acid acrylamide (dynamic crosslinker), 1 part of photoinitiator 184 (molecular formula: C13H 16 O2), 1.5 parts of TPO-L deep layer photoinitiator, 1.5 parts of mesoporous SiO2@TiO2 nanoparticles, 0.4 parts of BAPO (bisacylphosphine oxide); The first step (pre-polymerization stage): 1. Mix 2-EHA main monomer, GMA, Si-AC, HDDA, phenylboronic acid acrylamide, photoinitiator 184, and mesoporous SiO2@TiO2 nanoparticles, and irradiate with 365nm UV (100mW / cm², 5 minutes) under nitrogen protection. Control the conversion rate to 40-50%.

[0012] 2. Obtain a coatable prepolymer (viscosity ≈ 2500 cP, containing unreacted epoxy and borate precursors).

[0013] 3. Add the remaining materials to the prepolymer: TPO-L deep photoinitiator and BAPO, and stir evenly.

[0014] Step 2 (final solidification and dynamic reconstruction): 1. Before coating, first use a 405nm LED (200mW / cm², 30 seconds) to trigger BAPO and TPO-L to complete deep curing.

[0015] 2. Heat treatment was performed using a gradient cycle of 75°C → 85°C → 75°C for 10 minutes to activate borate ester bond exchange, eliminate internal stress, and improve fatigue resistance.

[0016] Example 2 First, weigh the following raw materials in parts by weight: 62 parts of 2-EHA main monomer (isooctyl acrylate, flexibility), 18 parts of GMA (glycidyl methacrylate), 6 parts of Si-AC (silane acrylate), 4 parts of HDDA (1,6-hexanediol diacrylate), 3 parts of phenylboronic acid acrylamide (dynamic crosslinker), 2 parts of photoinitiator 184 (molecular formula: C13H 16 O2), 1.5 parts of TPO-L deep layer photoinitiator, 1.2 parts of mesoporous SiO2@TiO2 nanoparticles, and 0.3 parts of BAPO (bisacylphosphine oxide); The first step (pre-polymerization stage): 1. Mix 2-EHA main monomer, GMA, Si-AC, HDDA, phenylboronic acid acrylamide, photoinitiator 184, and mesoporous SiO2@TiO2 nanoparticles, and irradiate with 365nm UV (110mW / cm², 7 minutes) under nitrogen protection, and control the conversion rate to 40-50%.

[0017] 2. Obtain a coatable prepolymer (viscosity ≈ 2500 cP, containing unreacted epoxy and borate precursors).

[0018] 3. Add the remaining materials to the prepolymer: TPO-L deep photoinitiator and BAPO, and stir evenly.

[0019] Step 2 (final solidification and dynamic reconstruction): 1. Before coating, first use a 405nm LED (220mW / cm², 35 seconds) to trigger BAPO and TPO-L to complete deep curing.

[0020] 2. Heat treatment was performed using a gradient cycle of 75°C → 85°C → 75°C for 12 minutes to activate borate ester bond exchange, eliminate internal stress, and improve fatigue resistance.

[0021] Example 3 First, weigh the following raw materials in parts by weight: 60 parts of 2-EHA main monomer (isooctyl acrylate, flexibility), 10 parts of GMA (glycidyl methacrylate), 5 parts of Si-AC (silane acrylate), 2 parts of HDDA (1,6-hexanediol diacrylate), 1 part of phenylboronic acid acrylamide (dynamic crosslinker), 1 part of photoinitiator 184 (molecular formula: C13H 16 O2), 1 part of TPO-L deep layer photoinitiator, 1 part of mesoporous SiO2@TiO2 nanoparticles, 0.2 parts of BAPO (bisacylphosphine oxide); The first step (pre-polymerization stage): 1. Mix 2-EHA main monomer, GMA, Si-AC, HDDA, phenylboronic acid acrylamide, photoinitiator 184, and mesoporous SiO2@TiO2 nanoparticles, and irradiate with 365nm UV (90mW / cm², 3 minutes) under nitrogen protection. The conversion rate is controlled at 40-50%.

[0022] 2. Obtain a coatable prepolymer (viscosity ≈ 2500 cP, containing unreacted epoxy and borate precursors).

[0023] 3. Add the remaining materials to the prepolymer: TPO-L deep photoinitiator and BAPO, and stir evenly.

[0024] Step 2 (final solidification and dynamic reconstruction): 1. Before coating, first use a 405nm LED (180mW / cm², 25 seconds) to trigger BAPO and TPO-L to complete deep curing.

[0025] Heat treatment at 2.75°C for 8 minutes activates borate ester bond exchange, eliminates internal stress and improves fatigue resistance.

[0026] The optical adhesive prepared in this embodiment was tested and compared with a conventional commercially available UV adhesive (such as 3M 8146). The comparison results are as follows: 1. Dynamic Mechanical Analysis (DMA): The storage modulus (E') shows a plateau at 60-80°C (boronate bond exchange region), demonstrating the dynamic properties.

[0027] 2. X-ray photoelectron spectroscopy (XPS): BOC bonds were detected (284.5 eV), confirming the formation of a dynamic network.

[0028] 3. Transmission electron microscopy (TEM): SiO2@TiO2 nanoparticles are distributed in a gradient pattern (no scattering at the interface). Dynamic mechanical analysis (DMA).

Claims

1. A method for preparing an optical adhesive with dynamic bond exchange and gradient curing functions, characterized in that: The preparation method comprises the following steps: First, prepare the following materials in parts by weight: 60-70 parts of 2-EHA main monomer, 10-20 parts of GMA, 5-10 parts of Si-AC, 1-5 parts of HDDA, 1-3 parts of phenylboronic acid acrylamide, 1-2 parts of photoinitiator 184, 1-1.5 parts of TPO-L deep layer photoinitiator, 1-1.5 parts of mesoporous SiO2@TiO2 nanoparticles, and 0.1-0.5 parts of BAPO; Next, start preparing the optical adhesive: The first step, pre-aggregation stage: 1.1): Mix 2-EHA main monomer, GMA, Si-AC, HDDA, phenylboronic acid acrylamide, photoinitiator 184, and mesoporous SiO2@TiO2 nanoparticles, irradiate with UV under nitrogen protection, and control the conversion rate at 40-50% to obtain a coatable prepolymer; 1.2): Add the remaining materials to the prepolymer: TPO-L deep photoinitiator and BAPO, and stir evenly; The second step is final solidification and dynamic reconstruction: 2.1): Coating, first use LED to trigger BAPO and TPO-L to complete deep curing; 2.2): Heat treatment activates borate ester bond exchange, eliminates internal stress and improves fatigue resistance to obtain the optical adhesive.

2. The method for preparing an optical adhesive having dynamic bond exchange and gradient curing functions according to claim 1, wherein: In step 1.1, 365 nm UV irradiation was performed under nitrogen protection, with an irradiation power of 100 mW / cm² and an irradiation time of 5 minutes.

3. The method for preparing an optical adhesive with dynamic bond exchange and gradient curing functions according to claim 1, wherein: In step 2.1, BAPO and TPO-L were triggered by a 405 nm LED with an LED power of 200 mW / cm² and an irradiation time of 30 seconds.

4. The method for preparing an optical adhesive having dynamic bond exchange and gradient curing functions according to claim 1, wherein: In step 2.2, a gradient cycle temperature increase of 75°C → 85°C → 75°C was used.

5. An optical adhesive with dynamic bond exchange and gradient curing functions, prepared by the preparation method according to any one of claims 1 to 4.

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